Hi David -
On thickness measurement, I prefer to coat a witness panel with some masked
areas to verify my process setup, then use a good high grade four place
micrometer. For in process verifications, I prefer to use a wet film
thickness gage, available from most paint stores. The witness panel noted
above can provide a comparison specimen to get your wet film measurements
coordinated, or your can calculate thickness loss based on mass loss of the
cured coating.
Of the application methods you mention, spray will give the best uniformity,
followed by dip. Note that spray has the shortcoming of being vulnerable to
shadowing and will not normally give good coverage under large bodied parts.
Brush is the least repeatible, and also won't do much of a job under large
bodied parts. Critical factors, regardless of method: mix viscosity;
clean/dry gas supply if spraying; uniform mix temperature. I can't say too
much about having good exhaust ventilation, set up to deal with the process
you are using.
And one question not asked: The cost of masking will generally be the most
expensive element of the coating process. Look into some good masking
boots, etc. They're a bit pricey, but can save a great deal of time and
money in production.
Regards - Kelly
-----Original Message-----
From: David Hipp <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Thursday, September 30, 1999 4:41 PM
Subject: [TN] Measuring conformal coat
>Good day. How do you measure conformal coating thickness, without
sectioning
>a board or a coupon? Which method (brush, dip, spray) has the best
>repeatability for thickness?
>We build board assemblies to IPC Class 2 and 3 and have no idea if we meet
>the requirements of paragraph 10.1.2.1.
>
>Regards,
>Dave Hipp
>Woodward Aircraft Engine Systems
>Electrical Production Engineering
>(815) 639-6732
>FAX (815) 636-6040
>
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