JP5495748B2 - Aluminum nitride powder - Google Patents

Description

  The present invention relates to a novel aluminum nitride (hereinafter referred to as AlN) powder. Specifically, the present invention provides an aluminum nitride powder obtained by pulverizing an AlN sintered body generated by disposal or the like and having stable sinterability as a raw material for sintering the AlN sintered body.

  Aluminum nitride has excellent properties such as high thermal conductivity, high plasma resistance, and high electrical insulation. For this reason, it is used as an insulating heat dissipation substrate utilizing high thermal conductivity and high electrical insulation, plasma resistance, thermal expansion coefficient equivalent to silicon, and high thermal conductivity for semiconductor manufacturing equipment materials.

  In order to provide the above-mentioned use, when firing a molded body of AlN powder or when processing an AlN sintered body obtained by firing, an AlN sintered body product in which cracks, cracks, etc. are generated, and the above manufacturing and processing In general, the end material of the AlN sintered body that is inevitably generated in the process is discarded. However, since an AlN sintered body such as a waste material (hereinafter also referred to as a waste AlN sintered body) made of such an AlN sintered body is a nitrogen-containing compound, ammonia may be generated if the landfill process is performed as it is. For this reason, a great deal of labor is required, such as the need to convert it to an oxide.

In recent years, as a method for effectively utilizing a waste AlN sintered body, it has been proposed to grind the AlN sintered body and utilize it as a filler for resin addition. Specifically, a resin composite obtained by pulverizing a waste AlN sintered body and mixing it with a resin is known (Patent Document 1).
In the reuse method of the waste AlN sintered body, a method of performing the grinding by mechanical crushing such as a vibration mill, a roll crusher, a ball mill, a stamp mill, or the like, in which the waste AlN sintered body and the grinding media are in direct contact with each other is adopted.

  However, in the conventional mechanical crushing methods that have been generally used, in order to pulverize to a few micron level that can be used as a raw material of the sintered body, it requires a corresponding stress and time. In the pulverization, the grain boundaries between the crystal grains constituting the sintered body and the breakage within the crystal grains, in particular, the breakage of the corners constituting the crystal grains, occur. It was inevitable that there were a large amount of irregularly shaped fragments (hereinafter referred to as fine powder) having a size of 1 μm or less in which the AlN crystal particles constituting the aggregate were broken in the grains. Since such fine powder is easily oxidized due to its surface area, when the obtained AlN powder is used as a raw material for an AlN sintered body, oxygen diffuses into the AlN crystal particles, and the thermal conductivity is remarkably reduced. It turns out that there is a problem.

  Although it is conceivable to remove fine powder produced by intragranular crushing from what was obtained by conventional mechanical pulverization, the amount thereof is large, and such fine powder has a strong cohesive force and is even larger. Since many particles adhere firmly to the particles, it is difficult to completely separate them. Further, even when the separation treatment is performed a plurality of times, not only the fine powder remains, but also the particles other than the fine powder are reduced by the separation treatment, so that the utilization rate of the waste AlN sintered body is lowered, It does not fundamentally solve the problem.

  Furthermore, according to the general mechanical pulverization method described above, since the AlN sintered body is generally high in hardness, mixing of metal elements derived from the apparatus due to scraping of the contacting member such as pulverization media is inevitable. The mixing of the metal impurities has few problems in the filler application, but when this is used as a raw material for an AlN sintered body, the thermal conductivity of the obtained AlN sintered body is remarkably lowered, and the color tone is further reduced. There are concerns about problems such as changes and deterioration of electrical characteristics.

  As described above, mixing of metal impurities causes deterioration of the characteristics of the aluminum nitride sintered body, and therefore, in order to avoid mixing of metal impurities, lining the portion of the crushing machine that contacts AlN with alumina has been studied. . In the case of adopting the above method, since alumina is cut instead of metal, it is possible to suppress mixing of metal elements. However, even in this case, it is unavoidable that a large amount of fine powder is generated as in normal mechanical crushing, and the problem of an increase in oxygen concentration derived from fine powder cannot be solved.

  On the other hand, a porcelain obtained by sintering using AlN sintered body pulverized particles and glass as raw materials has been proposed (Patent Document 2). In the above-mentioned Patent Document 2, in the pulverization of AlN sintered body (specific method is not shown), since the AlN sintered body breaks grain boundaries, the pulverized particles have a structure similar to a regular hexahedron. It is supposed to be shown. However, some AlN sintered bodies exhibit a structure similar to a regular hexahedron by being subdivided by grain boundary fracture, but as described above, intragranular fracture is simultaneously performed along with grain boundary fracture. It is inevitable that this occurs, and in the obtained pulverized particles, it is inevitable that a large amount of fine powder is present as a result of intragranular fracture, and as a result, the problem of reducing the thermal conductivity of the sintered body cannot be solved .

  Thus, it is difficult to avoid the generation of fine powder and the mixing of metal impurities at the same time by the conventional mechanical pulverization method.

Japanese Patent No. 3936990 JP-A-6-16477

  Therefore, the object of the present invention is to efficiently provide AlN powder with reduced generation of fine powder and reduced metal impurity concentration, which can be used stably as a raw material for the production of AlN sintered body. There is to do.

  As a result of intensive studies to solve the above problems, the inventors of the present invention selected a specific pulverization condition for an AlN sintered body and pulverized to a crystal grain size while preferentially causing grain boundary fracture. The present inventors have succeeded in obtaining a novel AlN powder that is almost free from mixing of fine powder and metal impurities generated by pulverization. In addition, the aluminum nitride powder can be used as a raw material AlN powder of an AlN sintered body alone or in combination with an AlN powder obtained by a direct nitridation method or a reduction nitridation method. The present inventors have found that a body can be obtained and have completed the present invention.

That is, according to the present invention, an aluminum nitride sintered body having an average grain diameter of 2 to 10 μm is preferentially caused to cause grain boundary fracture, and the equivalent diameter is 1 mm to 30 mm. Preliminarily pulverized, and then the pulverized product is subjected to collision pulverization using a collision-opposing jet mill. Provided is a method for producing an aluminum nitride powder in which the proportion of fine powder of 1 μm or less in the powder is 5% or less in terms of area ratio and the metal impurity concentration other than the sintering aid is 1500 ppm or less. .

Further, the AlN powder obtained by the method of the present invention has a small proportion of the fine powder, so that the density stabilization rate by the tapping test is fast, and the ratio of tap density to bulk density (tap density / bulk density) The characteristic of 0.9-1 is shown.

Although pulverization AlN powder obtained by the upper Symbol crushing method is to satisfy the amount of the fine powder may be further removed by classification device fines fraction present trace amounts.

  The preliminary pulverization and the collision pulverization are preferably performed in an inert gas atmosphere so that an increase in oxygen content can be prevented.

Although the AlN powder of the present invention is a powder obtained by pulverizing an AlN sintered body, there is almost no fine powder and the metal impurity concentration is very low. It has the characteristics that do not have. For this reason, oxidation due to moisture adsorption during storage and oxidation in each process during the production of a sintered body are less likely to occur due to the presence of such fine powder, and the decrease in thermal conductivity due to oxygen is suppressed, and thermal conductivity caused by metal impurities In addition, it is possible to manufacture a sintered body having stable characteristics with almost no decrease in electrical insulation.
Therefore, the range of use of crushed powder, which has conventionally been used only as a plastic filler, can be expanded, and it can contribute to the reduction of the environmental burden due to the disposal of the waste AlN sintered body.

  Also, in the AlN manufacturing process, the defective AlN substrate generated in such a process can be reused as a raw material for manufacturing an AlN sintered body without being discarded, so that the recovery rate of AlN is improved and low-cost AlN A manufacturing process of the sintered body can be realized.

Scanning electron micrograph showing the particle structure of the aluminum nitride powder of the present invention (Example 2) Scanning electron micrograph showing the particle structure of the aluminum nitride powder of the present invention (Example 4) Scanning electron micrograph showing the particle structure of aluminum nitride powder (Comparative Example 3) obtained by the conventional method

  A characteristic of the AlN powder of the present invention is a powder obtained by pulverizing an aluminum nitride sintered body, having an average particle diameter of 2 to 10 μm and observed in an electron micrograph of 3000 times. The proportion of fine powder of 1 μm or less in the powder is 5% or less in terms of area ratio, and metal impurities other than the sintering aid are 1500 ppm or less.

  In addition, the ratio for which the fine powder of 1 micrometer or less accounts in a powder can be confirmed with an electron micrograph, as shown in detail in the Example mentioned later. As a method for measuring the particle size of the powder, for example, measurement by a laser diffraction method is generally used. However, the above method cannot distinguish agglomerated particles or adhered particles from primary particles, and the amount of fine powder (ratio) ) Cannot be evaluated correctly, the reduction of fine powder, which is a feature of the present invention, cannot be made clear. That is, in the present invention, in order to grasp the agglomerated particles and adhered particles of the fine powder, the microphotograph taken at a magnification of 3000 times, the area occupied by the fine powder of 1 μm or less with respect to the area of all the particles in the visual field area. The percentage was determined. In the calculation of the above ratio, when the particles were observed to overlap each other, the area of each particle was included as the area.

  In order to use it as a raw material for producing an AlN sintered body which is the object of the present invention, the average particle size of the pulverized AlN powder of the present invention is 2 to 10 μm, preferably from the viewpoint of sinterability and ease of production. It is necessary to be 3 to 7 μm. That is, as the average particle size increases, the sinterability tends to decrease. When the average particle size exceeds 10 μm, it takes a lot of time or cannot be sintered. Implementation is difficult. In order to ensure an industrially acceptable sintering time (about 10 hours), when the AlN powder of the present invention is used alone, the average particle size is preferably 7 μm or less. Moreover, when using together with the AlN powder (henceforth a commercial AlN powder) obtained by the conventional reductive nitriding method and the direct nitriding method, the sinterability improves as the mixing ratio of the commercial AlN powder increases.

  On the other hand, AlN powder having an average particle diameter of less than 2 μm has good sinterability, but it is difficult to sufficiently prevent generation of the fine powder in production.

  The AlN powder of the present invention may be composed of the AlN powder having the above average particle diameter alone, or may be composed by mixing a plurality of types of AlN powders having such an average particle diameter.

  In the present invention, the AlN powder obtained by crushing one kind of AlN sintered body generally has a difference in particle size between D90 and D10 of 6 μm or less, preferably 5 μm or less.

  The greatest feature of the AlN powder of the present invention is that in the pulverized powder having the above average particle diameter, the proportion of fine powder of 1 μm or less in the powder is 5% or less, preferably 3% or less, more preferably in area ratio. Is less than 1%.

  The AlN powder of the present invention is obtained by pulverizing an AlN sintered body, and the above physical property values are obtained by pulverizing the AlN powder of the present invention to the level of crystal grains. This indicates that there are generally few irregularly shaped fine powders due to chipping in the crystal grains.

  As described above, the AlN powder of the present invention is stabilized with a small number of changes in density in the tapping test because there is almost no fine powder generated due to chipping of crystal particles. In particular, the AlN powder having a sharp particle size distribution exhibits a stability where the ratio of tap density to bulk density (tap density / bulk density) is 0.9 to 1.

  In contrast, the AlN powder for fillers obtained by the conventionally proposed crushing is obtained by mechanical crushing in which the pulverized product and the media are in direct contact with each other, and has a higher crushing media than the AlN crystal particles. The corners of the AlN crystal particles are broken by the contact with, and the abundance of the fine powder is remarkably increased. Incidentally, the proportion of fine powder of 1 μm or less in the AlN powder obtained by performing conventional mechanical pulverization is 20% or more in terms of area ratio. Moreover, the fine powder has strong cohesiveness and adhesiveness, and it is difficult to obtain a powder in which the proportion of fine powder of 1 μm or less in the powder is 5% or less in terms of area ratio by a separator using a cyclone or a sieve. In particular, in the mechanical crushing, there are many fine powders adhering to the surface of relatively large AlN crystal particles, but those adhering fine powders and fine powders aggregate to form relatively large agglomerated grains. Separation is difficult, and it is not suitable as an Al powder for producing an AlN sintered body, which is an object of the present invention. However, in filler applications, the AlN powder containing the fine particles is used without any problem.

  The AlN powder of the present invention is different from the particles obtained by the conventional reductive nitriding method and direct nitriding method in that the ridgeline forming the boundary of the crystal plane of the AlN crystal can be clearly confirmed in its appearance. It can be distinguished from the powder.

  The present invention aims to provide an AlN powder that can be effectively used as at least a part of a raw material for producing an AlN sintered body, and for that purpose, is one of the characteristics of the AlN sintered body. It is desirable that impurities that cause a decrease in high thermal conductivity be as small as possible. Examples of the impurities include oxygen and metal impurities.

  These impurities are classified into those contained in the waste AlN substrate itself and impurities mixed in during the grinding process. The impurities referred to in the present invention particularly refer to impurities mixed in the pulverizing process, and refer to metal elements other than metal elements derived from the sintering aid contained in the waste AlN substrate and oxygen. Specifically, alkaline earth metals, rare earth metals, and metal elements other than aluminum that are generally used as sintering aids are called metal impurities. In the present invention, the oxygen concentration other than the sintering aid is the amount of oxygen combined with the metal when the alkaline earth metal or rare earth metal is completely oxidized, as will be described in detail in the examples described later. The oxygen concentration removed from the total amount of oxygen contained in the aluminum nitride powder of the present invention.

  The metal impurity is a metal element other than the metal constituting the sintering aid and the aluminum nitride as described above, and is especially mixed from SUS, WC, ZrO2 or the like used as a grinding machine member and is burned with AlN. It is desirable that Fe, Cr, Ni, Mn, W, Zr, etc., which easily affect the physical properties of the aggregate, be as small as possible. In addition, it is desirable that Si (mixed from a member made of Si3N4) that is a semi-metal, which causes a decrease in thermal conductivity, and further that carbon that inhibits densification be mixed are also small.

  In addition, the AlN powder of the present invention has a metal impurity concentration (including Si) other than the sintering aid of 1500 ppm or less, desirably 1000 ppm or less, and more desirably 500 ppm or less. When the metal impurity concentration is higher than the above range, the thermal conductivity of the aluminum nitride sintered body is lowered and the appearance is deteriorated.

  In addition, since the oxygen concentration other than oxygen derived from the sintering aid greatly depends on the amount of fine powder, the present invention makes it possible to obtain aluminum nitride powder having a low oxygen concentration by reducing the amount of fine powder. That is, in the AlN powder of the present invention, the oxygen concentration other than oxygen derived from the sintering aid is 0.2 to 1.4% by weight or less, preferably 1.2% or less, more preferably 0.9% or less. It is desirable to be. This is a value including oxygen dissolved in the AlN crystal particles. When the oxygen concentration is higher than the above range, there arises a problem that the oxygen content is dissolved in the AlN particles and the thermal conductivity is lowered. Further, the lower the oxygen concentration, the better. However, it is preferable to set 0.2% by weight as the lower limit in view of the balance between economy and effect in industrial implementation.

  Such a pulverized AlN powder with few impurities can be suitably produced by a production method described later.

<Method for producing aluminum nitride powder>
The production method of the aluminum nitride powder of the present invention is not particularly limited, but if a suitable production method is exemplified, the AlN sintered body is preliminarily produced to a predetermined size by causing grain boundary fracture preferentially. There is a method of pulverizing and then impact pulverizing the preliminary pulverized product. In the above pulverization, the AlN sintered body and the pre-ground product are preferably crushed in an inert atmosphere.

(AlN sintered body)
As the AlN sintered body used in the method for producing an AlN powder of the present invention, the waste AlN sintered body is generally used. That is, in the process of firing AlN or the process of processing an AlN sintered body obtained by firing, it is inevitable in the process of manufacturing and processing of an AlN sintered body that has cracked or cracked. The end material of the AlN sintered body produced in the above, and the AlN sintered body which is out of the specifications by the dimensional inspection and the appearance inspection before shipment, etc. are mentioned.

  In addition, the aluminum nitride powder of the present invention basically depends on the particle size of the crystal particles of the AlN sintered body before crushing, and has an average particle size approximate to the average particle size of the crystal particles. Therefore, in order to obtain aluminum nitride powder having good sinterability, the average particle diameter of the crystal particles of the AlN sintered body is 2 to 10 μm, preferably 3 to 7 μm. It is desirable to obtain an AlN powder having a particle size.

Y ₂ O ₃ is generally used as the sintering aid used in the AlN sintered body, but other sintering aids can also be used. For example, alkaline earth compounds such as oxides and various salts such as CaO, SrO, BaO, or rare earth compounds such as La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ The thing which does not inhibit such heat conductivity is mentioned.

In addition, since the purity of the AlN sintered body is reflected in the characteristics of the obtained aluminum nitride powder, it has at least a purity equal to or higher than that of the AlN powder produced by the reduction nitriding method or the direct nitriding method. Is preferably used.
Specifically, the metal impurity concentration other than the sintering aid is 500 ppm or less, and the c-axis length correlated with the oxygen concentration dissolved in the aluminum nitride crystal particles is preferably 4.975 mm or more.

Of course, it is also possible to use a product recovered after it has been used as a product. In this case, it is particularly preferable to remove attached dirt and the like by washing or polishing. (Preliminary crushing)
Preliminary crushing to obtain the AlN preliminarily crushed material is an operation of preferentially causing the grain boundary fracture to make the AlN sintered body a predetermined size.

  Any suitable device for pre-crushing can be used without particular limitation as long as it is a device capable of preferentially causing grain boundary destruction. Examples of suitable crushing apparatuses include a stamp mill, a hammer crusher, and a jaw crusher.

  In order to prevent metal contamination, the preliminary crushing preferably has an equivalent diameter of 1 mm or more. In order to efficiently perform the subsequent pulverization treatment, the upper limit is preferably 30 mm or less.

  The atmosphere in the preliminary crushing should be an inert gas atmosphere that does not contain oxygen so that the contamination and oxidation of the AlN preliminary crushed material obtained in the preliminary crushing can be suppressed and the purity of the AlN preliminary crushed material can be maintained. Is desirable. Moreover, it is preferable that the crushing apparatus to be used is one that has been subjected to wear resistance treatment or that has a surface coated with a resin in order to prevent metal from mixing into the AlN sintered body.

  In the preliminary crushing of the AlN sintered body, since the size of the preliminary crushed material is large, it is possible to easily separate the fine powder even when the fine powder is generated during the preliminary crushing. Therefore, in the present invention, the obtained preliminarily crushed material may remove fine powder having a particle size of 1 μm or less using a classifier such as a cyclone, if necessary.

(Pulverization)
In the method for producing an aluminum nitride powder of the present invention, the AlN powder can be obtained by impact pulverization of the AlN preliminary crushed material. That is, according to the above pulverization method, since the pulverization progresses mildly compared with the conventional mechanical pulverization without colliding with a harder material than the AlN crystal particles, the grain boundary fracture of the AlN preliminary crushed material easily occurs. Even when the pulverization proceeds to the unit crystal particles, it is possible to effectively prevent the corners of the crystal particles from being broken and the abundance of the fine powder from being significantly increased. Further, since the pulverization proceeds due to the collision of AlNs, it is possible to effectively prevent the mixing of metal impurities due to the contact with the metal crushing media, which is seen in the conventional method.

  The apparatus used for the collision pulverization is preferably a collision-opposed jet mill. Moreover, inert gas, such as a noble gas and nitrogen gas, is used suitably as carrier gas used for collision crushing. The inert gas used as the carrier gas is preferably one that does not contain water as much as possible, and generally one from which water has been removed so as to have a dew point of −10 ° C. or lower is preferred. Moreover, dry air can also be used as an inert gas, and in that case, it is recommended that the water is removed so that a dew point of −20 ° C. or lower is obtained.

  Further, the concentration of the AlN preliminary crushed material in the carrier gas is preferably about 20 to 50% by volume, and the collision gas pressure is preferably selected from about 0.4 to 0.6 MPa.

(Classification)
In the present invention, it is desirable that the AlN powder obtained by the pulverization further removes fine powder of 1 μm or less by classification. For the classification, a known classification device is used without any particular limitation. For example, a typical classifier is preferably an air classifier. The classification point in classification is preferably determined in the range of 1.5 to 3 μm.

(Method for producing sintered body using AlN pulverized powder)
The pulverized AlN powder obtained by the present invention can be used alone to produce a sintered body. However, when obtaining a sintered body having a higher thermal conductivity, the AlN powder of the present invention is at least used. It is preferable to use it as a part of the raw material and use a commercially available AlN powder for the remainder. As such commercially available AlN powder, AlN powder obtained by a known method such as a direct nitriding method, a reductive nitriding method or the like is used without any particular limitation. It is desirable to be 3 μm.

  Further, in the embodiment in which the AlN powder of the present invention is used as a part of the raw material powder, the proportion of the raw material AlN powder is not particularly limited, but is 1 to 60% by weight, preferably 1 to 50% by weight, more preferably 1 to It is desirable to blend at a ratio of 30%.

  In the present invention, the raw material aluminum nitride powder is then molded and further fired to obtain an AlN sintered body. For this purpose, a known method is employed without any particular limitation. To give a specific example, a sintering aid powder is added in the range of 1 to 10 parts by weight to the raw material AlN powder, and further if necessary. Organic binders, plasticizers, dispersants, etc. are added and mixed with a planetary ball or the like by a mixer or dry or wet, for example, by a doctor blade method, press molding method, extrusion molding method, injection molding method, etc. It is preferable to mold.

  In this invention, when shape | molded with the said organic binder, it is common that the molded object performs a degreasing process prior to baking. As the degreasing treatment, known conditions can be used without particular limitation. For example, a method of treating at a temperature of 300 to 1000 ° C. for 1 to 10 hours in an oxidizing atmosphere or a non-oxidizing atmosphere is common. is there.

  In the present invention, known firing conditions are employed for firing without any particular limitation. For example, the degreased body is heated at a temperature of 1600 to 1900 ° C., preferably 1650 to 1850 ° C. in a non-oxidizing atmosphere such as nitrogen. The firing is preferably performed at 1680 to 1820 ° C. for 1 to 100 hours, preferably 2 to 50 hours, more preferably 2 to 30 hours.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

<Measurement method>
1) Proportion of fine powder In the particle size distribution measurement method using the laser diffraction method, which will be described later, fine powder is counted as agglomerated particles and adhered particles, and causes a large error in the amount of fine powder. . 20 fields of view were observed with a scanning electron microscope (S-2600N manufactured by Hitachi, Ltd.) at a magnification of 3.0K, and the total area of all particles (including particles of 1 μm or less) within the field of view (S _SUM ( The ratio of the area (S _SUM (FINE GRAIN)) occupied by fine powder of 1 μm or less to (GRAIN)) is analyzed using an image analysis system (IP-1000PC; manufactured by Asahi Kasei Kogyo Co., Ltd.). Area occupancy was calculated.
Fine powder area occupancy (%) = (S _SUM (FINE GRAIN) / S _SUM (GRAIN)) × 100 (1)
In the calculation of the above ratio, when the particles were observed to overlap each other, the area of each particle was included as the area.

2) Metal Impurity Concentration The metal concentration in the AlN sintered body and the pulverized product was decomposed by adding nitric acid and phosphoric acid to the AlN pulverized powder, and ICP emission spectroscopic analysis using ICPS-1000-II manufactured by Shimadzu Corporation. It was measured.

In the present invention, Al and a sintering aid (for example, common Y ₂ O ₃ , CaO, SrO, BaO oxides such as alkaline earth compounds such as various salts, La ₂ 0 ₃ , CeO ₂ , Metals other than Nd ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ and other elements that do not inhibit thermal conductivity such as rare earth compounds, specifically Fe, Cr, Ni, Mn , Si, W, Zr, and other metal concentrations are called metal impurity concentrations.

3) Oxygen concentration other than oxygen derived from the sintering aid The oxygen concentration in the pulverized product of the AlN sintered body is inert using an oxygen / nitrogen simultaneous analyzer (EMGA-620W / C) manufactured by Horiba, Ltd. The oxygen extracted by melting AlN in the gas by the impulse heating melting method was converted into a form of carbon monoxide, and the carbon monoxide was measured with a non-dispersive infrared detector. The measured value at this time is a.

For example, the case element aid was Y, the Y amount was quantified by ICP, in terms of Y ₂ O ₃ was complete oxidation of Y, the amount of oxygen contained in the Y ₂ O ₃ amount b To do. This oxygen amount b is converted to the oxygen concentration in the sintered body. This converted concentration is defined as b ′. The amount obtained by subtracting the oxygen concentration of b ′ from the oxygen concentration of a was defined as the oxygen concentration not derived from the sintering aid.

4) Bulk density and tap density JIS: R1628 (-1997) was used.

5) Particle size distribution It calculated | required by the laser diffraction method using Nikkiso MICROTRACK-HRA. Aluminum nitride powder was added to a solution obtained by adding 5% sodium pyrophosphate aqueous solution to 90 ml of water, and this was measured by dispersing it with a homogenizer at an output of 200 mA for 3 minutes. The average particle diameter (D50), D10 and D90 were determined from the above method. The data is a number distribution.

6) Density The density of the sintered body was measured by the Archimedes method.

7) Thermal conductivity The thermal conductivity of the produced AlN sintered body was measured by a laser flash method using LFA-502 manufactured by Kyoto Electronics Industry.

8) Bending strength According to JIS R1601, the crosshead speed was 0.5 mm / min and the span was 30 mm. As the test piece, a substrate having a width of 4 mm, a thickness of 0.635 mm, and a length of 40 mm was used.

9) Fracture toughness value It calculated by IF method from the Vickers hardness measured with the Vickers hardness tester AVK-CO by Akashi Co., Ltd. by the method according to JIS R1607.

(Manufacture of AlN sintered body)
The AlN sintered body for crushing and crushing was manufactured by the following method. An alumina ball with a diameter of 15 mm is placed in a nylon ball mill having an internal volume of 20 L, and then 5 parts by weight of yttrium oxide as a sintering aid, a dispersant and a solvent with respect to 100 parts by weight of AlN powder (H grade made by Tokuyama). And mixed for 14 hours. Thereafter, polyvinyl butyral and a plasticizer were added as binders and mixed for 18 hours to obtain an AlN slurry. After defoaming the AlN slurry, the viscosity was adjusted to 20,000 cps, and a molded body having a thickness of 0.75 mm was prepared by a doctor blade method.

  The obtained molded body was degreased in an air atmosphere at 500 ° C. for 4 hours, and fired in a nitrogen atmosphere at 1740 ° C. for 5 hours to obtain an AlN sintered body.

  The average grain size of the crystal grains constituting the obtained sintered body is 3.5 μm, the metal impurity concentration other than the sintering aid contained in the AlN sintered body is 100 ppm, and the c-axis length is It was 4.976 cm.

<Examples 1-3>
The obtained AlN sintered body was preliminarily crushed to a size of about 1 cm with a hammer mill using a hammer at a rotation speed of 750 rpm, and then an opposed jet mill (EJM00 type JEDI manufactured by Earth Technica) Was used to grind. The AlN pulverized powder was taken out from the pulverizer by setting the rotation speed of the attached classification rotor between 1000 and 2000 rpm. The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1.

  In addition, nitrogen gas with a dew point of −25 ° C. was used as the carrier gas used in the opposed jet mill. An SEM photograph of the particle structure of the powder classified at 1500 rpm is shown in FIG.

  Using the above pulverized AlN powder, mixing at a ratio of (AlN pulverized powder: AlN powder (H grade)), and adding yttrium oxide to 5 parts by weight with respect to 100 parts by weight of the AlN powder as the mixture did.

  Further, a dispersant and a solvent were added to the above composition and mixed for 14 hours. Thereafter, polyvinyl butyral and a plasticizer were added as binders and mixed for 18 hours to obtain an AlN slurry. The AlN slurry was defoamed, adjusted to a viscosity of 20,000 cps, and a molded body having a thickness of 0.75 mm was prepared by a doctor blade method.

  The obtained molded body was degreased in an air atmosphere at 500 ° C. for 4 hours, and fired in a nitrogen atmosphere at 1740 ° C. for 5 hours to obtain an AlN sintered body. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

<Example 4>
The powder obtained in Example 2 was classified once with an airflow classifier. The classification point was 2.5 μm, and the supply amount was 1.5 kg / hr. The yield of the powder obtained by classification was 83%. The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1. Moreover, the SEM photograph of the obtained powder is shown in FIG.

  Using the powder, a sintered body was produced in the same procedure as in Examples 1 to 3. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

<Example 5>
Waste obtained from an aluminum nitride substrate manufacturing plant with an average grain size of 7.5 μm, a metal impurity concentration other than a sintering aid contained in the AlN sintered body of 100 ppm, and a c-axis length of 4.9801 mm The AlN sintered body was preliminarily crushed to a size of about 1 cm with a hammer mill using a hammer at a rotational speed of 750 rpm, and then an opposed jet mill (EJM00 type JEDI manufactured by Earth Technica Co., Ltd.) was used. And crushed. The AlN pulverized powder was taken out from the pulverizer by setting the rotation speed of the attached classification rotor to 700 rpm. The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1.

  Using the powder, a sintered body was produced in the same procedure as in Examples 1 to 3. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

<Comparative Example 1>
The same procedure as in Example 1 was performed until the preliminary pulverization. However, pulverization with a hammer mill was continued until the obtained preliminary pulverized material passed through a 200-mesh sieve. The sieved pre-ground material is put together with Si ₃ N ₄ balls of φ = 3 mm into an alumina pot, applied to a dry ball mill, and pulverized until the average particle size becomes 3 to 4 μm by an analysis method using a microtrack. Went. The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1.

  Using the powder, a sintered body was produced in the same procedure as in Examples 1 to 3. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

<Comparative example 2>
The same procedure as in Example 1 was performed until the preliminary pulverization. However, pulverization with a hammer mill was continued until the obtained preliminary pulverized material passed through a 200-mesh sieve. The sieved pre-pulverized product was put into an alumina pot together with an alumina ball of φ = 3 mm, applied to a dry ball mill, and pulverized until the average particle size became 3 to 4 μm by an analysis method using a microtrack. . The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1.

  Using the powder, a sintered body was produced in the same procedure as in Examples 1 to 3. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

<Comparative Example 3>
The powder obtained in Comparative Example 2 was classified once with an airflow classifier. The classification point was 2.5 μm, and the supply amount was 1.5 kg / hr. The yield of the powder obtained by classification was 72%. The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1. Moreover, the SEM photograph of the obtained powder is shown in FIG. It can be seen that many fine particles and agglomerated particles remain even after the classification treatment.

  Using the powder, a sintered body was produced in the same procedure as in Examples 1 to 3. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

<Comparative Example 4>
The same procedure as in Example 1 was performed until the preliminary pulverization. However, pulverization with a hammer mill was continued until the obtained preliminary pulverized material passed through a 200-mesh sieve. Then, it grind | pulverized until the average particle diameter became 3-4 micrometers with the analysis method using a micro track | truck using the pin mill made from SUS304. The physical properties and impurity concentration of the obtained AlN pulverized powder are summarized in Table 1.

  Using the powder, a sintered body was produced in the same procedure as in Examples 1 to 3. Table 2 shows the mixing ratio of the AlN powder and the physical properties of the obtained sintered body.

Claims (2)

An aluminum nitride sintered body having an average grain size of 2 to 10 μm is preliminarily pulverized to a size such that the equivalent diameter is 1 mm or more and 30 mm or less by causing grain boundary fracture preferentially, The pulverized product is subjected to collision pulverization using a collision-opposing jet mill , the average particle diameter is 2 to 10 μm, and 1 μm in the powder observed in an electron micrograph of 3000 times The manufacturing method of the aluminum nitride powder whose ratio which the following fine powder occupies is 5% or less by area ratio, and metal impurity concentrations other than a sintering auxiliary agent are 1500 ppm or less . The preliminary grinding and the collision pulverization method for producing an aluminum nitride powder according to claim 1, wherein carried out under an inert gas atmosphere.

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