Yeah, maybe I wasn't very clear.
It's not the regular production I need to bake, but retrofits. Boards come in after some time in the field and they need several components changed. So remove coating, do the soldering and then wash.
Ioan Tempea, ing.
Ingénieur principal de fabrication / Senior Manufacturing Engineer
950 RUE BERGAR, LAVAL, QC, H7L 5A1
T+ 1 (450) 967-7100, EXT244
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Lauréat Dunamis 2012
Entreprise manufacturière / Gestion du capital humain
-----Message d'origine-----
De : Lloyd Duso [mailto:[log in to unmask]]
Envoyé : February-11-13 1:15 PM
À : [log in to unmask]
Objet : Re: [TN] Washing of acrylic conformal coatings
Yellowing of 1B31 from over baking? That I have never seen. Then again we have never done that, on purpose anyway. 1A33? Oh yeah. We had a company return boards to us because the coating turned amber. They said they did not bake them and that they came from the field that way. When asked "where in the field?", the reply was "They are traffic sensors mounted in the pavement of Arizona." Mystery solved.
As for the 1B31 in the wash, why are you running them through an inline wash after coating anyway? And how soon after coating?
Lloyd E Duso
Diamond-MT
Plant Manager
(814) 535-3505
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Monday, February 11, 2013 12:12 PM
To: [log in to unmask]
Subject: Re: [TN] Washing of acrylic conformal coatings
Really? I have not seen it myself, but will bow to your experience.
Usually, I only see yellowing when the coating has a urethane constituent to it, and 1B31 or 1B31S does not. Or at least I think not.
Doug Pauls
From: "Stadem, Richard D." <[log in to unmask]>
To: <[log in to unmask]>
Date: 02/11/2013 11:02 AM
Subject: Re: [TN] Washing of acrylic conformal coatings
Sent by: TechNet <[log in to unmask]>
Keep the bake time to no more than 1 hour, however. 1B31 can turn slightly yellow if baked for longer periods of time.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Monday, February 11, 2013 10:56 AM
To: [log in to unmask]
Subject: Re: [TN] Washing of acrylic conformal coatings
Still, I would incorporate a decent bake of these boards to make sure you get all the water out, both out of the board and out of the coating. I suggest 100C for at least 1 hour.
1B31 or 1B31S has a tendency to get soft and tacky if you get it very hot, say above 80C. We have here, for many years, done pad repair on coated boards, and the cure cycle for the epoxy is 100C for 1 hour. We have not seen a negative effect from this, but be aware that at 100C, you might have a little bit of movement of the coating, which is why we always dry such boards in a flat position. Keep that in mind especially around connectors.
On the other hand, heating to 100C may give you a minor benefit of "re-melting" it to the board surface.
Suggest you trial this on 1-2 boards first, then do a very close inspection on the boards for delamination, blisters, marks in the coating from oven grates, etc.
Doug Pauls
From: Ioan Tempea <[log in to unmask]>
To: <[log in to unmask]>
Date: 02/11/2013 10:26 AM
Subject: Re: [TN] Washing of acrylic conformal coatings
Sent by: TechNet <[log in to unmask]>
Sorry,
I should have mentioned, no chemicals, we're just doing DI aqueous wash!
But hi-pot just made it to the top of my list.
Thanks,
Ioan Tempea, ing.
Ingénieur principal de fabrication / Senior Manufacturing Engineer [signature002]<http://www.digico.cc/>
950 RUE BERGAR, LAVAL, QC, H7L 5A1<http://g.co/maps/2gh3f>
T+ 1 (450) 967-7100, EXT244
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[signature001] <http://www.facebook.com/pages/Digico/277076778479>
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Lauréat Dunamis 2012<http://digico.cc/dunamis-2012/>
Entreprise manufacturière / Gestion du capital humain
De : [log in to unmask] [mailto:[log in to unmask]]
Envoyé : February-11-13 11:21 AM
À : TechNet E-Mail Forum; Ioan Tempea
Objet : Re: [TN] Washing of acrylic conformal coatings
How do you know the dielectric properties have not been degraded as part of the exposure to your wash chemicals? 1B31S has good adhesion, but what about chemical resistance.
In your shoes, I would do a dielectric withstanding voltage test (also called a hipot test) to see if exposure to the wash results in a decrease in your voltage withstanding.
Doug Pauls
From: Ioan Tempea <[log in to unmask]<mailto:[log in to unmask]>>
To: <[log in to unmask]<mailto:[log in to unmask]>>
Date: 02/11/2013 10:11 AM
Subject: [TN] Washing of acrylic conformal coatings
Sent by: TechNet <[log in to unmask]<mailto:[log in to unmask]>>
________________________________
Dear Technos,
I know many of you already advocated against it, but my pain is so big that I need to check again.
Took 3 boards from the regular production, coated with 1B31S, and passed them in our in-line washer, at 135 F and 3ft/min. Except from coating starting peeling from 2-3 component tops, everything looks well.
Does this mean I'm OK, as I prefer touching-up the 2-3 components than doing repairs with no-clean?
What else should I check? Should I test anything else? How?
Thanks,
Ioan Tempea, ing.
Ingénieur principal de fabrication / Senior Manufacturing Engineer [signature002]<http://www.digico.cc/>
950 RUE BERGAR, LAVAL, QC, H7L 5A1<http://g.co/maps/2gh3f>
T+ 1 (450) 967-7100, EXT244
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[signature001] <http://www.facebook.com/pages/Digico/277076778479>
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Lauréat Dunamis 2012<http://digico.cc/dunamis-2012/>
Entreprise manufacturière / Gestion du capital humain
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