Low-temperature pump in the optical coating application

Jan 18


David Yvon

David Yvon

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Now the processes of optical film processing and manufacturing become increasingly complex.


In order to meet production and quality of coating,Low-temperature pump in the optical coating application Articles a large number of thorny problems need to be resolved. From leaning and preparation of the substrate to final inspection and testing, the hardest process is the coating process.

Diffusion pump has been used in optical coating neodymium fluoride industry for 30 years, many people used to it. With the coating quality requirements, the need for better vacuum equipment. With the cryogenic pump, it can provide clean, oil-free vacuum; Not only that, even in the personnel operating errors, power outages and equipment failure, the chamber and machined parts will not be contaminated. This diffusion pumps system failure in stark contrast. If the above diffusion pumps system failure, the need for disassembly, cleaning, reassembly, leak detection and process re-inspection process. Sudden vacuum failure, the conventional treatment takes several days to a week's time.

Cryogenic pump their own gas hold: there is no low-temperature heat pump components to cause deflation, nor will the thermal decomposition of water vapor into hydrogen and oxygen or methane. And, because there is no fluid, moving parts or seals exposed to vacuum, so the corrosion, pollution and other faults are not.

Large cryogenic pumping speed, shorten the coating cycle, to increase production. The only exposed at low temperature in a vacuum pump system is the low- temperature condensation on the surface plate, it can keep the temperature low enough to allow the coating chamber and condensing the gas into the cryogenic pump all. Cryogenic pump provides high pumping speed for water without any liquid nitrogen. Cryopump pumping speed ratio of the other gases in liquid nitrogen cold trap of the same size / diffusion pump combination of about 50% higher to 100%. The increase in pumping speed on the mean in a very short period of time can achieve the required vacuum, but in the process under the same conditions can make such as the reaction of hydrogen and oxygen gas partial pressure by 50% or more.

Cryogenic vacuum pump to provide high-quality coating products to increase production and quality. Previously, when the company's coated with oil diffusion pump, due to mainly the adhesion and hardness tests to 5lOmm and 32-inch (810mm) of the secondary coating chamber were 1 / 8 and 1 / 10, and After installing the pump in the secondary use of low-temperature coating rate of 0. The use of low-temperature production of the film after the pump intensity, solid, and has good abrasion resistance.

Even with the best most expensive synthetic oil diffusion pump, the vacuum chamber using high pressure switch, but also the need to prevent low-back pump oil: oil migration to the substrate or the internal cavity wall and the barium titanate surface and where the aggregate. Thus, with a second coating of the pollutants released by outgassing into the chamber again. Cavity becomes more and more dirty, resulting in adhesion and pinhole problems making production decreases. Closest to the pollution of the cavity wall of the optical coating suffered the greatest impact. Replaced by low-temperature back to the oil pump after eliminating pollution.

Low voltage pump will not reduce short-term or expensive power and makes the coating layer is damaged. Cryogenic pumps can rely on its low-temperature environment to maintain its power vacuum and to continue pumping in 10-20 minutes. This circuit breaker has been reset long enough time, and can save the production of potentially dangerous. Under normal use, low-temperature long-running pumps and compressors should be 20,000 to 30,000 hours without checking. Some users of the pump in the absence of any examination in the case have been running for 60,000 hours or longer. Regular maintenance is the main l million per hour to run the compressor unit to replace less expensive adsorber. In addition, because the pump is a low-temperature adsorption trap pump, and the cavity is used to condense and store the gas, so periodic regeneration is necessary, this is a very simple approach, can be generally accepted.

Cryopump regeneration need not be very frequent. A 48-inch vacuum chamber of the coating equipment, coating operation when the rotation of two classes, and class coating 12 times, only about every two required 120 coated with or after regeneration. Of course, in extreme conditions, very frequent regeneration may be necessary. For example, in the case of high water vapor loads in four layers of plastic film coated on a substrate, a 30-minute cycle time, plating 32 times per day, yield more than 38,000.

It is better to do the work with planning. The regeneration can be made on a regular basis which is convenient for the users. The typically situation is operating the machine on weekends without the human care. Even with a microprocessor controlled automatic regeneration system to complete the regeneration without the interference of producing. It is complete without a human’s help from the separation of the pump, shutting down, purification, heating and re-starting to run rough pumping. Many low-temperature pump users arrange the regeneration in early Monday morning so that the system is ready for the timing of the first use. In some cases, two cryogenic pumps can be use for recycling at the same time. Source:http://www.mhcocm.com