My results of specific types of IC chips, flatpacks and BGA

[kernels]

What an amazing result Tzoax, I am in disbelief about how good the yield is. Just another piece for your amazing thread. Thank you for the effort you put into this stuff and sharing it with us.

 

[Johnny5]

The one that can create problem is Sn²⁺ that makes a gel that traps gold when mixed with nitric acid or colloidal gold when mixed with gold chloride. Sn⁴⁺ as an oxide might be a lot easier to filter and will not reduce gold chloride. You could always try on a small sample to see if you can put gold in solution without making an unfiltrable (is that a word?) gel.

Göran

Would this cause the filtered powder to give a positive result, when tested with stannous chloride?

 

[g_axelsson]

You will get a positive result if you have gold present. The tin in that picture is either all oxidized and won't reduce any gold or if you get a barren solution the tin has already reduced the gold chloride back to metallic gold and then it's mixed in with the sludge.
If you still has excess of nitric acid then all the tin is oxidized.

Göran

 

[Tzoax]

Heat gun or hot sand bath will be much faster solution to recover tin than a knife. I was doing it with knife first too but after some time I moved to heat as I needed to scale up and make it all faster. Knife is ok for few pieces but your hands will be falling off after few hundreds and "production" will go down fast.

I prepared material for new test. This test will give me an answer is it better to process solder balls like i did in the first test (not melted) or when melted. And now i can compare new with old result and see the difference. So i prepared 104.9g of solder balls for this test (scrapped with knife or chisel).



After melting solder balls with hot air gun i poured the melted solder to water to make granules.



After measuring weight of solder granules, from original 104.9g of solder balls now solder granules weights 76.3g. That means that from 100% of solder balls - 72.7% goes to solder granules, and 27.3% to residues.
This is a picture of residue:



So this test will also give an answer is there considerable amount of gold in that 27.3% to residues. If my results after this test gives approximately same percentage of gold per kilogram (based on starting weight - not melted 104.9g) and my first test (1.42g/kg) then it will be much better, easier and faster to do collect solder that way - hot sand / air gun. Also, material will be pure, less of Cu and trash, less chemicals used etc. But first i will have to be sure that most of the gold will go to molten solder, that is why i am running this test. If there is considerable gold in that residue "trash" then i think mechanical separation will give more gold.

Anyway, i am optimist Pat, based on your document - 2.24g of gold for kilogram for pure solder (without trash/residues).

Alex

 

[kernels]

Bugger, now I'm going to be checking this thread every two hours for the next week again! Can't wait to see your results from this batch. I would recommend you process the residue first, should be a bit easier and we will get some information sooner!

 

[Tzoax]

Bugger, now I'm going to be checking this thread every two hours for the next week again! Can't wait to see your results from this batch. I would recommend you process the residue first, should be a bit easier and we will get some information sooner!

I already processed solder granules with HCl 2 days ago. It took 10 hours of simmer boiling with 600ml of 20% HCl to completely dissolve tin and lead. Yesterday i filtered the solution while still hot. Today i will incinerate filter paper. Tomorrow i will process it once again with hot HCl, filter and dissolve in AR. So in saturday i will have results for this one.

So far i see it is MUCH easier and faster to process it this way (melted solder granules) than solder balls. I hope the most of gold will be in there. After tin and lead dissolved - a light brown flakes formed at the bottom - same color like gold powder. And there is no junk or copper traces, this is very clean and fast way for processing it. The filter paper is very light, there is just a little of tin/lead left so that is why i will incinerate it just once.

I have one thought about solder in motherboards in general. I wonder what results would be if i grind just a thin layer of depopulated motherboards surface - taking off all of the solder, then melt the solder to granules and test it the same way like this. If this test gives a good results i think i will try it. Do you think it makes sense?

 

[g_axelsson]

It only makes sense to check the solder from motherboards and other circuit boards if the boards have flash plating on the solder pads. I don't know of any solder for general electronics that have gold as part of the mix, gold makes solder connections fragile and easily cracked if the level is just a few tens of a percent.

Göran

 

[kurtak]

Alex

Something to keep in mind when processing solder --- there are many different solder alloys used in electronics solders which means there is the possibility of encountering a number of different metals which can/will react different with (different) acids --- (different solders are used in different applications)

I have (or had) a paper (its several pages) that lists all the different solders used in electronics - which I have been looking for so I could provide a list of the different alloys here for you - its a paper I acquired 6 or 7 years ago & its not in the folder I normally keep that type info in so I will keep looking for it

My point is - depending on solder alloys & how the different elements react with different acids - is going to have (at least some) effect on the resulting residues left after HCl treatment

You have already talked about the lead in the solder so no need to talk more about that

However - two other elements "common" to electronic solder are antimony & silver - antimony being more common then silver

Antimony (being VERY common) is not effected by ether HCl or nitric (however - I am not sure how it is effected by AR) therefore the antimony will make up "part" of your residues after HCl treatment

Silver in solder (used for electronics) this is NOT a so to speak "silver solder" - rather - it is silver "bearing" solder --- meaning the solder (tin) is "bearing" a low percentage of silver (like 3 % or less)

Normally silver is not effected by HCl - however - because it is so diluted (finely divided) in the (tin) alloy - the HCl is likely going to cause the silver to convert (or at least partially convert) to silver chloride --- especially being as how you are running the HCl treatment hot

Therefore - IF - the solder you are working with is silver bearing - silver chloride (&/or silver) is going to make up "part" of residues after HCl treatment (along with antimony --- & ?)

I would test your residues for silver --- because of the likely hood of it being silver chloride & because it has been dried out - you will want to smelt it using soda ash as your flux - then test your smelted metal bead for silver

The silver (if its there) is likely not worth chasing (at least not on a small scale) but it would be nice to know if it is one of the elements in the solder so that you don't keep chasing it thinking its stannic tin & therefore trying to eliminate it by continued incineration & repeated HCL treatments --- in other words - trying to convert what you "think" is stannic tin (by incineration) to tin oxide & then trying to eliminate it with HCl --- as what you "think" is stannic tin - may in fact be silver chloride

Kurt

 

[patnor1011]

It only makes sense to check the solder from motherboards and other circuit boards if the boards have flash plating on the solder pads. I don't know of any solder for general electronics that have gold as part of the mix, gold makes solder connections fragile and easily cracked if the level is just a few tens of a percent.

Göran

RAM comes to mind, most of RAM I have seen does have plated pads where IC are attached, pinned and BGA both. Also majority of boards from laptop displays does have plated pads where IC, MLCC and resistors are attached.

 

[Tzoax]

Alex

Something to keep in mind when processing solder --- there are many different solder alloys used in electronics solders which means there is the possibility of encountering a number of different metals which can/will react different with (different) acids --- (different solders are used in different applications)

I have (or had) a paper (its several pages) that lists all the different solders used in electronics - which I have been looking for so I could provide a list of the different alloys here for you - its a paper I acquired 6 or 7 years ago & its not in the folder I normally keep that type info in so I will keep looking for it

My point is - depending on solder alloys & how the different elements react with different acids - is going to have (at least some) effect on the resulting residues left after HCl treatment

You have already talked about the lead in the solder so no need to talk more about that

However - two other elements "common" to electronic solder are antimony & silver - antimony being more common then silver

Antimony (being VERY common) is not effected by ether HCl or nitric (however - I am not sure how it is effected by AR) therefore the antimony will make up "part" of your residues after HCl treatment

Silver in solder (used for electronics) this is NOT a so to speak "silver solder" - rather - it is silver "bearing" solder --- meaning the solder (tin) is "bearing" a low percentage of silver (like 3 % or less)

Normally silver is not effected by HCl - however - because it is so diluted (finely divided) in the (tin) alloy - the HCl is likely going to cause the silver to convert (or at least partially convert) to silver chloride --- especially being as how you are running the HCl treatment hot

Therefore - IF - the solder you are working with is silver bearing - silver chloride (&/or silver) is going to make up "part" of residues after HCl treatment (along with antimony --- & ?)

I would test your residues for silver --- because of the likely hood of it being silver chloride & because it has been dried out - you will want to smelt it using soda ash as your flux - then test your smelted metal bead for silver

The silver (if its there) is likely not worth chasing (at least not on a small scale) but it would be nice to know if it is one of the elements in the solder so that you don't keep chasing it thinking its stannic tin & therefore trying to eliminate it by continued incineration & repeated HCL treatments --- in other words - trying to convert what you "think" is stannic tin (by incineration) to tin oxide & then trying to eliminate it with HCl --- as what you "think" is stannic tin - may in fact be silver chloride

Kurt

Thank you all for help and comments, and especially thank you Kurt for giving such a detailed explanations.

Unfortunately this last test with melted solder failed. But, everything is still there, i will process it next week, there will be no loss, i saved everything. Two unexplainable (for me) things happened. I could call them my mistakes, but either way i would like to understand what really happened. If anybody know how and why this happened it will be very interesting for me to learn it. So here is what happened:

First Question

-After 10 hours of simmer boiling 76.3g of melted solder in 20% HCl the only material that was left on the bottom was light (by weight) brown flakes, same color like gold powder.

-I planned to decant it while it was still very hot but i was in a hurry so i left it for tomorrow.

-So, next day, when solution was cold there was white lead crystals and gray powder - probably some form of tin/silver/antimony all along with "brown flakes".

-And here is when problem starts. When i started simmer boiling with HCl process again, there was no way to dissolve that gray material again (like it was dissolved day before that) even after several hours.

-Then i realized i made a "mistake" day before. I really should decant it when everything dissolves that first day - that way only thing that will left in beaker would be that brown flakes, there was no gray residues. And one more thing about those brown flakes - their shape was same shape like solder granules at first place, but much much smaller. And when i stir the solution i see that they are very light, but still drops at bottom of beaker.

-So, this is my first question - Why on a second day i couldn't dissolve everything (except those brown flakes) like i did a first day?


Second Question

-I filtered the solution

-There was not much of material left in filter paper - it was about 20 grams (weighted while still wet so i think there was about 10 grams of material left (if dried))

-I decided to not incinerate it. I process it directly with PMAR (HCl/KNO3)

-I started with 250ml of 20% HCl and added small portions of KNO3

-Interesting thing to add about "gold flakes". Now, when i added fresh HCl - brown gold flakes disappeared and solution becomes black

-Solution started to change color to yellow....more and more, and i was planning to dissolve (if possible) all of that gray material

-The color of solution was so strong yellow that is was slightly going to orange. I knew it was rich with gold.

-I couldn't dissolve that gray material from the bottom even after few hours so i was thinking it was silver and other tin states that not react with AR

-And then...i made another "mistake".... A big mistake.... If i decanted the gold chloride solution at that point, and leaving gray material in beaker - i am sure there will not be problems. But - instead i added a little water to dilute it a bit so i could easier decant it. But, instantly solution becomes white colored like milk.

-I was sure it was silver chloride so i was thinking there will not be problems - when solution cools and silver chloride settles i would decant/filter it.

-but....on my surprise - the color of filtered "gold chloride" solution becomes a very very pale yellow colored, like a very, very weak lemonade. "Something" obviously dropped gold from solution when i added water or while cooling.

-So, my second question is - why i have now "weak lemonade" when i saw "Fanta Exotic" was there?

Alex

 

[g_axelsson]

First Question

-After 10 hours of simmer boiling 76.3g of melted solder in 20% HCl the only material that was left on the bottom was light (by weight) brown flakes, same color like gold powder.

-I planned to decant it while it was still very hot but i was in a hurry so i left it for tomorrow.

-So, next day, when solution was cold there was white lead crystals and gray powder - probably some form of tin/silver/antimony all along with "brown flakes".

-And here is when problem starts. When i started simmer boiling with HCl process again, there was no way to dissolve that gray material again (like it was dissolved day before that) even after several hours.

-Then i realized i made a "mistake" day before. I really should decant it when everything dissolves that first day - that way only thing that will left in beaker would be that brown flakes, there was no gray residues. And one more thing about those brown flakes - their shape was same shape like solder granules at first place, but much much smaller. And when i stir the solution i see that they are very light, but still drops at bottom of beaker.

-So, this is my first question - Why on a second day i couldn't dissolve everything (except those brown flakes) like i did a first day?

One thing that could happen is that SnCl₂ reacts with oxygen from the atmosphere and creates various tin oxides. (The same thing that happens when stannous goes bad) These tin oxides can be really hard to dissolve again. For example SnO₂ is soluble in HCl but might require hours of reflux to dissolve. You could test NaOH too, might work better than HCl.
https://en.wikipedia.org/wiki/Tin_dioxide

The obvious solution that you already discovered is to filter it after it dissolved and before a lot of oxides are formed.

Second Question

-I filtered the solution

-There was not much of material left in filter paper - it was about 20 grams (weighted while still wet so i think there was about 10 grams of material left (if dried))

-I decided to not incinerate it. I process it directly with PMAR (HCl/KNO3)

-I started with 250ml of 20% HCl and added small portions of KNO3

-Interesting thing to add about "gold flakes". Now, when i added fresh HCl - brown gold flakes disappeared and solution becomes black

-Solution started to change color to yellow....more and more, and i was planning to dissolve (if possible) all of that gray material

-The color of solution was so strong yellow that is was slightly going to orange. I knew it was rich with gold.

-I couldn't dissolve that gray material from the bottom even after few hours so i was thinking it was silver and other tin states that not react with AR

-And then...i made another "mistake".... A big mistake.... If i decanted the gold chloride solution at that point, and leaving gray material in beaker - i am sure there will not be problems. But - instead i added a little water to dilute it a bit so i could easier decant it. But, instantly solution becomes white colored like milk.

-I was sure it was silver chloride so i was thinking there will not be problems - when solution cools and silver chloride settles i would decant/filter it.

-but....on my surprise - the color of filtered "gold chloride" solution becomes a very very pale yellow colored, like a very, very weak lemonade. "Something" obviously dropped gold from solution when i added water or while cooling.

-So, my second question is - why i have now "weak lemonade" when i saw "Fanta Exotic" was there?

Alex

That's a hard question... I don't know exactly what happened. Tin oxides could still be a thing. The added water have dissolved oxygen in it and might have created more tin oxides.
The color change might be from the aqua regia formed in solution. The yellow color of AR is from dissolved nitrosyl chloride, a yellow gas. https://en.wikipedia.org/wiki/Nitrosyl_chloride
When you added water it could have affected that compound making the color change.

This is just speculations, nothing that I have tested myself.

On another note... 250 ml HCl for dissolving 10g of material seems like a lot of acid.

Göran

 

[Tzoax]

Goran, thank you. I processed everything again (material + filter paper) with AR.

The obvious solution that you already discovered is to filter it after it dissolved and before a lot of oxides are formed.
Göran

I did it, i decanted it in filter while still hot and bright yellow colored.

I decided to repeat this process once again just in case there was still some gold left.

On my surprise solution was the same color - strong yellow.

And i did it once again - the same thing - solution was yellow.

Then, i had to stop because i had no more free time (i will continue today). So, i processed this remaining material 3 times with AR (about 125-150ml of each turn) and every time (after about 30 minutes of simmer boiling) solution was yellow like in the right picture.

On this picture - beaker on a left side is the AR solution from first time processing couple days ago, and beaker on a right side contains AR from today (3 times processing - but still this same color)

On another note... 250 ml HCl for dissolving 10g of material seems like a lot of acid.
Göran

Sorry, my mistake, it was about 120ml like in the picture, not 250ml. I confused because i used a larger beaker for processing with AR. For last 3 AR processes i used about 220ml total.


I can only guess why this is happening - why every time i use AR solution (from start) with this material solution have this yellow color (most probably gold chloride, i don't know what else could give this color).
I was thinking reason could be there was not enough time for gold to dissolve so i left it much more time to simmer boiling but...after total of 4 hours trying to dissolve it (total time of those 3 tries) there is still this color when processing it with fresh AR.

Does anyone have explanation for this?

This is first time i see this kind of reacting. In all of the cases i did the most of gold goes in a solution after first run. And on a second run of little of AR i always pick up remaining traces of gold to solution. But now... the color of AR is always strong yellow even after 3 times processing it (after first one).

Just to compare this with a test (before this one - with not melted solder balls). - after first AR almost all gold went to solution, i know that because i repeated AR run again to collect possible gold traces and color was very very pale. But now it is complete opposite - AR color gives stronger yellow color after second run - and even more stranger the color is permanent after 3 more runs.

 

[g_axelsson]

Yellow color in AR isn't a test for gold. Have you tested with stannous yet? You could test your filter papers because they usually contains enough gold chloride to tell you if the last filtration contained any gold.

At least iron could give yellow color in AR and I'm quite confident that there are other metals and compounds that can give the same color. Maybe there are some iron contamination in your HCl?

Göran

 

[Tzoax]

Yellow color in AR isn't a test for gold. Have you tested with stannous yet? You could test your filter papers because they usually contains enough gold chloride to tell you if the last filtration contained any gold.

At least iron could give yellow color in AR and I'm quite confident that there are other metals and compounds that can give the same color. Maybe there are some iron contamination in your HCl?

Göran

There was no iron, the start material was melted tin granules. I even tested it with neodymium magnet just in case before i started. Also there is no iron contamination in HCl, i know that because i never before had this color (when using this same HCl and when the gold was not present - it was always transparent, like water). It also didn't have any contact with iron or any other metal (it was not incinerated). I didn't test it for gold because i was thinking i could get false positive knowing there is possibility of a little tin dissolved there also. I will continue today several more runs if needed until i collect all of this yellow solution, there must be end of it at some point. I will continue with this until solution becomes transparent, like it always do, only then i will be sure all of the dissolving metals are in solution. Then i will evaporate it to reduce volume, neutralize and drop the gold.

I suspect it have some relation with the fact that this time i didn't incinerated material (after first AR run) at all. It was a main difference between this and previous test (with solder balls - where i incinerated material several times like described).

 

[Topher_osAUrus]

Silver chloride dissolved in HCl is also yellow

 

[Tzoax]

Silver chloride dissolved in HCl is also yellow

Topher, you are genius. Thank you!

If that is the case, everything makes sense.

The filter paper is full of silver chloride and there was some of silver chloride that went through the filter when i decanted this yellow solution while still hot, and now i see on the bottom white sediment, most probably AgCl. But solution is still yellow even after many hours (being cooled).

So, if i understand correctly - some of silver could be dissolved in HCl and the color is yellow and dissolved silver will stay in solution when cooled.

 

[FrugalRefiner]

Try diluting some of the solution. While silver chloride is slightly soluble in concentrated chloride solutions, it is much less soluble in dilute solutions. If you get a precipitate and the solution clears, Topher may have your answer.

Dave

 

[Tzoax]

Try diluting some of the solution. While silver chloride is slightly soluble in concentrated chloride solutions, it is much less soluble in dilute solutions. If you get a precipitate and the solution clears, Topher may have your answer.

Dave

Thank you Dave, i just added some water -20/30ml and white cloud of silver chloride formed at the top and it is slowly dropping to the bottom.

 

[Topher_osAUrus]

Silver chloride dissolved in HCl is also yellow

Topher, you are genius. Thank you!

If that is the case, everything makes sense.

The filter paper is full of silver chloride and there was some of silver chloride that went through the filter when i decanted this yellow solution while still hot, and now i see on the bottom white sediment, most probably AgCl. But solution is still yellow even after many hours (being cooled).
.

Throwing that word around quite liberally, aren't we? :lol: :lol:

I have a beaker of HCl that has silver chloride in it, that is from some of my first washes of powder. I tend to just reuse it when I'm doing a recovery dissolve of gold from goldfilled or karat, where there is already silver chloride that will be in the mix. I like to keep the HCl concentrated for the dissolving, so it works faster, only diluting it at the end. Sometimes my aqueous sulfamic addition is enough to make the chloride drop out, sometimes I have to add ice. Either way, I like to filter as little as possible. So the silver chloride and lead sulphate will be separated at another time.

Keep up the good work Alex, I enjoy your result thread very much.
8)

 

[Tzoax]

Throwing that word around quite liberally, aren't we? :lol: :lol:

I have a beaker of HCl that has silver chloride in it, that is from some of my first washes of powder. I tend to just reuse it when I'm doing a recovery dissolve of gold from goldfilled or karat, where there is already silver chloride that will be in the mix. I like to keep the HCl concentrated for the dissolving, so it works faster, only diluting it at the end. Sometimes my aqueous sulfamic addition is enough to make the chloride drop out, sometimes I have to add ice. Either way, I like to filter as little as possible. So the silver chloride and lead sulphate will be separated at another time.

Keep up the good work Alex, I enjoy your result thread very much.
8)

Well, i think you really deserved it this time. :lol:
Thank you Topher, you really helped me a lot to understand what was going on here.