Semiconductor PVD vacuum coating equipment
Semiconductor vacuum coating machine is composed of many precision parts, these parts are produced through many machining processes, such as welding, grinding, turning, planing, boring, milling and other processes. Because of these tasks, the surface of equipment parts will inevitably be contaminated with grease, grease, metal shavings, solder, polishing paste, sweat marks and other pollutants caused by processing. These pollutants are volatile under vacuum conditions, which will affect the ultimate vacuum of the equipment.
The working sequence of the mechanical pump, booster pump and oil diffusion pump of the vacuum coating machine is as follows:
1, mechanical pump
It works from the atmosphere. The exhaust effect of the mechanical pump is also related to the speed of the motor and the tightness of the belt. When the belt of the motor is relatively loose and the speed of the motor is slow, the exhaust effect of the mechanical pump will also become worse. Therefore, frequent maintenance and inspection are required. The sealing effect of mechanical pump oil also needs to be inspected frequently. If the oil is too little, the sealing effect will not be achieved, the pump will leak, and the oil will be too much, the suction hole will be blocked, and the suction will not be possible And exhaust, generally, 0.5 cm below the oil level line.
2, booster pump:
It is a mechanical pump with a pair of double-blade or multi-blade rotors that rotate synchronously at a high speed. Because its working principle is the same as that of a Roots blower, it can also be called a Roots vacuum pump. The pump is in the pressure range of 100-1 Pa It has a larger pumping speed, which makes up for the shortcomings of the mechanical pump's insufficient exhaust capacity in this range. This pump cannot start working from the atmosphere, nor can it directly discharge the atmosphere. Its role is only to increase the intake and exhaust The pressure difference between the ports, the rest needs a mechanical pump to complete, therefore, it must be equipped with a mechanical pump as a fore pump.
Oil diffusion pump: The ultimate vacuum of the mechanical pump is only 10-2 Pa. When it reaches 10-1 Pa, the actual pumping speed is only 1/10 of the theory. If you want to obtain a high vacuum, you must use an oil diffusion pump.
3, oil diffusion pump
The application pressure range is 10-1 Pa-10-7 Pa. It uses the diffusion phenomenon of gas to exhaust. It has the characteristics of simple structure, convenient operation and high pumping speed (up to 10+5 liters/sec). . The oil diffusion pump is mainly composed of a pump casing, a nozzle, a draft tube and a heater. The diffusion pump oil is mainly added (the Japanese model is D-704#). According to the number of nozzles, it can be divided into single-stage pump and multi-stage pump.
When the oil of the diffusion pump is heated by the electric furnace, the generated oil vapor provides the front pressure, and the mechanical pump acts as the front pump. When the diffusion pump oil is heated by the electric furnace, the generated oil vapor is sprayed downward through the umbrella nozzle along the guide tube. Because there is a vacuum of 1-10-1 Pa provided by the mechanical pump outside the nozzle, the oil vapor can be sprayed out for a certain distance to form a jet moving in the direction of the air outlet. The jet finally hits the pump wall cooled by the cooling water, condenses into a liquid, and flows back to the evaporator, that is, it relies on the evaporation of the oil-injection-condensation, and repeats the cycle to achieve pumping.
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