WO2025115640A1 - Resin composition - Google Patents

Abstract

The present invention provides a resin composition, a cured product of which has a high thermal conductivity by using a hexagonal boron nitride filler that has an average particle diameter of 1-10 μm and is capable of forming a thin film shape and reducing transmission loss. A resin composition according to the present invention contains an epoxy resin (A), a hexagonal boron nitride filler (B), and a silica filler (C). The total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200-1,200 parts by mass with respect to 100 parts by mass of the epoxy resin (A). The epoxy resin (A) contains a solid epoxy resin (A-1) and a liquid epoxy resin (A-2). The hexagonal boron nitride filler (B) has an average particle diameter D50 of 1-10 μm and a maximum particle diameter Dmax of 30 μm or less. The silica filler (C) has an average particle diameter D50 of 0.1-1 μm. The mass ratio of the content of the hexagonal boron nitride filler (B) to the content of the silica filler (C) is 85:15 to 30:70.

Description

resin composition

The present invention relates to a resin composition.

As electronic devices become more compact and perform better, the wiring in multilayer printed wiring boards is becoming finer and denser. A known manufacturing technique for multilayer printed wiring boards is the build-up method, in which insulating layers and conductor layers are alternately stacked. The insulating layer can be efficiently formed by using a film-like resin composition (resin composition film). A resin composition containing a thermosetting epoxy resin and silica is generally used as the resin composition film (Patent Document 1).

To form the insulating layer of a multilayer printed wiring board, a resin composition film is generally layered on top of a conductor layer, and the resin composition is thermally cured while the conductor layer and resin composition are brought into close contact with each other using a vacuum laminator or heat press, thereby laminating and bonding the two. For this reason, the resin composition film is required to have high fluidity under lamination conditions in order to follow the shape of the conductor layer, and for this reason it is common to use a combination of solid and liquid epoxy resins as epoxy resins.

In addition, in multilayer printed wiring boards, the thermal linear expansion of the insulating layer and the conductor layer (copper wiring) is significantly different, which raises reliability issues such as cracks occurring during thermal cycling, and the insulating layer is also required to have low linear expansion. In addition, with the increase in the amount of information handled in recent years, radio waves used for communication are becoming increasingly high frequency, and electronic equipment components used in information communication are also required to be compatible with higher frequencies, so it is becoming important to reduce transmission loss in information transmission during communication. For this reason, the materials that make up multilayer printed wiring boards are also required to have low relative dielectric constants and dielectric dissipation factors. For this reason, resin composition films are generally highly filled with silica, which has excellent dielectric properties (low relative dielectric constant and dielectric dissipation factor). In this case, because it is used in the form of a thin film, silica with a large particle size cannot be used as the filling silica, and silica with an average particle size of several μm is used.

In recent years, with the miniaturization and high performance of electronic devices, the density and mounting of semiconductor elements in multilayer printed wiring boards has been increasing. Accordingly, the amount of heat generated by semiconductor elements has also increased, making it important to efficiently dissipate the heat from the substrate. Therefore, in order to address such issues, it has been proposed to use a resin composition with high thermal conductivity using hexagonal boron nitride, which has a higher thermal conductivity than silica, as a resin composition film in the manufacture of multilayer printed wiring boards using the build-up method (Patent Document 2). Specifically, Example 5 of Patent Document 2 discloses a resin composition containing hexagonal boron nitride filler with an average particle size of 3.0 μm, an epoxy resin, and a curing agent. Unlike other thermally conductive fillers (e.g., aluminum nitride, silicon nitride, aluminum oxide, and magnesium oxide), hexagonal boron nitride has a small relative dielectric constant and dielectric loss tangent, and therefore has the characteristic that it can be used to produce a resin composition with a small relative dielectric constant and dielectric loss tangent, similar to the case of using silica.

JP 2011-132507 A JP 2013-221120 A

As described above, a resin composition that can be used as a resin composition film using hexagonal boron nitride filler with an average particle size of several micrometers has been disclosed, but there is a demand for even higher thermal conductivity. In general, the thermal conductivity can be improved by increasing the blending ratio of thermally conductive filler in a resin composition. Therefore, in order to achieve even higher thermal conductivity, the inventors prepared a resin composition in which the blending ratio of hexagonal boron nitride filler was increased. However, contrary to expectations, the thermal conductivity did not improve, and instead decreased.

The present invention was made in consideration of these circumstances, and aims to provide a resin composition that uses hexagonal boron nitride filler with an average particle size of 1 to 10 μm, which can be formed into a thin film and reduce transmission loss, and that has a high thermal conductivity when cured.

The present inventors have conducted extensive research to achieve the above object. As a result, they have found that the primary particles of the hexagonal boron nitride filler are plate-shaped and do not have a high affinity with the epoxy resin, and that the surface area is large when the particle size is small, and the adverse effects of poor affinity are prominent. Therefore, when the amount of filler is increased, the adhesion between the resin and the hexagonal boron nitride filler decreases, the heat conduction path is cut off, and the thermal conductivity decreases. For example, when only liquid epoxy resin is used as the epoxy resin, such as in the resin composition film described in JP 2022-185585 A, even a resin film using a hexagonal boron nitride filler with an average particle size of several μm can have a high thermal conductivity. However, when a solid epoxy resin is included as the epoxy resin, such as in the resin composition film used for manufacturing a multilayer printed wiring board, the solid epoxy resin has a high viscosity and is difficult to penetrate into the gaps in the hexagonal boron nitride filler, so it is difficult to obtain affinity between the epoxy resin and the hexagonal boron nitride filler, and it is considered that a high thermal conductivity cannot be obtained.

Further investigation based on this finding revealed that by using silica filler, which has a relatively high affinity with epoxy resin, the affinity between the epoxy resin and the filler is improved compared to when hexagonal boron nitride filler is used alone, and thermal conductivity is improved. Silica filler has a low relative dielectric constant and dielectric tangent, just like hexagonal boron nitride filler, so it does not worsen transmission loss and can solve the above problem.

In other words, the resin composition of the present invention contains an epoxy resin (A), a hexagonal boron nitride filler (B), and a silica filler (C), and the total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200 to 1200 parts by mass per 100 parts by mass of the epoxy resin (A), the epoxy resin (A) contains a solid epoxy resin (A-1) and a liquid epoxy resin (A-2), the hexagonal boron nitride filler (B) has an average particle size D50 of 1 to 10 μm and a maximum particle size Dmax of 30 μm or less, the silica filler (C) has an average particle size D50 of 0.1 to 1 μm, and the mass ratio of the hexagonal boron nitride filler (B) to the silica filler (C) is 85:15 to 30:70.

The present invention makes it possible to obtain a resin composition that has high thermal conductivity after curing and small relative dielectric constant and dielectric loss tangent. Such a resin composition can be used as a resin composition film that is excellent in terms of heat dissipation and dielectric properties, and makes it possible to efficiently produce multilayer printed wiring boards, component-embedded boards, prepregs, resin films with metal foil, and metal-clad laminates, etc.

Below, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment described below, and can be modified as desired without departing from the gist of the present invention.

Epoxy resin (A)
An epoxy resin is used as the resin of the resin composition of the present invention. The epoxy resin preferably contains a compound containing one or more epoxy groups in the molecule (hereinafter, sometimes referred to as "reactive epoxy resin"). In addition, such a reactive epoxy resin may be a low molecular compound having an epoxy group. It is more preferable that the reactive epoxy resin contains two or more epoxy resins in the molecule. The content of the reactive epoxy resin is preferably 50 mass% or more with respect to the total amount of epoxy resin. When the epoxy resin contains a reactive epoxy resin, in a scene where the resin composition of the present invention is used as a resin composition film for manufacturing a multilayer printed wiring board or the like, the resin composition film softens and has excellent fluidity, making it easier to follow the shape of the conductor layer of the multilayer printed wiring board, and after changing into a desired shape, it is heat-cured to have high strength and heat resistance, so that it is easy to improve the reliability of these boards. The upper limit of the content ratio of the reactive epoxy resin to the total amount of epoxy resin is not particularly limited, and the total amount of epoxy resin may be a reactive epoxy resin.

The epoxy resin includes both solid epoxy resin (A-1) and liquid epoxy resin (A-2). In the present invention, an epoxy resin that is solid at a temperature of 25°C is called solid epoxy resin (A-1), and an epoxy resin that is liquid at 25°C is called liquid epoxy resin (A-2).

By including the solid epoxy resin (A-1) in the epoxy resin (A), the strength and heat resistance of the resin composition after heat curing can be improved. On the other hand, many solid epoxy resins have high melt viscosity, and considering that the resin composition of the present invention is used as a resin composition film in the manufacture of multilayer printed wiring boards and the like, it is necessary to increase the fluidity of the resin composition film so that it can conform to the desired board shape, and therefore a liquid epoxy resin with high fluidity is used in combination with a solid epoxy resin with high heat resistance.

As solid epoxy resins, tetrafunctional naphthalene type epoxy resins, trifunctional naphthalene type epoxy resins, trisphenolmethane type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, naphthol novolac type epoxy resins, naphthol cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, biphenyl aralkyl type epoxy resins, bixylenol type epoxy resins, naphthylene ether type epoxy resins and fluorene type epoxy resins are preferred, and tetrafunctional naphthalene type epoxy resins, biphenyl aralkyl type epoxy resins, trisphenolmethane type epoxy resins, bixylenol type epoxy resins, naphthylene ether type epoxy resins and fluorene type epoxy resins are more preferred.

Commercially available solid epoxy resins include, for example:
"HP-4700" and "HP-4710" (tetrafunctional naphthalene type epoxy resin), "N-690" and "N-695" (cresol novolac type epoxy resin), "HP-7200", "HP-7200L" and "HP-7200H" (dicyclopentadiene type epoxy resin), "HP6000" and "HP-6000H" (naphthylene ether type epoxy resin), manufactured by DIC Corporation;
Nippon Kayaku Co., Ltd.'s "EPPN-501H", "EPPN-501HY" and "EPPN-502H" (trisphenolmethane type epoxy resin), "NC7000L", "NC-7000H" and "NC-7300L" (naphthol cresol novolac epoxy resin), "NC-3000H", "NC-3000", "NC-3000L", "NC-3100" and "NC-3500" (biphenylaralkyl type epoxy resin), "NC-2000-L" (phenylaralkyl type epoxy resin), "XD-1000-2L", "XD-1000" and "XD-1000-H" (dicyclopentadiene type epoxy resin), "LCE-2615" (tough type epoxy resin);
"ESN475" (naphthol novolac type epoxy resin) and "ESN485" (naphthol novolac type epoxy resin) manufactured by Nippon Steel Chemical Co., Ltd.;
Examples of the epoxy resin include "YX4000H" and "YL6121" (biphenyl type epoxy resin), "YX4000HK" (bixylenol type epoxy resin), and "YL7800" (fluorene type epoxy resin), all manufactured by Mitsubishi Chemical Corporation.
These may be used alone or in combination of two or more.

By including the liquid epoxy resin (A) in the epoxy resin (A-2), the melt viscosity of the resin composition can be reduced and the flowability can be improved. As a result, when the resin composition of the present invention is used as a resin composition film in the manufacture of a multilayer printed wiring board or the like, it becomes possible to achieve excellent flowability and conform to the shape of the conductor layer or the like when subjected to heat and pressure molding.

As liquid epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, and naphthalene type epoxy resins are preferred, and bisphenol A type epoxy resins and bisphenol F type epoxy resins are more preferred. Commercially available liquid epoxy resins include, for example, "jER828", "jER828EL", and "jER828US" (bisphenol A type epoxy resins), "jER806", "jER806H", and "jER807" (bisphenol F type epoxy resins), and "jER152" (phenol novolac type epoxy resins) manufactured by Mitsubishi Chemical Corporation, "ZX1059" (a mixture of bisphenol A type epoxy resins and bisphenol F type epoxy resins) manufactured by Nippon Steel Chemical Co., Ltd., and "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins) manufactured by DIC Corporation. These may be used alone or in combination of two or more.

The viscosity of the liquid epoxy resin (A-2) at 25°C is preferably 500 poise or less, more preferably 10 to 300 poise, and even more preferably 20 to 200 poise. By keeping it in this range, the melt viscosity of the resin composition can be kept low, and high fluidity can be obtained.

The content ratio of the solid epoxy resin (A-1) to the liquid epoxy resin (A-2) (solid epoxy resin:liquid epoxy resin) is preferably in the range of 9:1 to 1:9 by mass, more preferably in the range of 4:1 to 1:4, even more preferably in the range of 3:1 to 1:3, and particularly preferably in the range of 2:1 to 1:2. By setting the content ratio of the solid epoxy resin to the liquid epoxy resin in the above range, it becomes easy to achieve both high fluidity and heat resistance.

The epoxy equivalent of the epoxy resin (A) is preferably 50 to 4500, more preferably 50 to 3000, even more preferably 80 to 2000, and even more preferably 100 to 1000. By setting it within this range, the crosslink density of the cured product of the resin composition will be sufficient, making it easier to achieve sufficient heat resistance and mechanical strength when used as a resin composition film. The epoxy equivalent can be measured according to JIS K7236, and is the mass of resin per equivalent of epoxy groups.

Hexagonal boron nitride filler (B)
The resin composition of the present invention contains a hexagonal boron nitride filler having an average particle size D50 of 1 to 10 μm and a maximum particle size Dmax of 30 μm or less. By containing the hexagonal boron nitride filler in the resin composition, it becomes possible for the cured product of the resin composition to have high thermal conductivity. Furthermore, by making the average particle size 1 to 10 μm and the maximum particle size Dmax 30 μm or less, the resin composition can be easily molded into a film of about 10 μm to several hundred μm for use as an insulating layer of a multilayer printed wiring board, and high thermal conductivity can be easily obtained at that thickness. In addition, by making the maximum particle size Dmax within the above range, the melt viscosity of the resin composition is reduced, and in the case of using the resin composition in the manufacture of a multilayer printed wiring board or the like, it is also possible to improve the conformability to the shape of a conductor layer or the like when performing heat and pressure molding.

The average particle size D50 of the hexagonal boron nitride filler (B) is preferably 2.0 μm or more, and more preferably 3.0 μm or more. The average particle size D50 is preferably 8.0 μm or less, and more preferably 7.0 μm or less. The maximum particle size Dmax is preferably 25 μm or less, and more preferably 20 μm or less.

The D90/D10 of the hexagonal boron nitride filler (B) is preferably 9.0 or less, more preferably 7.0 or less, and even more preferably 6.0 or less. A small D90/D10 means that the particle size distribution is sharp and there are many particles with a size close to D50. A small D90/D10 allows for efficient interaction with silica particles, improving the affinity between the hexagonal boron nitride filler and the epoxy resin, and making it easier to improve thermal conductivity. There is no particular limit to the lower limit of D90/D10, and it is sufficient if it is equal to or greater than the theoretical lower limit of 1.0.

The D90 of the hexagonal boron nitride filler (B) is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. By setting D90 within the above range, it becomes easy to mold the resin composition into a film and use it as a build-up film.

The D10 of the hexagonal boron nitride filler (B) is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. By setting D10 within the above range, it is possible to suppress an increase in the viscosity of the resin composition.

In the present invention, the average particle size D50 is the particle size at which the cumulative 50% value is reached on a volume basis in the particle size distribution measured by the laser diffraction scattering method. Similarly, D10 is the particle size at which the cumulative 10% value is reached on a volume basis, and D90 is the particle size at which the cumulative 90% value is reached on a volume basis. Furthermore, the maximum particle size Dmax is the maximum value of the measured particle size.

The specific surface area SA of the hexagonal boron nitride filler (B) is not particularly limited, but is preferably 1.0 to 10 m ² /g. The specific surface area SA is more preferably 1.5 m ² /g or more, and even more preferably 2.0 m ² /g or more. The specific surface area SA is more preferably 9.0 m ² /g or less, and even more preferably 8.0 m ² /g or less. By having the specific surface area in the above range, it becomes easy to improve the thermal conductivity of the resin composition, and the dispersibility in the epoxy resin becomes good, and when used as a resin composition film, it becomes easy to make the melt viscosity of the resin composition low and in an optimal range. The specific surface area SA can be measured by the BET method (nitrogen adsorption one-point method) using nitrogen gas adsorption.

The oxygen content OC of the hexagonal boron nitride filler (B) is not particularly limited, but is preferably 1 mass% or less, more preferably 0.7 mass% or less, and even more preferably 0.5 mass% or less. By having the oxygen content in the above range, it becomes easy to improve the thermal conductivity of the resin composition.
The oxygen content OC of the hexagonal boron nitride filler (B) can be measured using the device described in the Examples.

The value obtained by dividing the average particle diameter D50 (μm) of the hexagonal boron nitride filler (B) by the product of the specific surface area SA (g/m ² ) and the oxygen content OC (%) (hereinafter, sometimes referred to as the "X value") is preferably 2 to 30. The X value is more preferably 3 or more, and more preferably 20 or less. In general, in the case of a hexagonal boron nitride filler, the thermal conductivity of a resin composition can be improved by increasing the average particle diameter D50. However, considering that the resin composition is used as an insulating layer of a multilayer printed wiring board, it is difficult to improve the thermal conductivity because the average particle diameter D50 cannot be increased, but by adjusting the specific surface area to be large and the oxygen content to be low, and setting the X value within the above range, it becomes easy to improve the thermal conductivity of the cured product of the resin composition.

The hexagonal boron nitride filler (B) of the present invention may be an independent single particle, or an agglomerated particle consisting of several small primary particles. It may also be a mixture of these single particles and agglomerated particles. Primary particles of hexagonal boron nitride are plate-shaped (flat) and have high in-plane thermal conductivity, but relatively low thermal conductivity in the thickness direction. Therefore, in order to improve the thermal conductivity in the thickness direction of the insulating layer of a multilayer printed wiring board, it is preferable to contain agglomerated particles to make it easier to form a thermal conduction path in the thickness direction of the insulating layer.

The manufacturing method of the hexagonal boron nitride filler (B) is not particularly limited, and hexagonal boron nitride filler manufactured by a known method can be used. Examples of methods for manufacturing hexagonal boron nitride include the melamine method in which a mixed powder of boron oxide and a nitrogen-containing organic compound is heated, the direct nitridation method in which boron carbide is heated in a nitrogen atmosphere, the reduction nitridation method in which a mixed powder of an oxygen-containing boron compound, carbon, and an oxygen-containing calcium compound is heated in a nitrogen atmosphere, and the gas phase synthesis method.

The melamine method is, for example, the method disclosed in JP 2022-185586 A, and the reduction nitridation method is, for example, the method disclosed in JP 2022-185585 A. Commercially available hexagonal boron nitride fillers include, for example, R-BN (manufactured by Nisshin Refratec Co., Ltd.) and UHP-S2 (manufactured by Resonac Co., Ltd.). It is also possible to use hexagonal boron nitride powder obtained by a known manufacturing method or commercially available hexagonal boron nitride powder by adjusting the particle size distribution using a sieve or a classifier so that the average particle size and maximum particle size are within the desired range. It is also possible to adjust the specific surface area using a sieve or a classifier.

The hexagonal boron nitride filler may be one obtained by the melamine method or the reduction nitridation method, or a commercially available product that has been subjected to a sintering treatment. The sintering treatment may be carried out, for example, at 1400 to 2000°C in an inert gas atmosphere such as nitrogen. The sintering treatment may be carried out using only hexagonal boron nitride, or may be carried out by adding a small amount of boron oxide to hexagonal boron nitride. The sintering treatment can efficiently reduce the oxygen content of the hexagonal boron nitride filler. In addition, the crystallinity of the hexagonal boron nitride filler is improved and the grains grow, making it possible to reduce the specific surface area. Note that the average particle size D50 and maximum particle size Dmax may increase after the sintering treatment due to grain growth and the formation of agglomerates between particles caused by the sintering treatment, so the particle size distribution may be adjusted, as necessary, by crushing, sieving, classifying devices, or the like so that the average particle size D50 and maximum particle size Dmax are within the desired range.

Silica filler (C)
The resin composition of the present invention is characterized in that it contains a silica filler having an average particle size D50 of 0.1 to 1 μm together with the hexagonal boron nitride filler (B). By blending such a silica filler and allowing it to coexist with the hexagonal boron nitride filler, the thermal conductivity of the cured product of the resin composition can be increased. The reason for this is not clear, but the present inventors believe it to be as follows.

As mentioned above, when hexagonal boron nitride filler with a small average particle size is mixed with epoxy resin, the adhesion between the epoxy resin and the hexagonal boron nitride filler is reduced due to the fact that the hexagonal boron nitride filler is a plate-like particle and does not have a high affinity with the epoxy resin, and the particle size is small and the surface area is large, resulting in a cutoff of the heat conduction path. Therefore, even if the content ratio of hexagonal boron nitride filler is increased, it is thought that the thermal conductivity will not improve but will decrease. Here, if silica filler, which has a higher affinity with epoxy resin than hexagonal boron nitride filler, is mixed, part of the surface of the hexagonal boron nitride filler will come into contact with the silica filler, so the area of contact between the hexagonal boron nitride filler and the epoxy resin can be reduced. In this case, it is necessary to use a small average particle size of 0.1 to 1 μm so that the silica filler can efficiently act on the surface of the hexagonal boron nitride filler. As a result, although the thermal conductivity of the silica filler itself is not high, it is possible to prevent the disruption of the thermal conduction path between the epoxy resin and the hexagonal boron nitride filler. Furthermore, it is presumed that the silica filler penetrates into the gaps between the hexagonal boron nitride filler, improving the dispersibility of the hexagonal boron nitride filler, spreading the thermal conduction path of the hexagonal boron nitride throughout the entire resin composition film, and thus achieving high thermal conductivity.

In addition, since silica filler has a smaller dielectric constant and dielectric dissipation factor than hexagonal boron nitride filler, adding it is unlikely to significantly increase the dielectric constant and dielectric dissipation factor of the resin composition. Therefore, when the resin composition is used as a film material for the insulating layer of a multilayer printed wiring board, it is easy to reduce transmission loss.

The average particle size D50 of the silica filler (C) is 0.1 to 1.0 μm. The average particle size D50 is preferably 0.15 μm or more, and more preferably 0.2 μm or more. The average particle size D50 is preferably 0.9 μm or less, and more preferably 0.8 μm or less. By having the average particle size D50 of the silica filler (C) within the above range, it is possible to act on the surface of the hexagonal boron nitride filler and improve the affinity between the hexagonal boron nitride filler and the epoxy resin.

The maximum particle size Dmax of the silica filler (C) is preferably 2 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less. If the maximum particle size Dmax is within the above range, it becomes easy to mold the resin composition into a film and use it as a build-up film.

The D90/D10 of the silica filler (C) is preferably less than 4.0, more preferably 3.0 or less, and even more preferably 2.5 or less. A small D90/D10 means that the particle size distribution is sharp and there are many particles with a size close to D50. A small D90/D10 allows the silica particles to act efficiently on the surface of the hexagonal boron nitride filler, which tends to improve the affinity between the hexagonal boron nitride filler and the epoxy resin. There is no particular limit to the lower limit of D90/D10, and it is sufficient if it is equal to or greater than the theoretical lower limit of 1.0.

The D90 of the silica filler (C) is preferably 1.5 μm or less, more preferably 1.2 μm or less, and even more preferably 1.0 μm or less. By setting the D90 within the above range, the silica filler can easily penetrate into the gaps between the hexagonal boron nitride filler, which makes it easier to improve the dispersibility of the hexagonal boron nitride filler.

The D10 of the silica filler (C) is preferably 0.05 μm or more, more preferably 0.08 μm or more, and even more preferably 0.1 μm or more. By setting D10 within the above range, it is possible to suppress an increase in the viscosity of the resin composition.

The specific surface area of the silica filler (C) is not particularly limited, but is preferably 2 to 40 m ² /g. The specific surface area is more preferably 3 m ² /g or more, and even more preferably 4 m ² /g or more. The specific surface area is more preferably 30 m ² /g or less, and even more preferably 20 m ² /g or less. By having a specific surface area within the above range, when combined with the hexagonal boron nitride filler (B) and blended into an epoxy resin, the silica filler can efficiently act on the surface of the hexagonal boron nitride filler.

The shape of the silica filler (C) is not particularly limited, but from the viewpoint of increasing affinity with the epoxy resin, it is preferable that it is spherical.

The method of producing the silica filler (C) is not particularly limited, and silica fillers produced by known methods can be used. Preferred spherical silica includes, for example, synthetic silica produced by a dry method or a wet method, and fused silica. Commercially available silica fillers include, for example, NSS-3N, SS-03, SS-04, and SS-07 (manufactured by Tokuyama Corp.), SO-C1 and SO-C2 (manufactured by Denka Co., Ltd.), and SFP-20M and SFP-30M (manufactured by Admatechs Corp.).

The silica filler (C) may be a filler that has been surface-treated with a surface treatment agent. By carrying out the surface treatment, the affinity between the silica and the epoxy resin is further improved, and it becomes easier to improve the fluidity of the resin composition. As the surface treatment agent, for example, known treatment agents such as silane compounds, aluminate coupling agents, and titanate coupling agents can be used without any particular restrictions. Among these, silane compounds that can react at a particularly high reaction rate are preferably used.

Specific examples of silane compounds used as the surface treatment agent include silane compounds having reactive functional groups, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-acryloxypropyltrimethoxysilane. , 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropylmethyldimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, and alkoxysilane such as allyltrimethoxysilane.

Examples of silane compounds with non-reactive functional groups include methyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trifluoropropyltrimethoxysilane, and trifluoropropylmethyldimethoxysilane.

Other usable silane compounds include chlorosilanes such as vinyltrichlorosilane, methyltrichlorosilane, dimethyldichlorosilane, trichloromethylsilane, ethyldimethylchlorosilane, propyldimethylchlorosilane, phenyltrichlorosilane, trifluoropropyltrichlorosilane, and isopropyldiethylchlorosilane.

Among silane compounds, those with high affinity for epoxy resins are preferred. Examples of silane compounds with high affinity include silane compounds having functional groups that can react with epoxy groups, such as glycidoxy groups and amino groups. Although they have low reactivity with epoxy groups, functional groups such as methacryloxy groups, acryloxy groups, phenyl groups, vinyl groups, and styryl groups also have high affinity with epoxy resins, and silane compounds having these functional groups are also suitable. When the surface treatment agent is used, the amount used is 0.1 to 5 parts by mass, preferably 0.5 to 4 parts by mass, per 100 parts by mass of the raw material powder before surface treatment.

The surface treatment method may be any known method without particular limitation, and may be either a dry surface treatment or a wet surface treatment. Dry surface treatment is a method of dry mixing without using a large amount of solvent when mixing the raw material powder with the surface treatment agent, such as a method of gasifying the surface treatment agent and mixing it with the raw material powder, a method of spraying or dropping the liquid surface treatment agent and mixing it with the raw material powder, and a method of diluting the surface treatment agent with a small amount of organic solvent to increase the amount of liquid, and then spraying or dropping it. Wet surface treatment is a method of mixing the raw material powder with the surface treatment agent with a solvent, such as a method of mixing the raw material powder with the surface treatment agent and the solvent, and then removing the solvent by drying or the like.

The relationship between the particle size of the silica filler (C) and the particle size of the hexagonal boron nitride filler (B) is not particularly limited, but it is preferable that the ratio of the D50 of the silica filler to the D50 of the hexagonal boron nitride filler (D50 of silica filler/D50 of hexagonal boron nitride filler) is 0.01 to 0.2. It is more preferable that the ratio is 0.05 or more, and more preferably 0.13 or less. By having the particle size ratio in the above range, the silica filler acts efficiently on the surface of the hexagonal boron nitride filler, making it easy to increase the thermal conductivity.

In the resin composition of the present invention, the total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200 to 1200 parts by mass per 100 parts by mass of the epoxy resin (A). This makes it possible to improve the thermal conductivity of the resin composition. The total content of the hexagonal boron nitride filler (B) and the silica filler (C) per 100 parts by mass of the epoxy resin (A) is preferably 300 parts by mass or more, and more preferably 400 parts by mass or more. The total content is preferably 1000 parts by mass or less, and more preferably 900 parts by mass or less.

The ratio of the content of the hexagonal boron nitride filler (B) to the content of the silica filler (C) (content of the hexagonal boron nitride filler (B): content of the silica filler (C)) is 85:15 to 30:70 by mass. The content ratio is preferably 80:20 to 35:65, and more preferably 75:25 to 40:60. If the amount of the hexagonal boron nitride filler (B) is too small, the proportion of the silica filler (C), which has low thermal conductivity, increases, making it difficult to obtain high thermal conductivity. If the amount of the silica filler (C) is too small, the adhesion between the hexagonal boron nitride filler and the epoxy resin cannot be improved, making it difficult to obtain high thermal conductivity.

Other Components The resin composition of the present invention may contain other components in addition to the epoxy resin (A), the hexagonal boron nitride filler (B), and the silica filler (C) within a range that does not impair the effects of the present invention. Examples of other components include a curing agent for the epoxy resin, a curing accelerator, other resins other than the epoxy resin, other fillers, a flame retardant, rubber particles, a thickener, a defoamer, a leveling agent, an adhesion imparting agent, an antioxidant, an ultraviolet degradation inhibitor, and a colorant.

The epoxy resin curing agent has a function of reacting with the epoxy resin and curing when the epoxy resin (A) contains a reactive epoxy resin. By including a curing agent for the epoxy resin in the resin composition of the present invention, it becomes easy to obtain a cured product having high strength and heat resistance when the resin composition of the present invention is thermally cured. The epoxy resin curing agent is not particularly limited, and a known curing agent can be used. Examples of the epoxy resin curing agent include phenol-based curing agents, naphthol-based curing agents, active ester-based curing agents, cyanate ester-based curing agents, benzoxazine-based curing agents, and acid anhydride-based curing agents. From the viewpoint of moldability of the resin composition into a film and heat resistance of the cured product, phenol-based curing agents, naphthol-based curing agents, and active ester-based curing agents are preferred. Active ester-based curing agents are more preferred because they reduce the dielectric tangent of the cured product of the resin composition film of the present invention and provide excellent dielectric properties. The curing agents may be used alone or in combination of two or more types.

As phenol-based and naphthol-based hardeners, taking into consideration the heat resistance and water resistance of the cured product, phenol-based and naphthol-based hardeners having a novolac structure are preferred. As phenol-based hardeners, phenol novolac, cresol novolac, bisphenol A-type novolac, phenol aralkyl novolac, biphenyl aralkyl novolac, aminotriazine novolac (phenol novolac containing a triazine structure), triphenylmethane novolac, and cyclopentadiene phenol novolac are preferred. As naphthol-based hardeners, naphthol aralkyl-type phenol novolac, aralkyl-type naphthol-phenol novolac, and naphthol-cresol-type novolac are preferred.

Commercially available phenol-based and naphthol-based hardeners include, for example, "GPH-103," "GPH-65," and "TKG-105" manufactured by Nippon Kayaku Co., Ltd.; "TD-2093," "TD-2090," "LF-6161," "LF-4871," "LA-7052," "LA-7054," "LA-1536," and "LA-1356" manufactured by DIC Corporation; "ZX-798" and "SN485" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "TPM-100" and "GPNX" manufactured by Gun-ei Chemical Co., Ltd.; and "S-TPM" and "J-DDP" manufactured by JFE Chemical Corporation.

The reactive group equivalent (hydroxyl group equivalent) of the phenol-based curing agent and naphthol-based curing agent is not particularly limited, but from the viewpoint of the moldability of the resin composition into a film and the heat resistance of the cured product, it is preferably 20 to 4000, more preferably 50 to 2000, and even more preferably 50 to 1000. The hydroxyl group equivalent is the mass of resin per equivalent of hydroxyl group.

Active ester-based hardeners include active ester-based hardeners with a dicyclopentadiene structure, active ester-based hardeners with a naphthalene structure, active ester-based hardeners containing acetylated phenol novolac, and active ester-based hardeners containing benzoylated phenol novolac. Taking into account the heat resistance and water resistance of the cured product, active ester-based hardeners with a dicyclopentadiene structure and active ester-based hardeners with a naphthalene structure are more preferred. Commercially available active ester-based hardeners include, for example, "HPC-8000-65T" (active ester-based hardener with a dicyclopentadiene structure) and "HPC-8150-62T" (active ester-based hardener with a naphthalene structure) manufactured by DIC Corporation.

The reactive group equivalent (active ester group equivalent) of the active ester curing agent is not particularly limited, but from the viewpoints of formability of the resin composition into a film and heat resistance of the cured product, it is preferably 50 to 2000, more preferably 50 to 1000, and even more preferably 100 to 500. The active ester group equivalent is the mass of resin per equivalent of active ester group.

The content of the curing agent in the resin composition of the present invention is not particularly limited, but taking into consideration the heat resistance and mechanical strength of the cured product, it is preferably 50 to 200 parts by mass, more preferably 65 to 150 parts by mass, and even more preferably 75 to 125 parts by mass, per 100 parts by mass of the epoxy resin (A). In addition, the ratio of the total number of reactive groups such as hydroxyl groups and active ester groups of the curing agent to the total number of epoxy groups of the epoxy resin (A) is not particularly limited, but is preferably 0.5 to 2, more preferably 0.6 to 1.5, and even more preferably 0.65 to 1.25. Here, the total number of epoxy groups of the epoxy resin (A) is the value obtained by dividing the mass of each epoxy resin by the epoxy equivalent, and the total number of reactive groups of the curing agent is the value obtained by dividing the mass of each curing agent by the reactive group equivalent.

The curing accelerator has the function of accelerating the reaction between the epoxy group of the epoxy resin (A) and the reactive group of the curing agent and the polymerization of the epoxy group. When the resin composition of the present invention contains an epoxy resin curing accelerator, when the epoxy resin (A) contains a reactive epoxy resin, the resin composition of the present invention can be easily cured when thermally cured, and it becomes easy to obtain high strength after curing. When the resin composition of the present invention contains an epoxy resin curing accelerator, the content is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the epoxy resin (A).

As the curing accelerator for the epoxy resin, any known accelerator can be used without particular limitation, and examples thereof include amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, and guanidine-based curing accelerators, with amine-based curing accelerators and imidazole-based curing accelerators being preferred. The curing accelerators may be used alone or in combination of two or more types.

Amine-based curing accelerators include, for example, trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene.

Examples of imidazole-based hardening accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-furan. phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-( 1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2- These include imidazole compounds such as phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds and epoxy resins.

Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate.

Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide.

By adding other resins to the resin composition of the present invention, the flexibility of the resin composition can be improved. This improves the coating properties when forming a resin composition film, resulting in a uniform film, and the film becomes more flexible, improving winding properties, and also making it easier to improve the impact resistance of the cured product and make it less likely to crack. Examples of other resins include thermoplastic resins such as phenoxy resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyimide resin, polyamideimide resin, polyethersulfone resin, polyphenylene ether resin, and polysulfone resin. Among these, phenoxy resin, which has a structure similar to that of epoxy resin, is preferred because of its good compatibility with epoxy resin. These thermoplastic resins may be used alone or in combination of two or more.

Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenol acetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any terminal structure such as a phenolic hydroxyl group or an epoxy group. The phenoxy resin may be used alone or in combination of two or more types. Examples of commercially available phenoxy resins include "YX6954BH30" (phenoxy resin containing a bisphenol acetophenone skeleton), "YX8100BH30" (phenoxy resin containing a bisphenol S skeleton), and "YX7553BH30" manufactured by Mitsubishi Chemical Corporation. The weight average molecular weight of the phenoxy resin is preferably 5,000 to 10,000. The weight average molecular weight is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography.

When the resin composition of the present invention contains a phenoxy resin, the content is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, and even more preferably 1 to 20 parts by mass, per 100 parts by mass of the epoxy resin (A).

The other fillers are fillers made of materials other than hexagonal boron nitride filler and silica filler, and may include, for example, aluminum nitride, aluminum oxide, zinc oxide, magnesium oxide, titanium oxide, silicon nitride, aluminum hydroxide, magnesium hydroxide, silicon carbide, calcium carbonate, barium sulfate, talc, or diamond.

The content of the other filler is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the total content of the hexagonal boron nitride filler (B) and the silica filler (C), and it is particularly preferable that the resin composition does not contain other fillers. If a large amount of other fillers is contained, the interaction between the hexagonal boron nitride filler (B) and the silica filler (C) may be inhibited. Furthermore, if a filler having a higher dielectric constant than hexagonal boron nitride and silica, such as aluminum nitride, aluminum oxide, and magnesium oxide, is contained, the dielectric loss may increase. When the resin composition contains other fillers, the particle size is preferably smaller than that of the hexagonal boron nitride filler (B), more preferably the average particle size is less than 2 μm, and even more preferably the average particle size is less than 1.5 μm. The maximum particle size of the other fillers is preferably smaller than the maximum particle size of the hexagonal boron nitride filler (B), more preferably less than 4.5 μm, and even more preferably less than 4 μm.

The resin composition of the present invention may contain a flame retardant or rubber particles as other components. Flame retardants impart flame retardancy when the resin composition of the present invention is used in a semiconductor product, and examples of such flame retardants include organic phosphorus flame retardants, organic nitrogen-containing phosphorus compounds, nitrogen compounds, silicone flame retardants, and metal hydroxides. These flame retardants may be used alone or in combination of two or more.

The resin composition contains rubber particles, which can reduce the internal stress caused by thermally curing the resin composition, reduce the warping of the cured product, and also provide impact resistance. Examples of rubber particles include fine particles such as core-shell type rubber particles, cross-linked acrylonitrile butadiene rubber particles, cross-linked styrene butadiene rubber particles, and acrylic rubber particles. The average particle size of the rubber particles is preferably 1 μm or less, and more preferably 0.8 μm or less.
Furthermore, the resin composition of the present invention may contain additives such as a thickener, an antifoaming agent, a leveling agent, an adhesion imparting agent, an antioxidant, an ultraviolet degradation inhibitor, and a colorant, as necessary.

The resin composition of the present invention has properties that allow it to be used as a material for forming an insulating layer in a multilayer printed wiring board, and has characteristics not found in conventional resin compositions, such as high thermal conductivity, low dielectric constant and low dielectric tangent after curing. By using such a resin composition as a film material for forming an insulating layer in a multilayer printed wiring board, it is possible to easily manufacture a multilayer printed wiring board with high heat dissipation and low transmission loss.

The thermal conductivity of the cured product obtained from the resin composition of the present invention is preferably 1.0 W/m·K or more, more preferably 1.5 W/m·K or more, even more preferably 2.0 W/m·K or more, and particularly preferably 2.5 W/m·K or more. The higher the thermal conductivity, the better, but it is generally 30 W/m·K or less. Thermal conductivity can be measured by temperature wave thermal analysis (i-phase method).

The dielectric constant of the cured product obtained from the resin composition of the present invention is preferably 3.5 or less, more preferably 3.2 or less. The smaller the dielectric constant, the better, but it is generally 2.0 or more. The dielectric tangent of the cured product is preferably 0.012 or less, more preferably 0.008 or less. The smaller the dielectric tangent, the better, but it is generally 0.001 or more. The dielectric constant and dielectric tangent can be measured by the cavity resonance perturbation method using a split cylinder resonator and a network analyzer at a temperature of 25°C and a frequency of 10 GHz.

The relative density of the cured product obtained from the resin composition of the present invention is preferably 0.80 or more, more preferably 0.90 or more, and even more preferably 0.95 or more. The relative density is expressed as the ratio of the density measured for a cured sample of the resin composition to the density (theoretical density) calculated from the density and compounding ratio of each material used, and is 1 when the theoretical density and the sample density are the same. A high relative density indicates that the resin composition has few defects such as voids and has excellent adhesion at the interface of each component, which makes it possible to increase the thermal conductivity of the cured product of the resin composition. The upper limit of the relative density is not particularly limited, but is usually 1.0 or less. The density of the cured product of the resin composition can be measured by the Archimedes method.

The method for producing the resin composition of the present invention is not particularly limited, and the resin composition can be produced by a known method using a blender or mixer, etc., by mixing the resin, the filler, and other components as necessary. When mixing, the components may be added simultaneously to a mixer or the like and mixed, or the components may be added sequentially to a mixer or the like and mixed. The order of addition is not particularly limited. Furthermore, the mixing may be performed under heating, or in an adjusted atmosphere such as an inert gas atmosphere, if necessary.

The resin composition of the present invention, when cured, has high thermal conductivity and low dielectric constant and dielectric tangent, and therefore can be suitably used for the insulating layer of the multilayer printed wiring board. In addition to these applications, the resin composition can be used in a wide range of applications requiring heat dissipation and dielectric properties, such as adhesive films, insulating layers for metal-clad laminates, sealing resins for component-embedded boards, insulating resin sheets such as prepregs, underfill materials, die bonding materials, semiconductor sealing materials, and hole-filling resins. When using the resin composition of the present invention for the applications described above, it is generally industrially preferable to use it as a resin composition film molded into a film-like form.

The resin composition film of the present invention is a film formed from the resin composition of the present invention, and the thickness of the film is preferably 5 to 250 μm. The thickness is more preferably 10 μm or more, even more preferably 20 μm or more, more preferably 200 μm or less, even more preferably 150 μm or less.

The method for producing the resin composition film of the present invention is not particularly limited, and the resin composition can be made into a film by a conventionally known method. Among them, a suitable method is, for example, a method in which the resin composition is dissolved in an organic solvent, the organic solvent and the resin composition are mixed to prepare a varnish of the resin composition, the varnish of the resin composition is applied to a support using a die coater, knife coater, comma coater, gravure coater, or the like, and the organic solvent is then dried by heating or blowing hot air, or the like.

The organic solvents include, for example, acetone, methanol, ethanol, butanol, 2-propanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 2-acetoxy-1-methoxypropane, toluene, xylene, methyl ethyl ketone, N,N-dimethylformamide, methyl isobutyl ketone, N-methyl-pyrrolidone, n-hexane, cyclohexane, cyclohexanone, and solvent naphtha, which is a mixture. These organic solvents may be used alone or in combination of two or more.

The boiling point of the organic solvent is preferably 200°C or less, and more preferably 180°C or less, since it can be easily removed during drying. The content of the organic solvent in the varnish of the resin composition is not particularly limited, and may be appropriately adjusted taking into consideration factors such as the coatability onto the support.

There are no particular limitations on the drying conditions, but it is preferable to dry the resin composition film so that the content of the organic solvent in the film is preferably 10% by mass or less, and more preferably 5% by mass or less. Although this varies depending on the boiling point of the organic solvent used in the resin composition varnish, for example, by drying by heating at 60°C to 150°C for 1 to 5 minutes, a resin composition film in which the resin composition has not been cured too much by heat can be obtained.

The resin composition film of the present invention is preferably in a partially cured state, so-called B-stage film. Because it is in a partially cured state and not completely cured, it can easily conform to the shape of the conductor layer during the manufacturing process of multilayer printed wiring boards and other semiconductor materials, and further curing can then proceed to improve strength and durability.

Various plastic films can be suitably used as the support. Examples of plastic films include polyester-based films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; olefin-based films such as polyethylene film and polypropylene film; and polyimide films. Among them, polyethylene terephthalate film, which has excellent smoothness and heat resistance and is inexpensive, is more preferable. Taking into consideration the wettability when applying the resin composition film and the releasability when manufacturing various semiconductor substrates, the coated side of the plastic film of the support may be subjected to a release treatment, matte treatment, corona discharge treatment, or the like. Metal foils such as copper foil and aluminum foil can also be used as the support. As the copper foil, rolled copper foil and electrolytic copper foil can be suitably used. By using a metal foil as the support, the process of laminating metal foils can be omitted in the manufacture of various substrates, and the adhesive strength can also be increased. The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 150 μm, more preferably in the range of 10 μm to 100 μm, and even more preferably in the range of 10 μm to 60 μm.

In the resin composition film, a protective film similar to the support may be further laminated on the surface not in contact with the support. The thickness of the protective film is not particularly limited, but is, for example, 5 μm to 40 μm. By laminating the protective film, it is possible to prevent the adhesion of dirt and the like to the surface of the resin composition film and to prevent scratches. By laminating the protective film, it is also possible to wind the resin composition film in a roll. When manufacturing multilayer printed wiring boards and other semiconductor materials, the protective film is peeled off before use.

The resin composition film has a high thermal conductivity, a low dielectric constant and a low dielectric loss tangent, and can be suitably used for forming an insulating layer of a multilayer printed wiring board. In the case of a high heat dissipation insulating layer of a metal-based substrate, the resin composition can be pressed at a high pressure of several MPa or more when curing. Therefore, it is possible to increase the adhesion to a certain extent even with epoxy resin and hexagonal boron nitride filler, which have poor affinity, and even if hexagonal boron nitride filler is highly filled in epoxy resin without mixing silica, the decrease in thermal conductivity may be suppressed. However, in the manufacture of multilayer printed wiring boards, high pressure cannot be applied and it is difficult to obtain high thermal conductivity, so the effect of using the resin composition of the present invention is remarkable. In addition, it can be used in a wide range of applications requiring heat dissipation, such as adhesive films, insulating layers of metal-clad laminates, sealing resins for component-embedded substrates, insulating resin sheets such as prepregs, underfill materials, die bonding materials, semiconductor sealing materials, and hole filling resins.

The present invention relates to, for example, the following aspects [1] to [5].
[1]
Contains an epoxy resin (A), a hexagonal boron nitride filler (B), and a silica filler (C),
a total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200 to 1,200 parts by mass relative to 100 parts by mass of the epoxy resin (A);
The epoxy resin (A) includes a solid epoxy resin (A-1) and a liquid epoxy resin (A-2),
The hexagonal boron nitride filler (B) has an average particle size D50 of 1 to 10 μm and a maximum particle size Dmax of 30 μm or less;
The average particle size D50 of the silica filler (C) is 0.1 to 1 μm,
The mass ratio of the content of the hexagonal boron nitride filler (B) to the content of the silica filler (C) is 85:15 to 30:70.
Resin composition.

[2]
The resin composition according to [1], wherein the ratio (D90/D10) of D90, which is the particle size at the cumulative 90% value on a volume basis, to D10, which is the particle size at the cumulative 10% value on a volume basis, in the particle size distribution of the hexagonal boron nitride filler (B), is 9.0 or less.

[3]
The resin composition according to [1] or [2], wherein in the particle size distribution of the silica filler (C), the ratio (D90/D10) of D10, which is the particle size at the cumulative 10% value on a volume basis, to D90, which is the particle size at the cumulative 90% value on a volume basis, is less than 4.0.

[4]
A resin composition film comprising the resin composition according to any one of [1] to [3].

[5]
A multilayer printed wiring board comprising the resin composition according to any one of [1] to [3] or a cured product thereof.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. The various materials used and the conditions for measuring physical properties are described below.

<Epoxy resin>
The following solid epoxy resin (A-1) was used:

NC-3000 (biphenyl aralkyl type epoxy resin manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 276, softening point 58°C)
EPPN-501HY (trisphenolmethane type epoxy resin manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 166, softening point 60°C)
LCE-2615 (tough type epoxy resin manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 490, softening point 102°C)
Each of the above solid epoxy resins was dissolved in methyl ethyl ketone, and used as a 50 mass % epoxy resin solution for preparing a resin composition.
As the liquid epoxy resin (A-2), jER828 (a bisphenol A type epoxy resin manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 189, viscosity (25° C.) 135 poise) was used.

<Hexagonal boron nitride filler>
The following hexagonal boron nitride fillers (B) were used. The physical properties of each filler are shown in Table 1.
B-1: Hexagonal boron nitride filler produced by the method described in Example 1 of JP 2022-185586 A. The obtained hexagonal boron nitride filler (B-1) had primary particles with a plate-like shape with a size of about 1 μm, and contained many strongly aggregated particles of several μm in size.

B-2: B-1 baked under the following conditions.
B-1 was subjected to a calcination treatment in a graphite Tammann furnace under a nitrogen gas atmosphere by increasing the temperature to 1500° C., heating at 1500° C. for 6 hours, and then increasing the temperature to 1940° C., heating at 1940° C. for 2 hours. After the calcination treatment, the mixture was sieved through a sieve with 45 μm openings to obtain a hexagonal boron nitride filler (B-2).

B-3: Hexagonal boron nitride filler produced by the method described in Example 5 of JP 2022-185585 A. The obtained hexagonal boron nitride filler (B-3) contained agglomerated particles in which the primary particles were plate-shaped and had a size of about several μm, and several of these particles were tightly aggregated.

B-4: B-3 baked under the following conditions.
B-3 was subjected to a calcination treatment in a graphite Tammann furnace under a nitrogen gas atmosphere by increasing the temperature to 1650° C., heating at 1650° C. for 6 hours, and then increasing the temperature to 1890° C., heating at 1890° C. for 2 hours. After the calcination treatment, the mixture was sieved through a sieve with 45 μm openings to obtain a hexagonal boron nitride filler (B-4).
B-5: R-BN (manufactured by Nisshin Refratec Co., Ltd.)

<Silica filler>
The following silica fillers (C) were used. All were spherical fillers, and their physical properties are shown in Table 2.
C-1: A silica filler produced by the method described in Example 9 of WO 2020/175160, which was surface-treated by the following method.
C-2: SO-C2 (manufactured by Admatechs Co., Ltd.) that was surface treated by the following method.

C-3: Sylfil NSS-3N (Tokuyama Corp.) that was surface treated in the following manner.
C-4: A silica filler produced by the method described in Example 7 of WO 2018/096876, which was surface-treated by the following method.
C-5: SO-C5 (manufactured by Admatechs Co., Ltd.) that was surface treated by the following method.

The surface treatment was carried out by placing 600 g of the raw material powder, 5 g of the surface treatment agent N-phenyl-3-aminopropyltrimethoxysilane (KBM-573, manufactured by Shin-Etsu Silicones), and 1,200 g of isopropyl alcohol in a glass eggplant flask, stirring with a fluororesin stirring blade for 30 minutes, and then removing the isopropyl alcohol under reduced pressure at 50°C using a rotary evaporator, followed by drying under reduced pressure at 100°C.

<Curing Agent>
The following epoxy resin hardeners were used:
HPC-8000-65T (active ester-based curing agent having a dicyclopentadiene structure, manufactured by DIC Corporation, active ester group equivalent weight 223, non-volatile content 65% by mass in toluene solution)
GPH-103 (biphenylaralkylphenol novolak manufactured by Nippon Kayaku Co., Ltd., hydroxyl equivalent 230, softening point 103° C.)
Solid GPH-103 was dissolved in methyl ethyl ketone and used as a 50% by mass solution for preparing the resin composition.

<Curing accelerator>
As the curing accelerator, 4-dimethylaminopyridine (DMAP, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used.

<Phenoxy resin>
The phenoxy resin used was YX6954BH30 (a phenoxy resin containing a bisphenol acetophenone skeleton, manufactured by Mitsubishi Chemical Corporation, with a weight average molecular weight of 40,670 and a cyclohexanone/methyl ethyl ketone (1/1) solution with a nonvolatile content of 30% by mass).

<Measurement of average particle size and maximum particle size of filler>
A hexagonal boron nitride filler was added to ethanol to a concentration of 0.2% by mass, and then the mixture was dispersed by irradiating it with ultrasonic waves at about 200 W for 20 minutes. The particle size distribution of the dispersed sample was measured using a laser diffraction scattering particle size distribution analyzer (MICROTRACK-MT3300EXII, manufactured by Microtrack-Bell, Inc.). The hexagonal boron nitride filler contained the above-mentioned strongly aggregated particles, and further, during the drying and baking processes during production, relatively weak aggregation occurred. During the stirring and dispersion process in the preparation of a varnish of the resin composition described below, these weak aggregations were broken down, leaving only the strongly aggregated particles, and therefore, in the measurement of the particle size distribution, the above-mentioned ultrasonic irradiation was carried out for the purpose of breaking down the weak aggregations.

For the silica filler after the surface treatment, the silica filler was added to ethanol so that the concentration became 0.2 mass %, and then the silica filler was dispersed by irradiating it with ultrasonic waves at about 200 W for 2 minutes. The particle size distribution of the dispersed sample was measured in the same manner as for the hexagonal boron nitride filler.
In the obtained volume frequency distribution (particle size distribution) of particle diameters, the volume frequency was accumulated from the smallest particle diameter, and the particle diameter at which the accumulated value was 50% was defined as the average particle diameter D50, the particle diameter at which the accumulated value was 10% was defined as D10, the particle diameter at which the accumulated value was 90% was defined as D90, and the maximum value of the measured particle diameters was defined as the maximum particle diameter Dmax.

<Measurement of the specific surface area of the filler>
The specific surface areas of the hexagonal boron nitride filler and the silica filler were determined by the BET method (single-point nitrogen adsorption method) using a flow-type automatic specific surface area measuring device (Shimadzu Corporation: Flowsorb II-2300). For the measurement, 2 g of powder sample was used, which had been dried in advance at 100°C for 1 hour in a nitrogen gas flow.

<Oxygen content of hexagonal boron nitride filler>
The oxygen content OC of the hexagonal boron nitride filler was measured using an oxygen/nitrogen analyzer (Horiba, Ltd.: EMGA-620).

<Measurement of thermal conductivity>
The resin composition films prepared in the examples and comparative examples were heat-cured at 180°C for 90 minutes. The thermal conductivity (W/m·K) of the obtained cured product was calculated by thermal diffusivity (m ² /sec) × density (kg/m ³ ) × specific heat (J/kg·K). The thermal diffusivity was measured by temperature wave thermal analysis (ai-Phase Mobile 1u, ISO22007-3, manufactured by Ai-Phase Corporation). The same test piece was measured 12 times and the average value was adopted. The density was measured using the Archimedes method (XS204V, manufactured by Mettler Toledo Co., Ltd.), and the specific heat was measured using a differential scanning calorimeter (DSC) method (Thermo Plus Evo DSC8230, manufactured by Rigaku Corporation).

<Measurement of relative density>
The relative density of the cured product was calculated as the ratio of the actual density measured above to the theoretical density calculated (actual value/theoretical value). The theoretical density was calculated from the blending ratio of each component, assuming that the densities of the hexagonal boron nitride filler, silica filler, and the remaining components excluding the filler component were 2.27 g/ ^m3 , 2.17 g/ ^m3 , and 1.17 g/ ^m3 , respectively.

<Measurement of relative permittivity and dielectric loss tangent>
The resin composition films prepared in the examples and comparative examples were cut into pieces of 50 mm x 50 mm in size, and cured by heat treatment at 180 ° C for 90 minutes to obtain evaluation samples. Next, a split cylinder resonator (manufactured by Keycom Co., Ltd.) was connected to a vector network analyzer (manufactured by Keysight Co., Ltd.: P9377B), the evaluation sample was set in the resonator, and measurements were performed in TE011 mode, and the relative dielectric constant and dielectric loss tangent were obtained from the results obtained. The measurements were performed at a temperature of 25 ° C.

Example 1
50 parts by mass of liquid epoxy resin (A-2) jER828, 133 parts by mass of hardener HPC-8000-65T (86.7 parts by mass as non-volatile content), 33 parts by mass of phenoxy resin YX6954BH30 (10 parts by mass as non-volatile content), 0.8 parts by mass of curing accelerator DMAP, and 333 parts by mass of silica filler (C-1) were measured and mixed by stirring. 50 parts by mass of solid epoxy resin (A-1) NC3000 as non-volatile content (100 parts by mass as prepared methyl ethyl ketone solution), 333 parts by mass of hexagonal boron nitride filler (B-1), and 300 parts by mass of methyl ethyl ketone were added and stirred for 30 minutes using a homodisper. Further, methyl ethyl ketone was appropriately added to adjust the viscosity, and then filtered and defoamed to prepare a varnish of the resin composition.

Next, the varnish of the resin composition obtained above was uniformly applied to the release-treated surface of a support (release-treated polyethylene terephthalate film (HY-NS80, manufactured by Higashiyama Film Co., Ltd., thickness 38 μm)) so that the thickness after drying would be 100 μm, and the film was dried at 80° C. for 3 minutes to produce a resin composition film (B stage).
The composition of the resin composition film and the evaluation results are shown in Table 3.

<Examples 2 to 29, Comparative Examples 1 to 9>
Resin composition films were produced in the same manner as in Example 1, except that the compositions were changed as shown in Tables 3 to 5. The compositions and evaluation results of the resin composition films are shown in Tables 3 to 5.

In Comparative Example 9, as in Patent Document 2, R-BN (hexagonal boron nitride filler (B-5)) manufactured by Nissin Refratec Co., Ltd. was used as the hexagonal boron nitride filler (B), and the content of the hexagonal boron nitride filler (B) in the resin composition was set to 49 mass% (33 volume%). The reason for the lower thermal conductivity compared to Patent Document 2 is thought to be due to the difference in the thermal conductivity of the resin itself, due to the different combination of epoxy resin and hardener. In order to improve the thermal conductivity of the resin composition of Comparative Example 9, the content of the hexagonal boron nitride filler was increased to 666 mass parts (Comparative Example 1), but the thermal conductivity instead decreased. On the other hand, Example 17, which used silica filler in addition to the hexagonal boron nitride filler (B-5), was able to obtain a higher thermal conductivity than Comparative Examples 1 and 9.

Comparative Example 1 and Example 19 have the same relative dielectric constant and dielectric tangent, and can reduce transmission loss. When comparing Comparative Example 2 with Examples 4, 9 to 11, and Comparative Example 5 with Examples 14 to 16, the thermal conductivity was also increased when hexagonal boron nitride filler and silica filler were used in combination.

In Examples 4, 9 to 11, in which the mass ratio of the hexagonal boron nitride filler (B) to the silica filler (C) is within the range of 85:15 to 30:70, a higher thermal conductivity was obtained than in Comparative Examples 3 and 4, which are outside the range. This is thought to be because Comparative Example 3 had a small amount of silica filler and did not achieve the effect of the present invention, and Comparative Example 4 had a small amount of hexagonal boron nitride filler, which has high thermal conductivity. Among Examples 4, 9 to 11, Examples 4 and 9, in which the mass ratio of the hexagonal boron nitride filler (B) to the silica filler (C) is within the range of 75:25 to 40:60, had a higher thermal conductivity than Examples 10 and 11, which are outside the range.

Hexagonal boron nitride filler (B) and silica filler (C) were used in combination, but Comparative Example 8, in which the average particle size D50 of the silica filler (C) exceeded 1 μm, had a lower thermal conductivity than Examples 4, 18, 19, and 28, in which the average particle size D50 of the silica filler was 0.1 to 1 μm. It is believed that the effect of the present invention was not obtained in Comparative Example 8 because the particle size of the silica filler was too large.

The above shows that by using a specific hexagonal boron nitride filler in combination with a silica filler, it is possible to obtain a resin composition that has a high thermal conductivity in the cured product and a small relative dielectric constant and dielectric tangent. It can be said that this resin composition can be suitably used as a film to form an insulating layer in a multilayer printed wiring board.

Claims (5)

Contains an epoxy resin (A), a hexagonal boron nitride filler (B), and a silica filler (C),
a total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200 to 1,200 parts by mass relative to 100 parts by mass of the epoxy resin (A);
The epoxy resin (A) includes a solid epoxy resin (A-1) and a liquid epoxy resin (A-2),
The hexagonal boron nitride filler (B) has an average particle size D50 of 1 to 10 μm and a maximum particle size Dmax of 30 μm or less;
The average particle size D50 of the silica filler (C) is 0.1 to 1 μm,
The mass ratio of the content of the hexagonal boron nitride filler (B) to the content of the silica filler (C) is 85:15 to 30:70.
Resin composition. The resin composition according to claim 1, wherein the ratio (D90/D10) of D10, the particle size at the cumulative 10% value on a volume basis, to D90, the particle size at the cumulative 90% value on a volume basis, in the particle size distribution of the hexagonal boron nitride filler (B) is 9.0 or less. The resin composition according to claim 1, wherein the ratio (D90/D10) of D10, the particle size at the cumulative 10% value on a volume basis, to D90, the particle size at the cumulative 90% value on a volume basis, in the particle size distribution of the silica filler (C) is less than 4.0. A resin composition film comprising the resin composition according to any one of claims 1 to 3. A multilayer printed wiring board comprising the resin composition or its cured product according to any one of claims 1 to 3.