Incinerated laptop mousepads- have I burned off the gold?

[haveagojoe]

Hi folks, I'm back on the forum after many years out..

I am trying to process about 20 laptop trackpad pcbs with gold tracing. They had some kind of sticky glue substance over the gold so I decided to incinerate them to get rid of it. I put them in an old soup can in a wood fire which I fanned by hand to get it nice and hot.

When I removed the boards after incineration there was no gold colour left, the remaining traces look grey.

Is it possible that the gold was evaporated and burned off in the fire leaving only copper behind? I have placed them in copper chloride solution ("AP") and am waiting to see if the traces dissolve. They haven't yet, and some seem to be coming off the boards as I would expect gold foils to do, but I'm concerned that the gold colour is no longer present, only dull grey.

Any thoughts?

 

[FrugalRefiner]

I would guess that the gold migrated / alloyed into the underlying traces of copper.

I wouldn't expect much from 20 laptop trackpads.

Dave

 

[haveagojoe]

I would guess that the gold migrated / alloyed into the underlying traces of copper.

I wouldn't expect much from 20 laptop trackpads.

Dave

Thanks for your reply, yes I don't expect much but it seemed worth a try as the gold tracing covers most of the face of the pcbs. If it's not likely to have burned off the gold then I'd like to keep going and try to get the foils. I have more of these trackpads to do in future but perhaps I'll need a different method to remove the glue.

Would copper chloride solution be sufficent to remove the copper from the alloy? Perhaps I should use dilute nitric? I would imagine it would be a bit like inquarted if it has alloyed with the copper.

 

[Darkthirty]

Hi folks, I'm back on the forum after many years out..

I am trying to process about 20 laptop trackpad pcbs with gold tracing. They had some kind of sticky glue substance over the gold so I decided to incinerate them to get rid of it. I put them in an old soup can in a wood fire which I fanned by hand to get it nice and hot.

When I removed the boards after incineration there was no gold colour left, the remaining traces look grey.

Is it possible that the gold was evaporated and burned off in the fire leaving only copper behind? I have placed them in copper chloride solution ("AP") and am waiting to see if the traces dissolve. They haven't yet, and some seem to be coming off the boards as I would expect gold foils to do, but I'm concerned that the gold colour is no longer present, only dull grey.

Any thoughts?

The can was probably tin plated inside. Tin melts @ 450F, copper melts at closer to 2000. Unlikely your wood fire got hot enough to melt the copper. Any alloying would be with the Sn.

 

[haveagojoe]

The can was probably tin plated inside. Tin melts @ 450F, copper melts at closer to 2000. Unlikely your wood fire got hot enough to melt the copper. Any alloying would be with the Sn.

Oh dear, yea you're probably right; in that case it's probably not worth messing about with any further. I should have thought about it a bit more carefully. Never mind.

 

[Thirmo21]

Oh dear, yea you're probably right; in that case it's probably not worth messing about with any further. I should have thought about it a bit more carefully. Never mind.

So the gold either stayed on copper or it alloyed with melted tin and its on bottom of can. You could shear off the bottom of can and try experiment lol.

 

[anarxi]

I would guess that the gold migrated / alloyed into the underlying traces of copper.

I wouldn't expect much from 20 laptop trackpads.

Dave

I saw information somewhere that the yield from one keyboard is 0.3 grams (300 milligrams) of silver.
gold is 2 times heavier than silver, let the layer be thinner, well, let’s say 100 milligrams per 1.
from a dozen already a gram.
at current gold prices - very good.

 

[anachronism]

As Dave pointed out quite correctly, 20 track pads won't have a high yield. Maybe not even give you enough gold to see. Anarxi I get your point but a lot of these yields were based upon older tech. The gold is extremely thin, and would likely be fine dust. As has already been pointed out incineration would only serve to make it even harder to get at it.

 

[anarxi]

burn several dozen keyboards in one jar, and then dissolve the jar in aqua regia...

 

[haveagojoe]

I saw information somewhere that the yield from one keyboard is 0.3 grams (300 milligrams) of silver.
gold is 2 times heavier than silver, let the layer be thinner, well, let’s say 100 milligrams per 1.
from a dozen already a gram.
at current gold prices - very good.

These are nothing like keyboards. Recovery wise they're closest to RAM fingers or mobile phone PCBs- gold plated over copper on a PCB. In future I'll try some other method to get the glue off and then they should work fine in AP. Then I just add the foils to my jar to refine all together at a later date. I don't worry about yields, I just wait until it looks like i've got enough foils to make it worthwhile.