Bond wire lift-off in IGBT modules due to thermomechanical induced stress

In this paper the bond wire lift-off failure mechanism experienced in insulated gate bipolar transistor modules, under realistic operation conditions, is investigated theoretically. This failure type is generally believed to be due to thermally induced stress arising from a mismatch in the coefficients of thermal expansion of the materials constituting the module. The theoretical evaluation is based on a finite element approach combined with empirical equations. Here the thermomechanical stress around the bond wire/substrate interface is evaluated. Based on the computations a new approach for characterizing degradation of bond wire junctions is proposed. From this function the lifetime as well as module performance may be evaluated for varying parameters: load, geometry etc.