TWI893017B - Silicon dioxide particles, resin composition, resin film and metal-clad laminate - Google Patents

Abstract

The present invention provides silicon dioxide particles capable of improving dielectric properties without compromising mechanical properties such as bendability, as well as a resin composition, a resin film, and a metal-clad laminate having improved dielectric properties by adding the silicon dioxide particles. The silica particles are used in a frequency range of 3 GHz to 20 GHz, have a mean particle size ( _D50) of 0.3 μm to 3 μm, and a specific surface area of more than 5 ^m² /g but less than 20 ^m² /g. The dielectric loss tangent (DLT) measured by the cavity perturbation method is 0.004 or less. The resin composition contains the silica particles and polyamide or polyimide, with the silica particle content ranging from 30 volume percent to 70 volume percent relative to the polyamide or polyimide.

Description

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

The present invention relates to silicon dioxide particles that can be preferably used in electrical and/or electronic devices used in high-frequency regions, a resin composition containing the silicon dioxide particles, a resin film using the resin composition, and a metal-clad laminate.

In recent years, demand for smaller and lighter electronic devices, such as mobile phones, light-emitting diode (LED) lighting fixtures, and parts surrounding automobile engines, has steadily increased. Consequently, flexible circuit boards, which contribute significantly to these reductions, have become widely used in the electronics field. In particular, flexible circuit boards using polyimide as the insulating layer are gaining widespread use due to their excellent heat and chemical resistance.

Meanwhile, with the advancement of performance and functionality in electrical and/or electronic devices, high-speed information transmission continues to advance. Consequently, components and parts used in these devices are also required to support high-speed transmission. To achieve electrical properties compatible with high-speed transmission, resin materials used in these applications are being sought to achieve low dielectric constants and dielectric loss tangents. For example, a low-dielectric resin composition has been proposed, in which a filler such as silica with a particle size of 1 μm or less is blended into polyimide at a level of 5% to 70% by weight of the total solids (Patent Document 1). In order to achieve a low dielectric loss tangent, a thermosetting resin composition has been proposed in which an inorganic filler such as silica is blended at a concentration of 60% by mass or more into a polyimide having structural units derived from a bismaleimide compound (Patent Document 2).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent No. 3560501

[Patent Document 2] Japanese Patent Publication No. 2018-012747

Silica particles tend to have a lower dielectric loss tangent as their particle size increases. Even when blended into resins such as polyimide, they significantly reduce the dielectric loss tangent of the resulting resin film. However, adding large silica particles can reduce the flexibility of the resin film.

The present invention aims to provide silica particles that can improve dielectric properties without compromising mechanical properties such as bendability, and further to provide a resin composition and resin film having improved dielectric properties by adding the silica particles.

The silica particles of the present invention are for use in the frequency range of 3 GHz to 20 GHz. The average particle size ( _D50) at which 50% of the cumulative value in the frequency distribution curve, as determined by volume-based particle size distribution measurement using the laser diffraction scattering method, is within the range of 0.3 μm to 3 μm. The specific surface area is within the range of greater than 5 ^m² /g and less than 20 ^m² /g. Furthermore, the dielectric loss tangent, as measured by the cavity perturbation method, is less than 0.004.

The resin composition of the present invention is a resin composition containing the silica particles and polyamic acid or polyimide. The content of the silica particles is in the range of 30 volume % to 70 volume % relative to the polyamic acid or polyimide.

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

The overall thickness of the resin film of the present invention can be in the range of 10 μm to 200 μm, and the thickness ratio of the silicon dioxide-containing polyimide layer can be greater than 50%.

The metal-clad laminate of the present invention comprises an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, wherein the insulating resin layer includes the resin film.

Despite having a small average particle size ( _D50 ) ranging from 0.3 μm to 3 μm, the silica particles of the present invention exhibit a low dielectric loss tangent due to controlled specific surface area, making them effective as insulating materials for high-frequency applications. Furthermore, the inclusion of these silica particles in the resin composition of the present invention improves dielectric properties without compromising mechanical properties such as flexibility. Therefore, electrical and/or electronic devices or electronic components using the resin composition of the present invention can cope with increasing high-speed transmission while ensuring reliability.

The following describes the implementation of the present invention.

[Silicon dioxide particles]

The silica particles of one embodiment of the present invention are used in the frequency range of 3 GHz to 20 GHz. More specifically, the silica particles are used as a material for parts or components in electrical and/or electronic devices used in the frequency range of 3 GHz to 20 GHz. The silica particles of this embodiment are preferably spherical in shape. Furthermore, the term "spherical" refers to particles having a shape that is nearly spherical and a ratio of the average major diameter to the average minor diameter of 1 or close to 1.

The silica particles of this embodiment have an average particle size ( _D50) , at which 50% of the cumulative values in the frequency distribution curve obtained by volume-based particle size distribution measurement using the laser diffraction scattering method are within the range of 0.3 μm to 3 μm, preferably 0.5 μm to 2.5 μm. Within this range, for example, a decrease in flexibility when blended into a resin film can be suppressed, while simultaneously improving dielectric properties. If the average particle size ( _D50 ) of the silica particles is less than 0.3 μm, the effect of reducing the dielectric loss tangent cannot be fully achieved. On the other hand, if the average particle size (D50 ₎ exceeds 3 μm, maintaining mechanical properties, such as reduced flexibility, becomes difficult when blended into a resin film.

Furthermore, the specific surface area of the silica particles of this embodiment is within the range of greater than 5 ^m² /g and less than 20 ^m² /g, preferably between 6 ^m² /g and 15 ^m² /g. By setting the specific surface area of the silica particles within this range, the volume density of the silica particles can be increased, thereby achieving a low dielectric loss tangent even with an average particle size _D50 as small as 0.3 μm to 3 μm. Specifically, the dielectric loss tangent of the silica particles, as measured by the cavity perturbation method, can be set to 0.004 or less. If the specific surface area is less than 5 m ² /g or exceeds 20 m ² /g, the dielectric loss tangent of the silica particles will not be sufficiently reduced, and the blending effect cannot be achieved. The specific surface area of silica particles can be determined using the Brunauer-Emmett-Teller (BET) specific surface area measurement method.

Furthermore, commercially available silica particles can be appropriately selected and used. For example, spherical amorphous silica powder (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: SP40-10), spherical amorphous silica powder (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: SPH507), and spherical amorphous silica powder (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: SPH516M) are preferably used. Two or more of these can be used in combination.

[Resin composition]

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

<Polyamide or polyimide>

Polyimide is generally represented by the following general formula (1). Such polyimide can be produced by a known method using substantially equal molar amounts of a diamine component and an acid dianhydride component for polymerization in an organic polar solvent. In this case, the molar ratio of the acid dianhydride component to the diamine component can be adjusted to achieve a desired viscosity, preferably within a molar ratio range of 0.980 to 1.03, for example.

Here, _Ar1 is a tetravalent organic group having one or more aromatic rings, and _Ar2 is a divalent organic group having one or more aromatic rings. Furthermore, _Ar1 can be considered a residual group of an acid dianhydride, and _Ar2 can be considered a residual group of a diamine. Furthermore, n represents the number of repetitions of the structural unit of general formula (1), and is 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 preferred, and examples thereof include acid dianhydrides that provide the following aromatic acid anhydride residue as Ar ₁ .

[Chemistry 2]

Acid dianhydrides can be used alone or in combination of two or more. Among these, preferably used are those selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), and 4,4'-oxydiphthalic dianhydride (ODPA).

As the diamine, for example, an aromatic diamine represented by H ₂ N—Ar ₂ —NH ₂ is preferred, and examples thereof include aromatic diamines having the following aromatic diamine residue as Ar ₂ .

[Chemistry 3]

Examples of these diamines include diaminodiphenyl ether (DAPE), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), paraphenylene diamine (p-PDA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (2,2-bis[4-(4-aminophenoxy)phenyl]propane). 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 a polyamide precursor, which is then heated to undergo ring closure (imidization). For example, the acid dianhydride and the diamine compound are dissolved in an organic solvent at approximately equimolar amounts and stirred at a temperature between 0°C and 100°C for 30 minutes to 72 hours to allow polymerization to proceed, thereby obtaining the polyamide. During the reaction, the reaction components are dissolved so that the generated precursor concentration in the organic solvent 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), hexamethylphosphatamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and cresol. 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 amount of the organic solvent used is not particularly limited, but it is preferably adjusted so that the concentration of the polyamide solution obtained by the polymerization reaction is approximately 5% to 30% by weight.

The synthesized polyamine is typically used as a reaction solvent solution. It can be concentrated, diluted, or replaced with another organic solvent as needed to form a resin composition. The method for imidizing the polyamine is not particularly limited; for example, a heat treatment in the aforementioned solvent at a temperature between 80°C and 400°C for 1 to 24 hours is preferably employed.

<Blending composition>

The content of silica particles in the resin composition is within the range of 30% to 70% by volume, preferably 30% to 60% by volume, relative to polyamide or polyimide. If the silica particle content is less than 30% by volume, the dielectric loss tangent reduction effect cannot be fully achieved. Furthermore, if the silica particle content exceeds 70% by volume, the resulting resin film becomes brittle, reducing its bendability. Furthermore, the viscosity of the resin composition increases during film formation, reducing workability.

The resin composition of this embodiment may contain an organic solvent. Examples of such organic solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphatamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and cresol. 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 to a concentration of about 5% to 30% by weight of the polyamide or polyimide.

Furthermore, the resin composition of this embodiment may optionally contain inorganic or organic fillers other than the aforementioned silica particles, as long as the effects of the invention are not impaired. Specifically, examples include silica particles that do not meet the aforementioned conditions, inorganic fillers such as aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride, and organic fillers such as fluorine-based polymer particles or liquid crystal polymer particles. These may be used alone or in combination. Furthermore, as necessary, plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants, and the like may be appropriately blended as other optional ingredients.

<Viscosity>

To improve the handling of the resin composition during application and facilitate the formation of a uniformly thick coating film, the viscosity of the resin composition is preferably within the range of 3,000 cps to 100,000 cps, and more preferably within the range of 5,000 cps to 50,000 cps. If the viscosity deviates from this range, defects such as uneven thickness and streaks may occur on the film during application using a coating machine.

<Preparation of resin composition>

When preparing the resin composition, for example, silica particles can be directly mixed into the polyamide resin solution. Alternatively, considering the dispersibility of the filler, silica particles can be pre-mixed in a reaction solvent containing either the dianhydride component or the diamine component, the raw materials for polyamide, and then the other raw materials can be added under stirring to carry out polymerization. In either method, the silica particles can be added all at once or added incrementally over several times. Furthermore, the raw materials can be added all at once or mixed incrementally over several times.

[resin film]

The resin film of this embodiment is a resin film having a single or multiple polyimide layers, and at least one of the polyimide layers may be a silicon dioxide-containing polyimide layer comprising a cured product of the resin composition.

In the resin film, the thickness of the silica-containing polyimide layer formed from the resin composition is preferably in the range of 10 μm to 200 μm, more preferably in the range of 25 μm to 100 μm. If the thickness of the silica-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 is not fully achieved. Conversely, if the thickness of the silica-containing polyimide layer exceeds 200 μm, there is a tendency for disadvantages such as a decrease in the bendability of the resin film.

The overall thickness of the resin film is preferably within the range of 10 μm to 200 μm, more preferably 25 μm to 100 μm. If the resin film thickness is less than 10 μm, problems such as wrinkling of the metal foil and tearing of the resin film may occur during the transport step during metal-clad laminate production. Conversely, if the resin film thickness exceeds 200 μm, the film's flexibility may be compromised.

Furthermore, the ratio of the thickness of the silicon dioxide-containing polyimide layer to the overall thickness of the resin film is preferably 50% or greater. If the ratio of the thickness of the silicon dioxide-containing polyimide layer to the overall thickness of the resin film is less than 50%, the dielectric properties cannot be sufficiently improved.

The method for forming the silicon dioxide-containing polyimide layer can be adopted without particular limitation by any known method. The most representative example is shown here.

First, the resin composition is cast directly onto an optional support substrate to form a coating film. Next, the coating film is dried to a certain extent at a temperature below 150°C to remove the solvent. If the resin composition contains polyamide, the coating film is then heat-treated for approximately 5 to 30 minutes at a temperature between 100°C and 400°C, preferably between 130°C and 360°C, for further imidization. This forms a polyimide layer containing silica on the support substrate. When using two or more polyimide layers, apply the first polyamide resin solution and dry it, then apply the second polyamide resin solution and dry it. The third polyamide resin solution, then the fourth polyamide resin solution, and so on, are applied and dried as many times as desired. Afterwards, it is preferable to heat-treat the imidization process at a temperature between 100°C and 400°C for approximately 5 to 30 minutes. If the heat treatment temperature is lower than 100°C, there is a concern that the dehydration and ring-closing reaction of the polyimide may not proceed sufficiently. Conversely, if it exceeds 400°C, there is a concern that the polyimide layer may deteriorate.

In addition, another example of forming a polyimide layer containing silicon dioxide is given.

First, a resin composition is cast onto an optional supporting substrate to form a film. The film-shaped product is then dried on the supporting substrate under heat to produce a self-supporting gel membrane. After the gel membrane is peeled off from the supporting substrate, if the resin composition contains polyamide, it is further heat-treated at high temperatures to imidize it, producing a polyimide resin membrane.

The supporting substrate used to form the silica-containing polyimide layer is not particularly limited; any substrate material may be used. Furthermore, when forming the resin film, it is not necessary to completely imidize the resin film on the substrate. For example, a semi-cured polyimide precursor resin film can be separated from the supporting substrate by peeling or other methods, and imidization can be completed after separation to form the resin film.

The resin film may consist solely of a polyimide layer containing an inorganic filler (including the aforementioned silica-containing polyimide layer) or may include a polyimide layer without an inorganic filler. When the resin film is formed into a multilayer structure, it is preferable that all layers contain an inorganic filler in order to improve dielectric properties. Furthermore, by having the adjacent layer to the polyimide layer containing an inorganic filler be a layer without an inorganic filler, or a layer with a low inorganic filler content, it is advantageously possible to prevent the inorganic filler from slipping during processing. In the case of a polyimide layer without an inorganic filler, its thickness is preferably set within a range of 1/100 to 1/2, and more preferably 1/20 to 1/3, of that of a polyimide layer containing an inorganic filler. In the case of a polyimide layer without an inorganic filler, if the polyimide layer contacts a 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, but is preferably within the range of 10× ^10-6 /K to 60× ^10-6 /K (10ppm/K to 60ppm/K), and more preferably within the range of 20× ^10-6 /K to 50× ^10-6 /K (20ppm/K to 50ppm/K). If the CTE of the resin film is less than 10× ^10-6 /K, it is prone to warping after being fabricated into a metal-clad laminate, resulting in poor handling. On the other hand, if the CTE of the resin film exceeds 60× ^10-6 /K, the dimensional stability of electronic materials such as flexible substrates is poor, and heat resistance tends to decrease.

<Dielectric loss tangent>

When used as an insulating resin layer in a circuit board, for example, a resin film should have a dielectric loss tangent (Tanδ) of 0.006 or less, and more preferably 0.004 or less, in the 3 GHz to 20 GHz range, as measured using a split post dielectric resonator (SPDR). To improve transmission loss in circuit boards, it is particularly important to control the dielectric loss tangent of the insulating resin layer. By keeping the dielectric loss tangent within this range, the effect of reducing transmission loss is maximized. Therefore, when a resin film is used as an insulating resin layer in high-frequency circuit boards, for example, it can effectively reduce transmission loss. If the dielectric loss tangent exceeds 0.006 at 3 GHz to 20 GHz, the resin film can be used as an insulating resin layer on circuit boards, which can lead to problems such as increased electrical signal loss in high-frequency signal transmission paths. While there is no specific lower limit for the dielectric loss tangent at 3 GHz to 20 GHz, physical property control is necessary when using the resin film as an insulating resin layer on circuit boards.

<Relative dielectric constant>

When used as an insulating resin layer on a circuit board, for example, a resin film should preferably have a relative dielectric constant of 4.0 or less at 3 GHz to 20 GHz to ensure impedance matching. A relative dielectric constant exceeding 4.0 at 3 GHz to 20 GHz can lead to deterioration in dielectric loss when used as an insulating resin layer on a circuit board, potentially causing problems such as increased electrical signal loss in high-frequency signal transmission paths.

<Metal clad laminate>

The metal-clad laminate of this embodiment includes an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, wherein at least one layer of the insulating resin layer comprises the 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 may include an adhesive for bonding the inorganic filler-containing polyimide layer to the metal foil. In the case of a double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer with an adhesive layer interposed therebetween, the thickness of the adhesive layer is preferably less than 30%, and more preferably less than 20%, of the thickness of the entire insulating resin layer to avoid compromising dielectric properties. Furthermore, when a bonding layer is interposed between a single-sided metal-clad laminate having a metal layer on only one side of the insulating resin layer, the thickness of the bonding layer is preferably less than 15% of the thickness of the entire insulating resin layer, and more preferably less than 10%, to avoid compromising dielectric properties. Furthermore, since the bonding layer constitutes a portion of the insulating resin layer, it is preferably a polyimide layer. From the perspective of imparting heat resistance, the glass transition temperature of the silica-containing polyimide, the primary material of the insulating resin layer, is preferably set to 300°C or higher. Setting the glass transition temperature to 300°C or higher allows for the appropriate selection of the acid dianhydride or diamine component constituting the polyimide.

Methods for producing metal-clad laminates in which a resin film serves as the insulating resin layer include, for example, heat-pressing a metal foil onto a resin film directly or via an adhesive, or forming a metal layer on the resin film by methods such as metal deposition. Furthermore, double-sided metal-clad laminates can be produced, for example, by forming a single-sided metal-clad laminate and then placing polyimide layers facing each other and heat-pressing them, or by press-bonding a metal foil to the polyimide layer of a 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 alloys thereof. Copper or copper alloys are particularly preferred. The metal layer may consist of metal foil or may be a film formed by metal deposition. In terms of direct application of the resin composition, either metal foil or metal plate can be used, with copper foil or copper plate being preferred.

The thickness of the metal layer is appropriately set depending on the intended use of the metal-clad laminate and is not particularly limited. For example, it is preferably within the range of 5μm to 3mm, and more preferably within the range of 12μm to 1mm. If the metal layer thickness is less than 5μm, there is a concern of problems such as wrinkling during transportation during the manufacture of the metal-clad laminate. Conversely, if the metal layer thickness exceeds 3mm, it becomes hard, impairing workability. Generally speaking, thicker metal layers are suitable for applications such as automotive circuit boards, while thinner metal layers are suitable for applications such as LED circuit boards.

[Example]

The present invention is described in detail below based on the following examples. However, the present invention is not limited to the scope of these examples. Furthermore, in the following examples, unless otherwise specified, various measurements and evaluations were performed as follows.

[Particle size determination]

Particle size was measured using a laser diffraction particle size distribution analyzer (Malvern, trade name: Master Sizer 3000) with water as the dispersion medium and a particle refractive index of 1.54 using the laser diffraction-scattering method.

[Method for determining true specific gravity]

True specific gravity was measured using a continuous automatic powder true density measuring device (manufactured by Seishin Enterprise Co., Ltd., trade name: AUTO TRUE DENSERMAT-7000) using the pycnometer method (liquid phase replacement method).

[Determination of specific surface area]

The specific surface area was measured in accordance with Japanese Industrial Standards (JIS) Z 8830:2013 using the BET specific surface area method using a specific surface area measuring apparatus (Macsorb 210, manufactured by Mountech).

[Determination of relative dielectric constant and dielectric loss tangent]

<Silicon dioxide particles>

The relative dielectric constant (ε ₁ ) and dielectric loss tangent (Tan δ ₁ ) of silicon dioxide particles at a specified frequency were measured using a dielectric constant measurement device manufactured by Kanto Electronics Application Development Co., Ltd., which utilizes the cavity perturbation method. The sample tube had an inner diameter of 1.68 mm, an outer diameter of 2.28 mm, and a height of 8 cm.

<Resin film>

The relative dielectric constant (ε 1 ) and dielectric loss tangent (Tan δ 1 ) of the resin film (after curing) were measured at a specified frequency using a vector network analyzer (Agilent _E8363C ) and SPDR resonator. The resin film was stored at a temperature of 24°C to 26°C and a humidity of 45% to 55 _% for 24 hours.

[Viscosity measurement]

The viscosity of the resin solution was measured at 25°C using an E-type viscometer (Brookfield, trade name: DV-II+Pro). The rotational speed was set to a torque range of 10% to 90%. The viscosity was read after 2 minutes from the start of the measurement, when the viscosity stabilized.

[Determination of Coefficient of Thermal Expansion (CTE)]

A 3 mm x 20 mm polyimide film was heated from 30°C to 250°C at a rate of 10°C/min using a thermomechanical analyzer (Bruker 4000SA) under a load of 5.0 g. The film was then held at this temperature for 10 minutes and then cooled at a rate of 5°C/min. The average coefficient of thermal expansion (CTE) from 250°C to 100°C was determined.

[Flexibility Evaluation]

1) 180° flexing:

According to JIS K5600-1, a 5cm x 10cm resin film is wrapped around a 5mm diameter metal rod at the center of its long side and bent uniformly for 1 to 2 seconds. Films that show no breakage or cracking even after a 180° bend are rated "good," while those that do breakage or cracking are rated "unacceptable."

2) Folding:

A 5cm x 5cm resin film was folded diagonally into a triangle and then restored to its original shape. Those with no breaks or cracks were rated "acceptable" and those with breaks or cracks were rated "unacceptable."

The abbreviations used in the examples represent 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-dimethylacetamide

Filler 1: Nippon Steel Chemicals & Materials Co., Ltd., trade name: SP40-10 (spherical amorphous silica powder, spherical shape, 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 ₁₀₀ : 30 μm)

Filler 2: Nippon Steel Chemicals & Materials Co., Ltd., trade name: SPH507 (spherical amorphous silica powder, spherical shape, silica 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: Nippon Steel Chemicals & Materials Co., Ltd., trade name: SPH516M (spherical amorphous silica powder, spherical shape, 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: Admatech, trade name: SE4050 (spherical amorphous silica powder, spherical shape, silica content: 99.99% by weight, true specific gravity: 2.2, specific surface area: 4.6 m ² /g, D ₅₀ : 1.5 μm, D ₁₀₀ : 6.0 μm)

The relative dielectric constant and dielectric loss tangent of fillers 1 to 4 are as follows.

<Padding 1>

1) Relative dielectric constant ε ₁ at 3 GHz: 3.05, dielectric loss tangent Tanδ ₁ : 0.0028

2) Relative dielectric constant ε ₁ at 5 GHz: 2.97, dielectric loss tangent Tanδ ₁ : 0.0028

3) Relative dielectric constant ε ₁ at 10 GHz: 2.78, dielectric loss tangent Tanδ ₁ : 0.003

<Padding 2>

1) Relative dielectric constant ε ₁ at 3 GHz: 2.98, dielectric loss tangent Tanδ ₁ : 0.0025

2) Relative dielectric constant ε ₁ at 5 GHz: 2.99, dielectric loss tangent Tanδ ₁ : 0.0026

3) Relative dielectric constant ε ₁ at 10 GHz: 2.88, dielectric loss tangent Tanδ ₁ : 0.0027

<Padding 3>

1) Relative dielectric constant ε ₁ at 3 GHz: 2.88, dielectric loss tangent Tanδ ₁ : 0.004

2) Relative dielectric constant ε ₁ at 5 GHz: 2.82, dielectric loss tangent Tanδ ₁ : 0.0039

3) Relative dielectric constant ε ₁ at 10 GHz: 2.76, dielectric loss tangent Tanδ ₁ : 0.004

<Padding 4>

1) Relative dielectric constant ε ₁ at 3 GHz: 3.10, dielectric loss tangent Tanδ ₁ : 0.0049

2) Relative dielectric constant ε ₁ at 5 GHz: 3.06, dielectric loss tangent Tanδ ₁ : 0.0049

3) Relative dielectric constant ε ₁ at 10 GHz: 2.92, dielectric loss tangent Tanδ ₁ : 0.0052

(Synthesis Example 1 to Synthesis Example 4)

To synthesize polyamine solutions A through D, DMAc was added to a 3000 ml separable flask under a nitrogen flow to achieve the solid concentrations shown in Table 1. The diamine and anhydride components listed in Table 1 were then stirred and dissolved at room temperature for 10 minutes. The solutions were then stirred at room temperature for 10 hours to allow polymerization to proceed, resulting in viscous polyamine solutions A through D.

[Example 1]

Mix 100.24 g of polyamine solution A and 9.37 g of filler 1 and stir until the solution becomes visually homogeneous to prepare polyamine solution 1 (viscosity: 27,500 cps, filler content relative to polyamine: 30% by volume).

A polyamide solution 1 was applied to a copper foil 1 (electrolytic copper foil, thickness: 12 μm) and dried at 130°C for 3 minutes. It was then subjected to a stepwise heat treatment from 155°C to 360°C for imidization, thereby preparing a metal-clad laminate 1.

The copper foil covering the metal laminate 1 was etched away to prepare a resin film 1. The CTE of the resin film 1 (thickness: 40 μm) was 33 ppm/K, with good 180° bending properties and acceptable folding properties. The dielectric loss tangent of the resin film 1 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0047

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0054

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0056

[Example 2]

Mix 100.36 g of polyamine solution A and 21.88 g of filler 1 and stir until the solution becomes visually homogeneous to prepare polyamine solution 2 (viscosity: 28,400 cps, filler content relative to polyamine: 50% by volume).

Similar to Example 1, a metal-clad laminate 2 and a resin film 2 were prepared. The CTE of the resin film 2 (thickness: 42 μm) was 31 ppm/K, its 180° bending performance was good, and its folding performance was poor. Furthermore, the dielectric loss tangent of the resin film 2 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0043

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0047

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0049

[Example 3]

Mix 99.92 g of polyamine solution B and 9.33 g of filler 1 and stir until the solution becomes visually homogeneous to prepare polyamine solution 3 (viscosity: 29,000 cps, filler content relative to polyamine: 30% by volume).

Similar to Example 1, a metal-clad laminate 3 and a resin film 3 were prepared. The CTE of the resin film 3 (thickness: 41 μm) was 35 ppm/K, its 180° bending properties were good, and its folding properties were acceptable. Furthermore, the dielectric loss tangent of the resin film 3 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0029

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0033

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0035

[Example 4]

Mix 100.00 g of polyamine solution B and 21.81 g of filler 1 and stir until the solution becomes visually homogeneous to prepare polyamine solution 4 (viscosity: 31,000 cps, filler content relative to polyamine: 50% by volume).

Similar to Example 1, a metal-clad laminate 4 and a resin film 4 were prepared. The CTE of the resin film 4 (thickness: 44 μm) was 30 ppm/K, its 180° bending performance was good, and its folding performance was poor. Furthermore, the dielectric loss tangent of the resin film 4 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0028

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0030

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0031

[Example 5]

80.00 g of polyamine solution C and 7.88 g of filler 1 were mixed and stirred until the solution became uniform visually. This prepared polyamine solution 5 (viscosity: 24,000 cps, filler content relative to polyamine: 30% by volume).

Similar to Example 1, a metal-clad laminate 5 and a resin film 5 were prepared. The CTE of the resin film 5 (thickness: 46 μm) was 41 ppm/K, its 180° bending properties were good, and its folding properties were acceptable. Furthermore, the dielectric loss tangent of the resin film 5 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0046

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0052

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0055

[Example 6]

80.00 g of polyamine solution D and 7.92 g of filler 1 were mixed and stirred until the solution became visually homogeneous, thereby preparing polyamine solution 6 (viscosity: 23,000 cps, filler content relative to polyamine: 30% by volume).

Similar to Example 1, a metal-clad laminate 6 and a resin film 6 were prepared. The CTE of the resin film 6 (thickness: 45 μm) was 46 ppm/K, with good 180° bending properties and acceptable folding properties. The dielectric loss tangent of the resin film 6 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0046

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0052

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0055

[Example 7]

80.00 g of polyamine solution D and 18.49 g of filler 1 were mixed and stirred until the solution became uniform visually. This prepared polyamine solution 7 (viscosity: 31,000 cps, filler content relative to polyamine: 50% by volume).

Similar to Example 1, a metal-clad laminate 7 and a resin film 7 were prepared. The CTE of the resin film 7 (thickness: 48 μm) was 28 ppm/K, its 180° bending properties were good, and its folding properties were acceptable. Furthermore, the dielectric loss tangent of the resin film 7 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0051

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0054

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0055

(Comparative example 1)

Polyamide solution A is coated on copper foil 1 and dried at 130°C for 3 minutes. It is then subjected to a stepwise heat treatment from 155°C to 360°C for imidization, thereby preparing a metal-clad laminate 8.

Similar to Example 1, a metal-clad laminate 8 and a resin film 8 were prepared. The CTE of the resin film 8 (thickness: 42 μm) was 17 ppm/K, its 180° bending properties were good, and its folding properties were acceptable. Furthermore, the dielectric loss tangent of the resin film 8 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0052

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0062

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0065

(Comparative example 2)

Copper foil 1 is coated with polyamide solution B and dried at 130°C for 3 minutes. It is then subjected to a stepwise heat treatment from 155°C to 360°C for imidization, thereby preparing a metal-clad laminate 9.

Similar to Example 1, a metal-clad laminate 9 and a resin film 9 were prepared. The CTE of the resin film 9 (thickness: 43 μm) was 18 ppm/K, its 180° bending properties were good, and its folding properties were acceptable. Furthermore, the dielectric loss tangent of the resin film 9 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0032

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0037

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0040

(Comparative example 3)

Polyamide solution C is coated on copper foil 1 and dried at 130°C for 3 minutes. It is then subjected to a stepwise heat treatment from 155°C to 360°C for imidization, thereby preparing a metal-clad laminate 10.

Similar to Example 1, a metal-clad laminate 10 and a resin film 10 were prepared. The resin film 10 (thickness: 41 μm) had a CTE of 51 ppm/K, good 180° bending properties, and acceptable folding properties. Furthermore, the dielectric loss tangent of the resin film 10 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0055

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0062

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0068

(Comparative example 4)

A polyamide solution D is coated on a copper foil 1 and dried at 130°C for 3 minutes. It is then subjected to a stepwise heat treatment from 155°C to 360°C for imidization, thereby preparing a metal-clad laminate 11.

Similar to Example 1, a metal-clad laminate 11 and a resin film 11 were prepared. The CTE of the resin film 11 (thickness: 42 μm) was 71 ppm/K, its 180° bending properties were good, and its folding properties were acceptable. Furthermore, the dielectric loss tangent of the resin film 11 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0069

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0077

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0079

[Comparative example 5]

100.24 g of polyamine solution A and 9.37 g of filler 4 were mixed and stirred until the solution became visually homogeneous, thereby preparing polyamine solution 12 (viscosity: 28,000 cps, filler content relative to polyamine: 30% by volume).

Similar to Example 1, a metal-clad laminate 12 and a resin film 12 were prepared. The CTE of the resin film 12 (thickness: 44 μm) was 34 ppm/K, and neither 180° bendability nor foldability was acceptable. Furthermore, the dielectric loss tangent of the resin film 12 was as follows.

1) Dielectric loss tangent Tanδ ₁ at 5GHz: 0.0051

2) Dielectric loss tangent Tanδ ₁ at 10 GHz: 0.0054

3) Dielectric loss tangent Tanδ ₁ at 20 GHz: 0.0055

While the embodiments of the present invention have been described in detail above for illustrative purposes, the present invention is not limited to these embodiments and is capable of various modifications.

Claims (4)

A resin composition comprising silica particles and polyamide or polyimide, wherein the silica particles have the following characteristics: a frequency distribution curve obtained by volume-based particle size distribution measurement using a laser diffraction scattering method in a frequency range of 3 GHz to 20 GHz, a mean particle size _D50 at which 50% of the cumulative value is within the range of 0.64 μm to 2.5 μm, and a specific surface area of 6.4 ^m2 /g or more and 12.7 ^m2 /g or less. /g or less, a dielectric loss tangent measured by a cavity perturbation method is less than 0.004, a ratio of an average major diameter to an average minor diameter is 1 or close to 1; and a content of the silicon dioxide particles is in a range of 30 volume % to 70 volume % relative to the polyamide or polyimide. A resin film having a single or multiple polyimide layers, wherein at least one of the polyimide layers is a silicon dioxide-containing polyimide layer comprising a cured product of the resin composition according to claim 1, the silicon dioxide-containing polyimide layer having a thickness in the range of 10 μm to 200 μm, and the overall thickness of the resin film in the range of 10 μm to 200 μm. The resin film according to claim 2, wherein the thickness ratio of the silicon dioxide-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, wherein: The insulating resin layer comprises the resin film according to claim 2 or 3.