JPH04357171A - Production of silicon nitride sintered product - Google Patents

Abstract

PURPOSE:To prevent the generation of stains and irregular colors on the surface of a sintered product and improve the thermal conductivity of the sintered product by adding a specific volume of carbon monoxide to a non-oxidative atmosphere, when a molded product containing AlN as a main component is sintered in the nitrogen-containing non-oxidative atmosphere. CONSTITUTION:Raw materials containing aluminum nitride as a main component and a sintering auxiliary such as Y2O3 or CaO are molded into a desired shape by a press-molding method, extrusion molding method, etc. The molded product is placed in a non-oxidative atmosphere containing nitrogen gas and further carbon monoxide in a volume ratio of 0.1-10000ppm, and subsequently sintered at a high temperature to produce an aluminum nitride sintered product. The addition of the carbon monoxide to the atmosphere permits to prevent the generation of stains caused by the irregular deposition of the sintering auxiliary. When a black-coloring agent is added, the generation of color irregularity can be prevented, because the color development of the black-coloring agent is accelerated by the carbon monoxide, and the thermal conductivity of the sintered product is enhanced, because the oxygen of impurities in the aluminum nitride crystals is reduced and removed.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for manufacturing an aluminum nitride sintered body, and more particularly to a method for manufacturing a sintered body that has high thermal conductivity and good appearance, and is suitable for use in circuit boards, etc. It is something.

0002

[Prior Art] Conventionally, aluminum nitride sintered bodies have been
Recently, semiconductors have been gaining popularity due to their excellent properties, such as high strength at room temperature and high temperatures, high electrical insulation, high thermal conductivity, and a coefficient of thermal expansion closer to that of single crystal silicon than alumina. Applications are being made to semiconductor components such as integrated circuit elements and substrates for various electronic components.

[0003] This aluminum nitride sintered body is usually
Y2 O3 as a sintering aid in aluminum nitride raw powder
It is obtained by firing a molded body to which rare earth element oxides such as oxides, alkaline earth element oxides such as CaO, etc. are added, at a temperature of 1500 to 2000°C in a non-oxidizing atmosphere containing nitrogen, for example. There is.

0004

[Problems to be Solved by the Invention] However, according to the method of firing in a nitrogen atmosphere, there is a problem that segregation of the sintering aid occurs on the surface of the sintered body, and stains are likely to occur. Furthermore, there is a problem in that the thermal conductivity is extremely reduced in the system in which a sintering aid is added.

[0005] Recently, it has also been proposed to blacken the sintered body by adding metal compounds of groups 4a to 8a of the periodic table. However, even during this blackening, color unevenness tends to occur, making it difficult to obtain uniform color development, which may result in poor appearance.

Furthermore, the addition of these blackening agents may affect the electrical properties of the sintered body, but among the blackening agents, Group 8 transition metals have relatively excellent electrical properties. Although it is easy to obtain, there is a problem that it has poor coloring properties and is difficult to use as a blackening agent.

[0007]

[Means for Solving the Problems] As a result of repeated studies on the above problems, the present inventors have found that when firing a molded product mainly composed of aluminum nitride in a non-oxidizing atmosphere, By mixing carbon monoxide in the sintered body, the occurrence of stains on the surface of the sintered body is reduced, and especially in systems containing various blackening agents, the coloring properties are good and there is no occurrence of color unevenness. The present inventors have discovered that the thermal conductivity is also improved.

That is, in the method for producing an aluminum nitride sintered body of the present invention, a molded body containing aluminum nitride as a main component is placed in a non-oxidizing atmosphere containing carbon monoxide in a volume ratio of 0.1 to 1000 ppm. It is characterized by being fired inside.

The present invention will be explained in detail below. According to the manufacturing method of the present invention, first, a molded body containing aluminum nitride as a main component is created. This compact is obtained by a conventionally well-known method, and specifically, Y2 O3 and Er2 O are added as sintering aids to aluminum nitride raw material powder.
3 Rare earth element compounds such as Yb2 O3 and Ho2 O3 and alkaline earth element compounds such as CaO and CaF2 are mixed in a total amount of 15% by weight or less. The aluminum nitride raw material used has an oxygen content of 2
Those having an average particle size of 5 μm or less and an amount of other metal impurities of 0.5% by weight or less are preferably used.

The mixture thus obtained is molded into a desired shape by known molding means such as press molding, sheet molding, and extrusion molding.

Next, the molded body is fired in a non-oxidizing atmosphere. The atmosphere at this time is composed of nitrogen, argon, hydrogen, etc., and according to the present invention, carbon monoxide is added to this atmosphere at a concentration of 0.1 to 1000 ppm, particularly 5 to 8 ppm.
Mix at a ratio of 00 ppm. This carbon monoxide can be produced, for example, by directly introducing carbon monoxide gas into the atmosphere, or by mixing an appropriate amount of oxygen gas or carbon dioxide gas into the atmosphere.
A method can be adopted in which carbon monoxide is produced by causing gas and carbon to react by bringing the gas into contact with a carbon material such as a carbon furnace. The amount of carbon monoxide was limited to the above range because
This is because if the amount is less than 0.1 ppm, it is impossible to prevent the occurrence of stains or color unevenness in the sintered body, and if it exceeds 1000 ppm, carbon will be mixed into the molded body from the atmosphere, reducing the sinterability of the system.

[0012] The temperature during firing is 1500 to 2100.
C., particularly 1550 to 1900 C., and the atmosphere may be either normal pressure or gas pressurization of 1.5 atm or more.

According to the manufacturing method of the present invention, the effect is particularly remarkable in systems containing blackening agents, and the blackening agents used include Ti, Zr, Nb, V, Ta, W, Mo, and F.
Transition metal elements such as E, Co, and Ni are included, and these are added in the form of oxides, carbides, nitrides, etc., and develop color due to reduction action, and the sintered body contains 0.0% per metal.
It is added at a ratio of about 0.05 to 5% by weight.

In addition, in the aluminum nitride sintered body obtained by the present invention, the amount of oxygen in the sintered body is reduced due to the presence of carbon monoxide during sintering. It is desirable that the amount of impurity oxygen in the sintered body is 1.5% by weight or less, and the amount of carbon in the sintered body also affects the sinterability, and if it remains as free carbon, it will adversely affect the properties of the sintered body. It is desirable that the amount is .1% by weight or less.

[0015]

According to the present invention, by mixing a predetermined amount of carbon monoxide gas into the atmosphere, it is possible to prevent the occurrence of stains, which are particularly noticeable in systems containing sintering aids. In addition, particularly in a system containing a blackening agent, the reducing action of the transition metal compound can be promoted to improve its color development, and the occurrence of color unevenness on the surface of the sintered body can be prevented. In addition, the reduction action can remove impurity oxygen present in the aluminum nitride crystals in the sintered body, thereby increasing the thermal conductivity of the sintered body.

[0016]

[Example] Oxygen content is 0 as aluminum nitride raw material.
89% by weight, an average particle size of 1.6 μm, and a cationic impurity amount of 0.5% by weight or less, the various sintering aids shown in Table 1 were added and mixed, and press molding was performed. It was fired under the conditions shown in 1.

[0017] The relative density of the obtained sintered body was calculated based on the Archimedes method, and the appearance of the sintered body was observed visually and with a stereoscopic binocular microscope, and the occurrence of stains and blackness were observed. . In addition, the amount of oxygen and carbon in the sintered body was measured, and the thermal conductivity of the sintered body was measured using a laser flash method. The results are shown in Table 1.

[0018] Furthermore, as a blackening material, TiO2, Mo
O3, WO3, Nb2 O5, V2 O5, N
Table 2 shows a system using iO and Co3O4.

[0019]

[Table 1]

[0020]

[Table 2]

[0021] As is clear from Tables 1 and 2, those in which a certain amount of CO gas was mixed into the firing atmosphere had a low CO gas concentration (Samples Nos. 1, 2, 9, 18, and 25).
There was almost no occurrence of stains or color unevenness in any case compared to the above. However, samples with too high a concentration of CO gas (sample N
o, 8, 21), insufficient sintering occurred and a decrease in thermal conductivity was observed.

[0022]

[Effects of the Invention] As described in detail above, the aluminum nitride sintered body of the present invention prevents the occurrence of stains in a system in which a sintering aid is added, and promotes color development in a system in which a blackening agent is added. By doing so, it is possible to prevent color unevenness and obtain a sintered body with high thermal conductivity.

Therefore, the present invention has excellent stability in characteristics and appearance when manufacturing circuit boards for semiconductors, heat sinks, and other circuit boards on which wiring layers are formed, and has an excellent effect on mass production of products. able to demonstrate.

Claims (2)

[Claims] 1. A method for producing an aluminum nitride sintered body, in which a molded body containing aluminum nitride as a main component is fired in a non-oxidizing atmosphere containing nitrogen, wherein a volume ratio of 0.1 to 1000 ppm is added to the atmosphere. A method for producing an aluminum nitride sintered body characterized by containing carbon monoxide. 2. The method for producing an aluminum nitride sintered body according to claim 1, wherein the amount of carbon in the sintered body is 0.1% by weight or less.