电迁移对全Cu3Sn焊点形貌及剪切性能的影响

Effect of Electromigration on Morphology and Shear Property of Full CuSn Solder Joints

在温度为120℃,电流密度分别为1×10^4、1.2×10^4、1.6×10^4 A/cm^2情况下对焊点通电,研究电迁移作用下Cu/Cu3Sn/Cu焊点微观形貌演变规律以及剪切性能的变化情况,。结果表明,在电流密度为1×10^4 A/cm^2时通电80 h,焊点中部出现蜂窝状空洞,随着通电时间增加,空洞面积不断变大,形成长条状空洞;进一步增加通电时间,在Cu3Sn层中间产生贯穿界面的裂纹状缺陷。增大电流密度,空洞等缺陷的形成时间大大缩短。利用剪切试验机测试不同电迁移实验条件下焊点的剪切强度,发现随着通电时间增加,焊点剪切强度不断下降,并且空洞面积越大,剪切强度下降幅度越大。

At the temperature of 120 ℃, the electric current density of 1 ×10^4 A/cm^2, 1.2×10^4 A/cm^2 and 1.6×10^4 A/cm^2 were applied on the joints respectively. The micromorphology evolution and shear property of Cu/Cu3Sn/Cu solder joints were investigated under electromigration(EM). The results show that cellular voids appear in the middle of joints when the current density is 1×10^4 A/cm^2 and the solder joint is electrified for 80 h. With the increase of electrification time, the area of voids increases continuously, and long-strip voids form. Then, when the electrification time increases further, crack-like defect which penetrates the interface forms in the middle of Cu3Sn layers. When the current density increases, the time for forming defects such as voids, etc, is greatly shortened. The shear tests were conducted on joints by shear test machine under different EM conditions. It is found that the joints’ strength decreases continuously when the EM time increases. Besides, the larger the void area is, the bigger the decrease extent of shear strength is.