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Date: Mon, 07 Jul 2014 09:33:46 -0700
From: Dave Curtis <davecurtis AT sonic DOT net>
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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] pour clearing around pads
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Reply-To: geda-user AT delorie DOT com

On 07/06/2014 11:41 PM, Gabriel Paubert wrote:
> On Sun, Jul 06, 2014 at 01:16:31AM -0400, DJ Delorie wrote:
>>> The peninsulas neck down to less than the minimum copper width rule.
>> I typically expand the pad clearances until such necks vanish.
> I did this until holes were added to polygons. Now I use holes to
> precisley control where the copper pour stops. But holes have
> they own problems (moving them, mostly, they are rigidly linked
> to the containing polygon), so I only draw them as the last step,
> when everything else is essentially ready for production.
With my current problem, progress > beauty, so I expanded the pad 
clearances :-/
>>> So, first off, I'm surprised that the Cu polygon allows Cu to pour into
>>> a space less than the minimum width rule.
>> Polygon pours are handled poorly in pcb.
> <snip>
>
>>> Third, is it legal to specify zero-width Pad[] elements in a footprint,
>>> and assign clearance values, in order to composite some clearance into
>>> the footprint?
>> I think this is fine, although perhaps a tiny non-zero width might be
>> needed.  I don't know if these cause outputs in the gerber file,
>> though, so be careful.
> I really recommend using polygon holes in this case, I did this before
> holes were supported, and this was much worse, despite the defects
> of the holes listed above.
Worse how?

I spent a few minutes looking at the code.  The gerber output has a 
check in the aperture selection code where if a zero-width aperture is 
requested, it returns NULL, which (if the comments are to be believed) 
suppresses any output in the gerber file for zero-thickness elements.

I'm not sure where to look for how a zero-thickness pad might cause 
phantom shorts or how it interacts with route blocking.  Clues welcome.
>
> 	Gabriel
Thanks for your comments.  Very helpful.

-dave
>