βSn组织和晶粒取向对焊锡接头可靠性影响机理研究进展

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 βSn c-axis is perpendicular to the substrate, the solder joints exhibit poor thermomechanical performance; there are few studies on the influence of βSn structure and grain orientations on the mechanical shear fatigue resistance of solder joints, but some published studies indicated that there is a strong correlation between them. In view of the strong influence of βSn structure and grain orientations on the reliabilities of solder joints, this paper also outlines the research progresses on controlling βSn structure and grain orientations, including using heterogeneous nucleating agents, polycrystalline and single-crystal Cobalt substrates, magnetic fields, and temperature gradients. Finally, this paper discusses the required future researches for improving the reliabilities of solder joints.