Effects of temperature and strain rate on mechanical behavior of low-silver lead-free solder under drop impact

This study uses finite element program to simulate the process of board-level drop for portable electronic devices, so as to create very-thin-profile fine-pitch BGA packages model. Based on the data from quasi-static tests and the experimental data measured by split Hopkinson pressure bar, the parameters of Cowper–Symonds model about solder joints were obtained, taking into consideration of strain rate effect and temperature effect. The results show that, the maximum stress in Cowper–Symonds material model considering strain rate effect is significantly lower than that in linear elastic material model, and the location of maximum stress is different. When the temperature is −45, 23 or 60 °C, low silver lead-free solder Sn0.3Ag0.7Cu shows temperature softening effect obviously. Under low temperature, stress is concentrated at the interface of solder, while under normal temperature or high temperature the phenomenon is different obviously. Additionally, compared with high silver solder, low silver solder has better resistance to drop at room temperature or under working conditions.