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From:
Ed Popielarski <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ed Popielarski <[log in to unmask]>
Date:
Mon, 28 Aug 2017 15:53:27 +0000
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text/plain (143 lines)
Fro0m my archives below. I have found this all to be valid and useful:

*****************snip**********************

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Tuesday, February 11, 2014 5:28 AM
To: [log in to unmask]
Subject: Re: [TN] [COM] Solder Mask Surface Tension for Conformal Coating Adhesion

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]>

*****************snip**********************

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

Regards,

Ed Popielarski
Engineering Manager


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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Kraszewski
Sent: Monday, August 28, 2017 7:26 AM
To: [log in to unmask]
Subject: [TN] Articles Referencing Surface Energy Required for Coating

I seem to  recall numerous industry articles (Pauls, Keeping, etc.)  referencing  that  ideally the surface energy of  a PCBA should be >~ 40 dyne cm  prior to coating. 
I have searched my files but cannot seem to find any of  them now. Only some referencing the need   to consider surface energy. 

Does someone have any  that reference " >~ 40 dyne cm  prior to coating"  readily available  that they can forward to me? 

Thanks 

Rich  Kraszewski 
Senior Staff Process Engineer
Plexus Engineering Solutions 


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