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Reply To: | TechNet E-Mail Forum. |
Date: | Tue, 19 Jan 1999 16:31:21 -0500 |
Content-Type: | text/plain |
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Doug Shawver wrote:
>
> snip <
> 1) Is there an industry specification that address the air gap required
> from the edge of ICT test pads to SMT component bodies?
>
> snip <
> board IPC-SM-782 section 5.7.2 would seem to allow a test pad to be .010"
> under the part. Obviously, this is not what we want.
>
> 2) Is there another industry specification such as IPC, Bellcore, etc. that
> addresses this issue?
> snip <
Hi, Doug !
Seems to me the successor document to -275 (20-whatever, not
online with it yet (cdtower coming this week!)) had some content
on this topic, at least at an interim stage. Not sure if it made
it to the released spec, will let you know when I know if no-one
else responds by then.
I have seen a number of CM standards with values ranging from
.025" to .040" clearance to 1206 bodies, increasing with component
height. Spacing to component pad should vary with solder method,
wave/fountain solder requiring more clearance than does reflow.
>
> 3) Is there a specification that defines the probe pin accuracy or location
> tolerance of
> .050", .075" and .100" probes used in a "standard" ICT test fixture?
>
No spec here but boy oh boy are there alot of contributors to
this issue, starting with Tooling hole size/location tolerance
and winding up at nail type and board finish. I think in the CM
spec's I've worked with this is accumulated into the specified
test pad size, usually a .040" preferred with a .035" possible
w/reduced reliability (gotta kick the test stand every so often
to get the board to seat).
> I've been reading IPC's tech-net and design-net mail for years and there is
> a wealth of knowledge in this mailing list.
>
Likewise! We live in an amazing age, and here we are communing
on the ways/means to make it even more so. Long live the TechNet!
Regards to all!
--
Jeff Seeger Applied CAD Knowledge Inc
Chief Technical Officer Tyngsboro, MA 01879
jseeger "at" appliedcad "dot" com 978 649 9800
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