跌落冲击载荷下焊锡接点金属间化合物层的动态开裂

跌落冲击载荷作用下，含铅焊锡接点与无铅焊锡接点的破坏模式明显不同，而导致这种差异的原因目前尚不明朗。本文提出了一种可用于模拟焊锡接点在跌落冲击载荷下破坏行为的有限元模型，此模型中，金属间化合物（IMC）与焊料间的界面采用粘性区模型（CZM）来模拟其损伤开裂过程，而IMC层内的破坏程度则通过计算其能量释放率来判断。通过对板级封装跌落冲击过程的数值模拟发现，与无铅焊锡接点（Sn3.5Ag）相比，含铅焊锡接点（Sn37Pb）与IMC间的CZM层更容易发生损伤破坏，而该层的开裂会减小IMC层的应力，即降低了其内部的裂纹驱动力，从而缓解了IMC层裂纹的起始和扩展。

DYNAMIC FRACTURING OF THE INTERMETALLIC COMPOUND LAYER IN SOLDER JOINTS UNDER IMPACT DROP LOADING

The great difference of the failure modes between lead-containing and lead-free solder joints subjected to drop impact loading has not been well understood. In this paper, a feasible finite element approach is proposed to model the cracking behavior of lead-containing and lead-free solder joints under drop impact loading. In the model, the damage at the intermetallic compound layer/solder bulk interface is calculated by the cohesive zone model, and the failure in the intermetallic compound layer is evaluated by computing the energy release rate. The numerical simulation result shows that, for the lead-containing Sn37Pb solder joint, the damage in the intermetallic compound layer/solder bulk interface initiates earlier and much greater than that in the lead-free Sn3.5Ag solder joint. This damage can relieve the stress in the intermetallic compound layer and reduce the risk of intermetallic compound layer fracturing in the lead-containing Sn37Pb solder joint.