Thermohydrodynamics Analysis on Mechanism of Bump Formation in Laser Texturing

Laser texturing is a technique to make texture on a hard disk for a computer with small bumps generated on NiP film on aluminum substrate by single shots of short pulsed Nd : YLF (Yttrium Lithium Fluoride) laser. It has been already used practically, but the mechanism of bump formation has not been elucidated yet. The purpose of this study is thermohy-drodynamics analysis on the mechanism of bump formation. The vaporization recoil pressure, Marangoni force that depends on temperature gradient and the surface tension are considered at the free surface. The VOF (Volume of Fluid) method is used for the analysis with the free surface. The mechanism of bump formation is presented from the calculated results.