The design of new, Pb-free solder alloys with improved properties

The goal of the research presented in this paper is to identify Pb-free alloys with melting temperatures close to or lower than that of the near-eutectic 40Pb-60Sn solder (melting point of 183/spl deg/C), and that with the best mechanical properties. We have obtained substantially improved mechanical properties through manipulation of alloy microstructures. The following three alloys with superior mechanical properties are discussed: i) Sn-3.5%Ag-1%Zn-0.5%Cu with a melting point of /spl sim/216/spl deg/C, ii) Sn-8%Zn-5%In-(0.1-0.5%)Ag with a melting point of /spl sim/187/spl deg/C, and iii) 54.5%Bi-45%Sn-0.5%Ag with a melting point of /spl sim/140/spl deg/C.