Reactivity between Sn–Ag Solder and Au/Ni–Co Plating to Form Intermetallic Phases

Abstract

For the formation of micro joint not to melt by secondary reflow soldering, we tried to enhance the reactivity of Sn–Ag solder with Au/Ni–20Co plating. It was confirmed that the addition of Co in Ni and existence of Au plating effectively accelerated the reaction and the Sn–Ag solder completely transformed to the intermetallic compounds with a higher melting temperature.Particularly, the addition of Co in Ni changed the interfacial reaction layer from Ni3Sn4 to (Ni,Co)Sn2 with higher diffusivity of Ni which enhanced the formation of the intermetallic phases. This process is expected to replace the packaging technology using high temperature solders.