JPH0524931A - Aluminum nitride sintered compact - Google Patents

Abstract

PURPOSE:To provide the AlN sintered which is dense and has a high thermal conductivity by decreasing the oxygen content in the sintered compact while assuring the contents of one or >=2 kinds of the elements constituting auxiliary component selected from alkaline earth elements and rare earth elements necessary for yielding the dense sintered body. CONSTITUTION:This aluminum nitride sintered compact consists essentially of aluminum nitride and contains the oxides of one or >=2 kinds of the elements selected from alkaline earth elements and rare earth elements as the auxiliary components. The content of the elements constituting the auxiliary components in the above-mentioned aluminum nitride sintered compact is >=4wt.% and <=15wt.%, the oxygen content thereof is <=2.3wt.% and the thermal conductivity thereof is >=170W/m.K.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body, and more particularly to a high thermal conductivity aluminum nitride sintered body having a novel composition.

[0002]

2. Description of the Related Art Aluminum nitride (AlN) is highly expected as a heat-dissipating substrate due to its properties such as high electrical insulation, thermal expansion coefficient close to that of Si, and high thermal conductivity.
As a result, studies have been actively conducted to improve the thermal conductivity, which is very important as the characteristics of AlN, by examining the AlN raw material powder and the sintering method.

By the way, the AlN sintered body is currently mixed with, mixed with, and granulated by mixing AlN powder as a main component and a sintering aid such as an oxide of an alkaline earth element or a rare earth element as a secondary component. A general method is to form a compact and obtain a dense sintered body by pressureless sintering. In order to obtain a dense sintered body, it is necessary that the amount of alkaline earth or rare earth element is 4 wt% or more. And this sintering aid is
Densification is made possible by reacting with oxygen that is unavoidably mixed in the AlN powder during sintering to generate a liquid phase composed of a composite oxide of alumina and a sintering aid. Further, since the formation of this composite oxide fixes the impurity oxygen at the grain boundary as a result and suppresses the solid solution of oxygen in the grain,
It also contributes to the improvement of thermal conductivity.

[0004]

The addition of the sintering aid to the AlN raw material powder as described above enables the AlN sintered body to be densified and to have high thermal conductivity, but the Al having higher thermal conductivity can be used.
In order to obtain N sintered body (for example, ≧ 170 W / m · K), some problems still remain.

One of them is to reduce the amount of oxygen in the sintered body. Recent AlN raw material powder has a metal impurity content of 1
Although it has become extremely high in purity of 00 ppm or less, it still contains 0.5 to 2.0 wt% of oxygen. While these oxygen have the aspect of impurities necessary for maintaining the AlN raw material powder in a stable state, they form a solid solution in the AlN grains during the sintering process and hinder the high thermal conductivity of the AlN sintered body. Become a factor. Therefore, as described above, a sintering aid is added, and the impurity oxygen existing in the AlN raw material powder during the sintering process is fixed to the grain boundary as a composite oxide of alumina and the sintering aid to achieve high thermal conductivity. I am trying. However, this method can achieve a thermal conductivity of ≤170 W / m · K, but it is difficult to achieve ≥170 W / m · K. Because, thermal conductivity ≧ 170 W / m
-When K is achieved, the complex oxide existing at the grain boundary becomes a factor that hinders high thermal conductivity. Therefore, a method of removing the composite oxide by sintering in a reducing nitrogen atmosphere has been studied.

Examples of the sintered body produced by this method include those disclosed in JP-A-60-65768, 60-71575, and 60.
The sintered bodies described in JP-A-127267 and JP-A-62-270467 are known, and this sintered body is one or two selected from alkaline earth elements and rare earth elements.
When the amount of the element that constitutes one or more subcomponents is 4 wt% or more, the oxygen amount is 2.3 wt% or more, and the thermal conductivity is 17%.
It is difficult to achieve a high thermal conductivity of 0 W / m · K or more.

The present invention has been made in consideration of the above points. By reducing the amount of oxygen in the sintered body while ensuring the amounts of sub-component elements necessary for obtaining a dense sintered body. The present invention provides a dense and highly heat-conductive AlN sintered body.

[0008]

In order to obtain a dense sintered body, the present inventor adopts a method of sintering by adding a substance that reduces the complex oxide at the grain boundary at the time of sintering. The present invention has been completed by finding that it is possible to reduce the amount of oxygen in the sintered body while ensuring the required amount of sub-component elements. That is, the present invention is mainly composed of aluminum nitride, and is selected from alkaline earth elements and rare earth elements as a subcomponent.
In an aluminum nitride sintered body containing an oxide of one kind or two or more kinds of elements, the amount of the element constituting the subcomponent is 4 wt.
% Or more and 15 wt% or less, the amount of oxygen is 2.3 wt% or less, and the thermal conductivity is 170 W / m · K or more. According to the present invention, high thermal conductivity is realized by more completely preventing solid solution of oxygen in grains and reducing the alumina content in the composite oxide, that is, the amount of oxygen.

The composition of the grain boundary phase of the aluminum nitride sintered body of the present invention is A ₂ R ₄ O ₉ or R ₂ O, where A is aluminum, R is an alkaline earth element or rare earth element, and O is oxygen. Examples of the composition may include compositions such as ₃ or the like, or a composition in which these substances are mixed. Here, examples of the alkaline earth element include Mg, Ca, Sr, and Ba, and Ca is particularly preferable. As rare earth elements, Sc, Y, La, Ce, Sm, Eu, Tm, Tb, D
Examples thereof include y, Nd, Gd, Pr, Ho, Er and Yb, and Y and Dy are particularly preferable.

Next, a manufacturing method for obtaining the AlN sintered body of the present invention will be described. First, one or both of the alkaline earth element and the rare earth element are added to the AlN powder in a predetermined amount, and a substance that reduces the composite oxide at the grain boundary during the sintering process is added. Examples of substances that reduce the complex oxides at the grain boundaries include organic binders, 2a group, 3a group, and 4a.
Examples thereof include carbides made of group 5a, 6a, and rare earth elements (particularly preferably made of Ca, Y, and Dy), carbon, and substances that become carbon by heat treatment.
Then, it is crushed and mixed using a ball mill or the like, and granulated by a spray dryer or the like. Next, the granulated powder is molded into a predetermined shape and then heated to remove hydrogen and oxygen contained in the binder. Subsequently, the molded body is set in a sintering furnace and sintered in a nitrogen gas atmosphere. At this time, in the case of obtaining an AlN sintered body having a thermal conductivity of ≧ 170 W / m · K, the substance forming the grain boundary phase in the sintered body is sufficiently reduced and nitrided at 1400 ° C. to 2000 ° C. To reduce.

The constituent phases other than AlN in the AlN sintered body produced by the above-mentioned sintering were identified by X-ray diffraction, and as a result, the amount of R and the substance reducing the complex oxide was added, and the sintering conditions. , Only A ₂ R ₄ O ₉ exists, A ₂ R ₄ O ₉ and R
Coexistence ₂ O _3, there are cases such as the presence of only R ₂ O _3, all their alkali earth element, the amount of rare earth element 4w
t% or more and 15 wt% or less, oxygen amount is 2.3 wt% or less,
The thermal conductivity is 170 W / m · K or more.

[0012]

According to the present invention, an aluminum nitride sintered body containing aluminum nitride as a main component and an auxiliary component containing one or more elements selected from alkaline earth elements and rare earth elements as oxides is conventionally used. Although the grain boundary phase is composed with a smaller amount of oxygen compared to
Sufficient densification is achieved, and an aluminum nitride sintered body having high thermal conductivity can be obtained.

[0013]

EXAMPLES Next, examples of the present invention will be described.

Average particle diameter 0.8 μm, oxygen content 1.2 wt%
Of aluminum nitride powder _{Y 2 O 3, Dy 2 O} 3 was added 5,7,9Wt%, respectively alone or in mixed state,
Furthermore, polyvinyl alcohol is used as a binder in 3, 5,
After adding 7 and 9 wt%, it was crushed, mixed and granulated using a ball mill. Next, add this granulated powder to 1 ton / cm ²
It was press-molded under the pressure of. Subsequently, the molded body was heated to 500 ° C. in a nitrogen gas atmosphere to remove hydrogen and oxygen. Then, it was set in a sintering path, and sintered at a temperature of 1900 ° C. and 2000 ° C. for 1 to 5 hours in a nitrogen gas atmosphere for sintering.

The amounts of alkaline earth and rare earth elements in the thus obtained sintered body were measured by high frequency inductively coupled plasma emission spectroscopy. Further, the amount of oxygen was measured by an inert gas melting infrared absorption method. Furthermore, the thermal conductivity at room temperature was measured by the laser flash method. The results are shown in Tables 1 and 2 together with the relative density.

[0016]

[Table 1]

[Table 2] From Table 1 and Table 2, the AlN sintered body of this example contains alkaline earth and rare earth elements in an amount of 4 wt% to 15 wt% and an oxygen amount of 2 wt% or less. It can be seen that a high thermal conductivity of 170 W / m · K can be achieved with a smaller amount of oxygen relative to the amount of rare earth element.

[0017]

As described above, according to the present invention,
The amount of alkaline earth and rare earth elements, which are subordinate elements, is 4 wt.
% And 15 wt% or less, the oxygen content is 2 wt% or less, and the thermal conductivity ≧ 170 W / m · K can be simultaneously satisfied to provide an aluminum nitride sintered body.

Claims (1)

Claim: What is claimed is: 1. An aluminum nitride sintered body containing aluminum nitride as a main component and an oxide of one or more elements selected from alkaline earth elements and rare earth elements as a subcomponent. , The amount of elements that make up the subcomponent is 4w
t% or more and 15 wt% or less, oxygen amount is 2.3 wt% or less,
An aluminum nitride sintered body having a thermal conductivity of 170 W / mK or more.