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Subject: Re: [geda-user] QFN packages solder mask
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From: "John Griessen (john AT ecosensory DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Message-ID: <9bbf8308-06e1-0d9b-85a7-0980e8525481@ecosensory.com>
Date: Wed, 18 Jan 2017 19:43:32 -0600
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On 01/18/2017 06:09 PM, John Luciani (jluciani AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> I am suggesting a single center copper pad on the PCB and multiple pads cut in the solder stencil. All of the QFN
> application notes I have read recommend similar things. Checkout TI SLUA271A "QFN/SON Attachment" or
> NXP SOT1189-1 footprint recommendation. There are a lot more notes out there but these are the two I found quickly.
> The TI datasheets usually have detailed recommendations.

I made that footprint with 9 center pads instead of one based on reading this from NXP/Freescale division:
http://www.nxp.com/assets/documents/data/en/application-notes/AN1902.pdf

> For devices with vias I add them to the footprint. For each device with a power pad I make a stencil footprint
> with the same name but a sfp extension. When making the stencil you can have a script replace footprints
> with stencil footprints.

Ah so.  That gets around the limitations of generated paste layer...  Redefine everything with a make script
for getting paste layer output.  Good thinking -- not compromised -- can tweak and get high yield.