The interface diffusion of 210Pb and 113Sn tracers was measured in oriented 38wt%Pb eutectic specimens with a lamellar structure. The product of the interface diffusion coefficient and the width, dD, obeyed an Arrhenius relationship at temperatures below 400K. The results (table 18) could therefore be described by:

210Pb:     D (m3/s) = 7 x 10-10 exp[-84.8(kJ/mol)/RT]

113Sn:     D (m3/s) = 7 x 10-12 exp[-77(kJ/mol)/RT]

An interface energy of 150mJ/m2 was deduced from the diffusion measurements. At temperatures above 400K, the diffusivities deviated from an Arrhenius relationship and rose steeply. They finally merged with previously determined grain-boundary diffusion data for polycrystalline Pb and Pb-Sn alloys. The effects were associated with changes in the microstructure during annealing, where the Pb and Sn phases separated to form equiaxed grains.

Interface Diffusion in Eutectic Pb-Sn Solder. D.Gupta, K.Vieregge, W.Gust: Acta Materialia, 1999, 47[1], 5-12

Table 18

Interface Diffusivity of 210Pb and 113Sn in Sn-38wt%Pb Lamellar Eutectic