JPH075377B2 - Black aluminum nitride sintered body and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black aluminum nitride sintered body used for insulating substrates, heat sinks, semiconductor package materials, etc., and a method for manufacturing the same, more specifically, high density and high thermal conductivity. The present invention relates to a method that is a sintered body having properties and can be manufactured at a low temperature.

2. Description of the Related Art In recent years, with high integration and high density of LSI, an insulating substrate material having good thermal conductivity has been demanded. Conventionally, an alumina sintered body is most often used as an insulating substrate material. However, the thermal conductivity of the alumina substrate is low (about 20 w / m.
k), but the thermal expansion coefficient is larger than that of silicon, so there were many problems such as poor bondability. Therefore, attention has been paid to an aluminum nitride (AlN) sintered body, which has a good thermal conductivity and a thermal expansion coefficient close to that of silicon. Furthermore, the aluminum nitride sintered body has a high mechanical strength (40 to 50 kg / mm ² ), a small dielectric constant, and excellent electrical characteristics. However, since aluminum nitride has a strong covalent bond and is a difficult-to-sinter material, it is difficult to obtain a dense sintered body.

Therefore, until now, various attempts have been made to obtain a dense aluminum nitride sintered body by a hot pressing method using a sintering aid or an atmospheric pressure sintering method, but the hot pressing method is not preferable because of poor productivity. In the atmospheric pressure sintering method, rare earth compounds and alkaline earth compounds are used as sintering aids to obtain dense and highly heat conductive sintered bodies.
A high temperature exceeding 10 ° C. is required, which is also not preferable in terms of productivity. Further, the obtained sintered body has a slight translucency, and when applied to a package, it is fully conceivable that the IC memory is adversely affected by transmission of ultraviolet rays and the like.

As a low-temperature sinterable AlN sintered body considering productivity, JP-A-6
1-117160 discloses a production method by simultaneous addition of a rare earth oxide and an alkaline earth oxide. This method is apt to cause uneven baking and uneven color, and needs to be improved.

In Japanese Patent Laid-Open Nos. 61-270262 and 61-270263, 4 of the periodic table
A high thermal conductivity aluminum nitride sintered body comprising a boride or carbide of a, 5a, 6a group element and aluminum nitride and a method for producing the same are described. However, further improvement has been desired in terms of obtaining higher thermal conductivity and black color.

The inventors of the present invention previously filed Japanese Patent Application No. 61-270390 and found low-temperature sinterability by adding calcium tungstate, but the thermal conductivity of the obtained sintered body is JP-A-61-270262, Similar to 61-270263, it remained at about 100 W / mk.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a black aluminum nitride sintered body exhibiting a black color and having high density and high thermal conductivity, and a method for producing the same, particularly a method capable of sintering at a low temperature.

Means for Solving the Problems The first aspect of the present invention is characterized by containing aluminum nitride as a main component and containing metallic tungsten, rare earth aluminum oxide, alkaline earth aluminum oxide, and rare earth alkaline earth aluminum oxide. And a black aluminum nitride sintered body. Secondly, the powder is mainly made of aluminum nitride, and the rare earth oxide and / or the powder of at least one compound which becomes the oxide by firing is 0.5 to 5% by weight in terms of the oxide and the alkaline earth metal. Of 0.1 to 15% by weight of the oxide of at least one tungstic acid compound powder, which is molded and fired in a non-oxidizing atmosphere, to produce a black aluminum nitride sintered body. Is the way.

Effect The present invention has the effect of simultaneously adding both components of a rare earth oxide and a tungstic acid compound of an alkaline earth metal to aluminum nitride powder as a sintering aid, and as a synergistic effect thereof, black aluminum nitride firing having high density and high thermal conductivity. The union is obtained at a relatively low temperature. In particular, it has been found that the tungstic acid compound of an alkaline earth metal greatly contributes to low-temperature sinterability and a black color having no color unevenness and burning unevenness, and the rare earth oxide contributes to improvement of heat conduction. The black color is due to the dispersion of fine metallic tungsten in the sintered body, and its volume resistivity value is 10 ¹² ohm.cm or more, which is a good insulating material.

Next, a specific manufacturing method of the present invention will be described. First, the aluminum nitride powder is a fine powder having an average particle size of 10 μm or less, preferably 2 μm or less. The oxygen content is not particularly specified, but is preferably 3% or less.

Among the sintering aids, rare earth oxide or its compound is S
Examples thereof include compounds such as c, Y, La, Ce, Pr, Nd, Sm, Er. Of these, compounds of Sc, Y, La, Ce, Er, and oxides of Y are preferable. In the present invention, Sc and Y are collectively referred to as rare earths in the periodic table. The powder of these compounds has a fine average particle size of 10 μm or less, and particularly preferably 5 μm or less.

As the tungstic acid compound of an alkaline earth metal which is another component of the sintering aid, compounds such as Ca, Sr and Ba can be mentioned, but calcium tungstate is preferred because of its easy availability. Powders of these compounds have an average particle size of 10 μm
The following fine particles, particularly 5 μm or less, are preferable.

The addition amount of these sintering aids is 0.5 to 5% by weight of rare earth oxide powder and 0.1 to 15% by weight of tungsten oxide of alkaline earth metal in terms of oxide, depending on the firing temperature and the desired physical properties. The optimum addition amount and the ratio of the alkaline earth tungstate compound to the rare earth oxide are determined.

That is, when the calcination temperature exceeds 1800 ° C., the amount of the alkaline earth tungstic acid compound that acts as a pigment is very small, and the rare earth oxide that contributes to heat conduction is added in a predetermined amount, preferably 3 to 7% by weight. It If the purpose is black only, the amount of rare earth oxide can be extremely small. When the firing temperature is 1800 ° C. or less, the tungstic acid compound of alkaline earth metal as an auxiliary agent for low temperature firing and coloring is required to have a predetermined amount, preferably 0.1 to 15% by weight, and a rare earth element that contributes to heat conduction. The oxide is preferably added in an amount of 0.5 to 5% by weight so long as it does not hinder the densification. If the total amount of the sintering aids is less than 0.6% by weight, the color development is insufficient even if the sintering temperature is increased, and it is meaningless to add more than 20% by weight in total. The sintering method follows the conventional method.

The aluminum nitride sintered body thus obtained is the first
As a result of X-ray diffraction of Example 1 and an electron micrograph thereof in FIG. 2, aluminum nitride (A,
Black or gray), metallic tungsten (W, white spherical particles), rare earth aluminum oxide (Y, G, white grain boundary phase is alumina, yttria oxide) are the main components, and alkaline earth aluminum oxide, and It is known that a complex oxide (unidentified phase X) presumed to be a rare earth alkaline earth aluminum oxide is present.

In addition to improving the conductor retrofit strength of this sintered body, it has the characteristic that a metal tungsten conductor with much lower conduction resistance can be obtained compared with the method of manufacturing an aluminum nitride sintered body that produces tungsten boride even with simultaneous firing. is doing.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Examples Example 1 4% by weight of calcium tungstate powder and 1% by weight of yttrium oxide powder were added to and mixed with aluminum nitride powder having an average particle size of 2 μm. Next, this mixture was pressed at room temperature at about 1200 kg / cm ² to obtain a molded body. Thereafter, this molded body was fired at 1700 ° C. for 3 hours in a nitrogen gas atmosphere to obtain an aluminum nitride sintered body. The obtained sintered body was dense and exhibited a black color with excellent light-shielding properties. The measured values of the density and the thermal conductivity are shown in Table 1.

Examples 2 to 10 1600 to 1800 were added in the same manner as in the above Examples by adding an appropriate amount of a powder of a tungstic acid compound of an alkaline earth metal and a powder of a rare earth oxide to the aluminum nitride powder used in Example 1.
Firing was performed at ℃ to obtain an aluminum nitride sintered body. The density and thermal conductivity were measured for each. The results obtained are shown in Table 1 together with the type, amount of addition, firing conditions and color of the sintering aid.

Example 11 To the aluminum nitride powder used in Example 1, 1.5% by weight of calcium tungstate powder and 3.5% by weight of yttrium oxide powder were added, and after molding in the same manner as in Example 1, the temperature was raised to 1700 ° C. in a nitrogen gas atmosphere. It was heated for 15 hours to obtain an aluminum nitride sintered body. The density of the obtained sintered body is 3.31 g / cc
And sufficiently dense and excellent in light-shielding property, and exhibited a black color. Its thermal conductivity was 170 w / m · k.

Comparative Example 1 3% by weight of tungsten oxide powder was added to the aluminum nitride powder used in Example 1 and fired at 1800 ° C. to prepare an aluminum nitride sintered body. The obtained sintered body was black gray and had a low thermal conductivity of 55 w / mk.

Comparative Example 2 5% by weight of yttrium oxide powder was added to the aluminum nitride powder used in Example 1 and fired at 1800 ° C. to prepare an aluminum nitride sintered body. The obtained sintered body had a light-transmitting light brown color, and color unevenness was partially observed.

Comparative Example 3 In the aluminum nitride powder used in the example, 3% by weight of tungsten oxide powder and 5% by weight of yttrium oxide powder were used.
Was added and fired at 1700 ° C., but a dense sintered body could not be obtained.

Comparative Example 4 4% by weight of calcium tungstate powder was added to the aluminum nitride powder used in Example 1 and fired at 1800 ° C. to prepare an aluminum nitride sintered body. The obtained sintered body was black, but the thermal conductivity was 100 w / mk.

Comparative Example 5 To the aluminum nitride powder used in Example 1, 4.5% by weight of calcium carbonate powder and 2.5% by weight of yttrium powder were added,
The aluminum nitride sintered body was prepared by firing at 1700 ° C.
The obtained sintered body exhibited a light-transmitting light gray color and uneven color was observed.

EFFECTS OF THE INVENTION As described above, according to the present invention, a black aluminum nitride sintered body having an excellent light-shielding property and having high thermal conductivity can be fired in a reduction firing furnace for alumina sintering. It is effective for mass production of substrates and co-firing circuit boards and has great industrial value.

[Brief description of drawings]

FIG. 1 shows the X-ray diffraction result of Example 1, and FIG. 2 shows Example 1.
3 is an electron micrograph showing the grain structure of the fracture surface of the.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Satoshi Nishiyama 3 Denjiyama, Narumi-cho, Midori-ku, Nagoya-shi, Aichi Narumi Technical Research Institute Kazuko Yanagi

Claims (4)

[Claims] 1. A black aluminum nitride sintered body containing aluminum nitride as a main component and containing metal tungsten, rare earth aluminum oxide, alkaline earth aluminum oxide, and rare earth alkaline earth aluminum oxide. 2. The black aluminum nitride sintered body according to claim 1, wherein the content of aluminum nitride is 80 to 99.4% by weight. 3. A powder of aluminum nitride as a main component, and a powder of a rare earth oxide and / or at least one compound which becomes the oxide by firing, in terms of the oxide.
0.5 to 5% by weight and at least one powder of a tungstic acid compound of an alkaline earth metal in terms of the weight of the oxide of 0.1.
A method for producing a black aluminum nitride sintered body, characterized by being formed by molding 1 to 15% by weight and firing in a non-oxidizing atmosphere. 4. The method for producing a black aluminum nitride sintered body according to claim 2, wherein the sintering temperature is 1800 ° C. or lower in the atmospheric pressure sintering method.