Laser type and their applications
In materials
processing CO2, YAG and excimer lasers are mainly used today. CO2 and
YAG lasers offer the maximum power outputs and can vaporize or melt
materials with the finely focused laser beam. The excimer laser emits
UV light and consequently opens up avenues, particularly in the micro
sector. The diode or semiconductor laser has also been adopted increasingly
in materials processing, both as a pumping light source for YAG lasers
and for direct use with thermal effects.
CO2
lasers
The CO2
laser, in which the active material is a mixture of gaseous helium,
nitrogen and carbon dioxide, currently
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Laser
drilled circuit board ready for galvanising
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achieves
the highest power output in continuous wave operation. With 10.6 micrometer
its wavelength is in the far infrared region. Depending on the application,
lasers are offered with ratings between 10 to 20,000 watts.
CO2 lasers
of the lower output class (up to about 500 watts) are mainly used for
processing non-metals. Metals with small cross sections can be cut,
drilled and welded. Typical applications include cutting acrylics in
the advertising industry, ceramic substrates in the electronics industry,
or industrial textiles, wood and paper. Perforating cigarette paper
also bears mentioning. A special application is sintering of ceramics
for “Rapid Prototyping”. In addition, low output CO2 lasers are integrated
into desktop systems with various uses in cutting and engraving.
In recent
years, the laser drilling of circuit boards has attained great importance.
In this process, holes (diameter approx 100 mm) are drilled in using
the laser and then galvanized for throughplating. If only dielectric
layers are laser drilled, CO2 lasers are mainly used. If, however, copper
layers are also laser drilled, systems with UV lasers (tripled frequency
solid-state lasers) or combined systems with CO2 and UV lasers are used.
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Production
of high power lasers as a matter for teamplayers
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CO2 lasers
with an output of 500 to 4000 watts are used mainly for cutting sheet
metal. This application is state-of-the-art, and today most CO2 lasers
are used in this way. With materials of up to 20mm thickness and small
or medium batch sizes, lasers have in many cases taken over from conventional
processes - for example punching or milling - because of their flexibility
and the ease with which cutting patterns can be programmed. Aluminium
and brass (aluminium: 8 mm, brass: 5 mm) in thickness can also be successfully
processed.
Another
application which was introduced early on and which has proven extremely
successful is cutting dies. In this process, the outline of an unfolded
folding box blank is cut in 18 mm plywood with the help of a laser.
Welding
is the main application for lasers with outputs of more than 4000 watts.
Depending on the laser output and the material to process, welding depths
of up to 20 mm are possible. To be economically viable, laser welding
must generally be done in high volume and requires a high degree of
automation, since it is an extremely fast process. More than 2000 systems
are already in use in production in Europe today.
Typical
applications in automotive industry are welding gearbox and engine parts,
or joining flat or pre-formed automobile body sheet metal. Applications
in other industrial branches are for example tube welding, respectively
welding of endless tubes. Applications laboratories are dealing with
other laser processes in new areas such as surface finishing (annealing,
remelting, alloying) to open up new fields for the CO2 laser.
