Ideal process for goldplated cardboards

[Marcel]

I got to buy 50 Kg of this nice looking material. It had never been soldered and came directly from a factory.
When I received the first batch I performed some testing and was disapointed by the low grade of goldplating. Using 300 gr heavyly plated material on both sides, the return was not even enough to make my scale return a reasonable result. So that I assume the material is a 0,1%. or lesser class goldplated board. (1 Kg boards = 1g gold).
I used A/P which was all the wrong way to do it, because the gold dissolved in some sort of "foam" that swam on top of the solution, sticked to the walls of any container and anything that cam in contact with it - no nice foils at all. I cannot tell wheter the gold even went into solution, because I didnt test ist, but itw as all a mess.
Secondly I discovered, that the boards where thicker layered with ugly nickel than usual. This nickel went into solution causing further trouble ( the salts from nickel itch very lasting persistant and they seem to go everywhere).
As for the sticking and swiming, I found out that because these boards never went into final production, they were not cleaned and still contain some layer of chemicals from initial production. This chemical attaches to the gold and makes it very hard to handle. So I must clean the boards before processing with isopropanol etc..

So my plans for now are:
Plan A:
- Grinding the surface of all boards with a electric grinder with integrated vacuum cleaner ( I have such a tool)
- Then aqua regia the fine powder
Plan B:
or sell the stull and give in.
Plan C:
or any other idea on how to revover that gold with minimal chemical treatment, because of the nickel that I shurely will grind of as well?
Any idea?

 

[Geo]

acid peroxide comes to mind. if you grind, you are sure to loose some of your gold.

 

[Palladium]

I don't see a problem with running them through ap. Could you tell us if your ap system is the same as ours. I've run a couple hundred lbs of them with no problem. Send them to me.

 

[patnor1011]

Many times and even if plating appears thick it is just flash plated. That kind of material will not produce foils but gold will disintegrate in fine powder many times looking like anything but gold.
I would not expect any big amount of foils from your boards. Most of gold from there will be in fine powder form.
I mentioned several times that I do not go by classic AP recipe, my AP is working slower but safer I would say. I use about 1-2l of HCl and only about 100-200ml of H2O2 3% strong.

 

[lazersteve]

I agree 100% with Pat, the boards are flash plated.

Here's a post on a way to quick strip them.

Stripping Flash Plated Boards

Steve

 

[niteliteone]

If these are the pictures of the boards that gave you 1 gram per kilogram you did pretty good.

The flash plating on circuit board componet pads are only a few mil's thick. The plating on fingers and card edges is much thicker. (generally 20-60 mil thick) the older the better.

Tom C.

 

[Marcel]

Thanks for the feedback. Yes this flashgold.
I think I will just wait a bit, then resell it, better than messing with it.
What you described is exactly what happened. Goldpowder, impossible to handle without loss, minimal yield - this is the kind of material for a professional refiner, not for my me..

 

[Geo]

did you check to see if the gold extends under the solder mask?

 

[Marcel]

Yes I did. But it does not. The goldplating seems to have been the last process. That can also bee seen on some boards, that where faulty production.
Seems that the gold has been sprayed onto the surfaces, I have some boards where it has formed drips of gold(!)
It´s a pity, look at this lovely stuff below. I got around 10 Kg alone from that must be around 90% gold covered on both sides... Still I cant get any reasonable amount out of it using A/P. All that thick copper and a very thick nickel layer underneath go into solution, messing up the whole thing. Here in germany we must use minmal chemicals since waste laws are very strict, so removing unwanted material seems not the way to go here? So far I am only processing material that supplies foils, since the ratio of copper vs gold is good and I need minimal chemicals.
Please also check the partly processed piece. Maybe someone who has experience with that kind of composition has another idea for me.

EDIT: I was thinking about coating the boards with a thin transparent layer, then my gold particles may not swim away and I could check if they went into solution or not. After processing the foil with the gold remains solid and I only had to dissolve the foil with aceton or some other solvent. Good or bad idea? The stuff women put on their nails could prob. do it..

 

[Geo]

are you testing your solutions with stannous chloride? this is just my opinion, but since you are left with few options and these boards have never had any solder, you may just use aqua regia and dissolve everything on the board.i don't advise this often but there are times when it is the best answer. the gold can be reclaimed in a more manageable state. it would save you from doing several different processes to get the gold and in the end, you will use less chemicals.

 

[steyr223]

As long we are on the subject first off Hello everyone. How thick are the traces in the boards and What kind of variations.the gold. Plated boards I.e.sound blaster or HP mother board, are these also class 00
1 more question the key pads for say most of your button contacts I know these are much heavier plated but in comparative to what as I'm sure they all very what would be the least. And most in Microns (hand held scanner keypads)
Thanks
Steyr223

 

[patnor1011]

With transparent coating I see problem with acid reaching base metals under plating.

 

[Marcel]

I applied nail polish on a small piece and then dropped it into AP. It worked fine (reaction started on teh edges where I cut the board and the copperlayers were vulnerable to the acid) and the particles stuck to the polish until they started to peel off and float around, so I was able to catch the gold. Still this was "no fun" since it came out as so little, tiny goldpowder within the polish and I prefer to pass the material on to someone who has an established process for that. Thanks to everybody anyway.

 

[maynman1751]

I think I'd do what Geo said. Dissolve everything, cement your values with copper and proceed from there. Is anyone in agreement? I'm still learning myself!

 

[niteliteone]

I think I'd do what Geo said. Dissolve everything, cement your values with copper and proceed from there. Is anyone in agreement? I'm still learning myself!

You are correct with boards like these.
Usually the flash plating is so thin it is almost impossible to recover it with conventional methods. So you have to go outside the box a little as long as you know what you are doing and how to deal with what comes up.

Tom C.