Diffusion-reaction in the Au-rich ternary Au-Pt-Sn system as a basis for ternary diffusion soldering

Basic thermodynamic considerations indicate nonequilibrium between gold-tin intermetallic phases and platinum. Therefore, diffusion and reactions in the Au-Pt-Sn(-Ti) thin-film system have been investigated, and a mechanism of reaction is proposed based on experimental results and thermodynamic considerations. The present paper may also help researchers understand previous results that could be interpreted differently based on the new results of this work and basic thermodynamic considerations. A ternary diffusion soldering concept has been proposed, and its application on up to 4-inch wafer-scale bonding was successful. Generalizations of the present approach to other bonding systems appears promising.