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

Abstract

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 Ag<inf>3</inf>Sn, Ni-Sn, FeSn<inf>2</inf> 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 FeSn<inf>2</inf> 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.