Investigation of electro-thermo-mechanical degradation and crack propagation of wire bonds in power modules using integrated phase field modelling and finite element analysis

Interfacial fatigue degradation and crack formation of wire bonds are one of the serious issues related to packaging in power modules that affect the reliability of power electronics. This work presents a new approach based on a combination of phase field modelling and finite element analysis to study the electro-thermo-mechanical behavior, the interface degradation and crack propagation processes of wire bonded interconnects in IGBT power modules. The strain energy density obtained from the macro-scale electro-thermo-mechanical analysis is transferred to the mesoscale phase field modelling to study the interface fatigue and crack propagation, considering the effect of wire grain morphology. The temperature and stress distribution characteristics of a typical IGBT power module with Al wire bonds under power cycling are investigated. Stress concentration at the interconnect interface caused by thermal strains between wire and chip is examined. The crack length increases with increasing cycle number. The presence of Al grain boundaries is found to have a significant impact on crack propagation, due to grain boundary energy and weakening effects. The developed model could provide new insights for predicting the lifetime and crack growth of power modules, and offer a pathway for the reliability optimization of wire bonds.