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

Abstract

Provided is a roughened copper foil which, when used in a copper-clad laminate board or a printed circuit board, is capable of attaining both excellent transmission properties and high peel strength. This roughened copper foil has a roughened surface on at least one side thereof, wherein the proportion of the sum of the frequency components at a frequency of 1 to 5, inclusive, constitutes at least 15.0% of the sum of the frequency components at a frequency of 1 to 511, inclusive, and the average value of the frequency components at a frequency of 13 to 511, inclusive, equals 0.010μm or less, when a cross-sectional curve having a target length of 64μm in the horizontal direction on the roughened surface is broken down into 512 frequency components by a Fourier transform at a frequency interval of 1 and a frequency range of 0 to 511, inclusive.

Description

[Technical Field]

[0001] This invention relates to roughened copper foil, copper-clad laminates, and printed circuit boards. [Background technology]

[0002] In the manufacturing process of printed circuit boards, copper foil is widely used in the form of copper-clad laminates, which are bonded to an insulating resin substrate. In this regard, it is desirable that the copper foil and the insulating resin substrate have high adhesion to prevent delamination of the wiring during the manufacturing of printed circuit boards. Therefore, in the case of copper foil for the manufacturing of conventional printed circuit boards, the bonding surface of the copper foil is roughened to create irregularities made of fine copper particles, and these irregularities are pressed into the interior of the insulating resin substrate by a pressing process to create an anchoring effect and improve adhesion.

[0003] As an example of copper foil subjected to such roughening treatment, Patent Document 1 (Japanese Patent Application Publication No. 2018-172785) discloses a surface-treated copper foil having a roughening treatment layer on at least one surface of the copper foil, wherein the arithmetic mean roughness Ra of the roughening treatment layer side surface is 0.08 μm or more and 0.20 μm or less, and the glossiness in the TD (width direction) of the roughening treatment layer side surface is 70% or less. With such a surface-treated copper foil, the shedding of roughening particles provided on the copper foil surface is well suppressed, and the occurrence of wrinkles and streaks when bonded to an insulating substrate is well suppressed.

[0004] Incidentally, with the increasing sophistication of portable electronic devices in recent years, signals, whether digital or analog, are becoming higher frequency in order to process large amounts of data at high speed, and printed circuit boards suitable for high-frequency applications are in demand. For such high-frequency printed circuit boards, it is desirable to reduce transmission loss in order to transmit high-frequency signals without degradation. A printed circuit board consists of copper foil processed into a wiring pattern and an insulating substrate, and the main losses in transmission loss are conductor loss due to the copper foil and dielectric loss due to the insulating substrate.

[0005] In this regard, roughened copper foil designed to reduce transmission loss has been proposed. For example, Patent Document 2 (Japanese Patent Publication No. 2015-148011) discloses a method for controlling the skewness Rsk of the copper foil surface, based on JIS B0601-2001, to a predetermined range of -0.35 to 0.53 by surface treatment, with the aim of providing a surface-treated copper foil with low signal transmission loss and a laminate using the same. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-172785 [Patent Document 2] Japanese Patent Publication No. 2015-148011 [Overview of the project]

[0007] As mentioned above, in recent years there has been a demand to improve the transmission characteristics (high-frequency characteristics) of printed circuit boards. To meet these demands, finer roughening treatments have been attempted on the bonding surface of copper foil with insulating resin substrate. That is, in order to reduce the unevenness of the copper foil surface, which is a factor that increases transmission loss, it is conceivable to perform fine roughening treatment on copper foil surfaces with small undulations (for example, the surface of double-sided smooth foil or the electrode surface of electrolytic copper foil). However, when copper-clad laminates are processed or printed circuit boards are manufactured using such roughened copper foil, problems can arise in which the peel strength between the copper foil and the substrate is generally low and the adhesion reliability is poor.

[0008] The present inventors have now found that by applying a surface profile that satisfies predetermined conditions when the cross-sectional curve of a roughened copper foil is Fourier transformed, it is possible to achieve both excellent transmission characteristics and high peel strength in copper-clad laminates or printed circuit boards manufactured using this material.

[0009] Therefore, an object of the present invention is to provide a roughened copper foil capable of achieving both excellent transmission characteristics and high peel strength when used in a copper-clad laminate or a printed wiring board.

[0010] According to the present invention, the following aspects are provided. [Aspect 1] A roughened copper foil having a roughened surface on at least one side, when the cross-sectional curve of 64 μm in the horizontal direction on the roughened surface is decomposed into 512 frequency components by Fourier transform in a frequency range of 0 or more and 511 or less and a frequency interval of 1, the ratio of the sum of frequency components of 1 or more and 5 or less to the sum of frequency components of 1 or more and 511 or less is 15.0% or more, and the average value of frequency components of 13 or more and 511 or less is 0.010 μm or less. [Aspect 2] The roughened copper foil according to Aspect 1, wherein the ratio of the sum of frequency components of 1 or more and 5 or less to the sum of frequency components of 1 or more and 511 or less is 18.0% or more and 90.0% or less. [Aspect 3] The roughened copper foil according to Aspect 1 or 2, wherein the ratio of the sum of frequency components of 13 or more and 511 or less to the sum of frequency components of 1 or more and 511 or less is 66.0% or less. [Aspect 4] The roughened copper foil according to any one of Aspects 1 to 3, wherein the average value of frequency components of 1 or more and 511 or less in the result of the Fourier transform is 0.007 μm or more. [Aspect 5] The roughened copper foil according to any one of Aspects 1 to 4, wherein the average value of frequency components of 1 or more and 5 or less in the result of the Fourier transform is 0.150 μm or more. [Aspect 6] The roughened copper foil according to any one of Aspects 1 to 5, wherein the average value of frequency components of 13 or more and 213 or less in the result of the Fourier transform is 0.025 μm or less. [Aspect 7] The roughened copper foil according to any one of Aspects 1 to 6, comprising a rust prevention treatment layer and / or a silane coupling agent treatment layer on the roughened treatment surface. [Aspect 8] The roughened copper foil according to any one of Aspects 1 to 7, wherein the roughened copper foil is an electrolytic copper foil and the roughened treatment surface is present on the deposition surface side of the electrolytic copper foil. [Aspect 9] A copper-clad laminate comprising the roughened copper foil according to any one of Aspects 1 to 8. [Aspect 10] A printed wiring board comprising the roughened copper foil according to any one of Aspects 1 to 8.

Brief Description of the Drawings

[0011] [Figure 1] A diagram for explaining Fourier transform, showing that Fourier transform is performed on the curve f(x) and decomposed into a plurality of frequency components. [Figure 2] A diagram for explaining that the surface unevenness of the roughened copper foil consists of roughened particle components and waviness components [Figure 3A] A diagram for explaining the relationship between the frequency components after Fourier transform and the waviness of the copper foil, showing the roughened treatment surface of the roughened copper foil on which roughened particles are formed on the copper foil with large waviness. [Figure 3B] A diagram for explaining the relationship between the frequency components after Fourier transform and the waviness of the copper foil, showing the roughened treatment surface of the roughened copper foil on which roughened particles are formed on the smooth copper foil. [Figure 4A] A diagram for explaining the relationship between the frequency components after Fourier transform and the roughened particles, showing the roughened treatment surface of the roughened copper foil having fine roughened particles. [Figure 4B] A diagram for explaining the relationship between the frequency components after Fourier transform and the roughened particles, showing the roughened treatment surface of the roughened copper foil having large roughened particles. [Figure 5] A schematic diagram showing an example of the roughened copper foil of the present invention.

Modes for Carrying Out the Invention

[0012] definition The following are definitions of terms and parameters used to specify the present invention.

[0013] In this specification, "cross-sectional curve" refers to the curve that appears at the cut surface when the actual surface of a sample is cut by a specified vertical plane, and corresponds to the "cross-sectional curve of the actual surface" as defined in JIS B0601-2013. The cross-sectional curve can be obtained by measuring the surface profile of a predetermined measurement area on the roughened surface using a commercially available laser microscope. Preferred measurement conditions for the laser microscope are shown in the examples described below.

[0014] In this specification, "Fourier transform" means transforming a curve f(x) of a target length L (μm) in the horizontal direction into a sine wave of one frequency or a sum of sine waves of two or more frequencies, and "frequency" means the number of waves (reciprocal of wavelength) within length L. As shown in the example in Figure 1, even a curve f(x) that at first glance looks very different from a sine wave can be represented as a sum of one or more sine waves by appropriately selecting the coefficients (amplitudes of the sine waves) for each frequency. In other words, when a Fourier transform is performed on a curve f(x) under predetermined conditions, the coefficients corresponding to each frequency are uniquely determined. In this specification, the frequency coefficients mentioned above are referred to as "frequency components". In the example shown in Figure 1, the frequency components at frequencies 1 (one wave in length L), 2 (two waves in length L), 3 (three waves in length L), 4 (four waves in length L), and 5 (five waves in length L) are 1.00, 0.05, 0.15, 0.03, and 0.10, respectively. Note that the frequency components are values ​​that take into account the magnitude (absolute value) of the amplitude in the original curve f(x), and as the amplitude of the curve f(x) increases, the frequency components at each frequency also increase.

[0015] The frequency components will be explained in more detail based on the example shown in Figure 1. In the following explanation, it is assumed that the Fourier transform of the example shown in Figure 1 was performed on a curve f(x) with a horizontal length L (μm) under the conditions of a frequency between 1 and 5 and a frequency interval of 1. For simplicity, in this example, it is assumed that there is no phase difference between the sine waves constituting the curve f(x). When a Fourier transform is performed on the curve f(x) under these conditions, the frequency components of each frequency and their proportions are as shown in Table 1.

[0016] [Table 1]

[0017] Based on the numerical values ​​of the frequency components at each frequency, it is possible to calculate the proportion of the frequency components within a given frequency range and the average value of the frequency components within that range. For example, in the above example, the proportion of the sum of frequency components between frequencies 1 and 3 (1.20 μm = 1.00 μm + 0.05 μm + 0.15 μm) to the sum of frequency components between frequencies 1 and 5 (1.33 μm) is 90.2% (= (1.20 / 1.33) × 100). Also, in the above example, the average value of the frequency components between frequencies 3 and 5 is 0.09 μm (= (0.15 μm + 0.03 μm + 0.10 μm) / 3).

[0018] In this specification, the Fourier transform shall be performed on a cross-sectional curve with a horizontal length L = 64 μm, under the conditions of a frequency range of 0 to 511 and a frequency interval of 1 (however, a frequency of 0 means that there are 0 waves in length L, and therefore it is not used in the calculation of various parameters). Therefore, frequency represents the number of waves per 64 μm, but the unit of frequency ( / 64 μm) shall not be stated in this specification. Note that when considering moving waves such as electromagnetic waves (waves that involve both time and space), the number of waves per unit time is called "frequency (Hz)", and the number of waves per unit space is called "wavenumber (m)". -1It is sometimes referred to as "wavenumber." In this specification, although the subject matter is the number of waves per unit space, the term "frequency" will be used instead of "wavenumber." This is because, in this technical field, it is common to refer to the number of waves per unit space as "frequency," and also because time-varying waves are not the subject matter of this specification, thus leaving no room for misunderstanding.

[0019] The Fourier transform described above can be performed using commercially available software (for example, "MountainsMap Imaging Topography 9.0" from Digital Surf). The analysis method using this software will be shown in the examples described below.

[0020] In this specification, the "electrode surface" of electrolytic copper foil refers to the surface that was in contact with the cathode during the manufacturing of the electrolytic copper foil.

[0021] In this specification, the "deposited surface" of electrolytic copper foil refers to the surface on which electrolytic copper is deposited during the manufacturing of the electrolytic copper foil, that is, the surface that is not in contact with the cathode.

[0022] Roughened copper foil The copper foil of the present invention is a roughened copper foil. This roughened copper foil has a roughened surface on at least one side. When the cross-sectional curve of the roughened surface of the roughened copper foil, with a horizontal length of 64 μm, is decomposed into 512 frequency components by a Fourier transform with a frequency range of 0 to 511 and a frequency interval of 1, the ratio of the sum of frequency components with frequencies from 1 to 5 to 1 to the sum of frequency components with frequencies from 1 to 511 is 15.0% or more. Furthermore, when the roughened copper foil is decomposed into 512 frequency components by the above Fourier transform, the average value of the frequency components with frequencies from 13 to 511 is 0.010 μm or less. In this way, by providing a surface profile that satisfies predetermined conditions when the cross-sectional curve of the roughened copper foil is Fourier transformed, it is possible to achieve both excellent transmission characteristics and high peel strength (e.g., normal peel strength and hydrochloric acid peel strength) in copper-clad laminates or printed circuit boards manufactured using this material. For the sake of explanation, the "proportion of the sum of frequency components with frequencies between A and B to the sum of frequency components with frequencies between 1 and 511" is sometimes simply referred to as the "proportion of frequency components with frequencies between A and B."

[0023] Excellent transmission characteristics and high peel strength are inherently difficult to achieve simultaneously. This is because, in order to obtain excellent transmission characteristics, it is necessary to reduce the surface irregularities of the copper foil, while in order to obtain high peel strength, it is necessary to increase the surface irregularities of the copper foil; the two are in a trade-off relationship. As shown in Figure 2, the surface irregularities of roughened copper foil consist of "roughened particle components" and "undulation components" with a longer period than the roughened particle components. Generally, in order to obtain excellent transmission characteristics, it is conceivable to perform a fine roughening treatment on a copper foil surface with small undulations (for example, the surface of a double-sided smooth foil or the electrode surface of an electrolytic copper foil) to form small roughened particles. However, when copper-clad laminates or printed circuit boards are manufactured using such roughened copper foil, the peel strength between the copper foil and the substrate is generally low.

[0024] In this regard, the configuration of the present invention makes it possible to desirablely achieve excellent transmission characteristics and high peel strength when used in copper-clad laminates or printed circuit boards. Although the mechanism is not entirely clear, it is thought that roughened copper foil satisfying the above-mentioned parameters has fine bumps (roughened particles) that are advantageous for transmission characteristics, and that the adhesion lacking due to the miniaturization of the bumps can be compensated for by the undulation of the copper foil, which unexpectedly has little effect on transmission characteristics. Here, in order to explain the relationship between frequency components and the undulation of the copper foil, an example of roughened copper foil in which roughened particles are formed on a copper foil surface with large undulations is shown in Figure 3A, and an example of roughened copper foil in which roughened particles are formed on a smooth copper foil surface is shown in Figure 3B. As shown in Figure 3A, roughened copper foil with large undulations has a roughened surface that is close to a (simple) shape of a low-frequency (long-wavelength) sine wave. For this reason, it is thought that the proportion of low-frequency components with frequencies between 1 and 5 becomes large as a result of the above-mentioned Fourier transform. On the other hand, as shown in Figure 3B, roughened copper foil with small undulations has a complex shape on its roughened surface that differs significantly from a sine wave. Therefore, it is thought that the result of the Fourier transform described above is a mixture of low-frequency and high-frequency components (i.e., the proportion of low-frequency components becomes smaller). Furthermore, to explain the relationship between frequency components and roughened particles, an example of roughened copper foil with fine roughened particles is shown in Figure 4A, and an example of roughened copper foil with coarse roughened particles is shown in Figure 4B. In this regard, when the Fourier transform described above is performed, roughened particles with a shorter period than the undulations can be represented by high-frequency (short-wavelength) components with frequencies between 13 and 511. Therefore, as shown in Figures 4A and 4B, it can be said that the smaller the roughened particles, the smaller the high-frequency components (amplitude of the sine wave). Therefore, when the above Fourier transform is performed, a roughened copper foil with a large proportion of low-frequency components and a small average value of high-frequency components can be said to have fine roughened particles that contribute to excellent transmission characteristics formed on the copper foil surface, which has large undulations that contribute to the reliability of adhesion between the copper foil and the substrate. Thus, it is considered that the roughened copper foil of the present invention can achieve both excellent transmission characteristics and high peel strength when used in copper-clad laminates or printed circuit boards.

[0025] The roughened copper foil has a frequency component ratio of 1 to 5 in the Fourier transform result of 15.0% or more, preferably 18.0% to 90.0%, more preferably 19.0% to 80.0%, and even more preferably 20.0% to 70.0%. The roughened copper foil within the above range has a desired undulation size, achieving high peel strength while maintaining excellent transmission characteristics.

[0026] The roughened copper foil preferably has a frequency component ratio of 13 to 511 frequencies in the Fourier transform result of 66.0% or less, more preferably 10.0% to 66.0%, even more preferably 15.0% to 65.0%, and particularly preferably 20.0% to 64.0%. The roughened copper foil within the above range will have a more desirable undulation size, achieving even higher peel strength while maintaining excellent transmission characteristics.

[0027] The roughened copper foil preferably has an average value of frequency components between 1 and 511 in the Fourier transform result of 0.007 μm or more, more preferably between 0.007 μm and 0.100 μm, even more preferably between 0.007 μm and 0.050 μm, and particularly preferably between 0.008 μm and 0.030 μm. The roughened copper foil within the above range has a desirable overall height (amplitude) of the copper foil, including the undulation component and the roughened particle component, and can achieve even higher peel strength while maintaining excellent transmission characteristics.

[0028] The roughened copper foil preferably has an average value of 0.150 μm or more for frequency components between 1 and 5 in the Fourier transform result, more preferably between 0.160 μm and 2.000 μm, even more preferably between 0.170 μm and 1.600 μm, and particularly preferably between 0.180 μm and 1.400 μm. The roughened copper foil within the above range will have a more desirable undulation size, achieving even higher peel strength while maintaining excellent transmission characteristics.

[0029] The roughened copper foil has an average value of frequency components between 13 and 511 in the Fourier transform result of 0.010 μm or less, preferably between 0.001 μm and 0.010 μm, and more preferably between 0.002 μm and 0.010 μm. The roughened copper foil within the above range has roughened particles of a desirable size, and can achieve excellent transmission characteristics while maintaining high peel strength.

[0030] The roughened copper foil preferably has an average value of frequency components between 13 and 213 in the Fourier transform result of 0.025 μm or less, more preferably 0.001 μm to 0.024 μm, even more preferably 0.003 μm to 0.022 μm, and particularly preferably 0.005 μm to 0.020 μm. The roughened copper foil within the above range has roughened particles of a more desirable size, and can achieve excellent transmission characteristics while maintaining high peel strength.

[0031] The thickness of the roughened copper foil is not particularly limited, but is preferably 0.1 μm to 210 μm, more preferably 0.3 μm to 105 μm, and even more preferably 7 μm to 70 μm. The roughened copper foil of the present invention is not limited to ordinary copper foil with roughened surface treatment, but may also be a copper foil with a carrier attached, with roughened or finely roughened surface treatment applied.

[0032] An example of the roughened copper foil of the present invention is shown in Figure 5. As shown in Figure 5, the roughened copper foil of the present invention can be preferably manufactured by roughening a copper foil surface having a predetermined undulation (for example, the deposition surface of an electrolytic copper foil) under desired low roughening conditions to form fine roughened particles. Therefore, according to a preferred embodiment of the present invention, the roughened copper foil is an electrolytic copper foil, and the roughened surface is located on the deposition surface side of the electrolytic copper foil. The roughened copper foil may have roughened surfaces on both sides, or it may have a roughened surface on only one side. The roughened surface typically comprises a plurality of roughened particles, and it is preferable that each of these plurality of roughened particles is made of copper particles. The copper particles may be made of metallic copper or a copper alloy.

[0033] The roughening treatment to form a roughened surface can preferably be carried out by forming roughened particles of copper or a copper alloy on a copper foil. The copper foil before the roughening treatment may be an unroughened copper foil or one that has undergone preliminary roughening. The surface of the copper foil to be roughened preferably has a ten-point average roughness Rz of 1.30 μm to 15.00 μm, measured in accordance with JIS B0601-1994, and more preferably 1.50 μm to 10.00 μm. Within this range, it is easier to impart the surface profile required for the roughened copper foil of the present invention to the roughened surface.

[0034] The roughening treatment is performed in a copper sulfate solution containing, for example, a copper concentration of 7 g / L to 17 g / L and a sulfuric acid concentration of 50 g / L to 200 g / L, at a temperature of 20°C to 40°C, at a rate of 10 A / dm 2 More than 50A / dm 2 It is preferable to perform electrolytic extraction as described below. This electrolytic extraction is preferably performed for 0.5 seconds to 30 seconds, more preferably for 1 second to 30 seconds, and even more preferably for 1 second to 3 seconds. However, the roughened copper foil according to the present invention is not limited to the above method and may be manufactured by any method.

[0035] When the above electrical analysis is performed, the following formula is used: R L = L / D C (where R L is the liquid resistance index (mm·L / mol), L is the distance between electrodes (anode - cathode) (mm), and D C is the charge carrier density (mol / L)) The liquid resistance index R L defined by is preferably 9.0 mm·L / mol or more and 20.0 mm·L / mol or less, and more preferably 11.0 mm·L / mol or more and 17.0 mm·L / mol or less. Thus, by increasing the liquid resistance index R L the voltage in the entire system increases, and the voltage during the nodule formation reaction also increases. As a result, this affects the nodule shape, and nodules of a shape suitable for imparting the surface profile required for the roughened copper foil of the present invention can be preferably formed. Note that the charge carrier density D C can be calculated by summing the product of the concentration and valence of each ion for all ions present in the plating solution. For example, when using a copper sulfate solution as the plating solution, the charge carrier density D C is given by the following formula: Dc = [H + × 1 + [Cu 2+ × 2 + [SO4 2- × 2 (where [H + is the hydrogen ion concentration (mol / L) in the solution, [Cu 2+ is the copper ion concentration (mol / L) in the solution, and [SO4 2- is the sulfate ion concentration (mol / L) in the solution) is calculated by

[0036] The relationship between the liquid resistance index R L and the voltage is explained as follows. First, according to Ohm's law, the following formula: V = ρ × L × I / S (where V is the voltage, ρ is the specific resistance, L is the electrode distance, I is the current, and S is the cross-sectional area between the electrodes) is derived. That is, the voltage V is proportional to the specific resistance ρ, the electrode distance L, and the current density (= I / S). And the specific resistance ρ is the charge carrier density D CIt is inversely proportional to (the distance L between poles and the charge carrier density D). Therefore, when the current density is constant, (it is proportional to the distance L between poles and the charge carrier density D C Increasing the liquid resistance index (which is inversely proportional to the voltage) also increases the voltage. Therefore, the liquid resistance index can be considered an indicator that correlates with the resistance of the solution.

[0037] If desired, the roughened copper foil may be treated with a rust-preventive coating to form a rust-preventive coating layer. The rust-preventive coating preferably includes a zinc plating treatment. The zinc plating treatment may be either zinc plating or zinc alloy plating, with zinc-nickel alloy plating being particularly preferred. The zinc-nickel alloy plating treatment may include at least Ni and Zn, and may further include other elements such as Sn, Cr, Co, and Mo. For example, by further including Mo in addition to Ni and Zn in the rust-preventive coating layer, the treated surface of the roughened copper foil will have better adhesion to the resin, chemical resistance and heat resistance, and less etching residue will remain.

[0038] In zinc-nickel alloy plating, the ratio of Ni deposition to the total amount of Zn deposition, Ni / (Zn+Ni), is preferably 0.3 to 0.9 by mass, more preferably 0.4 to 0.9, and even more preferably 0.4 to 0.8. Furthermore, the total amount of Zn and Ni deposition in zinc-nickel alloy plating is 8 mg / m². 2 More than 160mg / m 2 The following is preferred, and more preferably, 13 mg / m² 2 More than 130mg / m 2 More preferably, 19 mg / m² 2 More than 80mg / m 2 The following applies. On the other hand, in zinc-nickel-molybdenum alloy plating, the ratio of Ni deposition to the total amount of Zn deposition, Ni deposition, and Mo deposition, Ni / (Zn+Ni+Mo), is preferably 0.20 to 0.80 by mass ratio, more preferably 0.25 to 0.75, and even more preferably 0.30 to 0.65. Furthermore, the total deposition amount of Zn, Ni, and Mo in zinc-nickel-molybdenum alloy plating is 10 mg / m². 2More than 200mg / m 2 The following is preferred, and more preferably, 15 mg / m² 2 More than 150mg / m 2 More preferably 20 mg / m² 2 More than 90mg / m 2 The following applies: The amount of Zn, Ni, and Mo attached to a predetermined area (e.g., 25 cm²) on the roughened surface of the roughened copper foil. 2 The concentration of each element in the resulting solution can be calculated by dissolving it in acid and analyzing the concentration of each element in the solution based on ICP emission spectrometry.

[0039] The rust prevention treatment preferably includes a chromate treatment, and this chromate treatment is more preferably performed on the surface of the zinc-containing plating after the zinc-based plating treatment. This further improves rust prevention. A particularly preferred rust prevention treatment is a combination of zinc-nickel alloy plating (or zinc-nickel-molybdenum alloy plating) followed by a chromate treatment.

[0040] If desired, the roughened copper foil may be treated with a silane coupling agent on its surface, forming a silane coupling agent treated layer. This improves moisture resistance, chemical resistance, and adhesion to adhesives, etc. The silane coupling agent treated layer can be formed by appropriately diluting the silane coupling agent, applying it, and drying it. Examples of silane coupling agents include epoxy-functional silane coupling agents such as 4-glycidylbutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane; amino-functional silane coupling agents such as 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; mercapto-functional silane coupling agents such as 3-mercaptopropyltrimethoxysilane; olefin-functional silane coupling agents such as vinyltrimethoxysilane and vinylphenyltrimethoxysilane; acrylic-functional silane coupling agents such as 3-methacryloxypropyltrimethoxysilane and 3-acryloxypropyltrimethoxysilane; imidazole-functional silane coupling agents such as imidazolesilane; and triazine-functional silane coupling agents such as triazinesilane.

[0041] For the reasons stated above, it is preferable that the roughened copper foil has a rust-preventive treatment layer and / or a silane coupling agent treatment layer on the roughened surface, and more preferably both the rust-preventive treatment layer and the silane coupling agent treatment layer. When the rust-preventive treatment layer and / or the silane coupling agent treatment layer is formed on the roughened surface, the numerical values ​​of the frequency component parameters after the Fourier transform in this specification shall mean the numerical values ​​obtained by measuring and analyzing the surface of the roughened copper foil after the rust-preventive treatment layer and / or the silane coupling agent treatment layer have been formed. The rust-preventive treatment layer and the silane coupling agent treatment layer may be formed not only on the roughened surface side of the roughened copper foil, but also on the side where the roughened surface is not formed.

[0042] Copper-clad laminate The roughened copper foil of the present invention is preferably used in the manufacture of copper-clad laminates for printed circuit boards. That is, according to a preferred embodiment of the present invention, a copper-clad laminate equipped with the roughened copper foil is provided. By using the roughened copper foil of the present invention, it is possible to achieve both excellent transmission characteristics and high peel strength in the copper-clad laminate. This copper-clad laminate comprises the roughened copper foil of the present invention and a resin layer provided in close contact with the roughened surface of the roughened copper foil. The roughened copper foil may be provided on one side of the resin layer or on both sides. The resin layer comprises a resin, preferably an insulating resin. The resin layer is preferably a prepreg and / or a resin sheet. A prepreg is a general term for a composite material obtained by impregnating a substrate such as a synthetic resin plate, glass plate, glass woven fabric, glass nonwoven fabric, or paper with a synthetic resin. Preferred examples of insulating resins include epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenolic resin. Examples of insulating resins that constitute the resin sheet include epoxy resins, polyimide resins, and polyester resins. The resin layer may also contain filler particles made of various inorganic particles such as silica and alumina to improve insulation. The thickness of the resin layer is not particularly limited, but is preferably 1 μm to 1000 μm, more preferably 2 μm to 400 μm, and even more preferably 3 μm to 200 μm. The resin layer may be composed of multiple layers. The resin layer, such as a prepreg and / or resin sheet, may be provided on the roughened copper foil via a primer resin layer that is applied to the copper foil surface in advance.

[0043] Printed circuit board The roughened copper foil of the present invention is preferably used in the manufacture of printed circuit boards. That is, according to a preferred embodiment of the present invention, a printed circuit board equipped with the roughened copper foil is provided. By using the roughened copper foil of the present invention, both excellent transmission characteristics and high peel strength can be achieved in the printed circuit board. The printed circuit board according to this embodiment includes a layer structure in which a resin layer and a copper layer are laminated. The copper layer is a layer derived from the roughened copper foil of the present invention. The resin layer is as described above with respect to copper-clad laminates. In any case, a known layer structure can be used for the printed circuit board. Specific examples of printed circuit boards include single-sided or double-sided printed circuit boards in which circuits are formed on a laminate formed by bonding the roughened copper foil of the present invention to one or both sides of a prepreg and curing it, and multilayer printed circuit boards made by layering these. Other specific examples include flexible printed circuit boards, COF, TAB tapes, etc., in which circuits are formed by forming the roughened copper foil of the present invention on a resin film. Further specific examples include a build-up wiring board in which a resin-coated copper foil (RCC) is formed by applying the above-mentioned resin layer to the roughened copper foil of the present invention, the resin layer is laminated onto the above-mentioned printed circuit board as an insulating adhesive layer, and then a circuit is formed using methods such as the modified semi-additive method (MSAP) or subtractive method with the roughened copper foil as all or part of the wiring layer; a build-up wiring board in which the roughened copper foil is removed and a circuit is formed using the semi-additive method (SAP); and a direct build-up on a wafer in which the lamination of resin-coated copper foil and circuit formation are alternately repeated on a semiconductor integrated circuit. [Examples]

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

[0045] Examples 1-11 The roughened copper foil of the present invention was manufactured as follows.

[0046] (1) Manufacturing of electrolytic copper foil For Examples 1-8, 10, and 11, a sulfuric acid-acidified copper sulfate solution with the following composition was used as the copper electrolyte, a titanium electrode was used as the cathode, and a DSA (dimensionally stable anode) was used as the anode, with a solution temperature of 45°C and a current density of 55 A / dm². 2 Electrolysis was performed to obtain electrolytic copper foil A with the thickness shown in Table 2. At this time, an electrode whose surface roughness was adjusted by polishing the surface with a #1000 buff was used as the cathode. <Composition of sulfuric acid-acidified copper sulfate solution> - Copper concentration: 80g / L - Sulfuric acid concentration: 300g / L - Glue concentration: 5 mg / L - Chlorine concentration: 30 mg / L

[0047] On the other hand, for Example 9, a sulfuric acid-acidified copper sulfate solution with the composition shown below was used as the copper electrolyte to obtain electrolytic copper foil B with a thickness of 18 μm. At this time, all conditions other than the composition of the sulfuric acid-acidified copper sulfate solution were the same as those for electrolytic copper foil A. <Composition of sulfuric acid-acidified copper sulfate solution> - Copper concentration: 80g / L - Sulfuric acid concentration: 260g / L - Bis(3-sulfopropyl) disulfide concentration: 30 mg / L - Diallyldimethylammonium chloride polymer concentration: 50 mg / L - Chlorine concentration: 40 mg / L

[0048] (2) Roughening treatment Of the electrode surface and deposition surface of the electrolytic copper foil described above, roughening treatment was performed on the deposition surface side for Examples 1-6 and 9-11, and on the electrode surface side for Examples 7 and 8. The ten-point average roughness Rz measured using a contact surface roughness meter in accordance with JIS B0601-1994 for the deposition surface of the electrolytic copper foil used in Examples 1-6 and 9-11, and the electrode surface of the electrolytic copper foil used in Examples 7 and 8, is shown in Table 2.

[0049] For Examples 1 to 7, the roughening treatment (first roughening treatment) described below was performed. This roughening treatment was carried out by electrolysis in a copper electrolytic solution for roughening treatment (copper concentration: 7 g / L to 17 g / L, sulfuric acid concentration: 50 g / L to 200 g / L, liquid temperature: 30°C) under the conditions of liquid resistance index, current density, and time shown in Table 2 for each example, followed by washing with water.

[0050] For Examples 8-11, the first, second, and third roughening treatments shown below were performed in this order. - The first roughening treatment was performed by electrolysis in a copper electrolytic solution for roughening (copper concentration: 7 g / L to 17 g / L, sulfuric acid concentration: 50 g / L to 200 g / L, solution temperature: 30°C) under the conditions of liquid resistance index, current density, and time shown in Table 2, followed by washing with water. - The second roughening treatment was performed by electrolysis in a copper electrolytic solution for roughening treatment with the same composition as the first roughening treatment, under the conditions of liquid resistance index, current density, and time shown in Table 2, followed by washing with water. - The third roughening treatment was performed by electrolysis in a copper electrolytic solution for roughening (copper concentration: 65 g / L to 80 g / L, sulfuric acid concentration: 50 g / L to 200 g / L, solution temperature: 45°C) under the conditions of solution resistance index, current density, and time shown in Table 2, followed by washing with water.

[0051] (3) Rust prevention treatment The electrolytic copper foil after roughening was subjected to the rust prevention treatment shown in Table 2. For Examples 1-5 and 7, the roughened surface of the electrolytic copper foil was treated using a pyrophosphate bath with a potassium pyrophosphate concentration of 100 g / L, zinc concentration of 1 g / L, nickel concentration of 2 g / L, molybdenum concentration of 1 g / L, liquid temperature of 40°C, and current density of 0.5 A / dm². 2 Anti-corrosion treatment A (zinc-nickel-molybdenum-based anti-corrosion treatment) was performed. Furthermore, a pyrophosphate bath was used on the unroughened surface of the electrolytic copper foil, with a potassium pyrophosphate concentration of 80 g / L, a zinc concentration of 0.2 g / L, a nickel concentration of 2 g / L, a liquid temperature of 40°C, and a current density of 0.5 A / dm². 2For example, rust prevention treatment B (zinc-nickel rust prevention treatment) was performed. On the other hand, for Examples 6 and 8-11, rust prevention treatment B was performed on both sides of the electrolytic copper foil under the same conditions as the side of the electrolytic copper foil that had not undergone roughening treatment in Examples 1 and 5-8.

[0052] (4) Chromate treatment Chromate treatment was performed on both sides of the electrolytic copper foil that had undergone the above rust prevention treatment, forming a chromate layer on top of the rust prevention treatment layer. This chromate treatment was performed with a chromic acid concentration of 1 g / L, pH 11, liquid temperature of 25°C, and current density of 1 A / dm². 2 It was carried out under these conditions.

[0053] (5) Silane coupling agent treatment The copper foil subjected to the above chromate treatment was washed with water, and then immediately treated with a silane coupling agent to adsorb the silane coupling agent onto the chromate layer on the roughened surface. This silane coupling agent treatment was performed by showering a solution of the silane coupling agent, with pure water as the solvent, onto the roughened surface for adsorption. As the silane coupling agent, 3-aminopropyltrimethoxysilane was used in Examples 1 and 3-7, and 3-glycidoxypropyltrimethoxysilane was used in Examples 2 and 8-11. The concentration of the silane coupling agent was 3 g / L in all cases. After the adsorption of the silane coupling agent, the water was finally evaporated using an electric heater to obtain roughened copper foil of the predetermined thickness.

[0054] [Table 2]

[0055] evaluation The following evaluations were performed on the manufactured roughened copper foil.

[0056] (a) Frequency component parameters after Fourier transform The frequency component parameters after the Fourier transform of the cross-sectional curve on the roughened surface were calculated as follows. First, the roughened surface of the roughened copper foil was measured using a laser microscope (Olympus Corporation, OLS-5000) and surface shape data was acquired. The laser microscope measurement conditions were set to an objective lens magnification of 100x, optical zoom of 2x, and a measurement area of ​​64.419 μm vertically × 64.397 μm horizontally, with the acquisition mode set to accuracy priority mode. The observation orientation was such that the treatment lines of the copper foil (width direction during copper foil manufacturing) were perpendicular (not oblique) to the field of view.

[0057] The obtained surface topography data was analyzed using the image analysis software "MountainsMap Imaging Topography 9.0" (Digital Surf). Specifically, the above surface topography data (lext file format) was opened in the image analysis software, and the "Extract Cross Section" function in the software's "Operator" section was executed to extract a cross-sectional curve of 64 μm (entire area) perpendicular to the processing streak. A Fourier transform (frequency range: 0 to 511, frequency interval: 1) was performed on this cross-sectional curve by executing the "Frequency Spectrum" function in the software's "Analysis" section. The results were output as numerical values, and the frequency component parameters after the Fourier transform (percentage of frequency components between 1 and 5, percentage of frequency components between 13 and 511, average value of frequency components between 1 and 511, average value of frequency components between 1 and 5, average value of frequency components between 13 and 213) were calculated. The results are shown in Table 3.

[0058] (b) Peel strength between copper foil and substrate To evaluate the adhesion of roughened copper foil to insulating substrates under room temperature and acidic conditions, the normal peel strength and hydrochloric acid peel strength were measured as follows.

[0059] (b-1) Peeling strength under normal conditions Two prepregs (100 μm thick) mainly composed of polyphenylene ether, triallyl isocyanurate, and bismaleimide resin were prepared as insulating substrates and stacked. On these stacked prepregs, the manufactured surface-treated copper foil was laminated so that its roughened surface was in contact with the prepreg, and a load of 32 kgf / cm² was applied. 2 Copper-clad laminates were manufactured by pressing at 205°C for 120 minutes. Next, circuits were formed on these copper-clad laminates by etching to produce test substrates with 3 mm wide linear circuits. For Examples 1, 2, and 10, copper plating was performed on the copper foil side surface of the copper-clad laminate until the copper foil thickness reached 18 μm before circuit formation. For Examples 4-6 and 11, etching was performed on the copper foil side surface of the copper-clad laminate until the copper foil thickness reached 18 μm before circuit formation. The resulting linear circuits were peeled off the insulating substrate in accordance with Method A (90° peel) of JIS C 5016-1994, and the normal peel strength (kgf / cm) was measured. The quality of the obtained normal peel strength was evaluated according to the following criteria. The results are shown in Table 3. <Criteria for evaluating peel strength under normal conditions> - Good: Normal peel strength is 0.40 kgf / cm or higher. - Defective: Peel strength under normal conditions is less than 0.40 kgf / cm

[0060] (b-2) Hydrochloric acid peeling strength Prior to measuring the peel strength, the hydrochloric acid peel strength (kgf / cm) was measured using the same procedure as described above for normal peel strength, except that a test substrate equipped with a linear circuit was immersed in 14 wt% hydrochloric acid (at a liquid temperature of 26°C) for 30 minutes. The quality of the obtained hydrochloric acid peel strength was evaluated according to the following criteria. The results are shown in Table 3. <Evaluation Criteria for Hydrochloric Acid Peeling Strength> - Good: Hydrochloric acid peeling strength of 0.40 kgf / cm or higher - Defective: Hydrochloric acid peel strength is less than 0.40 kgf / cm

[0061] (c) Transmission characteristics A high-frequency substrate (Panasonic MEGTRON6N) was prepared as the insulating resin substrate. Roughened copper foil was laminated to both sides of this insulating resin substrate so that the roughened side was in contact with the insulating resin substrate. Using a vacuum press, the lamination was performed at a temperature of 190°C and a pressing time of 120 minutes to obtain a copper-clad laminate with an insulation thickness of 136 μm. Subsequently, the copper-clad laminate was etched to form microstrip lines with a characteristic impedance of 50 Ω, obtaining a transmission loss measurement substrate. The transmission loss (dB / cm) at 16 GHz was measured on the obtained transmission loss measurement substrate using a network analyzer (Keysight Technologies N5225B). The quality of the obtained transmission loss was evaluated according to the following criteria. The results are shown in Table 3. <Transmission Loss Evaluation Criteria> - Good: Transmission loss of -0.23 dB / cm or higher - Failure: Transmission loss less than -0.23 dB / cm

[0062] [Table 3]

Claims

1. A roughened copper foil having a roughened surface on at least one side, A roughened copper foil in which, when the cross-sectional curve of a target horizontal length of 64 μm on the roughened surface is decomposed into 512 frequency components by a Fourier transform with a frequency range of 0 to 511 and a frequency interval of 1, the ratio of the sum of frequency components with frequencies from 1 to 5 to 1 to the sum of frequency components with frequencies from 1 to 511 is 15.0% or more, and the average value of the frequency components with frequencies from 13 to 511 is 0.010 μm or less.

2. The roughened copper foil according to claim 1, wherein the ratio of the sum of frequency components with frequencies of 1 to 5 to the sum of frequency components with frequencies of 1 to 511 is 18.0% to 90.0%.

3. The roughened copper foil according to claim 1 or 2, wherein the ratio of the sum of frequency components with frequencies between 13 and 511 to the sum of frequency components with frequencies between 1 and 511 is 66.0% or less.

4. The roughened copper foil according to claim 1 or 2, wherein the average value of the frequency components with frequencies between 1 and 511 in the result of the Fourier transform is 0.007 μm or more.

5. The roughened copper foil according to claim 1 or 2, wherein the average value of the frequency components with frequencies of 1 to 5 in the result of the Fourier transform is 0.150 μm or more.

6. The roughened copper foil according to claim 1 or 2, wherein the average value of the frequency components with frequencies between 13 and 213 in the result of the Fourier transform is 0.025 μm or less.

7. The roughened copper foil according to claim 1 or 2, wherein the roughened surface is provided with a rust-preventive treatment layer and / or a silane coupling agent treatment layer.

8. The roughened copper foil according to claim 1 or 2, wherein the roughened copper foil is an electrolytic copper foil, and the roughened surface is located on the deposition surface side of the electrolytic copper foil.

9. A copper-clad laminate comprising the roughened copper foil described in claim 1 or 2.

10. A printed circuit board comprising roughened copper foil according to claim 1 or 2.

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