Significance of thermal cross-coupling effects in power semiconductor modules

In order to develop power electronic systems with high power densities the performance of the cooling system has to be increased. Thereby, the thermal resistance of power semiconductor modules is an important design aspect. However, the thermal resistance of modules is influenced by cross-coupling effects which are dependent on the module layout and the heatsink. These cross-coupling effects are not listed in the datasheet and need to be measured. In this paper, the thermal resistance of a power module is measured utilizing the indirect virtual junction temperature measurement. The measured values are compared to datasheet values. Thermal cross-coupling effects are analyzed for different module configurations. A simple measurement approach is outlined which measures several chips inside the module to analyze cross-coupling effects with respect to the module geometry. Significant deviations from the datasheet values are measured when operating under real world conditions.