High Temperature Characteristics of Composite Materials Composed of Silicone Gel and Barium Titanate in High Voltage Power Modules

The blocking voltage of silicon carbide (SiC) device is greater than 10 kV. High voltage can cause high electric field inside SiC power module. Improving the insulation properties of the encapsulation material of power module becomes an urgent requirement. The electrical field-dependent permittivity (FDP) material composed of silicone gel and barium titanate (BaTiO3) can be used to reduce the high electric field. However, the related research on FDP materials is limited to the room temperature conditions. It is not enough since the operating temperature of power module is higher than the room temperature because of the power loss, and the temperature has a great influence on the performance of FDP material. This article focuses on the high temperature performance of this composite material in reducing electric field. Firstly, the simulation results show that the triple point between metallization, ceramic and silicone gel is both stressed by high electric field and high temperature. Increasing the dielectric permittivity of the encapsulation material can reduce electric field stress. Secondly, the breakdown voltage and aging properties of silicone gel and the composite were analyzed. The Curie temperature of the FDP material was measured experimentally, which proved that the Curie point of the FDP material would not be changed by the silicone gel. Thirdly, the permittivity of FDP material at different temperatures and the mechanism of reducing the electric field stress are investigated.