Composite copper foil manufacturing method

Abstract

The present application relates to the technical field of copper-clad plate, and discloses a composite copper foil manufacturing method, which comprises the following steps: installing a copper foil layer, a fluorine-containing resin piece and a release layer to a preset installation position and performing lamination treatment, so that the copper foil layer and the release layer are respectively laminated on opposite sides of the fluorine-containing resin piece to obtain a laminated body; the fluorine-containing resin piece comprises at least one fluorine-containing resin layer; and the laminated body is subjected to hot-pressing treatment under preset hot-pressing conditions by means of a roller press to obtain a composite copper foil. The present application adopts a roll-to-roll process, simplifies the process flow and improves the production efficiency. When the hot-pressing treatment is performed, the stability and homogeneity of the fluorine-containing resin piece are ensured by controlling the hot-pressing conditions, the glue deficiency, shrinkage and warping defects of the composite copper foil are reduced, and the process stability of the composite copper foil is improved. Meanwhile, the release layer of the composite copper foil provides isolation and protection for the composite copper foil, so that the composite copper foil has good operability and the product qualification rate is improved.

Description

Technical Field

[0001] This invention relates to the field of copper clad laminate technology, and more particularly to a method for manufacturing composite copper foil. Background Technology

[0002] Flexible printed circuit boards (PCBs) are characterized by high density, small size, thinness, foldability, and good heat dissipation, and are currently widely used in smartphones, computers and peripherals, communication electronic products, and wearable devices. With the development of modern information technology, flexible PCBs are increasingly moving towards higher frequency and higher speed signal transmission. Copper-clad laminate (CCL) is the core material for PCB manufacturing; substandard quality CCL will severely affect the signal transmission performance of flexible PCBs, and may even cause signal loss.

[0003] Flexible copper-clad laminates (CCLs) consist of an insulating film (such as polyimide film, LCP film, etc.), an adhesive material (such as epoxy resin), and a metal foil (such as copper foil). Compared to epoxy resin, fluoropolymers have a lower dielectric constant and dielectric loss tangent, making them more suitable as adhesive materials. Existing technology involves coating a copper foil surface with a fluoropolymer dispersion, drying, and sintering to obtain a composite adhesive copper foil, which is then assembled with an insulating film to produce a high-performance flexible CCL. However, this method of producing flexible CCLs has the following drawbacks: Firstly, due to the complex process, it is difficult to control the uniformity of coating and sintering temperature, leading to uneven thickness, insufficient adhesive, and copper foil shrinkage and curling in the composite adhesive copper foil, resulting in poor process stability. Secondly, the adhesive side of the composite adhesive copper foil is easily contaminated or even damaged during assembly, leading to defective products and poor practical operability. Summary of the Invention

[0004] To address the problems of complex processes, poor stability, and poor practical operability in existing technologies, this invention provides a method for manufacturing composite copper foil.

[0005] This invention provides a method for manufacturing composite copper foil, comprising:

[0006] A copper foil layer, a fluoropolymer component, and a release layer are installed in a preset installation position and then laminated, such that the copper foil layer and the release layer are respectively stacked on opposite sides of the fluoropolymer component to obtain a laminate; the fluoropolymer component includes at least one fluoropolymer layer.

[0007] The laminate is hot-pressed under preset hot-pressing conditions using a roller press to obtain a composite copper foil.

[0008] The composite copper foil manufacturing method of this invention is based on a roll-to-roll process. A pre-formed copper foil layer, a fluoropolymer layer, and a release layer are stacked using a multi-axis feeding system to obtain a laminate. The laminate is then hot-pressed to obtain a roll of composite copper foil. This method simplifies the process, enables large-scale continuous production, saves production costs, and improves production efficiency. During the hot-pressing process, controlled hot-pressing conditions ensure the stability and homogeneity of the fluoropolymer components, reducing defects such as insufficient adhesive, wrinkling, and warping in the composite copper foil, and improving the process stability of the composite copper foil. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic flowchart of a composite copper foil manufacturing method according to an embodiment of the present invention;

[0011] Figure 2 This is a schematic diagram of the structure of a composite copper foil provided in an embodiment of the present invention;

[0012] Figure 3 This is a schematic diagram of the structure of the composite copper foil provided in another embodiment of the present invention.

[0013] The reference numerals in the accompanying drawings are as follows:

[0014] 10. Copper foil layer; 20. Fluoropolymer resin component; 30. Release layer. Detailed Implementation

[0015] To make the technical problems solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0016] In one embodiment, such as Figure 1 As shown, this invention discloses a method for manufacturing composite copper foil, comprising:

[0017] A copper foil layer, a fluoropolymer component, and a release layer are installed in a preset installation position and then laminated, such that the copper foil layer and the release layer are respectively stacked on opposite sides of the fluoropolymer component to obtain a laminate; the fluoropolymer component includes at least one fluoropolymer layer.

[0018] The laminate is hot-pressed under preset hot-pressing conditions using a roller press to obtain a composite copper foil.

[0019] Furthermore, the copper foil layer, fluorinated resin layer, and release layer are formed by unrolling pre-formed rolls of copper foil film, rolls of fluorinated resin film, and rolls of release film, respectively. These three types of raw material roll films can be purchased directly from commercial channels or prepared using corresponding production processes. The fluorinated resin component is a layered structure formed by stacking at least one layer of fluorinated resin film along its thickness direction. The laminate is a layered structure formed by stacking the copper foil film, fluorinated resin component, and release film sequentially from top to bottom along the thickness direction. Fluorinated resin refers to a polymer compound containing fluorine atoms in its molecule, such as polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Fluorinated resin refers to a material containing one or more fluorinated resins. The molding method used to prepare the fluorinated resin film is casting or extrusion molding. The composite copper foil manufacturing method of this invention employs a multi-axis feeding method to transport rolls of copper foil film, rolls of fluoropolymer film, and rolls of release film to a roller press. The preset installation positions are pre-defined installation positions corresponding to the various raw material rolls. Before transporting the rolls of copper foil film, fluoropolymer film, and release film to the roller press, each film needs to be laminated. The rolls of copper foil material, fluoropolymer material, and release material are installed at the preset installation positions, unfolded, and laminated, such that at least one fluoropolymer layer is stacked to form a fluoropolymer component. The copper foil layer and release layer are respectively stacked on opposite sides of the fluoropolymer component, resulting in a laminated body. The fluoropolymer component includes at least one fluoropolymer layer. When the fluoropolymer component is a single fluoropolymer layer, the fluoropolymer material is a roll of fluoropolymer film. When the fluoropolymer component is two or more mixed fluoropolymer layers, the fluoropolymer material is the corresponding number of rolls of fluoropolymer film.

[0020] The preset hot-pressing conditions are the pre-defined hot-pressing parameters of the roller press, including temperature, pressure, and roller linear speed parameters. Composite copper foil is a composite consisting of a copper foil layer, a fluoropolymer component, and a release layer. The fluoropolymer component acts as an adhesive layer. After the laminate formed by the roll of copper foil film, the roll of fluoropolymer film, and the roll of release film is fed into the roller press, the laminate is hot-pressed under the preset hot-pressing conditions. This causes the fluoropolymer component to adhere to the copper foil layer and the release layer on opposite sides. The laminate is then wound up using a roll-to-roll process to obtain a roll of composite copper foil.

[0021] like Figure 2 and Figure 3The composite copper foil shown includes a copper foil layer 10, a fluoropolymer resin component 20, and a release layer 30, arranged sequentially from top to bottom. The copper foil layer 10, the fluoropolymer resin component 20, and the release layer 30 each have two opposing end faces in the thickness direction, namely an upper surface and a lower surface. The fluoropolymer resin component 20 has an adhesive function; specifically, the upper surface of the fluoropolymer resin component 20 is bonded to the lower surface of the copper foil layer 10, and the lower surface of the fluoropolymer resin component 20 is bonded to the upper surface of the release layer 30.

[0022] The fluoropolymer component 20 includes at least one fluoropolymer layer. For example... Figure 2 In the composite copper foil shown, the fluoropolymer component 20 is a fluoropolymer layer, and the copper foil layer 10 and the release layer 30 are respectively bonded to the opposite end faces of the fluoropolymer layer. Figure 3 In the composite copper foil shown, the fluorinated resin component 20 consists of two layers of fluorinated resin, which are bonded together by their adjacent end faces. The copper foil layer 10 and the release layer 30 are bonded to the two distant end faces of the two fluorinated resin layers, respectively. (Not shown in the figure.) Depending on actual production needs, the fluorinated resin component 20 can also have 3, 4, 5, 6, 7, or 8 layers of fluorinated resin.

[0023] This embodiment is based on a roll-to-roll process. A pre-formed copper foil layer, a fluoropolymer layer, and a release layer are stacked using multi-axis feeding to obtain a laminate. The laminate is then hot-pressed to obtain a roll of composite copper foil. This simplifies the process, enables large-scale continuous production, saves production costs, and improves production efficiency. The pre-formed fluoropolymer layer achieves high homogeneity. Furthermore, by controlling the hot-pressing conditions, the stability of the fluoropolymer component is ensured, reducing defects such as insufficient adhesive, wrinkling, and warping in the composite copper foil, thus improving the process stability of the composite copper foil.

[0024] The composite copper foil obtained in this embodiment comprises, from top to bottom, a copper foil layer, a fluoropolymer component, and a release layer. Based on the fluoropolymer component, the composite copper foil possesses excellent dielectric properties, high peel strength, and good mechanical properties. The release layer provides good isolation and protection for the composite copper foil, preventing contamination or scratches to the adhesive material (fluoropolymer component), thus ensuring good operability and improving product yield. Simultaneously, the release layer is easy to peel off, facilitating the direct assembly of the composite copper foil with insulating films of different materials (such as fluoropolymer films, polyimide films, or LCP films) to obtain flexible copper-clad laminates, eliminating the need for an additional layer of pure adhesive and improving assembly efficiency.

[0025] Optionally, the preset hot-pressing conditions include:

[0026] The hot pressing temperature is 100℃~320℃, the hot pressing winding speed is 0.5~4m / min, and the hot pressing pressure is 2~7MPa.

[0027] Furthermore, the hot pressing parameters of the roller press include temperature, pressure, and roller linear speed parameters. The hot pressing temperature and pressure are related to the characteristics of the object being hot pressed. The roller linear speed represents the rotational speed of the roller press. The roller linear speed cannot be too low or too high; too low a speed will lead to reduced efficiency, while too high a speed will lead to unstable quality, both of which will affect the hot pressing effect. In the roll-to-roll process, the roller linear speed parameters are matched with the hot pressing winding speed. In this embodiment, the hot pressing temperature is 100℃~320℃, the hot pressing winding speed is 0.5~4m / min, and the hot pressing pressure is 2~7MPa. This allows the fluoropolymer-containing parts to bond to the copper foil layers and release layers on opposite sides, while ensuring high production efficiency.

[0028] Optionally, the hot pressing temperature includes 5 to 10 temperature gradient ranges;

[0029] Along the direction from the start of hot pressing to the end of hot pressing, the temperature in each of the temperature gradient intervals changes according to a trend of first increasing and then decreasing.

[0030] Furthermore, in one embodiment, a high-temperature roller press with multiple temperature gradient zones is used for hot pressing. Along the hot pressing start direction to the hot pressing end direction, the temperature in each temperature gradient zone changes with a trend of first increasing and then decreasing, sequentially including a preheating stage, a lamination stage, and a post-treatment stage. The temperature in the preheating stage is set lower than that in the lamination stage, which can eliminate stress in the rolled film material and prevent wrinkling and curling. The temperature in the lamination stage is set higher than that in the preheating and post-treatment stages, which can meet the material lamination requirements at different winding speeds, allowing the fluoropolymer component to bond to the copper foil layers and release layers on opposite sides. The temperature in the post-treatment stage is set lower than that in the lamination stage, which can release internal stress after lamination and improve the stability of the laminated copper foil. The temperature gradient zones can be uniformly distributed or unevenly distributed as needed. The larger the temperature gradient zone corresponding to the lamination stage, the better it is for increasing the winding speed and improving production efficiency. The roller press has multiple sets of pressure rollers, which are arranged sequentially and wrapped with smooth steel strips. By controlling the temperature of each set of pressure rollers, multiple different temperature gradient zones can be formed. If the number of pressure rollers in the roller press is small, the temperature gradient range corresponding to the lamination stage is small, resulting in a shorter hot pressing time in the core heating zone and lower peel strength of the composite copper foil. If the temperature gradient range corresponding to the lamination stage is too large, a larger number of pressure rollers are required, increasing the manufacturing difficulty of the roller press equipment and increasing production costs. The hot pressing temperature in this embodiment includes 5 to 10 temperature gradient ranges, which meets the lamination requirements without increasing additional production costs.

[0031] Optionally, the hot pressing temperature includes: a first temperature range of 100℃ to 200℃, a second temperature range of 200℃ to 250℃, a third temperature range of 250℃ to 320℃, a fourth temperature range of 280℃ to 300℃, a fifth temperature range of 200℃ to 280℃, a sixth temperature range of 150℃ to 200℃, and a seventh temperature range of 100℃ to 150℃.

[0032] Optionally, the melting temperature of the fluoropolymer part is 260-320°C, and the melting temperature of the release layer is 10°C or more higher than the melting temperature of the fluoropolymer part.

[0033] Furthermore, the melting temperature refers to the temperature corresponding to the maximum value of the melting peak as determined by differential scanning calorimetry (DSC). In one embodiment, the melting temperature of the fluoropolymer layer is greater than or equal to 250°C; preferably, the melting temperature of the fluoropolymer layer is 260–320°C; more preferably, the melting temperature of the fluoropolymer layer is 280–320°C; and most preferably, the melting temperature of the fluoropolymer layer is 290–310°C. The melting temperature of the release layer is higher than that of the fluoropolymer layer, which ensures the processing temperature window of the fluoropolymer layer during hot pressing. Preferably, the melting temperature of the release layer is at least 10°C higher than that of the fluoropolymer layer; more preferably, the melting temperature of the release layer is at least 20°C higher than that of the fluoropolymer layer.

[0034] The temperature gradient range in the hot-pressing temperature is matched with the melting temperatures of the fluoropolymer component and the release layer, ensuring that the peak temperature of the temperature gradient range is higher than the melting temperature of the fluoropolymer component but lower than the melting temperature of the release layer. In other words, the temperature during the lamination stage is higher than the melting temperature of the fluoropolymer component but lower than the melting temperature of the release layer. When the temperature gradient range in the hot-pressing temperature matches the melting temperatures of the fluoropolymer component and the release layer, the fluoropolymer component can bond the copper foil layers and the release layer on opposite sides in the molten state, while the state and properties of the release layer remain unchanged, ensuring its releaseability.

[0035] In one embodiment, the roller press has 10 rollers, and the temperature of each group of rollers is preset, divided into 7 temperature gradient intervals (e.g., the first group of rollers corresponds to the first temperature interval, the second and third groups of rollers correspond to the second temperature interval, the fourth and fifth groups of rollers correspond to the third temperature interval, the sixth and seventh groups of rollers correspond to the fourth temperature interval, the eighth group of rollers corresponds to the fifth temperature interval, the ninth group of rollers corresponds to the sixth temperature interval, and the tenth group of rollers corresponds to the seventh temperature interval). Specifically, the laminate enters the roller press and is forcibly fixed by two smooth and flat steel belts to ensure that each layer of the film has good flatness. Fluoropolymer films have a high coefficient of thermal expansion, and rapid temperature rise can easily lead to severe deformation of the fluoropolymer film. Therefore, the temperature of the first temperature interval in the preheating stage is set to 100°C to 200°C, and the temperature of the second temperature interval is set to 200°C to 250°C. The third temperature range in the lamination stage is set to 250℃~320℃, reaching the melting or viscous flow temperature of the fluoropolymer film. The fluoropolymer film plasticizes and begins to bond with the copper foil layer and release layer. The fourth temperature range in the lamination stage is set to 280℃~300℃, increasing the lamination zone length and hot-pressing time to further enhance bonding strength and improve winding speed and production efficiency. The fifth temperature range in the post-treatment stage is set to 200℃~280℃, the sixth temperature range to 150℃~200℃, and the seventh temperature range to 100℃~150℃. Gradual cooling releases internal stress between the copper foil layer and the fluoropolymer component, preventing stress shrinkage and cracking.

[0036] This embodiment sets the hot pressing temperature in each temperature gradient range to change in a trend of first increasing and then decreasing, and makes the temperature gradient range compatible with the melting temperature of the fluoropolymer component and the melting temperature of the release layer. This achieves a tight bond between the fluoropolymer component and the copper foil layer while maintaining good release properties between the fluoropolymer component and the release layer, forming a composite copper foil with excellent peel strength and good release properties.

[0037] Optionally, the copper foil layer is a rolled copper foil layer or an electrolytic copper foil layer;

[0038] The thickness of the copper foil layer is 1–40 μm;

[0039] The surface roughness Rz value of the copper foil layer near the end face of the fluoropolymer component is 0.5 to 2 μm, and the surface roughness Rz value of the copper foil layer away from the end face of the fluoropolymer component is 0.5 to 1 μm.

[0040] Furthermore, in one embodiment, the copper foil layer is either a rolled copper foil layer or an electrolytic copper foil layer. Depending on the preparation method, copper foil can be divided into two main categories: rolled copper foil and electrolytic copper foil. Rolled copper foil is made by repeatedly rolling a copper plate to form a raw foil, and then roughening the raw foil according to requirements. Electrolytic copper foil is made by dissolving copper to form a solution, then electrodepositing a copper sulfate electrolyte under direct current in a dedicated electrolytic device to form a raw foil, and finally performing surface treatment on the raw foil according to requirements. Because rolled copper foil has a smoother surface than electrolytic copper foil, it is beneficial for the rapid transmission of electrical signals, and its folding endurance and elasticity coefficient are greater than those of electrolytic copper foil, making it more suitable for the production of flexible copper-clad laminates. In a preferred embodiment, the copper foil layer is a rolled copper foil layer.

[0041] In this embodiment, the copper foil layer can be configured with different shapes, sizes, and thicknesses according to the needs of the circuit. Excessive copper foil layer thickness can lead to slower signal transmission speeds and increased signal loss. A copper foil layer thickness of 1–40 μm can meet the signal transmission requirements of high-frequency, high-speed flexible printed circuit boards. Preferably, the copper foil layer thickness is 1 μm or more, more preferably 2 μm or more, and particularly preferably 3 μm or more. Furthermore, the copper foil layer thickness is preferably 40 μm or less, more preferably 20 μm or less, and particularly preferably 15 μm or less. That is, the copper foil layer thickness can be 1–40 μm, 1–20 μm, 1–15 μm, 2–40 μm, 2–20 μm, 2–15 μm, 3–40 μm, 3–20 μm, 3–15 μm, 5–35 μm, or 5–20 μm.

[0042] As a crucial component of the conductive layer in the substrate, the surface roughness of the copper foil layer significantly impacts signal transmission loss. In this embodiment, the copper foil layer is a low-profile copper foil with a surface roughness of 3.5 μm. The low-profile copper foil's low surface roughness effectively addresses the attenuation and distortion of printed circuit board signals caused by the skin effect during high-frequency signal transmission. When the roughness Rz value of the end face of the copper foil layer near the fluoropolymer component is 0.5–2 μm, it facilitates adhesion between the copper foil layer and the fluoropolymer component. Conversely, when the roughness Rz value of the end face of the copper foil layer away from the fluoropolymer component is 0.5–1 μm, it promotes signal transmission. The use of a low-profile copper foil layer in the composite copper foil of this embodiment meets the low-loss requirements for high-frequency, high-speed signal transmission, thereby improving signal transmission quality.

[0043] This embodiment limits the type, thickness, and surface roughness of the copper foil layer to meet the signal transmission requirements of high-frequency, high-speed flexible printed circuit boards, reduce signal transmission loss, and improve signal transmission quality.

[0044] Optionally, the base material of the fluorinated resin layer includes a first fluorinated compound; the first fluorinated compound includes at least one of perfluoroethylene propylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and ethylene-chlorotrifluoroethylene copolymer.

[0045] Optionally, the first fluorinated compound may also include polytetrafluoroethylene.

[0046] Furthermore, in one embodiment, the fluorinated resin layer can be a thin film layer formed entirely of a fluorinated resin, that is, the base material of the fluorinated resin layer is any one of perfluoroethylene propylene (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0047] In another embodiment, the fluorinated resin layer may also be a thin film layer formed by mixing two or more fluorinated resins, that is, the base material of the fluorinated resin layer is a combination of at least two of polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE) and ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0048] Optionally, the base material of the fluorinated resin layer includes a second fluorinated compound and a non-fluorinated compound, wherein the second fluorinated compound includes at least one of polytetrafluoroethylene, perfluoroethylene propylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and ethylene-chlorotrifluoroethylene copolymer;

[0049] The fluorine-free compounds include at least one of epoxy resin, acrylic resin, carbamate resin, silicone rubber resin, cyanate resin, maleimide-cyanate resin, poly(p-cycloxylene) resin, hydrocarbon resin, polyphenylene ether resin, phenolic resin, bismaleimide resin, and polyimide resin.

[0050] Furthermore, in another embodiment, the fluoropolymer layer can also be a thin film layer composed of fluoropolymer and non-fluoropolymer in a certain proportion, wherein the fluoropolymer content in the fluoropolymer layer is greater than or equal to 60 wt% (e.g., 60 wt% fluoropolymer and 40% non-fluoropolymer), and preferably the fluoropolymer content in the fluoropolymer layer is greater than or equal to 90 wt%. When the fluoropolymer component comprises two or more fluoropolymer layers, the base material between adjacent fluoropolymer layers can be the same or different.

[0051] This embodiment limits the type of base material for the fluoropolymer layer to allow for better control of the melting temperature difference by utilizing the physical properties of different material types. This enables the fluoropolymer component to better bond the copper foil layer and release layer on both sides, ensuring product quality.

[0052] In one embodiment, the thickness of the fluoropolymer component is 1–50 μm, and the total thickness of the copper foil layer and the fluoropolymer component is 2–90 μm.

[0053] Furthermore, the thickness of the fluoropolymer component is preferably 1 μm or more, more preferably 2 μm or more, and particularly preferably 5 μm or more. Additionally, the thickness of the fluoropolymer component is preferably 50 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. That is, the thickness of the fluoropolymer component can be 1–50 μm, 1–15 μm, 1–10 μm, 2–50 μm, 2–15 μm, 2–10 μm, 5–40 μm, 5–30 μm, 5–15 μm, or 5–10 μm. When the thickness of the fluoropolymer component is 1–50 μm, and the total thickness of the copper foil layer and the fluoropolymer component is 2–90 μm, the composite copper foil exhibits good flexibility and excellent mechanical properties, which can prevent the signal transmission performance from being affected by excessive thickness between the copper foil layer and the fluoropolymer component.

[0054] In one embodiment, the release layer is a polytetrafluoroethylene layer; the thickness of the release layer is 1–100 μm.

[0055] Furthermore, polytetrafluoroethylene (PTFE) has a high melting temperature, thus exhibiting high-temperature resistance, and possesses anti-stick properties due to its low surface tension and low coefficient of friction. In one embodiment, using a PTFE layer as a release layer can both isolate and protect the composite copper foil, while also making the release layer easy to peel off from the composite copper foil.

[0056] A release layer is a thin film with a separable surface. It is required that, under limited conditions, it should not adhere to specific materials or should only exhibit slight adhesion. If the release layer is too thin, it will not provide effective isolation and protection; if it is too thick, it will lose its flexibility. In this embodiment, the release layer thickness is 1–100 μm; in a preferred embodiment, it is 5–100 μm; and in a more preferred embodiment, it is 10–50 μm. This embodiment, by limiting the type of release layer, ensures the high-temperature resistance of the release layer film and improves processing stability. This embodiment, by limiting the thickness of the release layer, maintains good flexibility while ensuring the release layer provides isolation and protection for the composite copper foil.

[0057] Optionally, the hot pressing treatment of the laminate under preset hot pressing conditions using a roller press includes:

[0058] The copper foil layer and the fluoropolymer component are bonded together such that the peel strength between the copper foil layer and the fluoropolymer component is greater than or equal to 0.4 N / mm;

[0059] The release layer is bonded to the other end face of the fluoropolymer component opposite to the copper foil layer, such that the peel strength between the release layer and the fluoropolymer component is less than or equal to 0.4 N / mm.

[0060] Furthermore, the fluorinated resin layer used in the composite copper foil has a low dielectric loss factor and stable Dk / Df performance under high temperature and high humidity environments, which can reduce signal loss during signal transmission, improve signal transmission quality, and meet the transmission requirements of high-frequency and high-speed signals. The dielectric constant (Dk) is a key parameter reflecting the dielectric or polarization properties of an insulating medium (e.g., resin) under the influence of an electrostatic field. The dielectric loss (Df) is the ratio of energy lost in the transmission line to the energy not yet lost in the transmission line. In one embodiment, the dielectric constant is 2.0–3.5, and the dielectric loss is 0.005–0.0002, which allows for faster signal transmission speed, stronger transmission capability, better transmission quality, and better signal integrity in the medium. In a preferred embodiment, the dielectric constant of the fluorinated resin layer at 10 GHz is 2.1–3.0, and the dielectric loss is 0.001–0.0002.

[0061] In addition to meeting dielectric performance requirements, fluoropolymer components also need to meet adhesion requirements during hot pressing. Adhesion performance is expressed as the peel strength between the fluoropolymer component and the copper foil layers and release layers on opposite sides. In one embodiment, the peel strength between the copper foil layer and the fluoropolymer component is greater than or equal to 0.4 N / mm; in a preferred embodiment, the peel strength is greater than or equal to 0.6 N / mm; and in a more preferred embodiment, the peel strength is greater than or equal to 0.8 N / mm, to meet the adhesion performance requirements of the fluoropolymer component to the copper foil layer. The composite copper foil of this embodiment exhibits high peel strength between the copper foil layer and the fluoropolymer component, which can meet a wide range of application scenarios.

[0062] Compared to the adhesion between the copper foil layer and the fluoropolymer component, the release layer has a weaker adhesive bond with the fluoropolymer component. In one embodiment, the peel strength between the release layer and the fluoropolymer component is less than or equal to 0.4 N / mm; in a preferred embodiment, the peel strength is less than or equal to 0.3 N / mm; and in a more preferred embodiment, the peel strength is less than or equal to 0.2 N / mm. This satisfies the adhesion performance between the fluoropolymer component and the release layer, making the release layer easy to peel off. In this embodiment, the composite copper foil has a low peel strength between the release layer and the fluoropolymer component, and the release layer is easy to peel off. This facilitates the direct assembly of the composite copper foil with insulating films of different materials (such as fluoropolymer film, polyimide film, or LCP film) to fabricate high-frequency, high-speed flexible copper-clad laminates, meeting the high-frequency, high-speed signal transmission requirements of printed circuit boards. It eliminates the need for an additional layer of pure adhesive for bonding, shortening the process flow, reducing production costs, and improving product yield.

[0063] Specific embodiments and comparative examples of the composite copper foil of the present invention are as follows:

[0064] Example 1

[0065] After the copper foil roll, fluoropolymer roll, and release layer roll are assembled, they are laminated so that the copper foil layer and the release layer are placed on opposite sides of the fluoropolymer component to obtain a laminate. The laminate is then hot-pressed under preset hot-pressing conditions using a roller press to obtain the composite copper foil of Example 1. The preset hot-pressing conditions include the following temperatures: a first temperature range of 120°C, a second temperature range of 250°C, a third temperature range of 300°C, a fourth temperature range of 300°C, a fifth temperature range of 200°C, a sixth temperature range of 150°C, and a seventh temperature range of 100°C.

[0066] The composite copper foil in Example 1 comprises, from top to bottom, a copper foil layer, a fluoropolymer component, and a release layer. The copper foil layer has a thickness of 18 μm and a surface roughness Rz value of 0.6 μm on the end face of the copper foil layer near the fluoropolymer component. The fluoropolymer component consists of a single fluoropolymer layer with a thickness of 5 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz. The release layer has a thickness of 50 μm.

[0067] Example 2

[0068] The composite copper foil of Example 2 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the third temperature range during hot pressing was 310°C. In the composite copper foil of Example 2, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 0.6 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 5 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz; the release layer had a thickness of 50 μm.

[0069] Example 3

[0070] The composite copper foil of Example 3 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the third temperature range during hot pressing was 300°C. In the composite copper foil of Example 3, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 0.6 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 10 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz; the release layer had a thickness of 50 μm.

[0071] Example 4

[0072] The composite copper foil of Example 4 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the third temperature range during hot pressing was 300°C. In the composite copper foil of Example 4, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 1.0 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 10 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz; the release layer had a thickness of 50 μm.

[0073] Example 5

[0074] The composite copper foil of Example 5 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the third temperature range during hot pressing was 300°C. In the composite copper foil of Example 5, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 1.0 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 15 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz; the release layer had a thickness of 50 μm.

[0075] Example 6

[0076] The composite copper foil of Example 6 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the third temperature range during hot pressing was 320°C. In the composite copper foil of Example 6, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 1.0 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 15 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz; the release layer had a thickness of 50 μm.

[0077] Example 7

[0078] The composite copper foil of Example 7 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the third temperature range during hot pressing was 300°C. In the composite copper foil of Example 7, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 0.6 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 15 μm, a Dk value of 2.2, and a Df value of 0.0004 at 10 GHz; the release layer had a thickness of 50 μm.

[0079] Comparative Example 1

[0080] Unlike the roll-to-roll manufacturing method of Example 1, a fluorinated resin dispersion was prepared based on the same base material as the fluorinated resin in Example 1. After coating the copper foil surface with the fluorinated resin dispersion to form a fluorinated resin layer, it was dried and sintered at 300°C to obtain the composite copper foil of Comparative Example 1.

[0081] In the composite copper foil of Comparative Example 1, the thickness of the copper foil layer is 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluorinated resin layer is 0.6 μm; the thickness of the fluorinated resin layer is 10 μm, and the Dk value is 2.2 and the Df value is 0.0004 at 10 GHz.

[0082] Comparative Example 2

[0083] Unlike the roll-to-roll manufacturing method of Example 1, a fluorinated resin dispersion was prepared based on the same base material as the fluorinated resin of Example 1. After coating the copper foil surface with the fluorinated resin dispersion to form a fluorinated resin layer, it was dried and sintered at 280°C to obtain the composite copper foil of Comparative Example 2.

[0084] In the composite copper foil of Comparative Example 2, the thickness of the copper foil layer is 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluorinated resin layer is 1.0 μm; the thickness of the fluorinated resin layer is 10 μm, and the Dk value is 2.2 and the Df value is 0.0004 at 10 GHz.

[0085] Comparative Example 3

[0086] The composite copper foil of Comparative Example 3 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein no temperature gradient range was defined during hot pressing, and the overall hot pressing temperature was set to 300°C. In the composite copper foil of Comparative Example 3, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 0.6 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 10 μm, a Dk value of 2.2 and a Df value of 0.0004 at 10 GHz; and the thickness of the release layer was 50 μm.

[0087] Comparative Example 4

[0088] The composite copper foil of Comparative Example 4 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperature in the first to fourth temperature ranges during hot pressing was set to 300°C. In the composite copper foil of Comparative Example 4, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 0.6 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 10 μm, a Dk value of 2.2 and a Df value of 0.0004 at 10 GHz; and the thickness of the release layer was 50 μm.

[0089] Comparative Example 5

[0090] The composite copper foil of Comparative Example 5 was obtained using the same roll-to-roll manufacturing method as in Example 1, wherein the temperatures in the third to seventh temperature ranges during hot pressing were all set to 300°C. In the composite copper foil of Comparative Example 5, the thickness of the copper foil layer was 18 μm, and the surface roughness Rz value of the end face of the copper foil layer near the fluoropolymer component was 0.6 μm; the fluoropolymer component consisted of a single fluoropolymer layer with a thickness of 10 μm, a Dk value of 2.2 and a Df value of 0.0004 at 10 GHz; and the thickness of the release layer was 50 μm.

[0091] The composite copper foils in the examples and comparative examples were tested. Specifically, the peel strength between the copper foil layer and the fluoropolymer component was tested; and the appearance quality grade of the composite copper foil was determined by observing whether there were defects such as missing adhesive, wrinkles, and bubbles in the fluoropolymer component. If no defects were found, it was recorded as good; if defects were found, the defect details were recorded. The test results are shown in Table 1.

[0092] Table 1. Performance test results of composite copper foil in the examples and comparative examples.

[0093] Example 1 0.492 good Example 2 0.561 good Example 3 0.683 good Example 4 0.952 good Example 5 1.029 good Example 6 1.642 good Example 7 0.744 good Comparative Example 1 0.603 Insufficient glue, shrinkage Comparative Example 2 0.875 Insufficient glue, shrinkage Comparative Example 3 0.732 Insufficient glue, shrinkage Comparative Example 4 0.717 Insufficient glue, shrinkage Comparative Example 5 0.688 Wrinkle

[0094] As can be seen from the test results in Table 1, compared with the comparative examples, the performance of the examples is significantly better. Examples 1-7 show high peel strength between the copper foil layer and the fluoropolymer component in the composite copper foil, with Examples 5 and 6 even exceeding 1 N / mm. Simultaneously, by controlling the hot-pressing temperature conditions, the stability and homogeneity of the fluoropolymer component are ensured, resulting in a good appearance quality grade for the composite copper foil. Compared with Example 1, and with Examples 6 and 7, Examples 2 and 6 have higher temperatures in the third temperature range during hot-pressing, which helps to improve the peel strength between the copper foil layer and the fluoropolymer component. Compared with Example 1, and with Examples 5 and 4, Examples 3 and 5 have a thicker fluoropolymer component, which helps to further improve the peel strength between the copper foil layer and the fluoropolymer component. Compared with Example 3, the copper foil layer in Example 4 has a larger surface roughness, which helps to further improve the peel strength between the copper foil layer and the fluoropolymer component. By comparing the peel strength between the copper foil layer and the fluoropolymer component in Examples 1 to 7, it can be seen that the factors affecting the peel strength between the copper foil layer and the fluoropolymer component include the roughness of the end face of the copper foil layer near the fluoropolymer component, the thickness of the fluoropolymer component, and the temperature corresponding to the composite stage during hot pressing.

[0095] Compared to Comparative Example 1 and Example 3, and Comparative Example 2 and Example 4, Comparative Examples 1 and 2 employed a coating and drying process, while Examples 3 and 4 employed a roll-to-roll process and controlled the hot-pressing temperature conditions. Examples 3 and 4 improved the peel strength between the copper foil layer and the fluoropolymer-containing component while also achieving a better appearance quality. Comparative Example 3 employed a roll-to-roll process but did not set a temperature gradient range for the hot-pressing temperature conditions. Comparative Examples 4 and 5 employed a roll-to-roll process but did not control the temperature gradient range for the hot-pressing temperature conditions in a manner that first increased and then decreased the temperature gradient. Compared to Example 3, Comparative Examples 3-5 showed improved peel strength between the copper foil layer and the fluoropolymer-containing component, but all exhibited significant wrinkling defects.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing composite copper foil, characterized in that, include: A copper foil layer, a fluoropolymer component, and a release layer are installed in a preset installation position and then laminated, such that the copper foil layer and the release layer are respectively stacked on opposite sides of the fluoropolymer component to obtain a laminate; the fluoropolymer component includes at least one fluoropolymer layer. The laminate is hot-pressed under preset hot-pressing conditions using a roller press to obtain a composite copper foil. The copper foil layer, the fluorinated resin component, and the release layer are respectively formed by unfolding a pre-formed roll of copper foil film, a roll of fluorinated resin film, and a roll of release film. The fluorinated resin component is a layered structure formed by stacking at least one layer of fluorinated resin film along the thickness direction. The laminate is a layered structure formed by stacking the copper foil film, the fluorinated resin component, and the release film sequentially from top to bottom along the thickness direction. The preset hot pressing conditions include a hot pressing temperature of 100℃ to 320℃, and the hot pressing temperature includes 5 to 10 temperature gradient intervals. Along the hot pressing start direction to the hot pressing end direction, the temperature of each temperature gradient interval changes according to the trend of first increasing and then decreasing.

2. The method for manufacturing composite copper foil according to claim 1, characterized in that, The preset hot pressing conditions include: The hot-pressing winding speed is 0.5~4m / min, and the hot-pressing pressure is 2~7MPa.

3. The method for manufacturing composite copper foil according to claim 1, characterized in that, The hot pressing temperatures include: a first temperature range of 100℃ to 200℃, a second temperature range of 200℃ to 250℃, a third temperature range of 250℃ to 320℃, a fourth temperature range of 280℃ to 300℃, a fifth temperature range of 200℃ to 280℃, a sixth temperature range of 150℃ to 200℃, and a seventh temperature range of 100℃ to 150℃.

4. The method for manufacturing composite copper foil according to claim 1, characterized in that, The melting temperature of the fluoropolymer part is 260~320℃, and the melting temperature of the release layer is more than 10℃ higher than the melting temperature of the fluoropolymer part.

5. The method for manufacturing composite copper foil according to claim 1, characterized in that, The copper foil layer is a rolled copper foil layer or an electrolytic copper foil layer; The thickness of the copper foil layer is 1~40μm; The surface roughness Rz value of the copper foil layer near the end face of the fluoropolymer component is 0.5~2μm, and the surface roughness Rz value of the copper foil layer away from the end face of the fluoropolymer component is 0.5~1μm.

6. The method for manufacturing composite copper foil according to claim 1, characterized in that, The base material of the fluorinated resin layer includes a first fluorinated compound; the first fluorinated compound includes at least one of perfluoroethylene propylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene and ethylene-chlorotrifluoroethylene copolymer.

7. The method for manufacturing composite copper foil according to claim 6, characterized in that, The first fluorinated compound also includes polytetrafluoroethylene.

8. The method for manufacturing composite copper foil according to claim 1, characterized in that, The base material of the fluorinated resin layer includes a second fluorinated compound and a non-fluorinated compound, wherein the second fluorinated compound includes at least one of polytetrafluoroethylene, perfluoroethylene propylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene and ethylene-chlorotrifluoroethylene copolymer; The fluorine-free compounds include at least one of epoxy resin, acrylic resin, carbamate resin, silicone rubber resin, cyanate resin, maleimide-cyanate resin, poly(p-cycloxylene) resin, hydrocarbon resin, polyphenylene ether resin, phenolic resin, bismaleimide resin, and polyimide resin.

9. The method for manufacturing composite copper foil according to claim 1, characterized in that, The hot pressing treatment of the laminated body under preset hot pressing conditions by a roller press includes: The copper foil layer and the fluoropolymer component are bonded together such that the peel strength between the copper foil layer and the fluoropolymer component is greater than or equal to 0.4 N / mm. The release layer is bonded to the other end face of the fluoropolymer component opposite to the copper foil layer, such that the peel strength between the release layer and the fluoropolymer component is less than or equal to 0.4 N / mm.

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