Hi Ramon,

No pardon required all input is great even if I can't use it in a
particular instance. I always learn something that I can tuck away in my
gorilla bag for a later day ;-)

We actually do exactly what you suggest, "The way that group does it is
by coating a thin layer of CC and letting it skin for 15 minutes and
then recoat. Very slow process."

We apply what we call a "Mist Coat" and let it set for a little bit
before we apply the final coat. This generally resolves a lot of issues
but in this case it failed us. Doing a mist coat does slow down the
process but it sure beats doing a bunch of touch up later.

Your comments did inspire one thought, if we were using lead free solder
this would probably not be an issue because the crappy looking solder
joints would be rough and grainy creating a surface for the conformal
coating to bite into :-)

Thanks for your reply,

KennyB

-----Original Message-----
From: Dehoyos, Ramon [mailto:[log in to unmask]] 
Sent: Friday, June 23, 2006 5:32 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coat Voids

        Hi Kenny:
        Pardon me for not being explicit enough. I was just giving an
example of how coating can pull away and letting you know that perhaps
by doing  extra cleaning the probability of a chemical in the vias may
be eliminated.  Have you tried to scratch the surface that looks like
there is no coating. It just may be thin and the fluorescence additives
do not show reflection. Not all the surfaces hold the coating the same
way. Rougher surfaces hold it better than smooth. Flat, short surfaces
hold it better than sharp or tall..... I know of a group that atomizes
the dispensing of the coating to ensure even coating. The way that group
does it is by coating a thin layer of CC and letting it skin for 15
minutes and then recoat. Very slow process. Another way would be to
thicken the coating, increase viscosity.
        Regards,
        Ramon

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken
Sent: Thursday, June 22, 2006 1:39 PM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coat Voids

I've had Steve post a picture of the missing coating on the via's. I
hope this helps make things a little clearer. A picture's worth...

http://stevezeva.homestead.com/files/Via_Coating_Dewetting.JPG 

Thanks Steve for posting this picture.

KennyB

-----Original Message-----
From: Bloomquist, Ken [mailto:[log in to unmask]]
Sent: Thursday, June 22, 2006 9:44 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coat Voids

Hi Ramon,

These voids have nothing to do with Kapton tape or silicone backed
adhesives. These are via's that are tiny and out in the middle of the
board. There is nothing else around them that is masked. The lack of
coating is only on the domed portion of the solder that is in the via
which protrudes slightly above the board surface. I'll try to get a
picture of the condition if the camera can pick up the black light.

Thanks,

KennyB

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