WBG Power Semiconductor Module Packaging Insulation Characteristics Under Electrothermal Stress

As core components of increasing power density, the new generation wide bandgap (WBG) power semiconductor modules are advancing toward higher voltage levels. However, the reliability of packaging insulation serves as a significant constraint, notably concerning the insulation degradation induced by high temperatures working conditions within confined spaces. In this article, a simplified power module test model featuring a directed bonding copper (DBC) and silicone gel was established. Through partial discharge (PD) tests across temperatures spanning 25 °C–175 °C and different etching distances for substrate layout, the insulation degradation mechanism of power modules at varying temperatures is comprehensively explored. The results indicate an obvious reduction in the PD inception voltage (PDIV) with rising temperature, exhibiting an uptrend over 75 °C. Simultaneously, the discharge amplitude initially increases and subsequently decreases with rising temperature. The thermal expansion of tiny air-gap defects within the silicone gel emerges as a significant factor influencing the module’s insulation characteristics. Ultimately, by establishing a proportional air-gap defect model, the electric field and space charge distribution were studied under electrothermal coupling, validating the effectiveness of the insulation defect mechanism.