The workflow of optical coaters usually includes the following main steps: pretreatment, coating, film monitoring and adjustment, cooling and removal. The specific process may vary depending on the type of equipment (such as evaporation coater, sputtering coater, etc.) and coating process (such as single layer film, multilayer film, etc.), but in general, the process of optical coating is roughly as follows:
First, the preparation stage
Cleaning and preparation of optical components:
Before coating, optical components (such as lenses, filters, optical glass, etc.) need to be thoroughly cleaned. This step is the basis for ensuring the quality of the coating. Commonly used cleaning methods include ultrasonic cleaning, pickling, steam cleaning and so on.
The clean optical elements are usually placed on the rotating device or clamping system of the coating machine to ensure that they can remain stable during the coating process.
Pretreatment of vacuum chamber:
Before placing the optical element into the coating machine, the coating chamber needs to be pumped to a certain degree of vacuum. The vacuum environment can effectively remove impurities, oxygen and water vapor in the air, prevent them from reacting with the coating material, and ensure the purity and quality of the film.
Generally, the coating chamber needs to achieve a high vacuum (10⁻⁵ to 10⁻⁶ Pa) or a medium vacuum (10⁻³ to 10⁻⁴ Pa).
Second, the coating process
Starting coating source:
The coating source is usually evaporation source or sputtering source. Different coating sources will be selected according to the coating process and material.
Evaporation source: The coating material is heated to an evaporative state using a heating device, such as an electron beam evaporator or a resistance heating evaporator, so that its molecules or atoms evaporate and are deposited on the surface of the optical element in a vacuum.
Sputtering source: By applying a high voltage, the target collides with ions, sputtering out the atoms or molecules of the target, which are deposited on the surface of the optical element to form a film.
Film material deposition:
In a vacuum environment, the coated material evaporates or sputters from a source (such as an evaporation source or target) and gradually deposits onto the surface of the optical element.
The deposition rate and film thickness need to be precisely controlled to ensure that the film layer is uniform, continuous, and meets the design requirements. Parameters during deposition (such as current, gas flow, temperature, etc.) will directly affect the quality of the film.
Film monitoring and thickness control:
In the coating process, the thickness and quality of the film is usually monitored in real time, and the commonly used monitoring tools are quartz crystal microbalance (QCM) ** and other sensors, which can accurately detect the deposition rate and thickness of the film.
Based on these monitoring data, the system can automatically adjust parameters such as the power of the coating source, the gas flow rate or the rotation speed of the component to maintain the consistency and uniformity of the film layer.
Multilayer film (if required) :
For optical components that require a multilayer structure, the coating process is usually carried out layer by layer. After the deposition of each layer, the system will carry out repeated film thickness detection and adjustment to ensure that the quality of each layer of film meets the design requirements.
This process requires precise control of the thickness and material type of each layer to ensure that each layer can perform functions such as reflection, transmission or interference in a specific wavelength range.
Third, cool and remove
CD:
After the coating is complete, the optics and the coating machine need to be cooled. Since equipment and components can become hot during the coating process, they need to be cooled to room temperature by a cooling system, such as cooling water or air flow, to prevent thermal damage.
In some high-temperature coating processes, cooling not only protects the optical element, but also enables the film to achieve optimal adhesion and stability.
Remove the optical element:
After cooling is complete, the optical element can be removed from the coating machine.
Before taking out, it is necessary to check the coating effect, including the uniformity of the film layer, film thickness, adhesion, etc., to ensure that the coating quality meets the requirements.
4. Post-processing (optional)
Film hardening:
Sometimes the coated film needs to be hardened to improve the scratch resistance and durability of the film. This is usually done by means such as heat treatment or ultraviolet radiation.
Film cleaning:
In order to remove contaminants, oils or other impurities from the surface of the film, it may be necessary to perform minor cleaning, such as cleaning, ultrasonic treatment, etc.
5. Quality inspection and testing
Optical performance test: After the coating is completed, a series of performance tests are carried out on the optical component, including light transmittance, reflectivity, film uniformity, etc., to ensure that it meets the technical requirements.
Adhesion test: By tape test or scratch test, check whether the adhesion between the film and the substrate is strong.
Environmental stability testing: Sometimes it is necessary to conduct stability testing under environmental conditions such as temperature, humidity, and ultraviolet light to ensure the reliability of the coating layer in practical applications.
–This article is released by vacuum coating machine manufacturer Guangdong Zhenhua
Post time: Jan-24-2025