I would certainly recommend you strip all the coating first. HCFC solvent is
a good stripper of acrylic as long as there's no transformers / inductors
which tend to be attacked. Rework then re-coat to give a real good finish.
Good luck
Bryan Kerr
Alenia Marconi Scotland
----- Original Message -----
From: Stephen R. Gregory <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, May 17, 1999 10:54 PM
Subject: [TN] Rework of Acrylic Conformal Coated Boards


> Hi ya'll!
>
> We just got a rework job in from a customer where we're gonna change a
PLCC28
> out for them, remove it and replace it with another. The board has been
> conformal coated with an Acrylic conformal coating (Humiseal type 1B73 I
> believe...).
>
> I know reworking can be done just by burning through the coating, and then
> cleaning up the pads real good before putting the new part back down.
We're
> water soluble, so we're gonna have to run the boards through the cleaner
to
> clean the flux residues...and I know that we'll damage the coating when
> putting it through the cleaner. On the boards that I've looked at, the
> coating has been compromised anyway on spots here and there just from the
> handling...acrylic is not too tough.
>
> I told our customer that the coating was gonna be pretty raggy looking
when
> he got the boards back from us, and we're not in the conformal coating
> business. But what's bothering me, is that I think they've got some spray
> cans and they're gonna try and touch-up things themselves...against my
strong
> recommendations. I think the boards should be stripped of the coating
that's
> on there now, baked, and then re-coated.
>
> But like I said, we're not in the conformal coating business, and I've not
> worked much with the stuff anyway. I'm just thinking logically about
it...am
> I sweating things too much?
>
> Thanks!
>
> -Steve Gregory-
>
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