The tracer diffusion coefficients of the elements as well as the integrated interdiffusion coefficients were determined for the Cu3Sn and Cu6Sn5 intermetallic compounds using incremental diffusion couples and Kirkendall marker shift measurements. The activation energies were determined for the former between 498 and 623K (225 and 350C) and for the latter between 423 and 473K (150 and 200C). Sn was found to be a slightly faster diffuser in Cu6Sn5, and Cu was found to be the faster diffuser in Cu3Sn. The results from the incremental couples were used to predict the behavior of a Cu/Sn couple where simultaneous growth of both intermetallics occurred. The waviness at the Cu3Sn/Cu6Sn5 interface and possible reasons for not finding Kirkendall markers in both intermetallics in the Cu/Sn couple were considered.

Diffusion Parameters and Growth Mechanism of Phases in the Cu-Sn System. A.Paul, C.Ghosh, W.J.Boettinger: Metallurgical and Materials Transactions A, 2011, 42[4], 952-63