Preparation method of electrolytic copper foil and electrolytic copper foil

Abstract

The invention discloses a preparation method of an electrolytic copper foil and the electrolytic copper foil, and belongs to the technical field of preparation of electrolytic metal foils. The preparation method of the electrolytic copper foil comprises the following steps: (1) mixing a solution A, hydrochloric acid and a thiourea additive to obtain an electrolyte; (2) performing electrochemical deposition on the electrolyte to prepare an electrolytic copper foil; the solution A is composed of copper sulfate and sulfuric acid; the thiourea additive is selected from trimethyl thiourea, tetramethyl thiourea or N-methyl thiourea. According to the preparation method, the microstructure, the surface appearance, the mechanical property and the electrochemical property of the copper foil are controlled by adopting a single thiourea additive, so that the electrolytic copper foil is good in structural stability and excellent in performance.

Description

Technical Field

[0001] This invention relates to the field of electrolytic metal foil preparation technology, and more particularly to a method for preparing electrolytic copper foil and the electrolytic copper foil itself. Background Technology

[0002] As 5G communication base stations, artificial intelligence servers, new energy vehicle electronic control systems, and high-end electronic devices continue to evolve towards higher frequencies, higher power densities, and miniaturization, they place increasingly stringent demands on the current carrying capacity, heat dissipation efficiency, and long-term reliability of printed circuit boards (PCBs). Especially in applications involving high-current, high-frequency signal transmission, PCBs not only need to withstand higher current densities and Joule heating but also must cope with the thermomechanical stress caused by repeated power cycles. Therefore, electrolytic copper foil, a key conductive material and heat dissipation path for PCBs, is rapidly developing towards a comprehensive improvement in performance, including higher thickness (≥60 µm), higher strength (tensile strength ≥600 MPa), good ductility (elongation ≥5%), and excellent high-temperature stability (resistance to high-temperature softening). This type of high-performance thick copper foil aims to meet the structural stability and electrical durability requirements of high-power modules, high-current multilayer wiring, and high-temperature operating conditions, providing a fundamental material guarantee for achieving high reliability and long-life operation of equipment.

[0003] Currently, the industry commonly employs an acidic electrolytic system with copper sulfate as the main salt in the preparation of conventional thick copper foil, and heavily relies on composite additive technology to control the crystal structure, surface morphology, and mechanical properties of the copper foil. Mainstream processes often utilize the compounding and synergistic effects of multiple additives, such as brighteners (e.g., sulfur-containing organic compounds), leveling agents (e.g., nitrogen-containing polymers), and positioning agents (e.g., polyether surfactants), to achieve control over the refinement of copper foil grains, densification of the structure, and mechanical strengthening. While this technical route is relatively mature and can increase the tensile strength of thick copper foils with a thickness of 60-105 µm to the 400-550 MPa range, its inherent limitations are fully apparent when facing ultra-high strength requirements above 600 MPa. These limitations mainly include: the mutual constraints of the additive mechanisms make it difficult to simultaneously achieve strength and ductility; under high current density and long-term electrodeposition conditions, the additives lack stability and are prone to decomposition, generating organic impurities that contaminate the electrolyte; and the existing system's ability to control the internal stress accumulation of thick foil is nearing its limit, easily leading to increased copper foil brittleness and the risk of cracking during subsequent processing.

[0004] Therefore, developing new additive systems or innovating electrodeposition processes has become an urgent technological direction to break through the current performance bottleneck of thick copper foil and meet the needs of future high-end applications. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing electrolytic copper foil and the electrolytic copper foil itself. The preparation method uses a single additive to achieve good structural stability and excellent performance of the electrolytic copper foil.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing electrolytic copper foil, comprising the following steps:

[0008] (1) Mix solution A, hydrochloric acid and thiourea additives to obtain an electrolyte;

[0009] (2) Electrolytic copper foil was prepared by electrochemical deposition of the electrolyte;

[0010] Solution A is composed of copper sulfate and sulfuric acid;

[0011] The thiourea additives are selected from trimethylthiourea, tetramethylthiourea, or N-methylthiourea.

[0012] During the deposition of thick copper foil, the accumulation of internal stress is the core problem leading to embrittlement, warping, and even cracking of the copper foil. The thiourea additive described in this invention selectively adsorbs and reacts at the interface on the cathode surface of electrochemical deposition. The adsorption layer formed can act as a "buffer interface," regulating the arrangement and matching of the crystal lattice during growth, effectively releasing some of the deposition stress, and thus finely controlling the electrocrystallization process of copper ions, thereby optimizing the microstructure, surface morphology, and overall performance of the copper foil.

[0013] By optimizing the concentration of thiourea additives, the strength of electrolytic copper foil can be improved while avoiding excessive increase in internal stress, thereby balancing the strength and ductility of electrolytic copper foil to a certain extent and preventing excessive embrittlement of the copper foil.

[0014] Preferably, the effective concentration of the thiourea additive in the electrolyte is 10-15 mg / L; in some specific embodiments of the present invention, it is preferably 10 mg / L or 15 mg / L.

[0015] The effective concentration refers to the concentration that actually exerts its effect.

[0016] Preferably, the concentration of copper ions in the electrolyte is 90~105 g / L; more preferably, it is 90 g / L.

[0017] The electrolyte contains 100-130 g / L sulfuric acid; more preferably 110 g / L.

[0018] In a further preferred embodiment of the present invention, the electrolyte has a copper ion concentration of 90 g / L, a sulfuric acid content of 110 g / L, and an effective concentration of thiourea additives of 10 mg / L or 15 mg / L.

[0019] In a preferred embodiment of the present invention, according to the preparation method of claim 1, the chloride ion content in the electrolyte is 10-30 mg / L; more preferably 16-24 mg / L; and even more preferably 21 mg / L.

[0020] Preferably, the mixing temperature in step (1) of this invention is 50°C to 60°C; more preferably, it is 53°C.

[0021] Preferably, in step (2) of this invention, the current density of electrochemical deposition is 40~50 A / dm³. 2 More preferably 45 A / dm 2 .

[0022] Preferably, the method for preparing the electrolytic copper foil of the present invention includes the following steps:

[0023] 1) Mixing metallic copper with sulfuric acid yields an electrolyte composed of copper sulfate and sulfuric acid;

[0024] 2) The electrolytic copper foil is prepared by mixing the thiourea additive solution, hydrochloric acid solution and the electrolyte and then electrochemically depositing the mixture.

[0025] Preferably, the preparation of the electrolytic copper foil is carried out using an electrolytic foil-making machine.

[0026] Electrolytic copper foil production equipment enables continuous, high-precision, and low-energy-consumption large-scale production of electrolytic copper foil. Simultaneously, it ensures stable performance and controllable quality of the electrolytic copper foil, meeting the demands of high-end applications for high-performance copper foil.

[0027] When preparing electrolytic copper foil using an electrolytic foil-making machine, the method for preparing the electrolytic copper foil includes the following steps:

[0028] 1) Add metallic copper to a tank containing sulfuric acid, and fill the tank with air using a blower to dissolve the copper and obtain an electrolyte composed of copper sulfate and sulfuric acid. After multi-stage filtration and purification and temperature adjustment by a heat exchanger, the concentration of copper ions, sulfuric acid, and electrolyte temperature in the electrolyte reach the specified conditions.

[0029] 2) Thiourea additive solution and hydrochloric acid solution are introduced into the raw foil electrolyte at a certain flow rate through a metering pump. Copper foil is obtained by electrolysis under a certain current density and a suitable linear velocity.

[0030] The present invention also provides an electrolytic copper foil, which is prepared by the above-described preparation method.

[0031] Preferably, the thickness of the electrolytic copper foil is ≥60 µm.

[0032] Preferably, the surface roughness of the electrolytic copper foil is 0.6~2.0 µm.

[0033] Preferably, the electrolytic copper foil has a room temperature tensile strength ≥700 MPa and an aged tensile strength ≥650 MPa.

[0034] Preferably, the electrolytic copper foil has a room temperature elongation ≥3.5% and an aging elongation ≥4%; the conditions for aging tensile strength and aging elongation are as follows:

[0035] The temperature was 150℃ and the time was 10 minutes.

[0036] The present invention also provides applications of the above-mentioned electrolytic copper foil in printed circuit boards, batteries or aerospace fields.

[0037] Compared with the prior art, the method for preparing electrolytic copper foil provided by the present invention includes the following steps: (1) mixing solution A, hydrochloric acid and thiourea additives to obtain an electrolyte; (2) electrochemically depositing the electrolyte to prepare electrolytic copper foil; wherein solution A is composed of copper sulfate and sulfuric acid; and the thiourea additive is selected from trimethylthiourea, tetramethylthiourea or N-methylthiourea. The preparation method of the present invention uses a single thiourea additive to control the microstructure, surface morphology, mechanical properties and electrochemical properties of the copper foil, resulting in good structural stability and excellent performance of the electrolytic copper foil. Attached Figure Description

[0038] Figure 1 SEM image of the rough surface of the electrolytic copper foil prepared in Example 1;

[0039] Figure 2 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 2;

[0040] Figure 3 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 3;

[0041] Figure 4 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 4;

[0042] Figure 5 The image shows a cross-sectional EBSD (electron backscattering diffraction) pattern of the electrolytic copper foil prepared in Example 4.

[0043] Figure 6 is a SEM image of the rough surface of the electrolytic copper foil prepared in Comparative Example 1.

[0044] Figure 7 is a SEM image of the rough surface of the electrolytic copper foil prepared in Comparative Example 2;

[0045] Figure 8 is a SEM image of the rough surface of the electrolytic copper foil prepared in Comparative Example 3. Detailed Implementation

[0046] To further illustrate the present invention, the preparation method of electrolytic copper foil and the electrolytic copper foil provided by the present invention will be described in detail below with reference to embodiments.

[0047] Example 1

[0048] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After passing through a multi-layer filtration device, the electrolyte is heated to 53°C by a heat exchanger and supplied to the electrolytic foil production machine.

[0049] (2) Trimethylthiourea and hydrochloric acid are introduced into copper sulfate electrolyte at a certain flow rate through a metering pump to obtain raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, the chloride ion content is 21 mg / L, and the effective concentration of trimethylthiourea is 10 mg / L.

[0050] (3) The electrolyte for the raw foil is passed through the foil-making machine at a certain current density (45 A / dm). 2 Copper foil with a thickness of 60 µm is produced by continuous electroplating on a cathode roller at a suitable linear speed. The physical properties are as follows: roughness Rz is 1.12 µm; room temperature tensile strength is 734 MPa and room temperature elongation is 4.63%; aged (150 ℃, 10 min) tensile strength is 699 MPa and aged elongation is 5.24%.

[0051] Figure 1 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 1.

[0052] Example 2

[0053] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After the electrolyte passes through a multi-layer filtration device, it is heated to a certain temperature by a heat exchanger and supplied to the electrolytic foil production machine.

[0054] (2) Additive tetramethylthiourea and hydrochloric acid are introduced into copper sulfate electrolyte at a certain flow rate through a metering pump to obtain raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, the chloride ion content is 21 mg / L, and the effective concentration of tetramethylthiourea is 10 mg / L.

[0055] (3) The electrolyte for the raw foil is passed through the foil-making machine at a certain current density (45 A / dm). 2Copper foil with a thickness of 60 µm is continuously electroplated on a cathode roller at a suitable linear speed, and its physical properties are as follows:

[0056] The surface roughness Rz is 1.01µm; the room temperature tensile strength is 732 MPa and the room temperature elongation is 4.16%; the aged (150℃, 10 min) tensile strength is 695 MPa and the aged elongation is 4.86%.

[0057] Figure 2 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 2.

[0058] Example 3

[0059] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After the electrolyte passes through a multi-layer filtration device, it is heated to a certain temperature by a heat exchanger and supplied to the electrolytic foil production machine.

[0060] (2) The additive N-methylthiourea and hydrochloric acid are introduced into the copper sulfate electrolyte at a certain flow rate through a metering pump to obtain the raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, the chloride ion content is 21 mg / L, and the effective concentration of N-methylthiourea is 10 mg / L.

[0061] (3) The electrolyte for the raw foil is passed through the foil-making machine at a certain current density (45 A / dm). 2 Copper foil with a thickness of 60 µm is continuously electroplated on a cathode roller at a suitable linear speed, and its physical properties are as follows:

[0062] The surface roughness Rz is 0.84 µm; the room temperature tensile strength is 798 MPa and the room temperature elongation is 3.88%; the aged (150℃, 10 min) tensile strength is 736 MPa and the aged elongation is 4.21%.

[0063] Figure 3 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 3.

[0064] Example 4

[0065] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After the electrolyte passes through a multi-layer filtration device, it is heated to a certain temperature by a heat exchanger and supplied to the electrolytic foil production machine.

[0066] (2) The additive N-methylthiourea and hydrochloric acid are introduced into the copper sulfate electrolyte at a certain flow rate through a metering pump to obtain the raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, the chloride ion content is 21 mg / L, and the effective concentration of N-methylthiourea is 15 mg / L.

[0067] (3) The electrolyte for the raw foil is passed through the foil-making machine at a certain current density (45 A / dm). 2 Copper foil with a thickness of 60 µm is produced by continuous electroplating on a cathode roller at a suitable linear speed. The physical properties are as follows:

[0068] The surface roughness Rz is 0.67 µm; the room temperature tensile strength is 807 MPa and the room temperature elongation is 3.64%; the aged (150℃, 10 min) tensile strength is 751 MPa and the aged elongation is 4.15%.

[0069] Figure 4 is a SEM image of the rough surface of the electrolytic copper foil prepared in Example 4.

[0070] Figure 5 The image shows a cross-sectional EBSD (electron backscattering diffraction) pattern of the electrolytic copper foil prepared in Example 4.

[0071] Comparative Example 1

[0072] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After the electrolyte passes through a multi-layer filtration device, it is heated to a certain temperature of 53°C by a heat exchanger and supplied to the electrolytic foil production machine.

[0073] (2) Hydrochloric acid is introduced into copper sulfate electrolyte at a certain flow rate through a metering pump to obtain raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, and the chloride ion content is 21 mg / L.

[0074] (3) The electrolyte for the raw foil is passed through the foil-making machine at a certain current density (45 A / dm). 2 Copper foil with a thickness of 60 µm is continuously electroplated on a cathode roller at a suitable linear speed, and its physical properties are as follows:

[0075] The surface roughness Rz is 1.74 µm; the room temperature tensile strength is 376 MPa and the room temperature elongation is 9.81%; the aged (150℃, 10 min) tensile strength is 370 MPa and the aged elongation is 11.84%.

[0076] Figure 6 is a SEM image of the rough surface of the electrolytic copper foil prepared in Comparative Example 1.

[0077] Comparative Example 2

[0078] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After the electrolyte passes through a multi-layer filtration device, it is heated to a certain temperature of 53°C by a heat exchanger and supplied to the electrolytic foil production machine.

[0079] (2) The additive N-methylthiourea and hydrochloric acid are introduced into the copper sulfate electrolyte at a certain flow rate through a metering pump to obtain the raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, the chloride ion content is 21 mg / L, and the effective concentration of N-methylthiourea is 5 mg / L.

[0080] (3) The electrolyte for the raw foil is passed through the foil-making machine at a certain current density (45 A / dm). 2 Copper foil with a thickness of 60 µm is continuously electroplated on a cathode roller at a suitable linear speed, and its physical properties are as follows:

[0081] The surface roughness Rz is 1.59 µm; the room temperature tensile strength is 453 MPa and the room temperature elongation is 8.62%; the aged (150℃, 10 min) tensile strength is 432 MPa and the aged elongation is 10.97%.

[0082] Figure 7 is a SEM image of the rough surface of the electrolytic copper foil prepared in Comparative Example 2.

[0083] Comparative Example 3

[0084] (1) Add elemental copper (purity > 99.5%) to a copper dissolving tank containing sulfuric acid to dissolve the copper into copper sulfate, and obtain an electrolyte composed of copper sulfate and sulfuric acid. After the electrolyte passes through a multi-layer filtration device, it is heated to a certain temperature of 53°C by a heat exchanger and supplied to the electrolytic foil production machine.

[0085] (2) The additive N-methylthiourea and hydrochloric acid are introduced into the copper sulfate electrolyte at a certain flow rate through a metering pump to obtain the raw foil electrolyte, wherein the copper ion concentration is 90 g / L, the sulfuric acid content is 110 g / L, the chloride ion content is 21 mg / L, and the effective concentration of N-methylthiourea is 10 mg / L.

[0086] (3) The electrolyte for the raw foil is passed through the raw foil machine at a certain current density (60 A / dm). 2Copper foil with a thickness of 60 µm is produced by continuous electroplating on a cathode roller at a suitable linear speed. The physical properties are as follows: roughness Rz is 1.56 µm; room temperature tensile strength is 680 MPa and room temperature elongation is 4.35%; aged (150 ℃, 10 min) tensile strength is 662 MPa and aged elongation is 5.21%.

[0087] Figure 8 is a SEM image of the rough surface of the electrolytic copper foil prepared in Comparative Example 3.

[0088] By comparing the mechanical property data of the electrolytic copper foils prepared in Example 3 and Comparative Examples 2 and 3, the results show that the electrolytic copper foils prepared by the method of the present invention have better room temperature or aged tensile strength than the electrolytic copper foils prepared in Comparative Examples 2 and 3.

[0089] By comparison Figure 3 and Figure 7 , 8 The results show that the electrolytic copper foil prepared by the method of the present invention has a smoother and more even surface.

[0090] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing electrolytic copper foil, characterized in that, Includes the following steps: (1) Mix solution A, hydrochloric acid and thiourea additives to obtain an electrolyte; (2) Electrolytic copper foil was prepared by electrochemical deposition of the electrolyte; Solution A is composed of copper sulfate and sulfuric acid; The thiourea additives are selected from trimethylthiourea, tetramethylthiourea, or N-methylthiourea.

2. The preparation method according to claim 1, characterized in that, The effective concentration of thiourea additives in the electrolyte is 10~15 mg / L.

3. The preparation method according to claim 1, characterized in that, The concentration of copper ions in the electrolyte is 90~105 g / L; The electrolyte contains 100-130 g / L of sulfuric acid.

4. The preparation method according to any one of claims 1-3, characterized in that, According to the preparation method of claim 1, the chloride ion content in the electrolyte is 10~30 mg / L.

5. The preparation method according to claim 1, characterized in that, The mixing temperature in step (1) is 50℃~60℃.

6. The preparation method according to claim 1, characterized in that, The current density for electrochemical deposition in step (2) is 40~50 A / dm. 2 .

7. An electrolytic copper foil, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

8. The electrolytic copper foil according to claim 7, characterized in that, The thickness of the electrolytic copper foil is ≥60 µm.

9. The electrolytic copper foil according to claim 8, characterized in that, The surface roughness of the electrolytic copper foil is 0.6~2.0 µm; The electrolytic copper foil has a room temperature tensile strength ≥700 MPa and an aged tensile strength ≥650 MPa; The electrolytic copper foil has a room temperature elongation of ≥3.5% and an aging elongation of ≥4%. The conditions for the aged tensile strength and aged elongation are as follows: The temperature was 150℃ and the time was 10 minutes.

10. The application of the electrolytic copper foil according to any one of claims 7 to 9 in the fields of printed circuit boards, batteries or aerospace.

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