Copper-clad laminate, flexible printed wiring board, and electronic device

Abstract

To provide a copper-clad laminate having high circuit linearity after etching.SOLUTION: A copper-clad laminate comprises a copper foil laminated on at least one surface of an insulating base material. When any four points are measured for the area ratio of crystal grains of the copper foil in which the orientation differs within 15° from each of the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation, an arithmetic average value of the maximum area ratio for each orientation is 20% or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a copper-clad laminate, a flexible printed wiring board using the same, and an electronic device.

Background Art

[0002] As a circuit wiring board for electronic devices, a flexible printed wiring board (flexible wiring board, hereinafter also referred to as "FPC") is widely used. An FPC is formed by etching a Copper Clad Laminate (copper-clad laminate, hereinafter also referred to as "CCL") in which a copper foil and a resin are laminated, and the upper surface thereof is covered with a resin layer called a coverlay. Examples of the resin laminated on the CCL include, but are not limited to, polyimide-based, liquid crystal polymer, and PTFE.

[0003] And, in order to form a target circuit, such a copper-clad laminate is printed with the circuit by a resist coating and exposure process, and further undergoes an etching process to remove unnecessary portions of the copper layer.

[0004] As a technology of the copper foil used for the copper-clad laminate, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2021-014603) discloses a rolled copper foil containing 99.9% by mass or more of Cu and 0.0005 to 0.0220% by mass of P as an additive element, with the balance being inevitable impurities, and having a crystal orientation density of less than 10 in the Copper orientation and a crystal orientation density of less than 20 in the Brass orientation for a copper foil for a flexible printed circuit board. According to the technical document, it is disclosed that a copper foil for a flexible printed circuit board with improved bendability of the CCL can be obtained by suppressing the development of the Cube orientation after recrystallization and reducing the crystal orientation density of the Brass orientation.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, with the miniaturization, thinning, and high performance of electronic devices, high-density mounting of FPCs is required. To mount FPCs at high density, circuit miniaturization is necessary. In fine circuits, it is important that the circuit width is constant throughout the entire circuit in order to maintain impedance consistency. This is because if the width of the circuit is not constant throughout the entire circuit, the circuit may stick to (contact) the adjacent circuit, resulting in defects. Therefore, it is required that the variation in the width of the circuit obtained by etching is small (circuit linearity).

[0007] The technology described in Patent Document 1 aims to improve the bendability of CCL and does not consider circuit linearity. Further, Patent Document 1 focuses on the crystal orientation density of the Copper orientation and Brass orientation of the copper foil itself. However, the present inventor has discovered that since the copper foil is heat-treated and recrystallized during CCL production, in order to improve circuit linearity, it is more important to control the microstructure of the copper foil after recrystallization, that is, the copper foil after CCL production.

[0008] The present invention has been completed in view of the above problems, and in one embodiment, an object is to provide a copper-clad laminate having high circuit linearity after etching. In another embodiment of the present invention, an object is to provide a flexible printed wiring board and an electronic device using such a copper-clad laminate.

Means for Solving the Problems

[0009] As a result of intensive studies by the present inventors, in a copper-clad laminate, by reducing the crystal grain area ratio in the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation of the copper foil, it was found that the etching rate difference in each orientation during etching can be suppressed, and the variation in the width of the circuit caused by the etching rate difference can be reduced. The present invention has been completed based on the above findings and is exemplified below.

[0010] [1] A copper-clad laminate in which a copper foil is laminated on at least one surface of an insulating substrate, Regarding the area ratio of crystal grains with an orientation difference of within 15° from each of the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation of the copper foil, when arbitrarily measuring four points, the arithmetic mean value of the maximum area ratio in each orientation is 20% or less, a copper-clad laminate. [2] The copper-clad laminate according to [1], including a surface treatment layer on the surface of the copper foil facing the insulating substrate. [3] The copper-clad laminate according to [1] or [2], wherein the copper foil is a rolled copper foil. [4] A flexible printed wiring board using the copper-clad laminate according to any one of [1] to [3]. [5] An electronic device using the flexible printed wiring board according to [4].

Advantages of the Invention

[0011] According to one embodiment of the present invention, a copper-clad laminate with high circuit linearity after etching can be provided. According to another embodiment of the present invention, a flexible printed wiring board and an electronic device using such a copper-clad laminate can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, embodiments of the present invention will be described with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and design changes, improvements, etc. can be appropriately made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0014] (1. Composition of Copper Foil) There is no particular limitation on the form of the copper foil that can be used in this embodiment. Typically, the copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil. Generally, an electrolytic copper foil is manufactured by electrolytically depositing copper on a drum of titanium or stainless steel from a copper sulfate plating bath, and a rolled copper foil is manufactured by repeating plastic working and heat treatment using rolling rolls. A rolled copper foil is often applied to applications where flexibility is required. Further, from the viewpoint of easy control of the crystal structure after recrystallization, in a preferred embodiment of the present invention, the copper foil is a rolled copper foil. In addition, when the term "copper foil" is used alone in this specification, it shall include a copper alloy foil.

[0015] As the copper foil material, in addition to high-purity copper such as tough pitch copper (C1100) and oxygen-free copper (C1020) complying with the JIS H 3100 (2018) standard, which are commonly used as conductor patterns of flexible printed wiring boards, copper alloys such as copper containing Sn, copper containing Ag, copper alloys added with P, Cr, Zr, Mg, etc., and Colson-based copper alloys added with Ni, Si, etc. can also be used. When containing P as an additive element, P is preferably 10 to 50 mass ppm. When containing P as an additive element, the crystal grain size after recrystallization by heat treatment during the manufacture of copper-clad laminates tends to be uniform, and furthermore, the bottom width of the circuit after etching tends to be constant. However, when the content of P exceeds 50 mass ppm (0.005 mass %), the conductivity decreases, making it unsuitable for flexible printed wiring boards.

[0016] The analysis of the P concentration can be carried out using the molybdophosphoric acid extraction molybdophosphoric acid blue absorptiometry (applicable to P concentration: 0.0005% to 0.01%) specified in JIS H 1058 (2013) (Method for determination of phosphorus in copper and copper alloys).

[0017] Also, the thickness of the copper foil does not particularly need to be limited, for example, it is 1 to 1000 μm, or 1 to 500 μm, or 1 to 300 μm, or 3 to 100 μm, or 5 to 70 μm, or 6 to 35 μm, or 9 to 18 μm.

[0018] In addition, at least one surface of the copper foil, for example, the surface facing the insulating base material, can be provided with a surface treatment layer. The surface treatment layer may be a roughening treatment layer. The roughening treatment usually aims to improve the peel strength of the copper foil after lamination on the surface of the copper foil that adheres to the resin substrate, that is, the surface on the surface treatment layer side, and is a treatment for forming a nodular electrodeposit on the surface of the degreased copper foil. Note that although the electrolytic copper foil has irregularities at the time of manufacture, the convex portions of the electrolytic copper foil can be enhanced by the roughening treatment to further increase the irregularities. The roughening treatment can be performed, for example, by forming roughening particles with copper or a copper alloy. The roughening treatment may be fine. The roughening treatment layer may be a layer made of any single substance selected from the group consisting of copper, nickel, cobalt, phosphorus, tungsten, arsenic, molybdenum, chromium, and zinc, or an alloy containing any one or more thereof. Further, after forming roughening particles with copper or a copper alloy, a roughening treatment can also be performed to provide secondary particles or tertiary particles with a single substance or an alloy of nickel, cobalt, copper, zinc, etc.

[0019] In addition, as the surface treatment layer, in addition to the roughening treatment layer, it may be one or more layers selected from the group consisting of a heat-resistant layer, a rust-proof layer, a chromate treatment layer, and a silane coupling treatment layer. These layers can be provided using known methods. In one embodiment, the copper foil does not include a surface treatment layer in the sense that the manufacturing method is simple. In the present invention, it is assumed that the copper foil after being laminated on the copper-clad laminate may also include a copper foil provided with a surface treatment layer. When a surface treatment layer is provided on the copper foil, it is difficult to observe the surface treatment layer separately from the copper foil when imaging the cross-section of the copper-clad laminate, but its area is less than 1% compared to the copper foil, and it has almost no influence on the ratio of the crystal orientation.

[0020] (2. Manufacturing method of copper foil) The manufacturing method of the copper foil of the present invention is not particularly limited as long as the characteristics of the crystal aggregate structure as described below can be achieved. For example, after adding additive elements to the copper ingot as necessary, melting and casting, hot rolling is performed, and then cold rolling and annealing are repeated to manufacture a foil with the desired final thickness.

[0021] Here, the copper foil of the present invention can be obtained by controlling the heating rate during annealing at a thickness of about 1.5 mm. By controlling the heating rate, the conduction of thermal energy to the copper material can be controlled. Thereby, the growth of crystal grains in a specific orientation can be suppressed, and even after the heat treatment during the production of the subsequent copper-clad laminate, the characteristics of the crystal aggregate structure as described below can be achieved. The heating rate mentioned here means the heating rate from 25°C to the maximum temperature reached by the copper material, and it is preferably 10°C / second or less. In the annealing process, the copper material is cooled after heating, and the cooling rate from the maximum temperature reached by the copper material until it drops by 200°C is preferably 12°C / second or less. The lower limits of the heating rate and the cooling rate are not particularly limited, but from the viewpoint of improving productivity, they are preferably 1°C / second or more, respectively.

[0022] (3. Copper-clad laminate) In one embodiment of the present invention, a copper-clad laminate in which a copper foil is laminated on at least one surface of an insulating substrate is provided. As the copper foil, the above-mentioned copper foil can be used. The insulating substrate is not particularly limited, and those known in the art can be used. The insulating substrate is typically a resin substrate. Examples of the resin substrate include paper-based phenolic resin, paper-based epoxy resin, synthetic fiber cloth-based epoxy resin, glass cloth / paper composite substrate epoxy resin, glass cloth / glass non-woven fabric composite substrate epoxy resin, glass cloth-based epoxy resin, polyester film, polyimide film, liquid crystal polymer, fluororesin, etc. When using a resin film as the resin substrate, particularly PET (polyethylene terephthalate), PI (polyimide), LCP (liquid crystal polymer), PEN (polyethylene naphthalate) can be mentioned, but it is not limited thereto.

[0023] The method for bonding the copper foil and the resin substrate is not particularly limited, and it can be carried out according to a method known in the art. For example, a material to be a resin substrate may be coated on the surface of the copper foil and heated to form a film. Also, when using a resin film as the resin layer, an adhesive may be used between the resin film and the copper foil, or the resin film may be thermocompression bonded to the copper foil without using an adhesive.

[0024] When using a film as the resin substrate, this film may be laminated on the copper foil via an adhesive layer. In this case, it is preferable to use an adhesive of the same composition as the film. For example, when using a polyimide film as the resin layer, it is preferable to also use a polyimide-based adhesive for the adhesive layer. Here, the polyimide-based adhesive refers to an adhesive containing an imide bond, and also includes polyetherimide, etc.

[0025] The copper-clad laminate manufactured as described above can be etched and used for the production of flexible printed wiring boards.

[0026] In one embodiment of the present invention, regarding the area ratio of crystal grains with an azimuth difference of within 15° from the <100> azimuth, <11-1> azimuth, <1-12> azimuth, and <001> azimuth of the copper foil of the copper-clad laminate, when arbitrarily measuring 4 points, the arithmetic mean value of the maximum area ratios of each azimuth is 20% or less. That is, at any 4 points of the copper foil of the copper-clad laminate, measure the area ratios of the crystal grains in the above 4 azimuths, record the highest area ratio among the area ratios measured at 4 points for each azimuth, and calculate the arithmetic mean value of the numerical values of the maximum area ratios of these 4 azimuths, which is 20% or less.

[0027] The reason why the circuit linearity after etching can be improved by controlling the arithmetic mean value of the maximum area ratios of each azimuth when arbitrarily measuring 4 points is as follows. That is, the circuit linearity after etching is caused by the etching rate difference in each azimuth during etching. However, if there is a dominant crystal azimuth, the influence of the etching rate due to the crystal azimuth is large, and an etching rate difference is likely to occur. On the other hand, if there is no dominant crystal azimuth, the difference in the etching rate at each location is not large, and the etching proceeds more evenly, so the circuit linearity is improved.

[0028] In the copper foil of the copper-clad laminate, since the main crystal aggregate structures are four orientations of {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation, when any four points are measured, the arithmetic mean value of the maximum area ratios of each orientation being 20% or less means that there is no dominant crystal orientation, which is desirable from the perspective of circuit linearity.

[0029] From the above perspective, regarding the area ratios of crystal grains with an orientation difference of within 15° from the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation of the copper foil of the copper-clad laminate, when any four points are measured, it is preferable that the arithmetic mean value of the maximum area ratios of each orientation is 20% or less, more preferably 18% or less, even more preferably 17% or less, even more preferably 16% or less, even more preferably 15% or less, and even more preferably 14% or less.

[0030] The lower limit of the area ratio occupied by the crystal grains of each of the above orientations is not particularly limited and can even be 0%. Also, when any four points are measured, as long as the arithmetic mean value of the maximum area ratios of each orientation is 20% or less, it is not necessary for the area ratios occupied by the crystal grains of each orientation to be the same or similar, and any numerical value is acceptable.

[0031] The area ratio occupied by the crystal grains of each of the above orientations is calculated by crystal orientation analysis in EBSD (Electron Back Scatter Diffraction) measurement. The actual measurement is to observe the cross-section of the copper foil of the copper-clad laminate after CP processing (cross-section sample preparation processing using a cross-section polisher) with SEM-EBSD (SU-70 manufactured by Hitachi High-Tech Corporation or an equivalent device, OIM DATA COLLECTION manufactured by TSL Solutions Co., Ltd., and OIM ANALYSIS manufactured by TSL Solutions Co., Ltd.) under the following conditions. Note that the EBSD measurement may be performed on the cross-section in the thickness direction of a sample plate (length 200 mm × width 200 mm) cut out from a copper-clad laminate.

[0032] ·SEM Conditions Type of electron gun: Field emission electron gun (Schottky type) Emitter of electron gun: ZrO tungsten cathode Type of objective lens: Out-lens type Presence or absence of focus correction: Yes (Dynamic focus: 24) Beam Conditions Accelerating voltage: 15 kV Working distance: 15 mm Magnification for observation: 2500 times Sample Tilt: 70.0 degrees ·EBSD Equipment Conditions Detector: Digital CCD camera manufactured by TSL Solutions Co., Ltd. Observation field of view: 30 μm × 20 μm or 32 μm × 20 μm Step size: 0.3 μm Data collection software: OIM Data Collection manufactured by TSL Solutions Co., Ltd. Phase: Copper Number of pixels of CCD camera: 1030 × 1300 pixels Binning: 8 × 8 Exposure (exposure time): Approximately 8 milliseconds Gain: 0.1 - 0.7 Presence or absence of background processing: Yes Scanning method of measurement points: Hexagonal glid ·Hough Transformation (1) Hough Type: Classic (2) Hough Resolution: Low (3) Classic Hough ·Convolution Mask: 9 × 9 ·Min Peak Magnitude: 5 ·Minimum Peak Distance: 23 ·Peak Symmetry: 0.70 ·Vertical Bias: 0 (4) General Parameter ·Binned Pattern Size: 120 ·Theta Step Size: 1° ·Rho Fraction: 90% ·Maximum Peak Count: 8 ·Minimum Peak Count: 3

[0033] Then, the analysis of the crystal orientation density function is performed. The area of crystal grains with an orientation difference within 15° from the Cube orientation {001}<100>, Copper orientation {112}<11-1>, Brass orientation {110}<1-12>, and Goss orientation {110}<001> is divided by the measured area to obtain the area ratio. For the collection of the above measurement data, OIM Data Collection manufactured by TSL Solutions Co., Ltd. is used, and for data analysis, OIM Analysis manufactured by TSL Solutions Co., Ltd. is used. Note that the information obtained from orientation analysis by EBSD includes orientation information up to a depth of several tens of nanometers where the electron beam penetrates the sample. Since it is sufficiently small compared to the measured area, it is described as the area ratio. <OIM Analysis Data Analysis Conditions> ·Perform Clean Up by Grain Dilation method once ·Perform Clean Up by Grain CI STANDARDIZATION method once ·Grain Tolerance angle: 5 ·New Map window Map Style Grayscale: <none>Select it. Color Coded: Select Crystal Orientation. Boundaries Second Partition: <none>Select it. · Crystal Orientation window (the screen displayed when clicking Edit of Color Coded in Map Style window) Select Representation: Euler Angles (Bunge). Check box for Enforce Orthotropic Sample Symmetry: Enter a dot. · Add Crystal Orientation Range window (the screen displayed when clicking Add in Crystal Orientation window) Orientation tab Select Phase: Copper. (1) Cube orientation {001}<100> Euler Angles (Bunge): (φ1, φ, φ2) = (0, 0, 0) Each input value of hkl: 001 Each input value of uvw: 100 Tolerance tab Input value of Minimum: 0 Input value of Maximum: 15 (2) Copper orientation {112}<11-1> Euler Angles (Bunge): (φ1, φ, φ2) = (270, 35.3, 45) Each input value of hkl: 112 Each input value of uvw: 11-1 Tolerance tab Input value of Minimum: 0 Input value of Maximum: 15 (3) Brass orientation {110}<1-12> Euler Angles (Bunge): (φ1, φ, φ2) = (54.7, 90, 45) Each input value of hkl: 110 Each input value of uvw: 1-12 Tolerance tab Input value of Minimum: 0 Maximum input value: 15 (4) Goss orientation {110} <001> Euler Angles (Bunge): (φ1, φ, φ2) = (90, 90, 45) Each input value of hkl: 110 Each input value of uvw: 001 Tolerance tab Minimum input value: 0 Maximum input value: 15 Regarding the measurement result of Crystal Orientation performed under the above - set conditions, the value of Total fraction is taken as the area ratio of each orientation.

[0034] Note that it should be noted that the above EBSD measurement is performed on the copper foil of the copper - clad laminate. As described above, since the copper foil is heat - treated and recrystallized during the manufacture of the copper - clad laminate, in order to improve the circuit linearity, the recrystallized copper foil should be evaluated. Even if the EBSD measurement is performed on the copper foil before the manufacture of the copper - clad laminate, that is, before the heat treatment during the manufacture of the copper - clad laminate, the area ratio occupied by the crystal grains in each orientation of the copper foil after lamination may vary, so appropriate evaluation may not be possible. Also, since the crystals in the copper foil have already been recrystallized by the heat treatment during the manufacture of the copper - clad laminate and the amount of heat applied to the copper foil by etching is small, it is considered that the area ratio occupied by the crystal grains in each orientation of the copper foil is hardly affected by etching. Therefore, the above EBSD measurement may be performed on the copper - foil circuit after etching.

[0035] (4. Flexible printed wiring board and electronic device) The flexible printed wiring board according to an embodiment of the present invention uses the above - mentioned copper - clad laminate. For example, the flexible printed wiring board can be manufactured by etching the surface - treated copper foil of the above - mentioned copper - clad laminate to form a circuit pattern. The method for forming the circuit pattern is not particularly limited, and known methods such as the subtractive method and the semi - additive method can be used. Among them, the subtractive method is preferred as the method for forming the circuit pattern.

[0036] When manufacturing a flexible printed circuit board by the subtractive method, it is preferably carried out as follows. First, a resist is applied to the surface of the surface-treated copper foil of the copper-clad laminate, exposed, and developed to form a predetermined resist pattern. Next, the surface-treated copper foil in the portion where the resist pattern is not formed (unnecessary portion) is removed by etching to form a circuit pattern. Finally, the resist pattern on the surface-treated copper foil is removed.

[0037] In addition, various conditions in this subtractive method are not particularly limited, and can be carried out according to conditions known in the art.

[0038] Since the flexible printed circuit board according to an embodiment of the present invention uses the above copper-clad laminate, it has excellent circuit linearity and is easy to miniaturize the circuit.

[0039] Further, another embodiment of the present invention is an electronic device using the flexible printed circuit board of the present invention. The type of the electronic device is not particularly limited, and examples include a personal computer and a mobile terminal that have particularly high requirements for miniaturization and high performance.

Example

[0040] Hereinafter, the present invention will be specifically described by way of examples. However, the description here is for illustrative purposes only and is not intended to be limiting.

[0041] (Comparative Example) An ingot was produced from electrolytic copper in a non-oxidizing atmosphere. The proportion of copper contained in the ingot was 99.96% by mass or more. Using this ingot, a foil with a final thickness of 12 μm was obtained. During the process, annealing was carried out at a thickness of 1.5 mm. At this time, the heating rate from 25°C to the maximum temperature reached by the copper material was 11.27°C / second (calculated value by heat transfer simulation based on operating conditions), and the cooling rate from the maximum temperature reached to 200°C was 13.74°C / second (calculated value by heat transfer simulation based on operating conditions).

[0042] After performing known surface treatment (including roughening treatment on the surface facing the resin substrate) on the obtained copper foil, a sample plate (200 mm × 200 mm) was cut out, bonded to a resin substrate (FRS manufactured by Kaneka Corporation, thickness 25 μm), and heat-treated at 360°C × 30 min using a high-temperature vacuum hot press device (KVHC-PRESS manufactured by Kitakawa Seiki Co., Ltd.) to obtain a copper-clad laminate.

[0043] (Example) An ingot was produced from electrolytic copper in a non-oxidizing atmosphere. The proportion of copper contained in the ingot was 99.96 mass% or more. Using this ingot, a foil with a final thickness of 12 μm was obtained. During the process, annealing was carried out at a thickness of 1.5 mm. At this time, the heating rate from 25°C to the maximum temperature reached by the copper material was 9.38°C / second (calculated value based on heat transfer simulation according to operating conditions), and the cooling rate from the maximum temperature reached until it dropped by 200°C was 11.16°C / second (calculated value based on heat transfer simulation according to operating conditions), and heat was applied more slowly than in the comparative example. In both the example and the comparative example, the maximum temperature reached by the copper material during annealing at a thickness of 1.5 mm was 400 - 600°C.

[0044] After performing known surface treatment (including roughening treatment on the surface facing the resin substrate) on the obtained copper foil, a sample plate (200 mm × 200 mm) was cut out, bonded to a resin substrate (FRS manufactured by Kaneka Corporation, thickness 25 μm), and heat-treated at 360°C × 30 min using a high-temperature vacuum hot press device (KVHC-PRESS manufactured by Kitakawa Seiki Co., Ltd.) to obtain a copper-clad laminate.

[0045] (Evaluation of circuit linearity) Regarding the copper-clad laminates obtained in the above Comparative Examples and Examples, a dry film resist (product name RY-5107, thickness 7 μm, manufactured by Resonac Co., Ltd.) was used, and the circuit portion of the copper foil was masked by photolithography, and dry film patterning with an L+S pitch of 50 μm was performed. Development, etching, and stripping of the resist were carried out using the "Development / Etching / Stripping Line" (equipment name: DERM) of Santechno Systems Co., Ltd. A straight circuit (see FIGS. 1(A) and 2(A)) was formed from the copper foil side of the copper-clad laminate by etching. The etching conditions are as follows. Etching conditions: Composition of the etching solution: CuCl 2 -2H 2 O = 3 mol / L (specific gravity 1.24), HCl = 4 mol / L, solution temperature = 50°C, spray pressure of the etching solution = 0.22 MPa, and the rolled copper foil with the circuit portion masked was etched to form a circuit.

[0046] Next, using a SEM (SU-70) manufactured by Hitachi High-Tech Corporation and an EBSD (OIM DATA COLLECTION, OIM ANALYSIS) manufactured by TSL Solutions Co., Ltd., image capture and EBSD analysis were performed on the copper foil circuit after etching. Regarding the cross-section, among the multiple circuits of each sample, four adjacent ones were selected for EBSD analysis of the cross-section. Since the TD cross-section of the copper foil was observed, the TD direction was made to coincide with the direction of the copper foil in terms of the measurement direction, but the ND direction in terms of the measurement was the MD direction of the copper foil. Therefore, by rotating 90° around the TD axis during the analysis by OIM ANALYSIS, the ND direction of the copper foil was made to coincide with the ND direction of the measurement.

[0047] (Area ratio of crystal grains) For the copper-clad laminates obtained in the above Comparative Examples and Examples, the orientations of individual crystal grains were identified by EBSD measurement under the aforementioned conditions. For the Comparative Examples and Examples, four arbitrarily selected points were measured respectively. Table 1 shows the arithmetic mean values of the maximum area ratios of each orientation when four arbitrarily selected points were measured for the area ratios of the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation.

[0048]

Table 1

[0049] As can be seen from FIGS. 1(A) and 1(B), in the copper-clad laminate of the Comparative Example, the etching of the copper foil did not proceed evenly, and the variation in the width of the circuit was large. On the other hand, as can be seen from FIGS. 2(A), 2(B), and Table 1, in the copper-clad laminate of the Example, when four arbitrarily selected points were measured, the arithmetic mean value of the maximum area ratio of each orientation was 20% or less, and since there was no dominant crystal orientation, the etching of the copper foil proceeded more evenly, the variation in the width of the circuit was small, and the circuit linearity was excellent.< / none> < / none>

Claims

1. A copper-clad laminate in which a copper foil is laminated on at least one surface of an insulating substrate, A copper-clad laminate, in which, when the area ratios of crystal grains whose orientations are within 15° of each other from the {001}<100> orientation, the {112}<11-1> orientation, the {110}<1-12> orientation, and the {110}<001> orientation of the copper foil are measured at any four points, the arithmetic average value of the maximum area ratios of each orientation is 20% or less.

2. The copper clad laminate according to claim 1 , further comprising a surface treatment layer on the surface of the copper foil facing the insulating substrate.

3. The copper clad laminate of claim 1 , wherein the copper foil is a rolled copper foil.

4. A flexible printed wiring board using the copper-clad laminate according to claim 1.

5. An electronic device using the flexible printed wiring board according to claim 4.

Images