Investigations of high-temperature tensile properties of Zn–25Sn–x(0.1–0.2)Cu–y(0.01–0.02)Ti high-temperature Pb-free solders

The use of Pb-containing solders in electronic products has been restricted due to their harm to both human health and the environment. Although the Sn–37Pb solder has been well replaced by Sn–3.0Ag–0.5Cu or other Pb-free solders, there is no drop in replacement for high-temperature Pb-free solders. In this study, the microstructure and high-temperature tensile properties of the Zn–25Sn–x(0.1–0.2)Cu–y(0.01–0.02)Ti high-temperature Pb-free solders were investigated. The design of the moderate alloy composition prevented undesirable Cu- and Ti-containing intermetallic compound formation that may cause alloy embrittlement. The solders exhibit superior tensile strength and competitive elongation compared with the conventional high-Pb solders and the other potential candidates. The Zn–25Sn–xCu–yTi solders can be strengthened in terms of the tensile strength enhancement without a loss of ductility under both room-temperature and high-temperature testing conditions. The minor Cu and Ti elements served as heterogeneous nucleation sites for inducing the microstructure refinement of the primary (Zn) phase. The Cu-in-Zn solid solution phenomenon as well as the formation of deformation twins during the high-temperature tensile test also contributed to the superior tensile properties of the designed alloys.