AN EXPERIMENTAL-TECHNIQUE FOR STUDYING MIXED-MODE FATIGUE-CRACK GROWTH IN SOLDER JOINTS

Failures of solder joints often result from development of cracks unde r complex mixed-mode loading conditions. In this study, a flexural pee l technique was developed to investigate the growth of cracks at the i nterface between solder and Cu substrate. The technique was based on a tri-layer solder/Cu joints, with the solder layer sandwiched between two Cu layers of desired thicknesses. Finite element analysis was used to calculate the mixed-mode condition at the crack tip as a function of the thicknesses of Cu outerlayers and the solder interlayer. The ap plication of this technique to studying interface crack growth under f atigue loading is demonstrated for eutectic solder joints.