Temperature Evolution as an effect of Wire-bond Failures in a Multi-Chip IGBT Power Module

Multi-chip power switches consist of several dies in parallel. The temperature of these dies is not equal and evolves during ageing, in part as a consequence of wire-bond degradation. The temperature distribution may impact the condition monitoring and the overall reliability. It is thus necessary to understand how the temperature distribution is modified by wire-bond degradation. In this paper, wirebond lift-offs are reproduced experimentally by sequentially sectioning the hottest wire of the hottest die of a multi-chip IGBT module. The results show that at the beginning of the degradation, hot spots move away from the more recent wire-bond lift-off, contributing to temperature equalization. However, this effect collapses as fewer bonds remain attached towards the end of the module life.