"New" PCB etching method

[$uperpuma]

basically he strung up his boards with fishing wire and suspended them in a mason jar of etchant....it works very well. just give them a shake every now and then and the excess copper flakes right off to the bottom.

[bside2234]

I don't use a fish tank powerhead. I use a fish tank air pump hooked up to a fish tank Bubble Bar suction cupped on the bottom of a tall Tupperware canister. It agitates the water really well and there are no metal/magnetic motor parts submersed in the chemical.

[~arph]

I have no idea whether it could etch enclosures... That is something I would like to find out though! If there is anyone else here that knows a little about their chemicals, please shed some light.

I don't know about the chemicals, but I did try etching an aluminium (hammond) enclosure using Amonium Persulfate.. I had the enclosure in the solution for about two full hours. All that happened was that the little bit of dissolved copper in the solution from a previous pcb etch actually plated on the aluminium. ( rubs right off though ). No etching whatsoever. So in short. No you can not use Amonium Persulfate to etch aluminium Hammond boxes.

[studiostud]

Just an update to this thread... I recently got curious about the HCL/Peroxide etching method and whether or not it worked on enclosures.  I tried it on a piece of aluminum that was cut out of a soda can.  I figured if it was going to work, it shouldn't take much time to see results with that thin of metal.  But after 15 min or so, I saw absolutely zero difference.  So I think this method only works with copper and not aluminum.  Thought I'd throw that out there so someone else doesn't have to learn the hard way.   

[Gurner]

Since this thread's purpose seems to be about squeezing the last bit of life out of etchant, ok then to the chemists among you ...is there anyway to remove the etched copper from the ferric cholride by way of electrolysis?

Now I know bo diddley squat about chemistry, but it'd be useful if you could remove the copper from the ferric cholride after etching ....this ought to prolong it's strength?

[ralley]

Just an update to this thread... I recently got curious about the HCL/Peroxide etching method and whether or not it worked on enclosures.  I tried it on a piece of aluminum that was cut out of a soda can.  I figured if it was going to work, it shouldn't take much time to see results with that thin of metal.  But after 15 min or so, I saw absolutely zero difference.  So I think this method only works with copper and not aluminum. 

Nope, HCL/Peroxide works fine on aluminium - I've etched a couple of enclosures like that.  This was etched with it:



The reason it didn't work on a drink I suspect is because the aluminium there is actually plastic coated
Rob.

[phector2004]

Since this thread's purpose seems to be about squeezing the last bit of life out of etchant, ok then to the chemists among you ...is there anyway to remove the etched copper from the ferric cholride by way of electrolysis?

Now I know bo diddley squat about chemistry, but it'd be useful if you could remove the copper from the ferric cholride after etching ....this ought to prolong it's strength?

Not a chemist, but I'm supposed to know this stuff cold after all these years of academic torture and lashings

Pretty interesting reaction. Ferric chloride is a lewis acid. Water (H-O-H) normally dissociates into H⁺ and OH^- in equal parts, to a small degree. When you throw FeCl₃ in, it dissociates to Fe³⁺ and 3Cl^-. The Fe³⁺ ions then accept the already dissolved OH^- and drive the dissociation of water. You get a ton more H⁺ in the water which contributes to its acidity. The iron ions combine with hydroxide ions and make ferric hydroxide (Fe(OH)₃) and the copper gets eaten away by by the H⁺ and Cl^- (effectively HCl) ions in solution.

Which proves that HCl/Peroxide will etch aluminum 

As for removing the copper from the solution, I think it'll be relatively hard. But both Fe(OH)₃ and CuCl₂ have low solubilities (I THINK, with copper chloride considerably more soluble), so most will be sediment. You can try taking the iron out with a strong magnet (and gloves!!!) and then decant the solution to remove the copper, but I'm not sure how that'll work out. Doubt this'll "prolong" anything though as you're losing "useable" ions in the process...

Good luck if you decide to experiment, let us know how it goes!

[studiostud]

Both of you are absolutely.... RIGHT.    I tried again with the can and left it for a lot longer and actually, this time I used only HCL.  I didn't add any peroxide.  The HCL did eventually eat through the coating and when it, it basically just dissolved all the aluminum, even under the big sharpie letters I made for the test.  I assume it's just because the aluminum is so thin and because I didn't tape the back side so there was no reason it shouldn't have eaten under my sharpie...

[KazooMan]

I am a chemist, although I have spent the last 35+ years doing synthetic organic (pharmaceutical) work and my inorganic is a bit rusty.

You need to get an understanding of redox potentials to determine just wat will "dissolve" what.  Metals and metal salts will interact depending on their respective redox potentials.  When you stick a board with "elemental" copper (copper 'zero') into a bath containing ferric (iron +++) ions, the relative electron potentials are such that the copper will gladly transfer an electron to the Fe+++.  Thus we get Fe++ (and later on other oxidation states) and we get Cu+ and later Cu++ with soluble copper species.  The ferric chloride or sodium (ammonium) persulfate is oxidizing the copper zero into soluble copper salts.  Simultaneously, the ferric ions (or the persulfate) are being reduced.

As far as simple aluminum enclosures are concerned, either strong acid or base will attack them, resulting in etching.  Strong acid works quite well.  Just plain muriatic acid will do the trick.  The ferric chloride does seem to work faster.

[phector2004]

neat, I was trying to figure out how the HCl oxidized the copper just on its own (figured it used dissolved O2 making it horribly slow compared to HCl/H2O2). Didn't think of the Fe3+ oxidizing. Does the HCl play any role in Ferric Chloride etching?

[Taylor]

I have only ever used muriatic+peroxide to etch my boxes (and boards). After getting the technique down I can get excellent, deep etches with it in a short time. So I can say from experience that it works quite well.