Manufacturing method for circuit board with heat sink

Abstract

The present invention provides a heat sink-attached circuit board (50) in which a conductor layer (30) constituting a circuit and a heat sink (10) are integrated with an insulating layer (20) therebetween. The heat sink (10) comprises a planar base plate (11) and a plurality of fins (12) protruding from a surface opposite the insulating layer (20). The insulating layer (20) is composed of a material including a thermoplastic resin and boron nitride particles.

Description

Circuit board with heat sink and method for manufacturing the circuit board with heat sink

[0001] The present invention relates to a circuit board with a heat sink and a method for manufacturing the circuit board with a heat sink.

[0002] A circuit board with a heat sink is known in which a conductor layer constituting a circuit and one surface of a large-capacity heat sink are integrated via an insulating layer (see, for example, Patent Document 1). Among these, a heat sink with fins is known for improving heat dissipation. For example, Patent Document 2 discloses a method for manufacturing an insulated circuit board with a heat sink, which includes an insulated circuit board having a circuit layer formed on one surface of a ceramic substrate and a metal layer formed on the other surface, and a heat sink having multiple fins on one surface, which is disposed on the metal layer opposite the ceramic substrate.

[0003] JP 2016-82108 A JP 2020-13915 A

[0004] During the manufacturing process of a heatsink-equipped circuit board, a finned heatsink is pressurized in the stacking direction when the conductor layer and insulating layer are integrated together. Increasing the pressure can improve the adhesion between the heatsink and the insulating and conductor layers, but there is a limit to the amount of pressure that can be applied, given the mechanical strength of the fins. Therefore, there is room for improvement in the adhesion between the conductor layer and the heatsink. After extensive research, the inventors discovered that by using an appropriate insulating layer, it is possible to achieve good adhesion between the conductor layer and the heatsink while also achieving an excellent balance of good thermal conductivity and insulation for transferring heat from the conductor layer to the heatsink, thereby completing the present invention.

[0005] According to the present invention, the following technology relating to a circuit board with a heat sink is provided.

[0006] [1] A circuit board with a heat sink, in which a conductor layer constituting a circuit and a heat sink are integrated via an insulating layer, wherein the heat sink comprises a flat base plate and a plurality of fins protruding from the surface opposite to the insulating layer, and the insulating layer is made of a material containing a thermosetting resin and boron nitride particles. [2] The circuit board with a heat sink according to [1], wherein the area surrounded by the outer peripheral edge of the conductor layer is included in the area of ​​the base plate covered by the insulating layer. [3] The circuit board with a heat sink according to [1] or [2], wherein the area surrounded by an outline connecting the outer ends of the fins is included in the area of ​​the base plate covered by the insulating layer. [4] The circuit board with a heat sink according to any one of [1] to [3], wherein the thermosetting resin includes at least one of an epoxy resin having a naphthalene skeleton and a trisphenolmethane type epoxy resin. [5] The circuit board with a heatsink according to any one of [1] to [4], wherein the content of the boron nitride particles is 60 mass% or more with respect to the total amount of the insulating layer. [6] The circuit board with a heatsink according to any one of [1] to [5], wherein the heatsink is made of at least one material selected from copper and aluminum. [7] A method for manufacturing a circuit board with a heatsink, comprising the steps of: preparing a heatsink comprising a flat base plate and a plurality of fins protruding from one side of the base plate; stacking an insulating layer and a conductor layer constituting a circuit, in this order, on the surface of the heatsink facing the base plate; and integrating the stacked heatsink, the insulating layer, and the conductor layer constituting the circuit by heating and pressurizing, wherein the insulating layer is made of a material containing a thermosetting resin and boron nitride particles. [8] A method for manufacturing a circuit board with a heat sink according to [7], wherein in the integrating step, heating and pressurizing are performed at 150 to 250°C and 5 to 15 MPa.[9] A method for manufacturing a circuit board with a heat sink according to [7] or [8], wherein the insulating layer satisfies the following condition: (Condition) When the curing torque of the insulating layer in a B-stage state is measured at 180°C using a curastometer, the gel time A required to reach 10% of the maximum torque is 30 to 180 seconds.

[10] A method for manufacturing a circuit board with a heat sink according to any one of [7] to [9], wherein in the step of laminating the insulating layer and the conductor layer constituting the circuit in this order on the surface of the heat sink facing the base plate, the insulating layer is in sheet form.

[11] A method for manufacturing a circuit board with a heat sink according to any one of [7] to

[10] , wherein in the step of integrating, the heat sink, the insulating layer, and the conductor layer constituting the circuit are integrated together.

[0007] According to the present invention, in a circuit board with a finned heat sink, good adhesion between the conductor layer and the heat sink can be obtained, while an excellent balance of good thermal conductivity for transferring heat from the conductor layer to the heat sink and insulation can be achieved.

[0008] 1A to 1C are cross-sectional views schematically showing a circuit board with a heat sink according to an embodiment, and FIG. 1B are cross-sectional views schematically showing one process of a method for manufacturing a circuit board with a heat sink according to an embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and their description will be omitted where appropriate. Note that the drawings are for illustrative purposes only. The shapes and dimensional ratios of the components in the drawings do not necessarily correspond to the actual products.

[0010] In this specification, the expression "a to b" in the description of a numerical range means from a to b, unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass or more and 5% by mass or less."

[0011] <Circuit Board with Heatsink> Fig. 1 is a cross-sectional view of a circuit board with a heatsink 50 according to this embodiment. As shown in Fig. 1, the circuit board with a heatsink 50 includes a conductor layer 30 constituting a circuit and a heatsink 10, which are integrated via an insulating layer 20. The heatsink 10 includes a flat base plate 11 and a plurality of fins 12 protruding from the surface opposite the insulating layer 20, and the insulating layer 20 is made of a material containing a thermosetting resin and boron nitride particles. With this configuration, the circuit board with a heatsink 50 can achieve good adhesion between the conductor layer 30 and the heatsink 10, while also achieving a good balance of good thermal conductivity and insulation for transferring heat from the conductor layer 30 to the heatsink 10.

[0012] Each component will be described in detail below.

[0013] [Heat Sink] The heat sink 10 has the function of dissipating heat generated in the conductor layer 30 and the like to the outside. The heat sink 10 of this embodiment includes a flat base plate 11 and a plurality of fins 12 protruding from the surface of the base plate 11 opposite to the insulating layer 20 side. The flat base plate 11 and the fins 12 may be joined by a known method or may be integrally molded.

[0014] The heat sink 10 is preferably made of at least one material selected from copper and aluminum, and is more preferably made of copper from the viewpoint of improving thermal conductivity, workability, and the like.

[0015] The thickness of the base plate 11 can be set appropriately depending on the application, but is preferably 0.2 to 1.5 mm, for example. Furthermore, by making the thickness of the base plate 11 0.5 to 1.5 times the thickness of the conductor layer 30, warping of the entire heatsink-equipped circuit board 50 can be suppressed, and adhesion can be easily improved.

[0016] The heat sink 10 has a plurality of fins 12 extending from one surface of the base plate 11, thereby increasing the surface area of ​​the heat sink 10 and improving heat dissipation efficiency. The plurality of fins 12 are flush. The heights of the plurality of fins 12 are uniform, and the upper surfaces of the fins 12 are flat, forming a surface, which allows stable production of the heat sink-equipped circuit board 50.

[0017] The shape of the fin 12 is not particularly limited, and may be, for example, a polygonal prism such as a square or hexagon, or a cylindrical shape. The quadrangular prism may be a prism having a square cross-section, a rectangular prism, a rhombic prism, a parallelogram prism, or the like. The cylindrical shape may be a prism having a circular, elliptical, or oval cross-section, for example.

[0018] The number of the fins 12 is not particularly limited and may be set appropriately in consideration of the intended use, mechanical strength, etc. The shapes of the fins 12 may be the same as or different from one another, or may differ only partially.

[0019] Furthermore, although the arrangement of the multiple fins 12 is not particularly limited, it is preferable that the area surrounded by the outline connecting the outer ends of the fins 12 is included in the area covered by the insulating layer 20 of the base plate 11. It is also preferable that the outer peripheral end of the base plate 11 does not have fins 12. This makes it possible to improve adhesion while maintaining mechanical strength against pressure applied during the manufacturing process of the heatsink-equipped circuit board 50.

[0020] The spacing between the fins 12 is not particularly limited, but is preferably 0.5 to 2.0 mm. By setting the spacing between the fins 12 to 0.5 mm or more, the cutting process of the fins 12 can be performed efficiently, and the mechanical strength can be maintained against pressure during the manufacturing process of the heatsink-equipped circuit board 50. Furthermore, by setting the spacing between the fins 12 to 2.0 mm or less, the heat dissipation performance of the heatsink 10 can be further improved.

[0021] [Insulating Layer] The insulating layer 20 is used to insulate the conductor layer 30 from leaking electricity to the heat sink 10. The insulating layer 20 is made of a resin material containing a thermosetting resin and boron nitride particles. This provides good thermal conductivity and insulation. Furthermore, when pressure is applied to the insulating layer 20 during the manufacturing process of the heat sink-equipped circuit board 50, the resin filling between the fillers is excellent, efficiently improving thermal conductivity and enhancing adhesion. Each component of the resin material will be described below.

[0022] (Resin Material) Thermosetting Resin Examples of the thermosetting resin include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol E-type epoxy resins, bisphenol S-type epoxy resins, bisphenol M-type epoxy resins (4,4'-(1,3-phenylenediisopridiene)bisphenol-type epoxy resins), bisphenol P-type epoxy resins (4,4'-(1,4-phenylenediisopridiene)bisphenol-type epoxy resins), and bisphenol Z-type epoxy resins (4,4'-cyclohexidienebisphenol-type epoxy resins); epoxy resins having a dicyclopentadiene skeleton, epoxy resins having a biphenyl skeleton, epoxy resins having an adamantane skeleton, epoxy resins having a phenol aralkyl skeleton, epoxy resins having a biphenyl aralkyl skeleton, epoxy resins having a naphthalene aralkyl skeleton, epoxy resins having a naphthalene skeleton, epoxy resins having a methoxynaphthalene aralkyl skeleton, trisphenolmethane-type epoxy resins, phenoxy resins, and cyanate resins. This makes it easier to improve the dispersibility of the boron nitride particles.

[0023] The thermosetting resin preferably contains one or more selected from phenoxy resin, bisphenol F type epoxy resin, epoxy resin having a naphthalene skeleton, and trisphenolmethane type epoxy resin. Among epoxy resins, it is more preferable to contain at least one of epoxy resin having a naphthalene skeleton and trisphenolmethane type epoxy resin, which have excellent dispersibility of boron nitride particles, thermal conductivity of the insulating layer sheet, and adhesion to copper or aluminum of the insulating layer sheet.

[0024] As the cyanate resin, a cyanate ester resin can be used. Specific examples of the cyanate ester resin include bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5 Examples of suitable cyanate ester resins include bifunctional cyanate resins such as 1,3-bis(4-cyanatophenyl-1-(methylethylidene))benzene, bis(4-cyanatophenyl)thioether, and bis(4-cyanatophenyl)ether; polyfunctional cyanate resins derived from phenol novolac, cresol novolac, and dicyclopentadiene structure-containing phenolic resins; and prepolymers of the cyanate ester resins exemplified above in which a portion of the resin has been triazine modified. Examples of commercially available cyanate ester resins that can be used include PT30, BA230, DT-4000, and DT-7000 manufactured by Lonza Japan.

[0025] The content of the thermosetting resin is preferably in the range of 1% by mass or more and 30% by mass or less, more preferably in the range of 5% by mass or more and 28% by mass or less, and even more preferably in the range of 10% by mass or more and 20% by mass or less, relative to the total amount of the resin material (solid content) constituting the insulating layer 20.

[0026] Boron Nitride Particles Boron nitride (BN) particles are inorganic fillers that impart thermal conductivity and electrical insulation. The boron nitride particles are preferably agglomerated particles formed by agglomeration of primary particles. The primary particles of the boron nitride particles may be plate-like, flaky, or spherical, and are preferably flaky. The boron nitride particles used in this embodiment are preferably agglomerated particles of scaly boron nitride. This allows the boron nitride particles to be aligned, making it easier to improve thermal conductivity.

[0027] The average longitudinal length of the scaly (or plate-like) primary particles of boron nitride (i.e., the maximum length in the direction perpendicular to the thickness direction of the scales) is, for example, 1 to 100 μm, preferably 3 to 90 μm. The average longitudinal length of the boron nitride particles is 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, and most preferably 40 μm or more, and is usually, for example, 100 μm or less, preferably 90 μm or less.

[0028] The average thickness of the primary particles of the scaly boron nitride (the thickness direction length of the scales, that is, the length in the short direction of the particles) is, for example, 0.01 to 20 μm, or preferably 0.1 to 15 μm.

[0029] The aspect ratio (length in the longitudinal direction / thickness) of the primary particles of the scaly boron nitride is in the range of, for example, 2 to 10,000, or preferably 10 to 5,000.

[0030] The average primary particle diameter measured by the light scattering method is a volume average particle diameter measured by a dynamic light scattering particle size distribution analyzer. If the average primary particle diameter of the boron nitride particles measured by the light scattering method is less than the above range, the insulating layer 20 may become brittle and may become difficult to handle.

[0031] Specific examples of commercially available boron nitride particles include the "PT" series (e.g., "PT-110") manufactured by Momentive Performance Materials Japan, Inc., and the "SHOB N UHP" series (e.g., "SHOB N UHP-1") manufactured by Showa Denko K.K.

[0032] The content of the boron nitride particles is preferably 60% by mass or more and 80% by mass or less, more preferably 65% ​​by mass or more and 78% by mass or less, and even more preferably 70% by mass or more and 75% by mass or less, based on the total amount of the material (solid content) constituting the insulating layer 20. The content ratio of the boron nitride particles on a volume basis is preferably 50 to 70% by volume, and more preferably 55 to 65% by volume, based on the total volume of the material (solid content) constituting the insulating layer 20.

[0033] The resin material constituting the insulating layer 20 may further contain components other than the thermosetting resin and boron nitride particles.

[0034] For example, when the resin material constituting the insulating layer 20 contains an inorganic filler other than boron nitride particles, the proportion of the boron nitride particles relative to the total amount of the inorganic filler is preferably 80 mass % or more, more preferably 90 mass % or more, even more preferably 95 mass % or more, particularly preferably 99 mass % or more, and may be 100 mass %. Examples of inorganic fillers other than boron nitride particles include silica, alumina, aluminum nitride, and silicon carbide.

[0035] For example, when an epoxy resin is used as the thermosetting resin, it is preferable to use a curing agent, such as a curing catalyst or a phenol-based curing agent.

[0036] Examples of the curing catalyst include organic metal salts such as zinc naphthenate, cobalt naphthenate, tin octoate, cobalt octoate, bisacetylacetonate cobalt(II), and trisacetylacetonate cobalt(III); tertiary amines such as triethylamine, tributylamine, and 1,4-diazabicyclo[2.2.2]octane; 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, and 2-phenyl-4-methyl-5-hydroxyimidazole. imidazoles such as triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, 1,2-bis-(diphenylphosphino)ethane, and the like; organic phosphorus compounds such as phenol, bisphenol A, nonylphenol, and the like; organic acids such as acetic acid, benzoic acid, salicylic acid, p-toluenesulfonic acid, and the like; and mixtures thereof.

[0037] When a curing catalyst is used, the content thereof is preferably 0.001 part by mass or more and 1 part by mass or less relative to the total amount of the materials (solid content) constituting the insulating layer 20 .

[0038] Examples of phenolic curing agents include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, naphthol novolac resin, aminotriazine novolac resin, novolac resin, and trisphenylmethane-type phenol novolac resin; modified phenolic resins such as terpene-modified phenolic resin and dicyclopentadiene-modified phenolic resin; aralkyl-type resins such as phenol aralkyl resins having a phenylene skeleton and / or a biphenylene skeleton and naphthol aralkyl resins having a phenylene skeleton and / or a biphenylene skeleton; bisphenol compounds such as bisphenol A and bisphenol F; and resol-type phenolic resins. These may be used alone or in combination of two or more. The content of the phenolic curing agent is preferably 0.1% by mass or more and 30% by mass or less, and more preferably 0.3% by mass or more and 15% by mass or less, of the total amount of materials (solid content) constituting the insulating layer 20.

[0039] The resin material constituting the insulating layer 20 may further contain a leveling agent, a coupling agent, an antioxidant, and the like.

[0040] Examples of the leveling agent include an acrylic copolymer, etc. The leveling agent is preferably used in an amount of 2 mass % or less, and more preferably 0.01 mass % or more and 1.0 mass % or less, based on the total amount of the resin material (solid content) constituting the insulating layer 20.

[0041] Examples of the coupling agent that can be used include epoxy silane coupling agents, cationic silane coupling agents, amino silane coupling agents, titanate-based coupling agents, and silicone oil-based coupling agents. The amount of the coupling agent added is preferably 0.1 parts by mass or more and 10 parts by mass or less, and particularly preferably 0.5 parts by mass or more and 7 parts by mass or less, per 100 parts by mass of the boron nitride particles.

[0042] The resin material (solid content) constituting the insulating layer 20 of this embodiment can be prepared by blending the above-mentioned thermosetting resin, boron nitride particles, other components, and solvent in the above-mentioned ratios and stirring and mixing them by a known method.

[0043] Examples of the solvent include organic solvents such as ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and amides such as N,N-dimethylformamide. Examples of the solvent also include aqueous solvents such as water and alcohols such as methanol, ethanol, propanol, and isopropanol.

[0044] When a solvent is used for stirring and mixing, the solvent is removed after stirring and mixing by, for example, leaving the mixture at room temperature for 1 to 48 hours, heating at 40 to 100°C for 0.5 to 3 hours, or heating at 20 to 60°C for 0.5 to 3 hours under a reduced pressure of 0.001 to 50 kPa.

[0045] The insulating layer 20 of this embodiment can be produced by forming it into a sheet in a B-stage state. That is, the insulating layer 20 is completely cured when it is integrated with the heat sink 10 and the conductor layer 30 under heat and pressure during the manufacturing process of the heat sink-equipped circuit board 50.

[0046] The insulating layer sheet in the B-stage state can be obtained, for example, by applying the resin material in varnish form to a substrate, drying it, and then applying heat and pressure in a press. Examples of the substrate include metal foils that form heat dissipation members, lead frames, and peelable carrier materials, but the varnish-like resin material can also be applied directly to the heat sink 10. The heat and pressure treatment is performed, for example, at 80 to 150°C for 5 minutes to 1 hour. The thickness of the insulating layer 20 can be, for example, 60 μm or more and 500 μm or less.

[0047] In this embodiment, the specific gravity of the sheet-like insulating layer 20 (insulating layer sheet) in the B-stage state is preferably 1.0 to 2.0, and more preferably 1.5 to 1.9, which allows for more appropriate pressure application during the manufacturing process of the heatsink-equipped circuit board 50, making it easier to improve adhesion between the heatsink 10 and the conductor layer 30.

[0048] Furthermore, when the curing torque of the sheet-like insulating layer 20 in a B-stage state is measured at 180°C using a curastometer, the gel time A required to reach 10% of the maximum torque is preferably 30 to 180 seconds, more preferably 40 to 140 seconds, and even more preferably 50 to 100 seconds. This allows for more appropriate pressure application during the manufacturing process of the heatsink-equipped circuit board 50, making it easier to improve adhesion between the heatsink 10 and the conductor layer 30. The gel time is measured using a curast analysis method.

[0049] The gel time A required for reaching 10% torque of the maximum torque can be adjusted by adjusting the temperature at which the varnish-like resin material is applied and then heated and pressurized, or by adjusting the structure and type of thermosetting resin in the resin material, the combination of curing agent or curing catalyst, and the amount of curing agent or curing catalyst added, etc.

[0050] [Conductor Layer] The conductor layer 30 is disposed on the heat sink 10 via the insulating layer 20 to form a circuit. The conductor layer 30 may be a known layer obtained by a known method.

[0051] Furthermore, the arrangement of the conductor layer 30 in a plan view is set as appropriate, but it is preferable that the area surrounded by the outer peripheral edge of the conductor layer 30 is included in the area covered by the insulating layer 20 of the base plate 11. In other words, it is preferable that the conductor layer 30 is arranged within the area of ​​the insulating layer 20, i.e., on the insulating layer 20. This allows the conductor layer 30 and the insulating layer 20 to be more reliably adhered to each other.

[0052] <Method of Manufacturing a Circuit Board with a Heat Sink> The method of manufacturing a circuit board with a heat sink 50 of this embodiment includes the following steps: preparing a heat sink 10 including a flat base plate 11 and a plurality of fins 12 protruding from one side of the base plate 11; stacking an insulating layer 20 and a conductor layer 30 constituting a circuit, in this order, on the surface of the heat sink 10 facing the base plate 11; and integrating the stacked heat sink 10, insulating layer 20, and conductor layer 30 by applying heat and pressure. This will be described below.

[0053] First, the heat sink 10 can be any of those described above. Next, the insulating layer 20 and the conductor layer 30 constituting the circuit are laminated in this order on the surface of the heat sink 10 facing the base plate 11. Next, as shown in FIG. 2, heat and pressure are applied in the lamination direction using a known press device to completely harden the insulating layer 20, thereby integrating the heat sink 10, the insulating layer 20, and the conductor layer 30. For example, the heat sink 10, the insulating layer 20, and the conductor layer 30 laminated in this order are placed on a metal plate 61, and then a cushioning material 70 is placed on top, followed by heat and pressure application with a metal plate 62. Heat and pressure conditions of 150 to 250°C, 5 to 15 MPa, and 30 to 120 minutes are preferred. This allows for a heat sink-equipped circuit board 50 to be obtained that has an excellent balance of thermal conductivity and insulation, which allows heat from the conductor layer 30 to be transferred to the heat sink 10, while also achieving good adhesion between the conductor layer 30 and the heat sink 10. The cushioning material 70 may be any known material as long as it has good heat resistance and cushioning properties. Heat resistance and cushioning properties may also be achieved by combining multiple materials or sheets. Materials other than the cushioning material 70 may also be used as appropriate.

[0054] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various other configurations can also be adopted.

[0055] Next, the present invention will be described in detail with reference to examples, but the content of the present invention is not limited to the examples.

[0056] Example 1 (1) Preparation of Insulating Layer Sheets A sheet resin composition was prepared to have the composition (mass %) shown in Table 1. Specifically, each component shown in Table 1 was added to a cyclohexanone solvent and stirred using a high-speed stirrer to a liquid temperature of 35 to 38°C, yielding a varnish-like sheet resin composition. The resulting sheet resin composition was then molded to form an insulating layer sheet. Specifically, the sheet resin composition was applied to a polyethylene terephthalate (PET) film, dried at 110°C for 15 minutes, and then heated and pressurized in a press at 10 MPa and 140°C for 5 minutes to obtain a B-stage insulating layer sheet. The resulting insulating layer sheets all had a thickness of 100 μm and a specific gravity of 1.9.

[0057] Example 2 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that the heating and pressing conditions in the press were changed to 10 MPa, 150°C, and 5 minutes. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

[0058] Example 3 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that the heating and pressing conditions in the press were changed to 10 MPa, 120°C, and 5 minutes. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

[0059] Example 4 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that the amount of the curing catalyst shown in Table 1 was changed from 0.5 parts by weight to 0.1 parts by weight. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

[0060] Example 5 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that the heating and pressing conditions in the press were changed to 10 MPa, 120°C, and 5 minutes, and the amount of the curing catalyst shown in Table 1 was changed from 0.5 parts by weight to 0.1 parts by weight. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

[0061] Example 6 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that the bisphenol F type epoxy resin shown in Table 1 was changed to an epoxy resin having a naphthalene skeleton. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

[0062] Example 7 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that 50 parts by weight of the bisphenol F type epoxy resin shown in Table 1 was changed to 30 parts by weight of an epoxy resin having a naphthalene skeleton and 20 parts by weight of a trisphenolmethane type epoxy resin. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

[0063] Comparative Example 1 A sheet for an insulating layer was obtained in the same manner as in Example 1, except that 300 parts by weight of the boron nitride particles shown in Table 1 were changed to 100 parts by weight of alumina particles. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 2.6.

[0064] The details of each component in Table 1 are as follows: (Thermosetting resin) Bisphenol F type epoxy resin: "830S" manufactured by DIC Corporation Epoxy resin having a naphthalene skeleton: "HP-4032" manufactured by DIC Corporation Trisphenolmethane type epoxy resin: "1032H60" manufactured by Mitsubishi Chemical Corporation Phenoxy resin: "YP55U" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. (Curing agent) Novolac type phenolic resin: "PR-51470" manufactured by Sumitomo Bakelite Co., Ltd. Imidazole: "2P4MZ" manufactured by Shikoku Chemicals Co., Ltd. (Inorganic filler) Boron nitride particles: "HP-40" manufactured by Mizushima Ferroalloy Co., Ltd. Alumina particles: "AO-509" manufactured by Admatechs Co., Ltd.

[0065] (2) Preparation of a circuit board with a heat sink The obtained insulating layer sheet and a 0.5 mm copper circuit were laminated in this order on a heat sink 10 ("Pin Fin Heat Sink" manufactured by Taiwa Kogyo Co., Ltd., flat plate thickness 2 mm, round fin pillars, pitch 1 mm), and heated and pressurized using a hot and pressurized press at 200°C, 10 MPa, and for 60 minutes to obtain a circuit board with a heat sink.

[0066] (3) Evaluation The following evaluations were carried out using the obtained insulating layer sheets. The results are shown in Table 1.

[0067] Measurement method for gel time A until 10% torque is reached The gel time A (GT) until 10% torque is reached of the obtained insulating layer sheet was measured using a curastometer. The measurement using the curastometer was carried out at 180°C, and the gel time A was defined as the time until 10% torque of the maximum torque was reached.

[0068] The following evaluations were carried out using the obtained circuit board with a heat sink. The results are shown in Table 1. Adhesion: Method for measuring shear adhesion strength The obtained circuit board with a heat sink was cut into a length of 3 mm and a width of 3 mm by cutting to prepare a test sample. The shear adhesion strength [MPa] of the prepared test sample was measured at room temperature (25°C) using a Bond Tester / DAGE-5000 device by moving a shear tool horizontally at a speed of 80 μm / sec with a distance of 20 μm from the upper surface of the copper circuit of the test sample.

[0069] Thermal conductivity and heat dissipation: The thermal conductivity of the circuit board with heat sink was measured in the thickness direction. Specifically, the thermal conductivity was calculated using the following formula from the thermal diffusion coefficient (α) measured by the laser flash method (half-time method), the specific heat (Cp) measured by the DSC method, and the density (ρ) measured in accordance with JIS-K-6911. The measurement temperature was 25°C. Formula: Thermal conductivity [W / (m K)] = α [mm ２ / s]×Cp[J / kg・K]×ρ[g / cm ３ ]

[0070] Breakdown Voltage The breakdown voltage (kV) was measured by a method in accordance with JIS C2110-1.

[0071]

[0072] This application claims priority based on Japanese Patent Application No. 2022-148869, filed September 20, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0073] REFERENCE SIGNS 10 Heat sink 11 Base plate 12 Fin 20 Insulating layer 30 Conductive layer 50 Circuit board with heat sink 61 Metal plate 62 Metal plate 70 Cushioning material

Claims

1. A step of preparing a heat sink including a flat base plate and a plurality of fins protruding from one side of the base plate; A step of heating and pressurizing a material containing a thermosetting resin and boron nitride particles at 80 to 140° C. for 5 minutes to 1 hour to obtain an insulating layer sheet in a B-stage state; laminating the insulating layer sheet and a conductor layer constituting a circuit in this order on a surface of the heat sink facing the base plate; a step of heating and pressurizing the laminated heat sink, the insulating layer sheet, and the conductor layer constituting the circuit to harden the insulating layer sheet, thereby obtaining an insulating layer and integrating them; A method for manufacturing a circuit board with a heat sink, comprising:

2. A method for manufacturing the circuit board with a heat sink according to claim 1, In the step of integrating, heating and pressurizing are performed at 150 to 250° C. and 5 to 15 MPa.

3. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising the steps of: The method for producing a circuit board with a heat sink, wherein the insulating layer sheet satisfies the following conditions: (Condition) When the curing torque of the insulating layer sheet in the B-stage state is measured at 180° C. using a curastometer, the gel time A required to reach 10% of the maximum torque is 30 to 180 seconds.

4. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising the steps of: In the integrating step, the heat sink, the sheet for insulating layer, and a conductor layer constituting the circuit are integrated together in a single step.

5. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising: A method for manufacturing a circuit board with a heat sink, wherein in the circuit board with a heat sink, a region surrounded by an outer edge of a conductor layer is included in a region of the base plate covered by the insulating layer.

6. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising: A method for manufacturing a circuit board with a heat sink, wherein in the circuit board with a heat sink, the area surrounded by an outline connecting the outer ends of the fins is included in the area of ​​the base plate covered by the insulating layer.

7. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising: The method for producing a circuit board with a heat sink, wherein the thermosetting resin contains at least one of an epoxy resin having a naphthalene skeleton and a trisphenolmethane type epoxy resin.

8. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising the steps of: A method for producing a circuit board with a heat sink, wherein the content of the boron nitride particles is 60 mass% or more based on the total amount of the insulating layer.

9. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising: The method for producing a circuit board with a heat sink, wherein the heat sink is made of at least one material selected from the group consisting of copper and aluminum.

10. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising the steps of: The method for producing a circuit board with a heat sink, wherein the sheet for an insulating layer further contains an imidazole.

11. A method for manufacturing a circuit board with a heat sink according to claim 1 or 2, comprising the steps of: A method for producing a circuit board with a heat sink, wherein the boron nitride is scaly boron nitride.