JPH06219842A - Composite ceramics - Google Patents

Abstract

PURPOSE:To reduce the porosity of composite ceramics consisting of aluminum nitride and a boron compd. and to enhance the heat conductivity and mechanical strength. CONSTITUTION:This composite ceramics constitute 5-40% of area of a grain boundary phase based on at least one of compds. of groups IIa and IIIa metals of the periodic table and contg. aluminum nitride and a boron compd. in a dispersed state.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an IC package material, I
The present invention relates to a composite ceramic that can be used as a C substrate material, a thermal shock resistant material, and a corrosion resistant material for molten metal.

[0002]

2. Description of the Related Art Sintered aluminum nitride has a high thermal conductivity and excellent electrical insulation properties, so it has been widely applied and put to practical use as an insulating / radiating substrate. In addition to having a high rate, it has properties such as low specific gravity, low coefficient of thermal expansion, high heat resistance, and resistance to molten metal such as Al that are useful as a high temperature / structural material.
Various studies have been made. As one of them, compounding with a boron compound has been studied, and many proposals have been made particularly for compounding with boron nitride (JP-A-60-19).
5059, JP 61-215264, JP 62
-56377, JP-A-1-246178, JP-A-1
No. 25284, JP-A-3-252367, and JP-A-4
-275979). The aluminum nitride sintered body compounded with boron nitride has the characteristics that the thermal shock resistance is improved and the machining is facilitated.

[0003]

However, in the case of ceramics composed of aluminum nitride and boron nitride, the porosity in the sintered body increases with an increase in the addition amount of boron nitride, and when 10 wt% of boron nitride is added. Reports that the porosity can reach 10%. When the porosity is increased in this way, the mechanical strength is lowered and the thermal conductivity, which is a characteristic of aluminum nitride, is also lowered. Therefore, its use as a high temperature / structural material is limited. Therefore, it is an object of the present invention to improve the thermal conductivity and mechanical strength of a composite ceramic composed of aluminum nitride and a boron compound.

[0004]

Means for Solving the Problems As a result of intensive studies made by the present inventors, the porosity is increased by adding a sintering aid in a larger amount than in the conventional composite ceramic made of aluminum nitride and boron nitride. It was found that it is possible to suppress the deterioration of high thermal conductivity and mechanical strength.
The present invention has been made on the basis of this finding, and the grain boundary phase mainly composed of at least one of the compounds of groups a and a of the periodic table occupies 5 to 40% in area ratio. ,
The composite ceramic is characterized in that aluminum nitride and a boron compound are dispersed in the grain boundary phase.

The present invention will be described in detail below. In conventional composite ceramics, a compound such as aluminum nitride and boron nitride, such as at least one oxide selected from Group 2a and Group 3a of the Periodic Table, is added as a sintering aid. The sintering aid forms a grain boundary phase of ceramics after sintering, and has been conventionally added in the range of 10 wt% or less. For example, in JP-A-60-195059, 0.01 to 10% by weight, preferably 0.05 to 5% by weight, of the sintering aid should be added to the mixture of aluminum nitride and boron nitride. Is listed. The present invention is characterized in that the sintering additive is added in an amount of 20 wt% or more, which is larger than the conventional amount. The structure of the composite ceramic of the present invention obtained by adding a large amount of the sintering aid in this manner will be described with reference to FIGS. 1 and 2. 1 and 2 are diagrams schematically showing the structure of the composite ceramic of the present invention.
FIG. 3 is a diagram schematically showing the structure of a conventional composite ceramic. The composite ceramics of the present invention shown in FIGS. 1 and 2 have a structure in which aluminum nitride particles 2 and boron compound particles 3 are present in a grain boundary phase 1. In addition, FIG. 1 shows the case where the boron compound particles are spherical, and FIG.
Indicates that the boron compound particles 3 are needle-shaped. On the other hand, the conventional composite ceramic shown in FIG. 3 has a structure in which the grain boundary phase 1 exists in a minute gap between the aluminum nitride 2 and the boron compound 3.

Since the composite ceramic of the present invention contains a large amount of a sintering aid, the porosity can be reduced to 5% or less in area ratio. In the composite ceramics of the present invention, the porosity was able to be greatly reduced to 5% or less in area ratio as compared with the conventional one, because a large amount of the liquefied grain boundary phase caused sufficient voids between the aluminum nitride and the boron compound during sintering. Probably because it was filled up. Therefore, in the present invention, the grain boundary phase has an area ratio of 5 to 40.
It has a structure that occupies%. Area ratio of grain boundary phase is 5%
If it is less than 40%, the porosity in the composite ceramic is not sufficiently reduced, and if it exceeds 40%, the characteristics of the aluminum nitride and boron compounds are not exhibited.

The composite ceramics of the present invention are oxides of Group 2a of the periodic table such as Ca and Sr and Group a of Y and Dy.
20-50w of at least one kind of carbide and nitride
It can be manufactured by sintering a mixture of t%, a boron compound of 0.5 to 30 wt% and the balance of aluminum nitride.

In the composite ceramic of the present invention, the boron compound brings about the effect of improving the thermal shock resistance. If the amount of the boron compound added is less than 0.5 wt%, the effect of improving the thermal shock resistance is not sufficient, and if it exceeds 30 wt%, the porosity is reduced even if a large amount of the sintering additive is added as in the present invention. Can not do. Therefore, it is added in the range of 0.5 to 30 wt%. The boron compound is preferably at least one selected from boron carbide, boron nitride and zirconium boride. The boron compound takes a shape such as a granular shape, a columnar shape, a needle shape, or a plate shape within the structure of the composite ceramics. Zirconium boride or the like becomes granular and contributes to increasing the hardness of the composite ceramic. Boron carbide or the like has a columnar shape, a needle shape, or a plate shape, and contributes to increase the toughness.

At least one of oxides, carbides, and nitrides of Groups 2a and 3a of the Periodic Table forms a grain boundary phase after sintering and is added in the range of 20 to 50 wt%. This is because if it is less than 20 wt%, the effect of reducing porosity in the composite ceramics is not sufficient, and if it exceeds 50 wt%, the characteristics of the aluminum nitride and boron compound are not exhibited. If the addition amount of the sintering aid is larger than the addition amount of the boron compound, the porosity can be made 0%. Further, even when the addition amount of the sintering aid is less than the addition amount of the boron compound, it is possible to make it 0% by controlling the sintering temperature.

The composite ceramics of the present invention can be produced by pressure sintering such as HIP, but can also be easily produced by atmospheric pressure sintering and can be obtained at a low production cost.

[0011]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. 20 to 50 wt% of at least one or more kinds of compound powder having an average particle size of 0.5 μm selected from Groups 2a and 3a of the periodic table, 20 to 80 wt% of an aluminum nitride powder having an average particle size of 0.5 μm, And average particle size 3μ
Using a powder prepared by mixing the boron compound powder of m in the range of 0.5 to 30 wt%, ethanol was used as a dispersion medium and mixed by a ball mill. This mixed powder was molded and sintered at 1800 ° C. for 1 hour in a nitrogen atmosphere. In this way
The composite ceramics shown in Tables 1 to 6 were produced. For comparison, ceramics having a compounding ratio outside the above range were produced. In Tables 1 to 6, the grain boundary phase amount and porosity of the obtained ceramics are shown in parallel. The grain boundary phase amount and the porosity are represented by the area ratio obtained by using a structure photograph by SEM (× 5000). Further, Di ₂ O ₃ in Table 3 is Nd
_An oxide composed of ₂ O ₃ : 75 wt% and Pr ₂ O ₃ : 25 wt% is shown. From the results of Tables 1 to 6, it was confirmed that the composite ceramic of the present invention is a dense sintered body having a low porosity.

Several kinds of ceramics shown in Tables 1 to 6 were selected, and the relationship between the boron compound and thermal conductivity and fracture toughness was investigated. The results are shown in FIGS. 4 to 8, and it can be seen that the thermal conductivity is maintained substantially constant and the fracture toughness value is improved even if the amount of the boron compound is increased. In addition, as compounds of Group 2a and Group 3a of the Periodic Table,
FIG. 4 shows Dy ₂ O ₃ , FIG. 5 shows Y ₂ O ₃ , FIG. 6 shows Dy ₂ O ₃ , and FIG.
Is CeO ₂ and FIG. 8 is Y ₂ O ₃ , each 25 wt%
Was added.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

[Table 5]

[0018]

[Table 6]

[0019]

According to the present invention, the porosity of the composite ceramic composed of aluminum nitride and a boron compound can be reduced, and the thermal conductivity and mechanical strength can be improved.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing the structure of a composite ceramic of the present invention, in which the boron compound is in the form of particles.

FIG. 2 is a diagram schematically showing the structure of the composite ceramic of the present invention, in which the boron compound is columnar, needle-shaped, or plate-shaped.

FIG. 3 is a diagram schematically showing the structure of a conventional composite ceramic.

FIG. 4 is a graph showing the relationship between the amount of B ₄ C and the thermal conductivity and fracture toughness value.

FIG. 5 is a graph showing the relationship between the amount of BN, thermal conductivity, and fracture toughness value.

FIG. 6 is a graph showing the relationship between the amount of TiB ₂ and thermal conductivity and fracture toughness value.

FIG. 7 is a graph showing the relationship between the amount of ZrB ₂ and thermal conductivity and fracture toughness value.

FIG. 8 is a graph showing the relationship between the amount of TaB ₂ and thermal conductivity and fracture toughness value.

[Explanation of symbols]

1 grain boundary phase, 2 aluminum nitride, 3 boron compound

Claims (4)

[Claims] 1. A grain boundary phase mainly composed of at least one compound of Group 2a and Group 3a of the Periodic Table has an area ratio of 5 to 5.
A composite ceramic, which occupies 40% and has aluminum nitride and a boron compound dispersed in the grain boundary phase. 2. The composite ceramic according to claim 1, wherein the boron compound is at least one of boron carbide, boron nitride, and zirconium boride. 3. A powder of at least one oxide of oxides, carbides and nitrides of Groups 2a and 3a of the Periodic Table.
0 to 50 wt%, boron compound powder 0.5 to 30 wt
%, And a mixed powder of which the balance is aluminum nitride powder is molded and sintered, which is a method for producing a composite ceramics. 4. The method for producing a composite ceramic according to claim 3, wherein the boron compound is at least one of boron carbide, boron nitride, and zirconium boride.