Experimental Study on Dielectric Behavior of Silicone Gel Under Long-term High Temperature Service

As a polymer with stable chemical properties and electrical strength, silicone gel is widely used in the packaging of IGBT. With the development of IGBT towards higher power, the reliability of packaging materials has attracted wide attention. In this research, a blast drying oven was used to simulate high-temperature service conditions in accelerated thermal aging tests. Broadband dielectric spectroscopy and power frequency breakdown voltage experimental test platforms were used to characterize the dielectric behavior of silicone gels at different aging stages. Finally, the mechanism was discussed by FTIR test. The experimental results show that ε' does not vary much in the frequency range, while ε” produces a relaxation phenomenon. In considering the influence of service time, the polarization is more pronounced due to the exposure of the shedding of the side chains and the Si-O-Si main chain to the electric field, which leads to an upward trend in both the ε' and ε'’. Similarly, due to the increase of free volume and the increase of microdefect, the power frequency breakdown electric field strength of the sample decreases. This research provides a basis for the performance improvement of silicone gel.