High Density Perforation of Thin Al-Foils with Ultra Short Pulse Lasers

The need for micro scaled features in medical devices and engineering products, like holes for filtration, separation and ventilation or small structures e.g. for hydrophobic effects, is constantly increasing. The size of these structures is often in the region of 20 mu m and smaller. One important aspect of the drilling or structuring process is the process stability and its influencing factors. For the laser perforation of a 15 am thick Aluminum foil with UV ps-pulses the process limits as well as the influencing factors are investigated. The pitch of the holes within the pattern as well as the number of pulses used for the percussion drilling of each of the holes are varied. The drilled holes are evaluated by means of hole diameter and precision of the hole shape in means of circularity and ellipticity. Holes with a diameter of < 6 mu m are drilled at a minimal pitch of 12 mu m. The ellipticity is mainly dependent on the heat distribution, the circularity on polarization effects. In contrast to the perforation process with ns-pulses polarization effects play a major role for the perforation process with ps-pulses.