JPS6121964A - Alumina sintered body and manufacture - 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 [Industrial Field of Application] The present invention relates to an alumina sintered body whose main components are silicon carbide and alumina fine powder with a homogeneous composition, and a method for producing the same. The present invention relates to an alumina sintered body that has excellent properties and is suitable for semiconductor packages, heat-resistant IC boards, various mechanical parts, etc., and a method for manufacturing the same.

[Conventional technology]

Alumina aggregates are generally materials with excellent room-temperature strength, heat resistance, hardness, chemical stability, and electrical insulation, and are widely used in corrosion-resistant and wear-resistant parts, electronic industry parts, spark plug parts, etc. ing. Among these, alumina sintered bodies are attracting attention as high-temperature parts, but their strength, hardness, and
Cree-1 characteristics, fracture resistance, and thermal shock resistance are insufficient, and even though substrates with high thermal conductivity (λ) are required for electronic industrial parts due to high speed and high density, λ is low and has poor heat dissipation.

Therefore, in order to solve the above-mentioned problems, alumina sintered bodies and alumina single crystal products produced by a hot press method in which high-purity alumina powder is sintered under high temperature and pressure are being considered.

However, although the high-purity alumina sintered body produced by the hot pressing method has improved thermal conductivity, its high-temperature strength and fracture resistance are insufficient and it is easily broken. Further, although the single crystal product has improved thermal conductivity and high temperature strength, it is extremely expensive.

On the other hand, composite sintered bodies in which zirconia is added to alumina or composite sintered bodies in which whiskers are mixed in alumina have been proposed, but the former sintered bodies tend to contain radioactive elements, so they are not suitable for use as electronic components. The latter sintered body is unsuitable, and the latter sintered body has directionality due to lie/vf inclusion, which is disadvantageous in terms of physical properties and increases cost.

Taking these things into consideration, the applicant previously proposed that ``a silicon carbide-containing material containing 0.6 to 40% by weight of silicon carbide and a mixed composition with the remainder being alumina as a main component. The above-mentioned silicon carbide-containing alumina sintered body is produced by uniformly containing SiC particles in AIto3 mainly by pressureless sintering to improve strength, hardness, and heat resistance. This invention aims to improve conductivity, #thermal shock resistance, etc.

[Problem that the invention seeks to solve]

The main purpose of the present invention is to eliminate and improve the drawbacks of the prior art, and further improve the physical properties, especially the fracture resistance (KIC), of the silicon carbide-containing alumina sintered body obtained by the prior invention. The present invention attempts to propose an alumina sintered body suitable for semiconductor packages, IC boards, mechanical parts, etc., by the invention described in the claims.

Next, the alumina sintered body of the present invention will be specifically explained.

[Means for solving the problems and their effects] According to the present invention, a carbonized carbonaceous material containing silicon carbide in a weight ratio of 0.6 to 40% and the balance being a mixed composition mainly composed of alumina. The silicon-containing alumina sintered body has a homogeneous composition in which the alumina particle size is 10/Jm or less,
It is possible to provide an alumina sintered body characterized by particularly excellent fracture resistance (KIC).

That is, first, according to the present invention, silicon carbide contained in the alumina pressureless sintered body needs to be in the range of 0.5 to 40% by weight. If the silicon carbide content is less than 0.5%, improvements in hardness, strength, fracture resistance, and thermal conductivity due to the inclusion of silicon carbide will not be sufficient, and if it is more than 40%, the sinterability of alumina and silicon carbide will be reduced. This makes it difficult to obtain a high-density alumina pressureless sintered body, and even if a high-density sintered body is obtained, there will be extremely large amounts of unevenness between the silicon carbide particles and the alumina particles, resulting in poor mechanical properties. This is because silicon carbide significantly reduces the thermal properties, and among these, the most preferable result is obtained when the silicon carbide content is in the range of 0.5 to 20%.

Next, according to the present invention, the remainder must have a homogeneous composition in which the particle size of alumina is substantially 10 μffl −0, 1 μm, and must be a main component other than the silicon carbide. . When the average grain size of alumina is 10 μmJ'' larger, the grain boundary fracture area becomes smaller and the surface energy (
r+) becomes smaller.

On the other hand, if the average particle size of alumina is smaller than 10 μm, the contact area of grain boundaries between alumina and alumina becomes large, and thus the surface energy (ri) becomes large. therefore,
It is believed that the fracture resistance of the alumina sintered body of the present invention is improved. It is surface energy, that is, absorbed energy due to plastic deformation, energy released during fracture, or energy associated with phase transformation, and KIC.
This is because they are in a proportional relationship. Therefore, in order to obtain a sintered body with excellent fracture resistance, such as the alumina sintered body of the present invention, the particle size of alumina must be made as small as possible and uniformly distributed to reduce the porosity between the grains. Eliminating preferential orientation of crystals improves Ktc.

In other words, if a discontinuous layer is formed at the grain boundaries between alumina and alumina or between alumina and silicon carbide, cracking of the grain boundaries may be likely to occur.

On the other hand 1. If the particle size of alumina is smaller than 0.1 μm, it is difficult to obtain an alumina sintered body with a sufficiently high density.

According to the present invention, the crystal structure of the alumina powder is α
Type alumina is preferred. The reason is that α-type alumina has excellent stability at high temperatures.

Furthermore, according to the present invention, silicon carbide must primarily have a β-type crystal structure. The reason for this is that β-hydrated silicon has a cubic crystal system and does not show anisotropy due to the physical properties of the particles, so an alumina sintered body with a stable microstructure can be obtained. It is. Further, the crystal structure of alumina is preferably α-type alumina. The reason is that α-type alumina has excellent stability at high temperatures.

According to the present invention, the average particle size of the silicon carbide is from 0.1 to
The thickness is preferably 2.0 μm.

Furthermore, if the particle size of silicon carbide is smaller than 0.1 μm, the cohesiveness becomes extremely strong and the dispersibility during mixing of raw materials becomes low. On the other hand, if the particle size of the expanded silicon is larger than 2.0 μm, the non-uniformity between the silicon carbide particles and the alumina particles becomes large, resulting in so-called mismatch, which deteriorates the mechanical and thermal properties of the sintered body. It turns out.

Further, according to the present invention, the content of silicon carbide is particularly 0.
．． It is preferably 5 to 5.0% by weight.

When the amount is 0.5% by weight or less, it becomes difficult to control grain growth of alumina, so grain boundary fracture is less likely to occur.

On the other hand, if the content of silicon carbide is 5.0% by weight or more, the number of discontinuous layers increases and the fracture resistance decreases.

Further, according to the present invention, silicon carbide is preferably uniformly dispersed in the alumina sintered body.

The reason for this is that if silicon carbide is not uniformly dispersed, the physical properties of the alumina sintered body will be non-uniform, and if the uniformity is extremely poor, unsintered areas will occur in the alumina sintered body, and the alumina This is because the mechanical properties and thermal properties of the pressureless sintered body show significant deterioration.

According to the present invention, the bulk density of the alumina sintered body containing silicon carbide is preferably 95% or more of the theoretical density, preferably 97% or more. The reason for this is that if the theoretical density is less than 95%, there will be many pores inside the sintered body, resulting in a decrease in thermal conductivity.

As described above, according to the present invention, the weight ratio of silicon carbide is 0.
．． In the alumina sintered body containing 5 to 40%, in particular, the particle size of α-type alumina is set to 10 μm or less, the particle size of β-type silicon carbide is Q, and a raw material is homogeneously mixed with fine powder of 1-2.0 μm. By using silicon carbide, the hardness of the alumina sintered body containing silicon carbide improves, since silicon carbide is essentially an extremely hard material, and because the silicon carbide is uniformly dispersed as fine particles, alumina The strength of the pressureless sintered body is also improved. In addition, because silicon carbide and alumina have different chemical compositions, crystal structures, and other properties, compositional and structural nonuniformities occur between microscopic silicon carbide particles and alumina particles. When a fracture crack propagates, the propagation energy is consumed to prevent the crack from progressing, which improves fracture resistance. Furthermore, since silicon carbide is a material with excellent thermal conductivity, the thermal conductivity of an alumina sintered body uniformly containing silicon carbide is improved.

Next, a method for producing an alumina sintered body according to the present invention will be explained.

According to the present invention, a uniformly mixed composition obtained by uniformly mixing a composition whose main components are 0.5 to 40% by weight of silicon carbide powder and the remainder being alumina powder with a particle size of 10 μm or less, and performing K in this manner. After shaping into a desired shape, the molded body was heated to 1300~
It requires pressureless sintering at a temperature of 1900°C.

The reason for mixing 0.6 to 40% by weight of silicon carbide powder and the reason for setting the particle size of A/L/Mina powder to 10 μm or less is that if the average particle size of silicon carbide powder is smaller than 0.01 μm, it tends to coagulate. This is because the dispersibility during mixing is extremely strong and the dispersibility during mixing is low.If the diameter is larger than 2.0 μm, the non-uniformity between the silicon carbide particles and the alumina particles becomes large, which deteriorates the mechanical properties and thermal properties of the alumina pressureless sintered body. This is because the properties deteriorate.

According to the present invention, silicon carbide is preferably uniformly dispersed in the alumina sintered body. The reason for this is that if silicon carbide is not uniformly dispersed, the physical properties of the alumina sintered body will be non-uniform, and if the uniformity is extremely poor, unsintered areas will occur in the alumina sintered body, and the alumina Mechanical properties of a pressureless sintered body and an alumina pressureless sintered body containing silicon carbide are obtained.

To the homogeneously mixed composition thus obtained, water or a solvent such as benzene, acetone, alcohol, trichloroethylene, toluene, quintylene, etc., and a dispersant if necessary are added, and the mixture is processed using a ball mill, attritor, homomixer, etc.
It is important to mix uniformly using one or more types of mixers such as a vibrating Miμ, a Colloid Mill 1 Henschel mixer, or a high-speed mixer. Furthermore, forming aids such as polyethylene glycol may be added at the initial or intermediate stage of mixing.
Polyvinyl alcohol, methylcellulose, glycerin, starch, gum arabic, phenolic resin, Capois,
Addition of sox, stearic acid, paraffin emulsion, etc. improves moldability.

Molding is carried out by, for example, pressure molding using a mold, rubber molding, injection molding, extrusion molding, casting molding, a doctor blade method, a calendar method, a vapor dipping method, etc. to obtain a desired molded product.

Further, according to the present invention, the molded body can be fired at normal pressure in an atmosphere containing one or more gases of hydrogen, humidified hydrogen, nitrogen, argon, and helium, but humidified hydrogen is most preferred. Also, AI in the atmosphere! o,”5i
It is preferable that one or more types of O1co gases are included. The reason is that SiC + AhOs → 340K A1zO
stc and Al2O5 react due to +CO reaction,
When a partial pressure of a gas such as Al5o or 5iO1CO exists in the atmosphere, the reaction between SiC and A1101 is suppressed and the dense S
This is because an alumina pressureless sintered body containing iC can be obtained. In addition, the molded body has a weight ratio of silicon carbide of 0.5 to 28
．． It is possible to embed it in a mixture of 2% and 71.8-99.596 alumina and sinter it. The reason for this is that during firing, a reaction between silicon carbide and alumina occurs in the mixture of silicon carbide and alumina, gases of AhOlSin and CO are generated, and the reaction between SiC and AhOs in the compact is suppressed, resulting in a dense structure. This is because SIC can be obtained easily and at low cost.

According to the present invention, 'supplementary molded body' i 1110~
Pressureless sintering is preferably performed in a temperature range of 1900°C. The reason for this is that if the temperature is lower than 1300°C, the sinterability of the alumina powder and silicon carbide powder is low and a sufficiently dense sintered body cannot be obtained. This is because the thermal conductivity of the alumina pressureless sintered body decreases greatly due to diffusion, and the most preferable range is 1400~
The temperature range is 1600″C.

According to the present invention, the silicon carbide powder mainly has a β-type crystal structure and has an average particle size of 0.01 to 2.0 μ'.
It is particularly preferable to use as a starting material a composition whose main component is alumina having an α-type crystal structure with an average particle diameter of 0.06 to 10 μm.

The alumina sintered body thus obtained has a bulk density of 95% or more, particularly preferably 98% or more of the theoretical density, and a fracture toughness (Krc) of 8-5 MPa 1
It is characterized by having one or more mountains.

Next, examples of the present invention will be described.

Example 1 β-type silicon carbide with an average particle size of 0.8 μm in a weight ratio of 0 to 20
% and α-type alumina with an average particle size of 0.4 μm in weight ratio of 78
Five types of 5102 with a weight ratio of 2% and an average particle size of 2.0 μm were prepared in Formulation 1, and 10 of water was added to 100g of each formulation.
F, polyviny-μ alcohol IVzy and 0.6 g of stearic acid were added, and the mixture was incubated in a ball milli μ for 24 hours. The mixture was dried and granulated using a spray fire, and a molded body having a molding pressure of 1.5 t/d and a molding pressure of φ40×5 t was obtained by a molding method. The compact was inserted into a tubular furnace and fired in a humidified hydrogen stream at a temperature of 1600° C. for 1 hour to obtain an alumina atmospheric pressure sintered compact.

Table 1 shows the results of measuring the bulk density of the sintered body thus obtained, the hardness by a micro Vickers hardness tester, the KIc by an indentation method, and the thermal conductivity by a laser flash method. Further, when the obtained sintered bodies were subjected to X-ray powder diffraction, it was found that β-type silicon carbide was contained in all the examples.

Comparative Example 1 50% by weight of β-type silicon carbide with an average particle size of 0.8 μm, 48% by weight of α-type alumina with an average particle size of 0.4 μm, and 5i02 with an average particle size of 2.0 μm by weight. A 2% blend was prepared and pressureless sintered in the same manner as in Example 1. The results are shown in Table 1.

Example 2 5% by weight of 15 silicon carbide with an average particle size of 0.8 μm and 90% by weight of α-type alumina with an average particle size of 0.4 μm
or 95% and 5iOi, Mn with an average particle size of 2.0 μm
O or Mg, Of, each 5% by weight formulation 4
Various types were prepared, mixed, dried and molded in the same manner as in Example 1, and then fired in a humidified hydrogen stream at a temperature of 1500° C. for 2 hours to obtain an alumina atmospheric pressure sintered body. Table 2 shows the physical properties of the sintered body thus obtained.

Example 8 Table 8 shows the results when an alumina pressureless sintered body was obtained by changing the average grain size and crystal structure of silicon carbide and the average grain size of alumina. In addition, silicon carbide, alumina and 5iOz
The composition-to-weight ratios were constant at 2%, 96%, and 296, respectively, and the compounding, molding, and baking were performed in the same manner as in Example 2.

Comparative Example 2 α-type silicon carbide with an average particle size of 10 μm and an average particle size of 0.4
Table 8 shows the physical properties of an alumina pressureless sintered body sintered using μm α-type alumina.

Example 4 βFjj primary silicon with an average particle size of 0.8 μm in a weight ratio of 896, α-type alumina with an average particle size of 0.4 μm in a weight ratio of 9496, and 5i02t1″ with an average particle size of 2.0 μm in a weight ratio of 8 % mixture was prepared, mixed and molded in the same manner as in Example 1, and then calcined in a humidified hydrogen stream at 1500''C or 1600℃ for 1 hour to obtain an alumina atmospheric pressure sintered body. The physical properties are shown in Table 4.

Comparative Example 8 The same molded body as in Example 4 was heated at 1260 °C in a humidified hydrogen stream.
Table 4 shows the results of firing for 1 hour at a temperature of 2000°C or 2000°C.

Example 5 2% by weight of β-type silicon carbide with an average particle size of 0.8 μm, 96% by weight of α-type alumina with an average particle size of 0.4 μm, and 2% by weight of 5i02 with an average particle size of 2 μm. Table 5 shows the results of mixing and molding the mixture in the same manner as in Example 1, and then sintering the molded body in a nitrogen, argon, humidified hydrogen stream, and a mixture of alumina and silicon carbide.

Comparative Example 4 A molded body was obtained in the same manner as in Example 5, and then fired in an oxygen stream. Table 5 shows the results.

Table 1 (It) Kxa = Fracture resistance (Sintering temperature 1
As is clear from the results of the above examples The fracture toughness of conventional alumina solids is 8.0 MPa fi”2
In contrast, the fracture resistance of the alumina sintered body of the present invention is improved to 8.8 to 8.9 MPam.

As is clear from the above results, according to the present invention, the sintered body obtained by the pressureless sintering method in which silicon carbide is uniformly dispersed in the alumina sintered body has excellent mechanical strength and heat resistance. It has excellent conductivity and electrical insulation, and combines the excellent electrical properties of the alumina sintered body with the excellent thermal conductivity of the silicon carbide sintered body, resulting in particularly excellent fracture resistance and mechanical strength. It is held together.

Claims (1)

[Claims] 1. In a silicon carbide-containing alumina sintered body composed of a mixed composition containing 0.5 to 40% by weight of silicon carbide and the remainder being alumina as a main component. An alumina sintered body characterized by having a homogeneous composition in which the particle size of alumina is 10 μm or less and having particularly excellent fracture toughness (K_I_C). 2. Bulk density is 95% or more of the theoretical density, particularly preferably 9
7%, and the cracking toughness (K_I_C) is 3.5M.
The alumina sintered body according to claim 1, characterized in that Pam^1^/^2 or more. 8. The silicon carbide mainly has a β-type crystal structure, and its average particle size is 0.1 to 2.0 μm, and 0.5 to 2.0 μm.
It contains 5%, and the remainder has an average particle size of 0.1~
3. The alumina-based sintered body according to claim 1 or 2, characterized in that the alumina-based sintered body is composed of a composition whose main component is alumina having a 10 μm α-type crystal structure. 4. Silicon carbide powder 0.5 to 40% by weight and the remainder having a particle size of 1
After uniformly mixing a composition mainly composed of alumina powder of 0 μm or less and molding the uniformly mixed composition thus obtained into a desired shape, the molded body was heated to a temperature of 1300 to 190
A method for producing an alumina sintered body, characterized by sintering under normal pressure at a temperature of 0°C. 5. The silicon carbide powder mainly has a β-type crystal structure, and its average particle size is 0.01 to 2.0 μm.
．． It contains 5 to 5%, and the remainder has an average particle size of 0.
．． 5. The manufacturing method according to claim 4, wherein the starting material is a composition containing alumina having an α-type crystal structure of 05 to 10 μm as a main component. 6. The alumina sintered body obtained by the pressureless sintering has a bulk density of 95% or more of the theoretical density, particularly preferably 9.
7% or more, and the cracking toughness (K_I_C) is 3.
5. The manufacturing method according to claim 4 or 5, characterized in that it is 5 MPam^1^/^2 or more.