From: Roger Johansson
Subject: Re: Printing dircetly onro PCB copper side Part II
Date: Sat, 14 Sep 2002 04:12:53 +0200
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A variation of the same x-y plotter idea:
Cover the laminate with wax, or anything not easily water soluble.
Put a steel pin in the plotter instead of the pen, a sharpened pointy
We use this steel pin to scratch the waxed surface, so the copper
layer is marked by the steel pin.
After that we etch the pcb, and the copper will be removed in these
tracks in the wax, to make the track in the copper deeper and a little
Get rid of the wax and the pcb is ready.
This method might give acceptably thin ditches between copper tracks.
For this method we only need a sharp steel needle and make sure it has
a suitable weight on it, when it is in the down position, to make
marks in the copper layer. (50gram?)
Getting back to the cutter method:
In SMD we usually get along with a module of 1.27mm, that is 0.05".
This is the distance between legs on many smd chips, for example.
So we need a track and the ditch beside it to be 1.27mm together.
We can use thin tracks, like .7mm, which gives us 1.27-0.7=.57mm
This allows the cutter tool to be .5mm or so.
I think it is possible to find or make such a cutting drill bit with
It comes down to what speed we need. A common 0.5mm drill bit would
suffice if we had all time in the world, it can also be moved
sideways, but only slowly, but to get higher speeds we need better
By the way, a suitable experiment pcb for smd could be a pcb covered
in parallell tracks placed at 1.27mm distance from each other.
(1mm tracks and .27mm ditches, for example)
Such a pcb would be a veroboard for smd, so to speak.
It is easy to cut those stripes with a small precision knife, to
create useful patterns.
Are such "smd stripboards" sold somewhere?
>An x-y-plotter cuts away the copper layer using a cutter tool, like a
>drill but we can move it in any direction.
>We set it to cut only the copper, so the cutting deep should be 1-2
>tenths of a millimeter or so, to make sure the 35-70um copper layer is
>We need a cutter tool which is very narrow, because we want to make
>thin distances between tracks.
>(this is the problem in this idea, to find a cutter head which can
>handle copper and glassfiber and is maybe a tenth of a millimeter in
>diameter. bigger tools are easier to find, if we can live with wider
>distances between tracks)
>If we can cut away copper without the usual procedure with UV-lamp,
>etching, etc, we get a very fast process to make a pcb, just send the
>gerber files (or whatever format is suitable) to the x-y-cutter.
>In these SMD-mounting times there is seldom a need for holes, but the
>same tool can easily drill holes too, just program it to cut deeper
>than usual cutting.
>Easy to make, just put a small electric drill, with a suitable drill
>bit or cutter tool, where you would normally attach the pen.