JPH0489359A - Light-nontransmittant aluminum nitride sintered body and production thereof - Google Patents

Abstract

PURPOSE:To obtain a white-based light-nontransmittant AlN sintered body which has high density and is excellent in thermal conductivity by mixing the prescribed amount of a sintering adjuvant contg. an element selected from Y and Ca with AlN powder little in the contents of cationic impurities and molding this mixture and burning this molded body in the specified burning conditions. CONSTITUTION:At least one kind of metal selected from yttrium and calcium or a metallic oxide (e.g. Y2O3) is added as a sintering adjuvant to high-purity aluminum nitride powder contg. <=0.3wt.% cationic impurities in a range within 0.01-5wt.% expressed in terms of oxide and mixed therewith. Then a binder is added to this mixed powder and this mixture is molded. This molded body is burned in a temp. range within 175O-1900 deg.C for 5-24 hours in the nonoxidative atmosphere surrounded by boron nitride. Thereby a light nontransmittant aluminum nitride sintered body is obtained which has >=3.1g/cm<3> density and a range within 7-20mum particle diameter and is preferable for an IC base plate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum nitride sintered body and a method for manufacturing the same, and more specifically, it relates to a white or beige non-sintered body with high density and excellent thermal conductivity. The present invention relates to a translucent aluminum nitride sintered body and a method for manufacturing the same.

[Conventional technology]

Alumina has traditionally been widely used in highly reliable IC substrates or package materials. With the increasing integration, speed, and output of LSIs, the amount of heat generated from semiconductor chips increases, and the need to efficiently dissipate heat outside the system increases. There is a demand for materials with excellent properties.

Aluminum nitride has high thermal conductivity and excellent electrical properties such as insulation resistance, dielectric strength, dielectric constant, and mechanical properties such as strength, and is attracting attention as an IC substrate and package material with excellent heat dissipation properties.

In order to obtain an aluminum nitride sintered body with high density and excellent thermal conductivity, Y2O3, Dy20+, CaO
, SrO, BaO, etc., must be added to the aluminum nitride powder, mixed, molded, and then fired in a non-oxidizing atmosphere.

[Invention or problem to be solved]

Aluminum nitride alone is difficult to sinter under pressure, so
In pressureless sintering, a liquid phase sintering method has traditionally been used in which oxides such as Y2O3 and CaO are added as sintering aids, and densification is achieved by utilizing the reaction between these aids and Al2O3 in the aluminum nitride surface layer. It's here.

That is, by using at least one metal selected from yttrium and alkaline earth metals or a metal compound thereof as a sintering aid, the density can be reduced to 3.1 g/c.
A dense sintered body of m3 or more was obtained.

In recent years, with improvements in manufacturing technology for aluminum nitride powder,
High purity aluminum nitride powder containing cationic impurities (Fe, Si, Ti, Ni, etc.) of 0.3% by weight or less can be obtained relatively easily. This high-purity aluminum nitride powder can be sintered under normal pressure using the above-mentioned sintering aid, and has a density of 3.1 g/Cm3.
A dense sintered body as described above can be obtained.

The aluminum nitride sintered body thus obtained generally exhibits a white or beige color, which is a color unique to aluminum nitride, and exhibits transparency in the visible and infrared regions. For this reason, when used as an LSI substrate or package, there is a problem in that transmitted visible or infrared light can cause malfunctions.

Furthermore, as disclosed in JP-A-63-242971 or JP-A-2-83266, W,
A method has been proposed in which a trace amount of metal impurities such as Ti or Zr is added to make the sintered body black and non-transparent, but this method is limited to black color and has a problem in terms of commercial value.

The purpose of the present invention is to add at least one selected from yttrium and calcium to high-purity aluminum nitride powder as a sintering aid to achieve non-translucent properties that could not be achieved by conventional sintering methods. The present invention relates to a non-transparent aluminum nitride sintered body with high density and excellent thermal conductivity, and a method for manufacturing the same.

[Means to solve the problem]

That is, the present invention provides aluminum nitride powder containing 0.3% by weight or less of cationic impurities, and at least one metal selected from yttrium and calcium, or 0.01 to 5% by weight in terms of oxide of at least one metal selected from yttrium and calcium. When baked in a non-oxidizing atmosphere, the density is 3.1.
The object of the present invention is to provide a non-transparent aluminum nitride sintered body, which is characterized by having a particle size of 7 to 20 μm, and a method for manufacturing the same.

According to the present invention, it is possible to obtain a non-transparent aluminum nitride sintered body that exhibits high density, excellent thermal conductivity, and exhibits white or grayish color, which could not be obtained by conventional sintering methods.

Aluminum nitride is usually produced by adding at least one metal selected from yttrium and alkaline earth metals or a compound of the metal as a sintering agent and sintering it at normal pressure in a non-oxidizing atmosphere to form a dense nitride. An aluminum sintered body has been obtained.

The aluminum nitride sintered body thus obtained is -
High density and high thermal conductivity for boat fishing. - For example, as disclosed in JP-A-59-50008, the aluminum nitride sintered body is a beige-colored semitransparent body, and the in-line transmittance for light with a wavelength of 6 μm is 22% (absorption coefficient 30.3 cm-'). Translucency is exhibited when the absorption coefficient is 60 cm-' or less at a wavelength of 6 μm.

The present inventors added at least one metal selected from yttrium and calcium or the metal compound as a sintering agent to aluminum nitride powder containing 0.3% by weight or less of cationic impurities, and after mixing and molding. , when the particles of the sintered body grow by firing in a non-oxidizing atmosphere surrounded by boron nitride at a temperature range of 1750 to 1900°C for 5 to 24 hours, and the particle size of the particles is 7 to 20 μm. The present inventors have discovered that a sintered body that exhibits non-transparent properties in the visible and infrared regions can be obtained, leading to the completion of the present invention.

The present invention will be explained in detail below.

The production method of the aluminum nitride powder used in the present invention is not particularly limited, or the aluminum nitride powder contains 0.3% by weight of cationic impurities.
It is preferable to use a fine powder with good purity containing the following, and it is preferable to use a powder having a median particle size of 4.0 μm or less. In particular, in order to achieve densification at a temperature of 1800° C. or lower, it is preferable to use a fine powder with a center particle size of 2.5 μm or lower.

If the amount of cationic impurities exceeds 0.3% by weight, a sintered body with high thermal conductivity cannot be obtained, which is not preferable.

As the sintering aid, at least one metal selected from yttrium and calcium or a compound of the metal can be used.

These metal compounds include oxides, hydroxides, carbonates, sulfates, nitrates, acetates, oxalates, halides,
Sulfides, higher fatty acid salts, etc. can be used.

In addition, the finer the particle size of these compounds, the more preferable they are. In particular, when using compounds that do not dissolve or are difficult to dissolve in the solvent used when mixing with aluminum nitride powder, the center particle size is usually 5.0 μm or less. It is preferable to use a fine powder of .

The amount of the sintering aid added is preferably in the range of 0.01 to 5% by weight in terms of oxide based on the aluminum nitride powder. If it is less than 0.01% by weight, the effect of the present invention cannot be obtained, while if it is more than 5% by weight, a dense sintered body can be obtained but only high thermal conductivity can be obtained, so it is not preferable to deviate from this range.

More preferably 0.0 for aluminum nitride powder
It is in the range of 5 to 3% by weight.

The aluminum nitride powder and the sintering aid may be mixed by dry mixing or wet mixing using a non-aqueous solvent such as alcohol, and it is usually preferable to use wet mixing using a non-aqueous solvent.

During wet mixing, to facilitate the next forming process,
A binder such as polyvinyl butyral, polyvinyl alcohol, or polyacrylic acid ester is usually added. In addition to the binder, various dispersants, plasticizers, wetting agents, etc. are also usually added.

As a mixing device, a commonly used device such as a ball mill or a kneader can be used. Further, the mixture is prepared into the form of dried or granulated granules, clay, or slurry depending on the molding method.

The molding method may be a known dry method such as a uniaxial press or a rubber press, or a wet method such as a doctor blade method or an extrusion method.

The obtained molded body is usually stored in a container called a sagger and sintered. Graphite, boron nitride, aluminum nitride, alumina, etc. can be used as the material, but
For high-temperature sintering at 1700° C. or higher, it is preferable to use a sagger made of graphite, boron nitride, aluminum nitride, or the like. In addition, when using a pot other than boron nitride,
It is necessary to surround the molded body with a plate-like material such as a boron nitride setter, and cover the molded body with boron nitride.

Sintering must be performed in a non-oxidizing atmosphere to prevent oxidation of aluminum nitride during sintering. As the non-oxidizing atmosphere, nitrogen, alcon, a mixed gas of nitrogen and hydrogen, a mixed gas of nitrogen and alcon, etc. can be used, and a nitrogen gas atmosphere is most preferable from the viewpoint of manufacturing cost and ease of handling the apparatus.

The sintering temperature can be in the range of 1,750 to 1,900°C, but is preferably in the range of 1,800 to 1,850°C.

The temperature increase rate is not particularly limited, and is usually 1 to 5.
'C/min range. Further, the holding time at the sintering temperature is in the range of 5 to 24 hours, preferably in the range of 11 to 15 hours. If the holding time is less than 5 hours, the grain growth will be small and the sintered body will exhibit translucency; if the holding time is longer than 24 hours, the grain growth will increase and the strength will decrease, making it impossible to obtain the desired sintered body. .

The sintering temperature and sintering time are such that the density of the aluminum nitride sintered body is 3.1 g/cm3 or more, and the particle size of the sintered body is 7.
The thickness can be appropriately selected within the above range so that the thickness is in the range of ~20 μm.

Even if the density of the sintered body is less than 3.1 g/cm 3 , the sintered body may appear dense in appearance or contain many pores within the sintered body, and as a result, the sintered body will not have high thermal conductivity.

If the particle diameter of the sintered body is 7 μm or less, it is not preferable because it exhibits transparency to light in the visible or infrared region, which deviates from the purpose of the present invention. On the other hand, if the particle size of the sintered body is 20 μm or more, the strength of the sintered body decreases, which is not preferable. A more preferable particle size is in the range of 11 to 17 μm.

〔Effect of the invention〕

The aluminum nitride sintered body obtained by the method of the present invention has a sintered body density of 3.1 g/cm3 or more, has almost no pores, has excellent thermal conductivity, and is white or beige in color. It is translucent.

This aluminum nitride sintered body exhibits non-transparent properties in the visible and infrared regions, and is useful for IC substrates and packages that do not malfunction.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

The various physical properties were measured using the following method and apparatus.

(Oxygen content) Method: Impulse heating-infrared absorption method Apparatus: TC-436 model manufactured by LECO (metal impurities) Method ICPC optical emission spectroscopy: (Kikki Shimadzu Corporation Cantolet GQ!1!-7
5 (Particle size distribution) Method, Sediclaf apparatus: (Sediclaf 5000ET manufactured by Kikki Shimadzu Corporation (
sintered compact density) Method: Archimedes method device (manufactured by Kiki Shimadzu Corporation) Solid specific gravity measuring device (sintered compact particle diameter) Calculated using the following formula by counting the number of grain boundaries within a minute.

Line segment length (μm) - Grain boundary number 1 (0,79)" (thermal conductivity) Method: Laser flash method equipment: Shinku Riko Co., Ltd. TC-7000 model (absorption coefficient) Method: Sintered body with a thickness of 0.5 mm A device that measures the in-line transmittance using an infrared spectrophotometer and calculates the absorption coefficient using the Beer-Lambert equation.Fourier transform infrared spectrophotometer manufactured by DIGLAB
FTS 40 Example 1 Oxygen content: 1.2%, iron: 15 ppm, obtained by the reduction nitriding method of alumina as aluminum nitride powder.
A powder containing 30 ppm of silicon and 15 ppm of titanium and having a center particle size of 1.2 μm was used.

20g of the above aluminum nitride powder and Y as a sintering aid
Put 0.6 g (3% by weight of aluminum nitride powder) of 2O3 (Nippon Yttrium Co., Ltd.) into a 250-mm polyethylene pound, add 25 g of n-butanol, and an acrylic binder (Sanyo Kasei Co., Ltd. CB-1). 1.og was added, and wet ball mill mixing was performed for 4 hours at a rotation speed of 60 rpm using a nylon coated ball with a 15 mm diameter iron core.

After drying the obtained slurry, it was lightly crushed in an agate mortar to prepare a powder for sintering. 150% of this sintering powder
After press molding at 0 kg/cm2, the clean molded body was placed in a crucible made of graphite, the molded body was surrounded by a boron nitride setter (Denka Kagaku Kogyo Co., Ltd. Denka Boron Nitride HC grade), and the molded body was heated at 1800 kg/cm2 in a nitrogen atmosphere. °
Normal pressure sintering was performed at C for 10 hours.

Table 1 shows the sintered density, thermal conductivity, particle size, and absorption coefficient at a wavelength of 6 μm of the obtained sintered body.

Example 2 Aluminum nitride powder was obtained by a reductive nitriding method of alumina. Oxygen content was 1.2%, iron was 15 ppm,
A sintered body was produced in the same manner as in Example 1 except that powder containing 4 ppm of silicon and 1 ppm of titanium and having a center particle size of 1.5 μm was used.

Table 1 shows the sintered density, thermal conductivity, particle size, and absorption coefficient at a wavelength of 6 μm of the obtained sintered body.

Example 3 Aluminum nitride powder was obtained by a reductive nitriding method of alumina with an oxygen content of 0.9% and iron of 10 ppm.
A sintered body was produced in the same manner as in Example 1, except that powder containing 130 ppm of silicon and 20 ppm of titanium and having a center particle size of 283 μm was used.

Table 1 shows the sintered density, thermal conductivity, particle size, and absorption coefficient at a wavelength of 6 μm of the obtained sintered body.

Table-1 Sintered density Thermal conductivity Particle size Absorption coefficient g/cm'
W/mK μm cm Example 1 3.28
207 14.1 87 Example 2 3.2
8 207 16.5 83 Example 3 3.
26 198 11.5 68 Comparative Example 1 A sintered body was produced in the same manner as in Example 1 except that the sintering time was changed to 3 hours.

Table 2 shows the sintered density, thermal conductivity, particle size, and absorption coefficient at a wavelength of 6 μm of the obtained sintered body.

Comparative Example 2 A sintered body was produced in the same manner as in Example 2 except that the sintering time was 3 hours.

Table 2 shows the sintered density, thermal conductivity, particle size, and absorption coefficient at a wavelength of 6 μm of the obtained sintered body.

Comparative Example 3 A sintered body was produced in the same manner as in Example 3 except that the sintering time was changed to 3 hours.

Table 2 shows the sintered density, thermal conductivity, particle size, and absorption coefficient at a wavelength of 6 μm of the obtained sintered body.

Table-2 Sintered density Thermal conductivity Particle size Absorption coefficient g/cm'
W, 'mK 1t m cm Comparative example 1 3
．． 32 220 3.6 54 Comparative Example 2
3.31 207 4.8 56 Comparative Example 3
3.31 194 4.1 55 Agent Patent Attorney Gentlemen Koen (and one other person) Procedural Amendment (Voluntary) Date of 1991/Month

Claims (2)

[Claims] (1) Aluminum nitride powder containing cationic impurities of 0.3% by weight or less and at least one metal selected from yttrium and calcium, or a metal compound thereof, in the range of 0.01 to 5% by weight in terms of oxide. The density of the product is 3.1g/cm^3 when added with
A non-transparent aluminum nitride sintered body having the above properties and having a particle size in the range of 7 to 20 μm. (2) At least one metal selected from yttrium and calcium or a metal compound selected from yttrium and calcium as a sintering aid in aluminum nitride powder containing 0.3% by weight or less of cationic impurities, calculated as 0.01 to 0.01% by weight or less as an oxide. After mixing and molding, it was added in a range of 5% by weight, and then heated in a non-oxidizing atmosphere surrounded by boron nitride at a temperature range of 1750 to 1900°C and 5% by weight.
2. The method for producing a non-transparent aluminum nitride sintered body according to claim 1, wherein the firing is performed for 24 hours.