Resin composition, resin sheet, and substrate having built-in electronic component

Abstract

The present disclosure addresses the problem of providing a resin composition that, even when containing a large amount of inorganic filler, has high filling properties and a low thermal expansion coefficient. The resin composition contains an epoxy resin (A), a curing agent (B), a polyester polyol resin (C), and an inorganic filler (D). The polyester polyol resin (C) content is greater than 0 mass% an no greater than 10 mass% with respect to the total amount of the resin composition. The inorganic filler (D) content is 70-98 mass% with respect to the total amount of the resin composition. The inorganic filler (D) has at least two peaks, these being a first peak and a second peak, in a volume-based particle size distribution measured by using a laser diffraction / scattering method. The size of the particle diameter indicated by the position of the first peak is 0.5-20 μm. The size of the particle diameter indicated by the position of the second peak is 0.1-4 μm.

Description

Resin Composition, Resin Sheet, and Substrate with Built-in Electronic Components

[0001] The present disclosure generally relates to a resin composition, a resin sheet, and a substrate with built-in electronic components, and more particularly to a resin composition having thermosetting properties, a resin sheet containing the resin composition, and a substrate with built-in electronic components.

[0002] Patent Document 1 discloses a resin composition. This resin composition contains (A) an epoxy resin, (B) at least one curing agent selected from an acid anhydride-based curing agent, an amine-based curing agent, and a phenol-based curing agent, (C) a polyester polyol resin having an aromatic structure, and (D) an inorganic filler. When the content of component (C) is 100% by mass of the non-volatile components in the resin composition, it is 2% by mass or more and 20% by mass or less.

[0003] However, in the resin composition described in Patent Document 1 containing 70% by mass or more of an inorganic filler, there is a problem that the fluidity is excessively impaired and the sealing portion of the circuit board is not sufficiently filled. Further, with the above resin composition, there is a possibility that it cannot be formed into a sheet shape.

[0004] Japanese Unexamined Patent Application Publication No. 2021 - 187923

[0005] An object of the present disclosure is to provide a resin composition, a resin sheet, and a substrate with built-in electronic components having high filling properties and a low coefficient of thermal expansion even when containing a large amount of an inorganic filler.

[0006] The resin composition according to one aspect of the present disclosure contains an epoxy resin (A), a curing agent (B), a polyester polyol resin (C), and an inorganic filler (D). The content of the polyester polyol resin (C) is more than 0% by mass and at most 10% by mass with respect to the total amount of the resin composition. The content of the inorganic filler (D) is 70% by mass or more and 98% by mass or less with respect to the total amount of the resin composition. The inorganic filler (D) has at least two peaks, a first peak and a second peak, in the volume-based particle size distribution measured by the laser diffraction / scattering method. The size of the particle diameter indicated by the position of the first peak is 0.5 μm or more and 20 μm or less. The size of the particle diameter indicated by the position of the second peak is 0.1 μm or more and 4 μm or less.

[0007] A resin sheet according to one aspect of the present disclosure comprises a resin layer containing the resin composition or a semi-cured product of the resin composition, and a support.

[0008] An electronic component-embedded substrate according to one aspect of the present disclosure comprises a substrate having holes, electronic components mounted in the holes, and a sealing portion that fills the holes and seals the electronic components. The sealing portion includes a cured product of the resin composition.

[0009] Figure 1 is a schematic cross-sectional view showing the manufacturing process of an electronic component embedded substrate according to this embodiment. Figure 2 is a schematic cross-sectional view showing the manufacturing process of an electronic component embedded substrate according to this embodiment. Figure 3 is a schematic cross-sectional view showing an electronic component embedded substrate according to this embodiment.

[0010] Embodiments of this disclosure will now be described. Note that the embodiments described below represent only a portion of the various embodiments of this disclosure. Furthermore, the embodiments described below can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. Also, the mechanisms of operation described below are speculative, and this disclosure is not bound by the following explanation of the mechanisms of operation.

[0011] 1. Overview The resin composition according to this embodiment contains an epoxy resin (A), a curing agent (B), a polyester polyol resin (C), and an inorganic filler (D). The content of the polyester polyol resin (C) is greater than 0% by mass and 10% by mass or less, based on the total amount of the resin composition. The content of the inorganic filler (D) is 70% by mass or more and 98% by mass or less, based on the total amount of the resin composition. The inorganic filler (D) has at least two peaks, a first peak and a second peak, in the volume-based particle size distribution (hereinafter simply referred to as "particle size distribution") measured by laser diffraction and scattering. The particle size indicated by the position of the first peak is greater than the particle size indicated by the position of the second peak.

[0012] According to the above configuration, the resin composition can have high filling properties and a low coefficient of thermal expansion even when it contains a large amount of inorganic filler. That is, because the resin composition contains polyester polyol resin (C) and inorganic filler (D), the coefficient of thermal expansion can be kept low. Conventionally, when a resin composition contains a large amount of inorganic filler, although the coefficient of thermal expansion can be kept low, the viscosity increases, and the fluidity decreases significantly. However, the inorganic filler (D) of this embodiment has at least a first peak and a second peak showing a particle size smaller than the first peak in its particle size distribution. In other words, since large and small particles are mixed in the inorganic filler (D), even if the resin composition contains a large amount of inorganic filler (D), the coefficient of thermal expansion can be reduced and the increase in viscosity can be suppressed, resulting in good fluidity and enabling high filling properties for electronic component substrates 1, circuit boards, etc.

[0013] The resin sheet according to this embodiment includes the above-mentioned resin composition or a semi-cured product thereof. That is, since the resin sheet is made from the above-mentioned resin composition, a resin sheet having high fillability and a low coefficient of thermal expansion can be obtained.

[0014] The electronic component-embedded substrate 1 according to this embodiment comprises a substrate having holes, electronic components mounted within the holes, and sealing portions that fill the holes and seal the electronic components. The sealing portions include a cured product of the resin composition. That is, since the sealing portions are formed using a resin composition having high fillability and low thermal expansion coefficient, incomplete filling of the holes with the resin composition is suppressed, and reflow resistance is improved, thereby suppressing mechanical damage to the electronic component-embedded substrate 1, such as delamination between the electronic components and the sealing portions. In other words, an electronic component-embedded substrate 1 with excellent reliability can be obtained.

[0015] 2. Resin Composition The resin composition according to this embodiment will now be described.

[0016] (1) The constituent resin composition contains epoxy resin (A), a curing agent (B), polyester polyol resin (C), and an inorganic filler (D). Note that epoxy resin (A), curing agent (B), and polyester polyol resin (C) may be collectively referred to as resin components.

[0017] <Epoxy Resin> As described above, the resin composition contains epoxy resin (A). Epoxy resin (A) is thermosetting. Epoxy resin (A) is a component that can enhance the glass transition temperature, adhesion to metals, heat resistance, electrical insulation, and flame retardancy of the cured product of the resin composition.

[0018] The epoxy resin (A) is a compound having at least one epoxy group in its molecule. The epoxy resin (A) may be solid or liquid at 25°C.

[0019] Examples of epoxy resins (A) include alkylphenol novolac type epoxy resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins; naphthol novolac type epoxy resins; phenol aralkyl type epoxy resins having a phenylene skeleton, biphenylene skeleton, etc.; biphenyl aralkyl type epoxy resins; naphthol aralkyl type epoxy resins having a phenylene skeleton, biphenylene skeleton, etc.; polyfunctional epoxy resins such as triphenolmethane type epoxy resins and alkyl-modified triphenolmethane type epoxy resins; triphenylmethane type epoxy resins; tetrakisphenolethane type epoxy resins; disin Examples of epoxy resins include chloropentadiene-type epoxy resins; stilbene-type epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resins and bisphenol F-type epoxy resins; biphenyl-type epoxy resins; naphthalene-type epoxy resins; alicyclic epoxy resins; brome-containing epoxy resins such as bisphenol A-type brome-containing epoxy resins; glycidylamine-type epoxy resins obtained by the reaction of polyamines such as diaminodiphenylmethane and isocyanuric acid with epichlorohydrin; and glycidyl ester-type epoxy resins obtained by the reaction of polybasic acids such as phthalic acid and dimer acid with epichlorohydrin, but are not particularly limited. The epoxy resin (A) contained in the resin composition may be one type or two or more types.

[0020] The content of epoxy resin (A) is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, relative to the total amount of epoxy resin (A), curing agent (B), and polyester polyol resin (C). In this case, the glass transition temperature, adhesion to metals, heat resistance, flame retardancy, and electrical insulation properties of the cured resin composition can be improved. Alternatively, the content of epoxy resin (A) is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and even more preferably 70% by mass or less, relative to the total amount of epoxy resin (A), curing agent (B), and polyester polyol resin (C). In this case, a decrease in the adhesion to metals and electrical insulation properties of the cured resin composition can be suppressed.

[0021] <Curing Agent> As described above, the resin composition contains a curing agent (B). The curing agent (B) is a component that reacts with the epoxy resin (A) to crosslink the molecular chains and undergo thermal curing. It is preferable that the curing agent (B) contains at least one selected from the group consisting of phenolic resin (B1) and amine compound (B2). In this case, the glass transition temperature, adhesion to metals, mechanical strength, degree of curing, etc. of the cured product of the resin composition can be improved, and a suitable balance of these physical properties can be achieved. It is more preferable that the curing agent (B) contains both a phenolic resin (B1) and an amine compound (B2).

[0022] Examples of phenolic resin (B1) include, but are not limited to, biphenyl aralkyl type phenolic resin, phenyl aralkyl type phenolic resin, novolac type phenolic resin, cresol novolac type phenolic resin, bisphenol A novolac type phenolic resin, naphthalene type phenolic resin, and tetrakisphenol type phenolic resin. The resin composition may contain only one type of phenolic resin (B1) or two or more types.

[0023] Examples of amine compounds (B2) include, but are not limited to, dicyandiamide (DICY); aromatic amine compounds such as metaphenylenediamine (MPDA) and diaminodiphenylmethane (DDM); alicyclic amine compounds such as diazabicycloundecene (DBU) and isophoronediamine (IPDA); and linear aliphatic amine compounds such as diethylenetriamine (DTA) and triethylenetriamine (TTA). The resin composition may contain only one or two or more amine compounds (B2).

[0024] The content of the curing agent (B) is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 20% by mass or more, relative to the total amount of epoxy resin (A), curing agent (B), and polyester polyol resin (C). In this case, the glass transition temperature and heat resistance of the cured product of the resin composition can be increased. Alternatively, the content of the curing agent (B) is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, relative to the total amount of epoxy resin (A), curing agent (B), and polyester polyol resin (C). In this case, the decrease in the brittleness of the cured product of the resin composition can be suppressed.

[0025] When the curing agent (B) contains a phenolic resin (B1) and an amine compound (B2), the mass ratio of the phenolic resin (B1) to the amine compound (B2) is preferably 5:1 to 1:5. In this case, the glass transition temperature, adhesion to metals, mechanical strength, degree of curing, etc. of the cured resin composition can be improved, and a favorable balance of these physical properties can be achieved.

[0026] <Polyester Polyol Resin> As described above, the resin composition contains polyester polyol resin (C). Polyester polyol resin (C) is a polyester resin having hydroxyl groups at the molecular ends. Polyester polyol resin (C) is thermoplastic and is a component that can reduce the thermal expansion coefficient of the cured product of the resin composition. At 25°C, polyester polyol resin (C) may be solid or liquid, but is preferably liquid. In this case, the viscosity of the resin composition and its semi-cured product may be reduced and the fluidity may be improved.

[0027] The polyester polyol resin (C) undergoes phase separation with the epoxy resin (A) and curing agent (B) within the resin component to form a sea-island structure. Specifically, in the cured resin, the polyester polyol resin (C) forms the island portions, while the epoxy resin (A) and curing agent (B) form the sea portions. By forming such a structure, when the cured resin composition is heated to a high temperature, the sea portions expand due to thermal expansion, while the island portions contract due to thermal expansion. Therefore, since the sea portions expand not only externally but also in the contracted parts of the island portions, the overall thermal expansion coefficient of the cured resin composition can be reduced.

[0028] Polyester polyol resin (C) is a condensation polymer of glycol and dicarboxylic acid. Examples of glycols include, but are not particularly limited, ethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and neopentyl glycol. The glycol is preferably polypropylene glycol. Examples of dicarboxylic acids include, but are not particularly limited, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, terephthalic acid residues, and isophthalic acid residues. The dicarboxylic acid is preferably isophthalic acid or sebacic acid. That is, polyester polyol resin (C) is preferably a polycondensate of polypropylene glycol and isophthalic acid or sebacic acid.

[0029] The weight-average molecular weight of the polyester polyol resin (C) is preferably 1000 or more, more preferably 1500 or more, and even more preferably 2000 or more. In this case, the thermal expansion coefficient of the cured resin composition can be suppressed, and bleed-out of the polyester polyol resin (C) from the resin composition or its cured product can be suppressed. Alternatively, the weight-average molecular weight of the polyester polyol resin (C) is preferably 10000 or less, more preferably 8000 or less, and even more preferably 5000 or less. In this case, the increase in viscosity of the resin composition and its semi-cured product can be suppressed, and fluidity can be improved. Note that the weight-average molecular weight refers to the weight-average molecular weight on a standard polystyrene basis measured using gel permeation chromatography (GPC).

[0030] The content of polyester polyol resin (C) is greater than 0% by mass, preferably 0.3% by mass or more, and more preferably 0.7% by mass or more, relative to the total amount of the resin composition. In this case, the thermal expansion coefficient of the cured product of the resin composition is suppressed. Alternatively, the content of polyester polyol resin (C) is 10% by mass or less, preferably 5% by mass or less, and more preferably less than 1% by mass, relative to the total amount of epoxy resin (A), curing agent (B), and polyester polyol resin (C). In this case, the decrease in the glass transition temperature of the cured product of the resin composition can be suppressed.

[0031] The glass transition temperature of the polyester polyol resin (C) is preferably -10°C or lower. In this case, the thermal expansion coefficient of the cured resin composition can be reduced. The glass transition temperature is more preferably -20°C or lower, and even more preferably -40°C or lower. The glass transition temperature may be -120°C or higher, or -100°C or higher. In this case, the effects of the present disclosure are more easily obtained.

[0032] <Inorganic Filler> As described above, the resin composition contains an inorganic filler (D). The inorganic filler (D) is a component that can reduce the thermal expansion coefficient of the cured product of the resin composition.

[0033] The inorganic filler (D) has at least a first peak and a second peak in its particle size distribution. The particle size indicated by the position of the first peak is preferably 0.5 μm to 20 μm, more preferably 1 μm to 15 μm, and even more preferably 3 μm to 10 μm. In this case, the decrease in fluidity of the resin composition and its semi-cured product can be suppressed, and the thermal expansion coefficient of the cured resin composition can be reduced. The particle size indicated by the position of the second peak is preferably 0.1 μm to 4 μm, more preferably 0.2 μm to 3 μm, and even more preferably 0.4 μm to 2 μm. In this case, the resin composition can contain a large amount of inorganic filler (D) while suppressing the decrease in fluidity of the resin composition and its semi-cured product, thereby having good fluidity, improving the ability to fill electronic substrates and the like, and reducing the thermal expansion coefficient of the cured product. Therefore, the inorganic filler (D) contains a mixture of particles with a large particle size indicated by the position of the first peak and particles with a small particle size indicated by the position of the second peak. As a result, even if the resin composition contains a large amount of inorganic filler (D), the thermal expansion coefficient of the cured resin composition is reduced, and the increase in viscosity of the resin composition and its semi-cured product is suppressed, allowing for good fluidity, and thus improving the ability to fill into electronic component substrates 1, etc.

[0034] The maximum particle size (D100) of the inorganic filler (D) is 30 μm or less. In this case, the resin composition and its semi-cured product can be sufficiently filled into gaps of 50 μm or less. Here, the maximum particle size (D100) refers to the particle size at 100% of the cumulative value in the particle size distribution.

[0035] Examples of inorganic fillers (D) include, but are not particularly limited to, silica such as fused silica or crystalline silica, alumina, titanium oxide, talc, calcined clay, uncalcined clay, mica, glass, calcium carbonate, magnesium carbonate, hydrotalcite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, calcium sulfate, calcium sulfite, zinc borate, barium metaborate, aluminum borate, calcium borate, sodium borate, aluminum nitride, silicon nitride, and boron nitride. The inorganic filler (D) is preferably silica. The inorganic filler (D) contained in the resin composition may be one type or two or more types.

[0036] The inorganic filler (D) preferably contains a first inorganic filler (D1) and a second inorganic filler (D2). The first inorganic filler (D1) gives the inorganic filler (D) a first peak in the particle size distribution. That is, when the inorganic filler (D) contains the first inorganic filler (D1), the first peak is the average particle size (D50) of the first inorganic filler (D1). Here, the average particle size (D50) means the particle size at 50% of the cumulative value in the particle size distribution. The second inorganic filler (D2) gives the inorganic filler (D2) a second peak in the particle size distribution. That is, when the inorganic filler (D) contains the second inorganic filler (D2), the second peak is the average particle size (D50) of the second inorganic filler (D2). In other words, in the particle size distribution, the particle size of the first inorganic filler (D1) is larger than the particle size of the second inorganic filler (D2).

[0037] The ratio of the first inorganic filler (D1) to the second inorganic filler (D2) is preferably 9:1 to 1:1, more preferably 8.5:1.5 to 6:5, and even more preferably 8:2 to 3:2. In this case, the inorganic filler (D) can be densely packed into the resin composition, and by suppressing a decrease in the fluidity of the resin composition and the semi-cured product, good fluidity can be obtained, thereby improving the ability to fill into electronic substrates and the like, and reducing the thermal expansion coefficient of the cured product.

[0038] The content of inorganic filler (D) is 70% by mass or more, preferably 75% by mass or more, and more preferably 80% by mass or more, based on the total amount of the resin composition. In this case, the thermal expansion coefficient of the cured resin composition can be reduced. Alternatively, the content of inorganic filler (D) is 98% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total amount of the resin composition. In this case, a decrease in the fluidity of the resin composition and its semi-cured product can be suppressed.

[0039] <Additives> The resin composition may further contain additives. The components and their content of the additives are not particularly limited, as long as they do not impair the effects of this embodiment. Examples of additives include, but are not particularly limited, curing accelerators, dispersants, coupling agents, leveling agents, thermoplastic resins other than polyester polyol resin (C), flame retardants, colorants, heat stabilizers, antioxidants, reaction initiators, defoamers, antistatic agents, dyes, pigments, polymerization inhibitors, lubricants, etc.

[0040] Examples of curing accelerators include imidazole compounds such as 2-ethyl-4-methylimidazole and 2-methylimidazole.

[0041] Examples of coupling agents include N-phenyl-3-aminopropyltrimethoxysilane, vinyltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, p-styryltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, glycidoxypropyltriethoxysilane, isocyanatetopropyltriethoxysilane, isocyanatetopropyltriethoxysilane, and mercaptopropylmethyldimethoxysilane.

[0042] <Volatile Components> From the perspective of handling the resin composition, the resin composition may further contain volatile components. When the resin composition contains volatile components, the fluidity during filling of the resin composition can be further improved. Volatile components are components that have volatility and become gaseous in the atmosphere. Specifically, the volatile components include volatile organic compounds (VOCs). Examples of volatile organic compounds include, but are not limited to, methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), etc.

[0043] (2) Manufacturing Method The resin composition according to the embodiment can be manufactured by uniformly mixing raw materials including an epoxy resin (A), a curing agent (B), a polyester polyol resin (C), an inorganic filler (D), etc. General mixers can be used for mixing the above raw materials.

[0044] (3) Physical Properties The melt viscosity of the resin composition at 150℃ is preferably 10000 Pa·sec or less, more preferably 1000 Pa·sec, and still more preferably 100 Pa·sec. In this case, since the resin composition and its semi-cured product can have good fluidity, for example, the resin composition or its semi-cured product can be sufficiently filled into gaps of 50 μm or less existing in the substrate with built-in electronic components 1, and the occurrence of unfilled parts can be suppressed. That is, when the melt viscosity is within the above range, the resin composition and its semi-cured product can have high filling properties. The lower limit of the melt viscosity of the resin composition at 150℃ is not particularly limited, but is, for example, 1 Pa·sec or more.

[0045] The thermal expansion coefficient of the cured product of the resin composition is preferably less than 40 ppm / ℃, more preferably 25 ppm / ℃ or less. In this case, since the expansion when the resin composition is heated to a high temperature is suppressed, mechanical damages such as peeling and cracking of the substrate with built-in electronic components 1 including the cured product of the resin composition when exposed to a high-temperature environment such as reflow heating can be suppressed. That is, the reflow resistance of the substrate with built-in electronic components forming the sealing part using the cured product of the resin composition can be improved.

[0046] 3. Resin Sheet The resin sheet 4 according to this embodiment includes a resin layer containing the above resin composition or a semi-cured product of this resin composition, and a support (not shown). That is, since the resin layer of the resin sheet 4 is made using the resin composition, the resin layer of the resin sheet 4 has good fluidity, has high filling properties for the substrate 1 with built-in electronic components, etc., and its cured product has a low thermal expansion rate. The resin composition is in the A-stage state, that is, the resin composition itself or the resin composition containing volatile components from which the volatile components have been volatilized. The semi-cured product is a resin composition in the B-stage state, which is cured to such an extent that the resin composition does not reach a complete cured state (C-stage state). That is, the resin sheet may be a resin composition in the A-stage state or a resin composition in the B-stage state.

[0047] The thickness of the resin sheet 4 is not particularly limited, but for example, it is 30 μm or more and 300 μm or less.

[0048] The manufacturing method of the resin sheet 4 is not particularly limited, but for example, it can be manufactured by applying the above resin composition on a support, drying it in an uncured state without reacting, and semi-curing it by drying and heat.

[0049] Examples of the support include paper, cloth, resin film, metal foil, etc., but it is not particularly limited.The support may be subjected to a release treatment such as applying a release agent to the surface on which the resin composition is applied. Examples of the method of applying the resin composition on the support include methods using a bar coater, die coater, doctor blade, baker applicator, etc., but it is not particularly limited. Examples of the drying method include natural drying, hot air drying, etc., but it is not particularly limited. The heating temperature when only drying or drying and semi-curing is preferably 50°C or more and 200°C or less, more preferably 70°C or more and 150°C or less.

[0050] Furthermore, the resin sheet 4 may have a release sheet (not shown) on one side. The release sheet is not particularly limited, but examples include PET film, fluororesin film, etc. The release sheet is peeled off from the resin sheet 4 before the heat pressing or heat lamination described later.

[0051] 4. Electronic Component Embedded Substrate The electronic component embedded substrate 1 according to this embodiment will now be described. For the sake of explanation, arrows indicating the X, Y, and Z axes that constitute a three-dimensional Cartesian coordinate system are shown in the drawings, but these arrows do not have any physical form. Hereinafter, the XY plane view means the view along the Z axis. The directions of the X, Y, and Z axes are examples and are not intended to limit the direction during manufacturing and use of the electronic component embedded substrate 1.

[0052] (1) The substrate 1 containing the constituent electronic components comprises a substrate 2 having holes 23, electronic components 3 mounted in the holes 23, and a sealing portion 41 that fills the holes 23 and seals the electronic components 3. The sealing portion 41 contains a cured product of the resin composition.

[0053] <Substrate> The substrate 2 is a plate-shaped insulating substrate having electrical insulating properties. The substrate 2 has a first main surface 21, a second main surface 22, and one or more holes 23. The first main surface 21 is a surface facing the positive Z-axis direction. The second main surface 22 is located on the opposite side of the first main surface 21. That is, the second main surface 22 is a surface facing the negative Z-axis direction. The holes 23 are holes formed at least from the first main surface 21 in the negative Z-axis direction. The holes 23 may or may not penetrate from the first main surface 21 to the second main surface 22, as shown in Figure 1. The thickness of the substrate 2 is, for example, 0.3 mm or more and 2.0 mm or less, but is not particularly limited. The holes 23 are arranged in the X-axis direction and the Y-axis direction. The pitch of adjacent holes 23 in the X-axis direction and the pitch of adjacent holes 23 in the Y-axis direction are not particularly limited. The pitch is the distance between the centers of adjacent holes 23. The arrangement of the multiple holes 23 can be, for example, a grid pattern, but is not particularly limited.

[0054] <Electronic Components> The electronic component 3 is embedded in the substrate 2. Specifically, the electronic component 3 is placed in the holes 23 of the substrate 2 (see, for example, Figure 1). The electronic component 3 includes at least one selected from the group consisting of active components and passive components. Examples of active components (semiconductor devices) include integrated circuits (ICs), discrete components (diodes, transistors, etc.), optoelectronic semiconductors (light-emitting devices, light-receiving devices, optical composite devices, etc.), and sensors (temperature sensors, pressure sensors, acceleration sensors, magnetic sensors, etc.), but are not particularly limited. Examples of passive components (electronic devices) include resistors, capacitors, inductors (coils), but are not particularly limited. In this way, various electronic components 3 can be embedded in the substrate 2.

[0055] <Sealing portion> The sealing portion 41 is filled into the holes 23 of the substrate 2, and adheres closely to the substrate 2 and the electronic component 3, fixing the electronic component 3. The sealing portion 41 includes a cured product of the resin composition. That is, after the resin composition or resin sheet 4 is heated, softened, and melted, it flows and fills into the holes 23, and the sealing portion 41 is formed by thermal curing and reaching the C-stage state.

[0056] <Adhesive Sheet> The electronic component substrate 1 may further include an adhesive sheet 5. The adhesive sheet 5 has a film and an adhesive layer. The adhesive sheet 5 extends in the X-axis and Y-axis directions and has thickness in the Z-axis direction. The surface of the adhesive sheet 5 facing the positive Z-axis direction is adhesive. That is, the adhesive layer is formed on one side of the film. Examples of the film include polyimide film, but are not particularly limited. The adhesive layer includes, for example, a silicone-based adhesive or an acrylic-based adhesive. Examples of the adhesive sheet 5 include a heat-resistant insulating polyimide adhesive sheet. The thickness of the adhesive sheet 5 is, for example, 10 μm or more and 80 μm or less, but is not particularly limited. Thus, if the thickness of the adhesive sheet 5 is 10 μm or more, the adhesive sheet 5 becomes less likely to be damaged. The adhesive sheet 5 is peeled off the electronic component substrate 1 after being heat-pressed or heat-laminated as described later. The adhesive sheet 5 may also be peeled off the electronic component substrate 1 after a post-curing process.

[0057] (2) Manufacturing Method The manufacturing method of the electronic component embedded substrate 1 according to this embodiment will be described with reference to the drawings.

[0058] The manufacturing method for the electronic component embedded substrate 1 according to this embodiment includes a placement step, a filling step, a post-curing step, and a peeling step. These steps will be described in order below. In this embodiment, a manufacturing method using a resin sheet 4 will be described.

[0059] <Placement Process> In the placement process, the electronic component 3 is placed in the hole 23 of the substrate 2 (see Figure 1). The shortest distance between the substrate 2 and the electronic component 3 is not particularly limited, but for example, it is 50 μm or less. When placing the electronic component 3, an adhesive sheet 5 is placed on the second main surface 22 of the substrate 2 in advance. That is, the adhesive sheet 5 closes the opening on the negative Z-axis side of the hole 23. Therefore, the electronic component 3 is temporarily fixed to the side of the adhesive sheet 5 that faces the positive Z-axis direction. The adhesive sheet 5 remains attached to the substrate 2 until the sealing portion 41 is formed, but once the sealing portion 41 is formed, it can be peeled off from the substrate 2 as needed.

[0060] <Filling Process> In the filling process, a portion of the resin composition is filled into the holes 23 from the first main surface 21 side of the substrate 2 (see Figure 2). The resin sheet 4 may be heated during filling. This improves the fluidity of the resin sheet 4, making it easier to fill into the holes 23. Specifically, first, the resin sheet 4 is placed on the first main surface 21 side of the substrate 2 to cover the opening of the hole 23 in the positive Z-axis direction. Next, in an atmosphere under atmospheric pressure (preferably under reduced pressure), the resin sheet 4 that overlaps the substrate 2 in the positive Z-axis direction is heat-pressed or heat-laminated. This causes a portion of the resin sheet 4, which has been heated and melted into a liquid state, to fill into the holes 23. When carried out in a reduced-pressure atmosphere, incomplete filling of the holes 23 by the resin sheet 4 can be suppressed. As described above, since the resin sheet 4 is present in the openings of multiple holes 23 in the positive Z-axis direction before heat pressing or heat lamination, the resin sheet 4 can be filled into multiple holes 23 at once by simply heat pressing or heat lamination, resulting in excellent workability. The resin sheet 4 that did not fit into the hole 23 remains on the first main surface 21 of the substrate 2 as an unfilled portion 42. The unfilled portion 42 is the resin sheet 4 or its cured product that exists outside the hole 23. Since the opening of the hole 23 in the negative Z-axis direction is covered with the adhesive sheet 5, leakage of the resin sheet 4 from the opening of the hole 23 in the negative Z-axis direction can be suppressed during the filling process. Furthermore, since the electronic component 3 is temporarily fixed to the adhesive sheet 5, displacement of the electronic component 3 can also be suppressed when the resin sheet 4 flows into the hole 23. The resin sheet 4 inside the hole 23 hardens and becomes a sealing portion 41. In other words, the sealing portion 41 is the cured product of the resin composition that exists inside the hole 23. For example, a vacuum hot press, vacuum laminator, or compression molding device can be used for the filling process.

[0061] A higher degree of reduced pressure (vacuum) is preferable (i.e., a lower pressure). This is because it suppresses voids and promotes the filling of the resin composition into the holes 23. In the filling process, the degree of reduced pressure is preferably -101 kPa or higher in gauge pressure. Furthermore, the degree of reduced pressure is preferably -50 kPa or lower, and more preferably -70 kPa or lower, in gauge pressure. Gauge pressure is the difference between absolute pressure and atmospheric pressure, and is a relative pressure with atmospheric pressure as the reference pressure of 0.

[0062] The temperature during heat pressing or heat lamination is preferably 80°C or higher, more preferably 130°C or higher. When the temperature during heat pressing or heat lamination is 80°C or higher, the fluidity of the resin sheet 4 is improved, making it easier to fill the holes 23 with the resin sheet 4. The temperature during heat pressing or heat lamination is preferably 220°C or lower, more preferably 180°C or lower. When the temperature during heat pressing or heat lamination is 220°C or lower, deformation of the holes 23 can be suppressed. The temperature during heat pressing or heat lamination may be kept constant at a predetermined temperature within the range of 80°C to 220°C, or it may be raised within the range of 80°C to 220°C.

[0063] The pressure applied to the electronic component substrate 1 during heat pressing or heat lamination is preferably 0.3 MPa or higher, more preferably 1 MPa or higher. In this case, the fluidity of the resin sheet 4 can be improved. Alternatively, the pressure applied to the electronic component substrate 1 during heat pressing or heat lamination is preferably 20 MPa or lower, more preferably less than 10 MPa. In this case, deformation of the holes 23 can be suppressed. The pressure applied to the electronic component substrate 1 during heat pressing or heat lamination may be a constant predetermined pressure within the range of 0.3 MPa to 20 MPa, or it may be increased within the range of 0.3 MPa to 20 MPa.

[0064] The time for heat pressing or heat lamination is preferably 1 minute (60 seconds) or more, more preferably 3 minutes (180 seconds) or more. Alternatively, the time for heat pressing or heat lamination is preferably 2 hours (7200 seconds) or less, more preferably 1 hour (3600 seconds) or less.

[0065] <Post-curing process> The post-curing process is a process that takes place between the filling process and the peeling process. In the post-curing process, post-curing is performed. That is, the resin sheet 4 after the filling process is heated. This allows the resin composition filled in the holes 23 to harden, and a sealing portion 41 is formed inside the holes 23. In addition, the resin composition of the unfilled portions 42 present on the first main surface 21 of the substrate 2 is also hardened.

[0066] The conditions for post-curing are not particularly limited, but for example, they are 130°C to 200°C and 0.5 hours to 8 hours.

[0067] <Peeling Process> In the peeling process, the adhesive sheet 5 is peeled off the substrate 2 (see Figure 2). By peeling off the adhesive sheet 5, the second main surface 22 of the substrate 2 is exposed. The second main surface 22 is flat, including the sealing portion 41 and the surface of the electronic component 3 in the negative Z-axis direction, because the adhesive sheet 5 covered it until the peeling process. Therefore, the second main surface 22 after the peeling process does not need to undergo post-processing such as polishing, or post-processing such as polishing may be performed as needed. In addition, if a release sheet, protective sheet, etc. are used in addition to the adhesive sheet 5, it is preferable to peel them off in the peeling process.

[0068] <Polishing Process> In the polishing process, the hardened unfilled portion 42 present on the first main surface 21 of the substrate 2 is polished until the first main surface 21 is exposed. By polishing the unfilled portion 42, the first main surface 21 becomes flat, and the substrate 1 with embedded electronic components is manufactured (see Figure 3). Alternatively, the substrate 2 and the sealing portion 41 may be polished together with the unfilled portion 42, as long as the electronic components 3 are not damaged.

[0069] Polishing methods include, but are not limited to, buffing, belt polishing, grinding wheel polishing, and lapping.

[0070] (Reliability) The electronic component embedded substrate 1 according to this embodiment has a sealing portion made from a cured resin composition having a low coefficient of thermal expansion, and therefore has good reflow resistance. Reflow resistance refers to the characteristic that no mechanical damage occurs even when reflow soldering is performed using a reflow oven. The upper limit of the temperature inside the reflow oven is not particularly limited, but for example, it is 260°C or less. If the reflow resistance is not good, delamination, cracks, etc. will occur inside and outside the electronic component embedded substrate 1 when reflow soldering is performed using a reflow oven. If this mechanical damage occurs in a product that has wiring etc., it will lead to the breakage of the wiring etc. Since the electronic component embedded substrate 1 according to this embodiment has good reflow resistance, it has excellent reliability.

[0071] 5. Aspects As will be clear from the above embodiments, this disclosure includes the following aspects. Hereafter, reference numerals are enclosed in parentheses solely to indicate their correspondence with the embodiments.

[0072] A resin composition according to a first aspect of this disclosure contains an epoxy resin (A), a curing agent (B), a polyester polyol resin (C), and an inorganic filler (D). The content of the polyester polyol resin (C) is greater than 0% by mass and 10% by mass or less, based on the total amount of the resin composition. The content of the inorganic filler (D) is 70% by mass or more and 98% by mass or less, based on the total amount of the resin composition. The inorganic filler (D) has at least two peaks, a first peak and a second peak, in a volume-based particle size distribution measured by laser diffraction and scattering. The particle size indicated by the position of the first peak is 0.5 μm or more and 20 μm or less. The particle size indicated by the position of the second peak is 0.1 μm or more and 4 μm or less.

[0073] According to this embodiment, even when the resin composition contains a large amount of inorganic filler, it can have high filling properties and a low coefficient of thermal expansion.

[0074] In the first embodiment, the resin composition according to the second aspect of the present disclosure comprises a curing agent (B) selected from the group consisting of phenolic resins (B1) and amine compounds (B2).

[0075] A resin composition according to a third aspect of the present disclosure, in the first or second aspect, comprises an inorganic filler (D) comprising a first inorganic filler (D1) that gives a first peak and a second inorganic filler (D2) that gives a second peak. The mass ratio of the first inorganic filler (D1) to the second inorganic filler (D2) is 9:1 to 1:1.

[0076] In the fourth aspect of the present disclosure, the resin composition is such that the polyester polyol resin (C) is liquid in any one of the first to third aspects.

[0077] In the fifth aspect of the present disclosure, the resin composition is such that, in any one of the first to fourth aspects, the average weight molecular weight of the polyester polyol resin (C) is 1,000 or more and 10,000 or less.

[0078] In the sixth aspect of the present disclosure, the resin composition is such that, in any one of the first to fifth aspects, the content of epoxy resin (A) is 20% by mass or more and 90% by mass or less, relative to the total amount of epoxy resin (A), curing agent (B), and polyester polyol resin (C).

[0079] In the seventh aspect of the present disclosure, the resin composition has a polyester polyol resin (C) content that is greater than 0% by mass and less than 1.0% by mass, based on the total amount of the resin composition, in any one of the first to sixth aspects.

[0080] The resin sheet (4) according to the eighth aspect of the present disclosure comprises a resin layer containing a resin composition or a semi-cured product of a resin composition according to any one of the first to seventh aspects, and a support.

[0081] According to this embodiment, a resin sheet (4) having high fillability and a low coefficient of thermal expansion can be obtained.

[0082] An electronic component-embedded substrate (1) according to the ninth aspect of the present disclosure comprises a substrate (2) having holes (23), electronic components (3) mounted in the holes (23), and a sealing portion (41) that fills the holes (23) and seals the electronic components (3). The sealing portion (41) comprises a cured product of a resin composition according to any one of the first to seventh aspects.

[0083] According to this embodiment, the incomplete filling of the resin composition into the holes (23) is suppressed, and reflow resistance is improved, thereby suppressing mechanical damage to the electronic component embedded substrate (1), such as delamination between the electronic component (3) and the sealing portion (41), and thus a highly reliable electronic component embedded substrate (1) can be obtained.

[0084] The present disclosure will be described in detail below with reference to examples. However, the present disclosure is not limited to the following examples.

[0085] (1) Preparation of Resin Compositions The components shown in Table 1 were mixed as raw materials for the resin compositions. Specifically, epoxy resin (A), curing agent (B), polyester polyol resin (C), inorganic filler (D), and additives were blended in the amounts shown in Table 1, diluted with MEK (methyl ethyl ketone) and DMF (N,N-dimethylformamide) as organic solvents, and then stirred and mixed to homogenize the mixture, thereby preparing the varnish-state resin compositions of the Examples and Comparative Examples with a solid content concentration of 92% by mass. Details of each component used are as follows.

[0086] <Epoxy Resins (A)> - Epoxy Resin #1: Manufactured by DIC Corporation, product name "Epiclon 850S", bisphenol A type epoxy resin - Epoxy Resin #2: Manufactured by Nippon Kayaku Co., Ltd., product name "NC3000", polyfunctional epoxy resin - Epoxy Resin #3: Manufactured by Nippon Steel Chemical & Material Co., Ltd., product name "YP50", phenoxy resin.

[0087] <Hardening Agent (B)> -Hardening agent #1: Manufactured by Meiwa Kasei Co., Ltd., product name "DL75", phenol novolac type phenolic resin -Hardening agent #2: Manufactured by Nippon Carbide Industries Co., Ltd., product name "Dicyandiamide (DICY)", amine compound.

[0088] <Polyester Polyol Resin (C)> - Polyester Polyol Resin #1: Manufactured by DIC Corporation, product name "FPS-120", liquid polyester polyol, weight-average molecular weight: 2000, viscosity at 75°C: 90 mPa / sec, glass transition temperature: -67°C.

[0089] <Inorganic filler (D)> - Inorganic filler #1: Silica, D50: 3.5 μm, D100: 10 μm - Inorganic filler #2: Silica, D50: 0.3 μm, D100: 2 μm.

[0090] <Additives> - Additive #1: Manufactured by Shikoku Chemicals Co., Ltd., product name "2E4MZ", curing accelerator, imidazole compound - Additive #2: Manufactured by DIC Corporation, product name "F-556", leveling agent - Additive #3: Manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-573", silane coupling agent - Additive #4: Manufactured by NOF Corporation, product name "Naimine L-202", dispersant, nonionic surfactant.

[0091] (2) Preparation of resin sheets A resin sheet with a thickness of 150 μm was prepared using the prepared resin composition. Specifically, each of the varnished resin compositions of Examples 1-2 and Comparative Examples 1-2 was applied to a PET film (manufactured by Mitsui Chemicals Tohcello Co., Ltd., product number "SP-PET O1"), which served as a support, using a bar coater. Then, it was dried in an oven at 100°C for 10 minutes to obtain a resin sheet with a thickness of 150 μm.

[0092] (3) Fabrication of circuit board with embedded electronic components First, the circuit board, adhesive sheet and electronic components were prepared.

[0093] A printed circuit board (manufactured by Panasonic Industries, Ltd., part number "R-1515V", size 50 mm x 50 mm x 1.4 mm thick) was used as the substrate. This substrate has a hole measuring 3 mm x 2.2 mm in the Z direction in an XY planar view.

[0094] A polyimide film (3M, part number "PIA220", 50 μm thick, 100 mm wide) was used as the adhesive sheet. The adhesive sheet is attached to the Z-axis negative direction surface (second main surface) of the substrate. The adhesive sheet seals the Z-axis negative direction opening of the hole.

[0095] A silicon chip (2 mm x 2 mm x 0.7 mm thick) was used as the electronic component. The silicon chip was placed inside the hole so that the shortest distance between the substrate and the electronic component was 50 μm, and then temporarily fixed to an adhesive sheet.

[0096] The resin layer side of a resin sheet was placed on the Z-axis positive plane (first main plane) of a substrate on which electronic components were arranged, and the resin composition was filled into the holes of the substrate by hot pressing under reduced pressure of -90 kPa, followed by post-curing. The conditions for hot pressing were a temperature of 150°C, a pressure of 5 MPa, and a time of 0.5 hours.

[0097] After curing, the adhesive sheet was peeled off. Next, any unfilled areas of the resin sheet formed on the first main surface of the substrate were removed by buffing. After polishing, the substrate was washed with water and dried at 125°C for 1 hour to produce a substrate with embedded electronic components.

[0098] (4) Evaluation The following evaluation items were used to evaluate the cured resin composition, resin sheet, and substrate with embedded electronic components. The results are shown in Table 1.

[0099] <Melting Viscosity> The melting viscosity of the resin layer of the fabricated resin sheet at 150°C was measured using a flow tester viscometer (Shimadzu Corporation, model number: CFT-500D).

[0100] <Coefficient of Thermal Expansion (CTE)> A laminate made by stacking multiple resin sheets from which the support had been peeled was partially cured using a hot press at a temperature of 150°C, a pressure of 5 MPa, and for 30 minutes. Next, the partially cured laminate was cured in an oven at 175°C for 90 minutes. After curing, the laminate was cut into pieces measuring 16 mm x 2 mm x 2 mm to form small pieces. The coefficient of thermal expansion (CTE) was measured using the obtained small pieces. The measurement conditions were as follows.

[0101] • Load: 10 mN • Measurement start temperature: Room temperature (but below 30°C) • Heating rate: 5°C / min • Measurement mode: Compression method.

[0102] The coefficient of thermal expansion was calculated using the following formula.

[0103]

[0104] L: Length of the long side of the small piece at 30°C. ΔL: Difference between the length of the long side of the small piece at 260°C and the length of the long side of the small piece at 30°C. ΔT: 230°C (= 260°C - 30°C).

[0105] The calculation results were classified according to the following criteria, and the thermal expansion coefficient was evaluated. Evaluation C indicates that the target was not met, evaluation B indicates a satisfactory result, and evaluation A indicates a more satisfactory result.

[0106] A: 25 ppm / °C or less. B: Greater than 25 ppm / °C and less than 40 ppm / °C. C: 40 ppm / °C or more.

[0107] <Filling Performance> The circuit board containing the electronic components was cut through the holes, and the cut surface was observed. The observation results were classified according to the following evaluation criteria, and the filling performance was evaluated. Evaluation B indicates that the target was not met, and evaluation A indicates a satisfactory result.

[0108] A: The holes are filled with resin composition, with almost no unfilled areas. B: There are clearly unfilled areas in the holes.

[0109] <Reflow Resistance> The electronic component embedded substrate was placed in a constant temperature and humidity chamber set to 60°C and 60% RH for 48 hours to absorb moisture. Next, the moisture-treated electronic component embedded substrate was heated in a reflow oven set to a maximum temperature of 260°C. After heating, the sample was cooled to room temperature. Next, the electronic component embedded substrate was cut through the holes, and the cut surface was observed. The observation results were classified according to the evaluation criteria below, and the reflow resistance was evaluated. Evaluation B is below the target, and evaluation A is a satisfactory result. Note that comparative example 1 did not undergo reflow resistance evaluation due to poor filling of the sealing area.

[0110] A: There is no change in appearance, and the interface between the electronic component inside the hole and the resin composition has not peeled off. B: Peeling has occurred at the interface between the electronic component inside the hole and the sealing part.

[0111]

[0112] 1. Electronic component embedded substrate 2. Substrate 21. First main surface 22. Second main surface 23. Hole 3. Electronic component 4. Resin sheet 41. Sealing portion 42. Unfilled portion 5. Adhesive sheet

Claims

1. A resin composition comprising an epoxy resin (A), a curing agent (B), a polyester polyol resin (C), and an inorganic filler (D), wherein the content of the polyester polyol resin (C) is greater than 0% by mass and 10% by mass or less of the total amount of the resin composition, the content of the inorganic filler (D) is 70% by mass or more and 98% by mass or less of the total amount of the resin composition, the inorganic filler (D) has at least two peaks, a first peak and a second peak, in a volume-based particle size distribution measured by laser diffraction-scattering, the particle size indicated by the position of the first peak is 0.5 μm or more and 20 μm or less, and the particle size indicated by the position of the second peak is 0.1 μm or more and 4 μm or less.

2. The resin composition according to claim 1, wherein the curing agent (B) comprises at least one selected from the group consisting of phenolic resin (B1) and amine compound (B2).

3. The resin composition according to claim 1, wherein the inorganic filler (D) comprises a first inorganic filler (D1) that gives the first peak and a second inorganic filler (D2) that gives the second peak, and the mass ratio of the first inorganic filler (D1) and the second inorganic filler (D2) is 9:1 to 1:

1.

4. The resin composition according to claim 1, wherein the polyester polyol resin (C) is in liquid form.

5. The resin composition according to claim 1, wherein the weight-average molecular weight of the polyester polyol resin (C) is 1,000 or more and 10,000 or less.

6. The resin composition according to claim 1, wherein the content of the epoxy resin (A) is 20% by mass or more and 90% by mass or less, relative to the total amount of the epoxy resin (A), the curing agent (B), and the polyester polyol resin (C).

7. The resin composition according to claim 1, wherein the content of the polyester polyol resin (C) is greater than 0% by mass and less than 1.0% by mass, relative to the total amount of the resin composition.

8. A resin sheet comprising a resin layer containing the resin composition described in any one of claims 1 to 7 or a semi-cured product of the resin composition, and a support.

9. A substrate with embedded electronic components, comprising a substrate having holes, electronic components mounted in the holes, and a sealing portion that fills the holes and seals the electronic components, wherein the sealing portion contains a cured product of the resin composition described in any one of claims 1 to 7.

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