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Static Electricity and Ferric Chloride (argh!)

Discussion in 'Electronic Basics' started by Puckdropper, Feb 17, 2007.

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  1. Puckdropper

    Puckdropper Guest

    I'm a little upset right now, so please consider that when reading. If
    you don't care, feel free to go to the next thread.

    I was working on etching a circuit board, and wasn't too happy with the
    progress of the etching process. Since warm etchant works better than
    cold etchant, I picked up the etching container (a little 4 oz container)
    and walked towards the garage heater (oil filled radiator type). After
    walking the grand total of 6 feet, I move to hold the etchant container
    closer to the heater and get shocked!

    On reflex, I jerk back from the heater, scattering and spilling the
    contents of the etchant container. The etchant gets all over my hands,
    the floor, my coat, and the heater. Luckily, I was able to avoid serious
    injury and minimize staining, but I can't trust that heater any more. I
    think the FeCl just ate through the paint before stopping, but I can't be

    Next time I get an idea like this, I'm either going to be more patient,
    or if I want to move the etchant container, I'll put the lid on first.
    Either one would have prevented the whole situation, and at the worst I'd
    be disappointed by a bad board. They're a lot cheaper than a heater.

  2. Chris

    Chris Guest

    Sorry for your troubles. I was once using ferric chloride with the GC
    "Professional Etching Kit" (before they started including an O-ring to
    keep the heater from contacting the plastic tank). Combination of
    circumstances, the heater was touching the wall of the tank when I
    plugged it in to warm up and melted through just as the solution was
    reaching temperature. I was in another part of the plant.

    By the time I came back to check if the etchant was up to temp most of
    the contents of the tank had poured out on the floor and had seeped
    into many different places in the lab. No fun to clean.

    Oh, well. DIY etching is a lot of trouble. And always use the
    included O-ring. ;-)

  3. Bob Masta

    Bob Masta Guest

    Besides heat, the other thing you might want to check is to
    make sure that your ferric chloride is not too concentrated.
    Yes, you read that right: Believe it or not, above a certain
    concentration etching slows down to a near-standstill.
    You not only need to attend to this when you buy
    new etchant (which is sometimes supplied at too-high
    concentration), but also as it ages. You'll need to ask
    a chemist for the explanation... it's something to do
    with site competition (or something equally unintuitive).
    But in the lab where I used to work, it was standard practice
    when the etchant started to slow down (after some number
    of boards were etched), to dilute it a little to bring it back up to
    speed. I wouldn't have thought that usage would have
    provoked a concentration increase, though it might have
    been due to evaporation.

    If you want the details on the proper concentration, see

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
  4. Aly

    Aly Guest


    Nasty old stuff that. Lately most the of the things I've been doing seem to
    revolve around the cooker in the kitchen. From using the oven at 250oC for
    SMD components, to using a saucepan on the stove with a sealable sandwich
    box floating in a pan of water. That's where the etching gets done. All
    very technical and high tech.

    A sandwich box I've found is the most brilliant thing for etching, and at
    50p each in the local supermarket too. Just stick it in a saucepan of hot
    water. As for storing unused ferric cloride I use an airtight coffee jar
    (glass being non reactive) stored under the sink in the dark.

    I once tipped my mixed solution down a stainless steel sink.... Don't do

    All experience and memorable though. :)
  5. Guest

    GAWWWWWWD!!!!, Does you mom know you're doing that in her kitchen?
  6. Chris Jones

    Chris Jones Guest

    If you ever go to using Ammonium Persulfate etchant, then don't put it in an
    airtight container. I learnt that the hard way. It makes some kind of gas
    and my bottle exploded unexpectedly, distributing etchant all over the

  7. Rich Grise

    Rich Grise Guest

    I etched a board with I think RS FeCL3; after I did the board, I dumped
    about a pint of the stuff down the storm drain.

    I wonder if I killed any fish? (this was about 5 miles from the ocean).

  8. none none

    none none Guest

    I ended up getting a 2.2gallon fish tank from petsmart and used an aquarium
    heater and aerator for the tank. I also drilled a hole in the bottom of the
    tank (it's a cheap tank, all plastic) and have a pump hooked up to pump the
    solution into a holding tank(only when using ferric Chloride) there is a
    valve on the bottom of the tank which allows me to drain the solution after
    os many uses
    but it helps being able to use the pump to both empty and fill the etching
    tank :p Don't use Ammonium Persulphate though in that setup unless your
    gonna drain teh tank after each use, that stuff doesn't keep very well.
  9. Puckdropper

    Puckdropper Guest

    (Bob Masta) wrote in
    I read that somewhere. You may have posted it yourself on Usenet
    previously. The Google Searches turned up quite a bit of good
    information before I even started.

  10. amdx

    amdx Guest

    Ok, my ferric chloride story, I'm etchimg pcbs in a ¼" glass tray I made

    Using silicone to stick sides to a 12"x12" bottom. Working on my wife's NEW

    stove that has stainless steel burner covers. To heat the solution I
    decided to leave

    the cover on the burner and set the burner on the lowest setting. So, I'm

    along just fine until I notice a little etchent on the porcelain, the bottom
    piece of

    glass developed a crack. Now the etchant leaked on to the stainless steel

    cover and onto the stove top, down the front and into the burner hole.

    After a major clean up, the only real damage was to the stainless burner

    It has a deep etched line where the crack in the glass was.

    I had used this method 5 or 6 times before the heated glass became a

    BTW the best trick I learned about etching is to float the pcb on top of

    etchant. Apply a piece of tape to the back side of the pcb to make a little

    point and just float it on top of the etchant. Etching goes much faster, I'll

    others explain why.

  11. ehsjr

    ehsjr Guest

    A sort of Rube-Goldberg method for heating the etchant
    is to use a hot plate. There are better methods, but
    this one is cost free for most people.

  12. Bob Masta

    Bob Masta Guest

    The method I use for heating is just to set the plastic
    etching tray on a waterproof (plastic coated) heating pad.
    This is the standard commercial home-use pad, with the
    fabric cover slipped off. It doesn't get anywhere near as
    hot as a hotplate, but that's a virtue... never boils over, etc.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
  13. Rich Grise

    Rich Grise Guest

    Go to the grocery and get a glass baking dish. :)

  14. I've only done a few boards so far, but I've found that floating the
    etchant tank (hahaha--it's a plastic sandwich box) in hot water does
    the trick nicely. No chance to overheat; spills go only into water,

  15. ehsjr

    ehsjr Guest

    Good idea - I just tried the heating pad method tonite,
    and I like it better than the hot plate. Thanks!

  16. Lionel

    Lionel Guest

    That's the same method I used to use. The only drawback I found was
    that it is easy to get careless when agitating the inner tray, &
    splash water or etchant everywhere.
  17. Oh man. I don't do the etching in the sink. Got a pregnant woman in
    the house. :)

    I go out to the porch on an old wood bench, with a cube heater blowing
    warm air over the pre-warmed etchant with the board in it. I use a cotton
    ball to rub etchant on the soldering side. I also like to float the board
    in the etchant on the component side for a while first, to give it a head
    start in dissolving before I start on the soldering side. I can usually do
    a pretty good 4cm by (say) 6cm board in 5 to 10 minutes.

  18. Lionel

    Lionel Guest

    Me either. Ever seen what ferric chloride does to stainless steel? ;)
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