COMPARISON OF CREEP LIFE ASSESSMENT BETWEEN TIN-BASED LEAD-FREE SOLDERS AND LEAD SOLDERS

摘要

The creep properties of tin-based lead-free solders Sn3.OAgO.5Cu and SnO.7CuO.lNi and lead solders 10Sn90Pb and 50Sn50Pb were investigated at temperatures between 298 K and 398 K. The creep-rupture time decreases with increasing initial stress and temperature. The analysis of the solder creep curves uses the Omega method. The creep rate ε is expressed by following formula: ln ε = ln ε_0 + Ωε, where ε_0 and Ω are experimentally determined. The parameter ε_0 increases with increasing initial stress and temperature. The activation energy for ε_0 is 108 kJ/mol for Sn3.0Ag0.5Cu and 85 kJ/mol for Sn0.7Cu0.1Ni. These energies suggest that the lattice diffusion of tin is dominant. The energy of 10Sn90Pb is 37 kJ/mol and that of 50Sn50Pb is 67 kJ/mol. The creep-rupture time is calculated using the parameters, ε_0 and Ω. The calculated creep-rupture time is in good agreement with the measured creep-rupture time.