Effects of Co additions on electromigration behaviors in Sn-3.0 Ag-0.5 Cu-based solder joint

摘要

As the miniaturization trend of electronic packing industry, electromigration (EM) has become a critical issue for fine pitch packaging. The EM effects on microstructure evolution of intermetallic compound layer (IMC) in Sn-3.0 Ag-0.5 Cu + XCo (X = 0, 0.05, 0.2 wt%) solder joint was investigated. Findings of this study indicated that current stressing of Sn-3.0 Ag-0.5 Cu-0.2 Co solder joint with 10 ~4 A/cm ~2 at 50 °C for 16 days, no remarkable EM damages exhibited in solder matrix. Whereas, after current stressing at 150 °C for 1 and 3 days, Sn-3.0 Ag-0.5 Cu specimens showed obvious polarity effect between cathode and anode. Different morphology changes were also observed at both sides. After current stressing for 1 day, two IMC layers, Cu _6Sn _5 and Cu _3Sn, with wave type morphology formed at cathode. Sn phases were also observed inside in the IMC layer. However, only Cu 6Sn 5 formed in anode. Three days later, Sn phases were found in anode. Besides, Co additions, aging treatment, Ag _3Sn, and other IMCs improved the resistance of EM by the evidence of retarding polarity effect.