Definition of C11000 Electrolytic ETP Copper
C11000, widely known as electrolytic tough pitch copper, is an unalloyed high-conductivity copper produced by electrolytic refining and then melted under a controlled oxygen balance. The small oxygen content that remains - typically 0.02 % to 0.04 % and never more than 0.06 % - is not a defect. It acts as a scavenger during melting by oxidising harmful impurities, and it leaves the metal with a guaranteed minimum conductivity of 100 % IACS in the annealed condition.
The grade is specified in ASTM B152 for plate, sheet and strip, ASTM B187 for rod, bar and busbar, ASTM B75 for seamless pipe, and EN 13601 for copper rod and bar intended for electrical purposes. Because the material is available as wire, bar, strip, tube and busbar from the same heat chemistry, a single design can use C11000 throughout the current path.
Chemical Composition
| Element | Limit |
|---|---|
| Cu + Ag, % min | 99.90 |
| Oxygen, % max | 0.06 |
| Tin, % max | 0.002 |
| Zinc, % max | 0.005 |
| Lead, % max | 0.005 |
| Iron, % max | 0.005 |
| Other specified elements, % max | 0.10 total |
Chemistry is the first control point for conductivity. Elements in solid solution, particularly phosphorus and iron, scatter electrons and depress conductivity far more efficiently than the same mass of oxygen, which is why the residual element limits are so tight.
Electrical, Physical and Mechanical Properties
| Property | Typical value |
|---|---|
| Electrical conductivity, annealed | 100 % IACS min, about 101 % IACS typical |
| Volume resistivity at 20 °C | about 1.72 µΩ·cm |
| Temperature coefficient of resistance | about 0.0039 per °C at 20 °C |
| Thermal conductivity | about 390 W/m·K |
| Density | 8.89 to 8.94 g/cm³ |
| Melting point | 1083 °C |
| Modulus of elasticity | 110 to 130 GPa |
| Soft (O60) tensile strength | about 220 MPa min |
| Half-hard (H02) tensile strength | about 260 to 300 MPa |
| Soft (O60) elongation | about 45 % |
| Soft (O60) hardness | about 40 to 50 HB |
Tempers follow the standard H designations: O60 for fully soft and highly formable material, H02 half-hard and H04 hard for busbar that needs stiffness as well as conductivity. Cold reduction raises tensile strength significantly while reducing conductivity only marginally, because the effect of strain on resistivity is small in a metal this pure.
Applications in Electrical and Power Systems
Busbar and busbar joints: rectangular and round bar to ASTM B187, used in switchgear, panelboards, battery racks and energy storage cabinets.
Conductors and windings: solid and stranded wire, magnet wire stock and transformer winding strip where a minimum 100 % IACS is required.
Contacts and current-carrying hardware: contact strips, connector bodies, terminals, earthing bars and fuse parts.
Power equipment: generator and motor components, welding shunts, induction furnace coils and traction current collectors.
New energy installations: electric vehicle charging connectors, high-current interconnects, inverter and converter busbars, and photovoltaic string hardware.
Thermal conductors: heat spreading plates, heat sink bases and water-cooled conductor assemblies in power electronics.
In each case the design driver is the same: keep voltage drop and I2R loss low while maintaining sufficient cross-section and stiffness for the mechanical duty.
Fabrication, Welding and Quality Control
Bending, punching and forming are carried out in the annealed temper and the part is then used in the cold-worked temper where stiffness is needed. Machining requires sharp tooling, positive rake angles and a generous cutting speed, because copper is soft, ductile and an excellent conductor of heat away from the cutting edge.
Soldering and brazing give sound joints on C11000. Resistance welding, including projection and seam welding, is widely used for strip. Where fusion welding is required, a deoxidised copper filler and a shielding gas free of hydrogen must be used, and the joint area should not be held above roughly 370 °C in a reducing atmosphere, because cuprous oxide can react with hydrogen to form steam and cause internal cracking.
Inspection for electrical duty normally combines chemical analysis of the heat, dimensional measurement, tensile or hardness tests for temper, and a resistivity measurement on a representative specimen, since resistivity is the property that the application depends on most directly.
FAQ
Q: What is the guaranteed conductivity of C11000 copper?
Annealed C11000 is specified at 100 % IACS minimum, with commercial material typically measuring about 101 % IACS. Harder tempers retain essentially the same conductivity.
Q: Why does C11000 copper contain oxygen?
The oxygen is left in deliberately as cuprous oxide, which scavenges impurities during melting and is harmless in service. It is why the grade must not be heated in hydrogen-rich atmospheres.
Q: Is C11000 suitable for busbar?
Yes. Bar, strip and channel to ASTM B187 in tempers up to hard are standard busbar material, offering high conductivity with enough stiffness to resist short-circuit forces.
Q: How is the correct temper selected?
Form the part in the soft temper and use it in the half-hard or hard temper. Start from the forming requirement, then verify that the resulting tensile strength and hardness meet the design load.
Q: Can C11000 be welded or only brazed?
Brazing, soldering and resistance welding are routine. Fusion welding needs a deoxidised filler and hydrogen-free shielding, and joint efficiency is lower than that of the annealed base metal.
Q: Which grades are close alternatives?
C10100 and C10200 offer oxygen-free behaviour with 101 % IACS, and C12200 gives freedom from hydrogen embrittlement at about 85 % IACS with lower cost.
