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Ferric chloride is a traditional home-use circuit board etchant. It's easy enough to come by, and the Ferric by itself is no big environmental problem. However, once you've etched a board with it, you're left with a solution with a bunch of copper chloride in it. This dissolved copper is an environmental problem, and you can't just pour it down the drain (legally) -- you're supposed to take it to a hazardous waste facility. (For instance: How to Dispose of Ferric Chloride in this FAQ. )
Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)
I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)
But how're you going to get CCiAHAS? Conveniently enough, by starting out with a simple two-ingredient starter etchant, and doing a bunch of etching.
Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)
I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)
But how're you going to get CCiAHAS? Conveniently enough, by starting out with a simple two-ingredient starter etchant, and doing a bunch of etching.
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Signing UpStep 1Ingredients: The Starter Etchant
For the starter etchant itself, you only need two ingredients: hydrochloric acid and hydrogen peroxide.
(OK, actually three. But the third one's copper. See the chemistry section for an explanation.)
Hydrochloric (muriatic acid, "pool acid", etc.) is available at a hardware store. The acid I got is 31.45% (or 10M) and should run around $5 per gallon. Which is more than you'll ever, ever need.
The peroxide is normal 3% for mouthwash or cleaning cuts, and can be bought at a drug store for $2-3 for a big bottle.
You'll also need a non-metallic container that fits your PCB and two standardized measuring cups.
As long as you're in the hardware store, pick up some acetone if you don't already have some. It's useful for removing the etch resist. (That's for another instructable.)
(OK, actually three. But the third one's copper. See the chemistry section for an explanation.)
Hydrochloric (muriatic acid, "pool acid", etc.) is available at a hardware store. The acid I got is 31.45% (or 10M) and should run around $5 per gallon. Which is more than you'll ever, ever need.
The peroxide is normal 3% for mouthwash or cleaning cuts, and can be bought at a drug store for $2-3 for a big bottle.
You'll also need a non-metallic container that fits your PCB and two standardized measuring cups.
As long as you're in the hardware store, pick up some acetone if you don't already have some. It's useful for removing the etch resist. (That's for another instructable.)
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I make the solution and put my copper (2X2 inch piece) in and it goes to town. First piece almost had to throw away because it was in there for about 20 minutes and almost etched all the way through. Worked great. I have it in a tupperware type container. Next day I went to etch another piece and nothing.... not even a little bubble. I let it sit for several hours and got the tiniest etch on it. Am I not storing the solution correctly or something?
Thanks and awesome instructable.
It's a well known fact in the industry.
Try using lab grade HCL and see if the iron free HCL works as well - - there may be an exchange principle involving iron in the reaction.
Excellent tips, tried it and etched a few boards with very good results and this could be the answer to my problem of now having to get Ferric Chloride (crystal form) by mail order in my locality.
Just one thing someone may be able to clear up for me though.
Adding the peroxide to my HCl which is 280-300g/litre makes the etchant dark brown so there's no way to assess the 'green-ness' of the mix. Tried with 2 different concentrations of standard hardware store acid with the same result but the etchant certainly does its job well so my only way of checking its state would be via specific gravity and ph. No amount of aeration with an air pump and a porous stone makes any difference to the colour or clarity.
Is there iron or some other contaminant in my HCl?
(Both the acid and the 6% peroxide appear perfectly clear & clean prior to mixing)
Also did some sample tests in test tubes with the resulting brown colour starting to develop from just a single drop of peroxide in 10ml of HCl.
Also, I've read that a very quick dip into etchant cleans it really good. I haven't tried that, but i do know that copper turns pink pretty fast after I put it into etchant (I think pink means it's REALLY clean).
I don't know what would help the toner adhere more though: the extreme clean of an etchant dip, or the added surface area from scuffing....???
Anyway... if you do scuff it, MAKE SURE YOU CLEAN THE LEFTOVER DUST really good!
I rub it till it shines really good.
Also I do the same to remove the toner i used to print the layout to the PCB.
thanx.. i ll try it
BTDT, got the acid-washed t-shirt.
Jim
The aluminum is sacrificed to aluminum chloride and the copper is precipitated out as pure copper powder. Filter out, rinse clean and dry. Recycle at nearly $4 a pound.
Hey! At least the spent etchant is now disposable.
http://en.wikipedia.org/wiki/Acetone_peroxide
Almoast 2 months of trying, I have dozens of failed ones laying here but finally I made a pcb that should work.
My times are extremely long!
30 minutes lighting (blacklight)
two hours developing (very strong solution of NaSiO4 (google says I should just dip it in there for a couple of seconds.... no)
And finally 1,5 to 2 hours etching. (for a small board, so not the 2 minutes like this tutorial the concentration was 23% HCL )
Also it etched unevenly , some parts are nice and some parts I had to scrape off copper and in other parts the traces were beginning to etch away...
(next time I will try that printer method)
Don't get me wrong, I'm very pleased that it worked now, but has anyone an Idea what I'm doing wrong?
It might still be poisonous, though.
cheers,
jm
Careful not to mix all 3, unless you're attempting to make unstable high explosives (Acetone peroxide http://en.wikipedia.org/wiki/Acetone_peroxide).
It's dangerous enough when you're attempting to make it, I wouldn't want anyone to accidentally make some and dry out the crystals, or store it in a container with a screw on top (The crystals will sublime, and recrystalize in the threads on the container. Unscrewing it will break the crystals and detonate. One person on internet forums has died this way).
Besides that, I'll be using this method from now on. I already have the peroxide and acid and acetone from...other projects *Wink*
Political note: The only thing to negotiate with terrorists is whether they will be SHOT, HUNG or BEHEADED when captured.
Thanks for the heads-up.
As for this instructable: the acetone is for cleaning off the etch-resist toner plastic after the board has been rinsed in water (very well!) so there's no risk of mixing it in with the etchant and making anything explosive by accident.
(Obligatory safety notes here: If you're cleaning stuff up with acetone, don't do it around fire -- the fumes are flammable. Concentrated HCl is bad for your skin, so don't spill it or inhale the fumes. 3% peroxide is good for your gums, and can help with gingivitis if you gargle for 30 sec.)
Because over here 23% is about the highest concentration easily accessible.
And I've tried the H2O2 / HCl ratio's 1/1 ; 2/1 ; 2/2. with little or no effect.
Then I have tried the vinegar method someone supposed here. With 80% vinegar. And the same ratios.
With vinegar it worked better (read "less worse") because the parts of copper wich should dissolve turned bright green. (it atcually looks very beautifull bit it is not really what I want)
This afternoon, I will try the same with battery acid 30-ish% H2SO4
If you've got 23% HCl, it should work fine either as-is, or with a 2:3 acid/H2O2 ratio.
I would _not_ substitute another acid unless you're sure-sure what you're doing.