Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Way back in my hand taping days before CAD layout tools, we would lay a board out using Mylar film, ruby tape and Bishop dip and doughnut  pads. This was done at 2:1 then sent to an industrial photo house to be reduced 2:1 on lito-film. IIRC it  was about $20 to $50 for a set of negatives and more if you wanted a set of contact positives.   I saved some cost at home by doing my own contact positives.  Making the contact prints was fairly easy -- just a couple pieces of glass to clamp the films together, a darkroom safe light, some slow litho-film, developer and fixer.  Took around 20 minutes to do the entire process.   The positives were used with boards spin coated with Shipley AZ111 positive resist, exposed then etched.  Turn around for the photo house was 24 hours but you could pay for 1 hour service if you were in a rush.  Eventually all the photo houses switched over to laser plotters once PCB CAD systems became available.  Even the photo plotting houses went by the way side once the PCB fabricators started to accept digital Gerber input files.

You can still buy litho-film, the developer and fixer from places like Freestyle Photographic Supplies. Though the web site seems to be down.  The ideal thing would be to build your own photo plotter

Criag