Melting plastic substrate with heat vs. dissolving gold

[the_photon]

Sirs,

I am in possession of several hundred slips of very thin PETE (polyethlyene terepthalate) films with gold wiring on them. They are electronics scrap from circa 1990 from a long ago defunkt electronics R&D firm.

My question is this: given that the PETE films are less than 1mm thick (not a traditional circuit board or anything), and the gold wiring on them is appx 0.001 inches thick, would it make more sense to just burn the plastic substrate film away with a butane torch and then attempt to melt the resulting gold wiring into a button in a crucible? Or is the standard Aqua Regia approach better? Will burning the plastic film away with a butane torch result in extremely impure or oxidized gold?

Thanks,

the_photon

 

[NobleMetalWorks]

Do these slips have a tiny silicon wafer in the center? It sounds like you have CPU's printed on plastic film, or something like it. I forget the name, but there was a R&D firm that went out of business in the 90s, that was trying to develop this type of technology. It never took off and all their R&D material was auctioned off in the 90s, from what I remember.

Can you post pictures of these?

Is the gold printed on the film on the outside, or is it between layers of the plastic film?

If it's between layers, it may be as simple as applying enough heat to make the two films come apart from each other. Or using a solvent that does the same. When two types of plastic are fused together with heat, they can still come apart if a little heat is applied. So long as they are dissimilar. It would also make sense that the film would be heat resistant considering the gold had to be hot enough to print the circuit on the film.

You also might want to clip a small piece of the plastic film, and test it in different solutions. The gold on the film is probably high karat, but may only be 22k. So you will have to recover/refine but dependent upon the film and how it interacts with acid solutions you may be limited to what you can use. If it's on cellulose or plastic will also make a difference.

Small tests with clipped off pieces of the material is probably your best move forward at this point, until you know what your reaction is going to be, you won't know the best way to recover the gold. Since none of us has enough information, it's hard to give good solid advice. If you post pictures someone may be able to tell you exactly how to deal with this material.

 

[the_photon]

Sir,

(sorry, I can't read your reply as I type mine . . . trying to remember what you said . . .)

Yes, the gold that I have is deposited on what I'm pretty sure is PETE -- and yes they HAD silicon wafers on the inside of them. I'd be happy to send you a scanned PDF file via email if you'd like to get in touch that way. To avoid spam-bots, my email address is my user-name on this forum followed by (at)sbcglobal.net

The name of the company was AK Technologies, located in Carrolton (a suburb of Dallas, Texas) They were contracting for a company in this state that is a household name for their calculators (sorry, trying to avoid spam bot litigation). My father was a machinist for them in the early '90s and yes they never got off the ground as I understand it. It was probably through no fault of their own -- now that I am 33 yrs old I understand this business concept.

The slips of PETE with gold deposition that I have are very much as you described, except that to the best of my abilities to tell, they are gold circuits deposited on a monolayer of PETE, not a layer of gold sandwiched between two layers of plastic. In the early 1990's I was in junior high school, going up to my dad's work and watching the robotic everything try to mass produce these things. My dad, in his industrious nature, saved the slips (which were going to be thrown in the trash) with the gold wiring in the off chance that they might be useful to his children someday in the distant future --- the now for me.

Are you aware of this company by any remote chance? Even more importantly, do you have any suggestions as to whether I should attempt to burn the plastic off or attempt to reclaim the gold via the Aqua Regia technique and it's variants? Any information, no matter how seemingly insignificant or unsuspecting may help me fulfill a lifelong dream of recovering this gold -- even if only a few hundred dollars worth.

Best regards,

the_photon

 

[NobleMetalWorks]

I am going to post my response here in the forum, for the benefit of people who might read this thread, and in case I am incorrect in what I say, so that someone might be able to correct or explain better, but I will follow this up with an email to you directly.

I have had experience with this type of material, and if these are similar to the ones I processed they are actually CPUs. If you still have the silicon wagers that were in the center, those might have gold on the bottom as well, mine did. I cannot remember the company that originally patented the process but their initials were KD, I'll look over my information to see if I can figure out exactly what they were. I do know that there were several companies that were attempting to use the same process to produce CPU's and other traditionally ceramic chips, with these film chips but then fiber CPU's were less expensive and production lines could be re-tooled to produce them so the technology was dated, before it was ever really researched and developed.

I am assuming you do not have experience recovering or refining precious metals, so my advice will be based on that assumption. If I am incorrect I apologize in advance. This does seem to be the case though, hope I am not stepping on toes. Also, my way might not be the best way, or it might not be the best way for you, it's only my advice and opinion.

Before you do anything, I would download and read at least the first few chapters of C. M. Hokes book, you can find the link to the PDF filehere: http://tinyurl.com/mfnyhs

Also, you may want to test the gold on the film to make sure there isn't some other layer of polymer or film that would prevent you from recovering the gold with an easier method.. Doing this will not only prove gold content, but also prove it's easily accessible or not. If the gold reacts, you are in luck, but if you plan on recovering it I would suggest completely reading Hoke before.

I don't know your background, so again please excuse me if I offend you. Some other things you may want to consider before delving into recovering and refining are these.

Equipment, you can do this inexpensively but you at least need to use equipment that is safe.

Well ventilated area, Aqua Regia gives off toxic and poisonous gases during it's consumption of metals, one gas in particular is especially troublesome, NOx. Even if you have a chemistry background and understand the concepts, dangers, safety issues I would still read Hoke.

Is the amount of gold you are recovering worth the time, effort, energy and cost to do so. It may be that it will be very profitable, or it might not be worth it if you have to invest too much money purchasing the correct equipment.

Would it be more cost effective to sell the items you have for someone else to recover, or, would it be more profitable to take it to a refinery that can do it for you. And then there is the issue of finding a refinery that is honest, and trustworthy. There is actually some really good information on this forum on how to represent your lot as it's being processed. You might want to read those posts as well.

To test for gold, and to see if the gold is on the top layer of the film, you can try one of several ways. The easiest to me seems to be to rub the gold part of the plastic film on a test stone, then use the 14lk test solution to see if it's gold. If you can rub the gold off, you know it's on the top layer which makes processing it much easier. That was the case with the ones I processed, so I went straight to Aqua Regia. And I didn't use heat. If you use poor man's Aqua Regia, you need to use heat, which could melt the plastic film considering how very thin it is. Stick with Nitric/HCl for your Aqua Regia, I used no heat and it stripped the gold right off leaving only the plastic film behind. Before doing this though, I would test a small piece of the plastic in Aqua Regia, just to make sure it doesn't want to decompose into a messy sludge. If it dissolves, then you obviously need to consider another method of recovery.

If everything is the same as what I processed, you should be left with the plastic films, and AU in solution. The next part of the process, to drop the gold, clean, and then perhaps refine further, is well documented and fairly easy to follow, so long as you have read Hoke first. You seem to at the very least, picked up enough from reading the forum, or your own experiences, to know you need to ask questions and refer to specific processes, however I cannot stress this enough. If you do not read Hoke, it will be difficult for people to help you because you won't know enough to ask the right questions to resolve whatever problems arise. You also will not be as well equipped to understand the answers that are given to you.

I wouldn't incinerate the plastic. The material left behind will make it even more difficult to recover the precious metals, plus when you incinerate you could loose values.

That's all I can think of right off the top of my head, I'll email this to you as well. There might be other people on the forum that can help you more, if you have any questions feel free to respond to my email, but I would ask that you post here as well as this forum is an important repository of information that cannot be found anywhere else.

Scott