Optical vacuum coating machine coating, the cause of poor film strength, the combination of substrate and film. In general, in anti-reflection films, this is the main reason for the weakness of the film. Since the surface of the substrate will inevitably have some harmful impurities attached to the surface during the optical cold working and cleaning process, and the surface of the substrate will always have some damage layers due to the effect of optical cold working, and impurities (such as water vapor) that penetrate into the damage layer , oil vapor, cleaning liquid, wiping liquid, polishing powder, etc., of which water vapor is the main one), it is difficult to remove it by ordinary methods, especially for substrates with good hydrophilicity and strong adsorption. When the film material molecules accumulate on these impurities, it affects the adhesion of the film layer, which also affects the film strength.

        In addition, if the hydrophilicity of the substrate is poor and the adsorption force is poor, the adsorption to the film layer is also poor, which will also affect the film strength. The chemical stability of the nitrate material is poor, and the surface of the substrate has been corroded during the circulation process in the pre-processing process, forming a corrosion layer or a hydrolysis layer (perhaps localized and extremely thin). When the film is plated on the corrosion layer or the hydrolysis layer, its adsorption is poor, and the film firmness is poor. The surface of the substrate has dirt, oil spots, gray spots, drool spots, etc., and the local film layer is poorly adhered, resulting in poor local film firmness.
      Improvement measures: (1) Strengthen the degreasing and decontamination treatment. If it is ultrasonic cleaning, it should focus on the degreasing function and ensure the effectiveness of the degreasing solution; if it is rubbed by hand, consider first wiping with calcium carbonate powder and then wiping.
      (2) Strengthen the pre-plating baking, if conditions permit, the substrate temperature can reach above 300 ℃, it is better, the constant temperature is more than 20 minutes, and the water vapor and oil vapor on the surface of the substrate can be volatilized as much as possible. *Note: The higher the temperature, the greater the adsorption capacity of the substrate, and it is also easy to absorb dust. Therefore, the cleanliness of the vacuum chamber should be improved. Otherwise, there will be dust attached to the substrate before plating, which will affect the film strength in addition to other defects. (The chemical desorption temperature of water vapor on the substrate in vacuum is above 260°C). However, not all parts need to be baked at high temperature. Some nitrate materials have high temperature, but the film strength is not high, and there will be color spots. This has a greater relationship with stress and material thermal matching. (iii) When conditions permit, the unit is equipped with a condenser (PLOYCOLD), which not only increases the vacuum pumping speed of the unit, but also helps to remove water vapor and oil and gas from the substrate.
      (iv) Improve the vacuum degree of vapor deposition. For a coating machine above 1 meter, the starting vacuum of vapor deposition should be higher than 3*10-3Pa. The larger the coating machine, the higher the starting vacuum of vapor deposition.
      (v) When conditions permit, the unit installs an ion source, bombards it before plating, cleans the surface of the substrate, and assists in the coating process, which is conducive to the compactness and firmness of the film.
      (vi) To remove moisture from the membrane material, place the membrane material to be used in a petri dish in a vacuum chamber to dry.
      (vii) Keep the working environment dry (including lens wiping, umbrella work area), and do not bring in too much water vapor when cleaning the working environment.
      The combination of the substrate and the film layer is one of the important reasons for the poor film strength of the optical vacuum coating machine, and it is also the reason why the processing manufacturers pay special attention.