Silicone encapsulants with high thermal stability for SiC power devices under high temperatures

Silicone carbide (SiC) electronic devices with high-power density put forward high temperature stability requirements for their insulation encapsulants. This work explores the thermal stability for three typical organic silicone encapsulant (SEMICOSIL 915HT, R-2188, Duraseal 1533) to obtain the suitable encapsulation materials in high temperatures. The results indicate that the reaction during the methyl oxidation stage of the thermal degradation process is similar to the initial reaction observed during the thermal oxidative aging process in silicone encapsulants. The activation energy for Duraseal 1533 for methyl oxidation reactions is relatively high. After 480 h of aging, for Duraseal 1533, the hardness changes least and the thermal expansion coefficient was the lowest with a change rate of only 0.07. It means that Duraseal 1533 is the suitable material for power devices under high temperatures. Our findings provide a preliminary method for assessing the long-tern thermal stability of silicone encapsulants and offers the guidance for selection of materials for high temperature SiC devices.