Interfacial reactions with lead (Pb)-free solders

The interfacial reactions of Cu and Ni base metals with several lead-free solders are investigated at their corresponding reflow temperatures. The solid-liquid reaction which occurs during the initial solder joint formation and rework process is simulated by the studied interfacial reactions. The Pb-free solders used in the investigation include: Bi/Sn, Sn/Ag, Sn/Sb and Sn. The Sn/Pb eutectic solder is also included as a benchmark to compare the reaction kinetics with those of the Pb-free solders. The dissolution kinetics of Cu and Ni into the Pb-free solders as well as the growth kinetics of the intermetallic phases are measured using cross-sectional metallography of reaction couples and are compared with those obtained from the Sn/Pb eutectic solder.