Non-Chemical How many processes?

[bswartzwelder]

I plan on processing some computer chips in the future, and want to do it with the least amount of trouble (mistakes). Time is of no consideration at this point, and I have some ideas on how to proceed, just want to see if my ideas agree with you guys. There are many different types of chips, so I assume there will be many different ways of processing.

1. First type of chips are the CPU chips with beautiful gold plated pins. The pins will not come off even after heating with a propane torch. I believe the pins are somehow embedded into the green fiberglass which the CPU is on. There are a few surface mount components which have been soldered in place on the fiberglass. I know the lead and tin may present problems, but they are in extremely small quantities. My idea: Soak in H2SO4 to get rid of solder, then pyrolyze and incinerate. This will release the pins. Place pins in AP to get rid of base metals. Process the ashes from the pyrolization/incineration process in AR. I am not good at panning, so that is not really an option for removing the gold from the ashes.

2. Second type of chip(s) also have beautiful gold plated pins. The pins will come off after heating, but with the number I have, this might take weeks, or even months. Also, if you heat them up and rap them onto a hard surface, any solder which is molten, could flow onto another pin nearby. This could possibly spread the solder over the whole batch of pins, making it into a bigger problem. My idea: Soak in H2SO4 to get rid of the solder and release the pins, then place the pins into AP to dissolve base metals. Process the pin-less chips with those from above.

3. Third type of chip looks like a black CPU chip, except it was soldered into place. I will include ALL surface mount chips in this process. When the circuit board on which the chip(s) were mounted was heated, the chip(s) popped right off. However, the underside of the chip is covered with little dots of solder. In some areas, there are even blobs of solder where the solder from numerous connections have amassed. There are some non-CPU chips which were soldered along their edges, but I don't see any pins. My idea: Soak in H2SO4 to get rid of the solder, then add to the chips above and process as above.

4. Fourth type of chips, are black chips with a row of pins (connectors) on 2 or all 4 sides of the chips. The pins/connectors made contact with a socket and the chips had to be pried loose. I do not see any gold plating anywhere on the connecting pins. Likewise, I do not see any solder anywhere on the chips. Too many chips to break off the connector pins, plus that leaves the pieces that are sandwiched between the top and bottom of the chip halves. My idea: Place in AP to dissolve base metals (connectors/pins). May take a long time to work up between the chip halves, but they can sit all winter long if need be. Then, process with chips in (1.) above. An alternative method would be to pyrolyze and incinerate first. Then sift the ashes very carefully through my classifying screens. I have screens ranging from 1/2 inch all the way down to 1/100 inch, so I know I could get the metal pins/connectors out somewhere along the line. Using AP first may take a long time and use up a fair amount of chemicals. Pyrolyzing/incinerating first will save on chemicals, and there should be no solder related issues. How much will I lose in values where the super thin gold wires are connected to the legs of the pins? Is it worth running in AP first?

What if I just throw everything into one bucket and start processing a handful at a time? Someone once mentioned putting chips into a blender or a meat grinder. If I just pyrolyze everything together, the pins which contain gold could attach to other pins which may or may not contain gold. Also, any gold interconnecting wire(s) inside the chips could get caught up in any solder not removed first. Am I making this too hard, or am I over simplifying it? There are so many different ways to approach this, and my first priority is to do it correctly and safely. My second priority is to keep loses to a minimum. I believe Samuel-a started a thread on how he did the green chips, I will start my reading there. But, I have more than just the green chips. I've made mistakes (by the busload) in the past. I just want to minimize those mistakes in the future. I also know that where chips are concerned, pyrolysis and incineration are the preferred way to go.

 

[bswartzwelder]

After having re-read the entire thread started by samuel-a, I see where Geo puts the green fiber CPU's in AP. That sounds like an easy way to start with them. I also re-read Geo's later posts, and see that he was using this process as late as July 25 of this year. Green fiber CPU's better look out. The AP bucket is calling your name. That's the first type of chips. Noly three more types to go.

While I'm at it, I have several pounds of gold plated pins. Most have some solder on them. What is the best method for removing the solder from the pins? Would a soak in H2SO4 work as well as boiling in HCl? Or, should the pins just go into the AP and let it get rid of all the base metals?

 

[Geo]

yes, i just place the whole CPU in the AP bucket. after all the foils are loose, i filter through a piece of linen cloth. wear gloves and remove the bases one at a time and spray the foils off that cling on. this will get about 90% of the foils. filter the solution again through coffee filter to get the fines. the fines will have stuff like tin oxide and lead chloride so be mindful of that. i should say, do not mix the foils from the linen cloth and the coffee filters together.

 

[bswartzwelder]

Thanks, Geo. I have processed quite a few finger contacts from circuit boards in AP. There was never an amount of solder present, so it didn't present a problem. I found a nice big kitchen strainer from WalMart that fits on the opening to a five gallon bucket perfectly. If anyone is looking for a fantastic strainer, the ones I have seen were all white with two black handles. They require the huge coffee filters (like the ones in commercial coffee makers) but the filters sit in them perfectly. Because of their size, the AP solution runs right through them, and 3 gallons gets filtered in just a few short minutes. I believe the price was about $1.97 each. After using one, I rinse it with a spray bottle of H2O.

Once dry, most of the foils will come out, but there also seems to be a lot that will not come out. Mostly very small pieces of gold which have broken up and gets stuck to the paper. I have 2 options to deal with this. One, place the used filters in something that will dissolve the gold like AR (or poormans AR) or incinerate them and process the ashes. I'm leaning towards the second method because it will involve less steps and I have other filter papers with much less gold on them.

In your method, you say to not mix the foils from the linen filter with the fines from the coffee filter. Since they all came from the same batch, aren't you just filtering according to size? Isn't there a possibility that all the foils contain some tin oxide or lead chloride? I would think boiling in HCl with a few drops of H2SO4 should help clean them up before the second dissolution on the way to final refining. In no way do I doubt what you're saying, but my question is: what is gained by doing it this way? I know there's a good, logical answer to this.

Also, you say linen cloth. All I know about cloth could be summed up in one (maybe two) short paragraphs. Would a cotton cloth filter work, or is the fact that it's linen critical as well? Where do you purchase linen cloth for a filter?

 

[maynman1751]

When I filter, I don't let the filter dry. I rinse the filter off with a spray bottle, right after filtering, into the vessel that I'm going to use for the HCl wash. That pretty much gets all of the values. The filter then goes in my used filter pile for later incineration and recovery of 'lost' values.

 

[Geo]

linen is used for bed sheets and table cloths. its relatively cheap and re-usable. after you filter and rinse the foils out, just hang it out to dry. linen is a fine weave and filters almost as well as a coffee filter. lts nothing special about the cloth other than its ability to trap the foils while allowing finer particles to go through the cloth. if you are only dealing with clean, solder free fingers, this would not be an issue. if you are doing any other scrap (fingers with solder,boards with solder,pins of any kind,whole CPU's) the foils will be trapped and other smaller particles (tin oxide,lead chloride,copper(I) chloride) will pass through the linen but will be trapped by a coffee filter. following this logic, the foils captured by the cloth filter will be cleaner and result in a cleaner solution when dissolved. the foils trapped in the coffee filter will have all the other nasty stuff you dont want in your solution and by not mixing them together gives you the opportunity to clean the foils up before dissolution by incinerating and washing in the necessary chemicals.

 

[bswartzwelder]

Geo,
That makes perfect sense, now that I think about it. I have only dealt with foils from finger contacts, and there was no solder or other contaminants present (other than the base metals). However, since I used a bubbler in my AP, as the solution would work its way up under a foil, the foil would break away in very tiny pieces. Much of what was captured by the coffee filter almost looked like a powder. Will be looking for a cheap sacrificial linen sheet next visit to the store.