Advanced housing materials for extreme space applications

Thermal stresses have a significant impact on the mechanical integrity and performance of RF hybrid circuits. To minimize this impact, a series of spray deposited Si-Al alloys were evaluated for use in electronic housing applications. Current housings for RF modules in space-based applications are generally made from either Kovar or 6061 Al. Although Kovar has a coefficient of thermal expansion (CTE) close to those of GaAs and Si, it also possesses a 10× reduction in thermal conductivity and a 3× increase in density compared with those of 6061 Al. Although it provides improved heat dissipation properties, 6061 Al has a CTE that is nearly 4× that of Kovar. The controlled expansion (CE) spray deposited Si-Al housing materials discussed herein combine a CTE approaching that of Kovar, with a thermal conductivity approaching that of 6061 Al, and a density that is less than that of both materials. The mechanical behavior of select Si-Al alloys was evaluated along with the application of these materials for direct attachment of active devices. Assemblies were thermal cycled from -55 to +125°C.