Detailed explanation of professional industry knowledge of flexible copper busbars

The flexible copper busbar is a flexible conductive component that is made up of multiple layers of ultra-thin copper foil or copper braid that are fused at the ends through diffusion welding, pressure welding or lamination processes. Its two ends are rigid connection areas that have been welded, and the middle area maintains inter-layer separation or a braided structure. Therefore, the whole body retains the inherent high conductivity of copper and obtains mechanical flexibility similar to a rope. Unlike traditional rigid copper busbars, flexible copper busbars do not rely on a single thickness of solid cross-section to carry current, but achieve the current-carrying function through a parallel combination of a large number of independent conductive units. The direct benefit of this structure is that it can be bent freely in multiple directions, and the minimum bending radius can usually reach about five times the thickness of the product itself, which is much smaller than the bending space required for rigid copper bars of the same cross-sectional area.

 

Distinguished from the cross-sectional shape, Round Braided Flexible Cords have a circular or elliptical cross-section, which is suitable for use in multi-angle free-bending situations, such as power transmission lines that need to rotate with the joints of robotic arms; while Flat Copper Braided Flexible Connectors have a flat strip-shaped cross-section, which is more advantageous in environments with limited space height but ample width, such as the interlayer connection between the internal power module of a photovoltaic inverter and the busbar capacitor. In addition, the name Braided Wire Flexible Copper emphasizes the craftsmanship of its braided structure - multiple strands of fine copper wires are cross-braided at specific pitches.

 

This structure has a better fatigue life than a laminated structure when subjected to reciprocating bending. For applications that require high-frequency bending or large swings, Round Stranded Flexible Cords, with its circular cross-section symmetry and isotropic bending characteristics, has become the preferred solution for connecting moving parts and fixed parts. In engineering practice, the length, end shape (flat, convex or with mounting holes), bending angle and surface treatment of flexible copper busbars can be customized according to the actual size and direction of the installation space, without being limited to standard straight section lengths or relying on complex bending molds like rigid copper busbars.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

There are two main forms of conductive base materials for flexible copper busbars: copper foil laminates and copper braided tapes. The material selection of both is based on high-purity electrical copper. For the laminated structure, electrolytic copper foil or rolled copper foil is used, with a copper content of ≥99.95% and a conductivity of ≥97% IACS. The thickness of the copper foil is usually between 0.03 mm and 0.3 mm, and the number of layers ranges from dozens to hundreds of layers. The total cross-sectional area determines the current carrying capacity of the product. For the braided structure, multiple strands of copper monofilaments with a diameter of 0.05 mm to 0.20 mm are twisted and braided. The braiding pitch and braiding density directly affect the flexibility and conductive cross-sectional area of ​​the product. In the production of Braided Wire Flexible Copper, the annealing state of the copper monofilament itself is crucial - hard copper wire is not flexible enough after braiding, and excessive annealing will lead to a decrease in strength, so it needs to be controlled within an appropriate range between semi-hard and soft.

 

For applications that require corrosion resistance or improved contact performance, Braided Tin Coated Copper Flexible Wire Connectors and Braided Tin Coated Copper Flexible Connectors are electroplated or hot-dip tinned after braiding or lamination is completed. The thickness of the tin layer is usually 3 μm to 10 μm. The surface of the tin-plated product is silver-white matte. The tin layer not only protects the copper matrix from oxidation, but also fills the microscopic gaps on the contact surface through plastic deformation during bolt tightening, reducing contact resistance. For round-section products such as Round Braided Stranded Flexible Cords and Round Stranded Flexible Cords, they are usually covered with an insulating sheath on the outer layer. The sheath material can be silicone rubber (temperature resistance -60°C to +200°C), polyvinyl chloride (temperature resistance -20°C to +70°C) or thermoplastic elastomer (oil and wear resistance). The color of the sheath can be distinguished according to phase sequence or circuit use.

 

In the actual application of Round Braided Flexible Cords, the wall thickness and material hardness of the sheath directly affect the bending radius and wear-resistant life of the product, and a reasonable selection needs to be made based on the risk of mechanical wear in the installation environment. For flat-section products such as Flat Copper Braided Flexible Connectors, since they are usually installed inside equipment and do not involve direct contact by personnel, they are in most cases supplied in the form of bare copper, and the ends are tinned or nickel-plated only when connected to aluminum terminals.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flexible copper busbars adopt differentiated manufacturing processes according to different structural forms. For laminated structure products, the core process is diffusion welding or pressure welding - multiple layers of thin copper foil are neatly stacked together according to the designed number of layers, fixed at both ends with special clamps, and sent into a diffusion welding furnace to be heated to near the copper recrystallization temperature (about 700°C to 850°C). At the same time, pressure is applied to the ends of the stack through the hydraulic system. Under the combined action of high temperature and pressure, atoms at the copper foil contact interface diffuse to each other to form a metallurgical bond. After welding is completed, the end becomes a dense copper block, whose mechanical properties and electrical conductivity are basically equivalent to the original copper material. Then the mounting holes are punched in the welding area according to the drawings, and the ends are milled, chamfered and other finishing processes are performed. For products that need to be bent into L-shape, Z-shape or arc shape, special molds are used for cold bending after welding is completed.

 

For braided structural products, the process starts with wire drawing - copper rods are drawn to copper monofilaments of the required diameter, which are annealed and twisted to form strands, and then the multiple strands are cross-braided at a set pitch on a braiding machine to form a tubular or ribbon braid. After braiding is completed, both ends are formed into rigid terminals through pressure welding or copper powder sintering process, and then the mounting holes are punched according to the drawings. For Round Braided Flexible Cords and Round Stranded Flexible Cords, the braided or stranded semi-finished products need to be wrapped with an insulating sheath through an extrusion or wrapping process. The sheath material is extruded through high-temperature melting and tightly adhered to the outer layer of the braid. After cooling, a uniform insulating layer is formed. For products that require tin plating, Braided Tin Coated Copper Flexible Wire Connectors and Braided Tin Coated Copper Flexible Connectors enter the electroplating process after weaving or lamination. First, degreasing and pickling are performed to remove surface oxides, and then electroplating or hot-dip tin plating is performed in a plating solution containing tin ions. After plating, pure water cleaning and drying are required.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flexible copper busbars have formed a mature application paradigm in many industrial fields. In the field of new energy, the DC connection between the photovoltaic inverter and the battery energy storage system is a typical scenario - the current output by the photovoltaic array enters the inverter through the combiner box, and the battery pack will expand and contract in the direction of the cell thickness during the charge and discharge cycle. At the same time, temperature changes inside the battery pack will also cause relative displacement of the connection points. The use of Copper Stranded Flexible Connection can effectively absorb this part of the displacement without causing stress on the pole terminals. In wind power converters, power modules need to be pulled out regularly for maintenance and inspection. Rigid connections cannot meet the requirements of the pull-out stroke, while flexible connections allow the modules to maintain electrical connectivity after being pulled out a certain distance on the slide rails.

 

After maintenance is completed, they can be pushed back to restore their original state. In the field of rail transit, the elastic power supply connection between the pantograph and the electrical equipment on the roof of the carriage is another mature application - the pantograph needs to swing with the height change of the catenary during the lifting process, and the vibration and shock during train operation also continue to act on the connection point. Braided Tin Coated Copper Flexible Wire Connectors have become a standard configuration in this scenario due to their fatigue resistance and anti-vibration characteristics. In addition, the jumper cables between train cars also use a large number of Round Braided Stranded Flexible Cords with circular cross-sections to withstand repeated bending without breaking when the couplers are connected and separated. In the field of smart manufacturing, industrial robots require continuous power transmission at the joints of their manipulators, and the range of motion of the joints often exceeds 180 degrees. Round Stranded Flexible Cords can be used to integrate power lines and signal lines into compact circular sheaths that bend as the joints rotate. At the same time, the flexibility provided by the braided structure ensures that the conductive cross-sectional area is not reduced after tens of thousands of operating cycles.

 

In the field of data centers, in power distribution solutions between dense cabinets, Braided Wire Flexible Copper is used to connect the bus ducts or power distribution units of adjacent cabinets. Its flexible characteristics allow the cabinets to be adjusted in position or replaced without having to re-make the connection row. The on-site installer only needs to make appropriate bends according to the actual deviation to complete the assembly. For outdoor or humid environments that require additional corrosion resistance, Braided Tin Coated Copper Flexible Connectors effectively delay the oxidation process by coating the surface of the copper braid with a tin layer. At the same time, the tin layer can also improve the contact performance with copper terminals or aluminum terminals.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We can provide customized design and sample production of CU Flex Busbar based on your installation space, current carrying requirements and bending frequency, ensuring that each product accurately matches your equipment terminals. You are welcome to provide installation space sketches or fault descriptions of existing rigid connections, and our application engineers will give suggestions for flexible modifications.