gEDA-user: *QFP* footprint naming conventions

[Dan McMahill <dan@mcmahill.net>]

Hi,

I've been going over a patch submitted to pcb by Wojciech Kazubski that
supplies several additions to the QFP family of footprints.

I would like to incorporate these changes, but would like to discuss
some naming conventions here first.  One goal I have is to make sure
what ever decisions are reached make it into the symbol document in gEDA
as well as the geda library in PCB.  I think this is crucial for making
things easier on everyone who is using these tools.

The basic issue is that the current document just has names like

QFP80
QFP100

see http://www.geda.seul.org/docs/20030525/symbols/node14.html for the
line which says:

 * Quad-side flat pack SMT are called QFPn. 

Unfortunately this doesn't quite cover what packages exist.  For
example, looking at an older National Semiconductor packaging databook,
I see

National package VHG80A is a square 12mm x 12mm QFP80 with 0.5 mm pin
pitch

National package VJE80A is a square 14mm x 14mm QFP80 with 0.65 mm pin
pitch

National package VCC80A is a rectangular 14mm x 20mm QFP80 with 0.8 mm
pin pitch

As another example, Analog Devices has a LQFP64 with 0.4 mm pin pitch
where a LQFP100 offered by Dallas Semiconductor has a 0.5 mm pin pitch.

The footprints provided by Wojciech use the following convention:

QFPn_R  is an 'n' pin rectangular QFP.  Examples are QFP80_R which
        corresponds to the National VCC80A mentioned above.


QFPn_x  is a 'x' mm x 'x' mm square QFP with 'n' pins.  

LQFPn_x is a 'x' mm x 'x' mm square LQFP with 'n' pins.  As an example,
        a LQFP80_12 is a 12mm x 12mm 80 pin LQFP like the National
        VHG80A mentioned above and a LQFP80_14 is a 14mm x 14mm 80 pin
        LQFP like the National VJE80A mentioned above.


Does this seem reasonable to everyone?  If so, I'll add the PCB
footprints and submit a patch to the gEDA symbol document.

On this topic can someone shed some light on the difference between QFP,
TQFP, and LQFP?  The QFP part is Quad Flat Package, but I'm not sure
about the T and L.

Thanks for your help and attention.

-Dan

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