Message-ID: <53B90489.6030106@gmail.com>
Date: Sun, 06 Jul 2014 10:10:49 +0200
From: onetmt <onetmt AT gmail DOT com>
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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] pour clearing around pads
References: <53b8d46a DOT 04a8e00a DOT 7266 DOT 6600SMTPIN_ADDED_BROKEN AT mx DOT google DOT com>
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Reply-To: geda-user AT delorie DOT com

On 06/07/2014 06:41, Lilith Bryant wrote:
> On 2014-07-06 04:11:18 PM, Dave Curtis wrote:
>> I'm working on a footprint where if I follow the data-sheet geometry and 
>> my normal design rules, I end up with a footprint where very skinny 
>> copper peninsulas sneak between pads when it is placed in a polygon.  
>> The peninsulas neck down to less than the minimum copper width rule.
>>
>> So, first off, I'm surprised that the Cu polygon allows Cu to pour into 
>> a space less than the minimum width rule.
>>
>> Secondly, I'm wondering if fab houses might flag that as a DRC violation 
>> even if pcb doesn't.
>>
> 
> I have had a fab house complain about this.  I ended up telling them to just 
> ignore it, and so far it hasn't been an issue but it does make me a little nervous,
> particularly what might happen to fine slivers that get undercut during etching.
> 
> Also, I don't do RF stuff, so ending up with unconnected islands is not a issue for
> me.

Also my fab used to complain about them; this is why now I carefully
draw by hand polygons, deleting them and reshamping them when sub-DRC
metals are created.

> 
> I have been meaning to write a polygon "bake" tool that fixes this, but have 
> been put off by the lack of a workable polygon library.   Pretty much just needs 
> to erode then dilate by the minimum clearance.    Was going to use shapely/GEOS 
> in python, but it's erosion doesn't seem to work :(   So it went into the too hard
> basket for the time being.    
> 
> 


-- 
Hofstadter's Law:
"It always takes longer than you expect, even when you take into account
Hofstadter's Law."