Abstract Reliability of Press-Pack IGBTs is a topic with limited published data and information. This paper presents results of a power cycling test with state-of-the-art high power devices. An accelerated lifetime test scheme was defined, and six out of eight devices were tested until failure. A microscopy analysis has been performed on some of the failed devices, and they have all failed in a very similar manner. In order to gain additional information about the thermal–mechanical stress, a detailed 3D Finite Element Method (FEM)-analysis has been conducted. The combined results from power cycling, microscopy and FEM have been concluded to two possible failure modes in Press-Pack IGBTs: Gate oxide damage and micro arcing.