Insulation and Reliability Enhancement by a Nonlinear Conductive Polymer-Nanoparticle Coating for Packaging of High-Voltage Power Devices

It is a challenging to package SiC power devices for high-voltage applications. Field-dependent conductivity (FDC) materials, which has nonlinear electric conductivity and were proved capable of reducing peak electric field intensity greatly at the triple points, had attracted much attention. However, it was more critical to make the FDC insulation reliable against high temperature and thermomechanical shocking. In this article, we proposed a new polyimide-based FDC coating (PI-FDC-C), which was capable of improving the equivalent heat resistance temperature by almost 100 C-degrees and reducing the thermomechanical stresses greatly by 45.1%, as a robust insulation for packaging high-voltage power devices. The partial discharge inception voltage (PDIV) of module demonstration could be improved by at least 55%. There was no degradation of nonlinear electric conductivity after 120-h storage at 200 C-degrees and no crack or interfacial delamination in the adjacent of the triple points even after 1000 cycles of the thermal shocking. It is quite encouraging to use the PI-FDC-C as a robust alternative to packaging high-voltage SiC power devices.