WO2019235593A1 - Corps fritté à base de nitrure de silicium lamellaire et son procédé de production - Google Patents

Corps fritté à base de nitrure de silicium lamellaire et son procédé de production Download PDF

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Publication number
WO2019235593A1
WO2019235593A1 PCT/JP2019/022621 JP2019022621W WO2019235593A1 WO 2019235593 A1 WO2019235593 A1 WO 2019235593A1 JP 2019022621 W JP2019022621 W JP 2019022621W WO 2019235593 A1 WO2019235593 A1 WO 2019235593A1
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silicon nitride
sintered body
earth metal
measured
plate
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PCT/JP2019/022621
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English (en)
Japanese (ja)
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卓司 王丸
耕司 柴田
道夫 本田
昌孝 藤永
山田　哲夫
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宇部興産株式会社
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Priority to JP2020523187A priority Critical patent/JP7062229B2/ja
Publication of WO2019235593A1 publication Critical patent/WO2019235593A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
    • C04B35/587—Fine ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
    • C04B35/593—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride obtained by pressure sintering
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/03—Use of materials for the substrate

Definitions

  • the present invention relates to a plate-like silicon nitride sintered body containing ⁇ -type silicon nitride as a main component, and particularly has a high thermal conductivity and a high mechanical strength and toughness, and is suitable for use as an insulating substrate and a circuit board.
  • the present invention relates to a shaped silicon nitride sintered body and a method for producing the same.
  • the silicon nitride sintered body is excellent in mechanical strength, toughness, thermal shock resistance, etc., so it is used for various machine parts and wear-resistant parts. In addition, it uses high electrical insulation and excellent thermal conductivity for electrical insulation. It is also applied to materials.
  • As conventional electrical insulating ceramics aluminum oxide, aluminum nitride and the like are known. Since aluminum oxide has low thermal conductivity, there is a problem that heat dissipation is insufficient for application to a power semiconductor or the like. On the other hand, aluminum nitride has a high thermal conductivity and excellent heat dissipation, but has a problem of cracking in the assembly process of the module because of its low mechanical strength and fracture toughness.
  • a circuit board on which a semiconductor element is mounted has a problem that due to a difference in thermal expansion from the semiconductor element, a crack or breakage occurs due to a thermal cycle, and the mounting reliability is lowered.
  • a plate-like silicon nitride sintered body that has both high thermal conductivity and excellent mechanical properties (strength and toughness) at a particularly high level.
  • Patent Document 1 describes a silicon nitride sintered body having a fracture toughness of 6 MPa ⁇ m or more and a thermal conductivity of 60 W / (m ⁇ K), but Al 2 O 3 is used as a sintering aid. Because of adding 0.1 wt% or more, the fracture toughness value is 7.4 MPa ⁇ m or less, and the thermal conductivity is 78 W / (m ⁇ K) or less.
  • D 10 , D 50 and D 90 have a particle size distribution of 0.5 to 0.8 ⁇ m, 2.5 to 4.5 ⁇ m and 7.5 to 10.0 ⁇ m, respectively,
  • a silicon nitride powder having an amount of 0.01 to 0.5 wt% and a ratio of ⁇ -type silicon nitride particles present in particles having an average particle diameter (D 50 ) or more is 1 to 50% has improved sheet formability. It is described that a sintered body having excellent, high strength, high toughness and excellent heat dissipation is provided. However, because the MgO / Y 2 O 3 weight ratio is 3.0, the bending strength is 850 MPa or less and the fracture toughness value is 7.5 MPa ⁇ m or less.
  • Patent Document 3 when the cut surface of the silicon nitride sintered body is observed, the number of columnar ⁇ -type silicon nitride particles whose major axis exceeds 10 ⁇ m is 20000 per mm 2. Silicon nitride having a thermal conductivity of 75 W / (m ⁇ K) or more at room temperature, 45 W / (m ⁇ K) or more from room temperature to 200 ° C., and a three-point bending strength of 800 MPa or more at room temperature Providing a sintered body is described.
  • the ⁇ fraction is 30 to 100%
  • the oxygen amount is less than 0.5 wt%
  • the average particle diameter is 0.2 to 10 ⁇ m
  • the aspect ratio is 10 or less
  • the particles The silicon nitride powder containing columnar particles in which grooves are formed in the major axis direction and having an Fe content and an Al content of 100 ppm or less, respectively, without requiring a high-cost firing method such as high-temperature and high-pressure firing, It is described that a silicon nitride sintered body having high thermal conductivity and high strength can be provided.
  • the bending strength is 850 MPa or less because the oxygen content of the raw material Si 3 N 4 powder is remarkably small, the average particle diameter is large, the amount of impurity Fe is high, and the MgO / RExOy weight ratio is 1.5 or more.
  • the fracture toughness value is not measured.
  • a silicon nitride substrate comprising a body is disclosed.
  • the MgO / Y 2 O 3 weight ratio calculated from the sintering aid composition described in Table 1 showing Examples and Comparative Examples is 0.055 to 0.194 (wt / wt), The blending ratio of MgO is small. For this reason, although the electrical characteristics of the obtained silicon nitride substrate are excellent, the bending strength remains at a low value of 750 MPa or less.
  • Patent Document 6 discloses a silicon nitride substrate in which the orientation ratio of silicon nitride particles in a plane perpendicular to the thickness direction is defined.
  • the three-point bending strength and the fracture toughness value of the obtained silicon nitride sintered body remain at 6.8 MPa ⁇ m or less because the weight ratio and addition amount of the sintering aid are different.
  • Patent Document 7 discloses a silicon nitride substrate in which the grain boundary phase is composed of an amorphous phase and a MgSiN 2 crystal phase, and does not include a crystal phase containing a rare earth element (RE), thereby improving thermal conductivity.
  • RE rare earth element
  • Patent Document 8 discloses characteristic values of a silicon nitride sintered body using, as a raw material, silicon nitride powder having a specific surface area of 5 to 30 m 2 / g produced by rotary kiln firing.
  • Tables 3 and 4 bending of silicon nitride sintered bodies obtained by adding yttrium oxide and aluminum oxide as sintering aids and sintering at 1780 ° C. for 2 hours in a nitrogen gas atmosphere, respectively.
  • the bending strength of the silicon nitride sintered body obtained by sintering at 1780 ° C. for 2 hours in a nitrogen gas atmosphere is 1020 to 1220 MPa. It is common knowledge of those skilled in the art that the silicon nitride sintered body to which aluminum oxide is added exhibits a remarkably low thermal conductivity.
  • the silicon nitride sintered body added with yttrium oxide and magnesium oxide shows a high thermal conductivity of 130 to 142 W / mK, but at a high temperature and a long time of 1900 ° C.-22 hours. In sintering, grain growth proceeds remarkably, so that only a low bending strength of 605 to 660 MPa is obtained. That is, a silicon nitride sintered body having both high thermal conductivity and excellent mechanical strength has not been obtained, and it is difficult to achieve both high thermal conductivity and excellent mechanical strength.
  • Patent Document 3 in order to achieve both high thermal conductivity and high mechanical strength, a high atmospheric pressure of 40 atm (4 MPa) or more is required, and thus a sintering furnace that can be used under high pressure is required. . As can be seen from the examples, at 9 atm (0.9 MPa), the characteristics are remarkably insufficient in both thermal conductivity and mechanical strength.
  • the present invention does not increase the atmospheric pressure during sintering as in Patent Document 3, and at a lower pressure, a plate-like silicon nitride-based ceramic having both high thermal conductivity and excellent mechanical properties.
  • the purpose is to provide ligation.
  • the inventors have determined that a specific specific surface area and oxygen Using silicon nitride powder having a content as a raw material, in combination with sheet forming conditions, by highly controlling grain growth in the sintering process, high thermal conductivity without increasing the atmospheric pressure during sintering It has been found that a silicon nitride sintered body having excellent mechanical properties (strength and fracture toughness) can be produced, and the present invention has been completed. That is, the present invention relates to the following matters.
  • the ratio of the measured alkaline earth metal content to the measured rare earth metal content as the sintered body is 0.26 ⁇ measured alkaline earth metal content / measured rare earth metal.
  • X-rays are applied to the surface where the content is ⁇ 1.30, the measured aluminum content is less than 50 ppm, the relative density is 98% or more, and the arithmetic average roughness Ra is 0.05 ⁇ m or more and 0.5 ⁇ m or less.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride obtained when irradiated with More than 0.95 and the number of columnar ⁇ -type silicon nitride particles whose major axis exceeds 10 ⁇ m when the cut surface perpendicular to the plate surface of the silicon nitride sintered body is observed. There, more than 500 per 1mm 2 1000 And characterized in that number or less.
  • This plate-like silicon nitride sintered body can be manufactured by sintering a plate-like formed body produced by a sheet forming process at an atmospheric gas pressure of 3 MPa or less.
  • the ratio between the measured alkaline earth metal content and the measured rare earth metal content of the sintered body is determined by comparing the ratio of the alkaline earth metal oxide and the rare earth metal oxide in the sintered body on an oxide basis. In terms of weight ratio, 0.34 ⁇ alkaline earth metal oxide / rare earth metal oxide ⁇ 1.95.
  • the plate-like silicon nitride sintered body has a thickness of 1.5 mm or less and a thickness / area ratio of 0.015 (1 / mm) or less.
  • the removal amount of the surface layer portion perpendicular to the thickness direction by grinding or polishing is preferably 0.03 mm or less per side.
  • the plate-like silicon nitride sintered body is characterized in that the measured oxygen content as the sintered body is 1.4 wt% or more and 2.9 wt% or less. .
  • the alkaline earth metal oxide is magnesium oxide
  • the rare earth metal oxide is at least one oxide selected from yttrium oxide, erbium oxide, scandium oxide, and lutetium oxide. To do.
  • the auxiliary element-derived metal element content which is the sum of the measured magnesium content as the sintered body and the measured rare earth metal content, is 1.8 wt% to 5.0 wt%. It is the above-mentioned plate-like silicon nitride sintered body.
  • the actual measured content of the magnesium as the sintered body and the rare earth metal are summed, it is converted into the total content of the magnesium oxide and the rare earth metal oxide in the sintered body based on the oxide. 2.7% to 6.8% by weight.
  • the open porosity on the surface polished to an arithmetic average roughness Ra of 0.06 ⁇ m or more and 0.4 ⁇ m or less is 1.0% or less, and the maximum opening diameter of the open pores is 1.0 ⁇ m. It is characterized by the following.
  • the silicon nitride sintered body is a plate-like silicon nitride sintered body in which uneven color tone is suppressed.
  • One aspect of the present invention is characterized in that a crystal phase of an Mg compound composed of MgSiN 2 or the like is substantially not included in a grain boundary of the silicon nitride sintered body.
  • the thermal conductivity is 90 W / (m ⁇ K) or more at room temperature
  • the four-point bending strength is 900 MPa or more at room temperature
  • K IC is 7.6 MPa ⁇ m or more.
  • the ratio of the measured magnesium content as the sintered body to the measured rare earth metal content is 0.26 ⁇ measured magnesium content / measured rare earth metal content ⁇ 1.05,
  • the auxiliary element-derived metal element content obtained by adding together the measured magnesium content and the measured rare earth metal content is 2.4 wt% to 4.0 wt%.
  • the ratio is 0.34 ⁇ magnesium oxide.
  • Content / rare earth metal oxide content ⁇ 1.37, and the total content of magnesium oxide and rare earth metal oxide is 3.4 wt% to 5.8 wt%.
  • the measured oxygen content as a sintered body is 1.75 wt% or more and 2.10 wt% or less.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride is 0. 69 to 0.87.
  • the number of columnar ⁇ -type silicon nitride particles having a long axis exceeding 10 ⁇ m is, characterized in that per 1 mm 2 is 1000 or more 5000 or less.
  • the thermal conductivity is 100 W / (m ⁇ K) or more at room temperature
  • the four-point bending strength is 1000 MPa or more at room temperature
  • the fracture toughness value measured by IF method (indentation method) K IC is 9.0 MPa ⁇ m or more.
  • the silicon nitride material has a specific surface area of 13.0 m 2 / g or more, an oxygen content of 1.2 wt% or more and 2.3 wt% or less, and an aluminum content of less than 50 ppm.
  • Silicon powder is used as a sintering aid, and the weight ratio of alkaline earth metal oxide to rare earth metal oxide satisfies 0.40 ⁇ alkaline earth metal oxide / rare earth metal oxide ⁇ 2.0. In such a compounding ratio, 3.2 to 7.0 wt% of an alkaline earth metal oxide and a rare earth metal oxide are added, and a starting composition (green sheet manufacturing raw material for manufacturing a silicon nitride sintered body) is obtained.
  • a plate-shaped molded body (green sheet) from the starting composition by a sheet molding process, and the plate-shaped molded body (green sheet) under a pressurized atmosphere with a nitrogen-containing gas pressure of 0.15 to 3 MPa.
  • the ratio of the measured alkaline earth metal content to the measured rare earth metal content is 0.26 ⁇ measured alkaline earth metal content / measured rare earth.
  • a plate-like silicon nitride sintered body having a metal content ⁇ 1.30, an actually measured aluminum content of less than 50 ppm, and a relative density of 98% or more is produced.
  • the plate-like silicon nitride sintered body having an actually measured oxygen content of 1.4 wt% or more and 2.9 wt% or less is manufactured.
  • the alkaline earth metal oxide is magnesium oxide
  • the rare earth metal oxide is at least one oxide selected from yttrium oxide, erbium oxide, scandium oxide, and lutetium oxide.
  • a silicon nitride-based sintered body is produced.
  • the weight ratio of magnesium oxide and rare earth metal oxide satisfies a ratio of 0.40 ⁇ magnesium oxide / rare earth metal oxide ⁇ 1.4, 4.0 to 6.0 wt% of magnesium oxide and rare earth metal oxide are added, and a plate-like molded body (green sheet) produced by a sheet molding process is added with a nitrogen-containing gas pressure of 0.15 to 0.9 MPa.
  • Sintering by holding for 6 to 20 hours at the maximum holding temperature in a temperature range of 1790 ° C or higher and 1880 ° C or lower in a pressurized atmosphere, and the measured magnesium content and measured rare earth metal content.
  • the ratio is 0.26 ⁇ measured magnesium content / measured rare earth metal content ⁇ 1.05, the measured aluminum content is less than 50 ppm, and the relative density is 98% or less. Characterized in that to produce a plate-shaped silicon nitride sintered body is.
  • an insulating substrate or circuit substrate using the plate-like silicon nitride sintered body described in the above paragraph.
  • a plate-like silicon nitride sintered body having both high thermal conductivity and excellent mechanical properties is provided. It can be manufactured without increasing the atmospheric pressure during sintering.
  • the silicon nitride sintered body In a silicon nitride sintered body, heat is transferred by lattice vibration (phonon). For this reason, phonon scattering by different ions causes a decrease in thermal conductivity.
  • the silicon nitride sintered body is composed of a silicon nitride particle phase and a grain boundary phase thereof. Since the thermal conductivity of the grain boundary phase is low, the thermal conductivity decreases as the grain boundary phase amount increases. Furthermore, since the pores remaining in the silicon nitride sintered body significantly reduce the thermal conductivity, it is necessary to be a dense sintered body.
  • the weight ratio of alkaline earth metal oxide to rare earth metal oxide is 0.40 ⁇ alkali as a sintering aid in the silicon nitride powder.
  • Alkaline earth metal oxide and rare earth metal oxide based on the total weight of the silicon nitride powder and the sintering aid, at a blending ratio satisfying earth metal oxide / rare earth metal oxide ⁇ 2.0 3.2-7.0 wt% is added, and the plate-like molded body produced by the sheet molding process is sintered at an atmospheric gas pressure of 3 MPa or less, and the measured alkaline earth metal content and measured rare earth as the sintered body Sintering in which the metal content ratio is 0.26 ⁇ measured alkaline earth metal content / measured rare earth metal content ⁇ 1.30, the measured aluminum content is less than 50 ppm, and the relative density is 98% or more. Let it be the body.
  • the ratio of the measured alkaline earth metal content and the measured rare earth metal content of the sintered body to the weight ratio of the alkaline earth metal oxide and the rare earth metal oxide in the sintered body on the basis of oxides 0.34 ⁇ alkaline earth metal oxide / rare earth metal oxide ⁇ 1.95.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of the ⁇ -type silicon nitride of the plate-like silicon nitride sintered body The measurement is performed by performing X-ray diffraction measurement on the surface polished with an arithmetic average roughness Ra of 0.05 ⁇ m to 0.5 ⁇ m. If the arithmetic average roughness Ra of the surface is not within this range, the I (101) / I (210) ratio cannot be measured accurately.
  • the arithmetic average roughness Ra of the surface of the silicon nitride sintered body is 0.05 ⁇ m or more and 0.5 ⁇ m or less
  • X-ray diffraction measurement may be performed on the surface of the sintered body.
  • the surface of the sintered body is polished so that the arithmetic average roughness Ra is 0.05 ⁇ m or more and 0.5 ⁇ m or less. Then, X-ray diffraction measurement is performed on the polished surface.
  • the polishing method for making the arithmetic average roughness Ra of the surface 0.05 ⁇ m or more and 0.5 ⁇ m or less is not particularly limited, and the polishing amount may be the minimum necessary to realize the arithmetic average roughness Ra, Generally, for example, about 10 ⁇ m is sufficient in the depth direction.
  • the X-ray diffraction pattern intensities on the (101) plane and the (210) plane are measured.
  • the diffraction intensity ratio I (101) / I (210) of the (101) plane of ⁇ -type silicon nitride of the silicon nitride sintered body is polished to an arithmetic average roughness Ra of 0.05 ⁇ m to 0.5 ⁇ m.
  • the surface of the silicon nitride sintered body of the present invention does not have to have an arithmetic average roughness Ra of 0.05 ⁇ m or more and 0.5 ⁇ m or less. May be.
  • the weight ratio of the alkaline earth metal oxide to the rare earth metal oxide (alkaline earth metal oxide / rare earth metal oxide) in the blending composition is less than 0.40, the ratio of the rare earth metal oxide increases.
  • the melting temperature of the grain boundary phase rises during the sintering process.
  • silica SiO 2
  • the relative density of the sintered body is lowered and a dense sintered body cannot be obtained.
  • the alkaline earth metal oxide / rare earth metal oxide representing the weight ratio of the alkaline earth metal oxide and the rare earth metal oxide is less than 0.40, or a value exceeding 2.0
  • the mechanical properties (strength and fracture toughness) are lowered, which is not preferable.
  • the weight ratio of the alkaline earth metal oxide / rare earth metal oxide in the blending composition is 0.43 or more, 0.45 or more, 0.50 or more, 1.40 or less, 1.00 or less, 0.66. It may be the following.
  • the addition amount of the alkaline earth metal oxide and rare earth metal oxide is less than 3.2 wt%, a high-density sintered body cannot be obtained, resulting in a decrease in thermal conductivity and mechanical properties (strength and fracture toughness). descend. Even if the addition amount of alkaline earth metal oxide and rare earth metal oxide exceeds 7.0 wt%, the mechanical properties (strength and fracture toughness) are hardly lowered, but the thermal conductivity is lowered, which is not preferable.
  • the addition amount of the alkaline earth metal oxide and the rare earth metal oxide is preferably 4.0 wt% or more and 6.0 wt% or less.
  • the addition amount of the alkaline earth metal oxide is more preferably 2.9 wt% or less.
  • the alkaline earth metal oxide and rare earth metal oxide added as a sintering aid is used in the sintering process. Part volatilizes by evaporation together with the silica component in the silicon nitride raw material. For this reason, the content of the sintering aid mainly contained in the grain boundaries of the silicon nitride sintered body differs from the composition of the starting material.
  • the ratio between the measured alkaline earth metal content and the measured rare earth metal content as the sintered body is 0.26 ⁇ measured alkaline earth metal content / measured rare earth metal content ⁇ 1.30.
  • the measured aluminum content is less than 50 ppm.
  • the measured alkaline earth metal / measured rare earth metal is less than 0.26, the relative density of the sintered body is lowered. Further, even if the measured alkaline earth metal content / measured rare earth metal content is less than 0.26, even if it is a value exceeding 1.30, the mechanical properties (strength and fracture toughness) are reduced, It is not preferable.
  • the weight ratio of the measured alkaline earth metal content / measured rare earth metal content of the sintered body may be 0.30 or more, 0.37 or more, 0.80 or less, or 0.55 or less.
  • the thermal conductivity of the grain boundary phase is low in the silicon nitride sintered body, the thermal conductivity decreases as the amount of the grain boundary phase increases.
  • the oxygen content is too low, densification becomes difficult, pores remain, and the thermal conductivity is significantly reduced. For this reason, it is necessary to reduce the oxygen content of the sintered body within a range where no pores remain.
  • the actually measured oxygen content of the silicon nitride sintered body in the present invention is 1.4 wt% or more and 2.9 wt% or less, preferably 1.4 wt% or more and 2.4 wt% or less, more preferably 1.75% by weight or more and 2.10% by weight or less.
  • the relative density of the sintered body becomes less than 98%.
  • a crystal phase is precipitated at the grain boundaries of the plate-like silicon nitride sintered body and color unevenness occurs, it is not preferable.
  • a plate-like silicon nitride sintered body having an actually measured oxygen content exceeding 2.9% by weight is not preferable because the thermal conductivity is lowered. Furthermore, when it joins directly with metal plates, such as copper and aluminum, a void generate
  • magnesium oxide is preferably used, and as the rare earth metal oxide, at least one oxide selected from yttrium oxide, erbium oxide, scandium oxide, and lutetium oxide is preferably used. Note that magnesium oxynitride or magnesium nitride may be used instead of magnesium oxide.
  • the weight ratio of magnesium oxide to rare earth metal oxide in the composition is preferably 0.40 ⁇ magnesium oxide / rare earth metal oxide ⁇ 1.4, and 0.40 ⁇ magnesium oxide / rare earth metal oxide ⁇ 1. It is more preferable that it is 0. Furthermore, it is particularly preferable that 0.40 ⁇ magnesium oxide / rare earth metal oxide ⁇ 0.66.
  • the ratio of the measured magnesium content to the measured rare earth metal content as the sintered body is 0.26.
  • ⁇ Measured magnesium content / measured rare earth metal content ⁇ 1.05, more preferably 0.26 ⁇ measured magnesium content / measured rare earth metal content ⁇ 0.75. Furthermore, it is particularly preferable that 0.26 ⁇ measured magnesium content / measured rare earth metal content ⁇ 0.49.
  • part of magnesium oxide and rare earth metal oxide added as a sintering aid is volatilized by evaporation together with the silica component in the silicon nitride raw material. Furthermore, nitrogen dissolves in the grain boundary phase that is in a molten state at a high temperature.
  • the plate-like silicon nitride sintered body of the present invention is characterized in that uneven color tone is suppressed.
  • the suppression of uneven color tone means that the material is highly reliable and does not easily deteriorate due to application of a stress cycle or thermal cycle.
  • the grain boundary of the plate-like silicon nitride sintered body of the present invention does not substantially contain a crystal phase of Mg compound made of MgSiN 2 or the like.
  • the fact that the crystal phase composed of MgSiN 2 is substantially not included means that the (121) X-ray diffraction peak intensity of the MgSiN 2 crystal phase constitutes the ⁇ -type silicon nitride constituting the silicon nitride sintered body Less than 0.0005 times the sum of X-ray diffraction peak intensities of (110), (200), (101), (210), (201), (310), (320) and (002) planes It means that.
  • the mechanical properties (bending strength and fracture toughness) of the silicon nitride sintered body tend to decrease. It is in. Specifically, the plate-like silicon nitride having a four-point bending strength in the present invention of 900 MPa or more at room temperature and a fracture toughness value K IC measured by IF method (indentation method) of 7.6 MPa ⁇ m or more. Since a sintered body cannot be obtained, it is not preferable.
  • magnesium oxide and yttrium oxide are preferably added as a sintering aid, and the addition amount is 4.0 wt% or more and 6.0 wt% or less, and its weight
  • a plate-like molded body (green sheet) produced by the sheet molding process is sintered at an atmospheric gas pressure of 3 MPa or less.
  • a sintered body having a relative density of 98% or more is obtained.
  • sintering is performed by holding for 6 to 20 hours at a maximum holding temperature of 1790 ° C. or higher and 1880 ° C.
  • a pressurized atmosphere with a nitrogen-containing gas pressure of 0.15 to 0.9 MPa, and a relative density of 98. % Or more, preferably 99.0% or more of a sintered body is obtained.
  • holding at a constant temperature for a certain time in a temperature range from 1520 ° C. to the maximum holding temperature is also effective in reducing residual pores.
  • the temperature is held at a predetermined temperature in the range of 1520 ° C. to 1670 ° C. for 1 to 3 hours. It is one of the indispensable requirements of the present invention to produce a plate-like silicon nitride sintered body that is dense and has few residual pores.
  • the sheet molding method is also referred to as a tape molding method.
  • a slurry containing 8 parts by mass or more of an organic binder or a resin binder with respect to 100 parts by mass of the raw material powder using a device such as a doctor blade or a die coater.
  • a green sheet is produced by casting it at a predetermined thickness.
  • Green sheet production by an extrusion molding method or an injection molding method is also included in the sheet molding method, but in the present invention, the CIP molding method and the die press molding method are not included in the sheet molding method.
  • the bending strength cannot be compared with the bending strength of the plate-like silicon nitride sintered body of the present invention.
  • the sheet forming method itself is known, and a known sheet forming method may be used in the present invention.
  • PVB polyvinyl butyral
  • dispersants such as alkylpolyamine composition
  • plasticizer such as dimethyl phthalate
  • a green sheet forming slurry containing a solvent such as a mixed solvent is prepared and cast on a carrier film with a predetermined thickness using an apparatus such as a doctor blade or a die coater to produce a green sheet.
  • a correlation is observed between the coating speed in sheet molding and the orientation of the ⁇ -type silicon nitride particles after sintering.
  • the coating speed of the green sheet is related to other production conditions such as the slurry composition and the sheet thickness, but is generally, for example, 0.02 to 0.5 m / min, and further 0.05 to 0.3 m. / Min, 0.1 to 0.2 m / min.
  • the sheet molding and sintering conditions for producing the plate-like silicon nitride sintered body of the present invention are such that the degree of orientation of ⁇ -type silicon nitride particles and the number of columnar ⁇ -type silicon nitride particles exceeding 10 ⁇ m. Since it is selected to be within the predetermined range of the present invention, the specific coating speed of the green sheet is selected in relation to it.
  • the green sheet can be a laminated green sheet in consideration of the thickness after sintering.
  • a green sheet or a laminated green sheet (hereinafter simply referred to as a green sheet) produced by a sheet forming method is usually cut into a molded body having a predetermined shape.
  • a plurality of green sheet molded bodies are stacked with a separating material (typically boron nitride powder having a particle size of about 4 to 20 ⁇ m) interposed therebetween, Degreased and sintered.
  • a plurality of green sheet compacts are stacked and placed in a container such as boron nitride, heated to 400-600 ° C.
  • the organic binder component added in advance can be sufficiently degreased (removed).
  • this degreased body is heat-treated as described later to produce a sintered body.
  • it is cooled to room temperature, and the resulting silicon nitride sintered body is peeled off by the separating material layer to obtain a plate-like silicon nitride sintered body.
  • the obtained plate-like silicon nitride sintered body is usually a blast-polished silicon nitride sintered body for a substrate having a desired surface roughness.
  • the removal thickness by blast polishing may be, for example, an average value of about 20 ⁇ m or less.
  • a lapping process or the like may be performed after blast polishing or without blast polishing.
  • a molded body (green sheet) using an organic binder or a resin binder not only is it easy to generate coarse pores in the molded body due to the aggregation of the binder, but also a small amount of carbon remains in the molded body even after degreasing. Affects the grain growth in the sintering process, so that the mechanical properties (bending strength and fracture toughness) of the obtained silicon nitride sintered body are deteriorated. In particular, the influence is remarkable in a plate-like silicon nitride sintered body. Furthermore, it is known that in a silicon nitride sintered body, the microstructure (particle size and aspect ratio, grain boundary phase composition and crystal phase) differs between the sintered body surface and inside.
  • the bending strength of the test piece obtained by grinding and removing the surface layer portion where the defects such as pores and cracks are easily generated by 0.2 mm or more is higher than the bending strength of the test piece leaving the surface layer portion.
  • the bending strength of a silicon nitride sintered body changes depending on the amount of organic binder or resin binder used and the cutting / polishing process when preparing the test piece. Even if the bending strength of the obtained test piece has already been disclosed, it cannot be said that it is equivalent to the bending strength of the plate-like silicon nitride sintered body in the present invention, and an equivalent bending strength value has already been obtained. It did not mean that it was disclosed.
  • the plate-like silicon nitride sintered body in the present invention can be produced by a sheet forming process, but has a thickness of 1.5 mm or less, preferably 1.0 mm or less, and a thickness / area ratio of 0.00. That which is 015 (1 / mm) or less.
  • the removal amount of the surface layer portion perpendicular to the thickness direction by grinding or polishing is preferably 0.02 mm or less per side.
  • the thickness obtained by peeling off with this separating material layer is 1.5 mm or less, preferably It is a plate-like silicon nitride sintered body having a thickness of 1.0 mm or less, a thickness / area ratio of 0.015 (1 / mm) or less, and a plate surface layer perpendicular to the thickness direction by grinding or polishing.
  • the removal amount of the part may be 0.02 mm or less per side.
  • a high thermal conductivity silicon nitride substrate for a power module is required to have a thickness of 0.32 ⁇ 0.05 mm.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride is about 1.0 or Since the value exceeds 1.0, it is not preferable in terms of the balance between thermal conductivity and mechanical properties. Further, in order to increase the atmospheric gas pressure above 3 MPa, a special sintering furnace that can be used under high pressure is required, which is not preferable because the equipment cost is significantly increased.
  • the number of silicon particles is a large value of 15223 to 19022 per 1 mm 2 .
  • the joined body with the metal preferably has a durability of 2000 cycles or more when a temperature rising / falling cycle from ⁇ 40 ° C. to 180 ° C. is repeated. Even if the desired surface roughness can be realized by lapping, which increases the cost, the open average porosity on the surface polished to an arithmetic average roughness Ra of 0.06 ⁇ m or more and 0.4 ⁇ m or less is large. Since the maximum opening diameter of the pores is a value exceeding 1.0 ⁇ m, it is not preferable.
  • the nitrogen-containing gas pressure is less than 0.15 MPa
  • the maximum holding temperature during sintering cannot be increased to 1790 ° C. or higher. If the maximum holding temperature is less than 1790 ° C., it is difficult to obtain a dense plate-like silicon nitride sintered body having a slow sintering speed and a relative density of 98% or more.
  • a dense silicon nitride sintered body is obtained at a maximum holding temperature of less than 1790 ° C., the growth of the columnar ⁇ -type silicon nitride particles is insufficient, and the silicon nitride sintered material having low thermal conductivity is low.
  • the thermal conductivity of the plate-like silicon nitride sintered body is 90 W / (m ⁇ K) or more.
  • the maximum holding temperature exceeds 1880 ° C., the growth of the columnar ⁇ -type silicon nitride particles is remarkably fast, and the number of long axis lengths exceeding 10 ⁇ m exceeds 10,000 per 1 mm 2. Absent. Further, the maximum holding temperature may be 1800 ° C. or higher, or 1850 ° C. or lower.
  • the holding time in the temperature range of 1790 ° C. or higher and 1880 ° C. or lower is less than 6 hours, it is difficult to obtain a plate-like silicon nitride sintered body having a desired relative density and desired columnar ⁇ -type silicon nitride particles. If the holding time in the temperature range of 1790 ° C. or higher and 1880 ° C. or lower exceeds 20 hours, not only does the growth of the columnar ⁇ -type silicon nitride particles progress, but it takes a long time to produce a plate-like silicon nitride sintered body. However, this is not preferable because it leads to an increase in cost.
  • a plate-like silicon nitride sintered body obtained under sintering conditions in which the growth of columnar ⁇ -type silicon nitride particles having a maximum holding temperature of over 1880 ° C. and a holding time of over 20 hours has a long axis
  • the number of ⁇ -type silicon nitride particles having a length exceeding 10 ⁇ m is remarkably increased, and although the thermal conductivity is high, the mechanical properties are remarkably inferior.
  • the bending strength decreases to less than 700 MPa.
  • the holding time in the said temperature range may be 8 hours or more, or 14 hours or less.
  • the temperature is gradually cooled to 1000 ° C. at a temperature lowering rate of 200 ° C./hr or less, or in the range of 1450 ° C. to 1650 ° C. It is also possible to further improve the thermal conductivity and mechanical properties by holding at temperature for a certain time.
  • the thermal conductivity and bending strength can be increased.
  • a correlation was observed between the coating speed in sheet molding and the orientation of ⁇ -type silicon nitride particles after sintering.
  • the orientation of ⁇ -type silicon nitride particles after sintering is controlled by adjusting the coating speed.
  • the plate-like silicon nitride sintered body of the present invention has an arithmetic average roughness Ra on the surface polished to 0.05 ⁇ m or more and 0.5 ⁇ m or less, further 0.40 ⁇ m or less, and further 0.30 ⁇ m or less.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride obtained when X-rays are irradiated is 0. .62 or more and 0.95 or less.
  • the plate-like silicon nitride sintered body of the present invention has columnar ⁇ -type silicon nitride particles on the surface polished to an arithmetic average roughness Ra of 0.05 ⁇ m or more, 0.40 ⁇ m or less, and further 0.30 ⁇ m or less.
  • the ratio I (101) / I (210) indicating the orientation ratio may be 0.69 or more and 0.87 or less, and further 0.70 or more and 0.83 or less.
  • the silicon nitride raw material inevitably contains a small amount of fine ⁇ -type silicon nitride particles. Since the fine ⁇ -type silicon nitride particles are columnar, if the coating speed at the time of forming the sheet is increased, the fine ⁇ -type silicon nitride particles tend to tilt in a direction perpendicular to the thickness direction of the substrate. In the sintering process, columnar ⁇ -type silicon nitride particles grow with the fine ⁇ -type silicon nitride particles oriented in this way as the nucleus, so columnar ⁇ -type silicon nitride obtained after sintering can be obtained by changing the coating speed. The degree of orientation of the particles can be controlled. In the present invention, the orientation of ⁇ -type silicon nitride particles after sintering is controlled by adjusting the coating speed.
  • a plate-like silicon nitride sintered body is mainly composed of coarse columnar particles and fine columnar particles, and the degree of orientation of the columnar particles is greatly influenced by the coarse columnar particles.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride decreases, It contains more columnar particles in which the inclination of the long axis of the columnar particles with respect to the direction parallel to the surface of the bonded body (direction perpendicular to the thickness direction) is within 45 degrees.
  • the value of I (101) / I (210) approaching zero indicates that the inclination of the major axis of the columnar particles with respect to the direction parallel to the surface is close to 0 degrees. Reducing the inclination of the major axis of the columnar particles with respect to the direction parallel to the surface is advantageous for realizing high strength.
  • the value of I (101) / I (210) is controlled to 0.62 or more and 0.95 or less, so that the surface of the sintered body is
  • the inclination of the long axis of the columnar particles relative to the parallel direction (the direction perpendicular to the thickness direction) is a value suitable for both excellent mechanical properties (high strength and high fracture toughness) and high thermal conductivity. Therefore, it is suitable for insulating substrate applications.
  • Patent Document 9 discloses silicon nitride ceramics characterized in that the c-axis of columnar ⁇ silicon nitride particles is oriented in the thickness direction of the substrate.
  • 90% or more of the ⁇ silicon nitride particles have a c-axis inclination within ⁇ 20 degrees with respect to the thickness direction of the substrate, and 50% or more of the ⁇ silicon nitride particles are of the substrate. It is described that the thermal conductivity of silicon nitride ceramics in which the inclination of the c-axis with respect to the thickness direction is within ⁇ 5 degrees is high.
  • ⁇ -type silicon nitride particles are not necessarily aligned and oriented parallel to the thickness direction, and the diffraction intensity I ((101) plane of ⁇ -type silicon nitride I ( If the ratio I (101) / I (210) of the diffraction intensities I (210) of the (101) and (210) planes is smaller than 0.95, not only high thermal conductivity can be realized, but also I (101) It was found that the mechanical properties (bending strength and fracture toughness value) can be improved by making / I (210) smaller than 0.95.
  • I (101) / I (210) exceeds 0.95, it is not preferable because mechanical properties (bending strength and fracture toughness value) are lowered.
  • I (101) / I (210) is less than 0.62, it is not preferable because the thermal conductivity is lowered.
  • a more preferable range of I (101) / I (210) is 0.69 to 0.87. Further, I (101) / I (210) may be 0.70 or more, 0.72 or more, 0.85 or less, or 0.80 or less.
  • the polished surface is a surface obtained by, for example, barrel polishing, honing, lapping, polishing and buffing.
  • the microstructure of the silicon nitride sintered body of the present invention includes columnar ⁇ -type silicon nitride particles having a major axis length of 10 ⁇ m or more of particles that are good heat conductors in a matrix.
  • the length of the major axis of the columnar ⁇ -type silicon nitride particles is determined by the oxygen content of the Si 3 N 4 powder used as a raw material and the sintering conditions (heating rate, maximum holding temperature, and holding time at the maximum holding temperature). Can be controlled by adjusting.
  • the number of columnar ⁇ -type silicon nitride particles whose major axis exceeds 10 ⁇ m is 500 or more per 1 mm 2.
  • the number is 10,000 or less, the bending strength and fracture toughness value are remarkably increased.
  • the number of columnar ⁇ -type silicon nitride particles the length of the long axis is more than 10 ⁇ m is preferably at 800 or more 9000 or less per 1 mm 2, further, it is 1000 or more 5000 or less per 1 mm 2 Is more preferable.
  • the surface may not be polished, but the surface is polished, the arithmetic average roughness Ra of the surface is 0.06 ⁇ m or more and 0.4 ⁇ m or less, Is preferably 0.30 ⁇ m or less and 0.20 ⁇ m or less.
  • the arithmetic average roughness Ra is less than 0.06 ⁇ m, the bending strength of the plate-like silicon nitride sintered body is lowered due to residual stress during processing.
  • the arithmetic average roughness Ra exceeds 0.4 ⁇ m, it is difficult to join the circuit forming metal plate, which is not preferable. In particular, it becomes difficult to join a copper plate or an aluminum plate by a direct joining method (DBC method) without using an active metal brazing material.
  • DBC method direct joining method
  • the open porosity of the surface polished to the arithmetic average roughness Ra of 0.06 ⁇ m or more and 0.4 ⁇ m or less is 1.0% or less, and the maximum opening diameter of the open pores is 1.0 ⁇ m or less. Excellent electrical characteristics can be expected when the maximum opening diameter of the open pores on the surface is 1.0 ⁇ m or less. In particular, the maximum opening diameter of open pores on the surface is more preferably 0.5 ⁇ m or less.
  • Such a plate-like silicon nitride sintered body having a small number of residual pores is suitable for electronic substrate applications such as an insulating substrate and a circuit substrate because of its excellent insulation resistance and withstand voltage.
  • the maximum opening diameter and open porosity on the polished surface were calculated as follows. First, using a scanning electron microscope (SEM), an image of 5 observation fields in a region set to 60 ⁇ m ⁇ 44 ⁇ m per observation field from the polished surface of the silicon nitride sintered body at an observation magnification of 2000 times was imported. The maximum opening diameter was determined by measuring the diameter of the largest open pore in 5 observation fields / total measurement area of 13200 ⁇ m 2 using an image analyzer (Mac-View manufactured by Mountec Co., Ltd.).
  • SEM scanning electron microscope
  • the same image analyzer 400 [mu] m 2 the area of measurement by 1 field in the image, the measurement field number 12, that is, the measured total area as 4800Myuemu 2, was determined area of open pores in the measurement the total area.
  • the area of the open pores was divided by the measured total area, and the ratio of the open pore area to the measured total area was defined as the surface open porosity. Thereby, the open porosity on the surface was able to be calculated.
  • silicon nitride powder having an oxygen content of 1.2 wt% or more and 2.3 wt% or less is used as the silicon nitride raw material.
  • a silicon nitride powder having a specific surface area of 13.0 m 2 / g or more is used.
  • a silicon nitride powder having a specific surface area of 13.0 m 2 / g or more, an oxygen content of 1.2 wt% or more and 2.3 wt% or less, and an aluminum content of less than 50 ppm is used as a silicon nitride raw material. use.
  • More preferred silicon nitride material has a specific surface area of 13.5m 2 /g ⁇ 25.0m 2 / g, the oxygen content is 2.2 wt% or less than 1.25 wt%. Particularly preferably, the specific surface area 15.1m 2 /g ⁇ 25.0m 2 / g, the oxygen content is 2.0 wt% or less than 1.3 wt%.
  • Oxygen contained in the silicon nitride raw material is classified into surface oxygen existing from the particle surface to 3 nm immediately below the particle surface and internal oxygen existing from 3 nm immediately below the particle surface to the inside.
  • the oxygen content is the sum of the surface oxygen content and the internal oxygen content.
  • the silicon nitride raw material has an FSO of 0.76 to 1.10 wt%, More preferred. Further, the FSO is particularly preferably 0.80 to 1.00% by weight.
  • a silicon nitride powder having a specific surface area of 13.0 m 2 / g or more, an oxygen content of 1.2 wt% or more and 2.3 wt% or less and an aluminum content of less than 50 ppm used in the present invention can be manufactured by the method disclosed in Patent Document 8, and the oxygen content existing from the particle surface to 3 nm immediately below the particle surface is defined as FSO (mass%), and the oxygen present from 3 nm directly below the particle surface to the inside When the content ratio of FIO (mass%) and the specific surface area is FS (m 2 / g), FSO / FS is 0.04 to 0.125 ((g ⁇ mass%) / m 2 ).
  • FIO / FS is 0.045 ((g ⁇ mass%) / m 2 ) or less, but is not limited thereto. Here, mass% and weight% are the same value.
  • the FSO / FS may be expressed as 0.4 to 1.25 (mg / m 2 ), and the FIO / FS may be expressed as 0.45 (mg / m 2 ) or less. .
  • Reducing the aluminum content of the silicon nitride powder to less than 50 ppm reduces the aluminum content in the raw material for producing the silicon nitride powder, and mixes aluminum oxide in the production process of the silicon nitride powder (for example, mixing from the grinding media). ) Is possible.
  • the specific surface area is 13.0 m 2 / g or more and the oxygen content is 1.2 wt% or more and 2.3 wt% or less
  • two types of silicon nitrides having different specific surface areas are used to control the particle size distribution.
  • Powder may be mixed.
  • a silicon nitride powder having a specific surface area of 10.0 m 2 / g or less and an oxygen content of less than 1.2% by weight and a specific surface area of 13.5 m 2 / g or more and an oxygen content of 1.3% by weight or more.
  • the specific surface area of the mixed silicon nitride raw material is 13.0 m 2 / g or more, the oxygen content is 1.2 wt% or more and 2.3 wt% or less, If the aluminum content is less than 50 ppm, the effect of the present invention can be obtained.
  • the specific surface area of the silicon nitride powder is less than 13.0 m 2 / g, the driving force for sintering is reduced, so that the amount of sintering aid added is not increased to an amount exceeding 7.0% by weight. It is difficult to obtain a plate-like silicon nitride sintered body.
  • the oxygen content is less than 1.2% by weight, the progress of the sintering is remarkably slow, and if the additive amount of the sintering aid is not increased to an amount exceeding 7.0% by weight, the density becomes high. It is difficult to obtain a plate-like silicon nitride sintered body.
  • the amount of the sintering aid added exceeds 7.0 wt%, the thermal conductivity is lowered, which is not preferable.
  • the open porosity on the surface polished to an arithmetic average roughness Ra of 0.06 ⁇ m or more and 0.4 ⁇ m or less exceeds 1.0%, and the open pores This is not preferable because the maximum opening diameter is a large value exceeding 1.0 ⁇ m.
  • the specific surface area is less than 13.0 m 2 / g and the oxygen content is less than 1.2% by weight, the maximum opening diameter of the open pores becomes a larger value, which is not preferable.
  • the mechanical properties strength and toughness
  • the maximum opening diameter is a large value exceeding 1.0 ⁇ m, the insulation resistance and the withstand voltage are deteriorated, and it becomes difficult to apply to an electrical insulating material such as an insulating substrate or a circuit board.
  • the oxygen content exceeds 2.3% by weight, although a high-density plate-like silicon nitride sintered body can be obtained, the thermal conductivity and mechanical properties (strength, fracture toughness) are lowered, which is not preferable. In particular, the decrease in thermal conductivity is significant.
  • a plate-like silicon nitride sintered body having both high thermal conductivity and excellent mechanical properties by a sheet forming process that has been insufficient in terms of both thermal conductivity and mechanical properties is advantageous in terms of manufacturing cost. That is, according to the present invention, the thermal conductivity is 90 W / (m ⁇ K) or more at room temperature, the four-point bending strength is 900 MPa or more at room temperature, and the fracture toughness value measured by IF method (indentation method).
  • a plate-like silicon nitride sintered body having a K IC of 7.6 MPa ⁇ m or more and having high thermal conductivity and excellent mechanical properties can be produced.
  • a balanced plate-like silicon nitride sintered body it can be used for electronic substrates such as insulating substrates and circuit boards.
  • the thermal conductivity is 100 W / (m ⁇ K) or more at room temperature
  • the four-point bending strength is 1000 MPa or more at room temperature
  • the fracture toughness value measured by IF method (indentation method) A plate-like silicon nitride sintered body having a K IC of 9.0 MPa ⁇ m or more and having high thermal conductivity and excellent mechanical properties can be produced.
  • Example 1 Magnesium oxide (MgO) powder (specific surface area 3 m 2 / g, manufactured by High Purity Chemical Laboratory) and yttrium oxide (Y 2 O 3 ) powder (specific surface area 3 m 2 / g, manufactured by Shin-Etsu Chemical Co., Ltd.) as sintering aids Prepared.
  • MgO magnesium oxide
  • Y 2 O 3 yttrium oxide
  • Balls made of silicon nitride which is a grinding medium, usually contain several percent of Al 2 O 3 and have a large amount of wear during ball milling, so the blended powder after raw material preparation has about 20 ppm of Al 2 O 3. It is mixed. For this reason, in this example, the Al 2 O 3 content is around 1.9 wt%, and the amount of Al 2 O 3 mixed at the time of raw material preparation using a silicon nitride ball particularly excellent in wear resistance was kept to a minimum.
  • silicon nitride (Si 3 N 4 ) powder having a specific surface area of 18.5 m 2 / g, oxygen content of 1.77 wt% and ⁇ -type silicon nitride content of 3.5% by mass Toluene-isopropanol-xylene solvent in which 3.5 parts by mass of the yttrium oxide and 2 parts by mass of the magnesium oxide are blended and 2 parts by mass of a sorbitan ester dispersant is dissolved in the powder and silicon nitride as a grinding medium It put into the resin pot for ball mills with the ball made, and wet-mixed for 24 hours.
  • the obtained green sheet was laminated and pressure-treated at a temperature of 120 ° C. and a predetermined pressure to produce a laminated molded body sheet having a baked dimension of about 0.35 mm. Appearance inspection was performed on the produced laminated molded sheet to confirm the presence or absence of cracks. And this laminated molded object sheet
  • the number of laminated green sheets is increased, and a disc-shaped test piece is used so that the baked dimensions are 10 mm in diameter and 1.0 mm in thickness.
  • the molded body sheet was cut out.
  • the laminated molded body sheet is placed in a boron nitride container with a separating material, and heated in air at 400 to 600 ° C. for 2 to 5 hours, thereby sufficiently adding the organic binder component added in advance. Degreased (removed).
  • the defatted body was heated to 1520 ° C. under a nitrogen atmosphere of 0.8 MPa, and the heating rate from 1520 ° C. to 1800 ° C. was set to 120 ° C./hr to 1800 ° C. Sintering was carried out for a time. Thereafter, the cooling rate to 1500 ° C. was set to 350 ° C./hr, and the mixture was cooled to room temperature.
  • the obtained silicon nitride sintered body was peeled off by the separating material layer to obtain a plate-like silicon nitride sintered body. .
  • the obtained plate-like silicon nitride sintered body was blast-polished to obtain a silicon nitride sintered body for a substrate having a desired surface roughness.
  • the removal thickness by blast polishing was 10 ⁇ m or less on average.
  • the total oxygen content FTO and the surface oxygen content FSO of the silicon nitride powder used in the present invention were measured by the following methods. First, the silicon nitride powder is weighed, and the total oxygen content FTO, which is the sum of the surface oxygen and internal oxygen of the silicon nitride powder, is determined by the inert gas melting-carbon dioxide infrared absorption method in accordance with the JIS R1603-10 oxygen determination method ( Measured by LECO, TC-136 type).
  • the silicon nitride powder and hydrofluoric acid aqueous solution were mixed with the weighed silicon nitride powder so that hydrogen fluoride was 5 parts by mass with respect to 1 part by mass of the silicon nitride powder, and stirred at room temperature for 3 hours. This was subjected to suction filtration, and the obtained solid was vacuum-dried at 120 ° C. for 1 hour, and then the weight and oxygen content of the hydrofluoric acid-treated powder were measured. This value was defined as FIO before correction (mass% relative to hydrofluoric acid-treated powder).
  • the internal oxygen amount FIO (mass% relative to the silicon nitride powder) was calculated from the following formula (1), and the surface oxygen content FSO (mass% relative to the silicon nitride powder) was calculated from the following formula (2).
  • the surface oxygen amount thus determined is attributed to oxygen existing in the range of 3 nm directly from the particle surface to the particle surface.
  • FIO (mass%) ((weight of hydrofluoric acid treatment powder) (g)) / (silicon nitride powder weight (g)) ⁇ FIO before correction (mass%) (1)
  • FSO (mass%) FTO (mass%) ⁇ FIO (mass%) (2)
  • the maximum opening diameter and open porosity on the polished surface were calculated as follows. First, using a scanning electron microscope (SEM), an image of 5 observation fields in a region set to 60 ⁇ m ⁇ 44 ⁇ m per observation field from the polished surface of the silicon nitride sintered body at an observation magnification of 2000 times was imported. The maximum opening diameter was determined by measuring the diameter of the largest open pore in 5 observation fields / total measurement area of 13200 ⁇ m 2 using an image analyzer (Mac-View manufactured by Mountec Co., Ltd.).
  • SEM scanning electron microscope
  • the same image analyzer 400 [mu] m 2 the area of measurement by 1 field in the image, the measurement field number 12, that is, the measured total area as 4800Myuemu 2, was determined area of open pores in the measurement the total area.
  • the area of the open pores was divided by the measured total area, and the ratio of the open pore area to the measured total area was defined as the surface open porosity. Thereby, the open porosity on the surface was able to be calculated.
  • the appearance of the obtained plate-like silicon nitride sintered body was inspected to determine the presence or absence of uneven color tone by visual observation, and the presence or absence of a pattern having a different color tone was confirmed by a CCD camera.
  • the bulk density of the obtained plate-like silicon nitride sintered body was measured by Archimedes method for measuring the weight and buoyancy of a test piece suspended on a thin wire.
  • the relative density ratio to the theoretical density based on the composition was determined from the bulk density.
  • the RINT-TTRIII type wide-angle X-ray diffractometer manufactured by Rigaku Corporation was used for measuring the X-ray diffraction pattern of the obtained plate-like silicon nitride sintered body.
  • the X-ray source is CuK ⁇ ray, and each diffraction peak ((110) plane, (200) plane, (101) plane, (210) plane, (201) plane, (310) plane, (320))) of ⁇ -type silicon nitride. ) Plane and (002) plane) and the presence or absence of diffraction peaks due to MgSiN 2 were examined.
  • the arithmetic average roughness Ra of the surface of the silicon nitride sintered body is not 0.05 ⁇ m or more and 0.5 ⁇ m or less, the surface is polished and the arithmetic average roughness Ra is set to 0. It adjusted to 05 to 0.5 micrometer. Furthermore, it was confirmed whether the crystal phase resulting from the sintering aid component other than ⁇ -type silicon nitride and MgSiN 2 was precipitated at the grain boundaries.
  • the arithmetic average roughness Ra of the surface of the obtained plate-like silicon nitride sintered body was measured according to JIS B0601-2001 (ISO 4287-1997).
  • a stylus type surface roughness meter a stylus having a stylus tip radius of 2 ⁇ m was applied to the polished surface of the silicon nitride sintered body, the measurement length was 5 mm, and the stylus scanning speed was 0.
  • the surface roughness was measured by setting it to 5 mm / second, and the average value of the five locations obtained by this measurement was used as the value of the arithmetic average roughness Ra.
  • a bending test piece having a width of 4.0 mm, a thickness of 0.35 mm and a length of 40 mm was used.
  • a universal material testing machine manufactured by Instron except that the thickness of the test piece (0.35 mmt) is different, it is a method in accordance with JIS R1601, using a four-point bending test jig with an inner span of 10 mm and an outer span of 30 mm. The four-point bending strength was measured.
  • the fracture toughness value of the obtained plate-like silicon nitride sintered body was measured by the IF method in accordance with JIS-R1607: 2015. A Vickers indenter is pushed into the mirror-polished surface of the plate-like silicon nitride sintered body for 15 seconds with a predetermined indenter indentation load (5 kgf (49 N)), and one diagonal line of the Vickers indentation is plate-like silicon nitride sintered The length of the diagonal line of the Vickers indentation and the crack length generated on the extension of the diagonal line were measured so as to be perpendicular to the thickness direction of the body. The fracture toughness value K IC was calculated from the obtained measured length.
  • a disk-shaped test piece having a diameter of 10 mm ⁇ and a thickness of 1 mmt was produced by the above-described method.
  • the thermal conductivity was measured at room temperature by a flash method in accordance with JIS R1611.
  • an area of 0.01 mm 2 (1/100 of 1 mm 2 ) of the cut surface of the plate-like silicon nitride sintered body is arbitrarily selected at an observation magnification of 1000 times. Three places were observed, the number of columnar ⁇ -type silicon nitride particles having a long axis exceeding 10 ⁇ m in the region was examined and converted into the number per 1 mm 2 , and the average value was obtained.
  • the obtained plate-like silicon nitride sintered body was crushed and crushed and passed through a sieve having an opening of 250 ⁇ m.
  • the oxygen content of the crushed material sample was measured by an inert gas melting-carbon dioxide infrared absorption method (manufactured by LECO, model TC-136) based on the JIS R1603-10 oxygen determination method.
  • each metal element (aluminum, yttrium, magnesium, scandium, erbium, lutetium) in the test solution was quantitatively analyzed using an ICPE-9820 type inductively coupled plasma optical emission spectrometry (ICP-AES) apparatus manufactured by Shimadzu Corporation.
  • ICP-AES inductively coupled plasma optical emission spectrometry
  • Tables 1, 2 and 3 show the measurement results of the evaluation items regarding the chemical composition and characteristics of the body.
  • Examples 1 to 52 are examples of the present invention
  • Comparative Examples 1 to 21 are comparative examples for the present invention.
  • the bending strength at room temperature is 4-point bending strength
  • the number of coarse ⁇ particles is the long axis of ⁇ -type silicon nitride particles observed in a 1 mm 2 area of the cut surface perpendicular to the plate surface of the silicon nitride sintered body. Represents the number of ⁇ -type silicon nitride particles having a length exceeding 10 ⁇ m.
  • Example 2 A plate-like silicon nitride sintered body was obtained in the same manner as in Example 1 except that the sintering temperature was raised to 1850 ° C. under the conditions described in Tables 1 and 2.
  • Table 2 shows the sintering conditions and the chemical composition of the obtained plate-like silicon nitride sintered body
  • Table 3 shows the characteristics of the obtained plate-like silicon nitride sintered body.
  • Example 3 Except for changing the holding time at the maximum temperature during sintering, a plate-like silicon nitride sintered body was obtained in the same manner as in Example 1 under the conditions described in Tables 1 and 2. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • Example 3 because the holding time at the maximum temperature was 6 hours, the oxygen content of the sintered body was slightly high, the number of coarse ⁇ particles decreased, and the thermal conductivity and fracture toughness value slightly decreased. did.
  • Example 5 Example 2 except that the silicon nitride raw material (specific surface area 16.9 m 2 / g, oxygen content 1.50 wt%, ⁇ -type silicon nitride content rate 3.0 mass%) and the maximum temperature holding time were changed. Similarly, a plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. High thermal conductivity and excellent mechanical properties (bending strength and fracture toughness value) even when the specific surface area of silicon nitride (Si 3 N 4 ) powder is 16.9 m 2 / g and the oxygen content is 1.50 wt% )showed that.
  • Si 3 N 4 silicon nitride powder
  • Example 6 In the same manner as in Example 2 except that the coating speed and the holding time at the maximum temperature in sheet forming using a doctor blade device were changed, a plate-like silicon nitride was formed under the conditions described in Table 1 and Table 2. An elementary sintered body was obtained. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. By extending the holding time at the maximum temperature, the number of coarse ⁇ particles increased and the thermal conductivity increased.
  • Example 7 By changing the coating speed in sheet forming using a silicon nitride raw material (specific surface area 13.7 m 2 / g, oxygen content 1.25 wt%, ⁇ -type silicon nitride content rate 2.2 mass%) and a doctor blade device, A plate-like silicon nitride sintered body was obtained in the same manner as in Example 1 under the conditions described in Table 1 and Table 2. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • the laminated molded body sheet density of Examples 7 and 8 increased to 1.97 g / cm 3
  • the laminated molded body sheet density of Example 9 increased to 1.95 g / cm 3
  • the oxygen content of the sintered body was slightly high.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) on the (101) plane and the diffraction intensity I (210) on the (210) plane was small. As a result, the thermal conductivity and fracture toughness value decreased.
  • Example 10 A plate-like silicon nitride sintered body was obtained in the same manner as in Example 7 except that the sintering conditions were changed under the conditions described in Tables 1 and 2.
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • the fracture toughness value K IC increased to 9.5 MPa ⁇ m by holding at 1850 ° C. for 20 hours.
  • Tables 1 and 2 were the same as in Example 3 except that the weight ratio of magnesium oxide to rare earth oxide (magnesium oxide / rare earth oxide) and the holding time at the maximum holding temperature during sintering were changed.
  • a plate-like silicon nitride sintered body was obtained under the conditions described in 1).
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. The oxygen content of the sintered body was slightly high, the number of coarse ⁇ particles decreased, and the thermal conductivity slightly decreased.
  • Example 14 Except that the rare earth oxide was changed to Sc 2 O 3 , Er 2 O 3 , or Lu 3 O 3 , a plate-like structure was formed under the conditions described in Table 1 and Table 2 in the same manner as in Example 2. A silicon nitride sintered body was obtained. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. In Example 16, the bending strength increased.
  • Example 17 The conditions described in Tables 1 and 2 were the same as in Example 2 except that the weight ratio of magnesium oxide and rare earth metal oxide and the coating speed in sheet forming using a doctor blade device were changed. A plate-like silicon nitride sintered body was obtained. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. Even when the weight ratio of magnesium oxide to rare earth metal oxide was changed, high thermal conductivity and excellent mechanical properties (bending strength and fracture toughness value) were exhibited.
  • Example 18 Example except that the weight ratio of magnesium oxide to rare earth metal oxide and the temperature rising rate from 1550 ° C. to the maximum holding temperature was changed to 140 ° C./hr in the temperature rising process, held at 1550 ° C. for 2 hours.
  • a plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2.
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. By holding at 1550 ° C. for 2 hours, the oxygen content of the sintered body was reduced as compared with the blend composition, and high thermal conductivity and excellent mechanical properties (bending strength and fracture toughness value) were exhibited.
  • Example 19 Except for changing the weight ratio of silicon nitride raw material (specific surface area 16.9 m 2 / g, oxygen content 1.50 wt%, ⁇ -type silicon nitride content 3.0 mass%) and magnesium oxide and rare earth metal oxide
  • plate-like silicon nitride sintered bodies were obtained under the conditions described in Tables 1 and 2.
  • Example 21 and 22 Except for changing the added amount and the weight ratio of magnesium oxide is a sintered aid (MgO) and yttrium oxide (Y 2 O 3), the same procedure as in Example 2, listed in Table 1 and Table 2 A plate-like silicon nitride sintered body was obtained under the conditions. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. In Example 22, because of the large amount of sintering aid added, the measured oxygen content of the sintered body was slightly high, and the thermal conductivity and fracture toughness values were slightly reduced.
  • MgO sintered aid
  • Y 2 O 3 yttrium oxide
  • Example 23 A plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2 in the same manner as in Example 2 except that the gas pressure during sintering was lowered to 0.4 MPa. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. At a gas pressure of 0.4 MPa, a silicon nitride sintered body having substantially the same characteristics as in the case of 0.8 MPa was obtained.
  • Example 24 The additive amount of the sintering aid is 6.5% by weight, the weight ratio of magnesium oxide to yttrium oxide is 0.4, the coating speed in the sheet molding using the doctor blade device, and the sintering conditions (maximum temperature) (Retention time at) was changed. Further, in Example 24, the temperature was raised from 1550 ° C. to the maximum holding temperature at 120 ° C./hr after holding at 1550 ° C. for 2 hours in the temperature raising process (in Examples 25 and 26, from 1520 ° C. to 1880 ° C.
  • Example 26 the silicon nitride raw material (specific surface area 13.7 m 2 / g, oxygen content 1.25 wt%, ⁇ -type silicon nitride content rate 2.2 mass%) was changed. It was. A plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • Example 24 since the number of coarse ⁇ particles was 3800, high thermal conductivity and excellent mechanical properties (strength and fracture toughness value) were exhibited.
  • Example 25 the mechanical properties (strength and fracture toughness value) were slightly decreased because of an increase in the number of coarse ⁇ particles.
  • Example 27 Except for changing the silicon nitride raw material (specific surface area 16.4 m 2 / g, oxygen content 1.46 wt%, ⁇ -type silicon nitride content 2.7 mass%) and using silicon nitride powder with aluminum content 40 ppm
  • silicon nitride raw material specific surface area 16.4 m 2 / g, oxygen content 1.46 wt%, ⁇ -type silicon nitride content 2.7 mass%)
  • silicon nitride powder with aluminum content 40 ppm silicon nitride powder with aluminum content 40 ppm
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. The characteristic deterioration was hardly recognized up to the measured aluminum content of 43 ppm of the sintered body.
  • Example 28 and 29 The surface polishing conditions of the obtained plate-like silicon nitride sintered body were changed, and in Example 29, a silicon nitride raw material (specific surface area 16.9 m 2 / g, oxygen content 1.50 wt%, ⁇ -type nitriding) A plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2 in the same manner as in Example 2 except that the silicon content was changed to 3.0% by mass.
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. The characteristic deterioration was hardly recognized up to the surface roughness range shown in Table 3, and high thermal conductivity and high bending strength were exhibited.
  • Example 30 to 32 While changing the coating speed in sheet forming using a doctor blade device, the sintering conditions (holding time at the maximum holding temperature) were changed, and the same conditions as in Example 4 were applied under the conditions described in Tables 1 and 2. Thus, a plate-like silicon nitride sintered body was obtained. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • Example 30 the thermal conductivity slightly decreased compared to Example 31 because the oxygen content of the sintered body was slightly high.
  • Example 32 the mechanical properties (strength and fracture toughness value) slightly decreased compared to Example 31 because the oxygen content of the sintered body was somewhat low.
  • Example 33 is an example in which the gas pressure during sintering was increased to 2.0 MPa.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. Even at a gas pressure of 2.0 MPa, the same characteristics as in the case of 0.8 MPa can be obtained. However, since the evaporation of magnesium oxide is suppressed due to the high gas pressure, the oxygen content of the sintered body is slightly increased. The remarkable characteristic improvement effect of raising the gas pressure to 2.0 MPa was not recognized.
  • Example 34 lapping was performed after blast polishing.
  • Table 1 and Tables were obtained in the same manner as in Example 2 except that the coating speed in sheet forming using a doctor blade device and the conditions for surface polishing of the obtained plate-like silicon nitride sintered body were changed.
  • a plate-like silicon nitride sintered body was obtained under the conditions described in 2.
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. In the surface roughness described in Table 3, it was found that the mechanical properties (strength and fracture toughness value) tend to be slightly lowered.
  • Examples 37 and 38 Except for changing the weight ratio of magnesium oxide and yttrium oxide, the coating speed in sheet forming using a doctor blade device, and the sintering conditions (maximum holding temperature and holding time), Under the conditions described in 1 and Table 2, a plate-like silicon nitride sintered body was obtained. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. The thermal conductivity slightly decreased because of the influence of the holding time at the maximum holding temperature or because the measured oxygen content of the sintered body was slightly high.
  • Example 39 Except for changing the coating speed in the sheet forming using the silicon nitride raw material and the doctor blade device, in the same manner as in Example 6, under the conditions described in Tables 1 and 2, the plate-like silicon nitride-based firing was performed. A ligature was obtained. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • Examples 40 to 46 the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body were examined in detail, particularly focusing on the influence of the weight ratio of magnesium oxide and yttrium oxide.
  • Example 40 to 42 The amount of sintering aid added was 5.9% by weight, the weight ratio of magnesium oxide to yttrium oxide, and the coating speed in sheet molding using a doctor blade device were varied. Example 2 except that the holding time at the same temperature as the holding temperature was changed.
  • magnesium oxide / yttrium oxide 0.44 (Example 42) showed high thermal conductivity and excellent mechanical properties (bending strength and fracture toughness value).
  • Example 43 to 45 The additive amount of the sintering aid is 5.5% by weight, the weight ratio of magnesium oxide to yttrium oxide, the coating speed in sheet molding using a doctor blade device, and the sintering conditions (nitrogen gas pressure, maximum holding temperature) The holding time at the same temperature was changed. Except for these changes, the procedure is the same as in the second embodiment.
  • a plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • Example 46 The same as in Example 8 except that the addition amount of the sintering aid was 5.5% by weight, the weight ratio of magnesium oxide to yttrium oxide, and the sintering conditions (maximum holding temperature) were changed.
  • a plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2.
  • Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • the weight ratio of magnesium oxide to yttrium oxide in the blending composition was set to 0.40 ⁇ magnesium oxide / rare earth metal oxide ⁇ 0.66, and the measured magnesium content as a sintered body was It was confirmed that the mass ratio of the measured yttrium content was more preferably 0.26 ⁇ measured magnesium content / measured yttrium content ⁇ 0.49.
  • Example 47 The amount of sintering aid added was 4.1 wt%, 3.5 wt% and 6.5 wt%, respectively.
  • the weight ratio of magnesium oxide to yttrium oxide, the coating speed in sheet forming using a doctor blade device, and the sintering conditions were changed. Except for these changes, the procedure is the same as in Example 6.
  • a plate-like silicon nitride sintered body was obtained under the conditions described in Tables 1 and 2. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body.
  • Example 47 the addition amount of the sintering aid is within a more preferable range (the content of the metal element derived from the assistant obtained by adding the measured magnesium content and the measured yttrium content as the sintered body is 2.52% by weight. Therefore, the thermal conductivity and mechanical properties (strength and fracture toughness value) almost comparable to Example 6 were exhibited.
  • Example 48 the amount of sintering aid added was slightly less than 4.0% by weight, so the mechanical time (strength and fracture toughness value) was slightly reduced. The heat conductivity slightly decreased because the amount of addition was slightly higher than 6.0% by weight. In Examples 48 and 49, the maximum opening diameter was slightly large.
  • Example 50 Silicon nitride raw material (specific surface area: 15.5 m 2 / g, oxygen content: 1.40 wt%, ⁇ -type silicon nitride content: 2.5 mass%), sintering conditions (retention time at maximum temperature), and obtained Except for changing the surface polishing conditions of the plate-like silicon nitride sintered body, the plate-like silicon nitride sintered under the conditions described in Tables 1 and 2 in the same manner as in Example 33. Got the body. Tables 2 and 3 show the chemical composition and characteristics of the obtained plate-like silicon nitride sintered body. Since the degree of blast polishing in the surface polishing process was weakened, the arithmetic average surface roughness Ra was 0.46 ⁇ m, and mechanical time (strength and fracture toughness value) was slightly reduced. The maximum opening diameter was also slightly large.
  • Examples 51 and 52 are examples in which the addition amounts of magnesium oxide (MgO) and yttrium oxide (Y 2 O 3 ), which are sintering aids, were changed.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. The measured oxygen content of the sintered body was 2.82% by weight in Example 51 and 2.99% by weight in Example 52. Increasing the amount of sintering aid added increased the oxygen content, Thermal conductivity decreased slightly. Further, in Example 52, the mechanical properties (bending strength and fracture toughness value) were slightly lowered.
  • thermal conductivity or mechanical properties (bending strength and fracture toughness value) was slightly lower.
  • the thermal conductivity or mechanical properties were slightly reduced.
  • the thermal conductivity and mechanical properties were slightly reduced.
  • Example In 51 and 52 thermal conductivity or mechanical properties (bending strength and fracture toughness value) were lower than those of the other examples.
  • the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride is less than 0.69 or more than 0.87 In Examples 9, 37, 48 and 52, thermal conductivity or mechanical properties (bending strength and fracture toughness value) were slightly decreased.
  • the thickness of the plate-like silicon nitride sintered body excluding the disk-shaped test piece for measuring the thermal conductivity is 0.33 to 0.48 mm
  • the area ratio was 1.0 ⁇ 10 ⁇ 4 to 1.9 ⁇ 10 ⁇ 4 (1 / mm)
  • the removal amount of the surface layer portion perpendicular to the thickness direction was 0.008 to 0.03 mm per side.
  • no color tone unevenness was observed in all examples.
  • a crystal phase of Mg compound such as MgSiN 2 was not detected.
  • no crystal phases of rare earth metal compounds such as N-merlite, H phase, J phase, K phase were detected.
  • Comparative Examples 1 and 2 are examples in which a powder having a low specific surface area or a powder having a low oxygen content is used as a silicon nitride raw material.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. As the specific surface area or oxygen content decreases, the relative density of the obtained plate-like silicon nitride sintered body decreases, and as a result, characteristics such as thermal conductivity, bending strength, and fracture toughness value decrease. did.
  • Comparative Example 3 is an example in which a powder having an excessively high oxygen content was used as the silicon nitride raw material.
  • Table 2 and Table 3 show the chemical composition and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2, with the holding time at the maximum temperature being 8 hours.
  • the measured oxygen content of the sintered body was 2.55% by weight, and because the oxygen content of the silicon nitride raw material was too high, the grain growth of ⁇ -type silicon nitride particles was insufficient (500 / mm 2 Less than).
  • the oxygen content was too high, the number of ⁇ -type silicon nitride particles having a long axis exceeding 10 ⁇ m decreased, and the thermal conductivity decreased.
  • Comparative Example 4 This is an example in which the silicon nitride raw material was changed and silicon nitride powder having an aluminum content of 50 ppm was used.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. When the measured aluminum content of the sintered body rose to 55 ppm, the thermal conductivity decreased.
  • Comparative Example 5 is an example in which the addition amounts of magnesium oxide (MgO) and yttrium oxide (Y 2 O 3 ), which are sintering aids, were changed.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2.
  • the addition amount of the sintering aid was decreased, the relative density of the obtained plate-like silicon nitride sintered body was lowered (the measured oxygen content of the sintered body was 1.34% by weight).
  • Comparative Examples 6 and 7 are examples in which the weight ratio of the alkaline earth metal oxide and the rare earth metal oxide was changed.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2.
  • the weight ratio of the measured magnesium content to the measured rare earth metal content of the silicon nitride sintered bodies obtained in Comparative Examples 6 and 7 was 0.15 respectively. Since the weight ratio of the alkaline earth metal oxide to the rare earth metal oxide in the blending composition was too high or too low, the obtained plate-like silicon nitride sintered body was obtained. The characteristics deteriorated.
  • Comparative Examples 8 to 10 are examples in which the sintering conditions are inappropriate, for example, the gas pressure during sintering is too low, the maximum holding temperature is too low, or the maximum holding temperature is too high.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. The measured oxygen content of the sintered body of Comparative Example 9 was 2.50% by weight.
  • the mechanical properties bending strength and fracture toughness value
  • the gas pressure during sintering was too low or when the maximum holding temperature was too low, the relative density of the sintered body was low and the thermal conductivity was also lowered.
  • Comparative Examples 11 and 12 are examples in which the holding time at the maximum temperature during sintering is too short or too long.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2.
  • the measured oxygen content of the sintered body of Comparative Example 11 was 2.48% by weight, and the grain growth of ⁇ -type silicon nitride particles was insufficient (less than 500 particles / mm 2 ). If the sintering conditions (when the holding time at the maximum temperature is too short or too long) are inappropriate, the mechanical properties (bending strength and fracture toughness value) are reduced. Further, when the holding time at the maximum temperature was too short, the thermal conductivity was lowered.
  • Comparative Example 13 In Comparative Example 13, the ratio of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of columnar ⁇ -type silicon nitride on the surface is changed by changing the sheet molding conditions I (101) In this example, / I (210) is greater than 0.95.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. When ⁇ -type silicon nitride particles were randomly aligned and oriented in the thickness direction, the mechanical properties (bending strength and fracture toughness value) decreased.
  • Comparative Example 14 is an example in which the weight ratio of the alkaline earth metal oxide and the rare earth metal oxide was changed.
  • Table 2 and Table 3 show the chemical composition and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2, with the holding time at the maximum temperature being 25 hours. If the weight ratio between the alkaline earth metal oxide and the rare earth metal oxide is too high, the obtained silicon nitride-based sintering is performed under the sintering conditions described in Table 2 (the retention time at the same temperature as the maximum temperature).
  • the weight ratio of the measured magnesium content to the measured rare earth metal content of the body was 1.40.
  • Comparative Example 15 is an example in which the weight ratio between the alkaline earth metal oxide and the rare earth metal oxide is small, the maximum temperature during sintering is too high, and the holding time is too long. If the weight ratio between the alkaline earth metal oxide and the rare earth metal oxide is too small, a high density silicon nitride sintered body can be obtained unless the nitrogen gas pressure is increased, the maximum holding temperature is raised, and the holding time is not lengthened. I can't.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2.
  • the weight ratio of the measured magnesium content to the measured rare earth metal content (measured magnesium content / measured rare earth metal content) of the obtained silicon nitride sintered body was 0.23. Since the composition of the auxiliary agent is inappropriate, when more severe sintering conditions are set, the number of ⁇ -type silicon nitride particles having a long axis exceeding 10 ⁇ m significantly increases (16000 particles / mm 2 ). Characteristics (bending strength and fracture toughness value) were significantly reduced. In addition, due to the high nitrogen gas pressure and the high maximum holding temperature, the plate-like silicon nitride sintered body that was taken out had significant color unevenness accompanying the growth of the precipitated crystal phase. .
  • Comparative Example 16 In Comparative Example 16, the ratio of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride is changed by changing the sheet molding conditions I (101) / I (210 ) Is a small example.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. Although the degree of orientation of the ⁇ -type silicon nitride particles could be controlled, coupled with the slightly short holding time at 1800 ° C. and the slightly higher measured oxygen content of the sintered body, the grain growth was insufficient. The thermal conductivity decreased due to the orientation of the columnar ⁇ -type silicon nitride particles in the plate surface direction.
  • Comparative Example 17 is an example in which the holding time at the maximum temperature during sintering is too short.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2.
  • the weight ratio (measured magnesium content / measured rare earth metal content) between the measured magnesium content and the measured rare earth metal content of the obtained silicon nitride-based sintered body is 0.25, and the measured oxygen content is 1. 0.09% by weight. Since more severe sintering conditions were set, the number of ⁇ -type silicon nitride particles having a long axis length exceeding 10 ⁇ m increased significantly (20000 particles / mm 2 ), and the fracture toughness value was low. Further, the open porosity on the polished surface was 1.8% and the maximum open pore diameter was 2.5 ⁇ m, which was difficult to apply to an insulating substrate or a circuit board.
  • Comparative Examples 19 and 20 are examples in which a powder having a low specific surface area and a low oxygen content or a high specific surface area and a high oxygen content was used as a silicon nitride raw material.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. In the case of a silicon nitride raw material having a low specific surface area and a low oxygen content, the relative density of the resulting silicon nitride sintered body is reduced, and as a result, thermal conductivity and mechanical properties (bending strength and fracture toughness value) ) Both declined.
  • Comparative Example 21 In Comparative Example 21, the weight ratio of magnesium oxide and rare earth metal oxide was changed to 2.20, and the amount of magnesium oxide added increased. The holding time at the maximum temperature during sintering was extremely shortened and set to 3 hours.
  • Tables 2 and 3 show the chemical compositions and properties of the plate-like silicon nitride sintered bodies obtained under the conditions described in Tables 1 and 2. Since the amount of magnesium oxide added is large, the weight ratio of the measured magnesium content to the measured rare earth metal content (measured magnesium content / measured rare earth metal content) of the obtained silicon nitride-based sintered body is 1.65. The measured oxygen content was as high as 2.60% by weight.
  • Comparative Example 10 in which the ratio I (101) / I (210) of the diffraction intensity I (101) of the (101) plane and the diffraction intensity I (210) of the (210) plane of ⁇ -type silicon nitride exceeds 0.95 , 13 and 15, the mechanical properties (bending strength and fracture toughness value) were significantly reduced.
  • Comparative Example 17 in which the ratio I (101) / I (210) of the diffraction intensity I (210) was 0.61, the thermal conductivity was lowered.
  • Comparative Examples 10, 12, 14, 15 and 18 in which the number of coarse ⁇ -type silicon nitride particles exceeds 10,000 particles / mm 2 although the thermal conductivity is high, the mechanical properties (bending strength and fracture toughness value) are high. It was falling.
  • Comparative Examples 1, 2, 5, 6, 8, 9, and 19 having a relative density of less than 98% and Comparative Examples 15 and 18 in which the number of coarse particles exceeding 10 ⁇ m exceeds 10,000, the open porosity is 1 It exceeded 0.0%, and the maximum opening diameter exceeded 1.0 ⁇ m.
  • the examples of the present invention are based on alkaline earth metal oxides (for example, magnesium oxide) and rare earth metal oxides (for example, yttrium oxide) which are sintering aids.
  • the total added amount is 3.2 wt% or more and 7.0 wt% or less, and the weight ratio satisfies 0.40 ⁇ alkaline earth metal oxide / rare earth metal oxide ⁇ 2.0.
  • the columnar ⁇ -type silicon nitride particles having a measured aluminum content of less than 50 ppm, a relative density of 98.6% or more, and a long axis length exceeding 10 ⁇ m in the silicon nitride sintered body per 1 mm 2 .
  • 101) / I (210) is 0.62 to 0.95 and the measured oxygen content is 1.4% to 2.9% by weight
  • the thermal conductivity at room temperature is 90 W / ( m ⁇ K) and above, excellent thermal and mechanical properties such as 4-point bending strength of 900 MPa or more, fracture toughness value K IC of 7.6 MPa ⁇ m or more, stable heat dissipation and excellent durability It was found that can be demonstrated In particular, since it has high thermal conductivity and high mechanical strength and toughness, it is suitable for use as an insulating substrate and a circuit board.
  • the thermal conductivity is 100 W / (m ⁇ K) or more at room temperature, and a high thermal conductivity is ensured, which is stable. Heat dissipation.
  • the plate-like silicon nitride sintered body of the present invention has a four-point bending strength of 1000 MPa or more and a fracture toughness value K IC of 9.0 MPa ⁇ m or more, particularly high thermal conductivity and high mechanical strength and toughness. Therefore, it is suitable for use as an insulating substrate and a circuit board.
  • the plate-like silicon nitride sintered body of the present invention has a microstructure in which the length of the long axis and the orientation state of the columnar ⁇ -type silicon nitride particles constituting the sintered body are highly controlled. Therefore, in addition to the mechanical properties of high strength / toughness inherent to the silicon nitride sintered body, it has high thermal conductivity. Since it has both high thermal conductivity and high mechanical strength and toughness, when used as an insulating substrate or circuit board, it can not only suppress the cracking of the board, but also has excellent thermal shock resistance and thermal cycle resistance. We can expect improvement.

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Abstract

L'objet de la présente invention est de fournir un corps fritté à base de nitrure de silicium lamellaire qui, avec une pression atmosphérique encore plus réduite lors du frittage, présente une conductivité thermique élevée et une excellente résistance mécanique. Ce corps fritté à base de nitrure de silicium lamellaire est obtenu par l'ajout de 3,2 à 7,0 % en poids d'oxydes de métaux alcalino-terreux et d'oxydes de métaux de terres rares en tant qu'auxiliaire de frittage selon un rapport de mélange qui conduit à un rapport pondéral des oxydes de métaux alcalino-terreux et des oxydes de métaux de terres rares qui satisfait à la relation 0,40 ≤ (oxydes de métaux alcalino-terreux)/(oxydes de métaux de terres rares) ≤ 2,0, et par le frittage d'un corps formé lamellaire produit par un procédé de formation de feuille sous une pression de gaz atmosphérique inférieure ou égale à 3 MPa, et est caractérisé en ce que le rapport du corps fritté de la teneur en métaux alcalino-terreux mesurée et de la teneur en métaux de terres rares mesurée satisfait à la relation 0,26 ≤ (teneur en métaux alcalino-terreux mesurée)/(teneur en métaux des terres rares mesurée) ≤ 1,30, la teneur en aluminium mesurée est inférieure à 50 ppm, la teneur en oxygène mesurée est de 1,4 à 2,9 % en poids, la densité relative est supérieure ou égale à 98 %, le rapport de l'intensité de diffraction du plan (101) et de l'intensité de diffraction I(210) du plan (210) du nitrure de silicium β dans une surface polie à un Ra de 0,05 à 0,5 μm est de 0,62 à 0,95, et le nombre de particules de nitrure de silicium β dans le corps fritté à base de nitrure de silicium qui présentent une longueur d'axe long supérieure à 10 µm est de 500 à 10 000 par 1 mm².
PCT/JP2019/022621 2018-06-07 2019-06-06 Corps fritté à base de nitrure de silicium lamellaire et son procédé de production WO2019235593A1 (fr)

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JPWO2021117829A1 (fr) * 2019-12-11 2021-06-17
WO2021200814A1 (fr) * 2020-03-30 2021-10-07 デンカ株式会社 Poudre de nitrure de silicium et procédé pour produire un corps fritté de nitrure de silicium
WO2021200830A1 (fr) * 2020-03-30 2021-10-07 デンカ株式会社 Poudre de nitrure de silicium et procédé pour produire un corps fritté de nitrure de silicium
JP2022027444A (ja) * 2020-07-29 2022-02-10 日本ファインセラミックス株式会社 窒化珪素基板およびその製造方法
WO2022156635A1 (fr) * 2021-01-20 2022-07-28 中国科学院上海硅酸盐研究所 Procédé de frittage par lots pour substrat céramique en nitrure de silicium à haute performance

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JPWO2021117829A1 (fr) * 2019-12-11 2021-06-17
WO2021117829A1 (fr) * 2019-12-11 2021-06-17 宇部興産株式会社 Corps fritté à base de nitrure de silicium de type plaque et son procédé de fabrication
JP7201103B2 (ja) 2019-12-11 2023-01-10 Ｕｂｅ株式会社 板状の窒化ケイ素質焼結体およびその製造方法
WO2021200814A1 (fr) * 2020-03-30 2021-10-07 デンカ株式会社 Poudre de nitrure de silicium et procédé pour produire un corps fritté de nitrure de silicium
WO2021200830A1 (fr) * 2020-03-30 2021-10-07 デンカ株式会社 Poudre de nitrure de silicium et procédé pour produire un corps fritté de nitrure de silicium
JP2022027444A (ja) * 2020-07-29 2022-02-10 日本ファインセラミックス株式会社 窒化珪素基板およびその製造方法
JP7434208B2 (ja) 2020-07-29 2024-02-20 日本ファインセラミックス株式会社 窒化珪素基板およびその製造方法
WO2022156635A1 (fr) * 2021-01-20 2022-07-28 中国科学院上海硅酸盐研究所 Procédé de frittage par lots pour substrat céramique en nitrure de silicium à haute performance

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