JP2684729B2 - Manufacturing method of aluminum nitride sintered body - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aluminum nitride sintered body, more specifically, in sintering at a temperature lower than conventional ones,
The present invention relates to a method for obtaining an aluminum nitride sintered body having a high density and good thermal conductivity.

[Problems to be solved by conventional technology and invention]

Alumina has been used for IC package and substrate materials.However, with high integration, high speed, and high output of LSI etc., the need to efficiently release the heat of the chip to the outside of the system has increased. Also, a material having good heat conductivity and excellent heat dissipation is demanded.

Aluminum nitride has high thermal conductivity and excellent electrical properties such as insulation resistance, withstand voltage, dielectric constant and mechanical properties such as strength.
It is a material that has attracted attention as a substrate material.

In order to obtain an aluminum nitride sintered body having excellent thermal conductivity, it is necessary to mold the aluminum nitride powder and sinter it densely.

Since aluminum nitride is difficult to sinter under normal pressure by itself, conventional oxides such as CaO and Y ₂ O ₃ are added as sintering aids in the atmospheric pressure sintering method. _The method of densification utilizing the reaction with ₂ O ₃ has been adopted.

For example, JP-B-47-18655 discloses a method of densifying by adding Y ₂ O ₃ and sintering, JP-B-58-49510.
The publication discloses a method of obtaining a dense aluminum nitride sintered body having a relative density of 98.5% or more by adding CaO, BaO, SrO or the like and sintering.

However, in order to obtain a dense sintered body with high thermal conductivity by pressureless sintering, a high temperature of 1800 ° C or higher is required when Y ₂ O ₃ is added, and usually 1700 ° C or higher even when CaO is added. High temperature sintering is required.

Alumina, which is currently used for IC packages and substrate materials, is usually sintered and densified at a temperature of 1500 to 1600 ° C. When an aluminum nitride sintered body is obtained by adding a sintering aid as described above to this temperature, the sintering temperature is considerably high, which is the reason why the cost of the aluminum nitride sintered body cannot be reduced. It is one.

Therefore, JP-A-61-209959 proposes a method capable of densification at 1600 ° C. by adding a rare earth oxide or fluoride and an alkaline earth oxide or fluoride. The conductivity is about 100 W / mK.

The present invention is intended to solve the problem of low temperature sintering of aluminum nitride powder, which could not be achieved by conventional sintering aids, and the object is to densify by sintering at a lower temperature than before. It is to provide a method for producing an aluminum nitride sintered body having high thermal conductivity.

[Means for solving the problem]

That is, according to the present invention, a compound of calcium and copper as a sintering aid in aluminum nitride powder is converted into CaO and CuO with respect to aluminum nitride in an amount of 0.01 to 3% by weight, and CuO / C.
After adding in a range of 1 or less in terms of aO, mixing and molding,
The present invention provides a method for producing an aluminum nitride sintered body, which comprises firing in a non-oxidizing atmosphere.

According to the present invention, it is possible to obtain an aluminum nitride sintered body having a density of 3.1 g / cm ³ or more and a high thermal conductivity even at a lower sintering temperature than conventional ones.

The reason why the aluminum nitride sintered body is densified at a low temperature in the present invention can be considered as follows.

That is, it is considered that the normal pressure sintering of aluminum nitride progresses the densification through the liquid phase. Therefore, it is considered that if a substance capable of forming a liquid phase at a lower temperature is added as a sintering aid, the densification of aluminum nitride will proceed from a lower temperature.

Therefore, Al ₂ O on the surface of aluminum nitride powder
It is considered that the densification progresses from a low temperature due to the melting of ₃ .

 Hereinafter, the present invention will be described in detail.

The manufacturing method of the aluminum nitride powder used in the present invention is not particularly limited, but fine powder having high purity is preferable. Regarding the particle size of the powder, it is preferable to use a powder having a central particle size of 4.0 μm or less. In particular, in order to densify at a temperature of 1600 ° C. or less, it is preferable to use fine powder having a central particle diameter of 2.0 μm or less if possible.

As the calcium and copper compounds used as a sintering aid, oxides, hydroxides, carbonates, sulfates, nitrates, acetates, oxalates, halides, sulfides, higher fatty acid salts and the like can be used. it can.

Further, a complex compound of calcium and copper, a complex compound of calcium and aluminum, a complex compound of copper and aluminum, and a complex compound of calcium, aluminum and copper can also be used.

Calcium and copper may be any substances as long as they are compounds, but compounds containing no water of crystallization are preferable.

For example, CaO, Ca (OH) ₂ , CaCO ₃ , CaSO ₄・ 2H ₂ O, Ca (N
_{O 3) 2 · 4H 2 O} , Ca (CH 3 COO) 2, Ca (COO) 2 · H 2 O, CaF 2,
CaS, Ca [CH ₃ (CH ₂ ) ₁₆ COO] ₂ , CuO, Cu ₂ O, Cu (OH) ₂ , CuCO
₃・ Cu (CH) ₂・ H ₂ O, CuSO ₄ , Cu (NO ₃ ) ₂・ 3H ₂ O, Cu (CH ₃
COO) ₂ , H ₂ O, Cu (COO) ₂ , CuF ₂ , CuS, Cu 〔CH ₃ (CH ₂ ) ₁₆ C
OO] ₂ , CuO · 2CaO, Ca ₂ AlO ₄ , CuO · Al ₂ O _{3 and the} like are used.

In addition, the finer the particle size of these compounds, the more preferable, especially when using a compound that does not dissolve or is difficult to dissolve in the solvent used when mixing with the aluminum nitride powder, usually the central particle size is 5.0 μm or less. It is preferable to use fine powder. The addition amount of these compounds is preferably 0.01 to 3% by weight in terms of CaO and CuO with respect to the aluminum nitride powder, and the molar ratio in terms of CuO / CaO is 1 or less.

If the amount of each additive deviates from this range, it is difficult to obtain a dense sintered body by pressureless sintering, and even if a dense sintered body is obtained, sufficiently high thermal conductivity cannot be obtained.
More preferably with respect to the aluminum nitride powder, CaO,
When converted to CuO, the CuO / CaO conversion molar ratio is 1 at 0.05 to 2% by weight.
The range is as follows.

The aluminum nitride powder and the calcium and copper compound powder can be mixed by dry mixing or wet mixing using a non-aqueous solvent such as alcohol, but usually wet mixing using a non-aqueous solvent is used. Is preferred. In the wet mixing, known binders such as polyvinyl butyral, polyvinyl alcohol, and polyacrylic acid ester are usually added to facilitate the subsequent molding step. In addition to the binder, various dispersants, plasticizers and wetting agents are usually added.

These additives and their addition amounts are appropriately selected and used according to the molding method described below.

As the mixing device, a ball mill, a kneader, or the like which is normally used can be used.

Further, the mixture is prepared in the form of dried, granulated granules, clay or slurry depending on the molding method.

As a molding method, known methods such as a dry method such as a uniaxial press and a rubber press, a wet method such as a doctor blade method, an extrusion method and the like can be used. Further, there is no problem even if a hot pressing method in which molding and sintering are simultaneously performed is used.

The obtained molded body is usually housed in a container called a bowl and sintered. Its material is graphite, boron nitride,
Aluminum nitride, alumina, or the like can be used, but it is preferable to use a vessel made of graphite, boron nitride, or aluminum nitride for high-temperature sintering at 1700 ° C. or higher. Alternatively, a powder bed method in which a compact is embedded in a powder containing aluminum nitride as a main component and then sintered can be used. Sintering needs to be performed in a non-oxidizing atmosphere in order to prevent oxidation of aluminum nitride during sintering. As the non-oxidizing atmosphere, nitrogen, argon, a mixed gas atmosphere of nitrogen and hydrogen, a mixed gas atmosphere of nitrogen and argon and the like can be used, but a nitrogen gas atmosphere is most preferable from the viewpoint of manufacturing cost, handling of the apparatus and the like.

The sintering temperature can be applied in the range of 1500 to 2000 ° C, but is preferably in the range of 1550 to 1850 ° C for practical use.

The temperature rising rate is not particularly limited, but is usually 1 to
Used in the range of 5 ° C / min.

The holding time at the sintering temperature is selected so that the density of the aluminum nitride sintered body becomes 3.1 g / cm ³ or more within the range of 2 to 20 hours, but preferably within the range of 2 to 8 hours. is there.

The density of the obtained aluminum nitride sintered body is preferably 3.1 g / cm ³ or more. Even if the density of the sintered body is less than 3.1 g / cm ³ , it seems that the sintered body is densified, but the sintered body contains many pores, and as a result, the sintered body does not have high thermal conductivity.

〔Example〕

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

The various properties were measured by the following methods and devices.

(Oxygen content) Impulse heating-infrared absorption method Device: LECO TC-436 type (Metallic impurities) ICP emission spectroscopy device: Shimadzu Corporation Cantlet GQM-75 (particle size distribution) Sedigraph device: Micromeritics SediGraph 5000ET (Sintered body density) Archimedes method Device: Shimadzu Corporation Fixed specific gravity measuring device (Thermal conductivity) Laser flash method Device: Vacuum Riko Co., Ltd. TC-7000 type Example 1 Aluminum nitride (AlN) powder of alumina A powder having an oxygen content of 1.3%, iron, silicon and titanium contents of 10, 60 and 16 ppm and a central particle size of 1.4 μm, which was obtained by the reduction nitriding method, was used. Calcium carbonate (CaCO ₃ ) as a calcium compound (Shiraishi calcium: Shiranka CCR), cupric oxide (CuO) as a copper compound (Hanui Chemical: Reagent GR grade)
Was used.

AlN powder 19.66g, CaCO ₃ powder 0.357g and CuO powder
Take 0.14 g in a 250 ml polyethylene pot, n-butanol 25 g, acrylic binder (Sanyo Kasei: CB-1) 4.0 g
Then, 1.0 g of a dispersant (Daiichi Kogyo Kagaku: Ceramo D-18) was added, and a wet coating ball mill was performed for 4 hours at a rotation speed of 60 rpm using a nylon coating ball containing a 15 mmφ iron core.

After the obtained slurry was dried, it was lightly crushed in an agate mortar to prepare a powder for sintering.

This sintering powder was put into a molding die, uniaxially pressed at 300 Kg / cm ² , and then rubber press molded at 1500 kg / cm ² to obtain a molded body having a diameter of 13 mm and a thickness of 10 mm.

This molded body was placed in a graphite container, embedded in a mixed powder of aluminum nitride and boron nitride, and placed in a nitrogen atmosphere.
Sintering was carried out at a temperature of 1550, 1600, 1700 and 1800 ° C for 5 hours under atmospheric pressure. The sintered body density and thermal conductivity of the obtained sintered body are shown in Table 1.
Shown in

The thermal conductivity was measured by depositing gold on a sintered body having a diameter of 10 mm and a thickness of 3 mm obtained by cutting after sintering and then applying carbon spray.

Table-1 Sintering temperature Sintered body density Thermal conductivity 1550 ° C 3.12g / cm ³ 112W / mK 1600 3.22 125 1700 3.24 150 1800 3.25 155 Example 2 The same AlN powder, CaCO ₃ and CuO powder as in Example 1 were used. A powder for sintering was prepared by the same method as in Example 1 except that the addition amounts of CaCO ₃ and CuO powder were changed as shown in Table 2.

These sintering powders were molded in the same manner as in Example 1, and then sintered under normal pressure at 1600 ° C. for 5 hours.

Table 2 shows the sintered body density and thermal conductivity of the obtained sintered body.

Comparative Example A powder for sintering obtained by adding only 3% by weight of yttrium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd.) as a sintering aid to the same AlN powder as in Example 1 was subjected to atmospheric pressure sintering at 1600 ° C. for 5 hours. To produce a sintered body.

The sintered body had a density of 2.87 g / cm ^{3 and} was hardly densified and had a low thermal conductivity of 68 W / mK.

〔The invention's effect〕

According to the present invention, when a compound of calcium and copper is used as a sintering aid, the aluminum nitride powder can be densified to 3.1 g / cm ³ or more at a temperature up to 1600 ° C., and it has high density and excellent thermal conductivity. An aluminum nitride sintered body is obtained. This is a material that makes it possible to sinter hardly-sinterable aluminum nitride at a temperature comparable to that of alumina, and can be expected to greatly reduce the manufacturing cost of the sintered body, which is industrially very important. It has an effect.

Claims (1)

(57) [Claims] 1. A compound of calcium and copper as a sintering aid in aluminum nitride powder, converted to CaO and CuO with respect to aluminum nitride, respectively by 0.01 to 3% by weight, and a CuO / CaO conversion molar ratio is within a range of 1 or less. 1. A method for producing an aluminum nitride sintered body, which comprises adding, mixing, molding, and firing in a non-oxidizing atmosphere.