Copper Alloys for Electrical Applications: C110 vs C220 vs C260 Guide

Quick Comparison: Electrical Copper Alloys

C11000 ETP Copper: The Electrical Conductivity Standard

C11000 Electrolytic Tough Pitch (ETP) copper is the international standard for electrical conductivity, defined as 101% IACS (International Annealed Copper Standard). This means C11000 conducts electricity better than the reference standard itself — a remarkable property that makes it the baseline against which all other conductor materials are measured. Every power cable, building wire, motor winding, and transformer coil in the IEC and NEC systems assumes C11000 conductivity as the design reference.

The 101% IACS conductivity translates to a resistivity of 1.671 μΩ·cm at 20°C, producing the lowest I²R (Joule heating) losses of any commercially available conductor material. For power distribution, this means smaller conductor cross-sections for a given ampacity, or equivalently, lower energy losses for a given conductor size. At utility-scale transmission (hundreds of MW), the difference between 101% IACS copper and 61% IACS aluminum conductor translates to millions of dollars in energy loss savings over the installation life.

C11000's limitations are mechanical. In the annealed condition (O60 temper), yield strength is only 69 MPa — insufficient for structural or spring applications without cold working. Spring temper (H08) raises yield to 365 MPa but at the cost of ductility (6% elongation) and slight conductivity reduction (~97% IACS). For electrical contacts, terminals, and connectors that require both conductivity and spring force, copper alloys (beryllium copper, phosphor bronze) are specified instead.

See C11000 vs C26000 for the copper-vs-brass conductivity comparison.

C22000 Commercial Bronze: The Balanced Copper-Zinc Alloy

C22000 commercial bronze (90% Cu / 10% Zn) occupies the middle ground between pure copper's conductivity and brass's mechanical strength. At 44% IACS, it retains roughly half the conductivity of C11000 — sufficient for many electrical applications where moderate current carrying capacity is combined with higher strength and better corrosion resistance than pure copper.

The 10% zinc addition increases yield strength by 20-40% over pure copper in equivalent tempers, while maintaining adequate formability for stamping, deep drawing, and cold heading operations. C22000 is the standard material for electrical connectors, switchgear contacts, and terminal lugs where the mechanical demands exceed what pure copper can provide in the required temper condition. The slightly lower cost (zinc is cheaper than copper) and improved machinability are secondary advantages.

C22000's golden color gives it the commercial name 'bronze' (it is technically a red brass, not a true tin-bronze). This aesthetic property makes it popular for architectural hardware, decorative electrical fixtures, and premium consumer electronics where appearance matters alongside performance.

C26000 Cartridge Brass: The Formability Champion

C26000 cartridge brass (70% Cu / 30% Zn) is the most formable copper alloy available, with an exceptional 66% elongation in the annealed condition. This property makes it the standard for deep-drawn electrical components: RF connectors, EMI shielding cans, battery contacts, and connector shells. The 30% zinc addition provides a 50% increase in tensile strength over pure copper (325 MPa vs 220 MPa annealed) while maintaining the ductility needed for complex forming operations.

At 28% IACS, C26000's electrical conductivity is only about one-quarter that of pure copper — a significant limitation for current-carrying applications. Cartridge brass is specified for connectors, contacts, and terminals where mechanical formability and moderate conductivity are needed, not for power conductors or bus bars where ampacity is the driving requirement.

The name 'cartridge brass' reflects its original application — ammunition casings — where the 70/30 composition provides the ideal combination of deep drawability, strength, and corrosion resistance. In electrical applications, the same formability enables complex connector geometries that would be impossible in pure copper or harder alloys. For deep-drawn EMI shielding enclosures, C26000 can achieve draw ratios exceeding 2.0:1 without intermediate annealing.

See C11000 vs C26000 for conductivity-vs-formability trade-offs, and C11000 vs C36000 for conductivity-vs-machinability.

Application-Specific Recommendations

Power Distribution and Building Wire

Use C11000 ETP copper exclusively. The 101% IACS conductivity minimizes I²R losses and maximizes ampacity per unit cross-section. No other copper alloy or aluminum conductor matches pure copper's loss performance in building wiring, motor windings, and transformer coils.

Bus Bars and Switchgear Connections

Use C11000 for high-current bus bars and C22000 for structural switchgear components that carry moderate current but require higher strength. For bus bars, the conductivity advantage of C11000 over alternatives directly reduces temperature rise under full-load conditions.

Electrical Connectors and Contacts

Use C26000 for deep-drawn connector shells and EMI shielding cans where formability is critical. Use C22000 for stamped contacts and terminals that need moderate conductivity with good strength. For spring contacts requiring high yield strength, specify beryllium copper (C17200) or phosphor bronze (C51000).

RF and Telecommunications

Use C26000 for RF connector bodies (SMA, N-type, BNC) where the skin effect confines current to the surface and bulk conductivity is less critical. The excellent formability enables precision thread rolling and dimensional control for impedance-matched connections.

Frequently Asked Questions

References & Standards

• ASTM International. Steel & Alloy Standards. astm.org
• ASM International. Materials Information Society. asminternational.org
• NIST. Materials Data. nist.gov
• World Steel Association. Steel Statistical Yearbook. worldsteel.org