Effects of In addition on the wettability, interfacial characterization and properties of ternary Sn–Cu–Ni solders

The thermal behavior, wettability, corrosion resistance, microhardness and interfacial reaction of quaternary Sn–0.7Cu–0.1Ni–xIn (x = 0, 0.5, 1.0 and 2.0 mass%) lead-free solder alloys were explored to reveal the effect of the indium (In) addition into the Sn–0.7Cu–0.1Ni solder on the properties of the solder alloy in the present investigation. The tested results revealed that the addition of small amount of In could lower both solidus and liquidus temperatures of the solder alloys. Moreover, the wettability of the solder alloy was remarkably improved by adding In element. The spreading area of Sn–0.7Cu–0.1Ni–1In was enhanced by 37% compared to that of Sn–0.7Cn–0.1Ni solder, meanwhile, the wetting angle of Sn–0.7Cu–0.1Ni solder was reduced by 39.1% with the addition of 2.0 wt% In. The intermetallic compound (IMC) formed between Sn–0.7Cu–0.1Ni–xIn solders and copper substrate was identified as (Cu,Ni)₆Sn₅ compound layer. The thickness and grains size of the IMC were slightly effected by the addition of In. The corrosion resistance of Sn–0.7Cu–0.1Ni–xIn solders increased with the addition of In, and the corrosion rate of Sn–0.7Cu–0.1Ni–1In solder was reduced by 62.8% compared with that of Sn–0.7Cu–0.1Ni solder in the 6% hydrochloric acid solution at ambient temperature for 14 days. Moreover, the hardness showed a decline of 14.7% when 2.0 wt% In was added into the Sn–Cu–Ni solder.