Feasibility Analysis of Metal C-Ring in Vacuum Gate Valve Application
Created on 2025.12.28
Abstract: As a core component controlling the on-off of media in vacuumsystems, the sealing performance of vacuum gate valves directly determines thesystem's vacuum degree, operational stability, and service life. Metal C-ringsare increasingly used in high-end sealing fields due to their excellenthigh-temperature resistance, corrosion resistance, deformation resistance, andlong-term sealing characteristics. Starting from the sealing requirements ofvacuum gate valves, this paper systematically analyzes the core feasibilityindicators of metal C-rings in vacuum gate valve applications, such asadaptability, sealing reliability, and working condition adaptability, combinedwith their structural and performance advantages. Meanwhile, potential problemsand corresponding solutions during application are discussed, providingtheoretical and practical references for the engineering application of metalC-rings in vacuum gate valves.
1. Introduction
Vacuum gate valves are widely used in high-end fields such assemiconductor manufacturing, photovoltaic industry, vacuum coating, andaerospace. Their core function is to realize rapid on-off and reliable sealingof vacuum systems. In these application scenarios, the system often putsforward strict requirements on seals, such as ultra-high vacuum environment(pressure ≤ 10⁻⁷ Pa), wide temperature range (-50℃ ~ 500℃ and above), strong corrosive media (such as plasma, chemical vapordeposition exhaust gas), and stability requirements for long-term frequentswitching.
At present, the commonly used seals for vacuum gate valves aremainly rubber seals (such as O-rings, materials including fluororubber,silicone rubber, etc.) and metal seals (such as metal O-rings, C-rings, waveplate seals, etc.). Although rubber seals have advantages such as low cost andeasy installation, they are prone to aging, volatilization (generatingoutgassing), deformation and other problems under high temperature, ultra-highvacuum and strong corrosion conditions, leading to decreased sealing performanceand shortened service life, which are difficult to meet the long-term stableoperation requirements of high-end vacuum systems.
As an efficient metal elastic seal, the unique C-shapedcross-sectional structure of metal C-rings endows them with good elasticcompensation capacity. Meanwhile, relying on the excellent characteristics ofmetal materials, they perform prominently in high-temperature resistance,corrosion resistance, low outgassing rate and other aspects. This paper aims todemonstrate the feasibility of metal C-rings in vacuum gate valve applicationsby analyzing their structural and performance characteristics, combined withthe sealing working principle and working condition requirements of vacuum gatevalves, and propose optimized technical directions for their application.
2. Structural andCore Performance Characteristics of Metal C-Rings
2.1 StructuralCharacteristics
The cross-section of metal C-rings is "C" shaped, usuallystamped from a single layer of thin metal sheet. Some high-end products adoptmulti-layer composite structures or surface coating treatments (such as goldplating, silver plating, nickel plating, etc.). Their core structural advantagelies in: when subjected to axial compression load, the opening of the C-ringwill undergo elastic expansion, making the outer (or inner) circular surface ofthe seal closely fit with the wall of the seal groove to form a line contactseal; at the same time, the arc-shaped side wall of the C-ring can absorb thedisplacement caused by assembly errors, valve body deformation and temperaturechanges through elastic deformation, thus having good compensation capacity. Inaddition, the hollow structure of the C-ring will form a certain pressurechamber inside during the compression process, further enhancing the sealingeffect. Especially in the vacuum environment, this "self-reinforcing"sealing characteristic is more significant.
2.2 CorePerformance Characteristics
1. Excellent high-temperature resistance: Metal C-rings are usuallymade of high-temperature resistant metal materials such as stainless steel(304, 316L), Inconel alloy, Hastelloy alloy, etc. The operating temperaturerange can cover -200℃ ~ 800℃, and some special materials can even work stablyin high-temperature environments above 1000℃, which is far superior to rubberseals (usually the maximum operating temperature ≤ 250℃).
2. Low outgassing rate, suitable for ultra-high vacuum: Metalmaterials themselves have high molecular stability and extremely lowvolatilization (outgassing rate) in vacuum environments. After appropriatesurface treatments (such as vacuum annealing, polishing), the outgassing ratecan be controlled below 10⁻¹⁰ Pa·m³/(s·m²), which can meet the sealing requirements of ultra-high vacuumsystems (≤ 10⁻⁷ Pa). However, rubber seals are difficult to adapt to ultra-highvacuum environments due to the easy volatilization of organic components intheir own materials.
3. Strong corrosion resistance: Metal C-rings made ofcorrosion-resistant alloy materials or with surface coating treatments canresist the erosion of corrosive media such as acids, alkalis, salts and plasma,and are suitable for vacuum systems with corrosive working conditions such aschemical vapor deposition (CVD) and plasma etching. In contrast, rubber sealsare prone to swelling and aging under strong corrosion environments, with highrisk of sealing failure.
4. Strong elastic compensation capacity and high sealingreliability: The cross-sectional structure of C-rings endows them with a largeelastic deformation range, which can effectively compensate for the flatnesserror of the sealing surface, the micro-deformation of the valve body undertemperature changes or pressure fluctuations, and the wear caused by frequentswitching, ensuring long-term sealing reliability. In addition, metal materialshave excellent fatigue resistance and much longer service life than rubberseals, which can reduce the maintenance frequency and downtime of the vacuumsystem.
5. Excellent pressure resistance: Metal C-rings can bear high axialcompression loads. In high-pressure difference vacuum systems (such as theswitching process between vacuum system and atmosphere), they are not prone toplastic deformation or failure, and their sealing stability is superior to thatof rubber seals.
3. Analysis ofSealing Requirements and Working Conditions of Vacuum Gate Valves
3.1 SealingWorking Principle
The sealing core of the vacuum gate valve is to drive the valveplate to move through a driving mechanism (such as a cylinder, motor), so thatthe seal on the valve plate closely fits with the sealing surface of the valvebody, blocking the gas flow between the vacuum system and the outside world (ordifferent chambers of the system). According to the different sealing parts, itcan be divided into valve plate sealing (primary sealing) and valve stemsealing (dynamic sealing). Among them, valve plate sealing directly determinesthe vacuum sealing performance of the system and is the core sealing link. Thesealing effect of the vacuum gate valve mainly depends on the fitting degreebetween the seal and the sealing surface, the elastic compensation capacity ofthe seal and the stability of the material.
3.2 Key WorkingCondition Requirements (Field-Specific Refinement)
1. Vacuum degree requirements: The requirements for vacuum degreeof vacuum gate valves in different application fields vary significantly, andthe core fields show a trend of ultra-high vacuum. Among them, the semiconductorfield (such as ion implantation and thin film deposition processes in chipmanufacturing) has the most stringent requirements for vacuum degree, whichneeds to reach the ultra-high vacuum level (≤ 10⁻⁹ Pa), and some advanced processes even require ≤ 10⁻¹¹ Pa to avoid contamination of the wafer surface by residual gas andaffect device performance; the photovoltaic field (such as PECVD coatingand metallization processes of crystalline silicon batteries) is mainly highvacuum to ultra-high vacuum (10⁻⁶ ~ 10⁻⁸ Pa), which needs to ensure the uniformity and purity of thecoating layer and prevent film defects caused by insufficient vacuum degree. Inaddition, low vacuum (10⁵ ~ 10⁻¹ Pa) is mainly used for pre-treatment of vacuum systems or on-offcontrol of auxiliary chambers in both fields.
2. Temperature working conditions: The temperature workingconditions in both fields show the characteristics of "high fluctuationand high extreme value", and there are significant differences betweenprocesses. The semiconductor field has a very large temperature span.For example, the low-temperature deposition process needs to be carried out ina low-temperature environment of -100℃ ~ -50℃, while the high-temperatureannealing and metallization processes need to be operated in a high-temperatureenvironment of 400℃ ~ 800℃, and some special processes can even reach above1000℃, requiring the seal to maintain stable elasticity in a wide temperaturerange; the photovoltaic field is mainly medium and high temperatureworking conditions. The temperature of the PECVD coating process is usually200℃ ~ 450℃, and the temperature of the crystalline silicon annealing processcan reach 600℃ ~ 900℃. There are frequent heating-cooling cycles (dozens oftimes a day), which puts forward extremely high requirements for the thermalfatigue resistance of the seal. In contrast, rubber seals are prone to agingand carbonization under the above high-temperature conditions, and brittlefracture under low-temperature conditions, which are difficult to adapt.
3. Medium working conditions: Both fields have corrosive media, andthe requirements for pollution control are strict. The corrosive media in the semiconductorfield are more complex. For example, the plasma etching process willproduce highly corrosive plasma and reaction exhaust gas containing fluorine,chlorine, bromine, etc., and the chemical vapor deposition (CVD) process willuse flammable, explosive and corrosive gases such as ammonia and silane. Thesemedia are easy to erode the seal and produce pollutants, requiring the seal tohave extremely strong corrosion resistance and non-release characteristics; thecorrosive media in the photovoltaic field mainly come from silane,ammonia exhaust gas in the PECVD process and residual acid-base substances inthe cleaning process. Although the corrosion is slightly lower than that in thesemiconductor field, it also requires the seal to have no pollutant release toavoid affecting the conversion efficiency of photovoltaic cells. In addition,the clean vacuum systems in both fields strictly prohibit the seal fromproducing volatiles or particulate impurities, and the problem of volatileorganic compounds (VOCs) release from rubber seals is difficult to solve.
4. Operation frequency: The high-frequency switching demand ofautomated production lines is significant, and the frequency stratification iscaused by process differences in the field. In the high-end chip productionlines (such as 7nm and below processes) in the semiconductor field, thedaily switching frequency of vacuum gate valves can reach thousands of times(some key chambers even tens of thousands of times), requiring the seal to haveextreme fatigue resistance and wear resistance; in the large-scale productionlines in the photovoltaic field, the daily switching frequency of vacuumgate valves is usually hundreds to one thousand times, which is lower than thatin the semiconductor field, but it needs to operate continuously for a longtime (usually only shut down for maintenance 1~2 times a month), and hasextremely high requirements for the long-term stability of the seal. Theservice life of rubber seals can usually only support thousands of switches.Frequent replacement will lead to production line shutdown and greatly increasemaintenance costs.
5. Assembly and maintenance: Both fields pursue "lowmaintenance and quick-change" sealing solutions to adapt to the efficientoperation needs of production lines. The vacuum chambers in thesemiconductorfield are mostly precision modular designs. The seals need to adapt to thenarrow seal groove space, and avoid contaminating the chamber duringreplacement, requiring the seals to be easy to install and accuratelypositioned; the photovoltaic field has a high degree of production linescale and a large number of equipment. It requires the replacement process ofthe seal to be simple and time-consuming, and to adapt to the seal groovestructure of the existing mainstream vacuum gate valves without large-scalemodification of the valve body. The customizability and wide compression rangeof metal C-rings can better adapt to the assembly and maintenance needs of bothfields.
4. FeasibilityAnalysis of Metal C-Ring Application in Vacuum Gate Valves
4.1 SealingPerformance Adaptability Analysis
The low outgassing rate of metal C-rings makes them perfectlysuitable for the sealing needs of ultra-high vacuum gate valves. In theultra-high vacuum environment, the organic components of rubber seals are easyto volatilize, and the generated outgassing will make it difficult to improvethe system vacuum degree, and the volatiles may contaminate the vacuum chamber;while metal C-rings adopt high-stability metal materials, and after vacuumannealing treatment, the outgassing rate can be reduced to an extremely lowlevel, which can effectively ensure the vacuum stability of the ultra-highvacuum system.
At the same time, the elastic compensation capacity of metalC-rings can effectively adapt to the flatness error of the sealing surface ofthe vacuum gate valve. Although the sealing surface of the vacuum gate valvebody is precision machined, there are still slight flatness deviations, and thevalve body may undergo micro-deformation under temperature changes or pressurefluctuations. During the compression process of the metal C-ring, the elasticexpansion of its C-shaped structure can make the sealing surface closely fitwith the wall of the seal groove, forming a reliable line contact seal,effectively making up for the machining error of the sealing surface and thedeformation of the valve body, and ensuring sealing reliability. In addition,the self-reinforcing sealing characteristic of the C-ring can further improvethe sealing effect in the vacuum environment: when the system vacuum degreeincreases, the pressure inside the C-ring is lower than the external vacuumenvironment, prompting the C-ring to expand further, enhancing the fittingpressure of the sealing surface, and achieving the effect of "the higherthe vacuum, the better the sealing". This characteristic is highlyconsistent with the sealing needs of the vacuum gate valve.
4.2 WorkingCondition Adaptability Analysis
1. Temperature adaptability: The operating temperature range ofmetal C-rings (-200℃ ~ 800℃) is much wider than that of rubber seals, which canadapt to the high and low temperature working conditions of vacuum gate valves.In high-temperature vacuum systems (such as vacuum coating, high-temperatureannealing), rubber seals are prone to aging, softening and even carbonization,leading to sealing failure; while metal C-rings made of high-temperatureresistant alloy materials can maintain stable elasticity and structuralstrength in high-temperature environments, and the sealing performance is notaffected. In low-temperature vacuum systems, metal materials have excellentlow-temperature toughness and will not harden and brittle fracture due to lowtemperature like rubber seals, ensuring sealing reliability.
2. Medium adaptability: Metal C-rings can effectively resist theerosion of harsh media such as plasma and corrosive exhaust gas by selectingcorrosion-resistant alloy materials (such as Hastelloy alloy, Inconel alloy) orperforming surface coating treatments (such as gold plating, nickel plating).In the plasma etching and CVD processes of semiconductor manufacturing, rubberseals are easily oxidized and eroded by plasma, leading to sealing failure andpollutant generation; while metal C-rings have good corrosion resistance, canwork stably for a long time, and have no pollutant release, which meets therequirements of clean vacuum systems.
3. Operation frequency adaptability: The fatigue resistance andwear resistance of metal materials are far superior to those of rubbermaterials. In the vacuum gate valve with frequent switching, metal C-rings canbear repeated compression and rebound, and are not prone to fatigue damage orwear. The service life can reach tens of thousands or even hundreds ofthousands of times, which is much longer than that of rubber seals (usuallythousands of times). It can significantly reduce the maintenance frequency anddowntime of the vacuum system and improve production efficiency.
4.3 Structure andAssembly Adaptability Analysis
The seal groove of the vacuum gate valve is usually a rectangulargroove or a trapezoidal groove. The cross-sectional size of the metal C-ringcan be customized according to the existing seal groove structure, withoutmajor modification of the valve body, and has good structural adaptability.Compared with metal O-rings, metal C-rings have a wider compression range(usually 15% ~ 30% of the cross-sectional height), lower requirements forassembly accuracy, and are easy to install and debug. In addition, metalC-rings are light in weight, will not cause additional burden on the drivingmechanism of the valve plate, and adapt to the lightweight design needs ofvacuum gate valves.
4.4 EconomicAnalysis
From the perspective of initial cost, the price of metal C-rings ishigher than that of rubber seals, but their service life is much longer thanthat of rubber seals, and they can reduce the downtime maintenance cost andproduct scrap cost caused by sealing failure (such as wafer contaminationcaused by sealing failure in semiconductor manufacturing). In high-end vacuumsystems, the long-term sealing characteristics of metal C-rings cansignificantly reduce the life-cycle cost and have good economic feasibility. Inaddition, with the maturity of metal C-ring manufacturing technology, theirproduction costs are gradually reduced, further improving the economicfeasibility of their application in vacuum gate valves.
5. PotentialProblems and Solutions During Application
5.1 PotentialProblems
1. Risk of sealing surface damage: The hardness of metal C-rings ishigher than that of rubber seals. If there are impurities (such as metalparticles, dust) on the sealing surface or the surface roughness is high, themetal C-rings may scratch the sealing surface during the closing process of thevalve plate, affecting the sealing performance.
2. Difficulty in compression control: The sealing performance ofmetal C-rings is sensitive to the compression amount. Too small compressionamount will lead to loose fitting of the sealing surface and leakage; too largecompression amount may cause plastic deformation of the C-ring and loss ofelastic compensation capacity. If the positioning accuracy of the drivingmechanism of the vacuum gate valve is insufficient, the compression amount maybe unstable, affecting the sealing effect.
3. Elasticity attenuation in low-temperature environment: Althoughthe low-temperature performance of metal C-rings is superior to that of rubberseals, the elasticity of some metal materials will attenuate to a certainextent in extremely low-temperature environments (such as below -150℃), whichmay affect the elastic compensation capacity of the seal.
5.2 Solutions
1. Optimize the processing and cleaning of the sealing surface:Improve the processing accuracy of the valve body sealing surface and reducethe surface roughness (Ra ≤ 0.8μm is recommended); add filtering devices in thevacuum system to reduce impurities entering the sealing part; perform softcoating treatment (such as silver plating, gold plating) on the surface of themetal C-ring to reduce the hardness of the seal and reduce damage to thesealing surface.
2. Improve the positioning accuracy of the driving mechanism: Adopthigh-precision driving mechanisms (such as servo motors, precision cylinders)and cooperate with displacement sensors to achieve precise control of thecompression amount; optimize the design of the seal groove according to thematerial and cross-sectional size of the metal C-ring, and reasonably set thecompression range (usually 20% ~ 25% is recommended) to ensure stable sealingperformance.
3. Select low-temperature suitable materials: In extremelylow-temperature working conditions, select metal materials with excellentlow-temperature toughness (such as austenitic stainless steel, Inconel alloy),or perform low-temperature aging treatment on metal C-rings to improve theirelastic stability in low-temperature environments.
6. Conclusions andProspects
6.1 Conclusions
Metal C-rings are highly consistent with the sealing needs ofvacuum gate valves due to their excellent high-temperature resistance,corrosion resistance, low outgassing rate, strong elastic compensation capacityand long-term sealing characteristics, and have good feasibility in theapplication of vacuum gate valves. Specifically reflected in: ① The sealingperformance is suitable for ultra-high vacuum, wide temperature range andcorrosive medium working conditions; ② The structure is suitable for the sealgroove design of existing vacuum gate valves, and the assembly is simple; ③ Thefatigue resistance is excellent, the service life is long, and the life-cyclecost is low. By optimizing the processing of the sealing surface, improving thepositioning accuracy of the driving mechanism and selecting suitable materials,the potential problems such as sealing surface damage and unstable compressionduring application can be effectively solved, further ensuring the sealingreliability.
6.2 Prospects
In the future, with the continuous improvement of the requirementsfor sealing performance of high-end vacuum systems, the application prospect ofmetal C-rings in vacuum gate valves will be broader. It is recommended tofurther optimize their application performance from the following aspects: ①Develop new composite metal materials to improve the corrosion resistance,low-temperature elasticity and wear resistance of the seal; ② Adopt advancedmanufacturing processes (such as 3D printing) to realize the personalizedcustomization of metal C-rings and adapt to complex sealing structures; ③Combine simulation technology to optimize the structural design of the sealgroove and C-ring, and improve the sealing performance and assembly accuracy; ④Carry out long-term working condition tests, accumulate application data ofmetal C-rings in different vacuum systems, and provide more complete technicalsupport for engineering applications.