These flex circuits included trace encapsulation with
polyimide coverfilm. Examination of x-sections showed
that the dendritic growth was following the field
lines between traces in the coverfilm adhesive. For
the materials that were failing, the adhesive itself
was acting like a solid state electrolyte. The
incubation period was related to the time it took for
the ionic level of the adhesive to attack the traces
and get copper in solution, creating something like a
plating cell.
By the way, all of the Rogers R/flex adhesives have
been tested and are immune to this effect.
Andy Magee
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_________________________________
Subject: FW: Re[2]: Humidity Testing
Author: Dill, Norm J::(DILLNJ) at ~FABRIK
Date: 7/11/96 5:46 AM
From: Dill, Norm J
Date: Thu, Jul 11, 1996 5:46 AM
Subject: FW: Re[2]: Humidity Testing
To: "'IPC - Technet Input'"
Andy,
Considering your test was run at 100 v with a .006"
spacing, is there any chance that airborne contaminants
contributed to your 300/500 hour failures?
Norm Dill
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______________________________ Reply Separator
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Subject: Re: Re[2]: Humidity Testing
Author: SIRGuru::(SIRGUR) at ~FABRIK
Date: 7/12/96 6:00 AM
From: [log in to unmask]
Date: Fri, Jul 12, 1996 6:00 AM
Subject: Re: Re[2]: Humidity Testing To: Magee, Andrew P
Good points, but if I may ask, were the flex circuits
totally capped by the polyimide film, or was it a surface
metalization. I would agree that it would take longer in
test before failures occur in a totally encapsulated case.
For the Bellcore coupons, it is a totally surface case,
with no barriers to moisture.
Doug Pauls
CSL
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Date: Fri, 12 Jul 1996 09:00:48 -0400
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Subject: Re: Re[2]: Humidity Testing
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