CF Flange Bellows

Updated: 2026-09-12

Overview

CF Flange Bellows are precision-engineered flexible connectors combining metal bellows with ConFlat (CF) flanges, the gold standard for ultra-high-vacuum (UHV) systems. The CF flange's copper gasket sealing mechanism achieves 10^-10 to 10^-11 mbar·L/s leak rates, while the bellows section accommodates movement and stress. Originally developed for particle physics research, these components now serve critical roles in semiconductor fabrication, space technology, and analytical instrumentation. Manufacturers typically use austenitic stainless steels (304, 316L) for general applications or specialized alloys like Inconel for extreme temperatures. The bellows are hydraulically formed to create uniform convolutions, ensuring consistent flexibility and fatigue resistance. CF flanges are machined to ISO 3669 or similar standards, with common sizes ranging from CF-16 to CF-400 diameters.

Structure and Working Principle

The assembly consists of three key elements: the welded metal bellows core, CF flanges welded at both ends, and often an internal liner or external braid for pressure reinforcement. The bellows geometry (convolution pitch, wall thickness) determines axial/angular movement capacity—typically ±5mm axial and ±3° angular deflection per convolution. During operation, the bellows flex to absorb thermal expansion from cryogenic to 450°C bake-out temperatures, while maintaining vacuum integrity. The CF flange's knife-edge bites into an oxygen-free high-conductivity (OFHC) copper gasket when torqued to 120–150 Nm, creating a permanent deformation seal. Unlike rubber seals, this metal-to-metal contact minimizes outgassing, making it ideal for UHV environments below 10^-9 mbar.

Key Features

Ultra-high vacuum compatibility stands as the defining feature, with helium leak rates <1×10^-10 mbar·L/s. The all-metal construction withstands repeated bake-out cycles up to 250–450°C without degradation. Electropolished interior surfaces (Ra <0.4 μm) reduce surface area for gas adsorption. Dual-purpose designs incorporate both flexibility and conductance—large-diameter models maintain >90% of straight-pipe conductance. Some variants feature integrated alignment pins or rotatable flanges for easier installation. For corrosive environments, manufacturers offer tantalum or gold-plated versions, while magnetic permeability-controlled alloys (e.g., 316L) prevent interference in sensitive applications.

Application Areas

In semiconductor manufacturing, CF Flange Bellows connect chambers in CVD, etching, and ion implantation systems, compensating for thermal shifts during wafer processing. Synchrotrons and fusion reactors use them between beamline components, where sub-micron alignment stability is critical. The aerospace sector employs these bellows in satellite propulsion systems and space environment simulators, leveraging their ability to function across extreme temperature cycles (-270°C to +500°C). Research facilities utilize them in particle detectors and cryogenic systems, often customizing lengths for specific experimental setups.

Maintenance and Precautions

Regular inspections should check for stress fatigue—visible as cracks near weld seams or flattened convolutions. Replace units showing >20% reduction in free length. During installation, use alignment tools to prevent torsional stress, and tighten flange bolts in a star pattern to ensure uniform gasket compression. For systems requiring frequent disassembly, consider silver-plated copper gaskets for reusable performance. Always perform helium leak testing after installation—industry standards typically specify <1×10^-9 mbar·L/s for UHV systems. Store unused bellows in dry nitrogen to prevent moisture-induced corrosion on sealing surfaces.

B2B Procurement Guide

Specify flange size (e.g., CF-40), overall length, and required movements (axial/lateral/angular). For semiconductor tools, request electropolished finishes and certify materials meet SEMI F20 standards. High-radiation environments may require traceable material certificates with impurity levels. Lead times for standard configurations range 2–4 weeks, while custom designs (e.g., offset geometries or special alloys) may take 8–12 weeks. Bulk orders of ≥50 units often qualify for 15–20% discounts. Key suppliers include VAT Valve, Agilent Technologies, and precision vacuum component specialists in Europe/Asia. Always request factory test reports for leak rate and pressure cycling performance.