Besides the usage of various laser beam sources, differerent procedures of laser drilling are available. The procedures can be classified by their qualtiy and drilling time:
Single pulse drilling
The simplest way of laser drilling is the single pulse drilling. This procedure uses a single temorally long laser pulse to drill through the material. Thin materials (< 2mm) can be drilled with high pulse energies and longer pulse durations (ms-µs).
Schematic representation of single pulse drilling
The percussion drilling gradually removes the material with the shooting of multiple pulses at the same spot. This allows holes with up to 20mm depth. Single and percussion drilling do not move the laser bea, during the process.
Schematic representation of percussion drilling
Conversely the laser drilling by trepanning and twist drilling moves the laser radiation around a centre. For trepanning the laser is guided into the centre of the hole and expands the diameter by that. The expansion is caused by a cutting process. The melt of the previos percussion process can escape by the bottom of the hole to improve the smothness of the drilling walls. For trepanning pulses in the range of micro and femto seconds are used that allow drill depths of up to 20mm. The usage of ultrashort pulse lasers makes evaporation to the dominant process, instead of melting. The missing of the weld pool dynamic causes not vertical drilling walls, what limits the miximal drilling depth.
Schematic representation of trepanning
To solve the problem of the limited drill depth, twist drilling is an established process of drilling with short pulse durations. Conversely to trepanning and percussion drilling the laser beam slitghtly displaced to the drilling axis and has an own rotation. The laser beam is circularly guided by a motorised twisting optic to the work piece. After some circulations of the beam the circular material removal creates a drilling hole. The slightle displacement results in a vertical hole with high an aspect ratio. By that the USP twist drilling allows laser drilling with vertical and smooth drilling walls and a low ellipticity.
Schematic representation of twist drilling
Depending on the quality requirement Pulsar Photonics uses percussion or trepanning drilling as well as twist drilling. More information about laser drilling by Pulsar Photonics are found here.