Believe it or not, I watched a guy lay out a 2 layer board, a quickie
surface mount design, he didn't use any text or number markings or
silkscreen, and was surprised when the fab house put the bottom layer on
top, and the top layer on bottom (It would have worked if it were
through-hole). If your layers are identified, then it's the board house's
fault, and they are at the very least liable for replacing the boards If
they are not labeled, it's yours, and unfortunately an expensive lesson.
David Ricketts
Pertek Engineering
Voice: 949-475-4485
Fax: 949-475-4493
> -----Original Message-----
> From: Genny Gibbard [SMTP:[log in to unmask]]
> Sent: Tuesday, October 16, 2001 10:07 AM
> To: [log in to unmask]
> Subject: [TN] PCB layers swapped
>
> 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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