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May 2011

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Subject:
From:
Ahne Oosterhof <[log in to unmask]>
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Date:
Thu, 19 May 2011 13:38:28 -0700
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Looks like it has chin whiskers. 

Ahne.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, May 19, 2011 12:54
To: [log in to unmask]
Subject: Re: [TN] Conformal Coating and FOD

Although this board wasn't conformal coated, this "FOD" was found in the
soldermask when I was working at a past employer:

http://stevezeva.homestead.com/StrangeMaskDefect.jpg

I wonder would you need to put this in a SEM to figure out if it is a tin
whisker or not?

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: Thursday, May 19, 2011 3:47 PM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coating and FOD

Not exactly the same, but.... When our interns are looking for tin whiskers,
they put the part in the Scanning Electron Microscope. If the FOD is dark -
it is non-metallic and not a tin whisker.  If it is "white", it is metallic
and most likely a whisker.  We have found very little metallic debris on
commercial boards that is not tin whiskers.  I know, I know, zinc whiskers
can come off the computer room floor gratings and deposit on electronics. We
haven't found any of those yet.  But some folks sure keep their personal
computers in some dusty, dirty locations.  TALK ABOUT DUST BUNNIES. 

Denny Fritz






-----Original Message-----
From: Douglas Pauls <[log in to unmask]>
To: TechNet <[log in to unmask]>
Sent: Thu, May 19, 2011 3:03 pm
Subject: [TN] Conformal Coating and FOD


Good afternoon all,
I have an interesting question to pose to the forum.  An internal debate 
resently rages internally, so I thought I would turn to cool rational 
eople (sit down Dewey).
When inspecting conformal coating, one of the things that "may" be 
onsidered a defect is the presence of Foreign Objects and Debris (FOD), 
hich "might" require disposition.
1.  Is there any guidelines you all use to differentiate FOD in coating 
hat requires action (e.g. FOD as a defect), vs. FOD that does not 
cosmetic only)?
.  If you differentiate bad FOD from doesn't-matter FOD, what criteria do 
ou use?
In essence, how much FOD is FOD.
Thanks.
Doug Pauls
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