What C11000 ETP Copper Is
C11000 is electrolytic tough pitch copper, the most widely used high conductivity copper grade. It is produced by refining copper electrolytically and then melting and casting it under oxidising conditions, so the metal contains a controlled amount of oxygen, normally in the range of about 0.02% to 0.04%, present as cuprous oxide particles in the copper matrix. The oxygen is a deliberate part of the grade: it ties up impurities and it does not harm electrical conductivity in ordinary service. It does mean that C11000 is not an oxygen-free grade, and the oxygen-free coppers used for critical electronic and vacuum duty are C10100 and C10200.
The grade is supplied as pipe, tube, sheet, strip, plate and bar, and it is the default choice for electrical conductors, busbars, terminals, shielding, heat sinks and general fabricated copper parts.
Composition and Physical Properties
| Property | Value for C11000 |
|---|---|
| Copper content | 99.90% min, including silver |
| Oxygen content | About 0.02% to 0.04% |
| Electrical conductivity | 100% IACS min in the annealed condition |
| Electrical resistivity | About 1.71 micro ohm cm at 20 C |
| Thermal conductivity | About 388 W/m.K |
| Density | About 8.89 g/cm³ |
| Melting point | About 1083 C |
| Modulus of elasticity | About 117 GPa |
These values are typical for the annealed grade. Conductivity falls slightly when the metal is cold worked and recovers after annealing, which is why the electrical requirement in the specification applies to the annealed condition.
Tempers and Mechanical Properties
C11000 pipe and tube are supplied in soft annealed and in a range of drawn tempers such as half hard and hard. The annealed temper gives the highest ductility for bending and flaring and is used where the tube will be formed after delivery. Drawn tempers give higher strength for straight runs and for parts that must resist pressure or hold a thread. Mechanical property limits, whether expressed as minimum tensile strength, minimum elongation or a hardness range, are taken from the referenced product standard and confirmed by test on each lot. Because the difference between tempers is a controlled amount of cold work, the order should state the temper designation, not only a hardness value.
Where C11000 Is Used in Electronic Equipment
Busbars, connectors and current carrying links in switchgear, inverters and power supplies.
Electromagnetic interference shielding, gaskets and enclosures, using the high conductivity of the grade to drain induced currents.
Heat sinks, cold plates and thermal spreaders for power electronics.
Waveguides, cavity components and cooling circuits in radio frequency equipment.
High purity gas and cooling water pipework inside equipment rooms.
Terminals, earthing bars and general fabricated copper parts.
Fabrication, Joining and Service Limits
Annealing and stress relieving are carried out at moderate temperature, and the recrystallised structure restores full conductivity after forming.
Bending, flaring and swaging are done in the annealed temper to avoid cracking, and tube ends should be deburred before any joint is made.
Soft soldering, silver brazing and resistance welding are all used for joints. Gas tungsten arc welding of thin wall tube requires care because copper conducts heat away quickly.
The oxygen content of C11000 makes it unsuitable for furnace brazing in a hydrogen or other reducing atmosphere, where steam forms inside the metal and causes cracking. Select oxygen-free C10100 or C10200 for those processes.
Where the pipe carries cooling water, keep the water chemistry under control and avoid contact with chloride bearing insulation materials.
Ordering and Inspection
An order for C11000 pipe should state the product form, outside diameter and wall thickness, temper, length, end finish, standard to be met and the test requirements. Typical inspection covers chemical analysis, tensile test, hardness, dimensional check, conductivity measurement and, for pressure service, a hydrostatic or pneumatic test. Where conductivity is critical, a quick electrical test on each lot is more informative than composition alone, because it detects the effect of tramp elements and of incorrect annealing. Marking and certification should be traceable to the heat number so that the material can be identified after installation.
FAQ
Q: Is C11000 an oxygen-free copper?
No. C11000 is electrolytic tough pitch copper and contains about 0.02% to 0.04% oxygen. The oxygen-free grades are C10100, which is oxygen-free electronic copper, and C10200.
Q: What conductivity does C11000 achieve?
The annealed grade is specified at 100% IACS minimum, which corresponds to a resistivity of about 1.71 micro ohm cm at 20 C.
Q: When should C10100 be used instead of C11000?
Use oxygen-free copper where the part will be brazed or annealed in a reducing atmosphere, or where it goes into vacuum, high frequency and semiconductor equipment.
Q: Can C11000 pipe be welded?
Yes. Soft soldering, silver brazing and fusion welding are used. For hydrogen bearing furnace processes, however, the oxygen content makes C11000 prone to cracking and an oxygen-free grade should be selected.
Q: How is the temper of a delivered pipe confirmed?
By a tension test and a hardness check against the limits of the referenced standard, with conductivity measured to confirm that the annealed condition has been reached.
Q: Which pipe size should I order for a cooling circuit?
Size is chosen from the flow rate, the allowable pressure drop and the working pressure, and the wall thickness is verified against the pressure rating required by the project specification.
