JP2752227B2 - AlN-BN composite sintered body and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an AlN—BN-based composite ceramics sintered body and a method for producing the same. For details, IC package materials, IC
AlN-BN that has characteristics such as electrical insulation, high thermal conductivity, low thermal expansion, low dielectric constant, and easy workability that can be used as a substrate material and a heat insulating material from room temperature to high temperature.
The present invention relates to a composite sintered body having improved mechanical strength, particularly at room temperature, of a system composite sintered body, and a method for producing the same.

2. Description of the Related Art Since AlN-BN composite sintered bodies have high thermal conductivity and can be cut at high speed with ordinary tools, they are used as so-called machinable ceramics (for example, Japanese Patent Application Laid-Open Nos. -195060, JP-A-61-63572, JP-A-62-56377, etc.). 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 high coefficient of thermal conductivity, a short signal delay time and a close signal expansion coefficient with Si, a semiconductor material. Applications as package materials and IC substrate materials are being studied (for example,
1-252584, JP-A-1-261279, etc.).

However, this composite sintered body is made of AlN or Al ₂ O ₃
As compared with other ceramic sintered bodies. The three-point bending strength reported so far is that AlN / BN (weight ratio) is 80/20.
Approximately 350MPa, approximately 230MPa at 65/35, and approximately 130MPa at 40/60, the bending strength decreases as the BN content increases.

In the case of a composite sintered body in which BN particles are oriented by the hot press method, the bending strength when the span is taken in the direction parallel to the hot press pressure axis is remarkably low, and the bending strength depends on the degree of orientation of the BN particles. 80/20, though different in value
Reported values of about 100 to 300 MPa.

Since these low flexural strengths are a major bottleneck in the use of materials, improvements have been desired.

SUMMARY OF THE INVENTION In view of this problem, the present invention has a high mechanical strength while maintaining excellent characteristics such as high thermal conductivity, electrical insulation, relatively low thermal expansion, low dielectric constant, and easy workability. It is an object of the present invention to provide an AlN-BN-based composite sintered body having improved resistance, and a method for producing the same.

In other words, the present invention provides a total amount of aluminum nitride and aluminum nitride polytype of 40 to 90% by weight (however, the aluminum nitride polytype is reduced to a total amount of aluminum nitride and aluminum nitride polytype). At least 1% by weight or more) and 10 to 60% by weight of hexagonal boron nitride.

Also, the total amount of aluminum nitride and aluminum nitride polytype is 40 to 90% by weight (however, the aluminum nitride polytype is contained at least 1% by weight or more based on the total amount of aluminum nitride and aluminum nitride polytype). An AlN-BN composite sintered body comprising 10 to 60% by weight of hexagonal boron nitride and 0.1 to 10% by weight of one or more of a calcium compound and an yttrium compound. Furthermore, the content of the aluminum nitride polytype in the sintered body of the present invention is 50% by weight or less of the total amount of the aluminum nitride and the aluminum nitride polytype.

Aluminum nitride powder 40 to 90% by weight, hexagonal boron nitride powder 10 to 60% by weight, and silicon oxide powder 0.5 to 1
The present invention relates to a method for producing an AlN-BN composite sintered body by heating a mixed powder consisting of 0% by weight under a vacuum or an inert gas atmosphere at 1600 to 2000 ° C and 5 to 100 MPa.

In addition, aluminum nitride powder 40 to 90% by weight, hexagonal boron nitride powder 10 to 60% by weight, silicon oxide powder 0.5 to 10% by weight, and calcium compound, yttrium compound of one or more of 0.1 to 2 A mixed powder consisting of 10% by weight is 1600-2000 in a vacuum or an inert gas atmosphere.
The present invention relates to a method for producing an AlN-BN composite sintered body by heating under pressure at 5 ° C. and 5 to 100 MPa. As calcium compounds, calcium oxide, calcium carbide, calcium carbonate, calcium nitrate, calcium fluoride, calcium hydroxide,
Examples of 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 described in detail.

The sintered body of the present invention comprises aluminum nitride and a polytype of aluminum nitride in a total amount of 40 to 90% by weight and hexagonal boron nitride of 10 to 60%.

Further, another sintered body of the present invention comprises a total amount of aluminum nitride and aluminum nitride polytype of 40 to 90% by weight, hexagonal boron nitride of 10 to 60% by weight, and one of a calcium compound and an yttrium compound. A sintered body comprising 0.1% to 10% by weight of one or more kinds.

By including the aluminum nitride polytype in the sintered body, the mechanical strength of the sintered body at room temperature is significantly improved. 2H, 27 for aluminum nitride polytype
There are several compounds having different crystal structures such as R, 21R, 12H, 15R, 8H (KHJack, J. Mat. Sci., 11 , 1135 (1976)).
However, the polytype of the aluminum nitride contained in the sintered body of the present invention does not matter in any case. It is known that these polytypes are formed when the system contains aluminum oxide, silicon oxide or the like, and particularly at a relatively low temperature when the system contains silicon oxide.

The upper limit of the content of the aluminum nitride polytype in the sintered body is 50% by weight or less, preferably 30% by weight or less, based on the total amount of the aluminum nitride and the 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 is all. If the polytype content exceeds these ranges and exceeds 50% by weight, the mechanical strength of the sintered body is significantly improved, but the thermal conductivity of the sintered body is reduced due to the low thermal conductivity of the polytype. Therefore, the high thermal conductivity inherent in the AlN-BN based sintered body may be impaired. When the content of the polytype is less than 1% by weight, the improvement in mechanical strength of the sintered body due to the inclusion of the polytype, which is the object of the present invention, is hardly recognized.

In order to improve the mechanical strength of the sintered body and obtain a high thermal conductivity by using the aluminum nitride polytype, one or more of the calcium compound and the yttrium compound are contained in the sintered body. Achieved by including them together with the type. The calcium compound and the yttrium compound are mainly formed by a reaction between the calcium compound and the yttrium compound added at the time of production, and the oxides inevitably generated on the surfaces of aluminum nitride and hexagonal boron nitride powder used as raw materials. You.

Examples of the compound to be formed include calcium aluminate, yttrium aluminate, calcium borate, yttrium borate, and compounds formed by a reaction between these compounds. It is known that some of these compounds exist depending on the ratio of CaO / Al ₂ O ₃ when taking, for example, calcium aluminate as an example. (RWNurse et.al .: Trans.Brit. Ceram .Soc., 64 ,
[9], 416 (1965), T. Nogucgi et.al .: Kogyo Kagaku Z
asshi, 70 [6] 839 (1967)), and any of the compounds contained in the sintered body of the present invention does not cause any problem.

Oxide impurities at the grain boundaries of aluminum nitride and hexagonal boron nitride particles constituting the sintered body are significantly reduced due to the formation of these compounds in the sintered body, resulting in a sintered body having a high thermal conductivity. Is obtained. Calcium compound present in the sintered body, as other things of the yttrium compound, when the sintering aid remains without reacting as it is,
When silicon oxide is added to form a polytype, a composite oxide of calcium and yttrium containing silicon can be used.

The composition ratio of the sintered body is 40 to 90% by weight in total of aluminum nitride and polytype of aluminum nitride, and 10 to 60% by weight of hexagonal boron nitride. In a composition in which the total amount of aluminum nitride and aluminum nitride polytype is around 40% by weight, the improvement in mechanical strength by aluminum nitride polytype is remarkably recognized. In the composition where the total amount of aluminum nitride and polytype of aluminum nitride is around 90% by weight, the hot-press method is used especially for the manufacturing method, and the orientation and lamination of flaky hexagonal BN particles are observed in the sintered body. In that case, the resulting mechanical strength can be significantly improved. (Taking the bending strength as an example, the case where the span is taken in the orientation and lamination direction of the BN particles, in other words, the case where the span is taken in the pressure axis direction of the hot press is remarkably improved.) If the total amount of aluminum nitride and aluminum nitride polytype is less than 40% by weight, although the mechanical strength is improved, the thermal conductivity of the sintered body is greatly reduced and the AlN-BN-based It is not preferable because excellent characteristics of the aggregate are lost. On the other hand, if the total amount of aluminum nitride and the polytype of aluminum nitride exceeds 90% by weight, the mechanical strength of the sintered body approaches that of the AlN sintered body, so that there is little problem in practical use. Even in a sintered body having anisotropy, since the BN content is small, remarkable anisotropy is not recognized, and no remarkable improvement in mechanical strength is exhibited.

The composite ceramic sintered body of the present invention can be manufactured, for example, by the following method, but this is a preferred example of the manufacturing method and is not necessarily limited to the following method. The composite ceramic sintered body of the present invention,
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 is placed under vacuum or an inert gas atmosphere.
It is obtained by heating under pressure at 1600 to 2000 ° C and 5 to 100 MPa.

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

When a powder having a fine average particle size is used, the sintered body becomes relatively isotropic, and a powder having a relatively large average particle size (having a remarkable flaky shape which is a typical shape of hexagonal boron nitride powder) When ()) is used, a sintered body having a relatively strong anisotropy is obtained. However, in the production method of the present invention, any of these methods does not cause any particular problem.

Considering the thermal conductivity, the smaller the oxygen content, the better.However, if the powder becomes finer, the oxygen content increases due to oxides inevitably generated on the surface.
It is desirable to select an appropriate one according to the application.

As the silicon oxide raw material powder, conventionally known ones can be used, and both crystalline and amorphous materials can be suitably used. The particle size is not particularly limited, but is preferably as fine as possible in consideration of reactivity and sinterability, and silicon oxide powder produced by a sedimentation method or the like is suitably used.

The silicon oxide powder used in the production method of the present invention is not limited to the case where the starting material itself is silicon oxide, but also one which becomes silicon oxide during firing, for example, an organometallic compound or a decomposition product thereof. Objects and the like can be used as needed.

The mixing ratio of the raw material powder is aluminum nitride powder 40 to 90
%, Hexagonal boron nitride powder 10 to 60% by weight, and silicon oxide powder 0.5 to 10% by weight. If the compounding ratio of the silicon oxide powder is less than 0.5% by weight, a remarkable improvement in mechanical strength due to the formation of the aluminum nitride polytype, which is the object of the present invention, is not recognized. It is preferably at least 2% by weight. If the compounding ratio is more than 10% by weight, the amount of aluminum nitride present in the sintered body decreases even in a composition having a large amount of aluminum nitride, and the polytype of aluminum nitride becomes dominant.
Depending on the composition, sialon is generated, and the thermal conductivity of the sintered body is lowered.
It is as follows.

The firing is performed at a temperature of 1600 to 2000 ° C. while applying a pressure of 5 to 100 MPa. If the firing temperature is lower than 1600 ° C., the sintered body will not be sufficiently densified, and a polytype of aluminum nitride will not be formed, so that the desired properties of the sintered body cannot be obtained. If the temperature is higher than 2000 ° C., it is not economical, and there is a possibility that some of the components may start to decompose.

If the pressure is less than 5 MPa, the desired characteristics cannot be obtained because the sintered body is still not sufficiently densified. If it exceeds 100 MPa, it is still not economical, and when a hot press method or the like is applied, disadvantages such as the limitation of the mold used are caused.

The pressing method may be any of uniaxial pressing such as hot pressing, isostatic pressing such as HIP and atmospheric gas pressure sintering, but when using isostatic pressing, there are many open pores in the powder compact. Since it is present, it is necessary to eliminate open pores by pre-sintering or to perform pre-treatment such as encapsulation.

The heating under pressure is preferably for 0.5 to 4 hours, more preferably for 1 to 2 hours. If the heating under pressure is less than 0.5 hours,
There are cases where the densification of the sintered body does not occur sufficiently and a satisfactory characteristic value cannot be obtained. Pressurized heating for more than 4 hours does not adversely affect the characteristic values, but is not economical.

The heating under pressure is desirably performed in a vacuum or in an atmosphere of an inert gas such as nitrogen or argon to prevent oxidation of the nitride particles.

Conventionally, it has been known that, in a sintered body obtained by adding silicon oxide to aluminum nitride, the bulk density decreases with an increase in the amount of silicon oxide added, and the bending strength also decreases (Yoneya, Inoue, Tsuge, Ceramic Association, 89 ,
[6], 330 (1981)), in the present invention, by forming a composite with hexagonal boron nitride and using a pressure heating method as a sintering method, sufficient densification is achieved and mechanical strength is reduced. Improvement is observed.

It is also known that the thermal conductivity decreases when Si is present as an impurity in the aluminum nitride sintered body,
("Ceramic substrates for functional circuits" p.62 (edited by the Electronic Materials Industries Association) 1985), the present invention minimizes this decrease in thermal conductivity by promoting the densification of the sintered body. .
However, when a sintered body having a higher thermal conductivity is required, 0.1 to 10% by weight of one or more of a calcium compound and a yttrium compound may be used as the fourth component.
This is achieved by using

Examples of the calcium compound include calcium oxide, calcium carbide, calcium carbonate, calcium nitrate, calcium fluoride, calcium hydroxide, calcium cyanide, and calcium cyanamide, and preferably calcium oxide, calcium carbide, calcium nitrate, and calcium cyanamide. As the yttrium compound, yttrium oxide, yttrium carbide, yttrium fluoride,
Yttrium nitrate, preferably yttrium oxide and yttrium fluoride.

A suitable addition amount of these compounds is 0.1 to 10% by weight, preferably 0.2 to 5% by weight. If the added amount is less than 0.1% by weight, no remarkable effect is exhibited, and if it exceeds 10% by weight, the thermal conductivity of the sintered body is lowered because the added amount is too large. Also, since the addition amount of these compounds has a relatively large effect on the thermal conductivity of the sintered body, it is necessary to determine the addition amount with care. By the addition of the fourth component, oxide impurities at the grain boundaries in the sintered body can be significantly reduced as described above. As a result, AlN having a small decrease in thermal conductivity and improved mechanical strength is obtained. -A BN composite sintered body is obtained.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Aluminum nitride powder having an average particle size of 1.8 μm, average particle size
2.5 μm hexagonal boron nitride powder, silicon dioxide powder (precipitated, special grade reagent) and calcium and yttrium compounds as sintering aids in the proportions shown in Table 1 were mixed in a ball mill for 24 hours. And wet mixing using acetone as a solvent. After thoroughly drying the obtained powder,
Fill into graphite dies and place in nitrogen gas atmosphere at 1800 ℃
Time hot press sintering was performed.

With respect to the obtained sintered body, identification and quantification of a crystal phase, bulk density, bending strength, and measurement of thermal conductivity were performed. The crystal phase was identified by powder X-ray diffraction after crushing the sintered body, and quantification 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 flexural strength was measured when a three-point flexural strength conforming to JIS standards was spanned 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 flexural strength varies in the range of 230 to 380 MPa depending on the composition, an improvement in flexural strength of about 20 to 100 MPa is observed as compared with a sintered body of substantially the same composition in Comparative Example 1 described later.

Comparative Example 1 The aluminum nitride powder and hexagonal boron nitride powder used in Example 1 were mixed with CaC ₂ as a sintering agent in the ratio shown in Table 1 and sintered by hot pressing in the same manner as in Example 1. A sintered body was prepared, and the sintered phase of the sintered body was identified and quantified, and the bulk density, bending strength, and thermal conductivity were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 2 Aluminum nitride powder having an average particle size of 1.8 μm and an average particle size of 1
0 μm hexagonal boron nitride powder, the silicon dioxide powder used in Example 1, and the CaC ₂ powder were blended in the proportions shown in Table 2 and wet-mixed in a ball mill for 24 hours using acetone as a solvent. Was. Sintering is performed at 1800 ° C as in Example 1
Time hot press sintering. About the obtained sintered body,
Identification and quantification of the crystal phase, bulk density,
The three-point bending strength and the thermal conductivity were measured.

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

Although the value of the thermal conductivity is slightly reduced as compared with Comparative Example 2 described below, the bending strength is remarkably improved, particularly when the span is set in a direction parallel to the hot press pressure axis. You can see that it is.

Comparative Example 2 The aluminum nitride powder, hexagonal boron nitride powder and CaC ₂ used in Example 2 were blended in the proportions shown in Table 2 to prepare a hot-press sintered body in the same manner as in Example 2.

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

Effect of the Invention As described above, the AlN-BN composite sintered body of the present invention has an IC
The AlN-BN composite sintered body, which can be used as a package material, IC board material, and as an electrically insulating heat radiation material from room temperature to high temperature, has significantly improved the mechanical strength, especially at room temperature. It can be applied to machinable ceramics, etc., and is extremely useful in industry.

Continuation of the front page (56) References JP-A-58-32073 (JP, A) JP-A-1-305862 (JP, A) JP-A-1-246178 (JP, A) JP-A-60-122772 (JP) , A) JP-A-62-65911 (JP, A)

Claims (6)

(57) [Claims] 1. A total amount of aluminum nitride and aluminum nitride polytype of 40 to 90% by weight (however, aluminum nitride polytype is at least 1% by weight or more based on a total amount of aluminum nitride and aluminum nitride polytype). And an AlN-BN composite sintered body comprising 10 to 60% by weight of hexagonal boron nitride. 2. The total amount of aluminum nitride and aluminum nitride polytype is 40 to 90% by weight (however, the aluminum nitride polytype is at least 1% by weight or more based on the total amount of aluminum nitride and aluminum nitride polytype). An AlN-BN composite sintered body comprising 10 to 60% by weight of hexagonal boron nitride and 0.1 to 10% by weight of one or more of a calcium compound and an yttrium compound. 3. The AlN-BN composite sintered body according to claim 1, wherein the content of the aluminum nitride polytype is 50% by weight or less based on the total amount of the aluminum nitride and the aluminum nitride polytype. . 4. An aluminum nitride powder of 40 to 90% by weight, a hexagonal boron nitride powder of 10 to 60% by weight, and a silicon oxide powder.
A method for producing an AlN-BN composite sintered body by pressurizing and heating a mixed powder of 0.5 to 10% by weight at 1600 to 2000 ° C and 5 to 100 MPa in a vacuum or an inert gas atmosphere. 5. Aluminum nitride powder 40 to 90% by weight, hexagonal boron nitride powder 10 to 60% by weight, silicon oxide powder 0.5 to 1
0% by weight and a mixed powder comprising 0.1 to 10% by weight of one or more of a calcium compound and an yttrium compound in a vacuum or an inert gas atmosphere for 1600 to 20%.
A method for producing an AlN-BN composite sintered body by heating under pressure at 00C and 5 to 100 MPa. 6. The calcium compound is calcium oxide, calcium carbide, calcium carbonate, calcium nitrate, calcium fluoride, calcium hydroxide, calcium cyanide,
Or AlN-BN according to claim 5, wherein the calcium cyanamide or the yttrium compound is yttrium oxide, yttrium carbide, yttrium fluoride or yttrium nitrate.
Method for producing a composite sintered body.