C110 Copper (ETP)
Also: C11000, CDA 110, UNS C11000, ETP copper, electrolytic tough pitch copper, Cu-ETP, CW004A, 2.0060, E-Cu, bus bar copper, pure copper, C101 / C102 (oxygen-free alternatives)
C110 is electrolytic tough pitch copper, 99.9% pure: the standard for bus bar, conductors and heat sinks at 100% IACS. Soft, formable, hard to machine. Values H02.
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At a glance
| Density | 8.94 g/cm³ (0.323 lb/in³) |
|---|---|
| Tensile strength | 290 MPa (42 ksi) typical H02; annealed about 220 MPa (32 ksi); hard (H04) about 345 MPa (50 ksi) |
| Yield strength | 250 MPa (36 ksi) typical H02 at 0.5% extension; annealed about 70 MPa (10 ksi); hard (H04) about 310 MPa (45 ksi) |
| Hardness | About 40 HRB typical H02; annealed about 40 HRF; hard (H04) about 50 HRB |
| Elongation | 14% typical H02; annealed 45-50%; hard (H04) about 6% |
| Modulus of elasticity | 117 GPa (17 Msi) |
| Thermal | Melts at 1065-1083 °C (1950-1980 °F); thermal conductivity ~390 W/m·K; electrical conductivity 100-101% IACS (100% minimum for ETP); expansion ~17 um/m·K |
| Composition | 99.90% min Cu (silver counted as copper), about 0.02-0.04% O |
Typical values, H02 (half-hard) flat products, 1 mm (0.040") thick; annealed (OS050) and hard figures as noted. Confirm against the mill certificate and the purchase spec.
- MachinabilityPoor
- About 20% of C360: gummy, with long stringy chips, built-up edge and heavy burrs. Very sharp, highly positive tooling, high speed, low feed and a good lubricant help; for machined conductors specify C145 tellurium copper (85% machinability, 93% IACS) instead.
- WeldabilityFair
- Solders and silver-brazes superbly. TIG welds with deoxidized ERCu filler and a 200-500 °C (400-950 °F) preheat because the conductivity pulls heat away; the oxygen causes porosity and, in hydrogen-bearing atmospheres, embrittlement. Use C101 / C102 oxygen-free copper for furnace-brazed or heavily welded parts.
- FormabilityExcellent
- Annealed copper bends flat on itself, spins, coins and draws deep; bus bar bends edgewise on a bar bender in half-hard temper at 1-2t. Work hardens quickly, so anneal between severe operations.
- Corrosion resistanceExcellent
- Resists atmosphere (green patina), fresh and sea water, most soils, non-oxidizing acids and alkalis. Attacked by ammonia, amines, oxidizing acids and sulfur compounds; tarnishes readily. Copper is noble, so aluminum, zinc or steel bolted to it corrode galvanically when wet.
C110 is the commercial pure copper: 99.90% minimum, with about 0.04% oxygen left in from refining (hence "tough pitch"). It is the conductivity standard, 100-101% IACS electrical and about 390 W/m·K thermal, so it is what bus bar, switchgear, transformer windings, grounding, welding cable lugs, heat sinks, cold plates, waveguides and RF parts are made from. It is stocked as bus bar, sheet, plate, rod, tube and wire in soft and cold-worked tempers.
It is soft and ductile: half-hard bar gives about 290 MPa (42 ksi) tensile and full hard about 345 MPa (50 ksi), with annealed stock down near 220 MPa (32 ksi). It forms, bends, spins, coins and draws easily, solders and silver-brazes very well, and plates with tin, silver or nickel directly. Strength is low and it creeps under sustained load at modest temperatures, so bolted bus joints use Belleville washers and clamped joints get a hard backing.
Two things to know before machining or heating it. It machines poorly (about 20% of C360): gummy, long stringy chips, built-up edge, burrs; the free-machining coppers C145 (tellurium) and C147 (sulfur) give 85% machinability at 90-95% IACS and are the usual substitutes for machined electrical parts. And the oxygen makes it hydrogen-embrittle when heated above about 400 °C (750 °F) in a reducing atmosphere (a hydrogen brazing furnace, a reducing torch flame), which cracks it; use oxygen-free C101 / C102 for parts that are furnace brazed, welded heavily or used in vacuum.
Heat treatment
Not hardenable; strength comes from cold work only. Anneal at 375-650 °C (700-1200 °F) in air or a neutral atmosphere, then air cool or water quench; keep hydrogen out of the furnace above about 400 °C (750 °F) or the oxygen in ETP copper reacts with it and the metal cracks along the grain boundaries. Stress relieve at 200-250 °C (400-480 °F). Hard tempers begin to soften above about 200 °C (400 °F) in service, which limits hot bus bar and heat-sink strength.
Tempers and conditions
- O60 / OS (soft annealed, by grain size)
- H01 (quarter hard)
- H02 (half hard)
- H04 (hard)
- M20 (hot rolled)
- H80 (hard drawn bus bar)
Stock forms
- Bus bar (flat and rectangular, rounded edge)
- Sheet, strip and plate
- Round and square rod
- Tube and bus pipe
- Wire and flexible braid
- Foil
Relative cost
Tier 3 of 5. Tracks the COMEX copper price: roughly 3-4x mild steel per pound and about the same as brass. Bus bar and sheet are commodity items from electrical distributors; oxygen-free C101 costs 10-20% more.
Typical applications
- Bus bar, switchgear and battery interconnects
- Transformer and motor windings and strap
- Grounding, lightning protection and earthing bars
- Heat sinks, cold plates and vapor chambers
- Waveguides, RF cavities and shielding
- Roofing, flashing and architectural cladding
- Cookware bottoms and heat spreaders
- Electrical terminals, lugs and contacts
Process compatibility
How C110 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | PoorPoor | Gummy and burr-prone; very sharp polished tooling and low feeds. Specify C145 tellurium copper for machined conductors when conductivity allows. |
| Waterjet Cutting | ExcellentExcellent | The usual way to profile bus bar and plate: no heat, no reflectivity problem, clean edges on any thickness. |
| Laser Cutting | FairFair | Highly reflective at fiber-laser wavelengths; modern fiber and green lasers cut sheet to about 6 mm (1/4") with nitrogen, with some edge dross. Waterjet or punch for thicker. |
| Press Brake Forming | ExcellentExcellent | Bus bar bends flatwise at 1t and edgewise on a bar bender; annealed sheet bends to 0t. Keep the bend radius up on hard temper. |
| Metal Stamping | ExcellentExcellent | Terminals, lugs and contacts stamp cleanly from strip; specify the temper for the spring or crimp behaviour needed. |
| Deep Drawing | ExcellentExcellent | Annealed copper draws deep cups and shells for cookware, cans and heat-sink bases; anneal between stages. |
| Welding | FairFair | TIG with ERCu filler and heavy preheat on thick sections; porosity from the oxygen. Solder, silver braze or use C101 / C102 for welded assemblies. Can copper be welded? |
| Laser Welding | FairFair | Reflective at 1 um; green and blue lasers now weld copper tabs and bus bars in battery assembly. Job-shop IR laser welding is unreliable on ETP. |
| Plating | ExcellentExcellent | Tin for solderability and bus joints, silver for high-current contacts, nickel for wear and a barrier; copper is the standard plating base and needs no strike. |
| Electroless Nickel Plating | GoodGood | Uniform hard barrier on heat sinks and RF parts; a palladium or nickel-strike activation gets it started on copper. |
| Annealing | ExcellentExcellent | Restores full ductility between draws and after cold work; keep the furnace atmosphere free of hydrogen above 400 °C (750 °F). |
| Metal 3D Printing | FairFair | Pure copper prints on green-laser and electron-beam machines and as CuCrZr on standard machines for heat exchangers; not ETP chemistry, and rare in job shops. |
| Heat Treating | Not recommendedNot recommended | No hardening treatment exists; only annealing and stress relief. For a strong conductive alloy use C172 beryllium copper or C18150 chromium zirconium copper. |
Design and sourcing tips
- Specify "C11000 per ASTM B187 (bus bar) or B152 (sheet)" with the temper (H02, H04, O60); conductivity is guaranteed at 100% IACS minimum by those specs.
- For machined conductors, change the alloy: C145 tellurium copper machines four times faster at 93% IACS; keep C110 for bent, stamped and drawn parts.
- Use oxygen-free C101 or C102 for anything furnace brazed in hydrogen, heavily welded, or used in vacuum; ETP copper embrittles and outgasses there.
- Bolted bus joints creep: specify Belleville washers, silver or tin plating at the joint, and a torque value; do not rely on a plain nut on copper.
- Isolate copper from aluminum and zinc-plated steel in wet locations, or bimetallic corrosion will eat the other metal.
- For heat sinks that only need 60-70% of the conductivity, 6061 or 6063 aluminum weighs a third as much and machines far better.
Frequently asked questions
- Is C110 copper pure copper?
- Yes, 99.90% minimum, with about 0.04% oxygen retained from refining. It is the standard commercial pure copper and the one meant when a drawing just says "copper". Oxygen-free grades C101 (99.99%) and C102 (99.95%) are purer and behave better when heated in hydrogen or used in vacuum.
- What is the difference between C110 and C101 copper?
- Oxygen. C110 (ETP) carries about 0.04% oxygen; C101 (OFE, oxygen-free electronic) is 99.99% copper with essentially none. Both conduct about 101% IACS. C101 does not hydrogen-embrittle when brazed or annealed in a reducing atmosphere, welds cleaner and outgasses less in vacuum, at 10-20% more cost. Most bus bar and sheet work is C110.
- Can C110 copper be machined?
- With difficulty. It is gummy, rated about 20% of free-cutting brass, and makes long stringy chips, built-up edge and burrs. Very sharp tooling and a good lubricant make simple features workable, but for machined electrical parts specify C145 tellurium copper (85% machinability, 93% IACS) or C147 sulfur copper.
- Can C110 copper be welded?
- It can be TIG welded with deoxidized ERCu filler and heavy preheat, but the oxygen causes porosity and the conductivity makes fusion hard to sustain. Soldering and silver brazing are the normal joining methods and work superbly. For furnace brazing in hydrogen or heavy welding, use oxygen-free C101 / C102.
- Does copper rust?
- No; rust is iron oxide. Copper tarnishes to brown and then to green patina (copper carbonate and sulfate), which protects the metal underneath, which is why copper roofs last a century. It is attacked by ammonia, oxidizing acids and sulfur compounds, and it corrodes any less noble metal bolted to it when wet.
Processes that commonly use it
Related materials
Where to verify these values
- ASTM B187, ASTM B152 and ASTM B133
- Copper Development Association (CDA) alloy data for C11000
- ASM Handbook, Volume 2: Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
- Producer data sheets for ETP copper bus bar and sheet (Aurubis, Wieland, Mueller)
