Abstract: In order to study the effect of intermetallic compound on mechanical properties of joint, the elastic modulus and hardness of intermetallic compounds were analyzed by nanoindentation method, and the creep strain rate sensitivity of solder matrix was obtained by Mayo-Nix method. From the physical analysis of nanoindentation curves, the elastic modulu of(Cu, Ni)₆Sn₅ in Sn-Cu-Ni joints is 113.2 GPa±4.8 GPa, while the hardness is 5.59 GPa±0.32 GPa. It is found that intermetallic compounds are the key factors in the reliability of lead-free joints, due to the big contrasts between mechanical properties of intermetallic compounds and solder matrix. The creep strain rate sensitivities of Sn-Cu-Ni, Sn-Cu-Ni-0.05Ce and Sn-Pb solder matrix are 0.1286, 0.1248, and 0.1832, and the creep stress exponents are 7.7760, 8.0128, and 5.4585, respectively, which indicate the improvement in creep resistance of Sn-Cu-Ni joints due to Ce addition.