Tungsten Heater for Aluminizing - Vacuum Conditions

Tungsten heater for vacuum evaporation means that evaporated material was heated to a considerably high temperature in vacuum to reach a vaporized state, then the vaporized material would deposit on the substrate surface and make a thin film, this process is called vapor deposition. In order to ensure the material can be evaporated effectively on the phosphor screen, the mean free path must be longer than the distance between evaporation source and the substrate. Therefore, the evaporation process must be carried out in a certain vapor pressure. Aluminum is malleable material, which is often made into a rod, sheet, foil, powder, ribbon and filamentous. It can form an oxidation film to prevent the metal from oxidizing in a wet environment.

First of all, open coating machines, vacuum vacuum degree should reach 5 × 10-5 Torr or more, and then pre-melt the evaporation material. Evaporation distance is 6.5 cm, deposition materials area diameter is 5.5 cm. Operators can add a bell and a support plate. The area of the film made by this method is small and it can only plate a fluorescent screen. Quality of aluminum film is better by this method, but efficiency is not good, a screen can only be plated for one time, and the film is uneven. Due to the distance of evaporation is short and the screen cannot withstand high temperatures, it can only evaporate quickly, then the area of the film is small.

Aluminum is evaporated directly in the vacuum of 2 × 10-1 Torr. Evaporation materials is the five aluminum, each length is 0.8 cm, and the total length of tungsten wire heater is 8.5 cm with a diameter of 0.5 mm, when a vacuum evaporation coating chamber reaches 2 × 10-1E, pre-melting the aluminum wire firstly, then add the air into chamber again, the degree of vacuum is adjusted to 2 × 10-1E. These vacuum conditions can be used to aluminizing, but the area of the film is also small.

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