Re-energizing PCB etchant

Discussion in 'General Electronics Chat' started by gramps, Sep 1, 2016.

  1. gramps

    Thread Starter New Member

    Dec 8, 2014
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    I use muratic acid and hydrogen peroxide to etch boards, and it works to my satisfaction. The problem that I have with it is that I can't seem to re-energize it to re-use the next time. I have read that some people say to add a little more hydrogen peroxide, others say to expose the solution to the air to absorb oxygen or to bubble air through it. None of these methods work for me and I end up making a new batch of etchant every time. My question is, has anyone been able to re-energize their muratic acid / hydrogen peroxide etching solutions?
     
  2. hp1729

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    Nov 23, 2015
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    I would think you would need to get rid of the copper. I have never tried this but could you pass a current through it and electroplate another chunk of copper? Or would that just boil away the hydrogen also? Add more hydrogen peroxide to compensate for that?
     
  3. GopherT

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    Nov 23, 2012
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    How are you storing the solution?

    Hydrogen peroxide doesn't last forever. It turns into oxygen + water over time. Then you end up with dilute HCl. After that you try to "reactivate" dilute HCl with more hydrogen peroxide?

    If Dilute HCl + hydrogen peroxide works, why did you use concentrated hydrochloric acid the first time? The answer is, it doesn't.

    The fact is, H2O2 is super cheap, HCl is cheap and you are wasting more time thinking about recycling garbage than the two chemicals are worth.
     
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  4. shortbus

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    While Gopher is right, I think what your trying to end up with is "cupric chloride" for etching. Also how are you storing your used etchant? Any thing with hydrogen peroxide in it should be stored in a dark bottle to keep the light from breaking it down. There are a lot of sites online explaining the making of cupric chloride etchant much better than I can. http://mad-science.wonderhowto.com/...utomatically-improves-after-each-use-0135192/

    https://www.google.com/search?q=copper+chloride&ie=utf-8&oe=utf-8#q=copper+chloride+pcb+etching
     
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  5. AlbertHall

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    Jun 4, 2014
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    I never needed the H2O2. Put some cooper wire in HCl and bubbled air through it. Makes the cupric chloride, then regenerate with acid and more air bubbles. This way you make more etchant as you etch.
     
  6. 42etus

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    Dec 24, 2015
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    Thanks for the replies. I have read articles about etching PCBs with HCl and H2O2 until my eyes hurt. I know that the chemistry suggests that it SHOULD be possible to re-energize the solution, but it has never worked for me. My question still remains though: Has anyone actually re-energized their used HCl and H2O2 solutions into a viable etchant?
     
  7. jpanhalt

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    Jan 18, 2008
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    Have you re-registered?

    John
     
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  8. gramps

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    Dec 8, 2014
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    My bad! I didn't realize that I was signed in under my kid's account.
     
  9. shortbus

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    while not using it myself, this is a doable process. But that said it isn't a "instant" process. You can't expect to just bubble air into a solution for a few minutes and be done with it, it take days, even weeks to happen.

    And hp1729 was wrong about removing the copper:
    The solution needs copper to be there. People that use this keep adding metallic copper(wire or by etching) and still bubbling air into it. The darker the solution is the more powerful it is. A good read on the process -
    http://techref.massmind.org/techref/pcb/etch/CuCl2.htm
     
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  10. gramps

    Thread Starter New Member

    Dec 8, 2014
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    Thanks for the link. It's got some good info. I have pretty much done what is outlined in the paper, but still don't get good results. My etching solution is a very pretty green, but still etches very slowly, 45 min to an hour for a 1 oz board.
     
  11. hrs

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    Jun 13, 2014
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    What concentrations are the acid and the peroxide? I would not dilute the H2O2 as suggested by that wonderhowto link. A chemist told me that re-energizing through bubbling will not work in a weak acid.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    With ferric-chloride etchant; you can use electrolysis to remove the copper.

    The sacrificial electrode needs to be iron - the other electrode will build up a thick plating of copper, so it might as well be copper to start with and you can weigh it in for scrap when it gets too big.

    But I've never heard of anyone going to all that effort.
     
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  13. gramps

    Thread Starter New Member

    Dec 8, 2014
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    The acid is from the hardware store for cleaning concrete. Label says 30% HCl. The H2O2 is drugstore stuff, 3%.
    Was the chemist implying that the solution needed to be a stronger acid or not acidic at all?
     
  14. hrs

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    Jun 13, 2014
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    The chemist said the acid needed to be stronger. But I was using 10% HCl and 3% H2O2 and couldn't get that to regenerate even after hours of bubbling. I think the 30% HCl is fine but adding an equal measure of 3% H2O2 will half the HCl concentration. I don't know what concentration is required for regeneration to work.
     
  15. AlbertHall

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    Jun 4, 2014
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    The acid I use is 32%, but I don't use any H2O2 so it isn't diluted. It does regenerate, just add acid and bubbles.
     
  16. gramps

    Thread Starter New Member

    Dec 8, 2014
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    Are you saying that your starter solution is only 32% HCl and that you later add air bubbles to re-generate the etchant?
    I'm under the impression that O2 (hence the H2O2) needs to be present initially to get the whole process started.
     
  17. AlbertHall

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    Jun 4, 2014
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    To get the thing started without H2O2 you have some acid with some copper and bubble it for quite a long time, ≈ 2 weeks. The O2 is needed but is coming from the air. As you etch the solution gets pale, then you add more acid (more Cl is needed) and bubble to regenerate. So now you have more etchant than you started with.
     
  18. gramps

    Thread Starter New Member

    Dec 8, 2014
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    Thanks for that explanation, that makes it a lot clearer.
     
  19. shortbus

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    Sep 30, 2009
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