Kathy

I suggest that your problem will be related to high humidity during
application. What you describe we would refer to as "blushing" or
"milk-effect". It is caused by excessive moisture either in the room during
application - usually spraying, but might originate from the air-line to the
gun.

In our coating facility - where they complained about the recent heat-wave
so now enjoy a "work naked bonus" - we maintain humidity using
de-humidifiers to between 40% and 60% RH. Too dry = ESD issues - Too humid =
Your problem.

Will it go away Yes! Dry / oven cure them as suggested, it wont leave any
cracks or holes! Then get your humidity under control.

Regards, Graham Naisbitt

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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kathy Kuhlow
Sent: Wednesday, July 18, 2001 10:11
To: [log in to unmask]
Subject: Re: [TN] White residue from conformal coating


Hans,
It appears to be in the coating.  On the uncoated boards there are no
visible residues, fingerprints, etc.   And it is very hot and humid today
and yesterday (dew point low to mid 70's).
Kathy

>>> [log in to unmask] 07/18/01 12:53PM >>>
Kathy,

Is the white residue in the coating or on the assemblies surface?

It's probably moisture related as has been discussed recently.

Do you dry the assemblies prior to coating?

Hans

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans M. Hinners
Process Engineer
Toppan Electronics, Inc.
770 Miramar Road
San Diego, CA 92126
(858) 695 - 2222 ext. 241
(858) 695 - 6823 fax
[log in to unmask]


-----Original Message-----
From: Kathy Kuhlow [mailto:[log in to unmask]]
Sent: Wednesday, July 18, 2001 10:24 AM
To: [log in to unmask]
Subject: [TN] White residue from conformal coating


What causes white residues after conformal coating?  The coating is an
acrylic and after the first coat there appears to be a white residue and
after the 24 hour cure the coating appears very dull and still has some of
the white residues.  The residues almost look like water flux residue but it
isn't.  The supplier that the coating was purchased from says it is strictly
humidity related and only a cosmetic issue.  There is no visible loss of
adhesion.  The solder mask is a LPI matte finish.  Can this be part of the
problem?

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