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Picture of Is the best PCB etchant in every kitchen ?
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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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NoahT31 month 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).

StuNutt1 month 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? :)

flurng1 month 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!

fezick11 months ago

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

Orngrimm fezick7 months ago

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)  fezick11 months 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).

MarcusN12 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.

rmazzupappa4 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?

(removed by author or community request)
You can SLOWLY add aluminium strips until it doesn't dissolve anymore. filter. the red sludge is the copper. sell it or dispose of it in the garbage. the liquid leftover is not poisonous anymore. neutralise it with a base an dispose of it.
(removed by author or community request)

Not 2 tbsp of it... But if you have around 1 kg it sells for around 7$. If you do it hobby-like you will probably NEVER accumulate this much copper from your few PCBs... Thats why i also said you can dispose of it or sell it. Dispose of it in the solid waste is the way to go for most of us hobbyists out there :)

baecker037 months 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.
cooldharap8 months 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.
Mason Wright7 months ago
Can I use your research for my science fair project later in the year
hackeinstien10 months ago

what if i add a few drops of hcl in it

hackeinstien10 months ago

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

Quesnelquack11 months ago

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 :)

crazypj11 months 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'

syedhamzahasan11 months ago

Nice instructable mate

Feynmaniac (author)  syedhamzahasan11 months ago

Thank you =)

michaelmacnz11 months ago

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

Feynmaniac (author)  michaelmacnz11 months 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 =)

weibbed11 months 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 weibbed11 months 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 0x5c11 months ago

Thanks for suggesting an alternative.

Whiternoise11 months ago

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?
inkspot09911 months 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)  inkspot09911 months ago

I think that would make a great experiment =)

shobley11 months 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.

Feynmaniac (author)  shobley11 months ago

Thank you for sharing this process. Without your blog I think I would never have imagined that this mix could work given the concentration of acetic acid in vinegar ! =)

I'm glad my main source actually likes this 'ible =) !

kbyrne11 months ago

Along this line is lowes muratic acid and hydrogen peroxide. Very low cost, foam brush used for board but no salt???

jhall30 kbyrne11 months ago

Muriatic acid is another name for hydrochloric acid, and is usually sold as a pool cleaner. I've found and purchased a 900ml bottle of a higher concentration on Amazon for just this purpose, but haven't tested it yet.

Feynmaniac (author)  kbyrne11 months ago

I think (I'm not sure) that HCl (muriatic acid) + Hydrogen peroxide does not need salt (NaCl) because it already has the chloride ions we are looking for to form cuppric chloride (CuCl2) :)

However I think this reaction creates toxic fumes, plus I feel more confident with a vinegar bottle than with a strong acid one ^^ !

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