Electrolyte additive, low-profile high-temperature high-elongation copper foil and preparation method thereof

Abstract

The invention relates to the field of electrolytic copper foil processing and application, and discloses an electrolyte additive, a low-profile high-temperature high-elongation copper foil and a preparation method of the low-profile high-temperature high-elongation copper foil, the electrolyte additive is added into a copper sulfate electrolyte for treating the copper foil, and the electrolyte additive comprises a composite additive A and a diluted hydrochloric acid aqueous solution, the composite additive A is an aqueous solution containing 3-6 g / L of dopamine butylamine, 5-20 g / L of N-allylthiourea and 1-5 g / L of pentapolyethylene glycol monodecyl ether. The electrolytic copper foil prepared by the preparation method disclosed by the invention has lower roughness while ensuring high elongation. The rough surface Rz of the 18-micron copper foil is 2.0-2.8 microns, the Sdr value is 6%-13%, the rough surface Rz of the 35-micron copper foil is less than or equal to 3.5 microns, and the rough surface Rz of the 12-micron copper foil is less than or equal to 2.0 microns. The rough surface electron microscope morphology of the electrolytic copper foil is in a more gentle peak shape.

Description

Technical Field

[0001] The present invention relates to the fields of electrolytic copper foil processing and application, and particularly to electrolyte additives, low-profile high-temperature high-elongation copper foil and its preparation method. Background Art

[0002] PCB (printed circuit board) is one of the key raw materials in the electronics and communication industries and is a crucial part of terminal communication products. As the communication era gradually shifts from 4G to 5G, PCB products, as carriers for signal transmission in the high-frequency and high-speed communication fields, play a crucial role. Electrolytic copper foil, as an important base material for PCB products, plays a vital role in the performance of PCB products and the efficiency of electrical signal transmission. In the actual signal transmission process, signal loss usually occurs, and one of the main sources of signal loss is conductor loss, including resistive loss caused by signal frequency changes and loss caused by the skin effect. According to the skin effect principle, we should preferably choose copper foil with lower roughness as the base material for high-frequency and high-speed circuit design.

[0003] Since the PCB product preparation process usually goes through a high-temperature lamination process, certain requirements are imposed on the high-temperature elongation of the electrolytic copper foil used. After high-temperature lamination, no adverse problems such as board explosion and open circuit will occur. High-temperature high-elongation copper foil (HTE) is a common and high-demand product among various types of electrolytic copper foils in the electronic circuit industry. At present, although high-temperature high-elongation electrolytic copper foil has a relatively high high-temperature elongation, the roughness of the matte surface of the copper foil is relatively high. The Rz of the matte surface of 18μm electrolytic copper foil is generally above 3.0μm. According to the skin effect, on the premise of ensuring the qualified high-temperature elongation of the copper foil, further reducing the roughness of the electrolytic copper foil can reduce the loss during the electrical signal transmission process and ultimately improve the performance of PCB products.

[0004] Currently, the commonly used additives for high-temperature high-elongation electrolytic copper foil are generally based on glue (such as gelatin, collagen, etc.). The leveling effect brought by this commonly used glue-based electrolytic copper foil additive is average and cannot meet the requirement of lower roughness of electrolytic copper foil. For example, in Chinese Patent CN113481551A, the Rz of the matte surface of the copper foil prepared with a gelatin-based additive is ≤5.1μm, and the roughness is relatively high. Summary of the Invention

[0005] The main object of the present invention is to solve the technical problem of the average leveling effect of high-temperature high-elongation electrolytic copper foil in the prior art. A low-profile high-temperature high-elongation copper foil, wherein the electrolyte additive is added to the copper sulfate electrolyte for treating the copper foil. The electrolyte additive comprises a composite additive A and a dilute hydrochloric acid aqueous solution. The composite additive A is an aqueous solution containing 3 - 6 g / L of dobutamine, 5 - 20 g / L of N-allylthiourea, and 1 - 5 g / L of pentaethylene glycol monodecyl ether.

[0006] The Cu in the electrolyte 2+ has a concentration of 85 - 110 g / L, and the H 2 SO 4 has a concentration of 90 - 130 g / L

[0007] The concentration of the composite additive A in the electrolyte is 5 - 60 mg / L, and the concentration of chloride ions in the electrolyte is 5 - 25 mg / L.

[0008] The copper foil is treated with a copper sulfate electrolyte containing the electrolyte additive described in any one of claims 1 - 3;

[0009] When the thickness of the copper foil is 18 μm, the Rz of the matte surface is 2.0 - 2.8 μm, and the Sdr value is 6% - 13%;

[0010] When the thickness of the copper foil is 35 μm, the Rz of the matte surface ≤ 3.5 μm, and the Sdr value is 6% - 13%;

[0011] When the thickness of the copper foil is 35 μm, the Rz of the matte surface ≤ 2.0 μm, and the Sdr value is 6% - 15%.

[0012] The crystal structure of the cross-section of the copper foil includes massive crystals and columnar crystals, and the crystal size distribution range is 0.2 μm - 11.2 μm.

[0013] After the copper foil is annealed, the grains will have a recrystallization process, and the grains of the copper foil will grow, mainly in large massive crystals, and the grain size distribution range becomes 1.0 μm - 16.0 μm.

[0014] The SEM morphology of the matte surface of the copper foil is a gentle mountain peak morphology.

[0015] The present invention also relates to a method for preparing a low-profile high-temperature high-elongation copper foil, which is prepared according to the following steps:

[0016] a. Add elemental copper wire coils to a spray-type copper dissolving tank containing sulfuric acid solution, obtain copper sulfate electrolyte through the spray copper dissolving system, and filter the copper sulfate electrolyte through the filtration system;

[0017] b. Weigh dobutamine, N-allylthiourea, and pentaethylene glycol monodecyl ether and add them to the additive configuration tank, add pure water to make up a volume of 60 L, and start mechanical stirring to configure a composite additive A solution containing 3 - 6 g / L of dobutamine, 5 - 20 g / L of N-allylthiourea, and 1 - 5 g / L of pentaethylene glycol monodecyl ether, and configure concentrated hydrochloric acid into a dilute hydrochloric acid aqueous solution with a concentration of 600 - 900 ppm;

[0018] c. Mix the composite additive A solution and hydrochloric acid solution prepared in step b evenly with the copper sulfate electrolyte through a peristaltic pump, and supply it to the electrolytic copper foil machine after filtration;

[0019] d. Continuously deposit a copper foil with a target thickness and low profile, high temperature and high elongation rate on the surface of the cathode titanium roller by adjusting the linear speed and winding tension.

[0020] The concentration of Cu in the electrolyte is 2+ 85 - 110 g / L, and the concentration of H 2 SO 4 is 90 - 130 g / L, the electrolysis current is 20 - 32 KA, the electrolyte temperature is 48 - 58 °C, and the current density is 5000 - 7000 A / m 2 .

[0021] The concentration of the composite additive A in the electrolyte is: 5 - 60 mg / L, and the concentration of chloride ions in the electrolyte is 5 - 25 mg / L.

[0022] The present invention has the following beneficial effects:

[0023] Under the synergistic effect of the three additives and chloride ions, the electrolytic copper foil prepared by the present invention has lower roughness while ensuring high elongation rate. The Rz value of the matte surface of the 18 μm copper foil is 2.0 - 2.8 μm, and the Sdr value is 6% - 13%. The Rz value of the matte surface of the 35 μm copper foil is ≤ 3.5 μm, and the Rz value of the matte surface of the 12 μm copper foil is ≤ 2.0 μm. The SEM morphology of the matte surface of the electrolytic copper foil is a smoother mountain shape. Description of the Drawings

[0024] Figure 1 SEM images of the shiny and matte surfaces of the 18 μm low-profile HTE copper foil prepared in Example 1;

[0025] Figure 2 SEM images of the shiny and matte surfaces of the 12 μm low-profile HTE copper foil prepared in Example 2;

[0026] Figure 3 Cross-sectional EBSD crystal structure diagrams of the 18 μm low-profile HTE copper foil prepared in Example 1 before and after annealing;

[0027] Figure 4 SEM images of the matte surfaces of the 12 μm and 18 μm low-profile HTE copper foils prepared in Comparative Example 1 and Comparative Example 2. Detailed Embodiments

[0028] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] The technical solution provided by the present invention is that in the composite additive A, dobutamine contains abundant hydroxyl functional groups and is negatively charged when ionized in the electrolyte. Since a large number of copper ions are gathered near the cathode, the interaction between the heterogeneous charges causes dobutamine to approach the cathode more quickly. Moreover, as nitrogen-containing organic substances, the amino groups in dobutamine and N-allylthiourea are easily ionized with H + Combined with positive charge, the cathode is more likely to gather electrons at the protrusions of the cathode surface due to the tip discharge, so the two additives are more likely to be adsorbed at the protrusions of the cathode surface, thereby hindering the deposition of copper ions here, making more copper ions deposited in the depressions of the cathode surface, playing a good leveling effect, and reducing the surface roughness of the deposited copper foil. At the same time, the sulfur-containing functional groups in the two additives can hinder the deposition rate of copper ions at the cathode, slow down the growth rate of crystal grains, and lead to more crystal nucleation, but the further growth process of the crystal is limited, so that the copper grains are finer and denser, and thus the roughness of the prepared copper foil is lower. The additive pentaethylene glycol monodecyl ether monomer contains 5 ether bonds, has extremely excellent hydrophilic properties, can be adsorbed on the surface of deposited copper, greatly reduces the surface tension of the interface, promotes the adsorbed additives to be oriented on the cathode surface, and makes the grains more uniform as a whole. At the same time, the active sites on the cathode surface are reduced and the deposition of copper is inhibited by the steric effect, the cathode polarization is enhanced, and the copper foil crystallization is fine and compact. Under the synergistic effect of the three additives and chloride ions, the electrolytic copper foil prepared by the present invention has a lower roughness while ensuring high elongation.

[0030] In order to prove that the low-profile, high-temperature, high-elongation electrolytic copper foil prepared by the additive formula of the present invention has a smoother SEM morphology and lower roughness and profile, the following is further described in detail in conjunction with specific implementation cases.

[0031] Example 1

[0032] S1. Appropriately mix the elemental copper wire (copper content ≥ 99.5%) put into the copper dissolution tank with concentrated sulfuric acid through a spray - type copper dissolution system. Utilize the heat released spontaneously by the reaction to control the temperature within a certain range and obtain copper sulfate electrolyte with a certain concentration (the acid concentration in the electrolyte is 110 g / L and the copper concentration is 95 g / L). After filtering the particulate impurities in the electrolyte through a three - stage filtration system, use a plate heat exchanger to control the temperature of the electrolyte supplied to the copper foil machine to 48 - 50 °C and then inject it into the copper foil machine to produce copper foil;

[0033] S2. Weigh a certain mass of dobutamine, N - allylthiourea, and pentaethylene glycol monodecyl ether additives and add them to the additive preparation tank. Add pure water to make up the volume to 60 L and start mechanical stirring to prepare a composite additive A solution. The concentrations of the three additives in the mixed solution are 3 g / L, 10 / L, and 2 g / L respectively. The configured concentration of chloride ions is 800 ppm.

[0034] S3. Inject the composite additive A in the additive preparation tank and the dilute hydrochloric acid in the hydrochloric acid preparation tank into the inlet of the precision filter through peristaltic pumps at flow rates of 3.0 L / h and 1.0 L / h respectively. After mixing evenly with the electrolyte, supply it to the copper foil machine;

[0035] S4. Set the current of the copper foil machine to 30000 A and the linear speed to 2.87 m / min. Continuously deposit on the surface of the cathode titanium roller through appropriate winding tension to prepare an electrolytic copper foil with a thickness specification of 18 μm;

[0036] Example 2

[0037] The difference from Example 1 is as follows:

[0038] In step S3, the flow rates of additive A and hydrochloric acid are 5.0 L / h and 1.5 L / h respectively. In step S4, the linear speed of the copper foil machine is 4.39 m / min. An electrolytic copper foil with a specification of 12 μm is prepared;

[0039] Example 3

[0040] The difference from Example 1 is as follows:

[0041] In step S3, the flow rates of additive A and hydrochloric acid are 1.5 L / h and 0.8 L / h respectively. In step S4, the linear speed of the copper foil machine is 1.51 m / min. An electrolytic copper foil with a specification of 35 μm is prepared;

[0042] Example 4

[0043] The difference from Example 1 is as follows:

[0044] The concentrations of dobutamine, N-allylthiourea, and pentaethylene glycol monodecyl ether in the composite additive A are 6 g / L, 18 g / L, and 3 g / L, respectively. The flow rates of additive A and hydrochloric acid are 2.2 L / h and 1.0 L / h. The electrolytic copper foil with a specification of 18 μm is prepared;

[0045] In order to prove that the HTE electrolytic copper foil prepared by the formula and preparation method used in the present invention has lower roughness and waviness than the HTE electrolytic copper foil prepared by the conventional adhesive-based additive formula, further, the collagen formula that is relatively commonly used in current HTE electrolytic copper foils is selected to prepare the electrolytic copper foil, and the relevant physical properties of the electrolytic copper foils in the control examples and the examples are tested.

[0046] Comparative Example 1

[0047] The difference from Example 1 is that the additive formula used in S2 is collagen white and Cl － , and the configured concentration of collagen is 3 g / L. The flow rate of the additive in S3 is 2.5 L / h. The electrolytic copper foil with a specification of 18 μm is prepared.

[0048] Comparative Example 2

[0049] The difference from Example 2 is that the additive formula used in S2 is collagen white and Cl － , and the configured concentration of collagen is 3 g / L. In S3, the flow rate of the additive collagen is 4.0 L / h. The electrolytic copper foil with a specification of 12 μm is prepared.

[0050] Comparative Example 3

[0051] The difference from Example 1 is that dobutamine is removed from the composite additive A solution in S2, and the electrolytic copper foil with a thickness specification of 18 μm is prepared.

[0052] The relevant physical property tests are carried out on the copper foils prepared in the above Examples 1-4 and Comparative Examples 1-2. The roughness test (Rz) is based on the test method IPC-TM-650, and the SJ-210 portable roughness meter of Mitutoyo, Japan is used to measure the roughness Rz value of the matte surface of the copper foil. The non-contact Rz value and sdr% of the matte surface of the copper foil are measured using an Olympus 3D measurement laser microscope. The tensile strength and elongation tests are based on the test method IPC-TM-650, and the AGS-X type tensile testing machine manufactured by SHIMADZU CORPORATION is used to obtain the test results. The relevant physical property test results of the electrolytic copper foils prepared in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1 and Table 2.

[0053] Table 1

[0054]

[0055]

[0056] Table II

[0057]

[0058] By comparing and analyzing the test results in Table I, it can be seen that for the low-profile high-temperature high-elongation electrolytic copper foil prepared with the additive formulation of the present invention, compared with the high-temperature high-elongation electrolytic copper foil prepared with the conventional additive formulation, both the contact roughness and the non-contact roughness can reach lower levels. The Rz values of the contact roughness of the 12-μm and 18-μm low-profile high-temperature high-elongation electrolytic copper foils are 1.78 and 2.34 μm respectively, which are reduced by 31.80% and 34.64% respectively compared with the conventional high-temperature high-elongation copper foil. And their sdr values are 5.24% and 7.99% respectively, which are reduced by 39.49% and 60.06% respectively compared with the conventional high-temperature high-elongation electrolytic copper foil. At the same time, as shown in the test results in Table II, the electrolytic copper foil prepared by the present invention can maintain the tensile strength and elongation levels of the conventional high-temperature high-elongation electrolytic copper foil. The additive formulation and preparation method provided by the present invention can prepare a low-profile high-temperature high-elongation electrolytic copper foil, which can reduce the signal loss during the electrical signal transmission of the downstream PCB products and ultimately improve the performance of the PCB products.

[0059] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte additive, characterized in that: The electrolyte additive is added to the copper sulfate electrolyte for treating copper foil, and the electrolyte additive comprises a composite additive A and a dilute hydrochloric acid aqueous solution, wherein the composite additive A is an aqueous solution comprising 3-6 g / L of dobutamine, 5-20 g / L of N-allyl thiourea, and 1-5 g / L of pentaethylene glycol monodecyl ether.

2. An electrolyte additive according to claim 1, characterized in that: The electrolyte contains Cu 2+ The concentration is 85-110g / L and the concentration of H2SO4 is 90-130g / L.

3. An electrolyte additive according to claim 1, characterized in that: The concentration of the composite additive A in the electrolyte is 5-60 mg / L, and the concentration of chloride ions in the electrolyte is 5-25 mg / L.

4. A low profile, high temperature and high elongation copper foil, characterized in that: The copper foil is obtained by treating a copper sulfate electrolyte containing the electrolyte additive according to any one of claims 1 to 3; When the copper foil has a thickness of 18 μm, the rough surface Rz is 2.0-2.8 μm, and the Sdr value is 6%-13%; When the copper foil has a thickness of 35 μm, the rough surface Rz is ≤ 3.5 μm, and the Sdr value is 6%-13%; When the copper foil has a thickness of 35 μm, the rough surface Rz is ≤ 2.0 μm, and the Sdr value is 6%-15%.

5. The low profile, high temperature and high elongation copper foil according to claim 4, characterized in that: The crystal structure of the copper foil cross section includes block crystals and columnar crystals, and the crystal size distribution range is 0.2 μm-11.2 μm.

6. The low profile, high temperature and high elongation copper foil according to claim 4, characterized in that: After the copper foil is annealed, the grains will undergo a recrystallization process, the grains of the copper foil will grow, and will be mainly large block crystals, and the grain size distribution range will become 1.0 μm-16.0 μm.

7. The low profile, high temperature and high elongation copper foil according to claim 4, characterized in that: The SEM morphology of the rough surface of the copper foil is a gentle peak morphology.

8. A method for preparing a low-profile, high-temperature, high-elongation copper foil, characterized in that: The low profile, high temperature and high elongation copper foil is prepared according to the following steps: a. Adding a single copper wire coil to a spray copper dissolving tank containing a sulfuric acid solution, obtaining a copper sulfate electrolyte through a spray copper dissolving system, and filtering the copper sulfate electrolyte through a filtration system; b. Weigh dobutamine, N-allyl thiourea, and pentaethylene glycol monodecyl ether into an additive configuration tank, add pure water to a volume of 60 L, and turn on mechanical stirring to prepare a composite additive A solution containing 3-6 g / L of dobutamine, 5-20 g / L of N-allyl thiourea, and 1-5 g / L of pentaethylene glycol monodecyl ether, and prepare concentrated hydrochloric acid to a concentration of 600-900 ppm dilute hydrochloric acid aqueous solution; c. The composite additive A solution and the hydrochloric acid solution prepared in step b are mixed evenly with the copper sulfate electrolyte by a peristaltic pump, and the electrolytic foil machine is supplied after filtration; d. By adjusting the line speed and winding tension, a low-profile, high-temperature, and high-elongation copper foil of target thickness is continuously deposited on the surface of the cathode titanium roller.

9. The method for preparing a low-profile, high-temperature, high-elongation copper foil according to claim 4, characterized in that: The electrolyte contains Cu 2+ The concentration is 85-110g / L, the H2SO4 concentration is 90-130g / L, the electrolysis current is 20-32KA, the electrolyte temperature is 48-58℃, and the current density is 5000-7000A / m 2 .

10. The method for preparing a low-profile, high-temperature, high-elongation copper foil according to claim 4, characterized in that: The concentration of the composite additive A in the electrolyte is 5-60 mg / L, and the concentration of chloride ions in the electrolyte is 5-25 mg / L.

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