Vacuum Coating System Shields - Aluminum
Challenge
Clean vacuum coating shields for a thin film coating systems manufacturer in order to recover specific precious metals and to recycle the same shields for use again in their coating systems.
Deposition
Gold, Iron, Nickel, Titanium, Copper, Vanadium and Zinc and many others
Substrate
Stainless Steel and Aluminum
Results
Two distinctly different substrate, stainless steel and aluminum were processed together with our new solution, and it was successful. We were able to yield 99.99% gold bullions to our client’s customer.
One of our clients, involved in cleaning precision parts, became interested in purchasing a license for out new technology so that they could serve new customers by cleaning and recouping precious metal depositions.
The client is skilled in cleaning precision parts with non-precious metal depositions.
The client had the ability to clean glass surfaces deposited with precious metals using the currently used weaker aqua regia (see our FAQs for more details). Once the deposition was dissolved by the weaker aqua regia, the client sent the solution to one of the major refineries, to obtain the precious metals. The glass was scrapped after cleaning. While the weaker aqua regia is OK to be used for glass surfaces, it could not process precious metals deposited onto other surfaces.
That was the case of the client’s new customer, a producer of BAK Batch Evaporators, MSP Sputters and Radiance Cluster Sputter systems. Their R&D department deposited most of the metals of the Periodic Table, gold including, which in turn coated not only the interior of the chamber, but also the shields during coatings tests of the established and new products.
We were given the task to demonstrate how to clean the precision parts and separate, purify and smelt gold into gold bullions.
Again, like in other cases, we started to consider the available technologies:
• As explained in other case studies and our FAQs, the cyanides could not be used, because they would not dissolve the gold trapped underneath the other deposited metals
• The currently used aqua regia would dissolve the stainless steel and aluminum shields in minutes, so the customer would have to keep buying precision shields.
• Blasting would mean separating the metals from the blasting media and then the consequent extraction (dissolution of metals from the media in liquid chemicals) most probably, by using the current state-of-art aqua regia. Since (i) it was not possible to blast just some of the precision shields, (ii) and the refiner’s facilities was not equipped to carry out extractions of tens of tons of blasting media, (iii) and lastly, since the extractions cause huge losses of precious metals, as well, we ruled this group of potential processes.
• The weaker aqua regia, potassium iodide/iodine, thiourea/sulfuric acid/iron (III) sulfate and some other processes were ruled out too, because they would not be reliable in large scale.
With the understanding that we were ideally looking for a technology that would
• Dissolve most of the deposited metals,
• Preserve the precision stainless steel and aluminum chamber shields, and was
• Robust and simple enough to scale-up, with very little setup, and would use inexperienced staff already working at our clients facility, the our new technology became the number 1 choice.
We were a bit concerned about the few number of precision shields that were made from aluminum (which is very sensitive to most chemicals), but the coating deposition on aluminum shields was not so thick, so we decided to take the risk. Normally, when aluminum parts are involved, we would use a more expensive version (chemicals) of our solution.
This chemically more expensive version is much more friendly to such sensitive materials, like aluminum, however, our client would need more certifications from local authorities to use some of these special chemicals. Since typically these certifications take time to obtain, we decided to use the strongest version of our new patented solution.
This proved to be the right choice. Separation of gold from “the other metals” was straightforward as usual, on a small scale.
The client’s staff could not repeat our trial experiment during the scale-up, however, we finished the recycling of the entire amount of gold ourselves. The final yield of gold (in 99.99% gold bullions) turned out the same as the expected theoretical yield obtained from Atomic Absorption Spectroscopy (AAS) analysis of the etching mix.
The client’s new customer was pleased with the results of both cleaning and recycling and our client delivered the information, results and our capabilities to their customers.