레이저 조사에 따른 마킹 메커니즘 분석과 온도 분포 해석

Abstract

Recently, many scientists have studied the interaction between laser beam and materials such as pit formations and heat transfer distributions according to laser irradiation. Nevertheless, they just predict those without mechanism analysis. Thus, we try to perform the numerical analysis for heat transfer distributions due to pit formations using the FEM (Finite Elements Method) by pulse laser irradiated to ABS plastic. ABS plastic is generally used for the industry and it is sensitive to the thermal. We also try to prove the mechanism of a pit formation by measuring a nano second time resolved reflectivity on real time. In this paper, we use the Q-switching Nd:YAG laser as a record laser and it forms pits at ABS plastic. In our experiments, wavelengths of 1064 ㎚ and 532 ㎚ are used, with 8 ㎱ pulse-width, irradiation energy per pulse ranging from 190 mJ to 340 mJ, pulse repetition (1, 5, 10 and 20 ㎐). Total irradiation energy to form pits is controlled by repetition pulse number. The pits are analyzed by optical microscopy and OCT (Optical Coherence Tomography) using non-contact method. This measurement give us the information of radius of pit and size of HAZ (Heat Affected Zone). These results are characterized by wavelength, energy and pulse repetition rate and they in accord with simulation. Magnitude of nano second time resolved reflectivity in order to analyze the mechanism of pit formations is dependence on wavelength, and nano second reflectivity has delay time. In case of has irradiation energy over 250 mJ, the reflectivity has side lobe which is based on mechanism analysis of pit formation.