Thermodynamic and kinetic study of phase transformations in solder/metal systems

摘要

Diffusion in both the Pd-Sn and Cu-Sn systems has been investigated using differential scanning calorimetry. Averaged interdiffusion coefficients for the PdSn_4, PdSn_2 and Cu_3Sn intermetallics have bene calculated. Where equilibrium concentrations in the diffusion couples are assumed. There is an obvious hierarchy within the Pd-Sn system where diffusion is fastest in the most Sn-rich intermetallic. COmparisons within each system, including consideration of the solute diffusion coefficients in pure Sn, provide evidence that in the most Sn Rich phase (e.g. PdSn_4) the interstitial diffusion of metal atoms is the dominant reaction mechanism.In contrast, the diffusion for the Cu-rich phase Cu_3Sn was found to be five orders of magnitude smaller than the soolute diffusion coefficient for Cu in pure Sn.