CN118805004A - Roughening copper foil, copper foil with carrier, copper clad laminate and printed circuit board - Google Patents

Abstract

Provided is a roughened copper foil that can achieve both high adhesion to thermoplastic resins and excellent high-frequency characteristics. The roughened copper foil has a roughened surface on at least one side. The skewness Ssk of the roughened surface is greater than 0.35, and the sum of the solid volume Vmp of the protruding peak and the solid volume Vmc of the center, i.e., Vmp+Vmc, is greater than 0.10μm ³ /μm ² and less than 0.28μm ³ /μm ^2. Ssk is a value measured in accordance with JIS B0681‑2:2018 under the condition that no cutoff based on the S filter is performed and the cutoff wavelength based on the L filter is 1.0μm. Vmp and Vmc are values measured in accordance with JIS B0681‑2:2018 under the condition that no cutoff based on the S filter and the L filter is performed.

Description

Roughened copper foil, copper foil with carrier, copper-clad laminate, and printed wiring board

Technical Field

The present invention relates to a roughened copper foil, a copper foil with a carrier, a copper-clad laminate, and a printed circuit board.

Background

With recent increases in functionality of portable electronic devices and the like, in order to process a large amount of information at high speed, a high frequency signal has been developed, and a printed circuit board suitable for high frequency applications such as 5G, millimeter wave, and base station antennas has been demanded. In such a high-frequency printed circuit board, a reduction in transmission loss is desired in order to be able to transmit a high-frequency signal without deteriorating the quality. The printed circuit board includes a copper foil processed into a wiring pattern and an insulating resin base material, and the transmission loss is mainly composed of conductor loss due to the copper foil and dielectric loss due to the insulating resin base material. Therefore, in order to reduce dielectric loss caused by the insulating resin base material, it is convenient to use a thermoplastic resin having a low dielectric constant. However, thermoplastic resins with low dielectric constants, typified by fluororesins and Liquid Crystal Polymers (LCPs), are low in chemical activity unlike thermosetting resins, and therefore have low adhesion to copper foil.

Therefore, a technique for improving adhesion between the copper foil and the thermoplastic resin has been proposed. For example, patent document 1 (international publication No. 2016/174998) discloses a copper foil having a roughened surface having a ten-point average roughness Rzjis of 0.6 μm or more and 1.7 μm or less and a half-width in a frequency distribution of the height of roughened particles of 0.9 μm or less. According to the copper foil, even for an insulating resin substrate such as a liquid crystal polymer film, chemical adhesion cannot be expected, high peel strength can be exhibited.

On the other hand, the conductor loss may increase due to the skin effect of the copper foil which appears more remarkably at higher frequencies. Therefore, in order to suppress transmission loss in high frequency applications, it is required to make the roughened particles finer in order to reduce the skin effect of the copper foil. As a copper foil having the fine roughened particles, for example, patent document 2 (international publication No. 2014/133164) discloses a surface-treated copper foil having a black roughened surface roughened by attaching copper particles (for example, substantially spherical copper particles) having a particle diameter of 10nm to 250 nm.

Prior art literature

Patent literature

Patent document 1: international publication No. 2016/174998

Patent document 2: international publication No. 2014/133164

Disclosure of Invention

As described above, the roughened particles of the copper foil for high-frequency use are required to be finer, but the adhesion between the copper foil and a resin (particularly, a thermoplastic resin) is likely to be lowered. In this regard, from the viewpoint of both high adhesion to thermoplastic resins and excellent high frequency characteristics, conventional copper foil is not necessarily sufficient, and there is room for improvement.

The inventors have now found that: the roughened copper foil surface can be provided with both high adhesion to the thermoplastic resin and excellent high-frequency characteristics by controlling the degree of offset Ssk and the sum of the physical volume Vmp of the protruding peak and the physical volume Vmc of the central portion to be within a predetermined range.

Accordingly, an object of the present invention is to provide a roughened copper foil which can achieve both high adhesion to a thermoplastic resin and excellent high-frequency characteristics.

According to the present invention, the following means are provided.

Mode 1

A roughened copper foil having a roughened surface on at least one side,

The inclination Ssk of the roughened surface is greater than 0.35, and the sum of the solid volume Vmp of the protruding peak and the solid volume Vmc of the center, that is, vmp+Vmc, is 0.10 μm ³/μm² or more and 0.28 μm ³/μm² or less,

The Ssk is according to JIS B0681-2:2018 is measured without performing the cut-off by the S filter and with a cut-off wavelength of 1.0 μm by the L filter,

The aforementioned Vmp and Vmc are according to JIS B0681-2:2018 does not perform the value measured under the condition of the cut-off based on the S filter and the L filter.

Mode 2

The roughened copper foil according to claim 1, wherein the roughened surface has a kurtosis Sku of 2.70 to 4.90,

The Sku is a composition according to JIS B0681-2:2018 does not perform the value measured under the condition of the cut-off based on the S filter and the L filter.

Mode 3

The roughened copper foil according to embodiment 1 or 2, wherein the load area ratio Smr1 of the roughened surface separating the protruding peak portion from the central portion is 11.2% or more,

The Smr1 is a compound according to JIS B0681-2:2018 is measured without performing the cut-off by the S filter and with a cut-off wavelength of 1.0 μm by the L filter.

Mode 4

The roughened copper foil according to any one of aspects 1 to 3, wherein the roughened surface further comprises a rust-preventive treatment layer and/or a silane coupling agent layer.

Mode 5

A copper foil with a carrier, comprising: the roughened copper foil according to any one of aspects 1 to 4, wherein the roughened copper foil is provided on the release layer with the roughened surface as an outer side.

Mode 6

A copper-clad laminate comprising the roughened copper foil according to any one of modes 1 to 4.

Mode 7

A printed wiring board comprising the roughened copper foil according to any one of modes 1 to 4.

Drawings

FIG. 1A is a view for explaining the process according to JIS B0681-2: the graph of the skewness Ssk measured at 2018 is a graph showing the surface and the height distribution thereof when Ssk < 0.

FIG. 1B is a view for explaining the process according to JIS B0681-2: the graph of the skewness Ssk measured at 2018 is a graph showing the surface and the height distribution thereof when Ssk > 0.

FIG. 2 is a view for explaining the process according to JIS B0681-2:2018 and a load area ratio.

FIG. 3 is a view for explaining the process according to JIS B0681-2: and 2018, a graph of the load area ratio Smr1 of the separation protrusion peak portion and the center portion and the load area ratio Smr2 of the separation protrusion valley portion and the center portion.

FIG. 4 is a view for explaining the process according to JIS B0681-2: a plot of the projected peak solid volume Vmp and the central solid volume Vmc measured at 2018.

Detailed Description

Definition of the definition

The following illustrates the definition of terms or parameters for a particular invention.

In the present specification, "skewness Ssk" or "Ssk" means that according to JIS B0681-2:2018, a parameter indicative of symmetry of the height distribution. When the value is 0, it means that the height distribution is vertically symmetrical, in other words, that projections (roughened particles or the like) having uniform sizes are arranged on the surface. In addition, as shown in fig. 1A, when the value is smaller than 0, the surface is represented by a thin valley, in other words, thick protrusions with rounded corners are arranged on the surface. On the other hand, when the value is larger than 0, as shown in fig. 1B, a surface having a small number of peaks is indicated, in other words, elongated protrusions are scattered on the surface.

In the present specification, the "load curve of face" (hereinafter, simply referred to as "load curve") means a load curve according to JIS B0681-2:2018, and represents a height of 0% -100% of the load area rate. As shown in fig. 2, the load area ratio is a parameter indicating the area of the region above a certain height c. The load area ratio at the height c corresponds to Smr (c) in fig. 2. As shown in fig. 3, the cut line of the load curve drawn from the load area ratio of 0% to the load curve with the load area ratio difference of 40% is moved from the load area ratio of 0%, and the position where the inclination of the cut line is most gentle is referred to as the center portion of the load curve of the surface. A straight line with the smallest sum of squares of deviations in the longitudinal axis direction with respect to the central portion is referred to as an equivalent straight line. The portion included in the height range of 0% to 100% of the load area ratio of the equivalent straight line is referred to as the center portion. The portion higher than the center portion is referred to as a protruding peak portion, and the portion lower than the center portion is referred to as a protruding valley portion.

In the present specification, as shown in fig. 3, "load area ratio Smr1 separating the protruding peak portion from the center portion" or "Smr1" means that according to JIS B0681-2:2018, which represents a parameter of the load area ratio at the intersection of the height of the upper portion of the center portion and the load curve of the surface (i.e., the load area ratio separating the center portion and the protruding peak portion). In the present specification, as shown in fig. 3, "load area ratio Smr2 separating the protruding valley portion from the center portion" means that according to JIS B0681-2:2018, which represents a parameter of the load area ratio at the intersection of the height of the lower portion of the center portion and the load curve (i.e., the load area ratio separating the center portion and the protruding valley portion).

In the present specification, as shown in fig. 4, "the entity volume Vmp of the protruding peak" or "Vmp" means that according to JIS B0681-2:2018, a parameter representing the volume of the protruding peak. In this specification, as shown in fig. 4, "the solid volume Vmc of the center portion" or "Vmc" means that according to JIS B0681-2:2018, a parameter representing the volume of the central portion. In the present specification, vmp and Vmc are calculated by designating the load area ratio Smr1 of the separation protruding peak portion and the central portion as 10% and designating the load area ratio Smr2 of the separation protruding valley portion and the central portion as 80%.

In the present specification, "vmp+vmc" refers to a parameter calculated by adding the solid volume Vmp (μm ³/μm²) of the protruding peak portion to the solid volume Vmc (μm ³/μm²) of the central portion. That is, vmp+vmc is a parameter corresponding to the volume of the bump per unit area.

In the present specification, "kurtosis Sku" means that according to JIS B0681-2: a parameter measured at 2018 that represents the sharpness of the height distribution is also called kurtosis. Sku=3 means that the height distribution is a normal distribution, in other words, that projections of uniform size are arranged on the surface. Sku >3 indicates sharp peaks and valleys on the surface, in other words, fine protrusions rising on the surface. If Sku <3, this means that the surface is flat, in other words, thick projections with rounded corners are arranged on the surface.

Ssk, vmp, vmc, sku and Smr1 can be calculated by measuring the surface profile of a predetermined measurement region (for example, a two-dimensional region of 64.397 μm× 64.463 μm) in the roughened surface by a commercially available laser microscope. In the present specification, ssk and Smr1 are measured without performing cut-off by an S filter and with a cut-off wavelength of 1.0 μm by an L filter. On the other hand, vmp, vmc, and Sku are measured without performing cut-off based on the S filter and the L filter. The preferable measurement conditions and analysis conditions of the surface profile by the laser microscope are shown in examples described below.

In the present specification, the "electrode surface" of the electrolytic copper foil refers to a surface on a side that contacts the cathode in the production of the electrolytic copper foil.

In the present specification, the "deposition surface" of the electrolytic copper foil means a surface on a side where electrolytic copper is deposited, that is, a surface on a side not in contact with the cathode, at the time of producing the electrolytic copper foil.

Roughened copper foil

The copper foil of the present invention is a roughened copper foil. The roughened copper foil has a roughened surface on at least one side. The skewness Ssk of the roughened surface is greater than 0.35. The sum of the solid volume Vmp of the protruding peak and the solid volume Vmc of the central portion, that is, vmp+vmc, is 0.10 μm ³/μm² or more and 0.28 μm ³/μm² or less. In this way, by controlling the sum of the actual volume Vmp of the deviated Ssk and the protruding peak and the actual volume Vmc of the central portion, that is, vmp+vmc, within a predetermined range on the surface of the roughened copper foil, both high adhesion to the thermoplastic resin and excellent high-frequency characteristics can be achieved.

As described above, in order to suppress transmission loss in high frequency applications, the roughening particles are required to be finer in order to reduce the skin effect of the copper foil. However, the anchoring effect of the copper foil having the fine roughened particles to the resin base material (that is, the physical adhesion improving effect by the irregularities on the copper foil surface) is reduced, and as a result, the adhesion to the resin is liable to be deteriorated. Particularly, thermoplastic resins with low dielectric constants, typified by fluororesins and Liquid Crystal Polymers (LCPs), are low in chemical activity unlike thermosetting resins, and therefore have low adhesion to copper foil. In this way, the adhesion between the copper foil having low roughness, which is advantageous in terms of high frequency characteristics, and the resin is easily deteriorated. In contrast, according to the roughened copper foil of the present invention, it is possible to unexpectedly achieve both high adhesion to thermoplastic resins and excellent high-frequency properties (e.g., reduction of skin effect).

The mechanism that can achieve both high adhesion to the resin and excellent high frequency characteristics is not necessarily determined, and is considered as follows, for example. That is, vmp+vmc in the roughened surface is a parameter corresponding to the volume of the roughened particles, and if the vmp+vmc is a value as small as 0.10 μm ³/μm² or more and 0.28 μm ³/μm² or less, the surface shape of the fine roughened particles effective for reducing the surface effect is obtained. On the other hand, the larger the number of Ssk of the roughened surface is, the more fine peaks are, i.e., the elongated roughened particles are scattered. Therefore, if Ssk of the roughened surface is a value greater than 0.35, the roughened particles have a fine elongated shape. As a result, a high anchoring effect with respect to the thermoplastic resin base material can be exhibited as compared with conventional roughly spherical roughened particles (ssk=about 0.2 to 0.3), extremely low-height and uniform roughened particles (ssk=about 0 to 0.1), or the like. In addition, the skin effect can be reduced compared to coarse and large roughened particles (Ssk < 0) in shape. As a result, it is considered that both high adhesion to the thermoplastic resin and excellent high-frequency characteristics can be achieved.

Therefore, ssk of the roughened surface of the roughened copper foil is greater than 0.35, preferably greater than 0.35 and 0.79 or less, and more preferably greater than 0.36 and 0.57 or less.

The roughened surface of the roughened copper foil has a vmp+vmc of 0.10 μm ³/μm² to 0.28 μm ³/μm², preferably 0.10 μm ³/μm² to 0.20 μm ³/μm², more preferably 0.15 μm ³/μm² to 0.20 μm ³/μm². The Vmp of the roughened surface is not particularly limited as long as vmp+vmc falls within the above range, and is typically 0.016 μm ³/μm² or less, more typically 0.006 μm ³/μm² or more and 0.015 μm ³/μm² or less, and further typically 0.007 μm ³/μm² or more and 0.015 μm ³/μm² or less. The Vmc of the roughened surface is not particularly limited as long as vmp+vmc falls within the above range, and is typically 0.25 μm ³/μm² or less, more typically 0.14 μm ³/μm² or more and 0.25 μm ³/μm² or less, and further typically 0.14 μm ³/μm² or more and 0.20 μm ³/μm² or less.

The Sku of the roughened surface of the roughened copper foil is preferably 2.70 to 4.90, more preferably 3.00 to 4.00, still more preferably 3.00 to 3.60. When Sku is within the above range, high adhesion to the thermoplastic resin and excellent high-frequency characteristics can be achieved in a further balance.

The Smr1 of the roughened surface of the roughened copper foil is preferably 11.2% or more, more preferably 11.2% or more and 13.4% or less, and still more preferably 11.3% or more and 12.4% or less. When Smr1 is within the above range, high adhesion to a thermoplastic resin and excellent high-frequency characteristics can be achieved in a further balance.

The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm or more and 35 μm or less, more preferably 0.5 μm or more and 5.0 μm or less, and still more preferably 1.0 μm or more and 3.0 μm or less. The roughened copper foil is not limited to the surface roughening treatment of a normal copper foil, and may be the surface roughening treatment of a copper foil with a carrier. Here, the thickness of the roughened copper foil is a thickness of a height excluding the roughened particles formed on the surface of the roughened surface (the thickness of the copper foil itself constituting the roughened copper foil).

The roughened copper foil has a roughened surface on at least one side. That is, the roughened copper foil may have roughened surfaces on both sides, or may have roughened surfaces on only one side. As described above, the roughened surface is typically provided with a plurality of roughened particles (preferably, roughened particles of elongated shape), and these plurality of roughened particles are preferably each formed of copper particles. The copper particles may be formed of metallic copper or a copper alloy.

The roughening treatment for forming the roughened surface may be preferably performed by forming roughened particles with copper or a copper alloy on the copper foil. The roughening treatment is preferably performed according to a plating method in which a 2-stage plating process is performed. In this case, in the plating step of the 1 st stage, electrodeposition is preferably performed using a copper sulfate solution having a copper concentration of 5g/L or more and 9g/L or less (more preferably 7g/L or more and 9g/L or less), a sulfuric acid concentration of 100g/L or more and 150g/L or less (more preferably 100g/L or more and 130g/L or less), and a tungsten concentration of 5mg/L or more and 20mg/L or less (more preferably 10mg/L or more and 20mg/L or less). The electrodeposition is preferably carried out at a liquid temperature of 20 ℃ to 50 ℃ (more preferably 30 ℃ to 50 ℃), The plating is performed under a plating condition having a current density of 10A/dm ² to 40A/dm ² (more preferably 20A/dm ² to 40A/dm ²), and an electric quantity of 50 A.s to 200 A.s (more preferably 50 A.s to 150 A.s). Particularly, in the plating step of the 1 st stage, fine roughened particles having a long-sized shape are easily formed on the treated surface by using a copper sulfate solution having a copper concentration lower than that of the conventional method and containing an inorganic additive in the above concentration range. In the plating step of the 2 nd stage, electrodeposition is preferably performed using a copper sulfate solution having a copper concentration of 40g/L or more and 70g/L or less (more preferably 50g/L or more and 70g/L or less) and a sulfuric acid concentration of 100g/L or more and 300g/L or less (more preferably 150g/L or more and 250g/L or less). The electrodeposition is preferably carried out at a liquid temperature of 30 ℃ to 60 ℃ (more preferably 40 ℃ to 50 ℃), A current density of 10A/dm ² or more and 40A/dm ² or less (more preferably 20A/dm ² or more and 40A/dm ² or less), And a plating condition in which the electric quantity is not less than 10 A.s and not more than 250 A.s (more preferably not less than 10 A.s and not more than 150 A.s). by performing such a plating step, roughened particles suitable for satisfying the above surface parameters are easily formed on the treated surface.

The roughened copper foil may be subjected to an anti-rust treatment to form an anti-rust treated layer, if necessary. The rust inhibitive treatment preferably includes a plating treatment using zinc. The plating treatment using zinc may be any one of a zinc plating treatment and a zinc plating alloy treatment, and the zinc plating alloy treatment is particularly preferably a zinc-nickel alloy treatment. The zinc-nickel alloy treatment may be a plating treatment containing at least Ni and Zn, and may further contain other elements such as Sn, cr, and Co. The Ni/Zn attachment ratio in the zinc-nickel alloy is preferably 1.2 to 10, more preferably 2 to 7, still more preferably 2.7 to 4 in terms of mass ratio. The rust inhibitive treatment preferably further includes a chromate treatment, and the chromate treatment is more preferably performed on a zinc-containing plated surface after the plating treatment using zinc. This can further improve rust resistance. Particularly preferred rust inhibitive treatments are combinations of zinc-nickel alloy plating treatments followed by chromate treatments.

The roughened copper foil may be a copper foil having a surface treated with a silane coupling agent and formed with a silane coupling agent layer, as required. This can improve moisture resistance, chemical resistance, adhesion to an adhesive or the like, and the like. The silane coupling agent layer may be formed by appropriately diluting and coating the silane coupling agent and drying. Examples of the silane coupling agent include epoxy-functional silane coupling agents such as 4-glycidyl butyl trimethoxy silane and 3-glycidoxypropyl trimethoxy silane, acrylic-functional silane coupling agents such as 3-aminopropyl trimethoxy silane, N- (2-aminoethyl) -3-aminopropyl trimethoxy silane, N-3- (4- (3-aminopropoxy) butoxy) propyl-3-aminopropyl trimethoxy silane, amino-functional silane coupling agents such as N-phenyl-3-aminopropyl trimethoxy silane, mercapto-functional silane coupling agents such as 3-mercaptopropyl trimethoxy silane, olefin-functional silane coupling agents such as vinyl trimethoxy silane and vinyl phenyl trimethoxy silane, or acrylic-functional silane coupling agents such as 3-methacryloxypropyl trimethoxy silane, imidazole-functional silane coupling agents such as imidazole silane, triazine-functional silane coupling agents such as triazine, and the like.

For the above reasons, the roughened copper foil is preferably further provided with an anti-rust treatment layer and/or a silane coupling agent layer on the roughened surface, and more preferably with both an anti-rust treatment layer and a silane coupling agent layer. In the case where the roughened surface is formed with the rust inhibitive treatment layer and/or the silane coupling agent layer, the numerical values of the various parameters of the roughened surface in the present specification refer to the numerical values obtained by measuring and analyzing the roughened copper foil after the formation of the rust inhibitive treatment layer and/or the silane coupling agent layer. The rust inhibitive treatment layer and the silane coupling agent layer may be formed not only on the roughened surface side of the roughened copper foil but also on the side where the roughened surface is not formed.

Copper foil with carrier

As described above, the roughened copper foil 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, there is provided a copper foil with a carrier, which comprises a carrier, a release layer provided on the carrier, and the above-mentioned roughened copper foil provided on the release layer with the roughened surface as the outer side. Of course, the copper foil with carrier may be composed of a known layer other than the roughened copper foil of the present invention.

The carrier is a support for supporting the roughened copper foil to improve its handling properties, and typically the carrier comprises a metal layer. Examples of such a carrier include aluminum foil, copper foil, stainless steel (SUS) foil, resin film having a surface coated with metal such as copper, glass, and the like, and copper foil is preferable. The copper foil may be any of a rolled copper foil and an electrolytic copper foil, and is preferably an electrolytic copper foil. The thickness of the support is typically 250 μm or less, preferably 9 μm or more and 200 μm or less.

The release layer has a function of reducing the peel strength of the carrier, ensuring the stability of the strength, and further suppressing interdiffusion possibly occurring between the carrier and the copper foil during press molding at high temperature. The release layer is usually formed on one side of the support, but may be formed on both sides. The release layer may be any one of an organic release layer and an inorganic release layer. Examples of the organic component used in the organic release layer include nitrogen-containing organic compounds, sulfur-containing organic compounds, carboxylic acids, and the like. Examples of the nitrogen-containing organic compound include triazole compounds and imidazole compounds, and triazole compounds are preferable in view of easy stability of releasability. Examples of the triazole compound include 1,2, 3-benzotriazole, carboxybenzotriazole, N' -bis (benzotriazolylmethyl) urea, 1H-1,2, 4-triazole, and 3-amino-1H-1, 2, 4-triazole. Examples of the sulfur-containing organic compound include mercaptobenzothiazole, cyanuric acid, and 2-benzimidazole mercaptan. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. Examples of the inorganic component used for the inorganic release layer include Ni, mo, co, cr, fe, ti, W, P, zn and a chromate treatment film. The formation of the release layer may be performed by bringing a solution containing the release layer component into contact with at least one surface of the support, fixing the release layer component to the surface of the support, or the like. When the support is brought into contact with the solution containing the release layer component, the contact may be performed by immersing in the solution containing the release layer component, spraying the solution containing the release layer component, flowing down the solution containing the release layer component, or the like. Further, a method of forming a film of the release layer component by a vapor phase method such as vapor deposition or sputtering may be employed. The fixation of the release layer component to the support surface may be performed by adsorption of a solution containing the release layer component, drying, electrodeposition of the release layer component in the solution containing the release layer component, or the like. The thickness of the release layer is typically 1nm to 1 μm, preferably 5nm to 500 nm.

Other functional layers may be provided between the release layer and the carrier and/or roughened copper foil, as desired. As examples of such other functional layers, an auxiliary metal layer may be cited. The auxiliary metal layer is preferably formed 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, it is possible to suppress interdiffusion which may occur between the carrier and the roughened copper foil during hot press molding at high temperature or for a long time, and to ensure the stability of the peel strength of the carrier. The thickness of the auxiliary metal layer is preferably 0.001 μm or more and 3 μm or less.

Copper-clad laminate

The roughened copper foil of the present invention is preferably used for producing a copper-clad laminate for a printed wiring board. That is, according to a preferred embodiment of the present invention, there is provided a copper-clad laminate provided with the roughened copper foil. By using the roughened copper foil of the present invention, both high adhesion to a thermoplastic resin base material and excellent high-frequency characteristics can be achieved in the processing of a copper-clad laminate. The 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 or both sides of the resin layer. The resin layer contains a resin, preferably an insulating resin. The resin layer is preferably a prepreg and/or a resin sheet. Prepreg refers to a generic term for composite materials in which a base material such as a synthetic resin sheet, a glass woven fabric, a glass nonwoven fabric, or paper is impregnated with a synthetic resin. In addition, from the viewpoint of improving insulation and the like, filler particles formed of various inorganic particles such as silica, alumina and the like may be contained in the resin layer. The thickness of the resin layer is not particularly limited, but is preferably 1 μm or more and 1000 μm or less, more preferably 2 μm or more and 400 μm or less, and still more preferably 3 μm or more and 200 μm or less. The resin layer may be composed of a plurality of layers. The resin layer such as prepreg and/or resin sheet may be provided on the roughened copper foil by a primer resin layer previously applied to the surface of the copper foil.

From the viewpoint of providing a copper-clad laminate suitable for high-frequency applications, the resin layer preferably contains a thermoplastic resin, and more preferably, most (for example, 50 wt% or more) or most (for example, 80 wt% or more or 90 wt% or more) of the resin component contained in the resin layer is a thermoplastic resin. Preferable examples of the thermoplastic resin 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), cyclic Olefin (COP), and any combination thereof. More preferable examples of the thermoplastic resin from the viewpoint of desired dielectric loss tangent and excellent heat resistance include Polysulfone (PSF), polyethersulfone (PES), amorphous Polyarylate (PAR), liquid Crystal Polymer (LCP), polyetheretherketone (PEEK), thermoplastic Polyimide (PI), polyamideimide (PAI), fluororesin, and any combination thereof. Particularly preferred thermoplastic resins from the standpoint of low dielectric constants are Liquid Crystal Polymers (LCPs) and/or fluororesins. Preferable examples of the fluororesin include Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), and any combination thereof. The adhesion of the insulating resin base material to the roughened copper foil is preferably performed by pressing while heating, whereby the thermoplastic resin can be softened and fine irregularities on the roughened surface can be obtained. As a result, the adhesion between the copper foil and the resin can be ensured by the anchor effect of the fine irregularities (particularly, elongated roughened particles) being trapped in the resin.

Printed circuit board with improved heat dissipation

The roughened copper foil of the present invention is preferably used for the production of printed circuit boards. That is, according to a preferred embodiment of the present invention, there is provided a printed wiring board comprising the roughened copper foil. By using the roughened copper foil of the present invention, excellent high-frequency characteristics and high-circuit adhesion can be achieved at the same time in the production of printed wiring boards. The printed circuit board of the present 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. In addition, the resin layer is as described for the copper-clad laminate. In short, the printed wiring board may have a known layer structure other than the roughened copper foil of the present invention. Specific examples of the printed circuit board include: the roughened copper foil of the present invention is bonded to one or both sides of a prepreg, and the resulting laminate is cured to form a circuit-forming one or both sides of a printed wiring board, a multilayered printed wiring board obtained by multilayered formation of these. Further, as other specific examples, there are flexible printed circuit boards, COFs, TAB tapes, and the like in which the roughened copper foil of the present invention is formed on a resin film to form a circuit. Further, as another specific example, there is mentioned: a resin-coated copper foil (RCC) coated with the resin layer is formed on the roughened copper foil of the present invention, the resin layer is laminated on the printed board as an insulating adhesive material layer, and then the roughened copper foil is used as all or a part of a wiring layer to form a laminated circuit board of a circuit by a modified semi-additive Method (MSAP), subtractive method or the like; removing the roughened copper foil, and forming a laminated circuit board of a circuit by a half-additive method (SAP); a direct lamination wafer direct buildup on wafer or the like is formed by alternately repeating lamination of a resin-coated copper foil and circuit formation on a semiconductor integrated circuit. Specific examples of the further development include an antenna element in which the above-mentioned copper foil with resin is laminated on a substrate to form a circuit, an electronic material for a panel display in which a pattern is formed by laminating an adhesive layer on glass or a resin film, an electronic material for window glass, and an electromagnetic wave shielding film in which a conductive adhesive is applied to a roughened copper foil of the present invention. In particular, a printed circuit board provided with the roughened copper foil of the present invention is suitable for use as a high-frequency substrate for use in applications such as an automobile antenna, a cellular phone base station antenna, a high-performance server, and a collision avoidance radar, which are used in a high frequency band of 10GHz or more in signal frequency.

Examples

The present invention will be further specifically described by the following examples.

Examples 1 to 11

The roughened copper foil of the present invention was produced as follows.

(1) Preparation of electrolytic copper foil

As a copper electrolyte, an acidic copper sulfate solution having the composition shown below was used, an electrode made of titanium having a surface roughness Ra of 0.20 μm was used as a cathode, DSA (dimensionally stable anode) was used as an anode, and electrolysis was performed at a solution temperature of 45℃and a current density of 55A/dm ² to obtain an electrolytic copper foil having a thickness of 18. Mu.m.

< Composition of sulfuric acid copper sulfate solution >

Copper concentration: 80g/L

Sulfuric acid concentration: 260g/L

-Bis (3-sulfopropyl) disulfide concentration: 30mg/L

Diallyl dimethyl ammonium chloride polymer concentration: 50mg/L

Chlorine concentration: 40mg/L

(2) Roughening treatment

The deposition surface of the electrolytic copper foil obtained was roughened. As shown in table 1, the roughening treatment was a 2-stage roughening treatment (first roughening treatment and second roughening treatment) for examples 1 to 6 and 8 to 11, and a 1-stage roughening treatment (first roughening treatment) for example 7. At this time, by appropriately changing the composition of the acidic copper sulfate solution and the electrodeposition conditions as shown in table 1, various samples having different characteristics of the roughened surface were produced.

Specifically, the roughening treatment conditions in each stage are as follows.

In the first roughening treatment, electroplating was performed under electrodeposition conditions (liquid temperature, current density, and electric quantity) shown in table 1 using an acidic copper sulfate solution containing sulfuric acid, copper sulfate, and sodium tungstate (examples 1 to 6, 8, and 9) as an inorganic additive as needed so as to obtain Cu concentration, sulfuric acid concentration, and W concentration shown in table 1.

In the second roughening treatment, electroplating was performed under electrodeposition conditions (liquid temperature, current density, and electric quantity) shown in table 1 using an acidic copper sulfate solution containing sulfuric acid and copper sulfate so as to have Cu concentration and sulfuric acid concentration shown in table 1.

(3) Rust-proof treatment

The roughened surface of the electrolytic copper foil is subjected to rust inhibitive treatment including zinc-nickel alloy plating treatment and chromate treatment. First, a zinc-nickel alloy plating treatment was performed at a liquid temperature of 40℃and a current density of 0.5A/dm ² using a solution containing a zinc concentration of 1g/L, a nickel concentration of 2g/L and a potassium pyrophosphate concentration of 80 g/L. Then, the surface subjected to the zinc-nickel alloy plating treatment was subjected to chromate treatment using an aqueous solution containing 1g/L of chromic acid at a pH of 12 and a current density of 1A/dm ².

(4) Silane coupling agent treatment

An aqueous solution having a concentration of 6g/L of 3-aminopropyl trimethoxysilane was adsorbed onto the roughened surface of the electrolytic copper foil, and water was evaporated by an electric heater, thereby performing a silane coupling agent treatment. At this time, the surface of the electrolytic copper foil which has not been subjected to roughening treatment was not subjected to silane coupling agent treatment.

TABLE 1

Evaluation

The roughened copper foils produced in examples 1 to 11 were subjected to various evaluations shown below.

< Surface Property parameter of roughened surface >

Surface roughness analysis by using a laser microscope was performed in accordance with JIS B0681-2:2018, a roughened surface of the roughened copper foil was measured. Specific measurement conditions are shown in table 2. The surface profile of the obtained roughened surface was analyzed under the conditions shown in table 2, ssk, sku, smr, vmp, and Vmc were calculated, and the sum (=vmp+vmc) of Vmp and Vmc was obtained as the volume of the roughened particles. For each example, the above-described parameter calculation was performed in 10 different fields of view, and the average value in all the fields of view was used as the surface property parameter of the roughened surface in the sample. The results are shown in Table 3.

TABLE 2

< Peel Strength for thermoplastic resin (liquid Crystal Polymer) >)

As a thermoplastic resin substrate, a Liquid Crystal Polymer (LCP) film (Kuraray co., ltd. Manufactured by VECSTAR CT-Q, thickness 50 μm×1 sheet) was prepared. The roughened copper foil thus obtained was laminated on a resin substrate so that the roughened surface thereof was in contact with the resin substrate, and was pressed under a pressing pressure of 4MPa and a temperature of 330 ℃ for 10 minutes using a vacuum press, to produce a copper-clad laminate. The copper-clad laminate was subjected to circuit formation by a subtractive method using a copper chloride etching solution, and a test substrate having a linear circuit 3mm wide was produced. The test substrate thus produced was peeled off from the thermoplastic resin substrate by the method A (90 DEG peel) of JIS C5016-1994 using a bench-type precision universal tester (AGS-50 NX, manufactured by Shimadzu corporation), and the normal peel strength (kgf/cm) was measured. The peel strength was judged to be acceptable when it was 0.60kgf/cm or more. The results are shown in Table 3.

< Evaluation of Transmission Property >

As an insulating resin substrate, a high-frequency substrate (MEGTRON N, 45 μm. Times.2 pieces in thickness, manufactured by Songshi Co., ltd.) was prepared. The roughened copper foil thus obtained was laminated on both surfaces of an insulating resin base material so that the roughened surface thereof was in contact with the insulating resin base material, and was pressed under a pressing pressure of 3MPa and a temperature of 190 ℃ for 90 minutes using a vacuum press, to obtain a copper-clad laminate. Then, a circuit formation (circuit height: 18 μm, circuit width: 300 μm, circuit length: 300 mm) by a subtractive method was performed on the copper-clad laminate using a copper chloride etching solution. Thus, a substrate for measuring transmission loss in which microstrip lines were formed so that the characteristic impedance became 50Ω±2Ω was obtained. The obtained transmission loss measurement substrate was measured under the following set conditions using a network analyzer (manufactured by Keysight Technology, N5225B), and the transmission loss L ₁ (dB) at 50GHz was measured. Then, the rate of increase (=l ₁/L₀) of the transmission loss L ₁ with respect to the transmission loss L ₀ (dB) at 50GHz of example 7 (comparative example) was calculated. The transmission loss increase rate is 1.10 or less, and is judged to be acceptable. The results are shown in Table 3.

(Set conditions)

-IF Bandwidth:100Hz

-Frequency:10MHz～50GHz

-Data points:501point

-Average:Off

-Correction method: SOLT (e-cal) [ Table 3]

Claims (7)

1. A roughened copper foil having a roughened surface on at least one side,

The inclination Ssk of the roughened surface is greater than 0.35, and the sum of the solid volume of the protruding peak portion Vmp and the solid volume of the central portion Vmc, that is, vmp+Vmc, is 0.10 μm ³/μm² or more and 0.28 μm ³/μm² or less,

The Ssk is according to JIS B0681-2:2018 is measured without performing the cut-off by the S filter and with a cut-off wavelength of 1.0 μm by the L filter,

The Vmp and Vmc are according to JIS B0681-2:2018 does not perform the value measured under the condition of the cut-off based on the S filter and the L filter.

2. The roughened copper foil according to claim 1, wherein the kurtosis Sku of the roughened surface is 2.70 or more and 4.90 or less,

The Sku is according to JIS B0681-2:2018 does not perform the value measured under the condition of the cut-off based on the S filter and the L filter.

3. The roughened copper foil according to claim 1 or 2, wherein the load area ratio Smr1 of the separated projecting peak portions and the central portion of the roughened surface is 11.2% or more,

The Smr1 is according to JIS B0681-2:2018 is measured without performing the cut-off by the S filter and with a cut-off wavelength of 1.0 μm by the L filter.

4. The roughened copper foil according to claim 1 or 2, further comprising an anti-rust treatment layer and/or a silane coupling agent layer on the roughened surface.

5. A copper foil with a carrier, comprising: a carrier, a release layer provided on the carrier, and the roughened copper foil according to claim 1 or 2 provided on the release layer with the roughened surface as an outer side.

6. A copper-clad laminate comprising the roughened copper foil according to claim 1 or 2.

7. A printed wiring board comprising the roughened copper foil according to claim 1 or 2.