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Burnt solder flux, safe to use acetone?

Discussion in 'Repairing Electronics' started by halleffector, Jun 19, 2017.

  1. halleffector

    halleffector Member

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    Is it safe to use acetone to remove burnt solder flux? If safe, will it do the job at all?
     
  2. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    You might have better luck with a a mixture of acetone and absolute ethanol. I don't have a clue as to what the pyrolysis products are, but some might be a little polar and absolute ethanol is a great solvent for such things. Just a little water (5%) changes the solvent potency of ethanol greatly. Absolute will dissolve fat; 95% is much less effective.

    In short, try acetone. If that doesn't work (I suspect it may not), change to 50% to 75% ethanol (absolute or denatured) in acetone. My usual elixir for removing excess flux is that mixture (i.e, 75% absolute ethanol, 25% acetone). Isopropyl alcohol may work as a substitute for the ethanol. I just happen to have a lot of ethanol on hand.

    John
     
  3. ci139

    ci139 Active Member

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    i wouldn't try this on PCB - if you don't intend to remove the copper as well
     
  4. dave

    Dave New Member

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  5. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Been using the ethanol-acetone mixture for more than 20 years. Haven't removed any noticeable amount of copper.

    What do you use to remove excess flux?

    John
     
  6. ci139

    ci139 Active Member

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    possible , whats your technique?
    my sharp fingernails , then pure ethanol if i am to do more soldering otherwise i don't care as i'm not selling anything

    the "paint removers" do not cause the copper to fall off - but when you next time solder with high temperature and try to make a firm connection between Cu and bad quality component lead by "rubbing" the solder to surfaces with the welder tip and the Cu is small area it might come off easier than just with excess temperature - i usually cover everything with solder in prior sometimes it's not enough to sucessful finish
     
    Last edited: Jun 27, 2017
  7. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Technique?
    I either immerse followed by toothbrush or just toothbrush alone for larger boards.

    I said nothing about "paint removers" -- a term that covers a very broad range of chemicals.

    John
     
  8. Pommie

    Pommie Well-Known Member Most Helpful Member

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    That would be where you are going wrong. Save your welder for car repairs and paint remover for decorating. Neither should go near electronics.

    Mike.
     
  9. ci139

    ci139 Active Member

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  10. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    ci139 : What's your point? Acetone does not remove copper traces from any PCB I have ever used. That gets back to your post #3. What evidence or literature can you present or cite to support your assertion?

    Since the OP asked in general whether acetone was safe, I stand by my response. I failed to mention, however, that if the PCB contains components that have "sensitive" plastic, like a plastic optical window, I will omit acetone from my brew and use just ethanol or isopropyl alcohol. That action is taken as an "abundance of caution." I do not know and have not tested the plastics used for such windows or LED's. Although, I have had no problems with ordinary LED's used to show an active state. Shrouded connectors and so forth have not been a problem. I would be concerned about using neat acetone on some of them, but as stated, I do not use neat acetone for removing excess flux nor recommend it.

    Additionally, with clear plastics, the effects of any organic solvent may not be immediate. Over a long time, the plastic may be more susceptible to crazing. One good example is acrylics (e.g., Plexiglas). It can be bonded with chlorinated hydrocarbons (e.g., chloroform), but that bond will show crazing years later. That is just one example, but relatively mild solvents like toluene or xylene or even oil-filled caulking can have the same effect.

    John
     
  11. ci139

    ci139 Active Member

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    and i said what i have experienced

    what i suppose to do now - try to remove a past evt. from world history - because it does not fit your like

    may be there are differences between acetone and acetone - or PCB and PCB - i don't know
     
  12. hyedenny

    hyedenny Member

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    Acetone removing copper??? Not a chance. Maybe you're thinking of Coppertone on asses?
    I've always had good luck with alcohol. What I've found to work even better, on suitable components, is household ammonia and a toothbrush followed by a rinse with water, then a good blow drying. Commercial processes often use aqueous washes.
     

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