Rodríguez-Quiñones, Regie I.
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Publication High temperature die attach by low temperature gold-tin solid-liquid interdiffusion(2012) Rodríguez-Quiñones, Regie I.; Quintero, Pedro O.; College of Engineering; Sundaram, Paul; Jia, Yi; Department of Mechanical Engineering; Romero, JuanThere is a need for electromechanical devices capable of operating in high temperature environments (>200°C) for a wide variety of applications. Today’s widebandgap semiconductor based power electronics have demonstrated a potential of operating above 400°C, although they are still limited by packaging. Among the most promising alternatives is the Au-Sn eutectic solder, which has been widely used due to its excellent mechanical and thermal properties. However, the operating temperature of this system is still limited to ~250°C owing to its melting temperature of 280°C. Therefore, a higher temperature resistant system is much needed, but one which does not affect the current processing temperature of ~325°C typically exhibited in most high temperature Pb-Free solders. This study presents the development and characterization of a fluxless die attach soldering process based on gold enriched solid liquid inter-diffusion (SLID). A low melting point material (eutectic Au-Sn) and a high melting point material (pure Au) were deposited onto two substrates, assembled as in a sandwich structure and then processed in a vacuum furnace at different temperatures and times. Microscopical examination revealed a bond formation consisting of intermetallic microstructures. Mechanical characterization of the each individual intermetallic phase was achieved by nanoindentation. Differential scanning calorimetry demonstrated the progression of the SLID process by quantifying the remaining low melting point phase as a function of time and temperature. Post-processed samples demonstrated the potential use of the Au-Sn SLID as a die attach technology as they proved the formation of sound joints that where thermally stable up to ~498°C after the completion of the SLID process.