JPH02157166A - Production of aluminum nitride sintered body - Google Patents

Abstract

PURPOSE:To obtain a high density AlN sintered body having superior heat conductivity by mixing AlN powder with specified sintering aids and subjecting his mixture to molding and sintering in a nonoxidizing atmosphere. CONSTITUTION:Ca and Cu compds. as sintering aids are added to AlN powder of <=4.0mum central particle size by 0.01-3wt.% each (expressed in terms of CaO ad CuO) basing on the amt. of the AlN in <=1 molar ratio of CuO to CaO, a Y compd. as a sintering aid is further added by 0.1-10wt.% (expressed in terms of Y2O3) and then a nonaq. solvent and a binder such as PVA are added. They are mixed, molded, heated to 1,500-2,000 deg.C at 1-5 deg.C/min heating rate in a nonoxidizing atmosphere and sintered for 2-20hr to obtain an AlN sintered body having >=3.15g/cm<3> density.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing an aluminum nitride sintered body, and more specifically, it relates to a method for producing an aluminum nitride sintered body having high density and good thermal conductivity. The present invention relates to a method of sintering at a lower temperature.

[Conventional technology and problems to be solved by the invention] Alumina has been used for IC packages and substrate materials, but as LSIs become more highly integrated, faster, and have higher output, it has become difficult to generate heat from chips. There is an increasing need to efficiently release heat from the system, and there is a demand for a material that has better thermal conductivity and better heat dissipation than alumina.

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 a material for packages and substrates with excellent heat dissipation. It is.

To obtain an aluminum nitride sintered body with excellent thermal conductivity,
It is necessary to shape the aluminum nitride powder and sinter it densely.

Aluminum nitride alone is difficult to sinter under pressure, so
Conventionally, in the pressureless sintering method, a method has been adopted in which oxides such as Cab and Y2O3 are added as sintering aids, and densification is achieved by utilizing the reaction between these aids and Al2O3 of the aluminum nitride surface layer.

For example, Japanese Patent Publication No. 47-18655 describes a method of densification by adding Y2O3 and sintering.
Japanese Patent No. B-49510 proposes a method of obtaining a dense aluminum nitride sintered body with a relative density of 98.5% or more by adding CaO1BaO1SrO 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 Y2O3 is added, and a temperature of 1700°C or higher is required even when CaO is added.
Sintering at a high temperature of ℃ or higher 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.

Compared to this temperature, when an aluminum nitride sintered body is obtained by adding a sintering aid as described above, the sintering temperature is considerably higher, and this is the reason why the cost of aluminum nitride sintered body cannot be reduced. They are one.

For this reason, Japanese Patent Application Laid-Open No. 61-209959 proposes a method in which densification can be achieved at 1600°C by adding rare earth oxides or fluorides and alkaline earth oxides or fluorides. Its thermal conductivity is 100
It is about tii/m.

The present invention attempts to solve the problem of low-temperature sintering of aluminum nitride powder, which could not be achieved with conventional sintering aids, and its purpose is to sinter aluminum nitride powder at a lower temperature than conventional methods. An object of the present invention is to provide a method for producing an aluminum nitride sintered body with high thermal conductivity.

[Means to solve the problem]

That is, in the present invention, calcium and copper compounds are added to aluminum nitride powder as sintering aids in an amount of 0.01 to 3% by weight in terms of CaO and CuO, respectively, based on aluminum nitride.
, the CuO/CaO equivalent molar ratio is in the range of 1 or less, and the yttrium compound is added in the range of 0.1 to 10% by weight in terms of Y2O3, and after mixing and molding, it is calcined in a non-oxidizing atmosphere. The present invention provides a method for producing a characteristic aluminum nitride sintered body.

According to the present invention, an aluminum nitride sintered body having a density of 3.15 g/m 3 or more and high thermal conductivity can be obtained even at a lower sintering temperature than conventional ones.

The reason why the aluminum nitride sintered body becomes dense from a low temperature and exhibits high thermal conductivity in the present invention has not yet been fully elucidated, but at present it can be considered as follows.

In other words, it is believed that pressureless sintering of aluminum nitride progresses densification through the liquid phase. Therefore, it is thought that if a substance that generates a liquid phase at a lower temperature is added as a sintering aid, the densification of aluminum nitride will proceed from a lower temperature.

When a compound of calcium and copper is mixed and a compound of yttrium is further added to the mixture, it reacts more easily with the 8L(], of the surface oxide layer of the aluminum nitride powder, and C
It is thought that an a-Cu-Y-AI-0-based liquid phase is generated and densification progresses from a low temperature.

The present invention will be explained in detail below.

The method of manufacturing the aluminum nitride powder used in the present invention is not particularly limited, but a fine powder with good purity is preferred.

As for the particle size of the powder, it is preferable to use a powder whose center particle size is 4.0 μm or less.

In particular, in order to achieve densification from a low temperature of 1600° C. or lower, it is preferable to use a fine powder with a center particle size of 2.0 μm or less if possible.

Calcium and copper compounds used as sintering aids include oxides, hydroxides, carbonates, sulfates, nitrates,
Acetate, oxalate, norogenide, sulfide, higher fatty acid salt, etc. can be used.

Yttrium compounds include oxides, nitrates, oxalates,
Halides and the like can be used.

Further, a composite compound containing two or more of calcium, copper, and isotria, or a composite compound of these and aluminum can be used.

Calcium, copper, and yttrium may be any compound as long as they are compounds, but compounds that do not contain water of crystallization are preferred.

For example, CaO1Ca(DH)2, [aCO3, C
aSO4-2H20゜Ca (NO3) 2 ・4H2
0, Ca (CH3COO) 2, Ca (COO) 2
・lI20, [aF2, CaS SCa (CII3
(CII2) l 6COO) 2, CuO1Cu20
, Cu(leaf)2, CuCO3・Cu(leaf)2・H2O5
CuSO4, CLI(NO3)2・3H2D, C1(
CH3C00)2・)I20SCu((1:00)z,
=5 -CuF2, CuS, Cu(CH3(CH2), 6Co
o) 2, Y2O3, Y (NO3) 3・9H20,
Y (Coo) 3・H2O5YF3・0.5H20,
Cu0.2CaO, Ca2Al0<, Ca2Al04, etc. are used.

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

In addition, the amount of these compounds added is within the range of 0.01 to 3% by weight for calcium and copper compounds in terms of CaO and uO, respectively, in the molar ratio of 1 or less in terms of CuO/CaO, and for yttrium and aluminum nitride powder. The content of the compound is preferably 0.1 to 10% by weight in terms of Y2O3.

If the amount of each additive deviates from this range, not only will it be difficult to obtain a dense sintered body by pressureless sintering, but even if a dense sintered body is obtained, a sufficiently high thermal conductivity will not be obtained.

More preferably, the addition amount of calcium and copper compounds to aluminum nitride is 0 in terms of CaO and CuO, respectively.
．． 05 to 2% by weight, CuO/CaO molar ratio is 1 or less, yttrium compounds are 0 when converted to Y2O3.
．． It is 5 to 5% by weight.

For mixing aluminum nitride powder with calcium, copper, and yttrium compound powder, dry mixing or wet mixing using a non-aqueous solvent such as alcohol can be used, but wet mixing using a non-aqueous solvent is usually used. It is preferable to use

During wet mixing, a known binder such as polyvinyl butyral, polyvinyl alcohol, or polyacrylic acid ester is usually added to facilitate the subsequent molding process.

In addition to the binder, various dispersants, plasticizers, and wetting agents are usually added. These additives and the amounts added are appropriately selected and used depending on the molding method described below.

As the mixing device, commonly used devices such as ball mills and kneaders can be used. Further, the mixture is prepared into the form of dried, granulated granules, clay, slurry, etc. depending on the molding method.

As a forming method, a known method such as a 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 can be used.

Further, there is no problem in using a hot press method in which molding and sintering are performed simultaneously.

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 of 1700° C. or higher, it is preferable to use a sagger made of graphite, boron nitride, or aluminum nitride. It is also possible to use a powder bed method in which the compact is embedded in powder whose main component is aluminum nitride and sintered.

To prevent oxidation of aluminum nitride during sintering,
It is necessary to carry out the process in a non-oxidizing atmosphere.

As the non-oxidizing atmosphere, nitrogen, argon, a mixed gas atmosphere of nitrogen and hydrogen, a mixed gas atmosphere of nitrogen and argon, etc. can be used, but a nitrogen gas atmosphere is most preferable from the viewpoint of manufacturing cost, ease of handling the apparatus, etc.

The sintering temperature can be in the range of 1,500 to 2,000°C, but in practice it is in the range of 1,550 to 1,850°C.

The temperature increasing rate is usually in the range of 1 to 5°C/min.

The holding time at the sintering temperature is within the range of 2 to 20 hours,
Density of aluminum nitride sintered body is 3.15g/cm3
The retention time is selected such that it is equal to or greater than 2, but preferably 2
A period of up to 8 hours is sufficient.

The density of the obtained aluminum nitride sintered body was 3.15 g/
It is preferable that it is at least cm3.

Even if the density of the sintered body is 3.15 g/cm3 or less, it appears dense in appearance, but the sintered body contains many pores, and as a result, the sintered body does not have high thermal conductivity.

〔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) Impulse heating-infrared absorption method device: LEC○ TC-436 type (metal impurities) ICPC optical emission spectroscopy;
aph 50001ET (sintered body density) Archimedes method M: ■Shimadzu solid-state specific gravity measuring device (thermal conductivity) Laser flannel method device; Vacuum Riko ■ TC-7000 model example I Aluminum chloride (AIN) Alumina as powder Oxygen content 1.3%, iron, silicon,
Powders with a titanium content of 10,60,16 ppm and a center particle size of 1.4 μm were used.

Calcium carbonate (CaC03) as a carunium compound
(Shiraishi Calcium: Shiroenka CCR), cupric oxide (Cub) as the copper compound (Gyudon Kagaku: Reagent GR grade), and yttrium oxide (Shin-Etsu Chemical grade) as the yttrium compound.

18.9g of the above AIN powder, 0.36g of CaCO3 powder
g and CuO powder 0.14 g, Y2[]3 powder 0.
Place 6g in a 250ml polyethylene pot and add 25g of n-butanol and 1 acrylic binder (Sanyo Chemical: CB).
-1) 4.0g and dispersant (Daiichi Kogyo Yakuhin; Ceramo D
-18) 1.0 g was added and wet ball milling was performed for 4 hours at a rotation speed of 5 Q 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.

Put this sintering powder into a mold with a weight of 300 kg/cm2.
The molded product was uniaxially pressed at 1500 kg/cm 2 and then rubber press molded at 1500 kg/cm 2 to obtain a molded product having a diameter of 13 mm and a thickness of 10 mm.

This molded body was placed in a graphite container, buried in a mixed powder of aluminum nitride and boron nitride, and heated in a nitrogen atmosphere.
5 at each temperature of 550.1600.1700.1800℃
Sintered under pressure for an hour.

Table 1 shows the sintered body density and thermal conductivity of the obtained sintered body.

Table-1 Sintering temperature Sintered compact density Thermal conductivity 1550°C 3.16 g/cm' 118 W/
mK1600 3.28 1421700
3.28 163 Example 2 Same as Example 1 except that the same aluminum nitride powder, calcium carbonate, cupric oxide, and yttrium oxide powder as in Example 1 were used, and the amounts of each added were changed as shown in Table 2. A powder for sintering was prepared by processing in a similar manner.

After molding these sintering powders in the same manner as in Example 1,
Normal pressure sintering was performed at 1600°C for 5 hours.

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

Table-2 No. Sintered body for sintering Heat transfer powder composition (g) Density Conductivity ＾IN C
aCO3CuOY2O3 (g/cm3) (W/mK
)2-1 19.2 0.3 0.2 0.3 3.
24 1322-2 18.5 0.5 0.3
0.7 3.26 1382-3 18.0 0
．． 9 0.5 0.6 3.27 1262-4
19.0 0.2 0.2 0.6 3.28
1492-5 19.2 0.1 0.1 0.6
3.28 147 Comparative Example Y2O used in Example 1 for ^IN powder similar to Example 1
A sintered body was prepared in the same manner as in Example 1 using the sintering powder obtained by adding 3% by weight of only the 3 powders.

Table 3 shows the density and thermal conductivity of the sintered body.

Table-3 Sintering temperature Sintered compact density Thermal conductivity 1550℃ 2.43 g/cm338 W/mK1
600 2.87 68 1700 2.97 87 1800 3.28 190 [Effects of the Invention] According to the invention, when a compound of calcium, copper and yttrium is used as a sintering aid, aluminum nitride can be formed at temperatures up to 1600°C. The powder can be densified to 3.15 g/cm3 or more, and an aluminum nitride sintered body with high density and excellent thermal conductivity can be obtained. This allows aluminum nitride, which is difficult to sinter, to be sintered at a temperature comparable to that of alumina, and is expected to significantly reduce the manufacturing cost of the sintered body, which is an extremely important effect industrially. It is something that has.

from) Heisei Deco year/July 22nd 1.Display of the incident Patent application filed in 1986 31st No. 95 2. Name of the invention Manufacturing method of aluminum nitride sintered body 3. Person who makes corrections Relationship with the incident

Claims (1)

[Claims] Calcium and copper compounds are added to aluminum nitride powder as sintering aids, respectively.
0.01 to 3% by weight in terms of O, a molar ratio of 1 or less in terms of CuO/CaO, and Y
A method for producing an aluminum nitride sintered body, characterized in that it is added in an amount of 0.1 to 10% by weight in terms of _2O_3, mixed, molded, and then fired in a non-oxidizing atmosphere.