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July 2006

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Subject:
From:
Tom Stearns <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Tom Stearns <[log in to unmask]>
Date:
Fri, 14 Jul 2006 12:28:43 -0400
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Steve:

Good to see your name in print---

duPont Pyralux acrylic  adhesive  has poor insulation resistance
particularly at elevated ie above 75C temps. It is also notoriously
susceptible to moisture absorption which adds to its conductivity. I believe
your problems will be significantly reduced if you avoid Pyralux acrylic.

The problem could also be traceable to poor inprocess rinsing or cleaning.
There are several standard methods for measuring IR in adhesive structures,
most involving an etched interdigitated grid. If you produce such patterns
and start a history of the measured values you will be able to track your
cleanliness.  Be sure to run the t est at elevated temperatures because this
is where the trouble starts.

You could have an undercured structure. Any ionic contamination will give
trouble, particularly at this high voltages. Is this necessary? Most
equipment today runs at very low voltages which partly explains the wide use
of duPont Acrylic.

Is there any tin or silver plating on the circuitry?

Tom Stearns
3 Brander Court
Nashua NH 03063
603 889 2522

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