Refining of fingers from a single card

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g_axelsson

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In another thread I offered to refine the gold from voltage regulators free of charge, the payment should have been the rest of the boards. In the end I managed to talk him out of it as postage would have cost more than the gold recovered. But he still wanted me to verify that it was plated gold so he sent me one card.

The board consisted of the long side with gold on nickel plated on copper base metal fingers. On the card were various components, large grey transformers or inductors, small integrated circuits, ceramic capacitors and other surface mount components. On one side were two aluminum plates for cooling the switch transistors. There were a couple of small golden supports for the cooling plates.

Top side with foils, small IC:s and a lot of capacitors
IMG_20160305_143527.jpg
Bottom side, with aluminum plates...
IMG_20160305_143556.jpg
... and without, cooling paste partly wiped off. Notice the small rectangular metal blocks. Probably for connecting the cooling plate thermally with the circuit board.
IMG_20160305_144124.jpg

After dismantling the interesting components I ended up with this :
IMG_20160310_123344.jpg
* Circuit board 27,3 g
* Gold plated fingers 2,9 g
* MLCC 4.0 g
* Golden supports 1,0 g
* Aluminum 15,7 g
* Small IC:s 1,5 g
Total weight 52,4 g
 
I started by dissolving one of the golden supports in diluted nitric acid. At first it was slow to react but after a while it started to pick up the pace. Soon I could see tiny golden particles floating in the liquid. In the end it broke apart into microscopic parts proving the plating was really thin.

Dissolving
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The remnants afterwards. mostly tiny bit of white mud.
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Next up I just threw the fingers into the same liquid and the acid soon started to attack the copper beneath the gold plating. Soon the plating from a few fingers fell off while other remained stuck to the circuit board. It seems like the through plated via holes let the gold cling to the board. A glass rod fixed the problem.
IMG_20160310_202049.jpg
Among the last things to go was the nickel plating under the gold. Some pieces remaining can be seen on this picture as white flakes.

White nickel plating remnants among the gold foils.
IMG_20160311_161556.jpg

Nice foils, holding together well means thicker foils.
IMG_20160312_164338.jpg
 
The liquid, the circuit board and the gold flakes were transferred into a beaker so I could easily remove the circuit boards and wash the foils a bit. Then it was transferred back into the measuring cylinder I used as a test tube. There is just a hint of blue copper nitrate after the wash but even with this little nitrates in solution it only took a few drops of hydrochloric acid to dissolve the foils completely.

Foils before adding HCl
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Foils dissolved, no additional nitric used
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Filtered gold chloride
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Remnants in the filter
IMG_20160315_102549.jpg
 
I added a bit of SMB to precipitate the gold. The solution first turned dark and then I could see some gold collecting on the bottom.

Precipitated gold
IMG_20160315_131102.jpg
The gold powder was collected in a small cavity dug in a piece of carbon and some grains of borax on top to keep it from blowing away when melting. Then I melted it with a oxyacetylen torch.
The resulting button was cleaned in sulfuric acid to remove any borax and then photographed on top of a ruler to calculate the weight.

Resulting gold button on top of a mm ruler.
IMG_20160404_090718.jpg

Comparison of my earlier buttons 52, 10 and 0,01 gram.
IMG_20160404_134009.jpg

The resulting button is circa 1 mm in diameter. This gives a volume of 4/3*3.14*(0.5)^3 = 0.5 mm3 which gives about 10 milligram of gold.
With 2,9 g fingers giving 10 mg gold we have 1000/2.9*0.010 = 3.5 g/kg or 40 cents per card in gold (@1225 $/ounce). Now I do have losses on the way so the real content might be closer to 5 g/kilo of the fingers.

How about the rest of the card?

The 1.5 g of IC:s contains gold bond wires, about 1 - 2 grams per kilo, 1-3 mg per card, let's say about 10 cents of gold here.
And the 4 g of MLCC probably around 2% of palladium and 5% of silver
4*0,02 = 0,08 g of palladium, 8 times as much as the gold but at 541 $/ounce it's worth 8*541/1225 = 3,5 times as much, about $1,40 per card.
4*0,05 = 0,2 g of silver, 20 times as much as the gold but at $15 per ounce it's only worth about 10 cents.
Total precious metal value of one card : 0,40+0,10+1,40+0,10 = 2 dollars.

Looking at the above number we can easily see that the MLCC:s are the most valuable thing on the cards while the gold fingers are the easiest value to collect. The numbers are only my approximations and only the gold fingers have been refined.
10-15 mg per card is 0,2-0,3 g/kilo or 200-300g/ton. Taking the palladium in account, it is even more valuable so this is good material although a bit tricky to process.

Göran
 
Nice work Göran! I love to do small scale runs like that. My very first little bead was about that same size, but I lost it to my basement floor right after I got it melted.

One small critique: as a mod and long time member, you are a role model and mentor for all us new guys. So if for no other reason than posing for the camera...
Gloves, man. Put on some gloves!! :mrgreen: :lol:

Yeah I know, another of my pitiful attempts at sarcasm. But even so, gloves! :lol:
 
Silver and gold bead measuring by Plattner 1830:

Two straight lines with a point of intersection and a gap of 0,9mm at 156mm length. The whole length is devided into 50 parts of 3,12mm (linear). Right row of numbers shows the weight in mg silver (for gold factor x2,136) equal to % in 100mg assayed ore, so you can measure down to 0,00003mg Ag or 0,00006408mg Au.

This was made of any hard material, glas, wood, something like that. The gold bead was put between those two straight lines and pulled with tweezers under a magnifier to the small end.

The flattening of the metal bead is already implemented by empirical means.

I can't tell how exact this is. But even rounded this is an accuracy I would never have assumed to be possible in 1830!
 

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That's an ingenious way to measure diameter and indirect weight.

I would use three pieces of glass (two as a wedge sitting on top of a third flat surface) and something of known thickness, for example an uncirculated coins edge to make the wedge. Then letting gravity move the small button down until it got stuck.

Göran
 
I know it's bad in principle, but I don't use gloves when doing a small scale test as this. The amounts of acid and liquids are just ml and not enough to do any damage on my hands. Whenever I pick up something, a beaker with liquid or handling an acid bottle I wash my hands directly afterwards when I'm done.

When working with "production" sized batches outside my workshop I use gloves, but this was done on the balcony where I run small tests.

This summer I'm planning on building a real lab with a fume hood and take my refining to the next level. Making it possible to refine year round.

Göran
 
Goran, you and Bjorn just have far too much patience and time on your hands :lol: :lol:
 
Thanks for posting this. I like the micro scale experiments. Seems like a great way to learn the process (or test a new one) without risking making a big mess. It's nice to see that even tiny amounts of gold can still be refined. Maybe not at a profit even if the scrap was free but educational and hobby refiner's don't have to count their own time.
 
g_axelsson said:
I know it's bad in principle, but I don't use gloves when doing a small scale test as this.

I'm guilty of it also. I was mainly just ribbing you a bit Göran. For me it's mainly not want to waste a cheap pair of gloves for 3 minutes of use. Especially since all I'm doing chemically for now is in test tubes, checking different pins, contacts and what not. Yet I suppose even the smallest exposures to this stuff can add up over time.

solar_plasma said:
Silver and gold bead measuring by Plattner 1830:

Could a device like this be used to guage purity as well? Say you had gold beads of the same known weight and purity. If dropped into the 'wedge' they should stop at the same point every time. If there was a metal of less density than gold mixed in the bead, the bead would have to be larger to make that known weight and would stop higher up in the 'wedge'.

Or would there just be too many variables to account for? Like the roundness of the bead, or probably a dozen other things I'm not thinking of...
 
I believe it is just like you assume, too many variables. The proper way would be an assay by weighing, cupelling to eliminate base metals (at least when we talk concentrates), then AR to eliminate silver and other PMs and weighing the difference. Only read, not tried yet. If I understood the pro's correctly, there is not one general way to assay, it depends on the material to be assayed. Though this seems to be the basic way, since it is referred in every chapter I read about assaying at prominent place.
 
There is also a difference between different acids and concentrations. Some acids and especially the metals dissolved could build up over time while other doesn't.

Before I started with refining I was already working with hydrochloric acid for my rock collection. I was removing lime stone to bring out hidden crystals I regularly picked stones from a vat with acid as long as I had fresh water standing by. :shock: This is nothing I would recommend, just something I did. The only dissolved metals were calcium and magnesium, together with weak hydrochloric it's all substances we have in our bodies so no large dangers of building up over time.

My old chemistry teacher did it all the times, so I guess I learned my bad habits from him. He even showed us the color changes of his fingers in different acids or silver nitrate. The sulfuric acid dip was fast and then followed by a long wash under the water tap. He was old school, from a time before everything had to be so safe that kids today never learn to think about dangers... but that's another rant for another day.

But I would never put my hands in copper chloride etch, copper, nickel, lead and so on is nothing I want in my body.

I guess what my position is, if you don't know what you are doing, use protection. But if you know what you are doing and accept the risks it's your prerogative to be stupid and put you in harms way.

I'm going to build a lab out of town, 90 km away, so any refining session will include driving to and from the lab and I believe that is my biggest danger when refining. Every year there are a couple of cars running into moose along that road so it's easy to put a number on that danger.

"The refining is fine, but all the moose is annoying!" :mrgreen:

Göran
 
I started to PM this to Göran but since it's now being discussed, I'd like to share with you all how I saw the light about 6 months ago.

I left a spotless beaker, containing fresh HCl / CuCl2, overnight. I merely picked it up the next morning to inspect it and put it back down. I guess HCl fumes are heavy and had condensed on the outside of the beaker, because just minutes later my index finger felt a "burning numbness" - if such an oxymoron is possible. So I washed under cool, then warmer, water and rubbed in some bicarb I keep handy, though in the kitchen. After washing out, there was a hole in my fingertip pad, just about 2mm wide and maybe a third as deep. But the whole fingertip had zero touch sensation for about a day. I wondered all that time whether I had either destroyed nerves or just poisoned them with copper, before it eventually came good.

I had been fortunate enough to learn a valuable lesson at a bargain price. Refine your fingers. Not your fingers.

Now I won't touch anything acid related without gloves. I mostly use a pair of fairly cheap thick nitrile gloves that look rather like the washing-up type. They're far thicker than the blue disposable nitrile type, are less likely to puncture, but the main point is I can put them on for 2 minutes and take them off again, over and over. Not only does it protect me, but it keeps my grubby paws off the gear.

I also will not deliberately put my gloved hand into acid as I see so many people doing. Just because I wear a seat belt and have air bags, doesn't mean I'm going to drive around into parked cars. In my opinion, if you get any significant amount of acid on your gloves, you're doing it wrong. Spoons, rods, tongs and the like are for putting in acid. Gloves are for accidents. Like goggles, they are for "that one time", though you've done it a thousand times before. They buy you time, but they're not impervious forever.
 
Ive taken GSP's advice and used short sleeves to refine. I can immediately tell if anything has come onto my skin and it's better that way than having it in the clothing and staying in contact with your skin for a long period of time. Personal choice on gloves is disposal Nitrile.

As you say Jason they don't last forever and I probably use a good 20 per day at the least because I change them constantly. Having a bucket of clean water around is good because you can wash your gloves off in it throughout the day after handling anything. I watched a youtube video recently and cringed at the guy handling concentrated Nitric with a pair of standard material gardening gloves. I'm still cringing as I type that because he would have been better with no gloves at all IMHO.

Nickvc and GSP and I believe 4metals have all alluded to using full gauntlets, and I think I am going to invest in a set.

Jason I've never had what you experienced because I've only found HCl to be a problem when it's in a cut (boy that smarts) but I have had a similar experience with Nitric.

Jon
 
spaceships said:
Ive taken GSP's advice and used short sleeves to refine. I can immediately tell if anything has come onto my skin and it's better that way than having it in the clothing and staying in contact with your skin for a long period of time. Personal choice on gloves is disposal Nitrile.

As you say Jason they don't last forever and I probably use a good 20 per day at the least because I change them constantly. Having a bucket of clean water around is good because you can wash your gloves off in it throughout the day after handling anything. I watched a youtube video recently and cringed at the guy handling concentrated Nitric with a pair of standard material gardening gloves. I'm still cringing as I type that because he would have been better with no gloves at all IMHO.

Nickvc and GSP and I believe 4metals have all alluded to using full gauntlets, and I think I am going to invest in a set.

Jason I've never had what you experienced because I've only found HCl to be a problem when it's in a cut (boy that smarts) but I have had a similar experience with Nitric.

Jon


Pretty sure that nitrile plus hno3 dont mix well... I think, if nitric is concentrated enough, the will burst into flames

So i have read... And watched on the interwebs... ...but, this is the internet...where everyone speaks french(its an american commercial..were idiots..), and there are hot young singles in YOUR area
 
spaceships said:
I watched a youtube video recently and cringed at the guy handling concentrated Nitric with a pair of standard material gardening gloves. I'm still cringing as I type that because he would have been better with no gloves at all IMHO.
That's how I learned to work with acids when I was in high school - no gloves. That was back in the 1970s, and we just didn't know better, but we did learn to be very careful since we didn't have that "safety net" to give us a false sense of security. We referred to nitric acid as "creeping" acid. Even when we put nitric in a beaker, and there was absolutely no liquid on the outside, if you picked the beaker up a while later and didn't wash your hands promptly, you end up with yellow fingers.

Topher_osAUrus said:
Pretty sure that nitrile plus hno3 dont mix well... I think, if nitric is concentrated enough, the will burst into flames
Only if it's fuming red or white. The 68 - 70% we usually use will not cause your hands to burst into flames.

Dave
 
The full length gauntlets are a must if your doing serious commercial refining, they are easy to put on and take off and are extremely durable, they even allow you to move, carefully and only short distances, beakers containing hot solutions. The one thing to avoid is handling sharp materials wearing them as they do puncture but as I said easy to remove them.
 
Solar said:
I can't tell how exact this is. But even rounded this is an accuracy I would never have assumed to be possible in 1830!

With a bead that small measuring the diameter is at best a guestimate, even if you can accurately determine the diameter. Action mining sold an assay kit for ore and to avoid the high price the kit would be if it required an analytical balance, they used a comparator and a chart to measure the bead. Then they gave you a chart of color to estimate purity. Given all of the assumptions, weight based on diameter, and percent gold based on color, it is at best a wildly speculative method to determine gold content. Neat technique to determine diameter of a perfect sphere, but little else.

I think refining such small quantities of gold leaves room for error, and usually the error is in the refiner's favor. I would think having digested the foils in acid, an AA analysis would give gold concentration which could be applied to the dilution factor. This will eliminate any losses due to melting and gathering all of the gold into a single bead, which in these micro quantities is difficult at best. This is how it is done professionally to obtain useful data on value per specific piece. This data is catalogued and only spoken about in select inner circles within any refining company. However knowing the actual recovered value of a specific circuit is valuable information.
 
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