The T.E.A. Co2
laser is used for laser marking and laser etching in many different industrial situations.
Transversely Excited Atmospheric
(T.E.A.)
lasers have been in general industrial use for laser marking operations
starting approximately in the early 1970s and late 1960’s. The T.E.A. Co2 laser has been used
extensively for laser marking and laser etching in many industries and on many
different types of products. The T.E.A.
Co2 laser has been used extensively in the dry food and pharmaceutical industries
for laser marking and laser etching of buy dates, product expiration dates, lot
numbers and serial numbers.
T.E.A.
Co2 laser marking is achieved via the use of a mask or stencil. As the laser beam passes through the stencil,
the outline of the mask or stencil is laser marked or laser etched onto the product. Changing the laser mark requires changing of
the mask or stencil. In the past this
was accomplished by an operator who manually changed the mask or stencil. This process continued until the introduction
of automatic mask changers or time clocks several years after the introduction
of the T.E.A. Co2 laser. Generally speaking, the use of T.E.A. Co2 mask lasers
is limited to applications where the laser mark does not require frequent
changes and the laser mark can be altered infrequently. Examples include, once at the end each shift,
once a day, or after a long batch processing run of products. Automatic time clock modules are available but
generally increment the time only every 15 or 30 minutes.
The
T.E.A. Co2 laser requires the use of an external laser gas bottle generally
consisting of the following components and approximate % combinations:
- Carbon
dioxide (CO2) (around 10-20 %)
- Nitrogen
(N2) (around 10-20%)
- Hydrogen
(H2)
- Helium
(He) (The remainder of the gas mixture)
The
gas mixture flows though the laser by use of an internal fan assembly inside
the laser head. The medium is combined
with an electrical discharge that excites the atmosphere and generates the
laser beam. This gas mixture is a
consumable of the T.E.A Co2 laser marking or laser etching process. For spark gap driven T.E.A. Co2 lasers a dry
air or nitrogen supply to the spark gap is also required.
T.E.A.
Co2 lasers employed for laser marking and laser etching are generally air
cooled except for the highest speed operations where water cooling may be
required. T.E.A. Co2 lasers generally
used in industrial laser marking and laser etching applications are capable of
laser marking or laser etching up to 90,000 parts per hour. Generally T.E.A. Co2 lasers used in
industrial laser marking or laser etching applications produce power levels
from 2.0 joules to 5.5 joules depending on the internal configuration of the
main capacitor size and rating coupled with the reflectivity of the laser font
optic.
T.E.A.
Co2 laser produce a very high peak power, up to 10x the peak power of
continuous wave Co2 lasers and therefore are extremely useful for Co2 laser
marking and laser etching of products that can be difficult for Co2 lasers such
as some plastics and resins. With some
materials, laser marking and laser etching with T.E.A. Co2 lasers will produce
a visible color change to the product. Laser
marking and laser etching sealed beam RF excited Co2 lasers will only produce
an etch with no color change. The T.E.A.
Co2 lasers can produce the change in color for some products along with a laser
etch due to the high peak power produced by the T.E.A. Co2 laser pulse.
T.E.A.
Co2 lasers have been used extensively up till now for laser marking and laser
etching of discrete electronic components such as T0220's and SOT23's. The T.E.A. lasers produce a white or blue
appearing laser mark on the component when the laser beam interacts with a
'laser friendly' ink on the surface of the component. In many of these applications the T.E.A. Co2
laser is coupled with a component tester.
If the component passes the test a laser mark is applied. If the component fails the test the part is
rejected from the line.
The
newest generation of T.E.A. Co2 lasers has very high repetition rates and are
used extensive in the Kapton industry for laser drilling purposes.
T.E.A.
Co2 lasers generally operate in the infrared light spectrum at 10.6 and 9.4
micrometers. Generally rear optics in
the laser cavity are 100% reflective to an extent causing self generated laser
beams inside the electrode gap and laser head.
The front optics in industrial applications vary between 40% to 70%
reflective based on the material being Co2 laser marked, laser etched or laser
drilled.
An
important advantage of the T.E.A. Co2 laser is that laser light wavelength can
be changed from 10.6 micrometers to 9.4 micrometers. This is achieved with the change of the font
optic coating. The use of laser light at
9.4 micrometers is very important for Co2 laser marking of certain plastics
such as PET or PETE and producing readable color changed Co2 laser marks on
bottles. Generally speaking T.E.A. Co2
laser front optics in industrial applications are geranium coated though
sometimes zinc selenide is used. Mirrors
for turning the laser beam are gold coated and the laser beam profile can
approach sizes of approximately 1" x 1" depending on the gap of the electrode
set.
Author
Bio
Jim
Morin writes for Worldwide Laser Service Corporation a company that specializes
in T.E.A. Co2 lasers. For more
information visit
http://www.wlsc.com 
