Vacuum Coater Film Uniformity Concept

Vacuum Coater Film Uniformity Concept

1. The uniformity in thickness can also be understood as roughness. On the scale of optical films (that is, 1/10 wavelength as a unit, about 100A), the uniformity of vacuum coating is quite good, and the roughness can be easily removed. The degree of control is within 1/10 of the wavelength of visible light, which means that there is no obstacle to the optical properties of the film. However, if it refers to the uniformity on the atomic layer scale, that is to say, to achieve 10A or even 1A surface flatness, the specific control factors will be explained in detail below according to different coatings.

2. Uniformity of chemical composition: That is to say, in the film, the atomic composition of the compound will easily produce uneven characteristics due to the small scale. If the coating process of SiTiO3 film is unscientific, the composition of the actual surface will not be the same. It is not SiTiO3, but may be other ratios. The coating film is not the chemical composition of the desired film, which is also the technical content of vacuum coating.

3. Uniformity of lattice order: This determines whether the film is single crystal, polycrystalline or amorphous, which is a hot issue in vacuum coating technology.

Vacuum coating machine ball mark method

The ball mark method is also a "qualitative" method for measuring the bonding force of the film base. When the coating surface is flat) or elliptical (when the coating surface is cylindrical) pits.

When grinding, you must master it well, and the depth of the pit must exceed the thickness of the coating. In addition, because the coating is very hard. The steel ball is difficult to wear through the coating directly, so when grinding, first apply a little diamond powder (with a particle size below 7um) on the grinding area of the steel ball, and spray alcohol to dilute the diamond powder and lubricate during grinding.

Under a microscope magnifying glass, magnify the pit 50-100 times. You will see a decomposition line between the coating and the substrate. Observe the shape of this dividing line to judge whether the bonding force between the coating and the substrate is good or not. If this line is very clear and neat. The coating adhesion is good. If this dividing line is canine-crossed or faulted, the coating adhesion is not good.

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