Anisotropic spreading of liquid metal on a rough intermetallic surface.(English)Zbl 1313.76042

Summary: An anisotropic wicking of molten Sn-Pb solder over an intermetallic rough surface has been studied. The phenomenon features preferential spreading and forming of an elliptical spread domain. A theoretically formulated model was established to predict the ratio of the wicking distance along the long axis $$(r_x)$$ to that along the short axis $$(r_y)$$ of the final wicking pattern. The phenomenon was simultaneously experimentally observed and recorded with a hotstage microscopy technique. The anisotropic wicking is established to be caused by a non-uniform topography of surface micro structures as opposed to an isotropic wicking on an intermetallic surface with uniformly distributed surface micro features. The relative deviation between the theoretically predicted $$r_x /r_y$$ ratio and the corresponding average experimental value is 5%. Hence, the small margin of error confirms the validity of the proposed theoretical model of anisotropic wicking.

MSC:

 76D45 Capillarity (surface tension) for incompressible viscous fluids
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