Accurate thermal boundary condition to predict hot spot temperature using Electro-Thermal Analysis

Abstract

This paper describes the prediction method of the bottom temperature of power Si MOSFET by using CFD (Computational Fluid Dynamics) analysis. For accurate thermal design of electronics, nano-micro scale hot spot temperature in semiconductor devices should be considered in thermal design. CFD analysis is widely used in thermal design of electronics. However, it is difficult to detect accurate temperature of nanomicro scale hot spots using CFD analysis. Then, the method to detect nano-micro scale hot spot temperature in semiconductor device is required. Electro-Thermal Analysis is attractive method to calculate temperature distribution of semiconductor devices. In Electro-Thermal Analysis, boundary conditions are important to calculate temperature distribution of semiconductor devices. Considering power Si MOSFET, which is widely used in semiconductor devices, the device is cooled from the bottom of the device. Therefore, the bottom boundary temperature of power Si MOSFET is dependent on cooling performance of cooling system. And temperature of the bottom surface is important for nano-micro scale hot spot estimation in Electro-Thermal Analysis. Then, in this paper, appropriate CFD modeling of power Si MOSFET is discussed for detecting the bottom temperature of power Si MOSFET. To verify the appropriate CFD modeling, the results of CFD analysis are compared with the experimental results, and the suitable assumption of heat generation in CFD analysis is discussed. From the result, the assumption of surface heat generation at the top of the power Si MOSFET is suitable assumption in CFD analysis. Therefore, it can be said, to calculate accurate nano-micro scale hot spot temperature in power Si MOSFET using Electro- Thermal Analysis, the bottom temperature as the important boundary condition in Electro-Thermal Analysis can be obtained by the CFD modeling. Further, it can be found that it is important to consider the heat transfer from the electrodes to the outside through the electrical wires in CFD modeling.