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Thin film sputtering machine - photos
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These are used for one off items. We used to have large units with rotating platters inside to ensure even depositing across lens surfaces. Sometimes hundreds of lenses at a time, sometimes just a couple depending on what was being run. Then the real fun happens having to clean all surfaces within the chamber and sandblasting the platters to prevent contamination in the next batch.
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Quote:
Originally Posted by
odd one
These are used for one off items. ................ Then the real fun happens having to clean all surfaces within the chamber and sandblasting the platters to prevent contamination in the next batch.
Isn't the residue from the blasting considered contamination? Is there a post blast cleaning?
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Quote:
Originally Posted by
tonyfoale
Isn't the residue from the blasting considered contamination? Is there a post blast cleaning?
Platters are removed and media blasted in a separate room then washed down in acetone. The inside of the chambers are often lined with an industrial strength tin foil to help facilitate ease of cleaning. The smallest bit of contamination can wreak havoc on the finished coating. This contamination is often in the form of lint or vaporized contaminants. This all happens at high temps and in a vacuum. Naturally this is all clean room operations. These contaminants typically lead to voids or inclusions in the coating. A certain amount can be acceptable depending on the spec that has to be held. Sometimes, depending on the spec of the lens, a bad coating run can lead to having to scrap the entire batch of lenses all together as the coating cannot always be removed (by diamond turning) and be able to maintain the raw lens specs i.e... edge and center thickness, etc. and sometimes the contract does not allow for rework. Between material and labor, this can be 100's of thousands of dollars depending on the lens material and work time involved. Most of the lenses that we manufactured were crystalline based and used in IR applications.
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Thanks for that. So contaminants are loose particles?
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Quote:
Originally Posted by
tonyfoale
Thanks for that. So contaminants are loose particles?
Yes, contaminants come in many forms but are typically undesirable particles that land on the surface being coated that then cause voids in the coating surface. These can also be introduced by debris left on the lens (or whatever is being coated) from improper/incomplete cleaning prior to coating or even from leaking seals on the vacuum pumps. There are a 100 ways a coating run can get messed up. Your iridium helmet shield is an example of a thin film deposited coating.
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Looks like an experimental University setup, with the VCR inlet fitting connected the compression fitting supply lines and a compressed air regulator being used for Nitrogen, wouldn't even let that into our teaching cleanroom!
