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etchant stir

Discussion in 'Electronic Basics' started by James Thompson, Jun 6, 2006.

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  1. I came up with probably an old scheme but simple enough to circulate etchant
    in a pcb tank.

    Start with a plastic soda cap, snip the edges of it to make fins. Then use
    silicone sealant to glue a small magnet inside the cap. Cap sits on bottom
    of tank, then.
    Affix another magnet to the shaft of a small dc motor mounted in a standoff
    base for your tank and directly under the cap. As motor spins, so does cap
    and etching solution. Simple enough you think?
  2. tombiasi

    tombiasi Guest

    I think you came up with a very good idea.
    The magnetic stirrer is not a new idea but maybe it was for you.
    Keep thinking.
  3. purple_stars

    purple_stars Guest

    i use rubber gloves so that i can "work" areas of the board that are
    persistent and have copper that doesn't want to etch off.
  4. Jasen Betts

    Jasen Betts Guest

    Chemists use a "stirring bean" which is basically a small bar magnet with an
    inert casing this goes into a beaker of liquid and is places on a base wiche
    produces a rotating magnetic field to stir chemicals automatically.

  5. James Beck

    James Beck Guest

    I used an aquarium air pump and a bubble wand to keep things moving back
    in the day.


  6. Yeah, saw them about thirty years ago already. We had even one build in a
    heating plate so you could heat (even boil) the liquid and stir it at the
    same time. Nevertheless it's an interesting DIY thing and I'd like to see a
    picture of it. After all, those 'professional' lab equipment comes with
    'professional' price tags which are beyond most hobby budgets.

    petrus bitbyter
  7. Yes, the bubble wand is ok but it also causes a mist to rise from the tank.
    I knew of the chemistry lab stir and it is what I wanted to duplicate for a
    DIY etchant tank stir, to eliminate as much misting of etchant as possible.
    I'm just doing a small tank as of now to see how well it works out. I have
    seen a few post talking about a pump for the etchant tanks and wanted to
    share my approach to it. JTT...
  8. James Beck

    James Beck Guest

    Two things, if you are losing that much etchant from misting, you have
    the air volume WAYYYYY to high and 2ndly cover the tank.

  9. Mike

    Mike Guest

    I wonder if you could heat the soda cap after cutting it and flatten
    the fins while putting a little twist in them to form a crude impeller
    to maybe move more liquid.
  10. Good idea. As an alternative, just stick a grab tab on the PCB and allow
    PCB to float on the surface (don't trap any bubbles). Microwave the etchant
    beforehand. Takes about 8 minutes to do a 6" by 4" PCB. (and no, the
    solution wasn't fresh :)
  11. I'm thinking that sanding or scribing some indentations in the plastic
    and using epoxy would last longer. Silicon glue tends to peel off plastics.

    I tried that about twenty years ago and had uneven etching patterns on
    my board around the vortex. Several aquarium air stones gave good
    bubbling dispersion.
  12. That was the idea in cutting it, to make tiny fins like an impeller. On the
    other hand, instead maybe dissect a chipset cooler fan and set it into the
  13. eBay and a little patience can significantly reduce that "professional"
    price tag.
  14. Christopher

    Christopher Guest

    Hello James,

    My method of etchant agitation is to place "one side" of the square
    rubber bowl I use on a egg shaped cam mounted in a slow motor.BBQ

    This will gently swoosh the solution back and forth.

    I have an old etchant heated spray tank all corroded sitting useless.
    It did kick up a lot of corrosive mist.

    My question, how do most of you home etchers dispose of the exhausted
    solution? Different areas probably have their own rules on this.

    Good Luck,

    * * *

    Temecula CA.USA
  15. kell

    kell Guest

    did kick up a lot of corrosive mist.
    I don't have the link, but somewhere I read about a two-step process
    that turns ferric chloride into rust and (I think) table salt. I think
    it uses baking soda and some other common household chemical...
    anybody got info on this?
  16. Rich Grise

    Rich Grise Guest

    Washing Soda. It's Sodium Carbonate, Na2CO3, and doesn't release hydrogen
    as it works. It turns the iron and copper ions into their carbonates,
    which are essentially just dirt, and the sodium eats the chlorine. :)

    I did a board once with about a pint of RS FeCl3, and just flushed it
    when I was done. The EPA hasn't shown up to clap me in irons, yet. ;-)

  17. kell

    kell Guest

    They're on the way. In a black helicopter.
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