JPH04154672A - Production of ceramic sintered compact for electronic part - Google Patents

Abstract

PURPOSE:To obtain the title sintered compact without causing variation in its composition by calcining a form containing a metallic oxide liable to migrate in calcining operation on a plate consisting of a ceramic sintered compact containing the same kind of metallic oxide liable to migrate in the calcining process. CONSTITUTION:A plate 4 consisting of a ceramic sintered compact containing a metallic oxide (e.g. Sb2O3) liable to migrate in calcining operation is set up on a stock 2, and plural metallic oxide form 1 (e.g. varistor form) each containing the same kind of metallic oxide as that mentioned above are set up upright adjacently to each other on the plate 4. The system as a whole is then put into a hot oven where the forms 1 are calcined, thus obtaining the objective ceramic sintered compact for electronic parts. Thereby, because of putting the plate 4 in between, the transfer (due to outflow, diffusion, etc.) of the metallic oxide liable to migrate in calcining from the forms 1 to the stock 2 side can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic sintered body for electron beam nodes such as ceramic varistors.

[Prior art and problems to be solved by the invention] ZnO
A voltage nonlinear resistor (hereinafter simply referred to as a varistor) whose main component is a varistor is produced by mixing several types of oxide raw materials, granulating them using an organic binder, and then granulating them into a disc-shaped disc ( It is obtained by finishing it into a varistor molded body and firing it. As a method for firing varistor molded bodies, there is a method in which a large number of varistor molded bodies are placed upright in a V-shaped groove of a mounting table whose main component is magnesium oxide (magnesia), and fired. According to this method, it is possible to avoid adhesion of varistor molded bodies to each other, which is a problem when a plurality of varistor molded bodies are stacked and fired.

However, with this firing method, the inventor of the present application has found that some metal oxides are sucked into the mounting table at the portions that come into contact with the mounting table during firing and in the vicinity thereof, causing a change in the composition ratio of the molded body. confirmed by.

Figure 5 shows 'ZnO produced by conventional firing method.
The distribution state of sb (antimony oxide) in the varistor sintered body 1b whose main component is sb is schematically shown by dots. As shown in the figure, the content of 5b203 is significantly reduced in the portion in contact with the mounting table 2 and in the vicinity thereof, and it can be seen that 5b203 is not uniformly distributed throughout the sintered body. 5b203 is a metal oxide that has the effect of suppressing the increase of crystal grains (ZnO crystal grains), and the crystal grain size is significantly large in the above portion where the S b 2 o-s content is small. was confirmed. If such a portion has a large crystal grain size, it becomes difficult to obtain a varistor with excellent surge resistance.

I just mentioned a varistor whose main component is ZnO,
Similar problems arise with ceramics of other compositions.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a ceramic sintered body for electronic components, which can suppress variations in the composition of starting materials.

[Means for Solving the Problems] The present invention for achieving the above object includes a step of forming a molded body of a plurality of metal oxides containing metal oxides that move during firing, and a step of preparing a mounting body made of a ceramic sintered body containing a metal oxide that is easy to oxidize, and a step of placing the molded body on the mounting body and firing the molded body to obtain a sintered body. The present invention relates to a method of manufacturing a ceramic sintered body for electronic components, characterized by having the following features.

Note that the present invention is suitable for producing a varistor whose main component is ZnO and also contains 5b203 (antimony oxide).
It is desirable to include g.

[Function] Since the mounting body according to the present invention contains the same metal oxide as the easily mobile metal oxide contained in the molded body, the metal oxide does not leak or diffuse from the molded body side to the mounting body side. It is possible to suppress movement caused by such factors.

This maintains the composition of the molded body and provides a high quality sintered body.

In the case of a varistor whose main component is ZnO, 5b
By including 203 in the mounting body, 5b20 of the molded body
The movement of No. 3 to the outside of the molded body is restricted.

Uniform grain size is achieved.

[Example] Next, a method for manufacturing a varistor element containing ZnO as a main component according to an example of the present invention will be described with reference to FIGS. 1 to 4 and 6.

First, 93.2 mol% ZnO (zinc oxide), 0.3 mol% Bi2O3 (bismuth oxide), 1.5 mol% 5
b203 (antimony oxide), 1°0 mol% 000
(cobalt oxide), 2.5 mol% Mg0 (magnesium oxide), 0.5 mol% Mn0 (manganese oxide), 1
．． 0.05 parts by weight of 820a per 100 parts by weight of the basic component consisting of 0 mol% Ni0 (nickel oxide)
<Boron oxide) and 0.003 parts by weight of Al2O3 (aluminum oxide) were mixed thoroughly in a ball mill, and this mixture was granulated in a spray dryer (granulator). Among the metal oxides mentioned above, 5b203 is a low melting point metal oxide with a melting point of about 656°C that functions to suppress the increase in the grain size of ZnO crystal grains when forming a varistor sintered body to be described later. It is.

Next, the granulated raw material is compression molded to a target size of approximately 1 mm in diameter.
A disc-shaped varistor molded body 1 with a diameter of 0 am and a thickness of approximately 31 mm was manufactured.

Next, in order to sinter the varistor molded body 1, a mounting table 2 and two mounting plates 4 having grooves 3 shown in FIGS. 1 to 3 were prepared. The mounting plate 4 is made of the same metal oxide as the raw material of the varistor molded body 1, that is, ZnO.

Bi2O3,5b203,CoOlMgOSMnOlN
This is a ceramic sintered body made by molding a mixture of iOSB O and Al2O3 into a plate shape and then firing it. However, the content of S b 203 in the mounting plate 4 is about 2.0 mol %, which is higher than the content of 5b203 contained in the raw material of the varistor molded body 1. The mounting table 2 is a sintered body whose main component is magnesium oxide (magnesia), and a V-shaped groove 3 is provided on one main surface thereof.

Next, the mounting plate 4 was placed on the two surfaces constituting the groove 3 of the mounting table 2, and a plurality of the above-mentioned varistor molded bodies 1 were placed upright thereon and adjacent to each other. As is clear from FIG. 1, the varistor molded body 1 contacts the mounting plate 4 at two places, and the other parts of the varistor molded body 1 contact the mounting plate 4.
Do not come into contact with

Further, the varistor molded body 1 does not touch the mounting table 2 at all.

With the varistor molded body 1 arranged as described above, the varistor molded body 1 was placed in a heating furnace together with the mounting table 2 and the mounting plate 4, and the varistor molded body 1 was fired. The heat treatment temperature and time for firing is 500℃
The temperature was raised to 1250° C. at a rate of about 00° C./hour and then about 50° C./hour, maintained at 1250° C. (peak temperature) for 1 hour, and then naturally cooled. Note that this heat treatment was performed in an air atmosphere. As a result, a sintered body 1a of the varistor molded body 1 was obtained. The composition of this sintered body 1a is substantially the same as that of the starting material.

Next, as shown in FIG. 6, Ag (silver) paste is coated on both sides of the varistor sintered body 1a and baked to form a pair of electrodes 5.
．． 6 was formed to complete the varistor element.

Next, in order to examine the surge withstand capacity of the varistor element, we first measured the voltage (varistor voltage) Via between the electrodes 5 and 6 when 1 mA was applied to the varistor element, and then measured the 8 A surge current of 250 OA for 20 μs was applied to the varistor element five times at 30 second intervals, and the varistor voltage Vlb at 1 mA was measured again. Then, the rate of change d of the varistor voltage was determined based on the initial varistor voltage Vla and the varistor voltage Vlb after the surge was applied using the following equation.

d-[(Via-Vlb)/Vial X 100
(%) The above measurements were repeated until the rate of change d of the varistor voltage became 10% or more. As a result, the rate of change d of the varistor voltage was 10% or more after 40 measurements. That is, the varistor voltage Vl decreased by 10% or more after applying the surge current 40×5-200 times.

On the other hand, when similar measurements were performed on the conventional varistor element shown in FIG. 5, the varistor voltage V1 decreased by more than 10% after 7 measurements (7×5-35 surge current applications). Since the greater the number of measurements (the number of times of surge current application), the greater the surge withstand capacity, the present invention strives to significantly improve the surge withstand capacity of the varistor element.

Note that the above measurement results are the average values of 10 varistor elements.

Furthermore, when the crystalline states of the varistor sintered body 1a according to this example and the conventional varistor sintered body 1b were observed under a microscope, it was found that the grain size of the varistor sintered body 1a according to this example was uniform and small. On the other hand, in the conventional varistor sintered body 1b, the grain size was non-uniform and large in the region where the concentration of 5b203 was low as shown in FIG.

Further, when the distribution concentration of 5b203 in the sintered body 1a of this example was measured, it was found that 5b203 was uniformly distributed as schematically shown by the dots in FIG. That is, this distribution corresponds to S b in the conventional sintered body 1b shown in FIG.
The distribution was significantly improved compared to that of 20a.

The uniform distribution of S b 20 g in this example is sbO
This is achieved by using a mounting plate 4 containing . The mounting plate 4 is made of the same material as the sintered body 1a, and the content of 5b203 is approximately 2.0% higher than that of the sintered body 1a.
Since it is mol%, 5b20 of molded body 1 during firing
8 is restricted from moving to the mounting plate 4 by diffusion or flow. When the movement of 5b203 and other low-melting point substances to the mounting plate 4 is suppressed in this way, crystal grains with good uniformity are formed, and the surge current withstand capacity is improved as described above.

[Modifications] The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

(1) The mounting table 2 may contain 5b203, which is a low melting point substance, and the mounting plate 4 may be omitted, and the compact 1 may be placed on the Sb 2 O-containing mounting table 2.

(2) The shape of the mounting plate 4 made of a sintered body can be changed in various ways, for example, it may have a cross-section shaped like a square square according to the shape of the groove 3 of the mounting table 2.

(3) Although it is desirable that the mounting body such as the mounting plate 4 be formed of the same material as the varistor sintered body 1a, the sintered body may have a different composition containing Sb 20 s.

(4) The present invention is particularly effective in preventing the outflow of metal oxides that have the function of suppressing crystal grain growth, such as 5b203, but it is also effective in preventing the outflow of low-melting point metal oxides such as Bi2O3 and 8203. Effective when applied.

(5) The mounting table 2 can be made of a sintered body made of Zr (zirconium), for example.

(6) The present invention can also be applied to the production of ceramic sintered bodies other than varistors.

[Effects of the Invention] As described above, according to the present invention, the uniformity of the distribution of easily mobile components can be improved, and a sintered body with good characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a front view showing an apparatus for manufacturing a varistor sintered body according to a first embodiment of the present invention, FIG. 2 is a partially cutaway plan view of the apparatus shown in FIG. 1, and FIG.
FIG. 4 is a perspective view showing the mounting table and the mounting plate shown in FIG.
5 is a diagram schematically showing the distribution of 03, FIG. 5 is a diagram schematically showing the distribution of 5b208 in a conventional varistor sintered body, and FIG. 6 is a front view showing a varistor element. 1. Molded body, 1a... Sintered body, 4... Antimony oxide; Mounting plate containing.

Claims (1)

[Scope of Claims] [1] A step of forming a molded body of a plurality of metal oxides containing a metal oxide that is easily mobile during firing, and a step of forming a ceramic sintered body containing the metal oxide that is easily mobile. Ceramic sintering for electronic components, characterized by comprising the steps of: preparing a mounting body consisting of the mounting body, and obtaining a sintered body by placing the molded body on the mounting body and firing the molded body. How the body is manufactured. [2] The method for manufacturing a ceramic sintered body for electronic components according to claim 1, wherein the easily mobile metal oxide is a substance having a melting point lower than the firing temperature. [3] The method for producing a ceramic sintered body for electronic components according to claim 2, wherein the molded body is a molded body of a varistor material containing zinc oxide as a main component, and the substance with a low melting point is antimony oxide.