JP7523534B2 - Hardened sheet and its manufacturing method - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title description 6
- 239000002245 particle Substances 0.000 claims description 135
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 110
- 229910052582 BN Inorganic materials 0.000 claims description 109
- 229920005989 resin Polymers 0.000 claims description 65
- 239000011347 resin Substances 0.000 claims description 65
- 239000000203 mixture Substances 0.000 claims description 37
- 239000011342 resin composition Substances 0.000 claims description 19
- 238000004898 kneading Methods 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 9
- 238000007872 degassing Methods 0.000 claims description 8
- 238000003825 pressing Methods 0.000 claims description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 11
- 239000003795 chemical substances by application Substances 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- 239000002904 solvent Substances 0.000 description 9
- 238000005259 measurement Methods 0.000 description 8
- 239000007822 coupling agent Substances 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- 238000009826 distribution Methods 0.000 description 5
- 239000003822 epoxy resin Substances 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 229920000647 polyepoxide Polymers 0.000 description 5
- SWXVUIWOUIDPGS-UHFFFAOYSA-N diacetone alcohol Chemical compound CC(=O)CC(C)(C)O SWXVUIWOUIDPGS-UHFFFAOYSA-N 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 239000002270 dispersing agent Substances 0.000 description 3
- RAXXELZNTBOGNW-UHFFFAOYSA-N imidazole Natural products C1=CNC=N1 RAXXELZNTBOGNW-UHFFFAOYSA-N 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 3
- 229910052753 mercury Inorganic materials 0.000 description 3
- -1 tetraphenylphosphonium tetraphenylborate Chemical compound 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- 239000000080 wetting agent Substances 0.000 description 3
- 239000005456 alcohol based solvent Substances 0.000 description 2
- 239000003849 aromatic solvent Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000001186 cumulative effect Effects 0.000 description 2
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000004210 ether based solvent Substances 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 239000005453 ketone based solvent Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000011164 primary particle Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 2
- 239000011800 void material Substances 0.000 description 2
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-UHFFFAOYSA-N 0.000 description 1
- ZNQVEEAIQZEUHB-UHFFFAOYSA-N 2-ethoxyethanol Chemical compound CCOCCO ZNQVEEAIQZEUHB-UHFFFAOYSA-N 0.000 description 1
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 238000007088 Archimedes method Methods 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 239000004640 Melamine resin Substances 0.000 description 1
- NTIZESTWPVYFNL-UHFFFAOYSA-N Methyl isobutyl ketone Chemical compound CC(C)CC(C)=O NTIZESTWPVYFNL-UHFFFAOYSA-N 0.000 description 1
- UIHCLUNTQKBZGK-UHFFFAOYSA-N Methyl isobutyl ketone Natural products CCC(C)C(C)=O UIHCLUNTQKBZGK-UHFFFAOYSA-N 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229920001807 Urea-formaldehyde Polymers 0.000 description 1
- UUQQGGWZVKUCBD-UHFFFAOYSA-N [4-(hydroxymethyl)-2-phenyl-1h-imidazol-5-yl]methanol Chemical compound N1C(CO)=C(CO)N=C1C1=CC=CC=C1 UUQQGGWZVKUCBD-UHFFFAOYSA-N 0.000 description 1
- 150000008065 acid anhydrides Chemical class 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 229920006243 acrylic copolymer Polymers 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000004645 aluminates Chemical class 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000000113 differential scanning calorimetry Methods 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- JDVIRCVIXCMTPU-UHFFFAOYSA-N ethanamine;trifluoroborane Chemical compound CCN.FB(F)F JDVIRCVIXCMTPU-UHFFFAOYSA-N 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 150000002460 imidazoles Chemical class 0.000 description 1
- 125000005647 linker group Chemical group 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 125000005641 methacryl group Chemical group 0.000 description 1
- 229920003986 novolac Polymers 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000000790 scattering method Methods 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 1
- AYEKOFBPNLCAJY-UHFFFAOYSA-O thiamine pyrophosphate Chemical compound CC1=C(CCOP(O)(=O)OP(O)(O)=O)SC=[N+]1CC1=CN=C(C)N=C1N AYEKOFBPNLCAJY-UHFFFAOYSA-O 0.000 description 1
- 125000003396 thiol group Chemical group [H]S* 0.000 description 1
- XZZNDPSIHUTMOC-UHFFFAOYSA-N triphenyl phosphate Chemical compound C=1C=CC=CC=1OP(OC=1C=CC=CC=1)(=O)OC1=CC=CC=C1 XZZNDPSIHUTMOC-UHFFFAOYSA-N 0.000 description 1
- 229920006305 unsaturated polyester Polymers 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/88—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts characterised primarily by possessing specific properties, e.g. electrically conductive or locally reinforced
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Health & Medical Sciences (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Composite Materials (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
Description
本開示は、硬化シート及びその製造方法に関する。 The present disclosure relates to a hardened sheet and a method for producing the same.
パワーデバイス、トランジスタ、サイリスタ、ＣＰＵ等の電子部品においては、使用時に発生する熱を効率的に放熱することが課題となっている。この課題に対して、熱伝導率が高いセラミックス粉末を含有する放熱部材が用いられる。 In electronic components such as power devices, transistors, thyristors, and CPUs, one issue is how to efficiently dissipate the heat generated during use. To address this issue, heat dissipation materials containing ceramic powder with high thermal conductivity are used.
セラミックス粉末としては、高熱伝導率、高絶縁性、低比誘電率等の特性を有している窒化ホウ素粉末が注目されている。窒化ホウ素粉末は、一般的に、窒化ホウ素の一次粒子が凝集してなる凝集粒子（塊状粒子）で構成されている。例えば、特許文献１には、凝集粒子の形状を一層球状化して充填性を高めると共に、粉末強度の向上を図り、さらには高純度化により、当該粉末を充填した伝熱シート等の絶縁性の向上および耐電圧の安定化を達成したとされる六方晶窒化ホウ素粉末が開示されている。As a ceramic powder, boron nitride powder has attracted attention due to its properties such as high thermal conductivity, high insulation, and low dielectric constant. Boron nitride powder is generally composed of agglomerated particles (lump particles) formed by the aggregation of primary particles of boron nitride. For example, Patent Document 1 discloses hexagonal boron nitride powder in which the shape of the agglomerated particles is made more spherical to improve packing properties and powder strength, and furthermore, the powder is highly purified to improve the insulation properties and stabilize the voltage resistance of heat transfer sheets and the like filled with the powder.
塊状窒化ホウ素粒子を伝熱シート等のシートに用いる場合、当該シートの熱伝導率の向上と耐電圧の向上とを同時に達成することが求められることがある。熱伝導率を向上させる方法の一つとして、塊状窒化ホウ素粒子の粒子径を大きくすることが考えられる。しかし、塊状窒化ホウ素粒子の粒子径を大きくすると、得られるシートの熱伝導率は向上するものの、シート中にボイドが発生しやすくなるため、耐電圧が低下しやすい。つまり、シートにおいて優れた熱伝導率及び耐電圧を両立することは、必ずしも容易でない。When using aggregate boron nitride particles in sheets such as heat transfer sheets, it is sometimes necessary to simultaneously improve the thermal conductivity and voltage resistance of the sheet. One method for improving thermal conductivity is to increase the particle size of the aggregate boron nitride particles. However, when the particle size of the aggregate boron nitride particles is increased, although the thermal conductivity of the resulting sheet improves, voids tend to occur in the sheet, which tends to reduce the voltage resistance. In other words, it is not necessarily easy to achieve both excellent thermal conductivity and voltage resistance in a sheet.
そこで、本発明は、一側面において、優れた熱伝導率及び耐電圧を両立できるシートを製造することを目的とする。Therefore, in one aspect, the present invention aims to produce a sheet that can achieve both excellent thermal conductivity and voltage resistance.
本発明者らの検討によれば、粒子径の大きな塊状窒化ホウ素粒子を含むシートの製造において、塊状窒化ホウ素粒子内の隙間の体積を基準として樹脂組成物中の不揮発分の量を適切に設定することにより、粒子径の大きな塊状窒化ホウ素粒子による熱伝導率の向上に加えて、最終的に得られるシート中のボイドを減らすことができ、結果として、耐電圧の向上も可能になることが判明した。According to the research of the present inventors, in the production of a sheet containing large-particle-sized agglomerated boron nitride particles, it has been found that by appropriately setting the amount of non-volatile matter in the resin composition based on the volume of the gaps within the agglomerated boron nitride particles, in addition to improving the thermal conductivity due to the large-particle-sized agglomerated boron nitride particles, it is possible to reduce voids in the final sheet, and as a result, improve the voltage resistance.
本発明の一側面は、樹脂を含む樹脂組成物と、平均粒子径が４５μｍ以上の塊状窒化ホウ素粒子とを混合して混合物を得る第１の工程と、混合物をシート状に成形すると共に、混合物中の樹脂を半硬化させて半硬化シートを得る第２の工程と、半硬化シートに対して加圧すると共に、半硬化シート中の樹脂を更に硬化させて硬化シートを得る第３の工程と、を備え、樹脂組成物中の不揮発分の体積が、混合物に含まれる塊状窒化ホウ素粒子内の隙間の全体積に対して、０．９～１．１倍である、硬化シートの製造方法である。One aspect of the present invention is a method for producing a cured sheet, comprising a first step of mixing a resin composition containing a resin with aggregate boron nitride particles having an average particle size of 45 μm or more to obtain a mixture, a second step of forming the mixture into a sheet and semi-curing the resin in the mixture to obtain a semi-cured sheet, and a third step of applying pressure to the semi-cured sheet and further curing the resin in the semi-cured sheet to obtain a cured sheet, in which the volume of the non-volatile content in the resin composition is 0.9 to 1.1 times the total volume of the gaps in the aggregate boron nitride particles contained in the mixture.
第１の工程は、樹脂組成物と塊状窒化ホウ素粒子とを混練して第１の組成物を得る第１の混練工程と、第１の組成物を脱気する脱気工程と、脱気後の第１の組成物を混練して第２の組成物を得る第２の混練工程と、を含んでよい。The first step may include a first kneading step of kneading a resin composition with agglomerated boron nitride particles to obtain a first composition, a degassing step of degassing the first composition, and a second kneading step of kneading the degassed first composition to obtain a second composition.
半硬化シートにおいて、半硬化させた樹脂は、塊状窒化ホウ素粒子の内部に充填されていてよく、塊状窒化ホウ素粒子同士の間に空隙が形成されていてよい。In the semi-cured sheet, the semi-cured resin may be filled inside the aggregate boron nitride particles, and voids may be formed between the aggregate boron nitride particles.
本発明の他の一側面は、樹脂の硬化物と、塊状窒化ホウ素粒子と、を含有する硬化シートであって、塊状窒化ホウ素粒子の平均粒子径が４５μｍ以上であり、硬化シートの耐電圧が３０ｋＶ／ｍｍ以上である、硬化シートである。Another aspect of the present invention is a cured sheet containing a cured resin and aggregate boron nitride particles, wherein the average particle size of the aggregate boron nitride particles is 45 μm or more, and the voltage resistance of the cured sheet is 30 kV/mm or more.
硬化シートの任意の５個の断面について、ＳＥＭにより倍率３００倍で１００μｍ×１００μｍの範囲を観察したときに、塊状窒化ホウ素粒子間にボイドが発生している断面が０個であってよい。When any five cross sections of the hardened sheet are observed using an SEM at a magnification of 300x over an area of 100 μm x 100 μm, there may be zero cross sections in which voids have occurred between the agglomerated boron nitride particles.
本発明の一側面によれば、優れた熱伝導率及び耐電圧を両立できるシートを製造することができる。 According to one aspect of the present invention, a sheet can be produced that has both excellent thermal conductivity and voltage resistance.
以下、本発明の実施形態について詳細に説明する。 The following describes in detail an embodiment of the present invention.
本発明の一実施形態は、樹脂組成物と塊状窒化ホウ素粒子とを混合して混合物を得る第１の工程と、混合物をシート状に成形すると共に、混合物中の樹脂を半硬化させて半硬化シートを得る第２の工程と、半硬化シートに対して加圧すると共に、半硬化シート中の樹脂を更に硬化させて硬化シートを得る第３の工程と、を備える、硬化シートの製造方法である。One embodiment of the present invention is a method for producing a cured sheet, comprising a first step of mixing a resin composition with agglomerated boron nitride particles to obtain a mixture, a second step of forming the mixture into a sheet and semi-curing the resin in the mixture to obtain a semi-cured sheet, and a third step of applying pressure to the semi-cured sheet and further curing the resin in the semi-cured sheet to obtain a cured sheet.
第１の工程で用いられる樹脂組成物は、少なくとも樹脂を含む。樹脂としては、例えば、エポキシ樹脂、シリコーン樹脂、シリコーンゴム、アクリル樹脂、フェノール樹脂、メラミン樹脂、ユリア樹脂、及び不飽和ポリエステルが挙げられる。The resin composition used in the first step contains at least a resin. Examples of the resin include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenolic resin, melamine resin, urea resin, and unsaturated polyester.
第１の工程で用いられる塊状窒化ホウ素粒子は、窒化ホウ素一次粒子の凝集体である。窒化ホウ素一次粒子は、例えば鱗片状の六方晶窒化ホウ素粒子であってよい。この場合、窒化ホウ素一次粒子の長手方向の長さは、例えば、１μｍ以上であってよく、１０μｍ以下であってよい。このような塊状窒化ホウ素粒子は、公知の方法により製造できる。The aggregate boron nitride particles used in the first step are aggregates of primary boron nitride particles. The primary boron nitride particles may be, for example, scaly hexagonal boron nitride particles. In this case, the longitudinal length of the primary boron nitride particles may be, for example, 1 μm or more and 10 μm or less. Such aggregate boron nitride particles can be produced by known methods.
第１の工程で用いられる塊状窒化ホウ素粒子の平均粒子径は、硬化シートの熱伝導率を向上させる観点から、４５μｍ以上であり、当該効果が更に得られやすくなる観点から、好ましくは、５０μｍ以上、６０μｍ以上、７０μｍ以上、又は８０μｍ以上である。塊状窒化ホウ素粒子の平均粒子径は、例えば１５０μｍ以下であってよい。The average particle size of the aggregate boron nitride particles used in the first step is 45 μm or more from the viewpoint of improving the thermal conductivity of the cured sheet, and is preferably 50 μm or more, 60 μm or more, 70 μm or more, or 80 μm or more from the viewpoint of making the effect more easily obtainable. The average particle size of the aggregate boron nitride particles may be, for example, 150 μm or less.
第１の工程で用いられる塊状窒化ホウ素粒子の平均粒子径は、レーザー回折散乱法により測定される。具体的な測定方法は、以下のとおりである。
まず、０．１２５質量％ヘキサメタリン酸ナトリウム水溶液８０ｍＬに塊状窒化ホウ素粒子０．１ｇを分散させた分散液（塊状窒化ホウ素粒子窒化ホウ素０．１ｇ／８０ｍＬ）を用意する。続いて、当該分散液についてホモジナイザーをかけずに、レーザー回折散乱法粒度分布測定装置（例えば、ベックマン・コールター株式会社製、「ＬＳ－１３ ３２０」）を用いて粒度分布を測定する。このとき、水の屈折率としては１．３３、窒化ホウ素粉末の屈折率としては１．７を用いる。そして、累積粒度分布の累積値５０体積％の粒径（メジアン径、ｄ５０）を算出し、当該粒径（メジアン径、ｄ５０）を塊状窒化ホウ素粒子の平均粒子径とする。
The average particle size of the aggregate boron nitride particles used in the first step is measured by a laser diffraction scattering method. The specific measurement method is as follows.
First, a dispersion liquid (lump boron nitride particles boron nitride 0.1 g/80 mL) is prepared by dispersing 0.1 g of lump boron nitride particles in 80 mL of 0.125 mass% sodium hexametaphosphate aqueous solution. Next, the particle size distribution of the dispersion liquid is measured using a laser diffraction scattering particle size distribution measuring device (for example, "LS-13 320" manufactured by Beckman Coulter, Inc.) without applying a homogenizer. At this time, the refractive index of water is 1.33, and the refractive index of boron nitride powder is 1.7. Then, the particle size (median diameter, d50) of the cumulative value of 50 volume % of the cumulative particle size distribution is calculated, and the particle size (median diameter, d50) is taken as the average particle size of the lump boron nitride particles.
樹脂組成物は、樹脂に加えて、必要に応じてその他の成分を更に含んでもよい。その他の成分としては、例えば、硬化剤、硬化促進剤（硬化触媒）、カップリング剤、湿潤分散剤、表面調整剤、及び溶媒が挙げられる。なお、本明細書では、樹脂組成物中の溶媒以外の成分を「不揮発分」と呼ぶ。In addition to the resin, the resin composition may further contain other components as necessary. Examples of other components include a curing agent, a curing accelerator (curing catalyst), a coupling agent, a wetting and dispersing agent, a surface conditioner, and a solvent. In this specification, components in the resin composition other than the solvent are referred to as "non-volatile components."
硬化剤は、樹脂の種類によって適宜選択される。例えば、樹脂がエポキシ樹脂である場合、硬化剤としては、フェノールノボラック化合物、酸無水物、アミノ化合物、及びイミダゾール化合物が挙げられる。硬化剤の含有量は、樹脂１００質量部に対して、例えば、０．５質量部以上又は１．０質量部以上であってよく、１５質量部以下又は１０質量部以下であってよい。The curing agent is appropriately selected depending on the type of resin. For example, when the resin is an epoxy resin, examples of the curing agent include phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 parts by mass or more, and 15 parts by mass or less or 10 parts by mass or less, relative to 100 parts by mass of the resin.
硬化促進剤（硬化触媒）としては、例えば、テトラフェニルホスホニウムテトラフェニルボレート、トリフェニルフォスフェイト等のリン系硬化促進剤、２－フェニル－４，５－ジヒドロキシメチルイミダゾール等のイミダゾール系硬化促進剤、及び、三フッ化ホウ素モノエチルアミン等のアミン系硬化促進剤が挙げられる。 Examples of curing accelerators (curing catalysts) include phosphorus-based curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenyl phosphate, imidazole-based curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole, and amine-based curing accelerators such as boron trifluoride monoethylamine.
カップリング剤としては、例えば、シラン系カップリング剤、チタネート系カップリング剤、及びアルミネート系カップリング剤が挙げられる。これらのカップリング剤に含まれる化学結合基としては、例えば、ビニル基、エポキシ基、アミノ基、メタクリル基、及びメルカプト基が挙げられる。Examples of coupling agents include silane coupling agents, titanate coupling agents, and aluminate coupling agents. Chemical bonding groups contained in these coupling agents include vinyl groups, epoxy groups, amino groups, methacryl groups, and mercapto groups.
湿潤分散剤としては、例えば、リン酸エステル塩、カルボン酸エステル、ポリエステル、アクリル共重合物、及びブロック共重合物が挙げられる。 Examples of wetting and dispersing agents include phosphate ester salts, carboxylate esters, polyesters, acrylic copolymers, and block copolymers.
表面調整剤としては、例えば、アクリル系表面調整剤、シリコーン系表面調整剤、ビニル系調整剤、及びフッ素系表面調整剤が挙げられる。 Examples of surface conditioners include acrylic surface conditioners, silicone surface conditioners, vinyl surface conditioners, and fluorine surface conditioners.
溶媒は、例えば樹脂を溶解させる溶媒であってよい。溶媒としては、例えば、アルコール系溶媒、グリコールエーテル系溶媒、芳香族系溶剤、及びケトン系溶剤が挙げられる。アルコール系溶媒としては、例えば、イソプロピルアルコール及びジアセトンアルコールが挙げられる。グリコールエーテル系溶媒としては、例えば、エチルセロソルブ及びブチルセロソルブが挙げられる。芳香族系溶剤としては、例えば、トルエン及びキシレンが挙げられる。ケトン系溶剤としては、例えば、メチルエチルケトン及びメチルイソブチルケトンが挙げられる。The solvent may be, for example, a solvent that dissolves the resin. Examples of the solvent include alcohol-based solvents, glycol ether-based solvents, aromatic solvents, and ketone-based solvents. Examples of the alcohol-based solvents include isopropyl alcohol and diacetone alcohol. Examples of the glycol ether-based solvents include ethyl cellosolve and butyl cellosolve. Examples of the aromatic solvents include toluene and xylene. Examples of the ketone-based solvents include methyl ethyl ketone and methyl isobutyl ketone.
第１の工程では、得られる混合物に含まれる塊状窒化ホウ素粒子内の隙間（複数の窒化ホウ素一次粒子により形成されている隙間）の全体積（言い換えれば、第１の工程で使用される塊状窒化ホウ素粒子内の隙間の全体積）に対する樹脂組成物中の不揮発分の体積を適切に設定する必要がある。これにより、硬化シートの耐電圧及び熱伝導率を向上させることができる。樹脂組成物中の不揮発分の体積は、混合物に含まれる塊状窒化ホウ素粒子内の隙間の全体積に対して、０．９～１．１倍である、り、硬化シートの耐電圧を更に向上させる観点から、好ましくは０．９２倍以上、より好ましくは０．９５倍以上、更に好ましくは０．９８倍以上の体積であり、好ましくは１．０８倍以下、より好ましくは１．０５倍以下、更に好ましくは１．０２倍以下の体積である。In the first step, it is necessary to appropriately set the volume of the non-volatile content in the resin composition relative to the total volume of the gaps (gaps formed by a plurality of boron nitride primary particles) in the aggregate boron nitride particles contained in the resulting mixture (in other words, the total volume of the gaps in the aggregate boron nitride particles used in the first step). This makes it possible to improve the withstand voltage and thermal conductivity of the cured sheet. The volume of the non-volatile content in the resin composition is 0.9 to 1.1 times the total volume of the gaps in the aggregate boron nitride particles contained in the mixture, and from the viewpoint of further improving the withstand voltage of the cured sheet, it is preferably 0.92 times or more, more preferably 0.95 times or more, and even more preferably 0.98 times or more, and is preferably 1.08 times or less, more preferably 1.05 times or less, and even more preferably 1.02 times or less.
塊状窒化ホウ素粒子内の隙間の体積は、細孔分布測定装置（例えば、島津製作所－マイクロメリティックス社製「オートポア Ｖ９６２０」）により測定される。具体的には、塊状窒化ホウ素粒子（体積Ｖ＝約０．０８８ｃｍ３）を粉体用セル（例えば５ｃｍ３）に採取し、初期圧７ｋＰａ（１．０ｐｓｉａ、細孔直径１８０μｍ相当）の条件で測定する。水銀パラメータは、装置デフォルトの水銀接触角１３０ｄｅｇｒｅｅｓ、水銀表面張力４８５ｄｙｎｅｓ／ｃｍに設定する。得られる細孔分布において、５μｍ未満の細孔は塊状窒化ホウ素粒子内の空隙に相当（５μｍ以上の細孔は塊状窒化ホウ素粒子間の空隙に相当）するものとして、５μｍ未満の細孔体積を、塊状窒化ホウ素粒子の体積Ｖあたりの粒子内の隙間の体積と定義する。 The volume of the gaps in the aggregate boron nitride particles is measured by a pore distribution measuring device (e.g., Shimadzu Micromeritics'"AutoporeV9620"). Specifically, aggregate boron nitride particles (volume V=about 0.088 cm 3 ) are collected in a powder cell (e.g., 5 cm 3 ) and measured under conditions of an initial pressure of 7 kPa (1.0 psia, equivalent to a pore diameter of 180 μm). The mercury parameters are set to the device's default mercury contact angle of 130 degrees and mercury surface tension of 485 dynes/cm. In the obtained pore distribution, pores less than 5 μm correspond to gaps in the aggregate boron nitride particles (pores 5 μm or more correspond to gaps between aggregate boron nitride particles), and the volume of pores less than 5 μm is defined as the volume of gaps in the particles per volume V of the aggregate boron nitride particles.
また、樹脂組成物の３０℃における粘度は、得られる半硬化シートにおいて、樹脂の半硬化物が塊状窒化ホウ素粒子の内部に更に好適に充填されると共に、塊状窒化ホウ素粒子同士の間に空隙が更に好適に形成される観点から、好ましくは１０Ｐａ・ｓ以下、より好ましくは５Ｐａ・ｓ以下、更に好ましくは１Ｐａ・ｓ以下である。当該粘度は、回転式粘度計を用いて、せん断速度１０（１／秒）の条件で測定される。The viscosity of the resin composition at 30°C is preferably 10 Pa·s or less, more preferably 5 Pa·s or less, and even more preferably 1 Pa·s or less, from the viewpoint of more suitably filling the interior of the aggregate boron nitride particles in the resulting semi-cured sheet and more suitably forming voids between the aggregate boron nitride particles. The viscosity is measured using a rotational viscometer at a shear rate of 10 (1/sec).
第１の工程は、好ましくは、樹脂組成物と塊状窒化ホウ素粒子とを混練して第１の組成物を得る第１の混練工程と、第１の組成物を脱気する脱気工程と、脱気後の第１の組成物を混練して第２の組成物を得る第２の混練工程と、を含んでいる。第１の工程がこれらの工程を含むことにより、得られる硬化シートにおけるボイドの発生を特に抑制できる。The first step preferably includes a first kneading step of kneading the resin composition with the aggregate boron nitride particles to obtain a first composition, a degassing step of degassing the first composition, and a second kneading step of kneading the degassed first composition to obtain a second composition. By including these steps in the first step, the occurrence of voids in the resulting cured sheet can be particularly suppressed.
第１の混練工程及び第２の混練工程では、常法により、樹脂組成物と塊状窒化ホウ素粒子との混練、又は脱気後の第１の組成物の混練が行われる。In the first kneading step and the second kneading step, the resin composition and the aggregate boron nitride particles are kneaded, or the first composition after degassing is kneaded, by conventional methods.
脱気工程では、例えば、第１の組成物を真空（例えば５００Ｐａ以下の圧力）下に置くことにより、第１の組成物中の空気を除去することができる。In the degassing process, for example, air can be removed from the first composition by placing the first composition under vacuum (e.g., a pressure of 500 Pa or less).
第２の工程では、例えば、まず、第１の工程で用意した組成物（第２の組成物）をシート状に成形する。具体的には、例えば、フィルムアプリケーターを用いて、当該組成物を基材上に塗工することにより、シート（未硬化シート）を得ることができる。続いて、未硬化シート中の樹脂を半硬化させることで、半硬化シートが得られる。樹脂を半硬化させる方法は、樹脂（及び必要に応じて用いられる硬化剤）の種類に応じて常法から適宜選択される。例えば、樹脂がエポキシ樹脂であり、上述した硬化剤が共に用いられる場合、第２の工程では、加熱により樹脂を硬化させることができる。この場合、加熱温度及び加熱時間を調整することにより、樹脂を半硬化させることができる。樹脂組成物が溶媒を含む場合は、第２の工程において、樹脂を半硬化させると共に、当該溶媒を揮発させてもよい。In the second step, for example, the composition (second composition) prepared in the first step is first formed into a sheet. Specifically, for example, the composition is applied to a substrate using a film applicator to obtain a sheet (uncured sheet). Then, the resin in the uncured sheet is semi-cured to obtain a semi-cured sheet. The method for semi-curing the resin is appropriately selected from conventional methods depending on the type of resin (and the curing agent used as necessary). For example, when the resin is an epoxy resin and the above-mentioned curing agent is used together, the resin can be cured by heating in the second step. In this case, the resin can be semi-cured by adjusting the heating temperature and heating time. When the resin composition contains a solvent, the resin may be semi-cured and the solvent may be volatilized in the second step.
樹脂が半硬化した状態（Ｂステージともいう）とは、その後の硬化処理によって、更に硬化させることができる状態を意味する。言い換えれば、半硬化させた樹脂（以下「樹脂の半硬化物」ともいう）は、硬化した樹脂と未硬化の樹脂との両方を含んでいる。樹脂が半硬化した状態であることは、例えば、示差走査熱量測定にて発熱ピークが観察されることにより確認することができる。樹脂の半硬化物は、更に硬化処理をすることで完全硬化（Ｃステージともいう）の状態になり得る。A semi-cured resin (also called B stage) means a state in which it can be further cured by a subsequent curing process. In other words, a semi-cured resin (hereinafter also called "semi-cured resin") contains both cured and uncured resin. The semi-cured state of a resin can be confirmed, for example, by observing an exothermic peak in differential scanning calorimetry. A semi-cured resin can be fully cured (also called C stage) by further curing.
この半硬化シートにおいて、樹脂の半硬化物は、塊状窒化ホウ素粒子のそれぞれの内部に充填されている。樹脂の半硬化物が塊状窒化ホウ素粒子の内部に充填されていることは、半硬化シートの断面を走査型電子顕微鏡（ＳＥＭ）により観察することで確認できる。半硬化シートは、塊状窒化ホウ素粒子の内部に充填されている樹脂の半硬化物に加えて、複数の塊状窒化ホウ素粒子同士を結着させるように、複数の塊状窒化ホウ素粒子間に配置された樹脂の半硬化物が更に含有してよい。In this semi-cured sheet, the semi-cured resin is filled inside each of the aggregate boron nitride particles. The fact that the semi-cured resin is filled inside the aggregate boron nitride particles can be confirmed by observing the cross section of the semi-cured sheet with a scanning electron microscope (SEM). In addition to the semi-cured resin filled inside the aggregate boron nitride particles, the semi-cured sheet may further contain semi-cured resin arranged between the aggregate boron nitride particles so as to bond the aggregate boron nitride particles together.
樹脂の半硬化物は、塊状窒化ホウ素粒子内の隙間（複数の窒化ホウ素一次粒子により形成されている隙間）のできる限り多くに充填されていることが好ましい。半硬化シートの断面をＳＥＭにより観察したときに、塊状窒化ホウ素粒子内の樹脂の半硬化物が充填されている面積に対する、塊状窒化ホウ素粒子内の隙間の面積の割合は、好ましくは１０面積％以下、より好ましくは５面積％以下、更に好ましくは３面積％以下である。当該割合は、半硬化シートの任意の５個の断面をＳＥＭにより２００倍で観察し、各断面における５粒の窒化ホウ素粒子について上記割合を算出し、算出された割合の平均値（計２５粒の窒化ホウ素粒子における割合の平均値）として求められる。It is preferable that the semi-cured resin fills as many of the gaps (gaps formed by multiple primary boron nitride particles) in the aggregate boron nitride particles as possible. When the cross section of the semi-cured sheet is observed by SEM, the ratio of the area of the gaps in the aggregate boron nitride particles to the area filled with the semi-cured resin in the aggregate boron nitride particles is preferably 10 area% or less, more preferably 5 area% or less, and even more preferably 3 area% or less. The ratio is determined by observing five arbitrary cross sections of the semi-cured sheet by SEM at 200 times, calculating the above ratio for five boron nitride particles in each cross section, and averaging the calculated ratios (average ratio for a total of 25 boron nitride particles).
半硬化シートにおいて、複数の塊状窒化ホウ素粒子同士の間には空隙が形成されている。複数の塊状窒化ホウ素粒子同士の間には空隙が形成されていることは、半硬化シートの断面をＳＥＭにより観察することで確認できる。In the semi-hardened sheet, gaps are formed between the multiple aggregate boron nitride particles. The fact that gaps are formed between the multiple aggregate boron nitride particles can be confirmed by observing the cross section of the semi-hardened sheet with a SEM.
半硬化シートの断面をＳＥＭにより観察したときに、樹脂の半硬化物及び塊状窒化ホウ素粒子の面積Ａ１と塊状窒化ホウ素粒子間の空隙の面積Ａ２との合計に対する、樹脂の半硬化物及び塊状窒化ホウ素粒子の面積Ａ１の比（Ａ１／（Ａ１＋Ａ２））は、例えば、０．４以上、０．５５以上、又は０．６以上であってよく、０．９以下、０．８以下、又は０．７以下であってよい。When a cross-section of the semi-cured sheet is observed by SEM, the ratio of the area A1 of the semi-cured resin and the agglomerated boron nitride particles to the sum of the area A1 of the semi-cured resin and the agglomerated boron nitride particles and the area A2 of the voids between the agglomerated boron nitride particles (A1/(A1+A2)) may, for example, be 0.4 or more, 0.55 or more, or 0.6 or more, and may be 0.9 or less, 0.8 or less, or 0.7 or less.
当該比は、以下の手順により測定される。
まず、渦電流式膜厚計（DeFelsko社、PosiTestor 6000）を用いて、半硬化シートにおける５点の膜厚を測定し、それらの平均値を半硬化シートの膜厚とする。続いて、半硬化シートの任意の５個の断面をＳＥＭにより倍率：２００倍で観察し、ＳＥＭ像を取得する。得られた各断面のＳＥＭ像において、半硬化シートの膜厚方向の両端のそれぞれから、上記で測定された半硬化シートの膜厚の５％の位置に、仮想線（半硬化シートの膜厚方向と垂直な線）を２本引く。これにより、当該２本の仮想線で挟まれた仮想的なシート（上記で測定された半硬化シートの膜厚の９０％の厚さを有する仮想的なシート）を規定する。そして、（当該仮想的なシートの膜厚に相当する長さ）×３００μｍの範囲で、上記のＡ１／（Ａ１＋Ａ２）を算出し、５個の断面において算出されたＡ１／（Ａ１＋Ａ２）の平均値として上記比が定義される。
The ratio is measured by the following procedure.
First, an eddy current film thickness meter (PosiTestor 6000, DeFelsko) is used to measure the film thickness at five points on the semi-cured sheet, and the average value is taken as the film thickness of the semi-cured sheet. Next, any five cross sections of the semi-cured sheet are observed by SEM at a magnification of 200 times to obtain an SEM image. In the SEM image of each cross section obtained, two virtual lines (lines perpendicular to the film thickness direction of the semi-cured sheet) are drawn at a position 5% of the film thickness of the semi-cured sheet measured above from each of both ends in the film thickness direction of the semi-cured sheet. This defines a virtual sheet (a virtual sheet having a thickness of 90% of the film thickness of the semi-cured sheet measured above) sandwiched between the two virtual lines. Then, the above A1/(A1+A2) is calculated within a range of (length equivalent to the film thickness of the virtual sheet) x 300 μm, and the above ratio is defined as the average value of A1/(A1+A2) calculated at the five cross sections.
半硬化シートでは、上述したとおり、塊状窒化ホウ素粒子間の空隙が意図的に形成されている一方で、意図せずに混入した気泡はほぼ含まれていない。つまり、複数の塊状窒化ホウ素粒子同士の間に形成された空隙は、気泡（樹脂の半硬化物のマトリックス中に存在する（樹脂の半硬化物のマトリックスに囲まれた）気泡）を含まない。As mentioned above, in the semi-cured sheet, while the voids between the aggregate boron nitride particles are intentionally formed, there are almost no unintentionally mixed-in air bubbles. In other words, the voids formed between multiple aggregate boron nitride particles do not contain air bubbles (air bubbles present in the matrix of the semi-cured resin (surrounded by the matrix of the semi-cured resin)).
半硬化シート中に含まれる気泡がきわめて少ないことは、半硬化シートの断面をＳＥＭにより観察することで確認できる。具体的には、半硬化シートに気泡が含まれる場合、当該気泡は、上記の空隙よりも広範囲にわたって（より多くの塊状窒化ホウ素粒子にまたがって）存在するため、半硬化シートの断面に占める樹脂の半硬化物及び塊状窒化ホウ素粒子の面積が小さくなる（例えば３０面積％以下になる）。この半硬化シートでは、半硬化シートの任意の５個の断面を観察したときに、１個の断面に占める樹脂の半硬化物及び複数の塊状窒化ホウ素粒子の面積が３０面積％以下となる断面が０個である。このような半硬化シートを用いると、絶縁性及び熱伝導性の点で更に優れる硬化シートを得ることができる。The fact that the semi-cured sheet contains very few air bubbles can be confirmed by observing the cross section of the semi-cured sheet with a SEM. Specifically, when the semi-cured sheet contains air bubbles, the air bubbles are present over a wider range (across more aggregate boron nitride particles) than the above-mentioned voids, so the area of the semi-cured resin and aggregate boron nitride particles in the cross section of the semi-cured sheet is small (for example, 30 area % or less). When any five cross sections of this semi-cured sheet are observed, there are no cross sections in which the area of the semi-cured resin and multiple aggregate boron nitride particles in one cross section is 30 area % or less. By using such a semi-cured sheet, a cured sheet with even better insulation and thermal conductivity can be obtained.
半硬化シートの厚みは、例えば、５０μｍ以上、８０μｍ以上、又は１００μｍ以上であってよく、１０００μｍ以下、８００μｍ以下、６００μｍ以下、４００μｍ以下、３００μｍ以下、又は２００μｍ以下であってよい。The thickness of the semi-hardened sheet may be, for example, 50 μm or more, 80 μm or more, or 100 μm or more, and may be 1000 μm or less, 800 μm or less, 600 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less.
第３の工程では、半硬化シートに対して加圧する。このときの圧力は、適宜選択することができ、例えば、７ＭＰａ以上、８ＭＰａ以上、又は１０ＭＰａ以上であってよく、１６ＭＰａ以下、１２ＭＰａ以下、又は１０ＭＰａ以下であってよい。In the third step, pressure is applied to the semi-hardened sheet. The pressure can be appropriately selected and may be, for example, 7 MPa or more, 8 MPa or more, or 10 MPa or more, and may be 16 MPa or less, 12 MPa or less, or 10 MPa or less.
第３の工程では、加圧に加えて、半硬化シート中の樹脂を更に硬化させることで、硬化シートが得られる。硬化シート中の樹脂は、完全に硬化した状態であってもよく、一部未硬化の樹脂を含んでいてもよい。樹脂を更に硬化させる方法は、樹脂（及び必要に応じて用いられる硬化剤）の種類に応じて常法から適宜選択される。例えば、樹脂がエポキシ樹脂であり、上述した硬化剤が共に用いられる場合、第３の工程では、加熱により樹脂を硬化させることができる。この場合の加熱温度は、例えば、１００℃以上であってよく、２５０℃以下であってよい。In the third step, in addition to applying pressure, the resin in the semi-cured sheet is further cured to obtain a cured sheet. The resin in the cured sheet may be in a completely cured state, or may contain some uncured resin. The method for further curing the resin is appropriately selected from conventional methods depending on the type of resin (and the curing agent used as necessary). For example, when the resin is an epoxy resin and the above-mentioned curing agent is used together, the resin can be cured by heating in the third step. The heating temperature in this case may be, for example, 100°C or higher and 250°C or lower.
硬化シートの厚みは、例えば、５０μｍ以上、８０μｍ以上、又は１００μｍ以上であってよく、１０００μｍ以下、８００μｍ以下、６００μｍ以下、４００μｍ以下、３００μｍ以下、又は２００μｍ以下であってよい。The thickness of the cured sheet may be, for example, 50 μm or more, 80 μm or more, or 100 μm or more, and may be 1000 μm or less, 800 μm or less, 600 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less.
以上の製造方法により得られる硬化シートは、一実施形態において、樹脂の硬化物と、塊状窒化ホウ素粒子と、を含有する。In one embodiment, the cured sheet obtained by the above manufacturing method contains a cured resin and aggregate boron nitride particles.
樹脂の硬化物は、例えば、上述した樹脂組成物の不揮発分を硬化させた硬化物であってよい。樹脂の硬化物は、完全に硬化した状態であってもよく、未硬化の樹脂を含んでいてもよい。The cured resin may be, for example, a cured product obtained by curing the non-volatile components of the resin composition described above. The cured resin may be in a completely cured state or may contain uncured resin.
硬化シート中の樹脂の硬化物の含有量は、硬化シートの全体積を基準として、例えば、４０体積％以上又は４５体積％以上であってよく、６０体積％以下又は５５体積％以下であってよい。The content of the cured resin in the cured sheet may be, for example, 40 volume % or more or 45 volume % or more, and 60 volume % or less or 55 volume % or less, based on the total volume of the cured sheet.
硬化シート中の塊状窒化ホウ素粒子の含有量は、硬化シートの全体積を基準として、例えば、４０体積％以上又は４５体積％以上であってよく、６０体積％以下又は５５体積％以下であってよい。The content of agglomerated boron nitride particles in the hardened sheet may be, for example, 40 volume % or more or 45 volume % or more, and 60 volume % or less or 55 volume % or less, based on the total volume of the hardened sheet.
硬化シート中の塊状窒化ホウ素粒子の平均粒子径は、硬化シートの熱伝導率を向上させる観点から、４５μｍ以上であり、当該効果が更に得られやすくなる観点から、好ましくは、５０μｍ以上、５５μｍ以上、又は６０μｍ以上である。硬化シート中の塊状窒化ホウ素粒子の平均粒子径は、例えば１５０μｍ以下又は１２０μｍ以下であってよい。The average particle size of the aggregate boron nitride particles in the cured sheet is 45 μm or more from the viewpoint of improving the thermal conductivity of the cured sheet, and is preferably 50 μm or more, 55 μm or more, or 60 μm or more from the viewpoint of making the effect more easily obtainable. The average particle size of the aggregate boron nitride particles in the cured sheet may be, for example, 150 μm or less or 120 μm or less.
硬化シート中の塊状窒化ホウ素粒子の平均粒子径は、以下の手順により求められる。すなわち、硬化シートの断面のＳＥＭ像において、５個の塊状窒化ホウ素粒子について最大長さをそれぞれ測定する。この最大長さの測定を硬化シートの異なる断面のＳＥＭ像５枚について行い、測定されたすべての塊状窒化ホウ素粒子（計２５粒）の最大長さの平均値として、硬化シート中の塊状窒化ホウ素粒子の平均粒子径が求められる。The average particle size of the aggregate boron nitride particles in the cured sheet is determined by the following procedure. That is, in an SEM image of the cross section of the cured sheet, the maximum length of each of five aggregate boron nitride particles is measured. This maximum length measurement is performed on five SEM images of different cross sections of the cured sheet, and the average particle size of the aggregate boron nitride particles in the cured sheet is determined as the average of the maximum lengths of all the measured aggregate boron nitride particles (total of 25 particles).
この硬化シートは、上記のように粒径の大きな塊状窒化ホウ素粒子を含んでいながら、高い耐電圧を達成できる。硬化シートの耐電圧は、３０ｋＶ／ｍｍ以上であり、高いほど好ましくは、例えば、３３ｋＶ／ｍｍ以上、３５ｋＶ／ｍｍ以上、又は４０ｋＶ／ｍｍ以上であってもよい。硬化シートの耐電圧は、耐電圧試験機（例えば、菊水電子工業製 ＴＯＳ５１０１）を用いて、ＪＩＳ Ｃ２１１０－１に従って測定される、耐電圧の最小値を意味する。This hardened sheet can achieve a high withstand voltage while containing large-particle-sized aggregate boron nitride particles as described above. The withstand voltage of the hardened sheet is 30 kV/mm or more, and the higher the value, the more preferable it may be, for example, 33 kV/mm or more, 35 kV/mm or more, or 40 kV/mm or more. The withstand voltage of the hardened sheet means the minimum withstand voltage value measured according to JIS C2110-1 using a withstand voltage tester (e.g., TOS5101 manufactured by Kikusui Electronics Co., Ltd.).
この硬化シートでは、ボイドの発生も抑制され得る。具体的には、硬化シートの任意の５個の断面について、ＳＥＭにより倍率３００倍で１００μｍ×１００μｍの範囲を観察したときに、塊状窒化ホウ素粒子間にボイドが発生している断面が０個である。本明細書において、ボイドとは、円相当径が１０μｍ以上の空隙を意味する。なお、円相当径とは、硬化シートの断面のＳＥＭ像におけるボイドの面積と等しい面積を有する円を仮定したときに、当該円の直径を意味する。図１には、ボイドが発生している硬化シートの断面のＳＥＭ像の一例を示す。In this cured sheet, the occurrence of voids can also be suppressed. Specifically, when any five cross sections of the cured sheet are observed with a 100 μm×100 μm area at a magnification of 300 times using an SEM, there are zero cross sections in which voids occur between the aggregate boron nitride particles. In this specification, a void means a gap with a circle equivalent diameter of 10 μm or more. The circle equivalent diameter means the diameter of a circle assuming an area equal to the area of the void in the SEM image of the cross section of the cured sheet. Figure 1 shows an example of an SEM image of a cross section of a cured sheet in which voids occur.
以上説明した硬化シートは、優れた熱伝導率及び耐電圧の両立が可能であるため、絶縁シート、熱伝導シート（放熱シート）等として好適に用いられる。The cured sheet described above has excellent thermal conductivity and voltage resistance, and is therefore suitable for use as an insulating sheet, a thermally conductive sheet (heat dissipation sheet), etc.
以下、実施例に基づき本発明を更に具体的に説明するが、本発明は以下の実施例に限定されるものではない。The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.
（実施例１）
塊状窒化ホウ素粒子（平均粒子径：８５μｍ、塊状窒化ホウ素粒子内の隙間の体積：５０体積％）１００体積部と、エポキシ樹脂（ＤＩＣ社製、製品名：ＨＰ４０３２）４１．５体積部と、硬化剤（ＤＩＣ社製、製品名：ＶＨ４１５０）５．１体積部と、２種の硬化促進剤（硬化触媒）（北興化学社製、製品名：ＴＰＰ）０．３体積部及び（四国化成工業社製、製品名：２ＰＨＺ－ＰＷ）０．５体積部と、カップリング剤（東レ・ダウコーニング社製、製品名：Ｚ６０４０）１．６体積部と、湿潤分散剤（ビックケミージャパン社製、製品名：ＤＩＳ－１１１）０．３体積部と、表面調整剤（ビックケミージャパン社製、製品名：ＢＹＫ－３００）０．４体積部と、を用いた。また、これらの各成分の合計１００質量部に対して、揮発成分である溶媒（東京化成工業社製、ジアセトンアルコール）を２０質量部用いた。上記の各成分のうち塊状窒化ホウ素粒子以外の成分と溶媒とで構成される樹脂組成物の３０℃における粘度は、１０Ｐａ・ｓであった。全て成分を、遊星式撹拌機（シンキー社「あわとり練太郎ＡＲ－２５０」）を用いて、公転速度２０００ｒｐｍ、自転速度８００ｒｐｍの条件で２分間混練して、第１の組成物を得た。
Example 1
The mixture used was 100 parts by volume of aggregate boron nitride particles (average particle size: 85 μm, volume of gaps within aggregate boron nitride particles: 50% by volume), 41.5 parts by volume of epoxy resin (manufactured by DIC Corporation, product name: HP4032), 5.1 parts by volume of curing agent (manufactured by DIC Corporation, product name: VH4150), 0.3 parts by volume of two types of curing accelerators (curing catalysts) (manufactured by Hokko Chemical Industry Co., Ltd., product name: TPP) and 0.5 parts by volume of (manufactured by Shikoku Chemical Industry Co., Ltd., product name: 2PHZ-PW), 1.6 parts by volume of coupling agent (manufactured by Dow Corning Toray Co., Ltd., product name: Z6040), 0.3 parts by volume of wetting and dispersing agent (manufactured by BYK Japan Co., Ltd., product name: DIS-111), and 0.4 parts by volume of surface conditioner (manufactured by BYK Japan Co., Ltd., product name: BYK-300). Furthermore, 20 parts by mass of a solvent (diacetone alcohol, manufactured by Tokyo Chemical Industry Co., Ltd.), which is a volatile component, was used relative to a total of 100 parts by mass of each of these components. The viscosity of a resin composition composed of the solvent and the components other than the aggregate boron nitride particles among the above-mentioned components was 10 Pa·s at 30° C. All the components were kneaded for 2 minutes using a planetary mixer (Thinky Corporation's "Awatori Rentaro AR-250") under conditions of a revolution speed of 2000 rpm and a rotation speed of 800 rpm, to obtain a first composition.
次に、５００Ｐａの減圧条件下で、第１の組成物を脱気した。脱気後の第１の組成物を、遊星式撹拌機（シンキー社「あわとり練太郎ＡＲ－２５０」）を用いて、公転速度２０００ｒｐｍ、自転速度８００ｒｐｍの条件で２分間再度混練して、第２の組成物を得た。Next, the first composition was degassed under reduced pressure conditions of 500 Pa. The degassed first composition was mixed again for 2 minutes using a planetary mixer (Thinky Corporation's "Awatori Rentaro AR-250") at a revolution speed of 2000 rpm and a rotation speed of 800 rpm to obtain a second composition.
続いて、フィルムアプリケーターを用いて、得られた第２の組成物を厚さ２００μｍのシート状に成形した後、熱風乾燥機を用いて、６０℃で３０分間及び１００℃で７０分間の条件で、樹脂を半硬化させた。これにより半硬化シートを得た。示差走査熱量計を用いて、得られた半硬化シートを２５～３００℃で測定したところ、発熱ピークが観察され、半硬化シート中の樹脂が半硬化した状態であることが確認された。また、得られた半硬化シートの断面をＳＥＭにより２００倍で観察した画像の一つを図２に示す。 Next, the obtained second composition was formed into a sheet having a thickness of 200 μm using a film applicator, and the resin was semi-cured using a hot air dryer at 60°C for 30 minutes and 100°C for 70 minutes. This resulted in a semi-cured sheet. When the obtained semi-cured sheet was measured at 25-300°C using a differential scanning calorimeter, a heat generation peak was observed, confirming that the resin in the semi-cured sheet was in a semi-cured state. Figure 2 shows one of the images of the cross section of the obtained semi-cured sheet observed at 200 times by SEM.
図２から分かるように、得られた半硬化シートでは、樹脂の半硬化物が、複数の塊状窒化ホウ素粒子のそれぞれの内部に充填されており、複数の塊状窒化ホウ素粒子同士の間には空隙が形成されていた。塊状窒化ホウ素粒子内の樹脂の半硬化物が充填されている面積に対する、塊状窒化ホウ素粒子内の隙間の面積の割合は、１面積％であった。樹脂の半硬化物及び塊状窒化ホウ素粒子の面積Ａ１と塊状窒化ホウ素粒子間の空隙の面積Ａ２との合計に対する、樹脂の半硬化物及び塊状窒化ホウ素粒子の面積Ａ１の比（Ａ１／（Ａ１＋Ａ２））は、０．７５であった。半硬化シートの任意の５個の断面を観察したときに、１個の断面に占める樹脂の半硬化物及び複数の塊状窒化ホウ素粒子の面積が３０面積％以下となる断面は０個であった。As can be seen from FIG. 2, in the obtained semi-cured sheet, the semi-cured resin was filled inside each of the multiple aggregate boron nitride particles, and gaps were formed between the multiple aggregate boron nitride particles. The ratio of the area of the gaps in the aggregate boron nitride particles to the area filled with the semi-cured resin in the aggregate boron nitride particles was 1 area %. The ratio (A1/(A1+A2)) of the area A1 of the semi-cured resin and aggregate boron nitride particles to the sum of the area A1 of the semi-cured resin and aggregate boron nitride particles and the area A2 of the gaps between the aggregate boron nitride particles was 0.75. When five arbitrary cross sections of the semi-cured sheet were observed, there were no cross sections in which the area of the semi-cured resin and multiple aggregate boron nitride particles in one cross section was 30 area % or less.
続いて、半硬化シートに対して、圧力１５ＭＰａ、温度１５０℃の条件で６０分間の加熱及び加圧を行うことにより、樹脂を更に硬化させて、厚み１００μｍの硬化シートを得た。得られた硬化シートの断面をＳＥＭにより３００倍で観察した画像の一つを図３に示す。The semi-cured sheet was then heated and pressurized at a pressure of 15 MPa and a temperature of 150°C for 60 minutes to further cure the resin and obtain a cured sheet with a thickness of 100 μm. Figure 3 shows an image of the cross section of the obtained cured sheet observed at 300 times by SEM.
＜硬化シート中の塊状窒化ホウ素粒子の平均粒子径＞
得られた硬化シートの断面のＳＥＭ像において、５個の塊状窒化ホウ素粒子について最大長さをそれぞれ測定した。この最大長さの測定を硬化シートの異なる断面のＳＥＭ像５枚について行い、測定されたすべての塊状窒化ホウ素粒子の最大長さの平均値を硬化シート中の平均粒子径として求めた。実施例１の硬化シート中の塊状窒化ホウ素粒子の平均粒子径は、６０μｍであった。
<Average particle size of boron nitride particles in the cured sheet>
In the SEM images of the cross sections of the obtained cured sheet, the maximum length of each of the five aggregate boron nitride particles was measured. This measurement of the maximum length was performed on five SEM images of different cross sections of the cured sheet, and the average value of the maximum lengths of all the measured aggregate boron nitride particles was calculated as the average particle size in the cured sheet. The average particle size of the aggregate boron nitride particles in the cured sheet of Example 1 was 60 μm.
＜耐電圧の測定＞
耐電圧試験機（菊水電子工業製 ＴＯＳ５１０１）を用いて、ＪＩＳ Ｃ２１１０－１に従って得られた硬化シートの耐電圧を測定した。実施例１の硬化シートの耐電圧の最小値は、３７ｋＶ／ｍｍであった。
<Measurement of withstand voltage>
The withstand voltage of the obtained cured sheet was measured in accordance with JIS C2110-1 using a withstand voltage tester (TOS5101 manufactured by Kikusui Electronics Co., Ltd.) The minimum withstand voltage of the cured sheet of Example 1 was 37 kV/mm.
＜熱伝導率の測定＞
得られた硬化シートから、１０ｍｍ×１０ｍｍの大きさの測定用試料を切り出し、キセノンフラッシュアナライザ（ＮＥＴＺＳＣＨ社製、ＬＦＡ４４７ＮａｎｏＦｌａｓｈ）を用いたレーザーフラッシュ法により、測定用試料の熱拡散率Ａ（ｍ２／秒）を測定した。また、測定用試料の比重Ｂ（ｋｇ／ｍ３）をアルキメデス法により測定した。また、測定用試料の比熱容量Ｃ（Ｊ／（ｋｇ・Ｋ））を、示差走査熱量計（ＤＳＣ；リガク社製、ＴｈｅｒｍｏＰｌｕｓＥｖｏＤＳＣ８２３０）を用いて測定した。これらの測定値を用いて、熱伝導率Ｈ（Ｗ／（ｍ・Ｋ））＝Ａ×Ｂ×Ｃの式から、硬化シートの熱伝導率を算出した。実施例１の硬化シートの熱伝導率は、１９Ｗ／ｍ・Ｋであり、１５Ｗ／ｍ・Ｋ以上の高い値であった。
<Measurement of thermal conductivity>
A measurement sample having a size of 10 mm x 10 mm was cut out from the obtained cured sheet, and the thermal diffusivity A (m 2 /sec) of the measurement sample was measured by a laser flash method using a xenon flash analyzer (NETZSCH, LFA447NanoFlash). The specific gravity B (kg/m 3 ) of the measurement sample was measured by the Archimedes method. The specific heat capacity C (J/(kg·K)) of the measurement sample was measured using a differential scanning calorimeter (DSC; Rigaku, ThermoPlusEvoDSC8230). Using these measured values, the thermal conductivity of the cured sheet was calculated from the formula thermal conductivity H (W/(m·K)) = A×B×C. The thermal conductivity of the cured sheet of Example 1 was 19 W/m·K, which was a high value of 15 W/m·K or more.
（実施例２）
平均粒子径：７０μｍ、塊状窒化ホウ素粒子内の隙間の体積：５０体積％の塊状窒化ホウ素粒子を用いた以外は、実施例１と同様に硬化シートを製造した。硬化シートの厚みは、１００μｍであった。硬化シートにおける塊状窒化ホウ素粒子の平均粒子径は、５０μｍであった。硬化シートの耐電圧の最小値は、４０ｋＶ／ｍｍであった。硬化シートの任意の５個の断面を実施例１と同様に観察したときに、塊状窒化ホウ素粒子間にボイドが発生している断面が０個であった。
Example 2
A cured sheet was produced in the same manner as in Example 1, except that aggregate boron nitride particles having an average particle size of 70 μm and a gap volume within the aggregate boron nitride particles of 50 volume % were used. The thickness of the cured sheet was 100 μm. The average particle size of the aggregate boron nitride particles in the cured sheet was 50 μm. The minimum voltage resistance of the cured sheet was 40 kV/mm. When five random cross sections of the cured sheet were observed in the same manner as in Example 1, there were no cross sections in which voids occurred between the aggregate boron nitride particles.
（実施例３）
平均粒子径：１１０μｍ、塊状窒化ホウ素粒子内の隙間の体積：５０体積％の塊状窒化ホウ素粒子を用い、半硬化シートの厚みを４００μｍに変更した以外は、実施例１と同様に硬化シートを製造した。硬化シートの厚みは、２５０μｍであった。硬化シートにおける塊状窒化ホウ素粒子の平均粒子径は、９０μｍであった。硬化シートの耐電圧の最小値は、３２ｋＶ／ｍｍであった。硬化シートの任意の５個の断面を実施例１と同様に観察したときに、塊状窒化ホウ素粒子間にボイドが発生している断面が０個であった。
Example 3
A cured sheet was produced in the same manner as in Example 1, except that aggregate boron nitride particles having an average particle size of 110 μm and a volume of gaps within the aggregate boron nitride particles of 50 volume % were used, and the thickness of the semi-cured sheet was changed to 400 μm. The thickness of the cured sheet was 250 μm. The average particle size of the aggregate boron nitride particles in the cured sheet was 90 μm. The minimum voltage resistance of the cured sheet was 32 kV/mm. When five random cross sections of the cured sheet were observed in the same manner as in Example 1, there were no cross sections in which voids occurred between the aggregate boron nitride particles.
実施例２，３のとおり、平均粒子径が異なる塊状窒化ホウ素粒子を用いた場合においても、ボイドが無く良好な硬化シートが得られることを確認できた。なお、実施例２及び実施例３のいずれにおいても、半硬化シートでは、樹脂の半硬化物が、複数の塊状窒化ホウ素粒子のそれぞれの内部に充填されており、複数の塊状窒化ホウ素粒子同士の間には空隙が形成されていた。実施例２及び実施例３のいずれにおいても、半硬化シートにおける上記の比（Ａ１／（Ａ１＋Ａ２））が０．４以上０．７以下の範囲にあり、半硬化シートの任意の５個の断面を観察したときに、１個の断面に占める樹脂の半硬化物及び複数の塊状窒化ホウ素粒子の面積が３０面積％以下となる断面は０個であり、塊状窒化ホウ素粒子内の隙間の面積の割合は１０面積％以下であった。実施例２及び実施例３のいずれにおいても、硬化シートの熱伝導率は、１５Ｗ／ｍ・Ｋ以上の高い値であった。As in Examples 2 and 3, it was confirmed that a good cured sheet without voids could be obtained even when using aggregated boron nitride particles with different average particle sizes. In both Examples 2 and 3, the semi-cured sheet had a semi-cured resin filled inside each of the aggregated boron nitride particles, and gaps were formed between the aggregated boron nitride particles. In both Examples 2 and 3, the above ratio (A1/(A1+A2)) in the semi-cured sheet was in the range of 0.4 to 0.7, and when any five cross sections of the semi-cured sheet were observed, there were no cross sections in which the area of the semi-cured resin and the aggregated boron nitride particles was 30 area % or less, and the ratio of the area of the gaps in the aggregated boron nitride particles was 10 area % or less. In both Examples 2 and 3, the thermal conductivity of the cured sheet was a high value of 15 W/m·K or more.
Claims (3)
前記混合物をシート状に成形すると共に、前記混合物中の前記樹脂を半硬化させて半硬化シートを得る第２の工程と、
前記半硬化シートに対して加圧すると共に、前記半硬化シート中の前記樹脂を更に硬化させて硬化シートを得る第３の工程と、を備え、
前記樹脂組成物中の不揮発分の体積が、前記混合物に含まれる前記塊状窒化ホウ素粒子内の隙間の全体積に対して、０．９～１．１倍である、硬化シートの製造方法。 A first step of mixing a resin composition containing a resin with aggregate boron nitride particles having an average particle size of 45 μm or more to obtain a mixture;
a second step of forming the mixture into a sheet and semi-curing the resin in the mixture to obtain a semi-cured sheet;
and a third step of applying pressure to the semi-cured sheet and further curing the resin in the semi-cured sheet to obtain a cured sheet.
a volume of non-volatile matter in the resin composition is 0.9 to 1.1 times the total volume of the gaps in the aggregate boron nitride particles contained in the mixture.
前記樹脂組成物と前記塊状窒化ホウ素粒子とを混練して第１の組成物を得る第１の混練工程と、
前記第１の組成物を脱気する脱気工程と、
脱気後の前記第１の組成物を混練して第２の組成物を得る第２の混練工程と、を含む、請求項１に記載の製造方法。 The first step comprises:
a first kneading step of kneading the resin composition and the aggregate boron nitride particles to obtain a first composition;
a degassing step of degassing the first composition;
and a second kneading step of kneading the degassed first composition to obtain a second composition.
半硬化させた前記樹脂が、前記塊状窒化ホウ素粒子の内部に充填されており、
前記塊状窒化ホウ素粒子同士の間に空隙が形成されている、請求項１又は２に記載の製造方法。 In the semi-cured sheet,
The semi-cured resin is filled inside the aggregate boron nitride particles,
The method according to claim 1 or 2, wherein voids are formed between the chunks of boron nitride particles.
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| JP2017222522A (en) | 2016-06-13 | 2017-12-21 | 株式会社トクヤマ | Hexagonal boron nitride powder and method for producing the same |
| WO2018066277A1 (en) | 2016-10-07 | 2018-04-12 | デンカ株式会社 | Boron nitride aggregated grain, method for producing same, and thermally conductive resin composition using same |
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