Vol.31 No.1

Editorial Office

Current Issue

Journal of the Microelectronics and Packaging Society 2024;31(1):
Ultrasensitive Crack-based Mechanosensor Inspired by Spider’s Sensory Organ

Suyoun Oh and Tae-il Kim

School of Chemical Engineering, Sungkyunkwan University, 585 Cheoncheon-dong, Jangan-gu, Suwon-si, Gyeonggi-do, 16419, Republic of Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 1-6.


Spiders detect even tiny vibrations through their vibrational sensory organs. Leveraging their exceptional vibration sensing abilities, they can detect vibrations caused by prey or predators to plan attacks or perceive threats, utilizing them for survival. This paper introduces a nanoscale crack-based sensor mimicking the spider’s sensory organ. Inspired by the slit sensory organ used by spiders to detect vibrations, the sensor with the cracks detects vibrations and pressure with high sensitivity. By controlling the depth of these cracks, they developed a sensor capable of detecting external mechanical signals with remarkable sensitivity. This sensor achieves a gauge factor of 16,000 at 2% strain with an applied tensile stress of 10 N. With high signal-to-noise ratio, it accurately recognizes desired vibrations, as confirmed through various evaluations of external force and biological signals (speech pattern, heart rate, etc.). This underscores the potential of utilizing biomimetic technology for the development of new sensors and their application across diverse industrial fields.


Biomimetics, Mechanosensor, Crack sensor, Spider’s sensory organ, Vibration

Research Trends in Thermal Interface Materials for Flexible and Stretchable Electronic Device

Young-Joo Park, Geon-Joo Jeong, and Kwang-Seok Kim

Carbon & Light Materials Group, Korea Institute of Industrial Technology, Jeonju 54853, Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 7-15.


In the trend of the multi-functionalization, miniaturization, and increased power output trends of flexible and stretchable electronic devices, the development of materials or structures with superior heat transfer characteristics has become a pressing issue. Traditional thermal interface materials (TIM) fail to meet the heat dissipation requirements of flexible and stretchable electronic devices, which must endure rapid bending, twisting, and stretching. To address this challenge, there is a demand for the development of TIM that simultaneously possesses high thermal conductivity and stretchability. This paper examines the research trends of liquid metal, carbon, and ceramic-based stretchable thermal interface materials and explores effective strategies for enhancing their thermal and mechanical properties.


Thermal interface materials, Flexible and stretchable electronic device, Thermal conductivity, Stretchability, Heat dissipation, Thermal management

State of Health and State of Charge Estimation of Li-ion Battery for Construction Equipment based on Dual Extended Kalman Filter

Hong-Ryun Jung1 , Jun Ho Kim1 , Seung Woo Kim1 , Jong Hoon Kim2 , Eun Jin Kang2 , and Jeong Woo Yun1,†

1School of Chemical Engineering, Chonnam National University, Gwangju 61186, Korea, 2Department of Electrical Engineering, Chungnam National University 34134, Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 16-22.


Along with the high interest in electric vehicles and new renewable energy, there is a growing demand to apply lithium-ion batteries in the construction equipment industry. The capacity of heavy construction equipment that performs various tasks at construction sites is rapidly decreasing. Therefore, it is essential to accurately predict the state of batteries such as SOC (State of Charge) and SOH (State of Health). In this paper, the errors between actual electrochemical measurement data and estimated data were compared using the Dual Extended Kalman Filter (DEKF) algorithm that can estimate SOC and SOH at the same time. The prediction of battery charge state was analyzed by measuring OCV at SOC 5% intervals under 0.2C-rate conditions after the battery cell was fully charged, and the degradation state of the battery was predicted after 50 cycles of aging tests under various C-rate (0.2, 0.3, 0.5, 1.0, 1.5C rate) conditions. It was confirmed that the SOC and SOH estimation errors using DEKF tended to increase as the C-rate increased. It was confirmed that the SOC estimation using DEKF showed less than 6% at 0.2, 0.5, and 1C-rate. In addition, it was confirmed that the SOH estimation results showed good performance within the maximum error of 1.0% and 1.3% at 0.2 and 0.3C-rate, respectively. Also, it was confirmed that the estimation error also increased from 1.5% to 2% as the C-rate increased from 0.5 to 1.5C-rate. However, this result shows that all SOH estimation results using DEKF were excellent within about 2%.


Lithium-ion battery, Construction equipment, Kalman filter, Equivalent circuit model, State of Health (SOH)

Prediction of Maximum Bending Strain of a Metal Thin Film on a Flexible Substrate Using Finite Element Analysis

Jong Hyup Lee and Young-Cheon Kim

School of Materials Science & Engineering, Research Center for Energy and Clean Technology, Andong National University, 1375, Gyeongdong-ro, Andong-si, Gyeongsangbuk-do 36729, Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 23-28.


Electronic products utilizing flexible devices experience harsh mechanical deformations in real-use environments. As a result, researches on the mechanical reliability of these flexible devices have attracted considerable interest among researchers. This study employed previous bending strain models and finite element analysis to predict the maximum bending strain of metal films deposited on flexible substrates. Bending experiments were simulated using finite element analysis with variations in the material and thickness of the thin films, and the substrate thickness. The results were compared with the strains predicted by existing models. The distribution of strain on the surface of film was observed, and the error rate of the existing model was analyzed during bending. Additionally, a modified model was proposed, providing mathematical constants for each case.


Bending strain, FE analysis, Metal thin film, Flexible substrate

Flexible Planar Heater Comprising Ag Thin Film on Polyurethane Substrate

Seongyeol Lee1 and Dooho Choi2,†

1School of Advanced Materials Engineering, Dong-Eui University, 176 Eomgwangro, Busan, 47340, Republic of Korea, 2School of Semiconductor & Electronic Engineering, Gachon University, 1342 Seongnam-daero, Sujeong-gu, Seongnam-si, Gyeonggi-do 13120, Republic of Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 29-34.


The heating element utilizing the Joule heating generated when current flows through a conductor is widely researched and developed for various industrial applications such as moisture removal in automotive windshield, high-speed train windows, and solar panels. Recently, research utilizing heating elements with various nanostructures has been actively conducted to develop flexible heating elements capable of maintaining stable heating even under mechanical deformation conditions. In this study, flexible polyurethane possessing excellent flexibility was selected as the substrate, and silver (Ag) thin films with low electrical resistivity (1.6 μΩ-cm) were fabricated as the heating layer using magnetron sputtering. The 2D heating structure of the Ag thin films demonstrated excellent heating reproducibility, reaching 95% of the target temperature within 20 seconds. Furthermore, excellent heating characteristics were maintained even under mechanically deforming environments, exhibiting outstanding flexibility with less than a 3% increase in electrical resistance observed in repetitive bending tests (10,000 cycles, based on a curvature radius of 5 mm). This demonstrates that polyurethane/Ag planar heating structure bears promising potential as a flexible/wearable heating element for curved-shaped appliances and objects subjected to diverse stresses such as human body parts.


Joule heating, Planar heater, Magnetron sputtering, Sheet resistance

Properties of Cu Pillar Bump Joints during Isothermal Aging

Eun-Su Jang1 , Eun-Chae Noh1 , So-Jeong Na2 , and Jeong-Won Yoon1,†

1Department of Advanced Materials Engineering, Chungbuk National University, Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Korea, 2Welding and Joining R&D Group, Korea Institute of Industrial Technology (KITECH), 156 Gaetbeol-ro, Yeonsu-Gu, Incheon 21999, Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 35-42.


Recently, with the miniaturization and high integration of semiconductor chips, the bump bridge phenomenon caused by fine pitches is drawing attention as a problem. Accordingly, Cu pillar bump, which can minimize the bump bridge phenomenon, is widely applied in the semiconductor package industry for fine pitch applications. When exposed to a high-temperature environment, the thickness of the intermetallic compound (IMC) formed at the joint interface increases, and at the same time, Kirkendall void is formed and grown inside some IMC/Cu and IMC interfaces. Therefore, it is important to control the excessive growth of IMC and the formation and growth of Kirkendall voids because they weaken the mechanical reliability of the joints. Therefore, in this study, isothermal aging evaluation of Cu pillar bump joints with a CS (Cu+ Sn-1.8Ag Solder) structure was performed and the corresponding results was reported.


Cu pillar bump, Intermetallic compound, Kirkendall void, Aging, Reflow soldering

Electrical Properties of Two-dimensional Electron Gas at the Interface of LaAlO3/SrTiO3 by a Solution-based Process

Kyunghee Ryu1 , Sanghyeok Ryou2 , Hyeonji Cho1 , Hyunsoo Ahn3 , Jong Hoon Jung3 , Hyungwoo Lee2,4,†, and Jung-Woo Lee1,†

1Department of Materials Science and Engineering Hongik University, Sejong 30016 Republic of Korea, 2Department of Energy Systems Research, Ajou University, Suwon 16499 Republic of Korea, 3Department of Physics, Inha University, Incheon 22212 Republic of Korea, 4Department of Physics, Ajou University, Suwon 16499 Republic of Korea

Journal of the Microelectronics and Packaging Society Vol. 31, No. 1, pp. 43-48.


: The discovery of a two-dimensional electron gas (2DEG) at the interface of LaAlO3 (LAO) and SrTiO3 (STO) substrates has sparked significant interest, providing a foundation for cutting-edge research in electronic devices based on complex oxide heterostructures. However, conventional methods for producing LAO thin films, typically employing techniques like pulsed laser deposition (PLD) within physical vapor deposition (PVD), are associated with high costs and challenges in precisely controlling the La and Al composition within LAO. In this study, we adopted a cost-effective alternative approach—solution-based processing—to fabricate LAO thin films and investigated their electrical properties. By adjusting the concentration of the precursor solution, we varied the thickness of LAO films from 2 to 65 nm and determined the sheet resistance and carrier density for each thickness. After vacuum annealing, the sheet resistance of the conductive channel ranged from 0.015 to 0.020 Ω·sq⁻¹, indicating that electron conduction occurs not only at the LAO/STO interface but also into the STO bulk region, consistent with previous studies. These findings demonstrate the successful formation and control of 2DEG through solution-based processing, offering the potential to reduce process costs and broaden the scope of applications in electronic device manufacturing.


Complex oxide thin films, SrTiO3, LaAlO3, Two-dimensional electron gas, Solution-based process