Heat dissipation circuit board, heat dissipation member, and method for manufacturing heat dissipation circuit board

Abstract

According to the present invention, a heat-dissipating circuit board is formed by providing a metal material adjacent to one surface of an insulating layer and providing a conductive metal layer to the other surface of the insulating layer. The metal material is a sheet of copper or a copper alloy or aluminum or an aluminum alloy and is 0.2–20 mm thick. The insulating layer is a metal oxide layer that has the composition AlxOyTz, is 0.2–30 μm thick, has a volume resistivity of at least 1000 GΩ·cm, and has a porosity of no more than 10%. The heat-dissipating circuit board has excellent heat-dissipation properties and insulation properties.

Description

[Technical Field]

[0001] The present invention relates to a heat dissipation circuit board, a heat dissipation member, and a method for manufacturing a heat dissipation circuit board. [Background technology]

[0002] Metallic heat dissipation components have traditionally been used to dissipate heat generated by electronic components such as semiconductor chips. Some of these heat dissipation components have an insulating layer to prevent electrical conduction. Ceramics made of metal oxides, thermosetting resins, plastics, and the like are used as insulating layers. Among these, ceramics have excellent heat resistance and insulation properties, but have the problem of insufficient thermal conductivity to dissipate the heat generated by the increasing currents typically seen in electric vehicles.

[0003] There are three main reasons why ceramics do not have sufficient thermal conductivity: first, it is difficult to process ceramics thinly, making it difficult to process them to thicknesses of 150 μm or less using the thermal sintering method; second, the adhesive used to bond ceramics to metal has low thermal conductivity; and third, ceramics formed using the thermal sintering method contain tiny air bubbles, resulting in an insufficient porosity.

[0004] To solve the above problems, Patent Document 1 proposes a technique for directly bonding an insulating layer and an aluminum plate by applying pressure under heat without using an adhesive layer. However, because the insulating layer is bonded under heat and pressure, if the insulating layer is thin it will crack, so the insulating layer must be 150 μm thick or thicker, which poses the problem of poor thermal conductivity.

[0005] Furthermore, Patent Document 2 proposes a metal base substrate in which an alumina layer is formed as an insulating layer on aluminum or an aluminum alloy. This patent document exemplifies a method of forming the alumina layer by anodization, but anodization makes it difficult to control the film thickness and results in insufficient dielectric breakdown field strength, so the alumina layer needs to be 30 to 200 μm thick to maintain insulation. Furthermore, the alumina layer obtained by anodization has hexagonal columnar cavities in the layer, resulting in high porosity and poor thermal conductivity, which is an issue.

[0006] Patent Document 3 also proposes an insulating substrate with an insulating film formed by thermally spraying ceramic powder onto the surface of a conductive base material. With the thermal spraying method, controlling the film thickness is difficult and pinholes may form in the insulating film, so the insulating film must be 80 to 300 μm thick, and the porosity is high, resulting in insufficient thermal conductivity.

[0007] Furthermore, Patent Document 4 proposes a method for forming a conductive metal oxide film on copper or its alloy. However, the method only targets conductive metal oxides, and there is no mention of insulating films. Furthermore, there is no mention of the porosity, density, or heat dissipation properties of the resulting metal oxide layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-157115 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-212788 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-207490 [Patent Document 4] Japanese Patent Application Publication No. 2018-172793 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a heat dissipation circuit board having excellent heat dissipation and insulation properties, and further to provide a heat dissipation member having the heat dissipation circuit board and a method for manufacturing the heat dissipation circuit board. [Means for solving the problem]

[0010] [Item 1] That is, the present invention relates to a heat dissipation circuit board including an insulating layer having a metal material adjacent to one side thereof and a conductive metal layer on the other side thereof, wherein the metal material is made of copper or a copper alloy, or aluminum or an aluminum alloy, and is in the form of a sheet having a thickness of 0.2 mm to 20 mm, and the insulating layer is a metal oxide layer represented by the composition formula AlxOyTz (wherein Al represents an aluminum atom, O represents an oxygen atom, and T represents one or more atoms other than Al and O, and x, y, and z represent a mass ratio, such that x + y + z = 100, where x is 30 to 60, y is 40 to 70, and z is 0 to 10), and has a thickness of 0.2 μm to 30 μm, a volume resistivity of 1000 GΩ cm or more, and a porosity of 10% or less.

[0011] [Item 2] The present invention also relates to the heat dissipation circuit board according to item 1, wherein the surface roughness (Ra1) of the metal material on the insulating layer side is 1.0 μm or less, and the surface roughness (Ra2) of the insulating layer on the conductive metal layer side is 0.3 μm or less.

[0012] [Item 3] The present invention also relates to the heat dissipation circuit board according to item 1 or 2, wherein the metal oxide layer has a carbon atom content of 0.1% by mass or more and 5% by mass or less.

[0013] [Item 4] The present invention also relates to a heat dissipation member in the heat dissipation circuit board according to any one of items 1 to 3 above, wherein the metal material is bonded to a heat sink with an adhesive or grease.

[0014] [Item 5] The present invention also relates to a method for producing a heat dissipation circuit board according to any one of items 1 to 3 above, wherein the insulating layer is formed by reacting a coating liquid containing an aluminum salt or complex on the metal material to form a film.

[0015] [Item 6] The present invention also relates to the method for producing a heat dissipation circuit board according to item 5, wherein the film-forming method comprises atomizing or dropletizing the coating liquid to obtain a mist or droplets, transporting the mist or droplets with a carrier gas, and then reacting the mist or droplets on the metal material in an atmosphere at a temperature of 230°C or higher and 450°C or lower.

[0016] [Item 7] The present invention also relates to the method for producing a heat dissipation circuit board according to item 5 or 6 above, wherein the coating liquid contains an aluminum complex in an amount of 0.2 mass % to 20 mass %. [Effects of the Invention]

[0017] The heat dissipation circuit board of the present invention has a thin film and an insulating metal oxide layer with low porosity formed adjacent (directly) on a metal material, and therefore heat is easily transferred between the metal material, which is a good thermal conductor, and the metal oxide layer, resulting in high heat dissipation and insulation properties.

[0018] Furthermore, although the metal oxide layer serving as the insulating layer is a thin film of 0.2 μm to 30 μm, if the surface roughness (Ra1) of the insulating layer side of the metal material is less than 1.0 μm, the insulating layer (metal oxide layer) will not crack even when repeatedly exposed to high temperatures, resulting in excellent durability. Furthermore, if the surface roughness (Ra2) of the insulating layer on the conductive metal layer side is 0.3 μm or less, the conductive metal layer will not crack even when repeatedly exposed to high temperatures, resulting in excellent durability. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of an insulating layer forming apparatus in the method for manufacturing a heat dissipation circuit board of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] <Heat dissipation circuit board> The heat dissipation circuit board of the present invention has a metal material adjacent to one side of an insulating layer and a conductive metal layer on the other side of the insulating layer. The heat dissipation circuit board is used primarily to dissipate heat generated from circuits, semiconductor chips, etc., and includes the metal material, the insulating layer, and the conductive metal layer. The conductive metal layer is provided for electrodes of the semiconductor chip, etc., and the metal material is provided to dissipate heat generated from the semiconductor chip, etc. The insulating layer is provided to insulate the conductive metal layer from the metal material.

[0021] <Metal materials> The metal material is made of copper or a copper alloy, or aluminum or an aluminum alloy, and is in the form of a sheet having a thickness of 0.2 mm to 20 mm. Copper atoms or aluminum atoms in the metal material bond directly or via oxygen atoms to aluminum atoms in the insulating layer (metal oxide layer) at the interface with the insulating layer, thereby enabling high adhesion between the metal material and the insulating layer.

[0022] The copper or copper alloy, or aluminum or aluminum alloy may be any known material as long as it has the heat dissipation properties required for a heat dissipation circuit board. Examples of the copper or copper alloy include compounds having the composition formula: CuxMyTz (Cu represents a copper atom, M represents a chromium, beryllium, molybdenum, nitrogen, or phosphorus atom, and T represents one or more atoms other than Cu and M. x, y, and z represent mass ratios, where x + y + z = 100, x is 60 or more and 100 or less, y is 0 or more and 40 or less, and z is 0 or more and 5 or less). Here, the more copper atoms in the metal material, the better. When high adhesion is required, x is more preferably 80 or more and 100 or less.

[0023] Furthermore, examples of the aluminum or aluminum alloy include compounds having the composition formula: AlxMyTz (Al represents an aluminum atom, M represents a copper, magnesium, or nitrogen atom, and T represents one or more atoms other than Al and M. x, y, and z represent mass ratios, where x+y+z=100, x is 80 or more and 100 or less, y is 0 or more and 20 or less, and z is 0 or more and 3 or less). Here, the more aluminum atoms there are in the metal material, the more preferable, and when high adhesion is required, x is more preferably 90 or more and 100 or less.

[0024] The compounds represented by the above composition formulas have high thermal conductivity and are therefore suitable as heat dissipation materials.

[0025] The metal material is in the form of a sheet having a thickness of 0.2 mm to 20 mm, preferably 0.5 mm to 20 mm. If the thickness of the metal material is less than 0.2 mm, the heat dissipation performance is insufficient, and if it is more than 20 mm, it causes inconvenience in the mounting process of the heat dissipation circuit board.

[0026] The surface roughness (Ra1) of the metal material on the insulating layer side is preferably 1.0 μm or less, more preferably 0.8 μm or less. If the surface roughness (Ra1) is greater than 1.0 μm, cracks may occur in the insulating layer when repeatedly exposed to high temperatures. If heat resistance of 150°C or higher is desired, the surface roughness (Ra1) is more preferably 0.8 μm or less.

[0027] The metal material is preferably chemically and / or physically smoothed so that the surface roughness (Ra1) is 1.0 μm or less. Physical smoothing is more preferable because microchemical changes on the surface of the metal material adversely affect adhesion to the metal oxide layer. An example of physical smoothing is buffing with added abrasive grains.

[0028] Here, the surface roughness (Ra1) is the "arithmetic mean roughness" and refers to a value calculated by measurement using a contact surface roughness meter, a laser microscope, an atomic force microscope, etc. The same applies to the surface roughness (Ra2) described below.

[0029] <Insulating layer> The insulating layer of the present invention is a metal oxide layer that is represented by the composition formula: AlxOyTz (wherein Al represents an aluminum atom, O represents an oxygen atom, and T represents one or more atoms other than Al and O. x, y, and z represent a mass ratio, where x+y+z=100, x is 30 or more and 60 or less, y is 40 or more and 70 or less, and z is 0 or more and 10 or less), and has a thickness of 0.2 μm or more and 30 μm or less, a volume resistivity of 1000 GΩ cm or more, and a porosity of 10% or less.

[0030] The metal oxide layer is an oxide of aluminum, and metal oxide layers represented by the above composition formula often have a volume resistivity of 1000 GΩ·cm or higher. However, from the viewpoint of improving insulation and thermal conductivity, x is preferably 40 or higher and 57 or lower, y is preferably 43 or higher and 60 or lower, and z is preferably 0.1 or higher and 8 or lower. If z is less than 0.1, the metal oxide film becomes too hard and is prone to cracking when strain occurs in the heat dissipation circuit board. Furthermore, if z is greater than 8, insulation properties may be impaired when a voltage greater than 400 V is applied. Furthermore, from the viewpoint of preventing a decrease in volume resistivity due to impurities, T is preferably a carbon atom, a hydrogen atom, a nitrogen atom, a phosphorus atom, a sulfur atom, a halogen atom, or a combination of these atoms.

[0031] The insulating layer has a thickness of 0.2 μm to 30 μm, and if higher insulation is required, the thickness is preferably 0.8 μm to 30 μm. If the thickness is less than 0.2 μm, the insulating performance will be poor, and if it is more than 30 μm, the insulating layer may crack when heated to 100° C. or higher.

[0032] The insulating layer has a volume resistivity of 1000 GΩ·cm or more when a DC voltage of 400 V is applied. Therefore, electricity sufficient to cause a short circuit will not flow between the conductive metal layer and the metal material at a voltage of 400 V or less. The insulating layer preferably has a volume resistivity of 2000 GΩ·cm (2 TΩ·cm) or more, and more preferably 80000 GΩ·cm (80 TΩ·cm) or more.

[0033] The insulating layer has a porosity of 10% or less. From the viewpoint of improving heat dissipation, the insulating layer preferably has a porosity of 5% or less, more preferably 3% or less, and even more preferably 1% or less. Here, porosity is a measured value sometimes called porosity, and is the volume ratio of the space occupied by gas in the metal oxide layer. The occurrence of gaps, cracks, voids, etc. in the insulating layer increases the porosity value. Known methods for measuring porosity include the Archimedes method, mercury porosity method, and weight porosity method, and are not particularly limited. However, the above-mentioned measurement methods cannot be applied to measuring porosities of 10% or less, such as the insulating layer (metal oxide layer) of the present invention. Therefore, to determine the porosity of 10% or less, an electron microscope photograph of the insulating layer (metal oxide layer) is taken, and the area (S1) of the insulating layer (total of the metal oxide and voids) and the area (S2) of the space in the electron microscope photograph are calculated, and then the porosity is calculated using the following formula. Porosity=S2×100 / S1(%)

[0034] The insulating layer preferably has a surface roughness (Ra2) of 0.3 μm or less, more preferably 0.1 μm or less, on the conductive metal layer side. If the surface roughness (Ra2) is greater than 0.3 μm, the conductive metal layer may crack when repeatedly exposed to high temperatures. If heat resistance of 150°C or higher is desired, the surface roughness (Ra2) is more preferably 0.1 μm or less.

[0035] The carbon atom content of the metal oxide layer is preferably 0.1% by mass or more, and more preferably 0.2% by mass or more, from the viewpoint of improving adhesion to metal materials and flexibility while maintaining heat dissipation and insulating properties. If the carbon atom content is lower than 0.1% by mass, the metal oxide layer becomes hard, and when the heat dissipation circuit board is bent, the adhesion and flexibility may be insufficient, leading to cracking. Furthermore, the carbon atom content is more preferably 5% by mass or less, and even more preferably 3% by mass or less. If the carbon atom content exceeds 3% by mass, insulation may be impaired when a voltage of 400 V or more is applied. The carbon atom content of the metal oxide layer can be measured by dynamic SIMS.

[0036] The method for forming the insulating layer (metal oxide layer) is not particularly limited, and examples of methods that can be used to achieve a porosity of 10% or less and a volume resistivity of 1000 GΩ cm or more include physical vapor deposition methods such as vacuum deposition, ion plating, and sputtering, chemical vapor deposition methods such as plasma CVD, atomic layer deposition (ALD), metalorganic CVD, and mist CVD, and coating methods in which a coating liquid is reacted on a metal material, such as spraying, inkjet, spin coating, and dip coating. Among these, chemical vapor deposition and coating methods are preferred because of their excellent film formation speed and uniformity.

[0037] In the chemical vapor deposition and coating methods, it is preferable to form a metal oxide layer by subjecting a coating liquid containing an aluminum salt or complex to a thermal reaction on a metal material in an atmosphere at a temperature of 230°C to 450°C, since copper atoms or aluminum atoms in the metal material bond directly or via oxygen bonds with aluminum atoms in the insulating layer, thereby improving interfacial adhesion. If the film formation temperature exceeds 450°C, the heat load on the metal material will be large, resulting in poor dimensional stability of the resulting heat dissipation circuit board. In addition, the large difference in thermal expansion coefficient between the metal material and the insulating layer may cause cracks in the metal oxide layer after returning to room temperature.

[0038] In particular, a method of forming a film by atomizing or misting a coating liquid and transporting the resulting mist or droplets onto a metal material using a carrier gas such as nitrogen, followed by heating and reacting the mist or droplets on the metal material in an atmosphere at a temperature of 230°C to 450°C (hereinafter referred to as mCVD) is the most preferred. This method is a type of chemical vapor deposition. By forming a coating liquid containing an aluminum salt or complex into fine droplets and allowing them to react, a thin, uniform film thickness and a porosity of 3% or less can be formed on a metal material with a surface roughness (Ra1) of 1.0 μm or less, resulting in a metal oxide layer with a surface roughness (Ra2) of 0.3 μm or less. Furthermore, this method increases the reactivity of the aluminum salt or aluminum complex in the coating liquid through atomization or mist formation, allowing the metal oxide layer to be formed at temperatures of 230°C to 450°C. This allows for film formation without deterioration of the metal material, and results in a metal oxide layer with high volume resistivity. Furthermore, by forming the film by mCVD in a temperature range of 230° C. to 450° C., it is possible to control the carbon atom content of the metal oxide layer within a range of 0.1% by mass to 5% by mass. For information on mCVD and its apparatus, see, for example, JP 2018-140352 A and JP 2018-172793 A.

[0039] The coating liquid preferably contains 0.2% to 20% by mass of an aluminum complex. If the aluminum complex content is less than 0.2% by mass, the film formation time may be long, and if it is more than 20% by mass, the surface roughness (Ra2) of the metal oxide layer may increase.

[0040] In the mCVD process, it is preferable to form the film in an environment with an oxygen concentration of 1% or less to prevent oxidation of the metal. Furthermore, it is preferable to use water as an oxidizing source to prevent the atomized coating liquid from igniting. Here, the oxidizing source is a source of oxygen atoms that converts aluminum salts or aluminum complexes into alumina.

[0041] In this way, by forming a coating liquid containing an aluminum salt or complex into minute droplets on a metal material and then allowing them to react, it is possible to fill in the irregularities on the surface of the metal material.

[0042] <Conductive metal layer> The material of the conductive metal layer of the present invention is not particularly limited as long as it is a metal commonly used for electrodes. Examples of the material of the conductive metal layer include copper, silver, chromium, ITO, and IZO. The thickness of the electrode is not particularly limited, and may be, for example, 0.5 μm or more and 0.5 mm or less.

[0043] In the heat dissipation circuit board, it is required that no current flows between the conductive metal layer and the metal material. To confirm this, a DC voltage of 5 V is applied to the metal material and the conductive metal layer, and no current of 1 mA or more flows.

[0044] The method for forming the conductive metal layer is not particularly limited, and examples thereof include laminating copper foil processed into a circuit shape, forming a plate and then etching it into a circuit shape, and vapor-depositing a conductive metal layer and then etching it into a circuit shape.

[0045] If necessary, an adhesive layer, an anchor layer, or the like may be provided between the insulating layer and the conductive metal layer.

[0046] When higher heat dissipation performance is desired, the heat dissipation circuit board of the present invention is preferably used as a heat dissipation component in which the metal material is bonded to a heat sink with an adhesive or grease, and the adhesive or grease preferably has high thermal conductivity.

[0047] A typical method of using the heat dissipation circuit board of the present invention is to provide a heating element, such as a semiconductor chip, on the conductive metal layer, which generates heat when electricity is passed through it, and the heat generated by the heating element is dissipated to the metal material via the insulating layer (metal oxide layer). [Example]

[0048] The present invention will be described in more detail below with reference to examples and comparative examples.

[0049] <Production example> <Preparation of coating liquid> A coating liquid was prepared using the raw materials and blending ratios (mass %) shown in Table 1.

[0050] [Table 1]

[0051] In Table 1, Al(acac)3 represents aluminum tris(acetylacetonate) ("Aluminum Chelate A", manufactured by Kawaken Fine Chemicals Co., Ltd.); Al(iPr)2Eacac is aluminum ethyl acetoacetate diisopropylate ("ALCH", manufactured by Kawaken Fine Chemicals Co., Ltd.); Al(Eacac)3 is aluminum tris(ethylacetoacetate) ("ALCH-TR", Kawaken Fine Chemicals Co., Ltd.); Al(Eacac)2acac represents aluminum monoacetylacetonate bis(ethylacetoacetate) ("Aluminum Chelate D", manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0052] Example 1 <Formation of insulating layer (metal oxide layer)> Using the film formation apparatus (mCVD apparatus) shown in Figure 1, an insulating layer (metal oxide layer) was formed on a metal material using the following method. A polypropylene film was fixed 1 cm from the bottom of a glass cylinder (13 cm diameter, 15 cm height) using an O-ring and caulking agent. A Teflon (registered trademark) lid was attached to the top of the cylinder, and two holes were drilled in the lid to insert glass pipes for nitrogen gas supply and mist delivery. The glass pipe for mist delivery was placed 1 cm to 2 cm from the metal material on the hot plate. The cylinder was immersed in a water bath, and an ultrasonic vibrator (ultrasonic atomization unit HMC-2401; Honda Electronics Co., Ltd.) was placed directly below the polypropylene. The hot plate was placed in a nitrogen-filled box, and the oxygen concentration was controlled at 1% or less. The coating solution described above was placed in the cylinder, and the ultrasonic vibrator was activated. Ultrasonic waves were transmitted to the coating solution via the water in the water tank and the polypropylene, atomizing a portion of the coating solution. The atomized coating liquid was transported onto a metal substrate (30 mm x 30 mm) using nitrogen gas. The metal substrate was heated by a hot plate, and the atomized coating liquid was chemically reacted on the metal substrate to form a metal oxide layer, resulting in a laminate. The thickness of the metal oxide layer was adjusted by the film formation time (the time the atomized coating liquid was sprayed onto the metal substrate) and measured using the following method. The nitrogen gas flow rate was 6 L / min, and the ultrasonic vibrator had a frequency of 2.4 MHz, a voltage of 24 V, and a current of 0.6 A. The conditions used, such as the metal substrate, coating liquid, and hot plate temperature, are shown in Table 2.

[0053] <Measuring the thickness of the metal oxide layer> The thickness of the metal oxide layer was measured by forming a metal oxide layer on chrome glass instead of the above-mentioned metal material, and measuring the thickness using a reflectance spectroscopic film thickness meter (F20; manufactured by Filmetrics, Inc.). It was assumed that the metal oxide layer was formed with the same film thickness on the chrome glass and the metal material. However, in Examples 6, 7, 9, and 13 and the Comparative Example described below, the metal oxide layer was not transparent, so cross sections were formed by ion milling, and micrographs were taken with a scanning electron microscope to measure the film thickness.

[0054] <Measurement of surface roughness of metal materials and metal oxide layers> The surface roughness of the metal material (Ra1) and the surface roughness of the metal oxide layer (Ra2) were measured using a contact surface roughness meter (DektakXT-S, manufactured by Bruker Japan Co., Ltd.) Measurements were taken over a 0.5 mm area at the center of the substrate, and the arithmetic mean roughness was calculated.

[0055] <Measurement of the composition of the metal oxide layer> The masses of aluminum atoms, oxygen atoms, and carbon atoms per unit volume and their ratios were calculated using dynamic SIMS. The measurement device used was a PHI ADEPT (manufactured by ULVAC-PHI, Inc.), and the primary ion species was Cs + The primary acceleration voltage was 5.0 kV, and the detection area was 45 × 45 μm. A 1 μm thick metal oxide was formed on glass as the sample. Measurements were taken from the center of the sample in the depth direction, and the point where silicon was detected was defined as the 1 μm depth. The mass ratios of the three atoms were calculated from the secondary ion intensities, relative sensitivity coefficients, and atomic weights of aluminum, oxygen, and carbon atoms. Since the total atomic mass of the three atoms per unit volume did not differ by more than 1% from the specific gravity of the metal oxide layer, the metal oxide layer was assumed to be primarily composed of these three atoms, and the mass ratios of the three atoms per unit volume were calculated as the composition ratio.

[0056] The laminate obtained above was subjected to the following evaluations.

[0057] <Adhesion> Adhesion was evaluated by the presence or absence of peeling between the metal material and the metal oxide after a thermal resistance test. Specifically, a 30mm x 30mm laminate was subjected to 100 thermal resistance cycles, with one cycle consisting of 35 minutes at -40°C and 35 minutes at 200°C, using an Espec Corp. TSA-103ES-W thermal resistance tester. After the test, the laminate was visually inspected, and the results were evaluated as follows: no peeling was good (◯), no peeling but cracks were fair (△), and peeling was poor (×).

[0058] <Insulation> A 10 mm diameter circular main electrode was formed on the metal oxide layer of a 30 mm x 30 mm laminate using silver paste (Dotite FA-451A; Fujikura Kasei Co., Ltd.) as a conductive metal layer to prepare a heat dissipation circuit board. Using the resulting heat dissipation circuit board, a 400 V DC voltage was applied between the metal material and the main electrode using an ADC 5450 high resistance meter, measuring the current. A volume resistivity of 2000 GΩ·cm or greater was evaluated as "good," a volume resistivity of 1000 GΩ·cm or greater but less than 2000 GΩ·cm was evaluated as "fair," and a volume resistivity of less than 1000 GΩ·cm was evaluated as "unacceptable."

[0059] <Porosity> A cross section of the metal oxide layer was formed using ion milling, and a micrograph measuring 500 nm x 500 nm or larger was obtained. The area of ​​the insulating layer (total of metal oxide and voids) in the micrograph (S1 = 500 nm x 500 nm) and the area of ​​the voids in the electron micrograph (S2) were calculated using the following formula. The area of ​​the voids was calculated by adding up the areas of all voids with a long side of 10 nm or larger. Porosity=S2×100 / S1(%) Those with a porosity of 10% or less were evaluated as good (◯), and those with a porosity of more than 10% were evaluated as unacceptable (×).

[0060] <Thermal conductivity (heat dissipation)> In a dry glove box purged with nitrogen from a cylinder, approximately 10 grains of non-deliquescent ammonium acetate (melting point 112°C) were placed on the metal oxide layer of a 30mm x 30mm laminate, and the laminate was then placed metal-side down on a hot plate at 120±3°C. The melting of the ammonium acetate was photographed enlarged with a CCD camera, and the time T1 required for the ammonium acetate to become completely liquid after being placed on the hot plate was measured. A time T1 of 120 seconds or less was evaluated as "good" (◯); a time T1 of less than 120 seconds but up to 150 seconds was evaluated as "fair" (△); and a time T1 of more than 150 seconds was evaluated as "unacceptable" (X).

[0061] <Confirmation of the formation of a conductive metal layer> A conductive metal layer of silver paste (Dotite FA-451A, manufactured by Fujikura Kasei Co., Ltd.) was screen printed onto the center of the metal oxide layer to form a 2 mm x 20 mm (thickness: 20-30 μm) area. The layer was then heated at 150°C for 30 min and then at 200°C for 24 h to form an electrode, producing a heat dissipation circuit board. A voltage of 5 V was applied to both ends of the long sides of the electrode, and the electrical resistance was measured. The electrical resistance was 5 x 10 -3 Ω·cm or less is considered good, and electrical resistance is 5×10 -3 If the electrical resistance was greater than 5×10 Ω·cm, it was marked as "×". If a crack occurred in the electrode, it was marked as "×". -3 Even if the resistance was below Ω·cm, if cracks were visible in the conductive metal layer, the rating was "Fair".

[0062] <Confirming electrical conductivity between the conductive metal layer and metal material> Using the heat dissipation circuit board obtained above, a voltage of 5 V was applied to the electrodes formed from silver paste and the metal material, and if the current that flowed was 1 mA or less, it was rated as good (◯), and if the current that flowed was more than 1 mA, it was rated as bad (×).

[0063] <Examples 2-12 and 14> A laminate was produced and evaluated as described above in the same manner as in Example 1, except that the conditions for forming the insulating layer (metal oxide layer) in Example 1 were changed to the conditions shown in Table 2. The results are shown in Table 2.

[0064] Example 13 Referring to the Chemical Engineering Journal "Production of Alumina Thin Films by CVD Method and Reaction Rate Analysis" (1998, Vol. 24, No. 1, pp. 81-85), an internally heated CVD device was used to form a metal oxide layer on a metal material using aluminum triisopropoxide as the raw material, to produce a laminate, and the above evaluation was carried out. Here, the film formation time was 90 minutes, the film formation temperature was 630°C, and the oxygen flow rate was 6 L / min. After film formation, the metal material had formed copper oxide and was blackened, and numerous cracks were visible in the metal oxide layer.

[0065] [Table 2]

[0066] <Comparative Example 1> A circuit board was obtained with reference to Example 1 of Patent Document 1. Specifically, a metal material (30 mm × 30 mm) made of aluminum and having a thickness of 0.4 mm and a metal oxide substrate (ceramic substrate; 30 mm × 30 mm) made of aluminum nitride (AlN) and having a thickness of 635 μm were laminated via a brazing foil (thickness 12 μm) made of an Al-7.5 mass % Si alloy, and the resulting laminate was heated at 630°C × 6.0 × 10 -4 The circuit boards were bonded by heating and pressing in a hot press in an atmosphere of 20 Pa. The obtained circuit boards were evaluated as described above. The results are shown in Table 3.

[0067] <Comparative Example 2> A circuit board was obtained with reference to Example 1 of Patent Document 2. Specifically, a 20 μm thick thermosetting resin composed of bisphenol A epoxy resin and 3,4-methyl-1,2,3,6-tetrahydrophthalic anhydride was applied to one side of a 0.3 mm thick aluminum metal material (30 mm × 30 mm), and the resin was cured by heating at 230°C for 3 hours. The side not coated with the thermosetting resin was then anodized in an oxalic acid aqueous solution to obtain an 80 μm thick anodized aluminum layer. The thickness of the anodized aluminum layer was measured by forming a cross section using an ion milling method, taking a micrograph using a scanning electron microscope, and measuring the film thickness. The obtained circuit board was subjected to the above evaluations. The results are shown in Table 3.

[0068] <Comparative Example 3> A circuit board was obtained with reference to Patent Document 3. Specifically, alumina powder (6103; manufactured by Metco) was sprayed onto one surface of a 0.5 mm thick copper metal material (30 mm × 30 mm) at 1650°C so that a metal oxide layer of 95 μm was formed. The thickness of the sprayed layer was measured by forming a cross section using an ion milling method, taking a micrograph using a scanning electron microscope, and measuring the film thickness. The obtained circuit board was subjected to the above evaluations. The results are shown in Table 3.

[0069] <Comparative Example 4> A circuit board was obtained with reference to Example 1 of Patent Document 4. Specifically, a metal oxide layer was formed on one surface of a 0.5 mm thick metal material (30 mm × 30 mm) made of SUS316 using the film-forming device used in Example 1 and a 1 wt % aqueous solution of tin (II) acetylacetonate as the coating liquid (referred to as Coating Liquid E in Table 3) at a hot plate temperature of 450°C. The thickness of the metal oxide layer was measured by forming a cross section using an ion milling method, taking a micrograph with a scanning electron microscope, and measuring the film thickness. The obtained circuit board was subjected to the above evaluations. The results are shown in Table 3.

[0070] <Comparative Example 5> A laminate was produced and evaluated as described above in the same manner as in Example 1, except that the conditions for forming the insulating layer (metal oxide layer) in Example 1 were changed to the conditions shown in Table 3. The results are shown in Table 3.

[0071] [Table 3]

[0072] The heat dissipation circuit board in Comparative Example 1 was manufactured by a heat pressing method, which is a common method for manufacturing heat dissipation circuit boards. The insulating layer of the heat dissipation circuit board obtained in Comparative Example 1 had a low porosity and was thick, resulting in lower thermal conductivity than the examples.

[0073] The heat dissipation circuit board produced by an anodic oxidation method was used in Comparative Example 2. The heat dissipation circuit board obtained in Comparative Example 2 not only had lower insulation properties than the examples, but also had insufficient heat dissipation properties.

[0074] The heat dissipation circuit board produced by the thermal spraying method is shown in Comparative Example 3. The heat dissipation circuit board obtained in Comparative Example 3 has a low porosity and is thick, resulting in lower thermal conductivity than the examples.

[0075] Comparative Example 4 is a heat dissipation circuit board manufactured by the mCVD method. The heat dissipation circuit board obtained in Comparative Example 4 had insufficient insulation and thermal conductivity because the composition of the insulating layer and the type of substrate were outside the scope of the claims of this patent. In addition, the surface roughness (Ra1) of the substrate was high, so cracks occurred in the electrodes during the formation of the conductive metal layer.

[0076] Comparative Example 5 is a heat dissipation circuit board manufactured by the same mCVD method as Comparative Example 4, and uses the insulating layer of the present invention. Although the insulation was higher than Comparative Example 4, the adhesion was low due to poor compatibility with the substrate, and the thermal conductivity was also low. In addition, the surface roughness (Ra1) of the substrate was high, so cracks occurred in the electrodes during the formation of the conductive metal layer.

Claims

1. A heat dissipation circuit board having a metal material provided adjacent to one surface of an insulating layer and a conductive metal layer provided on the other surface of the insulating layer, The metal material is made of copper or a copper alloy, or aluminum or an aluminum alloy, and is in the form of a sheet having a thickness of 0.2 mm or more and 20 mm or less; The insulating layer has a composition formula: AlxOyTz (wherein Al represents an aluminum atom, O represents an oxygen atom, and T represents one or more atoms other than Al and O; x, y, and z represent mass ratios, where x + y + z = 100, x is 30 or more and 60 or less, y is 40 or more and 70 or less, and z is 0 or more and 10 or less), and A heat dissipation circuit board comprising a metal oxide layer having a thickness of 0.2 μm or more and 30 μm or less, a volume resistivity of 1000 GΩ·cm or more, and a porosity of 10% or less.

2. 2. The heat dissipation circuit board according to claim 1, wherein the surface roughness (Ra1) of the metal material on the insulating layer side is 1.0 μm or less, and the surface roughness (Ra2) of the insulating layer on the conductive metal layer side is 0.3 μm or less.

3. 3. The heat dissipation circuit board according to claim 1, wherein the metal oxide layer has a carbon atom content of 0.1% by mass or more and 5% by mass or less.

4. 3. The heat dissipation circuit board according to claim 1, wherein said metal material is bonded to a heat sink with an adhesive or grease.

5. 3. A method for manufacturing a heat dissipation circuit board according to claim 1 or 2, The method for manufacturing a heat dissipation circuit board, wherein the insulating layer is formed by reacting a coating liquid containing an aluminum salt or complex on the metal material to form a film.

6. 6. The method for manufacturing a heat dissipation circuit board according to claim 5, wherein the film-forming method comprises atomizing or dropletizing the coating liquid to obtain a mist or droplets, transporting the mist or droplets with a carrier gas, and then reacting the mist or droplets on the metal material in an atmosphere at a temperature of 230°C or higher and 450°C or lower.

7. 6. The method for manufacturing a heat dissipation circuit board according to claim 5, wherein the coating liquid contains an aluminum complex in an amount of 0.2% by mass to 20% by mass.

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