JP2023028081A - Laminate for electronic circuit board - Google Patents

Abstract

To provide a laminate for an electronic circuit board in which a copper layer is hard to peel, excellent in peel strength and less in transmission loss, and a manufacturing method thereof.SOLUTION: A laminate for an electronic circuit board includes a copper layer on at least one surface of a resin layer containing a styrene-based resin having a syndiotactic structure, and a plurality of protrusions on the surface of the copper layer in contact with the resin layer. The protrusions have the shape of particles when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, the average aspect ratio of the particles is 1.3 to 5.0, and the average area of the particles is 0.005 to 0.025 μm2.SELECTED DRAWING: None

Description

The present invention relates to a laminate for electronic circuit board.

Polystyrene resins having a syndiotactic structure (hereinafter also referred to as SPS) have excellent properties such as mechanical strength, heat resistance, electrical properties, water absorption dimensional stability, and chemical resistance. Therefore, SPS is very useful as a resin used in various applications such as electrical/electronic equipment materials, automotive/electrical parts, household appliances, various machine parts, and industrial materials.
Furthermore, SPS is a hydrocarbon resin obtained by polymerizing styrene monomer, and since it has low dielectric loss and insulating properties, it is being studied for use as a material for electrical and electronic equipment among the above applications.

As an example of electronic device materials using SPS, for example, Patent Document 1 describes SPS, a polymer having a polar group, and a thermoplastic resin for the purpose of improving electrolytic corrosion resistance and reliability and responding to high-density mounting. discloses a printed wiring board obtained by laminating a flame-retardant resin composition and a glass cloth, and laminating a metal layer on at least one surface.

JP-A-9-077937

In recent years, as the performance of electronic devices has improved, miniaturization of wiring used in electronic circuits has been demanded. A problem arises that it is easy to peel off. Therefore, there is a demand for a circuit board in which even fine wiring is difficult to peel off.
In addition, high-frequency signals have come to be used for communication due to the advancement in performance and functionality of electronic devices and information terminals and the progress in information communication technology. Therefore, there is a demand for a material that can be used to manufacture a circuit board with little transmission loss even when a high-frequency signal is used.
Therefore, there has been a demand for a circuit board that achieves both improved adhesion between metal wiring and substrate resin and reduced transmission loss while meeting the demand for finer wiring.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a laminate for an electronic circuit board in which the copper layer is less likely to peel, has excellent peel strength, and has less transmission loss, and a method for producing the same.

As a result of extensive studies, the inventors of the present invention have found that a laminate having a copper layer having specific projections on at least one surface of an SPS layer solves the above problems. That is, the present invention relates to the following [1] to [18].

[1] A resin layer containing a styrene-based resin having a syndiotactic structure has a copper layer on at least one surface thereof, and a surface of the copper layer in contact with the resin layer has a plurality of projections, and the projections are made of the copper. It has a particle shape when viewed from the normal direction of the surface of the layer in contact with the resin layer, the average aspect ratio of the particles is 1.3 to 5.0, and the average area of the particles is 0.005 to 0.005. A laminate for an electronic circuit board, which is 0.025 μm ² .
[2] The laminate for an electronic circuit board according to [1] above, wherein the particles include particles having an acute angle.
[3] The surface of the copper layer in contact with the resin layer has an average roughness (Ra) of 0.10 to 0.50 μm, and the surface of the copper layer in contact with the resin layer has a maximum height roughness (Rz) of 1. The laminate for an electronic circuit board according to the above [1] or [2], which has a thickness of 0.00 to 5.00 μm.
[4] Any one of the above [1] to [3], wherein the surface of the copper layer in contact with the resin layer has a silicon element content of 7% or more as determined by atomic composition analysis using X-ray photoelectron spectroscopy. The laminate for an electronic circuit board according to 1.
[5] The laminate for an electronic circuit board according to any one of [1] to [4] above, wherein the particles include rhombic or approximately rhombic particles.
[6] The laminate for an electronic circuit board according to any one of [1] to [5] above, which has copper layers on both sides of the resin layer.
[7] The laminate for an electronic circuit board according to any one of [1] to [6] above, wherein the copper foil constituting the copper layer is an electrolytic copper foil.
[8] The laminate for an electronic circuit board according to any one of [1] to [7] above, wherein the resin layer further contains a styrene-based elastomer.
[9] The laminate for an electronic circuit board according to any one of [1] to [8] above, wherein the styrene resin having a syndiotactic structure has a weight average molecular weight of 100,000 to 300,000. .
[10] The laminate for an electronic circuit board according to any one of [1] to [9] above, wherein the copper layer has a thickness of 8 to 30 μm.
[11] The electronic circuit board laminate according to any one of the above [1] to [10], wherein the electronic circuit board laminate has a thickness of 10 to 3,000 μm.
[12] An electronic circuit board using the electronic circuit board laminate according to any one of [1] to [11] above.
[13] A pressing step of pressing and integrating a copper foil on at least one surface of a resin sheet containing a styrene resin having a syndiotactic structure at a pressing temperature equal to or lower than the melting point of the styrene resin;
A surface of the copper layer in contact with the resin layer has a plurality of protrusions, the protrusions having a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, A method for producing a laminate for an electronic circuit board, wherein the laminate for an electronic circuit board has an average aspect ratio of 1.3 to 5.0 and an average area of the particles of 0.005 to 0.025 μm ² .
[14] At least one surface of the copper foil has a plurality of projections, the projections have a particle shape when viewed from the normal direction of the copper foil surface, and the average aspect ratio of the particles is 1.3 to 5.0, and the average area of the particles is 0.005 to 0.025 μm ² .
[15] The method for manufacturing an electronic circuit board laminate according to the above [13] or [14], wherein the pressing pressure in the pressing step is 5 MPa or more and 20 Pa or less.
[16] The method for producing a laminate for an electronic circuit board according to any one of [13] to [15] above, wherein the resin sheet is a non-stretching sheet.
[17] Any one of the above [13] to [16], which has a step of kneading and casting a styrene resin having a syndiotactic structure and a styrene elastomer before the pressing step to obtain a resin sheet. 1. A method for producing a laminate for an electronic circuit board according to 1 above.
[18] The method for producing a laminate for an electronic circuit board according to [17] above, wherein in the step of obtaining the resin sheet, the styrene-based resin having a syndiotactic structure and the styrene-based elastomer are further kneaded with a nucleating agent.

ADVANTAGE OF THE INVENTION According to this invention, the laminated body for electronic circuit boards which a copper layer is hard to peel, is excellent in peeling strength, and has little transmission loss, and its manufacturing method can be provided.

1 is a scanning electron micrograph (magnification: 5,000 times) of the surface of the copper foil used in Example 1 and Comparative Examples 1 to 4 in contact with the resin sheet (the surface of the copper layer in contact with the resin layer). 1 is a scanning electron microscope photograph (magnification: 50,000 times) of the surface of the copper foil used in Example 1 in contact with the resin sheet (the surface of the copper layer in contact with the resin layer) and a binarized image of the photograph. . 1 is a scanning electron micrograph (magnification: 5,000 times) of a cross section of a copper foil (copper layer) used in Example 1 and Comparative Examples 1 to 4. FIG. 1 is scanning electron micrographs (magnification: 30,000 times) of cross sections of copper foils (copper layers) used in Example 1, Comparative Example 1, and Comparative Example 2. FIG.

The laminate for an electronic circuit board of the present invention has a copper layer on at least one surface of a resin layer containing a styrene-based resin having a syndiotactic structure, and has a plurality of protrusions on the surface of the copper layer in contact with the resin layer. and the protrusion has a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, the average aspect ratio of the particle is 1.3 to 5.0, and the particle has an average area of 0.005 to 0.025 μm ² .
Each item will be described in detail below.

[Laminate for electronic circuit board]
The laminate for an electronic circuit board of the present invention has a copper layer on at least one surface of a resin layer containing a styrene-based resin having a syndiotactic structure, and has a plurality of protrusions on the surface of the copper layer in contact with the resin layer. and the protrusion has a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, the average aspect ratio of the particle is 1.3 to 5.0, and the particle has an average area of 0.005 to 0.025 μm ² .

<Resin layer>
The resin layer in the laminate for an electronic circuit board of the present invention contains a styrene-based resin having a syndiotactic structure.
The content of the styrene-based resin having a syndiotactic structure in the resin layer is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and even more preferably. is 80% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 85% by mass or less. If the content of the styrene-based resin having a syndiotactic structure in the resin layer is within the above range, the laminate will be excellent in both high-frequency characteristics and toughness.
The resin layer may be a non-stretched sheet or a stretched sheet. When a non-stretching sheet is used, even if the pressing temperature is lower than the melting point of the resin sheet, the copper foil is easily adhered to the resin sheet, resulting in excellent peel strength. On the other hand, when the content of the styrene-based resin having a syndiotactic structure in the resin layer exceeds 95% by mass, a stretched sheet can be used for the resin layer. In this case, the laminated body is particularly excellent in high frequency characteristics.
Also, the thickness of the resin layer is preferably 60 to 192 μm, more preferably 69 to 161 μm, still more preferably 80 to 140 μm. If the thickness of the resin layer is within the above range, the insulating properties and toughness are excellent, and high-density circuits can be achieved. The resin layer may consist of a plurality of layers, in which case the total thickness of each layer is preferably within the above range.

(Styrene-based resin having a syndiotactic structure)
The styrene resin having a syndiotactic structure (hereinafter also simply referred to as a styrene resin) constituting the resin layer contains 75 mol % or more, preferably 85 mol % or more of racemic diad (r), racemic pentad (rrrr ) has a syndiotacticity of 30 mol % or more, preferably 50 mol % or more.
Tacticity refers to the proportion of phenyl rings in adjacent styrene units that alternate with respect to the plane formed by the backbone of the polymer block. Syndiotacticity can be quantified by a nuclear magnetic resonance method ( ¹³ C-NMR method). A diad indicates syndiotacticity with two consecutive monomer units and a pentad with five monomer units.

Examples of styrene-based resins include polystyrene and copolymers containing styrene as a main component, and polystyrene (styrene homopolymer) is preferred.
When a copolymer containing styrene as a main component is used as the styrene resin, the styrene content is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 mol% or more.

The weight average molecular weight of the styrene-based resin is preferably 100,000 to 300,000, more preferably 150,000 to 250,000, even more preferably 150,000 to 200,000. The weight average molecular weight is determined by gel permeation chromatography using monodisperse polystyrene as a standard. Specifically, it is obtained by the measuring method described in the Examples.
The softening point of the styrene resin is preferably higher than 260.degree. C., more preferably 261.degree. C. or higher, still more preferably 262.degree. A softening point can be measured based on JISK7206:2016, and can be specifically measured by the method shown in an Example.
The melting point of the styrene-based resin is preferably 265°C or higher, more preferably 267°C or higher, and even more preferably 269°C or higher. Moreover, 275 degrees C or less is preferable and 273 degrees C or less is more preferable. The melting point of the styrenic resin is measured by a differential scanning calorimeter (DSC measurement) according to the method described in JIS K 7121:1987 "Measuring the melting temperature after a certain heat treatment". The melting point of the resin can be obtained from the melting peak temperature obtained under the conditions of a rate of 20°C/min.

(Styrene-based elastomer)
The resin layer in the laminate for an electronic circuit board of the present invention may contain a styrene-based elastomer, and preferably contains a styrene-based elastomer from the viewpoint of obtaining particularly excellent toughness.
The content of the styrene-based elastomer in the resin layer is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 50% by mass or less. Yes, more preferably 30% by mass or less. Within the above range, a laminate having excellent toughness and low transmission loss can be obtained.

Specific examples of styrene elastomers include styrene isoprene styrene block copolymer (SIS), styrene butadiene styrene block copolymer (SBS), styrene ethylene propylene block copolymer (SEP), and styrene ethylene butylene styrene block copolymer. (SEBS), styrene ethylene propylene styrene block copolymer (SEPS), and styrene ethylene propylene styrene block copolymer (SEEPS). or in combination of two or more.
Among these styrene-based elastomers, styrene-ethylene-butylene-styrene block copolymers (SEBS) are preferred, and unmodified styrene-ethylene-butylene-styrene block copolymers (SEBS) are more preferred. By using unmodified SEBS, it is possible to impart toughness to the obtained laminate while maintaining insulation.
The MFR of the styrene-based elastomer is preferably 0.0 (No Flow) to 10 g/10 min under measurement conditions of a temperature of 230° C. and a load of 2.16 kgf.
The weight average molecular weight of the styrene elastomer is preferably 150,000 to 250,000.

(other additives, etc.)
The resin layer in the laminate for an electronic circuit board of the present invention may contain various additives.
Additives preferably used in the resin layer include nucleating agents, antioxidants, glass cloth, fillers, flame retardants, plasticizers, antistatic agents, colorants and the like.

As the nucleating agent, an organic nucleating agent and an inorganic nucleating agent can be used, but the organic nucleating agent is preferred.
Examples of organic nucleating agents include carboxylic acid salts such as metal salts of di-p-tert-butylbenzoic acid, metal salts of p-tert-butylbenzoic acid, sodium salts of cyclohexanecarboxylic acid, and sodium salts of β-naphthoic acid. Metal salts, organic phosphorus compounds such as 2,2′-methylenebis(4,6-di-t-butylphenyl) phosphate metal salts, and the like, preferably organic phosphorus compounds, more preferably phosphoric acid 2, 2'-methylenebis(4,6-di-t-butylphenyl) metal salt.
The content of the nucleating agent is preferably 0.1 to 1% by mass in the resin layer.

Antioxidants include pentaerythrityl-tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], n-octadecyl-3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate and other hindered phenol antioxidants, (2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite and other phosphorus antioxidants, preferably It is a hindered phenolic antioxidant.
The content of the antioxidant is preferably 0.01 to 0.5% by mass in the resin layer.

Examples of the glass cloth include glass cloth with a weaving method such as plain weave, twill weave, and open plain weave, preferably plain weave glass cloth.
The glass cloth is preferably a surface-treated glass cloth surface-treated with a coupling agent. A silane-based coupling agent and a titanium-based coupling agent can be used as the coupling agent used for the surface treatment.

<Copper layer>
The laminate for an electronic circuit board of the present invention has a copper layer on at least one surface of the resin layer, and has a plurality of protrusions on the surface of the copper layer in contact with the resin layer, and the protrusions are formed on the copper layer. It has a particle shape when viewed from the normal direction of the surface in contact with the resin layer, the average aspect ratio of the particles is 1.3 to 5.0, and the average area of the particles is 0.005 to 0.05. 025 μm ² .

As described above, the laminate for an electronic circuit board of the present invention has a copper layer on at least one side of the resin layer, and preferably has a copper layer on both sides of the resin layer. Having copper layers on both sides allows for more complex circuits and higher densities.
That is, in the laminate for an electronic circuit board of the present invention, a copper layer is laminated on at least one side of a resin layer containing a styrene resin having a syndiotactic structure, preferably a styrene resin having a syndiotactic structure. A copper layer is laminated|stacked on both surfaces of the resin layer to contain, and when a copper layer is laminated|stacked on both surfaces of a resin layer, it laminates|stacks in order of a copper layer, a resin layer, and a copper layer.

The copper layer of the laminate for an electronic circuit board of the present invention has a plurality of protrusions on the surface of the copper layer in contact with the resin layer from the viewpoint of achieving both peel strength and transmission loss reduction. The area occupied by the plurality of protrusions is preferably 50% or more, more preferably 70%, of the surface of the copper layer in contact with the resin layer when viewed from the normal direction of the surface in contact with the layer. or more, more preferably 90% or more, and even more preferably 95% or more. It may be 100%, or the surface of the copper layer in contact with the resin layer may be entirely covered with protrusions.

The plurality of protrusions have a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, and the particles preferably include particles having an acute angle, more preferably rhombic. Or it contains approximately diamond-shaped particles.
Of the surface of the surface of the copper layer in contact with the resin layer, the area occupied by protrusions having the shape of particles with acute angles is preferably 50% or more, more preferably 70% or more, and still more preferably 90%. or more, and more preferably 95% or more. It may be 100%, and the surface of the surface of the copper layer in contact with the resin layer may be entirely covered with projections having the shape of particles with acute angles.
Of the surface of the surface of the copper layer in contact with the resin layer, the area occupied by protrusions having the shape of rhombic or approximately rhombic particles is preferably 50% or more, more preferably 70% or more, and even more preferably. It is 90% or more, and more preferably 95% or more. It may be 100%, and the surface of the surface of the copper layer in contact with the resin layer may be entirely covered with projections having the shape of rhombus or approximately rhombus particles.

The average aspect ratio of the particles is 1.3 to 5.0, preferably 1.5 to 4.0, more preferably 2.0 to 3.5, still more preferably 2.5. ~3.0.
The average area of the particles is 0.005-0.025 μm ² , preferably 0.005-0.020 μm ² , more preferably 0.010-0.020 μm ² , still more preferably 0 0.010 to 0.015 μm ² .
The shape of the particles, that is, the shape of the protrusions on the surface of the copper layer in contact with the resin layer can be observed in an image of the surface obtained by magnifying and photographing using an electron microscope.
In the image, the areas and aspect ratios of 30 particles having the highest area among the particles observed on the outermost surface were measured, and the averaged values thereof were taken as the average aspect ratio of the particles and the average area of the particles, respectively. .
The aspect ratio was obtained by approximating an ellipse having the same area as the area of each particle, and determining the lengths of the major and minor axes.
Examples of specific measurement methods and calculation methods are shown in Examples.

Also, the average minor axis length of the particles is preferably 0.05 to 0.12 μm, more preferably 0.05 to 0.010 μm.
The average minor axis length of the particles is the average length of 30 minor axis lengths of the approximate ellipse used to calculate the aspect ratio.

The shape of the protrusions viewed from the side is preferably a dendritic shape.
The shape of the projection viewed from the side can be observed from the image obtained by photographing the cut surface of the copper layer cut in the thickness direction.
The width of the dendritic shape when the projections are viewed from the side is preferably 0.05 to 0.12 μm, and the height of the projections is preferably 0.05 to 0.30 μm.
The height of the projection can be measured from the image obtained by photographing the cut surface of the copper layer cut in the thickness direction.

The average roughness (Ra) of the surface of the copper layer in contact with the resin layer is preferably 0.10 μm or more, more preferably 0.13 μm or more, and preferably 0.50 μm or less, more preferably It is 0.40 μm or less, more preferably 0.30 μm or less, and even more preferably 0.20 μm or less.
In addition, from the viewpoint of achieving both peel strength and transmission loss reduction, the copper layer of the laminate for an electronic circuit board of the present invention has a maximum height roughness (Rz) of the surface of the copper layer in contact with the resin layer. 1.00 μm or more, more preferably 1.50 μm or more, still more preferably 2.00 μm or more, preferably 5.00 μm or less, more preferably 4.00 μm or less, still more preferably is 3.00 μm or less.
Specifically, the average roughness (Ra) and the maximum height roughness (Rz) can be measured by the methods of Examples.

The thickness of the copper layer is preferably 8 to 30 μm, more preferably 9 to 25 μm, still more preferably 10 to 20 μm, from the viewpoints of high density mounting, reliability and transmission loss.

The copper layer is composed of copper foil, and the copper foil that constitutes the copper layer is preferably at least one selected from the group consisting of rolled copper foil and electrolytic copper foil, and from the viewpoint of peel strength and transmission loss reduction, Electrolytic copper foil is more preferable.
The surface of the copper foil may have a plurality of projections of a specific particle shape as described above, and roughening treatment may be performed to adjust the projections on the surface to this shape. Examples of the roughening treatment method include formation of roughened particles by plating.
Furthermore, the copper foil may be a surface-treated copper foil that has been subjected to surface treatments such as heat-resistant treatment, antirust treatment, and chemical treatment.
Examples of the heat-resistant treatment and rust-proof treatment include a method of plating using metals having heat resistance and rust-proof properties, respectively.
Examples of the chemical treatment include treatment with a compound having both a reactive group that reacts with the copper foil surface and a reactive group that reacts with the resin layer surface, in order to enhance adhesion with the resin layer. Examples of such compounds include silane coupling agents. Examples of reactive groups that react with the resin layer surface include epoxy groups, amino groups, vinyl groups, acryl groups, isocyanate groups, mercapto groups, and the like.

The silicon element content of the surface of the copper layer in contact with the resin layer determined by atomic composition analysis using X-ray photoelectron spectroscopy is preferably 7% or more, more preferably 8% or more, and still more preferably 9%. % or more, and more preferably 10% or more. Although there is no upper limit, it is preferably 20% or less, more preferably 15% or less, and still more preferably 12% or less. When the content of silicon is within the above range, an electronic circuit board having excellent adhesiveness between the resin layer and the copper layer and excellent peel strength can be obtained.
The content of the silicon element can be specifically measured by the method described in Examples.

<Characteristics, etc. of laminate for electronic circuit board>
The thickness of the electronic circuit board laminate of the present invention is preferably 10 to 3,000 μm, and is preferably adjusted to an appropriate thickness depending on the application.
For example, when the electronic circuit board laminate of the present invention is used as a rigid electronic circuit board, the thickness of the electronic circuit board laminate is preferably 50 to 3,000 μm, more preferably 100 to 2,000 μm. 000 μm, more preferably 400 to 1,600 μm. When the laminate for an electronic circuit board of the present invention is used as a flexible substrate for an electronic circuit, the thickness of the laminate for an electronic circuit board is preferably 150 µm or less, more preferably 130 µm or less, and even more preferably. is 125 μm or less, preferably 10 μm or more, more preferably 50 μm or more, and still more preferably 100 μm or more. Within the above range, the strength is excellent, the transmission loss is small, and the resulting electronic circuit board and product can be miniaturized.

The laminate for an electronic circuit board of the present invention is preferably used for a high-frequency circuit board, a high-frequency antenna circuit board, etc., because the copper layer is difficult to peel off, the peel strength is excellent, and the transmission loss is small.

[Method for producing laminate for electronic circuit board]
The method for producing a laminate for an electronic circuit board of the present invention comprises a copper layer on at least one surface of the laminate for an electronic circuit board, that is, a resin layer containing a styrene-based resin having a syndiotactic structure, and a copper layer has a plurality of projections on the surface of the surface in contact with the resin layer of the copper layer, the projections have a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, and the average aspect of the particles The ratio is 1.3 to 5.0, and the average area of the particles is 0.005 to 0.025 μm ² . A method having steps is preferred.
Specifically, in the preferred method for producing a laminate for an electronic circuit board according to the present invention, a resin sheet containing a styrene resin having a syndiotactic structure is coated with a copper foil on at least one surface thereof, and the pressing temperature is set to the above styrene resin. The copper layer has a plurality of protrusions on the surface of the copper layer in contact with the resin layer, and the protrusions are normal to the surface of the copper layer in contact with the resin layer. For an electronic circuit board having a particle shape when viewed from a direction, the average aspect ratio of the particles being 1.3 to 5.0, and the average area of the particles being 0.005 to 0.025 μm ² . It is a method of obtaining a laminate.

In the above-described method for producing a laminate for an electronic circuit board, it is preferable to have a step of obtaining a resin sheet to be used in the pressing step. The step of kneading and casting the resin and the styrene-based elastomer is preferred.
Each step will be described below.

(Step of obtaining resin sheet)
The method for producing a laminate for an electronic circuit board according to the present invention comprises a step of kneading and casting a styrene resin having a syndiotactic structure and a styrene elastomer to obtain a resin sheet before the pressing step. is preferred.
The resin sheet used in the method for producing a laminate for an electronic circuit board of the present invention is preferably a non-stretching sheet. When a non-stretching sheet is used, even if the pressing temperature is lower than the melting point of the resin sheet, the copper foil is easily adhered to the resin sheet, resulting in excellent peel strength.
A specific process for obtaining a resin sheet will be described below.

The styrene-based resin having a syndiotactic structure and the styrene-based elastomer used in this step are preferably in the form of pellets.
The styrene-based resin having a syndiotactic structure and the styrene-based elastomer used in this step are preferably the styrene-based resin having a syndiotactic structure and the styrene-based elastomer described in the section <Resin layer> above, respectively. Elastomers, and preferred styrenic resins and styrenic elastomers are the same.
In this step, preferably, the styrene-based resin having a syndiotactic structure and the styrene-based elastomer are further kneaded with a nucleating agent.
Also preferably, an antioxidant is kneaded.
The amount of the styrene-based resin having a syndiotactic structure and the styrene-based elastomer used here is preferably the content in the resin layer described in the section <Resin Layer> above.
The content of the nucleating agent is preferably 0.1 to 1% by mass in the resulting resin sheet.
The blending amount of the antioxidant is preferably 0.05 to 0.5% by mass in the resulting resin sheet.
Kneading is preferably carried out with a twin-screw extruder, and the resulting kneaded mixture is pelletized and used for the next sheet production.

The pelletized kneaded mixture is preferably introduced into a single-screw extruder or a twin-screw extruder, melt-extruded through a T-die, and cooled and solidified by cast rolls to obtain a resin sheet.
The pelletized kneaded mixture is preferably pre-dried. Drying is preferably carried out by leaving in an environment of 60 to 150° C. for 10 minutes to 3 hours.
Next, the kneaded mixture is introduced into an extruder, and if the above drying cannot be performed or the drying is insufficient, it is preferable to use an extruder with a vacuum vent.
A gear pump is preferably installed after the extruder in order to suppress variations in the thickness of the resin in the flow direction and to obtain a resin sheet having a uniform thickness.
Furthermore, in order to avoid contamination with foreign matter, it is more preferable to provide a polymer filter after the gear pump.
Polymer filters include leaf disc type and candle type.
A sintered metal type is preferable as the filtering material of the polymer filter. The collected particle size is preferably 1 to 100 μm.
The extrusion temperature in the extruder is preferably 280-330°C. It is preferable to adjust the extruder temperature from the heater of the extruder to the polymer line, gear pump, polymer filter and T-die.

The cooling medium for the cast rolls is preferably oil or water, and the cooling temperature is preferably 50 to 95°C, more preferably 60 to 90°C.
In order to adhere the resin mixture melted and extruded from the T-die of the extruder to the cast roll, it is preferable to use an air chamber, an air knife system, an electrostatic application system, or a combination thereof.
By bringing the molten resin mixture into close contact with the cast roll and rapidly cooling it, a resin sheet can be stably and continuously obtained.
The drawing speed of the cast roll is preferably 0.5 to 30 m/min, more preferably 1 to 15 m/min.

(Pressing process)
A preferred method for producing a laminate for an electronic circuit board according to the present invention comprises a resin sheet containing a styrene-based resin having a syndiotactic structure obtained as described above, and a copper foil on at least one surface of the resin sheet. It is preferable to have a pressing step of pressing and integrating at a temperature below the melting point of the styrene resin.

The copper foil used in this pressing step is preferably the copper foil that constitutes the copper layer described in the section <Copper layer> above.
Specifically, the copper foil used in this pressing step has a plurality of protrusions on the surface of the copper foil contacting the resin sheet from the viewpoint of achieving both peel strength and transmission loss reduction. The area occupied by the plurality of protrusions is preferably 50% or more, more preferably 70% or more, of the surface of the surface of the copper foil in contact with the resin sheet when viewed from the normal direction of the surface in contact with , more preferably 90% or more, and even more preferably 95% or more. It may be 100%, or the surface of the copper foil that is in contact with the resin sheet may be entirely covered with protrusions.

The plurality of protrusions have a particle shape when viewed from the normal direction of the surface of the copper foil in contact with the resin sheet, and the particles preferably include particles having an acute angle, more preferably rhombic. Or it contains approximately diamond-shaped particles.
Of the surface of the surface of the copper foil in contact with the resin sheet, the area occupied by protrusions having the shape of particles with acute angles is preferably 50% or more, more preferably 70% or more, and still more preferably 90%. or more, and more preferably 95% or more. It may be 100%, and the surface of the surface of the copper foil in contact with the resin sheet may be entirely covered with projections having the shape of particles with acute angles.
Of the surface of the surface of the copper foil in contact with the resin sheet, the area occupied by projections having the shape of rhombic or approximately rhombic particles is preferably 50% or more, more preferably 70% or more, and even more preferably. It is 90% or more, and more preferably 95% or more. It may be 100%, and the surface of the surface of the copper foil in contact with the resin sheet may be entirely covered with projections having the shape of rhombus or approximately rhombus particles.

The average aspect ratio of the particles is 1.3 to 5.0, preferably 1.5 to 4.0, more preferably 2.0 to 3.5, still more preferably 2.5. ~3.0.
The average area of the particles is 0.005-0.025 μm ² , preferably 0.005-0.020 μm ² , more preferably 0.010-0.020 μm ² , still more preferably 0 0.010 to 0.015 μm ² .
The shape of the particles, that is, the shape of the projections on the surface of the copper foil that is in contact with the resin sheet, can be observed in an image of the surface obtained by magnifying and photographing using an electron microscope.
In the image, the areas and aspect ratios of 30 particles having the highest area among the particles observed on the outermost surface were measured, and the averaged values thereof were taken as the average aspect ratio of the particles and the average area of the particles, respectively. .
The aspect ratio was obtained by approximating an ellipse having the same area as the area of each particle, and determining the lengths of the major and minor axes.
Examples of specific measurement methods and calculation methods are shown in Examples.

Also, the average minor axis length of the particles is preferably 0.05 to 0.12 μm, more preferably 0.05 to 0.010 μm.
The average minor axis length of the particles is the average length of 30 minor axis lengths of the approximate ellipse used to calculate the aspect ratio.

The shape of the protrusions viewed from the side is preferably a dendritic shape.
The shape of the projection viewed from the side can be observed from the image obtained by photographing the cut surface of the copper foil cut in the thickness direction.
Further, the width of the dendritic shape when the projection is viewed from the side is preferably 0.05 to 0.12 μm, and the height of the projection is preferably 0.05 to 0.30 μm.
The height of the protrusions can be measured from the image obtained by photographing the cut surface of the copper foil cut in the thickness direction.

The average roughness (Ra) of the surface of the copper foil in contact with the resin sheet is preferably 0.10 μm or more, more preferably 0.13 μm or more, and preferably 0.50 μm or less, more preferably It is 0.40 μm or less, more preferably 0.30 μm or less, and even more preferably 0.20 μm or less.
In addition, from the viewpoint of achieving both peel strength and transmission loss reduction, the maximum height roughness (Rz) of the surface of the copper foil in contact with the resin sheet is preferably 1.00 μm or more, more preferably 1.50 μm or more. more preferably 2.00 μm or more, preferably 5.00 μm or less, more preferably 4.00 μm or less, and still more preferably 3.00 μm or less.
Specifically, the average roughness (Ra) and the maximum height roughness (Rz) can be measured by the methods of Examples.

The thickness of the copper foil is preferably 8 to 30 μm, more preferably 9 to 25 μm, still more preferably 10 to 20 μm, from the viewpoints of high density mounting, reliability and transmission loss.

The copper foil is preferably at least one selected from the group consisting of rolled copper foil and electrolytic copper foil, and more preferably electrolytic copper foil from the viewpoint of peel strength and transmission loss reduction.
The surface of the copper foil may have a plurality of projections of a specific particle shape as described above, and roughening treatment may be performed to adjust the projections on the surface to this shape. Examples of the roughening treatment method include formation of roughened particles by plating.
Furthermore, the copper foil may be a surface-treated copper foil that has been subjected to surface treatments such as heat-resistant treatment, antirust treatment, and chemical treatment.
Examples of the heat-resistant treatment and rust-proof treatment include a method of plating using metals having heat resistance and rust-proof properties, respectively.
Examples of the chemical treatment include treatment with a compound having both a reactive group that reacts with the copper foil surface and a reactive group that reacts with the resin sheet surface, in order to increase adhesion to the resin sheet. Examples of such compounds include silane coupling agents. Examples of reactive groups that react with the surface of the resin sheet include epoxy groups, amino groups, vinyl groups, acryl groups, isocyanate groups, mercapto groups, and the like.

The silicon element content of the surface of the copper foil in contact with the resin sheet determined by atomic composition analysis using X-ray photoelectron spectroscopy is preferably 7% or more, more preferably 8% or more, and still more preferably 9%. % or more, and more preferably 10% or more. Although there is no upper limit, it is preferably 20% or less, more preferably 15% or less, and still more preferably 12% or less.
The content of the silicon element can be specifically measured by the method described in Examples.

In this pressing step, the surface of the copper foil is laminated so that the surface having the plurality of protrusions is in contact with the resin sheet. Specifically, if the copper foil has been roughened, it is laminated so that the roughened surface is in contact with the resin sheet.
The copper foil may be laminated on at least one side of the resin sheet, preferably on both sides of the resin sheet.
In this pressing step, pressing may be performed at normal pressure or in a vacuum state, but it is preferable to press in a vacuum state. As a pressing method, a method of setting up and laminating copper foil/SPS resin/copper foil in this order between parallel flat hot plates may be used. , the SPS sheet may be paid out and continuously pressed.
When pressing in a vacuum state, it is preferable to use a vacuum press, and the degree of vacuum is preferably -0.05 MPa or less. Also, the press holding time is preferably 1 to 60 minutes.

This step preferably includes a pressing step of pressing and integrating a copper foil onto at least one surface of the resin sheet at a pressing temperature equal to or lower than the melting point of the styrene-based resin.
The pressing temperature is preferably 240-275°C, more preferably 250-270°C, still more preferably 255-265°C. Within the above range, the obtained laminate has excellent peel strength and a uniform thickness, and furthermore, it is possible to suppress the outflow of the resin during pressing for producing the laminate.

The press pressure may be adjusted according to the press temperature. It is preferable to adjust the press pressure to be low when the press temperature is high and to be high when the press temperature is low.
Specifically, the pressing conditions are preferably 5 MPa or more and 20 MPa or less, more preferably 6 MPa or more and 15 MPa or less, and still more preferably 8 MPa or more and 13 MPa or less.
The laminate produced under the above conditions has excellent peel strength, the resulting laminate has a uniform thickness, and there is little outflow of resin due to melt flow during the pressing process, resulting in excellent productivity. ing.

[Electronic circuit board]
The electronic circuit board of the present invention uses the laminate for an electronic circuit board.
That is, the electronic circuit board, which is the first embodiment of the electronic circuit board of the present invention, has a copper layer on at least one surface of a resin layer containing a styrene-based resin having a syndiotactic structure, and the resin layer of the copper layer has The contact surface has a plurality of projections, the projections have the shape of particles when viewed from the normal direction of the surface of the copper layer contacting the resin layer, and the particles have an average aspect ratio of 1.5. 3 to 5.0, and the average area of the particles is 0.005 to 0.025 μm ² .
Among these, it is preferable to use the resin laminate obtained by the method for producing a laminate for an electronic circuit board.

In the electronic circuit board laminate, the copper layer is difficult to peel off, the peel strength is excellent, and the transmission loss is small. preferable.

The electronic circuit board of the present invention is manufactured by patterning the copper layer of the electronic circuit board laminate. Patterning is preferably performed by etching the copper layer by photolithography.

The thickness of the electronic circuit board of the present invention may be the same as the thickness of the electronic circuit board laminate described above, preferably 10 to 3,000 μm, and is preferably adjusted to an appropriate thickness depending on the application. .
Specifically, in the case of a rigid electronic circuit board, the thickness of the electronic circuit board is preferably 50 to 3,000 μm, more preferably 100 to 2,000 μm, still more preferably 400 to 1 μm. , 600 μm. In the case of a flexible electronic circuit board, the thickness of the electronic circuit board is preferably 150 μm or less, more preferably 130 μm or less, still more preferably 125 μm or less, and preferably 10 μm or more. It is preferably 50 μm or more, and still more preferably 100 μm or more. Within the above range, the strength is excellent, the transmission loss is small, and the size of the product can be reduced.

The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these.

(1) Weight Average Molecular Weight of Resin Measured by a gel permeation chromatography (gel permeation chromatography, abbreviated as “GPC”) measurement method.
Measurement conditions are GPC apparatus manufactured by Tosoh Corporation (HLC-8321GPC/HT), GPC column manufactured by Tosoh Corporation (GMHHR-H(S)HT), using 1,2,4-trichlorobenzene as an eluent, Measured at 145°C.
It was calculated as a polystyrene equivalent molecular weight using a standard polystyrene calibration curve.

(2) Average roughness (Ra) and maximum height roughness (Rz) of copper foil surface (surface of copper layer in contact with resin layer)
It was measured using a confocal laser microscope OPTHLICS H1200 (manufactured by Lasertec).

(3) Projection shape on the surface of the copper foil (the surface of the copper layer in contact with the resin layer) The surface of the copper foil used in each example and comparative example (the surface of the copper layer in contact with the resin layer) was subjected to field emission scanning electron An image magnified 50,000 times was obtained using a microscope SU8200 (manufactured by Hitachi High-Tech Science Co., Ltd.).
From the image, the average aspect ratio of particles and the average area of particles for the projections having the shape of particles observed on the outermost surface were determined as follows.
Among the particles observed on the outermost surface in the image obtained by the electron microscope, at least 30 particles with clear outlines, no secondary agglomeration, and no (or little) overlap were selected. Next, 30 particles with the highest area were selected from the selected 30 or more particles, and binarization was performed by coloring the particles white and the background black. For the binarized image, the area and aspect ratio of each particle were measured using image analysis software (Image-Pro Plus 6.3J, manufactured by Media Cybernetics), and the averaged values were taken as the average aspect ratio of the particles and the average aspect ratio of the particles. was the average area of
The aspect ratio was determined by approximating the particles to an ellipse having the same area as the area of each particle determined by image analysis software, and determining the lengths of the major and minor axes. The elliptical shape obtained by approximation can be calculated from the contour of the particle to be analyzed by the image analysis software.
The average minor axis length of the particles is the average length of 30 minor axis lengths of the approximate ellipse used to calculate the aspect ratio.
FIG. 1 shows an image of the surface of the copper foil in contact with the resin sheet (the surface of the copper layer in contact with the resin layer) used in Examples and Comparative Examples, magnified 5,000 times by the above method.
FIG. 2 shows an image of the surface of the copper foil used in the example in contact with the resin sheet (the surface of the copper layer in contact with the resin layer) magnified 50,000 times by the above method, and an image obtained by the above method. A binarized image is shown.
3 (magnification: 5,000 times) and FIG. (Magnification: 30,000 times). The upper surface of the copper foil is the surface in contact with the resin sheet (the surface of the copper layer in contact with the resin layer). It can be seen that the shape of the protrusions present on the surface of the copper foil used in the examples, viewed from the side, is a dendritic shape.

(4) Atomic composition analysis (X-ray photoelectron spectroscopy (XPS))
Using an XPS device (“VersaProbe II” manufactured by ULVAC-Phi, Inc.), narrow scanning of each element was performed to determine the peak area of each element. Next, Table 1 shows the peak area of each element as the atomic ratio (%) of each element, with the sum of the peak areas of each element whose element symbols and electron orbitals are shown in Table 1 being 100%.

(5) Outflow of Resin The outflow of resin in the laminates of Examples and Comparative Examples was judged as follows. The thickness of the laminate before and after production (before and after pressing) is measured, and when the sheet thickness reduction (resin reduction amount) obtained by the following formula is 10% or more, "resin flows out", production The thickness of the laminate was measured before and after (before and after pressing), and when the sheet thickness reduction (resin reduction amount) obtained by the following formula was less than 10%, it was regarded as "no resin flow". The less the resin flows out, the less the loss of the resin sheet and the better the productivity. In addition, the laminate was cut into 160 mm × 160 mm, and the thickness was measured with a thickness gauge (gauge) every 5 mm in the direction perpendicular to the flow direction of the copper foil, and the difference between the maximum and minimum values was divided by the average value. The average thickness obtained by the method was defined as the "thickness of the laminate".
Sheet thickness reduction (%) = ([average thickness of resin sheet before pressing + thickness of copper foil (both sides: 24 μm) - thickness of laminate after pressing (average thickness)] / [before pressing Average thickness of resin sheet]) × 100

(6) Peel strength The peel strength of the laminate is the strength when peeling off the copper foil from the laminate.
The measurement was performed using a force gauge (trade name: DPRS-2TR, manufactured by Imada Co., Ltd.) as a measuring instrument in accordance with JPCA Electric Circuit Board Standards, 3rd Edition, Section 7 "Performance Test" under the following conditions.
Jig: 90 degree peeling jig (trade name: P90-200N-BB, manufactured by Imada Co., Ltd.)
Tensile speed: 50 mm/min The strength when peeled in the copper foil flow direction (copper foil winding direction) and the strength when peeled in the direction orthogonal to the copper foil flow direction were tested three times each. The average value of all measured values was taken as the peel strength of the laminate.

(7) Transmission loss evaluation (high frequency attenuation factor)
The laminates of Examples and Comparative Examples were etched by a photolithographic method to form microstrip lines (thin lines with a width of 270 μm left on one side of the copper layer, total length of 100 mm).
For the microstrip line, the S21 attenuation rate at a frequency of 65 GHz was measured using a network analyzer N5227 (manufactured by Keysight). Then, using a microstrip line for De-embedding with a total length of 25 mm, De-embedding was performed from the result of the S21 attenuation rate of the microstrip line with a total length of 100 mm, and the S21 attenuation rate (dB) (high frequency attenuation rate) of 75 mm length was measured. The smaller the absolute value of the high-frequency attenuation factor, the smaller the transmission loss.

[Manufacture of laminate for electronic circuit board]
Example 1
(1) Production of SPS sheet SPS (syndiotactic polystyrene, styrene homopolymer, weight average molecular weight 180,000) pellets 80 parts by mass, SEBS (styrene ethylene butylene styrene block copolymer, Septon 8006, manufactured by Kuraray Co., Ltd.) pellets 20 parts by mass, 0.5 parts by mass of a crystal nucleating agent (adekastab NA11, manufactured by ADEKA Co., Ltd.), and 0.2 parts by mass of an antioxidant (Irganox 1010, manufactured by BASF Japan Co., Ltd.) with a twin-screw extruder After melt-kneading at 290° C., pelletization was performed. The pellets obtained were dried at 80° C. for 3 hours.
The dried pellets were melted in a single-screw extruder with a screw diameter of 50 mm, extruded through a T-die under the following conditions, cooled with a cast roll, and wound up to obtain an SPS sheet with a thickness of 50 μm.
The temperature during extrusion was set at 300° C. for all of the extruder heater, polymer line, gear pump, polymer filter and T-die. The T-die was adjusted to have a lip width of 500 mm and a lip opening of 0.7 to 0.9 mm. The cast rolls used oil as cooling medium and the temperature was set at 80°C. The drawing speed of the cast roll was 2.0 m/min.

(2) Production of laminate The SPS sheet obtained in (1) was cut into a square of 100 mm × 100 mm, and two 50 µm-thick SPS sheets were laminated to form a 100 µm-thick resin layer having the following structure. , and the laminate is pressed with a vacuum press under the conditions of a vacuum degree of -0.1 MPa, a press temperature of 260 ° C., a press pressure of 10.0 MPa, and a press time of 3 minutes, and integrated into a laminate. got
The stacking order in the press machine is, from the top, the upper press plate of the vacuum press machine (160 mm × 160 mm), the aluminum plate (160 mm × 160 mm, thickness 1 mm), the electrolytic copper foil (CF-T4X-SV, 180 mm × 180 mm, thickness 12 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd., the surface with projections is used on the SPS sheet side.The projection shape and roughness of the surface with projections are shown in Table 1.), SPS obtained in (1) A resin layer with a thickness of 100 μm made by stacking two sheets (100 mm × 100 mm), electrolytic copper foil (CF-T4X-SV, 180 mm × 180 mm, thickness 12 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd., the surface with protrusions (Used on the SPS sheet side. The projection shape and roughness of the surface with projections are shown in Table 1.), an aluminum plate (160 mm × 160 mm, thickness 1 mm), a lower press plate (160 mm × 160 mm) of a vacuum press machine and bottom. Thus, a laminate having copper layers on both sides was obtained. The thickness (average thickness) of the laminate was 124 μm. Table 1 shows the values of peel strength and transmission loss evaluation. In addition, in each evaluation, the laminate was cut into a shape required for each evaluation and used.

Comparative Examples 1 and 3
(2) A laminate having copper layers on both sides in the same manner as in Example 1, except that the electrolytic copper foil (CF-T4X-SV) used in the production of the laminate was changed to the copper foil shown in Table 1. got The thickness (average thickness) of each laminate was 124 μm. Table 1 shows the values of peel strength and transmission loss evaluation.

Comparative example 2
A laminate having copper layers on both sides was obtained in the same manner as in Comparative Example 1 except that the pressing conditions of Comparative Example 1 were changed to the pressing temperature and pressing pressure shown in Table 1. The thickness (average thickness) of the laminate was 124 μm. Table 1 shows the values of peel strength and transmission loss evaluation.

Comparative example 4
(2) The electrodeposited copper foil (CF-T4X-SV) used in the production of the laminate was replaced with the electrodeposited copper foil (CF-T9DA-SV). ) in the same manner as in Example 1 to obtain a laminate having copper layers on both sides. The thickness (average thickness) of the laminate was 124 μm. Table 1 shows the peel strength values. It should be noted that transmission loss could not be evaluated because the copper layer was easily peeled off and a microstrip line could not be formed satisfactorily.

From the results in Table 1, it can be seen that the laminates for electronic circuit boards of the present invention, which are examples, have high peel strength, so that the copper layer is difficult to peel off, and the transmission loss is small. It can be seen that it is useful for substrates.

Claims (18)

Having a copper layer on at least one surface of a resin layer containing a styrene-based resin having a syndiotactic structure, and having a plurality of protrusions on the surface of the copper layer in contact with the resin layer,
The protrusions have a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer,
A laminate for an electronic circuit board, wherein the average aspect ratio of the particles is 1.3 to 5.0, and the average area of the particles is 0.005 to 0.025 μm ² . 2. The laminate for an electronic circuit board according to claim 1, wherein said particles include particles having an acute angle. The average roughness (Ra) of the surface of the copper layer in contact with the resin layer is 0.10 to 0.50 μm, and the maximum height roughness (Rz) of the surface of the copper layer in contact with the resin layer is 1.00 to The laminate for an electronic circuit board according to claim 1 or 2, which has a thickness of 5.00 µm. The electronic circuit board according to any one of claims 1 to 3, wherein the surface of the copper layer in contact with the resin layer has a silicon element content of 7% or more as determined by atomic composition analysis using X-ray photoelectron spectroscopy. Laminate for The laminate for an electronic circuit board according to any one of claims 1 to 4, wherein the particles include rhombus-shaped or approximately rhombus-shaped particles. 6. The laminate for an electronic circuit board according to claim 1, having copper layers on both sides of said resin layer. The laminate for an electronic circuit board according to any one of claims 1 to 6, wherein the copper foil constituting said copper layer is an electrolytic copper foil. The laminate for an electronic circuit board according to any one of claims 1 to 7, wherein said resin layer further contains a styrene-based elastomer. The laminate for an electronic circuit board according to any one of claims 1 to 8, wherein the styrene resin having a syndiotactic structure has a weight average molecular weight of 100,000 to 300,000. The laminate for an electronic circuit board according to any one of claims 1 to 9, wherein said copper layer has a thickness of 8 to 30 µm. The laminate for an electronic circuit board according to any one of claims 1 to 10, wherein the laminate for an electronic circuit board has a thickness of 10 to 3,000 µm. An electronic circuit board using the laminate for an electronic circuit board according to any one of claims 1 to 11. A pressing step of pressing and integrating a copper foil on at least one surface of a resin sheet containing a styrene resin having a syndiotactic structure at a pressing temperature equal to or lower than the melting point of the styrene resin,
A surface of the copper layer in contact with the resin layer has a plurality of protrusions, the protrusions having a particle shape when viewed from the normal direction of the surface of the copper layer in contact with the resin layer, A method for producing a laminate for an electronic circuit board, wherein the laminate for an electronic circuit board has an average aspect ratio of 1.3 to 5.0 and an average area of the particles of 0.005 to 0.025 μm ² . At least one surface of the copper foil has a plurality of projections, the projections have a particle shape when viewed from the normal direction of the copper foil surface, and the particles have an average aspect ratio of 1.3. 14. The method for producing a laminate for an electronic circuit board according to claim 13, wherein the average area of the particles is 0.005 to 0.025 μm ² . 15. The method for producing a laminate for an electronic circuit board according to claim 13 or 14, wherein the pressing pressure in said pressing step is 5 MPa or more and 20 MPa or less. The method for producing a laminate for an electronic circuit board according to any one of claims 13 to 15, wherein the resin sheet is a non-stretching sheet. The electronic according to any one of claims 13 to 16, which has a step of kneading and casting a styrene resin having a syndiotactic structure and a styrene elastomer before the pressing step to obtain a resin sheet. A method for producing a circuit board laminate. 18. The method for producing a laminate for an electronic circuit board according to claim 17, wherein in the step of obtaining the resin sheet, the styrene-based resin having a syndiotactic structure and the styrene-based elastomer are further kneaded with a nucleating agent.

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