Mechanism of laser drilling superhigh-aspect-ratio holes in polymers

A brief review of recent theoretical and experimental studies of multipulse laser drilling keyholes in polymers is presented. The stationary keyhole profile is obtained after irradiation by a quite great number of laser pulses due to self-organisation processes and is a new more stable state of the surface irradiated by intense light. This concept together with ample experimental data obtained for various polymers form the basis of the analytical model of multipulse drilling holes with a superhigh depth – diameter ratio (300–600) (the so-called aspect ratio) by using UV excimer KrF laser radiation. The model reveals the main factors controlling the parameters of drilling holes by nanosecond UV pulses and, in particular, determines the conditions for drilling holes with virtually parallel side walls and very high aspect ratios.