Resin composition

Abstract

The present invention provides a resin composition whose cured product has high thermal conductivity, which can be formed into a thin film shape and reduce transmission loss, using a hexagonal boron nitride filler having an average particle diameter of 1 to 10 μm. The resin composition of 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 to 1200 parts by mass with respect to 100 parts by mass of the aforementioned epoxy resin (A), the aforementioned epoxy resin (A) contains a solid epoxy resin (A-1) and a liquid epoxy resin (A-2), the aforementioned hexagonal boron nitride filler (B) has an average particle diameter D50 of 1 to 10 μm and a maximum particle diameter Dmax of 30 μm or less, the aforementioned silica filler (C) has an average particle diameter D50 of 0.1 to 1 μm, and the mass ratio of the content of the aforementioned hexagonal boron nitride filler (B) to the aforementioned silica filler (C) is 85:15 to 30:70.

Description

Technical Field

[0001] This invention relates to resin compositions. Background Technology

[0002] With the increasing performance and miniaturization of electronic devices, the wiring in multilayer printed circuit boards (PCBs) has become finer and denser. As a manufacturing technology for multilayer PCBs, a manufacturing method based on a lamination process of alternately stacking insulating and conductive layers is known. The aforementioned insulating layer can be efficiently formed using a thin-film resin composition (resin composition film). As a resin composition film, a resin composition containing thermosetting epoxy resin and silica is typically used (Patent Document 1).

[0003] To form the insulating layer of a multilayer printed circuit board, a resin composition film is typically laminated onto a conductor layer. A vacuum laminator or hot press is used to bond the conductor layer to the resin composition while simultaneously thermosetting the resin composition, thus achieving lamination and bonding. Therefore, the resin composition film requires high flowability under lamination conditions to conform to the shape of the conductor layer; hence, a combination of solid and liquid epoxy resins is often used as the epoxy resin.

[0004] Furthermore, in multilayer printed circuit boards, the thermal expansion of the insulating layer and the conductor layer (copper wiring) differs significantly, leading to reliability issues such as cracking due to thermal cycling. Low linear expansion is also required for the insulating layer. In addition, with the increasing amount of information processed in recent years and the advancement of higher frequencies in radio waves used for communication, electronic components used in information communication also need to cope with higher frequencies. Therefore, reducing transmission loss during information transmission has become important. Consequently, the materials constituting multilayer printed circuit boards are required to have low relative permittivity and low dielectric loss tangent. Therefore, silicon dioxide, which has excellent dielectric properties (low relative permittivity and low dielectric loss tangent), is typically highly filled into resin composition films. Since it is used in a thin film shape, silicon dioxide with a large particle size cannot be used as the filling material; instead, silicon dioxide with an average particle size of several μm is used.

[0005] In recent years, with the miniaturization and high performance of electronic devices, the density and mounting of semiconductor components in multilayer printed circuit boards have been developed. Along with this, the heat generated by semiconductor components has also increased, making efficient heat dissipation from the substrate crucial. Therefore, in the manufacture of multilayer printed circuit boards based on a stacking method, to address this issue, a resin composition with high thermal conductivity (hexagonal boron nitride, which has higher thermal conductivity than silicon dioxide) has been proposed as a resin composition film (Patent Document 2). Specifically, Example 5 of Patent Document 2 discloses a resin composition comprising hexagonal boron nitride filler with an average particle size of 3.0 μm, epoxy resin, and a curing agent. Hexagonal boron nitride differs from other thermally conductive fillers (e.g., aluminum nitride, silicon nitride, aluminum oxide, and magnesium oxide) in that it has a small relative permittivity and dielectric loss tangent, thus, similar to the case where silicon dioxide is used, it has the characteristic of being able to produce a resin composition with a small relative permittivity and dielectric loss tangent.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2011-132507

[0009] Patent Document 2: Japanese Patent Application Publication No. 2013-221120 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] As described above, resin compositions using hexagonal boron nitride fillers with an average particle size of several μm and capable of being used as thin films in resin compositions have been disclosed, but further high thermal conductivity is required. Generally, thermal conductivity can be improved by increasing the proportion of thermally conductive fillers in the resin composition. Therefore, in order to achieve further high thermal conductivity, the inventors prepared a resin composition with an increased proportion of hexagonal boron nitride fillers. However, contrary to expectations, the thermal conductivity did not increase, but instead decreased.

[0012] The present invention was made in view of the following circumstances, and its object is to provide a resin composition having a high thermal conductivity in the cured form, which can be formed into a thin film shape and reduce transport loss, said resin composition using hexagonal boron nitride filler with an average particle size of 1 to 10 μm.

[0013] Solution for solving the problem

[0014] The inventors conducted in-depth research to achieve the aforementioned objectives. The results showed that the primary particles of hexagonal boron nitride filler are plate-shaped, resulting in low affinity with epoxy resin. Small particle size leads to a large surface area, significantly exacerbating the adverse effects of poor affinity. Consequently, increasing the filler content reduces the adhesion between the resin and the hexagonal boron nitride filler, interrupting the thermal conductivity path and lowering the thermal conductivity. For example, as described in Japanese Patent Application Publication No. 2022-185585, even resin films using hexagonal boron nitride filler with an average particle size of several μm can exhibit high thermal conductivity when only liquid epoxy resin is used as the epoxy resin. However, in resin composition films used in the manufacture of multilayer printed circuit boards, which contain solid epoxy resin, the solid epoxy resin has high viscosity and does not easily penetrate into the gaps between the hexagonal boron nitride filler. Therefore, it is considered difficult to obtain the affinity between the epoxy resin and the hexagonal boron nitride filler, making it impossible to achieve high thermal conductivity.

[0015] Further research based on this insight revealed that by using silica fillers, which have a high affinity for epoxy resin, in combination with hexagonal boron nitride fillers, the affinity between epoxy resin and fillers is improved, resulting in increased thermal conductivity compared to using hexagonal boron nitride fillers alone. Silica fillers, like hexagonal boron nitride fillers, have low relative permittivity and low dielectric loss tangent, thus not worsening transmission losses and addressing the aforementioned issues.

[0016] That is, the resin composition of the present invention comprises epoxy resin (A), hexagonal boron nitride filler (B) and silica filler (C). Relative to 100 parts by weight of the epoxy resin (A), the total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200 to 1200 parts by weight. The epoxy resin (A) comprises solid epoxy resin (A-1) and liquid epoxy resin (A-2). The average particle size D50 of the hexagonal boron nitride filler (B) is 1 to 10 μm and the maximum particle size Dmax is less than 30 μm. The average particle size D50 of the silica filler (C) is 0.1 to 1 μm. The mass ratio of the contents of the hexagonal boron nitride filler (B) to the silica filler (C) is 85:15 to 30:70.

[0017] The effects of the invention

[0018] According to the present invention, a resin composition with high thermal conductivity and small relative dielectric constant and dielectric loss tangent can be obtained after curing. Such a resin composition can be used as a resin composition film with excellent heat dissipation and dielectric properties, and can be used to efficiently produce multilayer printed circuit boards, component-embedded substrates, prepregs, resin films with metal foil, and metal-clad laminates, etc. Detailed Implementation

[0019] Hereinafter, 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 implemented in any modified form without departing from the spirit of the present invention.

[0020] Epoxy resin (A)

[0021] Epoxy resin is used as the resin in the resin composition of the present invention. The aforementioned epoxy resin preferably includes compounds containing one or more epoxy groups within their molecules (hereinafter sometimes referred to as "reactive epoxy resin"). It should be noted that the aforementioned reactive epoxy resin may also be a low-molecular-weight compound having epoxy groups. More preferably, the aforementioned reactive epoxy resin contains two or more epoxy groups within its molecules. The content of the aforementioned reactive epoxy resin relative to the total amount of epoxy resin is preferably 50% by mass or more. By including reactive epoxy resin in the epoxy resin, when the resin composition of the present invention is used as a resin composition film for manufacturing multilayer printed circuit boards, etc., the resin composition film softens, exhibits excellent flowability, easily conforms to the shape of the conductor layer of the multilayer printed circuit board, etc., and becomes high in strength and heat resistance after being thermo-cured after being changed to the desired shape, thus easily improving the reliability of these substrates. There is no particular upper limit to the content ratio of reactive epoxy resin relative to the total amount of epoxy resin; the entire amount of epoxy resin may be reactive epoxy resin.

[0022] The aforementioned epoxy resin includes both solid epoxy resin (A-1) and liquid epoxy resin (A-2). In this invention, the epoxy resin that is solid at 25°C is referred to as solid epoxy resin (A-1), and the epoxy resin that is liquid at 25°C is referred to as liquid epoxy resin (A-2).

[0023] By including solid epoxy resin (A-1) in epoxy resin (A), the strength and heat resistance of the resin composition after thermosetting can be improved. On the other hand, most solid epoxy resins have high melt viscosity. If the resin composition of the present invention is to be used as a resin composition film in the manufacture of multilayer printed circuit boards, etc., it is necessary to improve the flowability so that the resin composition film follows the desired substrate shape. Therefore, a liquid epoxy resin with high flowability is used in conjunction with a solid epoxy resin with high heat resistance.

[0024] As solid epoxy resins, preferred types include 4-functional naphthalene-type epoxy resins, 3-functional naphthalene-type epoxy resins, triphenol-methane-type epoxy resins, phenol-formaldehyde varnish-type epoxy resins, cresol-formaldehyde varnish-type epoxy resins, bisphenol A-formaldehyde varnish-type epoxy resins, naphthol-formaldehyde varnish-type epoxy resins, naphthol-cresol-formaldehyde varnish-type epoxy resins, dicyclopentadiene-type epoxy resins, biphenyl aryl-type epoxy resins, xylenol-type epoxy resins, naphthylene ether-type epoxy resins, and fluorene-type epoxy resins. More preferred types include 4-functional naphthalene-type epoxy resins, biphenyl aryl-type epoxy resins, triphenol-methane-type epoxy resins, xylenol-type epoxy resins, naphthylene ether-type epoxy resins, and fluorene-type epoxy resins.

[0025] Commercially available solid epoxy resins include, for example:

[0026] The following epoxy resins manufactured by DIC Corporation are "HP-4700" and "HP-4710" (quadrifunctional naphthalene type epoxy resin), "N-690" and "N-695" (cresol phenolic varnish type epoxy resin), "HP-7200", "HP-7200L" and "HP-7200H" (dicyclopentadiene type epoxy resin), and "HP6000" and "HP-6000H" (naphthyl ether type epoxy resin);

[0027] The following epoxy resins manufactured by Nippon Kayaku Co., Ltd. are: “EPPN-501H”, “EPPN-501HY” and “EPPN-502H” (triphenol methane type epoxy resin), “NC7000L”, “NC-7000H” and “NC-7300L” (naphthol cresol phenolic varnish epoxy resin), “NC-3000H”, “NC-3000”, “NC-3000L”, “NC-3100” and “NC-3500” (biphenyl aryl type epoxy resin), “NC-2000-L” (phenyl aryl type epoxy resin), “XD-1000-2L”, “XD-1000” and “XD-1000-H” (dicyclopentadiene type epoxy resin), and “LCE-2615” (toughness type epoxy resin).

[0028] "ESN475" (naphthol phenolic resin clear varnish type epoxy resin) and "ESN485" (naphthol phenolic resin clear varnish type epoxy resin) manufactured by Nippon Steel Chemical Co., Ltd.

[0029] Mitsubishi Chemical Corporation manufactures "YX4000H" and "YL6121" (biphenyl type epoxy resin), "YX4000HK" (bixylenol type epoxy resin), and "YL7800" (fluorene type epoxy resin).

[0030] They can be used individually or in combination with two or more.

[0031] By including liquid epoxy resin (A-2) in epoxy resin (A), the melt viscosity of the resin composition can be reduced, and its flowability can be improved. Therefore, when the resin composition of the present invention is used as a resin composition film in the manufacture of multilayer printed circuit boards, etc., it exhibits excellent flowability during heat-pressurization molding and can follow the shape of conductor layers, etc.

[0032] As liquid epoxy resins, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic varnish type epoxy resin, and naphthalene type epoxy resin are preferred, with bisphenol A type epoxy resin and bisphenol F type epoxy resin being more preferred. Commercially available liquid epoxy resins include, for example, "jER828", "jER828EL", and "jER828US" (bisphenol A type epoxy resin), "jER806", "jER806H", and "jER807" (bisphenol F type epoxy resin), "jER152" (phenolic varnish type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical Co., Ltd.; and "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resin) manufactured by DIC Corporation. They can be used individually or in combination with two or more.

[0033] 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 setting it within this range, the melt viscosity of the resin composition is suppressed to a low level, resulting in high fluidity.

[0034] The content ratio of solid epoxy resin (A-1) to liquid epoxy resin (A-2) by mass is preferably in the range of 9:1 to 1:9, 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 solid epoxy resin to liquid epoxy resin within the above range, it is easy to balance high fluidity and heat resistance.

[0035] The epoxy equivalent of epoxy resin (A) is preferably 50 to 4500, more preferably 50 to 3000, even more preferably 80 to 2000, and still more preferably 100 to 1000. By setting it within this range, the crosslinking density of the cured resin composition becomes sufficient, easily resulting in sufficient heat resistance and mechanical strength when used as a resin composition film. It should be noted that the epoxy equivalent can be determined according to JIS K7236 and is the mass of resin per 1 equivalent of epoxy groups.

[0036] Hexagonal boron nitride filler (B)

[0037] The resin composition of the present invention comprises hexagonal boron nitride filler with an average particle size D50 of 1 to 10 μm and a maximum particle size Dmax of 30 μm or less. By including hexagonal boron nitride filler in the aforementioned resin composition, the cured resin composition can have high thermal conductivity. Furthermore, by setting the average particle size to 1 to 10 μm and the maximum particle size Dmax to 30 μm or less, it is easy to form a thin film of about 10 μm to several hundred μm for use as an insulating layer in a multilayer printed circuit board, and high thermal conductivity can be easily obtained at this thickness. In addition, by setting the maximum particle size Dmax to the aforementioned range, the melt viscosity of the resin composition becomes lower, and when used in the manufacture of multilayer printed circuit boards, etc., it is also possible to achieve good shape conformability of the conductor layer, etc., during heat and pressure molding.

[0038] The average particle size D50 of the hexagonal boron nitride filler (B) is preferably 2.0 μm or more, more preferably 3.0 μm or more. The aforementioned average particle size D50 is preferably 8.0 μm or less, more preferably 7.0 μm or less. Furthermore, the maximum particle size Dmax is preferably 25 μm or less, more preferably 20 μm or less.

[0039] The D90 / D10 ratio in 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 ratio means a narrow particle size distribution and a greater number of particles with a size close to D50. By making the D90 / D10 ratio small, it can interact efficiently with silica particles, improving the affinity of the hexagonal boron nitride filler with epoxy resin and easily increasing thermal conductivity. There is no particular limitation on the lower limit of D90 / D10; a theoretical lower limit of 1.0 or more is sufficient.

[0040] 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 the D90 to the aforementioned range, the resin composition can be easily formed into a film for use as a laminated film.

[0041] 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 the D10 to the aforementioned range, the viscosity increase of the resin composition can be suppressed.

[0042] It should be noted that, in this invention, the average particle size D50 is the particle size that represents the cumulative 50% value in the particle size distribution measured by laser diffraction scattering, on a volume basis. Similarly, D10 is the particle size that represents the cumulative 10% value in a volume basis, and D90 is the particle size that represents the cumulative 90% value in a volume basis. Furthermore, the maximum particle size Dmax is the maximum measured particle size.

[0043] The specific surface area SA of hexagonal boron nitride filler (B) is not particularly limited, but is preferably 1.0 to 10 m². 2 / g. The aforementioned specific surface area SA is more preferably 1.5m². 2 / g or more, further preferably 2.0m 2 / g or more. The aforementioned specific surface area SA is more preferably 9.0m². 2 / g or less, more preferably 8.0m 2 / g or less. By keeping the specific surface area within the aforementioned range, the thermal conductivity of the resin composition is easily improved. Furthermore, the dispersibility in the epoxy resin becomes better, and when used as a resin composition film, the melt viscosity of the resin composition is easily reduced to an optimal range. The specific surface area SA can be determined by the BET method (nitrogen adsorption single-point method) based on nitrogen adsorption.

[0044] The oxygen content (OC) of the hexagonal boron nitride filler (B) is not particularly limited, but is preferably 1% by mass or less, more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less. By keeping the oxygen content within the aforementioned range, the thermal conductivity of the resin composition can be easily improved.

[0045] The oxygen content (OC) of the hexagonal boron nitride filler (B) can be determined using the apparatus described in the examples.

[0046] The aforementioned average particle size D50 (μm) in the hexagonal boron nitride filler (B) divided by the aforementioned specific surface area SA (g / m²) 2 The value obtained by multiplying the oxygen content OC (%) by the aforementioned value (hereinafter sometimes referred to as "X value") is preferably 2 to 30. The X value is more preferably 3 or more, and more preferably 20 or less. Generally, in hexagonal boron nitride fillers, increasing the average particle size D50 can improve the thermal conductivity of the resin composition. However, considering the case where the resin composition is used as an insulating layer in a multilayer printed circuit board, it is difficult to increase the average particle size D50, thus making it difficult to improve the thermal conductivity. However, by adjusting the X value to the aforementioned range by increasing the specific surface area and decreasing the oxygen content, the thermal conductivity of the cured resin composition can be easily improved.

[0047] The hexagonal boron nitride filler (B) of the present invention can be an independent single particle or an aggregate of several small primary particles. Alternatively, it can be a mixture of these single particles and aggregates. The 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 the multilayer printed circuit board and to facilitate the formation of a thermal conduction path in the thickness direction of the insulating layer, it is preferable to include aggregates.

[0048] The manufacturing method of the aforementioned hexagonal boron nitride filler (B) is not particularly limited, and hexagonal boron nitride fillers manufactured using known methods can be used. Examples of methods for manufacturing hexagonal boron nitride include: the melamine method, which involves heating a mixed powder of boron oxide and a nitrogen-containing organic compound; the direct nitriding method, which involves heating boron carbide in a nitrogen atmosphere; the reduction nitriding method, which involves heating a mixed powder of oxygen-containing boron compound, carbon, and oxygen-containing calcium compound in a nitrogen atmosphere; and the gas-phase synthesis method.

[0049] For example, the method disclosed in Japanese Patent Application Publication No. 2022-185586 can be cited as a melamine process, and the method disclosed in Japanese Patent Application Publication No. 2022-185585 can be cited as a reduction nitriding process. Furthermore, commercially available hexagonal boron nitride fillers include, for example, R-BN (manufactured by Nissin Refratech Co., Ltd.) and UHP-S2 (manufactured by Resonac Co., Ltd.). It should be noted that hexagonal boron nitride powder obtained by known manufacturing methods or commercially available hexagonal boron nitride powder can also be used to adjust the particle size distribution using sieves or classifiers to achieve a desired average particle size and maximum particle size range. The specific surface area can also be adjusted using sieves or classifiers.

[0050] Hexagonal boron nitride filler can be obtained by calcining materials or commercially available products obtained through the melamine process or reduction nitriding process. The calcination process can be carried out, for example, in an inert gas atmosphere such as nitrogen at 1400–2000°C. The calcination process can be performed using only hexagonal boron nitride, or by adding a small amount of boron oxide to hexagonal boron nitride. Through the aforementioned calcination process, the oxygen content of the hexagonal boron nitride filler can be efficiently reduced. Furthermore, due to the increased crystallinity and grain growth of the hexagonal boron nitride filler, the specific surface area can also be reduced. It should be noted that due to the grain growth and interparticle aggregation caused by the aforementioned calcination process, the average particle size D50 and maximum particle size Dmax sometimes increase after calcination. Therefore, the particle size distribution can be adjusted as needed using crushing, sieving, or grading devices to bring the average particle size D50 and maximum particle size Dmax within the desired range.

[0051] Silica filler (C)

[0052] The resin composition of the present invention is characterized by comprising hexagonal boron nitride filler (B) and silica filler with an average particle size D50 of 0.1 to 1 μm. By blending such silica filler and allowing it to coexist with hexagonal boron nitride filler, the thermal conductivity of the cured resin composition can be improved. The reason for this is not yet clear, but the inventors believe it to be as follows.

[0053] As mentioned above, when hexagonal boron nitride filler with a small average particle size is incorporated into epoxy resin, the adhesion between the epoxy resin and the filler decreases due to the filler's plate-like particles, low affinity with epoxy resin, small particle size, and large surface area, thus disrupting the thermal conductivity path. Therefore, it is believed that even increasing the proportion of hexagonal boron nitride filler will not increase the thermal conductivity but rather decrease it. Here, if silica filler, which has a higher affinity for epoxy resin than hexagonal boron nitride filler, is incorporated, a portion of the hexagonal boron nitride filler surface will contact the silica filler, thereby reducing the contact area between the hexagonal boron nitride filler and the epoxy resin. In this case, to ensure that the silica filler effectively acts on the surface of the hexagonal boron nitride filler, a filler with an average particle size as small as 0.1–1 μm is required. As a result, although the thermal conductivity of the silica filler itself is not high, it can suppress the interruption of the thermal conduction path between the epoxy resin and the hexagonal boron nitride filler. Therefore, it is speculated that the silica filler enters the gap between the hexagonal boron nitride fillers, thereby improving the dispersion of the hexagonal boron nitride fillers. The thermal conduction path of the hexagonal boron nitride diffuses throughout the resin composition film, resulting in high thermal conductivity.

[0054] It should be noted that compared to hexagonal boron nitride filler, silica filler has a smaller relative permittivity and dielectric loss tangent. Therefore, even when mixed with silica, the risk of a significant increase in the relative permittivity and dielectric loss tangent of the resin composition is low. Consequently, when this resin composition is used as a thin film material for the insulating layer of a multilayer printed circuit board, transmission loss can be easily reduced.

[0055] The average particle size D50 of the silica filler (C) is 0.1 to 1.0 μm. Preferably, the average particle size D50 is 0.15 μm or more, more preferably 0.2 μm or more. Preferably, the average particle size D50 is 0.9 μm or less, more preferably 0.8 μm or less. By ensuring that the average particle size D50 of the silica filler (C) is within the aforementioned range, it acts on the surface of the hexagonal boron nitride filler, thereby improving the affinity between the hexagonal boron nitride filler and the epoxy resin.

[0056] 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. By keeping the maximum particle size Dmax within the aforementioned range, the resin composition can be easily formed into a film for use as a laminated film.

[0057] The D90 / D10 ratio in the silica filler (C) is preferably less than 4.0, more preferably less than 3.0, and even more preferably less than 2.5. A small D90 / D10 ratio means a narrow particle size distribution and a higher proportion of particles with a size close to D50. By making the D90 / D10 ratio small, silica particles can act efficiently on the surface of the hexagonal boron nitride filler, easily improving the affinity between the hexagonal boron nitride filler and the epoxy resin. There is no particular limitation on the lower limit of D90 / D10; a theoretical lower limit of 1.0 or higher is sufficient.

[0058] 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 to the aforementioned range, the silica filler can easily enter the gaps between the hexagonal boron nitride fillers, thereby improving the dispersibility of the hexagonal boron nitride fillers.

[0059] 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 the D10 to the aforementioned range, the viscosity increase of the resin composition can be suppressed.

[0060] The specific surface area of ​​silica filler (C) is not particularly limited, but is preferably 2 to 40 m². 2 / g. The aforementioned specific surface area is more preferably 3m². 2 / g or more, further preferably 4m 2 / g or more. More preferably, the specific surface area is 30m². 2 / g or less, more preferably 20m 2 / g or less. By keeping the specific surface area within the aforementioned range, it can act efficiently on the surface of the hexagonal boron nitride filler when combined with it in epoxy resin.

[0061] The shape of the silica filler (C) is not particularly limited, but from the viewpoint of improving its affinity with epoxy resin, a spherical shape is preferred.

[0062] The manufacturing method of the aforementioned silica filler (C) is not particularly limited, and silica fillers manufactured by known methods can be used. Preferred spherical silica fillers include, for example, synthetic silica and molten silica manufactured by dry or wet methods. Commercially available silica fillers include, for example, NSS-3N, SS-03, SS-04 and SS-07 (manufactured by Tokuyama Corporation), SO-C1 and SO-C2 (manufactured by Denka Corporation), and SFP-20M and SFP-30M (manufactured by Admatechs Corporation).

[0063] The silica filler (C) can be a filler that has undergone surface treatment with a surface treatment agent. By performing surface treatment, the affinity between silica and epoxy resin can be easily improved, thereby increasing the flowability of the resin composition. As the aforementioned surface treatment agent, known agents such as silane compounds, aluminate coupling agents, and titanate coupling agents can be used without particular limitation. Of these, silane compounds capable of reacting at a high reactivity rate are particularly preferred.

[0064] For the silane compound used as this surface treatment agent, specific examples include silane compounds having reactive functional groups, such as 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-propane... Acyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropylmethyldimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, alkoxysilanes such as p-styryltrimethoxysilane and allyltrimethoxysilane.

[0065] In addition, 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.

[0066] Other usable silane compounds include, for example, vinyltrichlorosilane, methyltrichlorosilane, dimethyldichlorosilane, trichloromethylsilane, ethyldimethylchlorosilane, propyldimethylchlorosilane, phenyltrichlorosilane, trifluoropropyltrichlorosilane, and isopropyldiethylchlorosilane.

[0067] Among silane compounds, those with high affinity for epoxy resins are preferred. Examples of silane compounds with high affinity include those with functional groups such as epoxypropoxy and amino groups that can react with epoxy groups. Additionally, silane compounds with functional groups such as methacryloyloxy, acryloyloxy, phenyl, vinyl, and styrene groups, which have high affinity for epoxy resins but low reactivity with epoxy groups, are also suitable. When using the aforementioned surface treatment agent, its amount is 0.1 to 5 parts by weight, preferably 0.5 to 4 parts by weight, relative to 100 parts by weight of the raw material powder before surface treatment.

[0068] As a method for this surface treatment, any known method can be used without particular limitation, and either dry or wet surface treatment methods can be employed. Dry surface treatment involves mixing the raw material powder with the surface treatment agent using a dry mixing method without the aid of a large amount of solvent. Examples include: methods that vaporize the surface treatment agent and mix it with the raw material powder; methods that spray or drop a liquid surface treatment agent into the raw material powder and mix it; and methods that dilute the surface treatment agent with a small amount of organic solvent to increase the liquid volume, and then spray or drop it. Wet surface treatment, on the other hand, involves mixing the raw material powder with the surface treatment agent using a solvent. Examples include methods that mix the raw material powder, surface treatment agent, and solvent, and then remove the solvent by drying.

[0069] There are no particular restrictions on the relationship between the particle size of the silica filler (C) and the particle size of the hexagonal boron nitride filler (B). 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 preferably 0.01 to 0.2. More preferably, the ratio is 0.05 or more, and even more preferably 0.13 or less. By keeping the particle size ratio within the aforementioned range, the silica filler acts efficiently on the surface of the hexagonal boron nitride filler, easily improving the thermal conductivity.

[0070] In the resin composition of the present invention, the total content of hexagonal boron nitride filler (B) and silica filler (C) is 200 to 1200 parts by weight relative to 100 parts by weight of epoxy resin (A). This improves the thermal conductivity of the resin composition. The total content of hexagonal boron nitride filler (B) and silica filler (C) relative to 100 parts by weight of epoxy resin (A) is preferably 300 parts by weight or more, more preferably 400 parts by weight or more. The aforementioned total content is preferably 1000 parts by weight or less, more preferably 900 parts by weight or less.

[0071] The ratio of hexagonal boron nitride filler (B) to silica filler (C) (content of hexagonal boron nitride filler (B): content of silica filler (C)) by mass is 85:15 to 30:70. The aforementioned ratio is preferably 80:20 to 35:65, and more preferably 75:25 to 40:60. If the amount of hexagonal boron nitride filler (B) is too small, the proportion of silica filler (C), which has low thermal conductivity, will increase, making it difficult to obtain high thermal conductivity. If the amount of 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.

[0072] Other ingredients

[0073] Without impairing the effects of the present invention, the resin composition of the present invention may contain other components besides epoxy resin (A), hexagonal boron nitride filler (B), and silica filler (C). Other components may include, for example, an epoxy resin curing agent, a curing accelerator, other resins besides epoxy resin, other fillers, flame retardants, rubber particles, thickeners, defoamers, leveling agents, adhesion promoters, antioxidants, UV degrading agents, and colorants.

[0074] The aforementioned epoxy resin curing agent is a substance that has the function of reacting with the epoxy resin and curing when the epoxy resin (A) includes a reactive epoxy resin. By including the epoxy resin curing agent in the resin composition of the present invention, a cured product with high strength and heat resistance can be easily obtained when the resin composition of the present invention is heat-cured. There are no particular limitations on the epoxy resin curing agent, and known curing agents can be used. Examples of epoxy resin curing agents include phenol-based curing agents, naphthol-based curing agents, reactive ester-based curing agents, cyanate ester-based curing agents, benzoxazine-based curing agents, and anhydride-based curing agents. From the viewpoint of the formability of the resin composition in the form of a film and the heat resistance of the cured product, phenol-based curing agents, naphthol-based curing agents, and reactive ester-based curing agents are preferred. From the viewpoint of reducing the dielectric loss tangent of the cured film of the resin composition of the present invention and obtaining excellent dielectric properties, reactive ester-based curing agents are more preferred. One type of curing agent can be used alone, or two or more types can be used in combination.

[0075] As phenol-based and naphthol-based curing agents, considering the heat resistance and water resistance of the cured product, phenol-based and naphthol-based curing agents with a phenolic varnish structure are preferred. As phenol-based curing agents, preferred types include phenolic varnish, cresol varnish, bisphenol A type phenolic varnish, phenol aralkyl varnish, biphenyl aralkyl varnish, aminotriazine varnish (phenolic varnish containing a triazine structure), triphenylmethane varnish, and cyclopentadiene phenolic varnish. As naphthol-based curing agents, preferred types include naphthol aralkyl type phenolic varnish, aralkyl type naphthol / phenolic varnish, and naphthol / cresol type phenolic varnish.

[0076] Commercially available phenol-based and naphthol-based curing agents 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 Co., Ltd., "ZX-798" and "SN485" manufactured by Nippon Steel Chemical Materials Co., Ltd., "TPM-100" and "GPNX" manufactured by Gunei Chemical Co., Ltd., and "S-TPM" and "J-DDP" manufactured by JFE Chemical Co., Ltd.

[0077] The reactive group equivalent (hydroxyl equivalent) of phenol-based and naphthol-based curing agents is not particularly limited, but from the viewpoint of the formability 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. It should be noted that the hydroxyl equivalent is the resin mass per 1 equivalent of hydroxyl groups.

[0078] Examples of reactive ester-based curing agents include reactive ester-based curing agents with a dicyclopentadiene structure, reactive ester-based curing agents with a naphthalene structure, reactive ester-based curing agents containing acetylated compounds of phenolic varnishes, and reactive ester-based curing agents containing benzoyl compounds of phenolic varnishes. Considering the heat resistance and water resistance of the cured product, reactive ester-based curing agents with a dicyclopentadiene structure and reactive ester-based curing agents with a naphthalene structure are more preferred. Commercially available reactive ester-based curing agents include, for example, "HPC-8000-65T" (reactive ester-based curing agent with a dicyclopentadiene structure) and "HPC-8150-62T" (reactive ester-based curing agent with a naphthalene structure) manufactured by DIC Corporation.

[0079] The reactive group equivalent (reactive ester equivalent) of the active ester curing agent is not particularly limited, but from the viewpoint of the formability of the resin composition as a film and the heat resistance of the cured product, it is preferably 50 to 2000, more preferably 50 to 1000, and even more preferably 100 to 500. It should be noted that the active ester equivalent is the resin mass per 1 active ester equivalent.

[0080] The content of the aforementioned curing agent in the resin composition of the present invention is not particularly limited. However, considering the heat resistance and mechanical strength of the cured product, it is preferably 50 to 200 parts by weight relative to 100 parts by weight of epoxy resin (A), more preferably 65 to 150 parts by weight, and even more preferably 75 to 125 parts by weight. Furthermore, the ratio of the total number of reactive groups such as hydroxyl and active ester groups in the curing agent to the total number of epoxy groups in 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 in epoxy resin (A) refers to the value obtained by dividing the mass of each epoxy resin by the epoxy equivalent and summing the values ​​of all epoxy resins. Similarly, the total number of reactive groups in the curing agent refers to the value obtained by dividing the mass of each curing agent by the reactive group equivalent and summing the values ​​of all epoxy resins.

[0081] The aforementioned curing accelerator is a substance that promotes the reaction between the epoxy groups of the epoxy resin (A) and the reactive groups of the curing agent, as well as the polymerization of the epoxy groups. By including the epoxy resin curing accelerator in the resin composition of the present invention, when the epoxy resin (A) contains a reactive epoxy resin, the resin composition of the present invention can be easily cured by heat curing, and high strength can be easily obtained after curing. When the resin composition of the present invention includes the epoxy resin curing accelerator, its content relative to 100 parts by weight of epoxy resin (A) is preferably 0.01 parts by weight to 5 parts by weight, more preferably 0.05 parts by weight to 3 parts by weight, and even more preferably 0.1 parts by weight to 2 parts by weight.

[0082] As a curing accelerator for epoxy resin, known curing accelerators can be used without particular restriction, such as amine-based, imidazole-based, phosphorus-based, and guanidine-based curing accelerators, with amine-based and imidazole-based curing accelerators being preferred. One curing accelerator can be used alone, or two or more can be used in combination.

[0083] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene.

[0084] Examples of imidazole-based curing accelerators include 2-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolium-(1'-methylimidazolium-2 ... Imidazole compounds such as 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 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 with epoxy resins.

[0085] 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.

[0086] 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-methylbiguanidine, 1-ethylbiguanidine, 1-n-butylbiguanidine, 1-n-octadecylbiguanidine, 1,1-dimethylbiguanidine, 1,1-diethylbiguanidine, 1-cyclohexylbiguanidine, 1-allylbiguanidine, 1-phenylbiguanidine, and 1-(o-tolyl)biguanidine.

[0087] By including other resins in the resin composition of the present invention, the flexibility of the resin composition can be improved. As a result, when forming a film of the resin composition, the coatability becomes good, a uniform film can be obtained, the film becomes soft, and the rollability is improved, or the impact resistance of the cured product is improved, thus reducing the likelihood of breakage. Examples of other resins include thermoplastic resins such as phenoxy resins, polyvinyl acetal resins, polyolefin resins, polybutadiene resins, polyimide resins, polyamide-imide resins, polyethersulfone resins, polyphenylene ether resins, and polysulfone resins. Among these, phenoxy resins, which have a structure similar to epoxy resins, have good compatibility with epoxy resins and are therefore preferred. These thermoplastic resins can be used alone or in combination of two or more.

[0088] Examples of phenoxy resins include those having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenol acetophenone, phenolic varnish, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane. The terminal structure of the phenoxy resin can be any structure such as a phenolic hydroxyl group or an epoxy group. A single phenoxy resin can be used alone, or two or more can be used in combination. Commercially available phenoxy resins include, for example, "YX6954BH30" (a phenoxy resin containing a bisphenol acetophenone skeleton), "YX8100BH30" (a 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 5000 to 10000. The weight-average molecular weight is the weight-average molecular weight converted to polystyrene, determined by gel permeation chromatography.

[0089] When the resin composition of the present invention contains a phenoxy resin, its content is preferably 0.1 to 50 parts by weight relative to 100 parts by weight of epoxy resin (A), more preferably 0.5 to 30 parts by weight, and even more preferably 1 to 20 parts by weight.

[0090] The aforementioned other fillers are fillers made of materials other than hexagonal boron nitride fillers and silica fillers, such as 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.

[0091] The content of other fillers relative to the total content of hexagonal boron nitride filler (B) and silica filler (C) is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. Particularly preferred is that the aforementioned resin composition does not contain any other fillers. If a large amount of other fillers is included, it may sometimes hinder the interaction between the hexagonal boron nitride filler (B) and the silica filler (C). Furthermore, if fillers such as aluminum nitride, aluminum oxide, and magnesium oxide, which have a higher relative dielectric constant than hexagonal boron nitride and silica, are included, dielectric loss may increase. When the aforementioned resin composition contains other fillers, their particle size is preferably smaller than that of the hexagonal boron nitride filler (B), more preferably less than 2 μm in average particle size, and even more preferably less than 1.5 μm in average particle size. The maximum particle size of the other fillers is preferably smaller than that of the hexagonal boron nitride filler (B), more preferably less than 4.5 μm, and even more preferably less than 4 μm.

[0092] The resin composition of the present invention may contain flame retardants or rubber particles as other components. Flame retardants are substances that impart flame retardancy when the resin composition of the present invention is used in semiconductor products; examples include organophosphorus flame retardants, organic nitrogen-containing phosphorus compounds, nitrogen compounds, organosilicon flame retardants, and metal hydroxides. These flame retardants may be used alone or in combination of two or more.

[0093] By including rubber particles in the aforementioned resin composition, the internal stress during thermosetting of the resin composition can be mitigated, thereby reducing warpage of the cured product, and impact resistance can also be imparted. Examples of rubber particles include core-shell 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, more preferably 0.8 μm or less.

[0094] Furthermore, the resin composition of the present invention may also include additives such as thickeners, defoamers, leveling agents, adhesion promoters, antioxidants, UV degrading agents, and colorants as needed.

[0095] The resin composition of the present invention has the property of being usable as a material for forming an insulating layer of a multilayer printed circuit board, and has features not found in conventional resin compositions, such as high thermal conductivity, low relative permittivity, and low dielectric loss tangent of its cured product. By using such a resin composition as a thin film material for forming an insulating layer of a multilayer printed circuit board, it is possible to easily manufacture multilayer printed circuit boards with high heat dissipation and low transmission loss.

[0096] The thermal conductivity of the cured product obtained from the resin composition of the present invention is preferably 1.0 W / m·K or higher, more preferably 1.5 W / m·K or higher, even more preferably 2.0 W / m·K or higher, and particularly preferably 2.5 W / m·K or higher. Higher thermal conductivity is preferred, but it is generally 30 W / m·K or lower. The thermal conductivity can be measured by temperature wave thermal analysis (Ai-Phase method).

[0097] The relative permittivity 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. A smaller relative permittivity is preferred, but it is generally 2.0 or more. Furthermore, the dielectric loss tangent of the cured product is preferably 0.012 or less, more preferably 0.008 or less. A smaller dielectric loss tangent is preferred, but it is generally 0.001 or more. The relative permittivity and dielectric loss tangent can be measured using a split cylindrical resonator and a network analyzer, by the resonant cavity perturbation method at a temperature of 25°C and a frequency of 10 GHz.

[0098] 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 obtained by measuring a cured sample of the resin composition to the density (theoretical density) calculated from the densities of the materials used and their mixing ratios; when the theoretical density matches the sample density, it is 1. A high relative density indicates fewer defects such as pores in the resin composition and excellent interfacial adhesion between the components, thereby improving the thermal conductivity of the cured resin composition. There is no particular upper limit to the relative density, which is typically 1.0 or less. It should be noted that the density of the cured resin composition can be determined by the Archimedes method.

[0099] The method for manufacturing the resin composition of the present invention is not particularly limited, and can be carried out by mixing the resin, filler, and other components as needed using known methods such as a mixer or blender. During the aforementioned mixing, each component can be added to the mixer or the like simultaneously, or each component can be added to the mixer or the like sequentially. The order of addition is not particularly limited. Furthermore, the aforementioned mixing can be carried out under heating as needed, or under an atmosphere such as an atmosphere containing inert gases.

[0100] The resin composition of the present invention is suitable for use as an insulating layer in the aforementioned multilayer printed circuit boards due to its high thermal conductivity, low relative permittivity, and low dielectric loss tangent. Furthermore, in addition to these applications, it can be widely used in various applications requiring heat dissipation and dielectric properties, such as adhesive films, insulating layers in metal-clad laminates, sealing resins for component-embedded substrates, insulating resin sheets such as prepregs, underfill materials, chip bonding materials, semiconductor sealing materials, and via-filling resins. When the resin composition of the present invention is used in the aforementioned applications, it is generally suitable for industrial use in the form of a resin composition film formed into a thin film.

[0101] The resin composition film of the present invention is obtained by molding the resin composition of the present invention into a film, and its thickness is preferably 5 to 250 μm. More preferably, the aforementioned thickness is 10 μm or more, further preferably 20 μm or more, more preferably 200 μm or less, and even more preferably 150 μm or less.

[0102] There are no particular limitations on the method for manufacturing the resin composition film of the present invention, and conventionally known methods can be used to thin the aforementioned resin composition. Among them, a preferred method is, for example, the following method: dissolving the resin composition in an organic solvent, mixing the organic solvent with the resin composition to prepare a varnish of the resin composition, applying the varnish of the resin composition to a support using a die coater, blade coater, comma coater, or gravure coater, and then drying the organic solvent by heating or blowing hot air.

[0103] Examples of the aforementioned 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 naphtha as a mixture. These organic solvents can be used individually or in combination of two or more.

[0104] From the perspective of easy removal during drying, the boiling point of the aforementioned organic solvent is preferably below 200°C, more preferably below 180°C. The content of the organic solvent in the varnish of the resin composition is not particularly limited, and can be appropriately adjusted considering factors such as coatability to the support.

[0105] The drying conditions are not particularly limited, but drying is preferably carried out when the content of organic solvent in the resin composition film is preferably 10% by mass or less, more preferably 5% by mass or less. Although it will vary depending on the boiling point of the organic solvent used in the varnish of the resin composition, for example, by heating and drying at 60°C to 150°C for 1 to 5 minutes, a resin composition film with a degree of non-excessive heat curing can be obtained.

[0106] The resin composition film of the present invention is preferably in a partially cured state, referred to as a so-called B-stage film. Because it is in a partially cured state and not fully cured, the shape of the conductor layer can be easily followed in the manufacturing process of multilayer printed circuit boards and other semiconductor materials, and further curing can be performed thereafter to improve strength and durability.

[0107] Various plastic films can be preferably used as the aforementioned support. Examples of plastic films include: polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PET), and polyethylene naphthalate (PET); olefin films such as polyethylene (PE) and polypropylene (PP); and polyimide films. Among these, polyethylene terephthalate (PET) films, which offer excellent smoothness and heat resistance and are inexpensive, are more preferred. Considering the wettability when coating the resin composition film and the demolding properties when manufacturing various semiconductor substrates, demolding treatment, matte treatment, or corona discharge treatment can be applied to the coated side of the plastic film of the support. Additionally, metal foils such as copper foil and aluminum foil can also be used as the support. For copper foil, rolled copper foil and electrolytic copper foil are preferred. By using metal foil as the support, the process of laminating metal foils can be omitted in the manufacturing of various substrates, and the bonding strength can also be improved. The thickness of the support is not particularly limited, but it is preferably in the range of 5μm to 150μm, more preferably in the range of 10μm to 100μm, and even more preferably in the range of 10μm to 60μm.

[0108] In the resin composition film, a protective film, similar to the support, can be further laminated on the surface that does not contact the support. The thickness of the protective film is not particularly limited, for example, it is 5 μm to 40 μm. By laminating the protective film, dust and other contaminants can be prevented from adhering to the surface of the resin composition film and from causing damage. The resin composition film can also be rolled into a roll by laminating the protective film. The protective film is then peeled off and used in the manufacture of multilayer printed circuit boards and other semiconductor materials.

[0109] The aforementioned resin composition film, due to its high thermal conductivity, low relative permittivity, and low dielectric loss tangent, is suitable for forming insulating layers in multilayer printed circuit boards. It should be noted that in high-heat-dissipating insulating layers on metal substrates, the resin composition can be cured under high pressures of several MPa or higher. Therefore, even epoxy resins and hexagonal boron nitride fillers with poor affinity can improve adhesion to some extent, and even without silica, a large amount of hexagonal boron nitride filler can be added to the epoxy resin to suppress the decrease in thermal conductivity. However, in the manufacture of multilayer printed circuit boards, high thermal conductivity is difficult to achieve due to the inability to apply high pressures, thus the effects of using the resin composition of the present invention become significant. Furthermore, it can be widely used in various 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, chip bonding materials, semiconductor sealing materials, and via-filling resins.

[0110] Example of method

[0111] The present invention relates to, for example, the following [1] to [5]. [1]

[0113] A resin composition comprising an epoxy resin (A), a hexagonal boron nitride filler (B), and a silica filler (C),

[0114] Relative to 100 parts by weight of the aforementioned epoxy resin (A), the total content of the aforementioned hexagonal boron nitride filler (B) and the aforementioned silica filler (C) is 200 to 1200 parts by weight.

[0115] The aforementioned epoxy resin (A) comprises solid epoxy resin (A-1) and liquid epoxy resin (A-2).

[0116] The aforementioned hexagonal boron nitride filler (B) has an average particle size D50 of 1–10 μm and a maximum particle size Dmax of less than 30 μm.

[0117] The average particle size D50 of the aforementioned silica filler (C) is 0.1–1 μm.

[0118] The mass ratio of the aforementioned hexagonal boron nitride filler (B) to the aforementioned silica filler (C) is 85:15 to 30:70. [2]

[0120] According to the resin composition described in [1], in the aforementioned particle size distribution of the hexagonal boron nitride filler (B), the ratio of particle size D90, which is the cumulative 90% value on a volume basis, to particle size D10, which is the cumulative 10% value on a volume basis (D90 / D10) is 9.0 or less. [3]

[0122] According to the resin composition described in [1] or [2], wherein in the particle size distribution of the aforementioned silica filler (C), the ratio of particle size D90, which is the cumulative 90% value on a volume basis, to particle size D10, which is the cumulative 10% value on a volume basis (D90 / D10) is less than 4.0. [4]

[0124] A resin composition film comprising any one of the resin compositions described in [1] to [3]. [5]

[0126] A multilayer printed circuit board comprising any one of the resin compositions described in [1] to [3] or a cured form thereof.

[0127] Example

[0128] The present invention will be described in more detail below through 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.

[0129] <Epoxy Resin>

[0130] Solid epoxy resin (A-1) uses the following substances.

[0131] NC-3000 (Biphenyl aryl epoxy resin manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 276, softening point 58℃)

[0132] ·EPPN-501HY (Triphenol methane type epoxy resin manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 166, softening point 60℃)

[0133] • LCE-2615 (a tough epoxy resin manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 490, softening point 102℃)

[0134] The aforementioned solid epoxy resins were dissolved in methyl ethyl ketone and used to prepare the resin composition in the form of a 50% by mass solution of epoxy resin.

[0135] The liquid epoxy resin (A-2) used is jER828 (bisphenol A type epoxy resin manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 189, viscosity (25°C) 135 poise).

[0136] <Hexagonal boron nitride filler>

[0137] The following materials are used in hexagonal boron nitride packing (B). The properties of each packing are shown in Table 1.

[0138] • B-1: Hexagonal boron nitride packing manufactured by the method described in Example 1 of Japanese Patent Application Publication No. 2022-185586. The resulting hexagonal boron nitride packing (B-1) has primary particles in a plate shape with a size of about 1 μm, and contains a large number of strongly aggregated particles with a size of several μm.

[0139] •B-2: The filler obtained by calcining B-1 under the following conditions.

[0140] Using a graphite-based Tammann furnace under a nitrogen atmosphere, B-1 was heated to 1500°C and heated at 1500°C for 6 hours, followed by heating to 1940°C and heating at 1940°C for 2 hours for calcination. After calcination, it was sieved through a 45μm mesh to obtain hexagonal boron nitride filler (B-2).

[0141] • B-3: A hexagonal boron nitride filler manufactured by the method described in Example 5 of Japanese Patent Application Publication No. 2022-185585. The resulting hexagonal boron nitride filler (B-3) has primary particles in a plate shape with a size of about several μm, and contains aggregated particles formed by strong aggregation of several primary particles.

[0142] •B-4: The filler obtained by calcining B-3 under the following conditions.

[0143] Using a graphite-made Taman furnace under a nitrogen atmosphere, B-3 was heated to 1650°C and heated at 1650°C for 6 hours, followed by heating to 1890°C and heating at 1890°C for 2 hours for calcination. After calcination, it was sieved through a 45μm sieve to obtain hexagonal boron nitride filler (B-4).

[0144] • B-5: R-BN (manufactured by Nissin Refratech Co., Ltd.)

[0145] [Table 1]

[0146]

[0147] <Silica filler>

[0148] The silica filler (C) uses the following materials. All are spherical fillers, and their properties are shown in Table 2.

[0149] • C-1: Silica filler that has undergone surface treatment using the method described in Example 9 of International Publication No. 2020 / 175160.

[0150] •C-2: Silica filler for which SO-C2 (manufactured by Admatechs Co., Ltd.) has undergone surface treatment by the following method.

[0151] •C-3: Silfil NSS-3N (manufactured by Tokuyama Corporation) has undergone surface treatment using the following method.

[0152] • C-4: Silica filler that has undergone surface treatment using the method described in Example 7 of International Publication No. 2018 / 096876.

[0153] • C-5: Silica filler with surface treated SO-C5 (manufactured by Admatechs) by the following method.

[0154] The surface treatment was carried out as follows: 600g of raw material powder, 5g of surface treatment agent N-phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Silicon KBM-573) and 1200g of isopropanol were placed in a glass eggplant-shaped flask and stirred for 30 minutes with a fluoropolymer stirring blade. Then, the isopropanol was removed by vacuum at 50°C using a rotary evaporator, and then dried under vacuum at 100°C.

[0155] [Table 2]

[0156]

[0157] <Curing agent>

[0158] The following substances are used as curing agents for epoxy resins.

[0159] HPC-8000-65T (a toluene solution containing a dicyclopentadiene structure, active ester curing agent manufactured by DIC Corporation, with an active ester equivalent of 223 and a non-volatile component of 65% by mass)

[0160] • GPH-103 (Biphenyl aryl phenol varnish manufactured by Nippon Kayaku Co., Ltd., hydroxyl equivalent 230, softening point 103℃)

[0161] Solid GPH-103 is dissolved in methyl ethyl ketone and used as a 50% by mass solution in the preparation of resin compositions.

[0162] <Curing Accelerator>

[0163] The curing accelerator used is 4-dimethylaminopyridine (DMAP, manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.).

[0164] <Phenoxy resin>

[0165] The phenoxy resin used is YX6954BH30 (a phenoxy resin containing a bisphenol acetophenone backbone, manufactured by Mitsubishi Chemical Corporation, with a weight-average molecular weight of 40670 and a non-volatile component of 30% by mass of cyclohexanone / methyl ethyl ketone (1 / 1) solution).

[0166] <Determination of the average and maximum particle size of the filler>

[0167] Hexagonal boron nitride filler was added to ethanol at a concentration of 0.2% by mass, and then subjected to ultrasonic irradiation at approximately 200W for 20 minutes to disperse it. The particle size distribution of the resulting sample was measured using a laser diffraction scattering particle size analyzer (MicrotracBEL Co., Ltd.: MICROTRACK-MT3300EXII). The hexagonal boron nitride filler contained the aforementioned strongly aggregated particles, and subsequently, relatively weak aggregation occurred during the drying and calcination processes in manufacturing. During the stirring dispersion in the preparation of the varnish of the resin composition described later, these weak aggregates disintegrated, leaving only the strongly aggregated particles. Therefore, the aforementioned ultrasonic irradiation was performed in the particle size distribution measurement to dissolve the weak aggregates.

[0168] For the surface-treated silica filler, the silica filler was added to ethanol at a concentration of 0.2% by mass, and then subjected to ultrasonic irradiation at about 200W for 2 minutes to disperse it. The particle size distribution of the resulting sample was measured in the same manner as that of the hexagonal boron nitride filler.

[0169] In the obtained volumetric frequency distribution (particle size distribution) of particle size, the volumetric frequency is accumulated starting from the side with the smallest particle size. The particle size with the accumulated value of 50% is taken as the average particle size D50, the particle size with the accumulated value of 10% is taken as D10, the particle size with the accumulated value of 90% is taken as D90, and the maximum value of the measured particle size is taken as the maximum particle size Dmax.

[0170] <Determination of the specific surface area of ​​the filler>

[0171] The specific surface areas of hexagonal boron nitride and silica fillers were determined using a flow-type automatic specific surface area measuring device (Shimadzu Corporation: FlowSorb II-2300 model) via the BET method (nitrogen adsorption single-point method). A 2g powder sample was used in the determination, pre-dried in a nitrogen stream at 100°C for 1 hour.

[0172] <Oxygen content of hexagonal boron nitride filler>

[0173] The oxygen content (OC) of the hexagonal boron nitride packing was determined using an oxygen / nitrogen analyzer (Horiba Manufacturing Co., Ltd.: EMGA-620).

[0174] <Determination of Thermal Conductivity>

[0175] 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 resulting cured product was expressed as a function of thermal diffusivity (m² / m²). 2 / second)×density (kg / m³) 3 The specific heat (J / kg·K) was calculated by multiplying the specific heat. It should be noted that the thermal diffusivity was determined using temperature wave thermal analysis (ai-Phase Mobile1u, ISO22007-3). Twelve measurements were performed on the same test piece, and the average value was used. Additionally, the density was determined using the Archimedes method (Mettler-Toledo XS204V), and the specific heat was determined using differential scanning calorimetry (DSC) (Rigaku Thermo Plus Evo DSC8230).

[0176] <Determination of Relative Density>

[0177] The relative density of the cured material is calculated by dividing the measured density value obtained above by the theoretical value calculated (measured value / theoretical value). Here, regarding the theoretical density value, the density of the remaining components excluding hexagonal boron nitride filler, silica filler, and filler components is set to 2.27 g / m³. 3 2.17g / m 3 1.17g / m 3 It is calculated based on the mixing ratio of each component.

[0178] <Determination of Relative Permittivity and Dielectric Loss Tangent>

[0179] The resin composition films prepared in the examples and comparative examples were cut into 50mm × 50mm pieces and cured by heat treatment at 180°C for 90 minutes to obtain evaluation samples. Next, a split cylindrical resonator (manufactured by KEYCOM Co., Ltd.) was connected to a vector network analyzer (manufactured by KEYSIAT Co., Ltd.: P9377B), and the aforementioned evaluation samples were placed on the resonator. Measurements were performed in TE011 mode, and the relative permittivity and dielectric loss tangent were determined from the results. It should be noted that the measurements were performed at a temperature of 25°C.

[0180] <Example 1>

[0181] Measure 50 parts by weight of liquid epoxy resin (A-2)jER828, 133 parts by weight of curing agent HPC-8000-65T (86.7 parts by weight based on non-volatile components), 33 parts by weight of phenoxy resin YX6954BH30 (10 parts by weight based on non-volatile components), 0.8 parts by weight of curing accelerator DMAP, and 333 parts by weight of silica filler (C-1), and mix them. Add 50 parts by weight of solid epoxy resin (A-1)NC3000 (100 parts by weight based on the prepared methyl ethyl ketone solution), 333 parts by weight of hexagonal boron nitride filler (B-1), and 300 parts by weight of methyl ethyl ketone as non-volatile components, and stir using a homogenizer for 30 minutes. Then, add an appropriate amount of methyl ethyl ketone to adjust the viscosity, filter, and degas to prepare a varnish of the resin composition.

[0182] Next, the varnish of the resin composition obtained above is uniformly coated on the release surface of the support (a release-treated polyethylene terephthalate film (manufactured by Higashiyama Film Co., Ltd., HY-NS80, thickness 38μm) with a dried thickness of 100μm, and dried at 80°C for 3 minutes to produce a resin composition film (B-stage).

[0183] The composition and evaluation results of the resin composition film are shown in Table 3.

[0184] <Examples 2-29, Comparative Examples 1-9>

[0185] The resin composition film was manufactured in the same manner as in Example 1, except that the composition was modified as shown in Tables 3-5. The composition and evaluation results of the resin composition film are shown in Tables 3-5.

[0186] [Table 3]

[0187]

[0188] [Table 4]

[0189]

[0190] [Table 5]

[0191]

[0192] Comparative Example 9, like Patent Document 2, used R-BN (hexagonal boron nitride filler (B-5)) manufactured by Nissin Refratech Co., Ltd. as the hexagonal boron nitride filler (B), resulting in a content of 49% by mass (33% by volume) of the hexagonal boron nitride filler (B) in the resin composition. It should be noted that the lower thermal conductivity compared to Patent Document 2 is attributed to the different combination of epoxy resin and curing agent, resulting in a difference in the thermal conductivity of the resin itself. To improve the thermal conductivity of the resin composition of Comparative Example 9, when the content of the hexagonal boron nitride filler was increased to 666 parts by mass (Comparative Example 1), the thermal conductivity actually decreased. On the other hand, Example 17, which used silica filler in addition to hexagonal boron nitride filler (B-5), achieved a higher thermal conductivity compared to Comparative Examples 1 and 9.

[0193] Comparative Example 1 and Example 19 have the same relative permittivity and dielectric loss tangent, which can reduce transmission loss. When Comparative Example 2 is compared with Examples 4, 9-11, and Comparative Example 5 is compared with Examples 14-16, the thermal conductivity also increases when both hexagonal boron nitride filler and silicon dioxide filler are used.

[0194] Examples 4, 9, to 11, where the mass ratio of hexagonal boron nitride filler (B) to silica filler (C) is in the range of 85:15 to 30:70, exhibit higher thermal conductivity compared to Comparative Examples 3 and 4, which are outside this range. This is believed to be because: Comparative Example 3 had a small amount of silica filler, which was insufficient to achieve the effects of the present invention; and Comparative Example 4 had a small amount of hexagonal boron nitride filler with high thermal conductivity. Examples 4, 9, and 11, where the mass ratio of hexagonal boron nitride filler (B) to silica filler (C) is in the range of 75:25 to 40:60, exhibit higher thermal conductivity compared to Examples 10 and 11, which are outside this range.

[0195] Although both hexagonal boron nitride filler (B) and silica filler (C) were used in Comparative Example 8, the average particle size D50 of the silica filler (C) exceeded 1 μm, resulting in lower thermal conductivity compared to Examples 4, 18, 19, and 28, where the average particle size D50 of the silica filler was 0.1–1 μm. In Comparative Example 8, it was considered that the effects of the present invention were not achieved due to the excessively large particle size of the silica filler.

[0196] The above demonstrates that by combining specific hexagonal boron nitride and silica fillers, a resin composition with high thermal conductivity, low relative permittivity, and low dielectric loss tangent can be obtained. Therefore, this resin composition is suitable for use as a thin film for forming insulating layers in multilayer printed circuit boards.

Claims

1. A resin composition comprising an epoxy resin (A), a hexagonal boron nitride filler (B), and a silica filler (C), Relative to 100 parts by weight of the epoxy resin (A), the total content of the hexagonal boron nitride filler (B) and the silica filler (C) is 200 to 1200 parts by weight. The epoxy resin (A) comprises solid epoxy resin (A-1) and liquid epoxy resin (A-2). The hexagonal boron nitride filler (B) has an average particle size D50 of 1–10 μm and a maximum particle size Dmax of less than 30 μm. The average particle size D50 of the silica filler (C) is 0.1–1 μm. The mass ratio of the hexagonal boron nitride filler (B) to the silica filler (C) is 85:15 to 30:

70.

2. The resin composition according to claim 1, wherein, In the particle size distribution of the hexagonal boron nitride filler (B), the ratio of particle size D90 (cumulative 90% value based on volume) to particle size D10 (cumulative 10% value based on volume), i.e., D90 / D10, is 9.0 or less.

3. The resin composition according to claim 1, wherein, In the particle size distribution of the silica filler (C), the ratio of particle size D90, which is the cumulative 90% value based on volume, to particle size D10, which is the cumulative 10% value based on volume, i.e., D90 / D10, is less than 4.

0.

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

5. A multilayer printed circuit board comprising the resin composition or cured form thereof as described in any one of claims 1 to 3.

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