JPS61286267A - Manufacture of aluminum nitride base sintered body - 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 Application Field] The present invention relates to a method for producing a high-density aluminum nitride sintered body, and in particular, the present invention relates to a method for manufacturing a high-density aluminum nitride sintered body, and in particular, the present invention relates to a method for manufacturing a high-density aluminum nitride sintered body. The present invention relates to a method for manufacturing an aluminum nitride sintered body having a high yield.

[Conventional technology]

In recent years, advances in electronic technology have led to higher density and higher speed calculation functions for electronic devices. As a result, wiring boards are required to have high integration and high reliability, especially those with characteristics such as low thermal expansion, high thermal conductivity, excellent dimensional stability, and long-term stability. has been done.

Various ceramic materials, such as sintered bodies of alumina, beryllia, tricarbide, or aluminum nitride, are known as wiring boards having the above-mentioned characteristics.
Among these, aluminum nitride sintered body is a material that has particularly excellent properties in terms of electrical insulation, thermal conductivity, coefficient of thermal expansion, mechanical strength, etc. among the properties required as a wiring board material, and is attracting attention. There is.

By the way, aluminum nitride itself is difficult to sinter and become dense, but recently sintering methods using various sintering aids have been proposed.

For example, JP-A-58-55877 discloses [(a) aluminum nitride powder, (b) at least one compound selected from calcium oxide, barium oxide, strontium oxide, and compounds that become oxides of these upon firing. and (6) carbon powder or powder of a substance that becomes carbon upon firing, is molded and then sintered. An invention is disclosed.

Japanese Unexamined Patent Publication No. 58-82072 describes a ``aluminum nitride sintered body comprising aluminum nitride as a main component, containing lithium or a lithium-containing substance, and having a density of 90% or more of the theoretical density.'' An invention is disclosed.

JP-A-58-82078 discloses an invention relating to ``a sintered body characterized by adding 0.1 to 30% by weight of boron nitride to aluminum nitride.''

[Problem that the invention seeks to solve]

By the way, according to the invention described in JP-A-58-55877, it is possible to obtain an aluminum nitride sintered body having high density, electrical insulation properties, and low thermal expansion. The disadvantage is that the thermal conductivity of the resulting sintered body is not very high.

Further, according to the inventions described in JP-A-58-82072 and JP-A-58-82078, both are aluminum nitride sintered bodies having high density, electrical insulation, low thermal expansion, and high thermal conductivity. However, there is no description of an aluminum nitride sintered body having a low dielectric constant that is suitable for use in applications such as hybrid IC substrates on which printed circuits are formed at high density.

Unlike the previously known aluminum nitride sintered bodies as described above, the present invention has electrical insulation properties, low thermal expansion properties, high thermal conductivity,
The object of the present invention is to provide a method for producing an aluminum nitride sintered body suitable for use as an electronic circuit board, which is excellent in all properties such as low dielectric property.

[Means to solve the problem]

According to the present invention, at least one boron-containing additive selected from the following group (a) is added to 100 parts by weight of aluminum nitride powder in terms of boron content of 0.
The above object is achieved by a method for manufacturing an aluminum nitride sintered body, which comprises adding 1 to 30 parts by weight, homogeneously mixing, and then firing in a non-oxidizing atmosphere to obtain a density of 2.75 f/14 or more. I can do that.

(a) Metal boron, boron carbide, boron aluminum mini 1
7A, boron phosphide, lanthanum boride, amorphous boron.

Next, the present invention will be explained in detail.

According to the present invention, at least one boron-containing additive selected from group (a) is added to 100 parts by weight of aluminum nitride powder in terms of boron content of 0.
．． It is necessary to add 1 to aO parts by weight. The reason is that the aluminum nitride sintered body obtained by adding a boron-containing additive as a sintering aid and sintering has electrical insulation properties,
It has extremely excellent mechanical properties required for electronic circuit board materials such as low thermal expansion and high conductivity, and also has low dielectric properties required in applications where high-density printed circuits are formed, such as high-priority IC boards. The reason for limiting the amount of the boron-containing additive added to 0.1 to 30 parts by weight in terms of boron content is that the added amount of the boron-containing additive is 0.1 to 30 parts by weight. If the amount is less than 1 part by weight, the effect as a sintering aid cannot be fully exhibited and it is difficult to obtain a high-density sintered body, whereas if the amount is more than 30 parts by weight, the sintering aid will be difficult to obtain. This is because not only does it become difficult to produce a high-density sintered body because it inhibits sintering, but also the properties of the obtained sintered body deteriorate.

The reason why an aluminum nitride sintered body with a low dielectric constant can be produced by using the boron-containing additive 'fI as a sintering aid is that aluminum nitride Aluminum nitride twisted ram powder, which is the main raw material for quality sintered bodies, contains oxygen or oxides that are unavoidably contained during the manufacturing or handling process. Conventional aluminum nitride sintered bodies had a high dielectric constant due to segregation in the grain boundary layer, but according to the present invention, boron is contained in the boron-containing additive added as a sintering aid. Boron easily oxidizes and diffuses in the sintering temperature range, and also combines with oxygen to form suboxides that easily volatilize, reducing the oxide layer that forms at the grain boundaries of aluminum nitride sintered bodies. This is thought to be because it is possible to

According to the present invention, as the boron-containing additive, at least one selected from metallic boron, boron carbide, aluminum boride, boron phosphide, lanthanum boride, and amorphous boron is used. According to the present invention, it is desirable that the aluminum nitride powder and the boron-containing additive are mixed in a homogeneous dispersion as much as possible, and the aluminum nitride powder has an average particle size of 20 μm or less, It is preferable to use a powder having an average particle size of 50 μm or less as the boron-containing additive.

In addition to the method of mixing the boron-containing additive in the form of fine powder, it can also be used by coating the surface of the aluminum nitride powder by, for example, chemical vapor deposition.

According to the present invention, the product formed from the aluminum nitride powder and the boron-containing additive is formed in a non-oxidizing atmosphere and densified to a density of 2.75 f or more.

According to the present invention, the temperature of the formed body is 1500 to 2000°C.
Fired within the temperature range of The reason is that the temperature is 150
This is because if the temperature is lower than 0°C, it is difficult to produce a dense sintered body, while if the temperature is higher than 2000″C, the crystal grains of the sintered body once sintered tend to become coarse.

Incidentally, the firing in the present invention can be performed by either a pressureless sintering method or a pressure sintering method.

According to the present invention, the atmosphere in which the compact made of the mixture of aluminum nitride powder and a boron-containing additive is fired is also extremely important in obtaining the sintered compact with a low dielectric constant, which is the object of the present invention. The compact is fired in a non-oxidizing atmosphere. The non-oxidizing atmosphere is advantageously, for example, at least one of argon, helium, hydrogen, nitrogen, etc., or vacuum. Note that among the non-oxidizing gases used as the non-oxidizing atmosphere, nitrogen reacts with boron in the boron-containing additive to produce boron nitride, so the reaction between boron and oxygen in aluminum nitride is completed. It is recommended that you refrain from using it until you do so.

The reason for this is that boron nitride is an extremely stable compound, and once boron nitride is formed, its effectiveness in removing oxygen from aluminum nitride is significantly reduced, making it difficult to produce a sintered body with a low dielectric constant. This is because it becomes difficult.

The aluminum nitride sintered body produced by the method of the present invention has an electrical resistivity at room temperature of 1018 ohm α or more, a thermal conductivity at room temperature of 0.15 d/α·s9 or more,
The average coefficient of thermal expansion from room temperature to 400″C is 4.O
The specific dielectric constant (I MHz) is within the range of X 10'' to 6.OX 1G-'/''C and is 7.5 or less, making it excellent for use as an electronic circuit board.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 100 f of aluminum nitride powder with an average particle size of 20 μm and an oxygen content of 1.5% by weight, 5 g of metal boron powder with an average particle size of 20 μm, and 400 pieces of benzene were charged into a silicon carbide pole mill. After mixing for 24 hours, the mixture was lyophilized.

An appropriate amount of this dried material was collected, molded, and then pressure sintered to obtain a sintered body.

The temperature was raised at a rate of 35°C/min from room temperature to 1500"O, held at 1500°C for 30 minutes, and then further raised at a rate of 10°C/min until a maximum temperature of 1900° It was held at C for 1 hour.

The atmosphere was heated under reduced pressure from room temperature to 1500°C.
At 0°C, the temperature was finally reached to I x 10-'Torr. In the high temperature range above 1500″C, a nitrogen stream was used at atmospheric pressure.

Molding pressure is no pressure from room temperature to 1500"C, 1500"
In the temperature range higher than °C, a pressure of 300 kW/eJ was applied.

The obtained sintered body has a density of 8.02 f/-, an electrical resistivity at room temperature of 8 x 1014 Ωα, and a quasi-conductivity at room temperature of 0.85 ed/ex see ”(:j
, the average coefficient of thermal expansion from room temperature to 400℃ is 4.2
X 10-'/”C1 relative permittivity (IMHg) is 4.9
It had extremely excellent properties as a substrate for electronic circuits.

Furthermore, the average bending strength of this sintered body was 88.8 kg/-, which was relatively high, and it was recognized that it could be sufficiently applied to use as a structural material.

Example 2, Comparative Example 1 Sintered bodies were obtained in the same manner as in Example 1, except that the blending ratio of aluminum nitride powder and metal boron powder was changed as shown in Table 1.

The properties of the obtained sintered body are shown in Table 1.

As can be seen from the results shown in Table 1, it was difficult to obtain a high-density sintered body in Comparative Example 1-1, in which the amount of metal boron added was small, whereas Comparative Example 1-1, in which the amount of metal boron added was large.
The sintered body of -2 was inferior in thermal conductivity and dielectric constant.

Comparative Example 2 A sintered body was obtained in the same manner as in Example 1, except that about 2.5 g of boron nitride was added in place of metallic boron so that the amount of boron added was almost the same as in Example 2-2.

The properties of the obtained sintered body are shown in Table 2.

From the results shown in Table 2, the thermal conductivity is 0.15 at/e.
x see "Q, dielectric constant was 8.0, sb, and the amount of boron added was inferior to Example 2-2, which had approximately the same amount.

Table 2 Example 8 A sintered body was obtained in the same manner as in Example 1, except that the firing atmosphere was fired in a nitrogen stream at atmospheric pressure without reducing the pressure.

The properties of the obtained sintered body are shown in Table WIJ2.

As can be seen from the results shown in Table 2, the thermal conductivity is 0.20 rd/cm met''C1 dielectric constant compared to the sintered body of Example 1 which was fired at 1500°C or less under reduced pressure. was slightly inferior at 7.4.

Example 4, Comparative Example 8 Sintered bodies were obtained in the same manner as in Example 1, except that the firing temperature, time, and molding pressure during firing were changed as shown in Table 3.

Table 8 shows the relationship between the sintering conditions and the density of the obtained sintered bodies.

Table 8: The sintered body of this example has an electrical resistance of 1012 Ω1 or more at room temperature and a thermal conductivity of 0.15 at room temperature.
cd/am sec"C or more, average thermal expansion coefficient from room temperature to 400"C is 6. OX 10-@/”C or less, and the relative dielectric constant (I MHz) was 7.5 or less. On the other hand, Comparative Example 8 in which the firing temperature was raised to 2100°C
In the sintered body, aluminum nitride was volatilized at a significantly low density.

Example 5 A sintered body was obtained in the same manner as in Example 1, except that metal boron was replaced with an amount that was approximately the same as 1.

All of the obtained sintered bodies had characteristics suitable as substrates for electronic circuits.

〔Effect of the invention〕

As described above, the present invention is superior to conventionally known aluminum nitride sintered bodies in all properties such as electrical insulation, low thermal expansion, high thermal conductivity, and low dielectricity. It is possible to produce an aluminum nitride sintered body which is extremely suitable as a substrate for electronic circuits, and is extremely useful industrially.

Claims (1)

[Claims] 1. For 100 parts by weight of aluminum nitride powder, the following (
a) At least one boron-containing additive selected from group 0.1 to 30 parts by weight in terms of boron content is added and mixed homogeneously, followed by firing in a non-oxidizing atmosphere;
A method for producing an aluminum nitride sintered body, characterized in that it has a density of 2.75 g/cm^3 or more. (a) metallic boron, boron carbide, aluminum boride,
Boron phosphide, lanthanum boride, amorphous boron. 2. The manufacturing method according to claim 1, wherein the aluminum nitride powder has an average particle size of 20 μm or less. 3. The manufacturing method according to claim 1 or 2, wherein the boron-containing additive is a powder having an average particle size of 50 μm or less.