Study of Interfacial Reactions Between Lead-Free Solders and Cu-xZn Alloys
The solid/liquid reaction couple technique was employed to investigate the interfacial reactions between Cu-xZn (x = 0 wt.%, 5 wt.%, 15 wt.%, 30 wt.%, 40 wt.%) alloys and lead-free solders Sn, Sn-3.0Ag-0.5Cu (SAC, in wt.%), and Sn-9Zn (SZ, in wt.%) alloys at 240°C, 270°C, and 300°C for 0.5 h to 100 h. (Cu,Zn)6Sn5 and (Cu,Zn)3Sn phases were formed in the Sn/Cu-xZn (x = 5 wt.%, 15 wt.%, 30 wt.%) reaction couples, but with increasing reaction temperature and time, (Cu,Sn)Zn phase was formed, replacing (Cu,Zn)3Sn phase. Metastable T phase and (Cu,Sn)Zn phase were formed in the Sn/Cu-40Zn reaction couple at 300°C. (Cu,Zn)6Sn5 and (Cu,Zn)3Sn phases formed in the SAC/Cu-xZn (x = 5 wt.%, 15 wt.%) reaction couples. Furthermore, (Cu,Zn)6Sn5 and (Cu,Zn)Sn phases were observed when the SAC solders reacted with Cu-30Zn and Cu-40Zn alloys. T phase and (Cu,Sn)Zn phase were formed in the SAC/Cu-40Zn reaction couple reacted at 300°C for 100 h. (Cu,Sn)Zn5 and (Cu,Sn)5Zn8 phases were formed in the SZ/Cu-Zn reaction couples at 240°C. However, with increasing reaction time and temperature, only (Cu,Sn)5Zn8 phase was detected. Therefore, it can be concluded that the intermetallic compound (IMC) formation was sensitive to both the reaction temperature and the Zn content in the Cu-Zn alloy.