Roughened copper foil, copper foil with carrier, copper-clad laminates, and printed circuit boards

Abstract

Provided is a roughened copper foil capable of having both high adhesiveness with a thermoplastic resin and excellent high frequency characteristics. The roughened copper foil has a roughened surface on at least one side thereof. The roughened surface is provided with a plurality of sheet-shaped roughened particles, and when the roughened surface is viewed in plan view, the width W1 of the sheet-shaped roughened particles is 2 nm-135 nm inclusive, the length L1 of the sheet-shaped roughened particles is 15 nm-490 nm inclusive, and the ratio L1 / W1 of the length L1 to the width W1 is 2.0-7.2, inclusive.

Description

[Technical Field]

[0001] This invention relates to roughened copper foil, copper foil with carrier, copper-clad laminate, and printed circuit board. [Background technology]

[0002] With the increasing sophistication of portable electronic devices in recent years, signals are becoming more high-frequency in order to process large amounts of information at high speed, and printed circuit boards (PCBs) suitable for high-frequency applications such as 5G, millimeter wave, and base station antennas are required. For such high-frequency PCBs, it is desirable to reduce transmission loss in order to transmit high-frequency signals without degrading their quality. A PCB consists of copper foil processed into a wiring pattern and an insulating resin substrate, and the transmission loss mainly consists of conductor loss due to the copper foil and dielectric loss due to the insulating resin substrate. Therefore, it is advantageous to use a thermoplastic resin with a low dielectric constant in order to reduce the dielectric loss due to the insulating resin substrate. However, thermoplastic resins with low dielectric constants, such as fluororesins and liquid crystal polymers (LCPs), differ from thermosetting resins in that they have low chemical activity and therefore have low adhesion to copper foil.

[0003] Therefore, technologies have been proposed to improve the adhesion between copper foil and thermoplastic resin. For example, Patent Document 1 (International Publication No. 2016 / 174998) discloses a copper foil having a roughened surface with a ten-point average roughness Rzjis of 0.6 μm to 1.7 μm, and a half-width of 0.9 μm or less in the frequency distribution of the height of the roughened particles. It is said that such a copper foil can exhibit high peel strength even to insulating resin substrates that cannot be expected to have chemical adhesion, such as liquid crystal polymer films.

[0004] On the other hand, conductor loss can increase due to the skin effect of copper foil, which becomes more pronounced at higher frequencies. Therefore, in order to suppress transmission loss in high-frequency applications, it is necessary to reduce the skin effect of copper foil by miniaturizing the roughening particles. As an example of copper foil having such fine roughening particles, Patent Document 2 (International Publication No. 2014 / 133164) discloses a surface-treated copper foil having a black roughened surface formed by attaching copper particles (for example, substantially spherical copper particles) with a particle size of 10 nm to 250 nm. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2016 / 174998 [Patent Document 2] International Publication No. 2014 / 133164 [Overview of the project]

[0006] As mentioned above, copper foil for high-frequency applications requires the coarsening of particles, but such copper foil tends to have poor adhesion to resins (especially thermoplastic resins). In this respect, existing copper foils are not necessarily sufficient in terms of achieving both high adhesion to thermoplastic resins and excellent high-frequency characteristics, and there is room for improvement.

[0007] The present inventors have now found that in a roughened copper foil having a roughened surface equipped with a plurality of plate-shaped roughened particles, by controlling the width W1, length L1, and the ratio L1 / W1 of the plate-shaped roughened particles to a predetermined range when the roughened surface is viewed from above, it is possible to achieve both high adhesion to thermoplastic resins and excellent high-frequency characteristics.

[0008] Therefore, the object of the present invention is to provide a roughened copper foil that can achieve both high adhesion to thermoplastic resins and excellent high-frequency characteristics.

[0009] According to one aspect of the present invention, a roughened copper foil having a roughened surface on at least one side, A roughened copper foil is provided, wherein the roughened surface comprises a plurality of plate-shaped roughened particles, and when the roughened surface is viewed from above, the width W1 of the plate-shaped roughened particles is 2 nm or more and 135 nm or less, the length L1 of the plate-shaped roughened particles is 15 nm or more and 490 nm or less, and the ratio L1 / W1, which is the ratio of the length L1 to the width W1, is 2.0 or more and 7.2 or less.

[0010] According to another aspect of the present invention, a copper foil with a carrier is provided, comprising a carrier, a release layer provided on the carrier, and the roughened copper foil provided on the release layer with the roughened surface facing outward.

[0011] According to yet another aspect of the present invention, a copper-clad laminate is provided which is equipped with the roughened copper foil.

[0012] According to yet another aspect of the present invention, a printed circuit board is provided which is equipped with the roughened copper foil. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram illustrates the load curve and load area ratio determined in accordance with ISO 25178. [Figure 2] This diagram illustrates the load area ratio Smr1 that separates the protruding peak and the core, as determined in accordance with ISO 25178. [Figure 3] This is a schematic cross-sectional view showing one embodiment of the roughened copper foil according to the present invention, and is a diagram for explaining a method for measuring the width W2 and length L2 of plate-shaped roughened particles. [Figure 4] This is an FE-SEM image of the roughened surface of the roughened copper foil in the carrier-attached copper foil fabricated in Example 2, observed from directly above. [Figure 5] This is the FE-SEM image from Figure 4 after contrast optimization. [Figure 6] This is a cross-sectional SEM image of the roughened copper foil in the carrier-attached copper foil fabricated in Example 2.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] definition The definitions of the terms or parameters used to specify the present invention are shown below.

[0015] In this specification, the "aspect ratio Str of surface texture" or "Str" is a parameter representing the isotropy or anisotropy of surface texture, measured in accordance with ISO 25178. Str ranges from 0 to 1. Usually, Str > 0.5 indicates strong isotropy, and conversely, Str < 0.3 indicates strong anisotropy.

[0016] In this specification, the "load curve of the surface" (hereinafter simply referred to as the "load curve") refers to a curve representing the height at which the load area ratio ranges from 0% to 100%, measured in accordance with ISO 25178. The load area ratio is a parameter representing the area of the region above a certain height c, as shown in FIG. 1. The load area ratio at height c corresponds to Smr(c) in FIG. 1. As shown in FIG. 2, a secant line of the load curve obtained by subtracting the load curve with a load area ratio difference of 40% from the load area ratio of 0% along the load curve is moved from the load area ratio of 0%. The position where the slope of the secant line becomes the gentlest is called the central part of the load curve. For this central part, a straight line with the minimum sum of squared deviations in the vertical axis direction is called the equivalent line. The part included in the height range from the load area ratio of 0% to 100% of the equivalent line is called the core part. The part higher than the core part is called the protruding peak part, and the part lower than the core part is called the protruding valley part.

[0017] In this specification, the "load area ratio Smr1 separating the protruding peak part and the core part" or "Smr1" is a parameter representing the load area ratio (i.e., the load area ratio separating the core part and the protruding peak part) at the intersection of the height of the upper part of the core part and the load curve, measured in accordance with ISO 25178, as shown in FIG. 2. The larger this value, the larger the proportion occupied by the protruding peak part.

[0018] The surface texture aspect ratio Str and the load area ratio Smr1 that separates the protruding peaks from the core can be calculated, respectively, by measuring the surface profile of a predetermined measurement area on the roughened surface using a commercially available laser microscope. In this specification, the values ​​of Str and Smr1 are those measured under conditions of a cutoff wavelength of 0.251 μm using an S filter and a cutoff wavelength of 4.5 μm using an L filter.

[0019] In this specification, the "electrode surface" of a carrier refers to the surface that was in contact with the cathode during carrier fabrication.

[0020] In this specification, the "deposition surface" of the carrier refers to the surface on which electrolytic copper is deposited during carrier preparation, that is, the surface that is not in contact with the cathode.

[0021] Roughened copper foil The copper foil according to the present invention is a roughened copper foil. Figure 3 shows one embodiment of the roughened copper foil according to the present invention. The roughened copper foil 10 shown in Figure 3 has a roughened surface 12 on at least one side. This roughened surface 12 comprises a plurality of plate-like roughened particles 12a. In particular, when the roughened surface 12 is viewed from above, the width W1 of the plate-like roughened particles 12a is 2 nm or more and 135 nm or less, the length L1 of the plate-like roughened particles 12a is 15 nm or more and 490 nm or less, and the ratio of length L1 to width W1, L1 / W1, is 2.0 or more and 7.2 or less. In a roughened copper foil 10 having a roughened surface 12 equipped with multiple plate-shaped roughened particles 12a, by controlling the width W1, length L1, and the ratio L1 / W1 of the plate-shaped roughened particles 12a to the above range when the roughened surface 12 is viewed from above, it is possible to achieve both high adhesion to thermoplastic resin and excellent high-frequency characteristics.

[0022] As mentioned above, in order to suppress transmission loss in high-frequency applications, it is necessary to reduce the roughening particles of copper foil to minimize the skin effect. However, copper foil with such fine roughening particles tends to have poor adhesion to resin because the anchoring effect with the resin substrate (i.e., the effect of improving physical adhesion by utilizing the irregularities on the surface of the copper foil) is reduced. In particular, low dielectric constant thermoplastic resins, such as fluororesins and liquid crystal polymers (LCPs), differ from thermosetting resins in that they have low chemical activity and therefore have low adhesion to copper foil. Thus, low-roughness copper foil, which is advantageous in terms of high-frequency characteristics, inherently tends to have poor adhesion to resin, and it is not easy to achieve both high adhesion to thermoplastic resins and excellent high-frequency characteristics.

[0023] As a result of investigating this problem, the inventors found that by miniaturizing the roughened particles and making their shape plate-like (in other words, increasing the aspect ratio of the particles), it is possible to achieve both high adhesion to thermoplastic resins and excellent high-frequency characteristics. Specifically, by making the roughened particles plate-like, the anchoring effect with the resin substrate is increased compared to conventional approximately spherical roughened particles. As a result, it was found that even though the bumps are fine and effective in reducing the skin effect, high adhesion to thermoplastic resins can be ensured. Furthermore, in order to miniaturize the bumps while fully exhibiting the anchoring effect with the resin substrate, it was found that it is effective to control the width W1 and length L1 of the plate-like roughened particles 12a, when viewed from above the roughened surface 12, to small values ​​of 2 nm to 135 nm and 15 nm to 490 nm, respectively, and to control the ratio of length L1 to width W1 L1 (aspect ratio) to a large value of 2.0 to 7.2. As a result, the roughened copper foil 10 of the present invention unexpectedly makes it possible to achieve both high adhesion to thermoplastic resins and excellent high-frequency characteristics (for example, reduction of the skin effect).

[0024] Therefore, the width W1 of the plate-shaped roughened particles 12a is 2 nm to 135 nm, preferably 30 nm to 90 nm, more preferably 30 nm to 85 nm, and even more preferably 35 nm to 80 nm. The length L1 of the plate-shaped roughened particles 12a is 15 nm to 490 nm, preferably 100 nm to 430 nm, more preferably 110 nm to 430 nm, and even more preferably 110 nm to 400 nm. Furthermore, the ratio L1 / W1 of the plate-shaped roughened particles 12a is 2.0 to 7.2, preferably 2.5 to 7.2, more preferably 3.1 to 4.5, and even more preferably 3.1 to 4.0. By doing so, a good balance between high adhesion to thermoplastic resin and excellent high-frequency characteristics can be achieved.

[0025] The width W1, length L1, and ratio L1 / W1 of the plate-shaped roughened particles 12a can be determined by observing the roughened surface 12 of the roughened copper foil 10 from directly above (Tilt: 0°) at a predetermined magnification (e.g., 50,000x) using a field emission scanning electron microscope (FE-SEM), and analyzing the acquired observation image using commercially available software. This analysis can be performed, for example, using the image analysis software "Image Pro 10" (manufactured by Media Cybernetics) in accordance with the conditions described in the examples of this specification. The above-mentioned values ​​for width W1, length L1, and ratio L1 / W1 of the plate-shaped roughened particles 12a represent the median values ​​of width W1, length L1, and ratio L1 / W1 measured from individual roughened particles, respectively.

[0026] Preferably, the roughened copper foil 10 has its width W2, length L2, and the ratio of length L2 to width W2 (L2 / W2) controlled to a predetermined range when the roughened surface 12 is viewed in cross-section. The width W2 of the plate-shaped roughened particles 12a refers to the distance between the roots of the plate-shaped roughened particles 12a that are connected to the roughened surface 12, as schematically shown in Figure 3. The length L2 of the plate-shaped roughened particles 12a refers to the distance from the highest point (the most protruding part) of the plate-shaped roughened particles 12a to the midpoint of the width W2 (the midpoint between the roots), as schematically shown in Figure 3.

[0027] The width W2 of the plate-shaped roughened particles 12a is preferably 15 nm to 250 nm, more preferably 40 nm to 130 nm, even more preferably 45 nm to 125 nm, and particularly preferably 45 nm to 120 nm. The length L2 of the plate-shaped roughened particles 12a is preferably 60 nm to 270 nm, more preferably 95 nm to 210 nm, even more preferably 100 nm to 200 nm, and particularly preferably 110 nm to 190 nm. Furthermore, the ratio L2 / W2 of the plate-shaped roughened particles 12a is preferably 1.5 to 6.6, more preferably 2.0 to 6.6, even more preferably 2.0 to 5.0, and particularly preferably 2.0 to 4.0. This allows for a better balance between high adhesion to thermoplastic resin and excellent high-frequency characteristics.

[0028] The width W2 and length L2 of the plate-shaped roughened particles 12a can be determined by continuously observing (slicing and viewing) the cross-section of the roughened copper foil using a focused ion beam scanning electron microscope (FIB-SEM) and analyzing the acquired images using commercially available software. This analysis can be performed, for example, using the 3D analysis software "Amira 5.5.0" (manufactured by Thermo Fisher SCIENTIFIC) and the image analysis software "Image Pro 10" (manufactured by Media Cybernetics) in accordance with the conditions described in the examples of this specification. The above-mentioned values ​​for width W2, length L2, and ratio L2 / W2 of the plate-shaped roughened particles 12a represent the median values ​​of width W2, length L2, and ratio L2 / W2 measured from individual roughened particles, respectively.

[0029] The roughened copper foil 10 preferably has an aspect ratio Str of the surface properties of the roughened surface 12 of 0.02 to 0.24, more preferably 0.08 to 0.24, even more preferably 0.10 to 0.24, and particularly preferably 0.10 to 0.23. This makes it easier to control the roughened particles into a plate-like shape, further improving adhesion with the thermoplastic resin.

[0030] Furthermore, the roughened copper foil 10 preferably has a load area ratio Smr1 that separates the protruding peaks and core portions on the roughened surface 12 of 1.0% to 15.0%, more preferably 5.0% to 10.5%, and even more preferably 5.0% to 10.2%. This allows for control over the orientation of the fine plate-like roughened particles so that they stand perpendicular to the roughened surface. As a result, while the fine bumps are effective in reducing the skin effect, they also exhibit a high anchoring effect with the resin, further improving adhesion.

[0031] The thickness of the roughened copper foil 10 is not particularly limited, but is preferably 0.1 μm to 35 μm, more preferably 0.5 μm to 5.0 μm, and even more preferably 1.0 μm to 3.0 μm. The roughened copper foil 10 is not limited to ordinary copper foil whose surface has been roughened, but may also be a copper foil with a carrier whose copper foil surface has been roughened. Here, the thickness of the roughened copper foil 10 is the thickness that does not include the height of the roughened particles formed on the surface of the roughened surface 12 (the thickness of the copper foil itself that constitutes the roughened copper foil 10). Copper foil having a thickness within the above range is sometimes called ultrathin copper foil.

[0032] The roughened copper foil 10 has a roughened surface 12 on at least one side. That is, the roughened copper foil 10 may have roughened surfaces 12 on both sides, or it may have a roughened surface 12 on only one side. As described above, the roughened surface 12 typically comprises a plurality of plate-like roughened particles 12a (bumps), and it is preferable that each of these plate-like roughened particles 12a is made of copper particles. The copper particles may be made of metallic copper or a copper alloy.

[0033] The roughening treatment for forming the roughened surface 12 can preferably be carried out by forming roughened particles of copper or a copper alloy on a copper foil. For example, this roughening treatment can preferably be performed by electrodepositing carboxybenzotriazole (CBTA) into a copper sulfate solution containing a copper concentration of 50 g / L to 90 g / L (more preferably 60 g / L to 80 g / L) and a sulfuric acid concentration of 125 g / L to 335 g / L (more preferably 140 g / L to 270 g / L) such that the CBTA concentration is 50 ppm to 300 ppm (more preferably 100 ppm to 250 ppm). This electrodeposition is performed at a current density of 10 A / dm 2 More than 30A / dm 2 (more preferably 12A / dm 2 More than 22A / dm 2 It is preferable to carry out the process under the following conditions: an electrical charge of 10 A·s to 150 A·s (more preferably 10 A·s to 75 A·s) and a liquid temperature of 40°C to 50°C (more preferably 42°C to 50°C). This makes it easier to form the plate-like roughened particles having the predetermined size described above on the treated surface.

[0034] Optionally, the roughened copper foil 10 may be subjected to rust prevention treatment to form a rust prevention layer. The rust prevention treatment preferably includes a zinc plating treatment. The zinc plating treatment may be either zinc plating or zinc alloy plating, with zinc-nickel alloy plating being particularly preferred. The zinc-nickel alloy plating treatment may include at least Ni and Zn, and may further include other elements such as Sn, Cr, and Co. The Ni / Zn adhesion ratio in the zinc-nickel alloy plating is preferably 1.2 to 10 by mass ratio, more preferably 2 to 7, and even more preferably 2.7 to 4. Furthermore, the rust prevention treatment preferably further includes a chromate treatment, and this chromate treatment is more preferably performed on the surface of the zinc-containing plating after the zinc plating treatment. This further improves rust prevention. A particularly preferred rust prevention treatment is a combination of zinc-nickel alloy plating and subsequent chromate treatment.

[0035] If desired, the roughened copper foil 10 may be treated with a silane coupling agent on its surface, forming a silane coupling agent layer. This improves moisture resistance, chemical resistance, and adhesion to adhesives, etc. The silane coupling agent layer can be formed by appropriately diluting the silane coupling agent, applying it, and drying it. Examples of silane coupling agents include epoxy-functional silane coupling agents such as 4-glycidylbutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane; amino-functional silane coupling agents such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; mercapto-functional silane coupling agents such as 3-mercaptopropyltrimethoxysilane; olefin-functional silane coupling agents such as vinyltrimethoxysilane and vinylphenyltrimethoxysilane; acrylic-functional silane coupling agents such as 3-methacryloxypropyltrimethoxysilane; imidazole-functional silane coupling agents such as imidazolesilane; and triazine-functional silane coupling agents such as triazinesilane.

[0036] For the reasons stated above, it is preferable that the roughened copper foil 10 further comprises a rust-preventive treatment layer and / or a silane coupling agent layer on the roughened surface 12, and more preferably both the rust-preventive treatment layer and the silane coupling agent layer. The rust-preventive treatment layer and the silane coupling agent layer may be formed not only on the roughened surface 12 side of the roughened copper foil 10, but also on the side where the roughened surface 12 is not formed.

[0037] Copper foil with carrier As described above, the roughened copper foil 10 of the present invention may be provided in the form of a copper foil with a carrier. That is, according to a preferred embodiment of the present invention, a copper foil with a carrier is provided, comprising a carrier, a release layer provided on the carrier, and the roughened copper foil 10 provided on the release layer with the roughened surface 12 facing outwards. However, aside from using the roughened copper foil 10 of the present invention, known layer configurations can be used for the copper foil with a carrier.

[0038] The carrier is a support for the roughened copper foil 10 to improve its handling properties, and a typical carrier includes a metal layer. Examples of such carriers include aluminum foil, copper foil, stainless steel (SUS) foil, resin films or glass with a metal coating on the surface of copper or the like, and preferably copper foil. The copper foil may be either rolled copper foil or electrolytic copper foil, but electrolytic copper foil is preferred. The thickness of the carrier is typically 250 μm or less, preferably 9 μm to 200 μm.

[0039] The release layer is a layer that weakens the peel strength of the carrier, ensures the stability of that strength, and further suppresses the mutual diffusion that may occur between the carrier and the copper foil during high-temperature press molding. The release layer is generally formed on one side of the carrier, but it may also be formed on both sides. The release layer may be either an organic release layer or an inorganic release layer. Examples of organic components used in the organic release layer include nitrogen-containing organic compounds, sulfur-containing organic compounds, and carboxylic acids. Examples of nitrogen-containing organic compounds include triazole compounds and imidazole compounds, among which triazole compounds are preferred because they tend to have stable release properties. Examples of triazole compounds include 1,2,3-benzotriazole, carboxybenzotriazole, N',N'-bis(benzotriazolylmethyl)urea, 1H-1,2,4-triazole, and 3-amino-1H-1,2,4-triazole. Examples of sulfur-containing organic compounds include mercaptobenzothiazole, thiocyanuric acid, and 2-benzimidazolethiol. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. On the other hand, examples of inorganic components used in the inorganic exfoliation layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, and chromate-treated films. The exfoliation layer can be formed by contacting a solution containing the exfoliation layer components with at least one surface of the carrier and fixing the exfoliation layer components to the surface of the carrier. When contacting the carrier with the solution containing the exfoliation layer components, this contact can be performed by immersion in the solution, spraying the solution, or letting the solution flow down. In addition, methods for forming a film of the exfoliation layer components by vapor phase methods such as vapor deposition or sputtering can also be employed. Furthermore, the exfoliation layer components can be fixed to the carrier surface by adsorption or drying of the solution containing the exfoliation layer components, or by electrodeposition of the exfoliation layer components in the solution. The thickness of the exfoliation layer is typically 1 nm to 1 μm, preferably 5 nm to 500 nm.

[0040] If desired, other functional layers may be provided between the release layer and the carrier and / or the roughened copper foil 10. An example of such other functional layers is an auxiliary metal layer. The auxiliary metal layer is preferably made of nickel and / or cobalt. By forming such an auxiliary metal layer on the surface side of the carrier and / or the surface side of the roughened copper foil 10, mutual diffusion that may occur between the carrier and the roughened copper foil 10 during hot press forming at high temperatures or for long periods of time can be suppressed, and the stability of the carrier's peel strength can be ensured. The thickness of the auxiliary metal layer is preferably 0.001 μm or more and 3 μm or less.

[0041] Copper-clad laminate The roughened copper foil 10 of the present invention is preferably used in the manufacture of copper-clad laminates for printed circuit boards. That is, according to a preferred embodiment of the present invention, a copper-clad laminate equipped with the roughened copper foil 10 is provided. By using the roughened copper foil 10 of the present invention, it is possible to achieve both high adhesion to a thermoplastic resin substrate and excellent high-frequency characteristics in the processing of a copper-clad laminate. This copper-clad laminate comprises the roughened copper foil of the present invention and a resin layer provided in close contact with the roughened surface of the roughened copper foil. The roughened copper foil may be provided on one side of the resin layer or on both sides. The resin layer comprises a resin, preferably an insulating resin. The resin layer is preferably a prepreg and / or a resin sheet. A prepreg is a general term for a composite material obtained by impregnating a substrate such as a synthetic resin plate, glass plate, glass woven fabric, glass nonwoven fabric, or paper with a synthetic resin. Furthermore, the resin layer may contain filler particles consisting of various inorganic particles such as silica and alumina from the viewpoint of improving insulation. The thickness of the resin layer is not particularly limited, but is preferably 1 μm to 1000 μm, more preferably 2 μm to 400 μm, and even more preferably 3 μm to 200 μm. The resin layer may consist of multiple layers. The resin layer, such as a prepreg and / or resin sheet, may be provided on the roughened copper foil via a primer resin layer that is applied to the copper foil surface in advance.

[0042] From the viewpoint of providing copper-clad laminates suitable for high-frequency applications, the resin layer preferably contains a thermoplastic resin, and more preferably, the majority (e.g., 50% by weight or more) or almost (e.g., 80% by weight or more or 90% by weight or more) of the resin components contained in the resin layer is a thermoplastic resin. Preferred examples of thermoplastic resins include polysulfone (PSF), polyethersulfone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyetheretherketone (PEEK), thermoplastic polyimide (PI), polyamideimide (PAI), fluororesin, polyamide (PA), nylon, polyacetal (POM), modified polyphenylene ether (m-PPE), polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cycloolefin (COP), and any combination thereof. From the viewpoint of desirable dielectric loss tangent and excellent heat resistance, more preferred examples of thermoplastic resins include polysulfone (PSF), polyethersulfone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyetheretherketone (PEEK), thermoplastic polyimide (PI), polyamideimide (PAI), fluororesins, and any combination thereof. From the viewpoint of low dielectric constant, liquid crystal polymer (LCP) and / or fluororesins are particularly preferred thermoplastic resins. Preferred examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), and any combination thereof. It is preferable to attach the insulating resin substrate to the roughened copper foil by pressing while heating, thereby softening the thermoplastic resin and allowing it to penetrate the fine irregularities of the roughened surface. As a result, the anchoring effect caused by the penetration of fine irregularities (especially plate-like roughened particles) into the resin ensures good adhesion between the copper foil and the resin.

[0043] Printed circuit board The roughened copper foil of the present invention is preferably used in the manufacture of printed circuit boards. That is, according to a preferred embodiment of the present invention, a printed circuit board equipped with the roughened copper foil is provided. By using the roughened copper foil of the present invention, it is possible to achieve both excellent high-frequency characteristics and high circuit adhesion in the manufacture of printed circuit boards. The printed circuit board according to this embodiment includes a layer structure in which a resin layer and a copper layer are laminated. The copper layer is a layer derived from the roughened copper foil of the present invention. The resin layer is as described above with respect to copper-clad laminates. In any case, other than using the roughened copper foil of the present invention, known layer structures can be used for printed circuit boards. Specific examples of printed circuit boards include single-sided or double-sided printed circuit boards in which circuits are formed on a laminate formed by bonding the roughened copper foil of the present invention to one or both sides of a prepreg and curing it, and multilayer printed circuit boards made by layering these. Other specific examples include flexible printed circuit boards, COF, TAB tapes, etc., in which circuits are formed by forming the roughened copper foil of the present invention on a resin film. Further specific examples include a build-up wiring board in which a resin-coated copper foil (RCC) is formed by applying the above-mentioned resin layer to the roughened copper foil of the present invention, the resin layer is laminated onto the above-mentioned printed circuit board as an insulating adhesive layer, and then a circuit is formed using methods such as the modified semi-additive method (MSAP) or subtractive method, with the roughened copper foil being used as all or part of the wiring layer; a build-up wiring board in which the roughened copper foil is removed and a circuit is formed using the semi-additive method (SAP); and a direct build-up on a wafer in which the lamination of resin-coated copper foil and circuit formation are alternately repeated on a semiconductor integrated circuit. More advanced specific examples include an antenna element in which the above-mentioned resin-coated copper foil is laminated onto a substrate to form a circuit, electronic materials for panel displays and window glass in which a pattern is formed by laminating it onto glass or resin film via an adhesive layer, and an electromagnetic wave shielding film in which a conductive adhesive is applied to the roughened copper foil of the present invention. In particular, the printed circuit board equipped with the roughened copper foil of the present invention is suitably used as a high-frequency substrate for applications such as automotive antennas, mobile phone base station antennas, high-performance servers, and collision avoidance radar, which are used in high-frequency bands of 10 GHz or higher signal frequencies. [Examples]

[0044] The present invention will be further explained by the following examples.

[0045] Examples 1-3 A copper foil with a carrier equipped with a roughened copper foil was fabricated as follows.

[0046] (1) Career preparation Using a copper electrolyte with the composition shown below, a cathode, and a DSA (dimensionally stable anode) as the anode, at a solution temperature of 50°C and a current density of 70 A / dm², 2 Electrolysis was performed to produce an electrolytic copper foil with a thickness of 18 μm as the carrier. At this time, an electrode whose surface roughness was adjusted by polishing the surface with a #1000 buff was used as the cathode. <Composition of copper electrolyte> - Copper concentration: 80g / L - Sulfuric acid concentration: 300g / L - Chlorine concentration: 30 mg / L - Glue concentration: 5mg / L

[0047] (2) Formation of the delamination layer The electrode surface of a carrier that had been pickled was immersed for 30 seconds at a liquid temperature of 30°C in an aqueous solution of carboxybenzotriazole (CBTA) containing 1 g / L of carboxybenzotriazole (CBTA), 150 g / L of sulfuric acid, and 10 g / L of copper, thereby adsorbing the CBTA component onto the electrode surface of the carrier. In this way, a CBTA layer was formed on the electrode surface of the carrier as an organic exfoliation layer.

[0048] (3) Formation of auxiliary metal layer The carrier on which the organic exfoliation layer has formed is immersed in a solution containing 20 g / L nickel, prepared using nickel sulfate, at a liquid temperature of 45°C, pH 3, and current density of 5 A / dm². 2 Under these conditions, nickel equivalent to a thickness of 0.001 μm was deposited onto the organic release layer. In this way, a nickel layer was formed on the organic release layer as an auxiliary metal layer.

[0049] (4) Formation of ultra-thin copper foil The carriers with the auxiliary metal layer were immersed in a copper solution having the composition shown below, and electrolysis was carried out at a solution temperature of 50 °C and a current density of 5 A / dm 2 or more and 30 A / dm 2 or less to form an ultra-thin copper foil with a thickness of 1.5 μm on the auxiliary metal layer. <Composition of the solution> - Copper concentration: 60 g / L - Sulfuric acid concentration: 200 g / L

[0050] (5) Roughening treatment The surface of the ultra-thin copper foil thus formed was subjected to a roughening treatment to form a roughened copper foil, thereby obtaining a copper foil with a carrier. This roughening treatment was carried out using an acidic copper sulfate solution having a copper concentration, a sulfuric acid concentration, and a carboxybenzotriazole (CBTA) concentration shown in Table 1 under the electrodeposition conditions (current density, amount of electricity, and liquid temperature) shown in Table 1. At this time, various samples having different characteristics of the roughened surface were produced by appropriately changing the composition of the acidic copper sulfate solution and the electrodeposition conditions as shown in Table 1.

[0051] (6) Rust prevention treatment A rust prevention treatment consisting of a zinc-nickel alloy plating treatment and a chromate treatment was carried out on the roughened surface of the obtained copper foil with a carrier. First, using a solution containing a zinc concentration of 1 g / L, a nickel concentration of 2 g / L, and a potassium pyrophosphate concentration of 80 g / L, a zinc-nickel alloy plating treatment was carried out on the surfaces of the roughened layer and the carrier under the conditions of a liquid temperature of 40 °C and a current density of 0.5 A / dm 2 . Next, using an aqueous solution containing chromic acid 1 g / L, a chromate treatment was carried out on the surface subjected to the zinc-nickel alloy plating treatment under the conditions of a pH of 12 and a current density of 1 A / dm 2 .

[0052] (7) Silane coupling agent treatment An aqueous solution having a 3-aminopropyltrimethoxysilane concentration of 6 g / L was adsorbed on the surface of the roughened copper foil side of the copper foil with a carrier, and the silane coupling agent treatment was carried out by evaporating moisture with a heater. At this time, the silane coupling agent treatment was not carried out on the carrier side.

[0053] Example 4 (comparison) Except for a) and b) below, roughened copper foil was prepared in the same manner as in Examples 1 to 3. a) Instead of using copper foil with a carrier, the following electrolytic copper foils were subjected to a roughening treatment on their deposited surfaces. b) In the roughening process, the composition of the acidic copper sulfate solution and the electrodeposition conditions were changed to the values ​​shown in Table 1.

[0054] (Preparation of electrolytic copper foil) A sulfuric acid-acidified copper sulfate solution with the following composition was used as the copper electrolyte, a titanium electrode with a surface roughness Ra of 0.20 μm was used as the cathode, and a DSA (dimensionally stable anode) was used as the anode, with a solution temperature of 45°C and a current density of 55 A / dm². 2 Electrolysis was performed to obtain an electrolytic copper foil with a thickness of 18 μm. <Composition of sulfuric acid-acidified copper sulfate solution> - Copper concentration: 80g / L - Sulfuric acid concentration: 260g / L - Bis(3-sulfopropyl) disulfide concentration: 30 mg / L - Diallyldimethylammonium chloride polymer concentration: 50 mg / L - Chlorine concentration: 40 mg / L

[0055] Example 5 (comparison) Except for changing the roughening process as described in a) to c) below, the roughened copper foil was manufactured in the same manner as in Example 4. a) The copper concentration and sulfuric acid concentration in the acidic copper sulfate solution were changed to the values ​​shown in Table 1. b) 9-phenylacridine (9PA) and chlorine were added to the acidic copper sulfate solution to the concentrations shown in Table 1. c) The electrodeposition conditions were changed to the values ​​shown in Table 1.

[0056] [Table 1]

[0057] evaluation The copper foils with carriers equipped with the roughened copper foils prepared in Examples 1-5 were evaluated in the following ways:

[0058] <Surface properties parameters of roughened surfaces> Surface roughness analysis was performed on the roughened surface of roughened copper foil in accordance with ISO 25178 using a laser microscope (OLS5000, manufactured by Olympus Corporation). Specifically, the surface profile of a 129.73 μm × 129.73 μm area on the roughened surface of the roughened copper foil was measured using the laser microscope with a 100x objective lens, under the scanning mode "3D Standard + Color" and the shooting mode "Auto". After removing spike noise and automatically removing tilt from the obtained surface profile of the roughened surface, the aspect ratio Str and the load area ratio Smr1, which separates the protruding peaks and core parts, were measured by surface texture analysis. At this time, shape removal (selecting "Multi-order curved surface, 3rd order") was performed using F calculation, and the cutoff wavelength using the S filter was set to 0.251 μm and the cutoff wavelength using the L filter was set to 4.5 μm. For each example, Str and Smr1 measurements were performed in eight different fields of view. The average values ​​of Str and Smr1 across all fields were adopted as the Str and Smr1 values ​​for the roughened surface of the sample, respectively. The results are shown in Table 2.

[0059] <Overhead SEM observation> To observe the roughened particles when viewing the roughened surface from a planar perspective, a field emission scanning electron microscope (FE-SEM, Hitachi High-Tech Corporation, SU8000) was used to observe the roughened surface of the roughened copper foil from directly above (Tilt: 0°) at a magnification of 50,000x. The obtained observation images were imported into image analysis software (Media Cybernetics, Image Pro 10), and the contrast was optimized using the "Automatic Optimal Value Setting" method. Here, the observation image (FE-SEM image) obtained in Example 2 is shown in Figure 4, and the image after contrast optimization of the same observation image is shown in Figure 5. Next, using the above analysis software, roughened particles with an average brightness density of 3 or more and 13 or less (i.e., roughened particles standing perpendicular to the roughened surface) were extracted, and the extracted roughened particles were approximated by ellipses, and their minor axis length and major axis length were measured, and the ratio of the major axis length to the minor axis length was calculated. For each example, the above procedure was performed on two different fields of view. From the data of all extracted roughened particles, the median of the short axis length, the median of the long axis length, and the median of the ratio of the long axis length to the short axis length were calculated and adopted as the width W1, length L1, and ratio L1 / W1 of the sample, respectively.

[0060] <Cross-sectional SEM observation> To observe the roughened particles when viewing the roughened surface in cross-section, continuous observation (slice and view observation) of the cross-section of roughened copper foil was performed under the following conditions using a focused ion beam scanning electron microscope (FIB-SEM, Carl Zeiss, Crossbeam540). (FIB conditions) - Ion species: Ga - Carbon deposition: Acceleration voltage 30kV, probe current 100pA, deposition area 13μm×13μm - Rough drilling: Acceleration voltage 30kV, probe current 30nA or 15nA - Cross-sectional machining (continuous): Acceleration voltage 30kV, probe current 300pA, depth step 5nm, pixels 5nm / pixel (SEM conditions) - Acceleration voltage: 2kV - Probe current: 69 pA - Working distance (WD): 5mm - Noise Reduction: Line Avg -Signal:InLens - Field of view: 5.12 μm × 3.84 μm

[0061] The obtained cross-sectional images of the roughened copper foil were subjected to 3D processing using 3D analysis software (Thermo Fisher SCIENTIFIC, Amira 5.5.0) and image analysis using image analysis software (Media Cybernetics, Image Pro 10). Figure 6 shows the cross-sectional image (cross-sectional SEM image) of the roughened copper foil obtained in Example 2. For all roughened particles present in the image, the width W2 (distance between the roots of the roughened particles) and length L2 (distance from the highest point of the roughened particle to the midpoint of the width W2 (midpoint between the roots)) were measured, and the ratio L2 / W2 of length L2 to width W2 was calculated. The above operations were performed for three different fields of view for each example, and the median values ​​of width W2, length L2, and ratio L2 / W2 were calculated from the data of all roughened particles and adopted as the width W2, length L2, and ratio L2 / W2 of the sample, respectively. The results are shown in Table 2.

[0062] <Peel strength against thermoplastic resins (liquid crystal polymers)> A liquid crystal polymer (LCP) film (Vecter CT-Q, manufactured by Kuraray Co., Ltd., 50 μm thick x 1 sheet) was prepared as the thermoplastic resin substrate. The obtained carrier-attached copper foil was laminated onto this thermoplastic resin substrate so that its roughened surface was in contact with the resin substrate. Using a vacuum press, the foil was pressed under the conditions of a press pressure of 4 MPa, a temperature of 330 °C, and a press time of 10 minutes. After pressing, the carrier was peeled off along with the release layer to produce a copper-clad laminate. Circuit formation was performed on this copper-clad laminate using a cupric chloride etching solution via the subtractive method to produce a test substrate with a 3 mm wide linear circuit. In Examples 1 to 3, after carrier peeling, copper plating was performed on the copper-clad laminate until the thickness of the copper layer was 18 μm before circuit formation. The fabricated test substrates were subjected to a benchtop precision universal testing machine (Shimadzu Corporation, AGS-50NX). The formed linear circuits were peeled from the thermoplastic resin substrate in accordance with Method A (90° peel) of JIS C 5016-1994, and the normal peel strength (kgf / cm) was measured. The results are shown in Table 2.

[0063] <Evaluation of transmission characteristics> High-frequency substrate (Panasonic Corporation, MEGTRON6N, 45 μm thick x 2 sheets) was prepared as an insulating resin substrate. Carrier-equipped copper foil obtained was laminated on both sides of this insulating resin substrate so that the roughened surface of the copper foil was in contact with the insulating resin substrate. Pressing was performed using a vacuum press at a press pressure of 3 MPa, a temperature of 190°C, and a press time of 90 minutes. After pressing, the carrier was peeled off along with the release layer to obtain a copper-clad laminate. Subsequently, circuit formation (circuit height: 18 μm, circuit width: 300 μm, circuit length: 300 mm) was performed on the copper-clad laminate using a cupric chloride etching solution via the subtractive method. In Examples 1 to 3, after carrier peeling, copper plating was performed until the thickness of the copper layer on the copper-clad laminate became 18 μm before circuit formation. In this way, a transmission loss measurement substrate was obtained in which microstrip lines were formed so that the characteristic impedance was 50 Ω ± 2 Ω. The transmission loss (dB) at 50 GHz was measured using a network analyzer (Keysight Technologies, N5225B) on the obtained transmission loss measurement board under the following settings. The results are shown in Table 2. (Setting conditions) -IF Bandwidth:100Hz - Frequency: 10MHz~50GHz -Data points: 501 points - Average: Off -Calibration method: SOLT (e-cal)

[0064] [Table 2]

Claims

1. A roughened copper foil having a roughened surface on at least one side, The roughened surface comprises a plurality of plate-shaped roughened particles, and when the roughened surface is viewed in plan view, the width W of the plate-shaped roughened particles １ The length of the plate-like roughened particles is 2 nm or more and 135 nm or less. １ The wavelength is 15 nm or more and 490 nm or less, and the width W １ The length L １ L is the ratio of １ / W １ A roughened copper foil in which the coefficient of gravity is between 2.0 and 7.

2.

2. The width W of the plate-like roughened particles １ The roughened copper foil according to claim 1, wherein the wavelength is 30 nm or more and 90 nm or less.

3. The length L of the plate-like roughened particles １ The roughened copper foil according to claim 1 or 2, wherein the wavelength is 100 nm or more and 430 nm or less.

4. The above-mentioned L １ / W １ is 2.5 or more and 7.2 or less, and the roughened copper foil according to any one of claims 1 to 3.

5. When the roughened surface is viewed in cross-section, the width W of the roughened particles is... ２ The length of the plate-like roughened particles is 15 nm or more and 250 nm or less. ２ The wavelength is 60 nm or more and 270 nm or less, and the width W ２ The length L ２ L is the ratio of ２ / W ２ A roughened copper foil according to any one of claims 1 to 4, wherein the coefficient is 1.5 or more and 6.6 or less.

6. The width W of the plate-like roughened particles ２ The roughened copper foil according to claim 5, wherein the wavelength is 40 nm or more and 130 nm or less.

7. The length L of the plate-like roughened particles ２ The roughened copper foil according to claim 5 or 6, wherein the wavelength is 95 nm or more and 210 nm or less.

8. Said L ２ / W ２ A roughened copper foil according to any one of claims 5 to 7, wherein the coefficient of the coefficient is 2.0 or more and 6.6 or less.

9. The roughened surface has a surface texture aspect ratio Str of 0.02 or more and 0.24 or less, and a load area ratio Smr1 separating the protruding peaks and the core portion of 1.0% or more and 15.0% or less. The roughened copper foil according to any one of claims 1 to 8, wherein Str and Smr1 are values ​​measured in accordance with ISO 25178 under conditions of a cutoff wavelength of 0.251 μm using an S filter and a cutoff wavelength of 4.5 μm using an L filter.

10. The roughened copper foil according to any one of claims 1 to 9, further comprising a rust-preventive treatment layer and / or a silane coupling agent layer on the roughened surface.

11. A copper foil with a carrier, comprising a carrier, a release layer provided on the carrier, and a roughened copper foil according to any one of claims 1 to 10 provided on the release layer with the roughened surface facing outward.

12. A copper-clad laminate comprising roughened copper foil according to any one of claims 1 to 10.

13. A printed circuit board comprising roughened copper foil according to any one of claims 1 to 10.

Images