JP7635897B2 - Manufacturing method for circuit board with heat sink - Google Patents

Description

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

A circuit board with a heat sink is known in which a conductor layer constituting a circuit and one side of a large-capacity heat sink are integrated via an insulating layer (for example, Patent Document 1). Among them, a heat sink with fins is known to improve 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 in which a circuit layer is formed on one side of a ceramic substrate and a metal layer is formed on the other side, and a heat sink having multiple fins on one side, which is disposed on the side of the metal layer opposite the ceramic substrate.

JP 2016-82108 A JP 2020-13915 A

In the manufacturing process of a circuit board with a heat sink, the finned heat sink is pressurized in the stacking direction when the conductor layer and the insulating layer are integrated together. At this time, the adhesion between the heat sink and the insulating layer and the conductor layer can be improved by increasing the pressure, but there is a limit to the pressure when considering the mechanical strength of the fins. Therefore, there is room for improvement in the adhesion between the conductor layer and the heat sink.
Therefore, the inventors conducted intensive research and discovered that by using an appropriate insulating layer, it is possible to obtain good adhesion between the conductor layer and the heat sink while also achieving an excellent balance of good thermal conductivity and insulation properties for transferring heat from the conductor layer to the heat sink, and thus completed the present invention.

According to the present invention, the following technology is provided for a circuit board with a heat sink:

[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,
The heat sink includes a flat base plate and a plurality of fins protruding from a surface opposite to the insulating layer,
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],
A circuit board with a heat sink, wherein an area surrounded by an outer peripheral edge of the conductor layer is included within an area of the base plate that is covered by the insulating layer.
[3] The circuit board with a heat sink according to [1] or [2],
A circuit board with a heat sink, wherein an area surrounded by an outline connecting the outer ends of the fins is included within an area of the base plate that is covered with the insulating layer.
[4] A circuit board with a heat sink according to any one of [1] to [3],
The 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.
[5] A circuit board with a heat sink according to any one of [1] to [4],
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.
[6] A circuit board with a heat sink according to any one of [1] to [5],
The heat sink of the circuit board is made of at least one material selected from the group consisting of copper and aluminum.
[7] 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;
laminating an insulating layer and a conductor layer constituting a circuit in this order on a surface of the heat sink facing the base plate;
a step of integrating the laminated heat sink, the insulating layer, and the conductor layer constituting the circuit by applying heat and pressure;
Including,
A method for manufacturing a circuit board with a heat sink, 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], comprising the steps of:
In the step of integrating, heating and pressurizing are performed at 150 to 250° C. and 5 to 15 MPa.
[9] A method for producing a circuit board with a heat sink according to [7] or [8], comprising the steps of:
A method for manufacturing a circuit board with a heat sink, wherein the insulating layer satisfies the following conditions:
(Condition) When the curing torque of the insulating layer in the B stage 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],
A method for manufacturing a circuit board with a heat sink, wherein in the process of laminating the insulating layer and the conductor layer constituting the circuit in this order on the base plate side surface of the heat sink, the insulating layer is sheet-shaped.
[11] A method for manufacturing a circuit board with a heat sink according to any one of [7] to [10],
In the integrating step, the heat sink, the insulating layer, and a conductor layer that constitutes the circuit are integrated together in a single step.

According to the present invention, in a circuit board with a finned heat sink, it is possible to obtain good adhesion between the conductor layer and the heat sink while achieving an excellent balance of good thermal conductivity and insulation for transferring heat from the conductor layer to the heat sink.

1 is a cross-sectional view that illustrates a schematic diagram of a heat sink-attached circuit board according to an embodiment. 5A to 5C are cross-sectional views each showing a schematic process of a method for manufacturing a circuit board with a heat sink according to an embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
In all drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. Note that the drawings are for explanatory purposes only. The shapes and dimensional ratios of the components in the drawings do not necessarily correspond to the actual products.

In this specification, the notation "a to b" in the explanation of a numerical range means from a to b, unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass to 5% by mass."

<Circuit board with heat sink>
FIG. 1 is a cross-sectional view of a heat sink-fitted circuit board 50 according to the present embodiment.
1, in the circuit board with heat sink 50, a conductor layer 30 constituting a circuit and a heat sink 10 are integrated via an insulating layer 20. The heat sink 10 includes a flat base plate 11 and a plurality of fins 12 protruding from the surface opposite to the insulating layer 20, and the insulating layer 20 is made of a material containing a thermosetting resin and boron nitride particles.
By having such a configuration, the circuit board with heat sink 50 can achieve good adhesion between the conductor layer 30 and the heat sink 10, while also achieving an excellent balance of good thermal conductivity and insulation for transferring heat from the conductor layer 30 to the heat sink 10.

The details of each component are explained below.

[heat sink]
The heat sink 10 has a 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 the insulating layer 20. The flat base plate 11 and the fins 12 may be joined by a known method, or may be integrally molded.

The heat sink 10 is preferably made of at least one material selected from copper and aluminum, and copper is more preferable from the viewpoint of improving thermal conductivity, processability, etc.

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. In addition, 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 heat sink-equipped circuit board 50 can be suppressed and adhesion can be improved.

The heat sink 10 has multiple fins 12 that stand upright from one side of the base plate 11, which increases the surface area of the heat sink 10 and improves heat dissipation efficiency. The multiple fins 12 are flush. The multiple fins 12 are of uniform height and the top surfaces of the fins 12 are flat, which allows for the stable manufacture of the heat sink-equipped circuit board 50.

The shape of the fin 12 is not particularly limited, but may be, for example, a polygonal columnar shape such as a square or hexagonal columnar shape, or a cylindrical shape. The above-mentioned quadrangular columnar shape may be a columnar shape having a square cross-sectional shape, a rectangular columnar shape, a rhombus columnar shape, a parallelogram columnar shape, etc. The above-mentioned cylindrical shape may be a columnar shape having a circular, elliptical, oval, etc. cross-sectional shape.

The number of fins 12 is not particularly limited and is set appropriately from the viewpoints of the application, mechanical strength, etc. The shapes of the fins 12 may be the same as each other, may be different, or may differ only in part.

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 base plate 11 does not have fins 12 at the outer peripheral end.
This makes it possible to improve adhesion while maintaining mechanical strength against pressure applied during the manufacturing process of the circuit board 50 fitted with a heat sink.

The spacing between the multiple fins 12 is not particularly limited, but is preferably 0.5 to 2.0 mm. By making the spacing between the fins 12 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 heat sink-equipped circuit board 50. In addition, by making the spacing between the fins 12 2.0 mm or less, the heat dissipation performance of the heat sink 10 can be further improved.

[Insulating layer]
The insulating layer 20 is used to provide insulation so that electricity passed through the conductor layer 30 does not leak to the heat sink 10 side.
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. In addition, the insulating layer 20 has excellent resin filling properties between the fillers and can efficiently improve thermal conductivity and increase adhesion by applying pressure during the manufacturing process of the heat sink-equipped circuit board 50.
Each component of the resin material will be described below.

(Resin material)
Thermosetting Resin Examples of the thermosetting resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol M type epoxy resin (4,4'-(1,3-phenylenediisopridiene) bisphenol type epoxy resin), bisphenol P type epoxy resin (4,4'-(1,4-phenylenediisopridiene) bisphenol type epoxy resin), and bisphenol Z type epoxy resin (4,4'-cyclohexydiene bisphenol type epoxy resin); 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.

The above-mentioned 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 the epoxy resins, it is more preferable to contain at least one of epoxy resin having a naphthalene skeleton, which has excellent dispersibility of boron nitride particles, thermal conductivity of the insulating layer sheet, and adhesion to copper and aluminum of the insulating layer sheet, and trisphenolmethane type epoxy resin.

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 bifunctional cyanate resins such as 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether, and bis(4-cyanatephenyl)ether; polyfunctional cyanate resins derived from phenol novolac, cresol novolac, and dicyclopentadiene structure-containing phenolic resins; and prepolymers in which the above-listed cyanate ester resins are partially converted to triazine.
Here, examples of commercially available cyanate ester resins that can be used include PT30, BA230, DT-4000, and DT-7000 manufactured by Lonza Japan.

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.

Boron nitride particles Boron nitride (BN) particles are an inorganic filler that imparts thermal conductivity and electrical insulation properties.
The boron nitride particles are preferably aggregated particles formed by agglomeration of primary particles. The primary particles of the boron nitride particles may be plate-like, scaly, or spherical, and are preferably scaly. The boron nitride particles used in this embodiment are preferably aggregated particles of scaly boron nitride. This allows the boron nitride particles to be aligned, making it easier to improve thermal conductivity.

The average longitudinal length of the scale-like (or plate-like) primary particles of boron nitride (the maximum length in the direction perpendicular to the thickness direction of the scale) 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.

In addition, the average thickness of the primary particles of the scaly boron nitride (the thickness direction length of the scales, i.e., the short direction length of the particles) is, for example, 0.01 to 20 μm, preferably 0.1 to 15 μm.

In addition, the aspect ratio (longitudinal length/thickness) of the primary particles of the scaly boron nitride is, for example, 2 to 10,000, preferably 10 to 5,000.

The average primary particle diameter measured by the light scattering method is the volume average particle diameter measured by a dynamic light scattering particle size distribution measuring device. If the average primary particle diameter of the boron nitride particles measured by the light scattering method does not fall within the above range, the insulating layer 20 may become brittle and its handleability may decrease.

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

The content of boron nitride particles is preferably 60 mass % or more and 80 mass % or less, more preferably 65 mass % or more and 78 mass % or less, and even more preferably 70 mass % or more and 75 mass % or less, relative to the total amount of materials (solid content) constituting the insulating layer 20.
The volumetric content of the boron nitride particles is preferably 50 to 70 volume %, and more preferably 55 to 65 volume %, based on the total volume of the material (solid content) that constitutes the insulating layer 20 .

The resin material constituting the insulating layer 20 may further contain components other than the above-mentioned thermosetting resin and boron nitride particles.

For example, when the resin material constituting the insulating layer 20 contains an inorganic filler other than boron nitride particles, the ratio of the boron nitride particles 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.

Hardener For example, when an epoxy resin is used as the thermosetting resin, it is preferable to use a hardener.
As the curing agent, it is preferable to use a curing catalyst or a phenol-based curing agent.

Examples of curing catalysts include organic metal salts such as zinc naphthenate, cobalt naphthenate, tin octoate, cobalt octoate, cobalt bisacetylacetonate (II), and cobalt trisacetylacetonate (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 2-phenyl-4,5-dihydroxymethylimidazole; organic phosphorus compounds such as triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, 1,2-bis-(diphenylphosphino)ethane; phenolic compounds such as phenol, bisphenol A, nonylphenol; organic acids such as acetic acid, benzoic acid, salicylic acid, p-toluenesulfonic acid; and the like, or mixtures thereof.

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

Examples of the phenol-based curing agent 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 phenol-based curing agent is preferably 0.1 mass % or more and 30 mass % or less, and more preferably 0.3 mass % or more and 15 mass % or less, based on the total amount of materials (solid content) constituting the insulating layer 20 .

The resin material constituting the insulating layer 20 may further contain a leveling agent, a coupling agent, an antioxidant, etc.

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

As the coupling agent, an epoxy silane coupling agent, a cationic silane coupling agent, an amino silane coupling agent, a titanate-based coupling agent, a silicone oil-type coupling agent, or the like can be used.
The amount of the coupling agent is preferably from 0.1 to 10 parts by mass, and particularly preferably from 0.5 to 7 parts by mass, per 100 parts by mass of the boron nitride particles.

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.

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 include water and aqueous solvents such as alcohols such as methanol, ethanol, propanol, and isopropanol.

When a solvent is used for stirring and mixing, the solvent is removed after stirring and mixing. To remove the solvent, for example, the mixture is left at room temperature for 1 to 48 hours, or heated at 40 to 100°C for 0.5 to 3 hours, or heated at 20 to 60°C for 0.5 to 3 hours in a reduced pressure atmosphere of 0.001 to 50 kPa.

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 heated and pressurized to be integrated with the heat sink 10 and the conductor layer 30 during the manufacturing process of the heat sink-equipped circuit board 50.

The insulating layer sheet in the B-stage state can be obtained, for example, by applying the above-mentioned resin material in a varnish form onto a substrate, drying it, and further subjecting it to a heat and pressure treatment in a press.
The substrate may be, for example, a metal foil that constitutes a heat dissipation member, a lead frame, a peelable carrier material, or the like, but a varnish-like resin material may also be applied directly onto the heat sink 10 .
The above heat and pressure treatment is carried out under conditions of, for example, 80 to 150° C. and 5 minutes to 1 hour.
The thickness of the insulating layer 20 can be, for example, not less than 60 μm and not more than 500 μm.

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. This allows more appropriate pressure to be applied during the manufacturing process of the heat sink-attached circuit board 50, making it easier to increase adhesion with the heat sink 10 and the conductor layer 30.

Furthermore, when the curing torque of the sheet-like insulating layer 20 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 preferably 30 to 180 (seconds), more preferably 40 to 140 seconds, and even more preferably 50 to 100 seconds. This allows more appropriate pressure to be applied in the manufacturing process of the heatsink-fitted circuit board 50, making it easier to improve adhesion between the heatsink 10 and the conductor layer 30.
The gel time is measured by a curast analysis method.

The gel time A required to reach 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.

[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 any known layer obtained by a known method.

The arrangement of the conductor layer 30 in 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.

<Method of manufacturing a circuit board with a heat sink>
The method for manufacturing the circuit board 50 with a heat sink of this embodiment includes the following steps.
A step of preparing a heat sink 10 including a flat base plate 11 and a plurality of fins 12 protruding from one surface of the base plate 11;
a step of laminating an insulating layer 20 and a conductor layer 30 constituting a circuit in this order on a surface of the heat sink 10 on the side of the base plate 11;
and a step of integrating the laminated heat sink 10, insulating layer 20, and conductor layer 30 by applying heat and pressure.
The following explains.

First, the above-mentioned material can be used as the heat sink 10. 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 on the base plate 11 side.
2, a known press device is used to apply heat and pressure in the stacking direction 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 are stacked in this order and placed on a metal plate 61, a cushion material 70 is placed on top, and the layers are heated and pressed together with a metal plate 62.
The heating and pressing conditions are preferably 150 to 250° C., 5 to 15 MPa, and 30 to 120 minutes.
This makes it possible to obtain a circuit board with a heat sink 50 that has good adhesion between the conductor layer 30 and the heat sink 10 while having an excellent balance of good thermal conductivity and insulation for transmitting heat from the conductor layer 30 to the heat sink 10.
The cushioning material 70 may be any material having good heat resistance and cushioning properties, and may be any known material. Heat resistance and cushioning properties may be obtained by combining a plurality of materials and sheets. Materials other than the cushioning material 70 may also be used as appropriate.

The above describes embodiments of the present invention with reference to the drawings, but these are merely examples of the present invention and various configurations other than those described above can also be adopted.

Next, the present invention will be described in detail using examples, but the contents of the present invention are not limited to the examples.

Example 1
(1) Preparation of Sheet for Insulation Layer A resin composition for a sheet was prepared so as 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 so that the liquid temperature became 35 to 38°C, to obtain a varnish-like resin composition for a sheet.
The obtained resin composition for sheet was then molded to form an insulating layer sheet. Specifically, the resin composition for sheet was applied onto a polyethylene terephthalate (PET) film, dried at 110° C. for 15 minutes, and then heated and pressed at 10 MPa and 140° C. for 5 minutes in a press machine to obtain an insulating layer sheet in a B-stage state.
The thickness of each of the obtained insulating layer sheets was 100 μm, and the specific gravity was 1.9.

Example 2
Except for changing the heating and pressing conditions in the press machine to 10 MPa, 150° C., and 5 minutes, a sheet for an insulating layer was obtained in the same manner as in Example 1. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

Example 3
Except for changing the heating and pressing conditions in the press machine to 10 MPa, 120° C., and 5 minutes, a sheet for an insulating layer was obtained in the same manner as in Example 1. The thickness of the obtained sheet for an insulating layer was 100 μm, and the specific gravity was 1.9.

Example 4
Except for changing the amount of the curing catalyst shown in Table 1 from 0.5 parts by weight to 0.1 parts by weight, an insulating layer sheet was obtained in the same manner as in Example 1. The insulating layer sheet obtained had a thickness of 100 μm and a specific gravity of 1.9.

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

Example 6
Except for changing the bisphenol F type epoxy resin shown in Table 1 to an epoxy resin having a naphthalene skeleton, an insulating layer sheet was obtained in the same manner as in Example 1. The insulating layer sheet obtained had a thickness of 100 μm and a specific gravity of 1.9.

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

<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.

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 with naphthalene structure: "HP-4032" manufactured by DIC Corporation; Trisphenol methane type epoxy resin: "1032H60" manufactured by Mitsubishi Chemical Corporation; Phenoxy resin: "YP55U" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. (hardener)
・Novolac type phenolic resin: "PR-51470" manufactured by Sumitomo Bakelite Co., Ltd. ・Imidazole: "2P4MZ" manufactured by Shikoku Kasei Co., Ltd. (inorganic filler)
・Boron nitride particles: "HP-40" manufactured by Mizushima Ferroalloy Co., Ltd. ・Alumina particles: "AO-509" manufactured by Admatechs Co., Ltd.

(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 that order on a heat sink 10 ("Pin Fin Heat Sink" manufactured by Taiwa Kogyo Co., Ltd., flat plate thickness 2 mm, round fin pillar, pitch 1 mm), and heated and pressed at 200°C, 10 MPa, and for 60 minutes using a hot and pressurized press device to obtain a circuit board with a heat sink.

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

Measurement method of 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 time until 10% torque of the maximum torque was reached was defined as the gel time A.

The obtained circuit board with a heat sink was subjected to the following evaluations. The results are shown in Table 1.
Adhesion: Method for measuring shear adhesion strength The obtained circuit board with heat sink was cut into a length of 3 mm and a width of 3 mm by cutting to prepare a test sample.
The prepared test samples were subjected to measurement of shear adhesion strength [MPa] at room temperature (25°C) using a bond tester/DAGE-5000 device, with a shear tool moved 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.

Thermal Conductivity and Heat Dissipation The thermal conductivity of the circuit board with heat sink in the thickness direction was measured.
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 ]

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

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

REFERENCE SIGNS 10: heat sink 11: base plate 12: fins 20: insulating layer 30: conductor layer 50: circuit board with heat sink 61: metal plate 62: metal plate 70: cushioning material

Claims (11)

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 : 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 , 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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1 , 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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, comprising the steps of:
A method for manufacturing a circuit board with a heat sink, wherein in the circuit board with a heat sink, a region surrounded by the outer edge of the conductor layer is included in a region of the base plate covered by the insulating layer. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, comprising the steps of:
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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, comprising the steps of:
The method for manufacturing 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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, 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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, comprising the steps of:
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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, 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. 3. A method for manufacturing a circuit board with a heat sink according to claim 1, comprising the steps of:
A method for producing a circuit board with a heat sink, wherein the boron nitride is scaly boron nitride.

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