Modeling of Substrate Remelting, Flow, and Resolidification in Microcasting

ABSTRACT

A millimeter-sized molten droplet impacting on a substrate of the same material was modeled. Numerical simulations of microcasting experiments were conducted with the different thermal contact resistances. It was found that the thermal contact resistance affects not only the droplet spreading but also the substrate remelting volume and remelting front configurations. Under the assumption of an appropriate thermal contact resistance, the numerical results of spreading factors, bump heights, and substrate remelting volumes agree well with the experimental data. The effects of droplet impacting velocity, superheat, and substrate temperature were also investigated in detail and some nonintuitional phenomena were discovered.

This research was supported by the Hong Kong Government under Research Grants Council Grant HKUST6043/99E.

Notes

h _cr = infinite; h _ls  = 10⁷ W/m² K, h _ss  = 10⁶ W/m² K, and h _cr = infinite if substrate remelting; h _ls  = 10⁶ W/m² K, h _ss  = 10⁵ W/m² K, and h _cr = infinite if substrate remelting