Picture of Is the best PCB etchant in every kitchen ?
After a lot of reading and inspiring from Instructables for two years now I decided to step ahead and do my first Instructable on two subjects I particularly like : PCB making & The scientific method.
Feel free to comment and criticize my work, I think scientific method is also about improving and discussing the best way to experiment :) !
English is not my native language so please excuse my hesitating grammar.
5/30 Edit : I would like to thank you all for supporting this Instructables in the Scientific Method contest =D See you for other experiments !

Most of us Instructables users etch PCBs occasionally if not on a daily basis. This process is not anodyne as it may have a great impact on the quality of the future circuit, the environment and, last but not least, on your wallet !

Ferric chloride is commonly used to etch PCBs as it is both reliable and efficient. However, it's a dangerous product which requires special care in handling. Recently, some alternatives have been found to accomplish the same task. Among them is an astonishing hydrogen peroxide, salt and vinegar mix which seems to be a “Mac Gyverish” way to print a circuit board.

Let's assess the “Mac Gyverish” hydrogen peroxide/vinegar/salt mix using the “tried and tested” ferric chloride solution as a control !

To etch a PCB one can either immerse the board into a bath of etchant (most common technique) or rub it with an impregnated sponge. I have tested both ways with each etchant so that makes a total of 4 experiments.

The techniques and etchants will be compared according to four criteria :

  • Time/Handling
  • Quality of resulting circuit
  • Cost
  • Environmental impact
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gaudat25 days ago

Another point to add. If you are using more concentrated vinegar (I got 25% ones from South Asian shops), you must add salt into the mixture to etch properly. I learned it the hard way... The etch was bubbling vigorously but the board doesn't seem to etch. Soon it gets too hot to handle and I have to chug it into the sink to stop the reaction. Now I have ugly brown stains on my table and the floor because of the copper...

BrunoD82 months ago

Tried this today, didn't went very well :( Or i was impatient :)

The PCB was immersed at least 1h (agitated the container each 5min), i still saw copper, didn't saw any bubbles or anything, so i decided to remove-it and give up for today... then i washed the toner out to find out it was working! The traces where there already! PCB ruined...

I think my problem was i used "cider vinegar" witch is only 4% acid.. i will buy the normal one and try again someday!

I will add a picture of my failure :)

Very nice tutorial! Thanks! This was the reason i tried to make a PCB at all, since i don't have easy access to the other chemicals!

BrunoD8 BrunoD828 days ago

Tried this again today. It went better, but this time i had to use normal paper so it didn't went very well. But with some jumper wires to fix some traces it should do the job....

Maybe the 3st try is the one that will be perfect :)

phoulihan2 months ago

Does anyone know if there's an alternative to hydrogen peroxide? It's heavily restricted in the EU because some idiots were using concentrated solutions to whiten their teeth.

Is that the reason?! I found it was being restricted in some countries and I'm really pissed off with the fact i cannot find hydrogen peroxide 110vol (33% concentration or so), but i couldn't know the reason about such restriction.I read the restrictions were due to the possible use of high concentrated hydrogen peroxide to make fuel.

Anyway if you look on the Internet, you can find some sites where it's explained the process to get high concentrates from common use 3% h.peroxide, basicly baking it in a kitchen oven in low temperature. And it works (it's said).

Honestly bleach is also dangerous and you can buy easily so I don't think the reason to restrict the hperoxide is by bleaching teeth. Surely something related to the paranoid about terrorists (and actually the terrorists dress smart and use ties).

jgroner made it!2 months ago

Bravo sir! Now I can officially say that, besides the copper board itself. This PCB was manufactured entirely from things I already had in the house.. and this is my first PCB!

makeosaurus3 months ago
Are you able to throw the used vinegar etchant down the Plughole????
DangerousTim3 months ago

Extremely helpful instructable! Thanks a bunch!

NoahT35 months ago

I mixed the solution all up and dropped the boards in. All the boards did was make bubbles, make an underwater steam look, and rust (well at least look like rusting). The solution was not turning green. So I left it on for 2-4hours then I came back and my room stunk (Bedroom. Also I have to sleep in an hour). After that I checked if the boards were done and I wiped of the boards to reveal more copper underneath. Then my parents checked and said it was a lung irritant and i should sleep in the basement (I'm 13yrs old).

StuNutt6 months ago

This has to be one of the best Instructables I've ever read! Not only is the 'ible itself, and its author, a total winner - The quality and content of the community feedback had me reading right through all 84 contributions on it.

There's obviously a lot more experimentation that can be done, but I don't think I'll ever buy ferric chloride again for the (fairly rare) occasions I make up a PCB - the half-used stuff just hangs around (and sometimes can't be found when I need it!) and then has to be disposed of, Is it too late to vote on this? :)

flurng6 months ago

Congratulations on creating a wonderful instructable, and thank you for publishing this useful and important information! Even more impressive is that English is not your primary language, yet your grammar and diction is easily far superior to most of the people I know, who (attempt to) speak English as their primary language! Well done, Sir! I suspect we'll be seeing many more great things from you in the future, and I will most definitely keep a close eye on your further input!

fezick1 year ago

So of course I wonder, can you extract the etched copper from the solution for later recycling or jewerly uses? Maybe through electrolysis?

You can. Just introduce another, more reactive metal... Like Aluminum. The reaction is 2Al + 3CuCl2 -> 2AlCl3 + 3Cu thus you end with very pure copper-powder.

Seen here

Or you can electrolyse it. Seen here:

Chemistry is so powerful. Especially when you know how to use it! Great comment.

Feynmaniac (author)  fezick1 year ago

I'm pretty sure you can recycle it for electrolysis. If you want you can check out this instructable : http://www.instructables.com/id/High-Quality-Coppe...

But for this electroplating you use copper acetate which means you'll have to avoid putting salt into the etching bath and adapt the mixture (you can stick to this instructable and simply put your board instead of copper scrubbers).

MarcusN16 months ago

This method IS NO GOOD IF YOU ARE LAYING OUT YOUR TRACES WITH PERMANENT MARKER ..you will watch , maybe hours, of work bubble away into blue goop in the bowl along with the copper...no good..you no like. I thought it would be nice if someone told you.

rmazzupappa9 months ago

I understand the hydrogen peroxide and vinegar are a 2:3 ratio, but how much salt should I add to get the etchant correct?

baecker031 year ago
anyone can dispose of ferric chloride if they remove the copper from the solution. once the copper is removed, it can be purified and reused to make other compounds.
cooldharap1 year ago

is any of these solutions reusable ?

every etchant based on CuCl2 is reusable. It may need oxygen if it turns dark green, more acid if it turns brown.
oxygen: bubble air in it with a cheap aquarium pump an a bubblestone.
acid: add more of your vinegar / HCl.
Can I use your research for my science fair project later in the year

what if i add a few drops of hcl in it

hey its not working jst wrkd fr the first time and irrespective of adding more of vinegar, h2o2&saltsalt

I like the way you approached the subject with rigorous attention to detail and a scientific frame of mind. A few comments if I may:

1) The number on the vinegar bottle I think is in degrees Baume (density) rather than % concentration. I am not sure how this converts with acetic acid. For instance 20 degrees Baume HCl is about 35% concentrated.

2) The fact that you got better results with wiping than immersion demonstrates an important principle with all etching baths: There has to be agitation of the etchant. I run an aquarium pump through mine to create bubbles.

3) Ferric Chloride works better at higher temperature - I run mine close to 40 degrees C.

4) In terms of economics one has to point out that Ferric Chloride can be re-used - many times!

5) Environmental effects of disposal are determined by the copper ion content: For some reason even the small concentrations such as in your little set-up would be frowned upon. Ferric chloride by itself consists of chemicals which are naturally occurring in soil. OTOH if you want to get rid of roots in your garden or septic tank what do they sell you? Copper sulphate! Go figure.

6) Finally, having said all that about FeCl3, I have more or less stopped using it in favour of electro-etching with copper sulphate as electrolyte. However, for the occasional PCB that may way too much hassle.

With rock salt as a close second for the roots,but no doubt the Copper sulphate works better,and is longer lasting in this old plumbers opinion.

Many many valid points- and a very helpful article overall! Disposal of dissolved copper is always tricky; the electrochemical properties of copper make it a very good accumulator of other metals within a system that we otherwise don't want accumulating, such as Zinc or Magnesium. Caution is never overdone in the lab or workshop! I'd love to put some of these ideas to the test myself :)

crazypj1 year ago

Can the dissolved copper be used for copper plating steel/iron/ferrous materials?

That way it's kind of reclaimed and made into something 'useful'

Nice instructable mate

Feynmaniac (author)  syedhamzahasan1 year ago

Thank you =)

Well done you... This makes it super simple to make a decision (choice) ... Thank you.

Feynmaniac (author)  michaelmacnz1 year ago

I thought it was a way to get an "objective" answer to this question of pcb etchant. It really seems to split people ^^

Thank you =)

weibbed1 year ago

Great Instructable! I'm just trying to make sure I got the solution proportions right for the hydrogen peroxide/vinegar/salt. Twothirds liter of hydrogen peroxide with one liter of vinegar and 1 TBSP salt? I got a little lost in the chemical formulas (which I am very glad you figured out and explained, but I'm just an end user, not a scientist!). I want to try etching some copper sheet for jewelry, not PCB boards. I plan on trying a Sharpie marker as the mask, since I know that works for PCB etchant on copper sheets.
Thanks for the idea to try. I rarely do metal etching since the disposal of the etchant intimidates me, but this would be great!

0x5c weibbed1 year ago

It won't work well. The hydrogen peroxide/vinegar/salt mix will dissolve the sharpie ink. It will be better for you to use the electroetching method (http://www.instructables.com/id/How-To-Electro-Etch-a-Solid-Metal-Plaque/?ALLSTEPS)

weibbed 0x5c1 year ago

Thanks for suggesting an alternative.

After staining more things than I care to count with ferric chloride I started using Sodium Persulphate. It requires a water bath to be quick, but this is fairly straightforward (just place the etch container in a bowl of very hot water). It's non-staining and the byproduct is copper sulphate solution. The main advantage is that it requires no agitation, the copper simply dissolves into the solution so you can easily check if it's done and there's no gunk to continually scrape off the boards. It's reasonably cheap, a small bag can be bought for £5/$5 on eBay and it lasts for a long time if you make up the solution as you go.

Don't fool yourself that persulfate is safe. I once spilled some on a blue bathroom rug. It left the fiber bleached yellowish white in no time.
Hmm wasn't aware of that, though wikipedia says it's essentially a bleach. May be just the thing to get rid of Ferric Chloride stains on my lab coat!

Also wasn't aware that it's used in hair bleaching products. Maybe a cheap source?
inkspot0991 year ago

I know that when using Hydrochloric Acid with Hydrogen Peroxide that using an air bubbler replenishes the oxygen and accelerates the action. I suspect that it would help with this Vinegar/Salt/H2O2 procedure also if doing a large board for example, or just to speed up the process.

Feynmaniac (author)  inkspot0991 year ago

I think that would make a great experiment =)

shobley1 year ago

This is fascinating... Thanks for taking the time to explain the process.

I don't know if I "invented" the process... but adding the salt seemed to do the trick for me, and created a bit of a debate when I published my findings.

I get quite a bit of email still from people who can't get the mixture to etch, so this will be a great resource to point them to.

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