The growth of intermetallic compounds in Au and In-48Sn diffusion couples was investigated at 70, 90 and 110C. An In2Au layer first formed at the boundary between Au and In-48Sn. This layer then grew towards the In-48Sn solder. At 70C, the temperature was so low that the diffusion reaction was insufficient to form a γ-phase layer within 600h. However, formation of a γ-phase layer was observed in samples which were annealed for over 700h. From these experimental results, the activation energy for the formation of In2Au was deduced to be 42.8kJ/mol, and this was supposed to be equal to the activation energy for the diffusion of Au atoms in In2Au.

Intermetallic Compound Layer Formation between Au and In-48Sn Solder. I.Shohji, S.Fujiwara, S.Kiyono, K.F.Kobayashi: Scripta Materialia, 1999, 40[7], 815-20