Experimental Investigations of Laser Micromachining of Metal Using Micro Thin Film Thermocouples

Laser-material interactions involved in laser micromachining are extremely complicated. In order to improve the fundamental understanding of the laser micromachining process, it is essential to investigate the complex phenomena and mechanisms of the physical processes within and close to the region of the interaction. Topographical characterizations of laser micromachining with various laser energy fluences were undertaken to correlate the resulting geometry changes with surface temperature measurements. Single pulses of laser beam with a nominal diameter of 47 μm were used. Possible changes of surface chemical composition induced by the laser micromachining process, in particular oxide formation, were also investigated around the laser spot. Moreover, C-type micro thin film thermocouples (TFTCs) with a junction size of 2 μm × 2 μm were fabricated to increase the maximum operation temperature and spatial resolution of temperature measurements. Surface temperature distribution around the laser spot was obtained in the range from 45 μm to 85 μm away from the center of laser spot. The result showed that there was a steep gradient of temperature in the radial direction and a superheated area around laser spot. It was also observed that the temperature profile matched the oxidation profile due to thermal effects.