非对称结构Cu/Sn-58Bi/Cu焊点中电迁移致组织演变及损伤(英文)

Electromigration induced microstructure evolution and damage in asymmetric Cu/Sn-58Bi/Cu solder interconnect under current stressing

采用原位SEM观察、FIB微区分析和有限元(FE)模拟研究了非对称结构Cu/Sn-58Bi/Cu微焊点中电迁移引起的组织演变及其损伤。结果表明,非对称结构微焊点中富Bi相偏聚和微裂纹等电迁移现象远比对称焊点中严重;FIB-SEM微观分析结果显示非对称焊点中沿电流方向上各个微区内电阻差异是导致焊点截面上电流非均匀分布和严重电迁移问题的关键因素,理论分析和模拟结果均表明电流拥挤容易发生在焊点内微区电阻较小的位置。

The electromigration induced microstructure evolution and damage in asymmetric Cu/Sn-58Bi/Cu solder interconnects were investigated by in-situ SEM observation, focused ion beam （FIB） microanalysis and finite element （FE） simulation. The SEM results show that the electromigration-induced local degradation of microstructures, i.e., segregation of Bi-rich phase and formation of microcracks, in the asymmetric solder interconnects is much severer than that in the symmetrical ones. FIB-SEM microanalysis reveals that the microregional heterogeneity in electrical resistance along different electron flowing paths is the key factor leading to non-uniform current distribution and the resultant electromigration damage. Theoretical analysis and FE simulation results manifest that the current crowding easily occurs at the local part with smaller resistance in an asymmetric solder interconnect. All results indicate that the asymmetric shape of the solder interconnect brings about the difference of the electrical resistance between the different microregions and further results in the severe electromigration damage.