Ioan,
The dyne pens are essentially an alcohol mixture. Wipe off the material
with a little isopropyl alcohol and a wipe and you should be good. They
don't leave a residue as far as I can tell.
Doug Pauls
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/07/2010 02:30 PM
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[TN] TR: [TN] Wrinkling of conformal coating
One more before the week-end. I have added a picture to the gallery,
showing a marking we see on some PCBs of this funky batch. Is this, by any
chance, what the surface energy crayons leave on the board if the test
fails?
http://ipc-technet.groupsite.com/galleries/photo/124230
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]>
W | www.digico.cc <http://www.digico.cc/>
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De : [log in to unmask] [mailto:[log in to unmask]]
Envoyé : May-07-10 12:17 PM
À : TechNet E-Mail Forum; Ioan Tempea
Objet : Re: [TN] Wrinkling of conformal coating
Ioan,
Was the board by any chance fused tin-lead or HASL coated? If a solder
mask is not processed according to the mask vendor's guidelines,
especially in relation to UV exposure and thermal bakes, then the solder
mask can absorb things like fusing fluids or HASL fluxes that then get
sealed in by the heat of fusion or by contacting molten metal. You can
sometimes see these coming out when you again expose the board to reflow
conditions. This is often why I run "heated controls" when I am doing an
ionic cleanliness witch hunt. If the bare board residue levels are
relatively close to the heated controls, then the mask is probably good.
If they are wildly different, then you have a potentially bad mask
problem.
What did the board look like visually when it came out of reflow. Did it
appear oily?
Doug Pauls
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/07/2010 11:07 AM
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Re: [TN] Wrinkling of conformal coating
In case you guys thought you got away by talking about alien espresso
machines, I have one more question.
Took a bare board from stores and stuck it into the reflow oven. I have
noticed smoke coming out from the tunnel while the PCB was in. Not huge or
thick, but just enough smoke to notice it. Could this mean anything
regarding the board, like not cured something, poor FR-4 or else?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask]
W | www.digico.cc
N'imprimer que si nécessaire - Print only if you must
Dear Technos,
Back to orange peeling, this time concerning conformal coating, please see
http://ipc-technet.groupsite.com/galleries/photo/124230
The coating is applied with an Asymtek Century machine and is a Conap 1170
acrylic.
· The board is left curing in ambient temperature, no
acceleration. Starting with an even coating, in about 20-30 minutes the
liquid seems to move towards a certain area (no rippling at this moment).
After another 10-15 minutes the rippling effect sets in.
· We thought that due to the almost 2 minutes lag between the
coating of the first and last image, the drying of the coating layer is
not even and the one side curing first pulls on the liquid at the other
end. So we've cut the panel in 2, accelerated the machine, the problem is
still there.
· The boards are laid as flat as possible, maybe not perfectly
horizontal, but not worse than others with the same coating, that do not
show any issue
· Just to make it more difficult: grabbed a non-populated panel
from the stores, coated it, placed on the same flat surface, and guess
what: no issues.
The PCB has Taiyo PSR 4000 MP soldermask.
So I would need your guidance in clarifying where is this coming from and
how to fix it.
Thank you,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]>
W | www.digico.cc <http://www.digico.cc/>
N'imprimer que si nécessaire - Print only if you must
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