solid state) or fi ber laser technology, are used to mark mainly metals and many plastics, whereas far infrared (10,600 nm) CO2
technology, particularly as the laser costs fall more in line with this market segment’s expectations.
lasers are used to process
mainly organic materials such as wood, leather, glass, foam, stone and plastic engraving. The shorter wavelengths such as green (532 nm) and UV (355 nm) are reserved for applications requiring high material absorption and low impact on the mate- rial (such as heat affected zone, recast, etc.). Short wavelength marking applications include solar panels, computer hard disk components, semicon- ductor components and medical device implants.
Micromachining Laser micromachining involves the machining of small features into various materials using lasers through material removal. By “small,” we defi ne the feature size as being less than 1 mm and the material thickness as being less than 1 mm, and both are usu- ally a lot less.
Printed circuit boards that are laser marked. Photo courtesy LNA Laser Technology
In addition, short wavelength lasers have a smaller focused spot size allowing for very small marking in certain micro applications. CO2
lasers are the most mature of the marking
laser technologies. The applications fi elds are well established and the architecture has remained relatively stable over the past few decades. The biggest changes in technology in this area have come in the 1 μm and under spectrum. The trend in technology over the last 20 years has allowed the lasers to become increasingly compact, effi cient and maintenance free, at a signifi cantly lower cost. Fiber laser technology, in particular, has had the most impact in the majority of industrial manufacturing applications. It is likely that future developments in laser marking will follow the trend of sub-nanosecond
LF8
AdvancedManufacturing.org
Lasers are used for a variety of reasons. First, the noncontact nature minimizes the risk of damage to the material and does not introduce tool wear. The feature resolution when using UV lasers is unmatched by any traditional machining technology, with the small- est attainable features on the order of a few microns, using UV lasers and high-quality optics. By choosing the correct wavelength and energy density on target, selective mate- rial removal can even be achieved. Finally, the use of lasers provides great fl exibility especially in the prototyping and R&D stages. For micromachining applica- tions the key to clean and low taper processing is peak power intensity, which is energy density per unit area. In other words, the best results are obtained when using lasers with high-pulse energy and short-pulse length and where the laser spot is
focused to a small size. This is one of the reasons that USP (ultra-short pulse, meaning picosecond and femtosecond lasers) are becoming very popular—the short-pulse length greatly increases peak power at the target, even with relatively low pulse energy. Armed with a variety of lasers with wavelengths from the IR through the UV, and pulse lengths from milliseconds to femtoseconds, numerous applica- tions can be addressed in the fi elds of automotive manufacturing, semiconductors, microelectronics, medical devices, alternative energy, aerospace and defense. All materials can be addressed by using the right laser and optical setup with the stipulation that maximum material thickness is somewhat dependent on the output power of the laser, especially when speed/cost are an issue.
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