Sn-0.7Cu-xZn와 OSP 표면처리 된 기판의 솔더접합부의 고속 전단강도에 미치는 Zn의 영향
Effect of Zn content on Shear Strength of Sn-0.7Cu-xZn and OSP surface finished Joint with High Speed Shear Test
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초록
본 연구에서는 Sn-0.7Cu-xZn 무연솔더와 OSP 표면처리 된 솔더접합부의 전단강도를 Zn 함유량에 따라 평가하였다. 다섯 종류의 Sn-0.7Cu-xZn (x=0, 0.5, 1.0, 1.5, 2.0 wt.%) 솔더페이스트를 제작한 뒤, OSP(organic solderability preservative) 표면처리 한 PCB(printed circuit board) 기판의 전극에 리플로우 공정으로 180 um 직경의 솔더볼을 형성하였다. 전단강도는 두 가지 조건의 전단속도(0.01, 0.1 m/s)로 고속전단시험(high speed shear test)을 통해 측정하였고, 고속전단시험 시에 측정된 F-x(Force-distance) curve를 통해 파괴에너지(fracture energy)를 계산하였다, SEM(주사전자현미경, scanning electron microscopy)과 EDS(energy dispersive spectroscopy) 분석을 통하여 단면과 파단면을 관찰하였고, 금속간화합물(intermetallic compound, IMC) 층을 분석하였다. Zn 함유량이 증가함에 따라 금속간 화합물 층의 두께는 감소하였고, Zn 함유량이 0.5 wt.%일 때 가장 높은 전단 강도(shear strength)를 나타내었다. 전체적으로 높은 전단속도 조건의전단강도 값이 낮은 전단속도 조건의 전단강도보다 높았다.
Abstract
We investigated effect of Zn content on shear strengh of Sn-0.7Cu-xZn and OSP surface finished solder joints. Five pastes of Sn-0.7Cu-xZn (x=0, 0.5, 1.0, 1.5, 2.0 wt.%) solders were fabricated by mixing of solder powder and flux using planatary mixer. 180 μm diameter solder balls were formed on OSP surface finished Cu electrodes by screen print method, and the reflow process was performed. The shear strength was evaluated with two high shear speeds; 0.01 and 0.1 m/s. The thickness of the intermetallic compound(IMC) layer was decreased with increasing Zn content in Sn-0.7CuxZn solder. The highest shear strength was 3.47 N at the Zn content of 0.5 wt.%. As a whole, the shear strength at condition of 0.1 m/s was higher than that of 0.01 m/s because of impact stress. Fracture energies were calculated by F-x (Forcedisplacement) curve during high speed shear test and the tendency of fracture energy and that of shear strength were good agreement each other. Fracture took place within solder matrix at lower Zn content, and fracture occured near the interface of OSP surface finished Cu electrode and solder at higher Zn content.
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