Modeling and experimental analysis of heat transfer for power electronic module integrated with phase change thermal management system

In hybrid electric vehicles, IGBT power module tends to dissipate more heat due to increase in functionality, miniaturization and placement close to or on-engine. Consequently, thermal stress in IGBT power module becomes to be one of main factors resulting in severe thermal reliability problems. In this paper, a novel cooling strategy is developed for cooling IGBT power module. To obtain high thermal conductivity and good temperature uniformity, a vapour chamber was applied to integrate with the IGBT power module instead of the original copper substrate. No thermal grease and additional cooling plate were, leading to significant reduction in thermal resistance. A thermal test rig and a thermal-mechanical coupling model was built to analyse temperature distribution, thermal stress, energy strain dissipation density and lifetime of whole module with consideration of effect of vapour chamber and working condition. The results indicate the junction temperature is about 3.8 ^oC lower than that of IGBT with copper substrate and chips temperature distributes uniformly. This paper also investigates the failure mechanism of solder layer under thermal cycling. It is found creep is principle damage in the thermal cycling and cracks induced by thermal loading are expected to initiate at the edge.