JPH0925170A - Aluminum nitride pressed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum nitride pressed body which is suitable for the production of an aluminum nitride sintered body having little warpage and no micropores. SOLUTION: This aluminum nitride pressed body comprising aluminum nitride, inorg. component including a sintering assistant and the like, and an org. component such as a binder and surfactant satisfies the following conditions. The occupancy ratio (R) of org. matter in pores calculated from R=1- (1-d1 / d2 )/(1-d3 /d4 )} ranges 0.04 to 0.22 and d1 >=1.8g/cm<3> , more preferably 1.86 to 2.3g/cm<3> , wherein d1 is the density of the formed body calculated from the measured weight and volume of the pressed body, d2 is the density of the formed body calculated from the intrinsic specific gravity of the org. component and the inorg. component which constitutes the pressed body, d3 is the density of the formed body calculated from the measured weight and volume of the inorg. component of the pressed body, and d4 is the density of the formed body calculated from the intrinsic specific gravity of the inorg. component which constitutes the pressed body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride pressed body suitable for producing an aluminum nitride sintered body having a small warpage and no micropores.

[0002]

2. Description of the Related Art Due to the recent increase in the amount of heat generated by IC chips accompanying the dramatic improvement in the degree of integration of LSIs, the conventionally used alumina has insufficient thermal characteristics and is reaching the limit of heat dissipation.

On the other hand, aluminum nitride powder has a high thermal conductivity and a high insulating property, and is in the spotlight as a raw material of an aluminum nitride sintered body which is extremely useful as an electronic material such as a package material. Conventionally, as a method for obtaining an aluminum nitride sintered body, after granulating aluminum nitride powder into granules by a known method such as a spray dryer method, the aluminum nitride granules are packed in a molding die and then a press molding machine is used. A method is known in which pressure is applied, a so-called dry press is used to obtain a pressed body, and the pressed body is fired.

However, when an aluminum nitride sintered body is produced by using the aluminum nitride pressed body obtained by the above-mentioned general method, the aluminum nitride sintered body has a small warp and has no micropores in the sintered body. It was difficult to obtain a solid body stably.

[0005]

[Means for Solving the Problems] The present inventors have conducted extensive studies to solve the above problems. As a result, in the aluminum nitride pressed body, the ratio of the organic component containing the binder as the main component in the voids formed by the inorganic component containing aluminum nitride as the main component, that is, in the aluminum nitride pressed body represented by the above formula. It was found that the occupancy ratio R of organic substances in the voids affects the residual form of carbon in the aluminum nitride powder compact after degreasing, which in turn causes warpage of the aluminum nitride sintered body obtained and generation of micropores. It was

As a result of further research, it has been found that an aluminum nitride press body in which the compact density d ₁ of the aluminum nitride press body and the organic matter occupancy R in the voids are adjusted within a specific range can achieve the above object. The inventors have found the present invention and have proposed the present invention.

That is, the present invention relates to an aluminum nitride press body composed of an inorganic component containing aluminum nitride as a main component and an organic component containing a binder as a main component, and the measured values of the weight and volume of the press body are used. The calculated compact density is d ₁ , the compact density obtained by calculating from the true specific gravity of the organic component and the inorganic component constituting the pressed body is d ₂ , and the weight and volume of the inorganic component of the pressed body are actually measured. the compact density was more calculated d _3, when the compact density was calculated from the true specific gravity of the inorganic component constituting the pressed body was d _4, the following equation R = 1 - {(1- d 1 / d ₂ ) / (1-d ₃ / d ₄ )}, the organic matter occupancy (R) in the void is 0.04 to
It is 0.22, and d ₁ is 1.8 g / cm ³ or more, which is an aluminum nitride pressed body.

The compact density d ₁ of the aluminum nitride pressed body of the present invention is the density obtained by measuring the dimensions and weight of the pressed body. The compact density d ₂ is a density calculated from the true specific gravities of all raw materials forming the aluminum nitride pressed body excluding the organic solvent, assuming that no pores are contained. Further, the density d ₃ of the molded body is the condition that the pressed body is not substantially expanded or contracted, that is, the molded body is baked at 600 ° C. for 5 hours to remove the organic component, and then the size and weight (inorganic component Is the density obtained by measuring (weight of). The compact density d ₄ is calculated from the true specific gravities of all the inorganic components containing aluminum nitride as the main component that constitutes the aluminum nitride pressed body,
The density is calculated by assuming that no pores are included.

The inorganic component forming the aluminum nitride pressed body of the present invention may be any one containing aluminum nitride as a main component. Generally, the inorganic component is aluminum nitride alone, or aluminum nitride and a sintering aid 0.1 to 1
0% by weight. 5% by weight of alumina if necessary
You may add in the following ratios.

As the aluminum nitride powder used in the present invention, known powders can be used without any limitation. Generally, in order to obtain an aluminum nitride sintered body having excellent thermal conductivity, it is preferable that the oxygen content and the amount of cationic impurities be small. That is, when AlN has an aluminum nitride composition, aluminum nitride powder having an oxygen content of 1.5% by weight or less and a cation impurity of 0.3% by weight or less is preferable. Furthermore, the oxygen content is 0.4 to 1.3% by weight,
Aluminum nitride powder having 0.2% by weight or less of cationic impurities is more preferable. The aluminum nitride in the present invention is a 1: 1 compound of aluminum and nitrogen, and all other compounds are treated as impurities. However,
The surface of the aluminum nitride powder is inevitably oxidized in air and Al-N bonds are replaced by Al-O bonds, but this bonded Al is not regarded as a cation impurity. Therefore, metallic aluminum having no Al—N or Al—O bond is a cation impurity.

The particles of the aluminum nitride powder used in the present invention preferably have a small particle size. For example, the average particle diameter (referred to as the average particle diameter of agglomerated particles measured by a centrifugal particle size distribution measuring device, such as CAPA500 manufactured by Horiba Ltd.) is preferably 5 μm or less, and more preferably 3 μm or less.

As the sintering aid which is one of the inorganic components other than the above-mentioned aluminum nitride powder, known sintering aids, for example, alkaline earth metal oxides such as calcium oxide and strontium oxide; yttrium oxide, Rare earth oxides such as lanthanum oxide; complex oxides such as calcium aluminate are generally used.

As the organic component constituting the aluminum nitride pressed body of the present invention, a surface active agent and a binder are usually used. If necessary, a lubricant for enhancing pressure transmission during press molding, a plasticizer for enhancing crushability of granules, and the like may be used in a proportion of 2% by weight or less with respect to the inorganic component.

When manufacturing a pressed body, generally, the ceramic powder is granulated into granules and pressed. Here, in the production of granules, a surfactant is often used in order to enhance the dispersibility of sludge. As the surface active agent of the present invention, known ones can be used without any limitation, but the hydrophilic / lipophilic balance (hereinafter abbreviated as HLB) is 4.5 to.
No. 18 is preferably used because the molding density of the aluminum nitride powder compact increases. In addition, H in the present invention
LB is a value calculated by the Davis equation.

Specific examples of the surface active agent that can be preferably used in the present invention include carboxylated trioxyethylene tridecyl ether and diglycerin monoole.
, Diglycerin monostearate, carboxylated heptaoxyethylene tridecyl ether, tetraglycerin monooleate, hexaglycerin monooleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate -T and the like. The surfactant in the present invention may be used as a mixture of two or more kinds, and the HLB at that time can be calculated by the arithmetic mean of the HLB of each surfactant.

In the present invention, as the binder, any known binder generally used for molding ceramic powder can be used without any limitation. For example, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, poly 2-ethylhexyl methacrylate, polybutyl methacrylate, polyacrylate, cellulose acetate butyrate, Oxygen-containing organic polymers such as nitrocellulose, methylcellulose, hydroxymethylcellulose, polyvinyl alcohol, polyoxyethylene oxide and polypropylene oxide; hydrocarbon-based synthetic resins such as petroleum resin, polyethylene, polypropylene and polystyrene Polyvinyl chloride; One or more organic polymers such as waxes and emulsions thereof are used in combination. Although the molecular weight of the organic polymer used as the binder is not particularly limited, it is generally 3,000 to 1,000.
000, preferably 5,000 to 300,000
It is preferable to use the above-mentioned one because the density of the aluminum nitride pressed body obtained by the press forming increases.

In the aluminum nitride pressed body of the present invention, the mixing ratio of the organic components such as the surface active agent and the binder and the inorganic components such as the aluminum nitride powder and the sintering aid is
Depending on the type of surface-active agent and binder, etc.,
The ratio of the organic component excluding the solvent may be 0.1 part by weight or more and less than 5 parts by weight with respect to 100 parts by weight of the inorganic component.

In the aluminum nitride press body of the present invention, one of the important requirements is that the occupancy ratio R of the organic matter in the void is 0.
It is in the range of 04 to 0.22. That is, when the organic substance occupancy rate R in the voids is smaller than 0.04, a good pressed body cannot be obtained due to insufficient strength of the pressed body.
When it is larger than 22, warpage is large and micropores are generated, which is not preferable. In order to obtain a good pressed aluminum nitride body and an aluminum nitride sintered body having a small warp and no micropores, the organic substance occupancy ratio R in the voids is further preferably in the range of 0.06 to 0.20. preferable.

The compact density d1 of the above-mentioned pressed body
Is important to be 1.8 g / cm ³ or more. That is, when the compact density d ₁ is lower than 1.8 g / cm ³ ,
Since the shrinkage rate due to sintering is large, warpage and deformation are large, and the effect of the present invention cannot be obtained, which is not preferable. The molded body density d ₁ may be in the above range, but 1.86 to
More preferably, it is 2.3 g / cm ³ . By the way, according to the method of the present invention described later, it is possible to manufacture up to about 2.4 g / cm ³ .

Further, at the time of press molding, the compression ratio obtained by dividing the compact density of the pressed body by the bulk specific gravity of the granule is 1.8 to
It is preferably 2.8. That is, when the compression ratio is smaller than 1.8, the granules are insufficiently crushed and voids are formed between the granules, which easily causes micropores in the sintered body. On the other hand, when it is larger than 2.8, the residual stress in the pressed body becomes large, and the warp of the sintered body tends to become large. More preferably, the compression ratio is in the range of 1.85 to 2.6.

Further, in manufacturing the aluminum nitride pressed body of the present invention, an organic solvent is generally used by mixing. However, since the organic solvent does not substantially exist in the pressed body after granulation and press molding, it is handled after being excluded from the organic components in calculation.

Examples of the organic solvent preferably used are ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as ethanol, propanol and butanol; benzene;
Aromatic hydrocarbons such as toluene and xylene; or one or two halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene and bromochloromethane
Mixtures of more than one species. The amount of organic solvent is 20 to
It is selected and used in the range of 200 parts by weight.

The above components are dispersed and mixed in a solvent to form a viscous slurry generally called mud, and then granulated by a known method such as a spray dryer method. A method in which the obtained aluminum nitride granules are packed in a molding die and pressed by a press molding machine to form a pressed body by a so-called dry pressing method is suitably adopted.

The compact density d ₁ which is a constituent factor of the aluminum nitride pressed body of the present invention is determined by the above-mentioned manufacturing method.
It can be adjusted mainly by the pressure density and the press molding pressure, which will be described later, of the granules used.

The granules preferably used in the present invention have an average particle size of 20 to 500 μm and 0.3 t / c.
When the granules are press-molded with m ² , the pressed density of the pressed body is preferably in the range of 1.8 to 2.3 g / cm ³ . In order to obtain a pressed body in which the granules are well crushed so that there are no voids between the granules and a sintered body having no micropores in the sintered body is obtained, the average particle size is further preferably in the range of 25 to 300 μm. Preferably, in order to obtain a pressed body with a small residual stress and a sintered body with a small warpage by a low pressing pressure, the pressure density is in the range of 1.86 to 2.2 g / cm ^3. More preferable. Here, the pressed density of the granules can be adjusted mainly by the mixing conditions in the above-mentioned production method, and the average particle size can be adjusted mainly by the operating conditions of the spray dryer.

The occupancy ratio R of organic matter in the voids, which is a constituent feature of the present invention, is mainly adjusted by the above-mentioned molding density d ₁ and molding densities d ₂ , d ₃ and d _{4 in} the above-mentioned manufacturing method. . Specifically, it can be adjusted by adjusting the press density of the granules used and the molding pressure, and also by adjusting the mixing ratio of the organic component excluding the solvent to the inorganic component containing aluminum nitride as the main component.

Further, the compression ratio, which is a constituent feature of the present invention, is
In the above production method, it can be adjusted mainly by the press molding pressure and the bulk density of the granules used. here,
The bulk density of the granules is adjusted mainly by the amount of solvent at the time of mixing in the above production method.

The aluminum nitride pressed body thus obtained is degreased and fired by a known method. For degreasing,
Generally, it is carried out in an air or nitrogen atmosphere, and the degreasing temperature is 300 to 1000 depending on the type of binder and the atmosphere.
It is arbitrarily selected from the range of ° C. The aluminum nitride powder compact after degreasing is 1700 to 195 in a non-oxidizing atmosphere.
It is fired at any temperature in the range of 0 ° C. In this way, it is possible to obtain an aluminum nitride sintered body having a small warpage and no micropores in the sintered body.

[0029]

When an aluminum nitride sintered body is manufactured using the aluminum nitride pressed body of the present invention, it is possible to obtain an aluminum nitride sintered body having a small warpage and no micropores in the sintered body. Therefore, there is no need for a post-process for warping correction such as warping back and surface processing,
It is possible to efficiently and inexpensively manufacture an industrial material such as a substrate having high electrical and mechanical reliability. Further, it is preferably used as an electronic material such as a co-firing substrate with a refractory metal such as tungsten, a metal bonded substrate, a substrate having a metallized surface such as fine pattern, or an industrial material such as a heat sink or a semiconductor device. It

Therefore, the aluminum nitride sintered body obtained by using the aluminum nitride pressed body of the present invention is an extremely useful material as the electronic material and industrial material which are required to have high reliability.

[0031]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Various physical properties in the following examples and comparative examples were measured by the following methods.

1) Specific surface area N ₂ was used by using "FLOW SOVE 2300" manufactured by Shimadzu Corporation.
It was determined by the BET method by adsorption.

2) Average Aggregate Particle Size It was determined by the centrifugal sedimentation method using "CAPA 500" manufactured by Horiba Ltd.

3) Amount of Impurities As for the cationic impurities, aluminum nitride powder was alkali-melted, neutralized with an acid, and manufactured by Shimadzu Corporation “ICPS-100”.
0 ”was used to quantify the solution by ICP emission spectroscopy.

The amount of impurity carbon was determined by burning aluminum nitride powder in an oxygen stream and using "EMIA-" manufactured by Horiba Ltd.
110 ”was used to quantify the amount of generated CO and CO ₂ gas.

The amount of impurity oxygen was generated by a high temperature pyrolysis method in a graphite crucible using aluminum nitride powder "EMGA-2800" manufactured by Horiba Ltd.
It was determined from the amount of O gas.

4) Granule average particle size: Obtained from the cumulative distribution 50 percent value of the particle size distribution described in "Chemical Engineering Handbook, 4th Edition", page 973, edited by Chemical Engineering Association.

5) Granule Pressing Density Using a mold having a diameter of 20 mm, the granules were pressed at a pressure of 0.3 t / cm ² to prepare pellets. The pressure density was determined from the weight and shape of the obtained pellets.

6) Granular Bulk Density The heavy bulk density was measured using "A / B / D powder property measuring instrument" manufactured by Tsutsui Rikagaku Kikai.

7) Compression Ratio: The density of the molded product of the pressed product was divided by the bulk specific gravity of the granules.

8) Molded product density (d ₁ , d ₂ , d ₃ , d ₄ ) The molded product density d ₁ is obtained by measuring the size and weight of the pressed product, and the molded product density d ₂ is calculated as follows. From the true specific gravity of all raw materials constituting the aluminum nitride pressed body excluding the solvent,
It was calculated by assuming that no pores are included. The compact density d ₃ was obtained by firing the above-mentioned pressed body at 600 ° C. for 5 hours to remove the organic components, and then measuring the dimensions and weight. Further, the compact density d ₄ was calculated from the true specific gravities of all the inorganic substances mainly composed of aluminum nitride constituting the aluminum nitride pressed body, by assuming that no pores were contained.

9) Density of Sintered Body The density was determined by the Archimedes method using "High-precision specific gravity meter DH" manufactured by Toyo Seiki.

10) Warp of Sintered Body The slits having a width obtained by adding 20 μm to the thickness of the sintered body were passed through the sintered body, and the passing rate was shown.

11) Sintered Micropores Photomicrographs were made at a magnification of 40 using a stereomicroscope.
Micropores of 20 μm or more per 1 cm 2 were counted and determined as the micropore density. The average value of 3 samples was used as the measured value.

Example 1 An iron core-containing nylon ball was placed in a nylon pot having an internal volume of 10 L, then 100 parts by weight of aluminum nitride powder shown in Table 1, 4 parts by weight of yttrium oxide, and hexaglycerin monoole as a surface-active agent. 0.5 parts by weight, n-butyl methacrylate as a binder, and toluene as a solvent in the amounts shown in Table 2, and the mixture was subjected to a ball mill mixing for the time shown in Table 2, and then a white mud was obtained. I got a bite.

The mud thus obtained was granulated by a spray dryer method to produce aluminum nitride granules having a size of φ70 to 100 μm. The bulk density and pressure density of the obtained granules were measured.

The granules were press-molded under the molding pressure shown in Table 2 to obtain a pressed body having a diameter of 40 mm and a thickness of 3.0 mm, the density of the molded body d ₁ , the occupancy ratio R of organic matter in the voids of the pressed body and The compression ratio was measured. Then, it was fired in air at 600 ° C. for 5 hours, then placed in a carbon crucible having an inner surface coated with boron nitride, and fired in a nitrogen atmosphere at 1800 ° C. for 5 hours to obtain a sintered body. The density, warpage, and micropore density of the sintered body were measured, and the results are shown in Table 2.

[0049]

[Table 1]

[0050]

[Table 2]

Claims (1)

[Claims] 1. An aluminum nitride press body comprising an inorganic component containing aluminum nitride as a main component and an organic component containing a binder as a main component, wherein the molded body is calculated from measured values of the weight and volume of the press body. Molding density calculated from the actual density of the molded body, which is obtained by calculating the density of d ₁ , the true specific gravity of the organic component and the inorganic component of the pressed body, and d ₂ , the measured value of the weight and volume of the inorganic component of the pressed body. Assuming that the body density is d ₃ , and the molded body density obtained by calculating from the true specific gravity of the inorganic components constituting the pressed body is d ₄ , the following formula R = 1-{(1-d ₁ / d ₂ ) / The organic matter occupancy (R) in the void calculated from (1-d ₃ / d ₄ )} is 0.04.
Is ~0.22, d ₁ is an aluminum nitride pressed product, characterized in that at 1.8 g / cm ³ or more.