Question about PCB etching with vinigar

[GhostGR]

Hi, i am planning on doing a project (an arduino severino 3) and i was looking for a safe way to etch the PCB. I stumbled on a solution that uses vinigar ,hydrogen peroxide and salt, but i could not find a solution that contains only hydrogen peroxide(and H2O) but i found this instead(Pictures attached).

It contains : Aqua(water),hydrogen peroxide(3.1%),alchohol denat, Etidronic Acid, Phosphoric acid, Disodium EDTA,phenacetin, Aloe* Barbadensis Leaf Juice Powder.

So my questions are:
1) Will this work ?
2) Is it safe ?
3) If it will not work, what etching solution can i use that is safe (i don't mind if it is slow), and if possible something easy to find in a supermarket.

Please excuse any orthographic or grammar mistakes english is not my main language.
Also sorry for the poor quality in the pics, it was because of the size limits.
-Thanks

[Aodhan145]

Whats wrong with good old fashioned ferric chloride? Its cheap, easy to get and etches nicely.

[GhostGR]

Whats wrong with good old fashioned ferric chloride? Its cheap, easy to get and etches nicely.

Yeah about that, it is not that easy to find in my country (Greece) and i can't make online purchases due to Capital Controls. Also i would like something a bit safer and easy to dispose.

-Thanks for your reply.

[Aodhan145]

Whats wrong with good old fashioned ferric chloride? Its cheap, easy to get and etches nicely.

Yeah about that, it is not that easy to find in my country (Greece) and i can't make online purchases due to Capital Controls. Also i would like something a bit safer and easy to dispose.

-Thanks for your reply.

Sorry I didn't see you were in Greece it must be difficult for you to source parts. With the safety issue, the chemical is only as safe as you handle it. What I mean is if you were gloves and goggles every time you handle it what can go wrong? I have got ferric chloride on my skin before but it has not caused any burns. Just respect the stuff and store it in a safe place and nothing should go wrong.

This uses HCl and hydrogen peroxide which should both be easily found in hardware shops or chemists etc.
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

[GhostGR]

Sorry I didn't see you were in Greece it must be difficult for you to source parts. With the safety issue, the chemical is only as safe as you handle it. What I mean is if you were gloves and goggles every time you handle it what can go wrong? I have got ferric chloride on my skin before but it has not caused any burns. Just respect the stuff and store it in a safe place and nothing should go wrong.

This uses HCl and hydrogen peroxide which should both be easily found in hardware shops or chemists etc.
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

Thanks for the link, i happen to have 2 bottles of HCL solution and its easy to find, but i don't know if the hydrogen peroxide i found will work because it isn't pure, it contains many other chemicals and im not sure if it will be safe to test.

Thank you for your help.

[IconicPCB]

hydrogen peroxide comes in various grades.
It is the main ingredient in hair bleaching products.

As a chemical  it is highly reactive and will discolor and burn the skin.. Talk to Your local cosmetics suppliers or manufacturers, you might get lucky and score some less adulterated peroxide.

[GhostGR]

hydrogen peroxide comes in various grades.
It is the main ingredient in hair bleaching products.

As a chemical  it is highly reactive and will discolor and burn the skin.. Talk to Your local cosmetics suppliers or manufacturers, you might get lucky and score some less adulterated peroxide.

Il ask around and see what i can find.
Thanks.

[Ian.M]

Air regenerated acid cupric chloride is probably your best choice.  You already have HCL.  All you need to get started is to dissolve enough copper in it, which you can do by oxidising (burning) fine stranded bare copper wire scrap to coat it woth black copper oxide and leaving it in the acid while bubbling air through it (or leave it a week or so in an open container).

See: https://wiki.london.hackspace.org.uk/w/images/1/1b/CuCl.pdf

[GhostGR]

Air regenerated acid cupric chloride is probably your best choice.  You already have HCL.  All you need to get started is to dissolve enough copper in it, which you can do by oxidising (burning) fine stranded bare copper wire scrap to coat it woth black copper oxide and leaving it in the acid while bubbling air through it (or leave it a week or so in an open container).

See: https://wiki.london.hackspace.org.uk/w/images/1/1b/CuCl.pdf

This looks interesting, i will try to see if i can do it with the vinegar and the H2O2,if not i might try this.
Thanks for the suggestion.

[sleemanj]

I have in the past used HCl and Sodium Percarbonate (aka Sodium Peroxyhydrate) which is the primary ingredient of many "whitening" laundry powders.

I'm afraid I don't have measurements, in my usual carelessfree style I just thought "yeah, probably about that".  I did do it outside naturally :-)

It's a while ago now, but from memory I dissolved about maybe 30g of the laundry powder in sufficient water to just accomplish that, maybe it was 75ml, something like that.  Once it was dissolved I put the PCB in HCl and added the dissolved solution. 

Sodium Percarbonate in water becomes Sodium Carbonate and Hydrogen Peroxide (it's sometimes called "solid hydrogen peroxide" because of this). 

Sodium Carbonate (Washing Soda) in the HCl produces (via Carbonic Acid) Carbon Dioxide, and especially because of potential laundry detergents in your powder it may result in some considerable initial foaming when you add the percarbonate solution to the HCl, so make sure your etching container has reasonably high sides just in case.

The complication of this is that of course the Sodium Carbonate also works to neutralise the HCl, so you will need sufficient acid that it's not fully neutralised by the sodium carbonate you are adding.

Of course, ideally, just get Hydrogen Peroxide and use that.  But if you're stuck on a desertGrecian island and all you have is HCl and laundry whitening powder, you might be able to get away with that :-)

NB: Vinegar is not strong enough to work with this, I've tried out of curiosity.

[DTJ]

Try to get some Ammonium Persulphate. It works well, is pretty cheap and is quite safe to use and dispose of.

[Ian.M]

The advantage of air regenerated acid cupric chloride is if you are going to be etching boards regularly.  Its waste product is more etchant and the only consumable apart from water is HCl. (though you do need a limited quantity of known concentration alkali for doing the titration to check the acid concentration).   This vastly eases responsible waste disposal.

[GhostGR]

In Greece you can not buy things with a visa card from abroad?

I have heard of people trying to make purchases from abroad with credit,debit and prepaid cards and it really is hit or miss. But the problem is to get any type of the aforementioned cards i need a bank account, when i tried to open one, the bank said i can't due to capital controls.

[GhostGR]

Thank you all for your contribution and your wonderful recommendations  , looks like i have a lot of options. Il ask around a local electronics forum and see if they know witch of these solutions is easy to find.

Thanks.

[DimitriP]

..and from the houshold cleaner aisle at the supermarket ....toilet bowl cleaner http://www.instructables.com/id/Etching-a-circuit-with-toilet-bowl-cleaner/
(just another way to get hydrogen chloride).

[TheAmmoniacal]

I use potassium peroxymonosulfate (CAS 70693-62-8), sold pure in 1 kg quantities at the pool supply store. Used to clarify the pool, prevent bacterial growth and algae. A topped teaspoon easily etches a small board, can take 15-20 minutes though at 50-60 C.

Also, no etchant is more or less "easy to dispose of", as the problem is the dissolved copper ions, not the oxidizer used.

All methods are safe, as they don't pose any harm to you.

[Ian.M]

Also, no etchant is more or less "easy to dispose of", as the problem is the dissolved copper ions, not the oxidizer used.

Most etchants are either disposable or have limited life ending when the copper concentration has become too high and/or the active etchant is exhausted.   Acid Cupric chloride is the only system where the waste copper becomes new etchant.  This does have the problem that the  etchant volume will grow as you re-balance the bath, so once you have enough on-hand for the largest board you want to
process, you do run into the disposal problem again.   

Even so, its not a major problem to precipitate out the copper - simply add an alkali or alkali earth metal carbonate till the solution stops fizzing, then add a slight excess and let the copper carbonate settle out.  You can use crushed natural chalk or limestone, or washing soda. Alternatively you can use potassium, sodium or calcium hydroxide (e.g Caustic soda or slaked lime) which will precipitate black copper oxide, but they are far harder to obtain, a lot more hazardous to use and don't give off carbon dioxide so its more difficult to determine how much to use to fully neutralise the acid.

Once the precipitate has fully settled it should leave a clear solution of calcium, sodium or potassium chloride depending on what you used to precipitate the copper, which will have a low enough copper concentration not to cause any problems if disposed of via the sewer system.   The sludge contains nearly all the copper and it can be rendered effectively inert by mixing it with cement powder, forming a paste that can be turned into a shallow mould and allowed to fully set, then rinsed and allowed to dry.   As copper carbonate or oxide is insoluble in an alkaline environment and the cement keeps it alkaline, even if you are less than scrupulous and dispose of it as domestic waste, it isn't a significant problem.

[rastro]

Hi, i am planning on doing a project (an arduino severino 3) and i was looking for a safe way to etch the PCB. I stumbled on a solution that uses vinigar ,hydrogen peroxide and salt, but i could not find a solution that contains only hydrogen peroxide(and H2O) but i found this instead(Pictures attached).

I used vinegar, hydrogen peroxide and salt with good results.  I bought white vinegar sold in most food stores.   Hydrogen peroxide you can buy at most pharmacies around 3-4% strength (Antiseptic  for sterilizing open cuts).  Are you saying that your pharmacy does not carry Hydrogen peroxide - typically in a brown plastic container. 

I also found it helpful to use a small heating pad under the container to warm the solution.  Typically takes 20-30 minutes - agitate every few minutes.  The liquid will take on a greenish/blue color.  There are instructional videos going through the process.

-rastro

[sleemanj]

  Hydrogen peroxide you can buy at most pharmacies around 3-4% strength (Antiseptic  for sterilizing open cuts).

H202 is a very common household chemical which you can buy in fairly large quantities (all be it at a low concentration).... if you live in the USA.

In at least some other places of the world, H202 is not a common household chemical at all and while your local chemists might sell it, it will be in a tiny bottle containing maybe 100ml at a low concentration and charge like a wounded bull for it.  Supply and demand, no demand so little supply.

The OP lives in Greece which brings with it some additional complexities due to the economic situation one would imagine.

[hendorog]

I've always been too chicken to ask for any chemicals at a pharmacy - I assume they will think I'm making drugs or something.

I just saw HCl is available at Bunnings.

[TheAmmoniacal]

Also, no etchant is more or less "easy to dispose of", as the problem is the dissolved copper ions, not the oxidizer used.

Most etchants are either disposable or have limited life ending when the copper concentration has become too high and/or the active etchant is exhausted.   Acid Cupric chloride is the only system where the waste copper becomes new etchant.  This does have the problem that the  etchant volume will grow as you re-balance the bath, so once you have enough on-hand for the largest board you want to
process, you do run into the disposal problem again.   

Even so, its not a major problem to precipitate out the copper - simply add an alkali or alkali earth metal carbonate till the solution stops fizzing, then add a slight excess and let the copper carbonate settle out.  You can use crushed natural chalk or limestone, or washing soda.  Once the precipitate has fully settled it should leave a clear solution of calcium or sodium chloride depending on what you used to precipitate the copper, which will have a low enough copper concentration not to cause any problems if disposed of via the sewer system.   The sludge contains nearly all the copper and it can be rendered effectively inert by mixing it with cement powder, forming a paste that can be turned into a shallow mould and allowed to fully set, then rinsed and allowed to dry.   As copper carbonate is insoluble in an alkaline environment and the cement keeps it alkaline, even if you are less than scrupulous and dispose of it as domestic waste, it isn't a significant problem.

All that is correct. Air regenerated acid cupric chloride etchant would be the least wasteful.

Hydrogen peroxide is harder to get in the EU, because bombs (like in Paris and Brussels). It is now illegal to sell concentrations above 12% (found in some hair bleaching products, but in small amounts), 3% is the only concentration found in common OTC products. If you want "pure" 3% H2O2 you need to go to a pharmacy, and often request it at the counter.

[tautech]

I've always been too chicken to ask for any chemicals at a pharmacy - I assume they will think I'm making drugs or something.

I just saw HCl is available at Bunnings.

Yep, many of the bigger hardware stores have it as "Spirits of Salts", stronger than most other dilutions at 33% HCL.
If you need lots, TMK Packers will supply direct if you visit them, $75 min purchase IIRC.
http://www.tmkpackers.co.nz/index.php/site/gallery/category/all

[Ian.M]

Yes.  Hydrogen Peroxide is *difficult* to get in Europe in significant volume at any reasonable concentration.  Attempting to do so other than for a company with a legitimate production process using it is likely to attract the attention of the authorities. 

However the waste product of HCl/H2O2 etching is a mix of cuprous and cupric chlorides, so the limited quantity you can buy over the counter is a quick way of etching your first board and then getting into acid cupric chloride etching.

I certainly wouldn't want to waste the stuff on peroxide/salt/vinegar etching.

[Ian.M]

You can get a few hundred ml at a fairly high price, but its rarely found on the shelves so you will have to ask for it, which is likely to attract official attention if you do so repeatedly.

[langwadt]

Yes.  Hydrogen Peroxide is *difficult* to get in Europe in significant volume at any reasonable concentration.  Attempting to do so other than for a company with a legitimate production process using it is likely to attract the attention of the authorities. 

However the waste product of HCl/H2O2 etching is a mix of cuprous and cupric chlorides, so the limited quantity you can buy over the counter is a quick way of etching your first board and then getting into acid cupric chloride etching.

I certainly wouldn't want to waste the stuff on peroxide/salt/vinegar etching.

Even not in pharmacy? 3% H2O2 is so useful in treating lacerations.

https://youtu.be/vVSC79nxCvI

[Kappes Buur]

I tried this some time ago http://quinndunki.com/blondihacks/?p=835
It works, but it takes quite some time to etch and you have to keep an eye on the process.

[IconicPCB]

I live in an area where i do not have town water.

Rain tanks rule. Of late we also have a bore with potable water. So when there is no rain.. the tanks get a helping of bore water and a dose of hydrogen peroxide to oxidise any dissolved minerals and cause them to drop out of solution. A 5 micron filter followed by a carbon filter cleans up the water.

Get my peroxide in 2 litre container and store it in the fridge to preserve it and slow down natural decomposition

[TheAmmoniacal]

This is to everyone, please don't take your science from SciShow.

[KL27x]

It is also easy to make ferric chloride, if you can't buy it. You have access to HCl. The easiest way to make ferric chloride solution is to mix HCl with powdered iron oxide (rust). Iron oxide is used in polishes and stains/paints among other things, and it is not that hard to find/buy. This is actually way easier than mixing up ferric chloride solution from "dry" FeCl2 and water. FeCl2 is a sticky/hygroscopic staining mess; in small quantities, half of it will stick in the bag/container. And it takes a bit of time for it to dissolve in water.

Failing that, the next easiest way to make it would be with powdered iron and HCl in a plastic or stainless steel bowl. Wet the iron with just a little HCl and let it dry out. Do that a couple times and you will have a bowl of rust.

Personally, I favor cupric chloride, but it kind of requires a significant upfront investment in time and/or money for the bubbler tank, since good aeration is necessary for it to work efficiently, IMO.

At any rate ferric chloride is pretty good for etching boards. It's considered the best of the acidic etchants because it is very fast, it works for a long time, and the (lack of) undercutting is tops for acid-based etchants. If you use it with a bubbler tank, you can use it like cupric. It will actually continue to work forever (but it will turn into curpric chloride moreso than ferric chloride over time, as you decant off the excess).

[savril]

You can make copper chloride without H2O2. You use just HCl (easy to get at hardware store), some copper and an air bubbler.
But it take days to make a sufficiently concentrated solution compared to using H2O2.

See http://techref.massmind.org/techref/pcb/etch/CuCl2.htm

[nidlaX]

https://youtu.be/vVSC79nxCvI

Funny, but do you think any type of chemical disinfectant is going to be preferential to not attacking your human cells? People disinfect wounds because sometimes it is not clear whether or not an application of antibiotics will be enough to kill the bacterial pathogens - especially in the age of MRSA. There is always the trade-off of damage to your cells v clearing potential pathogens. Washing with soap and water alone might be enough, but technique matters in this case - you need to really spend enough time to rinse the affected area.

[janoc]

You can get a few hundred ml at a fairly high price, but its rarely found on the shelves so you will have to ask for it, which is likely to attract official attention if you do so repeatedly.

Here in France you can get a small bottle (200-300ml) of 3% peroxide even in Carrefour, next to the cosmetic supplies, despite all the terrorism. Pharmacies are another option. The 3% one is the one used for disinfecting wounds and is not very useful for anything else.

However, getting a larger quantity or higher concentration is much more tricky - it would need to be ordered from a specialized distributor and will likely attract attention, because it can be used for many nefarious purposes (TATP is only one thing you can do with it ...). Moreover, a concentrated peroxide is a hazardous chemical that just loves to decompose when it gets in contact with something it can oxidize, going boom - it was used with a catalyst to trigger the decomposition as a rocket fuel! (not just as an oxidizer).

The 3% peroxide works for the etching though - but you will need quite a bit of it because of the low concentration. Acid/peroxide etching is not worth the trouble, IMO - messy, dangerous (droplets and fumes of concentrated HCL are very nasty, will corrode everything nearby even when stored in a closed bottle) and not easy to dispose of.

Ferric chloride or the ammonium persulfate are much preferable - lot safer and better results too.

[ZeTeX]

I'm using hydrogen peroxide + HCI to etch, it works quite good.
I've bought hydrogen peroxide 3% from an online store, and HCI are sold as toilet cleaners at 10% concentration in a green bottle, they're called "salt acid" for some reason in my country.

[KL27x]

Hair salon has high concentration peroxide. I dunno if they'll sell it to you.

[janoc]

Just buy hair bleaching products. They all contain hydrogen peroxide and that is pretty much what the hair salon would be using anyway instead of the plain peroxide. But the 3% one works too, just slower. Either way, I don't recommend this method for the reasons outlined earlier in this thread.

[ar__systems]

Whats wrong with good old fashioned ferric chloride? Its cheap, easy to get and etches nicely.

Actually, a lot. First of all it is highly corrosive, and you can't safely dispose of it. (dumping it into your toilet is not safe or legal). So it is not a good substance to keep at home.

[jpanhalt]

Be wary of hair salon hydrogen peroxide.  The percentage listed on the bottle is not your typical chemical percentage.  10% = 3% and 40% = 12%.   Of course 40 vol percent is more than 3%, but it is not almost 50% of the concentration used in rocket fuel.  There are also procedures for concentration hydrogen peroxide by using differential freezing.

All that being said, I use ferric chloride or the very similar cupric(II) chloride.  In fact, once you etch with ferric chloride, the solution is a mixture of ferric and cupric chlorides.

Joh

[helius]

Funny, but do you think any type of chemical disinfectant is going to be preferential to not attacking your human cells?

Yes, for example, mercurochrome does not cause stinging or delay healing. Betadine doesn't either. Healing is a complicated process and can't really be reduced to simplistic ideas about "toxicity" and so forth.
H2O2 is a decent antiseptic but by far its biggest drawback is that it has no long-lasting antimicrobial activity. Using too much of it can macerate the skin surrounding a wound to an undesirable extent.

[janoc]

Whats wrong with good old fashioned ferric chloride? Its cheap, easy to get and etches nicely.

Actually, a lot. First of all it is highly corrosive, and you can't safely dispose of it. (dumping it into your toilet is not safe or legal). So it is not a good substance to keep at home.

Well, dumping concentrated hydrochloric acid down your toilet is even less legal, not to mention the various copper compounds the mix will contain after the etching. The drugstore sold acid is meant to be used for cleaning (removing limescale) - but in a much diluted form, not as is!

Re corrosiveness - ferric chloride is corrosive only if you spill it. It doesn't produce fumes or anything else by itself. If you have corrosive fumes, then you have likely bought a commercial etching solution containing also hydrochloric acid instead of a pure FeCl3 solution. It is done to prolong the life of the solution - the added acid will help to regenerate the ferric chloride. 

On the other hand, hydrochloric acid fumes will corrode anything metallic up to the distance of several meters from where you have the bottle stored (depending on ventilation, of course), unless you have a lab-grade air-tight bottle for it. And even then it takes only tiny bit of contamination on the seal for the fumes to get out. Concentrated acid is also very aggressive if it gets on your skin or clothing (FeCl3 will only stain it) and the HCl fumes are very nasty, not to mention the fumes the solution with hydrogen peroxide releases while etching. So if you are looking for a safer alternative to FeCl3, hydrochloric acid certainly ain't it. The only thing going for it is the price and availability - almost every drugstore sells it.

[jpanhalt]

The single biggest use of ferric chloride is in sewage treatment plants.   How can it be so bad?  It is also used in the USA as a root killer to keep roots from clogging our septic lines.  Of course copper ions are a different story (maybe).   But any method of etching is going to produce the same amount of copper ions.  The cupric(II) chloride method that I mentioned has the advantage that you start with copper ions and end with a little more of the same ions.  It's perpetual etch, if you will.

You say it is illegal.  I suspect laws in France are different than in the USA. 

John

[janoc]

You say it is illegal.  I suspect laws in France are different than in the USA. 

That was ar__systems who said it was illegal and he (or she) is from Canada.

Dumping anything containing concentrated acid or heavy metals (like copper compounds) into sewage is illegal in France, though.

Not sure about pure ferric chloride, but considering it corrodes metals, it wouldn't surprise me if it was too, even though for different reasons. Adding it into a tank for sewage treatment is different than flushing it down the drain where it could corrode some piping or equipment on the way before it gets sufficiently diluted.

You are supposed to collect dangerous waste like this and bring it to the collection/recycling facility - most cities here have at least one place like that where it can be safely disposed of.

[jpanhalt]

Since you seem to have ruled out any method to etch copper as environmentally unfriendly, maybe you should switch to aluminum PCB's.   Soldering is a bit more difficult, but not impossible.

The best solution for you seems to be send your boards to a Chinese board house and wait.  It's cheaper, and so far as the Chinese tell us, environmentally friendly.

John

[Ian.M]

As readily available reasonably pure Hydrogen Peroxide tends to be no more than 3% (10 Vol. 0.88 Molar) concentration in many countries, it is desirable to use high concentration HCL to avoid excessive dilution, especially if you are planning to transition to air regenerated acid CuCl etching. 

As others have pointed out, HCl fumes are nasty, and attack most metals, so its essential to keep the acid and any mixed etchant in an appropriate container in a well ventilated space. Its not a good idea to store either in your electronics lab or machine shop.

10% HCL solution is only 3.3 Molar, and you are aiming for a HCL Molarity of around 2.5-3.0 in your working etchant, so you simply cant get there with an acceptable H2O2 concentration starting from 3% peroxide and 10% acid. (20% HCL solution is 6.6 Molar and 30% is 9.9 Molar).    If you are aiming at a 2 Molar Cu²⁺ concentration, that's a density of about 1.27, but if you start from 3% peroxide, and 20% HCL solution, you wont be able to get much past 0.5 Molar Cu²⁺ without air regeneration.

Also, once mixed, and even more so once there are metal ions in solution, the rate of decomposition of H2O2 drastically increases, so if you store it before its got a usable Cu⁺/Cu²⁺ concentration, it becomes useless.  That means you need to add enough scrap copper (preferably fine stranded wire) to the etchant to use up all the remaining peroxide before storage, then air regenerate before use.

If its quick & dirty etch and chuck, peroxide as hair bleach and HCl as toilet bowl cleaner may work. but both are likely to contain additives, and if you are unlucky, the additives may attack your etch resist resulting in pinholing, or partially protect the copper surface leaving unetched flecks of copper behind.  Its certainly not worth going the disposable HCl/H2O2 route if you can get commercially available PCB etchants.

[jpanhalt]

You can also use sulfuric acid (battery acid).  Works much the same, but doesn't have the HCl fumes.   Sulfuric acid is nonvolatile.

John

[KL27x]

Not sure about pure ferric chloride, but considering it corrodes metals, it wouldn't surprise me if it was too, even though for different reasons. Adding it into a tank for sewage treatment is different than flushing it down the drain where it could corrode some piping or equipment on the way before it gets sufficiently diluted.

All PCB etchants are corrosive. Watered down, any pcb etchant is less corrosive than grocery store vinegar, anyhow. There's a lot of water wherever your toilet leads, lol.

Best solution if you are worried is to not flush or dispose of your etchant. Just keep using it. Ferric chloride can be reused a lot. Add a little HCl and water as you go. When that gets too slow, add a bubbler. Next thing you know, you're etching with high concentration of cupric chloride. In my current cupric chloride tank is a small fraction of the first pint of Radio Shack ferric chloride I ever bought.

No need to ever throw it out. I have never thrown out etchant. I let the excess dry out in the sun and collect it for scrap. Copper is getting pretty expensive. The main leftover of my etchant is copper compounds.

[Tac Eht Xilef]

Sulfuric acid is nonvolatile.

I think you need to rethink that into "It's not terribly volatile @ STP, but increasingly volatile with temperature & when oxidising".

And for fuck's sake, don't mix it with peroxide unless you know what you're doing. Conc. H₂SO₄ (i.e. sulphuric drain cleaner, battery 'commissioning' acid, etc) + strong-ish (~30% or more) H₂O₂ makes a thing known coloquially as "piranha solution" for its volatility & ability to attack anything carbon-based - like the plastic container its handler is trying to contain it in, or the handler themselves...

[jpanhalt]

I think you need to rethink that into "It's not terribly volatile @ STP, but increasingly volatile with temperature & when oxidising".

And for fuck's sake, don't mix it with peroxide unless you know what you're doing. Conc. H₂SO₄ (i.e. sulphuric drain cleaner, battery 'commissioning' acid, etc) + strong-ish (~30% or more) H₂O₂ makes a thing known coloquially as "piranha solution" for its volatility & ability to attack anything carbon-based - like the plastic container its handler is trying to contain it in, or the handler themselves...

The vapor pressure of 80% (by weight) sulfuric acid is 10^-5 mmHg at 25°C and it goes down at lower concentrations (http://www.personal.psu.edu/mrh318/Gmitro-Vermeulen-AICE-1964.pdf ).  That is sufficiently low to qualify as "non-volatile."   The subject here was etching PCB's in ordinary conditions.  Get real.

John

[Canis Dirus Leidy]

Either way, I don't recommend this method for the reasons outlined earlier in this thread.

There exist safer (but slow) solution: 3% peroxide and citric acid plus some kitchen salt.

P.S. Can't say about USA/France/Japan etc, but in Russia you can buy all parts in local pharmacy and grocery store.

[janoc]

The vapor pressure of 80% (by weight) sulfuric acid is 10^-5 mmHg at 25°C and it goes down at lower concentrations (http://www.personal.psu.edu/mrh318/Gmitro-Vermeulen-AICE-1964.pdf ).  That is sufficiently low to qualify as "non-volatile."   The subject here was etching PCB's in ordinary conditions.  Get real.

John

I think his point was that it is definitely not safe thing to use to etch boards, not nitpicking about definition of "volatile". Yes, it isn't volatile in the sense that it will explode (at least not the acid alone).

However, if someone foolish enough mixes a sufficiently concentrated sulphuric acid with a peroxide thinking it will fume less than a HCl/peroxide mix, they are right - it won't.  Unfortunately, it will eat through almost anything you put it in, including common protective gloves. And if that mix encounters any organic contaminants - like finger grease left on the surface - it will react violently with them, even causing an explosion in the worst case.

And all that assumes they have done the mixing correctly in the first place - the mixing is very exotermic and loves to boil and create dangerous splashes if done wrong, so the fool attempting this could end up in a hospital  with horrible burns before even getting to the etching part.

That's hardly something I would call safe.

Back in the day we have been using even nitric acid to etch boards (try to find nitric acid in stores today!), but that doesn't mean I would recommend anyone trying to do so, especially without proper tools and knowledge how to do it safely.

[janoc]

There exist safer (but slow) solution: 3% peroxide and citric acid plus some kitchen salt.

P.S. Can't say about USA/France/Japan etc, but in Russia you can buy all parts in local pharmacy and grocery store.

I think this has also been done with vinegar instead of citric acid - which is what the OP was actually asking about, because they are unable to find pure peroxide.

3% peroxide should be easily available anywhere in stores or a pharmacy as a common disinfectant for wounds.