Surface-treated copper foil, copper-clad laminates, and printed wiring boards

Abstract

The present invention provides a surface-treated copper foil that exhibits excellent adhesion between a resin substrate and the surface-treated copper foil, has low transmission loss, and is suitable for producing printed wiring boards and the like that have good laser processability. The surface-treated copper foil has a roughened surface on at least one side on which roughening particles are formed, and the physical properties measured on the roughened surface satisfy the following (A), (B), and (C): (A) The specular reflectance of the roughened surface, measured using a spectrophotometer with a light source that emits 45° polarized light with a wavelength of 600 nm, at an incident angle and a reflection angle of 70°, is 0.20% or more and 0.90% or less. (a) The Y value of the brightness of the roughened surface is 10.0 or more and 15.5 or less. (c) The Ssk of the roughened surface measured using a laser microscope is 0.30 or more and 0.80 or less.

Description

[Technical Field]

[0001] The present invention relates to a surface-treated copper foil that can be suitably used in the production of printed wiring boards and the like, and to a copper-clad laminate and a printed wiring board that use the surface-treated copper foil. [Background technology]

[0002] In recent years, in order to accommodate improvements in the information processing speed of electronic devices and high-speed wireless communication, electronic circuit boards are required to transmit electrical signals at high speeds, and the use of high-frequency circuit boards is increasing. In high-frequency circuit boards, transmission loss must be reduced to enable high-speed transmission of electrical signals. Methods for reducing transmission loss include reducing the dielectric constant and dielectric loss tangent of resin substrates and reducing transmission loss in conductor circuit wiring (especially copper foil). One method for reducing the dielectric constant and dielectric loss tangent of a resin substrate is to select a resin (such as a liquid crystal polymer) with a low dielectric constant and dielectric loss tangent as the material for the resin substrate. However, depending on the type of resin, there is a problem in that it is difficult to obtain sufficient chemical adhesion between the resin substrate and copper foil even when a coupling agent or the like is used. Another method for reducing transmission loss in copper foil is to reduce surface irregularities using roughening particles, etc. However, reducing the surface irregularities has the problem of making it difficult to obtain sufficient physical adhesion (anchor effect) between the resin substrate and the copper foil.

[0003] As described above, there is a trade-off between the adhesion between a resin substrate and copper foil and transmission loss. Therefore, a conventional method has been to achieve adhesion between a resin substrate and copper foil by adjusting the surface roughness of the copper foil while reducing the dielectric constant and dielectric loss tangent of the resin substrate. For example, Patent Document 1 discloses a method of adjusting the surface roughness and lightness (brightness) of the copper foil to improve adhesion to a liquid crystal polymer film. Patent Document 2 also discloses a method of adjusting the height and aspect ratio of roughening particles on the copper foil surface to improve adhesion to a liquid crystal polymer film. However, while the techniques disclosed in Patent Documents 1 and 2 improve adhesion to a liquid crystal polymer film by increasing the surface roughness of the copper foil, they do not sufficiently reduce transmission loss, and there is a risk that they will not be able to meet the recent demand for low transmission loss.

[0004] Up until now, emphasis has been placed on reducing transmission loss and improving adhesion in high-frequency circuit boards. However, as electronic devices become smaller and thinner, there is a demand for highly integrated, small, high-density printed wiring boards, particularly for the various electronic components used in portable devices such as mobile phone terminals. In such small, high-density printed wiring boards, blind via holes are sometimes used for interlayer connections, and manufacturing processes in which via holes are formed by laser irradiation are becoming more common. Since roughening particles are always formed at the bottom of the via hole, when blind via holes are formed by laser irradiation, resin derived from the resin substrate may remain at the bottom of the formed blind via hole. Residual resin may prevent sufficient conductivity even after plating, which may reduce the connection reliability during interlayer connection, so it is preferable to have as little residual resin as possible. Therefore, copper foil is required to have a property that allows the resin adhered to the surface to be easily removed from the surface by laser irradiation (hereinafter referred to as "laser processability"). If copper foil has excellent laser processability, when a blind via hole is formed by laser irradiation, resin derived from the resin substrate is less likely to remain at the bottom of the formed blind via hole. At the bottom of the bottomed via hole where the interlayer connection conductor is formed, the metal constituting the interlayer connection conductor is integrated with the copper foil and the roughening particles, making it difficult to clearly identify the surface of the copper foil or the interface of the roughening particles in the interlayer connection conductor portion of the printed wiring board.

[0005] In order to achieve both good adhesion between the resin substrate and copper foil and laser processability, a method has been proposed in which copper foil is used, which can suppress the residue of resin originating from the resin substrate (Patent Document 3). The technology disclosed in Patent Document 3 makes it possible to prevent resin from the resin substrate from remaining at the bottom of a blind via hole formed by laser irradiation by providing a blackening treatment layer with high laser absorption on the surface of the copper foil.

[0006] However, in the technology disclosed in Patent Document 3, there is a risk of increased transmission loss due to the presence of a laser absorption layer or blackening treatment layer with high transmission loss at the interface between the resin substrate and the copper foil in areas other than the area where the blind via holes are formed, and therefore there is a risk that this technology will not be able to meet the low transmission loss that has been required in recent years. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-219379 [Patent Document 2] International Publication No. 2012 / 020818 [Patent Document 3] Japanese Patent Application Publication No. 11-284309 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a surface-treated copper foil and a copper-clad laminate that have excellent adhesion between a resin substrate and the surface-treated copper foil, have low transmission loss, and are suitable for producing printed wiring boards, etc. Another object of the present invention is to provide a printed wiring board that has excellent adhesion between a resin substrate and the surface-treated copper foil, have low transmission loss, and are suitable for laser processability. [Means for solving the problem]

[0009] The surface-treated copper foil according to one embodiment of the present invention is a surface-treated copper foil having a roughened surface on at least one side on which roughening particles are formed, and the physical properties measured on the roughened surface satisfy the following (a), (b), and (c): (A) The specular reflectance of the roughened surface, measured using a spectrophotometer with a light source that emits 45° polarized light with a wavelength of 600 nm, at an incident angle and a reflection angle of 70°, is 0.20% or more and 0.90% or less. (a) The Y value of the brightness of the roughened surface is 10.0 or more and 15.5 or less. (c) The Ssk of the roughened surface measured using a laser microscope is 0.30 or more and 0.80 or less.

[0010] Another aspect of the present invention is a surface-treated copper foil having a roughened surface on at least one side on which roughening particles are formed, and when the surface-treated copper foil is cut to reveal a cross section perpendicular to the roughened surface, the physical property values ​​of the roughened surface measured by observing the cross section with a scanning electron microscope satisfy the following (f), (g), and (h): (f) The average value h_ave of the cross-sectional particle height of the roughening particles is 0.35 μm or more and 0.70 μm or less. (g) The standard deviation w_σ of the cross-sectional particle width of the roughening particles is 0.05 μm or more and 0.10 μm or less. (H) The skewness h_sk of the cross-sectional particle height of the roughening particles is 0.80 or more and -2.50 × h_ave + 3.50 or less.

[0011] Furthermore, a copper-clad laminate according to yet another aspect of the present invention comprises the surface-treated copper foil according to the one aspect or the other aspect, and a resin substrate bonded to the roughened surface of the surface-treated copper foil. Furthermore, a printed wiring board according to yet another aspect of the present invention includes the copper-clad laminate according to the above-described yet another aspect. [Effects of the Invention]

[0012] The surface-treated copper foil and copper-clad laminate of the present invention have excellent adhesion between the resin substrate and the surface-treated copper foil, and can be used to produce printed wiring boards, etc. that have low transmission loss and good laser processability. The printed wiring board of the present invention has excellent adhesion between the resin substrate and the surface-treated copper foil, and has low transmission loss and good laser processability. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view illustrating the configuration of a copper-clad laminate according to an embodiment of the present invention. [Figure 2] FIG. 1 is a cross-sectional view showing the configuration of a printed wiring board in which a surface-treated copper foil and a resin base material are integrally bent. [Figure 3] 1 is a cross-sectional view showing the configuration of a printed wiring board that constitutes a stripline type transmission line. [Figure 4] 1A to 1C are diagrams illustrating the process of forming via holes, forming circuit patterns, and forming interlayer connectors in a copper-clad laminate. [Figure 5] 1A to 1C are diagrams illustrating a method for forming blind via holes in a double-sided copper-clad laminate by laser irradiation. [Figure 6] 1A and 1B are diagrams illustrating a method for forming blind via holes in a single-sided copper-clad laminate by laser irradiation. [Figure 7] FIG. 1 is a cross-sectional view of a via hole in a copper-clad laminate using a conventional surface-treated copper foil. [Figure 8] 1 is a cross-sectional view of a via hole in a copper-clad laminate using the surface-treated copper foil of the first embodiment and the second embodiment. FIG. [Figure 9] 1 is an SEM image of a cross section of a surface-treated copper foil. [Figure 10] 10 is a diagram illustrating a method for measuring the average value h_ave of the cross-sectional particle height of a roughening particle, the standard deviation w_σ of the cross-sectional particle width, and the skewness h_sk of the cross-sectional particle height. FIG. [Figure 11] 10 is a diagram illustrating a method for measuring the average value h_ave of cross-sectional particle heights, the standard deviation w_σ of cross-sectional particle widths, and the skewness h_sk of cross-sectional particle heights of roughening particles having special shapes. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described. Note that the embodiment described below is merely an example of the present invention. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0015] [Surface-treated copper foil according to the first embodiment] The surface-treated copper foil according to the first embodiment is a surface-treated copper foil having a roughened surface on at least one side on which roughening particles are formed, and the physical property values ​​measured on the roughened surface satisfy the following (a), (b), and (c): (A) The specular reflectance of the roughened surface, measured using a spectrophotometer with a light source that emits 45° polarized light with a wavelength of 600 nm, at an incident angle and a reflection angle of 70°, is 0.20% or more and 0.90% or less. (a) The Y value of the brightness of the roughened surface is 10.0 or more and 15.5 or less. (c) The Ssk of the roughened surface measured using a laser microscope is 0.30 or more and 0.80 or less.

[0016] The surface-treated copper foil according to the first embodiment has been subjected to a surface treatment such as a roughening treatment (e.g., copper plating) on ​​at least one of the front and back surfaces. The roughened surface has a roughened surface on which roughening particles are formed by the roughening treatment. The entire surface of the surface-treated copper foil may be a roughened surface, or a portion of the surface may be a roughened surface. When producing the surface-treated copper foil, the raw material copper foil is subjected to a roughening treatment. Examples of the raw material copper foil include electrolytic copper foil and rolled copper foil.

[0017] Furthermore, by using a surface-treated copper foil whose roughened surface satisfies all of the above-mentioned features (A), (B), and (C), it is possible to manufacture a printed wiring board or the like that has excellent adhesion between the resin substrate and the surface-treated copper foil, small transmission loss, and good laser processability. Furthermore, since the transmission loss is small even when a high-frequency signal is transmitted to the circuit of the manufactured printed wiring board, the surface-treated copper foil according to the first embodiment can be suitably used for manufacturing a printed wiring board used in the high-frequency band (a printed wiring board having a high-frequency circuit).

[0018] The surface-treated copper foil according to the first embodiment will be described in more detail. The mechanism by which the above effects are obtained is not entirely clear, but is presumed to be as follows.

[0019] (A) Specular reflectance First, the specular reflectance is measured under geometric conditions close to those of a surface, with both the incident angle and reflection angle being 70°, making it possible to perform evaluations that are sensitive to the surface shape. Furthermore, by spectrally analyzing the incident light and using the reflectance of light with lower energy (longer wavelength) than the copper plasma frequency, light absorption by the copper is suppressed, and reflection from the copper surface becomes dominant. The angle of reflection is largely dependent on the copper surface shape, and we believe that the specular reflection component, in particular, where the angle of incidence and reflection are the same, is influenced by the shape of the roughening particles formed on the surface. Therefore, we found that by using a spectrum with a wavelength of 600 nm, which is close to the average cross-sectional particle height h_ave of the roughening particles, it is possible to evaluate the shape of the roughening particles in a sensitive manner. Therefore, the higher the specular reflectance, the smaller the transmission loss, and the lower the specular reflectance, the better the adhesion between the resin substrate and the surface-treated copper foil.

[0020] (a) Y value of brightness The Y value of brightness, which is the reflectance when white light is incident at an angle of 45° and reflected at an angle of 0°, is presumed to be a value that sensitively reflects the shape of the roughening particles when the sample surface is viewed from above in a direction perpendicular to the surface of the sample, i.e., the particle width of the roughening particles, particularly since the reflection angle is 0°, which is perpendicular to the surface of the sample. The higher the brightness Y value, the larger the particle width of the roughening particles, which increases the resistance of the surface-treated copper foil to powder shedding (less likely to occur), and the lower the brightness Y value, the better the laser processability (reduction of resin residue at the bottom of the via hole).

[0021] (c) Ssk The Ssk of a roughened surface can be used to evaluate the bias in the distribution of roughening particle heights when the roughening particles are observed from the surface. The larger the Ssk, the easier it is for the laser light to reach the base of the roughening particles, resulting in better laser processability (reducing resin residue at the base of the roughening particles), and the smaller the Ssk, the better the resistance to powder shedding.

[0022] Although these three items (a), (b), and (c) each have a trade-off relationship, we have found that by controlling them within a predetermined range, copper foil exhibiting the above-mentioned effects can be obtained. One method for controlling these three items within a predetermined range is, for example, to perform a two-stage electroplating process using different electrolytic solutions during the roughening treatment, and then control the temperature ratio in the vertical direction inside the electrolytic bath in the second stage of electroplating. By controlling the temperature ratio in the vertical direction inside the electrolytic bath within a certain range, the growth rate of the roughening particles during the second stage of roughening treatment changes. Therefore, we believe that it is possible to form roughening particles with a biased distribution while achieving a predetermined distribution of specular reflectance and brightness Y value.

[0023] The specular reflectance of the roughened surface is measured using a spectrophotometer. Light from a light source is split into wavelengths of 600 nm, and the light is polarized at 45°. The specular reflectance of the roughened surface is measured under the conditions that the angle of incidence and the angle of reflection are both 70°. Note that "45° polarization" means that a polarizer that sets s-polarized light at 0° and p-polarized light at 90° is placed in front of the sample, and the light source is emitted with the polarizer at 45°. The specular reflectance of the roughened surface must be 0.20% or more and 0.90% or less, but the lower limit may be 0.26% or more, and the upper limit may be 0.78% or less.

[0024] In this specification, the Y value of brightness refers to the Y value representing reflectance in the XYZ color system defined by the International Commission on Illumination (CIE). The method for measuring the Y value of brightness of a roughened surface is not particularly limited, but it can be measured, for example, using a colorimeter. For example, the Y value of brightness of the roughened surface can be measured by irradiating the roughened surface with white light at an incident angle of 45° and a reflection angle of 0°. The brightness Y value of the roughened surface must be 10.0 or more and 15.5 or less, but the lower limit may be 11.0 or more, and the upper limit may be 15.0 or less, or 14.5 or less.

[0025] In the surface-treated copper foil according to the first embodiment, the Ssk of the roughened surface measured using a laser microscope is 0.30 or more and 0.80 or less. The Ssk of the roughened surface is measured by irradiating the roughened surface with a laser of a specific wavelength using a laser microscope. An example of the wavelength of the irradiated laser is 404 nm.

[0026] The numerical range of Ssk of the roughened surface must be 0.30 or more and 0.80 or less, but the lower limit may be 0.35 or more, and the upper limit may be 0.70 or less.

[0027] In the surface-treated copper foil according to the first embodiment, a nickel coating may be formed on the roughened surface, and the amount of nickel (Ni) deposited by the nickel coating is 0.20 mg / dm 2 More than 0.40mg / dm 2 If the surface-treated copper foil has a nickel coating, the rust prevention and heat resistance of the surface-treated copper foil will be improved.

[0028] At least one of a nickel coating, a zinc coating, and a chromium coating may be laminated on the roughened surface. The coating formed by laminating at least one of a nickel coating, a zinc coating, and a chromium coating functions as a rust-proofing layer, thereby further improving the rust prevention of the surface-treated copper foil.

[0029] A chemical adhesive layer containing a chemical adhesive may be further laminated on the rust-proofing layer. The chemical adhesive layer can be formed by a chemical adhesive treatment using a chemical adhesive such as a silane coupling agent. The chemical adhesive layer further enhances the adhesion between the surface-treated copper foil and the resin substrate. Note that the rust-proofing layer and the chemical adhesive layer are very thin, so they do not affect the shape of the roughening particles on the roughened surface of the surface-treated copper foil.

[0030] Furthermore, examples of methods for forming the chemical adhesive layer include a method in which a silane coupling agent solution is applied directly to the roughened surface of the surface-treated copper foil or indirectly via an anticorrosion layer or the like, and then air-dried (natural drying) or heat-dried. The applied silane coupling agent solution can be dried by evaporating water, but heat-drying at a temperature of 50°C or higher and 180°C or lower is preferred because it promotes the reaction between the silane coupling agent and the copper foil.

[0031] The chemical adhesive layer preferably contains one or more silane coupling agents selected from the group consisting of epoxy silanes, amino silanes, vinyl silanes, methacrylic silanes, acrylic silanes, styryl silanes, ureido silanes, mercapto silanes, sulfide silanes, and isocyanate silanes.These silane coupling agents have different effects depending on the interaction with the reactive functional groups contained in the resin of the resin substrate, so it is necessary to select an appropriate one taking into consideration its compatibility with the resin.

[0032] Specific examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and bis(3-(triethoxysilyl)propyl)disulfide. However, other silane coupling agents can also be appropriately selected and used. These silane coupling agents can be used alone or in combination of two or more.

[0033] [Surface-treated copper foil according to the second embodiment] The surface-treated copper foil according to the second embodiment is a surface-treated copper foil having a roughened surface on at least one side on which roughening particles are formed, and when the surface-treated copper foil is cut to reveal a cross section perpendicular to the roughened surface, the physical property values ​​of the roughened surface measured by observing the cross section with a scanning electron microscope satisfy the following (F), (G), and (H): (f) The average value h_ave of the cross-sectional particle height of the roughening particles is 0.35 μm or more and 0.70 μm or less. (g) The standard deviation w_σ of the cross-sectional particle width of the roughening particles is 0.05 μm or more and 0.10 μm or less. (H) The skewness h_sk of the cross-sectional particle height of the roughening particles is 0.80 or more and -2.50 × h_ave + 3.50 or less.

[0034] The surface-treated copper foil according to the second embodiment has been subjected to a surface treatment such as a roughening treatment (e.g., copper plating) on ​​at least one of the front and back surfaces. The roughened surface has a roughened surface on which roughening particles are formed by the roughening treatment. The entire surface of the surface-treated copper foil may be a roughened surface, or a portion of the surface may be a roughened surface. When producing the surface-treated copper foil, the raw material copper foil is subjected to a roughening treatment. Examples of the raw material copper foil include electrolytic copper foil and rolled copper foil.

[0035] Furthermore, by using a surface-treated copper foil whose roughened surface satisfies the above-mentioned features (f), (g), and (h), it is possible to manufacture a printed wiring board or the like that has excellent adhesion between the resin substrate and the surface-treated copper foil, small transmission loss, and good laser processability. Furthermore, since the transmission loss is small even when a high-frequency signal is transmitted to the circuit of the manufactured printed wiring board, the surface-treated copper foil according to the second embodiment can be suitably used for manufacturing a printed wiring board used in the high-frequency band (a printed wiring board having a high-frequency circuit).

[0036] The surface-treated copper foil according to the second embodiment will be described in more detail. The above-mentioned effects are achieved when the roughening particles on the roughened surface have a shape that satisfies the above-mentioned features (f), (g), and (h). While the mechanism is not entirely clear, it is presumed that the above-mentioned effects can be achieved by defining the ranges of parameters obtained from the distribution of the cross-sectional particle heights and widths of the roughening particles, which can only be accurately determined by observing a scanning electron microscope (SEM) image of the cross section of the surface-treated copper foil.

[0037] More specifically, the average cross-sectional particle height h_ave of the roughening particles is 0.35 μm or more and 0.70 μm or less, and the larger the average cross-sectional particle height h_ave of the roughening particles, the better the adhesion between the resin substrate and the surface-treated copper foil, and the smaller the average cross-sectional particle height h_ave of the roughening particles, the smaller the transmission loss. The standard deviation w_σ of the cross-sectional particle width of the roughening particles is 0.05 μm or more and 0.10 μm or less. The larger the standard deviation w_σ of the cross-sectional particle width of the roughening particles, the better the adhesion between the resin substrate and the surface-treated copper foil, and the smaller the standard deviation w_σ of the cross-sectional particle width of the roughening particles, the better the laser processability (reduction of resin residue at the bottom of the via hole).

[0038] Furthermore, the skewness h_sk of the cross-sectional particle height of the roughening particles is 0.80 or more and -2.50 × h_ave + 3.50 or less. The larger the skewness h_sk of the cross-sectional particle height of the roughening particles, the better the laser processability (reduction of resin residue at the base of the roughening particles), and the smaller the skewness h_sk of the cross-sectional particle height of the roughening particles, the better the resistance to powder shedding. Note that the "h_ave" in "0.80 or more and -2.50 × h_ave + 3.50 or less" is the average cross-sectional particle height h_ave of the roughening particles.

[0039] Although these three items (f), (g), and (h) each have a trade-off relationship, we have found that controlling them within a predetermined range can produce copper foil with the above-mentioned effects. One method for controlling these three items within a predetermined range is, for example, performing a two-stage electroplating process using different electrolytic solutions during the roughening treatment and controlling the vertical flow rate ratio of the electrolytic solution in the electrolytic bath in the second stage of electroplating. By controlling the vertical flow rate ratio of the electrolytic solution in the electrolytic bath within a certain range, it is expected that a height distribution will occur in the flow rate of the electrolytic solution near the cathode during the second stage of roughening treatment, which will affect the growth rate of the roughening particles. This will change the growth rate of the roughening particles during the second stage of roughening treatment. Therefore, while the average cross-sectional particle height h_ave and the standard deviation w_σ of the cross-sectional particle width of the roughening particles are within the above-mentioned predetermined range, a certain bias will occur in the distribution of the cross-sectional particle height of the roughening particles, and it is believed that roughening particles can be formed in which the skewness h_sk of the cross-sectional particle height of the roughening particles is within the above-mentioned predetermined range.

[0040] The cross-sectional particle height of the roughening particles in the surface-treated copper foil according to the second embodiment is the length of a specific roughening particle in the direction in which the roughening particle protrudes from the roughened surface of the surface-treated copper foil. The average cross-sectional particle height of the roughening particles must be 0.35 μm or more and 0.70 μm or less, but the lower limit may be 0.40 μm or more. The upper limit may be 0.60 μm or less.

[0041] The cross-sectional particle width of a roughening particle in the surface-treated copper foil according to the second embodiment is the length of a specific roughening particle in a direction perpendicular to the direction in which the roughening particle protrudes from the roughened surface of the surface-treated copper foil. The standard deviation of the cross-sectional particle width of the roughening particle must be 0.05 μm or more and 0.10 μm or less, with the lower limit being 0.06 μm or more. The upper limit being 0.09 μm or less.

[0042] At least one of a nickel coating, a zinc coating, and a chromium coating may be laminated on the roughened surface. The coating formed by laminating at least one of a nickel coating, a zinc coating, and a chromium coating functions as a rust-proofing layer, thereby further improving the rust prevention of the surface-treated copper foil.

[0043] A chemical adhesive layer containing a chemical adhesive may be further laminated on the rust-proofing layer. The chemical adhesive layer can be formed by a chemical adhesive treatment using a chemical adhesive such as a silane coupling agent. The chemical adhesive layer further enhances the adhesion between the surface-treated copper foil and the resin substrate. Note that the rust-proofing layer and the chemical adhesive layer are very thin, so they do not affect the shape of the roughening particles on the roughened surface of the surface-treated copper foil.

[0044] Furthermore, examples of methods for forming the chemical adhesive layer include a method in which a silane coupling agent solution is applied directly to the roughened surface of the surface-treated copper foil or indirectly via an anticorrosion layer or the like, and then air-dried (natural drying) or heat-dried. The applied silane coupling agent solution can be dried by evaporating water, but heat-drying at a temperature of 50°C or higher and 180°C or lower is preferred because it promotes the reaction between the silane coupling agent and the copper foil.

[0045] The chemical adhesive layer preferably contains one or more silane coupling agents selected from the group consisting of epoxy silanes, amino silanes, vinyl silanes, methacrylic silanes, acrylic silanes, styryl silanes, ureido silanes, mercapto silanes, sulfide silanes, and isocyanate silanes.These silane coupling agents have different effects depending on the interaction with the reactive functional groups contained in the resin of the resin substrate, so it is necessary to select an appropriate one taking into consideration its compatibility with the resin.

[0046] Specific examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and bis(3-(triethoxysilyl)propyl)disulfide. However, other silane coupling agents can also be appropriately selected and used. These silane coupling agents can be used alone or in combination of two or more.

[0047] [Copper-clad laminate] As shown in FIG. 1, the copper-clad laminate 30 according to this embodiment comprises a surface-treated copper foil 10 according to the first or second embodiment, and a resin substrate 20 bonded to the roughened surface 10a of the surface-treated copper foil 10.

[0048] The copper-clad laminate 30 according to this embodiment includes the surface-treated copper foil 10 according to the first or second embodiment. Therefore, by using the copper-clad laminate 30 according to this embodiment, it is possible to manufacture printed wiring boards and the like that have excellent adhesion between the resin substrate 20 and the surface-treated copper foil 10, small transmission loss, and good laser processability.

[0049] The type of resin forming the resin substrate is not particularly limited, but examples include thermoplastic resins such as liquid crystal polymer, polyether ether ketone, polyphenylene sulfide, polyphenylene ether, polyphenylene oxide, polyetherimide, polyethersulfone, polyethylene naphthalate, polyethylene terephthalate, thermoplastic polyimide, and cyclic polyolefin, as well as thermosetting resins such as polyimide, heat-resistant epoxy resin, cyanate-based resin (e.g., bismaleimide triazine), and thermosetting-modified polyphenylene ether.

[0050] Among these resins, preferred are liquid crystal polymers such as thermotropic liquid crystal polymers, rheotropic liquid crystal polymers, etc. Examples of thermotropic liquid crystal polymers include liquid crystal polyesters, and examples of liquid crystal polyesters include aromatic polyesters obtained by reacting an aromatic hydroxycarboxylic acid as an essential monomer with an aromatic dicarboxylic acid or an aromatic diol.

[0051] Specific examples of aromatic polyesters include polyesters synthesized from parahydroxybenzoic acid (PHB), phthalic acid, and 4,4'-biphenol, polyesters synthesized from PHB and 2,6-hydroxynaphthoic acid, and polyesters synthesized from PHB, terephthalic acid, and ethylene glycol.

[0052] [Printed wiring board] The printed wiring board according to this embodiment includes the copper-clad laminate according to the above embodiment. Since the printed wiring board according to this embodiment includes the surface-treated copper foil according to the first or second embodiment, the adhesion between the resin substrate and the surface-treated copper foil is excellent, the transmission loss is small, and the laser processability is good.

[0053] In the printed wiring board according to the present embodiment, the surface-treated copper foil and the resin substrate may be plastically deformed. The printed wiring board according to the present embodiment is composed of a metal foil and a resin substrate (e.g., a thermoplastic resin film), and therefore is easily plastically deformed. When heated, it becomes even more easily plastically deformed.

[0054] Furthermore, in the printed wiring board according to this embodiment, the surface-treated copper foil and the resin base material may be bent together. Fig. 2 is a cross-sectional view showing an example of a printed wiring board in which the surface-treated copper foil and the resin base material are bent together. In the printed wiring board according to this embodiment, the resin base material and the surface-treated copper foil have excellent adhesion to each other, so that the resin base material and the surface-treated copper foil can be bent together without peeling off when deformed.

[0055] The printed wiring board according to this embodiment can be subjected to various stresses and deformations within the scope of the present invention depending on the configuration of the electronic circuit board and the manufacturing conditions, but the printed wiring board according to this embodiment may or may not be bent when incorporated into an electronic device.

[0056] The printed wiring board according to this embodiment may form a transmission line. The printed wiring board according to this embodiment may also form a stripline, microstrip, or coplanar transmission line. Since the printed wiring board according to this embodiment has low transmission loss, it has good characteristics even when the roughened surfaces are opposed to each other, and can form transmission lines of any shape.

[0057] FIG. 3 is a cross-sectional view showing an example of a printed wiring board constituting a stripline transmission line. At least one of the multiple surface-treated copper foils of the printed wiring board of FIG. 3 is the surface-treated copper foil according to the first embodiment or the second embodiment. The surface-treated copper foil according to the first embodiment or the second embodiment has excellent adhesion to a resin substrate, low transmission loss, and excellent laser processability, and therefore can be used as any of the multiple surface-treated copper foils of the printed wiring board. That is, it can be used as the surface-treated copper foil located in the outermost layer of the printed wiring board, or as the surface-treated copper foil located inside the printed wiring board.

[0058] [Example] The present invention will be described in more detail below with reference to examples and comparative examples. [Examples and Comparative Examples of Surface-Treated Copper Foil According to the First Embodiment] [1] Preparation of copper foil substrate An electrolytic copper foil was prepared as the copper foil that would be the raw material for the surface-treated copper foil. This electrolytic copper foil would serve as the copper foil substrate for the roughening treatment. The electrolytic copper foil was produced by electrolysis under the following conditions. The electrolytic copper foil produced under the following conditions had a thickness of 12 μm and a surface roughness (ten-point average roughness Rzjis according to JIS B0601-2001) of 1.1 μm. The surface roughness was measured on the surface of the electrolytic copper foil using a contact-type surface roughness tester (Surfcorder SE1700 manufactured by Kosaka Laboratory Co., Ltd.).

[0059] <Manufacturing conditions for electrolytic copper foil> Copper concentration in electrolyte: 80g / L Electrolyte H2SO4 concentration: 70g / L Chlorine concentration of electrolyte: 25mg / L Bath temperature: 55℃ Current density: 45A / dm 2

[0060] <Additives to electrolyte and their concentrations> Sodium 3-mercapto-1-propanesulfonate: 2 mg / L Hydroxyethylcellulose: 10mg / L ·Low molecular weight glue (molecular weight 3000): 50mg / L

[0061] [2] Roughening treatment Next, one side of the copper foil substrate prepared in [1] above was subjected to a plating treatment as a roughening treatment to form a roughened surface, thereby producing a surface-treated copper foil. This plating treatment was a two-stage electroplating treatment. The first-stage plating treatment (1) used a first-stage treatment solution with the following composition, and the current density and current application time were as shown in Table 1. The second-stage plating treatment (2), which was performed following the first-stage plating treatment (1), used a second-stage treatment solution with the following composition, and the current density, current application time, and vertical temperature ratio in the electrolytic cell were as shown in Table 1. The vertical temperature ratio in the electrolytic cell was calculated by dividing the temperature (K) of the electrolytic solution above the opening in the electrolytic cell by the temperature (K) of the electrolytic solution below the opening in the electrolytic cell. If necessary, additional treatments may be performed before the first-stage plating treatment (1) and after the second-stage plating treatment (2).

[0062] <First stage processing solution> Copper (Cu) concentration: 60g / L Sulfuric acid (H2SO4) concentration: 120g / L Bath temperature: 60℃

[0063] <Second stage processing solution> Copper concentration: 20~30g / L H2SO4 concentration: 150g / L Molybdenum (Mo) concentration: 0.2 to 0.4 g / L Iron (Fe) concentration: 2g / L Bath temperature: 30~40℃

[0064] [3] Formation of base layer and intermediate layer Next, the roughened surface of the surface-treated copper foil produced in [2] above was metal-plated in the following order under the conditions below to form a base layer and an intermediate layer: nickel, zinc (Zn), and chromium (Cr).

[0065] <Niめっき> Ni concentration in plating solution: 40g / L H3BO3 concentration in plating solution: 5g / L Bath temperature: 20℃ Plating solution pH: 3.6 Current density: As shown in Table 1 Processing time: 10 seconds

[0066] <Znめっき> Zn concentration in plating solution: 2.5g / L NaOH concentration in plating solution: 40g / L Bath temperature: 20℃ Plating solution pH: 3.6 Current density: 0.3A / dm 2 Processing time: 5 seconds

[0067] <Crめっき> Cr concentration in plating solution: 5g / L Bath temperature: 30℃ Plating solution pH: 2.2 Current density: 5A / dm 2 Processing time: 5 seconds

[0068] [4] Formation of a silane coupling agent layer Finally, a silane coupling agent layer was formed on the intermediate layer (particularly the outermost Cr plating layer) formed in [3] above. The silane coupling agent layer was formed by applying a 3% by mass aqueous solution of 3-glycidoxypropyltrimethoxysilane onto the intermediate layer and drying it at 100°C. The amount of silane attached was 0.003 mg / dm2 in terms of silicon (Si) atoms. 2 is.

[0069] [Table 1]

[0070] The surface-treated copper foils of Examples A1 to A10 and Comparative Examples A1 to A10 were produced as described in [1] to [4] above. Some of the production conditions for the surface-treated copper foils were as described above, and the remaining conditions were as shown in Table 1. Various physical properties were measured for the roughened surface of each of the surface-treated copper foils obtained. Furthermore, the adhesion to the resin substrate, transmission loss, powder shedding resistance, copper foil oxidation, and laser processability were evaluated for each of the surface-treated copper foils obtained. The measurement and evaluation methods are explained below. The measurement and evaluation results are shown in Table 1.

[0071] <Specular reflectance of roughened surface> The specular reflectance of the roughened surface was measured using a spectrophotometer V-780 and absolute reflectance measurement unit ARSN-918i manufactured by JASCO Corporation. The incident light used for the measurement was 45° polarized light with a wavelength of 600.0 nm and a bandwidth of 5.0 nm, and no aperture was used.

[0072] The surface-treated copper foil was placed in a spectrophotometer so that the incident surface of the incident light was parallel to the transverse direction (TD), which is perpendicular to the machine direction (MD) of the copper foil when manufacturing the electrolytic copper foil, and the specular reflectance of the roughened surface was measured under the condition that the angle of incidence and the angle of reflection were both 70°. Dark correction and blank correction were performed, and the measurement was repeated once.

[0073] <Y value of brightness of roughened surface> The Y value of the XYZ color system specified by CIE was measured using a lightness meter color meter SM-T45 manufactured by Suga Test Instruments Co., Ltd. The measurement conditions were as follows: the color measurement conditions were a C illuminant and a 2-degree field of view, the optical conditions were in accordance with condition a of JIS Z8722:2009, and an aperture with a diameter of 30 mm was used.

[0074] <Sk of roughened surface> Using a Keyence Corporation VK-X3100 confocal laser microscope, the Ssk of the roughened surface was measured according to the method specified in ISO 25178. The wavelength of the laser light source was 404 nm. Measurements were taken at five randomly selected locations on the roughened surface, and the average value was used as the Ssk of the roughened surface.

[0075] The magnification of the objective lens of the confocal laser microscope was 100x, the scan mode was laser confocal, the measurement size was 2048 × 1536, the measurement quality was high-resolution, the pitch was 0.06 μm, and the light intensity was automatically adjusted. Ssk was calculated using the following filter processing and calculation conditions.

[0076] Calculation area: 142 μm (TD direction) × 106 μm (MD direction) Image processing: Reference plane setting (calculation area: entire) Smoothing (Gaussian, size 3x3) S filter: None F-operation: None L filter: 0.01 μm (Gaussian, end effect correction: ON)

[0077] <Amount of nickel deposited by nickel coating> The amount of nickel deposited on the roughened surface of the surface-treated copper foil was measured by X-ray fluorescence analysis using a scanning X-ray fluorescence analyzer, ZSX Primus IV, manufactured by Rigaku Corporation. The amount of nickel atoms was quantified using a calibration curve obtained using known standard samples.

[0078] <Adhesion to resin substrates> A surface-treated copper foil was laminated on one side of a 50 μm thick liquid crystal polymer film (manufactured by Ise Murata Manufacturing Co., Ltd., thickness precision: 0.7 μm, relative dielectric constant: 3.4, dielectric dissipation factor: 0.0020, ratio of maximum to minimum coefficient of linear thermal expansion: 1.4) so ​​that the roughened surface was in contact with the liquid crystal polymer film, and a polyimide film ("Upilex 20S" manufactured by UBE Corporation) was laminated on the other side as a release material to obtain a laminate.

[0079] This laminate was sandwiched between two 2 mm thick stainless steel plates, and the laminate sandwiched between the stainless steel plates was then sandwiched between two 1 mm thick stainless steel fiber woven fabric cushioning materials, and placed in a vacuum press. The vacuum press was then used to hold the laminate at a temperature of 300°C and a pressure of 3 MPa for 5 minutes. After cooling, the thermocompression-bonded laminate was removed from the vacuum press, and the release material was removed to obtain a single-sided copper-clad laminate.

[0080] Using a tensile testing machine ("AGS-H" manufactured by Shimadzu Corporation), the strength (unit: N / mm) was measured when the surface-treated copper foil was peeled off from this single-sided copper-clad laminate in a 180° direction at a speed of 50 mm / min in accordance with the method specified in JIS C6471-1995. Specifically, a 5 mm wide masking tape was attached to the copper foil of a single-sided copper-clad laminate, and the laminate was immersed in a ferric chloride solution to etch and remove unnecessary portions of the copper foil. The single-sided copper-clad laminate was then washed with water, the masking tape was peeled off, and the laminate was dried in a circulating oven at 80°C for 1 hour to form a 5 mm wide linear circuit pattern.

[0081] To prevent the test piece (single-sided copper-clad laminate) from bending and changing the peel angle when peeling the copper foil from the single-sided copper-clad laminate, the test piece was attached to a reinforcing plate with a thickness of 1 mm or more. One end of the formed circuit pattern was peeled off and the test piece was clamped in the tensile tester. The copper foil was then peeled at a 180° angle to the test piece at a speed of 50 mm / min for 10 mm or more. The average strength during this peeling was calculated, and this value was taken as the peel strength (N / mm). The results are shown in Table 1. In the examples and comparative examples, the 180° peel strength was measured as an index of the adhesion between the resin substrate and the surface-treated copper foil, and a 180° peel strength of 0.70 N / mm or more was evaluated as pass, and a 180° peel strength of less than 0.70 N / mm was evaluated as fail.

[0082] <Transmission loss> A double-sided copper-clad laminate was produced by bonding surface-treated copper foil to both sides of a 50 μm-thick liquid crystal polymer film (manufactured by Ise Murata Manufacturing Co., Ltd., thickness precision: 0.7 μm, relative dielectric constant: 3.4, dielectric dissipation factor: 0.0020, ratio of maximum to minimum coefficient of linear thermal expansion: 1.4) using a thermal fusion method.

[0083] Next, the surface-treated copper foil on one side of the double-sided copper-clad laminate was etched to form a linear pattern of a specified width (110 μm) and length (20 mm and 50 mm) as a signal layer, and the surface-treated copper foil on the other side was used as a ground layer to produce a circuit board with a microstrip line structure. Furthermore, this circuit board was dried by being kept in a circulating oven at 50°C for 24 hours, and then cooled to room temperature under the standard environment described in JIS C6481-1996 to prepare a circuit board for evaluating high frequency characteristics.

[0084] Both ends of the pattern on the circuit board for evaluating high-frequency characteristics, fabricated as described above, were clamped between test fixtures, and a high-frequency signal (40 GHz) was passed through the pattern to measure the strength of the passing signal (S21). The signal strength was measured using a PNA microwave network analyzer N5227B manufactured by Keysight Technologies Inc. and a universal test fixture 3680V manufactured by Anritsu Corporation. The above measurement was performed five times using the same pattern, and the average value was taken as the transmission loss for each circuit board.

[0085] The transmission loss per unit length was calculated from the difference between the transmission loss of the circuit board for evaluating high-frequency characteristics with a pattern length of 20 mm and the transmission loss of the circuit board for evaluating high-frequency characteristics with a pattern length of 50 mm, and from the difference in the pattern lengths of both circuit boards for evaluating high-frequency characteristics.

[0086] Furthermore, the transmission loss per unit length of the surface-treated copper foils of each of the Examples and Comparative Examples was indexed, with the transmission loss per unit length of Example B2 described later being taken as the reference value (100). The results are shown in Table 1. In the Examples and Comparative Examples, when the transmission loss index exceeded 115, the transmission loss was evaluated as being large and unacceptable, and this is indicated by an x ​​in Table 1. When the transmission loss index was 115 or less, the transmission loss was evaluated as being small and acceptable, and this is indicated by a ∘ in Table 1. When the transmission loss index was 100 or less, the transmission loss was evaluated as being particularly small and acceptable, and this is indicated by a ⊚ in Table 1.

[0087] <Laser processability (reduction of resin residue at the bottom of via holes)> When blind via holes are formed by laser irradiation, resin derived from the resin substrate may remain at the bottom of the formed blind via holes. If the resin remains, sufficient conductivity may not be obtained even when an interlayer connector is formed, and the connection reliability at the time of interlayer connection may decrease. Copper-clad laminates were produced using surface-treated copper foil, and their laser processability, i.e., whether or not resin derived from the resin substrate is likely to remain at the bottom of the formed blind via holes when formed by laser irradiation, was evaluated.

[0088] A single-sided copper-clad laminate was produced by bonding a 12 μm thick surface-treated copper foil to one side of a 50 μm thick liquid crystal polymer film (manufactured by Ise Murata Manufacturing Co., Ltd., thickness precision: 0.7 μm, relative dielectric constant: 3.4, dielectric dissipation factor: 0.0020, ratio of maximum to minimum coefficient of linear thermal expansion: 1.4) using a thermal fusion method.

[0089] Next, a carbon dioxide laser was used to irradiate the liquid crystal polymer film side of the single-sided copper-clad laminate, forming 150 via holes at random locations. The via holes had a diameter of 100 μm. The laser irradiation was performed under the following conditions: pulse width 1-5 μs, tip energy 1-3 mJ, mask diameter 1-3 mm, and number of shots 5-10, depending on the structure of the roughening particles.

[0090] After the via holes were formed, the roughened surface of the surface-treated copper foil at the bottom of the via holes was observed to check for the presence or absence of residual resin. The presence or absence of residual resin was confirmed by removing the surface-treated copper foil by etching after laser processing, and then observing with an optical microscope at 10x magnification to see if any resin remained as a film at the bottom of the via holes. Optical microscope observation was performed on all 150 via holes, and the number of via holes without residual resin was counted.

[0091] In the examples and comparative examples, when the number of via holes with no residual resin was 80 or more, the processability was evaluated as excellent and the result was "pass," and this is indicated by a double circle in Table 1. When the number of via holes with no residual resin was 40 to 79, the result was "pass," and this is indicated by a circle in Table 1. When the number of via holes with no residual resin was 39 or less, the result was "fail," and this is indicated by an x ​​in Table 1.

[0092] <Laser processability (reduction of resin residue at the base of roughening particles)> The present invention aims to provide a printed wiring board having excellent adhesion between a resin substrate and a surface-treated copper foil, low transmission loss, and good long-term connection reliability. Specifically, the present invention aims to prevent resin from remaining at the base of roughening particles in the surface-treated copper foil, thereby preventing cracks from occurring between the resin substrate and the surface-treated copper foil due to thermal stress during long-term use, which can cause poor connection or cracks, resulting in a decrease in connection reliability.

[0093] According to this embodiment, a printed wiring board can be provided that has excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and little resin residue at the base of the roughening particles (good laser processability).Since little resin residue at the base of the roughening particles occurs, long-term connection reliability can be ensured.

[0094] Copper-clad laminates were produced using the surface-treated copper foils, and their laser processability, i.e., whether or not resin derived from the resin substrate is likely to remain at the base of roughening particles in the formed blind via holes when formed by laser irradiation, was evaluated. As in the case of "Laser processability (suppression of resin residue at the bottom of via holes)," single-sided copper-clad laminates were prepared, and then via holes were formed using a carbon dioxide laser. The single-sided copper-clad laminates with via holes formed were then analyzed as follows.

[0095] First, the single-sided copper-clad laminate with via holes was pretreated. Osmium (Os) or platinum (Pt)-palladium (Pd) was vapor-deposited onto the single-sided copper-clad laminate. This allowed the bottom of the via holes to be observed using a scanning electron microscope (SEM). The single-sided copper-clad laminate was embedded in an embedding resin such as epoxy resin, and then cut to allow observation of the maximum diameter cross-section of the via holes. The exposed cross-section was then mirror-polished. Finally, polishing marks were removed using flat milling to obtain a sample for SEM observation.

[0096] The cross section of the sample was observed using a scanning electron microscope, and secondary electron images (SEM images) were obtained at 5,000x magnification. The acceleration voltage of the scanning electron microscope was 10 kV. SEM images with a width of 25 μm were obtained in one field of view, and SEM images were obtained in each of 10 fields of view. These 10 SEM images were then analyzed to evaluate the degree of resin remaining at the bottom of the via hole. This is explained below.

[0097] First, the contour of the surface shape of the roughened surface is extracted. Then, among the roughening particles present in a single field of view, the roughening particle with the highest tip is selected and that tip is taken as the highest point of that field of view. Furthermore, among the roughening particles present in a single field of view, the gap with the lowest bottom between the roughening particles is selected and that bottom of that gap is taken as the lowest point of that field of view.

[0098] Next, a highest line is drawn that passes through the highest point and is parallel to the surface of the copper foil (i.e., a line parallel to the width of the field of view), and a lowest line is drawn that passes through the lowest point and is parallel to the surface of the copper foil, and the area between these two lines is defined as the measurement area.The height (height from the lowest line) that is 25% of the height of this measurement area (the distance between the highest line and the lowest line) is defined as the "reference height."

[0099] At this reference height, gaps between roughening particles with a width of 0.2 μm or more were defined as "valleys" between the roughening particles. If resin remained in the valleys, the degree of resin remaining at the base of the roughening particles was evaluated based on the distance between the bottom of the valley and the surface of the remaining resin.

[0100] The degree of resin remaining at the base of the roughening particles was calculated for all valleys within a 25 μm area centered on the center of the bottom of the via hole, and the degree of resin remaining at the base of the roughening particles was calculated for a total of 10 fields of view.The laser processability (reduction of resin remaining at the base of the roughening particles) was then evaluated using the average value.The results are shown in Table 1.

[0101] In the examples and comparative examples, when the distance between the bottom of the valley and the surface of the remaining resin is 0.6 μm or less, it is evaluated as passing, and is indicated by a circle in Table 1. When the distance between the bottom of the valley and the surface of the remaining resin exceeds 0.6 μm, it is evaluated as failing, and is indicated by an x ​​in Table 1. The bottom of the valley is defined as the intersection of a line perpendicular to the line representing the reference height and passing through the center of the valley with the surface of the copper foil.

[0102] <Dust shedding resistance> After attaching a reference plate to the non-roughened side of the surface-treated copper foil, a piece of white dust-free paper was placed in contact with the roughened surface of the surface-treated copper foil. A 1 kg weight was placed on the white dust-free paper, and the white dust-free paper was moved 50 mm in a direction parallel to the contact surface between the roughened surface and the white dust-free paper at a speed of 100 mm / min.

[0103] The surface of the white dust-free paper was photographed using an optical microscope under reflected light to obtain a magnified image. The magnification was 20x. The brightest part of the enlarged image was assigned a brightness of 255, and the darkest part a brightness of 0. Areas with a brightness of 200 or less were considered to be copper powder transferred to the white dust-free paper (copper powder resulting from the roughening particles). The percentage of the area of ​​the enlarged image with a brightness of 200 or less (area ratio) was then calculated. The results are shown in Table 1. In the examples and comparative examples, when the area ratio was less than 0.5%, it was evaluated as passing, and indicated by a circle in Table 1. When the area ratio was 0.5% or more, it was evaluated as failing, and indicated by an x ​​in Table 1.

[0104] <Oxidation of copper foil> The surface-treated copper foil was placed in an oven and heated, and the presence or absence of discoloration after heating was confirmed. The heating conditions were a temperature of 250°C, a heating time of 30 minutes, and an air atmosphere. The results are shown in Table 1. In the examples and comparative examples, if the surface-treated copper foil did not discolor, it was evaluated as passing, and this is indicated by a circle in Table 1. If the surface-treated copper foil did discolor, it was evaluated as failing, and this is indicated by an x ​​in Table 1.

[0105] Comparing Examples A1 to A10 with Comparative Examples A1 to A6, it can be seen that Examples A1 to A10 have excellent laser processability. Residual resin at the bottom of the via hole is suppressed, and residual resin at the base of the roughening particles is also suppressed, reducing the number of fracture origins in the via hole for interlayer connection. This allows for a printed wiring board with excellent not only initial connection reliability but also long-term connection reliability.

[0106] Figure 7 shows a cross-sectional view of a copper-clad laminate using conventional surface-treated copper foil. The cross-section of a via hole in Figure 7 reveals that resin remains at the base of the roughening particles at the bottom of the via hole. This makes it easy for cracks to form at the interface between the interlayer connection conductor in the via hole and the surface-treated copper foil.

[0107] Fig. 8 is a cross-sectional view of a copper-clad laminate using the surface-treated copper foil of the first embodiment. Fig. 8 shows a cross-section of a via hole, and it can be seen that because the laser light is easily guided to the base of the roughening particles, the resin is prevented from remaining at the base of the roughening particles at the bottom of the via hole. This strengthens the bond between the interlayer connection conductor in the via hole and the surface-treated copper foil, making it less likely for cracks to form at the interface between the interlayer connection conductor and the surface-treated copper foil. The process for forming via holes, circuit patterns, and interlayer connectors in the copper clad laminate is as shown in FIG. 4, and the specific details are as follows.

[0108] An example of a process for forming blind via holes in a double-sided copper-clad laminate 100 by laser irradiation is shown in Figure 5. Also, an example of a process for forming blind via holes in a single-sided copper-clad laminate 100 by laser irradiation is shown in Figure 6. The process for forming blind via holes is almost the same for both double-sided and single-sided copper-clad laminates, so the following explanation will be given using a double-sided copper-clad laminate as an example. Note that the same reference numerals are used to designate corresponding components in Figures 5 and 6.

[0109] A copper clad laminate 100 shown in (a) of Fig. 5 is irradiated with a laser 130 to form a blind via hole (see (b) of Fig. 5). When forming a blind via hole by laser irradiation, residue 120 (metal originating from the surface-treated copper foil 111 and resin originating from the resin substrate 113) may remain at the bottom 140 of the blind via hole after processing by irradiating with the laser 130 (see (b) of Fig. 5).

[0110] Therefore, after the blind via holes are formed in the copper clad laminate 100, a desmear process is performed to remove residues 120 in the blind via holes (see (c) of FIG. 5). Then, after the desmear process, an interlayer connector 116 is formed. Methods for forming the interlayer connector 116 include a method of forming a plating film 115 and a method of filling the blind via holes with at least one of plating and metal paste to form the interlayer connector 116. As shown in Fig. 5(d), a plating process can be performed to form a plating film 115 on the inner surface of the blind via hole. Also, as shown in Fig. 5(e), the blind via hole can be filled with at least one of plating and metal paste to form an interlayer connector 116. Note that the top surface of the interlayer connector 116 does not need to be flush with the surfaces of the surface-treated copper foil 111 and the resin base material 113.

[0111] [Examples and Comparative Examples of Surface-Treated Copper Foil According to the Second Embodiment] [1] Preparation of copper foil substrate An electrolytic copper foil was prepared as the copper foil that would be the raw material for the surface-treated copper foil. This electrolytic copper foil would serve as the copper foil substrate for the roughening treatment. The electrolytic copper foil was produced by electrolysis under the following conditions. The electrolytic copper foil produced under the following conditions had a thickness of 12 μm and a surface roughness (ten-point average roughness Rzjis according to JIS B0601-2001) of 1.1 μm. The surface roughness was measured on the surface of the electrolytic copper foil using a contact-type surface roughness tester (Surfcorder SE1700 manufactured by Kosaka Laboratory Co., Ltd.).

[0112] <Manufacturing conditions for electrolytic copper foil> Copper concentration in electrolyte: 80g / L Electrolyte H2SO4 concentration: 70g / L Chlorine concentration of electrolyte: 25mg / L Bath temperature: 55℃ Current density: 45A / dm 2

[0113] <Additives to electrolyte and their concentrations> Sodium 3-mercapto-1-propanesulfonate: 2 mg / L Hydroxyethylcellulose: 10mg / L ·Low molecular weight glue (molecular weight 3000): 50mg / L

[0114] [2] Roughening treatment Next, one side of the copper foil substrate prepared in [1] above was plated as a roughening treatment to form a roughened surface, thereby producing a surface-treated copper foil. This plating treatment was a two-stage electroplating treatment. The first-stage plating treatment (1) used a first-stage treatment solution with the following composition, and the current density and current application time were as shown in Table 2. The second-stage plating treatment (2), which was performed following the first-stage plating treatment (1), used a second-stage treatment solution with the following composition, and the current density, current application time, and vertical flow rate ratio of the electrolyte solution in the electrolytic cell were as shown in Table 2. The vertical flow rate ratio of the electrolyte solution in the electrolytic cell was determined by dividing the flow rate of the electrolyte solution above the opening in the electrolytic cell by the flow rate of the electrolyte solution below the opening in the electrolytic cell. If necessary, additional treatments may be performed before the first-stage plating treatment (1) and after the second-stage plating treatment (2).

[0115] <First stage processing solution> Copper (Cu) concentration: 60g / L Sulfuric acid (H2SO4) concentration: 120g / L Bath temperature: 60℃

[0116] <Second stage processing solution> Copper concentration: 20~30g / L H2SO4 concentration: 150g / L Molybdenum (Mo) concentration: 0.2 to 0.4 g / L Iron (Fe) concentration: 2g / L Bath temperature: 30~40℃

[0117] [3] Formation of base layer and intermediate layer Next, the roughened surface of the surface-treated copper foil produced in [2] above was metal-plated in the following order under the conditions below to form a base layer and an intermediate layer: nickel, zinc (Zn), and chromium (Cr).

[0118] <Niめっき> Ni concentration in plating solution: 40g / L H3BO3 concentration in plating solution: 5g / L Bath temperature: 20℃ Plating solution pH: 3.6 Current density: As shown in Table 2 Processing time: 10 seconds

[0119] <Znめっき> Zn concentration in plating solution: 2.5g / L NaOH concentration in plating solution: 40g / L Bath temperature: 20℃ Plating solution pH: 3.6 Current density: 0.3A / dm 2 Processing time: 5 seconds

[0120] <Crめっき> Cr concentration in plating solution: 5g / L Bath temperature: 30℃ Plating solution pH: 2.2 Current density: 5A / dm 2 Processing time: 5 seconds

[0121] [4] Formation of a silane coupling agent layer Finally, a silane coupling agent layer was formed on the intermediate layer (particularly the outermost Cr plating layer) formed in [3] above. The silane coupling agent layer was formed by applying a 3% by mass aqueous solution of 3-glycidoxypropyltrimethoxysilane onto the intermediate layer and drying it at 100°C. The amount of silane attached was 0.003 mg / dm2 in terms of silicon (Si) atoms. 2 is.

[0122] [Table 2]

[0123] The surface-treated copper foils of Examples B1 to B10 and Comparative Examples B1 to B9 were produced as described in [1] to [4] above. Some of the production conditions for the surface-treated copper foils were as described above, and the other conditions were as shown in Table 2. The roughened surface of each of the surface-treated copper foils obtained was measured for various physical properties. Furthermore, each of the surface-treated copper foils obtained was evaluated for adhesion to the resin substrate, transmission loss, powder shedding resistance, copper foil oxidation, and laser processability. The measurement and evaluation methods are explained below. The measurement and evaluation results are shown in Table 2.

[0124] <Average value of cross-sectional particle height of roughening particles h_ave, standard deviation of cross-sectional particle width w_σ, and skewness of cross-sectional particle height h_sk> First, a square test piece with sides of 5 mm obtained by cutting out a surface-treated copper foil was filled with an epoxy resin or the like (e.g., an epoxy-based adhesive) and cured. The surface-treated copper foil and resin were then cut to reveal a cross section perpendicular to the roughened surface. This cross section was then precision-polished using an IM4000 ion milling machine manufactured by Hitachi High-Technologies Corporation. The precision polishing conditions were stage mode C1 (swing angle: ±15°, swing speed: 6 round trips / min), acceleration voltage: 6 kV, and polishing time: 30 minutes. The precision polishing using the ion milling machine was performed with a protrusion amount that did not cause cracking of the resin, deformation of the surface-treated copper foil, or deformation of the roughening particles during cutting. The protrusion amount was, for example, approximately 50 μm.

[0125] The cross section was then observed using a scanning electron microscope (SEM) SU8020 manufactured by Hitachi High-Technologies Corporation, and a secondary electron image at a magnification of 5,000 times (see the SEM image in Figure 9) was obtained. The acceleration voltage of the scanning electron microscope was 3 kV. From the observation of the cross section, an SEM image of a rectangular region measuring 19 μm in length and 500 μm in width was prepared.

[0126] A cross section was randomly extracted from one surface-treated copper foil, and an SEM image of a rectangular region measuring 19 μm in length and 500 μm in width was obtained from the cross section. Since one SEM image that can actually be obtained using a scanning electron microscope is an SEM image of a rectangular region measuring 19 μm in length and 25 μm in width, an SEM image of a rectangular region measuring 19 μm in length and 500 μm in width is obtained by connecting 20 SEM images of a rectangular region measuring 19 μm in length and 25 μm in width so that the imaged region is continuous. The following image analysis was performed on these 20 consecutive SEM images, so the following image analysis was performed on a region 500 μm in length in the horizontal direction of the SEM image. As a result of performing the following image analysis on this 500 μm-long region, the surface-treated copper foil according to the present invention was found to satisfy the constituent requirements of the present invention.

[0127] When observing with an SEM, the surface-treated copper foil should be adjusted so that it is horizontal in the cross-sectional SEM image. If necessary, a copper-clad laminate or printed wiring board may be used as the observation sample for taking the cross-sectional SEM image. When using a copper-clad laminate or printed wiring board, there is no need to peel the surface-treated copper foil from the resin substrate; the copper-clad laminate or printed wiring board can be cut as is to process and observe the cross section.

[0128] The dimensions of the roughening particles formed on the roughened surface were measured by image analysis of the SEM images obtained by the SEM observations at 5,000x magnification. Specifically, a single roughening particle was identified in the SEM image, and the cross-sectional particle height and width of that roughening particle were measured. The cross-sectional particle heights and widths of multiple roughening particles were then measured, and the average cross-sectional particle height h_ave, the standard deviation of the cross-sectional particle width w_σ, and the skewness of the cross-sectional particle height h_sk were calculated.

[0129] The SEM image was processed using image analysis software (open-source freeware "ImageJ") to emphasize the outlines of the roughening particles, and then "binarized" to color-code the roughening particles. Image processing was then performed to remove noise that occurred during the "binarization" process, and further image processing was performed to white out the roughening particle areas that were displayed in black during the "binarization" process. The outlines of the roughening particles were then extracted, and the cross-sectional particle height and width of the roughening particles at the outlines were measured using common measurement software (Photo Ruler, etc.).

[0130] The cross-sectional particle height and cross-sectional particle width of the roughening particles can be measured using known processing software such as "WinROOF" or "Photo Ruler," which are general image measurement software. A detailed explanation will be given later. An example of the simplest method for measuring roughening particles (image analysis method) will be described below with reference to FIG. 10.

[0131] First, as shown in FIG. 10(a), a line L is drawn on the SEM image. The line L is parallel to the direction in which the roughening particles protrude from the roughened surface of the surface-treated copper foil and passes through the tip (vertex) V of the roughening particle. Next, as shown in FIG. 10(b), a rectangle Sq is drawn on the SEM image. The rectangle Sq has two sides (two vertical sides) parallel to the line L and two sides (top and bottom sides) perpendicular to the line L. The rectangle Sq may be a square. The top side of the rectangle Sq passes through the tip V of the roughening particle, and the bottom side contacts the base of the roughening particle along the outline of the roughening particle. There are two bases of the roughening particle along the outline of the roughening particle, and the rectangle Sq is drawn so that the bottom side contacts the base with the longer vertical side. The base refers to the boundary between the roughening particle and the surface of the copper foil substrate before roughening treatment, or the boundary between adjacent roughening particles along the outline of the roughening particle.

[0132] The bottom side of the rectangle Sq may contact the base of the roughening particle at one point on the outline of the roughening particle (when the roughening particle protrudes in a direction not perpendicular to the roughened surface) or at two points (when the roughening particle protrudes in a direction perpendicular to the roughened surface). When the bottom side of the rectangle Sq and the base of the roughening particle on the contour line of the roughening particle meet at a single point, the point of contact becomes one of the two corners on the bottom side of the rectangle Sq, and this corner is designated as R1.

[0133] When the bottom edge of the rectangle Sq and the base of the roughening particle on the contour line of the roughening particle meet at two points, the two contact points are the two corners on the bottom edge of the rectangle Sq, and one of the two corners is designated as R1. Furthermore, whether the bottom side of the rectangle Sq intersects with the base part of the roughening particle's contour line at one point or at two points, the other of the two corners on the bottom side of the rectangle Sq is defined as R2 (see (b) of Figure 10).

[0134] When the bottom side of the rectangle Sq and the base of the roughening particle's outline meet at a single point, the vertical side that passes through the corner R2 of the two vertical sides connecting the top and bottom sides of the rectangle Sq intersects with the base R2' of the roughening particle's outline. This base R2' is the base part of the rectangle Sq that does not meet the bottom side of the rectangle Sq.

[0135] 10(c), the length of the vertical side of the rectangle Sq is defined as the cross-sectional particle height h of the roughening particle. The length of the upper or lower side is defined as the cross-sectional particle width w of the roughening particle. Except for the special examples below, a convex portion obtained by drawing one rectangle Sq and measuring the cross-sectional particle height h and cross-sectional particle width w is considered to be one roughening particle.

[0136] For the cross-sectional SEM image, a region of 500 μm in length in the width direction of the SEM image is observed, and the cross-sectional particle height h and cross-sectional particle width w of each roughening particle are measured throughout that region. Then, based on the number of roughening particles measured, the average cross-sectional particle height h_ave, the standard deviation of cross-sectional particle width w_σ, and the skewness of cross-sectional particle height h_sk are calculated for the roughening particles. The standard deviation of cross-sectional particle width w_σ and the skewness of cross-sectional particle height h_sk are defined by the following formulas. In the formulas, there is a symbol with a horizontal bar (-) above x (X bar), which represents the measured values ​​x1, x2, x3, . . ., xn means the average value of

[0137]

number

[0138]

number

[0139] Next, an example in which the particles are not measured as roughening particles and a method for measuring roughening particles having special shapes (the above special example) will be described with reference to FIG. 11 as needed. The cross section of a roughening particle that protrudes obliquely from the cut surface to the inside may be partially reflected in the observed cross section. Although such a roughening particle appears to be floating above the surface-treated copper foil in the observed cross section, such a roughening particle is not included in the measurement of the cross-sectional particle height and cross-sectional particle width.

[0140] Furthermore, although not shown, among the protrusions measured according to the above criteria, those with a cross-sectional particle height of 0.15 μm or less do not affect the transmission characteristics and adhesion that are the focus of the present invention, and accurate measurement is difficult. Therefore, those with a cross-sectional particle height of 0.15 μm or less are not included in the measurement of cross-sectional particle height and cross-sectional particle width, and in this case are not included in the "roughening particles" of the present invention.

[0141] 11(a), among the convex portions measured according to the above criteria, those for which the ratio (h / w) of cross-sectional particle height h to cross-sectional particle width w is less than 0.40 do not affect the transmission characteristics or adhesion that are of interest in the present invention. Therefore, those for which the ratio (h / w) of cross-sectional particle height h to cross-sectional particle width w is less than 0.40 are not subject to measurement of cross-sectional particle height and cross-sectional particle width, and in this case are not included in the "roughening particles" of the present invention.

[0142] Next, Fig. 11(b) shows an example of measurement of a protrusion with two or more tips. In this case, as shown in Fig. 11(b), based on the above definition, each tip is regarded as one roughening particle, and the cross-sectional particle height and cross-sectional particle width are measured. Figure 11(c) is also an example of measuring a convex part with two or more tips, but if the straight line L' drawn for one convex part intersects with two vertical sides of the rectangle Sq of another convex part, that one convex part is not measured. For example, in Figure 11(c), the straight line L' drawn for the tip V' of one convex part intersects with two vertical sides of the rectangle Sq of another convex part that has the tip V, so the one convex part that has the tip V' is not measured.

[0143] However, when two or more convex portions have a relationship in which the straight lines L' intersect with two vertical sides of the rectangle Sq of other convex portions that are different from each other, the convex portion with the highest cross-sectional particle height h is the object of measurement, and the other convex portions are not the object of measurement because they have little effect on the transmission characteristics and adhesion that are the focus of the present invention.

[0144] Figure 11(d) shows a measurement example in which a convex portion exists on top of a convex portion whose ratio (h / w) of cross-sectional particle height h to cross-sectional particle width w is less than 0.40 and whose base portion is relatively unclear. In this case, the unclear base portion is not the measurement target, and the focus is on the convex portion with a distinct base portion, and measurement can be performed based on the above definition. This is because smooth convex portions with unclear base portions do not affect the transmission characteristics or adhesion that are the focus of the present invention. For roughening particles having shapes other than those described above, the cross-sectional particle height h and cross-sectional particle width w are measured according to the above criteria, taking into consideration the effects on transmission characteristics and adhesion that are of interest in the present invention.

[0145] <Adhesion to resin substrates> A surface-treated copper foil was laminated on one side of a 50 μm thick liquid crystal polymer film (manufactured by Ise Murata Manufacturing Co., Ltd., thickness precision: 0.7 μm, relative dielectric constant: 3.4, dielectric dissipation factor: 0.0020, ratio of maximum to minimum coefficient of linear thermal expansion: 1.4) so ​​that the roughened surface was in contact with the liquid crystal polymer film, and a polyimide film ("Upilex 20S" manufactured by UBE Corporation) was laminated on the other side as a release material to obtain a laminate.

[0146] This laminate was sandwiched between two 2 mm thick stainless steel plates, and the laminate sandwiched between the stainless steel plates was then sandwiched between two 1 mm thick stainless steel fiber woven fabric cushioning materials, and placed in a vacuum press. The vacuum press was then used to hold the laminate at a temperature of 300°C and a pressure of 3 MPa for 5 minutes. After cooling, the thermocompression-bonded laminate was removed from the vacuum press, and the release material was removed to obtain a single-sided copper-clad laminate.

[0147] Using a tensile testing machine ("AGS-H" manufactured by Shimadzu Corporation), the strength (unit: N / mm) was measured when the surface-treated copper foil was peeled off from this single-sided copper-clad laminate in a 180° direction at a speed of 50 mm / min in accordance with the method specified in JIS C6471-1995. Specifically, a 5 mm wide masking tape was attached to the copper foil of a single-sided copper-clad laminate, and the laminate was immersed in a ferric chloride solution to etch and remove unnecessary portions of the copper foil. The single-sided copper-clad laminate was then washed with water, the masking tape was peeled off, and the laminate was dried in a circulating oven at 80°C for 1 hour to form a 5 mm wide linear circuit pattern.

[0148] To prevent the test piece (single-sided copper-clad laminate) from bending and changing the peel angle when peeling the copper foil from the single-sided copper-clad laminate, the test piece was attached to a reinforcing plate with a thickness of 1 mm or more. One end of the formed circuit pattern was peeled off and the piece was clamped in the tensile tester. The copper foil was then peeled at a 180° angle to the test piece at a speed of 50 mm / min for 10 mm or more. The average strength during this peeling was calculated, and this value was taken as the peel strength (N / mm). The results are shown in Table 2. In the examples and comparative examples, the 180° peel strength was measured as an index of the adhesion between the resin substrate and the surface-treated copper foil, and a 180° peel strength of 0.70 N / mm or more was evaluated as pass, and a 180° peel strength of less than 0.70 N / mm was evaluated as fail.

[0149] <Transmission loss> A double-sided copper-clad laminate was produced by bonding surface-treated copper foil to both sides of a 50 μm-thick liquid crystal polymer film (manufactured by Ise Murata Manufacturing Co., Ltd., thickness precision: 0.7 μm, relative dielectric constant: 3.4, dielectric dissipation factor: 0.0020, ratio of maximum to minimum coefficient of linear thermal expansion: 1.4) using a thermal fusion method.

[0150] Next, the surface-treated copper foil on one side of the double-sided copper-clad laminate was etched to form a linear pattern of a specified width (110 μm) and length (20 mm and 50 mm) as a signal layer, and the surface-treated copper foil on the other side was used as a ground layer to produce a circuit board with a microstrip line structure. Furthermore, this circuit board was dried by being kept in a circulating oven at 50°C for 24 hours, and then cooled to room temperature under the standard environment described in JIS C6481-1996 to prepare a circuit board for evaluating high frequency characteristics.

[0151] Both ends of the pattern on the circuit board for evaluating high-frequency characteristics, fabricated as described above, were clamped between test fixtures, and a high-frequency signal (40 GHz) was passed through the pattern to measure the strength of the passing signal (S21). The signal strength was measured using a PNA microwave network analyzer N5227B manufactured by Keysight Technologies Inc. and a universal test fixture 3680V manufactured by Anritsu Corporation. The above measurement was performed five times using the same pattern, and the average value was taken as the transmission loss for each circuit board.

[0152] The transmission loss per unit length was calculated from the difference between the transmission loss of the circuit board for evaluating high-frequency characteristics with a pattern length of 20 mm and the transmission loss of the circuit board for evaluating high-frequency characteristics with a pattern length of 50 mm, and from the difference in the pattern lengths of both circuit boards for evaluating high-frequency characteristics.

[0153] Furthermore, the transmission loss per unit length of Example B2 was set as the reference value (100), and the transmission loss per unit length of the surface-treated copper foils of each Example and Comparative Example was indexed. The results are shown in Table 2. In the Examples and Comparative Examples, when the transmission loss index exceeded 115, the transmission loss was evaluated as large and unacceptable, and this is indicated by an x ​​in Table 2. When the transmission loss index was 115 or less, the transmission loss was evaluated as small and acceptable, and this is indicated by a ∘ in Table 2. When the transmission loss index was 100 or less, the transmission loss was evaluated as particularly small and acceptable, and this is indicated by a ⊚ in Table 2.

[0154] <Laser processability (reduction of resin residue at the bottom of via holes)> When blind via holes are formed by laser irradiation, resin derived from the resin substrate may remain at the bottom of the formed blind via holes. If the resin remains, sufficient conductivity may not be obtained even when an interlayer connector is formed, and the connection reliability at the time of interlayer connection may decrease. Copper-clad laminates were produced using surface-treated copper foil, and their laser processability, i.e., whether or not resin derived from the resin substrate is likely to remain at the bottom of the formed blind via holes when formed by laser irradiation, was evaluated.

[0155] A single-sided copper-clad laminate was produced by bonding a 12 μm thick surface-treated copper foil to one side of a 50 μm thick liquid crystal polymer film (manufactured by Ise Murata Manufacturing Co., Ltd., thickness precision: 0.7 μm, relative dielectric constant: 3.4, dielectric dissipation factor: 0.0020, ratio of maximum to minimum coefficient of linear thermal expansion: 1.4) using a thermal fusion method.

[0156] Next, a carbon dioxide laser was used to irradiate the liquid crystal polymer film side of the single-sided copper-clad laminate, forming 150 via holes at random locations. The via holes had a diameter of 100 μm. The laser irradiation was performed under the following conditions: pulse width 1-5 μs, tip energy 1-3 mJ, mask diameter 1-3 mm, and number of shots 5-10, depending on the structure of the roughening particles.

[0157] After the via holes were formed, the roughened surface of the surface-treated copper foil at the bottom of the via holes was observed to check for the presence or absence of residual resin. The presence or absence of residual resin was confirmed by removing the surface-treated copper foil by etching after laser processing, and then observing with an optical microscope at 10x magnification to see if any resin remained as a film at the bottom of the via holes. Optical microscope observation was performed on all 150 via holes, and the number of via holes without residual resin was counted.

[0158] In the examples and comparative examples, when the number of via holes with no residual resin was 80 or more, the processability was very good and the result was evaluated as "pass," which is indicated by a double circle in Table 2. When the number of via holes with no residual resin was 40 to 79, the result was evaluated as "pass," which is indicated by a circle in Table 2. When the number of via holes with no residual resin was 39 or less, the result was evaluated as "fail," which is indicated by an x ​​in Table 2.

[0159] <Laser processability (reduction of resin residue at the base of roughening particles)> The present invention aims to provide a printed wiring board having excellent adhesion between a resin substrate and a surface-treated copper foil, low transmission loss, and good long-term connection reliability. Specifically, the present invention aims to prevent resin from remaining at the base of roughening particles in the surface-treated copper foil, thereby preventing cracks from occurring between the resin substrate and the surface-treated copper foil due to thermal stress during long-term use, which can cause poor connection or cracks, resulting in a decrease in connection reliability.

[0160] According to this embodiment, a printed wiring board can be provided that has excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and little resin residue at the base of the roughening particles (good laser processability).Since little resin residue at the base of the roughening particles occurs, long-term connection reliability can be ensured.

[0161] Copper-clad laminates were produced using the surface-treated copper foils, and their laser processability, i.e., whether or not resin derived from the resin substrate is likely to remain at the base of roughening particles in the formed blind via holes when formed by laser irradiation, was evaluated. As in the case of "Laser processability (suppression of resin residue at the bottom of via holes)," single-sided copper-clad laminates were prepared, and then via holes were formed using a carbon dioxide laser. The single-sided copper-clad laminates with via holes formed were then analyzed as follows.

[0162] First, the single-sided copper-clad laminate with via holes was pretreated. Osmium (Os) or platinum (Pt)-palladium (Pd) was vapor-deposited onto the single-sided copper-clad laminate. This allowed the bottom of the via holes to be observed using a scanning electron microscope (SEM). The single-sided copper-clad laminate was embedded in an embedding resin such as epoxy resin, and then cut to allow observation of the maximum diameter cross-section of the via holes. The exposed cross-section was then mirror-polished. Finally, polishing marks were removed using flat milling to obtain a sample for SEM observation.

[0163] The cross section of the sample was observed using a scanning electron microscope, and secondary electron images (SEM images) were obtained at 5,000x magnification. The acceleration voltage of the scanning electron microscope was 10 kV. SEM images with a width of 25 μm were obtained in one field of view, and SEM images were obtained in each of 10 fields of view. These 10 SEM images were then analyzed to evaluate the degree of resin remaining at the bottom of the via hole. This is explained below.

[0164] First, the contour of the surface shape of the roughened surface is extracted. Then, among the roughening particles present in a single field of view, the roughening particle with the highest tip is selected and that tip is taken as the highest point of that field of view. Furthermore, among the roughening particles present in a single field of view, the gap with the lowest bottom between the roughening particles is selected and that bottom of that gap is taken as the lowest point of that field of view.

[0165] Next, a highest line is drawn that passes through the highest point and is parallel to the surface of the copper foil (i.e., a line parallel to the width of the field of view), and a lowest line is drawn that passes through the lowest point and is parallel to the surface of the copper foil, and the area between these two lines is defined as the measurement area.The height (height from the lowest line) that is 25% of the height of this measurement area (the distance between the highest line and the lowest line) is defined as the "reference height."

[0166] At this reference height, gaps between roughening particles with a width of 0.2 μm or more were defined as "valleys" between the roughening particles. If resin remained in the valleys, the degree of resin remaining at the base of the roughening particles was evaluated based on the distance between the bottom of the valley and the surface of the remaining resin.

[0167] The degree of resin remaining at the base of the roughening particles was calculated for all valleys within a 25 μm area centered on the center of the bottom of the via hole, and the degree of resin remaining at the base of the roughening particles was calculated for a total of 10 fields of view.The laser processability (reduction of resin remaining at the base of the roughening particles) was then evaluated using the average value.The results are shown in Table 2.

[0168] In the examples and comparative examples, when the distance between the bottom of the valley and the surface of the remaining resin is 0.6 μm or less, it is evaluated as passing, and is indicated by a circle in Table 2. When the distance between the bottom of the valley and the surface of the remaining resin exceeds 0.6 μm, it is evaluated as failing, and is indicated by an x ​​in Table 2. The bottom of the valley is defined as the intersection of a line perpendicular to the line representing the reference height and passing through the center of the valley with the surface of the copper foil.

[0169] <Dust shedding resistance> After attaching a reference plate to the non-roughened side of the surface-treated copper foil, a piece of white dust-free paper was placed in contact with the roughened surface of the surface-treated copper foil. A 1 kg weight was placed on the white dust-free paper, and the white dust-free paper was moved 50 mm in a direction parallel to the contact surface between the roughened surface and the white dust-free paper at a speed of 100 mm / min.

[0170] The surface of the white dust-free paper was photographed using an optical microscope under reflected light to obtain a magnified image. The magnification was 20x. The brightest part of the enlarged image was assigned a brightness of 255, and the darkest part a brightness of 0. Areas with a brightness of 200 or less were considered to be copper powder transferred to the white dust-free paper (copper powder resulting from the roughening particles). The area ratio (area rate) of areas with a brightness of 200 or less in the enlarged image was then calculated. The results are shown in Table 2. In the examples and comparative examples, when the area ratio was less than 0.5%, it was evaluated as passing, and indicated by a circle in Table 2. When the area ratio was 0.5% or more, it was evaluated as failing, and indicated by an x ​​in Table 2.

[0171] <Oxidation of copper foil> The surface-treated copper foil was placed in an oven and heated, and the presence or absence of discoloration after heating was confirmed. The heating conditions were a temperature of 250°C, a heating time of 30 minutes, and an air atmosphere. The results are shown in Table 2. In the examples and comparative examples, when the surface-treated copper foil did not discolor, it was evaluated as passing, and this is indicated by a circle in Table 2. When the surface-treated copper foil did discolor, it was evaluated as failing, and this is indicated by an x ​​in Table 2.

[0172] Figure 7 shows a cross-sectional view of a copper-clad laminate using conventional surface-treated copper foil. The cross-section of a via hole in Figure 7 reveals that resin remains at the base of the roughening particles at the bottom of the via hole. This makes it easy for cracks to form at the interface between the interlayer connection conductor in the via hole and the surface-treated copper foil.

[0173] Fig. 8 is a cross-sectional view of a copper-clad laminate using the surface-treated copper foil of the first embodiment. Fig. 8 shows a cross-section of a via hole, and it can be seen that because the laser light is easily guided to the base of the roughening particles, the resin is prevented from remaining at the base of the roughening particles at the bottom of the via hole. This strengthens the bond between the interlayer connection conductor in the via hole and the surface-treated copper foil, making it less likely for cracks to form at the interface between the interlayer connection conductor and the surface-treated copper foil. The process for forming via holes, circuit patterns, and interlayer connectors in the copper clad laminate is as shown in FIG. 4, and the specific details are as follows.

[0174] An example of a process for forming blind via holes in a double-sided copper-clad laminate 100 by laser irradiation is shown in Figure 5. Also, an example of a process for forming blind via holes in a single-sided copper-clad laminate 100 by laser irradiation is shown in Figure 6. The process for forming blind via holes is almost the same for both double-sided and single-sided copper-clad laminates, so the following explanation will be given using a double-sided copper-clad laminate as an example. Note that the same reference numerals are used to designate corresponding components in Figures 5 and 6.

[0175] A copper clad laminate 100 shown in (a) of Fig. 5 is irradiated with a laser 130 to form a blind via hole (see (b) of Fig. 5). When forming a blind via hole by laser irradiation, residue 120 (metal originating from the surface-treated copper foil 111 and resin originating from the resin substrate 113) may remain at the bottom 140 of the blind via hole after processing by irradiating with the laser 130 (see (b) of Fig. 5).

[0176] Therefore, after the blind via holes are formed in the copper clad laminate 100, a desmear process is performed to remove residues 120 in the blind via holes (see (c) of FIG. 5). Then, after the desmear process, an interlayer connector 116 is formed. Methods for forming the interlayer connector 116 include a method of forming a plating film 115 and a method of filling the blind via holes with at least one of plating and metal paste to form the interlayer connector 116.

[0177] As shown in Fig. 5(d), a plating process can be performed to form a plating film 115 on the inner surface of the blind via hole. Also, as shown in Fig. 5(e), the blind via hole can be filled with at least one of plating and metal paste to form an interlayer connector 116. Note that the top surface of the interlayer connector 116 does not need to be flush with the surfaces of the surface-treated copper foil 111 and the resin base material 113. [Explanation of symbols]

[0178] 10. Surface-treated copper foil 10a: Roughened surface 20...Resin substrate 30 Copper-clad laminate

Claims

1. A surface-treated copper foil having a roughened surface on at least one side on which roughening particles are formed, wherein physical property values ​​measured on the roughened surface satisfy the following (a), (b), and (c): (A) The specular reflectance of the roughened surface, measured using a spectrophotometer having a light source that emits 45° polarized light with a wavelength of 600 nm, under the condition that the angle of incidence and the angle of reflection are both 70°, is 0.20% or more and 0.90% or less. (i) The Y value of the brightness of the roughened surface is 10.0 or more and 15.5 or less. (c) The Ssk of the roughened surface measured using a laser microscope is 0.30 or more and 0.80 or less.

2. A nickel coating is formed on the roughened surface, and the amount of nickel deposited by the nickel coating is 0.20 mg / dm 2 0.40mg / dm or more 2 2. The surface-treated copper foil according to claim 1, wherein:

3. A surface-treated copper foil having a roughened surface on at least one side on which roughening particles are formed, wherein when the surface-treated copper foil is cut to reveal a cross section perpendicular to the roughened surface, the physical property values ​​of the roughened surface measured by observing the cross section with a scanning electron microscope satisfy the following (f), (g), and (h): (f) The roughening particles have an average cross-sectional particle height h_ave of 0.35 μm or more and 0.70 μm or less. (g) The standard deviation w_σ of the cross-sectional particle width of the roughening particles is 0.05 μm or more and 0.10 μm or less. (h) The roughening particles have a skewness h_sk of 0.80 or more and -2.50 x h_ave + 3.50 or less in cross-sectional particle height.

4. A copper-clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 3 and a resin substrate bonded to the roughened surface of the surface-treated copper foil.

5. The copper clad laminate according to claim 4, wherein the resin substrate is formed from a thermoplastic resin.

6. The copper clad laminate according to claim 4, wherein the resin substrate is formed from a liquid crystal polymer.

7. A printed wiring board comprising the copper clad laminate according to claim 4.

8. The printed wiring board according to claim 7 , wherein the surface-treated copper foil and the resin base material are plastically deformed.

9. The printed wiring board according to claim 7 , wherein the surface-treated copper foil and the resin base material are integrally bent.

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