JPS6217076A - Aluminum nitride powder composition - 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 relates to an aluminum nitride powder composition for developing a highly thermally conductive ceramic made of a sintered body containing aluminum nitride as a main component.

(Prior art and its problems) In recent years, electronic components have become significantly smaller and more highly integrated, and as a result, the amount of heat generated per unit area of these components continues to increase. How to dissipate this heat is an important design point for electronic components, and the development of substrates and packages made of materials with high thermal conductivity is desired.

For this purpose, substrates made of sintered silicon carbide or sintered aluminum nitride have been proposed as an alternative to the alumina substrates that have been widely used in the past.

However, although silicon carbide has high thermal conductivity, it has poor electrical insulation properties and requires hot pressing to make it densified, which limits its field of use.

On the other hand, sintered aluminum nitride has a thermal conductivity that is 2 to 5 times that of alumina, although it is inferior to silicon carbide.
Moreover, its electrical insulation properties are comparable to alumina, and it can be densified by pressureless sintering, making it a highly versatile material.

It can be said to be a fee.
・[Aluminum nitride powder is a difficult-to-sinter substance, so
Addition of a sintering aid is essential to obtain a dense sintered body. Various substances have been proposed as sintering aids. For example, elements in group 1ea of the periodic table and elements in group 11a of the periodic table.
Examples include oxides of group elements (% Kosho 58-4951
0, Japanese Patent Publication No. 48-7486).

When using these sintering aids, the maximum thermal conductivity is shown when the amount is slightly larger than the minimum amount required for densification, and it is said that the thermal conductivity decreases when the amount is further increased. For example, when Y2O3 (yttrium oxide) is added in an amount of about 3i (external cutting to aluminum nitride powder), IQQ
Although it is described that it exhibits a thermal conductivity of W/m- (Ceramics Association 1981 Annual Conference Proceedings, p. 301), this is not a fully satisfactory value. Moreover, it has the disadvantage that its surface smoothness is inferior to that of an alumina substrate. Furthermore, when printing and baking conductor or resistor patterns on aluminum nitride substrates, pastes for general alumina substrates cannot be used, and the adhesion strength is not sufficient.

(Means for Solving the Problems) As a result of various studies aimed at solving the above-mentioned drawbacks, the inventors of the present invention have found that an excellent thermal It was discovered that an aluminum nitride sintered body having good conductivity, surface smoothness, and adhesion to conductors and resistors can be obtained, leading to the present invention.

That is, the present invention provides at least one sintering aid selected from compounds containing oxygen of group LA elements and [group 1A elements] to aluminum nitride powder containing oxygen of 3 or less illumination. This is an aluminum nitride powder composition characterized in that it is contained in a proportion exceeding 201% by weight or less.

The present invention will be explained in more detail below.

The aluminum nitride powder used in the present invention has 3 oxygen
If the amount of oxygen is greater than this, the thermal conductivity will decrease regardless of the amount of sintering aid added, making it impossible to achieve the intended purpose. In addition, the particle size is 10 μm in volume average diameter (measured with Microtrack).
The specific surface area is preferably 3 μm or less, and the specific surface area is preferably 3.5 m''/.li+ or more for sufficient densification during sintering.

As the above-mentioned aluminum nitride powder, commercially available products can be pulverized and used as required. Commercially available products are generally
They can be created by metal aluminum nitridation or by carbon reduction nitridation of alumina or aluminum hydroxide, but for the purposes of the present invention those obtained by the former method are preferred. In addition, there is no problem with the inclusion of a small amount of impurities (1°) The sintering aid used in the present invention contains elements of the LA group and
One or more compounds selected from the group element oxygen-containing compounds. [Compounds of group A elements include oxidized animal carbonates such as calcium, barium, and strontium, nitrates, and oxalates; , oxides of samarium, carbonates, oxalates, nitrates, etc., and one or more selected from these can be used. Among these, yttrium, cerium, and lanthanum oxides are preferred in terms of stability, availability, cost, etc. of the sintering aid.

The particle size of the sintering aid is preferably 10 μm or less, particularly 3 μm or less in terms of volume average diameter (measured with a microtrack) in order to achieve densification during sintering. The content of the sintering aid in the powder composition is preferably 5 to 20% by weight, preferably 10 to 15% by weight.

If the proportion of the sintering aid is higher than 20% by weight or less than 5% by weight, high thermal conductivity cannot be obtained, and the surface smoothness and adhesion of patterns of conductors, resistors, etc. Become less sexually active.

Next, a preferred method of creating a sintered body using the aluminum nitride powder composition of the present invention will be described. The aluminum nitride powder and sintering aid are mixed using a ball mill or the like. This mixed powder contains an organic binder such as polystyrene, polyvinyl alcohol, polyvinyl butyral,
Polymethyl methacrylate, polymethacrylate, paraffin, etc. (with addition of a solvent if necessary) are added and mixed, and then molded. As a molding method, methods depending on the shape of the product can be used, such as cold press molding, tape molding, extrusion molding, and injection molding.

Next, after the organic binder added during molding is decomposed by firing, the temperature is 1600-2000℃, preferably 1800-2000℃ in a non-oxidizing gas atmosphere such as nitrogen, argon, helium, etc.
Fire at 1,950°C. The sintering time is 60 minutes or more, preferably 60 minutes to 3 hours.

The obtained sintered body can be subjected to HIP (hot isostatic pressing) treatment to further increase the density and improve thermal conductivity and mechanical strength. In addition, as a sintering method, hot press is used at ℃. By using a hot press, densification becomes easier over a wide range of addition amounts of sintering aids, making it easier to achieve high thermal conductivity.

(Example) The present invention will be specifically explained below with reference to examples.

Example 1 Commercially available yttrium oxide powder (Y2O3) (average particle size 2 μm) was mixed with commercially available aluminum nitride powder (average particle size 2.5 μm, oxygen content 1.8% by weight) in the proportions shown in Table 1.
After mixing and pulverizing, polymethyl methacrylate (PMMA) was added to 100 parts by weight of this mixed powder.
15 parts by weight of a toluene solution of 5 parts by weight were added and mixed.

This slurry was press-formed into a disk shape with a diameter of 40mm and a thickness of 3*ttt at a rate of 500 kg/art2, fired in N2 gas at a temperature of 400°C for 3 hours to decompose and remove PMMA, and then heated in a graphite resistance heating furnace. Conditions shown in Table 1 (Experiment/16
1 to 4).

When the density and thermal conductivity of the sintered body were measured, the values shown in Table 1 were obtained. The thermal conductivity was measured using a radar flash thermal constant measuring device on a sample processed to 10 OX2 1 ton.

The relative density in the table is the value obtained by dividing the density of the sintered body by the apparent theoretical density calculated from the density and blending ratio of each raw material powder of the sintered body.

Example 2 Commercially available cerium oxide powder (CeO2) and aluminum nitride powder were blended in the proportions shown in Table 1, and mixed and ground. To 10 parts by weight of this mixed powder, 75 parts by weight of a mixed solvent with a 3/1/1 weight ratio of tricrene/butanol/tetrachlorethylene, 8 parts by weight of polyvinyl butyral, and 4 parts by weight of butyl phthaloyl butyl glycol were added. The mixture was mixed in a ball mill for 20 hours, and the resulting slurry was molded into a sheet with a thickness of IXI using a doctor spray P method.

This sheet was cut into a size of 50 w x 50 m, six sheets were laminated and bonded by thermocompression, and then heated in air at 500° C. for 1 hour 7 to remove organic matter. This was sintered in an argon atmosphere under the conditions listed in Table 1 (Experiments/165-8). Table 1 shows the measurement results of the relative density and heat pickling rate.

Example 3 Commercially available cerium oxide powder (C802) and aluminum nitride powder were mixed at the ratio shown in Experiment 49 in Table 1, and sintered by hot pressing. Its relative density and thermal conductivity are shown in Table 1.

Example 4 Commercially available lanthanum oxide (La2O3), neodymium oxide (N
d2O3), samarium oxide (Sm2O3), hydrogen oxide□
-ropium (E!u203), ytterbium oxide (
Yb2O3) powder was mixed with aluminum nitride powder in the proportions shown in Table 1. The rest was carried out in the same manner as in Example 2, and the density and thermal conductivity were measured and the results are shown in Table 1 (Experiments 410 to 18).

Comparative Examples Comparative examples using commercially available yttrium oxide (Y2O3) or cerium oxide (CeO2) are shown in Table 1 (Experimental Hawk 1).
9 to 26). The aluminum nitride powder used in experiments %22 and 23 had an oxygen content of 6.3% by weight.

Other conditions were the same as in Example 1.

Example 5 Using yttrium oxide (Y2O3) as a sintering aid,
A sintered body was obtained by adding 5.81% of aluminum nitride using the same operation button as in Example 2.

Its surface roughness is R1! It was found that the laminar thickness was 2 μm, which was significantly improved over the conventional 5 μm. In addition, when we printed and fired the Ag/pa conductor paste and measured its adhesion strength, it was found that the adhesive strength was 5 kg/2.
am'', and the adhesion strength was comparable to that of a normal alumina substrate.

(Effects of the Invention) According to the present invention, an aluminum nitride powder composition is provided that can produce a sintered body that exhibits high thermal conductivity and has excellent surface smoothness and adhesion strength for patterns such as conductors and resistors. can be obtained. In particular, the effect of imparting high thermal conductivity is epoch-making in that it is possible to achieve this by adding a high amount of sintering aid, whereas conventionally the amount of sintering aid added was kept as small as possible.

I'm not sure why I'm so busy, but I think it's as follows.

Depending on the amount of oxygen contained in aluminum nitride, by adding enough sintering aid to combine with them, alumina and aluminum nitride or the sintering aid can be mixed at the interface between aluminum nitride particles in the sintered body. It is possible to prevent the formation of compounds with a low symmetry crystal structure composed of.

In fact, according to transmission electron microscopy, a substance with a multilayer structure exists between aluminum nitride particles in a sintered body to which the amount of sintering aid added is less than the range of the present invention. Through its compositional analysis, we found that it was a compound of Al2O3 and A4N, and that Ce2O3/fLA had a hexagonal multilayer structure.
It was presumed to be a compound similar to 7203. It is presumed that the presence of these compounds causes a decrease in thermal conductivity.

In addition, when we observed the structure of a sintered body with a high thermal conductivity by adding a large amount of sintering aid using a scanning electron microscope, we found that the grain size was smaller than that of a sintered body with a low addition, and grain growth was suppressed. I found out that there is.

This is considered to be the reason for improving the surface smoothness of the sintered body.

In addition, the adhesion of printed patterns for conductors, resistors, etc. depends on the amount of auxiliary added, that is, the amount of oxide layer in the sintered body. This is thought to be because it blends well with the oxide layer between particles. Therefore, in order to obtain adhesion strength above a certain value, it is necessary to add the auxiliary agent in an amount above a certain value.

Incidentally, the sintered body manufactured using the aluminum nitride powder composition of the present invention is useful as a hybrid XC substrate, a heat sink, etc.

Claims (2)

[Claims] (1) For aluminum nitride powder containing 3% by weight or less of oxygen, at least one sintering aid selected from compounds containing oxygen of group IIa elements and group IIIa elements in an amount exceeding 5% by weight and 20% by weight. An aluminum nitride powder composition, characterized in that it contains aluminum nitride powder in a proportion of not more than 50%. (2) The aluminum nitride powder composition according to claim 1, wherein the content of the sintering aid is 10 to 15% by weight.