阅读说明：本技术 复合体 (Composite body ) 是由 井之上纱绪梨 岩切翔二 南方仁孝 吉松亮 古贺龙士 山口智也 于 2020-03-26 设计创作，主要内容包括：本发明的一个方面涉及复合体,其具备多孔性的氮化硼烧结体和填充于氮化硼烧结体的孔内的树脂,氮化硼烧结体的平均孔径为3.5μm以下。(One aspect of the present invention relates to a composite body including a porous boron nitride sintered body and a resin filled in pores of the boron nitride sintered body, wherein an average pore diameter of the boron nitride sintered body is 3.5 μm or less.)

1. A composite body comprising:

a porous boron nitride sintered body, and

a resin filled in the pores of the boron nitride sintered body,

the boron nitride sintered body has an average pore diameter of 3.5 μm or less.

2. The composite body according to claim 1, wherein the content of the boron nitride sintered body is 30 vol% or more and 60 vol% or less, and the content of the resin is 40 vol% or more and 70 vol% or less, based on the total volume of the composite body.

3. The composite body according to claim 1 or 2, wherein the porosity of the boron nitride sintered body is 10 vol% or more and 70 vol% or less.

Technical Field

The present invention relates to a composite.

Background

In electronic components such as power devices, transistors, thyristors, and CPUs, it is a problem to efficiently dissipate heat generated during use. To solve this problem, the following have been implemented: making an insulating layer of a printed wiring board mounted with an electronic component highly thermally conductive; an electronic component or a printed wiring board is mounted on a heat sink via an electrically insulating Thermal Interface material. A composite (heat dissipation member) composed of a resin and a ceramic such as boron nitride can be used for the insulating layer and the thermal interface material.

As such a composite, a composite in which ceramic powder is dispersed in resin has been used, and in recent years, a composite in which a porous ceramic sintered body (for example, a boron nitride sintered body) is impregnated with resin has been studied (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: international publication No. 2014/196496

Disclosure of Invention

Problems to be solved by the invention

According to the studies of the inventors of the present application, there is room for further improvement in insulation properties in a composite body in which a porous sintered boron nitride body is impregnated with a resin as described above.

Accordingly, an object of the present invention is to provide a composite having excellent insulation properties.

Means for solving the problems

One aspect of the present invention relates to a composite body including a porous boron nitride sintered body and a resin filled in pores of the boron nitride sintered body, wherein an average pore diameter of the boron nitride sintered body is 3.5 μm or less.

The content of the boron nitride sintered body may be 30 vol% or more and 60 vol% or less, and the content of the resin may be 40 vol% or more and 70 vol% or less, based on the total volume of the composite body.

The porosity of the boron nitride sintered body may be 10 vol% or more and 70 vol% or less.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a composite having excellent insulation properties.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

One embodiment of the present invention relates to a composite body including a porous boron nitride sintered body (hereinafter, also simply referred to as "boron nitride sintered body") and a resin filled in pores of the boron nitride sintered body. The resin may be filled in a part of the hole of the boron nitride sintered body, or may be filled in the entire hole. The resin may be partially cured (so-called B-stage) or entirely cured.

The boron nitride sintered body is a sintered body in which primary particles of boron nitride are sintered with each other. The boron nitride sintered body is a porous sintered body having a plurality of pores (micropores). The average pore diameter of the boron nitride sintered body may be, for example, 0.5 μm or more, and is preferably 0.6 μm or more, more preferably 0.8 μm or more, and further preferably 1 μm or more, from the viewpoint of being able to appropriately fill the pores with the resin. The average pore diameter of the boron nitride sintered body may be 3.5 μm or less, and is preferably 3.0 μm or less, more preferably 2.5 μm or less, further preferably 2.0 μm or less, and particularly preferably 1.5 μm or less, from the viewpoint of further improving the insulation property of the composite.

The average pore diameter of the boron nitride sintered body is defined as a pore diameter at which a cumulative pore volume reaches 50% of a total pore volume in a pore diameter distribution (horizontal axis: pore diameter, vertical axis: cumulative pore volume) measured using a mercury porosimeter. As the mercury porosimeter, for example, a mercury porosimeter manufactured by shimadzu corporation may be used, and the pressure measurement may be performed while increasing the pressure from 0.03 atm to 4000 atm.

The proportion of pores in the boron nitride sintered body (porosity) is set to nitrogenThe total volume of the boron nitride sintered body is preferably 10 vol% or more, 20 vol% or more, or 30 vol% or more, from the viewpoint of suitably improving the strength of the composite body by filling the resin, and is preferably 70 vol% or less, and more preferably 50 vol% or less, from the viewpoint of further improving the insulation property and thermal conductivity of the composite body. The volume density (D; g/cm) of the boron nitride sintered body obtained from the volume and mass thereof is determined as the ratio (porosity)³) And theoretical density of boron nitride (2.28 g/cm)³) Calculated according to the following formula:

the porosity (volume%) [1- (D/2.28) ] × 100.

The proportion of the boron nitride sintered compact in the composite body is preferably 30 vol% or more, more preferably 40 vol% or more, further preferably 50 vol% or more, and may be, for example, 90 vol% or less, 80 vol% or less, 70 vol% or less, or 60 vol% or less, based on the total volume of the composite body, from the viewpoint of further improving the insulation property and the thermal conductivity of the composite body.

The composite comprises 1 or 2 or more resins. Examples of the resin include epoxy resin, silicone resin, cyanate ester resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluorine resin, polyimide, polyamideimide, polyetherimide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, 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.

In one embodiment, the resin preferably contains an epoxy resin from the viewpoint of excellent heat resistance and excellent adhesion strength to a circuit. In this case, the composite can be preferably used for an insulating layer of a printed wiring board. In another embodiment, the resin preferably contains a silicone resin from the viewpoint of excellent heat resistance, flexibility, and adhesion to a heat sink or the like. In this case, the composite can be preferably used for a thermal interface material.

The content of the resin in the composite is not particularly limited, and may be, for example, 20 vol% or more, 25 vol% or more, 30 vol% or more, 35 vol% or more, or 40 vol% or more, or 75 vol% or less, 70 vol% or less, 65 vol% or less, 60 vol% or less, or 55 vol% or less, based on the total volume of the composite. The content of the resin in the composite can be measured by the method described in examples.

The composite may contain other components (including impurities) in addition to the boron nitride sintered body and the resin. Other components can be curing agent, inorganic filler, silane coupling agent, defoaming agent, surface conditioning agent, wetting dispersant and the like. From the viewpoint of excellent thermal conductivity, the composite preferably contains 1 or 2 or more kinds of inorganic fillers (ceramic powder) selected from the group consisting of alumina, silica, zinc oxide, silicon nitride, aluminum nitride, and aluminum hydroxide. The content of the other component may be 10% by volume or less, 5% by volume or less, 3% by volume or less, or 1% by volume or less, based on the total volume of the composite.

In the composite of the present embodiment, the resin can be sufficiently impregnated by using the boron nitride sintered body having an average pore diameter within a predetermined range. As a result, the composite of the present embodiment has excellent withstand voltage. Therefore, the composite is suitable for use as a material for electronic components. The withstand voltage of the composite is, for example, 4.3kV or more. The withstand voltage was measured by the method described in examples.

The composite described above is obtained, for example, by a production method including the steps of: the method for producing the boron nitride sintered body comprises a step of impregnating the boron nitride sintered body with a resin composition (impregnation step), and a step of curing the resin in the resin composition filled in the pores of the boron nitride sintered body (curing step).

In one embodiment, the impregnation step includes: step S1 of preparing a boron nitride sintered body and a resin composition; a step S2 of placing the boron nitride sintered body in a state of being immersed in the resin composition under reduced pressure conditions, and then placing the boron nitride sintered body in a state of being immersed in the resin composition under pressure conditions higher than the reduced pressure conditions; and a step S3 of subjecting the boron nitride sintered body in a state of being immersed in the resin composition to a pressure condition and thereafter subjecting the boron nitride sintered body in a state of being immersed in the resin composition to a pressure condition lower than the pressure condition.

In step S1, for example, a boron nitride sintered compact and a resin composition are prepared in an impregnation apparatus with a controllable pressure.

The boron nitride sintered body is obtained by molding a boron nitride powder and then sintering the molded product. That is, in one embodiment, a molding step of molding a boron nitride powder to obtain a boron nitride molded body and a sintering step of sintering the boron nitride molded body to obtain a boron nitride sintered body may be performed before the impregnation step. More specifically, in the forming step, for example, a slurry containing a boron nitride powder is spheroidized by a spray dryer or the like to obtain a spherical boron nitride powder, and the spherical boron nitride powder is formed by a press molding method or a Cold Isostatic Pressing (CIP) method. The pressure at the time of molding in the molding step is not particularly limited, and the lower the pressure, the smaller the average pore diameter of the obtained boron nitride sintered body.

In the molding step, a sintering aid is preferably added. The sintering aid may be, for example, an alkali metal or alkaline earth metal carbonate such as lithium carbonate, sodium carbonate, or calcium carbonate, boric acid, or a combination thereof. The amount of the sintering aid added may be, for example, 0.5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the total of the boron nitride powder and the sintering aid, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, further preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, from the viewpoint of suitably obtaining a boron nitride sintered body having the above-mentioned average pore diameter.

In the sintering step, the boron nitride molded body obtained in the molding step is sintered. The sintering temperature may be, for example, 1600 ℃ or higher, or 2200 ℃ or lower. The sintering time may be, for example, 1 hour or more, and 30 hours or less. The atmosphere during sintering may be an inert gas atmosphere such as nitrogen, helium, or argon.

The resin composition may further contain 1 or 2 or more kinds of solvents. 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.

In step S2, the pressure in the impregnation device is reduced to be a reduced pressure condition. The pressure P1 under the reduced pressure condition may be, for example, 1000Pa or less, 500Pa or less, 100Pa or less, or 50Pa or less.

In step S2, the boron nitride sintered body is immersed in the resin composition under the reduced pressure condition as described above, and left in the immersed state for a predetermined time under the reduced pressure condition. The predetermined time may be, for example, 10 minutes or more and 720 minutes or less. The temperature of the resin composition in this case may be, for example, 20 ℃ or higher and 150 ℃ or lower.

In step S2, the pressure in the impregnation device is increased to a pressure higher than the pressure P1 in the reduced pressure condition. The pressure P2 under such pressure conditions may be, for example, 0.01MPa or more, 0.05MPa or more, 0.08MPa or more, or 0.1MPa or more, 0.5MPa or less, 0.4MPa or less, 0.3MPa or less, or 0.2MPa or less, or may be atmospheric pressure (0.101325 MPa).

In step S2, the boron nitride sintered body is left in the state of being immersed in the resin composition under the pressure conditions as described above for a predetermined time. The predetermined time may be, for example, 1 minute or more and 60 minutes or less. The temperature of the resin composition in this case may be, for example, 20 ℃ or higher and 150 ℃ or lower.

In step S3, the pressure in the impregnation device is increased to provide the pressurizing condition. The pressure P3 under such pressurized conditions may be, for example, 0.2MPa or more, 0.5MPa or more, 1MPa or more, or 5MPa or more, or 20MPa or less, 10MPa or less, or 5MPa or less.

In step S3, the boron nitride sintered body is left in the state of being immersed in the resin composition under the pressure conditions as described above for a predetermined time. The predetermined time may be, for example, 5 minutes or more, 15 minutes or more, or 720 minutes or less. The temperature of the resin composition in this case may be, for example, 20 ℃ or higher and 150 ℃ or lower.

In step S3, the pressure in the impregnation device is then reduced to a pressure condition lower than the pressure P3 of the above-described pressurization conditions. The pressure P4 under these pressure conditions may be, for example, 0.01MPa or more, 0.05MPa or more, 0.08MPa or more, or 0.1MPa or more, 0.5MPa or less, 0.4MPa or less, 0.3MPa or less, or 0.2MPa or less, or atmospheric pressure.

In step S3, the boron nitride sintered body is left in the state of being immersed in the resin composition under the pressure conditions as described above for a predetermined time. The predetermined time may be, for example, 1 minute or more and 60 minutes or less. The temperature of the resin composition in this case may be, for example, 20 ℃ or higher and 150 ℃ or lower.

In the impregnation step described above, one or both of the steps S2 and S3 may be repeatedly performed a plurality of times. The number of times of performing the step S2 may be 2 or more, 5 or more, or 10 or more, and may be 20 or less, 15 or less, or 13 or less. The number of times of execution of the step S3 in the case of repeating the step S3 may be 2 or more, 5 or more, or 10 or more, and may be 20 or less, 15 or less, or 13 or less.

The production method may further include a step (curing step) of curing the resin in the resin composition filled in the pores of the boron nitride sintered body after the impregnation step. In the curing step, for example, the boron nitride sintered body and the resin composition filled therein are taken out from the impregnation device, and the resin is cured by heating and/or light irradiation depending on the kind of the resin (or the curing agent added as needed). In the curing step, a part of the resin may be cured (so-called B-staging) or the entire resin may be cured. The conditions for heating and light irradiation may be appropriately set according to the type of resin (or curing agent added as needed), the desired degree of curing, and the like.

Examples

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

(example 1)

< production of boron nitride sintered body >

After 9 parts by mass of amorphous boron nitride powder having an oxygen content of 2.0% and an average particle diameter of 3.4 μm, 13 parts by mass of hexagonal boron nitride powder having an oxygen content of 0.3% and an average particle diameter of 12.5 μm, 0.1 part by mass of calcium carbonate ("PC-700", manufactured by dolomite industries), and 0.2 part by mass of boric acid were mixed in a henschel mixer, 76.0 parts by mass of water was added and pulverized for 5 hours by a ball mill, an aqueous slurry was obtained. Further, polyvinyl alcohol ("GOHSENOL", manufactured by japan synthetic chemical corporation) was added to the aqueous slurry so as to be 0.5 mass%, and the mixture was heated and stirred at 50 ℃ until dissolved, and then spheroidized at a drying temperature of 230 ℃ by a spray dryer. As the spheroidizing device of the spray dryer, a rotary atomizer was used. The resulting treated product was filled in a boron nitride container and molded under pressure of 20MPa by Cold Isostatic Pressing (CIP). Next, the sintered body was sintered in a batch high-frequency furnace at 2050 ℃ for 10 hours under normal pressure and at a nitrogen flow rate of 5L/min, and then the sintered body was taken out from the boron nitride container.

< determination of average pore diameter >

The obtained boron nitride sintered body was measured for the pore size distribution at the time of pressurization (horizontal axis: pore size, vertical axis: cumulative pore volume) while increasing the pressure from 0.03 atm to 4000 atm, using a mercury porosimeter manufactured by Shimadzu corporation. From the pore size distribution, the average pore size was calculated as the pore size at which the cumulative pore volume reached 50% of the total pore volume. The results are shown in Table 1.

< measurement of porosity >

The volume and mass of the obtained boron nitride sintered body were measured, and the volume density (D; g/cm) was calculated from the volume and mass³). From this bulk density and the theoretical density of boron nitride (2.28 g/cm)³) The porosity was calculated according to the following formula:

the porosity (volume%) [1- (D/2.28) ] × 100.

The results are shown in Table 1.

< impregnation of resin composition >

The obtained boron nitride sintered body was impregnated with a resin composition by the following procedure.

A resin composition was obtained by mixing 61 parts by mass of a cyanate resin ("TA-CN", manufactured by Mitsubishi Gas Chemical Company, Inc.), 11 parts by mass of a maleimide resin ("BMI-80", manufactured by KI Kabushiki Kaisha) and 28 parts by mass of an epoxy resin ("HP-4032D", manufactured by DIC Co., Ltd.) at 130 ℃ for 1 hour.

Next, the following step S2 was repeatedly performed 8 times in the impregnation device with controllable pressure: the boron nitride sintered body was left to stand in a state of being immersed in the resin composition under a reduced pressure condition P1(30Pa) for a predetermined time T1(120 minutes), and thereafter, was left to stand in a state of being immersed in the resin composition under a pressure condition P2(0.6MPa) higher than the above reduced pressure condition P1 for a predetermined time T2(1 minute). Thereafter, the following step S3 was repeatedly performed 11 times: the boron nitride sintered body was left to be immersed in the resin composition under a pressure condition P3(4MPa) for a predetermined time T3(6 minutes), and thereafter, was left to be immersed in the resin composition under a pressure condition P4(0.1MPa) lower than the pressure condition P3 for a predetermined time T4(5 minutes).

In the above manner, a resin-filled boron nitride sintered body (composite) was obtained.

< determination of resin content >

The resin content of the resulting composite was measured by the following procedure. The results are shown in Table 1.

The content (volume%) of the resin in the composite was determined by measuring the volume density of the boron nitride sintered body and the volume density of the composite shown below.

The content (%) of the resin in the composite was ═ 100 × (composite bulk density-boron nitride sintered body bulk density)/(composite theoretical density-boron nitride sintered body bulk density)) × 100

The theoretical density of the composite is obtained by the following equation.

Theoretical density of composite (true density of boron nitride + true density of resin x) (volume density of 1-boron nitride sintered body/true density of boron nitride)

The bulk density of the boron nitride sintered body and the composite body was determined based on the volume calculated from the length (measured by a vernier caliper) of each side of the regular hexahedral boron nitride sintered body or the composite body and the mass of the boron nitride sintered body or the composite body measured by an electronic balance, according to the density and specific gravity measurement method measured by the geometry according to JIS Z8807: 2012 (see item 9 of JIS Z8807: 2012). The true densities of the boron nitride sintered body and the resin were determined from the volumes and masses of the boron nitride sintered body and the resin measured by a dry automatic densitometer according to the density and specific gravity measurement methods by the gas substitution method according to JIS Z8807: 2012 (see formulas (14) to (17) of item 11 of JIS Z8807: 2012).

< evaluation of insulation >

Each of the obtained composites was cut into a size of 20mm × 20mm, and a conductive tape having a size of 16mm × 16mm was bonded thereto to obtain a sample for evaluation. The dielectric breakdown voltage (kV) of the sample for evaluation was measured under a boosting condition of 0.5kV/30s using TOS5101, manufactured by Chrysanthemum electronics industries, Ltd. The results are shown in Table 1. The higher the dielectric breakdown voltage, the more excellent the insulation property.

(examples 2 to 5)

A boron nitride sintered body was produced in the same manner as in example 1, except that the amounts of amorphous boron nitride powder, calcium carbonate and boric acid, and the average particle diameter of hexagonal boron nitride were changed as shown in table 1. The average pore diameter and porosity of the obtained boron nitride sintered body were measured in the same manner as in example 1, and the results are shown in table 1. Next, a composite was obtained by impregnating the resin composition in the same manner as in example 1. The resin content and the insulation of the obtained composite were measured and evaluated in the same manner as in example 1, and the results are shown in table 1.

Comparative example 1

A boron nitride sintered body was produced in the same manner as in example 1, except that the amounts of amorphous boron nitride powder, calcium carbonate and boric acid to be blended and the CIP pressure were changed as shown in table 1. The average pore diameter and porosity of the obtained boron nitride sintered body were measured in the same manner as in example 1, and the results are shown in table 1. Next, the resin composition was impregnated in the same manner as in example 1, thereby obtaining a composite. The resin content and the insulation of the obtained composite were measured and evaluated in the same manner as in example 1, and the results are shown in table 1.

[ Table 1]

(examples 6 to 12 and comparative examples 2 to 4)

A boron nitride sintered body was produced in the same manner as in example 1, except that the amounts of amorphous boron nitride powder, calcium carbonate and boric acid to be blended and the CIP pressure were changed as shown in table 2. The average pore diameter and porosity of the obtained boron nitride sintered body were measured in the same manner as in example 1, and the results are shown in table 2.

Next, a composite was obtained by impregnating a resin composition in the same manner as in example 1, except that the pressure conditions, the time for placing under each pressure condition, and the number of times each step was performed in step S2 and step S3 were changed as shown in table 2. The resin content and the insulation of the obtained composite were measured and evaluated in the same manner as in example 2, and the results are shown in table 2.

[ Table 2]