# Circuit Board silver and gold recover



## bertthedude (Mar 10, 2022)

Like many I'm sure... I wish I would have found this site before I started... So it seems many videos on you tube seem to only have perfected material to work with. So here is what I did and where I'm out now. I removed everything from a bunch of random circuit boards. Pulled out all the capacitors and stuff garbage. For everything else that looked like it was gold plated I put in my smelter and roasted off all the plastic. I did not get hot enough to melt any gold or silver, but I had a good bit of melt metal on the bottom which I'm assuming was solder, aluminum, and maybe tin. I rinsed everything (but I sure not enough) I then put it all into an old coffee put and added 50% distilled water and 50% Nitric acid with a bubbler and turned the heat on. I like the coffee pot because it will turn off if it over heats. I keep checking every now again and re-start the coffee pot timer I did this pretty much all night. In the morning I have what looks to be black sludge. I pour half of this out and add more Nitric because it looks that all to Nitric has been spent. After a few hours my solution is a blue-ish green color. I filter the solution and have a pretty blue-ish green solution (I'm assuming a lot of copper is in it) and I have a black slime in the filter. (but at least I can still see the gold in the filter) I put a copper rod into the solution and all I get is a little white coloring on the copper. I took a sample and added some SMB. Very little reaction so I think most of the Nitric is spent. I took another sample and added Hydrochloric acid and nothing dropped out. I also did a stanos test and it did now indicate that there is any gold or platinum metals in solution... My first assumption is that the heavy amount of copper in my solution my have precipitated the silver into this black mud. At this point I'm not sure on what to do with this "mud" It has all my gold in it. I did take a sample and panned the "mud" but due to how fine the "mud" is I could see a lot of gold going over the edge even with a good amount of Jet Dry in the pan. Very super fine gold. I did look unto a lens and it was gold not brass or anything else. 

So my solution shows negative of Silver or gold- Should that just go into a stock pot?
And what do I do with this "mud"

Thanks Everyone! Feel free to give me a hard time for being a noob


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## nickvc (Mar 11, 2022)

Yep your first mistake is watching most but not all YouTube refiners .
There is rarely much silver in circuit boards but plenty of tin so adding nitric will form the dreaded metastanic salts which will mask any gold you recovered, if you have solder lumps from the roasting and it was in contact with any gold will have absorbed it.
The residue in your filter should be where your gold is and that will need incinerating to convert the metastanic back into tin which you can then remove using HCl , then pour off the solution and dissolve whatever is left using fresh HCl and minimum amounts of nitric.


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## bertthedude (Mar 11, 2022)

This sounds like a good plan. I did do a melt test last night on the "mud" which I'm assuming you are calling the metastanic salts... After it melted it formed mostly a very brittle black cake that I broke apart and viewed with a lens and I did see a good bit of silver looking metal. Which I assume now is tin. 
One question I do have is will HCL pull silver into solution? I see many conflicting answers to this and I would like a clear answer from people that do this a lot.

Thanks for the advice! Like I stated a few time I sure wish I had found this site well before I started this adventure! Would have saved me a lot of time and money


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## Alondro (Mar 11, 2022)

nickvc said:


> Yep your first mistake is watching most but not all YouTube refiners .
> There is rarely much silver in circuit boards but plenty of tin so adding nitric will form the dreaded metastanic salts which will mask any gold you recovered, if you have solder lumps from the roasting and it was in contact with any gold will have absorbed it.
> The residue in your filter should be where your gold is and that will need incinerating to convert the metastanic back into tin which you can then remove using HCl , then pour off the solution and dissolve whatever is left using fresh HCl and minimum amounts of nitric.


It gets really tricky when you have IC chips, which DO have silver all over their leads and internal contacts sometimes, as well as on the silicon chip itself. Then, sulfuric is really the only way to go. HCl will turn the silver plating into silver chloride, which is almost impossible to recover from all the junk solids. 

Nitric can still make a mess with IC chips if they have bismuth in them anywhere, or tin-plated leads (the bulky old-type ICs) or the solder dots of the modern flat types. And then there's aluminum, which forms aluminum nitride, not only insoluble, but impermeable to boot!

I did a test on a couple different chip pieces with nitric in test tubes. In EVERY case there was insoluble white goo at the end, in varying amounts. 

Really, I've decided to use nitric solely for the purification steps after the initial recovery, to form true AR for dissolving platinum, and to separate cemented silver-palladium powder recovered from capacitors (and chips). It's the most expensive of the common mineral acids, and the most dangerous. No reason to use it other than for fine purification and recovery of the Pt-group metals. 

Sulfuric makes SO2 gas, but with a simple gas-recovery setup, it's easy to catch virtually all of it and remake sulfuric acid (bubbling through 3% hydrogen peroxide in at least a double flask-bubbler series... can use 35%, but that reaction will get rather hot.) You end up with a weak sulfuric acid that can be used for base metal stripping, and catch the gas again. It extends your reagent's value.


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## Alondro (Mar 11, 2022)

bertthedude said:


> This sounds like a good plan. I did do a melt test last night on the "mud" which I'm assuming you are calling the metastanic salts... After it melted it formed mostly a very brittle black cake that I broke apart and viewed with a lens and I did see a good bit of silver looking metal. Which I assume now is tin.
> One question I do have is will HCL pull silver into solution? I see many conflicting answers to this and I would like a clear answer from people that do this a lot.
> 
> Thanks for the advice! Like I stated a few time I sure wish I had found this site well before I started this adventure! Would have saved me a lot of time and money


HCl won't pull silver into solution, but it will turn it into white silver chloride after a while. You can recover this from your mud by drying it in bright sunshine in a thin layer. The silver chloride will decompose from the UV light into chlorine gas which blows away, and metallic silver. 

Or, after filtering out the solids from the base metal-containing HCl solution, wash it, and then cover with distilled water, then you add NaOH and warm it, turning the silver chloride to silver oxide (and NaCl in solution). Wash the powder again, and add dextrose or sucrose (which are reducing sugars. Dark corn syrup is high dextrose and works great.) to turn the silver into metallic gray powder.

From either the Sun-drying method or the NaOH-sugar method, you'll have powder composed of powdered gold and silver. Then after washing a couple times, you can NOW dissolve the silver out with nitric and leave the gold behind in the mud.


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## bertthedude (Mar 11, 2022)

Alondro said:


> HCl won't pull silver into solution, but it will turn it into white silver chloride after a while. You can recover this from your mud by drying it in bright sunshine in a thin layer. The silver chloride will decompose from the UV light into chlorine gas which blows away, and metallic silver.
> 
> Or, after filtering out the solids from the base metal-containing HCl solution, wash it, and then cover with distilled water, then you add NaOH and warm it, turning the silver chloride to silver oxide (and NaCl in solution). Wash the powder again, and add dextrose or sucrose (which are reducing sugars. Dark corn syrup is high dextrose and works great.) to turn the silver into metallic gray powder.
> 
> From either the Sun-drying method or the NaOH-sugar method, you'll have powder composed of powdered gold and silver. Then after washing a couple times, you can NOW dissolve the silver out with nitric and leave the gold behind in the mud.





Alondro said:


> Then after washing a couple times,


You said after washing it a couple of times... This "mud" is very fine how do I go about washing it without losing to much of what I want... It seems that even the gold in it that I can see is very flour like gold that seems to want to come out when I wash. Any good tips?


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## orvi (Mar 12, 2022)

bertthedude said:


> You said after washing it a couple of times... This "mud" is very fine how do I go about washing it without losing to much of what I want... It seems that even the gold in it that I can see is very flour like gold that seems to want to come out when I wash. Any good tips?


Patience in decantation. Let it settle for a long time, than decant. Or opt for very good quality filter paper. With very fine gold particles after precipitation from the solution, filtration isn´t always the best idea.


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## Martijn (Mar 12, 2022)

If your gold dust wont settle, give the solution a gentle boil with a couple ml's of sulfuric acid.
It will make the gold cleaner and clump together better and sink faster.
It also helps with decanting the washes later on.


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## Alondro (Mar 12, 2022)

orvi said:


> Patience in decantation. Let it settle for a long time, than decant. Or opt for very good quality filter paper. With very fine gold particles after precipitation from the solution, filtration isn´t always the best idea.


I have the luck of owning an old 50ml conical tube centrifuge from a closing lab. It's perfect for spinning down up to a couple ounces of finely powdered PMs floating about.


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## kurtak (Mar 13, 2022)

Alondro said:


> It gets really tricky when you have IC chips, *which DO have silver* all over their leads


Sorry but that just is not true --- the leads - which are the wires that come off the CB & then go "into" the IC chip will be ether kovar or copper (kovar being the most common) are nickel plated - there is NO reason to plate them with silver


Alondro said:


> and internal contacts sometimes,


if you are talking about the bonding wires that make the connection between the "leads" & the silicon chip again they are NOT silver - they are ether gold bonding wires or they are aluminum bonding wire - in other words - if they are silver in color then they are aluminum NOT silver 


Alondro said:


> as well as on the silicon chip itself.


Again - just not true - at least as far as I have seen & I used to process 500 to 600 pounds of IC chips per year (talking about the black epoxy type chips)

if you are talking about ceramic chips that is a different story - which are a completely different process then black epoxy chips 



Alondro said:


> Then, sulfuric is really the only way to go.


If you are talking about using sulfuric to "carbonize" the epoxy - then you are talking about a process called "wet ashing" which is an EXTREMELY dangerous process & VERY inefficient way to carbonize chips 

It's a process used only by You Tube IDIOTS !!! --- & is STRONGLY advised against here on this forum

If you are going to ash (&/or carbonize) epoxy IC chips you are FAR BETTER served doing so by pyrolyzing/incineration --- which is discussed EXTENSIVELY here on this forum 

If you are talking about using sulfuric to deal with base metals that a different story --- however - IMO there are better ways to deal with base metals the sulfuric 


Alondro said:


> HCl will turn the silver plating into silver chloride,


again sorry but just not true - HCl alone will not react with silver (unless it is VERY finely divided plus heat - plating is not finely divided enough for HCl to react) there needs to be an oxidizer present to react with the silver in which case then (once the silver has been oxidized) the HCl will cause the creation of AgCl 


Alondro said:


> Nitric can still make a mess with IC chips if they have bismuth in them anywhere,


Again just not true - nitric dissolves bismuth - though yes - raising the Ph above 0 (over diluting) will cause bismuth pentahydrate to precipitate

Let me put it this way - after processing several hundred pound of chips per year & literally several tons over the years - bismuth - as a result of treating the ash with nitric has NEVER been a problem that created "a mess" 


Alondro said:


> or tin-plated leads (the bulky old-type ICs)


As I said before - the vast majority of leads are plated with nickel not tin


Alondro said:


> or the solder dots of the modern flat types.


you are talking about BGA type chips here - & yes if you put them in nitric the nitric will cause the tin solder balls to form the white goo called meta stannic acid - which yes will create a BIG mess - with is why (with this type chip) we first advise to treat with HCl to get rid of the tin --- in other words get rid of the tin before pyrolyzing/incineration 


Alondro said:


> And then there's aluminum, which forms aluminum nitride, not only insoluble, but impermeable to boot!


Again just not true - nitric (unless VERY dilute) does not react with aluminum - certainly not in a way that will cause a mess

Nitric acid - when applied to aluminum causes an aluminum "oxide" to form - a "few" atoms thick - on the surface of the aluminum- this oxide - on the surface - then causes the aluminum to "passivate" thereby preventing the nitric from further reacting with the aluminum


Alondro said:


> I did a test on a couple different chip pieces with nitric in test tubes. In EVERY case there was insoluble white goo at the end, in varying amounts.


As I said - yes - if tin (likely from solder) is involved - nitric will cause the problem of meta stannic acid - which as I also said is why treating with HCl "first" is suggested to get rid of the tin


Alondro said:


> Really, I've decided to use nitric solely for the purification steps after the initial recovery, to form true AR for dissolving platinum,


VERY rarely (if ever) is platinum found in electronic scrap


Alondro said:


> and to separate cemented silver-palladium powder recovered from capacitors


yes silver & palladium is found in SOME capacitors - but nitric will not separate them as nitric will dissolve both silver & palladium


Alondro said:


> (and chips).


but never in chips - at least not in the black epoxy chips - ceramic chips are a different story


Alondro said:


> It's the most expensive of the common mineral acids,


that depends on your source &/or amount you are buying 

When I was full time refining I bought 53% nitric in 55 gallon drums for around $3 per gallon & 67% nitric in 15 gallon kegs for around $7 -$8 per gallon 


Alondro said:


> and the most dangerous.


LOL - sulfuric acid is BY FAR more dangerous then nitric 

Not saying nitric is without danger - but lets be real here - sulfuric is MUCH MORE dangerous


Alondro said:


> No reason to use it other than for fine purification and recovery of the Pt-group metals.


Really ??? --- nitric is "required" to process silver - & though not required is certainly preferred for gold refining AR 


Alondro said:


> Sulfuric makes SO2 gas, but with a simple gas-recovery setup, it's easy to catch virtually all of it and remake sulfuric acid (bubbling through 3% hydrogen peroxide in at least a double flask-bubbler series


Here we go again with the sulfuric - which is BY FAR more dangerous then nitric --- & for what it is worth - you can recover your nitric by bubbling the nox fumes through H2O2 as well - which can as well be used for silver &/or base metal processing - thereby extending you (nitric) reagent value

I am sorry if what I have just posted sounds harsh - but some of what you have been posting here is at the very least "bad" information & in some cases actual mis-information & appears to simply be things you are posting here from watching to much You Tube which if full of bad &/or mis-information

So it is not my intent to be hash - but rather to make some corrections to what is clearly bad &/or mis-information being posted here

Kurt


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## Alondro (Mar 13, 2022)

kurtak said:


> Sorry but that just is not true --- the leads - which are the wires that come off the CB & then go "into" the IC chip will be ether kovar or copper (kovar being the most common) are nickel plated - there is NO reason to plate them with silver
> 
> if you are talking about the bonding wires that make the connection between the "leads" & the silicon chip again they are NOT silver - they are ether gold bonding wires or they are aluminum bonding wire - in other words - if they are silver in color then they are aluminum NOT silver
> 
> ...


Are we talking about the same IC chips? I have a bunch, the long thick rectangular old type, which absolutely have silver plating over brass. I even recovered silver from the plating. And on the inside, the bond wires were attached to little plates right at the tip of the 'arms' that are palladium plated over pure copper. Now, the chips came from very high-end industrial equipment made in the 1970's and 80's, so perhaps that's why? I have the consumer-grade ones too, and yes those are just kovar on the outside and aluminum-plated inside. I sort those differently. Those leads are magnetic. The high-grade ones I have separately aren't. I even have a handful of white-plastic-coated IC chips from a few old telecommunications CPU boards that were all gold inside when I cracked them open. As with all electronics, the super-expensive high-end stuff is WAYYYY beyond the 'garbage' sold to consumers, lol.

I even have some military-grade chips from specifically 1976, and those have a tremendous amount of silver and gold, and some canister IC transistors which are gold-plated inside and out, with the chip sitting on a bed of silver, and solid platinum electodes attached to the chip. Here's the inside of one I popped open today.




My descriptions of my protocols were highly incomplete, I was just making a rough list of topics. I burn all the chips first spread out in single layer on top of a steel mesh over a hot flame (except the ceramics, which are going to be a pain to crush and powder when I get to them) and then wash off the ash. I saw one vid you mentioned using sulfuric acid to dissolve the plastic, and I never thought that was a good idea. It's a waste of reagents, for one. And you end up with organic and metal acid sludge that's extremely toxic. The person doing that method was also clearly losing a lot of his PMs in other steps. The recovery was terrible. It's why I miss the downvotes on YT. I watched that one early last year, and only because I wanted to know why it had so many dislikes at the time. NOW it's hard for a beginner to judge if a method looks plausible or not, because YT decided to be dumb.

The newer flat chips mostly have tin solder, but I have found some that did contain bismuth solder. Those were very new chips, and upon looking into it, there was quite a push in the industry to use bismuth-based solders because of the low toxicity of bismuth salts, and because bismuth alloys so well with many metals (it can even be used for cupelling the same as lead, just more expensive; so it's sensible to recover it from the cupel). I was even able to turn it back to bismuth after it became goo in the rest tube, heating to decompose the nitrate, then reducing with carbon. I cooled it slowly in a little crucible inside hot bricks and sure enough, a little bit of the weird colorful and squarish bismuth crystal grew, just enough to confirm it. There's a reaction which takes place if the solution gets too warm during the reaction: it forms bismuth oxynitrate, also called bismuth subnitrate. I likely formed that because I had too little acid, since I was doing it in a test tube. This raised the pH above 1 while the solution was still quite hot and thus triggered the thermal decomposition of the bismuth nitrate.

And of course there's the indium solder found in some types of CPUs. It's tough to describe EVERY possible variation in one post!

I did somehow manage to turn silver plating into silver chloride in HCl in my test. Perhaps something else in the alloys of the base metal catalyzed it? Or could it simply be that the nano-layer plating was thin enough to completely react as the base metal was dissolved?

My mention of aluminum nitride goo is regarding aluminum brass used in some 'soft' gold-plated pins, which creates the aluminum nitride goo as the brass dissolves and frees the aluminum, which then becomes the nitride sludge. I happen to have quite a large number of that type of pin, again from that old industrial equipment where they are found in whole boards of connectors. Those I'll use HCl on, which dissolved the aluminum. 

But I have other components that are complicated in construction with many tiny internal parts and clearly have aluminum brass with silver and gold plated bits, as well as little internal nano wires. I don't even know the names of these components, they were only on a specific box of boards I bought. I suspect they're some sort of control or regulator unit for a highly specific application.

Perhaps it's my biochemical background, but I'm far more worried about nitric acid's carcinogenic by-products and the contact explosives it can create (nitroglycerine, trinitrotolunene/picric acid, and many fulminates) than sulfuric acid's vapors and ability to eat up organic material, which I can deal with thanks to my training in handling strong acids (I've worked with chlorosulfuric acid in organic synthesis). I have lab-grade glassware in plenty, and several laboratory fume vacs, chemical-resistant tubing, and lab heating blocks and plates and ceramic-coated magnetic stir bars meant for use in corrosive liquids, so I can deal with SO2 vapor easily. In my state as well, government tends to raise eyebrows on people buying large quantities of nitric acid, due to the afforementioned boom-booms it is used to synthesize. It's NJ, and they are EXTREMELY hard to deal with. Simple fountain fireworks were illegal here for decades, for instance. Sulfuric is found in hardware store industrial-strength drain-cleaners, and isn't regulated as much as nitric here. 

I've just found sulfate chemistry so simple to use. Oh, and the note of silver-palladium separation with sulfuric was just an off-note. In more detail, it's useful to pull BOTH metals out of a mix of parts, then cement on copper and THEN use nitric to redissolve them for further purification via silver chloride precipitation followed by palladium reduction methods. 

I wasn't posting whole protocols, since each one is a full page long! My protocols (I was a biomedical genetics researcher for 17 years) tend to be quite exhaustive in detail. And they differ for every subclass of components I've sorted. I have no less than 2 dozen jars of different electronics, even different classes of pins, and each one has it's own protocol associated with it. I still have to completely subclassify the capacitors, of which there are dozens of types. 

As you know, MLCCs alone have multiple types of metals on their ends: nickel, nickel-silver, silver, silver-palladium, and the rare 'holy grail' palladium-palladium ones. Thankfully, different-strength magnets do a good job of sorting them. Then there are the canister rolled foil-electrolyte types, most of which are aluminum, BUT some of the older ones also have a tantalum strip (and the double-ended ones which are often all tantalum, especially in the military-grade stuff I have), and I even found a handful of oldies with tell-tale purple-black tarnish on the leads which indeed was silver. Foil capacitors are a pain in the rear to sort. But tantalum is rocketing up in price, so I'm glad I saved them all. In fact, I just looked up tantalum prices again, and my jaw broke through the floor.


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## kurtak (Mar 15, 2022)

Sorry but I have been quite busy so have not had time to reply (but intend to)

However ---------



Alondro said:


> But tantalum is rocketing up in price, so I'm glad I saved them all. In fact, I just looked up tantalum prices again, and my jaw broke through the floor.


Not true - in fact tantalum is quite low right now at (around $9 per pound) considering back in Dec. 2000 it was around $35 (it's HIGH over the last 11 years)






 real time tantalum price chart - Search







www.bing.com





$9/lb is certainly not jaw dropping

even on the (last) month chart with a high of $11.75 is not jaw dropping

maybe you were looking at a per ton price if your jaw feel through the floor

Kurt


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## kurtak (Mar 15, 2022)

Hmmm

Just looked at this









Tantalum 99.95%Min United States Spot Historical Prices - Investing.com


Tantalum 99.95%Min United States Spot historical prices: closing price, open, high, low, change and %change of the Tantalum 99.95%Min United States Spot for the selected range of dates.



www.investing.com





Doesn't say per what though (pound - kilo - or other)

Kurt


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## Geo (May 22, 2022)

The silver in IC chips is the grounding base that the silica chip sit on. Normally an alloy of silver/palladium. The Pd is such a small percentage that it takes a lot of condensed material to add up. I possibly have upwards of 500 pounds of lead frames from IC chips after milling and classifying. Of that, I am guesstimating 100 pounds will be Kovar. Of the 400 pounds of copper left, I am expecting 3% silver or roughly 12 pounds.


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## Geo (May 22, 2022)

During milling, some of the silver is ground off and reports with the gold bonding wires. Upon leaching the final concentrates, I always have silver in the nitric acid leach. Always without exception.


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## Geo (May 22, 2022)

The silver in electronics is seldom exposed. If it is, it is always power transfer. Like silver plated buss. In consumer electronics, the silver will always be in the components. Surface mounted devices mostly/ MLCC's, brazing when two metals are bonded together. Even tantalum capacitors has a little silver, not the canister type but epoxy encapsulated ones as well. I will get some pics of the silver infused left over sludge and different stages of it today.


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