Can I go straight to Acid/Bleach with these boards?

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Anonymous

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Hi guys

I have a large quantity of "virgin" circuit boards as per the picture below. No solder, just gold/copper. I was wondering if I could forego the AP and drop these straight into Acid bleach and deal with the copper later or whether you thought this was a really really bad move?

Naturally I would break the actual boards free of the mounts.

Feel free to be blunt, I don't break easily or get offended.

For the record I have over 100 kg of these of varying types an naturally I have no idea what kind of yield to expect.

Thanks chaps. Jon
 

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Hi,

Nice boards no hard work on those. But I would use the AP first you don't want to deal with the copper later. I would say 1 to 1.5 grams per pound and maybe more.

Jack
 
does the gold plating extend under the green solder mask. its important to know this as it will add another step in the process. gently scratch a spot of green solder mask down to the metal beneath. use a sharp blade and carefully scratch down until the metal shows. if there is gold under the mask and you scratch too deep, you will remove the gold layer and see only copper.

as a side note, it will never be "just gold and copper" as theres a nickel barrier between the two on gold plating.
 
AP first as Jack pointed out and then hcl/Cl. AP is a reclaiming process and hcl/Cl is a refining process. if you tried to dissolve all the metal with hcl/Cl there will be some gold dissolve but due to the re-activity of the metals involved, as soon as the copper is exposed, it will dissolve before the gold. then any gold that did dissolve would just cement out of solution on the undissolved copper and will need to be dissolved again. this is a repeating cycle that will continue over and over until all the metal is dissolved. you will wind up with gallons of solution with gold in it when it should only be a few ounces.
 
Thanks Geo

I had that wrong, I thought I could just dissolve it all into solution and I ignored the reactivity of the other metals and the effect it would have.

Effectively you're saying although it's theoretically possible though, but would realistically NOT be a short cut and a pain in the butt?

Fine, I'll take the advice that Jack and yourself have kindly given and I'll go down the AP route as per standard.

Thanks guys.
 
Think of it this way. Would you rather run the AP process, then dissolve some fairly clean foils, and precipitate from a fairly clean, concentrated solution, or dissolve everything at once into a large volume of dirty solution, and try to precipitate from that?

Dave
 
When you dissolve gold with copper still remaining the gold plates back onto the remaining copper, with those circuit boards that means you could dissolve the exposed gold and copper, only to have your gold plate back out of solution onto the hidden copper under the solder mask, or if the board was a multilayer circuit board, your gold can plate out to copper in between layers of the fiberglass.

Basically dissolving the gold off of the circuit boards is just a bad idea.
Dissolving the copper out from under the gold and letting the gold flake off is the ticket.
 
Thanks everybody, I consider myself well and truly slapped back into place 8)

I'll trot off and get loads of buckets of AP "on the go" as I've been told to :oops:

If you like I'll do some weighed sample batches and report back the exact yields. Cheers again

Jon
 
spaceships said:
Thanks everybody, I consider myself well and truly slapped back into place 8)

I'll trot off and get loads of buckets of AP "on the go" as I've been told to :oops:

If you like I'll do some weighed sample batches and report back the exact yields. Cheers again

Jon
Click to expand...


Jon Photos and yields results are always very welcome , I would cut the boards in smaller pieces to make it easier to stir them.

good luck and looking forward to see some yields reports

scm
 
One thing I'm noticing already is that as opposed to big lumps of "gold" at the bottom of the AP like we get from fingers, there's a lot more finer particles in suspension in the AP. It seems to be a lot finer overall.

I've put a test batch through, and I'll have some figures for the end of the weekend. It's a Bank Holiday over here so I've got three days at it and another forum member is coming to help for a couple of days.

Regards

Jon
 
I can't wait to hear about how this one goes!

Although, I'm curious as to how you came across such a lot of these virgin boards.
They are certainly nice.
 
The gold plating over the copper on the boards will be much thinner than the plating on fingers or other connectors where they need to be plugged in and may be removed and plugged in several times, also where the connections need a good clean contact for the low voltage and very fast digital signals to cross, the gold over the traces on the boards does not need to be thick for wear, so once you dissolve the copper out from underneath it, the gold can just fall apart to fine powder, or even black powder depending how much oxidizer you use to remove the copper.

Do not forget your stannous chloride test once you get to the point of having dissolved away most all of the visible copper.

It can be easy to add too much oxidizer, the gold will not dissolve in the copper II chloride (unless you do use too much peroxide), and since the leach has a hard time getting past that thin gold barrier you can easily get impatient and add more peroxide than needed, which can also dissolve the gold, it would plate back out onto the copper as the oxidizer and acid dissolved copper, replacing the gold from solution as black powders, as long as some copper metal was still un-dissolved, note many circuit boards have multiple layers of copper traces, sandwiched in between layers of the fiber glass circuit board, you will also have copper trace’s under the solder mask, so with these you really do not want to dissolve gold that could be plated back out onto the copper in these places your acid have a hard time to get into, leaving your gold plated to the copper under the solder mask or between layers of your circuit boards, so be a little extra careful with how much peroxide you are adding, or use air from a fish tank pump, and give the boards the time they need.
 
To make the most on those boards sell them on eBay. They will more than not give any foils and you will be chasing gold dust around large amounts of liquid.

That gold is just to protect when it's being worked on. Its not on any wear point. wear points are where the thicker plating is found.

Joem had a bunch at one time.

Goodluck.

Eric
 
Eric thanks

You're spot on. I didn't pay much for them so I'm not going to be left out in the cold, so thankfully it's not a disaster.

I was wondering how on earth it could be so thin, thanks ever so much for explaining it to me.

Butcher thanks too Sir. Appreciate the input very much indeed.

Jon
 
I somehow missed this thread but here is my 2 cents.
They look nice but you will not see much of gold as foil in AP. This is rather flash plating and will disintegrate in powder or tiny flakes in AP. I did similar boards and yield was about 0.5-0.8g / kilogram.
 

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