# Ceramic cpu gold caps



## Jhr (Jun 14, 2016)

Hi guys.Is there any good way to process the gold lids from ceramic cpu.Im not sure if i can just put it into ar like that.Or must i first get rid of the base metal.I think if i use the cell it would be better.Im not sure which procces i must use on it


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## kernels (Jun 14, 2016)

Caveat: I'm a beginner, but have done a number of small experiments now. 

From my experience / experiments, getting rid of a lot of base metal for a small amount of gold is a bad idea. I believe you want to investigate a sulfuric cell or one of the gold leach solutions as a way to recover the gold and leaving the base metal behind. Obviously this information is very dependent on the ratio of gold to base-metal and what type of base metal it is.


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## Jhr (Jun 15, 2016)

Thank you for your replay.i think i will use the salfuric cell and try to recover the gold from there.


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## goldsilverpro (Jun 15, 2016)

The sulfuric stripper will strip the gold plating but probably not the gold/tin braze, if present.


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## samuel-a (Jun 20, 2016)

I have mentioned it in the past.
A cold, dilute nitric leach will strip the gold plating from those Kovar lids in few days.
It will not eat the kovar nor the gold, but it will take the nickel between them.


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## goldsilverpro (Jun 20, 2016)

The problem with those gold plated lids is that most all are attached with an 80/20, gold/tin braze and that's where the majority of the value is. I've never tried Sam's method of cold dilute HNO3 to dissolve the nickel. It sounds feasible for the gold plate but I have doubts about the braze. What's your experience with that, Sam.


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## samuel-a (Jun 27, 2016)

Chris,

It usually takes the nickel under the brazed area as well. There are some spots on the braze line that resist the attack. 
I believe it is due to the braze passing through the nickel layer and binding to the kovar base.


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## goldsilverpro (Jun 27, 2016)

I learned something and it's a good thing to put in my memory bank. I would therefore use Sam's method of weak cool nitric. I would give it a good stir every so often. The nitric will passivate the Kovar once the Ni is gone. The 80/20, Au/Sn eutectic melts at 280C (561F). They applied the braze a little hotter than that, but not much. That's not very hot but, in the middle of the lid, the Ni would be the thinnest and I can see the the braze penetrating the Ni there. No type of electroplating is uniform on a part. For the lid, the Au and Ni will be thickest on the corners/edges and thinnest on the center. The definition of eutectic is that particular alloy (in %'s) that has the lowest melting point. For Au/Sn, it is 80% Au/20% Sn.

What strength HNO3, Sam? How long does it take?


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## samuel-a (Jun 28, 2016)

I'm using 50/50 i.e.- nitric 67%/water. I'm sure even weaker 1/2 nitric/water will do the trick.
It does take a few days, depending on the ambient temperature.

The main issue, and it's not a big deal is that the foils are quite thick and it take some time washing if off the lid.
p.s. - i always twist the lid to 45 angle so nothing will lie flat on the bottom or on each other.

Heating this solution would be a bad choice - the kovar will react spontaneously at an unknown (to me) temperature all at once and may cause a major spill.


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## kernels (Jun 28, 2016)

Hi Sam, I assume this is no use with Pentium 4 lids then ? I believe they are plated copper / brass. How do you identify the kovar lids ? Are they strongly magnetic ?


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## UncleBenBen (Jun 28, 2016)

kernels said:


> How do you identify the kovar lids ? Are they strongly magnetic ?



Yes. Kovar is made up of mostly iron in the alloy.


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## saadat68 (Feb 2, 2019)

Hi 
After some research, I couldn't find a process for kovar CPU lids 
What is the best process? 
1- Process them in dilute nitric and separate gold foils with toothbrush? (As Sam explained)
2- Process them in hot nitric to dissolve kovar?
3- Process them in hot hcl to dissolve kovar?

And I must say acids are very cheap here!

Thanks


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## denim (Feb 2, 2019)

In my limited experience I have found dilute nitric works very well. Takes a little time (days) but gold comes off in nice foils.


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