On the use of high precision electrical resistance measurement for analyzing the damage development during accelerated test of Pb-free solder interconnects

The reliability of solder interconnects in electronic packages is of vital importance. However, the demand for rapid product development puts an urgent need to develop new and fast testing methods and protocols for accurate crack initiation and propagation measurements for the new generation lead free solder. The failure is mainly due to two consecutive processes: viscoplastic deformation ultimately leading to crack initiation and crack propagation that leads to final catastrophic failure. This study shows the capability of high precision DC electrical resistance measurement to distinguish and in-situ monitor both mentioned processes occurred in individual solder joint. The experimental measurements are supported by both model calculations and additional experiments. The method developed offers potential to minimize testing time to considerable extent for new solder joints. A new test protocol for estimating the crack initiation time in a solder joint is proposed. The new test protocol is based on a widely used energy based solder joint fatigue model in which the conventional damage metric is replaced by electrical resistance increase rate.