Electrical & power
Bus bars, terminal blocks, transformer windings, switchgear contacts. Anywhere current flows in volume.
ETP copper · UNS C11000
C110 Copper
Electrolytic Tough Pitch copper — 99.90% pure, the international reference standard for electrical conductivity. Bus bars, electrical contacts, RF enclosures, heat sinks, and any application where conductivity dominates.
Conductivity
100% IACS
Thermal cond.
388 W/m·K
Density
8.94 g/cc
Mach.
20 /100
When to use
Pick C110 when conductivity is the function.
C110 is the IACS conductivity benchmark — by definition, 100% IACS at 20 °C. Anything that needs to carry current or dissipate heat starts here: power bus bars, electrical contacts, transformer windings, RF/microwave housings, heat sinks for high-power electronics, and induction coils.
Three things to know up front: it’s soft (yield 70 MPa annealed — designs around mechanical loads need to compensate), it’s heavy (8.94 g/cc — denser than steel), and it’s gummy to machine. For high-volume parts where machinability matters more than absolute conductivity, consider C145 (tellurium copper) or C260 brass — both at lower IACS but much faster cutting.
Strengths
What no other metal offers.
- Conductivity reference100% IACS — the standard against which other metals are measured. Aluminum is 61%, gold 71%, silver 105%.
- Thermal conductivity388 W/m·K — among the highest of all metals. Heat sinks and cold plates start with copper.
- Solderable & weldableJoins easily. Standard substrate for solderable assemblies.
- Antimicrobial surfaceEPA-registered for surface bacteria reduction. Used in healthcare touchpoints.
- Plates & polishes wellSubstrate for silver, gold, tin plating in electronics.
- Recyclable infinitely100% recyclable without property loss. Fully circular material.
Trade-offs
What you accept.
- Soft & deformableYield 70 MPa annealed. Design around it — or specify temper (1/4-hard, 1/2-hard, full hard) at the cost of conductivity.
- Density penalty8.94 g/cc — heavier than steel. Power-density gains often offset, but worth knowing for portable assemblies.
- Gummy to machineMach rating 20/100. Long stringy chips, surface drag. Sharp tools and high feed rates required.
- Hydrogen embrittlement of ETPETP grades (with O₂) can crack if exposed to hydrogen at temperature. Use C101 (OFE oxygen-free) for vacuum brazing or H₂ atmospheres.
- TarnishesSurface oxide forms in air. Protect with conformal coating, plating, or oil for long-term storage.
- Cost$5–10/lb stock — multiples of aluminum. Often the choice is justified by performance, not cost.
Specs
Mechanical, physical & chemical data.
Properties shown for fully annealed (O60) condition — softest, most ductile, highest conductivity. Cold work raises strength substantially at the cost of some conductivity.
Mechanical
Properties (annealed O60)
| Ultimate tensile strength | 220 MPa (32 ksi) |
|---|---|
| Yield strength | 70 MPa (10 ksi) |
| Elongation at break | 45% |
| Modulus of elasticity | 117 GPa |
| Shear modulus | 44 GPa |
| Hardness (annealed) | 40 HV / 40 HRF |
| Hardness (full hard H04) | 100 HV / 60 HRB |
| Fatigue limit 10⁸ cycles | 76 MPa |
Source: Copper Development Association. H04 (full hard) values: UTS 380 MPa, YS 365 MPa, elongation 6%.
Physical & electrical
At room temperature
| Density | 8.94 g/cc (0.323 lb/in³) |
|---|---|
| Melting point | 1083 °C |
| Specific heat | 0.385 J/g·°C |
| Thermal conductivity | 388 W/m·K |
| Electrical conductivity | 100% IACS (101% absolute) |
| Resistivity | 1.71 µΩ·cm |
| CTE (20–100 °C) | 17.0 µm/m·°C |
| Magnetic | Diamagnetic |
Conductivity drops by roughly 0.4% per °C above 20 °C. Cold work drops conductivity ~3% from annealed to full hard.
Composition
Chemistry, weight %
| Copper (Cu) | 99.90 min |
|---|---|
| Oxygen (O) | 0.04 max |
| Sulfur (S) | 0.0025 max |
| Lead (Pb) RoHS-relevant | 0.005 max |
| Bismuth (Bi) | 0.001 max |
| Iron (Fe) | 0.005 max |
OFE (oxygen-free electronic) grade C101 is similar but with O ≤ 0.0010% — preferred when hydrogen exposure is a concern.
Specifications
Common purchase specs.
ASTM B187
Bar, bus bar, rod (ETP)
ASTM B152
Sheet, strip, plate
ASTM B188
Hollow rectangular bus bar
ASTM B370
Sheet for building construction
AMS 4500
Bar, soft (annealed)
AMS 4501
Bar, hard
AMS 4602
Plate, sheet
UNS C11000 / CDA 110
Equivalent designations
Machining
How we cut it.
Pure copper is gummy. Sharp tools, positive rake, high feed rates, and aggressive coolant. The surface wants to drag and burr — chip control is the whole game.
Cutting speed
300–600 SFM with carbide on annealed copper. Sharp polished tools mandatory.
Feed rate
Aggressive constant feed. Slow feeds cause rubbing and built-up edge.
Tooling
Polished carbide with positive rake. Avoid coatings that grab — uncoated or mirror-polished diamond cuts cleanest.
Coolant
Flood with water-soluble or fatty-acid lubricant. Helps chip break and surface finish.
Chip break
Use chip-breaker geometry. Stringy chips wrap on tool and damage finish.
Burrs are persistent
Plan a deburring operation. Vibratory finishing or hand-deburr for cosmetic edges.
Threading
Single-point preferred. Form taps work in soft annealed, but copper galls — lubricate generously.
Hard-temper for production
Half-hard or full-hard temper machines noticeably faster than annealed — at small conductivity penalty.
Applications
Where C110 earns its cost.
RF & microwave
Waveguide, microwave housings, antenna substrates. The high conductivity reduces insertion loss.
Thermal management
Heat sinks, cold plates, induction coils, vacuum chamber components. Heat flows where copper is.
Compare
Related materials.
Lighter conductor
Aluminum 6061 →
43% IACS, 1/3 the weight. Standard for weight-sensitive bus and structural conductors.
Structural alt.
316L Stainless →
When mechanical strength matters more than conductivity.
Insulator alt.
PEEK →
When you want the opposite — electrical insulation in the same envelope.
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