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CuCl etching

Discussion in 'Electronic Design' started by xray, Feb 12, 2005.

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  1. xray

    xray Guest

    In early Jan there was a discussion here about using CuCl to etch PC
    boards. Sorry, I lost the original thread.

    Someone mentioned a web page about this. I think that was my page. My
    site was in limbo at the time. I have finally gotten around to putting
    up some pages in a new location.

    Here's the page on CuCl etching...

    This information is all copied from a book of the 1980's. I did contact
    the author before posting. He goes into great detail on the process of
    keeping the chemistry right.

    All the pictures on this page are from the book. When I did my version,
    I found some porous plastic tubing in an aquarium store. I ran a few
    rows horizontally across the bottom of the tank as a bubbler. I adapted
    an aquarium heater in a large test tube. The heater was adjusted to a
    level that could cook fish, but all the parts were there, so the
    conversion was pretty easy.
  2. Tim Wescott

    Tim Wescott Guest

    That is a cool page. I suspect that I will always be too lazy to
    actually etch boards (that's what quick-turn houses are for), but it's
    good information if I ever decide to do so.
  3. Interesting, What is more, when the cuprous chloride has been formed, you can bubble acetylene through the soultion to make
    cuprous acetylide - explosive, but not as good as the silver variety.
  4. Mark Jones

    Mark Jones Guest

    Thanks for sharing. I think that was myself who commented in January. My design
    is slowly coming along, but I'm still not sure of several things yet so it is up
    in the air. So far it's looking like a five-division acrylic tank about
    13"x10"x1" per tank - one for developer, etchant, stripper, tin plate, and
    rinse. (Not necessarily in that order or same thickness, of course.) The hard
    part has been figuring out a way to seal the etchant tank during bubbling so
    etchant doesn't splatter all over the place or run or drip. Since HCl fumes are
    so nasty, I also thought about piping the etchant air exhaust into a bubbler in
    the rinse tank - hopefully counteracting the effects of developer and stripper
    alkalinity on the rinse water anyways. It's a W.I.P.

    I wanted to mention about disposal of excess CuCl - some peeps on sci.chemistry
    and I figure that adding magnesium to (rejuvinated) CuCl should produce harmless
    byproducts suitable for disposal. This has not been tested yet. A great place to
    get bulk magnesium is eBay of course. Whenever I get a chance to test this, I'll
    let us know the results.

    Did you say CuCl wouldn't etch very fast for you? To make my initial batch I
    took the H2O2/HCl reducer path and added some copper. This sat in a polyethylene
    bottle next to my bathroom register (heater vent) for about a week, etching
    happily whenever I'd throw in some copper. Half a gallon ate all three
    conductors of a beefy 6' computer electrical cord and then some. It did seem to
    be very slow, but of course the solution parameters was and still is nowhere
    near the recommended. In hindsight, it would have been much simper to just buy
    some CuO from eBay and mix it with HCl, done.

    It's pretty much stopped etching now, but the color is not anywhere near
    "olive-brown." It's more like a deep, slightly-opaque green, still in stark
    contrast to the "almost-glow-in-the-dark" bright translucent green when it
    started. I haven't been able to bubble it yet, and it still seems like the
    density is far too low (compared to the viscosity of FeCl), but we'll see what
    happens when it goes into the bubbler tank and gets some well-needed
    rejuvination and calibration. :)

  5. Mark Jones

    Mark Jones Guest

    A much safer alternative is ammonium tri-iodide. Take a pitri dish, add a few
    (read: one or two) iodine crystals, add just enough ammonia to cover. Ammonia in
    this case is household ammonia - the pure stuff would make the result far too
    unstable - breathing on it would set it off. Swirl gently, and after a few
    minutes the iodine crystals will turn purple. When wet, it is harmless. But once
    they dry, they become explosive. Apparently the molecules line up in very long
    chains when drying and are easily broken by physical force, creating a miniature
    atomic chain-reaction. The product of explosion is simple dis-assembly of the
    structure - it leaves an ammonia-and-iodine-stain on whatever unlucky thing
    touched it.
  6. Ah.... those were the days, when schools really taught chemistry.


    "Facts are stupid things.." -- Reagan, '88
  7. Jim Thompson

    Jim Thompson Guest

    I prefer fulminate of mercury myself (remember the movie "Mister
    Roberts" ;-)

    ...Jim Thompson
  8. I read in that Jim Thompson
    That is not too surprising since it's a compound, mercuric isocyanate,
    formed from mercury and *ethyl alcohol*, with a little help from nitric
  9. xray

    xray Guest

    That is a problem. I never solved it. The HCl fumes are indeed nasty,
    and heating the solution makes it worse. The bubbling tends to create an
    aerosol of the solution too which can badly stain anything it contacts.
    I have some plumbing in my batroom, where I tried this, that now has a
    nice rust coating.

    A tight cover and some kind of fume hood would definately be a good
    I guess you read the disposal idea from the book I copied? This was
    mainly in reference to FeCl but I guess would be ok for CuCl too. He
    talks about neutralizing it and then mixing it into concrete to make a
    brick that will contain the chemicals. I thought that was one of the
    best ideas I had heard.
    Yes. I can't remember the times now but it seemed to take about twice as
    long as I ecpected FeCl would. Maybe there was some problem with my
    set-up, but I mixed the chemical per the article and tests showed acid
    level and density to be about right.
  10. I read in that xray <>
    HCl vapour is very highly soluble in water. So you can absorb it in a
    water bath to recover the acid. It's so soluble that you have to take
    precautions to stop the water climbing up the input pipe after it. I kid
    you not; it's called 'suck back'. What you do is to terminate the pipe
    only JUST under the surface of the water, so if the water climbs up the
    pipe the level in the bath drops and exposes the end of the pipe.
  11. Hg(ONC)2

    "Mercury Fulminate is made by dissolving mercury in concentrated nitric acid and pouring the warm solution into alcohol, under
    carefully defined conditions, in a roomy and suitable apparatus. After an initial period of quiescence a stormy reaction of a
    complex nature sets in, and eventually mercury fulminate begins to separate in small grey needles. At the end of the reaction
    the cooled mother-liquor is decanted and the fulminate collected on a filter and well washed with cold water. Large crystals
    are removed by passing the product through a fine screen, and the product is washed again until it is quite free from acid. The
    brownish-grey crystals obtained in this way are stored in linen bags under water. The density of the crystals is about 4.3 ..."

    from Explosives by John Read, Pelican books 1942.

    "Chandelon's process. 1 part by weight of mercury is dissolved in 10 parts of nitric acid (sp. gr. 1.4) at a gentle heat; the
    solution at a temperature of about 55 degrees, is poured in a capacious flask (its capacity must be at least equal to six times
    the volume of the liquid) containing 8.3 parts of alcohol (of 0.83). The flask is connected by a cork and tube with a
    stoneware condenser to recover spirit.

    In about a quarter of an hour the reaction commences with a slight formation of gas bubbles; very soon the liquid boils, and the
    flask becomes filled with voluminous white vapour..."

    from A dictionary of applied chemistry by TE Thorpe 1891
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