Laminate and method for producing laminate

Abstract

According to one embodiment of the present invention, there is provided a laminate comprising a first metal layer, a second metal layer provided so as to face the first metal layer, an insulating layer provided between the first metal layer and the second metal layer and formed of a material including a resin, and a ceramic film provided between the insulating layer and the second metal layer.

Description

Laminate and method for manufacturing laminate

[0001] The present disclosure relates to laminates and methods for making laminates.

[0002] Patent Document 1 discloses a laminate capable of forming a metal base circuit board, in which the bonding surface between the insulating layer and the metal layer is roughened to have an increased surface roughness (maximum height roughness Rz) to improve the bonding reliability between the insulating layer and the metal layer.

[0003] Japanese Patent Application Laid-Open No. 2022-173751

[0004] When such a laminate is used in a wiring board for transmitting high-frequency signals, excellent transmission characteristics are required. However, when the second metal layer that can function as a circuit is roughened as in Patent Document 1, it is difficult to eliminate the possibility of loss in transmission, particularly of high-frequency signals.

[0005] In view of the above circumstances, the present disclosure provides a laminate in which bonding reliability is improved without roughening the portions that can function as circuits, and a method for manufacturing the same.

[0006] According to one aspect of the present invention, there is provided a laminate comprising a first metal layer, a second metal layer disposed opposite the first metal layer, an insulating layer disposed between the first metal layer and the second metal layer and made of a material containing resin, and a ceramic film disposed between the insulating layer and the second metal layer.

[0007] According to this aspect, the bonding reliability can be improved without roughening the second metal layer.

[0008] FIG. 1 is a cross-sectional view showing the configuration of a laminate according to a first embodiment. (a) to (c) are diagrams schematically showing a method for manufacturing a laminate according to the first embodiment. (b) to (c) are cross-sectional views showing the configuration of a laminate according to a second embodiment. (c) are cross-sectional views showing the configuration of a circuit board according to a third embodiment. (d) are schematic diagrams of a circuit board according to a third embodiment as viewed from above. (a) to (c) are diagrams schematically showing a method for manufacturing a circuit board according to the third embodiment. (d) are cross-sectional views showing the configuration of a circuit board according to a fourth embodiment. (a) to (c) are diagrams schematically showing a method for manufacturing a circuit board according to the fourth embodiment. (c) are schematic diagrams showing the configuration of a circuit tensile strength measuring device.

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Various features shown in the following embodiment can be combined with each other.

[0010] [First embodiment] [Laminate] First, a first embodiment of a laminate according to the present disclosure will be described. FIG. 1 is a cross-sectional view showing the configuration of a laminate according to the first embodiment. In the following description, the upper side in FIG. 1 will be referred to as "top" or "upper," and the lower side will be referred to as "bottom" or "lower." The laminate 1 shown in FIG. 1 includes a first metal layer 11, a second metal layer 12, an insulating layer 13, and a ceramic film 15. As shown in FIG. 1, the first metal layer 11 and the second metal layer 12 are disposed opposite each other. The insulating layer 13 is disposed between the first metal layer 11 and the second metal layer 12, and the ceramic film 15 is disposed between the insulating layer 13 and the second metal layer 12.

[0011] The constituent materials (metal materials) of the first metal layer 11 and the second metal layer 12 preferably have high thermal conductivity. The high thermal conductivity of the constituent materials of the first metal layer 11 and the second metal layer 12 can improve the heat dissipation characteristics of the laminate 1. For this reason, the laminate 1 can also be used in applications such as wiring boards that transmit high-frequency signals.

[0012] Specific examples of metal materials include iron, copper, aluminum, nickel, zinc, molybdenum, tungsten, gold, silver, platinum, and alloys containing at least one of these. The metal material is preferably copper. By using copper as the metal material, the first metal layer 11 and the second metal layer 12 can each have the advantages of high thermal conductivity, high workability, high mechanical strength, and low cost. The constituent materials of the first metal layer 11 and the second metal layer 12 may be the same or different from each other.

[0013] The surface roughness (maximum height roughness Rz) of the lower surface 121 of the second metal layer 12 (the surface on the insulating layer 13 side) is preferably small. For example, in order to solve the problem of reduced bonding reliability between the insulating layer and the metal, particularly after high-temperature treatment, the bonding surface between the insulating layer and the second metal layer on which a circuit can be formed may be roughened (the surface roughness (maximum height roughness Rz) is increased).

[0014] On the other hand, in the configuration of this embodiment, the ceramic film 15 is disposed between the second metal layer 12 and the insulating layer 13. The ceramic film 15 is well bonded to both the second metal layer 12 and the insulating layer 13. Furthermore, according to the studies of the present inventors, bonding reliability is maintained even when the laminate 1 is subjected to high-temperature treatment. That is, the bonding reliability between the second metal layer 12 and the insulating layer 13 can be improved without a roughening treatment for achieving a roughened state. In other words, it is not necessary to roughen the lower surface 121 of the second metal layer 12 (the surface on the insulating layer 13 side), which is the bonding surface with the ceramic film 15. Details of the ceramic film 15 will be described later.

[0015] Therefore, according to the configuration of this embodiment, the surface roughness (maximum height roughness Rz) of the lower surface 121 of the second metal layer 12, i.e., the bonding surface between the second metal layer 12 and the ceramic film 15, can be sufficiently reduced. This reduces transmission loss of signals such as electricity passing through the second metal layer 12 (including the region close to the insulating layer 13). Furthermore, since electric field concentration due to unevenness is unlikely to occur on the lower surface 121, a decrease in insulation strength due to electric field concentration can be suppressed. Furthermore, the thickness T12 of the second metal layer 12 is maintained relatively constant in the in-plane direction of the second metal layer 12. Therefore, unevenness in the transmission of signals such as high-frequency signals is unlikely to occur, and signals are easily transmitted uniformly in the in-plane direction of the second metal layer 12. Furthermore, since it is not necessary to form the second metal layer 12 thick to ensure the required thickness based on the thinnest portion, this contributes to the miniaturization (particularly, the low profile) of the second metal layer 12 and the entire laminate 1. The surface roughness (maximum height roughness Rz) of the lower surface 121 of the second metal layer 12 is preferably about 3 μm or less, more preferably about 1.5 μm or less, and even more preferably about 1 μm or less. By setting the surface roughness within this range, the thickness T12 of the second metal layer does not vary significantly, and the above-mentioned effects can be fully achieved.

[0016] Furthermore, the surface roughness (maximum height roughness Rz) of the lower surface 121 of the second metal layer 12 may be, for example, approximately 0.1 μm or more, approximately 0.2 μm or more, or approximately 0.3 μm or more. Thus, by providing the lower surface 121 of the second metal layer 12 with a certain degree of surface roughness (maximum height roughness Rz), it is possible to expect that the bonding strength between the second metal layer 12 and the ceramic film 15 can be ensured. Note that, in this specification, the upper and lower limits can be appropriately combined. That is, the surface roughness (maximum height roughness Rz) of the lower surface 121 of the second metal layer 12 (the surface facing the insulating layer 13) may be, for example, approximately 0.1 μm or more and 3 μm or less, approximately 0.2 μm or more and 1.5 μm or less, or approximately 0.3 μm or more and 1 μm or less.

[0017] Furthermore, the surface roughness (arithmetic mean roughness Ra) of the lower surface 121 of the second metal layer 12 is preferably about 1.5 μm or less, more preferably about 1 μm or less, and even more preferably about 0.5 μm or less. This reduces the overall unevenness (roughness) of the lower surface 121 of the second metal layer 12, thereby more reliably achieving the above-mentioned effects. Furthermore, the surface roughness (arithmetic mean roughness Ra) of the lower surface 121 of the second metal layer 12 may be, for example, about 0.001 μm or more, about 0.005 μm or less, or about 0.01 μm or less. That is, the surface roughness (arithmetic mean roughness Ra) of the lower surface 121 of the second metal layer 12 may be about 0.001 μm or more and about 1.5 μm or less, about 0.005 μm or more and about 1 μm or less, or about 0.01 μm or more and about 0.5 μm or less.

[0018] In this specification, the surface roughness (arithmetic mean roughness Ra) and the surface roughness (maximum height roughness Rz) can be measured using a laser microscope in accordance with JIS B 0601:2013 (ISO 4287:1997). Even in the state of the laminate 1, for example, a scanning electron microscope (SEM) image of the cross section of the laminate 1 can be obtained, and an approximate value of the surface roughness (maximum height roughness Rz) can be obtained according to JIS B 0601:2013 (ISO 4287:1997). Furthermore, when a numerical range is exemplified in this specification, the proportion of the portion satisfying the numerical range (e.g., the above-mentioned range of surface roughness (maximum height roughness Rz)) (e.g., the area of ​​the lower surface 121 of the second metal layer 12 where the surface roughness (maximum height roughness Rz) satisfies the above-mentioned range) is preferably 70% or more, more preferably 85% or more, even more preferably 90% or more, particularly preferably 95% or more, or even 100%.

[0019] The ratio T12 / T1 of the thickness T12 of the second metal layer to the thickness T1 of the laminate is preferably approximately 0.0001 or more and 0.9 or less, more preferably approximately 0.005 or more and 0.6 or less, and even more preferably approximately 0.01 or more and 0.4 or less. By sufficiently reducing the thickness T12 of the second metal layer, the laminate 1 can be miniaturized (particularly, reduced in height). As described above, by providing the ceramic film 15 between the second metal layer 12 and the insulating layer 13, such a small thickness T12 of the second metal layer (thin second metal layer 12) can be achieved. Furthermore, by ensuring a relatively large thickness T12 of the second metal layer, the heat capacity of the second metal layer 12 can be improved. Furthermore, due to the difference in thermal conductivity between the second metal layer 12 and the insulating layer 13, heat that is apparently reflected at the lower surface 121 of the second metal layer 12 is less likely to reach the upper surface 122 due to the large thickness T12 of the second metal layer 12. In other words, the heat dissipation characteristics of electronic components such as chips mounted on the upper surface 122 of the second metal layer 12 can be improved. Furthermore, the allowable current of the second metal layer 12 is increased, improving the current withstand capacity (resistance to large currents). Furthermore, the transmission efficiency of high-frequency signals passing through the second metal layer 12 can be improved.

[0020] Here, the thickness T1 of the laminate is not particularly limited, but is preferably about 0.1 mm to 100 mm, about 0.5 mm to 50 mm, or about 1 mm to 10 mm. The thickness T12 of the second metal layer is preferably about 0.005 mm to 10 mm, about 0.05 mm to 5 mm, or about 0.1 mm to 1 mm. In this specification, unless otherwise specified, the thickness (e.g., the thickness T1 of the laminate) refers to the arithmetic average of thicknesses measured at any three points on the side surface. The three points are assumed to be spaced apart by at least 10 mm in the in-plane direction.

[0021] On the other hand, the upper surface 111 of the first metal layer 11 (the surface on the insulating layer 13 side) is roughened to increase the bonding strength with the insulating layer 13. The first metal layer 11 is formed to have a certain thickness to ensure the mechanical strength of the laminate 1. Therefore, even if the thickness of the first metal layer 11 is reduced slightly by the roughening treatment, this is unlikely to be a problem.

[0022] The ratio T11 / T1 of the thickness T11 of the first metal layer to the thickness T1 of the laminate is preferably about 0.01 or more and about 1 or less, more preferably about 0.1 or more and about 1 or less, and even more preferably about 0.5 or more and about 0.9 or less. By satisfying these ranges, it is possible to ensure both the mechanical strength of the laminate 1 and its miniaturization (low profile). The thickness T11 of the first metal layer is not particularly limited, but is preferably about 0.01 mm or more and about 50 mm or less, about 0.1 mm or more and about 10 mm or less, or about 0.5 mm or more and about 5 mm or less.

[0023] An insulating layer 13 is disposed (interposed) between the first metal layer 11 and the second metal layer 12. The insulating layer 13 is composed of a material containing a resin. By including a resin in the insulating layer 13, the processability and heat shock resistance (cold and thermal shock resistance) of the insulating layer 13 can be improved. Furthermore, the laminate 1 can be lightweight and inexpensive. A thermosetting resin is preferably used as the resin. This improves the mechanical strength and heat resistance of the laminate 1, allowing the laminate 1 to be used in wiring boards that transmit high-frequency signals. Examples of thermosetting resins include epoxy resins, silicone resins, phenolic resins, cyanate resins, melamine resins, urea resins, thermosetting polyimide resins, bismaleimide resins, and unsaturated polyester resins. Among these, epoxy resins are preferably used as the thermosetting resin. The use of epoxy resins can improve the adhesiveness, property selectivity, heat resistance, and electrical insulation of the insulating layer 13.

[0024] In particular, it is preferable to use an epoxy resin that can be cured with a curing agent. By combining it with a curing agent, desired properties can be imparted to the insulating layer 13. That is, the material constituting the insulating layer 13 may also contain a curing agent. As the epoxy resin, for example, at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol S type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, polypropylene glycol type epoxy resin, polytetramethylene glycol type epoxy resin, naphthalene type epoxy resin, phenylmethane type epoxy resin, tetrakisphenolmethane type epoxy resin, biphenyl type epoxy resin, epoxy resin having a triazine ring, bisphenol A alkylene oxide adduct type epoxy resin, dicyclopentadiene type epoxy resin, cresol novolac type epoxy resin, and phenol novolac type epoxy resin can be used.

[0025] The curing agent may be any agent capable of curing the thermosetting resin, and may be appropriately selected depending on the type of thermosetting resin. When the thermosetting resin is an epoxy resin, examples of the curing agent (epoxy resin curing agent) include amine-based curing agents, phenol-based curing agents, acid anhydride-based curing agents, and thiol-based curing agents.

[0026] The content of the curing agent in the material constituting the insulating layer 13 is not particularly limited, but is preferably about 1 part by mass to 300 parts by mass, about 10 parts by mass to 200 parts by mass, about 20 parts by mass to 150 parts by mass, or about 50 parts by mass to 100 parts by mass relative to 100 parts by mass of the resin. The amount of the curing agent may be 0 parts by mass.

[0027] The material constituting the insulating layer 13 preferably further contains an inorganic filler dispersed in the resin. This allows the insulating layer 13 to have the advantages of both the resin and the inorganic filler. Examples of the inorganic filler include inorganic oxides and inorganic nitrides. Examples of the inorganic filler include aluminum oxide (Al ２ O ３Preferably, the laminate 1 contains at least one inorganic filler selected from the group consisting of zinc oxide (ZnO), magnesium oxide (MgO), beryllium oxide (BeO), aluminum nitride (AlN), and boron nitride (BN), as its main component. These inorganic fillers are preferred because they combine high thermal conductivity with excellent electrical insulation. The inclusion of such inorganic fillers allows the second metal layer 12 to dissipate heat while maintaining the electrical insulation of the insulating layer 13, and the laminate 1 can also be used in wiring boards that transmit high-frequency signals.

[0028] The content of inorganic filler in the material constituting the insulating layer 13 is preferably about 1% by volume or more and 99% by volume or less, more preferably about 10% by volume or more and 90% by volume or less, even more preferably about 20% by volume or more and 80% by volume or less, and particularly preferably about 30% by volume or more and 70% by volume or less. In this way, by containing a sufficient amount of inorganic filler, the heat dissipation performance of the insulating layer 13 is improved. On the other hand, by not using too much inorganic filler, the insulating performance of the insulating layer 13 can be ensured.

[0029] The ratio T13 / T1 of the thickness T13 of the insulating layer 13 to the thickness T1 of the laminate 1 is preferably approximately 0.017 or more and 0.1 or less, more preferably approximately 0.018 or more and 0.09 or less, and even more preferably approximately 0.02 or more and 0.085 or less. By ensuring a certain thickness T13 of the insulating layer 13, the insulating performance and mechanical strength of the laminate 1 can be sufficiently improved. Furthermore, by reducing the thickness T13 of the insulating layer 13, the overall size of the laminate 1 can be reduced. Furthermore, since the insulating layer 13 containing resin is thin, thermal resistance can be reduced. Therefore, heat dissipation from the laminate 1 can be efficiently achieved. Furthermore, by providing a dense ceramic film 15 between the second metal layer 12 and the insulating layer 13, the insulating layer 13 can be formed thin while maintaining both electrical insulation and mechanical strength of the laminate 1. The thickness T13 of the insulating layer may be, for example, about 1 μm to 50 mm, about 10 μm to 10 mm, or about 50 μm to 1 mm.

[0030] The ceramic film 15 is made of a material containing electrically insulating ceramics. Examples of electrically insulating ceramics include aluminum oxide (Al ２ O ３ ), magnesium oxide (MgO), silicon oxide (SiO ２ quartz, amorphous silica), zinc oxide (ZnO), titanium oxide (TiO ２ ), barium titanate (BaTiO ３ ), yttrium oxide (Y ２ O ３ ), zirconium oxide (ZrO ２ ), oxides such as silicon nitride (α-Si ３ N ４ , β-Si ３ N ４ ), hexagonal boron nitride (hBN), aluminum nitride (AlN), sialon (SiAlON), nitrides such as silicon carbide (SiC), cordierite (2MgO.2Al ２ O ３ 5SiO ２ ), steatite (MgO.SiO ２ ), forsterite (2MgO.SiO ２ ), mullite (3Al ２ O ３ 2SiO ２ ) and other composite oxides.

[0031] Among these, the ceramic film 15 preferably contains at least one selected from the group consisting of aluminum oxide, magnesium oxide, silicon oxide, zinc oxide, yttrium oxide, silicon nitride, boron nitride, titanium oxide, barium titanate, and aluminum nitride. By selecting such a ceramic, the laminate 1 can be provided with desired properties, such as electrical insulation, high thermal conductivity, high heat resistance, low noise, and flame retardancy. Furthermore, the ceramic film 15 more preferably contains at least one selected from the group consisting of aluminum oxide, magnesium oxide, yttrium oxide, zinc oxide, silicon oxide, silicon nitride, boron nitride, and aluminum nitride. These ceramics are suitable from the viewpoint of combining high electrical insulation, high thermal conductivity, high heat resistance, low noise, and flame retardancy. Furthermore, the ceramic content in the ceramic film 15 is preferably approximately 60% or more, approximately 70% or more, or approximately 80% or more, and particularly preferably approximately 90% or more, approximately 95% or more, or approximately 99% or more.

[0032] The ratio of the area of ​​voids in the cross section of the ceramic film 15 (porosity) is preferably, for example, approximately 20% or less, more preferably approximately 10% or less, and even more preferably approximately 5% or less. Forming the ceramic film 15 densely in this manner can further improve the bonding reliability from the second metal layer 12 to the insulating layer 13 while also improving the reliability of the insulating performance. Furthermore, the properties of the ceramics that make up the ceramic film 15, such as insulation, high thermal conductivity, high heat resistance, and low noise characteristics, can be fully utilized. The porosity of the ceramic film 15 may be, for example, 0.01% or more, 0.05% or more, or 0.1% or more. That is, the porosity of the ceramic film 15 may be, for example, approximately 0.01% or more and 20% or less, approximately 0.05% or more and 10% or less, or approximately 0.1% or more and 5% or less. Here, the porosity of the ceramic film 15 can be determined, for example, by acquiring a scanning electron microscope (SEM) image of the side or cross section of the ceramic film 15 (laminate 1) and performing image analysis in which areas in the SEM image that are darker than a predetermined threshold value are determined to be voids.

[0033] The ratio T15 / T13 of the thickness T15 of the ceramic film between the second metal layer 12 and the insulating layer 13 to the thickness T13 of the insulating layer is preferably about 0.001 to 0.1, more preferably about 0.002 to 0.095, and even more preferably about 0.005 to 0.05. By forming the ceramic film 15 thin (reducing the thickness T15 of the ceramic film), it is possible to firmly bond the second metal layer 12 and the insulating layer 13 without performing a roughening treatment while taking advantage of the advantages of the insulating layer 13 containing resin (i.e., excellent heat shock resistance, light weight, and low cost).

[0034] Furthermore, by ensuring a certain thickness T15 of the ceramic film, the advantages of the ceramic film 15, such as insulation, high thermal conductivity, high heat resistance, and low noise characteristics, can be enjoyed, and the second metal layer 12 and the insulating layer 13 can be reliably bonded. The thickness T15 of the ceramic film is preferably approximately 0.001 μm to 50 μm, approximately 0.01 μm to 10 μm, or approximately 0.1 μm to 5 μm. The laminate 1 having the above-described configuration can be used, for example, for the casing of electronic components such as microcomputers and semiconductor devices.

[0035] [Method for Manufacturing Laminate] Hereinafter, a method for manufacturing a laminate according to the first embodiment will be described with reference to Figures 2(a) to 2(c). Figures 2(a) to 2(c) are diagrams that schematically show the method for manufacturing a laminate according to the first embodiment. The method for manufacturing a laminate according to the first embodiment includes a first step of preparing a first metal layer 11, a second metal layer 12, and an insulating layer 13, a second step of arranging a ceramic film 15 between the second metal layer 12 and the insulating layer 13, and a third step of bonding the ceramic film 15 and the insulating layer 13 by applying pressure to the first metal layer 11 and the second metal layer 12 so that they approach each other, thereby obtaining a laminate 1.

[0036] (First Step) In the first step, the first metal layer 11, the second metal layer 12, and the insulating layer 13 are prepared. The first metal layer 11, the second metal layer 12, and the insulating layer 13 may be prepared by purchasing commercially available products or by creating them yourself. In the latter case, the first metal layer 11 and the second metal layer 12 can each be created by cutting out a metal plate, for example. Here, the thickness of the metal plate is selected so that the thickness T11 of the first metal layer and the thickness T12 of the second metal layer satisfy the thickness ratio described above.

[0037] The first metal layer 11 is further subjected to a roughening treatment on the upper surface 111. Roughening the upper surface 111 of the first metal layer 11 can improve the bonding reliability with the insulating layer 13. The method of the roughening treatment is not particularly limited, and examples thereof include chemical or physical etching, blasting, and buffing.

[0038] On the other hand, as described above, the lower surface 121 of the second metal layer 12 does not need to be roughened because the ceramic film 15 has the function of improving the bonding reliability with the insulating layer 13. Therefore, this embodiment has the advantage of saving the time and cost required for roughening the lower surface 121 and simplifying the manufacturing method of the laminate 1. Note that the lower surface 121 of the second metal layer 12 may be subjected to an appropriate polishing process or the like so as to satisfy the above-mentioned ranges of surface roughness (maximum height roughness Rz) and surface roughness (arithmetic mean roughness Ra). The polishing process is not particularly limited, and examples thereof include grindstone processing, lapping, buffing, barrel polishing, and electrolytic polishing.

[0039] In the first step, a semi-cured (B-stage) insulating layer 13 is prepared. For example, a resin-containing material is applied to a release sheet substrate such as a PET film to form a coating film. The thickness of the coating film is adjusted to, for example, approximately 100% to 150% or approximately 130% to 120% of the desired insulating layer thickness T13, taking into account shrinkage due to curing. The coating film is then semi-cured by low-temperature heat treatment. The heating temperature is preferably approximately 60°C to 150°C, and more preferably approximately 80°C to 120°C. The atmospheric pressure is preferably normal pressure, and the heating time is preferably approximately 30 minutes to 120 minutes, and more preferably approximately 50 minutes to 100 minutes. The insulating layer 13 may be subjected to a two-stage heat treatment: a first step in which the insulating layer 13 is semi-cured by pre-curing, and a third step in which the insulating layer 13 is fully cured (fully cured), as described below. This makes it possible to densify the insulating layer 13 and improve the electrical insulating properties and mechanical strength. In this way, the state shown in FIG.

[0040] 2(b), a ceramic film 15 is formed on the lower surface 121 of the second metal layer 12. Examples of methods for forming the ceramic film 15 include vapor phase deposition methods including physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, ion plating, molecular beam epitaxy, and laser ablation, chemical vapor deposition (CVD) methods such as thermal CVD, plasma CVD, and photo-CVD, liquid phase deposition methods including sol-gel methods, co-precipitation, Langmuir-Blodgett methods, electrolytic plating, and electroless plating, thermal spraying methods including flame spraying, plasma spraying, and high velocity flame spraying, and deposition methods using particle collision and deposition including cold spray (CS), aerosol deposition (AD), powder jet deposition (PJD), gas deposition (GD), and particle bombardment coating (EPID).

[0041] Of these, the ceramic film 15 is preferably formed by ion plating, high-velocity flame spraying, cold spraying, or aerosol deposition. These methods are suitable from the viewpoints of material selectivity for the ceramic film 15, bonding reliability, short film formation time, and practicality. Furthermore, the ceramic film 15 is more preferably formed by ion plating or aerosol deposition, with aerosol deposition being even more preferred. These methods are suitable from the viewpoints of the density of the ceramic film 15, controllability of physical properties, and the possibility of film formation at room temperature. In particular, the aerosol deposition method is also preferred from the viewpoints of reducing the environmental impact by saving power consumption, and reducing manufacturing costs.

[0042] When forming the ceramic film 15 by the ion plating method, a material containing ceramic is prepared as the material for the ceramic film 15. Then, the ceramic-containing material and the second metal layer 12 are placed in a chamber. At this time, the second metal layer 12 is placed so that the lower surface 121 of the second metal layer 12 faces the ceramic-containing material. The chamber is depressurized, and a negative charge is applied to the second metal layer 12, and a positive charge is applied to the sublimated ceramic-containing material, thereby depositing the ceramic-containing material on the lower surface 121 of the second metal layer 12.

[0043] In the thermal spraying method, a ceramic-containing material formed into a powder, rod, or other shape is supplied to a thermal spray gun and heated to a molten or semi-molten state. The lower surface 121 of the second metal layer 12 is placed facing the thermal spray gun. The molten or semi-molten ceramic-containing material is then sprayed from the thermal spray gun toward the second metal layer 12.

[0044] In the case of cold spray or aerosol deposition, particles composed of a material containing ceramics are prepared. These particles may be prepared by purchasing commercially available products or by self-preparation. In the latter case, the method for producing the particles is not particularly limited, and they can be prepared, for example, by mixing and pulverizing powdered materials, molding them in a mold, and sintering them in the solid state at atmospheric pressure. The particle diameter of the particles is, for example, approximately 0.1 μm to 10 μm. Here, the particle diameter can be, for example, the cumulative volume 50% diameter (D50) measured using a particle size distribution analyzer using a laser diffraction / scattering method.

[0045] In the cold spray method, particles are first supplied to a film formation apparatus and heated below their melting point. The lower surface 121 of the second metal layer 12 is placed facing the nozzle of the film formation apparatus. The heated particles are then sprayed from the nozzle toward the second metal layer 12. In the aerosol deposition method, the particles are mixed with an inert gas such as argon or nitrogen to form an aerosol. The lower surface 121 of the second metal layer 12 is placed in the chamber of the film formation apparatus so that it faces the nozzle of the film formation apparatus. The chamber is depressurized, and the aerosolized particles are sprayed from the nozzle toward the second metal layer 12. Nitrogen, for example, can be used as a carrier gas for transporting and spraying the aerosol. The spray speed from the nozzle is, for example, greater than subsonic speed and less than sonic speed.

[0046] In this manner, the ceramic film 15 is formed on the lower surface 121 of the second metal layer 12. Thereafter, the upper surface 111 of the first metal layer 11 and the ceramic film 15 of the first metal layer 11 with the ceramic film 15 attached thereto are arranged to face each other with the insulating layer 13 interposed therebetween, resulting in the state shown in FIG.

[0047] 2(c), in the third step, the upper surface 111 of the first metal layer 11 and the ceramic film 15 are brought into contact with the insulating layer 13, and pressure is applied so that the first metal layer 11 and the second metal layer 12 approach each other. The pressure can be applied by a method such as hot pressing or hot isostatic pressing (HIP). By applying heat during this pressure application, the insulating layer 13 in a semi-cured state can be hardened.

[0048] The pressure of the pressurization is not particularly limited, but is preferably about 1 MPa to 30 MPa, more preferably about 5 MPa to 25 MPa, and even more preferably about 8 MPa to 20 MPa. The heating temperature is preferably about 100°C to 300°C, more preferably about 130°C to 250°C, and even more preferably about 160°C to 200°C. The heating time is preferably about 90 minutes to 1200 minutes, more preferably about 120 minutes to 800 minutes, and even more preferably about 250 minutes to 600 minutes. The atmosphere during heating and pressurization can be, for example, air, reduced pressure, or an inert gas (e.g., argon, nitrogen, etc.) atmosphere, but a reduced pressure atmosphere is preferred. Heating and pressurization in a reduced pressure atmosphere can prevent gas from entering the semi-cured insulating layer 13 or between the layers, thereby improving the mechanical strength and bonding reliability of the laminate 1.

[0049] By heating in this manner, the semi-cured insulating layer 13 can be cured while being adhered closely to the lower surface 151 of the ceramic film 15 and the upper surface 111 of the first metal layer 11. Moreover, it is possible to suitably prevent the first metal layer 11, the second metal layer 12, and the ceramic film 15 from being excessively oxidized, deformed, etc. In this manner, the laminate 1 can be manufactured.

[0050] In this embodiment, the ceramic film 15 is formed on the lower surface 121 of the second metal layer 12 in the second step, but the ceramic film 15 may also be formed on the upper surface 132 of the insulating layer 13. Also, instead of forming the ceramic film 15 using a film forming apparatus, a thin ceramic plate may be prepared and placed between the second metal layer 12 and the insulating layer 13. In either case, the lower surface 121 of the second metal layer 12 and the upper surface 152 of the ceramic film 15 can be diffusion bonded, for example, in the third step.

[0051] Furthermore, although one semi-cured insulating layer 13 is prepared in this embodiment, two or more semi-cured insulating layers 13 may be prepared. The third step may then be performed with two or more semi-cured insulating layers 13 stacked on top of each other. In this case, the thickness T13 of one insulating layer 13 obtained by stacking and curing two or more semi-cured insulating layers 13 may be set to satisfy the above-mentioned range. In this way, when two or more semi-cured insulating layers 13 are stacked, the semi-curing time can be shortened.

[0052] Furthermore, in the third step of this embodiment, the insulating layer 13 in a semi-cured state (B stage) is heated and pressurized, but the insulating layer 13 may not be in a semi-cured state but may be in an uncured state (A stage). In this case, after the second step, a material containing resin is applied to at least one of the upper surface 111 of the first metal layer 11 and the lower surface 151 of the ceramic film 15. Then, the third step may be performed under the conditions described above. Alternatively, the third step may be performed in two stages: a heat treatment to bring the insulating layer 13 into a semi-cured state and a heat treatment to completely cure the insulating layer 13.

[0053] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 3. In each figure, the same components as those in the first embodiment (see Fig. 1, etc.) are designated by the same reference numerals. Note that the following description of the second embodiment will focus on differences from the first embodiment, and descriptions of similar matters will be omitted.

[0054] FIG. 3 is a cross-sectional view showing the configuration of a laminate according to a second embodiment. In the second embodiment, the laminate 1 is similar to the first embodiment, except that it further includes another ceramic film 14 disposed between the first metal layer 11 and the insulating layer 13. The constituent material of the other ceramic film 14 and the dimensions of the other ceramic film 14, such as the thickness T14, are the same as those described above for the ceramic film 15. The other ceramic film 14 does not need to roughen the upper surface 111 of the first metal layer 11 to improve the bonding reliability between the first metal layer 11 and the insulating layer 13. This reduces the time and cost required for roughening the first metal layer 11 and simplifies the manufacturing method of the laminate 1. Furthermore, since the thickness T11 of the first metal layer does not vary significantly, the mechanical strength of the laminate 1 can be maintained substantially constant in the in-plane direction of the first metal layer 11. The upper surface 111 of the first metal layer 11 preferably satisfies the same conditions for surface roughness (maximum height roughness Rz) and surface roughness (arithmetic mean roughness Ra) as the lower surface 121 of the second metal layer 12 .

[0055] The laminate 1 according to the second embodiment can be manufactured in the same manner as described in the first embodiment, except that the roughening treatment of the upper surface 111 of the first metal layer 11 is omitted and the other ceramic film 14 is provided. The other ceramic film 14 can be formed in the same manner as the ceramic film 15. That is, the manufacturing method of the laminate 1 further includes a step of disposing the other ceramic film 14 between the first metal layer 11 and the insulating layer 13. Then, in the third step (the step of obtaining the laminate), the other ceramic film 14 and the insulating layer 13 are bonded. In this manner, the laminate 1 shown in FIG. 3 can be obtained. The second embodiment also achieves the same effects and advantages as the first embodiment. In particular, the second embodiment does not require the roughening treatment, and therefore the laminate 1 can be manufactured in an easier manner, allowing for a lower profile.

[0056] [Third Embodiment] Next, a third embodiment of the present disclosure will be described with reference to FIGS. 4 to 6(c). In each figure, the same components as those in the first and second embodiments are designated by the same reference numerals. The following description of the third embodiment will focus on differences from the first and second embodiments, and similar aspects will be omitted. FIG. 4 is a cross-sectional view showing the configuration of a circuit board according to the third embodiment. FIG. 5 is a schematic diagram of a circuit board according to the third embodiment viewed from above. The third embodiment is similar to the second embodiment except for the configuration of the second metal layer 12. That is, as shown in FIGS. 4 and 5, the second metal layer 12 is divided into multiple terminals 12a to 12d.

[0057] Each of the terminals 12a to 12d (second metal layer 12) functions as at least one of wiring and terminals. In this specification, "wiring and terminal" refers not only to wiring and terminals in a circuit board (e.g., a flexible printed circuit board, etc.), but also to, for example, electrodes and mounting pads in a lead frame (e.g., for an integrated circuit, a semiconductor device, etc.). That is, in this embodiment, the laminate 1 is configured as a circuit board 1'. The circuit board 1' may actually be used as a flexible substrate, etc., or as a substrate in a lead frame. As shown in FIGS. 4 and 5, a portion of the insulating layer 13 is exposed from the second metal layer 12 (between the terminals 12a to 12d). This ensures insulation between the terminals 12a to 12d. While FIG. 3 illustrates the case where another ceramic film 14 is provided, the other ceramic film 14 may be omitted and the upper surface 111 of the first metal layer 11 may be roughened, as in the first embodiment. Furthermore, the shape and number of the terminals 12a to 12d are not limited to those shown in the drawings, and can be set appropriately depending on the purpose.

[0058] The circuit board 1' according to the third embodiment can be manufactured by the procedures shown in FIGS. 6(a) to 6(c). FIGS. 6(a) to 6(c) are schematic diagrams illustrating a method for manufacturing a circuit board according to the third embodiment. The method for manufacturing a laminate further includes, after the second step and before the third step, a step of forming the second metal layer 12 with the ceramic film 15 (the second metal layer 12 and the ceramic film 15) to obtain terminals 12a to 12d, as shown in FIG. 6(a). Forming the terminals 12a to 12d can be achieved using methods such as gas cutting, mechanical cutting, laser cutting, and water jet cutting. Among these, mechanical cutting such as wire cutting, band sawing, milling, and press working is preferred, with press working being more preferred. These methods are advantageous from the standpoints of material selectivity and low cost. Press working is particularly preferred from the standpoint of ease of mass production.

[0059] Thereafter, the third step is performed as shown in Fig. 6(b), and the circuit board 1' can be obtained as shown in Fig. 6(c). That is, except for forming the terminals 12a to 12d, the same method as described in the second embodiment can be used to manufacture the circuit board 1' in which the insulating layer 13 is exposed from the second metal layer 12 and the second metal layer 12 functions as at least one of wiring and terminals.

[0060] In this embodiment, the terminals 12a to 12d are formed after the second step and before the third step. This has the advantage that the ceramic film 15 only needs to be formed once. However, the terminals 12a to 12d may be formed before the second step, and then the ceramic film 15 may be formed on each of the terminals 12a to 12d. In this case, there is the advantage that the material for the ceramic film 15 can be saved. The third embodiment also has the same functions and effects as the first and second embodiments. In particular, according to the third embodiment, the laminate 1 can function as a circuit board 1'.

[0061] [Fourth Embodiment] Next, a fourth embodiment of the present disclosure will be described with reference to Figures 7 to 8(c). In each figure, the same components as those in the first to third embodiments are designated by the same reference numerals. The following description of the fourth embodiment will focus on differences from the first to third embodiments, and a description of similarities will be omitted. Figure 7 is a cross-sectional view showing the configuration of a circuit board according to the fourth embodiment.

[0062] The fourth embodiment is similar to the third embodiment, except that a portion of the ceramic film 15 is exposed from the second metal layer 12 (between the terminals 12a-12d). Even when the terminals 12a-12d are formed by cutting out portions of the second metal layer 12, the exposed ceramic film 15, rather than the insulating layer 13 containing resin, provides flame retardancy to the circuit board 1'. Furthermore, the heat resistance of the circuit board 1' can be improved by selecting the appropriate material for the ceramic film 15. While FIG. 3 illustrates the case where another ceramic film 14 is provided, the other ceramic film 14 may be omitted, and the upper surface 111 of the first metal layer 11 may be roughened, as in the first embodiment. Furthermore, the shape and number of the terminals 12a-12d are not limited to those shown in the figure and can be appropriately determined depending on the purpose.

[0063] The circuit board 1' according to the fourth embodiment can be manufactured by the procedure shown in FIGS. 8(a) to 8(c). FIGS. 8(a) to 8(c) are diagrams schematically illustrating a method for manufacturing a circuit board according to the fourth embodiment. In this embodiment, the method for manufacturing a laminate further includes a step of exposing the ceramic film 15 from the second metal layer 12 by removing at least a portion of the second metal layer 12 in the laminate 1. That is, first, as shown in FIG. 8(a), the laminate 1 is manufactured in the same manner as described in the second embodiment. Next, the second metal layer 12 is wet-etched to form terminals 12a to 12d.

[0064] First, as shown in FIG. 8( b), a mask M is formed on the upper surface 122 of the second metal layer 12 (the surface opposite to the ceramic film 15) in an area where the terminal 12 is to be formed. The mask M can be formed by, for example, photolithography, inkjet printing, screen printing, or the like. In particular, it is preferable to form the mask M by photolithography. By forming the mask M by photolithography, it is possible to precisely adjust the size and shape of the opening that exposes areas other than the area where the terminal 12 is to be formed. The thickness of the mask M is not particularly limited, but may be approximately 20 μm or more and 30 μm or less (preferably, approximately 25 μm or more and 30 μm or less).

[0065] Next, the second metal layer 12 is wet-etched using the mask M to form the terminals 12a to 12d. That is, the ceramic film 15 is exposed from the second metal layer 12. As the etching solution, a metal chloride aqueous solution, an alkaline aqueous solution, an acid aqueous solution, or the like can be used. The etching time for wet etching is not particularly limited, but is preferably about 20 minutes to 90 minutes. This makes it easy to minimize gouging or sagging of the terminals 12a to 12d.

[0066] Next, as shown in FIG. 8( c), the mask M is removed from the second metal layer 12 to obtain the circuit board 1′. The mask M can be removed using, for example, an alkaline remover or an organic remover. In this manner, the circuit board 1′ can be manufactured. Note that, instead of wet etching, dry etching using, for example, CF4, CHF3, oxygen, or a mixed gas containing these as a plasma gas, or laser processing, can also be used to form the terminals 12a-12d. The fourth embodiment also achieves the same effects and advantages as the first to third embodiments. In particular, according to the third embodiment, since the ceramic film 15, rather than the insulating layer 13, is exposed, the circuit board 1′ can effectively utilize the properties of ceramics (oxidation resistance, moisture resistance, heat resistance, weather resistance, and flame retardancy).

[0067] According to the above-described embodiments, it is possible to provide a laminate, a circuit board, and a manufacturing method thereof that improve the bonding reliability of the second metal layer without performing a roughening treatment. These laminates and circuit boards can minimize the transmission loss of high-frequency signals, and are therefore particularly suitable for use in precision equipment such as power semiconductors. While the embodiments of the present disclosure have been described above, the aspects described in each embodiment can be combined with each other. Furthermore, the present disclosure may be provided in the following aspects.

[0068] (1) A laminate comprising: a first metal layer; a second metal layer disposed opposite the first metal layer; an insulating layer disposed between the first metal layer and the second metal layer and made of a material containing resin; and a ceramic film disposed between the insulating layer and the second metal layer.

[0069] (2) The laminate according to (1) above, wherein the second metal layer has a surface roughness (maximum height roughness Rz) of 0.1 μm or more and 3 μm or less on the surface facing the insulating layer.

[0070] (3) In the laminate according to (1) or (2) above, the ceramic film comprises at least one selected from the group consisting of aluminum oxide, magnesium oxide, silicon oxide, zinc oxide, yttrium oxide, silicon nitride, boron nitride, titanium oxide, barium titanate, and aluminum nitride.

[0071] (4) A laminate according to any one of (1) to (3) above, wherein the ratio of the thickness of the ceramic film between the second metal layer and the insulating layer to the thickness of the insulating layer is 0.001 or more and 0.1 or less.

[0072] (5) The laminate according to any one of (1) to (4) above, wherein the ratio of the thickness of the insulating layer to the thickness of the laminate is 0.017 or more and 0.1 or less.

[0073] (6) The laminate according to any one of (1) to (5) above, wherein the material constituting the insulating layer further contains an inorganic filler dispersed in the resin.

[0074] (7) The laminate according to any one of (1) to (6) above, further comprising another ceramic film provided between the first metal layer and the insulating layer.

[0075] (8) In the laminate described in any one of (1) to (7) above, one of the ceramic film and the insulating layer is partially exposed from the second metal layer, and the laminate is a circuit board in which the second metal layer functions as at least one of wiring and a terminal.

[0076] (9) A method for manufacturing a laminate described in any one of (1) to (8) above, comprising the steps of: placing the ceramic film between the second metal layer and the insulating layer; and applying pressure to bring the first metal layer and the second metal layer closer to each other, thereby bonding the ceramic film and the insulating layer to obtain the laminate.

[0077] (10) A method for manufacturing a laminate described in (9) above, further comprising a step of placing the other ceramic film between the first metal layer and the insulating layer, and in the step of obtaining the laminate, the other ceramic film and the insulating layer are bonded together.

[0078] (11) In the method for manufacturing a laminate according to (9) or (10) above, one of the ceramic film and the insulating layer is partly exposed from the second metal layer, and the laminate is a circuit board in which the second metal layer functions as at least one of wiring and terminals. Of course, this is not limited to this. For example, the following configurations are also possible.

[0079] (12) The laminate according to any one of (1) to (6) and (8) above, wherein the surface of the first metal layer facing the insulating layer has been subjected to a roughening treatment.

[0080] (13) The laminate according to any one of (1) to (8) and (12) above, wherein the ratio of the area of ​​voids in the cross section of the ceramic film (porosity) is about 20% or less.

[0081] (14) A method for manufacturing a laminate described in any one of (9) to (11) above, wherein the ceramic film is disposed by forming the ceramic film on the insulating layer side of the second metal layer.

[0082] Finally, while various embodiments of the present disclosure have been described, they are presented as examples and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the claims.

[0083] For example, the insulating layer 13 may be composed of multiple types of laminated insulating layers. In this case, for example, in the first step, multiple types of insulating layers 13 in an uncured state (A stage) or a semi-cured state (B stage) may be prepared, and then, in the third step, they may be stacked and cured. Furthermore, the ceramic film 15 may be composed of multiple types of laminated ceramic films 15. In this case, for example, in the second step, particles that will become the constituent materials of the multiple types of ceramic films 15 may be sequentially loaded into a film-forming apparatus to laminate the ceramic films 15. The same applies to the other ceramic films 14. Furthermore, at least one of the first metal layer 11 and the second metal layer 12 may be composed of multiple types of metal layers. In this case, for example, in the first step, multiple types of metal plates may be stacked and bonded to prepare the first metal layer 11 or the second metal layer 12.

[0084] The present invention will be described in more detail below using the following examples and comparative examples, but the present invention is not limited to the following examples.

[0085] 1. Manufacturing of Circuit Board (Example 1) First Step: First, a copper plate (thickness 2 mm) was prepared as the first metal layer, and a copper foil (thickness 0.5 mm) was prepared as the second metal layer. A semi-cured insulating layer was prepared by the following procedure.

[0086] Naphthalene-type epoxy resin (manufactured by DIC Corporation, "HP-4032D", specific gravity 1.2 g / cm) as a thermosetting resin ３ ) 100 parts by mass, and a phenol novolak resin (manufactured by DIC Corporation, "VH-4150", specific gravity 1.1 g / cm) as a curing agent. ３ 12.4 parts by mass of boron nitride (manufactured by Denka Co., Ltd., "Developed High Thermal Conductivity Block Grade," average particle size 40 μm, specific gravity 2.27 g / cm 3) was prepared and stirred at 170° C. The resulting mixture was mixed with boron nitride (manufactured by Denka Co., Ltd., "Developed High Thermal Conductivity Block Grade," average particle size 40 μm, specific gravity 2.27 g / cm 3) as an inorganic filler. ３ ) 214.8 parts by mass, and a wetting and dispersing agent (manufactured by BYK Chemie, "DISPER BYK111", specific gravity 1.1 g / cm ３ 0.7 parts by mass of triphenylphosphine (manufactured by Hokko Chemical Co., Ltd., "TPP", specific gravity 1.1 g / cm ３ ) 0.6 parts by mass and an imidazole compound (manufactured by Shikoku Chemicals Corporation, "2PHZ-PW", specific gravity 1.1 g / cm ３ ) and 1 part by mass of the phenolic novolac resin were stirred and mixed. The stirring and mixing was carried out for 15 minutes using a planetary mixer. This resulted in a resin-containing material. The volumetric content of each component in the composition was 43.6% by volume of naphthalene-type epoxy resin, 5.9% by volume of phenolic novolac resin, 49.4% by volume of boron nitride, 0.3% by volume of wetting and dispersing agent, and 0.8% by volume of curing accelerator (0.3% by volume of triphenylphosphine, 0.5% by volume of imidazole compound).

[0087] The obtained resin-containing material was applied to a 0.038 mm thick polyethylene terephthalate film (hereinafter referred to as PET film) so that the thickness was 0.12 mm and the area was 45 mm x 45 mm. The PET film to which the resin-containing material was applied was heated and dried at 100°C for 70 minutes. This was repeated for two sheets, and two semi-cured (B-stage) insulating layers 13 were obtained.

[0088] Second Step: Another ceramic film and another ceramic film were formed on the upper surface of the first metal layer (the surface that will be the insulating layer side) and the lower surface of the second metal layer (the surface that will be the insulating layer side) (a ceramic film and a ceramic film were respectively disposed between the first metal layer and the insulating layer and between the second metal layer and the insulating layer). The formation of the ceramic film on the lower surface of the second metal layer will be described below, but the formation of the ceramic film on the upper surface of the first metal layer was also performed in a similar manner. As the ceramic film material, a film-forming powder was prepared by mixing 3 parts by mass of alumina powder ("AL-160SG-3" manufactured by Showa Denko K.K.) with a particle diameter of 0.4 μm and 1 part by mass of alumina powder ("ALM-43" manufactured by Sumitomo Chemical Co., Ltd.). The particle diameter was measured using a particle size distribution analyzer using a laser diffraction / scattering method, and the cumulative volume 50% diameter (D50) value was used. Using this film-forming powder, a ceramic film was formed on the underside of the second metal layer by aerosol deposition (the ceramic film was disposed between the second metal layer and the insulating layer). Specifically, the film-forming powder was loaded into the aerosol generator of an aerosol gas deposition device (manufactured by Fuchida Nano Giken Co., Ltd., "GD-AE03-DK") and aerosolized with nitrogen gas. At this time, the gas flow rate for stirring up the film-forming powder was set to 8 L / min.

[0089] The second metal layer was placed on an XY stage in the chamber with its underside facing the nozzle of the device. The chamber was depressurized to 20 Pa, and the aerosolized film-forming powder was sprayed toward the second metal layer while the second metal layer was being moved. At this time, the pressure in the chamber was 110 Pa. The movement speed of the second metal layer was 0.5 cm / sec. The gas flow rate for transporting the aerosol was 5 L / min, and the speed of the aerosol (film-forming powder) sprayed from the nozzle was 100 m / sec. The nozzle incident angle was 30°. A ceramic film was formed so that the thickness T15 of the ceramic film was approximately 1 μm.

[0090] Step 3: The two semi-cured (B-stage) insulating layers obtained in Step 1 were peeled from the PET film and placed on top of another ceramic film formed on the top surface of the first metal layer. Next, a second metal layer with a ceramic film formed on it was placed on the insulating layer so that the semi-cured insulating layer on the upper side (opposite the first metal layer) faced the underside of the ceramic film. The laminate was obtained by heating at 180°C for 410 minutes while applying a pressure of 10 MPa using a press.

[0091] Wet Etching Next, a mask was formed on the second metal layer of the laminate using an etching resist (UVM-900 U55, manufactured by Taiyo Ink Co., Ltd.) so that the area where the terminals were to be formed was located in the center or in four locations as shown in Figure 8(c). The mask was approximately 20 μm thick and cured by irradiating with ultraviolet light for 1 minute. The second metal layer was then etched using a mixed solution of sulfuric acid (0.72 mol / dL) and hydrogen peroxide (1.0 mol / dL) as an etching solution. The etching time was 20 minutes. The mask was then removed, washed, and dried to obtain the circuit board according to Example 1 having one or four circular terminals (second metal layer) with a diameter of 20 mm.

[0092] Example 2 The laminate and circuit board of Example 2 were obtained in the same manner as Example 1, except for the details described below. That is, in the first step, a roughening treatment was performed on the upper surface of the first metal layer (the surface facing the insulating layer). The roughening treatment was performed by etching for 2 minutes using a sulfuric acid (0.13 mol / dL)-hydrogen peroxide (0.082 mol / dL) mixed solution as an etching solution. The first metal layer was then washed. Then, in the second step, the formation of another ceramic film on the upper surface of the first metal layer was omitted. Next, in the third step, the first metal layer, two semi-cured insulating layers, and the second metal layer on which the ceramic film was formed were stacked in this order, and the third step was performed. At this time, the first metal layer was positioned so that the roughened upper surface that had been roughened faced the insulating layer.

[0093] Examples 3 and 4 The laminates and circuit boards according to Examples 3 and 4 were obtained in the same manner as in Example 2, except that only silicon nitride powder having a particle size of 0.9 μm (manufactured by Denka Co., Ltd., "9FWS") was used as the film-forming powder in the second step.

[0094] Example 5 A laminate and a circuit board according to Example 5 were obtained in the same manner as in Example 2, except that only spherical boron nitride powder having a particle diameter of 0.5 μm was used as the film-forming powder in the second step.

[0095] (Examples 6 to 7) The laminates and circuit boards according to Examples 6 and 7 were obtained in the same manner as in Example 2, except that only yttrium oxide powder having a particle diameter of 0.3 μm (manufactured by Shin-Etsu Chemical Co., Ltd., "UU") was used as the film-forming powder in the second step.

[0096] Comparative Example 1 A laminate and a circuit board according to Comparative Example 1 were obtained in the same manner as in Example 1, except for the details described below. That is, in the first step, a roughening treatment was applied to the upper surface of the first metal layer and the lower surface of the second metal layer. The roughening treatment was performed by etching for 2 minutes using a sulfuric acid (0.13 mol / dL)-hydrogen peroxide (0.082 mol / dL) mixed solution as an etching solution. The first metal layer and the second metal layer were then washed. Then, the second step was omitted, and the third step was performed with the first metal layer, two semi-cured insulating layers, and the second metal layer stacked in this order. At this time, the first metal layer and the second metal layer were positioned so that the roughened surface that had been subjected to the roughening treatment faced the insulating layer. Comparative Example 2 A laminate and a circuit board according to Comparative Example 2 were obtained in the same manner as in Comparative Example 1, except for omitting the roughening treatment.

[0097] 2. Measurement and Testing [Measurement of Surface Roughness (Maximum Height Roughness Rz) and Surface Roughness (Arithmetic Mean Roughness Ra) of Metal Layer] The upper surface of the first metal layer and the lower surface of the second metal layer obtained in the first step were observed using a confocal laser microscope (Keyence Corporation, VK-X1000). The objective lens was set to 50x magnification, the eyepiece to 20x magnification, and a laser with a wavelength of 661 nm was used. The observation results were analyzed using data analysis software to obtain a surface roughness curve with a reference length of 250 μm. A surface roughness curve was obtained at a random location on the upper surface of the first metal layer and the lower surface of the second metal layer for each example and comparative example. The surface roughness (maximum height roughness Rz) and surface roughness (arithmetic mean roughness Ra) were calculated using the method specified in JIS B 0601:2013 (ISO 4287:1997). For Comparative Example 1, the surface roughness (maximum height roughness Rz) and surface roughness (arithmetic mean roughness Ra) after the roughening treatment were measured.

[0098] [Ceramic Film Thickness Measurement] The thickness T15 of the ceramic film obtained by the second step in each example and the thickness T14 of the other ceramic films were measured using an eddy current film thickness meter (Fisher Instruments, ISOSCOPE® DMP10). While the thickness T15 of the ceramic film will be described below, the thickness T14 of the other ceramic film formed on the upper surface of the first metal layer in Example 1 was also measured in the same manner. The underside of the approximately square ceramic film was divided into nine approximately equal square regions, and nine measurement points were selected at the center of each of the square regions. The ceramic film thickness T15 was then measured at these nine points for each of the four ceramic film-coated second metal layers. For each example, the arithmetic mean of the measurement results for the four substrates x nine points was obtained as the ceramic film thickness T15. It is believed that the thicknesses T14 and T15 at this point are the same as the thicknesses T14 and T15 of the circuit board 1′ obtained after wet etching.

[0099] [Measurement of Insulating Layer Thickness] The insulating layer thickness T13 was measured using an eddy current film thickness meter (manufactured by Fisher Instruments, "ISOSCOPE (registered trademark) DMP10"). In the circuit board obtained after wet etching, the thickness up to the first metal layer 11 in the region exposed from the second metal layer (the sum of the ceramic film thickness T15 and the insulating layer thickness T13) was measured at five locations. The thickness T13 of the insulating layer was determined by subtracting the ceramic film thickness T15 from the arithmetic mean of the thicknesses at the five locations. [Measurement of Circuit Board (Laminate) Thickness] The thickness T1 of the circuit board (four terminals) obtained by wet etching in each example and comparative example was measured using a micrometer (manufactured by Mitutoyo Corporation, "MDC-25PX"). For the circuit boards in each example and comparative example, the thicknesses of the four terminals were measured, and the arithmetic mean was determined as the laminate thickness T1.

[0100] [Measurement of porosity of ceramic film] The porosity of the ceramic film in the circuit board of each example and comparative example was measured. First, a cross-sectional image of the circuit board was obtained using a scanning electron microscope (SEM) (manufactured by JEOL Ltd., "JSM-7001F"). The image was acquired at a 50,000x field of view, with an acceleration voltage of 5.0 kV, a spot size of 4 nm, and scan conditions of "FINE". Then, the acquired cross-sectional SEM image was binarized using image analysis processing software by adjusting the brightness threshold so that the areas where the ceramic was present (bright areas) and voids (dark areas) were separated, and the area percentage of the dark areas (voids) relative to the sum of the bright and dark areas was obtained as the porosity.

[0101] In the following tests, different circuit boards (not used in other tests) were used for each example and comparative example in order to avoid damaging the properties of the circuit board. Therefore, for each example and comparative example, only the number of circuit boards required for the following tests were manufactured.

[0102] [High-Temperature Resistance Test] The circuit boards (four terminals) of each Example and Comparative Example were left to stand at 280°C for 10 minutes under dry and normal pressure conditions to evaluate their high-temperature resistance. The high-temperature resistance was evaluated based on changes in appearance. Note that for the circuit board of Comparative Example 2, the second metal layer peeled off from the insulating layer at this point, so some of the subsequent measurements and evaluations were omitted.

[0103] [Circuit Tensile Strength Measurement] Circuit tensile strength measurements were performed on the circuit boards (one terminal) of each Example and Comparative Example 1. The circuit tensile strength measurements were performed using the device shown in FIG. 9. FIG. 9 is a schematic diagram showing the configuration of the circuit tensile strength measurement device. As shown in FIG. 9, the circuit board was placed upside down on the circuit tensile strength measurement device 2 so that the areas on the ceramic films 15 (insulating layers 13 in the case of Comparative Examples 1 and 2) on both sides of the terminal 12 were in contact with the support base 22. The support base 22 had a cylindrical shape with an inner diameter of 4 mm and an outer diameter of 6 mm. A reinforcing plate 21 was placed on the first metal layer 11. The bottom surface 231 of the stud pin 23 was bonded to the second metal layer 12 with epoxy adhesive 25. The adhesive strength was 700 kg / cm. ２ This was the case. Then, a load was gradually applied downward in FIG. 9 (in the direction of the arrow in the figure) via the gripper 24 fixed to the end of the stud pin 23 opposite the bottom surface 231. The load was increased at a rate of 3 kg / sec, and the adhesion strength (MPa) was calculated from the load at the point when the stud pin 23 peeled off from the circuit board. The layer in which peeling occurred was also visually confirmed. The location where this peeling occurred can be considered to be the location with the weakest adhesion in the thickness direction of the circuit board 1'.

[0104] [Peel Strength Measurement] The peel strength (peel strength) of the laminates of each Example and Comparative Example was measured in accordance with JIS C 6481-1996, item 5.7. First, a copper foil (second metal layer) with a width of 10±0.1 mm was left in the center of the laminate, and the copper foil (second metal layer) on both sides was removed to prepare a sample. Next, one end of the copper foil of the sample was peeled 30 mm and attached to a support bracket, and the peel strength was measured using a method compliant with the same regulations. Measurements were performed at room temperature (20°C) on samples in their initial state (normal state) without high-temperature treatment and on samples heated at 280°C for 30 minutes (high temperature). Note that in Comparative Example 2, the copper foil peeled off before measurement at the high temperature of 280°C, making it impossible to measure.

[0105] [Insulation Strength Measurement] The insulation strength of the circuit board 1' (four terminals) of each Example and Comparative Example 1 was measured using a high-voltage withstand voltage tester ("Safety Tester 7473" manufactured by Keisoku Giken Kenkyusho Co., Ltd.) in accordance with JIS C 2110-1:2016 (IEC 60243-1:2013) by performing a 10.2 20-second step-up voltage test. For each Example and Comparative Example 1 circuit board, the center of the terminal was selected as the measurement location. Measurements were performed on each of the four terminals in insulating oil at room temperature, with a starting voltage of AC 5.0 kV and voltage applied in specified voltage steps (500 V / 20 seconds). The voltage under the conditions before breakdown occurred was obtained as the breakdown voltage. For each Example and Comparative Example 1, measurements were performed using two circuit boards, and the arithmetic average of the voltages of the two boards x four was taken as the breakdown voltage of the circuit board. The arithmetic mean of the voltage was divided by the sum of the thickness T13 of the insulating layer, the thickness T14 of the other ceramic film, and the thickness T15 of the ceramic film, and the value was taken as the insulation strength (kV / mm).

[0106] [Measurement of High-Temperature Durability] The durability of the circuit boards (four terminals) of each Example and Comparative Example 1 was evaluated by performing a high-temperature Vt test (voltage-time testing) (long-term method) using a high-voltage withstand voltage tester (manufactured by Keisoku Giken Kenkyusho Co., Ltd., "Safety Tester 7473"). The air temperature was set to 150°C, and an applied voltage of DC 10 kV was used to measure the time (lifetime) until dielectric breakdown occurred. The measurement was performed for each of the four terminals, and the arithmetic mean of the lifespans of the four terminals was taken as the high-temperature durability of each Example and Comparative Example 1.

[0107] 3. Results It was confirmed that the ceramic film remained in the area exposed from the terminal (second metal layer) in each example. The measurement and test results are shown in Tables 1 and 2 below.

[0108]

[0109]

[0110] 4. Evaluation 4.1 Evaluation of high-temperature adhesion strength Based on the peel strength measurement results, the high-temperature adhesion strength of the laminate was evaluated according to the following evaluation criteria: [Evaluation criteria] A: Peel strength at high temperature is 13 N / cm or more B: Peel strength at high temperature is 11 N / cm or more and less than 13 N / cm C: Peel strength at high temperature is 10 N / cm or more and less than 11 N / cm D: Peel strength at high temperature is less than 10 N / cm E: Peel strength at high temperature cannot be measured

[0111] 4.2 Evaluation of thermal stability Based on the peel strength measurement results, the rate of change in peel strength was calculated using the following formula. Then, based on the obtained rate of decrease (%), the thermal stability of the laminate was evaluated in accordance with the following evaluation criteria. [Formula] [rate of decrease (%)] = (([peel strength under normal conditions] - [peel strength after high-temperature treatment]) / [peel strength under normal conditions]) x 100 [Evaluation criteria] A: rate of decrease is 10% or less B: rate of decrease is more than 10% and 20% or less C: rate of decrease is more than 20% and 30% or less D: rate of decrease is more than 30% E: rate of decrease cannot be calculated

[0112] 4.3 Insulation Strength Evaluation Based on the insulation strength measurement results, the insulation strength of the circuit board was evaluated according to the following evaluation criteria: [Evaluation Criteria] A: Insulation strength of 105 kV / mm or more B: Insulation strength of 100 kV / mm or more and less than 105 kV / mm C: Insulation strength of 95 kV / mm or more and less than 100 kV / mm D: Insulation strength of 80 kV / mm or more and less than 95 kV / mm E: Insulation strength of 80 kV / mm or more and less than 80 kV / mm

[0113] 4.4 Evaluation of High-Temperature Durability Based on the results of the high-temperature durability measurement, the high-temperature durability of the circuit board was evaluated according to the following evaluation criteria: [Evaluation criteria] A: Durability time is 100 hours or more B: Durability time is 90 hours or more and less than 100 hours C: Durability time is 70 hours or more and less than 90 hours D: Durability time is 50 hours or more and less than 70 hours E: Durability time is less than 50 hours

[0114] Table 3 below shows the evaluation results for each example and each comparative example.

[0115]

[0116] According to each example, high adhesion strength was achieved even at high temperatures without roughening treatment. The decrease in adhesion strength due to temperature change was also kept small. Furthermore, it was confirmed that the circuit boards of each example had improved insulation strength and high-temperature durability.

[0117] 1: laminate, 1': circuit board, 11: first metal layer, 111: top surface, 12: second metal layer, 12a: terminal, 12b: terminal, 12c: terminal, 12d: terminal, 121: bottom surface, 122: top surface, 13: insulating layer, 132: top surface, 14: other ceramic film, 15: ceramic film, 151: bottom surface, 152: top surface, 2: adhesion strength test device, 21: reinforcing plate, 22: support base, 23: stud pin, 231: bottom surface, 24: gripper, 25: epoxy adhesive, M: mask, T1: thickness of laminate, T11: thickness of first metal layer, T12: thickness of second metal layer, T13: thickness of insulating layer, T14: thickness of ceramic film, T15: thickness of other ceramic film

Claims

1. A laminate comprising: a first metal layer; a second metal layer disposed opposite the first metal layer; an insulating layer disposed between the first metal layer and the second metal layer and made of a material containing resin; and a ceramic film disposed between the insulating layer and the second metal layer.

2. A laminate according to claim 1, wherein the second metal layer has a surface roughness (maximum height roughness Rz) of 0.1 μm or more and 3 μm or less on the surface facing the insulating layer.

3. A laminate according to claim 1 or 2, wherein the ceramic film contains at least one material selected from the group consisting of aluminum oxide, magnesium oxide, silicon oxide, zinc oxide, yttrium oxide, silicon nitride, boron nitride, titanium oxide, barium titanate, and aluminum nitride.

4. A laminate according to any one of claims 1 to 3, wherein the ratio of the thickness of the ceramic film between the second metal layer and the insulating layer to the thickness of the insulating layer is 0.001 or more and 0.1 or less.

5. A laminate according to any one of claims 1 to 4, wherein the ratio of the thickness of the insulating layer to the thickness of the laminate is 0.017 or more and 0.1 or less.

6. A laminate according to any one of claims 1 to 5, wherein the material constituting the insulating layer further contains an inorganic filler dispersed in the resin.

7. The laminate according to any one of claims 1 to 6, further comprising another ceramic film provided between said first metal layer and said insulating layer.

8. A laminate according to any one of claims 1 to 7, wherein one of the ceramic film and the insulating layer is partially exposed from the second metal layer, and the laminate is a circuit board in which the second metal layer functions as at least one of wiring and terminals.

9. A method for manufacturing a laminate according to any one of claims 1 to 8, comprising the steps of: arranging the ceramic film between the second metal layer and the insulating layer; and applying pressure to bring the first metal layer and the second metal layer closer to each other, thereby bonding the ceramic film and the insulating layer together to obtain the laminate.

10. A method for manufacturing a laminate according to claim 9, further comprising the step of arranging the other ceramic film between the first metal layer and the insulating layer, wherein in the step of obtaining the laminate, the other ceramic film and the insulating layer are bonded together.

11. A method for manufacturing a laminate according to claim 9 or 10, wherein one of the ceramic film and the insulating layer is partially exposed from the second metal layer, and the laminate is a circuit board in which the second metal layer functions as at least one of wiring and terminals.

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