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Percussion drilling of blind holes and vias in Kapton ® film was investigated using Q-switched solid state lasers operating at UV (355nm) and VUV (266nm) wavelengths. Holes were analyzed using different methods such as scanning electron microscopy (SEM) and surface profilometry. Ablation rates for the two wavelengths are compared. No abrupt thresholds were found and there was no evidence of an incubation effect within the first few pulses. Introducing pauses during the drilling increased the number of shots required for perforation of the film. The effects of fluence on diameter, depth and taper of the holes are presented. Smaller and neater holes are achieved more accurately with a lower fluence. An observed skin effect brought about by long exposure to low fluence VUV laser light is also discussed.

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The relationship between focused spot size, pulse energy, and ablated hole diameter was explored using 266 nm nanosecond pulses and 775 nm femtosecond pulses on polyethylene terephthalate. The spot size of a Gaussian laser beam can be deduced from the diameters of holes machined with single shots at different pulse energies but the results can be influenced by such issues as the thickness of the material and the range of fluence chosen. These limitations of the method were investigated. Multiple shot craters were also measured but gave an overestimation of spot size, particularly in the femtosecond case. A model was developed to predict the diameter for a given energy and number of shots. Tests of the model gave results that agreed well with the predicted values. It was found that for the same total energy smaller holes can be obtained by decreasing the pulse energy and increasing the number of shots. An effective spot size for multiple shots was determined.