You can remove the conformal coat in the area of rework only and then touch
up the same rework area only.
You don't need to be in the CC business to touch it up, instead of spray
coating the CC back on, brushing on with an artist brush works just fine.
If the Customer intends to touch up using this method, I wouldn't be too
concerned. Usually, you spray a little CC in a cup and then dip the artist
brush into it and brush on the reworked area. This is done only after
retest.
The major concern here is the cleaning process. If you run the boards
through a cleaner - THAT is the real area of coating compromise. If the
cleaning could be just done locally to the area of rework, that would be far
preferred.
Jan Pelchat
SR QAE
Benchmark Electronics
Hudson Division
On Monday, May 17, 1999 5:55 PM, Stephen R. Gregory [SMTP:[log in to unmask]]
wrote:
> 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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