The impact of thermal cycling in humid environments on power electronic modules

The reliable operation of power electronic modules operating at high voltage is essential. The dielectric system within the power electronic module is reasonably simple but must be worked as hard as possible to achieve the highest module power densities. It is well known that a critical location in a power electronic module in terms of high voltage performance is the edge of the substrate metallisation where high electric fields can give rise to partial discharge within power electronic modules and can lead to eventual failure. This paper focuses on two particular issues. Firstly the performance of the gap between the substrate metallisation on which the collector and emitter of the device sit is examined. Secondly, the performance of the substrate-gel interface is examined once samples have been thermally aged in a humid environment.