Re: gEDA-user: PCB: rectangular polygons and route clearance in pcb-gtk

["James Johnston" <mail@xxxxxxxxxxxx>]

What milling machine / software are you using?

I have used an LPKF milling machine; no special considerations are needed
re. copper fills for the CAD design process.  Choosing whether to remove
excess copper or keep it is determined during the CAM process where the
standard PCB layout / drill files are converted into milling machine
directions.

Removing the excess copper is not as bad as you might think.  Use e.g. 1 mm
and 3 mm end-mills for this job keeps the process relatively inexpensive.
The LPKF software does isolation milling with the 8 mil bit, then switches
to the 1 mm end-mill and then the 3 mm end-mill, so that clean and precise
trace edges are maintained.  The small added cost is worth it to me, because
I don't put a solder mask on my milled boards.  Which means that isolation
milling only, increases the chance of solder bridges, never fun.  Especially
when dealing with surface-mount parts, if you get a solder bridge from a
surface-mount part's pin to a large copper fill underneath the part, it's
not fun - I often have to remove the entire part with hot air, clean things
up, and try again.  So I just remove that copper to save myself the trouble
later.  With a good milling machine, you can solder most any part.  I've
done small leadless packages like QFNs, and fine-pitch parts like TSSOP,
etc. without any solder mask.  It's not a problem.

Of course, I routinely keep copper on many of my PCBs for things like ground
/ power planes.  Usually I put ground on the bottom and keep signals on the
top as much as possible; it's worked for me so far for the relatively simple
PCBs I've done so far.

--James

-----Original Message-----
From: geda-user-bounces@xxxxxxxxxxxxxx
[mailto:geda-user-bounces@xxxxxxxxxxxxxx] On Behalf Of Kevin Bortis
Sent: Wednesday, July 30, 2008 15:22
To: geda-user@xxxxxxxxxxxxxx
Subject: gEDA-user: PCB: rectangular polygons and route clearance in pcb-gtk

Hi,

I try to draw my first PCB with the gEDA Tools. So far everything has
worked and the Layout is almost finished.

For the last stage it is required for me to add a massive cooper
polygon over the pcb, because our milling machine would not be happy
to mil all the copper away.

The tool makes a perfect clearance around the pad's, but not arround the
routes.

Has anyone an idea what i could change? Eventually I have done
something wrong with the layer because I don't really understand the
palette from solder over component, ... , silk, ..., to solder mask. I
have drawn the routes on the component layer.

The next problem is, how can I add pcb-outlines, fiducial marks and
add the (0,0) coordinate?

If someone has some general tips that are related to pcb and milling
machines I would be happy also.

Regards


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