Primary Creep in Sn3.8Ag0.7Cu Solder. Part I: Theory, Experiments, and Data Reduction

This article presents constant-load creep and stress relaxation data for Sn3.8Ag0.7Cu spanning a range of strain rates \( 10^{ - 8}\, \hbox{s}^{ - 1} < \dot{\varepsilon } < 10^{ - 4}\, \hbox{s}^{ - 1} , \) and temperatures 25°C, 75°C, and 100°C. Creep and stress relaxation measurements showed that transient creep caused faster strain rates during stress relaxation for a given stress than the corresponding minimum creep rate from constant-load creep tests. The extent of strain hardening during primary creep was a function of temperature and strain rate. Data reduction incorporated a fast Fourier transform method to remove spurious data from stress relaxation corresponding to the period of partial strain relaxation during loading.