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Date: Mon, 10 Feb 2014 15:15:21 +0100
From: Gabriel Paubert <paubert AT iram DOT es>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] How to identify nc pads in tsym files
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	Hi,

On Mon, Feb 10, 2014 at 02:16:54PM +0100, Richard Hughes wrote:
> Hi,
> 
> I'm dealing with a QFN16 package where the middle "pin" is used as a
> signal. The only way to get to the middle pin is a via (not sure this
> is a good idea...), or I can trivially use an nc pin on the package to
> get to the center.
> 
> In the tsym file I'm just commenting out the nc pins with a # at the
> start of the line, but this gives me a conflict when I check for
> unrouted signals in pcb. Should I be doing something different in the
> tsym file so that I notify pcb that the pin really is unconnected from
> anything internal and free to use for routing?

On this kind of package, typically the center pad is some kind of
ground/power. It's a bit surprising that you call it "signal", but
we've seen strange things. Also this kind of pad if often use to
help dissipate heat; in this case using a via (or several) to a
plane is recommended.

If you know the net name, you can always add a connection to the
symbol with the net= attribute.

Otherwise you can always explicitly show these pins on the symbol
and connect them to the net that goes to the center pad.

	Gabriel