A Hermetic Conformal Coating Based High-Temperature Encapsulation Method for 250 °C SiC Power Module

Featuring excellent material properties, silicon carbide (SiC) power devices emerge as the most promising candidates in high-temperature and high-power applications. However, existing silicone gel packaging techniques fail to meet the requirements for long-term reliable operations beyond 250 °C. To address this issue, this article proposes a hermetic conformal coating (HCC) packaging method. This innovative approach utilizes a conformal coating to ensure a reliable insulation during long-term service at 250 °C, while only introducing minor thermomechanical stress. Furthermore, hermetic sealing effectively safeguards the internal circuit by blocking water and oxygen and providing mechanical protection. A high temperature SiC power module based on HCC is fabricated, and its electrical characteristics are evaluated using a curve tracer and a double pulse test platform. Subsequently, a 250 °C high-temperature storage test and a thermal shock test (−55 °C to 250 °C) are conducted to compare the conventional silicone gel packaging method with the proposed approach. Experimental results demonstrate the superior performance of the proposed approach for long-term operation under high temperature and across a wide temperature range. Finally, a 600 V 250 °C continuous operation experiment is performed using a buck converter to validate the efficacy of the proposed HCC method.