JPH03150260A - Production of alumina substrate - Google Patents

Abstract

PURPOSE:To inexpensively obtain a dense alumina substrate having excellent surface smoothness by dispersing alumina powder into an organic solvent containing Mg-acetylacetonate dissolved therein, evaporating the solvent to form powder, heat-treating the powder, grinding, molding and calcining. CONSTITUTION:Magnesium-aceceylacetonate is dissolved in an organic solvent (e.g. ethanol). Then the alumina powder is dispersed into the solution to form a slurry and each alumina particle 1 is covered with a coating film 2 of the organic solvent containing the magnesium component. Then the organic solvent is evaporated from the slurry to give powder, which is heat-treated, further ground, the magnesium component in the coating film 2 is oxidized, an outer shell 3 of magnesium oxide are formed on the surface of the alumina particle 1 to produce a substrate raw material. Then the substrate raw material is molded and calcined to give an alumina substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing an alumina substrate, and more specifically, to a method for manufacturing an alumina ceramic substrate having a dense and extremely smooth surface.

[Background Art and its Problems 1] In recent years, as microelectronic components become faster and more densely packed, alumina ceramics are frequently used as substrate materials. As the characteristics of this substrate, importance is placed on electrical, mechanical, and thermal characteristics as well as surface smoothness. Particularly, in the case of substrates for thin film hybrid integrated circuits, a substrate having a high level of smoothness is desired, for example, due to the requirement of stabilizing the resistance value of a thin film resistor.

Therefore, as alumina substrates with smooth surfaces, there are glazed substrates whose surfaces are glazed and coated with glass glaze to make the surfaces smooth, and polished substrates whose surfaces are mechanically polished after firing. It is used. However, glazed substrates have the disadvantage of poor heat dissipation and poor heat resistance, and polished substrates have the problem of high polishing costs due to the high hardness of alumina. .

On the other hand, for 100wt% of alumina (AhOs) fine powder with a purity of 99.9% or more and an average particle size of 0.7uIn or less,
Magnesium oxide (MgO) 0-05~G-4wL%
When added, magnesium oxide acts as a grain growth inhibitor, controlling the growth of crystal grains to some extent during sintering, and increasing the I
The ability to obtain an alumina substrate with high Ii density and excellent surface smoothness is well known as the ^s-Fire method.

In this 8s-Fire method, it is necessary to completely and uniformly disperse the MgO particles in the alumina dispersion medium. However, since alumina has a substrate composition of 99.6 to 99.9
It accounts for 5wt%, and the particle size is 0. In order to allocate MgO particles to each alumina particle smaller than Hu, it is necessary to use MgO particles whose particle size is 61 orders of magnitude smaller than the alumina particles. For example, alumina is 99.90wt
0 is 0 in % and M. When the alumina particle size is 0.5#lI+ with a composition of lOwL%, the alumina particles and Mg
In order to have a one-to-one correspondence with O particles, it is necessary to make the particle size of MgO particles as fine as 0.05 tm or less. The smaller the amount of MgO added is, the smaller the particle size of the MgO particles needs to be.

However, in the conventional method of mechanically mixing alumina and MgO, the higher the Ra of the MgO particles, the more likely they are to aggregate during mixing, making it difficult to completely disperse the MgO particles in the alumina particles. For this reason, it is not possible to use MgO with a very small particle size, and the conventional As-Fi
In the re method, as above < 0.05~0.4w
t% of MgO was added.

However, it is considered that the amount of MgO added exceeds the amount necessary for suppressing alumina grain growth.

[Problems to be solved by the invention] However, the present invention has been made in view of the drawbacks of the conventional examples described above, and its purpose is to add a small amount of extremely <*a+ magnesium component to alumina. The objective is to enable complete dispersion in the Ni medium and to reduce the amount of magnesium oxide added.

[Means for Solving the Problems] Therefore, the method for manufacturing an alumina substrate of the present invention involves dispersing alumina powder in an organic solvent in which magnesium-acetylacetonate is dissolved to form a slurry, and dispersing the slurry from this slurry. After evaporating the organic solvent and turning it into powder, this powder is heat-treated and further crushed to prepare the substrate raw material.
The method is characterized in that an alumina substrate is manufactured by molding and firing this substrate raw material.

[Action] Magnesium-acetylacetonate 0 axis-aceLyleacetonate, which is an organometallic compound of Mg
), individual alumina particles of the alumina powder can be coated with an organic solvent containing magnesium-acetylacetonate. Thereafter, when the organic solvent is evaporated from the slurry, a magnesium component remains on the surface of the alumina powder particles, and by heat-treating this, an outer shell of magnesium oxide can be formed on the surface of each alumina particle. Therefore, even when using magnesium acetylacetonate containing a small amount of magnesium component, it is possible to reliably attach magnesium oxide to each alumina particle, and by manufacturing an alumina substrate using this as a substrate material, it is possible to It is possible to suppress grain growth and obtain an alumina substrate that is dense and has a high surface smoothness.

[Example 1 Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings.

First, dissolve the required amount of magnesium-acetylacetonate in an organic solvent such as toluene or ethanol, then add alumina powder to the organic solvent to form a slurry, stir well, and add the alumina particles to the organic solvent. Give a uniform pardon. In addition, what is the required amount of magnesium acetylacetonate?

Although it varies depending on the amount of alumina, particle size, etc., after firing the alumina substrate raw material, the amount of magnesium oxide (LOO) should be 5vt% or more based on 100wt% of alumina.

Through this step, each alumina particle 1 is individually wrapped in a coating 2 of an organic solvent containing a magnesium component, as shown in FIG. Next, the organic solvent is evaporated from this slurry to obtain a powder. 800 to 1000 to this powder
A heat treatment is performed at a temperature of 10.degree. C. for about 2 hours, and the powder sintered by the heat treatment is further crushed to make it finer. This results in
The magnesium component in the coating 2 is #lieed to form a magnesium oxide shell 3 on the surface of each alumina particle l. Therefore, even a small amount of magnesium oxide can be reliably attached to each alumina particle.

The alumina particles 1 surrounded by the outer shell 3 of magnesium oxide are used as a substrate raw material, a binder, a plasticizer, etc. are added as appropriate, and after being formed into the shape of a substrate by a doctor blade method, the alumina substrate is produced by firing. However, in the manufacturing process of this alumina substrate, each alumina particle l is made of magnesium oxide! Since it is covered by t3, a grain growth suppressing effect acts on each alumina particle, and an alumina substrate having a particle diameter of -1 and an extremely smooth surface can be obtained.

(Experiment example) According to the above manufacturing process, sample N shown in Table 1 below
Fabricate 20 (2 inch square alumina substrate) on Ll ~,
The surface roughness of the substrate of each sample NILl-llJIL20 and the maximum value and average value of its crystal diameter were measured.

Here, the alumina has a purity of 9199% and a particle size of 0.5#.
111 was used, and the amount of magnesium acetylacetonate added was the wt of magnesium oxide after firing.
0.001wt%, 0.005wt% in terms of percentage.

There were five types, 0.010 wt% and 0.050 wt%.

Organic solvent: toluene 50%, ethanol 50%
I used the one from Also, the heat treatment temperature is 700℃, 800℃
, 900°C, tooo°C, and 1100°C.

Furthermore, 10 wt% of PVD as a binder and 5 wt% of DOP as a plasticizer were added to the substrate raw material based on 100 vt% of the substrate raw material, and the mixture was molded into a 2-inch square plate shape and kept in air at 1550°C for 2 hours. Fired.

(Margins below) Table 1 As a result, the amount of magnesium acetylacetonate added was 0.0% in terms of % of magnesium oxide.
005wt% or more, heat treatment temperature is 800~tooo℃
It was found that good results could be obtained in the case of That is, as shown in Table 1, within the above conditions, the surface roughness of the substrate was 0.04~(LO5m), whereas outside the above conditions, it was 0.07~0.13111m.
, and the crystal diameter is 1.0 to 1.0 on average under the above conditions.
1.3111a, but outside the above conditions it was 1.3111a.
It showed a fairly large value of 6 to 3.1-.

From this, it has been revealed that according to the present invention, an alumina substrate having good surface smoothness can be produced by adding a very small amount of magnesium. In particular, magnesium
The amount of acetylacetonate added is preferably 0.005 wt% or more in terms of % of magnesium oxide, and the heat treatment temperature is preferably 800 to 1000°C.

[Effects of the Invention] According to the present invention, it has become possible to produce an alumina substrate with extremely good surface smoothness by adding a small amount of magnesium oxide compared to the conventional method in the As-Fire method. Ta.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic cross-sectional views for explaining the manufacturing process of a substrate raw material in one embodiment of the present invention. ■-...Alumina particles 2--Coating with organic solvent 3...Outer shell of magnesium oxide) ζ, -'-2'-, Figure 2

Claims (1)

[Claims] (1) Alumina powder is dispersed in an organic solvent in which magnesium-acetylacetonate is dissolved to form a slurry, the organic solvent is evaporated from this slurry to form a powder, and then this powder is heat-treated. , further crushing to prepare a substrate raw material, molding and firing this substrate raw material to produce an alumina substrate.