WO2023027122A1

WO2023027122A1 - Method for producing ceramic plate, ceramic plate, composite sheet and multilayer substrate

Info

Publication number: WO2023027122A1
Application number: PCT/JP2022/031927
Authority: WO
Inventors: 仁孝南方; 政秀金子; 亮吉松; 真也坂口
Original assignee: デンカ株式会社
Priority date: 2021-08-26
Filing date: 2022-08-24
Publication date: 2023-03-02
Also published as: JP7319482B2; JPWO2023027122A1

Abstract

One aspect of the present disclosure provides a method for producing a ceramic plate, the method comprising: a firing step in which a fired plate is obtained by firing a sheet that comprises a shaped plate containing boron nitride and a sintering assistant, and a boron nitride-containing layer that is provided on at least a part of a main surface of the shaped plate; and a removal step in which at least a part of a mold release layer that is derived from the boron nitride-containing layer of the fired plate is removed.

Description

Ceramic plate manufacturing method, ceramic plate, composite sheet, and laminated substrate

The present disclosure relates to a method for manufacturing a ceramic plate, a ceramic plate, a composite sheet, and a laminated substrate.

Components such as power devices, transistors, thyristors, and CPUs are required to efficiently dissipate the heat generated during use. In response to such demands, it has been conventional practice to increase the thermal conductivity of the insulating layer of the printed wiring board on which electronic components are mounted, or to place the electronic components or the printed wiring board through a thermal interface material having electrical insulation. It has been practiced to attach it to a heat sink. A composite sheet composed of a resin and a ceramic such as boron nitride is used as a heat dissipation member for such an insulating layer and thermal interface material.

As such a composite sheet, a composite sheet in which a porous ceramic plate (for example, a boron nitride sintered plate) is impregnated with a resin is being studied (for example, see Patent Document 1). In addition, in a laminate having a circuit board and a resin-impregnated boron nitride sintered body, the primary particles constituting the boron nitride sintered body are brought into direct contact with the circuit board to reduce the thermal resistance of the laminate and improve heat dissipation. is also being studied (see Patent Document 2, for example).

WO2014/196496 JP 2016-103611 A

A ceramic plate is generally manufactured by sintering a block-shaped molded body containing boron nitride and a sintering aid to obtain a sintered body, which is then cut into a predetermined thickness. On the other hand, in recent years, from the viewpoint of improving the yield, a method of directly preparing a ceramic plate by forming a thin compact containing boron nitride and a sintering aid and firing it has been adopted. .

In addition, in order to achieve a sufficient resin filling rate in the composite sheet, it is required that the pores of the ceramic plate have a large pore diameter. Therefore, it is conceivable to increase the content of the sintering aid contained in the sheet-shaped compact. According to the studies of the present inventors, when a plurality of sheet-shaped compacts are stacked and fired in a state where the content of the sintering aid is large, the resulting ceramic plates tend to adhere to each other. It has been found that the ceramic plate may be damaged during the peeling process. Therefore, when stacking sheet-shaped molded bodies, a release layer with low crystallinity and low strength is formed by providing a coating film of a slurry containing boron nitride between the sheet-shaped molded bodies and baking it. Attempts have been made to form it between ceramic plates to facilitate peeling. However, when a composite sheet is prepared by impregnating a ceramic plate obtained by such a method with a resin, the resulting composite sheet may not exhibit sufficient adhesion to an adherend.

An object of the present disclosure is to provide a ceramic plate capable of preparing a composite sheet with a resin, which has excellent adhesion to an adherend, and a method for manufacturing the same. Another object of the present disclosure is to provide a composite sheet having the ceramic plate described above and having excellent adhesion to an adherend.

The present disclosure provides the following [1] to [9].

[1]
A firing step of obtaining a fired plate by firing a sheet having a molded plate containing boron nitride and a sintering aid and a boron nitride-containing layer provided on at least part of the main surface of the molded plate;
and a removing step of removing at least part of a release layer derived from the boron nitride-containing layer of the fired plate.
[2]
further comprising a step of laminating a plurality of the sheets to obtain a laminate,
The manufacturing method according to [1], wherein the firing step is a step of firing the laminate to obtain a plurality of fired plates.
[3]
The manufacturing method according to [1] or [2], wherein the removing step is a step of polishing the fired plate from the release layer side.
[4]
The removing step is a step of polishing the thickness of the boron nitride-containing layer or more from the release layer side of the fired plate to reduce the height. A method for manufacturing a ceramic plate.
[5]
Composed of a sintered body containing primary particles of boron nitride,
A ceramic plate having a polished surface.
[6]
The ceramic plate according to [5], which has a median pore size of 1.5 to 4.0 μm.
[7]
The ceramic plate according to [5] or [6], which has a thickness of less than 2.0 mm.
[8]
A nitride sintered plate having pores and a resin filled in the pores,
A composite sheet, wherein the nitride sintered plate is the ceramic plate according to any one of [5] to [7].
[9]
A laminated substrate comprising the composite sheet according to [8] and a metal layer provided on the composite sheet.

As a result of detailed studies by the present inventors on the fact that the composite sheet as described above may not exhibit sufficient adhesion to the adherend, it was found that the release layer formed by firing has a scaly shape. It has been found that the primary particles of boron nitride tend to be oriented parallel to the main surface of the ceramic plate, which is one of the factors that reduce adhesion. The present disclosure is made based on this finding.

One aspect of the present disclosure is a fired plate by firing a sheet having a molded plate containing boron nitride and a sintering aid, and a boron nitride-containing layer provided on at least part of the main surface of the molded plate and a removing step of removing at least part of the release layer derived from the boron nitride-containing layer of the fired plate.

The method for producing a ceramic plate includes a removing step of removing a part of the release layer after preparing the fired plate by the firing step, thereby reducing the release layer that may reduce the adhesion to the adherend. A ceramic plate can be prepared. Therefore, a composite sheet with a resin prepared using the obtained ceramic plate can exhibit excellent adhesion to adherends.

The above-described method for manufacturing a ceramic plate further includes a step of stacking a plurality of the sheets to obtain a laminate, and the firing step is a step of firing the laminate to obtain a plurality of the fired plates. It's okay. Since the method for manufacturing a ceramic plate according to the present disclosure has a step of removing at least part of the release layer, even when the sheets are laminated and fired, the decrease in adhesiveness is suppressed Ceramics A board can be manufactured and productivity can be improved more.

The removing step may be a step of polishing the fired plate from the release layer side. By performing the removal step by polishing, the intended thickness can be removed more reliably.

The removal step may be a step of polishing a thickness of the boron nitride-containing layer or more from the release layer side of the fired plate to reduce the height. By setting the amount of polishing in the removal step to the range described above, the entire release layer can be removed more reliably, and a ceramic plate with better adhesion can be produced.

One aspect of the present disclosure provides a ceramic plate composed of a sintered body containing primary particles of boron nitride and having a polished surface.

By having a polished surface, the ceramic plate can exhibit excellent adhesiveness by removing surface portions that may reduce adhesiveness.

The median pore diameter may be 1.5-4.0 μm.

The thickness of the ceramic plate may be less than 2.0 mm.

One aspect of the present disclosure provides a composite sheet comprising a nitride sintered plate having pores and a resin filled in the pores, wherein the nitride sintered plate is the ceramic plate described above. do.

Since the composite sheet is composed of the ceramic plate described above, it can exhibit excellent adhesiveness when adhered to an adherend (for example, a metal sheet, etc.).

One aspect of the present disclosure provides a laminated substrate comprising the composite sheet described above and a metal layer provided on the composite sheet.

Since the laminated substrate includes the above-described composite sheet, it can exhibit excellent performance, for example, in terms of heat cycle characteristics.

According to the present disclosure, it is possible to provide a ceramic plate excellent in adhesiveness to adherends and capable of preparing a composite sheet with a resin, and a method for manufacturing the same. According to the present disclosure, it is also possible to provide a composite sheet having the ceramic plate described above and having excellent adhesion to an adherend.

FIG. 1 is a schematic diagram for explaining an example of a method for manufacturing a ceramic plate. FIG. 2 is a perspective view showing an example of a ceramic plate. FIG. 3 is a schematic cross-sectional view showing an example of a laminated substrate. FIG. 4 is a SEM image of the cross section of the ceramic plate in the example. FIG. 5 is a SEM image of a cross section of a ceramic plate in Comparative Example.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and overlapping descriptions are omitted in some cases. In addition, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratio of each element is not limited to the illustrated ratio.

The materials exemplified in this specification can be used singly or in combination of two or more unless otherwise specified. The content of each component in the composition means the total amount of the multiple substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. .

One embodiment of the method for producing a ceramic plate includes firing a sheet having a molded plate containing boron nitride and a sintering aid, and a boron nitride-containing layer provided on at least part of the main surface of the molded plate. and a removing step of removing at least part of the release layer derived from the boron nitride-containing layer of the fired plate.

FIG. 1 is a schematic diagram for explaining an example of a method for manufacturing a ceramic plate. FIG. 1(a) shows a step of preparing a sheet 10 having a molded plate 2 and boron nitride-containing layers 3 provided on both main surfaces of the molded plate 2 and firing it (firing step). be. FIG. 1(b) is a step (removal step) of removing at least part of the surface layers of both main surfaces of the fired plate 20 obtained by the firing step. The fired plate 20 includes a sintered body 4 (nitride sintered body) obtained by firing the molded plate 2, and the boron nitride-containing material provided on both main surfaces of the sintered body 4. and a release layer 5 obtained by firing the layer 3 . FIG. 1(c) shows a ceramic plate 100 obtained by removing the release layer 5 by the removal step described above. Although FIG. 1 shows an example in which the boron nitride-containing layer 3 is provided on both main surfaces of the molded plate 2, it may be formed on one main surface. Although FIG. 1 shows an example in which the release layer 5 is completely removed, it may be partially removed.

The molded plate used in the firing process may be prepared by, for example, the following method. That is, it may be formed by forming a raw material powder containing boron nitride and a sintering aid into a plate shape. The raw material powder may further contain, for example, boron carbonitride, etc., in addition to the boron nitride and the sintering aid.

The boron nitride may be amorphous boron nitride or hexagonal boron nitride. For boron nitride, for example, amorphous boron nitride powder having an average particle size of 0.5 to 10.0 μm or hexagonal boron nitride powder having an average particle size of 3.0 to 40.0 μm can be used.

Examples of sintering aids include alkali metal carbonates such as lithium carbonate and sodium carbonate, calcium carbonate, and boric acid.

A molded plate can be prepared by molding the raw material powder into a plate shape. The molding may be carried out by uniaxial pressing, cold isostatic pressing (CIP), or doctor blade. The molding method is not particularly limited, and press molding may be performed using a mold to form a molded plate. The molding pressure may be, for example, 5-350 MPa. The thickness of the shaped plate may be, for example, less than 2.0 mm. After preparing a block-shaped nitride sintered body, for example, compared to cutting it with a wire saw or the like to form a sheet, by forming it into a sheet from the stage before firing, material loss due to processing is reduced. be able to. Therefore, the ceramic plate can be manufactured with a high yield.

From the viewpoint of preparing a ceramic plate having a relatively large median pore size, the content of the sintering aid may be adjusted. The lower limit of the content of the sintering aid is, for example, 12% by mass or more, 13% by mass or more, 14% by mass or more, 15% by mass or more, 16% by mass or more, or 17% by mass, based on the total amount of the molded plate. Above, 20% by mass or more, or 23% by mass or more. By setting the lower limit of the content of the sintering aid within the above range, the median pore diameter of the obtained ceramic plate can be increased, and the filling of the resin can be made easier. On the other hand, when the content of the sintering aid is within the above range, when a plurality of molded plates are directly laminated, the sintered bodies after sintering may adhere to each other, but the present disclosure In the method for manufacturing a ceramic plate according to No. 1, since the release layer is provided, adhesion between the sintered bodies can be suppressed. The upper limit of the content of the sintering aid is, for example, 35% by mass or less, 32% by mass or less, 30% by mass or less, 27% by mass or less, or 25% by mass or less, based on the total amount of the molded plate. good. By setting the upper limit of the content of the sintering aid within the above range, the density of the sintered body can be kept within an appropriate range, and high thermal conductivity can be ensured. The content of the sintering aid may be adjusted within the above range, and may be, for example, 12 to 35% by weight, 15 to 27% by weight, or 15 to 25% by weight, based on the total amount of the molded plate. .

A boron nitride-containing layer is provided on the molded plate to prepare a sheet to be fired. FIG. 1(a) shows an example in which the boron nitride-containing layer 3 is uniformly provided on both main surfaces of the molding plate 2, but it is formed only on one main surface. may have been Further, in the process described later, it is sufficient that the sintered bodies 4 can be separated from each other as the release layer 5, and the boron nitride-containing layer 3 is provided not on the entire surface of the main surface of the molding plate 2 but partially. may be Further, a boron nitride-containing layer 3 may be further provided on the side surface of the molded plate 2 . The boron nitride-containing layer 3 may be uniformly provided on at least one major surface of the molded plate 2 for ease of preparation of the sheet.

The boron nitride-containing layer may be provided, for example, by preparing a slurry containing boron nitride and depositing the slurry on the main surface of the molding plate. The method of attaching the slurry to the molded plate is not particularly limited, and may be, for example, a method of coating the slurry or a method of immersing the molded plate in the slurry.

The slurry can be prepared by dispersing boron nitride in a mixture of terpineol, a high-boiling organic solvent such as toluene, and an organic paste that functions as a binder for the BN powder. Examples of the organic sizing agent include cellulose-based sizing agents such as methyl cellulose and ethyl cellulose, and acrylic resins such as polyisobutyl methacrylate. The boron nitride for forming the slurry may be amorphous boron nitride or hexagonal boron nitride. From the point of view, it is desirable to contain amorphous boron nitride with low crystallinity and to consist only of amorphous boron nitride. The slurry preferably does not contain sintering aids.

In the firing process, the sheet is fired to obtain a fired board. The lower limit of the firing temperature in the firing step may be, for example, 1600° C. or higher, 1650° C. or higher, 1700° C. or higher, or 1800° C. or higher. The upper limit of the firing temperature in the firing step may be, for example, 2200° C. or less, 2100° C. or less, or 2000° C. or less. The firing temperature may be adjusted within the ranges mentioned above, and may be, for example, 1600-2200°C, 1700-2100°C, or 1800-2100°C. Firing times may be, for example, 1-30 hours, 2-20 hours, 3-15 hours, or 4-10 hours.

The firing process may be performed under an inert gas atmosphere such as nitrogen, helium, and argon.

For firing, for example, a batch type furnace or a continuous type furnace can be used. Batch type furnaces include, for example, muffle furnaces, tubular furnaces, atmosphere furnaces, and the like. Examples of continuous furnaces include rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and large continuous furnaces. Thus, a sintered board can be obtained.

The removing step is a step of removing at least part of the release layer that constitutes the fired plate prepared as described above. By reducing the primary particles of boron nitride in the release layer that are oriented parallel to the main surface of the ceramic plate, the adhesion of the composite sheet prepared using the ceramic plate can be improved. The region of the release layer 5 on the side of the sintered body 4 can be affected by the sintering aid in the molding plate 2 during firing, so it is affected by the orientation of the boron nitride particles that make up the sintered body 4. Therefore, the effect of lowering the adhesiveness is not large. On the other hand, in the region of the release layer 5 on the side opposite to the sintered body 4 side, the primary particles of boron nitride tend to grow in the direction parallel to the main surface of the ceramic plate 100, which may reduce the adhesiveness. Therefore, by removing this region, the adhesion can be effectively improved. FIG. 1(c) shows an example assuming that the release layer 5 is completely removed, but from the above point of view, the release layer 5 may be partially removed. In the removing step, for example, the surface layer of the release layer 5 on the side opposite to the sintered body 4 side may be removed to reduce the height (reduce the thickness), and the release layer 5 is removed in a pattern. You may divide into a location and a location to maintain.

The means for removing the release layer 5 in the removing step may be, for example, polishing. For polishing, for example, sandpaper, a grinder, and the like can be used. When the median pore diameter of the ceramic plate is large (for example, 1.5 μm or more), it is desirable to use sandpaper or the like for polishing from the viewpoint of sufficiently suppressing breakage of the ceramic plate. The removing step may be a step of polishing the fired plate from the release layer side.

The removing step may be a step of polishing the fired plate 20 from the release layer 5 side by a thickness equal to or greater than the thickness of the boron nitride-containing layer 3 to reduce the height. By setting the amount of polishing in the removal step to the range described above, the entire release layer can be removed more reliably, and a ceramic plate with better adhesion can be produced.

In FIG. 1, the explanation is given on the assumption that one sheet is fired, but the above-described method for manufacturing the ceramic plate further includes a step of stacking a plurality of the sheets to obtain a laminate, and the firing step is the same as the above. It may be a step of sintering the laminate to obtain a plurality of the sintered plates. In this case, a plurality of molded plates forming a laminate are laminated with boron nitride-containing layers interposed therebetween. By firing the laminate in this manner, the ceramic plates are arranged with the release layer interposed therebetween, and the ceramic plates can be easily separated and taken out.

FIG. 2 is a perspective view showing an example of a ceramic plate. The ceramic plate 100 has a pair of

main surfaces

100a and 100b, at least one of which is a polished surface. One embodiment of the ceramic plate is composed of a sintered body containing primary particles of boron nitride and has a polished surface. At least one principal surface of the ceramic plate may be a polished surface, but both principal surfaces are preferably polished surfaces. The main surface of the ceramic plate is preferably not a cut surface (for example, a cut surface with a wire saw). The ceramic plate can be manufactured, for example, by the method for manufacturing a ceramic plate described above. The polished surface is a surface having polishing marks, which are fine grooves formed by polishing. Although the maximum value of the groove depth of the groove group varies depending on the polishing conditions, it may be, for example, 20 μm or less, or 10 μm or less. The depth of the grooves can be determined by measurement with an optical microscope. In the case of adopting the polishing condition to obtain a polished surface with high smoothness, polishing marks can be confirmed with a microscope. Further, polishing may be performed until the polished surface becomes a mirror surface. Since a mirror surface cannot be obtained without polishing, the fact that the main surface of the ceramic plate is a mirror surface means that the main surface of the ceramic plate is a polished surface. A mirror surface in this specification means a surface having an arithmetic mean roughness Ra of 0.00 described in JIS B 0601: 1994 "Product Geometric Characteristic Specifications (GPS) - Surface Texture: Contour Method - Terms, Definitions and Surface Texture Parameters". It means less than 2 μm. The arithmetic mean roughness Ra can be measured by a line contact type measuring instrument. As the line-contact type measuring instrument, for example, Mitutoyo Corporation's "Surface Roughness Measuring Instrument Surftest SJ-301" (product name) can be used.

The pore diameter of the ceramic plate may be adjusted from the viewpoint of maintaining the mechanical strength of the ceramic plate itself and improving the filling property of the resin. The lower limit of the median pore size of the ceramic plate may be, for example, 1.5 μm or more, 1.8 μm or more, or 2.0 μm or more. When the lower limit of the median pore diameter is within the above range, the filling rate of the resin can be further improved, and the adhesiveness to the adherend when preparing a composite sheet with the resin can be further improved. can be done. The upper limit of the median pore diameter of the ceramic plate may be, for example, 4.0 μm or less, 3.5 μm or less, or 3.0 μm or less. When the upper limit of the median pore diameter is within the above range, it is possible to suppress deterioration of the mechanical strength of the ceramic plate and to make the ceramic plate excellent in handleability. In addition, since the upper limit of the median pore diameter is within the above range, when a composite sheet with a resin is prepared, the contact area between the ceramic particles constituting the ceramic plate can be improved, and the thermal conductivity can be increased. can. The median pore size of the ceramic plate may be adjusted within the range described above, and may be, for example, 1.5-4.0 μm, 1.8-3.0 μm, or 2.0-3.0 μm.

The median pore diameter of the ceramic plate can be measured by the following procedure. First, using a mercury porosimeter, the pore size distribution is obtained when the ceramic plate is pressurized while increasing the pressure from 0.0042 MPa to 206.8 MPa. Next, when the horizontal axis is the pore diameter and the vertical axis is the cumulative pore volume, the pore diameter when the cumulative pore volume reaches 50% of the total pore volume is the median pore diameter. As the mercury porosimeter, for example, "Autopore IV9500" (trade name) manufactured by Shimadzu Corporation can be used.

The porosity of the ceramic plate, that is, the ratio of the pore volume (V1) in the ceramic plate may be, for example, 30 to 65% by volume, or 40 to 60% by volume. If the porosity is too large, the strength of the ceramic plate tends to decrease. On the other hand, if the porosity is too small, the amount of resin that exudes when the composite sheet is adhered to the adherend tends to be small.

The porosity of the ceramic plate is obtained by calculating the bulk density [B (kg/m ³ )] from the volume and mass of the ceramic plate, and calculating the bulk density and the theoretical density [A (kg/m ³ )] of the nitride. , can be obtained by the following formula (1). The theoretical density A of boron nitride is 2280 kg/m ³ .
Porosity (% by volume) = [1-(B/A)] x 100 (1)

The thickness of the ceramic plate may be, for example, less than 2.0 mm, less than 1.8 mm, or less than 1.6 mm. By using a ceramic plate having such a thickness, for example, it becomes easier to fill the pores of the ceramic plate with a resin, and a composite sheet having an excellent resin filling rate can be more easily prepared. can. From the viewpoint of ease of manufacturing the ceramic plate, the thickness of the ceramic plate may be, for example, 0.1 mm or more, or 0.2 mm or more. The thickness of the ceramic plate may be adjusted within the range described above, and may be, for example, 0.1 mm or more and less than 2.0 mm, or 0.2 mm or more and less than 1.6 mm. The thickness of the ceramic plate means a value measured along the direction perpendicular to the

main surfaces

100a and 100b. If the thickness of the ceramic plate is not constant, the thickness is measured at 10 arbitrary locations, and the arithmetic mean value is taken as the thickness of the ceramic plate.

The ceramic plate described above can be suitably used, for example, for manufacturing a composite sheet prepared by impregnating and semi-curing a resin composition. One embodiment of the composite sheet comprises a nitride sintered plate having pores and a resin filling the pores. The nitride sintered plate in the composite sheet is the ceramic plate described above.

The resin includes, for example, a semi-cured product (B stage) of a resin composition containing a main agent and a curing agent. The semi-cured product is obtained by partially progressing the curing reaction of the resin composition. The semi-cured product can be further cured by a subsequent curing treatment. The resin may contain a cured product (C stage) of the resin composition. The resin composition may be a thermosetting resin composition.

The semi-cured product may contain monomers such as a main agent and a curing agent in addition to the resin as a resin component. It can be confirmed by, for example, a differential scanning calorimeter that the resin contained in the composite sheet is a semi-cured product (B stage) before becoming a cured product (C stage).

The lower limit of the curing rate of the resin contained in the composite sheet may be, for example, 10% or more, 15% or more, 20% or more, 25% or more, or 30% or more. When the curing rate of the resin is within the above range, excessive outflow of the resin during adhesion to the adherend can be suppressed, and deterioration of adhesiveness can be suppressed. The upper limit of the curing rate of the resin may be, for example, 55% or less, 50% or less, or 45% or less. When the upper limit of the curing rate of the resin is within the above range, the resin melts moderately during adhesion to the adherend, and the resin spreads over the adhesion interface, thereby exhibiting better adhesiveness. The curing rate of the resin contained in the composite sheet may be adjusted within the range described above, and may be, for example, 10-55%, 25-50%, or 30-50%.

The cure rate of the resin can be determined by measurement using a differential scanning calorimeter. First, the calorific value Q per unit mass generated when 2 mg of the uncured resin composition is completely cured is measured. Then, a 10 mg sample taken from the resin included in the composite sheet is heated in the same manner, and the calorific value R per unit mass generated when the sample is completely cured is determined. At this time, the mass of the sample used for the measurement with the differential scanning calorimeter is the same as that of the resin composition used for the measurement of the calorific value Q. Assuming that c (% by mass) of a thermosetting component is contained in the resin, the curing rate of the resin composition impregnated in the composite sheet is obtained by the following formula (2). Whether or not the resin is completely cured can be confirmed by the end of heat generation in the heat generation curve obtained by differential scanning calorimetry.
Curing rate (%) of impregnated resin composition={1-[(R/c)×100]/Q}×100 (2)

The resin filling rate may be adjusted from the viewpoint of further increasing the adhesiveness of the composite sheet, and may be, for example, 90% by volume or more, 92% by volume or more, 94% by volume or more, or 96% by volume or more. The upper limit of the resin filling rate is not particularly limited, but may be, for example, 100% by mass or less, or 98% by volume or less. The resin filling rate may be adjusted within the range described above, and may be, for example, 90 to 100% by volume, or 94 to 100% by volume.

Resins include, for example, epoxy resins, silicone resins, cyanate resins, silicone rubbers, acrylic resins, phenolic resins, melamine resins, urea resins, bismaleimide resins, unsaturated polyesters, fluororesins, polyimides, polyamideimides, polyetherimides, poly Butylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide resin, maleimide-modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, AES (acrylonitrile/ethylene/propylene/diene rubber-styrene) resin, polyglycolic acid resin, polyphthalamide, and polyacetal.

The composite sheet described above has excellent adhesion to adherends, so it can be suitably used to prepare a laminated substrate by adhering it to a metal sheet or the like. One embodiment of a laminated substrate has the composite sheet and a metal layer provided on the composite sheet. The composite sheet and the metal layer may be bonded together by curing the resin forming the composite sheet. FIG. 3 is a cross-sectional view of an example of a laminated substrate cut in the thickness direction. Laminated substrate 300 includes composite sheet 200 , metal layer 30 adhered to main surface 200 a of composite sheet 200 , and metal layer 40 adhered to main surface 200 b of composite sheet 200 . In the modified example of the laminated substrate, it is not essential to provide both of the metal layers 30 and 40, and in the modified example of the laminated substrate 300, only one of the metal layers 30 and 40 may be provided.

The metal layers 30 and 40 are not particularly limited as long as they are made of metal. The metal layer may be, for example, a metal plate or a metal foil. The metal layers 30 and 40 may also have patterns such as circuits, for example. Materials for the metal layers 30 and 40 include, for example, aluminum and copper. The thickness of the metal layers 30, 40 may be, independently of each other, for example 0.035 mm or more or 10 mm or less. The material, thickness, presence/absence of patterns, etc. of the metal layers 30 and 40 may be the same or different.

The laminated substrate 300 may have a resin layer between the composite sheet 200 and the metal layers 30 and 40 within the scope of the present disclosure. This resin layer may be formed by curing the resin exuded from the composite sheet 200 . The composite sheet 200 and the metal layers 30 and 40 in the laminated substrate 300 are sufficiently firmly adhered by the exuded resin, and thus have excellent adhesiveness. Since such a laminated substrate is thin and has excellent adhesion and heat dissipation properties, it can be suitably used as a heat dissipation member for semiconductor devices and the like.

Although several embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. Also, the descriptions of the above-described embodiments can be applied to each other.

Hereinafter, the present disclosure will be described in more detail using examples and comparative examples. It should be noted that the present disclosure is not limited to the following examples.

(Example 1)
100 parts by mass of orthoboric acid manufactured by Shin Nippon Denko Co., Ltd. and 35 parts by mass of acetylene black (trade name: HS100) manufactured by Denka Co., Ltd. were mixed using a Henschel mixer. The obtained mixture was filled in a graphite crucible and heated at 2200° C. for 5 hours in an argon atmosphere in an arc furnace to obtain massive boron carbide (B ₄ C). The resulting mass was coarsely pulverized with a jaw crusher to obtain coarse powder. This coarse powder was further pulverized by a ball mill having silicon carbide balls (φ10 mm) to obtain pulverized powder.

The prepared pulverized powder was filled in a crucible made of boron nitride. After that, using a resistance heating furnace, heating was performed for 10 hours under conditions of 2000° C. and 0.85 MPa in a nitrogen gas atmosphere. Thus, a fired product containing boron carbonitride (B ₄ CN ₄ ) and boron nitride (BN) was obtained.

A sintering aid was prepared by blending powdered boric acid and calcium carbonate. In preparation, 50.0 parts by mass of calcium carbonate was blended with 100 parts by mass of boric acid. At this time, the atomic ratio of boron to calcium was 17.5 atomic % of calcium to 100 atomic % of boron. In this way, 20 parts by mass of the sintering aid was added to 100 parts by mass of the fired product, and mixed using a Henschel mixer to prepare powdery raw material powder.

Using a powder press, the raw material powder was pressed at 150 MPa for 30 seconds to obtain a sheet-like molded plate (length x width x thickness = 50 mm x 50 mm x 0.35 mm). Three molded plates were prepared by the same operation. The content of sintering aid in each molded plate was 16.6% by weight.

Next, 30 parts by weight of amorphous boron nitride (manufactured by Denka Co., Ltd., trade name: GP) was added to a release agent slurry consisting of a mixture of 60 parts by weight of terpineol, 30 parts by weight of toluene, and 10 parts by weight of polyisobutyl methacrylate. Dispersed to prepare a slurry. The resulting slurry was used to form a coating film (boron nitride-containing layer) having a thickness of 0.03 mm on one main surface of the molded plate by a doctor blade method. The molded plates provided with the coating film were laminated with each other with the coating film interposed therebetween to obtain a laminate.

The obtained laminate was placed in a boron nitride container and introduced into a batch-type high-frequency furnace. In a batch-type high-frequency furnace, it was heated for 5 hours under the conditions of atmospheric pressure, nitrogen flow rate of 5 L/min, and 2000° C. (firing step). After that, a laminate in which the boron nitride sintered plates (sintered bodies) and the release layers were alternately laminated was taken out from the boron nitride container. The boron nitride sintered plate constituting the laminate was peeled off using a thickness gauge leaf to obtain three fired plates with a release layer remaining on the surface layer. The thickness of the fired plate was 0.39 mm.

Both main surfaces of the fired plate were polished with sandpaper by 0.05 mm from the surface layer to remove the release layer remaining on the surface layer (removal step). Thus, a ceramic plate, which is a sintered body of boron nitride, was obtained. The thickness of the obtained ceramic plate was 0.29 mm. A cross-sectional SEM image of the ceramic plate is shown in FIG. As shown in FIG. 4, in the vicinity of the surface layer of the ceramic plate (the position indicated by the dotted line in FIG. 4), the primary particles of boron nitride that are oriented in a direction parallel to the main surface of the ceramic plate are removed. I was able to confirm that. Further, by observing the main surface of the obtained ceramic plate with an optical microscope, it was confirmed that groove groups were formed by polishing. The maximum depth of the grooves in the groove group was 10 μm. Also, the polishing was performed so that the arithmetic mean roughness Ra was within the range of 1.0 to 2.0 μm.

(Comparative example 1)
A sintered plate was prepared in the same manner as in Example 1 before the polishing step. This sintered plate was used as a ceramic plate of Comparative Example 1. The thickness of the ceramic plate was 0.40 mm. A cross-sectional SEM image of the ceramic plate is shown in FIG. As shown in FIG. 5, in the vicinity of the surface layer of the ceramic plate (the position indicated by the dotted line in FIG. 5), it was confirmed that the primary particles of boron nitride were oriented in a direction parallel to the main surface of the ceramic plate.

<Measurement of filling rate of resin (semi-cured product) and evaluation of adhesion>
Using the ceramic plates obtained in Example 1 and Comparative Example 1, each composite sheet with a resin was prepared, and the filling rate of the resin (semi-cured product) and the adherend were determined by the methods described below. Adhesion to metal sheets was evaluated. Table 1 shows the results.

[Production of composite sheet]
Commercially available bismaleimide (K-I Kasei Co., Ltd., trade name: BMI-80) 10 parts by mass epoxy resin (Mitsubishi Chemical Co., Ltd., trade name: Epicoat 807) 29.5 parts by mass, and commercially available cyanate resin ( 0.5 parts by mass of a commercially available curing agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Akmex H-84B) is blended with 60 parts by mass of Mitsubishi Gas Chemical Co., Ltd., trade name: TACN). A resin composition was prepared. The prepared resin composition was heated at 120° C. for 11 hours to adjust the curing rate to 13%. A resin composition having a curing rate of 13% was dropped onto the main surface of a ceramic plate heated to 160° C. while maintaining the temperature. Under atmospheric pressure, the resin composition dropped on the main surface of the ceramic plate is spread using a silicone rubber spatula, and while spreading the resin composition over the entire main surface, the pores of the ceramic plate are impregnated with the resin. A composition-impregnated body was obtained.

The resin composition-impregnated body was heated at 160°C for 5 minutes under atmospheric pressure to semi-cure the resin composition. Thus, a quadrangular prism-shaped composite sheet (length x width = 50 mm x 50 mm, thickness: 0.29 mm or 0.40 mm) was produced.

The curing rate of the resin composition contained in the semi-cured product was determined by measurement using a differential scanning calorimeter. In each of the composite sheets prepared using the ceramic plates of Example 1 and Comparative Example 1, the curing rate of the impregnated resin composition was 45%. These composite sheets were used as samples for evaluation of peel strength.

[Measurement of filling rate of resin (semi-cured product)]
The filling rate of the resin contained in the composite sheet was obtained by the following formula (3). The results were as shown in Table 1. In the following description of the filling rate, the ceramic plate is also referred to as a boron nitride sintered plate.

Filling rate of resin in composite sheet (volume %) = {(bulk density of composite sheet - bulk density of boron nitride sintered plate) / (theoretical density of composite sheet - bulk density of boron nitride sintered plate)} x 100... (3)

The bulk density of the boron nitride sintered plate and composite sheet conforms to JIS Z 8807:2012 "Method for measuring density and specific gravity by geometric measurement", and the length of each side of the boron nitride sintered plate or composite sheet (measured with a vernier caliper) and the mass of the boron nitride sintered plate or composite sheet measured with an electronic balance (see JIS Z 8807:2012, item 9). The theoretical density of the composite sheet was determined by the following formula (4).

Theoretical density of composite sheet = bulk density of boron nitride sintered plate + true density of resin x (1 - bulk density of boron nitride sintered plate / true density of boron nitride) … (4)

The true density of the boron nitride sintered plate and resin is measured using a dry automatic densitometer in accordance with JIS Z 8807:2012 "Method for measuring density and specific gravity by gas replacement method". (See formulas (14) to (17) in item 11 of JIS Z 8807:2012).

[Measurement of peel strength]
Each of the composite sheets obtained as described above is placed between two copper plates (a copper plate with a thickness of 0.035 mm and a copper plate with a thickness of 1.0 mm). A laminated sheet obtained by heating and pressing for 5 minutes under conditions of 200° C. and 5 MPa and then heating for 2 hours under conditions of 200° C. and atmospheric pressure was prepared and used as a measurement target. The measurement was carried out according to JIS K 6854-1: 1999 "Adhesive-Peeling adhesive strength test method", a 90 ° peel test was performed, and the peel strength of the composite at 20 ° C was measured using a universal testing machine (A&D Co., Ltd. (trade name: RTG-1310). The test was conducted by peeling off a copper plate having a thickness of 0.035 mm. Measurement was performed under conditions of test speed: 50 mm/min, load cell: 5 kN, and measurement temperature: room temperature (20°C).

2 Molded plate 3 Boron nitride-containing layer 4 Sintered body 5 Release layer 10 Sheet 20 Fired

plate

30, 40 Metal layer 100 Ceramic plate 200 Composite sheet 300... Laminated substrate.

Claims

A firing step of obtaining a fired plate by firing a sheet having a molded plate containing boron nitride and a sintering aid and a boron nitride-containing layer provided on at least part of the main surface of the molded plate;
and a removing step of removing at least part of a release layer derived from the boron nitride-containing layer of the fired plate.
further comprising a step of laminating a plurality of the sheets to obtain a laminate,
The manufacturing method according to claim 1, wherein the firing step is a step of firing the laminate to obtain a plurality of the fired plates.
The manufacturing method according to claim 1 or 2, wherein the removing step is a step of polishing the fired plate from the release layer side.
3. The method for manufacturing a ceramic plate according to claim 1, wherein the removal step is a step of polishing the thickness of the boron nitride-containing layer or more from the release layer side of the fired plate to reduce the height. .
Composed of a sintered body containing primary particles of boron nitride,
A ceramic plate having a polished surface.
The ceramic plate according to claim 5, which has a median pore size of 1.5 to 4.0 μm.
The ceramic plate according to claim 5 or 6, having a thickness of less than 2.0 mm.
A nitride sintered plate having pores and a resin filled in the pores,
A composite sheet, wherein the nitride sintered plate is the ceramic plate according to claim 5 or 6.
A laminated substrate comprising the composite sheet according to claim 8 and a metal layer provided on the composite sheet.