2024

Vol.31 No.1

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Vol. 26 No.1

The Latest Trends and Issues of Anion-based Memristor

Hong-Sub Lee

Department of Materials Science & Engineering, Kangwon National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 1-7.

Abstract

Recently, memristor (anion-based memristor) is referred to as the fourth circuit element which resistance state can be gradually changed by the electric pulse signals that have been applied to it. And the stored information in a memristor is non-volatile and also the resistance of a memristor can vary, through intermediate states, between high and low resistance states, by tuning the voltage and current. Therefore the memristor can be applied for analogue memory and/or learning device. Usually, memristive behavior is easily observed in the most transition metal oxide system, and it is explained by electrochemical migration motion of anion with electric field, electron scattering and joule heating. This paper reports the latest trends and issues of anion-based memristor.

Keywords

Memristor, Analog memory, Crossbar array architecture, Sneak current, Linearity

3D Porous Foam-based Triboelectric Nanogenerators for Energy Harvesting

Sangheon Jeon1, Jeonghwa Jeong2, and Suck Won Hong1,2,†

1Department of Cogno-Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University 2Department of Optics and Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 9-15.

Abstract

Here, we present a facile route to fabricate a vertically stacked 3D porous structure-based triboelectric nanogenerator (TENG) that can be used to harvest energy from the friction in a repetitive contact-separation mode. The unit component of TENG consists of thin Al foil electrodes integrated with microstructured 3D foams such as Ni, Cu, and polyurethane (PU), which provide advantageous tribo-surfaces specifically to increase the friction area to the elastomeric counter contact surfaces (i.e., polydimethylsiloxane, PDMS). The periodic contact/separation-induced triboelectric power generation from a single unit of the 3D porous structure-based TENG was up to 0.74 mW/m2 under a mild condition. To demonstrate the potential applications of our approach, we applied our TENGs to small-scale devices, operating 48 LEDs and capacitors. We envision that this energy harvesting technology can be expanded to the applications of sustainably operating portable electronic devices in a simple and cost-effective manner by effectively harvesting wasted energy resources from the environment.

Keywords

Triboelectric, Nanogenerator, Energy harvesting, 3D foam, PDMS

Development of Straightness Measurement System for Improving Manufacturing Process Precision

Eung Soo Kim

Department of Electronic Robot Engineering, Busan University of Foreign Studies

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 17-21.

Abstract

In this paper, a high precision straightness measurement system has been developed at low cost using a visible laser and CMOS image sensor. CMOS image sensor detected optical image and the variation of straightness was calculated by image processing. We have observed that the error of the developed straightness measurement system was 0.9% when a distance of 3m between laser and image sensor. And it can be applied to 3D printer and any other areas.

Keywords

Straightness, CMOS, Visible laser, Image sensor, 3D printer

The Effect of Crystallinity on the Photoluminescence of TiO2 Nanoparticles

Wooje Han and Hyung-Ho Park

Department of Materials Science and Engineering, Yonsei University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 23-28.

Abstract

The Titanium oxide (TiO2) is an attractive ceramic material which shows non-toxic, high refractive index, catalytic activity and biocompatibility, and can be fabricated at a low cost due to its high chemical stability and large anisotropy. TiO2 nanoparticles have been prepared by sol-gel method. The pH of solution can affect the TiO2 crystallinity during the formation of nanoparticles. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy in order to investigate their structural and photoluminescence properties. Through these analysis, the size of TiO2 nanoparticles were found to be smaller than 5 nm. As the crystallinity of the nanoparticles increased, the emission of PL in the 550 nm region increased. Therefore, luminescence characteristics can be improved by controlling the crystallinity of the TiO2 nanoparticles.

Keywords

TiO2, Nanoparticles, Photoluminescence

Effect of Material Property Uncertainty on Warpage during Fan Out Wafer-LevelPackaging Process

Geumtaek Kim1, Gihoon Kang1, and Daeil Kwon2,†

1School of Mechanical, Aerospace and Nuclear Engineering, UNIST 2Department of Mechanical Engineering, Konkuk University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 29-33.

Abstract

With shrinking form factor and improving performance of electronic packages, high input/output (I/O) density is considered as an important factor. Fan out wafer-level packaging (FO-WLP) has been paid great attention as an alternative. However, FO-WLP is vulnerable to warpage during its manufacturing process. Minimizing warpage is essential for controlling production yield, and in turn, package reliability. While many studies investigated the effect of process and design parameters on warpage using finite element analysis, they did not take uncertainty into consideration. As parameters, including material properties, chip positions, have uncertainty from the point of manufacturing view, the uncertainty should be considered to reduce the gap between the results from the field and the finite element analysis. This paper focuses on the effect of uncertainty of Young’s modulus of chip on fan-out wafer level packaging warpage using finite element analysis. It is assumed that Young’s modulus of each chip follows the normal distribution. Simulation results show that the uncertainty of Young’s modulus affects the maximum von Mises stress. As a result, it is necessary to control the uncertainty of Young’s modulus of silicon chip since the maximum von Mises stress is a parameter related to the package reliability.

Keywords

Fan out wafer level package, Warpage, Uncertainty, Finite element analysis

Observation of Diverse Aluminum Oxide Structures in a Phosphoric Acid Solution according to the Applied Anodization Voltage

Chanyoung Jeong

Department of Advanced Materials Engineering, Dong-Eui University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 35-39.

Abstract

To date, porous alumina structures have been implemented by electrochemical anodization technique. The anodizing methods can easy to make a porous aluminum oxide film with a regular arrangement, but oxide film with complex structure type such as pillar-on-pore is relatively difficult to implement. Therefore, this study aims to observe the change of anodized oxide pore size, thickness, and structure in a phosphoric acid solution according to applied anodization voltage conditions. For the implementation of hybrid composite oxide structures, it is possible to create by modulating anodization voltage. The experimental conditions were performed at the applied anodization voltage of 100 V and 120 V in 10% phosphoric acid solution, respectively. The experimental results were able to observe the structure of oxides in the form of porous and composite structures (pillar-on-pore), depending on each condition.

Keywords

Thin film growth, Anodizing, Aluminum surface parameter, Phosphoric acid, Hybrid anodic oxide structures

Vol. 26 No.2

Study on Influencing Factors of Adhesive Strength for Polymer Coating on Metal Adherend by Dolly Test

Ju-Hwan Baeg1, Hyun Park2, Sung In Lee3, Yungeun Ha1, Young-Rae Cho1,†

1Division of Materials Science and Engineering, Pusan National University 2Department of Navel Architecture and Ocean Engineering, Pusan National University 3Dongsung Chemtech

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 1-8.

Abstract

금속, 세라믹스, 플라스틱 등 고체의 표면에 적용되는 접착제와 페인트 도장막의 수요와 중요성은 점점 증가 하고 있다. 본 연구에서는 금속 피착재에 고분자 재료인 접착제 혹은 페인트 도장막을 적용할 때, 이들 고분자 코팅층과 금속 피착재 사이의 접착강도 측정시 영향인자에 대한 연구를 돌리테스트로 수행하였다. 접착제로는 2액형 에폭시 접착 제가 사용되었으며, 페인트로는 방청용 2액형 에폭시 페인트인 EH2350가 사용되었다. 특히, 영향인자로는 피착재의 종 류(Al, Fe, STS, Cu, Zn), 표면거칠기 및 표면오염(수돗물, 소금물) 등을 선택해서 접착강도에 미치는 영향에 대해 연구 하였다. 접착제와 피착재의 접착강도는 동일한 접착제를 사용해도 피착재의 종류가 달라지면 다르게 나타났으며, 수돗물 혹은 소금물로 산화 오염된 피착재의 표면은 페인트 도장공정 이전에 수돗물로 스프레이 세척이 필수적임을 알았다. 본 연구의 결과로 돌리테스트는 도장막과 피착재의 접착강도를 측정하는데 향후 널리 사용될 수 있음을 확인하였다.
The demand and importance of adhesives and paint coatings applied to solid surfaces such as metals, ceramics, and plastics are increasing. In this study, the influencing factors on the adhesive strength between the polymer coating and the metal adherend were investigated by Dolly test when the adhesive or the paint coating was applied on the metal adherend. Two-component epoxy adhesive was used as the adhesive, and EH2350, a two-component epoxy paint for anti-corrosion, was used as the paint. Especially, the effect of adherend metals(Al, Fe, STS, Cu, Zn), surface roughness and surface contamination(tap water, salt water) on adhesive strength was studied as influencing factors. The adhesive strength between adhesive and adherend was different when the type of metal adherend was different even when the same adhesive was used. It was found that spray water cleaning was necessary before the paint coating process on the surface of the oxide contaminated adherend with tap water or salt water. As a result of this study, it was confirmed that Dolly test can be widely used in the future to measure adhesive strength between paint coating and adherend.

Keywords

Adhesive strength, Polymer coating, Influencing factor, Paint coating, Dolly test

Double Exposure Laser Interference Lithography for Pattern Diversity using Ultraviolet Continuous-Wave Laser

Yong-Won Ma1, Jun Han Park2, Dan Hee Yun1, Cheongyeol Gwak1, Bo Sung Shin2,3,†

1Interdisciplinary Department for Advanced Innovative Manufacturing Engineering, Pusan National University 2Department of Cogno-Mechatronics Engineering, Pusan National University 3Department of Optics & Mechatronics Engineering, Pusan National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 9-14.

Abstract

The newly discovered properties of periodic nanoscale patterns have increasingly sparked research interests in various fields. Along this direction, it is worth mentioning that there had been rare studies conducted on interference exposure, a method of creating periodic patterns. Additionally, these few studies seemed to validate the existence of only exact quadrangle shapes and dot patterns. This study asserted the formation of wavy patterns associated to using multiple exposures of the ratio of the first exposure intensity to the second exposure intensity. Such patterns were designed and constructed herein via overlapping of two Gaussian beams relative to certain rotation angles, and with a submicron structure fabricated based on a 360-nm continuous-wave laser. Results confirmed that the proposed double exposure laser interference lithography is able to create circular, elliptical and wavy patterns with no need for complex optical components.

Keywords

Laser Interference Lithography, Multiple Exposure, Wave Pattern, Regular Submicron Pattern, Gaussian Beam

The Structural, Electrical, and Optical Properties of ZnO Ultra-thin Films Dependent on Film Thickness

Kyung-Mun Kang1, Yue Wang1, Minjae Kim1, Hong-Sub Lee2, Hyung-Ho Park1,†

1Department of Materials Science and Engineering, Yonsei University 2Department of Materials Science and Engineering, Kangwon National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 15-21.

Abstract

원자층 증착법(ALD: atomic layer deposition)으로 150oC에서 성장된 zinc oxide (ZnO) 초박막의 두께 변화에 따른 구조적, 전기적, 광학적 특성을 조사하였다. ZnO 박막을 증착하기 위해 금속 전구체와 반응물로 각각 diethylzinc와 deionized water를 사용하였다. ALD 사이클 당 성장률은 150 oC에서 약 0.21 nm/cycle로 일정 하였으며, 50 사이클 이 하의 샘플들은 초기 ALD 성장 단계에서 상대적으로 얇은 두께로 인하여 비정질 성질을 갖는 것으로 보였다. 100 사이 클에서 200 사이클로 두께가 증가함에 따라 ZnO 박막의 결정성이 증가하였고 hexagonal wurtzite 구조를 보였다. 또한, ZnO 박막의 입자 크기가 ALD 사이클의 수의 증가에 따라 증가되었다. 전기적 특성 분석 결과 박막 두께의 증가에 따라 서 비저항 값이 감소하였으며, 이는 박막 두께 증가에 따른 입자 크기 증가 및 결정성 개선으로 더 두꺼운 ZnO 박막에서 입자 경계의 농도 감소와 상관 관계가 있음을 알 수 있었다. 광학적 특성 분석 결과 근 자외선 영역 (300 nm~400 nm)에 서의 밴드 엣지 흡수가 증가 및 이동되었는데 이 현상은 ZnO 박막 두께의 증가에 따른 캐리어 농도의 증가가 기인 한 것 으로, 이 결과는 박막 두께의 증가에 따른 저항률 감소와 잘 일치한다. 결과적으로 박막의 두께가 증가하면 막 면의 응력 이 완화되어 밴드 갭이 감소하고 결정성 및 전도성이 향상됨을 알 수 있었다.
We investigated the structural, electrical and optical properties of zinc oxide (ZnO) ultra-thin films grown at 150oC by atomic layer deposition (ALD). Diethylzinc and deionized water were used as metal precursors and reactants, respectively, for the deposition of ZnO thin films. The growth rate per ALD cycle was a constant 0.21 nm/cycle at 150°C, and samples below 50 cycles had amorphous properties due to the relatively thin thickness at the initial ALD growth stage. With the increase of the thickness from 100 cycles to 200 cycles, the crystallinity of ZnO thin films was increased and hexagonal wurtzite structure was observed. In addition, the particle size of the ZnO thin film increased with increasing number of ALD cycles. Electrical properties analysis showed that the resistivity value decreased with the increase of the thin film thickness, which is correlated with the decrease of the grain boundary concentration in the thicker ZnO thin film due to the increase of grain size and the improvement of the crystallinity. Optical characterization results showed that the band edge absorption in the near ultraviolet region (300 nm~400 nm) was increased and shifted. This phenomenon is due to the increase of the carrier concentration with the increase of the ZnO thin film thickness. This result agrees well with the decrease of the resistivity with the increase of the thin film thickness. Consequently, as the thickness of the thin film increases, the stress on the film surface is relaxed, the band gap decreases, and the crystallinity and conductivity are improved.

Keywords

zinc oxide, atomic layer deposition, film thickness

Chemically Bonded Thermally Expandable Microsphere-silica Composite Aerogel with Thermal Insulation Property for Industrial Use

Kyu-Yeon Lee1, Varsha D. Phadtare1, Haryeong Choi1, Seung Hwan Moon2, Jong Il Kim2, Young Kwang Bae2, Hyung-Ho Park1,†

1Department of Materials Science and Engineering, Yonsei University 2Enterprise Research Institute, Eslin Corporation

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 23-29.

Abstract

Thermally expandable microsphere and aerogel composite was prepared by chemical compositization. Microsphere can produce synergies with aerogel, especially an enhancement of mechanical property. Through condensation between sulfonated microsphere and hydrolyzed silica sol, chemically-connected composite aerogel could be prepared. The presence of hydroxyl group on the sulfonated microsphere was observed, which was the prime functional group of reaction with hydrolyzed silica sol. Silica aerogel-coated microsphere was confirmed through microstructure analysis. The presence of silicon-carbon absorption band and peaks from composite aerogel was observed, which proved the chemical bonding between them. A relatively low thermal conductivity value of 0.063 W/m·K was obtained.

Keywords

Thermally expandable microsphere, aerogel, organic-inorganic, composites, insulator

Development of Polymer Elastic Bump Formation Process and Bump Deformation Behavior Analysis for Flexible Semiconductor Package Assembly

Jae Hak Lee, Jun-Yeob Song, Seung Man Kim, Yong Jin Kim, Ah-Young Park

Dept. of Ultra-Precision Machines and Systems, Advanced Manufacturing Systems Research Division Korea Institute of Machinery and Materials (KIMM)

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 31-42.

Abstract

본 연구에서는 유연한 접속부를 갖는 유연전자 패키지 플립칩 접속을 위해 폴리머 탄성범프를 제작하였으며, 범프의 온도 및 하중에 따른 폴리머 탄성 범프의 점탄성 및 점소성 거동을 해석 및 실험적으로 분석하고 비교 평가하였 다. 폴리머 탄성 범프는 하중에 의한 변형이 용이하여 범프 높이 평탄도 오차의 보정이 용이할 뿐만 아니라 소자가 형성 된 칩에 가해지는 응력 집중이 감소하는 것을 확인하였다. 폴리머 탄성 범프의 과도한 변형에 따른 Au Metal Cap Crack 현상을 보완하여 200 μm 직경의 Spiral Cap Type, Spoke Cap type 폴리머 탄성 범프 형성 기술을 개발하였다. 제안된 Spoke Cap, Spiral Cap 폴리머 탄성 범프는 폴리머 범프 전체를 금속 배선이 덮고 있는 Metal Cap 범프에 비해 범프 변 형에 의한 응력 발생이 적음을 확인할 수 있으며 이는 폴리머 범프 위의 금속 배선이 부분적으로 패터닝되어 있어 쉽게 변형될 수 있는 구조이므로 응력이 완화되는데 기인하는 것으로 판단된다. Spoke cap type 범프는 패드 접촉부와 전기적 접속을 하는 금속 배선 면적이 Spiral Cap type 범프에 비해 넓어 접촉 저항을 유지하면서 동시에 금속 배선에 응력 집중 이 가장 낮은 결과를 확인하였다.
In this study, polymer elastic bumps were fabricated for the flexible electronic package flip chip bonding and the viscoelastic and viscoplastic behavior of the polymer elastic bumps according to the temperature and load were analyzed using FEM and experiments. The polymer elastic bump is easy to deform by the bonding load, and it is confirmed that the bump height flatness problem is easily compensated and the stress concentration on thin chip is reduced remarkably. We also develop a spiral cap type and spoke cap type polymer elastic bump of 200 μm diameter to complement Au metal cap crack phenomenon caused by excessive deformation of polymer elastic bump. The proposed polymer elastic bumps could reduce stress of metal wiring during bump deformation compared to metal cap bump, which is completely covered with metal wiring because the metal wiring on these bumps is partially patterned and easily deformable pattern. The spoke cap bump shows the lowest stress concentration in the metal wiring while maintaining the low contact resistance because the contact area between bump and pad was wider than that of the spiral cap bump.

Keywords

flexible semiconductor package, polymer elastic bump, ultra thin chip, interconnection

Preparation of n-type Bi-Te-Se-based Thermoelectric Materials with Improved Reliability via hot Extrusion Process

Jeong Yun Hwang1, Yong-Nam Kim2, †, Kyu Hyoung Lee1, †

1Department of Materials Science and Engineering, Yonsei University 2Material Technology Center, Korea Testing Laboratory

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 45-49.

Abstract

높은 신뢰성의 n형 Bi-Te-Se계 열전소자 제조를 위한 열간압출 공정을 확립하였다. 용융-응고 공정을 이용하 여 Bi-Te-Se 원료잉곳을 합성하였으며, 고에너지 볼밀을 이용하여 평균 ~30 μm 크기의 분말로 분쇄하였다. 일축가압 공 정으로 분말을 직경 20 mm의 디스크 형태로 성형한 후 압출용 몰드 설계-제작 및 열간압출 공정 온도와 압력을 제어하 여 성형체로부터 00l 방향으로 결정 배향된 지름 1.8 mm의 원통형 고밀도 압출체를 제조하였다. 상온에서 최대 ~4.1 mW/ mK2의 높은 파워팩터를 나타냈으며, zone melting 공정으로 제조한 상용 열전소재와 비교하여 2배 이상 향상된 기계적 강도 (~50 MPa)를 구현하였다.
Herein we developed the hot extrusion technology to prepare n-type Bi-Te-Se-based thermoelectric materials with high reliability. Starting ingot was fabricated via melt-solidification process, then pulverized it into powders (~30 μm) by using high energy ball milling. By optimization of mold design and temperature-pressure conditions for hot extrusion, dense extrudate of 1.8 mm in diameter with high 00l orientation could be obtained from disc-shape compacted powders (20 mm in diameter). High power factor ~4.1 mW/mK2 and enhanced mechanical strength ~50 MPa were simultaneously observed at 300 K.

Keywords

Bi-Te-Se, thermoelectric, hot extrusion, power factor, mechanical strength

Electroplating of High Wear Resistant Rhodium using Pulse Current Plating Method

Seo-Hyang Lee, Jae-Ho Lee

Dept. of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 51-54.

Abstract

실리콘 기판상에 여러 조건의 전류밀도에서 로듐 도금을 실시하였다. 직류전원의 경우 전류밀도가 증가하면 로듐 표면에 균열이 발생하였다. 잔류응력을 낮추기 위하여 펄스전류를 인가하였다. 펄스전류의 off 시간이 도금층의 잔 류응력을 낮추는데 영향을 주었다. 펄스전류의 인가 주기를 5:5로 하였을 경우 균열 없는 로듐 도금층을 얻었다.
The electrodeposition of rhodium (Rh) on silicon substrate at different current conditions were investigated. The cracks were found at high current density during the direct current (DC) plating. The pulse current (PC) plating were applied to avoid the formation of cracks on the deposits. Off time in the pulse plating relieved the residual stress of the Rh deposits and consequently the current conditions for the crack-free Rh deposits were obtained. Optimum pulse current (PC) condition is 5:5 (on:off) for the crack-free Rh electroplating.

Keywords

Rhodium, electroplating, pulse current plating, residual stress

A Study on Optical Characteristic of Plasmonic Nanostructure Depending on Height of Deposited Silver

J. H. Kim, M. Y. Jeong

Department of Cogno-Mechatronics Engineering, Pusan National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 55-58.

Abstract

최근 표면 플라즈몬 효과는 광 신호 향상에 중요하게 대두되고 있는 분야로써, 약한 광학적 신호를 증가시킴 에 따라 바이오 분야나 뉴로사이언스에 매우 중요한 분야로 대두되었다. 플라즈모닉 구조를 제작하기 위해선 나노 구조 의 크기 높이 그리고 입사광의 입사각 등 다양한 변수들이 존재하는데 본 논문에서는 플라즈모닉 나노구조의 제작을 위 한 은 증착 높이에 따른 플라즈모닉 나노구조의 광학적 특성에 대한 연구를 진행하였다. 은 증착은 플라즈모닉 효과를 보 기 위해 다양하게 사용하고 있는 금속으로 특정 파장에 반응을 보기 위해 제작한 구조 형태와 유사한 구조를 시간영역 유한차분(FDTD)법을 통해 광 특성을 예측하여, 최종적으로 제작한 구조의 은 나노 입자 부근에 에너지가 집중되는 결과 를 확인하였다.
Surface plasmon effect was considered importantly because of the enhancement of optical signals. It is important to detect weak optical signal in neuroscience and bio technology due to detect weaker image or signal. The height of silver can change the optical characteristic of plasmonic nano structure including transmittance and reflectance. In this paper, the optical characteristic of plasmonic nano structure were confirmed by the FDTD analysis method depending on the silver height and it was confirmed that energy was concentrated at the center of nano structure, and high far-field gain and current density in particular wavelength coule be obtained.

Keywords

Plasmonic nanostructure, silver deposition, enhancement, surface plasmon

Development and Packaging of Multi-channel Imaging Module for Near-infrared Fluorescence Imaging System

Taehoon Kim1,2, Kyung Hwan Seo2, Hak Keun Lee2, Myung Yung Jeong1,2,†

1Department of Cogno-Mechatronics Engineering, Pusan National University 2Nawoo Vision Corporation

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 59-64.

Abstract

본 논문에서는 근적외선 다채널 형광 영상 시스템을 소개하고, 노출시간, 작동거리, 여기광의 강도에 따른 형 광 영상 시스템의 특성에 대해 분석하였다. 노출시간이 길수록, 작동거리가 짧을수록, 여기광의 강도가 강할수록 형광신 호가 증가하였다. 필터의 적절한 구성과 영상 모듈의 정밀한 패키징으로 배경신호의 증가를 억제하여 SBR이 증가하는 것을 확인하였다. 본 연구의 결과를 바탕으로 다채널 형광 영상 시스템을 활용할 수 있는 방안에 대해 제안하였다.
In this paper, we introduced a near-infrared multi-channel fluorescence imaging system and analyzed the effects of measurements variables such as exposure time, working distance and intensity of excitation light. Fluorescence signal is increased as exposure time becomes longer, excitation light intensity increases or working distance becomes smaller. Furthermore, the proper composition of optical filters and precise packaging of the imaging modules prevent the increase of background signal. Thus, we confirmed an increase in SBR. Based on the result of this research, we proposed a method to use a multi-channel fluorescence imaging system.

Keywords

Fluorescence, Multi-channel imaging, Fluorescence Imaging, Real-time imaging

Correct Errors

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 65-66.

Abstract

Keywords

Vol. 26 No.3

Wettability Evaluation by Wetting Balance Test and Wetting Characteristics of Solders

Wook Sang Jeon, Sri Harini Rajendran, Jae Pil Jung1,†

Department of Materials Science and Engineering, University of Seoul

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 1-6.

Abstract

Wettability is an important factor to decide solderability of solder, flux, other soldering-related materials and soldering conditions. The wettability also affects the reliability of solder joint. Wetting balance test is a good method for quantitatively measuring wettability between solder and substrate. The wetting balance test is easy to reproduce the wetting experiment and to measure the wetting time and force. And this test provides wetting curve to calculate the surface tension of the molten solder. Development of new solder has been continued in accordance with various and harsh environment in the electronics industry. In this paper, the principle of wetting balance test and recent research issues including nanocomposite solder are explained.

Keywords

wetting balance test, wettability, wetting angle, surface tension, nano-composite solder

Laser Micro-Joining and Soldering

Seung Jun Hwang1, Hye Jun Kang1, Jeng O Kim2, Jae Pil Jung1,†

1Department of Materials Science and Engineering, University of Seoul 2Korea Institute of Machinery & Materials

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 7-13.

Abstract

In this paper, the principles, types and characteristics of the laser and laser soldering are introduced. Laser soldering methods for electronics, metals, semiconductors are also presented. Laser soldering is a non-contact process that transfers energy to solder joint by a precisely controlled beam. Demands for laser soldering are increasing due to bonding for complex circuits and local heating in micro joint. Laser absorption ratio depends on materials, and each material has different absorption or reflectivity of the laser beam, which requires fine adjustment of the laser beam. Laser types and operating conditions are also important factors for laser soldering performance. In this paper, the performance of Nd:YAG laser soldering is compared to the hot blast reflow. Meanwhile, a diode laser gives different wavelength and smaller parts with high performance, but it has various reliability issues such as heat loss, high power, and cooling technology. These issues need to be improved in the future, and further studies for laser micro-joining and soldering are required.

Keywords

Laser micro-joining, laser soldering, electronics, semiconductor, packaging

Recent Overview on Power Semiconductor Devices and Package Module Technology

Kyoung-Ho Kim, Sung-Hoon Choa1,†

Graduate School of NID Fusion Technology, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 15-22.

Abstract

In these days, importance of the power electronic devices and modules keeps increasing due to electric vehicles and energy saving requirements. However, current silicon-based power devices showed several limitations. Therefore, wide band gap (WBG) semiconductors such as SiC, GaN, and Ga2O3 have been developed to replace the silicon power devices. WBG devices show superior performances in terms of device operation in harsh environments such as higher temperatures, voltages and switching speed than silicon-based technology. In power devices, the reliability of the devices and module package is the critically important to guarantee the normal operation and lifetime of the devices. In this paper, we reviewed the recent trends of the power devices based on WBG semiconductors as well as expected future technology. We also presented an overview of the recent package module and fabrication technologies such as direct bonded copper and active metal brazing technology. In addition, the recent heat management technologies of the power modules, which should be improved due to the increased power density in high temperature environments, are described.

Keywords

Power semiconductor, Package module, Wide Band Gap, Ceramic substrate, Thermal management

Technical Trends of Stretchable Electrodes

Su Bin Choi1, Cheul-Ro Lee1, Seung-Boo Jung2, Jong-Woong Kim1,†

1School of Advanced Materials Engineering, Chonbuk National University 2School of Advanced Materials Science & Engineering, Sungkyunkwan University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 23-36.

Abstract

Stretchable electronic systems have recently been gaining more and more attention because of their potential applications in various implements such as electronic skins and wearable/shape-deformable electronics. An essential factor of the stable stretchable device implementation is that all the elements constituting the system must have sufficient elasticity and exhibit stable performances even under repetitive stretching conditions. In this paper, we review the latest research results to secure the stable stretchability of electrodes among the various components of the system.

Keywords

Flexible, Stretchable, Electrode, Circuit, Wearabl

Suppressed Sheet Resistance of Ag Nanostructure Films by O2 Plasma Treatment

Wonkyung Kim1, Jong Wook Roh2,†

1Department of Materials Science and Engineering, Yonsei University 2School of Nano & Materials Science and Engineering, Kyungpook National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 37-41.

Abstract

Ag나노와이어 도전성 잉크를 플렉서블한 투명 기판 위에 코팅 후 이러한 여분의 유기물을 O2 플라즈마를 이 용하여 제거함으로써 Ag 나노와이어를 이용한 투명전극의 면저항과 광학적 특성을 최적화하였다. Ag 나노와이어 도전 성 잉크를 코팅한 후 30초간 O2 플라즈마 처리를 하였을 때 면저항은 최대 27 % 정도 감소하였으며, 잔류 유기물의 제 거를 통하여 그 광학적 특성도 향상됨을 알 수 있었다. 또한 O2 플라즈마 처리 시간이 30초 이상 증가할 경우 그 면저항 이 오히려 감소함을 확인하였는데, 이는 과도한 O2 플라즈마로 인하여 Ag나노와이어의 degradation이 일어나는데 그 원 인이 있음을 확인하였다.
Sheet resistance reduction in the Ag nanowire (NW) coated films is accomplished with slight improvement of optical properties for the application of transparent conducting electrodes by using O2 plasma treatment. The sheet resistance was optimized after 30 seconds O2 plasma treatment, showing the 27 % of maximum decrease of sheet resistance. It is found that the O2 plasma treatment get rid of the residual organic materials at the junction of Ag NWs. However, the Ag NWs may be also snapped by the excessive O2 plasma treatment can showing the collapses of Ag NWs networks. Furthermore, the optical properties such as optical transmittance and haze were monotonically improved with the O2 plasma treatment time until 90 seconds.

Keywords

Nanowires, Silver, Transparent electrodes, Plasma

Improving Joint Reliability of Lead-free Solder on Flexible Substrate under Cyclic Bending by Adding Graphene Oxide Po

Yong-Ho Ko1,2,3,†, Dong-Yurl Yu1, Junhyuk Son1, Junghwan Bang1, Taek-Soo Kim2,‡

1Joining R&D Group, Korea Institute of Industrial Technology 2Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology 3Industrial Materials and Smart Manufacturing Engineering, University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 43-49.

Abstract

본 연구에서는 그래핀 산화(graphene oxide, GO) 분말 복합 Sn-3.0Ag-0.5Cu(in wt.%) 솔더페이스트를 이용한 플렉시블 기판과 SOP(small outline package) 사이의 솔더 접합부의 굽힘 신뢰성 향상에 관한 새로운 접근을 제안하였다. 솔더페이스트에 GO의 첨가는 녹는점에 약간의 영향을 미치었으나 그 차이는 미미한 것으로 나타났다. 한편, GO의 첨가 는 리플로우 공정 동안 솔더 접합부의 금속간화합물(intermetallic compound, IMC) 성장과 두께를 억제 할 수 있음을 확 인하였다. 더욱이 접합부의 신뢰성에 미치는 영향을 살펴보고자 반복 굽힘 시험을 진행하였으며 GO 분말의 첨가로 솔더 접합부의 반복 굽힘 신뢰성 향상 시킬 수 있었다. 0.2 wt.%의 GO가 첨가된 솔더 접합부의 경우 GO가 첨가되지 않은 경 우에 비하여 굽힘 수명은 20% 가량 증가하는 것으로 나타났다. GO가 첨가된 경우 솔더 접합부의 인장 강도와 연성이 증 가하게 나타났는데 이러한 GO 첨가에 의한 기계적 특성 향상이 솔더 접합부의 반복 굽힘 신뢰성 향상에 기여한 것으로 추측된다.
In this study, a new approach using graphene oxide (GO) powder-composited Sn-3.0Ag-0.5Cu(in wt.%) solder paste for improving the bending reliability of solder joints between a flexible substrate and small outline package (SOP) was suggested. The GO addition slightly affected the melting temperature, however, the change in the melting temperature was not significant. Meanwhile, we observed the addition of GO could suppress IMC growth and IMC thickness of solder joint during the reflow process. Moreover, the cyclic bending test was also performed for evaluation of reliability in solder joint and we could improve the cyclic bending reliability of solder joint by adding GO powders. For 0.2 wt.% of GO added to the solder joint, the bending lifetime was increased to 20% greater than that without GO. Pull strength and ductility of the solder joint with GO were also higher than those of the joint without GO and it was assumed that this effect by adding GO could contribute to improve cyclic bending reliability of solder joint.

Keywords

graphene oxide (GO), flexible substrate, small outline package (SOP), solder joint, cyclic bending test

Analysis of Ar Plasma Effects for Copper Nitride Passivation Formation via Design of Experiment

Hae-Sung Park1, Sarah Eunkyung Kim2,†

1Department of Mechanical Engineering, Seoul National University of Science and Technology 2Graduate School of Nano-IT Design Convergence, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 51-57.

Abstract

구리 표면을 대기 중의 산화로부터 보호하기 위해서 아르곤(Ar)과 질소(N2) 가스를 이용하는 two-step플라즈 마 공정으로 산화 방지층인 구리 질화물 패시베이션 형성을 연구하였다. Ar 플라즈마는 구리 표면에 존재하는 이물질을 제거하는 동시에 표면을 활성화시켜 다음 단계에서 진행되는 N2 플라즈마 공정 시 질소 원자와 구리의 반응을 촉진시키 는 역할을 수행한다. 본 연구에서는 two-step 플라즈마 공정 중 Ar 플라즈마 공정 조건이 구리 질화물 패시베이션 형성 에 미치는 영향을 실험계획법의 완전요인설계를 통하여 분석하였다. XPS 분석에 의하면 Ar 플라즈마 공정 시 낮은 RF 파워와 압력을 사용할 경우 구리 산화물 피크(peak) 면적은 감소하고, 반대로 구리 질화물(Cu4N, Cu3N) 피크 면적은 증 가하였다. Ar 플라즈마 공정 시 구리 질화물 형성의 주 효과는 RF 파워로 나타났으며 플라즈마 공정 변수간 교호작용은 거의 없었다.
To protect the Cu surface from oxidation in air, a two-step plasma process using Ar and N2 gases was studied to form a copper nitride passivation as an anti-oxidant layer. The Ar plasma removes contaminants on the Cu surface and it activates the surface to facilitate the reaction of copper and nitrogen atoms in the next N2 plasma process. This study investigated the effect of Ar plasma on the formation of copper nitride passivation on Cu surface during the twostep plasma process through the full factorial design of experiment (DOE) method. According to XPS analysis, when using low RF power and pressure in the Ar plasma process, the peak area of copper oxides decreased while the peak area of copper nitrides increased. The main effect of copper nitride formation in Ar plasma process was RF power, and there was little interaction between plasma process parameters.

Keywords

Design of experiment, full factorial, plasma treatment, passivation layer, Cu-Cu bonding

Solution-Processed Fluorine-Doped Indium Gallium Zinc Oxide Channel Layers for Thin-Film Transistors

Sunho Jeong

Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 59-62.

Abstract

본 논문은 용액공정용 불소 도핑된 인듈 갈륨 징크 산화물 반도체를 연구하였으며, 박막 트랜지스터 적용 가 능성을 확인하였다. 용액형 산화물 반도체를 형성하기 위해, 금속염 전구체 기반 용액을 제조하였으며, 추가적인 불소 도 핑을 유도하기 위해 화학적 첨가제로서 암모늄 플로라이드를 이용하였다. 열처리 온도 및 불소 도핑양에 따른 전기적 물 성을 고찰함으로서, 300도 저온 열처리를 통해 제조된 산화물 반도체층의 전기적 특성을 향상시켰다. 20 mol% 불소를 도핑하는 경우, 1.2 cm2/V·sec의 이동도 및 7×106의 점멸비 특성이 발현 가능함을 확인하였다.
In this study, we have developed solution-processed, F-doped In-Ga-Zn-O semiconductors and investigated their applications to thin-film transistors. In order for forming the appropriate channel layer, precursor solutions were formulated by dissolving the metal salts in the designated solvent and an additive, ammonium fluoride, was incorporated additionally as a chemical modifier. We have studied thermal and chemical contributions by a thermal annealing and an incorporation of chemical modifier, from which it was revealed that electrical performances of the thin-film transistors comprising the channel layer annealed at a low temperature can be improved significantly along with an addition of ammonium fluoride. As a result, when the 20 mol% fluorine was incorporated into the semiconductor layer, electrical characteristics were accomplished with a field-effect mobility of 1.2 cm2/V·sec and an Ion/off of 7×106.

Keywords

solution, oxide, semiconductor, fluorine

Bonding Property and Reliability for Press-fit Interconnection

Sangjoo Oh, Dajung Kim, Won Sik Hong, Chulmin Oh

Electronic Convergence Material & Device Research Center, Korea Electronics Technology Institute

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 63-69.

Abstract

전자부품에 대한 보드실장은 아직까지 솔더를 이용한 접합기술을 주로 이용하고 있다. 그러나, 솔더의 크? 및 피로특성으로 인한 접합부 내구한계로, 자동차 전장모듈에서는 반영구적인 접합기술인 프레스 핏(Press-fit) 접합기술 적 용을 확대하고 있다. 프레스 핏 접합은 프레스 핏 금속단자를 보드내 쓰루 홀(Through hole)에 기계적으로 삽입하여 체 결하는 접합기술로써, 적절한 금속단자의 소성변형으로 쓰루 홀 내부 표면접합을 밀착시킴으로써 강건한 접합을 유도한 다. 본 논문에서는 보드내 쓰루 홀 크기 및 표면처리에 따른 프레스 핏 접합 특성 및 신뢰성을 솔더링과 함께 비교하기 위해, 보드 쓰루 홀 크기에 따른 삽입강도 및 삽발강도를 평가하였으며, 열충격 시험을 통한 실시간 저항변화를 통해 프 레스 핏 및 솔더링 접합부의 저항변화를 관찰하였다. 또한, 각 접합부위 분석을 통한 프레스 핏 및 솔더링 접합열화를 분 석하여 주요 파손모드를 고찰하고자 하였다.
Soldering technology has been used in electronic industry for a long time. However, due to solder fatigue characteristics, automotive electronics are searching the semi-permanent interconnection technology such as press-fit method. Press fit interconnection is a joining technology that mechanically inserts a press fit metal terminal into a through hole in a board, and induces a strong bonding by closely contacting the inner surface joining of the through hole by plastic deformation of press-fit terminal. In this paper, the bonding properties of press-fit interconnection are investigated with PCB hole size and surface finishes. In order to compare interconnection reliability between the press fit and soldering, the change in resistance of the press-fit and soldering joints was observed during thermal shock test. After thermal cycling, the failure modes are investigated to reveal the degradation mechanism both press-fit and soldering technology.

Keywords

Press-fit, Surface finish, Reliability, Interconnection

A Comparison Study on Various Quantum Dots Light Emitting Diodes Using TiO2 Nanoparticles as Inorganic Electron Transport Layer

Moonbon Kim, Changgi Yoon, Jiwan Kim

Department of Advanced Materials Engineering, Kyonggi University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 71-74.

Abstract

본 연구는 발광층으로의 전자 주입을 억제하기 위해 ZnO 나노입자보다 낮은 전자 이동도를 갖는 TiO2 나노입 자를 무기 전자 수송층으로 사용하여 standard와 inverted 두 가지 구조의 양자점 전계발광 소자를 제작하고 그 특성을 비 교하였다. Standard 구조의 소자에서는 전류 밀도가 낮은 것에 비해 inverted 구조의 소자에서는 전류 밀도가 매우 높은 것을 확인하였다. 휘도의 경우 inverted 구조의 소자가 standard 구조의 소자보다 더 높았지만 높은 전류 밀도로 인해 낮 은 전류 효율을 나타냈다. 또한 전류 밀도가 높은 만큼 구동 전압이 높았으며, 방출 파장 스펙트럼에서 적색 편이를 확인 하였다. Standard 구조의 소자에서 나타난 낮은 전류 밀도를 통해, TiO2 나노입자가 양자점 전계발광 소자에서 전자 주입 을 억제할 수 있는 가능성을 확인하였다.
In this study, we fabricated two standard and inverted quantum dot light emitting diodes (QLEDs) using TiO2 nanoparticles (NPs) with lower electron mobility than ZnO NPs as inorganic electron transport layer to suppress electron injection into the emitting layer. Current density was much higher for the inverted QLEDs than the standard ones. The inverted QLEDs were brighter, but showed low current efficiency due to the high current density. In addition, as the current density was higher, the driving voltage was higher, and the red shift was confirmed in the emission wavelength spectrum. The low current density in the standard structured devices showed that the possibility that TiO2 NPs could suppress the electron injection in the QLEDs.

Keywords

TiO2 NPs, Quantum dots, Electron transport layer

Thickness Effect of SiOx Layer Inserted between Anti-Reflection Coating and p-n Junction on Potential-Induced Degradation (PID) of PERC Solar Cells

Dongwook Jung1, Kyoung-suk Oh2, Eunjin Jang1, Sung-il Chan2, Sangwoo Ryu1,†

1Department of Advanced Materials Engineering, Kyonggi University 2New & Renewable Energy Research Center, Korea Electronics Technology Institute

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 75-80.

Abstract

친환경 및 고효율의 장점 때문에 신재생 에너지원으로 널리 사용되고 있는 실리콘 태양 전지는 모듈을 직렬 연결하여 발전할 때 500-1,500 V의 전압이 걸리게 된다. 모듈 프레임과 태양 전지 사이에 걸린 이러한 고전압 차에 의해 장시간 가동시 효율 및 최대 출력이 감소하는 현상인 potential-induced degradation(PID)은 실리콘 태양 전지의 수명을 단축시키는 주요 원인 중 하나로 알려져 있다. 특별히 전면 유리의 Na+ 이온이 고전압에 의해 반사방지막을 거쳐 실리콘 내부로 확산하여 실리콘 내부 적층 결함 등에 축적되는 것이 PID의 원인으로 보고되고 있다. 본 연구에서는 p-형 PERC (Passivated Emitter and Rear Cell) 구조 실리콘 태양전지를 대상으로 Na+ 이온의 확산 장벽으로 작용할 수 있는 SiOx 층 이 p-n 접합과 반사방지막 사이에 삽입되었을 때 그 두께가 PID 현상 완화에 미치는 영향을 연구하였다. 96 시간 동안 1,000 V의 전압을 연속적으로 가한 후 병렬 저항, 효율 및 최대 출력을 측정한 결과 삽입된 SiOx 장벽층의 두께가 7-8 nm 이상일 때 비로소 PID 현상이 효과적으로 완화되는 것으로 나타났다.
Silicon solar cells have been widely used as a most promising renewable energy source due to eco-friendliness and high efficiency. As modules of silicon solar cells are connected in series for a practical electricity generation, a large voltage of 500-1,500 V is applied to the modules inevitably. Potential-induced degradation (PID), a deterioration of the efficiency and maximum power output by the continuously applied high voltage between the module frames and solar cells, has been regarded as the major cause that reduces the lifetime of silicon solar cells. In particular, the migration of the Na+ ions from the front glass into Si through the anti-reflection coating and the accumulation of Na+ ions at stacking faults inside Si have been reported as the reason of PID. In this research, the thickness effect of SiOx layer that can block the migration of Na+ ions on the reduction of PID is investigated as it is incorporated between anti-reflection coating and p-n junction in p-type PERC solar cells. From the measurement of shunt resistance, efficiency, and maximum power output after the continuous application of 1,000 V for 96 hours, it is revealed that the thickness of SiOx layer should be larger than 7-8 nm to reduce PID effectively.

Keywords

potential-induced degradation, Na+ ion migration, PERC, silicon solar cell, shunt resistance

Effects of Graphene Oxide Addition on the Electromigration Characteristics of Sn-3.0Ag-0.5Cu Pb-free Solder Joints

Kirak Son1, Gahui Kim1, Yong-Ho Ko2,3,‡, Young-Bae Park1,†

1School of Materials Science and Engineering, Andong National University 2Joining R&D Group, Korea Institute of Industrial Technology 3Industrial Materials and Smart Manufacturing Engineering, University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 81-88.

Abstract

본 연구에서는 그래핀 산화(graphene oxide, GO) 분말 첨가가 ball grid array(BGA) 패키지와 printed circuit board(PCB)간 Sn-3.0Ag-0.5Cu(SAC305) 무연솔더 접합부의 electromigration(EM) 수명에 미치는 영향에 대하여 보고 하 였다. 솔더 접합 직후, Ni/Au표면처리된 패키지 접합계면에서는 (Cu,Ni)6Sn5가 생성되었으며 organic solderability preservative(OSP) 표면처리 된 PCB 접합계면에서는 Cu6Sn5 금속간화합물(intermetallic compound, IMC)이 생성되었다. 130oC, 1.0×103 A/cm2 전류밀도 하에서 EM 수명평가 결과, GO를 첨가하지 않은 솔더 접합부의 평균 파괴 시간은 189.9 hrs으로 도출되었고, GO를 첨가한 솔더 접합부의 평균 파괴 시간은 367.1 hrs으로 도출되었다. EM에 의한 손상은 패키 지 접합계면에 비하여 pad 직경이 작은 PCB 접합계면에서 전자 유입에 의한 Cu의 소모로 인하여 발생하였다. 한편, 첨 가된 GO는 하부계면의 Cu6Sn5 IMC와 솔더 사이에 분포하는 것을 확인하였다. 따라서, SAC305 무연솔더에 첨가된 GO 가 전류 집중 영역에서 Cu의 빠른 확산을 억제하여 우수한 EM 신뢰성을 갖는 것으로 생각된다.
In this study, the effects of graphene oxide (GO) addition on electromigration (EM) lifetime of Sn-3.0Ag- 0.5Cu Pb-free solder joint between a ball grid array (BGA) package and printed circuit board (PCB) were investigated. After as-bonded, (Cu,Ni)6Sn5 intermetallic compound (IMC) was formed at the interface of package side finished with electroplated Ni/Au, while Cu6Sn5 IMC was formed at the interface of OSP-treated PCB side. Mean time to failure of solder joint without GO solder joint under 130oC with a current density of 1.0×103 A/cm2 was 189.9 hrs and that with GO was 367.1 hrs. EM open failure was occurred at the interface of PCB side with smaller pad diameter than that of package side due to Cu consumption by electrons flow. Meanwhile, we observed that the added GO was distributed at the interface between Cu6Sn5 IMC and solder. Therefore, we assumed that EM reliability of solder joint with GO was superior to that of without GO by suppressing the Cu diffusion at current crowding regions.

Keywords

Graphene oxide (GO), Pb-free solder, Electromigration (EM), Sn-3.0Ag-0.5Cu (SAC305), Intermetallic compound (IMC)

Vol. 26 No.4

Al-Cu Electrode Laser Welding for Rechargeable Battery

Seung Jun Hwang, Tae Wan Kim, Wook Sang Jeon, and Jae Pil Jung

Department of Materials Science and Engineering, University of Seoul

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 1-6.

Abstract

Recently, as electric vehicles and hybrid vehicles are widely used, the use of rechargeable batteries is increasing. Electric and hybrid cars are made up of hundreds to thousands of electric cells depending on the car model. And the assembly process of the cells and modules requires a variety of bonding process. Meanwhile, in order to connect several cells in series, Cu used as a cathode and Al of an anode must be bonded. In this paper, the characteristics of Al and Cu metals, laser types, characteristics and principles of welding lasers for welding of Cu and Al electrodes are introduced.

Keywords

laser welding, Al-Cu electrode, rechargeable battery, electric and hybrid vehicle

TLP and Wire Bonding for Power Module

Hyejun Kang and Jaepil Jung

Department of Materials Science and Engineering, University of Seoul

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 7-13.

Abstract

Power module is getting attention from electronic industries such as solar cell, battery and electric vehicles. Transient liquid phase (TLP) boding, sintering with Ag and Cu powders and wire bonding are applied to power module packaging. Sintering is a popular process but it has some disadvantages such as high cost, complex procedures and long bonding time. Meanwhile, TLP bonding has lower bonding temperature, cost effectiveness and less porosity. However, it also needs to improve ductility of the intermetallic compounds (IMCs) at the joint. Wire boding is also an important interconnection process between semiconductor chip and metal lead for direct bonded copper (DBC). In this study, TLP bonding using Sn-based solders and wire bonding process for power electronics packaging are described.

Keywords

power module, TLP bonding, wire bonding, electronics packaging

Technical Trends of Metal Nanowire-Based Electrode

Yoo Bin Shin, Yun Hee Ju, and Jong-Woong Kim

School of Advanced Materials Engineering, Chonbuk National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 15-22.

Abstract

Metallic nanowires (MNWs) have recently been considered as one of the most promising candidates for flexible electrodes of advanced electronics including wearable devices, electronic skins, and soft robotics, since they have high aspect ratio in physical shape, low percolation threshold, high ductility and optical transparency. Herein, we review the latest findings related to the MNWs and discuss the properties and potentials of this material that can be used in implementation of various advanced electronic devices.

Keywords

Metallic nanowires (MNWs), percolated network, flexibility, optical transparency

Numerical Analysis of Thermal Deformation of a PCB for Semiconductor Package at Panel, Strip and Unit Levels

Seunghyun Cho1, and Youngbae Ko2,†

1Mechanical Engineering Department, Dongyang Mirae University, 2Molds & Dies Technology R&BD Group, KITECH

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 23-31.

Abstract

본 논문에서는 다구찌법과 유한요소법의 수치해석을 통해 인쇄회로기판의 열변형과 열변형에 미치는 설계인 자의 영향도를 계산하였다. 인쇄회로기판의 패널과 스트립 레벨은 큐어링 온도조건에서, 유닛 레벨은 리플로우 온도조건 에서 수치해석을 수행하였다. 해석결과에 따르면 패널의 열변형이 스트립과 유닛의 열변형량과 형상에 가장 큰 영향을 미치며, 특히 z방향 변형량이 xy평면 방향의 변형량보다 크게 발생하였다. 열변형에 대한 설계인자의 영향도 분석 결과 에 의하면 열변형을 줄이기 위한 설계인자들의 영향도와 설계조건이 패널, 스트립과 유닛 레벨에 따라 달라지기 때문에 반도체 패키지의 신뢰성 향상을 목적으로 유닛 레벨의 열변형을 제어하기 위해서는 패널 레벨의 열변형을 제어할 필요 가 있고 인쇄회로기판의 층별 두께는 설계인자 수준의 중간으로 선정하는 것이 필요하다.
In this study, we conducted numerical analyses using the Taguchi method and finite element method to calculate the thermal deformation of a printed circuit board and the effect of design factors on the thermal deformation. Analysis results showed that the thermal deformation of the panel had the strongest effect on the thermal deformation and shape of the strip and unit. In particular, the deformation in the z direction was larger than that in the xy-plane direction. The effect of design factors and the design conditions for reducing the thermal deformation of the panel and strip changed at the unit level. Therefore, it is recommended that panel-level thermal deformation must be controlled to reduce the final thermal deformation at the unit level because the thermal deformation of the strip strongly affects that of the unit.

Keywords

PCB, Panel, strip, unit, thermal deformation, FEM

A Study on Thermal Properties of Epoxy Composites with Hybrid Fillers

Seungmin Lee, Hokyun Rho, and Sang Hyun Lee

Department of Advanced Chemicals & Engineering, Chonnam National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 33-37.

Abstract

본 연구는 에폭시 내 Cu, h-BN 및 GO 분말을 포함한 이종의 필러를 활용하여 점진적인 열적 특성을 구현하 였다. 단일 복합체 내에서 상대적으로 무거운 Cu 및 h-BN 분말은 하부 층에 주로 존재하는 반면, 가벼운 GO 분말은 복 합체의 상부층에 분산되었다. 이종 필러를 함유한 GO/h-BN (GO/Cu) 에폭시 복합체의 열전도도는 0.55(0.52) W/m·K에 서 2.82(1.37) W/m·K로 점진적으로 증가했다. 반대로 열팽창 계수는 GO/Cu와 GO/h-BN 에폭시 복합체 내에서 51 ppm/ oC에서 23 ppm/oC으로, 57 ppm/oC에서 32 ppm/oC으로 각각 감소되었다. 이러한 복합체 내의 열적 특성의 변화는 열전 도도, 형태 및 필러의 비중에 따른 분포를 포함하여 필러의 고유한 물성에 의해 발생한다. 서로 다른 물성을 가진 필러 물 질을 동일한 매트릭스 내에 도입을 통한 점진적 열적 특성의 구현은 반도체/플라스틱, 금속/플라스틱, 반도체/금속 등의 이종 구조로 이루어진 계면에서 효과적인 열전달을 위한 계면소재로서 유용할 것이다.
In this study, the graded thermal properties of composites are obtained by difference in specific gravity of fillers including Cu, h-BN and GO powders in epoxy. Relatively heavy powders such as Cu and h-BN compared to GO mostly at the bottom layer, while light GO powders were dispersed in the top layer in the composites. The thermal conductivity of composites was gradually increased from 0.55 (0.52) W/mK to 2.82 (1.37) W/mK for GO/h-BN (GO/ Cu) epoxy composites from surface to bottom. On the contrary, the coefficient of thermal expansion was decreased from 51 ppm/oC to 23 ppm/oC and from 57 ppm/ oC to 32 ppm/oC for GO/Cu and GO/h-BN, respectively. The variation of thermal properties in composites is attributed due to intrinsic material properties of filler including thermal conductivity, morphology and the distribution by the specific weight of fillers. This simple strategy for realizing graded thermal composites by introducing different filler materials would be effective heat transfer at interface of heterostructure with large thermal properties such as inorganic semiconductor/plastic, metal/plastic, and semiconductor/metal.

Keywords

composites, fillers, epoxy, thermal conductivity, thermal expansion coefficient

Analysis on Effective Elastic Modulus and Deformation Behavior of a Stiffness-Gradient Stretchable Electronic Package with the Island-Bridge Structure

Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 39-46.

Abstract

Polydimethylsiloxane (PDMS)를 베이스 기판으로 사용하고 이보다 강성도가 높은 flexible printed circuit board (FPCB)를 island 기판으로 사용하여 island-bridge 구조의 soft PDMS/hard PDMS/FPCB 신축 패키지를 형성하고, 이의 유효 탄성계수와 변형거동을 분석하였다. 각기 탄성계수가 0.28 MPa, 1.74 MPa 및 1.85 GPa인 soft PDMS, hard PDMS, FPCB를 사용하여 형성한 soft PDMS/hard PDMS/FPCB 신축 패키지의 유효 탄성계수는 0.58 MPa로 분석되었 다. Soft PDMS/hard PDMS/FPCB 신축 패키지에서 soft PDMS의 변형률이 0.3이 되도록 인장시 hard PDMS와 FPCB 의 변형률은 각기 0.1과 0.003이었다.
A stiffness-gradient soft PDMS/hard PDMS/FPCB stretchable package of the island-bridge structure was processed using the polydimethylsiloxane (PDMS) as the base substrate and the more stiff flexible printed circuit board (FPCB) as the island substrate, and its effective elastic modulus and stretchable deformation characteristics were analyzed. With the elastic moduli of the soft PDMS, hard PDMS, and FPCB to be 0.28 MPa, 1.74 MPa, and 1.85 GPa, respectively, the effective elastic modulus of the soft PDMS/hard PDMS/FPCB package was analyzed as 0.58 MPa. When the soft PDMS of the soft PDMS/hard PDMS/FPCB package was stretched to a tensile strain of 0.3, the strains occurring at hard PDMS and FPCB were found to be 0.1 and 0.003, respectively.

Keywords

stretchable package, stretchable substrate, PDMS, FPCB, elastic modulus, stretchable deformation

Stretchable Deformation-Resistance Characteristics of the Stiffness-Gradient Stretchable Electronic Packages Based on PDMS

Dae Ung Park and Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 47-53.

Abstract

Polydimethylsiloxane (PDMS)를 베이스 기판으로 사용하고 이보다 강성도가 높은 polytetrafluoroethylene (PTFE)를 island 기판으로 사용한 soft PDMS/hard PDMS/PTFE 구조의 강성도 경사형 신축 패키지를 형성하고, 이의 신 축변형에 따른 저항특성을 분석하였다. PDMS/PTFE 기판패드에 50 μm 직경의 칩 범프들을 anisotropic conductive paste 를 사용하여 실장한 플립칩 접속부는 96 mΩ의 평균 접속저항을 나타내었다. Soft PDMS/hard PDMS/PTFE 구조의 신 축 패키지를 30% 변형률로 인장시 PTFE의 변형률이 1%로 억제되었으며, PTFE 기판에 형성한 회로저항의 중가는 1% 로 무시할 정도였다. 0~30% 범위의 신축변형 싸이클을 2,500회 반복시 회로저항이 1.7% 증가하였다.
Stiffness-gradient stretchable electronic packages of the soft PDMS/hard PDMS/PTFE structure were processed using the polydimethylsiloxane (PDMS) as the base substrate and the more stiff polytetrafluoroethylene (PTFE) as the island substrate, and their stretchable deformation-resistance characteristics were characterized. The flip-chip joints, formed by bonding the chip bumps of 50 μm-diameter onto the PDMS/PTFE substrate pads, exhibited an average contact resistance of 96 mΩ. When the stretchable package of the soft PDMS/hard PDMS/PTFE structure was deformed to 30% elongation, the strain on the PTFE was restrained to 1%, resulting in a negligible resistance increase of 1% in the daisychain circuit formed on the PTFE island substrate. The circuit resistance increased for 1.7% after 2,500 cycles of 0~30% stretchable deformation.

Keywords

stretchable packaging, stretchable substrate, PDMS, PTFE, flip chip, stretchable deformation

Elastic Properties and Repeated Deformation Reliabilities of Stiffness-Gradient Stretchable Electronic Packages

Kee Sun Han and Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 55-62.

Abstract

Polydimethylsiloxane (PDMS)를 베이스 기판으로 사용하고 이보다 강성도가 높은 flexible printed circuit board (FPCB)를 island 기판으로 사용한 soft PDMS/hard PDMS/FPCB 구조의 강성도 경사형 신축패키지를 형성하고, 이의 탄성특성 및 인장 싸이클과 굽힘 싸이클에 따른 신뢰성을 분석하였다. Soft PDMS, hard PDMS, FPCB의 탄성계수 가 각기 0.28 MPa, 1.74 MPa, 2.25 GPa일 때 soft PDMS/hard PDMS/FPCB 신축패키지의 유효 탄성계수는 0.6 MPa로 분석되었다. 0~0.3 범위의 인장 싸이클을 15,000회 인가시 신축패키지의 저항변화률은 2.8~4.3% 이었으며, 굽힘반경 25 mm의 굽힘 싸이클을 15,000회 인가시 저항변화률은 0.9~1.5% 이었다.
Stiffness-gradient stretchable electronic packages of the soft PDMS/hard PDMS/FPCB structure were processed using the polydimethylsiloxane (PDMS) as the base substrate and the more stiff flexible printed circuit board (FPCB) as the island substrate. The elastic characteristics of the stretchable packages were estimated and their long-term reliabilities on stretching cycles and bending cycles were characterized. With 0.28 MPa, 1.74 MPa, and 1.85 GPa as the elastic moduli of the soft PDMS, hard PDMS, and FPCB, respectively, the effective elastic modulus of the soft PDMS/ hard PDMS/FPCB package was estimated as 0.6 MPa. The resistance of the stretchable packages varied for 2.8~4.3% with stretching cycles ranging at 0~0.3 strain up to 15,000 cycles and for 0.9~1.5% with 15,000 bending cycles at a bending radius of 25 mm.

Keywords

stretchable packaging, stretchable substrate, PDMS, FPCB, flip chip, long-term reliability

Effect of Temperature and Compressive Stress on the Dielectric and Piezoelectric Properties of PIN-PMN-PT Single Crystal

Jae Gwang Lim1, Jae Hwan Park1,†, Jeongho Lee2, and Sang Goo Lee2

1Department of Electronic Engineering, Korea National University of Transportation, 2Ibule Photonics

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 63-68.

Abstract

온도 및 압축응력 변화에 따른 PIN-PMN-PT계 압전 단결정의 유전 특성과 압전 특성을 조사하였다. 단결정의 결정상은 110oC 영역에서 강유전 rhombohedral 구조에서 tetragonal 구조로, 190oC 영역에서 tetragonal 구조로부터 상유 전 cubic 구조로 변화하였다. 전계 인가에 따른 분극 및 변위의 변화율로부터 압전상수와 비유전율을 계산하였으며, 이는 계측기로부터 측정된 값과 유사한 수준을 나타내었다. 샘플에 인가되는 압축응력이 증가할수록 압전상수 d33과 비유전율 값은 증가하는 경향성을 나타내었다. 측정 온도 5oC에서 샘플에 인가되는 압축응력이 60 MPa인 경우 d33 값이 4500 pC/ N로 계산되었으며, 측정 온도 60oC인 경우, 샘플에 인가되는 압축응력이 40 MPa 일 때 비유전율 62000이 계산되었다. 압축응력이 높아질 때 압전상수와 비유전율 값이 상승한 것은 rhombohedral 상에서 orthorhombic 상으로의 전이에 기인 한 것으로 판단된다.
Dielectric and piezoelectric properties of PIN-PMN-PT piezoelectric single crystals with variation of temperature and compressive stress were investigated. The crystal phase of the single crystal was changed from the ferroelectric rhombohedral structure to tetragonal structure in the 110oC region and from the tetragonal structure to the paraelectric cubic structure in the 190oC region. The piezoelectric constant and relative dielectric constant were calculated from the rate of change of polarization and displacement with the application of electric field, which was similar to the value measured from the instrument. As the compressive stress applied to the sample increased, the piezoelectric constant d33 and relative dielectric constant values tended to increase. When the compressive stress applied to the sample at 5oC was 60 MPa, the d33 was calculated as 4,500 pC/N. At 60oC, the relative dielectric constant of 62000 was calculated when the compressive stress applied to the sample was 40 MPa. The increase in piezoelectric constant and relative dielectric constant when the compressive stress increased could be attributed to the phase transition from the rhombohedral structure to orthorhombic.

Keywords

Pb(In1/2Nb1/2)O3, PMN-PT, single crystal, piezoelectric coefficient, strain

Effect of Measuring Method on the Evaluation of Piezoelectric and Dielectric Properties of PMN-PT Single Crystal

Yong Soo Kim1, Jae Hwan Park1,†, Jeongho Lee2, and Sang Goo Lee2

1Department of Electronic Engineering, Korea National University of Transportation, 2Ibule Photonics

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 69-74.

Abstract

PMN-PT 단결정 시편의 유전 및 압전 특성의 측정 결과에 미치는 측정 기구물의 영향을 고찰하였다. 샘플에 교류 전기신호를 인가하는 지그핀의 압력이 감소할수록 공진저항은 낮게 측정되고 기계적 품질계수는 높게 계산되었다. 지그핀의 스프링 텐션이 20 grf인 경우 기계적 품질계수는 418으로 측정되었고, 스프링 텐션이 200 grf인 경우 품질계수 값은 절반으로 감소하였다. 4-프로브 방식의 픽스쳐는 압전특성 측정에는 부적합하지만 유전손실 값의 측정에는 가장 적 합하였다. 정확한 PMN-PT의 압전특성 평가를 위하여 지그핀의 스프링 텐션을 최대한 낮추는 것이 필요하며, 정확한 유 전특성의 평가를 위하여 4-프로브 방식이 적합함을 알 수 있다.
The influence of measuring fixtures on the measurement of dielectric and piezoelectric properties of PMNPT single crystal specimens was investigated. As the pressure of the jig pin which applied the AC electrical signal to the sample decreased, the lower resonance resistance was measured and the higher mechanical quality factor was calculated. The mechanical quality factor was 418 when the spring tension of the jig pin was 20grf, and the value of the quality factor was reduced by half when the spring tension was 200grf. The 4-probe fixture method is unsuitable for measuring piezoelectric properties, but it was suitable for the measurement of dielectric loss. In order to accurately evaluate the piezoelectric properties of PMN-PT, it is necessary to lower the spring tension of the jig pin as much as possible.

Keywords

PMN-PT, single crystal, piezoelectric, dielectric, test fixture

Reliability Assessment of Flexible InGaP/GaAs Double-Junction Solar Module Using Experimental and Numerical Analysis

Youngil Kim, Xuan Luc Le, and Sung-Hoon Choa

Graduate School of Nano IT Design Fusion Technology, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 75-82.

Abstract

유연 태양 전지는 최근 휴대용 배터리, 웨어러블 소자, 로봇, 드론 및 비행기와 같은 광범위한 응용 분야로 인 해 큰 주목을 받고 있다. 특히, 고효율 및 높은 신뢰성을 갖는 유연 실리콘 및 화합물 반도체 태양 전지의 요구가 계속 증 가하고 있다. 본 연구에서는 유연 InGaP/GaAs 2중 접합 태양전지 모듈을 개발하였다. 특히 제작된 유연 태양전지 모듈 의 신뢰성을 확보하기 위하여, 풍속 및 주위 온도가 태양 전지 작동 온도에 미치는 영향을 수치해석으로 분석하였다. 3 종류의 풍속(0 m/s, 2.5 m/s 및 5 m/s) 및 2종류의 주변 온도 조건(25oC 및 33oC)에 대하여 태양 전지 모듈의 온도 분포 를 해석하였다. 유연 태양전지 모듈의 유연성은 굽힘 시험 및 굽힘 수치해석을 통하여 평가하였다. 25oC 온도조건에서 풍 속이 0 m/s 일 때, 태양 전지 셀의 최대 온도는 149.7oC이다. 풍속이 2.5 m/s로 증가되었을 경우, 태양 전지의 온도는 66.2oC로 크게 감소되었다. 또한 풍속이 5 m/s 인 경우, 태양 전지의 온도는 48.3oC로 급격히 감소함을 알 수 있었다. 주 변 온도 또한 태양 전지의 작동 온도에 영향을 미친다. 2.5 m/s의 풍속에서 주변 온도가 33oC로 증가할 경우, 태양 전지 의 온도는 74.2oC로 약간 증가하였다. 따라서 태양 전지 셀의 온도에 영향을 미치는 가장 중요한 인자는 풍속으로 인한 열 방출 효과임을 알 수 있었다. 또한 태양 전지의 최대 온도는 사용된 소재들의 유리 전이 온도보다 낮기 때문에, 열 변 형 및 모듈의 열화 가능성은 매우 낮을 것으로 예측된다. 제작된 태양전지 모듈은 굽힘 반경 7 mm까지 굽힐 수 있어 비 교적 우수한 유연성을 갖고 있었다. 또한 향후 neutral plane 해석을 통하여 태양전지 셀을 neutral plane에 위치시키면 유 연성이 크게 증가할 것으로 예측된다.
Flexible solar cells have attracted enormous attention in recent years due to their wide applications such as portable batteries, wearable devices, robotics, drones, and airplanes. In particular, the demands of the flexible silicon and compound semiconductor solar cells with high efficiency and high reliability keep increasing. In this study, we fabricated a flexible InGaP/GaAs double-junction solar module. Then, the effects of the wind speed and ambient temperature on the operating temperature of the solar cell were analyzed with the numerical simulation. The temperature distributions of the solar modules were analyzed for three different wind speeds of 0 m/s, 2.5 m/s, and 5 m/s, and two different ambient temperature conditions of 25oC and 33oC. The flexibility of the flexible solar module was also evaluated with the bending tests and numerical bending simulation. When the wind speed was 0 m/s at 25 oC, the maximum temperature of the solar cell was reached to be 149.7oC. When the wind speed was increased to 2.5 m/s, the temperature of the solar cell was reduced to 66.2oC. In case of the wind speed of 5 m/s, the temperature of the solar cell dropped sharply to 48.3oC. Ambient temperature also influenced the operating temperature of the solar cell. When the ambient temperature increased to 33oC at 2.5 m/s, the temperature of the solar cell slightly increased to 74.2oC indicating that the most important parameter affecting the temperature of the solar cell was heat dissipation due to wind speed. Since the maximum temperatures of the solar cell are lower than the glass transition temperatures of the materials used, the chances of thermal deformation and degradation of the module will be very low. The flexible solar module can be bent to a bending radius of 7 mm showing relatively good bending capability. Neutral plane analysis was also indicated that the flexibility of the solar module can be further improved by locating the solar cell in the neutral plane.

Keywords

Flexible, Solar cell, Thermal analysis, Bending, Flexibility

Preparation and Photoluminescence Properties of LiBaPO4:Eu2+ Phosphors by Solid State Reaction Method

In Yong Park

Department of Materials Science and Engineering, Hanbat National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 83-88.

Abstract

화학양론적 조성과 비화학양론적 조성을 갖는 LiBaPO4:Eu2+ 계 형광체를 고상반응으로 제조한 후 환원 분위 기에서 열처리한 다음 분말의 결정구조와 광 특성을 X선 회절 분석과 발광 분석을 통하여 조사하였다. XRD 분석 결과, 900℃에서 중간상으로서 Ba3(PO4)2 상이 주 결정상 LiBaPO4와 함께 나타났다. 1,100oC에서 낮은 농도의 유로피움이 도 핑된 조성의 결정구조는 삼방정(trigonal) 구조에 속하는 반면, 4 mol% Eu2+ 이상의 조성에서는 단사정(monoclinic) 계를 나타내었다. 4 mol% 이상의 Eu2+이 첨가된 비화학양론적 조성에서는 단일상의 LiBaPO4가 형성되었다. 단일상의 LiBaPO4:Eu2+ 계 형광체는 480nm에서의 청록색 발광스펙트럼을 나타내었다.
LiBaPO4:Eu2+ phosphors with stoichiometric and nonstoichiometric compositions were prepared using a solid state reaction followed by heat treatment in reduced atmosphere, and the crystal structures and photoluminescence(PL) properties of the powders were investigated by x-ray powder diffraction and luminescence spectrometer. At 900oC, the Ba3(PO4)2 phase as the intermediate phase was observed with the LiBaPO4 phase as the main crystalline phase. Samples with a low europium concentration at 1,000oC belonged to the trigonal structure, whereas samples with Eu2+ content more than 4 mol% showed monoclinic structure. In the nonstoichiometric compositions of 4 mol% Eu2+ and above, a single phase of Eu2+-doped LiBaPO4, showing bluish green emission, was formed.

Keywords

LiBaPO4:Eu2+, Phosphor, Photoluminescence, Monoclinic, Trigonal

Fabrication and Adhesion Strength Evaluation of Glass Sealants for Ceramic to Ceramic Component Joining

Yu Jin Heo and Hyo Tae Kim

Nanomaterials and Nanotechnology Center Korea Institute of Ceramic Engineering and Technology

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 89-94.

Abstract

전력저장용 전기에너지 저장장치의 일종인 NaS 전지 단위 셀을 개발함에 있어서 알파-알루미나 절연세라믹 캡과 베타-알루미나 전해질 튜브 간의 세라믹-세라믹 상호 접합을 위하여 글라스 기반의 실링소재가 필요하다. 본고에서 는 이 세라믹-세라믹 접합용 글라스 실링 페이스트를 제조함에 있어서, 열간 칭법에 의한 글라스 프릿 제조와 상분석, 분말입도 분석 및 글라스 조성에 따른 열팽창계수 변화 및 표면거칠기를 분석하였다. 또한 글라스 실란트의 접합력 평가 를 위해 종래 솔더 볼 조인트의 접합력 평가용 분석장비인 Dage bond tester를 이용하여 세라믹-세라믹 컴포넌트의 작은 접합면에 대한 접합력 측정 방법을 제안하였다.
Glass base sealant is required as a ceramic-ceramic joining material between α-alumina insulation cap and β-alumina electrolyte tube in the development of NaS battery cell package for electrical energy storage system. The fabrication of glass frit by thermal quenching method, phase analysis, particle size analysis, coefficient of thermal expansion and surface roughness according to the glass compositions were analyzed for the fabrication of glass sealing paste for ceramic-ceramic joining. Also, a new evaluation method of the adhesion strength of glass sealant at the small area in ceramic-ceramic joining component was proposed using conventional Dage bond tester that was used to measure the adhesion of solder ball joint.

Keywords

Glass sealant, ceramic-ceramic joining, NaS cell package, adhesion strength, energy storage system

Stress Conversion Factor on Penetration Depth of Knoop Indentation for Assessment of Nano Residual Stress

Won Jun Kim, Yeong Jin Kim, and Young-Cheon Kim

School of Materials Science & Engineering, Research Center for Energy and Clean Technology, Andong National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 95-100.

Abstract

연속압입시험법은 기존의 잔류응력 측정기법에 대한 대체기법으로 많은 분야에서 연구되고 있다. Knoop 압입 자는 이러한 압입시험에서 잔류응력의 방향성을 결정하기 위해 이용되어 왔다. 기존 연구에 의하면 Knoop 압입자의 두 가지 응력환산계수의 비는 실험적으로 0.34로 고정되어 있는 것으로 알려져 있으나 이에 대하여 정량적인 분석이 부족하 고, 깊이에 따른 실험결과는 미비하여 산업현장에 적용하기에 장벽이 존재한다. 본 연구에서는 연속압입시험법을 이용한 잔류응력의 방향성 측정을 위하여 응력환산계수의 비를 유한요소해석을 이용하여 측정하였다. 본 연구에서는 유한요소 해석을 이용하여 압입깊이에 따른 응력환산계수의 비를 분석하고자 하였다. 이론적인 Knoop 압입자와 시편을 모델링하 여 일축 잔류응력 상태에서 각각의 응력환산계수를 산출하였다. 압입자 장축 및 단축 방향의 응력환산계수를 주어진 깊 이에 따라 예측할 수 있는 모델을 제시하였고, 그 원인을 분석하였다.
Nanoindentation has been widely used for evaluating mechanical properties of nano-devices, from MEMS to packaging modules. Residual stress is also estimated from indentation tests, especially the Knoop indenter which is used for the determination of residual stress directionality. According to previous researches, the ratio of the two stress conversion factors of Knoop indentation is a constant at approximately 0.34. However, the ratio is supported by insufficient quantitative analyses, and only a few experimental results with indentation depth variation. Hence, a barrier for in-field application exists. In this research, the ratio of two conversion factors with variation in indentation depth using finite elements method has been attempted at. The magnitudes of each conversion factors were computed at uniaxial stress state from the modelled theoretical Knoop indenter and specimen. A model to estimate two stress conversion factor of the long and short axis of Knoop indenter at various indentation depths is proposed and analyzed.

Keywords

Residual stress, Instrumented indentation, Anisotropy, Knoop indenter

Measurement of EMC/PCB Interfacial Adhesion Energy of Chip Package Considering Warpage

Hyeong Jun Kim1, Kwang Ho Ahn1, Seung Jin Oh1, Do Han Kim2, Jae Sung Kim2, Eun Sook Kim2, and Taek-Soo Kim1,†

1Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 2R&D Group, SIMMTECH Co.

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 101-105.

Abstract

칩 패키지에는 생산 공정 및 운송, 보관 과정에서 발생하는 외부 환경 변화로부터 인쇄 회로 기판(printed circuit board, PCB)을 보호하기 위해 에폭시 몰딩(epoxy molding compound, EMC)이 사용된다. PCB와 EMC의 접합 신뢰성은 제품의 품질 및 수명에 중요한 요소이며 이를 보증하기 위해 제품 설계 및 생산 단계에서 그 접합 에너지를 정밀하게 측 정하고, 이에 영향을 끼치는 요소를 통제하여 공정을 최적화 시켜야 한다. 본 논문은 이중 외팔보(double cantilever beam, DCB) 시험을 이용하여 휨(warpage)이 있는 칩 패키지의 EMC와 PCB의 계면 접합 에너지를 측정하고 보정하는 방법에 대해 소개한다. DCB 시험법은 이종 재료의 계면 접합 에너지를 측정하는 전통적인 방법이며 정밀한 접합 에너지 측정을 위해 평평한 기판이 필수적이다. 그러나 칩 패키지는 내부 구성 요소들의 열팽창 계수 차이로 인해 휨이 발생하기 때문 에 평평한 기판을 제작하여 정밀한 접합 에너지를 측정하는데 어려움이 있다. 이를 극복하고자 본 연구에서는 휨이 있는 칩 패키지로 DCB 시험법을 위한 시편을 제작하고, 기판의 복원력을 보정하여 접합 에너지를 계산하였다. 보정된 접합 에너지는 동일 조건에서 제작된 칩 패키지 중 휨이 없는 시편을 선별하여 측정한 접합 에너지와 비교, 검증하였다.
The adhesion reliability of the epoxy molding compound (EMC) and the printed circuit board (PCB) interface is critical to the quality and lifetime of the chip package since the EMC protects PCB from the external environment during the manufacturing, storage, and shipping processes. It is necessary to measure adhesion energy accurately to ensure product reliability by optimizing the manufacturing process during the development phase. This research deals with the measurement of EMC/PCB interfacial adhesion energy of chip package that has warpage induced by the coefficient of thermal expansion (CTE) mismatch. The double cantilever beam (DCB) test was conducted to measure adhesion energy, and the spring back force of specimens with warpage was compensated to calculate adhesion energy since the DCB test requires flat substrates. The result was verified by comparing the adhesion energy of flat chip packages come from the same manufacturing process.

Keywords

Chip Package, EMC, PCB, Adhesion, Warpage

Carbon Nanotube Passivation layer for Increasing the Solar Water Splitting Performance of CdS/CuInGaSe Photocathode

Hyojung Bae1, Young-Hee Ko2, Jun-Beom Park3, Hang-Ju Ko3, Sang-Wan Ryu1, and Jun-Seok Ha1,†

1Optoelectronics Convergence Research Center, Chonnam National University, 2Kumhotire R&D center, 3Korea Photonics Technology Institute

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 107-111.

Abstract

We report the fabrication of a CdS/CuInGaSe (CdS/CIGS) structure with carbon nanotubes and its application as a photocathode for photoelectrochemical water splitting. CIGS thin films were fabricated using co-evaporation by RF magnetron sputtering, while CdS was fabricated by chemical bath deposition. Spray coated multi-wall carbon nanotube (CNT) film on CdS/CIGS thin film was investigated as a photocathode. The CNT-coated CdS/CIGS showed superior photocurrent density and exhibited improved photostability.

Keywords

CNT, CIGS, Photocathode, Hydrogen, Water splitting

Growth of α-Ga2O3 Epitaxial Films on Al2O3 by Halide Vapor Pressure Epitaxy

Daejang Lee1, An-Na Cha2, Junseong Park2, Hogyun Noh2, Youngboo Moon1, and Jun-Seok Ha2,3,†

1UJL Inc., 2School of Applied Chemical Engineering, Chonnam National University, 3Optoelectronics Convergence Research Center, Chonnam National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 113-118.

Abstract

In this study, we investigated the growth of single-crystallinity α-Ga2O3 thin films on c-plane sapphire substrates using halide vapor pressure epitaxy. We also found the optimal growth conditions to suppress the phase transition of α-Ga2O3. Our results confirmed that the growth temperature and partial pressure of the reactive gas greatly influenced the crystallinity. The optimal growth temperature range was about 460~510oC, and the α-Ga2O3 thin films with the highest crystallinity were obtained at a III/VI ratio of 4. The thickness and surface morphology of the thin films was observed by scanning electron microscopy. The film thickness was 6.938 μm, and the full width at half maximum of the ω-2θ scan rocking curve was as small as 178 arcsec. The optical band gap energy obtained was 5.21 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The etch pit density was found to be as low as about 6.0 × 104 cm−2.

Keywords

HVPE, α-Ga2O3, Al2O3, Heteroepitaxy, Single crystal

Power Generation Properties and Bending Characteristics of a Flexible Thermoelectric Module Fabricated using PDMS Filling Method

Kee Sun Han and Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 119-126.

Abstract

18쌍의 Bi2Te3계 p-n 가압소결체 열전레그들로 구성되어 있으며 상하부 기판이 없고 내부는 polydimethylsiloxane (PDMS)로 충진되어 있는 유연열전모듈을 형성하고, 이의 발전특성과 굽힘특성을 분석하였다. 유 연열전모듈을 팔목에 부착하였을 때 서있는 정적인 상태에서는 2.23 mV의 open circuit 전압과 1.69 μW의 최대출력전 력이 얻어졌으며, 걸어가는 동적인 상태에서는 3.32 mV의 open circuit 전압과 3.41 μW의 최대출력전력이 얻어졌다. 유 연열전모듈에 굽힘곡률반경 25 mm로 30,000회까지 반복굽힘 싸이클을 인가하여도 저항변화율이 1% 미만으로 유지되 었다.
A flexible thermoelectric module, which consisted of 18 pairs of Bi2Te3-based hot-pressed p-n thermoelectric legs, were processed by filling the module inside with polydimethylsiloxane (PDMS) and removing the top and bottom substrates. Its power generation properties and bending characteristics were measured. With putting the flexible module on the wrist, an open circuit voltage of 2.23 mV and a maximum output power of 1.69 μW were generated during staying still. On the other hand, an open circuit voltage of 3.32 mV and a maximum output power of 3.41 μW were obtained with walking motion. The resistance variation of the module was kept below 1% even after applying 30,000 bending cycles with a bending curvature radius of 25 mm.

Keywords

flexible thermoelectrics, flexible thermoelectric module, energy harvesting, PDMS, wearable device

Surface Modification of Ba0.6Sr0.4TiO3 by Trimethylsilyl Chloride as a Silylation Agent

Chan Lee, Wooje Han, and Hyung-Ho Park

Department of Materials Science and Engineering, Yonsei University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 127-132.

Abstract

본 연구에서는 liquid-solid solution 합성법을 통해 고유전 페로브스카이트 구조의 barium strontium titanate (Ba0.6Sr0.4TiO3, BSTO)를 합성하여 trimethylsilyl chloride(TMCS)를 silylation agent로 이용한 표면개질을 진행하였 다. Silylation 표면개질을 활용하여 기존 BSTO 나노입자 표면에 있던 -OH 리간드와 TMCS가 갖고 있는 Cl을 반응 시켜 나노입자 표면의 리간드를 -Si, -CH3로 치환하였다. 다양한 TMCS 농도의 변화를 주어 silylation을 진행했고, Fourier-transform infrared spectroscopy 및 X 선 회절 분석, 전계방사 주사전자현미경을 통해 silicon network 및 결 정구조, 나노입자의 크기를 확인하였다. 접촉각 변화 관찰을 통해 가장 많이 silylation된 BSTO 나노입자에서 120.9o 인 소수성 특성을 확인하였다. 나노입자의 silylation을 통해 D.I water 내 BSTO 나노입자의 소수화 정도를 확인하 였다.
In this study, barium strontium titanate (BSTO) with high dielectric perovskite structure was synthesized by liquid-solid solution synthesis and the surface was modified using trimethylsilyl chloride (TMCS) as a silylation agent. Silylation surface modification is a method of reacting -OH ligand on the surface of BSTO nanoparticles with Cl in TMCS to generate HCl and replacing the ligand on the surface of nanoparticles with -Si, -CH3. Silylation was optimized by varying the concentration of TMCS, and the structure of the silicon network was confirmed by Fouriertransform infrared spectroscopy. In addition, the crystallinity of BSTO nanoparticles was confirmed by X-ray diffractometer and the size of the nanoparticles was calculated using Scherrer equation. The field emission scanning electron microscopic image observed the change of the surface-modified BSTO particle size, and the contact angle measurement confirmed the hydrophobic property of the contact angle of 120.9o in the optimized nanoparticles. Finally, the surface-modified BSTO dispersion experiment in de-ionized water confirmed the hydrophobic degree of the nanoparticles.

Keywords

Nanoparticle, BSTO, Silylation, Surface modification

Thermal Cycle Reliabilties and Cracking Characteristics of Electroplated Cr/Ni-P Coatings

Jina Lee1, Kirak Son1, Kyu Hwan Lee2, and Young-Bae Park1,†

1School of Materials Science and Engineering, Andong National University, 2Surface Technology Division, Korea Institute of Materials Science

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 133-140.

Abstract

열 사이클 조건이 전해 Cr/Ni-P 이중도금 시편의 접합강도 및 균열성장거동에 미치는 영향을 분석하였다. 전 해 Ni-P 도금층을 열처리를 통해 결정화 시킨 후 전해 Cr 도금 후 한번 더 열처리한 결과, Cr/Ni-P 계면에서 상호확산으 로 인해 Cr-Ni 고용체 band layer가 관찰되었다. 열 사이클 전 접합강도는 25.6 MPa이였으나, 1,000사이클 후 Cr 도금층 의 균열 밀도 및 표면 거칠기 증가로 인해 도금층과 접착제 사이의 기계적 고착효과가 향상되어 접착제와 Cr 도금층 사 이에서 박리되었고, 접합강도는 47.6 MPa로 점차적으로 증가하였다.
The effects of thermal cycle conditions on the bonding strength and crack propagation behaviors in electroplated Cr/electroplated Ni-P coatings were systematically evaluated. 1st heat treatment was performed at 500oC for 3 hours after electroplating Ni-P, and then, 2nd heat treatment was performed at 750oC for 6 hours after electroplating Cr. The measured bonding strength by ASTM C633 were around 25.6 MPa before thermal cycling, while it increased to 47.6 MPa, after 1,000 cycles. Increasing thermal cycles led to dominant fail mode with cohesive failure inside adhesive, which seemed to be closely related to the increasing bonding strength possibly not only due to higher Cr surface roughness, but also to penetrated channeling crack density. Also, increasing density of penetrated channeling cracks in electroplating Cr layer led to slightly stronger bonding strength due to mechanical interlocking effects of adhesive inside channeling cracks.

Keywords

Cr/Ni-P plating, thermal cycle, penetrated channeling crack, bonding strength

Sensitivity Improvement of Shadow Moiré Technique Using LED Light and Deformation Measurement of Electronic Substrate

Heeju Yang, and Jinwon Joo1,†

School of Mechanical Engineering, Chungbuk National University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 141-148.

Abstract

모바일 기기로 사용되는 전자기판은 여러 가지 다양한 재료로 구성되어 있으며, 제조시나 사용 환경에서 온도 가 변하면 각 재료의 열팽창 계수의 차이로 인하여 변형과 응력집중이 발생하게 된다. 그림자 무아레 방법은 비접촉으로 전체 영역에 걸친 면외변위를 측정하는 광학적 방법이지만 고감도 적용을 위해서는 탈봇 현상의 극복이 필요하다. 본 논 문에서는 그림자 무아레 기법에서 발생하는 탈봇 현상을 극복하기 위하여 다양한 파장의 LED 광원을 이용하고, 파장의 변화가 탈봇 거리에 미치는 영향에 대해 연구하였다. 위상 이동법을 이용함으로써 10 μm/fringe 이내의 측정 감도를 확 보할 수 있는 실험방법을 제안하고 이를 평가하였으며, 이 방법을 모바일 회로 기판의 열변형 측정에 적용하였다. 백색광 을 사용한 경우에서는 탈봇 현상으로 인하여 측정이 불가능한 영역이 여러 군데 존재하였으나, 파란색 LED 광을 사용한 경우에는 대부분의 영역에서 감도 6.25 μm/fringe의 정밀한 무아레 무늬를 얻어낼 수 있음을 확인하였다.
Electronic substrates used in a mobile device is composed of various materials, and when the temperature is changed during manufacturing or operating, thermal deformation and stress concentration occur due to the difference in thermal expansion coefficient of each material. The shadow moiré technique is a non-contact optical method that measures shape or out-of-plane displacement over the entire area, but it is necessary to overcome the Talbot effect for high sensitivity applications. In this paper, LED light sources of various wavelengths was used to overcome the Talbot effect caused in the shadow moiré technique. By using the phase shift method, an experimental method to retain the measurement sensitivity within 10 μm/fringe was proposed and evaluated, and this method is applied to the thermal deformation measurement of the mobile electronic substrate. In the case of using white light, there were several areas that could not be measured due to the Talbot effect, but in the case of using blue LED light, it was shown that a precise moiré pattern with a sensitivity of 6.25 μm/fringe could be obtained in most areas.

Keywords

Shadow moiré, Phase shift, Talbot effect, Blue LED, Talbot distance

Stretchable Characteristics and Power Generation Properties of a Stretchable Thermoelectric Module Filled with PDMS

Kee Sun Han and Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 149-156.

Abstract

5쌍의 Bi2Te3계 p-n 가압소결체 열전레그들로 구성되어 있으며 상하부 기판이 없고 내부는 polydimethylsiloxane (PDMS)로 충진되어 있는 신축열전모듈을 형성하고, 이의 신축특성과 발전특성을 분석하였다. 신축열전모듈에 변형률 0~0.1 범위의 신축변형 싸이클을 10회 인가하여도 모듈의 integrity가 잘 유지되었으며, 인장변형률이 0.2로 증가시 Cu 전 극과 열전레그 사이의 접합부 파단에 의해 모듈이 open 되었다. 신축열전모듈은 열전레그 양단간의 온도차가 2.2 K일 때 4.6 mV의 open circuit 전압을 나타내었으며, 변형률 0~0.1 범위의 인장변형에 의한 open circuit 전압의 변화는 5% 미만 이었다. 신축열전모듈은 0.1의 변형률로 인장된 상태에서 레그 양단간 온도차 2.2 K에 의해 18.5 μW의 최대발전출력을 나타내었다.
A stretchable thermoelectric module consisting of 5 pairs of Bi2Te3-based hot-pressed p-n thermoelectric legs was processed by filling the module inside with polydimethylsiloxane (PDMS) and removing the top and bottom substrates. Its stretchable characteristics and power generation properties were measured. The integrity of the module was kept well even after 10 strain cycles ranging from 0 to 0.1. With increasing the tensile strain to 0.2, the module circuitry became open because of joint failure between Cu electrodes and thermoelectric legs. The stretchable thermoelectric module exhibited an open circuit voltage of 4.6 mV with a temperature difference of 2.2K across both ends of thermoelectric legs, and changes in its open circuit voltage were below 5% for tensile strains of 0~0.1. Being elongated for a strain of 0.1, it exhibited the maximum output power of 18.5 μW with the temperature difference of 2.2K across its both ends.

Keywords

stretchable thermoelectrics, stretchable thermoelectric module, energy harvesting, PDMS, wearable device

Point Defect Engineering Approaches to Enhance the Performance of Thermoelectric Materials

Hyun-Sik Kim1, Hyung Mo Jeong2, Soon-Mok Choi3,†, and Kyu Hyoung Lee4,‡

1Department of Materials Science and Engineering, Hongik University, 2Department of Materials Science and Engineering, Kangwon National University, 3School of Energy, Materials and Chemical Engineering, Korea University of

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 157-161.

Abstract

소재의 전기전도 거동과 열전도 거동을 독립적으로 제어하는 기술은 열전소재의 성능증대를 위한 효과적인 전 략 중 하나로 인식되고 있다. 이를 구현하기 위해 다결정 소재가 근본적으로 포함하고 있는 결함구조와 열전소재의 물성 과의 상관관계에 대한 수많은 연구가 진행되고 있으며, 최근 0 차원의 점결함 형성에 의해 전기전도 특성을 증대함과 동 시에 열전도 특성을 저감하는 결과가 보고되고 있다. 본 논문에서는 점결함 형성에 의한 소재의 전기전도 거동 및 열전 도 거동 변화에 대해 이론적 고찰을 진행하고, 벌크 열전소재에서 실험적으로 구현된 결과와 연계하여 고성능 열전소재 개발에 필수적인 소재설계 지침에 대한 실효적인 정보를 제공하고자 한다.
Independent control of electronic and thermal transport behaviors is one of the most effective approaches to enhance the performance of thermoelectric materials. To address this, many researches on the relationship between defect structures and thermoelectric properties have been carried out since defects are intrinsic ingredients of polycrystalline materials. Recently, experimental results of simultaneously improved electronic and thermal transport properties have been reported via the formation of 0-dimensional point defects. Here, theoretical backgrounds to the engineering of electronic and thermal transport behaviors by the formation of point defects are discussed and related experimental considerations are also presented in order to provide a practical guide for the development of highperformance thermoelectric materials.

Keywords

Thermoelectric, Electronic transport, Thermal transport, Defect structures, Point defect

Effect of Sn Decorated MWCNT Particle on Microstructures and Bonding Strengths of the OSP Surface Finished FR-4 Components Assembled with Sn58%Bi Composite Solder Joints

Hyun-Joon Park, Choong-Jae Lee, Kyung Deuk Min, and Seung-Boo Jung

School of Advanced Materials Science and Engineering, Sungkyunkwan University

Journal of the Microelectronics and Packaging Society, Vol. 26, No. , pp. 163-169.

Abstract

전자제품에서 사용되던 Sn-Pb계 솔더합금은 RoHS, WEEE, REACH 등의 환경규제에 의해 무연솔더합금(Pb free solder alloy)으로 빠르게 대체되고 있다. 그 중에서도 Sn58%Bi(in wt.%) 합금은 융점이 낮고 Sn-Pb계 합금에 비해 기계적특성이 우수하여, 전자제품 솔더합금으로 사용하기 위한 연구가 진행되고 있다. 그러나 Sn58%Bi 솔더합금은 구성 원소인 Bi의 취성으로 인해 기계적인 신뢰성이 저하되는 문제를 개선할 필요가 있다. 따라서 본 연구에서는 다양한 함량 의 Sn-MWCNT (multiwalled carbon nanotube) 입자를 첨가한 Sn58%Bi 복합솔더를 제조한 후, OSP처리된 FR-4 기판 및 FR-4 컴포넌트를 리플로우(reflow) 횟수를 1회부터 7회까지 진행하였다. 접합시편의 접합강도 및 파괴에너지는 전단 시험(die shear test)을 통해 측정하였고, 주사전자현미경(scanning electron microscope, SEM)으로 미세조직 및 파괴모드 를 분석하였다. Sn-MWCNT 첨가에 의해 Sn58%Bi 복합솔더 접합부에서 조직 미세화가 관찰되었고, 함량이 0.1 wt.%일 때 접합강도와 파괴에너지는 각각 20.4%, 15.4% 만큼 증가하였다. 또한 파단면에서 연성파괴(ductile failure) 영역이 관 찰되었으며, F-x(force-displacement to failure) 그래프를 통해 Sn-MWCNT의 첨가가 복합솔더의 연성(ductility)을 증가 시킨 것을 확인할 수 있었다.
Sn-Pb solder alloys in electronics rapidly has been replaced to Pb free solder alloys because of various environmental regulations such as restriction of hazardous substances directive (RoHS), European Union waste electrical, waste electrical and electronic equipment (WEEE), registration evaluation authorization and of chemicals (REACH) etc. Because Sn58%Bi (in wt.%) solder alloy has low melting point and higher mechanical properties than that of Sn-Pb solder, it has been studied to manufacture electronic components. However, the reliability of Sn58%Bi solder could be lowered because of the brittleness of Bi element included in the solder alloy. Therefore, we observed the microstructures of Sn58%Bi composite solders with various contents of Sn-decorated multiwalled carbon nanotube (Sn-MWCNT) particles and evaluated bonding strength of the FR-4 components assembled with Sn58%Bi composite solder. Also, microstructures and bonding strengths of the Sn58%Bi composite solder joints were evaluated with the number of reflows from 1 to 7 times, respectively. Bonding strengths and fracture energies of the Sn58%Bi composite solder joints were measured by die shear test. Microstructures and fracture modes were observed with scanning electron microscope (SEM). Microstructures in the Sn58%Bi composite solder joints were finer than that of only Sn58%Bi solder joint. Bonding strength and fracture energy of Sn58%Bi composite solder including 0.1 wt.% of Sn-decorated MWCNT particles increased up to 20.4% and 15.4% at 5 times in reflow, respectively.

Keywords

Sn58%Bi composite solder, multiwalled carbon nanotube (MWCNT), Microstructure, Intermetallic compound (IMC), bonding strength, fracture energy

  • Vol. 25 No.1
  • Vol. 25 No.2
  • Vol. 25 No.3
  • Vol. 25 No.4

Vol. 25 No.1

Effects of Encapsulation Layer on Center Crack and Fracture of Thin Silicon Chip using Numerical Analysis

Sung-Hoon Choa1, Young-Moon Jang2, Haeng-Soo Lee3, †

1Graduate School of NID Fusion Technology, Seoul National University of Science and Technology, 232 Gongneung-Ro, Nowon-Gu, Seoul, 01811, Korea 2Dept. Of Manufacturing System and Design Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea 3Department of Mechanical Engineering, Ulsan College, 101 Bongsu-Ro, Dong-Gu, Ulsan, 44022, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 1-10.

Abstract

최근 플렉서블 OLED, 플렉서블 반도체, 플렉서블 태양전지와 같은 유연전자소자의 개발이 각광을 받고 있다. 유연소자에 밀봉 혹은 봉지(encapsulation) 기술이 매우 필요하며, 봉지 기술은 유연소자의 응력을 완화시키거나, 산소나 습기에 노출되는 것을 방지하기 위해 적용된다. 본 연구는 봉지막(encapsulation layer)이 반도체 칩의 내구성에 미치는 영향을 고찰하였다. 특히 다층 구조 패키지의 칩의 파괴성능에 미치는 영향을 칩의 center crack에 대한 파괴해석을 통하여 살펴보았다. 다층구조 패키지는 폭이 넓어 칩 위로만 봉지막이 덮고있는 “wide chip”과 칩의 폭이 좁아 봉지막이 칩과 기판을 모두 감싸고 있는 “narrow chip”의 모델로 구분하였다. Wide chip모델의 경우 작용하는 하중조건에 상관없이 봉지막의 두께가 두꺼울수록, 강성이 커질수록 칩의 파괴성능은 향상된다. 그러나 narrow chip모델에 인장이 작용할 때 봉지막의 두께가 두껍고 강성이 커질수록 파괴성능은 악화되는데 이는 외부하중이 바로 칩에 작용하지 않고 봉지막을 통하여 전달되기에 봉지막이 강하면 강한 외력이 칩내의 균열에 작용하기 때문이다. Narrow chip모델에 굽힘이 작용할 경우는 봉지막의 강성과 두께에 따라 균열에 미치는 영향이 달라지는데 봉지막의 두께가 작을 때는 봉지막이 없을 때보다 파괴성능이 나쁘지만 강성과 두께의 증가하면neutral axis가 점점 상승하여 균열이 있는 칩이 neutral axis에 가까워지게 되므로 균열에 작용하는 하중의 크기가 급격히 줄어들게 되어 파괴성능은 향상된다. 본 연구는 봉지막이 있는 다층 패키지 구조에 다양한 형태의 하중이 작용할 때 패키지의 파괴성능을 향상시키기 위한 봉지막의 설계가이드로 활용될 수 있다.
Recently, there has been rapid development in the field of flexible electronic devices, such as organic light emitting diodes (OLEDs), organic solar cells and flexible sensors. Encapsulation process is added to protect the flexible electronic devices from exposure to oxygen and moisture in the air. Using numerical simulation, we investigated the effects of the encapsulation layer on mechanical stability of the silicon chip, especially the fracture performance of center crack in multi-layer package for various loading condition. The multi-layer package is categorized in two type – a wide chip model in which the chip has a large width and encapsulation layer covers only the chip, and a narrow chip model in which the chip covers both the substrate and the chip with smaller width than the substrate. In the wide chip model where the external load acts directly on the chip, the encapsulation layer with high stiffness enhanced the crack resistance of the film chip as the thickness of the encapsulation layer increased regardless of loading conditions. In contrast, the encapsulation layer with high stiffness reduced the crack resistance of the film chip in the narrow chip model for the case of external tensile strain loading. This is because the external load is transferred to the chip through the encapsulation layer and the small load acts on the chip for the weak encapsulation layer in the narrow chip model. When the bending moment acts on the narrow model, thin encapsulation layer and thick encapsulation layer show the opposite results since the neutral axis is moving toward the chip with a crack and load acting on chip decreases consequently as the thickness of encapsulation layer increases. The present study is expected to provide practical design guidance to enhance the durability and fracture performance of the silicon chip in the multilayer package with encapsulation layer.

Keywords

봉지막, 에너지 방출율, 인장, 굽힘. Encapsulation Layer, Energy Release Rate, Tension, Bending.

A Study on the Silver Nanoparticle Deposition for Optical Amplification

J. S. Kang, J. H. Kim, M. Y. Jeong†

Department of Cogno-Mechatronics Engineering, Pusan National University, Geumjeong-gu, Busan 46241, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 11-16.

Abstract

본 논문에서는 UV 나노임프린트 공정으로 제작한 나노 콘 형태의 구조물 위에 은 나노 입자를 증착하여 광 증폭용 구조 형태를 제작하고자 하였다. 은 나노 입자의 증착은 하부 기판 표면의 젖음 특성에 따른 액적의 증발 거동을 이용하였으며, 기판 하부 열에너지의 차이에 따라서 액적 중심부부터 가장자리까지 증착 형태가 변화함을 확인하였다. 제작한 구조 형태와 유사한 구조를 시간영역 유한차분(FDTD)법을 통해 광 특성을 예측하여, 최종적으로 제작한 구조의 은 나노 입자 부근에 에너지가 집중되는 결과를 확인하였다.
In this study, we deposited silver nanoparticles on the nanocone array structure which was fabricated by the UV nanoimprint process for optical signal amplification. The deposition of the silver nanoparticles was based on the evaporation behavior of the solution droplet according to wettability of surface and the deposition pattern changed from the center of the droplet to the edge depending on the difference of thermal energy. The optical property of silver nanoparticles that were deposited on imprinted nanohole patterns was simulated by the Finite difference time domain (FDTD) analysis method, and it was confirmed that energy was concentrated around the silver nanoparticle of the finally fabricated structure.

Keywords

UV nanoimprint lithography, Hydrophobic nanocone array, Droplet evaporation, Silver nanoparticle deposition.

Study on Effects of Solder Joint aging on the Reliability of Embedded Package Solder Joints using Numerical analysis

Seunghyun Cho1, Junyoung Jang2, 3, Youngbae Ko3, †

1Department of Mechanical Engineering, Dongyang Mirae University, 445, Gyeongin-ro, Guro-gu, Seoul 08221, Korea 2Department of Mechanical Engineering, Inha University, 100 Inha-ro, Nam-gu Incheon 22212, Korea 3Molds & Dies Technology R&D Group, KITECH, 156, Gaetbeol-ro, Yeonsu-gu, Incheon 21999, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 17-22.

Abstract

본 논문에서는 임베딩 패키지의 솔더 조인트 신뢰성에 미치는 솔더 조인트의 에이징 효과를 유한요소법에 의한 수치해석을 통해 연구하였다. SAC305 솔더 조인트의 에이징 시간은 0, 60, 180 일이 적용되었고 신뢰성 분석을 위해 패키지 휨, ECS(Equivalent Creep Strain) 및 TSED(Total Strain Energy Density)이 분석되었다. 연구결과에 따르면 임베딩 패키지의 휨이 비임베딩 패키지에 비해 감소하여 임베딩 패키지내 솔더 접합부의 신뢰성이 높을 것으로 예측되었다. 또한, 에이징 시간이 길수록 임베디드 패키지의 휨이 감소하지만 솔더 조인트의 신뢰성 수명도 감소할 것으로 분석되었다.
In this paper, the effects of solder joint aging on the reliability of embedded package solder joints were investigated using numerical analysis by finite element method. Solder joints were SAC305 with aging time 0, 60, 180 days. For reliability analysis, warpage of package and equivalent creep strain (ECS) and total strain energy density (TSED) of solder joint were analyzed. The analysis results show that the package warpage is decreased in the case of the embedded package compared to the non embedded package, and the reliability life of the solder joint is predicted to be high. Also, it was interpreted that the longer the aging time, the less the warpage of the embedded package, but the reliability life of the solder joint would be shortened.

Keywords

Embedded package, SAC305, ANAND model, Warpage, TSED, FEM.

Effect of Solder Printing Conditions and External Factors on Printing Efficiency

Chung-Soo Ha, Hyuk-Ku Kwon†

Department of Nanobiotronics, Graduate School of Hoseo University, 20, Hoseo-ro 79beon-gil, Baebang-eup, Asan-si, Chungcheongnam-do 31499, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 23-28.

Abstract

최근 4차 산업혁명의 조류 하에 표면 실장 분야에서도 Smart Factory 구현을 위한 노력이 활발히 이루어지고 있다. 표면 실장 분야에서도 이러한 변화와 발 맞추어 많은 연구가 진행되고 있으며, 그중 핵심 공정이라 할 수 있는 솔더 인쇄 공정의 최적화에 대한 방법과 인쇄 효율에 영향을 미치는 인쇄 외적 요소에 대한 영향도를 분석하였다. 이 분석에는 설비에서 제공하는 Big Data를 활용하여 통계적 방법으로 접근하였고, 신뢰성 높은 결과와 함께 시뮬레이션을 통해 결과을 예측할 수 있는 가능성을 확인하였다. 이 연구가 실장 분야의 Smart Factory 구현에 조금이나마 기여가 되었으면 하는 바람이다.
Under the 4th Industrial Revolution, implementation of Smart Factory in the field of surface mounting is an emerging issue. In the field of surface mounting, many researches are going on in line with these changes. Among them, we analyzed the method of optimizing the solder printing process which is a core process and the influence of the external factors affecting the printing efficiency. In this analysis, the Big Data provided by the SPI Machine was used to approach the statistical method, and the possibility of predicting the result through simulation with reliable results was confirmed. I hope this study contributes a little to the Smart Factory implementation.

Keywords

surface mount technology(SMT), solder paste inspector(SPI), solder printing condition, external factor, response surface model(RSM)

Reliability study on rolling deformation of ITO thin film on flexible substrate

Jae-Geun Seol, Dong-Jun Lee, Tae-Wook Kim, Byoung-Joon Kim†

School of Materials Science & Engineering, Andong National University, 1375, Gyeongdong-ro, Andong-si, Gyeongsangbuk-do 36729, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 29-34.

Abstract

미래의 전자 기기는 접고 굽히고 둘둘 마는 등 다양한 변형에도 전기적 안정성을 가지는 기기들로 발전할 것이며, 반복 기계적 변형 하에서 유연 전자 소자의 전기적 신뢰성 확보가 중요한 이슈로 부각되고 있다. 본 연구에서는 반복 롤링 변형이 가능한 장치를 개발하고 이를 이용해, 현재 유연 전자 소자용 투명 전극 소재로 가장 널리 사용 중인 ITO 박막의 반복 롤링 실험 중 전기적 특성 변화를 연구하였다. 전극과 기판의 상대적 위치에 의해 인장 응력과 압축 응력이 가해지므로, Outer rolling 및 Inner rolling의 두 조건에서 실험을 진행하여 응력 상태에 따른 전기적 신뢰성 차이를 연구하였다. 그 결과, inner rolling의 경우 outer rolling에 비해 더 우수한 전기적 안정성을 나타냈으며, 이는 inner bending에 의한 압축 응력 상태의 경우 crack closing 변형에 따라 전기저항이 상대적으로 낮게 증가하는 것으로 해석된다. 또한, 롤링 바퀴 수에 따른 피로 저항성을 실시간 전기저항 측정을 통해 연구하였으며, 그 결과, 롤링 바퀴 수가 증가할수록 피로 파괴 영역이 증가하므로 전기저항이 더욱 크게 증가하는 것으로 나타났다. 본 연구를 통해 롤링 조건에서 유연 전극의 신뢰성에 대해 이해하고, 이는 향후 유연 전자소자용 고신뢰성 전극 개발에 활용 될 수 있을 것으로 기대한다.
Flexible electronics must be stable under various deformations such as bending, folding, and rolling. The reliability of ITO (Indium Tin Oxide) film used widely as a transparent electrode for flexible electronics has been studied using rolling fatigue test and bending test. During repeated rolling deformations, the electrical resistance was in-situ measured with different number of rotation. During rolling fatigue test, the electrical resistance of ITO film was significantly increased with increasing the number of rotation. As the stress state of ITO film is different according to the relative position of ITO and substrate, the rolling fatigue test was investigated under both outer and inner bending conditions. Inner rolling fatigue test showed superior electrical stability because the crack nucleation and propagation were retarded under compressive stress state.

Keywords

ITO film, Rolling test, Fatigue, Reliability.

Carbon strain sensor using Nd: YAG laser Direct Writing

Donghyun Joo1, Sangwoo Yoon2, Joohan Kim2, Woo-Tae Park1, 2, †

1Convergence Institute of Biomedical Engineering and Biomaterial, Seoul National University of Science and Technology, 232, Gongneung-ro, Nowon-gu, Seoul 01811, Korea 2Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, 232, Gongneung-ro, Nowon-gu, Seoul 01811, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 35-40.

Abstract

Nd:YAG Laser를 이용하여 polyimide film에 탄화(carbonization)를 진행하여 Carbon을 생성하여 저가의 센서를 간단한 제조과정으로 만들었다. 이를 통하여 유연한 저가형 압저항 센서의 특성에 관한 연구를 수행하였다. 기존에 많은 연구들이 Polyimide에 10.6 μm의 파장을 가지는 CO2 laser를 이용하여 carbonization을 하여 센서를 제작하였다. 본 논문에서는 polyimide film에 1.064 μm의 파장을 가지는Nd:YAG laser 를 이용하여 carbonization(탄화공정)을 진행하였다. 또한 Nd:YAG laser를 사용하여 polyimide film위에 직접 탄화시키며 carbon을 생성하는 최적의 전력밀도(W/cm2)과 속도(scan rate) 조건 조합을 찾아 해상도를 높였다. CO2 laser를 사용하였던 기존의 선행연구에서는 carbon생성의 최소 선폭이 140~220 μm의 길이를 가졌지만, 본 연구에서는 카본의 생성되는 선폭이 35~40 μm 으로 축소시켰다. 이번 연구에서 제작된 센서의 초기 면저항은 100~300 Ω/□ 이였다. 곡률 반경 21 R 로 인장을 하였을 때 저항이 30% 줄어들었고, 이를 통하여 계산된 게이지 팩터는 56.6이였다. 본 연구는 압저항 센서를 제조하기 위한 단순하고, 매우 유연하고 저렴한 공정을 제공한다.
Nd:YAG laser was used to carbonize polyimide films to produce carbon films. This is a simple manufacturing process to fabricate low cost sensors. By applying this method, we studied characteristics of flexible and low-cost piezoresistive. Previously, many studies focused on carbonization of polyimide using CO2 laser with wavelength of 10.6 μm. In this paper, carbonization (carbonization process) was performed on polyimide films using an Nd:YAG laser with a wavelength of 1.064 μm. In order to increase the resolution, we optimized the laser conditions of the power density (W/cm2) and the beam scan rate. In previous studies using CO2 laser, the minimum line width was 140~220 μm but in this study, carbon line width was reduced to 35~40 μm. The initial sheet resistance of the carbon sensor was 100~300 Ω/□. The resistance decreased by 30% under stretched with a curvature radius of 21 R. The calculated gauge factor was 56.6. This work offers a simple, highly flexible, and low-cost process to fabricate piezoresistive sensors.

Keywords

Carbonization, Carbon, Laser, Polyimide, Piezoresistive, Strain Sensor.

Warpage Analysis during Fan-Out Wafer Level Packaging Process using Finite Element Analysis

Geumtaek Kim, Daeil Kwon†

School of Mechanical, Aerospace and Nuclear Engineering, UNIST, 50, UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 41-45.

Abstract

기술의 발전과 전자기기의 소형화와 함께 반도체의 크기는 점점 작아지고 있다. 이와 동시에 반도체 성능의 고도화가 진행되면서 입출력 단자의 밀도는 높아져 패키징의 어려움이 발생하였다. 이러한 문제를 해결하기 위한 방법으로 산업계에서는 팬아웃 웨이퍼 레벨 패키지(FO-WLP)에 주목하고 있다. 또한 FO-WLP는 다른 패키지 방식과 비교해 얇은 두께, 강한 열 저항 등의 장점을 가지고 있다. 하지만 현재 FO-WLP는 생산하는데 몇 가지 어려움이 있는데, 그 중 한가지가 웨이퍼의 휨(Warpage) 현상의 제어이다. 이러한 휨 변형은 서로 다른 재료의 열팽창계수, 탄성계수 등에 의해 발생하고, 이는 칩과 인터커넥트 간의 정렬 불량 등을 야기해 대량생산에 있어 제품의 신뢰성 문제를 발생시킨다. 이러한 휨 현상을 방지하기 위해서는 패키지 재료의 물성과 칩 사이즈 등의 설계 변수의 영향에 대해 이해하는 것이 매우 중요하다. 이번 논문에서는 패키지의 PMC 과정에서 칩의 두께와 EMC의 두께가 휨 현상에 미치는 영향을 유한요소해석을 통해 알아보았다. 그 결과 특정 칩과 EMC가 특정 비율로 구성되어 있을 때 가장 큰 휨 현상이 발생하는 것을 확인하였다.
As the size of semiconductor chip shrinks, the electronic industry has been paying close attention to fan-out wafer level packaging (FO-WLP) as an emerging solution to accommodate high input and output density. FO-WLP also has several advantages, such as thin thickness and good thermal resistance, compared to conventional packaging technologies. However, one major challenge in current FO-WLP manufacturing process is to control wafer warpage, caused by the difference of coefficient of thermal expansion and Young’s modulus among the materials. Wafer warpage induces misalignment of chips and interconnects, which eventually reduces product quality and reliability in high volume manufacturing. In order to control wafer warpage, it is necessary to understand the effect of material properties and design parameters, such as chip size, chip to mold ratio, and carrier thickness, during packaging processes. This paper focuses on the effects of thickness of chip and molding compound on 12” wafer warpage after PMC of EMC using finite element analysis. As a result, the largest warpage was observed at specific thickness ratio of chip and EMC.

Keywords

Fan out wafer level package, Warpage, EMC, FEA.

Vol. 25 No.2

High reliability nano-reinforced solder for electronic packaging

Do-hyun Jung1, Bum-gyu Baek2, Song-hee Yim2, Jae Pil Jung1, †

1Department of Materials Science and Engineering, University of Seoul, 163, Seoulsiripdae-ro, Dongdaemun-gu, Seoul 02504, Korea 2KD One Co. Ltd., 22 Gukhoedaero 76-gil, Seoul 11560, Republic of Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 1-8.

Abstract

In the soldering industry, a variety of lead-free solders have been developed as a part of restricting lead in electronic packaging. Sn-Ag-Cu (SAC) lead-free solder is regarded as one of the most superior candidates, owing to its low melting point and high solderability as well as the mechanical property. On the other hand, the mechanical property of SAC solder is directly influenced by intermetallic compounds (IMCs) in the solder joint. Although IMCs in SAC solder play an important role in bonding solder joints and impart strength to the surrounding solder matrix, a large amount of IMCs may cause poor strength, due to their brittle nature. In other words, the mechanical properties of SAC solder are of some concern because of the formation of large and brittle IMCs. As the IMCs grow, they may cause poor device performance, resulting in the failure of the electronic device. Therefore, new solder technologies which can control the IMC growth are necessary to address these issues satisfactorily. There are an advanced nanotechnology for microstructural refinement that lead to improve mechanical properties of solder alloys with nanoparticle additions, which are defined as nano-reinforced solders. These nano-reinforced solders increase the mechanical strength of the solder due to the dispersion hardening as well as solderability of the solder. This paper introduces the nano-reinforced solders, including its principles, types, and various properties.

Keywords

nano-reinforced solder, lead-free, intermetallic compound, solderability, mechanical properties

Aluminum alloys and their joining methods

Do-hyun Jung, Jae Pil Jung†

Department of Materials Science and Engineering, University of Seoul, 163, Seoulsiripdae-ro, Dongdaemun-gu, Seoul 02504, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 9-18.

Abstract

Aluminum (Al) and its alloys have been used widely in a variety of industries such as structural, electronic, aerospace, and particularly automotive industries due to their lightweight characteristic, outstanding ductility, formability, high oxidation and corrosion resistance, and high thermal and electrical conductivity. Al have different kinds of alloys according to the various additional elements system and they should be selected properly depending on their effectiveness and suitability for their particular purpose. The major elements for Al alloys are silicon (Si), magnesium (Mg), manganese (Mn), copper (Cu), and zinc (Zn). In order for Al alloys to use for each industry, it is necessary to study of Al to Al joining and/or the Al to dissimilar materials joining to combine the individual parts into one. Many studies on joining technologies about Al to Al and Al to dissimilar materials have been performed such as press joining, bolted joint, welding, soldering, riveting, adhesive bonding, and brazing. This study reviews a variety of Al alloys and their joining method including its principles and properties with recent trends.

Keywords

aluminum, joining, dissimilar materials, welding, brazing

Ultra-thin aluminum thin films deposited by DC magnetron sputtering for the applications in flexible transparent electrodes

Daekyun Kim, Dooho Choi†

School of Advanced Materials Engineering, Dong-Eui University, 176 Eomgwangro, Busan 47340, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 19-24.

Abstract

광전소자용 투명전극으로 적용하기 위한 초박형 Al 박막에 대한 기초연구를 수행하였다. 유리 기판 상에 3-12 nm의 두께를 가지는 Al 박막을 형성하였으며, 박막의 두께가 7 nm 이상일 때부터 면저항이 측정되었으며 두께가 증가할 때 면저항이 점진적으로 감소하였다. 박막 내 그레인 크기(Grain size)는 두께가 증가할수록 비례하여 증가하였다. 광 투과도의 경우 가시광선영역(380~770 nm) 파장 기준으로, 3 nm 박막 두께에서 평균 85%의 투과도가 측정된 데 반하여, 4, 5 nm 두께에서 평균 50, 60%로 급격하게 감소되기 시작하며 그 이후 두께 증가에 따라 투과도가 점진적으로 감소하였다. 본 연구결과는 향후 Oxide/Metal/Oxide(OMO) 구조의 고투과, 저저항 투명전극 적용을 위한 기초 결과로 활용될 것으로 기대된다.
In this study, the feasibility of Al-based transparent electrodes for optoelectronic devices was investigated. Al thin films having thickness in the range of 3-12 nm were deposited on glass substrates, and sheet resistance was measured for films thicker than 7 nm and the values continue to decrease with increasing film thickness. The grain size in the films was found to increase with increasing grain size. 85% visible light transmittance was measured at the thickness of 3 nm, and decreased to 50% and 60% when the film thickness reaches 4 nm and 5 nm, respectively. The results of this study can be used in the applications of oxide/metal/oxide type transparent electrodes.

Keywords

Sputtering, Aluminum, Thin film growth, Transparent electrode, Electrical resistance

Properties of Lead-free Solder Joints on Flexible Substrate for Automotive Electronics

Sungdo Ahn1, Kyeonggon Choi2, Dae Young Park1, 2, Gyu-Won Jeong1, 3, Seungju Baek1, 4, Yong-Ho Ko1, †

1Joining R&D Group, Korea Institute of Industrial Technology, 156, Gaetbeol-ro, Yeonsu-gu, Incheon 21999, Korea 2Department of Material Science and Engineering, Inha University, 40, Soseong-ro, Michuhol-gu, Incheon 22201, Korea 3School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Korea 4Dept. of Materials Science and Engineering, Incheon National University, 119, Academy-ro, Yeonsu-gu, Incheon 22012, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 25-30.

Abstract

Sn-Pb솔더는 그동안 자동차 전장품에서 많이 사용되어 왔다. 그러나 최근에 환경과 인체에 대한 유해성 때문에 end-of-life vehicle (ELV)과 같은 국제 환경 규제로 인하여 Pb의 사용이 금지되었다. 이러한 이유로 자동차 전장품을 위한 Pb-free 솔더링에 관한 많은 연구들이 보고 되어 왔다. 한편, 자동차의 연료 효율성과 공간 활용을 위하여 유연성과 경량의 특성을 가지는 플렉시블 기판이 자동차 전장품에 사용되고 있다. 자동차 전장품에 대한 Pb-free 솔더 접합부 특성에 관한 연구들이 많이 진행되었음에도 불구하고 자동차의 사용 환경을 고려한 플렉시블 기판 솔더 접합부에 대한 신뢰성 특성에 관한 연구는 아직 부족한 실정이다. 본 연구에서는 organic solderability preservative (OSP) 및 electroless nickel immersion gold (ENIG) 표면처리 된 플렉시블 기판 위 Sn3.0Ag0.5Cu, Sn0.7Cu, Sn0.5Cu0.01Al(Si) 세 가지 Pb-free 솔더 접합부에 대한 특성을 보고 하였다. 솔더 조성과 기판 표면처리에 따른 접합부의 특성 및 신뢰성을 비교 평가 하기 위하여 인장 강도 시험, 열 충격 시험과 반복 굽힘 시험을 진행 하고 그 결과를 분석하였다. OSP 표면처리 된 기판 접합부에 대한 반복 굽힘 시험 결과 세 종류의 솔더 접합부 모두 파괴는 솔더 내부에서 일어 났으며 Sn3.0Ag0.5Cu 솔더의 접합부에서 반복 굽힘 수명이 가장 길게 나타났다.
Sn-Pb solder has been used in automotive electronics for decades. However, recently, due to the environmental and health concerns, some international environmental organizations such as the end-of-life vehicle (ELV) enacted legislation banning of the Pb usage in automotive electronics. For this reason, many studies to develop and promote Pb-free soldering have been significantly reported. Meanwhile, because of flexibility and lightweight, flexible printed circuit boards (FPCBs) have been increasingly used in automotive electronics for lightweight to improve fuel efficiency and space utilization. Although the properties of lead-free solders for automotive electronics have been widely studied, there is a lack of research on the reliability performance of the lead-free solder joint on FPCB under user conditions. This study reported the properties of solder joints between Pb-free solders such as Sn3.0Ag0.5Cu, Sn0.7Cu and Sn0.5Cu0.01Al (Si), and various FPCBs finished with organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG). To evaluate on joint properties and reliabilities with different solder compositions and surface-finishing materials, pull strength test, thermal shock test, and bending cycle test were performed and analyzed. After the bending cycle test of solder joint on OSP-finishing, the fractures were occurred in solder and the lifetime of Sn3.0Ag0.5Cu solder joint was the longest.

Keywords

Pb-free solder, flexible printed circuit board, OSP, ENIG, thermal shock test, bending cycle test

Aluminum based ZnO/Al/ZnO flexible Transparent Electrodes Fabricated by Magnetron sputtering

GeumHyuck Bang, Dooho Choi†

School of Advanced Materials Engineering, Dong-Eui University, 176 Eomgwangro, Busan 47340, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 31-34.

Abstract

차세대 유연 광전소자 적용을 위한 금속-산화물 샌드위치 구조인 ZnO/Al/ZnO 박막의 유연투명전극 기초연구를 수행하였다. 모든 증착은 유연성을 가지는 PET 기판 상에서 이루어졌으며, 상·하부 ZnO층의 두께가 광 투과도에 미치는 영향을 확인하기 위하여 Al 층의 두께는 모두 8 nm로 고정시킨 채 상부 ZnO 층의 두께는 5-70 nm, 하부 ZnO 층의 두께는 2.5-20 nm까지 변화를 주었다. 가시광선영역(380 nm-770 nm) 파장대를 가지는 광원의 투과도에 대하여 측정한 결과, 상부 ZnO 층의 두께가 30 nm이며 하부 ZnO 층의 경우 2.5 nm 일 때 가장 높은 투과도를 보였다. 400 nm 파장기준 투과도 62%, 면저항 19 Ω/□, 그리고 곡률반경 5 mm 조건에서의 휨 테스트 후 면저항과 투과도의 변화가 발생하지 않는 ZnO/Al/ZnO 유연투명전극 결과를 보고한다.
In this study, the feasibility of ZnO/Al/ZnO flexible transparent electrodes for future flexible optoelectronic devices was investigated. All depositions were performed on PET substrates. The thicknesses of the top and bottom ZnO layers were 5-70 nm and 2.5-20 nm, respectively. The highest visible light transmittance was recorded when the thicknesses of the top and bottom ZnO layers 30 nm and 2.5 nm, respectively. 62% optical transmittance (at the wavelength of 400 nm) and sheet resistance of 19 Ω/□ were measured. After repetitive bending test at a curvature radius of 5 mm, the transmittance and sheet resistance did not change.

Keywords

Sputtering, Aluminum, ZnO, Thin film, Transparent electrode

Research on Fabrication of Silicon Lens for Optical Communication by Photolithography Process

Junseong Park1, 2, Daejang Lee1, Hokyun Rho1, Sunggeun Kim1, Jaeyeong Heo1, Sangwan Ryu1, Sung-Ju Kang2, †, Jun-Seok Ha1, 2, †

1Optoelectronics Convergence Research Center, Chonnam National University, 77 Yong-bong-ro, Buk-gu, Gwangju 61186, Korea 2School of Chemical Engineering, Chonnam National University, 77 Yong-bong-ro, Buk-gu, Gwangju 61186, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 35-40.

Abstract

광결합 효율(Fiber coupling efficiency)을 개선하기 위해서는 Laser diode에서 넓은 각도로 방출된 빛을 광섬유의 중심(Core) 부분으로 모아주는 집광렌즈(Collimating lens)가 필수적이다. 현재 사용되는 집광렌즈는 형틀(Mold)을 이용한 글래스 몰드(Glass mold) 공법이 널리 사용되고 있다. 이 방식은 생산단가가 저렴하지만, 정교한 성형이 어렵고 구면수차와 같은 품질문제가 있다. 본 연구는 기존의 글래스 몰드 공법을 반도체 공정으로 대체함으로써 표면 가공의 정밀도를 높이고, 렌즈의 재질 또한 반도체 공정에 적합한 실리콘으로 변경하였다. 반도체공정은 PR을 이용한 포토리소그래피(Photolithography) 공정과 플라즈마를 이용한 건식 식각(Dry etching) 공정으로 구성된다. 광결합 효율은 실리콘 렌즈의 광학적 특성을 평가하기 위해 초정밀 정렬 시스템을 사용하여 측정되었다. 그 결과, 렌즈 직경 220 μm 일 때의 최대 광결합 효율은 50%로 측정되었고, 렌즈 직경 210-240 μm 범위에서는 최고 광결합 효율 대비 5% 이하의 광결합 특성저하를 보여줌을 확인하였다.
In order to improve the coupling efficiency, a collimator lens that collects the light emitted from the laser diode at a wide angle to the core of the optical fiber is essential. Glass mold method using a mold is widely used as a collimator lens currently used. Although this method is inexpensive to produce, it is difficult to form precisely and quality problems such as spherical aberration. In this study, the precision of surface processing was improved by replacing the existing glass mold method with the semiconductor process, and the material of the lens was changed to silicon suitable for the semiconductor process. The semiconductor process consists of a photolithography process using PR and a dry etching process using plasma. The optical coupling efficiency was measured using an ultra-precision alignment system for the evaluation of the optical characteristics of the silicon lens. As a result, the optical coupling efficiency was 50% when the lens diameter was 220 μm, and the optical coupling property was 5% or less with respect to the maximum optical coupling efficiency in the lens diameter range of 210-240 μm.

Keywords

Silicon Lens, Aspherical Lens, Optical Coupling Efficiency, Reflow, Photolithography, Dry Etching

Comparison of Quantitative Interfacial Adhesion Energy Measurement Method between Copper RDL and WPR Dielectric Interface for FOWLP Applications

Gahui Kim1, Jina Lee1, Se-hoon Park2, Sumin Kang3, Taek-Soo Kim3, Young-Bae Park1, †

1School of Materials Science and Engineering, Andong National University, 1375 Gyeongdong-ro, Andong-si, Gyeongsangbuk-do 36729, Korea 2ICT device Packaging Research Center, Korea Electronics Technology Institute, 25 Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, Korea 3Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291, Daehak-ro, Yuseong-gu, Daejeon 34141, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 41-48.

Abstract

Fan-out wafer level packaging (FOWLP) 적용을 위한 최적의 Cu 재배선 계면접착에너지 측정방법을 도출하기 위해, 전기도금 Cu 박막과 WPR 절연층 계면의 정량적 계면접착에너지를 90° 필 테스트, 4점 굽힘 시험법, double cantilever beam (DCB) 측정법을 통해 비교 평가 하였다. 측정 결과, 세 가지 측정법 모두 배선 및 패키징 공정 후 박리가 일어나지 않는 산업체 통용 기준인 5 J/m2보다 높게 측정되었다. 또한, DCB, 4점 굽힘 시험법, 90° 필 테스트 순으로 계면접착에너지가 증가하는 거동을 보였는데, 이는 계면파괴역학 이론에 의해 위상각 증가에 따라 이종재료 계면균열 선단의 전단응력성분 증가에 따른 소성변형에너지 및 계면 거칠기 증가 효과에 의한 것으로 설명이 가능하다. FOWLP 재배선에 대한 최적의 계면접착에너지 도출을 위해서는 시편제작 공정, 위상각 차이, 정량적 측정 정확도 및 결합력 크기 등을 고려하여 4점 굽힘 시험법 또는 DCB 측정법을 적절히 혼용 사용하는 것이 타당한 것으로 판단된다.
The quantitative interfacial adhesion energy measurement method of copper redistribution layer and WPR dielectric interface were investigated using 90° peel test, 4-point bending test, double cantilever beam (DCB) measurement for FOWLP Applications. Measured interfacial adhesion energy values of all three methods were higher than 5 J/m2, which is considered as a minimum criterion for reliable Cu/low-k integration with CMP processes without delamination. Measured energy values increase with increasing phase angle, that is, in order of DCB, 4-point bending test, and 90° peel test due to increasing roughness-related shielding and plastic energy dissipation effects, which match well interfacial fracture mechanics theory. Considering adhesion specimen preparation process, phase angle, measurement accuracy and bonding energy levels, both DCB and 4-point bending test methods are recommended for quantitative adhesion energy measurement of RDL interface depending on the real application situations.

Keywords

Fan-out wafer level packaging, Interfacial adhesion energy, Peel test, 4-point bending test, Double cantilever beam test

Effect of Si grinding on electrical properties of sputtered tin oxide thin films

Seungbum Cho, Sarah Eunkyung Kim†

Graduate School of Nano-IT Design Convergence, Seoul National University of Science and Technology, 232, Gongneung-ro, Nowon-gu, Seoul 01811, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 49-53.

Abstract

최근 유연 소자, 투명 소자, MEMS 소자와 같은 다양한 소자를 결합하는 시스템 집적화 기술이 많이 개발되고 있다. 이러한 다종 소자 시스템 제조 기술의 핵심 공정은 칩 또는 웨이퍼 레벨의 접합 공정, 기판 연삭 공정, 그리고 박막 기판 핸들링 기술이라 하겠다. 본 연구에서는 Si 기판 연삭 공정이 투명 박막 트랜지스터나 유연 전극 소재로 적용되는 산화주석 박막의 전기적 성질에 미치는 영향을 분석하였다. Si 기판의 두께가 얇아질수록 Si d-spacing은 감소하였고, Si 격자 내에 strain이 발생하였다. 또한, Si 기판의 두께가 얇아질수록 산화주석 박막 내 캐리어 농도가 감소하여 전기전도도가 감소하였다. 얇은 산화 주석 박막의 경우 전기전도도는 두꺼운 산화 주석 박막보다 낮았으며 Si 기판의 두께에 의해 크게 변하지 않았다.
Recently, technologies for integrating various devices such as a flexible device, a transparent device, and a MEMS device have been developed. The key processes of heterogeneous device manufacturing technology are chip or wafer-level bonding process, substrate grinding process, and thin substrate handling process. In this study, the effect of Si substrate grinding process on the electrical properties of tin oxide thin films applied as transparent thin film transistor or flexible electrode material was investigated. As the Si substrate thickness became thinner, the Si d-spacing decreased and strains occurred in the Si lattice. Also, as the Si substrate thickness became thinner, the electric conductivity of tin oxide thin film decreased due to the lower carrier concentration. In the case of the thinner tin oxide thin film, the electrical conductivity was lower than that of the thicker tin oxide thin film and did not change much by the thickness of Si substrate.

Keywords

tin oxide, Si grinding, lattice strain, stacked thin film

Vol. 25 No.3

Dependence of Doping on Indium Content in InGaN/GaN Multiple Quantum Wells for Effective Water Splitting

Hyojung Bae1, Seung Wan Bang2, Jin-Woo Ju3, Jun-Seok Ha1, 2, †

1Optoelectronics Convergence Research Center, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Korea 2School of Applied Chemical Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Korea 3Photonic Device Research Center, Korea Photonics Technology Institute, Gwangju 61007, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 1-5.

Abstract

본 연구에서는 InGaN/GaN multi quantum well (MQW)에서 Indium (In) 도핑효과에 따른 광전기화학적 특성을 관찰하였다. 기판으로는 Sapphire을 사용하였고, 각 Quantum well (QW)을 구성하고 있는 InGaN의 조성을 다르게 하였다. 투과도 측정 결과 일정한 In 조성을 가진 InGaN/GaN MQW에 비해 각 QW의 In 조성을 다르게 한 InGaN/GaN MQW에서 흡수도가 향상되는 것을 확인할 수 있었다. 이는 각각 다른 In 조성을 가진 InGaN 층이 더 넓은 영역의 스펙트럼 에너지를 가지는 빛을 흡수하기 때문인 것으로 생각된다. 광학적 특성을 평가하기 위해 진행한 상온 photoluminescence (PL) 실험을 진행한 결과, 역시 다양한 In 조성을 가진 InGaN/GaN MQW이 더 넓은 파장에서 발광이 나타나는 것을 확인할 수 있었다. 이들 샘플에 대한 광전기화학적 특성평가를 통하여, gradation In 조성을 가지고 있는 InGaN/GaN MQW이 일정한 In 조성을 가지는 InGaN/GaN MQW에 비해 광전기화학적 물분해 능력이 월등히 향상됨을 확인하였다.
In this study, the effects of indium (In) doping in InGaN/GaN multi quantum well (MQW) on photoelectrochemical (PEC) properties were investigated. Each quantum well (QW) layer with controlled In content were grown on sapphire substrate. Before growth of MQW, GaN growth consisted of various stages in the following order: buffer GaN growth, undoped GaN growth, and Si-doped n-type GaN growth. Absorbance of InGaN/GaN MQW having different In composition was higher than that of the InGaN/GaN MQW having a constant In composition. It indicates that InGaN layer having different In composition absorbs light having a broad spectrum energy. These results are in agreement with those in photoluminescence (PL). After evaluation of PEC properties, it demonstrated that InGaN/GaN MQW having different In composition was improved InGaN/GaN MQW having constant In composition in PEC water splitting ability.

Keywords

InGaN/GaN, Multi quantum well, Photoelectrochemical, Water splitting, Hydrogen generation.

Effect of Post-annealing on the Interfacial adhesion Energy of Cu thin Film and ALD Ru Diffusion Barrier Layer

Minsu Jeong1, Hyeonchul Lee2, Byung-Hyun Bae3, Kirak Son5, Gahui Kim5, Seung-Joon Lee4, Soo-Hyun Kim4, Young-Bae Park5, †

1Amkor Technology Korea Inc., 150, Songdomirae-ro, Yeonsu-gu, Incheon 21991, Korea 2STATS ChipPAC Korea LTD., 191, Jayumuyeok-ro, Jung-gu, Incheon 22379, Korea 3VITZROTECH Co., Ltd., 327, Byeolmang-ro, Danwon-gu, Ansan-si, Gyeonggi-do 15603, Korea 4School of Materials Science and Engineering, Yeungnam University, 280, Daehak-ro, Gyeongsan-si, Gyeongsangbuk-do 38541, Korea 5School of Materials Science and Engineering, Andong National University, 1375, Gyeongdong-ro, Andong-si, Gyeongsangbuk-do 36729, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 7-12.

Abstract

차세대 초미세 Cu 배선 적용을 위한 원자층증착법(atomic layer deposition, ALD)을 이용하여 증착된 Ru확산 방지층과 Cu 박막 사이의 계면 신뢰성을 평가하기 위해, Ru 공정온도 및 200°C 후속 열처리 시간에 따라 4점굽힘시험으로 정량적인 계면접착에너지를 평가하였고, 박리계면을 분석하였다. 225, 270, 310°C 세 가지 ALD Ru 공정온도에 따른 계면접착에너지는 각각 8.55, 9.37, 8.96 J/m2로 유사한 값을 보였는데, 이는 증착온도 변화에 따라 Ru 결정립 크기 등 미세조직 및 비저항의 차이가 적어서, 계면 특성도 거의 차이가 없는 것으로 판단된다. 225°C의 공정온도에서 증착된 Ru 박막의 계면접착에너지는 200°C 후속 열처리시 250시간까지는 7.59 J/m2 이상으로 유지되었으나, 500시간 후에는 1.40 J/m2로 급격히 감소하였다. 박리계면에 대한 X-선 광전자 분광기 분석 결과, 500시간 후 Cu 계면 산화로 인하여 계면접착 에너지가 감소한 것으로 확인되었다. 따라서 ALD Ru 박막은 계면신뢰성이 양호한 차세대 Cu 배선용 확산방지층 후보가 된다고 판단된다.
The effects of Ru deposition temperature and post-annealing conditions on the interfacial adhesion energies of atomic layer deposited (ALD) Ru diffusion barrier layer and Cu thin films for the advanced Cu interconnects applications were systematically investigated. The initial interfacial adhesion energies were 8.55, 9.37, 8.96 J/m2 for the sample deposited at 225, 270, and 310°C, respectively, which are closely related to the similar microstructures and resistivities of Ru films for ALD Ru deposition temperature variations. And the interfacial adhesion energies showed the relatively stable high values over 7.59 J/m2 until 250h during post-annealing at 200°C, while dramatically decreased to 1.40 J/m2 after 500 h. The X-ray photoelectron spectroscopy Cu 2p peak separation analysis showed that there exists good correlation between the interfacial adhesion energy and the interfacial CuO formation. Therefore, ALD Ru seems to be a promising diffusion barrier candidate with reliable interfacial reliability for advanced Cu interconnects.

Keywords

Cu interconnect, ALD, Ru, 4-point bending test, interfacial adhesion energy.

Optimization of Soldering Process of Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu-1.6Bi-0.2In Alloys for Solar Combiner Junction Box Module

Byung-Suk Lee1, Chul-Min Oh2, Hyun Kwak3, Tae-Woo Kim3, Heui-Bog Yun3, Jeong-Won Yoon1, 4, †

1Welding and Joining R&D Group, Korea Institute of Industrial Technology (KITECH), 156, Gaetbeol-ro, Yeonsu-gu, Incheon 21999, Korea 2Eletronic Convergence Material & Device Research Center, Korea Electronics Technology Institute (KETI), 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, Korea 3MIRAE E & I, 33, Digital-ro 9-gil, Geumcheon-gu, Seoul 08511, Korea 4Critical Materials and Semiconductor Packaging Engineering, University of Science and Technology (UST), 217, Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 13-19.

Abstract

본 연구에서는 태양광 접속함 모듈 적용을 위한 유연 솔더(Sn-Pb) 및 무연 솔더(Sn-3.0Ag-0.5Cu 및 Sn-1.0Ag-0.7Cu-1.6Bi-0.2In)의 특성을 비교 평가하였다. 접속함 내에는 전압 및 전류 검출용 모듈, 고내압용 다이오드가 실장된 정류모듈 등 다양한 모듈이 내장되어있다. 본 연구에서는 솔더링특성, 인쇄성, 솔더형상 검사, X-ray를 이용한 솔더 내 void 검사 및 접합강도를 측정하였고, 무연 솔더 합금의 공정최적화는 step 1과 step 2로 구분하여 검토를 실시하였다. Step 1은 유연 솔더와 무연 솔더 페이스트 인쇄 검사 시험을 1차와 2차로 나누어 실험을 진행하였고 printability는 void 함량 및 접합강도의 상관관계로 검토하였다. 전체적으로 유연 솔더의 특성은 무연 솔더에 비하여 상대적으로 우수하였다. Step 2는 리플로우 공정의 최고점 온도 변화에 따른 접합부 특성 변화를 관찰하였다. 리플로우 최고 온도가 증가할수록 접합부 내의 void 함량이 2~4% 정도 감소하였고, 접합강도는 약 0.5 kgf 범위내에서 큰 차이 없이 나타났다. 기판 표면처리종류에 있어서는 ENIG 표면처리가 OSP 및 Pb-free 솔더 표면처리보다 우수한 접합강도를 나타내었다. 1종류의 무연솔더와 OSP 표면처리로 접합된 태양광 접속함 모듈의 500 싸이클 열충격 신뢰성시험 전후에 전기적 특성변화는 0.3% 내의 범위에서 안정적으로 작동함을 확인하였다.
The soldering property of Pb-containing solder(Sn-Pb) and Pb-free solders(Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu-1.6Bi-0.2In) for solar combiner box module was compared. The solar combiner box module was composed of voltage and current detecting modules, diode modules, and other modules. In this study, solder paste printability, printing shape inspection, solder joint property, X-ray inspection, and shear force measurements were conducted. For optimization of Pb-free soldering process, step 1 and 2 were divided. In the step 1 process, the printability of Pb-containing and Pb-free solder alloys were estimated by using printing inspector. Then, the relationship between void percentages and shear force has been estimated. Overall, the property of Pb-containing solder was better than two Pb-free solders. In the step 2 process, the property of reflow soldering for the Pb-free solders was evaluated with different reflow peak temperatures. As the peak temperature of the reflow process gradually increased, the void percentage decreased by 2 to 4%, but the shear force did not significantly depend on the reflow peak temperature by a deviation of about 0.5 kgf. Among different surface finishes on PCB, ENIG surface finish was better than OSP and Pb-free solder surface finishes in terms of shear force. In the hermal shock reliability test of the solar combiner box module with a Pb-free solder and OSP surface finish, the change rate of electrical property of the module was almost unchanged within a 0.3% range and the module had a relatively good electrical property after 500 thermal shock cycles.

Keywords

Sn-Pb solder, Sn-3.0Ag-0.5Cu, Sn-1.0Ag-0.7Cu-1.6Bi-0.2In, Reflow temperature, Surface finish.

Improvement in Thermomechanical Reliability of Power Conversion Modules Using SiC Power Semiconductors: A Comparison of SiC and Si via FEM Simulation

Cheolgyu Kim1, Chulmin Oh2, Yunhwa Choi3, Kyung-Oun Jang4, Taek-Soo Kim1, †

1Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291, Daehak-ro, Yuseong-gu, Daejeon 34141, Korea 2Electronic Convergence Material & Device Research Center, Korea Electronic Technology Institute, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, Korea 3JMJ Korea Co., Ltd., 102, Gilju-ro 425beon-gil, Bucheon-si, Gyeonggi-do 14487, Korea 4Power conversion, Fairchild Semiconductor Ltd., 55, Pyeongcheon-ro 850beon-gil, Bucheon-si, Gyeonggi-do 14487, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 21-30.

Abstract

Driven by the recent energy saving trend, conventional silicon based power conversion modules are being replaced by modules using silicon carbide. Previous papers have focused mainly on the electrical advantages of silicon carbide semiconductors that can be used to design switching devices with much lower losses than conventional silicon based devices. However, no systematic study of their thermomechanical reliability in power conversion modules using finite element method (FEM) simulation has been presented. In this paper, silicon and silicon carbide based power devices with three-phase switching were designed and compared from the viewpoint of thermomechanical reliability. The switching loss of power conversion module was measured by the switching loss evaluation system and measured switching loss data was used for the thermal FEM simulation. Temperature and stress/strain distributions were analyzed. Finally, a thermal fatigue simulation was conducted to analyze the creep phenomenon of the joining materials. It was shown that at the working frequency of 20 kHz, the maximum temperature and stress of the power conversion module with SiC chips were reduced by 56% and 47%, respectively, compared with Si chips. In addition, the creep equivalent strain of joining material in SiC chip was reduced by 53% after thermal cycle, compared with the joining material in Si chip.

Keywords

Power conversion module, silicon carbide (SiC), switching loss, thermal FEM simulation, thermomechanical reliability.

A Study of Failure Mechanism through abnormal AlXOY Layer after pressure Cooker Test for DRAM device

Deuk-Sung Choi†, Seung-Hyun Jeong, Chae-Hyoung Choi

Division. of Electronics & Information Engineering, Yeungnam University College, Hyeonchung-ro 170, Nam-gu, Daegu 42415, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 31-36.

Abstract

본 연구에서는 DRAM 소자의 Pressure Cooker Test (PCT) 신뢰성 평가 후 발생한 불량 원인에 대한 연구를 진행하였다. 불량 시료의 물리적 관측 결과 변색, Al의 부식 및 손실, 그리고 금속 간 중간 절연막 박리 등이 관측되었다. 추가 물리적 화학적 분석 결과 비정상적인 물질인 AlXOY 층을 발견하였다. 불량 원인을 파악 하기 위해 package ball 크기 실험 및 보호막 pin hole 등의 연관성 실험을 진행하였으나 원인으로 판명되지 않았다. 또한 EMC 물질에 포함되어 있는 Cl에 의한 Al 할로겐화 평가를 진행하였다. 진행 결과 약간의 개선 효과를 보였지만 완벽한 문제 해결을 이루어 내지 못했다. Galvanic corrosion 가능성 가설을 세웠고, 면밀한 분석 결과 pad open 지역에서 Ti 잔존물을 발견할 수 있었다. 검증 실험으로 repair 식각 분리 실험을 진행하여 개선 효과를 보았다. 개선 된 조건에서 PCT 신뢰성 기준치를 만족 하는 결과를 얻었다. 금번 PCT 불량 메카니즘은 다음과 같이 설명할 수 있다. 공정 repair etch시 Ti 잔류물이 남아 Galvanic 메커니즘에 의해 Al이 이온화 된다. 이온화 된 Al이 후속 PCT 신뢰성 측정 시 H2O와 반응하여 비 정상 물질인 AlXOY를 생성하였다.
This research scrutinizes the reason of failure after pressure cooker test (PCT) for DRAM device. We use the physical inspecting tools, such as microscope, SEM and TEM, and finally find the discolor phenomenon, corrosion of Al and delamination of inter-metal dielectric (IMD) in the failed devices after PCT. Furthermore, we discover the abnormal AlXOY layer on Al through the careful additional measurements. To find the reason, we evaluate the effect of package ball size and pinhole in passivation layer. Unfortunately, those aren`t related to the problems. We also estimate halide effect of Al. The halogens such like Cl are contained within EMC material. Those result in the slight improving of PCT characteristics but do not perfectly solve the problems. We make a hypothesis of Galvanic corrosion. We can find the residue of Ti at the edge of pad open area. We can see the improving the PCT characteristics by the time split of repair etch. The possible mechanism of the PCT failure can be deduced as such following sequence of reactions. The remained Ti reacts on the pad Al by Galvanic corrosion. The ionized Al is easily react with the H2O supplied under PCT environment, and finally transfers to the abnormal AlXOY layer.

Keywords

Pressure Cooker Test (PCT), reliability test, aluminum corrosion, abnormal AlxOY layer, delamination, halide, Galvanic corrosion.

Fabrication of Fluorescent Oxygen Sensor Probe Module Based on Planner Lightwave Circuits using UV Imprint Lithography

Ki Do Ahn, Seung hun Oh†

Korea Electronics Technology Institute (KETI), 226 Chemdandwagi-ro, Buk-gu Gwangju 61011, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 37-41.

Abstract

본 논문에서는 UV 임프린트 기반의 평면 광 회로층을 이용한 산소농도 검출용 집적형 형광 프로브 모듈을 제안하였다. 제안된 형광 프로부 모듈은 광원과 형광 신호를 고효율로 전송할 수 있게 동일 광 경로를 가지는 비대칭 1×2 빔 분배기 형태로 설계되었으며, 이를 UV 임프린트 공정을 통해 제작하였다. 제작된 광 회로층의 끝단에 최적의 형광 염료 농도로 센서막을 코팅하여 산소 농도 검출용 광학 프로브 모듈을 구현하였다. 제작된 형광 프로부 모듈을 이용한 산소 농도 측정용 센서 시스템은 0%에서 20%의 가스 농도 범위에서 약 0.3%의 분해능까지 산소 농도를 검출 할 수 있었다. 이러한, 평면 광회로 기반의 형광 프로브 모듈은 저가의 집적형 산소 센서 검출 시스템을 가능하게 하여, 화학분야, 바이오 분야, 그리고 대기 및 수질 환경을 모니터링 하는 분야에 적용될 수 있을 것으로 기대된다.
This paper presents the integrated fluorescent oxygen sensor probe module based on planner lightwave circuits using UV imprint lithography. The oxygen sensor system is consisted of the optical source part, optical detector part and optical sensing probe part to be composed of the planner lightwave circuit and oxygen sensitive thin film layer. Firstly, we optimally designed the planner lightwave circuit with asymmetric 1×2 beam splitter using beam propagation method. Then, we fabricated the planner lightwave circuits using UV imprint lithography process. This planner lightwave circuits transmitted the optical power with 76% efficiency and the fluorescence signal with 70% efficiency. The oxygen sensitive thin film layer is coated on the end face of planner lightwave circuit. The oxygen sensor system using this sensor probe module with planner lightwave circuit could measure the concentration with 0.3% resolution from 0% to 20% gas range. This optical oxygen sensor probe module make it possible to compact, simple and cheap measurement system.

Keywords

Oxygen sensor probe module, UV imprint lithography, Fluorescence signal, Planner lightwave circuits.

Wearable Resistive Strain Sensor Networked by Wireless Data Transfer System

Je-Heon Oh, Sung-Ju Lee, Hae-Rin Shin, Seung-Rok Kim, Ju-Hyun Yoo, Jin-Woo Park†

Department of Materials Science and Engineering, College of Engineering, Yonsei University, 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 43-47.

Abstract

본 연구에서는 silver nanowire (AgNW)를 polydimethylsiloxane (PDMS) 기판에 embedding하여 손가락 움직임을 전기 신호로 읽을 수 있는 투명 저항식 변형 센서를 제작하였다. 이후 bluetooth를 이용한 무선 통신의 방식으로 변형 센서가 내는 데이터를 컴퓨터와 스마트폰 앱으로 전송하는 근거리 통신을 가능하게 하였다. 최종적으로 데이터 가공공정을 통하여 스마트폰 앱으로 변형 센서에 의한 손가락 움직임을 읽고 이미지를 변환시키는 프로그램을 제작하여 컴퓨터와 스마트폰 앱으로 확인하였다.
In this study, we fabricated transparent resistive strain sensor by embedding silver nanowire in polydimethylsiloxane (PDMS) substrate to sense the finger bending motion electrically. Using bluetooth as wireless data transfer system, strain data was transferred to computer and smart phone application enabling near field communication. Additionally, we made a program translating resistance change by finger motion strain to save images and confirmed that it worked at application and computer.

Keywords

Wireless data transfer, Silver nanowire, Polydimethylsiloxane, Strain sensor, Bluetooth.

Durability of Nano-/micro- Pt Line Patterns Formed on Flexible Substrate

Tae Wan Park, Young Joong Choi, Woon Ik Park†

Electronic Convergence Materials Division, Korea Institute of Ceramic Engineering & Technology, Jinju 52851, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 49-53.

Abstract

정렬된 미세 패턴을 형성하는 기술은 차세대 전자소자를 제작함에 있어서 기틀이 되는 기반기술이기 때문에, 최근 더욱 미세한 패턴을 구현하기 위하여 많은 노력들이 이루어지고 있다. 그 중, 본 연구에서는 패터닝 공정에 있어서 비용이 저렴하고 단시간 내에 고해상도 미세패턴의 형성이 가능한 장점을 갖는 나노 패턴전사 프린팅 공정을 이용하였다. 투명하고 유연한 기판 위에 250 nm, 500 nm, 그리고 1 μm의 선폭을 갖는 Pt 금속 라인 패턴을 성공적으로 형성하였으며, 벤딩기기를 사용하여 500회 벤딩평가 후 패턴의 파괴가 일어나는지에 대한 내구성을 평가하였고, 전자현미경을 통하여 분석하였다. 벤딩 전과 후의 패턴에 대한 손상 여부에 대하여 확인한 결과, 다양한 선폭의 금속 라인 패턴이 초기 상태와 변함없이 형상을 유지할 뿐만 아니라, 패턴주기 또한 안정적으로 유지됨을 확인할 수 있었다. 이러한 결과를 볼 때, 나노 패턴 전사 프린팅 공정은 다양한 금속 패턴을 형성하는데 매우 유용하다고 판단되며, 향후 차세대 유연 전자소자 또는 배선 및 인터커넥션 기술로 응용이 가능할 것으로 기대된다.
Since various methods to form well-aligned nano-/micro- patterns are underlying technologies to fabricate next generation wearable electronic devices, many efforts have been made to realize finer patterns in recent years. Among lots of patterning methods, the present invention includes a nano-transfer printing (n-TP) process which is advantageous in that a processing cost is low and high-resolution patterns can be formed within a short processing time. We successfully achieved pattern formation of highly ordered Pt lines with line-width of 250 nm, 500 nm, and 1 μm on transparent and flexible substrates. In addition, we analyzed the durability of the patterns, showing excellent stability of line-shape even after a physical and repeated bending test of 500 times using a bending machine. As a result, it is expected that a n-TP process is very useful for forming various metal patterns, and it is also expected to be applied to wiring and interconnection technology of next generation flexible electronic devices.

Keywords

Metal line pattern, Nano-transfer printing, Bending test, Durability.

Analysis of Shear Stress Type Piezoresistive Characteristics in Silicon Diaphragm Structure

Chae-Hyoung Choi1, †, Deuk-Sung Choi1, Chang-Hoi Ahn2

1Division. of Electronics & Information Engineering, Yeungnam University College, Hyeonchung-ro 170, Nam-gu, Daegu 42415, Korea 2Department of Electronic Engineering, Yeungnam University, 280 Deahak-Ro, Gyeongsan, Gyeongbuk 38541, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 55-59.

Abstract

본 연구에서는 Si/SiO2/Si-sub 구조의 SDB (silicon-direct-bonding) 웨어퍼 상에 형성된 다이아프램(diaphragm)에 제조된 전단응력형 압전저항 특성을 분석하였다. 다이아프램은 MEMS (Microelectromechanical System) 기술을 이용해 형성하였다. TMAH 수용액을 이용해 웨이퍼 후면을 식각하여 형성된 다이아프램 구조는 각종 센서제작에 활용할 수 있다. 본 연구에서는 다이아프램 상에 형성시킨 전단응력형 압전저항의 최적의 형상조건을 ANSYS 시뮬레이션을 통하여 찾고 실제 반도체 미세가공기술을 이용해 다이아프램 구조를 형성시키고 이에 붕소(boron)을 주입하여 형성시킨 전단응력형 압전저항의 특성을 시뮬레이션 결과와 비교 분석하였다. 압력감지 다이아프램은 정방형으로 제조되었다. 다이아프램의 모서리의 중심부에서 동일한 압력에 대한 최대 전단응력은 구조물이 정방형일 때 발생한다는 것을 실험으로 확인할 수 있었다. 따라서 압전저항은 다이아프램의 가장자리 중앙에 위치시켰다. 제조된 전단응력형 압전저항은 시뮬레이션 결과와 잘 일치하였고 2200 μm × 2200 μm 크기의 다이아프램에 형성된 압전저항의 감도는 183.7 μV/kPa로 나타났으며 0~100 kPa 범위의 압력에서 1.3%FS의 선형성을 가졌으며 감도의 대칭성 또한 우수하게 나타났다.
In this paper, we investigated the characteristics of shear stress type piezoresistor on a diaphragm structure formed by MEMS (Microelectromechanical System) technology of silicon-direct-bonding (SDB) wafers with Si/SiO2/Si-sub. The diaphragm structure formed by etching the backside of the wafer using a TMAH aqueous solution can be used for manufacturing various sensors. In this study, the optimum shape condition of the shear stress type piezoresistor formed on the diaphragm is found through ANSYS simulation, and the diaphragm structure is formed by using the semiconductor microfabrication technique and the shear stress formed by boron implantation. The characteristics of the piezoelectric resistance are compared with the simulation results. The sensing diaphragm was made in the shape of an exact square. It has been experimentally found that the maximum shear stress for the same pressure at the center of the edge of the diaphragm is generated when the structure is in the exact square shape. Thus, the sensing part of the sensor has been designed to be placed at the center of the edge of the diaphragm. The prepared shear stress type piezoresistor was in good agreement with the simulation results, and the sensitivity of the piezoresistor formed on the 2200 μm × 2200 μm diaphragm was 183.7 μV/kPa and the linearity of 1.3 %FS at the pressure range of 0~100 kPa and the symmetry of sensitivity was also excellent.

Keywords

MEMS, SDB wafer, TMAH aqueous solution, exact square diaphragm structure, shear stress type piezoresistor, ANSYS simulation.

A Study on the Self-annealing Characteristics of Electroplated Copper Thin Film for DRAM Integrated Process

Deuk-Sung Choi†, Seung-Hyun Jeong

Division. of Electronics & Information Engineering, Yeungnam University College, Hyeonchung-ro 170, Nam-gu, Daegu 42415, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 61-66.

Abstract

본 연구에서는 DRAM 제조 집적공정의 금속배선으로 사용하는 구리의 자기 열처리(self-annealing) 후 박막 특성 변화에 대한 연구를 진행하였다. 구리를 증착하고 상온에서 시간이 경과하면 구리가 성장하여 결정체 크기 변화가 생기는데 이를 자기 열처리라고 부른다. 구리 금속의 증착은 전기 도금법(electroplating)을 사용하였다. 구리 도금액으로 유기 첨가물이 다른 두 가지 시료인 기준 도금액과 평가 도금액 두 용액에 대해 평가 하였다. 자기 열처리 시간이 경과함에 따라 시간에 대해 면 저항 값의 변화가 없는 영역과 이후 급격하게 떨어지는 구간으로 나누어지고 최종적으로 포화면 저항 값을 보인다. 최종적인 면 저항 값은 초기 값 대비 20% 개선 효과를 보인다. 평가 전해액의 자기 열처리 효과가 기준 용액 대비 더 빠른 시간 안에 이루어졌는데 이는 유기 첨가물의 차이 때문이다. 개선의 효과 분석으로 TEM 장비를 이용하여 결정체 변화를 관찰하였고 자기 열처리 공정에 의해 효과적인 결정체 성장이 이루어졌음을 발견했다. 또한 단면 TEM 측정 결과 자기 열처리 된 시료는 전류 방향으로의 결정체 경계면 숫자가 줄어드는 bamboo 구조를 보인다. 열적 열하 특성(thermal excursion characteristics) 측정 결과 고온 열처리 대비 자기 열처리 시료가 hillock 특성이 보이지 않고 이는 박막의 신뢰성 특성을 향상 시킨다. Electron backscattered diffraction (EBSD) 측정 결과 결정체가 2 μm까지 성장한 결정체를 관찰하였고 스트레스에 의한 void를 억제하는데 유리한 (100) 면 비중이 증가하는 방향으로 결정체 성장이 이루어짐을 알 수 있다.
This research scrutinizes the self-annealing characteristics of copper used to metal interconnection for application of DRAM fabrication process. As the time goes after the copper deposited, the grain of copper is growing. It is called self-annealing. We use the electroplating method for copper deposition and estimate two kinds of electroplating chemicals having different organic additives. As the time of self-annealing is elapsed, sheet resistance decreases with logarithmic dependence of time and is finally saturated. The improvement of sheet resistance is approximately 20%. The saturation time of experimental sample is shorter than that of reference sample. We can find that self-annealing is highly efficient in grain growth of copper through the measurement of TEM analysis. The structure of copper grain is similar to the bamboo type useful for current flow. The results of thermal excursion characteristics show that the reliability of self-annealed sample is better than that of sample annealed at higher temperature. The self-annealed sample is not contained in hillock. The self-annealed samples grow until 2 μm and develop in [100] direction more favorable for reliability.

Keywords

self-annealing, electroplated copper, DRAM process integration, sheet resistance, reliability, thermal excursion characteristics.

Fabrication Process and Power Generation Characteristics of Thermoelectric Thin Film Devices for Micro Energy Harvesting

Tae Sung Oh†

Department of Materials Science and Engineering, Hongik University, 94, Wausan-ro, Mapo-gu, Seoul 04066, Korea

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 67-74.

Abstract

두께 2.5~10 μm인 n형 Bi2Te3와 p형 Sb2Te3 레그 8쌍으로 구성되어 있는 in-plane형 열전박막소자를 전기도금법으로 Si submounts에 형성하고, LED 칩의 구동에 의해 발생하는 겉보기 온도차 ΔT와 레그 두께에 따른 발전특성을 분석하였다. LED 방출열에 의해 인가된 ΔT가 7.4K일 때 각기 두께 2.5 μm, 5 μm 및 10 μm의 p-n 레그들로 구성된 열전박막소자는 6.1 mV, 7.4 mV 및 11.8 mV의 open circuit 전압을 나타내었으며, 6.6 nW, 12.8 nW 및 41.9 nW의 최대 출력전력을 나타내었다.
Thermoelectric thin film devices of the in-plane configuration consisting of 8 pairs of n-type Bi2Te3 and p-type Sb2Te3 legs were processed on Si submounts by electrodeposition. The thermoelectric generation characteristics of the thin film devices were investigated with respect to the apparent temperature difference ΔT caused by LED lighting as well as the change of the leg thickness. When ΔT was 7.4 K, the open circuit voltages of 6.1 mV, 7.4 mV, and 11.8 mV and the maximum output powers of 6.6 nW, 12.8 nW, and 41.9 nW were measured for the devices with the thermoelectric legs of which thickness were 2.5 μm, 5 μm, and 10 μm, respectively.

Keywords

thermoelectrics, energy harvesting, LED, thin films, electrodeposition.

Vol. 25 No.4

Organic-inorganic Hybrid Dielectric with UV Patterning and UV Curing for Global Interconnect Applications

Changmin Song1, Haesung Park2, Hankyeol Seo3, Sarah Eunkyung Kim1, †

1Graduate School of Nano-IT Design Convergence, Seoul National University of Science and Technology 2Department of Mechanical Engineering, Seoul National University of Science and Technology 3Media IT Engineering Program, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 1-7.

Abstract

As the performance and density of IC (integrated circuit) devices increase, power and signal integrities in the global interconnects of advanced packaging technologies are becoming more difficult. Thus, the global interconnect technologies should be designed to accommodate increased input/output (I/O) counts, improved power grid network integrity, reduced RC delay, and improved electrical crosstalk stability. This requirement resulted in the fine-pitch interconnects with a low-k dielectric in 3D packaging or wafer level packaging structure. This paper reviews an organic-inorganic hybrid material as a potential dielectric candidate for the global interconnects. An organic-inorganic hybrid material called polysiloxane can provide spin process without high temperature curing, an excellent dielectric constant, and good mechanical properties.

Keywords

Dielectric, PSSQ, Global Interconnect, UV Curing, Metallization.

Transient Liquid Phase Diffusion Bonding Technology for Power Semiconductor Packaging

Jeong-Hyun Lee1, Do-hyun Jung2, Jae-Pil Jung1, †

1Department of Materials Science and Engineering, University of Seoul 2Lightweight Materials Technology Center

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 9-15.

Abstract

This paper shows the principles and characteristics of the transient liquid phase (TLP) bonding technology for power modules packaging. The power module is semiconductor parts that change and manage power entering electronic devices, and demand is increasing due to the advent of the fourth industrial revolution. Higher operation temperatures and increasing current density are important for the performance of power modules. Conventional power modules using Si chip have reached the limit of theoretical performance development. In addition, their efficiency is reduced at high temperature because of the low properties of Si. Therefore, Si is changed to silicon carbide (SiC) and gallium nitride (GaN). Various methods of bonding have been studied, like Ag sintering and Sn-Au solder, to keep up with the development of chips, one of which is TLP bonding. TLP bonding has the advantages in price and junction temperature over other technologies. In this paper, TLP bonding using various materials and methods is introduced. In addition, new TLP technologies that are combined with other technologies such as metal powder mixing and ultrasonic technology are also reviewed.

Keywords

Transient liquid phase bonding, Power module, High temperature, SiC, Solder.

High Technology and Latest Trends of WBG Power Semiconductors

Jeong-Hyun Lee, Do-hyun Jung1, Seung-jin Oh2, Jae-Pil Jung

Department of Materials Science and Engineering, University of Seoul 1Lightweight Materials Technology Center 2Duksan Hi-Metal Co. Ltd.

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 17-23.

Abstract

Recently, electric semiconductors became an issue because of efficient use of energy and compaction of electronics. Silicon electric semiconductors are difficult to put into it because of its physical limitations. Hence, the study of WBG (Wideband Gap) semiconductors like SiC and GaN began. These devices received attention because it can be miniaturized and worked at high temperatures over 300°C. WBG MOSFET electric semiconductors can show performance like silicon IGBT. This can solve the current problem of IGBT tail. The current study shows the technical principles and issues related to SiC and GaN power semiconductors. WBG devices can achieve high performance compared to silicon, but its performance can’t be fully utilized because of lack in bonding technology. Therefore, this review introduces research on WBG devices and their packaging issues.

Keywords

WBG, SiC, GaN, Power semiconductor, Power module.

Technology of Stretchable Interconnector and Strain Sensors for Stretchable Electronics

Jin Yeong Park1, Won Jae Lee1, Hyun Jin Nam2, Sung-Hoon Choa1, †

1Graduate School of Nano IT Design Fusion, Seoul National University of Science and Technology 2Dept. Of Manufacturing System and Design Engineering, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 25-34.

Abstract

In this paper, we review the latest technical progress and commercialization of stretchable interconnectors, stretchable strain sensors, and stretchable substrates for stretchable electronics. The development of stretchable electronics can pave a way for new applications such as wearable devices, bio-integrated devices, healthcare and monitoring, and soft robotics. The essential components of stretchable electronic devices are stretchable interconnector and stretchable substrate. Stretchable interconnector should have high stretchability and high electrical conductivity as well as stability under severe mechanical deformation. Therefore several nanocomposite-based materials using CNT, graphene, nanowire, and metal flake have been developed. Geometric engineering such as wavy, serpentine, buckled and mesh structure has been well developed. Stretchable substrate should also pose high stretchability and compatibility with stretchable sensing or interconnecting material. We summarize the recent research results of new materials for stretchable interconnector and substrate as well as strain sensors. The Important challenges in development of the stretchable interconnector and substrate are also briefly discussed.

Keywords

Stretchable electronics, Interconnector, Strain sensor, Stretchable substrate.

Synthesis of Organic-inorganic Core-shell Nanoparticle Powder using Immersion Annealing Process

Young Joong Choi, Hyunsung Jung, Jiwon Bang, Woon Ik Park

Electronic Convergence Materials Division, Korea Institute of Ceramic Engineering & Technology (KICET)

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 35-40.

Abstract

다양한 디바이스 응용분야에 블록공중합체가 사용되기 위해, 블록공중합체의 형상을 제어하기 위한 간단하면서도 실용적인 합성방법이 필요하다. 하지만 콜로이드성의 형판을 사용하는 기존의 방식은 공정이 복합하고 비용이 많이 발생하여, 고순도의 코어-쉘 나노입자를 대량생산하기에 적합하지 않다. 본 논문에서 PS-b-PDMS 블록공중합체를 담금 어닐링하여, 20 nm 이하크기를 가지는 PS가 봉입된 코어-쉘 구조의 SiOx나노입자를 합성하였다. 또한, 어닐링 공정에 사용되는 헵테인과 에탄올의 혼합비율이 자기조립된 PS-b-PDMS 블록공중합체 나노입자의 형상에 어떠한 영향을 미치는지 분석하였으며, 최적의 담금어닐링 조건에서 나노입자가 worm-like구조로 변화하는 것을 확인하였다. 이러한 파우더 합성법은 다른 용매기반의 블록공중합체 합성방법에 응용이 가능할 것으로 생각되며, 새로운 가이드라인을 제공할 것으로 예상된다.
Simple and useful synthetic process to control the morphology of block copolymers (BCPs) is required for implementation in various device applications. However, the conventional method to use colloidal templates is not enough to realize the production of pure and massive core-shell nanoparticles due to the cost-intensive complex process. Here, we introduce a novel and facile synthesis method to realize the formation of core-shell SiOx nanoparticle power by employing an immersion annealing of a sphere-forming poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) BCP. We successfully obtained a PS-encapsulated SiOx nanoparticle with a diameter of ~20 nm. In addition, we analyzed how the mixing ratio of heptane/ethanol affects the BCP morphology of self-assembled PS-b-PDMS nanoparticles, showing a worm-like structure under the optimum immersion conditions. This useful approach is expected to be extendable to other solvent-based BCP synthesis, providing a new guideline for unique BCP production.

Keywords

block copolymer, core-shell, immersion annealing, morphology control.

Process Induced Warpage Simulation for Panel Level Package

Ayoung Moon, Sungdong Kim

Department of Mechanical System Design Engineering, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 41-45.

Abstract

패널 레벨 패키지(Panel Level Package)에서 공정 단계별로 발생하는 휨(warpage)에 대해 유한요소법을 이용하여 전산모사를 진행하였다. 5 × 5 mm2 크기의 실리콘 칩이 총 221개가 포함된 122.4 × 93.6 mm2 크기의 패널에 대해서 ① EMC 몰딩, ② detach core 부착, ③ 가열, ④ 캐리어 분리, ⑤ 냉각의 5 단계에 대해서 해석을 수행하였으며, 캐리어와 detach core 소재로 유리와 FR4의 조합이 휨 현상에 미치는 영향을 조사하였다. 캐리어 및 detach core의 소재에 따라 공정 단계별로 휨의 경향이 다르게 나타나고 있으나, 최종적으로는 유리를 캐리어로 사용하는 경우에 detach core의 소재와 관계없이 FR4 캐리어에 비해 낮은 휨 값을 나타내었으며 유리 캐리어와 유리 detach core의 조합에서 가장 낮은 휨값이 관찰되었다.
We have simulated the process induced warpage for panel level package using finite element method. Silicon chips of 5 × 5 mm2 were redistributed on 122.4 × 93.6 mm2 size panel and the total number of redistributed chips was 221. The warpage at each process step, for example, ① EMC molding, ② attachment of detach core, ③ heating, ④ removal of a carrier, and ⑤ cooling was simulated using ANSYS and the effects of detach core and carrier materials on the warpage were investigated. The warpage behaved complexly depending on the materials for the detach core and carrier. However, glass carrier showed the lower warpage than FR4 carrier regardless of detach core material, and the minimum warpage was observed when the glass was used for the detach core and carrier at the same time.

Keywords

warpage, FEM, PLP, carrier, detach core.

Durability Improvement of Functional Polymer Film by Heat Treatment and Micro/nano Hierarchical Structure for Display Applications

N. E. Yeo1, W. K. Cho1, D.-I. Kim2, M. Y. Jeong1, 3, †

1Department of Cogno-Mechatronics Engineering, Pusan National University 2Opto-mechatronics Research Institute, Pusan National University 3Department of Opto-Mechatronics Engineering, Pusan National University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 47-52.

Abstract

본 연구에서는 디스플레이에 적용되는 기능성 고분자 필름의 나노구조에 의한 기계적 물성 저하 문제를 해결하기 위해 열처리 방법과 멀티스케일 계층구조를 통한 PMMA(Poly(methyl-methacrylate)) 필름의 내구성 향상에 대해 연구하였다. PMMA 필름의 기계적 특성을 향상시키기 위한 열처리 공정은 고온/고압의 자유제적 제어공정과 고온 공정 후 급속히 냉각시키는 공정으로 구성되어 있으며, 열 나노임프린트를 이용하여 스크래치로부터 나노구조를 보호하기 위한 멀티스케일 계층구조를 형성하였다. 연필경도 시험에 의해 발생한 미세구조의 손상에 대한 평가를 위해 표면 형상 변화와 기능성 변화를 평가하였으며, 이를 통하여 열처리와 멀티스케일 계층구조가 스크래치에 의한 정접촉각 감소와 투과율 손실 저감에 효과적임을 확인하였다.
In this study, the effects of the heat treatment and multi-scale hierarchical structures on the durability of the nano-patterned functional PMMA(Poly(methyl-methacrylate)) film was evaluated. The heat treatments that consisted of high-pressure/high-temperature flat pressing and rapid cooling process were employed to improve mechanical property of the PMMA films. Multi-scale hierarchical structures were fabricated by thermal nanoimprint to protect nano-scale structures from the scratch. Examination on surface structures and functionalities such as wetting angle and transmittance revealed that the preopposed heat treatment and multi-scale hierarchical structures are effective to minimize surface damages.

Keywords

Anti-scratch performance, Nano-pattern, Multiscale-pattern, Heat treatments, Residual stresses.

Study of Organic-inorganic Hybrid Dielectric for the use of Redistribution Layers in Fan-out Wafer Level Packaging

Changmin Song, Sarah Eunkyung Kim

Graduate school of Nano-IT Design Convergence, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 53-58.

Abstract

집적회로 소자의 축소가 물리적 한계에 도달 한 이후 3D 패키징, 임베디드 패키징 및 팬 아웃 웨이퍼 레벨 패키징(FOWLP, fan-out wafer level packaging)과 같은 혁신적인 패키징 기술들이 활발히 연구되고 있다. 본 연구에서는 FOWLP의 다층 재배선(redistribution layer)에 사용하기 위한 유무기 하이브리드 유전체 소재의 공정을 평가하였다. 폴리이미드(PI) 또는 폴리파라페닐렌벤조비스옥사졸(PBO)과 같은 현 유기 유전체와 비교하여 폴리실세스키옥산(polysilsesquioxane, PSSQ)라고 불리는 유무기 하이브리드 유전체는 기계적, 열적 및 전기적 안정성을 향상시킬 수 있고, UV 노광을 통하여 경화 공정과 패턴 공정을 동시에 할 수 있는 장점이 있다. 폴리실세스키옥산 용액을 6 인치 Si 웨이퍼에 스핀 코팅한 후 pre-baking과 UV 노광 공정을 이용하여 패턴 및 경화를 진행하였다. 10분의 UV 노광 시간으로 경화와 2 μm 라인 패턴 형성이 동시에 진행됨을 확인하였고, 경화된 폴리실세스키옥산 유전체의 유전상수는 2.0에서 2.4 로 측정되었다. 폴리실세스키옥산 소재를 이용하여 고온 경화 공정없이 UV 노광 공정만으로 경화와 패턴을 할 수 있는 공정 가능성을 보였다.
Since the scaling-down of IC devices has been reached to their physical limitations, several innovative packaging technologies such as 3D packaging, embedded packaging, and fan-out wafer level packaging (FOWLP) are actively studied. In this study the fabrication of organic-inorganic dielectric material was evaluated for the use of multistructured redistribution layers (RDL) in FOWLP. Compared to current organic dielectrics such as PI or PBO an organicinorganic hybrid dielectric called polysilsesquioxane (PSSQ) can improve mechanical, thermal, and electrical stabilities. polysilsesquioxane has also an excellent advantage of simultaneous curing and patterning through UV exposure. The polysilsesquioxane samples were fabricated by spin-coating on 6-inch Si wafer followed by pre-baking and UV exposure. With the 10 minutes of UV exposure polysilsesquioxane was fully cured and showed 2 μm line-pattern formation. And the dielectric constant of cured polysilsesquioxane dielectrics was ranged from 2.0 to 2.4. It has been demonstrated that polysilsesquioxane dielectric can be patterned and cured by UV exposure alone without a high temperature curing process.

Keywords

FOWLP, polysilsesquioxane, Hybrid dielectrics, Redistribution layer, UV curing.

Comparison of Thermal Energy Harvesting Characteristics of Thermoelectric Thin-Film Modules with Different Thin-Film Leg Diameters

Woo-Jun Kim, Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 67-74.

Abstract

두께가 20 μm 이며, 직경이 각기 100 μm, 300 μm, 500 μm인 p형 Sb2Te3와 n형 Bi2Te3 박막레그들을 전기도금하여 열전박막모듈을 형성한 후, 박막레그의 직경에 따른 출력전압과 출력전력을 비교하였다. 100 μm 직경 박막레그들로 구성된 모듈은 ΔT = 36.7K에서 365 mV, 300 μm 직경 박막레그들로 형성한 모듈은 ΔT = 37.5K에서 142 mV, 500 μm 직경 박막레그들로 제작한 모듈은 ΔT = 36.1K에서 53 mV의 open circuit 전압을 나타내었다. 100 μm 직경 박막레그 모듈은 ΔT = 36.7K에서 845 μW, 300 μm 직경 박막레그 모듈은 ΔT = 37.5K에서 631 μW, 500 μm 직경 박막레그 모듈은 ΔT = 36.1K에서 276 μW의 최대출력전력을 나타내었다.
Thermoelectric thin film modules were fabricated by electroplating p-type Sb2Te3 and n-type Bi2Te3 thin film legs with the same thickness of 20 μm and different diameters of 100 μm, 300 μm, and 500 μm, respectively. The output voltage and output power of thin film modules were measured and compared as a function of the leg diameter. The modules processed with thin film legs of 100 μm, 300 μm, and 500 μm-diameter exhibited open circuit voltages of 365 mV at ΔT = 36.7K, 142 mV at ΔT = 37.5K, and 53 mV at ΔT = 36.1K, respectively. Maximum output powers of 845 μW at ΔT = 36.7K, 631 μW at ΔT = 37.5K, and 276 μW at ΔT = 36.1K were obtained for the modules fabricated with the thin film legs of 100 μm, 300 μm, and 500 μm-diameter, respectively.

Keywords

thermoelectrics, energy harvesting, leg diameter, thin film, electrodeposition.

Structural Characteristics of Ar-N2 Plasma Treatment on Cu Surface

Hae-Sung Park1, Sarah Eunkyung Kim2, †

1Department of Mechanical Engineering, Seoul National University of Science and Technology 2Graduate School of Nano-IT Design Convergence, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 75-81.

Abstract

Cu-Cu 웨이퍼 본딩 강도를 향상시키기 위한 Cu 박막의 표면처리 기술로 Ar-N2 플라즈마 처리 공정에 대해 연구하였다. Ar-N2 플라즈마 처리가 Cu 표면의 구조적 특성에 미치는 영향을 X선 회절분석법, X선 광전자 분광법, 원자간력현미경을 이용하여 분석하였다. Ar 가스는 플라즈마 점화 및 이온 충격에 의한 Cu 표면의 활성화에 사용되고, N2 가스는 패시베이션(passivation) 층을 형성하여 −O 또는 −OH와 같은 오염으로부터 Cu 표면을 보호하기 위한 목적으로 사용되었다. Ar 분압이 높은 플라즈마로 처리한 시험편은 표면이 활성화되어 공정 이후 더 많은 산화가 진행되었고, N2 분압이 높은 플라즈마 시험편에서는 Cu-N 및 Cu-O-N과 같은 패시베이션 층과 함께 상대적으로 낮은 수치의 산화도가 관찰되었다. 본 연구에서는 Ar-N2 플라즈마 처리가 Cu 표면에서 Cu-O 형성 억제 반응에 기여하는 것을 확인할 수 있었으나 추가 연구를 통하여 질소 패시베이션 층이 Cu 웨이퍼 전면에 형성되기 위한 플라즈마 가스 분압 최적화를 진행하고자 한다.
The effect of Ar-N2 plasma treatment on Cu surface as one of solutions to realize reliable Cu-Cu wafer bonding was investigated. Structural characteristic of Ar-N2 plasma treated Cu surface were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscope. Ar gas was used for a plasma ignition and to activate Cu surface by ion bombardment, and N2 gas was used to protect the Cu surface from contamination such as −O or −OH by forming a passivation layer. The Cu specimen under high Ar partial pressure plasma treatment showed more copper oxide due to the activation on Cu surface, while Cu surface after high N2 gas partial pressure plasma treatment showed less copper oxide due to the formation of Cu-N or Cu-O-N passivation layer. It was confirmed that nitrogen plasma can prohibit Cu-O formation on Cu surface, but nitrogen partial pressure in the Ar-N2 plasma should be optimized for the formation of nitrogen passivation layer on the entire surface of Cu wafer.

Keywords

Ar-N2 plasma, Nitride passivation, Cu-Cu bonding, Wafer level bonding.

Effect of NCF Trap on Electromigration Characteristics of Cu/Ni/Sn-Ag Microbumps

Hyodong Ryu1, Byeong-Rok Lee2, Jun-beom Kim3, Young-Bae Park1, †

1School of Materials Science and Engineering, Andong National University 2STATS ChipPAC Korea Ltd. 3HANA Micron Inc.

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 83-88.

Abstract

Cu/Ni/Sn-Ag 미세범프 접합 공정후 Ni/Sn-Ag접합계면에 잔류한 비전도성 필름(non-conductive film, NCF) trap 형성이 전기적 신뢰성에 미치는 영향을 분석하기 위해 온도 150°C, 전류밀도 1.5 × 105 A/cm2 조건에서 electromigration(EM) 신뢰성 실험을 진행하였다. EM 신뢰성 실험 결과, NCF trap이 거의 없는 Cu/Ni/Sn-Ag 미세범프가 NCF trap 이 형성된 미세범프 보다 약 8배 긴 EM 수명을 보여주고 있다. 저항 변화 및 손상계면에 대한 미세구조 분석결과, Ni/Sn-Ag접합계면에 공정 이슈에 의해 형성된 NCF trap이 Ni-Sn 금속간화합물/Sn-Ag솔더계면에 보이드를 유발하여 EM 원자 확산을 방해하기 때문에 빠른 보이드 성장에 의한 전기적 손상이 일찍 발생하는 것으로 판단된다.
The electromigration (EM) tests were performed at 150°C with 1.5 × 105 A/cm2 conditions in order to investigate the effect of non-conductive film (NCF) trap on the electrical reliability of Cu/Ni/Sn-Ag microbumps. The EM failure time of Cu/Ni/Sn-Ag microbump with NCF trap was around 8 times shorter than Cu/Ni/Sn-Ag microbump without NCF trap. From systematic analysis on the electrical resistance and failed interfaces, the trapped NCF-induced voids at the Sn-Ag/Ni-Sn intermetallic compound interface lead to faster EM void growth and earlier open failure.

Keywords

non-conductive film, underfill, Cu/Ni/Sn-Ag microbump, intermetallic compound, electromigration.

Comparative Study on the Characteristics of Heat Dissipation using Silicon Carbide (SiC) Powder Semiconductor Module

Cheong-Ha Jung, Won Seo, Gu-Sung Kim

Electronic Packaging Research Center, Kangnam University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 89-93.

Abstract

1200V 이상 급의 전기자동차의 파워 모듈에 적용되는 세라믹 기판은 구동 전력으로 고전력이 인가되는 특성상 고열전도도, 고 전기절연성, 저열팽창계수, 급격한 온도 변화에 대한 저항성의 특성이 요구된다. 방열기판에 적용되는 세라믹 중 질화알루미늄과 질화규소는 그 요구를 충족하는 소재로서 고려되고 있다. 이에 따라 본 논문에서는 질화알루미늄과 질화규소의 방열기판 소재로서의 특성을 상용해석프로그램을 통해 비교하였다. 그 결과 질화규소는 질화알루미늄에 대해 각각 동일한 조건의 열을 부여하는 공정을 시물레이션으로 구현했을 때 스트레스와 휨이 덜 발생하여 더 우세한 내충격성, 내stress성을 보였다. 열전도도 측면에서는 질화알루미늄이 방열 소재로서 더 우수한 특성을 지니지만 신뢰성 측면에서는 질화규소가 더 우세함을 시물레이션을 통해 관찰하였다.
Ceramic substrates applied to power modules of electric vehicles are required to have properties of high thermal conductivity, high electrical insulation, low thermal expansion coefficient and resistance to abrupt temperature change due to high power applied by driving power. Aluminum nitride and silicon nitride, which are applied to heat dissipation, are considered as materials meeting their needs. Therefore, in this paper, the properties of aluminum nitride and silicon nitride as radiator plate materials were compared through a commercial analysis program. As a result, when the process of applying heat of the same condition to aluminum nitride was implemented by simulation, the silicon nitride exhibited superior impact resistance and stress resistance due to less stress and warping. In terms of thermal conductivity, aluminum nitride has superior properties as a heat dissipation material, but silicon nitride is more dominant in terms of reliability.

Keywords

Silicon Nitride, Aluminum Nitride, SiC Semiconductor.

High Thermal Conductivity h-BN/PVA Composite Films for High Power Electronic Packaging Substrate

Seong Tae Lee, Chi Heon Kim, Hyo Tae Kim

Nano Materials and Convergence Center, Korea Institute of Ceramic Engineering and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 95-99.

Abstract

최근 고집적 고출력 전자 패키지의 효율적인 열전달을 위한 기판 및 방열소재로서 절연성 고열전도 필름의 수요가 커지고 있어, 알루미나, 질화알루미늄, 질화보론, 탄소나노튜브 및 그래핀 등의 고열전도 필러소재를 사용한 고방열 복합소재에 대한 많은 연구가 이루어지고 있다. 그 중에서도 육방정 질화보론(h-BN) 나노시트가 절연성 고열전도 필러 소재로서 유력한 후보 물질로 선택되고 있다. 본 연구는 이 h-BN 나노시트와 PVA로 된 세라믹/폴리머 복합체 필름의 방열특성 향상에 관한 것이다. h-BN 나노시트는 h-BN 플레이크 원료 분말을 유기용매를 사용한 볼밀링과 초음파 처리에 의한 물리적 박리공정으로 만들었으며, 이를 사용한 h-BN/PVA 복합 필름을 제조한 결과 성형된 복합필름의 면방향과 두께방향 열전도도는 50 vol%의 필러함량에서 각각 2.8 W/m·K 및 10 W/m·K 의 높은 열전도도가 나타났다. 이 복합필름을 PVA의 유리전이온도 이상에서 일축 가압하여 h-BN 판상분말의 얼라인먼트를 향상시킴으로써 면방향 열전도도를 최대 13.5 W/m·K까지 증가시킬 수 있었다.
High thermal conductivity films with electrically insulating properties have a great potential for the effective heat transfer as substrate and thermal interface materials in high density and high power electronic packages. There have been lots of studies to achieve high thermal conductivity composites using high thermal conductivity fillers such alumina, aluminum nitride, boron nitride, CNT and graphene, recently. Among them, hexagonal-boron nitride (h-BN) nano-sheet is a promising candidate for high thermal conductivity with electrically insulating filler material. This work presents an enhanced heat transfer properties of ceramic/polymer composite films using h-BN nano-sheets and PVA polymer resins. The h-BN nano-sheets were prepared by a mechanical exfoliation of h-BN flakes using organic media and subsequent ultrasonic treatment. High thermal conductivities over 2.8 W/m·K for transverse and 10 W/m·K for in-plane direction of the cast films were achieved for casted h-BN/PVA composite films. Further improvement of thermal conductivity up to 13.5 W/m·K at in-plane mode was achieved by applying uniaxial compression at the temperature above glass transition of PVA to enhance the alignment of the h-BN nano-sheets.

Keywords

Boron nitride, nano-sheets, polyvinyl alcohol, composites, packaging substrate.

Joule-heating Induced Crystallization (JIC) of Amorphous Silicon Films

Da-Yeong Ko, Jae-Sang Ro

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 101-104.

Abstract

An electric field was applied to a Mo conductive layer in the sandwiched structure of glass/SiO2/Mo/SiO2/a-Si to induce Joule heating in order to generate the intense heat needed to carry out the crystallization of amorphous silicon. Polycrystalline silicon was produced via Joule heating through a solid state transformation. Blanket crystallization was accomplished within the range of millisecond, thus demonstrating the possibility of a new crystallization route for amorphous silicon films. The grain size of JIC poly-Si can be varied from few tens of nanometers to the one having the larger grain size exceeding that of excimer laser crystallized (ELC) poly-Si according to transmission electron microscopy. We report here the blanket crystallization of amorphous silicon films using the 2nd generation glass substrate.

Keywords

Crystallization, Thin Film Transistor, Poly-Si, Joule-heating, AMOLED.

Improvement of Electrochemical Reduction Characteristics of Carbon Dioxide at Porous Copper Electrode using Graphene

Seung Wan Bang1, Hokyun Rho1, Hyojung Bae2, Sung-Ju Kang1, †, Jun-Seok Ha1, 2, †

1Department of Advanced Chemicals & Engineering, Chonnam National University 2Optoelectronics Convergence Research Center, Chonnam National University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 105-109.

Abstract

본 연구는 구리의 이산화탄소 환원 촉매 특성을 향상시키기 위해 전극 촉매 물질인 다공성 구리에 그래핀을 적용하였다. Thermal Chemical Vapor Deposition(TCVD)법을 이용하여 직접적으로 그래핀이 혼합된 다공성 구리를 제조하였다. 0.1 M KHCO3 전해액을 사용하여, −1.0 V ~ −1.4 V의 인가전위로 전기화학 실험을 수행한 결과, 그래핀이 혼합된 다공성 구리 전극의 전류 밀도는 다공성 구리에 비해 1.8 배 이상 증가하였다. 생성물을 평가한 결과, 다공성 구리 전극에서 CO와 H2만 생성된 반면 그래핀이 포함된 다공성 구리의 생성물은 CO 뿐만이 아닌 CH4와 C2H4가 생성되었다. 이는 그래핀으로 인해 이산화탄소 흡착 시간이 길어짐으로써 반응 중 생성된 중간체들이 전극 표면에 머무르는 시간이 길어졌으며, 결과적으로 C2 화합물 생성 반응까지 연속적으로 진행될 수 있었다고 판단된다.
We studied graphene synthesis to porous Cu to improve the characteristics of carbon dioxide reduction of cu. Cu powders were formed through Thermal Chemical Vapor Deposition(TCVD) to Porous Cu/Graphene structures synthesized with graphene. As a result of electrochemical experiments using a 0.1 M KHCO3 electrolyte at an applied potential of −1.0 V to −1.4 V, the current density of Porous Cu/Graphene was 1.8 times higher than that of Porous Cu. As a result of evaluating the product, CO and H2 were generated to Porous Cu electrode. On the other hand, the product of porous Cu/Graphene produced CO, CH4 and C2H4. It is considered that the graphene causes longer carbon dioxide adsorption time, which means that the intermediates formed during the reaction remain on the electrode surface for a longer time. As a result, it can be concluded that the production reaction of the C2 compound could be continuously performed.

Keywords

Copper, Porous, Electrochemical, Carbon dioxide, Graphene.

Interfacial Adhesion Enhancement Process of Local Stiffness-variant Stretchable Substrates for Stretchable Electronic Packages

Donghyeun Park, Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 111-118.

Abstract

강성도가 서로 다른 두 polydimethylsiloxane (PDMS) 탄성고분자와 flexible printed circuit board (FPCB)로 이루어진 soft PDMS/hard PDMS/FPCB 구조의 강성도 국부변환 신축기판을 개발하기 위해 PDMS와 FPCB를 acrylic-silicone 양면테이프를 사용하여 접합한 후 접합공정에 따른 PDMS/FPCB 계면접착력을 분석하였다. 완전 경화된 PDMS에 acrylic-silicone 양면테이프의 silicone 접착제로 접착한 FPCB의 pull 강도는 259 kPa이었으며, pull 시험시 PDMS와 silicone 접착제 사이에서 박리가 발생하였다. 반면에 60°C에서 15~20분 유지하여 반경화시킨 PDMS에 acrylic-silicone 양면테이프의 silicone 접착제로 FPCB를 접착 후 60°C에서 12시간 유지하여 PDMS를 완전 경화시키면 pull 강도가 1,007~1,094 kPa로 크게 향상되었으며, pull 시험시 계면 박리가 acrylic-silicone 양면테이프의 acrylic 접착제와 FPCB 사이에서 발생하였다.
In order to develop a local stiffness-variant stretchable substrate with the soft PDMS/hard PDMS/FPCB configuration consisting of two stiffness-different polydimethylsiloxane (PDMS) parts and flexible printed circuit board, a FPCB was bonded to PDMS using the acrylic-silicone double-sided tape and the interfacial adhesion of the PDMS/FPCB was evaluated. The pull strength of the FPCB, which was bonded to the fully cured PDMS using the silicone adhesive of the double-sided tape, was 259 kPa and the delamination during the pull test occurred at the interface between the PDMS and the silicone adhesive. On the contrary, the bonding process, for which the FPCB was bonded using the silicone adhesive to the PDMS partially cured for 15~20 minutes at 60°C and then the PDMS was fully cured for 12 hours at 60°C, exhibited the remarkably enhanced pull strength of 1,007~1,094 kPa. With the above mentioned bonding process, the delamination during the pull test was observed at the interface between the FPCB and the acrylic adhesive of the acrylic-silicone double sided tape.

Keywords

stretchable packaging, stretchable substrate, PDMS, FPCB, adhesion silicone adhesive.

Optical Properties of All Solution processed ZnO/Ag/ZnO Multilayers

Hyungin Lee, Jiwan Kim

Department of Advanced Materials Engineering, Kyonggi University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 119-122.

Abstract

본 논문은 용액공정으로 제작한 ZnO/Ag/ZnO 다층구조의 투과도에 대해 연구하였다. 다양한 두께의 ZnO/Ag/ZnO 다층구조를 스핀코팅을 이용해 제작하였고 광학적 특성을 측정하였다. ZnO는 졸겔법으로 제작하였고 Ag는 Ag 용액을 이용해 스핀코팅으로 증착하였다. 최적화된 Ag 두께를 찾기 위해 Ag 용액의 농도, 스핀코팅의 회전속도를 조절하고 두께와 면저항을 측정하였다. ZnO/Ag/ZnO 다층구조의 투과도는 가시광 영역에서 최대 63%까지 증가하였다. 적외선 영역에서 ZnO/Ag/ZnO 다층구조의 투과도는 Ag 용액의 농도가 2.5wt%일 때 투과도가 35%까지 감소하였다.
Various ZnO/Ag/ZnO multilayers were fabricated and their optical properties were investigated. Top and bottom ZnO layers were formed by sol-gel method and mid-metal layers were deposited by spin coating. To find suitable deposition condition of Ag, we measure thickness and sheet resistance of Ag monolayer. After the optimization of Ag monolayer, we fabricate ZnO/Ag/ZnO multilayers. Transmittance of ZnO/Ag/ZnO multilayers increased to 63%. In near IR region, transmittance of ZnO/Ag/ZnO multilayers decreased to 35% when the concentration of Ag solution was 2.5wt%.

Keywords

ZnO, OMO multilayers, All solution process.

Effects of Flux Activator on Wettability and Slump of Sn-Ag-Cu Solder Paste

Soonyong Kwon1, 2, Wonil Seo1, Yong-Ho Ko1, Hoo-Jeong Lee2, Sehoon Yoo1, †

1Joining R&D Group, Korea Institute of Industrial Technology 2School of Advanced Material Science and Engineering, Sungkyunkwan University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 123-128.

Abstract

플럭스의 활성제 종류에 따른 솔더페이스트의 인쇄성 및 젖음성을 평가하였다. 활성제는 디카르복실산 계열로 탄소기의 개수가 0인 옥살산, 1인 말론산, 2인 숙신산, 3인 글루타르산, 4인 아디프산, 5인 피메릭산이 사용되었다. SMT scope로 250°C에서 용융솔더를 실시간 관찰했을 때, 글루타르산을 사용한 솔더가 가장 매끈한 표면을 갖고, 젖음성도 우수함을 알 수 있었다. 슬럼프율은 탄소기 개수가 1, 2, 3인 말론산, 숙신산, 글루타르산을 활성제로 사용했을 때 작았고, 퍼짐성은 활성제의 탄소기 개수가 2 이상인 숙신산, 글루타르산, 아디프산, 피메릭산을 사용했을 때 우수하였다. 웨팅밸런스로 젖음성을 분석한 결과 탄소기 개수가 3이상일 때, 제로크로스타임이 1초 이하로 우수함을 알 수 있었다. 탄소기 개수가 0, 1인 옥살산, 말론산을 플럭스 활성제로 사용하였을 때, 제로크로스 타임이 길고 최대 젖음력이 낮았다. DSC와 TGA를 통해 옥살산과 말론산을 활성제로 사용한 플럭스는 솔더링 시 분해가 발생되고, 이로 인해 활성도가 떨어져서 디웨팅 등이 발생하였다. 글루타르산은 재산화가 적고, 높은 젖음성과 낮은 슬럼프 특성을 보여 주었다.
Effect of activators in flux on the printability and wettability of a solder paste was evaluated in this study. The activators in this study were dicarboxylic acids, which were oxalic acid (n = 0), malonic acid (n = 1), succinic acid (n = 2), glutaric acid (n = 3), adipic acid (n = 4), and pimelic acid (n = 5). When the solder pastes were observed with a SMT scope, solder with glutaric acid showed clean and shiny surface when it was melted. Slump ratio of the solder pastes was low when the carbon numbers of the dicarboxylic acid were 1-3. Spreadability was high when the carbon number was over 2. Zero cross time of wetting balance test was under 1 sec when the carbon number was over 3. When activator was oxalic acid or malonic acid, zero cross time was over 1 sec and maximum wetting force was low. Fluxes with the oxalic acid and malonic acid showed decomposition at the temperature close to melting point. Among the dicarboxylic acids, glutaric acid provided excellent slump, spreadability, and wettability.

Keywords

flux, solder paste, dicarboxylic acid, wettability, printability, Sn-Ag-Cu.

Mechanical and Optical Characteristics of Transparent Stretchable Hybrid Substrate using PDMS and Ecoflex Material

Won Jae Lee1, So-Yeon Park2, Hyun Jin Nam3, Sung-Hoon Choa1, †

1Graduate School of Nano IT Design Fusion, Seoul National University of Science and Technology 2Department of Materials Science and Engineering, Seoul National University of Science and Technology 3Dept. Of Manufacturing System and Design Engineering, Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 129-135.

Abstract

신축성 기판은 신축성 전자소자의 신축성, 공정성, 내구성을 결정하는 매우 중요한 소재로서 신축성 전자소자를 개발함에 있어서 우선적으로 고려해야 된다. 특히 현재 사용되는 신축성 기판은 히스테리시스가 존재하여 센서 및 기타 응용에 많은 어려움이 있다. 본 연구에서는 신축성 소재 기판으로 사용되는 PDMS와 Ecoflex를 혼합한 PDMS-Ecoflex 하이브리드 신축성 기판을 제작하여 신축성과 히스테리시스 특성을 향상하고자 하였다. 인장 시험을 통하여 신축성 하이브리드 기판의 기계적 거동을 관찰하였으며, 투과도 측정을 통하여 투과도를 평가하였다. Ecoflex의 함량이 증가할수록 하이브리드 신축성 기판은 더 유연해지며, 탄성계수는 감소한다. 또한 PDMS 기판은 270% 변형률에서 파단이 발생한 반면, PDMS-Ecoflex 하이브리드 기판은 500%의 변형률까지 파단되지 않으며 우수한 신축성을 갖는 것을 알 수 있었다. 반복 인장시험에서 PDMS와 Ecoflex의 혼합비를 2:1로 제작된 기판은 히스테리시스가 발생하였다. 반면 1:1의 혼합비로 제작된 기판의 경우 50%, 100%의 변형률에서는 히스테리시스가 발생하지 않았다. 결론적으로 500% 이상의 신축성을 갖으면서 히스테리시스가 없은 기판을 제작하였다. 기판의 혼합비에 따른 광투과도 측정 결과, Ecoflex 기판의 투과도는 68.6% 이였으나, PDMS-Ecoflex 함량이 2:1, 1:1인 하이브리드 기판의 경우, 각각 78.6%, 75.4%의 투과율을 보이며, 향후 투명 신축성 기판으로서 개발 가능성을 보여주었다.
In the stretchable electronic devices, the stretchable substrate is a very essential material which determines the stretchability, performances and durability of the stretchable electronic devices. In particular, the current stretchable materials have hysteresis making difficult to used as sensors and other electronic devices. In this study, we developed a PDMS-Ecoflex hybrid stretchable substrate mixed with PDMS and Ecoflex material in order to increase stretchability and improve hysteresis characteristics. Mechanical behavior of the hybrid substrate was evaluated using a tensile test, and optical transmittance of the hybrid substrate was also measured. As the content of Ecoflex increases, the PDMS-Ecoflex hybrid substrate becomes more flexible, and the elastic modulus decreases. In addition, the PDMS substrate failed a tensile strain of 270%, while the PDMS-Ecoflex hybrid substrate did not fail even at 500% strain indicating excellent stretchability. In the repeated tensile test, the hybrid substrate with 2:1 mixing ratio of PDMS and Ecoflex showed hysteresis. On the other hand, in the case of the hybrid substrate with the mixing ratio of 1:1, hysteresis did not occur at a strain of 50% and 100%. Hence, we developed a stretchable substrate with over 150% stretchability and no hysteresis characteristics. The optical transmittance of the Ecoflex substrate was 68.6%, whereas the transmittances of the hybrid substrate with mixing ratio of 2:1 and 1:1 were 78.6% and 75.4%, respectively. These results indicate that the PDMS-Ecoflex hybrid substrate is a potential candidate for a transparent stretchable substrate.

Keywords

Stretchable Substrate, PDMS, Ecoflex, Mechanical Properties.

The Effects of ZnO Sub-layer Thickness on the Room Temperature Ferromagnetism of (ZnO/Co) Multilayer

Sung-geun Kang1, Sungdong Kim2, †

1Amkor Technology Korea 2Dept. of Mechanical System Eng. Seoul National University of Science and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 137-142.

Abstract

(ZnO/Co) 다층박막 구조를 이용하여 Co 도핑한 ZnO의 상온강자성 특성을 조사하였으며, 특히 ZnO 박막층의 두께가 (ZnO/Co) 다층박막의 상온강자성 특성에 미치는 영향을 조사하였다. ZnO 박막층의 두께가 20Å, 40Å일 때 증착상태에서는 각각 반자성과 강자성 특성을 나타내었으며 진공열처리 후에는 모두 강자성 특성을 나타내었다. 특히 (ZnO 40Å/Co xÅ)는 열처리 후에 음의 잔류자화 거동을 나타내었다. UV-Vis 분석을 통해서 Co 일부가 Zn와 치환되어 위치하고 있음을 확인할 수 있었으며, 열처리 전후에 대한 XPS 및 HRTEM EDS 분석에서 Co 클러스터의 형성은 관찰되지 않았다.
Room temperature ferromagnetism of Co doped ZnO was studied using (ZnO/Co) multilayer structure, and the effects of ZnO sub-layer thickness on the RT ferromagnetism was investigated. As for the as-deposited state, the diamagnetism was observed for (ZnO 20Å/Co xÅ) while the ferromagnetism was observed for (ZnO 40Å/Co xÅ). After vacuum-annealed, both showed the RT ferromagnetism and (ZnO 40Å/Co xÅ) structure interestingly showed negative remanence magnetization behavior. UV-Vis spectrometer revealed that Co atoms were substituted with Zn in ZnO and Co cluster was not found in XPS and HRTEM EDS analysis.

Keywords

ferromagnetism, DMS, ZnO, Co, multilayer.

The Effect of Acetonitrile on the Texture Properties of Sodium Silicate Based Silica Aerogels

Younghun Kim1, Taehee Kim1, Jong Gil Shim2, Hyung-Ho Park1, †

1Department of Materials Science and Engineering, Yonsei University 2GLChem Co., ltd.

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 143-148.

Abstract

물유리 기반 실리카 에어로겔은 실리카 알콕사이드 기반 실리카 에어로겔에 비해 단가가 싸지만 기공률 및 비표면적과 같은 기공 특성이 상대적으로 열악하여 수요가 감소되고 있다. 이를 해결하기 위해 본 연구에서는 졸 상태에서 건조 제어 화학 첨가제(drying control chemical additive)인 아세토니트릴(acetonitrile)을 첨가하여 물성을 향상시키고자 하였다. 상압 건조 물유리 기반 실리카 에어로겔은 졸-겔 공정을 통해 제조되었으며, 졸 상태에서 물유리와 0, 0.05, 0.1, 0.15, 0.2의 몰 비율로 아세토니트릴을 첨가하여 실험을 수행하였다. 최종 생성물의 물성은 퓨리에 분광기(Fourier transform infrared), 접촉각측정기(contact angle measurement), Brunauer-Emmett-Teller 및 Barrett-Joyner-Halenda 분석기와 전계방사형 주사전자현미경(field emission scanning electron microscopy)를 이용하여 분석하였다. 졸 상태에서 물유리와의 몰 비율이 0.15인 아세토니트릴을 첨가한 샘플의 경우, 높은 비표면적 (577 m2/g), 높은 기공 부피 (3.29 cc/g), 높은 기공률 (93%)을 보유하여 실리카 알콕사이드 기반 실리카 에어로겔과 유사한 기공구조를 나타낼 수 있음을 확인하였다.
Sodium silicate based silica aerogels are lower in cost than silica alkoxide based silica aerogels, but the demand is decreasing as their physical properties are lowered. In this research, acetonitrile as a drying control chemical additive (DCCA) is added in the sol state to improve the pore-structural properties of sodium silicate based silica aerogel by preventing the agglomeration of particles and cross-linked bond. The sodium silicate based silica aerogel by ambient pressure drying were prepared by sol-gel process. Acetonitrile/Na2SiO3 molar ratio of 0, 0.05, 0.1, 0.15, and 0.2 was added to the sol state. The physical properties of the final product were analyzed using Fourier transform infrared, contact angle measurement, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda measurements and field emission scanning electron microscopy. It was confirmed that the sample with adding 0.15 molar ratio of acetonitrile and sodium silicate showed a high specific surface area (577 m2/g), a high pore volume (3.29 cc/g), and a high porosity (93%) comparable to the porestructural properties of silica alkoxide based silica aerogels.

Keywords

acetonitrile, drying control chemical additive, sodium silicate, silica aerogel, ambient pressure drying.

Fabrication and Evaluation of Heat Transfer Property of 50 Watts Rated LED Array Module Using Chip-on-board Type Ceramic-metal Hybrid Substrate

Yu Jin Heo, Hyo Tae Kim

Nano Materials and Convergence Center, Korea Institute of Ceramic Engineering and Technology

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 149-154.

Abstract

가로등 및 방폭등용 고출력 LED 조명 시스템의 광원으로서, 다수의 LED 칩이 실장된 50와트급 LED 어레이 모듈을 chip-on-board형 고방열 세라믹-메탈 하이브리드 기판을 사용하여 제작하였다. 고방열 세라믹-메탈 하이브리드 기판은 고열전도 알루미늄 금속 열확산 기판에 저온소결용 글라스-세라믹 절연 페이스트와 은 전극 페이스트를 후막 스크린 공정에 의해 도포한 다음, 건조 후 515°C 에서 동시소성하여 LED 칩을 실장할 세라믹 절연층과 은전극 회로층을 형성하여 제조하였다. 이 하이브리드 기판의 방열특성 평가를 위한 비교 샘플로서 기존의 에폭시 기반 FR-4 복합수지로 만든 써멀비아형 PCB 기판에도 동일한 디자인의 LED 어레이 모듈을 제작한 다음, 다중채널 온도측정장치와 열저항 측정기로 방열특성을 비교 분석하였다. 그 결과, 4 × 9 type LED 어레이 모듈에서 세라믹-메탈 하이브리드 기판의 열저항은 써멀비아형 FR-4 기판에 비하여 약 1/3로 나타났으며, 이것은 곧 방열성능이 적어도 3배 이상 높은 것으로 볼 수 있다.
This paper describes the fabrication and heat transfer property of 50 watts rated LED array module where multiple chips are mounted on chip-on-board type ceramic-metal hybrid substrate with high heat dissipation property for high power street and anti-explosive lighting system. The high heat transfer ceramic-metal hybrid substrate was fabricated by conformal coating of thick film glass-ceramic and silver pastes to form insulation and conductor layers, using thick film screen printing method on top of the high thermal conductivity aluminum alloy heat-spreading panel, then co-fired at 515°C. A comparative LED array module with the same configuration using epoxy resin based FR-4 PCB with thermalvia type was also fabricated, then the thermal properties were measured with multichannel temperature sensors and thermal resistance measuring system. As a result, the thermal resistance of the ceramic-metal hybrid substrate in the 4 × 9 type LEDs array module exhibited about one third to the value as that of FR-4 substrate, implying that at least triple performance of heat transfer property as that of FR-4 substrate was realized.

Keywords

Heat transfer, LED module, ceramic-metal, hybrid substrate, thermal resistance.

Flip Chip Process on the Local Stiffness-variant Stretchable Substrate for Stretchable Electronic Packages

Donghyeun Park, Tae Sung Oh

Department of Materials Science and Engineering, Hongik University

Journal of the Microelectronics and Packaging Society, Vol. 25, No. , pp. 155-161.

Abstract

강성도가 서로 다른 polydimethylsiloxane (PDMS) 탄성고분자와 flexible printed circuit board (FPCB)로 이루어진 PDMS/FPCB 구조의 강성도 국부변환 신축기판에 100 μm 직경의 Cu/Au 범프를 갖는 Si 칩을 anisotropic conductive adhesive (ACA)를 사용하여 플립칩 본딩 후, ACA내 전도성 입자에 따른 플립칩 접속저항을 비교하였다. Au 코팅된 폴리머 볼을 함유한 ACA를 사용하여 플립칩 본딩한 시편은 43.2 mΩ의 접속저항을 나타내었으며, SnBi 솔더입자를 함유한 ACA로 플립칩 본딩한 시편은 36.2 mΩ의 접속저항을 나타내었다. 반면에 Ni 입자를 함유한 ACA를 사용하여 플립칩 본딩한 시편에서는 전기적 open이 발생하였는데, 이는 ACA내 Ni 입자의 함유량이 부족하여 entrap된 Ni 입자가 하나도 없는 플립칩 접속부가 발생하였기 때문이다.
A Si chip with the Cu/Au bumps of 100-μm diameter was flip-chip bonded using different anisotropic conductive adhesives (ACAs) onto the local stiffness-variant stretchable substrate consisting of polydimethylsiloxane (PDMS) and flexible printed circuit board (FPCB). The average contact resistances of the flip-chip joints processed with ACAs containing different conductive particles were evaluated and compared. The specimen, which was flip-chip bonded using the ACA with Au-coated polymer balls as conductive particles, exhibited a contact resistance of 43.2 mΩ. The contact resistance of the Si chip, which was flip-chip processed with the ACA containing SnBi solder particles, was measured as 36.2 mΩ, On the contrary, an electric open occurred for the sample bonded using the ACA with Ni particles, which was attributed to the formation of flip-chip joints without any entrapped Ni particles because of the least amount of Ni particles in the ACA.

Keywords

stretchable packaging, stretchable substrate, PDMS, FPCB, flip chip, contact resistance.