Copper Clad Aluminium Bus-bars (CCA) is a bimetallic composite conductor material with aluminum as the base and an outer copper layer. Through a specific process, a metallurgical bond at the copper-aluminum interface is achieved, combining the high conductivity of copper with the lightweight characteristics of aluminum.
Copper Clad Aluminium (CCA) busbars take full advantage of the excellent surface conductivity of copper (as current mainly flows due to the skin effect) while also utilizing the lightweight and cost-effective nature of aluminum.
Copper Clad Aluminium (CCA) busbars are used for efficient power distribution, combining copper’s high conductivity and aluminum’s lightweight advantages, and are widely applied in power, electronics, and transportation industries.
Copper Clad Aluminum Busbar Structure
- Outer Copper Layer: Electrolytic copper with a purity of ≥99.9%, typically covering 10%~30% of the total cross-section (e.g., 0.1~0.5mm), providing excellent conductivity and corrosion resistance.
- Inner Aluminum Core: Industrial pure aluminum (e.g., 1060 or 6063 alloy), accounting for 70%~90%, reducing weight and cost.
- Thickness: Copper layer varies (e.g., 10-20% of the cross-sectional area), balancing conductivity and cost.
- Bonding Process: Cold rolling, hot rolling composite, or continuous extrusion technology ensures a metallurgical bond at the copper-aluminum interface (atomic-level bonding) to prevent delamination.
The manufacturing processes include hydrostatic extrusion, rolling bonding, explosion welding, cladding welding, and solid-liquid thermal composite rolling, among which rolling technology enables efficient continuous production.
Copper Clad Aluminum Busbar Characteristics
- Electrical Performance: The copper surface ensures high conductivity, and the AC load capacity is close to 85% of pure copper busbars. A 10% increase in cross-section can achieve equivalent current carrying capacity. This design optimally utilizes the skin effect, where the outer copper layer carries most of the current.
- Lightweight: Aluminum’s density is only about 37-40% of copper, meaning that the same weight of CCA busbars can be 2-2.5 times longer than copper busbars.
- Strength and Flexibility: It has good tensile strength and elongation, ensuring durability during bending, cutting, or forming operations.
- Thermal Management: The combination of copper’s thermal conductivity and aluminum’s lower mass helps with efficient heat dissipation—crucial for high-current applications.
- Cost-Effectiveness and Sustainability: The cost is 30%-60% lower than pure copper busbars. Using less copper reduces material costs while maintaining performance. Lower resource consumption also contributes to a more environmentally friendly and sustainable electrical solution.
- Corrosion Resistance: The copper layer protects the aluminum core, reducing oxidation and creep risks, thereby extending service life.
Copper Clad Aluminum Busbar Technical Specifications (Typical Values)
| Parameter | Description |
| Current Capacity | Adjusted according to size and cladding ratio (e.g., 1000–5000 A). |
| Surface Treatment | Can be tin-plated or zinc-plated to enhance corrosion resistance. |
| Conductivity | The copper layer contributes about 80% of conductivity, with an overall conductivity reaching 65% of pure copper. |
| Current Carrying Capacity | 70%-80% of pure copper busbars for the same cross-section, requiring temperature rise testing for validation. |
| Weight | Density is approximately 3.63 g/cm³ (pure copper is 8.96 g/cm³), achieving a weight reduction of 50%-60%. |
| Temperature Adaptability | Operating temperature: -40℃~150℃. Due to differences in copper and aluminum thermal expansion coefficients, expansion gaps need to be designed (e.g., 1.5mm per meter reserved). |
| Standards | ASTM B566 (cladding material), IEC 61439 (switchgear). |
| Electrical Conductivity | Approximately 65% relative to pure copper, but due to surface current distribution, AC load performance is close to 85% of copper. |
| Density | Approximately 3.63 to 3.96 g/cm³. |
| Elongation | About 15% in the soft state. |
| Mechanical Strength | Tensile strength: 90~150 MPa (affected by the aluminum core). Bending radius should be ≥4 times the thickness to prevent cracking. |
Advantages of Copper Clad Aluminum Busbar
- Cost-Effectiveness: Copper-clad aluminum (CCA) busbar is cheaper than solid copper, with material costs 40% to 60% lower than pure copper, especially when copper prices are high.
- Lightweight: Compared to solid copper, the aluminum core reduces weight by approximately 30%.
- Enhanced Conductivity: Offers higher conductivity than pure aluminum (e.g., 65–70% IACS, with 10–20% copper cladding).
- Corrosion Resistance: The copper layer prevents aluminum oxidation, with the copper coating passing a 1000-hour salt spray test (ASTM B117).
- Skin Effect Efficiency: In AC applications, current primarily flows on the copper surface, improving performance.
- Thermal Management: Copper aids in heat dissipation, enhancing thermal stability.
- Energy Saving: Reduces energy consumption by 30% in transportation and improves installation efficiency by 20%.
Applications of Copper Clad Aluminum Busbar
CCA busbars are widely used in various fields, including:
- Power Systems: Transformer winding wire (saving 30% copper), busway (carrying capacity 600~5000A), substations, switchgear, grounding bars.
- New Energy: Photovoltaic inverter connectors (1000-hour salt spray resistance), electric vehicle battery busbars (35% weight reduction), solar/wind farms, battery systems.
- Rail Transit: Electric vehicles, high-speed rail pantograph sliders (0.3mm wear-resistant copper layer), subway busbars.
- Construction Industry: LED lighting conductive rails, data center power distribution systems (40% cost reduction compared to solid copper busbars).
- Industrial Equipment: Control cabinets, relay systems, and motor control centers.
Comparison of Copper Clad Aluminum Busbar with Other Materials
Comparison with Solid Copper Busbar
Compared to solid copper: lower cost, lighter weight, slightly reduced conductivity.
Advantages over pure copper busbars:
- Weight Reduction: CCA busbars are significantly lighter than pure copper busbars, making them easier to handle and install while reducing support and transportation costs.
- Cost Savings: Lower copper content significantly reduces material costs without greatly affecting conductivity.
- Performance Balance: While pure copper has slightly better conductivity, CCA busbars perform well in high-frequency and high-current applications due to the effective utilization of the copper surface.
Comparison with Solid Aluminum Busbar
Better conductivity and corrosion resistance, slightly higher cost.
- Conductivity: CCA busbars provide higher electrical conductivity, especially suitable for high-frequency and high-current load applications.
- Corrosion Resistance: The copper layer of CCA busbars offers superior resistance in corrosive environments, making them ideal for harsh conditions.
- Cost: While CCA busbars have better performance, they are more expensive. Solid aluminum busbars, with lower costs, are suitable for applications where high conductivity and corrosion resistance are not primary concerns.
Therefore, choosing between CCA busbars and solid aluminum busbars depends on the specific application:
If high conductivity and corrosion resistance are required, and a slightly higher cost is acceptable, CCA busbars are the better choice. If cost is the primary concern and the application environment is relatively mild, solid aluminum busbars offer an economical and practical solution.
Comparison of Oxygen-Free Copper and Copper Clad Aluminum
Choosing between oxygen-free copper and copper-clad aluminum requires considering factors such as conductivity, cost, weight, and corrosion resistance based on the specific application.
| Characteristic | Oxygen-Free Copper | Copper Clad Aluminum |
| Conductivity | Provides the highest conductivity, suitable for applications requiring extremely high conductivity. | Lower conductivity than oxygen-free copper but higher than solid aluminum busbars. |
| Corrosion Resistance | Superior corrosion resistance. | The copper layer provides good protection, suitable for most environments. |
| Cost | Higher cost, especially in large-scale applications. | Significantly lower cost than oxygen-free copper, ideal for cost-sensitive applications. |
| Weight | Heavier, higher density. | Lighter, suitable for weight-sensitive applications. |
| Manufacturing Complexity | Easier to process, simple production process. | More complex manufacturing process but still offers high cost-performance value. |
Copper-clad aluminum busbars achieve a clever balance between performance and cost-effectiveness. By combining the best properties of copper and aluminum, CCA busbars have become an excellent choice for modern high-performance electrical systems in industrial, commercial, and transportation applications.
CCA busbar specification and AC ampacity reference table
| ize(W×T)mm×mm | Current carring capacity(25℃)/A | ||||||||
| VPCu=20% | VPCu=25% | VPCu=30% | |||||||
| 50K | 65K | 75K | 50K | 65K | 75K | 50K | 65K | 75K | |
| 15.00×4.00 | 193 | 213 | 222 | 196 | 210 | 225 | 200 | 213 | 229 |
| 20.00×4.00 | 250 | 276 | 288 | 254 | 273 | 293 | 259 | 277 | 298 |
| 25.00×4.00 | 310 | 341 | 355 | 314 | 339 | 363 | 321 | 345 | 370 |
| 30.00×4.00 | 326 | 361 | 375 | 336 | 362 | 387 | 347 | 372 | 399 |
| 30.00×5.00 | 425 | 453 | 476 | 438 | 453 | 489 | 450 | 466 | 503 |
| 30.00×6.00 | 486 | 538 | 562 | 499 | 539 | 579 | 514 | 554 | 595 |
| 30.00×8.00 | 579 | 643 | 678 | 596 | 644 | 697 | 613 | 662 | 717 |
| 30.00×10.00 | 638 | 711 | 724 | 658 | 712 | 745 | 676 | 733 | 767 |
| 40.00×4.00 | 453 | 498 | 517 | 465 | 500 | 532 | 479 | 513 | 547 |
| 40.00×5.00 | 538 | 604 | 633 | 554 | 605 | 652 | 570 | 622 | 670 |
| 40.00×6.00 | 612 | 677 | 708 | 630 | 679 | 728 | 649 | 698 | 750 |
| 40.00×8.00 | 725 | 805 | 847 | 746 | 806 | 873 | 767 | 829 | 897 |
| 40.00×10.00 | 790 | 894 | 949 | 814 | 896 | 977 | 837 | 921 | 1005 |
| 50.00×5.00 | 665 | 735 | 765 | 684 | 736 | 788 | 703 | 758 | 810 |
| 50.00×6.00 | 755 | 836 | 872 | 777 | 836 | 898 | 799 | 861 | 923 |
| 50.00×8.00 | 891 | 989 | 1042 | 918 | 990 | 1072 | 944 | 1019 | 1103 |
| 50.00×10.00 | 969 | 1061 | 1107 | 998 | 1061 | 1139 | 1026 | 1092 | 1172 |
| 60.00×5.00 | 759 | 856 | 892 | 781 | 858 | 918 | 804 | 882 | 945 |
| 60.00×6.00 | 861 | 952 | 995 | 886 | 953 | 1025 | 911 | 980 | 1053 |
| 60.00×8.00 | 1011 | 1123 | 1182 | 1041 | 1124 | 1216 | 1070 | 1156 | 1252 |
| 60.00×10.00 | 1093 | 1215 | 1279 | 1125 | 1218 | 1318 | 1157 | 1253 | 1355 |
| 80.00×6.00 | 1081 | 1197 | 1250 | 1113 | 1198 | 1287 | 1145 | 1232 | 1323 |
| 80.00×8.00 | 1265 | 1405 | 1479 | 1302 | 1407 | 1523 | 1340 | 1448 | 1566 |
| 80.00×10.00 | 1362 | 1505 | 1583 | 1402 | 1507 | 1629 | 1442 | 1550 | 1676 |
| 100.00×6.00 | 1283 | 1419 | 1483 | 1320 | 1422 | 1527 | 1358 | 1462 | 1571 |
| 100.00×8.00 | 1504 | 1669 | 1758 | 1548 | 1672 | 1811 | 1593 | 1719 | 1862 |
| 100.00×10.00 | 1620 | 1790 | 1883 | 1668 | 1793 | 1938 | 1716 | 1844 | 1993 |
| 120.00×8.00 | 1740 | 1932 | 2035 | 1791 | 1935 | 2095 | 1842 | 1990 | 2154 |
| 120.00×10.00 | 1890 | 2090 | 2197 | 1946 | 2094 | 2261 | 2002 | 2153 | 2326 |
| 140.00×8.00 | 1996 | 2216 | 2333 | 2054 | 2218 | 2402 | 2114 | 2282 | 2471 |
| 140.00×10.00 | 2199 | 2447 | 2556 | 2264 | 2452 | 2631 | 2329 | 2522 | 2706 |
| 160.00×8.00 | 2223 | 2468 | 2599 | 2289 | 2472 | 2660 | 2354 | 2543 | 2753 |
| 160.00×10.00 | 2449 | 2718 | 2846 | 2521 | 2730 | 2929 | 2594 | 2809 | 3014 |
| 180.00×8.00 | 2465 | 2736 | 2882 | 2538 | 2740 | 2967 | 2611 | 2819 | 3053 |
| 180.00×10.00 | 2717 | 3023 | 3157 | 2796 | 3029 | 3250 | 2877 | 3116 | 3343 |
| 180.00×12.00 | 2816 | 3156 | 3297 | 2902 | 3165 | 3398 | 2989 | 3258 | 3498 |
| 200.00×8.00 | 2701 | 2998 | 3157 | 2784 | 3007 | 3255 | 2866 | 3095 | 3330 |
| 200.00×10.00 | 2980 | 3317 | 3463 | 3069 | 3324 | 3566 | 3159 | 3422 | 3671 |
| 200.00×12.00 | 3093 | 3464 | 3627 | 3187 | 3474 | 3734 | 3282 | 3577 | 3840 |
Copper-Clad Aluminum Busbar Manufacturing Process
- Continuous Extrusion: The aluminum core is extruded through a die while the copper strip is clad and cold-welded simultaneously, with a speed of up to 10m/min.
- Hot Rolling Composite: Copper and aluminum billets are heated to 500°C and rolled, with the interface diffusion layer thickness controlled between 5~10μm.
- Copper Plating: The aluminum busbar is electroplated with copper (thickness 0.05~0.2mm), offering low cost but weaker bonding strength.
Limitations of Copper-Clad Aluminum Busbar
- End Face Treatment: After cutting, tin plating or welding is required to seal the aluminum core to prevent galvanic corrosion (potential difference of 0.2V).
- High-Frequency Loss: Due to the skin effect, high-frequency resistance is 15%~25% higher than pure copper (>1MHz).
- Processing Requirements: Bending requires special molds (R radius ≥ 4T), and sharp right-angle bends are prohibited.
Selection and Usage Considerations for Copper-Clad Aluminum Busbars
How to Choose the Right Copper-Clad Aluminum Busbar
Selection and Usage Guidelines
Cross-Section Design: According to IEC 61558 standards, the current-carrying capacity must be derated by a factor of 0.8.
A. Key Parameter Selection
| Parameter | Description |
| Conductivity | Preferred Value: Choose models with conductivity ≥ 65% IACS (International Annealed Copper Standard), such as a nominal conductivity of 58 MS/m (approximately 85% IACS). |
| Application Scenario: For high-frequency applications (>1MHz), consider the skin effect and ensure the copper layer thickness is ≥ 0.2mm. | |
| Cross-Section Specification | Current-Carrying Capacity Calculation: Based on the formula I=K×S√(ΔT) (K is the material coefficient, 0.8~0.9 for copper-clad aluminum, 1.0 for pure copper). For example, a 100×10mm² busbar has a current-carrying capacity of approximately 2500A at a temperature rise of 40°C. |
| Copper Layer Quality | Thickness Inspection: Use an eddy current thickness gauge to verify the copper layer proportion (10%~30%). For example, a nominal 0.3mm copper layer must have an error within ±0.02mm. |
| Bonding Strength: Choose metallurgical bonding processes (cold rolling/hot rolling composite), ensuring interface bonding strength ≥ 50MPa (copper plating only 15~30MPa). |
B. Process and Certification
| Process Type | Advantages | Disadvantages | Application Scenarios |
| Cold Rolling Composite | Strong bonding strength, moderate cost | Low production efficiency | High-current industrial busbars |
| Hot Rolling Composite | Suitable for mass production | High energy consumption, copper layer prone to oxidation | Power transformer windings |
| Electroplating Method | Thin copper layer (0.05mm), low cost | Weak bonding, prone to peeling | Low-frequency low-voltage distribution boxes |
C. Application Scenario Matching
| Application Field | Selection Key Points | Case |
| New Energy Sector (Photovoltaic/Storage) | Salt spray resistance ≥ 1000 hours, copper layer thickness ≥ 0.25mm, recommended 6063 aluminum alloy core. | Photovoltaic inverter DC side using 120×8mm busbar, copper layer ratio 20%. |
| Rail Transit | Fatigue strength ≥ 120MPa, bending radius ≥ 6 times thickness, recommended continuous extrusion process. | High-speed rail pantograph slider using 0.5mm copper layer + 6082 aluminum core. |
What to Pay Attention to During Use
A. Installation and Connection
End Surface Treatment:
- After cutting, must be tin-plated/sprayed with conductive adhesive, sealing exposed aluminum core (to prevent galvanic corrosion).
- Laser cutting is recommended to avoid burrs (ordinary saw cutting requires additional chamfering).
Connection Method:
Bolt Connection: Use stainless steel or silver-plated bolts (anti-oxidation), torque adjusted according to cross-section:
| Bolt Specification | Recommended Torque (N·m) | Washer Requirement |
| M8 | 15~20 | Silver-plated copper washer + spring washer |
| M12 | 45~50 | Thickness ≥ 2mm, surface roughness Ra ≤ 1.6μm |
Welding:
- TIG welding (copper side): Use copper-silicon welding wire (e.g., ERCuSi-A), preheat temperature 200~250℃.
- MIG welding (aluminum side): Use Al-Mg welding wire (ER5356), shielding gas Ar ≥ 80%.
B. Environmental Adaptability
Temperature Compensation:
- Reserve expansion gap per meter: ΔL = α × L × ΔT (α copper-aluminum difference approx. 4×10⁻⁶/℃, ΔT is temperature difference).
- Example: For a 10-meter-long busbar with a temperature difference of 80℃, reserve gap 10×4×10⁻⁶×80×1000 = 3.2mm.
Anti-Corrosion Measures:
- Humid/salt spray environment: End section with heat shrink tubing (temperature resistance 125℃) + silicone sealant.
- Chemical corrosion environment: Surface coated with epoxy resin (thickness ≥ 50μm).
Special Installation Requirements
- Connectors: Use tin-plated or bimetallic terminal lugs to prevent electrochemical corrosion.
- Handling: Avoid damaging the copper layer to protect the aluminum core.
- Environment: Avoid moisture/chemical exposure unless well insulated.
Connection Method:
- Welding: Use TIG welding (copper side) or MIG welding (aluminum side) with Al-Cu transition welding wire.
- Bolt Connection: Use silver-plated washers, torque controlled within ±10% (e.g., M12 bolt 45N·m).
- Anti-Corrosion Measures: Apply epoxy resin or heat shrink tubing at terminals, periodic insulation check needed in humid environments.
Common Issue Responses
Issue 1: Overheated Joints
Solution: Retighten bolts (torque error ±5%), polish contact surface, then apply electrical compound grease.
Issue 2: Local Copper Layer Peeling
Solution: Clean and repair with cold-pressed Cu-Al transition sheet or local tin plating.
Issue 3: Vibration-Induced Fatigue Fracture
Solution: Install rubber damping pads, switch to flexible connections (e.g., braided transition segments).
Copper-clad aluminum busbars optimize material ratio and processing to balance cost and performance, particularly for weight-sensitive high-current scenarios. Proper installation and adherence to specifications, along with operational environment evaluation, ensure service life (typically designed for 20~30 years).
CCA busbars provide a balanced solution for applications prioritizing cost, weight, and efficiency. Their hybrid design addresses the limitations of pure metals, making them an ideal choice for modern electrical systems where both performance and economics are critical. Proper installation and maintenance ensure longevity and reliability.