Characteristics and Microstructural Development of Cold-Sprayed Copper Coating on Aluminum

The cold spray method is a coating process that should improve the wettability of solder to aluminum surfaces. In this study, Cu powder particles were deposited on commercially pure Al via cold spraying, and the characteristics and microstructural developments of the deposited layer, interface, and substrate were investigated. Cu coatings, with an electronic resistivity similar to that of commercial solder, could be formed on the Al substrate. Solid-state bonding was partially achieved between the Cu particles. Interdiffusion occurred at the interface between the cold sprayed Cu particles and the Al substrate, forming the reaction phases, and the Cu coating was bonded to Al substrate along almost the entire bond interface. The impact of high-velocity particles induced dynamic recrystallization and grain refinement of Al, resulting in increased hardness near the surface of the Al substrate. The thickness of the hardened region was similar to 10 mu m. Tin-based solder paste exhibited good wettability to the cold-sprayed Cu coating.