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Two comments,
a) Dewetting of coating is generally caused by the surface not being clean
enough/residue. We use a variety of UR type coatings on plastic devices and
don't have a wetting issue. You may want to investigate the cause /correct the
process.
b) For hardware already coated, I would suggest that dewetted areas that don't
reduce the electrical spacing between non-common conductors to less than the
design limit (ie. electrical spacing required as a function typically of voltage
differntial) should not be reworked. See ANSI/J-STD-001B section 10.1.2.2 for
some additional insites.
Jim Maguire
Senior Principal Engineer
Boeing Defense & Space Group
PO Box 3999 M/S 3W-97
Seattle, WA 98124-2499
Phone 206-657-9063
FAX 206-657-8903
Email: [log in to unmask]
______________________________ Reply Separator _________________________________
Subject: FWD: pwb-cca : conformal coating
Author: [log in to unmask] at esdigate
Date: 10/23/96 4:37 AM
Technet,
I'm forwarding this from a colleague.
Cindy Kemp
Lockheed Martin
Orlando, FL
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From: [log in to unmask]
Date: Tue, 22 Oct 96 16:35:22 EDT
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To: [log in to unmask]
Subject: pwb-cca : conformal coating
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hi group;
We are finding that in designs using conformal coating (UR) over plastic parts
that the cc is dewetting on the parts.
Question - is this seen as a problem ?
I am proposing that a note should be added to our designs as follows:
CONFORMAL COAT DEWETTING ON PLASTIC ENCAPSULATED MICROCIRCUIT
COMPONENT BODY IS ACCEPTABLE.
If there is a better way please let me here from you.
What is the real would doing ?
thanx; Skip Greb
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