Recent Progress of Experimental and Measuring Technology. Evaluation of Crack Propagation for Sn63-Pb37 Solder Bumps.

Abstract

Fatigue life estimation of solder bumps is one of the most critical technologies for the development of ball grid array packages. Since the recent trend in the package development is toward smaller solder bumps, the estimation of the crack initiation and initial crack propagation rate is essential in the reliability design. In this study, mechanical fatigue tests were carried out using Sn63-Pb37 solder bump specimens. The initial crack propagation rate of the solder bumps was estimated based on the load drop, because the crack observation with destructive test is not suitable for the uniform evaluation of many results. A simple estimation of the crack propagation based on the linear damage law was applied. The trend of the simple estimation results corresponded well with the experimental results of crack propagation. The estimation method of crack propagation based on the fracture mechanics was also examined so as to reduce error in reliability design. Creep J-integral range was calculated using the elastic-creep FEM analysis. The relationship between the crack propagation rate and creep J-integral range was obtained. It was confirmed that the initial crack propagation of micro solder joints could be accurately evaluated using the creep J-integral range.