High-aspect-ratio microdrilling in polymeric materials with intense KrF laser radiation

UV laser microdrilling of high-aspect-ratio holes has been studied by using an intense beam with a low numerical aperture (KrF laser). The UV laser ab lation produces a minimum of thermal or mechanical damage on the target. Un der some particular experimental conditions (many high-fluence pulses), it is shown that long deep holes are obtained with reproducible aspect ratio ( up to Phi/d approximate to 600) in a variety of materials. Experiments with polymers (PMMA, PC, PET, PI, PS, PEEK) show that the more absorbing the po lymer is, the better the resolution. However highly absorbing materials exh ibit a low ablation rate. These promising results on laser microdrilling ca n be extended to new applications, for example, when the beam/target relati ve movement is computer driven. For instance this approach can be applied t o cutting micro-objects with complicated shape or to machining fragile or b rittle materials.