JP2023030680A - Copper-clad laminate and electronic circuit board - Google Patents

Abstract

To provide a copper-clad laminate which reduces surface roughness of a polyimide film and suppresses warpage in a manufacturing process.SOLUTION: A copper-clad laminate has a polyimide film and a copper film, wherein the polyimide film contains a polyimide resin and liquid crystal polymer particles, and in the liquid crystal polymer particles, a major axis, a minor axis and a thickness defined below satisfy the following conditions (A) and (B): (A) an average value of a major axis/minor axis ratio that is a ratio of the major axis to the minor axis of 1.2 or more; and (B) an average value of a degree of flatness that is a ratio of the minor axis to the thickness of 1.2 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to copper-clad laminates. The present invention also relates to a method for manufacturing an electronic circuit board using the copper-clad laminate.

Electronic circuit boards are widely used in products such as mobile communication devices such as mobile phones and smart phones, their base station devices, network-related electronic devices such as servers and routers, and large computers. These products use high-frequency electrical signals in order to transmit and process large amounts of information at high speed, but since high-frequency signals are very susceptible to attenuation, the electronic circuit board should also be designed to minimize transmission loss. Ingenuity is required.

In recent years, flexible copper-clad laminates including a copper layer and a resin layer have been used for electronic circuit boards. In the process of manufacturing flexible copper-clad laminates, heat is applied to copper-clad laminates due to thermosetting, etc., but copper-clad laminates are laminates of copper and resin layers, and both the copper and resin layers are heat sensitive. Due to expansion and contraction, dimensional fluctuation due to these expansion and contraction is a problem. In order to solve such problems, a base metal layer and a copper layer of a specific thickness are laminated on at least one surface of a specific polyimide film without using an adhesive for the purpose of improving the dimensional stability after processing. A two-layer copper-clad laminate having a specific dimensional change in the longitudinal (MD) direction has been proposed (see Patent Document 1). However, there is still a demand for a copper-clad laminate in which warpage during the manufacturing process is suppressed.

JP 2016-87898 A

In addition, when fine particles are added as an additive to the polyimide film that constitutes the copper-clad laminate, it is difficult to control the orientation within the polyimide film, and the surface roughness of the polyimide film may be adversely affected. .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a copper-clad laminate in which the surface roughness of the polyimide film is reduced and warping during the manufacturing process is suppressed. Another object of the present invention is to provide an electronic circuit board using the copper-clad laminate.

As a result of intensive studies to solve the above problems, the present inventors found that in a copper clad laminate comprising a polyimide film and a copper foil, the polyimide film contains specific flat liquid crystal polymer particles as an additive. , the long axis of the flat liquid crystal polymer particles can be easily oriented in the horizontal axis (MD direction) of the polyimide film, the surface roughness of the polyimide film can be reduced, and warping of the copper clad laminate in the manufacturing process can be suppressed. I found out. The present invention has been completed based on such findings.

That is, according to one aspect of the present invention,
A copper-clad laminate comprising a polyimide film and a copper foil,
The polyimide film contains polyimide resin and liquid crystal polymer particles,
The liquid crystal polymer particles have the following conditions (A) and (B):
(A) the average value of the length, which is the ratio of the length and breadth, is 1.2 or more;
(B) the average value of the flatness, which is the ratio of the minor axis to the thickness, is 1.2 or more;
A copper clad laminate is provided that satisfies:

In an aspect of the present invention, the cumulative distribution 50% diameter _D50 in the particle size distribution of the liquid crystal polymer particles is 20 μm or less, and the cumulative distribution 90% diameter _D90 is 2.5 times or less of _D50 . is preferred.

In an aspect of the present invention, the liquid crystal polymer particles contain a structural unit (I) derived from a hydroxycarboxylic acid, a structural unit (II) derived from a diol compound, and a structural unit (III) derived from a dicarboxylic acid. preferably included.

In the aspect of the present invention, the structural unit (I) derived from hydroxycarboxylic acid is preferably a structural unit derived from 6-hydroxy-2-naphthoic acid.

In the aspect of the present invention, the composition ratio of the structural unit (I) is preferably 40 mol % or more and 80 mol % or less with respect to the structural units of the liquid crystal polymer particles as a whole.

In the aspect of this invention, it is preferable that content of the said liquid crystal polymer particle is 10 mass parts or more and 90 mass parts or less with respect to 100 mass parts of said polyimide resins.

In the aspect of this invention, it is preferable that the thickness of the said polyimide film is 5 micrometers or more and 100 micrometers or less.

In the aspect of this invention, it is preferable that surface roughness Ra of the said polyimide film is 1.0 micrometers or less.

According to another aspect of the present invention, there is provided an electronic circuit board comprising the above copper clad laminate, the electronic circuit board having a circuit pattern on the copper foil surface of the copper clad laminate.

According to the copper-clad laminate comprising the polyimide film and the copper foil according to the present invention, the surface roughness of the polyimide film can be reduced, and warping of the copper-clad laminate during the manufacturing process can be suppressed. Further, according to the present invention, it is possible to provide an electronic circuit board using the copper-clad laminate.

1 is a photograph of an ultra-thin section in the cross-sectional direction of a polyimide film obtained using liquid crystal polymer particles A of an example, taken with an optical microscope.

Modes for carrying out the invention

[Copper clad laminate]
A copper-clad laminate according to the present invention comprises a polyimide film and a copper foil. The polyimide film may be laminated on at least one surface of the copper foil, and may be laminated on both surfaces.

(Copper foil)
The copper foil is not particularly limited, and conventionally known copper foils can be used. Examples of copper foil include rolled copper foil and electrolytic copper foil. As the copper foil, one subjected to various surface treatments (roughening, rust prevention, etc.) can also be used. The antirust treatment includes plating using a plating solution containing Ni, Zn, Sn, etc., and mirror surface treatment such as chromate treatment. The thickness of the copper foil is not particularly limited, and is preferably 1 to 100 μm, more preferably 5 to 50 μm, for example.

(polyimide film)
A polyimide film contains a polyimide resin and liquid crystal polymer particles. By including specific flat liquid crystal polymer particles in the polyimide film, the surface roughness of the polyimide film can be reduced and the warping of the copper-clad laminate during the manufacturing process can be suppressed.

Although the present invention is not bound by theory, the mechanism of the effect of suppressing the warping of the copper-clad laminate by containing the specific flat liquid crystal polymer particles in the polyimide film is considered as follows. When the polyimide film contained flat liquid crystal polymer particles instead of spherical liquid crystal polymer particles as an additive, the warpage of the copper-clad laminate was sometimes increased. This is because when the liquid crystal polymer particles in the polyimide film move during heating and curing in the manufacturing process of the copper clad laminate, and the long axes of the flat liquid crystal polymer particles exist randomly, especially in the direction perpendicular to the surface of the polyimide film, It is thought that the shrinkage of the polyimide film increases at the end of curing, and the warpage of the copper-clad laminate also increases. However, by gradually raising the temperature during curing of the polyimide film, the movement of the flat liquid crystal polymer particles is suppressed, and the long axis of the flat liquid crystal polymer particles tends to be oriented along the horizontal axis (MD direction) of the polyimide film. It is considered to be. As a result, by using specific flat liquid crystal polymer particles instead of spherical liquid crystal polymer particles, it is possible to obtain a copper plate laminate having a large effect of suppressing warping in the manufacturing process.

The conditions for film formation of the polyimide film (heating/curing conditions) are not particularly limited. It is preferable that the resin is cured by heating to at least 300° C. at a rate of temperature increase of 5.0° C./min or more.

Although the thickness of the polyimide film is not particularly limited, it is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, and still more preferably 15 μm or more and 50 μm or less. If the thickness of the polyimide film is within the above numerical range, the copper-clad laminate is suitable as a flexible printed wiring board.

The surface roughness Ra of the polyimide film is preferably 1.0 μm or less, more preferably 0.9 μm or less, and even more preferably 0.8 μm or less. If the surface roughness Ra of the polyimide film is within the above numerical range, transmission loss can be suppressed. The surface roughness Ra of the polyimide film can be measured using a commercially available laser microscope.

(liquid crystal polymer particles)
The liquid crystal polymer particles have the major axis, minor axis, and thickness defined below under the following conditions (A) and (B):
(A) the average value of the length, which is the ratio of the length and breadth, is 1.2 or more;
(B) the average value of the flatness, which is the ratio of the minor axis to the thickness, is 1.2 or more;
is characterized by satisfying By adding such flattened liquid crystal polymer particles to the polyimide film, the long axis of the liquid crystal polymer particles becomes easier to align with the horizontal axis (MD direction) of the polyimide film, and while suppressing surface roughness, copper clad lamination It is possible to enhance the effect of suppressing warpage of the plate.

Furthermore, the liquid crystal polymer particles (A) preferably have an average value of length and shortness, which is the ratio of the length and breadth, of 1.5 or more, more preferably 1.7 or more, and the upper limit is particularly Although not limited, it may be, for example, 10 or less, 5 or less, or 3 or less. In addition, (B) the average value of the flatness, which is the ratio of the minor axis to the thickness, is preferably 1.5 or more, more preferably 1.7 or more, and the upper limit is not particularly limited, but for example , may be 10 or less, 5 or less, or 3 or less. When the average value of (A) and (B) satisfies the above numerical range, the effect of suppressing warpage of the copper-clad laminate can be further enhanced while suppressing surface roughness.
The major axis, minor axis and thickness of the liquid crystal polymer particles can be calculated by observing the cross section of the film to which the liquid crystal polymer particles have been added with an optical microscope and analyzing the cross section image. Specifically, at least 100 or more liquid crystal polymer particles were measured for their major diameter, minor diameter and thickness Feret diameter, and the average value was calculated. The major axis, minor axis and thickness of the liquid crystal polymer particles can be adjusted by the synthesis method of the liquid crystal polymer particles, the pulverization method, the sieve conditions after pulverization, and the like.

The particle size distribution of the liquid crystal polymer particles can be measured using a laser diffraction/scattering particle size distribution analyzer. The cumulative distribution 50% diameter D ₅₀ (hereinafter referred to as “D ₅₀ ”) in the particle size distribution represents the value of the particle size at which the cumulative distribution from the small particle size side is 50%, and the cumulative distribution 90% diameter D ₉₀ (hereinafter referred to as “D ₉₀ ”) represents the value of the particle size at which the cumulative distribution from the small particle size side is 90%.
The liquid crystal polymer particles preferably have a _D50 of 20 μm or less in the particle size distribution and a _D90 of 2.5 times or less of the _D50 .
_D50 is preferably 0.1 μm or more, more preferably 1 μm or more, still more preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 12 μm. or less, more preferably 10 μm or less, still more preferably 6 μm or less.
_D90 is preferably 2.2 times or less, more preferably 2.0 times or less, and even more preferably 1.8 times or less _{of D50} .
By adjusting the values of _D50 and _D90 , which are parameters in the particle size distribution of the liquid crystal polymer particles, within the above range, the liquid crystal polymer particles can be added even if the polyimide film is a thin film, resulting in a thin film. warpage of the copper-clad laminate can be suppressed. The values of _D50 and _D90 can be adjusted by the pulverization method of the liquid crystal polymer particles, the sieve conditions after pulverization, and the like.

The liquid crystallinity of the liquid crystal polymer particles is measured by using a polarizing microscope (trade name: BH-2) manufactured by Olympus Co., Ltd. equipped with a microscope hot stage (trade name: FP82HT) manufactured by Mettler Co., Ltd., and heating the liquid crystal polymer particles with a microscope. It can be confirmed by observing the presence or absence of optical anisotropy after heating and melting on a stage.

The melting point of the liquid crystal polymer particles is preferably 270° C. or higher, and the lower limit is preferably 280° C. or higher, more preferably 290° C. or higher, and still more preferably 300° C. or higher. is 370° C. or lower, preferably 360° C. or lower, and more preferably 350° C. or lower. By setting the melting point of the liquid crystal polymer within the above numerical range, the heat resistance of the polyimide film obtained by adding the liquid crystal polymer particles can be improved. In this specification, the melting point of the liquid crystal polymer particles conforms to the test methods of ISO11357 and ASTM D3418, and is measured using a differential scanning calorimeter (DSC) manufactured by Hitachi High-Tech Science Co., Ltd. be able to.

The content of the liquid crystal polymer particles is preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, and still more preferably 30 parts by mass with respect to 100 parts by mass of the polyimide resin. It is more than 70 mass parts or less. If the content of the liquid crystal polymer particles is within the above numerical range, the effect of suppressing warping of the copper-clad laminate can be enhanced.

(liquid crystal polymer)
The composition of the liquid crystal polymer, which is the raw material of the liquid crystal polymer particles, is not particularly limited. and a structural unit (III) derived from an aromatic dicarboxylic acid. Furthermore, the liquid crystal polymer may further contain a structural unit (IV) as a structural unit other than the structural units (I) to (III). Each structural unit contained in the liquid crystal polymer will be described below.

(Structural unit (I) derived from hydroxycarboxylic acid)
The unit (I) constituting the liquid crystal polymer is a structural unit derived from a hydroxycarboxylic acid, preferably a structural unit derived from an aromatic hydroxycarboxylic acid represented by the following formula (I). In addition, as for structural unit (I), only 1 type may be contained and 2 or more types may be contained.

上記式中Ａｒ^１は、所望により置換基を有するフェニル基、ビフェニル基、４，４’－イソプロピリデンジフェニル基、ナフチル基、アントリル基およびフェナントリル基からなる群より選択される。これらの中でもナフチル基が好ましい。置換基としては、水素、アルキル基、アルコキシ基、ならびにフッ素等が挙げられる。アルキル基が有する炭素数は、１～１０であることが好ましく、１～５であることがより好ましい。また、直鎖状のアルキル基であっても、分岐鎖状のアルキル基であってもよい。アルコキシ基が有する炭素数は、１～１０であることが好ましく、１～５であることがより好ましい。

Ar ¹ in the above formula is selected from the group consisting of optionally substituted phenyl, biphenyl, 4,4'-isopropylidenediphenyl, naphthyl, anthryl and phenanthryl groups. Among these, a naphthyl group is preferred. Substituents include hydrogen, alkyl groups, alkoxy groups, fluorine, and the like. The number of carbon atoms in the alkyl group is preferably 1-10, more preferably 1-5. Moreover, it may be a linear alkyl group or a branched alkyl group. The number of carbon atoms in the alkoxy group is preferably 1-10, more preferably 1-5.

Examples of monomers that give the structural unit represented by formula (I) include 6-hydroxy-2-naphthoic acid (HNA, formula (1) below), and acylates, ester derivatives, and acid halides thereof. be done.

The lower limit of the composition ratio (mol%) of the structural unit (I) to the structural units of the entire liquid crystal polymer is preferably 40 mol% or more, more preferably 45 mol% or more, and still more preferably 50 mol%. is more preferably 55 mol% or more, and the upper limit is preferably 80 mol% or less, more preferably 75 mol% or less, still more preferably 70 mol% or less, and furthermore More preferably, it is 65 mol % or less. When two or more kinds of structural units (I) are contained, the total molar ratio thereof should be within the range of the above compositional ratio.

(Structural Unit (II) Derived from Diol Compound)
The unit (II) constituting the liquid crystal polymer is a structural unit derived from a diol compound, preferably a structural unit derived from an aromatic diol compound represented by the following formula (II). In addition, as for structural unit (II), only 1 type may be contained and 2 or more types may be contained.

上記式中Ａｒ^２は、所望により置換基を有するフェニル基、ビフェニル基、４，４’－イソプロピリデンジフェニル基、ナフチル基、アントリル基およびフェナントリル基からなる群より選択される。これらの中でもフェニル基およびビフェニル基が好ましい。置換基としては、水素、アルキル基、アルコキシ基、ならびにフッ素等が挙げられる。アルキル基が有する炭素数は、１～１０であることが好ましく、１～５であることがより好ましい。また、直鎖状のアルキル基であっても、分岐鎖状のアルキル基であってもよい。アルコキシ基が有する炭素数は、１～１０であることが好ましく、１～５であることがより好ましい。

Ar ² in the above formula is selected from the group consisting of optionally substituted phenyl, biphenyl, 4,4'-isopropylidenediphenyl, naphthyl, anthryl and phenanthryl groups. Among these, a phenyl group and a biphenyl group are preferred. Substituents include hydrogen, alkyl groups, alkoxy groups, fluorine, and the like. The number of carbon atoms in the alkyl group is preferably 1-10, more preferably 1-5. Moreover, it may be a linear alkyl group or a branched alkyl group. The number of carbon atoms in the alkoxy group is preferably 1-10, more preferably 1-5.

Monomers that give the structural unit (II) include, for example, 4,4-dihydroxybiphenyl (BP, formula (2) below), hydroquinone (HQ, formula (3) below), methylhydroquinone (MeHQ, formula (4) below. ), 4,4′-isopropylidenediphenol (BisPA, formula (5) below), and acylated products, ester derivatives, and acid halides thereof. Among these, 4,4-dihydroxybiphenyl (BP) and their acylated products, ester derivatives and acid halides are preferably used.

The lower limit of the composition ratio (mol%) of the structural unit (II) to the structural units of the entire liquid crystal polymer is preferably 10 mol% or more, more preferably 12.5 mol% or more, and still more preferably 15 mol%. mol% or more, and more preferably 17.5 mol% or more, and the upper limit is preferably 30 mol% or less, more preferably 27.5 mol% or less, and still more preferably 25 mol%. % or less, and more preferably 22.5 mol % or less. When two or more kinds of structural units (II) are contained, the total molar ratio thereof should be within the range of the above compositional ratio.

(Structural Unit (III) Derived from Aromatic Dicarboxylic Acid)
The unit (III) constituting the liquid crystal polymer is a structural unit derived from a dicarboxylic acid, preferably a structural unit derived from an aromatic dicarboxylic acid represented by the following formula (III). In addition, as for structural unit (III), only 1 type may be contained and 2 or more types may be contained.

上記式中Ａｒ^３は、所望により置換基を有するフェニル基、ビフェニル基、４，４’－イソプロピリデンジフェニル基、ナフチル基、アントリル基およびフェナントリル基からなる群より選択される。これらの中でもフェニル基およびナフチル基が好ましい。置換基としては、水素、アルキル基、アルコキシ基ならびにフッ素等が挙げられる。アルキル基が有する炭素数は、１～１０であることが好ましく、１～５であることがより好ましい。また、直鎖状のアルキル基であっても、分岐鎖状のアルキル基であってもよい。アルコキシ基が有する炭素数は、１～１０であることが好ましく、１～５であることがより好ましい。

Ar ³ in the above formula is selected from the group consisting of optionally substituted phenyl, biphenyl, 4,4'-isopropylidenediphenyl, naphthyl, anthryl and phenanthryl groups. Among these, a phenyl group and a naphthyl group are preferred. Substituents include hydrogen, alkyl groups, alkoxy groups, fluorine, and the like. The number of carbon atoms in the alkyl group is preferably 1-10, more preferably 1-5. Moreover, it may be a linear alkyl group or a branched alkyl group. The number of carbon atoms in the alkoxy group is preferably 1-10, more preferably 1-5.

Monomers that give the structural unit (III) include terephthalic acid (TPA, formula (6) below), isophthalic acid (IPA, formula (7) below), and 2,6-naphthalenedicarboxylic acid (NADA, formula (8) below. ), and their acylated products, ester derivatives, acid halides and the like.

The lower limit of the composition ratio (mol%) of the structural unit (III) to the structural units of the entire liquid crystal polymer is preferably 10 mol% or more, more preferably 12.5 mol% or more, and still more preferably 15 mol%. mol% or more, and more preferably 17.5 mol% or more, and the upper limit is preferably 30 mol% or less, more preferably 27.5 mol% or less, and still more preferably 25 mol%. % or less, and more preferably 22.5 mol % or less. When two or more kinds of structural units (II) are contained, the total molar ratio thereof should be within the range of the above compositional ratio. The composition ratio of the structural unit (II) and the compositional ratio of the structural unit (III) are substantially equivalent ((structural unit (II)≈structural unit (III)).

(Structural Unit (IV) Derived from Another Monomer)
The liquid crystal polymer may further contain structural units other than the above structural units (I) to (III). Structural unit (IV) is derived from a monomer other than the monomer that gives the structural units (I) to (III), and is polymerizable with the monomer that gives the structural units (I) to (III). It is not particularly limited as long as it is derived from a polymerizable monomer. Polymerizable groups include, for example, hydroxy groups, carboxyl groups, amine groups, and amide groups. The monomer that gives the structural unit (IV) has one or more, preferably two or more of these polymerizable groups. When two or more polymerizable groups are included, those polymerizable groups may be the same or different. Only one kind of structural unit (IV) may be contained, or two or more kinds thereof may be contained.

が挙げられる。 Examples of the structural unit (IV) include the following structural unit (IV-1):

is mentioned.

Monomers that give the structural unit (IV-1) include acetaminophenone (AAP, the following formula (9)), p-aminophenol, 4′-acetoxyacetanilide, and acylates, ester derivatives, and acid halides thereof. is mentioned.

が挙げられる。 Further, as the structural unit (IV), for example, the following structural unit (IV-2):

is mentioned.

Examples of monomers that give the structural unit (V-2) include 1,4-cyclohexanedicarboxylic acid (CHDA, formula (10) below), acylated products, ester derivatives, and acid halides thereof.

The composition ratio (mol %) of the structural unit (IV) to the structural units of the liquid crystal polymer as a whole can be appropriately set according to the composition ratio of the structural units (I) to (III). Specifically, if the composition ratio of each structural unit is appropriately set so that the monomer ratio (molar ratio) between the carboxyl group and the hydroxy group and/or amine group in the monomer charge is in the range of about 1:1. good.

Preferred formulations of the liquid crystal polymer include the following.
45 mol% ≤ 6-hydroxy-2-naphthoic acid-derived structural unit (I) ≤ 75 mol%
12 mol% ≤ structural unit (II) derived from aromatic diol compound ≤ 27.5 mol%
3 mol% ≤ structural unit (IIIA) derived from terephthalic acid ≤ 25 mol%
2 mol% ≤ 2,6-naphthalene dicarboxylic acid-derived structural unit (IIIB) ≤ 9 mol%
is.
Furthermore, more preferred formulations of the liquid crystal polymer include the following.
50 mol% ≦ 6-hydroxy-2-naphthoic acid-derived structural unit (I) ≦ 70 mol%
15 mol% ≤ structural unit (II) derived from aromatic diol compound ≤ 25 mol%
9 mol% ≤ structural unit (IIIA) derived from terephthalic acid ≤ 22 mol%
Structural unit (IIIB) derived from 3 mol% ≤ 2,6-naphthalenedicarboxylic acid ≤ 6 mol%
is.
Further, even more preferred formulations of liquid crystal polymers include the following.
54 mol% ≤ 66 mol% structural unit (I) derived from 6-hydroxy-2-naphthoic acid
17 mol% ≤ structural unit (II) derived from aromatic diol compound ≤ 23 mol%
11 mol% ≤ structural unit (IIIA) derived from terephthalic acid ≤ 20 mol%
Structural unit (IIIB) derived from 3 mol% ≤ 2,6-naphthalenedicarboxylic acid ≤ 6 mol%
is.
If each structural unit is within the above range with respect to the structural units of the liquid crystal polymer as a whole, liquid crystal polymer particles having a low dielectric loss tangent can be obtained.

(Method for producing liquid crystal polymer)
The liquid crystal polymer can be produced by polymerizing monomers that optionally give structural units (I) to (III) and optionally monomers that give structural unit (IV) by a conventionally known method. In one embodiment, the liquid crystal polymer according to the present invention can also be produced by two-step polymerization in which a prepolymer is prepared by melt polymerization and then polymerized in solid state.

In melt polymerization, from the viewpoint of efficiently obtaining a liquid crystal polymer, the monomers that optionally provide the structural units (I) to (III) and the monomers that optionally provide the structural unit (IV) are combined in a predetermined blend to 100 mol. %, it is preferable to conduct the reaction under reflux of acetic acid in the presence of 1.05 to 1.15 molar equivalents of acetic anhydride with respect to all the hydroxyl groups possessed by the monomer.

When the polymerization reaction is carried out in two steps of melt polymerization and subsequent solid phase polymerization, the prepolymer obtained by the melt polymerization is cooled and solidified, pulverized into powder or flakes, and then solid phase polymerized by a known solid phase polymerization method. For example, a method of heat-treating the prepolymer resin in an inert atmosphere such as nitrogen or under vacuum at a temperature range of 200 to 350° C. for 1 to 30 hours is preferably selected. The solid phase polymerization may be carried out while stirring, or may be carried out in a still state without stirring.

A catalyst may or may not be used in the polymerization reaction. As the catalyst to be used, conventionally known catalysts for polymerization of liquid crystal polymers can be used, such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide. Examples include metal salt catalysts, nitrogen-containing heterocyclic compounds such as N-methylimidazole, organic compound catalysts, and the like. The amount of the catalyst used is not particularly limited, but it is preferably 0.0001 to 0.1 parts by weight with respect to 100 parts by weight of the total amount of the monomers.

A polymerization reactor for melt polymerization is not particularly limited, but a reactor generally used for reactions of high-viscosity fluids is preferably used. Examples of these reactors include, for example, an anchor type, multi-stage type, spiral band type, spiral shaft type, etc., or a stirred tank type polymerization reactor having a stirring device with stirring blades of various shapes modified from these, or , kneaders, roll mills, Banbury mixers, and the like, which are generally used for kneading resins.

[Manufacturing method of copper-clad laminate]
A method for manufacturing a copper-clad laminate comprising a polyimide film and a copper foil according to the present invention includes a coating step and a film forming step. Each step will be described in detail below.

(Coating process)
The coating step is a step of coating one side of the copper foil with a composition containing liquid crystal polymer particles and polyamic acid. A method for applying the composition onto the copper foil is not particularly limited, and a conventionally known method can be used. Examples of the coating method include coating with a die or knife coater. The liquid crystal polymer particles are as described above.

(Filming process)
The film-forming step is a step of curing the composition by heating the copper foil coated with the composition in two stages to form a polyimide film. In the first stage of heating, from normal temperature to 180 to 220° C., 1.5° C./min or less, preferably 0.1° C./min or more and 1.4° C./min or less, more preferably 0.5° C./min or more. Heat at a heating rate of 1.2° C./min or less. Subsequently, in the second stage heating, from 180 to 220 ° C. to at least 300 ° C., 5.0 ° C./min or more, preferably 6.0 ° C./min or more and 15 ° C./min or less, more preferably 7.0 C./min or more and 12.degree. C./min or less. The final temperature reached may be 300°C or higher, preferably 320 to 400°C, more preferably 330 to 370°C. Furthermore, after the temperature is raised to the target temperature, it may be held for preferably 1 minute or more, more preferably 5 minutes or more and 5 hours or less, and more preferably 30 minutes or more and 3 hours or less. By heating under these conditions, it is possible to suppress warping of the copper-clad laminate while progressing curing.

(electronic circuit board)
The electronic circuit board has a circuit pattern on the copper foil surface of the copper-clad laminate according to the present invention. Patterning methods for forming a circuit pattern on the copper foil surface of a copper-clad laminate include, for example, a semi-additive method and a subtractive method. The semi-additive method includes a method of patterning the copper foil surface of the copper-clad laminate with a resist film, performing electrolytic copper plating, removing the resist, and etching with an alkaline solution. Moreover, the thickness of the circuit pattern layer in the printed wiring board is not particularly limited.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples.

<Synthesis of liquid crystal polymer>
6-hydroxy-2-naphthoic acid (HNA) 60 mol%, 4,4-dihydroxybiphenyl (BP) 20 mol%, terephthalic acid (TPA) 15.5 mol%, 2,6 -Add 4.5 mol% of naphthalene dicarboxylic acid (NADA), charge potassium acetate and magnesium acetate as catalysts, depressurize the polymerization vessel-nitrogen injection three times to perform nitrogen substitution, then acetic anhydride (for hydroxyl groups 1.08 molar equivalents) was further added, the temperature was raised to 150° C., and the acetylation reaction was carried out under reflux for 2 hours.

After the acetylation was completed, the polymerization vessel in which acetic acid was distilled was heated at a rate of 0.5° C./min, and when the melt temperature in the vessel reached 310° C., the polymer was withdrawn and cooled to solidify. The resulting polymer was pulverized to a size that passed through a sieve with an opening of 2.0 mm to obtain a prepolymer.

Next, the prepolymer obtained above is heated from room temperature to 310°C over 14 hours with a heater in an oven manufactured by Yamato Scientific Co., Ltd., and then held at 310°C for 1 hour to form a solid phase. Polymerization was carried out. After that, the heat was spontaneously released at room temperature to obtain a liquid crystal polymer. Using an Olympus polarizing microscope (trade name: BH-2) equipped with a Mettler microscope hot stage (trade name: FP82HT), the liquid crystal polymer is heated and melted on the microscope heating stage to obtain an optical difference. It was confirmed from the presence or absence of tropism that it exhibits liquid crystallinity.

<Production of liquid crystal polymer particles>
(Production example A)
The powder of the liquid crystal polymer synthesized above was pulverized at a pressure of 0.65 MPa and a resin feed rate of 5 kg/5 using a device that combined a SPK-12 jet mill manufactured by Nippon Pneumatic Industry Co., Ltd. with a DSF-10 classifier manufactured by the same company. Pulverization was continuously performed for 60 minutes under the conditions of h to obtain flat liquid crystal polymer particles A.

(Manufacturing example B)
For 100 parts by mass of the liquid crystal polymer powder synthesized above, a twin-screw extruder (Japan Steel Works, Ltd.) was added to 900 parts by mass of polystyrene (manufactured by PS Japan Co., Ltd., "SGP10") as a thermoplastic resin. (manufactured by TEX-α)), the mixture was melt-kneaded at a cylinder temperature of 340° C. and a screw rotation speed of 125 rpm to obtain a composition. The composition was extruded from a circular nozzle at a resin extrusion rate of 10 kg/hr to obtain extruded strands, cut and pelletized.
Subsequently, 100 g of the resulting composition pellets were put into 900 g of toluene heated to 40° C. in a 2 L flask and stirred for 30 minutes to dissolve polystyrene in toluene. The insoluble components were recovered by suction filtration, and the insoluble components were additionally washed three times with 90 g of toluene at 40°C. After the additional washing, the insoluble components were recovered by filtration through a 1 μm filter and dried to obtain liquid crystal polymer particles B.

<Evaluation of liquid crystal polymer particles>
(Measuring length and flatness of particles)
A polyamic acid varnish was prepared in a glass vessel equipped with a stirrer, and the liquid crystal polymer particles synthesized above dispersed in a dispersion medium were added and stirred to obtain a suspension. At that time, the concentration of the liquid crystal polymer particles was adjusted to 10 to 20 parts by mass with respect to 100 parts by mass of polyamic acid. The resulting suspension was applied to a glass substrate, dried and cured at 300° C. to produce a film with a thickness of about 25 μm. The obtained film was cut in the cross-sectional direction using a cryomicrotome to prepare an ultra-thin section with a thickness of 2.5 μm. The resulting ultra-thin section was observed with an optical microscope (manufactured by Keyence Corporation, model number: VHX6000) at a magnification of 1000 times, and at least 100 particles were subjected to image processing in two directions (minor axis direction / vertical direction). The Feret diameter was measured, and the average value of the ratio (minor diameter/thickness) was taken as the flatness of the particles. FIG. 1 is a photograph taken with an optical microscope of an ultra-thin section of the film obtained using the liquid crystal polymer particles A in the cross-sectional direction.

Next, a cryomicrotome is used to cut the film in the horizontal direction to prepare an ultra-thin section with a thickness of 1 μm. The resulting ultra-thin section was observed with an optical microscope, and at least 100 liquid crystal polymer particles were subjected to image processing to measure Feret diameters in two directions (major axis direction and lateral axis direction), and the ratio (major axis / minor axis ) was taken as the length of the particles.

(Measurement of particle size distribution)
The particle size distribution of each of the liquid crystal polymer particles synthesized above was measured with a laser diffraction/scattering method particle size distribution analyzer (LS 13 320 dry system, manufactured by Beckman Coulter, equipped with a Tornado dry powder module). _D50 and _D90 , which are parameters indicating the particle size distribution, were obtained as calculation results from the measured data. Table 1 shows the results.

(Measurement of melting point)
The melting point of each liquid crystal polymer particle synthesized above was measured by a differential scanning calorimeter (DSC) manufactured by Hitachi High-Tech Science Co., Ltd. in accordance with the test methods of ISO11357 and ASTM D3418. At this time, after the temperature was raised from room temperature to 360 to 380°C at a temperature elevation rate of 10°C/min to completely melt the polymer, the temperature was lowered to 30°C at a rate of 10°C/min, and further at a rate of 10°C/min. The apex of the endothermic peak obtained when the temperature was raised to 380° C. was taken as the melting point (Tm ₂ ). Table 1 shows the measurement results.

<Production of copper-clad laminate>
(Example 1)
60% m-toluidine (tol), 40% 4,4'-diaminodiphenyl ether (DDE), and N,N-dimethylacetamide to a given concentration were placed in a glass vessel equipped with a stirrer, and a nitrogen atmosphere was added. Stir at 25° C. to obtain a solution. 100% pyromellitic dianhydride (PMDA) was added in several portions to this solution and stirred at 25° C. under a nitrogen atmosphere to obtain a polyamic acid varnish. To the resulting polyamic acid varnish was added 50 parts by mass of liquid crystal polymer particles A per 100 parts by mass of polyamic acid in the varnish to obtain a composition.

After applying the obtained composition on a copper foil (thickness: 18 μm), it was heated from 30° C. to 200° C. at a temperature increase rate of 1.0° C./min, followed by 8.0° C./min. It was heated up to 350° C. at a heating rate and held at 350° C. for 1 hour. The composition was cured by heating to form a polyimide film (thickness: 40 μm) on the copper foil to produce a copper-clad laminate A.

Similarly, after applying the obtained composition on a copper foil, it was heated from 30 ° C. to 200 ° C. at a temperature increase rate of 2.0 ° C./min. A control copper-clad laminate (control product) was produced in the same manner except that the material was heated to 350° C. at a temperature rate and held at 350° C. for 1 hour.

(Comparative example 1)
A copper clad laminate B was produced in the same manner as in Example 1, except that the liquid crystal polymer particles B were used instead of the liquid crystal polymer particles A.

Similarly, after applying the obtained composition on a copper foil, it was heated from 30 ° C. to 200 ° C. at a temperature increase rate of 2.0 ° C./min. A control copper-clad laminate (control product) was produced in the same manner except that the material was heated to 350° C. at a temperature rate and held at 350° C. for 1 hour.

(Comparative example 2)
A copper-clad laminate C was produced in the same manner as in Example 1, except that silica particles (silica fine particles SFP-130MC manufactured by Denka Co., Ltd.) were used instead of the liquid crystal polymer particles A.

Similarly, after applying the obtained composition on a copper foil, it was heated from 30 ° C. to 200 ° C. at a temperature increase rate of 2.0 ° C./min. A control copper-clad laminate (control product) was produced in the same manner except that the material was heated to 350° C. at a temperature rate and held at 350° C. for 1 hour.

<Evaluation of copper clad laminate>
(Measurement of orientation)
The polyimide film produced above was cut in the cross-sectional direction using a cryomicrotome to prepare an ultra-thin slice with a thickness of 2.5 μm. The obtained ultrathin section was observed with an optical microscope (manufactured by Keyence Corporation, model number: VHX6000) at an observation magnification of 1000 times, and image processing was performed for at least 100 particles to determine the Feret diameter in the longitudinal direction and the vertical direction. Feret diameter was measured. The ratio (a/b) of the average value a of Feret diameters in the longitudinal direction to the average value b of Feret diameters in the vertical direction was calculated, and the results are shown in Table 2.

(Measurement of surface roughness)
Each film produced above was cut into strips of 3 mm×80 mm to obtain film samples. Subsequently, the surface roughness of the film sample was measured using an Olympus OLS5000 laser microscope. Table 2 shows the measurement results.

(Measurement of warpage reduction amount)
Each copper-clad laminate produced above was cut into a size of 100 mm×100 mm to obtain a sample. After standing on a stand (horizontal surface) with the copper foil of the sample facing downward and the polyimide film facing upward, the width of rise at the four corners was measured, and the average value was taken as the warpage value. Similarly, the warpage value was measured for a copper-clad laminate (control product) as a control. The amount of warpage reduction (mm) is calculated using the following formula:
Warpage reduction amount=warpage value of control product−warpage value of copper-clad laminate, and the results are shown in Table 2.

Claims (9)

A copper-clad laminate comprising a polyimide film and a copper foil,
The polyimide film contains polyimide resin and liquid crystal polymer particles,
The liquid crystal polymer particles have the following conditions (A) and (B):
(A) the average value of the length, which is the ratio of the length and breadth, is 1.2 or more;
(B) the average value of the flatness, which is the ratio of the minor axis to the thickness, is 1.2 or more;
A copper clad laminate that satisfies The copper according to claim 1, wherein the cumulative distribution 50% diameter _D50 in the particle size distribution of the liquid crystal polymer particles is 20 µm or less, and the cumulative distribution 90% diameter _D90 is 2.5 times or less of _D50 . tension laminate. Claim 1 or 2, wherein the liquid crystal polymer particles contain a structural unit (I) derived from a hydroxycarboxylic acid, a structural unit (II) derived from a diol compound, and a structural unit (III) derived from a dicarboxylic acid. The copper-clad laminate according to . 4. The copper-clad laminate according to claim 1, wherein the structural unit (I) derived from hydroxycarboxylic acid is a structural unit derived from 6-hydroxy-2-naphthoic acid. The copper clad laminate according to any one of claims 1 to 4, wherein the composition ratio of the structural unit (I) is 40 mol% or more and 80 mol% or less with respect to the structural units of the entire liquid crystal polymer particle. board. The copper clad laminate according to any one of claims 1 to 5, wherein the content of the liquid crystal polymer particles is 10 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the polyimide resin. The copper-clad laminate according to any one of claims 1 to 6, wherein the polyimide film has a thickness of 5 µm or more and 100 µm or less. The copper-clad laminate according to any one of claims 1 to 7, wherein the polyimide film has a surface roughness Ra of 1.0 µm or less. An electronic circuit board comprising the copper clad laminate according to any one of claims 1 to 8,
An electronic circuit board having a circuit pattern on the copper foil surface of the copper-clad laminate.

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