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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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JesusGeek2 months ago

I use 1:1 ratio of vinegar and hydrogen peroxide, and add salt as I go. It works pretty well, but my main issues are

(1) What do I do with all this copper acetate! (main leftover solution, no I do not want to electroplate with it)

(2) Effective way to transfer traces onto board (soon to try using glossy magazine paper, gloss photo paper leaves broken traces all over, and using a laser printer)

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.

Thanks, but how should sell the copper? If I collect about 2 Tbsp worth of it, where should I?

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 :)

Ok, thanks for clarifying.

(Now he strips all his copper wire to make a few bucks)

fezick4 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 fezick15 days 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:

Feynmaniac (author)  fezick4 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).

baecker0321 days 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 month 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
hackeinstien3 months ago

what if i add a few drops of hcl in it

hackeinstien3 months ago

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

Quesnelquack4 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 :)

crazypj3 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'

Nice instructable mate

Feynmaniac (author)  syedhamzahasan4 months ago

Thank you =)

michaelmacnz4 months ago

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

Feynmaniac (author)  michaelmacnz4 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 =)

weibbed4 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 weibbed4 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 0x5c4 months ago

Thanks for suggesting an alternative.

Whiternoise4 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?
inkspot0994 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)  inkspot0994 months ago

I think that would make a great experiment =)

shobley4 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)  shobley4 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 =) !

kbyrne4 months ago

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

jhall30 kbyrne4 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)  kbyrne4 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 ^^ !

Interesting result. I have experiment with both method, but with some what different result. What I find is it is very hard to get consistent result with peroxide/vinegar/salt. Sometimes it will etch quickly and sometimes not (or not at all), which is most of the time. Also it is not Sharpie friendly, ie. it dissolve the ink, which is not good if you make any correction on your board. Although clear varnish will work, but it is less convenience. The long etch time leads to under cutting of tracks and pitting on large copper area which is not good. Compare this with Ferric chloride, my initial impression was this is bad stuff; it stain everything, hard to dispose of and expensive. But then I came across this, the Edinburgh Etch:

http://www.nontoxicprint.com/etchcopperandbrass.ht...

By adding Citric Acid (lemon juice if you like) to the Ferric chloride, it improve the efficiency and the longevity of your etchant, ie. number of time you can use it. if you use Ferric chloride before, you know the more you use it the less effective it is as it form a layer of sediment at the bottom of the bottle, the citric acid remove this. Also, I find the temperature does matter. I usually have the Ferric chloride sitting in a warm water bath and it etch fast! normally 25-30C is good enough.

I don't do a lot of PCB, but the time I do, I like it to work first time, so I need something that will have a long shelf life and consistent in result. The Edinburgh Etch does give me that. BTW, proper way to neutralise and dispose of Ferric chloride is also well known; Calcium Bicarbonate or baking power. I do consider

peroxide/vinegar/salt as my secondary method, as say, you can get the stuff any where and it is not toxic.

Anyway, well done as I was waiting for someone to do a more qualitative work on peroxide/vinegar/salt method.

Keep up the good work!

I did not refer to this in my experiment but it’s true that efficiency really depends upon your Vinegar/Hydrogen Peroxide. Once I used what remained of an old vinegar bottle and I can tell you the result was quite sad ^^


However did you try to sprinkle some salt over your board while in the bath ? :)

I did, but the result again vary so much (from adding a tea spoon to half a bag) that it is hard to get consistent result, ie. a consistent repeatable recipe.

Pader4 months ago

Good instructable, we all need to make circuit boards at some time.

I have used a slight variation in the past which has given fairly good results and I find superior to ferric chloride etching. Instead of the vinegar and salt, I use ordinary, proprietary stone and patio cleaner which is available in 5ltr drums for around £12 (around US$20) in most garden centres or builder's merchants.

The cleaner that I have used contains 15% hydrohloric acid. This combined with the Hydrogen Peroxide provides me with the Cupric Chloride etchant. Better still, I do not have to throw the used etchant away because the more copper dissolved in the solution, the faster the etching qualities.

I have found that the faster a board is etched, the better the resolution as the etchant does not have time to seep under the mask. to help with this, I use a loop of PVC tube with small 'pinholes' along it's length in the bottom of the etching tray and connect it to a cheap aquarium type air pump. I also heat the etchant to around 60 degrees Fahrenheit.

I have no idea about the chemistry data involved, I picked the idea up at sometime during my advanced years. Perhaps you could do a similar analysis to your etchant for this one?

cburg4 months ago

Very Nice write up. I have tried to use Hydrogen Peroxide with small amounts of muriatic acid. I found it to work well; however, it was not until I began to use stronger Hydrogen Peroxide that I got even greater results. Turns out at any beauty shop supply store as the stuff in quarts and gallons up to 40%. the cost is still not what Ferric Chloride cost and there is no shipping problems.

Now I want to use you figures and look into the use of salt. I think we have a winner!

Thanks again for come great information.

Cburg

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