Investigation of the Electromigration Behavior of Solder Bump Under Different Conditions

Cu-pillar bumping is a next-generation flip chip interconnection between chip & packages (FCBGA/FCCSP), especially for fine pitch applications. This research uses the Finite Element Analysis to study the impact of different factors on electromigration of pillar solder under constant current, including the pillar shapes, pillar orientation,_solder materials and solder void. From the results, it is better to design the current flow in the X axis of pillar solder due to lower down the current density. It has up to ~35% difference by comparing the current flow in Y axis and X axis. In addition, it has around 10% improvement when the activation energy (Ea) is changed from 0.8 to 0.98 by comparing with elliptical pillar and rectangular pillar. If the initial void occurs at the higher current concentration region, it will speed up the electromigration process and reduce the life of solder joint.