AU-SN ALLOY PHASE-DIAGRAM AND PROPERTIES RELATED TO ITS USE AS A BONDING MEDIUM

Au-Sn eutectic alloy has been successfully used in microelectronic packaging for high reliability applications where a hard solder as well as a low processing temperature are required. A new multilayer bonding technology not only has produced nearly perfect bonding but also has reduced the processing temperature even below the eutectic melting point. Knowledge of the different phases of the alloy and their formation, as well as the interdiffusion that occurs, thus becomes important in studying the bonding principle and the long-term reliability. In this paper, we review a large number of publications on the Au-Sn system and summarize the important properties. We hope that this summary would further enhance the development of new Au-Sn bonding methods as a result of an overall understanding of oxidation and diffusion properties.