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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。
In situ SEM observation, FIB microanalysis and finite element analysis (FEM) were used to investigate the tissue evolution and damage induced by electromigration in asymmetric Cu / Sn-58Bi / Cu micro-spot welds. The results show that the electromigration of the Bi-rich phase and the micro-cracks in the asymmetric micro-spot are far more serious than those in the symmetrical spot. The FIB-SEM microscopic analysis shows that the resistance in the micro-zone along the current direction in the asymmetrical spot The difference is the key factor leading to the non-uniform current distribution and severe electromigration in the cross-section of the solder joint. Both theoretical analysis and simulation results show that the current crowding easily occurs in the micro-resistance of the solder joint.