电迁移促进Cu/Sn-58Bi/Cu焊点阳极界面Bi层形成的机理分析  

Mechanism investigation of Bi layer formation at anode interface in Cu/Sn-58Bi/Cu solder joint induced by electromigration

作　　者：何洪文[1,2] 徐广臣[1] 郭福[1] 

机构地区：[1]北京工业大学材料科学与工程学院,北京100124 [2]清华大学机械工程系,北京100084

出　　处：《焊接学报》2010年第10期35-38,42,共5页Transactions of The China Welding Institution

基　　金：教育部新世纪优秀人才支持计划资助项目(04-0202)

摘　　要：研究了Cu/Sn-58Bi/Cu对接接头焊点在电流密度为5×103～1.2×104A/cm2条件下钎料基体中阳极界面Bi层的形成机理.电迁移过程中,Bi元素为主要的扩散迁移元素,在电迁移力的作用下由阴极向阳极进行迁移.由于Bi原子的扩散迁移速度比Sn原子要快,促使Bi原子首先到达阳极界面.大量的Bi原子聚集在阳极界面时,形成了压应力,迫使Sn原子向阴极进行迁移,于是在阳极界面处形成了连续的Bi层.阴极处由于金属原子的离去,形成了拉应力,导致了空洞和裂纹在界面处的形成.Bi层的形态主要分为平坦的Bi层和带有凹槽的Bi层.Bi原子进行扩散迁移的通道有三种:Bi晶界、Sn晶界和Sn/Bi界面.随着电流密度和通电时间的增加,Bi层的厚度逐渐增加.电迁移力和焦耳热的产生成为Bi原子扩散迁移的主要驱动力.Mechanism of Bi layer formation at the anode interface in Cu/Sn-58Bi/Cu solder joint was investigated under current density of 5×103 to 1.2×104 A/cm2.During electromigration process,Bi was the main diffusing species which migrated from the cathode side to the anode side under electromigration force.Bi was the first species to reach anode interface because the diffusion velocity of Bi is faster than that of Sn.Therefore,compressive stress was formed at the anode interface when much more Bi atoms accumulated there and compelled Sn to migrate towards the cathode side,and the continuous Bi layer was formed at the anode interface.In the mean time,tensile stress was formed at the cathode interface due to the departure of metal atoms,which led to voids and cracks formation.The morphology of the Bi layer included planar-type layer and groove-type layer.The diffusing channels of the Bi atoms were Bi grain boundaries,Sn grain boundaries and Sn/Bi interfaces.With the current density and stressing time increasing,the Bi layer thickness increased.The electromigration force and Joule heating took on the main driving force for Bi diffusion and migration.

关 键 词：电迁移 Bi层 电流密度 焦耳热 

分 类 号：TG115[金属学及工艺—物理冶金]