Development of Nonlinear Resistive Field Grading Materials for Electric Field Mitigation in Power Electronic Modules

The increasing blocking voltage and compact packaging of wide bandgap (WBG) semiconductor-based power electronic converters (PEC) cause extremely high electric field stress near the triple-points where metallic electrode, dielectric substrate, and silicone gel are in close proximity. The intensified local electric stresses initiate partial discharge (PD) leading to the degradation and aging of electrical insulators. In this study, the electric stress reducing ability of nonlinear field grading material (NLRFG) is investigated by performing finite element analysis (FEA). Electric field magnitudes near the triple points of an insulated metal substrate (IMS) with and without the incorporation of NLRFG materials are compared by applying 60 Hz AC voltage according to the PD test standard. In addition, the fabrication process and characterization of the NLRFG materials are reported in detail.