1. Basic structure of vacuum coating machine
Vacuum coating machine is a device that deposits thin film on the surface of substrate by physical or chemical methods under vacuum environment. Its core structure includes the following parts:
1. Vacuum system: It is composed of mechanical pump, molecular pump, diffusion pump, etc., which is used to pump the coating chamber to a high vacuum environment of 10⁻³~10⁻⁶ Pa (refer to "Vacuum Coating Technology Manual"). For example, the mechanical pump can reduce the pressure to 1~10 Pa, and the molecular pump can further reduce it to below 10⁻⁴ Pa.
2. Coating chamber: The main body is a stainless steel cavity, which is corrosion-resistant and has strong sealing. The size ranges from 0.5 m³ for small laboratories to 5 m³ for industrial grade (such as ULVAC's ARL-300 model).
3. Evaporation source: Select resistance heating, electron beam or magnetron sputtering source according to process requirements. For example, the power of electron beam evaporation source can reach 10 kW, and the evaporation rate is about 1~5 nm/s.
2. Differences in the composition of different types of coating machines
1. Physical vapor deposition (PVD) equipment:
- Magnetron sputtering coating machines need to be equipped with target materials (such as titanium targets, aluminum targets) and magnetic field systems, and the working gas pressure is usually 0.1~10 Pa.
- Arc ion coating machines add arc sources, the current can reach 100~200 A, and the film adhesion is stronger.
2. Chemical vapor deposition (CVD) equipment:
- Reactive gases (such as SiH₄, CH₄) need to be introduced, and a gas flow control system is equipped, with an accuracy of ±1 sccm (standard milliliters/minute).
3. Auxiliary systems and key technical parameters
1. Control system: PLC or industrial computer is used to monitor vacuum, temperature (±1℃ accuracy), and film thickness (measured by quartz crystal oscillation method, accuracy ±0.1 nm) in real time.
2. Cooling system: The design flow rate of the water cooling pipeline is usually 20~50 L/min to ensure the long-term operation stability of the equipment.
IV. Application scenarios and selection recommendations
1. Optical coating: requires high uniformity (±1% thickness deviation), and needs to select a multi-crucible electron beam evaporation source.
2. Tool coating: focuses on hardness (such as TiN coating can reach 2000 HV), and arc ion plating equipment is preferred.
Through the above analysis, users can choose the matching coating machine type and configuration according to actual needs (such as film performance, production efficiency).
