Interfacial Reactions in Lead-Free Solder/Cu-2.0Be (Alloy 25) Couples

The interfacial reactions between lead-free solders Sn, Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and Sn-9 wt.% Zn (SZ), and Cu-2.0 wt.% Be (Alloy 25) were investigated using the liquid/solid couple technique. The couples were reacted at 240-270 degrees C for 0.5-10 h. The results revealed that only the scallop-shaped (Cu, Be)(6)Sn-5 phase was formed at 240 degrees C for 0.5-2 h in the Sn/Alloy 25 couple. At a longer time (> 4 h) or higher temperature (255 degrees C and 270 degrees C), the (Cu, Be)(3)Sn phase was observed at the interface. In the SAC/Alloy 25 couple, the results were similar to that in the Sn/Alloy 25 couples. Only the scallop-shaped (Cu, Be, Ag)(6)Sn-5 phase was formed for the short reaction time or at lower reaction temperature. With increasing reaction times and temperatures, both the (Cu, Be, Ag)(6)Sn-5 and (Cu, Be, Ag)(3)Sn phases were observed at the SAC/Alloy 25 interface. In the SZ/Alloy 25 couple, the (Cu, Sn)Zn-5 and (Cu, Sn)(5)Zn-8 phases were observed. Of these three couples, the intermetallic compound (IMC) thickness obeyed the parabolic law, and the IMC growth mechanism was diffusion-controlled.

Automated summary

The interfacial reactions between lead-free solders Sn, Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and Sn-9 wt.% Zn (SZ), and Cu-2.0 wt.% Be (Alloy 25) were investigated using the liquid/solid couple technique. Different intermetallic compounds were observed at the interfaces under different reaction conditions, with the thickness following a parabolic law and growth mechanism being diffusion-controlled.