What Copper-Clad Aluminium Wire Is
Copper-clad aluminium (CCA) wire is a bimetallic composite conductor made by bonding a copper layer over a solid aluminium core rod and then drawing the assembly down to the finished diameter. Because the two metals are joined metallurgically under pressure, the copper-to-aluminium interface runs continuously along the whole length of the wire instead of sitting on the surface as a plating that can flake off.
At radio and higher frequencies, current crowds toward the conductor surface through the skin effect, so the copper layer carries most of the signal path while the lightweight aluminium core supplies mechanical support. Copper usually accounts for 10% to 15% of the cross-sectional area, which places CCA wire between pure aluminium and pure copper in both conductivity and cost.
Key Characteristics of CCA Wire
Conductivity: about 61% to 65% IACS depending on the copper-to-aluminium volume ratio, against 100% IACS for annealed copper and roughly 61% for pure aluminium.
Density: near 3.32 g/cm3 at a 10% copper volume fraction, some 37% lighter than solid copper at 8.96 g/cm3, which reduces sag and handling weight on long runs.
Corrosion resistance: the outer copper layer shields the aluminium core from moisture and airborne contaminants, so the strand resists outdoor and humid service far better than bare aluminium.
Flexibility: annealed grades accept repeated bending during installation, although the bimetal interface tolerates fewer flex cycles than an all-copper conductor.
Cost stability: only the skin is priced on the copper market, so material cost tracks copper far less closely than a solid copper conductor.
Strength: tensile strength is higher than annealed aluminium of equal diameter because the copper skin stiffens the assembly.
Typical Property Comparison
| Property | Copper-clad aluminium, 10% Cu | Annealed copper | Aluminium 1350 |
|---|---|---|---|
| Density, g/cm3 | 3.32 | 8.96 | 2.70 |
| Conductivity, % IACS | 61 to 65 | 100 to 101 | 61 |
| Tensile strength, MPa | 100 to 200 | 200 to 250 | 60 to 100 |
| Core melting point, °C | about 660 | 1085 | about 660 |
| Relative material cost | Medium to low | High | Low |
The figures above are typical ranges for commercial annealed grades. A specific cable design should always be checked against the conductor data sheet issued with the reel.
Where Copper-Clad Aluminium Wire Is Used
Because the composite conductor performs best where the working voltage and the thermal load stay moderate, its main markets are:
Low-voltage power distribution conductors, service drop wires and jumper links on overhead lines.
Lighting equipment, lamp holders, low-voltage switchgear and control panel wiring.
Coaxial cable outer conductors, shielding braids and network drop cables, where the skin effect makes the copper layer electrically dominant.
Winding wire for transformers, inductors and chokes operating at elevated frequency, where weight saving matters more than DC resistance.
Battery interconnects, grounding straps and flexible jumpers in vehicles and portable equipment.
Service Limits and Installation Practice
The largest single limitation is thermal. The aluminium core melts near 660 °C while copper melts at 1085 °C, so the composite conductor must not be installed in circuits that are required to keep operating during a fire, in fire-resistant walls, in fire doors or in any route with a fire rating. Sustained operation above roughly 150 °C also speeds diffusion at the bimetal interface and raises joint resistance, so high-temperature windings remain the domain of solid copper.
Size by current and voltage drop: CCA is commonly selected one or two AWG steps larger than the copper equivalent to reach the same performance.
Terminate with bimetal or tinned lugs approved for aluminium; clamping bare copper against bare aluminium in damp service invites galvanic corrosion of the core.
Apply an antioxidant compound to stranded conductors before crimping, and re-torque bolted joints after the first thermal cycle to control creep.
Store coils dry, keep the ends sealed, and reject reels whose copper layer is scratched through to the core.
Frequently Asked Questions
Q: Is copper-clad aluminium wire a direct substitute for copper wire?
Not at the same cross-section. CCA reaches roughly 61% to 65% IACS, so a larger gauge is normally needed for an equivalent voltage drop, and the substitution should be confirmed against the circuit design.
Q: Why does CCA wire work well at high frequency?
Alternating current concentrates near the surface, so the copper skin carries most of the current while the aluminium core only carries the mechanical load and a small share of the current.
Q: Can copper-clad aluminium wire be used in fire-rated circuits?
No. With a core melting point near 660 °C, the conductor cannot be relied on where fire resistance is required, including fire walls, fire doors and similar rated assemblies.
Q: How should CCA wire be stored before installation?
Keep reels in a dry, ventilated store, leave the protective wrapping on until the reel is used, and keep the conductor ends sealed so moisture cannot reach the aluminium core.
Q: Does the copper layer ever separate from the core?
The bond is metallurgical, so separation is not expected in normal service. Damage usually starts from mechanical abrasion or from repeated flexing at a termination, which is why correct lugs and strain relief matter.
Q: Which industries buy copper-clad aluminium wire most often?
Cable makers, lighting and low-voltage equipment builders, antenna and coaxial cable producers, and vehicle or equipment harness manufacturers are the most frequent users.
