Nonlinear Resistive Electric Field Grading in High-Voltage, High-Power Wide Bandgap Power Module Packaging

Wide bandgap (WBG) power modules made from materials such as SiC and GaN (and soon Gm(2)O(3) and diamond) able to tolerate higher voltages and currents than Si-based modules are the most promising solution to reducing the size and weight of power electronics systems. Using higher blocking voltages for WBG modules and not increasing the insulating dimensions of the module to an appropriate size, will increase electric field stress within the module. The higher electric stress, the more risk for unacceptable partial discharge (PD) activity and in turn, gradual insulation degradation, leading to breakdown and the module failure. The insulation material in the power modules vulnerable to PDs is silicone gel, which is used for encapsulation. Thus, electric field reduction techniques are proposed to address this issue. The proposed geometrical techniques cannot solve alone this issue. In this paper, we introduce a new method that is a combination of applying nonlinear field dependent conductivity (FDC) materials to high electric stress regions with geometrical techniques that can thoroughly address the electrical field enhancement issue within WBG modules.