In order to obtain the necessary vacuum degree, the pvd coating machine is generally realized by the combined pumping of a mechanical pump, a Roots pump and a diffusion pump. So what are the specific principles of these four types of vacuum systems? The following is a detailed introduction to the vacuum editor.

The first type: mechanical pump, mechanical pump is the most widely used pump, and it is indispensable in various vacuum units. The following takes the rotary vane mechanical pump as an example to describe the pumping process of the mechanical pump. The rotor of the rotary vane mechanical pump consists of a circular shaft and a rotary vane embedded in the circular shaft cutout. The axis of the rotor is deviated from the axis of the cavity, and the rotor rotates.
When moving, the rotary vane can always maintain sliding contact with the stator (ie, the inner wall of the mechanical pump). Since the volume of the container is inversely proportional to the pressure under the condition of constant temperature, the purpose of exhausting can be achieved by the constant change of the volume of the space limited by the rotary vane when the mechanical pump rotates.
The second type: Roots pump, Roots pump is also a kind of rotary pump, which relies on a pair of 8-shaped involute rotors to pump air through constant speed reverse rotation while maintaining a certain gap. When it works, the two rotors rotate in the casing, and the gas enters the cavity from the air inlet. With the change of the position of the rotor, the cavity is isolated from the upper air inlet of the casing in turn, and is immediately connected to the lower air outlet. The machine is connected, so as to discharge the gas out of the pump. Since the rotor is continuously rotating, the gas can also be continuously extracted.
The third type: oil diffusion pump. The working principle of oil diffusion pump is based on the Bernoulli principle of continuous fluid. The high vacuum degree below 10 Torr can be obtained by pumping with diffusion pump. The invention of diffusion pump makes vacuum technology happen. A huge change, because the ultimate vacuum pumped by mechanical pumps in the past is generally only
Can reach 10 Torr.
In the process of using the diffusion pump, attention must be paid to the flow and temperature of the cooling water, and the high vacuum valve can be opened only after the oil in the diffusion pump is heated to boiling, otherwise a large amount of oil will be returned to the vacuum chamber. After the diffusion pump of the pvd coating machine stops working, it must cool down sufficiently with the mechanical pump continuing to work before shutting down.