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

摘要

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 embrit-tlement. 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.