Tinned round copper wire
Tinned round copper wire is a composite wire with a uniform layer of tin electroplated on the surface of pure copper. Due to copper’s high conductivity and tin’s solderability and corrosion resistance, it is a common material in electronic cables, electrical connectors, winding coils, and other fields. It comes in a wide range of diameters, from ultra-fine 0.02 mm to thick 10 mm copper wire. The tin coating thickness typically ranges from 1 to 8 microns. The base material is made of T2 or T3 copper or oxygen-free copper, with a tin coating purity of ≥99.0%. Bright or matte tin finishes are available depending on the application.
In terms of production technology, the manufacture of tinned round copper wire requires precision processes, including substrate pretreatment, electroplating, and post-processing. Substrate pretreatment includes degreasing, pickling, and electrolytic polishing. Organic solvents are used to remove surface oils and contaminants, followed by pickling with hydrochloric acid or sulfuric acid to remove the oxide film. Electrolytic polishing reduces the surface roughness of the copper wire to Ra ≤ 0.1μm, ensuring uniform adhesion of the tin coating. Electroplating typically uses either acid sulfate or alkaline tinning. Acid tinning is suitable for fine-diameter copper wire. The plating bath consists of stannous sulfate, sulfuric acid, and additives. The current density is 1-3A/dm², the temperature is 20-30°C, and the line speed is 15-40 m/min. Alkaline tinning is suitable for coarse-diameter copper wire. The plating bath contains sodium stannate and sodium hydroxide, resulting in a thicker coating. During the electroplating process, an online thickness monitoring system controls the coating thickness, with a deviation of ≤±0.3 μm. Post-processing includes cleaning, thermal diffusion treatment and coating. First, the residual plating solution is rinsed with deionized water. The thermal diffusion treatment is carried out at 150-200°C to form a small amount of copper-tin alloy layer with tin and copper to enhance the bonding strength. Finally, insulating paint or grease is applied as needed.
The performance advantages of tinned round copper wire make it irreplaceable in the field of electrical connections. First, excellent solderability. The tin coating has good fluidity and wettability, allowing for strong solder joints without the need for additional flux. With a weld strength of ≥ 15MPa, it is suitable for automated welding production lines. Second, excellent corrosion resistance. The tin coating forms an oxide film in the atmosphere, which resists minor corrosion. Its salt spray resistance can reach over 200 hours, 5-10 times that of pure copper wire. Third, excellent conductivity. Although the tin coating has a higher resistivity than copper, the thinner the coating is, the overall conductivity can still reach over 95% IACS, with little impact on current transmission. Fourth, excellent lubricity. The tin coating has a smooth surface with a friction coefficient of ≤0.2, which reduces friction damage during winding and improves production efficiency. Fifth, easy processing. Tinned round copper wire can be easily bent and twisted, with a minimum bend radius of up to 1 times the wire diameter, making it suitable for connectors with complex shapes.
Tinned round copper wire is a fundamental material in the electrical and electronics industry. In the field of electronic cables, the conductors of USB cables and data cables are often made of twisted tinned round copper wire with a diameter of 0.05-0.2 mm, leveraging its solderability to facilitate terminal soldering. In the field of electrical connectors, the pins of plugs and sockets use tinned round copper wire with a diameter of 0.5-2 mm to ensure conductivity and wear resistance during insertion and removal. In the field of motor windings, the stator windings of small motors use enameled tinned round copper wire with a diameter of 0.1-0.5 mm, balancing insulation and subsequent soldering requirements. In the field of power equipment, tinned round copper wire is used for contact leads of low-voltage switches and relays to improve connection reliability. In the field of automotive wiring harnesses, the copper conductors of in-vehicle wiring harnesses are often tinned to withstand the humid environment inside the vehicle and extend its service life. With the popularization of electronic devices, the application range of tinned round copper wire continues to expand.
Industry trends indicate that tinned round copper wire is moving toward ultra-fine diameters, lead-free manufacturing, and high uniformity. Breakthroughs in ultra-fine tinned copper wire production technology have enabled the stable production of wire with a diameter of 0.01 mm, suitable for the internal connections of microelectronic devices. Lead-free tinning processes (such as tin-silver-copper alloy plating) are replacing traditional pure tin plating, meeting RoHS environmental requirements while improving solder joint strength and high-temperature resistance. High-precision electroplating technology, through the use of pulse plating and a uniform flow field design, controls coating thickness deviations to within ±0.1 micron, enhancing product consistency. Furthermore, the promotion of green production processes, employing cyanide-free plating solutions and wastewater recycling systems, reduces environmental pollution and increases tin recovery rates to over 95%. With the development of industries such as 5G communications and new energy vehicles, demand for high-performance tinned round copper wire will continue to grow, driving the industry to achieve greater progress in process innovation and environmentally friendly production.
