Investigation of the Phase Equilibria of Sn-Cu-Au Ternary and Ag-Sn-Cu-Au Quaternary Systems and Interfacial Reactions in Sn-Cu/Au Couples

Abstract

The phase equilibria of the Sn-Cu-Au ternary, Ag-Sn-Cu-Au quaternary systems and interfacial reactions between Sn-Cu alloys and Au were experimentally investigated at specific temperatures in this study. The experimental results indicated that there existed three ternary intermetallic compounds (IMCs) and a complete solid solubility between AuSn and Cu 6 Sn 5 phases in the Sn-Cu-Au ternary system at 200°C. No quaternary IMC was found in the isoplethal section of the Ag-Sn-Cu-Au quaternary system. Three IMCs, AuSn, AuSn 2 , and AuSn 4 , were found in all couples. The same three IMCs and (Au,Cu)Sn/ (Cu,Au) 6 Sn 5 phases were found in all Sn-Cu/Au couples. The thickness of these reaction layers increased with increasing temperature and time. The mechanism of IMC growth can be described by using the parabolic law. In addition, when the reaction time was extended and the Cu content of the alloy was increased, the AuSn 4 phase disappeared gradually. The (Au, Cu)Sn and (Cu , Au) 6 Sn 5 layers played roles as diffusion barriers against Sn in Sn-Cu/Au reaction couple systems.

Cross-Interaction Between Au/Sn and Cu/Sn Interfacial Reactions

“…Both diagrams suggested that a continuous solid solution exists between the Cu 6 Sn 5 phase and the AuSn phase. 12,13 In the present study, the reflow temperature (250°C) falls within the range of 200°C to 360°C, so the interfacial reaction product at the Sn/Cu interface should likely be the ternary Au-Cu-Sn solid-solution phase.…”

Interfacial reactions in Au/Sn/Cu sandwich specimens

“…However, these phases are kinetically not easy to form and have not been observed in the ternary phase diagram determinations [20,23].…”

“…It could be a very fine eutecticlike mixture of the AuSn 4 and (Cu,Au) 6 Sn 5 phases or a new AuSn-Cu ternary phase. However, a ternary phase with this composition has never been reported [20,23]. Further studies are needed to characterize this phase region.…”

Interfacial Reactions in Sn/Fe-xNi Couples

“…This metallurgical treatment method has been applied in several systems. 10,11,[18][19][20][21] Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the surface morphology. The compositions of the IMCs formed at the interface were determined using electron probe microscopy analysis (EPMA).…”