Dielectric Properties Characterization and Evaluation of Commercial Silicone Gels for High-Voltage High-Power Power Electronics Module Packaging

The lack of a method to select the suitable silicone gel from various commercial silicone gels for encapsulation in next-generation high-voltage high-power electronics modules has become a challenge. In this article, a comprehensive evaluation approach of three commercial silicone gels is carried out via multiple characterizations in terms of surface microstructure, main internal components, dc volume resistivity, dielectric properties, breakdown strengths under dc and ac voltages, thermogravimetric properties, and glass transition temperature. This study shows that the analytical tools set proposed in this article can be used as an efficient guideline for comparing different types of silicone gels and selecting suitable silicone gels for different applications. For example, the drawn radar chart intuitively shows that Gel 3 has the best all-around performance in both electrical and thermal properties, and Gel 1 has the highest thermal stability. The surface microstructure and internal functional groups of the three silicone gels are almost the same. The glass transition temperatures of the three silicone gels were also measured, and the thermo gravimetric analysis (TGA) showed that the three silicone gels had high thermal stability. According to the test results and analytical tools established in this article, we were able to identify silicone gels suitable for different applications. In this regard, Gel 3 is suitable for applications with higher voltage levels (10-20 kV), while Gel 1 and Gel 2 are suitable for lower voltage levels.