Dielectric Characterization of Polyimide for UWBG Power Module Packaging at High Temperature

Recent emergence of ultra-wide bandgap (UWBG) semiconductor-based power electronic modules provide fast switching speed, high voltage rating, and high gravimetric and volumetric power densities with high-temperature operation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(&gt;250^{\circ} \mathrm{C}\right)$</tex>. In these power module packaging, encapsulation plays a crucial role in providing protection against electrical breakdown, mechanical stress, chemical erosions, etc. Consequently, encapsulant materials with superior dielectric properties, high thermal and mechanical stability are required for UWBG-based power electronic packaging. Conventional encapsulant Silicone Gel (SG) struggles when the operating temperature rises above 200° C. Polyimide (PI), known for its outstanding operating temperature and mechanical properties, shows its potential to replace SG for high-temperature and high-power-density applications. In this study, the mechanical and thermal performance of SG and PI is compared using Finite Element Analysis (FEA). For this purpose, a numerical model of a basic power module has been developed in COMSOL Multiphysics that compares the mechanical stability of SG and PI as encapsulants. Stress and temperature distribution in the power module have been compared for both SG and PI. This study demonstrates significant improvement in the mechanical and thermal behavior of the power module when PI is used as an encapsulant. The numerical comparison conducted in this study highlights the potential of PI as a robust encapsulant for hightemperature operation in UWBG-based power electronic packaging.