MLCC stands for Multi Layer Ceramic Capacitor and is a sandwich construction of metal plates separated by thin layers of ceramics (often barium titanate, BaTiO3). The metal plates consists of a few different alloys and have changed over time. In early years it contained a lot palladium and silver but after around year 2000 improvements in manufacturing made it possible to replace the palladium with cheaper nickel and copper.
Since nickel is magnetic it is possible to separate nickel based MLCC:s from palladium based ones using a magnet. But older MLCC:s sometimes had silver connector at the ends with a protective nickel plate on top, so they will also show a reaction to a strong magnet.
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Refining MLCC:s can be done in several ways, smelting or via wet chemistry.
If possible, smelting is the preferred way to recover the silver and palladium from MLCC:s.
- The MLCC:s are smelted in a graphite crucible with borax and cryolite as flux.
- The molten mass is poured into a cone mold for the metal to pool into the bottom.
- The recovered metal is then refined or sent out to an external refinery.
Since the MLCC:s usually have a couple of tricky metals the refining can be done in a few different ways. This is one way.
- Washing in hydrochloric acid to remove the tin. Prolonged treatment could dissolve the ceramics too, freeing the internal metal electrodes.
- Wash in water and then crush the ceramics to access the internal metal.
- Dissolve silver, nickel and palladium with nitric acid.
- precipitate the silver as silver chloride and filter it off.
From this solution of palladium nitrate there are several ways to go.
- Cementing directly on copper to form a palladium powder.
- Denoxing and cementing the palladium chloride with zinc or aluminum.
- Denoxing and continue on the palladium refining track.
- GRF : Palladium from MLCC recovered with aluminum foil
- GRF : Lazersteve doubly refined palladium from MLCC
- GRF : Melting MLCC for extracting the metal
- GRF : Test run of melting MLCC:s in an induction furnace
- GRF : Cementing from a denoxed solution of palladium
- GRF : Smelting MLCC:s in Pakistan
- GRF : Another MLCC thread discussing smelting
- Wikipedia : Article on ceramic capacitors