Removing solder from printed circuit boards

[haveagojoe]

You can clearly see where the gold was visible and where the acid ate away the solder.

I haven't been able to get it much better than that with HCl, I assume because of where the solder is alloyed with the gold below. I just try to reduce and minimize the amount of tin as best I can.

 

[VolkD]

I haven't been able to get it much better than that with HCl, I assume because of where the solder is alloyed with the gold below. I just try to reduce and minimize the amount of tin as best I can.

How long did it take you to get the solder to stick?

 

[haveagojoe]

How long did it take you to get the solder to stick?

I guess you mean to dissolve? I do it without heating, using 10% HCl, usually after about 48 hours it's mostly gone, or is soft enough to remove with a toothbrush. Sometimes it needs longer but the main thing is to avoid dissolving copper, so not to leave it too long. I feel like it's good to keep it covered to minimize the oxygen it can get, I'm not sure how much difference that makes though.

 

[Yggdrasil]

I guess you mean to dissolve? I do it without heating, using 10% HCl, usually after about 48 hours it's mostly gone, or is soft enough to remove with a toothbrush. Sometimes it needs longer but the main thing is to avoid dissolving copper, so not to leave it too long. I feel like it's good to keep it covered to minimize the oxygen it can get, I'm not sure how much difference that makes though.

I once tried to cover it with a teaspoon of vegetable oil.
But at the same time I had a temperature probe sitting in the beaker.
It was an oversight as it was probably made of stainless steel.
Anyway the morning after it had dissolved the metal just at the surface of the liquid.
It seemed like some kind of concentration or galvanic reaction had happened.
So if you are going to use this make sure all is below the surface.

 

[VolkD]

I guess you mean to dissolve? I do it without heating, using 10% HCl, usually after about 48 hours it's mostly gone, or is soft enough to remove with a toothbrush. Sometimes it needs longer but the main thing is to avoid dissolving copper, so not to leave it too long. I feel like it's good to keep it covered to minimize the oxygen it can get, I'm not sure how much difference that makes though.

Of course, I meant to dissolve .Time is very important to me, but your method is also interesting. This is because I made a few tiles. If I wanted to do all the tiles I have, I would need about 20l of acid. With your method, much less. Besides, I only have one place where I can heat and if I heat these tiles, I can't do other things. That's also time.

 

[Marcel]

I came back today and was shocked by the number of posts that were extremely misleading , along with a few that claimed to be “best practice.” Now, after my rant, here’s the constructive part:


First off: If you want to make money by recovering precious metals (and non-precious ones like copper and tin, too), TAKE YOUR TIME! Recovering metals is not a fast-money scheme. Several factors determine the speed and effectiveness of recovery: the chemicals used, time, and energy (heat). I recommend preferring energy and time over the excessive use of chemicals. This approach greatly reduces the waste you create and minimizes the hazards associated with toxic byproducts.


Stop trying to turbocharge the recovery process with overly strong reagents like nitric acid, “Poor Man’s AR,” excessive hydrogen peroxide, and other “exotic” chemicals.


Removing electronic components from boards is quite simple—especially when dealing with primarily SMD (surface mount) components rather than through-hole components.


I’ve seen the most sensible and best-practice advice from @goldman1959 on this topic:
https://goldrefiningforum.com/threads/removing-solder-from-printed-circuit-boards.35832/post-389406

Micro Scrapping (Small-Scale Recovery): Separating Tin from SMD Components​

Step 1:


Use a heat gun and a stainless steel spatula to scrap all the components off the boards, aiming to separate the tin from the components in this initial step. This method primarily uses energy (heat) and requires minimal labor and time. You’ll end up with a mix of components and tin.


I demonstrated in a video around 2013 how to use this mix as a starting point for a manual collector technique. By roasting the components, the tin adheres to other tin particles, while the components oxidize—thereby separating the tin from relatively clean components.


Here is my video of doing this:



Step 2:


In a second step, here’s another video that shows how you can use the tinned components to initiate a collector process, capturing all the tin (which also contains traces of precious metals). Although I missed recording the actual collecting process, the method is fairly straightforward:
When you heat the mix of components and tin, the copper pads oxidize and turn black. These oxidized pads no longer adhere to tin. As you heat the mixture further, the tin melts and coalesces into droplets. By stirring the heated mix, you can form a large tin ball, leaving behind components that are completely free of tin. In the video, you’ll see the small tin bars I produced using this method.

Roasting/Oxidizing the solderpads of SMD components and seperating the tin and the components works like a charm! I did develop this method more than a decade ago and I rarely have seen anyone using this method.

Experimental Recovery technique by M.A. Buth (Not established yet in industrial scale)
Grind components use tin as collector, sperate the tin balls by gravity:



Alternative Chemical Processing:

If you absolutely want to use chemicals, I recommend using dilute sulfuric acid and giving it sufficient time to work.


I strongly disagree with mixtures that recommend combining urea with ammonium, potassium, or sodium nitrate. This is complete nonsense! Why combine nitrates and urea in the same solution? Urea will only reduce the effectiveness of the nitrate component. Moreover, introducing nitrates along with heat may dissolve precious metals, among other issues.


Final Thoughts:


PLEASE, stop believing that there is one magic chemical that can achieve recovery instantly with zero waste. Take your time and use minimal resources. You will be rewarded with finely divided fractions of soft metals, other base metals, and precious metals, which can then be processed using the appropriate chemicals. Forget the “from rags to riches” schemes—they simply do not exist in recovery. If you need fast money, consider trading or selling your material on a daily basis for arbitrage. However, once you begin treating it with chemicals, it’s best to do things properly and allow the reactions the time they need. That is the only sustainable approach.

Go check out one of the books (f.e. The Gold Hunter's Guide where this method is proposed and explained) I wrote about these "life-hacks" "Underground refiner" tricks and tipps instead of trying to reinvent the wheel. It is all there!
Btw: Today industrial refiners use the same method! They used hot air in a metal rotating drum. Components will be oxidized and fall of whereas the tin will gather in large droplets. (Maybe the chinesse read my book and watched my old videos on my experiments on that also )

(From "The Gold Hunter's Guide", by M.A. Buth)

Sorry, but some of the stuff got me really annoyed. Need to cool down now!
Sub my dusted YT channel( https://www.youtube.com/user/adrenalinemedia), if there is enough interest I will create and upload some new Recovery & Refining stuff I have been working on in the last years.

---

 

[Yggdrasil]

9I came back today and was shocked by the number of posts that were extremely misleading , along with a few that claimed to be “best practice.” Now, after my rant, here’s the constructive part:


First off: If you want to make money by recovering precious metals (and non-precious ones like copper and tin, too), TAKE YOUR TIME! Recovering metals is not a fast-money scheme. Several factors determine the speed and effectiveness of recovery: the chemicals used, time, and energy (heat). I recommend preferring energy and time over the excessive use of chemicals. This approach greatly reduces the waste you create and minimizes the hazards associated with toxic byproducts.


Stop trying to turbocharge the recovery process with overly strong reagents like nitric acid, “Poor Man’s AR,” excessive hydrogen peroxide, and other “exotic” chemicals.


Removing electronic components from boards is quite simple—especially when dealing with primarily SMD (surface mount) components rather than through-hole components.


I’ve seen the most sensible and best-practice advice from @goldman1959 on this topic:
https://goldrefiningforum.com/threads/removing-solder-from-printed-circuit-boards.35832/post-389406

Micro Scrapping (Small-Scale Recovery): Separating Tin from SMD Components​

Step 1:


Use a heat gun and a stainless steel spatula to scrap all the components off the boards, aiming to separate the tin from the components in this initial step. This method primarily uses energy (heat) and requires minimal labor and time. You’ll end up with a mix of components and tin.


I demonstrated in a video around 2013 how to use this mix as a starting point for a manual collector technique. By roasting the components, the tin adheres to other tin particles, while the components oxidize—thereby separating the tin from relatively clean components.


Here is my video of doing this:



Step 2:


In a second step, here’s another video that shows how you can use the tinned components to initiate a collector process, capturing all the tin (which also contains traces of precious metals). Although I missed recording the actual collecting process, the method is fairly straightforward:
When you heat the mix of components and tin, the copper pads oxidize and turn black. These oxidized pads no longer adhere to tin. As you heat the mixture further, the tin melts and coalesces into droplets. By stirring the heated mix, you can form a large tin ball, leaving behind components that are completely free of tin. In the video, you’ll see the small tin bars I produced using this method.

Roasting/Oxidizing the solderpads of SMD components and seperating the tin and the components works like a charm! I did develop this method more than a decade ago and I rarely have seen anyone using this method.

Experimental Recovery technique by M.A. Buth (Not established yet in industrial scale)
Grind components use tin as collector, sperate the tin balls by gravity:



Alternative Chemical Processing:

If you absolutely want to use chemicals, I recommend using dilute sulfuric acid and giving it sufficient time to work.


I strongly disagree with mixtures that recommend combining urea with ammonium, potassium, or sodium nitrate. This is complete nonsense! Why combine nitrates and urea in the same solution? Urea will only reduce the effectiveness of the nitrate component. Moreover, introducing nitrates along with heat may dissolve precious metals, among other issues.


Final Thoughts:


PLEASE, stop believing that there is one magic chemical that can achieve recovery instantly with zero waste. Take your time and use minimal resources. You will be rewarded with finely divided fractions of soft metals, other base metals, and precious metals, which can then be processed using the appropriate chemicals. Forget the “from rags to riches” schemes—they simply do not exist in recovery. If you need fast money, consider trading or selling your material on a daily basis for arbitrage. However, once you begin treating it with chemicals, it’s best to do things properly and allow the reactions the time they need. That is the only sustainable approach.

Go check out one of the books (f.e. The Gold Hunter's Guide where this method is proposed and explained) I wrote about these "life-hacks" "Underground refiner" tricks and tipps instead of trying to reinvent the wheel. It is all there!
Btw: Today industrial refiners use the same method! They used hot air in a metal rotating drum. Components will be oxidized and fall of whereas the tin will gather in large droplets. (Maybe the chinesse read my book and watched my old videos on my experiments on that also )
View attachment 67512
(From "The Gold Hunter's Guide", by M.A. Buth)

Sorry, but some of the stuff got me really annoyed. Need to cool down now!
Sub my dusted YT channel( https://www.youtube.com/user/adrenalinemedia), if there is enough interest I will create and upload some new Recovery & Refining stuff I have been working on in the last years.

---

Excellent reality check
Thanks.

 

[haveagojoe]

@Marcel I agree with your main point that trying to speed up processes is on the whole a bad idea. I also agree that magic recipes for solder removal are nonsense.

a few that claimed to be “best practice.”

---

I think I should respond to this, since you may be referring to my comment on another thread:
"I believe it's good practice to remove tin solder first with HCl anyway when doing Copper Chloride etching"

https://goldrefiningforum.com/threads/ap-on-my-way.35819/post-388830

This was a misleading comment. I do believe it's good practice to remove tin solder first, but not necessarily with HCl, that's just how I do it.

The heat-based method you demonstrate would likely be much more effective; unfortunately it's not very practical for me at the moment, but I will look into it further if I start working with larger volumes.

Edit to add: I should also re-itterate that my main method for recovering gold from soldered boards is by simply cutting them up with snips to retrieve the unsoldered gold parts, which I prioritize. Soldered segments are likely more effort than they are worth at the hobby level so I generally set them aside until I have a big enough pile to justify the acid and time.

 

[Barstool miner]

Of course, I wasn't satisfied with the previous experiment, so I did another experiment today. This time with hydrochloric acid and the addition of citric acid. After about three hours, I took the tiles out of the bath.

View attachment 67506View attachment 67507View attachment 67508View attachment 67509View attachment 67510View attachment 67511
You can clearly see where the gold was visible and where the acid ate away the solder. But I have a feeling that in some places the solder was applied over the gold layer. I was stupid not to take a before and after photo of the plate.

Can you recover the Tin and lead separately from this Solder Leach?

 

[Yggdrasil]

Can you recover the Tin and lead separately from this Solder Leach?

Separating them is easy, just add Sulfuric acid, Lead Sulfate is not soluble.
But to reclaim Tin you will probably need to go the electrolytic way.

 

[Shark]

Not drum scale but works decent for a small scale home user.

 

[VolkD]

I agree with your main point that trying to speed up processes is on the whole a bad idea. I also agree that magic recipes for solder removal are nonsense.

This is completely too generalized.
People are different, we have different needs and of course completely different possibilities. Both from a financial aspect, from the aspect of tools and machines and of course also from the aspect of time.
It all depends on what you can afford. I certainly lack time the most. I probably won't live more than a year.
So I would rather not talk about the meaning of accelerating procedures. Otherwise, I prefer to stick to research in physics and chemistry. But I myself get angry when someone tells me that everything is known anyway and research is pointless. I get even more angry when someone claims that only their method is correct, but does not state the starting point.
If I take micro scrapping as an example. My attitude towards this is completely different from, say, the attitude of industrial work. I am basically an electronics engineer and I know components very well. I can get $1 for the connector in the picture below. The gold on it will not reach this value for a long time. It's similar for a lot of other chips, which I save and put in bags and upload to a database that is accessible to everyone at
http://material.volkd.si/PREGLED.ASPX
And of course, some starting points are elsewhere and not at the point of money.

 

[Ayham Hafez]

If you just want to get plated gold from pcb, best option is to use cyanide leaching, with cyanide you will save time and money, it's not feasible to use strong acids like HCl or Sulphuric acid to get low grade plated gold, usually plating gold on pcb is done after soldering the pcb so tin-lead solders will not cover any gold.

For small scale, leaching pcb with cyanide will get gold also from pins, so next step of gold recovery will be only with IC chips, you can seperate all pcb components using heat gun or any heat source then incinerate and mill everything then use 200 mesh sifting screen to separate all large particles including pins which already leached by cyanide, after that you can wash the ash and extract gold from bonding wires, I use this approach when I have small amount of pcb and don't want to go with smelting.

 

[VolkD]

What about the safety aspect of working with cyanide?

 

[Ayham Hafez]

What about the safety aspect of working with cyanide?

For me, cyanide less harmful than Nitric acid and easier to deal than HCl or H2SO4, just use low cyanide concentration like 1 to 2 grams per liter (avoid using excess cyanide to decrease HCN gas), and after finishing just use bleach to safely destroy cyanide and avoid generating HCN gas, don't forget to use proper gloves and filter mask.

 

[VolkD]

For me, cyanide less harmful than Nitric acid and easier to deal than HCl or H2SO4, ...

Unfortunately, it is impossible to get this chemical in our country. I can get HCl 30% in any drugstore at a very good price (1.6€ per liter).

 

[Ayham Hafez]

Unfortunately, it is impossible to get this chemical in our country. I can get HCl 30% in any drugstore at a very good price (1.6€ per liter).

1.6 EUR per liter is not cheap, I get HCl 33% about 0.25 EUR in my country, and cyanide about 13.3 EUR per kilogram, even though cyanide method much cheaper cause if you will use HCl to make copper chloride to get gold foils you will spend a lot of time and you will not get all gold yield cause some gold will go into solution and to get it you need to wait couple days and filter whole solution to get very small gold powder, I stopped dealing with AP since more than one year, believe me its not feasible at all, direct aqua regia or dilute nitric-sulphuric leaching much better (but not the best)

 

[VolkD]

1.6 EUR per liter is not cheap, I get HCl 33% about 0.25 EUR in my country, and cyanide about 13.3 EUR per kilogram, ...

Are we talking about potassium cyanide? Well, prices and numbers are relative. In our country, 1kg of bread costs €4.8.

 

[Ayham Hafez]

Are we talking about potassium cyanide? Well, prices and numbers are relative. In our country, 1kg of bread costs €4.8.

If bread costs like that then HCl price is not so high as I thought.

Potassium cyanide usually much expensive than sodium cyanide, both have same gold leaching effect.

 

[haveagojoe]

This is completely too generalized.
People are different, we have different needs and of course completely different possibilities. Both from a financial aspect, from the aspect of tools and machines and of course also from the aspect of time.
It all depends on what you can afford. I certainly lack time the most. I probably won't live more than a year.
So I would rather not talk about the meaning of accelerating procedures. Otherwise, I prefer to stick to research in physics and chemistry. But I myself get angry when someone tells me that everything is known anyway and research is pointless. I get even more angry when someone claims that only their method is correct, but does not state the starting point.

Apologies Volk, I don't mean to make you angry. I understand and respect your approach and I acknowledge your circumstances. I only say "on the whole", meaning "for most people" or "in most cases". Of course things are not the same for everyone, it was indeed a generalization.

I do think some of the recipes suggested in this thread are questionable, but like you I am interested in experimentation and the potential for new methods, so I retract my remark labeling them as nonsense.

However, for the benefit of readers, and ultimately in the interest of safety, I think it would be beneficial to provide the formula for reactions when novel ideas are proposed, so that members can follow the logic of the proposal and discuss its potential. I worry that without understanding why chemicals are used, particularly in combination, a new approach could potentially become a recipe for disaster in the hands of an inexperienced reader.