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How to remove this protective layer?

Discussion in 'Repairing Electronics' started by huuquanspkt, Nov 22, 2017.

  1. huuquanspkt

    huuquanspkt New Member

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    I have a device like in the picture.
    It is protected by a layer of chemicals. Anyone know what that is chemicals.
    And How to remove the chemical class and take power circuit ?
    Thanks Everyone
     

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  2. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Welcome to ETO.

    Sorry, your image doesn't show and/or I need to register there to see it. Please upload to the ETO site and post again.
     
  3. Inquisitive

    Inquisitive Super Moderator

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    Picture uploaded by Moderator

    Potted.png
     
  4. dave

    Dave New Member

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  5. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    I added the image to the original question. Best to keep it there.

    Matt
     
  6. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    It is called "potting." From the looks of the scrape marks, it looks like a hard substance, rather than rubbery. It could be a low-temperature thermal setting compound but is more likely a catalyzed plastic, like epoxy but not necessarily epoxy.

    In any event the chances of finding a solvent to dissolve that mass without damaging the electronics are slim. You could try dissolving a chip in acetone, methyl ethyl ketone (MEK), or chloroform/methylene dichloride.

    Most likely, you will need to remove most of the solid by careful chipping and grinding. Then, clean up with a solvent or heat. Many epoxies become plastic at 130° to 145°C. Obviously, the box it is in will be a hindrance, so if it can be sacrificed, I would saw through the sides and peel it away. If you can get it an X-ray, that will help.

    How valuable is it and is it worth all that work? If it contains an MCU, then getting the potting compound off will not be the end of your problem.
     
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  7. Rich D.

    Rich D. Member

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    There is another way. It's used in laboratories for chip manufacturers. It's called "Reactive Ion Etching". It involves putting the device in a chamber and creating a high vacuum. Then introduce a bit of CH4 or some other gas. This then is bombarded with 100 to 200 watts of RF energy and it basically bombards the organic materials with high energy ions and they vaporize and are sucked away in the vacuum. It does cost tens of thousands of dollars though.

    https://www.2spi.com/category/plasma-prep-rie/plasma-etcher-asher/
     
  8. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    You can also, in theory, use nitric acid. Potential problem with destroying all organic compounds is the PCB is probably organic as are the packages for most transistors, IC's, etc,

    EDIT: Oh, BTW, the process you describe is very similar to what we called electrochemical ionization (CI) is mass spectrometry may years ago (https://en.wikipedia.org/wiki/Chemical_ionization). Much better methods are available today such as MALDI.
     
    Last edited: Nov 22, 2017
  9. huuquanspkt

    huuquanspkt New Member

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    Thank jpanhalt , inside it do not have MCU
     
  10. huuquanspkt

    huuquanspkt New Member

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