Need advice on pins from fiber cpu's

[tomysole]

I recently removed the pins off of a few dozen fiber CPU's and have been leaching them in HCL for a few days. Almost all of the gold foils are now removed from the kovar insides and most are floating in the solution. However, there is still a large amount of the foils that are mixed with the left over black metal stuff that has yet to be absorbed by the HCl.

I'm trying to find the best way to get as much of the foils out of the batch as possible but don't want to mix them with all the black metal gunk. Should I just keep filtering the spent (greenish-black) fluid out and adding new hcl until it dissolves all the metals? Will it eventually dissolve all that black stuff?

 

[samuel-a]

tomysole

Some small portion of the "black stuff" you see in the bottom may very well be gold powder.

If your HCl leach doesn't dissolve anymore base metals, then replace it and repeat the leach until you see no more pins body's. To get the most out of your HCl leach, heating it is required.

Whatever left unreacting to the HCl is usually gold (foils or powder) and sometimes Silver (as silver chloride). When all of the base metals are gone (or most of it), push forward with AR or HCl/chlorox.


This subject had been discussed here many times before, do a quick search to find more information.

 

[tomysole]

Awesome response! Thanks for your help

 

[Geo]

if there is very little base metal left, you can try this, it works well for me.

there are a few CPU's that have copper legs. not many, but enough to cause a problem with the hcl dissolution. when further boiling in hcl does not release any more foils, remove from heat and allow to cool until warm to the touch. filter while warm. add filter and filtrate to a clean beaker and push it all down to the bottom with a stirring rod and add enough hcl to cover the material. add bleach in small increments and stir, wait for a minute and add some more. after three additions, on the last addition, empty contents into a clean filter and filter all the material including the old filter.after all the fluid has drained, add another small dose of bleach the material in the filter and let it drain. if done correctly, you should have removed all the gold that was on the material as well as foils and any powder.

 

[tomysole]

Thanks GEO.....another helpful post!