JPH02212364A - Production of ceramic body of aluminum nitride - Google Patents

Abstract

PURPOSE:To obtain the ceramic body capable of low-temp. sintering and having high thermal conductivity by adding powders selected from respective powders of Si3N4, SiC, BN, and Al2O3 and a glass powder, each of which has a grain size one-half or less of the grain size of AlN powder, to the AlN powder and then subjecting the resulting powder mixture to compacting and to sintering. CONSTITUTION:One or more powders selected from respective powders of silicon nitride, silicon carbide, boron nitride, and alumina and a glass powder, each of which has a central grain size one-half or less of the central grain size of an aluminum nitride powder, are added to the aluminum nitride powder of 2-50mum central grain size. Subsequently, a proper binder is added to the above powders, and the resulting powder mixture is compacted and sintered, by which the ceramic body of aluminum nitride can be obtained. By this method, the green compact on which a wiring is previously printed by using a paste of copper, silver, etc., can be sintered together with the above material used in wiring simultaneously at a temp. not exceeding the melting point of the above material used in wiring. The resulting sintered compact has a thermal conductivity considerably higher than 3W/mK which is the thermal conductivity of the conventional alumina-glass substrate.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a fired body mainly made of aluminum nitride, which can be fired simultaneously with copper, silver, silver-palladium, gold, etc. and has high thermal conductivity. This relates to a manufacturing method.

[Conventional technology]

As electronic devices become more and more highly integrated, the amount of heat generated per unit area by the device is increasing, but because the thermal conductivity of the substrate is low, the heat generated by the device causes the temperature of the device to rise. It has become a problem that the increase in the number of semiconductor devices increases and impairs the functionality of devices, which is hindering further integration.

Therefore, there is a need for a substrate material with high thermal conductivity that can efficiently dissipate the heat generated by the device.Currently, aluminum nitride is attracting attention as a highly thermally conductive material, but its firing requires sintering aid. 1600-2000℃ even if using agent
high temperatures are required.

Generally, electronic circuits are made by printing a powder paste of copper, silver, silver-palladium, gold, etc. on an aluminum nitride substrate obtained by sintering at high temperatures to form wiring, and then below the melting point of the wiring material. It is manufactured by baking the wires, and then attaching the elements.

Furthermore, in order to more efficiently and inexpensively manufacture hybrid ICs using multilayer substrates with higher packaging density, alumina-glass substrates that can be fired at low temperatures are being manufactured.

For example, alumina and glass powders are mixed with a suitable binder, etc., a green sheet is made using the doctor blade method, and a powder paste of copper, silver, silver-palladium, gold, etc. is printed on it. A method has been adopted in which wiring is formed and fired at a temperature that does not melt the wiring material, and firing of the green sheet and baking of the wiring are performed simultaneously.

Among these wiring materials, copper has the highest melting point < 10
Since the temperature is 84°C, the firing must be at least 1050°C or lower.

Wiring is drawn with metal powder paste on the aluminum nitride molded body, which is molded without using glass by mixing a few percent of sintering aids such as yttrium oxide or calcium oxide, and is fired to sinter the aluminum nitride. It is possible to bake the wiring at the same time, but the sintering temperature is 1600-2000℃.
The metals that can be baked in the 0°C range are limited to tungsten and molybdenum, which have relatively high electrical resistance.

[Problem to be solved by the invention] The thermal conductivity of the alumina sintered body substrate is about 10 to 20 W/m, but the thermal conductivity of the alumina-glass composite fired body for simultaneous firing that can be fired at low temperature is difficult. The rate is at most 311/m
K, and cannot be said to have thermal conductivity sufficient to deal with the problem of heat radiation from the element.

On the other hand, when co-firing aluminum nitride compacts, it is easy to obtain aluminum nitride with a thermal conductivity of 100 W/m or more;
Because it requires a high temperature of ~2000°C, it not only requires an expensive furnace for high-temperature firing and a lot of energy, but also only tungsten or molybdenum can be used as the wiring material, and the electrical resistance of the wiring material is high. That is the problem.

Therefore, copper, silver, and silver, which have low electrical resistance, are used as wiring materials.
In order to use palladium-based materials, gold, etc., it is necessary to sinter the material below its melting point, and we investigated an aluminum nitride-glass composite as a material that can be sintered even at low temperatures and has high thermal conductivity.

The idea that an aluminum nitride composition that can be fired at low temperatures can be obtained by adding glass powder that forms a liquid phase below 1050°C to aluminum nitride powder, which has a higher thermal conductivity than alumina, has already been proposed. Although disclosed in JP-A No. 63-210043, it was not possible to stably obtain dense and high thermal conductivity.

[Means to solve the problem]

In order to solve this problem, we mixed aluminum nitride powder with other ceramic powders with high thermal conductivity, and as a result of repeated research and examination on the relationship between the particle size of these powders and the thermal conductivity of the fired body, we found that Aluminum nitride powder is mixed with powder of at least one selected from silicon nitride, silicon carbide, boron nitride, and alumina, whose center particle size is 172 or less than that of the aluminum nitride powder, and the mixture is heated to a liquid phase at 1050°C or less. It has been found that firing using a low melting point substance that produces as a sintering aid is effective in making the fired body denser and improving its thermal conductivity.

In general, it is easier to obtain fine powders from silicon nitride, silicon carbide, boron nitride, etc. than from aluminum nitride, and by mixing these ceramic powders with different center particle sizes with aluminum nitride, the bulk of the compact before firing can be increased. The density can be increased, and thereby a dense fired body with high thermal conductivity can be stably obtained.

That is, the present invention provides an aluminum nitride powder having a center particle size of 2 to 50 μm, and at least one selected from silicon nitride, silicon carbide, boron nitride, and alumina, and having a center particle size of 172 or less of the center particle size of the aluminum nitride powder. The present invention relates to a method for manufacturing an aluminum nitride ceramic body, which comprises adding powders of at least one type and a glass powder, molding, and then firing.

According to the present invention, a dense fired body with high thermal conductivity can be stably obtained.

The present invention will be explained in detail below.

In order to obtain a high bulk density, it is effective to use a combination of one or more types of ceramic powder having a center particle size smaller than that of the aluminum nitride powder.

However, if the largest center particle size of the ceramic powder to be mixed is larger than the center particle size of the aluminum nitride powder, which is 172, there will be no densification effect, so the center particle size ratio should be 172 or less, preferably 173 or less, and more preferably is less than 1/4.

In addition, even if the ratio of the center particle sizes is 172 or less, if the center particle size of the aluminum nitride powder is too small, it will be difficult to mix uniformly. The effect of improving bulk density may not be obtained.

Furthermore, if the aluminum nitride particles used are too large, molding becomes difficult, especially when trying to mold the aluminum nitride into a thin sheet of several hundred micrometers.

Therefore, the range of the median particle size of the aluminum nitride powder that can be used is 2 to 50 μm, preferably 3 to 30 μm, and more preferably 5 to 20 μm.

The proportion of the ceramic powder to be mixed with respect to the aluminum nitride powder is in the range of 10 to 50% by weight, preferably 20 to 40% by weight.

As for glass, borosilicate glass is used,
Lead borosilicate glass and phosphate glass can also be used.

For example, S10. is 40 to 70% by weight, B, 0. is 5~
20% by weight, ^120. is 5 to 15% by weight, MgO is 1
-10% by weight, and 1 to 5% by weight of Na and 0 can be used.

If the amount of glass powder added is too small, the amount of liquid phase generated during firing will not be densified, and if it is too large, the improvement of thermal conductivity will be inhibited, so the amount of glass powder added is determined based on the total powder. It is 10 to 70% by volume.

In order to produce a molded body, a method can be applied in which a suitable binder is added to the mixed powder, mixed in a ball mill or the like, and the slurry is molded into a sheet shape using a doctor blade method.

As the binder, polyvinyl butyral, polymethyl methacrylate, etc. can be used.

Alternatively, a mixed powder obtained by drying a slurry produced in a wet ball mill or by dry mixing may be molded by press molding.

Note that the present invention does not particularly limit the molding method.

The obtained molded body is printed with a paste of copper, silver, silver-palladium, gold, or the like.

There are no particular limitations on the printing method either.

The obtained compact is fired in air or in a non-oxidizing atmosphere at a temperature below the melting point of the material used for the wiring to obtain an aluminum nitride aluminum fired product.

EXAMPLES The present invention will be explained below with reference to examples, but the present invention is not limited to these examples.

The various physical properties were measured using the following equipment and method.

(Oxygen content) Impulse heating-infrared absorption method device: Horiba, Ltd. EMGA-2800 (particle size distribution) X-ray transmission sedimentation method device: Micromeritics Sedigr
aph 5000BT (thermal conductivity) Laser flash method device: Shinku Riko TC-7000 model Example 1 Silicon nitride with a center particle size of 1.2 μm in aluminum nitride powder with a center particle size of 3.1 μm and an oxygen content of 0.8% by weight The powder was added to the aluminum nitride powder at a weight ratio of 172, and mixed in a dry ball mill to obtain a mixed powder.

To the mixed powder, 5102-820s glass powder was mixed to make up 40% by volume of the total, and the mixture was heated to 300% by volume in a mold.
molded at a pressure of 1,500 g/cm'', and then 1500 g/cm
After performing rubber pressing of m', it was fired at 950°C for 30 minutes to obtain a fired body.

The thermal conductivity was IOW/m.

Example 2 Center particle size 3: 1 μm Silicon nitride powder with a center particle size of 0.7 μm was added to aluminum nitride powder with an oxygen content of 0.8% by weight at a weight ratio of 172 to the aluminum nitride powder, A mixed powder was obtained by mixing in a dry ball mill.

A sintered body was obtained in the same manner as in Example 1 by mixing Sin, -B, and Os-based glass powders to the mixed powder in an amount of 40% by volume of the total.

Thermal conductivity was 14 W/mK.

Example 3 40 parts by weight of silicon carbide powder having a center particle size of 0.3 μm was added to 60 parts by weight of aluminum nitride powder having a center particle size of 5.0 μm and an oxygen content of 0.7% by weight, and mixed in a wet ball mill.

To the mixed powder, Sl[12-Bz[13-based glass powder was mixed in an amount of 50% by volume of the total powder, and a fired body was obtained in the same manner as in Example 1.

The thermal conductivity was 21 W/m.

Example 4 Two alumina powders with a center particle size of 1.8 μm were added to aluminum nitride powder with a center particle size of 5.0 μm and an oxygen content of 0.7% by weight.
:1 weight ratio was added to obtain a mixed powder.

5i02-820. Glass powders were mixed in an amount of 50% by volume of the total, polyvinyl butyral was used as a binder, and mixed in a wet ball mill in a trichlene-ethanol mixed solvent system.

The obtained slurry was formed into a sheet by the doctor blade method, and after punching it into a square with a side of 2 inches using a die,
It was baked at 50°C for 30 minutes.

The thermal conductivity was 911/mK.

Comparative Example 1 40 parts by weight of silicon nitride powder having a center particle size of 2.2 μm was added to 60 parts by weight of aluminum nitride powder having a center particle size of 3.1 μm and an oxygen content of 0.8% by weight, and mixed in a wet ball mill.

A sintered body was obtained in the same manner as in Example 1 by adding SiO□-B203 glass powder to the mixed powder in an amount of 50% by volume.

Thermal conductivity was 5 W/mK.

Comparative Example 2 One part of silicon nitride with a center particle size of 1.5 μm was added to aluminum nitride powder with a center particle size of 1.5 μm and an oxygen content of 0°9% by weight.
They were added at a weight ratio of 1:1 and mixed using a dry ball mill.

5i02-820. A sintered body was obtained in the same manner as in Example 1 by mixing the glass powders in an amount of 50% by volume of the total.

The thermal conductivity was 2 W/m.

Comparative Example 3 One part of silicon nitride with a center particle size of 1.5 μm was added to aluminum nitride powder with a center particle size of 1.5 μm and an oxygen content of 0.7% by weight.
They were added at a weight ratio of 1:1 and mixed using a dry ball mill.

A 5i02-820+ type glass powder was mixed with the mixed powder so as to account for 50% by volume of the total powder, and a fired body was obtained in the same manner as in Example 1.

The thermal conductivity was 4 W/mK.

Comparative Example 4 5102-820S glass powder was mixed with aluminum nitride powder having a center particle diameter of 1.5 μm and an oxygen content of 0.9% by weight to make it 50% by volume of the whole, and a fired body was prepared in the same manner as in Example 1. I got it.

Thermal conductivity was 2W/mK.

〔Effect of the invention〕

According to the present invention, it is possible to co-fire with copper, silver, silver-palladium, gold, etc., and it can be fired at a low temperature of 1050°C or less, and the thermal conductivity of the conventional alumina-glass substrate is 3
It is possible to obtain a fired ceramic body mainly composed of aluminum nitride, which has a thermal conductivity considerably higher than W/mK.

Claims (1)

[Claims] Aluminum nitride powder with a center particle size of 2 to 50 μm,
The center particle size is 1/2 of the center particle size of the aluminum nitride powder.
A method for producing an aluminum nitride ceramic body, which comprises adding glass powder and at least one powder selected from the following silicon nitride, silicon carbide, boron nitride, and alumina, molding, and then firing.