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. Among 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, the crystal grain with the highest area ratio accounts for 26% or less of the total area.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 undergoes a circuit printing process by resist coating and exposure, and further undergoes an etching process to remove unnecessary portions of the copper layer.

[0004] As a technology of copper foil used for a copper-clad laminate, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2021-014603) discloses a rolled copper foil containing 99.9 mass% or more of Cu and 0.0005 to 0.0220 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 this 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 a fine circuit, it is important that the circuit width is constant throughout the circuit in order to maintain impedance consistency. This is because if the circuit width is not constant throughout the circuit, the circuit may stick to (contact) the adjacent circuit, which may cause defects. Therefore, it is required that the variation in the circuit width obtained by etching is small (circuit linearity).

[0007] The technology described in Patent Document 1 aims to improve the bendability of CCL, and no consideration has been given to 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 ratios 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 differences in each orientation during etching can be suppressed, and the variation in the width of the circuit due to the etching rate differences 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, Among the crystal grains with an orientation difference of 15° or less from the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation of the copper foil, the area ratio occupied by the crystal grain with the highest area ratio is 26% or less. A copper-clad laminate. [2] The sum of the area ratios of the crystal grains with an orientation difference of 15° or less from the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation of the copper foil is 36% or less. The copper-clad laminate according to [1]. [3] The copper-clad laminate according to [1] or [2], including a surface treatment layer on the surface of the copper foil facing the insulating substrate. [4] The copper foil is a rolled copper foil. The copper-clad laminate according to any one of [1] to [3]. [5] A flexible printed wiring board using the copper-clad laminate according to any one of [1] to [4]. [6] An electronic device using the flexible printed wiring board according to [5].

Effect 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 Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out 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. Also, 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 with a rolling roll and heat treatment. A rolled copper foil is often applied to applications where flexibility is required. Also, 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. Note that when the term "copper foil" is used alone in this specification, it includes copper alloy foils.

[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 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 Corson-based copper alloys added with Ni, Si, etc. can also be used. When containing P as an additive element, it is preferable that P is 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 and it is not suitable for flexible printed wiring boards.

[0016] The analysis of P concentration can be carried out using the molybdophosphoric acid extraction molybdophosphoric acid blue absorptiometry (applicable to P concentration: 0.0005% to 0.01%) defined 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, but 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 generally refers to a treatment for forming a pitted electrodeposition on the surface of the degreased copper foil for the purpose of improving 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. Although the electrolytic copper foil has unevenness at the time of manufacture, the convex portions of the electrolytic copper foil can be enhanced by the roughening treatment to further increase the unevenness. 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 for providing secondary particles or tertiary particles with a single substance or an alloy of nickel, cobalt, copper, zinc, etc. can also be performed.

[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 needed, melting and casting, hot rolling is performed, and cold rolling and annealing are repeated to manufacture a foil having 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 manufacture of the subsequent copper-clad laminate, the characteristics of the crystal aggregate structure as described below can be achieved. The heating rate referred to here means the heating rate from 25°C to the maximum temperature reached by the copper material, and it is preferably 10°C / sec or less. Further, in the annealing process, the copper material is cooled after heating, but the cooling rate until the temperature of the copper material drops by 200°C from the maximum temperature reached is preferably 12°C / sec 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 / sec 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-described 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, and the like. When a resin film is used 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 of adhering 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 applied to the surface of the copper foil and heated to form a film. Alternatively, a resin film may be used as the resin layer, and 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 base material, 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 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 and the like.

[0025] The copper-clad laminate manufactured as described above can be etched and used for manufacturing a flexible printed wiring board.

[0026] In one embodiment of the present invention, among the crystal grains with an orientation difference of within 15° from the <100> orientation, <11-1> orientation, <1-12> orientation, and <001> orientation of the copper foil of the copper-clad laminate, the area ratio occupied by the crystal grain with the highest area ratio is 26% or less.

[0027] The reason why the circuit linearity after etching can be improved by controlling the maximum value of the area ratio of the crystal grains in each orientation is as follows. That is, the circuit linearity after etching is caused by the etching rate difference in each orientation during etching. However, if there is a dominant crystal orientation, the influence of the etching rate due to the crystal orientation is large, and an etching rate difference is likely to occur. On the other hand, if there is no dominant crystal orientation, 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] And in the copper foil of the copper-clad laminate, the main crystal aggregate structure is the four orientations of <100> orientation, <11-1> orientation, <1-12> orientation, and <001> orientation. Therefore, the maximum value of the area ratio occupied by the crystal grains in these orientations being 26% or less means that there is no dominant crystal orientation, which is desirable from the perspective of circuit linearity.

[0029] From the above viewpoints, among the crystal grains with an orientation difference of within 15° from the <100> orientation of {001}, the <11-1> orientation of {112}, the <1-12> orientation of {110}, and the <001> orientation of {110} of the copper foil of the copper-clad laminate, the area ratio occupied by the crystal grain with the highest area ratio is preferably 25% or less, more preferably 24% or less, even more preferably 23% or less, even more preferably 22% or less, even more preferably 21% or less, and even more preferably 20% or less.

[0030] The lower limit of the area ratio of the crystal grains with an orientation difference of within 15° from the <100> orientation of {001}, the <11-1> orientation of {112}, the <1-12> orientation of {110}, and the <001> orientation of {110} of the copper foil of the copper-clad laminate is not particularly limited and can even be 0%. Also, if the area ratio occupied by the crystal grain with the highest area ratio is 26% or less, it is not necessary for the area ratios occupied by the crystal grains in each orientation to be the same or similar, and any value in the range of 0 to 26% may be used.

[0031] In a preferred embodiment of the present invention, the total area ratio of the crystal grains with an orientation difference of within 15° from the <100> orientation of {001}, the <11-1> orientation of {112}, the <1-12> orientation of {110}, and the <001> orientation of {110} of the copper foil of the copper-clad laminate is 36% or less. As described above, in the copper foil of the copper-clad laminate, the main crystal aggregate structure has four orientations: the <100> orientation of {001}, the <11-1> orientation of {112}, the <1-12> orientation of {110}, and the <001> orientation of {110}. Therefore, if the total area ratio of these crystal grains is 36% or less, it is presumed that the variation in the etching rate due to the crystal orientation is small and the circuit linearity is improved.

[0032] The area ratio occupied by the crystal grains in each of the above directions is calculated by crystal orientation analysis in EBSD (Electron Back Scatter Diffraction) measurement. For actual measurement, the copper foil cross-section of the copper-clad laminate is observed under the following conditions by 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.) after CP processing (cross-section sample preparation processing using a cross-section polisher). Note that the EBSD measurement may be performed on the thickness-direction cross-section of a sample plate (length 200 mm × width 200 mm) cut out from the copper-clad laminate.

[0033] ·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 Acceleration voltage: 15 kV Working distance: 15 mm Observation magnification: 2500 times Sample Tilt: 70.0 degrees ·EBSD Device 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: Present Scanning method of measurement points: Hexagonal glid · Hough transform (1) Hough Type: Classic (2) Hough Resolution: Low (3) Classic Hough · Convolution Mask (convolution mask): 9×9 · Min Peak Magnitude (minimum peak intensity): 5 · Min Peak Distance (minimum peak distance): 23 · Peak Symmetry (peak symmetry): 0.70 · Vertical Bias (vertical bias): 0 (4) General Parameter · Binned Pattern Size (compressed pattern size): 120 · Theta Step Size (angle step size): 1° · Rho Fraction (rho fraction): 90% · Max Peak Count (maximum peak count): 8 · Min Peak Count (minimum peak count): 3

[0034] 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 measurement 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 in the orientation analysis by EBSD includes the 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. <Data Analysis Conditions for OIM Analysis> ·Perform Clean Up once using the Grain Dilation method ·Perform Clean Up once using the Grain CI STANDARDIZATION method ·Grain Tolerance angle: 5 ·New Map window Map Style Grayscale: <none>Select it. Select Color Coded: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 results of Crystal Orientation conducted under the above - set conditions, the value of Total fraction shall be taken as the area ratio of each orientation.

[0035] It should be noted that the above EBSD measurement is to be carried out 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 circuit linearity, the recrystallized copper foil should be evaluated. Even if the EBSD measurement is carried out 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 of 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 of each orientation of the copper foil is hardly affected by etching. Therefore, the above EBSD measurement may be carried out on the copper foil circuit after etching.

[0036] (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.

[0037] When manufacturing a flexible printed circuit board by the subtractive method, it is preferably performed 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.

[0038] In addition, various conditions in this subtractive method are not particularly limited and can be carried out according to conditions known in the art.

[0039] 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.

[0040] 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, but examples include a personal computer and a mobile terminal that have particularly high requirements for miniaturization and high performance.

Example

[0041] 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.

[0042] (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 performed 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 a decrease of 200°C was 13.74°C / second (calculated value by heat transfer simulation based on operating conditions).

[0043] 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.

[0044] (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 to a decrease of 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.

[0045] 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.

[0046] (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 portions of the copper foil were masked by photolithography to perform dry film patterning with an L+S pitch of 50 μm. 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 subjected to etching treatment to form a circuit.

[0047] 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 capturing and EBSD analysis were performed on the copper foil circuit after etching. Regarding the cross-section, among multiple circuits of each sample, 4 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, during the analysis by OIM ANALYSIS, the ND direction of the copper foil was made to coincide with the ND direction of the measurement by rotating it 90° around the TD axis.

[0048] (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 locations (n1 to n4) were measured respectively. Table 1 shows the area ratio occupied by the crystal orientation with the highest area ratio and the total area ratio of the crystal grains in the four orientations for the {001}<100> orientation, {112}<11-1> orientation, {110}<1-12> orientation, and {110}<001> orientation.

[0049]

Table 1

[0050] 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 there was a large variation in the width of the circuit. 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, the area ratio occupied by the crystal grains with the highest area ratio was 26% 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 the area ratio of the crystal grains having the highest area ratio among the crystal grains having an orientation difference of 15° or less from the {001}<100> orientation, the {112}<11-1> orientation, the {110}<1-12> orientation, and the {110}<001> orientation of the copper foil is 26% or less.

2. The copper-clad laminate according to claim 1, wherein the total area ratio of crystal grains having an orientation difference of 15° or less from the {001}<100> orientation, the {112}<11-1> orientation, the {110}<1-12> orientation, and the {110}<001> orientation of the copper foil is 36% or less.

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

4. The copper clad laminate according to claim 1 or 2, wherein the copper foil is a rolled copper foil.

5. A flexible printed wiring board using the copper-clad laminate according to claim 1 or 2.

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

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