Copper Clad Aluminium (CCA)
Copper clad aluminium is a bimetallic conductor in which a layer of copper is metallurgically bonded to an aluminium core, so the material has a copper surface and an aluminium body. It is made as wire, flat bar (busbar), plate, strip and foil, typically with 10 – 35 % copper by volume. This guide explains how CCA is produced, what it can and cannot do compared with solid copper and solid aluminium, and how to choose the right form and copper ratio.
- Structure
- Copper skin, aluminium core
- Copper ratio
- 10 – 35 % by volume
- Forms
- Wire, bar, plate, strip, foil
- Standards
- ASTM B566 · ASTM B1005
What copper clad aluminium is
CCA is not plated aluminium. The copper layer is joined to the aluminium over the whole interface by pressure and heat, so the two metals form a solid-state metallurgical bond and are worked together, drawn, rolled, bent and punched, as a single material. A properly bonded CCA product does not delaminate when bent, twisted or cut.
The idea is to put each metal where it does most good. Copper on the outside gives a surface that is easy to solder, crimp and bolt, resists oxidation, and makes reliable contact with existing copper terminals. Aluminium in the core supplies most of the cross-section at about 30 % of the density of copper and a fraction of its cost per kilogram.
The copper fraction is expressed by volume (or by area of the cross-section), and it stays constant as the material is drawn or rolled to smaller sizes. Wire normally carries 10 % or 15 % copper; busbar and plate typically 20 – 35 %; strip and foil cover a wide range depending on whether one or both faces are clad.
How copper clad aluminium is produced
| Process | How it works | Typical products |
|---|---|---|
| Cladding and welding (tape cladding) | Copper tape is formed around a clean aluminium rod, seam-welded, then drawn so the layers bond under pressure | CCA wire for coaxial cable, braid, winding wire |
| Continuous casting / cast-cladding | Molten aluminium is cast into a pre-formed copper tube, then the composite is rolled or drawn | Flat bar, rod and busbar |
| Hydrostatic extrusion and co-extrusion | A copper-sleeved aluminium billet is extruded under fluid pressure so both metals flow together | Rod, bar and profiled sections |
| Roll bonding (cold or hot) | Wire-brushed copper and aluminium strips are stacked and rolled with heavy reduction, then annealed to strengthen the bond | Plate, sheet, strip, foil; one-side, two-side and inlay |
| Explosion bonding | An explosive charge drives the copper plate onto the aluminium at high velocity | Thick plate, transition blocks, electrolytic cell connectors |
Whatever the route, the critical factor is the interface. Copper and aluminium form brittle intermetallic compounds (Al2Cu, AlCu, Al4Cu9) when they are held at high temperature. A thin intermetallic layer is tolerable; a thick one makes the bond brittle and raises interface resistance. Producers therefore control annealing temperature and time carefully, and users should avoid exposing CCA to prolonged temperatures above roughly 200 – 250 °C, and to any heating approaching 400 °C, which published studies associate with rapid intermetallic growth and debonding.
How copper ratio affects density, conductivity and weight
Because the two metals act in parallel, density and DC conductivity follow a simple rule of mixtures. The table shows calculated values for common copper ratios and what they mean in practice.
| Copper by volume | Density (g/cm³) | Weight vs copper, same size | Calculated conductivity | Area needed vs copper, same resistance | Weight vs copper, same resistance |
|---|---|---|---|---|---|
| 10 % | 3.32 | 37 % | ≈ 65 % IACS | 1.54 × | 58 % |
| 15 % | 3.63 | 41 % | ≈ 67 % IACS | 1.50 × | 61 % |
| 20 % | 3.94 | 44 % | ≈ 69 % IACS | 1.45 × | 64 % |
| 25 % | 4.25 | 48 % | ≈ 71 % IACS | 1.41 × | 68 % |
| 30 % | 4.56 | 51 % | ≈ 73 % IACS | 1.38 × | 71 % |
| 35 % | 4.87 | 55 % | ≈ 75 % IACS | 1.34 × | 73 % |
Rule-of-mixtures values calculated from copper (8.89 g/cm³, 100 % IACS) and an aluminium core of 2.70 g/cm³ and 61 % IACS. They are upper estimates: hard tempers and 1060/1070 cores conduct slightly less. Guaranteed values are the minimums in the governing standard and on the test certificate.
Read the last column carefully. For DC or low-frequency AC, a CCA conductor of equal resistance weighs about 60 – 75 % of the copper it replaces, while a solid aluminium conductor of equal resistance weighs only about 50 %. CCA is therefore not the lightest option; its value is that it combines most of aluminium's savings with a copper surface. At radio frequencies, where current crowds into the outer skin, a CCA conductor with enough copper thickness behaves almost exactly like solid copper, which is why CCA dominates coaxial cable inner conductors.
Forms of copper clad aluminium
CCA wire
10 % and 15 % copper, hard or annealed, to ASTM B566. Used for coaxial cable centre conductors, braided shields, magnet and winding wire and speaker wire.
CCA busbar (flat bar)
20 – 30 % copper flat bar for switchgear, busway, earthing and battery connections, covered by ASTM B1005.
CCA plate and sheet
One-side (Cu/Al), two-side (Cu/Al/Cu) or reverse (Al/Cu/Al) laminates for terminals, transition plates and heat spreaders.
CCA strip and coil
Thin roll-bonded strip, including inlay and edge-lay types, for battery connectors, stamped terminals and LED substrates.
Bimetal washers and transitions
Discs and blocks with copper on one face and aluminium on the other, placed between copper and aluminium conductors.
Bimetal lugs and terminals
Friction-welded or clad lugs that let aluminium cable terminate on copper equipment.
CCA compared with solid copper and solid aluminium
| Criterion | Solid copper | Copper clad aluminium | Solid aluminium |
|---|---|---|---|
| DC conductivity | 100 % IACS | About 64 – 75 % IACS | About 61 % IACS (1350) |
| Weight for equal resistance | 100 % | About 60 – 75 % | About 50 % |
| Contact surface | Copper | Copper | Aluminium; needs plating or compound |
| Termination with copper lugs | Direct | Direct | Bimetal lugs or transition needed |
| Strength and fatigue | Highest | Between the two; core dominates | Lowest (1350); alloys like 6101 better |
| Heat tolerance | High | Limited by interface (avoid long exposure above about 200 – 250 °C) | Moderate |
| Recycling | Simple, high value | Needs separation of metals | Simple |
| Material cost | Highest | Intermediate | Lowest |
The right answer depends on what limits your design. If weight is the limit and the joints can be engineered for aluminium, solid aluminium is lighter and cheaper still. If the conductor must terminate on copper hardware without special parts, or must be soldered, CCA earns its place. If space is the limit, copper remains the most compact choice.
Where CCA is not the right choice
- Building wiring and Ethernet cable. Many building codes and the TIA/ISO structured-cabling standards require solid copper conductors. CCA "network cable" sold as Cat 5e or Cat 6 does not meet those standards and runs hotter in Power over Ethernet service.
- High-temperature terminations. Joints that run hot for long periods can grow intermetallic compounds at the copper-aluminium interface.
- Severe flexing. Repeated bending fatigues the softer aluminium core sooner than solid copper.
- Cut ends in damp environments. The exposed aluminium core at a cut face is a galvanic couple with the copper skin; seal ends or keep them dry.
- Where the specification says copper. Substituting CCA without approval is a common source of disputes and failed inspections; always declare the material.
Standards for copper clad aluminium
| Standard | Scope |
|---|---|
| ASTM B566 / B566M | Copper-clad aluminium wire: 10 % and 15 % copper classes, annealed and hard |
| ASTM B1005 | Copper-clad aluminium bar for electrical purposes (bus bar): 20, 25 and 30 % copper, annealed (A) and hard (H) classes |
| ASTM B209 / EN 485 | Aluminium sheet and plate (core material reference) |
| ASTM B152 / EN 1652 | Copper sheet, strip and plate (cladding material reference) |
| IEC 61439 | Switchgear assemblies, when CCA busbar is used inside them |
For roll-bonded plate and strip there is no single international product standard, so orders are normally placed to an agreed specification covering layer ratio, total thickness tolerance, temper, bond strength (peel or shear test), bend test and conductivity. Ask for those values on the test certificate.
How to specify copper clad aluminium
- Form and dimensionsWire diameter, or bar/plate/strip thickness, width and length or coil size.
- Structure and copper ratioCopper by volume (for example 15 % wire, 25 % bar) and, for plate and strip, one-side, two-side or inlay layout with layer thicknesses.
- Core and copper gradesUsually 1060 or 1070 aluminium core with C11000 or C10200 copper; state any alternatives.
- Temper and propertiesAnnealed or hard, minimum tensile strength, elongation and conductivity.
- Tests and documentsBond test, bend test, resistivity, dimensions; EN 10204 3.1 certificate and packing list.
- DeliveryPacking (reels, coils, wooden cases), quantity, destination and Incoterm (EXW, FOB, CIF, DAP).
References and standards
- ASTM B566/B566M – Standard Specification for Copper-Clad Aluminum Wire
- ASTM B1005 – Standard Specification for Copper-Clad Aluminum Bar for Electrical Purposes (Bus Bar)
- ASTM B209 – Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate
- The Aluminum Association – Aluminum Electrical Conductor Handbook
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
Copper clad aluminium (aluminum): frequently asked questions
What is copper clad aluminum?
Copper clad aluminum (CCA) is an aluminium core with a copper layer bonded to it metallurgically, not plated. It is produced as wire, busbar, plate, strip and foil, usually with 10 – 35 % copper by volume.
Is CCA as good as copper?
Not for DC resistance: CCA conducts roughly 64 – 75 % as well as copper, so a larger cross-section is needed for the same resistance. Its surface behaves like copper for soldering, crimping and bolting, and at radio frequencies it performs almost like solid copper.
How much lighter is CCA than copper?
Size for size, CCA with 10 – 35 % copper weighs about 37 – 55 % as much as copper. For the same resistance the saving is smaller, about 25 – 40 %, because the CCA section has to be larger.
Can CCA be soldered and crimped?
Yes. The copper surface accepts normal solders and crimp terminals. Avoid overheating during soldering and protect cut ends from moisture, where the aluminium core is exposed.
Is CCA cable allowed for building wiring?
Generally not. Most electrical codes and structured-cabling standards require solid copper (or approved aluminium) conductors for fixed building wiring and Ethernet cabling. CCA is used in coaxial cable, winding wire, busbar and specialised assemblies where it is specified and approved.
What copper ratio should I choose?
Wire is normally 10 % or 15 % copper. Busbar is commonly 20 – 30 %. Higher copper content raises conductivity and joint robustness, while lower content saves weight and cost. Match the ratio to the governing standard and your termination method.
Specifying copper clad aluminium?
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