DYNAMICS OF LIQUID-DROP SPREADING IN METAL-METAL SYSTEMS

This paper analyses the observed spreading kinetics of drops of a Ni-1 1P braze and of copper on metal substrates. The observed spreading rat es were initially fast but decreased progressively in accord with the de Gennes model in which a surface energy driving force is balanced by a viscous impedance. However, the observed spreading rates depended o n the chemistries of the substrates and were usually far slower than t hose predicted by the de Gennes model. It is suggested that these disc repancies are due to the reactivity of the systems and a concentration of the viscous damping in narrow regions adjacent to the braze/substr ate interfaces.