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Bubble Etcher

Discussion in 'Electronic Basics' started by Rodney, Aug 5, 2005.

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  1. Rodney

    Rodney Guest


    Just in case some people here may be wondering how to speed up the etching
    process for PCB's, one way to do it is to use a bubble etcher. Basically
    all you
    have to do is install a perforated plastic tube in the bottom of your
    etching tank and force air through it. The bubbling action constantly
    agitates the etchant and thus greatly speeds up the etching process. I'm
    using some aquarium tubing with small holes drilled in it and I use an
    airbrush compressor as an air source in my small tank. For a larger tank
    you can use 1/2" ABS pipe and the exhaust of a canister style vacuum cleaner
    such as a Shop Vac for an air source. You should use an adjustable valve in
    the air line to regulate the flow so as not to spray etchant all over the
    place. In this type of tank the circuit board must be hung vertically in
    the etchant.
    Heating the etchant is also recommended.
    Have a good day.

  2. jim dorey

    jim dorey Guest

    some etchant can become airborne when it's bubbled, making breathing
    rather dificult, proper ventilation will fix that.
    depending on etchant formula it may be a good idea to heat it constantly
    or not, i not then heating to operating temperature. some produce heat
    when they work, constant heating could cause it to go exothermic, meaning
    it would boil and perhaps cause fire or explosion, maybe a gaseous acid as
    well. as long as you don't exceed a certain rate of copper absorbed in a
    set timeframe things should be fine with preheating.
  3. Chris

    Chris Guest

    Good morning, Rodney. Someone who's interested in this type of etching
    setup might want to look at the GC/Waldom Electronics Cat. No. 22-0394
    "Professional" etching system. It uses a setup similar to the one
    you're talking about, with an aquarium heater and a small aquarium
    pump. I found it to be useful for small quantity ferric chloride board

    A couple of caveats about using this type of setup. First, heated
    etchant will emit fumes, which are corrosive. This kind of thing
    should only be done in a well-ventilated area, and away from computers
    or other electronics. Second, while the aquaruim controller provides
    pretty good temp control (once you get the dial setting right -- use a
    thermometer to get the controller to the right setting), the temp
    control only works well with a constant etchant level. As etchant
    evaporates, the level changes, and the temp control will be affected.
    Not only that, but if the etchant level gets too low, the glass of the
    aquarium heater will crack.

    The aquarium heater itself hangs from the side of the etchant tank on
    the inside. If the glass of the heater comes in contact with the
    plastic tank, it can melt through, causing a disaster. GC now provides
    an O-ring to slip around the side of the glass heater to help avoid
    this problem. The O-ring should be used at all times. But, in order
    to be safe, the whole tank should be placed in a large pan which would
    catch the etchant in the event of a melt-through of the plastic tank
    (voice of bitter experience here).

    One other note -- it's very important to physically place the aquarium
    pump over the level of the top of the etching tank. When power to the
    pump is turned off (or in the event of a power failure) etchant can
    back up the air tube into the pump. That's disastrous for the pump,
    and will cause failure in the near term.

    This type of hobbyist system is good for small quantity, single sided
    boards where the minimum trace widths aren't too demanding. It's
    difficult in this type of setup to get a double-sided board to etch
    well. It can be of use to periodically flip the board over, turning it
    around and upside-down, to try to even out the etch. This setup also
    assumes you will have some scrap around your circuit, because the edge
    of the board in the aerator/holder doesn't etch.

    Anyone using this setup for real should obtain a spare O-ring and a
    spare aquarium heater (which has been preset to the right temp) in case
    of component failure.

    Good luck
  4. Rodney

    Rodney Guest

    I've noticed that you can purchase a small check valve for aquarium pumps
    which would prevent any back-flow of etchant in the lines.
    If you hang the board vertically in the tank it should etch evenly on both

    I would also add that placing a cover over the tank while etching would stop
    and mist from escaping into the open air.
  5. Rodney

    Rodney Guest

    If you run the lines up and over the side of the tank there shouldn't be
    any back-flow of etchant but the check valve might also be a good idea.
    Keeping the air line fairly long might also be a good idea. I haven't seen
    any problem with back-flow in my system so far but I'm not using an aquarium

  6. Rodney

    Rodney Guest

    Thanks for the input Chris

  7. Rodney

    Rodney Guest

    Thanks for the input Chris

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