Research Progress on the Influence Mechanisms of βSn Structure and Grain Orientation on the Reliabilities of Solder Joints

Electronic solder joints that interconnect different components are the key parts in integrated circuits. Since solder joints service with high current density, thermal cycling, and mechanical loading, they commonly suffer from electromigration,thermomechanical fatigue, and mechanical fatigue. A typical solder joint usually contains few βSn grains with random orientations,which causes that the three main reliabilities of solder joints are heavily influenced by βSn structure and grain orientation, considering βSn is physically anisotropic. This paper bases on the key physical properties of βSn, analyzes the failure mechanisms of electromigration, thermomechanical fatigue, and mechanical fatigue of solder joints, summarizes the effects of βSn structure and grain orientation on these failures, confirms that when the c-axis of βSn is parallel to the current direction, the solder joints have the worst resistance to electromigration but the best thermal cycling performance;however, some studies have shown that when