Degradation evolution in high power IGBT modules subjected to sinusoidal current load

In this paper the degradation evolution and distribution in high power IGBT module interconnects are investigated. Modules are subjected to advanced active thermal cycling by applying a sinusoidal current load switched by the device. A series of samples subjected to an increasing number of power cycles under conditions resembling real life operation are considered. Under the given load conditions the dominating failure mechanisms are bond wire lift-off and metallization reconstruction. Both failure processes are investigated using micro-sectioning approach and scanning electron microscopy combined with focused ion beam milling. The degradation evolution and distribution are analysed and discussed in relation to load conditions. It is clear that both bond wire lift-off and metallization reconstruction are complicated micro-structural processes affected by numerous stressors. Especially, the fractures causing bond wire lift-off are observed to consist of several sub-phases—delamination, intergranular, and transgranular crack propagations.