基于显式动力学的焊点冲击失效分析

组件级高速剪切测试是用来研究芯片封装中Sn-Ag-Cu焊点冲击可靠性问题的一个重要手段。实验研究表明:随着冲击速度的增加,焊点封装结构的失效会由焊锡母材的韧性破坏向界面金属间化合物(IMC)的脆性断裂过渡；同时,其荷载-位移响应曲线形态也会发生显著的改变。为了能够更详细地了解封装结构的冲击失效行为,并进一步改进其结构设计,该文提出结合焊锡材料应变率相关的动态硬化特性,利用渐进损伤模型来模拟其动态损伤过程；同时,引进一种能够有效表征复合型裂纹扩展的内聚力模型来模拟IMC的脆性动态断裂。与实验结果的对比表明:该文提出的方法能够较为有效地表征焊点封装结构在不同冲击速度下的失效行为。

IMPACT FAILURE ANALYSIS OF SOLDER JOINT BASED ON EXPLICIT DYNAMIC METHOD

The component-level high-speed shear test is an important means of studying the reliability of an Sn-Ag-Cu solder joint in an electronic package caused by impact loading. Experimental studies show that the failure of a solder joint structure will transfer from the ductile damage of solders to the brittle fracture of interfacial intermetallic compounds (IMC) with the increase of impact velocity; at the same time, the shape of load-displacement response curve will also have a notable change. In order to better understand the impact failure of the package structure, and further improve its structural design, a new finite element simulation method was proposed. In this method, the progressive damage model was used to simulate the damage process by considering the strain-rate-dependent dynamic hardening characteristics of solders; and a mixed-mode cohesive zone model was developed and used to simulate the brittle fracture of IMC. Comparisons with the experimental results show that the proposed method can effectively characterize the failure behavior of a solder joint structure at different impact velocities.