EEVblog #1197 - DIY PCB Etching With Water

[asgard]

Okay, better way to concentrate ferrous solutes from tap water:

1. use a conic separation funnel with a good stopcock ($30.45 USD at Amazon).
2. Fill with your tap water and mount at least one good neodymium magnet near the bottom .
3. Leave the stopcock closed and let the water evaporate out the top.
4. Refill as desired until complete, and again at the very last time of the period.
5. You will get higher concentrations of all dissolved salts that occur at the outflow of your water treatment plant.  I do not know the ambient water hardness figures in Sydney, but it surely cannot be worse than the waters here in the far upper Sacramento River valley area (Redding).

I think you will get reagent contamination primarily from Mg and Cu salts.  The copper is most concerning as that will affect the reaction rates of the FeCl3 + Cl case.

[Brumby]

I like the evaporative method myself, but it is rather slow.

I do not know the ambient water hardness figures in Sydney, but it surely cannot be worse than the waters here in the far upper Sacramento River valley area (Redding).

Sydney's water hardness is pretty good.

If you want hard water, go to Adelaide.  Their water is so hard they only mix sand and aggregate with it when making concrete.

[Mike Warren]

I thought everyone knew this technique.

Homeopathic PCB etching.

[kosine]

Seems that in principle the idea isn't that crazy.

I tried a very dilute ferric chloride solution last night (maybe around 2-3%), and the copper had all been etched away when I checked this morning. (Water was cold, not heated.)

Might be an interesting follow-up experiment to see just how dilute you can go. <1% might even work since the total amount of copper being removed is tiny. A comparable amount of FeCl3 might be all it takes.

I'm trying it again with just a few drops.

[orion242]

Found adding a few grams of graphene per ounce of water dramatically sped up etching.   Still nothing to write home about over the standard methods.

[coppercone2]

Seems that in principle the idea isn't that crazy.

I tried a very dilute ferric chloride solution last night (maybe around 2-3%), and the copper had all been etched away when I checked this morning. (Water was cold, not heated.)

Might be an interesting follow-up experiment to see just how dilute you can go. <1% might even work since the total amount of copper being removed is tiny. A comparable amount of FeCl3 might be all it takes.

I'm trying it again with just a few drops.

i think you get more undercutting if its slow?

[kosine]

i think you get more undercutting if its slow?

That did cross my mind. I haven't tried masking off anything yet, just curious about the minimum concentration. Probably not going to be a great technique for tiny traces, but maybe try that experiment next.

Current few-drops test is actually looking promising. Only been a few hours but the copper has turned quite brown already, so something is happening. Will see what happens over night.

[AlfBaz]

I take iron supplements and do laps every day in a chlorinated swimming pool so I decided to try it with my urine.
Turns out I don't even need magnets

[wilfred]

I take iron supplements and do laps every day in a chlorinated swimming pool so I decided to try it with my urine.
Turns out I don't even need magnets

OK, now I know you're just taking the piss.

[Brumby]

(Gotta pay that one )

[kosine]

Took nearly a week but amazingly it worked!

A little over 50g of water with under 0.5g of etchant solution at around 10C. Bottle doesn't state the concentration, but probably about 30% ferric chloride. So roughly we're down to around 0.25% or 2500ppm.

[Psi]

Sometimes if you see a house with copper spouting/guttering and there's a spot where water is leaking out and then down the side of the house you will notice that area is cleaner and free from any mold spots.
I'm pretty sure the rainwater is getting some tiny amount of copper salts dissolved into it as it comes into contact with the copper. Then this is acting as a fungicide as it runs down the side of the house.

Even at super low concentrations chemical reactions still occur, they just take super long