Cu/Sn-58Bi/Cu焊点电迁移行为研究

采用双辊快速凝固技术制备了Sn-58Bi钎料薄带,并制备Cu/Sn-58Bi/Cu线性焊点。使用电子探针(EPMA)及能谱分析(EDS)研究焊点在电流密度为1×10^4 A/cm^2(25℃)下界面金属间化合物(IMC)、元素扩散与钎料基体组织演变规律。结果表明,随着通电时间延长阳极界面处的IMC层的形状从扇贝状转变为锯齿状,阴极界面处的IMC层由扇贝形变为不规则,其厚度逐渐增加。阳极由于Bi的偏聚形成了富Bi层,Sn在阴极偏聚,基体共晶组织(Bi+β-Sn)粗化。基于线性拟合可知,阳极和阴极的界面IMC层的生长系数n分别为0.263和0.442,其生长机制可归结为体积扩散。

Electromigration Behavior of Cu/Sn-58Bi/Cu Solder Joints

The Sn-58 Bi solder ribbon was prepared by the twin-roll rapid solidification technique,and the Cu/Sn-58 Bi/Cu linear solder joints were prepared.The interface IMC,element diffusion and microstructure evolution of solder joints were analyzed by EPMA and EDS after the current density of 1×10^4 A/cm^2(25℃).The results reveal that the morphology of the anode IMC layer is changed from scallop shape to zigzag shape,and the cathode IMC layer is changed from scallop shape to irregular one with the increase of thickness gradually.Bi is segregated toward the anode to form a Bi-rich layer,and Sn is segregated at the cathode.And the matrix eutectic structure(Bi+β-Sn)is coarsened.Based on linear fitting,the growth coefficient n of IMC layer of the anode and cathode are 0.263 and 0.442,respectively,and the growth mechanism is attributed to volume diffusion.