Inelastic strain evolution in solder joint under thermal-mechanical coupled fatigue loading

In SMT, it is not easy to study the failure process of solder joint under thermal-mechanical coupled fatigue loading. However, it is very important for the electrical circuit working in the thermal and vibration coupled environment. In this paper, the inelastic strain evolution in lead-free solder joint under thermal, mechanical, thermal-mechanical coupled fatigue loading was studied by numerical simulation, respectively. And the effect of amplitude and frequency of mechanical fatigue loading on inelastic strain in solder joint were investigated. It was shown that under thermal-mechanical coupled fatigue loading, there is a large value distribution of inelastic strain near the corner of the border between the chip and solder material. When the amplitude and frequency of mechanical fatigue loading are both small, the creep strain in solder joint is dominant. Otherwise, the plastic strain is larger than creep strain.