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
------------------------------------------------------------------------
[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
------------------------------------------------------------------------
[signature001] <http://www.facebook.com/pages/Digico/277076778479>
------------------------------------------------------------------------
Lauréat Dunamis 2012<http://digico.cc/dunamis-2012/>
Entreprise manufacturière / Gestion du capital humain
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