JPH0223496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a novel aluminum nitride composition that can be used as a raw material for aluminum nitride green sheets and aluminum nitride sintered sheets, which are sintered bodies thereof. For details, (i) particle size is 2 μm or less,
Contains particles of 3 μm or less in a ratio of 70% by volume or more, has an oxygen content of 1.5% by weight or less, has an aluminum nitride purity of 95% or more, and does not contain iron, chromium, nickel, cobalt, zinc, or titanium as impurities. Aluminum nitride powder having a total weight of 0.1% by weight or less based on the total weight, () a binder made of an organic polymer compound that decomposes at a temperature of 1400°C or less, and (iii) Group a or Group a of the periodic table. A sintering aid consisting of a metal oxide consisting of a metal oxide or a metal compound capable of forming the metal oxide at a temperature of 1600°C or less, the above (I),
() and (), and the binder is 0.1 to 30 parts by weight per 100 parts by weight of aluminum nitride powder.
Part by weight and the sintering aid are aluminum nitride powder
This is an aluminum nitride composition in which 0.05 to 5 parts by weight of an oxide is blended per 100 parts by weight. A feature of the present invention is that a sintered body obtained by firing a green sheet made of the composition can be obtained as a transparent body. Conventionally, ceramic substrates have been used in various industrial and consumer electronic devices for mounting electronic devices such as transistors, ICs, and LSIs, forming circuits, and insulating them. For example, an alumina substrate is a typical example. However, in recent years, the heat conductivity of alumina substrates is insufficient in fields that require particularly high thermal conductivity, such as power transistors and high-power hybrid ICs, and there has been a demand for the development of high thermal conductivity ceramic substrates as an alternative. For this purpose, attempts have been made to develop highly thermally conductive ceramic substrates using various ceramics. however,
At present, a highly thermally conductive ceramic substrate that is industrially satisfactory has not yet been developed. Based on the above background, the inventors of the present invention have earnestly attempted to develop a highly thermally conductive ceramic substrate. If we compare only the performance of high thermal conductivity, for example, aluminum nitride sintered bodies have several times higher thermal conductivity than alumina sintered bodies, but green sheets are manufactured using conventionally known aluminum nitride powder. This is difficult, and even if the green sheet was produced, it was not possible to sinter the green sheet to obtain a sintered sheet that could be used as a material for electronic substrates. For this reason, it was thought that it would be impossible to industrially produce a sintered sheet using aluminum nitride as a raw material.
Although the inventors have believed that the above conclusion is correct,
In the process of developing high-purity aluminum nitride powder, if a specific aluminum nitride powder is used as a raw material, not only can a good green sheet be manufactured, but the green sheet can even be sintered under pressure. It was discovered that the sintered sheet obtained by sintering not only has high thermal conductivity but also has high strength and can be used as an industrially excellent electronic board. Thereafter, based on the above findings, various statistical experiments were repeated, and the present application was completed and proposed here. Therefore, an object of the present invention is to obtain a raw material composition that is easy to handle as a raw material for industrially obtaining an aluminum nitride sintered body that has translucency, high strength, and excellent thermal conductivity. There is a particular thing. In other words, the present invention is based on (I) an oxygen content containing particles having an average particle size of 2 μm or less and 3 μm or less in a proportion of 70% by volume or more;
1.5% by weight or less, aluminum nitride purity is 95%
Above, the total weight of iron, chromium, nickel, cobalt, zinc and titanium as impurities is
Aluminum nitride powder of 0.1% by weight or less; () A binder made of an organic polymer compound that decomposes at a temperature of 1400°C or less; () A metal oxide of Group A or Group A of the Periodic Table; A sintering aid consisting of a metal compound that can form the metal oxide at temperature, consisting mainly of the above (I), () and (), and the binder is 0.1 to 30 parts by weight per 100 parts by weight of aluminum nitride powder. and the sintering aid is added as an oxide to 100 parts by weight of aluminum nitride powder.
It is an object of the present invention to provide a raw material composition for producing an aluminum nitride sintered body having translucency and containing 0.05 to 5 parts by weight. Note that aluminum nitride in the present invention is a 1:1 compound of aluminum and nitrogen, and anything other than this is treated as an impurity in principle. However, since the surface of the aluminum nitride powder is inevitably oxidized in the air and Al--N bonds replace Al--O bonds, aluminum with Al--O bonds is not considered to be a cationic impurity. Also, components that serve as sintering aids are not considered cationic impurities. Furthermore, the average particle diameter in the present invention refers to the volume-based median particle diameter measured by a light transmission type particle size distribution analyzer. The greatest feature of the present invention lies in the aluminum nitride powder which is the main component of the composition of the present invention. The aluminum nitride powder has the characteristics of being highly purified as aluminum nitride, being a fine powder with an extremely small average particle size, and containing an extremely small amount of oxygen, compared to conventionally known powders. That is, the aluminum nitride powder used in the present invention has an average particle size of 2 μm or less, an oxygen content of 1.5% by weight or less, and a purity of aluminum nitride.
More than 95% aluminum nitride powder. In particular, it is preferable that the aluminum nitride powder particles have small particle diameters, and in general, it is most preferable that the aluminum nitride powder contains particles with a diameter of 3 μm or less at a ratio of 70% by volume or more. Conventionally, industrially produced aluminum nitride on the market has an average particle size of
There is no material with a diameter of 2 μm or less and an oxygen content of 1.5% by weight. It was not impossible to obtain particles with an average particle size of 2 μm or less in the laboratory by crushing and classifying them, but when aluminum nitride is crushed, the surface of the aluminum nitride is oxidized during the crushing process, which reduces the oxygen content. 1.5% by weight as inventive
It cannot be reduced to less. In addition, it has conventionally been believed that the higher the oxygen content in aluminum nitride powder, the better the sinterability, but in the present invention, as mentioned above, aluminum nitride powder with a small average particle size and preferably uniform particle size is used. In general, the lower the oxygen content, the less it will adversely affect the sinterability, and the better the thermal conductivity of the sintered body will be.
Therefore, the average particle size and oxygen content of the aluminum nitride powder are extremely important requirements from the viewpoint of the sinterability and thermal conductivity properties imparted to the sintered body. Further, the aluminum nitride powder used in the present invention preferably has an aluminum nitride purity of 95% by weight or more, preferably 97% by weight or more. Aluminum nitride powder contains compounds that are included in its raw materials and are unavoidable during production. Compounds that become these impurities vary depending on the purity of the raw material used to manufacture aluminum nitride powder and cannot be definitively limited, but generally include carbon, silicon, manganese, iron, chromium, nickel,
It is a compound containing cobalt, copper, zinc, titanium, etc. as cationic components. These impurity compounds generally have a large effect on the properties of the aluminum nitride sintered body, such as thermal conductivity, so the content of the metal compounds as impurities is preferably 0.3% by weight or less as metal. It is preferable to use 0.2% by weight or less, more preferably 0.1% by weight or less. In particular, among the above impurity component metals, iron, chromium, nickel, cobalt, copper,
The aluminum nitride powder, which is zinc or titanium and contains impurities of 0.1% by weight or less based on the metal, imparts translucency to the aluminum nitride sintered body. When producing the aluminum nitride powder used in the present invention, a compound corresponding to the sintering aid described below is added to the raw material in advance, and the aluminum nitride powder obtained by firing is obtained in a form containing the sintering aid. It will be done. One of the preferable usage forms of such aluminum nitride powder is one in which the components (i) and (ii) of the present invention are blended in advance. The aluminum nitride powder suitably used in the present invention may be obtained by any manufacturing method as long as it has the properties described above. A more specific description of one method for producing aluminum nitride powder that is generally preferably used is as follows. That is, (1) fine alumina powder with an average particle size of 2 μm or less and fine carbon powder with an ash content of 0.2% by weight or less and an average particle size of 1 μm or less are intimately mixed in a liquid dispersion medium, and at this time, the alumina The weight ratio of fine powder to said carbon fine powder is 1:0.36 to 1:1; (2) The resulting intimate mixture is suitably dried and calcined at a temperature of 1400 to 1700°C under an atmosphere of nitrogen or ammonia. (3) Then, the obtained fine powder is heated at a temperature of 600 to 900°C in an oxygen-containing atmosphere to remove unreacted carbon, and the aluminum nitride content is at least 95% by weight, and the bond is maximum oxygen content
A fine aluminum nitride powder having an average particle diameter of 2 μm or less is produced, with a content of 1.5% by weight and a maximum content of metal compounds as impurities of 0.3% by weight as metal. It can be manufactured by According to the above method, it is possible to avoid the step of pulverizing aluminum nitride obtained by firing the raw material. By avoiding the pulverization process, impurities mixed in during the pulverization process can be removed.
In addition, it is possible to prevent the surface of aluminum nitride from being oxidized during grinding and increasing the oxygen content. The advantages of omitting the step of crushing aluminum nitride are also extremely large. In order to obtain aluminum nitride with good properties while omitting the above-mentioned pulverization step, it is important to adopt a so-called wet mixing method in which the fine alumina powder and the fine carbon powder are mixed in a liquid dispersion medium in the manufacturing process. It is. The wet mixing method not only allows the raw materials to be mixed closely, but also surprisingly prevents the raw material particles from agglomerating and becoming coarse. The resulting intimate mixture is then calcined to yield fine-grained and even-grained aluminum nitride. Moreover, as mentioned above, it is possible to completely prevent impurity components mixed in during the grinding process, etc., and it is also possible to prevent oxidation of the aluminum nitride surface, so it has excellent sinterability and high purity compared to conventional methods. A sintered body with high thermal conductivity and translucency can be produced, and aluminum nitride with excellent properties can be produced. The liquid medium that can be used in the wet mixing is not particularly limited, and any known wet mixed solvent can be used. Generally, water, hydrocarbons, aliphatic alcohols, or mixtures thereof are preferably employed industrially. Hydrocarbons are, for example, ligroin, petroleum ether, hexane, benzene, toluene, etc., and aliphatic alcohols are, for example, methanol, ethanol, isopropanol, etc. Further, the wet mixing is preferably carried out in an apparatus made of a material that can avoid contamination of the aluminum nitride with impurity components that remain even after firing.
In general, the wet mixing can be carried out at normal temperature and pressure, and is not adversely affected by temperature and pressure. Further, as the mixing device, any known device or means may be used as long as the mixing device is selected from the material and does not produce residual impurity components even after firing. For example, it is common to use a mill with built-in spheres or rods as a mixing device, but the inner walls of the mill, the materials of the spheres or rods, etc. remain in the resulting aluminum nitride even after firing. In order to avoid contamination with impurity components, it is preferable to use aluminum nitride itself or high purity alumina of 99.9% by weight or more. Further, all surfaces of the mixing device that come into contact with the raw materials may be made of plastic or may be coated with plastic. The plastic is not particularly limited, and for example, polyethylene, polypropylene, nylon, polyester, polyurethane, etc. can be used. In this case, since the plastic may contain various metal components as stabilizers, it should be checked in advance before use. In addition, in the above method, alumina and carbon with specific properties are used in order to omit the pulverization step in the manufacturing process and to obtain fine aluminum nitride powder with good sinterability, an average particle size of 2 μm or less, and high purity. It is essential to do so. The fine alumina powder must have an average particle diameter of 2 μm or less, and preferably has a purity of at least 99.0% by weight, more preferably at least 99.9% by weight. Carbon fine powder has the highest ash content
It should be used with a purity of 0.2% by weight, preferably a maximum of 0.1% by weight. Furthermore, since the average particle size of the carbon affects the particle size of the aluminum nitride obtained, it is necessary to use it as a fine powder with an average particle size of 1 μm or less. As the carbon, carbon black, graphitized carbon black, etc. can be used, but carbon black is generally preferred. The raw material usage ratio of alumina and carbon varies depending on the properties of the alumina and carbon, such as their purity and particle diameter, and is therefore preferably determined by conducting a preliminary test in advance. Usually alumina and carbon,
The weight ratio of alumina to carbon is 1:0.36 to 1:
1, preferably wet mixing in the range of 1:0.4 to 1:1. The wet mixed raw materials are dried if necessary and then fired at a temperature of 1400 to 1700°C under a nitrogen atmosphere. If the firing temperature is lower than the above temperature, the reduction and nitrogenation reaction will not proceed industrially sufficiently, which is not preferable. Furthermore, if the firing temperature is higher than the above temperature, a portion of the aluminum nitride obtained will sinter, causing agglomeration between particles, making it difficult to obtain aluminum nitride having the desired particle size, which is not preferable. According to the present invention, the nitride fine particles obtained by firing are then heat-treated at a temperature of 600 to 900°C in an oxygen-containing atmosphere to oxidize and remove unreacted carbon contained in the nitride fine particles. It is subjected to a process of When mixing the raw materials in (1) above, by adding the necessary amount of a metal oxide that will become a sintering aid or a compound that will become the metal oxide, which will be described later, a sintering aid can be added to the obtained aluminum nitride powder in advance. This results in aluminum nitride powder containing a chemical agent. Such aluminum nitride powder is also suitably used in the present invention. One of the other components that make up the aluminum nitride composition of the present invention is a binder. The binder used in the present invention is an organic polymer compound that decomposes at temperatures below 1400°C. The aluminum nitride composition of the present invention is generally sintered at a temperature of 1600 to 2000°C, for example via an aluminum nitride green sheet,
It is suitably used as a sintered aluminum nitride sheet. In this case, if a large amount of decomposition residue of the binder remains in the sintered body, it becomes difficult to obtain the desired physical properties of the sintered body, such as high strength, high thermal conductivity, or translucency. According to the findings of the present inventors, the binder having the above requirements does not substantially remain in the sintered body, or even if it remains, the amount is such that it does not impair the desired physical properties of the sintered body. Therefore, it is necessary to select the type and process it. Binders that are generally used for molding ceramic powders are not particularly limited and may be used in the present invention, but in general, binders that decompose in a temperature range of 1400° C. or lower are preferred as determined by thermogravimetric analysis (TG). More preferably, a binder is selected whose decomposition residue is 5% by weight or less based on the binder. More specific examples of binders preferably used in the present invention include polyvinyl butyral, polymethyl methacrylate, cellulose acetate butyrate, nitrocellulose, polyacrylic acid ester, polyvinyl alcohol, methylcellulose, hydroxymethylcellulose, and Oxygen-containing organic polymers such as polyethylene oxide, other petroleum resins, hydrocarbon-based synthetic resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride; acrylic resins and their emulsions; waxes and their emulsions, and other organic polymers Or a mixture of two or more types is used. As mentioned above, the surface of the aluminum nitride powder used in the present invention is inevitably oxidized and has Al--O bonds. Therefore, it is particularly preferable to use the oxygen-containing organic polymer as a binder since it exhibits a strong bonding force based on its excellent chemical affinity with the surface of the aluminum nitride powder. The organic polymer used as the binder is not particularly limited, but generally has a molecular weight of 3,000 to 1,000,000, preferably 5,000.
300,000 is more preferable because the above-mentioned molded product, such as a green sheet, is flexible and tough and can be easily handled during various processing. Among the organic polymers, oxygen-containing organic polymers are particularly preferred, and polyvinyl butyral having a molecular weight of 30,000 to 100,000 is most preferred. The amount of binder used varies depending on the type of binder and the type of solvent described below, and also depends on the application of the aluminum nitride composition, such as the thickness, strength, and processability of the aluminum nitride green sheet, as well as the sintering of the green sheet. Although it cannot be definitively defined as it varies depending on the physical properties required for the aluminum nitride sintered sheet obtained by the process, generally aluminum nitride powder 100
0.1 to 30 parts by weight, preferably 4 to 30 parts by weight
It may be selected from a range of 10 parts by weight. One of the other components that make up the aluminum nitride composition of the present invention is a sintering aid. The sintering aid used in the present invention serves to improve the sinterability, particularly the pressureless sinterability, of aluminum nitride powder. At the same time, it has a number of industrially immeasurable advantages, such as lowering the sintering temperature and shortening the sintering time. The sintering aid used in the present invention is
The metal oxide is selected from metal oxides of Group A or Group A, or metal compounds that can form the metal oxide at a temperature of 1600° C. or lower. The metals belonging to group a of the periodic table are generally beryllium, magnesium, calcium, strontium, barium, and particularly calcium, strontium, and barium are preferred. Yttrium or lanthanum group metals are preferably used as metals belonging to group a of the periodic table, and more specifically, yttrium, lanthanum, cerium, praseosium, neodymium, promethium, samarium, europium, cadrinium, terbium, and dysprosium. , holminium, erbium, thulium, ytterbium, lutetium, etc., and particularly yttrium, lanthanum, cerium, neodymium, etc. are preferable. These metals belonging to group a or group a of the periodic table may generally be used as metal oxides, but as mentioned above, they can be used as metal compounds that become metal oxides under the conditions in which aluminum nitride powder is sintered. You can also do that. The metal compound may be, for example, a nitrate, carbonate, or chloride. The amount of the sintering aid used is based on 100 parts by weight of the aluminum nitride powder when the sintering aid is converted into an oxide.
It may be selected from the range of 0.05 to 5 parts by weight, preferably 0.1 to 4 parts by weight. Since the amount of these additives varies depending on the oxygen content, impurity content, particle size, etc. in the aluminum nitride powder, the appropriate amount to be used may be determined in advance according to these properties. The aluminum nitride composition of the present invention is prepared by mixing the aluminum nitride powder, the binder, and the sintering aid in the proportions described above, as well as adding and mixing a deflocculant, a plasticizer, etc. as necessary. It is not a hindrance and is often used as a preferred embodiment. For example, when the aluminum nitride powder, binder, and sintering aid of the present invention are dispersed and mixed in a solvent as described in detail later, it is often preferable to use a deflocculant to promote the dispersion. It is in a similar manner. As the deflocculant, any compound known to be generally used in molding ceramic powder may be used without particular limitation. Typical deflocculants that are generally suitably used include, for example, glycerin or sorbitol esters of fatty acids such as glycerin trioleate and sorbitan trioleate; natural fish oil; nonionic synthetic surfactants;
Higher fatty acids; benzenesulfonic acid, etc. The amount of these deflocculants to be used varies depending on the type of deflocculant, the type of the mixed system to be added, etc., and cannot be absolutely limited, but in general, it is preferably 0.01 to 5 parts by weight per 100 parts by weight of aluminum nitride powder. It is preferable to select from the range of 0.1 to 3 parts by weight. Although the peptizer may be mixed in any order, generally the aluminum nitride powder and the sintering aid are mixed in advance with the peptizer in a dispersion medium, and then the binder or the plasticizer described later is added. It is preferable to add and mix them to prepare a slurry. Further, the plasticizer is used for the purpose of imparting flexibility to a specific molded product when the aluminum nitride composition of the present invention is processed into a specific molded product. The plasticizer is not particularly limited, and any plasticizer known to be used for the above purpose in molding general ceramic powder can be used. Typical examples that are particularly preferably used include generally polyethylene glycol and its derivatives; phthalate esters such as dimethyl phthalate, dibutyl phthalate, butylbenzyl phthalate and dioctyl phthalate; stearic acid such as butyl stearate. Esters; Tri-cresol phosphate; Tri-N
-butyl phosphate; glycerin, etc.
The amount of these plasticizers added varies depending on the type of binder, the properties of aluminum nitride, the type and amount of solvent used, etc., and cannot be absolutely limited, but in general, it is preferably 15 parts by weight or less per 100 parts by weight of aluminum nitride. may be appropriately selected from the range of 0.4 to 15 parts by weight, more preferably 3 to 10 parts by weight. The usage mode of the aluminum nitride composition of the present invention will be explained below. When used, it is generally preferable to use it in a form dispersed in a dispersion medium. The role of the dispersing medium is generally to disperse the aluminum nitride powder and the sintering aid, and also to dissolve the binder or optionally used plasticizer to form a uniform slurry. After the slurry is formed into a specific shape, such as a sheet, the solvent is preferably substantially removed by drying and does not remain in the aluminum nitride molded product, such as a green sheet. Therefore, the dispersion medium, ie, the solvent, is not particularly limited as long as it satisfies the above-mentioned requirements for dispersibility, solubility, and drying properties, but it is generally preferable to select a non-aqueous solvent. Specific examples of typical solvents that are particularly preferably used include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, alcohols such as ethanol, propanol and butanol, benzene, toluene and xylene. It is preferable to use one or a mixture of two or more of aromatic hydrocarbons or halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene, and bromochloromethane.
The amount of solvent used is not particularly limited, but if the amount of solvent is too large, the particles of aluminum nitride powder and sintering aid will tend to settle and separate during storage, molding, or drying of the slurry, and if it is too small, the particles may become sheet-like. Since molding becomes difficult, an appropriate amount may be selected and used in advance. Generally, the amount of the solvent depends on its type and the types and amounts of the binder and plasticizer, but it is preferably selected in the range of 30 to 100 parts by weight per 100 parts by weight of the aluminum nitride powder. The mixing conditions for the aluminum nitride composition of the present invention are not particularly limited, and the mixing may be carried out at room temperature and normal pressure, and the mixing device will be explained based on the mixing mode of the raw materials for producing the aluminum nitride powder in order to prevent the mixing of impurity components. It is preferable to choose the material as shown above or choose one covered with plastic. Most generally, it is preferable to use a mill that has a built-in spherical object, rod-like object, or the like. The above-mentioned mixture is generally used as a viscous paint-like slurry called slurry, so that it can be easily handled during molding. The aluminum nitride composition obtained as described above, that is, the aluminum nitride powder of (i) above, (ii) a binder, and (iii) a sintering aid, or if necessary, a plasticizer, a peptizer, etc., in a solvent. Mix to form a slurry. This slurry is formed into a sheet on a film made of a synthetic resin such as polyethylene, polypropylene, polyester, polyamide, polyvinyl chloride, etc. using a sheet forming machine such as a doctor blade type sheet forming machine. Next, the sheet-like molded product is dried by scattering the solvent at a temperature between room temperature and the boiling point of the solvent to form a so-called aluminum nitride green sheet. The aluminum nitride green sheet generally has a glossy appearance, is flexible, and has strong properties against bending. The aluminum nitride green sheet already has a tensile strength of 25 kg/cm ² or more. The above aluminum nitride green sheet can be used as is for the production of a sintered sheet as described below, but it is generally heated under an atmosphere of an oxygen-containing gas such as air at a temperature at which the binder, plasticizer, peptizer, etc. are decomposed. For example, 300~1400℃, preferably 500~
It is preferable to carry out the thermal decomposition treatment at a temperature of 1000°C. The aluminum nitride green sheet or the sheet subjected to the above heat treatment is then subjected to a sintering process. The sintering process is not particularly limited, and any known sintering method used for nitrides may be employed. Generally, sintering may be carried out at a temperature of 1,600 to 2,100° C. under normal pressure, in an inert atmosphere, for example, in a nitrogen atmosphere.
The pressure during the sintering is generally normal pressure, but a sintering furnace maintained under a certain degree of pressure with an inert gas may also be used. Further, the time required for sintering varies depending on various conditions such as the thickness of the sheet material to be sintered and the sintering temperature, and cannot be absolutely limited, but it may generally be selected from a range of 30 minutes to 24 hours.
It is preferable that appropriate ranges of these conditions be determined in advance according to various conditions prior to implementation. The sintered sheet obtained by the above sintering process generally has a sintered density of 2.7 g/cm ³ or more, preferably 2.9 g/cm ³
More preferably, it is 3.0 g/cm ³ or more. The sheet is generally obtained with a side length of at least 5 mm or more and a thickness in the range of 0.05 to 10 mm. These sintered sheets form excellent sheet-like products with a bending strength of at least 20 kg/mm ² . The sintered sheet also has excellent thermal conductivity, generally exhibiting a thermal conductivity of 60 watts/mK or more. Furthermore, the sintered sheet can be made into a translucent sheet by controlling the amount of impurities mixed in the aluminum nitride powder, which is the raw material.
A sintered sheet with an absorption coefficient of 60 cm ^-1 or less for light with a wavelength of 6 μm can be obtained. An aluminum nitride sintered sheet having these excellent properties was proposed for the first time by the present invention, and the industrial merits of the present invention are immeasurable. EXAMPLES In order to explain the present invention more specifically, the present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. The various analytical methods and analytical devices used in the following Examples and Comparative Examples are as follows. Cation analysis: Plasma emission spectrometer (ICP-AES, manufactured by Daini Seiko) Carbon analysis: Carbon in metal analyzer (manufactured by Horiba, Ltd.)
EMIA-3200) Oxygen analysis: Metal oxygen analyzer (Horiba, Ltd.)
EMGA-1300) Nitrogen analysis: Melting separation neutralization titration method
CAPA-500) Thermal conductivity measuring device: Rigaku laser method thermal constant measuring device PS-7 Light transmittance measuring device: Hitachi Self-recording spectrophotometer 330 type Infrared spectrophotometer 260-30 type In addition, sintered bodies The light transmittance of was calculated using the following formula. I/Io=(1-R) ² e ^- 〓 ^t ...(1) Here, Io is the intensity of incident light, I is the intensity of transmitted light,
R is the reflectance, t is the thickness of the sintered body, and μ is the absorption coefficient. R is determined by the refractive index of the sintered body, and if the refractive index is n, R is expressed by the following equation when measured in air. R=(1-n) ² /(1+n) ² ...(2) μ in formula (1) is an index representing the translucency of the sintered body, and μ is shown in the examples below. value is
Calculated according to formula (1). Example 1 The purity is 99.99% (impurity analysis values are shown in Table 1), the average particle diameter is 0.52 μm, and the proportion of particles of 3 μm or less is
100 parts by weight of 95 vol% alumina and 50 parts by weight of carbon black having an ash content of 0.08 wt% and an average particle size of 0.45 μm were uniformly mixed in a ball mill using a nylon pot and a nylon-coated ball using ethanol as a dispersion medium. After drying the resulting mixture, it was placed in a flat plate made of high-purity graphite and heated at a temperature of 1600° C. for 6 hours while continuously supplying nitrogen gas at 3/min in an electric furnace. The resulting reaction mixture was heated in air at a temperature of 750° C. for 4 hours to oxidize and remove unreacted carbon. The white powder obtained is
As a result of Xray diffraction analysis, it is single phase AlN, Al ₂ O ₃
There was no diffraction peak. The average particle size of the powder was 1.31 μm, and particles of 3 μm or less accounted for 90% by volume. When observed using a scanning electron microscope, this powder was found to be uniform particles with an average size of about 0.7 μm. Further, the measured value of the specific surface area was 4.0 m ² /g. The analytical values of this powder are shown in Table 2. Table 1 Al ₂ O ₃ powder analysis values Al ₂ O ₃ content 99.99% Element Content (PPM) Mg < 5 Cr < 10 Si 30 Zn < 5 Fe 22 Cu < 5 Ca < 20 Ni 15 Ti < 5 Table 2 AlN Powder analysis value AlN content 97.8% Element content Mg < 5 (PPM) Cr 21 ( ) Si 125 ( ) Zn 9 ( ) Fe 20 ( ) Cu < 5 ( ) Mn 5 ( ) Ni 27 (〃) Ti < 5 (〃) Co < 5 (〃) Al 64.8 (wt%) N 33.4 (〃) O 1.1 (〃) C 0.11 (〃) Aluminum nitride powder 100 thus obtained
Calcium oxide is 1.0 part by weight as a sintering aid, and the molecular weight is 30,000 or more as a binder.
34000 polyvinyl butyral (7.3 parts by weight), 1.6 parts by weight of glycerin trioleate as a deflocculant, and 12.2 parts by weight of dibutyl phthalate as a plasticizer, 61 parts by weight of a toluene-ethanol mixed solvent (mixed weight ratio toluene/ethanol = 60/ 40) The slurry was prepared by mixing in the container. Furthermore, as a result of previously measuring the thermal decomposition curve of the polyvinyl butyral in air using thermogravimetric analysis (TG), the decomposition started at about 200°C and ended at about 600°C, leaving virtually no residue. I confirmed that there was no. The above mixing procedure was as follows. That is,
Into a nylon pot with an internal volume of 2, put nylon-coated steel balls with a diameter of 15 mm in a number that accounts for about 50% of the pot's internal volume, and then add aluminum nitride powder, calcium oxide, glycerin trioleate, and the above solvent by each weight above. After adding the parts, the rotation speed
Ball mill mixing was performed at 60 rpm for 24 hours. Thereafter, the above weight parts of polyvinyl butyral and dibutyl phthalate were added to the pot and mixed for an additional 24 hours. In this way, a white, viscous, paint-like slurry was prepared. The obtained slurry was formed into a sheet on a polypropylene film using a dokuder blade type sheet forming machine, and then the formed product was heated at room temperature for 5 hours.
Thereafter, it was dried at 60° C. for 6 hours to scatter the solvent, thereby producing an aluminum nitride composition of the present invention in the form of a sheet with a width of about 10 cm and a thickness of about 0.8 mm.
This sheet-like aluminum nitride composition (also referred to as aluminum nitride green sheet) has a white, glossy appearance, and is flexible and strong against bending. A test piece was punched out from an aluminum nitride green sheet and subjected to a tensile test using an autograph, and the tensile strength was 25 kg/cm ² . 5cm of the above aluminum nitride green sheet
It was punched into a square plate of 5cm x 5cm, heated in an electric furnace at 650°C in an air atmosphere of 1 atm for 3 hours to thermally decompose and remove the binder, plasticizer and peptizer, and aluminum nitride. Obtained a square plate. This square plate was sintered at 1900℃ for 3 hours in a nitrogen atmosphere of 1 atm.
A sintered aluminum nitride sheet with a size of 4.3 cm x 4.3 cm and a thickness of 0.7 mm was obtained. This sintered sheet was a yellowish translucent body with a density of 3.2 g/cm ³ . The bending strength of this sintered sheet is 42Kg/ ^mm2 , and the thermal conductivity is
The transmittance of 6 μm light is 28% (μ = 23
cm ^-1 ). Comparative Example 1 A slurry and an aluminum nitride green sheet were prepared in exactly the same manner as in Example 1, except that no sintering aid was added. The aluminum nitride green sheet was punched into a square plate shape of 5 cm x 5 cm.
650℃ in an air atmosphere of 1 atm using an electric furnace.
The binder, plasticizer and peptizer were thermally decomposed and removed by heating for 3 hours to obtain an aluminum nitride square plate. As a result of heating this square plate at 1900°C for 3 hours in a nitrogen atmosphere of 1 atm, the density was 2.4 g/cm ³ and Example 1~
The aluminum nitride sintered sheet obtained in step 5 (density 2.95
~3.23 g/cm ³ ), the resulting aluminum nitride square plate had a significantly lower degree of densification. Furthermore, the aluminum nitride square plate obtained in this comparative example is a gray opaque body with a low thermal conductivity of 37 W/nk, and cannot be used industrially as a substrate for electronic materials. Example 2 Alumina with a purity of 99.3% and an average particle size of 0.58 μm
100 parts by weight and ash content 0.15wt%, average particle size is 0.44μm
Using a nylon pot and ball, 80 parts by weight of carbon black was uniformly mixed with hexane as a dispersion medium. After drying the resulting mixture, place it in a high-purity high-lead flat plate and add ammonia gas to the furnace at 1/min.
The mixture was heated at a temperature of 1650° C. for 4 hours while being continuously supplied with water. The resulting reaction product was heated in air at a temperature of 750° C. for 6 hours to oxidize and remove unreacted carbon. The average particle size of the powder was 1.42 μm, and particles of 3 μm or less accounted for 84% by volume. Table 3 shows the analysis results of the powder.
Shown below. Table 3 Analysis values of AlN powder AlN content 96.9% Element Content Mg 48 (PPM) Cr 110 ( ) Si 2500 ( ) Zn 20 ( ) Fe 370 ( ) Cu < 5 ( ) Mn 40 ( ) ) Ni 120 ( ) Ti 25 ( ) Co < 5 ( ) Al 64.9 (wt%) N 33.1 ( ) O 1.3 ( ) C 0.16 ( ) Except for using the aluminum nitride powder obtained above An aluminum nitride green sheet was produced using the same formulation and method as in Example 1. This green sheet had a bulk density of 2.0 g/cm ³ and a tensile strength of 22 Kg/cm ² . 5cm of the above aluminum nitride green sheet
It was punched out into a rectangular plate shape of 5cm x 0.8mm thick. This was heated in a 1 atm nitrogen-hydrogen mixed gas (hydrogen 5 vol%) atmosphere from room temperature to 1900°C for 5 hours.
Then, it was sintered at 1900° C. for 3 hours under a nitrogen gas atmosphere of 1 atm. In addition, as a result of measuring the weight loss of the aluminum nitride green sheet during the temperature increase process using a separate TG, it was found that the binder and
The plasticizer and deflocculant were decomposed and scattered, and even if there was any residue, it was less than 5% of the blended amount. The aluminum nitride sintered sheet obtained above is 4.2 cm
It had a shape of x4.2 cm and a thickness of 0.7 mm, and was a yellowish translucent body with a density of 3.1 g/cm ³ . The bending strength of the sintered sheet is 37 Kg/mm ² , the thermal conductivity is 68 W/m K, and the transmittance of light at 6 μm is 6% (μ =
53cm ^-1 ). Example 3 100 parts by weight of the same alumina used in Example 1, 50 parts by weight of carbon black with an ash content of 0.08 wt% and an average particle size of 0.45 μm, and 1.3 parts by weight of calcium carbonate with an average particle size of 3 μm were coated with polyurethane resin. Using a pot and a ball, ethanol was used as a dispersion medium and the mixture was uniformly mixed using a ball mill. After drying this mixture, it was reacted and oxidized under the same conditions as in Example 1 to obtain aluminum nitride powder. The average particle diameter of the obtained powder was 1.44 μm, and particles of 3 μm or less accounted for 86% by volume. Table 4 shows the analytical values of this powder. This powder is aluminum nitride powder that already contains calcium oxide as a sintering aid. Table 4 Analysis values of AlN powder AlN content 96.9wt% Element Content Ca 0.09 (PPM) Mg <5 (〃) Cr 17 (〃) Si 86 (〃) Zn 12 (〃) Fe 25 (〃) Cu <5 ( ) Mn 4 ( ) Ni 27 ( ) Ti < 5 ( ) Co < 5 ( ) Al 65.0 (wt%) N 33.1 ( ) O 1.5 ( ) C 0.15 ( ) Above aluminum nitride An aluminum nitride green sheet was produced using the same formulation and method as in Example 1, except that powder was used and calcium oxide was not newly added. The bulk density of the aluminum nitride green sheet is 2.2g/ ^cm3 ,
The tensile strength was 23Kg/ ^cm2 . The above aluminum nitride green sheet was punched into the same shape as in Example 2, and then the aluminum nitride sintered sheet was obtained under the same firing and sintering conditions as in Example 2. The sintered sheet is 4.3cm x 4.3cm, thickness 0.7
It was in the shape of a rectangular plate with a diameter of 3.1 g/cm ³ . The bending strength of this sintered sheet is 42Kg/ ^mm2 , the thermal conductivity is 110W/m・K, and the transmittance for 6μm light is 30% even though it is processed and polished to a thickness of 0.5mm.
(μ=21cm ^-1 ). Example 4 The aluminum nitride powder obtained in Example 1, calcium oxide as a sintering aid, polymethyl methacrylate with a molecular weight of about 50,000 as a binder, and the following deflocculant, plasticizer, and solvent were mixed in the same manner as in Example 1. A viscous paint-like slurry was obtained. Aluminum nitride powder (Example 1) 100 parts by weight Calcium oxide (sintering aid) 3.0 Polymethyl methacrylate (binder) 5.8 Dioctyl phthalate (plasticizer) 14.8 Sorbitan trioleate (peptizer) 0.8 Normal butanol (Solvent) 55 In addition, as a result of measuring the thermal decomposition behavior of the above polymethyl methacrylate in air using TG,
Decomposes in the temperature range of approximately 200℃ to approximately 550℃, 650℃
Substantially no residue remained. The thermal decomposition of dioctyl phthalate and sorbitan trioleate was also investigated using the same method, and it was confirmed that they decompose and scatter at temperatures up to about 400°C. Using the slurry obtained above, an aluminum nitride green sheet having a width of about 10 cm and a thickness of 0.76 mm was produced in the same manner as in Example 1. The aluminum nitride green sheet had a bulk density of 2.4 g/cm ³ and a tensile strength of 19 Kg/cm ² . From the obtained aluminum nitride green sheet
Punch out a square plate-shaped sample of 5.8cm x 5.8cm and 0.76mm thickness.
This was heated and sintered under the same conditions as Example 1.
A translucent aluminum nitride sintered sheet having a shape of 5.0 cm x 5.0 cm and a thickness of 0.64 mm was produced. The density of the sintered sheet is 3.2g/ ^cm3 , and the bending strength is 45
Kg/mm ² , and the thermal conductivity was 82 W/m·K. Example 5 Slime and aluminum nitride green sheets were prepared in exactly the same manner as in Example 1, except that the metal compounds shown in Table 5 were used as sintering aids in the amounts shown in the same table. The aluminum nitride green sheet was heated in the same manner as in Example 1 and sintered at the sintering temperature shown in Table 5 to obtain a sintered aluminum nitride sheet. The results are shown in Table 5. 【table】

Claims (1)

[Claims] 1 (I) An aluminum nitride having an average particle diameter of 2 μm or less, containing particles of 3 μm or less in a ratio of 70% by volume or more, an oxygen content of 1.5% by weight or less, and an aluminum nitride purity.
Aluminum nitride powder containing 95% or more and a total weight of iron, chromium, nickel, cobalt, zinc and titanium as impurities of 0.1% by weight or less, () A bond consisting of an organic polymer compound that decomposes at a temperature of 1400°C or less () A sintering aid consisting of a metal oxide of group a or group a of the periodic table, or a metal compound that can become the metal oxide at a temperature of 1600°C or less, the above (I), (), and (), the binder is 0.1 to 30 parts by weight per 100 parts by weight of aluminum nitride powder, and the sintering aid is as an oxide per 100 parts by weight of aluminum nitride powder.
A raw material composition for producing a translucent aluminum nitride sintered body containing 0.05 to 5 parts by weight. 2 Aluminum nitride powder is a mixture of alumina powder with an average particle size of 2 μm or less and fine carbon powder with an ash content of 0.2% by weight or less and an average particle size of 1 μm or less in a liquid dispersion medium, and the mixture is placed in a nitrogen or ammonia atmosphere. Baked at a temperature of 1400-1700℃ under
The translucent aluminum nitride according to claim 1, which is obtained by heating the obtained fine powder at a temperature of 600 to 900°C in an oxygen-containing atmosphere to remove carbon. Raw material composition for producing sintered bodies. 3. The raw material composition for producing a translucent aluminum nitride sintered body according to claim 1, wherein the aluminum nitride powder contains 0.3% by weight or less of a metal compound as an impurity. 4. The raw material composition for producing a translucent aluminum nitride sintered body according to claim 1, wherein the binder is an oxygen-containing organic polymer. 5 Molecular weight of oxygen-containing organic polymer is 3000~
1,000,000, the atomic composition for producing an aluminum nitride sintered body having translucency according to claim 5. 6. The translucent nitriding material according to claim 1, wherein the sintering aid is a metal oxide of calcium, strontium, barium, yttrium, or lanthanum, or a metal compound capable of forming the metal oxide at a temperature of 1600°C or lower. Raw material composition for producing aluminum sintered bodies. 7. The raw material composition for producing a translucent aluminum nitride sintered body according to claim 1, which is formed into a sheet shape.