Characteristics Analysis of Silicone Gel Electrical Treeing for Power Device Packaging Under High Temperature Coupled Square Wave Pulse Electric Field

Silicone carbide power devices present the advantage of having a high temperature resistance, high voltage resistance, fast switching speed, high operating frequency and low conduction loss. However, their high power density characteristic results in a sharp rise in the operating temperature of power devices. As a common packaging insulation material for high-voltage power devices, the high temperature seriously affects the insulation performance of silicone gel. In this paper, an electrical treeing test platform under electrothermal coupling field is set up. The step voltage and staircase voltage are respectively used to simulate the instantaneous sudden change voltage of the power device in the actual work and the continuous stable voltage under the on-state and off-state. A negative square wave pulse electric field is applied to the test sample, and the change rule of the initial voltage of the silicone gel electrical treeing with temperature under step voltage and staircase voltage in the range of 20° to 180° is explored. The influencing mechanism of temperature on the initiation and growth of electrical treeing under different voltage methods was analyzed from two aspects: crosslinking degree and bubble dynamic behaviors.