Matthew,
I agree whole-heartedly with Michael from Lockheed Martin. We first
look to IPC-782A, then to the vendor recommendation which we
scrutinize closely. We also on occasion use the 782A calculator.
Although we have developed our own spec's for pad and stencil design
for fine pitch. Something that is easy to overlook in 782A is at the
bottom of the page on many components Spec's is a recommendation for
those components if used in a bottomside-glue-wave application, and
they work well. One very important factor is the stencil thickness you
standardize on. I have worked with .008", .007" and .006", and if you
use stencils on the thicker side you will have to some reductions on
some apertures. I personally like using .006" for everything, we
reduce all apertures .0005"/side; since our stencil printers have
positioning accuracy of .0005" this insures maximum gasketing. We then
reduce our fine pitch apertures per our internal super-secret specs
(Just call me the James Bond of fine pitch...yeh, RIGHT!).
Anyway, get on the phone and register with NEPCON WEST now, since
there are at least two sessions offered that cover this exact topic,
one which is offered by the Illustrious Bob Willis in WS-23, "Fine
Pitch Design for Manufacture and Assembly" (you owe me a coffee for
this, Bob, heh-heh). Seriously, the info you come away with will be
well worth the expense.
Good Luck.
Jeff Hempton
United Technologies Electronic Controls
______________________________ Forward Header __________________________________
Subject: [TN] SMT land pattern standards?
Author: Matthew Lamkin <[log in to unmask]> at
Internet
Date: 1/21/99 8:07 AM
Hi there all you IPC guys, can someone help me to determine what the
best collection
of standard SMT land pattern designs is?
I use convection reflow on a QUAD machine for the majority and will
shortly be using wave solder on a BLUNDELL machine.
We are having a few problems that are being claimed as wrong footprint
sizes, and to be honest this could be true as
the footprints were not entered into our CADSTAR cad system in-house.
There seems to be little published material available in the U.K. as
complete documents to specify
sizes for the most commonly used devices & I was wondering if anyone
could tell me what the IPC-SM-782A
document is like ?
I.E. how many components does it cover & how much detail does it give
for each one ? Does it give clear differences
between each soldering method & how good are these footprint
sizes?
Any footprints that have been designed in-house have come from differing
manufacturers data books that could
be out of date or the component could come from differing manufacturers.
Any help is appreciated.
T.T.F.N
Matthew Lamkin
Printed Circuit Board Draughtsman
Protec Fire Detection PLC
Churchill Way,
Nelson, Lancs
BB9 6RT.
Tel 01282 717393
Fax 01282 717273
Email = [log in to unmask]
Company Web Site = http://www.protec-fire-detection.plc.uk
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