Aachen, Germany - Over the past few years, the use of ultrashort (also known as ultrafast) pulsed lasers in material processing has been riding a wave of success. Reasons include the laser’s outstanding properties as well as the opportunity to process nearly any type of material with the highest degree of precision. Because the range of possible applications is continually expanding, market growth currently stands at between 20 and 25 percent per year.
Typically, the technology is used in areas such as mould technology, laser cutting, and laser drilling for microcomponents, sieves, and filters, as well as thin-film coating for solar technologies and the manufacture of OLEDs. When it comes to microstructuring, however, today’s technology has often found itself pushed to its limits from an efficiency standpoint.
Because of these efficiency concerns, the current tool of choice for large-area surface microstructuring is the nanosecond laser (ns laser) – which has firmly established itself on the market thanks to impressive cost efficiency. The drawback is that the precision of the microstructuring is limited by the accompanying melt processes; components often require extensive reworking. By contrast, an ultrashort pulsed laser produces surface structures that do not require any further processing. They are accurate to within a few micrometers laterally and to within 100 nm in depth.
The dominant role of evaporation in the ablation process with USP lasers means that ablation rates are around a factor of 10 lower than they are with ns lasers. From a business perspective, this has often made using USP lasers to mass produce microcomponents seem unattractive. What is more, current USP laser systems generally cannot make use of more than 20 percent of the available laser energy in the 50 to 100 W power range.
In an effort to improve the efficiency of USP lasers in this range, researchers from Fraunhofer ILT have developed a technique that allows laser ablation to run in parallel. This multibeam technology has now been thoroughly tested and enables the laser beam to be split up into more than 100 beamlets. As a result, a workpiece can be processed at 100 places at once, which speeds up the work process accordingly. The technology means that almost all of the capacity offered by current high-performance USP laser systems can be brought to bear on the workpiece.
An intelligently networked system
Pulsar Photonics GmbH, a Fraunhofer ILT spin-off, has developed a tool system that includes not only intelligent measurement technology but also the option to segment the beam. Beam segmentation essentially boosts the efficiency of workpiece processing itself; the system’s integrated measurement sensors simplify and automate both the definition of parameters during machine preparation and the monitoring of quality once the work has been completed. As a result, the setup process takes far less time than it otherwise might.
For instance, users can conduct initial machine preparation with the part already in the machine because its sensors help them to quickly determine which laser parameters will yield the best processing results. Quality assurance is immediate because the sensors show users how deep the microstructures are or the diameter of the holes drilled. In this way, contract manufacturers can hand the customer verified parts as soon as production is complete. The adaptable USP laser system can also be used for a variety of applications beyond surface structuring, including drilling and cutting by ablation.
Recurring structures and large-scale surface functionalization
Because of its design, the multibeam technology is primarily suited to the manufacture of components that feature recurring patterns and set structural arrangements, or else for working on several components with the same structure simultaneously. And in many applications, this sort of repeating structure is exactly what is required, such as the large-scale functionalization of surfaces where the aim is to reduce friction or to produce thin-film masks and microfilters.
Pulsar Photonics (Aachen) will showcase its tool system and multibeam scanner from April 7-11, 2014 at the Hannover Messe. Scientists from Fraunhofer ILT will be at the joint Fraunhofer production to showcase techniques for functional coating and microjoining as well as to demonstrate the diverse applications of the ultrashort pulsed laser.
International Laser Technology Congress AKL’14
Dipl.-Ing. Joachim Ryll of Pulsar Photonics GmbH will give a talk at AKL’14 in Aachen on May 9, 2014, on how to improve efficiency when working materials using USP lasers by ensuring the best possible system
Above: Recurring lettering imprinted on a steel foil using the multibeam scanner. Copyright Pulsar Photonics GmbH.
Tool system made up of galvanometer, multibeam scanner, camera, and topography sensors. Copyright Pulsar Photonics GmbH.