Electrical Treeing Failure in Silicone Gel under Positive Repetitive Square Voltage in High-Voltage IGBT Module Encapsulation

The insulating properties of silicone gel, which is widely used as the encapsulation of power electronic modules, directly determines their electrical insulation reliability, so the effects of applied voltage parameters in practical application scenarios should be investigated. In this paper, the effects of the frequency, rise time, and duty cycle of the positive repetitive square voltage on the initiation and growth characteristics of electrical trees in silicone gel are investigated by means of a pin-plate electrode structure to simulate spike-like defects in power electronic modules. The frequency mainly affected the growth characteristics of electrical trees after the initiation of electrical trees. The rise time has an effect on the tree inception voltage (TIV), and the duty cycle not only affect the growth characteristics of electrical trees but also the TIV. The related mechanisms are discussed and explained in detail. The findings are expected to provide a guidance for the design optimization and of reliability improvement of the encapsulation in high voltage power electronic modules.