Tzoax said:
I have sucessfuly processed Black MMX processors this way:
- removing copper hearsinks, all SMD components and black chips which I processed like all the other IC chips
-simmer boiling in a 16-18% HCl for about 2 hours, all of the tin dissolved.
- decanting tin bearing HCl solution, washed beaker with water several times
-Added fresh HCl and adding KNO3 until all of the metals dissolves.
-watch out, when the reaction is nearly ended it will be vigorous reaction, you will need much bigger beaker filled maximum to 1/3 of the volume.
-after that, regular denoxing, filtering and gold dropping
I had some losses when processing these, but even with the losses I had 1.5g of gold per kg or 0.03 per piece of this kind of processors, including black chips with dies.
I hope this helped a bit.
Did you wash away the black sludge that is produced when the tin dissolves? It contains gold.
I have only done one test run to refine a kilo (53 CPU:s) and I have so far recovered 3.3g. I think I have a few tenth of a gram left to recover, judging from the color of the second leach of the solids. I'm doing a second leach since I suspect that I ran out of nitric, newbie mistake, adding too little nitric acid. :mrgreen:
I also have to recover the gold from the dilute washing water I used on the CPU:s after dissolving the pins. The water was turbid even after filtering, but after standing for a while a fine black sediment appeared at the bottom of the beaker.
Göran