Ceramic substrates dependent electrical field distribution at triple points in SiC power modules under pulse waves and high temperatures

Electrical field (E-field) distortion at triple points would cause insulation failures insides silicon carbide power modules, which is closely related to surrounding ceramic substrates’ electrical parameters. Herein, we investigate the effects of ceramic substrates on frequency and temperature dependent E-field intensity at triples points under positive polarity square wave. The E-field intensities vary little with frequencies. Notably, E-field intensity with Al₂O₃ and AlN substrate packages increases by 69.3% and 48.3% from 18 kV/mm, while that with Si₃N₄ substrate package stay almost stable around 18 kV/mm from 100°C to 200°C, which demonstrates that Si₃N₄ substrate can be used to suppress E-field distortion under high temperatures. Moreover, it is found that temperature dependent E-field intensity is governed by electrical conductivity ratio between ceramic and silicone encapsulants. A modified quantitative relationship among materials parameters, temperature, E-field intensity at triple points is proposed. This paper provides the fundamental understanding of selection for packaging materials for high-temperature power modules, which is critical for high-density power electronics systems.