Implementation of a Thermodynamic Framework for Damage Mechanics of Solder Interconnects in Microelectronics Packaging

A thermodynamic framework for damage mechanics is proposed. The damage evolution function uses entropy as a damage metric. A damage-coupled viscoplastic model with kinematic and isotropic hardening is implemented in a commercial finite element code to simulate the thermo-mechanical behavior of eutectic solder interconnectsin micro electronics packaging. The damage, asan internal state variable, is coupled witha unified viscoplastic constitutive model to characterize the cyclic deterioration of the material under thermo-mechanic fatigue loads. Several computational simulations of uniaxial monotonic tensile and cyclic shear tests are conducted to validate the model with experimentalresults. The behavior of a Ball Grid Array (BGA) package under thermo-mechanic fatigue loading is also simulated and compared with experimental results.