Method for producing resin composition layer

Abstract

A method for producing a resin composition layer which comprises a resin composition comprising an agglomerated inorganic filler and a heat-curable resin, the method comprising the following steps (a) and (b). (a) A step for subjecting a carrier film and a sheet formed on the carrier film using the resin composition to a press treatment under the condition of a press temperature of 0 to 110°C, inclusive, and a press pressure of 40 to 1000 MPa, inclusive; and (b) a step for subjecting the sheet that has been undergone the step (a) to a press treatment under the condition of a press temperature of 70 to 250°C, inclusive, and a press pressure of 3 to 100 MPa, inclusive, to produce a resin composition layer.

Description

[Technical field]

[0001] The present invention relates to a method for producing a resin composition layer, a resin composition layer obtained by the method, and a composite molded body including the resin composition layer. The resin composition layer and the composite molded body obtained by the method for producing a resin composition layer of the present invention can be suitably used as a heat dissipation material for, for example, a power semiconductor device. [Background technology]

[0002] Much research has been done on heat dissipation sheets with good thermal conductivity and excellent insulation. In particular, attempts have been made to obtain heat dissipation resin sheets that satisfy high levels of thermal conductivity and insulation by mixing fillers into the resin. Various oxides and nitrides are used as fillers contained in heat dissipation resin sheets, and many studies have been done on their particle size and particle size distribution.

[0003] Conventionally, hexagonal boron nitride has been considered as a filler contained in heat dissipation sheets. Hexagonal boron nitride is generally a thin plate-like crystal, and the plane direction of the thin plate is Although the thermal conductivity is high, the thermal conductivity in the thickness direction of the thin plate is low. When boron nitride is added, the boron nitride is oriented parallel to the sheet surface when the sheet is formed. Therefore, sufficient thermal conductivity cannot be obtained in the thickness direction of the sheet.

[0004] Agglomerated boron nitride filler is a material that can increase the thermal conductivity of the sheet in the thickness direction. By using agglomerated boron nitride filler, the thermal conductivity of the sheet in the thickness direction can be improved.

[0005] As an agglomerated boron nitride filler, a card-house structured agglomerated boron nitride filler has been developed (see, for example, Patent Document 1). Furthermore, a card-house structured agglomerated boron nitride filler has been developed that has a relatively large average particle size and is less likely to collapse even when pressure is applied (see, for example, Patent Document 2). The card-house structure of the agglomerated boron nitride filler ensures a heat conduction path due to the card-house structure, so by including this in a heat dissipation sheet, the sheet has excellent thermal conductivity in the thickness direction. Agglomerated boron nitride filler is made by agglomerating boron nitride particles without using a separate binder. Therefore, even if an external force is applied when forming the sheet, the card-house structure does not easily collapse, maintaining a heat conduction path and allowing heat to be dissipated in the thickness direction of the sheet, achieving excellent thermal conductivity (see, for example, Patent Document 3). As a molding method for increasing the thermal conductivity in the thickness direction of a sheet, a method is known in which aggregated boron nitride fillers in the sheet are brought into surface contact with each other to increase the thermal conductivity (see, for example, Patent Document 4).

[0006] In Patent Documents 1 to 4, a thermosetting resin composition containing an aggregated boron nitride filler is applied to a substrate, and then heated and pressurized to form an aggregated boron nitride filler-containing resin composition layer. However, no detailed consideration is given to the pressing conditions or the pressing process.

[0007] Patent Document 5 discloses a method for obtaining a B-stage resin sheet by drying a coating layer of a resin composition containing boron nitride filler and alumina, and laminating the layers under heat and pressure, and for obtaining a C-stage cured resin sheet laminate by sandwiching the B-stage resin sheet between copper foils with copper foils on both sides.

[0008] [Patent Document 1] Patent No. 5679083 [Patent Document 2] JP 2016-135730 A [Patent Document 3] International Publication No. 2015 / 119198 [Patent Document 4] International Publication No. 2019 / 189746 [Patent Document 5] JP 2016-79304 A

[0009] The aggregated boron nitride fillers disclosed in Patent Documents 1 to 3 have fine voids between the fillers. Therefore, further improvement of insulation is required. In Patent Document 4, no consideration is given to the handleability of the sheet, and improvement of the handleability is required for larger areas.

[0010] In Patent Document 5, the press pressure in the B stage is low to obtain flowability of the sheet, so voids remain in the sheet, resulting in low voltage resistance. In Patent Document 5, the remaining voids make the sheet brittle, and further improvement in handling is required to increase the area of ​​the sheet. Summary of the Invention

[0011] An object of the present invention is to provide a method for producing a resin composition layer, which, when producing a resin composition layer formed using a resin composition containing an aggregated inorganic filler and a thermosetting resin, can improve the handleability of a sheet formed using the resin composition, reduce damage and defects to the film due to handling, and improve the voltage resistance, adhesion, and heat resistance of the resin composition layer.

[0012] The present inventors have found that in a method for producing a resin composition layer containing aggregated inorganic filler and a thermosetting resin, the above-mentioned problems can be solved by carrying out a specific pressing step. The present invention relates to the following.

[0013] [1] A method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b): (a) pressing a carrier film and a sheet formed on the carrier film using the resin composition under conditions of a pressing temperature of 0° C. or higher and 110° C. or lower and a pressing pressure of 40 MPa or higher and 1000 MPa or lower (b) A process of pressing the sheet that has been subjected to the process (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

[0014] [2] The method for producing a resin composition layer according to [1], wherein a reaction rate of the thermosetting resin in the sheet after the step (a) determined by the following method (hereinafter referred to as "reaction rate (A)") is less than 50%. <Measurement and calculation method of reaction rate (A)> (a) For the sheet before and after the process, the heat generation amount is calculated from the heat generation peak obtained by heating the sheet from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) using the following formula. Reaction rate (A) (%) = (1 - (amount of heat generated after (a) process / amount of heat generated before (a) process)) x 100

[0015] [3] The method for producing a resin composition layer according to [1] or [2], wherein, when the pressing temperature in the step (b) is Tb (°C) and the pressing temperature in the step (a) is Ta (°C), Tb>Ta and 30°C≦Tb-Ta≦220°C.

[0016] [4] The method for producing a resin composition layer according to any one of [1] to [3], wherein the reaction rate of the thermosetting resin in the sheet after the step (b) determined by the following method (referred to as "reaction rate (B)") is 60% or more. <Measurement and calculation method of reaction rate (B)> For the sheet (a) before the process and (b) after the process, the heat generation amount is calculated from the heat generation peak obtained by heating from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) using the following formula. Reaction rate (B) (%) = (1-((b) heat generation after process / (a) heat generation before process)) x 100

[0017] [5] The method for producing a resin composition layer according to any one of [1] to [4], wherein, when the pressing pressure in the step (b) is Pb (MPa) and the pressing pressure in the step (a) is Pa (MPa), Pa>Pb and Pa / Pb is 1.5 or more and 50 or less.

[0018] [6] The method for producing a resin composition layer according to any one of [1] to [5], wherein Fb / Fa is 0.7 or more and 1.2 or less, where Fb is the film thickness after the step (b) and Fa is the film thickness after the step (a).

[0019] [7] The method for producing a resin composition layer according to any one of [1] to [6], wherein the pressing in the step (a) is a flat plate pressing.

[0020] [8] The method for producing a resin composition layer according to any one of [1] to [6], wherein the pressing treatment in the step (a) is a roll pressing treatment.

[0021] [9] The method for producing a resin composition layer according to any one of [1] to [6], wherein the pressing treatment in the step (a) is a hydrostatic pressing treatment.

[0022]

[10] The method for producing a resin composition layer according to any one of [1] to [9], wherein the thermosetting resin contains an epoxy compound.

[0023]

[11] The method for producing a resin composition layer according to

[10] , wherein the thermosetting resin contains an epoxy compound having a weight-average molecular weight of 10,000 or more and an epoxy compound having a weight-average molecular weight of 600 or less.

[0024]

[12] The method for producing a resin composition layer according to

[10] or

[11] , wherein the thermosetting resin contains an epoxy compound having a weight average molecular weight of 600 or less and containing three or more epoxy groups in one molecule.

[0025]

[13] The method for producing a resin composition layer according to any one of [1] to

[12] , wherein the aggregated inorganic filler contains an aggregated boron nitride filler.

[0026]

[14] The method for producing a resin composition layer according to

[13] , wherein the aggregated inorganic filler comprises an aggregated boron nitride filler having a house-of-cards structure.

[0027]

[15] A resin composition layer obtained by the production method according to any one of [1] to

[14] .

[0028]

[16] A composite molded article having a layer of the resin composition according to

[15] and a metal part.

[0029]

[17] A method for producing a composite molded product having a resin composition layer and a metal part, the method comprising forming the resin composition layer by the method for producing a resin composition layer according to any one of [1] to

[14] . Effect of the Invention

[0030] According to the present invention, in producing a resin composition layer containing an aggregated inorganic filler and a thermosetting resin, a specific pressing process is carried out to improve the handling properties of a sheet formed using the resin composition, reduce damage or defects of the film caused by handling, and improve the voltage resistance, adhesiveness, and heat resistance of the resulting resin composition layer. Furthermore, the improved adhesiveness is expected to reduce the thermal resistance at the interface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments. The present invention is not limited to the following embodiments, and can be modified in various ways within the scope of the present invention.

[0032] [Method for producing resin composition layer] The method for producing a resin composition layer of the present invention is a method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, and includes the following steps (a) and (b). (a) pressing a carrier film and a sheet formed on the carrier film using the resin composition under conditions of a pressing temperature of 0° C. or higher and 110° C. or lower and a pressing pressure of 40 MPa or higher and 1000 MPa or lower (b) A process of pressing the sheet that has been subjected to the process (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

[0033] Hereinafter, the resin composition layer produced by the method for producing a resin composition layer of the present invention may be referred to as the "resin composition layer of the present invention". In addition, the resin composition containing the aggregated inorganic filler and the thermosetting resin for forming the resin composition layer of the present invention may be referred to as the "resin composition of the present invention". In the present invention, the term "sheet" refers to a film-like material formed on a carrier film from the resin composition of the present invention, and is to be distinguished from the resin composition layer of the present invention obtained by curing this.

[0034] The method for producing a resin composition layer of the present invention may include other steps in addition to the above steps (a) and (b). For example, other steps may be included between steps (a) and (b). For example, a drying step, a smoothing step, a lamination step, etc. may be included.

[0035] In the method for producing a resin composition layer of the present invention, a sheet formed on a carrier film is subjected to a pressing process to form the resin composition layer of the present invention. The resin composition layer of the present invention may be used for various purposes as it is formed on the carrier film according to the purpose and production process, or may be separated from the carrier film and used for various purposes as a single resin composition layer. The resin composition layer of the present invention may be covered with a protective sheet or the like. One of the preferred embodiments is a composite molding having a metal portion on one or both sides of the resin composition layer of the present invention. The resin composition of the present invention may contain other components in addition to the aggregated inorganic filler and the thermosetting resin.

[0036] [Resin composition] The resin composition of the present invention will be described.

[0037] <Agglomerated inorganic filler> The resin composition of the present invention contains an aggregated inorganic filler. The resin composition of the present invention preferably contains a large amount of aggregated inorganic filler in order to improve the thermal conductivity of the resin composition layer produced and to control the linear expansion coefficient. By containing the aggregated inorganic filler, the aggregated inorganic fillers are deformed by contacting each other in the steps (a) and (b) described below, and the surface contact forms more heat conduction paths, which tends to result in high thermal conductivity. The aggregated morphology of the aggregated inorganic filler can be confirmed by a scanning electron microscope (SEM). The resin composition of the present invention may contain, in addition to the aggregated inorganic filler, a non-aggregated inorganic filler and an organic filler.

[0038] As the aggregated inorganic filler, an electrically insulating filler can be used, and examples thereof include fillers composed of at least one type of particles selected from the group consisting of metal carbides, metal oxides, and metal nitrides. Examples of metal carbides include silicon carbide, titanium carbide, tungsten carbide, and the like. Examples of metal oxides include magnesium oxide, aluminum oxide, silicon oxide, calcium oxide, zinc oxide, yttrium oxide, zirconium oxide, cerium oxide, ytterbium oxide, and sialon (ceramics composed of silicon, aluminum, oxygen, and nitrogen). Examples of metal nitrides include boron nitride, aluminum nitride, silicon nitride, and the like.

[0039] In power semiconductor applications, insulation is required, so the aggregated inorganic filler has a volume resistivity of 1×10 12 Ω cm or more, especially 1×10 13 It is preferable that the resin composition is made of an inorganic compound having excellent insulating properties of Ω·cm or more. Among them, oxides and nitrides are preferable because the resin composition layer formed has sufficient electrical insulating properties.

[0040] More specifically, such an aggregated inorganic filler is alumina (Al2O3, volume resistivity 1×10 14 Ω·cm), Aluminum Nitride (AlN, volume resistivity > 1×10 14 Ω·cm), boron nitride (BN, volume resistivity 1×10 14 Ω·cm), silicon nitride (Si3N4, volume resistivity > 1×10 14 Ω cm), silica (SiO2, volume resistivity > 1×10 14 As the aggregated inorganic filler, alumina, aluminum nitride, boron nitride, and silica are preferable, and alumina and boron nitride are particularly preferable.

[0041] The aggregated inorganic filler may be surface-treated with a surface treatment agent. As the surface treatment agent, a known surface treatment agent can be used.

[0042] The aggregated inorganic filler may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0043] Although there is no particular limitation on the method or degree of aggregation of the aggregated inorganic filler used in the present invention, it is preferable to use the following aggregated boron nitride filler as the aggregated inorganic filler. The following aggregated boron nitride filler may be used in combination with a filler of a different shape and type from the aggregated boron nitride filler.

[0044] <Agglomerated boron nitride filler> Boron nitride has high thermal conductivity, but is scaly, and exhibits high thermal conductivity in the direction of the scales, but low thermal conductivity in the direction perpendicular to the scales. For ease of handling, it is preferable to use agglomerated particles in which the scales are collected and aggregated into a sphere. When agglomerated boron nitride fillers are stacked like cabbage, they are preferably aligned in the direction of the surface, with the radial direction of the agglomerated particles being the direction with better thermal conductivity. It is more preferable that the agglomerated boron nitride filler has a house-of-cards structure.

[0045] The "house of cards structure" is described, for example, in Ceramics 43 No. 2 (published by the Ceramic Society of Japan in 2008), and is a structure in which plate-like particles are not oriented but are laminated in a complex manner. More specifically, an aggregated boron nitride filler having a house of cards structure is an aggregate of boron nitride primary particles, and has a structure in which the flat and end faces of the primary particles are in contact with each other to form, for example, a T-shaped aggregate.

[0046] The agglomerated boron nitride filler used in the present invention is particularly preferably an agglomerated boron nitride filler having the above-mentioned house-of-card structure. By using an agglomerated boron nitride filler having a house-of-card structure, the thermal conductivity can be further increased.

[0047] The new Mohs hardness of the agglomerated boron nitride filler is not particularly limited, but is preferably not more than 5. There is no particular lower limit to the new Mohs hardness of the agglomerated boron nitride filler, but it is, for example, not less than 1. When the new Mohs hardness is 5 or less, the particles dispersed in the resin composition tend to come into surface contact with each other, forming heat conduction paths between the particles, and tend to improve the heat conductivity of the formed resin composition layer.

[0048] The volume average particle diameter of the aggregated boron nitride filler is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more. The volume average particle diameter of the aggregated boron nitride filler is preferably 100 μm or less, more preferably 90 μm or less. When the volume average particle diameter is 10 μm or more, the number of particles in the resin composition and the resin composition layer of the present invention is relatively small, and the number of interparticle interfaces is reduced, so that the thermal resistance is reduced, and the resulting resin composition layer may have a high thermal conductivity. When the volume average particle diameter is the above upper limit or less, the surface smoothness of the formed resin composition layer tends to be excellent.

[0049] The volume average particle size of the agglomerated boron nitride filler means the particle size at which the cumulative volume is 50% when a cumulative curve is drawn with the volume of the powder used for measurement being 100%. Measurement methods include a wet measurement method in which a sample in which aggregated particles are dispersed in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer is measured using a laser diffraction / scattering particle size distribution measuring device, and a dry measurement method in which measurement is performed using Malvern's "Morphologi." The same applies to the volume average particle diameters of other aggregated inorganic fillers and non-aggregated inorganic fillers.

[0050] <Breaking strength of aggregated inorganic filler> The breaking strength of the aggregated inorganic filler is not particularly limited, but is preferably 300 MPa or less, more preferably 100 MPa or less, even more preferably 50 MPa or less, even more preferably 20 MPa or less, particularly preferably 15 MPa or less, and most preferably 10 MPa or less. When the breaking strength is equal to or less than the upper limit, the aggregated structure of the aggregated inorganic filler is deformed when pressed, and the aggregated inorganic filler particles are more likely to come into surface contact with each other. The lower limit of the breaking strength of the aggregated inorganic filler is not particularly limited, but from the viewpoint of ease of handling, it is preferably 2.5 MPa or more, more preferably 3 MPa or more, even more preferably 3.5 MPa or more, and particularly preferably 4 MPa or more.

[0051] <Elastic modulus of aggregated inorganic filler> The elastic modulus of the aggregated inorganic filler is not particularly limited, but is preferably 10 MPa or more, more preferably 20 MPa or more, even more preferably 30 MPa or more, still more preferably 48 MPa or more, particularly preferably 50 MPa or more, and most preferably 55 MPa or more. If the elastic modulus is equal to or more than the lower limit, the aggregated inorganic filler tends to plastically deform in the direction of the pressing pressure, and collapse of the aggregated structure can be suppressed. The upper limit of the elastic modulus of the aggregated inorganic filler is not particularly limited, but in terms of making it easier to obtain sufficient deformation, it is preferably 5 GPa or less, more preferably 2 GPa or less, even more preferably 1.5 GPa or less, still more preferably 1 GPa or less, particularly preferably 500 MPa or less, particularly preferably 300 MPa or less, and most preferably 250 MPa or less.

[0052] When the aggregated inorganic filler has the above elastic modulus range, it tends to maintain a spherical shape during press processing. When the aggregated inorganic filler has a breaking strength within the above range, the part where the aggregated inorganic fillers contact each other tends to deform, and surface contact tends to be facilitated. As a result, while maintaining a high thermal conductivity inside the aggregated inorganic filler, the contact thermal resistance of the interface between the aggregated inorganic fillers and the interface between the metal part described later and the resin composition layer of the present invention can be reduced, and the overall thermal conductivity can be improved.

[0053] When the agglomerated inorganic filler is present in a resin composition layer, the breaking strength and elastic modulus of the agglomerated inorganic filler can be measured after removing the resin of the resin composition layer by baking so as not to alter the agglomerated inorganic filler, and then extracting the agglomerated inorganic filler.

[0054] <Content of aggregated inorganic filler> The content of the aggregated inorganic filler in the resin composition layer of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more, based on 100% by mass of the resin composition layer. Also, the content is preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The combination of the upper and lower limits of the content of the aggregated inorganic filler in the resin composition layer of the present invention is not particularly limited, but is preferably 30% by mass or more and 99% by mass or less, more preferably 40% by mass or more and 90% by mass or less, and particularly preferably 50% by mass or more and 80% by mass or less.

[0055] Therefore, the content of the aggregated inorganic filler in the resin composition of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more, based on 100% by mass of the solid content in the resin composition, and is preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The combination of the upper and lower limits of the content of the aggregated inorganic filler in the resin composition layer of the present invention is not particularly limited, but is preferably 30% by mass or more and 99% by mass or less, more preferably 40% by mass or more and 90% by mass or less, and particularly preferably 50% by mass or more and 80% by mass or less. Here, the solid content in the resin composition refers to the total of all components in the resin composition other than the solvent.

[0056] When the content of the aggregated inorganic filler is equal to or more than the lower limit, the effect of improving thermal conductivity and the effect of controlling the linear expansion coefficient due to the inclusion of the aggregated inorganic filler tend to be sufficiently obtained. When the content of the aggregated inorganic filler is equal to or less than the upper limit, the voids in the resin composition layer tend to be reduced, and the insulation property and the interfacial adhesion in the composite molded product tend to be improved.

[0057] <Other non-agglomerated inorganic fillers> In the present invention, in addition to the agglomerated inorganic filler, other non-agglomerated inorganic fillers may be used in combination. There are no limitations on the shape of the non-aggregated inorganic filler, and examples of the shape include spherical, whisker, fibrous, and plate-like shapes. Other non-aggregated inorganic fillers may be scaly primary particles of boron nitride, etc., and are not limited to their shape. The other non-aggregated inorganic fillers (non-aggregated inorganic fillers) may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0058] <Spherical filler> As a non-agglomerated inorganic filler to be used other than the agglomerated inorganic filler, a spherical filler is preferably used.

[0059] The thermal conductivity of the spherical filler is not particularly limited, but is 1 W / m·K or more, preferably 10 W / m·K or more, more preferably 15 W / m·K or more, and even more preferably 20 W / m·K or more, for example, 20 to 30 W / m·K. The spherical filler preferably has a new Mohs hardness of 3.1 or more, for example, 5-10. By using such spherical fillers in combination with the above-mentioned aggregated inorganic filler, the adhesive strength to metal and heat dissipation properties of the resulting resin composition layer can be improved.

[0060] Here, the term "spherical" refers to anything that is generally recognized as being spherical. For example, an average circularity of 0.4 or more may be considered spherical, and an average circularity of 0.6 or more may be considered spherical. Usually, the upper limit of the average circularity is 1. The circularity can be measured by processing the projected image, for example, with an FPIA series from Sysmex Corporation.

[0061] The spherical filler is preferably at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, and magnesium oxide. By using these preferable spherical fillers, the heat dissipation properties of the obtained resin composition layer can be further improved.

[0062] The volume average particle diameter of the spherical filler is preferably in the range of 0.5 μm or more and 40 μm or less. When the volume average particle diameter is 0.5 μm or more, the resin and the filler can easily flow during hot molding, and it is considered that the interfacial adhesive strength in the composite molded product of the present invention described later can be increased. When the volume average particle diameter is 40 μm or less, the dielectric breakdown characteristics of the resin composition layer can be easily maintained.

[0063] <Content of other non-agglomerated inorganic fillers> When the agglomerated inorganic filler is used in combination with other non-agglomerated inorganic fillers, the content ratio of the agglomerated inorganic filler to the other non-agglomerated inorganic fillers in the resin composition of the present invention and the resin composition layer of the present invention is not particularly limited, but is preferably 99:1 to 1:99 in mass ratio, and more preferably 95:5 to 9:91.

[0064] For the same reasons as for the content of the agglomerated boron nitride filler in the resin composition layer of the present invention, the total content of the agglomerated inorganic filler and other non-agglomerated inorganic fillers in the resin composition layer of the present invention is preferably 30 mass% or more, more preferably 40 mass% or more, even more preferably 45 mass% or more, and particularly preferably 50 mass% or more, based on 100 mass% of the resin composition layer, while it is preferably 99 mass% or less, more preferably 90 mass% or less, even more preferably 85 mass% or less, and particularly preferably 80 mass% or less.

[0065] Therefore, the total content of the aggregated inorganic filler and other non-aggregated inorganic fillers in the resin composition of the present invention is preferably 30 mass% or more, more preferably 40 mass% or more, even more preferably 45 mass% or more, and particularly preferably 50 mass% or more, based on 100 mass% of the solid content in the resin composition, while it is preferably 99 mass% or less, more preferably 90 mass% or less, even more preferably 85 mass% or less, and particularly preferably 80 mass% or less.

[0066] When the total content of the aggregated inorganic filler and the other non-aggregated inorganic fillers is equal to or greater than the lower limit, the effect of improving thermal conductivity and the effect of controlling the linear expansion coefficient due to the inclusion of the inorganic filler tend to be sufficiently obtained. When the total content of the aggregated inorganic filler and the other non-aggregated inorganic fillers is equal to or less than the upper limit, voids can be reduced, and insulation properties and interfacial adhesion in the composite molded body tend to be improved.

[0067] <Other organic fillers> The resin composition and the resin composition layer of the present invention may contain an organic filler in addition to the aggregated inorganic filler. In the present invention, the organic filler is a component that does not contain an epoxy group, does not fall within the definition of a thermosetting catalyst, and is solid at room temperature and is composed of organic components. Examples of the organic filler include natural products such as wood flour, cellulose that may be modified, starch, various organic pigments, thermoplastic resins, thermosetting resins, etc. Specific examples include acrylic resin particles, nylon resin particles, polyester resin particles, polystyrene resin particles, silicone resin particles, etc.

[0068] The inclusion of an organic filler may impart appropriate elongation to the resin composition, reduce the stress that occurs, and suppress the occurrence of cracks during a temperature cycle test.

[0069] The upper limit of the average particle size of the organic filler is preferably 100 μm or less, more preferably 50 μm or less. By having the average particle size be equal to or less than the upper limit, it is possible to form resin composition layers of various thicknesses while suppressing the decrease in thermal conductivity. The average particle size of the organic filler is also a volume average particle size determined from the volume average particle size distribution measurement results measured by a laser diffraction particle size distribution measurement device.

[0070] The organic filler may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0071] <Thermosetting resin> The thermosetting resin contained in the resin composition of the present invention is not particularly limited as long as it can be cured in the presence of a curing agent or a curing catalyst to give a cured product.

[0072] Specific examples of thermosetting resins include epoxy resins, phenolic resins, polycarbonate resins, unsaturated polyester resins, cyanate resins, maleimide resins, urethane resins, melamine resins, and urea resins. Among these, epoxy resins are preferred from the viewpoints of viscosity, heat resistance, moisture absorption, and ease of handling. Examples of epoxy resins include epoxy group-containing silicon compounds, aliphatic epoxy resins, bisphenol A or F epoxy resins, novolac epoxy resins, alicyclic epoxy resins, glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, multifunctional epoxy resins, and polymeric epoxy resins.

[0073] <Epoxy resin> Epoxy resin is a general term for compounds that have one or more oxirane rings (epoxy groups) in their molecules. The oxirane ring (epoxy group) contained in the epoxy resin may be either an alicyclic epoxy group or a glycidyl group, but from the viewpoint of reaction rate or heat resistance, a glycidyl group is preferable.

[0074] The epoxy resin used in the present invention may be an aromatic oxirane ring (epoxy group)-containing compound. Specific examples thereof include bisphenol-type epoxy resins obtained by glycidylating bisphenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol AD, tetramethyl bisphenol S, and tetrafluorobisphenol A, biphenyl-type epoxy resins, dihydroxynaphthalene, 9,9-bis(4-hydroxyphenyl)fluorene, and other divalent phenols, glycidylating trisphenols such as 1,1,1-tris(4-hydroxyphenyl)methane, and other epoxy resins obtained by glycidylating tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, and novolac-type epoxy resins obtained by glycidylating novolacs such as phenol novolac, cresol novolac, bisphenol A, novolac, and brominated bisphenol A novolac.

[0075] The epoxy resin contained in the resin composition of the present invention is not particularly limited, but may preferably contain one or more selected from various bisphenol-type epoxy resins obtained by glycidylating bisphenols, such as bisphenol A-type epoxy resins and bisphenol F-type epoxy resins; various biphenyl-type epoxy resins obtained by glycidylating biphenyls, aliphatic epoxy resins, epoxy resins obtained by glycidylating aromatic compounds having a plurality of hydroxyl groups, such as dihydroxynaphthalene and 9,9-bis(4-hydroxyphenyl)fluorene; epoxy resins obtained by glycidylating trisphenols, such as 1,1,1-tris(4-hydroxyphenyl)methane, and epoxy resins obtained by glycidylating tetrakisphenols, such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; novolac-type epoxy resins obtained by glycidylating novolacs, such as phenol novolac, cresol novolac, bisphenol A novolac, and brominated bisphenol A novolac; and silicone-containing epoxy resins.

[0076] The epoxy resin used in the present invention may be one type, or a combination of multiple types of epoxy resins.

[0077] The molecular weight of the epoxy resin used in the present invention is not particularly limited. From the viewpoints of film-forming property, low moisture absorption, and flexibility, the epoxy resin used in the present invention preferably contains a high molecular weight epoxy resin. Specifically, the high molecular weight epoxy resin is preferably an epoxy resin having a weight average molecular weight of 10,000 or more, more preferably an epoxy resin having a weight average molecular weight of 15,000 or more. The high molecular weight epoxy resin is preferably an epoxy resin having a weight average molecular weight of 200,000 or less, more preferably an epoxy resin having a weight average molecular weight of 180,000 or less.

[0078] High molecular weight epoxy resins are preferred because they are more hydrophobic, and specifically, the epoxy equivalent of the epoxy component is preferably as large as possible. Specifically, the epoxy equivalent is preferably 5,000 g / equivalent or more, more preferably 7,000 g / equivalent or more, and is preferably 100,000 g / equivalent or less.

[0079] From the viewpoint of increasing the storage modulus of the resin composition layer of the present invention, the epoxy resin used in the present invention preferably contains an epoxy resin having a weight average molecular weight of 600 or less, particularly 550 or less. The lower limit of the weight average molecular weight of this epoxy resin is not particularly limited, but is usually 100 or more.

[0080] The epoxy resin having a weight average molecular weight of 600 or less used in the present invention is preferably an epoxy resin having two or more epoxy groups in one molecule. It is more preferable that the epoxy resin contains a multifunctional epoxy resin having three or more epoxy groups in one molecule and a weight average molecular weight of 600 or less, which will be described later. The epoxy resin having a weight average molecular weight of 600 or less may be a combination of a multifunctional epoxy resin having three or more epoxy groups in one molecule and an epoxy resin having two or less epoxy groups in one molecule.

[0081] The thermosetting resin of the resin composition of the present invention preferably contains an epoxy resin having a weight average molecular weight of 10,000 or more and an epoxy resin having a weight average molecular weight of 600 or less, from the viewpoints of film-forming properties, coatability, and heat resistance after curing.

[0082] The weight average molecular weight of the epoxy resin is a value calculated as polystyrene, measured by gel permeation chromatography. The epoxy equivalent of an epoxy resin is defined as "the weight of an epoxy resin containing one equivalent of epoxy groups" and can be measured in accordance with JIS K7236.

[0083] (Multifunctional epoxy resin with molecular weight of 600 or less) The resin composition of the present invention more preferably contains, as the thermosetting resin, a polyfunctional epoxy resin having a molecular weight of 600 or less and three or more epoxy groups in one molecule.

[0084] From the viewpoint of increasing the storage modulus of the resin composition layer of the present invention, particularly the storage modulus at high temperatures which is important when the amount of heat generated is large, such as in power semiconductors, an epoxy resin having three or more oxirane rings (epoxy groups) in the molecule is preferred, and an epoxy resin having four or more oxirane rings (epoxy groups) in the molecule is more preferred. By having a plurality of oxirane rings (epoxy groups), particularly glycidyl groups, in the molecule, the crosslink density of the formed resin composition layer is improved, resulting in higher strength. As a result, when internal stress occurs in the resin composition layer during a moisture absorption reflow test, the resin composition layer does not deform or break, but maintains its shape, thereby suppressing the occurrence of voids and other voids in the resin composition layer.

[0085] From the viewpoint of increasing the storage modulus of the resin composition layer, the molecular weight of the polyfunctional epoxy resin is preferably 600 or less, and more preferably 550 or less. The lower limit of the molecular weight of the polyfunctional epoxy resin is not particularly limited, but is usually 100 or more.

[0086] By adding a polyfunctional epoxy resin, it is possible to introduce highly polar oxirane rings (epoxy groups) at a high density, which increases the effects of physical interactions such as van der Waals forces and hydrogen bonds, improving the adhesion between the metal part and the resin composition layer in the composite molded product described below. The addition of a polyfunctional epoxy resin can increase the storage modulus of the resin composition layer after thermal curing, which allows the cured resin composition to penetrate into the irregularities of the metal part as an adherend, and thereby exerts a strong anchor effect, improving the adhesion between the metal part and the resin composition layer.

[0087] Specifically, the polyfunctional epoxy resin is preferably an epoxy resin having three or more epoxy groups. Examples of the polyfunctional epoxy resin that can be used include Mitsubishi Chemical's jER630, Sumitomo Chemical's ELM-434 series and ELM-100 series, Nagase ChemteX's EX321L, EX-411, and EX-512, and Showa Denko's BATG and PETG.

[0088] The polyfunctional epoxy resin may be used alone or in combination of two or more kinds.

[0089] <Thermosetting resin content> In the resin composition layer of the present invention, the main component of the resin components excluding the inorganic filler is preferably a thermosetting resin, and more preferably contains an epoxy resin. Here, the main component refers to the component that is present in the largest amount.

[0090] The resin composition layer of the present invention preferably contains 5 to 90% by mass, particularly 10 to 60% by mass of a thermosetting resin in 100% by mass of the resin composition layer. Therefore, the proportion of the thermosetting resin in 100% by mass of the solid content in the resin composition of the present invention is preferably 5 to 90% by mass, particularly 10 to 60% by mass. When the content of the thermosetting resin is equal to or more than the above lower limit, the moldability is good, and when it is equal to or less than the above upper limit, the content of other components can be secured, and the thermal conductivity can be increased.

[0091] The content of the thermosetting resin in the resin component excluding the inorganic filler in the resin composition layer of the present invention is not particularly limited, but is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 45% by mass or more. Therefore, the content of the thermosetting resin in the solid content excluding the inorganic filler in the resin composition of the present invention is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 45% by mass or more. The upper limit of the content of the thermosetting resin in the resin component excluding the inorganic filler is 100% by mass, and all components other than the inorganic filler may be thermosetting resins. When the proportion of the thermosetting resin is within the above range, the composition has low moisture absorption, high elastic modulus, and high toughness, and the reaction can be easily controlled. This tends to result in the effects of high reflow resistance, high reliability in cycle tests, and high thermal conductivity.

[0092] The content of the high molecular weight epoxy resin having a weight average molecular weight of 10,000 or more, which is the aforementioned suitable epoxy resin, in the resin component of the resin composition layer of the present invention and the resin composition of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 90% by mass or less. The content of epoxy resin having a weight average molecular weight of 600 or less in the resin component of the resin composition layer of the present invention and the resin composition of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 90% by mass or less. The content ratio of the high molecular weight epoxy resin having a weight average molecular weight of 10,000 or more to the epoxy resin having a weight average molecular weight of 600 or less is preferably 1:18 to 18:1 in terms of mass ratio. When the content of the high molecular weight epoxy resin is equal to or more than the above lower limit, the film-forming property of the resin composition of the present invention tends to be improved, and when the content is equal to or less than the above upper limit, the strength of the resin composition layer of the present invention can be excellent.

[0093] <Other ingredients> The resin composition and the resin composition layer of the present invention may contain other components in addition to the aggregated inorganic filler and the thermosetting resin. Examples of the other components include the above-mentioned non-aggregated inorganic filler and organic filler, as well as the following curing catalysts, curing agents, surface treatment agents such as silane coupling agents, insulating carbon components such as reducing agents, viscosity adjusters, dispersants, thixotropy imparting agents, flame retardants, colorants, organic solvents, and thermoplastic resins.

[0094] <Curing catalyst> The resin composition of the present invention may contain a curing catalyst (thermosetting catalyst) in order to adjust the curing speed and the physical properties of the cured product.

[0095] The curing catalyst is not particularly limited, but is appropriately selected according to the type of thermosetting resin and other components used. Specific examples of the curing catalyst include chain or cyclic tertiary amines, organic phosphorus compounds, quaternary phosphonium salts, diazabicycloalkenes such as organic acid salts, etc. As the curing catalyst, organic metal compounds, quaternary ammonium salts, metal halides, etc. can also be used. As the organic metal compounds, zinc octylate, tin octylate or aluminum acetylacetone complex, gallium acetylacetone complex, imidazoles, etc. are listed. From the viewpoint of heat resistance and stability, imidazoles are particularly preferred. These may be used alone or in combination of two or more.

[0096] The curing catalyst is preferably contained in an amount of 0.1 to 10% by mass, particularly 0.1 to 5% by mass, based on 100% by mass of the resin composition of the present invention excluding the solvent and inorganic filler. When the content of the curing catalyst is equal to or more than the lower limit, the progress of the curing reaction can be sufficiently promoted to achieve good curing. When the content of the curing catalyst is equal to or less than the upper limit, the curing speed is not too fast, and therefore the storage stability of the resin composition of the present invention can be improved.

[0097] When the curing catalyst is solid, its average particle size is not particularly limited, but the average particle size of at least one curing catalyst is preferably 15 μm or less, more preferably 10 μm or less. By having the average particle size be equal to or less than the above upper limit, the solubility of the curing catalyst in the resin component tends to be improved, the reaction rate tends to be improved, and the elastic modulus of the formed resin composition layer tends to be higher, and the glass transition temperature tends to be increased. Furthermore, the dispersibility of the curing catalyst tends to be improved, and the storage stability of the resin composition of the present invention tends to be improved. The lower limit of the average particle size of the curing catalyst is not particularly limited.

[0098] <Hardening agent> The resin composition of the present invention may contain a curing agent. The curing agent is not particularly limited, but examples of the curing agent include phenolic resins, aliphatic amines, aromatic amines, modified amines, polyamide resins, imidazoles, polymercaptans, polysulfides, acid anhydrides, carboxylic acid-containing compounds, and dicyandiamide.

[0099] Among these, for example, phenol resin, acid anhydride having aromatic skeleton or alicyclic skeleton, or water additive of said acid anhydride or modified product of said acid anhydride are preferable. By using these preferable curing agents, it is likely to be possible to obtain a resin composition layer having excellent balance of heat resistance, moisture resistance and electrical properties. Only one type of curing agent may be used, or two or more types may be used in combination.

[0100] The phenolic resin used as the curing agent is not particularly limited. Specific examples of the phenolic resin include phenolic novolac, o-cresol novolac, p-cresol novolac, t-butylphenol novolac, dicyclopentadiene cresol, polyparavinylphenol, bisphenol A type novolac, xylylene modified novolac, decalin modified novolac, poly(di-o-hydroxyphenyl)methane, poly(di-m-hydroxyphenyl)methane, or poly(di-p-hydroxyphenyl)methane. Among them, in order to further improve the flexibility and flame retardancy of the resin composition and to improve the mechanical properties and heat resistance of the resin composition layer, a novolac type phenolic resin having a rigid main chain skeleton or a phenolic resin having a triazine skeleton is preferred. In order to improve the flexibility of the resin composition of the present invention and the toughness of the resin composition layer of the present invention, a phenolic resin having an allyl group is preferred.

[0101] Commercially available phenolic resins include MEH-8005, MEH-8000H and NEH-8015 (all manufactured by Meiwa Chemical Industry Co., Ltd.), YLH903 (manufactured by Mitsubishi Chemical Corporation), LA-7052, LA-7054, LA-7751, LA-1356 and LA-3018-50P (all manufactured by Dainippon Ink Co., Ltd.), as well as PSM6200, PS6313 and PS6492 (manufactured by Gun-ei Chemical Industry Co., Ltd.).

[0102] The acid anhydride having an aromatic skeleton, the water additive of the acid anhydride, or the modified product of the acid anhydride used as the curing agent is not particularly limited.Specific examples include SMA resin EF30 and SMA resin EF60 (both manufactured by Sartomer Japan), ODPA-M and PEPA (both manufactured by Manac), Ricadit MTA-10, Ricadit TMTA, Ricadit TMEG-200, Ricadit TMEG-500, Ricadit TMEG-S, Ricadit TH, Ricadit MH-700, Ricadit MT-500, Ricadit DSDA and Ricadit TDA-100 (all manufactured by New Japan Chemical), EPICLON B4400, and EPICLON B570 (all manufactured by Dainippon Ink and Chemicals).

[0103] The acid anhydride having an alicyclic skeleton, the water addition product of the acid anhydride, or the modified product of the acid anhydride is preferably an acid anhydride having a polyalicyclic skeleton, the water addition product of the acid anhydride, or the modified product of the acid anhydride, or an acid anhydride having an alicyclic skeleton obtained by the addition reaction of a terpene compound and maleic anhydride, the water addition product of the acid anhydride, or the modified product of the acid anhydride.Specific examples include Ricadit HNA and Ricadit HNA-100 (both manufactured by New Japan Chemical Co., Ltd.), and Epicure YH306 and Epicure YH309 (both manufactured by Mitsubishi Chemical Corporation).

[0104] The curing agent is preferably contained in an amount of 0 to 70% by mass, particularly 0 to 55% by mass, based on 100% by mass of the resin composition of the present invention excluding the solvent and inorganic filler. If the content of the curing agent is equal to or greater than the lower limit, sufficient curing performance can be obtained. If the content of the curing agent is equal to or less than the upper limit, the reaction proceeds effectively, the crosslinking density is improved, the strength is increased, and the film formability is improved.

[0105] When the thermosetting resin is an epoxy resin, the content of reactive groups in the curing agent is not particularly limited, but may be 0 equivalents relative to the amount of epoxy groups in the thermosetting resin, and is preferably 0.05 equivalents or more, more preferably 0.1 equivalents or more, and even more preferably 0.15 equivalents or more. The content of reactive groups in the curing agent is preferably 2 equivalents or less, more preferably 1.2 equivalents or less, relative to the amount of epoxy groups in the thermosetting resin. By setting the content of the reactive group of the curing agent to the amount of epoxy groups in the thermosetting resin at or above the lower limit, the curing rate is prevented from decreasing, epoxy groups are less likely to remain, and the strength of the resin composition layer formed is improved and the moisture absorption is inhibited. By setting the content of the reactive group of the curing agent to the amount of epoxy groups in the thermosetting resin at or below the upper limit, the elastic modulus of the resin composition layer formed tends to be high.

[0106] <Dispersant> The resin composition of the present invention may contain a dispersant. By containing a dispersant, it is possible to form a uniform resin composition layer, and the thermal conductivity and dielectric breakdown properties of the obtained resin composition layer may be improved.

[0107] The dispersant preferably has a functional group containing hydrogen atoms having hydrogen bonding properties. The dispersant has a functional group containing hydrogen atoms having hydrogen bonding properties, which can further improve the thermal conductivity and dielectric breakdown properties of the resin composition layer formed. Examples of the functional group containing hydrogen atoms having hydrogen bonding properties include a carboxyl group (pKa=4), a phosphoric acid group (pKa=7), and a phenol group (pKa=10).

[0108] The pKa of the functional group containing a hydrogen atom having hydrogen bonding ability is preferably in the range of 2 to 10, more preferably in the range of 3 to 9. When the pKa is 2 or more, the acidity of the dispersant is in an appropriate range, and the reaction of the epoxy resin in the thermosetting resin component may be easily suppressed. Therefore, when the molded product in an uncured state is stored, the storage stability tends to be improved. When the pKa is 10 or less, the function as a dispersant is sufficiently performed, and the thermal conductivity and dielectric breakdown characteristics of the formed resin composition layer tend to be sufficiently improved.

[0109] The functional group containing a hydrogen atom capable of bonding with hydrogen is preferably a carboxyl group or a phosphate group, which can further increase the thermal conductivity and dielectric breakdown characteristics of the resulting resin composition layer.

[0110] Specific examples of the dispersant include polyester-based carboxylic acid, polyether-based carboxylic acid, polyacrylic-based carboxylic acid, aliphatic-based carboxylic acid, polysiloxane-based carboxylic acid, polyester-based phosphoric acid, polyether-based phosphoric acid, polyacrylic-based phosphoric acid, aliphatic-based phosphoric acid, polysiloxane-based phosphoric acid, polyester-based phenol, polyether-based phenol, polyacrylic-based phenol, and polysiloxane-based phenol, etc. Only one type of dispersant may be used, or two or more types may be used in combination.

[0111] <Thermoplastic resin> The resin composition of the present invention may contain a thermoplastic resin. By containing a thermoplastic resin, it may be possible to impart appropriate elongation to the formed resin composition layer, relieve the generated stress, and suppress the generation of cracks in a temperature cycle test.

[0112] As the thermoplastic resin, any generally known thermoplastic resin can be used. Specific examples of the thermoplastic resin include vinyl polymers such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, (meth)acrylic resin, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer, polyesters such as polylactic acid resin, polyethylene terephthalate, and polybutylene terephthalate, polyamides such as nylon and polyamidoamine, polyvinyl acetal resins such as polyvinyl acetoacetal, polyvinyl benzal, and polyvinyl butyral resins, ionomer resins, polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyacetal, ABS resin, LCP (liquid crystal polymer), fluororesin, urethane resin, silicone resin, various elastomers, and modified products of these resins.

[0113] The thermoplastic resin may be uniform in the resin phase of the resin composition layer to be formed, or may be phase-separated and have a recognizable shape. In the case of phase separation, the shape of the thermoplastic resin in the resin composition layer may be particulate or fibrous. The thermoplastic resin may be contained as the organic filler described above.

[0114] <Organic solvent> The resin composition of the present invention may contain an organic solvent in order to improve the coatability in the coating step described below.

[0115] Examples of the organic solvent that may be contained in the resin composition of the present invention include methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether acetate, butyl acetate, isobutyl acetate, and propylene glycol monomethyl ether. The organic solvent may be used alone or in combination of two or more kinds.

[0116] When the resin composition of the present invention contains an organic solvent, the content thereof is preferably used so that the solids concentration (total of components other than the solvent) in the resin composition of the present invention is 10 mass % or more, particularly 40 mass % or more, and 90 mass % or less, particularly 80 mass % or less, from the viewpoint of coatability in the coating step.

[0117] <Method of producing resin composition> The resin composition of the present invention can be obtained by uniformly mixing the aggregated inorganic filler, the thermosetting resin, and other components added as necessary by stirring or kneading. For mixing, a general kneading device such as a mixer, a kneader, or a single-screw or twin-screw kneader can be used. When mixing, heating may be performed as necessary.

[0118] The order of mixing the various components may be arbitrary as long as there are no particular problems, such as the generation of reactions or precipitates. For example, a method may be used in which a thermosetting resin component is mixed and dissolved in an organic solvent (e.g., methyl ethyl ketone) to prepare a resin liquid, and then a sufficiently mixed aggregated inorganic filler and other components are added to the obtained resin liquid and mixed.

[0119] [Method of manufacturing resin composition layer] The method for producing a resin composition layer of the present invention includes steps (a) and (b). The reason why the manufacturing method of the present invention provides the effects of improving the handleability, voltage resistance, adhesiveness, and heat resistance is believed to be as follows.

[0120] In step (a), a pressing process is performed at a specific pressing pressure and pressing temperature. The pressing process is performed at a temperature lower than the curing temperature of the thermosetting resin contained in the resin composition of the present invention, and pressing can be performed while suppressing the reaction rate of the thermosetting resin. As a result, the thermosetting resin can easily enter the voids originating from the aggregated inorganic filler, and the voids can be reduced. The resin penetrates into the voids originating from the aggregated inorganic filler, reducing the brittleness of the resin composition layer obtained, and improving the handleability. Furthermore, in step (b), the sheet that has undergone step (a) is pressed at a specific pressure and temperature. By performing the specific press treatment in step (b) while suppressing the reaction rate of the thermosetting resin after step (a), it is possible to improve adhesion, and by allowing the reaction after step (b) to proceed sufficiently, it is possible to improve voltage resistance and heat resistance. In addition, by setting the pressing temperature in step (b) to be higher than that in step (a), the fluidity of the thermosetting resin before curing is increased, and voids can be further reduced. By going through steps (a) and (b), a resin composition layer with improved voltage resistance, adhesiveness, and heat resistance can be obtained.

[0121] <(a) Process> Step (a) is a step of pressing a sheet having a layer of the resin composition of the present invention formed on a carrier film under conditions of a pressing temperature of 0°C or higher and 110°C or lower and a pressing pressure of 40 MPa or higher and 1000 MPa or lower.

[0122] In the step (a), a sheet is formed on a carrier film using the resin composition of the present invention, and the sheet with the carrier film is subjected to a press treatment under specific conditions. By performing the press treatment under specific conditions with the sheet with the carrier film in the step (a), the sheet handling property up to the step (b) can be improved.

[0123] The method for forming a sheet using the resin composition of the present invention is not particularly limited, but may be a method for forming a sheet by a coating process. In this case, the resin composition of the present invention may contain an organic solvent to improve the coating property.

[0124] The method of applying the resin composition of the present invention is not particularly limited, and any method such as a dip method, a spin coat method, a spray coat method, a blade method, or the like can be adopted. For application, a coating device such as a spin coater, a slit coater, a die coater, or a blade coater can be used. With these devices, it is possible to uniformly form a sheet (coating film) of a predetermined thickness on a carrier film.

[0125] The carrier film to be used is not particularly limited, but is preferably one that does not dissolve in the resin composition of the present invention and is less deformed by the pressing temperature and pressure in step (a). Examples of the carrier film include olefin-based films, polyester films such as PET (polyethylene terephthalate), polyimide films, and copper materials.

[0126] When a sheet is formed using the resin composition of the present invention containing an organic solvent, it is preferable to remove the solvent by a step such as drying before pressing in step (a). The solid content of the sheet before pressing in step (a) is preferably 95% by mass or more, more preferably 98% by mass or more.

[0127] The drying step is not particularly limited, but is usually carried out at a temperature of 10 to 150°C, preferably 25 to 120°C, and more preferably 30 to 110°C. By keeping the drying temperature at or below the upper limit, the curing of the thermosetting resin in the sheet is suppressed, and the resin flows in the subsequent pressing step, tending to make it easier to remove voids. By keeping the drying temperature at or above the lower limit, the organic solvent can be effectively removed.

[0128] The drying time is usually 5 minutes to 10 days, preferably 10 minutes to 3 days, more preferably 20 minutes to 1 day, and particularly preferably 30 minutes to 4 hours, when drying at less than 80°C. When drying at 80°C or higher, the drying time is preferably 1 minute or more, preferably 30 minutes or less, more preferably 20 minutes or less, even more preferably 15 minutes or less, and particularly preferably 10 minutes or less. When the drying time is equal to or more than the above lower limit, the organic solvent can be sufficiently removed, and the residual solvent tends to be prevented from becoming voids in the sheet. When the drying time is equal to or less than the above upper limit, the productivity tends to be improved and the manufacturing cost tends to be reduced.

[0129] The pressing temperature in step (a) is from 0° C. to 110° C., preferably from 3° C. to 100° C., more preferably less than 100° C., and even more preferably not more than 95° C. By keeping the temperature within this range, the reaction rate of the thermosetting resin in step (a) is suppressed, and a sheet with good handleability tends to be obtained.

[0130] The pressing pressure in step (a) is 40 MPa or more and 1000 MPa or less, preferably 45 MPa or more, more preferably 50 MPa or more, and preferably 900 MPa or less, more preferably 700 MPa or less, and further preferably 500 MPa or less. By keeping the pressure within this range, voids are reduced and a resin composition layer with good thermal conductivity tends to be obtained.

[0131] The time for the press treatment in step (a) is not particularly limited, but is preferably 1 minute or more, more preferably 3 minutes or more, and is preferably 5 hours or less, more preferably 2 hours or less. By keeping the pressing time within the above range, a sheet having good handling properties and adhesion to metal parts tends to be obtained.

[0132] The reaction rate of the thermosetting resin contained in the sheet after the step (a) (hereinafter, sometimes referred to as "reaction rate (A)") is not particularly limited, but is preferably less than 50%. The reaction rate (A) is more preferably 40% or less, further preferably 30% or less, and particularly preferably 20% or less. When the reaction rate (A) of the thermosetting resin is equal to or less than the above upper limit, a sheet with good handling properties and adhesiveness tends to be obtained. The reaction rate (A) of the thermosetting resin in the sheet is calculated from the heat release amount of the exothermic peak obtained when the temperature of the sheet before and after the step (a) is raised from 40°C to 250°C at 10°C / min by differential scanning calorimetry (DSC) using the following formula. Reaction rate (A) (%) = (1 - (amount of heat generated after (a) process / amount of heat generated before (a) process)) x 100

[0133] The thickness (Fa) of the sheet after the step (a) is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 1000 μm or less, more preferably 800 μm or less. When the thickness (Fa) of the sheet is equal to or more than the lower limit, insulation tends to be obtained, and when the thickness (Fa) is equal to or less than the upper limit, thermal resistance tends to be reduced. The thickness of the sheet can be measured using a contact or non-contact type film thickness gauge. The same applies to the film thickness (Fb) of the resin composition layer after the step (b).

[0134] The pressing treatment in step (a) is not particularly limited, but plate pressing, roll pressing, and hydrostatic pressing are preferred.

[0135] The specific configuration of the flat plate press machine for performing the press treatment is not particularly limited, and examples thereof include a device equipped with a pair of parallel flat plates (press platens) with a mirror-polished hard chrome plating layer disposed on the surface, a pressure control means for controlling the press pressure by the press platens, and a heating means for heating the press platens to a predetermined temperature, in which a sheet is sandwiched between the pair of press platens and pressed from both sides while being heated to the predetermined temperature. In step (a), by performing a flat plate press treatment in which pressure is applied with the highly smooth press platen surfaces, the surface of the sheet is easily smoothed, and the adhesion between the formed resin composition layer and the metal part tends to be improved.

[0136] By carrying out the roll press treatment, the sheet surface can be smoothed in step (a), which tends to improve productivity. The specific configuration of the roll machine for performing the roll press treatment is not particularly limited, and various roll machines such as a type equipped with a pair of nip rolls, a multi-stage nip roll type, etc. Examples of roll machines for performing the roll press treatment include a device equipped with a preheat roll for preheating (not necessary in some cases), at least a pair of nip rolls, and preferably a heating means for heating the nip rolls, and configured to pressurize and smooth the surface of the sheet by sandwiching the sheet between the pair of nip rolls and pressing it from both sides.

[0137] By performing isostatic pressing, it becomes possible to perform high-pressure pressing over a large area, which tends to suppress press unevenness in the sheet. In isostatic pressing, multiple sheets can be processed at the same time, which tends to improve productivity. The specific configuration of the isostatic press is not particularly limited. For example, it may be one that includes a pressure vessel filled with a liquid such as oil or water, a pressure cylinder that pressurizes the liquid, a control means for controlling the pressure at which the liquid is pressurized, and a heating means for heating the liquid to a predetermined temperature. More specifically, it may be an apparatus that vacuum-packs a sheet with a carrier film, immerses it in a liquid such as oil or water of an isostatic press, and performs isostatic pressing, whereby the sheet is pressed with a uniform pressure and the surface of the sheet is smoothed.

[0138] <(b) Process> The step (b) is a step of pressing the sheet that has been subjected to the step (a) at a pressing temperature of 70° C. to 250° C. and a pressing pressure of 3 MPa to 100 MPa to obtain a resin composition layer.

[0139] The method for carrying out the pressing treatment in step (b) is not particularly limited, and the pressing treatment can be carried out, for example, by plate pressing.

[0140] In step (b), a sheet that has been subjected to step (a) is provided, and the press treatment may be performed on a single sheet, a laminate of carrier film / sheet / metal part, a laminate of metal part / sheet, etc. The manufacturing method of the present invention is a method with excellent adhesiveness, and is suitable for a manufacturing method in which a laminate including a metal part and a sheet is press treated.

[0141] The pressing temperature in step (b) is 70° C. or higher and 250° C. or lower, preferably 75° C. or higher, more preferably 80° C. or higher, and preferably 240° C. or lower, more preferably 230° C. or lower, and further preferably 220° C. or lower. By keeping the temperature within this range, a resin composition layer having high elastic modulus, adhesiveness, and heat resistance tends to be obtained.

[0142] The pressing pressure in step (b) is 3 MPa or more and 100 MPa or less, preferably 3.5 MPa or more, and more preferably 4 MPa or more. By keeping the pressure in this range, a resin composition layer excellent in withstand voltage, thermal conductivity, and adhesiveness tends to be obtained.

[0143] The time for the press treatment in the step (b) is not particularly limited, but is preferably 5 minutes or more, more preferably 10 minutes or more, and is preferably within 24 hours. The time for the press treatment is preferably such that the reaction rate (B) of the thermosetting resin described below is 60% or more.

[0144] The reaction rate of the thermosetting resin contained in the sheet after the step (b) (hereinafter, sometimes referred to as "reaction rate (B)") is not particularly limited, but is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 80% or more. The upper limit of the reaction rate (B) is not particularly limited, but is 100%. When the reaction rate (B) of the thermosetting resin is in the above range, sufficient curing proceeds, and a resin composition layer having excellent heat resistance and adhesiveness tends to be obtained. The reaction rate (B) of the thermosetting resin in the sheet is calculated from the heat generation amount of the exothermic peak obtained when the temperature of the sheet before the step (a) and after the step (b) is raised from 40°C to 250°C at a rate of 10°C / min by differential scanning calorimetry (DSC) using the following formula. Reaction rate (B) (%) = (1-((b) heat generation after process / (a) heat generation before process)) x 100

[0145] The thickness (Fb) of the resin composition layer after the step (b) is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 1000 μm or less, more preferably 800 μm or less. When the thickness (Fb) of the resin composition layer is equal to or more than the lower limit, insulation tends to be obtained, and when the thickness is equal to or less than the upper limit, thermal resistance tends to be reduced.

[0146] <Combination of process (a) and process (b)> The pressing conditions in steps (a) and (b) and the film thickness of the sheet and the resin composition layer are not particularly limited as long as they are within the above-mentioned ranges, but the following combinations are particularly preferred.

[0147] The pressing temperature in the (b) step is Tb (°C), and the pressing temperature in the (a) step is Ta (°C). Tb>Ta, and 30°C≦Tb-Ta≦220°C It is preferable that: Tb-Ta is preferably 30° C. or higher, more preferably 40° C. or higher, and preferably 220° C. or lower, more preferably 200° C. or lower, and even more preferably 180° C. or lower. When Tb-Ta is within the above range, there is a tendency that the handleability of the sheet and the adhesiveness of the resin composition layer can be compatible.

[0148] The press pressure in step (b) is Pb (MPa) and the press pressure in step (a) is Pa (MPa). Pa>Pb and Pa / Pb is 1.5 to 50 It is preferable that: Pa / Pb is preferably 1.5 or more, more preferably 1.8 or more, even more preferably 2 or more, and is preferably 50 or less, more preferably 45 or less, and even more preferably 40 or less. When Pa / Pb is in the above range, voids in the resin composition layer can be reduced, and the shape of the aggregated inorganic filler can be appropriately maintained, thereby making it possible to obtain a resin composition layer having excellent voltage resistance and thermal conductivity.

[0149] Regarding the film thickness of the resin composition layer and the sheet, when the film thickness of the resin composition layer after the (b) step is Fb and the film thickness of the sheet after the (a) step is Fa, it is preferable that the ratio (Fb / Fa) is 0.7 or more and 1.2 or less. Fb / Fa is preferably 0.7 or more, more preferably 0.8 or more, even more preferably 0.85 or more, and is preferably 1.2 or less, more preferably 1.1 or less. An Fb / Fa ratio within the above range indicates that (a) voids in the sheet after the process are efficiently reduced, and (b) the change in film thickness before and after the process is small, and tends to result in a resin composition layer with excellent voltage resistance and thermal conductivity.

[0150] In the present invention, it is particularly preferable to, in step (a), form a sheet on a carrier film using the resin composition of the present invention, and perform a press treatment together with the carrier film, and, in step (b), perform a press treatment on a laminate including the metal part and the sheet with the sheet that has been subjected to step (a) in contact with the metal part.

[0151] [Thermal conductivity and withstand voltage of resin composition layer] The thermal conductivity and voltage resistance of the resin composition layer of the present invention are not particularly limited, but the thermal conductivity is preferably 8 W / mK or more, more preferably 9 W / mK or more, and even more preferably 10 W / mK or more. The withstand voltage of the resin composition layer of the present invention is preferably 30 kV / mm or more, more preferably 35 kV / mm or more, and particularly preferably 40 kV / mm or more. In the present invention, the method for measuring the thermal conductivity and the withstand voltage is not particularly limited, but examples thereof include the methods shown in the examples given later.

[0152] [Composite molded body] The composite molded product of the present invention is formed by laminating and integrating the resin composition layer of the present invention and a metal part. The metal part may be provided on only one surface of the resin composition layer of the present invention, or on two or more surfaces. For example, the resin composition layer may have a metal part on only one surface, or on both surfaces. The metal part may be patterned.

[0153] Such a composite molded product of the present invention can be produced, for example, by using a metal part as a substrate (carrier film), forming the resin composition of the present invention into a sheet on this substrate, and pressing it in the above-mentioned steps (a) and (b). In step (b), a composite molded product having metal parts on both sides can be obtained by overlapping it with another metal plate.

[0154] In addition, the composite molded body of the present invention can also be produced by peeling a sheet-like resin composition formed on a substrate (carrier film) separate from the metal part from the carrier film after step (a), placing it on a metal member that will become the metal part, and performing pressing in step (b).

[0155] In this case, the sheet-like resin composition of the present invention is peeled off from the carrier film after step (a) in the same manner as described above, except that it is applied onto a carrier film such as PET which may be treated with a release agent, and this sheet-like resin composition is placed on another metal plate or sandwiched between two metal plates, and then integrated by pressing in step (b).

[0156] The metal plate may be a metal plate of about 10 μm to 10 cm thick made of copper, aluminum, nickel-plated metal, etc. The surface of the metal plate may be physically roughened or chemically treated with a surface treatment agent, etc. From the viewpoint of adhesion between the resin composition layer and the metal plate, it is more preferable that the metal plate is subjected to such treatment.

[0157] [Semiconductor devices] The composite molded article of the present invention can be used as a semiconductor device, and in particular, can be effectively used as a power semiconductor device that can achieve high output and high density by operating at high temperatures. EXAMPLES

[0158] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples as long as it does not depart from the gist of the present invention. The various conditions and values ​​of the evaluation results in the following examples indicate the preferred ranges of the present invention, similar to the preferred ranges in the embodiments of the present invention. The preferred ranges of the present invention can be determined by taking into consideration the preferred ranges in the above-mentioned embodiments and the values ​​in the following examples or the ranges indicated by a combination of the values ​​of the examples.

[0159] [raw materials] The raw materials used in the examples and comparative examples are as follows.

[0160] <Thermosetting resin> Resin component 1: Epoxy resin produced according to the epoxy resin production method disclosed in the examples of JP 2006-176658 A Weight average molecular weight in polystyrene equivalent: 30,000 Epoxy equivalent: 9,000g / equivalent Resin component 2: Bisphenol A type liquid epoxy resin Weight average molecular weight: 600 or less Resin component 3: Biphenyl type solid epoxy resin Weight average molecular weight: 600 or less Resin component 4: Non-aromatic multifunctional epoxy resin containing a structure having 4 or more glycidyl groups per molecule Weight average molecular weight: 600 or less

[0161] <Agglomerated inorganic filler> Inorganic filler 1: Boron nitride agglomerated particles having a house-of-cards structure produced according to the method for producing boron nitride agglomerated particles disclosed in the examples of WO 2015 / 561028. New Mohs hardness: 2 Volume average particle size: 45μm

[0162] <Other fillers> Inorganic filler 2: Admatechs, spherical alumina particles New Mohs hardness: 9 Volume average particle size: 6.5 μm Thermal conductivity: 20~30W / m K

[0163] <Hardening agent> Hardener 1: Meiwa Chemical Industries, Ltd. "MEH-8000H" Phenol Resin Hardener

[0164] <Curing catalyst component> Curing catalyst 1: Shikoku Kasei "Curesol 2E4MZ-A" Curing catalyst 2: Shikoku Kasei "Curesol 2PHZ-PW"

[0165] [Measurement method] <Reaction rate of thermosetting resin> Differential scanning calorimetry (DSC) was performed on the sheets formed before and after each of steps (a) and (b) (resin composition layer after step (b)). The reaction rates were calculated from the heat release amount of the exothermic peak obtained when the temperature was raised from 40°C to 250°C at a rate of 10°C / min, using the following formula. Reaction rate (A) of step (a) (%) = (1 - (amount of heat generated after step (a) / amount of heat generated before step (a))) x 100 Reaction rate of step (b) (B) (%) = (1-(amount of heat generated after step (b) / amount of heat generated before step (a))) x 100

[0166] <Thermal conductivity in the thickness direction of the resin composition layer> Using a thermal resistance measuring device (Mentor Graphics Corporation, product name "T3ster"), the thermal resistance values ​​of resin composition layers with different thicknesses produced under the same composition and conditions were measured, and the thermal conductivity was calculated from the slope of a graph plotting the thermal resistance value against the thickness.

[0167] <Withstand voltage of resin composition layer> In the insulating oil, the voltage applied to the resin composition layer was increased by 500 V every minute to determine the voltage at which the resin composition layer was broken down. The obtained breakdown voltage value was converted into a breakdown voltage per mm of film thickness to obtain the withstand voltage (kV / mm).

[0168] <Sheet handling test (mandrel test)> (a) The sheet with the carrier film after the process was subjected to a bending test at 24°C with the carrier film facing inward according to JISK 5600-5-1. A 180° bending test was performed using a mandrel with a diameter of 8 mm. Those with visible cracks or peeling were rated as ×, and those without cracks or peeling were rated as ◯.

[0169] [Example 1] Using a planetary stirring device, resin component 1, resin component 2, resin component 4, curing agent 1, curing catalyst 1, inorganic filler 1, and inorganic filler 2 were mixed to obtain a mixture in the mass ratio shown in composition A in Table 1 below. When preparing this mixture, a slurry-like resin composition was prepared using 18.5 mass% each of methyl ethyl ketone and cyclohexanone so that the mixture constituted 63 mass% (solid content concentration) of the coating slurry.

[0170] The obtained slurry-like resin composition was applied onto a PET film by a doctor blade method, and after heat drying at 60°C for 120 minutes, the PET film was pressed at 50°C and 147 MPa for 10 minutes using a flat plate press in step (a) to obtain a sheet having a thickness of 150 μm. The total content of methyl ethyl ketone and cyclohexanone in the sheet was 1 mass% or less (solid content concentration 99 mass% or more). (a) The reaction rate (A) of the thermosetting resin in the sheet after the process was less than 10%.

[0171] After laminating a copper substrate on the sheet that had been subjected to step (a), curing was performed for 30 minutes at 175°C and 9.8 MPa in step (b) to obtain a resin composition layer. The thickness of the resin composition layer was 141 μm, and the ratio of film thickness after step (b) to film thickness after step (a) (Fb / Fa) was 0.94. The evaluation results of the handling properties of the sheet (mandrel test) are shown in Table 2A. The reaction rate (B) of the thermosetting resin in the resin composition layer after the step (b) was 90% or more, and the withstand voltage of the resin composition layer was 53 kV / mm.

[0172] The thermal conductivity of the resin composition layer of Example 1 was measured for the following samples having the same composition and having been subjected to the same steps (a) and (b). The sheet-shaped resin composition after step (a) was sandwiched between PET films and cured at a predetermined pressure and temperature in step (b) to obtain a resin composition layer. In addition, in the same manner, after removing the carrier film from the sheet after step (a), each sample of two, three, and four sheets was sandwiched between PET films, and treated at a predetermined pressure / temperature in step (b) to obtain four types of resin composition layers with different thicknesses. The thermal conductivity of the resin composition layer was measured by the above method and was found to be 15 W / mK. These results are summarized in Table 2A.

[0173] <Examples 2 to 6 and Comparative Examples 1 to 7> According to the method of Example 1, a resin composition was prepared from the composition A or B shown in Table 1, and processed under the pressing conditions and by the pressing method shown in Tables 2A and 2B. The results are summarized in Tables 2A and 2B.

[0174] [Table 1]

[0175] [Table 2A]

[0176] [Table 2B]

[0177] It can be seen from Tables 2A and 2B that, by carrying out the treatment at the prescribed pressure / temperature in steps (a) and (b) according to the present invention, a resin composition layer having good withstand voltage and thermal conductivity can be obtained.

[0178] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-069766 filed on April 8, 2020, the entirety of which is incorporated by reference.

Claims

1. A method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b): A method for producing a resin composition layer, wherein, when the pressing temperature in the step (b) is Tb (°C) and the pressing temperature in the step (a) is Ta (°C), Tb>Ta and 30°C≦Tb-Ta≦220°C. (a) A step of subjecting a carrier film and a sheet formed on the carrier film using the resin composition to a press treatment under conditions of a press temperature of 0° C. or more and 110° C. or less and a press pressure of 40 MPa or more and 1000 MPa or less. (b) A step of pressing the sheet subjected to the step (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

2. A method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b): A method for producing a resin composition layer, wherein the pressing pressure in the step (b) is Pb (MPa) and the pressing pressure in the step (a) is Pa (MPa), Pa>Pb and Pa / Pb is 1.5 or more and 50 or less. (a) A step of subjecting a carrier film and a sheet formed on the carrier film using the resin composition to a press treatment under conditions of a press temperature of 0° C. or more and 110° C. or less and a press pressure of 40 MPa or more and 1000 MPa or less. (b) A step of pressing the sheet subjected to the step (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

3. A method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b): The method for producing a resin composition layer, wherein Fb / Fa is 0.7 or more and 1.2 or less, where Fb is the film thickness after the step (b) and Fa is the film thickness after the step (a). (a) A step of subjecting a carrier film and a sheet formed on the carrier film using the resin composition to a press treatment under conditions of a press temperature of 0° C. or more and 110° C. or less and a press pressure of 40 MPa or more and 1000 MPa or less. (b) A step of pressing the sheet subjected to the step (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

4. A method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b): The thermosetting resin comprises an epoxy compound having a weight average molecular weight of 10,000 or more and an epoxy compound having a weight average molecular weight of 600 or less. (a) A step of subjecting a carrier film and a sheet formed on the carrier film using the resin composition to a press treatment under conditions of a press temperature of 0° C. or more and 110° C. or less and a press pressure of 40 MPa or more and 1000 MPa or less. (b) A step of pressing the sheet subjected to the step (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

5. A method for producing a resin composition layer made of a resin composition containing an aggregated inorganic filler and a thermosetting resin, the method comprising the following steps (a) and (b): The method for producing a resin composition layer, wherein the thermosetting resin contains an epoxy compound having a weight average molecular weight of 600 or less and containing three or more epoxy groups in one molecule. (a) A step of subjecting a carrier film and a sheet formed on the carrier film using the resin composition to a press treatment under conditions of a press temperature of 0° C. or more and 110° C. or less and a press pressure of 40 MPa or more and 1000 MPa or less. (b) A step of pressing the sheet subjected to the step (a) under conditions of a pressing temperature of 70° C. or more and 250° C. or less and a pressing pressure of 3 MPa or more and 100 MPa or less to obtain a resin composition layer.

6. The method for producing a resin composition layer according to any one of claims 1 to 5, wherein the reaction rate of the thermosetting resin in the sheet after the step (a) obtained by the following method (referred to as "reaction rate (A)") is less than 50%. <Method of measuring and calculating reaction rate (A)> (a) The sheet before and after the step is subjected to differential scanning calorimetry (DSC) and heated from 40° C. to 250° C. at a rate of 10° C. / min. The calorific value is calculated from the calorific value of the exothermic peak obtained by the DSC measurement using the following formula. Reaction rate (A) (%)=(1-(amount of heat generated after step (a) / amount of heat generated before step (a)))×100

7. The method for producing a resin composition layer according to any one of claims 1 to 6, wherein the reaction rate of the thermosetting resin in the sheet after the step (b) obtained by the following method (referred to as "reaction rate (B)") is 60% or more. <Method of measuring and calculating reaction rate (B)> The heat generation amount is calculated from the heat generation peak obtained by heating the sheet before the (a) step and after the (b) step at 10° C. / min from 40° C. to 250° C. by differential scanning calorimetry (DSC) using the following formula. Reaction rate (B) (%)=(1-(amount of heat generated after (b) step / amount of heat generated before (a) step))×100

8. The method for producing a resin composition layer according to any one of claims 1 to 7, wherein the pressing in the step (a) is a flat plate pressing.

9. The method for producing a resin composition layer according to any one of claims 1 to 7, wherein the pressing treatment in the step (a) is a roll pressing treatment.

10. The method for producing a resin composition layer according to any one of claims 1 to 7, wherein the pressing treatment in the step (a) is a hydrostatic pressing treatment.

11. The method for producing a resin composition layer according to any one of claims 1 to 10, wherein the aggregated inorganic filler comprises an aggregated boron nitride filler.

12. The method for producing a resin composition layer according to claim 11, wherein the aggregated inorganic filler comprises an aggregated boron nitride filler having a house of cards structure.

13. A method for producing a composite molded product having a resin composition layer and a metal part, the resin composition layer being formed by the method for producing a resin composition layer according to any one of claims 1 to 12. The method for producing a composite molded product.

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