OFHC Copper CF Tube Assemblies – UHV Connection & Pinch-Off

The OFHC Copper CF Tube Assemblies are designed for reliable connection, filling, evacuation and permanent sealing in high-vacuum (HV) and ultra-high vacuum (UHV) systems.

Manufactured from high-purity OFHC copper (≥99.99%), these assemblies combine excellent thermal conductivity, vacuum compatibility and high ductility.

During the high-temperature vacuum brazing process, the copper tubes become soft annealed, making them particularly suitable for pinch-off sealing applications as well as conventional vacuum connections.

Technical Specifications

Tube Material: OFHC Copper (≥99.99% purity)

Copper Condition: Soft annealed through vacuum brazing

Tube Length: 160 mm (approx. 6.3 inches)

Tube Diameters: 3/8" (9.525 mm OD) or 1/2" (12.7 mm OD)

CF Flange Sizes: DN16CF (1⅓") and DN40CF (2¾")

CF Flange Type: Rotatable

End Configurations: Open tube end or VCR8 1/2" male connection

Brazing Process: High-vacuum brazing at 1050°C ±15°C using BNi-2 nickel-based brazing alloy

Vacuum Compatibility: HV and UHV

Manufacturing: Swiss Made

Soft-Annealed Copper & Pinch-Off Applications

The OFHC copper tubes are exposed to temperatures of approximately 1050°C during the vacuum brazing process. This thermal treatment effectively anneals the copper, resulting in a soft and highly ductile material condition.

Unlike hard-drawn copper tubing, the soft-annealed tubes are easier to deform, making them particularly suitable for applications requiring mechanical compression or permanent pinch-off sealing.

The 3/8" tubes are suitable for manual pinch-off tools, while the 1/2" tubes can be used with appropriate pneumatic pinch-off equipment.

Successful vacuum-tight pinch-off sealing depends on the tool geometry, compression process and operating conditions.

Manufacturing Process

All assemblies are manufactured using a controlled high-vacuum brazing process at 1050°C ±15°C, with BNi-2 nickel-based brazing alloy.

This process provides a reliable metallurgical connection between the copper tube and the adjoining components while simultaneously soft annealing the OFHC copper tubing.

The assemblies are precision manufactured and cleaned for high-vacuum applications.

VCR Connection Options

Selected configurations are available with a VCR8 1/2" male connection, providing a metal-gasket sealing interface for vacuum systems.

The VCR male gland is supplied with its matching male nut, installed during assembly.

Please note: The corresponding female nut and metal gasket are not included and must be ordered separately.

Typical Applications

The OFHC Copper CF Tube Assemblies are suitable for vacuum chamber connections, gas filling and evacuation lines, permanent pinch-off sealing, cryogenic systems, scientific research equipment and other HV/UHV applications requiring clean, reliable copper tubing connections.

Custom Configurations

Standard assemblies are supplied with 160 mm copper tubes in the available CF flange and end-connection configurations.

Custom tube lengths, flange configurations and connection designs are available upon request.

Acknowledgement

Special thanks to Peng Yuan Han (@dso.org.sg) for valuable technical input and collaboration.