JPH02221162A - Production of aluminum nitride-based 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 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 is what we are trying to provide.

[Conventional technology]

As the integration of electronic devices continues to advance,
Accordingly, the amount of heat generated by the device per unit area is increasing, but because the thermal conductivity of the substrate is low, the heat generated by the device can cause the temperature of the device to rise, causing problems in the device's function. This has become a problem and 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 elements, and aluminum nitride is currently attracting attention as a highly thermally conductive material.

However, even if a sintering aid is used, a high sintering temperature of 1,600 to 2,000°C is required.

In general, one-element circuits are produced by printing wiring on an aluminum nitride substrate obtained by sintering at high temperatures and printing a powder paste of copper, silver, silver-palladium, gold, etc., at a temperature below the melting point of the wiring material. It is manufactured by attaching the elements after baking and baking the wiring.

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, a green sheet is prepared by mixing alumina and glass powders with an appropriate binder, etc., using the doctor blade method, and then printing a powder paste of copper, silver, silver-palladium, gold, etc. on top of the green sheet. A method has been adopted in which wiring is formed and fired at a temperature at which the wiring material does not melt, and firing of the green sheet and baking of the wiring are performed simultaneously.

Among these wiring materials, copper has the highest melting point of 1084
℃, it must be fired at at least 1050°C or lower.

without using substances that form a liquid phase at low temperatures;
Wiring is drawn with metal powder paste on a molded aluminum nitride body formed by adding a few percent of sintering aids such as Jum or calcium oxide, and then fired to simultaneously sinter the aluminum nitride and bake the wiring. However, metals that can be fired at a sintering temperature in the range of 1600 to 2000°C are
It is limited to tungsten or molybdenum, which have relatively high electrical resistance.

[Problem to be solved by the invention]

An alumina sintered substrate has a thermal conductivity of about 10 to 20 W/mK, but an alumina-glass composite sintered body for simultaneous firing that can be fired at a low temperature has a thermal conductivity of 3 W/m at most.
It cannot be said that the thermal conductivity is sufficient to deal with the problem of heat dissipation of the element.

In addition, when co-firing a molded body of aluminum nitride, the thermal conductivity of aluminum nitride is 100 W/m.
can be easily obtained, but sintering requires 1600 ~
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. has become a problem.

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

The idea that an aluminum nitride composition that can be fired even at low temperatures can be obtained by adding glass powder to aluminum nitride powder, which has a higher thermal conductivity than alumina, was already disclosed in JP-A-63-210043. However, it was not possible to obtain stable, dense, and high thermal conductivity.

[Means to solve the problem]

In order to solve this problem, we have repeatedly researched and considered the relationship between aluminum nitride powder and the thermal conductivity of its fired product, and have found that the amount of oxide layer present on the surface of aluminum nitride powder is the thermal conductivity of the fired product. found that there is a relationship between

In order to obtain high thermal conductivity by adding several percent of a sintering aid and sintering at a high temperature of 1,600°C or higher, it is said that it is better to have a lower oxygen content in the raw material, aluminum nitride powder. ing.

However, it has been found that when mixed with glass powder and fired at 1050° C. or lower, higher thermal conductivity can be obtained if the oxygen content is higher to some extent.

Therefore, it is necessary to use aluminum nitride powder with a high oxygen content or to sinter it in air at about 1000°C.
By oxidizing aluminum nitride powder by some method to increase the oxygen content, a fired body with high thermal conductivity can be obtained.

That is, the present invention relates to a method for producing an aluminum nitride fired body, which comprises adding glass powder to aluminum nitride powder having an oxygen content of 2 to 15% by weight, molding, and then firing.

According to the present invention, an aluminum nitride fired body having high thermal conductivity can be obtained.

The present invention will be explained in detail below.

In the present invention, experiments using aluminum nitride powder with various oxygen contents revealed that the oxygen content was at least 2% by weight or more, preferably 2.5% by weight or more, and more preferably 3% by weight or more. .

Furthermore, if the oxygen content is too high, the oxidized layer on the particle surface inhibits heat conduction, making it impossible to obtain the high thermal conductivity inherent to aluminum nitride.

Therefore, if the oxygen content exceeds 15% by weight, the thermal conductivity of the fired body decreases, so the oxygen content is 15% by weight or less, preferably 12% by weight or less, and more preferably 8% by weight or less.

As for the glass, borosilicate glass is used.

For example, 40 to 70% by weight of 5102, B20. is 5
~20% by weight, ^1,0. A composition comprising 5 to 15% by weight of MgO, 1 to 10% by weight of MgO, and 1 to 5% by weight of Na2O can be used.

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

To obtain a molded body, a suitable binder or the like is added to aluminum nitride and glass powder, mixed in a ball mill or the like, and the slurry is formed into a sheet shape using a doctor blade method.

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

Further, a mixed powder obtained by drying a slurry produced in a wet ball mill, or by dry mixing the slurry can also be molded by press molding.

The present invention does not particularly limit the molding method.

The resulting molded body is printed with a powder paste of copper, silver, silver-palladium, gold, etc., and then heated in the air or nitrogen atmosphere at a temperature below the melting point of the material used for wiring, for example 1050°C for copper. Thereafter, it is fired to obtain an aluminum nitride fired body.

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 5QQQεT (thermal conductivity) Laser flash method device: Shinku Riko TC-7000 model Example 1 Aluminum nitride powder with a center particle size of 1.5 μm and an oxygen content of 0.8% by weight was oxidized at 850°C in air. A powder with an oxygen content of 2.1% by weight was obtained.

To the aluminum nitride powder, add 50% by volume of Sl-8203 type glass powder, and heat it in a mold to 30% by volume.
(Molded at a pressure of 1Kg/c++l, further 1500K
A rubber press of g/cm was performed.

The obtained molded body was fired at 950°C for 30 minutes.

The thermal conductivity of the fired body was log/mK.

Example 2 Aluminum nitride powder with a center particle size of 1.5 μm and an oxygen content of 0.8% by weight was oxidized in air at 850° C. to obtain a powder with an oxygen content of 5.7% by weight.

5it), -82[] for the aluminum nitride powder
A sintered body was obtained in the same manner as in Example 1, except that 3-series glass powder was added at a concentration of 50% by volume.

The thermal conductivity of the fired body was 19 W/mK.

Example 3 Aluminum nitride powder with a center particle size of 1.3 μm and an oxygen content of 1.8% by weight was oxidized in air at 850° C. to obtain a powder with an oxygen content of 9.6% by weight.

5i02-820. Add glass powder to 40% by volume and mold to 30% by volume.
0Kg/c++! molded at a pressure of 1,500 kg.
/cIIi rubber press was performed.

The obtained molded body was fired at 950°C for 30 minutes.

The thermal conductivity of the fired body was LOW/mK.

Example 4 Aluminum nitride powder with a center particle size of 1.3 μm and an oxygen content of 1.8% by weight was oxidized in air at 850° C. to obtain a powder with an oxygen content of 13.3% by weight.

3102-82[+3
A fired body was obtained in the same manner as in Example 3 except that glass powder was added at a concentration of 40% by volume.

The thermal conductivity of the fired body was 9 W/mK.

Example 5 Aluminum nitride powder with a center particle size of 3.0 μm and an oxygen content of 1.4% by weight was oxidized in air at 1000° C. to obtain a powder with an oxygen content of 3.5% by weight.

For the aluminum nitride powder, S+02-8203
Add system glass powder to 50% by volume, add triolein as a dispersant and polyvinyl butyral as a binder in a tricrene-ethanol mixed solvent system,
A slurry was obtained by mixing in a ball mill.

Using the slurry, a tape was cast by a doctor blade method, and after drying, it was punched out to obtain a molded product.

The obtained molded body was fired at 950°C for 30 minutes.

The thermal conductivity of the fired body was 19 W/mK.

Example 6 Aluminum nitride powder with a center particle size of 3.0 μm and an oxygen content of 1.4% by weight was oxidized in air at 1000° C. to obtain a powder with an oxygen content of 7.9% by weight.

A sintered body was obtained in the same manner as in Example 5 by adding 5I02-BzO3 glass powder to the aluminum nitride powder at a concentration of 50% by volume.

The thermal conductivity of the fired body was 17 W/mK.

Comparative Example 1 S10□-B20. A fired body was obtained in the same manner as in Example 1 by adding glass powder of 50% by volume.

The thermal conductivity of the fired body was 2W/1TIK.

Comparative Example 2 5iOa-820s glass powder was added to 50% by volume of aluminum nitride powder with a center particle size of 3.0 μm and an oxygen content of 1.4% by weight, and a fired body was produced in the same manner as in Example 1. Obtained.

The thermal conductivity of the fired body was 4 W/mK.

Comparative Example 3 Aluminum nitride powder with a center particle size of 1.5 μm and an oxygen content of 0.9% by weight was oxidized in air at 1000° C. to obtain a powder with an oxygen content of 25.4% by weight.

5i02-821:h for the aluminum nitride powder
Example 1
A fired body was obtained in the same manner as above.

The thermal conductivity of the fired body was 3 W/mK.

〔Effect of the invention〕

According to the present invention, the nitrided substrate can be fired at a low temperature of 1050°C or less, which allows co-firing with copper, silver, silver-palladium, gold, etc., and has higher thermal conductivity than conventional alumina-glass substrates. A fired body mainly made of aluminum can be obtained.

Claims (1)

[Claims] A method for producing an aluminum nitride fired body, which comprises adding glass powder to aluminum nitride powder having an oxygen content of 2 to 15% by weight, molding, and then firing.