We allow limited debris on the board surface at a density of no more
than 3 non-conductive fibres per sq.cm. Usual additional caveats ref min
dielectric separations apply and no metallic debris is permitted. We
have recently installed a clean room facility for coating application
which renders this requirement obsolete, but in my experience under
normal factory air some FOD is almost inevitable

Regards
Ian Fox

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: 19 May 2011 20:03
To: [log in to unmask]
Subject: [TN] Conformal Coating and FOD

Good afternoon all,

I have an interesting question to pose to the forum.  An internal debate
presently rages internally, so I thought I would turn to cool rational
people (sit down Dewey).

When inspecting conformal coating, one of the things that "may" be
considered a defect is the presence of Foreign Objects and Debris (FOD),
which "might" require disposition.

1.  Is there any guidelines you all use to differentiate FOD in coating
that requires action (e.g. FOD as a defect), vs. FOD that does not
(cosmetic only)?
2.  If you differentiate bad FOD from doesn't-matter FOD, what criteria
do you use?

In essence, how much FOD is FOD.

Thanks.

Doug Pauls

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