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PCB electrolytic etching

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  1. Jul 2, 2017 #1
    I am undertaking a personal project that requires me to etch some circuit boards. This needs to be done on the cheap and in this instance it is not feasible to send to a PCB company. I am a bit put off by the nasty chemicals and the need for correct disposal. I know you can use Vinegar and Hydrogen Peroxide but I think it's still best to avoid if possible. I have had nightmares that someone might drink it by accident or something - I will be doing this at home.

    I looked into using conductive inks but it seems like the ones that are any good are really expensive.

    What do you think of this idea?

    1. Screen print one of the cheap conductive inks onto a blank sheet of FR4 (no copper clad) to lay the tracks of the circuit.

    2. Then electroform with copper so that you are left with copper tracks that have less resistance than the original conductive ink tracks

    Not sure if that process is already well established but I couldn't find much on google. Do you think that would give a similar level of robustness and quality as if you had used chemical etching? I know that if you use salt as an electrolyte it can give off chlorine gas, what would be the safest option for electrolyte? I see copper sulphate mentioned a lot, is that a good choice?

    Many thanks for your time, help and suggestions
     
    Last edited: Jul 2, 2017
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  3. Jul 2, 2017 #2

    berkeman

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    Thank you for acknowledging that. The leftovers after etching cannot be disposed of except via a hazardous waste facility. You may have some free household hazardous waste disposal facilities in your area (there is one in my area), and you could check to see if they would take the leftovers.
    There are some very inexpensive options for having your small PCB project fab'ed via e-mail and snail mail. What companies have you looked at so far? I think we had a thread a while back in the EE forum with lists of such companies and good reviews (including good prices). I'll see if I can find the thread with a search...
     
  4. Jul 2, 2017 #3

    Borek

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    Somehow I doubt in the good cohesion of copper to the board (especially as there is some ink below)..

    I made PCB boards at home with laser printer, thermotransfer and persulfate etching, works quite nice. Yes, it leaves some copper sulfate solution that one day I will need to get rid off (local regulations where I live are not very precise at the moment, so I can keep it here for time being).
     
  5. Jul 2, 2017 #4

    Borek

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    Don't look at soldering, but this is how the etched PCB (after thermotransfer) looks like.

    IMG_5814.jpg
     
  6. Jul 2, 2017 #5

    berkeman

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    Last edited: Jul 2, 2017
  7. Jul 2, 2017 #6
    Yes, I was also wondering if it would hold. Do you think adding a layer of varnish at the end might help? That looks to have turned out pretty well.
     
  8. Jul 2, 2017 #7

    berkeman

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  9. Jul 2, 2017 #8

    Borek

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    Hardly, it is what is below the copper that is important.

    There are definitely techniques that allow electrolytic deposition of copper on many materials (I remember reading about recipes using conductive graphite coating), perhaps some of them are based on special inks, but I doubt they will be cheaper. Besides, after using them you will have to get rid of the excess electrolyte, which has very similar composition to that of the used etchant.
     
  10. Jul 4, 2017 #9

    Tom.G

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    For small and very simple boards you can use copperclad board and isolate the traces using a handheld rotary cutting tool such as:
    https://www.dremel.com/en_US/tools/-/search-tools/find-by-category/27343/rotary.

    It does take a little practice. Clamp the copperclad so it won't move and hold the rotary tool with both hands resting on the table-top. I used cut-off abrasive discs in the tool, seemed to have better control than with the other tool bits available. I have heard of others using a drill press. You can put an end mill in it and mill around the traces that way. (Sort of a manually operated milling machine.:wink:)

    I did the layout on the computer and printed a mirror image on ordinary paper with a Laser printer. If your software allows it, marking just the edges of traces works fairly well and you don't have to clean excess toner off the copperclad before soldering.

    I used the wifes' clothes iron to transfer the pattern to the copperclad. Put the copperclad on a solid surface and wrap the paper pattern around two edges and tape it in place. The iron has to be fairly hot, the printer fuser runs about 430°F and paper ignites at 451°F. I don't know the actual melting point of the toner.

    If you need a Ground plane, connect all the excess copper together.
     
  11. Jul 4, 2017 #10

    Borek

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    That's basically how the thermotransfer works and how the board above was prepared, trick is - one you have the toner on the copper it is much easier to etch, than to use dremel. I am using iron set to just above two dots (a bit hotter than for cotton) and I am heating the PCB directly, then it is enough to put the printout for the toner to be transferred (bit of pressing and massaging through some kind of cloth helps). If the paper is well selected (a thin, coated one works best, not your standard printer paper) it is pretty easy to remove it with a bath made of a washing liquid (no idea about the proportions I am using, but it is way more concentrated than what is used just for washing).

    Plenty of DIY tutorials on the web.
     
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