Gold recovery from ceramic eproms

[Rreyes097]

Hey everyone! Well I've been sitting on these ceramic eproms for quite some time now. Mostly because I didn't know how to exactly process them. And when I did find out how to process them I learned that there wasn't too much gold to be had from them.

97 small ceramic Eproms w/gold visible
43 Large c. Eproms w/ gold
49 large c. Eproms w/o gold
39 small c. Eproms w/o gold
That's the total of what I have. I didn't weigh them unfortunately. But there's the eproms with gold visible and there is the ones without. And large and small. Some of these had no windows so I guess those are called proms? Well since it looks to be a simple process I was hoping to put this up there and post my results from them. But before I started I want to make sure of something.
First of these ones without gold visible. So does that mean I process them with nitric and distilled water to get silver? Or just aqua regia for hopefully gold? If there's no gold visible and there's no silver, should I even process them?
Second is there silver at all? Meaning should I hit all of them with nitric first to recover any silver? My plan is straight to aqua regia, this I got from researching on the forum. Is there any other way that y'all would recommend? Any advice is always welcomed! Here are some pics for your viewing pleasure

 

[Christian333]

Hey everyone! Well I've been sitting on these ceramic eproms for quite some time now. Mostly because I didn't know how to exactly process them. And when I did find out how to process them I learned that there wasn't too much gold to be had from them.

97 small ceramic Eproms w/gold visible
43 Large c. Eproms w/ gold
49 large c. Eproms w/o gold
39 small c. Eproms w/o gold
That's the total of what I have. I didn't weigh them unfortunately. But there's the eproms with gold visible and there is the ones without. And large and small. Some of these had no windows so I guess those are called proms? Well since it looks to be a simple process I was hoping to put this up there and post my results from them. But before I started I want to make sure of something.
First of these ones without gold visible. So does that mean I process them with nitric and distilled water to get silver? Or just aqua regia for hopefully gold? If there's no gold visible and there's no silver, should I even process them?
Second is there silver at all? Meaning should I hit all of them with nitric first to recover any silver? My plan is straight to aqua regia, this I got from researching on the forum. Is there any other way that y'all would recommend? Any advice is always welcomed! Here are some pics for your viewing pleasure

The braze under the microchip can be a white metal alloy of gold. Would be great if you could process those separatly and report any gold recovered.

Janie

 

[Rreyes097]

The braze under the microchip can be a white metal alloy of gold. Would be great if you could process those separatly and report any gold recovered.

Janie

But sure what you mean. Process the ones that don't have gold showing?

 

[Christian333]

But sure what you mean. Process the ones that don't have gold showing?

Yes, the ones with no visable gold.

Janie

 

[Rreyes097]

I was planning on processing them separately. I just don't know for sure if they contain any silver. Or should I just try aqua regia first?

 

[Christian333]

I was planning on processing them separately. I just don't know for sure if they contain any silver. Or should I just try aqua regia first?

Nitric leach would be a good plan.

Janie

 

[Rreyes097]

Nitric leach would be a good plan.

Janie

Thought so. But for both?

 

[Christian333]

Thought so. But for both?

Yes, for both. Save the Aqua Regia for refining step.

Janie

 

[Rreyes097]

Yes,

for both. Save the Aqua Regia for refining step.

Janie

Ok I'll do that. Thanks buddy.

 

[Rreyes097]

Well I think the nitric was a waste of time because I'm not seeing any silver or silver chloride. But oh well!

 

[Martijn]

I once had a bunch of eproms with only a gold plating layer under the chip and aluminum bonding wires. Not worth chasing for me.

 

[Rreyes097]

I agree. But I also have a bunch and they were taking up space and seemed easy to process so I figured I'd go ahead and get my 0.2 g of gold.
But I couldn't find out if the non gold ones had silver so I had to try.

 

[Rreyes097]

Well looks like it's harder than I originally thought. Because the gold ones aren't dissolving in the aqua regia. Even with heat. Any ideas?

 

[Yggdrasil]

Well looks like it's harder than I originally thought. Because the gold ones aren't dissolving in the aqua regia. Even with heat. Any ideas?

So the Gold don not dissolve or the whole thing?
I came across some material some time ago and it did not dissolve.
I scratched my head twisting my mind and ended up overshooting the Nitric, in the end it turned out it was coated with a clear coating.
Maybe it needs a roasting?

 

[Rreyes097]

That's what I'm thinking. Because some of them have a clear coating on the outside. A very small amount have dissolved, well the little bit that's on there in the first place. Or it could have come off with the chip. And might be floating around sealed in a clear coat. I rinsed it and broke up a few, hoping it would allow the acid a path. But I was lazy and didn't do them all unfortunately. But if they aren't dissolved by morning I'll rinse then off again and roast them thanks. I was also worried that it might have been that white grayish substance that's found in the middle of the top and bottom pieces. I thought it was just an adhesive or glass of some sort? Well I was worried that it was metastannic acid. I was going to be highly upset because this was supposed to be a easy recovery for minimal gain. But not looking like that now.

 

[snail]

Used to soak them in dilute warm HCl in a jar with a lid in till the filler and legs came loose, sometimes took days.

I believe the adhesive layer your referring to is a silica filled epoxy. The HCl eventually decomposed it.

 

[Rreyes097]

Used to soak them in dilute warm HCl in a jar with a lid in till the filler and legs came loose, sometimes took days.

I believe the adhesive layer your referring to is a silica filled epoxy. The HCl eventually decomposed it.

Yeah, so I went ahead and took them out of the AR and rinsed thoroughly. I then torched them. But I had to be careful because if I hit them directly with the torch the silicon chip would pop off and fly out. I hope I torched it enough but last time I checked there didn't seem to be any change.

 

[Alondro]

Yeah, so I went ahead and took them out of the AR and rinsed thoroughly. I then torched them. But I had to be careful because if I hit them directly with the torch the silicon chip would pop off and fly out. I hope I torched it enough but last time I checked there didn't seem to be any change.

My plan for processing these when I do them will be to simply pulverize them. I have an idea for boring a flat-bottomed pit in a section of a log, then put a circle of sheet iron in the bottom. Attach a bumpy piece of iron to the bottom of a wooden pole a little shorter than the diameter of the hole, then pound and rotate so the chips are crushed.

 

[Rreyes097]

Well I didn't do that because there's only good under the chip. No gold bonding wires, just that little bit of gold braze under the chips. So I suppose you could do that but you might be better off clipping the sides of them so there's only the middle section. And just throw away the top and the legs. Then if you still want to the pulverize the middle section that you keep? I'm no expert and you see that I'm not getting any better results. So I hope whatever you do that it works. Good luck!

 

[eaglekeeper]

When you get them in heated AR you might get some white stuff coating the chips. Some of it might be silver chloride and some will be the adhesive that bonded the two ceramic halves together. It shouldn't cause too much problem, it'll filter of okay.