Why do vacuum coating machines use high-purity gas when coating films? Professionals who know more deeply in the vacuum coating industry may know better that vacuum coating machines use high-purity gas when coating films in a vacuum chamber, so as to ensure that the coated products are benign products.

In vacuum ion plating, the color of liquid gas produced by different gases will be different. When argon is generally used to create plating environment for titanium and chromium plating, silver and yellow products can be produced by filling industrial gas with nitrogen, but if you want to produce black or gray products, you need to add acetylene gas and oxygen to produce blue products. Besides gas, the color of products produced is also affected by pressure, temperature, time and other conditions. Under the condition of high vacuum degree, high-purity plating metal (such as aluminum) will fly freely and settle on the workpiece surface after evaporation at high temperature, forming a plating layer. Argon is a protective gas to prevent the oxidation reaction from affecting the coating quality.

Argon does not participate in the reaction, but only increases the air pressure and improves the discharge conditions of the target during coating. Argon is not used for coating, but mainly used to create the coating environment. Nitrogen and argon are inert gases. After rushing in, one can eliminate oxygen and prevent oxidation, and the other is that the content ratio of nitrogen and argon in the diffusion pump is different, so different colors can be coated, mainly to change the color of the coated products. If it means the gas used to adjust the pressure during coating, I think it is as follows: If argon is only a pressure saving, the primary pressure can be ignored, but the secondary pressure should be less than 0.5 atmospheric pressure. Nitrogen is the same, mainly because if it is large, it will cause the pressure in the vacuum chamber to change too sharply, resulting in errors. If the ion source is used, the argon gas inlet should not be too large, which will lead to excessive ion quantity and burn out parts. The pressure is no different from the above.    

Any solid material will dissolve and adsorb some gases in the atmospheric environment, and when the material is placed in a vacuum state, it will release gas due to desorption and analysis. The rate of outgassing is proportional to the gas content in the material. Different materials have different gas composition, temperature and time.   

Various pumps have different pumping rates for gases with different components. When vacuumizing, the atmosphere in the container is pumped away first (this part of gas is pumped away quickly, and the gas in the furnace is basically exhausted at 10-1Pa), then the gas desorbed from the surface of the material, the gas diffused from the inside of the material to the surface, and the gas infiltrated into the vacuum through the wall of the container. Therefore, after the goods enter the furnace, they must be insulated and degassed, because the goods will absorb some impurity gases before entering the furnace, so we should use proper heating to make these gases. Taking stainless steel as an example, in addition to the gas adsorbed on its surface, some gases will be precipitated in the steel during constant heating and heat preservation. The existence of these gases often has a great influence on the purity and color of the film, and also has a great influence on the adhesion of the film.   

Therefore, when coating with vacuum coater, gas plays a key role, which is an indispensable step in the coating process.