JP2000327430A - Aluminum nitride sintered compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sintered compact, consisting of aluminum nitride and a sintering aid and having crystal grains in the grain boundary, high in mechanical strength by limiting to a specific value the ratio of the grain diameter of the crystal grains in the grain boundary when the accumulated value reaches 75% to that of aluminum nitride crystal grains when the accumulated value reaches 50% in an optional cross-section. SOLUTION: This aluminum nitride sintered compact has 0.5-1.5 ratio of the grain diameters above defined. The production method comprises mixing aluminum nitride and the sintering aid wetly so that the ratio of the average grain size of the aluminum nitride powder before mixed to that of the mixed powder is 1.1-2 to obtain the mixed slurry, drying and compacting the mixed slurry to obtain a green body and sintering the green body under a non-oxidizing atmosphere. The sintering aid is desirably yttrium oxide, which forms crystal grains in the grain boundary by reacting with oxygen contained in the aluminum nitride starting powder as an impurity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aluminum nitride sintered body having both high mechanical strength and high thermal conductivity.

[0002]

2. Description of the Related Art In recent years, as semiconductors become more highly integrated, there has been a demand for a material for a substrate for mounting semiconductors having excellent heat radiation characteristics, which can replace conventional alumina. Among them, aluminum nitride sintered body is a material that has excellent electrical insulation and a thermal conductivity that is more than ten times higher than that of alumina. The range of use as a substrate for use is expanding.

[0003] Of these, particularly in the use of a high-output semiconductor mounting substrate, a thin plate of copper or the like is bonded to an aluminum nitride sintered substrate in order to mount a semiconductor, or a further heat sink material (radiation) is used. Aluminum nitride itself is often used under various stresses such as bonding to metal members such as fins. In addition to high thermal conductivity, aluminum nitride sintered body with higher strength than before is required. It was started.

[0004] In order to improve the mechanical strength of the aluminum nitride sintered body, for example, Japanese Patent Application Laid-Open No. 4-50171 has been proposed.
Japanese Patent Application Laid-Open No. 5-238830 proposes a method for controlling a linear shrinkage rate at the time of raising the temperature of firing, and a method for controlling a cooling rate after firing. Also, Japanese Patent Application Laid-Open
Japanese Patent Application No. 172921 proposes a method of controlling the particle size distribution of a sintered body by adding a Si component, Al ₂ O _3, or the like.

[0005]

However, the method of controlling the linear shrinkage rate at the time of temperature increase described in JP-A-4-50171 described above requires a sintering furnace equipped with a thermal dilatometer. For example, special equipment is required, and it is difficult to apply it to an actual manufacturing apparatus. In addition, Japanese Patent Application Laid-Open
In any of the methods described in JP-A-238830 and JP-A-7-172921, the structure of the sintered body must be precisely controlled.
However, the method described in Japanese Patent Application Laid-Open Publication No. H11-270699 has a problem in that it is necessary to strictly control the particle size existence ratio per 1 μm of the sintered body, and it is difficult to control the ratio in a large sintered body or a mass production scale. Was.

Therefore, there has been a demand for the development of an aluminum nitride sintered body which is excellent in mass productivity, has high mechanical strength of mass-produced products and high reliability, and has a high thermal conductivity and a method for producing the same.

[0007]

The present inventors have intensively studied to solve the above-mentioned problems. As a result, it has been found that the size of the grain boundary phase crystal particles generated by the reaction between the sintering aid and the impurity oxygen in the aluminum nitride affects the strength.

That is, in a brittle material such as ceramics, when a tensile stress is applied, the stress concentrates on a large defect in the material, and breakage occurs therefrom. In general, the following relationship is established between the strength (σ _f ), the fracture toughness value (K _IC ), and the defect length (c).

Σ _f = K _IC / (πc) ^{(1/2) In} an ideal sintered body having no defects, the defect length (c) can be considered as the maximum particle diameter of the matrix, that is, the aluminum nitride crystal particles. Therefore, as a result of estimating the strength of an ideal aluminum nitride sintered body having no defect from the known fracture toughness value and the maximum particle size, an ideal strength of 60 kgf / mm ² can be obtained. However, in a conventional aluminum nitride sintered body, 30 to 45 kgf / mm
Only about ² strength is obtained.

The inventors have observed a large number of fractured surfaces of the test pieces subjected to the bending test, and carefully examined the starting point of fracture (referred to as a fracture source). As a result, many of them have gathered grain boundary phase crystal grains. It was found that the resulting aggregated particles were larger than the aluminum nitride crystal particles, and the strength decreased as the size increased.

Based on these results, the size of the grain boundary phase crystal particles formed by the reaction between the sintering aid and the impurity oxygen in the aluminum nitride powder is controlled to be substantially the same as the size of the aluminum nitride crystal particles. As a result, they found that an aluminum nitride sintered body having excellent mass productivity, high mechanical strength during mass production, and high thermal conductivity was obtained, and further research was carried out, thereby completing the present invention.

That is, the present invention provides a sintered body comprising aluminum nitride and a sintering aid, wherein the sintered body has grain boundary phase crystal grains, and the grain boundary phase crystal grains at an arbitrary cut surface of the sintered body. An aluminum nitride sintered body characterized in that a ratio of a cumulative value of 75% particle diameter to a cumulative value of 50% particle diameter of aluminum nitride crystal particles is 0.5 to 1.5.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum nitride sintered body of the present invention is a sintered body composed of aluminum nitride and a sintering aid, and must have the following properties.

The aluminum nitride sintered body of the present invention needs to have grain boundary phase crystal grains.

The grain boundary phase is a phase present at the grain boundaries of the aluminum nitride crystal grains.

Further, the grain boundary phase crystal particles may constitute the above-mentioned grain boundary phase, a sintering aid alone, a reaction product of the sintering aids, or a mixture of the sintering aid and impurity oxygen in aluminum nitride. It is a crystal particle composed of a reaction product or the like. For example, when the sintering aid is yttrium oxide, it generally reacts with impurity oxygen contained in the aluminum nitride raw material powder to produce 3Y ₂ O _{3.
5Al 2 O 3 (YAG),} Y 2 O 3 · Al 2 O 3 (YAL),
Grain boundary phase crystal grains made of 2Y ₂ O ₃ .Al ₂ O ₃ (YAM) or the like are formed.

As the sintering aid used in the present invention, the above-mentioned yttrium oxide is most preferred, but is not limited thereto, and other known sintering aids can also be used. For example, in addition to Y ₂ O ₃ , LaO ₃ , CeO ₂ , Ho
O ₃ , Yb ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₃ , Sm ₂ O ₃ , Dy ₂
One or a mixture of two or more of rare earth oxides such as O ₃ and alkaline earth metal oxides such as CaO and SrO can be mentioned.

In the aluminum nitride sintered body of the present invention, the ratio between the particle diameter of the cumulative value of 75% of the grain boundary phase crystal grains and the particle diameter of the cumulative value of 50% of the aluminum nitride crystal grains is 0 at an arbitrary cut surface. 0.5 to 1.5.

Here, the particle size of the cumulative value is a particle size at a value accumulated from the smallest particle in the particle size distribution.
In the present invention, the particle diameter was calculated using a particle size distribution obtained by accumulating individual crystal grains obtained by image analysis of a microstructure of an arbitrary cross section of the sintered body from a smaller area. For example, the particle diameter of 50% of the cumulative value of the aluminum nitride crystal particles is determined by dividing the particle diameter of the crystal particles corresponding to the cumulative area of 50% of the total area of all the aluminum nitride crystal particles obtained by image analysis into the particle size distribution. It is a value obtained from the above.

When the ratio of the particle diameters is in the range of 0.5 to 1.5, the size of the grain boundary phase crystal grains is substantially the same as the size of the aluminum nitride crystal grains as the matrix. In addition, since there are few particles larger than the aluminum nitride crystal particles, a microstructure uniformly dispersed in the sintered body is obtained, and the bending strength and the thermal conductivity of the present invention can be achieved.

When the ratio of the particle diameters is larger than 1.5, the strength is greatly reduced due to the increase of grain boundary phase crystal grains larger than the aluminum nitride crystal grains, which is not preferable.

Conversely, if the ratio of the particle diameters is smaller than 0.5, impurity oxygen in the aluminum nitride crystal particles in the sintered body remains, so that the effect of improving the thermal conductivity is reduced, which is not preferable. .

In the aluminum nitride sintered body of the present invention, the average particle size of the aluminum nitride crystal grains is not particularly limited, but considering the mechanical strength of the sintered body,
It is preferably 10 μm or less, more preferably 7 μm or less.

The particle size distribution of the aluminum nitride crystal particles is not particularly limited. However, considering that the number of crystal particles having a size of less than 1 μm is 20% or less, considering that a sintered body having a high thermal conductivity is obtained. preferable.

The grain size distribution of the grain boundary phase crystal grains is not particularly limited, but it is preferable that crystal grains having a size of less than 1 μm be 20% or less in view of obtaining a sintered body having a high thermal conductivity. Further, it is preferable that the crystal grains having a size exceeding 10 μm be 1% or less, more preferably 0.5% or less, in order to obtain a high-strength sintered body.

Further, the cumulative value of the grain boundary phase crystal grains is 50
% And the cumulative value of aluminum nitride crystal particles of 50%
% Is preferably equal to the particle diameter in consideration of the effects of the present invention. Specifically, the ratio of the particle diameter of the cumulative value of 50% of the grain boundary phase crystal particles to the particle diameter of the cumulative value of 50% of the aluminum nitride crystal particles may be in the range of 0.7 to 1.2. Is more preferable.

The aluminum nitride sintered body of the present invention needs to have grain boundary phase crystal grains uniformly distributed.
A uniform distribution in the range of ０．６0.60 is preferred.

In the aluminum nitride sintered body of the present invention, the concentration of the grain boundary phase generated by the sintering aid is 4.5 to 4.5.
It is preferably 9.0 wt%. When the concentration of the grain boundary phase generated by the sintering aid is less than 4.5 wt%, impurity oxygen remains in the aluminum nitride crystal particles in the sintered body, and therefore, the sintered body having a high thermal conductivity. When the content is more than 9.0 wt%, the bending strength is lowered due to the formation of aggregates of the grain boundary phase crystal particles, and the sintered body of the grain boundary phase crystal particles is reduced. It is not preferable because a sintering ratio becomes too large to obtain a sintered body having a high thermal conductivity.

The aluminum nitride sintered body of the present invention has a bending strength of 50 kgf / mm ² or more and a thermal conductivity of 160 W by controlling the crystal grains as described above.
/ MK or more.

The shape of the aluminum nitride sintered body of the present invention,
Although the size is not particularly limited, the effect is particularly remarkable in a plate-like object having a thickness of 100 mm or less, preferably 0.3 to 10 mm.

FIG. 1 shows an embodiment of the aluminum nitride sintered body of the present invention, and FIG. 2 shows an embodiment of a conventionally known aluminum nitride sintered body. The black portions indicate aluminum nitride crystal grains, and the white portions indicate grain boundary phase crystal particles.

As shown in the figure, the conventional aluminum nitride sintered body has a large number of very large grain boundary phase crystal grains as compared with the aluminum nitride sintered body of the present invention.
Does not satisfy the requirements of the present invention.

The method for producing the aluminum nitride sintered body of the present invention is not particularly limited as long as it has the properties specified in the present invention, but the properties specified in the present invention are preferably determined by the following method. Can be achieved.

That is, the ratio of the average particle size of the aluminum nitride powder before mixing to the average particle size of the mixed powder composed of the aluminum nitride powder and the sintering aid is in the range of 1.1 to 2. In this method, a slurry is obtained by wet mixing, and then the slurry is dried and molded to obtain a green body, and the green body is fired in a non-oxidizing atmosphere.

The details will be described below.

In the present invention, as the above-mentioned aluminum nitride powder, known ones can be used without any particular limitation. However, in view of obtaining a dense sintered body, the average particle size before mixing is 5%.
It is preferably at most 3 μm, more preferably at most 3 μm.

In consideration of obtaining a sintered body having a high thermal conductivity, it is preferable that the average particle diameter of the aluminum nitride powder is 0.8 μm or more and the oxygen concentration is 1.0 wt% or less. The aluminum nitride powder having an average particle size smaller than 0.8 μm is not preferable because the surface area is large and the oxygen concentration tends to be high, and as a result, it is difficult to obtain an aluminum nitride sintered body having high thermal conductivity.

As the sintering aid powder, known powders can be used without any particular limitation. However, in view of obtaining a dense sintered body having a high thermal conductivity, oxides of the above-mentioned rare earth elements and alkaline earths are considered. Oxides of similar metals are preferred, and among them, yttrium oxide is preferred. The amount of addition was 3.0 per 100 parts by weight of aluminum nitride powder.
It is preferred that the amount be up to 8.0 parts by weight. With the above addition amount, it is easy to control the ratio of the cumulative value of 75% of the grain boundary phase crystal grains to the cumulative value of 50% of the aluminum nitride crystal grains within the range specified in the present invention. Become.

In the present invention, the green body is obtained by a method such as pressing or sheet forming by adding an organic binder or the like to a mixed powder comprising an aluminum nitride powder and a rare earth compound powder.

As the binder, known binders can be used without any particular limitation. Specifically, polyvinyl butyral, ethyl celluloses, acrylic resins, and the like can be used. Among them, polyvinyl butyral and poly n-butyl methacrylate are preferable because of their excellent green formability.

The mixing ratio of the organic binder to the mixed powder is 2 to 15 parts by weight for obtaining a pressed product and 100 to 5 parts by weight for obtaining a sheet with respect to 100 parts by weight of the mixed powder. An addition of 15 parts by weight is preferably employed.

As a method of forming a green body using the above-mentioned organic binder, the mixed powder and the organic binder are added to an organic solvent such as alcohols and toluene, a dispersant such as glycerin compounds, and a plasticizer such as phthalic esters. Then, a slurry is formed by mixing well with a ball mill to form a sheet-like green body by a doctor blade method, or a granule is formed by a spray dry method, and then a block-like green body is formed by a die press. The method of doing is general.

One of the features of the manufacturing method of the present invention is as follows.
The wet mixing is performed so that the ratio between the average particle diameter of the aluminum nitride powder before mixing and the average particle diameter of the mixed powder including the aluminum nitride powder and the sintering aid is in the range of 1.1 to 2. .

If the ratio of the average particle size of the aluminum nitride powder before mixing to the average particle size of the mixed powder comprising the aluminum nitride powder and the sintering aid is in the range of 1.1 to 2, The aluminum powder and the sintering aid are each appropriately pulverized.

When the ratio of the average particle diameters of the powders is smaller than 1.1, the aluminum nitride powder and the sintering aid powder are hardly pulverized, and only the respective powders are uniformly mixed. is there. In this case, since coarse particles of the sintering aid that have not been crushed are present in the mixed powder, there are also many aggregates of coarse grain boundary phase crystal particles in the sintered body after high-temperature firing, It is difficult to obtain the sintered body of the present invention.

On the other hand, when the ratio of the average particle diameter of the powder is larger than 2, the aluminum nitride powder and the sintering aid powder are crushed to the size of the primary particles. As a result, the specific surface area of the aluminum nitride powder increases, so that the oxygen concentration of the powder increases, and the sintered body obtained by sintering the powder at a high temperature tends not to achieve the high thermal conductivity that is the object of the present invention. Becomes

It is preferable that the crushed fine powder of the sintering aid is uniformly dispersed in a slurry of the mixed powder or a green body after the slurry is dried. For example, when the slurry is uniformly dispersed, the slurry is formed into a sheet-like green body by a doctor blade method, and the state of the green body of the sintering aid is represented by a reflection electron image of a scanning electron microscope (SEM). It can be confirmed by observing with.

In the present invention, the ratio between the average particle size of the aluminum nitride powder before mixing and the average particle size of the mixed powder composed of the aluminum nitride powder and the sintering aid is in the range of 1.1 to 2. The method of wet mixing is not particularly limited, but the above range can be easily achieved by using a ball mill and a method using a ball of a specific hardness.

That is, the hardness of the material of the ball surface used during mixing is 900 kgf / mm ² (Vickers hardness).
As described above, a ball having a total ball density of ³ to 6.5 g / cm ³ and a ball diameter of 5 to 20 mm is preferable.

With respect to a ball having such characteristics, for example, a ceramic ball, specifically, Al ₂ O ₃ , Z
balls made of rO ₂ , Si ₃ O ₄ , SiAlON, and AlN. Among them, alumina balls are particularly preferable in consideration of obtaining the aluminum nitride sintered body of the present invention.

The conditions of the wet mixing (filling rate into the container,
The number of rotations, the amount of solvent used, the mixing time, etc.) may be appropriately determined according to the hardness, density, and ball diameter of the ball used.

The green body using the above-mentioned organic binder is usually degreased before sintering to obtain a degreased body. The degreasing is performed by heat treatment in an oxidizing gas such as oxygen or air, or a reducing gas such as hydrogen, an inert gas such as argon or nitrogen, carbon dioxide and a mixed gas thereof, or a humidified gas atmosphere containing a mixture of steam. This is generally done. The degreasing temperature is 300 ° C ~ 1
200 ° C, and the degreasing time is in the range of 1 minute to 500 minutes,
What is necessary is just to select suitably according to the compounding ratio of the said organic binder, and a degreasing method. At that time, it is preferable that the oxygen concentration of the degreased body be adjusted to 2.5 wt% or less by adjusting the atmosphere, the temperature, and the holding time. By setting the oxygen concentration to 2.5 wt% or less, it becomes easy to improve the thermal conductivity of the aluminum nitride sintered body.

In the present invention, the green body and the degreased body are determined in a non-oxidizing atmosphere in accordance with the amount of the sintering aid added to the raw material and the size and thickness of the green body and the degreased body. It may be fired at the optimum densification temperature. Here, the optimum densification means that the sample density (referred to as relative density) with respect to the theoretical density of the sintered body is 98% or more.

The optimum densification temperature can be determined by examining a densification curve (shrinkage curve) of each sample in advance, and may be generally selected from the range of 1650 to 1800 ° C. If the sintering temperature is lower than 1650 ° C., a dense sintered body cannot be obtained, and the bending strength of the sintered body becomes low because the strength of the non-dense part is low. When the firing temperature is higher than 1800 ° C., the crystal grain size of the sintered body exceeds 10 μm due to the promotion of the grain growth of the sintered body, and it becomes difficult to obtain the sintered body having the bending strength of the present invention.

As the non-oxidizing atmosphere, for example, an atmosphere consisting of a gas such as nitrogen, argon, helium, hydrogen alone or a mixed gas, or a vacuum (or reduced pressure) atmosphere is used.

The above sintering is usually carried out in a firing container. As the firing container, a known container used for firing aluminum nitride can be used. To give a specific example, a box-shaped closed container made of aluminum nitride or boron nitride can be mentioned.

In addition, bedding powder generally used for preventing fusion due to firing may be interposed between the compacts and degreased bodies, and further between the firing container. As the spreading powder, for example, boron nitride powder or the like is used.

The calcination time is not particularly limited, but is preferably set to usually 1 minute to 20 hours, more preferably 1 hour to 10 hours.

As described above, the aluminum nitride sintered body of the present invention has high mechanical strength and high thermal conductivity. Also, the insulation resistance, the dielectric constant, other physical properties of the sintered body, and the appearance of the sintered body are good.

[0060]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention.

The various physical properties in the following Examples and Comparative Examples were measured by the following methods. 1) Average particle size of aluminum nitride powder and mixed powder MICROTRAC II (LEED & NORTHRUUP)
(Manufactured by K.K.). The aluminum nitride powder was dispersed in water and measured. The mixed powder was measured by dispersing it in ethanol to prepare a dry powder in which the organic solvent component was completely removed from the slurry after mixing and desolvation by heating or the like. 2) Aluminum nitride crystal grain size and grain boundary phase crystal grain size An image analysis system (IP-1)
000PC, manufactured by Asahi Kasei Kogyo Co., Ltd.) and the respective particle sizes were determined by the following methods.

First, an arbitrary cross section of the sintered body to be evaluated was polished to a mirror surface and heat-treated for several minutes at 1600 to 1650 ° C., which is a temperature at which aluminum nitride crystal grains do not grow. By this treatment, only the crystal grain boundary portion is etched because the etching rate at the crystal grain boundary is higher than other portions, and a surface is obtained in which each of the aluminum nitride crystal grains and the grain boundary phase crystal grains can be identified. be able to.

Next, the surface is scanned with a scanning electron microscope (S
Observed using EM), a microstructure photograph was obtained at a magnification such that 200 to 300 observed particles were included in one field of view, and the average number of observed particles was 1000 to 100.
A plurality of photographs were prepared so as to have 2,000. In the microstructure photograph, as shown in FIGS. 1 and 2, the aluminum nitride crystal grains are shown in gray to black and the grain boundary phase crystal grains are shown in white, so that these grains can be easily identified. .

Finally, the images of these microstructures were taken as images, and the areas and circle equivalent diameters of 1000 to 2000 individual aluminum nitride crystal grains were determined using a computer image analysis system. Regarding the grain boundary phase crystal grains in the microstructure photograph, the area and the circle equivalent diameter were determined in the same manner as the aluminum nitride crystal grains. The aluminum nitride crystal grains and the grain boundary phase crystal grains are substantially equiaxed, and the particle diameter can be represented by a circle equivalent diameter. Further, at the time of analysis, crystal particles whose particles were broken at the end of the analysis image were excluded from evaluation targets. Further, when two or more grain boundary phase crystal grains are in contact with each other, if the length of the boundary between the two crystal grains is larger than the average particle diameter of the grains, one grain of the crystal grains is combined into one grain. Treated as 3) Measurement of the degree of dispersion of grain boundary phase crystal particles Using the photograph of the microstructure used for the measurement of the crystal particle diameter, using the above-mentioned image analysis system, the distance between centers of gravity method (dispersion from the distance between centers of gravity of adjacent particles Of the grain boundary phase particles in the sintered body. The degree of dispersion is represented by the ratio between the average deviation of the distance between particles and the average distance between particles, and the smaller the value, the better the dispersion. 4) Measurement of bending strength According to JIS R1601, crosshead speed 0.5m
A three-point bending test was performed at m / min and a span of 30 mm. The width of the test piece was 4 mm, the sintered body was cut out to a width of 6 mm, and both ends were ground by 1 mm to obtain a predetermined width. The thickness of the sample subjected to sheet processing was the thickness of the sintered body itself, and the upper and lower surfaces of the test piece were the surfaces of the sintered body that were not ground and polished. 4) Measurement of thermal conductivity The thermal conductivity was measured by a laser flash method using a thermal constant measuring apparatus PS-7 manufactured by Rigaku Denki KK Thickness correction was performed using a calibration curve.

Example 1 A nylon pot having an inner volume of 2.4 L was placed in a nylon pot having a diameter of 10 mm.
Alumina balls (surface hardness 1100kgf / m
m ² , a density of 3.6 g / cm ³ ), then an average particle size of 1.5 μm, a specific surface area of 2.6 m ² / g, and an oxygen concentration of 0.
100 parts by weight of 8 wt% aluminum nitride powder, 5 parts by weight of yttrium oxide powder having a specific surface area of 12.5 m ² / g as a sintering aid, ² parts by weight of sorbitan triolate as a surfactant, and toluene, ethanol as a solvent.
Butanol was added in an amount of 35 parts by weight (each volume ratio was 75: 20: 5) and wet-mixed. At this time, the alumina balls were filled with 40% (apparent volume) of the inner volume of the pot. Mixing is performed at 70 rpm and 2 rpm.
Performed for 4 hours. Further, the obtained slurry was combined with 11 parts by weight of polyvinyl butyral as an organic binder, 3.5 parts by weight of di-n-butyl phthalate as a plasticizer, and 45 parts by weight of toluene, ethanol, and butanol as a solvent (each volume). The ratio was 75: 20: 5), and a second wet mixing was performed for 18 hours. The resulting slurry was desolvated to a viscosity of 10,000 to 25,000 cps. To produce a green body having a thickness of Further, the sheet-like green body was processed into a green body having a long side of 63 mm and a short side of 44 mm by a punching press machine.

The obtained green body was dried at 600
Degreasing treatment at a temperature of 240 ° C. for 240 minutes and an oxygen concentration of 2.2 w
A t% defatted body was obtained.

Further, the degreased body was placed in a firing container made of boron nitride, and heated at a temperature of 1740 ° C. in a nitrogen gas atmosphere.
After firing for a long time, a dense and translucent sintered body having a density of 3.28 g / cm ³ or more was obtained. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Example 2 The same operation as in Example 1 was performed except that the firing was performed at a temperature of 1770 ° C. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Example 3 The amount of the solvent added during the first wet mixing was 30 parts by weight,
The same operation as in Example 1 was performed, except that 50 parts by weight of the solvent to be added at the time of the second wet mixing was added. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Example 4 At the time of the first wet mixing, an alumina ball was filled to 33% of the inner volume of the pot and 40 parts by weight of the solvent was added. The amount of the solvent added at the time of the second wet mixing was 40% by weight. The same operation as in Example 1 was performed, except that the addition was carried out at a temperature of 1760 ° C. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Example 5 The same operation as in Example 1 was performed except that the amount of yttrium oxide powder was changed to 4.5 parts by weight. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Example 6 Example 1 was repeated except that aluminum nitride powder having an average particle size of 2.5 μm, a specific surface area of 3.9 m ² / g, and an oxygen concentration of 0.98 wt% was used, and the powder was fired at 1790 ° C. The same operation as described above was performed. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Comparative Example 1 A ball (surface hardness: 100 kgf / mm ² or less, density: 3.5 g / cm ³ ) in which an iron core having a diameter of about 25 mm was coated with nylon on a mill ball was used, except that it was fired at 1770 ° C. The same operation as in Example 1 was performed. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Comparative Example 2 An aluminum nitride powder having an average particle size of 2.5 μm, a specific surface area of 3.9 m ² / g and an oxygen concentration of 0.98 wt% was used, and an iron core having a diameter of about 25 mm was coated on a mill ball with nylon. Ball (surface hardness 100 kgf / mm ² or less,
Density of 3.5 g / cm ³ ) and 1800
The same operation as in Example 1 was performed, except that the firing was performed at a temperature of ° C. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

Comparative Example 3 Aluminum nitride powder having an average particle size of 2.5 μm, a specific surface area of 3.9 m ² / g and an oxygen concentration of 0.98 wt% was used, and 2.5 parts by weight of yttrium oxide powder was added. A ball (surface hardness: 100 kgf / mm ² or less, density: 3.5 g / cm ³ ) in which a steel ball having a diameter of about 25 mm was coated with nylon on a mill ball, and 1800 ° C.
The same operation as in Example 1 was performed except that the firing was carried out. Table 1 shows the manufacturing conditions of the sintered body, and Table 2 shows the microstructure and characteristics of the sintered body.

[0076]

[Table 1]

[Table 2]

According to the present invention, a sintered body having a microstructure in which grain boundary phase crystal grains of the same size as aluminum nitride crystal grains are uniformly dispersed has high strength and high thermal conductivity. Also, wet mixing is performed so that the ratio of the average particle size of aluminum nitride before mixing to the average particle size of the mixed powder composed of aluminum nitride powder and the sintering aid is within a certain range, and the slurry is formed. Since it is easily obtained by firing the body, it enables mass production of high-strength, high-thermal-conductivity aluminum nitride sintered bodies without the need for complicated or complicated manufacturing processes, and is applicable to large-sized sintered bodies. And its industrial value is great.

[Brief description of the drawings]

FIG. 1 shows a microstructure SE of an aluminum nitride sintered body of the present invention.
It is an M photograph (2000 times magnification).

FIG. 2 is a microstructure SEM of a conventional aluminum nitride sintered body.
It is a photograph (2000 times magnification).

Claims (2)

[Claims] In a sintered body comprising aluminum nitride and a sintering aid, grain boundary phase crystal particles are uniformly distributed, and
Cumulative value of grain boundary phase crystal particles at an arbitrary cut surface of the sintered body 75% particle diameter and cumulative value of aluminum nitride crystal particles of 50%
% Aluminum particle sintered body, characterized by having a ratio of 0.5 to 1.5. 2. A wet process is performed so that the ratio of the average particle size of the aluminum nitride powder before mixing to the average particle size of the mixed powder composed of the aluminum nitride powder and the sintering aid is in the range of 1.1 to 2. 2. The method for producing aluminum nitride according to claim 1, wherein the slurry is obtained by mixing, and then the slurry is dried and formed to obtain a green body, and the green body is fired in a non-oxidizing atmosphere.