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Electro Etching ......(NO acid)

Discussion in 'General Electronics Chat' started by Rolf, Nov 18, 2007.

  1. Rolf

    Rolf Member

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    Today I grabbed a un-etched PCB with a P&P (Press & Peel) circuit on it.
    Then I rounded up a unregulated DC power supply, 10v-19v, 3.0 amp max.
    After soldering a wire to the PCB and connecting it to the minus and the plus went to a small copper plate that I submerged in a plastic tray with enough water to cover. Made sure that the two didn't have a change to touch.

    Than I added a little vinegar and a very small amount of table salt, don't ask me how much! Shortly thereafter bubbles started to form at the copper anode.

    This was set up next to the kitchen sink, without my wife's permission!

    Then I sat down to watch football, it was after all Sunday. During the advertising I went to check on my little experiment. No smell at all and couple of hours later about 95% of the PCB copper had migrated to the anode!

    I should be able to etch the remaining copper with a standard etching solution in a matter of a few minutes at the most.

    The advantage of all this is that you have much less exposure to noxious smells and of cause much less hazard's material to dispose of.
     
    Last edited: Nov 18, 2007
  2. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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  3. Rolf

    Rolf Member

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    Quite a difference in chemistry.

    Yes, his is similar but he uses Old Sulphuric Battery Acid (diluted) but I use Vinegar and Salt. Quite a difference in chemistry, I would think but then I am no chemist.
    And I can pick up the PCB, for inspection with my bare fingers, no rubber gloves needed.
    The reason for the experiment was to determine if I could cut down on the amount of hazardous chemicals used.
     
  4. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    What you are dong is great, just wanted to give Chemlec his due... I am interested in giving it a try. Please post more details when you have them. These days it is not uncommon for to make a half dozen or more of the same boards for my students/kids. This sort of thing could cut down on the chemical cost.
     
  5. Sceadwian

    Sceadwian Banned

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    http://en.wikipedia.org/wiki/Electro_chemical_machining

    It has limited usefulness in PCB etching, chemical methods aren't really that bad and the electro-chemical method stops working if electrical contact is broken and can etch underneath the masking media more readily than a pure chemical reaction can so it becomes impractical for fine traces. If appropriate agitation is used in a chemical bath the copper removal rate on a PCB is almost completely uniform, the electrochemical method depends highly on the cathode to anode surface area ratio and distance of the applied electric fields. Current density variations occur from these difference and from the variations in the copper thickness and how that thickness effects the current density over time as the board etches at different points. I think it's most common industrial usage is as a final polish and surface finishing process on complex geometries, like turbine blades made out of exotic metals, because the pieces are relatively large so their electrical coupling is very strong, something as thin as the copper trace on a PCB is tenuous at best.. The surface area and current density calculations are so far past nightmarish that it would be applicable at best as an art, one however which I would respect, but art non-the-less. As you scale up the process chemical etching a board becomes more viable not less, otherwise this kind of thing would be used for mass production of PC boards, and it's not.
     
    Last edited: Nov 19, 2007
  6. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    Given that etchants are not expensive it will not save a lot of money. But this is just the sort of thing that I like to play with. None of the practical concerns carry much weight because it is interesting. I think there is a place for that here. If not there should be.
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Rather a misleading title? - 'no acid' - you then proceed to add acetic acid to the mix :p
     
  8. ClydeCrashKop

    ClydeCrashKop Member

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    Do that outside. Those bubbles are hydrogen.
     
  9. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    I am not sure what you mean by quite a difference in chemistry. The advantage of using sulfuric acid in electrolysis versus NaCl as your primary electrolyte is there is no chance to produce chlorine gas.

    Although an explosion is probably unlikely if the process is well ventilated, hydrogen and chlorine form a classic, photochemically calatyzed, explosive mixture. John

    Edit: Of course, chlorine by itself is a poisonous gas and has been used in warfare for that purpose.
     
    Last edited: Nov 19, 2007
  10. Sceadwian

    Sceadwian Banned

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    If you want to go caveman, a basic graphite electrode can shape titanium in something as simple as salt water. Sulfuric acid is used yes, but only because it's a more efficient electrolyte. Proper venting for byproduct gases is a no-brainer, especially in a water based solution, electrolyte construction is 100% based on application to reduce byproducts and hence increase efficiency.
     

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