Design of Tungsten Heater for Vacuum Coating

The main raw material of tungsten heater is tungsten filament. Due to its high melting point and strong corrosion resistance, it is widely used in vacuum gilding, aluminum and other decorative items. Vacuum coating is a kind of technology for making film by physical methods. The technology was developed in the 1930s, once it has been introduced, it enjoyed a great popular. This technology was first used in the production of optical lenses, such as telescope disk for sailing. Later it extended to other functional film, music aluminum, decorative coating and surface modification, such as machine tool coating, change processing hardness. Tungsten heater can be twisted into a single strand or multi-strand shape in according with different applications.

Firstly, before designing the appearance of tungsten heater, hank knotting and the heater surface should keep clean, bright without any cracks and visible contamination of impurities, such as oxides and filament drawing lubricants. If there exist impurities on its surface, it will affect the quality of vacuum and influence on the free evaporation rate of the metal, which will reduce the effect of vacuum coating. For the superficial area of tungsten, under the premise of constant power, it should be as large as possible. Size of superficial area is in direct proportion to rate of evaporation, the larger the area, the faster the evaporation. What’s more, it has a direct impact on the quality of vapor deposition and the infiltration flow performance of aluminum.

If it is a single strand tungsten filament, people should choose a relatively thin one whose appearance diameter should be between 0.5 ~ 0.8mm. In the design of the inner diameter of the spiral time, people need to consider whether aluminum can be put in it for many times. On the other hand, it should be ensure that the heat can be effectively concentrated. The pitch of screw thread should be designed for concentrating the heat and the appearance tension of molten aluminum in order to avoid droplet phenomenon.

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