Correlation between creep and uniaxial ratchetting of SN/37PB and SN/3AG/0.5CU solder alloys

Ratchetting deformations of solder alloys are significant deformations for the safety and reliability of solder joints of electronic packaging. This paper discusses a correlation between creep and uniaxial ratchetting deformations to clarify the difference in the time-dependent deformations between lead-free and lead-containing solder alloys. Uniaxial ratchetting tests are conducted by cyclic tension-compression and cyclic tension-unloading with the several ratios of maximum to minimum stresses. Additional creep tests are also conducted after the uniaxial ratchetting tests to clarify the effect of the uniaxial ratchetting on the creep deformation. A method to evaluate the uniaxial ratchetting deformation is discussed using the creep curves. The results show that the uniaxial ratchetting deformation correlates to the creep deformation and that the correlation is different between the lead-free and lead-containing solder alloys.