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

Abstract

The present invention relates to a surface-treated copper foil which comprises a copper foil and a surface treatment layer that is provided on at least one surface of the copper foil. The surface treatment layer contains Cr and at least one element selected from the group consisting of P, S, and N. When the surface of the surface treatment layer is measured by XPS, the ratio of the atomic ratio of Cr to the total atomic ratio of Cr, Zn, P, S, and N is 70.0% or more. When the surface of the surface treatment layer is measured by XPS, the ratio of the total atomic ratio of P, S, and N to the atomic ratio of Cr is 15.0% or less.

Description

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

[0001] This disclosure relates to surface-treated copper foil, copper-clad laminates, and printed circuit boards, and more particularly to surface-treated copper foil, copper-clad laminates, and printed circuit boards used in the formation of circuits requiring high-frequency characteristics.

[0002] Copper-clad laminates consist of copper foil and a resin layer on the surface of the copper foil, and are widely used in various applications such as flexible printed circuit boards. Flexible printed circuit boards are manufactured by chemically etching the copper foil of a copper-clad laminate to form circuits (also called "wiring patterns"), and then soldering electronic components onto these circuits.

[0003] As a copper foil provided in a copper-clad laminate, a surface-treated copper foil is known in which a roughening treatment layer is provided on the surface of the copper foil (for example, Patent Document 1). When this surface-treated copper foil is heat-pressed and bonded to a resin substrate which will become the resin layer, the molten resin flows around the roughened particles on the surface of the surface-treated copper foil, thereby firmly maintaining the interface between the copper foil surface and the resin layer (anchor effect). This suppresses the delamination of the circuit from the resin layer.

[0004] In recent years, with the increasing speed and capacity of communications in electronic devices such as personal computers and mobile terminals, electrical signals have become more high-frequency, creating a demand for flexible printed circuit boards capable of handling these frequencies. In particular, as the frequency of an electrical signal increases, signal power loss (attenuation) becomes greater, making data difficult to read. Therefore, reducing signal power loss is essential.

[0005] The causes of signal power loss (transmission loss) in electronic circuits can be broadly divided into two categories. The first is conductor loss, i.e., loss due to the copper foil. The second is dielectric loss, i.e., loss due to the resin layer. In the high-frequency range, current has the characteristic of flowing along the surface of the conductor (i.e., the skin effect). Therefore, if the surface of the copper foil is rough, the current will flow along a complex path. Consequently, from the viewpoint of reducing conductor loss of high-frequency signals, forming a roughened layer on the surface of the copper foil is disadvantageous. On the other hand, regarding the resin layer, by using low-dielectric materials such as PFA (materials with a relative permittivity of less than 2.5 and a dielectric loss tangent of less than 0.001), transmission loss when high-frequency (especially above 5 GHz) AC current flows through the circuit can be suppressed.

[0006] Japanese Patent Publication No. 2012-112009

[0007] As described above, in conventional technology, the adhesion between the copper foil and the resin layer depends on a roughened layer applied to the surface of the copper foil, but the formation of a roughened layer is disadvantageous for reducing conductor loss of high-frequency signals. Against this backdrop, there has been a desire for the development of a technology that can improve adhesion with the resin layer without relying on a roughened layer.

[0008] The embodiments of the present invention have been made to solve the above-mentioned problems, and aim to provide surface-treated copper foil, copper-clad laminates, and printed circuit boards that exhibit excellent adhesion to resin layers.

[0009] The inventors of the present invention conducted intensive research on surface-treated copper foil in order to solve the above problems. As a result, they discovered that when a surface treatment layer provided on at least one side of the copper foil contains a predetermined element and satisfies predetermined conditions in XPS measurement of the surface of the surface treatment layer, the adhesion to the resin layer is improved, and thus completed the embodiments of the present invention.

[0010] In other words, embodiments of the present invention relate to a surface-treated copper foil comprising a copper foil and a surface treatment layer provided on at least one surface of the copper foil, wherein the surface treatment layer contains at least one element selected from the group consisting of P, S, and N, and Cr, and when the surface of the surface treatment layer is measured by XPS, the ratio of the atomic ratio of Cr to the sum of the atomic ratios of Cr, Zn, P, S, and N is 70.0% or more, and when the surface of the surface treatment layer is measured by XPS, the ratio of the sum of the atomic ratios of P, S, and N to the atomic ratio of Cr is 15.0% or less.

[0011] Furthermore, embodiments of the present invention relate to a copper-clad laminate comprising the surface-treated copper foil and a resin layer on the surface-treated layer of the surface-treated copper foil.

[0012] Furthermore, embodiments of the present invention relate to a printed circuit board comprising the copper-clad laminate, wherein the surface-treated copper foil of the copper-clad laminate has a wiring pattern shape.

[0013] According to embodiments of the present invention, it is possible to provide surface-treated copper foil, copper-clad laminates, and printed circuit boards that exhibit excellent adhesion to resin layers.

[0014] Preferred embodiments of the present invention will be described below, but the present invention should not be construed as being limited thereto, and various modifications and improvements can be made based on the knowledge of those skilled in the art, without departing from the spirit of the invention. The multiple components disclosed in the following embodiments can be combined in appropriate ways to form various inventions. For example, some components may be removed from all the components shown in the following embodiments, or components from different embodiments may be combined in appropriate ways.

[0015] In this specification, a numerical range expressed using "~" means a range that includes the numbers before and after "~" as the lower and upper limits, unless otherwise specified. In this specification, a numerical range that includes "greater than" or "less than" means a range that does not include the number as the lower or upper limit. Furthermore, in numerical ranges described in steps in this specification, the upper limit of one step may be replaced with the upper limit of another step described numerical range or the value shown in the example. Furthermore, in numerical ranges described in steps in this specification, the lower limit of one step may be replaced with the lower limit of another step described numerical range or the value shown in the example.

[0016] The surface-treated copper foil according to an embodiment of the present invention comprises a copper foil and a surface treatment layer provided on at least one surface of the copper foil. The surface treatment layer may be provided on only one surface of the copper foil, or on both surfaces of the copper foil. When the surface treatment layer is provided on both surfaces of the copper foil, the types of surface treatment layers may be the same or different.

[0017] The surface treatment layer comprises at least one element selected from the group consisting of P, S, and N, and Cr. By providing a surface treatment layer containing such elements, adhesion to the resin layer may be improved when a resin layer is provided on the surface treatment layer. The surface treatment layer may optionally contain other elements (e.g., Zn, Ni, W, Co, Fe, Mo, and other impurity elements). Hereinafter, in this specification, "containing a predetermined element" means that the predetermined element is detected when the surface of the surface treatment layer is measured by XPS (X-ray photoelectron spectroscopy) (i.e., the atomic ratio of the predetermined element is above the detection limit).

[0018] The surface treatment layer has a ratio of the atomic ratio of Cr to the sum of the atomic ratios of Cr, Zn, P, S, and N (hereinafter sometimes abbreviated as "Cr / (Cr+Zn+P+S+N)") of 70.0% or more, preferably 80.0% or more, and more preferably 90.0% or more, when the surface is measured by XPS. By controlling Cr / (Cr+Zn+P+S+N) within this range, the adhesion to the resin layer is improved when a resin layer is provided on the surface treatment layer. As a general trend, it has been found that the adhesion to the resin layer decreases when the Zn content in the surface treatment layer is high. Therefore, by increasing Cr / (Cr+Zn+P+S+N) as described above, the effect of adhesion inhibition by Zn can be relatively reduced, and the adhesion to the resin layer is considered to improve. Note that the upper limit of Cr / (Cr+Zn+P+S+N) is not particularly limited and can be, for example, 99.0%.

[0019] Furthermore, when the surface of the surface treatment layer is measured by XPS, the ratio of the sum of the atomic ratios of P, S, and N to the atomic ratio of Cr (hereinafter sometimes abbreviated as "(P+S+N) / Cr") is 15.0% or less, preferably 13.0% or less, and more preferably 11.0% or less. By controlling (P+S+N) / Cr within this range, the adhesion to the resin layer is improved when a resin layer is provided on the surface treatment layer. The inventors believe this is because these light elements (P, S, N) inhibit adhesion to the resin layer. More specifically, they believe this is because these light elements have poor compatibility with fluororesins. Also, from the viewpoint of adhesion to the resin layer, it is preferable that at least one element selected from the group consisting of P, S, and N is included in the surface treatment layer to some extent, and (P+S+N) / Cr is preferably 2.0% or more, more preferably 3.5% or less, and even more preferably 5.0% or more.

[0020] In one preferred embodiment of the present invention, the surface-treated copper foil has a Cr atomic ratio of preferably 5.0 at% or more, more preferably 7.5 at% or more, and even more preferably 10.0 at% or more, when the surface of the surface-treated layer is measured by XPS. By controlling the Cr atomic ratio within this range, the adhesion to the resin layer is stably improved. The upper limit of Cr is not particularly limited and can be, for example, 20.0 at%.

[0021] In one preferred embodiment, the surface-treated copper foil of the present invention has a Zn atomic ratio of preferably 5.0 at% or less, more preferably 3.0 at% or less, and even more preferably 1.0 at% or less, when the surface of the surface-treated layer is measured by XPS. By controlling the Zn atomic ratio within this range, acid resistance is improved. Improved acid resistance means that the rate of change in peel strength before and after immersion of the copper-clad laminate in an acid such as hydrochloric acid or sulfuric acid is reduced. In this disclosure, the Zn atomic ratio refers to the ratio of the Zn atomic ratio to the sum of the atomic ratios of C, N, O, Si, P, S, Cr, Fe, Co, Ni, Cu, Zn, Mo, and W. The lower limit of Zn is not particularly limited and can be, for example, 0.0 at%.

[0022] In another preferred embodiment, the surface-treated copper foil according to the present invention has a ratio of the atomic ratio of Zn to the sum of the atomic ratios of Cr, Zn, P, S, and N (hereinafter sometimes abbreviated as "Zn / (Cr+Zn+P+S+N)") when the surface of the surface-treated layer is measured by XPS, which is 50.0% or less, preferably 40.0% or less, more preferably 30.0% or less, and even more preferably 25.0% or less. As described above, as a general trend, if the Zn content in the surface-treated layer is high, the adhesion to the resin layer decreases. Therefore, by controlling Zn / (Cr+Zn+P+S+N) within this range, the adhesion to the resin layer is improved when a resin layer is provided on the surface-treated layer. The lower limit of Zn / (Cr+Zn+P+S+N) is not particularly limited and can be, for example, 0.5% or 0.0%.

[0023] In another preferred embodiment, the surface-treated copper foil according to the present invention has a ratio of the atomic ratio of Si to the sum of the atomic ratios of Cr, Zn, P, S, N, and Si (hereinafter sometimes abbreviated as "Si / (Cr+Zn+P+S+N+Si)") when the surface of the surface-treated layer is measured by XPS, which is preferably 7.0% or less, more preferably 5.0% or less, and even more preferably 3.0% or less. In conventional surface-treated copper foil, surface treatment using a silane coupling agent is sometimes performed to improve adhesion to the resin layer, but in this case, Si / (Cr+Zn+P+S+N+Si) exceeds 7.0%. In contrast, the surface-treated copper foil according to the embodiment of the present invention can improve adhesion to the resin layer without performing surface treatment using a silane coupling agent, so that Si / (Cr+Zn+P+S+N+Si) can be within the above range. When the resin layer contains fluororesin, surface treatment using a silane coupling agent tends to actually decrease the adhesion between the surface-treated copper foil and the resin layer. The reason for this is thought to be that fluororesins are extremely stable unless surface modification such as plasma treatment is performed, and therefore do not bond with silane coupling agents. Furthermore, if the resin layer contains a highly heat-resistant resin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and the bonding of the surface-treated copper foil and the resin layer is performed by hot pressing at high temperatures (e.g., 300°C or higher), the silane coupling agent may not contribute to bonding with the resin layer due to deterioration or burning out. Note that the lower limit of Si / (Cr+Zn+P+S+N+Si) is not particularly limited and may be 0% (Si may not be included), but it can be, for example, 0.1%.

[0024] Herein, the atomic ratio of each element is obtained by measuring the surface of the surface-treated layer using XPS. The XPS measurement shall be performed under the following conditions. If the instrument operation software or data analysis software is updated, the software shall be operated and set to be equivalent to the conditions described herein. Instrument: PHI 5000 VersaProbe II manufactured by ULVAC, Inc. Ultimate vacuum: 8.2 × 10⁻⁶-8Pa Excitation source: Monochromatic AlKα Output: 25.0W Beam diameter: 100 μmφ Incident angle: 90 degrees Extraction angle: 45 degrees Neutralization gun: None In addition, the following orbitals are used in the calculations for XPS measurements. That is, the elements to be measured by XPS are C, N, O, Si, P, S, Cr, Fe, Co, Ni, Cu, Zn, Mo, and W. C: 1s (284.7 eV) N: 1s (400 eV) O: 1s (531 eV) Si: 2s (151 eV) P: Sum of P2p's 2p3 / 2 (130 eV) and 2p1 / 2 (131 eV) S: Sum of S2p's 2p3 / 2 (167 eV) and 2p1 / 2 (168 eV) Cr: 3p (44 eV) Fe: 3p (54 eV) Co: 3p (61 eV) Ni: 2p3 / 2 (854 eV) Cu: 2p3 / 2 (932 eV) Zn: 2p3 / 2 (1022 eV) Mo: Sum of Mo3d's 3d5 / 2 (231 eV) and 3d3 / 2 (235 eV) W: 4d5 / 2 (244 eV) Furthermore, in calculating the peak area of ​​each element, the peak area with the bond energy closest to the above bond energy is calculated after removing the background using the Shirley method. Also, for P, S, and Mo, since it is difficult to separate the two peaks mentioned above, the sum of the peak areas of both peaks is calculated. In addition, for XPS measurements, for each element, the spectrum is acquired in a range of 6 eV before and after the above bond energy (for example, 400 eV ± 6 eV for N) under the narrow scan conditions shown below. Pass energy: 117.4 eV (common to all elements) Step energy: 0.5 eV (common to all elements) Number of integrations: 100 (common to all elements) Note that for P, S, Cr, Fe, Co, and Mo, the spectrum is acquired in the following range instead of the range of 6 eV before and after. P: 124 eV to 137 eV S: 161 eV to 174 eV Cr: 38 eV to 49 eV Fe: 49 eV to 58 eV Co: 58 eV to 63 eV Mo: 225 eV to 237 eV The quantitative value is calculated from the calculated peak area using the relative sensitivity coefficient method. The sensitivity coefficient for each element is the value recommended by the instrument manufacturer. No corrections such as matrix correction are performed during the calculation. The surface of the object to be measured is not decontaminated before performing the XPS measurement.Decontamination refers to removing material from the surface of an object being measured, for example, by sputtering.

[0025] In another preferred embodiment, the surface-treated copper foil according to the present invention has a root mean square height Sq (hereinafter sometimes abbreviated as "Sq") of the surface of the surface-treated layer, which is preferably 0.30 μm or less, more preferably 0.25 μm or less, and even more preferably 0.20 μm or less. Here, Sq is a height parameter defined in ISO 25178-2:2012 and represents the variation in the height of the protrusions on the surface of the surface-treated layer. Therefore, a large Sq on the surface of the surface-treated layer means that there is a large variation in the height of the protrusions on the surface of the surface-treated layer. By controlling Sq within the above range, the conductor loss of high-frequency signals due to the skin effect can be reduced. The lower limit of Sq on the surface is not particularly limited and may be 0 μm, but for example, it may be 0.01 μm or 0.05 μm.

[0026] The surface height (Sq) of the surface treatment layer is determined by measurement in accordance with ISO 25178-2:2012. Specifically, the Sq measurement is performed under the following conditions: The root mean square height (Sq) of the surface treatment copper foil is measured using a laser microscope (LEXT OLS5100) manufactured by Evident Co., Ltd. The Sq measurement result is the average of the results obtained from measurements at five arbitrary locations. The measurement temperature is set to 23-25°C. The main settings for the laser microscope are as follows. If the device operation software or data analysis software is updated, the software should be operated and set to the same conditions as those described in this specification. Objective lens: MPLAPON 50x LEXT (Magnification: 50x, Numerical aperture: 0.95, Working distance: 0.35 mm, Depth of focus: 0.44 μm, Focusing spot diameter: 0.52 μm) Optical zoom magnification: 1x Scanning mode: 3D accuracy priority + color Image size: 257 μm x 256 μm, 1024 x 1024 pixels Laser intensity: 100 Offset: 0 Confocal level: 0 Beam diameter aperture: Off Brightness uniformity correction: On Optical noise filter: On Cutoff: No filter, no F calculation Filter: Gaussian Auto gain: On Brightness: Auto-adjusted Noise reduction: Yes Tilt correction: Yes

[0027] In another preferred embodiment of the present invention, the surface-treated copper foil has a Cr deposition amount in the surface treatment layer, preferably 5 to 100 μg / dm 2 More preferably 5 to 50 μg / dm 2 This configuration ensures stable and improved adhesion between the resin layer and the surface treatment layer when a resin layer is provided on top of the surface treatment layer.

[0028] In this specification, the amount of Cr deposited in the surface treatment layer is measured as follows: First, a 0.1 dm × 0.2 dm sample is cut from the surface-treated copper foil, the surface treatment layer is dissolved in a nitric acid solution, and the concentration of Cr in the sample solution is quantified using an ICP emission spectrometer, and the amount of each metal deposited per unit area (μg / dm²) is determined. 2) is calculated. Specifically, a Hitachi High-Tech PS3520UVDD2 (AN-063 ICP3520UV-DD2) ICP emission spectrometer is used as the ICP emission spectrometer, and the following conditions are met. Note that if the instrument operation software or data analysis software is updated, the software should be operated and set to be equivalent to the conditions described in this specification. Wavelength: 267.795 nm Integration time: 1.0 second Number of integrations: 3 Quantitative method: Calibration curve method Blank subtraction: None Output: 1.2 kW Pre-exposure time: 30 seconds Washing time: 20 seconds In addition, the standard solutions used for measurement by ICP-OES are prepared with Cr concentrations of 0, 0.5, and 1.0 μg / mL to form a calibration curve, and the Cr concentration in the sample is adjusted to be within this range. Note that if the instrument operation software or data analysis software is updated, the software should be operated and set to be equivalent to the conditions described in this specification.

[0029] The type of surface treatment layer in the surface-treated copper foil according to the embodiment of the present invention is not particularly limited as long as it satisfies the above-described characteristics, but it is preferable that the surface treatment layer includes a chromate layer and that the chromate layer is the outermost layer. If the surface treatment layer has a chromate layer as the outermost layer, adhesion to the resin layer is easily improved when a resin layer is provided on the surface treatment layer. In addition, since the chromate layer has a rust-preventive effect, there is no need to apply rust-preventive treatment to the surface of the chromate layer.

[0030] The chromate layer can be formed by electroplating. The conditions are not particularly limited and can be adjusted according to the electroplating equipment used, but the conditions for forming the chromate layer using a general electroplating equipment are as follows. Here, it is preferable to set the pH of the plating solution to a certain extent. Known pH adjusting agents such as sulfuric acid, nitric acid, and potassium hydroxide can be used. The chromate treatment may be performed once or multiple times. Plating solution composition: 1 to 10 g / L of Cr salt (e.g., K2Cr2O7), 0 to 0.25 g / L of Zn salt (e.g., ZnSO4・7H2O) Plating solution pH: 3.0 to 12.0, preferably 4.0 to 10.0 Plating solution temperature: 25 to 60°C Plating conditions: Current density 0.1 to 1.4 A / dm 2The time is 0.8 to 5.0 seconds. The chromate layer can also be formed by immersion. In that case, the copper foil should be immersed in the above plating solution for 0.1 to 60 seconds. As a pH adjusting agent for the plating solution, for example, sulfuric acid or potassium hydroxide can be used as appropriate. The P, S, and N contained in the surface treatment layer are thought to originate from the anions contained in the plating bath. Therefore, by using the above-described plating bath composition for the chromate layer, the surface treatment layer will contain at least one selected from the group consisting of P, S, and N, and Cr.

[0031] While it is easy to determine whether the chromate layer is the outermost layer if the details of the surface treatment layer are clear, this determination can be difficult if the details of the surface treatment layer are unclear. Therefore, one criterion for determining whether the chromate layer is the outermost layer is shown below. In this specification, when the surface treatment layer is measured by XPS depth analysis, if the maximum value of Cr appears within 3.0 nm (in terms of SiO2) from the surface of the surface treatment layer, it can be determined that the chromate layer is the outermost layer of the surface treatment layer.

[0032] Here, the XPS depth analysis of the surface treatment layer will be performed under the following sputtering conditions. Other conditions will be the same as those for the XPS measurement described above. <Sputtering Conditions> Ion species: Ar + Acceleration voltage: 3kV; Sweep area: 3mm x 3mm; Sputtering rate: 1.9nm / min (SiO2 equivalent)

[0033] In the surface-treated copper foil according to the embodiment of the present invention, the surface treatment layer is preferably the surface in contact with the resin. The resin preferably contains fluorine from the viewpoint of reducing dielectric loss, and preferably has a repeating CF2CF2 structure. Examples of such resins include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), fluoroethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), and polytetrafluoroethylene (PTFE). These can be used individually or in combination of two or more. The reason why the repeating CF2CF2 structure is advantageous in terms of reducing dielectric loss is as follows. - Because fluorine atoms, which have high electronegativity, strongly attract electrons, it is difficult for the electron cloud of CF2 to be biased (i.e., polarization) due to external factors. - Because the atomic radius of fluorine atoms is small and they are densely arranged as CF2 molecules, there is no molecular movement due to external factors. - The repeating structure of CF2CF2 forms a helical structure, and the dipole moment of CF2 is directed toward the center line of the helical structure, so the dipole moments of the entire molecule cancel each other out and the polarizability is extremely small.

[0034] The surface treatment layer may further include an underlayer located between the copper foil and the chromate layer. The underlayer preferably contains one or more elements selected from Ni, W, Co, Fe, and Mo. An underlayer containing such elements can improve various substrate properties, such as weather resistance, acid resistance, and solder heat resistance, without hindering adhesion between the copper foil and the chromate layer. Weather resistance refers to the resistance to discoloration when the surface-treated copper foil is heated in the atmosphere.

[0035] It is preferable that the base layer is in contact with the copper foil. By bringing the base layer into contact with the copper foil, the above effects can be obtained more reliably.

[0036] The undercoat can be formed by electroplating. The conditions are not particularly limited and can be adjusted according to the electroplating equipment used, but the conditions for forming the undercoat using a general electroplating equipment are as follows. Note that electroplating may be performed once or multiple times. Plating solution composition: 0-150 g / L Ni salt (e.g., NiSO4・6H2O), 0-50 g / L W salt (e.g., Na2WO4・2H2O), 0-150 g / L Co salt (e.g., CoSO4・7H2O), 0-150 g / L Fe salt (e.g., FeSO4・7H2O), 0-30 g / L Mo salt (e.g., Na2MoO4・2H2O), 0-30 g / L complexing agent (e.g., trisodium citrate dihydrate, trisodium ammonium citrate) Plating solution pH: 2.0-6.0 Plating solution temperature: 30-60°C Plating conditions: Current density 0.1-10.0 A / dm 2 , time 0.8 to 5.0 seconds

[0037] In another preferred embodiment, the surface-treated copper foil according to the present invention may have a further surface-treated layer on the side of the copper foil opposite to the side on which the above-mentioned surface-treated layer is provided. The further surface-treated layer preferably contains Zn and Ni, and more preferably contains Cr. The inclusion of Zn and Ni in the further surface-treated layer ensures the weather resistance of the further surface-treated layer. In one preferred embodiment, the further surface-treated layer is a surface that is etched for the purpose of circuit formation.

[0038] The copper foil used for the surface-treated copper foil according to the embodiment of the present invention is not particularly limited, and may be either electrolytic copper foil or rolled copper foil. Electrolytic copper foil is generally produced by electrolytically depositing copper from a copper sulfate plating bath onto a titanium or stainless steel drum, and has a flat S surface (shiny surface) formed on the rotating drum side and an M surface (matte surface) formed on the opposite side of the S surface. The M surface of electrolytic copper foil generally has fine uneven portions. Additionally, the S surface of electrolytic copper foil has fine uneven portions because polishing streaks of the rotating drum formed during polishing are transferred thereto. Note that the surface treatment layer may be provided on either the S surface or the M surface of the electrolytic copper foil. Rolled copper foil has fine uneven portions on its surface because oil pits are formed by rolling oil during rolling.

[0039] The material for the copper foil is not particularly limited, but when the copper foil is a rolled copper foil, high-purity copper such as tough pitch copper (JIS H3100, alloy number C1100) and oxygen-free copper (JIS H3100, alloy number C1020 or JIS H3510, alloy number C1011), which are commonly used for circuit patterns of printed wiring boards, can be used. In addition, copper alloys such as Sn-containing copper, Ag-containing copper, copper alloys added with Cr, Zr, Mg or the like, and Corson copper alloys added with Ni, Si or the like can also be used. In this specification, the term "copper foil" is a concept that also includes copper alloy foil.

[0040] The thickness of the copper foil is not particularly limited, and may be, for example, 1 to 1000 µm, 1 to 500 µm, 1 to 300 µm, 3 to 100 µm, 5 to 70 µm, 6 to 35 µm, or 9 to 18 µm.

[0041] The surface-treated copper foil according to the embodiment of the present invention may optionally be provided with a roughening treatment layer between the copper foil and an underlayer. By providing the roughening treatment layer, when a resin layer is provided on the surface treatment layer, the adhesiveness to the resin layer can be further improved. However, the surface-treated copper foil according to the embodiment of the present invention can sufficiently secure adhesiveness to the resin layer even without providing a roughening treatment layer. In addition, a surface-treated copper foil not having a roughening treatment layer does not cause conductor loss resulting from the roughened portion, and is therefore suitable for producing energy-saving high-frequency circuits.

[0042] A copper-clad laminate according to an embodiment of the present invention includes the above-described surface-treated copper foil, and a resin layer provided on the surface-treated layer of the surface-treated copper foil. This copper-clad laminate can be produced by bonding a resin base material that forms the resin layer to the surface-treated layer of the above-described surface-treated copper foil. The resin base material is not particularly limited, and those known in the art can be used. Examples of resin base materials include paper base phenolic resins, paper base epoxy resins, synthetic fiber cloth base epoxy resins, glass cloth-paper composite base epoxy resins, glass cloth-glass nonwoven fabric composite base epoxy resins, glass cloth base epoxy resins, polyester films, polyimide resins, liquid crystal polymers, fluororesins such as PTFE, and polyolefin resins.

[0043] In the copper-clad laminate according to an embodiment of the present invention, in one preferred aspect, the resin layer preferably contains a fluorine-containing resin. Since the fluorine-containing resin has excellent dielectric properties, it enables the formation of circuits that require high-frequency characteristics. Further, the resin layer more preferably contains a resin having a repeating structure of CF2CF2. With a resin having such a repeating structure, the above effects are likely to be stably obtained. Examples of such resins include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), fluoroethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), and polytetrafluoroethylene (PTFE). These may be used alone or in combination of two or more kinds.

[0044] The method for bonding the surface-treated copper foil and the resin base material is not particularly limited, and can be performed according to methods known in the art. For example, the surface-treated copper foil and the resin base material may be laminated and then thermocompression-bonded. The copper-clad laminate produced as described above can be used for the production of printed wiring boards. Since the copper-clad laminate according to an embodiment of the present invention uses the above-described surface-treated copper foil, it has excellent adhesiveness to the resin layer.

[0045] A printed circuit board according to an embodiment of the present invention comprises the above-described copper-clad laminate, wherein the surface-treated copper foil of the copper-clad laminate has a wiring pattern shape. This printed circuit board can be manufactured by chemically etching the surface-treated copper foil of the copper-clad laminate to form a wiring pattern (circuit). The method for forming the wiring pattern is not particularly limited, and known methods such as the subtractive method and the semi-additive method can be used. Among these, the subtractive method is preferred for forming the wiring pattern.

[0046] When manufacturing printed circuit boards by the subtractive method, it is preferable to do so as follows: First, a predetermined resist pattern is formed by applying a resist to the surface of the surface-treated copper foil of a copper-clad laminate, exposing it to light, and developing it. Next, the surface-treated copper foil in areas where the resist pattern is not formed (i.e., unwanted areas) is removed by chemical etching to form a wiring pattern. Finally, the resist pattern on the surface-treated copper foil is removed. The various conditions in this subtractive method are not particularly limited and can be carried out in accordance with conditions known in the art. Since the printed circuit board obtained in this way uses the above-mentioned copper-clad laminate, it has excellent adhesion between the resin layer and the wiring pattern.

[0047] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these embodiments.

[0048] (Examples 1-28, Comparative Examples 1-8, and Reference Examples 1-3) Rolled copper foil with a thickness of 18 μm (manufactured by JX Metals Corporation) was prepared. One side of the copper foil was electrolytically degreased and pickled. Then, on the electrolytically degreased and pickled side, a base layer was sequentially formed using electroplating under the conditions shown in Table 1-1, and a chromate layer was sequentially formed using electroplating or immersion under the conditions shown in Table 1-2 to produce a surface-treated copper foil. The base layer was formed in Examples 14-28, Comparative Examples 3-8, and Reference Example 2. The plating solution used for forming the chromate layer was K2Cr2O7 as the Cr salt and ZnSO4・7H2O as the Zn salt. The temperature of the plating solution for the base layer was 50°C, and the temperature of the plating solution for the chromate layer was 55°C. In Reference Example 1, no surface treatment was performed, and in Reference Example 3, a roughening treatment was performed. Note that the pH of the plating solution for chromate layer formation in Examples 1-12 and Comparative Examples 1-2 is different. Also, the pH of the plating solution for chromate layer formation in Examples 14-22, Examples 25-26, and Comparative Examples 5-6 is different. The pH of the plating solution for chromate layer formation in Examples 21 and 23-24 is the same. Also, the pH of the plating solution for chromate layer formation in Examples 2, 13, 26-28, Comparative Examples 3-4, and Comparative Examples 7-8 is the same. Furthermore, the pH of the plating solution for chromate layer formation in Examples 1 and 18, Examples 4 and 25, Examples 3 and 14, Examples 5 and 16, Examples 6 and 15, and Examples 8 and 19 is the same.

[0049]

[0050]

[0051] The surface-treated copper foils obtained in the above examples, comparative examples, and reference examples were evaluated as follows.

[0052] <XPS Analysis of the Surface Treatment Layer> The atomic ratio of each element was measured using XPS on the surface treatment layer of the surface treatment copper foil in Examples 1 to 28 and Comparative Examples 1 to 8 under the conditions described above. The results are shown in Table 2-1. In Table 2-1, NA means that the analysis was not performed. Based on these measurement results, it was confirmed that the surface treatment layers of Examples 1 to 26 contain at least one element selected from the group consisting of P, S, and N, and Cr. As described later, from the results of Example 26, it was determined that the surface treatment layers of Examples 27 to 28 contain at least one element selected from the group consisting of P, S, and N, and Cr. Furthermore, based on the obtained atomic ratios of each element, the following were calculated: the ratio of the atomic ratio of Cr to the sum of the atomic ratios of Cr, Zn, P, S, and N (referred to as "Cr ratio" in Table 2-1); the ratio of the sum of the atomic ratios of P, S, and N to the atomic ratio of Cr (referred to as "P+S+N ratio" in Table 2-1); the ratio of the atomic ratio of Zn to the sum of the atomic ratios of Cr, Zn, P, S, and N (referred to as "Zn ratio" in Table 2-1); and the ratio of the atomic ratio of Si to the sum of the atomic ratios of Cr, Zn, P, S, N, and Si (referred to as "Si ratio" in Table 2-1). The atomic ratios of Cr (referred to as "Cr ratio" in Table 2-1) and Zn (referred to as "Zn ratio" in Table 2-1) are also shown together. Note that in Table 2-1, examples where the Si ratio is "≦7.0%" do not include Si as an element measured by XPS. These examples use C, N, O, P, S, Cr, Fe, Co, Ni, Cu, Zn, Mo, and W as the elements to be measured, and there is no data on the atomic ratio of Si. However, these examples, like Examples 24-26 which use Si as the element to be measured, do not undergo silane coupling treatment, and therefore, like Examples 24-26, there is a high probability that the Si content will be 7% or less (more specifically, 5% or less). Although Example 26 also does not undergo silane coupling treatment, Si exceeding the detection limit was detected due to contamination. In Examples 27, 28, Comparative Example 7, and Comparative Example 8, XPS analysis of the surface of the surface treatment layer and analysis of the amount of Cr deposited on the surface treatment layer, which will be described later, were not performed. However, since the plating conditions of the surface treatment layer in Examples 27 and 28 are the same as in Example 26, there is a high probability that similar results will be obtained.Furthermore, since Comparative Example 7 and Comparative Example 8 have the same plating conditions for the surface treatment layer as Comparative Example 3, there is a high probability that results similar to those of Comparative Example 3 can be obtained.

[0053] <Amount of Cr Adhered in Surface Treatment Layer> For the surface treatment layers of several surface-treated copper foils, the amount of Cr adhered was measured in accordance with the conditions described above. The results are shown in Table 2-1. As an example, when the amount of Cr adhered is 10 μg / dm 2 , the amount of Cr adhered is represented as "5 to 100" in Table 2-1. It should be noted that the evaluation results described in parentheses mean results estimated from other test results. The inventors consider that the amount of Cr adhered does not vary greatly because the Cr salt concentration in the plating solution for the chromate layer is the same in all Examples and Comparative Examples. Therefore, the amount of Cr adhered in Examples 1 to 13 and Examples 23 to 24 described in parentheses, similarly to Examples 14 to 22 and Examples 25 to 26, is 5 to 100 μg / dm 2 , there is a high probability that it falls within the range.

[0054] <Root Mean Square Height Sq of the Surface of the Surface Treatment Layer> For the surface-treated copper foils of Reference Examples 1 to 3, the root mean square height Sq of the surface of the surface treatment layer was measured in accordance with the conditions described above. The results are shown in Table 2-2.

[0055] <Preparation of Copper-Clad Laminate> Using the resin base materials shown in Table 2-1, the surface-treated copper foils obtained in Examples 1 to 28 and Comparative Examples 1 to 8, the resin base material, and the surface-treated copper foil manufactured by JX Metals Corporation were laminated in this order, and vacuum hot pressing was performed to prepare a copper-clad laminate. At this time, the chromate layer side of the surface-treated copper foils obtained in the above Examples and Comparative Examples and the roughened surface side of the surface-treated copper foil manufactured by JX Metals Corporation were arranged to face the resin base material. In addition, vacuum hot pressing was performed under the conditions of a temperature of 310° C., a pressure of 0.1 MPa, a pressing time of 10 minutes, and a cooling time of about 2 hours for all resin base materials. Regarding the resin base materials shown in Table 2-1, PFA is NEOFLON (registered trademark) AF-0050 (thickness: 50 μm) manufactured by Daikin Corporation, FEP is NEOFLON (registered trademark) (thickness: 50 μm) manufactured by Daikin Corporation, and ETFE is a general commercial product (thickness: 50 μm) manufactured by As One Corporation.

[0056] <Peel Strength> Surface-treated copper foil obtained in Examples 1-30 and Comparative Examples 1-8 of copper-clad laminates was chemically etched to form 1 mm wide wiring in the MD direction (longitudinal direction of the rolled copper foil). The wiring was formed according to the usual method. The surface-treated copper foil side manufactured by JX Metals Corporation was bonded to a rigid substrate and cut to a predetermined size to serve as a test piece for measurement. Next, the strength (MD90° peel strength) when peeling this test piece (surface-treated copper foil) at a 90° angle to the surface of the resin substrate, i.e., vertically upward relative to the surface of the resin substrate, was measured. The pulling speed was set to 50 mm / min. Five measurements were taken, and the average value was used as the peel strength result. In some cases, the peel strength was too strong, making measurement difficult with 1 mm wide wiring. In such cases, 0.4 mm wide wiring was formed and the peel strength was measured. The results are shown in Table 2-1.

[0057]

[0058]

[0059] As shown in Table 2-1, when comparing surface-treated copper foils in Examples 1 to 28 with identical resin substrates, it was found that they had higher peel strength and superior adhesion to the resin layer compared to surface-treated copper foils in Comparative Examples 1 to 8.

[0060] Table 2-2 shows the root mean square height Sq for Reference Examples 1 to 3. Reference Example 1 (no surface treatment) and Reference Example 2 (with undercoat and chromate layer) showed similar Sq values, and were found to be significantly lower than Reference Example 3 (with roughening treatment). Since Reference Example 1 (no surface treatment) and Reference Example 2 (with undercoat and chromate layer) showed similar Sq values, it can be inferred that both the undercoat and chromate layer were smooth. Reference Example 2 and Examples 1 to 28 differed in the Zn concentration in the plating conditions of the chromate layer. However, the Zn concentration in the plating conditions of the chromate layer did not affect the Sq value of the chromate layer. From this, it can be said that there is a high probability that the Sq value of the surface of the surface-treated layer in Examples 1 to 28 is similar to that of Reference Example 2, regardless of the presence or absence of an undercoat.

[0061] As can be seen from the above results, according to the embodiments of the present invention, it is possible to provide surface-treated copper foil, copper-clad laminates, and printed circuit boards that have excellent adhesion to resin layers.

[0062] Therefore, embodiments of the present invention can be as follows.

[0063] [1] A surface-treated copper foil comprising a copper foil and a surface treatment layer provided on at least one surface of the copper foil, wherein the surface treatment layer contains at least one element selected from the group consisting of P, S, and N, and Cr, and when the surface of the surface treatment layer is measured by XPS, the ratio of the atomic ratio of Cr to the sum of the atomic ratios of Cr, Zn, P, S, and N is 70.0% or more, and when the surface of the surface treatment layer is measured by XPS, the ratio of the sum of the atomic ratios of P, S, and N to the atomic ratio of Cr is 15.0% or less.

[0064] [2] The surface-treated copper foil according to [1], wherein when the surface of the surface-treated layer is measured by XPS, the ratio of the atomic ratio of Si to the sum of the atomic ratios of Cr, Zn, P, S, N, and Si is 7.0% or less.

[0065] [3] The surface-treated copper foil according to [1] or [2], wherein the root mean square height Sq of the surface of the surface-treated layer is 0.30 μm or less.

[0066] [4] The surface-treated copper foil according to any one of [1] to [3], wherein when the surface of the surface-treated layer is measured by XPS, the ratio of the atomic ratio of Zn to the sum of the atomic ratios of Cr, Zn, P, S, and N is 50.0% or less.

[0067] [5] The surface-treated copper foil according to any one of [1] to [4], wherein when the surface of the surface-treated layer is measured by XPS, the sum of the atomic ratios of P, S and N to the atomic ratio of Cr is 5.0% or more.

[0068] [6] The surface treatment layer has a Cr deposition amount of 5 to 100 μg / dm 2 The above describes the surface-treated copper foil described in any one of [1] to [5].

[0069] [7] The surface-treated copper foil according to any one of [1] to [6], wherein the surface treatment layer includes a chromate layer, and the chromate layer is the outermost layer.

[0070] [8] The surface-treated copper foil further comprises a surface treatment layer on the side of the copper foil opposite to the side on which the surface treatment layer is provided, wherein the further surface treatment layer comprises Zn and Ni, according to any one of [1] to [7].

[0071] [9] The surface-treated copper foil according to [8], wherein the further surface-treated layer further comprises Cr.

[0072]

[10] The surface treatment layer is the surface that adheres to the resin, the surface treated copper foil according to any one of [1] to [9].

[0073]

[11] The resin is a surface-treated copper foil according to

[10] , comprising fluorine.

[0074]

[12] A copper-clad laminate comprising a surface-treated copper foil according to any one of [1] to

[11] and a resin layer on the surface-treated layer.

[0075]

[13] The copper-clad laminate according to

[12] , wherein the resin layer comprises a resin containing fluorine.

[0076]

[14] The copper-clad laminate according to

[12] or

[13] , wherein the resin layer comprises a resin having a repeating CF2CF2 structure.

[0077]

[15] A printed circuit board comprising a copper-clad laminate according to any one of

[12] to

[14] , wherein the surface-treated copper foil of the copper-clad laminate has a wiring pattern shape.

[0078] (Potential Contribution to SDGs) According to the above embodiment, it is possible to provide surface-treated copper foil, copper-clad laminates, and printed circuit boards with excellent adhesion to resin layers, which may improve product yield in the manufacture of electronic devices and the like. Improved product yield leads to a stable supply of products and a reduction in the loss of metal raw materials, which are limited resources. Therefore, the above embodiment may contribute to Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation," and Goal 12, "Ensure sustainable consumption and production patterns," of the United Nations-led Sustainable Development Goals (SDGs).

Claims

1. A surface-treated copper foil comprising a copper foil and a surface treatment layer provided on at least one surface of the copper foil, wherein the surface treatment layer contains at least one element selected from the group consisting of P, S, and N, and Cr, and when the surface of the surface treatment layer is measured by XPS, the ratio of the atomic ratio of Cr to the sum of the atomic ratios of Cr, Zn, P, S, and N is 70.0% or more, and when the surface of the surface treatment layer is measured by XPS, the ratio of the sum of the atomic ratios of P, S, and N to the atomic ratio of Cr is 15.0% or less.

2. The surface-treated copper foil according to claim 1, wherein when the surface of the surface-treated layer is measured by XPS, the ratio of the atomic ratio of Si to the sum of the atomic ratios of Cr, Zn, P, S, N, and Si is 7.0% or less.

3. The surface-treated copper foil according to claim 1 or 2, wherein the root mean square height Sq of the surface of the surface-treated layer is 0.30 μm or less.

4. The surface-treated copper foil according to claim 1 or 2, wherein when the surface of the surface-treated layer is measured by XPS, the ratio of the atomic ratio of Zn to the sum of the atomic ratios of Cr, Zn, P, S, and N is 50.0% or less.

5. The surface-treated copper foil according to claim 1 or 2, wherein when the surface of the surface-treated layer is measured by XPS, the sum of the atomic ratios of P, S, and N to the atomic ratio of Cr is 5.0% or more.

6. The surface treatment layer has a Cr deposition amount of 5 to 100 μg / dm 2 The above describes the surface-treated copper foil according to claim 1 or 2.

7. The surface-treated copper foil according to claim 1 or 2, wherein the surface treatment layer includes a chromate layer, and the chromate layer is the outermost layer.

8. The surface-treated copper foil according to claim 1 or 2, wherein the surface-treated copper foil comprises a further surface-treated layer on the side of the copper foil opposite to the side on which the surface-treated layer is provided, and the further surface-treated layer comprises Zn and Ni.

9. The surface-treated copper foil according to claim 8, wherein the further surface-treated layer further comprises Cr.

10. The surface-treated copper foil according to claim 1 or 2, wherein the surface-treated layer is the contact surface with the resin.

11. The surface-treated copper foil according to claim 10, wherein the resin contains fluorine.

12. A copper-clad laminate comprising a surface-treated copper foil as described in claim 1, and a resin layer on the surface-treated layer.

13. The copper-clad laminate according to claim 12, wherein the resin layer comprises a resin containing fluorine.

14. The copper-clad laminate according to claim 12, wherein the resin layer comprises a resin having a repeating CF2CF2 structure.

15. A printed circuit board comprising a copper-clad laminate according to any one of claims 12 to 14, wherein the surface-treated copper foil of the copper-clad laminate has a wiring pattern shape.

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