JPS6355162A - High heat conductivity sintered body and manufacture - Google Patents

Abstract

(57) [Abstract] 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 a sintered body made of EIiO and AZN and a method for manufacturing the same, and particularly to a sintered body with high thermal conductivity and a method for manufacturing the same.

[Conventional technology]

E]10 and Mu/N are known as materials with strong covalent bonds, and since both are thermally and chemically stable materials, they have the potential to be used as heat-resistant structural materials and corrosion-resistant materials. It is the material. On the other hand, 81 (:! and AIIIN
Its crystal structure is similar to that of diamond, and pure single crystals have extremely high thermal conductivity.

By the way, in the field of semiconductor industry, large-scale integrated circuits 0. SI), etc., the elements constituting circuits such as semiconductor chips are being formed at an increasingly high density.

For this reason, it has become an extremely important technology to dissipate and dissipate the heat generated when semiconductor devices are operated. For this purpose, GaAs
There is a growing demand for materials that have a coefficient of thermal expansion close to that of semiconductor materials such as semiconductor materials, and also have high thermal conductivity.

In response to the above-mentioned demands, a sintered body containing SiOIc Ego as a material with good heat dissipation properties was developed in JP-A-57-
It is disclosed in Japanese Patent No. 2591. This material has a high thermal conductivity of approximately 270 w/m·k at room temperature, is an electrical insulator, and has a thermal expansion coefficient close to that of a single crystal of 81. In addition, AlN sintered body is known as a material with good heat dissipation properties and a coefficient of thermal expansion of 81, which is close to that of GaAs single crystal, and is promising as a material for heat dissipation. Value is 20 at room temperature
Below 0'W/m°. Also, the Journal of American Ceramics (J.
Oeram.

Eioc, ) Volume 66, No. 5, Nos. C-40 to C-41
(1985) discusses the influence of hot pressing temperature on the thermal diffusivity and thermal conductivity of SiC-AlN materials, but the thermal conductivity is 100 W/m・k.
Only the following values are obtained. Furthermore, JP-A-58-91
No. 059 and Japanese Unexamined Patent Publication No. 59-49474 also disclose a sintered body in which a sintering aid is added to an 810-ZN material, and a method for producing the same. All of these have thermal conductivity values of at most 150 W/m''k or less.

[Problem that the invention seeks to solve]

The above-mentioned through, SiO sintered body, human IN sintered body, 5iO-
Both AlN-based sintered bodies are materials with extremely excellent properties. However, since BeO is added to the SiC sintered body, consideration must be given to the harmfulness of Boo when handling it. Furthermore, for AlN sintered bodies and 810-mu/N-based sintered bodies, it is desired to improve the thermal conductivity of the sheath layer.

An object of the present invention is to provide a material whose thermal expansion coefficient is close to that of Sl or GaA3 single crystal, a material with high thermal conductivity, and which does not use harmful substances, and a method for producing the same.

[Means for solving problems]

To summarize the present invention, the first invention of the present invention relates to a highly thermally conductive sintered body, which contains 50 to 80% by weight of SiO and 50 to 20% by weight of IN, and has a density of 5%. 1
2/α3 or more, thermal conductivity at 20℃ is 300 W/
It is characterized by being greater than or equal to m.k.

The second invention of the present invention relates to a method for manufacturing a highly thermally conductive sintered body, and the second invention relates to a method for manufacturing a highly thermally conductive sintered body, and the second invention relates to a method for manufacturing a highly thermally conductive sintered body, and the Be contained in the α-type or β-type SiO crystal acts as an acceptor or donor.
, B, l, N are α1 weight or less, and the amount of other cation impurities is 11 weight or less (however, free g1, free SiO
2. Si with an average particle size of 10 μm or less (excluding free C)
JUN powder containing 50 to 80% by weight of C powder, the amount of impurity oxygen in the powder is 1% by weight or less, the content of field ion impurities is α5% by weight or less, and the average particle size is 1.0 μm or less. After mixing and molding 50 to 20% by weight, 10 M
Sintering is carried out under a pressure of more than Pa, and the density is 51971M”
The above is characterized in that a sintered body having a thermal conductivity at 10°C of 500 W/nl' or more is obtained.

The above purpose is to combine high-purity A/ and N, since each alone has high thermal conductivity and a coefficient of thermal expansion close to that of Sl or GaAs single crystal. By producing a compact sintered body at a low temperature that does not diffuse a large amount into the interior of the body, and without impairing the high thermal conductivity that each of 810 and IN individually has (achieved by obtaining a sintered body made of SiO and AlN). be done.

In the present invention, SiC is Be, B, A/ which acts as an acceptor or donor contained in the EliO crystal.
.

N is α1% by weight or less, and the amount of other cationic impurities is 1% by weight.
2 weight or less (however, free Si, free EliO, free C
Use fine powder with an average particle size of 10 μm or less. SiC originally has a crystal structure similar to diamond, and a pure single crystal has extremely high thermal conductivity.

Further, the thermal conductivity of SiO decreases as the amount of impurities contained in SiC increases. Particularly electrically active 81
The thermal conductivity varies greatly depending on the content of impurities that act as acceptors and donors in the zero crystal, and the smaller the content of these impurities, the higher the thermal conductivity. In addition, B10 has a thermal expansion coefficient of 8
1 It also has the characteristic of being close to a single crystal.

On the other hand, in AeN, the amount of impurity oxygen in the powder is 1 weight or less,
The amount of cationic impurities is 15% by weight or less and the average particle size is 1.
Use a fine powder with a density of 0μ or less. MutN also has a crystal structure similar to diamond, and pure single crystal is known to have high thermal conductivity, although it is not as high as 810-. Further, htx has a characteristic that its coefficient of thermal expansion is close to that of GaAs single crystal.

The gIC powder used in the present invention contains Be that acts as an acceptor or donor in EliO crystals.

The reason why the content of B, Al, and H is 11% by weight or less is that these impurities have a particularly large effect on the thermal conductivity of SiO, and as the amount of these impurities increases, the thermal conductivity decreases. be. However, if the amount of these impurities is [L1 weight - or less], a sintered body with high thermal conductivity can be obtained. Also, if the amount of other cationic impurities increases, will the thermal conductivity increase? In order to reduce the amount, it is necessary to keep it below a certain amount. If the amount of other cationic impurities is 12% by weight or less, a sintered body with high thermal conductivity can be obtained. SiO powder has an average particle size of 10μ
Use a fine powder that is less than fake. If the average particle size of the SiO powder is too large, it becomes impossible to obtain a sintered body with a close surface, resulting in a sintered body with low thermal conductivity. If you try to obtain a dense sintered body using EliO powder with a large average particle size, the sintering temperature will need to be extremely high, and the resulting sintered body will have a significantly low thermal conductivity. It becomes something.

In the AlN powder used in the present invention, the amount of impurity oxygen is 1% by weight or less, and the amount of cationic impurities is 15% by weight.
The reason for the following is that if the amount of these impurities is greater than the above amount, the thermal conductivity of the obtained sintered body will be significantly reduced. Further, as the AlN powder, fine powder having an average particle size of 1.0 μm or less is used. If the average particle size of the AtN powder is too small, a dense sintered body cannot be obtained, and the result is a sintered body with low thermal conductivity.

If you try to obtain a dense sintered body using IN powder with a large average particle size, the sintering temperature will need to be extremely high, and the resulting sintered body will have a significantly low thermal conductivity. It ends up.

When producing a highly thermally conductive sintered body, it is necessary to pay attention to the following points. The first
is the blending ratio of SiO and MujN.

It is preferable that the blending ratio of SiC and AZBi is 50 to 80% by weight of SiC and the balance is AlN. When the amount of EliO is less than 50% by weight, it is 250W/I at room temperature! l-
This is because a sintered body having a large thermal conductivity exceeding k cannot be obtained. Furthermore, if the amount of 81C exceeds 80% by weight, the sintering properties will be significantly deteriorated, making it impossible to obtain a dense sintered body, resulting in a sintered body with low thermal conductivity. If you try to obtain a dense sintered body by adding more than 80% by weight of SiC, you will have to sinter at a high temperature, and for this reason, the resulting sintered body will be a sintered body with low thermal conductivity. It becomes a body.

As a pretreatment for obtaining a sintered body, a binder is added to the mixture of EIiC and A/H to facilitate molding. Various organic substances are known as binders. As a binder for manufacturing the sintered body of the present invention, a sintered body having sufficient desired performance can be obtained by using a conventionally known organic binder, but water is used as a solvent to dissolve the binder. I don't like that. That is, water used as a solvent reacts with A4N during powder mixing, and AlN is oxidized, making it impossible to obtain a sintered body with high thermal conductivity. The EllG and AlN powders must be thoroughly mixed to form a uniform mixture. In particular, E10
This is because if there are powder aggregates, this part will not be densified during sintering. Various methods are known for mixing, but
In order to obtain the sintered body of the present invention, a sintered body having the desired performance can be obtained by mixing the ingredients by a conventionally known method. However, if impurities are mixed during mixing, a sintered body with high thermal conductivity cannot be obtained, so it is preferable to use a material made of SiC, AjN, or EliO-mu/N for mixing. In order to obtain a uniform compact from the mixed powder, it is preferable to granulate it by an appropriate method.

If the granulation operation is carried out using conventionally known techniques, a sintered body having the desired performance can be obtained. mixture,
The granulated powder mixture is then preformed. Even if the preforming is performed by a conventionally known method, a sintered body having the desired performance can be obtained.

There are several important conditions when sintering with compacts. The atmosphere during sintering must be non-oxidizing. Specifically, in vacuum, hydrogen, nitrogen, helium,
Sintering is performed in an atmosphere of neon, argon, etc. If sintering is performed in an oxidizing atmosphere, SiC and iN, especially IN, will be severely oxidized, making it impossible to obtain a sintered body with excellent thermal conductivity. Sintering temperature is also extremely important. The sintering temperature needs to be 1750°C or higher. This is because otherwise, a dense sintered body cannot be obtained, and the obtained sintered body has a low thermal conductivity. Also, the upper limit of sintering temperature is 1900℃
It is. If the sintering temperature is high (e.g. 1900°C), the obtained sintered body will be sufficiently densified but the AI and N will be
If the amount of iO diffused into the crystal lattice is large, the thermal conductivity of the sintered body will be significantly reduced. Sintering temperature is 1
When the temperature is 900° C. or lower, as long as the sintering time is not unnecessarily long, diffusion of At and N into the SiO crystal is small, and a sintered body with high thermal conductivity can be obtained. The compact is pressurized during sintering. There are several methods for pressurizing the molded body, but the pressurizing pressure must be 10 MPa or more. Otherwise, a sufficiently dense sintered body will not be obtained, resulting in a sintered body with low thermal conductivity. A preferable example of the pressurizing method is a hot press method or a hot isostatic press method, but other methods may also be used.

The optimal value of the sintering time is determined by a combination of the various conditions described above, but the time is selected to be at least sufficient for the density of the sintered body to be 51 f/2 or more. This is because if the density of the sintered body is low, a sintered body with high thermal conductivity cannot be obtained.

The sintered body manufactured so as to satisfy the various conditions described above has a density of 51 f/era or more and a thermal conductivity of 300 W/m·k or more at 20°C.

〔Example〕

The content of the present invention will be explained below with reference to specific examples, but the present invention is not limited to these examples.Example 1 The SiO powder used as a starting material has the following properties: Average particle size α5μ crystals Form α Impurity amount (weight) Free silicon α86 Free silicic acid 2.10 Free carbon α50 Boron 0. OOl Aluminum 0.008 Iron 0. o 06 Titanium Q, 12 Vanadium Q, 005 Chromium α005 Nickel α003 Nitrogen 0.008 In addition, the starting material AlN powder has the following properties: Average particle size cL8μm Crystal system Hexagonal impurity amount (wt%) Oxygen l180 Carbon 0.15 Silicon Q,10 Iron α08 Magnesium α05 Other cations Q,01 The sintered body was manufactured by the following procedure. EliC powder'5
0. O? and iN powder 1i0? was weighed out, placed in a pot made of SiC, and mixed in a ball mill for 20 hours using a pole made of EIiO. Next, 20 m of polybutyl alcohol dissolved in n-butyl alcohol (0%, 5%) was added to the above powder mixture, followed by ball mill mixing for 1 hour, and then the n-butyl alcohol was volatilized. The powder mixture was then passed through a 64 mesh sieve to eliminate coarse granulated powder. The granulated powder was then put into a mold having an inner diameter of 50 mm, and a load of 100 MPa was applied to form a compact. Next, the molded body was placed in a graphite mold and set in a furnace. After the furnace is evacuated, the molded body in the graphite mold is
15 at 1850℃ by increasing the temperature while applying a load of 0MPa.
A sintered body was obtained by holding for a certain period of time.

Further, sintered bodies having the compositions shown in Table 1 were manufactured by the same procedure as described above. No. 5 shown in Table 1 has the same composition as described above. Table 1 also shows the characteristics of the obtained sintered body.

Table 1 As is clear from Table 1, when the amount of 5iCO is 50 to 80% by weight, the density of the sintered body is 51 f/lTN” or more, and 2
A sintered body having a thermal conductivity of 500 W/m·k or more at 0° C. can be obtained.

Example 2 The SiO and A7'N powders used as starting materials were those described in Example 1, and the SiC powder was 50%. Of and AjN powder 15.
02 was weighed out and hot pressed in the manner described in Example 1 to obtain a sintered body. In this example, sintered bodies were manufactured by varying the temperature during hot pressing.

Table 2 shows the properties of the obtained sintered body. If the temperature of hot pressing is 1750 to 1900℃, the sintered body becomes dense with a density of 11 r/m" or more, and the thermal conductivity at 20℃ is improved. A rate of 500 W/m·k or more can be obtained.

Table 2 Example 5 The starting materials SiO and 1M powder were those described in Example 1, and SiO powder 5Q, Of and AlN powder 1all were used.
IIF was weighed out and hot pressed in the manner described in Example 1 below to obtain a sintered body. In this example, the hot press temperature was 1900° C., the hot press load was varied, and sintering was performed for 15 hours.

Table 3 shows the properties of the obtained sintered body, and if the hot press load is 10 MPa or more, the sintered body has a density of 11.
? It is denser than 7cm'' and has a thermal conductivity of S OOW/m·k or more at 20°C.

Table 5 Example 4 The SiC and AlN powders used as starting materials were those described in Example 1, and the SiO powder was 50%. OP and IN powder 110f
was weighed and hot pressed in the manner described in Example 1 below to obtain a sintered body. In this example, the temperature and time of hot pressing were varied.

Table 4 shows the characteristics of the obtained sintered body. If the hot pressing temperature is as low as 1750° C., a dense sintered body with high thermal conductivity cannot be obtained even if the hot pressing time is prolonged.

Further, if the hot pressing temperature is higher than 1900° C., a sintered body with high thermal conductivity cannot be obtained even if the hot pressing time is shortened.

Table 4 Example 5 The starting materials SiO and AlN powders described in Example 1 were used, and EliC! Powder 510? and AlN powder 1K
Of was weighed and hot pressed in the manner described in Example 1 below to obtain a sintered body. In this example, the atmosphere of the hot press was changed. Specifically, various gases were introduced into the furnace, which had been evacuated in Example 1, up to atmospheric pressure. The types of gases used were hydrogen, nitrogen, argon, helium, neon, and a mixed gas of 80% nitrogen and 20% hydrogen. The sintered bodies obtained in any of the atmospheres are shown in Table 1.
It had the same characteristics as No.

Example 6 The SiC and AlN powders as starting materials were those described in Example 1, and B10 powder 5Q, Of and AlN powder 1&
The l1lIP was weighed out, and a molded body was obtained in the manner described in Example 1 below. The molded body was placed in a capsule made of Pyrex glass, evacuated, and then sealed.

The capsules were then heated and pressurized using a hot air static press method. Argon gas was used as the atmosphere gas, and [lL5
A sintered body was obtained by heating and pressing for a period of time. The obtained sintered body is the first
It had the same characteristics as No. 3 in the table.

Example 7 The starting EIiO powder has an average particle size, free Si, free C1 of 810. Powders with the same properties as described in Example 1 were used except for different amounts, and the same AlN powder as described in Example 1 was used. The sintered body was prepared using SiO powder 3 in the same manner as described in Example 1.
αOf and Mu/N powder 150f were weighed, mixed, molded, and then hot pressed. The sintered body of this example is the raw material S
A sintered body was manufactured under the same conditions as in Example 1 except that the iC powder was different.

Table 5 shows the characteristics of the obtained sintered body. When the average particle size of the raw material EIiC powder is 10 μm or less, a dense sintered body with high thermal conductivity can be obtained.

Table 5 Example 8 The starting material 1llio powder was the same powder as described in Example 1, and the AlN powder had the same properties as described in Example 1 except for the difference in average particle size. Using the powders, 5i(j powder 3αOf and iN powder 15.Of were weighed and hot pressed in the same manner as described in Example 1) to obtain a sintered body.

Table 6 shows the properties of the obtained sintered bodies. If the average particle size of the raw material AlN powder is 1.0 μm or less, a dense sintered body with high thermal conductivity can be obtained.

Table 6 Example 9 The SiO powders listed in Table 7 were used as starting materials, and the S1C powder 5α02 and the AtN powder 1 described in Example 1 were used.
aOf was weighed and then hot pressed in the same manner as described in Example 1 to obtain a sintered body.

Tables 7 and 8 show the characteristics of the obtained sintered bodies. The sintered bodies are all dense with a density of 3.1r/α3 or more, but Be,
If the amounts of B, A/, and H are 0.1 wt % or less, and the amount of other cationic impurities is n, 2 wt % or less, a sintered body with high thermal conductivity can be obtained.

Table 8 Example 10 The starting material EliO powder was the powder described in Example 1, and the Mu/N powder was a powder having the characteristics described in Table 9.

Table 9 SiO powder 3αO2 and AlN powder 1i02 were weighed and hot pressed in the same manner as described in Example 1 to obtain a sintered body. Table wJ10 shows the characteristics of the obtained sintered body. All sintered bodies are densified to more than 1 f/lJ, but if the impurity oxygen in the AlN powder is less than 1% by weight and the content of cationic impurities is less than 15% by weight, the thermal conductivity will be lower. A large sintered body can be obtained.

Table 10 Example 11 The 8LO powder used as a starting material had the following characteristics.

Average particle size Q, 5μ Crystal form β Impurity amount (wt%) Free silicon LL50 Free silicic acid 132 Free carbon 138 Aluminum 0. OO2 Iron [1004 Nitrogen 11006 In addition, the same powder as described in Example 1 was used as the IN powder as the starting material. SiO powder SαO2 and AtN powder 1&0? was weighed out and then hot pressed in the same manner as described in Example 1 to obtain a sintered body. The sintered body was densified to a density of 525 l/m' and had a thermal conductivity of 310 W/m-k at 20°C.

Example 12 In order to investigate the mechanical properties of the 1310-AeN sintered body of the present invention, the bending strength and fracture toughness values were measured at 20°C. For comparison, the bending strength and fracture toughness values of the EIiO sintered body manufactured in Comparative Example 1, which will be described later, were also measured. Table 11 shows the bending strength and fracture toughness values of each material. As can be seen from Table 11, the bending strength of the material of the present invention is slightly lower than that of the comparative example, but the fracture toughness value is approximately 1.5 times higher. Therefore, the 5iO-AtN-based sintered body according to the present invention has high resistance to destruction, and is advantageous when used as a structural material.

Table 11 Example 15 The SiC-AlN sintered body of the present invention has a microstructure in which 810 crystal grains and htx crystal grains are mixed.

SiOFj, is made of extremely hard material compared to AlN. Day 10 of the present invention - When machining is performed using an AlN-based sintered body and a diamond whetstone, the SiC crystal grains serve as a sharpening for the whetstone during machining, making the machining very easy. That is, the machining resistance when machining the EliC-AlN sintered body of the present invention is about 1/2 of that when machining the E10 sintered body. In addition, when processing for a long time,
Although it is necessary to dress the diamond grinding wheel from time to time, when processing the SiO-AtN based sintered body of the present invention, S
Compared to processing iO sintered bodies, the dressing interval of the grindstone can be increased approximately three times, allowing efficient processing.

Comparative Example 1 The starting raw materials SiG powder and AlN powder were the same as those described in Example 1, and SiO powder 49, 05
' and AlN powder 1. Of was weighed and then hot pressed in the same manner as described in Example 1 to obtain a sintered body. Furthermore, in this comparative example, sintered bodies were obtained by changing the temperature of the hot press. Table 12 shows the properties of the obtained sintered bodies.

The sintered body is not densified unless the hot press temperature is 1950° C. or higher, and the densified sintered body has a low thermal conductivity because the hot press temperature is high.

Table 12 [Effects of the Invention] According to the present invention, a sintered body is provided which has a coefficient of thermal expansion of 81, which is close to that of a GaAs single crystal, has a high thermal conductivity, and does not use any harmful substances. Ru.

Claims (4)

[Claims] 1. 50-80% by weight of SiC and 50-2% of AlN
Contains 0% by weight, density is 3.1g/cm^3 or more, 20
A highly thermally conductive sintered body having a thermal conductivity of 500 W/m·k or more at °C. 2. Be, B, Al, and N acting as acceptors or donors contained in α-type or β-type SiC crystal are 0.1
50 to 50% of SiC powder with an amount of other cationic impurities of 0.2% by weight or less (excluding free Bi, free SiO_2, and free C) and an average particle size of 10 μm or less.
80% by weight, the amount of impurity oxygen in the powder is 1% by weight or less, and the content of cationic impurities is 0.5% by weight or less,
After mixing and molding 50 to 20% by weight of AlN powder with an average particle size of 1.0 μm or less, sintering is performed in a non-oxidizing atmosphere at a temperature of 1750 to 1900°C and a pressure of 10 MPa or more to improve the density. is 3.1g/cm^3 or more, 20
A method for producing a highly thermally conductive sintered body, the method comprising obtaining a sintered body having a thermal conductivity of 300 W/m·k or more at °C. 3. The method for producing a highly thermally conductive sintered body according to claim 2, wherein the sintering is performed by hot pressing in a non-oxidizing atmosphere. 4. The method for producing a highly thermally conductive sintered body according to claim 2, wherein the sintering is performed by hot isostatic pressing in a non-oxidizing gas atmosphere.