Effect of Temperature on Electrical Treeing in Silicone Gel for Power Modules

Silicone gel is widely used to encapsulate power electronic modules. The weakness of the electrical insulation is surface discharges initiated at the gel-substrate-electrode triple junction and the subsequent formation of cavities, so-called electrical trees. Although power modules are operated at high temperatures, few researchers study the influence of temperature on electrical treeing in silicone gel. Thus, the effect of temperature on cavity propagation and phase-resolved partial discharge (PRPD) pattern in silicone gel are investigated. When the temperature is higher, the PD amplitude is larger, the cavity length is longer, and the void number is larger. The cavity length at high temperatures is more than two times as long as that at room temperature. Therefore, it is necessary to understand electrical treeing in silicone gel at high temperatures to improve the reliability of power modules.