原位研究Cu/Sn-37Pb/Cu微焊点液-固电迁移行为  

In Situ Study on Liquid-Solid Electromigration Behavior in Cu/Sn-37Pb/Cu Micro-Interconnect

作　　者：张志杰[1] 黄明亮[2] ZHANG Zhijie;HUANG Mingliang(School of Materials Science and Engineering.Jiangsu University of Science and Technology Zhenjiang 212003,China;School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]江苏科技大学材料科学与工程学院,镇江212003 [2]大连理工大学材料科学与工程学院,大连116024

出　　处：《金属学报》2020年第10期1386-1392,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.51801079;U1837208和51671046;江苏省自然科学基金青年基金项目No.BK20180987。

摘　　要：利用同步辐射实时成像技术原位研究了Cu/Sn-37Pb/Cu微焊点在185℃、1×10^4A/cm^2电流密度条件下液-固电迁移过程中Pb原子的扩散迁移行为及其析出机制。在微焊点加热熔化阶段,Pb原子向阳极定向迁移并聚集形成富Pb相,其厚度随时间的延长而增大;在保温阶段,阳极的富Pb相部分溶解,Pb原子反向扩散至阴极,最终钎料内部形成两相平衡组织;在冷却凝固阶段,Pb原子再次向阳极定向迁移,直至凝固,最终钎料内部形成三相组织:富Pb相、Sn-Pb相和富Sn相。基于加热阶段富Pb相的生长动力学,计算获得Pb原子在185℃下的有效电荷数(Z*)为-3.20,为Pb原子的电迁移方向提供了判断依据。Pb原子在电迁移中的反常迁移行为归因于电迁移通量(Jem)与化学势通量(Jchem)的竞争机制。Electromigration(EM), which describes the mass transport due to momentum exchange between conducting electrons and diffusing metal atoms under an applied electric field, has become a serious reliability issue in high-density packaging. With the increasing demands for miniaturization, liquidsolid(L-S) EM will pose a critical challenge to the reliability of solder interconnects. In this work, synchrotron radiation real-time imaging technology is used to in situ study the interfacial reaction and atom migration in Cu/Sn-37Pb/Cu solder interconnects undergoing L-S EM at 185 ℃ with a current density of 1.0×10^4 A/cm^2. In the heating stage, Pb atoms directionally migrate from the cathode toward the anode, resulting in the growth of Pb-rich phase at the anode. In the dwelling stage, Pb atoms diffuse backward, then equilibrium phase is obtained. In the cooling stage, Pb atoms directionally migrate from the cathode toward the anode again until the solder solidified, three phases is obtained: the Pb-rich phase, the Sn-Pb phase and the Sn-rich phase. The abnormal migration behavior of Pb atoms in different stages is determined by the combined effect of the chemical potential gradient flux(Jchem) and EM-induced flux(Jem). Jem is determined by the effective charge number(Z*) of Pb atoms, which was calculated to be -3.20 at 185 ℃ based on the growth kinetics of the Pb-rich layer model.

关 键 词：同步辐射实时成像技术 Sn-37Pb微焊点 液-固电迁移 界面反应 有效电荷数 

分 类 号：TG115[金属学及工艺—物理冶金]