Etching with Muriatic Acid and Hydrogen Peroxide

[billstein]

Hi all. Just tried etching with Muriatic Acid and Hydrogen Peroxide using a 1 to 1 ratio and its taking forever. Much longer than Ferric Chloride. Is there any way to speed up the process? Would heating it up a bit first help?

Some details that might help. The copper clad is 1 oz. Its been in there for over 30 minutes and looks like its about 50% finished. Is this normal?

[Guitarmageddon]

It depends on the strength of the hydrogen peroxide, usually it's only 3-5%. I get 30% from my pharmacist, but it's very dangerous stuff.
Here's the link that got me started:
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/
Constant agitation really helps, but watch out for the fumes and splashes on your hands, or worse, in your eyes.

[rullywowr]

I use a 2 part h202 to one part acid.  And yes, heating the solution helps.  I use a warm water bowl which I carefully float the etching bowl into. 

[madbean]

Are you sure you have 1oz copper? A 1:1 ratio should etch a few boards between 5 and 10 minutes.

[Gledison]

Check if your H2O2 is still ok! ( put in a wound and see if still bubbling )
You can also try to add a bit more of h2O2 to your etching solution!
Using a higher concentraion of peroxide is dangerous and you have to be very carefull!
Happy etching

[billstein]

Are you sure you have 1oz copper? A 1:1 ratio should etch a few boards between 5 and 10 minutes.

It is 1 ounce for sure. Last night was a bit cold and I was out in the garage. I'll try warming it up first and see if that helps.

I was concerned about it sitting to long and etching into the traces at spots but it turned out fine, so I guess it's no big deal.

[gtr2]

I've had this same problem.

My theory is that some of the newer "safer" muratic acid that they sell at the big box stores do not work as well.  Also some hydrogen peroxides contain phosphoric acid.  Not sure if that matters either.

But the mix that doesn't work well on copper clad can pretty much disintegrate an aluminum enclosure in a few minutes...

I'm definitely not a chemist but I think some of the inert ingredients in some of the products cause the solution to not work as well on copper.

[billstein]

I've had this same problem.

My theory is that some of the newer "safer" muratic acid that they sell at the big box stores do not work as well.  Also some hydrogen peroxides contain phosphoric acid.  Not sure if that matters either.

But the mix that doesn't work well on copper clad can pretty much disintegrate an aluminum enclosure in a few minutes...

I'm definitely not a chemist but I think some of the inert ingredients in some of the products cause the solution to not work as well on copper.

I did use the safer muriatic acid and was wondering if that had anything to do with it.

[peterc]

I heard about this combination and how quick it was, couldn't wait to try it.

I went through this same process as you, carefully measuring quantities, getting the right concentration of H2O2, etc.

Took absolute ages. Then I found a webpage (unfortunately gone) about a guy who built his own 737 cockpit to fly in conjunction with MS Flight Sim and who had to etch his own PCBs, and the solution was really simple.

Get the etch going as above, and then slowly add H2O2 until you see a sudden change in the surface of the copper. It is almost like a clear circle emerging outwards and the PCB, and the etch really starts happening. Sometimes I only pour a little H2O2 in and other times what feels like quite a lot, but the boards etches really quickly, almost before your eyes.

I battled for years with Ferric Chloride and other etchants, this was quite amazing for me. I don't heat the solution at all.

Good luck.

[Gledison]

I've had this same problem.

My theory is that some of the newer "safer" muratic acid that they sell at the big box stores do not work as well.  Also some hydrogen peroxides contain phosphoric acid.  Not sure if that matters either.

But the mix that doesn't work well on copper clad can pretty much disintegrate an aluminum enclosure in a few minutes...

I'm definitely not a chemist but I think some of the inert ingredients in some of the products cause the solution to not work as well on copper.

Hey mate,
You can try sulfuric acid instead of hydrochloric acid! 3:1 hydrogen peroxide!
The best would be to use a 30% hydrogen peroxide solution BUT you have to be carefull! You need to create a steong oxidant solution and higher the concentration quicker the etch!
Im still on ferric chloride and quite happy with it. Just heat it up a bit on a hot water bath and the etching takes 15 min..
Cheers

[rullywowr]

I heard about this combination and how quick it was, couldn't wait to try it.

I went through this same process as you, carefully measuring quantities, getting the right concentration of H2O2, etc.

Took absolute ages. Then I found a webpage (unfortunately gone) about a guy who built his own 737 cockpit to fly in conjunction with MS Flight Sim and who had to etch his own PCBs, and the solution was really simple.

Get the etch going as above, and then slowly add H2O2 until you see a sudden change in the surface of the copper. It is almost like a clear circle emerging outwards and the PCB, and the etch really starts happening. Sometimes I only pour a little H2O2 in and other times what feels like quite a lot, but the boards etches really quickly, almost before your eyes.

I battled for years with Ferric Chloride and other etchants, this was quite amazing for me. I don't heat the solution at all.

Good luck.

This is great info.  I usually start with a 2part H2O2 to 1 part Muriatic Acid.  If the etch solution isn't working well, just add more H2O2. 

Also, in the states we have two national hardware stores...Lowe's and Home Depot.  I forget which one, but one store only carries the "safer" muriatic acid (which doesn't work as well as the regular "non-safe").  A gallon of acid will last you for many, many etches and hydrogen peroxide is readily available anywhere.

I also highly recommend floating your plastic etch container in another plastic container of hot water which really speeds up the etch.  About 5 minutes (10 min max) seems to do the trick.  Gently swish it from side to side to move the liquid around.  Just please be safe, wear safety glasses, do it outside in a well ventilated area, and don't breathe the fumes.

[croquet hoop]

If the etch solution isn't working well, just add more H2O2.

That would be the best thing to do. What activates the acid is the oxygen; not enough oxygen = slow action. But the more you add H2O2, the more you dilute the muriatic acid (this is why the stronger 30% hydrogen peroxide is better), so you have to find a balance. I read that some people just "add oxygen" by letting the acid container open for a while, but it may be worth a try (provided there is no child or pet around).

[sdlogan9]

I am going to try to make some of this stuff!

[irmcdermott]

Just be sure to do it in a well ventilated area. I'd also recommend wearing some sort of mask when handling the HCl, it tends to fume up when you first open it, and doesn't feel too great in the nose.

[m-Kresol]

I've had this same problem.

My theory is that some of the newer "safer" muratic acid that they sell at the big box stores do not work as well.  Also some hydrogen peroxides contain phosphoric acid.  Not sure if that matters either.

But the mix that doesn't work well on copper clad can pretty much disintegrate an aluminum enclosure in a few minutes...

I'm definitely not a chemist but I think some of the inert ingredients in some of the products cause the solution to not work as well on copper.

Hey mate,
You can try sulfuric acid instead of hydrochloric acid! 3:1 hydrogen peroxide!
The best would be to use a 30% hydrogen peroxide solution BUT you have to be carefull! You need to create a steong oxidant solution and higher the concentration quicker the etch!
Im still on ferric chloride and quite happy with it. Just heat it up a bit on a hot water bath and the etching takes 15 min..
Cheers

Sorry to jump on the train so late (didn't see the thread in December), but I have to intervene here! DO NOT EVER, EVER, EVER mix sulfuric acid with hydrogen peroxide, especially in their concentrated forms! This stuff is for professionals only and we hardly ever use it! It forms peroxodisulfuric acid, which is also called Piranha solution. It is one of the most aggressive acids I know of and I only use it to clean porous glass filters, if nothing else does the job.
This stuff forms EXPLOSIVE compounds (I know of some rather unpleasant accidents), so please DO NOT use this stuff. If anything, it will also eat your protective coating (photoresist or toner transfer) and possibly your epoxy substrate.

As for hydrochloric acid (muriatic acid) with H2O2, I also have to advise you to work with safety goggles, gloves and in a well ventilated area! You will form chlorine gas, which is toxic (gives nice lung edema) and also a strung oxidizing agent. I only used ironchloride so far and that has done the trick for me. If you really want to use muriatic acid and H2O2, just dose enough of the peroxide so you see a reaction going on. For your own safety, I recommend not taking to much of it.