JPS6029213B2 - 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, and provides a semiconductor ceramic capacitor having 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.

Traditionally, Ti03 series porcelain or SrTi03 series porcelain has been used for ceramic capacitors. These porcelains have a high yield rate and high insulation properties. When such porcelain is used in a capacitor, the capacitance depends on the yield rate of the porcelain. For example, the capacitance can be controlled to some extent by 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. 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 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 crystal 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 lightning conductor, it has excellent withstand voltage and can obtain resistance values and capacitances 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 locality 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. BACKGROUND ART Conventionally used ceramic elements for grain boundary type semiconductor ceramic capacitors include BaTi03 in which oxides such as Sr, Bi, Zr, or Sn are dissolved as a solid solution.

This apparently has an effective dielectric constant of 40,000 to 70,000.
Although it is large, the capacitance temperature change rate is large and 2000
is the standard, and the maximum rate of change is around ±50% within the temperature range of -2500 to 8500 °C. The dielectric loss (tan6) is also as large as 0.0 cormness. In addition, Dy, Ce, Mn, Ta, W, Nb, S
Added oxides such as i, and even SrTi03
There is one using semiconductor porcelain made of CaTi03 partially substituted with CaTi03. This S'Ti03-based semiconductor porcelain has a significantly smaller capacitance temperature change rate of about 15% compared to the European Ti03-based one, and its dielectric loss (n6) is also 0.007 to 0.03. However, the temperature required for binding is 14
It is not common because it is high at 600C or more. 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 dielectric constant and a small dielectric loss. In particular, 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
0.02 to 52.00 mol% and Sr○ component is 49.
With respect to the weight part of the main component 10 consisting of 98 to 48.00 mol%, 0.1 to 8.5 weight% of Bi203 component and 0.04% of at least one of Ta205 component, NQ05 component, and Sb2Q component. The purpose is to sinter the composition to which ~2.2 parts by weight has been added in a mixed gas atmosphere of nitrogen and hydrogen, thereby converting the grain boundary layer of semiconductor ceramic into an insulator. Furthermore, if necessary, a metal electrode is formed by thermal spraying using at least one of AI, Cu, and Zn, or an alloy thereof. According to this method,
By changing the proportions of the components, 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 this process 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 dielectric constant decreases, the dielectric loss and the capacitance temperature change rate 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 50.02~
It is desirable that the content be within the range of 52.00 mol%. Sr.
○If the amount of the component increases, the dielectric constant, capacitance temperature change rate, and insulation resistance will deteriorate, and it will be difficult to convert the ceramic element into a semiconductor.

On the other hand, if the amount decreases, the effect of improving the capacitance-temperature change rate and insulation resistance will be poor, and the loss of insulation will also increase. It is desirable that it be within the range of %. The Bi203 component is particularly useful in reducing high frequency dielectric losses in porcelain. However, if there is too much of it, not only will the porcelain become rough and the dielectric loss at high frequencies increase, but also the life characteristics of the insulation resistance will deteriorate. On the other hand, if the amount is too small, the porcelain becomes unstable with respect to its diffusion temperature, and dielectric loss at high frequencies also worsens. Therefore, the Bi203 component has a main component of 10
It is desirable that the amount is 0.1 to 8.5 parts by weight relative to 0 parts by weight. Components such as Ta2Q, Nb205, and SQ03 are effective in converting SrTi03-based ceramics into semiconductors, but using only these components causes poor reproducibility and increases dielectric loss at high frequencies, which is not preferable. By including the rollers together with the Bi203 component in the S-Ti02 based porcelain, the specific resistance of the semiconductor porcelain is stabilized and reproducibility is improved. In addition, dielectric loss and capacitance temperature change rate at high frequencies are also improved. However, if there is too much of it, the dielectric constant decreases, making it difficult to sinter a delicate ceramic element, and dielectric loss also worsens. When it decreases, the dielectric constant decreases significantly and the capacitance temperature change rate increases. Therefore, the total amount of the above components is 0.04 to 100 parts by weight of the main component of the above composition.
It is desirable that the amount is within the range of 2.2 parts by weight. moreover,
In the present invention, the reason why the firing atmosphere is a mixed gas of nitrogen and hydrogen is to reduce the specific resistance of the porcelain and to prevent the crystal grains themselves from becoming insulators in the process of generating insulators at the grain boundaries. This is to prevent this.

In the above composition, it is essential to use this mixed gas atmosphere. Next, regarding the method of the present invention,
An explanation will be given based on an example.

[Example 1] First, Ti02 and SrC, which are industrial raw materials with a purity of 98% or more,
03, Bj203, and Ta205 with a purity of 99% or more
, NQ05, and SQ03 were prepared and mixed to have the composition ratios shown in Table 1.

Note that the types of both Ti and Sr are not particularly limited as long as they become oxides during the firing process. Raw material powders prepared to have a predetermined composition ratio were placed in a urethane-lined pocket, wet-mixed using a urethane ball, and then water in the mixture was evaporated. And 1160o
Temporarily calcined at o for 2 hours and then finely ground to approximately 700
It was molded into a disk shape with a diameter of 15 sides and a thickness of 0.8 ribs at a pressure of 9/8 k. This molded body was held and fired in a mixed gas atmosphere of nitrogen and hydrogen for 1,360 to 1,450,002 hours. The firing was carried out in an alumina combustion tube using an SIC heating element. On the surface of the obtained semiconductor ceramic element, Cu
At least one of No. 20, Cbi○, Bj203, etc. was applied as a diffusing substance at a rate of 0.1 to 3, and heat treated at 1100 to 1300 o'clock 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, silver paste was baked on both sides of the semiconductor ceramic element to form Ag electrodes.

For comparison, ceramic elements were fired in nitrogen, hydrogen, and air, respectively (Samples 29, 30, and 31). Tables 1 and 2 show the characteristics of each sample.

In the same table, the dielectric constant (g) is a value measured at a temperature of 20 oo and a frequency of IKH2. Dielectric loss (tan
6) is the value measured at the frequencies of IKHZ and IMHZ at a temperature of 20 qC. The rate of change in capacitance with temperature was evaluated by the rate of change in temperature at 155 o'clock C and 8,500 o'clock, using the rate of change in temperature at 20° C. as a standard. Further, the insulation resistance is a value measured at a temperature of 20° C. with an applied voltage of 50 V DC voltage. The humidity resistance load life characteristics are as follows for a completed product with lead wires soldered to the element and an insulating coating applied, under a DC voltage of 100 V at 200 V in an atmosphere of a temperature of 40 oo and a humidity of 95%.
Table 2 Samples 1 to 9 in Table 1, which were evaluated by the insulation resistance value after applying field time, were samples in which only the composition ratio of the main component was changed, and as is clear from this, the main component was the same as that of the present invention. When the composition ratio is within this range, the dielectric properties and insulation resistance are excellent.

In other words, the concession factor is 40,000 or more, and the dielectric loss is IM.
The HZ is 1.0% or less, the capacitance temperature change rate is approximately within ±13%, and the insulation resistance is on the order of 1 piMQ-skin or more.
In particular, sample 4 has excellent characteristics overall, and has extremely excellent characteristics as a capacitor. Samples 10 to 18 are samples in which only the amount of Bj203 component added is changed, and samples 11 to 17 have very good dielectric loss and insulation resistance within the range of the present invention.

Samples 19 to 25 are samples in which the amounts of each component of Ta2Q, Nb2Q, and Sb203 were varied.

Further, Samples 26 to 30 show the influence of the firing atmosphere on the characteristics, and Sample 31, which was irradiated in air, had extremely poor dielectric constant and capacitance temperature change rate.

In addition, Sample 29 fired only in nitrogen and Sample 30 fired only in hydrogen had poor transfer body loss and capacity temperature change rate. From this, it can be seen that the firing atmosphere is preferably a mixed gas of nitrogen and hydrogen. [Example 2] Ti02 component is 50.12%, Sr○ component is 49.88%
Bj203 to 100 parts by weight of the main component which is mol%
The raw materials were mixed so that the components were 3.0 parts by weight, the Ta205 component was 0.15 parts by weight, and the NQ05 component was 0.05 parts by weight, and fired under the same conditions as Sample 4 of Example 1. Diffusion substances shown in Table 3 were diffused.

AI was deposited on the obtained semiconductor ceramic element by thermal spraying, and Cu was further sprayed thereon to form electrodes.
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. As is clear from the upper table of Table 3, it can be seen that semiconductor ceramic capacitors with excellent characteristics can be obtained when Cu, Bi, or both components are used as the diffusion material.

[Example 3] 3.0 parts by weight of Bi203 component and 0.15 parts by weight of Ta205 component for 100 parts by weight of the main components with Ti02 being 50.12 mol% and Sr○ content being 49.88 mol%. The raw materials were blended so that the NQ05 component was 0.05 parts by weight, and electrodes were attached to the semiconductor ceramic element obtained by firing under the same conditions as Sample 4 of Example 1 by thermal spraying.

Note that for the AI electrode, solderable Cu was further thermally sprayed on top of the AI electrode. For comparison, an A-phantom electrode was formed by high-temperature baking. 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 4. Table 4 *) The AI-0r alloy is an alloy in which AI has 80 atoms purple and 0r has 20 atoms purple.

As is clear from Table 4, sufficiently excellent characteristics can be obtained even with Ag competitive electrodes. However, it is clear that a ceramic capacitor with an even higher dielectric constant can be produced by attaching electrodes using the blasting method. In particular, AI is used as an electrode material.
, Cu, Zn and other metal materials are readily available and inexpensive;
It was put into mass production because of its ease of handling. 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. Bi_2O_3 component is added in an amount of 0.1 to 100 parts by weight based on 100 parts by weight of the main component consisting of 50.02 to 52.00 mol% of TiO_2 component and 49.98 to 48.00 mol% of SrO component. 8.5 parts by weight, and Ta_2O_5 component, N
The powder obtained by adding one or more of the b_2O_5 component and the Sb_2O_3 component in a total amount of 0.04 to 2.2 parts by weight is molded into a desired shape, and then molded in an atmosphere of a mixed gas of nitrogen and hydrogen. Sintered at a temperature of 1360℃ to 1450℃,
A semiconductor porcelain characterized in that the crystal grain boundary layer of the obtained semiconductor porcelain body is coated with an oxide of one or both of Cu and Bi, and then heat-treated at a temperature of 1100°C to 1300°C to form an insulator. Method of manufacturing capacitors. 2 0.1 to 8.5 parts by weight of Bi_2O_3 component to 100 parts by weight of the main component consisting of 50.02 to 52.00 mol% of TiO_2 component and 49.98 to 48.00 mol% of SrO component, and Ta_2O_5 component, N
The powder obtained by adding one or more of the b_2O_5 component and the Sb_2O_3 component in a total amount of 0.04 to 2.2 parts by weight is molded into a desired shape in an atmosphere of a mixed gas of nitrogen and hydrogen. Sintered at a temperature of 1360℃ to 1450℃,
An oxide of one or both of Cu and Bi is applied to the surface of the obtained semiconductor ceramic body, and heated at 1100°C to 13°C.
The grain boundary layer is made into an insulator by heat treatment at a temperature of 00°C, and then at least one member selected from the metal group of Al, Cu, and Zn, or an alloy thereof is sprayed onto this insulator. A method of manufacturing a semiconductor ceramic capacitor, comprising: forming an electrode.