On Jan 24, 2010, at 4:43 AM, Bob Paddock wrote:
CO2 laser is the wrong wavelength to cut metal. Only a couple
percent of the radiation is absorbed. Great for plastics, though,
and many other materials. With respect to >PCB etching, one
thing I've thought about but haven't yet tried is simply using
paint. Apply a thin code of flat black paint as a resist (I'm
guessing enamel would work best) >and let the laser ablate the
paint where you want to etch.
We already use commercial grade pre-photosensitized FR4 laminate, so
doing painting and such is not needed. My only concern was that
there
might be issues of the wave-lengths between the LASER and the
laminate
being miss-matched, but if the process is actually based on heat then
it is a non-issue.
Now that will depend on your photochemistry. CO2 laser is not in
the visible spectrum. You'd have to check the sensitivity of the
photo emulsion w.r.t. wavelength. Most litho films are not
sensitive even to red, but do go up into ultra-violet. I can't
remember if CO2 is longer or shorter than visible light. In any
case, you'd get by with very low power.