Hi all,

So I've seen Doug's reply and Ioan's reply. I'm going to reply and see if
anybody gets this...

Steve

On Wed, Mar 20, 2024 at 6:34 AM Ioan Tempea <
[log in to unmask]> wrote:

> Thanks Doug,
>
> Can't get it more thorough than that!
>
> We do have a Surface Analyst so I guess I'll request a side by side
> dyne/contact angle characterization, to get the angle equivalents of 40+
> dynes.
>
> Best regards,
>
> Ioan
>
> -----Message d'origine-----
> De : TechNet <[log in to unmask]> De la part de Pauls, Doug O Collins
> Envoyé : March 20, 2024 8:18 AM
> À : [log in to unmask]
> Objet : Re: [TN] Surface energy for conformal coating
>
> You're welcome.
>
> Indiscrete Answers
> - We will typically take surface energy readings when we qualify a new
> board site, then monitor a few incoming lots, but often we do not test
> again unless we have reason to go looking.  The dyne pens, while
> inexpensive and easy to use, are variable in interpretation.  A more
> accurate and repeatable measurement can be made with instruments designed
> to measure surface tension and surface energy.  There is one by Kruss, out
> of Switzerland, and one from Brighton Science (formerly BTG Labs) (Surface
> Analyst).  We have both.  Both work.
> -  Yes, manufacturing processes can impact surface energy.  When we
> qualify a site, we have a qualification vehicle fabricated by the candidate
> site that then goes through our manufacturing processes.  Then we measure
> surface energy to see how much the manufacturing process impacted the
> surface.  We  have some very robust cleaning processes, so we seldom see
> the surface energy go down if the solder mask was fully cured to start with.
>
> Douglas Pauls | Sr. Technical Fellow | Electronics AMT COLLINS AEROSPACE
> 400 Collins Road NE, MS 108-101, Cedar Rapids, IA  52498  USA
> Tel: +1 319 295 2109 | Mobile: +1 319 431 3773
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Ioan Tempea
> Sent: Wednesday, March 13, 2024 6:11 AM
> To: [log in to unmask]
> Subject: [External] Re: [TN] Surface energy for conformal coating
>
> Thanks Doug!
>
> Indiscreet questions:
> - How do you make sure your spec is what you get? Do you request dyne
> testing by the PCB fab?
> - Do you measure dynes at Incoming or just in case you have issues on the
> assembly line?
> - Does surface energy variate during assembly? I mean a 40+ dynes/cm at
> Incoming, will it stay the same after 2 reflows, some TH assembly, rework,
> staking, etc., even with proper cleaning?
>
> Best regards,
>
> Ioan
>
> -----Message d'origine-----
> De : TechNet <[log in to unmask]> De la part de Pauls, Doug Collins Envoyé :
> March 12, 2024 10:03 PM À : [log in to unmask] Objet : Re: [TN] Surface
> energy for conformal coating
>
> Ioan,
> In general, I have used this rule of thumb:
> <30 dynes/cm - you will see problems with adhesion and wetting.
> 30-35 dynes/cm - you will still see problems with adhesion and wetting,
> but not as much as under 30.
> 35-40 dynes/cm - generally decent adhesion and wetting but occasional
> issues
> 40+ dynes/cm - good adhesion and wetting.  Collins specifies >44 dynes/cm
> for its solder mask.
>
> Douglas Pauls | Sr. Technical Fellow | Electronics AMT COLLINS AEROSPACE
> 400 Collins Road NE, MS 108-101, Cedar Rapids, IA  52498  USA
> Tel: +1 319 295 2109 | Mobile: +1 319 431 3773
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Ioan Tempea
> Sent: Monday, March 11, 2024 2:42 PM
> To: [log in to unmask]
> Subject: [External] [TN] Surface energy for conformal coating
>
> Hello Technos,
>
> Some many years ago I have discovered, with help from this illustrious
> panel, the existence of the dyne pens. Have used them for a while and them
> moved to microelectronics, where I have spent 11 years without any contact
> with conformal coating. So I've kinda forgot some details.
> Where I work we have the Surface Analyst device, measuring contact angles
> and this is supposed to obsolete the use of dyne pens.
>
> The trouble is I can't remember what dyne values are related to good
> coating wetting. Or even better, which contact angles are preferred?
>
> Can anyone help?
> I'm interested in both solder masked PCBs and Au plated ceramics and the
> optimal values I believe differ from PCB to ceramics.
>
> Also, do you have any good articles or textbooks to recommend on this
> matter?
>
> Thanks,
>
> Ioan
>


-- 
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133
Cell Phone: (918) 706-2779

-- 


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