As long as the coating has the specified thickness, taking into account that the coating thickness could be thinner adjacent to the bubble, then bubbles should only be treated as a process indicator.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, March 21, 2013 11:19 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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