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MetalKeen CNC machines custom L-shape copper seals and UHV gaskets from high-purity OFHC C10100 and C11000 copper. Our precision-machined L-section copper gaskets provide reliable metal-to-metal sealing for ConFlat CF, ISO-K, and custom vacuum flanges in semiconductor, research, and aerospace vacuum systems. Every seal is annealed, precision-dimensioned, and cleanroom-packaged for immediate installation.
An L-shape copper seal (also called an L-section copper gasket, L-profile vacuum seal, or angular copper gasket) is a precision-machined soft metal seal with an L-shaped cross-section. Unlike standard flat copper gaskets, the L-shape provides:
Enhanced mechanical compliance — The vertical leg of the "L" acts as a spring-like element, maintaining seal force under thermal cycling
Improved centering — The profile self-aligns within the flange groove, preventing radial displacement during assembly
Higher sealing load concentration — The sharp edge or controlled contact line generates localized plastic deformation for leak-tight metal-to-metal sealing
Reusability — Annealed OFHC copper allows multiple re-torque cycles before replacement
L-shape copper seals are the preferred sealing solution for ultra-high vacuum (UHV) and high-temperature applications where elastomer O-rings cannot survive.
Table
Material | UNS / Grade | Purity | Key Properties | Best For |
|---|---|---|---|---|
OFHC Copper | C10100 | ≥ 99.99% Cu | Highest purity; lowest outgassing; excellent ductility | UHV semiconductor chambers; particle accelerators |
ETP Copper | C11000 | ≥ 99.90% Cu | High conductivity; cost-effective; good machinability | General HV vacuum systems; research instruments |
Oxygen-Free Copper | C10200 | ≥ 99.95% Cu | Balance of purity and cost; good for moderate UHV | Industrial vacuum coating; analytical instruments |
Tellurium Copper | C14500 | ≥ 99.5% Cu + Te | Enhanced machinability; reduced tool wear | Complex profiles; high-volume production |
Why OFHC C10100 for UHV Seals?
Extremely low oxygen content (< 5 ppm) prevents hydrogen embrittlement and virtual leaks
Minimal outgassing — No volatile oxides or impurities in vacuum
Superior ductility when annealed — Conforms to flange surface imperfections as low as Ra 0.2 μm
Non-magnetic — Critical for electron microscopy and ion beam systems
Table
Profile | Cross-Section | Sealing Mechanism | Reusability | Best Application |
|---|---|---|---|---|
L-Shape | Angular L-section | Line contact + elastic compliance | 3–5 cycles | UHV flanges; thermal cycling; alignment-critical joints |
Flat Gasket | Rectangular | Full-face compression | 1–2 cycles | Low-cost HV seals; static ambient joints |
O-Ring Gasket | Circular / Round wire | Hertzian point contact | 1 cycle (single use) | Standard ConFlat CF seals; lowest cost UHV |
Octagonal / Oval | Faceted polygon | Multi-line contact | 2–3 cycles | High-pressure vacuum; alternative to flat gaskets |
Custom Profile | Client-specific | Application-defined | Varies | Proprietary chamber interfaces; legacy tool support |
When to Choose L-Shape:
Flange design includes a groove or step that matches the L-profile
System experiences frequent bakeout cycles (150–250°C) requiring elastic recovery
Radial alignment is critical to protect internal components (electrodes, insulators)
Reusability is desired to reduce maintenance downtime and seal inventory
Table
Specification | Details | |
|---|---|---|
Outer Diameter (OD) | 10 mm – 600 mm (custom larger on request) | |
Inner Diameter (ID) | 5 mm – 550 mm | |
L-Section Height | 1.5 mm – 15 mm | |
L-Section Thickness | 0.5 mm – 5 mm | |
Cross-Section Tolerance | ±0.02 mm (standard); ±0.01 mm (precision UHV) | |
OD/ID Concentricity | ≤ 0.03 mm TIR | |
Surface Roughness — Sealing face | Ra ≤ 0.4 μm (standard); Ra ≤ 0.2 μm (premium UHV) | |
Edge Condition | Burr-free; chamfered or radiused per drawing | |
Annealing — Post-machining | Hydrogen atmosphere or vacuum anneal at 350–450°C | Restores full ductility; relieves machining stress |
Table
Step | Process | Quality Control |
|---|---|---|
Material Verification — PMI + MTR | Confirm copper grade and purity | Certificate of compliance |
Blank Preparation — Sawing or stamping | Cut ring blanks from copper plate or bar | Dimensional check; material traceability |
CNC Turning — OD, ID, and cross-section profile | Precision lathe with live tooling | CMM verification of L-profile dimensions |
CNC Milling — Grooves, notches, or venting slots (if required) | 4-axis machining center | Dimensional inspection |
Deburring — Manual and vibratory | Remove all sharp edges and machining burrs | Visual inspection under magnification |
Cleaning — Degreasing and ultrasonic wash | Remove cutting fluids and particles | Residue testing |
Annealing — Hydrogen or vacuum furnace | Soft anneal to full ductility | Hardness test (HV < 60 confirms anneal) |
Final Cleaning — DI water rinse; cleanroom dry | Particle-free surface | Particle count verification |
Packaging — Nitrogen-purged; cleanroom bag | Prevent oxidation and contamination | Sealed with desiccant |
Table
Test | Method | Standard | Purpose |
|---|---|---|---|
Dimensional Inspection — CMM | 3D coordinate measurement | ISO 9013 | Verify OD, ID, L-profile height, and concentricity |
Surface Roughness — Profilometer | Contact stylus measurement | ISO 4287 | Confirm sealing face Ra ≤ 0.4 μm |
Hardness Test — Vickers microhardness | HV 0.1 or HV 0.05 | ASTM E384 | Verify proper annealing (HV 50–70 for annealed OFHC) |
Visual Inspection — Magnification | 10×–30× stereo microscope | Customer spec | Detect cracks, scratches, or inclusion defects |
Cleanliness Verification — Residue analysis | Solvent extraction and weighing | SEMI / Customer spec | Confirm absence of oils and particulates |
Leak Test — Optional on assembled flange | Helium mass spectrometer | ASTM E498 | Validate seal performance in actual joint |
Our CNC-machined L-shape copper seals are used in critical vacuum and pressure systems:
Table
Industry / System | Application | Typical Size |
|---|---|---|
Semiconductor Manufacturing — CVD, PVD, etch chamber flanges | Process chamber viewport, gas inlet, pump port seals | CF 35, CF 63, CF 100, CF 150 |
Scientific Research — UHV surface science, MBE, STM | Analysis chamber seals; cryostat interfaces | CF 16, CF 40, CF 63 |
Particle Accelerators — Beam lines, RF cavities, vacuum sectors | Large-diameter sector gaskets; custom profiles | ISO 200 – ISO 630; custom 500+ mm |
Electron Microscopy — SEM, TEM, FIB column seals | Column joint seals; specimen chamber gaskets | CF 35, CF 63; miniature custom sizes |
Aerospace & Defense — Space simulation chambers; propulsion test | Large thermal-vacuum chamber door seals | Custom OD 300–800 mm |
Medical & Pharmaceutical — Electron beam sterilization; vacuum dryers | Chamber door seals; process port gaskets | ISO 80 – ISO 160 |
Thin Film Coating — Optical coating; roll-to-roll vacuum web | Deposition chamber seals; winding chamber gaskets | ISO 100 – ISO 320 |
Table
Flange Standard | Seal Interface | L-Seal Application |
|---|---|---|
ConFlat (CF) Flange — ISO 3669 | Knife-edge to flat copper gasket (typically round wire) | L-shape variant for grooved CF adapters; custom legacy tools |
ISO-K / ISO-F Flange — ISO 1609 | O-ring groove with centering ring | L-shape copper seal replaces elastomer for high-temp/bakeable joints |
ASA / ANSI Flange — Bolted flat face | Flat gasket or O-ring | L-shape seal for upgraded bakeable conversion |
Custom / Proprietary Flange — OEM-specific | Grooved or stepped recess | L-shape matched to groove geometry for self-centering |
KF (NW) Flange — ISO 2861 | Elastomer centering ring | Miniature L-shape copper seals for high-vacuum mini-conflat adapters |
Table
Parameter | Recommendation |
|---|---|
Flange Surface Finish | Ra ≤ 0.4 μm; no scratches deeper than 0.05 mm |
Bolt Torque | Gradual star-pattern tightening to manufacturer spec (typically 10–15 N·m for CF 63) |
Bakeout Temperature | ≤ 250°C for standard annealed copper; ≤ 450°C for high-temp annealed |
Reusability | 3–5 re-torque cycles typical for L-shape profile; inspect for cracks or permanent deformation |
Replacement Indicator | Visible circumferential crack; thickness reduction > 10%; permanent set > 0.1 mm |
Storage | Cleanroom bag; nitrogen atmosphere; room temperature; avoid sulfurous environments |
✅ High-Purity OFHC Copper — C10100 and C11000 with full material certification
✅ Precision CNC Machining — L-profile tolerances to ±0.01 mm; concentricity ≤ 0.03 mm
✅ Post-Machining Annealing — Hydrogen or vacuum annealed for maximum ductility
✅ Cleanroom Processing — Particle-free cleaning and nitrogen-purged packaging
✅ Custom Profiles — Any OD/ID, L-height, groove geometry, or vent slot configuration
✅ Vacuum-Ready Delivery — No additional cleaning required before installation
✅ Small to Large Diameter — From CF 16 miniature seals to 600+ mm custom accelerator gaskets
Q1: What is an L-shape copper seal, and how does it differ from a standard flat copper gasket? An L-shape copper seal has an angular L-shaped cross-section rather than a simple rectangular or round profile. The vertical leg of the L provides elastic compliance that helps maintain sealing force during thermal expansion and contraction, while the horizontal leg provides the primary sealing surface. Compared to flat gaskets, L-shape seals offer better self-centering in grooved flanges, improved resistance to thermal cycling, and higher reusability (3–5 cycles vs. 1–2 for flat gaskets).
Q2: Why is OFHC (C10100) copper recommended for UHV seals instead of regular copper? OFHC (Oxygen-Free High Conductivity) C10100 copper contains ≥ 99.99% copper with oxygen content below 5 ppm. This matters for UHV because: (1) low oxygen prevents hydrogen embrittlement and virtual leaks during bakeout; (2) extreme purity means minimal outgassing from volatile impurities; (3) superior ductility when annealed allows the seal to conform to microscopic surface imperfections on the flange knife-edge. Standard ETP copper (C11000) is acceptable for high vacuum but not recommended for UHV below 10⁻⁸ Torr.
Q3: Can L-shape copper seals be reused, and how many times? Yes. Properly annealed L-shape copper seals can typically be reused 3–5 times before replacement, provided the seal shows no visible circumferential cracks, permanent deformation exceeding 0.1 mm, or thickness reduction greater than 10%. The L-profile's elastic leg recovers better than flat gaskets after torque release. Always inspect the seal under magnification and re-anneal if the hardness exceeds HV 80 before reuse.
Q4: What flange types are compatible with L-shape copper seals? L-shape copper seals are designed for flanges with a matching groove or step that accommodates the vertical leg of the L. They are commonly used with custom OEM chamber flanges, modified ISO-K/ISO-F flanges (replacing elastomer O-rings for bakeable applications), and legacy ConFlat adapters with grooved sealing surfaces. We machine seals to match your specific flange groove geometry from your drawing or sample.
Q5: What surface finish is required on the sealing face of the copper seal? MetalKeen machines L-shape copper seals to Ra ≤ 0.4 μm on the sealing face as standard, with Ra ≤ 0.2 μm available for critical UHV applications. While the seal itself must be smooth, the mating flange surface should also be Ra ≤ 0.4 μm with no radial scratches deeper than 0.05 mm. The combination of smooth seal and flange ensures intimate metal-to-metal contact without leak paths.
Q6: Do you provide post-machining annealing for copper seals? Yes. All our OFHC copper seals undergo hydrogen atmosphere annealing or vacuum annealing at 350–450°C after CNC machining. This is critical because machining work-hardens the copper, reducing ductility. Annealing restores the soft, ductile condition (HV 50–70) required for the seal to plastically deform and fill flange surface irregularities during torquing. We verify annealing effectiveness with Vickers hardness testing.
Q7: What is the typical lead time for custom L-shape copper seals? Standard lead time for prototype quantities (1–10 pieces) is 2–3 weeks. Volume production (100–1000+ pieces) typically requires 4–6 weeks depending on size and profile complexity. Large-diameter custom seals (>300 mm OD) may require 5–7 weeks due to raw material sourcing and extended machining time. Expedited delivery is available for chamber maintenance shutdowns.
