Cutting
Shear or saw like copper. The cut face exposes aluminium, so keep cut ends away from damp zones or seal them with lacquer, heat-shrink or a plated cap.
Bimetallic busbar
Copper Clad Aluminium Bus Bar
A copper clad aluminium (CCA) bus bar is a rectangular aluminium conductor fully sheathed in a bonded copper layer, typically 20 – 30 % copper by volume. It bolts, plates and terminates like a copper bar while weighing well under half as much size for size. Metline supplies CCA busbar to ASTM B1005 for switchgear, busway, earthing and battery systems worldwide, with test certificates for bond, conductivity and dimensions.
- Copper content
- 20 %, 25 %, 30 % by volume
- Classes
- Annealed (A) and hard (H)
- Typical size
- 3 – 12 mm × 10 – 200 mm
- Standard
- ASTM B1005
What a CCA bus bar is
In a CCA bus bar the copper wraps the whole perimeter of the aluminium core, including the edges, and is bonded to it along its full length. This is different from a plated aluminium bar, where a few microns of tin or copper sit on the surface, and from a roll-bonded plate, where only the faces are clad. Because the sheath is continuous, every surface the installer touches, drills near or bolts against is copper.
The bar is usually produced by casting or cladding aluminium inside a copper shell and then rolling or drawing the composite to its final rectangular section. Annealing after working builds the metallurgical bond and sets the temper. The copper fraction is fixed by the starting geometry and stays the same through all later reductions, so a 25 % bar is 25 % copper at any size.
The aim is a busbar that can drop into a copper design with minimal change to terminals, hardware and assembly practice, while removing a large part of the copper weight and cost. It is an established alternative to copper in low-voltage switchgear, distribution boards, busway, earthing systems, data-centre power distribution and battery energy storage.
CCA bus bar specification
Typical specification
- Standard
- ASTM B1005 (copper-clad aluminium bar for electrical purposes); other specifications by agreement
- Copper content
- 20 %, 25 % or 30 % by volume (ASTM B1005 classes 20, 25, 30); other ratios by agreement
- Temper / class
- A = annealed (soft, for bending and forming); H = hard (higher strength, straight runs)
- Core aluminium
- 1060 or 1070 (EC-grade aluminium on request)
- Cladding copper
- C11000 (Cu-ETP), equivalent to T2; C10200 on request
- Thickness
- About 3 – 12 mm
- Width
- About 10 – 200 mm, depending on thickness
- Edges
- Rounded or full-radius edges; copper continuous around the edges
- Lengths
- Straight lengths such as 3 m or 4 m, cut lengths and fabricated parts to drawing
- Surface
- Bare copper, electro-tinned, nickel- or silver-plated
Exact size limits depend on the copper ratio and production route; confirm the section you need when you enquire.
ASTM B1005 defines the bar by copper volume and temper class and sets requirements for tensile and bend properties, interface bonding, density, resistivity, dimensional tolerances, inspection and packaging. Order to the standard and the certificate will report each of these against its limits.
Density, conductivity and weight by copper ratio
The table shows calculated values for the three ASTM B1005 copper contents and, for comparison, a lower and higher ratio.
| Copper by volume | Density (g/cm³) | Weight vs copper, same size | Calculated conductivity | Area needed vs copper, same resistance | Weight vs copper, same resistance |
|---|---|---|---|---|---|
| 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.
Two practical points come out of the numbers. Size for size, a CCA bar has about 1.4 – 1.45 times the resistance of copper, so for the same current and temperature rise the section must normally be enlarged, either by a wider bar or an extra bar in parallel. Even after that enlargement, a 25 % CCA bar weighs only about two thirds of the copper it replaces. Annealed bar conducts slightly better than hard bar of the same ratio.
Common sizes: weight and DC resistance (25 % copper)
Calculated for 25 % copper bar. Weights include the copper sheath. Use these figures for first sizing and weight estimates; ratings for an assembly must be confirmed by temperature-rise calculation or test.
| Size (mm) | Area (mm²) | CCA weight (kg/m) | Copper bar weight (kg/m) | CCA DC resistance at 20 °C (µΩ/m) | Copper DC resistance (µΩ/m) |
|---|---|---|---|---|---|
| 20 × 4 | 80 | 0.34 | 0.71 | 305 | 216 |
| 30 × 5 | 150 | 0.64 | 1.33 | 162 | 115 |
| 40 × 5 | 200 | 0.85 | 1.78 | 122 | 86 |
| 50 × 5 | 250 | 1.06 | 2.22 | 97 | 69 |
| 40 × 10 | 400 | 1.70 | 3.56 | 61 | 43 |
| 60 × 10 | 600 | 2.55 | 5.33 | 41 | 29 |
| 80 × 10 | 800 | 3.40 | 7.11 | 30 | 22 |
| 100 × 10 | 1000 | 4.25 | 8.89 | 24 | 17 |
| 120 × 10 | 1200 | 5.10 | 10.67 | 20 | 14 |
Ampacity tables published by producers are usually based on a single bar in free air at 25 – 35 °C ambient with a stated temperature rise (for example 50, 65 or 75 K). They are useful for comparison but are not a substitute for design verification, because enclosure, spacing, orientation and the number of parallel bars all change the result. As a first rule, a CCA bar of the same width as an existing copper bar and about 40 % greater thickness, or the same thickness and about 40 % greater width, will have similar resistance.
Cutting, punching, bending and jointing CCA bus bar
Punching and drilling
Standard copper tooling works. Hole walls show aluminium but carry little current; the joint current passes through the copper faces under the washer.
Bending
Use annealed (A) class for flat-wise and edgewise bends. A generous inside radius, typically at least one to two times thickness flat-wise, protects the copper layer from thinning or cracking.
Bolted joints
Prepare and torque joints as for copper. Use disc-spring washers to maintain contact pressure, since the aluminium core expands more and creeps more than copper.
Plating
Tin, nickel and silver plate onto the copper surface by normal processes. Tinning is common for humid or polluted sites.
Heat
Avoid brazing, welding and long exposure to high temperature. Heat grows brittle intermetallics at the interface; mechanical or friction-welded terminations are preferred.
Insulation methods used on copper bar, such as epoxy powder coating and heat-shrink sleeving, apply to CCA unchanged. Because the bar is lighter, supports and insulators can sometimes be reduced, but short-circuit forces depend on current and spacing, not bar weight, so bracing must still be checked.
Where CCA bus bar is used
| Application | Why CCA works | Typical spec |
|---|---|---|
| Low-voltage switchgear and distribution boards | Copper joints with lower bar weight and cost | 25 – 30 %, H class for straight runs, A class for bent droppers |
| Busway / bus duct | Long conductor runs where weight and cost add up | 20 – 25 %, tinned or silver-plated joint areas |
| Earthing and equipotential bars | Copper surface for lugs and clamps | 20 – 30 %, often tinned |
| Battery energy storage and UPS | Lighter interconnects with copper terminals | 25 – 30 %, nickel- or tin-plated |
| Transformer and rectifier connections | Copper terminations on equipment, aluminium-like weight | 30 % |
| Data-centre power distribution | High-current busbars over long distances | 20 – 30 % |
A typical retrofit uses CCA for the main horizontal busbars of a switchboard, where lengths are longest, while short droppers and breaker connections may stay in copper or move to annealed CCA bent to shape. For a full comparison of options, see our copper vs aluminium vs CCA busbar article and the copper busbar guide.
Inspection and testing
- Copper ratio: measured on a polished cross-section; sheath thickness checked on faces and edges.
- Bond integrity: bend, twist or peel tests to the order specification; no separation at the interface.
- Resistivity: DC resistance of a measured length, corrected to 20 °C, against the class minimum.
- Mechanical properties: tensile strength and elongation for the A or H class.
- Dimensions and edges: thickness, width, edge radius, straightness and twist.
- Surface: free of cracks, laps, blisters and exposed aluminium on faces and edges.
- Documents: EN 10204 3.1 certificate, packing list and, on request, third-party inspection.
How to order CCA bus bar from Metline
- SpecifyCopper ratio, class (A or H), thickness, width, length or drawing, plating and quantity, plus the standard (ASTM B1005 or your own specification).
- ReviewWe check the section against the copper design it replaces and confirm resistance and weight.
- QuotePrice, test plan and delivery terms (EXW, FOB, CIF or DAP).
- Inspect and packBars are inspected, interleaved to protect the copper surface and packed in wooden cases for export.
- ShipBy sea or air with the test certificate and packing list.
References and standards
- ASTM B1005 – Standard Specification for Copper-Clad Aluminum Bar for Electrical Purposes (Bus Bar)
- ASTM B187/B187M – Standard Specification for Copper Bar, Bus Bar, Rod, and Shapes
- IEC 61439-1 – Low-voltage switchgear and controlgear assemblies: general rules
- The Aluminum Association – Aluminum Electrical Conductor Handbook
Copper clad aluminium (aluminum) bus bar: FAQ
What standard covers copper clad aluminum bus bar?
ASTM B1005 covers copper-clad aluminium bar for electrical purposes. It defines 20, 25 and 30 % copper classes in annealed (A) and hard (H) conditions and sets requirements for bonding, resistivity, mechanical properties and tolerances.
How does CCA busbar compare with copper busbar?
Size for size, a 25 % CCA bar weighs about 48 % as much as copper and has about 1.4 times the DC resistance. For equal resistance the CCA section is enlarged by about 40 %, and it then weighs about two thirds of the copper bar.
Can CCA busbar be bent?
Yes. Order annealed (A) class for bending and use an inside radius of at least one to two times the thickness for flat-wise bends. Hard (H) class is intended for straight runs.
Do the drilled holes expose aluminium?
The hole wall shows aluminium, but the joint current flows through the copper faces clamped under the bolt and washer. Use disc-spring washers and, in damp locations, a tinned surface and sealed cut ends.
Can CCA busbar be welded or brazed?
It is not recommended. High temperatures grow brittle copper-aluminium intermetallics at the interface. Use bolted, clamped or friction-welded terminations.
Which copper ratio should I choose?
25 % is a common balance. Choose 30 % where joints are numerous or the bar runs hot, and 20 % where weight and cost are the priority and the section can be made larger.
Ready to switch to CCA bus bar?
Send the copper sizes you use today and your quantity. We will propose equivalent CCA sections and quote with certificates and export packing.
