OFHC Copper Gaskets for CF Flanges
Model:KXT 1230
Kaxite OFHC Copper Gaskets for CF Flanges (KXT 1230) are punched from 1/4-hard, high-purity oxygen-free copper. They seal CF16–CF250 Conflat flanges, reach UHV 10⁻¹¹ Pa, and tolerate 450°C bakeout. Chemically cleaned, deburred, and individually packaged for vacuum-grade cleanliness.
10⁻¹¹ Pa
UHV Rating
450°C
Bakeout
CF16 – CF250
Flange Range
1/4 Hard
OFHC Copper
01
What is a CF flange and why does it need an OFHC copper gasket?
The physics behind the UHV metal seal
Direct answer: A CF (Conflat) flange uses a stainless steel knife-edge that bites into a soft metal gasket to create a leak-tight UHV seal. OFHC (oxygen-free high conductivity) copper is the standard gasket material because it is very clean, easily formed, has a wide temperature range, and has an extremely low outgassing rate — critical requirements for ultra-high vacuum.
Metal-to-Metal Seal
The stainless steel knife edge permanently cold-flows the copper gasket, producing a seal with no polymer content and no gas permeation path.
Wide Temperature Range
Unlike elastomer gaskets, copper has no melting or hardening limit within UHV service. Systems can be baked to 450°C to accelerate outgassing.
Ultra-Low Outgassing
OFHC copper is chemically cleaned and deburred to minimize surface contamination — the primary source of outgassing in UHV chambers.
Full CF Compatibility
Manufactured to fit every standard CF flange size from CF16 to CF250, matching all common gauge, feedthrough and instrument connections.
02
What CF flange sizes and dimensions does Kaxite supply?
Standard sizes CF16 through CF250 with outer and inner diameter, order number and weight
Direct answer: Kaxite supplies 10 standard OFHC copper gasket sizes — CF16, CF25, CF35, CF50, CF63, CF80, CF100, CF150, CF200 and CF250. Non-standard sizes and dimensions are manufactured on request.
| Type | A — OD (mm) | B — ID (mm) | Order No. | Weight (kg) |
|---|---|---|---|---|
| CF16 | 21.3 | 16.2 | 7355 | 0.01 |
| CF25 | 35 | 25.6 | 7356 | 0.01 |
| CF35 | 48.1 | 36.8 | 7357 | 0.02 |
| CF50 | 61.6 | 52 | 7358 | 0.02 |
| CF63 | 82.4 | 63.6 | 7359 | 0.05 |
| CF80 | 99 | 82 | 7360 | 0.07 |
| CF100 | 120.5 | 102 | 7361 | 0.07 |
| CF150 | 171.3 | 152.5 | 7362 | 0.10 |
| CF200 | 222.1 | 203 | 7363 | 0.14 |
| CF250 | 273.1 | 254 | 7364 | 0.20 |
Standard CF dimensions. Non-standard copper gasket seals are manufactured upon request. Individually packaged for clean handling.
CF16 CF25 CF35 CF50 CF63 CF80 CF100 CF150 CF200 CF250
03
How is a CF flange copper gasket installed correctly?
Five steps to a leak-tight UHV seal
Step 1 — Verify knife-edge condition Inspect both CF flange knife edges for scratches or burrs. Any damage will prevent proper cold-flow of the copper and cause a leak.
Step 2 — Insert a new, individually packaged gasket Place the OFHC copper gasket carefully between the knife edges. Keep the gasket in its original package until the moment of use to avoid surface contamination.
Step 3 — Tighten bolts in a cross pattern Gradually tighten the flange bolts in an alternating cross pattern in at least two passes. The knife edges cut into the copper to produce a metal-to-metal UHV seal.
Step 4 — Bake if UHV cleanliness is required OFHC copper gaskets tolerate bakeout up to 450°C. For systems that require frequent bakeouts, use silver or gold plated copper gaskets to prevent sticking.
Step 5 — Replace after every opening CF copper gaskets are single-use. The knife edge permanently deforms the copper, so always replace with a fresh gasket each time the flange is opened.
04
Which industries use OFHC copper CF gaskets?
Six sectors that rely on metal UHV sealing
Semiconductor
Vacuum chambers, ion implanters, plasma etch systems and thin-film deposition tools that require UHV cleanliness and no polymer outgassing.
Surface Science
XPS, AES, LEED and other surface analysis systems — where copper gaskets tolerate repeated bakeouts at 450°C without degradation.
Accelerator & Synchrotron
Beamline vacuum joints that must resist radiation and maintain UHV over long service intervals.
Analytical Instruments
Mass spectrometers, electron microscopes and other tools built on CF flange systems for UHV sealing.
Thin Film Deposition
Sputtering, evaporation, CVD and PVD chamber flanges where outgassing must be kept to an absolute minimum.
Industrial Vacuum
Freeze dryers, vacuum furnaces and other industrial high-vacuum processes that require metal gasket integrity.
05
Frequently asked questions about OFHC copper CF gaskets
Answers to common procurement and engineering questions
Q1What is an OFHC copper gasket for CF flanges?
An OFHC (oxygen-free high conductivity) copper gasket is a knife-edge metal seal used between two CF (Conflat) flanges to create a leak-tight ultra-high vacuum connection. It is punched from 1/4-hard, high-purity oxygen-free copper stock and chemically cleaned to minimize scratches and burrs.
Q2What vacuum level can OFHC copper CF gaskets achieve?
Knife-edge CF flange gaskets can operate down to 10⁻¹³ torr (10⁻¹¹ Pa) — the ultra-high vacuum range used in semiconductor, surface science and accelerator applications.
Q3What is the maximum bakeout temperature?
CF flanges with OFHC copper gaskets can be heated to 450°C for bakeout — critical for driving off adsorbed water and hydrocarbons in UHV chambers.
Q4What sizes are available?
Kaxite supplies 10 standard sizes — CF16, CF25, CF35, CF50, CF63, CF80, CF100, CF150, CF200 and CF250 — plus non-standard sizes manufactured to customer drawings.
Q5Are CF copper gaskets reusable?
No. CF copper gaskets are single-use. The knife edge permanently deforms the copper, so a new gasket must be used each time the flange is opened to maintain vacuum integrity.
Q6When should I use silver or gold plated copper instead of plain copper?
Silver or gold plated copper gaskets are recommended for systems that require frequent high-temperature bakeouts. The plating prevents copper diffusion and sticking to the flange after repeated thermal cycles.
Q7Can I use a copper gasket on an aluminum CF flange?
No. Aluminum CF flanges must use aluminum gaskets, never copper. Aluminum gaskets may only be used on stainless steel CF flanges if baking is restricted to 200°C.
Q8How are Kaxite OFHC copper gaskets cleaned and packaged?
Every gasket is chemically cleaned and processed through proprietary deburring and polishing procedures designed specifically for vacuum applications. Each gasket is individually packaged for clean handling.
Q9What is the MOQ and lead time?
MOQ depends on size and quantity — small trial orders are possible for standard sizes. Sample lead time is typically 5–7 days. Production lead time for standard and custom orders is typically 15–25 days after order confirmation.
Q10Can Kaxite manufacture non-standard copper gaskets?
Yes. Kaxite manufactures non-standard copper gasket seals upon customer requirement. Provide inner diameter, outer diameter, thickness and knife-edge profile details for a custom quotation.
06
Why choose Kaxite for OFHC copper CF gaskets?
Four reasons engineers worldwide specify Kaxite
10+ Years of Experience Ningbo Kaxite Sealing Materials Co., Ltd. has more than a decade of sealing materials production experience.
Complete CF Range Full range of standard sizes CF16 through CF250 — plus non-standard sizes manufactured to your drawing.
Vacuum-Grade Cleanliness Proprietary deburring and polishing processes designed specifically for vacuum applications.
Individually Packaged Every OFHC copper, silver-plated, and annealed gasket is individually packaged for clean handling.
Request a quote for OFHC Copper Gaskets for CF Flanges
Send us your CF flange size (CF16 to CF250), quantity, and preferred material — plain OFHC copper, silver-plated, gold-plated, aluminum, nickel, or fluorocarbon. Kaxite's technical team will respond within 2 business hours with pricing and lead time. For non-standard sizes, include a drawing with inner and outer diameters, thickness, and knife-edge profile.
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