Silver-indium phase diagram and its applications to electronic packaging

In this paper, we will review the silver-indium (Ag-In) phase diagram and explores its unique features that enable the development of new bonding processes for electronic packaging. Its melting range covers 156°C to 952°C, from In melting point to Ag melting point. It consists of three intermetallic compounds (IMC), AgIn₂, and Ag₂In, and Ag₃In, and a solid solution (Ag). Our experimental results do not show the Ag₃In compound. In a Ag-rich joint design, only Ag₂In and (Ag) show up. By further annealing at 250°C for 350 hours or 400°C for 5 hours, Ag₂In converts to (Ag) by reacting with Ag. With the proper structure to begin with, a joint can be made at 180°C that contains only Ag₂In and (Ag), achieving a melting temperature of 600°C. Annealing to convert Ag₂In to (Ag) will increase the melting to higher than 800°C. Accordingly, various processes can be designed and developed for different packaging applications ranging from automotive electronics, high temperature electronics, and oil exploration.