One of the electronics magazines I read covered this process (using a
modified flatbed plotter to apply resist directly to PCB's) in detail a few
months ago.  They compared various types of pens, and showed excellent
photographs of the results with each (which were disappointing for all but
one type).  It looked like a really useful technique, if you had access to
an old plotter.

I don't remember which mag it was, but I'll look it up and post the
reference in the next few days.  And if some of you beg _really_ nicely, I
might be persuaded to scan the article and email it to anyone who request
it.

BTW, if anyone knows of a good (cheap) source for a used plotter for this
purpose, please reply directly to me.


CIAO - Martin R. Green
elimar@bigfoot.com

----------
From:   Andrew Russell Morris[SMTP:amorris@MINDSPRING.COM]
Sent:   Saturday, September 13, 1997 5:08 PM
To:     PICLIST@mitvma.mit.edu
Subject:        Re: [OT] Plot on Copper

I thought about doing this several years ago and called the manufacturer of
my plotter (Graphtec) and they put me in contact with someone who was doing
that with black India drafting ink. I never tried it. Has anybody elde
tried that? It's cheap and readily available at any drawing supply or
office supply store and can be put in any refillable plotter pen.


At 01:56 PM 9/12/97 -0400, you wrote:
>I have a HP 7221 (7225?) that I have used many times to plot an etch
>resist pattern on copper clad board. I took a standard HP plotter pen,
>removed everything except the body, then bored it out in a lathe to fit
>a permanent ink pen. (You can probably do this by hand reaming with an
>appropriate set of drills or careful sanding and filing.) I found that a
>Sanford ultra fine point Sharpie worked the best. You need to adjust you
>pen speed and width settings to get the best line while still moving
>fast enough so that the pen tip does not dry out. Width setting is
>important so that you don't overlap what has already been plotted as the
>partially dried ink will clog up the pen tip. Likewise, don't let the
>pen dry out in the holder between plots. I used drafting tape to hold
>the board in place. I successfully did a design once with pads for a
>flat pack IC that came out useable.
>
>I also experimented with other brands of pens (and pencils!). I never
>was able to get good results with a Berol Fine Point Permanent (which
>is, BTW, the "etch resist" pen that GC electronics, Kepro, and Radio
>Shack used to sell for more than a whole box of the same pen at a office
>supply store). I never could keep the tips from drying out during the
>plot. I have also found that for extremely fine line drawings on paper
>or vellum (not film), a Pilot Precise roller ball gave excellent
>results. Text smaller than 1/16 inch was clearly readable!
>
>
>Frank Richterkessing
>
>FRANK.RICHTERKESSING@APPL.GE.COM
>