Fabrication and characteristics of Cu@Ag composite solder preform by electromagnetic compaction for power electronics

Cu@Ag core-shell particles not only have advantages of Cu and Ag elements but also inhibit Ag migration and Cu oxidation issues. These particles can be potential die attach materials for power electronics. However, micro/nano particles sintering normally form residuals and voids due to binder. Electromagnetic compaction (EMC) can fabricate Cu@Ag solder preforms with low porosity and high internal stress, which can be a trigger to successfully decrease the bonding temperature and pressure during die attach process in previous work. In this work, Cu@Ag solder preform was fabricated by electroless plating and EMC. Effects of EMC parameters on microstructure, property and formation mechanism of Cu@Ag powders were systematically investigated. As the input voltage increased from 2800V to 4400V, the compaction pressure rose to nearly 2700N. The compactness and density of Cu@Ag solder preform increased linearly, while their roughness and resistivity dropped significantly. Besides, thermal stability, oxidation resistance and 2 corrosion resistance of Cu@Ag solder preforms also increased with higher compactness.