By: David Ashkenasi¹, Tristan Kaszemeikat¹, Norbert Mueller¹, Reinhard Dietrich¹, Daniel Jahns¹,Gerd Illing¹, Hans Joachim Eichler^1,2 Tino Petsch³, Jens Hänel³, Christian Scholz³

To exploit the advantages of laser technology for material processing, e.g. micro drilling and cutting, versatile trepanning systems based on rotating optics have been designed and implemented. Depending on the development stage, the trepanning systems enable the controlled adjustment of beam displacement and inclination during fast rotation.

The typical specifications of the new versatile trepanning systems, developed by the LMTB and redesigned by 3D-Micormac, are the following:

• Free choice of laser wavelength (from the UV to the NIR, 10 µm is a future option)
• Free choice of laser pulse width (from sub-ps to ms, or even cw)
• Free choice of focusing optics with a focal length  ³ 60 mm  (e.g. doublet lens, gradient lenses, etc.)
• Drilling / cutting diameter: 50 to 1500 µm (larger diameters are optionally addressable)
• Laser beam inclination angle: -5..0°..+5° (0° = cylindrical, i.e. taper-less)
• Rotation speed: set at 18,000 rpm and 10,000 rpm
• Protection window disks and processing gas nozzle are included in all types
• Low weight and compact size for straightforward work-station integration: from <4 kg, <(200 x 120 x 120) mm³ to  <7 kg, <(200 x 250 x 120) mm³ , depending on the type (manual or motorized).

The trepanning systems are customized for very different laser parameters, e.g. for ultra-short laser pulses at wavelengths of 355, 515, 532, 1030, 1064 and 1550 nm.  The implementation of the newly developed trepanning systems can be identified already in several R&D laser laboratories and in 24/7 productions facilities around the world.

Fig. 1a presents an example of nanosecond laser drilling of aluminum nitride (AlN) ceramic. The laser system utilized for this application is an industrial q-switched, diode-pumped Nd:YVO₄ laser system with an amplifier unit manufactured by IB-Laser, Berlin, generating ca. 30 ns laser pulses at a maximum average power of 38 W @ 20 kHz at a wavelength of 1064 nm. Fig. 1b depicts a typical SEM image of the cylindrical bore wall at cross section. Note the smooth processed side-wall surface, demonstrating the exceptional processing quality using standard nanosecond laser pulse technology. The angular beam steering and circular pulse distribution in laser trepanning generally yields far improved processing conditions compared to conventional laser percussion with a fixed focusing optics alone.

The primary processing results with the novel trepanning systems utilizing nanosecond laser pulse technology are very encouraging. Further studies with different materials are conducted at the LMTB laser application laboratory to optimize the laser trepanning system for even more precise and reliable micro drilling. Present investigations include applications using picosecond laser pulses and other materials, such as metals.