On 15/07/2011 02:00, Dwayne Reid wrote:
>   But that has me wondering: how do people define these footprints?
>

I have wondered about this too :-)

I name the footprints with the pitch and manufacturer, and if they have=20
their own naming system I usually use that (whatever they call the=20
footprint in their datasheet), or maybe the JEDEC code if they refer to=20
that (usually you get a note saying it conforms with JEDEC code xxxx)
If there is no "special" name then I use something like e.g. in=20
microchip footprint library: TQFP100_12x12_P0.4

It's a pain, I wish there was a bit more effort to maybe standardise the=20
naming or manufacturers provide a reference document with recommended=20
footprints for all their parts (some are better than others for this=20
kind of thing) Often I find you get a drawing of the chip dimensions on=20
the manufacturers website but no recommended footprint drawing.
When this is the case I type the code (common name, JEDEC name, etc)=20
into Google and use the best I can find, or design from the chip=20
dimensions. I think there are a few tools that do this automatically for=20
you, you just type the dimensions in and it calculates the standard=20
footprint (e.g. Altium and DesignSpark have this built in - I bet=20
there's probably a free web based one somewhere too)
I keep a folder with these footprint datasheets and link them to the=20
footprints in Kicad so I can check the dimensions easily.
I used to have a standard SMD footprint library (e.g. SOIC8, SOIC20,=20
TQFP64, etc) for all parts, but I learnt that different manufacturers=20
seem to have different ideas about the same names, so now I make a=20
separate library for each manufacturers footprints. It's a bit more=20
work, and I probably have quite a few duplicate footprints with=20
different names, but at least I know I can trust them.


--=20
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