JP5217097B2 - Method for producing spherical silicon carbide fine particles - Google Patents

Description

  The present invention comprises a high-purity monodispersed spherical silicon carbide fine particle useful for a filler for semiconductor encapsulant or a raw material for sintering for manufacturing mechanical parts and electronic parts, and crystalline silicon carbide. The present invention also relates to amorphous silicon carbide ceramics that can be sintered at a low temperature and are excellent in environmental resistance, heat resistance, and oxidation resistance, and methods for producing the same.

  As is well known, when ceramic powder is used as a filler for semiconductor encapsulants, or as a raw material for sintering for manufacturing machine parts and electronic parts, the purity of the ceramic powder as the starting material affects the performance of the product. It is. However, not only the purity but also physical properties such as the particle shape, particle size distribution, and degree of aggregation of the raw material powder have a great influence on the performance of products using ceramics.

  In recent years, in response to the trend toward smaller and lighter electronic devices and higher performance, device complexity, semiconductor package miniaturization, thinning, and narrow pitch are increasingly accelerating. As the mounting method, surface mounting suitable for high-density mounting on a wiring board or the like is becoming mainstream. As described above, semiconductor sealing materials are also required to have high performance, in particular, improvement of functions such as solder heat resistance, moisture resistance, low thermal expansion, mechanical characteristics, and electrical insulation. In order to satisfy these requirements, a semiconductor sealing material in which an epoxy resin is filled with an inorganic powder having the above properties as a filler is generally used. The inorganic powder filled in the semiconductor sealing material is desirably highly filled in an epoxy resin from the viewpoints of soldering heat resistance, moisture resistance, low thermal expansion, and improvement in mechanical strength. Semiconductor component sealing materials for electronic components that are becoming smaller and thinner are required not to impair fluidity and moldability even when highly filled with a filler. For this purpose, the filler is preferably spherical, has an appropriate particle size distribution, and has little aggregation.

  It is well known that the purity of the ceramic powder as a starting material has a great influence on the properties of the ceramic sintered body when the ceramic powder is formed and sintered to obtain a ceramic sintered body. However, not only the purity but also the physical properties such as the particle shape, particle size, specific surface area, and degree of aggregation of the ceramic powder have a great influence on the properties of the ceramic sintered body. For example, the particle shape is generally preferably spherical. That is, since the powder prepared by pulverizing the ingot has anisotropy in the particle shape, generally, when the shape deviates from the spherical shape, the relative density of the molded body is lowered and the density is inhomogeneous. . Sintering such a molded body does not increase the density of the sintered body, but also causes anisotropy in shrinkage during sintering, causing warping and cracking.

  Methods for obtaining ceramic particles with high sphericity include rolling granulation method, spray drying method, flame melting method and the like. The rolling granulation method is a method of obtaining a small granulated product by mixing a liquid binder with a rotating dish, a rotating cylinder, or a rotating cone-shaped drum and rotating it to discharge a large granulated product. The rolling granulation method can obtain a relatively large amount of powder, but it is difficult to obtain fine particles of micron size or less suitable for sintering. Also, there are problems such as contamination of impurities from the wall surface and residual binder, which is not suitable for obtaining high-purity micron-sized powder.

  The spray drying method is generally a method of obtaining fine particles by spraying a liquid material such as slurry in a high-temperature air stream and drying at high speed. Although a large amount of fine particles can be produced, there are problems that it is difficult to obtain fine particles of micron size or less suitable for sintering, that the particles are likely to be porous, and that aggregation is likely to occur.

  The flame melting method is a method in which raw material powder is supplied into a high-temperature flame, and the molten droplets are cooled and collected to obtain fine particles, and can be said to be suitable for obtaining spherical fine particles. However, since a high-temperature flame is used, there is a problem that if the flame temperature is too high, a molten mass is formed or the burner is clogged, so that stable production is difficult. Furthermore, composition deviation due to contamination of impurities from the wall surface or volatilization of the low boiling point composition may occur, and it cannot be said that it is optimal for obtaining a high-purity powder. In addition, the melt flame method is suitable for obtaining oxide ceramics such as silica, alumina, and mullite, but is not suitable for obtaining non-oxide ceramics and does not exhibit a clear melting point like silicon carbide ceramics. It is difficult to apply to materials.

  Accordingly, in the first aspect, the present invention provides a high-purity, monodispersed spherical silicon carbide fine particle that is useful as a filler for a semiconductor encapsulant or a raw material for sintering for manufacturing mechanical parts and electronic parts. And its manufacturing method.

  Amorphous silicon carbide ceramics mainly composed of Si, M, C and O (M is boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten, zirconium, chromium, iron, iridium, osmium) , Platinum, rhenium, rhodium, ruthenium) is excellent in environmental resistance, heat resistance and wear resistance at a high temperature of 1000 ° C. or higher, and has high rigidity, high thermal conductivity, low thermal expansion, It is a material with low specific gravity and excellent properties.

As a material exhibiting high temperature characteristics equivalent to amorphous silicon carbide ceramics mainly composed of Si, M, C, and O, there is crystalline silicon carbide ceramics mainly composed of carbon and silicon. Crystalline silicon carbide ceramics are atmospheric pressure sintering method using sintering aid, atmospheric pressure sintering method, hot pressing method (HP method), hot isostatic pressing method (HIP method), chemical vapor deposition It is manufactured by the method (CVD method), reaction sintering method or the like. Silicon carbide is a crystal having a stable covalent bond, and has excellent heat resistance at high temperatures as described above, but has a disadvantage of high sintering temperature. For example, atmospheric pressure sintering of boron carbide compound B ₄ C-based auxiliary requires 2000 to 2200 ° C., and it is 2000 ° C. or higher even by the HP method or HIP method. On the other hand, the CVD method can produce silicon carbide ceramics at a low temperature, but has a drawback in that it is limited to a thin film shape. The reaction sintering method is a method in which silicon and carbon are densified while reacting, and the sintering temperature is about 1500 ° C., which is relatively low. However, unreacted free silicon remains in the sintered body. It will be inferior in mechanical strength and heat resistance.

  As described above, silicon carbide ceramics have excellent characteristics as high-temperature structural materials, but high sintering temperatures necessitate special sintering equipment, leading to high costs and limited application range. The current situation is. If the sintering temperature can be lowered while maintaining the high temperature characteristics of silicon carbide, the production cost can be lowered and the application range can be greatly expanded.

  In contrast, amorphous silicon carbide ceramics mainly composed of Si, M, C, and O have environmental resistance, heat resistance, and oxidation resistance ranging from room temperature to their own decomposition temperature. Is equivalent to crystalline silicon carbide ceramics. Furthermore, the sintering temperature for obtaining amorphous silicon carbide ceramics can be significantly lower than the sintering temperature of crystalline silicon carbide ceramics.

  Amorphous silicon carbide ceramics mainly composed of Si, M, C and O are formed by using amorphous silicon carbide fine particles as raw material powder, and then heated and sintered at a temperature below the crystallization temperature. It is obtained by doing. Examples of a method for obtaining amorphous silicon carbide fine particles as a raw material powder include gas phase reaction methods such as gas phase thermal decomposition of trimethylsilane. However, fine particles of the gas phase reaction method have a small particle size and a relatively small particle size distribution, but have a low bulk density, and it is difficult to sufficiently increase the relative density of the compact. Even if such a molded body is sintered, cracking and warping are likely to occur during sintering, and it is difficult to obtain a high-quality sintered body. In order to obtain a high-quality silicon carbide ceramic sintered body, amorphous silicon carbide fine particles having a sufficiently small particle diameter and excellent dispersibility, filling property, and fluidity are indispensable.

  The second aspect of the present invention is a high-temperature structural material or high-temperature heat-resistant filter that can be sintered at a lower temperature than crystalline silicon carbide and has excellent environmental resistance, heat resistance, and oxidation resistance at high temperatures. It is an object of the present invention to provide an amorphous silicon carbide ceramic mainly containing Si, M, C and O, and a method for producing the same.

The present invention provides the following to solve the above problems.
[1] Spherical silicon carbide fine particles having an average particle size in the range of 50 to 100,000 nm and a sphericity in the range of 0.9 to 1.0.

[2] The spherical silicon carbide fine particles as described in [1] above, wherein the particle diameter variation coefficient (CV value) is 20% or less.

[3] The spherical silicon carbide fine particles as described in [2] above, wherein the average particle diameter is in the range of 50 to 2,000 nm.

[4] (a) Mainly general formula

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.)
An organosilicon precursor polymer comprising a polycarbosilane having a main chain skeleton represented by the formula: a polycarbosilane having a number average molecular weight of 200 to 10,000, or a modified polycarbosilane having a structure obtained by modifying the polycarbosilane with an organometallic compound. Providing a process;
(B) After the organosilicon precursor polymer is mixed with a poor solvent and heated to dissolve, the precursor polymer is precipitated by cooling the solution, and the precipitate is filtered to obtain a spherical precursor polymer. Obtaining a fine particle of
(C) a step of preheating the spherical precursor polymer fine particles in an atmosphere containing oxygen and performing an infusibilization treatment;
(D) A method for producing spherical silicon carbide fine particles, comprising a step of firing the infusible spherical precursor polymer fine particles in a vacuum or in an inert gas atmosphere.

[5] (a) Mainly general formula

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.)
An organosilicon precursor polymer comprising a polycarbosilane having a main chain skeleton represented by the formula: a polycarbosilane having a number average molecular weight of 200 to 10,000, or a modified polycarbosilane having a structure obtained by modifying the polycarbosilane with an organometallic compound. Providing a process;
(B) A precursor polymer is precipitated by mixing a solution in which the organosilicon precursor polymer is dissolved in a good solvent and a poor solvent for the organosilicon precursor polymer, and the precipitate is separated by filtration. Obtaining precursor polymer fine particles; and
(C) a step of preheating the spherical precursor polymer fine particles in an atmosphere containing oxygen and performing an infusibilization treatment;
(D) A method for producing spherical silicon carbide fine particles, comprising a step of firing the infusible spherical precursor polymer fine particles in a vacuum or in an inert gas atmosphere.

[6] The method for producing spherical silicon carbide fine particles according to the above [4] or [5], wherein the modified polycarbosilane is polymetallocarbosilane.

[7] A method for producing an amorphous silicon carbide ceramic sintered body characterized by heat-sintering at 1400 to 1600 ° C. in an inert gas atmosphere using the spherical silicon carbide fine particles according to [3] above as a raw material .

[8] An amorphous silicon carbide ceramic sintered body obtained by the method described in [7] above and having a relative density of 98% or more.

[9] A silicon carbide based ceramic porous body obtained by the method described in [7] above, having an average pore diameter in the range of 50 to 500 nm and a porosity of 30 to 60%.

[10] Amorphous spherical silicon carbide fine particles in which the spherical silicon carbide fine particles are substantially composed of Si, M, C and O (M is boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten, Zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium, ruthenium), and a silicon carbide ceramic sintered body containing Si, M, C, and O as main components. The amorphous silicon carbide ceramic sintered body according to the above [8] or [9], which is an amorphous silicon carbide ceramic sintered body.

  According to the first aspect of the present invention, high-purity, monodispersed spherical silicon carbide fine particles useful as a filler for semiconductor encapsulating materials, or as a raw material for sintering for manufacturing mechanical parts and electronic parts, etc. Can be manufactured in large quantities.

  According to the second aspect of the present invention, the average particle size is in the range of 50 to 2,000 nm, the sphericity is in the range of 0.9 to 1.0, and the particle size variation coefficient (CV value). ) Is 20% or less, and by using the amorphous spherical silicon carbide fine particles having high dispersibility, filling properties, and fluidity as raw material powder, the density of the compact can be sufficiently increased, Amorphous silicon carbide ceramics mainly composed of Si, M, C, and O having excellent high temperature characteristics at a sintering temperature lower than that of crystalline silicon carbide can be obtained. In addition, it can sinter at lower temperatures than crystalline silicon carbide, has superior environmental resistance, heat resistance, and oxidation resistance, and is low in amorphous silicon carbide ceramics that are useful as high-temperature structural materials or high-temperature heat-resistant filters. It can be obtained at a low cost, and the application range can be greatly expanded.

(Silicon carbide fine particles and production method thereof)
The silicon carbide fine particles produced in the first aspect of the present invention are SiC, SiC _x O _y , SiM _x C _y O _z (M is a metal element), etc., as long as they contain silicon and carbon. However, it is not limited to these.

  (A) Mainly general formula

(However, R in the formula is preferably a hydrogen atom, a lower alkyl group or a phenyl group.)
An organosilicon precursor polymer comprising a polycarbosilane having a main chain skeleton represented by the formula: a polycarbosilane having a number average molecular weight of 200 to 10,000, or a modified polycarbosilane having a structure obtained by modifying the polycarbosilane with an organometallic compound. Step to provide.
(B) After the precursor polymer is mixed with a poor solvent and dissolved by heating, the precursor polymer is precipitated by cooling this solution, and the precipitate is filtered to obtain fine particles of the spherical precursor polymer. Obtaining step.
(C) A step of pre-heating the spherical precursor polymer fine particles in an oxygen-containing atmosphere to perform infusibilization treatment.
(D) A step of firing spherical precursor polymer fine particles in a vacuum or in an inert gas atmosphere.

Alternatively, the silicon carbide fine particles of the present invention are produced from the following steps.
(A) Mainly general formula

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.)
An organosilicon precursor polymer comprising a polycarbosilane having a main chain skeleton represented by the formula: a polycarbosilane having a number average molecular weight of 200 to 10,000, or a modified polycarbosilane having a structure obtained by modifying the polycarbosilane with an organometallic compound. Providing a process;
(B) A precursor polymer is precipitated by mixing a solution in which the organosilicon precursor polymer is dissolved in a good solvent and a poor solvent for the organosilicon precursor polymer, and the precipitate is separated by filtration. Obtaining precursor polymer fine particles; and
(C) a step of preheating the spherical precursor polymer fine particles in an atmosphere containing oxygen and performing an infusibilization treatment;
(D) A method for producing spherical silicon carbide fine particles, comprising a step of firing the infusible spherical precursor polymer fine particles in a vacuum or in an inert gas atmosphere.

  This will be described in more detail below.

  The fine particle production first step (a) is a step of producing a polymer which is a precursor of spherical silicon carbide fine particles which is the final product.

When the target spherical fine particles are SiC _x O _y (wherein x is a number of 1 or more and y is a number of 0 or more and less than 2), the general formula is mainly used.

(However, R in the formula is preferably a hydrogen atom, a lower alkyl group or a phenyl group.)
A polycarbosilane having a main chain skeleton represented by the formula and having a number average molecular weight of 200 to 10,000 can be used as the precursor polymer. The lower alkyl group preferably has 1 to 4 carbon atoms. The number average molecular weight is preferably 1000 to 5000.

The target spherical fine particles are SiM _x C _y O _z (M is selected from boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium, ruthenium. In the case of a composition in which x is a number greater than 0 and less than 1, y is a number greater than or equal to 1 and z is a number greater than or equal to 0 and less than 2, the organometallic compound of polycarbosilane Modified polycarbosilane having a modified structure can be used as the precursor polymer.

  The organometallic compound for modifying polycarbosilane is not particularly limited. For example, polymetallocarbosilane obtained by the technique disclosed in Japanese Patent Publication No. 61-49335 can be used as the precursor polymer. The polymetallocarbosilane obtained by this method is obtained by reacting a polycarbosilane represented by the above general formula with a titanium alkoxide or a zirconium alkoxide in an inert atmosphere to at least part of the silicon atoms of the polycarbosilane. Is a polytitanocarbosilane or polyzirconocarbosilane having a number average molecular weight of 1,000 to 50,000, which is produced by bonding the alkoxide with titanium or zirconium through an oxygen atom.

The organic group R of the titanium alkoxide Ti (OR) ₄ or zirconium alkoxide Zr (OR) ₃ is not particularly limited as long as it is decomposed and removed in the third step, but each independently represents a hydrogen atom, an alkyl group (having 1 to 3 carbon atoms). 20, more preferably 1-4, but at least one R is not a hydrogen atom). The resulting polytitanocarbosilane or polyzirconocarbosilane has a structure in which titanium or zirconium atoms are bonded to Si atoms of the polycarbosilane of the above general formula via oxygen atoms of titanium alkoxide or zirconium alkoxide. The remaining bond of the titanium or zirconium atom bonded to the Si atom via an oxygen atom remains as an alkoxide group, or a part or all of them are bonded to another Si atom via an oxygen atom to form a polycarbohydrate. A crosslinked structure of silane can be formed. The above reaction between polycarbosilane and titanium alkoxide or zirconium alkoxide is known and described in JP-A-56-74126. JP-A 56-74126 describes only titanium and zirconium alkoxides as metal alkoxides, but other metals (for example, boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten, zirconium, It is clear that alkoxides of at least one metal element selected from chromium, iron, iridium, osmium, platinum, rhenium, rhodium and ruthenium can be used as well.

Other organometallic compounds that modify polycarbosilane include general formula MR _x (M is boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium) Further, metal acetylacetonate having a basic structure of at least one metal element selected from rhodium and ruthenium, R is an acetylacetonate group, and x is an integer greater than 1 can also be used. In this case as well, in the same manner as the method disclosed in Japanese Patent Publication No. 61-49335, polycarbosilane represented by the above general formula and metal acetylacetonate are heated and reacted in an inert atmosphere to obtain polycarbosilane. A polymetallocarbosilane having a number average molecular weight of 1,000 to 50,000 in which at least part of silicon atoms of silane is bonded to the metal atoms of the metal acetylacetonate via oxygen can be produced.

  In the second step (b) of fine particle production, the precursor polymer is mixed with a poor solvent and dissolved by heating, and then the precursor polymer is precipitated by cooling the solution, and the precipitate is filtered off. In this process, fine particles of spherical precursor polymer are obtained, and a so-called fine particle precipitation phenomenon due to cooling crystallization is utilized.

  The poor solvent that can be used in the present invention is a solvent having a characteristic that the precursor polymer cannot be dissolved around room temperature, but can be dissolved by heating near the boiling point of the poor solvent. That is, any solvent that can dissolve and precipitate the precursor polymer by repeating heating and cooling may be used. Usable solvents include n-butanol, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, ethyl acetate, methyl ethyl ketone, diethyl carbonate, methanol, n-propanol, isopropyl There are alcohol, methanol, N, N-dimethylformamide, butyl acetate, acetone, isopropyl ether, acetonitrile, dimethyl carbonate and the like. Or what combined these 2 or more types can also be used. However, the solvent used in the present invention is not limited to the solvents listed here.

  The crystallizer used in the present invention is not particularly limited, but a stirring type crystallizer capable of efficiently forming fine particles and efficiently collecting the fine particles by a filtration operation is preferable. In the present invention, the precursor polymer fine particles are precipitated by a cooling operation. As a cooling method, self-evaporation, external circulation cooling, and jacket cooling can be adopted. preferable.

  As the stirring blade of the crystallization tank, a paddle blade, a propeller blade, a turbine blade, a max blend blade, a full zone blade, a Kaneka blade, an H blade, an anchor blade, or the like can be used. The particle size distribution of the precursor polymer obtained by crystallization depends on the temperature and concentration homogeneity of the precursor polymer solution. Further, the crystallized precursor polymer fine particles have a spherical shape due to the interfacial tension. In order to reduce the particle size distribution, it is better to stir strongly. However, when the shearing stress of stirring is excessively large, coalescence and destruction of the precipitated precursor polymer occur, and the sphericity is lowered. In order to efficiently stir the solution while maintaining high sphericity, it is preferable to stir with a Max Blend blade or a full zone blade.

  The particle diameter of the precursor polymer fine particles obtained by cooling crystallization can be controlled by the cooling rate of the precursor polymer solution. The crystallization phenomenon is a combination of nucleation and growth in a supersaturated solution. In the case of obtaining small fine particles, when the cooling rate is increased, the degree of supersaturation is increased, the number of nuclei generated is increased, and the growth of the particles is suppressed to obtain small particles. On the other hand, when obtaining fine particles having a large particle size, the supersaturation degree is decreased by decreasing the cooling rate, the number of nuclei is decreased, and the particle growth is promoted to obtain large particles. It is also effective to reduce the degree of supersaturation by adding an operation to keep the temperature of the solution constant at the time when nuclei are generated. The time for keeping the temperature constant is usually 1 to 100 minutes. Even if the holding time is about 1 minute, it is effective, but in order to increase the particle diameter more effectively, the holding time is preferably 30 minutes or more. In the cooling crystallization method, precursor polymer fine particles of 50 to 10,000 nm can be obtained.

  Moreover, a microreactor method can also be employed as another example of a crystallizer that can be used in the present invention. There are various types of microreactors. Here, a double tube microreactor method will be described as an example.

  A double-tube microreactor is one in which an inner tube with an inner diameter of about 0.5 mm is inserted inside an outer tube with an inner diameter of about 2 mm. By flowing a poor solvent solution of a precursor polymer from the inner tube through the outer tube, Precursor polymer fine particles are deposited in the mixed portion of both liquids. By maintaining the mixed portion of both liquids in a laminar mixed state, monodisperse and spherical particles can be obtained. By controlling the ratio of the precursor solution to the poor solvent, precursor polymer fine particles of 50 to 100,000 nm can be obtained.

  A known method can be adopted for filtering the precursor polymer fine particles. For example, in the method using a filtration membrane, the nominal pore size of the filtration membrane is 0.1 to 1 μm, preferably 0.2 to 0.5 μm, and the material of the filtration membrane is not particularly limited. And organic films such as cellophane, acetylcellulose, polyacrylonitrile, polysulfone, polyolefin, polyamide, polyimide, and polyvinylidene fluoride, and inorganic films such as graphite, ceramics, and porous glass. Moreover, if it is a laboratory scale, filter media, such as a PTFE membrane filter, can be used. This filtration operation can be performed under reduced pressure or increased pressure, but is not particularly limited.

  The precursor polymer fine particles recovered by the filtration operation are dried to remove the residual solvent, but the drying method is not particularly limited. For example, natural drying, hot air drying, reduced pressure drying, freeze drying, supercritical drying and the like can be employed.

  In the third step (c) for producing fine particles, the spherical precursor polymer fine particles are preheated in an atmosphere containing oxygen to perform an infusible treatment. This step is performed for the purpose of preventing the fine particles from melting and adhering to the adjacent fine particles during the subsequent baking. The treatment temperature and treatment time vary depending on the composition and are not particularly defined, but generally treatment conditions of several hours to 30 hours are selected in the range of 50 to 400 ° C. Further, the oxidizing atmosphere may contain moisture, nitrogen oxides, ozone, etc. that enhance the oxidizing power of fine particles, and the oxygen partial pressure may be changed intentionally.

  The fourth step (d) for producing the fine particles is a step of firing the spherical precursor polymer fine particles in vacuum or in an inert gas.

  Spherical silicon carbide fine particles can be obtained by firing in an atmosphere containing an inert gas or oxygen in the range of 500 to 2000 ° C., and the composition of the spherical silicon carbide fine particles is controlled by the firing temperature and firing atmosphere. be able to.

When the raw material precursor polymer is polycarbosilane, when calcined in a range of 500 to 1600 ° C. in a vacuum or an inert gas, SiC _x O _y fine particles (wherein x is a number of 1 or more, y is greater than 0 and 2 The following number) is obtained: On the other hand, when calcined at 1600 ° C. or higher, SiC fine particles are obtained by desorbing oxygen by decomposition and desorption of SiO gas and CO gas.

If the raw material precursor polymer is polymetallocarbosilane, vacuum or SiM _x C _y O _z particles (wherein the firing in the range of 500 to 1600 ° C. in an inert gas, M is boron, hafnium, molybdenum, niobium, tantalum , Titanium, vanadium, tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium, ruthenium, x is a number greater than 0 and less than 1, y is a number greater than or equal to 1 , Z is a number greater than 0 and less than or equal to 2). On the other hand, in Si _x M _y C particles (formula by oxygen decomposed by elimination of the firing SiO gas and CO gas is desorbed at 1600 ° C. or more, M is boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium , Tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium, ruthenium, and x and y are positive numbers satisfying x + y = 1. The firing apparatus is not particularly limited as long as the firing atmosphere can be controlled.

  In the present invention, the sphericity of the silicon carbide fine particles is defined as the ratio (DS / DL) between the maximum diameter (DL) of the particles and the short diameter (DS) orthogonal thereto. For such sphericity, first, a field emission scanning electron microscope (manufactured by Hitachi, Ltd .: S-4200) is photographed to confirm that there are no non-spherical fine particles. The short diameter (DS) and the maximum diameter (DL) were determined for each of the 10 pieces, and the average value of the ratio (DS / DL) was defined as the sphericity.

  The average particle size and particle size variation of the silicon carbide fine particles were determined as follows. First, a field emission scanning electron micrograph of fine particles (manufactured by Hitachi, Ltd .: S-4200) was taken, and the ferret diameter was measured for 200 of these images, and the average particle diameter was determined from this value. The coefficient of variation (CV value) of the particle size was obtained by the following equation using the particle size of 200 particles.

  CV value (%) = (particle diameter standard deviation (σ) / average particle diameter (Dn)) × 100

  The spherical silicon carbide fine particles according to the present invention preferably have an average particle size in the range of 50 to 100,000 nm and a sphericity in the range of 0.9 to 1.0. Moreover, it is preferable that a particle diameter variation coefficient (CV value) is 20% or less. The average particle size is more preferably in the range of 50 to 5,000 nm, more preferably 50 to 2,000 nm. The sphericity is more preferably in the range of 0.95 to 1.0. The particle diameter variation coefficient (CV value) is more preferably 18% or less.

  The average particle size of the spherical silicon carbide fine particles of the present invention is controlled by the conditions of the fine particle production second step (b), but the average particle size of the spherical silicon carbide fine particles is in the range of 50 to 50,000 nm. Fine particles with high sphericity and monodisperse and no aggregation can be obtained. On the other hand, when the average particle size is less than 50 nm, the particle size is too small and aggregation occurs, making it impossible to utilize the characteristics of monodispersed spherical fine particles. Further, filtration becomes difficult due to clogging of the filtration membrane.

  When the sphericity of the spherical ceramic fine particles of the present invention is less than 0.9, or when the particle diameter variation coefficient (CV value) exceeds 20%, it is used as a semiconductor sealing material used for small-sized, thin-film electronic components and the like. In some cases, it is inferior in high filling property, fluidity and moldability. Further, when used as a raw material for a ceramic sintered body, the relative density of the molded body is lowered and the density is inhomogeneous, so that a high-quality sintered body cannot be obtained.

(Amorphous silicon carbide ceramics and manufacturing method thereof)
The ratio of each element constituting the amorphous silicon carbide ceramics mainly composed of Si, M, C and O produced in the second aspect of the present invention is usually Si: 30 to 60% by weight, M : 0.5-35 wt%, preferably 1-10 wt%, C: 25-40 wt%, O: 0.01-30 wt%.

  The amorphous silicon carbide ceramics mainly comprising Si, M, C and O of the present invention has an average particle size in the range of 50 to 2,000 nm and a sphericity of 0.9 to 1.0. The amorphous spherical silicon carbide fine particles having a particle diameter variation coefficient (CV value) of 20% or less are sintered in the range of 1400 to 1600 ° C.

  In particular, the amorphous spherical silicon carbide fine particles as the raw material are amorphous spherical silicon carbide fine particles substantially composed of Si, M, C and O (M is boron, hafnium, molybdenum, niobium, tantalum). And at least one metal element selected from titanium, vanadium, tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium and ruthenium). By using this raw material, an amorphous silicon carbide ceramic sintered body containing Si, M, C and O as main components can be obtained.

  Amorphous silicon carbide fine particles suitable as the raw material powder of the present invention can be obtained by the method for producing silicon carbide fine particles described in the first aspect of the present invention, and particularly as described below. Can be suitably obtained.

  In the method for producing silicon carbide fine particles described in the first aspect of the present invention, the fourth step (d) of fine particle production is a step of firing the spherical precursor polymer fine particles in vacuum or in an inert gas, Amorphous spherical silicon carbide fine particles can be preferably obtained by firing in an inert gas or an atmosphere containing oxygen in the range of 500 to 1600 ° C. in the fourth step (d). The composition of the elementary fine particles can be controlled by the firing temperature and firing atmosphere.

  When the raw material precursor polymer is polycarbosilane, when calcined in vacuum or in an inert gas in the range of 500 to 1600 ° C., SiCxOy fine particles (wherein x is a number of 1 or more, y is a number of 0 to 2 ) Is obtained. On the other hand, when calcined at 1600 ° C. or higher, oxygen is desorbed due to decomposition and desorption of SiO gas and CO gas, resulting in crystalline SiC fine particles, which are not suitable as the raw material powder of the present invention.

  When the raw material precursor polymer is polymetallocarbosilane, SiMxCyOz fine particles (wherein M is boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, when fired in the range of 500 to 1600 ° C. in vacuum or inert gas) At least one metal element selected from tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium, ruthenium, x is a number greater than 0 and less than 1, y is a number greater than 1, and z is greater than 0 A number of 2 or less). On the other hand, when calcined at 1600 ° C. or higher, oxygen is desorbed by decomposition and desorption of SiO gas and CO gas, so that crystalline SixMyC fine particles (wherein M is boron, hafnium, molybdenum, niobium, tantalum, titanium, vanadium, And at least one metal element selected from tungsten, zirconium, chromium, iron, iridium, osmium, platinum, rhenium, rhodium, and ruthenium, and x and y are positive numbers satisfying x + y = 1). Not suitable. The firing apparatus is not particularly limited as long as the firing atmosphere can be controlled.

  In the second aspect of the present invention, the above-mentioned amorphous spherical silicon carbide fine particles, which are raw material powders, are molded into a required shape by a known molding method such as a press molding method.

  The amorphous spherical silicon carbide fine particles, which are raw material powders suitable for the present invention, may have an average particle diameter in the range of 50 to 2,000 nm and a sphericity in the range of 0.9 to 1.0. preferable. The average particle size is 50 to 1,000 nm, more preferably 50 to 500 nm. The sphericity is more preferably in the range of 0.95 to 1.0. Moreover, it is preferable that a particle diameter variation coefficient (CV value) is 20% or less. The particle diameter variation coefficient (CV value) is more preferably 18% or less.

  The average particle diameter of the amorphous spherical silicon carbide fine particles used as the raw material powder of the present invention is controlled by the conditions of the fine particle production second step (b), but the average particle diameter of the spherical silicon carbide fine particles is 50 to 50. When the thickness is in the range of 2,000 nm, fine particles with high sphericity and monodisperse and no aggregation can be obtained. On the other hand, when the average particle size is less than 50 nm, the particle size is too small and the particles are aggregated, so that the relative density of the molded body cannot be sufficiently increased, and a high-quality sintered body cannot be obtained. On the other hand, when the average particle size exceeds 2,000 nm, the particles are too large and sintering does not proceed, so that a sintered body having sufficient strength cannot be obtained.

  Even when the sphericity of the spherical ceramic fine particles of the present invention is less than 0.9 or when the particle diameter variation coefficient (CV value) exceeds 20%, the filling property and fluidity at the time of molding are inferior, The density cannot be increased sufficiently, and a high-quality sintered body cannot be obtained.

  In the present invention, the above-mentioned amorphous spherical silicon carbide fine particles, which are raw material powders, are molded into a required shape by a known molding method such as a press molding method.

  Thereafter, the molded body is sintered at a temperature of 1400 ° C. to 1600 ° C. in a non-pressurized atmosphere of an inert gas, whereby the intended silicon carbide ceramic is obtained.

When the sintering temperature is around 1400 ° C., a porous silicon carbide sintered body in which the raw material powder is necked is obtained, and this can be applied to uses such as a heat-resistant filter and an environmental catalyst. The porous silicon carbide sintered body preferably has an average pore diameter of 50 to 500 nm and a porosity of 30 to 60%. When the average pore diameter of the porous silicon carbide sintered body is smaller than 50 nm, the ratio of the continuous air holes becomes small, the fluid permeation characteristics and the like in the ceramic porous body are lowered, and the function as the porous body cannot be achieved. . On the other hand, if the average pore diameter is larger than 0.5 μm, sufficient strength required for use cannot be obtained. Similarly, when the porosity is less than 30%, the proportion of the continuous air holes becomes small, the fluid permeation characteristics and the like in the ceramic porous body are lowered, and the function as the porous body cannot be achieved. On the other hand, if the porosity is larger than 60%, sufficient mechanical strength required for use cannot be obtained.
The porous silicon carbide sintered body is useful for gas filters that can be used at high temperatures, gas separation membranes, and liquid filters that remove microparticles such as bacteria.

When the sintering temperature is raised to around 1600 ° C., a dense sintered body can be obtained. In order to obtain a denser sintered body, other firing methods such as an atmospheric pressure sintering method, a hot press method, a hot isostatic pressing (HIP) method, and the like can be applied.
The dense silicon carbide-based sintered body is useful for structural materials, corrosion-resistant materials, sliding materials and the like used at high temperatures, for example, semiconductor manufacturing device members, vacuum device members, heating elements, and the like.

Examples of the present invention are shown below.

Reference example 1
To 100 g of polycarbosilane having a number average molecular weight of 1200, 100 g of toluene and 64 g of tetrabutoxyzirconium were added, preheated at 100 ° C. for 1 hour, and then slowly heated to 150 ° C. to distill off the toluene and allowed to react for 5 hours. Further, the temperature was raised to 340 ° C. and reacted for 5 hours to synthesize modified polycarbosilane. This modified polycarbosilane was dissolved in xylene to prepare a xylene solution having a solid concentration of 50% by weight.

Example 1
60 g of the modified polycarbosilane xylene solution of Reference Example 1 was added dropwise to 400 g of 1,3-dimethyl-2-imidazolidinone heated to 125 ° C. and allowed to cool to 25 ° C. in 0.5 hours. The mixture was then cooled to 5 ° C. over 0.5 hours with further stirring. The resulting suspension was filtered to obtain about 30 g of modified polycarbosilane fine particles. The modified polycarbosilane fine particles are heated to 150 ° C. stepwise in air and then infusible, and then fired in argon gas at 1300 ° C. for 1 hour to obtain silicon carbide fine particles having an average particle size of 50 nm as a raw material powder. It was. The sphericity of the fine particles was 0.97, and the CV value was 16%.

Example 2
60 g of the modified polycarbosilane xylene solution of Reference Example 1 was added dropwise to 300 g of 1,3-dimethyl-2-imidazolidinone heated to 125 ° C., and allowed to cool to 5 ° C. in 24 hours. The resulting suspension was filtered to obtain about 30 g of modified polycarbosilane fine particles. The modified polycarbosilane fine particles are heated to 150 ° C. in air stepwise to be infusible, then fired in argon gas at 1300 ° C. for 1 hour, and the raw material powder is silicon carbide fine particles having an average particle diameter of 4,500 nm Got. The sphericity of the fine particles was 0.96, and the CV value was 19%.

Example 3
After granulating by adding about 5 parts by weight of a binder to 100 parts by weight of the silicon carbide fine particles obtained in Example 1, a molded body was produced at a molding pressure of 1 ton / cm ² . Then, after degreasing | defatting in the argon gas atmosphere with respect to the said molded object, sintering was performed on the conditions of 1600 degreeC x 3 hours, and the dense silicon carbide sintered body was obtained. The relative density of this silicon carbide ceramic was 98.8%. Further, X-ray diffraction measurement of the silicon carbide ceramic was performed, but no clear diffraction peak corresponding to β-SiC or ZrC was observed, and it was confirmed that the silicon carbide ceramic was substantially amorphous.

Example 4
After granulating by adding about 5 parts by weight of a binder to 100 parts by weight of the silicon carbide fine particles obtained in Example 1, a molded body was produced at a molding pressure of 1 ton / cm ² . Then, after performing degreasing | defatting in the argon gas atmosphere with respect to the said molded object, sintering was performed on the conditions of 1400 degreeC * 3 hours, and the porous silicon carbide sintered body was obtained. This porous silicon carbide ceramic had an average pore diameter of 50 nm and a porosity of 34%. Further, X-ray diffraction measurement of the silicon carbide ceramic was performed, but no clear diffraction peak corresponding to β-SiC or ZrC was observed, and it was confirmed that the silicon carbide ceramic was substantially amorphous.

Reference example 1
After granulating by adding about 5 parts by weight of a binder to 100 parts by weight of the silicon carbide fine particles obtained in Example 2, a molded body was produced with a molding pressure of 1 ton / cm ² . Then, after degreasing | defatting in the argon gas atmosphere with respect to the said molded object, sintering was performed on the conditions of 1600 degreeC x 3 hours, However, Densification does not advance but the sintered compact which hold | maintains a shape is obtained. I couldn't.

Comparative Example 1
After adding and granulating about 5 parts by weight of binder to 100 parts by weight of silicon carbide fine particles (average particle size: 0.03 μm) obtained by vapor phase thermal decomposition of trimethylsilane, forming 1 ton / cm ² A molded body was produced under pressure. Then, after degreasing | defatting in the argon gas atmosphere with respect to the said molded object, sintering was performed on the conditions of 1600 degreeC x 3 hours, but the sintered compact which hold | maintains a shape was not obtained.

Claims (3)

(A) Mainly general formula

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.)
An organosilicon precursor polymer comprising a polycarbosilane having a main chain skeleton represented by the formula: a polycarbosilane having a number average molecular weight of 200 to 10,000, or a modified polycarbosilane having a structure obtained by modifying the polycarbosilane with an organometallic compound. Providing a process;
(B) After the organosilicon precursor polymer is mixed with a poor solvent and heated to dissolve, the precursor polymer is precipitated by cooling the solution, and the precipitate is filtered to obtain a spherical precursor polymer. Obtaining a fine particle of
(C) a step of preheating the spherical precursor polymer fine particles in an atmosphere containing oxygen and performing an infusibilization treatment;
(D) A method for producing spherical silicon carbide fine particles, comprising a step of firing the infusible spherical precursor polymer fine particles in a vacuum or in an inert gas atmosphere. (A) Mainly general formula

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.)
An organosilicon precursor polymer comprising a polycarbosilane having a main chain skeleton represented by the formula: a polycarbosilane having a number average molecular weight of 200 to 10,000, or a modified polycarbosilane having a structure obtained by modifying the polycarbosilane with an organometallic compound. Providing a process;
(B) A precursor polymer is precipitated by mixing a solution in which the organosilicon precursor polymer is dissolved in a good solvent and a poor solvent for the organosilicon precursor polymer, and the precipitate is separated by filtration. Obtaining precursor polymer fine particles; and
(C) a step of preheating the spherical precursor polymer fine particles in an atmosphere containing oxygen and performing an infusibilization treatment;
(D) A method for producing spherical silicon carbide fine particles, comprising a step of firing the infusible spherical precursor polymer fine particles in a vacuum or in an inert gas atmosphere.   The method for producing spherical silicon carbide fine particles according to claim 1 or 2, wherein the modified polycarbosilane is polymetallocarbosilane.