Conformal coating and its alternative

Discussion in 'The Projects Forum' started by lamb, Jun 21, 2012.

  1. lamb

    Thread Starter New Member

    Jun 21, 2012
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    I understand that the conformal coating is needed to protect the circuitry in the board from moisture and lets just say our environment. But is there any alternative to this?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    You could place the circuit in a hermetically sealed enclosure. This is done frequently for military and space applications, but it is far more expensive than conformal coating.
     
  3. #12

    Expert

    Nov 30, 2010
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    I notice that my Fluke voltmeter is sealed with an o-ring. That is a crude form of hermetic sealing. Though not worthy of space flight, it does help keep the guts from corroding. Some projects and their enclosures could benefit from this approach. It depends on how perfect you need the protection to be.
     
  4. ghebaur

    Member

    Jun 17, 2014
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    I'm reviving this thread so i don't start a new one for the same thing.

    Is it ok to use car spray paint or lacquer as conformal coating?
     
  5. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Your mileage will vary. Some chemicals will cause the exact problems you are trying to avoid. Others may not age well, or perform as desired under conditions of heat and humidity.

    You really should use something specifically formulated for electronic use.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There is the old electrical standby Glyptal can be had at Electrical Contract Suppliers.
    Max.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    My "electronic" conformal coating from MG Chemicals is labeled "acrylic lacquer." Its MSDS doesn't list any special ingredients.

    One advantage of a lacquer is that it can be removed, if necessary, with solvent. Any clear lacquer should work the same. I would avoid a pigmented lacquer, as opposed to those with transparent dyes. Not all lacquers are acrylic. Lacquers based on other polymers, such as nitrocellulose should also work fine.

    Lacquers have pretty good peel strength, are flexible and relatively soft, and the solvents in them generally make them tolerant to surface contamination..

    Clear polyurethanes are popular today because of their solvent resistance, hardness, and compliance with VOC. But, they do not have great peel strength, particularly if the surface is shiny or has any contamination on it. Polyurethane finishes are also more prone to filiform corrosion. That was a real problem with early use on aluminum surfaces of airplanes. So, I would not recommend a polyurethane unless you have some assurance it is OK for electronics.

    John
     
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
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    also, coatings must be specified for use on microwave circuits too, there are lots of "insulatoras" that absorb rf at microwave frequencies, and can upset stripline circuit impedance.
     
  9. Kermit2

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    Feb 5, 2010
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    Shellac is an old time insulator for electricity. It is waterproof, and inert.

    Avoid really high temps. It is easily removed with alcohol.
     
  10. MaxHeadRoom

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  11. KMoffett

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  12. atferrari

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    Jan 6, 2004
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    Dictionary seems of no help.

    What is the actual meaning of "conformal"? Where is that word derived from?
     
  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    It means 'following the shape of'.
    Latin: 'con' = together, 'forma' = form/shape
     
    atferrari likes this.
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    In this case probably because the coating 'Conforms' to a certain protection standard for a defined operating condition.
    My guess!
    Max
     
  15. ghebaur

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    Jun 17, 2014
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    I'v been reading your suggestions and an idea come up. I think is better to use primer instead of paint or lacquer, it protects against corrosion and moisture too.
     
  16. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Depends on the type of primer.:rolleyes: Primer used for automotive applications does none of the things you have stated. Automotive primer is not waterproof and doesn't stop corrosion. If you primer bare metal and don't top coat it, it will soon rust. Even humidity in the air will penetrate auto primer in short order.


    The Glyptal or one of the other paints of this type, as others said is the way to go. Here is a less expensive alternative -

    http://www.mscdirect.com/product/de...__15557577904_c_S&026=-99&025=c&item=84253244


    Never used it for this application, but have you considered spray on truck bed liner? https://www.duplicolor.com/products/truckBedCoating/ You can get it at most auto parts places.
     
    Last edited: Aug 15, 2014
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