Wetting process and interfacial characteristic of Sn–3.0Ag–0.5Cu have been investigated at temperatures ranging from 503 K to 673 K on Cu, Ni, stainless steel and quartz, respectively. The reactive wetting behavior of Sn–3.0Ag–0.5Cu melt alloy on Cu and Ni substrates were investigated. Contact angles decrease as exponential decay and equilibrium contact angles decrease between the solder and Cu, Ni substrates monotonously with the temperature increasing. The configuration of the triple line of Sn–3.0Ag–0.5Cu/Cu is discussed by the description of equilibrium. The calculated results based on experimental values of tension balances along each of the three interfaces at this final state show good agreement with theoretical analysis. Intermetallics of the Sn–3.0Ag–0.5Cu/Ni interface are identified as (Cu, Ni)6Sn5 adjacent to the solder and Ni3Sn4 adjacent to the Ni substrate, respectively. The contact angles between Sn–3.0Ag–0.5Cu and quartz, stainless steel substrates were measured to be greater than 90°, which means non-wetting, in the temperature range from 503 K to 673 K. Liquid–solid interfacial energy between the solder and different substrates are obtained based on the surface tension of molten solder and equilibrium contact angles at different temperatures. These results are of practical interest for composite lead-free solders preparations and joining of Sn–3.0Ag–0.5Cu to various substrates.
