Surface-treated copper foil, copper-clad laminate, and printed wiring board

Abstract

A surface-treated copper foil is provided, which exhibits excellent adhesion to resin-based substrates and surface-treated copper foil, low transmission loss, and good laser processability, enabling the manufacture of printed wiring boards and the like. The surface-treated copper foil has a roughened surface with roughening particles formed on at least one side, and the physical properties measured on the roughened surface satisfy the following (a), (i), and (u): (a) The normal reflectance of the roughened surface, measured using a spectrophotometer with a light source emitting 45° polarized light at an emission wavelength of 600 nm, under conditions where both the incident angle and reflection angle are 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. (u) The Ssk value 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 surface-treated copper foil that is well used in the manufacture of printed wiring boards, copper-clad laminates using the surface-treated copper foil, and printed wiring boards. Background Technology

[0002] In recent years, to cope with the increasing information processing speed of electronic devices and high-speed wireless communication, the application of high-frequency circuit boards is increasing, requiring high-speed transmission of electrical signals. In high-frequency circuit boards, reducing transmission loss is necessary for high-speed signal transmission. Methods to reduce transmission loss include lowering the dielectric constant and dielectric loss tangent of the resin substrate, and reducing transmission loss in the circuit wiring (especially copper foil) that acts as a conductor.

[0003] One method to achieve low dielectric constant and low dielectric loss tangent in resin-based substrates is to select resins with low dielectric constant and low dielectric loss tangent (such as liquid crystal polymers) as the material for the resin-based substrate. However, depending on the type of resin, there is a problem that even with the use of coupling agents, it is difficult to obtain sufficient chemical adhesion between the resin-based substrate and the copper foil.

[0004] Furthermore, one method to reduce transmission loss in copper foil is to reduce surface roughness caused by roughening particles, etc. However, if surface roughness is reduced, it becomes difficult to achieve sufficient physical adhesion (anchoring effect) between the resin substrate and the copper foil.

[0005] As mentioned above, there is a trade-off between the adhesion between the resin substrate and the copper foil and the transmission loss. Therefore, conventionally, methods have generally achieved good adhesion between the resin substrate and the copper foil by adjusting the surface roughness of the copper foil while simultaneously achieving a low dielectric constant and a low dielectric loss tangent for the resin substrate. For example, Patent Document 1 discloses a method for adjusting the surface roughness and brightness value (brightness) of the copper foil to improve adhesion to the liquid crystal polymer film. Furthermore, Patent Document 2 discloses a method for adjusting the height and aspect ratio of the roughened particles on the surface of the copper foil to improve adhesion to the liquid crystal polymer film. However, while the techniques disclosed in Patent Documents 1 and 2 improve adhesion to the liquid crystal polymer film by increasing the surface roughness of the copper foil, the reduction in transmission loss is insufficient and may not be able to meet the demands for lower transmission losses in recent years.

[0006] Furthermore, to date, the reduction of transmission loss and the improvement of sealing have been emphasized in high-frequency circuit boards. However, with the miniaturization and thinning of electronic devices, especially in various electronic components used in portable devices such as portable telephone terminals, highly integrated small and high-density printed wiring boards are required.

[0007] In such small and high-density printed circuit boards, blind vias are sometimes used for interlayer connections, and the manufacturing process of forming vias using laser irradiation is becoming increasingly common. Since roughened particles inevitably form at the bottom of the via, resin residue from the resin substrate sometimes remains at the bottom of the formed blind via using laser irradiation. If resin residue remains, sufficient conductivity cannot be achieved even with plating, and the reliability of the connection during interlayer bonding may decrease. Therefore, it is preferable to have minimal resin residue.

[0008] Therefore, for copper foil, the property that the resin adhering tightly to the surface must be easily removed from the surface by laser irradiation (hereinafter referred to as "laser processability"). If the copper foil has excellent laser processability, then in the formation of blind holes using laser irradiation, it is difficult for resin from the resin-based substrate to remain at the bottom of the formed blind holes.

[0009] Furthermore, in the bottom of the via where the interlayer interconnect conductor is formed, the metal constituting the interlayer interconnect conductor, the copper foil, and the roughening particles are integrated. Therefore, in the interlayer interconnect conductor section of the printed circuit board, it is difficult to clearly define the surface of the copper foil and the interface of the roughening particles.

[0010] In order to balance the adhesion between the resin substrate and the copper foil and the laser processability, a method is proposed to use copper foil that can suppress the residue of resin from the resin substrate (Patent Document 3).

[0011] In the technology disclosed in Patent Document 3, by providing a blackening treatment layer with high laser absorption on the surface of the copper foil, it is possible to suppress the resin residue from the resin substrate at the bottom of the blind hole formed by laser irradiation.

[0012] However, in the technology disclosed in Patent Document 3, the transmission loss may increase because there is 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 region where the blind hole is formed. Therefore, it may not be able to meet the requirements for low transmission loss in recent years.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent Application Publication No. 2005-219379

[0016] Patent Document 2: International Publication No. 2012 / 020818

[0017] Patent Document 3: Japanese Patent Application Publication No. 11-284309

[0018] The technical problem of this invention is to provide a surface-treated copper foil and a copper-clad laminate capable of manufacturing printed wiring boards with excellent adhesion between a resin substrate and surface-treated copper foil, low transmission loss, and good laser processability. Furthermore, another technical problem of this invention is to provide a printed wiring board with excellent adhesion between a resin substrate and surface-treated copper foil, low transmission loss, and good laser processability. Summary of the Invention

[0019] The main point of the surface-treated copper foil according to one aspect of the present invention is that at least one side has a roughened surface with roughening particles formed thereon, and the physical property values ​​measured on the roughened surface satisfy the following (a), (i) and (u).

[0020] (a) Using a spectrophotometer with a light source of 45° polarized light with an emission wavelength of 600 nm, the normal reflectance of the roughened surface is measured to be 0.20% or more and 0.90% or less under the conditions that both the incident angle and the reflection angle are 70°.

[0021] (i) The Y value of the brightness of the roughened surface is 10.0 or higher and 15.5 or lower.

[0022] (ウ) The Ssk value of the roughened surface, as measured by laser microscope, is 0.30 or higher and 0.80 or lower.

[0023] Furthermore, the main point of another aspect of the present invention is that, in the case of having a roughened surface with roughening particles formed on at least one side, when the surface-treated copper foil is cut to produce a cross section orthogonal 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 (カ), (キ) and (ク).

[0024] (カ) The average height h_ave of the cross-section of the roughened particles is above 0.35 μm and below 0.70 μm.

[0025] (キ) The standard deviation w_σ of the cross-sectional particle width of the roughened particles is 0.05 μm or more and 0.10 μm or less.

[0026] (ク) The skewness h_sk of the cross-sectional particle height of the roughened particle is greater than or equal to 0.80 and less than -2.50×h_ave+3.50.

[0027] Furthermore, the main feature of another aspect of the present invention is that it comprises: a surface-treated copper foil as described in one or the other aspect above; and a resin substrate adhered to the roughened surface of the surface-treated copper foil.

[0028] Furthermore, the main point of the printed wiring board according to another aspect of the present invention is that it has the copper-clad laminate according to yet another aspect.

[0029] The surface-treated copper foil and copper-clad laminate of the present invention can be used to manufacture printed wiring boards with excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and good laser processability. In the printed wiring board of the present invention, the resin substrate and the surface-treated copper foil exhibit excellent adhesion, low transmission loss, and good laser processability. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view illustrating the structure of the copper-clad laminate involved in this embodiment.

[0031] Figure 2 This is a cross-sectional view showing the structure of a printed wiring board in which surface-treated copper foil and a resin substrate are integrally bent.

[0032] Figure 3 This is a cross-sectional view showing the structure of a printed wiring board that constitutes a stripline transmission line.

[0033] Figure 4 It is a diagram illustrating the process of forming vias, circuit patterns, and interlayer interconnects in a copper-clad laminate.

[0034] Figure 5 This diagram illustrates a method for forming blind vias by irradiating two copper-clad laminates with a laser.

[0035] Figure 6 This diagram illustrates a method for forming blind vias on a single-sided copper-clad laminate using laser irradiation.

[0036] Figure 7 This is a cross-sectional view of the vias in a copper-clad laminate that uses existing surface-treated copper foil.

[0037] Figure 8 This is a cross-sectional view of the through-holes in a copper-clad laminate using surface-treated copper foil according to the first and second embodiments.

[0038] Figure 9 This is an SEM image of a cross-section of a surface-treated copper foil.

[0039] Figure 10This is a diagram illustrating the measurement methods for the average value h_ave of the cross-sectional particle height, the standard deviation w_σ of the cross-sectional particle width, and the skewness h_sk of the cross-sectional particle height.

[0040] Figure 11 This is a diagram illustrating the measurement methods for the average value h_ave of the cross-sectional particle height, the standard deviation w_σ of the cross-sectional particle width, and the skewness h_sk of the cross-sectional particle height for roughened particles with special shapes. Detailed Implementation

[0041] One embodiment of the present invention will be described. Furthermore, the embodiment described below represents an example of the present invention. In addition, various modifications or improvements can be made to this embodiment, and such modifications or improvements may also be included in the present invention.

[0042] [The surface-treated copper foil according to the first embodiment]

[0043] The surface-treated copper foil according to the first embodiment is a surface-treated copper foil having a roughened surface with roughened particles formed on at least one side, and the physical property values ​​measured on the roughened surface satisfy the following (a), (i) and (u).

[0044] (a) Using a spectrophotometer with a light source of 45° polarized light with an emission wavelength of 600 nm, the normal reflectance of the roughened surface is measured to be 0.20% or more and 0.90% or less under the conditions that both the incident angle and the reflection angle are 70°.

[0045] (i) The Y value of the brightness of the roughened surface is 10.0 or higher and 15.5 or lower.

[0046] (ウ) The Ssk value of the roughened surface, as measured by laser microscope, is 0.30 or higher and 0.80 or lower.

[0047] The surface-treated copper foil according to the first embodiment involves subjecting at least one of its two surfaces to a roughening treatment (e.g., copper plating). The roughened surface has roughened particles formed through the roughening treatment. The entire surface of the surface-treated copper foil may be roughened, or only a portion of it may be roughened. In manufacturing the surface-treated copper foil, a roughening treatment is performed on a copper foil that serves as a raw material. Examples of raw copper foils include electrolytic copper foil and rolled copper foil.

[0048] Furthermore, if a surface-treated copper foil with a roughened surface simultaneously satisfies the aforementioned components (a), (i), and (u), it is possible to manufacture printed wiring boards with excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and good laser processing properties. Moreover, even when transmitting high-frequency signals to the circuitry of the manufactured printed wiring board, the transmission loss is low. Therefore, the surface-treated copper foil according to the first embodiment can be well used in the manufacture of printed wiring boards (printed wiring boards with high-frequency circuits) used in the high-frequency band.

[0049] The surface-treated copper foil according to the first embodiment will be described in further detail.

[0050] The mechanism by which the above effects are achieved is not necessarily certain, but the following is a hypothesis.

[0051] (ア) Regular reflectance

[0052] First, since it is positive reflectivity under near-surface geometry conditions where both the incident angle and reflection angle are 70°, it is possible to perform evaluations that are sensitive to surface shape.

[0053] Furthermore, by spectral dispersion of the incident light, using light with energy (longer wavelength) lower than the plasma frequency of copper, the absorption of light caused by copper is suppressed, and the reflection from the copper surface becomes dominant. It is speculated that the large reflection angle is largely due to the surface shape of the copper, particularly the orthographic component, where the incident and reflection angles are the same, is affected by the shape of the roughening particles formed on the surface. Therefore, it was found that by using spectral dispersion at a wavelength of 600 nm, close to the average height h_ave of the cross-section of the roughening particles, a sensitive evaluation reflecting the shape of the roughening particles can be performed. Thus, higher orthographic reflectivity results in lower transmission loss, while lower orthographic reflectivity leads to better adhesion between the resin substrate and the surface-treated copper foil.

[0054] (i) Y value of brightness

[0055] The Y value of brightness, which is the reflectance of white light at an incident angle of 45° and a reflection angle of 0°, is particularly presumed to be a value that sensitively reflects the shape of the roughened particles when the sample surface is observed from above in a direction orthogonal to the sample surface, i.e., the particle width of the roughened particles.

[0056] Because the higher the brightness Y value, the larger the particle width of the roughened particles, the higher the powder shedding resistance of the surface-treated copper foil (it is difficult to produce powder shedding). The lower the brightness Y value, the better the laser processing performance (suppression of resin residue at the bottom of the via).

[0057] (ウ)Ssk

[0058] The Ssk of the roughened surface can be used to evaluate the deviation in the height distribution of the roughened particles when observed from the surface. The larger the Ssk, the easier it is for the laser to reach the root of the roughened particles, thus resulting in excellent laser processability (suppression of resin residue at the root of the roughened particles). The smaller the Ssk, the better the resistance to powdering.

[0059] These three items (a), (i), and (u) each have a trade-off relationship, but it has been found that by controlling them within a predetermined range, a copper foil achieving the aforementioned effect can be obtained. As a method for controlling these three items within the predetermined range, for example, a two-stage electroplating process is performed using different electrolytes during the roughening treatment, and the temperature ratio in the vertical direction within the electrolytic cell is controlled in the second stage of electroplating. By controlling the temperature ratio in the vertical direction within the electrolytic cell within a certain range, the growth rate of the roughening particles in the second stage of roughening treatment varies. Therefore, it can be considered that roughening particles with a predetermined distribution of Y values ​​for positive reflectivity and brightness, but with a deviation in distribution, can be formed.

[0060] The normal reflectance of the roughened surface was measured using a spectrophotometer. Furthermore, the normal reflectance of the roughened surface was measured by emitting 45° polarized light, splitting the light from the light source into wavelengths of 600 nm, with both the incident and reflection angles at 70°. "45° polarized light" refers to emitting light from the light source at a 45° angle, with a polarizer (0° for s-polarization and 90° for p-polarization) positioned in front of the sample.

[0061] The surface roughened requires a normal reflectance of 0.20% or higher and 0.90% or lower, but the lower limit can be 0.26% or higher. Furthermore, the upper limit can be 0.78% or lower.

[0062] In this specification, the Y value of luminance refers to the Y value of reflectance in the XYZ color system specified by the International Commission on Illumination (CIE). The method for measuring the Y value of the luminance of the roughened surface is not particularly limited; for example, it can be measured using a colorimeter. For instance, white light can be shone onto the roughened surface, and the Y value of the luminance can be measured under conditions such as an incident angle of 45° and a reflection angle of 0°.

[0063] The Y-value of the roughened surface brightness needs to be above 10.0 and below 15.5, but its lower limit can also be above 11.0. In addition, its upper limit can be below 15.0 or below 14.5.

[0064] 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 higher and 0.80 or lower. 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.

[0065] The Ssk value for roughening the surface needs to be between 0.30 and 0.80, but its lower limit can also be above 0.35. In addition, its upper limit can also be below 0.70.

[0066] Furthermore, in the surface-treated copper foil according to the first embodiment, a nickel coating may also be formed on the roughened surface, and the amount of nickel (Ni) in the nickel coating may be 0.20 mg / dm². 2 Above and 0.40 mg / dm 2 The following applies. If a nickel coating is applied, the surface-treated copper foil exhibits even better rust resistance and heat resistance.

[0067] Alternatively, at least one of nickel, zinc, and chromium coatings can be laminated onto the roughened surface. The coating formed by laminating at least one of nickel, zinc, and chromium coatings functions as a rust-preventive layer, thus further improving the rust resistance of the surface-treated copper foil.

[0068] Furthermore, a chemical adhesive layer containing a chemical adhesive can be further laminated on the rust-preventive layer. This chemical adhesive layer can be formed using a chemical adhesive treatment with a silane coupling agent or similar chemical adhesive. The chemical adhesive layer further improves the adhesion between the surface-treated copper foil and the resin substrate. Additionally, because the rust-preventive layer and the chemical adhesive layer are very thin, they do not affect the shape of the roughening particles on the roughened surface of the surface-treated copper foil.

[0069] Furthermore, as a method for forming the chemical adhesive layer, one example is to apply a silane coupling agent solution directly or indirectly, such as through a rust-preventing layer, to the roughened surface of a surface-treated copper foil, followed by air drying (natural drying) or heat drying. Drying the applied silane coupling agent solution only requires water evaporation, but heat drying at a temperature above 50°C and below 180°C is preferred in terms of promoting the reaction between the silane coupling agent and the copper foil.

[0070] The chemical adhesive layer preferably contains one or more silane coupling agents selected from epoxy silanes, amino silanes, vinyl silanes, methacrylic silanes, acrylic silanes, styryl silanes, urea silanes, mercapto silanes, thioether silanes, and isocyanate silanes. These silane coupling agents exhibit different effects due to their interaction with the reactive functional groups contained in the resin of the resin substrate; therefore, compatibility with the resin must be considered when selecting an appropriate silane coupling agent.

[0071] Specific examples of the aforementioned silane coupling agents include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanate propyltriethoxysilane, bis(3-(triethoxysilyl)propyl)disulfide, etc. However, even silane coupling agents other than these can be appropriately selected for use. Furthermore, these silane coupling agents can be used alone or in combination of two or more.

[0072] [The surface-treated copper foil according to the second embodiment]

[0073] The surface-treated copper foil involved in the second embodiment is a surface-treated copper foil having a roughened surface with roughening particles formed on at least one side. When the surface-treated copper foil is cut to produce a cross section orthogonal to the roughened surface, the physical property values ​​of the roughened surface measured by observing the cross section using a scanning electron microscope satisfy the following (カ), (キ) and (ク).

[0074] (カ) The average height h_ave of the cross-section of the roughened particles is above 0.35 μm and below 0.70 μm.

[0075] (キ) The standard deviation w_σ of the cross-sectional particle width of the roughened particles is 0.05 μm or more and 0.10 μm or less.

[0076] (ク) The skewness h_sk of the cross-sectional particle height of the roughened particle is greater than or equal to 0.80 and less than -2.50×h_ave+3.50.

[0077] The second embodiment of the surface-treated copper foil involves subjecting at least one of its two surfaces to a roughening treatment (e.g., copper plating). The roughened surface has roughened particles formed through the roughening treatment. The entire surface of the surface-treated copper foil may be roughened, or only a portion of it may be roughened. In manufacturing the surface-treated copper foil, a roughening treatment is performed on a copper foil that serves as a raw material. Examples of raw copper foils include electrolytic copper foil and rolled copper foil.

[0078] Furthermore, if a surface-treated copper foil with a roughened surface meets the aforementioned configurations (カ), (キ), and (ク), it is possible to manufacture printed wiring boards with excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and good laser processability. Moreover, even when transmitting high-frequency signals to the circuitry of the manufactured printed wiring board, the transmission loss is low. Therefore, the surface-treated copper foil according to the second embodiment can be well used in the manufacture of printed wiring boards used in the high-frequency band (printed wiring boards with high-frequency circuits).

[0079] The surface-treated copper foil according to the second embodiment will be described in further detail. The above-described effect is achieved when the roughening particles of the roughened surface satisfy the shapes of the aforementioned configurations (カ), (キ), and (ク). The mechanism is not necessarily clear, but it is speculated that the above-described effect is obtained by specifying a parameter range, which is obtained by accurately determining the distribution of cross-sectional particle height and cross-sectional particle width of the roughening particles through observation of scanning electron microscope (SEM) images of the cross-section of the surface-treated copper foil.

[0080] More specifically, the average value of the cross-sectional particle height h_ave of the roughened particles is above 0.35μm and below 0.70μm. However, the larger the average value of the cross-sectional particle height h_ave of the roughened particles, the better the adhesion between the resin substrate and the surface-treated copper foil. The smaller the average value of the cross-sectional particle height h_ave of the roughened particles, the smaller the transmission loss.

[0081] Furthermore, the standard deviation w_σ of the cross-sectional particle width of the roughened particles is greater than 0.05 μm and less than 0.10 μm. However, the larger the standard deviation w_σ of the cross-sectional particle width of the roughened particles, the better the adhesion between the resin substrate and the surface-treated copper foil. The smaller the standard deviation w_σ of the cross-sectional particle width of the roughened particles, the better the laser processability (suppression of resin residue at the bottom of the via).

[0082] Furthermore, the skewness h_sk of the cross-sectional particle height of the roughened particles is 0.80 or higher and -2.50×h_ave+3.50 or lower. However, the larger the skewness h_sk of the cross-sectional particle height of the roughened particles, the better the laser processability (suppression of resin residue at the root of the roughened particles), and the smaller the skewness h_sk of the cross-sectional particle height of the roughened particles, the better the powder shedding resistance. In addition, "h_ave" in "0.80 or higher and -2.50×h_ave+3.50 or lower" refers to the average h_ave of the cross-sectional particle height of the roughened particles.

[0083] These three items (カ), (キ), and (ク) each have a trade-off relationship, but it has been found that by controlling them within a predetermined range, copper foil achieving the aforementioned effect can be obtained. As a method for controlling these three items within the predetermined range, for example, a method is as follows: Two-stage electroplating is performed using different electrolytes during the roughening process, and in the second stage of electroplating, the vertical outflow ratio of the electrolyte in the electrolytic cell is controlled. By controlling the vertical outflow ratio of the electrolyte in the electrolytic cell within a certain range, it is anticipated that the flow rate of the electrolyte near the cathode, which affects the growth rate of the roughened particles, will have a high degree of distribution in the second stage of roughening. As a result, the growth rate of the roughened particles changes in the second stage of roughening. Therefore, the average value h_ave of the cross-sectional particle height of the roughened particles and the standard deviation w_σ of the cross-sectional particle width of the roughened particles are within the aforementioned predetermined range, and the distribution of the cross-sectional particle height of the roughened particles deviates to a certain extent. Therefore, it is considered that roughened particles with a cross-sectional particle height skewness h_sk within the aforementioned predetermined range can be formed.

[0084] Furthermore, in the second embodiment, the cross-sectional particle height of the roughened particles in the surface-treated copper foil refers to the length of a specific roughened particle in the direction in which it protrudes from the roughened surface of the surface-treated copper foil. The average cross-sectional particle height of the roughened particles needs to be between 0.35 μm and 0.70 μm, but its lower limit can also be 0.40 μm or more. Furthermore, its upper limit can also be 0.60 μm or less.

[0085] Furthermore, in the second embodiment, the cross-sectional particle width of the roughening particles in the surface-treated copper foil refers to the length of the roughening particle in a direction orthogonal to the direction in which the roughening particle protrudes from the roughened surface of the surface-treated copper foil, when considering a specific roughening particle. The standard deviation of the cross-sectional particle width of the roughening particles needs to be 0.05 μm or more and 0.10 μm or less, but its lower limit can also be 0.06 μm or more. Furthermore, its upper limit can also be 0.09 μm or less.

[0086] Alternatively, at least one of nickel, zinc, and chromium coatings can be laminated onto the roughened surface. The coating formed by laminating at least one of nickel, zinc, and chromium coatings functions as a rust-preventive layer, thus further improving the rust resistance of the surface-treated copper foil.

[0087] Furthermore, a chemical adhesive layer containing a chemical adhesive can be further laminated on the rust-preventive layer. This chemical adhesive layer can be formed using a chemical adhesive treatment with a silane coupling agent or similar chemical adhesive. The chemical adhesive layer further improves the adhesion between the surface-treated copper foil and the resin substrate. Additionally, because the rust-preventive layer and the chemical adhesive layer are very thin, they do not affect the shape of the roughening particles on the roughened surface of the surface-treated copper foil.

[0088] Furthermore, as a method for forming the chemical adhesive layer, one example is to apply a silane coupling agent solution directly or indirectly, such as through a rust-preventing layer, to the roughened surface of a surface-treated copper foil, followed by air drying (natural drying) or heat drying. Drying the applied silane coupling agent solution only requires water evaporation, but heat drying at a temperature above 50°C and below 180°C is preferred in terms of promoting the reaction between the silane coupling agent and the copper foil.

[0089] The chemical adhesive layer preferably contains one or more silane coupling agents selected from epoxy silanes, amino silanes, vinyl silanes, methacrylic silanes, acrylic silanes, styryl silanes, urea silanes, mercapto silanes, thioether silanes, and isocyanate silanes. These silane coupling agents exhibit different effects due to their interaction with the reactive functional groups contained in the resin of the resin substrate; therefore, compatibility with the resin must be considered when selecting an appropriate silane coupling agent.

[0090] Specific examples of the aforementioned silane coupling agents include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanate propyltriethoxysilane, bis(3-(triethoxysilyl)propyl)disulfide, etc. However, even silane coupling agents other than these can be appropriately selected for use. Furthermore, these silane coupling agents can be used alone or in combination of two or more.

[0091] [Copper-clad laminate]

[0092] like Figure 1 As shown, the copper-clad laminate 30 of this embodiment includes a surface-treated copper foil 10 as described in the first embodiment or the second embodiment, and a resin substrate 20 adhered to the roughened surface 10a of the surface-treated copper foil 10.

[0093] Since the copper-clad laminate 30 involved in this embodiment has the surface-treated copper foil 10 involved in the first embodiment or the second embodiment, if the copper-clad laminate 30 involved in this embodiment is used, it is possible to manufacture printed wiring boards with excellent adhesion between the resin substrate 20 and the surface-treated copper foil 10, low transmission loss and good laser processing performance.

[0094] There is no particular limitation on the type of resin used to form the resin-based substrate. Examples include liquid crystal polymers, polyetheretherketones, polyphenylene sulfide, polyphenylene ether, polyphenylene oxide, polyetherimide, polyethersulfone, polyethylene naphthalate, polyethylene terephthalate, thermoplastic polyimide, cyclic polyolefins and other thermoplastic resins, polyimide, heat-resistant epoxy resin, cyanate ester resins (e.g., bismaleimide triazine), thermosetting modified polyphenylene ether and other thermosetting resins.

[0095] Among these resins, liquid crystal polymers such as thermotropic liquid crystal polymers and lyotropic liquid crystal polymers are preferred. Examples of thermotropic liquid crystal polymers include liquid crystal polyesters; for instance, aromatic polyesters obtained by reacting aromatic dicarboxylic acids or aromatic diols with aromatic hydroxycarboxylic acids as essential monomers are also examples of liquid crystal polyesters.

[0096] Specific examples of aromatic polyesters include polyesters synthesized from p-hydroxybenzoic acid (PHB), phthalic acid and 4,4'-biphenyl; polyesters synthesized from PHB and 2,6-hydroxynaphthoic acid; and polyesters synthesized from PHB, terephthalic acid and ethylene glycol.

[0097] Printed wiring board

[0098] The printed wiring board according to this embodiment includes the copper-clad laminate described in this embodiment. The printed wiring board according to this embodiment includes the surface-treated copper foil described in the first or second embodiment; therefore, the resin substrate and the surface-treated copper foil exhibit excellent adhesion, low transmission loss, and good laser processing capability.

[0099] In the printed wiring board of this embodiment, both the surface-treated copper foil and the resin substrate can be plastically deformed. The printed wiring board of this embodiment is composed of metal foil and a resin substrate (e.g., a thermoplastic resin film), making it prone to plastic deformation. This plastic deformation is even more likely to occur when heated.

[0100] Furthermore, in the printed wiring board of this embodiment, the surface-treated copper foil and the resin substrate can also be bent integrally. Figure 2 This is a cross-sectional view showing an example of a printed wiring board in which a surface-treated copper foil and a resin substrate are integrally bent. In the printed wiring board according to this embodiment, the resin substrate and the surface-treated copper foil have excellent adhesion, so that when deformed, the resin substrate and the surface-treated copper foil will not peel off and can be bent integrally.

[0101] The printed wiring board involved in this embodiment can be subjected to various stresses and deformations within the scope of the present invention, depending on the structure and manufacturing conditions of the electronic circuit board. However, when the printed wiring board involved in this embodiment is assembled into an electronic device, it may or may not be bent.

[0102] Furthermore, the printed wiring board according to this embodiment can also be used to construct transmission lines. Additionally, the printed wiring board according to this embodiment can also be used to construct stripline, microstrip, or coplanar transmission lines. Because the printed wiring board according to this embodiment has low transmission loss, it exhibits good characteristics even when the roughened surfaces are opposite each other, and can be used to form transmission lines of all shapes and sizes.

[0103] Figure 3 This is a cross-sectional view showing an example of a printed wiring board that constitutes a stripline transmission line. Figure 3 At least one of the multiple surface-treated copper foils in the printed wiring board is the surface-treated copper foil involved in the first embodiment or the second embodiment. The surface-treated copper foil involved in the first embodiment or the second embodiment has excellent adhesion to the resin substrate, low transmission loss, and excellent laser processing properties, and therefore can be used as any one of the multiple surface-treated copper foils in the printed wiring board. That is, it can be used as the outermost surface-treated copper foil of the printed wiring board, or it can be used as the surface-treated copper foil located inside the printed wiring board.

[0104] [Example]

[0105] The following examples and comparative examples illustrate the invention in more detail.

[0106] [Examples and comparative examples of surface-treated copper foil according to the first embodiment]

[0107] [1] Preparation of copper foil substrate

[0108] Electrolytic copper foil is prepared as the raw material for surface-treated copper foil. This electrolytic copper foil becomes the copper foil substrate for roughening treatment. The electrolytic copper foil is manufactured by electrolysis under the following conditions. Furthermore, the electrolytic copper foil manufactured under the following conditions has 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 is measured on the surface of the electrolytic copper foil using a contact surface roughness measuring machine (Surfcorder SE1700 manufactured by Kosaka Research Institute Co., Ltd.).

[0109] <Manufacturing conditions for electrolytic copper foil>

[0110] Copper concentration in the electrolyte: 80 g / L

[0111] H2SO4 concentration in the electrolyte: 70 g / L

[0112] Chlorine concentration of electrolyte: 25 mg / L

[0113] Bath temperature: 55℃

[0114] Current density: 45A / dm 2

[0115] <Additives and Concentrations in the Electrolyte> Sodium 3-mercapto-1-propanesulfonate: 2 mg / L Hydroxyethylcellulose: 10 mg / L Low molecular weight adhesive (molecular weight 3000): 50 mg / L [2] Roughening treatment Next, a roughened surface is formed by performing a plating process on one side of the copper foil substrate prepared in [1] above, and a surface-treated copper foil is manufactured. This plating process is a two-stage electroplating process. In the first stage plating process (1), a first-stage treatment solution with the following composition is used, and the current density and energizing time are as described in Table 1. In addition, in the second stage plating process (2) following the first stage plating process (1), a second-stage treatment solution with the following composition is used, and the current density, energizing time, and vertical temperature in the electrolytic cell are as described in Table 1. The vertical temperature ratio in the electrolytic cell is obtained by dividing the electrolyte temperature (K) at the upper part of the opening position in the electrolytic cell by the electrolyte temperature (K) at the lower part of the opening position in the electrolytic cell. In addition, additional treatments may be performed before the first stage plating process (1) and after the second stage plating process (2) as needed.

[0116] <First Stage Treatment Solution>

[0117] Copper (Cu) concentration: 60 g / L

[0118] Sulfuric acid (H2SO4) concentration: 120 g / L

[0119] Bath temperature: 60℃

[0120] <Second Stage Treatment Solution>

[0121] Copper concentration: 20-30 g / L

[0122] H2SO4 concentration: 150g / L

[0123] Molybdenum (Mo) concentration: 0.2–0.4 g / L

[0124] Iron (Fe) concentration: 2 g / L

[0125] Bath temperature: 30~40℃

[0126] [3] Formation of the basal layer and intermediate layer

[0127] Next, on the roughened surface of the surface-treated copper foil manufactured in [2] above, metal plating is performed in the following order of nickel, zinc (Zn), and chromium (Cr) under the following conditions to form a base layer and an intermediate layer.

[0128] <Ni plating>

[0129] Ni concentration in the plating solution: 40 g / L

[0130] H3BO3 concentration in plating solution: 5 g / L

[0131] Bath temperature: 20℃

[0132] The pH of the plating solution is 3.6.

[0133] Current density: as shown in Table 1

[0134] Processing time: 10 seconds

[0135] <Zn plating>

[0136] Zn concentration in the plating solution: 2.5 g / L

[0137] NaOH concentration in the plating solution: 40 g / L

[0138] Bath temperature: 20℃

[0139] The pH of the plating solution is 3.6.

[0140] Current density: 0.3 A / dm 2

[0141] Processing time: 5 seconds

[0142] <Cr plating>

[0143] Cr concentration in plating solution: 5 g / L

[0144] Bath temperature: 30℃

[0145] The pH of the plating solution is 2.2.

[0146] Current density: 5A / dm 2

[0147] Processing time: 5 seconds

[0148] [4] Formation of silane coupling agent layer

[0149] Finally, a silane coupling agent layer is formed on the intermediate layer (especially the Cr-plated layer on the outermost surface) formed in [3]. The silane coupling agent layer is formed by coating the intermediate layer with an aqueous solution of 3% by mass of 3-epoxypropoxypropyltrimethoxysilane and drying it at 100°C. The amount of silane attached is 0.003 mg / dm³ in terms of silicon (Si) atoms. 2 .

[0150] [Table 1]

[0151] As described above in [1] to [4], surface-treated copper foils of Examples A1 to A10 and Comparative Examples A1 to A10 were manufactured. Some of the manufacturing conditions for the surface-treated copper foils were as described above, and others were as described in Table 1.

[0152] For the roughened surfaces of the obtained surface-treated copper foils, various physical properties were measured. Furthermore, the adhesion to the resin substrate, transmission loss, dusting resistance, oxidation resistance, and laser processability of each surface-treated copper foil were evaluated. The measurement and evaluation methods are described below. The measurement and evaluation results are shown in Table 1.

[0153] <Positive reflectivity of roughened surfaces>

[0154] The orthogonal reflectance of the roughened surface was measured using a V-780 spectrophotometer manufactured by Nippon Spectrophotometer Co., Ltd., and an ARSN-918i absolute reflectance measurement unit. The incident light used in 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.

[0155] The surface-treated copper foil was placed on a spectrophotometer with the incident light plane parallel to the transverse (TD) direction orthogonal to the flow direction (MD) of the copper foil during manufacturing. The normal reflectance of the roughened surface was measured under conditions where both the incident angle and the reflection angle were 70°. Dark correction and blank correction were performed, and the process was repeated once.

[0156] <Y value of brightness of roughened surface>

[0157] The Y value of the XYZ color system specified in CIE was measured using a Suga Testing Machine Co., Ltd. SM-T45 luminance meter and colorimeter. The measurement conditions are as follows: A C light source with a 2-degree field of view; optical conditions according to condition a of JIS Z8722:2009; and an aperture with a diameter of 30 mm.

[0158] <Ssk for roughening surfaces>

[0159] The Ssk of the roughened surface was measured using a confocal laser microscope (VK-X3100) manufactured by Keyence Corporation, according to the method specified in ISO 25178. The wavelength of the laser source was 404 nm. Measurements were taken at five randomly selected locations on the roughened surface, and the average value was taken as the Ssk of the roughened surface.

[0160] In addition, the confocal laser microscope uses a 100x objective lens, a laser confocal scanning mode, a measurement size of 2048×1536, high-precision measurement quality, a spacing of 0.06μm, and automatic light intensity adjustment. Furthermore, Ssk calculations are performed under the filter processing and computational conditions shown below.

[0161] Area of ​​the operand: 142μm (TD direction) × 106μm (MD direction)

[0162] Image Processing: Reference Plane Setting (Area of ​​Operands: Overall)

[0163] Smoothing process (Gaussian, size 3×3)

[0164] S-filter: None

[0165] F-operation: None

[0166] L-filter: 0.01μm (Gaussian, terminal effect correction: ON)

[0167] <Nickel adhesion based on nickel coating>

[0168] The amount of nickel deposited was determined by fluorescence X-ray analysis of the roughened surface of a surface-treated copper foil using a scanning fluorescence X-ray analyzer (ZSX Primus IV) manufactured by Rigaku Corporation. Furthermore, the amount of nickel atoms was quantified using a calibration curve obtained with known standard samples.

[0169] <Adhesion to resin-based substrates>

[0170] A surface-treated copper foil is laminated on one side of a 50 μm thick liquid crystal polymer film (manufactured by Ise-Murata Manufacturing Co., Ltd., thickness accuracy: 0.7 μm, relative permittivity: 3.4, dielectric loss tangent: 0.0020, ratio of maximum to minimum thermal expansion coefficient: 1.4) with a roughened surface in contact with the liquid crystal polymer film. On the other side, a polyimide film ("Upirex 20S" manufactured by UBE Co., Ltd.) is laminated as a release material to obtain a laminate.

[0171] The laminate is held between two 2mm thick stainless steel plates, and then the part holding the laminate between the stainless steel plates is held between two 1mm thick stainless steel fiber fabrics as cushioning material, and placed in a vacuum press. The press is then held at 300°C and 3MPa for 5 minutes. After cooling, the heat-pressed laminate is removed from the vacuum press, the release material is removed, and a single-sided copper-clad laminate is obtained.

[0172] Using a tensile testing machine ("AGS-H" manufactured by Shimadzu Corporation), the strength (unit: N / mm) of surface-treated copper foil being peeled off from the single-sided copper-clad laminate at a speed of 50 mm / min in a 180° direction was determined according to the method specified in JIS C6471-1995.

[0173] Specifically, a 5mm wide mask tape is adhered to the copper foil of a single-sided copper-clad laminate, and then immersed in a ferric chloride solution to etch away unwanted portions of the copper foil. Afterward, the single-sided copper-clad laminate is washed with water and the mask tape is peeled off. It is then dried in a circulating oven at 80°C for 1 hour to form a 5mm wide linear circuit pattern.

[0174] When peeling copper foil from a single-sided copper-clad laminate, the test piece is adhered to a reinforcing plate with a thickness of 1 mm or more in a manner that does not cause the test piece (single-sided copper-clad laminate) to buckle and change the peeling angle. After peeling one end of the formed circuit pattern and clamping it on the tensile testing machine, the copper foil is peeled relative to the test piece at a speed of 50 mm / min in a 180° direction for more than 10 mm. The average value of the total strength during this period is calculated and taken as the peel strength (N / mm). The results are shown in Table 1.

[0175] In the examples and comparative examples, the 180° peel strength was measured as an indicator of the adhesion between the resin substrate and the surface-treated copper foil. A peel strength of 0.70 N / mm or higher was considered acceptable, while a peel strength of less than 0.70 N / mm was considered unacceptable.

[0176] <Transmission Loss>

[0177] A double-sided copper-clad laminate is fabricated by bonding surface-treated copper foil to both sides of a 50μm thick liquid crystal polymer film (manufactured by Ise-Murata Manufacturing Co., Ltd., thickness accuracy: 0.7μm, relative permittivity: 3.4, dielectric loss tangent: 0.0020, ratio of maximum to minimum thermal expansion coefficient: 1.4).

[0178] Next, the surface-treated copper foil on one side of the above-mentioned two-sided copper-clad laminate is etched to form a linear pattern with a predetermined width (110μm) and length (20mm and 50mm) as a signal layer, and the surface-treated copper foil on the other side is used as a ground layer to fabricate a circuit substrate with a microstrip structure.

[0179] Furthermore, after drying the circuit board in a circulating oven at 50°C for 24 hours, it was cooled to room temperature under the standard conditions described in JISC6481-1996 to produce a circuit board for evaluating high-frequency characteristics.

[0180] The two ends of the pattern of the high-frequency characteristic evaluation circuit board fabricated in the above manner were clamped into a test fixture, and a high-frequency signal (40 GHz) was allowed to flow through the pattern. The strength of the transmitted signal (S21) was measured. The signal strength was measured using a PNA microwave network analyzer N5227B manufactured by Keysight Technologies Co., Ltd., and a general-purpose test fixture 3680V manufactured by Anritsu Co., Ltd. The above measurement was performed five times with the same pattern, and the average value was taken as the transmission loss of each circuit board.

[0181] Then, based on 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 the difference in the pattern length of the two circuit boards for evaluating high-frequency characteristics, the transmission loss per unit length is calculated.

[0182] Furthermore, using the transmission loss per unit length of Example B2 described later as a baseline value (100), the transmission loss per unit length of the surface-treated copper foil in each example and comparative example was indexed. The results are shown in Table 1. In the examples and comparative examples, when the index of the transmission loss exceeds 115, the transmission loss is considered large and unacceptable, and is indicated by × in Table 1. Furthermore, when the index of the transmission loss is 115 or less, the transmission loss is considered small and acceptable, and is indicated by ○ in Table 1. Furthermore, when the index of the transmission loss is 100 or less, the transmission loss is particularly small and acceptable, and is indicated by ◎ in Table 1.

[0183] <Laser processability (suppression of resin residue at the bottom of vias)>

[0184] In the formation of blind vias using laser irradiation, resin residue from the resin-based substrate sometimes remains at the bottom of the formed blind via. If resin residue remains, even if interlayer bonding is formed, sufficient conductivity may not be achieved, reducing the reliability of the interlayer bonding connection. This study evaluates the laser processability of surface-treated copper foil used to fabricate copper-clad laminates, specifically whether it is difficult for resin residue from the resin-based substrate to remain at the bottom of the formed blind vias using laser irradiation.

[0185] A single-sided copper-clad laminate is fabricated by bonding a 12μm thick surface-treated copper foil to one side of a 50μm thick liquid crystal polymer film (manufactured by Ise-Murata Manufacturing Co., Ltd., thickness accuracy: 0.7μm, relative permittivity: 3.4, dielectric loss tangent: 0.0020, ratio of maximum to minimum thermal expansion coefficient: 1.4).

[0186] Next, a carbon dioxide laser is irradiated onto the liquid crystal polymer film side of the aforementioned single-sided copper-clad laminate to form 150 vias at arbitrary locations. The diameter of the vias is 100 μm. Furthermore, the laser irradiation is performed under the following conditions, based on the structure of the roughened particles: pulse width 1–5 μs, front-end energy 1–3 mJ, mask diameter 1–3 mm, and irradiation number 5–10 shots.

[0187] After the vias are formed, the roughened surface of the copper foil at the bottom of the via is observed to confirm the presence or absence of resin residue. The presence or absence of resin residue is confirmed by observing the bottom of the via as a film residue using an optical microscope at 10x magnification after laser processing and etching to remove the surface-treated copper foil. All 150 vias were observed using an optical microscope, and the number of vias without resin residue was counted.

[0188] In the examples and comparative examples, when the number of vias with no resin residue was 80 or more, the processability was excellent, and therefore the result was deemed acceptable, indicated by the ◎ mark in Table 1. Furthermore, when the number of vias with no resin residue was 40 or more but less than 79, the result was deemed acceptable, indicated by the ○ mark in Table 1. Finally, when the number of vias with no resin residue was 39 or less, the result was deemed unacceptable, indicated by the × mark in Table 1.

[0189] <Laser processability (suppression of resin residue at the root of roughened particles)>

[0190] The technical problem of this embodiment is to provide a printed wiring board with excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and good long-term connection reliability. Specifically, it suppresses the residue of resin at the root of the roughened particles of the surface-treated copper foil, and suppresses cracking between the resin substrate and the surface-treated copper foil caused by thermal stress during long-term use, which would lead to poor connection, cracking, and reduced connection reliability.

[0191] According to this embodiment, a printed wiring board can be provided that exhibits excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and minimal resin residue at the roots of roughened particles (resin has excellent laser processability). Because resin residue at the roots of roughened particles is minimal, long-term connection reliability can be ensured.

[0192] Surface-treated copper foil was used to fabricate copper-clad laminates, and its laser processability was evaluated. Specifically, in the formation of blind vias using laser irradiation, it was determined whether resin from the resin-based substrate could not easily remain at the root of the roughened particles within the formed blind vias.

[0193] Similar to the case of "laser processability (suppression of resin residue at the bottom of vias)" described above, vias were formed using a carbon dioxide laser after fabricating a single-sided copper-clad laminate. The single-sided copper-clad laminate with the vias formed was then analyzed as follows.

[0194] First, the single-sided copper-clad laminate with vias is pretreated. Osmium (Os) or platinum (Pt)-palladium (Pd) is deposited onto the single-sided copper-clad laminate. This allows the bottom of the vias to be observed using a scanning electron microscope (SEM). The single-sided copper-clad laminate is then embedded with an embedding resin such as epoxy resin. The laminate is cut to the maximum diameter section that allows observation of the vias, and the resulting section is mirror-polished. Finally, the polishing marks are removed by planar grinding to obtain the sample for SEM observation.

[0195] The cross-section of the above-mentioned sample was observed using a scanning electron microscope (SEM), obtaining secondary electron images (SEM images) at a magnification of 5,000x. The accelerating voltage of the SEM was 10 kV. SEM images with a width of 25 μm were acquired in one field of view, and SEM images were acquired in 10 fields of view. Then, the degree of resin residue at the bottom of the guide pores was evaluated by image analysis of these 10 SEM images. This is explained below.

[0196] First, extract the contour lines of the surface shape of the roughened surface. Then, among the roughened particles within a field of view, select the roughened particle with the highest front end and use its front end as the highest point of that field of view. Furthermore, among the roughened particles within a field of view, select the gap with the lowest bottom between the roughened particles and use the bottom of that gap as the lowest point of that field of view.

[0197] Next, draw a straight line passing through the highest point and parallel to the surface of the copper foil (i.e., a straight line parallel to the width of the field of view), namely the highest line, and a straight line passing through the lowest point and parallel to the surface of the copper foil, namely the lowest line. The area between these two lines is defined as the measurement area. Then, the height of 25% of the height of this measurement area (the distance between the highest and lowest lines) (the height from the lowest line) is set as the "reference height".

[0198] At this reference height, gaps with a width of 0.2 μm or more between roughened particles are defined as "valleys" between roughened particles. Furthermore, when resin remains in the valleys, the degree of resin residue at the roots of the roughened particles is evaluated based on the distance between the bottom of the valley and the surface of the remaining resin.

[0199] In all valleys within a 25 μm length centered on the bottom center of the via, the degree of resin residue at the root of the roughened particles was calculated, across a total of 10 fields of view. Laser processability (suppression of resin residue at the root of the roughened particles) was then evaluated based on their average values. The results are shown in Table 1.

[0200] In the examples and comparative examples, a distance of 0.6 μm or less between the bottom of the valley and the surface of the residual resin was considered acceptable, and is indicated by an ○ mark in Table 1. Conversely, a distance exceeding 0.6 μm was considered unacceptable, and is indicated by an × mark in Table 1. Furthermore, the bottom of the valley is defined as the intersection of a line orthogonal to the line representing the aforementioned reference height and passing through the center of the valley with the surface of the copper foil.

[0201] <Dust resistance>

[0202] After attaching a reference plate to the side of the copper foil that has not undergone surface roughening treatment, bring white lint-free paper into contact with the roughened side of the copper foil. Place a 1kg weight on the white lint-free paper and move the white lint-free paper 50mm in a direction parallel to the contact surface of the roughened side and the white lint-free paper at a speed of 100mm / min.

[0203] Using an optical microscope, a magnified image of the surface of white lint-free paper was obtained by photographing it under reflected illumination. The magnification was 20x. With the brightest areas of the magnified image set to a luminance of 255 and the darkest areas set to a luminance of 0, areas with a luminance below 200 were considered as copper powder transferred onto the white lint-free paper (copper powder caused by roughening particles). The area ratio (area percentage) of areas with a luminance below 200 in the magnified image was then calculated. The results are shown in Table 1.

[0204] In the examples and comparative examples, areas with a percentage of less than 0.5% were evaluated as acceptable and are indicated by an ○ in Table 1. Conversely, areas with a percentage of 0.5% or more were evaluated as unacceptable and are indicated by an × in Table 1.

[0205] <Oxidation of Copper Foil>

[0206] The surface-treated copper foil was placed in an oven for heating, and it was confirmed whether discoloration occurred after heating. The heating conditions were: temperature 250°C, heating time 30 minutes, and air atmosphere. The results are shown in Table 1. In the examples and comparative examples, the surface-treated copper foil was evaluated as acceptable when no discoloration occurred, and is indicated by ○ in Table 1. Conversely, the surface-treated copper foil was evaluated as unacceptable when discoloration occurred, and is indicated by × in Table 1.

[0207] Comparing Examples A1-A10 with Comparative Examples A1-A6, it is evident that Examples A1-A10 exhibit excellent laser processability in both aspects. Because resin residue at the bottom of the vias is suppressed, and resin residue at the roots of roughened particles is also suppressed, the number of fracture initiation points for the vias used for interlayer bonding is reduced. Therefore, a printed wiring board with good initial and long-term bonding reliability can be obtained.

[0208] Figure 7 This is a cross-sectional view of a copper-clad laminate using existing surface-treated copper foil. Figure 7 The cross-section of the via is shown, revealing resin residue at the roots of the roughened particles present at the bottom of the via. Therefore, the interface between the interlayer conductor and the surface-treated copper foil within the via is prone to crack initiation.

[0209] Figure 8 This is a cross-sectional view of a copper-clad laminate using the surface-treated copper foil of the first embodiment. Figure 8 The cross-section of the via is shown, revealing that because the laser can easily be directed to the roots of the roughened particles, resin residue at the roots of the roughened particles present at the bottom of the via is suppressed. Therefore, due to the strengthened bonding between the interlayer conductor and the surface-treated copper foil within the via, crack initiation is less likely to occur at the interface between the interlayer conductor and the surface-treated copper foil.

[0210] In addition, the processes for forming vias, circuit patterns, and interlayer interconnects in copper-clad laminates include... Figure 4 As shown, its specific content is as follows.

[0211] Figure 5 This illustrates an example of a process for forming blind vias on a double-sided copper-clad laminate 100 using laser irradiation. Furthermore, Figure 6 This illustration shows an example of a process for forming blind vias on a single-sided copper-clad laminate 100 using laser irradiation. The process for forming blind vias is largely the same for both single-sided and double-sided copper-clad laminates; therefore, the following explanation uses a double-sided copper-clad laminate as an example. Furthermore, in Figure 5 and Figure 6 In the figures, the corresponding components are labeled with the same reference numerals.

[0212] Towards Figure 5 The copper-clad laminate 100 shown in (a) is irradiated with laser 130 to form a blind via (see reference). Figure 5 (b)). In the formation of blind holes using laser irradiation, sometimes residue 120 remains at the bottom 140 of the blind hole after processing by laser irradiation 130 (caused by the metal of the surface-treated copper foil 111, or by the resin of the resin substrate 113) (see reference). Figure 5 (b)

[0213] Therefore, the copper-clad laminate 100 after blind via formation is subjected to desmearing treatment to remove residue 120 from the blind via (refer to...). Figure 5 (c) Then, after descaling, an interlayer connector 116 is formed. As a method for forming the interlayer connector 116, examples include forming a coating 115 and filling the blind hole with at least one of plating and metal paste to form the interlayer connector 116.

[0214] like Figure 5 As shown in (d), a plating process is performed to form a coating 115 on the inner surface of the blind hole. Furthermore, as... Figure 5 As shown in (e), the interlayer connector 116 can be formed by filling the blind via with at least one of plating and metal paste. In addition, the upper surface of the interlayer connector 116 does not need to be on the same plane as the surface treated copper foil 111 and the resin substrate 113.

[0215] [Examples and comparative examples of surface-treated copper foil according to the second embodiment]

[0216] [1] Preparation of copper foil substrate

[0217] Electrolytic copper foil is prepared as the raw material for surface-treated copper foil. This electrolytic copper foil becomes the copper foil substrate for roughening treatment. The electrolytic copper foil is manufactured by electrolysis under the following conditions. Furthermore, the electrolytic copper foil manufactured under the following conditions has 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 is measured on the surface of the electrolytic copper foil using a contact surface roughness measuring machine (Surfcorder SE1700 manufactured by Kosaka Research Institute Co., Ltd.).

[0218] <Manufacturing conditions for electrolytic copper foil>

[0219] Copper concentration in the electrolyte: 80 g / L

[0220] H2SO4 concentration in the electrolyte: 70 g / L

[0221] Chlorine concentration of electrolyte: 25 mg / L

[0222] Bath temperature: 55℃

[0223] Current density: 45A / dm 2

[0224] <Additives and Concentrations in the Electrolyte> Sodium 3-mercapto-1-propanesulfonate: 2 mg / L Hydroxyethylcellulose: 10 mg / L Low molecular weight adhesive (molecular weight 3000): 50 mg / L [2] Roughening treatment Next, a roughened surface is formed by performing a plating process on one side of the copper foil substrate prepared in [1] above, and a surface-treated copper foil is manufactured. This plating process is a two-stage electroplating process. In the first stage plating process (1), a first-stage treatment solution with the following composition is used, and the current density and energizing time are as described in Table 2. In the second stage plating process (2) following the first stage plating process (1), a second-stage treatment solution with the following composition is used, and the current density, energizing time, and the vertical outflow rate of the electrolyte in the electrolytic cell are as described in Table 2. The vertical outflow rate of the electrolyte in the electrolytic cell is obtained by dividing the outflow rate of the electrolyte above the opening position in the electrolytic cell by the outflow rate of the electrolyte below the opening position in the electrolytic cell. In addition, additional treatments may be performed before the first stage plating process (1) and after the second stage plating process (2) as needed.

[0225] <First Stage Treatment Solution>

[0226] Copper (Cu) concentration: 60 g / L

[0227] Sulfuric acid (H2SO4) concentration: 120 g / L

[0228] Bath temperature: 60℃

[0229] <Second Stage Treatment Solution>

[0230] Copper concentration: 20-30 g / L

[0231] H2SO4 concentration: 150g / L

[0232] Molybdenum (Mo) concentration: 0.2–0.4 g / L

[0233] Iron (Fe) concentration: 2 g / L

[0234] Bath temperature: 30~40℃

[0235] [3] Formation of the basal layer and intermediate layer

[0236] Next, on the roughened surface of the surface-treated copper foil manufactured in [2] above, metal plating is performed in the following order of nickel, zinc (Zn), and chromium (Cr) under the following conditions to form a base layer and an intermediate layer.

[0237] <Ni plating>

[0238] Ni concentration in the plating solution: 40 g / L

[0239] H3BO3 concentration in plating solution: 5 g / L

[0240] Bath temperature: 20℃

[0241] The pH of the plating solution is 3.6.

[0242] Current density: as shown in Table 2

[0243] Processing time: 10 seconds

[0244] <Zn plating>

[0245] Zn concentration in the plating solution: 2.5 g / L

[0246] NaOH concentration in the plating solution: 40 g / L

[0247] Bath temperature: 20℃

[0248] The pH of the plating solution is 3.6.

[0249] Current density: 0.3 A / dm 2

[0250] Processing time: 5 seconds

[0251] <Cr plating>

[0252] Cr concentration in plating solution: 5 g / L

[0253] Bath temperature: 30℃

[0254] The pH of the plating solution is 2.2.

[0255] Current density: 5A / dm 2

[0256] Processing time: 5 seconds

[0257] [4] Formation of silane coupling agent layer

[0258] Finally, a silane coupling agent layer is formed on the intermediate layer (especially the Cr-plated layer on the outermost surface) formed in [3]. The silane coupling agent layer is formed by coating the intermediate layer with an aqueous solution of 3% by mass of 3-epoxypropoxypropyltrimethoxysilane and drying it at 100°C. The amount of silane attached is 0.003 mg / dm³ in terms of silicon (Si) atoms. 2 .

[0259] [Table 2]

[0260] As described above in [1] to [4], surface-treated copper foils of Examples B1 to B10 and Comparative Examples B1 to B9 were manufactured. Some of the manufacturing conditions for the surface-treated copper foils were as described above, and others were as described in Table 2.

[0261] For the roughened surfaces of the obtained surface-treated copper foils, various physical properties were measured. Furthermore, the adhesion to the resin substrate, transmission loss, dusting resistance, oxidation resistance, and laser processability of each surface-treated copper foil were evaluated. The measurement and evaluation methods are described below. The measurement and evaluation results are shown in Table 2.

[0262] <The average height of the cross-section particles h_ave, the standard deviation of the width of the cross-section particles w_σ, and the skewness of the height of the cross-section particles h_sk of the roughened particles>

[0263] First, after embedding and curing a 5mm square test piece obtained by cutting out surface-treated copper foil using epoxy resin (e.g., epoxy-based adhesive), the surface-treated copper foil and resin were cut to create a cross-section orthogonal to the roughened surface. This cross-section was then precision-ground using an IM4000 ion polishing apparatus manufactured by Hitachi Advanced Technology Co., Ltd. The precision polishing conditions were: table mode C1 (oscillation angle: ±15°, oscillation speed: 6 reciprocations / min), accelerating voltage 6kV, and polishing time 30 minutes. Furthermore, the precision polishing using the ion polishing apparatus was performed with a protrusion that did not cause resin breakage, deformation of the surface-treated copper foil, or deformation of the roughened particles during cutting. The protrusion was, for example, approximately 50μm.

[0264] Then, using a scanning electron microscope (SEM) SU8020 manufactured by Hitachi High Technology Co., Ltd., the above cross-section was observed, and a secondary electron image at 5,000x magnification was obtained (see reference). Figure 9 (SEM images). The accelerating voltage of the scanning electron microscope was 3kV. Based on the observation of the above cross-section, SEM images of a rectangular region with a length of 19μm and a width of 500μm were prepared.

[0265] Furthermore, a cross-section is randomly generated from a surface-treated copper foil, and an SEM image of a rectangular region measuring 19 μm in length and 500 μm in width is obtained from this cross-section. An 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. Therefore, an SEM image of a rectangular region measuring 19 μm in length and 500 μm in width refers to an image formed by acquiring and connecting 20 SEM images of this rectangular region in a continuous manner. The following image analysis is performed on these 20 consecutive SEM images, specifically on a region with a horizontal length of 500 μm. The result of the following image analysis on this 500 μm region is that the surface-treated copper foil according to the present invention satisfies the constituent requirements of the present invention.

[0266] During SEM observation, the surface-treated copper foil is adjusted to be horizontal within the SEM image of the cross-section. Additionally, copper-clad laminates or printed circuit boards can be used as needed in the specimens for which SEM images of the cross-section are taken. When using copper-clad laminates or printed circuit boards, it is not necessary to peel the surface-treated copper foil from the resin substrate; the copper-clad laminate or printed circuit board can be directly cut for cross-sectional processing and observation.

[0267] Furthermore, the size of the roughening particles formed on the roughened surface was measured by image analysis of a 5,000x SEM image obtained from the aforementioned SEM observation. Specifically, in the SEM image, a roughening particle was identified, and its cross-sectional particle height and width were measured. Then, the cross-sectional particle height and width were measured for multiple roughening particles, 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.

[0268] For the aforementioned SEM images, image processing software (the open-source and free software "imageJ") was used to emphasize the contours of the coarsened particles. Then, binarization was performed to differentiate the coarsened particles by color. Following this, image processing was performed to remove noise generated during binarization. Finally, image processing was performed to make the areas of coarsened particles displayed as black after binarization blank. Afterward, the contour lines of the coarsened particles were extracted, and general measurement software (such as Photo Ruler) was used to measure the cross-sectional particle height and width of the coarsened particles within the contour lines.

[0269] Furthermore, the measurement of the cross-sectional particle height and width of the roughened particles can be performed using well-known image processing software such as "WinROOF" and "Photo Ruler." Detailed explanations will follow. See below for reference. Figure 10 An example of the simplest method for measuring roughened particles (image analysis method) is illustrated.

[0270] First, such as Figure 10 As shown in (a), a straight line L is drawn on the SEM image, parallel to the direction in which the roughening particles protrude from the roughened surface of the surface-treated copper foil and passing through the leading edge (vertices) V of the roughening particles. Next, as... Figure 10As shown in (b), a rectangle Sq is drawn on the SEM image, having two sides parallel to line L (two vertical sides) and two sides orthogonal to line L (top and bottom sides). The rectangle Sq can also be a square. The top side of the rectangle Sq passes through the front end V of the roughening particle, and the bottom side connects to the root portion of the roughening particle in the outline of the roughening particle. In the outline of the roughening particle, the root portion of the roughening particle has two locations, but the rectangle Sq is drawn such that the bottom side contacts the longer root portion of the vertical side. Furthermore, the root portion refers to the boundary point between the surface of the copper foil substrate before roughening treatment and the roughening particle, or the boundary point with an adjacent roughening particle, in the outline of the roughening particle.

[0271] The bottom edge of the rectangle Sq has two possible scenarios: one where it connects with the root portion of the roughened particle in the outline of the roughened particle (where the roughened particle protrudes in a direction not orthogonal to the roughened surface) and the other where it connects with the root portion of the roughened particle in a direction orthogonal to the roughened surface.

[0272] When the bottom edge of rectangle Sq and the root part of the roughened particle in the outline of the roughened particle meet at a point, since the meeting point is one of the two corners on the bottom side of rectangle Sq, this corner is set as R1.

[0273] When the bottom edge of rectangle Sq and the root part of the roughened particle in the outline of the roughened particle are connected at two points, since the two connection points are the two corners on the bottom side of rectangle Sq, one of the two corners is set as R1.

[0274] Furthermore, in either the case where the lower edge of rectangle Sq intersects the root portion of the roughened particle in the outline of the roughened particle at one point, or in the case where they intersect at two points, the other corner of the two corners on the lower side of rectangle Sq is set to R2 (refer to...). Figure 10 (b)

[0275] When the bottom edge of rectangle Sq connects at a point with the root portion of the roughened particle in the outline of the roughened particle, the vertical edge of the two vertical edges connecting the top and bottom edges of rectangle Sq, through angle R2, intersects the root portion R2' of the roughened particle in the outline of the roughened particle. This root portion R2' is the root portion that does not connect with the bottom edge of rectangle Sq.

[0276] Moreover, such as Figure 10As shown in (c), the length of the vertical side of the rectangle Sq is set as the cross-sectional particle height h of the roughening particle. Furthermore, the length of the top or bottom side is set as the cross-sectional particle width w of the roughening particle. Additionally, except for the special cases described below, a convex portion of a rectangle Sq for which the cross-sectional particle height h and cross-sectional particle width w are measured is considered a roughening particle.

[0277] Regarding the SEM image of the cross-section, a 500 μm region in the width direction of the SEM image was observed. Within this entire region, the cross-sectional particle height h and cross-sectional particle width w of each roughened particle were measured. Then, based on the number of roughened particles measured, the average cross-sectional particle height h_ave, the standard deviation w_σ of the cross-sectional particle width, and the skewness h_sk of the cross-sectional particle height were calculated. Furthermore, the standard deviation w_σ of the cross-sectional particle width and the skewness h_sk of the cross-sectional particle height are defined by the following mathematical formulas. In the mathematical formulas, a horizontal bar (-) is placed above x (x-bar), which indicates the measured values ​​x1, x2, x3, ..., x... n The average value.

[0278] [Mathematical Expression 1]

[0279] [Mathematical Expression 2]

[0280] Next, refer to the requirements Figure 11 The method for measuring roughening particles that are not measured as roughening particles and those with special shapes (the aforementioned special examples) will be explained.

[0281] Sometimes, roughened particles that protrude further inward than the cut surface are partially reflected in the observation section. Such roughened particles appear to float from the surface-treated copper foil in the observation section, but they are not included in the measurement of particle height and width.

[0282] Furthermore, although not illustrated, protrusions with a cross-sectional particle height of 0.15 μm or less, as measured against the aforementioned benchmark, do not affect the transmission characteristics and sealing properties of interest in this invention, and are also difficult to measure accurately. Therefore, protrusions with a cross-sectional particle height of 0.15 μm or less are not considered for measuring the cross-sectional particle height and width, and this situation is not included in the "roughened particles" of this invention.

[0283] Furthermore, such as Figure 11As shown in (a), convex portions where the ratio (h / w) of the cross-sectional particle height h to the cross-sectional particle width w, as measured by the above-mentioned benchmark, is less than 0.40, will not affect the transmission characteristics and sealing properties of interest in this invention. Therefore, particles with a ratio (h / w) of less than 0.40 for the cross-sectional particle height h and cross-sectional particle width are not considered as objects of measurement for cross-sectional particle height and width, and this situation is not included in the "roughened particles" of this invention.

[0284] then, Figure 11 Example (b) is a measurement case where the front end has two or more protrusions. In this case, such as Figure 11 As shown in (b), based on the above definition, each front end can be regarded as a roughened particle, and the height and width of the cross-section particle can be measured.

[0285] Figure 11 (c) is also a measurement example with two or more protrusions at the front end, but if the straight line L' drawn for one protrusion intersects with the two longitudinal sides of the rectangle Sq of other protrusions, that protrusion is not considered as the measurement object. For example, in Figure 11 In (c), the straight line L' drawn for the front end V' of a convex part intersects the two longitudinal sides of the rectangle Sq with the other convex parts having the front end V, so the convex part with the front end V' is not considered as the measurement object.

[0286] However, when two or more protrusions are in a relationship where they are straight lines L' and the two longitudinal sides of a rectangle Sq of different other protrusions intersect, the protrusion with the highest cross-sectional particle height h is taken as the measurement object. Other protrusions are not taken as measurement objects because they have little impact on the transmission characteristics and tightness that are of interest in this invention.

[0287] Figure 11 Example (d) is a measurement case where the ratio of the cross-sectional particle height h to the cross-sectional particle width w (h / w) is less than 0.40, and other protrusions exist on a protrusion with a relatively blurred root portion. In this case, the blurred root portion is not considered as the measurement object; the measurement is performed on the protrusion with a distinguishable root portion based on the above definition. This is because a gentle protrusion with a blurred root portion would not normally affect the transmission characteristics and sealing properties that are of interest in this invention.

[0288] For roughened particles with shapes other than those described above, considering the effects on the transport characteristics and adhesion that are of interest in this invention, the cross-sectional particle height h and cross-sectional particle width w are measured based on the above-mentioned criteria.

[0289] <Adhesion to resin-based substrates>

[0290] A surface-treated copper foil is laminated on one side of a 50 μm thick liquid crystal polymer film (manufactured by Ise-Murata Manufacturing Co., Ltd., thickness accuracy: 0.7 μm, relative permittivity: 3.4, dielectric loss tangent: 0.0020, ratio of maximum to minimum thermal expansion coefficient: 1.4) with a roughened surface in contact with the liquid crystal polymer film. On the other side, a polyimide film ("Upirex 20S" manufactured by UBE Co., Ltd.) is laminated as a release material to obtain a laminate.

[0291] The laminate is held between two 2mm thick stainless steel plates, and then the part holding the laminate between the stainless steel plates is held between two 1mm thick stainless steel fiber fabrics as cushioning material, and placed in a vacuum press. The press is then held at 300°C and 3MPa for 5 minutes. After cooling, the heat-pressed laminate is removed from the vacuum press, the release material is removed, and a single-sided copper-clad laminate is obtained.

[0292] Using a tensile testing machine ("AGS-H" manufactured by Shimadzu Corporation), the strength (unit: N / mm) of surface-treated copper foil being peeled off from the single-sided copper-clad laminate at a speed of 50 mm / min in a 180° direction was determined according to the method specified in JIS C6471-1995.

[0293] Specifically, a 5mm wide mask tape is adhered to the copper foil of a single-sided copper-clad laminate, and then immersed in a ferric chloride solution to etch away unwanted portions of the copper foil. Afterward, the single-sided copper-clad laminate is washed with water and the mask tape is peeled off. It is then dried in a circulating oven at 80°C for 1 hour to form a 5mm wide linear circuit pattern.

[0294] When peeling copper foil from a single-sided copper-clad laminate, the test piece is adhered to a reinforcing plate with a thickness of 1 mm or more in a manner that does not cause the test piece (single-sided copper-clad laminate) to buckle and change the peeling angle. After peeling one end of the formed circuit pattern and clamping it on the tensile testing machine, the copper foil is peeled relative to the test piece at a speed of 50 mm / min in a 180° direction for more than 10 mm. The average value of the total strength during this period is calculated and taken as the peel strength (N / mm). The results are shown in Table 2.

[0295] In the examples and comparative examples, the 180° peel strength was measured as an indicator of the adhesion between the resin substrate and the surface-treated copper foil. A peel strength of 0.70 N / mm or higher was considered acceptable, while a peel strength of less than 0.70 N / mm was considered unacceptable.

[0296] <Transmission Loss>

[0297] A double-sided copper-clad laminate is fabricated by bonding surface-treated copper foil to both sides of a 50μm thick liquid crystal polymer film (manufactured by Ise-Murata Manufacturing Co., Ltd., thickness accuracy: 0.7μm, relative permittivity: 3.4, dielectric loss tangent: 0.0020, ratio of maximum to minimum thermal expansion coefficient: 1.4).

[0298] Next, the surface-treated copper foil on one side of the above-mentioned two-sided copper-clad laminate is etched to form a linear pattern with a predetermined width (110μm) and length (20mm and 50mm) as a signal layer, and the surface-treated copper foil on the other side is used as a ground layer to fabricate a circuit substrate with a microstrip structure.

[0299] Furthermore, after drying the circuit board in a circulating oven at 50°C for 24 hours, it was cooled to room temperature under the standard conditions described in JISC6481-1996 to produce a circuit board for evaluating high-frequency characteristics.

[0300] The two ends of the pattern of the high-frequency characteristic evaluation circuit board fabricated in the above manner were clamped into a test fixture, and a high-frequency signal (40 GHz) was allowed to flow through the pattern. The strength of the transmitted signal (S21) was measured. The signal strength was measured using a PNA microwave network analyzer N5227B manufactured by Keysight Technologies Co., Ltd., and a general-purpose test fixture 3680V manufactured by Anritsu Co., Ltd. The above measurement was performed five times with the same pattern, and the average value was taken as the transmission loss of each circuit board.

[0301] Then, based on 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 the difference in the pattern length of the two circuit boards for evaluating high-frequency characteristics, the transmission loss per unit length is calculated.

[0302] Furthermore, using the transmission loss per unit length of Example B2 as a baseline value (100), the transmission loss per unit length of the surface-treated copper foil in each example and comparative example was indexed. The results are shown in Table 2. In the examples and comparative examples, when the index of the transmission loss exceeds 115, the transmission loss is considered large and unacceptable, and is indicated by × in Table 2. Furthermore, when the index of the transmission loss is 115 or less, the transmission loss is considered small and acceptable, and is indicated by ○ in Table 2. Furthermore, when the index of the transmission loss is 100 or less, the transmission loss is particularly small and acceptable, and is indicated by ◎ in Table 2.

[0303] <Laser processability (suppression of resin residue at the bottom of vias)>

[0304] In the formation of blind vias using laser irradiation, resin residue from the resin-based substrate sometimes remains at the bottom of the formed blind via. If resin residue remains, even if interlayer bonding is formed, sufficient conductivity may not be achieved, reducing the reliability of the interlayer bonding connection. This study evaluates the laser processability of surface-treated copper foil used to fabricate copper-clad laminates, specifically whether it is difficult for resin residue from the resin-based substrate to remain at the bottom of the formed blind vias using laser irradiation.

[0305] A single-sided copper-clad laminate is fabricated by bonding a 12μm thick surface-treated copper foil to one side of a 50μm thick liquid crystal polymer film (manufactured by Ise-Murata Manufacturing Co., Ltd., thickness accuracy: 0.7μm, relative permittivity: 3.4, dielectric loss tangent: 0.0020, ratio of maximum to minimum thermal expansion coefficient: 1.4).

[0306] Next, a carbon dioxide laser is irradiated onto the liquid crystal polymer film side of the aforementioned single-sided copper-clad laminate to form 150 vias at arbitrary locations. The diameter of the vias is 100 μm. Furthermore, the laser irradiation is performed under the following conditions, based on the structure of the roughened particles: pulse width 1–5 μs, front-end energy 1–3 mJ, mask diameter 1–3 mm, and irradiation number 5–10 shots.

[0307] After the vias are formed, the roughened surface of the copper foil at the bottom of the via is observed to confirm the presence or absence of resin residue. The presence or absence of resin residue is confirmed by observing the bottom of the via as a film residue using an optical microscope at 10x magnification after laser processing and etching to remove the surface-treated copper foil. All 150 vias were observed using an optical microscope, and the number of vias without resin residue was counted.

[0308] In the examples and comparative examples, when the number of vias without resin residue was 80 or more, the processability was excellent, and therefore the result was deemed acceptable, indicated by the ◎ mark in Table 2. Furthermore, when the number of vias without resin residue was 40 or more but less than 79, the result was deemed acceptable, indicated by the ○ mark in Table 2. Finally, when the number of vias without resin residue was 39 or less, the result was deemed unacceptable, indicated by the × mark in Table 2.

[0309] <Laser processability (suppression of resin residue at the root of roughened particles)>

[0310] The technical problem of this embodiment is to provide a printed wiring board with excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and good long-term connection reliability. Specifically, it suppresses the residue of resin at the root of the roughened particles of the surface-treated copper foil, and suppresses cracking between the resin substrate and the surface-treated copper foil caused by thermal stress during long-term use, which would lead to poor connection, cracking, and reduced connection reliability.

[0311] According to this embodiment, a printed wiring board can be provided that exhibits excellent adhesion between the resin substrate and the surface-treated copper foil, low transmission loss, and minimal resin residue at the roots of roughened particles (resin has excellent laser processability). Because resin residue at the roots of roughened particles is minimal, long-term connection reliability can be ensured.

[0312] Surface-treated copper foil was used to fabricate copper-clad laminates, and its laser processability was evaluated. Specifically, in the formation of blind vias using laser irradiation, it was determined whether resin from the resin-based substrate could not easily remain at the root of the roughened particles within the formed blind vias.

[0313] Similar to the case of "laser processability (suppression of resin residue at the bottom of vias)" described above, vias were formed using a carbon dioxide laser after fabricating a single-sided copper-clad laminate. The single-sided copper-clad laminate with the vias formed was then analyzed as follows.

[0314] First, the single-sided copper-clad laminate with vias is pretreated. Osmium (Os) or platinum (Pt)-palladium (Pd) is deposited onto the single-sided copper-clad laminate. This allows the bottom of the vias to be observed using a scanning electron microscope (SEM). The single-sided copper-clad laminate is then embedded with an embedding resin such as epoxy resin. The laminate is cut to the maximum diameter section that allows observation of the vias, and the resulting section is mirror-polished. Finally, the polishing marks are removed by planar grinding to obtain the sample for SEM observation.

[0315] The cross-section of the above-mentioned sample was observed using a scanning electron microscope (SEM), obtaining secondary electron images (SEM images) at a magnification of 5,000x. The accelerating voltage of the SEM was 10 kV. SEM images with a width of 25 μm were acquired in one field of view, and SEM images were acquired in 10 fields of view. Then, the degree of resin residue at the bottom of the guide pores was evaluated by image analysis of these 10 SEM images. This is explained below.

[0316] First, extract the contour lines of the surface shape of the roughened surface. Then, among the roughened particles within a field of view, select the roughened particle with the highest front end and use its front end as the highest point of that field of view. Furthermore, among the roughened particles within a field of view, select the gap with the lowest bottom between the roughened particles and use the bottom of that gap as the lowest point of that field of view.

[0317] Next, draw a straight line passing through the highest point and parallel to the surface of the copper foil (i.e., a straight line parallel to the width of the field of view), namely the highest line, and a straight line passing through the lowest point and parallel to the surface of the copper foil, namely the lowest line. The area between these two lines is defined as the measurement area. Then, the height of 25% of the height of this measurement area (the distance between the highest and lowest lines) (the height from the lowest line) is set as the "reference height".

[0318] At this reference height, gaps with a width of 0.2 μm or more between roughened particles are defined as "valleys" between roughened particles. Furthermore, when resin remains in the valleys, the degree of resin residue at the roots of the roughened particles is evaluated based on the distance between the bottom of the valley and the surface of the remaining resin.

[0319] In all valleys within a 25 μm length centered on the bottom center of the via, the degree of resin residue at the root of the roughened particles was calculated, across a total of 10 fields of view. Laser processability (suppression of resin residue at the root of the roughened particles) was then evaluated based on their average values. The results are shown in Table 2.

[0320] In the examples and comparative examples, a distance of 0.6 μm or less between the bottom of the valley and the surface of the residual resin was considered acceptable, and is indicated by an ○ mark in Table 2. Conversely, a distance exceeding 0.6 μm was considered unacceptable, and is indicated by an × mark in Table 2. Furthermore, the bottom of the valley is defined as the intersection of a line orthogonal to the line representing the aforementioned reference height and passing through the center of the valley with the surface of the copper foil.

[0321] <Dust resistance>

[0322] After attaching a reference plate to the side of the copper foil that has not undergone surface roughening treatment, bring white lint-free paper into contact with the roughened side of the copper foil. Place a 1kg weight on the white lint-free paper and move the white lint-free paper 50mm in a direction parallel to the contact surface of the roughened side and the white lint-free paper at a speed of 100mm / min.

[0323] Using an optical microscope, a magnified image of the surface of white lint-free paper was obtained by photographing it under reflected illumination. The magnification was 20x. With the brightest areas of the magnified image set to a luminance of 255 and the darkest areas set to a luminance of 0, areas with a luminance below 200 were considered as copper powder transferred onto the white lint-free paper (copper powder caused by roughening particles). The area ratio (area percentage) of areas with a luminance below 200 in the magnified image was then calculated. The results are shown in Table 2.

[0324] In the examples and comparative examples, areas with a percentage of less than 0.5% were evaluated as acceptable and are indicated by an ○ in Table 2. Conversely, areas with a percentage of 0.5% or more were evaluated as unacceptable and are indicated by an × in Table 2.

[0325] <Oxidation of Copper Foil>

[0326] The surface-treated copper foil was placed in an oven for heating, and it was confirmed whether discoloration occurred after heating. The heating conditions were: temperature 250°C, heating time 30 minutes, and air atmosphere. The results are shown in Table 2. In the examples and comparative examples, the surface-treated copper foil was evaluated as acceptable when no discoloration occurred, and is indicated by ○ in Table 2. Conversely, the surface-treated copper foil was evaluated as unacceptable when discoloration occurred, and is indicated by × in Table 2.

[0327] Figure 7 This is a cross-sectional view of a copper-clad laminate using existing surface-treated copper foil. Figure 7 The cross-section of the via is shown, revealing resin residue at the roots of the roughened particles present at the bottom of the via. Therefore, the interface between the interlayer conductor and the surface-treated copper foil within the via is prone to crack initiation.

[0328] Figure 8 This is a cross-sectional view of a copper-clad laminate using the surface-treated copper foil of the first embodiment. Figure 8 The cross-section of the via is shown, revealing that because the laser can easily be directed to the roots of the roughened particles, resin residue at the roots of the roughened particles present at the bottom of the via is suppressed. Therefore, due to the strengthened bonding between the interlayer conductor and the surface-treated copper foil within the via, crack initiation is less likely to occur at the interface between the interlayer conductor and the surface-treated copper foil.

[0329] In addition, the processes for forming vias, circuit patterns, and interlayer interconnects in copper-clad laminates include... Figure 4 As shown, its specific content is as follows.

[0330] Figure 5 This illustrates an example of a process for forming blind vias on a double-sided copper-clad laminate 100 using laser irradiation. Furthermore, Figure 6This illustration shows an example of a process for forming blind vias on a single-sided copper-clad laminate 100 using laser irradiation. The process for forming blind vias is largely the same for both single-sided and double-sided copper-clad laminates; therefore, the following explanation uses a double-sided copper-clad laminate as an example. Furthermore, in Figure 5 and Figure 6 In the figures, the corresponding components are labeled with the same reference numerals.

[0331] Towards Figure 5 The copper-clad laminate 100 shown in (a) is irradiated with laser 130 to form a blind via (see reference). Figure 5 (b)). In the formation of blind holes using laser irradiation, sometimes residue 120 remains at the bottom 140 of the blind hole after processing by laser irradiation 130 (caused by the metal of the surface-treated copper foil 111, or by the resin of the resin substrate 113) (see reference). Figure 5 (b)

[0332] Therefore, the copper-clad laminate 100 after blind via formation is subjected to desmearing treatment to remove residue 120 from the blind via (refer to...). Figure 5 (c) Then, after descaling, an interlayer connector 116 is formed. As a method for forming the interlayer connector 116, examples include forming a coating 115 and filling the blind hole with at least one of plating and metal paste to form the interlayer connector 116.

[0333] like Figure 5 As shown in (d), a plating process is performed to form a coating 115 on the inner surface of the blind hole. Furthermore, as... Figure 5 As shown in (e), the interlayer connector 116 can be formed by filling the blind via with at least one of plating and metal paste. In addition, the upper surface of the interlayer connector 116 does not need to be on the same plane as the surface treated copper foil 111 and the resin substrate 113.

[0334] Explanation of reference numerals in the attached figures

[0335] 10: Surface-treated copper foil

[0336] 10a: Roughened surface

[0337] 20: Resin-based substrate

[0338] 30: Copper-clad laminate.

Claims

1. A surface-treated copper foil having a roughened surface with roughening particles formed on at least one side, wherein the physical property values ​​measured on said roughened surface satisfy the following (a), (i) and (u). (a) Using a spectrophotometer with a light source emitting 45° polarized light at an emission wavelength of 600 nm, the normal reflectance of the roughened surface, measured under conditions where both the incident angle and reflection angle are 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 higher and 15.5 or lower. (ウ) The Ssk value of the roughened surface, as measured using a laser microscope, is 0.30 or higher and 0.80 or lower.

2. The surface-treated copper foil according to claim 1, wherein, A nickel coating is formed on the roughened surface, and the amount of nickel adhered to the nickel coating is 0.20 mg / dm². 2 Above and 0.40 mg / dm 2 the following.

3. A surface-treated copper foil having a roughened surface with roughening particles formed on at least one side, wherein when the surface-treated copper foil is cut to produce a cross section orthogonal 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 (カ), (キ) and (ク). (k) The average height h_ave of the cross-section of the roughened particles is greater than 0.35 μm and less than 0.70 μm. (キ) The standard deviation w_σ of the cross-sectional particle width of the roughened particles is 0.05 μm or more and 0.10 μm or less. (c) The skewness h_sk of the cross-sectional particle height of the roughened particle is greater than or equal to 0.80 and less than or equal to -2.50×h_ave+3.

50.

4. A copper-clad laminate, comprising: 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-based substrate is formed from 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 of claim 4.

8. The printed wiring board according to claim 7, wherein, The surface-treated copper foil and the resin-based substrate undergo plastic deformation.

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

Images