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From: nivek@rover.ri.cmu.edu (Kevin Dowling)
Newsgroups: sci.electronics
Subject: PC Boards: Gerber formats
Message-ID: <6261@pt.cs.cmu.edu>
Date: 25 Sep 89 03:45:34 GMT
Organization: Carnegie-Mellon University, CS/RI
Lines: 39


We've been using McCadd, a schematic entry program, routing and layout
package for the Macintosh. For output it can print on the Laserwriter
(Postscript) so we can preview mask layouts.  Reprographics places that
generate artwork for PCB production usually use 'Gerber' formats however.
McCadd does supply a Gerber translator for their product as do other PC
layout programs on the market.

From what I understand the Gerber format was first done by a PCB company
that established this standard to communicate with these NC controlled X/Y
tables that moves a little aperture wheel around and blinks a light on and
off while tracing lines and pads out on a photo-sensitive surface.

This has caused some headaches for us. We'd like to just ship a McCadd file
off and forget about the rest but there are not great numbers of photoplot
houses with all the right tools. "Just send us Gerber formats, or some HP
format" is the usual response. With some work we can generate the Gerber
formats and the drill tape...

My questions are: Have there been proposed new formats for describing PC
board layouts? Could postscript or PICT or some subset of these be used to
generate layouts? Is Gerber good enough for the forseeable future?

Since masks for PC production are just dark and light areas you can just
'paint' a board using a single small aperature and lots of time, but are
there printers of high-resolution that can plot 1:1 masks on mylar directly?
How about a system that could write on boards directly?  (A PCB printer!)

There has been a proliferation of PCB generation programs, there are several
for the PC, a couple for the Mac, and other workstation based.  Do all these
generate Gerber formats?

				nivek

Aka :	Kevin Dowling		Bell:	(412) 268-8830
Arpa:	nivek@rover.ri.cmu.edu	Mail:	Robotics Institute
				Carnegie Mellon University
				Pgh, PA 15213-3890