JPH03112846A - Production of sintered ceramic - Google Patents

Abstract

PURPOSE:To obtain a sintered material having improved degreasing property and sinterability and high sintered density and free from warpage by specifying the particle size distribution of principal particles, especially the distribution at the fine particle side, in the calcination of a mixture containing principal ceramic particles, sintering assistant particles and an organic binder. CONSTITUTION:A mixture containing principal ceramic particles, sintering assistant particles and an organic binder is calcined in a non-oxidizing atmosphere to obtain a sintered material. The principal particles to be used in the above process are those having particle size distribution having an average particle diameter of <=5mum and containing <=15wt.% of particles having particle size of <=1.0mum. Gaps between the particles in degreasing step can be secured by this process to improve the degreasing efficiency and, accordingly, uniformly remove the residual binder in calcination step. When the content of the principal particles finer than 1.0mum exceeds 15%, the flow of gas in the degreasing step becomes difficult to cause insufficient sintered density. When the average particle diameter exceeds 5mum, the sinterability becomes poor to increase the problem of void formation.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic sintered body having excellent degreasing efficiency and sinterability, and relates to a method for manufacturing a ceramic sintered body having excellent degreasing efficiency and sinterability. used for substrates) etc.

[Conventional technology]

Conventionally, basic ceramic particles used, for example, in the production of ceramic multilayer wiring boards, have been used with only the average particle size being regulated.

[Problem to be solved by the invention]

In the conventional manufacturing method, usually 14
When firing is performed at a temperature of 00 to 1600° C., if ceramic elementary particles with a large average particle size are used, a considerable number of large ceramic elementary particles will normally be present therein.

These large particles cause uneven sintering and tend to cause voids, so the sintered density cannot be sufficiently improved. However,
The use of ceramic basic particles with a small average particle size generally improves the sinterability of the ceramic basic particles, but when firing in a non-oxidizing atmosphere, the sintered density does not increase and the sintering Body quality does not necessarily improve.

The present invention solves the above problems, and the particle size distribution of basic ceramic particles, especially the distribution on the fine particle side, has good degreasing properties.
This was completed based on the new discovery that it greatly affects sinterability. That is, an object of the present invention is to provide a manufacturing method that is excellent in degreasing and sintering properties, that is, a method for manufacturing a high-quality ceramic sintered body with a high sintered density and little warpage.

[Means to solve the problem]

The method for manufacturing a ceramic sintered body of the present invention is a method of manufacturing a sintered body by molding a mixture containing ceramic basic particles, sintering aid particles, and an organic binder and firing it in a non-oxidizing atmosphere. The particle size distribution of the ceramic substrate particles is characterized in that particles of 1.0 μm or less account for 15% by weight (hereinafter referred to as %) or less, and the average particle size is 5 μm or less.

When using an organic binder, especially when using a relatively large amount (in the case of sheet molding, injection molding, etc.), it is usually kept at a temperature at which the components constituting the molded product do not oxidize (in the case of an alumina multilayer wiring board, the wiring pattern To prevent oxidation of the tungsten or molybdenum contained in the tungsten or molybdenum, degreasing is performed in the air (up to about 200 to 300°C), and then in a non-oxidizing atmosphere for 1
Calculate at 400-1600°C. However, if this vanida is not efficiently removed during the degreasing and firing steps, it will remain in the sintered body as carbon, which will inhibit firing and create voids inside, resulting in an increase in sintered density. As a result of various studies, the inventors of the present invention have discovered that, as a result of various studies, there is a problem in that the removal of the binder is uneven, resulting in warping of the substrate and the like. The present invention
As a result of extensive research, we have discovered that these problems can be solved by changing the particle size distribution of basic ceramic particles.

The types of the ceramic basic particles, sintering aid, and organic binder are selected depending on the purpose and use. The amount of the binder added is also not particularly limited. However, the present invention is particularly suitable for cases in which sheet molding, injection molding, or extrusion molding is used relatively frequently. This is because particle size distribution greatly affects degreasing efficiency.

The particle size distribution of the ceramic particles is such that particles of 1.0 μm or less account for 15% or less. If this value is exceeded, the number of fine particles increases, and gas passage during the degreasing process is insufficient, resulting in a low de-fingering efficiency, resulting in a large number of voids inside, and insufficient sintering density.

Furthermore, in this case, since the degreasing is not uniform, the residual binder is not removed uniformly during the firing process.
After firing, the sintered body, especially the substrate, becomes more warped. In addition, if the average particle size of the ceramic particles exceeds 5 μm, the particle size becomes large, and a considerable number of large particles, especially 10 to 20 μm or more, will be present, resulting in insufficient sinterability and voids. This causes the sintered density to deteriorate.

The degreasing is carried out in an oxidizing atmosphere, usually in the atmosphere. Further, the firing atmosphere is a non-oxidizing atmosphere, which is usually a nitrogen-hydrogen mixed reduction snow atmosphere or the like. As the firing temperature, the temperature used in the above-mentioned atmosphere firing (usually about 1400 to 1600°C) is used.

[Effect]

In the degreasing and firing under each of the above atmospheres, the particle size distribution of the ceramic basic particles was such that the particles of 1.0 μm or less were 15
% or less, so the voids between the particles are ensured during the degreasing process, and sufficient gas passage is ensured.
Therefore, the degreasing efficiency is improved. Furthermore, since the degreasing efficiency is improved, residual binder is uniformly removed in the firing step 51.

Further, since the average particle size of the ceramic basic particles is 5 μm or less, there are extremely few coarse particles of 10 to 20 μm or more, and therefore, the sinterability is excellent.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

First, alumina (
Test powder products h1 to h6 of basic particles) were prepared.

The particle size distribution was measured by a laser particle size distribution measuring method using "Microtrack" (trade name, manufactured by LEEDS & NORTHRUP), and the average particle size was defined as the particle size value at which the cumulative number was 50%. The results of the particle size distribution at Nα2.6 are shown in FIG.

After that, each powder (total of 10
0 parts), add a predetermined amount of organic solvent (for example, methyl ethyl ketone, toluene) and silica stone (made of alumina), mix and grind in a rotary mill, and then add butyral resin (about 8 parts) and plasticizer (about 4 parts). and mix to prepare a homogeneous slurry. Using this slurry, a green sheet with a thickness Q of 5 mm was produced by tape casting, and four layers of this green sheet were laminated. Next, this laminate was cut into a size of 36 x 24 mm.

This was then heated in air at a heating rate of 30°C/hour for 25 minutes.
It was heated to 0°C and degreased. Thereafter, the object to be fired is fired in a reducing atmosphere of a mixed gas of hydrogen (approximately 50% by volume) and nitrogen (approximately 50% by volume) so that the firing target reaches the temperatures shown in Figures 1 and 2 between 1440 and 1560°C. Thus, each sintered plate Nα1 to Nα6 was created. Note that this Nα2.3 is the product of the present invention, and the others are comparative example products.

The firing density of each sintered plate is shown in FIG. 1, and the amount of warpage (warp depth, μm) is shown in FIG. According to this result, the sintered plate Nα2.3 included in the range of the present invention has a high sintered density, reaching almost the theoretical density at a temperature of 1500 to 1560°C, and the sintering temperature range in which the theoretical density is reached is wide. Also, regarding the amount of warpage, Nα2.3 is extremely small at any firing temperature.

On the other hand, Nα5.6, which has many fine particles, has many voids inside, has a low sintering density, and has a large amount of warpage.

Furthermore, the higher the firing temperature, the lower the firing density and the greater the amount of warpage. This is because the higher the temperature, the more difficult the gas passage becomes and the degreasing becomes insufficient and uneven, which increases the number of voids that are thought to be caused by the gasification of the binder and carbon trapped inside, and also reduces the amount of warpage. It shows that there will be more. Furthermore, although the sintered density of Nα1, which has a large number of coarse particles, increases as the sintering temperature rises, it does not reach the theoretical density, indicating that the sinterability is insufficient.

From the above, the sintered plate Nα2.3 according to the present invention has very high precision with few internal voids, high firing density, and small amount of warpage. In addition, a stable sintered plate was obtained with a theoretical density and a small amount of warpage over a wide firing temperature range.

〔Effect of the invention〕

According to this manufacturing method, since it has the above-mentioned effects, it has excellent degreasing properties and sintering properties, and has an extremely good balance between the two. Therefore, according to the present manufacturing method, both of these factors are combined, resulting in fewer internal voids, higher sintering density, less warping of the sintered body (especially the substrate), and a firing temperature range in which the above-mentioned favorable effects can be achieved. Since the area is wide, it is possible to produce products with stable sintering.

From the above, the present invention shows that high-quality sintered bodies can be produced even under normal economical degreasing and firing conditions, especially when using sheet molding, injection molding, etc. that use a relatively large amount of organic binder. In particular, it is extremely useful for manufacturing ceramic multilayer wiring boards and the like.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the particle size distribution of basic ceramic particles, firing temperature, and firing density in Examples, and Figure 2 is a graph similarly showing the relationship between the particle size distribution of basic ceramic particles, firing temperature, and amount of warpage. , Figure 3 shows the test powder product Nα2.
6 is a graph showing the particle size distribution of (ceramic substrate particles).

Claims (1)

[Claims] (1) In a method of manufacturing a sintered body by molding a mixture containing ceramic basic particles, sintering aid particles, and an organic binder and firing it in a non-oxidizing atmosphere, the particle size distribution of the ceramic basic particles is as follows: A method for producing a ceramic sintered body, characterized in that the content of particles of 1.0 μm or less is 15% by weight or less, and the average particle size is 5 μm or less.