Thermal Verification of a High-Temperature Power Package Utilizing Silicon Carbide Devices

The researchers at Arkansas Power Electronics International, Inc. and ROHM CO., LTD. have simulated and tested high-temperature packaging technologies for SiC devices in an effort to develop more accurate modeling parameters for future applications. The laboratory test consists of parallel SiC power DMOSFETs, manufactured by Rohm, and SiC power VJFETs operating under self-regulating current sharing conditions. To produce accurate thermal simulations, thermal models require numerous design parameters that are constrained to strict tolerances. Moreover, this presents an interesting challenge at junction temperatures (Tj) over 175 °C as most individual components have not been previously tested or verified at these temperatures. To extract these parameters at high-temperatures, the researchers have modeled a complete thermal system (including bare die, substrate, package, heatsink, and all thermal interfaces between said components) then built and tested an identical system to characterize the system’s parameters over temperature. Specifically, the advantages between different types of thermal interfaces, including die attaches, substrate attaches, and thermal greases, were characterized over temperature. A high resolution thermal imaging camera was used to capture surface temperatures of the system to compare with simulation results. Due to mismatches in emissivity between components, multiple high-temperature conformal coatings were tested and characterized over temperature, as well. In this paper, the researchers will present the results of the laboratory testing that included the characterization of SiC DMOSFETs and SiC VJFETs operating up to 300 °C, as well as the thermal simulation results.