Curable composition

Abstract

[Problem] To provide a curable composition which has excellent flowability, from which it is possible to form a cured product having excellent electrical characteristics (low relative dielectric constant, low dielectric loss tangent, etc.) and crack resistance, and also having excellent mechanical characteristics, insulating properties, etc., and which is useful for electronic component device applications such as in a build-up film or an underfill material and for a sealing material of a semiconductor device. [Solution] A curable composition comprising: an epoxy resin; a curing agent; solid silica particles having a mean particle diameter (D50) of not less than 0.1 µm to less than 4 µm; and hollow silica particles having a mean particle diameter (D50) of 0.1-4 µm, wherein the absolute value of the difference in the mean particle diameter (D50) between the solid silica particles and the hollow silica particles is more than 0.1 µm, and the total content of the solid silica particles and the hollow silica particles is not less than 25 vol%.

Description

curable composition

[0001] The present invention relates to a curable composition. More specifically, the present invention relates to a curable composition comprising an epoxy resin, a curing agent, and inorganic particles.

[0002] In recent years, to cope with the miniaturization of electronic devices, the acceleration of signals, and the increase in wiring density, there has been a demand for high-performance insulating materials (low dielectric constant, low dielectric loss tangent, low thermal expansion, etc.) for sealing resin compositions, build-up substrates, adhesive films, insulating resin sheets such as prepregs, and printed circuit boards for communication equipment, and various studies have been conducted. Patent Document 1 proposes a resin composition containing epoxy resin, a curing agent, hollow silica, and fused silica, in which the content of hollow silica and the total content of hollow silica and fused silica are within a predetermined range, as a material for adhesive films, prepregs, etc. for electronic component applications. Furthermore, flip-chip bonding is used as a semiconductor chip mounting method that can cope with the miniaturization of electronic devices, the acceleration of signals, and the increase in wiring density. In flip-chip bonding, the gap between the semiconductor chip and the substrate is sealed with a material called underfill. Patent Document 2 proposes a sealing resin composition containing epoxy resin, a curing agent, silica filler, and specific hollow silica particles.

[0003] Japanese Patent Publication No. 2013-173841 Japanese Patent Publication No. 2023-127421

[0004] In these resin compositions, the physical properties of the epoxy resin form the basis for various properties such as workability, moldability, electrical properties, moisture resistance, heat resistance, and mechanical properties. On the other hand, when increasing the content of inorganic fillers to improve electrical properties (relative permittivity, low dielectric loss tangent, etc.) while ensuring the uniformity of the resulting cured product, the dispersibility of the constituent components tends to decrease, and the effect is not fully obtained. Even in the resin compositions of Patent Document 1 or 2, there is still room for improvement in order to obtain a composition that provides physical properties such as electrical properties based on silica fillers, while also being able to handle narrow gaps and having excellent fluidity, filling ability, moldability, temperature cycle resistance, moisture resistance, and crack resistance. In particular, when hollow silica particles are applied as a component of a resin composition for underfill material use with the aim of improving electrical properties, a trade-off relationship may arise in which the viscosity of the composition tends to increase and the narrow gap filling ability tends to decrease. The inventors focused on the physical properties of silica particles in such resin compositions and conducted a detailed study of their behavior. As a result, they found that by blending solid silica particles of a specific particle size and hollow silica particles of a specific particle size in a predetermined ratio, the above-mentioned tendency can be eliminated, improving the dispersion state of silica particles in the composition while also improving fluidity and packing ability in narrow gaps. Furthermore, they found that such a composition can form cured products (including molded products such as films) with excellent electrical properties (low dielectric constant, low dielectric loss tangent, etc.) and crack resistance, leading to the present invention. The object of the present invention is to provide a curable composition that can form cured products with excellent electrical properties (low dielectric constant, etc.) and crack resistance, as well as mechanical properties and insulating properties, and which also has excellent fluidity.

[0005] The present invention has the following embodiments: [1] A curable composition comprising an epoxy resin, a curing agent, solid silica particles having an average particle diameter (D50) of 0.1 μm or more and less than 4 μm, and hollow silica particles having an average particle diameter (D50) of 0.1 μm or more and 4 μm or less, wherein the absolute value of the difference in average particle diameter (D50) between the solid silica particles and the hollow silica particles is greater than 0.1 μm, and the total content of the solid silica particles and the hollow silica particles is 25 volume% or more. [2] The curable composition of [1], wherein the ratio of the hollow silica particles to the total amount of the solid silica particles and the hollow silica particles is 5 volume% or more. [3] The curable composition of [1] or [2], wherein the average particle diameter (D50) of the solid silica particles is greater than the average particle diameter (D50) of the hollow silica particles. [4] A curable composition according to any one of [1] to [3], wherein the ratio of the average particle diameter (D50) of the hollow silica particles to the average particle diameter (D50) of the solid silica particles is 0.1 to 0.8. [5] A curable composition according to any one of [1] to [4], wherein the average particle diameter (D50) of the solid silica particles is smaller than the average particle diameter (D50) of the hollow silica particles. [6] A curable composition according to any one of [1] to [5], wherein the ratio of the average particle diameter (D50) of the hollow silica particles to the average particle diameter (D50) of the solid silica particles is greater than 1 and less than or equal to 10. [7] A curable composition according to any one of [1] to [6], wherein the epoxy resin comprises at least one epoxy resin, which is a bisphenol-type epoxy resin or a glycidylamine-type epoxy resin. [8] The curable composition according to [7], wherein the at least one epoxy resin is an epoxy resin with an epoxy group equivalent of 200 g / eq or less. [9] The curable composition of [7] or [8] wherein the epoxy resin comprises both the bisphenol-type epoxy resin and the glycidylamine-type epoxy resin.

[10] The curable composition of any one of [1] to [9] wherein the curing agent is an aromatic amine-based curing agent or an acid anhydride-based curing agent.

[11] The curable composition of any one of [1] to

[10] wherein the curing agent comprises at least one of bisanilines or diaminobenzenes.

[12] A cured product of any curable composition of any one of [1] to

[11] .

[13] The curable composition of any one of [1] to

[11] for use in electronic component devices.

[14] A curable composition according to any of [1] to

[11] , for use as a encapsulant, build-up film, or underfill material for semiconductor devices.

[0006] According to the present invention, it is possible to provide a curable composition with excellent fluidity that can form a cured product that has excellent electrical properties (such as low dielectric constant) and crack resistance, as well as mechanical properties and insulating properties.

[0007] In this specification, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. Furthermore, in numerical ranges described in this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages.

[0008] The present invention relates to a curable composition (hereinafter also referred to as "this composition") comprising an epoxy resin, a curing agent, solid silica particles having an average particle diameter (D50) of 0.1 μm or more and less than 4 μm, and hollow silica particles having an average particle diameter (D50) of 0.1 μm or more and 4 μm or less, wherein the absolute value of the difference in average particle diameter (D50) between the solid silica particles and the hollow silica particles is greater than 0.1 μm, and the total content of the solid silica particles and the hollow silica particles is 25 volume% or more.

[0009] This composition can form cured products with excellent electrical properties (low dielectric constant, low dielectric loss tangent, etc.) and crack resistance, as well as mechanical properties and insulating properties. Because this composition has excellent fluidity, it can be effectively used in various applications that take advantage of these properties, such as in electronic component devices like semiconductor device encapsulants, build-up films, or underfill materials. The reason why this composition yields cured products with excellent fluidity, electrical properties (low dielectric constant, low dielectric loss tangent, etc.), crack resistance, mechanical properties, and insulating properties is not entirely clear, but it is thought to be as follows.

[0010] This composition contains solid silica particles and hollow silica particles as silica particles, with an average particle diameter (D50) within a specific range, where the absolute difference in D50 between the solid silica particles and the hollow silica particles is greater than 0.1 μm, and the total content of solid silica particles and the hollow silica particles is 25% by volume or more. In other words, this composition contains solid silica particles and hollow silica particles, each with different average particle diameters (D50) ranging from submicron to micron order. When the D50 of the solid silica particles is greater than that of the hollow silica particles, the solid silica particles are more likely to exhibit a stress-buffering effect in the composition, and also act as a driving force to promote the flow of the hollow silica particles, which are smaller than the solid silica particles, thus making it easier to homogenize the composition. Therefore, the packing efficiency of silica particles when mounting this composition into electronic components and other devices is easily improved, and the fluidity into narrow gaps is also easily improved. Furthermore, when the D50 of solid silica particles is smaller than that of hollow silica particles, it is presumed that the loosely aggregated solid silica particles buffer the stress generated in the composition, and also flow between the hollow silica particles which are larger than the solid silica particles, promoting multiphase flow and making it easier to homogenize the composition. Therefore, the packing of silica particles when mounting the composition into electronic components and other devices is easily improved, and the fluidity into narrow gaps is also easily improved. Consequently, in all cases, the composition has excellent fluidity, and the cured product of the composition is considered to have high electrical properties, low thermal expansion coefficient and elastic modulus, excellent stress suppression effect inside the package, and excellent crack resistance. This tendency becomes more pronounced in preferred embodiments of the composition described later, such as when the content of hollow silica (volume %) relative to the total content of solid silica particles and hollow silica particles increases.

[0011] In this composition, examples of epoxy resins include various bisphenol-type epoxy resins such as bisphenol A type, bisphenol F type, bisphenol S type, and bisphenol AF type; glycidylamine-type epoxy resins, phenol novolac-type epoxy resins, alkylphenol novolac-type epoxy resins, biphenyl-type epoxy resins, aralkyl-type epoxy resins, naphthol-type epoxy resins, anthracene-type epoxy resins, dicyclopentadiene-type epoxy resins, naphthalene-type epoxy resins, anthracene-type epoxy resins, adamantane-type epoxy resins, epoxidized products of condensates of phenols and aromatic aldehydes having a phenolic hydroxyl group, biphenylaralkyl-type epoxy resins, fluorene-type epoxy resins, xanthene-type epoxy resins, triglycidyl isocyanurate, and the like. One type of epoxy resin may be used alone, or two or more types may be used in combination. In particular, it is preferable to include at least one epoxy resin, such as a bisphenol-type epoxy resin or a glycidylamine-type epoxy resin. Furthermore, it is more preferable that at least one of the epoxy resins, such as a bisphenol-type epoxy resin or a glycidylamine-type epoxy resin, has an epoxy group equivalent of 200 g / eq or less.

[0012] When epoxy resin reacts with a curing agent, hydroxyl groups are generated in the reactant as the epoxy ring opens. As the content of such hydroxyl groups increases, the hydrophilicity of the reactant increases, its hygroscopicity increases, and its electrical properties tend to deteriorate. In this composition, it is even more preferable that the epoxy resin contains both a bisphenol-type epoxy resin and a glycidylamine-type epoxy resin, with an epoxy group equivalent of 200 g / eq or less. In this case, the cured product produced by the curing reaction of this composition can be considered to have small hydrophobic parts derived from the epoxy resin with an epoxy group equivalent of 200 g / eq or less, and hydrophilic parts derived from hydroxyl groups and amino groups, and it is presumed that its surfactant action enhances the interaction between the constituent components, particularly the interaction between the epoxy resin and the solid silica particles and hollow silica particles. As a result, it is considered that the dispersibility of solid silica particles and hollow silica particles in this composition or its cured product is likely to improve. Furthermore, if the epoxy resin constituting this composition contains an epoxy resin with an epoxy group equivalent of 200 g / eq or less, the total number of crosslinking points during curing can be reduced, and the amount of hydroxyl groups generated during curing is reduced. Therefore, it is considered that a cured product with good electrical properties, etc., based on the epoxy resin, solid silica particles, and hollow silica particles can be easily obtained from this composition.

[0013] In this composition, if the epoxy resin contains other epoxy resins (epoxy resins with an epoxy group equivalent of 200 g / eq or less) in addition to the epoxy resin with an epoxy group equivalent of 200 g / eq or less, it is preferable that the content of the other epoxy resins in relation to the total amount of epoxy resin is less than or equal to the content of the epoxy resin with an epoxy group equivalent of 200 g / eq or less. In other words, it is preferable that the ratio of the content of other epoxy resins to the content of epoxy resins with an epoxy group equivalent of 200 g / eq or less in the epoxy resin is 1 or less, and more preferably 0.4 or more and 1 or less. The epoxy equivalent in this specification is the mass of resin per epoxy group (g / eq) and is determined according to JIS K 7236. Specifically, it can be measured by weighing 0.2 g of epoxy resin, dissolving it in 10 ml of chloroform, adding 20 ml of glacial acetic acid and 10 ml of tetraethylammonium bromide acetic acid solution, and titrating with a 0.1 mol / L perchloric acid acetic acid solution.

[0014] The epoxy resin is preferably an epoxy resin having two or more epoxy groups in one molecule. The epoxy resin may be solid or liquid at room temperature (25°C), and it is more preferable that it be liquid at room temperature from the viewpoint of improving the handling and filling properties of the composition. The viscosity of the liquid epoxy resin is preferably 0.0001 to 10 Pa·s when measured at 25°C using an E-type viscometer.

[0015] In this composition, suitable curing agents include amine-based curing agents, acid anhydride-based curing agents, and phenol-based curing agents, which are known as curing agents for epoxy resins. Among these, aromatic amine-based curing agents or acid anhydride-based curing agents are preferred. When these high-temperature curing curing agents are used, the above-described mechanism of action is particularly likely to manifest in the high-temperature range where the fluidity of this composition increases, and the effects such as the electrical properties of the cured product of this composition are more easily expressed.

[0016] Examples of aromatic amine-based curing agents include bisanilines such as 3,5-diethyltoluene-2,4-diamine and 3,5-diethyltoluene-2,6-diamine; diaminobenzenes such as 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, 1,3,5-triethyl-2,6-diaminobenzene, and dimethylthiotoluenediamine; and 3,3'-diethyl-4,4'-diaminodiphenylmethane and 3,5,3',5'-tetramethyl-4,4'-diaminodiphenylmethane. Examples of acid anhydride-based curing agents include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexanetetracarboxylic dianhydride, ethylene glycol bis-anhydrotrimellitate, glyceryl bis(anhydrotrimellitate) monoacetate, dodecenyl succinic anhydride, aliphatic dibasic acid polyanhydride, and chlorenic anhydride.

[0017] In particular, it is more preferable that the curing agent contains at least one of bisanilines or diaminobenzenes. In this specification, "bisanilines" means compounds in which multiple structural units (aniline units) are linked together, in which a primary amino group or a secondary amino group is directly bonded to one of the six carbon atoms forming the benzene ring. The amino groups in the molecules of bisanilines are far apart, and it is presumed that they are less likely to exhibit the above-mentioned surfactant activity in the cured product. In this specification, "diaminobenzenes" means compounds having a structure in which a primary amino group or a secondary amino group is directly bonded to two of the six carbon atoms forming the benzene ring. The amino groups in the molecules of diaminobenzenes are closer together than in bisanilines, and it is presumed that they are more likely to exhibit the above-mentioned surfactant activity in the cured product.

[0018] Commercially available amine-based curing agents may be used. Examples of amine-based curing agents that are bisanilines include "KAYAHARD® A-A" (trade name, active hydrogen equivalent 64 g / mol) manufactured by Nippon Kayaku Co., Ltd. Examples of amine-based curing agents that are diaminobenzenes include "jER® Cure WA" (trade name, active hydrogen equivalent 45 g / mol) manufactured by Mitsubishi Chemical Corporation and "EH-105L" (trade name, active hydrogen equivalent 54 g / mol) manufactured by ADEKA Corporation.

[0019] Commercially available acid anhydride-based curing agents may be used. Examples of acid anhydride-based curing agents include "HN-2200" (166 g / eq equivalent of acid anhydride) and "MHAC-P" (178 g / eq equivalent of acid anhydride) from Resonaq Corporation, "Ricacid® MH-700" (166 g / eq equivalent of acid anhydride) and "Ricacid® HNA-100" (179 g / eq equivalent of acid anhydride) from Shin Nippon Rika Co., Ltd., and "YH306" and "YH307" from Mitsubishi Chemical Corporation.

[0020] Furthermore, the equivalent ratio of epoxy resin to curing agent in this composition (number of functional groups that can react with epoxy in the curing agent / number of functional groups in the epoxy resin) is preferably 1.5 to 2.0, more preferably 0.6 to 1.3, from the viewpoint of minimizing the amount of unreacted material, and even more preferably 0.8 to 1.2 from the viewpoint of curability and reliability.

[0021] The total content of solid silica particles and hollow silica particles in the whole composition is 25% by volume or more, preferably 40% by volume or more, and more preferably 50% by volume or more. It is preferable that the total content of solid silica particles and hollow silica particles is 80% by volume or less. When the total content of solid silica particles and hollow silica particles is within the above range, the above-described mechanism of action is easily manifested in the composition, resulting in excellent fluidity and ease of handling. Furthermore, the electrical properties and crack resistance of the cured product are more easily improved. The silica constituting the silica particles may be fused silica or crystalline silica.

[0022] In this composition, the ratio of hollow silica particles to the total amount of solid silica particles is preferably 5% by volume or more, more preferably 10% by volume or more, and particularly preferably 15% by volume or more. It is preferable that this ratio be less than 50% by volume. When the ratio of hollow silica particles to the total amount of solid silica particles is within the above range, it is preferable from the viewpoint of further improving the electrical properties and crack resistance of the cured product of this composition.

[0023] The average particle size (D50) of solid silica particles is 0.1 μm or more and less than 4 μm. Preferably, the average particle size (D50) of solid silica particles is greater than 0.1 μm, and more preferably 0.2 μm or more. The average particle size (D50) of solid silica particles may be 3 μm or less, 2 μm or less, or less than 1 μm. The average particle size of solid silica particles is determined by laser diffraction / scattering. Specifically, the particle size distribution is measured by laser diffraction / scattering, the total volume of the particle collection is set to 100%, and a cumulative curve is obtained. The particle size at the point on the cumulative curve where the cumulative volume is 50% is D50. The specific gravity of solid silica particles is 1.6 g / cm³. ３ 2.2g / cm or more ３ Preferably, it is 1.8 g / cm³. ３ 2.2g / cm or more ３ It is more preferable that it be less than . In this specification, solid silica particles refer to particles with a hollow ratio of less than 10%, and are distinguished from hollow silica particles by their hollow ratio.

[0024] The absolute value of the difference in average particle diameter (D50) between solid silica particles and hollow silica particles is greater than 0.1 μm. Preferably, the absolute value of this difference is 0.15 μm or more, more preferably 0.25 μm or more, and preferably 0.5 μm or more. Preferably, the absolute value of this difference is 2.5 μm or less, more preferably 2 μm or less, and even more preferably less than 2 μm. Note that the D50 of hollow silica particles refers to the D50 of secondary particles of hollow silica particles, and details will be described later.

[0025] The ratio of the average particle diameter (D50) of hollow silica particles to the average particle diameter (D50) of solid silica particles is preferably 0.1 to 10. If the D50 of solid silica particles is greater than the D50 of hollow silica particles, the ratio is more preferably 0.1 to 0.8, more preferably greater than 0.3 and 0.8 or less, and even more preferably 0.4 or greater and 0.8 or less. In this case, the above-mentioned mechanism of action is more likely to manifest. On the other hand, if the D50 of solid silica particles is smaller than the D50 of hollow silica particles, the ratio is more preferably greater than 1 and 10 or less, and even more preferably 2 to 10. In this case, the above-mentioned mechanism of action is more likely to manifest. The ratio is preferably 1.2 or greater, more preferably 1.3 or greater, and even more preferably 1.5 or greater. Furthermore, the ratio is preferably 6 or less, more preferably less than 4, and even more preferably 3 or less.

[0026] The hollow silica particles in this composition have a shell layer (solid film) containing silica, and have a space inside the shell layer. The presence of a space inside the shell layer of a hollow silica particle can be confirmed by transmission electron microscopy (TEM) or scanning electron microscopy (SEM) observation. In the case of SEM observation, the hollowness can be confirmed by observing a broken particle with a partial opening. Spherical particles with a space inside, which can be confirmed by TEM or SEM observation, are defined as "primary particles." Note that, due to the firing and drying processes during manufacturing, the primary particles are partially bonded together, so hollow silica particles are often aggregates of secondary particles formed by the aggregation of primary particles. Furthermore, "having a space inside the shell layer" means that when observing the cross-section of a single primary particle, the shell layer surrounds a single space, resulting in a hollow state. In other words, one hollow particle has one large space and a shell layer surrounding it. If the hollow silica particles have a structure in which there is a space within the shell, more space can be secured in the composition containing the particles, and the dielectric constant can be lowered, so this composition can be suitably used in electronic component devices.

[0027] The specific gravity of hollow silica particles is 0.3 g / cm³. ３ 1.00g / cm or more ３ Less than 0.4-0.8 g / cm³３ is more preferable. In the present specification, the "specific gravity" of the hollow silica particles means the density of the particles determined by density measurement using a dry pycnometer with argon gas (hereinafter, also referred to as "Ar density"). When the Ar density is within the above range, not only is the above-described mechanism of action more likely to be exhibited, but it is also easy to reduce the relative permittivity in the cured product of the present composition.

[0028] The density of the hollow silica particles determined by density measurement using a dry pycnometer with helium gas (hereinafter, also referred to as He density) is 2.00 to 2.35 g / cm ３ is preferable. Since helium gas permeates through fine voids, the He density can also be positioned as the density corresponding to the true density of the silica portion of the silica particles having a space inside. When the He density is within the above range, the residual amount of silanol contained in the hollow silica particles decreases, so it is easy to reduce the dielectric loss tangent.

[0029] The specific gravity (Ar density) of the hollow silica particles can be adjusted by adjusting the primary particle diameter and the shell thickness. In the sample of hollow silica particles, the ratio of complete hollow particles (hollow particle ratio) that have a space part inside without the shell layer being damaged is such that the apparent density of the hollow silica sample becomes smaller as the hollow particle ratio is higher, and the apparent density of the hollow silica sample becomes higher as the hollow particle ratio is lower. Utilizing this, when assuming a yield of 100%, the hollow particle ratio can be obtained from the theoretical density obtained from the charged amount of the raw material and the apparent density measured with a dry pycnometer. In this case, the hollow particle ratio is preferably 90% or more, more preferably 95% or more. In addition, the hollow particle ratio in this case is preferably 100% or less.

[0030] Also, when manufacturing hollow silica particles, the hollow particle ratio can be determined from the weight change during heat treatment using the cake after filtration before removing the oil core. When the cake after filtration is loosened and dried overnight, the oil component in the damaged particles volatilizes, and the oil component in the complete hollow particles is retained. Since the weight change amounts during heat treatment when all the charged oil components have volatilized (hollow particle ratio 0%) and when all are retained (hollow particle ratio 100%) can be calculated from the amount of raw material charged, the hollow particle ratio can be determined from the weight change when a sample dried overnight after filtration is heat-treated up to 800°C. In this case, the hollow particle ratio is preferably 90% or more, more preferably 95% or more. Note that the hollow particle ratio in this case is preferably 100% or less.

[0031] The BET specific surface area of the hollow silica particles is preferably 1 to 100 m ２ / g, and more preferably 1 to 50 m ２ / g. When the BET specific surface area is within the above range, not only is the above-described mechanism of action more likely to be manifested, but also the dispersibility of the hollow silica particles in the present composition is particularly likely to be improved, and it is easy to suppress the increase in the viscosity of the present composition. The BET specific surface area can be measured by the multipoint method using nitrogen gas after drying the hollow silica particles at 230°C until the pressure reaches 50 mTorr using a specific surface area measuring device (such as "TriStar II 3020" manufactured by Shimadzu Corporation).

[0032] Also, when the specific gravity (Ar density) of the hollow silica particles is A (g / cm ３ ) and the BET specific surface area is B (m ２ / g), the product of the two (A × B) is preferably 1 to 120 m ２ / cm ３ . A × B is more preferably 80 m ２ / cm ３ or less, and even more preferably 40 m ２ / cm ３ or less. A × B is more preferably 2 m ２ / cm ３ or more, and more preferably 2.5 m ２ / cm ３The above is more preferable. A×B can also be regarded as the specific surface area per volume when hollow silica particles are dispersed in a solvent. For example, when hollow silica particles are added to a resin, it represents the specific surface area of the portion occupied by the hollow silica particles in a predetermined volume in the resin. When A×B is within the above range, not only is the above-described mechanism of action more likely to be expressed, but also since the specific surface area of the hollow silica particles in the composition is small, it is easier to suppress the increase in the viscosity of the present composition. Further, when A×B is within the above range, it is easy to lower the relative permittivity and dielectric loss tangent of the cured product of the present composition and improve the electrical properties.

[0033] It is preferable that the sphericity of the hollow silica particles is 0.75 to 1.0. When the sphericity is within the above range, the hollow silica particles are less likely to be damaged, it is easier to maintain the Ar density and specific surface area, and it is easier to lower the dielectric loss tangent. The sphericity is represented by the average value obtained by measuring the maximum diameter (DL) and the minimum diameter (DS) orthogonal thereto for any 100 particles in an image obtained by a scanning electron microscope (SEM), and calculating the ratio (DS / DL) of the minimum diameter (DS) to the maximum diameter (DL).

[0034] It is preferable that the average value (average primary particle diameter) of the size of the primary particles of the hollow silica particles is in the range of 50 nm to 10 μm. The average primary particle diameter is more preferably 70 nm or more, and even more preferably 100 nm or more. The average primary particle diameter is more preferably 5 μm or less, and even more preferably 3 μm or less. When the average primary particle diameter of the hollow silica particles is within the above range, it is easy to handle and it is easy to control the specific surface area, oil absorption amount, pore volume, and the amount of SiOH on the particle surface. The average primary particle diameter is measured as the average value of the sizes of any 100 primary particles from an SEM observation image. The average primary particle diameter can also be regarded as being reflected in the surface state of the secondary particles (aggregated particles) of the hollow silica particles, and is a parameter that determines the specific surface area and oil absorption amount.

[0035] The hollow silica particles have the average primary particle diameter described above, preferably 35% or more of the total primary particles have a particle diameter within ±40% of the average primary particle diameter, more preferably 50% or more of the total primary particles have a particle diameter within ±40% of the average primary particle diameter, and even more preferably 70% or more of the total primary particles have a particle diameter within ±40% of the average primary particle diameter. In this case, the size of the hollow silica particles becomes more uniform, and shell defects of the hollow silica particles are less likely to occur.

[0036] The average particle size (D50) of the secondary particles (aggregated particles) of the hollow silica particles is 0.1 μm or more and 4 μm or less. Preferably, D50 is greater than 0.1 μm, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. More preferably, D50 is 3 μm or less, and even more preferably 2 μm or less. When D50 is within the above range, not only is the above-described mechanism of action more easily expressed, but the dispersion stability of the hollow silica particles in this composition is more easily improved, and the increase in viscosity of the composition is more easily suppressed. Furthermore, granularity in the cured product of this composition is more easily reduced.

[0037] Furthermore, the coarse particle size (D90) of the secondary particles of the hollow silica particles is preferably 1 to 30 μm. More preferably, D90 is 3 μm or more, and even more preferably 5 μm or more. More preferably, D90 is 25 μm or less, and even more preferably 20 μm or less. When D90 is within the above range, it is easier to increase the productivity of hollow silica particles and to reduce granularity in the cured product of this composition. The particle size of the secondary particles of the hollow silica particles (aggregation diameter when primary particles aggregate) is determined by laser diffraction and scattering. That is, the particle size distribution is measured by laser diffraction and scattering, and a cumulative curve is obtained with the total volume of the particle collection set to 100%, and the particle size at the point where the cumulative volume is 50% on that cumulative curve is D50, and the particle size at the point where the cumulative volume is 90% is D90.

[0038] The shell thickness of hollow silica particles is preferably 0.01 to 0.3, more preferably 0.02 or greater, and even more preferably 0.03 or greater, when the diameter of the primary particle is set to 1. Furthermore, the shell thickness of hollow silica particles is more preferably 0.2 or less, and even more preferably 0.1 or less, when the diameter of the primary particle is set to 1. When the shell thickness relative to the diameter of the primary particle is within the above range, it is easier to maintain the strength of the hollow silica particles and to exhibit properties based on their hollow shape. The shell thickness is determined by measuring the shell thickness of individual particles using a transmission electron microscope (TEM).

[0039] SiO in hollow silica particles ２ The content is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more. SiO in hollow silica particles ２ The content may be 100% by mass, and is preferably 99.99% by mass or less. Here, SiO in hollow silica particles ２ The content refers to the amount of silica (SiO₂) contained in the shell layer that makes up the hollow silica particles. ２ This is the content of SiO in hollow silica particles, for example, "SiO in hollow silica particles" ２ "Having a content of 99% by mass or more" means that 99% by mass or more of the shell layer constituting the hollow silica particles is silica (SiO₂ ２ This means that it contains ). Residues in hollow silica particles include alkali metal oxides and silicates, alkaline earth metal oxides and silicates, carbon, etc. In other words, hollow silica particles may contain one or more metals M selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba. When metal M is included in hollow silica particles, it acts as a flux during firing, which reduces the specific surface area and tends to lower the dielectric loss tangent.

[0040] Metal M is incorporated into the hollow silica particles between the reaction step and the washing step during the manufacturing process. For example, metal M can be incorporated into the hollow silica particles by adding a metal salt of metal M to the reaction solution used to form the silica shell during the reaction step, or by washing the hollow silica precursor with a solution containing metal ions of metal M before firing. In the hollow silica particles of this composition, the concentration of metal M is preferably 50 ppm by mass or more and 1% by mass or less, more preferably 100 ppm by mass or more, even more preferably 150 ppm or more, and also preferably 1% by mass or less, more preferably 5000 ppm by mass or less, and even more preferably 1000 ppm by mass or less. When the total concentration of metal M is within the above range, the flux effect during firing promotes the condensation of bonded silanol groups, reducing the number of remaining silanol groups and thus lowering the dielectric loss tangent.

[0041] In the hollow silica particles of this composition, it is preferable that the metal M is at least Na, and the Na content is less than 1000 ppm by mass. In other words, in this composition, the SiO in the hollow silica particles ２ It is particularly preferable that the content is 99% by mass or more, and the Na content is less than 1000 ppm by mass. In this case, not only is the above-described mechanism of action more easily expressed, but the hollow silica particles have an excellent balance of electrical properties and strength, and cracking is also easily suppressed. The composition of the shell layer of the hollow silica particles can be measured by ICP emission spectrometry or flame atomic absorption spectrometry, etc.

[0042] The hollow silica particles are preferably obtained by a manufacturing method that includes, for example, preparing an oil-in-water emulsion in which the oil phase is dispersed in water, containing an aqueous phase, an oil phase, and a surfactant; obtaining a hollow silica precursor in which a shell layer containing silica is formed on the outer circumference of the core in this oil-in-water emulsion; removing the core from this precursor; and heat-treating it. Specifically, the method described in International Publication No. 2023 / 100676 is preferred. When alkali metal silicates are used as the silica raw material for forming the shell layer, the amount of carbon (C) component derived from the raw material in the shell layer of the resulting hollow silica particles will be less compared to when silicon alkoxides are used as the silica raw material.

[0043] The pore volume of the hollow silica particles is set to 0.2 cm², from the viewpoint of suppressing moisture adsorption and not degrading the electrical properties of the cured product of this composition. ３ It is preferable that the amount is less than or equal to / g. The pore volume is determined by the BJH method based on nitrogen adsorption using a specific surface area and pore distribution measuring device (for example, "BELSORP-mini II" from Microtrac-Bel, "Tristar II" from Micromeritic, etc.).

[0044] The surface of the hollow silica particles may be treated with a silane coupling agent. In this case, the amount of silane coupling agent attached is preferably in the range of 1 to 10 parts by mass per 100 parts by mass of hollow silica particles. When the surface of the hollow silica particles is treated with a silane coupling agent, the amount of remaining surface silanol groups is reduced, the surface becomes hydrophobic, moisture adsorption is suppressed and dielectric loss can be improved, and the affinity with the epoxy resin in this composition is increased, making it easier to disperse and improving the strength of the cured product of this composition. Examples of silane coupling agents include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, organosilazane compounds, etc. These may be used individually or in combination of two or more. The treatment of the surface of the hollow silica particles with a silane coupling agent can be confirmed by detecting peaks due to substituents of the silane coupling agent using IR. The amount of silane coupling agent attached can be measured by the amount of carbon.

[0045] The relative permittivity of hollow silica particles at 1 GHz is preferably 1.0 to 5.0, and more preferably 1.3 to 3.5. Furthermore, the dielectric loss tangent of hollow silica particles at 1 GHz is preferably 0.0001 to 0.05. The relative permittivity and dielectric loss tangent can be measured, for example, using a Keycom "Vector Network Analyzer E5063A" by the perturbation resonator method.

[0046] The total content of solid silica particles and hollow silica particles in the whole composition is preferably 25% by volume or more, more preferably 40% by volume or more, and more preferably 50% by volume or more. The total content of solid silica particles and hollow silica particles is preferably 80% by volume or less. The content of epoxy resin in the whole composition is preferably 10% by mass or more, more preferably 20% by mass or more. The content of epoxy resin is preferably 40% by mass or less. The content of curing agent in the whole composition is preferably 5% by mass or more. The content of curing agent is preferably 15% by mass or less, and more preferably 10% by mass or less.

[0047] Furthermore, in this composition, the ratio of the volume percentage of epoxy resin to the total volume percentage of solid silica particles and hollow silica particles is preferably 0.5 or more and 1 or less, and more preferably 0.6 or more and 0.9 or less. When this ratio is within the above range, not only is the above-mentioned mechanism of action more easily expressed, but the solid silica particles, hollow silica particles and epoxy resin in this composition exhibit excellent dispersibility, and the properties based on the solid silica particles and hollow silica particles are easily exhibited in the cured product of this composition (including molded products such as films). In addition, the cured product of this composition exhibits excellent crack resistance.

[0048] This composition may further contain a curing accelerator as needed. Examples of curing accelerators include cycloamidine compounds such as 1,8-diazabicyclo[5.4.0]undecene-7, 1,5-diazabicyclo[4.3.0]nonene, and 5,6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene-7; tertiary amine compounds such as triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 1-methylimidazole. Examples of conventionally known compounds used in the curing of epoxy resins include imidazole compounds such as benzoyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine, and 2-heptadecylimidazole; and phenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate. These may be used individually or in combination of two or more. If the composition contains a curing accelerator, its content is not particularly limited and can be appropriately selected as long as it is an amount that exhibits a curing-accelerating effect between the epoxy resin and the curing agent. For example, it is preferably 0.1 to 40% by mass relative to the total amount of epoxy resin and curing agent.

[0049] This composition may further contain a coupling agent. When a coupling agent is included, the interfacial adhesion between the epoxy resin constituting this composition and the solid silica particles and hollow silica particles, as well as the interfacial adhesion between this composition and the components of electronic parts, tends to become stronger, and the filling properties also tend to improve. Examples of coupling agents include aminosilanes having one or more selected from the group consisting of primary, secondary, and tertiary amino groups; epoxysilanes such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropylmethyldimethoxysilane; silane compounds such as mercaptosilane, alkylsilane, ureidosilane, and vinylsilane; titanium compounds; aluminum chelates; and aluminum / zirconium compounds. These may be used individually or in combination of two or more. Among these, silane compounds are preferred from the viewpoint of reactivity with solid silica particles and hollow silica particles. If the composition contains a coupling agent, its content is preferably 0.05 to 10% by mass relative to the total mass of the epoxy resin and curing agent constituting the composition.

[0050] This composition may further contain a flexible agent as needed. When a flexible agent is included, the thermal shock resistance of this composition and the stress on semiconductor devices are easily reduced. Examples of flexible agents include rubber particles such as styrene-butadiene rubber, nitrile-butadiene rubber, butadiene rubber, urethane rubber, acrylic rubber, and silicone rubber. These may be used individually or in combination of two or more. The average primary particle diameter of such rubber particles is preferably 0.05 to 10 μm, and more preferably 0.1 to 5 μm. When the average primary particle diameter is within the above range, the dispersibility in this composition and the stress reduction effect are easily improved, as are the penetration into fine gaps and fluidity of this composition, and the generation of voids and unfilled portions is easily suppressed. When this composition further contains a flexible agent, its content is preferably 1 to 30% by mass relative to the total components of this composition other than solid silica particles and hollow silica particles.

[0051] This composition may further contain an ion trapping agent as needed. When an ion trapping agent is included, the migration resistance, moisture resistance, and high-temperature storage characteristics of semiconductor devices such as ICs to which this composition is applied tend to improve.

[0052] This composition may further contain other additives, such as colorants, leveling agents, surfactants, inorganic fillers different from the solid silica particles and hollow silica particles described above, thixotropic agents, viscosity modifiers, defoaming agents, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, conductive agents, mold release agents, and flame retardants, to the extent that they do not impair the effects of the present invention.

[0053] This composition is obtained by mixing epoxy resin, a curing agent, solid silica particles, hollow silica particles, and additives as needed. This composition may be obtained by mixing the epoxy resin, curing agent, solid silica particles, and hollow silica particles all at once, or by mixing them in multiple stages. When mixing, it is preferable to mix in such a way that the total mass of the epoxy resin, curing agent, solid silica particles, hollow silica particles, and any additives added as needed does not change substantially, and mixing in a closed system is preferable. As a result, a composition is obtained in which each component is uniformly mixed and highly degassed.

[0054] The mixing apparatus for obtaining this composition is not particularly limited as long as it can sufficiently disperse and mix each component. Examples include stirring devices equipped with blades such as Henschel mixers, pressure kneaders, Banbury mixers, and planetary mixers; grinding devices equipped with media such as ball mills, attritors, basket mills, sand mills, sand grinders, Dino mills, disper mats, SC mills, spike mills, and agitator mills; and dispersion devices equipped with other mechanisms such as roll mills, microfluidizers, nanomizers, ultimateizers, ultrasonic homogenizers, desolvers, dispersers, high-speed impellers, thin-film swirling high-speed mixers, rotational and revolving agitators, and V-type mixers. The mixing method may be either batch or continuous.

[0055] The composition is preferably liquid at room temperature (25°C). The viscosity of the liquid composition is preferably 200 Pa·s or less, and more preferably 100 Pa·s or less. The viscosity of the composition is preferably 0.01 Pa·s or more, and more preferably 0.1 Pa·s or more. In this case, not only is the above-described mechanism of action more easily expressed, but the composition produces less foam, and it is easier to ensure fluidity and permeability that can accommodate the miniaturization of electronic components, the fine pitch of connection terminals of semiconductor elements, and the fine wiring of wiring boards in recent years. In addition, the cured product of the composition becomes denser, and the physical properties based on solid silica particles and hollow silica particles are easily expressed to a high degree. Furthermore, the cured product of the composition tends to have excellent crack resistance. The viscosity of the composition is determined by measuring the composition using a B-type viscometer with an appropriate rotor under conditions of 25°C and a rotation speed of 5 rpm.

[0056] This composition can be used for electronic component devices such as encapsulants, build-up films, and underfill materials for semiconductor devices, and is preferably used as an encapsulant or underfill material for semiconductor devices. For example, a specific example of using this composition as an underfill material is to apply this composition to one end of a semiconductor element while maintaining a substrate equipped with a semiconductor element at 70 to 130°C, fill the gap between the substrate and the semiconductor element with the composition by capillary action, and then seal the gap between the substrate and the semiconductor element by curing the composition while maintaining the substrate at 80 to 200°C. The filling time is preferably within 1200 seconds. The curing time of this composition is preferably 0.1 to 6 hours.

[0057] This composition can be suitably used as a encapsulant, build-up film, or underfill material for semiconductor devices in which electronic components such as semiconductor chips, transistors, diodes, thyristors, capacitors, resistors, resistor arrays, coils, and switches are mounted on support members such as lead frames, pre-wired tape carriers, rigid and flexible wiring boards, glass, and silicone wafers. In particular, it is suitable as an underfill material for flip-chip devices, and specifically, it can be suitably used as an underfill material for semiconductor devices such as flip-chip BGA / LGA and COF (Chip On Film), in which semiconductor elements are flip-chip bonded by bump connection to wiring formed on rigid and flexible wiring boards or glass. In other words, the present invention also includes encapsulants, build-up films, or underfill materials for semiconductor devices made from this composition.

[0058] The present invention also relates to a cured product of the composition. The cured product of the composition may be a cured product used as a encapsulant or underfill material for the semiconductor device described above, or it may be in the form of a molded product such as the build-up film described above.

[0059] The relative permittivity (Dk) of the cured product of this composition is preferably 3.5 or less, more preferably 3.1 or less, at a frequency of 10 GHz. The relative permittivity is preferably 1.5 or more. Furthermore, the dielectric loss tangent (Df) of the cured product of this composition is preferably 0.022 or less, more preferably 0.020 or less, even more preferably 0.012 or less, and particularly preferably 0.009 or less, at a frequency of 10 GHz. When the relative permittivity and dielectric loss tangent of the cured product at a frequency of 10 GHz are within the above ranges, the electrical properties are excellent, and transmission loss in the circuit is easily suppressed. The relative permittivity and dielectric loss tangent can be measured, for example, using the apparatus described in the examples.

[0060] The average linear expansion coefficient of the cured product of this composition is preferably 10 to 80 ppm / °C. When the average linear expansion coefficient is within the above range, the electrical properties tend to be excellent. The average linear expansion coefficient is determined using a thermomechanical analyzer (for example, "TMA7100" manufactured by Hitachi High-Tech Science Corporation), by heating the cured product under a load of 98 mN and a heating rate of 5°C / min, measuring the temperature increase from 25°C to 230°C using the compression method, and obtaining the linear expansion coefficient from the tangent slope from 80°C to 100°C.

[0061] Although the present composition and its cured product have been described above, the present invention is not limited to the configuration of the embodiments described above. For example, the present composition and its cured product (including molded products such as films) may have other arbitrary configurations added to the configuration of the above embodiments, or may be replaced with any arbitrary configuration that performs similar functions.

[0062] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. 1. Preparation of each component [Silica particles] <Solid silica particles> Solid silica 1: "FB-5SDC" manufactured by Denka Co., Ltd., median diameter 5.0 μm Solid silica 2: "FB-3SDC" manufactured by Denka Co., Ltd., median diameter 3.0 μm Solid silica 3: "SO-C4" manufactured by Admatex Co., Ltd., median diameter 1.1 μm Solid silica 4: "SO-C2" manufactured by Admatex Co., Ltd., median diameter 0.5 μm Solid silica 5: "UFP-40" manufactured by Denka Co., Ltd., median diameter 0.07 μm <Hollow silica particles> Hollow silica 1: "HS-200" manufactured by AGC Inc., median diameter 2.0 μm Hollow silica 2: "HS-070" manufactured by AGC Inc., median diameter 0.5 μm Hollow silica 3: "Thru-Ria (registered trademark) 4110" manufactured by JGC Catalysts & Chemicals, Inc., median diameter 0.06 μm. The median diameter of the silica particles was measured using a diffraction scattering particle distribution analyzer (MT3300) manufactured by Microtrac-Bell, Inc., and is the median value of the particle distribution (diameter), representing the average particle diameter (D50) of the silica particles. The measurement was performed twice, and the average value was calculated.

[0063] [Epoxy Resins] Epoxy Resin 1: Mitsubishi Chemical Corporation's "jER806", bisphenol F type epoxy resin, epoxy group equivalent 167 g / eq Epoxy Resin 2: Mitsubishi Chemical Corporation's "jER630", glycidylamine type epoxy resin, epoxy group equivalent 96 g / eq Epoxy Resin 3: DIC Corporation's "HP-4032D", naphthalene type epoxy resin, epoxy group equivalent 141 g / eq [Hardening Agents] Hardening Agent 1: Mitsubishi Chemical Corporation's "jER Cure WA", diaminobenzenes Hardening Agent 2: Nippon Kayaku Co., Ltd.'s "Kaya Hard A-A", bisanilines [Other Components] Coloring Agent: Mitsubishi Chemical Corporation's "MA-100" (carbon black) Coupling Agent: Shin-Etsu Chemical Co., Ltd.'s "KBM-403" (silane coupling agent)

[0064] 2. Examples of Manufacturing Curable Compositions [Example 1] A curable composition 1 was obtained by mixing parts by mass of silica particles such that the composition contained 40% by volume of solid silica 3 and 10% by volume of hollow silica 1, parts by mass of epoxy resins 1, 2, and 3, with the content ratios of epoxy resin 1 (50% by mass), 2, and 3 in the total epoxy resin, and parts by mass of curing agents 1 and 2, with the content ratios of curing agent 1 (70% by mass) and 2 (30% by mass) in the total curing agent. When mixing, a coloring agent and a coupling agent were also used, with the coloring agent at 0.5 phr and the coupling agent at 3.0 phr relative to the total mass of epoxy resin and curing agent. The total content of silica particles, epoxy resin, and curing agent in curable composition 1 was 67% by mass, 24% by mass, and 9% by mass, respectively.

[0065] [Examples 2 to 11] Curable compositions 2 to 11 were obtained by performing the same procedure as in Example 1, except that the types and volume percentages of solid silica and hollow silica were changed as shown in Table 1.

[0066] 3. Evaluation of Curable Compositions 3-1. Relative Permittivity (Dk) The curable compositions obtained in each example were poured into a mold and molded under conditions of a mold temperature of 150°C and a curing time of 2 hours to obtain a plate-shaped cured product (80 mm long, 40 mm wide, 0.2 mm thick). The obtained cured product was used as a test piece, and the relative permittivity (Dk) was measured at 25±3°C and 10 GHz using a dielectric constant measuring device "Network Analyzer N5227A" (manufactured by Agilent Technologies), and evaluated according to the following criteria. <Evaluation Criteria for Dk> ◎: Dk is 3.05 or less ○: Dk is greater than 3.05 and 3.1 or less ×: Dk is greater than 3.1

[0067] 3-2. Viscosity The viscosity (Pa·s; initial viscosity) of the curable compositions obtained in each example immediately after preparation was measured using a Toki Sangyo Co., Ltd. Type B viscometer "TVB-10" (rotor used: rotor H7) by rotating at 25°C and 5 rpm for 1 minute, and evaluated according to the following criteria. <Evaluation Criteria> ◎: Initial viscosity is 15.0 Pa·s or less ○: Initial viscosity is greater than 15.0 Pa·s and 18.0 Pa·s or less △: Initial viscosity is greater than 18.0 Pa·s and 20.0 Pa·s or less ×: Initial viscosity is greater than 20.0 Pa·s

[0068] 3-3. Crack Evaluation The curable compositions obtained in each example were poured into a mold and molded at a temperature of 150°C for a curing time of 2 hours to obtain cured discs. The obtained discs were dried at 120°C for 12 hours, then allowed to absorb moisture at 85°C and 60% RH for 168 hours, and passed through a far-infrared heating type reflow oven (245°C, heating time 10 seconds) three times. The presence or absence of cracks on the surface of the discs was then checked under a microscope.

[0069] The results are shown in Table 1. The curable compositions of Examples 1 to 8 have low viscosity, and their cured products exhibit excellent dielectric constant and crack resistance.

[0070] The curable composition of the present invention exhibits excellent fluidity, as well as superior electrical properties (low dielectric constant, low dielectric loss tangent, etc.) and crack resistance, and can form cured products with mechanical properties and insulating properties. Taking advantage of these properties, the curable composition of the present invention can be effectively used in electronic component devices such as encapsulants, build-up films, or underfill materials for semiconductor devices.

Claims

1. A curable composition comprising an epoxy resin, a curing agent, solid silica particles with an average particle diameter (D50) of 0.1 μm or more and less than 4 μm, and hollow silica particles with an average particle diameter (D50) of 0.1 μm or more and 4 μm or less, wherein the absolute value of the difference in average particle diameter (D50) between the solid silica particles and the hollow silica particles is greater than 0.1 μm, and the total content of the solid silica particles and the hollow silica particles is 25 volume% or more.

2. The curable composition according to claim 1, wherein the ratio of the hollow silica particles to the total amount of the solid silica particles and the hollow silica particles is 5% by volume or more.

3. The curable composition according to claim 1, wherein the average particle diameter (D50) of the solid silica particles is greater than the average particle diameter (D50) of the hollow silica particles.

4. The curable composition according to claim 1, wherein the ratio of the average particle diameter (D50) of the hollow silica particles to the average particle diameter (D50) of the solid silica particles is 0.1 to 0.

8.

5. The curable composition according to claim 1, wherein the average particle diameter (D50) of the solid silica particles is smaller than the average particle diameter (D50) of the hollow silica particles.

6. The curable composition according to claim 1, wherein the ratio of the average particle diameter (D50) of the hollow silica particles to the average particle diameter (D50) of the solid silica particles is greater than 1 and less than or equal to 10.

7. The curable composition according to claim 1, wherein the epoxy resin comprises at least one epoxy resin, which is a bisphenol-type epoxy resin or a glycidylamine-type epoxy resin.

8. The curable composition according to claim 7, wherein the at least one epoxy resin is an epoxy resin with an epoxy group equivalent of 200 g / eq or less.

9. The curable composition according to claim 7, wherein the epoxy resin comprises both the bisphenol-type epoxy resin and the glycidylamine-type epoxy resin.

10. The curable composition according to claim 1, wherein the curing agent is an aromatic amine-based curing agent or an acid anhydride-based curing agent.

11. The curable composition according to claim 1, wherein the curing agent comprises at least one of bisanilines or diaminobenzenes.

12. A cured product of a curable composition according to any one of claims 1 to 11.

13. A curable composition according to any one of claims 1 to 11, for use in electronic component devices.

14. A curable composition according to any one of claims 1 to 11, for use as a encapsulant, build-up film, or underfill material for semiconductor devices.

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