Abstract: The effects of Nd addition(0, 0.05, 0.5wt%) on the microstructure and shear strength of SAC solder joint under as-reflowed and 150℃ isothermal-aging process were investigated. Experimental results showed that Nd addition can obviously improve the shear strength and microstructure of the SAC solder joints. The growth rate of the SAC/Cu interfacial layer as well as the coarsen rate of Cu₆Sn₅ particles in the Sn matrix during aging process was both restrained by Nd addition, which would enhance the reliability of the solder joint during service process. Moreover, during aging process, the shear strength reduction rate of SAC-0.05Nd solder joint was lower than that of SAC, but the shear strength reduction rate of SAC-0.5Nd solder joint showed no obvious difference compared with that of SAC because of the coarsen of NdSn 3 phase in aging process.