LED Coating System Shields
Challenge
Process the shields used in coatings systems that deposit and manufacture LED lights to recover, recycle and recoup several layers of metal coatings.
Deposition
Gold, Platinum, Titanium and Aluminum.
Substrate
Stainless Steel
Results
One of the largest producers of LED’s was sending their physical vapor deposition (PVD) coating chamber precision shields, which were coated with gold, platinum, titanium, nickel, aluminum, and other metal depositions to a refiner in order to recoup those precious metals and to clean and re-use their expensive stainless steel (SS) precision shields.
The refiner was using cyanide technology at room temperature.
Not only are cyanides highly toxic, they work on “naked” gold layers only (definition: “naked” on surface and not encapsulated or trapped between other metallic layers). Therefore, if there is a layer of gold buried beneath layers of other metals, the gold does not dissolve and it is lost, which reduces the yield significantly.
The precision stainless steel shields are dipped into cyanides, some of gold dissolves, and the reaction stops. It stops because the cyanides are not able to dissolve the “other non-gold deposited metals.”
In order to get to the gold buried encapsulated or underneath the other metals, the precision stainless steel shields that were submerged in toxic cyanides, are then taken out of the solution, blasted by abrasive media, and dipped back to the cyanide solution.
Needless to say, blasting does not distinguish between the deposition and substrate. Therefore, some of the gold and platinum are blasted off including potentially the other metals and often the stainless steel substrate, which then is not as accurate if re-used or worst have to be thrown out because they no longer meet specifications.
Let us mark this as the FIRST LOSS of GOLD and PLATINUM in this type of processing.
The precision parts are then returned to the cyanides, and the process of alternating between cyanides and blasting is usually repeated three to four times.
This now accounts for SECOND – FOURTH LOSS OF GOLD and PLATINUM.
What became evident is that the blasting media containing the precious metals, by customer or order, were not accounted for as belonging to each customer and respective order. Especially, since the blasting media used to process one customer to the next, including all orders of different customers were collected together, instead of being separated order-per-order, customer-per-customer. Thus, no customer received the benefit or more importantly the credit back for precious metals that were rightly theirs.
So, let’s count that as the FIFTH LOSS of GOLD and PLATINUM. We were informed that the blasting media, collected from many orders of different customers, were supposedly sent to a refiner abroad to recover precious metals.
Last but definitely not least, surprise came at the end.
When the used coated shields come in from the customer for cleaning, they are weighed. After the cleaning process they are weighed again and the resulted weights are compared. The data gathered, that compared the aforementioned weight differences representing the gold that was recouped, was provided to us for review.
The results showed that over 90% of the weight difference was gold. To our shock, the (1) platinum and the (2) gold that were left in the blasting media, the (3) titanium and the (4) aluminum were not accounted for in the report at all. We know this because all the blasting media received from all customers were processed together, instead of separated by customer, so there was no way to find out what the yield was for the other metals.
So, if there is 90% of gold, say 90 troy ounces of gold in 100 troy ounces of the original deposition weight, as indicated in the report, then there is only 10 troy ounces left for the non-accounted-metals.
According to our results, using our patented solutions, the “other deposited metals” content, together with the platinum we recouped, was a minimum 18%.
It suggested to us that there is a significant difference between what is reported to management and what is received in reality. So we needed to go further with our investigations.
Obviously we did not buy the inventory results at all.
The fact that the precious metals in the blasting media were not included in the reports, so the THIRD to FOURTH losses of precious metals in blasting media were not counted for at all was really alarming. Because, if it were, the recovery of deposition would exceed 100% …meaning how can you recover more precious metals than you initially deposited?
The LED manufacturer had no idea about any of this.
One would wonder why not? Why didn’t they know? And what does this mean to the bottom line?
This case study is different from the Au-PET case study.
There the gold deposited onto PET, and in a very uniform layer.
So it is possible to send the same amount of PET film with gold to different refiners and compare their results – as seen in the Au-PET case study.
In this case, we are talking about stainless steel shielding from the PVD chambers with many metals and precious metals deposited onto the SS.
The amount of all deposited metals and precious metals depends on the (1) kind of the PVD process used, the (2) length of time the chamber shields are used prior to cleaning, and (3) the position of the stainless steel shield in the chamber and the line-of-site from the coating source (shutters, as and example, usually obtain most coating of deposited metals).
We found that it maybe very difficult for a customer to compare refiners and often without knowing the details the customer has to rely on trust and the refiner’s references and history. But, does that mean they are obtaining all their precious metals? As reviewed above, even when going to one of the three major refiners in the market, the devil is in the details.
We were asked to try to improve this situation for the customer.
It quickly became quite obvious, that the cyanide technology was the root cause of all these associated problems and relatively low yields.
If there was a technology that would dissolve all coated and deposited metals, no blasting media would be needed, nothing would be sent outside the control of the customer or abroad, the precious metals would not travel between the liquid solution and blasting room, no questionable yield reports would need to be reviewed or deciphered.
Was there an existing technology available?
(1) As explained above, it’s better if the cyanides would not be used;
(2) The aqua regia would dissolve the stainless shielding, so the customer would have to keep buying precision shields again and again;
(3) Blasting would mean extraction (dissolution of metals from the media in liquid chemicals) would be mandatory and most probably by the aqua regia. Since (i) it was not possible to blast some of the shields, (ii) the refiner’s facilities were not equipped to carry out extractions of tens of tons of blasting media, (iii) and since the extractions causes huge loss of precious metals as well, we ruled out blasting – standard aqua regia processing.
(4) We tested all the other available technologies, like weaker aqua regia, potassium iodide/iodine, thiourea/sulfuric acid/iron(III) sulfate and some other processes. All of them were ruled out, because they would be problematic to scale-up to production demands among other obvious reasons.
We knew that we were ideally looking for a technology that would, first, dissolve most of the deposited coatings metals, second, preserve the stainless steel precision shields, and third, a robust and simple enough to scale-up and processed by minimal trained personnel.
A review of our completed research and development provided the necessary technologies that we could apply to solve this challenge. We then customized these technologies and developed a novel new process and technology, which we patented.
These new solutions and processes proved to be the technology for these varied challenges and also provided what our customer was hoping to achieve, while surpassing all of our expectations.
We were able to dissolve the entire coating deposition, preserve all the precision-machined stainless steel shields, our patented process could be scaled-up and we were able to etch away (dissolve) the coating deposition in one processing tank!
The liquid containing the dissolved metals, then underwent just one filtration (to remove dirt that is usually present on precision parts) to a second processing tank where the gold and the platinum was fully separated and recouped in solid form.
Since this was the only transfer of the precision stainless steel shields in liquid form, we were able to keep any loss of the solution to an absolute minimum.
The high purity of gold and platinum obtained only further solidified our confidence in our new technology's ability to perform.
From the technological point of view, there is literally nothing that would hinder the customer from getting the maximum yield of precious metals that they started with in the deposition.
We helped to scale-up our technology at the refiner and are confident that the customer is getting the fair and optimum amount of precious metals returned to positively affect their bottom line.