Influence of Content of Ni and Ag on Microstructure and Joint Strength of Lead-Free Solder Joint with Sn-Ag-Cu-Ni-Ge

Abstract

An influence of content of Ni and Ag in a Sn-Ag-Cu-Ni-Ge lead-free solder has been investigated on microstructure and joint strength of the soldered joint under heat exposure conditions. The growth kinetics of the reaction layer formed at the joint interface has been investigated, and the apparent activation energy of the reaction layer growth has been also examined. Moreover, the soldered joints with Sn-Ag and Sn-Ag-Cu solders were prepared and were compared with the joints with the Sn-Ag-Cu-Ni-Ge solders.

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

“…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.…”

“…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.…”

“…Figure 5 shows ball shear strength for each solder joint evaluated by conventional ball shear test. 4,5) The test was conducted at shear speed of 15 mm/min (2:5 Â 10 À4 m/s). In the case of slow shear speed, SA, SAC and S3ACNG joints showed similar shear strength during aging at 393 K. Their values were lower than those of SACNG, SAC0.15NG and SAC0.25NG until the aging time was over 600 h, although the effect of solder composition on ball shear strength was slight when the aging time was 1000 h. Compared impact shear strength shown in Fig.…”

“…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.…”

“…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 purpose of this study is to investigate the impact properties of the Sn-Ag-Cu-Ni-Ge solder ball joints in the aged conditions.…”