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March 2013

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From:
Phil Bavaro <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Thu, 21 Mar 2013 17:01:43 +0000
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Wow.......I would not call us relentless....but definitely "purdy-sistent".

Ok this is just my thoughts for getting the discussion going....I have been out of conformal coat on a daily basis for years so consider the source:

1a.  Bubbles in between leads that do not connect the leads together.  The problem is you cannot really tell if the bubble actually exposes the lead or not....abut I am referring to the case where it appears that the cured bubble does not expose the lead surface.

1b.  "Tiny Bubbles..." yes, from the song...but in this case I mean the very small bubbles which are distributed uniformly over a flat unencumbered surface.

2.  Bubbles which require disposition are those that negate their intended thickness and coverage.  By this I mean when it looks like the bubble is reaaaalllly thin covering the exposed electrical connection.

3.  My answers definitely have a type in mind.....epoxy.   I don't have experience with XY or silicone cc's.

Yeah....I am hesitating to send this comment in....oh well, you are the Grand Pupah and should know how to take with a grain of salt.




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, March 21, 2013 8:19 AM
To: [log in to unmask]
Subject: [TN] Conformal Coat and Bubbles

OK, Minions, your next question in the quest to improve J-STD-001 and
A-610 relates to bubbles in the conformal coating.

I think we can all agree that the ideal conformal coating layer contains
no bubbles or voids and is "purdy".    BUT:

1.  Are there bubbles in coatings in areas where they will not impact reliability and their presence should be viewed as a "Process Indicator"?
If so, where and what limits would you use?

2.  What would you classify as a bubble requiring disposition, i.e.
Becomes an actionable defect?  If so, where and why?

3.  Would any of your answers change depending on what KIND of coating it is, i.e. Acrylic vs. silicone vs. Parylene?

Well, OK, that is three questions.  I'm on a roll.


Doug Pauls
Chairman, IPC Cleaning and Coating Committees Galactic Emporer



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