Jim,
We have have not found it necessary to clean before conformal coating unless
reqired by a customer.  We produce mixed technology boards and use no-clean
paste and no clean wave flux.  The conformal coating applied here is a
polyurethane and it is applied using a robotic applicator.  Your fluxing and
solder pre-heat must be in control both to prevent dewetting of the coating
from flux residues and also because of the damage "uncured" flux residues
can do to the assembly in the field.  I know the debates and comments
regarding its usefulness, but periodic ionic contamination measurements can
be instructive.  Additionally, any handling and hand assembly must be done
with care to prevent oils etc. from causing dewetting of the coating.

If you need to know what pastes, fluxes and coatings we use, contact me
offline.

George Carroll
[log in to unmask]

-----Original Message-----
From: West, Jim [mailto:[log in to unmask]]
Sent: Wednesday, June 27, 2001 12:01 PM
To: [log in to unmask]
Subject: [TN] Conformal coating


Hi,

Do boards have to be cleaned before you apply conformal coating?  Does it
depend on what type of flux is used?  Example would be no-clean flux, you
can apply conformal coating over it right?

Thanks,
Jim

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