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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