Vacuum obtaining is also known as “vacuum pumping”, which refers to the use of different vacuum pumps to remove the air inside the container, so that the pressure inside the space drops to below one atmosphere. At present, in order to get the vacuum and commonly used devices including rotary vane mechanical vacuum pumps, Roots pumps, oil diffusion pumps, composite molecular pumps, molecular sieve adsorption pumps, titanium sublimation pumps, sputtering ion pumps and cryogenic pumps and so on. In these pumps, the first four pumps are categorized as gas transfer pumps (transfer vacuum pumps), which means that the gas molecules are continuously sucked into the vacuum pump and discharged to the external environment to realize the evacuation; the last four pumps are categorized as gas capture pumps (capture vacuum pumps), which are molecularly condensed or chemically bonded on the inner wall of the pumping chamber to obtain the required vacuum. Gas-capture pumps are also called oil-free vacuum pumps because they do not use oil as a working medium. Unlike transfer pumps, which permanently remove the gas, some capture pumps are reversible, allowing the collected or condensed gas to be discharged back into the system during the heating process.
Transfer vacuum pumps are divided into two main categories: volumetric and momentum transfer. Volumetric transfer pumps usually include rotary vane mechanical pumps, liquid ring pumps, reciprocating pumps and Roots pumps; momentum transfer vacuum pumps usually include molecular pumps, jet pumps, oil diffusion pumps. Capture vacuum pumps usually include low-temperature adsorption and sputtering ion pumps.
In general, the coating process is different, the vacuum coating chamber vacuum should reach different levels, and in vacuum technology, more to the background vacuum (also known as intrinsic vacuum) to express its level. The background vacuum refers to the vacuum of the vacuum coating chamber through the vacuum pump to meet the needs of the coating process of the highest vacuum, and the size of this vacuum, mainly dependent on the vacuum pumping capacity. Vacuum coating room by its vacuum system vacuum can reach the highest vacuum is called the limit vacuum (or limit pressure). Table 1-2 lists the working pressure range of some common vacuum pumps and the ultimate pressure that can be obtained. The shaded portions of the table represent the pressures that can be obtained by each vacuum pump when used in combination with other equipment.
–This article is released by vacuum coating machine manufacturer Guangdong Zhenhua
Post time: Aug-30-2024