On Tue, 1 May 2007 08:47:20 -0700, you wrote:

>>
>> 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.
>
>Two reasons, as far as I can tell: Firstly, because it's interesting.

Fine. No problem with that, as long as it's regarded as a learning excercise and not something
likely to be better/cheaper/more useful than simpler methods...

>Secondly, using a laser has the potential of higher precision, because
>it eliminates the step of making a mask for the photoresist.

Precision ( accuracy) isn't usually a big deal - laser printers are easilya dequate in this respect.
Resolution may be theoretically better, however I think the limits of the resist itself, plus the
home etching process mean you wouldn't get much improvement in what would be achievable. 
In theory, direct laser might me more accurate & have teh potential for more resolution, but
building laser optics to work better than what can be achieved with a print+expose method would be
pretty tricky.

You can reliably get 50 tracks/inch with 1200dpi laser on tracing paper and a simple
(non-collimated) UV box.  
It's unlikely you would be doing PCBs that need more than that density which didn't also need proper
vias & resists, therefore best left to proper fab houses. 


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist