Resin sheet

Abstract

To provide a resin sheet or the like capable of obtaining a cured product having a low linear expansion coefficient and a low dielectric loss tangent and suppressing the occurrence of swelling.SOLUTION: There is provided a resin sheet which comprises a resin composition layer having a first surface and a support bonded to the first surface of the resin composition layer, wherein the resin composition layer contains an inorganic filler, in a cross-section perpendicular to the first surface where the distance from the edge of one side of the support to the outer edge of the resin composition layer is 1.5 mm by laminating the resin sheet on an inner layer substrate, followed by thermally curing the resin composition layer at 180°C for 30 minutes without peeling off the support, when the ratio (%) of the area of the inorganic filler part per unit area in the cured product of the resin composition layer is defined as Si(A) and in a cross-section perpendicular to the first surface where the distance from the edge toward the edge of the opposite side of the edge is 1.5 mm, when the ratio (%) of the area of the inorganic filler part per unit area in the cured product of the resin composition layer is defined as Si(B), Si(A)-Si(B) is 5% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin sheet, and further to a circuit board and a semiconductor device obtained by using the resin sheet. [Background technology]

[0002] Circuit boards such as printed wiring boards are widely used in various electronic devices. A known method for manufacturing circuit boards is a build-up method in which insulating layers and conductor layers are alternately stacked on an inner layer substrate. The insulating layer is formed, for example, by forming a resin composition layer containing a resin composition and curing the resin composition layer. A known method for forming a resin composition layer on an inner layer substrate is to laminate a resin sheet including a support and a resin composition layer onto the inner layer substrate (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-172221 Summary of the Invention [Problem to be solved by the invention]

[0004] The inner layer substrate may have components and a conductor layer on its surface. From the viewpoint of satisfactorily embedding the components and the conductor layer in the resin composition layer during lamination, the resin composition contained in the resin composition layer is required to have high fluidity during lamination.

[0005] On the other hand, in order to suppress warpage of the circuit board, the insulating layer is required to have a low thermal expansion coefficient, and in order to meet the advanced requirements of recent years, the insulating layer of the circuit board is further required to have a low dielectric loss tangent.

[0006] During the process of manufacturing a circuit board, heat and pressure are applied to the resin composition layer during the process of laminating an inner layer substrate and a resin sheet, causing the resin composition layer to fluidize. As a result, a portion of the resin composition layer may seep out from the gap between the inner layer substrate and the support. This portion of the resin composition layer or insulating layer that seeps out from the gap between the inner layer substrate and the support is called a "bleed-out portion." It has been discovered that, particularly in resin composition layers with low linear expansion coefficients and low dielectric tangents, bulging occurs in the bleed-out portion of the insulating layer. Generally, a conductor layer is formed on the insulating layer, and an annealing treatment is performed after the formation of the conductor layer. This annealing treatment can cause bulging in the bleed-out portion of the insulating layer. Such bulging may hinder the smooth execution of subsequent processes (e.g., processes for forming additional insulating layers and conductor layers).

[0007] The present invention has been devised in view of the above-mentioned problems, and aims to provide a resin sheet that can give a cured product having a low linear expansion coefficient, a low dielectric tangent, and suppressed blistering; and a circuit board and a semiconductor device that include an insulating layer formed using the resin sheet. [Means for solving the problem]

[0008] As a result of intensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by laminating a resin sheet to an inner layer substrate, and then heat-curing the resin composition layer at 180°C for 30 minutes without peeling off the support to obtain a cured product of the resin composition layer, and adjusting the resin composition layer so that Si(A) - Si(B) satisfies the relationship of 5 or less, where Si(A) is the proportion (%) of the inorganic filler partial area per unit area in the cured product in a cross section perpendicular to the first surface, at a distance of 1.5 mm from one edge of the support toward the outer edge of the cured product, and Si(B) is the proportion (%) of the inorganic filler partial area per unit area in the cured product in a cross section perpendicular to the first surface, at a distance of 1.5 mm from the edge toward the edge of the side opposite to the edge.

[0009] That is, the present invention includes the following. [1] A resin composition layer having a first surface; a support bonded to the first surface of the resin composition layer, the resin composition layer contains an inorganic filler, After laminating the resin sheet onto the inner layer substrate, the resin composition layer is thermally cured at 180°C for 30 minutes without peeling off the support to obtain a cured resin composition layer; In a cross section in a direction perpendicular to the first surface at a distance of 1.5 mm from an end of one side of the support toward the outer edge of the cured product of the resin composition layer, Si(A) is defined as the proportion (%) of the inorganic filler portion area per unit area in the cured product of the resin composition layer, In a cross section perpendicular to the first surface at a distance of 1.5 mm from an end of one side of the support toward the end of the side opposite to said end, when the proportion (%) of the inorganic filler portion area per unit area in the cured product of the resin composition layer is defined as Si(B), A resin sheet in which Si(A)-Si(B) satisfies the relationship of 5% or less. [2] The resin sheet according to [1], wherein the resin composition layer is thermally cured at 200°C for 90 minutes, and the cured product has a dielectric loss tangent of 0.0030 or less. [3] The resin sheet according to [1] or [2], wherein the resin composition layer is heat-cured at 200°C for 90 minutes and the cured product has a thermal expansion coefficient of 20 ppm / °C or less. [4] The resin sheet according to any one of [1] to [3], wherein the resin composition layer contains (B) an epoxy resin. [5] The resin sheet according to any one of [1] to [4], wherein the resin composition layer contains (C) an active ester-based curing agent. [6] The resin sheet according to [4] or [5], wherein the resin composition layer contains (C) an active ester-based curing agent and (D) a curing agent, and the ratio (M(C+D) / M(B)) of the number of epoxy groups in the (B) component, M(B), to the number of active groups in the (C) component and the (D) component, M(C+D), is 0.7 or more. [7] The resin sheet according to any one of [1] to [6], wherein the content of the inorganic filler is 70% by mass or more when the nonvolatile components in the resin composition layer are taken as 100% by mass. [8] A circuit board comprising a cured layer obtained by curing a resin composition layer of the resin sheet according to any one of [1] to [7]. [9] A step of laminating an inner layer substrate and the resin sheet according to any one of [1] to [7] so that the inner layer substrate and the resin composition layer are in contact with each other; curing the resin composition layer; A method for manufacturing a circuit board, wherein the step of laminating an inner layer substrate and a resin sheet includes allowing a portion of a resin composition layer to seep out from a gap between the inner layer substrate and the support.

[10] A semiconductor device comprising the circuit board described in [8]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a resin sheet that can give a cured product having a low linear expansion coefficient, a low dielectric tangent, and suppressed blistering; and a circuit board and a semiconductor device that include an insulating layer formed using the resin sheet. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a resin sheet according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating the state after laminating a resin sheet according to one embodiment of the present invention onto an inner layer substrate and thermally curing it. [Figure 3] FIG. 3 is a schematic cross-sectional view illustrating a method for manufacturing a circuit board according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below based on preferred embodiments. However, the present invention is not limited to the following embodiments and examples, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents. In this specification, the term "cured product" also refers to a resin composition layer that is in a semi-cured state when cured at 180°C for 30 minutes.

[0013] [Resin sheet] The resin sheet of the present invention is a resin sheet including a resin composition layer having a first surface and a low dielectric dissipation factor and a low coefficient of linear thermal expansion (CTE), and a support bonded to the first surface of the resin composition layer, wherein the resin composition layer contains an inorganic filler, After laminating the resin sheet to the inner layer substrate, the resin composition layer is thermally cured at 180°C for 30 minutes without peeling off the support to obtain a cured resin composition layer, and in a cross section perpendicular to the first surface at a distance of 1.5 mm from one edge of the support toward the outer edge of the cured resin composition layer, the proportion (%) of the inorganic filler portion per unit area in the cured resin composition layer is defined as Si(A), and in a cross section perpendicular to the first surface at a distance of 1.5 mm from the edge of one edge of the support toward the edge of the opposite side, the proportion (%) of the inorganic filler portion per unit area in the cured resin composition layer is defined as Si(B), where Si(A) - Si(B) satisfies the relationship of 5% or less. In the present invention, by adjusting the components contained in the resin composition layer so that Si(A) - Si(B) is 5 or less, the occurrence of blistering is suppressed.

[0014] In this specification, the inorganic filler component area refers to the area occupied by the inorganic filler, and the inorganic filler refers to the inorganic filler (A) described below.

[0015] FIG. 1 shows a schematic cross-sectional view of an example of a resin sheet of the present invention. The resin sheet 200 of the present invention includes a support 220 and a resin composition layer 210 having a first surface 210a and a second surface 210b. The first surface 210a and the second surface 210b are on opposite sides in the thickness direction of the resin composition layer 210. The support 220 is bonded to the first surface 210a of the resin composition layer 210. The resin sheet 200 may optionally have a protective film 240 provided on the surface of the resin composition layer 210 that is not bonded to the support 220, i.e., on the second surface 220b. The protective film 240 is provided to prevent the second surface 210b of the resin composition layer 210 from being scratched or being contaminated by dust or other foreign matter. The resin sheet 200 is typically used after the protective film 240 is peeled off.

[0016] FIG. 2 is a schematic cross-sectional view of an example of a resin sheet 200 of the present invention laminated to an inner substrate 100 and thermally cured. As shown in FIG. 2, when the inner substrate 100 and the resin sheet 200 are laminated together, most of the resin composition layer 210 is cured in the gap 300 between the inner substrate 100 and the support 220 to form a cured product 211. However, a portion 230 of the resin composition layer 210 seeps out of the gap 300 and hardens to form a cured product. That is, the portion 230 of the resin composition layer 210 seeps out from the end 221 of the support 220 to the outer edge 212, and this exuded portion 230 forms a bleed-out portion and hardens in a blistered state. In the gap 300, the resin composition layer 210 is covered by the support 220 and the inner substrate 100. This prevents the loss of components from the resin composition layer 210 due to evaporation. In contrast, the bleed-out portion is a portion that seeps out from the gap 300 between the inner layer substrate 100 and the support 220. In other words, there is no support 220 above the resin composition layer 210. Therefore, when the resin composition layer 220 is subjected to heat during curing, some of the components in the resin composition layer 210 may evaporate and be lost from the bleed-out portion before reacting. For this reason, it is presumed that, in the past, the amount of the component in question decreased in the bleed-out portion, causing a change in the compatibility of the resin composition layer during curing (during the curing reaction), resulting in the occurrence of swelling in the bleed-out portion.

[0017] As described above, the resin sheet of the present invention reduces components lost from the resin composition layer before reaction due to heating, thereby suppressing swelling in the bleed-out portion. To reduce the Si(A)-Si(B) ratio to 5% or less, adjustments are made to reduce the difference in compatibility between the resin composition layer heat-cured while covered with a support and the resin composition layer in the bleed-out portion. When the resin composition layer is exposed to heat during curing, some of the components in the resin composition layer may evaporate and be lost from the bleed-out portion before reacting. Therefore, it is presumed that the amount of the component in the bleed-out portion decreases, changing the compatibility of the resin composition layer during curing, resulting in swelling in the bleed-out portion. In the present invention, suppression of swelling in the bleed-out portion is achieved by employing a composition with excellent compatibility in the resin composition layer.

[0018] Si(A) is measured as follows. A resin sheet is laminated onto an inner layer substrate so that the resin composition layer is in contact with the inner layer substrate, resulting in an inner layer substrate with a laminated resin sheet. After lamination, without peeling off the support, the inner layer substrate with the laminated resin sheet is heated in an oven at 180°C for 30 minutes to thermally cure the resin composition layer and obtain a cured resin composition layer. After thermal curing, an arbitrary end of one side of the support is selected, and a cross-section is made so that a portion perpendicular to the first surface of the resin composition layer is exposed 1.5 mm from the end toward the outer edge where the cured resin composition layer has exuded (L1, L1 in Figure 2 is 1.5 mm), thereby preparing a sample. The sample is subjected to image analysis of the obtained SEM image using an SEM (scanning electron microscope) to determine Si(A). In the image analysis, the resin component portion and the inorganic filler component portion are binarized into black and white, and the number of pixels in the inorganic filler component portion is treated as the area of ​​the inorganic filler portion. When measuring Si(A), the area of ​​the inorganic filler component portion in the region from d1 (μm) to d2 (μm) from the first surface of the cured resin composition layer is determined. This allows the ratio Si(A), the inorganic filler portion area per unit area in the region from d1 (μm) to d2 (μm) from the first surface, to be determined. When measuring Si(A), d1 = 0 μm and d2 = 5 μm are typically used. The width of the measurement region (measurement distance in a direction parallel to the first surface) is typically 7.5 μm.

[0019] Si(B) is measured as follows. A resin sheet is laminated onto an inner layer substrate so that the resin composition layer is in contact with the inner layer substrate, resulting in an inner layer substrate with a laminated resin sheet. After lamination, without peeling off the support, the inner layer substrate with the laminated resin sheet is heated in an oven at 180°C for 30 minutes to thermally cure the resin composition layer and obtain a cured resin composition layer. After thermal curing, an arbitrary end of the support is selected, and a cross-section is made so that a portion perpendicular to the first surface of the resin composition layer is exposed 1.5 mm toward the edge of the side opposite the selected end (L2, L2 in Figure 2 is 1.5 mm), thereby preparing a sample. The sample is then subjected to image analysis of the obtained SEM image to determine Si(B). In the image analysis, the resin component portion and the inorganic filler component portion are binarized into black and white, and the number of pixels in the inorganic filler component portion is treated as the area of ​​the inorganic filler portion. When measuring Si(B), the area of ​​the inorganic filler component in the region from d1 (μm) to d2 (μm) from the first surface of the cured resin composition layer is determined. The widths of the measurement regions are set equal for Si(A) and Si(B), and when measuring Si(B), d1 is typically 0 μm and d2 is typically 5 μm, as in the measurement of Si(A). The width of the measurement region (measurement distance in a direction parallel to the first surface) is typically 7.5 μm. This allows the ratio of the inorganic filler area per unit area, Si(B), to be determined in the region from d1 (μm) to d2 (μm) from the first surface. The inner layer substrate and lamination method will be described later. More specific methods for measuring Si(A) and Si(B) can be performed using the methods described in the Examples below.

[0020] When measuring the area of ​​the inorganic filler portion, the conditions are calibrated to ensure the accuracy of image analysis. Such calibration can be performed by setting a binarization threshold so that the value of (number of pixels in the inorganic filler component portion) / (total number of pixels in the cross section of the cross-sectional sample) × 100 substantially coincides with the volume percent value of the inorganic filler component of the cross-sectional sample.

[0021] Si(A) is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. The lower limit is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more.

[0022] Si(B) is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. The lower limit is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more.

[0023] From the viewpoint of suppressing the occurrence of blistering, Si(A)-Si(B) is 10% or less, preferably 8% or less, more preferably 7.5% or less, and even more preferably 6% or less, 5% or less, or 4% or less. There is no particular lower limit, but it may be 0% or more, 0.1% or more, etc.

[0024] <Resin composition layer> The resin sheet has a resin composition layer containing (A) an inorganic filler. The resin composition layer may further contain, as necessary, (B) an epoxy resin, (C) an active ester curing agent, (D) other curing agents, (E) an organic filler, (F) a curing accelerator, (G) a high-molecular-weight component, (H) other additives, and (I) a solvent.

[0025] Examples of methods for reducing Si(A)-Si(B) to 5% or less include the following. Some resin components in the resin composition layer may be partially vaporized before reacting due to heat. Therefore, for example, the difference may be reduced to 5% or less by reducing such vaporizable components. Furthermore, some resins that are solid at room temperature may be vaporized due to heat. Therefore, the amount of resin components lost during heating may be reduced by appropriately adjusting the amount of such resins. Here, the resin components refer to the non-volatile components in the resin composition layer excluding inorganic fillers.

[0026] Furthermore, when a resin composition layer is formed using a resin varnish containing a solvent (I), the resin composition layer may contain the solvent (I). Although the amount of solvent (I) in the resin composition layer is generally small, the solvent (I) evaporates due to heat, which can cause the above-mentioned difference to increase. Therefore, when a resin composition layer is formed using a resin varnish, it is preferable to thoroughly dry the resin composition layer during its production process to reduce the amount of solvent (I) remaining in the resin composition layer. Since the ease of drying typically varies depending on the type of solvent (I), it is preferable to set specific drying conditions according to the type of solvent (I).

[0027] -(A) Inorganic filler- The resin composition layer contains an inorganic filler (A) as the component (A). By including the inorganic filler (A), a cured product having a low dielectric loss tangent and a low linear thermal expansion coefficient can be obtained. The inorganic filler (A) is usually contained in the resin composition layer in the form of particles. The component (A) may be used alone or in combination of two or more.

[0028] (A) Inorganic fillers are inorganic compounds. Examples of (A) inorganic filler materials include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium titanate zirconate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, silica is particularly preferred. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. Spherical silica is preferred.

[0029] (A) Examples of commercially available inorganic fillers include "SP60-05" and "SP507-05" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YC100C," "YA050C," "YA050C-MJE," "YA010C," "SC2500SQ," "SO-C4," "SO-C2," and "SO-C1" manufactured by Admatechs Co., Ltd.; "UFP-30," "DAW-03," and "FB-105FD" manufactured by Denka Company, Limited; "Silfil NSS-3N," "Silfil NSS-4N," and "Silfil NSS-5N" manufactured by Tokuyama Corporation; and "CellSpheres" and "MGH-005" manufactured by Taiheiyo Cement Corporation.

[0030] The average particle size of the (A) inorganic filler is preferably 0.01 μm or more, more preferably 0.1 μm or more, even more preferably 0.3 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less.

[0031] (A) The average particle size of an inorganic filler can be measured by a laser diffraction / scattering method based on Mie scattering theory. Specifically, a volumetric particle size distribution of the inorganic filler is created using a laser diffraction / scattering particle size distribution analyzer, and the median diameter is used as the average particle size. A measurement sample can be prepared by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing the mixture ultrasonically for 10 minutes. The volumetric particle size distribution of the inorganic filler is measured using a laser diffraction particle size distribution analyzer with blue and red light source wavelengths using a flow cell system, and the average particle size can be calculated as the median diameter from the particle size distribution obtained. Examples of laser diffraction particle size distribution analyzers include the LA-960 manufactured by Horiba, Ltd.

[0032] The BET specific surface area of ​​the (A) inorganic filler is preferably 0.1 m 2 / g or more, more preferably 0.5m 2 / g or more, more preferably 1m 2 / g or more, preferably 100m 2 / g or less, more preferably 70m 2 / g or less, more preferably 40m 2 / g or less.

[0033] (A) The specific surface area of ​​the inorganic filler can be measured according to the BET method by adsorbing nitrogen gas onto the sample surface using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) and calculating the specific surface area using the BET multipoint method.

[0034] The (A) inorganic filler is preferably treated with a surface treatment agent from the viewpoint of improving moisture resistance and dispersibility. Examples of the surface treatment agent include a fluorine-containing silane coupling agent, an aminosilane coupling agent, an epoxysilane coupling agent, a mercaptosilane coupling agent, a silane coupling agent, an alkoxysilane, an organosilazane compound, and a titanate coupling agent. One type of surface treatment agent may be used alone, or two or more types may be used in any combination.

[0035] Examples of commercially available surface treatment agents include Shin-Etsu Chemical Co., Ltd.'s "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM803" (3-mercaptopropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBE903" (3-aminopropyltriethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical Co., Ltd.'s "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM-4803" (long-chain epoxy-type silane coupling agent), and Shin-Etsu Chemical Co., Ltd.'s "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane).

[0036] The degree of surface treatment with the surface treatment agent preferably falls within a specific range from the viewpoint of improving the dispersibility of the inorganic filler. Specifically, 100% by mass of the inorganic filler is preferably surface-treated with 0.2% to 5% by mass of the surface treatment agent, more preferably with 0.2% to 3% by mass of the surface treatment agent, and even more preferably with 0.3% to 2% by mass of the surface treatment agent.

[0037] The degree of surface treatment with the surface treatment agent can be evaluated by the amount of carbon per unit surface area of ​​the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of ​​the inorganic filler is set to 0.02 mg / m 2 More than 0.1 mg / m is preferable. 2 More preferably, 0.2 mg / m or more 2 On the other hand, from the viewpoint of preventing an increase in the melt viscosity of the resin composition layer, it is more preferable that the amount of the resin composition layer is 1.0 mg / m 2 Less than 0.8 mg / m is preferred 2 Less than 0.5 mg / m is more preferable. 2 The following is even more preferred:

[0038] (A) The amount of carbon per unit surface area of ​​an inorganic filler can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solid content, the amount of carbon per unit surface area of ​​the inorganic filler can be measured using a carbon analyzer. An "EMIA-320V" manufactured by Horiba, Ltd., or the like can be used as the carbon analyzer.

[0039] The degree of surface treatment with a surface treatment agent can be evaluated by the amount of carbon per unit mass of the inorganic filler. The amount of carbon per unit mass of the inorganic filler is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, and is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less. The amount of carbon per unit mass of (A) inorganic filler can be measured using a carbon analyzer, just like the amount of carbon per unit surface area of ​​(A) inorganic filler.

[0040] The content of the (A) inorganic filler is preferably 40% by mass or more, more preferably 45% by mass or more, particularly preferably 50% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 74% by mass or more, 75% by mass or more, or 76% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 85% by mass or less, based on the total nonvolatile components in the resin composition layer as 100% by mass. By adjusting the content of the (A) inorganic filler within this range, a cured product with a low dielectric loss tangent and linear thermal expansion coefficient can be obtained. Furthermore, in a resin composition layer containing a large amount of (A) inorganic filler, the compatibility between the resin component and the inorganic filler during curing differs between the support and the bleed-out portion, which tends to cause swelling in the bleed-out portion. In contrast, the resin sheet of the present invention satisfies the relationship Si(A)-Si(B) of 5% or less, thereby suppressing swelling in the bleed-out portion despite containing such a content of the (A) inorganic filler.

[0041] In the present invention, unless otherwise specified, the content of each component in the resin composition layer is a value when the non-volatile components in the resin composition layer are 100% by mass, and the non-volatile components refer to the components other than the solvent that make up the resin composition layer.

[0042] -(B) Epoxy resin- The resin composition layer may contain a (B) epoxy resin as the (B) component. By containing the (B) epoxy resin, a cured product exhibiting good mechanical strength and insulation reliability can be obtained. The (B) epoxy resin may be used alone or in combination of two or more types.

[0043] (B) Epoxy resins include, for example, bixylenol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol novolac type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, glycidylamine type epoxy resins, and glycidyl ester type Examples of the epoxy resin include epoxy resins, glycidyl cyclohexane-type epoxy resins, alkyl diglycidyl ether-type epoxy resins, cresol novolac-type epoxy resins, biphenyl-type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane-type epoxy resins, cyclohexane dimethanol-type epoxy resins, naphthylene ether-type epoxy resins, trimethylol-type epoxy resins, tetraphenylethane-type epoxy resins, and phenolphthalimidine-type epoxy resins. One type of epoxy resin may be used alone, or two or more types may be used in combination.

[0044] The resin composition layer preferably contains, as component (B), an epoxy resin having two or more epoxy groups in one molecule. From the viewpoint of significantly achieving the desired effects of the present invention, the proportion of the epoxy resin having two or more epoxy groups in one molecule relative to 100% by mass of the epoxy resin (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0045] Epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). The resin composition layer may contain, as component (B), only a liquid epoxy resin, only a solid epoxy resin, or a combination of a liquid epoxy resin and a solid epoxy resin.

[0046] The liquid epoxy resin is preferably a liquid epoxy resin having two or more epoxy groups in one molecule.

[0047] Preferred liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, glycidyl amine type epoxy resins, and epoxy resins having a butadiene structure, glycidyl cyclohexane type epoxy resins, phenolphthalimidine type epoxy resins, and alkyl diglycidyl ether type epoxy resins, and more preferred are bisphenol A type epoxy resins, bisphenol F type epoxy resins, and naphthalene type epoxy resins.

[0048] Specific examples of liquid epoxy resins include "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins) manufactured by DIC Corporation; "828US", "jER828EL", "825", and "Epikote 828EL" (bisphenol A type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER807" and "1750" (bisphenol F type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630" and "630LSD" (glycidyl amine type epoxy resins) manufactured by Mitsubishi Chemical Corporation; and "ZX1" manufactured by Nippon Steel Chemical & Material Co., Ltd. Examples of epoxy resins that can be used include "EX-721" (a glycidyl ester epoxy resin) manufactured by Nagase ChemteX Corporation, "Celloxide 2021P" (an alicyclic epoxy resin having an ester skeleton) manufactured by Daicel Corporation, "PB-3600" (an epoxy resin having a butadiene structure) manufactured by Daicel Corporation, "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane epoxy resins) manufactured by Nippon Steel Chemical & Material Co., Ltd., and "YED216D" (an alkyl diglycidyl ether epoxy resin) manufactured by Mitsubishi Chemical Corporation. These may be used alone or in combination of two or more.

[0049] As the solid epoxy resin, a solid epoxy resin having two or more epoxy groups in one molecule is preferred, a solid epoxy resin having three or more epoxy groups in one molecule is more preferred, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is even more preferred.

[0050] Preferred solid epoxy resins include bixylenol-type epoxy resins, naphthalene-type epoxy resins, naphthalene-type tetrafunctional epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, and tetraphenylethane-type epoxy resins, and biphenyl-type epoxy resins are more preferred.

[0051] Specific examples of solid epoxy resins include "HP4032H" (naphthalene type epoxy resin), "HP-4700", "HP-4710" (naphthalene type tetrafunctional epoxy resin), "N-690" (cresol novolac type epoxy resin), "N-695" (cresol novolac type epoxy resin), "HP-7200", "HP-7200HH", "HP-7200H" (dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000", "HP6000L" (naphthylene ether type epoxy resin), manufactured by DIC Corporation; "EPPN-502H" (trisphenol type epoxy resin), "NC7000L" (naphthol novolac type epoxy resin), "NC3000H", "NC3000", "NC3000L" manufactured by Nippon Kayaku Co., Ltd.; Examples include "NC3100" (biphenyl-type epoxy resin); "ESN475V" (naphthalene-type epoxy resin) and "ESN485" (naphthol novolac-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YL6121" (biphenyl-type epoxy resin), "YX4000HK" (bixylenol-type epoxy resin), and "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100" and "CG-500" manufactured by Osaka Gas Chemical Co., Ltd.; "YL7760" (bisphenol AF-type epoxy resin), "YL7800" (fluorene-type epoxy resin), "jER1010" (solid bisphenol A-type epoxy resin), and "jER1031S" (tetraphenylethane-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "WHR-991S" (phenolphthalimidine-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more.

[0052] When a liquid epoxy resin and a solid epoxy resin are used in combination as component (B), the ratio by mass (liquid epoxy resin:solid epoxy resin) is preferably 1:0.1 to 1:20, more preferably 1:0.15 to 1:10, and particularly preferably 1:0.2 to 1:5. However, because some liquid epoxy resins may volatilize when heated, the specific mass ratio is preferably set depending on the types of liquid epoxy resin and solid epoxy resin so that Si(A)-Si(B) can be kept at 5% or less.

[0053] The epoxy equivalent of component (B) is preferably 50 g / eq to 5000 g / eq, more preferably 50 g / eq to 3000 g / eq, even more preferably 80 g / eq to 2000 g / eq, and even more preferably 110 g / eq to 1000 g / eq. This range ensures that the cured product of the resin composition layer has sufficient crosslink density. The epoxy equivalent is the mass of an epoxy resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

[0054] From the viewpoint of significantly achieving the desired effects of the present invention, the weight average molecular weight (Mw) of the component (B) is preferably 100 to 5000, more preferably 150 to 3000, and even more preferably 200 to 1500. The weight average molecular weight of the epoxy resin is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0055] From the viewpoint of obtaining a cured product exhibiting good mechanical strength and insulating reliability, the content of component (B) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on 100% by mass of the nonvolatile components in the resin composition layer, and the upper limit is preferably 40% by mass or less, more preferably 35% by mass or less, and particularly preferably 30% by mass or less.

[0056] From the viewpoint of obtaining a cured product exhibiting good mechanical strength and insulating reliability, the content of component (B) is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on 100% by mass of the resin component in the resin composition layer, and the upper limit is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

[0057] In the present invention, the resin component in the resin composition layer refers to the non-volatile components in the resin composition layer excluding the inorganic filler.

[0058] -(C) Active ester curing agent- The resin composition layer may contain an active ester curing agent (C) as component (C). This active ester curing agent (C) as component (C) does not include any of the above-mentioned components (A) and (B). The active ester curing agent (C) can reduce the polarity of the cured resin composition layer, thereby effectively reducing the dielectric loss tangent of the insulating layer. Resin composition layers containing a large amount of active ester curing agent (C) to achieve a low dielectric loss tangent tend to cause swelling in the bleed-out area due to slight differences in compatibility during curing between the area under the support and the bleed-out area. In contrast, the resin composition layer of the present invention satisfies the relationship Si(A)-Si(B) of 5% or less, thereby suppressing swelling even when containing a large amount of active ester curing agent (C). The component (C) may be used alone or in combination of two or more types.

[0059] The active ester curing agent (C) may be a compound having one or more active ester groups per molecule. Among these, the active ester curing agent (C) is preferably a compound having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds.

[0060] The (C) active ester curing agent is preferably one obtained by a condensation reaction between a carboxylic acid compound and / or a thiocarboxylic acid compound and a hydroxy compound and / or a thiol compound. From the viewpoint of improving heat resistance in particular, an active ester resin obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester resin obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound is more preferred. Examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0061] Specifically, the active ester curing agent (C) is preferably a dicyclopentadiene-type active ester resin, a naphthalene-type active ester resin containing a naphthalene structure, an active ester resin containing an acetylated product of phenol novolac, or an active ester resin containing a benzoylated product of phenol novolac, and among these, a naphthalene-type active ester resin is more preferred. As the dicyclopentadiene-type active ester resin, an active ester resin containing a dicyclopentadiene-type diphenol structure is preferred.

[0062] Commercially available products of (C) active ester curing agents include, for example, "EXB9451", "EXB9460", "EXB9460S", "EXB-8000L", "EXB-8000L-65M", "EXB-8000L-65TM", "HPC-8000L-65TM", "HPC-8000", "HPC-8000-65T", "HPC-8000H", and "HPC-8000H-65TM" (manufactured by DIC Corporation) as active ester resins containing a dicyclopentadiene-type diphenol structure; and "HP-B-8151-62T", "EXB-8100L-65T", "EXB-8150-60T", and "EXB-8 Examples of such active ester resins include "EXB-9416-70BK", "HPC-8150-60T", "HPC-8150-62T", and "EXB-8" (manufactured by DIC Corporation); an active ester resin containing phosphorus, such as "EXB9401" (manufactured by DIC Corporation); an active ester resin which is an acetylated product of phenol novolac, such as "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester resins which are benzoylated products of phenol novolac, such as "YLH1026", "YLH1030", and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); and an active ester resin containing a styryl group and a naphthalene structure, such as "PC1300-02-65MA" (manufactured by Air Water Inc.).

[0063] The active ester group equivalent of the (C) active ester curing agent is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., even more preferably 100 g / eq. to 500 g / eq., and particularly preferably 100 g / eq. to 300 g / eq. The active ester group equivalent represents the mass of the resin per equivalent of the active ester group.

[0064] In one example, the weight average molecular weight (Mw) range of the (C) active ester curing agent may be the same as the weight average molecular weight (Mw) range of the (A) epoxy resin.

[0065] The quantitative ratio of (B) epoxy resin to (C) active ester curing agent, expressed as the ratio of [total number of active groups in active ester curing agent] / [total number of epoxy groups in epoxy resin], is preferably 0.4 or more, more preferably 0.5 or more, even more preferably 0.7 or more, 0.8 or more, 0.9 or more, or 1.0 or more, and is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. Here, the "number of epoxy groups in the epoxy resin" refers to the sum of all values ​​obtained by dividing the mass of the non-volatile components of the epoxy resin present in the resin composition layer by the epoxy equivalent. Furthermore, the "number of active groups in the active ester curing agent" refers to the sum of all values ​​obtained by dividing the mass of the non-volatile components of the active ester curing agent present in the resin composition layer by the active ester group equivalent. By setting the quantitative ratio of the epoxy resin to the active ester curing agent within this range, the effects of the present invention can be significantly achieved.

[0066] From the viewpoint of obtaining a cured product with a low dielectric loss tangent, the content of component (C) is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, based on 100% by mass of the nonvolatile components in the resin composition layer, and the upper limit is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 13% by mass or less.

[0067] From the viewpoint of obtaining a cured product with a low dielectric loss tangent, the content of component (C) is preferably 10% by mass or more, more preferably 13% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the resin component in the resin composition layer, and the upper limit is preferably 50% by mass or less, more preferably 48% by mass or less, particularly preferably 45% by mass or less, or 42% by mass or less.

[0068] -(D) Hardener- The resin composition layer may contain a (D) curing agent (excluding those corresponding to the (C) component) as the (D) component. By including the (D) curing agent, a bond can be formed by reaction with the (B) epoxy resin, thereby curing the resin composition layer. The (D) curing agent as the (D) component does not include those corresponding to the above-mentioned (A) to (C) components. Examples of the (D) curing agent include phenol-based curing agents, naphthol-based curing agents, carbodiimide-based curing agents, benzoxazine-based curing agents, and cyanate ester-based curing agents. Among these, the (D) curing agent preferably contains a phenol-based curing agent and / or a carbodiimide-based curing agent, from the viewpoint of significantly achieving the effects of the present invention. The (D) curing agents may be used alone or in combination of two or more.

[0069] As the phenol-based curing agent and naphthol-based curing agent, a phenol-based curing agent having a novolac structure or a naphthol-based curing agent having a novolac structure is preferred from the viewpoint of heat resistance and water resistance. Furthermore, from the viewpoint of adhesion to the conductor layer, a nitrogen-containing phenol-based curing agent is preferred, and a triazine skeleton-containing phenol-based curing agent is more preferred.

[0070] Specific examples of phenol-based curing agents and naphthol-based curing agents include "MEH-7700," "MEH-7810," and "MEH-7851" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN," "CBN," and "GPH" manufactured by Nippon Kayaku Co., Ltd.; "SN170," "SN180," "SN190," "SN475," "SN485," "SN495," "SN-495V," "SN375," and "SN395" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; and "TD-2090," "LA-7052," "LA-7054," "LA-1356," "LA3018-50P," "EXB-9500," and "KA-1163" manufactured by DIC Corporation.

[0071] The carbodiimide curing agent is a compound having one or more carbodiimide groups (-N=C=N-) in one molecule, and the carbodiimide curing agent is preferably a compound having two or more carbodiimide groups in one molecule.

[0072] Specific examples of commercially available carbodiimide curing agents include Carbodilite V-03 (carbodiimide group equivalent: 216 g / eq.), V-05 (carbodiimide group equivalent: 262 g / eq.), V-07 (carbodiimide group equivalent: 200 g / eq.), and V-09 (carbodiimide group equivalent: 200 g / eq.), all manufactured by Nisshinbo Chemical Inc.; and Stavaxol P (carbodiimide group equivalent: 302 g / eq.), all manufactured by Arxada.

[0073] Specific examples of benzoxazine-based curing agents include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemical Industry Co., Ltd.

[0074] Examples of cyanate ester curing agents include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether, and bis(4-cyanatephenyl)ether; multifunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester curing agents include "PT30" and "PT60" (phenol novolac type multifunctional cyanate ester resins), "ULL-950S" (multifunctional cyanate ester resin), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine converted to a trimer), all of which are manufactured by Arxada.

[0075] The ratio (M(C+D) / M(B)) of the number of epoxy groups in component (B), M(B), to the number of active groups in components (C) and (D), M(C+D), is preferably 0.5 or more, more preferably 0.7 or more, even more preferably 0.80 or more, 1.0 or more, 1.1 or more, 1.2 or more, or 1 or more. From the viewpoint of significantly achieving the effects of the present invention, the upper limit is preferably 2.00 or less, more preferably 1.90 or less, even more preferably 1.80 or less, 1.7 or less, 1.6 or less, or 1.5 or less. The "number of epoxy groups in the epoxy resin," M(B), refers to the sum of all values ​​obtained by dividing the mass of the non-volatile components of the epoxy resin (B) present in the resin composition layer by the epoxy equivalent. Furthermore, the "number of active groups in the curing agent," M(C+D), refers to the sum of all values ​​obtained by dividing the total mass of the non-volatile components of the active ester curing agent (C) and the curing agent (D) present in the resin composition layer by the active group equivalent.

[0076] The content of component (D) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, based on 100% by mass of the nonvolatile components in the resin composition layer, and the upper limit is preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 10% by mass or less.

[0077] The content of component (D) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on 100% by mass of the resin component in the resin composition layer, and the upper limit is preferably 35% by mass or less, more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

[0078] -(E)Organic filler- The resin composition layer may contain an organic filler as component (E). The organic filler as component (E) does not include those corresponding to the above-mentioned components (A) to (D). The component (E) may be used alone or in combination of two or more.

[0079] The component (E) is present in the resin composition layer in the form of particles. Examples of the component (E) include rubber particles, polyamide fine particles, silicone particles, and core-shell particles. In the present invention, it is preferable to use either rubber particles or core-shell particles in order to significantly achieve the desired effects of the present invention.

[0080] Examples of the rubber component contained in the rubber particles include olefin-based thermoplastic elastomers such as polybutadiene, polyisoprene, polychlorobutadiene, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-isobutylene copolymer, acrylonitrile-butadiene copolymer, isoprene-isobutylene copolymer, isobutylene-butadiene copolymer, ethylene-propylene-diene terpolymer, and ethylene-propylene-butene terpolymer; and acrylic-based thermoplastic elastomers such as poly(propyl meth)acrylate, poly(butyl meth)acrylate, poly(cyclohexyl meth)acrylate, and poly(octyl meth)acrylate. Preferred are olefin-based thermoplastic elastomers, and more preferably styrene-butadiene copolymers. Furthermore, silicone-based rubbers such as polyorganosiloxane rubbers may be mixed into the rubber component. The rubber component contained in the rubber particles has a glass transition temperature of, for example, 0°C or lower, preferably -10°C or lower, more preferably -20°C or lower, and even more preferably -30°C or lower.

[0081] As the rubber particles, commercially available products may be used, such as "EXL2655" manufactured by Dow Chemical Japan, and "AC3401N" and "AC3816N" manufactured by Aica Kogyo Co., Ltd.

[0082] Core-shell particles are particulate organic fillers consisting of a core particle containing a rubber component as described above and one or more shell layers covering the core particle. Furthermore, the core-shell particles are preferably core-shell graft copolymer particles consisting of a core particle containing a rubber component as described above and a shell formed by graft copolymerization of a monomer component copolymerizable with the rubber component contained in the core particle. The term "core-shell" as used here does not necessarily refer only to particles in which the core particle and the shell are clearly distinguishable, but also includes particles in which the boundary between the core particle and the shell is unclear, and the core particle does not necessarily have to be completely covered by the shell.

[0083] The rubber component is preferably contained in the core-shell graft copolymer particles in an amount of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. The upper limit of the rubber component content in the core-shell graft copolymer particles is not particularly limited, but from the viewpoint of sufficiently covering the core particles with the shell portion, it is preferably, for example, 95% by mass or less, and more preferably 90% by mass.

[0084] Examples of monomer components that form the shell portion of the core-shell graft copolymer particles include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, and glycidyl (meth)acrylate; (meth)acrylic acid; N-substituted maleimides such as N-methylmaleimide and N-phenylmaleimide; maleimide; α,β-unsaturated carboxylic acids such as maleic acid and itaconic acid; aromatic vinyl compounds such as styrene, 4-vinyltoluene, and α-methylstyrene; and (meth)acrylonitrile, among which (meth)acrylic acid esters are preferred, and methyl (meth)acrylate is more preferred.

[0085] Commercially available core-shell graft copolymer particles include, for example, "CHT" manufactured by Samsung SDI; "B602" manufactured by Techno UMG; "Paraloid EXL2602," "Paraloid EXL2603," "Paraloid EXL2655," "Paraloid EXL2311," "Paraloid EXL2313," "Paraloid EXL2315," "Paraloid KM330," "Paraloid KM336P," and "Paraloid KCZ201" manufactured by Dow Chemical Japan; "Metablen C-223A," "Metablen E-901," "Metablen S-2001," "Metablen W-450A," and "Metablen SRK-200" manufactured by Mitsubishi Rayon; and "Kane Ace M-511," "Kane Ace M-600," "Kane Ace M-400," "Kane Ace M-580," and "Kane Ace MR-01" manufactured by Kaneka Corporation. These may be used alone or in combination of two or more.

[0086] The average particle size (average primary particle size) of the core-shell graft copolymer particles is not particularly limited, but is preferably 20 nm or more, more preferably 50 nm or more, even more preferably 80 nm or more, particularly preferably 100 nm or more, and preferably 5,000 nm or less, more preferably 2,000 nm or less, even more preferably 1,000 nm or less, particularly preferably 500 nm or less. The average particle size (average primary particle size) of the core-shell graft copolymer particles can be measured using a zeta potential particle size distribution analyzer or the like.

[0087] The content of component (E) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, and is preferably 5% by mass or less, more preferably 4.5% by mass or less, and even more preferably 3% by mass or less, assuming that the non-volatile components in the resin composition layer are 100% by mass.

[0088] The content of component (E) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, and is preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less, assuming that the resin component in the resin composition layer is 100% by mass.

[0089] -(F) Curing accelerator- The resin composition layer may contain a (F) curing accelerator as the (F) component. The (F) curing accelerator as the (F) component does not include those corresponding to the above-mentioned (A) to (E). By including the (F) component, it becomes possible to further accelerate the curing of the (B) component. The (F) component may be used alone or in combination of two or more.

[0090] Examples of component (F) include phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, imidazole-based curing accelerators, metal-based curing accelerators, amine-based curing accelerators, etc. Among these, curing accelerators selected from amine-based curing accelerators and metal-based curing accelerators are preferred, and imidazole-based curing accelerators are particularly preferred.

[0091] Examples of the phosphorus-based curing accelerator include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butyldimethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, and tetraphenylphosphonium tetra-p-tolylborate. aromatic phosphonium salts such as tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone adducts such as triphenylphosphine-p-benzoquinone adduct; aliphatic phosphines such as tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine;Dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, tris(2,5-dimethylphenyl)phosphine, tris(2,6-dimethylphenyl)phosphine aromatic phosphines such as benzene, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2'-bis(diphenylphosphino)diphenyl ether;

[0092] Examples of the urea-based curing accelerator include 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea; 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(2-methylphenyl)-1,1-dimethylurea, 3-(4-methylphenyl)-1,1-dimethylurea, and 3-(3,4-dimethylphenyl)-1,1-dimethylurea. aromatic dimethylureas such as toluene bis(dimethylurea), 3-(4-isopropylphenyl)-1,1-dimethylurea, 3-(4-methoxyphenyl)-1,1-dimethylurea, 3-(4-nitrophenyl)-1,1-dimethylurea, 3-[4-(4-methoxyphenoxy)phenyl]-1,1-dimethylurea, 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea, 3-[3-(trifluoromethyl)phenyl]-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea), and N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea].

[0093] Examples of guanidine curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide.

[0094] Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-methylimidazole. Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct , 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, and other imidazole compounds, as well as adducts of imidazole compounds with epoxy resins.

[0095] As the imidazole-based curing accelerator, commercially available products may be used, such as "1B2PZ", "2MZA-PW", "2PHZ-PW", and "C11Z-A" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0096] Examples of metal-based curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0097] Examples of the amine-based curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene.

[0098] As the amine-based curing accelerator, commercially available products may be used, for example, "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0099] The content of component (F) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more, and is preferably 1% by mass or less, more preferably 0.9% by mass or less, and even more preferably 0.8% by mass or less, assuming that the non-volatile components in the resin composition layer are 100% by mass.

[0100] The content of component (F) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, assuming that the resin component in the resin composition layer is 100% by mass.

[0101] -(G)High molecular weight component- The resin composition layer may contain a (G) high molecular weight component as the (G) component. The (G) high molecular weight component as the (G) component does not include components (A) to (F) described above. The (G) component may be used alone or in combination of two or more.

[0102] From the viewpoint of obtaining a cured product with an even more excellent dielectric tangent, the weight average molecular weight (Mw) of component (G) is preferably at least 5,000, more preferably at least 8,000, and even more preferably at least 10,000. There are no particular limitations on the upper limit of Mw, but it is preferably not more than 100,000, more preferably not more than 80,000, and even more preferably not more than 50,000. The Mw of component (G) can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

[0103] Examples of component (G) include thermoplastic resins such as phenoxy resin, polyimide resin, polycarbonate resin, polyvinyl acetal resin, polyolefin resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polyetheretherketone resin, polystyrene resin, polyester resin, etc. Among these, from the viewpoint of obtaining a cured product excellent in dielectric loss tangent, component (G) preferably contains at least one selected from phenoxy resin, polyimide resin, and polycarbonate resin, and more preferably phenoxy resin.

[0104] Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenolacetophenone, novolac, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group.

[0105] Commercially available phenoxy resins include, for example, "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both of which are phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel Chemical & Material Co., Ltd.; and "YL7500BH30," "YX6954BH30," "YX7553," "YX7553BH30," "YL7769BH30," "YL6794," "YL7213," "YL7290," and "YL7482" manufactured by Mitsubishi Chemical Corporation.

[0106] The polyimide resin may be a resin having an imide structure. Polyimide resins are generally obtained by an imidization reaction between a diamine compound and an acid anhydride. Commercially available polyimide resins may be used, such as "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd.

[0107] Polycarbonate resins are resins having a carbonate structure. Examples of such resins include carbonate resins without reactive groups, hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, urethane group-containing carbonate resins, and epoxy group-containing carbonate resins. Here, the reactive group refers to a functional group that can react with other components, such as a hydroxy group, a phenolic hydroxyl group, a carboxy group, an acid anhydride group, an isocyanate group, a urethane group, or an epoxy group.

[0108] Commercially available polycarbonate resins can be used, including "FPC0220" and "FPC2136" manufactured by Mitsubishi Gas Chemical Company, "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Corporation, and "C-1090," "C-2090," and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd.

[0109] The content of component (G) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 8% by mass or less, more preferably 6% by mass or less, and even more preferably 5% by mass or less, assuming that the non-volatile components in the resin composition layer are 100% by mass.

[0110] The content of component (G) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 15% by mass or less, assuming that the resin component in the resin composition layer is 100% by mass.

[0111] -(H) Other additives- In addition to the components described above, the resin composition layer may further contain (H) other additives as optional components. Examples of (H) other additives include elastomers, polymerization initiators, organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds, colorants such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, and carbon black, polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine, leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents, thickeners such as bentone and montmorillonite, antifoaming agents such as silicone-based antifoaming agents, acrylic-based antifoaming agents, fluorine-based antifoaming agents, and vinyl resin-based antifoaming agents, ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers, adhesion improvers such as urea silanes, adhesion promoters such as triazole-based adhesion promoters, tetrazole-based adhesion promoters, and triazine-based adhesion promoters, and hindered phenol-based fluorescent brightening agents such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); dispersants such as phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers; photopolymerization initiation aids such as tertiary amines; and photosensitizers such as pyrarizones, anthracenes, coumarins, xanthones, and thioxanthones. (H) Other additives may be used singly or in combination of two or more.

[0112] -(I) Solvent- The resin composition layer may further contain an arbitrary solvent as a volatile component in addition to the nonvolatile components described above. (I) As the solvent, any known solvent can be used appropriately, and the type is not particularly limited, but an organic solvent is preferred. (I) Solvents include, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, and anisole; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of suitable solvents include ether ester solvents such as ethyl acetate; ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. (I) The solvents may be used alone or in combination of two or more in any ratio.

[0113] Usually, all or most of the (I) solvent is removed by drying during the production process of the resin composition layer. Therefore, the resin composition layer may not contain the (I) solvent. Furthermore, when the resin composition layer contains the (I) solvent, it is preferable that the amount of the (I) solvent is small.

[0114] The thickness of the resin composition layer is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less, from the viewpoint of reducing the thickness of the printed wiring board and providing a cured product with excellent insulating properties even when the cured product of the resin composition layer is thin. The lower limit of the thickness of the resin composition layer is not particularly limited, but may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, etc.

[0115] <Support> The resin sheet has a support, and the support is bonded to the first surface of the resin composition layer. Examples of the support include a film made of a plastic material, a metal foil, and a release paper, and a film made of a plastic material and a metal foil are preferred.

[0116] When a film made of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, with inexpensive polyethylene terephthalate being particularly preferred.

[0117] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. The copper foil may be a foil made of a single metal, copper, or an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0118] The surface of the support that is to be bonded to the resin composition layer may be subjected to a matte treatment, a corona treatment, or an antistatic treatment.

[0119] The support may also be a support with a release layer, which has a release layer on the surface that bonds to the resin composition layer. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available products may also be used as the support with a release layer, including, for example, "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation, "Lumirror T60" manufactured by Toray Industries, Inc., "Purex" manufactured by Teijin Limited, and "Uni-Peel" manufactured by Unitika Limited, which are PET films having a release layer primarily composed of an alkyd resin-based release agent.

[0120] The thickness of the support is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and is preferably 75 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less. When a support with a release layer is used, it is preferable that the thickness of the entire support with a release layer is within the above range.

[0121] <Protective film> The resin sheet may further have a protective film conforming to the support laminated on the second surface of the resin composition layer (i.e., the surface of the resin composition layer not bonded to the support, the surface opposite the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, adhesion of dust and the like to the surface of the resin composition layer and scratches can be suppressed.

[0122] <Method of manufacturing resin sheet> The resin sheet can be produced, for example, by a method including forming a resin composition layer on a support. Specifically, the resin sheet may be produced by a production method including, in this order, a step of preparing a resin varnish containing the resin composition, a step of applying the resin varnish to a support, and a step of drying the applied resin varnish to form a resin composition layer.

[0123] The resin varnish may be produced by mixing the components that can be contained in the resin composition and a solvent. The solvent (I) described above may be used as the solvent for the resin varnish. The components may be mixed partially or entirely at the same time, or may be mixed sequentially. The temperature may be appropriately set during the process of mixing the components, and thus heating and / or cooling may be performed temporarily or throughout. Furthermore, stirring or shaking may be performed during the process of mixing the components.

[0124] The resin varnish can be applied using a coating device such as a die coater. Drying can be performed by, for example, heating, hot air blowing, or other drying methods. The drying conditions are preferably set so as to obtain a mass loss rate that satisfies the above-mentioned requirement (R). For example, the drying temperature is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher, and is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The drying time is preferably 60 seconds or higher, more preferably 90 seconds or higher, and even more preferably 120 seconds or higher, and is preferably 10 minutes or shorter, more preferably 8 minutes or shorter, and even more preferably 6 minutes or shorter.

[0125] The resin sheet can be stored in a rolled state. When the resin sheet has a protective film, it can be used by peeling off the protective film.

[0126] <Physical properties of resin sheet> The resin sheet exhibits low dielectric properties and a low linear thermal expansion coefficient, and since the Si(A)-Si(B) ratio is 5% or less, it exhibits the characteristic of suppressing the occurrence of blistering. To evaluate the occurrence of blistering, the resin sheet is laminated so that the resin composition layer of the resin sheet contacts the inner layer substrate. After lamination, the resin composition layer is thermally cured, and then the support is peeled off to expose the surface of the thermally cured resin composition layer (cured product), which is then roughened. After the roughening treatment, a conductor layer is formed on the roughened surface to obtain an evaluation substrate. At this time, no blistering is confirmed even when visually inspecting the edge of the bleed-out portion of the evaluation substrate. Details of the evaluation of blistering can be evaluated using the method described in the Examples below.

[0127] A cured product obtained by thermally curing a resin composition layer at 190°C for 90 minutes exhibits the characteristic of a low dielectric loss tangent. Therefore, the cured product provides an insulating layer with a low dielectric loss tangent. The dielectric loss tangent is preferably 0.020 or less, more preferably 0.010 or less, and even more preferably 0.005 or less. The lower limit of the dielectric loss tangent may be 0.0001 or more. The dielectric loss tangent can be measured according to the method described in the Examples below.

[0128] A cured product obtained by thermally curing a resin composition layer at 190°C for 90 minutes exhibits the characteristic of a low linear thermal expansion coefficient. Thus, the cured product provides an insulating layer with a low linear thermal expansion coefficient. The linear thermal expansion coefficient is preferably 100 ppm / °C or less, more preferably 50 ppm / °C or less, and even more preferably 30 ppm / °C or less. The lower limit of the linear thermal expansion coefficient may be 0.01 ppm / °C or more. The linear thermal expansion coefficient can be measured according to the method described in the Examples below.

[0129] The resin sheet of the present invention can be used to form an insulating layer, and is particularly preferably used to form an insulating layer for a circuit board. The resin sheet of the present invention may also be used for other purposes, such as forming a solder resist, an underfill material, a die bonding material, a hole filling resin, a sealing resin, a component embedding resin, etc.

[0130] <Circuit board> A circuit board according to one embodiment of the present invention includes a cured material layer formed by curing the resin composition layer of the resin sheet described above. Typically, a circuit board includes an insulating layer, which includes a cured material layer formed by curing a resin composition layer. Therefore, the insulating layer includes a cured material of the resin composition. The insulating layer may include only the cured material. The thickness of the insulating layer is not particularly limited and may be, for example, within the same range as the thickness of the resin composition layer of the resin sheet. Since the insulating layer is formed by a cured material layer formed by curing a resin composition layer, it can typically have a low dielectric loss tangent within the same range as the dielectric loss tangent of the cured material layer. Furthermore, the insulating layer can typically have a low linear thermal expansion coefficient within the same range as the linear thermal expansion coefficient of the cured material layer.

[0131] The circuit board preferably includes an inner layer substrate and the insulating layer on the inner layer substrate. The circuit board may also include a conductor layer. For example, the conductor layer may be provided on an insulating layer. An example of a preferred method for manufacturing a circuit board will now be described.

[0132] A preferred example of a method for manufacturing a circuit board includes the steps of: a step (I) of laminating an inner layer substrate and a resin sheet so that the inner layer substrate and the resin composition layer are bonded to each other; Step (II) of curing the resin composition layer; Includes:

[0133] A preferred example of a method for manufacturing a circuit board includes a step (I) of laminating a resin sheet and an inner layer substrate. The resin sheet and the inner layer substrate are laminated so that the resin composition layer of the resin sheet and the inner layer substrate are bonded. This lamination forms a resin composition layer on the inner layer substrate.

[0134] An "inner layer substrate" is a member that serves as the base material of a circuit board, and examples thereof include glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The inner layer substrate may have a conductor layer on one or both sides. The conductor layer of the inner layer substrate may be patterned. An inner layer substrate having a conductor layer (circuit) formed on one or both sides of the substrate is sometimes called an "inner layer circuit board." The term "inner layer substrate" also includes intermediate products on which insulating layers and / or conductor layers are to be further formed during the production of a circuit board. In addition, inner layer substrates with built-in components may also be used.

[0135] The inner layer substrate and the resin sheet can be laminated, for example, by thermocompression bonding the resin sheet to the inner layer substrate from the support side. Examples of the member for thermocompression bonding the resin sheet to the inner layer substrate (hereinafter also referred to as the "thermocompression bonding member") include a heated metal plate (such as a SUS plate) or a metal roll (such as a SUS roll). Note that rather than pressing the thermocompression bonding member directly onto the resin sheet, it is preferable to press it via an elastic material such as heat-resistant rubber so that the resin sheet can sufficiently conform to the surface irregularities of the inner layer substrate.

[0136] The inner layer substrate and the resin sheet may be laminated by a vacuum lamination method. In the vacuum lamination method, the thermocompression temperature is preferably in the range of 60°C to 160°C, more preferably 80°C to 140°C, the thermocompression pressure is preferably in the range of 0.098MPa to 1.77MPa, more preferably 0.29MPa to 1.47MPa, and the thermocompression time is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The lamination is preferably carried out under reduced pressure conditions of 26.7hPa or less.

[0137] Lamination can be performed using a commercially available vacuum laminator, such as a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a vacuum applicator manufactured by Nikko Materials Co., Ltd., or a batch-type vacuum pressure laminator.

[0138] FIG. 3 is a schematic cross-sectional view illustrating a method for manufacturing a circuit board according to one embodiment of the present invention. As shown in FIG. 3, when laminating an inner substrate 100 and a resin sheet 200, most of the resin composition layer 210 is provided in a gap 300 between the inner substrate 100 and the support 220, but a portion 230 of the resin composition layer 210 seeps out of the gap 300. Thus, step (I) involves the portion 230 of the resin composition layer 210 seeping out of the gap 300. This seeped portion 230 forms a bleed-out portion. In the following description, the bleed-out portion will be denoted by the same reference numeral "230" as the portion 230 of the resin composition layer 210 seeping out of the gap 300. By using the resin sheet described above, swelling of the bleed-out portion 230 can be suppressed.

[0139] The method for manufacturing a circuit board according to the present invention may include smoothing the resin sheet after lamination under normal pressure (atmospheric pressure), for example, by pressing the resin sheet from the support side with a thermocompression member. The pressing conditions for the smoothing may be the same as those for the thermocompression bonding of the lamination. The smoothing may be performed using a commercially available laminator. The lamination and smoothing may be performed consecutively using the commercially available vacuum laminator.

[0140] The method for producing a circuit board according to the present invention includes a step (II) of curing the resin composition layer after the step (I). By curing the resin composition layer in the step (II), an insulating layer can be formed.

[0141] Specific curing conditions for the resin composition layer may be those typically employed when forming an insulating layer for a circuit board. Typically, curing of the resin composition layer proceeds by thermal curing. Therefore, step (II) may include thermally curing the resin composition layer. The thermal curing conditions for the resin composition layer may vary depending on the types of components contained in the resin composition. For example, the curing temperature is preferably 120°C to 240°C, more preferably 150°C to 220°C, and even more preferably 170°C to 210°C. The curing time is preferably 5 to 120 minutes, more preferably 10 to 100 minutes, and even more preferably 15 to 100 minutes.

[0142] Furthermore, when the resin composition layer is thermally cured, the method for producing a circuit board may include preheating the resin composition layer at a temperature lower than the curing temperature before the thermal curing. For example, prior to thermal curing of the resin composition layer, the resin composition layer may be preheated for typically 5 minutes or more, preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes, and even more preferably 15 minutes to 100 minutes, at a temperature of typically 50°C to 150°C, preferably 60°C to 140°C, and more preferably 70°C to 130°C. Preheating is typically performed after step (I). Furthermore, when a smoothing treatment is performed after laminating the inner layer substrate and the resin sheet, preheating can be performed after the smoothing treatment.

[0143] The method for producing a circuit board according to the present invention may include a step of peeling off the support of the resin sheet after laminating the inner layer substrate and the resin sheet. The peeling off of the support may be carried out between steps (I) and (II), or after step (II). Furthermore, when the method for producing a circuit board includes step (III) of forming holes in the insulating layer, step (IV) of roughening the insulating layer, and step (V) of forming a conductor layer, as described below, the peeling off of the support may be carried out between steps (II) and (III), between steps (III) and (IV), or between steps (IV) and (V).

[0144] The method for producing a circuit board according to the present invention may include, after step (II), step (III) of forming holes such as via holes or through holes in the insulating layer. The method for forming the holes may be selected depending on factors such as the composition of the resin composition layer used to form the insulating layer. For example, holes may be formed by processing methods such as drilling, laser processing, and plasma processing, with laser processing being preferred. For example, holes may be formed by irradiating the insulating layer with laser light after peeling off the support, or by irradiating the insulating layer with laser light through the support. The dimensions and shape of the holes may be determined appropriately depending on the design of the circuit board.

[0145] The method for manufacturing a circuit board according to the present invention may include a step (IV) of roughening the insulating layer. The roughening treatment can roughen the surface of the insulating layer. Furthermore, the roughening treatment can remove smears (resin residues) from the insulating layer. Therefore, this roughening treatment is sometimes called a "desmear treatment." For example, when holes are formed in the step (III), smears may form in the holes. Therefore, it is preferable to perform the roughening treatment of the step (IV) after the step (III) to remove the smears.

[0146] The procedure and conditions for the roughening treatment are not particularly limited, and known procedures and conditions that are commonly used when forming an insulating layer for a circuit board can be adopted. For example, the roughening treatment may be performed by subjecting the insulating layer to a swelling treatment using a swelling liquid, an oxidation treatment using an oxidizing agent, and a neutralization treatment using a neutralizing liquid in this order.

[0147] Examples of swelling liquids used in the roughening treatment include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. Examples of the alkaline solution include sodium hydroxide solution and potassium hydroxide solution. Examples of commercially available swelling liquids include "Swelling Dip Securigance P" and "Swelling Dip Securigance SBU" manufactured by Atotech Japan. Swelling treatment using a swelling liquid can be performed by immersing the insulating layer in the swelling liquid at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing swelling of the resin in the insulating layer to an appropriate level, it is preferable to immerse the insulating layer in the swelling liquid at 40°C to 80°C for 5 to 15 minutes.

[0148] Examples of oxidizing agents used in the roughening treatment include alkaline permanganate solutions prepared by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. Oxidation treatment using an oxidizing agent such as alkaline permanganate solution is preferably carried out by immersing the insulating layer in an oxidizing agent solution heated to 60°C to 100°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigance P" manufactured by Atotech Japan.

[0149] The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and a commercially available product such as "Reduction Solution Securigant P" manufactured by Atotech Japan can be cited as an example. Neutralization treatment using a neutralizing solution can be carried out by immersing the surface that has been oxidized with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, a preferred method is to immerse the object that has been oxidized with an oxidizing agent in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

[0150] The method for producing a circuit board according to the present invention may include a step (V) of forming a conductor layer on an insulating layer. When the method for producing a circuit board includes the steps (III) or (IV), the step (V) of forming a conductor layer is usually preferably carried out after the steps (III) and (IV).

[0151] The conductive material used for the conductor layer is not particularly limited. In a preferred embodiment, the conductor layer contains one or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. The conductor layer may be a single metal layer or an alloy layer. Examples of alloy layers include layers formed from an alloy of two or more metals selected from the above group (e.g., nickel-chromium alloy, copper-nickel alloy, and copper-titanium alloy). Among these, from the viewpoints of versatility in forming the conductor layer, cost, ease of patterning, etc., single metal layers of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or alloy layers of nickel-chromium alloy, copper-nickel alloy, or copper-titanium alloy are preferred. Single metal layers of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or alloy layers of nickel-chromium alloy are more preferred, and single metal layers of copper are even more preferred.

[0152] The conductor layer may have a single layer structure or a multi-layer structure including two or more single metal or alloy layers made of different types of metals or alloys. When the conductor layer has a multi-layer structure, the layer in contact with the insulating layer is preferably a single metal layer of chromium, zinc, or titanium, or an alloy layer of a nickel-chromium alloy.

[0153] The thickness of the conductor layer depends on the design of the circuit board, but is preferably 3 μm to 35 μm, and more preferably 5 μm to 30 μm.

[0154] The conductor layer may be formed by plating. For example, a conductor layer having a desired wiring pattern can be formed by plating the surface of the insulating layer using a conventionally known technique such as a semi-additive method or a full-additive method. From the viewpoint of ease of production, the semi-additive method is preferred. An example of forming a conductor layer by a semi-additive method will be described below.

[0155] First, an electroless plated layer (plating seed layer) is formed on the surface of the insulating layer by electroless plating. Next, a mask pattern is formed on the formed electroless plated layer, exposing a portion of the electroless plated layer corresponding to the desired wiring pattern. After forming an electroless plated layer on the exposed electroless plated layer by electrolytic plating, the mask pattern is removed. Thereafter, unnecessary electroless plated layer is removed by etching, thereby forming a conductor layer having the desired wiring pattern.

[0156] When a conductor layer is formed on an insulating layer, the manufacturing method of a circuit board usually includes performing an annealing treatment after the formation of the conductor layer. The annealing treatment can improve the adhesion between the insulating layer and the conductor layer. Furthermore, while the heat of the annealing treatment has conventionally caused swelling in the bleed-out portion, this embodiment can suppress swelling in the bleed-out portion. The annealing treatment can be performed, for example, by heating at 100°C to 200°C for 20 minutes to 180 minutes.

[0157] In the method for manufacturing a circuit board, each of the above steps may be performed only once or may be repeated two or more times. For example, steps (I) to (V) may be performed repeatedly to form a circuit board having a multilayer structure, such as a multilayer printed wiring board having a plurality of insulating layers and conductor layers.

[0158] The method for manufacturing a circuit board may further include any optional steps in addition to the steps described above. For example, the method for manufacturing a circuit board may include a step of providing a semiconductor chip so that the semiconductor chip is bonded to the conductor layer. Specifically, when manufacturing a circuit board for a semiconductor chip package including a semiconductor chip, the method for manufacturing a circuit board may include a step of providing the semiconductor chip. The semiconductor chip may be bonded under appropriate conditions that allow conductive connection between the terminal electrodes of the semiconductor chip and the conductor layer formed on the insulating layer. For example, conditions used in flip-chip mounting may be employed. The semiconductor chip may be bonded via an insulating adhesive or by reflow bonding. If necessary, the provided semiconductor chip may be filled with a mold underfill material. The method for manufacturing a circuit board may also include, for example, a step of forming a sealing layer, a step of forming a solder resist layer, and a step of dicing the manufactured circuit board into individual pieces.

[0159] Examples of circuit boards include printed wiring boards and semiconductor chip packages. Examples of semiconductor chip packages include FC-CSP, MIS-BGA package, ETS-BGA package, fan-out type WLP (Wafer Level Package), fan-in type WLP, fan-out type PLP (Panel Level Package), and fan-in type PLP. In these semiconductor chip packages, it is preferable to form a rewiring formation layer using an insulating layer obtained by curing the above-mentioned resin composition layer. However, the circuit board is not limited to those exemplified here.

[0160] [Semiconductor Devices] The circuit board can be used for manufacturing a semiconductor device. The semiconductor device includes the above-described circuit board. Examples of the semiconductor device include various semiconductor devices used in electrical appliances (e.g., computers, mobile phones, smartphones, tablet devices, wearable devices, digital cameras, medical equipment, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.). [Example]

[0161] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass", respectively.

[0162] <Synthesis Example 1: Synthesis of active ester compound (A)> A flask equipped with a thermometer, dropping funnel, condenser, distillation column, and stirrer was charged with 320 g (2.0 mol) of 2,7-dihydroxynaphthalene, 184 g (1.7 mol) of benzyl alcohol, and 5.0 g of paratoluenesulfonic acid monohydrate. The mixture was stirred at room temperature while blowing in nitrogen. The temperature was then raised to 150 °C and the mixture was stirred for 4 hours while distilling off the resulting water. After the reaction was complete, 900 g of methyl isobutyl ketone and 5.4 g of 20% aqueous sodium hydroxide were added to neutralize the mixture. The aqueous layer was then removed by separation, and the mixture was washed three times with 280 g of water. The methyl isobutyl ketone was removed under reduced pressure to obtain 460 g of benzyl-modified naphthalene compound (A-1). The resulting benzyl-modified naphthalene compound (A-1) was a black solid with a hydroxyl equivalent weight of 180 g / equivalent.

[0163] A flask equipped with a thermometer, dropping funnel, condenser, distillation column, and stirrer was charged with 203.0 g of isophthalic acid chloride (molar number of acid chloride groups: 2.0 mol) and 1400 g of toluene. The system was then purged with nitrogen under reduced pressure and dissolved. Next, 113.9 g (0.67 mol) of orthophenylphenol and 240 g of benzyl-modified naphthalene compound (A-1) (molar number of phenolic hydroxyl groups: 1.33 mol) were charged and the system was then purged with nitrogen under reduced pressure and dissolved. Next, 0.70 g of tetrabutylammonium bromide was dissolved. While purging with nitrogen gas, the system was maintained at 60°C or below, and 400 g of 20% aqueous sodium hydroxide solution was added dropwise over 3 hours. Stirring was then continued under these conditions for 1.0 hour. After the reaction was completed, the mixture was allowed to stand for separation, and the aqueous layer was removed. Water was then added to the toluene layer containing the dissolved reactant, and the mixture was stirred and mixed for 15 minutes. The mixture was then allowed to stand and separated, and the aqueous layer was removed. This procedure was repeated until the pH of the aqueous layer reached 7. The water was then removed by decanting, yielding an active ester compound (A) in the form of a toluene solution with a nonvolatile content of 65% by mass. The active ester equivalent of the resulting active ester compound (A) was 238 g / eq.

[0164] <Production of resin varnish> Each component in the table below was weighed, mixed with 10 parts of MEK (methyl ethyl ketone) and 10 parts of cyclohexanone, and uniformly dispersed using a high-speed rotary mixer to obtain a resin varnish. In the table below, the numerical values ​​in the column for the components used in producing the resin varnish represent the blending amount of each component (converted to nonvolatile content).

[0165] <Examples 1 to 4, Comparative Example 1> A polyethylene terephthalate film ("AL5" manufactured by Lintec Corporation, thickness 38 μm) with a release layer was prepared as a support. A resin varnish was uniformly applied onto the release layer of this support so that the thickness of the resin composition layer after drying would be 40 μm. The resin varnish was then dried at 100° C. for 3 minutes to obtain a resin sheet A including a support and a resin composition layer. [Table 1] *1: Indicates the content (mass%) when the non-volatile components in the resin composition (layer) are taken as 100 mass%. *2: Indicates the content (mass%) when the resin component in the resin composition (layer) is taken as 100 mass%.

[0166] The details of each component listed in the table are as follows: Component (A) SO-C2: Spherical silica surface-treated with an amine-based alkoxysilane compound ("KBM573" manufactured by Shin-Etsu Chemical Co., Ltd.), with an average particle size of 0.5 μm and a specific surface area of ​​5.8 m 2 / g, manufactured by Admatechs Co., Ltd. (B) Component HP-4032-SS: Naphthalene-type epoxy resin (functional group equivalent weight 144g / eq., manufactured by DIC Corporation) NC-3000L: Biphenyl-type epoxy resin (functional group equivalent weight 270 g / eq., manufactured by Nippon Kayaku Co., Ltd.) YX4000HK: Bixylenol-type epoxy resin (functional group equivalent weight 194g / eq., manufactured by Mitsubishi Chemical Corporation) ESN-475V: Naphthalene-type epoxy resin (functional group equivalent weight 332g / eq., manufactured by Nippon Steel Chemical & Material Co., Ltd.) 2021P: Alicyclic epoxy resin with an ester structure (functional group equivalent weight 137g / eq., manufactured by Daicel Corporation) ZX-1658GS: 1,4-glycidylcyclohexane type epoxy resin (functional group equivalent weight 133g / eq., manufactured by Nippon Steel Chemical & Material Co., Ltd.) (C) Component HPC-8150-62T: Dicyclopentadiene-type active ester curing agent (functional group equivalent weight 230 g / eq., toluene solution with non-volatile content of 62% by mass, manufactured by DIC Corporation) HPC-8000L-65MT: Dicyclopentadiene-type active ester curing agent (functional group equivalent weight 220 g / eq., toluene solution with non-volatile content of 65% by mass, manufactured by DIC Corporation) Active ester compound (A): Synthesized in Synthesis Example 1 (D) Component LA-3018-50P: Phenolic curing agent with a triazine skeleton and novolac structure (functional group equivalent weight 151 g / eq., 1-methoxy-2-propanol solution with 50% nonvolatile content by mass, manufactured by DIC Corporation) V-03: Carbodiimide curing agent (functional group equivalent weight 216 g / eq., toluene solution with non-volatile content of 50% by mass, manufactured by Nisshinbo Chemical Inc.) (E) Component EXL-2655: Core-shell particles containing rubber components in the core, manufactured by Dow (F) Component 1B2PZ: Imidazole curing accelerator, manufactured by Shikoku Chemicals Corporation (G) Component YX7553BH30: Phenoxy resin (1:1 solution of MEK and cyclohexanone with 30% non-volatile content, manufactured by Mitsubishi Chemical Corporation) YX7200BH35: Phenoxy resin (MEK solution with 35% non-volatile content, manufactured by Mitsubishi Chemical Corporation)

[0167] <Measurement of dielectric constant and dielectric loss tangent> The resin sheet A obtained in each of the examples and comparative examples was cured in an oven at 190°C for 90 minutes. The support was peeled off from the resin sheet A taken out of the oven to obtain a cured resin composition layer. The cured product was cut into a length of 80 mm and a width of 2 mm to be used as a cured product for evaluation.

[0168] The dielectric constant and dielectric loss tangent of each cured evaluation material were measured by the cavity resonance perturbation method using an Agilent Technologies HP8362B at a measurement frequency of 5.8 GHz and a measurement temperature of 23°C. Measurements were performed on two test pieces, and the average was calculated.

[0169] <Measurement of coefficient of linear thermal expansion (CTE)> Resin sheet A obtained in each of the examples and comparative examples was cured in an oven at 190°C for 90 minutes and then peeled off from the support to obtain a cured resin composition layer. This cured material was cut into a length of 20 mm and a width of 6 mm to prepare evaluation samples. The average coefficient of linear thermal expansion (CTE) of each evaluation sample was measured by a tensile load method using a TMA device manufactured by Rigaku Corporation. Specifically, the evaluation sample was placed in a long length on the TMA device, and measurements were performed twice consecutively under the measurement conditions of a load of 1 g and a heating rate of 5°C / min (the first time the temperature was raised from 25°C to 200°C, and the second time the temperature was raised from 25°C to 250°C).

[0170] <Evaluation of edge swelling and calculation of inorganic filler component area ratio> (1) Preparation of inner layer board Both sides of a glass cloth-based epoxy resin double-sided copper-clad laminate (copper foil thickness 18 μm, substrate thickness 0.8 mm, Panasonic "R1515A", substrate dimensions 510 mm × 340 mm) with an inner layer circuit formed were etched 1 μm with a microetching agent (MEC "CZ8101") to roughen the copper surface.

[0171] (2) Lamination of resin sheet A Resin sheet A, cut to a size of 490 mm x 320 mm, was laminated onto both sides of the inner layer substrate using a batch-type vacuum pressure laminator (Nikko Materials Co., Ltd., two-stage build-up laminator "CVP700") so that the resin composition layer was in contact with the inner layer substrate. The lamination was carried out by reducing the pressure for 30 seconds to 13 hPa or less, and then by heating at 120°C and a pressure of 10 kgf / cm. 2 Then, the adhesive was applied at 120°C and a pressure of 14 kgf / cm for 30 seconds. 2 The mixture was heat-pressed for 60 seconds.

[0172] (3) Thermal curing of the resin composition layer The inner layer substrate laminated with resin sheet A was then placed in a 130°C oven and heated for 30 minutes, and then transferred to a 170°C oven and heated for 30 minutes to thermally cure the resin composition layer and form an insulating layer. The support was then peeled off to obtain cured substrate A having an insulating layer, inner layer substrate, and another insulating layer in this order. Due to thermal curing, part of the resin composition layer oozed out of the gap between the inner layer substrate and the support, forming a bleed-out portion in cured substrate A.

[0173] (4) Roughening treatment A desmear treatment as a roughening treatment was performed on the cured substrate A. The desmear treatment was the following wet desmear treatment.

[0174] Cured Substrate A was immersed in a swelling solution (Atotech Japan's "Swelling Dip Securigant P," an aqueous solution of diethylene glycol monobutyl ether and sodium hydroxide) at 60°C for 5 minutes, then in an oxidizing solution (Atotech Japan's "Concentrate Compact CP," an aqueous solution of potassium permanganate approximately 6% and sodium hydroxide approximately 4%) at 80°C for 20 minutes, then in a neutralizing solution (Atotech Japan's "Reduction Solution Securigant P," an aqueous sulfuric acid solution) at 40°C for 5 minutes, and then dried at 80°C for 15 minutes.

[0175] (5) Formation of the conductor layer A conductor layer was formed on the roughened surface of the insulating layer using a semi-additive process. Specifically, the roughened substrate was immersed in an electroless plating solution containing PdCl2 at 40°C for 5 minutes, and then in an electroless copper plating solution at 25°C for 20 minutes. Next, the substrate was heated at 150°C for 30 minutes for annealing, after which an etching resist was formed and a pattern was formed by etching. Copper sulfate electroplating was then performed to form a 25 μm-thick conductor layer, which was then annealed at 190°C for 60 minutes to obtain evaluation substrate A.

[0176] (6) Evaluation of edge swelling The bleed-out portion formed at the end of the insulating layer of the evaluation substrate A was visually observed to check for the presence or absence of swelling in the bleed-out portion.

[0177] (7) Calculation of the inorganic filler component area ratio and calculation of Si(A)-Si(B) An arbitrary edge of the support was selected for cured substrate A, and a cross section 1.5 mm away from that point toward the outer edge where the cured resin composition layer had exuded was observed using a scanning electron microscope (SII NanoTechnology Inc., focused ion beam / scanning ion microscope "SMI3050SE") to obtain an SEM image of the cross section of cured substrate A. For the obtained SEM image, the area ratio Si (A) of the inorganic filler component in the region from d1 (μm) to d2 (μm) from the main surface of the cured body was calculated (unit: %).

[0178] Specifically, the obtained SEM image was saved as an image, and image analysis software (ImageJ, manufactured by the National Institutes of Health, USA) was used to convert it into a black-and-white binary image, with the resin component parts colored black and the inorganic filler component parts other than the resin components colored white, and the percentage of the area of ​​the inorganic filler components (Si(A) value) was calculated as the number of pixels in the white part for each region. When calculating Si(A), d1 = 0 μm, d2 = 5 μm, and the width of the measurement region was 7.5 μm.

[0179] When measuring the percentage of the inorganic filler component area, the conditions were calibrated by setting a binarization threshold so that the value of (number of pixels in the inorganic filler component part) / (total number of pixels in the cross section of the cross section sample) × 100 was within the range of ±3 of the volume percentage value of the inorganic filler component of the cross section sample.

[0180] An arbitrary edge of the support was selected for cured substrate A, and a cross section at a location 1.5 mm away in the direction of the side opposite that edge was observed using a scanning electron microscope (SII NanoTechnology Inc., focused ion beam / scanning ion microscope "SMI3050SE") to obtain an SEM image of the cross section of cured substrate A. For the obtained SEM image, the area ratio Si(B) of the inorganic filler component in the region from d1 (μm) to d2 (μm) from the main surface of the cured body was calculated (unit: %).

[0181] Specifically, the obtained SEM image was saved as an image, and image analysis software (ImageJ, manufactured by the National Institutes of Health, USA) was used to convert it into a black-and-white binary image, with the resin component parts colored black and the inorganic filler component parts other than the resin components colored white, and the percentage of the area of ​​the inorganic filler components (Si(B) value) was calculated as the number of pixels in the white part for each region. When calculating Si(B), d1 = 0 μm, d2 = 5 μm, and the width of the measurement region was 7.5 μm.

[0182] When measuring the percentage of the inorganic filler component area, the conditions were calibrated by setting a binarization threshold so that the value of (number of pixels in the inorganic filler component part) / (total number of pixels in the cross section of the cross section sample) × 100 was within the range of ±3 of the volume percentage value of the inorganic filler component of the cross section sample.

[0183] The difference between the obtained Si(A) value and Si(B) value (Si(A)-Si(B)) was also calculated.

[0184] [Table 2]

[0185] From the above table, it can be seen that Examples 1 to 3, in which the difference between Si(A) and Si(B) is 5% or less, have low dielectric loss tangents and linear thermal expansion coefficients, and furthermore, the occurrence of blistering is suppressed. Furthermore, Example 4 has higher dielectric loss tangents and linear thermal expansion coefficients than Examples 1 to 3 and Comparative Example 1, and therefore no blistering occurred.

[0186] On the other hand, in Comparative Example 1, although the dielectric loss tangent and the linear thermal expansion coefficient are low, the difference between Si(A) and Si(B) exceeds 5%, and therefore, it is clear that swelling occurs. [Explanation of symbols]

[0187] 100 Inner layer board 200 Resin Sheet 210 Resin composition layer 210a 1st page 210b 2nd side 212 outer edge 220 Support 230 Bleed-out portion (part of the resin composition layer) 240 Protective Film 300 Gap

Claims

1. a resin composition layer having a first surface; A resin sheet comprising: a support bonded to the first surface of the resin composition layer; the resin composition layer contains an inorganic filler, After laminating the resin sheet onto the inner layer substrate, the resin composition layer is thermally cured at 180°C for 30 minutes without peeling off the support to obtain a cured resin composition layer; In a cross section in a direction perpendicular to the first surface at a distance of 1.5 mm from an end of one side of the support toward the outer edge of the cured product of the resin composition layer, Si(A) represents the proportion (%) of the inorganic filler portion area per unit area in the cured product of the resin composition layer, In a cross section perpendicular to the first surface at a distance of 1.5 mm from an end of one side of the support toward the end of the side opposite to the end, when the ratio (%) of the area of ​​the inorganic filler portion per unit area in the cured product of the resin composition layer is Si(B), A resin sheet in which Si(A)-Si(B) satisfies the relationship of 5% or less.

2. The resin sheet according to claim 1, wherein the resin composition layer is thermally cured at 200°C for 90 minutes, and the cured product has a dielectric loss tangent of 0.0030 or less.

3. The resin sheet according to claim 1, wherein the resin composition layer has a thermal expansion coefficient of 20 ppm / °C or less when heat-cured at 200°C for 90 minutes.

4. The resin sheet according to claim 1 , wherein the resin composition layer comprises (B) an epoxy resin.

5. The resin sheet according to claim 1 , wherein the resin composition layer contains (C) an active ester-based curing agent.

6. 5. The resin sheet according to claim 4, wherein the resin composition layer comprises an active ester-based curing agent (C) and a curing agent (D), and a ratio (M(C+D) / M(B)) of the number of epoxy groups in the component (B), M(B), to the number of active groups in the components (C) and (D), M(C+D), is 0.7 or more.

7. The resin sheet according to claim 1 , wherein the content of the inorganic filler is 70% by mass or more when the nonvolatile components in the resin composition layer are taken as 100% by mass.

8. A circuit board comprising a cured layer obtained by curing a resin composition layer of the resin sheet according to any one of claims 1 to 7.

9. a step of laminating an inner layer substrate and the resin sheet according to any one of claims 1 to 7 so that the inner layer substrate and the resin composition layer are in contact with each other; and curing the resin composition layer; A method for manufacturing a circuit board, wherein the step of laminating an inner layer substrate and a resin sheet includes allowing a portion of a resin composition layer to seep out from a gap between the inner layer substrate and the support.

10. A semiconductor device comprising the circuit board according to claim 8.

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