Etching with HCl and H2O2 problems - any chemists in the house?

[nobodysweasel]

So I've been trying to use the method for making Copper Chloride etchant using this method: http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/.  I've made two batches with the same (bad) results both times.  I've done everything exactly like the instructions say - 2 parts 3% hydrogen peroxide to 1 part HCL (~31%).  I've checked my bottles several times and there's nothing funny in there.  The first boards etch wonderfully and the solution turns green.  Both times I've waited a few weeks until I'm ready to etch again (keeping the etchant in a sealed plastic container).  And when I do, it doesn't work at all.  Within 5-10 minutes my copper turns sort of reddish and after that nothing changes.  The first time I tried this I left the board in for 24 hours out of curiosity and it looked exactly the same as it did after 5 minutes.  I've tried adding more acid.  I've tried adding more hydrogen peroxide.  I make sure to agitate the solution while I'm trying to etch.  Nothing works.  And it's been exactly the same twice now.  Does anyone have any thoughts on what's going wrong here?  I was really hopeful about this, and I'd like to avoid going back to Ferric Chloride if I can manage it.  Thanks in advance.

For reference, here is what's happening to my boards.  The top is after about an hour in the solution (looks like this after about 5 minutes) and the bottom is untouched copper clad for comparison:


And here's what my etchant looks like.  Green as can be:


(Sorry for the bad picture quality.  Webcam and all.)

[kingswayguitar]

Sorry to hear about your frustrating results.  This is the method I use and it works well for me.  After three batches I mix an entirely new solution.  And batch 2 and 3 take progressively longer, about 30-40 minutes by the time I get to batch 3 (very green).  Between each batch I juice it up with some additional peroxide (never measured it but probably 1/4 to 1/3 of the total volume).  And it definitely needs to be warm, even warmer than room temp especially by the third batch.  My house is cool in the winter (about 70F or 18C) and I can't get it going without heating it at that temp.

I never found additional hcl helped unless i also added more peroxide, and peroxide on its own was good enough to juice it up.  I'm no chemist but experimented lots with this.

You say the copper turns reddish, I would suspect some unwanted contaminant is reacting with your stuff??  Again, not a chemist, take my comments with a grain of salt.

When you seal the container between etches, does it build up effervesence/pressure?  When I release my cap again after a while there is internal pressure built up.

good luck

[R O Tiree]

Hydrogen peroxide reduces to water and oxygen under the influence of UV light. Since it's in a UV-transparent container, this is why you're finding that your etchant doesn't work after a few weeks, I think.

[bukas]

i etch my boards using HCl and H2O2 but i don't reuse my mixture which is HCl 7/10 H2O2 2.5/10 and water 0.5/10 ( this ratio is very rough ). reason for that are prices 0.5e for 1l of HCl 12% and 1e max for 300ml H2O2 12%. enough to etch about 10 pedal boards...

[kingswayguitar]

Hydrogen peroxide reduces to water and oxygen under the influence of UV light. Since it's in a UV-transparent container, this is why you're finding that your etchant doesn't work after a few weeks, I think.

Ahhhhhhhh!!!!!!!!!!!!!!

Thanks for that advice.  I store my mix in used peroxide containers (solid brown) so no UV there.  But while I'm working it's all exposed.

[jdub]

I've found that using a high-concentration H2O2 makes a huge difference- I use this stuff http://www.sallybeauty.com/on/demandware.store/Sites-SA-Site/default/Product-Show?pid=SBS-760625&dwvar_SBS-760625_webSize=16.0000+OZ, which is 40% and has to be gotten in a beauty supply shop, since your local drugstore probably won't have concentrations that high.  I've been reusing the same mixture I made up nearly 6 months ago simply by adding a bit more this stuff (not too much- maybe an eighth of a cup, give or take?)- mix it up and once it gets going it'll etch a board in less than 5 minutes, and agitating makes it go even faster.  I should note that every so often you have to add a little more HCl to keep the levels correct- how often depends on how much etching you do.  Also, you have to be careful because apparently overdoing the peroxide can produce chlorine gas, so proper ventilation is a must.  I also warm up the solution when etching by putting some hot water in a small plastic tub and setting my (smaller) etching container in that- seems to help. 

[John Lyons]

Just add in a little more of each when you go to etch.
Add them in the same ratio as the initial solution.
Pour enough of the old solution into your container to cover your board(s)
and then add in some fresh peroxide and acid. It takes a little longer than a
fresh batch but this will recharge your old solution.

Temperature does not matter as far as I have found. I etch in 30 degree+/- weather
all winter, snow and ice ! Works the same as in summer when it's 80 degrees ish.
I keep my old solution in clear juice bottles. Not sure about the UV issue...

[nobodysweasel]

Thanks for the great replies.  I'm still not totally sure where to go with this, but I have some ideas.  I've been searching online and I'm starting to suspect that I'm making Copper(I) oxide (wikipedia article here:http://en.wikipedia.org/wiki/Copper%28I%29_oxide).  It is red and is the product of Cu and O2.  I suspect that since I'm leaving the bottle near a window when not in use, UV radiation is converting the H2O2 into water and O2.  Since it's a closed container I'm getting lots of dissolved oxygen in solution and creating oxidizing conditions, which just converts the copper on the surface to Copper(I) oxide and prevents the whole thing from etching.  I'd ruled out oxidation before because copper oxidizes green (like old pennies and the statue of liberty), but I didn't know about Copper (I) oxide which can be red.  Anyway, now I have a hypothesis and it should be easy to test.  I'll mix up a new batch and keep it in a closed closet between etching and see how that goes.  Hopefully I'll get better results this time....

[bukas]

H2O2 has job to oxidase copper, HCls job is to remove oxidased copper from board. you can notice this when you place your board in pure HCl, it will become light colored.

if your boards only gets oxidased ( get dark red) it means mixture needs more HCl, and dont forget to stir xD

btw what do you use to draw connections ?

[CodeMonk]

I also don't reuse batches, but for me the supplies are cheap.
I use a 3/2 mix of 30% Muratic acid and 3% H202
Roughly $10 for a gallon of etchant.
I also use this :



Hooked up to an aquarium pump that puts out 2,200cc per minute.
The pump I have has two outputs so I hooked them both up.
I get a really nice bubbling going on with this setup.
Etches a double sided board in about 5 minutes.

The black material is a piece of hard rubber I got from the padding that goes in the bottom of a horse trailer.
Drill a bunch of holes and good to go.
I added another batch of holes and stuck some bits of plastic toothpicks in them to support the board.
I only fill it up enough to just barely cover the board.

The little container its in previously held some potato salad I got at walmart.


Edit:
Drilling the rubber:
I start by drilling holes from the side, all the way through in one direction (starting from where the hoses go in).
Then one the top.
Then from the other sides to form a matrix, then drill the little holes.
And finally seal the holes I drilled on the sides with hot glue.