I agree with Ken.  One suggestion is to mask the inductor off and not even coat it.

Andrew Kettlewell
Sr Process Engineer
Sypris Electronics
Tampa, Fl



-----Original Message-----
From: Bloomquist, Ken <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, 24 Jan 2006 12:15:19 -0800
Subject: Re: [TN] Conformal Coat (Urethane) & bubbles


Kelly,

I have to ask, do you really care? What purpose does conformal coating
on top of potting compound do? It doesn't appear that it violates any
electrical spacing or opens up any base metal to the environment.

If it were me I think I'd just leave it alone and live with the bubbles.
Of course that just my .02's worth

Kennyb

-----Original Message-----
From: Kelly Morris [mailto:[log in to unmask]]
Sent: Tuesday, January 24, 2006 10:23 AM
To: [log in to unmask]
Subject: Re: [TN] Conforma Coat (Urethane) & bubbles

>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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