JP7405560B2 - Resin compositions, resin films, and metal-clad laminates - Google Patents

Description

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

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, as electrical and electronic devices become more sophisticated and functional, information transmission speeds are progressing. Therefore, parts and materials used in electrical and electronic equipment are also required to support high-speed transmission. Attempts have been made to reduce the dielectric constant and dielectric loss tangent of resin materials used in such applications so that they have electrical properties compatible with high-speed transmission. As an example, a resin-coated copper foil has been proposed that has a resin layer containing a resin mixture containing an epoxy resin, a polyimide resin, and an aromatic polyamide resin, an imidazole curing catalyst, and an inorganic filler, and has dielectric properties compatible with high frequency transmission. (For example, Patent Document 1).

International publication WO2017/014079

Although Patent Document 1 describes that the dielectric loss tangent of the resin layer can be reduced by adding an inorganic filler such as silica, there is no detailed study on the specific structure of the inorganic filler suitable for that purpose. Furthermore, the addition of an inorganic filler has the problem of reducing the bendability of the resin film.

An object of the present invention is to provide a resin composition and a resin film whose dielectric properties are improved by adding an inorganic filler without impairing mechanical properties such as bendability.

The resin film of the present invention is a resin film having a single layer or multiple polyimide layers,
At least one of the polyimide layers is a spherical silica-containing polyimide layer, and the spherical silica-containing polyimide layer is a cured product of a resin composition comprising polyamic acid or polyimide and spherical silica particles. In the resin film of the present invention, the frequency distribution curve of the spherical silica particles obtained by volume-based particle size distribution measurement using a laser diffraction scattering method satisfies the following conditions a to c, and the content of the spherical silica particles satisfies the following conditions. The amount is within the range of 20 to 65% by volume based on the total amount of spherical silica particles and the polyamic acid or polyimide.
a) The average particle diameter D ₅₀ at which the cumulative value is 50% is within the range of 9.0 to 12.0 μm.
b) The particle diameter _D90 at which the cumulative value is 90% is within the range of 15 to 20 μm.
c) The particle diameter _D100 at which the cumulative value is 100% is 25 μm or less.

In the resin film of the present invention, the spherical silica particles may further satisfy the following condition d.
d) It has a maximum frequency value F1 and a maximum frequency value F2, with F1 being in the range of 9.0 to 14.0 μm and F2 being in the range of 0.5 to 3.0 μm.

In the resin film of the present invention, the spherical silica particles may further satisfy the following condition e.
e) It has a maximum frequency value F1 and a maximum frequency value F2, and the ratio of F1 and F2 (F1/F2) is within the range of 3 to 28.

In the resin film of the present invention, the thickness of the spherical silica-containing polyimide layer is within the range of 5 to 150 μm.

In the resin film of the present invention, the particle diameter D ₁₀₀ of the spherical silica particles may be within a range of 0.05 to 0.7 relative to the thickness of the spherical silica-containing polyimide layer.

The resin film of the present invention has a thickness within the range of 5 to 150 μm, and the thickness ratio of the spherical silica-containing polyimide layer may be 50% or more.

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

By containing spherical silica particles having a specific particle size distribution represented by conditions a to c, the resin composition of the present invention can improve dielectric properties without deteriorating mechanical properties such as bendability. It becomes possible. Therefore, in electric/electronic equipment and electronic parts using the resin composition of the present invention, it is possible to cope with high-speed transmission and ensure reliability.

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 silica particles that are an inorganic 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 silica particles>
Spherical silica particles are silica particles that are nearly perfectly spherical in shape, and the ratio of the average major axis to the average minor axis is 1 or close to 1. For spherical silica particles, a frequency distribution curve obtained by volume-based particle size distribution measurement using a laser diffraction scattering method satisfies the following conditions a to c.
a) The average particle diameter D ₅₀ at which the cumulative value is 50% is within the range of 9.0 to 12.0 μm.
b) The particle diameter _D90 at which the cumulative value is 90% is within the range of 15 to 20 μm.
c) The particle diameter _D100 at which the cumulative value is 100% is 25 μm or less.

Regarding condition a, if the average particle diameter D ₅₀ of the spherical silica particles is less than 9.0, the effect of improving dielectric properties becomes small. On the other hand, if the average particle diameter D ₅₀ exceeds 12.0 μm, it becomes difficult to maintain mechanical properties such as filling becomes difficult and bendability decreases when a resin film is formed.
Regarding conditions b and c, the abundance ratio of spherical silica particles with a particle size of 15 to 25 μm is suppressed, and the maximum particle size of 25 μm or less eliminates coarse particles. Good bendability can be achieved.

Moreover, it is preferable that the spherical silica particles further satisfy the following conditions d and e.
d) It has a maximum frequency value F1 and a maximum frequency value F2, with F1 being in the range of 9.0 to 14.0 μm and F2 being in the range of 0.5 to 3.0 μm.
e) It has a maximum frequency value F1 and a maximum frequency value F2, and the ratio of F1 and F2 (F1/F2) is within the range of 3 to 28.
Regarding conditions d and e, by containing a certain amount of small spherical silica with a particle size in the range of 0.5 to 3.0 μm in the spherical silica particles, the decrease in bendability when formed into a film is suppressed. At the same time, the dielectric properties can be further improved.

Note that commercially available products can be appropriately selected and used as the spherical silica particles. For example, spherical cristobalite silica powder (manufactured by Nippon Steel Chemical & Materials, trade name: CR10-20), spherical amorphous silica powder (manufactured by Nippon Steel Chemical & Materials, trade name: SC70-2), etc. can be preferably used. . Two or more types of these can be used in combination.

<Blend composition>
The content of spherical silica particles in the resin composition is within the range of 20 to 65% by volume, preferably within the range of 30 to 60% by volume, based on the total amount of the spherical silica particles and polyamic acid or polyimide. . If the content of spherical silica particles is less than 20% by volume, the effect of lowering the dielectric loss tangent cannot be sufficiently achieved. Furthermore, if the content of spherical silica particles exceeds 65% by volume, the resin film will become brittle and have poor bending properties, and when attempting to form a resin film, the viscosity of the resin composition will increase. , 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 silica 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, silica particles that do not meet the above conditions a to c, inorganic fillers such as aluminum oxide, 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 silica particles may be directly blended into a resin solution of polyamic acid. Alternatively, considering the dispersibility of the filler, spherical silica 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 silica particles may be added at once, or may be added little by little over several portions. 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 spherical silica-containing polyimide layer made of a cured product of the resin composition. good.

In the resin film, the thickness of the spherical silica-containing polyimide layer formed from the resin composition is preferably within the range of 5 to 150 μm, and more preferably within the range of 45 to 100 μm. Further, the particle diameter D ₁₀₀ of the spherical silica particles is preferably within the range of 0.05 to 0.7 relative to the thickness of the spherical silica-containing polyimide layer. If the particle diameter D ₁₀₀ of the spherical silica particles is less than 0.05 with respect to the thickness of the spherical silica-containing polyimide layer, the effect of improving dielectric properties may be insufficient; if it exceeds 0.7, the spherical The smoothness of the surface of the silica-containing polyimide layer may be impaired, and the bendability may be reduced when a resin film is formed.

The thickness of the entire resin film is, for example, preferably within the range of 5 to 150 μm, more preferably within the range of 45 to 80 μm. If the thickness of the resin film is less than 5 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 that the bendability of the resin film decreases.

Further, the ratio of the thickness of the spherical silica-containing polyimide layer to the total thickness of the resin film is preferably 50% or more. If the ratio of the thickness of the spherical silica-containing polyimide layer to the total thickness of the resin film is less than 50%, a sufficient effect of improving dielectric properties cannot be obtained.

The method for forming the spherical silica-containing 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 spherical silica-containing polyimide layer can be formed on the supporting substrate. 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 spherical silica-containing 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 spherical silica-containing 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 containing an inorganic filler such as spherical silica particles (including the above-mentioned spherical silica-containing polyimide layer), or may have a polyimide layer containing no inorganic filler. When the resin film has a laminated structure of multiple layers, it is preferable that all the layers contain an inorganic filler in consideration of improving dielectric properties. However, by making the layer adjacent to the polyimide layer containing inorganic filler a layer that does not contain inorganic filler or a layer with a low content of inorganic filler, it is possible to prevent the inorganic filler from slipping off during processing. It can be effective. When having a polyimide layer that does not contain an inorganic filler, its thickness is, for example, within the range of 1/100 to 1/2, preferably within the range of 1/20 to 1/3 of the polyimide layer containing the inorganic filler. That's good. When the polyimide layer does not contain an inorganic 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 not particularly limited, but is preferably within the range of, for example, 5×10 ⁻⁶ to 40×10 ⁻⁶ /K (5 to 40 ppm/K), and 10×10 ⁻⁶ /K (5 to 40 ppm/K). It is more preferably within the range of ⁶ to 35×10 ⁻⁶ /K (10 to 35 ppm/K). 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, if the thermal expansion coefficient of the resin film exceeds 40×10 ⁻⁶ /K, the dimensional stability as an electronic material such as a flexible substrate will be poor, and the heat resistance will also tend to decrease.

<Dielectric loss tangent>
For example, when a resin film is applied as an insulating resin layer of a circuit board, in order to reduce dielectric loss during high-frequency signal transmission, the film as a whole has a The dielectric loss tangent (Tan δ) at 10 GHz is preferably 0.005 or less, more preferably 0.004 or less. In order to improve the transmission loss of a circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer, and by controlling the dielectric loss tangent within the above range, the effect of lowering the transmission loss increases. Therefore, when the resin film is applied, for example, as an insulating resin layer of a high frequency circuit board, transmission loss can be efficiently reduced. If the dielectric loss tangent at 10 GHz exceeds 0.005, when the resin film is applied as an insulating resin layer of a circuit board, problems such as increased electrical signal loss on the high frequency signal transmission path are likely to occur. Although the lower limit of the dielectric loss tangent at 10 GHz is not particularly limited, it is necessary to consider physical property control when applying the resin film as an insulating resin layer of a circuit board.

<Relative dielectric constant>
When the resin film is applied, for example, as an insulating resin layer of a circuit board, the relative permittivity of the film as a whole at 3 to 20 GHz is preferably 4.0 or less in order to ensure impedance matching. If the relative permittivity at 3 to 20 GHz exceeds 4.0, when the resin film is applied as an insulating resin layer of a circuit board, it will lead to worsening of dielectric loss and a large loss of electrical signals on the high frequency signal transmission path. Inconveniences such as

<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 an inorganic 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 is 30% of the total thickness of the insulating resin layer so as not to impair the dielectric properties. It is preferably less than 20%, more preferably less than 20%. In addition, when interposing an adhesive layer in a single-sided metal-clad laminate having a metal layer on only one side of the insulating resin layer, the thickness of the adhesive layer is set to 15% of the total thickness of the insulating resin layer so as not to impair the dielectric properties. %, 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.

Examples are shown below to explain the features of the present invention more specifically. However, the scope of the present invention is not limited to the examples. In addition, in the following examples, various measurements and evaluations are as follows unless otherwise specified.

[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 when the viscosity stabilized was read one minute after starting the measurement.

[Measurement of relative permittivity and dielectric loss tangent]
<Silica particles>
Using a dielectric constant measurement device manufactured by Kanto Denshi Application Development Co., Ltd. using the cavity resonator perturbation method, the dielectric constant measurement mode was set to TM101, and the relative dielectric constant (ε1) and dielectric loss tangent (Tan δ1) of silica particles were measured at a frequency of 10 GHz. did. The sample tube has an inner diameter of 1.68 mm, an outer diameter of 2.8 mm, and a height of 8 cm.
<Resin film>
The relative permittivity and dielectric loss tangent are calculated using a vector network analyzer (manufactured by Agilent, trade name: Vector Network Analyzer E8363C) and an SPDR resonator. ) and dielectric loss tangent (Tan δ1) were measured. The resin film used in the measurement was left for 24 hours at a temperature of 24 to 26°C and a humidity of 45 to 55%.

[Measurement method of coefficient of linear thermal expansion (CTE)]
A resin film with a size of 3 mm x 20 mm was heated from 30° C. to 265° C. at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA). After further holding at that temperature for 10 minutes, it was cooled at a rate of 5°C/min, and the average coefficient of thermal expansion (coefficient of thermal expansion) from 200°C to 100°C was determined.

[Method of measuring particle size]
The particle diameter was measured by a laser diffraction/scattering measurement method using a laser diffraction particle size distribution analyzer (manufactured by Malvern, trade name: Master Sizer 3000).

[Measurement method 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).

[Evaluation of bendability]
In accordance with JISK5600-1, the center of the long side of a 5cm x 10cm resin film is bent uniformly for 1 to 2 seconds as if wrapped around a 5mmφ metal rod, and even if the resin film is bent at 180 degrees, it will not break. Or, those with no cracks were rated as "good," and those with breakage or cracks were rated as "unacceptable."

Abbreviations used in Synthesis Examples, Comparative Examples, and Examples indicate the following compounds.
PMDA: Pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane m-TB: 2,2'-dimethyl-4,4'-diaminobiphenylDMAc: N,N-dimethylacetamide
Filler 1: manufactured by Nippon Steel Chemical & Materials Co., Ltd., product name: CR10-20 (spherical cristobalite silica powder, true spherical, silica content: 99.4% by weight, cristobalite phase: 98% by weight, true specific gravity: 2.33, Specific surface area; 0.63 m ² /g, D ₅₀ ; 10.8 μm, D ₉₀ ; 16.4 μm, D ₁₀₀ ; 24.1 μm, particle diameter at maximum frequency value F1: 11.2 μm, maximum frequency value F1; 10. 6%, particle size at maximum frequency value F2; 1.0 μm, maximum frequency value F2; 1.4%, F1/F2; 11.2, relative dielectric constant at 10 GHz; 3.16, dielectric loss tangent at 10 GHz; 0. 0008)
Filler 2: manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SC70-2 (spherical amorphous silica powder, true spherical, silica content: 99.9% by weight, true specific gravity: 2.33, specific surface area: 1. 1 m ² /g, D ₅₀ ; 11.7 μm, D ₉₀ ; 16.4 μm, D ₁₀₀ ; 24.1 μm, maximum frequency value F1 particle diameter: 11.2 μm, maximum frequency value F1; 10.8%, maximum frequency Particle diameter of value F2: 1.5 μm, maximum frequency value F2: 1.2%, F1/F2: 7.5, relative dielectric constant at 10 GHz: 3.08, dielectric loss tangent at 10 GHz: 0.0015)
Filler 3: manufactured by Nippon Steel Chemical & Materials Co., Ltd., product name: SP40-10 (spherical amorphous silica powder, true spherical, silica content: 99.9% by weight, true specific gravity: 2.21, specific surface area: 8. 6 m ² /g, D ₅₀ ; 2.5 μm, D ₉₀ ; 3.6 μm, D ₁₀₀ ; 7.0 μm, particle diameter at maximum frequency value F1; 2.2 μm, maximum frequency value F1; 9.0%, maximum frequency Particle diameter of value F2: 0.9 μm, maximum frequency value F2: 4.3%, F1/F2: 2.4, relative dielectric constant at 10 GHz: 2.78, dielectric loss tangent at 10 GHz: 0.0030)

(Synthesis example 1)
21.65 g of m-TB (101.66 mmol) and 255 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen stream. After completely dissolving, 17.46 g of PMDA (80.03 mmol) and 5.90 g of BPDA (20.01 mmol) were added and stirred at room temperature for 18 hours to form polyamic acid solution A (solid content concentration: 15%). I got it. The viscosity of the obtained polyamic acid solution A was 22,400 cps.

(Synthesis example 2)
29.21 g of BAPP (71.15 mmol) and 255 g of DMAc were placed in a 300 ml separable flask and stirred at room temperature under a nitrogen stream. After completely dissolving, 14.74 g of PMDA (67.60 mmol) and 1.05 g of BPDA (3.56 mmol) were added and stirred at room temperature for 18 hours to obtain polyamic acid solution B. The viscosity of the obtained polyamic acid solution B (solid content concentration: 15%) was 21,074 cps.

[Example 1]
70.0 g of polyamic acid solution A and 7.8 g of filler 1 were mixed and stirred until a visually uniform solution was obtained. The filler content (32.6% by volume relative to the total amount ) was prepared.
Polyamic acid solution 1 was applied onto copper foil 1 (electrolytic copper foil, thickness: 12 μm) and dried at 130° C. for 3 minutes. Thereafter, a stepwise heat treatment was performed from 155° C. to 360° C. to imidize the material, thereby preparing a metal-clad laminate 1.
The copper foil of the metal-clad laminate 1 was removed by etching to prepare a resin film 1. Resin film 1 (thickness: 46.1 μm) had a dielectric constant of 2.78, a dielectric loss tangent of 0.0037, a CTE of 34 ppm/K, and had good bendability. Table 1 shows the evaluation results for Resin Film 1.

[Example 2]
60.0 g of polyamic acid solution A and 20.0 g of filler 1 were mixed and stirred until a visually uniform solution was obtained. The filler content (59.2% by volume relative to the total amount ) was prepared.
A metal-clad laminate 2 and a resin film 2 were prepared in the same manner as in Example 1. Resin film 2 (thickness: 78.1 μm) had a dielectric constant of 2.71, a dielectric loss tangent of 0.0028, a CTE of 34 ppm/K, and had good bendability. Table 1 shows the evaluation results for Resin Film 2.

[Example 3]
58.7 g of polyamic acid solution B and 6.1 g of filler 1 were mixed and stirred until a visually uniform solution was obtained. The filler content (30.0% by volume relative to the total amount ) was prepared.
A metal-clad laminate 3 and a resin film 3 were prepared in the same manner as in Example 1. The dielectric constant of the resin film 3 (thickness: 51.6 μm) was 3.04, the dielectric loss tangent was 0.0044, and the bendability was good. Table 1 shows the evaluation results for resin film 3.

[Example 4]
70.0 g of polyamic acid solution A and 7.8 g of filler 2 were mixed and stirred until a visually uniform solution was obtained. The filler content (33.8% by volume relative to the total amount ) was prepared.
A metal-clad laminate 4 and a resin film 4 were prepared in the same manner as in Example 1. Resin film 4 (thickness: 50.4 μm) had a dielectric constant of 2.84, a dielectric loss tangent of 0.0038, a CTE of 28.2 ppm/K, and had good bendability. Table 1 shows the evaluation results of resin film 4.

[Example 5]
60.0 g of polyamic acid solution A and 20.0 g of filler 2 were mixed and stirred until a visually uniform solution was obtained. Filler content (60.5% by volume relative to the total amount ) was prepared.
A metal-clad laminate 5 and a resin film 5 were prepared in the same manner as in Example 1. Resin film 5 (thickness: 79.3 μm) had a dielectric constant of 2.75, a dielectric loss tangent of 0.0028, a CTE of 20.4 ppm/K, and had good bendability. Table 1 shows the evaluation results of resin film 5.

[Example 6]
56.2 g of polyamic acid solution B and 5.5 g of filler 2 were mixed and stirred until a visually uniform solution was obtained. The filler content (30.0% by volume relative to the total amount ) was prepared.
A metal-clad laminate 6 and a resin film 6 were prepared in the same manner as in Example 1. The resin film 6 (thickness: 50.7 μm) had a dielectric constant of 3.04, a dielectric loss tangent of 0.0047, and had good bendability. Table 1 shows the evaluation results of the resin film 6.

(Comparative example 1)
70.0 g of polyamic acid solution A was applied onto copper foil 1 and dried at 130° C. for 3 minutes. Thereafter, a stepwise heat treatment was performed from 155° C. to 360° C. to imidize the material, thereby preparing a metal-clad laminate 7.
In the same manner as in Example 1, the copper foil of the metal-clad laminate 7 was removed by etching to prepare a resin film 7. Resin film 7 (thickness: 26.7 μm) had a dielectric constant of 3.13, a dielectric loss tangent of 0.0056, a CTE of 21.3 ppm/K, and had good bendability. The evaluation results of resin film 7 are shown in Table 2.

(Comparative example 2)
60.0 g of polyamic acid solution B was applied onto copper foil 1 and dried at 90° C. for 1 minute and at 130° C. for 5 minutes. Thereafter, a stepwise heat treatment was performed from 155° C. to 360° C. to imidize the material, thereby preparing a metal-clad laminate 8.
In the same manner as in Example 1, the copper foil of the metal-clad laminate 8 was removed by etching to prepare a resin film 8. Resin film 8 (thickness: 41.4 μm) had a dielectric constant of 3.16, a dielectric loss tangent of 0.0062, a CTE of 51.3 ppm/K, and had good bendability. The evaluation results of resin film 8 are shown in Table 2.

(Reference example 1)
Polyamic acid solution 9 was prepared in the same manner as in Example 1 except that 55.0 g of polyamic acid solution A and 36.3 g of filler 1 were mixed.
A polyamic acid solution 9 was applied onto the copper foil 1, a metal-clad laminate 9 was prepared in the same manner as in Example 1, and then a resin film 9 was prepared. Resin film 9 (thickness: 117.8 μm) had a dielectric constant of 2.56, a dielectric loss tangent of 0.0015, a CTE of 31 ppm/K, and poor bendability. Table 3 shows the evaluation results of resin film 9.

(Reference example 2)
Polyamic acid solution 10 was prepared in the same manner as in Example 1 except that 55.6 g of polyamic acid solution A and 36.3 g of filler 2 were mixed.
Polyamic acid solution 10 was applied onto copper foil 1, metal-clad laminate 10 was prepared in the same manner as in Example 1, and then resin film 10 was prepared. The resin film 10 (thickness: 116.7 μm) had a dielectric constant of 2.75, a dielectric loss tangent of 0.0018, a CTE of 13 ppm/K, and poor bendability. Table 3 shows the evaluation results of the resin film 10.

(Reference example 3)
Polyamic acid solution 11 was prepared in the same manner as in Example 1 except that 56.2 g of polyamic acid solution B and 5.5 g of filler 3 were mixed.
Polyamic acid solution 11 was applied onto copper foil 1, metal-clad laminate 11 was prepared in the same manner as in Example 1, and then resin film 11 was prepared. The resin film 11 (thickness: 45.6 μm) had a dielectric constant of 3.25, a dielectric loss tangent of 0.0052, a CTE of 40.9, and had good bendability. Table 3 shows the evaluation results for resin film 11.

The polyimide films containing spherical silica particles with an average particle diameter _D50 of 10 μm or more in Examples 1 to 6 had lower dielectric constants and dielectric loss tangents than the silica-free polyimide films of Comparative Examples 1 and 2. ing.
Moreover, the polyimide films of Reference Examples 1 and 2 containing 70 vol % or more of spherical silica particles had worse bending properties compared to Examples.
Furthermore, the polyimide film of Reference Example 3 containing spherical silica particles with a small average particle diameter D ₅₀ of 2.5 μm had a higher dielectric constant and dielectric loss tangent than those of Examples, and the effect of improving dielectric properties was small.

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 (6)

A resin film having a single layer or multiple polyimide layers,
At least one layer of the polyimide layer is a spherical silica-containing polyimide layer, and the spherical silica-containing polyimide layer is a cured product of a resin composition consisting of polyamic acid or polyimide and spherical silica particles, and the laser diffraction The frequency distribution curve of the spherical silica particles obtained by volume-based particle size distribution measurement using a scattering method is under the following conditions a to c;
a) The average particle diameter D ₅₀ at which the cumulative value is 50% is within the range of 9.0 to 12.0 μm;
b) The particle diameter _D90 at which the cumulative value is 90% is within the range of 15 to 20 μm;
c) The particle diameter _D100 at which the cumulative value is 100% is 25 μm or less;
and the content of the spherical silica particles is within the range of 20 to 65% by volume based on the total amount of the spherical silica particles and the polyamic acid or the polyimide,
A resin film characterized in that the thickness of the spherical silica-containing polyimide layer is within a range of 5 to 150 μm. The spherical silica particles further meet the following conditions d;
d) having a maximum frequency value F1 and a maximum frequency value F2, with F1 being within a range of 9.0 to 14.0 μm and F2 being within a range of 0.5 to 3.0 μm;
The resin film according to claim 1, which satisfies the following. The spherical silica particles further meet the following conditions e;
e) It has a maximum frequency value F1 and a maximum frequency value F2, and the ratio of F1 and F2 (F1/F2) is within the range of 3 to 28;
The resin film according to claim 1 or 2, wherein the resin film satisfies the following. The resin film according to claim 1, wherein the particle diameter D ₁₀₀ of the spherical silica particles is within a range of 0.05 to 0.7 with respect to the thickness of the spherical silica-containing polyimide layer. The resin film according to claim 1, wherein the resin film has a thickness in a range of 5 to 150 μm, and a thickness ratio of the spherical silica-containing polyimide layer is 50% or more. 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 any one of claims 1 to 5.