Sorry, should have gone into greater depth. My preferred method is to use
dyne pens, such as the ones you would find here:
http://www.accudynetest.com/adtpen.html
http://www.enerconind.com/Treating/Products/Dyne-Pens.aspx?aliaspath=/redirector
You generally want a surface energy above 40 dynes/cm. You can check your
surface energy in a number of areas on a sample bare board. If it greatly
varies, you have a problem with the solder mask cure or cleanliness. A
heat bump may help complete the cure and a run through the Omegameter may
help clean the mask. Plasma treatment also works to increase surface
energy.
Doug Pauls
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/06/2010 07:15 AM
Please respond to
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Ioan Tempea <[log in to unmask]>
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Subject
Re: [TN] Wrinkling of conformal coating
Doug,
I wish the substance was old... and smart, like us!
You are putting me in a tough situation here. How to check surface energy,
what should be the good values and how to fix it if not OK?
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
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-----Message d'origine-----
De : Douglas Pauls [mailto:[log in to unmask]]
Envoyé : May-06-10 8:10 AM
À : [log in to unmask]
Objet : Re: [TN] Wrinkling of conformal coating
For what it is worth, I think that the coating is simply too old. Isn't
the cause for most wrinkles? Some days I just slay me.
One thing that you might check as well is the surface energy of your
masked surface. Some of the other suggestions from the forum are your
more likely culprits, but you may be seeing some form of dewetting as
well, that causes the coating to pull away from one area and congregate in
another. Sometimes it is not the mask, but how the mask has been
processed that is the issue.
Doug Pauls
Graham Collins <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/05/2010 02:13 PM
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TechNet E-Mail Forum <[log in to unmask]>; Please respond to
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Re: [TN] Wrinkling of conformal coating
For my guess I'll go with either too thick, or contamination on the panel
making it try to dewet.
Questions: is this a new problem on a product you have been successfully
coating until now? Have you measured the thickness to ensure it is within
normal range?
Suggestion: Could you do two thinner coats and let it flash off a bit
between coats?
regards,
Graham Collins
Halifax Production Engineering
L-3 communications Electronic Systems
(902) 873-2000 ext. 6215
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Wednesday, May 05, 2010 3:59 PM
To: [log in to unmask]
Subject: [TN] Wrinkling of conformal coating
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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