Processing of Silvar for MIC Packaging Applications

Materials with high thermal conductivity and thermal expansion coefficient matching with that of GaAs are being used for packaging high-density microwave integrated circuits (MICs) due to their ability of faster heat dissipation. Powder metallurgy (P/M) has emerged as a promising technique for the processing of metal matrix composites (MMCs) in satellite applications such as thermal management materials. Individual components in these composites must retain their metallurgical identity. The present study investigates the processing of silvar (Fe–Ni–Co–Ag) alloys for thermal management materials. For these silvar alloys, composition was varied by varying the silver content from 15 to 35 wt. %. The compacts were pressed at 400 and 600 MPa and sintered/infiltrated at 1100 $^{circ}{hbox {C}}$, 1150 $^{circ}{hbox {C}}$, and 1225 $^{circ}{hbox {C}}$. Quantitative metallographic measurements were performed on all sample and the results were discussed. It was observed that all samples were sintered without any shape distortion. Microstructural evaluation reveals that higher compaction pressure resulted in highly contiguous structure. In spite of density differences between constituents, none of the alloys showed segregation. Coefficient of thermal expansion (CTE) values of the liquid phase sintered composites is near to the values obtained by rule of mixtures.