Electroplating solution for reducing roughness of smooth surface of electrolytic copper foil and surface treatment method

Abstract

The invention belongs to the technical field of copper foil processing, and particularly relates to an electroplating solution for reducing the smooth surface roughness of an electrolytic copper foil and a surface treatment method, and the electroplating solution for reducing the smooth surface roughness of the electrolytic copper foil comprises the following components: 30-55 g / L of Cu < 2 + >, 60-110 g / L of H2SO4, 20-60 ppm of Cl <->, 3-20 ppm of a brightener, 2-10 ppm of a leveling agent, 5-15 ppm of a dispersion stabilizer, and the balance of water. According to the electroplating solution, the roughness of the smooth surface of the copper foil can be reduced, the rough surface and the smooth surface of the copper foil have the characteristic of ultralow roughness, signal transmission loss under high frequency can be effectively reduced when a circuit is prepared, and the electroplating solution is more suitable for transmission of high-frequency and high-speed signals.

Description

Technical Field

[0001] This invention relates to an electroplating solution and surface treatment method for reducing the surface roughness of electrolytic copper foil, belonging to the field of copper foil processing technology. Background Technology

[0002] With the rapid development of next-generation information technologies such as 5G / 6G communication, the Internet of Things (IoT), artificial intelligence (AI), and cloud computing, the demands of electronic devices for signal transmission speed and stability have significantly increased. High-frequency, high-speed circuits, as core components of modern electronic devices, directly affect signal transmission quality and efficiency. Against this backdrop, electrolytic copper foil, as a key material for high-frequency, high-speed circuit substrates, faces increasingly stringent performance requirements, especially in terms of surface roughness, which needs further optimization to meet the demands of high-frequency applications.

[0003] High-frequency, high-speed circuits are primarily used to process high-frequency signals and transmit data at high speeds. Their core design goal is to reduce signal loss and interference during transmission. Signal loss mainly stems from the skin effect and surface roughness of conductors. The skin effect refers to the concentration of current on the conductor's surface under high-frequency signals, while surface roughness exacerbates electromagnetic wave scattering and reflection, leading to a decrease in signal integrity. Therefore, reducing the surface roughness of copper foil is one of the core technical challenges in improving the performance of high-frequency, high-speed circuits.

[0004] Electrolytic copper foil typically consists of a smooth surface (S-surface, the surface in contact with the cathode roller) and a rough surface (M-surface). Currently, by optimizing the electrolyte additive formulation and controlling the copper ion deposition process, the microstructure of the rough surface can be improved, resulting in a uniform and dense crystalline structure, thereby achieving ultra-low roughness (e.g., the rough surface roughness Rz of HVLP copper foil can be controlled below 0.5 μm). However, for the smooth surface, although its initial roughness is low, it still needs to be further reduced in high-frequency and high-speed applications. Since the morphology of the smooth surface is directly affected by the surface condition of the cathode roller, and existing cathode roller manufacturing processes and polishing techniques cannot stably control the smooth surface roughness Rz below 1.0 μm, there is an urgent need to further develop new electroplating solutions and surface treatment processes to overcome this technical bottleneck. Summary of the Invention

[0005] The present invention aims to address the shortcomings in the performance of copper foil produced by existing copper foil production technology, and provides an electroplating solution and surface treatment method for reducing the surface roughness of electrolytic copper foil.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: One objective of this invention is to provide an electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising the following components: Cu 2+ 30-55g / L, H2SO460-110g / L, Cl- 20-60ppm, brightener 3-20ppm, leveling agent 2-10ppm, dispersant stabilizer 5-15ppm, the remainder is water.

[0007] The beneficial effects of the present invention are as follows: the above-mentioned electroplating solution of the present invention can reduce the roughness of the smooth surface of copper foil, so that both the rough and smooth surfaces of the copper foil have ultra-low roughness. The fabricated circuit can effectively reduce signal transmission loss at high frequencies and is more suitable for the transmission of high-frequency and high-speed signals.

[0008] Based on the above technical solution, the present invention can also be improved as follows: Furthermore, Cu 2+ 30-50g / L, H2SO480-100g / L, Cl - 30-50 ppm, brightener 6-15 ppm, leveling agent 4-8 ppm, dispersant stabilizer 8-12 ppm, the remainder is water.

[0009] Furthermore, the brightener is sodium polydisulfide dipropane sulfonate (SPS).

[0010] Furthermore, the leveling agent is acesulfame K (C4H4KNO4S).

[0011] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: Common acid copper leveling agents are mainly compounds containing nitrogen, sulfur, and other elements. The corresponding polar functional groups preferentially adsorb onto the microscopic protrusions on the surface of the copper foil, adjusting the microscopic uniformity of copper deposition. In this invention, acesulfame potassium is used as a leveling agent. Since acesulfame potassium is a six-membered heterocyclic compound containing both N and S elements, the sulfonyl group (-SO2-) and carbonyl group (-C=O) bonds in the molecule have high energy and are not easily broken. Compared with five-membered heterocyclic thiazole compounds, it has higher chemical stability and thermal stability. By selecting a leveling agent, this invention can more effectively reduce the roughness of the smooth surface of electrolytic copper foil, while ensuring the stability of the electroplating solution and the electroplating efficiency.

[0012] Furthermore, the dispersion stabilizer is polyoxyethylene ether.

[0013] Furthermore, the dispersant stabilizer is any one of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

[0014] The second objective of this invention is to provide a surface treatment process for reducing the surface roughness of electrolytic copper foil, using the aforementioned electroplating solution for reducing the surface roughness of electrolytic copper foil.

[0015] Furthermore, it specifically includes the following steps: Step S1: Pickling the electrolytic green foil; Step S2: Electroplating is performed using the electroplating solution described above for reducing the surface roughness of electrolytic copper foil, at a temperature of 35-50℃, preferably 40-45℃, and a current density of 8-35 A / dm. 2 Preferred A / dm 2 The electroplating time is 6-20 seconds, preferably 10-16 seconds.

[0016] Furthermore, in step S1, acid washing is performed using a sulfuric acid solution at a temperature of 20-35℃ for 8-20 seconds.

[0017] Furthermore, in step S2, the cathode is an electrolytic green foil, preferably an HVLP green foil, and the anode is a titanium-coated iridium dioxide foil, with the anode located on one side of the smooth surface of the electrolytic green foil.

[0018] The beneficial effects of this invention are as follows: After surface treatment of the electrolytic green foil, the surface roughness of the obtained electrolytic copper foil is reduced to below 1.0 μm, realizing the characteristic of ultra-low roughness on both sides of the copper foil. The fabricated circuit can effectively reduce signal transmission loss at high frequencies and is more suitable for the transmission of high-frequency and high-speed signals. Attached Figure Description

[0019] Figure 1 SEM image of the smooth surface of HVLP green foil; Figure 2 SEM image of the smooth surface of electrolytic copper foil after HVLP raw foil has undergone the process described in Example 1 of this invention; Figure 3 This is a schematic diagram of the continuous electroplating process of the present invention; Figure 4 This is a schematic diagram of the continuous electroplating process of the present invention. Detailed Implementation

[0020] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] Example 1 An electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising Cu 2+ 40g / L, H2SO4 90g / L, Cl - 30 ppm, sodium polydisulfide dipropane sulfonate 12 ppm, acesulfame potassium 8 ppm, nonylphenol polyoxyethylene ether 10 ppm, the remainder being pure water.

[0022] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 10% sulfuric acid pure aqueous solution at 20°C for 20 seconds.

[0023] Step S2, using HVLP copper foil as the cathode with the bright side facing down, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 40°C and a current density of 20 A / dm³. 2 Electroplating time: 12 seconds.

[0024] Example 2 An electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising Cu 2+ 35g / L, H2SO4 80g / L, Cl - 50 ppm, sodium polydisulfide dipropane sulfonate 15 ppm, acesulfame potassium 6 ppm, nonylphenol polyoxyethylene ether 8 ppm, the remainder being pure water.

[0025] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 16% sulfuric acid pure aqueous solution at 32°C for 14 seconds.

[0026] Step S2, using HVLP copper foil as the cathode with the bright side facing upwards, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 4 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 42°C and a current density of 15 A / dm³. 2 Electroplating time: 16 seconds.

[0027] Example 3 An electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising Cu 2+ 50g / L, H2SO4 100g / L, Cl - 35 ppm, sodium polydisulfide dipropane sulfonate 8 ppm, acesulfame potassium 8 ppm, fatty alcohol polyoxyethylene ether AEO-7 12 ppm, the remainder is pure water.

[0028] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 18% sulfuric acid aqueous solution at 35°C for 8 seconds.

[0029] Step S2, using HVLP copper foil as the cathode with the bright side facing down, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 45°C and a current density of 22 A / dm³. 2 Electroplating time: 15 seconds.

[0030] Example 4 An electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising Cu 2+ 40g / L, H2SO4 90g / L, Cl - 40 ppm, sodium polydisulfide dipropane sulfonate 6 ppm, acesulfame potassium 4 ppm, nonylphenol polyoxyethylene ether 10 ppm, the remainder being pure water.

[0031] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 12% sulfuric acid aqueous solution at 30°C for 10 seconds.

[0032] Step S2, using HVLP copper foil as the cathode with the bright side facing down, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 45°C and a current density of 30 A / dm³. 2 Electroplating time: 12 seconds.

[0033] Example 5 An electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising Cu 2+ 50g / L, H2SO4 80g / L, Cl - 40 ppm, sodium polydisulfide dipropane sulfonate 10 ppm, acesulfame potassium 6 ppm, nonylphenol polyoxyethylene ether 8 ppm, the remainder being pure water.

[0034] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 12% sulfuric acid aqueous solution at 26°C for 15 seconds.

[0035] Step S2, using HVLP copper foil as the cathode with the bright side facing upwards, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 4 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 42°C and a current density of 30 A / dm³. 2 Electroplating time: 10 seconds.

[0036] Example 6 An electroplating solution for reducing the surface roughness of electrolytic copper foil, comprising Cu 2+ 50g / L, H2SO4 80g / L, Cl - 40 ppm, sodium polydisulfide dipropane sulfonate 10 ppm, acesulfame potassium 6 ppm, nonylphenol polyoxyethylene ether 8 ppm, the remainder being pure water.

[0037] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 12% sulfuric acid aqueous solution at 26°C for 15 seconds.

[0038] Step S2, using HVLP copper foil as the cathode with the bright side facing upwards, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 4 (As shown in the image), electroplating is performed in the above-mentioned electroplating solution at a temperature of 45°C and a current density of 15 A / dm³. 2 Electroplating time: 14 seconds.

[0039] Comparative Example 1 An electroplating solution for reducing the surface roughness of electrolytic copper foil, wherein Cu 2+ 40g / L, H2SO4 90g / L, Cl - 30 ppm, sodium polydisulfide dipropane sulfonate 12 ppm, tetrahydrothiazolyl thione 8 ppm, nonylphenol polyoxyethylene ether 10 ppm, the remainder being pure water.

[0040] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 10% sulfuric acid pure aqueous solution at 20°C for 20 seconds.

[0041] Step S2, using HVLP copper foil as the cathode with the bright side facing down, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 40°C and a current density of 20 A / dm³. 2 Electroplating time: 12 seconds.

[0042] Comparative Example 2 An electroplating solution for reducing the surface roughness of electrolytic copper foil, wherein Cu 2+ 50g / L, H2SO4 100g / L, Cl - 35 ppm, sodium polydisulfide dipropane sulfonate 8 ppm, 2-mercaptobenzoimidazole 8 ppm, fatty alcohol polyoxyethylene ether AEO-7 12 ppm, the remainder being pure water.

[0043] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 18% sulfuric acid aqueous solution at 35°C for 8 seconds.

[0044] Step S2, using HVLP copper foil as the cathode with the bright side facing down, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 45°C and a current density of 22 A / dm³. 2 Electroplating time: 15 seconds.

[0045] Comparative Example 3 An electroplating solution for reducing the surface roughness of electrolytic copper foil, wherein Cu 2+ 50g / L, H2SO4 100g / L, Cl - 35 ppm, sodium polydisulfide dipropane sulfonate 8 ppm, 2-mercaptobenzoimidazole 8 ppm, fatty alcohol polyoxyethylene ether AEO-7 12 ppm, the remainder being pure water.

[0046] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 18% sulfuric acid aqueous solution at 35°C for 8 seconds.

[0047] Step S2, using HVLP copper foil as the cathode with the bright side facing down, and titanium-coated iridium dioxide as the anode, with the anode plate located on the bright side of the copper foil ( Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 35°C and a current density of 22 A / dm³. 2 Electroplating time: 15 seconds.

[0048] Comparative Example 4 An electroplating solution for reducing the surface roughness of electrolytic copper foil, wherein Cu 2+ 40g / L, H2SO4 90g / L, Cl - 40 ppm, sodium polydisulfide dipropane sulfonate 6 ppm, polyethyleneimine alkyl salt 4 ppm, nonylphenol polyoxyethylene ether 10 ppm, the remainder being pure water.

[0049] The surface treatment of HVLP green foil using the above electroplating solution is carried out by the following specific process steps: Step S1: Immerse the HVLP raw foil in a 12% sulfuric acid pure aqueous solution at 30°C for 10 seconds.

[0050] Step S2, the HVLP copper foil serves as the cathode with its bright side facing down, and the anode is titanium-coated iridium dioxide. The anode plate is located on the bright side of the copper foil. Figure 3 (As shown in the image) Electroplating is performed in the above-mentioned electroplating solution at a temperature of 45°C and a current density of 30 A / dm³. 2 Electroplating time: 12 seconds.

[0051] test Copper foil samples from Examples 1-6, copper foil samples from Comparative Examples 1-4, and HVLP green foil were used. The line roughness Rz of the smooth surface of the copper foil was tested using a non-contact laser confocal microscope OLS5000. The test data are shown in Table 1.

[0052] Table 1. Test results of smooth surface roughness of copper foil samples

[0053] Furthermore, adopt Figure 3 or Figure 4 The surface was continuously treated by electroplating in the corresponding electroplating solution for 10 minutes. Then, copper foil samples from Examples 1-6 and Comparative Examples 1-4 were taken, and the line roughness Rz of the smooth surface of the copper foil was tested using a non-contact laser confocal microscope OLS5000. The test data are shown in Table 2.

[0054] Table 2. Surface roughness data of copper foil samples (after 10 minutes of electroplating).

[0055] Table 1, comparing the surface roughness data of HVLP green foil samples from Examples 1-6, shows that surface treatment of the copper foil surface using the electroplating solution developed in this invention can effectively reduce the surface roughness of the electrolytic copper foil. Before treatment, the surface roughness Rz of the HVLP green foil was 1.276 μm, and from... Figure 1 SEM images show obvious textures on the smooth surface of the HVLP green foil. After surface electroplating treatment of the HVLP green foil using the electroplating solution developed in this invention, its surface roughness Rz can be reduced to below 0.6 μm, and from... Figure 2 SEM images show that the texture of the smooth copper foil surface has been filled in, resulting in lower roughness. The surface roughness data of the copper foil samples in Examples 1-6 and Comparative Examples 1-4 demonstrate that, compared to common acid copper leveling agents, acesulfame K has a stronger leveling ability, resulting in lower surface roughness of the electroplated copper foil after leveling.

[0056] Furthermore, Table 2 focuses on the chemical and thermal stability of acesulfame K as an acid copper leveling agent. In Table 2, after continuous electroplating for a period of time (10 min), the surface roughness data of the copper foil samples from Examples 1-6 and Comparative Examples 1-4 show that the surface roughness Rz of the samples from Examples 1-6 can be maintained within 0.7 μm, with little difference from the corresponding roughness data in Table 1; while the surface roughness of the samples from Comparative Examples 1-4 shows a significant increase compared to Table 1, and the increase is more pronounced at higher electroplating temperatures. Therefore, the acesulfame K used in this invention as a leveling agent exhibits better stability than commonly used acid copper leveling agents.

[0057] Lower roughness ensures that the fabricated electronic circuit products have lower losses when transmitting signals along the upper and lower surfaces of the copper foil at high frequencies and high speeds.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electroplating solution for reducing the surface roughness of electrolytic copper foil, characterized in that, It contains the following components: Cu 2+ 30-55g / L, H2SO4 60-110g / L, Cl - 20-60ppm, brightener 3-20ppm, leveling agent 2-10ppm, dispersant stabilizer 5-15ppm, the remainder is water.

2. The electroplating solution for reducing the surface roughness of electrolytic copper foil according to claim 1, characterized in that, Cu 2+ 30-50g / L, H2SO4 80-100g / L, Cl - 30-50 ppm, brightener 6-15 ppm, leveling agent 4-8 ppm, dispersant stabilizer 8-12 ppm, the remainder is water.

3. The electroplating solution for reducing the surface roughness of electrolytic copper foil according to claim 1 or 2, characterized in that, The brightener is sodium polydithiopropane sulfonate.

4. The electroplating solution for reducing the surface roughness of electrolytic copper foil according to claim 1 or 2, characterized in that... The leveling agent is acesulfame potassium.

5. The electroplating solution for reducing the surface roughness of electrolytic copper foil according to claim 1 or 2, characterized in that, The dispersion stabilizer is polyoxyethylene ether.

6. The electroplating solution for reducing the surface roughness of electrolytic copper foil according to claim 5, characterized in that, The dispersant stabilizer is any one of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

7. A surface treatment process for reducing the surface roughness of electrolytic copper foil, characterized in that, The electroplating solution for reducing the surface roughness of electrolytic copper foil as described in any one of claims 1-6 is used.

8. The surface treatment process for reducing the surface roughness of electrolytic copper foil according to claim 7, characterized in that, Specifically, the steps include the following: Step S1: Pickling the electrolytic green foil; Step S2: Electroplating is performed using the electroplating solution described above for reducing the surface roughness of electrolytic copper foil, at a temperature of 35-50℃ and a current density of 8-35 A / dm. 2 The electroplating time is 6-20 seconds.

9. The surface treatment process for reducing the surface roughness of electrolytic copper foil according to claim 8, characterized in that, In step S1, acid washing is performed using sulfuric acid solution at a temperature of 20-35℃ for 8-20 seconds.

10. The surface treatment process for reducing the surface roughness of electrolytic copper foil according to claim 9, characterized in that, In step S2, the cathode is an electrolytic green foil, and the anode is a titanium-coated iridium dioxide foil, with the anode located on one side of the smooth surface of the electrolytic green foil.

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