What Is C10100 Oxygen-Free Copper?
C10100 is the highest-purity wrought copper in common industrial use - the oxygen-free electronic (OFE) grade, also written Cu-OFE and known internationally as oxygen-free high-conductivity copper (OFHC). It is produced by melting and refining electrolytic copper in a controlled atmosphere so that the oxygen that would normally remain in tough-pitch copper is chemically removed. The result is a metal with a copper content of 99.99 % or more and an oxygen content of 0.001 % or less.
Removing the oxygen changes the behaviour of the material in three important ways. First, electrical and thermal conductivity reach the practical maximum for copper. Second, the material can be annealed in a reducing atmosphere without the hydrogen embrittlement that affects oxygen-bearing grades. Third, it can be bent, formed and welded without the internal voids that form when dissolved oxygen reacts with hydrogen at high temperature. For medical devices, where a component may be formed to a tight radius, sterilised and then expected to remain leak-tight for years, those three properties are the reason the grade is specified.
Composition and Purity
| Element | Requirement |
|---|---|
| Copper (Cu) | 99.99 % minimum |
| Oxygen (O) | 0.001 % maximum |
| Individual impurities (Pb, Bi, Fe, Zn, Ag and others) | Each held to a few parts per million |
| Total of named impurities | Very low; the sum is what separates C10100 from C10200 |
The distinction from C10200 matters for buyers: C10200 is also an oxygen-free grade, but its copper minimum is 99.95 % and its impurity allowance is looser. C10100 is reserved for situations where conductivity, vacuum behaviour or non-magnetic purity is critical.
Physical and Mechanical Properties
The properties below are typical of commercially available C10100 in the annealed and cold-worked conditions used for formed components.
| Property | Typical value |
|---|---|
| Tensile strength | 222 – 385 N/mm² depending on temper |
| Proof strength (0.1 % offset) | 60 – 325 N/mm² |
| Elongation | From about 60 % annealed down to about 4 % in the hardest temper |
| Hardness | 45 – 115 HV |
| Electrical conductivity | 102 % IACS average with a guaranteed minimum of 101 % IACS |
| Thermal conductivity | 386 – 394 W/m·K at 20 °C |
| Crystal structure | Face-centred cubic; non-magnetic |
The wide spread of the mechanical values is not scatter but temper: a soft annealed strip will sit near the top of the elongation range and the bottom of the strength range, and a hard-rolled foil at the opposite end. Purchase orders should therefore state the temper as well as the alloy, otherwise the material cannot be specified reproducibly.
Forms Supplied
C10100 is available in a range of mill forms so that a medical device design can be built from one consistent alloy:
Seamless copper pipe and tube, capillary sizes upwards.
Solid round rod and bar, machined into electrodes and connectors.
Soft sheet and strip for stamped and deep-drawn parts.
Thin foil for shielding and for flexible conductors.
Stranded and braided flexible cable.
Where a component is formed and then welded or brazed, all of the constituent parts should be the same grade, because mixing an oxygen-bearing copper into the assembly reintroduces the porosity risk that the oxygen-free grade was chosen to avoid.
Bending, Forming and Heat Treatment
C10100 is supplied bendable precisely because it is soft and free of the oxide inclusions that initiate cracking in a bend. Practical guidance for forming medical components:
Start from the fully annealed temper for any bend tighter than a few times the material thickness. Bending cold-worked stock to a tight radius produces outer-fibre cracking.
Support the bore during tube bending with a mandrel, and use a bend radius suited to the wall thickness; wall thinning on the extrados should stay within the drawing tolerance.
Annealing is carried out in a protective or reducing atmosphere. Because the oxygen content is negligible, the material tolerates a hydrogen-bearing atmosphere without becoming embrittled.
Where a part has been severely cold worked - for example after deep drawing or repeated bending - a stress relief treatment restores ductility and dimensional stability before the part reaches final inspection.
Machining is straightforward; the material is gummy rather than hard, so sharp tooling, generous rake angles and effective coolant keep the surface finish acceptable.
Applications in Medical and Related Equipment
The combination of very high conductivity, low oxygen and reliable ductility places C10100 in a number of critical applications:
Anodes and electrode components in diagnostic and therapeutic equipment.
Busbars and bus conductors inside power supply modules and imaging systems.
Coaxial cable, hollow conductors and waveguides.
Glass-to-metal seals, vacuum seals, klystrons and other vacuum electronic devices.
Lead-in wires, rectifier parts and transistor components.
Medical gas and instrument tubing where a clean, low-contamination bore is required.
The non-magnetic nature of the alloy is as important as its conductivity in imaging equipment, because a magnetic component would distort the field and disturb the image.
Inspection and Handling Notes
Purchasers normally require a chemical analysis certificate confirming the copper and oxygen limits, a conductivity test, and mechanical testing of the temper that was ordered. Additional points worth specifying are a cleanliness requirement for tube bores, freedom from surface oxide and scale, and packaging that protects bright surfaces from tarnish in transit. Oxygen-free copper is readily contaminated by handling; gloves and clean wrapping preserve the surface condition that gives glass-to-metal seals their gas-tightness.
FAQ
Q: What does OFE mean for C10100?
OFE stands for oxygen-free electronic, the highest-purity oxygen-free copper grade, specified to 99.99 % copper minimum with oxygen at or below 0.001 %. It is used where electrical conductivity, vacuum performance or non-magnetic behaviour is critical.
Q: Why is C10100 described as bendable copper?
Because its very low oxygen content leaves no oxide inclusions to initiate cracking, the fully annealed material can be bent and formed to tight radii without the surface ruptures and internal voids that occur in oxygen-bearing copper.
Q: What is the electrical conductivity of C10100?
Its conductivity averages about 102 % IACS with a guaranteed value of 101 % IACS, the highest of the commercially available wrought coppers.
Q: Can C10100 be annealed in hydrogen?
Yes. The absence of oxygen prevents the steam-pocket formation that causes hydrogen embrittlement, so a reducing hydrogen atmosphere can be used safely to clean and anneal the material.
Q: Is C10100 magnetic?
No, it is non-magnetic, which is why it is preferred for components in magnetic resonance imaging and other field-sensitive equipment.
Q: How does C10100 differ from C10200?
C10200 is the general-purpose oxygen-free grade with 99.95 % copper minimum and slightly looser impurity limits; C10100 is the electronic grade with 99.99 % copper minimum and tighter control, giving marginally higher conductivity and cleaner vacuum performance.
Summary
C10100 oxygen-free bendable copper is chosen where the three properties of maximum conductivity, clean vacuum behaviour and reliable formability must all be present at once. Specify the temper, confirm the oxygen and impurity limits on the mill certificate, and protect the surface during handling; the grade will then deliver the consistent electrical and forming performance that medical and vacuum equipment designs depend on.
