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January 1999

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Subject:
From:
Jeff Seeger <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 19 Jan 1999 16:31:21 -0500
Content-Type:
text/plain
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text/plain (64 lines)
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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