Suzanne,
I have now apparently had enough Mt. Dew to formulate a coherent response
(like YOU can talk Hillman).

We have products within our system that does have parylene coating.  While
expensive and very production friendly, it does give a good chemically
resistant coating that is uniformly deposited on all surfaces.  Done
properly, you have a total continuous barrier to the environment.  How
thick depends on the board topography, but a target of about 0.5 mil is a
good figure.  I have  never done a study on how much or how little parylene
is needed to pass salt fog tests.  Lamar Young at SCS may have more data on
that.

On some products we have gone to parylene coating because we cannot pass
some of the more stringent salt spray/fog tests with our standard acrylic
coating.  It is my observation that this is most often due to variability
in the coating process or coating technique, rather than a shortcoming of
the acrylic material itself, since the majority of our products routinely
pass salt fog testing with acrylic.  This testing is most often done on the
top level unit, but in some cases we do it at the individual assembly
level.  The key to passing salt fog testing is to have a continuous barrier
presented to the salt environment, whether parylene or any other form of
protective coating.

Doug Pauls
Rockwell Collins




                      Suzanne Nachbor
                      <suzanne.nachbor@HON        To:       [log in to unmask]
                      EYWELL.COM>                 cc:
                      Sent by: TechNet            Subject:  [TN] Salt fog testing and paralyne
                      <[log in to unmask]
                      c.org>


                      07/07/2003 02:15 PM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to
                      suzanne.nachbor






Does anyone have literature or real life testing on the performance of
paralyne under a salt fog test?  What thickness was required to pass salt
fog testing?  Was the cca directly exposed or was it inside a box/device?

Suzanne Nachbor
Supplier Quality Engineer/Commodity Lead
Phone:  763-957-3923
Fax:  763-792-2486
e-mail:  [log in to unmask]

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