Heat sink-attached circuit board and manufacturing method thereof

Abstract

A heat sink-attached circuit board (50) comprises a circuit layer (30) and a heat sink (10) which are integrated via an insulating layer (20), wherein the heat sink (10) has a flat base plate (11), a sealing resin (40) is provided between a plurality of circuit bodies (31) constituting the circuit layer (30), the upper surface (32) of the circuit layer (30) is disposed below the upper surface (41) of the sealing resin (40), and a portion of the upper surface (32) of the circuit layer (30) is exposed from the sealing resin (40).

Description

Circuit board with heat sink and manufacturing method thereof

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

[0002] A conventional circuit board with a heat sink is described in Japanese Patent Laid-Open No. 2016-82108 (Patent Document 1). This circuit board with a heat sink is formed by integrating a conductor layer constituting a circuit and one surface of a large-capacity heat sink via an insulating layer.

[0003] JP 2016-82108 A

[0004] When many circuits are arranged in a small space on the above-mentioned circuit board with a heat sink, it may be difficult to ensure a creepage distance between the circuits.

[0005] The circuit board with a heat sink of the present disclosure is a circuit board with a heat sink in which a circuit layer and a heat sink are integrated via an insulating layer, the heat sink has a flat base plate, a sealing resin is provided between multiple circuit bodies that make up the circuit layer, the upper surface of the circuit layer is arranged below the upper surface of the sealing resin, and a portion of the upper surface of the circuit layer is exposed from the sealing resin.

[0006] a first arrangement step of arranging the plurality of circuit bodies in the first mold so that the plurality of convex portions contact one side of the plurality of circuit bodies; a second arrangement step of stacking an insulating layer and the base plate on the other side of the plurality of circuit bodies and arranging the insulating layer between the base plate and the plurality of circuit bodies; a third arrangement step of assembling the first mold and the second mold to form the cavity; and a step of forming an encapsulating resin by filling the cavity with an encapsulating resin composition.

[0007] According to the present disclosure, it is possible to provide a circuit board with a heat sink that can easily ensure creepage distances between a plurality of circuit bodies.

[0008] Fig. 1 is a plan view of a circuit board with a heat sink according to an embodiment. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1. Fig. 4 is an enlarged view of Fig. 3. Fig. 5 is an explanatory diagram illustrating a first arrangement step. Fig. 6 is an explanatory diagram illustrating a second arrangement step. Fig. 7 is an explanatory diagram illustrating a third arrangement step.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. [1] A circuit board with a heat sink of the present disclosure is a circuit board with a heat sink in which a circuit layer and a heat sink are integrated via an insulating layer, the heat sink has a flat base plate, a sealing resin is provided between a plurality of circuits constituting the circuit layer, an upper surface of the circuit layer is disposed below an upper surface of the sealing resin, and a portion of the upper surface of the circuit layer is exposed from the sealing resin.

[0010] With this configuration, a portion of the upper surface of the circuit layer is exposed from the sealing resin, and the other portion of the upper surface of the circuit layer is covered with the sealing resin, making it easy to ensure creepage distances between the multiple circuit bodies.

[0011] [2] In the above [1], it is preferable that a plurality of through holes are formed in the circuit body.

[0012] According to this configuration, the plurality of through holes in the circuit body can be used to position the plurality of circuit bodies on the heat sink-equipped circuit board.

[0013] [3] A method for manufacturing a circuit board with a heat sink according to the present disclosure includes the steps of: preparing a heat sink having a flat base plate; preparing a plurality of circuit bodies; preparing a mold including a first mold having a plurality of convex portions and a second mold that, together with the first mold, forms a cavity in which the plurality of convex portions are arranged; a first arrangement step of arranging the plurality of circuit bodies in the first mold so that the plurality of convex portions contact one side of the plurality of circuit bodies; a second arrangement step of stacking an insulating layer and the base plate on the other side of the plurality of circuit bodies and arranging the insulating layer between the base plate and the plurality of circuit bodies; a third arrangement step of assembling the first mold and the second mold to form the cavity; and a step of forming an encapsulating resin by filling the cavity with an encapsulating resin composition.

[0014] According to this method for manufacturing a circuit board with a heat sink, the portions of the circuit body that come into contact with the protrusions can be exposed from the sealing resin, while the portions of the circuit body that do not come into contact with the protrusions can be buried in the sealing resin. This makes it easier to ensure creepage distance between the multiple circuit bodies. Furthermore, according to the above method for manufacturing a circuit board with a heat sink, the process of removing part of the sealing resin to expose part of the top surfaces of the multiple circuit bodies after forming the sealing resin is not required.

[0015] [4] In the above [3], it is preferable that in the step of preparing the plurality of circuit bodies, a plurality of through holes are formed in the plurality of circuit bodies, and in the step of preparing the mold, a plurality of protrusions are formed on the first mold, and in the first positioning step, the plurality of circuit bodies are positioned relative to the first mold by inserting the protrusions into the through holes.

[0016] According to this method for manufacturing a circuit board with a heat sink, it is possible to position a plurality of circuit bodies on the circuit board with a heat sink.

[0017] [Details of the Embodiments of the Present Disclosure] The following describes embodiments of the present disclosure. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. In the drawings, for the convenience of explanation, some components may be exaggerated or simplified. Furthermore, the dimensional ratios of each part may differ between drawings. In this specification, "orthogonal" does not only refer to a strict orthogonal relationship, but also includes a roughly orthogonal relationship within the scope of the operation and effect of this embodiment.

[0018] 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."

[0019] 1 to 7, an embodiment of the present disclosure will be described. In the following description, the direction indicated by the arrow Z is defined as upward, the direction indicated by the arrow X is defined as forward, and the direction indicated by the arrow Y is defined as leftward. Note that, in some cases, when multiple identical components are used, only some of the components will be designated by reference numerals, and the reference numerals for the other components will be omitted.

[0020] (Circuit Board 50 with Heat Sink) As shown in FIGS. 1 and 2, the circuit board 50 with heat sink includes a heat sink 10, an insulating layer 20, a circuit layer 30, and a sealing resin 40.

[0021] (Heat Sink 10) The heat sink 10 has a function of dissipating heat generated in the circuit layer 30 etc. to the outside. That is, the heat sink 10 has thermal conductivity. The heat sink 10 includes a flat base plate 11.

[0022] The heat sink 10 is made of, for example, a metal. The metal constituting the heat sink 10 is preferably at least one selected from copper and aluminum, and more preferably copper from the viewpoint of improving thermal conductivity, workability, etc.

[0023] 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 circuit layer 30, warping of the entire heatsink-equipped circuit board 50 can be suppressed, and adhesion can be easily improved.

[0024] The heat sink 10 may also include multiple fins (not shown) that protrude from the surface of the base plate 11 opposite the insulating layer 20. By providing multiple fins on the heat sink 10, the surface area of ​​the heat sink 10 can be increased, thereby improving heat dissipation efficiency.

[0025] 2 , the insulating layer 20 is disposed between the circuit layer 30 and the heat sink 10. The insulating layer 20 provides insulation between the circuit layer 30 and the heat sink 10. The outer peripheral edge of the insulating layer 20 is covered with a sealing resin 40. This makes it possible to prevent the insulating layer 20 from peeling off from the heat sink 10.

[0026] The insulating layer 20 is preferably made of a 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 heatsink-equipped circuit board 50, the boron nitride particles disperse, efficiently improving thermal conductivity and increasing adhesion.

[0027] The thermosetting resin may be one or more selected from the group consisting of 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, and cyanate resins. This facilitates improving the dispersibility of the boron nitride particles.

[0028] 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.

[0029] The content of the thermosetting resin is preferably in the range of 1 mass % to 30 mass % and more preferably in the range of 5 mass % to 28 mass % relative to the total amount of materials (solid content) constituting the insulating layer 20 .

[0030] 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, scaly, or spherical, and are preferably scaly. 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The content of the boron nitride particles is 60% by mass or more and 80% by mass or less, and more preferably 65% ​​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.

[0037] The material constituting the insulating layer 20 may further contain components other than the thermally conductive resin and boron nitride particles.

[0038] 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.

[0039] Examples of the curing catalyst include tertiary amines such as triethylamine, tributylamine, and 1,4-diazabicyclo[2.2.2]octane; imidazoles such as 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, 2-phenyl-4-methyl-5-hydroxyimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole; organic phosphorus compounds such as triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, and 1,2-bis-(diphenylphosphino)ethane; phenolic compounds such as phenol, bisphenol A, and nonylphenol; organic acids such as acetic acid, benzoic acid, salicylic acid, and p-toluenesulfonic acid; and mixtures thereof.

[0040] 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 .

[0041] 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.

[0042] The material constituting the insulating layer 20 may further contain a leveling agent, a coupling agent, an antioxidant, and the like.

[0043] Examples of the leveling agent include acrylic copolymers, 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 materials (solid content) constituting the insulating layer 20.

[0044] 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.

[0045] The 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.

[0046] 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.

[0047] The insulating layer 20 of this embodiment can be fabricated by forming it into a sheet in a B-stage state. That is, the insulating layer 20 is fully cured when it is heated and pressurized to be integrated with the heat sink 10 and the circuit layer 30 during the manufacturing process of the heat sink-equipped circuit board 50. For example, the insulating layer 20 can be formed into a sheet by applying the above-mentioned varnish-like material to a substrate and then heat-treating and drying the applied material. Examples of substrates include metal foils that form heat dissipation members, lead frames, and releasable carrier materials, but the insulating layer 20 can also be applied directly to the heat sink 10. The heat treatment to dry the applied film 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 to 500 μm.

[0048] In this embodiment, the specific gravity of the sheet-like insulating layer 20 in the B-stage state is preferably 1.0 to 2.0, which allows the insulating layer 20 to be more appropriately pressurized during the manufacturing process of the heatsink-equipped circuit board 50, making it easier to improve adhesion between the heatsink 10 and the circuit layer 30.

[0049] (Circuit Layer 30) As shown in Fig. 2, the circuit layer 30 is disposed on the heat sink 10 via the insulating layer 20. The insulating layer 20 is interposed between the circuit layer 30 and the heat sink 10. The circuit layer 30 is composed of a plurality of circuit bodies 31. The circuit bodies 31 are plate-shaped. Metals that can be used to compose the circuit layer 30 (circuit bodies 31) include copper, aluminum, nickel, gold, silver, stainless steel, and the like.

[0050] 1, in this embodiment, the circuit body 31 is elongated in the front-rear direction and has a rectangular shape in a plan view. The plurality of circuit bodies 31 are arranged side by side in the left-right direction. Note that the shape and arrangement of the plurality of circuit bodies 31 in a plan view may differ from those in this embodiment.

[0051] It is preferable that the area surrounded by the outer peripheral edge of the circuit 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 circuit layer 30 is disposed inside the insulating layer 20 in a plan view. That is, it is preferable that the circuit layer 30 is disposed on the insulating layer 20. This allows the circuit layer 30 and the insulating layer 20 to be more reliably adhered to each other.

[0052] 2 , spaces between the plurality of circuit bodies 31 are filled with sealing resin 40. The upper surface 32 of the circuit body 31 has an exposed portion 32A exposed from the sealing resin 40 and a covered portion 32B covered by the sealing resin 40. The upper surface 32 of the circuit body 31 is disposed below the upper surface 41 of the sealing resin 40. With this configuration, the upper surface 32 of the circuit layer 30 is partially covered by the sealing resin 40, making it easier to ensure a creepage distance between the plurality of circuit bodies 31.

[0053] 1 and 3, a plurality of through holes 33 are formed in the circuit body 31. In this embodiment, the plurality of through holes 33 are arranged on the outer periphery of the circuit body 31. As will be described later, the plurality of through holes 33 can be used to position the plurality of circuit bodies 31 (circuit layers 30) in the heatsink-equipped circuit board 50.

[0054] 2, the sealing resin 40 is provided between the plurality of circuit bodies 31. The sealing resin 40 covers the outer peripheral edge of the circuit body 31. The sealing resin 40 has a plurality of openings 42 that expose the exposed portions 32A of the circuit body 31 upward. In a plan view, the plurality of openings 42 are arranged inside the circuit body 31.

[0055] 4, the sealing resin 40 may partially fill the through hole 33. The sealing resin 40 may also have a recess 43 recessed from the upper surface 41. The recess 43 is disposed inside the through hole 33 in a plan view. The bottom surface of the recess 43 is disposed inside the through hole 33 in the up-down direction. The recess 43 is a portion corresponding to a protrusion 61D of a first mold 61 described later.

[0056] The sealing resin 40 is obtained by using a sealing resin composition containing, for example, a thermosetting resin, an inorganic filler, a curing agent, a curing accelerator, a coupling agent, and the like.

[0057] The sealing resin 40 of the circuit board 50 with a heat sink may be in either a B-stage state or a C-stage state, and is preferably semi-cured after molding such as transfer or compression.

[0058] The thermosetting resin is preferably an epoxy resin. Specific examples of the epoxy resin include crystalline epoxy resins such as bisphenol-type epoxy resins (e.g., biphenyl-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and tetramethylbisphenol F-type epoxy resins), stilbene-type epoxy resins, and hydroquinone-type epoxy resins; novolac-type epoxy resins (e.g., cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, and naphthol novolac-type epoxy resins); aralkyl-type epoxy resins (e.g., phenylene-skeleton-containing phenol aralkyl-type epoxy resins, biphenylene-skeleton-containing phenol aralkyl-type epoxy resins, phenylene-skeleton-containing naphthol aralkyl-type epoxy resins, and alkoxynaphthalene-skeleton-containing phenol aralkyl-type epoxy resins); trifunctional epoxy resins (e.g., triphenolmethane-type epoxy resins, alkyl-modified triphenolmethane-type epoxy resins); modified phenol-type epoxy resins (e.g., dicyclopentadiene-modified phenol-type epoxy resins, terpene-modified phenol-type epoxy resins); and heterocycle-containing epoxy resins (e.g., triazine-nucleus-containing epoxy resins). These may be used alone or in combination of two or more.

[0059] Examples of the inorganic filler include silicates such as talc, calcined clay, uncalcined clay, mica, and glass; oxides such as titanium oxide, alumina, boehmite, and silica; carbonates such as calcium carbonate, magnesium carbonate, and hydrotalcite; hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide; sulfates or sulfites such as barium sulfate, calcium sulfate, and calcium sulfite; borates such as zinc borate, barium metaborate, aluminum borate, calcium borate, and sodium borate; nitrides such as aluminum nitride, boron nitride, silicon nitride, and carbon nitride; titanates such as strontium titanate and barium titanate, etc. These may be used alone or in combination of two or more.

[0060] The curing agent is not particularly limited as long as it reacts with the thermosetting resin to cure it, and examples thereof include linear aliphatic diamines having 2 to 20 carbon atoms, such as ethylenediamine, trimethylenediamine, tetramethylenediamine, and hexamethylenediamine, as well as amines such as metaphenylenediamine, paraphenylenediamine, paraxylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodicyclohexane, bis(4-aminophenyl)phenylmethane, 1,5-diaminonaphthalene, metaxylenediamine, paraxylenediamine, 1,1-bis(4-aminophenyl)cyclohexane, and dicyanodiamide; resole-type phenolic resins, such as aniline-modified resole resins and dimethyl ether resole resins; phenol novolac resins, cresol resins, and the like. Examples of the organic acid include novolac-type phenolic resins such as phenol novolac resin, tert-butylphenol novolac resin, and nonylphenol novolac resin; phenol aralkyl resins such as phenylene skeleton-containing phenol aralkyl resin and biphenylene skeleton-containing phenol aralkyl resin; phenolic resins having a condensed polycyclic structure such as a naphthalene skeleton or an anthracene skeleton; polyoxystyrene such as polyparaoxystyrene; alicyclic acid anhydrides such as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA), and aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), and benzophenonetetracarboxylic acid (BTDA); polymercaptan compounds such as polysulfide, thioester, and thioether; isocyanate compounds such as isocyanate prepolymers and blocked isocyanates; and organic acids such as carboxylic acid-containing polyester resins. These may be used alone or in combination of two or more.

[0061] Examples of the curing accelerator include phosphorus atom-containing compounds such as organic phosphines, tetra-substituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, or adducts of phosphonium compounds and silane compounds; amidine compounds such as 1,8-diazabicyclo(5,4,0)undecene-7 and imidazole; nitrogen atom-containing compounds such as tertiary amines, amidinium salts, or ammonium salts, such as benzyldimethylamine; and phenolic compounds such as phenol, bisphenol A, nonylphenol, and 2,3-dihydroxynaphthalene. Examples of the organic phosphines include triphenylphosphine, tri-p-tolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, and 1,2-bis-(diphenylphosphino)ethane.

[0062] As the coupling agent, for example, various silane-based compounds such as epoxysilane, mercaptosilane, aminosilane, alkylsilane, ureidosilane, and vinylsilane, titanium-based compounds, aluminum chelates, and aluminum / zirconium-based compounds can be used.

[0063] In addition to the above components, various additives may be contained, such as thermosetting resins other than the above epoxy resins, such as phenolic resins, epoxy resins, unsaturated polyester resins, melamine resins, and polyurethanes; colorants such as carbon black; mold release agents such as natural waxes, synthetic waxes, higher fatty acids or metal salts thereof, paraffin, and polyethylene oxide; ion scavengers such as hydrotalcite; stress reducing agents such as silicone oil and silicone rubber; flame retardants such as aluminum hydroxide; and antioxidants.

[0064] Such an encapsulating resin composition can be obtained by a known method, and can be prepared as a varnish-like composition by, for example, dissolving, mixing, and stirring the above-mentioned components in a solvent using various mixers such as those used in an ultrasonic dispersion system, a high-pressure collision dispersion system, a high-speed rotation dispersion system, a bead mill system, a high-speed shear dispersion system, or a rotation-revolution dispersion system.

[0065] (Method of Manufacturing the Circuit Board 50 with a Heat Sink) Next, an example of a method of manufacturing the circuit board 50 with a heat sink of this embodiment will be described with reference to Figures 5 to 7. Figures 5 to 7 are explanatory diagrams showing the components of the circuit board 50 with a heat sink (plurality of circuit bodies 31, insulating layer 20, and heat sink 10) and mold 60 (first mold 61 and second mold 62) in the cross section B-B of Figure 1. Note that the lower parts in Figures 5 to 7 correspond to the upper parts in Figure 3. For example, the illustrated lower surfaces of the plurality of circuit bodies 31 in Figures 5 to 7 correspond to the upper surfaces 32 of the plurality of circuit bodies 31 in Figure 3.

[0066] The manufacturing method of the circuit board 50 with a heat sink includes a step of preparing a heat sink 10, a step of preparing a plurality of circuit bodies 31, a step of preparing a mold 60, a first placement step, a second placement step, a third placement step, and a step of forming the sealing resin 40.

[0067] First, the heat sink 10, the plurality of circuit bodies 31, and the insulating layer 20 can be made of the materials described above.

[0068] The mold 60 is used to form the encapsulating resin 40. As shown in Fig. 7, the mold 60 has a cavity 63 to be filled with an encapsulating resin composition. The mold 60 includes a first mold 61 and a second mold 62. The cavity 63 is formed by assembling the first mold 61 and the second mold 62 together.

[0069] 5, the first mold 61 is, for example, tray-shaped. The first mold 61 includes, for example, a base wall 61A, a peripheral wall 61B extending upward from the outer periphery of the base wall 61A, and a plurality of protrusions 61C protruding upward from the base wall 61A inside the peripheral wall 61B. The first mold 61 of this embodiment also includes a plurality of protrusions 61D protruding upward from the base wall 61A. The protrusions 61D protrude from the base wall 61A by a greater amount than the protrusions 61C.

[0070] As shown in FIG. 7 , the second mold 62 is, for example, tray-shaped. The second mold 62 includes, for example, a base wall 62A and a peripheral wall 62B extending downward from the outer periphery of the base wall 62A. The first mold 61 and the second mold 62 are assembled so that the end surface of the peripheral wall 61B of the first mold 61 and the end surface of the peripheral wall 62B of the second mold 62 are in close contact with each other, thereby forming a cavity 63. A plurality of convex portions 61C and a plurality of protrusions 61D are arranged within the cavity 63. The mold 60 is also provided with an injection port (not shown) that communicates with the cavity 63. The cavity 63 can be filled with an encapsulating resin composition through the injection port.

[0071] 5 , in the first placement step, the plurality of circuit bodies 31 are placed in the first mold 61 so that the plurality of convex portions 61C come into contact with one surface (the lower surface in the figure) of the plurality of circuit bodies 31. At this time, the plurality of circuit bodies 31 are positioned relative to the first mold 61 by inserting the protrusions 61D into the through holes 33. A gap is provided between the protrusions 61D and the inner surface of the through holes 33.

[0072] 6 , in the second arrangement step, the insulating layer 20 and the base plate 11 (heat sink 10) are laminated on the other (upper) surface of the plurality of circuit bodies 31, and the insulating layer 20 is disposed between the base plate 11 and the plurality of circuit bodies 31. At this time, the insulating layer 20 and the base plate 11 that have been preliminarily pressure-bonded may be laminated on the plurality of circuit bodies 31.

[0073] 7 , in the third arrangement step, a first mold 61 and a second mold 62 are assembled to form a cavity 63. That is, an end face of a peripheral wall 61B of the first mold 61 and an end face of a peripheral wall 62B of the second mold 62 are brought into close contact with each other. At this time, the second mold 62 may be pressed against the heat sink 10, thereby compressing the insulating layer 20 by the plurality of circuit bodies 31 and the base plate 11.

[0074] The second and third arrangement steps may be performed at the same time. For example, the insulating layer 20 and the heat sink 10 may be positioned in the second mold 62, and then the second mold 62 and the first mold 61 may be assembled together.

[0075] Subsequently, the cavity 63 is filled with the encapsulating resin composition through the injection port, thereby forming the encapsulating resin 40. At this time, by appropriately adjusting the pressure at which the encapsulating resin composition is filled, the insulating layer 20 can be completely cured.

[0076] In the process of forming the sealing resin 40, the sealing resin composition is not filled in the areas where the multiple convex portions 61C are arranged. As a result, the surface of the circuit body 31 that was in contact with the multiple convex portions 61C becomes an exposed portion 32A that is exposed from the sealing resin 40. In other words, the multiple convex portions 61C form an opening 42 in the sealing resin 40. Furthermore, since the sealing resin composition is not filled in the areas where the multiple protrusions 61D are arranged, a recess 43 is formed in the sealing resin 40. The sealing resin composition penetrates into the through hole 33 through the gap between the inner surface of the through hole 33 and the protrusions 61D. As a result, the area of ​​the through hole 33 closer to the insulating layer 20 is filled with the sealing resin 40.

[0077] After the sealing resin 40 is formed, the mold 60 is removed, thereby completing the manufacturing of the circuit board 50 with a heat sink.

[0078] According to the above-described method for manufacturing the heatsink-equipped circuit board 50, the plurality of protrusions 61C of the first mold 61 can easily expose a portion (exposed portion 32A) of the upper surface 32 of the circuit layer 30 from the sealing resin 40. Therefore, for example, after the sealing resin 40 is formed, it is not necessary to perform a step of removing a portion of the sealing resin 40 to expose the exposed portion 32A. Therefore, for example, even if a plating layer is formed on the upper surface 32 of the circuit layer 30, damage to the plating layer can be prevented during the process of forming the exposed portion 32A.

[0079] (Effects of the embodiment) (1) The circuit board 50 with a heat sink according to the embodiment is a circuit board 50 with a heat sink in which a circuit layer 30 and a heat sink 10 are integrated via an insulating layer 20, the heat sink 10 has a flat base plate 11, sealing resin 40 is provided between a plurality of circuit bodies 31 that constitute the circuit layer 30, an upper surface 32 of the circuit layer 30 is arranged below an upper surface 41 of the sealing resin 40, and a part (exposed portion 32A) of the upper surface 32 of the circuit layer 30 is exposed from the sealing resin 40.

[0080] With this configuration, a portion (exposed portion 32A) of the upper surface 32 of the circuit layer 30 is exposed from the sealing resin 40, and another portion (covered portion 32B) of the upper surface 32 of the circuit layer 30 is covered by the sealing resin 40, making it easier to ensure the creepage distance between multiple circuit bodies 31.

[0081] (2) In the embodiment, the circuit body 31 has a plurality of through holes 33 formed therein.

[0082] With this configuration, the plurality of through holes 33 of the circuit body 31 can be used to position the plurality of circuit bodies 31 on the heat sink-equipped circuit board 50 .

[0083] (3) A manufacturing method of a heat sink-equipped circuit board 50 according to the embodiment includes the steps of: preparing a heat sink 10 having a flat base plate 11; preparing a plurality of circuit bodies 31; preparing a mold 60 having a first mold 61 having a plurality of protrusions 61C and a second mold 62 that, together with the first mold 61, forms a cavity 63 in which the plurality of protrusions 61C are arranged; a first arrangement step of arranging the plurality of circuit bodies 31 on the first mold 61 so that the plurality of protrusions 61C contact one side of the plurality of circuit bodies 31; a second arrangement step of stacking an insulating layer 20 and a base plate 11 on the other side of the plurality of circuit bodies 31 and arranging the insulating layer 20 between the base plate 11 and the plurality of circuit bodies 31; a third arrangement step of assembling the first mold 61 and the second mold 62 to form the cavity 63; and a step of filling the cavity 63 with an encapsulating resin composition to form the encapsulating resin 40.

[0084] According to this manufacturing method for the circuit board 50 with a heat sink, the portion of the circuit body 31 that contacts the protrusion 61C can be exposed from the sealing resin 40, and the portion of the circuit body 31 that does not contact the protrusion 61C can be embedded in the sealing resin 40. Therefore, it is easy to ensure the creepage distance between the plurality of circuit bodies 31. Furthermore, according to the manufacturing method for the circuit board 50 with a heat sink, after the sealing resin 40 is formed, a step of removing a portion of the sealing resin 40 to expose a portion of the upper surface 32 of the plurality of circuit bodies 31 is not required.

[0085] (4) In the embodiment, in the process of preparing the plurality of circuit bodies 31, a plurality of through holes 33 are formed in the plurality of circuit bodies 31, in the process of preparing the mold 60, a plurality of protrusions 61D are formed in the first mold 61, and in the first placement process, the protrusions 61D are inserted into the through holes 33 to position the plurality of circuit bodies 31 relative to the first mold 61.

[0086] According to this manufacturing method of the circuit board 50 fitted with a heat sink, the multiple circuit bodies 31 can be positioned on the circuit board 50 fitted with a heat sink.

[0087] (Other Embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0088] In the above embodiment, the circuit body 31 has the through-hole 33. However, the circuit body does not have to have a through-hole.

[0089] In the above embodiment, the sealing resin 40 has the recess 43. However, the sealing resin does not have to have the recess.

[0090] DESCRIPTION OF SYMBOLS 10: Heat sink 11: Base plate 20: Insulating layer 30: Circuit layer 31: Circuit body 32: Upper surface 32A: Exposed portion 32B: Covered portion 33: Through hole 40: Sealing resin 41: Upper surface 42: Opening 43: Recess 50: Circuit board with heat sink 60: Mold 61: First mold 61A: Base wall 61B: Peripheral wall 61C: Convex portion 61D: Protrusion 62: Second mold 62A: Base wall 62B: Peripheral wall 63: Cavity

Claims

1. A circuit board with a heat sink, in which a circuit layer and a heat sink are integrated via an insulating layer, the heat sink has a flat base plate, a sealing resin is provided between a plurality of circuit bodies that make up the circuit layer, the upper surface of the circuit layer is disposed below the upper surface of the sealing resin, and a portion of the upper surface of the circuit layer is exposed from the sealing resin.

2. The circuit board with a heat sink according to claim 1, wherein a plurality of through holes are formed in said circuit body.

3. A method for manufacturing a circuit board with a heat sink, comprising: a step of preparing a heat sink having a flat base plate; a step of preparing a plurality of circuit bodies; a step of preparing a mold comprising: a first mold having a plurality of protrusions; and a second mold which, together with the first mold, forms a cavity in which the plurality of protrusions are arranged; a first arrangement step of arranging the plurality of circuit bodies in the first mold so that the plurality of protrusions contact one side of the plurality of circuit bodies; a second arrangement step of stacking an insulating layer and the base plate on the other side of the plurality of circuit bodies and arranging the insulating layer between the base plate and the plurality of circuit bodies; a third arrangement step of assembling the first mold and the second mold to form the cavity; and a step of forming an encapsulating resin by filling the cavity with an encapsulating resin composition.

4. A method for manufacturing a circuit board with a heat sink as described in claim 3, wherein in the step of preparing the plurality of circuit bodies, a plurality of through holes are formed in the plurality of circuit bodies; in the step of preparing a mold, a plurality of protrusions are formed on the first mold; and in the first positioning step, the plurality of circuit bodies are positioned relative to the first mold by inserting the protrusions into the through holes.

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