Indentation Creep Behavior of Sn-4.8Bi-0.7Cu Lead-free Solder

The indentation creep property of Sn-4.8Bi-0.7Cu lead-free solder at 40~115℃ and 10~25MPa was tested.The constitutive equation was obtained.Changes of the micro-structure and organization before creep and after creep, and the creep mechanisms were analyzed.The results show that the stress exponent n is 3.0, creep activation energy Q is 45kJ/mol, and the material structure constant A is 6.3×10^-9.The constitutive equation of the indentation creep steady-state creep rate =6.3×10^-9σ^3.0exp (-4.5×10⁴/RT).The creep deformation of solder increases accelerately with the increase in temperature and stress.The ashine massive phase Bi and small flake Cu₆Sn₅ (IMC) are precipitated before creep.The matrix Sn is strengthened by anew dissolving phase Bi and dispersive distribution of Cu₆Sn₅ (IMC) after creep, which improves the creep resistance of Sn-4.8Bi-0.7Cu solder.