Stability limits of laser drilled hole arrays on large areas

Large area micro drilling utilizing short pulsed solid state lasers is a promising manufacturing technique for filtration technology. High degree of perforation and high quality of the drilled hole arrays regarding roundness and diameter variation of holes are the main challenges. The goal is to achieve high a degree of perforation with round and large holes and a constant pitch. The resulting variation of hole roundness and mechanical stability limitations of the percussion drilled foil using a ns pulsed laser source with a wavelength of 355 nm when drilling a 50 µm thin Aluminum (Al) foil are here presented. Different drilling strategies are investigated in relation to roundness, hole diameter, and heat propagation. The quality of drilled holes decreases with decreasing pitch and hole diameter. This can be related to thermal effects and pointing stability of the laser beam. Both effects are directional in the here used setup and can therefore be superposed positively or negatively. Due to adapted superposition of the effects the roundness of the holes can be maximized.