Effects of dwell time on the fatigue life of Sn3.8Ag0.7Cu and Sn3.0Ag0.5Cu solder joints during simulated power cycling

Compared to Sn-Pb solder joints, our understanding of the fatigue of SnAgCu solder joints is far from complete. The challenges to achieving a complete understanding of SnAgCu solder joint fatigue arise partly from their significantly different creep behavior and vulnerability to microstructure evolution (aging). In this paper, we present results from thermal fatigue tests carried out with the help of a simulated power cycling tester. The test specimens were 1.27mm pitch Ceramic Ball-Grid Array (CBGA) components with two leadfree solder alloy compositions - Sn3.8AgO.7Cu and Sn3.OAgO.5Cu. The components were subjected to hot dwells at 100 degrees C for 10, 30 and 60 minutes to study the effect of dwell time on the fatigue life - a total of 48 components were tested. The resulting failure data was fit to a Weibull distribution. The packages were stored at room temperature prior to testing and the effect of the time of storage on the fatigue life was also studied. Finite element analyses were performed to study the effect of hot dwell time on the fatigue life of the CBGA component.