JP7441029B2 - Resin film and metal clad laminate - Google Patents

Description

The present invention relates to a resin composition containing spherical alumina particles as a thermally conductive filler, a resin film using the same, and a metal-clad laminate.

In recent years, there has been an increasing demand for smaller and lighter electronic devices, such as mobile phones, LED lighting equipment, and parts related to automobile engines. Along with this trend, flexible circuit boards, which are advantageous for making devices smaller and lighter, have come to be widely used in the electronic technology field. Among these, flexible circuit boards having polyimide as an insulating layer are widely used because of their good heat resistance and chemical resistance. On the other hand, with the recent miniaturization of electronic devices, the degree of circuit integration has increased, and in order to speed up information processing and improve reliability, technology is being developed to improve the heat dissipation characteristics of the heat generated within the devices. is attracting attention.

In order to improve the heat dissipation characteristics of the heat generated within an electronic device, it is considered effective to increase the thermal conductivity of the electronic device. Therefore, a technique of incorporating a thermally conductive filler into an insulating resin layer constituting a wiring board or the like is being considered. More specifically, studies are being conducted to disperse and blend fillers with high thermal conductivity such as aluminum oxide, boron nitride, aluminum nitride, and silicon nitride into the resin forming the insulating resin layer. Techniques have been proposed in which a thermally conductive filler is blended into polyimide having high heat resistance (for example, Patent Documents 1 to 4).

Patent No. 5235211 Patent No. 5442491 Patent No. 5665449 Patent No. 5297740

When the filling rate of the thermally conductive filler is increased, there is a problem that the viscosity of the polyimide solution and its precursor polyamic acid solution tends to increase, and many voids are generated in the insulating resin layer during the formation process of the insulating resin layer. Therefore, there was a problem in that the voltage resistance was reduced.

An object of the present invention is to provide a resin composition in which the viscosity can be adjusted even when filled with a large amount of spherical filler, and voids are less likely to occur in polyimide.

The resin film of the present invention is a resin film having a single or multiple polyimide layers, at least one of the polyimide layers being a thermally conductive polyimide layer,
The thermally conductive polyimide layer is a cured product of a resin composition comprising polyamic acid or polyimide, and spherical alumina particles, and the content of the spherical alumina particles is such that the content of the spherical alumina particles and the polyamic acid or the It is within the range of 5 to 80% by volume based on the total amount with polyimide.

In the resin film of the present invention, 90% by weight or more of the spherical alumina particles meet the following conditions a to c;
a) The average particle diameter _D50 at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement by laser diffraction scattering method is 50% is within the range of 0.5 to 5 μm;
b) Circularity is 0.9 or more;
c) True specific gravity is within the range of 3.4 to 3.8;
It satisfies the following.

In the resin film of the present invention, the spherical alumina particles further meet the following conditions d and e;
d) The particle diameter _D90 at which the cumulative value is 90% is within the range of 2.0 to 6.0 μm;
e) The particle diameter _D10 at which the cumulative value is 10% is within the range of 0.3 to 1.8 μm;
It may be one that satisfies the following.

In the resin film of the present invention, the maximum particle diameter of the spherical alumina particles may be 15 μm or less.

In the resin film of the present invention, the thickness of the thermally conductive polyimide layer is within the range of 2 to 100 μm.

In the resin film of the present invention, the maximum particle diameter of the spherical alumina particles may be within the range of 0.05 to 0.7 with respect to the thickness of the thermally conductive polyimide layer.

The metal-clad laminate of the present invention is a metal-clad laminate comprising an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, wherein the insulating resin layer is formed of the resin film described above. It consists of

In the resin composition of the present invention, by using spherical alumina particles of which 90% by weight or more satisfy conditions a to c, the increase in viscosity of the resin composition is suppressed, and the dispersibility of the spherical alumina particles is suppressed. Excellent. Furthermore, even when a large amount of spherical alumina particles are contained, the generation of voids in the insulating resin layer is suppressed or reduced, so that it is possible to provide excellent voltage resistance.

Embodiments of the present invention will be described below.

[Resin composition]
A resin composition according to one embodiment of the present invention is a resin composition containing polyamic acid or polyimide and spherical alumina particles that are a thermally conductive filler. The resin composition may be a varnish (resin solution) containing polyamic acid, or a polyimide solution containing solvent-soluble polyimide.

<Polyamic acid or polyimide>
Polyimide is generally represented by the following general formula (1). Such a polyimide can be produced by a known method in which the diamine component and the acid dianhydride component are used in substantially equimolar amounts and polymerized in an organic polar solvent. In this case, the molar ratio of the acid dianhydride component to the diamine component may be adjusted in order to keep the viscosity within a desired range, and the range is, for example, within a molar ratio of 0.980 to 1.03. It is preferable to do so.

Here, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and Ar ₂ is a divalent organic group having one or more aromatic rings. Ar ₁ can be said to be a residue of an acid dianhydride, and Ar ₂ can be said to be a residue of a diamine. Further, n represents the number of repeats of the structural unit of general formula (1), and is a number of 200 or more, preferably 300 to 1000.

As the acid dianhydride, for example, an aromatic tetracarboxylic dianhydride represented by O(OC) ₂ -Ar ₁ -(CO) ₂ O is preferable, and the aromatic acid anhydride residue shown below is represented by Ar _1. An example of what to give is given.

Acid dianhydrides can be used alone or in combination of two or more. Among these, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 3,3',4,4'-benzophenonetetracarboxylic dianhydride anhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), and 4,4'-oxydiphthalic dianhydride (ODPA). is preferred.

As the diamine, for example, an aromatic diamine represented by H ₂ N--Ar ₂ --NH ₂ is preferable, and an aromatic diamine that gives the following aromatic diamine residue as Ar ₂ is exemplified.

Among these diamines, diaminodiphenyl ether (DAPE), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), paraphenylenediamine (p-PDA), 1,3-bis(4-amino phenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 2,2-bis[4 Suitable examples include -(4-aminophenoxy)phenyl]propane (BAPP) and 2,2-bis(trifluoromethyl)benzidine (TFMB).

Polyimide can be produced by reacting an acid dianhydride and a diamine compound in a solvent to produce a polyamic acid precursor, followed by thermal ring closure (imidization). For example, a polyamic acid can be obtained by dissolving approximately equimolar amounts of an acid dianhydride and a diamine compound in an organic solvent, stirring at a temperature within the range of 0 to 100°C for 30 minutes to 24 hours, and causing a polymerization reaction. In the reaction, the reaction components are dissolved in the organic solvent so that the amount of the precursor to be produced is within the range of 5 to 30% by weight, preferably within the range of 10 to 20% by weight. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. Further, the amount of such an organic solvent to be used is not particularly limited, but it should be adjusted to an amount such that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. is preferred.

It is usually advantageous to use the synthesized polyamic acid as a reaction solvent solution, but if necessary, it can be concentrated, diluted, or substituted with another organic solvent to form a resin composition. The method of imidizing polyamic acid is not particularly limited, and for example, heat treatment such as heating in the above-mentioned solvent at a temperature within the range of 80 to 400° C. for 1 to 24 hours is preferably employed.

<Spherical alumina particles>
Spherical alumina particles are alumina particles whose shape is close to a true sphere. 90% by weight or more of the spherical alumina particles satisfy the following conditions a to c.

Condition a):
The average particle diameter D ₅₀ at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement by laser diffraction scattering method is 50% is within the range of 0.5 to 5 μm.
If the average particle diameter _D50 is less than 0.5 μm, the effect of improving thermal conductivity will be reduced. Furthermore, if the average particle diameter _D50 of the spherical alumina particles exceeds 5 μm, it becomes difficult to fill the particles, and when a resin film is formed, voids may be generated due to increased stress due to resin contraction around the resin film, which may reduce the effectiveness of the invention. Control becomes difficult.

b) Circularity is 0.9 or more.
Circularity refers to the ratio of the perimeter of the particle to a circle having the same projected area. When the circularity of the spherical alumina particles is 0.9 or more, there is less α phase (the surface becomes smooth), so when a resin film is formed, voids are less likely to form on the surface in contact with polyimide. . When the circularity is less than 0.9, the contact area between the spherical alumina particles is large, making it difficult for water generated when curing the polyamic acid and the solvent to be volatilized to escape from the insulating layer, so that voids are likely to occur. Furthermore, if the circularity is less than 0.9, the contact area between the spherical alumina particles and the resin becomes large, and the viscosity of the resin composition to which the spherical alumina particles are added increases, making it difficult to apply the resin.

c) True specific gravity is within the range of 3.4 to 3.8.
If the true specific gravity is less than 3.4, the heat dissipation effect will be weakened. When the true specific gravity exceeds 3.8, the difference in specific gravity with the resin becomes large, and the spherical alumina particles may settle and segregate, or the dispersibility of the spherical alumina particles may deteriorate. Note that when the true specific gravity is made larger than 3.8, the crystallinity of the spherical alumina particles increases, so the thermal conductivity becomes higher, but the upper limit is set at 3.8 in consideration of dispersibility.

When 90% by weight or more of the spherical alumina particles satisfy the above conditions a to c, the viscosity of the resin composition can be easily adjusted and the dispersibility of the spherical alumina particles can be improved.

It is preferable that the spherical alumina particles further satisfy the following conditions e and f.
e) The particle diameter D ₉₀ at which the cumulative value is 90% is within the range of 2.0 to 6.0 μm.
f) The particle diameter _D10 at which the cumulative value is 10% is within the range of 0.3 to 1.8 μm.
By satisfying conditions e and f, the width of the particle size distribution becomes wider, which makes it easier to adjust the viscosity of the resin composition, and makes it difficult for voids to form when a resin film is formed. Further, by mixing spherical alumina particles with different particle sizes, it is possible to increase the amount of the alumina particles mixed, and the thermal conductivity of the resin film can be improved.

Furthermore, it is preferable that the maximum particle diameter of the spherical alumina particles is 15 μm or less. By setting the maximum particle size to 15 μm or less, the surface smoothness when formed into a resin film is improved. When the maximum particle diameter exceeds 15 μm, irregularities occur on the surface when a resin film is formed, and voids tend to occur at the interface between the spherical alumina particles and the resin.

In the present invention, commercially available products can be appropriately selected and used as the spherical alumina particles. Examples of such commercial products include spherical alumina (trade names: AZ4-10, AZ2-05, AX1M, etc.) manufactured by Nippon Steel Chemical & Materials. Two or more of these can be used in combination.

<Blend composition>
The content of spherical alumina particles in the resin composition consisting of polyamic acid or polyimide and spherical alumina particles is preferably within the range of 5 to 80% by volume based on the total amount of the spherical alumina particles and polyamic acid or polyimide. is in the range of 20 to 70% by volume, more preferably in the range of 30 to 60% by volume, most preferably in the range of 40 to 55% by volume. If the content of the spherical alumina particles is less than 5% by volume, the thermal conductivity will be low, making it impossible to obtain sufficient properties as a heat dissipation material. Furthermore, if the content of spherical alumina particles exceeds 80% by volume, not only will the resin film become brittle and difficult to handle, but also the viscosity of the resin composition will increase when trying to form a resin film. , workability also decreases.

The resin composition of this embodiment can contain an organic solvent. Examples of organic solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl Examples include sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and cresol. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The content of the organic solvent is not particularly limited, but it is preferable to adjust the amount so that the concentration of polyamic acid or polyimide is about 5 to 30% by weight.

Furthermore, the resin composition of the present embodiment may contain an inorganic filler or an organic filler other than the spherical alumina particles satisfying the above conditions a to c, if necessary, to the extent that the effects of the invention are not impaired. good. Specifically, for example, alumina particles that do not meet the above conditions a to c, inorganic fillers such as silicon dioxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and fluorine Examples include organic fillers such as polymer particles and liquid crystal polymer particles. These can be used alone or in combination of two or more. Furthermore, if necessary, other optional components such as a plasticizer, hardening accelerator, coupling agent, filler, pigment, flame retardant, etc. can be appropriately blended.

<Viscosity>
The viscosity of the resin composition is preferably within the range of 5,000 cps to 100,000 cps, for example, 10,000 cps to 100,000 cps, as a viscosity range that improves handling properties when coating resin composition particles and facilitates forming a coating film of uniform thickness. More preferably, it is within the range of 50,000 cps. If the viscosity is outside the above range, defects such as uneven thickness and streaks are likely to occur in the film during coating with a coater or the like.

<Preparation of resin composition>
When preparing a resin composition, for example, spherical alumina particles may be directly blended into a resin solution of polyamic acid. Alternatively, considering the dispersibility of the filler, spherical alumina particles are mixed in advance into a reaction solvent containing one of the acid dianhydride component and diamine component, which are raw materials for polyamic acid, and then the other raw material is added to the reaction solvent while stirring. may be added to advance the polymerization. In either method, the entire amount of spherical alumina particles may be added at one time, or may be added little by little over several times. Further, the raw materials may be added all at once, or may be mixed little by little in several batches.

[Resin film]
The resin film of this embodiment is a resin film having a single layer or multiple polyimide layers, and at least one of the polyimide layers is a thermally conductive polyimide layer made of a cured product of the above resin composition. good.

In the resin film, the thickness of the thermally conductive polyimide layer formed from the resin composition is preferably within the range of 2 to 100 μm, and more preferably within the range of 4 to 50 μm. Further, it is preferable that the maximum particle diameter of the spherical alumina particles is within the range of 0.05 to 0.7 with respect to the thickness of the thermally conductive polyimide layer. If the maximum particle diameter of the spherical alumina particles is less than 0.05 with respect to the thickness of the thermally conductive polyimide layer, the thermal conductivity may be insufficient; if it exceeds 0.7, the thermal conductivity The surface smoothness of the layer may be impaired.

The thickness of the entire resin film is, for example, preferably within the range of 2 to 100 μm, more preferably within the range of 4 to 50 μm. If the thickness of the resin film is less than 2 μm, problems such as wrinkles in the metal foil are likely to occur during the transportation process during production of the metal-clad laminate. On the other hand, if the thickness of the resin film exceeds 100 μm, it tends to be disadvantageous in terms of high thermal conductivity, flexibility, etc. Note that the resin film preferably has a withstand voltage of 1 kV or more.

The method of forming the thermally conductive polyimide layer is not particularly limited, and any known method can be employed. The most typical example is shown here.
First, a resin composition is directly cast-coated onto an arbitrary supporting substrate to form a coating film. Next, the coating film is dried to remove some of the solvent at a temperature of 150° C. or lower. When the resin composition contains polyamic acid, the coated film is then further subjected to heat treatment for imidization at a temperature range of 100 to 400°C, preferably 130 to 360°C for about 5 to 30 minutes. In this way, a thermally conductive polyimide layer can be formed on the supporting base material. In the case of two or more polyimide layers, a first resin solution of polyamic acid is applied and dried, and then a second resin solution of polyamic acid is applied and dried. From then on, apply the polyamic acid resin solution in the same manner as necessary, sequentially, as needed. ,dry. Thereafter, it is preferable to perform imidization by heat treatment at a temperature range of 100 to 400° C. for about 5 to 30 minutes. If the heat treatment temperature is lower than 100°C, the dehydration ring-closing reaction of the polyimide will not proceed sufficiently, whereas if it exceeds 400°C, the polyimide layer may deteriorate.

Another example of forming a thermally conductive polyimide layer will also be given.
First, a resin composition is cast onto an arbitrary support base material and molded into a film. This film-like molded product is heated and dried on a supporting base material to form a self-supporting gel film. After the gel film is peeled off from the supporting base material, if the resin composition contains polyamic acid, it is further heat-treated at a high temperature to imidize it to form a polyimide resin film.

The supporting base material used for forming the thermally conductive polyimide layer is not particularly limited, and any base material may be used. Further, in forming the resin film, it is not necessary to form the resin film completely imidized on the supporting base material. For example, a resin film in a semi-cured polyimide precursor state can be separated from a supporting base material by means such as peeling, and after separation, imidization can be completed to obtain a resin film.

The resin film may consist only of a polyimide layer (including the above thermally conductive polyimide layer) containing a thermally conductive filler such as spherical alumina particles, or it may have a polyimide layer that does not contain a thermally conductive filler. good. When the resin film has a laminated structure of multiple layers, in consideration of thermal conductivity, it is preferable that all the layers contain a thermally conductive filler. However, by making the layer adjacent to the polyimide layer containing thermally conductive filler a layer that does not contain thermally conductive filler or a layer with a low content of thermally conductive filler, it is possible to prevent the thermally conductive filler from slipping during processing. This can have the advantageous effect of preventing When the polyimide layer does not contain a thermally conductive filler, its thickness is, for example, within the range of 1/100 to 1/2, preferably 1/20 to 1/3 of the thickness of the polyimide layer containing the thermally conductive filler. It is better to keep it within the range. When the polyimide layer does not contain a thermally conductive filler, the adhesion between the metal layer and the insulating resin layer is improved by bringing the polyimide layer into contact with the metal layer.

The coefficient of thermal expansion (CTE) of the resin film is preferably within the range of, for example, 5×10 ⁻⁶ to 30×10 ⁻⁶ /K (5 to 30 ppm/K), and 10×10 ⁻⁶ to 25×10 ^-6 /K (10 to 25 ppm/K) is more preferable. If the thermal expansion coefficient of the resin film is smaller than 5×10 ⁻⁶ /K, curling tends to occur after forming the metal-clad laminate, resulting in poor handling properties. On the other hand, when the thermal expansion coefficient of the resin film exceeds 30×10 ⁻⁶ /K, the dimensional stability as an electronic material such as a flexible substrate tends to be poor, and the heat resistance also tends to decrease.

The thermal conductivity λz in the thickness direction of the resin film is, for example, preferably 0.5 W/mK or more, more preferably 1.0 W/mK or more, and most preferably 1.5 W/mK or more. . If the thermal conductivity λz is less than 0.5 W/mK, the purpose cannot be achieved in application to heat dissipation. In particular, when the thermal conductivity λz is 1.0 W/mK or more, excellent heat dissipation properties can be obtained, and the resin film can be applied to many uses other than heat dissipation substrates, for example. Further, the thermal conductivity of the resin film is advantageously 1.0 W/mK or more in the planar direction, and preferably 2.0 W/mK or more.

<Metal-clad laminate>
The metal-clad laminate of this embodiment is a metal-clad laminate including an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, and at least one layer of the insulating resin layer. is made of the above resin film. The metal-clad laminate may be a single-sided metal-clad laminate having a metal layer on only one side of the insulating resin layer, or a double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer. .

The metal-clad laminate of this embodiment does not exclude the use of an adhesive for bonding the polyimide layer containing a thermally conductive filler and the metal foil. However, when interposing an adhesive layer in a double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer, the thickness of the adhesive layer should be 30% of the total thickness of the insulating resin layer so as not to impair thermal conductivity. %, more preferably less than 20%. In addition, when interposing an adhesive layer in a single-sided metal-clad laminate that has a metal layer on only one side of the insulating resin layer, the thickness of the adhesive layer should be the same as the thickness of the entire insulating resin layer so as not to impair thermal conductivity. It is preferably less than 15%, more preferably less than 10%. Furthermore, since the adhesive layer constitutes a part of the insulating resin layer, it is preferably a polyimide layer. The glass transition temperature of polyimide, which is the main material of the insulating resin layer, is preferably 300° C. or higher from the viewpoint of imparting heat resistance. A glass transition temperature of 300° C. or higher can be achieved by appropriately selecting the acid dianhydride and diamine components mentioned above that constitute the polyimide.

Methods for manufacturing metal-clad laminates using resin films as insulating resin layers include, for example, applying heat and pressure to the resin film directly or using an arbitrary adhesive, or applying resin to the resin film using methods such as metal vapor deposition. Examples include a method of forming a metal layer on a film. Note that double-sided metal-clad laminates can be formed, for example, by forming a single-sided metal-clad laminate, then facing each other and pressing the polyimide layers together using heat press, or by applying metal foil to the polyimide layer of a single-sided metal-clad laminate. It can be obtained by a method of crimping and forming.

<Metal layer>
The material of the metal layer is not particularly limited, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and these. Examples include alloys of Among these, copper or copper alloy is particularly preferred. The metal layer may be made of metal foil, or may be made by vapor-depositing metal onto a film. Further, since the resin composition can be directly applied, either metal foil or metal plate can be used, and copper foil or copper plate is preferable.

The thickness of the metal layer is not particularly limited as it is appropriately set depending on the purpose of use of the metal-clad laminate, but is preferably within the range of 5 μm to 3 mm, and more preferably within the range of 12 μm to 1 mm. If the thickness of the metal layer is less than 5 μm, problems such as wrinkles may occur during transportation during manufacturing of metal-clad laminates. On the other hand, if the thickness of the metal layer exceeds 3 mm, it will be hard and have poor workability. Regarding the thickness of the metal layer, generally, a thick metal layer is suitable for applications such as an automotive circuit board, and a thin metal layer is suitable for applications such as an LED circuit board.

The present invention will be specifically illustrated below based on Examples, but the present invention is not limited to these Examples.

The abbreviations used in this example are shown below.
m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl PMDA: Pyromellitic dianhydride DAPE: 4,4'-diaminodiphenyl ether DMAc: N,N-dimethylacetamide Filler 1: Nippon Steel Chemical & Manufactured by Material Co., Ltd., product name: AZ4-10 (spherical alumina, true sphericity, circularity: 0.96, true specific gravity: 3.73, D ₅₀ ; 3.6 μm, D ₁₀ ; 1.88 μm, D ₉₀ ; 5. 92 μm, maximum particle size; 10 μm, Al ₂ O ₃ ; 99.9%)
Filler 2: manufactured by Nippon Steel Chemical & Materials Co., Ltd., product name: AZ2-05 (spherical alumina, true sphericity, circularity: 0.91, true specific gravity: 3.42, D ₅₀ ; 1.9 μm, D ₁₀ ; 0. 99 μm, D ₉₀ ; 3.12 μm, maximum particle size; 6 μm)
Filler 3: manufactured by Nippon Steel Chemical & Materials Co., Ltd., product name: AX1M (spherical alumina, true sphericity, circularity: 0.90, true specific gravity: 3.63, _D50 : 0.9 μm, _D10 : 0.36 μm, _D90 : 2.13 μm, maximum particle size: 13 μm)
Filler 4: Manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-3 (alumina, polyhedral spherical, true specific gravity: 3.98, D ₅₀ ; 3.4 μm, D ₁₀ ; 2.2 μm, D ₉₀ ; 5.0 μm, largest particle Diameter: 10μm)
Filler 5: Manufactured by Sumitomo Chemical Co., Ltd., trade name: AA-04 (alumina, polyhedral spherical, true specific gravity: 3.98, D ₅₀ ; 0.5 μm, D ₁₀ ; 0.2 μm, D ₉₀ ; 1.8 μm, largest particle Diameter: 15μm)

Moreover, the following evaluation method was followed for each characteristic evaluated in the examples.

[Measurement of particle size]
Using a laser diffraction particle size distribution analyzer (manufactured by Malvern Co., Ltd., trade name: Master Sizer 3000), water was used as a dispersion medium, and the particle diameter was measured by a laser diffraction/scattering measurement method.

[Measurement of circularity]
The average circularity was measured by dynamic flow particle image analysis using a wet flow particle size/shape analyzer (manufactured by Sysmex Corporation, product name: FPIA-3000), and the circularity of alumina particles with a particle size of 3 μm or more was measured. I asked for In addition, the circularity of alumina particles with a particle diameter of less than 3 μm was determined by observing the cross section of the resin film with a Schottky field emission scanning electron microscope (manufactured by JEOL, trade name: JSM-7900F). The average circularity of the filler particles contained in the sample was calculated from image analysis.

[Measurement of true specific gravity]
The measurement was carried out by the pycnometer method (liquid phase displacement method) using a continuous automatic powder true density measuring device (manufactured by Seishin Enterprise Co., Ltd., trade name: AUTO TRUE DENSERMAT-7000).

[Measurement of thickness direction thermal conductivity (λz)]
The resin film was cut into a size of 20 mm x 20 mm, and using a laser flash device (manufactured by Bruker AXS, trade name: LFA 447 Nanoflash), the thermal diffusivity in the thickness direction was determined by DSC (differential scanning calorimetry). Specific heat and density by gas displacement method were each measured, and thermal conductivity (W/m·K) was calculated based on these results.

[Measurement of viscosity]
The viscosity of the resin solution was measured at 25° C. using an E-type viscometer (manufactured by Brookfield, trade name: DV-II+Pro). The rotational speed was set so that the torque was 10% to 90%, and the value was read when the viscosity stabilized 2 minutes after starting the measurement.

[Evaluation of voids]
Observe the cross section of the resin film with a scanning electron microscope (SEM). If there are no voids, it is rated "good", if the void size is less than 1 μm, it is "fair", and if the void size is 1 μm or more, it is rated "fair". was rated "unacceptable".

Synthesis example 1
Under a nitrogen stream, 124.44 g of m-TB (0.585 mol) and 95.87 g of DAPE (0.479 mol) were dissolved in 2550 g of DMAc with stirring in a 3000 ml separable flask. Then, 229.69 g of PMDA (1.053 mol) was added thereto. Thereafter, the solution was continuously stirred at room temperature for 3 hours to carry out a polymerization reaction to obtain a brown viscous polyamic acid solution a (solid content concentration: 15%) with a viscosity of 19,000 cps.

[Example 1]
168.5 g of polyamic acid solution a and 31.5 g of filler 1 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 1 (viscosity: 20,000 cps, content of filler relative to the total amount of filler 1 and polyamic acid) 30% by volume).
Polyamic acid solution 1 was applied onto copper foil 1 (electrolytic copper foil, thickness: 35 μm) so that the thickness after curing would be 25 μm, and the solution was heated and dried at 130° C. to remove the solvent. Thereafter, stepwise heat treatment was performed from 130 to 300° C. to complete imidization, and a copper-clad laminate 1 was produced.
Regarding the copper-clad laminate 1, the copper foil was removed by etching to produce a resin film 1 (filler content: 30% by volume). Table 1 shows the evaluation results for Resin Film 1.

[Example 2]
139.2 g of polyamic acid solution a and 60.8 g of filler 1 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 2 (viscosity: 19,800 cps, content of filler relative to the total amount of filler 1 and polyamic acid) 50% by volume).
A copper clad laminate 2 and a resin film 2 were produced in the same manner as in Example 1. Table 1 shows the evaluation results for Resin Film 2.

[Example 3]
168.5 g of polyamic acid solution a and 31.5 g of filler 2 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 3 (viscosity: 20,200 cps, content of filler relative to the total amount of filler 2 and polyamic acid) 30% by volume).
A copper clad laminate 3 and a resin film 3 were produced in the same manner as in Example 1. Table 1 shows the evaluation results for resin film 3.

[Example 4]
139.2g of polyamic acid solution a and 60.8g of filler 2 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 4 (viscosity: 20,100 cps, content of filler relative to the total amount of filler 2 and polyamic acid) 50% by volume).
A copper clad laminate 4 and a resin film 4 were produced in the same manner as in Example 1. Table 1 shows the evaluation results of resin film 4.

[Example 5]
139.2 g of polyamic acid solution a, 16.9 g of filler 3, and 43.9 g of filler 1 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 5 (viscosity: 21,000 cps, filler 1 and filler 3) The content of the filler relative to the total amount with the polyamic acid was 50% by volume, _D50 : 2.8 μm, _D10 : 0.6 μm, _D90 : 5.2 μm, and maximum particle size: 12 μm).
A copper clad laminate 5 and a resin film 5 were produced in the same manner as in Example 1. Table 1 shows the evaluation results of resin film 5.

[Example 6]
99.1 g of polyamic acid solution a, 28.1 g of filler 3, and 72.8 g of filler 1 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 6 (viscosity: 21,200 cps, filler 1 and filler 3) The content of the filler relative to the total amount with the polyamic acid was 70% by volume, _D50 : 2.8 μm, _D10 : 0.6 μm, _D90 : 5.2 μm, and maximum particle size: 12 μm).
A copper clad laminate 6 and a resin film 6 were produced in the same manner as in Example 1. Table 1 shows the evaluation results of the resin film 6.

[Example 7]
139.2 g of polyamic acid solution a, 18.2 g of filler 3, 6.1 g of filler 2, and 36.5 g of filler 1 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 7 (viscosity: 21,000 cps , filler content with respect to the total amount of filler 1, filler 2, filler 3, and polyamic acid; 50 volume %, D ₅₀ ; 2.4 μm, D ₁₀ ; 0.6 μm, D ₉₀ ; 5.1 μm, maximum particle diameter ; 12 μm) was obtained.
A copper clad laminate 7 and a resin film 7 were produced in the same manner as in Example 1. The evaluation results of resin film 7 are shown in Table 1.

[Example 8]
99.1 g of polyamic acid solution a, 30.3 g of filler 3, 10.1 g of filler 2, and 60.6 g of filler 1 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 8 (viscosity: 22,000 cps , filler content with respect to the total amount of filler 1, filler 2, filler 3, and polyamic acid; 70 volume %, D ₅₀ ; 2.4 μm, D ₁₀ ; 0.6 μm, D ₉₀ ; 5.1 μm, maximum particle diameter ; 12 μm) was obtained.
A copper clad laminate 8 and a resin film 8 were produced in the same manner as in Example 1. Table 1 shows the evaluation results for resin film 8.

Comparative example 1
139.2 g of polyamic acid solution a and 60.8 g of filler 4 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 9 (viscosity: 28,900 cps, content of filler relative to the total amount of filler 4 and polyamic acid) 50% by volume).
A copper clad laminate 9 and a resin film 9 were produced in the same manner as in Example 1. The evaluation results of resin film 9 are shown in Table 2.

Comparative example 2
139.2 g of polyamic acid solution a, 16.9 g of filler 5, and 43.9 g of filler 4 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 10 (viscosity: 42,600 cps, filler 4 and filler 5) The content of the filler relative to the total amount with the polyamic acid was 50% by volume, and the maximum particle diameter was 15 μm).
A copper clad laminate 10 and a resin film 10 were produced in the same manner as in Example 1. The evaluation results of the resin film 10 are shown in Table 2.

Comparative example 3
99.1 g of polyamic acid solution a, 28.1 g of filler 5, and 72.8 g of filler 4 were mixed with a centrifugal stirrer until uniform, and polyamic acid solution 11 (viscosity: 47,800 cps, filler 4 and filler 5) The content of the filler relative to the total amount with the polyamic acid was 70% by volume, and the maximum particle diameter was 15 μm).
A copper clad laminate 11 and a resin film 11 were produced in the same manner as in Example 1. The evaluation results of resin film 11 are shown in Table 2.

Although the embodiments of the present invention have been described above in detail for the purpose of illustration, the present invention is not limited to the above embodiments and can be modified in various ways.

Claims (3)

A resin film having a single layer or multiple polyimide layers,
At least one of the polyimide layers is a thermally conductive polyimide layer,
The thermally conductive polyimide layer is a cured product of a resin composition comprising polyamic acid or polyimide, and spherical alumina particles, and the content of the spherical alumina particles is such that the content of the spherical alumina particles and the polyamic acid or the It is within the range of 5 to 80% by volume based on the total amount with polyimide,
90% by weight or more of the spherical alumina particles meet the following conditions a to c;
a) The average particle diameter _D50 at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement by laser diffraction scattering method is 50% is within the range of 0.5 to 5 μm;
b) Circularity is 0.9 or more;
c) True specific gravity is within the range of 3.4 to 3.8;
The spherical alumina particles satisfy the following conditions d and e;
d) The particle diameter _D90 at which the cumulative value is 90% is within the range of 2.0 to 6.0 μm;
e) The particle diameter _D10 at which the cumulative value is 10% is within the range of 0.3 to 1.8 μm;
It satisfies the following.
The thickness of the thermally conductive polyimide layer is within the range of 2 to 100 μm, and the maximum particle diameter of the spherical alumina particles is within the range of 0.05 to 0.7 with respect to the thickness of the thermally conductive polyimide layer. A resin film characterized by: The resin film according to claim 1, wherein the maximum particle diameter of the spherical alumina particles is 15 μm or less. A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer,
A metal-clad laminate, wherein the insulating resin layer is made of the resin film according to claim 1.