Study on the Influence of Pressure on Bubble Movement in Silicone Gel

Silicone gel has sealing, viscosity, high temperature resistance and good insulation properties, and is widely used in the packaging of high pressure IGBT devices. The residual bubbles in the process of potting and degassing of silicone gel are easy to produce partial discharge or even breakdown, which seriously affects the insulation reliability of IGBT devices. The motion characteristics of bubbles in silicone gel during potting and degassing were studied in this paper. The motion characteristics of bubbles are simulated by VOF method. The results show that the bubbles in silicone gel are spherical and their trajectories are straight lines under different pressure changes. The bubble rises at a constant speed under normal pressure, increases rapidly during depressurization, decreases during pressurization, and increases slowly under vacuum. The research results in this paper provide guidance for bubble removal and degassing curve optimization of silicone gel in IGBT device potting and degassing process.