JPS6019134B2 - 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 ceramic capacitor, which has 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 that can produce .

BACKGROUND ART Traditionally, Ti03-based porcelain or SrTi03-based porcelain has been used for ceramic capacitors. 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 surface or inner surface of 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. A surface layer type semiconductor ceramic capacitor has a thin insulating layer formed on the surface of its ceramic element, and utilizes the capacitance created by the thin insulating layer.

Structurally, most of the thickness of the ceramic element is occupied by dielectric material, and the thin layer on the surface acts as the dielectric material, making it possible to obtain a capacitor for low voltage use and large capacity. On the other hand, grain boundary layer type semiconductor ceramic capacitors insulate the crystal grain boundary layer by coating the surface of the semiconductor ceramic element with a metal that acts as an insulator, such as Cu or Mn oxide, and heat-treating the surface. It becomes a thing. Since such a grain boundary layer is made into a dielectric material, it has excellent withstand voltage and can obtain resistance values and capacitance suitable for high voltage applications. Whether the insulating layer is mainly formed 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. A ceramic element conventionally used in a grain boundary type semiconductor ceramic capacitor is one in which BaTiO3 is bathed in an oxide such as Sr, Bi, Zr, or Sn.

Although this apparently has a large effective mysterious electric constant of 40,000 to 70,000, the capacitance temperature change rate is large, and the maximum change rate is around 50% in the temperature range of 12yo to 85qo, with 2000 being the cold standard. The dielectric loss (tan6) is also as large as 0.0 slope. Also, SrTi0
3 to which oxides such as Dy, Ce, Mn, Ta, W, Nb, Si or Bi are added, and furthermore, SrTi0
A semiconductor ceramic made of CaTi03 is used in which a part of 3 is replaced with CaTi03. This SrTi03-based semiconductor ceramic has a significantly smaller capacitance temperature change rate of about ±15% than the mother Ti03-based one, and its dielectric loss (n8) is also small at 0.007 to 0.03. I am getting things too. However, the temperature required for sintering is 1
It is not common because it is high at over 400q0. 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 that has a large apparent effective permittivity and low dielectric loss. 4. In particular, it has the characteristics of a significantly small capacitance change rate over a low temperature range, a large resistance value and a high breakdown voltage, and good life characteristics. be.

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.
To 10 parts by weight of the main component consisting of 80 to 46.78 mol %, 0.01 to 1. a parts by weight,
And a composition in which 0.01 to 1.2 parts by weight of at least one of Ta205 component, Nb2Q component, and Sb203 component is added is sintered in a neutral or reducing atmosphere,
The purpose is to make it into semiconductor porcelain.

A further object of the present invention is to make the grain boundary layer of the semiconductor porcelain an insulator. Furthermore, there are also mountains, Cu, Zn, Pb and S.
The purpose of the present invention is to form a metal electrode by a thermal spraying method using at least one of n or an alloy mainly composed of the same. According to this method, the magnitude of the dielectric constant and the rate of change in capacitance with temperature can be freely selected by changing the proportions of the components, and the manufacturing thereof is also easy.

Furthermore, the ceramic element obtained by sintering can be easily connected with lead wires by soldering. Here we will discuss the reasons for determining the composition of semiconductor porcelain.

In the main components, when the Tj02 component increases, the yield factor decreases, the dielectric loss and the capacitance temperature change rate increase, and the resistance of the ceramic element decreases. Moreover, when the amount decreases, the dielectric constant decreases. Therefore, it is desirable that the composition ratio of the main components be within the range of 50.20 to 53.22 mol%. When the Su0 component increases, the dielectric constant, capacitance temperature change rate, and insulation resistance deteriorate, and it becomes difficult for the ceramic element to become a semiconductor. Conversely, when the amount decreases, the effect of improving the capacitance temperature change rate and insulation resistance becomes poor, and the dielectric loss also increases. Therefore, this composition ratio is 46.78 to 49.80 mol% in the main component.
It is desirable that it be within the range of . As subcomponents, metal components such as Ta, Nb, Tj, and W, and Ta2Q and Nb2
4. Adding oxide components such as Sb203 at the same time is effective in lowering the leech formation temperature of the ceramic element and creating a semiconductor ceramic element with low resistivity. This is effective in obtaining a semiconductor ceramic capacitor with low body loss and stable life characteristics. Note that if the amount of the metal component added is too large, the dielectric constant will decrease and the dielectric loss will also worsen. When it decreases, the dielectric constant decreases significantly, the capacitance temperature change rate increases, and the insulation resistance also decreases. Therefore, the amount of metal components is
With respect to 10 parts by weight of the main component in the above composition, the total amount is 0.
It is desirable that the amount is within the range of 0.01 to 1.2 parts by weight. In addition, components such as Ta core 5, N wide 05, and SQ03 are S
Although it is effective in converting rTi03-based ceramics into semiconductors, if the amount is too large, the dielectric constant decreases and the loss in the conductor deteriorates. When it decreases, the yield rate will drop significantly and the resistivity of the porcelain body will become extremely unstable. Therefore, the total amount of the above components is 100% of the main component of the above composition.
It is desirable that the amount is in the range of 0.01 to 1.5 parts by weight. Furthermore, in the present invention, the firing atmosphere is made neutral or reducing in order to prevent the explosiveness of the metal components, reduce the resistivity of the porcelain to below 0.50, and then This is to prevent the crystal particles themselves from becoming an insulator at a temperature that causes an insulator to be formed in the field.

Note that the resistivity value of the insulating layer formed at the grain boundaries is preferably 1070 or more. Next, the method of the present invention will be explained based on examples.

[Example 1] First, Tj02 and SrC, which are industrial raw materials with a purity of 98% or more,
Prepare 03, SQ03, Nb2Q and Ta205,
Furthermore, metal powders of Ta, Nb, W, and Ti having a purity of 99.99% or higher were prepared.

Then, the raw flour powder prepared to have the composition ratio shown in Table 1 was placed in a urethane-lined pot, wet-mixed using a urethane ball, and then water in the mixture was evaporated.
Then, this was made with a diameter of 15 ribs at a pressure of about 700k9' ground.
It was molded into a disk shape with a thickness of 0.8 ribs. The molded body was heated at 1300 to 1400 o○ for 2 hours in a neutral or reducing atmosphere.
It was held for a while and fired. Nitrogen gas or argon gas was used as the neutral atmosphere, and hydrogen gas was used as the reducing atmosphere. Of course, an inert gas other than nitrogen gas or argon gas may be used to create a neutral atmosphere. The firing was carried out in an alumina combustion tube using an SIC heating element. C on the surface of the obtained semiconductor ceramic element.
For u20, Bi203, and P, at least one of 04 and Mn02 is applied as a diffusing substance for 0.3 to 3 times,
It was heat-treated at 1100 to 1300 oo in the atmosphere and diffused.

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, silver paste was baked on both sides of the semiconductor ceramic element to form Ag electrodes.

For comparison, the porcelain body was fired in air (Sample 29)
. Table 1* Comparative Example The electrical characteristics of each of the above samples were measured.

The results are summarized in Table 2. In addition, in this table, the dielectric constant and dielectric loss (tan6) are
This is a value measured at a frequency of IKHZ at 00. In addition, the rate of change in capacitance is determined by the rate of change in dielectric constant with temperature, that is, 2
Based on 0oo, evaluation was made based on the rate of change in values at -2yC and 8500. Moreover, the insulation resistance is a value when the applied voltage is measured as a DC voltage of 50V. Furthermore, the high temperature load life characteristics are as follows:
It is expressed as the rate of change in capacitance with respect to the initial value after 1000 hours of application. Table 2 * Comparative Examples Samples 1 to 9 in the above table are samples in which only the composition ratio of the main component was changed.As is clear from these samples, when the main component has a composition ratio within the range of the present invention, It has excellent silkworm characteristics, capacity temperature change rate, and high-temperature life characteristics.

In particular, sample 5 had excellent characteristics overall, and also had extremely excellent characteristics as a capacitor.
Samples 10 to 26 are examples in which the amount of subcomponents added was changed, and samples 14 to 17, 20 to 22, and 26 according to the present invention
It can be seen that this is superior to other samples.

Further, when compared with Samples 10 and 11, it can be seen that the high temperature life characteristics are improved when both the metal component and the oxide component are added. Samples 27 to 29 show the influence of the firing atmosphere on the characteristics, and sample 29 fired in air has extremely poor yield rate and capacity temperature change rate.

Therefore, the firing atmosphere needs to be neutral or reducing. [Example 2] In the main components, Tj02 was 51.5 mol% and S component was 48.5 mol%, and Ta and Nb components were each 0.1 parts by weight with respect to 100 parts by weight of the main components. ,SQ
A semiconductor ceramic element was produced in the same manner as in Example 1 by blending the raw materials so that the 03 component was 0.25 parts by weight and the Ta2Q component was 0.2 parts by weight.

Note that nitrogen gas was used in the firing atmosphere. Electrodes were attached to the obtained semiconductor ceramic element by a thermal spraying method.
Regarding the electrode, there is also a C that can be soldered on top of it.
U was sprayed. The characteristics of the semiconductor ceramic capacitor thus produced were measured under the same conditions as in Example 1.

The results are shown in Table 3. Table 3 *I Pb-Sn alloy has 30% Pb and Sn is an alloy of Atomic Energy Association o *2 AI "0r alloy has AI of 80%, 0
This is an alloy in which r is 20%.

Samples 30 to 36 show the relationship between the difference in electrode formation methods and the characteristics as a ceramic capacitor. It can be seen from this that although it is possible to obtain sufficiently excellent characteristics as a capacitor even with Ag baked electrodes, it is possible to produce a ceramic capacitor with an even higher dielectric constant by attaching the electrodes by thermal spraying. In particular, N and Cu are used as electrode materials.
, easy availability of metal materials such as Zn, Pb, and Sn;
It is suitable for mass production because of its low cost and ease of handling. These can be used alone or as an alloy. As explained above, according to the method of the present invention, it is possible to easily mass-produce semiconductor ceramic capacitors having excellent various characteristics, and it is possible to provide capacitors useful as electronic components.

Claims (1)

[Claims] 1 Ta and Nb are added as subcomponents to 100 parts by weight of the main component consisting of 50.20 to 53.22 mol% of TiO_2 component and 49.80 to 46.78 mol% of Sro component. , at least one metal component among TiW is 0.0
1 to 2 parts by weight, and Ta_2O_5 component and Nb_2O
Grain boundaries of a semiconductor ceramic body obtained by adding 0.01 to 1.5 parts by weight of at least one of the _5 component and the Sb_2O_3 component and sintering in a neutral or cyclic atmosphere. A method for manufacturing a semiconductor ceramic capacitor, characterized in that the layers are made of an insulating material. 2 Among 100 parts by weight of the main component consisting of 50.20 to 53.22 mol% of the TiO_2 component and 49.80 to 46.78 mol% of the Sro component, among Ta, Nb, Ti, and W are added as subcomponents. At least one metal component.
01 to 1.2 parts by weight, and Ta^2O_5 component and Nb
Grain boundary layer of a semiconductor ceramic body obtained by adding 0.01 to 1.5 parts by weight of at least one of the _2O_5 component and the Sb_2O_3 component and sintering in a neutral or reducing atmosphere. is made into an insulator, and then at least one selected from the group of metals Al, Cu, Zn, Pb and Sn, or an alloy thereof, is thermally sprayed onto the semiconductor porcelain body to form an electrode. Method for manufacturing semiconductor ceramic capacitors.