Abstract: SnCu eutectic solder alloys have been regarded as one of the most promising Pb-free substitutes for the SnPb solders for its low cost and good mechanical properties.Creep property of solder alloys is one of the important factors to affect the reliability of soldered joints.A novel high temperature creep strain equipment was used to test stress exponent and creep activation energy of single shear lap creep specimens of SnCu eutectic soldered joints with a 1 mm² cross-sectional area.The final constitutive equation of the composite soldered joints was established and its creep mechanism was investigated.Results indicate under low temperature and high stress, the stress exponents of the soldered joints is 8.73, and the creep activation energies is varied in 59.1-63.2 kJ/mol.The dislocation climbing is dominated by dislocation pipe diffusion process.Under high temperature and low stress, the stress exponents of the soldered joints is 6.45 and the creep activation energies is varied from 88.4-97.5 kJ/mol.The dislocation climbing is dominated by the lattice self-diffusion process.