A Study of Ablation by Short Wavelength Pulse Laser

A Photothermal Modeling for Etching Mechanism of Polymer

Abstract

The ablating behavior of polyimide irradiated by 266nm, 532nm, and 1064nm YAG lasers has been studied. The etching mechanism is discussed by calculations based on solutions of the one-dimensional heat equation and experimental observations. These experiments reveal that calculations are in accord with several observations and that low-damage pattern is obtained with the ideal temperature distribution based on high absorption coefficient of short wavelength laser. It can be calculated from this photothermal modeling that surface of polyimide is raised to the volatile temperature by a single irradiation with the threshold laser energy density for ablation on each laser. Polyimide is seemed to produce low-damage pattern becacuse of its little stored heat, even if it is given the repeated irradiation by 266nm YAG laser with high pulse repetition rate. It is roughly estimated that the pulse repetition rate with thermal damage by stored heat is higher than 1000pps.