🚀 go-pugleaf

I've got a question about PC board fabrication.

The major cost of producing a PC layout is the artwork, of course.
One thing that I've been tempted to do is to produce a (negative)
etching template on a PostScript engine, on paper.  A film negative
can then be produced using a ThermoFax [1] machine, and the photoresist
exposed through this negative.

I've already done the first stage of this -- producing board artwork
in PostScript (Don't ask about the software -- it's a hideous kludge,
and I'm not willing to put in the effort right now to get it to the
point where anyone else could use it).  With careful tweaking of the
`scale' operator, I can overcome aspect ratio problems on the printer
(at least on the Imagen I'm using -- a desktop model might have
problems with nonlinearity in positioning) and place the image within
acceptable dimensional tolerances.

Has anyone any experience with exposing photoresist through ThermoFax
film?  Is the film sufficiently transparent to UV (in the clear areas)
and sufficiently opaque (in the dark areas) to make the photoresist
take a good image?  I'm willing to do touchup work with opaquing ink
(for holes in the black areas) and an X-Acto knife (for specks), but I
would prefer to avoid nasty surprises.

If it's feasible, this would seem to be a really neat technique,
particularly for basement operations; most schools have a ThermoFax
machine or two somewhere.  I'd be surprised if someone out there
hasn't tried it already.

Comments?  Pitfalls that I'm overlooking?
--------------------
[1] ThermoFax is a process for producing overhead transparencies.
There is no problem with aspect ratio control, as there might be with
the technique of photocopying onto acetate, because ThermoFax is a
contact printing process.

Kevin Kenny			UUCP: {uunet,pur-ee,convex}!uiucdcs!kenny
Department of Computer Science	ARPA Internet or CSNet: kenny@CS.UIUC.EDU
University of Illinois
1304 W. Springfield Ave.
Urbana, Illinois, 61801		Voice: (217) 333-6680