Metal foil, metal foil with carrier, copper clad laminate and printed circuit board

Abstract

The present invention discloses a metal foil, a metal foil with a carrier, a copper-clad laminate, and a printed circuit board. A plurality of protrusions are distributed on one side of the metal foil, and the protrusions have a microscopic shape in which a lower half of the protrusion connected to the one side of the metal foil has a restricting portion, the diameter of a circumscribed circle of a cross section of the restricting portion is smaller than the skin depth of the metal foil, and the surface area of ​​the portion of the protrusion on the restricting portion is larger than the surface area of ​​the other portion of the protrusion. According to the embodiment of the present invention, not only the transmission loss of high frequency signals in the metal foil is reduced, but also excellent peel strength is provided between both the signal transmission circuit manufactured and formed from the metal foil and the dielectric layer.

Description

[Technical Field]

[0001] The present invention relates to the technical field of materials, and in particular to metal foils, metal foils with carriers, copper clad laminates and printed circuit boards. [Background technology]

[0002] Printed circuit boards (PCBs) are widely used in electronic devices. As the functionality of semiconductor electronic devices continues to improve, the integration density of electronic devices and data transmission speeds in electronic devices are also increasing. As a result, the signal transmission circuits on PCBs, which act as signal transmission carriers, are becoming increasingly dense. As a result, the signal transmission circuits are becoming thinner and thinner, and the signal current frequencies in the signal transmission circuits are becoming higher. Therefore, the transmission efficiency of high-frequency signals has become one of the evaluation standards for the performance of printed circuit boards. A printed circuit board is structured with metal foils and a dielectric layer bonded between the metal foils. After etching the metal foil, a signal transmission circuit for signal transmission is formed, and the dielectric layer primarily provides insulation. The metal foil is typically a copper foil layer, and the dielectric layer is typically a resin layer. The signal transmission circuit formed by etching the metal foil is bonded to the resin layer via the surface of the circuit.

[0003] The physical mechanisms of signal transmission loss in printed circuit boards include conductor loss due to the metal foil of the board and dielectric loss due to the dielectric layer. By selecting a special resin layer to counter the dielectric loss due to the dielectric layer, the dielectric loss of the dielectric layer can be reduced to an ideal level. Therefore, conductor loss due to the metal foil is one of the main factors in signal transmission loss in printed circuit boards. The electromagnetic skin effect, which increases with increasing signal frequency, is one of the most important characteristics of conductor loss. The underlying cause is that high-frequency signal current flows through a thinner surface layer of the metal surface of the transmission circuit. The higher the signal frequency, the shallower the current flows through the metal foil signal transmission circuit. There are many papers studying the relationship between circuit board transmission line signal loss and metal surface roughness. For example, the paper "Signal Transmission Loss due to Copper Surface Roughness in High-Frequency Region" explains signal loss due to copper foil surface roughness and points out that the lower the copper foil surface roughness, the lower the signal loss. Therefore, high-frequency signal transmission requires that metal surface roughness be as low as possible. However, as the integration density of printed circuit boards continues to increase, the signal transmission circuits formed on the copper foil layers of printed circuit boards become thinner, resulting in a smaller bonding area between the copper foil signal transmission circuits and the dielectric layer. This reduces the bonding strength between the copper foil signal transmission circuits and the dielectric layer, making them more susceptible to delamination. The bonding strength between the copper foil layer and the dielectric layer is another important factor affecting the performance of printed circuit boards. This is because the signal transmission circuits on the copper foil layer bond with the dielectric layer through surface roughness, which allows them to adhere to the resin layer. As signal transmission circuits become thinner, the paper "Non-Classical Conductor Losses due to Copper Foil Roughness and Treatment" points out that the adhesion strength between copper foil and the dielectric layer is related to the copper foil's roughness, and that the greater the copper foil's roughness, the greater the adhesion strength with the dielectric layer of the printed circuit board and the higher the peel strength between the copper foil and the dielectric layer.Therefore, in view of the trend toward finer signal transmission circuits due to the high integration of printed circuit boards, the surface roughness of copper foils is required to be increased in order to ensure the bonding strength between the signal transmission circuits and the dielectric layer.

[0004] Generally, in order to reduce the transmission loss of high frequency signals, the prior art requires that the roughness of the metal foil be as small as possible, while in consideration of the trend toward high density and finer circuits on printed circuit boards, the roughness of the metal foil be as large as possible. In other words, these two requirements for the surface morphology of the metal foil in the prior art are contradictory, and it is not possible to achieve both the transmission loss of high frequency signals in the metal foil and the peel strength between the high density signal transmission circuit on the metal foil and the dielectric layer. Summary of the Invention [Problem to be solved by the invention]

[0005] At least one objective of the embodiments of the present invention is to provide a metal foil, a metal foil with a carrier, a copper-clad laminate, and a printed circuit board that not only reduces the transmission loss of high-frequency signals in the metal foil, but also provides excellent peel strength between the signal transmission circuit and the dielectric layer formed from the metal foil, making the two less likely to peel off and fall off, and enables the use of the metal foil to manufacture high-density, fine-circuit high-frequency circuit boards. [Means for solving the problem]

[0006] In order to solve the above problems, the embodiment of the present invention has a plurality of protrusions distributed on one surface, The protrusion provides a metal foil having a microscopic shape in which the lower half of the protrusion connected to one surface of the metal foil has a regulating portion, the diameter of the circumscribed circle of the cross section of the regulating portion is smaller than the skin depth of the metal foil, and the surface area of ​​the portion of the protrusion on the regulating portion is larger than the surface area of ​​other portions of the protrusion.

[0007] As an improvement to the above solution, the skin depth δ is JPEG0007771219000001.jpg17170, where σ is the conductivity of the material of the protrusion, f is the signal frequency when the metal foil serves as a signal transmission carrier, and μ is the magnetic permeability.

[0008] As an improvement to the above solution, the height of the restriction portion relative to the one surface of the metal foil is 2 μm or less, and the height of the protrusion relative to the one surface of the metal foil is 4 μm or less.

[0009] As an improvement of the above solution, the ratio of the vertical length of the portion of the protrusion above the restricting portion to the height of the protrusion is 1 / 2 to 5 / 6.

[0010] As an improvement of the above solution, the protrusions are tree-shaped, icicle-shaped or teardrop-shaped.

[0011] As an improvement to the above solution, the protrusion includes a stem extending outward from the one surface and having the regulating portion, and a branch extending outward from the surface of the stem at a portion above the regulating portion.

[0012] As an improvement of the above solution, the material composition of the trunk is the same as the metal foil.

[0013] As an improvement of the above solution, the material composition of the trunk part is different from that of the metal foil, and the material of the trunk part is at least one selected from copper, nickel, zinc, chromium, aluminum, silicon, alumina particles, industrial diamond particles.

[0014] As an improvement of the above solution, on said one side at least 10% of said protrusions have said microscopic morphology.

[0015] As an improvement of the above solution, on said one side at least 50% of said protrusions have said microscopic morphology.

[0016] As an improvement of the above solution, on said one side at least 90% of said protrusions have said microscopic morphology.

[0017] As an improvement of the above solution, the signal frequency f is between 1 Hz and 100 GHz.

[0018] As an improvement of the above solution, said metal foil comprises copper foil and / or aluminum foil.

[0019] As an improvement of the above solution, the metal foil is a single layer metal structure or a multi-layer metal structure consisting of at least two single layer metals.

[0020] Another embodiment of the present invention provides a metal foil with a carrier, comprising a carrier layer and the metal foil described in any one of the above solutions, wherein the carrier layer is releasably attached to the other side of the metal foil opposite to the one side.

[0021] As an improvement of the above solution, the metal foil with a carrier further comprises a release layer located between the carrier layer and the metal foil, so that both the metal foil and the carrier layer are releasably provided.

[0022] As an improvement of the above solution, the metal foil with a carrier further includes a first adhesive layer provided between the carrier layer and the release layer.

[0023] As an improvement to the above solution, the first adhesive layer is a metal adhesive layer, and the metal adhesive layer is made of one or more of copper, zinc, nickel, iron, and manganese, or is made of one of copper or zinc and one of nickel, iron, and manganese.

[0024] As an improvement of the above solution, the metal foil with a carrier further includes a first antioxidant layer provided on a surface of the metal foil adjacent to the carrier layer.

[0025] As an improvement of the above solution, the first anti-oxidation layer material is at least one of nickel, copper alloy, and chromium.

[0026] As an improvement of the above solution, the metal foil with a carrier further comprises a second anti-oxidation layer provided on the surface of the metal foil remote from the carrier layer.

[0027] As an improvement to the above solution, the material of the second anti-oxidation layer is at least one of nickel, chromium, and zinc.

[0028] Another embodiment of the present invention provides a copper clad laminate obtained using the metal foil according to any one of the above solutions or the metal foil with a carrier according to any one of the above solutions.

[0029] As an improvement of the above solution, the copper clad laminate further comprises a dielectric layer provided on one side of at least one of the metal foils.

[0030] As an improvement to the above solution, the material of the dielectric layer is at least one selected from polyimide (e.g., thermoplastic polyimide), modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polyethylene naphthalate, polystyrene, polyvinyl chloride, polysulfone, polyphenylene sulfide, polyether ether ketone, polyphenylene oxide, polytetrafluoroethylene, liquid crystal polymer, polyparabanic acid, epoxy glass cloth, and BT resin.

[0031] As an improvement of the above solution, the copper clad laminate further includes a second adhesive layer provided on the one side of the metal foil.

[0032] As an improvement of the above solution, the material of the second adhesive layer is at least one selected from polystyrene-based, vinyl acetate-based, polyester-based, polyethylene-based, polyamide-based, rubber-based or acrylate-based thermoplastic resins, phenol-based, epoxy-based, thermoplastic polyimide, urethane-based, melamine-based or alkyd-based thermosetting resins, BT resin, and ABF resin.

[0033] Another embodiment of the present invention provides a printed circuit board obtained using the metal foil according to any one of the above solutions, the metal foil with a carrier according to any one of the above solutions, or the copper clad laminate according to any one of the above solutions. [Effects of the Invention]

[0034] Compared with the prior art, the metal foil, the metal foil with a carrier, the copper-clad laminate, the printed circuit board, and the method for manufacturing the metal foil according to the embodiments of the present invention have at least one of the following beneficial effects: The metal foil has a plurality of protrusions distributed on one surface, and the protrusions have a microscopic shape in which a lower half of the protrusions connected to the one surface has a restricting portion, the diameter of a circumscribing circle of a cross section of the restricting portion is smaller than the skin depth of the metal foil, and the surface area of ​​the portion of the protrusion on the restricting portion is larger than the surface area of ​​the other portion of the protrusion. In this way, when a signal transmission circuit is manufactured and formed using the metal foil, the restricting portion of the protrusion has a large impedance, and the narrower the restricting portion of the protrusion, the larger the impedance of that portion of the protrusion. Since the diameter of the circumscribing circle of the cross section of the restricting portion of the lower half of the protrusion is smaller than the skin depth, the restriction by the restricting portion of the lower half of the protrusion makes it difficult for high-frequency signal current in the metal foil to pass through the restricting portion of the protrusion, thereby reducing the high-frequency signal current flowing above the protrusion. Therefore, the effect of the protrusions on the surface of the metal foil on high-frequency signal loss in a signal transmission circuit manufactured and formed from the metal foil described in the embodiment of the present invention is reduced, thereby reducing the transmission loss of high-frequency signals in the signal transmission circuit manufactured and formed from the metal foil. Since the surface area of ​​the portion of the protrusion above the restricting portion is larger than the surface area of ​​the other portion of the protrusion, the surface area of ​​the portion of the protrusion above the restricting portion is larger than the surface area of ​​the portion of the protrusion above the restricting portion, and the protrusion has a relatively large surface area, and there is a large contact area between the signal transmission circuit formed by manufacturing from metal foil and the dielectric layer, circuit The metal foil has excellent peel strength between it and the dielectric layer, making it difficult for the layers to peel off and fall off, and it is possible to manufacture high-density, fine-circuit high-frequency circuit boards using the metal foil. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a schematic diagram of a longitudinal cross section of a metal foil according to one embodiment of the present invention. [Figure 2] The overall structure of the protrusion in FIG. [Figure 3] 10 is a schematic diagram of the flow of high-frequency signal current in a metal foil when the width of the lower part of a protrusion in the metal foil is greater than the skin depth. FIG. [Figure 4] 1 is a schematic diagram of the flow of high-frequency signal current in a metal foil when the minimum width of the lower half of a protrusion of the metal foil according to one embodiment of the present invention is smaller than the skin depth. [Figure 5] 1 is a structural schematic diagram of a metal foil according to one embodiment of the present invention. [Figure 6] 3 is an electron microscope image of a metal foil having a plurality of protrusions on one surface according to an embodiment of the present invention; FIG. [Figure 7] 10 is an electron microscope view of a metal foil having a plurality of the protrusions on one surface according to a further embodiment of the present invention. FIG. [Figure 8] FIG. 1 is an electron microscope image of a normal metal foil. [Figure 9] FIG. 2 is a slice scanning curve diagram of protrusions of a metal foil according to one embodiment of the present application and a normal metal foil. [Figure 10] 10 is the corresponding spatial Fourier transform logarithmic spectrogram of the curve in FIG. 9. [Figure 11] FIG. 2 is a structural schematic diagram of a crimping unit used in the process of testing the peel strength between a surface of a metal foil having protrusions and a resin layer in one embodiment of the present invention. [Figure 12] 1 is a structural schematic diagram of a metal foil with a carrier according to one embodiment of the present invention. [Figure 13] FIG. 2 is a structural schematic diagram of a metal foil with a carrier according to another embodiment of the present invention. [Figure 14] FIG. 2 is a structural schematic diagram of a metal foil with a carrier according to another embodiment of the present invention. [Figure 15]FIG. 2 is a structural schematic diagram of a metal foil with a carrier according to another embodiment of the present invention. [Figure 16] FIG. 2 is a structural schematic diagram of a metal foil with a carrier according to another embodiment of the present invention. [Figure 17] 1 is a structural schematic diagram of a copper clad laminate according to one embodiment of the present invention. [Figure 18] 2 is a structural schematic diagram of a copper clad laminate according to another embodiment of the present invention; FIG. [Figure 19] 2 is a structural schematic diagram of a copper clad laminate according to a further embodiment of the present invention; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, the technical solutions of the embodiments of the present invention will be clearly and completely described with reference to the drawings of the embodiments of the present invention, and it is obvious that the described embodiments are not all embodiments but only some embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by a person skilled in the art without any inventive effort fall within the protection scope of the present invention.

[0037] 1, an embodiment of the present invention provides a metal foil 1 having a plurality of protrusions 2 distributed on one surface of the metal foil 1, and the protrusions 2 have the following microscopic shape: Referring to FIG. 2, the lower half of the protrusions 2 connected to the one surface of the metal foil 1 has a restriction portion 100, the diameter of the circumscribed circle of the cross section of the restriction portion 100 is smaller than the skin depth of the metal foil 1, and the surface area of ​​the portion of the protrusion 2 at the restriction portion 100 is larger than the surface area of ​​the other portions of the protrusion 2.

[0038] Specifically, the skin depth δ is JPEG0007771219000002.jpg21170, where σ is the conductivity of the material of the protrusions 2 on the metal foil 1, f is the signal frequency when the metal foil 1 serves as a signal transmission carrier, and μ is the magnetic permeability.

[0039] The protrusions 2 may be understood to refer to portions that protrude from the surface of the metal foil 1. Specifically, portions that protrude from the surface of the metal foil 1 relative to other surrounding portions are called protrusions 2. The protrusions 2 are uniformly distributed on the surface of the metal foil 1. The protrusions 2 are formed by electroplating on the surface of the metal foil 1. Specifically, the protrusions 2 are formed simultaneously during the manufacturing process of the metal foil 1; for example, the metal foil 1 is formed by electroplating, and the protrusions 2 are formed on the surface of the metal foil 1 by electroplating during the process of electroplating the metal foil 1. As another alternative method, the protrusions 2 and the surface of the metal foil 1 are not integrally formed. For example, the protrusions 2 are formed on the surface of the metal foil 1 by sputtering.

[0040] Specifically, the protrusions 2 may be formed of a plurality of particle clusters or may have a monomer structure, and the structure of the protrusions 2 is not specifically limited here.

[0041] 2, the lower half of the protrusion 2 is a portion of the protrusion 2 located below the boundary line at 1 / 2 the height of the protrusion 2 in the height direction of the protrusion 2 (this portion is close to the one surface of the metal foil). Referring to FIG. 2, the method for measuring the height of the protrusion 2 is as follows: in a longitudinal cross-sectional view of the metal foil 1, both sides of the protrusion 2 are within a predetermined sampling length (which may be set to the maximum diameter value R of the diameters of the circumscribing circles of the cross sections of the protrusion 2 at each point), and the first lowest point on one surface of the metal foil 1 on both sides is the first lowest point (for example, on the left side of the longitudinal cross-section of the protrusion 2 in FIG. 2, the first lowest point on one surface of the metal foil on that side is a, and on the right side of the longitudinal cross-section of the protrusion 2, the first lowest point on one surface of the metal foil on that side is b), and the midpoint in the height direction of the two lowest points is c. If point c is taken as the midpoint of the bottom of the protrusion, the height of the protrusion 2 is the vertical distance between the highest point d of the protrusion 2 and the midpoint c of the bottom of the protrusion 2. 2, the connecting line ab may be regarded as the boundary between the protrusion 2 and the metal foil 1. Here, the above description is merely a general example.

[0042] Here, the portion where the diameter of the circumscribing circle of the cross section of the lower half of the protrusion 2 is smaller than the skin depth of the metal foil 1 is the "restriction portion" of the present invention.

[0043] The embodiments of the present invention have at least one of the following advantageous effects: a plurality of protrusions are distributed on one surface of the metal foil, and the protrusions have a microscopic shape in which a lower half of the protrusions has a restricting portion whose circumscribing circle has a diameter smaller than the skin depth in cross section, and the surface area of ​​the portion of the protrusion above the restricting portion is larger than the surface area of ​​the remaining portion of the protrusion. When a signal transmission circuit is manufactured using the metal foil, the restricting portion of the protrusion has a large impedance, and the narrower the restricting portion of the protrusion, the higher the impedance at that portion of the protrusion. Because the diameter of the circumscribing circle of the lower half of the protrusion is smaller than the skin depth, the restriction by the restricting portion of the lower half of the protrusion makes it difficult for high-frequency signal current in the metal foil to pass through the restricting portion of the protrusion, thereby reducing the high-frequency signal current flowing above the protrusion. This reduces the effect of the protrusions on the surface of the metal foil on high-frequency signal loss in a signal transmission circuit manufactured and formed from the metal foil according to the embodiments of the present invention, thereby reducing the transmission loss of high-frequency signals in the signal transmission circuit manufactured and formed from the metal foil. Since the surface area of ​​the portion of the protrusion above the restricting portion is larger than the surface area of ​​the other portion of the protrusion, the surface area of ​​the portion of the protrusion above the restricting portion is larger than the surface area of ​​the portion of the protrusion above the restricting portion, and the protrusion has a relatively large surface area, and there is a large contact area between the signal transmission circuit formed by manufacturing from metal foil and the dielectric layer, circuit The metal foil has excellent peel strength between it and the dielectric layer, making it difficult for the layers to peel off and fall off, and it is possible to manufacture high-density, fine-circuit high-frequency circuit boards using the metal foil.

[0044] In order to make the above description easier to understand, the following specific explanation will be given here. First, a plurality of protrusions 2 are distributed on the one surface, and the lower half of the protrusions 2 has a restricting portion whose circumscribed circle diameter in cross section is smaller than the skin depth. In this way, the high-frequency signal current is restricted from flowing to the upper part of the protrusions 2, reducing the loss effect on the high-frequency current at the protrusions 2 of the metal foil 1. This reduces the effect of the protrusions 2 on the surface of the metal foil 1 on high-frequency signal loss in a signal transmission circuit manufactured and formed from the metal foil 1 described in the embodiment of the present invention, thereby reducing the transmission loss of high-frequency signals in the signal transmission circuit manufactured and formed from the metal foil 1.

[0045] Furthermore, the adhesive strength between the metal foil 1 and the dielectric layer 9 on which the signal transmission circuit is fabricated primarily depends on the physical and chemical adhesion between the two layers. Reducing the surface profile of the metal foil 1 reduces the adhesive capacity. Peel strength (P / S) measures the adhesive strength of laminated materials. A low P / S can lead to delamination problems between the metal foil 1 and the dielectric layer 9 of a printed circuit board. Specifically, during the manufacturing, assembly, and use of a printed circuit board, the adhesive at the interface between the metal foil 1 and the dielectric layer 9 on which the signal transmission circuit is fabricated and formed must be very strong. During processing, the interface is exposed to corrosive chemicals, and during use, it is exposed to high temperatures, high humidity, cold, impact, vibration, shear stress, and other conditions. Therefore, a certain peel strength is required between the metal foil 1 and the dielectric layer 9 of the printed circuit board to prevent delamination and separation.

[0046] Regarding the issue of peel strength between the metal foil and the dielectric layer, in the prior art, based on the theory of elasticity, referring to Formula 1, the factors that affect high peel strength between the metal foil 1 and the dielectric layer 9 are mainly the thickness y0 of the metal foil 1 into the dielectric layer 9, and the tensile strength σ of the dielectric layer 9. N, the thickness δ of the metal foil 1, and the ratio between the coefficient E of the metal foil 1 and the coefficient Y of the dielectric layer 9. In the prior art, the thickness of the dielectric layer 9 of the metal foil 1 is equal to the height of the dielectric layer 9 on the surface 2 of the metal foil 1 that contacts the dielectric layer 9, and the height of the dielectric layer 9 on the surface 2 of the metal foil 1 that contacts the dielectric layer 9 is related to the roughness of the surface of the metal foil 1. Therefore, it is recognized that the thickness y0 of the dielectric layer 9 of the metal foil 1 can be expressed by the roughness of the surface of the metal foil 1. As can be seen from Formula 1, when other parameter variables are constant, the higher the roughness of the protrusions 2, the higher the peel strength between the metal foil 1 and the dielectric layer 9, while the lower the peel strength between the metal foil 1 and the dielectric layer 9.

[0047]

number

[0048] Thus, in consideration of the trend toward high-density, finer circuits in printed circuit boards, the prior art teaches that the roughness of the copper foil should be as high as possible to increase the peel strength between the metal foil 1 and the dielectric layer 9. Furthermore, the prior art further teaches the opposite, that the related art requires the roughness of the metal foil 1 to be as small as possible to reduce the transmission loss of high-frequency signals. That is, the two requirements for the surface morphology of the metal foil 1 in the prior art are contradictory. Roughness can reflect the height of the surface profile of the metal foil 1. Therefore, it is generally recognized that the prior art requires the height of the surface profile of the metal foil 1 to be as small as possible to reduce the transmission loss of high-frequency signals in the metal foil 1, and requires the height of the surface profile of the metal foil 1 to be as large as possible to improve the peel strength between the high-density signal transmission circuit in the metal foil 1 and the resin layer.

[0049] The present invention progressively improves the surface morphology of metal foil 1 in printed circuit boards with high-density, fine circuits not by improving the roughness of the metal foil 1, but by focusing on the structure of protrusions 2 on the metal foil 1, with one side of the metal foil 1 having a plurality of protrusions 2, the lower half of each protrusion connected to the one side having a restricting portion, the diameter of the circumscribed circle of the cross section of each restricting portion being smaller than the skin depth of the metal foil, and the surface area of ​​the portion of each protrusion on the restricting portion being larger than the surface area of ​​the remaining portions of each protrusion. Here, the phrase "the surface area of ​​the portion of each protrusion on the restricting portion being larger than the surface area of ​​the remaining portions of each protrusion" in this application refers to a tree, a head and neck, or a general structure in Figure 1 or 2 where the upper portion has a larger surface area and the lower portion has a smaller surface area (at least smaller than the upper portion). The portion of the entire protrusion 2 that comes into contact with the dielectric layer 9 (e.g., a resin layer) is generally the upper structure of the protrusion 2, and if the upper structure of the protrusion 2 has a large surface area, the contact area between the protrusion 2 and the dielectric layer 9 will be correspondingly large, and the larger the contact area between the two, the stronger the bonding force between them, i.e., the greater the peel force between the metal foil 1 and the dielectric layer 9. As can be seen from this, when the metal foil 1 has a plurality of protrusions 2 described in the present application and the protrusions 2 have the above-mentioned microscopic shape, the peel force between the metal foil 1 and the dielectric layer 9 is significantly increased, i.e., there is a large peel strength between the metal foil 1 and the dielectric layer 9. The lower half of the protrusion 2 has a restricting portion in which the diameter of the circumscribed circle in the cross section is smaller than the skin depth, i.e., smaller than the skin depth of the protrusion 2 material. During the flow of the high-frequency signal current on the surface of the metal foil 1, the impedance at the point of minimum width is large, so the high-frequency signal current does not continue to flow along the protrusion 2 to the top of the protrusion 2, i.e., it is restricted to the above-mentioned minimum width of the protrusion 2, and the high-frequency signal current basically does not flow to the top of the minimum width, i.e., the high-frequency signal current flowing through the protrusion 2 is finite, and the protrusion 2 on the surface of the metal foil 1 has little impact on the high-frequency signal loss of the signal transmission circuit manufactured and formed from the metal foil 1 described in the embodiment of the present invention, thereby reducing the transmission loss of the high-frequency signal in the signal transmission circuit manufactured and formed from the metal foil 1.

[0050] Thus, in an embodiment of the present invention, by forming a plurality of protrusions 2 on the surface of the metal foil 1, the metal foil 1 can achieve both low high-frequency signal transmission loss and high peel strength between the high-density signal transmission circuit formed from the metal foil 1 and the dielectric layer. This overcomes the technical prejudice that the profile height of the surface morphology of the metal foil 1 in the prior art cannot achieve both of these points, and initiates a new technological revolution in the raw materials of high-density, thin-circuit printed circuit boards.

[0051] The lower half of the protrusion 2 has a restricting portion whose circumscribed circle diameter in cross section is smaller than the skin depth, thereby significantly weakening the current skin effect generated by the protrusion 2 on the one surface of the metal foil 1. To understand this, we will now refer to both Figures 3 and 4. Due to the skin effect of current, the current of the signal transmission circuit in the metal foil 1 flows only on the outer surface of the metal layer, that is, on the surface layer whose thickness is the skin depth. As shown in FIG. 3, if the lower half of the protrusion 2 is wide and greater than the skin depth, the current flows along the entire surface of the protrusion 2, resulting in significant signal transmission loss. As shown in FIG. 4, if the width of the lower half of the protrusion 2 (in this case, the base portion) is small and smaller than the skin depth, the impedance of the base portion is high, and the current of the signal transmission circuit in the metal foil 1 cannot flow to the protrusion 2 but instead bypasses the protrusion 2 and flows on the surface layer of the signal transmission circuit. In this case, the protrusion 2 does not essentially increase signal transmission loss in the metal foil 1. Furthermore, in an embodiment of the present invention, the surface area of ​​the portion of the protrusion 2 above the restricting portion is larger than the surface area of ​​the other portions of the protrusion, thereby improving the contact area between the protrusion 2 and the dielectric layer 9 and improving the peel strength between the high-density signal transmission circuit in the metal foil 1 and the resin layer.

[0052] 6 is an electron microscope image of a metal foil 1 having a plurality of protrusions 2 on one surface according to one embodiment of the present invention, in which the lower half of each of the plurality of protrusions 2 has a restriction portion 100, and the diameter of the circumscribed circle of the cross section of the restriction portion 100 is smaller than the skin depth of the metal foil. As can be seen from FIG. 6, most of the protrusions 2 on the metal foil 1 have a narrow bottom width and a wide top average width, resulting in a narrow bottom and wide top structure. This reduces the skin effect of the current in the protrusions 2 on the metal foil 1, and the protrusions 2 also have a large contact area with the dielectric layer 9. FIG. 7 is an electron microscope image of a metal foil 1 according to another embodiment of the present invention, having a plurality of protrusions 2 on one surface. The lower half of each of the protrusions 2 has a restriction portion 100, the diameter of the circumscribing circle of the cross section of which is smaller than the skin depth of the metal foil. The surface area of ​​the portion of the protrusion above the restriction portion is larger than the surface area of ​​the remaining portion of the protrusion. Thus, the skin effect of current on the metal foil 1 at the protrusions 2 is small, and the protrusions 2 also have a large contact area with the dielectric layer 9. FIG. 8 is an electron microscope image of a typical metal foil 1, having a roughened surface on one side with multiple profile peaks. The roughened surface has a circumscribing circle of the cross section of the restriction portion of the lower half of the profile peaks, the diameter of which is larger than the skin depth. That is, the profile peaks have a wide bottom and a narrow top, i.e., a wide bottom and a narrow top. The large skin effect of current on the metal foil 1 at the profile peaks is likely to result in high-frequency signal transmission loss.

[0053] Further, please refer to FIGS. 9 and 10. In actual manufacturing, due to the statistical nature of electrochemically formed metal lattices, the size and shape of the protrusions 2 formed on the surface of the copper foil have a certain distribution. Generally, the shape, size, and distribution of the protrusions 2 are determined by the process. FIG. 9 shows slice scanning curves of one side of two copper foils, reflecting the morphological profile of the one side of the two copper foil products. The laser scans one side of the protrusions from top to bottom. As shown in FIG. 9, there are two curves. The upper curve is the profile curve of the one side of the copper foil of the present invention where the protrusions are formed, and the lower curve is the profile curve of the one side of the conventional copper foil where the protrusions are not formed. As can be seen from FIG. 9, the one side of the copper foil of the present invention has higher protrusions 2 than the one side of the conventional copper foil. However, because the laser scans from top to bottom, the protrusions 2 in the curves do not represent the actual shape of the protrusions 2. If the diameter of the base of the protrusion 2 is smaller than the diameter of the top of the protrusion, the measurement will not capture the shape of the base of the protrusion. However, this measurement can quickly determine the diameter size and distribution of the protrusions 2, providing an effective method for comparing and optimizing different protrusion 2 formation processes. Fourier spectrum analysis is one of the most effective methods for analyzing the size of microscopic protrusions 2 on the surface of a metal foil 1 and statistically analyzing the distribution of the protrusions 2. Figure 10 shows a spatial Fourier transform logarithmic spectrogram corresponding to the curve in Figure 9. The logarithmic spectrogram has two spectral curves: the lower spectral curve represents the spectral curve of the conventional copper foil, and the upper spectral curve represents the spectral curve of a copper foil according to an embodiment of the present application, having a plurality of protrusions 2 on one side. The spectral curves are obtained by performing a Fourier transform on the surface aspect test data of the two copper foils. The horizontal axis in the logarithmic spectrogram is the normalized spatial frequency data, and the vertical axis in the logarithmic spectrogram is the logarithmic spectral intensity obtained after performing a logarithmic operation (20logA) on the original amplitude, so the unit of the vertical axis is dB (decibels). The purpose of this transformation is to observe periodic signals that are covered by low-amplitude noise by enhancing these low-amplitude and relatively high-amplitude components.

[0054] 9 and 10, the protrusions on one side of the copper foil of the present invention shown in the drawings are different in size and distribution from the protrusions on one side of a conventional copper foil. Here, the conventional copper foil mentioned above is not a conventional copper foil product, but a comparative example of the copper foil of the present invention.

[0055] For example, the height of the surface of the restricting portion relative to the metal foil may be 2 μm or less (e.g., smaller than 1.5 μm, 1.2 μm, 1 μm, 0.8 μm, 0.5 μm, etc.), which effectively avoids the problem that the skin effect caused by the current flowing through the metal foil is weak at the protrusion, and therefore the skin effect of the current in the metal foil 1 at the protrusion 2 is large, which is likely to cause transmission loss of high frequency signals.

[0056] For example, the height of the protrusion 2 is not particularly limited, and may be, for example, 4 In this way, if the protrusions 2 have the above-described height and have the microscopic shape of the present invention, the peel strength of the metal foil 1 is further increased, making the metal foil 1 more suitable for high-frequency circuit boards with high-density, fine circuits.

[0057] For example, the ratio of the vertical length of the portion of the protrusion above the regulating portion to the height of the protrusion is 1 / 2 to 5 / 6. Thus, the portion of the protrusion above the regulating portion is relatively long across the entire protrusion, and the surface of the portion of the protrusion above the regulating portion is relatively large compared to the surface of other portions of the protrusion. As a result, the surface area of ​​the upper portion of the protrusion is relatively large, and there is a large contact area between the signal transmission circuit and the dielectric layer, which are manufactured from metal foil. There is also excellent peel strength between the signal transmission circuit and the dielectric layer, making them less likely to delaminate and fall off.

[0058] For example, the shape of the protrusions 2 is not particularly limited and may be, for example, tree-like, icicle-like, or teardrop-like. Furthermore, when the protrusions 2 are tree-like, icicle-like, or teardrop-like, the specific structure of the wider upper portion is not particularly limited and may be selected by those skilled in the art as needed. As discovered by the inventors, when the protrusions 2 are tree-like, icicle-like, or teardrop-like, the protrusions 2 have low high-frequency signal transmission loss. Because the upper portions of the tree-like, icicle-like, or teardrop-like protrusions 2 have a large surface area, a large contact area can be formed between the protrusions 2 and the dielectric layer 9, thereby improving the bonding strength between the metal foil 1 and the dielectric layer 9. This increases the peel strength between the metal foil 1 and the dielectric layer 9, meeting the needs of high-density, fine-circuit high-frequency circuit boards. Furthermore, the protrusions 2 may be tooth-like, as long as they have the above-mentioned microscopic shape. Here, the shape and structure of the protrusions 2 are not specifically limited.

[0059] For example, the metal foil 1 may include copper foil and / or aluminum foil, i.e., the metal foil 1 may be copper foil or aluminum foil, or may include copper foil and aluminum foil (corresponding to the metal foil 1 being arranged so as to be laminated with a copper foil layer and an aluminum foil layer), or one layer of metal foil 1 may include copper and aluminum simultaneously.

[0060] For example, the metal foil 1 may have a single layer structure or a multi-layer structure consisting of at least two single metal layers.

[0061] For example, the thickness of the metal foil 1 is 9 μm or less. In order to meet the manufacturing requirements of the microscopic signal transmission circuit of the circuit board, the thickness of the metal foil 1 may be preferably 6 μm, 5 μm, 4 μm, or 2 μm, etc., thereby obtaining an ultra-thin metal foil 1 for forming the microscopic signal transmission circuit.

[0062] Compared to the prior art, the metal foil 1 according to the embodiment of the present invention not only reduces the transmission loss of high-frequency signals in the metal foil 1, but also provides excellent peel strength between the signal transmission circuit formed from the metal foil 1 and the resin layer, making them less likely to peel off and fall off. In order to verify this, the inventor provides the following test example, taking the metal foil 1 as an example, as a copper foil. Test example 1 is the copper foil of the present invention, and test example 2 is a normal copper foil as a comparative example of the present application. The normal copper foil is a product that does not have the protrusions 2 and their microscopic morphology described in the present invention.

[0063] Test Example 1: A plurality of protrusions 2 are distributed on one surface of the copper foil, and when the frequency is 1 GHz, one-third or more of the protrusions 2 have a restriction portion in the lower half connected to the one surface of the protrusion, the diameter of the circumscribed circle of the cross section of the restriction portion is smaller than the skin depth of the metal foil, and the surface area of ​​the portion on the restriction portion of the protrusion has a microscopic shape that is larger than the surface area of ​​the other portion of the protrusion, and the skin depth δ is JPEG0007771219000004.jpg17170, where σ is the conductivity of the material of the protrusion 2 on the copper foil, f is the signal frequency when the copper foil is used as a signal transmission carrier, and μ is the magnetic permeability.

[0064] For example, when the dielectric layer 9 is a resin layer (the same applies to the following test examples), the peel strength between the one side of the copper foil and the resin layer is 10 N / cm through testing, and the transmission loss of high-frequency signals of the copper foil can be found in Table 1.

[0065] The peel strength between the one surface of the copper foil and the resin layer was tested as follows. This test method is a thermal stress peel strength test method, which tests the peel strength of the metal coating layer subjected to thermal shock and evaluates the deterioration of the peel strength of the copper foil sample after thermal shock. The specific explanation is as follows (for the test standard of this test method, please refer to standard IPC-TM-650 2.4.8): (1) Sample production stage: 1. Crimping parameters: Crimping by crimping device, crimping dimensions 120 x 180mm, number 1pc. 2. Pressing aids: Kraft paper 81, steel plate 82, release film 83, PP sheet 84, PI coating film 85. (2) Test operation stage: 1. As shown in FIG. 11, pressure bonding is performed using a laminated structure of copper foil / PP sheet 84 / PI coating film 85. 2. Determine whether electroplating thickness treatment is required, and bake in an oven at 160°C for 90 minutes after electroplating. 3. Solder float in a solder groove at 288°C for 10 seconds. 4. Using a design knife, divide the test sample strips into strips with a width of 5 mm. 5. Adhere the PI surface to the roller of the peel strength tester, peel off about 2 cm of thin copper, and clamp it. 6. Pull vertically upwards and record six sets of peel strength data after stabilization. Calculate the average value of the six peel strength data and record it as F (N / cm). The pressure bonding conditions are as follows: the metal foil 1 is pressure bonded using a pressure bonding device, and the pressure bonding parameters are as follows: 1) Temperature rise stage (<90℃) pressure maintained at 8kgf / cm 2 , heating rate: 3.5 °C / min. 2) At 90°C, the pressure is increased to 30 kgf / cm. 2 , heating rate: 4.5 °C / min. 3) High temperature stage (200℃) pressure maintained at 30kgf / cm 2 , duration 2h. 4) Cool to 50°C, release pressure and sample. Note: Pressure refers to surface pressure and indicates the pressure applied to a unit area.

[0066] The test method for the transmission loss of high frequency signals of the copper foil is as follows. It is typically a double-sided laminate structure, with the signal line being a 50 ohm microstrip line, and the dielectric layer being a 25 μm polyimide. Crimping parameters: Crimping dimensions 200 x 250 mm, number 1 pc, 185°C * 3 min * 120 kg / cm 2 . Pressure-bonding auxiliary materials: Kraft paper 81, steel plate 82, TPX, PET, prepreg, E copper. 1. The bonding is performed using a laminated structure of copper foil / prepreg / hard plate / prepreg / copper. 2. Electroplating was performed to a thickness of 20 μm, and the plate was baked in an oven at 160°C for 30 minutes before testing. The crimping conditions are as follows: the metal foil 1 is crimped using a crimping device, and the crimping parameters are as follows: 1) Temperature rise stage (<90℃) pressure maintained at 8kgf / cm 2 , heating rate: 3.5℃ / min. 2) At 90°C, the pressure is increased to 30 kgf / cm. 2 , heating rate: 4.5℃ / min. 3) High temperature stage (200℃) pressure maintained at 30kgf / cm 2 , duration 2h. 4) Cool to 50°C, release pressure and sample. Note: Pressure refers to surface pressure and indicates the pressure applied to a unit area. 3. The baked sample is cut and attached to a thermosetting board to obtain a test board. 4. Weld the test plate and then test it using a network analyzer.

[0067] Note that the description of Test Example 1 may be referred to for the test method for the peel strength between the copper foil and the resin layer and the test method for the transmission loss of high frequency signals in the copper foil in the following test examples.

[0068] Test example 2 This is a normal sample test. The copper foil described in the present application in Test Example 1 was replaced with a normal copper foil (a normal copper foil that does not have the protrusions 2 and their microscopic morphology described in the present application), and the other test conditions were the same as those in Test Example 1.

[0069] According to the test, the peel strength between the ordinary copper foil and the resin layer is 4 N / cm. For the transmission loss of high frequency signals of the ordinary copper foil, see Table 1.

[0070] [Table 1]

[0071] As can be seen from the above tests, when comparing the copper foil of the present application with a normal copper foil, i.e., when comparing a copper foil having the structure of the protrusions 2 and its microscopic morphology of the present application with a normal copper foil not having the protrusions 2 and its microscopic morphology of the present application, the copper foil of the present application has low transmission loss of high frequency signals and high peel strength with the dielectric layer, and therefore has significant advantages when manufacturing high frequency circuit boards with high density and fine circuits.

[0072] 5 , the protrusion 2 includes a trunk 20 and branch portions 21. The trunk 20 extends outward from the one surface, and the branch portions 21 extend outward from the surface of the trunk 20. During the transmission of high-frequency signal current, the current flows along the metal surface and is restricted by the restricting portion of the trunk 20. This restricts the current from continuing upward along the trunk 20 to the branch portions 21. This significantly limits the loss of high-frequency signal current transmission through the metal foil 1 in the protrusion 2. Furthermore, the branch portions 21 extending outward from the surface of the trunk 20 increase the bonding area between the signal transmission circuit formed from the metal foil 1 and the dielectric layer, further enhancing the bonding strength between the signal transmission circuit formed from the metal foil 1 and the dielectric layer. Furthermore, excellent peel strength is provided between the signal transmission circuit formed from the metal foil 1 and the dielectric layer, making them less likely to delaminate and fall off. Furthermore, the metal foil 1 can be used to manufacture high-density, fine-circuit high-frequency circuit boards. Here, the number and shape of the branches 21 in the trunk 20 are not particularly limited, and those skilled in the art may select them as needed.

[0073] Furthermore, the material component of the trunk portion 20 may be the same as or different from the metal foil 1. For example, when the metal foil 1 is a copper foil or an aluminum foil, or contains copper and aluminum, the material component of the trunk portion 20 may be at least one of copper, nickel, zinc, chromium, aluminum, silicon, alumina particles, and industrial diamond particles. This provides more possibilities for the formation method of the protrusions 2, trunk portion 20, and branch portion 21, and also provides more design possibilities for the protrusions 2, trunk portion 20, and branch portion 21. The industrial diamond particles are industrial diamond particles at the μm level.

[0074] For example, the proportion of the protrusions 2 having the microscopic morphology in the metal foil 1 on one side is not particularly limited, and for example, at least 10% of the protrusions 2 may have the microscopic morphology, preferably at least 50% of the protrusions 2 have the microscopic morphology, and more preferably at least 90% of the protrusions 2 have the microscopic morphology. As the inventors have discovered, the greater the proportion of the protrusions 2 having the microscopic morphology in the metal foil 1 on one side, the lower the high-frequency signal transmission loss and the higher the peel strength between the protrusions 2 and the dielectric layer, making it more suitable for products with high requirements for high-frequency signal transmission loss and peel strength.

[0075] For example, when the metal foil 1 is used as a signal transmission carrier, the specific value of the signal frequency f is not particularly limited, and may be determined based on the actual use environment of the product, and may be, for example, 1 Hz to 100 GHz.

[0076] Referring to Figure 12, another embodiment of the present invention provides a metal foil 1 with a carrier, which includes a carrier layer 3 and the metal foil 1 described in any one of the above solutions, and the carrier layer 3 is releasably arranged on one side of the metal foil 1 on which the protrusions 2 are provided.

[0077] Referring to Figure 13, specifically, the carrier-attached metal foil 1 further includes a release layer 4, and the release layer 4 is located between the carrier layer 3 and the metal foil 1, so that both the metal foil 1 and the carrier layer 3 are arranged in a peelable manner.

[0078] Furthermore, when the carrier layer 3, the release layer 4 and the metal foil 1 are stacked in order, the peel strength between the metal foil 1 and the release layer 4 is greater than the peel strength between the release layer 4 and the carrier layer 3, and thus the carrier layer 3 can be smoothly peeled off from the metal foil 1.

[0079] The carrier layer 3 functions as a carrier substrate for the metal foil 1. The function of the release layer 4 is to reduce the phenomenon of interpenetration between the carrier layer 3 and the metal foil 1, while facilitating the release between the carrier layer 3 and the metal foil 1.

[0080] In an embodiment of the present invention, the use of the above-mentioned metal foil 1 not only reduces the transmission loss of high-frequency signals in the metal foil 1, but also provides excellent peel strength between the signal transmission circuit formed from the metal foil 1 and the resin layer, making the two less likely to peel off and fall off, and making it possible to manufacture high-density, thin-circuit high-frequency circuit boards using the metal foil 1.

[0081] For example, the release layer 4 may be made of one or more of nickel, silicon, molybdenum, graphite, titanium, and niobium, or may be made of an organic polymer material. Preferably, the thickness of the release layer 4 is 10 to 500 Å. If the release layer 4 is too thick, it is difficult to form a uniform metal foil 1, and a large number of pinholes are likely to occur in the metal foil 1 (if the metal foil 1 has pinholes, it is likely to cause a short circuit after etching into a circuit). If the release layer 4 is too thin, it is difficult to separate the release layer 4 from the metal foil 1. Therefore, by setting the thickness of the release layer 4 to 10 to 500 Å, it is possible to ensure the formation of a uniform metal foil 1, avoid the formation of a large number of pinholes in the metal foil 1, and facilitate the separation between the release layer 4 and the metal foil 1.

[0082] The carrier layer 3 may be a copper carrier, an aluminum carrier, an organic film, or the like, and the carrier layer 3 must have a certain thickness because it mainly performs a loading function. When the carrier layer 3 is a copper carrier or an aluminum carrier, the thickness of the carrier layer 3 is preferably 9 to 50 μm, and when the carrier layer 3 is an organic film, the thickness of the carrier layer 3 is preferably 10 to 100 μm.

[0083] Referring to FIG. 14, in the above embodiment, the metal foil with a carrier 1 further includes a first adhesive layer 7 provided between the carrier layer 3 and the release layer 4.

[0084] In this embodiment, a first adhesive layer 7 is provided, which provides strong peel strength between the release layer 4 and the carrier layer 3, effectively ensuring that the carrier layer 3 can be stably peeled off from the metal foil 1, thereby obtaining a complete ultra-thin metal foil 1. In addition, by using the first adhesive layer 7 to treat the surface of the carrier layer 3, the entire surface of the carrier layer 3 becomes more uniform and dense, allowing the ultra-thin metal foil 1 to be peeled off from the carrier layer 3 and have fewer pinholes, which is beneficial for subsequent circuit manufacturing.

[0085] Specifically, the first adhesive layer 7 is a metal adhesive layer. Exemplarily, the metal adhesive layer is made of one or more of copper, zinc, nickel, iron, and manganese, or is made of one of copper or zinc and one of nickel, iron, and manganese.

[0086] 15, in an embodiment of the present invention, in order to prevent oxidation of the carrier layer 3, a first oxidation prevention layer 5 is provided on one side of the carrier layer 3 that is close to the metal foil 1, and the first oxidation prevention layer 5 is provided on one side of the carrier layer 3 that is close to the metal foil 1, thereby preventing oxidation of the carrier layer 3 and protecting the carrier layer 3. Referring to FIG. 16, in order to prevent oxidation of the metal foil 1, a second oxidation prevention layer 6 is provided on one side of the metal foil 1 that is away from the carrier layer 3, and the second oxidation prevention layer 6 is provided on one side of the metal foil 1 that is away from the carrier layer 3, thereby preventing oxidation of the metal foil 1 and protecting the metal foil 1.

[0087] Specifically, the first anti-oxidation layer 5 is made of at least one of nickel, copper alloy, and chromium.

[0088] Specifically, the second antioxidant layer 6 contains nickel and zinc.

[0089] Another embodiment of the present invention provides a copper clad laminate obtained using the metal foil 1 according to any one of the above solutions or the metal foil 1 with a carrier according to any one of the above solutions.

[0090] 17 and 18, the copper-clad laminate further includes a dielectric layer provided on one surface of at least one of the metal foils. Specifically, the material of the dielectric layer is at least one selected from polyimide (e.g., thermoplastic polyimide), modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polyethylene naphthalate, polystyrene, polyvinyl chloride, polysulfone, polyphenylene sulfide, polyether ether ketone, polyphenylene oxide, polytetrafluoroethylene, liquid crystal polymer, polyparabanic acid, epoxy glass cloth, and BT resin.

[0091] 19, the copper clad laminate further includes a second adhesive layer provided on the one surface of the metal foil. Specifically, the material of the second adhesive layer is at least one selected from polystyrene-based, vinyl acetate-based, polyester-based, polyethylene-based, polyamide-based, rubber-based or acrylate-based thermoplastic resins, phenol-based, epoxy-based, thermoplastic polyimide, urethane-based, melamine-based or alkyd-based thermosetting resins, BT resin, and ABF resin.

[0092] Another embodiment of the present invention provides a printed circuit board (not shown) obtained using the metal foil 1 described in any one of the above solutions, the metal foil 1 with a carrier described in any one of the above solutions, or the copper-clad laminate described in any one of the above solutions.

[0093] The above are only selective embodiments of the present invention, and those skilled in the art may make some modifications and substitutions without departing from the technical principles of the present invention, and these modifications and substitutions shall also fall within the protection scope of the present invention. [Explanation of symbols]

[0094] 1...metal foil, 2...protrusion, 20...trunk, 21...branch, 3...carrier layer, 4...peeling layer, 5...first antioxidant layer, 6...second antioxidant layer, 7...first adhesive layer, 81...kraft paper, 82...steel plate, 83...release film, 84...PP sheet, 85...PI coating film, 9...dielectric layer, 10...second adhesive layer, 100...regulating portion.

Claims

1. A metal foil for a circuit board, comprising: a plurality of protrusions are distributed on one surface of the metal foil; the protrusion has a microscopic shape in which a lower half of the protrusion connected to the one surface of the metal foil has a restricting portion, the diameter of a circumscribing circle of a cross section of the restricting portion is smaller than the skin depth of the metal foil, and the surface area of ​​a portion of the protrusion on the restricting portion is larger than the surface area of ​​other portions of the protrusion, a ratio of a vertical length of a portion of the protrusion above the restricting portion to a height of the protrusion is 1 / 2 to 5 / 6; A metal foil for circuit boards, characterized in that some of the protrusions have a structure that is narrow at the bottom and wide at the top.

2. The skin depth δ is 2. The metal foil for circuit boards according to claim 1, wherein σ is the conductivity of the material of the protrusion, f is the signal frequency when the metal foil is used as a signal transmission carrier, and μ is the magnetic permeability.

3. 2. The metal foil for circuit boards according to claim 1, characterized in that the height of the regulating portion relative to the one surface of the metal foil having the protrusion is 2 μm or less, the height being the maximum distance between the highest point of the regulating portion and the one surface of the metal foil having the protrusion, and the height of the protrusion relative to the one surface of the metal foil is 4 μm or less.

4. 2. The metal foil for circuit boards according to claim 1, wherein the protrusions are tree-shaped, icicle-shaped, or teardrop-shaped.

5. 2. The metal foil for circuit boards according to claim 1, wherein the protrusion includes a stem extending outward from the one surface and having the regulating portion, and a branch extending outward from the surface of the stem at a portion above the regulating portion.

6. 6. The metal foil for circuit boards according to claim 5, wherein the material composition of said trunk portion is the same as that of said metal foil.

7. 6. The metal foil for circuit boards according to claim 5, wherein the material composition of the substrate is different from the material composition of the metal foil, and the material of the substrate is at least one selected from copper, nickel, zinc, chromium, aluminum, silicon, alumina particles, and industrial diamond particles.

8. At least 10% of the protrusions on said surface have said microscopic morphology; or At least 50% of the protrusions on said surface have said microscopic morphology; or 2. The metal foil for circuit boards according to claim 1, wherein at least 90% of the protrusions on said one surface have said microscopic morphology.

9. 3. The metal foil for circuit boards according to claim 2, wherein the signal frequency f is 1 Hz to 100 GHz.

10. 2. The metal foil for circuit boards according to claim 1, wherein the metal foil comprises copper foil and / or aluminum foil.

11. 2. The metal foil for circuit boards according to claim 1, wherein the metal foil is a single-layer metal structure or a multi-layer metal structure consisting of at least two single-layer metal layers.

12. A carrier-attached metal foil comprising a carrier layer and the metal foil for circuit boards according to any one of claims 1 to 11, The metal foil with a carrier is characterized in that the carrier layer is releasably provided on the other surface of the metal foil opposite to the one surface.

13. The metal foil with a carrier according to claim 12, further comprising a release layer positioned between the carrier layer and the metal foil so that both the metal foil and the carrier layer are releasably provided.

14. The metal foil with a carrier according to claim 13 , further comprising a first adhesive layer provided between the carrier layer and the release layer.

15. the first adhesive layer is a metal adhesive layer; The metal foil with a carrier according to claim 14, wherein the metal adhesive layer is made of at least one material selected from the group consisting of copper, zinc, nickel, iron, and manganese.

16. The metal foil with a carrier according to claim 12, further comprising a first antioxidant layer provided on a surface of the metal foil adjacent to the carrier layer.

17. The metal foil with a carrier according to claim 16, wherein the material of the first anti-oxidation layer is at least one of nickel, chromium, and a copper alloy.

18. The metal foil with a carrier according to claim 12, further comprising a second antioxidant layer provided on a surface of the metal foil remote from the carrier layer.

19. The metal foil with a carrier according to claim 18, wherein the material of the second anti-oxidation layer is at least one of nickel, chromium, and zinc.

20. A copper clad laminate comprising the metal foil according to claim 1.

21. 21. The copper clad laminate of claim 20, further comprising a dielectric layer disposed on said one side of at least one of said metal foils.

22. The copper clad laminate of claim 21, characterized in that the material of the dielectric layer is at least one selected from polyimide, modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polyethylene naphthalate, polystyrene, polyvinyl chloride, polysulfone, polyphenylene sulfide, polyether ether ketone, polyphenylene oxide, polytetrafluoroethylene, liquid crystal polymer, polyparabanic acid, epoxy glass cloth, and BT resin.

23. The copper clad laminate of claim 20 , further comprising a second adhesive layer provided on the one surface of the metal foil.

24. The copper clad laminate of claim 23, wherein the material of the second adhesive layer is at least one selected from polystyrene-based, vinyl acetate-based, polyester-based, polyethylene-based, polyamide-based, rubber-based or acrylate-based thermoplastic resins, phenol-based, epoxy-based, thermoplastic polyimide, urethane-based, melamine-based or alkyd-based thermosetting resins, BT resin, and ABF resin.

25. A printed circuit board obtained by using the metal foil for circuit boards according to claim 1.

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