The effect of Sn grain number and orientation on the shear fatigue life of SnAgCu solder joints

A study of the dependence of room temperature shear fatigue lifetime of SnAgCu solder joints on Sn grain number and orientation was conducted. Both essentially single Sn grain and multi (two or three) Sn grain samples are found in many SnAgCu solder joints in the field, and these Sn grain morphologies were examined here. The mean fatigue lifetime was found to be significantly longer for samples with multiple Sn grains than for samples with single Sn grains. For single grain samples, correlations between Sn grain orientation (with respect to the loading direction) and lifetime were observed, providing insight on early failures in SnAgCu solder joints.