JPS6029212B2 - 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 .

Conventionally, Tj03-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 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 porcelain capacitor is one in which an insulating layer with a capacitance ratio is formed at grain boundaries on the normal outer or inner surface of a semiconductor porcelain. 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 of 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 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. Among the ceramic elements conventionally used in grain boundary type semiconductor ceramic capacitors are BaTi03 with oxides such as Sr, Bi, Zr, or Sn fixed thereon.

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 20oo
The maximum rate of change is around ±50% within the temperature range from -25q○ to 8500°C. And the Kenka body loss (tan8) is also large at 0.0 g star degree. Also, SrTi0
3 to which oxides such as Dy, Ce, Mn, Ta, W, Nb, Si or Bi are added, and furthermore, SrTj0
There is one that uses semiconductor porcelain made of CaTiO3 in which part of 3 is substituted with CaTiO3. 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 (n6) is also small at 0.007 to 0.03. I am getting things too. However, the temperature required for burning stripes is 1
Since it is high at over 400oo, it is not a one-off. 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, and has a large effective dielectric constant.
It has the characteristics of low dielectric loss, particularly a significantly small temperature change rate of capacitance over a wide temperature range, and high insulation resistance.

The method of the present invention is characterized in that the Ti02 component is 5
0.08 to 53 mol%, the S component is 32.9 to 37 mol%, the Ca○ component is 9 to 17 mol%, and the Bi03 component is 0.02 to 1 mol%. On the other hand, the value of at least one oxide, chloride, or metal among Sb, Nb, and Ta is 0.02
The purpose is to phosphorize the composition to which ~1.99 parts by weight has been added in a neutral or reducing atmosphere to produce semiconductor porcelain.
A further object of the present invention is to make the grain boundary layer of semiconductor ceramic an insulator. Furthermore, a metal electrode is formed by a lacquering method using at least one of Cu, Cu, an alloy mainly composed of Cu, or a Pb-Sn alloy. According to this method, by changing the proportions of the components, the magnitude of the yield rate and the rate of change in capacity with temperature can be freely selected, and the manufacturing thereof is also easy.

A ceramic element obtained by rough sintering can be easily connected with a lead wire by soldering. Here we will discuss the reasons for determining the composition of semiconductor porcelain.

Among the main components, when the Ti02 component increases, the yield rate decreases, the dielectric loss and the capacitance temperature change rate increase, and the ceramic body becomes rough. Furthermore, when the amount decreases, dielectric loss increases and the capacitance temperature change rate also increases. Therefore, its composition ratio is 50.08 to 5 as the main component.
It is desirable that the content be within the range of 3 mol%. When the S component increases, the dielectric constant, dielectric loss, capacitance temperature change rate, and insulation resistance deteriorate.

On the other hand, if the amount decreases, the porcelain becomes semiconducting and becomes bulky, and dielectric loss and capacitance temperature change rate worsen. Therefore, the component of S is 32.9 to 37 in the main component.
It is desirable that the amount be within the range of mol%. When the Ca○ component increases, it becomes difficult to make it into a semiconductor, and the yield rate also deteriorates. Moreover, when it decreases, the effect of improving the capacitance temperature change rate becomes poor. For this reason, it is desirable that the Ca◯ component is in the range of 9 to 17 mol% in the main components. When the Bi203 component increases, although the apparent electric current increases, it becomes difficult to sinter a delicate ceramic body, and dielectric loss also worsens.

When it decreases, the yield rate, capacitance temperature change rate, and insulation resistance deteriorate. Therefore, it is desirable that the Bi203 component is in the range of 0.02 to 1 mol% in the main component. The subcomponents such as Sb, Nb, and Ta are
It is effective in converting porcelain into semiconductors.

These components may be added in the form of a single metal, or in the form of an oxide or a compound that becomes an oxide during the firing process. However, if there is too much of it, the dielectric constant decreases and the loss in the conductive body also worsens. When it decreases, the dielectric constant decreases to 4.0, the resistivity of the ceramic body becomes extremely unstable, and its reproducibility becomes poor. Therefore, the total amount of the above components is desirably within the range of 0.02 to 2.5 parts by weight based on 100 parts by weight of the main components of the above composition. Furthermore, in the present invention, the firing atmosphere is made neutral or reducing in the process of lowering the resistivity of the porcelain and subsequently generating an insulator at the grain boundaries.
It is also necessary to prevent the crystal grains themselves from becoming insulators and to convert them into semiconductors.

Furthermore, when a metal is used as a subcomponent, it is effective in suppressing the explosiveness of metal powder and preventing explosion accidents. Note that the specific resistance value of the insulating layer formed at the grain boundaries is 1
070 or more is preferable. Next, the method of the present invention will be explained based on examples.

[Example 1] First, Ti02 and SrC, which are industrial raw materials with a purity of 98% or more,
03, CaC03, and Bj203 were prepared, and high-purity Sb, Nb, Ta, or their oxides or chlorides were also prepared as subcomponents.

These were mixed to have the composition ratio shown in Table 1, placed in a urethane-lined pot mill, wet mixed using a urethane ball, and then water in the mixture was evaporated.
Then, apply this to the diameter 15 side at a pressure of about 700 kg/ground.
It was molded into a disk shape with a thickness of 0.8 skin. This molded body was held and fired at 1300 to 1400° C. for 2 hours in a neutral or reducing atmosphere. 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. On the surface of the obtained semiconductor ceramic element, Cu
20, Bi203, P is coated with at least one of 04 and Mn02 as a diffusing substance for 0.5 to 3 times,
It was heat treated at 1,100 to 130,000 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, a porcelain body was fired in air (Sample 28)
. Table 1 Table 1 (Continued) G. Comparative Example The electrical characteristics of each of the above samples were investigated.

The results are shown in Table 2. In this table, the dielectric constant (g) and dielectric loss (tan6) are as follows at a temperature of 20°C.
This is a value measured at a frequency of IKHZ. The capacitance temperature change rate was evaluated based on the rate of change in temperature of the electrostatic rate, that is, the rate of change in values at -25qC and 85o0 with 2000 as a standard.

Furthermore, the insulation resistance is a value when the applied voltage is measured as a DC voltage of 50V. Samples 1 to 9 in the upper table of Table 2 are samples in which only the composition ratio of the main component was changed, and as is clear from these samples, samples 2 to 7 whose main components are within the range of the present invention have dielectric properties and capacitance. It is superior to comparative samples 1, 8, and 9 in terms of temperature change rate and insulation resistance.

In particular, sample 5 has excellent characteristics overall and has extremely excellent characteristics as a capacitor. Samples 10 to 25 are samples in which only the added amount of the subcomponent was changed, and samples 11 to 22 have very good dielectric loss and insulation resistance within the range of the present invention. The form of the subcomponent added may be a simple metal or another compound as long as it can become an oxide during firing, and combinations thereof are also within the scope of the present invention. If so, you know it's good enough. Further, Samples 26 to 28 show the influence of the firing atmosphere on the characteristics, and Sample 28 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] Among the main components, Ti02 is 51.2 mol%, S component is 33.6 mol%, Ca○ component is 14.4 mol%, Bj2
In addition, 0.1 part by weight of the NQ05 component and 0.1 part by weight of the Ta20 component were added so that the content of the NQ03 component was 0.8 mol%.
The raw materials were mixed so that the 5 components were 0.1 part by weight and the SQ03 component was 0.2 parts by weight, and a semiconductor ceramic element was produced in the same manner as in Example 1.

Note that nitrogen gas was used in the firing atmosphere. Electrodes were attached to the obtained semiconductor ceramic element by thermal spraying. Furthermore, N
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 *1) AI-0r alloy has AI of 80, 0r or 2
o*2) Pb-Sn alloy, which is an alloy with 0 atoms*, is Pb
It is an alloy with 30 atoms of Sn and 70 atoms of Sn.

Samples 29 to 34 show the relationship between the differences in electrode formation methods and the characteristics as a ceramic capacitor. It can be seen from this that although sufficiently excellent characteristics can be obtained with Ag baked electrodes, a ceramic capacitor with an even higher dielectric constant can be produced by attaching the electrodes by thermal spraying. In particular, N, Cu, Zn, Pb, Sn are used as electrode materials.
These metal materials are suitable for mass production because they are readily available, inexpensive, and easy to handle. 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 TiO_2 component is 50.08 to 53 mol%, SrO
As a subcomponent, S
b, an oxide of at least one of Nb and Ta;
Chloride or metal equivalent value of 0.02 to 1.
1. A method for manufacturing a semiconductor ceramic capacitor, which comprises adding 99 parts by weight and sintering in a neutral or reducing atmosphere, and further converting the crystal grain boundary layer of the obtained semiconductor ceramic body into an insulator. 2 TiO_2 component is 50.08 to 53 mol%, SrO
As a subcomponent, S
b, an oxide of at least one of Nb and Ta;
Chloride or metal equivalent value of 0.02 to 1.
99 parts by weight was added and sintered in a neutral or reducing atmosphere to make the grain boundary layer of the obtained semiconductor ceramic body an insulator. A method for manufacturing a semiconductor ceramic capacitor, which comprises forming electrodes by thermally spraying at least one metal selected from the metal group Zn, an alloy mainly containing Zn, or a Pb-Sn alloy.