The effects of 248 nm KrF excimer laser irradiation on combinations of different thickness PET films and different stainless steel mask mesh opening sizes were considered as a possible method to achieve different size perforations on different thickness PET films, in order to provide an effective and controllable perforation technology. Therefore, ablation behavior of PET films has been investigated for different laser energy fluence and number of laser pulses. Morphology of irradiated samples was observed by optical microscopy, and atomic forced microscopy to study topography and microstructures after laser ablation. An attempt has been made of correlate these findings with the orientation, strength and mechanical properties of the polymer.

The experimental results reveal that the percentage of perforation and the average perforated area increase with increasing number of pulses for all film thicknesses. The affected area, defined as the perforated area plus the heat affected zone (a black-char-region around the perforated area) decrease with increasing number of pulses. Due to the heat conducted from the steel mash wire, especially at cell corners, the perforation process seems to start initially at the cell corners. High laser fluence seems to lead to surface depressions due to thermal shock and surface stress waves along the process directions confirmed by tensile testing and x-ray analyses. The presence and the geometry of surface depressions were confirmed by atomic forced microscopy.

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