Copper foil and preparation method and application thereof

Abstract

The invention relates to the technical field of copper foil surface treatment, in particular to a copper foil and a preparation method and application thereof. The copper foil comprises an electrolytic copper raw foil, and a roughening treatment layer, a catechol-based polymer layer and a silane coupling agent layer which are sequentially laminated on the rough surface of the electrolytic copper raw foil. According to the copper foil, the catechol-based polymer layer is introduced between the roughening treatment layer and the silane coupling agent layer, the catechol-based polymer layer contains rich functional groups such as hydroxyl and amino, the number of attachment sites of a silane coupling agent on the surface of the copper foil is increased, and then the binding force of the silane coupling agent and the copper foil is increased; meanwhile, rich functional groups can also improve the binding force between the copper foil and various base materials, so that the copper foil has higher peel strength under the condition of keeping lower roughness during application.

Description

Technical Field

[0001] This application relates to the field of copper foil surface treatment technology, and in particular to a copper foil, its preparation method and application. Background Technology

[0002] Printed circuit boards, also known as PCBs, are printed circuit boards with interconnections and printed components formed on a substrate according to a predetermined design. Printed circuit boards are an indispensable component in modern electronic devices.

[0003] Copper foil is a critical conductive material in printed circuit boards (PCBs). With the rapid development of high-frequency, high-speed electronic devices, the requirements for PCB signal transmission performance are becoming increasingly stringent. To address this, HVLP (High Very Low Profile) copper foil has been developed, with a surface roughness controllable below 3μm, effectively reducing high-frequency signal transmission loss. However, due to its ultra-low roughness, HVLP copper foil suffers from insufficient peel strength, severely impacting the reliability and long-term durability of PCBs. Summary of the Invention

[0004] Based on this, this application provides a copper foil, its preparation method and application, which maintains low roughness while having high peel strength.

[0005] A first aspect of this application provides a copper foil comprising an electrolytic copper foil and a roughening treatment layer, a catechol polymer layer, and a silane coupling agent layer sequentially stacked on the rough surface of the electrolytic copper foil.

[0006] In some embodiments, the catechol-based polymer layer satisfies at least one of the following conditions:

[0007] (1) Thickness is 20nm~100nm;

[0008] (2) The raw materials for preparing catechol polymers include at least one of norepinephrine and dopamine.

[0009] In some embodiments, the surface of the copper foil having the silane coupling agent layer satisfies at least one of the following characteristics:

[0010] (1) Roughness Rz≤1.1μm;

[0011] (2) The interface expansion area ratio Sdr ≤ 3.5%;

[0012] (3) The peak density Spd is 40000 / mm 2 ~58000 / mm 2 ;

[0013] (4) The arithmetic mean curvature Spc at the peak is 5.5 μm. -1 ~7.5μm -1 ;

[0014] (5) Peel strength ≥ 1.2 N / mm;

[0015] (6) Copper tooth height ≤ 500nm.

[0016] In some embodiments, the surface roughness parameters of the electrolytic copper foil satisfy the following: surface roughness Rz ≤ 0.4 μm, interface spread area ratio Sdr ≤ 2%, maximum height Sz ≤ 1.0 μm, arithmetic mean height Sa ≤ 0.15 μm, and peak density Spd ≤ 1500 / mm². 2 The arithmetic mean curvature Spc at the peak ≤ 4 μm -1 ; and / or,

[0017] The thickness of the electrolytic copper foil is 12μm~50μm.

[0018] In some embodiments, the copper foil further includes a metal protective barrier layer disposed between the roughening treatment layer and the catechol-based polymer layer, the metal protective barrier layer being made of at least one of nickel, titanium, tin, tungsten, molybdenum, and zinc; and / or,

[0019] The silane coupling agent layer contains a silane coupling agent, which includes at least one of aminosilane, epoxysilane, and mercaptosilane.

[0020] A second aspect of this application provides a method for preparing copper foil, the method comprising the following steps:

[0021] A roughening treatment layer, a catechol-based polymer layer, and a silane coupling agent layer are sequentially formed on the rough surface of the electrolytic copper foil.

[0022] In some embodiments, the step of forming the catechol-based polymer layer includes:

[0023] The roughened layer is brought into contact with a catechol monomer solution, and a catechol polymer layer is formed by polymerization reaction.

[0024] Optionally, the catechol monomer includes at least one of norepinephrine and dopamine;

[0025] Optionally, the polymerization reaction takes 30s to 120s;

[0026] Optionally, the concentration of the catechin monomer in the catechin monomer solution is 2 mg / L to 8 mg / L.

[0027] In some embodiments, the step of forming the roughening layer includes:

[0028] The electrolytic copper foil is pickled, and then the rough surface of the pickled electrolytic copper foil is roughened at least once to form a roughening layer.

[0029] The roughening process includes a roughening process followed by a curing process.

[0030] A third aspect of this application provides the application of the copper foil described above or the copper foil prepared by the method described above in the preparation of printed circuit boards.

[0031] A fourth aspect of this application provides a printed circuit board, including a substrate and a copper foil disposed on the substrate, wherein the copper foil includes the copper foil described above or copper foil prepared by the method described above.

[0032] This application has the following beneficial effects:

[0033] The copper foil described in this application introduces a catechol-based polymer layer between the roughening treatment layer and the silane coupling agent layer. The catechol-based polymer layer contains abundant functional groups, such as hydroxyl and amino groups, which increases the number of adhesion sites of the silane coupling agent on the surface of the copper foil, thereby increasing the bonding force between the silane coupling agent and the copper foil. At the same time, the abundant functional groups can also improve the bonding force between the copper foil and various substrates, so that the copper foil can have high peel strength while maintaining low roughness when applied.

[0034] The copper foil provided in this application also avoids the negative impact of traditional roughening technology on signal integrity, and can adapt to harsh environments such as high temperature, high humidity, and mechanical vibration. It provides a high-reliability material solution for next-generation high-frequency and high-speed PCBs, effectively solving the application bottleneck of HVLP copper foil in 5G communication, autonomous driving, advanced packaging and other fields, and promoting the development of the electronics industry towards higher performance, smaller size and longer life. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart illustrating a method for preparing copper foil according to some embodiments.

[0037] Figure 2 Here is a rough SEM image of the copper foil prepared in Example 1;

[0038] Figure 3 Here is a rough SEM image of the copper foil prepared in Example 2;

[0039] Figure 4 Here is a rough SEM image of the copper foil prepared in Example 3;

[0040] Figure 5 SEM image of the rough surface of the copper foil prepared in Comparative Example 1;

[0041] Figure 6 A cross-sectional SEM image of the copper foil prepared in Example 1;

[0042] Figure 7 SEM image of the cross-section of the copper foil prepared for Comparative Example 1. Detailed Implementation

[0043] To facilitate understanding of this application, a more comprehensive description of the application will be provided below in conjunction with specific embodiments. Preferred embodiments of the application are given in the specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:

[0046] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0047] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0048] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0049] In this application, terms such as "further," "even more," "particularly," "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later, but should not be construed as limiting the preceding technical solution or restricting the scope of protection herein. Unless otherwise specified herein, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0050] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.

[0051] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0052] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0053] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this application, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to such processes, methods, products, or devices.

[0054] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0055] In the flowchart of this application, although the steps are shown sequentially according to the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps. They can be executed in other orders. Moreover, at least some of the steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. Their execution order is not necessarily sequential, but can be performed alternately or in turn with at least some of other steps or other sub-steps or stages.

[0056] Because HVLP copper foil typically has low roughness, traditional HVLP copper foil suffers from low peel strength, which can lead to problems such as interlayer delamination, circuit detachment, and pad peeling during PCB manufacturing and use, severely impacting product yield and long-term reliability. Currently, the peel strength of HVLP copper foil is mainly improved through surface roughening treatments (such as micron-nano nodular structures) and chemical coupling agents (such as silane modification). However, these methods still have certain limitations; for example, excessive roughening increases surface roughness, weakening the high-frequency performance advantages of HVLP copper foil.

[0057] A first aspect of this application provides a copper foil comprising an electrolytic copper foil and a roughening treatment layer, a catechol polymer layer, and a silane coupling agent layer sequentially stacked on the rough surface of the electrolytic copper foil.

[0058] The aforementioned copper foil incorporates a catechol-based polymer layer between the roughening treatment layer and the silane coupling agent layer. This catechol-based polymer layer contains abundant functional groups, such as hydroxyl and amino groups, which increases the number of adhesion sites for the silane coupling agent on the copper foil surface. This, in turn, increases the bonding strength between the silane coupling agent and the copper foil. At the same time, the abundant functional groups also improve the bonding strength between the copper foil and various substrates, enabling the copper foil application to maintain a low roughness while exhibiting high peel strength.

[0059] The aforementioned copper foil also avoids the negative impact of traditional roughening techniques on signal integrity, and can withstand harsh environments such as high temperature, high humidity, and mechanical vibration, providing a high-reliability material solution for next-generation high-frequency and high-speed PCBs. It effectively solves the application bottlenecks of HVLP copper foil in 5G communication, autonomous driving, and advanced packaging, driving the electronics industry towards higher performance, smaller size, and longer lifespan.

[0060] Electrolytic copper foil is formed by electrochemical deposition onto the surface of a cathode roller. The smooth surface of the electrolytic copper foil refers to the side directly deposited onto the cathode roller surface. Because it is in close contact with the highly polished titanium roller (cathode), its surface is smooth as a mirror, hence the term "smooth surface" or "roller surface." The rough surface of the electrolytic copper foil refers to the side opposite the smooth surface. Compared to the smooth surface where the crystal structure is affected by the grain morphology of the titanium roller surface during copper ion deposition, the rough surface of the foil experiences relatively free grain growth, resulting in a rougher structure. Its roughness is higher than that of the smooth surface, hence the term "rough surface" or "deposition surface." In this application, the smooth surface of the electrolytic copper foil may not be treated. Only after adding a roughening treatment layer, a catechol-based polymer layer, and a silane coupling agent layer to the rough surface of the electrolytic copper foil, the surface roughness is still greater than that of the smooth surface. It is understood that the copper foil mainly includes two surfaces: one is the smooth surface of the copper foil (i.e., the smooth surface of electrolytic copper foil); the other is the rough surface of the copper foil, i.e., the surface that has undergone coarse curing treatment and has the above-mentioned silane coupling agent layer in this application.

[0061] In some embodiments, the surface roughness Rz of the copper foil having a silane coupling agent layer is ≤1.1μm.

[0062] In some specific examples, the surface roughness Rz of the copper foil with the silane coupling agent layer is in the range of 0.7 μm ≤ Rz ≤ 1.0 μm. As an example, the roughness Rz of the rough surface of the copper foil can be 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm.

[0063] In some embodiments, the interfacial extension area ratio Sdr of the surface of the copper foil having the silane coupling agent layer is ≤3.5%.

[0064] In some specific examples, the interfacial extension area ratio Sdr of the surface of the copper foil with the silane coupling agent layer satisfies the range of 3.2% ≤ Sdr ≤ 3.5%. As an example, the interfacial extension area ratio Sdr can be 3.2%, 3.3%, 3.4%, or 3.5%.

[0065] In some embodiments, the peak density Spd of the surface of the copper foil with the silane coupling agent layer is 40,000 / mm². 2 ~58000 / mm 2 As an example, the peak density Spd of the rough surface of the copper foil can be 40,000 / mm². 2 45000 / mm 2 50000 / mm 2 55000 / mm 2 58000 / mm 2 Or any value within the range formed by any two of these point values ​​as endpoints.

[0066] In some embodiments, the arithmetic mean curvature Spc of the peak vertices of the surface of the copper foil where the silane coupling agent layer is provided is 5.5 μm. -1 ~7.5μm -1 As an example, the arithmetic mean curvature Spc of the peaks of the rough surface of the copper foil can be 5.5 μm. -1 5.8μm -1 6μm -1 6.2μm -1 6.5μm -1 6.8μm -1 7μm -1 7.2μm -1 7.5μm -1 Or any value within the range formed by any two of these point values ​​as endpoints.

[0067] In some embodiments, the surface of the copper foil with the silane coupling agent layer has a peel strength ≥1.2 N / mm. Understandably, the peel strength reflects the bonding strength between the copper foil and the substrate, which can be common PCB substrates such as FR-4 and PPO.

[0068] Understandably, FR-4 stands for Flame-Retardant 4, which is a flame-retardant epoxy glass cloth laminate, or simply epoxy glass fiber cloth substrate. It is a composite material with epoxy resin as the base material and glass fiber cloth as the reinforcing material, and its flame retardant rating reaches the UL94 V-0 standard.

[0069] Understandably, PPO, short for polyphenylene oxide, is a thermoplastic engineering plastic.

[0070] In some embodiments, the height of the copper teeth on the surface of the copper foil where the silane coupling agent layer is provided is ≤500nm. It can be understood that copper teeth refer to the dense needle-like or spherical copper nodule structure formed after rough curing treatment on the rough surface of the electrolytic green foil, and the height of the copper teeth refers to the height of the copper nodule structure formed after rough curing treatment of the rough surface of the copper foil.

[0071] In some specific examples, the copper tooth height on the surface of the copper foil with the silane coupling agent layer is 100nm~500nm.

[0072] Understandably, the roughening treatment layer is formed by roughening the rough surface of the electrolytic copper foil. The roughening treatment usually involves electroplating and curing the rough surface of the electrolytic copper foil to form small copper nodules that are firmly bonded to the rough surface of the electrolytic copper foil.

[0073] In some embodiments, the copper foil further includes a metal protective barrier layer disposed between the roughening treatment layer and the catechol polymer layer. The metal protective barrier layer can be obtained by electroplating a non-copper metal on the surface of the roughening treatment layer. The metal protective barrier layer can play a role in corrosion resistance and oxidation resistance.

[0074] In some embodiments, the metal protective barrier layer is made of at least one of nickel, titanium, tin, tungsten, molybdenum, and zinc. Understandably, the metal protective barrier layer may comprise a stack of one or more single-layered metals from the aforementioned metal materials.

[0075] In some specific examples, the metal protective barrier layer includes a nickel plating sublayer, a zinc plating sublayer, and a chromium plating sublayer stacked sequentially in a direction away from the roughening treatment layer.

[0076] Understandably, catechol-based polymers refer to polymers formed by the self-polymerization of catechol monomers (i.e., compounds containing catechol groups). This process is usually based on the oxidation initiation, free radical coupling, and cross-linking reactions of the catechol groups (ortho-dihydroxy groups) in their molecules, ultimately forming a polymer network.

[0077] In some embodiments, the thickness of the catechol-based polymer layer can be 20 nm to 100 nm. Exemplarily, it can be 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value within a range formed by any two of these point values ​​as endpoints.

[0078] In some embodiments, the raw materials for preparing the catechol-based polymer layer include at least one of norepinephrine and dopamine. Dopamine may be provided by dopamine hydrochloride.

[0079] In some embodiments, the electrolytic copper foil is an ultra-low profile copper foil, and its surface roughness parameters meet the following requirements: surface roughness Rz ≤ 0.4 μm, interface spread area ratio Sdr ≤ 2%, maximum height Sz ≤ 1.0 μm, arithmetic mean height Sa ≤ 0.15 μm, and peak density Spd ≤ 1500 / mm². 2 ~58000 / mm 2 The arithmetic mean curvature Spc at the peak ≤ 4 μm -1 .

[0080] In some embodiments, the thickness of the electrolytic copper foil is 12 μm to 50 μm. Exemplarily, it can be 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0081] Furthermore, the thickness of the electrolytic copper foil is 12μm~35μm.

[0082] In some embodiments, the material of the silane coupling agent layer is a silane coupling agent, which includes at least one of aminosilane, epoxysilane, and mercaptosilane.

[0083] In some specific examples, aminosilanes include 3-aminopropyltriethoxysilane.

[0084] In some specific examples, epoxy silanes include 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0085] In some specific examples, mercaptosilanes include 3-mercaptopropyltriethoxysilane.

[0086] A second aspect of this application provides a method for preparing copper foil, the method comprising the following steps: sequentially forming a roughening treatment layer, a catechol-based polymer layer, and a silane coupling agent layer on the rough surface of an electrolytic copper foil.

[0087] In some embodiments, the step of forming the roughening layer includes:

[0088] The electrolytic copper foil is pickled, and then the rough surface of the pickled electrolytic copper foil is roughened at least once to form a roughening layer, thus obtaining roughened copper foil.

[0089] The roughening process includes a roughening process followed by a curing process.

[0090] In some embodiments, the pickling process parameters include: the pickling solution contains 3 g / L to 5 g / L copper ions and 90 g / L to 110 g / L of a primary inorganic acid; the pickling temperature can be 30°C to 35°C, and the pickling solution flow rate is 3.5 m³ / h. 3 / h~4.5m 3 / h. Understandably, acid washing of electrolytic copper foil can remove the oxide layer and some impurities and dirt from the surface of the foil.

[0091] In some embodiments, the first inorganic acid includes at least one of sulfuric acid and hydrochloric acid.

[0092] Understandably, the roughening treatment involves electrodeposition in a roughening solution, which can form copper nodules on the rough surface of the electrolytic copper foil. In some embodiments, the roughening solution includes 8 g / L to 10 g / L of copper ions, 10 g / L to 20 g / L of a second inorganic acid, and 2 mg / L to 8 mg / L of a roughening additive, wherein the roughening additive is selected from at least one of sodium tungstate, sodium molybdate, ammonium metatungstate, and sodium hyaluronate.

[0093] In some implementations, the parameters for the roughening treatment include: a roughening fluid flow rate of 3.5 m³ / h. 3 / h~6m 3 / h, operating temperature 30℃~35℃, current density 15A / dm 2 ~75A / dm 2 The electrodeposition time is 4s~6s.

[0094] In some embodiments, the second inorganic acid includes at least one of sulfuric acid and hydrochloric acid.

[0095] Understandably, the curing process involves electrodepositing the roughened copper foil in a curing solution. This curing process allows the copper nodules formed during the roughening process to firmly bond to the copper foil surface. In some embodiments, the curing solution includes 30 g / L to 60 g / L of copper ions and 90 g / L to 110 g / L of a third inorganic acid.

[0096] In some implementations, the curing process parameters include: a curing liquid flow rate of 3.5 m³ / min. 3 / h~6m 3 / h, operating temperature 30℃~35℃, current density 20A / dm 2 ~40A / dm 2 The electrodeposition time is 3s~5s.

[0097] In some embodiments, the third inorganic acid includes at least one of sulfuric acid and hydrochloric acid.

[0098] In some implementations, the roughening process can be performed 2 to 4 times. For example, it can be performed 3 times, and the conditions for the 3 roughening processes can be the same or different.

[0099] In some embodiments, the step of forming the catechol-based polymer layer includes: contacting the roughened layer with a catechol monomer solution, and then forming the catechol-based polymer layer via a polymerization reaction. Understandably, in the step of forming the catechol-based polymer layer, the smooth surface of the copper foil does not come into contact with the catechol monomer solution.

[0100] Understandably, catechin monomers usually refer to compounds containing catechin groups, which can undergo self-polymerization under weakly alkaline conditions to form polymer layers.

[0101] In some embodiments, the catechol monomer includes at least one of norepinephrine and dopamine.

[0102] In some embodiments, the polymerization reaction time is 30s to 120s, optionally 40s to 80s. For example, it can be 40s, 45s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, or any value within a range formed by any two of these point values ​​as endpoints.

[0103] In some embodiments, the concentration of catechol monomers in the catechol monomer solution is 2 mg / L to 8 mg / L. Exemplarily, it can be 2 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L, 7 mg / L, or 8 mg / L.

[0104] In some embodiments, the solvent used to prepare the catechol monomer solution can be a Tris (tris(hydroxymethyl)aminomethane)-hydrochloric acid buffer solution with a pH of 8 to 8.5.

[0105] In some embodiments, a silane coupling agent layer is formed on the surface of the catechol-based polymer layer, including:

[0106] The catechin polymer layer was immersed in a silane coupling agent solution and then dried.

[0107] In some embodiments, the material of the silane coupling agent layer is a silane coupling agent, which includes at least one of aminosilane, epoxysilane, and mercaptosilane.

[0108] In some specific examples, the immersion time is 6 to 10 seconds. For example, it can be 6 seconds, 7 seconds, 8 seconds, 9 seconds, or 10 seconds.

[0109] In some specific examples, the concentration of the silane coupling agent in the silane coupling agent solution is 0.2 wt% to 1 wt%. Exemplarily, it can be 0.2 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, or 2 wt%.

[0110] In some embodiments, the drying conditions include a temperature of 100°C to 200°C and a time of 5 to 20 seconds.

[0111] In some embodiments, the preparation method further includes a step of forming a metal protective barrier layer on the surface of the roughened layer between the step of forming the roughened layer and the step of forming the catechol-based polymer layer. It is understood that when the preparation method includes the step of forming a metal protective barrier layer on the surface of the roughened layer, the step of forming the catechol-based polymer layer involves contacting the roughened layer with a catechol monomer solution and forming the catechol-based polymer layer through a polymerization reaction.

[0112] In some embodiments, the method for preparing the copper foil includes the following steps S1 to S4;

[0113] S1: A roughening treatment layer is formed on the rough surface of the electrolytic copper foil;

[0114] S2: A metal protective barrier layer is formed on the surface of the roughening treatment layer;

[0115] S3: A catechol-based polymer layer is formed on the surface of the metal protective barrier layer;

[0116] S4: A silane coupling agent layer is formed on the surface of the catechol-based polymer layer.

[0117] In some implementations, a metal protective barrier layer can be formed by electrodeposition on the surface of the roughened layer.

[0118] In some embodiments, the step of forming the metal protective barrier layer includes:

[0119] The roughened copper foil obtained by roughening treatment is electrodeposited in a metal electroplating solution;

[0120] The metals mentioned above are non-copper metals and may include at least one of titanium, tin, tungsten, molybdenum and zinc.

[0121] In some embodiments, the roughened copper foil obtained by roughening treatment is electrodeposited sequentially in a nickel plating solution, a zinc plating solution, and a chromium plating solution to form a metal protective barrier layer on the surface of the roughened layer. The metal protective barrier layer includes a nickel plating sublayer, a zinc plating sublayer, and a chromium plating sublayer sequentially stacked in a direction away from the roughened layer.

[0122] In some specific examples, the parameters for electrodeposition in a nickel plating solution include: the nickel plating solution contains 1 g / L to 5 g / L of nickel ions, and the flow rate of the nickel plating solution is 3.5 m³ / L. 3 / h~6m 3 The operating temperature is 30℃~35℃, and the current density is 0.2A / dm³. 2~ 1A / dm 2 The electrodeposition time is 8-16 s.

[0123] In some specific examples, the parameters for electrodeposition in the zinc plating solution include: the zinc plating solution contains 1 g / L to 3 g / L of zinc ions, and the zinc plating solution flow rate is 3.5 m³ / L. 3 / h~6m 3 The operating temperature is 30℃~35℃, and the current density is 0.2A / dm³. 2 ~1A / dm 2 The electrodeposition time is 6~16s.

[0124] In some specific examples, the parameters for electrodeposition in the chromium plating solution include: the chromium plating solution contains 1 g / L to 3 g / L of chromium ions, and the flow rate of the chromium plating solution is 3.5 m³ / L. 3 / h~6m 3 The operating temperature is 30℃~35℃, and the current density is 0.2A / dm³. 2 ~1A / dm 2 The electrodeposition time is 6~16s.

[0125] A third aspect of this application provides the application of the copper foil described above or the copper foil prepared by the method described above in the preparation of printed circuit boards.

[0126] A fourth aspect of this application provides a printed circuit board comprising a substrate and the aforementioned copper foil disposed on the substrate.

[0127] To make the objectives and advantages of this application clearer, the copper foil and its effects of this application are further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and should not be used to limit this application. Unless otherwise specified, the following embodiments do not include components other than unavoidable impurities. Unless otherwise specified, the drugs and instruments used in the embodiments are conventional choices in the art. Experimental methods in the embodiments that do not specify specific conditions are implemented according to conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0128] Example 1

[0129] S1: The ultra-low profile electrolytic copper green foil is acid-washed to remove the oxide layer and some impurities from the surface. The thickness of the ultra-low profile electrolytic copper green foil is 18μm, and the surface roughness parameters are: Rz 0.2μm~0.4μm, Ra 0.03μm~0.08μm, Sdr 0.02%~0.05%, Sz 0.4μm~1.0μm, Sa 0.05μm~1.0μm, Spd 100mm. 2 ~1000 / mm 2 Spc is 0.02μm -1 ~0.05μm -1 The pickling solution contained 5 g / L copper ions and 110 g / L sulfuric acid. The temperature of the pickling solution was 32℃, and the flow rate was 4 m³ / s. 3 / h;

[0130] The rough surface of the pickled electrolytic copper foil is roughened three times to form a roughened layer on the rough surface of the electrolytic copper foil. Each roughening process includes a roughening process and a curing process in sequence.

[0131] The roughening treatment involves electrodeposition in a roughening solution containing a roughening additive. In this embodiment, a mixed additive of sodium tungstate and sodium metatungstate is used, with a sodium tungstate concentration of 30 mg / L and a sodium metatungstate concentration of 25 mg / L. The composition, flow rate, operating temperature, and current density of the roughening solution are identical for all three roughening treatment steps. Specifically, the copper ion concentration in the roughening solution is 10 g / L, the sulfuric acid concentration is 17 g / L, and the roughening additive concentration is 3 mg / L; the operating temperature is 33°C, and the flow rate is 4 m³ / L. 3 / h; current density is 65A / dm2 The electrodeposition times corresponding to the three roughening treatments were 4s, 6s, and 4s, respectively.

[0132] The curing process involves electrodepositing the roughened copper foil in a curing solution to ensure that the roughened copper nodules firmly bond to the surface of the raw foil. The parameters for all three curing processes are identical: a copper ion concentration of 50 g / L, a sulfuric acid concentration of 110 g / L, an operating temperature of 32°C, and a curing solution flow rate of 4.2 m³ / L. 3 / h, current density is 20A / dm 2 The electrodeposition time was 4 seconds.

[0133] S2: A metal protective barrier layer is formed on the surface of the roughening treatment layer. The metal protective barrier layer includes a nickel plating sublayer, a zinc plating sublayer, and a chromium plating sublayer stacked sequentially in a direction away from the roughening treatment layer. The specific steps are as follows:

[0134] A roughened copper foil was electrodeposited in a nickel plating solution to obtain a nickel sublayer. The nickel ion concentration in the nickel plating solution was 1.5 g / L, the operating temperature was 33℃, and the flow rate of the nickel plating solution was 4 m³ / L. 3 / h, current density is 0.3A / dm 2 The electrodeposition time was 12 s;

[0135] Then, electrodeposition was performed in the zinc plating solution to obtain a zinc sublayer on the surface of the nickel sublayer. The zinc ion concentration in the zinc plating solution was 2 g / L, the operating temperature was 32℃, and the flow rate of the zinc plating solution was 3.5 m³ / L. 3 / h, current density is 0.2A / dm 2 The electrodeposition time was 10 s;

[0136] Then, electrodeposition is performed in the chromium plating solution to obtain a chromium sublayer on the surface of the zinc sublayer, resulting in an intermediate copper foil; wherein, the chromium ion concentration in the chromium plating solution is 2 g / L, the working temperature is 30℃, and the flow rate of the chromium plating solution is 4 m³ / L. 3 / h, current density is 0.5A / dm 2 The electrodeposition time was 10 s;

[0137] S3: Forming a catechol-based polymer layer on the surface of the metal protective barrier layer, the specific steps are as follows:

[0138] The aforementioned metal protective barrier layer is brought into contact with a catechol monomer solution, and a catechol polymer layer is formed on the surface of the metal protective barrier layer (i.e., the chromium plating sublayer surface) through a polymerization reaction to obtain a polymer-modified copper foil; the reaction time is 60 s; wherein, the catechol monomer is norepinephrine and dopamine hydrochloride in a mass ratio of 1:1, the total concentration of catechol monomer in the catechol monomer solution is 2 mg / L, and the solvent of the catechol monomer solution is Tris hydrochloric acid buffer with a pH of 8.5;

[0139] S4: A silane coupling agent layer is formed on the surface of the catechol-based polymer layer. The specific steps are as follows:

[0140] The polymer-modified copper foil obtained in step S3 was immersed in a 0.5 wt% silane aqueous solution for 10 s, and the silane coupling agent was 3-aminopropyltriethoxysilane; the copper foil was then removed and baked in an oven at 150°C for 8 s.

[0141] Example 2

[0142] The procedure is basically the same as in Example 1, except that in step S3, the concentration of the catechol monomer is 6 mg / L.

[0143] Example 3

[0144] The process is basically the same as in Example 1, except that in step S1, the thickness of the ultra-low profile electrolytic copper foil used is 12 μm.

[0145] Example 4

[0146] The process is basically the same as in Example 1, except that in step S1, the thickness of the ultra-low profile electrolytic copper foil used is 35 μm.

[0147] Example 5

[0148] The process is basically the same as in Example 1, except that in step S4, 3-(2,3-epoxypropoxy)propyltrimethoxysilane of the same mass concentration is used instead of 3-aminopropyltriethoxysilane.

[0149] Example 6

[0150] The process is basically the same as in Example 1, except that the polymerization reaction time in step S3 is 120 s.

[0151] Comparative Example 1

[0152] The process is basically the same as in Example 1, except that step S3 is not performed; instead, a silane coupling agent layer is directly formed on the surface of the chromium sublayer obtained in step S2.

[0153] Comparative Example 2

[0154] The process is basically the same as in Example 3, except that step S3 is not performed; instead, a silane coupling agent layer is directly formed on the surface of the chromium sublayer obtained in step S2.

[0155] Comparative Example 3

[0156] The process is basically the same as in Example 4, except that step S3 is not performed; instead, a silane coupling agent layer is directly formed on the surface of the chromium sublayer obtained in step S2.

[0157] Test case

[0158] The surface roughness parameters, microstructure, and electrical properties of the copper foils prepared in Examples 1-6 and Comparative Examples 1-3 were tested.

[0159] The morphology and height of the copper teeth were measured using a Zeiss Sigma 300 electron microscope. SEM images of the rough surfaces of the copper foils prepared in Examples 1-3 are shown below. Figures 2-4 As shown, the rough surface SEM image of the copper foil prepared in Comparative Example 1 is as follows. Figure 5 As shown, the cross-sectional SEM image of the copper foil prepared in Example 1 is as follows. Figure 6 As shown, the cross-sectional SEM image of the copper foil prepared in Comparative Example 1 is as follows. Figure 7 As shown.

[0160] The surface roughness of the copper foils prepared in Examples 1-6 and Comparative Examples 1-3 was tested using an Olympus OLS5100 from Japan. The measured results of Rz, Sd, Spd, and Spc are shown in Table 1.

[0161] The peel strength between the copper foils prepared in Examples 1-6 and Comparative Examples 1-3 and the PPO and FR4 substrates was tested. The test method is as follows:

[0162] (1) Press the copper foil with the PPO substrate and then test the peel strength a0 of the copper foil; press the copper foil with the PPO substrate to obtain a composite board, perform a 10-minute tin immersion treatment on the composite board, then test the peel strength a1 of the copper foil, and calculate the thermal decay rate r1 according to r1=( a0- a1) / a0;

[0163] (2) Press the copper foil with the FR4 substrate and then test the peel strength b0 of the copper foil; press the copper foil with the FR4 substrate to obtain a composite board, perform a 10-minute tin immersion treatment on the composite board, then test the peel strength b1 of the copper foil, and calculate the thermal decay rate r2 according to b1=( b0- b1) / a0.

[0164] The peel strength test data were obtained using a computer-controlled electronic universal testing machine manufactured by Rigel Instruments. The test results are shown in Table 2.

[0165] The electrical performance (i.e., electrical transmission loss) of the copper foils prepared in Examples 1-6 and Comparative Examples 1-3 was tested at different measurement frequencies. The electrical transmission loss was measured using a network analyzer (Agilent Technologies E5080A) at frequencies (0.01-40 GHz) on the fabricated circuit boards (using a two-port testing method). The PCB structure was an L1 microstrip line structure (EM890) with an impedance of 50 Ω. The test results are shown in Table 3.

[0166] Table 1

[0167]

[0168] Table 2

[0169]

[0170] Table 3

[0171]

[0172] Combination Figures 2-7 It can be seen that for raw foils of different thicknesses, the SEM morphology of the treated surface of the copper foil did not change significantly after adding intermediate modification in the surface treatment step, and the addition of intermediate modification did not increase the copper tooth height of the treated surface.

[0173] As shown in Tables 1-3, compared with the comparative example, the copper foil prepared in the example, while maintaining a low roughness level, exhibits significantly improved peel strength after lamination with FR4 and PPO, and its electrical signal transmission performance does not decrease after being fabricated into a PCB. Furthermore, the peel strength attenuation rate of the copper foil prepared in the example after 10 minutes of tin immersion is significantly lower than that of the corresponding comparative example.

[0174] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0175] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A copper foil, characterized in that, The copper foil includes an electrolytic copper foil and a roughening treatment layer, a catechol polymer layer, and a silane coupling agent layer sequentially stacked on the rough surface of the electrolytic copper foil.

2. The copper foil according to claim 1, characterized in that, The catechol-based polymer layer satisfies at least one of the following conditions: (1) Thickness is 20nm~100nm; (2) The raw materials for preparing the catechol-based polymer layer include at least one of norepinephrine and dopamine.

3. The copper foil according to claim 1, characterized in that, The surface of the copper foil having the silane coupling agent layer satisfies at least one of the following characteristics: (1) Roughness Rz≤1.1μm; (2) The interface expansion area ratio Sdr ≤ 3.5%; (3) The peak density Spd is 40000 / mm 2 ~58000 / mm 2 ; (4) The arithmetic mean curvature Spc at the peak is 5.5 μm. -1 ~7.5 / μm -1 ; (5) Peel strength ≥ 1.2 N / mm; (6) Copper tooth height ≤ 500nm.

4. The copper foil according to any one of claims 1 to 3, characterized in that, The surface roughness parameters of the electrolytic copper foil satisfy the following: surface roughness Rz ≤ 0.4 μm, interface expansion area ratio Sdr ≤ 2%, maximum height Sz ≤ 1.0 μm, arithmetic mean height Sa ≤ 0.15 μm, and peak density Spd of 1500 / mm². 2 ~58000 / mm 2 The arithmetic mean curvature Spc at the peak ≤ 4 μm -1 ; and / or, The thickness of the electrolytic copper foil is 12μm~50μm.

5. The copper foil according to any one of claims 1 to 3, characterized in that, The copper foil further includes a metal protective barrier layer disposed between the roughening treatment layer and the catechol-based polymer layer, wherein the material of the metal protective barrier layer includes at least one selected from nickel, titanium, tin, tungsten, molybdenum, and zinc; and / or, The silane coupling agent layer contains a silane coupling agent, which includes at least one of aminosilane, epoxysilane, and mercaptosilane.

6. A method for preparing copper foil, characterized in that, The preparation method includes the following steps: A roughening treatment layer, a catechol-based polymer layer, and a silane coupling agent layer are sequentially formed on the rough surface of the electrolytic copper foil.

7. The preparation method according to claim 6, characterized in that, The steps for forming the catechol-based polymer layer include: The roughened layer is brought into contact with a catechol monomer solution, and a catechol polymer layer is formed through a polymerization reaction.

8. The preparation method according to claim 7, characterized in that, The catechol monomer includes at least one of norepinephrine and dopamine; and / or, The polymerization reaction takes 30 s to 120 s; and / or, The concentration of the catechin monomer in the catechin monomer solution is 2 mg / L to 8 mg / L.

9. The preparation method according to claim 7 or 8, characterized in that, The steps for forming the roughening layer include: The electrolytic copper foil is pickled, and then the rough surface of the pickled electrolytic copper foil is roughened at least once to form a roughening layer. The roughening process includes a roughening process followed by a curing process.

10. The application of the copper foil according to any one of claims 1 to 5 or the copper foil prepared by the method according to any one of claims 6 to 9 in the preparation of printed circuit boards.

11. A printed circuit board, characterized in that, It includes a substrate and a copper foil disposed on the substrate, wherein the copper foil includes the copper foil according to any one of claims 1 to 5 or the copper foil prepared by the method according to any one of claims 6 to 9.

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