2019 Volume 60 Issue 6 Pages 888-894
The purpose of the present study is to investigate the melting properties, microstructures, tensile properties and fatigue properties of Sn–5Sb–(0.05–0.50)Ni (mass%) high-temperature lead-free solders. The solidus temperature and liquidus temperature of the Sn–5Sb–Ni solders are approximately equal to those of the Sn–5Sb alloy. From the result of EPMA mapping analysis and the Sn–Sb–Ni ternary phase diagram, the Sn–5Sb–Ni solders are found to consist of β-Sn, SbSn and NiSb phases. As the amount of Ni in the Sn–5Sb–Ni solder increases, the number of NiSb phases increases and the phases are coarsened so that the 0.1% proof stress and tensile strength increase, and the elongation decreases at 25°C. In contrast, the effects of the Ni content on the tensile properties are negligible at 150°C and 200°C. The fatigue ductility exponent α of the Sn–5Sb–Ni solders is smaller than that of the Sn–5Sb solder at 25°C. At 150°C and 200°C, the α values of Sn–5Sb–0.05Ni and Sn–5Sb–0.10Ni remain small, whereas those of Sn–5Sb–0.25Ni and Sn–5Sb–0.50Ni increase. This means that the Sn–5Sb–Ni solders with 0.05–0.10 mass% Ni have superior fatigue properties to the Sn–5Sb solder in the temperature range from 25°C to 200°C.