On Tue, 1 May 2007 07:14:21 -0700, you wrote:

>> If photoresist boards can be "influenced" by these high powered lasers then it could be a cheapish way of "printing" directly onto PCBs.
>>
>> Thoughts are to either have a rotary indexed table or maybe reverse engineer a cheap laser printer and pass the board through using the printer optics to raster print the image onto the board.
>>
>> Anyone know what happens to photoresist under a moderate power laser beam ?
>>
>
>The laser from a DVD burner most likely won't have any effect on the
>resist. It's wavelength is about 650 nm, whereas the resist is
>sensitive to UV. You may have luck if you were to use the laser from a
>Blu-Ray burner, but that will set you back many hundreds of dollars.
>
>The guts from a laser printer won't cut it either, because they use a
>much lower power laser, and it's 780 nm, which is even further from
>the seisitivity of the PCB resist. In addition, the spot from the
>laser printer moves very fast across the surface, so will never stay
>in one place long enough to affect the resist, unless you were to
>write the same scan line many thousands of times before stepping on.
>It might be possible to istall the laser from a Blu-ray burner into a
>laser printer.. but then all the optics would be wrong and the beam
>would need to be refocussed and realigned somehow.
>
>I think a more promising route is to use a much higher powered laser,
>and find a positive acting resist that hardens with heat, or use a
>resist that the laser selectively ablates. I'm building such a system
>at the moment, using a CO2 laser, but it won't be functional for a few
>more months.

Why bother ? I can't see any benefit in doing this - printing artwork on tracing paper on a laser
printer and using a conventional UV exposure box will always be so much quicker and cheaper. 
Plenty of info here : www.electricstuff.co.uk/pcbs.html

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