Dynamic Modeling Method of Electro-Thermo-Mechanical Degradation in IGBT Modules

A degradation model investigating the electro-thermo-mechanical fatigue, experienced by insulated gate bipolar transistors modules, is presented. To illustrate the concept, a specific case of power modules subjected to active power cycling which induce failure through bond wire lift-off is considered. Bond wire lift-off is believed to be due to thermally induced stress arising from a mismatch in the coefficients of thermal expansion between the wires and the given substrate. Overall, the theoretical evaluation is based on determining the thermo-mechanical stress around the bond wire/substrate interface through multiphysics-based models. The simulation detail and included equations are specified according to the region of interest and their complexity. In common, however, is the use of the finite element method combined with empirical equations. The final result is a numerical approach to evaluate the damage accumulated by a given load which may be used for prediction of lifetime or optimization of work points and module geometry.