Sputtering Metal Coatings On Non-metal Substrates.
I am investigating vacuum deposition of metal films on non-metal substrates (ceramic and glass). My questions are similar to #3305, but more general. Can the "sputtering" process deposit a thick enough coating of metal to be used as decorative jewelry? I would like to coat mostly copper, gold, and silver. Does the metal need to be vaporized while it is being sputtered onto the substrate? What typical vacuum pressures are needed (in Torr)?
- Amery, Wisconsin
Sputtering is the mechanism for forming the metal vapor. Sputtered coatings can be deposited thick enough for decorative purposes. Silver, gold, and copper all sputter rather easily.
By just sputtering the metal onto the substrate, you will have a difficult time getting good adhesion. You'll need ion bombardment. Typically, this is achieved by using an unbalanced magnetron sputtering source, and biasing the substrate negatively. However, for insulators, you should use an ion beam in lieu of the biasing.
The deposition is usually carried out at a vacuum pressure around 1 to 10 mTorr Ar backfill, but the pressure before the coating process is begun must be much lower -- under 0.01 mTorr -- to prevent water contamination.
You may also consider cathodic arc deposition. The cathodic arc is another way of producing a metal vapor, the difference being that arc systems are simpler to operate, coat faster for many metals, and the metal is very highly ionized for better adhesion. Decorative coatings on door and faucet hardware is now coated by cathodic arc, providing "lifetime" finishes. The coating is not gold, copper, or silver, but variations of metal oxides. ZrN with varying amounts of C provide gold and brass colors, CrN the silver finishes. If you wish to pursue this option further, please contact me.
PVD Consultant - San Diego, California
A Client has requested a metal finish on some set pieces that we are fabricating. Can this sputtering process be used to coat 20 lb density sign foam. If not, do you have any suggestions on how to achieve a metal look on this foam? The Client has requested that some gears would appear to be brass, steel, copper and/or bronze.
- San Bernardino, California
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