Experimental investigation of deep-hole micro-drilling of glass using LIPAA process

This paper aims to study the mechanism of glass deep-hole micro-drilling by the Laser-Induced Plasma-Assisted Ablation (LIPAA) process. The Micro-drilling of glass was studied under various laser intensities. Nd:YAG nanosecond pulsed laser with 12 ns pulse duration was used as the laser light source. Copper was used as the metal target for the experiments. It is shown that laser glass micro-drilling is divided into two ablation stages. In the first stage, ablation is done by the brittle failure of glass caused by the collision of plasma plume with the glass surface. Exertion of mechanical pressure is also an important factor in the first few laser shots. Due to mechanical failure, glass microstructure changes in the focal spot. Second stage ablation is directly conducted by the thermal mechanism through absorption of laser by the glass. The hole produced on the glass by thermal mechanism is free of cracks. Cylindricity and roundness of the hole are very desirable. Laser intensity plays a vital role in material removal rate, hole depth and diameter. The process can be used for high-speed deep-hole micro-drilling of transparent materials to laser with good surface integrity and high-aspect ratio.