JPH046162A - Aln-bn-based composite sintered body and production thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an M N-BN composite ceramic sintered body and a method for manufacturing the same. For more information, please see our electrical insulation properties, high thermal conductivity, low thermal expansion, low dielectric constant, ease of processing, etc., which can be used as IC package materials, IC substrate materials, electrical insulation heat dissipation materials from room temperature to high temperatures, etc. The present invention relates to an IN-BN composite sintered body having improved mechanical strength, particularly at room temperature, and a method for producing the same.

Conventional technology AlN-BN composite sintered bodies have high thermal conductivity and can be cut at high speed with ordinary tools, so they are used as so-called machinable ceramics (for example, in Japanese Patent Application Laid-Open No. 1983-1983).
5058, JP 80-195080, JP 81-6
3572, Japanese Unexamined Patent Publication No. 62-58377, etc.) has been put into practical use. In addition, by taking advantage of the characteristics of BN such as low thermal expansion and low dielectric constant, it is possible to obtain a composite with a thermal expansion coefficient close to that of the semiconductor material Si, short signal delay time, and high thermal conductivity. Applications as packaging materials and IC board materials are being considered (for example, Japanese Patent Laid-Open No. 1-25
2584, JP-A-1-261279, etc.).

However, this composite sintered body is made of AlN or M
Compared to other ceramic sintered bodies such as 2O3, it had the disadvantage of low bending strength.

The three-point bending strength reported so far is A!
lN/BN (weight ratio) is 80/20te 350MPa
Degree, Et5/3! +r about 230MPa, 40
/ [1 Offi is about 130 MPa, and the bending strength decreases as the BH content increases.

Furthermore, in a composite sintered body in which 88 grains are oriented by the hot press method, the bending strength when the span is taken parallel to the hot press pressure axis is significantly low, and the bending strength depends on the degree of orientation of the 88 grains. Although the value of the value is different, 80
/ 2 (lte) values of about 100 to 300 MPa have been reported.

These low bending strengths are a major bottleneck in the use of these materials, so improvements have been desired.

Problems to be Solved by the Invention In view of this problem, the present invention has been developed to improve mechanical strength while maintaining excellent characteristics such as high thermal conductivity, electrical insulation, relatively low thermal expansion, low dielectric constant, and easy workability. An object of the present invention is to provide an M N-BN-based composite sintered body with improved properties, and a method for manufacturing the same.

Means/effect for solving the problem, that is, the present invention provides an AlN-BN composite sintered material consisting of aluminum nitride and polytype aluminum nitride in a total amount of 40 to 80% by weight, and hexagonal boron nitride material of 0 to 60% by weight. It is a body.

In addition, the total amount of polytypes of aluminum nitride and aluminum nitride is 40 to 80% by weight, and hexagonal boron nitride is
It is an AlN-BN based composite sintered body consisting of 0.1-10% by weight of GO and one or more of calcium compounds and yttrium compounds. Further, the content of aluminum nitride polytype in the sintered body of the present invention is 50% by weight or less of the total amount of aluminum nitride and aluminum nitride polytype.

Further, a mixed powder consisting of 40 to 90% by weight of aluminum nitride powder, 10 to 60% by weight of hexagonal boron nitride powder, and 0.5 to 10% by weight of silicon oxide powder was heated to 1600 to 100% by weight under vacuum or an inert gas atmosphere. 2000℃, 5-100
The present invention relates to a method for producing an M N-BN composite sintered body by pressurizing and heating at MPa.

Also, aluminum nitride powder 40-90% by weight, hexagonal boron nitride powder 10-60% by weight, silicon oxide powder 0.5
~10% by weight, and 0.1 to 10% by weight of one or more of calcium compounds and yttrium compounds under vacuum or inert gas atmosphere at 1600 to 2000°C and 5 to 100NPa. The present invention relates to a method for producing an AlN-BN composite sintered body by pressurizing and heating. Calcium compounds include calcium oxide, calcium carbide, calcium carbonate, calcium nitrate, calcium fluoride, calcium hydroxide, calcium cyanide, calcium cyanamide, and yttrium compounds include yttrium oxide, yttrium carbide, yttrium fluoride, and yttrium nitrate. .

Hereinafter, the sintered body of the present invention will be explained in detail.

The sintered body of the present invention consists of a total amount of 40 to 80% by weight of aluminum nitride and polytype aluminum nitride, and 10 to 60% of hexagonal boron nitride.

Another sintered body of the present invention contains a total of 40 to 90% by weight of aluminum nitride and a polytype of aluminum nitride, 10 to 60% by weight of hexagonal boron nitride, and one of a calcium compound and a yttrium compound. It is a sintered body consisting of 0.1 to 10% by weight of one or more types.

By including polytype aluminum nitride in the sintered body, the mechanical strength of the sintered body at room temperature is significantly improved. 2H127 for aluminum nitride polytype
There are several different crystal structures such as R, 21R, 12H, 15R, and 8H (K, H, Jack).

J, Mat, Sci, 11.1135 (197
B)) The polytype of aluminum nitride contained in the sintered body of the present invention may be any of these polytypes without any particular problem.

It is known that these polytypes are formed when the system contains aluminum oxide, silicon oxide, etc., and particularly when silicon oxide is contained, they are formed at relatively low temperatures.

The polytype content of aluminum nitride in the sintered body is
The upper limit is 50% by weight or less, preferably 30% by weight or less, based on the total amount of aluminum nitride and aluminum nitride polytype. The lower limit is also 1% by weight or more, preferably 2% by weight or more, more preferably 5% by weight based on the total amount of aluminum nitride and aluminum nitride polytype.
That's all. If the polytype content exceeds these ranges and exceeds 50% by weight, the mechanical strength of the sintered body will be significantly improved, but the thermal conductivity of the sintered body will be poor due to the low thermal conductivity of the polytype. There is a possibility that the high thermal conductivity that the AlN-BN-based sintered body traditionally has will be lost. Furthermore, when the polytype content is less than 1% by weight, the mechanical strength of the sintered body is hardly improved by including the polytype, which is the object of the present invention.

When trying to improve the mechanical strength of the sintered body and obtain high thermal conductivity by using a polytype of aluminum nitride, one or more of calcium compounds and yttrium compounds are added to the polytype of the sintered body. This is achieved by including the type together with the type. These calcium compounds and yttrium compounds are mainly formed by the reaction between the calcium compounds and yttrium compounds added during manufacturing and the oxides that inevitably form on the surface of the aluminum nitride and hexagonal boron nitride powders used as raw materials. Ru.

Examples of the compounds formed include calcium aluminate, yttrium aluminate, calcium borate, yttrium borate, and compounds produced by reactions between these compounds. These compounds include, for example, calcium aluminate, aO#Vj203
It is known that some compounds exist depending on the ratio of (R, W, Nurse et al,
: Trans, Br1t, Ceram,
Sac,.

64, [9], 41B (1985),
T, Nogucgi et al.: Kog
y.

Agaku Zasshi, 70 [81839 (
19B? )) The compound contained in the sintered body of the present invention may be any one of them without any particular problem.

The formation of these compounds in the sintered body significantly reduces oxide impurities at the grain boundaries of the aluminum nitride and hexagonal boron nitride particles that make up the sintered body, resulting in a sintered body with high thermal conductivity. is obtained. Other calcium compounds and yttrium compounds present in the sintered body include:
If the sintering aid remains unreacted, or if silicon oxide is added to form a polytype, complex oxides of calcium and yttrium containing silicon may be used.

The composition ratio of the sintered body is 40 to 80% by weight in total of aluminum nitride and aluminum nitride polytype, and 10 to 60% by weight of hexagonal boron nitride.

When the total amount of aluminum nitride and aluminum nitride polytype is around 40% by weight, the mechanical strength is significantly improved by the aluminum nitride polytype. For compositions in which the total amount of aluminum nitride and aluminum nitride polytypes is around 80% by weight, the orientation and stacking of flaky hexagonal BN particles are observed in the sintered body, especially when the hot pressing method is used as the manufacturing method. In some cases, the resulting mechanical strength can be significantly improved. (For example, bending strength is significantly improved when the span is taken in the direction of orientation and stacking of BN particles, or in other words, when the span is taken in the direction of the pressure axis of Ho/Dobres.) If the total amount of aluminum nitride and aluminum nitride polytype is less than 40% by weight, the mechanical strength will improve, but the thermal conductivity of the sintered body will decrease significantly, and the AlN-BN This is undesirable because the excellent characteristics of the sintered body are lost, and conversely, the total amount of aluminum nitride and aluminum nitride polytype is 80%.
If the BN content exceeds % by weight, the mechanical strength of the sintered body approaches that of an AlN sintered body, so it is unlikely to cause a big problem in practice, and even in a sintered body with anisotropy, the BN content As the amount decreases, no significant anisotropy is observed, and no significant improvement in mechanical strength occurs.

The composite ceramic sintered body of the present invention can be manufactured, for example, by the method described below, but this is a preferred example of the manufacturing method and is not necessarily limited to the following method. -2x sintered body contains 40-90% by weight of aluminum nitride powder, 10-60% by weight of hexagonal boron nitride powder, and 0% by weight of silicon oxide powder.
．． A mixed powder consisting of 5 to 10% by weight is heated at 1600 to 2000°C and 5 to 100 MP under vacuum or inert gas atmosphere.
It can be obtained by heating under pressure at step a.

As the aluminum nitride raw material powder, conventionally known ones can be used, but from the viewpoint of increasing the bulk density and high thermal conductivity of the sintered body, the average particle size is 5 gm or less, preferably 2 gm or less, The oxygen content is 3.0 wt% or less, preferably 1.5 wt% or less. Conventionally known hexagonal boron nitride raw material powders can also be used.

When a powder with a small average particle size is used, the sintered body becomes relatively isochronic, and a powder with a relatively large average particle size (one that exhibits a pronounced flaky shape, which is a typical shape of hexagonal boron nitride powder) ), the result is a sintered body with relatively strong anisotropy, but in the manufacturing method of the present invention, there is no particular problem in using any of them.

Taking thermal conductivity into account, it is better to have a lower oxygen content, but as the powder becomes finer, the oxygen content increases due to oxides that inevitably form on the surface, so the oxygen content may vary depending on the purpose and use. It is desirable to select an appropriate one.

As the silicon oxide raw material powder, conventionally known ones can be used, and both crystalline and amorphous types can be suitably used. Although the zero particle size is not particularly limited, consideration should be given to reactivity and sinterability. In this case, it is preferable that the powder be as fine as possible, and silicon oxide powder produced by a precipitation method or the like is preferably used.

In addition, the silicon oxide powder used in the production method of the present invention can be used not only when the starting material itself is silicon oxide, but also from materials that become silicon oxide during firing, such as organometallic compounds or their decomposition products. Items can also be used as needed.

The blending ratio of raw material powder is aluminum nitride powder 40-9
0% by weight, 10-60% by weight of hexagonal boron nitride powder, and 0.5-10% by weight of silicon oxide powder. This is because if the blending ratio of silicon oxide powder is less than 0.5% by weight, the remarkable improvement in mechanical strength due to the formation of a polytype of aluminum nitride, which is the objective of the present invention, will not be observed, and it is preferably 1% by weight or more. , more preferably 2% by weight or more. In addition, if the blending ratio exceeds 10% by weight, the amount of aluminum nitride present in the sintered body decreases even in a composition with a large amount of aluminum nitride, and the polytype of aluminum nitride becomes dominant, and depending on the composition, sialon may be generated. This is not preferable because it lowers the thermal conductivity of the sintered body, and more preferably 5% by weight or less.

Firing at a temperature of 1600-2000℃, 5-100MP
If the sintering temperature is lower than 1600° C. while applying a pressure, the sintered body will not be sufficiently densified and the polytype of aluminum nitride will not be formed, making it impossible to obtain the desired properties of the sintered body. If the temperature exceeds 2000°C, it is not only uneconomical but also undesirable because some of the constituent components may begin to decompose.

If the pressure is less than 5NPa, the sintered body will not be sufficiently densified and the desired characteristics will not be obtained.
If it exceeds Pa, it is still not economical, and when applying a hot press method, for example, there are problems such as the molds that can be used are limited.

Pressure methods include uniaxial pressure such as hot press, HIP,
Any pressure method such as atmospheric gas pressure sintering may be used, but
When using constant pressure, there are many open pores in the powder compact, so it is necessary to eliminate the open pores by pre-sintering or
Requires preliminary processing such as capsule processing.

The heating time under pressure is preferably 0.5 to 4 hours, more preferably 1 to 2 hours. If the pressure and heating time is less than 0.5 hours, the sintered body may not be sufficiently densified, and satisfactory characteristic values may not be obtained. Further, although heating under pressure for more than 4 hours does not adversely affect the characteristic values, it is not economical.

Further, in order to prevent oxidation of the nitride particles, the pressurized heating is preferably performed in a vacuum or in an inert gas atmosphere such as nitrogen or argon.

Conventionally, it is known that in sintered bodies made by adding silicon oxide to aluminum nitride, the bulk density decreases as the amount of silicon oxide added increases, and the bending strength also decreases ( Yoneya, Benjo, Tsuge, Ceramics Association Journal, 89, [
81, 330 (1981)), but in the present invention, by combining it with hexagonal boron nitride and using a pressure heating method as the sintering method, sufficient densification is achieved and mechanical strength is improved. Is recognized.

It is also known that the presence of Si as an impurity in aluminum nitride sintered bodies reduces thermal conductivity;
Ceramic Substrates for Functional Circuits Jp, 82 (Electronic Materials Industries Association G) 1985), the present invention minimizes this decrease in thermal conductivity by promoting densification of the sintered body. However, if a sintered body with higher thermal conductivity is required, one or more of calcium compounds and yttrium compounds may be used as the fourth component.
This can be achieved by using 1 to 10% by weight.

Calcium compounds include calcium oxide, calcium carbide, calcium carbonate, calcium nitrate, calcium fluoride, calcium hydroxide, calcium cyanide, and calcium cyanamide, preferably calcium oxide,
They are calcium carbide, calcium nitrate, and calcium cyanamide.

Yttrium compounds include yttrium oxide, yttrium carbide, yttrium fluoride, and yttrium nitrate, with yttrium oxide and yttrium fluoride being preferred.

Suitable addition amounts of these compounds are 0.1 to 10% by weight,
Preferably it is 0.2 to 5% by weight. If the amount added is less than 0.1% by weight, no significant effect will be exhibited, and if it exceeds 10% by weight, the amount added will be too large and will actually reduce the thermal conductivity of the sintered body. Since the amount has a relatively large effect on the thermal conductivity of the sintered body, it is necessary to carefully determine the amount added. By adding this fourth component, as mentioned above, it is possible to significantly reduce the oxide impurities at the grain boundaries in the sintered body, and as a result, the thermal conductivity decreases less.
An AllN-0N composite sintered body with improved mechanical strength is obtained.

The present invention will be explained below using examples, but the present invention is not limited only to these examples.

Example 1 Aluminum nitride powder with an average particle size of 1.8 JLm, hexagonal boron nitride powder with an average particle size of 2.5 JLm, silicon dioxide powder (manufactured by Precipitation, special grade reagent), and a calcium compound as a sintering aid. , yttrium compounds were blended in the proportions shown in Table 1, and wet mixing was performed in a ball mill for 24 hours using acetone as a solvent. After sufficiently drying the obtained powder, it was filled into a graphite die and heated for 160 min in a nitrogen gas atmosphere.
Hot press sintering was performed at 0"0 for 2 hours.

Regarding the obtained sintered body, the crystal phase was identified and quantified, and the bulk density, bending strength, and thermal conductivity were measured. Identification of the crystal phase was performed by powder X-ray diffraction after pulverizing the sintered body, and quantitative determination was performed by X-ray diffraction using aluminum oxide (corundum) as an internal standard. The bulk density was measured by the Archimedes method using water, and the bending strength was measured by three-point bending strength in accordance with JIS standards when the span was taken in a direction perpendicular to the hot press pressure axis.

Thermal conductivity was measured by the laser flash method. The results are shown in Table 1.

Although the bending strength varies in the range of 230 to 380 MPa depending on the composition, it is observed that the bending strength is improved by about 20 to 100 MPa compared to the sintered body of Comparative Example 1, which will be described later, having approximately the same composition.

Comparative Example 1 CaC2 was added as a sintering aid to the aluminum nitride powder and hexagonal boron nitride powder used in Example 1 in the proportions shown in Table 1, and sintered by the hot press method in the same manner as in Example 1. A body was prepared, and the sintered phase of the sintered body was identified and quantified, and the bulk density, bending strength, and thermal conductivity of the sintered body were measured using the same method as in Example 1. The results are shown in Table 1.

Example 2 Aluminum nitride powder with an average particle size of 1.8 g m, hexagonal boron nitride powder with an average particle size of 10 ILm, and the silicon dioxide powder and CaC2 powder used in Example 1 in the proportions shown in Table 2 and wet mixing was performed in a ball mill for 24 hours using acetone as a solvent. Sintering was carried out by hot press sintering at 1600° C. for 2 hours as in Example 1. Regarding the obtained sintered body, the crystal phase was identified and quantified, and the bulk density, three-point bending strength, and thermal conductivity were measured in the same manner as in Example 1.

Since remarkable anisotropy was observed in the sintered body, three-point bending strength and thermal conductivity were measured in the direction perpendicular to and parallel to the hot press pressure axis, respectively. The results are shown in Table 2.

Although the thermal conductivity value is slightly lower than Comparative Example 2 described later, the bending strength is significantly improved, especially when the span is taken parallel to the hot press pressure axis. You can see that

Comparative Example 2 The aluminum nitride powder, hexagonal boron nitride powder, and CaC2 used in Example 2 were blended in the proportions shown in Table 2, and a hot-pressed sintered body was produced in the same manner as in Example 2.

Table 2 shows the results of identification and quantification of the crystal phase, bulk density, bending strength, and thermal conductivity of the obtained sintered body.

(Left below) Effects of the Invention As stated above, the AlN-BN composite sintered body of the present invention is an AlN compound that can be used as an IC puff cage material, an IC substrate material, and an electrically insulating heat dissipating material ranging from room temperature to high temperature.
-The mechanical strength of the -BN-based composite sintered body, especially at room temperature, has been significantly improved, and in addition to the above-mentioned uses, it can be applied to machinable ceramics, etc., and is extremely useful industrially.

Claims (6)

[Claims] 1. Total amount of aluminum nitride and polytype of aluminum nitride 40-90% by weight, and hexagonal boron nitride 1
An AlN-BN composite sintered body containing 0 to 60% by weight. 2. Total amount of aluminum nitride and polytype of aluminum nitride 40-90% by weight, hexagonal boron nitride 10-6
0% by weight, and 0.1 to 10% by weight of one or more of calcium compounds and yttrium compounds. 3. A according to claim 1 or 2, wherein the content of aluminum nitride polytype is 50% by weight or less based on the total amount of aluminum nitride and aluminum nitride polytype.
IN-BN composite sintered body. 4. A mixed powder consisting of 40 to 80% by weight of aluminum nitride powder, 10 to 80% by weight of hexagonal boron nitride powder, and 0.5 to 10% by weight of silicon oxide powder was heated at 1600 to 2000°C under vacuum or an inert gas atmosphere. , 5-100M
A method for producing an AlN-BN composite sintered body by pressurizing and heating with Pa. 5. Aluminum nitride powder 40-90% by weight, hexagonal boron nitride powder 10-60% by weight, silicon oxide powder 0.5%
~10% by weight, and a mixed powder consisting of 0.1 to 10% by weight of one or more of calcium compounds and yttrium compounds under vacuum or an inert gas atmosphere.
A method for producing an AlN-BN composite sintered body by pressurizing and heating at 1600 to 2000°C and 5 to 100 MPa. 6. A claim in which the calcium compound is calcium oxide, calcium carbide, calcium carbonate, calcium nitrate, calcium fluoride, calcium hydroxide, calcium cyanide, or calcium cyanamide, and the yttrium compound is yttrium oxide, yttrium carbide, yttrium fluoride, or yttrium nitrate. Item 5. The method for producing an AlN-BN composite sintered body according to item 5.