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March 2004

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Subject:
From:
Dwight Mattix <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 23 Mar 2004 19:33:03 -0800
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text/plain (138 lines)
I agree not enough info.  You've asked a question that raises many more
questions.  However, shooting from the hip and dark memories from far in
the past...
If woven glass polymide then think polymide = brittle.  So how about drill
quality? That is to say, what about leakage currents due to crazing and
moisture/chemical intrusion into dielectric along he damaged glass/resin
interface?  CAF?

cheers,
Dwight Mattix

At 02:03 PM 3/23/2004 +0000, Graham Naisbitt wrote:
>David
>
>This is another really misleading statement:
> >
> > BTW Omega meters are NOT to be used to determine if you have ionic
> > contamination.
> > Only to used used to detect variations in conductivity from one
> > "batch/production run" to another.
> >
>These instruments were intended to detect ionic contaminants on the surfaces
>under test. You measure the resistivity or conductivity of the test solution
>(IPA/Water) before testing and again after testing - any change to the
>resistivity or conductivity is what in your opinion?
>
>What is true, is that these machines were only ever intended to be used as a
>process control method. Ask Dr Jack Brouse.
>--
>Regards Graham Naisbitt
>
>[log in to unmask]
>
>Cell: 079 6858 2121
>Office: +44 (0)1252 813706
>
>Concoat Limited - Engineering Reliability in Electronics
>
>NEW Additional Web address: www.conformalcoating.com
>
>www.concoat.co.uk     www.concoatsystems.com
>
>
>
>
>
>
>
> > Polyimide is well known as a moisture absorbent. I suspect this will be
> > a factor in your problem.
> >
> > David A. Douthit
> > Manager
> > LoCan LLC
> >
> >
> >
> > Russell Burdick wrote:
> >
> >> Here's a question for all you electrical fans...( ha, ha, ha, not
> >> those type
> >> of shorts)
> >>
> >> We are getting high resistance shorting on multilayer polyimide only
> >> boards.
> >> Inner layers test out with no problem. Immediately after outer layer etch
> >> there are the shorts. Omega meter testing shows no ionic contamination at
> >> this stage. Baking prior to ET reduces the number of shorts, although
> >> after
> >> a few days the shorts are back. Construction of board is foil copper at
> >> lamination, not cap-core.
> >>
> >> As usual, any and all help is greatly appreciated.
> >>
> >> Russ
> >>
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