Curpric Chloride Etchant?

[Wolfman29]

Hey everyone.

I have been etching PCBs lately to make various circuits (fun, interesting, and useful), and I have stumbled upon this:
Stop using Ferric Chloride etchant! (A better etching solution.)

It seems likes it's a good idea and easy to use - essentially, use a normal HCl:2*H2O2 etchant and etch copper into it (quick process) and then it will produce a *new* etchant.

I tried that, and I am left with a cyan-blue solution that doesn't seem to want to etch my PCBs... I've had a PCB sitting in the solution for over 40 minutes now and it doesn't look like it has reduced the copper at all... does anyone know what could be going wrong?

EDIT: Alright, problem solved. It's starting to etch. I guess it's just a really, REALLY slow process, which is fine, if it actually is regenerative, which it should be. Good stuff!

Let this be a lesson to those who like etching!

 

[Benm]

I have used this process in the past, and its very effective. It does help to heat at agitate the etchant however. Instrucables lists a mixture of 2 parts 3% H2O2 to 1 part 30% HCl, which results in a final concentration of 2% H2O2 and 10% HCl, which is on the low side. If possible, up the H2O2 concentration (try finding 10 or 30% H2O2) to a final concentration of 4 to 5%.

Also, the process needs some copper ions to work. You can use a bit of spent etchant and mix that in with a new batch to expedite the process. If you are stating from scrach, i'd suggest tossing in some braided copper wire or copper shavings, and let those etc away before you start on useful PCBs.

 

[Wolfman29]

Hmm. Interesting. Good thing that it's 110 degrees outside (I just leave it outside on the counter and check it every 10-15 minutes). I will look into more concentrated H2O2 though.

Regarding the copper ions - it's interesting, because the initial solution, HCL + H2O2, is an incredibly fast etchant. So the copper ions are already there

 

[Flaminpyro]

I wonder if there is a way to remove the copper from the solution, maybe with electrolysis so as not to pollute the environment when disposing of the spent solution.
And if the copper is removed maybe there would be no need to get rid of it, maybe just top it off with a bit of fresh chems.

 

[Wolfman29]

Well, interestingly enough, this method is regeneratable because the copper is *used* in the etchant (the cupric chloride is the etchant).

 

[Benm]

The copper -does- accumulate in the solution, as CuCl2. This is not really a problem though, since it is very soluble in water (over a pound a liter), so you can etch a huge amount of copper away using a small volume of etchant. Once it becomes saturated you should drop it off at a collection point for domestic chemical waste.

PCB's are usually covered with 1 oz/ft2 of copper, so even if you completely etch all of that away, it would take something like a square meter of pcb to saturate a liter of etchant.

The other end of the equation is the water/HCl/H2O2 balance. You can regenerate the bath by adding H2O2 and HCl solution when required, but this will increase the total volume. On the other hand, some of the water evaporates from the solution (especially if you regenerate by bubbling air through).

All in all it IS a very clean process, especially compared to using Fe(III) chloride, which leaves you with a murky etching solution with some copper in it, and the iron chloride can form chuncks etc.

 

[qumefox]

I thought this mixture was supposed to turn green, not blue?

 

[Wolfman29]

I thought it was too! I guess I haven't dissolved enough copper in it yet?

 

[qumefox]

Might be using the wrong chemicals. The copper itself is what's green. the h2o2 and the HCL will both be clear. There shouldn't be anything to turn blue.

It should go from clear to green.

 

[Wolfman29]

Certainly not using the wrong chemicals.... It's not necessarily blue. It's more of an aqua color. It may be a really watered down green that it's supposed to turn... I will try dissolving some copper in it tomorrow and just leaving it to sit and absorb some more copper.

 

[qumefox]

Possibly.

Also, wasn't it you that was wanting a howto on photo transfer PCB creation?

How to make a printed circuit board (PCB) using the UV light LED method.

 

[Wolfman29]

Yes, that was me! Thanks for the link - I will take a look into it. Hey, did you manage to get those lens shipped off? Or gonna ship 'em Monday?

P.S. How's your hand?

 

[qumefox]

They're in the envelope, they'll go out in the morning and you'll probably get them wed.

And my hand hurts. Actually worse than it did yesterday.

 

[Wolfman29]

Great! And I'm sorry to hear that.

So I took a look at that instructables... it doesn't seem that bad, just seems like a lot of money/time is invested in order to get results that I can pretty easily get with the toner/acid method.

 

[ShortyInCanada]

If you allow all the fluid to evaporate and you harvested the copper chloride crystals you could use them for fun in any flame to turn it green. It is the main colorant in many pyrotechnics for green or even blue. (I would love to get my hands on all that I could.)

You could also just mix the crystals back into a bit of water and then soak some dried wood in it for a few days, let the wood dry out again, and when you throw a piece or two on a campfire everyone starts going "Oooooo" and "Aaaaaaa" as the green flames start showing.
Then you can make up some crazy story about how you used a green laser on the wood for hours before bringing it or something equally rediculous. Just keep a straight face.
Then use a red laser in the smoke and claim it's better because the flames were green......
Let all the witnesses tell the stories afterwards...:crackup:
That's the kind of thing I do.

 

[Wolfman29]

HAHAHAHAHAHAHAHA.

THAT'S BRILLIANT!

Totally gonna do that if I get the chance