Fabrication of Palladium-Free Nickel-Coated Carbon Fiber Reinforced Sn-3.0Ag-0.5Cu Composite Solder

Palladium-free nickel coating was deposited on the surface of carbon fibers by an electroless plating method. Nickel coated carbon fibers reinforced Sn-3.0Ag-0.5Cu composite solder was prepared using the powder metallurgy technique. The microstructure of the composite solder was analyzed by SEM, EDS and OM. The effect of nickel coated carbon fiber contents on the microstructure and properties of the composites solder was studied. The results show that the nickel coated carbon fibers are mainly distributed in the grain boundary of the composite solder. The dispersity of the coated carbon fiber decreases with its content increasing, while the melting point of the composite solder changes little. When the coated carbon fiber content is greater than 1% (mass fraction), obvious agglomeration appears in the reinforced phase, which leads to the higher electrical resistivity. The 1% addition of coated carbon fiber will be helpful to decrease the surface tension of liquid composite solder between the flux and copper substrate, which causes the excellent wetting effect. At the same time, the current density of solder matrix decreases, which results in the lower electrical resistivity of the composite solder.