TW202124280A - Silica particle, resin composition, resin film and metal-clad laminate capable of improving dielectric properties without impairing mechanical properties - Google Patents

Abstract

The present invention provides silica particles capable of improving dielectric properties without impairing mechanical properties such as bendability, and a resin composition, a resin film and a metal-clad laminate having improved dielectric properties by adding the silica particles. The silica particles are used in a frequency range of 3 GHz to 20 GHz. An average particle diameter D50 in which an accumulated value in a frequency distribution curve obtained by a volume-based particle size distribution measurement by a laser diffraction scattering method is 50% is 0.3 [mu]m to 3 [mu]m. The specific surface area is in the range of more than 5 m2/g and less than or equal to 20 m2/g. The tangent of dielectric loss angle measured by the cavity resonator perturbation method is less than or equal to 0.004. The resin composition contains the silica particles and a polyamic acid or a polyimide. The content of the silica particles is in a range of 30% to 70% by volume relative to the polyamic acid or the polyimide.

Description

Silicon dioxide particles, resin composition, resin film and metal-clad laminate

The present invention relates to a silicon dioxide particle, a resin composition containing the silicon dioxide particle, and a resin using the resin composition that can be preferably used in electrical and/or electronic equipment used in a high-frequency region Film and metal-clad laminates.

In recent years, as represented by mobile phones, light emitting diode (LED) lighting appliances, and related parts around automobile engines, the requirements for miniaturization and light weight of electronic equipment have been increasing. Along with this, flexible circuit boards, which are advantageous for downsizing and lightening of equipment, are widely used in the field of electronic technology. Furthermore, flexible circuit boards in which polyimide is used as an insulating layer are widely used due to their good heat resistance, chemical resistance, and the like.

On the other hand, with the increase in performance or functionality of electrical and/or electronic equipment, high-speed transmission of information continues to develop. Therefore, parts or components used in electrical and/or electronic equipment are also required to cope with high-speed transmission. Regarding resin materials used in such applications, in order to have electrical characteristics corresponding to high-speed transmission, attempts have been made to achieve low dielectric constant and low dielectric loss tangent. For example, a low-dielectric resin composition in which fillers such as silica having a particle size of 1 μm or less are blended in polyimide at 5 wt% to 70 wt% of the total solid content (Patent Document 1) . In addition, in order to achieve a low dielectric loss tangent, it has also been proposed to mix 60% by mass or more of inorganic fillers such as silica in a polyimide having a structural unit derived from a bismaleimide compound. The thermosetting resin composition (Patent Document 2). [Prior Art Literature]

[Patent Literature] [Patent Document 1] Japanese Patent No. 3660501 [Patent Document 2] Japanese Patent Laid-Open No. 2018-012747

[The problem to be solved by the invention] The larger the particle size of the silica particles, the lower the dielectric loss tangent, and even when they are blended in a resin such as polyimide, the effect of reducing the dielectric loss tangent of the resin film is large. On the other hand, when silicon dioxide particles with a large particle size are added, there is a problem of reducing the bendability of the resin film.

The object of the present invention is to provide silicon dioxide particles that can achieve improved dielectric properties without impairing mechanical properties such as bending properties, and to provide silicon dioxide particles whose dielectric properties are improved by adding the silicon dioxide particles. Resin composition and resin film.

[Technical Means to Solve the Problem] The silica particles of the present invention are silica particles used in the frequency range of 3 GHz to 20 GHz, and are obtained by volume-based particle size distribution measurement using the laser diffraction scattering method The cumulative value in the frequency distribution curve becomes 50% when the average particle diameter D ₅₀ is in the range of 0.3 μm to 3 μm, and the specific surface area is in the range of more than 5 m ² /g and 20 m ² /g or less, using resonance The dielectric loss tangent measured by the cavity perturbation method is less than 0.004.

The resin composition of the present invention is a resin composition containing the silicon dioxide particles and polyamide acid or polyimide. Compared with the polyamide acid or polyimide, the silica particles The content is in the range of 30% by volume to 70% by volume.

The resin film of the present invention is a resin film having a single or multiple polyimide layers, and at least one layer of the polyimide layer is a polyimide containing silicon dioxide containing a cured product of the resin composition The thickness of the polyimide layer containing silicon dioxide is in the range of 10 μm to 200 μm.

The overall thickness of the resin film in the resin film of the present invention may be in the range of 10 μm to 200 μm, and the proportion of the thickness of the silicon dioxide-containing polyimide layer may be 50% or more.

The metal-clad laminate of the present invention 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 the insulating resin layer includes the resin film.

[Effects of the Invention] Although the average particle diameter D ₅₀ of the silica particles of the present invention is as small as 0.3 μm to 3 μm, by controlling the specific surface area, the dielectric loss tangent is low, so it can be effectively used for high-surface Frequency insulating material. In addition, the resin composition of the present invention can improve the dielectric properties without degrading mechanical properties such as bendability by containing the silicon dioxide particles. Therefore, in electric and/or electronic equipment or electronic parts using the resin composition of the present invention, it is possible to cope with high-speed transmission and to ensure reliability.

Hereinafter, embodiments of the present invention will be described.

[Silica Particles] The silicon dioxide particles according to an embodiment of the present invention are used in the frequency range of 3 GHz to 20 GHz. More specifically, it is silicon dioxide particles used as a material for parts or components in electrical and/or electronic equipment used in the frequency range of 3 GHz to 20 GHz. The shape of the silica particles of this embodiment is preferably spherical. In addition, the term "spherical" refers to particles having a shape close to a spherical shape, and the ratio of the average long diameter to the average short diameter is 1 or close to 1.

_{The silica particles of the present embodiment have an average particle size D 50} of 0.3 μm to 3 μm in which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement by the laser diffraction scattering method becomes 50%. Within the range, it is preferably within the range of 0.5 μm to 2.5 μm. If it is within the above range, for example, it is possible to suppress a decrease in the bending properties when blended into a resin film, and at the same time improve the dielectric properties. If the average particle size D _{50 of the} silicon dioxide particles is less than 0.3 μm, the effect of reducing the dielectric loss tangent cannot be sufficiently obtained. On the other hand, if the average particle diameter D ₅₀ exceeds 3 μm, it will become difficult to maintain mechanical properties such as reduced bendability when blended into a resin film.

In addition, the specific surface area of the silicon dioxide particles of the present embodiment is in the range of more than 5 m ² /g and 20 m ² /g or less, preferably in the range of 6 m ² /g to 15 m ² /g. By setting the specific surface area of the silica particles within the above range, the bulk density of the silica particles can be increased. Therefore, even if the average particle diameter D _{50 is as} small as the range of 0.3 μm to 3 μm, low density can be obtained. The tangent of the dielectric loss angle. Specifically, the dielectric loss tangent of the silicon dioxide particles measured by the cavity perturbation method can be set to 0.004 or less. When the specific surface area is 5 m ² /g or less or exceeds 20 m ² /g, the dielectric loss tangent of the silicon dioxide particles is not sufficiently low, and the effect of blending cannot be obtained. The specific surface area of the silica particles can be determined by the Brunauer-emmett-teller (BET) specific surface area measurement method.

In addition, the silica particles can be suitably selected from commercially available products and used. For example, spherical amorphous silicon dioxide powder (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SP40-10), spherical amorphous silicon dioxide powder (manufactured by Nippon Steel Chemical & Materials Co., Ltd., Trade name: SPH507), spherical amorphous silicon dioxide powder (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SPH516M), etc. These can be used in combination of two or more kinds.

[Resin composition] The resin composition of one embodiment of the present invention is a resin composition containing polyamide acid or polyimide, and the aforementioned silica particles as an inorganic filler. The resin composition may be a varnish (resin solution) containing polyamide acid, or a polyimide solution containing solvent-soluble polyimide.

＜Polyamide 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 a diamine component and an acid dianhydride component of substantially equal moles are used and polymerized in an organic polar solvent. In this case, in order to set the viscosity to a desired range, the molar ratio of the acid dianhydride component to the diamine component can be adjusted, and the range is, for example, preferably within the range of 0.980 to 1.03 in molar ratio. .

[化1]

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. Furthermore, Ar ₁ can be said to be a residue of acid dianhydride, and Ar ₂ can be said to be a residue of diamine. Moreover, n represents the repeating number of the structural unit of General formula (1), and is 200 or more, Preferably it is the number of 300-1000.

As the acid dianhydride, for example, _{an aromatic tetracarboxylic dianhydride represented by O(OC) 2} -Ar ₁ -(CO) ₂ O is preferable, and the following aromatic acid anhydride residues can be exemplified as the acid bis of Ar ₁ anhydride.

[化2]

The acid dianhydride can be used alone or in combination of two or more kinds. Among these, it is preferable to use pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3',4,4'- biphenyl tetracarboxylic dianhydride, BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (3,3',4,4'-benzophenone tetracarboxylic dianhydride, BTDA), 3,3',4 ,4'-diphenyl sulfone tetracarboxylic dianhydride (3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, DSDA), and 4,4'-oxydiphthalic dianhydride (4, 4'-oxydiphthalic dianhydride, ODPA).

As the diamine, for example, _{an aromatic diamine represented by H 2} N-Ar ₂ -NH ₂ is preferable, and an aromatic diamine in which the following aromatic diamine residue is provided as Ar ₂ can be exemplified.

[化3]

Among these diamines, diamino diphenyl ether (DAPE), 2,2'-dimethyl-4,4'-diamino biphenyl (2,2'-dimethyl-4 ,4'-diamino biphenyl, m-TB), p-phenylene diamine (paraphenylene diamine, p-PDA), 1,3-bis(4-aminophenoxy)benzene (1,3-bis(4-amino phenoxy)benzene, TPE-R), 1,3-bis(3-aminophenoxy)benzene (1,3-bis(3-amino phenoxy)benzene, APB), 1,4-bis(4-amine) Phenyloxy)benzene (1,4-bis(4-aminophenoxy)benzene, TPE-Q), and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (2, 2-bis[4-(4-amino phenoxy)phenyl]propane, BAPP), and 2,2-bis(trifluoromethyl)benzidine (TFMB) are preferred .

Polyimide can be produced by reacting an acid dianhydride and a diamine compound in a solvent to generate polyimide as a precursor, and then heating and ring-closing (imidizing) it. For example, the acid dianhydride and the diamine compound are dissolved in an organic solvent at approximately equal moles, and stirred at a temperature in the range of 0°C to 100°C for 30 minutes to 72 hours to undergo polymerization reaction, thereby obtaining a polyamide Amino acid. At the time of the reaction, the reaction component is dissolved so that the produced precursor is in the range of 5 wt% to 30 wt% in the organic solvent, preferably 10 wt% to 20 wt%. As the organic solvent used in the polymerization reaction, for example, N,N-dimethyl formamide (N,N-dimethyl formamide, DMF), N,N-dimethylformamide (N,N-dimethyl formamide, acetamide, DMAc), N,N-diethyl acetamide, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP), 2-butanone, dimethyl sulfoxide (dimethyl sulfoxide, DMSO), hexamethylphosphamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, Cresol and so on. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. In addition, the amount of such an organic solvent used is not particularly limited, but it is preferably adjusted so that the concentration of the polyamide acid solution obtained by the polymerization reaction becomes about 5 to 30% by weight.

The synthesized polyamide acid is generally advantageously used as a reaction solvent solution, and can be concentrated, diluted, or replaced with other organic solvents as necessary to form a resin composition. The method for imidizing the polyamide is not particularly limited. For example, it can be preferably used in the solvent and heating under a temperature in the range of 80°C to 400°C for 1 hour to 24 hours. One heat treatment.

＜Allocation composition＞ The content of the silicon dioxide particles in the resin composition is in the range of 30% by volume to 70% by volume, preferably in the range of 30% by volume to 60% by volume, relative to the polyamide acid or polyimide. If the content of silicon dioxide particles is less than 30% by volume, the effect of reducing the dielectric loss tangent cannot be sufficiently obtained. In addition, if the content of silicon dioxide particles exceeds 70% by volume, the resin film will become brittle and bendability will decrease. In addition, when the resin film is to be formed, the viscosity of the resin composition will increase and the workability will also increase. reduce.

The resin composition of this embodiment may contain an organic solvent. Examples of the organic solvent include: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl 2-pyrrolidone (NMP), 2-butanone, dimethyl sulfide (DMSO), hexamethylphosphamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxins Alkane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, cresol, etc. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. The content of the organic solvent is not particularly limited, but it is preferably adjusted so that the concentration of polyamide acid or polyimide is used in an amount of about 5% to 30% by weight.

Furthermore, the resin composition of this embodiment may contain inorganic fillers or organic fillers other than the said silica particle as needed, in the range which does not impair the effect of this invention. Specifically, for example, silicon dioxide particles or inorganic fillers such as aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride that do not meet the above conditions can be cited , Organic fillers such as fluorine-based polymer particles or liquid crystal polymer particles. These can be used singly or in combination of two or more. Furthermore, if necessary, plasticizers, hardening accelerators, coupling agents, fillers, pigments, flame retardants, etc. can be suitably formulated as other optional components.

＜Viscosity＞ As the viscosity range for improving the handleability when applying the resin composition and facilitating the formation of a uniform thickness of the coating film, the viscosity of the resin composition is preferably in the range of 3000 cps to 100,000 cps, and more preferably 5000 cps. Within the range of ~50,000 cps. If it deviates from the above-mentioned viscosity range, defects such as uneven thickness and streaks are likely to occur on the film when the coating operation is performed using a coater or the like.

＜Preparation of resin composition＞ When preparing the resin composition, for example, silica particles can be directly blended in a resin solution of polyamide acid. Or considering the dispersibility of the filler, it is also possible to pre-prepare silica particles in a reaction solvent containing any one of the acid dianhydride component and the diamine component as the raw material of the polyamide acid, and then add the other silica particles under stirring. A raw material is polymerized. In either method, the silicon dioxide particles can be added all at once, or added little by little. In addition, the raw materials can also be put together, or they can be mixed little by little.

[Resin Film] The resin film of this embodiment is a resin film having a single or multiple polyimide layers, and at least one layer of the polyimide layer is a silicon dioxide-containing polyimide layer containing a cured product of the resin composition That's it.

In the resin film, the thickness of the silicon dioxide-containing polyimide layer formed of the resin composition is, for example, preferably in the range of 10 μm to 200 μm, and more preferably in the range of 25 μm to 100 μm. If the thickness of the silicon dioxide-containing polyimide layer is less than 10 μm, the resin film becomes brittle, and the effect of improving the dielectric properties of the resin film cannot be sufficiently obtained. Conversely, if the thickness of the silicon dioxide-containing polyimide layer exceeds 200 μm, there is a tendency that the flexibility of the resin film decreases.

The thickness of the entire resin film is, for example, preferably in the range of 10 μm to 200 μm, and more preferably in the range of 25 μm to 100 μm. If the thickness of the resin film is less than 10 μm, defects such as wrinkles in the metal foil and cracks in the resin film are likely to occur in the transport step when manufacturing the metal-clad laminate. Conversely, if the thickness of the resin film exceeds 200 μm, there is a tendency for disadvantages such as reduction in the bendability of the resin film.

In addition, the ratio of the thickness of the polyimide layer containing silicon dioxide to the thickness of the entire resin film is preferably 50% or more. When the ratio of the thickness of the silicon dioxide-containing polyimide layer to the thickness of the entire resin film is less than 50%, the effect of improving the dielectric properties cannot be sufficiently obtained.

The method of forming the silicon dioxide-containing polyimide layer can adopt a known method without particular limitation. The most representative example is shown here. First, the resin composition is directly cast-coated on an arbitrary supporting substrate to form a coating film. Next, the coating film is dried and removed to a certain extent at a temperature of 150°C or less. In the case where the resin composition contains polyamide acid, the coating film is then applied at a temperature range of 100°C to 400°C, preferably 130°C to 360°C, for 5 minutes to 30 minutes for further imidization. About the heat treatment. In this way, a polyimide layer containing silicon dioxide can be formed on the supporting substrate. In the case of a polyimide layer having two or more layers, the resin solution of the first polyamide acid is applied and dried, and then the resin solution of the second polyamide acid is applied and dried. Thereafter, in the same manner as the third polyamide resin solution, the fourth polyamide resin solution, ..., the polyamide resin solution is sequentially applied and dried as many times as necessary. After that, it is preferable to perform a heat treatment in a temperature range of 100°C to 400°C for about 5 minutes to 30 minutes to perform imidization. If the temperature of the heat treatment is lower than 100°C, the dehydration ring-closing reaction of the polyimide may not proceed sufficiently, and on the contrary, if it exceeds 400°C, the polyimide layer may deteriorate.

In addition, another example of forming a polyimide layer containing silicon dioxide is given. First, the resin composition is stream-coated onto an arbitrary supporting base material to be molded into a film shape. The self-supporting gel film is prepared by heating and drying the film-like molded article on a supporting substrate. After the gel film is peeled from the supporting substrate, when the resin composition contains polyamide, it is further heat-treated at a high temperature to be imidized to form a polyimide resin film.

The support substrate used to form the silicon dioxide-containing polyimide layer is not particularly limited, and a substrate of any material can be used. In addition, when forming the resin film, it is not necessary to form a resin film that has completely completed the imidization on the substrate. For example, it is also possible to separate the resin film in the semi-cured state of the polyimide precursor state from the supporting substrate by a method such as peeling, and complete the imidization after the separation to form a resin film.

The resin film may only include a polyimide layer containing an inorganic filler (including the silicon dioxide-containing polyimide layer), or may have a polyimide layer that does not contain an inorganic filler. When the resin film has a multilayer laminate structure, considering the improvement of dielectric properties, it is preferable that all layers contain an inorganic filler. Among them, by making the layer adjacent to the polyimide layer containing the inorganic filler a layer that does not contain the inorganic filler or a layer with a low content, there is an advantageous effect of preventing the inorganic filler from slipping off during processing. In the case of having a polyimide layer containing no inorganic filler, its thickness is preferably set to, for example, within the range of 1/100 to 1/2 of that of the polyimide layer containing inorganic filler, and is preferably set to 1/ Within the range of 20～1/3. In the case of having a polyimide layer that does not contain an inorganic filler, if the polyimide layer is in contact with the metal layer, the adhesion between the metal layer and the insulating resin layer is improved.

The coefficient of thermal expansion (CTE) of the resin film is not particularly limited. For example, it is preferably 10×10 ^-6 /K～60×10 ^-6 /K (10 ppm/K～60 ppm/K). Within the range, it is more preferably within the range of 20×10 ^-6 /K to 50×10 ^-6 /K (20 ppm/K to 50 ppm/K). If the thermal expansion coefficient of the resin film is less than 10×10 ^-6 /K, curling is likely to occur after the metal-clad laminate is made, and handling properties are poor. On the other hand, if the thermal expansion coefficient of the resin film exceeds 60×10 ^-6 /K, the dimensional stability as an electronic material such as a flexible substrate is poor, and the heat resistance also tends to decrease.

＜Dielectric loss tangent＞ For example, when the resin film is suitable as an insulating resin layer of a circuit board, in order to reduce the dielectric loss during high-frequency signal transmission, the entire film is measured with a split post dielectric resonator (SPDR) The dielectric loss tangent (Tanδ) at 3 GHz to 20 GHz is preferably 0.006 or less, more preferably 0.004 or less. In order to improve the transmission loss of the circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer. By setting the dielectric loss tangent within the above range, the effect of reducing the transmission loss increases. Therefore, when the resin film is applied as an insulating resin layer of, for example, a high-frequency circuit board, transmission loss can be efficiently reduced. If the dielectric loss tangent at 3 GHz to 20 GHz exceeds 0.006, when the resin film is used as the insulating resin layer of the circuit board, problems such as increased loss of electrical signals on the transmission path of high-frequency signals are likely to occur. . The lower limit of the dielectric loss tangent at 3 GHz to 20 GHz is not particularly limited, but it is necessary to consider the control of physical properties when the resin film is used as the insulating resin layer of the circuit board.

＜Relative dielectric constant＞ For example, when the resin film is suitable as an insulating resin layer of a circuit board, in order to ensure impedance matching, it is preferable that the relative dielectric constant at 3 GHz to 20 GHz is 4.0 or less as the entire film. If the relative dielectric constant at 3 GHz to 20 GHz exceeds 4.0, when the resin film is used as the insulating resin layer of the circuit board, the dielectric loss will deteriorate, and electrical signals will easily occur on the transmission path of high-frequency signals. The loss becomes larger and other undesirable conditions.

＜Metal clad laminates＞ 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 includes the resin film. The metal-clad laminate may be a single-sided metal-clad laminate having a metal layer only on one side of the insulating resin layer, or may be a double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer.

The metal-clad laminate of the present embodiment does not exclude the use of an adhesive for bonding the polyimide layer containing an inorganic filler to the metal foil. Among them, in the case where an adhesive layer is interposed between a metal-clad laminate having metal layers on both sides of the insulating resin layer, in order not to impair the dielectric properties, the thickness of the adhesive layer is preferably set to be less than the thickness of the entire insulating resin layer 30%, more preferably set to less than 20%. In addition, when an adhesive layer is interposed 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 preferably set to be less than full insulation in order not to impair the dielectric properties. 15% of the thickness of the resin layer, more preferably less than 10%. In addition, the adhesive layer constitutes a part of the insulating resin layer, so it is preferably a polyimide layer. From the viewpoint of imparting heat resistance, the glass transition temperature of the silicon dioxide-containing polyimide, which is the main material of the insulating resin layer, is preferably set to 300°C or higher. When the glass transition temperature is 300°C or higher, the acid dianhydride or diamine component constituting the polyimide can be appropriately selected.

As a method of manufacturing a metal-clad laminate having a resin film as an insulating resin layer, for example, a method of heating and pressing a metal foil to the resin film directly or via an arbitrary adhesive, or a method such as metal vapor deposition The method of forming the metal layer on the resin film, etc. In addition, the double-sided metal-clad laminate can be formed by, for example, forming a single-sided metal-clad laminate, and then make the polyimide layers face each other and press them to form a method, or press metal foil on It can be obtained by the method of forming the polyimide layer of the single-sided metal-clad laminate.

＜Metal layer＞ The material of the metal layer is not particularly limited. Examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and these Alloys and so on. Among them, copper or copper alloy is particularly preferred. The metal layer may include a metal foil, or may have a metal vapor-deposited on the film. In addition, in terms of being able to directly apply the resin composition, a metal foil or a metal plate can be used, and a copper foil or a copper plate is preferred.

The thickness of the metal layer is appropriately set according to the purpose of use of the metal-clad laminate, and therefore is not particularly limited. For example, it is preferably in the range of 5 μm to 3 mm, and more preferably in the range of 12 μm to 1 mm. If the thickness of the metal layer is less than 5 μm, defects such as wrinkles may occur during transportation such as the manufacture of the metal-clad laminate. Conversely, if the thickness of the metal layer exceeds 3 mm, it will become hard and workability will deteriorate. Regarding the thickness of the metal layer, a thick metal layer is generally suitable for applications such as a circuit board for vehicles, and a thin metal layer is suitable for applications such as a circuit board for LEDs. [Example]

Hereinafter, the content of the present invention will be specifically described based on examples, but the present invention is not limited to the scope of these examples. In addition, in the following examples, unless otherwise specified, various measurements and evaluations were performed as follows.

[Determination of particle size] A laser diffraction particle size distribution measuring device (manufactured by Malvern, trade name: Master Sizer 3000) was used, water was used as the dispersion medium, and the particle refractive index was 1.54. The diffraction-scattering method is used to measure the particle size.

[Method of measuring true specific gravity] Use a continuous automatic powder true density measuring device (manufactured by Seishin Corporation, trade name: AUTO TRUE DENSERMAT-7000), using a pycnometer method (liquid phase displacement method) Determination of true specific gravity.

[Determination of specific surface area] According to the Japanese Industrial Standards (JIS) Z 8830:2013, the BET specific surface area measurement method is used, and the specific surface area measurement device (manufactured by Mountech Co., Ltd., trade name: Macsorb 210) ) Determine the specific surface area.

[Measurement of relative permittivity and dielectric loss tangent] <Silicon dioxide particles> Using a dielectric constant measurement device manufactured by Kanto Electronics Application Development Co., Ltd. using the cavity perturbation method to measure silicon dioxide particles at a predetermined frequency The relative permittivity (ε ₁ ) and the dielectric loss tangent (Tanδ ₁ ). Furthermore, the inner diameter of the sample tube is 1.68 mm, the outer diameter is 2.28 mm, and the height is 8 cm. <Resin film> Using a vector network analyzer (manufactured by Agilent, trade name: vector network analyzer E8363C) and an SPDR resonator, the resin film (cured resin) at a specified frequency is measured Film) relative permittivity (ε ₁ ) and dielectric loss tangent (Tanδ ₁ ). In addition, the resin film used in the measurement was left for 24 hours under the conditions of temperature: 24°C to 26°C and humidity: 45% to 55%.

[Determination of Viscosity] The viscosity of the resin solution was measured using an E-type viscometer (manufactured by Brookfield, trade name: DV-II+Pro) at 25°C. Set the rotation speed so that the torque is 10% to 90%. After 2 minutes have passed after the start of the measurement, read the value when the viscosity is stable.

[Determination of Coefficient of Thermal Expansion (CTE)] For a polyimide film with a size of 3 mm×20 mm, a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA) was used, and a load of 5.0 g was applied and the temperature was increased from 30 to 30 at a heating rate of 10°C/min. The temperature was raised to 250°C, and then kept at the temperature for 10 minutes, then cooled at a rate of 5°C/min, and the average coefficient of thermal expansion (coefficient of thermal expansion, CTE) from 250°C to 100°C was obtained.

[Evaluation of Flexibility] 1) 180° bendability: According to JISK5600-1, the center of the long side of the resin film with a size of 5 cm×10 cm is wound on a metal rod of 5 mmϕ and uniformly bent in 1 to 2 seconds, and the resin film is bent even at 180° If there is no break or crack, it is set as “good”, and if there is a break or crack, it is set as “not”. 2) Foldability: After folding the resin film with a size of 5 cm×5 cm into a triangle along the diagonal, return it to its original shape. Set the resin film with no breaks or cracks as "Yes", and set the resin film with breaks or cracks as "No".

The abbreviations used in the examples and the like indicate the following compounds. m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene BAPP: 2,2-bis[ 4-(4-Aminophenoxy)phenyl]propane TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl PMDA: pyromellitic dianhydride BPDA: 3,3',4,4'-Biphenyltetracarboxylic dianhydride 6FDA: 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride DMAc: N,N-dimethylethane Amide filler 1: manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SP40-10 (spherical amorphous silica powder, spherical, silica content rate: 99.9% by weight, true specific gravity: 2.21, ratio Surface area: 8.6 m ² /g, D ₅₀ : 2.5 μm, D ₁₀₀ : 30 μm) Filler 2: manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SPH507 (spherical amorphous silicon dioxide powder, spherical, Silicon dioxide content: 99.99% by weight, true specific gravity: 2.21, specific surface area: 6.4 m ² /g, D ₅₀ : 0.83 μm, D ₁₀₀ : 8.7 μm) Filler 3: manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SPH516M (spherical amorphous silica powder, spherical, silica content: 99.98% by weight, true specific gravity: 2.21, specific surface area: 12.7 m ² /g, D ₅₀ : 0.64 μm, D ₁₀₀ : 1.3 μm) Filler 4: manufactured by Admatech, trade name: SE4050 (spherical amorphous silicon dioxide powder, spherical, silicon dioxide content: 99.99% by weight, true specific gravity: 2.2, ratio Surface area: 4.6 m ² /g, D ₅₀ : 1.5 μm, D ₁₀₀ : 6.0 μm)

The relative dielectric constants and dielectric loss tangents of fillers 1 to 4 are as follows. <Filling 1> 1) Relative permittivity ε ₁ under 3 GHz: 3.05, Dielectric loss tangent Tanδ ₁ : 0.0028 2) Relative permittivity ε ₁ under 5 GHz: 2.97, Dielectric loss tangent Tanδ ₁ ：0.0028 3) Relative permittivity ε ₁ under 10 GHz: 2.78, Dielectric loss tangent Tanδ ₁ : 0.003 <filler 2> 1) Relative permittivity ε ₁ under 3 GHz: 2.98, Dielectric loss tangent Tanδ ₁ : 0.0025 2) Relative permittivity ε ₁ under 5 GHz: 2.99, Dielectric loss tangent Tanδ ₁ : 0.0026 3) Relative permittivity ε ₁ under 10 GHz: 2.88, Dielectric loss tangent Tanδ ₁ ：0.0027 ＜filler 3＞ 1) Relative permittivity ε _{1 at} 3 GHz: 2.88, Dielectric loss tangent Tanδ ₁ : 0.004 2) Relative permittivity ε _{1 at} 5 GHz: 2.82, Dielectric loss tangent Tanδ ₁ ：0.0039 3) Relative permittivity ε _{1 at} 10 GHz: 2.76, Dielectric loss tangent Tanδ ₁ : 0.004 <filler 4> 1) Relative permittivity ε _{1 at} 3 GHz: 3.10, dielectric loss Angular tangent _{Tanδ 1} : 0.0049 2) Relative permittivity ε _{1 at} 5 GHz: 3.06, Dielectric loss tangent _{Tanδ 1} : 0.0049 3) Relative permittivity ε _{1 at} 10 GHz: 2.92, Dielectric loss tangent Tanδ ₁ : 0.0052

(Synthesis example 1~Synthesis example 4) In order to synthesize polyamic acid solution A to solution D, in a 3000 ml separable flask under nitrogen flow, DMAc of the solvent was added so as to achieve the solid content concentration shown in Table 1, and the two components shown in Table 1 were stirred. The amine component and the acid anhydride component are dissolved at room temperature for 10 minutes. After that, the solution was continuously stirred at room temperature for 10 hours and polymerization reaction was carried out, thereby preparing viscous solutions A to D of polyamic acid.

[Table 1] Synthesis example Polyamide acid solution type Viscosity [cps] Diamine component [g] Anhydride component [g] DMAc [g] Solid content concentration [wt%] 1 A 22,400 m-TB (159.25) TPE-R (24.32) PMDA (143.12) BPDA (48.31) 2125 15 2 B 33,040 m-TB (176.97) BAPP (10.55) PMDA (175.06) BPDA (12.42) 2125 15 3 C 21,074 BAPP (243.32) PMDA (143.12) BPDA (8.74) 2125 15 4 D 28,000 TFMB (156.45) 6FDA (218.55) 2125 15

[Example 1] 100.24 g of polyamide acid solution A and 9.37 g of filler 1 were mixed, and stirred until they became the same solution visually, to prepare polyamide acid solution 1 (viscosity: 27,500 cps, filler relative to polyamide Amino acid content: 30% by volume). The polyamide acid solution 1 was coated on a copper foil 1 (electrolytic copper foil, thickness: 12 μm), and dried at 130° C. for 3 minutes. After that, stepwise heat treatment is performed from 155° C. to 360° C. and imidization is performed, thereby preparing the metal-clad laminate 1. The copper foil of the metal-clad laminate 1 is removed by etching, and a resin film 1 is prepared. The CTE of resin film 1 (thickness: 40 μm) is 33 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 1 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0047 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0054 3) 20 GHz tangent Tanδ _1: 0.0056

[Example 2] 100.36 g of polyamide acid solution A and 21.88 g of filler 1 were mixed, and stirred until they became the same solution visually, to prepare polyamide acid solution 2 (viscosity: 28,400 cps, filler relative to polyamide Amino acid content: 50% by volume). In the same manner as in Example 1, a metal-clad laminate 2 and a resin film 2 were prepared. The CTE of the resin film 2 (thickness: 42 μm) is 31 ppm/K, 180° bendability is good, and foldability is not. In addition, the dielectric loss tangent of the resin film 2 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0043 2) 10 GHz tangent Tanδ _1: 0.0047 3) dielectric loss tangent angle at 20 GHz Tanδ _1: 0.0049

[Example 3] 99.92 g of polyamide acid solution B and 9.33 g of filler 1 were mixed and stirred until they became the same solution visually to prepare polyamide acid solution 3 (viscosity: 29,000 cps, filler relative to polyamide Amino acid content: 30% by volume). In the same manner as in Example 1, a metal-clad laminate 3 and a resin film 3 were prepared. The CTE of the resin film 3 (thickness: 41 μm) is 35 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 3 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0029 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0033 3) 20 GHz tangent Tanδ _1: 0.0035

[Example 4] 100.00 g of polyamide acid solution B and 21.81 g of filler 1 were mixed, and stirred until it became the same solution visually to prepare polyamide acid solution 4 (viscosity: 31,000 cps, filler relative to polyamide Amino acid content: 50% by volume). In the same manner as in Example 1, a metal-clad laminate 4 and a resin film 4 were prepared. The CTE of the resin film 4 (thickness: 44 μm) is 30 ppm/K, 180° bendability is good, and foldability is not. In addition, the dielectric loss tangent of the resin film 4 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0028 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0030 3) 20 GHz tangent Tanδ _1: 0.0031

[Example 5] 80.00 g of polyamide acid solution C and 7.88 g of filler 1 were mixed and stirred until they became the same solution visually to prepare polyamide acid solution 5 (viscosity: 24,000 cps, filler relative to polyamide Amino acid content: 30% by volume). In the same manner as in Example 1, a metal-clad laminate 5 and a resin film 5 were prepared. The CTE of the resin film 5 (thickness: 46 μm) is 41 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 5 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0046 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0052 3) 20 GHz tangent Tanδ _1: 0.0055

[Example 6] 80.00 g of polyamide acid solution D and 7.92 g of filler 1 were mixed and stirred until they became the same solution visually to prepare polyamide acid solution 6 (viscosity: 23,000 cps, filler relative to polyamide Amino acid content: 30% by volume). In the same manner as in Example 1, a metal-clad laminate 6 and a resin film 6 were prepared. The CTE of the resin film 6 (thickness: 45 μm) is 46 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 6 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0046 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0052 3) 20 GHz tangent Tanδ _1: 0.0055

[Example 7] 80.00 g of polyamide acid solution D and 18.49 g of filler 1 were mixed and stirred until they became the same solution visually to prepare polyamide acid solution 7 (viscosity: 31,000 cps, filler relative to polyamide Amino acid content: 50% by volume). In the same manner as in Example 1, a metal-clad laminate 7 and a resin film 7 were prepared. The CTE of the resin film 7 (thickness: 48 μm) is 28 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 7 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0051 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0054 3) 20 GHz tangent Tanδ _1: 0.0055

(Comparative Example 1) The polyamide acid solution A was coated on the copper foil 1, and dried at 130°C for 3 minutes. After that, stepwise heat treatment is performed from 155° C. to 360° C. and imidization is performed to prepare a metal-clad laminate 8. In the same manner as in Example 1, a metal-clad laminate 8 and a resin film 8 were prepared. The CTE of the resin film 8 (thickness: 42 μm) is 17 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 8 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0052 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0062 3) 20 GHz tangent Tanδ _1: 0.0065

(Comparative Example 2) The polyamide acid solution B was coated on the copper foil 1, and dried at 130°C for 3 minutes. After that, stepwise heat treatment is performed from 155° C. to 360° C. and imidization is performed, thereby preparing the metal-clad laminate 9. In the same manner as in Example 1, a metal-clad laminate 9 and a resin film 9 were prepared. The CTE of the resin film 9 (thickness: 43 μm) is 18 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 9 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0032 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0037 3) 20 GHz tangent Tanδ _1: 0.0040

(Comparative Example 3) The polyamide acid solution C was coated on the copper foil 1, and dried at 130°C for 3 minutes. After that, stepwise heat treatment is performed from 155° C. to 360° C. and imidization is performed, so that the metal-clad laminate 10 is prepared. In the same manner as in Example 1, a metal-clad laminate 10 and a resin film 10 were prepared. The CTE of the resin film 10 (thickness: 41 μm) is 51 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 10 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0055 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0062 3) 20 GHz tangent Tanδ _1: 0.0068

(Comparative Example 4) The polyamide acid solution D was coated on the copper foil 1, and dried at 130°C for 3 minutes. After that, stepwise heat treatment is performed from 155° C. to 360° C. and imidization is performed, so that the metal-clad laminate 11 is prepared. In the same manner as in Example 1, a metal-clad laminate 11 and a resin film 11 were prepared. The CTE of the resin film 11 (thickness: 42 μm) is 71 ppm/K, 180° bendability is good, and foldability is acceptable. In addition, the dielectric loss tangent of the resin film 11 is as follows. 1) a dielectric loss tangent angle at 5 GHz Tanδ _1: dielectric loss angle at 0.0069 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0077 3) 20 GHz tangent Tanδ _1: 0.0079

[Comparative Example 5] 100.24 g of polyamide acid solution A and 9.37 g of filler 4 were mixed, and stirred until they became the same solution visually, to prepare polyamide acid solution 12 (viscosity: 28,000 cps, filler relative to polyamide Amino acid content: 30% by volume). In the same manner as in Example 1, the metal-clad laminate 12 and the resin film 12 were prepared. The CTE of the resin film 12 (thickness: 44 μm) is 34 ppm/K, and both 180° bendability and foldability are impossible. In addition, the dielectric loss tangent of the resin film 12 is as follows. 1) a dielectric loss tangent at 5 GHz tangent Tanδ _1: dielectric loss angle at 0.0051 2) 10 GHz tangent Tanδ _1: dielectric loss angle at 0.0054 3) 20 GHz tangent Tanδ _1: 0.0055 or more, for illustrative The purpose of is to describe the embodiments of the present invention in detail, but the present invention is not restricted by the embodiments and can be modified in various ways.

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Claims (5)

A silicon dioxide particle used in the frequency range of 3 GHz to 20 GHz. The silicon dioxide particle is characterized by: a frequency distribution curve obtained by a volume-based particle size distribution measurement using a laser diffraction scattering method The average particle size D ₅₀ is within the range of 0.3 μm to 3 μm, and the specific surface area is within the range of more than 5 m ² /g and 20 m ² /g or less, using the cavity perturbation method. The measured dielectric loss tangent is 0.004 or less. A resin composition containing the silicon dioxide particles according to claim 1 and polyamide acid or polyimide, the resin composition being characterized by: The content of the silicon dioxide particles is in the range of 30% by volume to 70% by volume relative to the polyamide acid or polyimide. A resin film having a single-layer or multi-layer polyimide layer, and the resin film is characterized in: At least one layer of the polyimide layer is a silicon dioxide-containing polyimide layer containing a cured product of the resin composition as described in claim 2, and the silicon dioxide-containing polyimide layer is The thickness is in the range of 10 μm to 200 μm. The resin film according to claim 3, wherein the thickness of the entire resin film is in the range of 10 μm to 200 μm, and the proportion of the thickness of the silicon dioxide-containing polyimide layer is 50% or more. A metal-clad laminated board includes an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer. The metal-clad laminated board is characterized in that: The insulating resin layer includes the resin film as described in claim 3 or 4.