Effects of high temperature aging on the microstructural evolution and mechanical behavior of SAC305 solder joints using synchrotron X-ray microdiffraction and nanoindentation

Abstract

Isothermal aging causes degradation in the mechanical behavior of lead-free solder materials used in microelectronic packaging, leading to significant reductions in product reliability. In this work, we have characterized the aging-induced changes that occur in the mechanical properties and creep behavior of actual solder joints. These changes occur due to microstructure evolution and residual strains/stresses in the solder material, and measurement of these evolutions are critical to developing a fundamental understanding of solder aging phenomena. The enhanced high-energy X-ray microdiffraction beamline present at the synchrotron at the Advanced Light Source at Lawrence Berkeley National Laboratory was employed to characterize the solder joints after various aging times at 125 °C. Aging-induced changes in the Sn grain orientation, Sn grain distribution, and residual strain distribution were measured. The observed microstructural evolution was then correlated with changes in the mechanical response of the solder joints measured using nanoindentation.