Arnaud,
You are welcome. You can find this information in the newly published
IPC-HDBK-830 Rev A, The Conformal Coating Handbook. If I recall
correctly, it is also found in IPC-HDBK-840, the Solder Mask Handbook. You
will not find it in IPC-SM-840 (solder mask) or IPC-CC-830 (coating),
because the problem is always the other guys fault. If you are a solder
mask guy, the fault is the coating. If you are a coating guy, the fault
is the mask. The reason that it is not in the solder mask spec is that
the surface energy is often more dependent on how the material was
applied, processed and developed, more so than one of the material
characteristics. Since the intelligence of the solder mask processing is
beyond the control of the solder mask vendor, it is not part of SM-840.
There is an ASTM standard from which the dyne pens are pulled: ASTM-D-2578
? 08 Standard Test Method for Wetting Tension of Polyethylene and
Polypropylene Films. That ASTM method will tell you how to make your own
calibrated alcohol solutions. I find it easier to buy a set every year
rather than having to store some of the chemicals year after year.
Doug Pauls
From: GRIVON Arnaud <[log in to unmask]>
To: <[log in to unmask]>
Date: 02/11/2014 02:06 AM
Subject: Re: [TN] [COM] Solder Mask Surface Tension for Conformal
Coating Adhesion
Sent by: TechNet <[log in to unmask]>
Hello,
Thank you for the clear information provided.
As a supplement, I would be interested in someone could give the reference
of the mentioned ASTM standard for surface energy measurement by Dyne
Pens.
Also wondering why there is no IPC standard or guideline on this topic, as
conformal coating adhesion on solder mask is a quite common concern within
the industry.
It looks like indications given by Doug are acknowledged as good practice
and therefore could be introduced within IPC standards.
Best regards,
Arnaud Grivon
-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de Lee Hitchens
Envoyé : mardi 4 février 2014 07:26
À : [log in to unmask]
Objet : Re: [TN] [COM] Solder Mask Surface Tension for Conformal Coating
Adhesion
Hi Arnaud
I agree with Doug on this on using Dyne Pens although with no clean
processing generally you are lucky if you can get close to the range of
35-40! We tend to be working in the lower range of this.
It's also solder resist / coating dependent. Don't dismiss the energy
value out of hand immediately. There is no logic sometimes to selection.
We found one case where we tried absolutely any coating we could find to
stick to a solder resist and only one did. No idea why and none of the
chemists could explain.
Best Regards
Lee Hitchens
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: 03 February 2014 17:01
To: [log in to unmask]
Subject: Re: [TN] [COM] Solder Mask Surface Tension for Conformal Coating
Adhesion
Arnaud,
I think you are asking about surface energy rather than surface tension.
We use the readily available Dyne Pens which have solutions calibrated
back to an ASTM standard.
I generally use this rule of thumb regardless of the coating used.
Under 30 dynes/cm: Coating adhesion will be poor
30-35 dynes/cm: Coating adhesion will be slightly better, but you can
expect more frequent cases of delamination.
35-40 dynes/cm: Coating adhesion generally good, but can have some
periodic delamination or adhesion issues.
40-45 dynes/cm: Coating adhesion is good and only rarely will you see
delamination problems
45+ dynes.cm: Good adhesion.
Of course, there will always be special cases but this is a good starting
point.
Doug Pauls
From: GRIVON Arnaud <[log in to unmask]>
To: <[log in to unmask]>
Date: 02/03/2014 10:48 AM
Subject: [TN] [COM] Solder Mask Surface Tension for Conformal
Coating Adhesion
Sent by: TechNet <[log in to unmask]>
Hello TechNet,
I would like to sense the best practices in terms of solder mask surface
tension with respect to conformal coating adhesion :
- Which standard/test method are you using?
- Which requirement (e.g. minimum value in dyn/cm²) would you
accept for the various CC types (acrylics, urethanes, silicone, parylene)?
Thanks in advance for the insights.
Best regards,
Arnaud Grivon
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