New excimer laser marking method using MMD

Abstract

Higher and higher through-puts in marking industry are todays requirements. Mainly packaging industry or cable marking companies ask for part-by-part varying markings like serial numbers, weight, date or barcodes. That gives a need to develop a flexible, high-speed on-the-fly marking technique. Current laser marking techniques like direct writing using a scanned laser beam or excimer laser fixed mask projection offer proven quality and either flexibility or detailism. Their drawbacks are limited speed (direct writing) and invariability (fixed mask projection). The Fraunhofer IWS developed a marking system using excimer laser mask projection with a micro mirror device (MMD) as computer-controlled 'flexible mask.' The idea is to generate complex markings within one laser pulse so the marking speed is only limited by the laser repetition rate. The IWS used a 308nm excimer laser and a reflective phase-shifting mask from Fh IMS to demonstrate the marking capabilities. It was possible to generate free-programmable, high-contrast markings on common materials like paper and plastic. Furthermore, it could be shown that the technique is also usable to generate 3D structures in PI. Result of the studies is the development of a very fast marking technique using MMDs in combination with short wavelength and short pulse lasers. It also has high potential in 3D laser micromachining.