Processing large gold circuit boards

[Thinksilver]

I have quite a few circuit boards between 1 and 2 square feet in size. These are high-end with gold throughout.
I can remove most of the components including the CPUs, but what is the best procedure to use for the gold recovery?

 

[ericrm]

can you put picture?

 

[Thinksilver]

Below are three representative examples of these boards.

 

[Marcel]

I would cut one of these golden strips out and use A/P for a small test run. If they come off as foils you are a lucky guy :mrgreen:
.. if not i pass the question on.

 

[Geo]

actually they are the same type boarde you have, the difference is, these have been soldered. passive stripping with hcl to remove components. monitor this closely using one test board. leave submerged in hcl for 4-6 hours and check to see if the components are loose. if you notice the gold degrading, stop. the gold will develop a coating of tin that has been dissolved and look dull, but will wipe off showing gold.if the components are loose where they can be pulled off the board, thats as far as you need to go. after the components are off move to AP without a bubbler. it will take longer and will need to be agitated several times a day but the foils should remain intact and not degrade. do not add heat to any of these processes. use one board as a test through entire process. (you may cut one board in quarters to make it easier)

 

[Thinksilver]

Thanks for your suggestions. I believe I will begin with one board only and physically separate the gold bus areas from the rest of the board using a small band saw. Then, I will use an AP process to remove the gold and see how that goes. If that works, I will then saw the remainder of the board into workable sections, maybe 4" squares, and employ HCL to strip the remaining components. Then, I can remove the rest of the gold from the pieces with AR.

 

[Geo]

if you plan on using AR, be sure all tin is removed. tin in a nitrate solution creates metastannic acid, a white, gelatinous substance that makes a mess and traps your gold.