Journal of the Microelectronics and Packaging Society

Nonwet (Head in Pillow) 불량은 SMT(surface mount technology) 공정 불량 유형 중 하나로 이 불량은 solder paste misalign, reflow 조건, package warpage, package ball size 등과 같은 인자에 따라 불량이 발생을 한다. 이에 본 논 문은 Nonwet 발생 인자 중 ① reflow 조건 ② package ball & solder paste misalign ③ package ball 크기 type에 대한 인 자를 선정하여 nonwet 실험을 진행하였다. 먼저 reflow 조건의 경우 soldering 시간이 길 경우 nonwet risk가 증가를 하 나, reflow 공정에 N2를 적용할 시 solder ball 산화 억제에 따른 nonwet 개선을 확인 할 수 있었다. 또한 package ball과 solder paste misalign 발생 시 ball과 paste의 접촉 깊이가 20 μm 이하의 경우 nonwet에 취약 했으며, package ball 체면 적이 작을수록 nonwet 관점 개선됨을 확인 할 수 있었다.
Nonwet (Head in Pillow) defect is one of the defects in SMT (surface mount technology) process, the defect is caused by several factors, such as solder paste misalignment, reflow condition, package warpage and package ball size. This paper focused on ① reflow condition ② package ball & solder paste misalignment ③ package ball size for nonwet experiment. The first, on the case of reflow condition, there would be high risk of nonwet defect when the soldering time was increased, but N2 was adopted to reflow process, there could be no or low risk of nonwet defect because of oxidation barrier control. And when the contact depth between Solder ball and solder paste was below 20 μm, there could be high risk of nonwet defect. Also smaller package ball would have low risk of nonwet defect.

Keywords Nonwet, Head in Pillow, Small ball, Reflow, Soak time, keeping time, ball misalignment