A copper plating electrolyte for steel wire and a method for preparing copper-coated steel wire
Patent Information
- Application Number
- CN202611060576.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-16
- Publication Date
- 2026-09-29
AI Technical Summary
[0003]然而，现有的铜包钢线在生产过程中仍存在技术缺陷，受电场边缘效应及镀液流场不对称影响，线材表面的初始电流密度分布不均，导致铜离子沉积速率存在固有差异，因此，导致电镀铜层出现厚度不均、局部偏厚或偏薄的现象，对导电性有消极影响
该镀铜电解液为高铜离子浓度体系，满足在高电流密度下生产；通过聚乙二醇、聚二硫二丙烷磺酸钠和含有季铵基团的三苯甲烷类整平剂与季铵盐类聚合物整平剂的组合整平剂复配使用，实现在不同电流密度区域更精细的调控，从而获得更平整、致密的镀铜层，进而提高铜包钢丝的导电率和厚度均匀性。
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Figure CN122833673A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrolytic copper foil production technology, specifically to a copper-plating electrolyte for steel wire and a method for preparing copper-clad steel wire. Background Technology
[0002] Copper-clad steel wire, as a multi-metal composite wire, combines the excellent conductivity of copper wire, the high strength and good bending properties of steel wire, and the excellent corrosion resistance and high-temperature oxidation resistance of nickel plating. Copper-clad steel wire has gradually replaced traditional tin-plated copper wire and is widely used in electronic component leads, jumpers, terminals, and the core wires of radio frequency cables, becoming an indispensable and ideal conductor material in the communications, electronics, and power industries. The surface quality and thickness of the copper-clad steel wire directly affect its electrical performance and long-term reliability.
[0003] However, existing copper-clad steel wires still have technical defects in the production process. Affected by the edge effect of the electric field and the asymmetry of the plating solution flow field, the initial current density distribution on the wire surface is uneven, resulting in inherent differences in the copper ion deposition rate. Therefore, the electroplated copper layer exhibits uneven thickness, with some areas being too thick or too thin, which has a negative impact on conductivity. Summary of the Invention
[0004] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide a copper plating electrolyte for steel wire. By using a combination of polyethylene glycol, sodium polydisulfide dipropane sulfonate, and a leveling agent containing quaternary ammonium groups (triphenylmethane-based) and quaternary ammonium salt polymer leveling agents, more precise control can be achieved in different current density regions, thereby obtaining a smoother and denser copper plating layer, and thus improving the conductivity and thickness uniformity of the copper-clad steel wire.
[0005] To achieve the above-mentioned process effects, the technical solution of the present invention is as follows: a copper plating electrolyte for steel wire, wherein the electrolyte comprises copper sulfate pentahydrate with a concentration of 290~310g / L, sulfuric acid with a concentration of 75~85g / L, chloride ions with a concentration of 45~55mg / L, polyethylene glycol with a concentration of 5~6mg / L, an accelerator with a concentration of 0.8~1.5mg / L, a leveling agent with a concentration of 9~12mg / L, and water; The accelerator is sodium polydisulfide dipropane sulfonate; The leveling agent is a combination of a triphenylmethane leveling agent containing quaternary ammonium groups and a quaternary ammonium salt polymer leveling agent.
[0006] The preferred technical solution is that the mass ratio of the triphenylmethane leveling agent containing quaternary ammonium groups to the quaternary ammonium salt polymer leveling agent is (3~5):1.
[0007] The preferred technical solution is that the triphenylmethane leveling agent containing quaternary ammonium groups is Rhodamine B or Basic Blue 7.
[0008] A preferred technical solution is that the quaternary ammonium salt polymer leveling agent is obtained by nucleophilic substitution polymerization of dimethylaminoethyl ether and dichloroethyl ether.
[0009] A preferred technical solution is that the mass ratio of the dimethylaminoethyl ether to the dichloroethyl ether is (0.9~1):1.
[0010] A preferred technical solution is that the molecular weight of the polyethylene glycol is 7000~8000.
[0011] A preferred technical solution is that the electrolyte comprises copper sulfate pentahydrate with a concentration of 295-305 g / L, sulfuric acid with a concentration of 77-83 g / L, chloride ions with a concentration of 47-53 mg / L, polyethylene glycol with a concentration of 5-6 mg / L, an accelerator with a concentration of 0.8-1.5 mg / L, a leveling agent with a concentration of 9-12 mg / L, and water.
[0012] The second objective of this invention is to overcome the deficiencies in the prior art and provide a method for preparing copper-clad steel wire, comprising the following steps: S1: Prepare nickel-plated steel wire and copper-plated electrolyte; S2: After the nickel-plated steel wire is laid out, it is sequentially electroplated with copper-plating electrolyte, rinsed four times with water, and rinsed with hot water to obtain copper-clad steel wire.
[0013] The preferred technical solution is that the electroplating current density is 30~60A / dm². 2 .
[0014] The preferred technical solution is that the feeding speed of the nickel-plated steel wire is 15~20m / min.
[0015] The advantages and beneficial effects of this invention are as follows: The copper plating electrolyte is a high copper ion concentration system, which meets the requirements for production at high current densities. By using a combination of polyethylene glycol, sodium dithiodipropane sulfonate, and triphenylmethane leveling agents containing quaternary ammonium groups and quaternary ammonium salt polymer leveling agents, more precise control can be achieved in different current density regions, thereby obtaining a smoother and denser copper plating layer, which in turn improves the conductivity and thickness uniformity of the copper-clad steel wire. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of a cross-section of a measuring point of the copper-clad steel wire in Embodiment 1 of the invention; Figure 2 This is a schematic diagram of the cross-section of a certain measuring point of the copper-clad steel wire in Embodiment 8 of the invention. Detailed Implementation
[0017] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.
[0018] Configuration of nickel-plated steel wire After degreasing and pickling, stainless steel wire is immersed in a nickel plating electrolyte, which includes nickel aminosulfonate at a concentration of 30-80 g / L, nickel chloride at a concentration of 3-12 g / L, and boric acid at a concentration of 40-60 g / L, to obtain nickel-plated steel wire with a nickel plating layer thickness of 0.5-1.5 μm.
[0019] Copper plating electrolyte The electrolyte comprises copper sulfate pentahydrate at a concentration of 290-310 g / L, sulfuric acid at a concentration of 75-85 g / L, chloride ions at a concentration of 45-55 mg / L, polyethylene glycol at a concentration of 5-6 mg / L, an accelerator at a concentration of 0.8-1.5 mg / L, a leveling agent at a concentration of 9-12 mg / L, and water; wherein the accelerator is sodium polydithiopropane sulfonate.
[0020] The copper content in the copper pentahydrate is 25.6%, and the copper ion concentration is 74.24~79.36 g / L. A high copper ion concentration is beneficial for operation at high current densities and can increase the cathode limiting current density. If the copper sulfate concentration is too low, although the electrolyte dispersion is good, the current efficiency will decrease, and the copper plating layer will exhibit surface roughness and uneven color, negatively impacting the leveling performance, brightness, and density of the plating layer. If the copper sulfate concentration is too high, due to the excessively fast deposition rate, the copper plating layer will exhibit surface roughness, burrs, and copper sulfate crystal precipitation. Further, the copper ion concentrations are specified at points of 75 g / L, 76 g / L, 77 g / L, 78 g / L, and 79 g / L, as well as the range using these two points as the maximum and minimum values.
[0021] Sulfuric acid can improve the conductivity of a solution and maintain its stability. When the concentration of sulfuric acid is too low, it will reduce the dispersion and stability of the copper plating electrolyte, increase consumption and cause the pH value to rise, which will easily trigger Cu(OH)2 precipitation and make the surface of the copper plating layer rough and porous. When the concentration is too high, it will reduce the current efficiency and inhibit the diffusion of copper ions and additives to the cathode.
[0022] Chloride ions play a dual role in acidic copper plating systems: they synergistically form an inhibitory adsorption layer with polyethylene glycol and synergistically accelerate the process with sodium polydithiopropane sulfonate. When the chloride ion concentration in the copper plating electrolyte is too high, it leads to decreased current efficiency and faster accelerator consumption, thus affecting plating stability. Conversely, if the chloride ion concentration is too low, it may weaken its synergistic regulatory effect on additives, resulting in a rough copper plating layer surface, reduced gloss, and even defects such as particle deposition and scorching.
[0023] The concentration of polyethylene glycol (PEG) is controlled at a low level of 5-6 mg / L to allow it to synergistically cooperate with chloride and copper ions to form a thin but effective adsorption film on the wire surface, providing basic leveling. The inhibitory effect and adsorption behavior of PEG increase with increasing molecular weight. However, because PEG decomposes during electroplating, low molecular weight PEG molecules cannot effectively inhibit copper deposition, leading to plating solution failure. Therefore, the molecular weight of PEG is typically 7000-8000.
[0024] Sodium polydisulfide dipropanesulfonate competes with polyethylene glycol for adsorption, promoting copper deposition in microscopic low current density regions (such as depressions), thus achieving a "bottom-filling" effect. In copper foil preparation, it plays a role in controlling grain size and refining the coating. The sulfur-sulfur single bonds in the sodium polydisulfide dipropanesulfonate molecule break, transforming into two 3-mercapto-1-propanesulfonate sodium salt molecules. These 3-mercapto-1-propanesulfonate sodium salts can promote copper deposition under the influence of chloride ions.
[0025] In copper plating electrolyte, the leveling agent (which suppresses high current areas), polyethylene glycol (which forms a basic suppression layer), and accelerator (which promotes overall deposition) work synergistically. In high current areas, the leveling agent dominates the suppression, while in low current areas, polyethylene glycol mainly maintains basic suppression and allows the accelerator to play its role, thereby achieving uniform deposition.
[0026] Compound leveling agent The leveling agent is a compound of triphenylmethane leveling agent containing quaternary ammonium groups and quaternary ammonium salt polymer leveling agent; furthermore, the mass ratio of triphenylmethane leveling agent containing quaternary ammonium groups to quaternary ammonium salt polymer leveling agent is (3~5):1.
[0027] When depositing copper at high current density, the leveling agent needs to have sufficiently strong inhibition properties; otherwise, it is very easy to cause shrinkage defects (voids), and the surface smoothness and uniformity of the copper plating layer will decrease.
[0028] Among them, quaternary ammonium salt polymer leveling agents can both exert an inhibitory effect similar to that of inhibitors and possess the leveling effect of quaternary ammonium salts.
[0029] Quaternary ammonium salt polymer leveling agents are obtained by polymerizing di(dimethylaminoethyl) ether with dichloroethyl ether at a mass ratio of (0.9~1):1. Preparation of the quaternary ammonium salt polymer: Di(dimethylaminoethyl) ether is dissolved in deionized water to prepare a system concentration of 30%~35%, under which the reaction is more complete. The temperature is raised to 60℃, and then dichloroethyl ether is added dropwise, allowing the reaction to proceed fully for 7 hours.
[0030] The flexible COC linking units in quaternary ammonium salt polymer leveling agents can maintain the appropriate rigidity of the molecular chain, enhance the diffusion ability of polymer molecules, and enhance the directional coordination ability with copper ions. In electroplating, the quaternary ammonium salt cations and ether bonds can also form a stable electrostatic coupling with sodium polydisulfide dipropane sulfonate, which can improve the smoothness of electroplated copper.
[0031] The triphenyl structure of triphenylmethane leveling agents exhibits excellent performance in inhibiting copper deposition. Further examples of triphenylmethane leveling agents include Rhodamine B and Basic Blue 7. In Basic Blue 7, the phenyl and amino substitutions extend the occupied molecular orbitals to adjacent benzene ring regions, enhancing the molecule's electron-donating ability, which facilitates the adsorption of the leveling agent on the electrode surface. Meanwhile, the oxygen-containing functional groups in Rhodamine B contribute to improving the adsorption capacity of the leveling agent.
[0032] The working principle of triphenylmethane leveling agents is as follows: the triphenylmethane leveling agent molecules adsorbed on the electrode benefit from the abundant π electron cloud of the benzene ring, which can generate a strong interaction with the d orbitals of metal ions participating in the reduction reaction on the wire surface, thereby forming a strong coordination effect.
[0033] The combination of triphenylmethane leveling agents containing quaternary ammonium groups and quaternary ammonium salt polymer leveling agents allows for more robust adsorption on the wire surface due to the multiple active sites on the quaternary ammonium salt polymer chains. Under high current density, the electric field is stronger, and the consumption and desorption are faster. The stronger adsorption force maintains the leveling effect, and the polymer molecules can form a denser adsorption film on the wire surface, more effectively inhibiting copper deposition in high current density areas, thereby achieving leveling. The molecular weight of the triphenylmethane leveling agent differs from that of the quaternary ammonium salt polymer, resulting in different migration rates. In dynamic continuous production scenarios, the two complement each other to achieve more precise control over different current density areas, thereby obtaining a smoother and denser copper plating layer.
[0034] Example 1
[0035] The copper plating electrolyte for steel wire includes copper sulfate pentahydrate at a concentration of 300 g / L, sulfuric acid at a concentration of 80 g / L, chloride ions at a concentration of 50 mg / L, polyethylene glycol (molecular weight of 8000) at a concentration of 5.5 mg / L, sodium polydisulfide dipropane sulfonate at a concentration of 1.2 mg / L, leveling agent at a concentration of 10 mg / L, and water.
[0036] The leveling agent is a blend of a triphenylmethane-based leveling agent containing quaternary ammonium groups and a quaternary ammonium salt polymer leveling agent in a mass ratio of 4:1. The triphenylmethane-based leveling agent is Basic Blue 7.
[0037] Quaternary ammonium salt polymer leveling agents are obtained through nucleophilic substitution polymerization of dimethylaminoethyl ether and dichloroethyl ether at a mass ratio of 0.97:1. Dimethylaminoethyl ether is dissolved in deionized water to prepare a system concentration of 33%, under which the reaction is more complete. The temperature is raised to 60°C, and then dichloroethyl ether is added dropwise, allowing the reaction to proceed fully for 7 hours.
[0038] The preparation method of copper-clad steel wire includes the following steps: S1: Prepare nickel-plated steel wire and copper-plated electrolyte; S2: After the nickel-plated steel wire is unwound, it undergoes sequential electroplating with copper-plating electrolyte, four consecutive water rinses, and a hot water rinse to obtain copper-clad steel wire. The unwound speed of the nickel-plated steel wire is 16 m / min, and the electroplating current density is 30 A / dm³. 2 The temperature for the four-stage water wash is room temperature, and the conductivity of pure water is <40µs / cm; the temperature for the hot water wash is 90℃.
[0039] Example 2
[0040] Example 2 is based on Example 1, except that in the compound leveling agent, the triphenylmethane leveling agent is Rhodamine B, and the mass ratio of the triphenylmethane leveling agent containing quaternary ammonium groups to the quaternary ammonium salt polymer leveling agent remains unchanged. The production process parameters remain unchanged.
[0041] Example 3
[0042] Example 3 is based on Example 1, except that the copper plating electrolyte for the steel wire includes copper sulfate pentahydrate at a concentration of 290 g / L, sulfuric acid at a concentration of 75 g / L, chloride ions at a concentration of 45 mg / L, polyethylene glycol (molecular weight 8000) at a concentration of 5.5 mg / L, sodium polydithiopropane sulfonate at a concentration of 1.2 mg / L, a leveling agent at a concentration of 10 mg / L, and water. The production process parameters remain unchanged.
[0043] Example 4
[0044] Example 4 is based on Example 1, except that the copper plating electrolyte for the steel wire includes copper sulfate pentahydrate at a concentration of 310 g / L, sulfuric acid at a concentration of 85 g / L, chloride ions at a concentration of 55 mg / L, polyethylene glycol (molecular weight 8000) at a concentration of 5.5 mg / L, sodium polydithiopropane sulfonate at a concentration of 1.2 mg / L, a leveling agent at a concentration of 10 mg / L, and water. The production process parameters remain unchanged.
[0045] Example 5
[0046] Example 5 is based on Example 1, except that in the preparation of the quaternary ammonium salt polymer leveling agent, the mass ratio of dimethylaminoethyl ether to dichloroethyl ether is 1.1:1, while other components remain unchanged. The production process parameters remain the same.
[0047] Example 6
[0048] Example 6 is based on Example 1, except that the mass ratio of triphenylmethane leveling agent to quaternary ammonium salt polymer leveling agent is 3:1, while other components remain unchanged. The production process parameters remain the same.
[0049] Example 7
[0050] Example 7 is based on Example 1, except that the mass ratio of triphenylmethane leveling agent to quaternary ammonium salt polymer leveling agent is 6:1, while other components remain unchanged. The production process parameters remain the same.
[0051] Example 8
[0052] Example 8 is based on Example 1, except that the composition remains the same, and in step S2 of the method for preparing copper-clad steel wire, the electroplating current density is 60 A / dm. 2 Other production process parameters remain unchanged.
[0053] Comparative Example 1 Comparative Example 1 is based on Example 1, except that the leveling agent in the copper plating electrolyte for steel wire only includes triphenylmethane leveling agents containing quaternary ammonium groups, while other components remain unchanged. The production process parameters remain the same.
[0054] Comparative Example 2 Comparative Example 2 is based on Example 1, except that the leveling agent in the copper plating electrolyte for steel wire consists only of quaternary ammonium salt polymer leveling agents, while other components remain unchanged. The production process parameters remain the same.
[0055] Performance tests of copper-clad steel wire in the examples and comparative cases: 1. Conductivity: Take a 1m sample wire, measure the resistance value using a resistance tester, and find the corresponding temperature coefficient from the temperature coefficient table. Conductivity % = (1724.1 * temperature coefficient) / (wire diameter * wire diameter * 0.7854 * resistance value) * 100%.
[0056] 2. Copper plating thickness: Using metallographic microscopy (cross-section method), five measurement points were selected within any section of the copper-clad steel wire, and vertical cross-section processing was performed to calculate the overall average value H of the copper plating thickness at the five measurement points.
[0057] 3. Uniformity of copper plating thickness: Among the 5 test points, the maximum average value of copper plating thickness is A, the minimum average value of copper plating thickness is a, and the thickness deviation = (Aa) / (H*2)*100%.
[0058] The performance test results of the examples and comparative examples are as follows:
[0059] Compared to Example 1, Rhodamine B in Example 2 has a lower adsorption capacity and lower smoothness than Basic Blue 7. Therefore, the uniformity of the copper plating layer thickness decreases. The copper plating layer thickness of the resulting copper-clad steel wire decreases, and the conductivity also decreases.
[0060] Compared to Example 1, in Example 5, the excessively high content of dimethylaminoethyl ether in the synthesis of quaternary ammonium salt polymers led to an increase in the amount of reaction residue and the viscosity of the reaction system, which negatively affected the leveling performance of the polymer, and consequently also negatively affected the conductivity and thickness uniformity of the copper plating layer.
[0061] Compared to Example 1, Comparative Example 1 only includes triphenylmethane leveling agents containing quaternary ammonium groups and lacks quaternary ammonium salt polymer leveling agents. The copper plating electrolyte in this system has an imbalance in controlling the copper deposition rate, resulting in a poorer inhibition effect and a loose deposited copper plating layer, which in turn has a negative impact on the conductivity and thickness uniformity of the copper plating layer.
[0062] Compared to Example 1, Comparative Example 2 only included a quaternary ammonium salt polymer leveling agent. This was not conducive to suppressing copper deposition in high current density regions under high current density conditions, resulting in a reduced copper plating layer thickness and poor thickness uniformity. A combination of quaternary ammonium salt polymer leveling agents and triphenylmethane leveling agents containing quaternary ammonium groups (both macro and small molecules), along with accelerators and polyethylene glycol inhibitors, is necessary to achieve better leveling performance in the current density region.
[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A copper-plating electrolyte for steel wire, characterized in that, The electrolyte comprises copper sulfate pentahydrate at a concentration of 290-310 g / L, sulfuric acid at a concentration of 75-85 g / L, chloride ions at a concentration of 45-55 mg / L, polyethylene glycol at a concentration of 5-6 mg / L, an accelerator at a concentration of 0.8-1.5 mg / L, a leveling agent at a concentration of 9-12 mg / L, and water. The accelerator is sodium polydisulfide dipropane sulfonate; The leveling agent is a combination of a triphenylmethane leveling agent containing quaternary ammonium groups and a quaternary ammonium salt polymer leveling agent.
2. The copper plating electrolyte for steel wire according to claim 1, characterized in that, The mass ratio of the triphenylmethane leveling agent containing quaternary ammonium groups to the quaternary ammonium salt polymer leveling agent is (3~5):
1.
3. The copper plating electrolyte for steel wire according to claim 1 or 2, characterized in that, The triphenylmethane leveling agent containing quaternary ammonium groups is Rhodamine B or Basic Blue 7.
4. The copper plating electrolyte for steel wire according to claim 1 or 2, characterized in that, The quaternary ammonium salt polymer leveling agent is obtained by nucleophilic substitution polymerization of dimethylaminoethyl ether and dichloroethyl ether.
5. The copper plating electrolyte for steel wire according to claim 4, characterized in that, The mass ratio of the dimethylaminoethyl ether to dichloroethyl ether is (0.9~1):
1.
6. The copper plating electrolyte for steel wire according to claim 1, characterized in that, The molecular weight of the polyethylene glycol is 7000-8000.
7. The copper plating electrolyte for steel wire according to claim 1, characterized in that, The electrolyte comprises copper sulfate pentahydrate at a concentration of 295-305 g / L, sulfuric acid at a concentration of 77-83 g / L, chloride ions at a concentration of 47-53 mg / L, polyethylene glycol at a concentration of 5-6 mg / L, an accelerator at a concentration of 0.8-1.5 mg / L, a leveling agent at a concentration of 9-12 mg / L, and water.
8. A method for preparing copper-clad steel wire, characterized in that, Includes the following steps: S1: Prepare nickel-plated steel wire and copper-plated electrolyte; S2: After the nickel-plated steel wire is laid out, it is sequentially electroplated with copper-plating electrolyte, rinsed four times with water, and rinsed with hot water to obtain copper-clad steel wire.
9. The method for preparing copper-clad steel wire according to claim 8, characterized in that, In step S2, the electroplating current density is 30~60 A / dm². 2 .
10. The method for preparing copper-clad steel wire according to claim 8, characterized in that, In step S2, the feeding speed of the nickel-plated steel wire is 15~20m / min.