# Dropping Gold - and unidentified metal with Copper



## Rodger Hamilton (Nov 6, 2012)

Hi all, so I may not be so new at this as I have been extracting gold from fingers for a few months now. But having finished with all the fingers I began work on those square BGA “flat packs” found on modern DDR2 RAM sticks. But I seem to have a problem... well maybe not a problem but a puzzling situation.

After dissolving the gold in HCL-CL, and allowing the excess chlorine to dissipate, I then place copper in the solution and leave it alone for some time to precipitate the gold.
The gold comes down soon after as a clumpy brown powder and eventually the solution tests negative for gold, however, if the excess copper remains in this barren solution it is soon takes on a metallic white coat. This coat is shiny and crystalline and I am almost sure it's not a salt.

I do not think it's silver as I do not use nitric acid when recovering, so no Silver Nitrate in solution. As far as I know, Silver Chloride is insoluble in acidic Gold Chloride, and would settle out of the solution at some point (before I put in the copper).

I previously removed all the solder by heating the chips whole in HCL, then washing with water before processing, so I am sure it's not lead (if from solder). Although I must say even after repeated washes in HCL, the clean solder pads were silvery in color. Perhaps Antimony from the solder, but copper should not displace it from solution as it is higher in the reactivity series.

I tried to “time” the precipitation by waiting until I think all the gold was down, but before the copper took on that metallic coat, and then test for PMs, but there was no reaction (fresh batch of stannus). Perhaps there is such a small amount of the other metal that it doesn’t show up in the test.

Now I realize that copper drops everything below in the series, but I cannot think of any other metals that could be in those chips to end up in solution with the gold chloride. However, as I understand it, some folks report there may be Palladium in some types of flat pack chips... can this be confirmed?

I suspect it is lower than gold in the series because it comes out of solution after gold, I am at a loss... any help would be grateful.


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## jimdoc (Nov 6, 2012)

You should get some "DMG" dimethylglyoxime to test for palladium.

Jim


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## patnor1011 (Nov 7, 2012)

Pd or AgPd alloy are commonly used as plating inside chip packages.


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## Rodger Hamilton (Nov 8, 2012)

Thanks for the replies, this in some way confirms my suspicion that it is Palladium inside the chips.

At the moment I am collecting the cemented powders and will attempt to separate the metals at a later date, at that point I will get the DMG and confirm.

Again, thanks for your help.


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## butcher (Nov 8, 2012)

Did you notice patnor1011, sells testing solutions, I bought some from Pat and was pleased to get them.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=58&t=9158


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## Lino1406 (Nov 9, 2012)

Solder you do not remove with HCl
unless it is lead free. Most probably
you have CuCl, by reaction of copper
and CuCl2.
Lino1406, author "25 recovery
procedures..."


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## Rodger Hamilton (Nov 9, 2012)

butcher said:


> Did you notice patnor1011, sells testing solutions, I bought some from Pat and was pleased to get them.
> 
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=58&t=9158


I did indeed notice the link... checked it out and the price appears reasonable, good to know, thanks.



Lino1406 said:


> Solder you do not remove with HCl
> unless it is lead free. Most probably
> you have CuCl, by reaction of copper
> and CuCl2.
> ...


I've removed leaded solder with HCL... works except for the chloride needles, but hot water takes care of that. Is there a better way... without nitric acid?
Wouldn't copper (I) chloride dissolve in the HCL wash... after cementing?


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## Lino1406 (Nov 9, 2012)

Since you did not mention that wash
I assumed it did not take place


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## kraguj (Apr 20, 2013)

Could somebody mention which other metals except Ag,Au,Pd and Pt, could be cemented by Cu plate 
from HCl + Cl solution? 
It is whitish grinish colored and easily disolved in HCl!?


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## g_axelsson (Apr 20, 2013)

kraguj said:


> Could somebody mention which other metals except Ag,Au,Pd and Pt, could be cemented by Cu plate
> from HCl + Cl solution?
> It is whitish grinish colored and easily disolved in HCl!?


Sounds like you have copper chloride.

Göran


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