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Pure and Oxygen-Free Copper

Pure copper is at least 99.3 % Cu and is bought for conductivity: electrolytic tough-pitch C11000 carries 100 % IACS electrically and about 390 W/m·K thermally, second only to silver. It is soft (about 70 MPa yield annealed, 300 MPa after heavy cold work) and strengthened only by cold work, so it goes into bus bars, windings, heat sinks, gaskets and vacuum hardware rather than structure. The grades differ mainly in oxygen and phosphorus content, which decides how they behave when brazed, welded or heated in hydrogen.

Popular pure copper grades

Compare in the explorer
GradeYield, MPaTensile, MPaDensity, g/cm³MachinabilityWeldabilityBest for
C11000692218.94PoorFairBus bar, terminals, heat sinks; the default
C10100692358.94PoorVery goodHighest-purity OFE copper for vacuum and RF
C10200692218.94PoorGoodOxygen-free copper for brazed and welded parts
C12200762358.94PoorExcellentDHP tube, spun and torch-brazed parts
C145002753108.94ExcellentPoorMachinable conductors, connector bodies
C182004305008.89FairPoorWelding electrodes, hot or loaded conductors
C180005856908.78FairFairMold inserts and electrodes needing strength

All 101 pure copper grades

Choose pure copper for

Bus bars, terminals and grounding hardware, coil windings, heat sinks and cold plates, vacuum chambers and RF cavities, crush gaskets, deep-drawn and spun shells — any part whose job is moving current or heat rather than carrying load.

Look elsewhere when

The part needs strength (C17200 beryllium copper reaches 1,100 MPa; C18200 keeps 80 % IACS at 400 MPa), it is a small turned part in volume (C14500 or brass C36000), it has to spring (C51000 phosphor bronze), or the conductor can be aluminum for weight (1350 aluminum gives 61 % IACS at a third of the density).

Yield strength against electrical conductivity, Pure & oxygen-free copper among every copper alloy grade

No materials in view have both of these properties.

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Pure copper by application

Electrical conductors
C11000 for bus bar, terminals and windings in air. C10100 or C10200 when the part is hydrogen-brazed, run in vacuum or cooled to cryogenic temperatures, where oxygen-free copper keeps its ductility and conductivity.
Heat sinks and cold plates
C11000 plate and bar, machined or skived; C10200 when channels are vacuum-brazed closed. Copper conducts heat more than twice as well as 6061 aluminum, at three times the weight.
Tube, spun and brazed parts
C12200 DHP for tube, fittings and anything torch-brazed — the phosphorus deoxidizer prevents hydrogen embrittlement. C11000 sheet for deep-drawn shells.
Machined conductors
C14500 tellurium copper for connector bodies and screw-machine electrical parts; C18200 when the part is a resistance-welding electrode or a heat-loaded contact.

Working with pure copper

Machining
Soft and gummy: it smears, welds to the tool and throws long stringy chips. Sharp positive-rake carbide, high speed, generous coolant and half-hard stock help; ±0.05 mm on thin walls needs light finishing passes. C14500 cuts about four times faster with short chips.
Joining
Silver-brazes and soft-solders better than any other metal. TIG welding needs 300–500 °C preheat on thick sections because the heat conducts away; weld C10200 or C12200 rather than C11000, whose oxygen gives porosity and hydrogen embrittlement in the joint.
Forming
Annealed C11000 and C12200 deep-draw, spin and coin as readily as any metal, with about 45 % elongation. Tempers run from O60 soft through H01–H04 quarter- to full-hard; cold work is the only way to raise strength, and a 370–650 °C anneal removes it again.
Finishing
Tin, silver or nickel plate for contacts and solderability; bright dip or benzotriazole passivation slows tarnish; clear lacquer for decorative work. Copper is not anodized. Oxygen-free grades bake out cleanly for ultra-high vacuum.

Other copper alloy series

Pure and Oxygen-Free Copper — frequently asked

What is pure copper?

Pure copper is at least 99.3 % Cu and is bought for conductivity: electrolytic tough-pitch C11000 carries 100 % IACS electrically and about 390 W/m·K thermally, second only to silver. It is soft (about 70 MPa yield annealed, 300 MPa after heavy cold work) and strengthened only by cold work, so it goes into bus bars, windings, heat sinks, gaskets and vacuum hardware rather than structure. The grades differ mainly in oxygen and phosphorus content, which decides how they behave when brazed, welded or heated in hydrogen.

Which grade of pure copper should I use?

C11000 for bus bar, terminals, heat sinks and anything electrical that is not brazed in a reducing atmosphere. C10100 or C10200 oxygen-free copper for vacuum, cryogenic and RF parts and whenever the copper will be hydrogen-brazed or welded — the 200–400 ppm oxygen in C11000 turns to steam and embrittles it. C12200 (DHP) for tube, spun and torch-brazed plumbing parts; it gives up conductivity (85 % IACS) for immunity to hydrogen embrittlement. C14500 tellurium copper when a conductor has to be machined in volume: 93 % IACS with four times the machinability of C11000. C18200 chromium copper and C18000 when the conductor also needs strength or runs hot — 80 % and 45 % IACS with 400–550 MPa yield after aging.

Which grade of pure copper is the strongest?

QBe1.9 has the highest yield strength in the series at 1,070 MPa; TBe1.9 follows at 1,030 MPa. Values are for each grade's default condition.

Which grade of pure copper is easiest to machine?

ZCuPb20Sn5 (machinability excellent, 92/100), then C14510 (88/100).

Is pure copper heat-treatable?

No. These grades are strengthened by cold work and softened by annealing, not by heat treatment; the conditions are listed on each grade page.

C110 or C101 / C102 — do I need oxygen-free copper?

Only if the part will be brazed or welded in hydrogen, used in vacuum, or run cryogenic. C11000 contains 200–400 ppm oxygen as Cu₂O; above about 370 °C hydrogen diffuses in, forms steam at the oxide and cracks the metal. C10200 (10 ppm oxygen) avoids that at the same conductivity, and C10100 adds a 99.99 % purity guarantee for RF cavities and semiconductor hardware. For air-side bus bar and heat sinks, C11000 is the cheaper and equal choice.

How strong can pure copper get?

Annealed C11000 yields at about 70 MPa; full-hard H04 strip reaches 300–350 MPa yield with little ductility left, and it softens again above about 200 °C. If the part needs more, move to a precipitation-hardened high-copper alloy: C18200 gives about 400 MPa at 80 % IACS, C17510 about 700 MPa at 50 % IACS, and C17200 up to 1,100 MPa at 22 % IACS.