JP7550869B2 - Composite and manufacturing method thereof, and laminate and manufacturing method thereof - Google Patents

Description

The present disclosure relates to a composite and a method for manufacturing the same, as well as a laminate and a method for manufacturing the same.

Power devices, transistors, thyristors, CPUs, and other components are required to efficiently dissipate heat generated during use. To meet this demand, efforts have traditionally been made to increase the thermal conductivity of the insulating layer of printed wiring boards on which electronic components are mounted, or electronic components or printed wiring boards have been attached to heat sinks via thermal interface materials that have electrical insulation. For such insulating layers and thermal interface materials, composites made of resin and ceramics such as boron nitride are used as heat dissipation members.

As such a composite, composites in which a porous ceramic sintered body (e.g., boron nitride sintered body) is impregnated with resin have been studied (see, for example, Patent Document 1). Also, in a laminate having a circuit board and a resin-impregnated boron nitride sintered body, it has been studied to reduce the thermal resistance of the laminate and improve heat dissipation by directly contacting the primary particles constituting the boron nitride sintered body with the circuit board (see, for example, Patent Document 2).

International Publication No. 2014/196496 JP 2016-103611 A

In recent years, with the increasing integration of circuits in semiconductor devices, etc., there is a demand for miniaturization of various components such as heat dissipation components. Under these circumstances, in order to ensure the reliability of semiconductor devices, etc., it is considered necessary to have heat dissipation components that can suppress insulation breakdown even when miniaturized. On the other hand, miniaturization also requires high positional accuracy, so excellent handleability is also necessary.

The present disclosure provides a composite body and a method for producing the same that can flexibly accommodate a prioritized characteristic among various characteristics such as adhesion, thermal conductivity, insulation reliability, and handleability. The present disclosure also provides a laminate body and a method for producing the same that can flexibly accommodate a prioritized characteristic among various characteristics such as thermal conductivity, insulation reliability, and handleability.

In one aspect, the present disclosure provides a composite containing a resin and a porous nitride sintered body, in which at least a portion of the resin fills the pores of the nitride sintered body, and the curing rates of the resin at the surface and in the interior are different from each other.

The above composite can sufficiently increase the adhesive strength with the adherend attached to the composite by making the curing rate of the resin in the surface portion smaller than the curing rate of the resin in the interior. This can sufficiently increase the thermal conductivity and insulation reliability. On the other hand, if the curing rate of the resin in the surface portion is made larger than the curing rate of the resin in the interior, the handleability can be improved. In addition, in this case, since the curing rate of the resin in the interior can be made smaller, the flexibility is improved, the adhesion with the adherend is improved, and the insulation reliability can also be increased. In this way, the above composite can have a higher degree of design freedom than a composite in which the curing rate of the resin in the surface portion and the interior is the same. Therefore, it is possible to provide a laminate that can flexibly respond to the priority characteristics among various characteristics such as adhesion, thermal conductivity, insulation reliability, and handleability.

The interior of the composite may be made of a resin filler in which a nitride sintered body is filled with resin, and the surface may be made of a resin layer that covers at least a part of the resin filler. This can further improve adhesion to other components and further increase thermal conductivity and insulation reliability.

In the above composite, the difference between the maximum and minimum values of the resin curing rate may be 30% or more. The absolute value of the difference between the resin curing rate inside the composite and the resin curing rate at the surface may be 10% or more. Such a composite can be more flexibly adapted to the prioritized properties.

In the above composite, the resin may have a higher cure rate in the interior than in the surface. This can sufficiently increase the insulation reliability, thermal conductivity, and adhesive strength with the adherend.

In the above composite, the resin may have a higher cure rate on the surface than in the interior. Such a composite has excellent handleability. In addition, the resin has a higher flexibility because the cure rate of the interior resin can be reduced. This allows the composite to smoothly deform to conform to the shape of the adherend when attached to the adherend, improving adhesion to other components. This also allows high insulation reliability to be maintained.

In one aspect, the present disclosure provides a laminate in which any of the composites described above and a metal sheet are laminated. This laminate includes any of the composites described above. Therefore, it is possible to flexibly respond to prioritized characteristics among various characteristics such as thermal conductivity, insulation reliability, and handleability.

In one aspect, the present disclosure provides a method for producing a composite, the method comprising: an impregnation step of impregnating a porous nitride sintered body with a first resin composition to obtain a resin-impregnated body; a curing step of heating the resin-impregnated body to cure or semi-cure the first resin composition filling the pores to obtain a resin-filled body containing the first resin; and a coating step of coating at least a portion of the surface of the resin-filled body with a second resin, the first resin and the second resin having different curing rates.

In the composite obtained by the above manufacturing method, the curing rate of the first resin contained in the resin filler is different from that of the second resin covering the resin filler. In such a composite, the adhesive force with the adherend can be sufficiently increased by making the curing rate of the second resin smaller than that of the first resin. This allows the thermal conductivity and insulation reliability to be sufficiently increased. On the other hand, by making the curing rate of the second resin larger than that of the first resin, the handleability can be increased. In addition, in this case, since the curing rate of the first resin can be reduced, the flexibility is improved, the adhesion with the adherend is improved, and the insulation reliability can be increased. In this way, the composite obtained by the above manufacturing method has a higher degree of design freedom than a composite in which the curing rates of the first resin and the second resin are the same. Therefore, it is possible to manufacture a laminate that can flexibly respond to the priority characteristics among various characteristics such as adhesion, thermal conductivity, insulation reliability, and handleability.

In the coating process, the second resin composition may be applied to the resin filler and heated to coat the resin filler with the second resin. This makes it possible to obtain a composite having different cure rates between the first resin and the second resin in a simple manner. In addition, the entire surface of the resin filler can be smoothly coated with the second resin.

In the coating process, at least a portion of the surface of the resin filler may be coated with a sheet of a second resin. This makes it possible to obtain a composite in which the first resin and the second resin have different cure rates in a simple manner.

In the coating process, a semi-cured product of the second resin composition may be adhered to the resin filler and heated to coat at least a portion of the surface of the resin filler with the second resin. Alternatively, in the coating process, the resin filler may be coated with a sheet of the second resin. This method allows for the smooth production of a composite with excellent dimensional accuracy.

In one aspect, the present disclosure provides a method for producing a laminate, which includes a lamination step of laminating a composite obtained by any one of the above-mentioned production methods with a metal sheet, and applying heat and pressure. This production method uses the above-mentioned composite, and therefore can produce a laminate that can flexibly respond to a priority characteristic among various characteristics such as thermal conductivity, insulation reliability, and handleability.

According to the present disclosure, it is possible to provide a composite body and a method for manufacturing the same that can flexibly accommodate a prioritized characteristic among various characteristics such as adhesion, thermal conductivity, insulation reliability, and handleability. It is also possible to provide a laminate body and a method for manufacturing the same that can flexibly accommodate a prioritized characteristic among various characteristics such as thermal conductivity, insulation reliability, and handleability.

FIG. 1 is a perspective view showing an example of a composite body. FIG. 2 is a cross-sectional view taken along line II-II of FIG. FIG. 3 is a cross-sectional view showing another example of the composite body. FIG. 4 is a cross-sectional view showing an example of a laminate. FIG. 5 is a cross-sectional view showing another example of the laminate.

Hereinafter, several embodiments of the present disclosure will be described, possibly with reference to the drawings. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

The composite of one embodiment contains a resin and a porous nitride sintered body. At least a portion of the resin contained in the composite fills the pores of the nitride sintered body. The curing rates of the resin on the surface and inside of the composite are different from each other.

An example of a porous nitride sintered body is a boron nitride sintered body. The nitride sintered body contains nitride particles and pores formed by sintering primary particles of nitride together. The average pore size of the pores of the nitride sintered body may be 5 μm or less, 4 μm or less, or 3.5 μm or less. Since the size of the pores of such a nitride sintered body is small, the contact area between the particles of the nitride can be sufficiently large. Therefore, the thermal conductivity can be increased. The average pore size of the pores of the nitride sintered body may be 0.5 μm or more, 1 μm or more, or 1.5 μm or more. Such a nitride sintered body can be sufficiently deformed when pressure is applied during bonding, so it has excellent adhesion to other members (adherends). One example of the range of the average pore size is 0.5 to 5 μm.

The average pore size of the pores in the nitride sintered body can be measured by the following procedure. First, the composite is heated to remove the resin. Then, using a mercury porosimeter, the nitride sintered body is pressurized while increasing the pressure from 0.0042 MPa to 206.8 MPa, and the pore size distribution is determined. With the horizontal axis representing the pore size and the vertical axis representing the cumulative pore volume, the average pore size is the pore size at which the cumulative pore volume reaches 50% of the total pore volume. A mercury porosimeter manufactured by Shimadzu Corporation can be used.

The porosity of the nitride sintered body, i.e., the ratio of the volume of the pores in the nitride sintered body (V1), may be 30 to 65 volume %, or 40 to 60 volume %. If the porosity is too large, the strength of the nitride sintered body tends to decrease. On the other hand, if the porosity is too small, less resin tends to seep out when the composite is bonded to another member.

The porosity can be calculated by calculating the bulk density [B (kg/m ³ )] from the volume and mass of the nitride sintered body, and then using this bulk density and the theoretical density [A (kg/m ³ )] of the nitride according to the following formula (1). The nitride sintered body may contain at least one selected from the group consisting of boron nitride, aluminum nitride, and silicon nitride. In the case of boron nitride, the theoretical density A is 2280 kg/m ^3. In the case of aluminum nitride, the theoretical density A is 3260 kg/m ^3. In the case of silicon nitride, the theoretical density A is 3170 kg/m ³ .
Porosity (volume%) = [1 - (B / A)] x 100 (1)

When the nitride sintered body is a boron nitride sintered body, the bulk density B may be 800 to 1500 kg/ ^m3 , or 1000 to 1400 kg/ ^m3 . If the bulk density B is too small, the strength of the nitride sintered body tends to decrease. On the other hand, if the bulk density B is too large, the filling amount of the resin decreases, and the good adhesiveness of the composite may be impaired.

The resin contained in the composite is a cured product (C stage) or semi-cured product (B stage) of a resin composition containing a base agent and a curing agent. A cured product is one in which the curing reaction of the resin composition has progressed completely. A semi-cured product is one in which the curing reaction of the resin composition has progressed partially. The semi-cured product can be further cured by a subsequent curing treatment. Taking advantage of the semi-cured state, it may be temporarily pressure-bonded to another member such as a metal sheet, and then heated to obtain a laminate.

The resin may include a thermosetting resin produced by the reaction of the base agent and the curing agent in the resin composition. The semi-cured product may include, as the resin component, a monomer such as a base agent and a curing agent in addition to the thermosetting resin. Whether the resin contained in the composite is a semi-cured product (B stage) before becoming a cured product (C stage) can be confirmed, for example, by a differential scanning calorimeter.

The resin may include at least one selected from the group consisting of epoxy resin, silicone resin, cyanate resin, silicone rubber, acrylic resin, phenolic resin, melamine resin, urea resin, bismaleimide resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, polybutylene 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. One of these may be included alone, or two or more may be included in combination.

When the composite is used as an insulating layer of a printed wiring board, the resin may contain an epoxy resin from the viewpoint of improving heat resistance and adhesive strength to the circuit. When the composite is used as a thermal interface material, the resin may contain a silicone resin from the viewpoint of improving heat resistance, flexibility, and adhesion to a heat sink, etc.

The volume ratio of the resin in the composite may be 30 to 60 volume %, or may be 35 to 55 volume %, based on the total volume of the composite. The volume ratio of the nitride particles constituting the nitride sintered body in the composite may be 40 to 70 volume %, or may be 45 to 65 volume %, based on the total volume of the composite. A composite with such a volume ratio can achieve both excellent adhesion and high levels of strength.

The mass ratio of the resin in the composite may be 15 to 50 mass % or 25 to 40 volume % based on the total mass of the composite. The mass ratio of the nitride particles constituting the nitride sintered body in the composite may be 50 to 85 mass % or 60 to 75 mass % based on the total volume of the composite. A composite with such mass ratios can achieve both excellent adhesion and high levels of strength.

The shape of the composite is not particularly limited, and may be, for example, a sheet (composite sheet). The curing rate of the resin inside the composite (internal curing rate) can be obtained by collecting a resin (first resin) from a cross section cut so that the center of the resin filler is exposed, and measuring the curing rate of the collected first resin. The curing rate of the resin on the surface of the composite (surface curing rate) can be obtained by collecting a resin (second resin) from the surface of the composite, and measuring the curing rate of the collected second resin. The curing rates of the first resin and the second resin can be obtained by the method described in the examples. Even when the surface of the composite is composed of a resin filler, the curing rate of the resin on the surface of the composite (surface curing rate) can be obtained by collecting a resin (second resin) from the surface of the composite, and measuring the curing rate of the collected second resin.

The first resin and the second resin can be obtained by curing or semi-curing the first resin composition and the second resin composition, respectively. The first resin and the second resin may be formed using the same monomer or oligomer, or may be formed using different monomers or oligomers.

The difference between the maximum and minimum values of the cure rate of the resin contained in the composite may be 30% or more, 40% or more, or 50% or more. In this way, by increasing the difference, a composite can be obtained that has even greater flexibility in material design according to prioritized characteristics. From the viewpoint of ease of manufacture, the difference between the maximum and minimum values of the cure rate of the resin contained in the composite may be 90% or less, or 80% or less.

The maximum cure rate of the resin contained in the composite may be 50-100%, or may be 60-90%. The minimum cure rate of the resin contained in the composite may be 5% or more, 10% or more, or 20% or more.

Figure 1 is a perspective view showing an example of a composite. The composite 10 in Figure 1 is in the form of a sheet, and the entire surface is covered with a resin layer. The thickness of the composite 10 may be, for example, less than 10 mm, less than 5 mm, or less than 2 mm. The lower limit of the thickness of the composite 10 may be 0.1 mm. This allows the composite 10 to be sufficiently miniaturized. Such a composite 10 is suitable for use, for example, as a component of a semiconductor device.

The thickness of the composite 10 is measured along a direction perpendicular to the main surface. When the thickness of the composite 10 is not constant, the thickness may be measured at 10 selected locations, and the average value may be within the above-mentioned range. The size of the main surface of the composite 10 is not particularly limited. The main surface of the composite 10 may be, for example, ⁵⁰ mm2 or more, ²⁰⁰ mm2 or more, or ¹⁰⁰⁰ mm2 or more.

Figure 2 is a cross-sectional view of the composite 10 of Figure 1 taken along line II-II. That is, Figure 2 shows a cross section of the composite 10 cut along the thickness direction of the composite 10. The composite 10 comprises a resin filler 12 as the interior of the composite 10, and a resin layer 14 as the surface portion of the composite 10. The entire surface of the resin filler 12 is covered with the resin layer 14. The resin filler 12 includes a porous nitride sintered body and a first resin filled in at least a portion of the pores. The first resin may be a cured product of a resin composition, or may be a semi-cured product.

The filling rate of the resin in the resin filler 12 may be 85% by volume or more. This allows the electrical insulation and thermal conductivity to be sufficiently high. From a similar perspective, the filling rate may be 88% by volume or more, 90% by volume or more, or 92% by volume or more.

The resin layer 14 is composed of a cured or semi-cured product of the resin composition. The thickness of the resin layer 14 may be 0.005 mm or more, or 0.01 mm or more, from the viewpoint of sufficiently increasing the adhesion with other members. The thickness of the resin layer 14 may be 0.5 mm or less, or 0.2 mm or less, from the viewpoint of sufficiently maintaining the high thermal conductivity of the composite 10. The thickness of the resin filler 12 may be, for example, less than 9 mm, less than 4 mm, or less than 1.5 mm, from the viewpoint of sufficiently increasing the thermal conductivity. The lower limit of the thickness of the composite 10 may be 0.2 mm. If the thickness of the resin filler 12 and the resin layer 14 is not constant, 10 arbitrary points are selected to measure the thickness, and the average value is obtained. The average value may be within the above-mentioned range.

The cure rate (internal cure rate) of the first resin in the resin filler 12 constituting the interior of the composite 10 may be greater than the cure rate (surface cure rate) of the second resin in the surface portion (resin layer 14) of the composite 10. That is, the cure rate of the first resin in the interior of the composite 10 may be greater than that of the second resin constituting the resin layer 14. In this case, when the composite 10 and another member are pressure-bonded, uncured resin components seep out from the resin layer 14, thereby increasing the adhesive strength between the composite 10 and the adherend. In addition, such a composite 10 has sufficiently high insulation reliability and excellent thermal conductivity.

The curing rate of the second resin at the surface of the composite 10 (surface curing rate) may be greater than the curing rate of the first resin inside the composite 10 (internal curing rate). Such a composite has excellent handleability because stickiness at the surface and bleeding of the resin components are suppressed. In addition, the composite 10 has excellent flexibility because the internal curing rate is lower than the surface curing rate. Therefore, it can deform smoothly when pressed against another member. Therefore, it has excellent adhesion to another member (adherend).

The absolute value of the difference between the internal hardening rate and the surface hardening rate may be 10% or more, 20% or more, or 30% or more. In this way, by increasing the difference, a composite can be obtained that has even greater flexibility in material design according to prioritized properties. From the viewpoint of ease of manufacture, the absolute value of the difference between the internal hardening rate and the surface hardening rate may be 80% or less, 70% or less, or 60% or less.

In this example, the entire surface of the resin filler 12 is covered with the resin layer 14, but the composite is not limited to this example. For example, only a portion of the surface of the resin filler 12 may be covered with the resin layer 14. The main surface of the composite 10 in this example was rectangular, but is not limited to this shape. For example, the main surface may be a polygon other than a rectangle, or may be circular. The corners may be chamfered, or a portion may be cut out. The composite may also have a through hole that penetrates in the thickness direction.

Figure 3 is a cross-sectional view showing another example of a composite. Figure 3 shows a cross-section of the composite 10A cut along the thickness direction of the composite 10A. The composite 10A has a resin filler 12 inside the composite 10A and a resin layer 14A covering a part of the surface of the resin filler 12. As in this example, the resin impregnated body constituting the interior of the composite does not have to be completely covered by the resin layer constituting the surface. That is, a part of the resin impregnated body may be exposed to the outside. The resin filler 12 in Figure 3 includes a porous nitride sintered body and a first resin filled in at least a part of the pores. The first resin may be a cured product of a resin composition, or may be a semi-cured product.

1 and 2 in that the resin layer 14A covers only a portion of the surface of the resin filler 12. The other configuration of the composite 10A may be the same as that of the composite 10. In the composite 10A, the resin layer 14A covers a portion of the main surfaces 12a and 12b of the resin filler 12. Meanwhile, the other portions of the main surfaces 12a and 12b of the resin filler 12 and the side surface 12c of the resin filler 12 are exposed to the outside.

For example, by making the curing rate (internal curing rate) of the first resin contained in the resin filler 12 greater than the curing rate (surface curing rate) of the second resin contained in the resin layer 14A, it is possible to increase the adhesive strength of the resin layer 14A while suppressing stickiness on the side surface 12c.

For example, by making the curing rate (surface curing rate) of the second resin constituting the resin layer 14A greater than the curing rate (internal curing rate) of the first resin contained in the resin filler 12, it is possible to increase the adhesive strength at the side surface 12c while suppressing stickiness on the main surface (resin layer 14A) of the composite 10A.

In the example of FIG. 3, the resin layer 14A covers a portion of both main surfaces 12a, 12b of the resin filler 12, but is not limited thereto. In another example, the resin layer 14A may cover the entirety of both main surfaces 12a, 12b of the resin filler 12. In yet another example, the resin layer 14A may cover only one main surface 12a (or main surface 12b) of the resin filler 12. In yet another example, it may cover only the side surface 12c of the resin filler 12. In yet another example, multiple resin layers may be stacked to form the surface portion of the composite. The composites 10, 10A may be formed into a laminate by stacking metal sheets, or may be used as a heat dissipation member as is.

In one embodiment, the laminate is formed by laminating a composite and a metal sheet. Examples of the composite include those exemplified above. The metal sheet is not particularly limited as long as it is made of metal and has a sheet shape. The adherend (other member) mentioned in the description of the composite above may be a metal sheet. The metal sheet may be a metal plate or a metal foil. Examples of materials for the metal sheet include aluminum and copper.

Figure 4 is a cross-sectional view showing an example of a laminate. Figure 4 shows a cross-section of the laminate 20 cut along the lamination direction. The laminate 20 comprises the composite 10 of Figures 1 and 2 and a metal sheet 22 laminated on the main surface of the composite 10. The material and thickness of the multiple metal sheets 22 may be the same as each other or may be different. In addition, it is not necessary to provide the metal sheet 22 on both main surfaces of the resin filler 12. In a modified example, the metal sheet 22 may be provided on only one main surface of the resin filler 12.

The metal sheet 22 in the laminate 20 is in contact with the resin layer 14. The metal sheet 22 and the composite 10 are bonded with high adhesion. Since the metal sheet 22 and the composite 10 are bonded with high adhesion in the laminate 20, the laminate 20 can be suitably used, for example, as a heat dissipation member in a semiconductor device. The thickness of the laminate 20 may be, for example, less than 12 mm, less than 6 mm, or less than 3 mm. The lower limit of the thickness of the laminate 20 may be 0.6 mm. This allows the laminate 20 to be sufficiently miniaturized. Such a laminate 20 is suitably used, for example, as a component of a semiconductor device. An example of the thickness of the laminate 20 may be 0.6 mm or more and less than 12 mm.

Since the laminate 20 includes the composite 10, it is possible to achieve both high levels of thermal conductivity and insulation reliability. For example, when the curing rate (surface curing rate) of the second resin contained in the resin layer 14 is greater than the curing rate (internal curing rate) of the first resin contained in the resin filler 12, the stickiness of the exposed portion of the composite 10 exposed in the laminate 20 can be suppressed. This provides sufficiently excellent handling properties. On the other hand, when the internal curing rate is greater than the surface curing rate, the adhesive strength between the resin layer 14 and the metal sheet 22 can be sufficiently increased. Such a laminate 20 can provide sufficiently high thermal conductivity and insulation reliability.

Figure 5 is a cross-sectional view showing another example of a laminate. Figure 5 shows a cross-section of laminate 20A cut along the lamination direction. Laminate 20A comprises composite 10A of Figure 3 and a metal sheet 22 laminated on resin layer 14A. The material and thickness of the multiple metal sheets 22 may be the same as or different from each other. In laminate 20A, side surface 12c of resin filler 12 is exposed to the outside.

For example, when the cure rate (internal cure rate) of the first resin contained in the resin filler 12 is greater than the cure rate (surface cure rate) of the second resin constituting the resin layer 14A, the laminate 20A can suppress stickiness on the side surface 12c. This provides sufficiently excellent handling properties. In addition, since the surface cure rate is greater than the internal cure rate, the adhesive strength between the resin layer 14A and the metal sheet 22 can be sufficiently increased. Such a laminate 20A can provide sufficiently high thermal conductivity and insulation reliability.

On the other hand, when the cure rate (surface cure rate) of the second resin constituting the resin layer 14A is greater than the cure rate (internal cure rate) of the first resin contained in the resin filler 12, the side 12c of the resin filler 12 has a high adhesive strength. Therefore, the laminate 20A can be firmly fixed to another member using the side 12c. In this way, the laminate can be designed with a high degree of freedom according to the shape of the laminate and the prioritized characteristics.

In the above example, the surface portion is composed of a resin layer, but is not limited to such an example. For example, the resin layer 14A may not be present, and the resin filler 12 may be exposed on the surface portion of the composite. That is, the interior and surface portion of the composite may be composed of the resin filler 12, and the curing rate of the resin in the interior and the surface portion may be different. In this case, the thickness of the surface portion may be 0.005 mm or more, or may be 0.01 mm or more, from the viewpoint of sufficiently increasing the adhesion with other members. The thickness of the surface portion may be 0.5 mm or less, or may be 0.2 mm or less, from the viewpoint of sufficiently maintaining the high thermal conductivity of the composite. An example of the thickness of the surface portion is 0.005 to 0.5 mm.

A manufacturing method for a composite according to one embodiment includes an impregnation step in which a porous nitride sintered body is impregnated with a first resin composition to obtain a resin-impregnated body, a curing step in which the resin-impregnated body is heated to cure or semi-cure the resin composition filling the pores to obtain a resin-filled body containing the first resin, and a coating step in which the resin-filled body is coated with a second resin.

A porous nitride sintered body can be obtained by the following sintering process. First, a raw material powder containing a nitride is prepared. The nitride contained in the raw material powder may contain at least one nitride selected from the group consisting of boron nitride, aluminum nitride, and silicon nitride. When boron nitride is contained, the boron nitride may be amorphous boron nitride or hexagonal boron nitride. When preparing a boron nitride sintered body as the nitride sintered body, for example, amorphous boron nitride powder having an average particle size of 0.5 to 10 μm or hexagonal boron nitride powder having an average particle size of 3.0 to 40 μm can be used as the raw material powder.

In the sintering step, the compound containing the nitride powder may be molded and sintered to obtain a nitride sintered body. The molding may be performed by uniaxial pressing or cold isostatic pressing (CIP). A sintering aid may be blended before molding to obtain the compound. Examples of the sintering aid include metal oxides such as yttria oxide, aluminum oxide, and magnesium oxide, alkali metal carbonates such as lithium carbonate and sodium carbonate, and boric acid. When a sintering aid is blended, the blending amount of the sintering aid may be, for example, 0.01 parts by mass or more, or 0.1 parts by mass or more, relative to a total of 100 parts by mass of the nitride and the sintering aid. The blending amount of the sintering aid may be, for example, 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less, relative to a total of 100 parts by mass of the nitride and the sintering aid. By setting the amount of the sintering aid to be within the above range, it becomes easier to adjust the average pore size of the nitride sintered body to the range described below.

The compound may be formed into a sheet-like compact by, for example, a doctor blade method. The forming method is not particularly limited, and the compact may be formed by press molding using a mold. The forming pressure may be, for example, 5 to 350 MPa. The shape of the compact may be a sheet-like shape with a thickness of less than 2 mm. If a nitride sintered body is produced using such a sheet-like compact, a sheet-like composite with a thickness of less than 2 mm can be produced without cutting the nitride sintered body. In addition, compared to cutting a block-shaped nitride sintered body into a sheet-like shape, by forming the nitride sintered body into a sheet-like shape from the compact stage, material loss due to processing can be reduced. Therefore, the composite can be produced with a high yield.

The sintering temperature in the sintering step may be, for example, 1600°C or higher, or 1700°C or higher. The sintering temperature may be, for example, 2200°C or lower, or 2000°C or lower. The sintering time may be, for example, 1 hour or more, or 30 hours or less. The sintering atmosphere may be, for example, an inert gas atmosphere such as nitrogen, helium, or argon.

For example, a batch furnace or a continuous furnace can be used for sintering. Examples of the batch furnace include a muffle furnace, a tubular furnace, and an atmosphere furnace. Examples of the continuous furnace include a rotary kiln, a screw conveyor furnace, a tunnel furnace, a belt furnace, a pusher furnace, and a large continuous furnace. In this manner, a nitride sintered body can be obtained. The nitride sintered body may be in the form of a block.

When the nitride sintered body is in a block shape, a cutting step may be performed to process the nitride sintered body so that the thickness is less than 2 mm. In the cutting step, the nitride sintered body is cut using, for example, a wire saw. The wire saw may be, for example, a multi-cut wire saw. By such a cutting step, a sheet-like nitride sintered body having a thickness of, for example, less than 2 mm can be obtained. This allows the nitride sintered body to be smoothly impregnated with the first resin composition in the subsequent impregnation step.

In the impregnation process, the pores of the nitride sintered body are impregnated with a first resin composition having a viscosity of 10 to 500 mPa·s to obtain a resin-impregnated body. Reducing the thickness of the nitride sintered body makes it possible to smoothly impregnate the first resin composition. In addition, by setting the viscosity of the first resin composition within a range suitable for impregnation, the filling rate of the resin filler can be sufficiently high.

The viscosity of the first resin composition when the nitride sintered body is impregnated with the first resin composition may be 440 mPa·s or less, 390 mPa·s or less, or 340 mPa·s or less. By lowering the viscosity of the resin composition in this way, the impregnation of the resin composition can be sufficiently promoted. The viscosity of the first resin composition when the nitride sintered body is impregnated with the first resin composition may be 15 mPa·s or more, or 20 mPa·s or more. By setting a lower limit on the viscosity of the first resin composition in this way, it is possible to suppress the resin composition that has once impregnated into the pores from flowing out of the pores. The viscosity of the first resin composition may be adjusted by partially polymerizing the monomer component. The above viscosity of the first resin composition is the viscosity of the first resin composition at the temperature (T1) when the nitride sintered body is impregnated with the resin composition. This viscosity is measured using a rotational viscometer at a shear rate of 10 (1/sec) and at a temperature (T1). Therefore, the viscosity when the first resin composition is impregnated into the nitride sintered body may be adjusted by changing the temperature T1.

The temperature (T1) when the nitride sintered body is impregnated with the first resin composition may be, for example, equal to or higher than the temperature (T2) at which the first resin composition is semi-cured, and lower than the temperature T3 (= T2 + 20°C). The temperature (T2) may be, for example, 80 to 140°C. The impregnation of the nitride sintered body with the first resin composition may be carried out under pressure or under reduced pressure. The method of impregnation is not particularly limited, and the nitride sintered body may be immersed in the first resin composition, or the first resin composition may be applied to the surface of the nitride sintered body.

The impregnation process may be performed under either reduced pressure or pressurized conditions, or a combination of impregnation under reduced pressure and impregnation under pressurized conditions may be performed. When the impregnation process is performed under reduced pressure, the pressure in the impregnation apparatus may be, for example, 1000 Pa or less, 500 Pa or less, 100 Pa or less, 50 Pa or less, or 20 Pa or less. When the impregnation process is performed under pressurized conditions, the pressure in the impregnation apparatus may be, for example, 1 MPa or more, 3 MPa or more, 10 MPa or more, or 30 MPa or more.

By adjusting the pore size of the pores in the nitride sintered body, it is possible to promote impregnation of the resin composition by capillary action and adjust the filling rate of the resin in the resin filler. From this perspective, the average pore size of the nitride sintered body may be 0.5 to 5 μm, or 1 to 4 μm.

The first resin composition may be, for example, one that becomes the resin described in the description of the composite by a curing or semi-curing reaction. The resin composition may contain a solvent. The viscosity of the first resin composition may be adjusted by changing the amount of the solvent, or the viscosity of the first resin composition may be adjusted by partially progressing the curing reaction. Examples of the solvent include aliphatic alcohols such as ethanol and isopropanol, ether alcohols such as 2-methoxyethanol, 1-methoxyethanol, 2-ethoxyethanol, 1-ethoxy-2-propanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, and 2-(2-butoxyethoxy)ethanol, glycol ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone, and hydrocarbons such as toluene and xylene. One of these may be contained alone, or two or more may be contained in combination.

The first resin composition is thermosetting and may contain, for example, at least one selected from the group consisting of a compound having a cyanate group, a compound having a bismaleimide group, and a compound having an epoxy group, and a curing agent.

Examples of compounds having a cyanate group include dimethylmethylenebis(1,4-phenylene)biscyanate and bis(4-cyanatephenyl)methane. Dimethylmethylenebis(1,4-phenylene)biscyanate is commercially available, for example, as TACN (trade name, manufactured by Mitsubishi Gas Chemical Company, Inc.).

Examples of compounds having a bismaleimide group include N,N'-[(1-methylethylidene)bis[(p-phenylene)oxy(p-phenylene)]]bismaleimide and 4,4'-diphenylmethane bismaleimide. N,N'-[(1-methylethylidene)bis[(p-phenylene)oxy(p-phenylene)]]bismaleimide is commercially available, for example, as BMI-80 (trade name, manufactured by K.I. Chemicals Co., Ltd.).

Examples of compounds having an epoxy group include bisphenol F type epoxy resins, bisphenol A type epoxy resins, biphenyl type epoxy resins, and polyfunctional epoxy resins. For example, 1,6-bis(2,3-epoxypropan-1-yloxy)naphthalene, which is commercially available as HP-4032D (manufactured by DIC Corporation, trade name), may be used.

The curing agent may contain a phosphine-based curing agent and an imidazole-based curing agent. The phosphine-based curing agent can promote the triazine production reaction by trimerization of a compound having a cyanate group or a cyanate resin. Examples of the phosphine-based curing agent include tetraphenylphosphonium tetra-p-tolylborate and tetraphenylphosphonium tetraphenylborate. Tetraphenylphosphonium tetra-p-tolylborate is commercially available, for example, as TPP-MK (trade name, manufactured by Hokko Chemical Industry Co., Ltd.).

Imidazole-based curing agents generate oxazoline and promote the curing reaction of compounds having epoxy groups or epoxy resins. Examples of imidazole-based curing agents include 1-(1-cyanomethyl)-2-ethyl-4-methyl-1H-imidazole and 2-ethyl-4-methylimidazole. 1-(1-cyanomethyl)-2-ethyl-4-methyl-1H-imidazole is commercially available, for example, as 2E4MZ-CN (trade name, manufactured by Shikoku Chemicals Corporation).

The content of the phosphine-based curing agent may be, for example, 5 parts by mass or less, 4 parts by mass or less, or 3 parts by mass or less, relative to 100 parts by mass of the total amount of the compound having a cyanate group, the compound having a bismaleimide group, and the compound having an epoxy group. The content of the phosphine-based curing agent may be, for example, 0.1 parts by mass or more, or 0.5 parts by mass or more, relative to 100 parts by mass of the total amount of the compound having a cyanate group, the compound having a bismaleimide group, and the compound having an epoxy group. When the content of the phosphine-based curing agent is within the above range, the resin-impregnated body can be easily prepared.

The content of the imidazole-based curing agent may be, for example, 0.1 parts by mass or less, 0.05 parts by mass or less, or 0.03 parts by mass or less, relative to 100 parts by mass of the total amount of the compound having a cyanate group, the compound having a bismaleimide group, and the compound having an epoxy group. The content of the imidazole-based curing agent may be, for example, 0.001 parts by mass or more, or 0.005 parts by mass or more, relative to 100 parts by mass of the total amount of the compound having a cyanate group, the compound having a bismaleimide group, and the compound having an epoxy group. When the content of the imidazole-based curing agent is within the above range, the resin-impregnated body is easily prepared.

The first resin composition may contain components other than the base agent and the curing agent. The other components may further contain, for example, other resins such as phenolic resins, melamine resins, urea resins, and alkyd resins, silane coupling agents, leveling agents, defoamers, surface conditioners, and wetting and dispersing agents. The content of these other components may be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less based on the total amount of the first resin composition.

A curing step may be carried out after the impregnation step. In the curing step, the first resin composition contained in the resin-impregnated body is cured or semi-cured to obtain a resin-filled body containing the first resin. In the curing step, the first resin composition is cured or semi-cured by heating and/or light irradiation depending on the type of the first resin composition (or the curing agent added as necessary).

In the curing step, the heating temperature when the first resin composition is cured or semi-cured by heating may be, for example, 80 to 130°C. The first resin obtained by semi-curing or curing the first resin composition may contain, as a resin component, at least one thermosetting resin selected from the group consisting of cyanate resin, bismaleimide resin, and epoxy resin, and a curing agent. In addition to these components, the first resin may contain components derived from other resins such as phenolic resin, melamine resin, urea resin, and alkyd resin, as well as silane coupling agents, leveling agents, defoamers, surface conditioners, and wetting and dispersing agents.

A coating process may be performed after the curing process. In the coating process, for example, the second resin composition is applied to the resin filled body obtained in the curing process, and the resin filled body is heated to coat the resin filled body with the second resin. The coating method is not particularly limited, and the resin filled body may be immersed in the second resin composition, or the second resin composition may be applied to a part or all of the surface of the resin filled body. The amount of the second resin composition that adheres to the resin filled body may be adjusted by the viscosity of the second resin composition.

The viscosity of the second resin composition when it is attached to the resin filled body may be, for example, 10 to 500 mPa·s or less, or 15 to 400 mPa·s. The above viscosity of the second resin composition is the viscosity at the temperature (T4) of the second resin composition when it is attached to the resin filled body. This viscosity is measured using a rotational viscometer at a shear rate of 10 (1/sec) and at a temperature (T4). The viscosity when the second resin composition is attached to the resin filled body may be adjusted by changing the temperature (T4). This viscosity may be adjusted by changing the temperature (T4) of the second resin composition, or may be adjusted by changing the amount of solvent mixed in the same manner as the first resin composition.

The components contained in the second resin composition may be the same as those exemplified in the first resin composition. Therefore, duplicate descriptions are omitted here. The compositions of the second resin composition and the first resin composition may be the same or different. After the second resin composition is attached to the resin filler, the second resin composition is cured or semi-cured to obtain the second resin. Depending on the type of the second resin composition (or the curing agent added as necessary), the second resin composition is cured or semi-cured by heating and/or light irradiation.

The heating temperature when the second resin composition is cured or semi-cured by heating may be, for example, 80 to 130°C. When the first resin composition and the second resin composition have the same composition, the curing rate of the second resin can be made smaller than that of the first resin by setting the heating temperature here lower than that during the curing process. On the other hand, when the second resin composition is photocurable, the curing rate of the second resin can be made larger than that of the first resin by irradiating light to the second resin composition attached to the surface of the resin filler. In this way, a composite can be produced in which the curing rates of the first resin contained in the resin filler and the second resin coating the resin filler are different from each other.

The second resin obtained by semi-curing or curing the second resin composition may contain at least one thermosetting resin selected from the group consisting of cyanate resins, bismaleimide resins, and epoxy resins, as well as a curing agent as a resin component. In addition to these components, the second resin may contain other resins such as phenolic resins, melamine resins, urea resins, and alkyd resins, as well as components derived from silane coupling agents, leveling agents, defoamers, surface conditioners, and wetting and dispersing agents.

By providing the second resin in a layer, the composite 10 shown in Figures 1 and 2, or the composite 10A shown in Figure 3 can be manufactured. Furthermore, this manufacturing method allows the entire surface of the resin filler to be smoothly coated with the second resin. However, it is not essential to coat the entire surface of the resin filler, and only a portion of the surface of the resin filler may be coated with the second resin.

In a modified example of the above-mentioned method for manufacturing a composite, in the coating step, a semi-cured product of the second resin composition is adhered to the surface of the resin filler and heated to coat the resin filler with the second resin. The semi-cured product used here may be, for example, in a sheet shape. Since the semi-cured product contains uncured components, when the resin filler and the sheet-shaped semi-cured product are pressed together, the uncured components contained in the uncured product seep out. This causes the resin filler and the sheet-shaped semi-cured product to adhere closely to each other. Then, by heating this semi-cured product, a composite can be manufactured in which the curing rates of the first resin contained in the resin filler and the second resin coating the resin filler are different from each other. The difference in the curing rates of the first resin and the second resin can be adjusted by adjusting the curing rate of the sheet-shaped semi-cured product and/or the magnitude of the curing rate of the first resin in the resin filler. In this example, since a sheet-shaped semi-cured product is used, a composite with excellent dimensional accuracy can be smoothly manufactured.

In yet another modified example, a composite may be obtained by adhering a sheet-shaped semi-cured material (second resin) to the resin filled body in the coating process. In this example, a sheet-shaped semi-cured material is adhered to the resin filled body, and then the composite can be produced without heating the semi-cured material. With this production method, the first resin and the second resin are not heated simultaneously, so the internal curing rate, the surface curing rate, and the difference between them can be precisely controlled. In this example, a sheet-shaped semi-cured material is used, so a composite with excellent dimensional accuracy can be produced smoothly. In addition, the number of heating cycles can be reduced, so the composite can be produced efficiently.

A method for producing a composite according to another embodiment includes a first impregnation step of impregnating a first porous nitride sintered body with a first resin composition to obtain a first resin-impregnated body, a second impregnation step of impregnating a second porous nitride sintered body with a second resin composition to obtain a second resin-impregnated body, a first curing step of heating the first resin-impregnated body to cure or semi-cure the first resin composition filled in the pores to obtain a first resin-filled body containing a first resin, a second curing step of heating the second resin-impregnated body to cure or semi-cure the second resin composition filled in the pores to obtain a second resin-filled body containing a second resin, and a joining step of sandwiching and joining the first resin-filled body between a pair of second resin-filled bodies to obtain a composite. The joining may be performed with the resin on the surface of each filler. The curing rates of the first resin contained in the first resin-filled body and the second resin contained in the second resin-filled body are different from each other.

The first resin composition, the second resin composition, the first resin, and the second resin may be the same as those in the above-mentioned embodiment. The first nitride sintered body and the second nitride sintered body may be the same as those in the above-mentioned embodiment. The size and material of the first nitride sintered body and the second nitride sintered body may be the same as each other or different from each other. The first resin filling body and the second resin filling body may also be the same as those in the above-mentioned embodiment. According to this manufacturing method, a composite body having no resin layer and having a resin-impregnated body exposed on the surface can be manufactured. That is, the interior of the composite is composed of the first resin filling body, and the surface portion of the composite is composed of the second resin filling body.

The composite obtained by the above manufacturing method has a higher degree of freedom in design compared to a composite in which the first resin and the second resin have the same cure rate. Therefore, it is possible to flexibly respond to the priority characteristics among various characteristics such as adhesion, thermal conductivity, insulation reliability, and handling properties.

A method for producing a laminate according to one embodiment includes a lamination step in which a composite produced by any one of the above-mentioned production methods is laminated with a metal sheet, and the composite is heated and pressurized. The metal sheet may be a metal plate or a metal foil.

In the lamination process, a metal sheet is placed on the main surface of the composite. With the main surfaces of the composite and metal sheet in contact with each other, pressure is applied in the direction in which the main surfaces face each other, and heat is also applied. Note that pressure and heat do not necessarily need to be applied simultaneously; heating may be applied after pressure and bonding.

The laminate thus obtained can be used for the manufacture of semiconductor devices, etc. A semiconductor element may be provided on one of the metal sheets. The other metal sheet may be joined with a cooling fin.

Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. For example, in the sintering process, a nitride sintered body may be obtained by hot pressing, which simultaneously performs molding and sintering. Also, the second resin may be formed in an island shape rather than a layer shape.

The contents of the present disclosure will be explained in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the examples below.

Example 1
<Preparation of nitride sintered body>
100 parts by mass of orthoboric acid manufactured by Shin-Nihon Denko Co., Ltd. and 35 parts by mass of acetylene black (product name: HS100) manufactured by Denka Co., Ltd. were mixed using a Henschel mixer. The resulting mixture was filled into a graphite crucible and heated in an arc furnace in an argon gas atmosphere at 2200°C for 5 hours to obtain lumpy boron carbide (B ₄ C). The resulting lumpy matter was coarsely crushed with a jaw crusher to obtain a coarse powder. The coarse powder was further crushed with a ball mill having silicon carbide balls (φ10 mm) to obtain a crushed powder.

The prepared pulverized powder was filled into a crucible made of boron nitride. Then, the powder was heated in a resistance heating furnace under a nitrogen gas atmosphere at 2000° C. and 0.85 MPa for 10 hours. In this way, a fired material containing boron carbonitride (B ₄ CN ₄ ) was obtained.

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

The compound was pressed at 150 MPa for 30 seconds using a powder press to obtain a sheet-shaped compact (length x width x thickness = 50 mm x 50 mm x 0.38 mm). The compact was placed in a boron nitride container and introduced into a batch-type high-frequency furnace. In the batch-type high-frequency furnace, it was heated for 5 hours under conditions of normal pressure, nitrogen flow rate of 5 L/min, and 2000°C. The boron nitride sintered body was then removed from the boron nitride container. In this way, a sheet-shaped (rectangular columnar) boron nitride sintered body was obtained. The thickness t of the boron nitride sintered body was 0.4 mm.

<Measurement of average pore size>
The pore volume distribution of the obtained boron nitride sintered body was measured using a mercury porosimeter (apparatus name: Autopore IV9500) manufactured by Shimadzu Corporation while increasing the pressure from 0.0042 MPa to 206.8 MPa. The pore diameter at which the cumulative pore volume reached 50% of the total pore volume was defined as the "average pore diameter". The results are shown in Table 1.

<Porosity Measurement>
The volume and mass of the obtained boron nitride sintered body were measured, and the bulk density B (kg/m ³ ) was calculated from the volume and mass. The bulk density B of the boron nitride sintered body was calculated based on the volume calculated from the length of each side of the boron nitride sintered body (measured with a vernier caliper) and the mass of the boron nitride sintered body measured with an electronic balance in accordance with JIS Z 8807:2012 "Method of measuring density and specific gravity by geometric measurement" (see item 9 of JIS Z 8807:2012). The porosity was calculated from the bulk density B and the theoretical density of boron nitride (2280 kg/m ³ ) using the following calculation formula (1). The results are shown in Table 1.
Porosity (volume%) = [1 - (B / 2280)] x 100 (1)

<Preparation of resin-impregnated body>
A resin composition was prepared by mixing 10 parts by mass of a commercially available curing agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name: Acmex H-8) with 100 parts by mass of a commercially available epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: Epicoat 807). The prepared resin composition was heated at 120°C for 15 minutes. While maintaining the temperature of the resin composition at 100°C, the resin composition was dripped onto the upper main surface of the boron nitride sintered body using a dispenser to impregnate the boron nitride sintered body. The amount of the resin composition dripped was 1.5 times the total volume of the pores of the boron nitride sintered body. A part of the resin composition did not impregnate the boron nitride sintered body and remained on the main surface.

Under atmospheric pressure, the resin composition remaining on the upper main surface of the boron nitride sintered body was smoothed using a stainless steel scraper (manufactured by Narby Co., Ltd.). Excess resin composition was removed to obtain a resin-impregnated body with a smooth main surface.

<Preparation of resin filled body>
The resin impregnated body was heated at 160°C for 60 minutes under atmospheric pressure to semi-cure the resin composition, and a resin filled body containing a boron nitride sintered body and a resin (semi-cured product) filled in its pores was obtained. The mass of the resin (first resin) contained in the resin filled body was calculated from the masses of the boron nitride sintered body and the resin filled body. Based on the calculation result, the mass ratio of the first resin in the resin filled body was calculated. The results are shown in Table 1.

<Measurement of Filling Ratio of First Resin (Semi-Cured Product)>
The filling rate of the first resin contained in the resin filler was calculated by the following formula (2). The results are shown in Table 1.

Filling rate (volume %) of first resin = {(bulk density D of resin filler - bulk density B of boron nitride sintered body) / ((theoretical density of resin filler - bulk density B of boron nitride sintered body)} x 100 ... (2)

The bulk density D of the resin filler was calculated based on the volume calculated from the length of each side of the resin filler (measured with a vernier caliper) and the mass of the resin filler measured with an electronic balance in accordance with JIS Z 8807:2012 "Method of measuring density and specific gravity by geometric measurement" (see JIS Z 8807:2012, item 9). The theoretical density of the resin filler was calculated using the following formula (3).

Theoretical density of resin filler = bulk density of boron nitride sintered body + true density of first resin × (1 - bulk density B of boron nitride sintered body / true density of boron nitride) … (3)

The true density of the boron nitride sintered body and the first resin was determined from the volume and mass of the boron nitride sintered body and the resin measured using a dry automatic density meter in accordance with JIS Z 8807:2012 "Method for measuring density and specific gravity by the gas displacement method" (see formulas (14) to (17) in Item 11 of JIS Z 8807:2012).

<Preparation of Complex>
The above-mentioned resin composition was heated at 160°C for 30 minutes. 100 parts by mass of the resin composition subjected to such heat treatment was mixed with 100 parts by mass of a solvent (acetone) to prepare a resin-containing liquid. The resin filler obtained by the above-mentioned procedure was immersed in a resin-containing liquid whose temperature was adjusted to 100°C for 10 seconds. Then, the resin filler with the resin composition attached to the surface was taken out from the resin-containing liquid. The taken-out resin filler was left at room temperature for 30 minutes. At this time, the entire resin filler was brought to room temperature, so that the resin composition on the surface was solidified and handling became possible. In this way, a composite was obtained having a resin filler containing a first resin and a resin layer (second resin) on its surface. The thickness of the resin layer of the second resin on each main surface was 0.02 mm.

The mass of the resin layer (second resin) of the composite was calculated from the mass of the resin filler and the composite. Based on the calculation results, the mass ratio of the second resin to the entire composite, the mass ratio of the first resin to the entire composite, the mass ratio (y) of the second resin to the entire resin components contained in the composite (first resin + second resin), and the mass ratio (x) of the first resin to the entire resin components (first resin + second resin) were calculated. The results are shown in Table 2.

<Measurement of Resin Curing Rate in Composite>
The cure rates of the resin layer (second resin) on the surface of the composite and the first resin contained inside the composite (the center of the resin filler) were determined by the following procedure. First, a part of the resin layer on the surface of the composite was scraped off to obtain a resin sample 1. The composite was also cut in the center along the thickness direction. Then, the resin in the center of the resin-impregnated body was scraped off from the cut surface to obtain a resin sample 2.

2 mg of resin composition in an uncured (uncured) state was heated, and the amount of heat Q (J/g) generated until the resin composition was completely cured was measured using a differential scanning calorimeter. Next, resin sample 1 (2 mg) and resin sample 2 (10 mg) were taken and heated in the same manner. The amounts of heat R1 (J/g) and R2 (J/g) generated until resin sample 1 and resin sample 2 were completely cured were measured using the same differential scanning calorimeter.

The resin filler and the composite were each heated at 600°C for 1 hour to volatilize the resin components, and the content c2 (mass%) and content c1 (mass%) of the thermosetting component contained in the resin layer (second resin) in the resin filler and the composite were determined from the mass difference before and after heating.

Using the calorific value Q, the calorific values R1 and R2, and the contents c1 and c2 obtained by the above procedure, the cure rates of the resin in the interior and surface of the composite were calculated by the following formulas (4) and (5). The results are shown in Table 3. In Table 3, the values calculated by formulas (4) and (5) are shown as the "surface cure rate" and the "internal cure rate", respectively. Table 3 also shows the absolute value of the difference between the surface cure rate and the internal cure rate.
Cure rate of resin on surface portion (%)={1-[(R1/c1)×100]/Q}×100 (4)
Internal resin cure rate (%) = {1 - [(R2/c2) x 100]/Q} x 100 ... (5)

<Evaluation of handling>
The handleability of the composite at room temperature (about 20° C.) was evaluated according to the following criteria. The results are shown in Table 3.
A: The surface is not sticky and is not easily deformed when held in the hand.
B: The surface is sticky or is easily deformed when held in the hand.
C: The surface is sticky and easily deformed when held in the hand.

<Evaluation of dielectric breakdown voltage>
The composite was placed between two copper plates, and heated and pressed for 5 minutes under conditions of 200°C and 5 MPa. The laminate was further heated for 2 hours under conditions of 200°C and atmospheric pressure to produce a laminate. An etching resist agent was screen-printed on one side of the obtained laminate so as to form a circle having a diameter of 20 mm. An etching resist agent was screen-printed on the entire surface of the other side of the laminate. After printing, the etching resist agent was irradiated with ultraviolet light to harden it and form a resist. Next, the copper plate on the side on which the circular resist was formed was etched with a cupric chloride solution, and a circular copper circuit having a diameter of 20 mm was formed on one side of the laminate. In this way, a laminate in which a circular copper circuit was formed was obtained. This was used as a sample, and the dielectric breakdown voltage was measured using a voltage tester (manufactured by Kikusui Electronics Co., Ltd., device name: TOS-8700) according to JIS C2110-1:2016. The results are shown in Table 3.

<Evaluation of Thermal Resistance of Laminate>
The composite was placed between two copper plates and heated and pressed at 200°C and 5 MPa for 5 minutes. It was further heated at 200°C and atmospheric pressure for 2 hours to produce a laminate. The laminate thus obtained was used as the measurement subject. The thermal resistance of the laminate was measured according to ASTM-D5470. The results are shown in Table 3.

Example 2
<Preparation and evaluation of nitride sintered bodies>
A boron nitride sintered body was produced and each measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

<Preparation of resin-impregnated body>
The compound having a cyanate group was weighed out in a container so that it was 80 parts by mass, the compound having a bismaleimide group was weighed out in a container so that it was 20 parts by mass, and the compound having an epoxy group was weighed out in a container so that it was 50 parts by mass. 1 part by mass of a phosphine-based curing agent and 0.01 part by mass of an imidazole-based curing agent were added to a total amount of 100 parts by mass of the above three types of compounds, and mixed. Since the compound having an epoxy group was in a solid state at room temperature, it was mixed in a state heated to about 80 ° C. The viscosity of the obtained resin composition at 100 ° C. was 10 mPa · sec. The prepared resin composition was heated to 100 ° C. While maintaining the temperature of the resin composition at 100 ° C., the resin composition was dripped onto the upper main surface of the boron nitride sintered body using a dispenser to impregnate the boron nitride sintered body. The amount of the resin composition dripped was 1.5 times the total volume of the pores of the boron nitride sintered body. A part of the resin composition did not impregnate the boron nitride sintered body and remained on the main surface.

The compounds and curing agents used in preparing the above-mentioned resin composition are as follows:

<Compound having specific functional group>
Compound having a cyanate group: dimethylmethylenebis(1,4-phenylene)biscyanate (manufactured by Mitsubishi Gas Chemical Company, Inc., product name: TA-CN)
Compound having a bismaleimide group: N,N'-[(1-methylethylidene)bis[(p-phenylene)oxy(p-phenylene)]]bismaleimide (manufactured by K.I. Chemicals Co., Ltd., product name: BMI-80)
Compound having an epoxy group: 1,6-bis(2,3-epoxypropan-1-yloxy)naphthalene (manufactured by DIC Corporation, product name: HP-4032D)

<Curing Agent>
Phosphine-based curing agent: Tetraphenylphosphonium tetra-p-tolylborate (manufactured by Kagaku Co., Ltd., product name: TPP-MK)
Imidazole-based curing agent: 1-(1-cyanomethyl)-2-ethyl-4-methyl-1H-imidazole (manufactured by Shikoku Chemical Industry Co., Ltd., product name: 2E4MZ-CN)

Under atmospheric pressure, the resin composition remaining on the upper main surface of the boron nitride sintered body was smoothed using a stainless steel scraper (manufactured by Narby Co., Ltd.). Excess resin composition was removed to obtain a resin-impregnated body with a smooth main surface.

<Preparation and evaluation of resin-filled bodies>
The resin-impregnated body was heated at 80° C. for 15 hours under atmospheric pressure to semi-cure the resin composition. In this manner, a resin-filled body was produced. In the same manner as in Example 1, the mass ratio of the resin (first resin) in the resin-filled body and the filling rate of the first resin were calculated. The results are shown in Table 1.

<Preparation and Evaluation of Composites and Laminates>
The resin composition used in the preparation of the resin-impregnated body was heated at 120°C for 7 hours. 100 parts by mass of the resin composition subjected to such heat treatment was mixed with 100 parts by mass of a solvent (acetone) to prepare a resin-containing liquid. The resin-filled body obtained by the above procedure was immersed in a resin-containing liquid whose temperature was adjusted to 100°C for 10 seconds. Thereafter, the resin-filled body with the resin composition attached to its surface was taken out from the resin-containing liquid. The taken-out resin-filled body was heated at 120°C for 60 minutes to remove the solvent and semi-cure the resin composition on the surface. In this way, a composite having a resin-filled body and a resin layer of the second resin on its surface was obtained. The thickness of the resin layer of the second resin on each main surface was 0.1 mm.

In the same manner as in Example 1, the mass ratio of the second resin (resin layer) to the entire composite, the mass ratio of the first resin to the entire composite, the mass ratio (y) of the second resin to the entire resin components (first resin + second resin) contained in the composite, and the mass ratio (x) of the first resin were calculated. The results are shown in Table 2. In the same manner as in Example 1, the obtained composite was evaluated, and a laminate was produced and evaluated. The results are shown in Table 3.

(Comparative Example 1)
<Preparation and evaluation of nitride sintered bodies>
A boron nitride sintered body was produced and each measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

<Preparation and evaluation of resin-impregnated bodies, resin-filled bodies, composite bodies, and laminates>
In the "preparation of resin-filled body", the heating time of the resin-impregnated body at 160 ° C. was 30 minutes, and in the "preparation of composite body", the resin-filled body was removed from the resin-containing liquid and then heated at 160 ° C. for 30 minutes. Except for this, a resin-filled body, a composite body, and a laminate were prepared in the same manner as in Example 1. The obtained resin-filled body and composite body were evaluated, and a laminate was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 3.

<Evaluation of adhesive strength>
A composite (length x width x thickness = 50 mm x 20 mm) of Example 1 or Comparative Example 1 was placed between a sheet-shaped copper foil (length x width x thickness = 100 mm x 20 mm x 0.035 mm) and a sheet-shaped copper plate (length x width x thickness = 100 mm x 20 mm x 1 mm) to produce a laminate including the copper foil, the composite, and the copper plate in this order. The laminate was heated and pressed for 5 minutes under conditions of 200°C and 5 MPa, and then heat-treated for 2 hours under conditions of 200°C and atmospheric pressure. A laminate was thus obtained.

Using this laminate as a sample, a universal testing machine (manufactured by A&D Co., Ltd., product name: RTG-1310) was used to carry out a 90° peel test in accordance with JIS K 6854-1:1999 "Adhesive-Peel Adhesion Strength Test Method." The 90° peel test peel was carried out at the adhesive interface between the sheet-like copper foil and the composite. The measurement was carried out under the following conditions: test speed: 50 mm/min, load cell: 5 kN, measurement temperature: room temperature (20°C). As a result, the adhesive strengths of the laminates of Example 1, Example 2, and Comparative Example 1 were 3.0 N/cm, 0.8 N/cm, and 0.2 N/cm, respectively.

10, 10A... composite body, 12... resin filler, 12a, 12b... main surfaces, 12c... side surfaces, 14, 14A... resin layer, 20, 20A... laminate, 22... metal sheet.

Claims (10)

A composite material containing a resin and a porous nitride sintered body,
At least a portion of the resin is filled into pores of the nitride sintered body,
The composite has a higher cure rate for the resin in the interior than for the resin in the surface portion,
A composite body, wherein the curing rate of the resin is 20 to 90%, and the difference between the curing rate of the resin in the interior and the curing rate of the resin in the surface portion is 30 to 60%. A composite material containing a resin and a porous nitride sintered body,
At least a portion of the resin is filled into pores of the nitride sintered body,
The composite has a higher cure rate for the resin in a surface portion than for the resin in an interior portion,
A composite body , wherein a difference between a cure rate of the resin in the interior and a cure rate of the resin in the surface portion is 10% or more . the interior portion is constituted by a resin filled body in which the nitride sintered body is filled with the resin,
The composite body according to claim 1 or 2 , wherein the surface portion is formed of a resin layer that covers at least a portion of the resin filler. A laminate comprising the composite according to any one of claims 1 to 3 and a metal sheet. an impregnation step of impregnating a porous nitride sintered body with a first resin composition to obtain a resin-impregnated body;
a curing step of heating the resin-impregnated body to semi-cure the first resin composition filled in the pores to obtain a resin-filled body containing a first resin;
A coating step of coating at least a part of the surface of the resin filler with a second resin to obtain a composite body,
The composite has a first resin having a higher curing rate than the second resin, a curing rate of the resin contained in the composite is 20 to 90%, and a difference between the curing rate of the first resin and the curing rate of the second resin is 30 to 60%. an impregnation step of impregnating a porous nitride sintered body with a first resin composition to obtain a resin-impregnated body;
a curing step of heating the resin-impregnated body to semi -cure the first resin composition filled in the pores to obtain a resin-filled body containing a first resin;
A coating step of coating at least a part of the surface of the resin filler with a second resin to obtain a composite body,
The method for manufacturing a composite, wherein the second resin has a higher curing rate than the first resin, and the difference between the curing rate of the first resin and the curing rate of the second resin is 10% or more . The method for producing a composite according to claim 5 or 6 , wherein in the coating step, a second resin composition is applied to the resin filler, and the resin filler is heated to coat the resin filler with the second resin. The method for producing a composite body according to claim 5 or 6 , wherein in the covering step, at least a part of the surface of the resin filler is covered with the second resin in a sheet form. 7. The method for producing a composite according to claim 5 or 6, wherein in the coating step, a semi-cured product of a second resin composition is adhered to the resin filler and heated to coat at least a portion of the surface of the resin filler with the second resin. A method for producing a laminate, comprising a lamination step of laminating the composite obtained by the method according to any one of claims 5 to 9 with a metal sheet, and heating and pressing the laminate.

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