Rich Rich Rich,
You are supposed to answer all the hard questions for me so I don't have
to work so hard <grin>.
Let me ask the question another way. Plexus, being a high quality
reputable EMS company, has acceptability standards on conformal coating
film quality, both your own and imposed upon you by your customers. Do
your customers ever differentiate conditions where bubbles are acceptable?
Or are they all - here are our specifications, but we have no idea where
they come from or their basis in reality? I can't really point fingers in
this case. Our own internal standards say that a bubble cannot be greater
than 90 mil diameter, or a cluster of bubbles cannot be greater than 90
mils. Been that way for decades and damned if I can find any technical
studies here upon which that figure was founded.
The more I work on this, the more I realize that bubbles in coating are
something that is hard to quantify, but "I know it when I see it" kinda
thing.
And for #3, would you lump together all liquid coatings in terms of
bubbles, irregardless of coating chemistry, and make a separate set of
criteria for vapor deposited coatings such as Parylene?
Doug Pauls
From: Richard Kraszewski <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>,
"[log in to unmask]" <[log in to unmask]>
Date: 03/21/2013 10:47 PM
Subject: RE: [TN] Conformal Coat and Bubbles
#1 Yes allowed. AABUS(sorry- yes I know, not much help here).
#2 I have seen reference to a defense sector customer spec referencing a
bubble defined as being an issue if greater than or equal to 1/16 of an
inch. No supporting data for this.
#3 No, if for no other reason than FOD.
Rich Kraszewski
(920)969-6075
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, March 21, 2013 9:19 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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