The 260 °C phase equilibria of the Sn-Sb-Cu ternary system and interfacial reactions at the Sn-Sb/Cu joints

The isothermal section of the Sn-Sb-Cu ternary system at 260 °C has been determined in this study by experimental examination. Experimental results show no existence of ternary compounds in the Sn-Sb-Cu system. An extensive region of mutual solubility existing between the two binary isomorphous phases, Cu3Sn and Cu4Sb, was determined and labeled as δ. Intermetallic compounds (IMCs) Cu2Sb, SbSn, and Cu6Sn5 are in equilibrium with the δ solid solution. Up to about 6.5 at.%Sb can dissolve in the Cu6Sn5 phase, and the solubility of Sn in the Cu2Sb is approximately 6.2 at.%. Each of the Sb and SbSn phases has a limited solubility of Cu. Only one stoichiometric compound, Sb2Sn3, exists. Besides phase equilibria determination, the interfacial reactions between the Sn-Sb alloys and Cu substrates were investigated at 260 °C. Sb was observed to be present in the Cu6Sn5 and δ phases, and Sb did not form Sn-Sb IMCs in the interfacial reactions. Moreover, the addition of up to 7 wt% of Sb into Sn does not significantly affect the total thickness of IMC layers. It was found that the phase formations in the Sn-Sb/Cu couples are very similar to those in the Sn/Cu couples.