Constitutive modeling of time-dependent cyclic straining for solder alloy 63Sn-37Pb

In this paper, a damage-coupled unified visco-plastic constitutive model is proposed for 63Sn-37Pb alloy used in solder joints of surface-mount IC packages and semiconductor devices that are subjected to mechanical fatigue loading at two constant high temperatures. The model accounts for the time and temperature dependence of the kinematic hardening, and is represented by the back stress state variable which evolves according to the hardening-recovery equations with different evolution rates. The damage evolution equation, including cyclic plastic damage and time-dependent cyclic damage, is established, and a failure criterion is proposed based on the damage accumulation in materials. The model is used to predict the effects of strain rates, temperature and dwell time on both the deformation and fatigue life of 63Sn-37Pb solder alloy under cyclic straining with and without dwell time at two temperatures.