Interfacial Reactions During Soldering with Lead-Tin Eutectic and Lead (Pb)-Free, Tin-Rich Solders

Lead (Pb)-containing solders used for the interconnections of microelectronic sub-system assembly and packaging have been a subject of the environmental issues recently. Extensive research and development activites for replacing Pb-containing solders with Pb-free solders are in progress in electronic industries, Universities and National Laboratories. One key technical issue recognized with the Pb-free, Sn-rich solders is a need to develop a good barrier metallurgy to control the interfacial reactions, namely, dissolution of the base metal(s) and concurrent formation of inter-metallics at the soldering interfaces. In this study, the interfacial reactions of Cu and Ni metallization with several Pb-free and Pb-containing solders are investigated. The dissolution kinetics of the base metal(s) as well as the growth kinetics of the inter-metallics are discussed.