Electroless Sn–Ni alloy plating with high Sn content free of activation pretreatment

Electroless plating technique was used to coat Sn–Ni alloy on copper substrate with high Sn content by adding the amounts of thiourea as special complexing agent and sodium hypophosphite as reducing agent to an acidic electroless plating bath of SnCl2 and NiCl2, which avoided activation pretreatment in plating process. The Sn content of the Sn–Ni layer increased with lowing temperature which reached 60 wt.% under optimum plating conditions. The effect of thiourea and sodium hypophosphite amount, plating temperature, and the acidity of plating bath was also discussed in this article. The corrosion-resistance properties of Sn–Ni alloy layer proved to be good by testing the anodic polarization curves of the alloy layer.