Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!samsung!munnari.oz.au!oby
From: oby@munnari.oz.au (David O'Brien)
Newsgroups: sci.electronics
Subject: Re: PCB making ?
Summary: re PCB making
Message-ID: <2952@munnari.oz.au>
Date: 22 Dec 89 00:41:25 GMT
References: <2652@servax0.essex.ac.uk> <317@marvin.moncam.co.uk>
Sender: news@cs.mu.oz.au
Lines: 39

In article <317@marvin.moncam.co.uk>, emmo@moncam.co.uk (Dave Emmerson) writes:
> In article <2652@servax0.essex.ac.uk>, zotog@SunLab14.essex.ac.uk	 (Zotos G) writes:
> >[] 
> > 
> > Is it posible to photocopy the piece of paper with the track layout on a
> > clear plastic film used on overhead projectors and use this as the film
> > plased on the premade positive photoresist PCB and then to expose that 
> > in UV light ?
> > 
> 
> Very unlikely. Even if you can get enough density in the image area,
> it will tend to be grainy. Also, you may not get 1:1 copies
> 
> You need to use 'Ortho Lith' photographic film, in a lith developer, or
> at least a VERY high-contrast developer. You can handle this in red
> safelight and dish develop it quite easily.
> 
> Dave E.


  I have found these Overhead Projection transparency films produce
  grainy artwork,and if used develop pourous Photoresist finish.      

  A way to remedy this is to print Two of these grainy artwork sheets 
  at the same time,with the artwork in the same position on the Copier
  then expose the PCB using these two sheets together.
  The effect is that the grains of both sheets combine to give a better
  quality artwork,and the resulting PCB will have clean tracks without
  the small pits associated with tiny holes in the Photoresist
  The Quality of the Photocopier is a big factor also.

  Try it ,it works

  David Obrien
  Department of Computer Science
  University of Melbourne
  Parkville, Victoria
  Australia