LAMINATE AND METHOD FOR MANUFACTURING LAMINATE

Abstract

To provide a laminate which has an insulating layer formed using a silicone resin and metal layers adjacent to the insulating layer, where the insulating layer and the metal layers are bonded to each other with a sufficient bonding strength, and interfacial peeling between the insulating layer and the metal layers is sufficiently suppressed.SOLUTION: A laminate has a first metal layer, a second metal layer and an insulating layer arranged between the first metal layer and the second metal layer, where the insulating layer contains a silicone resin cured product, a polyvinyl alcohol-based emulsifier, and an inorganic filler.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminate suitable for use as a metal base circuit board, and a method for producing the same. [Background technology]

[0002] A variety of circuit boards have been put to practical use as circuit boards on which electronic and electrical components such as semiconductor elements are mounted to form hybrid integrated circuits. Circuit boards are classified based on the board material into resin circuit boards, ceramic circuit boards, metal-based circuit boards, etc.

[0003] Resin circuit boards are inexpensive, but because the thermal conductivity of the board is low, their applications are limited to those requiring relatively low power. Ceramic circuit boards, due to the characteristics of ceramics, such as high electrical insulation and heat resistance, are suitable for applications requiring relatively high power, but have the disadvantage of being expensive. On the other hand, metal-based circuit boards have intermediate properties between the two, and are suitable for general-purpose applications requiring relatively high power, such as inverters for refrigerators, inverters for commercial air conditioners, power sources for industrial robots, and power sources for automobiles.

[0004] For example, Patent Document 1 discloses a method for obtaining a circuit board having excellent stress relaxation properties, heat resistance, moisture resistance, and heat dissipation properties by using a composition for circuit boards containing a specific epoxy resin, a curing agent, and an inorganic filler as essential components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-266535 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, as the applications of metal-based circuit boards expand, there is a demand for diversity in insulating layers. For example, silicone resin is known as an insulating resin. Silicone resin is expected to be used for insulating layers of metal-based circuit boards because it can exhibit good insulating properties over a wide temperature range. However, according to the findings of the present inventors, it is difficult to ensure sufficient adhesion between an insulating layer formed using silicone resin and an adjacent metal layer.

[0007] Therefore, one object of the present invention is to provide a laminate comprising an insulating layer formed using a silicone resin and a metal layer adjacent to the insulating layer, in which the insulating layer and the metal layer are bonded with sufficient adhesive strength, and in which interfacial peeling between the insulating layer and the metal layer is sufficiently suppressed.

[0008] In the manufacture of laminates such as metal base circuit boards, a method is known in which a coating liquid containing an insulating resin and an organic solvent is applied onto a metal layer, followed by drying and curing when forming an insulating layer, but this method has the problem that the use of an organic solvent places a burden on the equipment and working environment.

[0009] It is therefore an object of the present invention to provide a method for producing the above laminate, which method imposes less strain on facilities and the working environment. [Means for solving the problem]

[0010] The present invention includes the following aspects. (1) A laminate comprising a first metal layer, a second metal layer, and an insulating layer disposed between the first metal layer and the second metal layer, the insulating layer containing a cured silicone resin, a polyvinyl alcohol-based emulsifier, and an inorganic filler. (2) The laminate according to (1), wherein the polyvinyl alcohol-based emulsifier is a partial hydrolyzate of poly(vinyl carboxylate). (3) The laminate according to (1) or (2), wherein the polyvinyl alcohol-based emulsifier has a first structural unit represented by the following formula (1-1) and a second structural unit represented by the following formula (1-2): [ka] [ka] [In the formula, R represents a hydrogen atom, an alkyl group, or a phenyl group.] (4) The laminate according to any one of (1) to (3), wherein the polyvinyl alcohol-based emulsifier has a degree of polymerization of 500 or more. (5) The laminate according to any one of (1) to (4), wherein the content of the polyvinyl alcohol-based emulsifier in the insulating layer is 0.1 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the cured silicone resin. (6) The laminate according to any one of (1) to (5), wherein the content of the inorganic filler in the insulating layer is 10 vol % or more and 90 vol % or less, based on the total volume of the insulating layer. (7) The laminate according to any one of (1) to (6), wherein the first metal layer is a metal plate and the second metal layer is a metal foil. (8) The laminate according to any one of (1) to (6), wherein the first metal layer is a metal plate, and the second metal layer is a metal circuit portion. (9) A method for producing a laminate, comprising: a preparation step of preparing a coating liquid containing a silicone resin, a polyvinyl alcohol-based emulsifier, an inorganic filler, and water; and a heating step of laminating a first metal layer, a semi-cured product of a coating film of the coating liquid, and a second metal layer, and heating the resulting mixture while applying pressure in the lamination direction to obtain a laminate comprising the first metal layer, an insulating layer including the cured product of the coating film, and the second metal layer. (10) The manufacturing method according to (9), wherein the preparation step includes an emulsification step of mixing the silicone resin, the polyvinyl alcohol-based emulsifier, and water to emulsify the silicone resin to obtain an emulsion, and an inorganic filler mixing step of mixing the emulsion with the inorganic filler to obtain the coating liquid. (11) The manufacturing method according to (9) or (10), wherein the heating step includes a coating film forming step of applying the coating liquid onto the first metal layer or the second metal layer to form a coating film, a semi-curing step of semi-curing the coating film, and a curing step of stacking the first metal layer, the semi-cured product of the coating film, and the second metal layer in this order, and heating them while applying pressure in the stacking direction to cure the coating film. (12) The method according to any one of (9) to (11), further comprising a circuit forming step of removing a portion of the second metal layer to form a metal circuit portion. Effect of the Invention

[0011] According to the present invention, there is provided a laminate comprising an insulating layer formed using a silicone resin and a metal layer adjacent to the insulating layer, the insulating layer and the metal layer being bonded with sufficient adhesive strength, and interfacial peeling between the insulating layer and the metal layer being sufficiently suppressed. Also, according to the present invention, there is provided a method for producing the laminate, which can produce the laminate while sufficiently suppressing the load on the equipment and the working environment. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of a laminate. [Diagram 2] FIG. 2 is a cross-sectional view illustrating an embodiment of a circuit board. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Preferred embodiments of the present invention will now be described in detail.

[0014] (Laminate) The laminate of the present embodiment includes a first metal layer, a second metal layer, and an insulating layer disposed between the first metal layer and the second metal layer. In the present embodiment, the insulating layer contains a silicone resin cured product, a polyvinyl alcohol-based emulsifier (hereinafter also referred to as a PVA-based emulsifier), and an inorganic filler.

[0015] In the laminate of this embodiment, since the insulating layer contains a silicone resin cured product, it can maintain good insulation properties over a wide temperature range. In addition, since the insulating layer of the laminate of this embodiment contains a PVA-based emulsifier, the adhesiveness that is low with only the silicone resin cured product is compensated for by the PVA-based emulsifier, and the insulating layer and the metal layer are bonded with sufficient adhesive strength. Therefore, the laminate of this embodiment is excellent in reliability because interfacial peeling between the insulating layer and the metal layer is sufficiently suppressed.

[0016] The first metal layer may be, for example, a metal plate.

[0017] The metal material constituting the metal plate is not particularly limited, and examples thereof include aluminum, aluminum alloys, copper, copper alloys, iron, and iron alloys such as stainless steel. The metal plate may be made of one type of metal material, or may be made of two or more types of metal materials. In addition, the metal plate may have a single-layer structure or a multi-layer structure.

[0018] The thickness of the metal plate is not particularly limited, and may be, for example, 0.5 to 3.0 mm from the viewpoint of suitability for producing a circuit board.

[0019] The second metal layer may be, for example, a metal foil.

[0020] The metal material constituting the metal foil is not particularly limited, and examples thereof include copper, aluminum, nickel, etc. The metal foil may be composed of one type of metal material, or may be composed of two or more types of metal materials. In addition, the metal foil may have a single-layer structure or a multi-layer structure.

[0021] The thickness of the metal foil is not particularly limited, and may be, for example, 0.009 to 1.0 mm from the viewpoint of suitability for producing a circuit board.

[0022] The insulating layer is disposed between the first metal layer and the second metal layer, and contains a cured silicone resin, a PVA-based emulsifier, and an inorganic filler.

[0023] The silicone resin cured product is a cured product obtained by curing a silicone resin. The silicone resin cured product may be a cured product of a silicone resin or a cured product of a mixture of a silicone resin and a curing agent.

[0024] The silicone resin is not particularly limited, and examples of the silicone resin include addition reaction curing type silicone, both-end epoxy-modified silicone, one-end epoxy-modified silicone, and side-chain epoxy-modified silicone.

[0025] The silicone resin may be a commercially available product. Examples of commercially available silicone resins include TSE3221S (manufactured by Momentive Corporation), KF-105 (manufactured by Shin-Etsu Chemical Co., Ltd.), and KF-1001 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0026] The curing agent is not particularly limited, and any known curing agent for curing silicone resins can be used without particular limitation. Examples of the curing agent include amine resins, acid anhydride resins, and phenolic resins.

[0027] The curing agent may be a commercially available product, for example, D400 (product name) manufactured by Huntsman Chemical Industries, Ltd., H84B (product name) manufactured by Nippon Gosei Kako Co., Ltd., TD2131 (product name) manufactured by Tohto Kasei Co., Ltd., and the like.

[0028] The content of the silicone resin cured product in the insulating layer may be, for example, 10% by volume or more, preferably 15% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more, based on the total volume of the insulating layer. The content of the silicone resin cured product in the insulating layer may be, for example, 90% by volume or less, preferably 80% by volume or less, more preferably 70% by volume or less, and even more preferably 60% by volume or less, based on the total volume of the insulating layer.

[0029] The PVA-based emulsifier can be said to be an emulsifier made of a polymer having a vinyl alcohol unit. The vinyl alcohol unit is a structural unit represented by the following formula (1-1). [ka]

[0030] The PVA-based emulsifier may further have other structural units in addition to the vinyl alcohol unit. Examples of the other structural units include a structural unit represented by the following formula (1-2). [ka]

[0031] In formula (1-2), R represents a hydrogen atom, an alkyl group, or a phenyl group.

[0032] R is preferably an alkyl group or a phenyl group, more preferably an alkyl group. The alkyl group may be, for example, an alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms.

[0033] In a preferred embodiment, the PVA-based emulsifier may be a polymer having a first structural unit represented by formula (1-1) and a second structural unit represented by formula (1-2).

[0034] The total content of the first constituent units and the second constituent units in the PVA-based emulsifier may be, for example, 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass.

[0035] The ratio (M1 / (M1+M2)) of the total number (M1) of the first constituent units to the total number (M1+M2) of the first constituent units and the second constituent units in the PVA-based emulsifier may be, for example, 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more. This tends to further improve the water solubility of the PVA-based emulsifier. In addition, the above ratio (M1 / (M1+M2)) may be, for example, 0.95 or less, preferably 0.90 or less, more preferably 0.85 or less. This tends to further improve the emulsifiability of the silicone resin, and to further reduce the viscosity of the aqueous solution when the silicone resin is emulsified. The above ratio (M1 / (M1+M2)) can also be referred to as the degree of saponification.

[0036] The polymerization degree of the PVA-based emulsifier may be, for example, 500 or more, more preferably 1500 or more. This tends to further improve the emulsification of the silicone resin. The polymerization degree of the PVA-based emulsifier may be, for example, 8000 or less, preferably 5000 or less, more preferably 3500 or less. This tends to lower the aqueous solution viscosity when the silicone resin is emulsified. The polymerization degree can also be the total number of repeating units in the PVA-based emulsifier. For example, when the repeating units in the PVA-based emulsifier are the first structural unit and the second structural unit, the polymerization degree of the PVA-based emulsifier can be expressed by the total number (M1+M2) of the first structural unit and the second structural unit.

[0037] The PVA-based emulsifier may be a partial hydrolyzate of poly(vinyl carboxylate). Poly(vinyl carboxylate) is a polymer of vinyl carboxylate, and can also be said to be a polymer having the repeating unit represented by formula (1-2).

[0038] The partial hydrolysate of poly(vinyl carboxylate) may be a poly(vinyl carboxylate) in which a part of the constitutional unit represented by formula (1-2) has been converted to a constitutional unit represented by formula (1-1) by hydrolysis. That is, the hydrolysate of poly(vinyl carboxylate) has a first constitutional unit represented by formula (1-1) and a second constitutional unit represented by formula (1-2).

[0039] The content of the PVA-based emulsifier in the insulating layer may be, for example, 0.1 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the silicone resin cured product. This tends to further improve the adhesive strength to the metal layer. In addition, the content of the PVA-based emulsifier in the insulating layer may be, for example, 40 parts by mass or less, preferably 35 parts by mass or less, more preferably 33 parts by mass or less, and even more preferably 30 parts by mass or less, relative to 100 parts by mass of the silicone resin cured product. This tends to make the insulating layer less hygroscopic.

[0040] The inorganic filler may be, for example, a known inorganic filler used in applications requiring insulation and thermal conductivity. The inorganic filler may include, for example, one or more selected from the group consisting of aluminum oxide (alumina), silicon oxide, silicon nitride, boron nitride, aluminum nitride, and magnesium oxide, and from the viewpoint of further improving insulation reliability under high humidity environment, may include one or more selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, boron nitride, and aluminum nitride, and may include one or more selected from the group consisting of aluminum oxide, boron nitride, and aluminum nitride.

[0041] The shape of the inorganic filler may be, for example, particulate, scaly, polygonal, etc. The average particle size of the inorganic filler may be 0.05 μm or more, 0.1 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more from the viewpoint of improving thermal conductivity, and may be 200 μm or less, 150 μm or less, 100 μm or less, or 80 μm or less from the viewpoint of further improving insulation. In this specification, the average particle size of the inorganic filler means the d50 diameter in the volume-based particle size distribution of the inorganic filler. The volume-based particle size distribution of the inorganic filler is measured by a laser diffraction particle size distribution measuring device.

[0042] The content of the inorganic filler in the insulating layer may be, for example, 10% by volume or more, preferably 20% by volume or more, more preferably 30% by volume or more, and even more preferably 50% by volume or more, based on the total volume of the insulating layer. This tends to further improve the thermal conductivity of the insulating layer. The content of the inorganic filler in the insulating layer may be, for example, 90% by volume or less, preferably 80% by volume or less, more preferably 75% by volume or less, and even more preferably 70% by volume or less, based on the total volume of the insulating layer. This tends to further improve the insulation of the insulating layer.

[0043] The insulating layer may further contain other components in addition to those mentioned above.

[0044] Examples of other components include a defoamer, a leveling agent, a silane coupling agent, and a wetting and dispersing agent.

[0045] The content of other components in the insulating layer may be, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and may be 0 part by mass, relative to 100 parts by mass of the cured silicone resin.

[0046] The thickness of the insulating layer is not particularly limited, and from the viewpoint of being suitable for producing a circuit board, it may be, for example, 20 μm or more, preferably 60 μm or more, more preferably 70 μm or more. This tends to further improve the insulation. The thickness of the insulating layer may be, for example, 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less. This tends to further improve the thermal conductivity.

[0047] In the laminate of this embodiment, the second metal layer may form a metal circuit portion. Such a laminate can be suitably used as a metal base circuit board. The metal circuit portion may be formed, for example, by removing a part of the metal foil (processing it into a predetermined pattern).

[0048] Fig. 1 is a schematic cross-sectional view showing one embodiment of a laminate. The laminate 10 shown in Fig. 1 includes a first metal layer 1, an insulating layer 2 disposed on the first metal layer 1, and a second metal layer 3 disposed on the insulating layer 2. In the laminate 10, the first metal layer 1 and the second metal layer 3 are separated by the insulating layer 2.

[0049] In the laminate 10, the second metal layer 3 is disposed over substantially the entire surface of the insulating layer 2, but in other embodiments, the second metal layer may be disposed over only a portion of the insulating layer.

[0050] Fig. 2 is a schematic cross-sectional view showing one embodiment of a circuit board (laminate). The circuit board 20 shown in Fig. 2 includes a first metal layer 1, an insulating layer 2 disposed on the first metal layer, and a metal circuit portion 4 disposed on the insulating layer 2. In the circuit board 20, the first metal layer 1 and the metal circuit portion 4 are separated by the insulating layer 2.

[0051] The circuit board 20 may be, for example, formed by removing a portion of the second metal layer 3 of the laminate 10 to form a metal circuit section 4 having a predetermined pattern.

[0052] (Method of manufacturing laminate) The laminate of the present embodiment can be produced by a production method including, for example, a preparation step of preparing a coating liquid containing a silicone resin, a PVA-based emulsifier, an inorganic filler, and water, and a heating step of laminating a first metal layer, a semi-cured product of a coating film of the coating liquid, and a second metal layer, and heating while applying pressure in the lamination direction to obtain a laminate including the first metal layer, an insulating layer including a cured product of the coating film, and the second metal layer.

[0053] In the manufacturing method of this embodiment, since the insulating layer is formed using a water-based coating liquid, special equipment for removing the organic solvent, etc. is not required, and deterioration of the working environment due to the volatilization of the organic solvent can be avoided. That is, according to the manufacturing method of this embodiment, the laminate can be manufactured while sufficiently suppressing the load on the equipment and the working environment.

[0054] Examples of the silicone resin, the PVA-based emulsifier, and the inorganic filler are as described above.

[0055] In the coating liquid, the silicone resin may be emulsified and dispersed with a PVA-based emulsifier. The coating liquid may be, for example, a dispersion liquid obtained by dispersing an inorganic filler in an emulsion of a silicone resin.

[0056] The content of the silicone resin in the coating liquid may be, for example, 2.5% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on the total amount of non-volatile content in the coating liquid. The content of the silicone resin in the coating liquid may be, for example, 65% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total amount of non-volatile content in the coating liquid.

[0057] The content of the PVA-based emulsifier in the coating liquid may be, for example, 0.1 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the silicone resin. This tends to further improve the emulsification of the silicone resin. In addition, the content of the PVA-based emulsifier in the coating liquid may be, for example, 40 parts by mass or less, preferably 35 parts by mass or less, more preferably 33 parts by mass or less, and even more preferably 30 parts by mass or less, relative to 100 parts by mass of the silicone resin. This tends to make the insulating layer less hygroscopic.

[0058] The content of the inorganic filler in the coating liquid may be, for example, 30 parts by mass or more, preferably 100 parts by mass or more, more preferably 300 parts by mass or more, and even more preferably 600 parts by mass or more, relative to 100 parts by mass of the silicone resin. This tends to further improve the thermal conductivity of the insulating layer. In addition, the content of the inorganic filler in the coating liquid may be, for example, 3500 parts by mass or less, preferably 3000 parts by mass or less, more preferably 2000 parts by mass or less, and even more preferably 1000 parts by mass or less, relative to 100 parts by mass of the silicone resin. This tends to further improve the insulation of the insulating layer.

[0059] The content of water in the coating liquid is not particularly limited, and it is preferable that the coating liquid has a suitable viscosity range as described below. The content of water in the coating liquid may be, for example, 500 parts by mass or more, preferably 600 parts by mass or more, more preferably 700 parts by mass or more, and even more preferably 800 parts by mass or more, relative to 100 parts by mass of silicone resin. This tends to make it easier to apply the coating liquid with a uniform thickness. In addition, the content of water in the coating liquid may be, for example, 1500 parts by mass or less, preferably 1400 parts by mass or less, more preferably 1300 parts by mass or less, and even more preferably 1200 parts by mass or less, relative to 100 parts by mass of silicone resin. This tends to prevent the coating liquid from flowing during coating, making it easier to control the film thickness.

[0060] The coating liquid may further contain components other than those described above. For example, the coating liquid may further contain a curing agent. Examples of the curing agent are as described above.

[0061] The content of the curing agent in the coating liquid is not particularly limited, and it is preferable to mix the curing agent so that the active hydrogen equivalent (or acid anhydride equivalent) of the curing agent is 0.01 to 1.25 per epoxy equivalent of the epoxy contained in the silicone resin.

[0062] The coating liquid may further contain, as components other than those mentioned above, a defoaming agent, a leveling agent, a silane coupling agent, a wetting and dispersing agent, and the like.

[0063] The viscosity of the coating liquid at 25°C may be, for example, 10 cps or more, preferably 1000 cps or more, more preferably 3000 cps or more. This tends to make it easier to apply the coating liquid with a uniform thickness. The viscosity of the coating liquid at 25°C may be, for example, 100,000 cps or less, preferably 50,000 cps or less, more preferably 10,000 cps or less. This tends to make it harder for voids to be included in the coating liquid. The viscosity of the coating liquid indicates a value measured by a rotation method.

[0064] The preparation process may include, for example, an emulsification process in which a silicone resin, a PVA-based emulsifier, and water are mixed together to emulsify the silicone resin to obtain an emulsion. There are no particular limitations on the mixing method in the emulsification process, and the method may be appropriately selected from methods in which dispersion is performed using a known stirring and mixing device such as a homogenizer, a disperser, or a clearmix.

[0065] The preparation step may further include an inorganic filler mixing step of mixing the emulsion obtained in the emulsification step with an inorganic filler to obtain a coating liquid. The mixing method in the inorganic filler mixing step is not particularly limited and may be appropriately selected from known mixing methods.

[0066] In the heating step, a laminate is prepared by laminating a first metal layer, a semi-cured product of a coating film of a coating liquid, and a second metal layer, and the laminate is heated while being pressurized in the lamination direction, whereby the semi-cured product is cured to form an insulating layer.

[0067] The pressure conditions in the heating step are not particularly limited, and may be, for example, 0.1 MPa or more, preferably 0.5 MPa or more, more preferably 1 MPa or more. This tends to reduce the porosity in the insulating layer. The pressure conditions in the heating step may be, for example, 50 MPa or less, preferably 30 MPa or less, more preferably 20 MPa or less. This tends to suppress the resin flow of the obtained cured product.

[0068] The heating temperature in the heating step may be any temperature that can cure the coating film. The heating temperature may be, for example, 60°C or higher, preferably 80°C or higher, and more preferably 100°C or higher. This tends to reduce unreacted monomers. The heating temperature may be, for example, 220°C or lower, preferably 200°C or lower, and more preferably 180°C or lower. This tends to reduce the porosity of the resulting insulating layer.

[0069] The heating step may include, for example, a coating film forming step of applying a coating liquid onto the first metal layer or the second metal layer to form a coating film.

[0070] The coating method in the coating film forming step is not particularly limited and may be appropriately selected from known coating methods. In the coating film forming step, at least a part of the volatile matter (for example, water) in the coating film may be removed.

[0071] The heating step may further include a semi-curing step of semi-curing the coating film obtained in the coating film forming step. The semi-curing step may be, for example, a step of semi-curing the coating film by heating. In the semi-curing step, at least a part of the volatile matter (e.g., water) in the coating film may be removed by heating, and it is preferable that most of the volatile matter in the coating film (e.g., 90 mass% or more, preferably 95 mass% or more) is removed.

[0072] The heating temperature in the semi-curing step may be any temperature that allows the coating film to be semi-cured. The heating temperature may be, for example, 50°C or higher, preferably 55°C or higher, and more preferably 60°C or higher. This tends to reduce the amount of residual solvent in the insulating layer. The heating temperature may be, for example, 150°C or lower, preferably 120°C or lower, and more preferably 100°C or lower. This tends to make it easier to control the reaction.

[0073] The heating step may further include a curing step of stacking the first metal layer, the semi-cured coating film, and the second metal layer in this order, and heating them while applying pressure in the stacking direction. The pressure conditions and heating temperature in the curing step are as described above.

[0074] The manufacturing method of this embodiment may further include a circuit formation step of forming a metal circuit portion by removing a part of the second metal layer. According to the manufacturing method including this step, a laminate useful as a metal base circuit board having a metal circuit portion formed thereon is manufactured.

[0075] The method for removing a portion of the second metal layer in the circuit formation step is not particularly limited, and may be, for example, etching.

[0076] In the circuit formation step, the second metal layer is removed so as to form a metal circuit portion having a predetermined pattern.

[0077] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. EXAMPLES

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0079] Example 1 (1) Preparation of emulsion An addition reaction type silicone with a viscosity of 3.5 Pa s (TSE325-B, manufactured by Momentive Corp.) was used as the silicone resin, and a PVA resin (1) (B-17, manufactured by Denka Co., Ltd., saponification degree 88.0 mol%, polymerization degree 1700, hydrophobic group: acetyl group) was used as the emulsifier. 1.36 g of PVA resin was added to 37.2 g of distilled water at room temperature while stirring, and heated at 90° C. for 60 minutes to obtain an aqueous PVA solution. While stirring the aqueous PVA solution at 3000 rpm using a high-speed emulsifying disperser (manufactured by Primix Corporation, trade name Homomixer MARK II 2.5 type), 4.13 g of silicone resin was added over 5 minutes, and further stirred and mixed at 5000 rpm for 5 minutes to obtain an emulsion. (2) Preparation of coating solution Boron nitride (product name: XGP, manufactured by Denka Co., Ltd.) was used as the inorganic filler. To 60 parts by mass of the emulsion, 40 parts by mass of inorganic filler was added and kneaded at 2000 rpm for 3 minutes with a planetary mixer (manufactured by Thinky Corporation, product name: Awatori Rentaro AR-310) to obtain a coating liquid. (3) Manufacturing of laminates The coating solution was applied onto a copper foil having a thickness of 70 μm (manufactured by Furukawa Electric Co., Ltd., product name: electrolytic copper foil, thickness 70 μm) and dried at 60° C. for 1 hour to bring it into a B-stage (semi-cured) state. The amount of the coating solution applied was adjusted so that the thickness of the insulating layer after curing would be 175 μm. Thereafter, a 1.5 mm thick aluminum plate (manufactured by Amano Aluminum Co., Ltd., product name A1050, thickness 1.5 mm) was placed on top of the coating liquid in the B-stage state, and the laminated state was heat-treated at 200°C for 6 hours using a heat press method to harden the semi-cured material, thereby obtaining a laminate.

[0080] (4) Evaluation 4-1 Emulsion stability: The emulsion was evaluated according to the following criteria. A: After storing at 5℃ for 24 hours, no changes were observed in the emulsion and it was usable. B: After being stored at 5℃ for 24 hours, the emulsion separated and could not be used. 4-2 Adhesion: The laminate was evaluated according to the following criteria. The copper foil of the obtained laminate was masked at a predetermined position with an etching resist, and then the etching resist was removed to produce a metal base circuit board with a copper foil pattern of 10 mm x 100 mm. Next, the peel strength between the copper foil and the insulating layer was measured under conditions of 23 ± 2 °C and 50% relative humidity according to the method specified in JIS C 6481. The measurement was repeated five times, and the arithmetic average value was taken as the peel strength. The peel strength should be 1 N / cm or more. 4-3 Evaluation of electrical characteristics (voltage resistance): Evaluation was performed according to the following criteria. After masking predetermined positions of the copper foil of the obtained laminate with an etching resist, the etching resist was removed to prepare a metal base circuit board, and the withstand voltage was measured according to the method specified in JIS C 2110. The withstand voltage is preferably 30 kV / mm or more. 4-4 Evaluation of thermal conductivity (λ): Evaluation was performed according to the following criteria. A cured product was prepared from the obtained coating liquid, and the thermal conductivity (λ) was calculated by multiplying the thermal diffusivity (α), specific gravity (Cp), and specific heat (ρ) according to the following formula. The thermal diffusivity was measured by the laser flash method after processing the sample into a size of 10 mm wide x 10 mm wide x 10 mm thick. The measurement device used was a xenon flash analyzer (NETZSCH, product name LFA447NanoFlash). The specific gravity was measured using the Archimedes method. The specific heat was measured using a differential scanning calorimeter (TA Instruments, product name Q2000) in a nitrogen atmosphere, heating from room temperature to 400°C at a heating rate of 10°C / min. A thermal conductivity of 3W / (m·K) or more is desirable. Thermal conductivity (λ) = Thermal diffusivity (α) × Specific heat (Cp) × Specific gravity (ρ)

[0081] Example 2 An emulsion, a coating liquid, and a laminate were obtained in the same manner as in Example 1, except that the PVA resin (1) was changed to a PVA resin (2) (trade name B-17S, manufactured by Denka, saponification degree 88.0 mol%, polymerization degree 1700, hydrophobic group: acetyl group).

[0082] Example 3 An emulsion, a coating liquid, and a laminate were obtained in the same manner as in Example 1, except that the PVA resin (1) was changed to a PVA resin (3) (trade name B-33, manufactured by Denka, saponification degree 88.0 mol%, polymerization degree 3300, hydrophobic group: acetyl group).

[0083] Example 4 The silicone resin was changed to an addition reaction type silicone with a viscosity of 58 Pa·s (manufactured by Momentive, product name TSE3221S). The PVA aqueous solution was changed to a PVA aqueous solution obtained by adding 1.65 g of PVA resin (1) to 38.9 g of distilled water at room temperature while stirring, and heating at 90°C for 60 minutes. The emulsifier was prepared by adding 4.13 g of silicone resin over 5 minutes while stirring the PVA aqueous solution at 3000 rpm using a high-speed emulsifying disperser (manufactured by Primix, product name Homomixer MARK II 2.5 type) and further stirring and mixing at 5000 rpm for 5 minutes. The coating liquid was prepared by adding 39 parts by mass of inorganic filler to 61 parts by mass of the emulsion, and kneading the mixture at 2000 rpm for 3 minutes using a planetary mixer (Thinky Corporation, product name: Awatori Rentaro AR-310). A laminate was obtained in the same manner as in Example 1, except that the above coating liquid was used.

[0084] Example 5 The silicone resin used was a mixture of 1.5 g of epoxy-modified silicone (Shin-Etsu Chemical Co., Ltd., product name KF-1001) with a viscosity of 16.5 Pa·s and 1.5 g of epoxy-modified silicone (Shin-Etsu Chemical Co., Ltd., product name KF-105) with a viscosity of 0.015 Pa·s, and 0.61 g of aliphatic amine (Huntsman Co., Ltd., product name D-400, amine equivalent 200) was used as the curing agent. The PVA aqueous solution was an aqueous solution obtained by adding 0.0036 g of PVA resin (Mitsubishi Chemical Co., Ltd., product name Gohsenex LW-100, saponification degree 43.1 mol%, hydrophobic group: polyoxyethylene group) to 193.5 g of stirred distilled water at room temperature and heating at 90°C for 60 minutes. The PVA aqueous solution was stirred at 3000 rpm using a high-speed emulsifying disperser (manufactured by Primix Corporation, product name Homomixer MARK II 2.5 type), while 3.61 g of a mixture of silicone resin and curing agent was added over 5 minutes, and further stirred and mixed at 5000 rpm for 5 minutes to obtain an emulsion. As inorganic fillers, 13.3 parts by mass of alumina (manufactured by Denka, product name DAS45, maximum particle size 70 μm, average particle size 45 μm), 13.3 parts by mass of alumina (manufactured by Denka, product name DAS10, maximum particle size 21 μm, average particle size 10 μm), and 11.4 parts by mass of alumina (manufactured by Sumitomo Chemical, product name AA2, maximum particle size 5 μm, average particle size 2 μm) were used. The coating liquid was prepared by adding the inorganic filler to 61 parts by mass of the emulsion and kneading the mixture at 2000 rpm for 3 minutes using a planetary mixer (manufactured by Thinky Corporation, product name: Awatori Rentaro AR-310). A laminate was obtained in the same manner as in Example 1, except that the above coating liquid was used.

[0085] Comparative Example 1 A coating liquid and a laminate were obtained in the same manner as in Example 1, except that no PVA resin was used.

[0086] Comparative Example 2 A coating liquid and a laminate were obtained in the same manner as in Example 1, except that the silicone resin was changed to an addition reaction type silicone with a viscosity of 58 Pa·s (TSE3221S, product name, manufactured by Momentive Corporation) and no PVA resin was used.

[0087] The results of the examples and comparative examples are shown in Tables 1 and 2. In Table 1, the "amount of PVA emulsifier" indicates the amount (parts by mass) of the PVA emulsifier used per 100 parts by mass of the combined total of the silicone resin and the curing agent.

[0088] [Table 1]

[0089] [Table 2] [Explanation of symbols]

[0090] 1...first metal layer, 2...insulating layer, 3...second metal layer, 4...metal circuit portion, 10...laminate, 20...circuit board (laminate).

Claims

1. a first metal layer, a second metal layer, and an insulating layer disposed between the first metal layer and the second metal layer; The insulating layer comprises a cured silicone resin, a polyvinyl alcohol-based emulsifier, and an inorganic filler.

2. 2. The laminate of claim 1, wherein the polyvinyl alcohol emulsifier is a partial hydrolyzate of a poly(vinyl carboxylate).

3. The laminate according to claim 1 or 2, wherein the polyvinyl alcohol-based emulsifier has a first structural unit represented by the following formula (1-1) and a second structural unit represented by the following formula (1-2): 【Chemistry 1】 【Chemistry 2】 [In the formula, R represents a hydrogen atom, an alkyl group, or a phenyl group.]

4. The laminate according to any one of claims 1 to 3, wherein the polyvinyl alcohol-based emulsifier has a degree of polymerization of 500 or more.

5. The laminate according to any one of claims 1 to 4, wherein the content of the polyvinyl alcohol-based emulsifier in the insulating layer is 0.1 parts by mass or more and 40 parts by mass or less relative to 100 parts by mass of the silicone resin cured product.

6. The laminate according to any one of claims 1 to 5, wherein the content of the inorganic filler in the insulating layer is 10 vol% or more and 90 vol% or less, based on the total volume of the insulating layer.

7. The laminate according to any one of claims 1 to 6, wherein the first metal layer is a metal plate and the second metal layer is a metal foil.

8. The laminate according to any one of claims 1 to 6, wherein the first metal layer is a metal plate, and the second metal layer is a metal circuit portion.

9. A preparation step of preparing a coating liquid containing a silicone resin, a polyvinyl alcohol-based emulsifier, an inorganic filler, and water; a heating step of laminating a first metal layer, a semi-cured product of the coating film of the coating liquid, and a second metal layer, and heating the laminate while applying pressure in the lamination direction to obtain a laminate including the first metal layer, an insulating layer including the cured product of the coating film, and the second metal layer; A method for manufacturing a laminate comprising the steps of:

10. The preparation step includes: an emulsification step of mixing the silicone resin, the polyvinyl alcohol-based emulsifier, and water to emulsify the silicone resin to obtain an emulsion; an inorganic filler mixing step of mixing the emulsion with the inorganic filler to obtain the coating liquid; The method of claim 9, comprising:

11. The heating step comprises: a coating film forming step of applying the coating liquid onto the first metal layer or the second metal layer to form a coating film; a semi-curing step of semi-curing the coating film; a curing step of laminating the first metal layer, the semi-cured product of the coating film, and the second metal layer in this order, and heating the laminate while applying pressure in the lamination direction to cure the coating film; The method of claim 9 or 10, comprising:

12. The method according to any one of claims 9 to 11, further comprising a circuit forming step of forming a metal circuit portion by removing a part of the second metal layer.

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