The design and properties of new, Pb-free solder alloys

Environmental and health concerns about the toxicity of Pb in solders have prompted a great deal of research to find suitable Pb-free replacement alloys. The goal of the research presented in this paper is to identify Pb-free alloys as close in melting temperature to the near-eutectic 40 Pb-60 Sn solder (melting point of 183°C) that possess the best combination of mechanical properties. Enhanced mechanical properties are achieved through metallurgical manipulation of alloy microstructures. Three alloys are presented with superior mechanical properties: i) Sn-3.5 Ag-1 Zn with a melting point of ~217°C, ii) Sn-3.5Ag-1 Zn-0.5 Cu with a melting point of ~226°C, and iii) Sn-8Zn-5In-(O.1-0.5)Ag with a melting point of ~187°C