Design and Evaluation Methodology of Bi₂O₃/Epoxy-Based Composite Coatings for Radiation Hardening by Packaging

The high-cost problem in radiation hardening for specific types of aerospace integrated circuits can be effectively addressed by adopting composite coatings, which demonstrate advantages such as low cost, lightweight, and broad versatility. This study analyzed the radiation environment within spacecraft interiors and investigated the mechanisms of electron radiation protection by coatings, highlighting the performance advantages of Bi₂O₃/epoxy resin (Bi₂O₃/EP) composites. A co-simulation model of “coating + circuit” was established to determine the radiation protection efficiency (RPE) under various electron energies, coating compositions, and thicknesses. Furthermore, a calculation method for the comprehensive RPE under continuous electron spectra was developed. The study proposed a novel evaluation metric, the shielding effectiveness comprehensive index (SECI), which incorporates both RPE and areal density. FLASH circuit samples packaged with Bi₂O₃/EP composite coatings were fabricated and subjected to thermal-mechanical-electrical reliability testing. Electron irradiation experiments on both the standalone coatings and the package-hardened circuits were conducted, with coating results validating the high accuracy of the simulation model. Additionally, a novel RPE evaluation method based on the intrinsic electrical parameters variations (IEPV) of circuit was introduced. This method successfully determined the RPE of coatings against 5 MeV electrons in the practical circuit application state, achieving a simulation error of less than 25%. The SECI and IEPV evaluation methodologies proposed herein provide valuable technical guidance for designing protective coatings for circuits and enable effective assessment of the radiation resistance for package-hardened circuits.