Comparison of heat resistance of silicone products used for encapsulant in power modules

Power devices are developing towards high power density and miniaturization, which proposes requirements for the heat resistance of encapsulation materials. In this paper, six kinds of silicone products widely used as the encapsulant in power modules were compared. Based on thermal gravimetric analysis (TGA), morphology, and Fourier infrared spectroscopy (FTIR) results, it was found that few heat-resisting fillers filled silicone elastomers with the excellent short-time and long-time heat resistance is potential to apply in power modules at high temperature. For commercial silicone gel, with increase of aging time, the hardness is increased due to compacted molecular network and reduced free volume, which is caused by thermal oxygen aging reaction. Due to the inhomogeneous reacted regions and adhesion to ceramic substrate, the inhomogeneous stress leads to the breakage of hardened silicone gels. This paper provides the deep understanding of behaviors of silicone gel and verify the feasibility of silicone elastomers at high temperature, which is beneficial to high-temperature encapsulation for power modules, especially for SiC products.