BGA 무연솔더(Sn-3.0Ag-0.5Cu)와 무전해 Ni-W-P 도금층 계면의 열 안정성에 대한 연구
Study on Thermal Stability of the Interface between Electroless Ni-W-P Deposits and BGA Lead-Free Solder (Sn-3.0Ag-0.5Cu)
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초록
본 연구에서는 무연 솔더 중 우수한 특성을 보여 실용화된 Sn-3.0Ag-0.5Cu 조성의 솔더를 사용하여 2주 동안의 시효조건에서 W의 함량이 무전해 Ni-W-P 도금층과 솔더와의 계면에서의 IMC 생성에 미치는 영향에 대해서 조사하였다. 도금층내 인의 함량은 8 wt.%로 고정하였고, 텅스텐의 함량은 각각 0, 3, 6 및 9 wt.%로 변화시켰으며, 모든 시료는255oC에서 리플로우한 후, 200oC에서 2주 동안 시효처리하였다. 각각의 시료에서 (Cu,Ni)6Sn5와 (Ni,Cu)3Sn4의 IMC가관찰되었으며, 시효처리시간의 증가에 따라 UBM과 무연납의 계면에서 생성된 IMC가 증가함을 보였고, W의 함량이 높을수록 열적 안정성이 증가하여 Ni(W)3P의 생성 속도를 늦춰 그에 따른 영향으로 IMC의 두께가 증가함을 보였다.
Abstract
In this study, we investigated the morphology and thermal stability of interfacial phases in joint between lead free solder(Sn-3.0Ag-0.5Cu) and electroless Ni-W-P under bump metallizations(UBM) with different tungsten contents as a function of thermal aging. Content of phosphorus of each deposits was fixed at 8 wt.%, and content of tungsten was variated each 0, 3, 6 and 9 wt.%. Specimens were prepared by reflowing at 255oC, aging range was 200oC and up to 2 weeks. After reflow process, in the electroless Ni(W)-P/solder joint, the interfacial intermetallic compound(IMC) was showed both (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. UBM and generated IMC at the interface of lead free solder was proportionally increased with aging time. The thickness of IMC was increased because the generation rate of Ni(W)3P decreased with increasing contents of W.
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