Reliability of Solder Joint with Sn–Ag–Cu–Ni–Ge Lead-Free Alloy under Heat Exposure Conditions

Abstract

The reliability of a solder ball joint with a Sn-Ag-Cu-Ni-Ge lead-free alloy, which is expected to be an advanced lead-free solder, was investigated under heat exposure conditions. Solder ball joints with a eutectic Sn-Ag alloy and a ternary Sn-Ag-Cu alloy were also prepared to compare with that of the Sn-Ag-Cu-Ni-Ge alloy. Microstructual observations of the cross sections of the solder ball joints were conducted to investigate microstructural evolutions in the solders and the growth kinetics of reaction layers formed at joint interfaces. The influence of heat exposure treatment on joint strength was investigated by ball shear test. Moreover, the influence of surface treatment of a Cu pad on the reliability of the solder joint was also investigated.

Impact Properties of Lead-Free Sn-Ag-Cu-Ni-Ge Solder Joint with Cu Electrode

“…The peak temperature and duration time over 493 K in reflow soldering were set to be 516 K and 44 s, respectively. 4,5) After reflow soldering, the subsequent aging treatment were conducted at 393 K for 300 h, 600 h and 1000 h.…”

“…The diameter of each solder ball was 0.3 mm. Following the experimental procedure of the previous reports, 4,5) the solder ball was joined on a Cu pad on an FR-4 substrate by reflow soldering with non-clean flux. The diameter of the Cu pad was 0.2 mm and the surface of the Cu pad was finished with organic solderability preservative.…”

“…4,5) From the investigation results of ball shear strength, it was clarified that the Sn-Ag-Cu-Ni-Ge solder joint has excellent heat resistance compared with those of the joints using the Sn-Ag and Sn-Ag-Cu solders. 4) Moreover, it has been reported that the supplement of a little amount of Ni into the Sn-Ag-Cu solder is effective to prevent the growth of the reaction layer formed in the joint interface. 5) For solder ball joints, the impact reliability is one of the crucial issues 6) besides thermal fatigue, heat resistance and so on.…”

The Recrystallization of Microelectronic Lead-Free Solders

“…However, recrystallization should not be overlooked. Also, the Ag content in related SAC studies [1][2][3][15][16][17] has been limited to the range 3:5$4:5 mass%; low Ag solders (< 3:5 mass%) have still not been examined. Notably, Fulong Zhu 21) reported the dynamic recovery characteristics of Sn-0.7Cu-Ni solders (compared with the traditional Sn63/Pb37 alloy; Sn-0.7Cu-Ni alloy is not a common solder alloy), revealing that recrystallization is worthy of research.…”

“…[1][2][3][4][5][6] Notably, when the interface layer is undamaged during reliability testing, cracks or strain energy will propagate into the bulk solders. So, studying the fracture mechanism of the solder itself is of great importance.…”