Everyone knows that in the process of vacuum coating equipment, it needs to be monitored for a long time, because the position of the coated product will change during the coating process. If it is not corrected in time, the material will be wasted. The following is the method of monitoring the coating equipment:
1. Visual monitoring: The use of eye monitoring, because the film in the growth process, due to interference phenomena there will be color changes, we are based on the color change to control the film thickness, this method has a certain error, it is not very accurate, it is necessary to rely on experience.
2. Extremum monitoring method: When the film thickness increases, the reflectance and penetration rate will change. And when the reflectivity or penetration rate reaches the extreme value point, the optical thickness ND of the coating can be known as the 1/4 integer of the monitoring wavelength (in). However, the method error of the extreme value is relatively large, because when the reflectance or penetration rate changes very slowly near the extreme value, that is, the film thickness ND increases a lot, and the R/T changes. The more reflecting sensitive position is at one-eighth wavelength.
3. Fixed value monitoring method: This method uses the stop plating point not at the quarter wavelength of the monitoring wavelength, and then the computer calculates the reflectivity (or penetration) of the total film thickness at the fixed wavelength, which is to stop Coating point.
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