The solid-liquid interfacial reactions between Cu-xZn (x=0, 5, 15, 30, 40 wt%) alloys with Sn, Sn-3.0Ag-0.5Cu (SAC, in wt%) and Sn-9Zn (SZ, in wt%) reacted at 240 ℃, 270 ℃ and 300 ℃ for 0.5h to 100 h were investigated in this study. The (Cu,Zn)6Sn5 and (Cu,Zn)3Sn phases were formed in the Sn/Cu-xZn (x=5, 15, 30 wt.%) reaction couples. When the temperature was higher than 270 ░C, The layered (Cu,Sn)Zn phase was formed in the Sn/Cu-40Zn reaction couple. In addition, after aging at 300 ░C, the metastable T phase and (Cu,Sn)Zn phase was formed at the interface. In the SAC/Cu-xZn (x=5, 15, 30 wt.%) reaction couples, when Zn contents were more than 40 wt.%, the (Cu,Zn)6Sn5 and (Cu,Zn)3Sn phases were observed. Moreover, the (Cu,Zn)6Sn5 phase was transformed to the (Cu,Sn)Zn phase at the SAC/Cu-40Zn reaction couple due to the consumption of the Cu atoms. The (Cu,Sn)Zn5 and (Cu,Sn)5Zn8 phases were formed in the SZ/Cu-xZn (x=0, 5, 15, 30, 40 wt.%) reaction couples. With the increase of the reaction times and temperatures, the (Cu,Sn)Zn5 phase disappeared at the interface. The results revealed that the IMC formation in the SZ/Cu-xZn couple strongly depended on the Zn concentration effect in the Sn-xZn alloys.
Keywords: interfacial reactions; lead-free solders; Cu-Zn alloys; reaction couples