The influence of Ag upon the kinetics of the solid-state reactive diffusion between Pd and Sn was experimentally examined using Sn/(Pd–Ag)/Sn diffusion couples with a Ag concentration of 75at%. The diffusion couples were isothermally annealed at 433, 453 and 473K for periods of up to 1365h. During annealing, a compound layer predominantly consisting of polycrystalline PdSn4 and Ag3Sn lamellae was formed at the (Pd–Ag)/Sn interface in the diffusion couple. The square of the thickness of the compound layer increased in proportion to the annealing time. This relationship was called the parabolic relationship. On the other hand, the interlamellar spacing in the compound layer was proportional to a power function of the annealing time, and thus grain growth occurred in the compound layer. The exponent of the power function was close to 1/3. The parabolic relationship of the layer growth and the occurrence of the grain growth guarantee that the growth of the compound layer was controlled by volume diffusion. The addition of Ag with 75at% into Pd decreased the parabolic coefficient by 93, 88 and 78% at 433, 453 and 473K, respectively. Hence, Ag works as an effective suppressant against the growth of the compound during the solid-state reactive diffusion between Pd and Sn.

Influence of Ag on Kinetics of Solid-State Reactive Diffusion between Pd and Sn. T.Sakama, M.Kajihara: Materials Transactions, 2009, 50[2], 266-74