JPH02157167A - 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 this mixture to molding and sintering in a nonoxidizing atmosphere. CONSTITUTION:Ca and Cu oxides as sintering aids are added to AlN powder of <=4.0mum central particle size by 0.01-3wt.% each (expressed in terms of CaO and CuO) basing on the amt. of the AlN in <=1 molar ratio of CuO to CaO 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 and sintered for 2-20hr to obtain an AlN sintered body having >=3.1g/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, and more specifically, it is sintered at a lower temperature than conventionally, and has a high density and good thermal conductivity. The present invention relates to a method for obtaining an aluminum nitride sintered body having the following properties.

[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 cao and Y20° are added as sintering aids, and densification is achieved by utilizing the reaction between these aids and the 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.
8-49510 proposes a method of obtaining a dense aluminum nitride sintered body with a relative density of 98.5% or more by adding CaO1BaO1Sr[ ] and sintering.

However, in order to obtain a dense sintered body with high thermal conductivity by pressureless sintering, when Y2O3 is added, a high temperature of 1800°C or higher is required, and even when Can is added, the temperature is usually 1700°C or higher.
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 bodies cannot be reduced. They are one.

For this reason, JP-A No. 61-209959 proposes a method that can be densified at 1600°C by adding rare earth oxides or fluorides and alkaline earth oxides or fluorides, but the heat conductivity is 100
It is about W/mK.

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 manufacturing 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 C, aO, and CuO, respectively, with a molar ratio of CuO/CaO. The object of the present invention is to provide a method for producing an aluminum nitride sintered body, characterized in that the aluminum nitride sintered body is added in an amount of 1 or less, mixed, formed, and then fired in a non-oxidizing atmosphere.

According to the present invention, the density can be maintained at 3.0% even at a lower sintering temperature than conventional ones. At Ig/cm3 or more, an aluminum nitride sintered body with high thermal conductivity can be obtained.

The reason why the aluminum nitride sintered body becomes dense from a low temperature in the present invention can be considered as follows.

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

Therefore, this liquid phase contains Al2 on the surface of the aluminum nitride powder.
It is thought that densification progresses from low temperatures due to the infiltration of O3.

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 having a center particle size of 4.0 μm or less. In particular, in order to achieve densification at a 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.

As calcium and copper compounds used as sintering aids, oxides, hydroxides, carbonates, sulfates, nitrates, acetates, oxalates, halides, sulfides, higher fatty acid salts, etc. can be used. can.

Moreover, a composite compound of calcium and copper, a composite compound of calcium and aluminum, a composite compound of copper and aluminum, and a composite compound of calcium, aluminum, and copper can also be used.

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

For example, Cab, Ca(OH)2. CaCO3,C
aSO4・2H20゜Ca(NO3)2'4H20,C
,a(CH3COO)2. ca(coo)2・h2゜CaF2. CaS, Ca [CHs(Ct12)+
6COO〕2. CuO.

Cu2O, Cu (leaf) 2. CuCO3・Cu(leaf)2
・H2O, CuSO2゜Cu(No3)2・3H20,
Cu(C113COO)2・H2O, CI(Coo)2
゜CuF2CuS, [l:u[:CH3(CH2)
16COO]2+ CuF2CuS.

CaAl, 04. CuO-Al2O, etc. are used.

In addition, the finer the particle size of these compounds, the better, and especially when using compounds that do not dissolve or are difficult to dissolve in the solvent used when mixing with the aluminum nitride powder, 1.
1 It is preferable to use fine powder with a center particle size of 5.0 μm or less. Further, the amount of these compounds added is 0.000% in terms of CaO and CuO, respectively, relative to the aluminum nitride powder.
The CuO/CaO molar ratio is preferably in the range of 01 to 3% by weight and 1 or less.

=6 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. do not have. More preferably, each CaO
, CuO/C at 0.05 to 2% by weight in terms of CuO
The molar ratio in terms of a and b is in the range of 1 or less.

For mixing aluminum nitride powder and powder of calcium and copper compounds, 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. is preferred. 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 their added amounts are appropriately selected and used depending on the molding method described below.

As the mixing device, commonly used devices such as a ball mill and a mixer 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. Sintering must be performed in a non-oxidizing atmosphere to prevent oxidation of aluminum nitride during sintering. As the non-oxidizing atmosphere, nitrogen, agon, 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 is preferably in the range of 1,550 to 1,800°C.

The heating rate is not particularly limited, but is usually 1 to 5.
A range of °C/min is used.

The holding time at the sintering temperature is selected within the range of 2 to 20 hours such that the density of the aluminum nitride sintered body becomes 3.1 g/cm3 or more, but preferably 2 to 20 hours.
The range is 8 hours.

The density of the obtained aluminum nitride sintered body is 3.1 g/c
It is preferable that it is m3 or more. The density of the sintered body is 3, 1
Even if it is less than g/cm3, the sintered body appears to be 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 The present invention will be specifically explained below 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: ■Shimadzu Corporation Cantore) GQM-75 (particle size distribution) Sedigraph device: Micromeritics 5ediGra
ph 5000BT (density of sintered body) Archimedes method device: ■ Shimadzu Corporation Solid specific gravity measuring device (thermal conductivity) Laser flash method device: Vacuum Riko ■ TC-7000 model Example 1 Aluminum nitride (AIN) Reduction nitridation of alumina as powder Oxygen content 1.3%, iron, silicon,
Powders with a titanium content of 10 and 60.16 ppm, respectively, and a center particle size of 1.4 μm were used. Calcium carbonate (CaCO3) as a calcium compound (Shiraishi Calcium Nibai Enka CCR), cupric oxide (CuO) as a copper compound
(half-time chemistry; reagent GR grade) was used.

The above AIN powder 19.66g, CaCL powder 0.
357g and 0.14g of CuO powder in 250ml
25g of n-butanol in a polyethylene pot
Acrylic binder (Sanyo Chemical: CB-1) 4.0g
and dispersant (Daiichi Kogyo Yakuhin; Ceramo D-18) 1.0
Wet ball milling was carried out for 4 hours at a rotation speed of 5 Qrpm 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 of 300Kg/cm2
The molded product was uniaxially pressed at a pressure of 1,500 kg/cm2, and then rubber press-molded at a pressure of 1500 kg/cm2 to obtain a molded product having a diameter of 13 mm and a thickness of 10+++ m.

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.

The thermal conductivity was measured by evaporating gold onto a sintered body having a diameter of 10 mm and a thickness of 3 mm obtained by sintering and cutting, followed by carbon spraying.

Table-1 Sintering temperature Sintered compact density Thermal conductivity 1550℃ 3.12 g/cm31121'l/
mK1600 3.22 1251700
3.24 1501800 3.25
155 Example 2 AIN powder, CaCO3 and CuO as in Example 1
Powder for sintering was prepared using the same method as in Example 1 except that the amounts of CaCO3 and CuO powder were changed as shown in Table 2.

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. Sintering powder composition (g) Sintered body density Thermal conductivity IN ClICO3CUD (g/cm3)
(III/mK)2-1 19.3 0.4
0.3 3.21 1222-2 19.0
0.8 0.2 3.19 1172-3 18
．． 6 0.9 0.5 3.20 1202-4
19.5 0.3 0.2 3.23 128
2-5 19.8 0.15 0.05 3.24
132 Comparative Example A sintering powder obtained by adding only 3% by weight of yttrium oxide powder (Shin-Etsu Chemical grade) as a sintering aid to the same HEIN powder as in Example 1 was sintered at 1600°C for 5 hours under normal pressure. A sintered body was created by sintering.

The density of the sintered body was 2.87 g/cm3, which was hardly densified, and the thermal conductivity was a low value of 68 W/mK.

〔Effect of the invention〕

According to the present invention, when a compound of calcium and copper is used as a sintering aid, aluminum nitride powder can be densified to 3.1 g/cm3 or more at temperatures up to 1600°C, resulting in high density and excellent thermal conductivity. An aluminum nitride sintered body is obtained. This allows aluminum nitride, which is difficult to sinter, to be sintered at a temperature similar to that of alumina, and is expected to significantly reduce the manufacturing cost of the sintered body, making it an extremely important product from an industrial perspective. It is effective.

14 complete

Claims (1)

[Claims] Calcium and copper compounds were added to aluminum nitride powder as sintering aids, respectively.
0.01 to 3% by weight in terms of CuO, CuO/CaO
A method for producing an aluminum nitride sintered body, which comprises adding the aluminum nitride sintered body in a converted molar ratio of 1 or less, mixing and shaping, and then firing in a non-oxidizing atmosphere.