can I clean dirty solution

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J

justme2

Well-known member
Joined
Dec 14, 2013
Messages
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I hand stripped larger components from my mother boards and cut my gold plated mother boards into 6" squares and put them in AP to depopulate small components and solder. Big mistake, I now have a dirty solution of gold flakes and powder + some tiny green mmlcs and a grey clowd that is probably solder and lead.

As soon as I saw this I pulled the boards out and stopped the process. I have a solution of about 1g flakes and the trash. Is there a way to clean this solution.

The rescued boards still have 90% plating remaining. I don't want to continue the process until I figure out what I did wrong. I have read so many different process I must have gotten confused some where.
 
Replace the boards and let the process continue. As the mess has already been made, there's no need in stopping now. After all the foils are loose, filter out all the solids and rinse well with water. This will take some time because you need to let everything settle before decanting the rinse. Next, dry the material and incinerate it to at least 400 degrees F. Do not use a flame from above like from a torch. After the material cools, do a hard boil in hcl. this should remove tin and lead. If the hcl changes color during this boil, repeat using fresh hcl until the hcl stays clear. Rinse with clean water and dissolve the foils. It really doesnt matter what else is in the mix as you will remove this in the filter after the foils are dissolved.
 
Foils act weird when heated with a torch directly. They will pop and jump all over the place like Mexican jumping beans. I use to use an old toaster oven i got at a yard sale and a stainless bowl with a lid.
 
After the AP process, the metals are finely divided. Tin and lead make up a large portion of the solder. If you use a flame from above, you run the risk of melting the components back together. Even though gold melts above 1900 degrees F, tin and lead melt at much lower temperatures. Melted metal acts as a solvent to other metals and molten tin or lead will dissolve gold and create an alloy. the incineration will help convert the tin oxide and lead chloride back to elemental metal. You want it converted but not melted. An open flame from a torch (in this instance) would cause more problems than it will fix.
 
I took Geo's advice and heated in HCL twice then in water twice, it cleaned up a lot of the junk.
I still have a little brown sludge.

However I may have jumped the gun, I changed the AP and used new solution. I did this in three batches just in case I ran into a problem. The only batch that had a problem was the first batch and it was a small one.
first batch .2g foils
second batch 1.7g foils
Third batch is still in process but looks close to the second.
These were very large military server boards. I expected about 7g so, I'm a little disappointed but, I also see some black traces, I will save those and all the solutions for later investigation.

Thanks again for the kind help. mcw
 
It has been a weeks work but I have recovered most of the foil from the board. next time I will fully study and learn the incineration process for any more mother boards.

My last batch looks to be about 1.5 /2 g. It has a lot of trash, fibers and a lot of grey dust. Should I proceed with a hot HLC bath hot the toaster oven path? Both have been suggested, or should I go directly to A/cl which was suggested earlier.

Also there are some gold left on the board pieces in the pin slots. They are in the form of very small thread spool shaped tubes. The pins plugged into these in loo of solder on modern boards. . Because of the shape they won't drop out of the board.
 
I would do the HCl/Cl then filter. Don't drop with SMB unless the solution is clear. Like you could read a news paper from the other side. If not wait until it is and decant.
 
It has been a weeks work but I have recovered most of the foil from the board. next time I will fully study and learn the incineration process for any more mother boards.

My last batch looks to be about 1.5 /2 g. It has a lot of trash, fibers and a lot of grey dust. Should I proceed with a hot HLC bath or the toaster oven path? Both have been suggested, or should I go directly to A/cl which was suggested earlier.

Also there are some gold left on the board pieces in the pin slots. They are in the form of very small thread spool shaped tubes. The pins plugged into these in loo of solder on modern boards. . Because of the shape they won't drop out of the board.

I have 22 more lbs of these boards from missile systems that have the same amount of plating but these boards are silver and fail every test but platinum. If I find they are platinum coated I will need a tole refiner. At this stage in my progress they are way over my head. Thanks in advance. mcw
 
You can rinse the foils from the through holes with a spray bottle set to stream. It's slow and you may be able to speed it up by using a tub and a garden water hose. The foils will settle and you can pour the water off leaving the foils. I have learned that trying to retrieve every single foil is not only a waste of time but it may cause you to actually lose more by being overly cautious. Through the various processes, you will have losses in each process. The more times you handle or process translates into loss. You will eventually have less lose due to experience gained.
 
Thanks Geo. Hard to give up any of those shiny little dudes, but I see and agree with your point. "overlook the dollar searching for a Penney." :| .
 
In regards to dealing with the plated through holes, the foils that get stuck in these. I've found that if I take the board and give it a sharp whack against something most will get knocked out. About half of them will spray onto the surface I whack onto and about half will stick to the board by water surface tension. Of course you'll want to do this on the bottom of a plastic tub so capturing the foils will be easy. A squirt with a spray bottle will wash off the foils stuck to the surface.
 

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