Abstract: The change in shear force and evolution of interfacial microstructure of Sn-3.8Ag-0.7Cu-0.05Nd/Cu solder joint at the temperature 150 ℃ were investigated. The effect of rare earth Nd on the high temperature reliability of the solder joint and the corresponding enhanced mechanism were discussed. The results showed that the shear force of Sn-3.8Ag-0.7Cu-0.05Nd/Cu solder joint was significantly higher than that of Sn-3.8Ag-0.7Cu/Cu solder joint after different aging hours, and the decrease rate of shear force of Sn-3.8Ag-0.7Cu-0.05Nd/Cu solder joint was lower than that of the original solder joint during the aging process. This is because 0.05% Nd could reduce the interfacial diffusion coefficient from 1.88×10⁻¹⁰ cm²/h to 1.10×10⁻¹⁰ cm²/h, that is to say, the high temperature reliability of solder joints could be improved by inhibiting the coarsening of interfacial intermetallic compounds.