| A damage coupled thermo-viscoplastic constitutive model has been developed to predict thermomechanical fatigue life of eutectic Pb/Sn solder joints in microelectronics packaging. The damage, as an internal state variable with evolution function, corresponds to microstructure degradation. The damage coupled constitutive model reflects the interaction between damage and mechanical response of material under fatigue loading. The entropy, which is a measure of the disorder of thermodynamic system, is used as the metric of material damage.; The time and temperature dependent material parameters of eutectic Pb/Sn solder alloys involved in the constitutive model have been experimentally determined. And the damage coupled constitutive model has been programmed as user-defined subroutines and implemented into nonlinear finite element procedure of ABAQUS for numerical simulation.; Thermal and isothermal validation testing have been performed using test vehicle and actual microelectronics packaging module. The numerical model and simulation procedure have been verified by monotonic uniaxial tensile testing and monotonic shear testing under different temperatures and strain rates, isothermal cyclic shear testing, and thermal cycling of actual BGA microelectronics packages. |
