Genny,

I believe this is what the layer stack coupon was intended to prevent.  Obviously, it was not
checked anywhere during the fabrication process.  I would certainly check out your PWB
supplier for this oversite, since it is a fundamental check on FAI or QA audits for PWB
builds.

If they don't include this as part of their check process, or if they do and did not perform
it, you are "at risk" either way.

DT





Genny Gibbard wrote:

> Good morning,
> My morning has not been so good.  I have a build of PCB's (over 300 boards)
> where two inner layers have been swapped.  The board fabricator constructed
> the board in the wrong order.  These boards are RF in nature and have
> frequencies approaching 2GHz on them.  In many places we put a signal trace
> on the inner layer furthest from the component side and then a wide grounded
> trace over it on the closer inner layer as shielding.  So not only is there
> no longer shielding over many traces, these signals are also about .03"
> closer to the component circuitry than they used to be.  Can you contemplate
> the nightmare of spurious issues that have been created?  We did not notice
> the problem until they were fully populated and almost thru our testing
> process and started failing one of the tests miserably.
> Needless to say, we will be revising our inspection techniques to try to
> catch occurrences like this much sooner.
>
> I was wondering if anyone knows of a way that layer order could be
> electrically tested for on a bare board, that we could require our
> fabricator to complete?
>
> Genny Gibbard (mailto:[log in to unmask])
>
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--
Darrel Therriault
VP, Mfg. Operations
INCEP Technologies, Inc
(858)547-9925 223
[log in to unmask]

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