# PCB etchant (ferric chloride)



## solar seeker (Aug 6, 2010)

I bought a bottle of PCB etchant for $9.00 at radio shack which is ferric chloride and hydrochloric acid. This solution has been quite helpful in removing the copper out from under the gold plating on circuit board fingers. According to what I've been reading the solution reduces copper metal into copper chloride which also reduces copper metal into the chloride form the iron (ferric) chloride also reduces iron metal in the same way but notably slower. The solution can be regenerated indefinitely if more chlorine ions are provided by addition of hydrochloric (muriatic) acid. The solution is also regenerated by the oxygen in common air, there for a $3-20 fish tank bubbler with a piece of hose will restore the solution, likewise hydrogen peroxide will do the same thing. For those who don't have access to PCB etchant solution, a mixture of hydrogen peroxide,hydrochloric acid, and copper or iron metal will provide a starter solution which will ,according to the above reactions, continue to "grow" without ever needing to be thrown away. If the solution "grows" to a sufficient quantity the copper metal can be dropped out of solution and sold or the solution itself can be dried for storage and later use. The dry or liquid form could also be put into a camp fire or the dry form may be mixed with a pyrotechnic mixture to color the flames a pretty blue color. I would suggest using one batch each for iron and for copper in order to make recovery of these metals easier.

There are is at least one down side to using this solution which is that it takes days to dissolve copper metal off of circuit boards at room temperature but it works fairly well when heated but not boiled. Another down side is that it may only target copper and iron in which case it may not remove dissolve base metals like lead.

To sum it up this is significantly cheaper than using nitric acid for recovering gold from circuit board fingers and it's far easier to buy or make.


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## g_axelsson (Aug 6, 2010)

You need to add hydrochloric acid too to keep the solution fresh.

/Göran


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## qst42know (Aug 6, 2010)

This is often discussed on the forum referred to as acid/peroxide or in short as AP. 

Lazersteve had a more detailed document on the chemistry of the process on his website.


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## solar seeker (Aug 6, 2010)

In response to the above posts . post 1: Yes you do have to add muriatic acid to regenerate the solution but an air bubbler will make the solution last longer between additions of acid. post 2: While it is true that you start with an AP solution you needn't add hydrogen peroxide once you have a sufficient quantity of copper and or ferric chloride in the solution. The only things you add after that point are air,HCl,and your metal to be dissolved. Also AP will ,if what I'm reading is accurate , dissolve gold. coper and ferric chloride will not.


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## lazersteve (Aug 6, 2010)

Ferric Chloride will not regenerate with oxygen and/or HCl as copper II chloride will. Once the ferric chloride has reacted it's spent. Copper II Chloride is easily regenerated. The above referenced document gives all the details. 

Iron build up in copper chloride solutions leads to the reaction eventually stopping.

Ferric Chloride Chemistry

Pay close attention to the section "Colour in Use".

I have many hours of hands on use of Ferric Chloride and Copper Chloride enchants and can assure you the Ferric Chloride soluiton does not lend itself to economical regeneration. Copper II Chloride (aka Acid Peroxide) is easily regenerated.

Steve


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## DNIndustry (Sep 25, 2010)

adding small doses of peroxide does accellerate. the bubblerwont. The iron Fe2 and fe3 ions act as an accelerating catalyst to h202. Just as Silver and platinum does. (bell rocket jet pack)


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## m109a3 (Dec 13, 2011)

if this removed the copper and released the gold foil would that be 24k? could a person run this on say 100Lbs and get a real yield from this 9.00 bottle of etchant ?
would it help with things like cell phone boards also . 

thanks


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## Geo (Dec 14, 2011)

i have, myself preached the use of ferric chloride, but it should not be done by the beginner or novice as the iron lends itself to the finished product and will need to be dealt with. as far as etchants go copper II chloride is a sure winner especially for someone just starting out or on a small budget. ferric chloride has its place in refining just as every other process but to rely solely on it to process with would be a mistake. take for example gold plated pins that are Kovar or another iron based metal, ferric chloride may be a better choice for this material if its already seperated. AP will digest iron and Kovar but much slower and will add iron and nickle to your solution.


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## butcher (Dec 14, 2011)

No (it would not be 24k if melted), you are still left with much impurity, the gold flake
will be of high karat (if melted), but will need to be refined for high purity. The problem with selling gold in melted form (depending on buyer) is there is not an easy way for him to test the gold if it is higher than 18K to 22K, and if it does not have the characteristic pipe of pure gold, you may loose some gold having to sell it as a lower karat than it may be, you may be able to sell it to a refiner, but the amount of gold is small you may lose money on assay and other costs, you have recovered the gold in an easily to refine state, it is just a little more work to learn and finish the process to make fine gold, something you can be proud of when it shines in your hand.
Do not melt flakes if you want to refine them.

One problem you may run into starting with ferric chloride solutions (which cannot be regenerated easily without chlorine), (which then could not be used in this process as you would form aqua regia and put gold into solution with copper), ferric chloride will form insoluble iron oxides and hydroxides (especially when heated) which are insoluble yellow or red powders, which are very resistant to acids even aqua regia, and your gold can be mixed with these iron powders, also making it harder to put (all) of your gold back into solution,

You can avoid this problem if you start with copper II chloride (acid/peroxide solution).


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## m109a3 (Dec 15, 2011)

Hay thanks everyone for the help. I almost made a mistake now what do I do with the radio shack etching stuff " new unopened " cant seem to find my slip for it . .... gzz


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## Geo (Dec 15, 2011)

store credit?


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## henn111 (Mar 4, 2012)

Would this be a good method to strip gold plating off circuit boards using ferric (and keeping it active using HCL) then filter the gold flake and rinse/wash throughly. Then put 
the flake into nitric acid to totally eliminate all base metal. Filter gold flake and rinse very well and then go with the AR process??


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## Geo (Mar 4, 2012)

that's a lot of steps to do one thing. ferric chloride is not re-usable. its not like copper chloride where you keep the PH low and keep using it. its a one shot pony.


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## qst42know (Mar 4, 2012)

henn111 said:


> Would this be a good method to strip gold plating off circuit boards using ferric (and keeping it active using HCL) then filter the gold flake and rinse/wash throughly. Then put
> the flake into nitric acid to totally eliminate all base metal. Filter gold flake and rinse very well and then go with the AR process??



Ferric chloride = iron and hydrochloric. Why use something that is partially used up?


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## Harold_V (Mar 9, 2012)

henn111 said:


> Would this be a good method to strip gold plating off circuit boards using ferric (and keeping it active using HCL) then filter the gold flake and rinse/wash throughly. Then put the flake into nitric acid to totally eliminate all base metal. Filter gold flake and rinse very well and then go with the AR process??


The thing of uppermost importance for you to learn from this is that you should not go from nitric to HCl, or HCl to nitric, without incineration. Even with careful washing, you risk residual acid remaining that will form AR, dissolving traces of your values. 

Harold


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## upcyclist (Apr 9, 2016)

I just found Lazersteve's link to "Ferric Chloride Chemistry" and it's just what I was looking for--I think.

Some folks at my jewelry/lapidary guild are doing copper etching and use ferric chloride. In my naivete, I said that I had "ferric-ish chloride-ish" from my waste disposal process and gave them some. And of course it did nothing, because it's fully saturated. I knew there had to be more chemistry at work, since the reactivity series tells me that an acidic solution fully saturated with iron (and more active stuff, but this last batch had a nice iron greenish-yellow) won't do anything with copper.

Now I see I need to cut it with water, then precipitate some ferric hydroxide and add it back to the mix. I'll give that a shot.


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## butcher (Apr 9, 2016)

This may help some, Iron chloride leach and Copper chloride leach are very similar, and different at the same time, sometime we can have a mixture of the two (if we have both iron and copper in a chloride solution).

https://en.wikipedia.org/wiki/Redox
http://goldrefiningforum.com/phpBB3/download/file.php?id=25069
http://goldrefiningforum.com/phpBB3/download/file.php?id=25049
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=11890&p=198155&hilit=ferric+chloride#p198155
http://en.wikipedia.org/wiki/Copper(II)
http://artmondo.net/printworks/articles/ferric.htm
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=46&t=20006&p=204406&hilit=ferric+chloride#p204406
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=19816&p=203499#p203499
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=23092&p=242526&hilit=ferric+chloride#p242526
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=19838&hilit=ferric+chloride
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=46&t=20006&start=0
http://goldrefiningforum.com/phpBB3/search.php?keywords=ferric+chloride+&terms=all&author=butcher&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search


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## upcyclist (Apr 9, 2016)

Thanks! I'll look those over. If it were me, I'd just use nitric acid or copper chloride to etch the copper


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## M0ne4gold2 (Apr 14, 2019)

Hi all I'm newbie at this process ui started out with preoixde and hcl using one 1:1 ratio filled above the material (cpu pin, an Mlcc). At first the mixture turned a murky greenish sludge floating around the material I was etching and the acid floating above so 8 decide to make another batch with out any material it so I pour the old batch into the new and the solution turned red what should to correct this if it's a no no and secondly what steps I need to take to keep this from happening again?


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## butcher (Apr 15, 2019)

M0ne4gold2,
asking the same question in two threads is double posting it is not only against the rule but make a mess of the forum for others trying to learn and find answers to their questions, please keep the same type of questions in one thread, no double posting, please.

Looks like you are using too much oxidizer and dissolving most all of the metals many of which will begin to cement back out the less reactive metals back out of solution as the oxidation capability of the solution has depleted in the bulk of undissolved metals. With tin in the solution, you can begin to lose gold as it forms colloids which will not precipitate and will not show up with a stannous test.

You are working with a very simple process, and making several simple mistakes, spend some time studying the process so you can gain an understanding of how it works and how to perform it properly.

Study how the cupric chloride process works and seperate your scrap...


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