JPH0274565A - Aluminum nitride based calcined compact - Google Patents

Abstract

PURPOSE:To provide Si3N4 calcined compact enabling low-temperature calcination, having high thermal conductivity and suitable in mass production by using compounds of Ca and Y together at specific amounts and controlling O, Si and Fe content to specific values. CONSTITUTION:The aimed calcined compact consisting essentially of AlN, simultaneously containing Ca compound and Y compound as auxiliary and each containing the former at an amount of 0.005-4wt.% as CaO and the latter at an amount of 0.2-10wt.% as Y2O3. In the aimed calcined compact, the purpose is achieved by each controlling amount (excess amount of 0) of 0 obtained by subtracting amount of 0 in the auxiliary from total amount of 0, amount of Si and amount of Fe to <=3wt.%, <=0.7wt.% and <=0.5wt.%. In this case, when either one of Ca and Y compounds is deviated from the above-mentioned range, high thermal conductivity is not attained. When excess amount of 0 exceeds 3wt.%, thermal conductivity is largely lowered. Further, it is required that especially Si and Fe is kept to the above-mentioned range among cation impurities contained in the calcined compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aluminum nitride sintered body having high thermal conductivity.

[Background technology]

In recent years, with the development of LSI, insulating materials with high thermal conductivity have been required for mounting semiconductor elements that generate a large amount of heat, such as highly integrated circuits, power transistors, and laser diodes.

Conventionally, beryllium oxide (Bed)-based sintered bodies have been used as such ceramic materials with high thermal conductivity, but their range of use is limited due to their toxicity.

Therefore, aluminum nitride (AβN), which has high thermal conductivity, is stable, has high high-temperature strength, and has good electrical insulation, is being used as a highly thermally conductive substrate material to replace beryllium oxide.

Aluminum nitride powder is difficult to sinter, and it is difficult to sinter it alone. Therefore, a sintered body is manufactured by adding a sintering aid to the aluminum nitride raw material powder. As a binder, compounds of group Ua metals (alkaline earth metals) or group A metals (Y and rare earth metals) of the periodic table, such as typically Y2O or CaO, can be added alone. Proposed. (Unexamined Japanese Patent Publication No. 60-12
(No. 7267, Japanese Unexamined Patent Publication No. 50-23411) [Problems to be solved by the invention] However, when Y2O is added alone, an aluminum nitride sintered body having high thermal conductivity can be obtained, but the raw material It is expensive and has a high firing temperature of about 1850° C. or higher, which is disadvantageous for mass production. On the other hand, when CaO is added alone, the raw material is inexpensive and the firing temperature is low at about 1750° C. or less, which is advantageous for mass production, but has the problem of low thermal conductivity.

[Object of the Invention] An object of the present invention is to provide an aluminum nitride sintered body that can be fired at low temperatures, has good thermal conductivity, and is suitable for mass production.

[Means for solving problems]

In view of the above-mentioned problems, the present inventor has conducted extensive research and has found a sintered body made of aluminum nitride as a main ingredient, to which a certain amount of a Ca compound and a Y compound are added as auxiliary agents, and then fired. It has been found that a sintered body in which the oxygen (Si and Fe) (J) in the sintered body is controlled to a certain amount or less has a high thermal conductivity, and can be fired at a high density and at a low temperature.

According to the present invention, in an aluminum nitride sintered body mainly composed of aluminum nitride, at least C is used as an auxiliary agent.
Using compound a and compound Y, the Ca compound is 0.005 to 4% by weight as CaO, and the Y compound is 0.00% by weight as Y2O3.
Contained at a ratio of 2 to 10% by weight, and the remaining oxygen amount after subtracting the oxygen amount in the auxiliary agent from the total oxygen amount of the sintered body is 3% by weight or less, and the Si content is 0.7% by weight or less The above object is achieved by controlling the Fe content to 0.5% by weight or less.

The invention will now be explained with the following examples.

One feature of the present invention is that Ca compound and y
The point is that the compound is used at the same time. Ca compound is CaO
The proportion of Y compound is 0.2 to 10% by weight as Y2O3, preferably Ca00.
01-2.7 Shigesato%, y2o, 2.0-8.5% by weight
Contains S in total. As a result, higher heat conductivity is achieved due to the synergistic effect of both than when each is added alone, and low-temperature firing is possible. However, even if either of the Ca compounds exceeds the above range, High thermal conductivity cannot be obtained.

Another feature of the present invention is that the amount of oxygen remaining after subtracting the amount of oxygen mixed in from the auxiliary component from the total amount of oxygen present in the sintered body (hereinafter simply referred to as excess oxygen amount) is 3% by weight or less. ,
In particular, it is 2.6% by weight or less. This excess oxygen is mainly mixed in as impurities and adsorbed oxygen from aluminum nitride raw materials, etc., or mixed in during processing such as crushing during the manufacturing process.This excess oxygen greatly contributes to thermal conductivity, and the amount of excess oxygen increases. If it exceeds 3% by weight, the thermal conductivity will decrease significantly.

Furthermore, another feature of the present invention is that among the cationic impurities mixed into the sintered body, particularly the Si content and the Fe content are simultaneously limited to a specific amount or less. These are also easily mixed in from the raw material powder or during the grinding process, but according to the present invention, the Si content is reduced to 0.7% by weight or less, especially 0.2% by weight.
% by weight or less, Fe content is 0.5% by weight or less, especially 0.5% by weight or less.
High thermal conductivity can be achieved by controlling the content to 2% by weight or less.

According to the present invention, in the aluminum nitride sintered body, C
A compound amount, Y compound amount, excess oxygen amount, Si content, F
By setting the e content within the above-mentioned range, a thermal conductivity of 100 w/m'' or more can be achieved.

The Ca compound used as an auxiliary agent in producing the aluminum nitride sintered body of the present invention is Cab.

CaF 21 CaC2l CaB6 , CaCl z
1CaCO31CaCNz, CaJz, Y compounds include Y2O2, YF3. YN, YHz, YC, Y
Examples include B6, each with a CaO conversion of 0.005~
It is mixed with aluminum nitride powder at a ratio of 4% by weight, or 0.2 to 10% by weight in terms of Y2O3.

A binder may be added to the mixed powder if desired, and the mixture may be molded using a known molding method. Specifically, uniaxial press, rubber press, doctor blade molding, casting molding, etc. may be employed.

The molded body is then fired, and by using the composition described above, firing can be performed at 1600 to 1850°C. The atmosphere during firing is a non-oxidizing atmosphere such as nitrogen, hydrogen, Ar, Hele, or a mixture thereof, and the firing means include normal pressure firing, hot press firing, nitrogen gas pressure firing, etc. However, from the viewpoint of mass production, normal pressure firing is preferable.

The aluminum nitride sintered body thus obtained is a highly dense body with a relative density of 95 or more, but according to the present invention, in order to obtain high thermal conductivity, the amount of excess oxygen, Si content,
It is necessary to control the Fe content to a predetermined amount or less.

To do this, first, aluminum nitride raw material powder must have an oxygen content of 3% by weight or less, a Si content of 0.7% by weight or less, and a Fe
It is necessary to use a material with a content of 0.5% by weight or less, and to avoid contamination during grinding, the lining of the grinder,
Alternatively, the grinding media may be made of, for example, high-purity alumina, plastic (resin), wear-resistant silicon nitride, silicon carbide, or hc.
When mixing or wet mixing, it is necessary to take measures such as increasing the viscosity of the slurry as much as possible and shortening the time.

The invention will now be explained with the following examples.

[Example Table 1] Various aluminum nitride powders with an average particle size of 0.5 to 3 μm, an oxygen content of 2.8% by weight or less, a Si content of 0.6% by weight or less, and an Fe content of 4.5% by weight or less A Ca compound and a Y compound as shown in the following were added and blended, and the mixture was wet-mixed in methanol using a ball mill.

Paraffin wax, stearic acid, and a small amount of binder were added to this and mixed at a molding pressure of 1000 kg.
/cm2.

Next, the obtained molded body was subjected to a binder removal treatment at 300° C. for 2 hours by a conventional method, and then fired under the firing conditions shown in Table 1 in a nitriding atmosphere.

The relative density of the obtained sintered body was measured according to the Archimedes method, and the thermal conductivity was measured using the laser flash method.

In addition, the amount of excess oxygen is determined by measuring the total amount of oxygen using LECO's simultaneous oxygen and nitrogen analyzer. It was calculated by subtracting it from the amount of oxygen. Furthermore, the Si content and Fe content in the sintered body were determined by ICP method.

In addition, as a comparative example, aluminum nitride raw material powders with different amounts of excess oxygen, Si content, and Fe content were used, and the production was performed in the same manner as described above except for changing the grinding balls or grinding time. , Si content, and Fe content were obtained, and their properties were measured in the same manner as described above.

According to the results in Table 1, all of the samples 11k116-23 in which any of the Ca compound amount, Y compound amount, excess oxygen amount, Si content, and Fe content deviated from the range of the present invention were heat transfer only. When the temperature is low, especially when the amount of Ca compound is small (N119,23), it is necessary to set the firing temperature high.

In contrast, sample floors 1 to 15 of the present invention all have 185
It has a relative density of 98% or more by firing at 0°C or less,
Moreover, a sintered body with a thermal conductivity of 100 W/m'k or more was obtained. Among them, those with an auxiliary component content of 4% or more (floor l ~7.9~12.15) are 125w/m'
K or more was achieved, and the total amount of auxiliary components was 8% by weight.
145 w/m' for those with a (yzo3/cao) weight ratio of 10 or more (lhl ~4.9-11)
More than k was achieved.

〔Effect of the invention〕

As detailed above, the aluminum nitride sintered body of the present invention exhibits excellent properties such as a thermal conductivity of 100 w/m'k or more, has excellent sinterability when fired under normal pressure, and has a high density. Since a sintered body can be obtained, it is excellent in mass production, and is particularly effective as a substrate material for semiconductor element mounting substrates that require high thermal conductivity, as well as heat dissipation substrates for cyrisks.

Claims (1)

[Claims] A sintered body mainly composed of aluminum nitride and containing a Ca compound and a Y compound as auxiliaries, wherein the Ca compound is 0.005 to 4% by weight as CaO, and the Y compound is Y
Contained in a proportion of 0.2 to 10% by weight as _2O_3,
The amount of oxygen remaining after subtracting the amount of oxygen in the auxiliary agent from the total amount of oxygen in the sintered body is 3% by weight or less, the Si content is 0.7% by weight or less, and the Fe content is 0.5% by weight or less. An aluminum nitride sintered body characterized by: