Investigate influence of solder thickness on the fatigue failure behavior of solder joint under high temperature

Solder joint thickness has an important effect on the fatigue failure behavior of solder joint. In this study, fatigue behavior of solder joints with different solder thickness (0.1mm, 0.2mm, 0.3mm) were studied under 398K. The failure path and rupture morphology were observed utilizing scanning electron microscopy (SEM) in order to reveal the failure mechanism. Moreover, fatigue life was evaluated using the Coffin-Masson model and the influence of solder thickness on the fatigue exponent and coefficient was analyzed. The result shows that fatigue life of solder joint increases with the solder thickness. Solder joins of lowest thickness has the fast maximum load drop rate. Besides, the fatigue ductility exponent in Coffin-Masson model decrease with the solder thickness, so, the higher solder thickness means super fatigue resistance. On the other hand, fatigue crack is initiated at the corner of the solder joint, and propagated in the solder matrix with a direction paralleling to the loading direction. A deformation concentrated zone along the diagonal of solder joint is formed with increasing the solder thickness, inducing a step-like fracture morphology and all samples show a ductility rupture mode.