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| Date: | Tue, 24 Jan 2006 11:03:07 -0500 |
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Hi,
Since you say that the component is concave, there is a possibility that the urethane coating is collecting together due to this concavity. When the coating thickness increases, the chances of bubbling increase. There is always a possibility that the surface is not clean enough.....try the following
1. take a fine grit paper and if possible rub gently to try to roughen the surface to make the coating stick (this is especially useful for IC topside, where the surface is very smooth
2. spray a very fine mist of Xylene and wait for a couple of minutes before spraying (this worked wonders for me for a board that was dewetting like crazy)
Amol Kane
M.S (Industrial Eng.)
Process Engineer
Harvard Custom Manufacturing
941 Route 38 Owego, NY 13827
Phone: (607) 687-7669 x349
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair K. Hogg
Sent: Tuesday, January 24, 2006 10:40 AM
To: [log in to unmask]
Subject: Re: [TN] Conforma Coat (Urethane) & bubbles
This is just a guess, and nothing more, but could there possibly be outgassing from something in the component? I'm pretty skeptical of this, since any outgassing should have already occurred, but may be happening due to the rise in temperature?
>>> [log in to unmask] 01/24/06 10:25AM >>>
We've got a problem here, where we're hand spraying a urethane conformal
coat on over a rectangular inductor.
The inductor body is a plastic tube, with potting to fill.
The top is not always flat (sometimes concave).
The problem is that bubbles appear in the conformal coat on the potted
surface, sometimes right after bake and sometimes days after.
Any ideas on what the root cause is and how to prevent the bubbles?
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