Thanks Valerie (and everyone who has replied to this),

I don't know if we'll get to the cross-sectioning stage with this.
The problem has been found after the boards have been fully loaded.
The manufacturer has AOI equipment and the boards were bare-board tested
prior to loading.
We have recently had other quality problems with this manufacturer and
are not on good business terms at the moment, so I can't go into too
many details.
Previous work by this same manufacturer has been excellent in the past. 
It really measures as though the trace has a definite high
resistance-per-inch.
I'll certainly let you know if we find anything.

regards,

Phil.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Valerie St.Cyr
Sent: Tuesday, 14 December 2004 1:30 AM
To: [log in to unmask]
Subject: Re: [TN] Resistive internal layers


Here's a thought: if all the tracks on a particular layer exhibit high
resistance then likely that layer was either reworked or may have
excessive oxide treatment. If, however, it is only the one track, then
the
problem is with the track itself. In the past we have found that a
"dishdown" or nick or "mousebite", anything that reduces the volume of
copper in a spot on the track is now a "bottleneck" that increases the
line resistance. The other possibility is that a via in that net has low
copper or copper voiding, which would also show up as high resistance on
the net.

To really root cause the problem would require doing some cross-sections
...

Good luck and let us know what you find.

Regards, Valerie

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