Reactive flow of molten Pb(Sn) alloys in Si grooves coated with Cu film

We present an experimental study of the wetting behavior of Pb on flat and grooved Cu surfaces. The alloying of even 1--2 wt. % Sn into Pb can lead to dramatic changes in wetting angle and length flow into the grooves. The observed flow behavior disagrees with models based on the classical Washburn flow [E. W. Washburn, Phys. Rev. 17, 273 (1921)]. We conclude that the driving force of reactive wetting must take into account, besides the capillary force, the free energy change due to intermetallic compound formation.