JPH07172921A - Aluminum nitride sintered body and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] Suppress both the grain growth of AlN sintered compacts, refine the structure of sintered compacts, and appropriately control the grain size distribution to improve the strength and fracture toughness of sintered compacts. (EN) Provided are an AlN sintered body improved and improved in both mechanical strength and fracture toughness value without impairing the heat dissipation characteristic of aluminum nitride, and a method for producing the same. [Structure] It has a crystal structure composed of aluminum nitride crystal grains, a fracture toughness value of 2.8 MN / m ^3/2 or more, a three-point bending strength of 490 MPa or more, and a thermal conductivity of 150 W / m · K.
The above is characterized. In the crystal structure,
The proportion of crystal grains having a grain size of less than 1 μm is 10% by volume or less, and the proportion of crystal grains having a grain size of 1 μm or more and less than 2 μm is 10 to 20.
Volume% or less, the proportion of crystal grains having a grain size of 2 μm or more and less than 3 μm is 10 to 30 vol% or less, the proportion of crystal grains having a grain size of 3 μm or more and less than 4 μm is 30 to 50 vol% or less, and the grain size is 4 μm
The grain size distribution is adjusted so that the proportion of crystal grains having a size of m or more and less than 5 μm is 5 to 10% by volume or less, and the proportion of crystal grains having a particle size of 5 μm or more is 10% by volume.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body used for a semiconductor substrate or the like and a method for producing the same, and particularly to the strength and fracture toughness values without impairing the thermal conductivity peculiar to aluminum nitride. The present invention relates to an aluminum nitride sintered body that is significantly improved and has excellent heat dissipation, and a manufacturing method.

[0002]

2. Description of the Related Art Sintered ceramics, which are superior in properties such as strength, heat resistance, corrosion resistance, wear resistance, and lightness, compared with conventional metal materials, are used in semiconductor substrates, electronic equipment materials, engine members, It is widely used as a material for high speed cutting tools, nozzles, bearings, and other mechanical parts, functional parts, structural materials and ornamental materials used under severe temperature, stress and wear conditions that conventional metal materials do not have.

In particular, an aluminum nitride (AlN) sintered body is an insulator having a high thermal conductivity and has a coefficient of thermal expansion close to that of silicon (Si). Therefore, the aluminum nitride (AlN) sintered body is used as a heat sink or a substrate of a highly integrated semiconductor device. Expanding applications.

Conventionally, the above-mentioned aluminum nitride sintered body is generally mass-produced by the following manufacturing method. That is,
A sintering aid to the aluminum nitride raw material powder, an organic binder, and various additives and solvents as required, to prepare a raw material mixture by adding a dispersant, the resulting raw material mixture doctor blade method or A thin plate-shaped or sheet-shaped molded body is formed by the slurry casting method, or a raw material mixture is press-molded to form a thick plate-shaped or large-sized molded body. Next, the obtained molded product is heated and degreased in an atmosphere of air or nitrogen gas to remove and degrease the hydrocarbon components and the like used as the organic binder from the molded product. The degreased compact is heated to a high temperature in a nitrogen gas atmosphere or the like and densified and sintered to form an aluminum nitride sintered compact.

In the above manufacturing method, when an ultrafine raw material powder having an average particle diameter of about 0.5 μm or less is used as the raw material AlN powder, a considerably dense sintered body can be obtained by using the AlN powder alone. However, a large amount of impurities such as oxygen adhering to the surface of the raw material powder and the like are solid-solved in the AlN crystal lattice at the time of sintering, or Al-O- which hinders the propagation of lattice vibration.
As a result of producing a compound oxide such as an N compound, the thermal conductivity of the AlN sintered body that did not use a sintering aid was relatively low.

On the other hand, when AlN powder having an average particle size of 1 μm or more is used as the raw material powder, the sinterability of the raw material powder alone is not good. Was difficult to obtain, and there was a drawback that mass productivity was low. Therefore, in order to efficiently manufacture a sintered body by the atmospheric pressure sintering method, in order to prevent the densification of the sintered body and the impurity oxygen in the AlN raw material powder from forming a solid solution in the AlN crystal grains. In addition, as a sintering aid,
It is generally practiced to add rare earth oxides such as yttrium oxide (Y ₂ O ₃ ) and alkaline earth metal oxides such as calcium oxide.

These sintering aids react with the impurity oxygen and Al ₂ O ₃ contained in the AlN raw material powder to form a liquid phase to achieve the densification of the sintered body, and at the same time, to form the impurity oxygen into particles. It is believed that it can be fixed as a phase phase and achieve high thermal conductivity.

[0008]

However, in the above-mentioned conventional production method, since the wettability between AlN and the liquid phase compound is originally low and the liquid phase itself tends to segregate, the liquid after the sintering is dissolved. When the phase solidifies, the liquid phase is AlN
It tends to remain so as to be unevenly distributed in the interstices of the grains and to solidify to form a coarse and brittle grain boundary phase. Further, the grain growth of the crystal grains is likely to proceed, coarse crystal grains having an average grain size of 5 to 10 μm are easily formed in the crystal structure of the sintered body as shown in FIG. 2, and the fine pores do not disappear. Remain in the crystal grains, hinder the densification of the sintered body, and finally the three-point bending strength is 350
There is a problem that only an aluminum nitride sintered body having a low strength of about 400 MPa and a fracture toughness value of 2.8 MN / m ^3/2 or less can be obtained.

In order to solve the above problems, an AlN sintered body having a crystal structure as fine as possible is formed by using a raw material powder of aluminum nitride having a uniform particle size and various additives are added. Then, the device which raises sinterability is also tried. The inventors of the present invention have also devised a method of improving the sinterability to obtain a high-strength AlN sintered body by including, for example, a W component. However, it has been found that the inclusion of the W component makes the crystal structure finer and more uniform, so that the strength of the sintered body is improved, but the fracture toughness value is decreased. Therefore, it is difficult to obtain an AlN sintered body for a semiconductor substrate, which has excellent strength and toughness values.

In recent years, the above-mentioned aluminum nitride material having high thermal conductivity (high heat dissipation) is becoming widespread in order to cope with the heat generation amount which is increased with the high integration and high output of semiconductor elements. As for sex, generally satisfactory results have been obtained. However, since the strength and toughness of the structural member are insufficient as described above, for example, a slight bending stress that acts when mounting a semiconductor substrate formed of an aluminum nitride sintered body on a mounting board and an impact force that acts during handling. As a result, the semiconductor substrate is easily damaged and the manufacturing yield of the semiconductor circuit substrate is significantly reduced.

The present invention has been made to solve the above-mentioned problems, and the size and grain size distribution of the crystal grains of an AlN sintered body are properly controlled to control the strength and fracture toughness of the sintered body. It is an object of the present invention to provide an AlN sintered body which is improved and has improved mechanical strength without impairing heat dissipation characteristics, and a manufacturing method thereof.

[0012]

In order to achieve the above object, the inventor of the present invention has a method of synthesizing aluminum nitride raw material powder,
The grain size distribution of the AlN raw material powder, the type and amount of the sintering aid and additives added to the raw material aluminum nitride powder are changed variously to obtain the crystal structure, crystal grain size distribution, strength characteristics and fracture toughness of the sintered body. We also conducted an experimental study on the effect on the heat transfer characteristics.

As a result, when a predetermined amount of AlN raw material powder was compounded with a small amount of Si component as an additive in addition to the sintering aid, and the mixture was compacted and sintered, the average crystal grain size was 2 A microstructure of ˜4.5 μm and a grain size distribution of crystal grains wider than that of the conventional one was obtained, and an AlN sintered body having excellent strength characteristics and fracture toughness values was obtained. The present invention has been completed based on the above findings.

That is, the aluminum nitride sintered body according to the present invention has a crystal structure composed of aluminum nitride crystal grains, has a fracture toughness value of 2.8 MN / m ^3/2 or more, a three-point bending strength of 490 MPa or more, Thermal conductivity is 150 W / mK
The above is characterized. Further, it contains 1 to 10% by weight of an oxide of at least one element selected from the group IIIa elements of the periodic table, Ca, Sr, and Ba, and Si
The component concentration is 0.01 to 0.2% by weight, and Al ₂ O ₃
It is characterized in that the content is 1.5% by weight or less. The Si component is SiO ₂ , Si ₃ N ₄ , SiC, Si ₂
It may be contained as at least one silicon compound selected from N ₂ O, β-sialon, α-sialon and polytype aluminum nitride (Al—Si—O—N). Furthermore, Ti, Fe, Ni, Cr, Co, L
It is preferable that at least one metal element selected from i and Mg is contained in an amount of 0.05 to 0.5% by weight in terms of oxide.
The content of impurity cations such as Mo is preferably 0.2% by weight or less. Further, the average crystal grain size of the sintered body is 2 to
It is recommended to set it to 4.5 μm. AlN having the above composition and having the above-described wide crystal grain size distribution
The sintered body has a thermal conductivity of 150 W / m · K or more, a three-point bending strength of 490 MPa, and a fracture toughness value of 2.8 MN / m ^3/2 or more.

Further, in the method for producing an aluminum nitride sintered body according to the present invention, an aluminum nitride raw material powder containing 0.2% by weight or less of impurity cations other than the above additives is added to a group IIIa element of the periodic table. , 1 to 10% by weight of an oxide of at least one element selected from Ca, Sr and Ba,
Si component 0.01-0.2 wt% and Al ₂ O ₃ 1.
5% by weight or less is added to form a mixed powder, and the obtained formed body is sintered in a temperature range of 1650 to 1900 ° C. in a non-oxidizing atmosphere.

The aluminum nitride (AlN) raw material powder used in the method of the present invention, which is the main component of the sintered body, has an oxygen content of 1.5% by weight or less in consideration of sinterability and thermal conductivity. Is suppressed to an average particle size of 0.5 to 2
A fine AlN raw material powder having a size of about μm, preferably 1.5 μm or less is used.

By the way, the aluminum nitride raw material powder is
Generally, those manufactured by the direct nitriding synthesis method or the reduction nitriding synthesis method are used. The direct nitriding synthesis method is a method in which an aluminum metal rod is used as an electrode to perform arc discharge in a nitrogen stream to generate highly purified AlN at the tip of the electrode. On the other hand, the reduction nitriding synthesis method is to reduce aluminum oxide by mixing fine particles of aluminum oxide with graphite as a reducing agent or an organic compound that produces graphite, and heating the mixture in a nitrogen or ammonia stream. This is a method of nitriding at the same time to synthesize aluminum nitride.

As the raw material powder for the aluminum nitride sintered body according to the present invention, a raw material powder produced by any of the above synthesis methods may be used, but a nitriding mixture of both raw material powders having different particle size distributions is used. The use of the aluminum mixed powder causes a larger variation in the grain size distribution, and the resulting crystal grain size distribution of the sintered body also becomes wider, so that an AlN sintered body satisfying both high strength and high toughness can be obtained. , And more preferable.

Oxides of Group IIIa elements, Ca, Sr, and Ba of the periodic table act as sintering aids, and in order to densify the AlN sintered body, 1 to 10% by weight relative to the AlN raw material powder.
It is added in the range of. Specific examples of the above-mentioned sintering aid include oxides of rare earth elements (Y, Sc, Ce, Dy, etc.), nitrides, oxides of alkaline earth metals (Ca), or compounds obtained by a sintering operation. Materials are used, especially yttrium oxide (Y ₂ O ₃ ), cerium oxide (Ce
O) and calcium oxide (CaO) are preferred. When the amount of the sintering aid added is less than 1% by weight, the effect of improving the sinterability is not sufficiently exerted, the sintered body is not densified and a low-strength sintered body is formed, or AlN Oxygen dissolved in the crystal,
A sintered body having a high thermal conductivity cannot be formed. On the other hand, if the addition amount exceeds 10% by weight, not only the effect as a sintering aid reaches a saturated state and becomes meaningless, but
On the contrary, the thermal conductivity of the AlN sintered body obtained by sintering is lowered, while a large amount of the grain boundary phase remains in the sintered body, and the volume of the grain boundary phase removed by heat treatment is large. Voids may remain in the tying body, increasing the shrinkage rate and making it more likely to cause deformation.

The Si component has the effects of improving the sinterability and lowering the sintering temperature, but grain growth of the sintered body can be suppressed by adding it in combination with the above-mentioned sintering aid. , Is added to form a fine AlN crystal structure and enhance the structural strength of the sintered body. Examples of the Si component include SiO ₂ , Si ₃ N ₄ , SiC, Si ₂ N ₂ O,
It is desirable to use silicon compounds such as β-sialon, α-sialon and polytype aluminum nitride (Al—Si—O—N). The content of this silicon compound is adjusted to the range of 0.01 to 0.2% by weight as the Si component. When the content of the Si component is less than 0.01% by weight, the grain growth inhibiting effect is insufficient, and the crystal structure becomes coarse, so that a high-strength AlN sintered body cannot be obtained. on the other hand,
The content is 0. ． If the amount exceeds 2% by weight, the thermal conductivity of the sintered body may decrease and the bending strength may decrease.

Al ₂ O ₃ has the effect of further improving the fracture toughness value of the AlN sintered body, and the content of this Al ₂ O ₃ is adjusted within the range of 1.5% by weight or less. Al ₂ O
_If the content of ₃ exceeds 1.5% by weight, the thermal conductivity of the sintered body will decrease. The more preferable content of Al ₂ O ₃ is 1% by weight or less. This Al ₂ O
_{The three} components can be added by adding them separately as an additive, or by forming Al ₂
A method in which O ₃ is mixed and added, or Al _{2 which} is generated by surface oxidation by heating AlN raw material powder in an oxygen-containing atmosphere
A method of adding an O ₃ component may be used.

Further, AlN produced by the direct nitriding synthesis method.
When the raw material powder is used, strength and toughness values can be secured to some extent without adding the above Al ₂ O ₃ component. However, it has been confirmed that when the AlN raw material powder produced by the reduction nitriding synthesis method is used, the toughness value is significantly improved by adding the Al ₂ O ₃ component.

Ti, Fe, Ni, Cr, Co, Li, M
The oxide of g is effective for improving the characteristics of the AlN sintered body such as forming an opaque sintered body by coloring while lowering the sintering temperature to improve the sinterability. You may add in the range of 0.05-0.5 weight% in conversion. If the added amount is less than 0.05% by weight, the above characteristic improving effect becomes insufficient, while if the added amount exceeds 0.5% by weight, the heat of the AlN sintered body becomes similar to other impurities. Reduces conductivity.

Since impurity cations such as Mo other than the above-mentioned various additives easily form a compound that inhibits the heat conduction of the AlN sintered body, the content in the AlN sintered body is 0.2% by weight.
It is set below.

The above AlN raw material powder, various sintering aids, Si
Si compounds for components and Al ₂ added as necessary
O ₃ is put into a pulverizing mixer such as a ball mill,
A raw material mixture is obtained by mixing for a predetermined time. Next, the obtained raw material mixture is filled in a mold having a predetermined shape and pressure-molded to form a molded body. At this time, an organic binder such as paraffin or stearic acid should be added to the raw material mixture in an amount of 5 to 10 in advance.
By adding the weight%, the molding operation can be smoothly carried out.

As the molding method, a general-purpose die pressing method, sludge casting method, hydrostatic pressing method, extrusion molding method or sheet molding method such as doctor blade method can be applied.

Subsequent to the above molding operation, the molded body is heated in a non-oxidizing atmosphere, for example, in a nitrogen gas atmosphere at a temperature of 400 to 400 ° C.
By heating to 800 ° C., the previously added organic binder is thoroughly degreased and removed.

Next, the plurality of sheet-shaped compacts subjected to the degreasing treatment are stacked in multiple stages in a firing furnace through a powder made of, for example, ceramics sintered powder, and in this arrangement, the plurality of compacts are collectively packaged. And sintered at a predetermined temperature. For the sintering operation, the molded body is heated to a temperature of 16 in a non-oxidizing atmosphere such as nitrogen gas.
It is carried out by heating at 50 to 1900 ° C. for about 2 to 6 hours. In particular, by adding the Si component, 1720-1
It becomes possible to sinter at a temperature of about 780 ° C., which is lower than the conventional temperature. The sintering atmosphere may be a non-oxidizing atmosphere that does not react with AlN, but is usually a nitrogen gas or a reducing atmosphere containing nitrogen gas. H ₂ gas or CO gas may be used as the reducing gas. The sintering may be performed in an atmosphere including vacuum (including a slight reducing atmosphere), reduced pressure, increased pressure and normal pressure. When sintered at a low temperature such as a sintering temperature of less than 1650 ° C., although it depends on the particle size of the raw material powder and the amount of oxygen contained, it is difficult to densify, and problems such as strength and thermal conductivity tend to occur. When firing at a temperature higher than ℃, the vapor pressure of AlN itself in the firing furnace becomes high, which may make densification difficult and the thermal conductivity may sharply decrease. Therefore, the sintering temperature is set to the above range. .

Then, a raw material mixture having a predetermined composition in which a sintering aid and a Si component are added to the above AlN raw material powder is molded, degreased and sintered to obtain an average crystal grain size of 2 to 2.
It has a fine crystal structure of about 4.5 μm, and the ratio of the crystal grains having a grain size of less than 1 μm is 10 in the crystal structure.
Volume% or less, the proportion of crystal grains having a grain size of 1 μm or more and less than 2 μm is 10 to 20 vol% or less, the proportion of crystal grains having a grain size of 2 μm or more and less than 3 μm is 10 to 30 vol% or less, and a grain size of 3 μm
The ratio of crystal grains of m or more and less than 4 μm is 30 to 50% by volume or less, and the ratio of crystal grains of 4 μm or more and less than 5 μm is 5 or less.
10% by volume or less, the ratio of crystal grains with a grain size of 5 μm or more is 1
It has a crystal grain size distribution of 0% by volume or less, a thermal conductivity of 150 W / mK or more, and a bending strength of 49.
A high strength and high toughness AlN sintered body having a fracture toughness value of 0 MPa or more and 2.8 MN / m ^3/2 or more can be obtained.

[0030]

According to the aluminum nitride sintered body and the method of manufacturing the same having the above-described structure, the group IIIa elements, Ca, and S of the periodic table are used.
A predetermined amount of S together with a sintering aid composed of oxides of r and Ba
Since the i component and, if necessary, Al ₂ O ₃ are added together to form an AlN sintered body, a crystal structure in which the size of the crystal grains and the grain size distribution thereof are appropriately controlled by the Si component can be obtained. Therefore, an aluminum nitride sintered body having excellent strength characteristics and fracture toughness values can be obtained.

[0031]

EXAMPLES Next, the aluminum nitride sintered body according to the present invention will be described more specifically with reference to the following examples.

Examples 1 to 30 Aluminum nitride powder (A) produced by the reduction nitriding synthesis method, containing 0.8% by weight of oxygen as an impurity, and having an average particle diameter of 1 μm, produced by the direct nitriding synthesis method, Contains 1.2 wt% oxygen, average particle size 1.3μ
m aluminum nitride powder (B), aluminum nitride powder (C) prepared by mixing aluminum nitride powders (A) and (B) at a weight ratio of 1: 1 with respect to three types of aluminum nitride raw material powders. As shown in Tables 1 and 2, Si component and Y ₂ O ₃ and Ti as sintering aids
O ₂ , Fe ₂ O ₃ , NiO, Cr ₂ O ₃ , CoO, Li ₂
O, MgO, SiO ₂ , Si ₃ N ₄ , SiC, Si ₂ N
₂ O, α-sialon, β-sialon, polytype A
A predetermined amount of 1N, CaO, BaO, SrO, and Al ₂ O ₃ was added, and the mixture was mixed in a ball mill for 20 hours with ethyl alcohol as a solvent to prepare a raw material mixture. Next, 5.5 wt% of polyvinyl alcohol (PVA) as an organic binder was added to this raw material mixture to prepare granulated powder. Next, the obtained granulated powder is filled in a molding die of a press molding machine and compression-molded in a uniaxial direction with a pressing force of 1200 kg / cm ² , and a corner of 50 mm length × 50 mm width × 5 mm thickness A large number of plate-shaped compacts were prepared. Subsequently, each molded body was heated in air at 450 ° C. for 1 hour to be degreased.

Next, the degreased compacts were placed in an AlN firing container, and densification and sintering were carried out for 4 hours at a firing lower limit temperature of 1720 to 1780 ° C. shown in Tables 1 and 2 in a firing furnace. The AlN sintered bodies according to Examples 1 to 30 were manufactured by cooling at a cooling rate of 200 ° C./hr.

Comparative Example 1 On the other hand, the raw material preparation, molding, degreasing and sintering were carried out under the same conditions as in Example 1 except that the Si component was not added at all and only the conventional sintering aid was added and sintering was performed at 1800 ° C. Then, an AlN sintered body according to Comparative Example 1 having the same dimensions was manufactured.

Comparative Example 2 In addition, an excessive amount of SiO ₂ as a Si component was 0.3% by weight.
An AlN sintered body according to Comparative Example 2 was manufactured by treating under the same conditions as in Example 3 except that (Si conversion) was added.

Comparative Example 3 Y ₂ O ₃ as a sintering aid was added in an excessive amount of 15% by weight,
An AlN sintered body according to Comparative Example 3 was manufactured in the same manner as in Example 3 except that it was sintered at 1800 ° C.

Comparative Example 4 In addition to Y ₂ O ₃ as a sintering aid, 1% by weight of TiO ₂ was added, and Si ₃ N ₄ as a Si component was added in an excessive amount of 0.3% by weight (converted to Si). The same treatment as in Example 16 was carried out except that the AlN sintered body according to Comparative Example 4 was manufactured.

Comparative Example 5 In addition to Y ₂ O ₃ as a sintering aid, WO ₃ was added at 0.3% by weight.
In addition to adding Si ₃ N ₄ as a Si component to 0.
A according to Comparative Example 5 was processed in the same manner as in Example 16 except that 1 wt% (as Si) was added and sintering was performed at 1760 ° C.
An IN sintered body was manufactured.

Comparative Example 6 Si component was not added at all, and Ti was added in addition to the conventional sintering aid.
An AlN sintered body according to Comparative Example 6 having the same dimensions as the raw material preparation, molding, degreasing and sintering treatment under the same conditions as in Example 16 except that 0.2% by weight of O ₂ was added and sintered at 1800 ° C. Was manufactured.

Comparative Example 7 In addition to Y ₂ O ₃ as a sintering aid, 0.2% by weight of TiO ₂ and 0.05% by weight of Si ₃ N ₄ as a Si component (S
An AlN sintered body according to Comparative Example 7 was manufactured in the same manner as in Example 20, except that Al ₂ O ₃ was added in excess of 2% by weight and sintered at 1780 ° C.

Comparative Examples 8 to 9 The SiN component was not added to the AlN raw materials (B) and (C) used in Examples 8 and 9, respectively, and only the conventional sintering aid was added and sintered at 1800 ° C. Except for the above, raw material adjustment, molding, degreasing and sintering were performed under the same conditions as in Example 1 to produce AlN sintered bodies according to Comparative Examples 8 and 9 having the same dimensions.

In order to evaluate the strength characteristics and heat dissipation characteristics of the AlN sintered bodies according to Examples 1 to 30 and Comparative Examples 1 to 9 thus obtained, the three-point bending strength, the fracture toughness value, and the heat resistance of each sample were evaluated. The conductivity, average crystal grain size (D50) and grain size distribution of crystal grains were measured, and the results shown in Tables 3 and 4 below were obtained. The fracture toughness value is a value measured by the new original method in the microindentation method.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

As is clear from the results shown in Tables 3 and 4, Si is added in addition to the sintering aids such as Y ₂ O ₃ and CaO.
Al according to Examples 1 to 30 in which a small amount of each component is added in combination
In the N sintered body, the crystal grain size is 2 to 4.5 μm.
m is extremely fine and has a grain size of 1μ in the crystal structure.
The ratio of crystal grains less than m is 10% by volume or less, and the grain size is 1 μm.
The proportion of crystal grains having a size of 2 μm or more and less than 2 μm is 10 to 20% by volume or less, and the proportion of crystal grains having a particle size of 2 μm or more and less than 3 μm is 10 or less.
˜30% by volume or less, the proportion of crystal grains having a particle size of 3 μm or more and less than 4 μm is 30 to 50% by volume or less, and the particle size is 4 μm or more 5
The grain size distribution of the crystal grains is controlled such that the proportion of crystal grains of less than μm is 5 to 10% by volume or less and the proportion of crystal grains of 5 μm or more is 10% by volume or less, and in addition to high bending strength, It was found that both the fracture toughness value and the thermal conductivity were excellent.

On the other hand, the AlN sintered bodies according to Comparative Example 1, Comparative Example 6, Comparative Example 8 and Comparative Example 9 in which no Si component is added are superior to Examples 1 to 30 in thermal conductivity. On the other hand, the bending strength is generally low, and there are difficulties in durability and handleability. Further, in the samples of Comparative Example 2 and Comparative Example 4 in which the Si component was added in an excessive amount, the thermal conductivity was insufficient, and Y ₂ O ₃ as a conventional sintering aid was used.
It was confirmed that, in the sample of Comparative Example 3 in which was added in an excessive amount, both the thermal conductivity and the strength were reduced despite the addition of the Si component.

Further, WO instead of the sintering aid such as TiO _{2 is} used.
_The AlN sintered body according to Comparative Example 5 in which ₃ is added has bending strength and thermal conductivity equivalent to those of Examples 1 to 30, but has a low fracture toughness value and has a problem in durability and handleability. A according to Comparative Example 7 in which an excessive amount of Al ₂ O ₃ was added
The bending strength and fracture toughness values of the 1N sintered body are from Examples 1 to 1.
Although it was equivalent to 30, it was confirmed that the thermal conductivity was lowered.

The fracture surfaces of the AlN sintered bodies according to Examples 1 to 30 were observed with a scanning electron microscope (SEM). As a result, as shown in FIG. Was observed, and it was confirmed that the grain boundary phase was uniformly dispersed and formed around each AlN crystal grain. On the other hand, in the sintered bodies according to Comparative Example 1, Comparative Example 6, Comparative Example 8 and Comparative Example 9, since the grain growth suppressing effect by the addition of the Si component is small, the AlN particles themselves are coarse as shown in FIG. However, the coarse grain boundary phase was formed so as to be aggregated around the adjacent AlN grains.

Further, in the sintered body according to Comparative Example 5,
As shown in FIG. 3, the grain growth is excessively suppressed by the combined addition of the Si component and WO ₃ , and a fine grain structure with a uniform grain size and a narrow grain size distribution is formed. This is the cause of the decrease in the fracture toughness value. It is estimated that

[0052]

As described above, according to the ceramic sintered body and the method of manufacturing the same according to the present invention, a predetermined amount of the sintering aid including the group IIIa element of the periodic table, oxides of Ca, Sr, and Ba is used. Since the AlN sintered body is obtained by adding the Si component in a composite manner, crystal grain growth due to the Si component is effectively suppressed, and a fine crystal structure having a wide grain size distribution can be obtained. Therefore, an aluminum nitride sintered body having excellent strength characteristics and fracture toughness values can be obtained.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing a crystal structure of an aluminum nitride sintered body according to the present invention.

FIG. 2 is a scanning electron micrograph showing a crystal structure of a conventional aluminum nitride sintered body.

FIG. 3 is a scanning electron micrograph showing the crystal structure of an aluminum nitride sintered body having a low toughness value according to Comparative Example 5.

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[Procedure amendment]

[Submission date] May 17, 1994

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Subsequent to the above molding operation, the molded body is heated to 400 to 550 ° C. in air, or in a non-oxidizing atmosphere such as a nitrogen gas atmosphere at a temperature of 400 to 800.
By heating to 0 ° C., the previously added organic binder is thoroughly degreased and removed.

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Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area 104 D

Claims (8)

[Claims] 1. A fracture toughness value of 2.8 MN / m ^3/2 or more, having a crystal structure of aluminum nitride crystal grains, 3
Point bending strength of 490 MPa or more, thermal conductivity of 150 W /
An aluminum nitride sintered body characterized by having a value of m · K or more. 2. In the crystal structure, the proportion of crystal grains having a grain size of less than 1 μm is 10% by volume or less, and the grain size is 1 μm or more and 2 μm or less.
The ratio of crystal grains of less than m is 10 to 20% by volume, the ratio of crystal grains of 2 μm or more and less than 3 μm is 10 to 30% by volume, and the ratio of crystal grains of 3 μm or more and less than 4 μm is 30% or less. 5. The ratio of crystal grains having a particle size of 50% by volume or less and a particle size of 4 μm or more and less than 5 μm is 5 to 10% by volume or less, and the ratio of crystal grains having a particle size of 5 μm or more is 10% by volume or less. The aluminum nitride sintered body described. 3. Periodic table group IIIa element, Ca, Sr, Ba
1 to 1 oxide of at least one element selected from
The content of Si is 0.01 to
0.2 wt% and Al ₂ O ₃ content of 1.5 wt%
It is the following, The aluminum nitride sintered compact of Claim 1 or 2 characterized by the following. 4. The Si component is SiO ₂ , Si ₃ N ₄ , or S.
iC, Si ₂ N ₂ O, β-sialon, α-sialon and polytype aluminum nitride (Al-Si-O
The aluminum nitride sintered body according to claim 3, which is contained as at least one silicon compound selected from -N). 5. Ti, Fe, Ni, Cr, Co, Li,
4. The aluminum nitride sintered body according to claim 3, which contains 0.05 to 0.5% by weight in terms of oxide of at least one metal element selected from Mg. 6. The aluminum nitride raw material powder is added to the periodic table.
1-10 wt% of oxide of at least one element selected from IIIa group elements, Ca, Sr, and Ba, 0.01-0.2 wt% of Si component, and Al ₂ O ₃ of 1. 5% by weight
A method for producing an aluminum nitride sintered body, which comprises molding a mixed powder containing the following and sintering the obtained molded body in a temperature range of 1650 to 1900 ° C. in a non-oxidizing atmosphere. 7. An aluminum nitride raw powder of 0.05 to
7. Aluminum nitride sintering according to claim 6, characterized in that 0.5% by weight is replaced by an oxide of at least one metal element selected from Ti, Fe, Ni, Cr, Co, Li and Mg. Body manufacturing method. 8. The method for producing an aluminum nitride sintered body according to claim 6, wherein the oxygen content of the aluminum nitride raw material powder is set to 1.5% by weight or less.