Metal foil, composite metal foil, metal-clad laminated board and circuit board

Abstract

The invention discloses a metal foil, a composite metal foil, a metal-clad laminate and a circuit board, the metal foil comprises a crystal structure with a plurality of crystal face orientations, the crystal structure comprises a (220) crystal face, a (200) crystal face, a (111) crystal face and a (311) crystal face, the (220) crystal face is a preferred orientation crystal face, and the orientation degree of the (220) crystal face is greater than or equal to 60%. The metal foil comprises the crystal structure with a plurality of crystal face orientations, so that the metal foil has good mechanical performance, the tensile strength of the metal foil can be improved, the preferred orientation crystal face in the crystal structure is limited to be the (220) crystal face, the orientation degree of the (220) crystal face is larger than or equal to 60%, and the tensile strength of the metal foil can be improved. And the signal transmission loss of the metal foil can be obviously reduced, so that the metal foil has good conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of metal foils, and in particular to a metal foil, a composite metal foil, a metal-coated laminate, and a circuit board. Background Art

[0002] With the rapid development of global information technology towards digitalization and networking, there is currently a need to meet the requirements of ultra-large-capacity information transmission, high-speed, and ultra-high-density information processing. This undoubtedly poses more stringent requirements on the performance of electrolytic metal foils. In the scenario of high-frequency signal transmission, the stability and reliability of signal transmission are significantly affected by the crystal structure characteristics of the metal foil and the microscopic profile of the metal foil surface.

[0003] The crystal structure of the metal foil is directly related to the loss and interference degree of high-frequency signals during their movement in the conductor. Any non-uniform lattice arrangement or excessive grain boundaries will increase the fluctuation of the resistivity, resulting in energy dissipation during signal transmission, thereby weakening the signal intensity and quality. In addition, the electromagnetic characteristics of the grain boundaries may also cause additional noise, further interfering with the purity of the signal, which is a major obstacle that must be overcome to ensure stable high-frequency signal transmission.

[0004] To ensure the stability and reliability of signal transmission, the prior art usually epitaxially electroplates on a single-crystal substrate to obtain a highly ordered metal thin film. However, in traditional epitaxial electroplating, as the coating thickness increases, twins appear and further lead to the transformation of the coating structure into polycrystalline, resulting in the fact that the epitaxial electroplating on a traditional single-crystal substrate can only obtain a single-crystal thin film with a thickness of a few micrometers, resulting in relatively weak mechanical properties. Summary of the Invention

[0005] The present invention provides a metal foil, a composite metal foil, a metal-coated laminate, and a circuit board. By including a crystal structure with several crystal plane orientations in the metal foil, the metal foil has good mechanical properties and can improve the tensile strength of the metal foil. By defining the preferred orientation crystal plane in the crystal structure as the (220) crystal plane, and the orientation degree of the (220) crystal plane is greater than or equal to 60%, the signal transmission loss of the metal foil can be significantly reduced, making the metal foil have good electrical conductivity.

[0006] To solve the above technical problems, in the first aspect of the embodiments of the present invention, a metal foil is provided. The metal foil includes a crystal structure with several crystal plane orientations. The crystal structure includes a (220) crystal plane, a (200) crystal plane, a (111) crystal plane, and a (311) crystal plane. The (220) crystal plane is the preferred orientation crystal plane, and the orientation degree of the (220) crystal plane is greater than or equal to 60%.

[0007] As a preferred solution, the orientation degree of the (220) crystal plane is 60% - 80%.

[0008] As a preferred solution, the degree of orientation of the (220) crystal plane is 60% to 80%; and / or,

[0009] the degree of orientation of the (200) crystal plane is 2% to 15%; and / or,

[0010] the degree of orientation of the (111) crystal plane is 10% to 22%; and / or,

[0011] the degree of orientation of the (311) crystal plane is 1% to 10%;

[0012] wherein, the sum of the degrees of orientation of the (220) crystal plane, the (200) crystal plane, the (111) crystal plane and the (311) crystal plane is less than or equal to 100%.

[0013] As a preferred solution, within a preset observation range, the size of the grains in the crystal structure is 0.2 μm to 3 μm; wherein, the size of the grains is the diameter of the maximum circumscribed circle along the width direction of the grains.

[0014] As a preferred solution, within a preset observation range, the standard deviation of the circumscribed circle diameters of all the grains is 0.1 μm to 0.6 μm.

[0015] As a preferred solution, the metal foil is provided with a first side surface, and the roughness Rz of the first side surface is 3.8 μm to 4.5 μm.

[0016] As a preferred solution, the side surface of the metal foil opposite to the first side surface is a second side surface, and the roughness Ra of the second side surface is 0.1 μm to 0.28 μm.

[0017] As a preferred solution, a plurality of metal teeth are provided on the first side surface, and the height of the metal teeth is 1 μm to 5 μm.

[0018] As a preferred solution, the maximum surface undulation height of the metal foil is less than 3.5 μm; wherein, the maximum surface undulation height is the distance between the highest point and the lowest point on any surface of the metal foil.

[0019] As a preferred solution, the coefficient of thermal expansion of the metal foil is 20 ppm / K to 26 ppm / K; and / or,

[0020] the mass resistivity of the metal foil is less than 0.166.

[0021] In the second aspect of the embodiments of the present invention, a composite metal foil is provided, the composite metal foil includes an additional layer and the metal foil as described in any one of the first aspect, and the additional layer and the metal foil are stacked.

[0022] As a preferred solution, there are two or more additional layers.

[0023] A third aspect of the embodiments of the present invention provides a method for preparing a metal foil, including:

[0024] Preparing a main copper sulfate electrolyte;

[0025] Adding an additive to the main copper sulfate electrolyte to obtain an electrolyte; wherein, the additive includes a (220) crystal plane promoter and a (220) crystal plane inhibitor;

[0026] Performing electrodeposition on the electrolyte to obtain the metal foil according to any one of the first aspect.

[0027] A fourth aspect of the embodiments of the present invention provides a metal-clad laminate, and the metal-clad laminate includes the metal foil according to any one of the first aspect.

[0028] A fifth aspect of the embodiments of the present invention provides a circuit board, and the circuit board includes a circuit board substrate and the metal foil according to any one of the first aspect, and the metal foil is laminated with the circuit board substrate; or, the circuit board is made of the metal-clad laminate according to the fourth aspect as one of the materials.

[0029] Compared with the prior art, the beneficial effect of the embodiments of the present invention is that, due to the crystal structure with several crystal plane orientations included in the metal foil, the metal foil has good mechanical properties and can improve the tensile strength of the metal foil. By defining the preferred orientation crystal plane in the crystal structure as the (220) crystal plane and the orientation degree of the (220) crystal plane being greater than or equal to 60%, the signal transmission loss of the metal foil can be significantly reduced, making the metal foil have good electrical conductivity. Description of the Drawings

[0030] Figure 1 is a schematic structural diagram of the first metal foil in the embodiments of the present invention;

[0031] Figure 2 is a schematic structural diagram of the second metal foil in the embodiments of the present invention;

[0032] Figure 3 is a cross-sectional morphology diagram of the metal foil in Embodiment 1 provided by the present invention;

[0033] Figure 4 is a cross-sectional morphology diagram of the metal foil in Comparative Example 1 provided by the present invention;

[0034] Figure 5 is a cross-sectional morphology diagram of the metal foil in Comparative Example 2 provided by the present invention;

[0035] Figure 6 is a schematic structural diagram of the composite metal foil in the embodiments of the present invention;

[0036] Figure 7 is a schematic flow chart of the method for preparing a metal foil in an embodiment of the present invention;

[0037] Among them, 1. Metal foil; 2. Crystal structure; 3. Metal tooth; 4. Additional layer. Specific embodiments

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0039] In the description of the present application, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0040] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are only for the purpose of illustration and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0041] In the description of the present application, it should be noted that unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0042] Please refer to Figure 1 , in the first aspect of the embodiment of the present invention, a metal foil 1 is provided. The metal foil 1 includes a crystal structure 2 having a plurality of crystal plane orientations. The crystal structure 2 includes (220) crystal planes, (200) crystal planes, (111) crystal planes, and (311) crystal planes. The (220) crystal plane is a preferred orientation crystal plane, and the orientation degree of the (220) crystal plane is greater than or equal to 60%.

[0043] Specifically, in this embodiment, by defining that the metal foil 1 includes a crystal structure 2 having a plurality of crystal plane orientations, the metal foil 1 in this embodiment is a polycrystalline metal foil. It can be understood that in a polycrystalline structure, due to the anisotropy of crystals, the stresses on grains with different orientations are not the same. The resolved shear stresses acting on the slip systems of each grain vary greatly due to the different grain orientations. Therefore, each grain does not start to deform simultaneously. Grains in a favorable orientation first undergo slip, while grains in an unfavorable orientation have not yet started to slip.

[0044] The slip system orientations and slip directions of grains with different orientations are also different, and slip cannot directly continue from one grain to another. This results in that when a polycrystal undergoes plastic deformation, each grain must slip on several slip systems, including slip systems with unfavorable orientations, to coordinate the deformation of each grain. The atoms on the grain boundary are arranged irregularly, the lattice distortion is severe, and the grain orientations on both sides of the grain boundary are different, and the slip directions and slip planes are not consistent with each other. Therefore, it is extremely difficult for slip to directly continue from one grain to the next grain, and the grain boundary has a hindering effect on slip, resulting in a smaller amount of deformation near the grain boundary. Therefore, compared with a single-crystal metal foil, the crystal structure 2 of the polycrystalline metal foil in this embodiment includes (220) crystal planes, (200) crystal planes, (111) crystal planes, and (311) crystal planes, which can ensure that the metal foil 1 has the advantages of a good polycrystalline structure. To a certain extent, it can ensure that different grains have different slip system orientations and slip directions due to different orientations, so that the crystal structure 2 of the metal foil 1 is not easily plastically deformed, and further ensures that the metal foil 1 has better mechanical properties and has better advantages in terms of tensile strength, friction resistance, and fatigue resistance.

[0045] Furthermore, in this embodiment, it is also specified that in the crystal structure 2 of the metal foil 1, the (220) crystal plane is the preferred orientation crystal plane, so that the metal foil 1 in this embodiment has the advantages of both polycrystalline structure and single crystal structure. It should be noted that the orientation degree refers to the frequency or proportion of a certain crystal plane in the crystal structure 2 under a specified orientation, which can be measured by X-ray diffraction technology (XRD), and the relative orientation degree of different crystal planes is determined by measuring the intensity and position of the diffraction peak. Specifically, the orientation degree of a certain crystal plane is the ratio between the peak value of the X-ray diffraction intensity of this crystal plane and the total peak value of the X-ray diffraction intensities of all crystal planes. Taking the calculation of the orientation degree of the (220) crystal plane as an example, the orientation degree of the (220) crystal plane = the peak value of the X-ray diffraction intensity of the (220) crystal plane / the total peak value of the X-ray diffraction intensities of all crystal planes. Since there is anisotropy during the electro-deposition of metals, the growth directions and growth rates of each crystal plane are different. The grains growing rapidly along a certain crystal plane direction cover the grains growing along other crystal plane directions, and finally the microstructure forms a preferred orientation for growth on a specific crystal plane. And the crystal structure 2 of the metal foil 1 is directly related to the loss and interference degree of high-frequency signals during their movement in the conductor. Any non-uniform lattice arrangement will increase the grain boundary energy, increase the energy dissipation of the electrical signal during transmission, thereby weakening the intensity and quality of the signal, and reducing the conductivity of the material. In addition, the electromagnetic properties of the grain boundary may also cause additional noise, further interfering with the purity of the signal. Therefore, in this embodiment, by specifying that the preferred orientation crystal plane in the crystal structure 2 is the (220) crystal plane, it can be ensured that more grains grow along the (220) crystal plane direction, making the lattice arrangement of the metal foil 1 relatively uniform, thereby significantly reducing the signal transmission loss of the metal foil 1 and enabling the metal foil 1 to have good electrical conductivity.

[0046] In addition, the number of slip systems that can be activated by the grains growing along the (220) crystal plane direction is the least under different tensile directions. Therefore, under the same conditions, the metal foil 1 with the (220) crystal plane preferred orientation has more excellent tensile strength.

[0047] Furthermore, in this embodiment, it is also specified that the orientation degree of the (220) crystal plane is greater than or equal to 60%. It can be understood that the orientation degree of the crystal plane refers to the orientation distribution of the grains inside the crystal structure 2. By specifying that the orientation degree of the (220) crystal plane is greater than or equal to 60%, it can effectively ensure that the proportion of the grains growing along the (220) crystal plane direction is large enough. While ensuring that the metal foil 1 has good tensile strength, it can better reduce the signal transmission loss of the metal foil 1 and ensure that the metal foil 1 has good electrical conductivity.

[0048] As a preferred solution, the orientation degree of the (220) crystal plane is 60% - 80%.

[0049] Specifically, in this embodiment, the orientation degree of the (220) crystal plane is further limited to 60% - 80%. For example, the orientation degree of the (220) crystal plane can be 60%, 62%, 65%, 67%, 69%, 70%, 72%, 74%, 76%, 78%, 79%, 80%, etc., and this embodiment does not make specific limitations here. By limiting the orientation degree of the (220) crystal plane within the above range, it can not only ensure that the proportion of grains growing along the (220) crystal plane direction will not be too low, so as to better reduce the signal transmission loss of the metal foil 1 and ensure that the metal foil 1 has good electrical conductivity, but also ensure that the proportion of grains growing along the (220) crystal plane direction will not be too high, so as to ensure that the metal foil 1 has the advantages of a good polycrystalline structure and can significantly improve the tensile strength of the metal foil 1.

[0050] As a preferred solution, the orientation degree of the (220) crystal plane is 60% - 80%;

[0051] Furthermore, the orientation degree of the (200) crystal plane is 2% - 15%;

[0052] Furthermore, the orientation degree of the (111) crystal plane is 10% - 22%;

[0053] Furthermore, the orientation degree of the (311) crystal plane is 1 - 10%;

[0054] Among them, the sum of the orientation degrees of the (220) crystal plane, (200) crystal plane, (111) crystal plane and (311) crystal plane is less than or equal to 100%.

[0055] It is worth noting that a large number of experimental results show that 20% - 50% of the material properties are affected by texture, and texture will affect various mechanical and physical properties of materials such as elastic modulus, Poisson's ratio, strength, toughness, plasticity, magnetism, electrical conductivity, and linear expansion coefficient. In order to ensure that the metal foil 1 has good mechanical properties, physical properties and electrical conductivity, this embodiment limits the orientation degree of each oriented crystal plane.

[0056] Specifically, in this embodiment, the orientation degree of the (220) crystal plane is limited to 60% - 80%, which can not only ensure that the proportion of grains growing along the (220) crystal plane direction will not be too low, so as to better reduce the signal transmission loss of the metal foil 1 and ensure that the metal foil 1 has good electrical conductivity, but also ensure that the proportion of grains growing along the (220) crystal plane direction will not be too high, so as to ensure that the metal foil 1 has the advantages of a good polycrystalline structure and can significantly improve the tensile strength of the metal foil 1.

[0057] Furthermore, in this embodiment, the orientation degree of the (200) crystal plane is limited to 2% - 15%. For example, the orientation degree of the (200) crystal plane can be 2%, 4%, 5%, 7%, 9%, 11%, 13%, 15%, etc., and this embodiment does not make specific limitations here. It can be understood that in terms of electrical conductivity, the crystal structure 2 corresponding to the (200) crystal plane has poorer electrical conductivity compared to the crystal structure 2 corresponding to the (111) crystal plane. The reason is that the atomic arrangement of the crystal structure 2 corresponding to the (200) crystal plane is relatively loose, and the migration path of electrons is longer. Therefore, when the proportion of grains growing along the (200) crystal plane direction in the metal foil 1 is small, it means that more grain orientations tend to be the (111) crystal plane orientation, which helps to improve the electrical conductivity and conductance of the metal foil 1, especially crucial in electronic and semiconductor applications.

[0058] In terms of surface roughness, the surface of the metal foil 1 with the crystal structure 2 oriented in the (200) crystal plane is usually relatively rough, which easily leads to more surface defects during the production process. Reducing the proportion of grains growing along the (200) crystal plane direction in the metal foil 1 helps to obtain a smoother surface, thereby improving the quality of the metal foil 1, and is suitable for precision electronic devices and high-end circuit boards (such as high-frequency circuits).

[0059] In terms of mechanical properties, the metal foil 1 with the crystal structure 2 oriented in the (200) crystal plane is relatively brittle, and its tensile strength and ductility are poor. Reducing the proportion of grains growing along the (200) crystal plane direction in the metal foil 1 can improve the tensile strength, ductility, and toughness of the metal foil 1, making it more stable during the production process and reducing the risk of cracks and fractures. This is especially important for applications that require high strength and high toughness (such as flexible circuit boards).

[0060] In terms of surface flatness, the surface flatness of the metal foil 1 directly affects its subsequent processing and use performance. The metal foil 1 with the crystal structure 2 oriented in the (200) crystal plane has an uneven distribution of its crystal structure 2, resulting in an uneven surface. Reducing the proportion of grains growing along the (200) crystal plane direction in the metal foil 1 helps to improve the overall flatness of the metal foil 1, especially in occasions that require high-precision processing, such as the manufacture of high-end electronic components.

[0061] In terms of processing performance, the processing performance of the metal foil 1 (such as cutting, winding, etc.) is closely related to the crystal form. The metal foil 1 with the crystal structure 2 oriented in the (200) crystal plane is prone to cracks and fractures, especially in the case of thin metal foil 1. If the proportion of grains growing along the (200) crystal plane direction in the metal foil 1 is small, its overall processability will be improved, and it will be easier to adapt to subsequent processing steps, such as thin film deposition, winding, and cutting.

[0062] Therefore, in this embodiment, by limiting the degree of orientation of the (200) crystal plane to 2% - 15%, it can be ensured that the proportion of grains growing along the (200) crystal plane direction in the metal foil 1 will not be too high, thereby improving the electrical conductivity, mechanical properties, and processing properties of the metal foil 1, reducing the surface roughness of the metal foil 1, and improving the surface flatness of the metal foil 1.

[0063] Furthermore, in this embodiment, the degree of orientation of the (111) crystal plane is limited to 10% - 22%. For example, the degree of orientation of the (111) crystal plane can be 10%, 12%, 14%, 15%, 17%, 19%, 21%, 22%, etc., and this embodiment does not make specific limitations here. It can be understood that in terms of mechanical properties, especially in terms of ductility and tensile strength, although the metal foil 1 with a crystal structure 2 of (111) crystal plane orientation has good electrical conductivity, its relatively low ductility and poor tensile strength may cause cracks or fractures to easily occur during certain processing. Reducing the proportion of grains growing along the (111) crystal plane direction helps to improve the overall ductility of the metal foil 1, making it more suitable for applications that require high tensile strength and durability, such as flexible printed circuits (FPCs) and applications in certain high-stress environments.

[0064] In terms of processing properties, the metal foil 1 with a crystal structure 2 of (111) crystal plane orientation has a high grain density, so it is relatively brittle. Especially in extremely thin metal foils 1, it may cause fractures, peeling, or uneven deposition during processing. Reducing the proportion of grains growing along the (111) crystal plane direction helps to improve the performance of the metal foil 1 in subsequent processing (such as winding, cutting, heat treatment, etc.) and reduces processing problems caused by brittleness.

[0065] In terms of surface defects and roughness, the surface of the metal foil 1 with a crystal structure 2 of (111) crystal plane orientation is relatively flat. However, if the proportion of grains growing along the (111) crystal plane direction is too high, it may cause more surface defects or microcracks to form during electrolysis and processing, affecting product quality. Reducing the proportion of grains growing along the (111) crystal plane direction can effectively avoid excessive surface defects, improve the uniformity and surface quality of the metal foil 1, and is suitable for applications with high requirements for surface finish.

[0066] In terms of the flexibility of the metal foil 1, the metal foil 1 with a crystal structure 2 of (111) crystal plane orientation has strong rigidity and may not be suitable for products that require high flexibility (such as flexible printed circuits, bendable electronic devices, etc.). Reducing the proportion of grains growing along the (111) crystal plane direction will improve the overall flexibility of the metal foil 1, making it more suitable for use in fields that require flexible materials.

[0067] In terms of internal stress and grain boundary defects, the metal foil 1 with a crystal structure 2 having a (111) crystal plane orientation is usually relatively dense and has a large internal stress, which may lead to crack propagation and instability of the metal foil 1. By reducing the proportion of grains growing along the (111) crystal plane direction, the generation of internal stress and grain boundary defects can be effectively reduced, thereby improving the stability and reliability of the metal foil 1.

[0068] Therefore, in this embodiment, by limiting the orientation degree of the (111) crystal plane to 10% - 22%, it can be ensured that the proportion of grains growing along the (111) crystal plane direction in the metal foil 1 is not too high, thereby improving the mechanical properties, processing properties, and overall flexibility of the metal foil 1, and reducing the surface defects, surface roughness, internal stress, and grain boundary defects of the metal foil 1.

[0069] Furthermore, in this embodiment, the orientation degree of the (311) crystal plane is limited to 1% - 10%. For example, the orientation degree of the (311) crystal plane can be 1%, 3%, 4%, 5%, 6%, 7%, 9%, 10%, etc., and this embodiment does not make specific limitations here. It can be understood that in terms of surface flatness and smoothness, the metal foil 1 with a crystal structure 2 having a (311) crystal plane orientation is generally relatively rough and prone to surface defects (such as higher surface roughness). If the proportion of grains growing along the (311) crystal plane direction is small, the surface smoothness of the metal foil 1 can be improved, making it suitable for applications in high-precision electronic products (such as high-frequency circuits and precision PCB manufacturing).

[0070] In terms of electrical conductivity performance, if the metal foil 1 is mainly oriented with the (111) crystal plane of the face-centered cubic crystal form, it usually exhibits better electrical conductivity. Taking copper as an example, the (111) crystal plane is the most densely packed plane of copper, having lower resistance and better electrical conductivity performance. If the proportion of grains growing along the (311) crystal plane direction is small, it helps to improve the overall electrical conductivity of the metal foil 1.

[0071] In terms of tensile strength and toughness, the metal foil 1 with a crystal structure 2 having a (311) crystal plane orientation is relatively brittle, which may lead to a decrease in the tensile strength of the metal foil 1. Reducing the proportion of grains growing along the (311) crystal plane direction helps to enhance the mechanical properties of the metal foil 1, improve its tensile strength and toughness, and make it more stable during the processing.

[0072] In terms of grain boundary defects, the metal foil 1 with a crystal structure 2 having a (311) crystal plane orientation is more likely to generate defects at the grain boundaries, especially during heat treatment or electrolysis. If the proportion of grains growing along the (311) crystal plane direction is too large, it is easy to cause weakening of the grain boundaries in the metal foil 1, increasing the risk of its cracking or peeling. Reducing the proportion of grains growing along the (311) crystal plane direction helps to improve the overall stability and durability of the metal foil 1.

[0073] In terms of processability, during the manufacturing process of the metal foil 1, the distribution of crystal forms has a great influence on its subsequent processability. The relatively small proportion of grains growing along the (311) crystal plane direction is beneficial to improving the flexibility of the metal foil 1, making it smoother during further processing (such as winding, cutting, etc.) and reducing the risk of fracture during processing.

[0074] Therefore, in this embodiment, by limiting the orientation degree of the (311) crystal plane to 1% - 10%, it can be ensured that the proportion of grains growing along the (311) crystal plane direction in the metal foil 1 will not be too high, thereby improving the surface flatness, surface finish and processability of the metal foil 1, enhancing the conductivity, tensile strength and flexibility of the metal foil 1, and reducing the grain boundary defects of the metal foil 1.

[0075] It should be noted that the crystal structure 2 of the metal foil 1 in this embodiment may only include the (220) crystal plane, (200) crystal plane, (111) crystal plane and (311) crystal plane, so that the sum of the orientation degrees of the (220) crystal plane, (200) crystal plane, (111) crystal plane and (311) crystal plane is equal to 100%, or it may also include the orientation of other crystal planes in addition to the (220) crystal plane, (200) crystal plane, (111) crystal plane and (311) crystal plane, so that the sum of the orientation degrees of the (220) crystal plane, (200) crystal plane, (111) crystal plane and (311) crystal plane is less than 100%. This embodiment does not make specific limitations here.

[0076] As a preferred solution, within the preset observation range, the size of the grains in the crystal structure 2 is 0.2 μm - 3 μm; wherein, the size of the grains is the diameter of the largest circumscribed circle along the width direction of the grains. For example, the preset observation range is 5000 - 20000 μm 2 。

[0077] Specifically, in this embodiment, by limiting within a preset observation range, the size of the grains in the crystal structure 2 is 0.2 μm to 3 μm. For example, the size of the grains can be 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.7 μm, 1.9 μm, 2.1 μm, 2.3 μm, 2.5 μm, 2.7 μm, 2.9 μm, 3 μm, etc., and this embodiment does not make specific limitations here. It can be understood that the grain size has a certain influence on the plastic deformation of the polycrystalline structure. The finer the grains, the higher the strength. The reason is that the finer the grains, the more grain boundaries there are, and the greater the resistance to dislocation movement, making it difficult for the crystal structure 2 of the metal foil 1 to undergo plastic deformation. In addition, the finer the grains, the higher the plastic toughness. The reason is that the more grains there are, the more dispersed the deformation, the higher the uniformity, and the cracking caused by stress concentration will be reduced, and a larger deformation amount can be tolerated, showing high plasticity. In fine-grained materials, the stress concentration is small, cracks are not easily initiated, there are many grain boundaries, and cracks are not easily propagated. More energy can be absorbed during the fracture process, showing high toughness. Therefore, by limiting the size of the grains in the crystal structure 2 to the above size range in this embodiment, it is possible to ensure that the grain size is small, enabling the metal foil 1 to have better plastic properties and improving the heat resistance of the metal foil 1.

[0078] As a preferred solution, within the preset observation range, the standard deviation of the circumscribed circle diameters of all grains is 0.1 μm to 0.6 μm.

[0079] Specifically, within the preset observation range, this embodiment further limits the standard deviation of the circumscribed circle diameters of all grains to 0.1 μm to 0.6 μm. For example, the standard deviation of the circumscribed circle diameters of all grains is 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, etc., and this embodiment does not make specific limitations here. Thus, for each grain, it is possible to ensure the width uniformity of the grains as a whole, effectively enhancing the structural strength of the grains and enabling the metal foil 1 to have good mechanical properties; for all grains, it is possible to ensure that the size difference between the grains is small, ensuring the grain size uniformity of the crystal structure 2 as a whole, effectively enhancing the mechanical strength of the crystal structure 2, and enabling the metal foil 1 to have good mechanical properties.

[0080] As a preferred solution, the metal foil 1 is provided with a first side surface, and the roughness Rz of the first side surface is 3.8 μm to 4.5 μm.

[0081] Specifically, in this embodiment, the preferred orientation crystal plane in the crystal structure 2 of the metal foil 1 is designed to be the (220) crystal plane, and the orientation degree of the (220) crystal plane is greater than or equal to 60%. As a result, the roughness Rz of the first side of the metal foil 1 can be optimized to 3.8 μm to 4.5 μm, that is, the roughness Rz of the matte surface of the metal foil 1 is 3.8 μm to 4.5 μm. For example, the roughness Rz of the first side is 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, etc., and this embodiment does not make specific limitations here. It can be understood that in the field of high-frequency circuit design, as the operating frequency increases, the skin effect causes the current to tend to flow on the surface of the conductor. At this time, the roughness of the surface of the metal foil 1 becomes particularly critical. A larger roughness will cause the skin depth to further decrease, the current to be more concentrated on the extreme surface layer of the conductor, and the insertion loss to increase significantly. The system needs more power to compensate for the loss, or it will cause problems such as signal intensity attenuation during signal transmission. In addition, the too rough surface of the metal foil 1 will also cause an increase in the scattering of electromagnetic waves, resulting in an increase in the standing wave ratio and intermodulation distortion, which will all have a negative impact on the signal integrity of the circuit and the overall performance of the system. Therefore, the roughness Rz of the first side in this embodiment can be limited within a small range, so as to reduce the skin effect, and the roughness Rz of the first side is not too small, so as to ensure the bonding force between the metal foil 1 and other substrates after surface roughening.

[0082] As a preferred solution, one side of the metal foil 1 facing away from the first side is the second side, and the roughness Ra of the second side is 0.1 μm to 0.28 μm.

[0083] Specifically, this embodiment further limits the roughness Ra of the second side of the metal foil 1 facing away from the first side to 0.1 μm to 0.28 μm, that is, the roughness Ra of the smooth surface of the metal foil 1 is 0.1 μm to 0.28 μm. For example, the roughness Ra of the second side is 0.1 μm, 0.12 μm, 0.14 μm, 0.16 μm, 0.18 μm, 0.2 μm, 0.21 μm, 0.23 μm, 0.25 μm, 0.27 μm, 0.28 μm, etc., and this embodiment does not make specific limitations here. By limiting the roughness Ra of the second side within the above range, the surface finish and surface flatness of the second side of the metal foil 1 can be ensured, which is convenient for its subsequent processing and guarantees its service performance.

[0084] As a preferred solution, there are several metal teeth 3 on the first side, and the height of the metal teeth 3 is 1 μm to 5 μm.

[0085] Specifically, as Figure 2As shown, in this embodiment, a number of metal teeth 3 are provided on the first side of the metal foil 1. By setting the preferred orientation crystal plane in the crystal structure 2 as the (220) crystal plane, and the orientation degree of the (220) crystal plane being greater than or equal to 60%, metal teeth 3 with a relatively high height can be formed on the first side. Specifically, the height of the metal teeth 3 is 1 μm to 5 μm. For example, the height can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.9 μm, 3.1 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.7 μm, 4.9 μm, 5 μm, etc., and this embodiment does not make specific limitations here. By forming metal teeth 3 with a relatively high height on the first side, when the metal foil 1 is laminated with the circuit board substrate, the metal foil 1 can be better embedded into substrates such as PTFE (Polytetrafluoroethylene), improving the bonding force between the metal foil 1 and the circuit board substrate.

[0086] As a preferred solution, the maximum surface undulation height of the metal foil 1 is less than 3.5 μm; wherein, the maximum surface undulation height is the distance between the highest point and the lowest point on any surface of the metal foil 1.

[0087] Specifically, in this embodiment, by setting the preferred orientation crystal plane in the crystal structure 2 as the (220) crystal plane, and the orientation degree of the (220) crystal plane being greater than or equal to 60%, it can be ensured that the surface undulation degree of the metal foil 1 is relatively small. Specifically, the maximum surface undulation height of the metal foil 1 is less than 3.5 μm. For example, the maximum surface undulation height of the metal foil 1 is 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm, 1.5 μm, 1.7 μm, 1.9 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, etc., and this embodiment does not make specific limitations here, so as to better ensure the surface flatness of the metal foil 1, facilitate its subsequent processing and ensure its use performance. In addition, the surface undulation degree of the metal foil 1 is relatively small, and the surface roughness of the surface metal foil 1 is relatively low, so that the skin effect of the metal foil 1 is relatively low, improving the current transmission efficiency.

[0088] As a preferred solution, the coefficient of thermal expansion of the metal foil 1 is 20 ppm / K to 26 ppm / K; and / or,

[0089] The mass resistivity of the metal foil 1 is less than 0.166.

[0090] Specifically, in this embodiment, by setting the preferred orientation crystal plane in the crystal structure 2 as the (220) crystal plane, and the orientation degree of the (220) crystal plane being greater than or equal to 60%, it is possible to ensure that the expansion coefficient and mass resistivity of the metal foil 1 are relatively low. It can be understood that materials with a low expansion coefficient have a small degree of volume expansion when heated, can maintain a high degree of dimensional stability, and when the temperature changes, materials with a low expansion coefficient can reduce the stress caused by thermal expansion and contraction. Therefore, in this embodiment, the expansion coefficient of the metal foil 1 is limited to 20 ppm / K to 26 ppm / K. For example, the expansion coefficient of the metal foil 1 can be 20 ppm / K, 20.3 ppm / K, 20.7 ppm / K, 21 ppm / K, 21.4 ppm / K, 21.8 ppm / K, 22.5 ppm / K, 23 ppm / K, 23.4 ppm / K, 23.9 ppm / K, 24.5 ppm / K, 25 ppm / K, 26 ppm / K, etc. This embodiment does not make specific limitations here, so as to ensure that the metal foil 1 in this embodiment has good high-temperature stability.

[0091] Furthermore, since the lower the mass resistivity, the better the electrical conductivity of the material, therefore, in this embodiment, the mass resistivity of the metal foil 1 is less than 0.166. For example, the mass resistivity of the metal foil 1 can be 0.113, 0.125, 0.134, 0.147, 0.158, 0.161, 0.163, 0.165, etc. This embodiment does not make specific limitations here, so as to ensure that the metal foil 1 in this embodiment has good electrical conductivity.

[0092] The metal foil 1 provided by the embodiment of the present invention has the following beneficial effects in at least one of the following aspects:

[0093] (1) By including the crystal structure 2 with several crystal plane orientations in the metal foil 1, the metal foil 1 has good mechanical properties, and can improve the tensile strength of the metal foil 1. By limiting the preferred orientation crystal plane in the crystal structure 2 as the (220) crystal plane, and the orientation degree of the (220) crystal plane being greater than or equal to 60%, the signal transmission loss of the metal foil 1 can be significantly reduced, making the metal foil 1 have good electrical conductivity.

[0094] (2) By setting the crystal planes in the crystal structure 2 to include the (220) crystal plane, (200) crystal plane, (111) crystal plane, and (311) crystal plane, and limiting the orientation degree of each orientation crystal plane, it is possible to ensure that the metal foil 1 has good mechanical properties, physical properties, and electrical conductivity.

[0095] (3) By limiting the grain size in the crystal structure 2 within the preset observation range to be 0.2 μm to 3 μm, it can ensure that the grain size is relatively small, enabling the metal foil 1 to have better plastic properties and improving the heat resistance of the metal foil 1. In addition, by limiting the standard deviation of the circumscribed circle diameters of all grains to be 0.1 μm to 0.6 μm, the mechanical strength of the crystal structure 2 can be effectively enhanced, enabling the metal foil 1 to have good mechanical properties.

[0096] (4) By designing the preferred orientation crystal plane in the crystal structure 2 of the metal foil 1 to be the (220) crystal plane, and the orientation degree of the (220) crystal plane being greater than or equal to 60%, the roughness Rz of the first side and the roughness Ra of the second side on the metal foil 1 are relatively small, effectively reducing the skin effect, ensuring the surface finish and surface flatness of the second side of the metal foil 1, facilitating its subsequent processing and ensuring its service performance.

[0097] (5) By designing the preferred orientation crystal plane in the crystal structure 2 of the metal foil 1 to be the (220) crystal plane, and the orientation degree of the (220) crystal plane being greater than or equal to 60%, metal teeth 3 with a relatively high height can be formed on the first side, and the surface undulation degree of the metal foil 1 is relatively small. In addition, it ensures that the expansion coefficient and mass resistivity of the metal foil 1 are relatively low.

[0098] To demonstrate the beneficial effects of the metal foil provided by the embodiments of the present invention, the following will be described in conjunction with examples and comparative examples.

[0099] Example 1: A metal foil, in which the preferred orientation crystal plane in its crystal structure is the (220) crystal plane, and the orientation degree of the (220) crystal plane is 70.57%.

[0100] Comparative Example 1: A metal foil, in which the orientation degree of the (220) crystal plane in its crystal structure is 58.59%.

[0101] Comparative Example 2: A metal foil, in which the orientation degree of the (220) crystal plane in its crystal structure is 43.1%.

[0102] Specifically, in Example 1, Comparative Example 1, and Comparative Example 2, the XRD intensities of each orientation crystal plane are shown in Table 1 below.

[0103] Table 1 XRD Intensities of Each Orientation Crystal Plane

[0104]

[0105] Furthermore, the mass resistivities of Example 1, Comparative Example 1, and Comparative Example 2 were tested, and the test results are shown in Table 2 below.

[0106] Table 2 Comparison of Mass Resistivities

[0107] Sample <![CDATA[Mass resistivity (Ω·g / m 2 , 20 °C)]]> Comparative Example 1 0.166 Comparative Example 2 0.174 Example 1 0.163

[0108] As can be seen from Table 2, in Example 1, the preferred orientation crystal plane in the crystal structure is the (220) crystal plane, and the orientation degree of the (220) crystal plane satisfies being greater than or equal to 60%. Therefore, compared with Comparative Example 1 and Comparative Example 2, the mass resistivity of Example 1 is lower and the electrical conductivity is better.

[0109] Furthermore, the surface roughness of Example 1, Comparative Example 1, and Comparative Example 2 was tested, and the peel strength after laminating with the PTFE substrate was tested, as shown in Table 3 below.

[0110] Table 3 Comparison of surface roughness and peel strength

[0111] Sample Roughness Rz of the matte surface (μm) Roughness Ra of the smooth surface (μm) Peel strength (N / mm) Comparative Example 1 4.89 0.38 3.35 Comparative Example 2 4.79 0.30 3.27 Example 1 4.21 0.19 3.31

[0112] As can be seen from Table 3, in Example 1, the preferred orientation crystal plane in the crystal structure is the (220) crystal plane, and the orientation degree of the (220) crystal plane satisfies being greater than or equal to 60%. Therefore, compared with Comparative Example 1 and Comparative Example 2, whether it is the rough surface roughness or the smooth surface roughness, Example 1 is lower, which can significantly reduce the skin effect, thereby improving the current transmission efficiency, and at the same time ensuring good peel strength.

[0113] In addition, as Figures 3 to 5 shown, are the schematic cross-sectional morphology diagrams of Example 1, Comparative Example 1, and Comparative Example 2 respectively. It can be seen from the figure that compared with Comparative Example 1 and Comparative Example 2, the surface undulation degree of Example 1 is smaller, that is, the surface flatness of Example 1 is better than that of Comparative Example 1 and Comparative Example 2.

[0114] Furthermore, the mechanical properties of Example 1, Comparative Example 1, and Comparative Example 2 were tested, and the test results are shown in Table 4 below.

[0115] Table 4 Comparison of mechanical properties

[0116]

[0117] As can be seen from Table 4, in Example 1, the preferred orientation crystal plane in the crystal structure is the (220) crystal plane, and the orientation degree of the (220) crystal plane satisfies being greater than or equal to 60%. Therefore, in terms of these mechanical properties such as the maximum load force, RT tensile strength, RT elongation, 180°C tensile strength, and 180°C elongation, Example 1 is much better than Comparative Example 1 and Comparative Example 2, that is, Example 1 has better mechanical properties.

[0118] Please refer to Figure 6 , in the second aspect of the embodiments of the present invention, a composite metal foil is provided. The composite metal foil includes an additional layer 4 and the metal foil 1 as in any one of the first aspect, and the additional layer 4 and the metal foil 1 are stacked.

[0119] As a preferred solution, there are two or more additional layers 4.

[0120] It should be noted that the additional layer 4 in this embodiment includes but is not limited to a carrier layer, a release layer, a heat-resistant layer, a conductive layer, an antioxidant layer, etc. Different additional layers 4 can be stacked on the metal foil 1 based on actual application requirements, and this embodiment does not make specific limitations here. In addition, by setting the additional layer 4 to be two or more layers, the composite metal foil has better performance.

[0121] Please refer to Figure 7 , the third aspect of the embodiment of the present invention provides a method for preparing a metal foil, including the following steps S1 to S3:

[0122] Step S1, prepare a main copper sulfate electrolyte.

[0123] Step S2, add additives to the main copper sulfate electrolyte to obtain an electrolyte; wherein, the additives include a (220) crystal plane promoter and a (220) crystal plane inhibitor.

[0124] Step S3, perform electrodeposition on the electrolyte to obtain the metal foil according to any one of the first aspect.

[0125] Specifically, in this embodiment, electrolytic copper is first used as a raw material and dissolved in a copper sulfate solution to prepare a main copper sulfate electrolyte. Further, in order to form a metal foil with a (220) crystal plane preferred orientation, additives including a (220) crystal plane promoter and a (220) crystal plane inhibitor need to be added to the main copper sulfate electrolyte. It can be understood that the (220) crystal plane promoter can promote the preferred growth of the (220) crystal plane, improving the tensile strength and elongation of the metal foil, while the (220) crystal plane inhibitor inhibits the growth of the (220) crystal plane and promotes the preferred growth of the (200) crystal plane, competing with the (220) crystal plane promoter to inhibit the grain size of the metal foil, making the surface of the prepared metal foil flat and synchronously improving the tensile strength and elongation of the metal foil.

[0126] Place the electrolyte in an electrolytic cell, with an anode and a cathode placed on both sides of the electrolytic cell, and pass direct current. When the current passes through the solution, copper ions will be reduced on the cathode to form a copper foil. By controlling parameters such as current density, temperature, solution concentration, and pH value, the thickness and quality of the copper foil can be adjusted. The deposition rate of the copper foil during the electrolysis process is relatively slow, usually between a few micrometers and dozens of micrometers. When the copper foil is deposited to a certain thickness, it needs to be taken out from the electrolytic cell. The copper foil is usually peeled off from the cathode to form a thin sheet. Then, the electrolytic copper foil is washed to remove residual chemical substances and impurities on the surface. In addition, the surface of the copper foil usually needs to be chemically or mechanically treated to improve its flatness, adhesion, and conductivity. For example, heat treatment, polishing, coating a protective film, etc. The washed copper foil needs to be dried to remove moisture. It should be noted that the edges and surfaces of the copper foil may be irregular and need to be trimmed to meet the product requirements.

[0127] As a preferred solution, the (220) crystal plane promoter is any one or more of sodium polydithiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate, phenyl polydithiopropane sulfonate, and sodium N,N-dimethyldithiocarbonylpropane sulfonate;

[0128] (220) crystal plane inhibitor is any one or more of gelatin, collagen, peptone, and tryptone.

[0129] As a preferred solution, the (220) crystal plane promoter is specifically sodium polydithiopropane sulfonate, and the concentration of sodium polydithiopropane sulfonate is 5 ppm to 10 ppm; and / or,

[0130] (220) crystal plane inhibitor is specifically collagen, and the concentration of collagen is 8 ppm to 15 ppm.

[0131] Specifically, in this embodiment, sodium polydithiopropane sulfonate is used as the (220) crystal plane promoter, and the concentration of sodium polydithiopropane sulfonate is limited to 5 ppm to 10 ppm. For example, the concentration of sodium polydithiopropane sulfonate can be 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, etc. This embodiment does not make specific limitations here. Sodium polydithiopropane sulfonate has a depolarizing effect and can promote the 2+ reduction of Cu, increase the surface particles of the copper foil, promote the preferential growth of the (220) crystal plane, and improve the tensile strength and elongation of the copper foil.

[0132] In addition, in this embodiment, collagen is used as the (220) crystal plane inhibitor, and the concentration of collagen is limited to 8 ppm to 15 ppm. For example, the concentration of collagen can be 8 ppm, 9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, 15 ppm, etc. This embodiment does not make specific limitations here. Collagen has a strong polarization effect and can inhibit the 2+ reduction of Cu, reduce the particles on the surface of the copper foil, inhibit the growth of the (220) crystal plane, promote the preferential growth of the (200) crystal plane, compete with sodium polydithiopropane sulfonate, inhibit the grain size of the copper foil, make the surface of the prepared copper foil flat, and simultaneously improve the tensile strength and elongation of the copper foil.

[0133] As a preferred solution, the additive further includes polyethylene glycol, and the concentration of polyethylene glycol is 0 ppm to 5 ppm; and / or,

[0134] In the main electrolyte of copper sulfate, the concentration of copper ions is 70 g / L to 100 g / L, the concentration of sulfuric acid is 140 g / L to 180 g / L, and the concentration of chloride ions is 40 mg / L; and / or,

[0135] Electrodeposition is performed on the electrolyte. Specifically:

[0136] Direct current with a current density of 55 A / dm 2 ~75 A / dm 2 is used to perform electrodeposition on the electrolyte, and the temperature of the plating solution during the electrodeposition process is 48 °C to 52 °C.

[0137] It should be noted that the additive in this embodiment further includes polyethylene glycol, and its concentration is 0 ppm to 5 ppm. For example, the concentration of polyethylene glycol can be 0 ppm, 1 ppm, 2 ppm, 3 ppm, 4 ppm, 5 ppm, etc. This embodiment does not make specific limitations here. Adding polyethylene glycol can assist in refining grains, make the deposited layer dense, improve the tensile strength of the copper foil, and reduce pinholes and penetration points.

[0138] Further, in this embodiment, the concentrations of copper ions, sulfuric acid, and chloride ions in the main electrolyte of copper sulfate are further limited. Specifically, the concentration of copper ions is 70 g / L to 100 g / L. For example, the concentration of copper ions can be 70 g / L, 72 g / L, 75 g / L, 77 g / L, 79 g / L, 81 g / L, 83 g / L, 85 g / L, 87 g / L, 89 g / L, 94 g / L, 96 g / L, 98 g / L, 100 g / L, etc., and this embodiment does not make specific limitations here; the sulfuric acid concentration is 140 g / L to 180 g / L. For example, the sulfuric acid concentration can be 140 g / L, 143 g / L, 148 g / L, 151 g / L, 154 g / L, 157 g / L, 159 g / L, 162 g / L, 165 g / L, 167 g / L, 170 g / L, 172 g / L, 176 g / L, 180 g / L, etc., and this embodiment does not make specific limitations here. By limiting the sulfuric acid concentration within this range, the effect of refining the crystal lattice can be achieved; the chloride ion concentration is 40 mg / L. At this concentration, the cathode current density can be increased and the grain size can be refined.

[0139] Further, during the electroplating process, in this embodiment, the current density of the direct current used is limited to 55 A / dm 2 ~75 A / dm 2 , for example, the current density of the direct current can be 55 A / dm 2 、57 A / dm 2 、59 A / dm 2 、61 A / dm 2 、63 A / dm 2 、65 A / dm 2 、67 A / dm 2 、69 A / dm 2 、71 A / dm 2 、73 A / dm 2 、75 A / dm 2 etc., and this embodiment does not make specific limitations here. Within this current density range, the crystal lattice can be refined and the crystal forming probability of preferential growth on the (220) crystal plane can be increased.

[0140] In the fourth aspect of the embodiments of the present invention, a metal-coated laminate is provided. The metal-coated laminate includes a metal foil as described in any one of the embodiments of the first aspect.

[0141] In the fifth aspect of the embodiments of the present invention, a circuit board is provided. The circuit board includes a circuit board substrate and a metal foil as described in any one of the embodiments of the first aspect, and the metal foil is laminated with the circuit board substrate; or, the circuit board is made of a metal-coated laminate as described in the fourth aspect as one of the materials.

[0142] The metal foil, composite metal foil, method for preparing metal foil, metal-coated laminate and circuit board provided by the embodiments of the present invention have a crystal structure including several crystal plane orientations in the metal foil, so that the metal foil has good mechanical properties and can improve the tensile strength of the metal foil. By defining the preferred orientation crystal plane in the crystal structure as the (220) crystal plane and the orientation degree of the (220) crystal plane being greater than or equal to 60%, the signal transmission loss of the metal foil can be significantly reduced, making the metal foil have good electrical conductivity.

[0143] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A metal foil, characterized in that: The metal foil includes a crystal structure with several crystal plane orientations, including a (220) crystal plane, a (200) crystal plane, a (111) crystal plane and a (311) crystal plane. The (220) crystal plane is a preferentially oriented crystal plane, and the orientation degree of the (220) crystal plane is greater than or equal to 60%.

2. The metal foil according to claim 1, characterized in that The orientation degree of the (220) crystal plane is 60% to 80%.

3. The metal foil according to claim 1, characterized in that The orientation degree of the (220) crystal plane is 60% to 80%; and / or, The orientation degree of the (200) crystal plane is 2% to 15%; and / or, The orientation degree of the (111) crystal plane is 10% to 22%; and / or, The orientation degree of the (311) crystal plane is 1 to 10%; The sum of the orientation degrees of the (220) crystal plane, the (200) crystal plane, the (111) crystal plane and the (311) crystal plane is less than or equal to 100%.

4. The metal foil according to claim 1, characterized in that In a preset observation range, the size of the grains in the crystal structure is 0.2 μm to 3 μm; wherein the size of the grains is the diameter of the largest circumscribed circle along the width direction of the grains.

5. The metal foil according to claim 4, characterized in that Within a preset observation range, a standard deviation of the circumscribed circle diameters of all the grains is 0.1 μm to 0.6 μm.

6. The metal foil according to claim 1, wherein The metal foil has a first side surface, and the roughness Rz of the first side surface is 3.8 μm to 4.5 μm.

7. The metal foil according to claim 6, characterized in that A side surface of the metal foil facing away from the first side surface is a second side surface, and a roughness Ra of the second side surface is 0.1 μm to 0.28 μm.

8. The metal foil according to claim 7, characterized in that The first side surface is provided with a plurality of metal teeth, and the height of the metal teeth is 1 μm to 5 μm.

9. The metal foil according to claim 1, wherein The maximum surface undulation height of the metal foil is less than 3.5 μm; wherein the maximum surface undulation height is the distance between the highest point and the lowest point on any surface of the metal foil.

10. The metal foil according to claim 1, wherein The expansion coefficient of the metal foil is 20ppm / K to 26ppm / K; and / or, The mass resistivity of the metal foil is less than 0.

166.

11. A composite metal foil, characterized in that: The composite metal foil comprises an additional layer and the metal foil according to any one of claims 1 to 10, wherein the additional layer and the metal foil are stacked.

12. The composite metal foil according to claim 11, characterized in that The number of the additional layers is two or more.

13. A method for preparing a metal foil, characterized in that: include: Prepare copper sulfate main electrolyte; Adding additives to the copper sulfate main electrolyte to obtain an electrolyte; wherein the additives include (220) crystal face promoters and (220) crystal face inhibitors; The electrolyte is subjected to electrodeposition to obtain the metal foil according to any one of claims 1 to 10.

14. A metal-clad laminate, characterized in that: The metal-clad laminate includes the metal foil according to any one of claims 1 to 10.

15. A circuit board, characterized in that: The circuit board comprises a circuit board substrate and the metal foil as claimed in any one of claims 1 to 10, wherein the metal foil is pressed together with the circuit board substrate; or, the circuit board is made of the metal-clad laminate as claimed in claim 14 as one of the materials.

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