Solderability of Ni, Fe Elemental and Alloy Platings by SnAgCu

To provide good adhesion in solder joint for reliable devices, wetting property of lead free solders on FeNi substrate is of great importance for processing and reliability considerations in soldered assemblies. Nowadays, ternary SnAgCu eutectic alloy is considered as one of the leading Pb-free solders for its attractive mechanical and physical properties. Thus the wetting property of SnAgCu eutectic solder on four Ni-Fe electroplatings with variable composition were investigated and evaluated by a Wilhelmy-type wetting balance tester in this study. The Ni and Ni-52Fe platings exhibited shorter time for wetting initiation and smaller contact angle than the other two platings. It is also observed Ni-52Fe plating had the smallest contact angle of 30deg in all platings. Characterized by XPS, it was found that the oxidation layers on Ni and Ni-52Fe platings were much thinner than the other two high Fe bearing platings. Thus, the addition of Fe in Ni plating can effectively enhance the solderability. But more than 75% iron in the plating decreased the solderability, because thick iron-oxide layer formed over the plating surfaces can suppress wetting process.