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        Sun, 13 Sep 2015 14:35:13 -0700 (PDT)
Date: Sun, 13 Sep 2015 23:35:11 +0200
From: "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] zero soldermask clearance not caught by DRC
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Precedence: bulk

> > Usually solder mask is a little bit larger to not cover any of the 
> > pad. I guess you will be able to solder the part even if "visible" pad 
> > is a little bit smaller because of tolerance problem with solder mask.
> >
> 
> Yes, I agree with you.
> 
> ... In a perfect world, 0.0 gap from pad to mask is okay. But, 
> because the board manufacturer cannot guarantee this precision, they 
> like to add a gap such that under worst case the mask doesn't cover the 
> pad.

Then it could be argued if this tolerance should be pot on each individual pin or once in for solder openings in the *.pcb file.