Preparation method of copper foil and copper-clad plate

Abstract

The invention discloses a preparation method of a copper foil and a copper-clad plate, and the preparation method of the copper foil comprises the following steps: carrying out electro-deposition on an electroplating solution to obtain a raw foil; the raw foil is subjected to acid pickling, roughening, curing, ashing, passivation and silane coupling agent spraying treatment; wherein in the step of roughening treatment, an adopted roughening treatment solution is prepared from 9 g / L to 11 g / L of copper ions, 140 g / L to 160 g / L of sulfuric acid, 0.13 g / L to 3 g / L of sodium tungstate, 0.083 g / L to 1 g / L of titanous sulfate and 15 ppm to 85 ppm of chloride ions; the roughening treatment temperature is 20-35 DEG C, the liquid feeding flow is 4-6 m < 3 > / h, the roughening current is 1000-5000 A, and the roughening time is 4-5 s. Through the method, the copper foil with low roughness and high peel strength can be obtained.

Description

Technical Field

[0001] This application relates to the technical field of electrolytic copper foil preparation, in particular to a method for preparing copper foil and a copper clad laminate. Background Art

[0002] With the booming development of communication technologies such as millimeter-wave radar, artificial intelligence (AI), and 5G, the high-frequency and high-speed functions have put forward higher requirements of low loss, high frequency, and high reliability for PCB substrate materials. Among them, electrolytic copper foil, as the conductor material of PCB substrates, plays a decisive role in the signal transmission integrity. Due to the intensification of the skin effect caused by the high speed and high frequency of signals, the higher the frequency, the narrower the transmission range of the signal on the conductor surface, and the more serious the standing wave and reflection, resulting in an increase in attenuation. Therefore, compared with conventional copper foils, some high-speed PCB substrates use RTF copper foils, VLP copper foils, or HVLP copper foils with low roughness. At the same time, to improve the reliability of PCB substrate materials, it is necessary to roughen the bonding surface between the copper foil and the substrate to ensure the bonding force, and also take into account the impact of this treatment on signal transmission attenuation, striving to maintain the overall stability of the PCB while meeting the requirements of high-performance signal transmission.

[0003] However, for the copper foils prepared by the existing technology, the roughness of some treatment surfaces and the bonding force with the substrate cannot be taken into account simultaneously, that is, the surface roughness of the copper foil and its peel strength when used on high-frequency and high-speed circuit boards cannot meet the requirements at the same time. Summary of the Invention

[0004] To solve the problems of high surface roughness and poor peel strength of copper foils existing in the prior art, this application provides a method for preparing copper foils and a copper clad laminate.

[0005] To solve the above problems, the first aspect of this application provides a method for preparing copper foil, including: obtaining a raw foil by electrodepositing an electroplating solution; performing pickling, roughening, curing, ashing, passivating, and spraying a silane coupling agent on the raw foil; wherein, in the step of roughening treatment, the roughening treatment solution used includes 9 g / L - 11 g / L of copper ions, 140 g / L - 160 g / L of sulfuric acid, 0.13 g / L - 3 g / L of sodium tungstate, 0.083 g / L - 1 g / L of titanium sulfate, and 15 ppm - 85 ppm of chloride ions; the treatment temperature of the roughening is 20°C - 35°C, the upflow rate is 4 m3 / h - 6 m3 / h, the roughening current is 1000 A - 5000 A, and the roughening time is 4 s - 5 s.

[0006] In some of these embodiments, in the step of roughening treatment, the roughening treatment solution includes 0.5 g / L - 1 g / L of sodium tungstate, 0.1 g / L - 0.3 g / L of titanium sulfate, and 50 ppm - 80 ppm of chloride ions; the roughening treatment temperature is 30°C - 35°C, the upper liquid flow rate is 5 m3 / h, the roughening current is 1500 A - 3500 A, and the roughening time is 4.5 s.

[0007] In some of these embodiments, in the step of spraying the silane coupling agent treatment, the silane coupling agent solution used contains 1.0 g / L - 3.0 g / L of silane coupling agent, and the spraying time is 2 - 4 s;

[0008] The silane coupling agent is one or more of amino silane coupling agent and epoxy silane coupling agent.

[0009] In some of these embodiments, in the step of passivation treatment, the passivation solution used is composed of chromate and deionized water; or, the passivation solution is composed of chromate, zinc salt, and deionized water; the passivation solution includes 1.2 g / L - 1.8 g / L of chromium ions (Cr 6+ ), the pH value range of the passivation solution is 0.95 - 10.5, the upper liquid flow rate is 6 m 3 / h - 8 m 3 / h, and the passivation current is 50 A - 100 A.

[0010] In some of these embodiments, in the step of ashing treatment, the ashing solution used includes 1.5 g / L - 3.0 g / L of zinc ions, 0.05 g / L - 0.2 g / L of nickel ions, and 80 g / L - 100 g / L of potassium pyrophosphate; the pH value range of the ashing solution is 9 - 11, the upper liquid flow rate is 15 m3 / h, and the ashing current is 10 A - 70 A.

[0011] In some of these embodiments, in the step of curing treatment, the curing solution used includes 45 g / L - 55 g / L of copper ions and 100 g / L - 120 g / L of sulfuric acid; the treatment temperature is 30°C, the upper liquid flow rate is 5 m3 / h - 10 m3 / h, and the curing current is 1000 A - 2500 A.

[0012] In some of these embodiments, in the step of pickling treatment, the pickling solution used includes 30 g / L - 50 g / L of copper ions and 90 g / L - 120 g / L of sulfuric acid; the pickling temperature is 20°C - 30°C, the upper liquid flow rate is 5 m3 / h - 9 m3 / h, and the pickling time is 4 s - 5 s.

[0013] In some of these embodiments, in the step of electro-depositing an electroplating solution to obtain a raw foil, the electroplating solution includes copper sulfate, sulfuric acid, and an additive; wherein, the concentration of the copper sulfate is 90 g / L - 110 g / L, the concentration of the sulfuric acid is 100 g / L - 120 g / L, and the additive includes at least one of a leveling agent, a brightening agent, and a gloss agent; the upflow rate is 60 m 3 / h - 65 m 3 / h, and the electroplating temperature is 50°C - 55°C.

[0014] To solve the above problems, a second aspect of the present application provides a copper-clad laminate, wherein the copper-clad laminate includes a substrate and a copper foil, the copper foil is disposed on the substrate, and the copper foil is prepared by the method for preparing a copper foil provided in any of the above embodiments.

[0015] In some of these embodiments, the line roughness Rz of the copper foil is less than 1.2 μm, the copper nodule diameter is 0.3 μm - 0.8 μm, the nickel electrodeposition amount is less than 0.5 ppm / m 2 , and the peel strength from the substrate is greater than 1.0 N / mm.

[0016] The beneficial effects of the present application are: Compared with the prior art, in the method for preparing a copper foil provided in the embodiments of the present application, the roughening treatment solution used in the roughening treatment process includes 9 g / L - 11 g / L of copper ions, 140 g / L - 160 g / L of sulfuric acid, 0.13 g / L - 3 g / L of sodium tungstate, 0.083 g / L - 1 g / L of titanium sulfate, and 15 ppm - 85 ppm of chloride ions; the roughening treatment temperature is 20°C - 35°C, the upflow rate is 4 m 3 / h - 6 m3 / h, the roughening current is 1000 A - 5000 A, and the roughening time is 4 s - 5 s; on the one hand, trace elements tungsten and titanium are added to the roughening treatment solution, and it does not contain Fe, Co, NdFeB. The nickel electrodeposition amount of the copper foil obtained in the present application is extremely small, less than 0.5 ppm / m 2 , and basically no ferromagnetism will be generated; on the other hand, by controlling the roughening current conditions, the line roughness Rz of the copper foil is less than 1.2 μm, the copper nodule diameter is 0.3 μm - 0.8 μm, and the nickel electrodeposition amount is less than 0.5 ppm / m 2 , the copper nodule refinement effect is optimized, the roughness of the copper foil is reduced, and the requirements of fast transmission speed, small loss, and high frequency under high-frequency and high-speed signals can be met; on the other hand, the peel strength between the copper foil and the substrate is greater than 1.0 N / mm, and it has a stable and reliable substrate bonding force. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic flow chart of the preparation method of copper foil provided by some embodiments of the present application.

[0019] Figure 2 It is a picture of a as - prepared raw foil taken by a Scanning Electron Microscope (SEM) provided by some embodiments of the present application.

[0020] Figure 3 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 1 of the present application.

[0021] Figure 4 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 2 of the present application.

[0022] Figure 5 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 3 of the present application.

[0023] Figure 6 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 4 of the present application.

[0024] Figure 7 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 5 of the present application.

[0025] Figure 8 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 6 of the present application.

[0026] Figure 9 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 7 of the present application.

[0027] Figure 10 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Embodiment 8 of the present application.

[0028] Figure 11 It is an SEM picture of the copper foil obtained by the copper foil preparation method provided in Comparative Example 1 of the present application. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0030] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless clearly indicated otherwise in the context. "Plural" generally includes at least two, but does not exclude the case of including at least one.

[0031] It should be understood that the term "and / or" used herein is only a description of the associated relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after. The terms "first", "second", etc. in the description and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0032] It should be understood that the term "including", "comprising", or any other variation used herein is intended to cover a non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article, or device. Without further limitation, the elements defined by the statement "including..." do not exclude the existence of additional identical elements in the process, method, article, or device including the said elements.

[0033] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present application, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0034] References to "embodiments" in this specification mean that a particular feature, structure, or characteristic described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase does not necessarily refer to the same embodiment at every occurrence in the specification, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0035] With the booming development of communication technologies such as millimeter-wave radar, artificial intelligence (AI), and 5G, the high-frequency and high-speed functions pose higher requirements of low loss, high frequency, and high reliability on PCB substrate materials. Among them, copper foil, as the conductor material of PCB substrates, plays a decisive role in signal transmission integrity. Due to the intensification of the skin effect caused by the high speed and high frequency of signals, the higher the frequency, the narrower the transmission range of signals on the conductor surface, and the more serious the standing waves and reflections, resulting in an increase in attenuation. Therefore, compared with conventional copper foils, some high-speed PCB substrates use RTF copper foils, VLP copper foils, or HVLP copper foils with low roughness. At the same time, to improve the reliability of PCB substrate materials, it is necessary to roughen the bonding surface between the copper foil and the substrate to ensure the bonding force, and also take into account the impact of this treatment on signal transmission attenuation, striving to maintain the overall stability of the PCB while meeting the requirements of high-performance signal transmission.

[0036] However, the surface roughness of some treatment surfaces of the copper foils prepared by the prior art and the bonding force with the substrate cannot be taken into account simultaneously, that is, the surface roughness of the copper foil and its peel strength when used on high-frequency and high-speed circuit boards cannot meet the requirements simultaneously.

[0037] To solve the above technical problems, the present application provides a method for preparing a copper foil, including: electro-depositing an electroplating solution to obtain a raw foil; pickling, roughening, curing, ashing, passivating, and spraying a silane coupling agent on the raw foil; wherein, in the step of roughening treatment, the roughening treatment solution used includes 9 g / L - 11 g / L of copper ions, 140 g / L - 160 g / L of sulfuric acid, 0.13 g / L - 3 g / L of sodium tungstate, 0.083 g / L - 1 g / L of titanium sulfate, and 15 ppm - 85 ppm of chloride ions; the roughening treatment temperature is 20°C - 35°C, the up-flow rate is 4 m 3 / h - 6 m 3 / h, the roughening current is 1000 A - 5000 A, and the roughening time is 4 s - 5 s.

[0038] The copper foil preparation method provided by the embodiments of the present application uses a roughening treatment solution during the roughening treatment process, which includes 9 g / L - 11 g / L of copper ions, 140 g / L - 160 g / L of sulfuric acid, 0.13 g / L - 3 g / L of sodium tungstate, 0.083 g / L - 1 g / L of titanium sulfate, and 15 ppm - 85 ppm of chloride ions; the roughening treatment temperature is 20°C - 35°C, the upflow rate is 4 m 3 / h - 6 m 3 / h, the roughening current is 1000 A - 5000 A, and the roughening time is 4 s - 5 s; on the one hand, trace elements tungsten and titanium are added to the roughening treatment solution, and it does not contain Fe, Co, NdFeB. The electroplated amount of nickel on the copper foil obtained in this application is extremely small, less than 0.5 ppm / m 2 , and ferromagnetic properties are basically not generated; on the other hand, by controlling the roughening current conditions, the line roughness Rz of the copper foil is less than 1.2 μm, the copper nodule diameter is 0.3 μm - 0.8 μm, and the electroplated amount of nickel is less than 0.5 ppm / m 2 , optimizing the refinement effect of copper nodules, reducing the roughness of the copper foil, and meeting the requirements of fast transmission speed, low loss, and high frequency under high-frequency and high-speed signals; on the other hand, the peel strength between the copper foil and the substrate is greater than 1.0 N / mm, having a stable and reliable substrate bonding force.

[0039] Please refer to Figure 1 , Figure 1 , which is a schematic flow chart of the copper foil preparation method provided by some embodiments of the present application. The preparation method includes:

[0040] Step S11: Electro-deposit the electroplating solution to obtain a raw foil.

[0041] Electro-deposit the electroplating solution on the cathode roller to obtain a raw foil. In other words, use the cathode roller to electro-deposit the electroplating solution to generate a raw foil.

[0042] Specifically, the electroplating solution includes copper sulfate (CuSO4), sulfuric acid (H2SO4), and additives, etc. Among them, copper sulfate is the main component in the electroplating solution, providing copper ions (Cu 2+ ), and these copper ions are deposited on the surface of the workpiece to be plated during electroplating to form a copper coating. The concentration of copper sulfate is 90 g / L - 110 g / L, which can provide recombinant copper ions during electroplating and reduce the risk of solution instability or coating quality decline caused by too high a concentration at the same time.

[0043] Sulfuric acid acts as a conductive agent in the electroplating solution, increasing the conductivity of the solution, improving the uniformity of the current distribution during electroplating, and improving the uniformity and quality of the coating. The concentration of sulfuric acid is 100 g / L - 120 g / L, which helps to maintain the acidity of the solution and ensure the stability of the electroplating process and the uniformity of the coating.

[0044] The additive includes at least one of a leveling agent, a brightening agent, and a gloss agent. Among them, the leveling agent, also known as the brightening agent, can improve the dispersion ability and throwing power of the electroplating solution, enabling copper ions to deposit more uniformly, including complex shapes and deep hole parts. The leveling agent can reduce the roughness of the coating, make the coating surface smoother and flatter, and improve the appearance quality and corrosion resistance of the coating. The gloss agent can further improve the brightness of the coating, make the coating surface brighter, and enhance its decorative and protective properties.

[0045] Step S11 specifically includes placing the cathode roller in the electrolytic cell. The electrolytic cell is filled with an electroplating solution. One end of the cathode roller is externally connected to a circuit, and electricity is passed through to deposit and form a raw foil. Among them, a flow control device is also provided in the electrolytic cell to control the incoming liquid flow rate of the electrolytic cell.

[0046] In step S11, the electroplating temperature for the electroplating solution deposition / electroplating treatment is 50 - 55 °C, and the incoming liquid flow rate is 60 m 3 / h - 65 m 3 / h.

[0047] Among them, the incoming liquid flow rate is the amount of liquid entering the electrolytic cell per hour or the flow rate of the electroplating solution flowing into the electroplating bath per hour. The incoming liquid flow rate controls the stability of the electroplating solution and the condition of the foil surface, and can ensure the supply of sufficient electroplating solution and the uniformity of the copper foil. In some embodiments of the present application, the HVLP copper foil (also known as double-sided bright copper foil) can be produced by the double-sided bright electrolytic copper foil process. During the production process, through special treatment, both sides of the copper foil have a low roughness. This copper foil has the characteristics of high purity, flat surface, and low roughness, which helps to reduce the loss during signal transmission and improve the signal integrity.

[0048] Step S12: Perform pickling, roughening, curing, ashing, passivation, and spraying of a silane coupling agent on the raw foil.

[0049] Among them, pickling is to soak the raw foil in the pickling solution to remove the oxide layer, oil layer, other foreign matter contamination, etc. on the surface of the copper foil.

[0050] In some embodiments, in the step of pickling treatment, the pickling solution used includes 30 g / L - 50 g / L of copper ions and 90 g / L - 120 g / L of sulfuric acid. The pickling temperature is 20 °C - 30 °C, the incoming liquid flow rate is 5 m 3 / h - 9 m 3 / h, and the pickling time is 4 s - 5 s.

[0051] Copper ions can be provided by copper sulfate or copper chloride, which can adjust the chemical balance of the solution and reduce the excessive corrosion of the raw foil by the pickling solution. When the raw foil is immersed in the pickling solution, chemical reactions such as ion exchange will occur. The concentration of copper ions is 30g / L - 50g / L, which can inhibit the excessive erosion of hydrogen ions in the pickling solution on the raw foil and play a certain buffering role.

[0052] Sulfuric acid can react with the oxides and other impurities on the surface of the raw foil to remove the oxide layer. The concentration of sulfuric acid is 90g / L - 120g / L, ensuring sufficient dissolution ability for the oxide layer and other impurities. If the concentration of sulfuric acid is too low, it cannot effectively remove impurities such as the oxide layer; if the concentration is too high, it may cause excessive corrosion of the raw foil and damage the physical and chemical properties of the raw foil.

[0053] Furthermore, in some embodiments, the pickling temperature is 20°C - 30°C, which allows the chemical reactions of pickling to proceed at a relatively stable rate. If the temperature is too low, the chemical reaction rate is slow, which will lead to an extended pickling time, affecting production efficiency and may not be able to completely remove impurities; if the temperature is too high, it may exacerbate the corrosion of the copper foil by the pickling solution and may also trigger some side reactions, resulting in changes in the composition of the pickling solution or damage to the surface quality of the copper foil.

[0054] Among them, the upflow rate is 5m 3 / h - 9m 3 / h, which can keep the fresh pickling solution in continuous contact with the surface of the copper foil, timely carry away the reaction products and dissolved impurities, and prevent the accumulation of reaction products on the surface of the copper foil, affecting the pickling effect. If the upflow rate is too small, the impurity concentration in the local pickling solution will be too high, reducing the pickling efficiency; if the flow rate is too large, it may cause energy waste and significant wear of the equipment, and may also generate a large physical impact on the surface of the copper foil, affecting the integrity of the copper foil.

[0055] Furthermore, the pickling time is 4s - 5s, which can ensure that impurities are fully removed, but too long a time will increase the risk of corrosion of the copper foil, while too short a time may not achieve the ideal cleaning effect and some impurities will remain.

[0056] The roughening treatment is to put the raw foil into an electroplating tank filled with roughening treatment solution, and form a layer of copper crystal nuclei on the surface of the raw foil through the action of current, and grow these crystal nuclei into copper nodule particles. This process can significantly increase the specific surface area of the copper foil, thereby improving the bonding strength between the copper foil and the substrate and enhancing the peel strength of the copper clad laminate.

[0057] In some embodiments, in the roughening treatment step, the roughening treatment solution used includes 9 g / L - 11 g / L of copper ions, 140 g / L - 160 g / L of sulfuric acid, 0.13 g / L - 3 g / L of sodium tungstate (Na2WO4), 0.083 g / L - 1 g / L of titanium(III) sulfate (Ti2(SO4)3), and 15 ppm - 85 ppm of chloride ions.

[0058] Among them, copper ions provide a copper source and are the main components for forming copper crystal nuclei and copper nodule particles. Copper sulfate or copper chloride can be added to the roughening treatment solution. Sulfuric acid can provide an acidic environment and also increase the conductivity of the solution, ensuring that the current can be evenly distributed, thereby improving the electroplating efficiency.

[0059] Sodium tungstate may act as an additive in the roughening treatment solution and can affect the formation rate and growth mode of copper crystal nuclei. For example, it may adsorb on the surface of copper crystal nuclei, regulate the growth direction, rate, and distribution of copper nodules, and then regulate the uniformity and size of the growth of copper nodule particles, improving the uniformity of surface roughness.

[0060] Titanium(III) sulfate can regulate the formation rate of crystal nuclei, making the grains more dense. For example, it can promote the formation of copper ions at appropriate positions by changing the electrochemical state of the copper foil surface and help stabilize the growth process of crystal nuclei, preventing the crystal nuclei from aggregating too quickly or growing unevenly. The higher the concentration of titanium(III) sulfate, the faster the nucleation rate, but if the content is too high, multi-level dendrites will be formed, affecting the etching effect of the circuit board.

[0061] Chloride ions help improve the conductivity and stability of the roughening treatment solution, and at the same time can refine the grains and improve the surface quality of the copper foil.

[0062] Furthermore, in the roughening treatment step, the temperature of the roughening treatment (i.e., the reaction temperature during the roughening treatment process) is 20°C - 35°C, the upper liquid flow rate is 4 m 3 / h - 6 m3 / h, the roughening current is 1000 A - 5000 A, and the roughening time is 4 s - 5 s. Among them, too high a temperature will cause the reaction to be too fast, making it difficult to control the uniformity of copper nodule particles; too low a temperature may reduce the reaction rate, affecting production efficiency. The upper liquid flow rate is to control the flow rate of the roughening solution to ensure that the copper foil surface evenly contacts the roughening solution. Too low a flow rate may lead to uneven reactions, and too high a flow rate may waste the roughening solution. Too low a roughening current results in insufficient copper nodule particles, and too high a current results in too large or uneven particles. The control of the roughening time is to improve the particle size and distribution uniformity. Too short a time may result in insufficient particles, and too long a time may result in too large particles.

[0063] In some embodiments, in the roughening treatment step, the roughening treatment solution includes 0.5 g / L - 1 g / L of sodium tungstate, 0.1 g / L - 0.3 g / L of titanium sulfate, and 50 ppm - 80 ppm of chloride ions. Further, the roughening treatment temperature is 30°C - 35°C, the upflow rate is 5 m 3 / h, the roughening current is 1500 A - 3500 A, and the roughening time is 4.5 s.

[0064] The curing treatment can reinforce the formed copper nodule particles and enhance the structural stability of the copper nodule particles. Generally, it is carried out at a lower current. Repeating the roughening and curing steps can make the copper nodules grow densely. In some embodiments, in the curing treatment step, the curing solution used includes 45 g / L - 55 g / L of copper ions and 100 g / L - 120 g / L of sulfuric acid; the treatment temperature is 30°C, the upflow rate is 5 m3 / h - 10 m3 / h, and the curing current is 1000 A - 2500 A. By controlling each parameter in the above curing treatment step, effective reinforcement of the copper nodule particles formed by roughening can be achieved, and at the same time, the copper nodule particles grow more densely, providing better conditions for the subsequent application of the copper foil (such as combination with other materials or improvement of surface properties).

[0065] The ashing treatment process can further change the chemical composition or microstructure of the copper foil surface and form a barrier layer on the surface. The barrier layer helps to improve the chemical corrosion resistance and oxidation resistance of the copper foil. In some embodiments, in the ashing treatment step, the ashing solution used includes 1.5 g / L - 3.0 g / L of zinc ions (Zn 2+ ), 0.05 g / L - 0.2 g / L of nickel ions (Ni 2+ ), and 80 g / L - 100 g / L of potassium pyrophosphate; the pH value range of the ashing solution is 9 - 11, the upflow rate is 15 m 3 / h, and the ashing current is 10 A - 70 A.

[0066] Among them, the zinc ions react with other substances on the copper foil surface or in the solution to form compounds with anti-corrosion and anti-oxidation properties. The concentration of zinc ions is 1.5 g / L - 3.0 g / L. If the concentration of zinc ions is too low, a complete and effective barrier layer may not be formed; if the concentration is too high, the formed barrier layer may be too thick or uneven, affecting other properties of the copper foil.

[0067] Nickel ions can further improve the oxidation resistance and corrosion resistance of the barrier layer. The concentration of nickel ions is 0.05 g / L - 0.2 g / L. Subtle changes in the concentration of nickel ions also have a greater impact on the performance of the barrier layer. Within this concentration range, the stability and durability of the barrier layer can be enhanced, and the surface quality can be taken into account.

[0068] Potassium pyrophosphate exists as a complexing agent or buffer, which can form complexes with metal ions (such as zinc ions, nickel ions, etc.) in the solution, thereby regulating the activity and reaction rate of metal ions, enabling them to deposit on the copper foil surface at an appropriate rate to form a barrier layer. The concentration of potassium pyrophosphate is 80 g / L - 100 g / L, which helps to ensure its stable complexing and buffering effects in the solution. If the concentration of potassium pyrophosphate is too low, the conductivity and stability of the solution are insufficient, affecting the deposition effect; if the concentration is too high, the solution may become too viscous, affecting the deposition rate.

[0069] The pH value of the ashing solution affects the existence form and reaction activity of metal ions. In the embodiments of the present application, the pH value of the ashing solution ranges from 9 to 11, which can provide a suitable chemical environment for the deposition reactions of zinc ions, nickel ions, etc., ensuring that they can effectively participate in the formation reaction of the barrier layer. If the pH value is too low or too high, it may cause precipitation, hydrolysis or other side reactions of metal ions, affecting the formation and performance of the barrier layer.

[0070] The upper liquid flow rate is 15 m 3 / h, and the ashing current is 10 A - 70 A. Among them, the upper liquid flow rate can ensure that the ashing solution flows through the copper foil surface at a certain flow rate, ensuring that fresh ashing solution can continuously contact the copper foil surface, providing sufficient reactants for the formation of the barrier layer, and taking away the by-products generated during the reaction, enabling the reaction to proceed continuously and stably. Within the range of the ashing current, metal ions will deposit on the copper foil surface at an appropriate rate under the action of the electric field and participate in the formation of the barrier layer. If the ashing current is too small, the deposition rate may be too slow, affecting the formation efficiency of the barrier layer; if the ashing current is too large, it may lead to uneven deposition and even damage the structure of the already formed barrier layer, affecting the performance and quality of the barrier layer.

[0071] The passivation treatment of the copper foil with a barrier layer is carried out by surface passivation (i.e., anti-oxidation treatment) with a chromate (or chromate and zinc salt) solution, so that a complex film layer mainly composed of chromium (or chromium-zinc) is formed on the copper foil surface, preventing the copper foil from oxidizing and discoloring due to direct contact with air, and at the same time improving the heat resistance of the copper foil (higher zinc content results in better high-temperature resistance), which can ensure the storage period of the copper foil.

[0072] In some embodiments, in the step of passivation treatment, the passivation solution used is composed of chromate and deionized water; or, the passivation solution is composed of chromate, zinc salt and deionized water; the passivation solution contains 1.2 g / L - 1.8 g / L of Cr 6+ ions, the pH value of the passivation solution ranges from 0.95 to 10.5, and the upper liquid flow rate is 6 m 3 / h - 8 m 3 / h, and the passivation current is 50A - 100A. In this way, the copper foil after plating the barrier layer can be processed to form an effective passivation film with uniform distribution, providing anti-oxidation and heat resistance properties for the copper foil, and ensuring the stability and quality of the copper foil during storage and use.

[0073] Spraying a silane coupling agent is a process of forming a protective film or coupling layer on the material surface by spraying a solution containing a silane coupling agent. Among them, in some embodiments, the silane coupling agent is one or more of an amino silane coupling agent, an epoxy silane coupling agent, and a vinyl silane coupling agent.

[0074] In some embodiments, in the step of spraying the silane coupling agent treatment, the silane coupling agent solution used contains 1.0g / L - 3.0g / L of the silane coupling agent, and the spraying time is 2 - 4s. By spraying the silane coupling agent, on the one hand, the antioxidant ability of the copper foil at room temperature can be improved; on the other hand, when pressing at high temperature, the silane can make the copper foil and the resin substrate bond better through coupling, improving the peel strength. It can enhance the bonding force between the copper foil and the substrate, and at the same time improve the electrical properties of the copper foil surface.

[0075] This step includes but is not limited to three roughing and three solidifying treatments and multiple pickling treatments, etc., which are not limited here. The electrolytic copper foil is obtained through the above steps.

[0076] In this embodiment, trace elements tungsten and titanium are added to the roughening treatment solution, and it does not contain Fe, Co, NdFeB. The electroplating amount of nickel on the copper foil obtained in this application is extremely small, less than 0.5ppm / m 2 , and basically no ferromagnetism will be generated; the additives are simple and inorganic non-toxic additives, and are not easy to deteriorate after long-term use; by controlling the current conditions, the copper nodules are refined well, and the diameter of the obtained copper nodules is 0.3μm - 0.8μm, and the line roughness Rz of the copper foil is less than 1.2μm, reducing the roughness of the copper foil, which can meet the requirements of fast transmission speed, small loss, and high frequency under high-frequency and high-speed signals; on the other hand, the peel strength between the copper foil and the substrate is greater than 1.0N / mm, having a stable and reliable substrate bonding force.

[0077] This application also provides a copper clad laminate, including a substrate and a copper foil, the copper foil is disposed on the substrate, and the copper foil is prepared by the preparation method of the copper foil provided in any one of the above embodiments.

[0078] Among them, the substrate can be FR-4, high-frequency and high-speed substrate, or FR-7 prepreg laminate.

[0079] Further, in the embodiments of this application, the line roughness Rz of the copper foil is less than 1.2μm, the size of the copper nodules is between 0.3μm - 0.8μm, and the electroplating amount of nickel is less than 0.5ppm / m 2, the peel strength with the substrate is greater than 1.0 N / mm.

[0080] The preparation method of the copper foil provided by the present application and the performance of the obtained copper foil will be described in detail below through specific examples.

[0081] Example 1

[0082] Preparation of raw foil: Prepare an electroplating solution with a copper ion (which can be provided by copper sulfate or copper chloride) concentration of 90 g / L - 110 g / L and a sulfuric acid (H2SO4) concentration of 100 g / L - 120 g / L; put the above electroplating solution into an electrolytic cell, use a pure copper plate as the anode plate and a titanium plate as the cathode plate, and perform electrodeposition at a temperature of 50°C - 55°C to obtain a raw foil, and its SEM image is as Figure 2 shown; among them, the upper liquid flow rate is 60 m 3 / h - 65 m 3 / h.

[0083] Pickling treatment: Prepare a pickling solution with a sulfuric acid concentration of 100 g / L and a copper ion concentration of 40 g / L; put the above raw foil into the pickling solution and perform pickling treatment at room temperature of 25°C. Among them, the upper liquid flow rate is 5 m 3 / h, and the pickling time is 4.5 s.

[0084] Roughening treatment: Prepare a roughening treatment solution with a copper ion (which can be provided by copper sulfate or copper chloride) concentration of 10 g / L, a sulfuric acid concentration of 150 g / L, a sodium tungstate concentration of 0.1 g / L, a titanous sulfate concentration of 0.1 g / L, and a chloride ion concentration of 20 ppm; put the above pickled raw foil into the roughening treatment solution and perform roughening treatment at 25°C; among them, the upper liquid flow rate of the roughening treatment is 5 m 3 / h, the roughening current is the standard current (3500 A / 2100 A / 1500 A), and the roughening time is 4.5 s.

[0085] Curing treatment: Prepare a curing solution with a copper sulfate concentration of 50 g / L and a sulfuric acid concentration of 110 g / L; put the above roughened raw foil into the curing solution and perform curing treatment at a temperature of 40°C to obtain an electrolytic copper foil. Among them, the upper liquid flow rate of the curing treatment is 8 m 3 / h, and the curing current is 2000 A.

[0086] Ashing treatment: Prepare an ashing solution with a zinc ion concentration of 2 g / L, a nickel ion concentration of 0.01 g / L, and a potassium pyrophosphate concentration of 100 g / L, where the pH value of the ashing solution is 10; put the above cured raw foil into the ashing solution and perform ashing treatment to obtain an electrolytic copper foil. Among them, the upper liquid flow rate of the ashing treatment is 15 m 3 / h, and the ashing current is 50 A.

[0087] Passivation treatment: Prepare a passivation solution with a concentration of 1.2 g / L of chromium ions (Cr 6+ ), where the pH value of the passivation solution is 10; put the above-mentioned ashed raw foil into the passivation solution for passivation treatment to obtain an electrolytic copper foil. Among them, the upflow rate of the passivation treatment is 8 m 3 / h, and the passivation current is 85 A.

[0088] Spraying silane coupling agent treatment: Using deionized water as the basic solvent, prepare a silane coupling agent solution with a concentration of 1.0 - 3.0 g / L of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; spray the silane coupling agent solution on the above-mentioned passivated raw foil for spraying silane coupling agent treatment to obtain a copper foil, as Figure 3 shown. Among them, the spraying time is 2.5 s.

[0089] Example 2

[0090] The method for preparing the copper foil provided in Example 2 is basically the same as the method for preparing the copper foil provided in Example 1, the difference being that in the roughening treatment step of Example 2, the concentration of sodium tungstate in the roughening treatment solution is 0.5 g / L, the concentration of titanium sulfite is 0.3 g / L, and the concentration of chloride ions is 50 ppm, and the contents and parameters of other substances remain unchanged. The copper foil obtained in Example 2 is as Figure 4 shown.

[0091] Example 3

[0092] The method for preparing the copper foil provided in Example 3 is basically the same as the method for preparing the copper foil provided in Example 1, the difference being that in the roughening treatment step of Example 3, the concentration of sodium tungstate in the roughening treatment solution is 1 g / L, the concentration of titanium sulfite is 0.5 g / L, and the concentration of chloride ions is 80 ppm, and the contents and parameters of other substances remain unchanged. The copper foil obtained in Example 3 is as Figure 5 shown.

[0093] Example 4

[0094] The method for preparing the copper foil provided in Example 4 is basically the same as the method for preparing the copper foil provided in Example 1, the difference being that in the roughening treatment step of Example 4, the concentration of sodium tungstate in the roughening treatment solution is 0.5 g / L, the concentration of titanium sulfite is 0.3 g / L, and the concentration of chloride ions is 50 ppm, and the roughening temperature is 35 °C, and the contents and parameters of other substances remain unchanged. The method for preparing the copper foil provided in Example 4 is different from the method for preparing the copper foil provided in Example 2 in that the roughening temperature of Example 4 is 35 °C. The copper foil obtained in Example 4 is as Figure 6 shown.

[0095] Example 5

[0096] The preparation method of the copper foil provided in Example 5 is basically the same as that provided in Example 1, except that in the roughening treatment step of Example 5, the concentration of sodium tungstate in the roughening treatment solution is 0.5 g / L, the concentration of titanium sulfite is 0.3 g / L, the concentration of chloride ions is 50 ppm, and the roughening temperature is 45 °C. The contents and parameters of other substances remain unchanged. Compared with the preparation method of the copper foil provided in Example 2, the difference in the preparation method of the copper foil provided in Example 5 is that the roughening temperature of Example 5 is 45 °C. The copper foil obtained in Example 5 is as Figure 7 shown.

[0097] Example 6

[0098] The preparation method of the copper foil provided in Example 6 is basically the same as that provided in Example 1, except that in the roughening treatment step of Example 6, the concentration of sodium tungstate in the roughening treatment solution is 0.5 g / L, the concentration of titanium sulfite is 0.3 g / L, the concentration of chloride ions is 50 ppm, and the roughening current is 4500 A. The contents and parameters of other substances remain unchanged. Compared with the preparation method of the copper foil provided in Example 2, the difference in the preparation method of the copper foil provided in Example 6 is that the roughening current of Example 6 is 4500 A. The copper foil obtained in Example 6 is as Figure 8 shown.

[0099] Example 7

[0100] The preparation method of the copper foil provided in Example 7 is basically the same as that provided in Example 1, except that in the roughening treatment step of Example 7, the concentration of sodium tungstate in the roughening treatment solution is 0.5 g / L, the concentration of titanium sulfite is 0.3 g / L, the concentration of chloride ions is 50 ppm, and the roughening current is 2000 A. The contents and parameters of other substances remain unchanged. Compared with the preparation method of the copper foil provided in Example 2, the difference in the preparation method of the copper foil provided in Example 7 is that the roughening current of Example 7 is 2000 A. The copper foil obtained in Example 7 is as Figure 9 shown.

[0101] Example 8

[0102] The preparation method of the copper foil provided in Example 8 is basically the same as that of the copper foil provided in Example 1, except that in the roughening treatment step of Example 8, the concentration of sodium tungstate in the roughening treatment solution is 0.5 g / L, the concentration of titanium sulfite is 0.3 g / L, and the concentration of chloride ions is 50 ppm, and the contents and parameters of other substances remain unchanged; and in the step of spraying the silane coupling agent treatment, the silane coupling agent in the silane coupling agent solution is N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane with a concentration of 1.5 g / L. Compared with the preparation method of the copper foil provided in Example 2, the difference in the preparation method of the copper foil provided in Example 8 is that in the step of spraying the silane coupling agent treatment of Example 8, the silane coupling agent in the silane coupling agent solution is N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane with a concentration of 1.5 g / L. The copper foil obtained in Example 8 is as Figure 10 shown.

[0103] Comparative Example 1

[0104] The preparation method of the copper foil provided in Comparative Example 1 is basically the same as that of the copper foil provided in Example 1, except that in the roughening treatment step of Comparative Example 1, sodium tungstate and titanium sulfite are not included in the roughening treatment solution, and the contents and parameters of other substances remain unchanged. The copper foil obtained in Comparative Example 1 is as Figure 11 shown.

[0105] The copper foils obtained in Examples 1-8 and Comparative Example 1 were subjected to performance tests.

[0106] Roughness test

[0107] For the copper foil samples of Examples 1-8 and Comparative Example 1, the surface roughness value of the copper foil treatment surface was measured using a Mitutoyo roughness meter SJ-30L in accordance with GBT5230-2020. The average value was taken from 3 measurement points, and the test results are shown in Table 1.

[0108] Peel strength test

[0109] The copper foil samples of Examples 1-8 and Comparative Example 1 were laminated on FR-4 prepreg sheets and baked at 177 °C for 24 h, and then the peel strength test was carried out using a peel strength tester. The test results are shown in Table 1.

[0110] Table 1 shows the performance of the copper foils obtained in Examples 1-8 and Comparative Example 1

[0111] Table 1:

[0112] Number Line roughness Rz (μm) Peel strength (N / mm) Example 1 1.13 1.29 Example 2 0.81 0.96 Example 3 0.93 1.02 Example 4 0.95 1.06 Example 5 1.04 1.08 Example 6 1.15 1.30 Example 7 0.67 0.84 Example 8 0.93 1.15 Comparative Example 1 1.33 1.42

[0113] From the above table and Figure 3 - 11It can be seen that under the same current in Examples 1-3, the concentration of appropriate trace elements (sodium tungstate and titanium sulfate) plays an important role in the growth of copper nodules. Among them, the copper foil prepared in Example 2 grows more uniformly compared to the copper foils prepared in Example 1 and Example 3. Therefore, the best effect is achieved when the roughening solution contains 0.5-1 g / L of sodium tungstate and 0.1-0.3 g / L of titanium sulfate. When the sodium tungstate is less than 0.5 g / L and the titanium sulfate is less than 0.1 g / L, Rz > 1 μm. When the sodium tungstate is higher than 1 g / L and the titanium sulfate is higher than 0.3 g / L, although Rz is less than 1 μm, the agglomerated growth of copper nodules is serious. In Example 4, the roughening treatment temperature is higher than that in Example 2, and the copper nodules grow more densely. In Example 5, the roughening treatment temperature is higher than that in Example 4, and the density of copper nodules decreases. Therefore, the appropriate roughening treatment temperature is 30-35 °C. When it is lower than 35 °C, Rz < 0.9 μm and the peel strength is less than 1 N / mm. When it is higher than 35 °C, Rz > 0.9 μm and the peel strength is greater than 1 N / mm. In Comparative Example 1, without adding tungsten and titanium, the copper nodules are coarser and Rz > 1 μm.

[0114] It can be seen from Examples 1, 6, and 7 that under the condition of appropriate trace element content, increasing the roughening current makes the copper nodules grow thicker, and decreasing the roughening current results in uneven electroplating in some areas of the copper nodules. Observing the electron microscope pictures, the growth situation in Example 2 is the best, and the other physical properties are also the best.

[0115] It can be seen from Examples 2 and 8 that by replacing the silane coupling agent with N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, compared with 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, when the concentration is the same at 1.5 g / L, the bonding strength between the copper foil and the substrate can be increased from 0.96 N / mm to 1.15 N / mm. In the examples of the present application, the concentration of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane is 1.0-3.0 g / L. Within this range, it can not only improve the bonding strength between the copper foil and the substrate but also avoid material waste.

[0116] The roughness of the copper foil provided in the examples of the present application is less than 1.2 μm, the line roughness Rz of the copper foil is less than 1.2 μm, the size of the copper nodules is 0.3 μm - 0.8 μm, and the nickel electroplating amount is less than 0.5 ppm / m 2 , and the peel strength with the FR-4 prepreg laminate is greater than 1.0 N / mm. Therefore, through the above roughening treatment, a copper foil with small roughness and high peel strength can be prepared, which has a stable and reliable bonding strength with the substrate while meeting the high-speed signal transmission ability.

[0117] The above are only embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present application.

Claims

1. A method for preparing a copper foil, characterized in that: include: Electrodepositing the electroplating solution to obtain a raw foil; The raw foil is pickled, roughened, cured, ashed, passivated and sprayed with a silane coupling agent; In the step of roughening treatment, the roughening treatment liquid used includes 9g / L-11g / L copper ions, 140g / L-160g / L sulfuric acid, 0.13g / L-3g / L sodium tungstate, 0.083g / L-1g / L titanium sulfate and 15ppm-85ppm chloride ions; the roughening treatment temperature is 20℃-35℃, and the upper liquid flow rate is 4m 3 / h-6m 3 / h, the roughening current is 1000A-5000A, and the roughening time is 4s-5s.

2. The method for preparing copper foil according to claim 1, characterized in that: In the step of roughening treatment, the roughening treatment liquid includes 0.5g / L-1g / L sodium tungstate, 0.1g / L-0.3g / L titanium sulfate and 50ppm-80ppm chloride ions; the roughening treatment temperature is 30℃-35℃, and the upper liquid flow rate is 5m 3 / h, the coarsening current is 1500A-3500A, and the coarsening time is 4.5s.

3. The method for preparing copper foil according to claim 1, characterized in that: In the step of spraying the silane coupling agent, the silane coupling agent solution used contains 1.0 g / L-3.0 g / L of silane coupling agent, and the spraying time is 2-4 s; The silane coupling agent may be one or more of an aminosilane coupling agent and an epoxysilane coupling agent.

4. The method for preparing copper foil according to claim 1, characterized in that: In the passivation treatment step, the passivation solution used is composed of chromate and deionized water; or, the passivation solution is composed of chromate, zinc salt and deionized water; wherein the passivation solution includes 1.2g / L-1.8g / L of chromium ions (Cr 6+ ), the pH value of the passivation solution ranges from 0.95 to 10.5, and the upper liquid flow rate is 6m 3 / h-8m 3 / h, passivation current is 50A-100A.

5. The method for preparing copper foil according to claim 1, characterized in that: In the step of ashing, the ashing liquid used includes 1.5g / L-3.0g / L zinc ions, 0.05g / L-0.2g / L nickel ions, and 80g / L-100g / L potassium pyrophosphate; the pH value of the ashing liquid ranges from 9 to 11, and the upper liquid flow rate is 15m 3 / h, the ashing current is 10A-70A.

6. The method for preparing copper foil according to claim 1, characterized in that: In the curing step, the curing liquid used includes 45g / L-55g / L copper ions and 100g / L-120g / L sulfuric acid; the treatment temperature is 30°C, and the upper liquid flow rate is 5m 3 / h-10m 3 / h, the curing current is 1000A-2500A.

7. The method for preparing copper foil according to claim 1, characterized in that: In the pickling step, the pickling solution used includes 30g / L-50g / L copper ions and 90g / L-120g / L sulfuric acid; the pickling temperature is 20℃-30℃, and the upper liquid flow rate is 5m 3 / h-9m 3 / h, pickling time 4s-5s.

8. The method for preparing copper foil according to claim 1, characterized in that: In the step of electroplating the electroplating solution to obtain the raw foil, the electroplating solution includes copper sulfate, sulfuric acid and additives; wherein the concentration of the copper sulfate is 90g / L-110g / L, the concentration of the sulfuric acid is 100g / L-120g / L, and the additives include at least one of a moving agent, a leveling agent and a brightener; the upper liquid flow rate is 60m 3 / h-65m 3 / h, the electroplating temperature is 50℃-55℃.

9. A copper clad laminate, characterized in that: include: Base material; A copper foil is disposed on the substrate, and the copper foil is prepared by the method for preparing the copper foil according to any one of claims 1 to 8.

10. The copper clad laminate according to claim 9, characterized in that: The copper foil has a line roughness Rz of less than 1.2 μm, a copper nodule diameter of 0.3 μm-0.8 μm, and a nickel electrodeposition amount of less than 0.5 ppm / m 2 , and the peel strength with the substrate is greater than 1.0N / mm.

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