Copper foil and laminates, and methods for manufacturing the same.

Abstract

The purpose of the present invention is to provide a copper foil, with which a wiring board capable of exhibiting both RF characteristics and a high peeling strength can be fabricated using a resin base material made of LCP. The copper foil has a surface, a part or the entirety of which is provided with irregularities having: an Ra of 0.01-0.10 μm inclusive and an RSm of 1.20-4.00 μm inclusive; an Rz of 0.1-0.90 μm inclusive and an RSm of 1.20-4.00 μm inclusive; or an Ra of 0.034-0.092 μm inclusive, an Rz of 0.25-0.87 μm inclusive, and an RSm of 1.21-3.57 μm inclusive.

Description

Technical Field

[0001] The present invention relates to copper foils, laminates, and methods for producing them.

Background Art

[0002] The demand for liquid crystal polymer (LCP) is increasing, mainly for high-speed transmission and precision components in the fields of electric and electronic and information and communication. This is considered to be because LCP has characteristics such as high heat resistance, low water absorption rate and small dimensional change due to humidity, and excellent electrical characteristics. In order to obtain high adhesion to copper foil, methods such as using a rough copper foil and surface modification by UV irradiation or plasma treatment on LCP have been used (Japanese Patent Application Laid-Open No. 2003-221456, Japanese Patent Application Laid-Open No. 2008-103559, Japanese Patent Application Laid-Open No. 2012-140552).

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to provide a copper foil capable of achieving both good high-frequency characteristics and high peel strength when a wiring board is produced using a resin base material made of LCP.

Means for Solving the Problems

[0004] ] As a result of intensive research to obtain a copper foil having high adhesion to LCP, the inventors of the present application have found that by forming irregularities having a specific shape on the surface of the copper foil, it is possible to provide high adhesion to LCP, and thus the present invention has been completed.

[0005] Embodiments of the present invention are as follows. (1) A copper foil having irregularities on part or all of its surface, wherein Ra of the irregularities is 0.01 μm or more and 0.10 μm or less, and RSm is 1.20 μm or more and 4.00 μm or less. (2) A copper foil having irregularities on part or all of its surface, wherein the Rz of the irregularities is 0.2 μm or more and 0.90 μm or less, and the RSm is 1.20 μm or more and 4.00 μm or less. (3) The copper foil according to item 1 or 2, wherein the surface of the surface has an Ra of 0.034 μm or more and 0.092 μm or less, an Rz of 0.25 μm or more and 0.87 μm or less, and an RSm of 1.21 μm or more and 3.57 μm or less. (4) The copper foil according to any one of the first to third paragraphs, wherein in a grayscale image of the surface taken by scanning electron microscope (SEM) at a magnification of 50,000, the area ratio of the binarized convex portion in the image binarized with a threshold of 120 is 42% or more and 90% or less. (5) The copper foil according to paragraph 4, wherein in a grayscale image of the surface taken by a scanning electron microscope (SEM) at a magnification of 50,000, the area ratio of the binarized convex portion in the image binarized with a threshold of 120 is 58% or more and 81% or less. (6) The copper foil according to paragraph 4, wherein in a grayscale image of the surface taken by scanning electron microscope (SEM) at a magnification of 50,000, the area ratio of the binarized convex portion in the image binarized with a threshold of 120 is 58% or more and 73% or less. (7) The copper foil according to any one of the first to sixth paragraphs, wherein, in a scanning electron microscope (SEM) image of a cross section perpendicular to the surface, straight lines parallel to the surface of the copper foil are drawn from the highest and lowest points of the irregularities, and these are designated as level 1 and level 0, respectively, and the number of intersections between the level 0.5 line and the contour of the surface is 5 or more and 50 or less per any 2.3 μm. (8) The copper foil according to paragraph 7, wherein, in a scanning electron microscope (SEM) image of a cross section perpendicular to the surface, straight lines parallel to the surface of the copper foil are drawn from the highest and lowest points of the irregularities, and these are designated as level 1 and level 0, respectively, and the number of intersections between the level 0.5 line and the contour of the surface is 10 or more and 20 or less per any 2.3 μm. (9) The copper foil according to any one of the first to eighth paragraphs, wherein a first layer containing copper oxide is present on part or all of the surface of the copper foil. (10) The copper foil according to paragraph 9, wherein a second layer containing a metal other than copper is present on the surface of the first layer. (11) The copper foil described in item 10, wherein the second layer is a plated film. (12) The copper foil described in item 10 or 11, wherein the metal other than copper contains nickel. (13) The average amount of adhesion in the second layer is 0.8 to 6.0 mg / dm 2 The copper foil described in any one of items 10 to 12. (14) A laminate in which copper foil described in any one of items 1 to 13 is laminated on a resin substrate. (15) A laminate in which copper foil is laminated on a resin substrate, wherein in a scanning electron microscope (SEM) image of a cross section perpendicular to the interface between the resin substrate and the copper foil, a straight line parallel to the interface is drawn from the highest and lowest points of the irregularities present at the interface, and these lines are designated as level 1 and level 0, respectively, and the number of intersections between the level 0.5 line and the irregularities is 5 or more and 50 or less per any 2.3 μm. (16) The laminate according to paragraph 15, wherein the number of intersections is 10 or more and 20 or less per any 2.3 μm. (17) The laminate according to any one of claims 14 to 16, wherein the copper foil comprises the copper foil according to any one of claims 1 to 14. (18) Electronic components mounted on copper foil as described in any one of paragraphs 1 to 13. (19) Electronic components mounted on a laminate as described in any one of paragraphs 14 to 17. (20) A method for producing copper foil according to any one of paragraphs 1 to 13, comprising a first step of forming the surface irregularities by treating a copper foil material with an oxidizing agent, wherein the oxidizing agent contains a hydroxide in an amount of 20 g / L or more and 160 g / L or less. (21) The method for producing copper foil according to paragraph 20, wherein the hydroxide is sodium hydroxide, potassium hydroxide, or a combination thereof. (22) The method for producing copper foil according to item 20 or 21, wherein the oxidizing agent contains 60 g / L or less of chlorite. (23) The method for producing copper foil according to paragraph 22, wherein the chlorite is sodium chlorite, potassium chlorite, or a combination thereof. (24) A method for producing copper foil according to item 22 or 23, wherein the ratio of the content of chlorous acid to the content of hydroxide is greater than 0 and 1.0 or less. (25) A method for manufacturing copper foil according to any one of items 20 to 24, comprising a second step, performed before the first step, of treating the copper foil material with an alkaline solution of pH 9 or higher. (26) A method for manufacturing copper foil according to any one of the items 20 to 25, comprising a third step of treating the copper foil with a solvent, which is performed after the first step. (27) A method for manufacturing copper foil according to any one of items 20 to 26, comprising a fourth step of treating the copper foil with a reducing agent, which is performed after the first step. (28) A method for manufacturing copper foil according to any one of items 20 to 27, comprising a fifth step of plating the copper foil, which is performed after the first step. (29) A method for manufacturing copper foil according to any one of claims 20 to 28, comprising a sixth step of treating the copper foil with a coupling agent, which is performed after the first step. (30) A method for manufacturing a laminate, comprising the step of laminating copper foil described in any one of items 1 to 13 onto a resin substrate. (31) A method for producing a laminate according to paragraph 30, wherein the resin substrate contains a liquid crystal polymer (LCP).

[0006] ==Cross-reference with related literature== This application claims priority based on Japanese Patent Application No. 2020-150136, filed on 7 September 2020, which is incorporated herein by reference. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows scanning electron microscope (SEM) images of the copper foil surface in typical examples and comparative examples of the present invention. [Figure 2]Figure 2 shows the images of the copper foil surface of an embodiment of the present invention before and after binarization using a scanning electron microscope (SEM). [Figure 3] Figure 3 shows a method in one embodiment of the present invention in which, using a scanning electron microscope (SEM) image of a cross-section perpendicular to the copper foil surface, straight lines parallel to the copper foil surface are drawn from the highest and lowest points of the irregularities present on the copper foil surface, designated as level 1 and level 0 (A), a straight line for level 0.5 is drawn (B), and the number of intersections between the level 0.5 straight line and the irregularities is counted (C). [Modes for carrying out the invention]

[0008] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but are not necessarily limited thereto. The object, features, advantages, and ideas of the present invention will be apparent to those skilled in the art from the description herein, and those skilled in the art will be able to easily reproduce the present invention from the description herein. The embodiments and specific examples of the invention described below are examples of preferred embodiments of the present invention and are provided for illustrative or explanatory purposes only; the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications and modifications can be made based on the description herein, within the intent and scope of the present invention as disclosed herein.

[0009] <Copper foil> One embodiment of the present invention is a copper foil having irregularities on part or all of its surface. The RSm of the irregularities is preferably 1.20 or more, more preferably 1.21 or more, still more preferably 1.50 or more, and preferably 5.00 or less, more preferably 4.00 or less, still more preferably 3.57 or less, and still more preferably 3.00 or less. The Ra of the irregularities is preferably 0.005 or more, more preferably 0.01 or more, still more preferably 0.034 or more, and still more preferably 0.05 or more, and preferably 0.20 or less, more preferably 0.10 or less, still more preferably 0.092 or less, and still more preferably 0.07 or less. The Rz of the irregularities is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.25 or more, and still more preferably 0.30 or more, and preferably 1.00 or less, more preferably 0.90 or less, still more preferably 0.87 or less, and still more preferably 0.8 or less. As a combination of numerical values, it is preferable that Ra is 0.01 or more and 0.10 or less, and RSm is 1.20 or more and 4.00 or less, or Rz is 0.2 or more and 0.90 or less, and RSm is 1.20 or more and 4.00 or less. Also, it is preferable that Ra is 0.034 or more and 0.092 or less, Rz is 0.25 or more and 0.87 or less, and RSm is 1.21 or more and 3.57 or less.

[0010] Note that RSm represents the average of the lengths (i.e., the lengths of the contour curve elements: Xs1 to Xsm) of one cycle of irregularities included in the roughness curve at a certain reference length (lr), and is calculated by the following formula. Formula 1

[0011] JPEG0007837056000001.jpg13170 Here, 10% of the arithmetic mean roughness (Ra) is defined as the minimum height of the irregularities, and one cycle of irregularities is defined with 1% of the reference length (lr) as the minimum length.

[0012] The arithmetic mean roughness (Ra) represents the average of the absolute values of Z(x) (i.e., the height of peaks and the depth of valleys) in the contour curve (y = Z(x)) at the reference length l, which is expressed by the following formula. Formula 2

[0013] JPEG0007837056000002.jpg13170As an example, RSm can be calculated in accordance with "(JIS B 0601:2001)" by creating a contour curve from the observation results of a confocal microscope.

[0014] Also, Rz (maximum height) represents the sum of the maximum value of the peak height Zp and the maximum value of the valley depth Zv in the contour curve (y = Z(x)) at the reference length l, and Ra (arithmetic mean roughness) represents the average of the absolute values of Z(x) (i.e., the height of peaks and the depth of valleys) in the contour curve (y = Z(x)) at the reference length l. These Rz and Ra can be calculated by the methods defined in JIS B 0601:2001 (conforming to the international standard ISO13565-1).

[0015] The copper foil may contain tough pitch copper, deoxidized copper, or oxygen-free copper, or may be composed of tough pitch copper, deoxidized copper, or oxygen-free copper, but it is more preferably oxygen-free copper with an oxygen content of 0.0005 mass% or less.

[0016] The copper foil may be a single copper foil such as an electrolytic copper foil or a rolled copper foil, or a plurality of copper foils may be laminated. The thickness of the copper foil is not particularly limited, but is preferably 0.1 μm or more and 100 μm or less, and more preferably 0.5 μm or more and 50 μm or less.

[0017] In a grayscale image of the surface of copper foil taken with a scanning electron microscope (SEM) at a magnification of 50,000x, in the binarized image with a grayscale value of 120 as the threshold, the area ratio of the convex parts is preferably 40% or more, more preferably 42% or more, even more preferably 58% or more, even more preferably 60% or more, and also preferably 95% or less, more preferably 90% or less, even more preferably 81% or less, even more preferably 73% or less, and even more preferably 70% or less. In terms of numerical combinations, it is preferably 42% to 90%, more preferably 58% to 81%, and even more preferably 58% to 73%.

[0018] Furthermore, in a scanning electron microscope (SEM) image taken at a magnification of 50,000x of a cross-section perpendicular to the surface of the copper foil, straight lines parallel to the surface of the copper foil are drawn from the highest and lowest points of the unevenness, designated as level 1 and level 0, respectively. Preferably, the number of intersections between the level 0.5 line and the contour of the surface is 3 or more per 2.3 μm, more preferably 5 or more, and even more preferably 10 or more. Also, it is preferably 50 or less, more preferably 20 or less, and even more preferably 13 or less. As for the combination of values, it is preferably 5 to 50 per 2.3 μm, and more preferably 10 to 20.

[0019] A first layer containing copper oxide may be present on part or all of the surface or part or all of the back surface of the copper foil. This copper oxide includes copper oxide (CuO) and / or cuprous oxide (Cu2O). This layer containing copper oxide can be formed by oxidizing the surface of the copper foil. This oxidation treatment roughens the surface of the copper foil. After the oxidation treatment, a solvent may be used to adjust the shape of the protrusions on the oxidized conductor surface. Alternatively, the surface of this layer containing copper oxide may be reduced with a reducing agent. The resistivity of pure copper is 1.7 × 10⁻⁶. -8 While (Ωm) is the case for copper oxide, it is 1 to 10 (Ωm), and for cuprous oxide it is 1 × 10 6 ~1 × 107 Because of its (Ωm) conductivity, the conductivity of the layer containing copper oxide formed by the oxidation treatment is lower than that of pure copper.

[0020] A second layer containing a metal other than copper may be present on the surface of the first layer of copper foil. The second layer may be made of a metal other than copper. The metal included in the second layer is not particularly limited, but may include at least one metal selected from the group consisting of Sn, Ag, Zn, Al, Ti, Bi, Cr, Fe, Co, Ni, Pd, Au, and Pt. In particular, to provide acid resistance and heat resistance, it is preferable to include a metal that has higher acid resistance and heat resistance than copper, such as Ni, Pd, Au, and Pt.

[0021] The amount of the second layer attached is not particularly limited, but is between 0.8 and 6.0 mg / dm 2 It is preferable that this is the case. The amount of the second layer attached is calculated by dissolving the second layer in, for example, an acidic solution, measuring the amount of metal by ICP analysis, and dividing it by the planar field of view area of ​​the structure.

[0022] <Laminate> A laminate can be constructed using copper foil together with an insulator. The copper foil described above can be used. This laminate is called a copper-clad laminate (CCL) and can be used as a substrate for printed circuit boards.

[0023] The insulator may include a sheet-like resin substrate impregnated with resin, or it may consist of a sheet-like resin substrate impregnated with resin. The laminate can be made by attaching copper foil to one or both sides of the insulator. The laminate may be a three-layer structure (i.e., a metal layer, an adhesive layer, and a resin layer) in which copper foil and resin substrate are bonded together using an adhesive, mainly used in TAB (tape-automated bonding) mounting, or a two-layer structure (i.e., a metal layer and a resin layer) without adhesive, used in COF (chip on film) mounting. In addition, the resin substrate may be layered on a substrate such as paper or glass and heat-pressed together as an insulator, in which case copper foil is attached to the side opposite to the substrate.

[0024] The resin contained in the resin substrate is not particularly limited, but may be a thermoplastic resin or a thermosetting resin, and is preferably polyphenylene ether (PPE), epoxy, polyphenylene oxide (PPO), polybenzoxazole (PBO), polytetrafluoroethylene (PTFE), liquid crystal polymer (LCP), triphenylphosite (TPPI), fluororesin, polyetherimide, polyetheretherketone, polycycloolefin, bismaleimide resin, low dielectric constant polyimide, cyanate resin, or a mixture thereof. The resin substrate may further contain inorganic fillers or glass fibers. The thickness of the resin substrate is not particularly limited, but is preferably 1 μm or more and 100 mm or less.

[0025] In a scanning electron microscope (SEM) image at a magnification of 50,000x taken of a cross-section perpendicular to the interface between the resin substrate and the copper foil, lines parallel to the interface are drawn from the highest and lowest points of the surface irregularities at the interface, designated as level 1 and level 0, respectively. Preferably, the number of intersections between the level 0.5 line and the surface contour is 3 or more per 2.3 μm, more preferably 5 or more, and even more preferably 10 or more. It is also preferably 50 or less, more preferably 20 or less, and even more preferably 13 or less. As for the combination of values, it is preferably 5 to 50 per 2.3 μm, and more preferably 10 to 20. Furthermore, the surface shape of the copper foil may change before and after lamination with the resin substrate, but it is preferable that it does not change significantly.

[0026] <Method for manufacturing copper foil> One embodiment of the present invention is a method for manufacturing copper foil as described above, comprising one or more steps selected from: a first step of forming a first layer containing copper oxide on the surface of part or all of the copper foil; a second step of forming a second layer containing a metal other than copper on the surface of the first layer; and a third step of performing a coupling treatment on the surface of the second layer. When multiple steps are performed, it is preferable to perform the steps with higher numbers later, such as performing the second step after the first step, but it is most preferable to perform three steps in this order.

[0027] First, as a first step, the surface of the copper foil may be oxidized with an oxidizing agent to form a layer containing copper oxide and to form fine irregularities on the surface. The oxidation treatment may be a single-sided or double-sided treatment. The first step may include a surface roughening treatment such as soft etching or etching performed before the oxidation treatment. Furthermore, the first step may include a degreasing treatment performed before the oxidation treatment, an acid cleaning treatment to homogenize the surface by removing the oxide film present on the original copper foil that will be used as the material, and an alkali treatment treatment after acid cleaning to prevent the acid from being introduced into the oxidation treatment. The method of alkali treatment is not particularly limited, but preferably an alkaline aqueous solution of 0.1 to 10 g / L, more preferably 1 to 2 g / L, such as an aqueous sodium hydroxide solution, and treatment should be performed at 30 to 50°C for about 0.5 to 2 minutes.

[0028] The oxidizing agent used in the first step preferably contains a hydroxide or consists of a hydroxide. Examples of hydroxides include sodium hydroxide and potassium hydroxide. In this case, the overall concentration of the hydroxide is 20 g / L or more and 160 g / L or less. The oxidizing agent may also contain a hydroxide and a chlorite, or consist of a hydroxide and a chlorite. Examples of chlorites include sodium chlorite and potassium chlorite. In this case, the overall concentration of the chlorite is higher than 0 g / L and 60 g / L or less. The oxidizing agent may also contain 3-glycidyloxypropyltrimethoxysilane (3-GT). In this case, the concentration of 3-glycidyloxypropyltrimethoxysilane is higher than 0 g / L and may be 10 g / L or less, preferably 5 g / L or less, and more preferably 1 g / L or less. In summary, the oxidizing agent preferably contains 20-160 g / L of hydroxide, 0-60 g / L of chlorite, and 0-10 g / L of 3-glycidyloxypropyltrimethoxysilane, or consists of these. Furthermore, the ratio of the chlorite content to the hydroxide content is preferably between 0 and 1.0. These elements are particularly important for the production of the copper foil of this disclosure.

[0029] Various additives (for example, phosphates such as trisodium phosphate dodecahydrate) and surface-active molecules may be added to the oxidizing agent. Examples of surface-active molecules include porphyrin, macro-ring porphyrin, expanded porphyrin, ring-contracted porphyrin, linear porphyrin polymer, porphyrin sandwich coordination complex, porphyrin sequence, silane, tetraorgano-silane, aminoethyl-aminopropyl-trimethoxysilane, (3-aminopropyl)trimethoxysilane, (1-[3-(trimethoxysilyl)propyl]urea)((l-[3-(Trimethoxysilyl)propyl]urea)), (3-aminopropyl)triethoxysilane, ((3-glycidyloxypropyl)trimethoxysilane) Examples include (3-chloropropyl)trimethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, dimethyldichlorosilane, 3-(trimethoxysilyl)propyl methacrylate, ethyltriacetoxysilane, triethoxy(isobutyl)silane, triethoxy(octyl)silane, tris(2-methoxyethoxy)(vinyl)silane, chlorotrimethylsilane, methyltrichlorosilane, silicon tetrachloride, tetraethoxysilane, phenyltrimethoxysilane, chlorotriethoxysilane, ethylene-trimethoxysilane, amines, sugars, etc.

[0030] The oxidation reaction conditions are not particularly limited, but the temperature of the oxidizing solution is preferably 40 to 95°C, and more preferably 45 to 80°C. The reaction time is preferably 0.5 to 30 minutes, and more preferably 1 to 10 minutes.

[0031] Before performing the first step, a surface roughening treatment such as soft etching or etching is not required, but may be performed. Furthermore, a second step may be performed before the oxidation treatment, including degreasing, acid cleaning to homogenize the surface by removing the native oxide film, or alkaline treatment after acid cleaning to prevent the introduction of acid into the oxidation step. The method of alkaline treatment is not particularly limited, but preferably, an alkaline aqueous solution of 0.1 to 10 g / L, more preferably 1 to 2 g / L, such as an aqueous sodium hydroxide solution, is used, and the treatment is performed at 30 to 50°C for about 0.5 to 2 minutes. The alkaline aqueous solution preferably has a pH of 9 or higher, or a pH of 10 or higher.

[0032] A third step may be performed after the first step, in which the copper foil, particularly the layer containing copper oxide, is treated with a solvent.

[0033] The solvent used in this third step is not particularly limited, but chelating agents are examples. Biodegradable chelating agents are particularly preferred, and examples include ethylenediaminetetraacetic acid, diethanolglycine, L-glutamic acid diacetate tetrasodium, ethylenediamine-N,N'-disuccinic acid, 3-hydroxy-2,2'-iminodisuccinate sodium, methylglycine diacetate trisodium, aspartate diacetate tetrasodium, N-(2-hydroxyethyl)iminodiacetate disodium, and sodium gluconate.

[0034] The pH of the solvent solution is not particularly limited, but it is preferably alkaline, more preferably pH 8 to 10.5, even more preferably pH 9.0 to 10.5, and even more preferably pH 9.8 to 10.2.

[0035] Furthermore, a fourth step may be performed after the first step or after the third step, in which the copper oxide contained in the first layer is treated with a reducing agent. Examples of reducing agents used in this fourth step include dimethylamine borane (DMAB), diborane, sodium borohydride, and hydrazine.

[0036] Next, a fifth step may be performed to form a second layer on the copper foil on which the first layer has been formed, either after the first step or after the third or fourth step. The second conductive layer can be formed as a plated film by, for example, plating the surface of the first conductive layer. The plating method is not particularly limited, and examples include electroplating, electroless plating, chemical conversion treatment, and vacuum deposition such as sputtering, but electroplating is preferred because it is preferable to form a uniform and thin plated film.

[0037] When forming a second layer on a copper foil surface that has a first layer containing copper oxide by electroplating, the copper oxide on the surface is first reduced to cuprous oxide or pure copper, using up charge. This creates a time lag before plating occurs, after which the metal forming the second layer begins to deposit. The amount of charge varies depending on the type of plating solution and the amount of copper oxide, but for example, when applying Ni plating to a copper component, in order to keep the thickness within a desirable range, the area dm of the copper component to be electroplated must be... 2 It is preferable to apply a charge of 15C to 75C, and more preferably 25C to 65C. Through the plating process, some or all of the copper oxide formed in the oxidation process is reduced to copper, and the conductivity of the layer containing copper oxide is increased, making it easier for electrical conductivity to occur between the copper foil and the second layer.

[0038] The method for checking whether conductivity is present is not particularly limited, but for example, the planar viewing area of ​​the second layer is 4 μm. 2 In contrast, when a voltage of -0.5V is applied between the copper foil and the second layer, if the region in the atomic force microscope (AFM) current image where the current value is -60nA or less accounts for 2.5%, 5%, or 10% or more of the planar field of view area of ​​the second layer, it can be determined that there is conductivity between the copper foil and the second layer. Alternatively, when a substrate for printed circuit boards is manufactured using a laminate, if electronic components are mounted on the second layer and it functions as an electrical circuit, it can be determined that there is conductivity between the copper foil and the second layer.

[0039] Next, after the first step, or after the third, fourth, or fifth step, a sixth step may be performed on the surface of the second layer, including a coupling treatment using a silane coupling agent. This can impart stronger adhesion to the resin substrate to the surface of the second layer. Further details are described in Japanese Patent Application No. 2019-236800, and its entirety is incorporated herein by reference.

[0040] The silane coupling agent used is preferably one having two or three hydrolyzable groups, and the hydrolyzable groups are preferably methoxy or ethoxy groups.

[0041] While not particularly limited, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-ureidopropyltrialkoxysilane, 3-acryloxypropyltrimethoxysilane, etc. can be used.

[0042] In the sixth step, specifically, a solution of the silane coupling agent dispersed in water or an organic solvent is applied or sprayed onto the surface of the second layer to adsorb it, and then dried. The solution of the silane coupling agent dispersed in water or an organic solvent is not particularly limited, but is preferably 0.5% or more, 1% or more, 2% or more, 4% or more, or 8% or more by weight, and preferably 20% or less, 15% or less, or 10% or less. The temperature and time for drying are not particularly limited as long as the solvent, water or organic solvent, is completely evaporated, but is preferably dried at 70°C for 1 minute or more, more preferably at 100°C for 1 minute or more, and even more preferably at 110°C for 1 minute or more.

[0043] <Method for manufacturing laminates> Next, an insulator is laminated onto the copper foil surface that has undergone the treatment described above. If the insulator includes or consists of a resin substrate, the insulating layer can be laminated, for example, by thermocompressing the resin substrate onto the conductive foil. The thermocompression conditions may be those recommended by each substrate manufacturer (e.g., temperature, pressure, time).

[0044] The resin substrate is not particularly limited, but it is preferable that it contains or consists of a liquid crystal polymer (LCP). Known LCPs, including commercially available products, can be used, such as polycondensates of ethylene terephthalate and p-hydroxybenzoic acid, polycondensates of phenol and phthalic acid and p-hydroxybenzoic acid, and polycondensates of 2,6-hydroxynaphthoic acid and p-hydroxybenzoic acid. Thermotropic liquid crystal polymers are particularly preferred.

[0045] <Manufacturing method for printed circuit boards> Using the laminate produced in this manner, a printed wiring board (PWB) can be manufactured, and then electronic components can be soldered onto it to produce a printed circuit board (PCB).

[0046] The wiring board using the copper foil or laminate of this disclosure can be suitably used as a high-frequency circuit board. [Examples]

[0047] (1) Treatment of copper foil The copper foil used in the examples and comparative examples, and their treatments, are summarized in Table 1 (Examples) and Table 2 (Comparative Examples).

[0048] In Comparative Example 11, copper foil (FV-WS, thickness: 18 μm) (manufactured by Furukawa Electric Co., Ltd.) was used, but in the Examples and other Comparative Examples, electrolytic copper foil satisfying Rz 0.3 μm or less and rolled copper foil satisfying Rz 0.6 μm or less were used. For the electrolytic copper foil, the shiny side (glossy side; the side that is flat when compared to the opposite side) was used as the surface on which the LCP was laminated. Since there is no difference in the surface shape of the copper foil depending on the side, one side was used for the rolled copper foil. Multiple test pieces were prepared under the same conditions for the copper foils of the Examples and Comparative Examples. The copper foil of Comparative Example 11 was not subjected to any of the following treatments. [Table 1] [Table 2]

[0049] (1-1) Oxidation treatment Copper foil was immersed in the oxidizing agents shown in Tables 1 and 2 under the conditions shown in Tables 1 and 2 to oxidize both sides of the copper foil. After the oxidation treatment, the copper foil was washed with water and then dried.

[0050] (1-2) Electrolytic Plating The copper foil, after oxidation treatment, was electroplated on both sides under the conditions shown in Tables 1 and 2. After electroplating, the copper foil was washed with water and then dried.

[0051] (1-3) Coupling process After plating, the copper foil was immersed in the silane coupling agent solutions described in Tables 1 and 2, and then heat-treated under the conditions shown in Tables 1 and 2.

[0052] (1-4) Lamination with LCP In the case of Vexter CT-Q film (LCP) (manufactured by Kuraray Co., Ltd., 50 μm thick), it was heated at 0 MPa using a vacuum press until it reached 260°C, and held at 260°C for 15 minutes. Then, it was pressurized to 4 MPa and heated until it reached 320°C, and held at 320°C for 10 minutes. After that, it was cooled while maintaining the 4 MPa pressurization.

[0053] In the case of Vexter CT-Z film (LCP) (manufactured by Kuraray Co., Ltd., 50 μm thick), it was heated at 0 MPa using a vacuum press until it reached 260°C, and held at 260°C for 15 minutes. Then, it was pressurized to 4 MPa and heated until it reached 300°C, and held at 300°C for 10 minutes. After that, it was cooled while maintaining the 4 MPa pressurization.

[0054] (4) Method for evaluating copper foil Figure 1 shows a scanning electron microscope (SEM) image of a typical surface of the obtained copper foil.

[0055] (4-1) Amount of Ni attached The amount of Ni deposited on each test specimen was measured. First, the copper pieces were dissolved in 12% nitric acid, and the resulting liquid was analyzed using an ICP emission spectrometer 5100 SVDV ICP-OES (manufactured by Agilent Technologies) to measure the Ni concentration and calculate the amount of Ni deposited per unit surface area.

[0056] (4-2) Ra, Rz, RSm For each specimen, a contour curve was created from observation results using a confocal microscope OPTELICS H1200 (Lasertec Corporation), and Ra, Rz, and RSm were calculated according to the method specified in JIS B 0601:2001. The measurement conditions were as follows: scan width 100 μm, scan type area, light source blue, cutoff value 1 / 5. The object lens was set to x100, contact lens to x14, digital zoom to x1, and Z pitch to 10 nm. Data was acquired at three locations, and Rz was the average value of the three locations.

[0057] (4-3) Area ratio of convex parts in surface images A grayscale image of the copper foil surface, obtained by scanning electron microscopy (SEM) at a magnification of 50,000x, was binarized using WinROOF2018 (ver. 4.5.5) (Mitani Corporation) with a threshold of 120. The area ratio of the convex parts was then measured in the binarized image. Examples of images before and after binarization are shown in Figure 2.

[0058] (4-4) Number of intersections Using a scanning electron microscope (SEM), in images of a cross-section perpendicular to the interface between the LCP and the copper foil on the copper foil surface or laminate, if the distance between two parallel lines passing through the highest and lowest points of the surface or interface irregularities is minimized, that is, if all irregularities fall between these two parallel lines and the distance between these lines is minimized, then these lines are considered parallel to the surface or interface, and are designated as Level 1 and Level 0, respectively (Figure 3A). Then, a third parallel line corresponding to Level 0.5, which lies between these two, is drawn (Figure 3B), and the number of intersections between this line and the irregularities is counted (Figure 3C). Note that a cross-section perpendicular to the copper foil surface or interface refers to a cross-section perpendicular to a line, using an image with a resolution sufficient to make the surface or interface appear as a straight line.

[0059] (4-5) High frequency characteristics The core material was Vecter CT-Z film (LCP) (manufactured by Kuraray, 50 μm thick), and the cover material was Vecter CT-F film (LCP) (manufactured by Kuraray, 25 μm thick). Using a vacuum press, the materials were heated at 0 MPa until they reached 260°C and held at 260°C for 15 minutes. Then, the pressure was increased to 4 MPa and heated until they reached 300°C and held at 300°C for 10 minutes. After that, the materials were cooled while maintaining the 4 MPa pressure and thermocompressed to create a 100 mm long microstrip line. The circuit width was 95 μm and the characteristic impedance was 50 Ω. High-frequency signals up to 20 GHz were transmitted through this transmission line using a network analyzer, and the transmission loss was measured.

[0060] (4-6) Peel strength The printed circuit board was fabricated by masking the laminate with 10 mm wide tape and etching it. The peel strength was then measured when peeling the copper foil from the resin at a speed of 50 mm / min in a 90° direction.

[0061] (5) Evaluation results of copper foil The evaluation results are shown in Table 3 (Examples) and Table 4 (Comparative Examples). [Table 3] [Table 4]

[0062] (4-1) Amount of Ni attached There was no significant difference in this value between the examples and the comparative examples.

[0063] (4-2) Ra, Rz, RSm In the examples, Ra was in the range of 0.034 μm to 0.092 μm, Rz was in the range of 0.25 μm to 0.87 μm, and RSm was in the range of 1.21 μm to 3.57 μm. In the comparative examples, none of the test specimens had any of the three values ​​within the above ranges.

[0064] Furthermore, when Ra was set to a range of 0.01 μm to 0.10 μm and RSm to a range of 1.20 μm to 4.00 μm, all of the examples fell within this range, but all of the comparative examples' Ra values ​​were outside this range.

[0065] Furthermore, when Rz was set to the range of 0.1 μm to 0.90 μm and RSm to the range of 1.20 μm to 4.00 μm, all of the examples fell within this range, but all of the comparative examples' Rz values ​​were outside this range.

[0066] (4-3) Number of intersections As described above, the number of intersections measured in the examples was all within the range of 10 to 20 per 2.3 μm, but in the comparative examples, most were outside that range.

[0067] (4-4) Area ratio of convex parts in surface images When the area ratio of the binarized convex portion was set to a range of 58% to 73%, all of the comparative specimens fell outside this range.

[0068] Furthermore, when the area ratio of the binarized convex portion was set to a range of 58% to 81%, all of the examples fell within that range. Most of the comparative examples were outside this range.

[0069] (4-5) High frequency characteristics High-frequency characteristics were evaluated as follows: ○ (good) for -4dB or higher, and × (poor) for less than -4dB.

[0070] (4-6) Peel strength In the examples, the peel strength was 0.61 kgf / cm or higher in all cases, but in the comparative examples, all test specimens with high-frequency characteristics were 0.59 kgf / cm or lower.

[0071] (summary) As shown in Comparative Examples 1, 2, 7, and 8, when the ratio of sodium chlorite concentration to alkali is higher than appropriate, the copper foil surface will have needle-like structures with poor affinity to the LCP resin compared to the examples, and sufficient peel strength cannot be obtained. As shown in Comparative Examples 3, 5, and 6, when the alkali concentration is lower than appropriate, it is not possible to create a shape on the copper foil surface that has high affinity with LCP, as in the examples, and sufficient peel strength cannot be obtained. As shown in Comparative Examples 4, 10, and 11, when the alkali concentration is higher than appropriate, the surface roughness of the copper foil becomes excessively large, and good high-frequency characteristics cannot be obtained. As shown in Comparative Example 9, although the sodium chlorite concentration ratio to alkali is appropriate, when the sodium chlorite concentration is higher than appropriate, the copper foil surface has needle-like structures with poor affinity to the LCP resin compared to the example, and sufficient peel strength cannot be obtained. As shown in Comparative Example 12, if the plating particles on the copper foil surface are too large, good high-frequency characteristics cannot be obtained. Conventionally, when using coarse copper foil, physical adhesion with LCP can be achieved through the anchoring effect, but the skin effect results in high transmission loss, and it cannot be said that the requirements for high-frequency characteristics are fully met. Furthermore, when using conventional low-roughness copper foil, the poor affinity between LCP and copper foil presents challenges in adhesion between LCP and copper foil. However, as disclosed herein, when a wiring board is fabricated using a copper piece having the above-described combination of Ra, Rz, and RSm and a resin substrate made of LCP, a wiring board can be obtained that has good high-frequency characteristics while simultaneously achieving high peel strength. [Industrial applicability]

[0072] The present invention makes it possible to provide copper foil that, when a wiring board is manufactured using a resin substrate made of LCP, can obtain a wiring board that has both good high-frequency characteristics and high peel strength.

Claims

1. The surface has irregularities in some or all of it, and the irregularities are Ra is 0.01 μm or more and 0.10 μm or less, and A copper foil having an RSm of 1.20 μm or more and 4.00 μm or less, A layer containing a metal other than copper exists on the aforementioned surface. A copper foil for forming a laminate by laminating a resin substrate onto the aforementioned surface.

2. The surface has irregularities in some or all of it, and the irregularities are Rz is 0.2 μm or more and 0.90 μm or less, and A copper foil having an RSm of 1.20 μm or more and 4.00 μm or less, A layer containing a metal other than copper exists on the aforementioned surface. A copper foil for forming a laminate by laminating a resin substrate onto the aforementioned surface.

3. The aforementioned irregularities, Ra is between 0.034 μm and 0.092 μm. Rz is 0.25 μm or more and 0.87 μm or less, and The copper foil according to claim 1 or 2, wherein the RSm is 1.21 μm or more and 3.57 μm or less.

4. In the grayscale image of the aforementioned surface obtained by scanning electron microscope (SEM) at a magnification of 50,000x, in the image binarized with a grayscale value of 120 as the threshold, The copper foil according to any one of claims 1 to 3, wherein the area ratio of the binarized convex portion is 42% or more and 90% or less.

5. In the grayscale image of the aforementioned surface obtained by scanning electron microscope (SEM) at a magnification of 50,000x, in the image binarized with a grayscale value of 120 as the threshold, The copper foil according to claim 4, wherein the area ratio of the binarized convex portion is 58% or more and 81% or less.

6. In the grayscale image of the aforementioned surface obtained by scanning electron microscope (SEM) at a magnification of 50,000x, in the image binarized with a grayscale value of 120 as the threshold, The copper foil according to claim 4, wherein the area ratio of the binarized convex portion is 58% or more and 73% or less.

7. In the scanning electron microscope (SEM) image of a cross-section perpendicular to the aforementioned surface, The copper foil according to any one of claims 1 to 6, wherein straight lines parallel to the surface of the copper foil are drawn from the highest and lowest points of the unevenness, and these are designated as level 1 and level 0, respectively, and the number of intersection points between the level 0.5 line and the contour of the surface is 5 or more and 50 or less per any 2.3 μm.

8. In the scanning electron microscope (SEM) image of a cross-section perpendicular to the aforementioned surface, The copper foil according to claim 7, wherein straight lines parallel to the surface of the copper foil are drawn from the highest and lowest points of the unevenness, and these are designated as level 1 and level 0, respectively, and the number of intersection points between the level 0.5 line and the contour of the surface is 10 or more and 20 or less per any 2.3 μm.

9. The copper foil according to any one of claims 1 to 8, wherein a first layer containing copper oxide is present on part or all of the surface of the copper foil.

10. The copper foil according to claim 9, wherein a second layer containing a metal other than copper is present on the surface of the first layer.

11. The copper foil according to claim 10, wherein the second layer is a plating film.

12. The copper foil according to claim 10 or 11, wherein the metal other than copper includes nickel.

13. The average adhesion amount in the second layer was 0.8–6.0 mg / dm ２ The copper foil according to any one of claims 10 to 12.

14. A laminate comprising a resin substrate on which copper foil according to any one of claims 1 to 13 is laminated, wherein the resin substrate is laminated on the surface of the laminate.

15. A laminate in which a copper foil according to any one of claims 1 to 13 is laminated on a resin substrate, In a scanning electron microscope (SEM) image of a cross-section perpendicular to the interface between the resin substrate and the copper foil, From the highest and lowest points of the irregularities present at the interface, straight lines parallel to the interface are drawn and designated as Level 1 and Level 0, respectively. The number of intersection points between the Level 0.5 line and the irregularities is 5 or more and 50 or less per 2.3 μm. A layer containing a metal other than copper exists on the surface of the copper foil. A laminate in which a resin substrate is laminated on the aforementioned surface.

16. The laminate according to claim 15, wherein the number of intersections is 10 or more and 20 or less per any 2.3 μm.

17. The laminate according to any one of claims 14 to 16, wherein the copper foil comprises the copper foil described in any one of claims 1 to 13.

18. An electronic component to which the laminate according to any one of claims 14 to 17 is attached.

19. A method for manufacturing copper foil according to any one of claims 1 to 13, The process includes a first step of forming the aforementioned irregularities by treating the copper foil material with an oxidizing agent, The oxidizing agent contains hydroxide in a concentration of 20 g / L or more and 160 g / L or less. A method for manufacturing copper foil.

20. The method for producing copper foil according to claim 19, wherein the hydroxide is sodium hydroxide, potassium hydroxide, or a combination thereof.

21. The method for producing copper foil according to claim 19 or 20, wherein the oxidizing agent contains 60 g / L or less of chlorite.

22. The method for producing copper foil according to claim 21, wherein the chlorite is sodium chlorite, potassium chlorite, or a combination thereof.

23. A method for producing copper foil according to claim 21 or 22, wherein the ratio of the content of the chlorite to the content of the hydroxide is greater than 0 and 1.0 or less.

24. A method for manufacturing copper foil according to any one of claims 19 to 23, comprising a second step performed before the first step, in which the copper foil material is treated with an alkaline solution with a pH of 9 or higher.

25. A method for manufacturing copper foil according to any one of claims 19 to 24, comprising a third step of treating the copper foil with a dissolving agent, which is performed after the first step.

26. A method for manufacturing copper foil according to any one of claims 19 to 25, comprising a fourth step of treating the copper foil with a reducing agent, which is performed after the first step.

27. A method for manufacturing copper foil according to any one of claims 19 to 26, comprising a fifth step of plating the copper foil, which is performed after the first step.

28. A method for manufacturing copper foil according to any one of claims 19 to 26, comprising a sixth step of treating the copper foil with a coupling agent, which is performed after the first step.

29. A method for manufacturing a laminate, comprising the step of laminating copper foil according to any one of claims 1 to 13 onto a resin substrate.

30. The method for producing a laminate according to claim 29, wherein the resin substrate contains a liquid crystal polymer (LCP).

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