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




R Sedlak <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
12/12/2004 08:54 PM
Please respond to TechNet E-Mail Forum; Please respond to R Sedlak


        To:     [log in to unmask]
        cc:
        Subject:        Re: [TN] Resistive internal layers
Phil:  You are probably on the right track looking at the oxide.

Since the assembly people are so fixed on the appearance of the
oxide...(sigh), the fabricators may re-run panels down the oxide line if
they come out initially looking "weird"... Each time they are run down the
modern "alternate" oxide line, they lose about 2 microns (80 microinches)
of Copper.  Would this cause the problem you are seeing?

Rudy Sedlak
RD Chemical Company

DUTTON Phil <[log in to unmask]> wrote:
Hello Technetters,

We have a multilayer board that is exhibiting higher than expected
resistance on an internal layer track.
The track is 0.006" and about 1.5 inches long, yet has a resistance of
approximately 1 ohm. From what we can tell, the track has not been over
etched. I'm wondering if anyone can shed some light on what could be the
cause of this. I'm thinking that the layer may have had an excessive
'black oxide'treatment to promote adhesion. Is this possible?

thanks,


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