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Date: Wed, 12 Feb 2014 11:03:09 +0100
From: onetmt <onetmt AT gmail DOT com>
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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] How to identify nc pads in tsym files
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Reply-To: geda-user AT delorie DOT com

Il 10/02/2014 14:16, Richard Hughes ha scritto:
> 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.

Why not? Here is a small example of a HTSSOP16; even if there is room to
connect the power pad to a plane (or to a signal, if you need), I
generally assign another pad on solder side - both for electrical
connection and thermal dissipation:

Pad[2970um  2275um 2970um  2275um 3000um  200um    3140um "17"   "17"
   "square,nopaste"]
Pad[2970um  2275um 2970um  2275um 2600um  200um    3140um "17"   "17"
   "square"]
Pad[2970um  2275um 2970um  2275um 3000um    0um       0um "17"   "17"
   "square,onsolder,nopaste"]

and I place 4 or 5 small vias in it; in this way I can also drain excess
paste from the component side pad, thus reducing the risk to make short
circuits with signal pads (the draining effect can also be increased by
leaving unmasked the pad on the solder side).

In this way you can connect to pin 17 from the solder side, thus leaving
unconnected NC pads, by modifying the third no.17 pad definition as:

Pad[2970um  2275um 2970um  2275um 3000um  200um       0um "17"   "17"
   "square,onsolder,nopaste"]

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