Calculation of tempearture distribution of power Si MOSFET with electro-thermal analysis The effect of boundary condition

This paper describes the effect of the boundary condition at the bottom surface of the power Si MOSFET on the analysis results of electro-thermal analysis of the power Si MOSFET. In general, the bottom surface of a semiconductor device is assumed 350 K to calculate the temperature distribution. However, in fact, the temperature of the bottom surface of the device is not constant, and the temperature is affected by the ambient surrounding (for example, cooling method, ambient temperature and so on). Additionally, because the boundary condition of the bottom temperature affects to the temperature distribution of the device, the boundary condition of the analysis is important. In this study, we assumed the heat transfer coefficient at the bottom surface of the device in electro-thermal analysis, and investigated the effect of the cooling performance on the bottom temperature and the temperature distribution. From the results, the heat transfer coefficient should be more than 5 × 10⁷ W/(m²·K) to cool the bottom surface at 350 K in the examined calculation condition. Further, when the cooling performance is higher, the temperature distribution of the device is unhomogeneous.