A Study on the Bonding Reliability of SiC Waveguide Loads for Satellite Communication

Absorbing materials serve as vital passive components in antenna, microwave transmission, and test systems by eliminating unwanted microwave energy to enhance performance. In waveguide systems, these materials are precision-cut and securely fixed to match waveguide geometries, ensuring efficient energy absorption without impedance mismatch. This study investigates the bonding of silicon carbide (SiC) absorbers to rectangular waveguides using EC2216 epoxy adhesive, focusing on optimizing adhesion reliability and electrical performance. Vacuum outgassing tests revealed that post-curing degassing reduced the adhesive’s Total Mass Loss (TML) from 1.2% to 0.55%, substantially lowering low-pressure discharge risks in orbital operations. However, adjusted vacuum baking parameters (200 Pa, 90°C, 48 hours) achieved a practical TML of 0.71% to balance performance with production efficiency. Post-environmental shear force analyses identified critical interface dependencies: untreated aluminum conductive oxidation interfaces demonstrated superior bonding strength compared to copper-gold-plated or aluminum-silver-plated surfaces. Residual organic films and brighteners from waveguide cavity treatments were pinpointed as primary causes of absorber delamination post-thermal shock, severely undermining cavity bonding reliability. Electromagnetic simulations further examined adhesive overflow effects on wedge-shaped absorbers’ microwave performance, emphasizing the necessity of precise adhesive application to maintain absorption efficiency. The findings underscore the interplay between material processing, interfacial treatments, and long-term operational stability, providing actionable guidelines for optimizing waveguide load designs and expanding their applicability in high-reliability microwave systems. Key takeaways include the importance of surface cleanliness in adhesion integrity, the trade-offs in degassing protocols for space-grade components, and the superiority of minimally processed aluminum interfaces in harsh environments.