3D Thermal-Fluid and Stress Analysis for Single Chip SiC Power Sub-Modules
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1158-F03-06
3D Thermal-Fluid and Stress Analysis for Single Chip SiC Power Sub-Modules Bang-Hung Tsao1, Katie Sondergelt1, Jacob Lawson1, James Scofield2, Levi Elston 2 1
University of Dayton Research Institute, 300 College Park, Dayton, OH 45469, USA
2
Air Force Research Laboratory, 1950 Fifth Street, WPAFB, OH 45433, USA
ABSTRACT A three dimensional thermal-fluid and stress model of a single chip SiC power submodule was generated using ANSYS in order to determine the maximum temperature and deformation under various conditions. The effects of heat flux, working fluid temperature and differential pressure on temperature and thermal stress contours were of particular concern. Steady state analysis with water as the working fluid, a simulated heat flux of 11.12x104 W/m2, an interface coupling film coefficient of either 30 or 200 W/m2-K between the cooling plate and fluid, and ambient film coefficients from 6 W/m2-K to 300 W/m2-K, predicts maximum device junction temperatures between 374 and 316 K, and corresponding deformations from .0351% to .0293%. Under the same boundary and loading conditions, but with air as the working fluid, the deformations reached .0405% to .0296%, with temperatures between 427 and 316 K. Transient analysis also showed junction temperatures in the predicted range and determined the time to reach steady state to be between 150 and 2500 seconds depending on the boundary conditions. Experiments were conducted in order to validate ANSYS results. INTRODUCTION SiC is an excellent candidate for modern power electronics due to its superior breakdown voltage, thermal conductivity, and inherent resistance to radiation and chemical attack [1]. Discrete SiC devices have many advantages, most notably, reduced switching losses, high voltage, and high temperature capability [2]. As a result, the use of SiC devices can increase system efficiency and reduce volume and weight. Though a SiC switch module potentially requires less cooling and offers increased reliability, power module failure mechanisms tend to be thermally activated or enhanced [3]. These thermo-mechanical failure modes are expected to be significantly accelerated under some of the high temperature operating conditions projected for SiC power electronic devices. The objective of this study was to use ANSYS [4] finite element analysis (FEA) to predict temperature and stress distributions for notional SiC power module geometries under various loading and environmental conditions to be subsequently validated by experiment. EXPERIMENT Modeling Setup A schematic of the simulation model geometry is shown in Figure 1. To simulate the effect of energizing the “device,” a heat flux of 11.12x104 W/m2 was applied to the SiC chip through the heater. To represent modest convective cooling, ambient heat transfer coefficients were applied as constants on all exposed surface areas of the solid materials: film coefficients of
6 and 25 W/m2-K which are in the natural air convection cooling range, and coefficients of 50, 150 and 300 W/m2K which are commen
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