Abstract: The effects of Nd addition on the microstructure and mechanical properties of Sn-0.7Cu-0.05Ni/Cu soldered joints under as-reflowed and 150 °C isothermal-aging process were investigated. The results indicated that an appropriate amount of Nd addition could obviously improve the interfacial microstructure and the mechanical properties of Sn-0.7Cu-0.05Ni soldered joints. The optimum properties were obtained while Nd addition was 0.06wt. %. Besides, the growth of the Sn-Cu-Ni/Cu intermetallic compound layer under aging process was restrained by adding 0.06wt.% Nd, which would enhance the reliability of the soldered joints during service process. After aging for 1 440 h, the shear force of Sn-0.7Cu-0.05Ni-0.06Nd soldered joints still ranked the best among all of the tested solders, increased by 31.9% compared to the Nd-free Sn-Cu-Ni soldered joints.