JPS6030094B2 - Manufacturing method of semiconductor ceramic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor porcelain capacitor, and provides a semiconductor porcelain capacitor with a large capacity, low loss, a small temperature change rate of capacitance over a wide temperature range, and a large resistance value. The purpose is to provide a method for manufacturing the same.

Powdered Ti03-based porcelain or SITi03-based porcelain is used for the secondary ceramic capacitor. These ceramics have a large dielectric constant and high insulation properties. When such porcelain is used in a capacitor, the capacitance depends on the dielectric constant of the porcelain, and the capacitance can be controlled to some extent by, for example, adjusting the thickness of the porcelain element or the area of its silver electrode-applied surface. It is something that can be done. The semiconductor ceramic capacitor of the present invention uses a semiconductor ceramic element having a relatively low resistivity, unlike the above-described ceramic element in which the ceramic element is an insulator.

To put it simply, a semiconductor ceramic capacitor is one in which a capacitive insulating layer is formed at grain boundaries on the normal outer or inner surface of a semiconductor ceramic. In such semiconductor ceramic capacitors, the former is called a surface layer type, and the latter is called a grain boundary layer type.

There are many types of semiconductor ceramic capacitors known so far, but most of them can be classified into one of the above two types. Surface layer semiconductor ceramic capacitors are
A thin insulating layer is formed on the surface of the ceramic element, and the resulting capacitance is utilized.

Structurally, most of the thickness of the ceramic element is occupied by the conductor, and the thin layer on the surface acts as a dielectric, making it possible to obtain a capacitor with a large capacity for low voltage use. On the other hand, grain boundary layer type semiconductor ceramic capacitors have a metal layer on the surface of the semiconductor ceramic element that acts as an insulator.
For example, the grain boundary layer is made into an insulator by applying Cu or Mn oxide and heat-treating it. Since such a grain boundary layer is made into a dielectric material, it has excellent withstand voltage and can obtain resistance values and capacitances suitable for high voltage applications. Whether the insulating layer is mainly generated on the surface of the semiconductor ceramic element or at the grain boundaries of the crystal is subtly influenced by the diffusion of oxygen into the element and the localization of impurities.

Furthermore, when semiconductor ceramics are used as capacitors, their characteristics are greatly influenced by the composition of the semiconductor ceramics and further by its subcomponents. One of the ceramic elements that has been used for some time in grain boundary type semiconductor ceramic capacitors is BaTiO3 with oxides such as S, Bi, Zr, or Sn precipitated thereon.

Although this apparently has a large effective yield rate of 40,000 to 70,000, the capacitance temperature change rate is large, and the maximum rate of change is around ±50% within the temperature range from -30q○ to 8500° with 20°○ as the standard. The dielectric loss (tan6) is also as large as 0.09 degrees Fahrenheit. Also SITi0
3 to which oxides such as Dy, Ce, Mn, Ta, W, Nb, Si or Bi are added, and furthermore, Srh03
There is one that uses semiconductor porcelain made of CaTj03 with a part of it replaced. This SrTi03-based semiconductor ceramic has a capacitance temperature change rate of about 15%, which is significantly smaller than that of the BaTi03-based one, and its dielectric loss (tan8) is 0.007 to 0.03, which is 4. And things are being obtained.

However, it is not common because the temperature required for dawning is as high as 140,000 or higher, and it must be fired in a reducing atmosphere, and there is also the problem that the characteristics of the resulting porcelain, such as resistivity, vary widely. The present invention makes it possible to manufacture a ceramic capacitor that eliminates the above-mentioned drawbacks, and the resulting capacitor is a grain boundary layer type semiconductor ceramic capacitor, which has a large field of view and effective power yield ratio, and has a low dielectric loss. It has the following characteristics: the temperature change rate of capacitance is extremely small over a wide temperature range, the resistance value is large and the breakdown voltage is high, and the life characteristics are good.

The method of the present invention is characterized in that the Ti02 component is 5
0.20 to 53.22 mol% and Sr○ component is 49.
With respect to the main component consisting of 80 to 46.78 mol%, Ta
, Nb, Sb, Bi, La, Nd, Ge, VV, Y, P
r, Ti, Mo, Dy, Gd, ln, Si, AI, Pb
, Zr, Sn, Ba, Ca, Mn, Fe, Zn and M
Adding and mixing at least one element selected from the group of elements g, its oxide, chloride, or carbonate as a subcomponent;
This mixture is fired in a neutral atmosphere in which carbon powder, carbon lumps, or carbon containers are placed. According to this method, semiconductor ceramic suitable as a capacitor material can be obtained. By changing the composition ratio, the magnitude of the apparent dielectric constant and the rate of change in capacitance with temperature can be freely selected, and manufacturing is also easy. Furthermore, the ceramic element obtained by firing can be easily connected with a lead wire by soldering. Here we will discuss the reasons for determining the composition of semiconductor porcelain.

In the main components, when the Ti02 component increases, the dielectric constant decreases, the dielectric loss and the rate of change in capacitance with temperature increase, and the resistance of the ceramic element decreases. Furthermore, when the amount decreases, the dielectric constant decreases and the capacitance temperature change rate increases.
Therefore, the composition ratio of the main components is 50.20~
It is desirable that the content be within the range of 53.22 mol%. As the S component increases, the dielectric constant decreases, and the ceramic element becomes less likely to become a semiconductor.

Conversely, when the amount decreases, the effect of improving the rate of change in capacitance with temperature becomes poor. Therefore, it is desirable that the composition ratio of the main components be within the range of 46.78 to 49.80 mol%. In addition, the subcomponents Ta and N
b, Sb, Bi, La, Nd, Ge, VV, Y, Pr,
Ti, Mo, Dy, Gd, ln, Sr, Si, AI, P
Each of the components b, Zr, Sn, B3, Ca, Zn, Mn, Fe, and Mg has the function of promoting semiconducting of SrTi03-based ceramics and is effective in improving the temperature change in dielectric constant. . The amount added is 0.01-2% by weight
is particularly appropriate. When components other than those mentioned above are added to the main components, the variation in the specific resistance of the porcelain increases and the reproducibility deteriorates. To explain this point in more detail,
Conventionally, semiconductor ceramic elements have been produced by adding monovalent, trivalent, or pentavalent elements to SrTj03-based ceramics and firing them in a neutral or reducing atmosphere.

A common firing method is to place a molded porcelain composition in a combustion tube made of chamots or alumina, and then fire it in a vacuum or in a reducing atmosphere. When actually firing, AI203 is used to prevent reactions between fired products.
and Z-2 are used, but these have a negative effect on the semiconducting of porcelain, and if oxides with poor purity are used, Fe components may be mixed in. It is not possible to obtain the low specific resistance that is supposed to be achieved. Moreover, its high purity is expensive, and even if it is used, it is not possible to obtain semiconductor ceramics with low resistivity as described above. Furthermore, when SrTi03 ceramic is fired in an atmosphere with a high oxygen partial pressure, it loses its semiconductivity and becomes a high-resistance material. The method of the present invention can solve all of these problems,
This was discovered as a result of studying the material used to underlay the molded product during firing, as well as the material for the container.

That is, in the method of the present invention, carbon powder, carbon lumps, a mixture of carbon and Zr02, or ZrC is used as the underlay material for the molded SrTi03-based porcelain composition, and a force-bonding container is used. There is.

By using such a carbon material during firing, it could not be obtained using conventional methods. 0.80
- It is possible to obtain a ceramic element with a low resistivity of less than .

The carbon material can completely prevent reactions between the fired products during firing, and AI203 and Zr
This is superior to 02. Furthermore, in the present invention, the reason why the firing atmosphere is neutral or reducing is to prevent the explosiveness of the metal components used as subcomponents, as well as to prevent the oxidation of carbon; This is to effectively utilize the reduction effect.

Next, the method of the present invention will be explained based on examples.

First, the industrial raw materials with a purity of 98% or higher, Ti02 and S, are
3 and Ta, Nb, Sb, Bi, La, Nd, Ce,
VV, Y, Pr, Ti, Mo, Dy, Gd, ln, Sr
, Si, Mountain, Pb, Zr, Sn, B9, Ca, Zn, M
Metal powders of n, Fe, and Mg, oxides, carbonates, and chlorides were prepared, and the raw material powders were mixed to a predetermined composition ratio and placed in a urethane-lined pot, and mixed in a striped manner using a urethane ball. Then the mixture was evaporated.

Then, by applying a pressure of about 700 k9/ground, it is molded into a willow disc shape with a diameter of 15 cm and a thickness of 0.8 k9, and this molded body is heated under a neutral atmosphere of argon or nitrogen to
0oo for 2 hours and fired. An alumina combustion tube was used for firing, and the molded products were stacked as shown in Figure 1. In the figure, 1 is a carbon container, and 2 is a molded product stacked on top of it. As the underlay material 3 of the molded product 2, a mixture of carbon powder and Z powder was used. Furthermore, as the underlay material 3, Zr02 powder is used instead of the above mixture, or as shown in Fig. 2, Zr02 powder is used as the underlay material 2, and carbon Also for the case where lump 4 is derived,
By firing or using an alumina port,
It was also fired as a base material. On the surface of the obtained ceramic element, Cra○, Bi203, Phiro04 and Mn0
At least one of 2 and the like was applied as a diffusing substance in 9 of 1 to 3, and heat treated at 1100 to 1300 qo in the atmosphere to diffuse it.

The thus obtained porcelain body was examined using an X-ray microanalyzer, and it was confirmed that ions of a diffusive substance were present in the grain boundaries. Further, electrodes were formed on both sides of the semiconductor ceramic element by using AI metallicon or Ag coating.

The characteristics of each of these samples were measured. The characteristics of each of these samples were measured. In addition, the specific resistance after semiconductor processing was also investigated. In the table below, the dielectric constant (G) and dielectric loss (Gn6) are calculated by increasing the temperature by 2.
This is a value measured at a frequency of IKHz at 0oC. Also, the capacitance temperature change rate is the dielectric constant temperature change rate, that is, 20
Based on qo, evaluation was made based on the rate of change in value at -2500 and 85°C. However, *Comparative examples, Samples 10 and 11: A mixture of carbon powder and Zr02 powder was used as the underlay material, Samples 12 and 13: Alumina boat, and a power bond was placed before and after the molded product.

Sample 14: Alumina boat, Zr02 as underlay material
Use powder. Remaining sample: Use carbon boat. As is clear from the above table, according to the method of the present invention, a semiconductor ceramic capacitor having a large dielectric constant, a small dielectric loss, and a small rate of change in capacitance with temperature can be obtained. In particular, sample 5 has extremely excellent characteristics, and its insulation resistance is extremely high at 8×1 PQ-arc when a DC voltage of 50 V is applied. Moreover, it has excellent voltage characteristics for both AC and DC, and has good life under high temperature load and under high humidity load. By the way, in Samples 1 to 9, the type ratio of the subcomponents was kept constant, and the composition ratio of the main component was varied.

Samples 10 to 14 are samples in which the types and ratios of the components are constant, but the firing conditions are changed. In Samples 15 to 25, the main component was kept constant, and the additive form, type, etc. of the subcomponents were changed.

Samples 26 to 29 had the same composition ratio, but the firing atmosphere was changed.

Among them, Sample 26 was fired in a hydrogen atmosphere, but in this case, it was difficult to convert the ceramic into a semiconductor, and it was easy to convert it into an insulator during the diffusion process. Furthermore, during firing,
In the case of using a carbon component, when a carbon boat is used, the specific resistance of the obtained semiconductor porcelain is the lowest, and even if carbon powder is used as the underlay material, one with sufficiently satisfactory characteristics can be produced.

However, when using carbon lumps, pay attention to the relationship with the amount of molded product to be fired. That is, although it is sufficient when the molded product is small, the reproducibility of the characteristics becomes poor when the molded product is large, so it is desirable to use a carbon boat. As described above, according to the method of the present invention, a semiconductor ceramic capacitor with excellent characteristics can be manufactured with good reproducibility.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams for explaining the method of manufacturing a semiconductor ceramic capacitor according to the present invention. 1... Boat, 2... Molded product, 3...
...Material for underlay, 4...Carbon lump. Figure 1 Figure 2

Claims (1)

[Claims] 1 Ta, Nb, Sb, Bi, La, N
d, Ge, W, Y, Pr, Ti, Mo, Gd, Sr, S
i, Al, Pb, Zr, Sn, Ba, Ca, Zn, Mn
Adding and mixing at least one metal selected from the element group Fe, its oxide, chloride, or carbonate as a subcomponent, and disposing this mixture in a carbon powder, a carbon lump, or a carbon container. A method for manufacturing a semiconductor ceramic capacitor, which comprises firing in a neutral atmosphere to insulate the crystal grain boundary layer of the obtained semiconductor ceramic body.