Wetting behavior and evolution of microstructure of Sn-3.5Ag solder alloy on electroplated 304 stainless steel substrates

In the present study, wetting characteristics and evolution of microstructure of Sn–3.5Ag solder on Ag/Ni and Ni electroplated 304 stainless steel (304SS) substrates have been investigated. Solder alloy spread on Ag/Ni plated 304SS substrates exhibited better wetting as compared to Ni/304SS substrate. The formations of irregular shaped and coarser IMCs were found at the interface of solder/Ni/304SS substrate region whereas, solder/Ag/Ni/substrate interface showed continuous scallop and needle shaped IMCs. The precipitation of Ag3Sn, Ni–Sn, FeSn2 and lesser percentage of Fe–Cr–Sn IMCs were found at the interface of solder/Ag/Ni/substrate region whereas, solder/Ni/304 SS substrate exhibited predominantly FeSn2 and Fe–Cr–Sn IMCs. Presence of higher amount of Fe–Cr–Sn IMCs at the solder/Ni/304SS substrate interface inhibited the further wetting of solder alloy.