STATISTICAL ANALYSIS OF FEMTOSECOND PULSES LASER ON HOLE DRILLING OF SILICON WAFER

This study investigated the relationship and parameters interactions between five independent variables in laser percussion drilling of micro-hole. Experiments were conducted on single crystal silicon wafer with material thickness of 725 μm using femtosecond (fs) laser with wavelength of 775 nm and pulse duration of 200 fs. Laser power, focus position, number of pulses, workpiece temperature and assist liquid were selected as independent process variables. Taguchi L18 orthogonal array was applied to design the experiments. The drilling process was evaluated in terms of entrance hole diameter and exit hole diameter. The analysis of the variance (ANOVA) was used to determine the significant parameters that are affecting the entrance hole diameter and exit hole diameter. The result shows that laser power and focus position has highly significant effect on entrance hole diameter. The number of pulses, focus position and assist liquid however has highly significant effect on exit hole diameter.