Nanosecond and sub-nanosecond pulsed laser ablation of thin single and multi-layer packaging films

Translating single and multi-layer packaging films are exposed to 0.5-0.8 ns laser pulses of wavelength 1064 nm and 10-12.5 ns laser pulses of wavelength 515 nm. Ablation depths and threshold fluences are reported for single-layer polyethylene (PE), polypropylene (PP) and aluminium of thickness 20-50 μm. Interaction and cut widths are reported for the same single-layer films and for four multi-layer films comprising aluminium-polypropylene and aluminium-paper. Ablation of the PE and PP films is only possible in the tested parameter range with 0.5 ns, 1064 nm pulses. Though a one order of magnitude reduction in the ablation threshold of aluminium is observed with 0.5-0.8 ns, 1064 nm pulses, the efficiency of material removal for fluences >8 J cm-2 is superior with 10-12.5 ns, 515 nm pulses. Multi-layer film response is found to be heavily dictated by the thickness of metallic layers. For multi-layer films with aluminium layers of thickness 7-9 μm, adjacent layers are removed by inter-layer heat conduction from the aluminium layer, in some cases leading to very large cut widths. For multi-layer films with aluminium layers of thickness <0.1 μm, direct ablation of all layers must take place for complete film penetration. The study provides quantitative results regarding process efficiency and quality for application of pulsed laser sources within the packaging industry.