JPH05345675A - Setter for burning semiconductor ceramic - Google Patents

Abstract

PURPOSE:To provide a setter for burning a semiconductor ceramic having excellent workability without causing adhesion to or reaction with the ceramic formed article to be burned. CONSTITUTION:The setter forms a SrTiO3 layer through a ZrO2-SrTiO3 intermediate layer on at least either one surface of a ZrO2 sheet. This setter is obtained by applying a SrTiO3 based ceramic having same composition as a semiconductor ceramic onto the surface of the ZrO2 sheet and burning the ceramic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a setter for firing semiconductor ceramics, and particularly to a setter used for firing semiconductor ceramics used for electronic parts such as capacitors and thermistors.

[0002]

2. Description of the Related Art The above-mentioned semiconductor ceramics are usually prepared by calcining ceramic powders mixed in a predetermined ratio, then crushing and granulating, and then press-molding them into a predetermined shape.
It is generally manufactured by firing this ceramic molded body.

Firing of this ceramic molded body is carried out by vertically stacking the molded body on a setter made of Al ₂ O ₃ , ZrO ₂ or the like.
Alternatively, either of the methods of arranging a large number of them side by side and firing them was performed. Then, in order to prevent a reaction between the molded bodies, a powder having the same composition as that of the molded bodies is used as spread powder (together powder) between these molded bodies.

However, when these powders are used as spread powder, they cause adhesion or reaction to the ceramic body to be fired, which adversely affects the physical properties of the sintered body. As a result, homogeneous semiconductor ceramics could not be obtained, and the yield was significantly reduced. In particular, the ceramic to-be-fired body that comes into contact with the firing setter is inevitable to be contaminated from the setter even with the spread powder, and as a result, the lowest fired body that comes into contact with the setter was discarded as a defective product. ..

On the other hand, the following proposals have heretofore been made to prevent the above-mentioned harmful effects. That is, at the time of firing the ceramic body as an electronic component, the ceramic body is formed by interposing a sintered body made of the same material as the ceramic body between the ceramic bodies which are unsintered bodies. This is a method for manufacturing a ceramic body to be fired (Japanese Patent Laid-Open No. 2461/1990)
(See Publication No. 05).

[0006]

According to this prior art, since a sintered body having the same composition as the ceramic body to be burned is used instead of the floor powder, adhesion of the floor powder to the ceramic body to be burned or The reaction can be prevented, and the yield can be improved.

However, since the pre-sintered body contacts and reacts with the setter for firing, even if the pre-sintered body in contact with the setter is interposed with the pre-sintered body, it is still affected by contamination from the setter. I was left with challenges. In particular, this tendency was remarkable when SrTiO ₃ was fired in a high temperature reducing atmosphere.

Further, according to this conventional technique, when a pre-sintered body having the same composition as the ceramic compact to be fired is subjected to firing in a reducing atmosphere, one of the pre-sintered bodies is placed between the ceramic compacts. The work of sandwiching one is required. As a result, there is a problem that workability is significantly deteriorated and productivity is low.

The object of the present invention relates to a firing setter which can advantageously solve the above problems of the prior art, and in particular, firing of semiconductor ceramics which is excellent in workability without causing adhesion or reaction to a ceramic object to be fired. To provide a setter for

[0010]

Means for Solving the Problems As a result of intensive studies for realizing the above object, the present inventors have found that ZrO ₂ having excellent heat resistance.
The firing setter obtained by coating and firing ceramics having the same composition as the semiconductor ceramics on the plate does not cause adhesion or reaction with respect to the ceramic firing target.
Moreover, the present invention has been conceived by finding that it is effective for facilitating the firing work of semiconductor ceramics and improving productivity.

That is, according to the present invention, on at least one surface of the ZrO ₂ plate, Sr having the same composition as that of the semiconductor ceramics is used.
By coating and firing TiO ₃ ceramics,
A setter for firing semiconductor ceramics, comprising a SrTiO ₃ layer formed on the surface of a ZrO ₂ plate via a ZrO ₂ —SrTiO ₃ intermediate layer.

[0012]

The characteristic of the setter of the present invention is that the SrTiO ₃ layer having the same composition as the semiconductor ceramics is formed on the ZrO ₂ plate via the ZrO ₂ —SrTiO ₃ intermediate layer. The setter is based on ZrO ₂ which is a heat resistant material,
In addition, between the SrTiO ₃ layer and the ZrO ₂ plate, ZrO ₂
Since -SrTiO ₃ intermediate layer is present, durable overall setter, and nor adversely affect reacts with the ceramic to be fired.

As a result, in the setter of the present invention,
Since the SrTiO ₃ layer having the same composition as the semiconductor ceramics is formed on the contact surface with the ceramic fired body, there is no contamination from the setter, and the ceramic fired body or ceramic powder (laying powder) does not adhere or react. The semiconductor ceramics can be fired. Moreover, since the setter of the present invention can be used in direct contact with the ceramic body to be burned, as compared to the case of the conventional technique in which a sintered body of SrTiO ₃ is interposed between the setter and the body to be fired. , The workability can be greatly improved.

[0014] In the present invention, ZrO ₂ -SrTiO ₃ intermediate layer and SrTiO ₃ layer, SrTiO ₃ ceramic target heating subject the same composition
The system ceramics, coated ZrO ₂ substrate is obtained by firing, ZrO ₂ -Sr having an action as described above
In order to effectively form the TiO ₃ intermediate layer, the SrTiO ₃ -based ceramics on this substrate are strongly reductively fired, and
It is desirable to use a material that easily reacts with the ZrO ₂ plate to some extent.

The sintering setter of the present invention is as follows.
A mixed powder, a calcined powder, or a calcined powder (sintered powder) having the same composition as the semiconductor ceramics is well mixed with an organic binder aqueous solution such as polyvinyl alcohol to form a slurry, which is thinly applied on the ZrO ₂ plate, and then debinding, It is manufactured by firing in a reducing atmosphere and baking a ceramic layer on a ZrO ₂ plate.

In the firing setter of the present invention, ZrO ₂
The -SrTiO ₃ interlayer and SrTiO ₃ layer, may also be formed only on one surface of the ZrO ₂ plate, or may also be formed on both surfaces.
For example, in firing performed by vertically stacking ceramic molded bodies on a ZrO ₂ substrate, the former case is preferably used as a bottom member of vertically fired bodies, and the latter case is vertically stacked fired bodies. It is preferably used by interposing between the bodies.

[0017]

【Example】

(Example 1) First, composition ratio _{SrCO 3: 50mol%, TiO 2} : 49~51
_{mol%, Nb 2 O 5:} 0.1~0.2mol% and MnCO _3: 0.05~0.1mol%
SrCO ₃ , TiO ₂ , Nb ₂ O ₅ and MnCO ₃ are weighed so that
A ball mill was used to mix for 20 hours to obtain a raw material mixed powder. Then, an appropriate amount of this mixed powder was thoroughly mixed with an organic binder aqueous solution (5% polyvinyl alcohol aqueous solution) to form a slurry, which was thinly applied to a commercially available ZrO ₂ plate. And 1150-1200
It baked at 2 degreeC for 2-4 hours, and obtained the board | substrate for baking. Note that this heat treatment has the effect of improving the adhesion to the substrate at the same time as the mixed powder reacts.

Next, on this fired substrate, a molded body made of powder having the same composition as the above-mentioned mixed powder that has been calcined, molded, and degreased is powdered so that the molded bodies do not adhere to each other. )
I sprinkled them on top of each other and layered several. Then, in a N ₂ / H ₂ reducing atmosphere,
Primary baking was performed at 50 to 1520 ° C. for 2 to 4 hours. next,
Bi ₂ O ₃ based diffusing agent was applied to the obtained ceramic sintered body,
Secondary firing was carried out at 1150 to 1250 ° C. for 1 hour in the atmosphere.
Next, an electrode was formed by baking an Ag paste to obtain a grain boundary type semiconductor capacitor.

Table 1 shows the results of measuring the electrical characteristics (capacitance, dielectric loss tangent tan δ, insulation resistance IR) of the semiconductor capacitor obtained by firing the molded body that was in contact with the firing setter of the present invention. As a comparative example, without using the firing setter of the present invention, that is, ZrO ₂ without coating
The electrical characteristics of the semiconductor capacitor obtained by firing the molded body that was in contact with the plate are shown. The size of the molded body is 8.0 mmφ
The capacitance and dielectric loss tangent tanδ are measured at 1kHz, and the insulation resistance IR is 25V for 20 seconds. Also, Table 1
The data shown in is the average value of 20 data.

As is clear from the results shown in Table 1, when the firing setter of the present invention was used, it was obtained as compared with the comparative example in which the ceramic molded body was directly placed on the ZnO ₂ substrate and fired. It was found that the effect on the physical properties (electrical properties) of the product was extremely small. That is, it was found that the firing setter of the present invention did not cause adhesion or reaction with the ceramic compact to be fired.

[0021]

[Table 1]

(Example 2) First, the composition ratio was SrCO ₃ : 50 mol.
%, TiO ₂ : 49 to 51 mol%, Nb ₂ O ₅ : 0.1 to 0.2 mol% and MnCO ₃ :
SrCO ₃ , TiO ₂ , Nb ₂ O ₅ and Mn so as to be 0.05 to 0.1 mol%
CO ₃ was weighed and mixed with a ball mill for 20 hours to obtain a raw material mixed powder. Next, this mixed powder and an appropriate amount of the fired powder (both powders) of the same composition were well mixed with an organic binder aqueous solution (5% polyvinyl alcohol aqueous solution) to form a slurry, which was thinly applied to a commercially available ZrO ₂ plate. And 2 at 1150-1200 ℃
It baked for 4 hours and obtained the setter for baking. Note that this heat treatment has the effect of improving the adhesion to the substrate at the same time as the mixed powder reacts.

Next, on the setter for firing, a molded body made of powder having the same composition as the mixed powder calcined, molded, and degreased is powdered (fired with the same composition so that the molded bodies are not fused to each other). (Powder) and layered several. Then, primary baking was performed at 1450 to 1520 ° C. in a N ₂ / H ₂ reducing atmosphere for 2 to 4 hours.
Next, a Bi ₂ O ₃ -based diffusing agent was applied to the obtained ceramic sintered body, and secondary firing was performed at 1150 to 1250 ° C. for 1 hour in the air. Next, an electrode was formed by baking Ag paste to obtain a grain boundary type semiconductor capacitor.

Table 2 shows the results of measuring the electrical characteristics (capacitance, dielectric loss tangent tan δ, insulation resistance IR) of the semiconductor capacitors obtained by firing the molded body that was in contact with the firing setter of the present invention. As a comparative example, without using the firing setter of the present invention, that is, ZrO ₂ without coating
The electrical characteristics of the semiconductor capacitor obtained by firing the molded body that was in contact with the plate are shown. The size of the molded body is 8.0 mmφ
The capacitance and dielectric loss tangent tanδ are measured at 1kHz, and the insulation resistance IR is 25V for 20 seconds. Also, Table 2
The data shown in is the average value of 20 data.

As is clear from the results shown in Table 2, when the firing setter of the present invention was used, it was obtained as compared with the comparative example in which the ceramic molded body was directly placed on the ZnO ₂ substrate and fired. It was found that the effect on the physical properties (electrical properties) of the product was extremely small. That is, it was found that the firing setter of the present invention did not cause adhesion or reaction with the ceramic compact to be fired.

[0026]

[Table 2]

[0027]

As described above, according to the present invention, a semiconductor ceramic firing setter according to the present invention, on the ZrO ₂ plate, ZrO ₂ -SrTi
SrTi with the same composition as the semiconductor ceramics through the O ₃ intermediate layer
Since the O ₃ layer is formed, the semiconductor ceramics can be easily fired without causing adhesion or reaction to the ceramic molded body to be fired. Moreover,
Since it can be used by directly contacting with the ceramic fired object,
Workability can be greatly improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Sato 5-9-6 Tokodai, Tsukuba-shi, Ibaraki Nippon Heavy Industries, Ltd. Tsukuba Research Institute

Claims (1)

[Claims] To claim 1 wherein at least one surface of the ZrO ₂ plate, applying a SrTiO ₃ based ceramic is the same composition as the semiconductor ceramic, by baking, ZrO ₂ on the surface of the ZrO ₂ plate
A semiconductor ceramic firing setter having an SrTiO ₃ layer formed via an SrTiO ₃ intermediate layer.