The Influence of Cathode Temperature of Vacuum Coating Equipment on Arc
The temperature of the cathode of the vacuum coating equipment has a relatively large impact on the arc. Whether the temperature control is timely and reasonable directly affects the coating effect and production efficiency of the substrate. Therefore, general manufacturers generally need to hire professionals with coating technology experience and understanding to operate the vacuum coating machine, which can not only control costs, but also improve efficiency. How does the target temperature of the cathode of the vacuum coater affect the arc? The stability of target cathodic arc combustion depends on the evaporation temperature of the cathode surface. Lowering the cathode surface temperature will bring about higher arc combustion stability. At the same time, lowering the temperature of the cathode evaporation surface will also reduce a large number of particles and large sputtering in the metal vapor.
By observing the combustion process of the cathode arc of the target of the vacuum ion coater, we found that the arc spot is very rough before the arc is extinguished. Sometimes even cluster arc spots appear. After extinguishing, the target surface is red, and the target surface temperature is very high. The appearance of the rough arc spot makes the arc current more concentrated on a certain point on the target surface, which leads to excessive concentration of the arc spot current on the target surface under the arc spot, which increases the temperature of the target surface under the arc spot and generates a large amount of thermionic emission. The result of a large number of thermionic emission from the surface of the target, on the one hand, neutralizes a large amount of space charge, so that the electric field on the cathode surface becomes a deceleration field, and even the electric field on the cathode surface is equal to zero. On the other hand, a large amount of thermionic emission has a considerable cooling effect on the surface of the cathode. Therefore, there is neither a strong electric field generated by space charges to maintain surface emission, nor a very high surface temperature to generate thermionic emission, which causes the arc to extinguish.
Therefore, in the design of the multi-arc target source of the vacuum coating machine, attention should be paid to the sufficient cooling of the cathode target. Use direct water cooling. In indirect water cooling, adjacent parts such as the cathode base should be made of materials with good thermal conductivity (such as copper, aluminum, etc.)
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