ABSTRACT

During the Second World War, a situation occurred-in retrospect rife with irony given the current subject of this book-when wartime demands for tin (Sn) led to an effort to develop Snfree solder alloys. The results of this effort were not entirely successful and produced lead (Pb)- rich alloys that exhibited poor wetting properties in comparison to their Sn-Pb predecessors that were Sn-rich. A deep appreciation developed for the excellent wetting characteristics with which Sn endows many solder alloys. Now, some 60 years later, a markedly different imperative has served to initiate an effort to identify a set of candidate Pb-free solder alloys capable of replacing the existing Pb-Sn alloy set. This effort is spurred by health concerns over Pb in the waste stream and by economic concerns that thosewith Pb-freemicroelectronics products would attain an edge in the market place based on the environmentally benign character of their products.