What are the functions of the auxiliary vacuum system in the vacuum leak detection of the PVD coating machine?
The function of the auxiliary vacuum system is to remove part of the gas from the parts of the vacuum coating machine to be inspected. It is a set of devices that enables the vacuum leak detection device to have stable working conditions, as well as clear time and response time. Considering the gas volume of the tested coating equipment components, the auxiliary vacuum system should be required to have a certain pumping speed. The selection of the pumping speed of the auxiliary vacuum system requires comprehensive consideration from the cleaning time and the reaction time. In addition, in order to make the pre-pumping time as short as possible when detecting leaks in large quantities of components, the pumping speed of the auxiliary vacuum system should also be considered from the pumping time of the leak detector.
For the small volume, air leakage rate and deflation rate, the parts of the equipment under inspection can be directly connected with the external flange of the leak detection device for leak detection, without the auxiliary vacuum system. For parts of the equipment to be inspected with a large deflation rate and leakage rate or with a large volume, if the leak detection device is directly connected, the vacuum degree of the leak detection device may not be pumped up, and the vacuum leak detection device may not operate. To detect leaks in this state, you can only adjust the throttle valve to open it slightly, which in turn will cause the entire reaction time to become longer. In addition, during the initial vacuuming of the parts of the equipment to be inspected, substances such as water vapor and oil vapor may cause the contamination of the leak detection device. Therefore, this is another important aspect of the auxiliary vacuum system that needs to be used for vacuum leak detection. factor.
Even if the volume of the parts of the vacuum equipment to be inspected is small, if a large-scale leak detection is required, an auxiliary vacuum system is also required. Otherwise, the efficiency of leak detection will be extremely low, and if an auxiliary vacuum system is added, the length of leak detection operation can be effectively saved.
The auxiliary vacuum system is composed of the fore pump, the secondary pump, the valve, the standard leak and the vacuum gauge standard leak. The fore-stage pump usually uses a gas ballast mechanical pump, and whether a secondary pump is required depends on the specific situation. The secondary pump can be a Roots pump or a diffusion pump. Some leak detection devices come with a series of valves, which can be used to perform rough extraction and leak detection on small, small, out-gassing and leak-free parts of the equipment under the vacuum pumping system of the leak detection device, without the need Plus auxiliary vacuum system. However, from the perspective of maintaining the stability of the sensitivity of the leak detection device, it is best not to use the vacuum pump that comes with the leak detection device for rough pumping.
There are two ways to connect the leak detection device and the auxiliary vacuum pumping system, each of which has different characteristics. When testing clean coating machine parts without large leaks, the leak detection device needs to be connected to the low vacuum (front stage) side; conversely, for contaminated equipment parts, in the case of large leaks, To find small leaks, the leak detection device needs to be installed on the side of the high vacuum. The position where the leak detection device is connected should be such that the maximum conductance between the leak detection device and the parts of the equipment under test is to allow higher concentration of helium to enter the leak detection device. When the leak detection device is connected to the low vacuum side, due to the unstable pumping speed of the foreline pump, the leak detection device will increase the noise and reduce the leak detection sensitivity to a certain extent, so it is best to connect one in series on the low vacuum side Diffusion pump, or add a regulator bottle. In the design of the auxiliary vacuum system, the connecting flange of the leak detection device should be reserved on both the low vacuum side and the high vacuum side.
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