Are my chips close?

[Alabama938]

Hello, really enjoy the info here.

Have 20 chips, did dilute nitric twice and nearly all have dropped the pins, but these squares that came out of the smashed chips look untouched? Should I separate these out and do another treatment? They look, in person, too thick to be foils, like they feel firm when stirring.

Alabama

 

[canedane]

My guess is some of the pins have so heavy goldplating so the acid can not have contact to the brass .
Take one pin and flat it with a hammer and try again in a test tube.

And other answer can be some of the pins are kovar, it takes a longer time.
Good luck.
Henrik

 

[Shark]

I can't recall the name of the metal in those square pieces, but yes, they are harder to process. Many people take them off with heat before hand. I am sure someone will be along to tell us what it is soon.

Swirl the solution around a few times and watch the pins. If they seem to float freely, they are done, or very near done.

I would usually run ceramic processors in AR, I prefer poormans AR for ceramics but regular nitric works just as well. You can drain the solution off and start the AR process with what you have remaining. This would allow for a less dirty solution in your AR at this point.

 

[Alabama938]

The pins do not float at all they actually sink really fast… They look hollow and when I take one out and put it in concentrated nitric nothing happens. That’s why I was asking a question about the squares because they do the same thing...nothing.

 

[Shark]

You mention concentrated nitric. Are you using any water at all? In some cases dilute nitric will actually work better than full strength. One of my favorites is to use the nitric until it seems to slow down, then heat it gently. I used many old coffee makers for this back then so I didn't risk over heating it. To much heat with strong acids can result in a sudden boil over. The lower heat also helped avoid breaking glass from heating it up to fast. If the material seems heavy, as you describe, I would try a bit of heat. I use a hot plate and the pyroceram dishes from Corningware. It holds up well and can be found reasonable at yard sales and flea markets. Even then, start with low heat and work it up. It really would help to know what you have to work with.

After a closer look at your picture, I would do another round of the nitric, with gentle heat. The more base metals you can remove, the easier it is to work with in AR.

 

[acpeacemaker]

Just saying thanks for posting pics wearing gloves. Even if it was just to hold up the beaker to snap a pic. Seems like I've seen a lot the other way around the past few months on posts...

Those little square pieces I used to have a lot better success when I cut them in half with tin snips. The acid seemed to penetrate easier. And as shark said, heat can play a major impact on things.

Andrew

 

[Alabama938]

@andrew you’re welcome, I’ll def try cutting them up

@shark I used dilute acid with gentle heat twice, the concentrated bit was just a pipette worth to test a pin. I don’t like the idea of hot acid...so once it gets going I’ve been letting it react off heat and reheating after dies down...trying to waste as little nitric as possible

 

[kurtak]

Hello, really enjoy the info here.

Have 20 chips, did dilute nitric twice and nearly all have dropped the pins, but these squares that came out of the smashed chips look untouched? Should I separate these out and do another treatment? They look, in person, too thick to be foils, like they feel firm when stirring.

Alabama

Per the underlined - you say "came out of" --- do you mean that they came out if the cavity inside of ceramic CPUs --- or where they the lids on top of the cavity of ceramic CPUs

Can you show a pic of "both" sides of the squares ?

As for the pins (that come off CPUs) most of them are kovar (an iron alloy) they are hard to dissolve - don't waste your nitric - use HOT HCl (to recover foils) - or dissolve it all with HOT AR then drop your gold

Kurt

 

[Alabama938]

@Kurtak
I will share some pictures when I get home… These came out of the cavity after I smashed them (i960 chips). I filtered and rinsed them thoroughly last night so I could inspect them further… Appreciate the response

 

[Alabama938]

So I was wrong, it seems to cap the Pin side inner rim covering What I’m guessing is the actual CPU. Clearly from the inside of one of the chips (shown) there’s still some tiny foils/wires. My new question then is should I try to put the gold in solution as opposed to more BM.

 

[Shark]

You can go either way. Both have advantages and disadvantages. Both will work. I would do the base metal removal if your fairly inexperienced at AR. If I were to the Hydrochloric for removing the base metals I would be sure to use up any remaining nitric before going to HCl. Boiling HCl isn't near as bad as nitric, but it does become more dangerous with heat. This will leave you with fairly nice gold foils to work with, making the AR job easier at times.

If you go the AR route, it leaves you a dirty solution that can be hard to drop at times or stubborn to settle. Smaller quantities I would do the AR from the start, And drop with iron sulfate (copperas). I just prefer it when dropping from a dirty solution. SMB will work, it just drags more base metals down with the gold when working with dirty solutions. If your confident in you ability to clean dirty gold, or aren't striving for real high purity, this may be the way to go.

Both work, it is just a matter of which your most comfortable with. I would not go with nitric because HCl will remove iron a bit better. The kovar inside the pins are made of iron.

(Thanks Kurt, I can never remember the word kovar)

(Thanks for bringing this up, it reminded me where I put the two pounds of pins I had stashed.)

 

[Alabama938]

@Kurt

When you say HCl, are you meaning just boiling in straight HCl? If a straight HCl boil augmented with nitric (AR). Would pull gold into solution, That does seem more efficient though it may require more refining… Is there any issue with gold cementing on undissolved kovar pins?

 

[nickvc]

If you choose to go for the AR process you have to dissolve all the metals or gold will cement back out of solution, if you now opt to use HCl to remove the iron then you need to remove all traces of the nitric or some of your gold will go into solution, if you have fairly small amounts of material a good wash several times with agitation should clean the material enough to remove the vast majority of the nitric residue and allow you to continue to process in HCl, test your solution after reaction has stopped just to check you have no values in solution.

 

[kurtak]

Thanks for the pics --- besides the pins being made of kovar the lid on the pin side of the CPU should also be kovar (check it with a magnet to make sure because I have seen copper lids on "some" CPUs)

Kovar is a nickel/cobalt/iron alloy - HCl is better then nitric at dissolving iron - because of the nickel & cobalt in kovar it is much more resistant to acids - VERY resistant to nitric & more resistant to HCl then just iron

Therefore kovar can be dissolved with HCl but you need to get it HOT - like hot enough to bring it to a low simmer boil & even then it is slow at dissolving the kovar - depending on batch size & with larger pieces (like the lids) it can take a couple days & even needing to pour off the HCl & start with fresh HCl a couple times --- again depending on batch & beaker size - so yes you can dissolve the kovar with just HCl - but its slow - even hot

with this method you get rid of the kovar first - leaving you with foils - so you use less nitric because you only need to dissolve the foils with AR & the dissolved foil solution will be cleaner

AR - Nitric (an oxidizer) added to the HCl makes the acid "more" reactive to the kovar thereby speeding up the dissolving of it - but even with AR you want to run the reaction at a low simmer boil for it to be really effective

As we know AR dissolves gold - so when you are trying to dissolve kovar with AR yes gold also dissolves - but then as long as there is un-dissolved kovar - the kovar try's to cement the gold out of solution while at the same time working at dissolving the gold --- therefore with this method you need to use enough AR & run it long enough to dissolve ALL of both the kovar & gold - you also need to add "extra" nitric at the end of the process to "make sure" both the kovar & gold is all dissolved - so you end up with a fair amount of free nitric in your AR at the end of the process - which then needs to be de-noxed before you can drop the gold --- so MORE nitric with this process

The square in the cavity of the CPU is the silicon die (which what does the processing when the computer is running) & it is bonded to the inside of cavity with gold & that gold goes fully under the die - so you need to run it in the AR (at a simmer boil) to dissolve the gold completely from under the die - you know its done when the die releases from the ceramic & see no more gold on the ceramic &/or on the underside of the die

Personally I always used the AR method for doing ceramic CPUs ---broke them into pieces - put them in the beaker & ran them in hot AR till I was sure all the kovar & gold was dissolved - filtered the solution (it will be VERY dirty) then de-nox the AR & drop the gold --- I used that method because I could be done (have my gold back) in one day --- whereas with the HCL method it could take 2 - 3 days before I had my gold back

Hope that helped

Kurt

 

[Ohiogoldfever]

Great explanation Kurtak. Thanks!