Because of its high melting point, low equilibrium vapor pressure, and very stable chemical properties at high temperatures, tungsten is selected as the emission material and used as a variety of tungsten evaporation sources.
1. Filament and spiral tungsten evaporation sources, among which spiral cone evaporation sources are generally used to evaporate hot particles, bulk materials and materials that are not easily infiltrated with the evaporation source, such as copper, silver, chromium, etc. Other shapes of evaporation sources are suitable for a small amount of materials with excellent wettability, such as aluminum.
2. Disc-shaped and boat-shaped tungsten evaporation sources. The tungsten boat is stamped and processed from a thin tungsten plate. When the plating material is heated in the tungsten boat, a molten pool is formed in the boat and evaporates. The powdered coating material can be made into pellets of appropriate size and placed in a boat for evaporation.
If the plating material needs to be liquefied in the vaporization process, a boat-shaped or disc-shaped tungsten container must be used to hold the plating material, and the container can only be stored under the vacuum chamber. The vaporized plating material is transported from bottom to top, and the workpiece to be plated is placed above the container. If the vaporization process does not involve liquefaction, or the molten pool is small, there is no need for a container, and the evaporation source can be placed at will. The direction of vapor transport is not limited to from bottom to top. The vaporized coating material can fly to the surface of the workpiece to be plated from all directions, which is conducive to uniform coating.
