Spray coating is best by far.  You have the capability to spraycoat, why
even bother with brush coat unless it's for localized rework?  We coat our
boards 3 +/- 2 mills thick in two spray coats.  We use a 2-part
polyurethane. Spray coating also prevents excessive fillets under components
that can be destructive to glass-bodied diodes at low temperature exposure
(-25 deg. F).  Spray will always give superior, uniform coverage.

Rainer Blomberg
Staff Production Engineer




-----Original Message-----
From: Alberto Callo [mailto:[log in to unmask]]
Sent: Wednesday, February 23, 2000 12:03 PM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coating Thickness Gau


Hello Tom and everyone,

I am currently writing the procedures for conformal coating within my
company.  We are experimenting all with two methods: brushing and
spraying and the combination of both.  What is your exprience regarding
conformal coating process? and how did you get best results?.  Our
boards are hybrid, some are 90% through hole.

So far we've found that spraying the board first with a thin coat and
then brushing works the best.  Brushing itself causes lots of bubbles.

Thanks



Tom Burek wrote:
>
> The best way I know is when you conformal coat you include a glass coupon
in the lot you are processing.  First you measure and record the thickness
of the glass at least three areas on the glass.  You process the glass the
same way and at the same time as your PCA's (spray, dip, etc.).  When you
are through processing and curing the conformal coat you measure the glass
in the same three places.  The difference being the thickness.
> Tom Burek
>
>  -----Original Message-----
> From: [log in to unmask] [SMTP:MIME :[log in to unmask]]
> Sent: Tuesday, February 22, 2000 6:10 PM
> To: [log in to unmask]
> Subject: [TN] Conformal Coating Thickness Gauge
>
>  << File: ENVELOPE.TXT >>
>
--------------------------------------------------------------------------
--
> Hello everyone,
>
> Can anyone direct me to the best way (or inspection equipment) to inspect
>
> the thickness on conformal coatings? TIA.
>
> Jason Gregory
> Production Manager
> Electrospec
> (713)784-4900
> (713)784-1194 fax
>
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