Damage Mechanics and Experiments of Lead-free Solder Alloy

Based on DSCM (digital speckle correlation method), a novel video control experimental technique was developed for assessing mechanical behavior of SnAgCu solder alloy. A series of experimental tests in tension on a SnAgCu solder alloy have been conducted under various constant strain rates ranging from 10E-5/s to 10E-3/s and at 298K to 423K. The experimental results have revealed the presence of both the nucleation and growth deformation mechanisms of voids. A viscoplastic constitutive model with void damage, including strain softening and strain hardening, was developed for analyzing the effect of voids on reliability of lead-free solders. Based on the Gurson-Tvergaard plastic potential equation and orthogonal rules, the void volume fraction was used as damage variable and was introduced into the material constitutive law to simulate the macroscopic mechanical response of SnAgCu solder alloy under different temperature and strain rates. The simulation results compared with the experimental measurements. The predictions have shown the ability of the viscoplastic model coupled with void damage to correctly describe the experimental observations: nonlinearity, strain rate sensitivity and void damage evolution are well captured.