JPH02192467A - Production method of aluminum nitride-hexagonal boron nitride 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 Field of Industrial Application The present invention is a material that has high thermal conductivity in a specific plane and that can be used as an IC substrate material, an IC package material, or an electrically insulating heat dissipating material. The present invention relates to a method for manufacturing an aluminum nitride-hexagonal boron nitride yarn sintered body, which is an insulator.

Conventional technology Aluminum nitride-hexagonal boron nitride yarn composite sintered body is
Because it is a machinable ceramic with high thermal conductivity, it has a wide range of applications as a ceramic for electronic materials and structural materials, and numerous patent applications have been filed.

For example, in JP-A-80-195059, aluminum nitride particles made of aluminum nitride, boron nitride, group IIa metal, [[[group a metal compound] and having polygonal fracture surfaces are filled, and the grain boundaries are filled with aluminum nitride particles. There is a description of a sintered body in which a thin layer of boron nitride is present in part or all of the body. A feature of this sintered body is that it can be cut at high speed using ordinary tools.

It states that it is a so-called machinable ceramic composite sintered body.

In addition, Japanese Patent Application Laid-Open No. 80-195080 describes the particle size and purity of aluminum nitride powder when manufacturing this composite sintered body.
JP-A-81-83572 discloses the range of temperature increase rate during sintering.

Furthermore, Japanese Patent Laid-Open No. 131-3131110 discloses a method for manufacturing a composite sintered body under nitrogen gas pressure.

Furthermore, patent application No. 82-3298, which is an invention of the present inventors,
28 contains 40 to 95 parts by weight of boron nitride, 5 to 80 parts by weight in total of aluminum nitride and aluminum oxynitride, and 0.01 to 5 parts by weight of at least one of a calcium compound and a yttrium compound. There is a description regarding a composite sintered body and a method for manufacturing the same using a pressure heating method. The characteristics of the sintered body include thermal conductivity, electrical insulation, low coefficient of thermal expansion, low dielectric constant, and excellent machinability. The thermal conductivity of these sintered bodies is 40~
A value of about 135W/Otori/K has been reported.

On the other hand, as an example of improving the thermal conductivity in a specific plane of the sintered body, there is a
There are 55132. In the specification, the anisotropy of thermal conductivity is 20 to 80 parts by weight of hexagonal boron nitride, 80 to 20 parts by weight of aluminum nitride, and 0.2 to 5 parts by weight of a sintering aid. and anisotropy in which the higher thermal conductivity value is 150 W/m or more, and the anisotropy obtained by hot pressing at 1700 to 2200 ° C. There is a description of the method for manufacturing the sintered body.

The higher value of thermal conductivity is 153 to 258 W/l.
111K, low method is reported to be 16-80W/IIIK, and other features include good machinability. However, when considering the use for IC substrates and IC packages, it goes without saying that materials with higher thermal conductivity are required in order to improve the efficiency of heat dissipation from semiconductor chips.

Problems to be Solved by the Invention In view of these problems, an object of the present invention is to provide a method for manufacturing an aluminum nitride-boron nitride yarn composite sintered body that has higher thermal conductivity within a certain plane.

Means for solving the problems, that is, the present invention provides (1) aluminum nitride 95-5
After uniaxially molding a mixed powder consisting of 5 to 95 parts by weight of hexagonal boron nitride, and 0.2 to 5 parts by weight of a sintering aid at a pressure of 5 MPa or more, the axial direction of the uniaxial molding was The present invention relates to a method for producing an aluminum nitride-hexagonal boron nitride yarn sintered body, which comprises filling a die with a molded body so as to match the pressing axis direction of hot press sintering and hot press sintering.

Further, (2) the present invention relates to a method for producing the aluminum nitride-hexagonal boron nitride yarn sintered body, wherein the average particle size of the hexagonal boron nitride powder bundle used as a raw material is IILm or more.

action The present invention will be explained in detail below.

According to the manufacturing method of the present invention, after uniaxially molding the raw material mixed powder at a pressure of 5 Pa or higher, it is filled into a die so that the pressing axis direction of the uniaxial molding matches the pressing axis direction of hot press sintering. Then hot press sintering is performed.

By performing uniaxial forming at a pressure of 5 MPa or more as a pre-process of hot press sintering, it is possible to orient and stack the boron nitride particles during this uniaxial forming, and after that, the processing of the uniaxial forming By filling the uniaxial compact into a graphite die and hot press sintering so that the pressure axis direction matches the pressure axis direction of hot press sintering, the orientation of boron nitride particles that occurred during uniaxial forming It can promote lamination.

As a result, a sintered compact with greater anisotropy is obtained compared to the case where the powder is directly filled into a graphite die or uniaxially formed at 5) lPa without vortex and then hot press sintered. Therefore, the thermal conductivity in the direction perpendicular to the hot press pressure axis (uniaxial molding pressure axis) is significantly improved. On the other hand, the thermal conductivity in the direction parallel to the hot press pressure axis (uniaxial molding pressure axis) slightly decreases but hardly changes.

The molding pressure for uniaxial molding is preferably 5 MPa or more. 5MP
If it is less than a, orientation and stacking of boron nitride particles during uniaxial molding will hardly occur, and the effect of increasing thermal conductivity due to uniaxial molding will not be recognized. In addition, the higher the molding pressure is, the more pronounced the orientation and stacking of boron nitride particles is, which is preferable, but above a certain pressure, the degree of orientation and stacking of boron nitride particles becomes less noticeable as the pressure increases. It is not a good idea to use a higher pressure than necessary.If the particle size of boron nitride particles is about lpm,
Approximately Pa is one guideline for the upper limit of the molding pressure.

The raw material mixed powder contains 95 to 5 parts by weight of aluminum nitride, 5 to 95 parts by weight of hexagonal boron nitride, and 0.2 parts by weight of a sintering aid.
~5 parts by weight.

In a composition where aluminum nitride is around 95 parts by weight,
Although the effect of improving thermal conductivity due to orientation and lamination of boron nitride is not so great, a sintered body with relatively high bending strength, Vickers hardness, etc., and a relatively high coefficient of thermal expansion can be obtained.

Furthermore, in a composition in which aluminum nitride is around 5 parts by weight, a remarkable effect of improving thermal conductivity is observed due to the orientation and lamination of boron nitride.

Further, a sintered body having this composition has a not so great bending strength, but a sintered body having extremely good cutting workability.

If the mixing ratio of the raw material powder exceeds these ranges and the content of aluminum nitride exceeds 95 parts by weight, the effect of orientation and stacking of boron nitride particles cannot be expected because the amount of hexagonal boron nitride contained is small. In addition, when the content of aluminum nitride is less than 5 parts by weight, although an improvement in thermal conductivity is observed due to the oriented spring lamination of boron nitride particles, a large amount of sintering aid is required to obtain a dense sintered body. agent is required,
For this reason, it is difficult to obtain a sintered body with high thermal conductivity, making it unsuitable for use as IC substrates, packaging materials, and the like.

The particle size of the boron nitride particles used as a raw material is preferably IBm or more.If powder with a zero particle size of less than 1 gm is used, oriented Φ stacking of boron nitride particles during uniaxial molding and hot press sintering will not occur significantly. First, the sintered body becomes more isotropic. In particular, the effect of orientation and stacking of boron nitride particles by the uniaxial molding of the present invention is hardly realized.The particle size of the boron nitride particles mentioned here refers to the size of the flaky boron nitride particles in the plane direction. It is not the size in the thickness direction.

The raw material mixed powder contains 0.2 to 5 parts by weight of a sintering aid in addition to aluminum nitride and boron nitride.

If it is less than 0.2 parts by weight, no effect as a sintering aid can be expected, and if it is more than 5 parts by weight, the thermal conductivity of the sintered body will decrease, which is undesirable. The conductivity, especially the higher value, is sensitive to the amount of sintering aid added, so when trying to produce a sintered body with high thermal conductivity, the amount added must be determined carefully. be.

Sintering aids include calcium oxide, calcium carbide,
Known materials such as calcium cyanamide, yttrium oxide, and yttrium carbide can be used. however,
When considering the orientation and stacking of boron nitride particles, it is possible to react with the oxides that are inevitably generated on the surface of aluminum nitride powder or boron nitride powder and generate a liquid phase at a lower temperature. Calcium-based compounds are more preferable in terms of their properties.

For mixing these powders, dry mixing or wet mixing using a known method such as a ball mill can be used, but wet mixing is preferable. The dispersion medium used for wet mixing is not particularly limited, and alcohols, hydrocarbons, and ketones are commonly used. Since water may react with the nitride powder to generate ammonia, it is better not to use it unless it is particularly necessary.

After the raw material mixed powder is uniaxially molded as described above, it is filled into a graphite die so that the pressing axis direction of the uniaxial molding matches the pressing axis direction of hot press sintering, and hot press sintering is performed. , hot press sintering is a well-known method for producing boron nitride-aluminum nitride sintered bodies.
It is carried out under conditions of 0° C. and about 5 to 50) IPa.

If the temperature is lower than 1700°C, a sintered body with desired physical properties, especially high thermal conductivity, cannot be obtained, and if it exceeds 2200°C, it is not economical, and if the pressure is lower than 5 NPa, the sintered body becomes densified. If the pressure exceeds 50 MPa, the dies that can be used during hot pressing are limited. The holding time at the maximum temperature can be selected to be up to 4 hours; holding times longer than 4 hours are not economical, although the properties of the sintered body are not significantly affected.

The atmosphere during sintering is preferably an inert gas atmosphere such as nitrogen gas to prevent oxidation of the nitride. However, if certain sintering aids are used, sintering in a vacuum may not be possible. By doing this, these sintering aids or reaction products between the sintering aid and other components may be released out of the system relatively quickly, and as a result, the thermal conductivity of the sintered body may be improved. In such cases, it is preferable to sinter in vacuum.

The present invention will be explained below using examples.

Example 1 A hexagonal boron nitride powder bundle with an average particle size of 6 ILm, aluminum nitride powder with an average particle size of 1.8 μm or less, and calcium carbide as a sintering aid were mixed in the proportions shown in Table 1, and the mixture was mixed in a ball mill. Wet mixing was performed using acetone as a solvent for 24 hours.

After drying the obtained powder, uniaxial molding was performed under the conditions shown in Table 1, and it was filled into a graphite die so that the pressing axis direction of the uniaxial molding coincided with the pressing axis direction of the hot press. minute 2
Hot press sintering was performed at 1800° C. for 2 hours under a pressure of 40 MPa in a nitrogen stream. Cooling rate is 10℃/s
It was set as in.

The bulk density and thermal conductivity of the obtained sintered body were measured. Since the sintered body has anisotropy, the thermal conductivity values are also shown in the direction perpendicular to and parallel to the hot press pressure axis. The bulk density was measured by the Archimedes method using water, and the thermal conductivity was measured by the laser flash method. For comparison, the table also shows the values of the sintered bodies when uniaxial molding was performed at low pressure and when uniaxial molding was not performed.

The results are shown in Table 1. As shown in Table 1, in any composition with an aluminum nitride content of 95 to 5 parts by weight, in a sintered body uniaxially formed at a pressure of 5 MPa or more, No uniaxial molding or 5 MP
Thermal conductivity value in the direction perpendicular to the hot press pressure axis (higher value) compared to the sintered body uniaxially formed at less than a
It can be seen that the power is improved to 5 to 50 W/m-. On the other hand, the value in the direction parallel to the pressure axis of the hot press (lower value)
Although it may be slightly lower, there is almost no change in the bulk density value, and there is almost no difference in the bulk density value between the two.

Example 2 Orthogonal boron nitride raw material was made into powder with an average particle size of 10 gm,
In addition, yttrium oxide was added as a sintering aid, and hot press sintering was performed in the same manner as in Example 1.

The bulk density and thermal conductivity measurement results of the obtained sintered bodies are shown in Table 1.For all compositions, for the sintered bodies uniaxially formed at a pressure of 511 [Pa or higher and for the other sintered bodies. , almost the same results as in the example were obtained, and the higher thermal conductivity value was improved to 20 to 35 W/■.

(Left below) Effects of the Invention As stated above, the method for producing an aluminum nitride-boron nitride thread composite ceramic sintered body of the present invention involves the following steps:
)! After uniaxial forming at a pressure of Pa or more, the molded body is filled into a die so that the pressure axis during forming coincides with the pressure axis of hot press sintering, and hot press sintering is performed.
This makes it possible to improve the thermal conductivity in the direction perpendicular to the pressure axis of the hose breath.

Therefore, it is suitable as a method for manufacturing an aluminum nitride-boron nitride yarn composite sintered body with high thermal conductivity that can be used as a material for IC substrates and IC packages, and is extremely useful industrially.

Claims (2)

[Claims] 1. A mixed powder consisting of 95 to 5 parts by weight of aluminum nitride, 5 to 95 parts by weight of hexagonal boron nitride, and 0.2 to 5 parts by weight of a sintering aid is uniaxially formed at a pressure of 5 MPa or more, and then An aluminum nitride-hexagonal boron nitride based sintered body characterized by filling a die with a molded body and hot press sintering so that the pressing axis direction coincides with the pressing axis direction of hot press sintering. Production method. 2. The method for producing an aluminum nitride-hexagonal boron nitride sintered body according to claim 1, wherein the hexagonal boron nitride powder used as the raw material has an average particle diameter of 1 μm or more.