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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 found I had really long etch times until I added the bubbler. Even with a temp of about 110 F it would take hours. When I built the bubbler I started getting good results consistently.
P.S.
Try putting a penny in some solution, it's pretty strange.
You can scratch through the coating on pads with your soldering iron tip and add solder or just use alcohol and a cotton swab to clear the pads.
I have an old ceramic toilet tank and lid in my back yard for this purpose. The tank lid sits on the ground, I put the acid bottle on it, then put the tank upside down on top as a cover. The flush hole and bolt holes provide some ventilation and the ceramic tank protects the plastic bottle from deterioration due to sunlight.
A 5-gallon plastic paint bucket and lid will work as well, except that the plastic will gradually embrittle with exposure to sunlight and will have to be replaced from time to time.
I have been playing around with this etchant as I have used ferric chloride in the past and it stains and is a pain to dispose of (properly). I mix up the Peroxide (3% Drug store version) and Muriatic acid (Dynamic Paint Products, no %info on bottle). The Muriatic acid definitely fumes when you open the bottle so it's strong.
I mix at 2:1 Peroxide to HCL and it etches the first boards just fine (just a couple minutes). The resulting solution is a light green and after a couple boards the colour doesn't change much and it pretty much seems to stop etching. I didn't see if it took 8 hours but after 30 min there was still copper.
I too am trying to figure out what may be going wrong. I tried adding more HCL to the bath and it didn't seem to do anything so I added some peroxide to match the HCL I added but no result (in the 30 min I had the board in). My etchant never gets that dark green/brown I see in your images. Any advice or tips?
Thanks!
1. i polish it witch some polishing paste, dont forget edges
2. clean the result with some alcohol or similiar to remove the paste and any smear (fingerprints), this can protect copper from etching away too, best thing is to use gloves from this point. dont touch the copper board with your hands
if it's polished and clean, its ready to be sprayed with photoresist or for hand drawing ...
i do all of this and i dont have problems, i use FeCl3
To me the plain HCL and peroxide solution seems useless unless you're just going to use it for one day. It won't last any time at all in this form. You can't store it in an airtight container because it will explode due to pressure building (a caution many people seem to forget on pages like this). You can't add more peroxide (or acid) to rejuvenate the solution because you're adding mostly water when you do this so it just makes things worse each time you do it. I can't figure out why people think it's so great. Maybe they're just using it once or I'm doing something horribly wrong.
I think the "end" solution of cupric chloride is the only proper thing that will last. I'm in the process of trying to make this but it's slow going and difficult to manage. What I did was use the same 1 part acid to 2 parts peroxide and then immediately start dissolving a specific amount of copper based loosely on the formulas on that other page (Adam's stuff; he doesn't say how to do it with peroxide) with a bubbler in the tank. After a couple of days I still have a little copper left and my solution is turning brown. My specific gravity is somewhat low so I'm hoping evaporation will improve that. Not sure where to go from here. I don't know what my acid level is so I don't know if I should wait a while longer and hope it greens up with the bubbler or if I should add more acid (that will reduce my specific gravity even more, not desirable). The hardest part of this seems to be figuring out if you need more oxygen or if the solution is out of acid because you can't tell from the color of the solution alone. I wish a simple pH test would work for the acid test, the titration procedure seems like a lot of hassle if you don't have lab equipment.
Just an update on my original solution. Once all the solid copper was gone it almost immediately turned green. I added more acid and did the titration test. I'm currently at 3 M acid (perfect) and specific gravity of 1.2 (too much water from my initial peroxide, for sure).
What is the concentration of your acid? Is the peroxide fresh?
At this point, there's only two ingredients, so that makes troubleshooting easy....
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.