What factors will affect the coating performance of vacuum coating machine?

What factors will affect the coating performance of vacuum coating machine?

   If a vacuum coating machine wants to coat a good film, it must ensure that many factors are in a normal state, such as vacuum coating, base target distance, evaporation temperature, substrate temperature, residual gas pressure and other factors. There is a deviation in a certain factor. It will affect the performance of the coating layer of the vacuum coating machine. The following is a vacuum editor to explain in detail what factors will affect the coating performance of the vacuum coating machine. I hope it can help you:

1. Evaporation rate

      The size of the evaporation rate has a great influence on the deposited film. Since the coating structure formed by the low deposition rate is loose and easy to deposit large particles, in order to ensure the compactness of the coating structure, it is very safe to choose a higher evaporation rate. When the pressure of the residual gas in the vacuum chamber is constant, the bombardment rate of bombarding the substrate is a constant value. Therefore, after selecting a higher deposition rate, the residual gas contained in the deposited film will be reduced, thereby reducing the chemical reaction between the residual gas molecules and the particles of the evaporated film material. Therefore, the purity of the deposited film can be improved. It should be noted that if the deposition rate is too high, it may increase the internal stress of the film, resulting in an increase in defects in the film layer, and even cracking of the film layer in severe cases. In particular, in the process of reactive evaporation, a lower deposition rate can be selected in order to enable the reaction gas and the evaporated film material particles to react sufficiently. Of course, different evaporation rates should be used for different material evaporation. As a practical example of how a low deposition rate can affect the performance of a film is the deposition of a reflective film. For example, when the film thickness is 600x10-8cm and the evaporation time is 3s, the reflectivity is 93%. However, if the evaporation rate is slowed down under the same film thickness, it takes 10 min to complete the film deposition. At this time, the thickness of the film is the same. However, the reflectivity has dropped to 68%.

2. Substrate temperature

      The substrate temperature also has a large effect on the evaporative coating. Residual gas molecules adsorbed on the substrate surface at high substrate temperatures are easily removed. In particular, the exclusion of water vapor molecules is more important. Moreover, it is not only easy to promote the transition from physical adsorption to chemical adsorption at a higher temperature, thereby increasing the binding force between particles. Moreover, the difference between the recrystallization temperature of the vapor molecules and the substrate temperature can be reduced, thereby reducing or eliminating the internal stress on the film-substrate interface. In addition, since the substrate temperature is related to the crystalline state of the film, amorphous or microcrystalline coatings tend to be easily formed under low or no heating conditions on the substrate. Conversely, when the temperature is higher, it is easy to generate a crystalline coating. Increasing the substrate temperature is also beneficial to the improvement of the mechanical properties of the coating. Of course, the substrate temperature should not be too high to prevent re-evaporation of the evaporated coating.

3. Influence of residual gas pressure in vacuum chamber on film performance

      The pressure of the residual gas in the vacuum chamber has a great influence on the membrane performance. If the pressure is too high, the residual gas molecules are not only easy to collide with the evaporated particles, so that the kinetic energy of the people shooting on the substrate is reduced, which affects the adhesion of the film. Moreover, excessive residual gas pressure will seriously affect the purity of the membrane and reduce the performance of the coating.

4. The effect of evaporation temperature on the evaporation coating

      The effect of evaporation temperature on film performance is shown by the evaporation rate as a function of temperature. When the vaporization temperature is high, the heat of vaporization will decrease. If the film material is evaporated above the evaporation temperature, even a slight change in temperature can cause a rapid change in the evaporation rate of the film material. Therefore, it is very important to precisely control the evaporation temperature during the deposition of the film to avoid a large temperature gradient when the evaporation source is heated. For the film material that is easy to sublime, the film material itself is selected as the heater, and measures such as evaporation are also very important. .

The above four aspects are the most common factors affecting the performance of the coating layer of the vacuum coating machine, and they are also the most conventional influencing factors. During the coating process of the vacuum coating machine, it is necessary to ensure that these factors are in a normal state.