Among commercially pure coppers, Copper 110 (C11000, ETP) and Copper 101 (C10100, OFE) are two widely used grades, each optimized for specific applications.
While both offer outstanding conductivity and formability, their differences in purity, oxygen content, microstructure, and suitability for vacuum or high-reliability applications make the choice between them critical for engineers, designers, and materials specialists.
Standards & Nomenclature
Copper 110 (C11000) is commonly referred to as Cu-ETP (Electrolytic Tough Pitch Copper).
It is standardized under UNS C11000 and the EN designation Cu-ETP (CW004A). C11000 is widely manufactured and supplied in various product forms including wire, rod, sheet, and plate, making it a versatile choice for general electrical and industrial applications.
Copper 101 (C10100), on the other hand, is known as Cu-OFE (Oxygen-Free Electronic Copper).
It is ultra-pure copper with extremely low oxygen content, standardized under UNS C10100 and EN Cu-OFE (CW009A).
C10100 is specifically refined to eliminate oxygen and oxide inclusions, which makes it ideal for vacuum, high-reliability, and electron-beam applications.
Specifying the UNS or EN designation along with the product form and temper is critical for ensuring the material meets the required performance characteristics.
Chemical Composition and Microstructural Differences
The chemical composition of copper directly influences its purity, electrical and thermal conductivity, mechanical behavior, and suitability for specialized applications.
While both Copper 110 (C11000, ETP) and Copper 101 (C10100, OFE) are classified as high-purity coppers, their microstructures and trace element content differ significantly, affecting performance in critical applications.
| Element / Characteristic | C11000 (ETP) | C10100 (OFE) | Notes |
| Copper (Cu) | ≥ 99.90% | ≥ 99.99% | OFE has ultra-high purity, beneficial for vacuum and electronic applications |
| Oxygen (O) | 0.02–0.04 wt% | ≤ 0.0005 wt% | Oxygen in ETP forms oxide inclusions; OFE is essentially oxygen-free |
| Silver (Ag) | ≤ 0.03% | ≤ 0.01% | Trace impurity, minor impact on properties |
| Phosphorus (P) | ≤ 0.04% | ≤ 0.005% | Lower phosphorus in OFE reduces risk of embrittlement and oxide formation |
Physical Properties: Copper 110 vs 101
Physical properties such as density, melting point, thermal conductivity, and electrical conductivity are fundamental for engineering calculations, design, and material selection.
Copper 110 (C11000, ETP) and Copper 101 (C10100, OFE) share very similar bulk properties because both are essentially pure copper, but minor differences in purity and oxygen content can slightly affect performance in specialized applications.
| Property | Copper 110 (C11000, ETP) | Copper 101 (C10100, OFE) | Notes / Implications |
| Density | 8.96 g/cm³ | 8.96 g/cm³ | Identical; suitable for weight calculations in structures and conductors. |
| Melting Point | 1083–1085 °C | 1083–1085 °C | Both grades melt at nearly the same temperature; processing parameters for casting or brazing are equivalent. |
| Electrical Conductivity | ~100 % IACS | ~101 % IACS | OFE offers marginally higher conductivity due to ultra-low oxygen and impurity content; relevant in high-precision or high-current applications. |
| Thermal Conductivity | 390–395 W·m⁻¹·K⁻¹ | 395–400 W·m⁻¹·K⁻¹ | Slightly higher in OFE, which improves heat transfer efficiency in thermal management or vacuum applications. |
| Specific Heat Capacity | ~0.385 J/g·K | ~0.385 J/g·K | Same for both; useful for thermal modeling. |
| Coefficient of Thermal Expansion | ~16.5 × 10⁻⁶ /K | ~16.5 × 10⁻⁶ /K | Negligible difference; important for joint and composite design. |
| Electrical Resistivity | ~1.72 μΩ·cm | ~1.68 μΩ·cm | Lower resistivity of C10100 contributes to slightly better performance in ultra-sensitive circuits. |
Mechanical Properties and Temper/Condition Effects
Mechanical performance of copper depends strongly on processing temper, including annealing and cold working.
Copper 101 (C10100, OFE) generally offers higher strength in cold-worked conditions due to its ultra-high purity and oxide-free microstructure,
whereas Copper 110 (C11000, ETP) exhibits superior formability and ductility, making it well-suited for forming-intensive applications such as deep drawing or stamping.
Mechanical Properties by Temper (Typical Values, ASTM B152)
| Property | Temper | Copper 101 (C10100) | Copper 110 (C11000) | Test Method |
| Tensile Strength (MPa) | Annealed (O) | 220–250 | 150–210 | ASTM E8/E8M |
| Tensile Strength (MPa) | Cold-Worked (H04) | 300–330 | 240–270 | ASTM E8/E8M |
| Tensile Strength (MPa) | Cold-Worked (H08) | 340–370 | 260–290 | ASTM E8/E8M |
| Yield Strength, 0.2% offset (MPa) | Annealed (O) | 60–80 | 33–60 | ASTM E8/E8M |
| Yield Strength, 0.2% offset (MPa) | Cold-Worked (H04) | 180–200 | 150–180 | ASTM E8/E8M |
| Yield Strength, 0.2% offset (MPa) | Cold-Worked (H08) | 250–280 | 200–230 | ASTM E8/E8M |
| Elongation at Break (%) | Annealed (O) | 45–60 | 50–65 | ASTM E8/E8M |
| Elongation at Break (%) | Cold-Worked (H04) | 10–15 | 15–20 | ASTM E8/E8M |
| Brinell Hardness (HBW, 500 kg) | Annealed (O) | 40–50 | 35–45 | ASTM E10 |
| Brinell Hardness (HBW, 500 kg) | Cold-Worked (H04) | 80–90 | 70–80 | ASTM E10 |
Annealed (O) Temper: Both grades are soft and highly ductile. C11000's higher elongation (50–65%) makes it ideal for deep drawing, stamping, and electrical contact manufacturing.
Cold-Worked (H04/H08) Temper: C10100's ultra-purity enables more uniform work hardening, resulting in tensile strength 30–40% higher than C11000 in H08 temper.
This makes it suitable for load-bearing or precision components, including superconducting coil windings or high-reliability connectors.
Brinell Hardness: Increases proportionally with cold working. C10100 achieves higher hardness for the same temper due to its clean, oxide-free microstructure.
Manufacturing and fabrication behavior
Copper 110 (C11000, ETP) and Copper 101 (C10100, OFE) behave similarly in many fabrication operations because both are essentially pure copper, but the difference in oxygen and trace impurities produces meaningful practical contrasts during forming, machining and joining.
Forming and cold-working
Ductility and bendability:
Annealed material (O temper): both grades are highly ductile and accept tight bends, deep drawing and severe forming.
Annealed copper can typically tolerate very small inside bend radii (close to 0.5–1.0 × sheet thickness in many cases), making it excellent for stamping and intricate shaped parts.
Cold-worked tempers (H04, H08, etc.): strength rises and ductility falls as temper increases; minimum bend radii must be increased accordingly.
Designers should size bend radii and fillets based on temper and intended post-forming stress relief.
Work hardening & drawability:
C10100 (OFE) tends to harden more uniformly during cold work because of its oxide-free microstructure; this yields higher achievable strength in H-tempers and can be advantageous for parts that require higher mechanical performance after drawing.
C11000 (ETP) is extremely forgiving for progressive drawing and stamping operations because oxide stringers are discontinuous and typically do not interrupt forming at commercial strain levels.
Annealing and recovery:
Recrystallization for copper occurs at relatively low temperatures compared with many alloys; depending on prior cold work, recrystallization onset may begin within roughly 150–400 °C.
Industrial full-anneal practice commonly uses temperatures in the 400–650 °C range (time and atmosphere selected to avoid oxidation or surface contamination).
OFE parts intended for vacuum use may be annealed in inert or reducing atmospheres to preserve surface cleanliness.
Extrusion, rolling and wire drawing
Wire drawing: C11000 is the industry standard for high-volume wire and conductor production because it combines excellent drawability with stable conductivity.
C10100 is also draw-able to fine gauges but is selected when downstream vacuum performance or ultra-clean surfaces are required.
Extrusion & rolling: Both grades extrude and roll well. Surface quality of OFE is typically superior for high-precision rolled products because of the absence of oxide inclusions; this can reduce interdendritic tearing or micro-pits in demanding surface finishes.
Typical Industrial Applications
C11000 (ETP):
Power distribution busbars, cables, and connectors
Transformers, motors, switchgear
Architectural copper and general fabrication
C10100 (OFE):
Vacuum chambers and ultra-high-vacuum equipment
Electron-beam, RF, and microwave components
Semiconductor manufacturing and cryogenic conductors
High-reliability laboratory instrumentation
Summary: C11000 is suitable for general electrical and mechanical use, whereas C10100 is required when vacuum stability, minimal impurities, or ultra-clean processing are essential.
Cost & availability
C11000: This is the standard, high-volume copper product.
It is generally less expensive and more widely stocked by mills and distributors, making it the default choice for mass production and budget-sensitive applications.
C10100: Carries a premium price due to additional refining steps, special handling requirements, and smaller production volumes.
It is available, but typically only in limited product forms (bars, plates, sheets in select tempers) and often requires longer lead times.
For high-volume components where cost efficiency is critical, C11000 is usually specified.
Conversely, for niche applications such as vacuum or high-purity electronic components, the performance benefits of C10100 justify the higher cost.
Comprehensive Comparison: Copper 110 vs 101
| Feature | Copper 110 (C11000, ETP) | Copper 101 (C10100, OFE) | Practical Implications |
| Copper Purity | ≥ 99.90% | ≥ 99.99% | OFE copper offers ultra-high purity, crucial for vacuum, high-reliability, and electron-beam applications. |
| Oxygen Content | 0.02–0.04 wt% | ≤ 0.0005 wt% | Oxygen in C11000 forms oxide stringers; C10100's near-zero oxygen prevents oxide-related defects. |
| Electrical Conductivity | ~100 % IACS | ~101 % IACS | OFE offers slightly higher conductivity, relevant in precision electrical systems. |
| Thermal Conductivity | 390–395 W·m⁻¹·K⁻¹ | 395–400 W·m⁻¹·K⁻¹ | Minor difference; OFE slightly better for heat-sensitive or high-precision applications. |
| Mechanical Properties (Annealed) | Tensile 150–210 MPa, Elongation 50–65% | Tensile 220–250 MPa, Elongation 45–60% | C11000 more formable; C10100 stronger in annealed or cold-worked states. |
| Mechanical Properties (Cold-Worked H08) | Tensile 260–290 MPa, Elongation 10–15% | Tensile 340–370 MPa, Elongation 10–15% | C10100 benefits from higher work hardening due to ultra-clean microstructure. |
Fabrication/Forming |
Excellent formability for stamping, bending, drawing | Excellent formability, superior work hardening and dimensional stability | C11000 suited for high-volume fabrication; C10100 preferred for precision components or high-reliability parts. |
| Joining (Brazing/Welding) | Flux-assisted brazing; standard welding | Fluxless brazing, cleaner welds, preferred for electron-beam or vacuum welding | OFE critical for vacuum or high-purity applications. |
| Vacuum/Cleanliness | Acceptable for low/medium vacuum | Required for UHV, minimal outgassing | OFE chosen for ultra-high-vacuum or contamination-sensitive environments. |
| Cryogenic Performance | Good | Excellent; stable grain structure, minimal thermal expansion variation | OFE preferred for superconducting or low-temperature instrumentation. |
| Cost & Availability | Low, widely stocked, multiple forms | Premium, limited forms, longer lead times | Choose C11000 for cost-sensitive, high-volume applications; C10100 for high-purity, specialized applications. |
| Industrial Applications | Busbars, wiring, connectors, sheet metal, general fabrication | Vacuum chambers, electron-beam components, high-reliability electrical paths, cryogenic systems | Match grade to operational environment and performance requirements. |
FAQ
Is C10100 significantly better electrically than C11000?
No. The electrical conductivity difference is minor (~100% vs 101% IACS). The primary advantage is ultra-low oxygen content, which benefits vacuum and high-reliability applications.
Can C11000 be used in vacuum equipment?
Yes, but its trace oxygen may outgas or form oxides under ultra-high vacuum conditions. For strict vacuum applications, C10100 is preferred.
Which grade is standard for power distribution?
C11000 is the industry standard for busbars, connectors, and general electrical distribution due to its conductivity, formability, and cost efficiency.
How should OFE copper be specified for procurement?
Include UNS C10100 or EN Cu-OFE designation, oxygen limits, minimum conductivity, product form, and temper. Request Certificates of Analysis for trace oxygen and copper purity.
Are there intermediate copper grades between ETP and OFE?
Yes. Phosphorus-deoxidized coppers and high-conductivity variants exist, designed for improved solderability or reduced hydrogen interaction. Selection should match the application requirements.
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