JPH0840773A - Aluminum nitride ceramic and its production - Google Patents

Abstract

PURPOSE:To provide an aluminum nitride ceramic high in thermal conductivity and having a high strength. CONSTITUTION:100 pts.wt. of aluminum nitride powder having an oxygen content of <=1.3wt.%, 0.1-20 pts.wt. of carbon, 0.3-50 pts.wt. of aluminum oxide, 0.01-15 pts.wt. of yttrium oxide, and, if necessary, further a binder, a dispersant, etc., are mixed and molded. In the mixture, the carbon is added in an amount which is more excessive than a chemical equivalent required for the reaction with oxygen contained in the aluminum nitride powder. The aluminum oxide is added for reacting with the excessive carbon. The obtained molded product is sintered to obtain the aluminum nitride ceramic having a thermal conductivity of >=180(W/m.k) at 25 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ceramics used for electronic device materials such as IC substrates and package materials, and more particularly to aluminum nitride ceramics having high thermal conductivity and excellent heat dissipation, and ceramics thereof. It relates to a manufacturing method.

[0002]

2. Description of the Related Art The thermal conductivity of aluminum nitride is about 320 (W / mK), which is 1.5 times that of metallic aluminum. In addition to such high thermal conductivity, the aluminum nitride ceramics (Al
N ceramics) has attracted attention as an IC substrate and a packaging material.

However, in practice, it is not easy to sinter aluminum nitride powder to obtain ceramics having high thermal conductivity. In order to improve the thermal conductivity of AlN ceramics, various methods have been developed so far. These methods can be roughly divided into two. The first is a method of making ceramics more dense. In this method, it is attempted to improve the thermal conductivity by densely sintering AlN, which is a material that has a high covalent bond and is difficult to sinter. As a concrete method, first, a method of adding a sintering aid such as Y ₂ O ₃ for densification has been reported (for example, Shinozaki et al., 1985 Proceedings of the Ceramic Society Annual Meeting (19
85) p. 517-518). It has also been reported that it is effective to remove sintering inhibitors such as carbon (eg, Kurokawa et al., J. Am. Cera).
m. Soc. , 71 [7] p. 588-94). Second
Is to remove oxides. It is considered that when AlN is oxidized, vacancies are formed, which impede phonon transfer which is responsible for heat conduction of AlN, and thus the thermal conductivity of AlN ceramics is lowered. Therefore, the second
The method (2) attempts to improve the thermal conductivity by adding a substance that binds to the oxide in AlN and removing the oxide in AlN. As a specific method, for example, Y ₂
It is disclosed that an oxide is trapped by adding a sintering aid such as O ₃ (for example, Japanese Patent Publication No. 60-1272).
67 publication). Also disclosed is a method of adding carbon to react with and remove oxides (eg, Huseby).
Et al., USP 4,578,364 and corresponding JP-A-6
No. 1-146769). Aluminum nitride ceramics obtained by this method are
It has a thermal conductivity of 41 to 164 (W / m · K).

Carbon contributes to the improvement of thermal conductivity in terms of oxide removal, while carbon left unreacted hinders densification of AlN. Therefore, JP-A-61-146769
Japanese Unexamined Patent Publication (Kokai) discloses that carbon is added in an amount necessary to react with oxygen (oxide) contained in the AlN powder to be sintered, and if carbon is added in excess of that, sintering becomes difficult, which is preferable. Suggests not.

On the other hand, when the AlN powder contains a large amount of metallic impurities such as Fe, Si and Mg, these impurities also hinder the phonon transmission. Therefore, a method of improving the thermal conductivity of the AlN ceramics has been attempted by increasing the purity of the AlN powder.

However, there is a demand for a method of further improving the thermal conductivity over the method described above.

Further, aluminum nitride ceramics having high strength as well as high thermal conductivity are desired.

One object of the present invention is to provide aluminum nitride ceramics having high thermal conductivity with high reproducibility.

A further object of the present invention is to provide an aluminum nitride ceramic which has not only high thermal conductivity but also high strength.

[0010]

The method according to the present invention is a method for producing aluminum nitride ceramics by sintering aluminum nitride powder, wherein aluminum nitride powder is prepared and its oxygen content (hereinafter x weight% and And (a) at least the following materials (a) to (d) are prepared and mixed, and (a) the oxygen content is x% by weight (where x ≦ 1.3). 100 parts by weight of said aluminum nitride powder which is: (b) at least one substance selected from the group consisting of carbon and a compound capable of liberating carbon by heating at a temperature lower than the temperature for sintering. A carbon source consisting of
An amount that provides a predetermined amount of carbon in the mixture in excess of 0.75 x parts by weight within the range of 0.1 to 20 parts by weight, (c)
An aluminum oxide source consisting of aluminum oxide and at least one substance selected from the group consisting of compounds that can be converted to aluminum oxide by heating at or below the temperature for sintering, Amounts of Al ₂ O ₃ in the range of 3 to 50 parts by weight in the mixture, and (d) oxides and fluorides of elements 2A and 3A of the Periodic Table, and the temperature or the temperature for said sintering. A sintering aid made of a substance selected from the group consisting of compounds that can be converted into oxides of 2A and 3A group elements by heating at a lower temperature, with 0.01 to 2% of the 2A and 3A group elements. An amount in the range of 15 parts by weight, molding the resulting mixture,
The obtained molded body is fired in a non-oxidizing atmosphere containing a gas selected from the group consisting of nitrogen, ammonia and a combination thereof, and has a thermal conductivity of 180 (W
/ M · K) or more to obtain ceramics.

Further, according to the present invention, it is possible to provide a novel aluminum nitride ceramics produced by the above method.
It has the property of (vi).

(I) 180 (W / m · at 25 ° C.)
It has a thermal conductivity of K) or higher. (Ii) The amount of dissolved oxygen is 0.5% by weight or less.

(Iii) The maximum diameter of the pores is 20 μm or less. (Iv) It has a bending strength of 35 kg / mm ² or more.

(V) Indicates a Weibull coefficient of 7.0 or more. (Vi) The content of 2A and 3A group elements in the periodic table is 0.01 to 15% by weight.

The aluminum nitride powder used in the present invention is
Although it may be prepared by any manufacturing method, it is preferable to use one manufactured by a direct nitriding method or a reduction nitriding method. The particle size of the aluminum nitride powder may be within the range that does not impair the formability and sinterability, and the specific surface area according to the BET surface area measurement is 1.0 to 2 in particular.
Those of 0 m ² / g can be preferably used. This powder preferably has high purity. For example, AlN powder having a Si content of 200 ppm or less is preferable. On the other hand, the powder may contain a group IVa, Va, or VIa group element compound of the periodic table for the purpose of coloring the AlN ceramics or the like. In that case, the periodic table IVa, Va, VI
It is preferable to mix the additives so as not to exceed 15% by weight in terms of the group a element. Here, the IVa group element is Ti, Zr, or Hf, and the Va group element is
V, Nb, Ta, and the VIa group elements are Cr, Mo,
W.

The oxygen content in the aluminum nitride powder is
For example, it can be measured by an infrared absorption method.
Oxygen content in aluminum nitride powder is 1.3% by weight
Below, it is preferably limited to 0.5% by weight or less. 1.
If the oxygen content is higher than 3% by weight, the powder used contains a large amount of oxynitride, which makes it difficult to remove it.

When the oxygen content in 100 parts by weight of aluminum nitride powder is x% by weight, the carbon source is 0.1-2.
In the range of 0 parts by weight, it is added in an amount to provide an excess of carbon exceeding 0.75 x parts by weight. 0.75 x parts by weight is the chemical equivalent of carbon needed to react with x wt% oxygen. The present invention is characterized by adding carbon in excess of this chemical equivalent. The carbon source is, for example,
2-fold excess-500-fold excess, ie 1.5x-375x
Parts by weight, preferably 4 fold excess to 400 fold excess or 3
x-300x parts by weight of carbon, which is added.

As the carbon source, first, a material composed of carbon (C) can be preferably used. In this case, the weight ratio of carbon atoms in the carbon source is approximately 1. As such a carbon source, for example, powder of at least one material selected from the group consisting of carbon black, coke, graphite, diamond and combinations thereof can be preferably used. For even distribution,
In the carbon source, it is desirable that the particle size, the specific surface area, the pH, and the content of the volatile component are within a specific range. Especially regarding the particle size, the BET specific surface area value is 20
It is preferable to use one having a density of 0 m ² / g or more. BET
A carbon black fine powder having a specific surface area value of 200 m ² / g or more is a more preferable material.

On the other hand, as the carbon source, it is possible to use a material made of a compound capable of decomposing by heating at a temperature lower than the temperature for sintering to release carbon atoms. For example, a material that decomposes at a temperature of 150 ° C. to 1000 ° C. without generating much volatilization to generate carbon can be preferably used. Further, in order to generate carbon, the heating of these compounds is performed in a non-oxidizing atmosphere, for example, a non-oxidizing atmosphere containing nitrogen or ammonia. Such heating can be performed in the firing process for forming ceramics. As such a carbon source, fatty acids such as stearic acid, dibutyl phthalate, aromatic compounds such as dioctyl phthalate, organic polymers or organic resins such as styrene resins, acrylic resins, phenol resins and urethane resins, glucose, fructose, Organic compounds including carbohydrates such as sucrose and starch can be used. More specifically, polyacrylonitrile, polyvinyl alcohol,
Polyvinyl butyral, polyethylene terephthalate,
Dibutyl phthalate, dioctyl phthalate, glucose,
At least one compound selected from the group consisting of fructose, sucrose and combinations thereof can be preferably used. Even when such a carbon source is used, it is preferable to select a material capable of uniformly dispersing carbon in the green body. Therefore, materials that can be added in the form of solutions or liquids are preferred. If such a material is selected, the reaction between the oxynitride and carbon proceeds uniformly, and unevenness in the composition and color tone of the resulting ceramic can be reduced.

In the present invention, the amount of free carbon is 0.1.
~ 20 parts by weight of carbon source are added. When the addition amount is less than 0.1 part by weight, the effect of removing the oxynitride is small, and it becomes difficult to obtain high thermal conductivity with high reproducibility. On the contrary, when the amount added is more than 20 parts by weight, the excess carbon cannot be removed completely by adding aluminum oxide, and the residual carbon hinders the sintering of AlN. in this case,
It becomes difficult to obtain dense ceramics.

In the present invention, the excess carbon added to remove the oxynitride reacts during sintering, so that 0.3 to 50 is added.
Add parts by weight of aluminum oxide source. Assuming that the amount of carbon brought from the carbon source to the mixture is y parts by weight, the aluminum oxide source may be, for example, Al ₂ O ₃ of 0.3 to 50.
Within the range of parts by weight, 1.9x (y-0.75x) to
An amount of 8.0 × (y-0.75x) parts by weight, preferably added, can be added. For example, x = 0.4, y =
In the case of 1.3, the aluminum oxide source can be preferably added in an amount that provides 1.9 to 8.0 parts by weight of Al ₂ O ₃ . Aluminum oxide (Al ₂ O ₃ ) is preferably used as the aluminum oxide source. The aluminum oxide used may be in the form of α-type or γ-type. On the other hand, as the aluminum oxide source, a compound that can be converted into aluminum oxide at a temperature for sintering, for example, 1750 ° C to 2050 ° C, or a lower temperature, for example, 700 ° C to 1750 ° C can be used. Examples of such compounds include aluminum inorganic salts such as aluminum hydroxide, aluminum nitrate, aluminum sulfate and aluminum phosphate, aluminum organic acid salts such as aluminum stearate, and alkoxide compounds such as aluminum isopropoxide. . In particular, aluminum hydroxide, aluminum nitrate, aluminum sulfate, aluminum phosphate,
A compound selected from the group consisting of aluminum stearate and a combination thereof can be preferably used.

When a compound other than Al ₂ O ₃ is used as the aluminum oxide source, the addition amount is determined in consideration of the stoichiometric amount of Al ₂ O ₃ produced from the compound. For example, when determining the amount of addition, it is possible to determine the amount of addition, assuming that all of the aluminum oxide source Al is converted to Al ₂ O ₃ . In this case, the amount of Al ₂ O ₃ derived from the aluminum oxide source is determined by (weight of aluminum oxide source × weight ratio of aluminum in aluminum oxide source × 1.889). The value 1.889 is the molecular weight of Al ₂ O ₃ / (Al ₂
Weight of Al contained in 1 mol of O ₃ ) = 101.96 / 5
3.963.

As described above, the amount of aluminum oxide added is limited to 0.3 to 50 parts by weight in terms of aluminum oxide. If the addition amount is less than 0.3 parts by weight, it becomes difficult to sufficiently remove the residual carbon,
It becomes difficult to obtain dense ceramics. On the other hand, when the addition amount is more than 50 parts by weight, the formation of oxynitride due to the reaction between aluminum oxide and AlN becomes remarkable in the firing process, which hinders the improvement of the thermal conductivity. Further, the addition amount of aluminum oxide is preferably set in the range of 1.9 times to 8.0 times the free carbon amount obtained by (y-0.75x), and more preferably 1.99 to 3 times. Is. Further, it is preferable to suppress aggregation of aluminum oxide in order to sufficiently bring out the effect of the aluminum oxide source. Therefore, the particle size of the aluminum oxide source used is preferably 50 μm or less, more preferably 20 μm or less, and further preferably 5 μm or less. Also, the aluminum oxide source can be added in the form of a solution. It is important to select a material and a mixing / dispersing method capable of uniformly dispersing in the green body.

In the present invention, 2A and 3 of the periodic table
Sintering selected from the group consisting of oxides and fluorides of Group A elements and compounds that can be converted to oxides of Group 2A and 3A elements by heating at or below the temperature for sintering. Further auxiliaries are added. Yttrium (Y), calcium (Ca), strontium (Sr), scandium (Sc), or a lanthanoid element is selected as the 2A and 3A group elements of the periodic table. Therefore, the sintering aid is yttrium oxide, calcium oxide, strontium oxide,
It can be selected from the group consisting of scandium oxide and oxides of lanthanide series elements. Examples of oxides of lanthanoid elements include praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, and ytterbium oxide. On the other hand, as the fluoride of the 2A and 3A group elements, for example, calcium fluoride, strontium fluoride, barium fluoride, yttrium fluoride or the like can be used. Further, as a compound that can be converted into an oxide of a 2A or 3A group element by heating, a hydroxide or the like of these elements can be used. These sintering aids are converted into the elements of the 2A and 3A groups in an amount of 0.01 to
15 parts by weight, that is, {(0.01 to 15) / (weight ratio of 2A and 3A group elements in the sintering aid)} parts by weight is added. The preferable addition amount is 0.1 to 15 parts by weight in terms of 2A and 3A group elements. If the addition amount is less than 0.01 part by weight, it becomes impossible to obtain sufficiently dense ceramics. On the other hand, if the amount added exceeds 15% by weight, the thermal conductivity of the obtained AlN ceramics will decrease.

In the process of the present invention, (a)-
In order to mix the materials of (d), known methods such as a dry mixing method using a V-type mixer or a bowl mill mixer and a wet mixing method using a bowl mill mixer can be used. The mixing method and mixing conditions are not particularly limited. During the mixing, other additives such as an organic binder, a plasticizer, a dispersant, a defoaming agent, or a combination thereof can be added, if necessary. Paraffin or the like is used as the organic binder. As the dispersant, for example, ethyl alcohol or the like is used.

A mixture containing the materials (a) to (d) and optionally other additives is molded. In the molding process,
Dry press molding method, doctor blade sheet molding method,
Known molding methods such as an extrusion molding method, a slip casting molding method, and an injection molding method are used. The molding method is not particularly limited. Also, a binder system suitable for those molding methods can be arbitrarily selected.

The compact is heat treated to form a sintered body. In the heat treatment, first, in order to release carbon from the carbon source, the molded body may be heated at 150 to 1000 ° C. The heating for liberating carbon is preferably performed in a non-oxidizing atmosphere having an oxygen partial pressure of 1% by volume or less. As the non-oxidizing atmosphere, a non-oxidizing atmosphere containing at least one gas selected from the group consisting of nitrogen and ammonia, an inert gas atmosphere such as vacuum and argon, and an atmosphere in which hydrogen is added to the inert gas. Etc. can be used. Sintering is performed after the carbon has been sufficiently liberated, or while carbon is liberated. Sintering is at least one selected from the group consisting of nitrogen and ammonia.
It is desirable to carry out under a non-oxidizing atmosphere containing two gases. At this time, the partial pressure of nitrogen, ammonia, or a mixture thereof is preferably 5% by volume or more. If the partial pressure of the added gas is higher than 5% by volume, a more effective rate can be obtained for the reduction and removal reaction of oxynitride. The firing temperature is preferably 1300 ° C. or higher. When the temperature is lower than 1300 ° C., the reduction and removal reaction of oxynitride becomes slow. In addition, in order to more efficiently remove oxynitrides during firing, the temperature of the molded body is from 1300 ° C., the temperature at which the composite oxide of the sintering aid and aluminum oxide is generated by the reaction, for example, the sintering aid. When Y ₂ O ₃ is used as
It is preferable that it takes 1 hour or more to reach 35 ° C. Therefore, the heating step for sintering is, for example, a first heating step of holding the molded body at 1300 ° C. to 1700 ° C. for 1 hour or more, and then 1700 ° C. to 205 ° C.
A second heating step of holding the shaped body at 0 ° C., preferably 1750 ° C. to 2000 ° C. can be included. When firing is performed at a temperature of 1300 ° C. or higher, the non-oxidizing atmosphere preferably has a dew point of −30 ° C. or lower.

The aluminum nitride ceramics obtained by the above-mentioned method has less oxynitride, smaller pore diameter, higher thermal conductivity and higher than those obtained by the conventional method. Have strength. The ceramic of the present invention has a high thermal conductivity of 180 (W / m · K) or higher at 25 ° C. Further, according to the present invention, it is possible to provide a denser ceramic having a maximum pore size of 20 μm or less. Such dense ceramics are JIS
According to R1607, it can have a bending strength of 35 kg / mm ² or more, preferably 40 kg / mm ² or more. JIS R1607 stipulates the measurement of bending strength (flexural strength) by a bending test using a three-point support method. Further, in the ceramic of the present invention, the amount of dissolved oxygen in the AlN sintered grains is 0.5% by weight or less. With this ceramic, it is possible to obtain a high value for the Weibull coefficient that indicates reliability with respect to strength.
It is possible to provide a ceramic having a value of 7.0 or more, preferably 8.0 or more.

[0029]

The present inventors conducted an analysis of the factors that reduce the thermal conductivity of AlN ceramics, and conducted intensive studies on the countermeasures. Then, by the method described above,
It has been found that an AlN ceramic having a thermal conductivity of 180 (W / m · K) or more can be produced industrially and stably.

As schematically shown in FIG. 1, AlN powder used as a raw material, particularly Al prepared by a reduction nitriding method.
The N powder has a high oxygen content inside the particles as well as on the surface of the particles. For AlN powder having such an oxygen concentration distribution, USP4 of Huseby et al.
As shown in 758 and 364, it is difficult to effectively reduce even the oxygen remaining inside when carbon equivalent to the amount necessary for the reaction with oxygen contained in the AlN powder is added. all right. The maximum thermal conductivity of the ceramics manufactured in the publication is 164 W / m · K.
It was considered to be due to the fact that unreacted oxide remained.

Further, in order to improve the thermal conductivity of AlN ceramics, the present inventors have made it possible to improve the thermal conductivity of AlN ceramics, in addition to the conventionally known densification of ceramics and removal of oxides, oxynitriding existing in AlN ceramics. It became clear that the removal of things is very important. The oxide in AlN typified by α-Al ₂ O ₃ is removed by the reaction with the oxide by the oxide trap or the carbon additive by the addition of the sintering aid such as Y ₂ O ₃ . However, oxynitrides have been difficult to remove by these methods. In the conventional method, oxynitride remains in the AlN ceramics even after sintering, which causes a decrease in the thermal conductivity of the ceramics by inhibiting phonon transmission.
Further, it was found that the oxynitride hinders the densification of the ceramics, resulting in a decrease in the thermal conductivity.

Surprisingly to the above-mentioned problems of internal oxygen and oxynitride, the addition of excess carbon causes
The internal oxygen can be effectively reduced, and the oxynitride can be removed by the reaction. At the same time, by adding an aluminum oxide source, it is possible to remove the carbon that remains without reacting with the oxynitride, so that the addition of carbon does not adversely affect the sintering inhibition, and it is dense and has a high thermal conductivity. It has been found that high ceramics can be obtained. It was speculated that the above was made possible because the reaction temperature of carbon and oxynitride was lower than the reaction temperature of carbon and aluminum oxide. Then, by using a mixture in which an excess carbon source and aluminum oxide are added, it has become possible to obtain ceramics having higher thermal conductivity and strength. The present invention will be described in more detail below.

[0033]

【Example】

Example 1 100 parts by weight of AlN powder having an average particle size of 0.65 μm and an oxygen content of 0.8% by weight produced by a reduction nitriding method, BE
10 parts by weight of carbon black having a T value of 500 m ² / g,
28 parts by weight of α-type aluminum oxide having an average particle size of 1.2 μm, 5 parts by weight of yttrium oxide having an average particle size of 0.8 μm,
And 7 parts by weight of paraffin as a binder were ball milled in ethyl alcohol. The obtained slurry was spray-dried and press-molded. Paraffin was volatilized and removed by keeping the press-molded body at 700 ° C. for 3 hours in a nitrogen atmosphere.

The sintered body was heated in a furnace in a nitrogen atmosphere, and it took 3 hours and 45 minutes to raise the temperature from 1300 ° C to 1735 ° C. Continue to set the temperature in the furnace to 1
The temperature was raised to 800 ° C., and the molded body was baked at 1800 ° C. for 3 hours. In such firing, the carbon monoxide concentration in the atmosphere was 150 ppm and the dew point was -55 ° C. As a result of the firing, a milky white aluminum nitride ceramics having a uniform color tone was obtained. The composition of the liquid phase generated in such a firing process is mainly YAG (3Y ₂ O ₃ .5AlN ₂
O ₃ ), and the production temperature of the liquid phase was 1735 ° C.

The amount of solid solution oxygen of the obtained AlN ceramics was determined as follows. First, the total oxygen content of the ceramics and the contents of the periodic table IIa and IIIa group elements were determined by an infrared absorption method and an ICP analysis method (inductively coupled plasma optical emission spectroscopy). Next, the amount of oxygen contained in the grain boundary composition identified by the X-ray diffraction pattern was calculated, and this value was subtracted from the total amount of oxygen to obtain the amount of solid solution oxygen. Also,
The thermal conductivity of ceramics was calculated by obtaining the heat capacity and thermal diffusivity by the laser flash method, the density by the Archimedes method, and the product of these three. As a result, the amount of dissolved oxygen was 0.18% by weight, and the thermal conductivity was 207 (W / m · K).

Ceramics 50 produced by the same method
The average thermal conductivity of the sheets is 209.3 (W / m · K), the maximum value is 225 (W / m · K), and the minimum value is 195.
(W / mK), and the difference between the maximum and minimum values is 20
(W / m · K).

On the other hand, the obtained ceramics is 1 inch ×
After cutting into 1 inch × 3 mm, the surface was mirror-polished to a surface roughness (Ra) of 0.05 μm, and then the pores on the polished surface were observed with an optical microscope at a magnification of 400 times. As a result, the maximum diameter of pores was 8 μm. Also, JIS
The bending strength was determined by a three-point bending test based on R1607. As a result of measuring the bending strength of 50 samples, an average value of 45 kg / mm ² was obtained. The Weibull coefficient was as high as 9.7.

Comparative Example 1 100 parts by weight of the AlN powder used in Example 1, 5 parts by weight of yttrium oxide powder, and 7 parts by weight of paraffin as a binder were ball-milled in ethyl alcohol. Next, ceramics were produced by the same method as in Example 1.

The thermal conductivity of the 50 ceramics thus obtained has an average value of 215.7 (W / m · K), a maximum value of 237 (W / m · K) and a minimum value of 183 (W / m · K).・ K)
The difference between the minimum value and the maximum value was 54 (W / m · K). Furthermore, the pore size, bending strength, and Weibull coefficient were determined by the method described in Example 1. As a result, the maximum pore diameter was 25 μm, the average value of the bending strength for 50 samples was 33 kg / mm ² , and the Weibull coefficient thereof was 5.6. Thus, the ceramics produced in this comparative example had a lower strength than that of Example 1.

Example 2 Ceramics were prepared and evaluated according to the method described in Example 1 by changing the amounts of yttrium oxide, carbon and aluminum oxide added. Table 1 shows the results.

[0041]

[Table 1]

Example 3 In the same manner as in Example 1, various sintering aids were used to prepare and evaluate ceramics. The results are shown in Table 2.

[0043]

[Table 2]

Example 4 100 parts by weight of aluminum nitride powder having an average particle size of 0.65 μm, an oxygen content of 1.0% by weight, and an α-type aluminum oxide 10 having an average particle size of 0.5 μm produced by the direct nitriding method.
By weight, 3 parts by weight of yttrium oxide having an average particle size of 0.7 μm, 7 parts by weight of paraffin as a binder, and 50 parts by weight of glucose as a carbon source were mixed in the same manner as in Example 1 and press-molded. It was By holding the obtained press-molded body in a nitrogen atmosphere at 700 ° C. for 3 hours, carbon was liberated and paraffin was volatilized and removed. As a result of analysis by LECO method for obtaining the amount of free carbon, a value of 4.5% by weight was obtained, which was 5.3 parts by weight in terms of parts by weight.

The molded body was heated at 1800 ° C. in a nitrogen atmosphere for 3 hours.
It was fired for a time to obtain an AlN ceramic. By the method described in Example 1, the amount of solid solution oxygen and the thermal conductivity of the obtained ceramics were determined. As a result, the amount of dissolved oxygen was 0.
It was 35% by weight and the thermal conductivity was 185 (W / m · K). Further, as a result of obtaining the maximum pore diameter, bending strength, and Weibull coefficient of the obtained ceramics by the same method as in Example 1, the maximum diameter of the pores was 11 μm, and the average bending strength of 50 samples was It was 52 kg / mm ² , and the Weibull coefficient was 8.8.

[0046]

As described above, according to the present invention, it becomes possible to industrially stably produce aluminum nitride ceramics having a thermal conductivity of 180 (W / m · K) or more. Further, according to the present invention, it becomes possible to obtain a more dense ceramic having high strength. The ceramic of the present invention having such excellent properties is applied as a highly reliable substrate or package material.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the distribution of oxygen concentration in AlN powder particles.

Claims (6)

[Claims] 1. A method for producing aluminum nitride ceramics by sintering aluminum nitride powder, comprising the steps of preparing aluminum nitride powder and determining its oxygen content (hereinafter x weight%), at least the following: (A) to (d) of each of the materials are prepared and mixed, and (a) the oxygen content is x% by weight (where x ≦ 1.
3) 100 parts by weight of the aluminum nitride powder, (b) at least one selected from the group consisting of carbon and a compound capable of liberating carbon by heating at a temperature lower than the temperature for sintering. A carbon source consisting of the substance of 0.1 to 20 parts by weight in the range of 0.1 to 20 parts by weight.
An amount that provides a predetermined amount of carbon in the mixture in excess of 75 x parts by weight, (c) consisting of aluminum oxide and a compound that can be converted to aluminum oxide by heating at or below the temperature for sintering. An aluminum oxide source consisting of at least one substance selected from the group, which provides the mixture with Al ₂ O ₃ in the range of 0.3 to 50 parts by weight, and (d) Groups 2A and 3A of the Periodic Table. From materials selected from the group consisting of elemental oxides and fluorides, and compounds that can be converted to oxides of Group 2A and 3A elements by heating at or below the temperatures for sintering. 2A and 3 above.
An amount of the Group A element in the range of 0.01 to 15 parts by weight, a step of shaping the obtained mixture, and a step of shaping the obtained shaped body with a gas selected from the group consisting of nitrogen, ammonia and a combination thereof. Firing in a non-oxidizing atmosphere containing 180 ° C. and a thermal conductivity of 180 (W
/ M · K) or more of the step of obtaining ceramics,
Manufacturing method of aluminum nitride ceramics. 2. The temperature for the sintering is 1300 ° C. or higher, and the temperature of the molded body is changed from the temperature of 1300 ° C. to
The manufacturing method according to claim 1, wherein in order to raise the temperature to a temperature at which a liquid phase is generated by the reaction of the sintering aid and the aluminum oxide, it takes 1 hour or more. 3. The carbon source is carbon black powder,
Graphite powder, coke powder, diamond powder,
Selected from the group consisting of fatty acids, aromatic compounds, organic resins and carbohydrates, wherein the aluminum oxide source is aluminum oxide, aluminum hydroxide, aluminum nitrate,
Aluminum sulphate, aluminum phosphate and aluminum stearate, and the sintering aid is selected from the group consisting of yttrium oxide, calcium oxide, strontium oxide, scandium oxide, and oxides of the lanthanoid series elements. The manufacturing method according to claim 1 or 2, characterized in that: 4. The mixing step, wherein at least one material selected from the group consisting of an organic binder, a plasticizer, a dispersant, and an antifoaming agent is added.
The manufacturing method according to any one of 1. 5. The firing step comprises 150 ° C. to 1000 ° C.
The manufacturing method according to any one of claims 1 to 4, comprising a step of heating the molded body under a non-oxidizing atmosphere at a temperature in the range of 10 to release carbon from the carbon source. . 6. An aluminum nitride ceramic having the following properties (i) to (vi) produced by the method of claim 1. (I) It has a thermal conductivity of 180 (W / m · K) or higher at 25 ° C. (Ii) The amount of dissolved oxygen is 0.5% by weight or less. (Iii) The maximum diameter of pores is 20 μm or less. (Iv) It has a bending strength of 35 kg / mm ² or more. (V) Indicates a Weibull coefficient of 7.0 or more. (Vi) The content of 2A and 3A group elements in the periodic table is 0.01 to 15% by weight.