굽힘 하중하에서 유연 및 무연 솔더 조인트의 신뢰성 평가
Reliability Assessments of Lead-contained and Lead-free BGA Solder Joints under Cyclic Bending Loads
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초록
최근에 모바일 기기의 사용이 늘어남에 따라 굽힘 응력에 대한 패키지 접합부의 신뢰성에 대한 관심이 다시 높아지고 있다. 기존의 굽힘실험은 생산공정 및 운반 등에 파손을 방지하기 위해서 수행되었으나 최근에는 모바일 기기의 이동 및 사용에 따라 발생되는 응력에 대한 저항성 평가나 드롭시험의 대용으로 수행되고 있다. 본 연구에서는 정확한 4점 굽힘 실험 방법을 도입하여 유연 솔더 조인트와 무연 솔더 조인트의 굽힘 피로 시험에 대한 저항성을 평가하고, 단면 관찰과 유한요소법을 이용한 해석을 수행하였다. 높은 하중이 작용하게 되면, 유연 솔더 조인트가 보다 긴 피로수명을 갖으며, 낮은 하중이 작용할 때는 무연 솔더 조인트가 긴 수명을 가지게 된다. 크랙은 시편의 외각에서 발생되어 안쪽으로 진행하게 되며, 소성변형이 손상의 대부분을 자치하게 된다.
Abstract
Mobile products, such as cellular phones, PDA and notebook, are subjected to many different mechanical loads, which include bending, twisting, impact shock and vibration. In this study, a cyclic bending test of the BGA package was performed to evaluate the fatigue life. Special bending tester, which was suitable for electronic package, was developed using an electromagnetic actuator. A nonlinear finite element model was used to simulate the mechanical bending deformation of solder joint in BGA packages. The fatigue life of lead-free (95.5Sn4.0Ag0.5Cu) solder joints was compared with that of lead-contained (63Sn37Pb). When the applied load to the specimen is small, the lead-free solder has longer fatigue life than lead-contained solder. The fatigue crack is initialized at the exterior solder joints and is propagated into the inner solder joints.
참고문헌 (13)
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