JPS63302509A - Manufacture of ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain a small-sized large-capacitance ceramic capacitor, mechanical strength of which is held even when a dielectric layer is thinned and which has large insulation resis tance and large withstanding voltage, at low cost through a simple process by combining reducing baking treatment and oxidizing baking treatment regarding the double layer body of a irreversible oxidizing thick-film non-baked body and a reversible oxidizing thick-film non-baked body and forming the dielectric layer and a semiconductor layer. CONSTITUTION:The double layer body 13 of a irreversible oxidizing thick-film non-baked body 11 and a reversible oxidizing thick-film non-baked body 12 is shaped, reducing baking treatment and oxidizing baking treatment are combined regarding the double layer body 13, and a dielectric layer 12' is formed from the reversible oxidizing thick-film non-baked body 12 while a semiconductor layer 11' is shaped from the irreversible oxidizing thick-film non-baked body 11, thus shaping a ceramic capacitor body 16 consisting of the dielectric layer 12' and the semiconductor layer 11'. The double layer body 13 such as the double layer green sheet 13 of the non-baked body 11 such as an irreversible oxidizing thick-film green sheet 11 composed of SrTiO3, Nb2O5 and GeO2 and the non-baked body 12 such as a reversible oxidizing thick-film green sheet 12 made up of SrTiO3, CaTiO3 and CuO is baked in a reducing atmosphere and changed into a semiconductor, and baked in an oxidizing atmosphere, thus manufacturing the ceramic capacitor body 13' consisting of the dielectric layer 12' such as a dielectric ceramic layer 12' and the semiconductor layer 11' such as a semiconductor ceramic layer 11'.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a ceramic capacitor, and more particularly to a method of manufacturing a ceramic capacitor that enables smaller size and larger capacity.

BACKGROUND OF THE INVENTION Electrical equipment is becoming lighter, thinner, shorter and smaller, and there is a demand for smaller parts. Magnetic capacitors are also being miniaturized, and efforts are being made to increase their capacitance. Widely used, especially in consumer electrical equipment (Plat-shaped and cylindrical types are known for the ceramic capacitors used, but if the dielectric layer shape is kept constant, the capacitance will increase unless the thickness is thinned.) is not obtained.

However, as shown in FIG. 5, for example, in a hollow cylindrical capacitor in which an electrode 2.3 is formed on a cylindrical dielectric layer 1, if the dielectric layer 1 is made too thin, the mechanical strength decreases and it may crack. Therefore, it is not desirable. In order to maintain this mechanical strength, a minimum thickness of 0.25 m is required.

Therefore, reduction and reoxidation type semiconductor ceramic capacitors have been developed that can maintain mechanical strength even if the dielectric layer is made thinner. This reduction and reoxidation type semiconductor ceramic capacitor is
For example, as described in Japanese Patent Application Laid-Open No. 56-79423, a sintered body is formed by firing a porcelain material as shown in FIG. Then, silver 5 containing glass drift is applied to this bifocal surface, and then reoxidized to form an oxide layer 6 on the surface, and then one of the reoxidized layers is removed as shown in FIG. 6(b). After that, an ohmic electrode 7 is formed.

In this way, compared to a structure in which electrodes are provided on both surfaces of the semiconductor ceramic substrate via a reoxidation layer, the capacitance is reduced by 2.
Since it is twice as large, it is preferable from the viewpoint of miniaturization and high capacity.

Problems to be Solved by the Invention However, in the conventional manufacturing method of semiconductor ceramic capacitors, when reoxidizing the surface of the semiconductor substrate,
The glass electrode material is heated to 0-1050°C to undergo vapor phase diffusion, but this is not only difficult to control the temperature, but if the thickness of the re-oxidized layer is less than 10 μm, the oxidation may be incomplete. This causes problems with insulation resistance and voltage resistance. Furthermore, a step of removing one side of the main surface of the re-oxidized layer is required, resulting in a problem that the step becomes complicated.

An object of the present invention is to provide a method for manufacturing a small, large-capacity ceramic capacitor that maintains mechanical strength even when the dielectric layer is thin, has high insulation resistance, and has high withstand voltage and can be obtained at low cost through simple steps.

Means for Solving the Problems In order to solve the above problems, the present invention forms a two-layer body of an irreversibly oxidizable thick film green body and a reversibly oxidizable thick film green body, and By using a combination of reduction firing treatment and oxidation firing treatment, it is possible to convert reversibly oxidizable thick film green bodies into dielectric materials.
%t and forming a semiconductor layer from an irreversibly oxidized thick film green body, and forming a ceramic capacitor body made of the dielectric layer and the semiconductor layer. I will provide a.

Oxidation treatment and reduction treatment of a two-layer body consisting of an irreversible oxidizing thick-film green body that does not oxidize even after oxidation treatment once concentrated and a reversible oxidizing thick-film green body that can be oxidized and reduced. Since these are used in combination, a dielectric layer can be formed by oxidizing the reversibly oxidizable thick film green body, and a semiconductor layer can be formed by reducing the irreversibly oxidizable thick film green body. In this case, even if the dielectric layer is made thin, it can be reinforced with a semiconductor layer, and since the oxidation conditions for forming the dielectric layer can be well selected, uniformity can be ensured.

Embodiment Next, an embodiment of the present invention will be explained based on FIGS. 1 to 4.

Example 1 In Fig. 1, 11 is an irreversible oxidizing thick film green sheet;
Reference numeral 2 denotes a reversible oxidizable thick-film green sheet, and both are molded under heat and pressure to form a thick-film two-layer green sheet 13.

The above-mentioned irreversible oxidizing thick film Green Sea) 11 is strontium titanate (SrTiOB5) 97.67% in bundle amount,
Powders of 1.33N of niobium oxide (Nb205) and 1.00ml of germanium oxide (Ge02) were blended, and this blend was mixed with ethanol in a conventional manner, pulverized, and dried. 5M polyvinyl alcohol as binder to weight part
10 parts by weight of water were added and mixed in a ball mill for about 10 hours, and this mixture was molded into a sheet with a thickness of about 0.3 mm by extrusion molding.

Further, the reversible oxidizable thick film green sheet 12 is made of strontium titanate (SrTiO2) 90 mo1%,
Powders of 9 mol % of calcium titanate (CaTi03) and 1 mol % of copper oxide (Cub) were blended, mixed and crushed in the same manner as above, and then dried.
10 parts by weight of carboxymethyl cellulose as a binder and 10 parts by weight of water were added to Juhaija and mixed in a ball mill for about 15 hours to form a slurry, which was then formed into a sheet with a thickness of about 0.070 mm by a doctor blade method.

A disk having a diameter of about 13 nm was produced by punching and molding the thick two-layer green sheet 13.

This disk was placed in a reducing atmosphere (H25vo6%, N295vo
J%) at 1,400 to 1,450°C for about 4 hours to form a semiconductor. Next, it was fired for 2 hours in an oxidizing atmosphere (atmosphere) at a temperature of 1200 to 1300°C. This allows the second
As shown in the figure, two-layer firing is performed: a dielectric ceramic layer 12°, which is a fired body of reversible oxidizable thick film green sheet 1-12, and a semiconductor ceramic layer 11'', which is a fired body of irreversible oxidizable thick film green sheet 11. A ceramic capacitor main body 13' is produced.

Next, zinc electrode paste (60 parts by weight of zinc powder, 5 parts by weight of ethyl cellulose and 35 parts by weight of butyl calpitol as a binder) is applied to both sides of this 13" capacitor body.
is coated, dried, and baked at 500° C. for 30 minutes to form lead wire reading electrodes 14 and 15, thereby obtaining a semiconductor ceramic capacitor 16.

Regarding this semiconductor ceramic capacitor, the capacitance C (μF
/cat), dielectric loss (tanδ), withstand voltage (IR
(Ω)] and the results are shown in Table 1 along with the above formulation.

Note that the above capacitance and dielectric loss are calculated at a temperature of 20°C and a frequency of I.
KHz AC voltage (effective value) 1. Measured value when applying OV, insulation resistance is DC 100 at a temperature of 20°C.
The measured value after applying ν and the withstand voltage are the measured values after applying 50 V DC for 1 minute.

Examples 2 to 5 In the same manner as in Example 1, except that the composition of the reversible oxidizable thick film green sheet was as per the relevant section in Table 1, and the thickness was changed to 0.05 mm. A semiconductor ceramic capacitor was manufactured and measured in the same manner as in Example 1. The results are shown in Table 1.

Examples 6 to 10 In the same manner as in Example 1, except that the composition of the reversible oxidizable thick film green sheet was changed to the corresponding ingredients in Table 2, and the thickness was changed to 0.10 mm. A semiconductor ceramic capacitor was manufactured and measured in the same manner as in Example 1. The results are shown in Table 2.

Note that in addition to Nb2O5 and GeO2, the additives used for controlling the Ti valence in the irreversible oxidation thick film green sheet material include Ta2.
05, WO5, 5c20B, Y2O3, La2O5
, Nd2O5, and other rare earth oxides.

Further, although the above-mentioned zinc bridge was used, nickel electrodes, silver electrodes, etc. can also be used.

Comparative Example 1 Same as Example 1 except that the irreversible oxidizable thick film green sheet was not used, the composition of the reversible oxidizable thick film green sheet was as shown in Table 3, and the thickness was set to 0.250. A semiconductor ceramic capacitor having an electrode provided on a dielectric single layer was manufactured using the same method, and the results of measurement in the same manner as in Example 1 are shown in Table 3.

Example 11 In Example 1, the composition of the irreversibly oxidizable thick film green sheet was changed to barium titanate (i(aT+03)99.3m
o1%, niobium oxide (Nb205) 0.3 mo1%, a sheet was formed by the doctor blade method rather than the extrusion molding method, and the thickness was 0.3 mo. The composition is barium titanate (BaT
i05) 90.5 mo1%, neodymium oxide (NdzO
s) 3 mo1%, titanium dioxide (Ti02) 6 m
A thick film two-layer green sheet was prepared in the same manner except that the slurry was mixed with 0.5 mol% of manganese oxide (MnO) and 0.5 mol of manganese oxide (MnO) for 10 hours, and the thickness of the sheet made from the slurry was 0.03 m. A disk with a diameter of 20 mm was punched out from this, and then fired in the atmosphere at 1350° C. for 3 hours to obtain a fired body.

Next, a reducing atmosphere (N295 vo1%, H25voJ
%) at 1200° C. for 2 hours to convert it into a semiconductor.

Further, the fired body was heat-treated at 1100° C. for 2 hours in the atmosphere. As a result, as in FIG. 1 (b) of Example 1, the dielectric ceramic layer, which is the fired body of the reversibly oxidizable thick film green sheet,
A ceramic capacitor body is produced which is made of a two-layer fired body of semiconductor ceramic layers, which is a fired body of irreversibly oxidizable thick film green sheets.

Next, silver paste (1
1! 60 parts of powder, 15 parts by weight of polyvinyl alcohol as a binder, and 25 parts by weight of water) were coated and dried, and then baked at 800° C. for 30 minutes to produce a semiconductor ceramic capacitor with electrodes formed thereon.

This was also measured in the same manner as in Example 1, and the results are shown in Table 4.

Examples 12 to 13 Semiconductor ceramic capacitors were produced in the same manner as in Example 11, except that the thickness of the reversible oxidizable thick film green sheet was as described in the respective appropriate columns of the table, and Table 4 shows the results measured in the same manner as in Example 1.
Shown below.

Comparative Example 2 In the reduction-reoxidation type capacitor shown in FIG. 6(b) as described in JP-A-56-79423,
Table 4 shows the results of measuring the electrical properties in the same manner as in Example 1 when the re-oxidation layer (dielectric layer) was made to have a thickness of approximately 10 μm as in Example 11.

In the above Examples 11-13, the irreversible oxidation thick film green sheet used Nb2o5 as a valence control agent in BaTiO3 in its composition, but in addition to this, Nb2o5 was used as a valence control agent.
．． 1 to 0.5 mo1% of La, oxide of rare earth elements such as Nd, Ta205, WO5, MoO3, GeO2
Products containing at least one of these can also be used.
Moreover, the thickness of the sheet can also be set to 0.2 to 0.4 mm. In addition, the composition of the reversible oxidizable thick film green sheet is BaTiO3, TiO2, MnO, and Nd20.
Although B was added, BaTi03-Ln-based oxide-Ti02
However, a material made by adding Mn to a system showing rare earth elements such as Ln, a, Nd, and Ce can also be used, and the thickness of the sheet can also be 0.02 to 0.1 mm. In addition, the conditions for heating and pressing these irreversible oxidizing thick film green sheets and reversible oxidizing thick film green sheets to form a two-layer body and then firing in the atmosphere are 1300 to 1450°C, 2 to 3
The conditions for firing in a reducing atmosphere are 1200
~1300℃, 1-2 hours, and reoxidation conditions are 110℃
For example, it may be carried out at 0 to 1200°C for 1 to 2 hours. Further, as the electrode, not only a silver electrode but also a zinc electrode and other electrodes made of the materials exemplified in the modified examples of Examples 1-10 can be used.

(Margins below this page) Example 15 Although the above description was about a flat semiconductor ceramic capacitor,
As shown in FIG. 3, irreversible oxidizing green columnar part 17
was inserted into the reversible oxidizable green cylindrical portion 18 and bonded under heat and pressure to form a two-layer green body 19, which was then treated in the same manner as in Example 1 or Example 11 above, using a combination of reduction firing treatment and oxidation firing treatment. As shown in FIG.
The semiconductor ceramic capacitor 22 can also be manufactured by forming the ceramic capacitor main body 19' made of a two-layer fired body of the semiconductor layer 17' and the semiconductor layer 17', and further forming the electrodes 20 and 21. The materials for the reversible oxidizable green cylindrical part and the irreversible oxidizable green cylindrical part can be the same as those shown in the above embodiments.

From the above results, it can be seen that in the examples, the irreversible oxidizable thick film green sheet is 0.31 m and the reversible oxidizable thick film green sheet is 0.03 to 0.3 m. Thickness of the fired ceramic capacitor body consisting of In &! '0.25f1 or more, which can be made thicker than the single-layer capacitor body of the comparative example, and can maintain sufficient physical and mechanical strength.

In addition, since the dielectric layer formed from the reversibly oxidizable thick film green sheet has a thickness of 0.1 n or less, the capacitance is also large (possible), and the resistivity of the semiconductor layer is also sufficiently small, so loss (tan δ ) can also be made smaller.

In the present invention, the unfired body includes both those obtained by adding a binder or the like to each material, or those obtained by burning and removing the organic substances.

As described in detail, according to the present invention, the reversibly oxidizable thick film green body and the irreversibly oxidizable thick film green body can each be formed into a sheet, cylinder, or rod shape, and The reversibly oxidizable thick film green body can be thinned and the irreversibly oxidizable thick film green body can be thickened and stacked one on top of the other, and the firing process can be performed on these. This allows the dielectric layer to be made thinner and its strength to be reinforced by the thicker semiconductor layer. Furthermore, if the dielectric layer is, for example, 10 μm thick, the thickness of the dielectric layer of a conventional single-layer ceramic capacitor is 2 μm in terms of mechanical strength.
Compared to 50 μl11 or more, its thickness is about 25 μl.
The capacitance can be increased by about 25 times.

In this way, the thickness of the dielectric layer that is oxidized is predetermined by the thickness of the sheet or cylinder before firing, and the oxidation conditions can be set arbitrarily. The thickness of the dielectric layer produced by this method does not change depending on temperature conditions, and a uniform dielectric layer with fewer defects due to insufficient oxidation can be formed, making it possible to form a uniform dielectric layer that is less likely to have defects caused by insufficient oxidation. Not only can a capacitance that is 2 to 4 times higher than that of conventional capacitors be obtained, but also, especially when the dielectric layer is made thinner, the inferior voltage resistance and decrease in insulation resistance that are observed in conventional reduction-reoxidation type ceramic capacitors do not occur. do not have.

Further, there is no step of removing part of the reoxidation layer unlike in the case of conventional reduction and reoxidation type semiconductor ceramic capacitors, and the manufacturing process can be simplified and made more efficient.

In this way, it is possible to provide a flat or cylindrical semiconductor ceramic capacitor having a dielectric layer on only one side, and it can also be made smaller and have a higher capacity, so it can be used as various capacitors required for miniaturized electrical equipment. Various temperature characteristics can be realized, and capacitors with all characteristics from temperature compensation to high dielectric constant can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a two-layer green sheet in the manufacturing process of a semiconductor ceramic capacitor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a semiconductor ceramic capacitor according to this embodiment, and FIG.
A) and (B) are a perspective view and a side view showing a two-layer green body of a cylindrical semiconductor ceramic capacitor according to another embodiment, and FIG.
A), (B), and (C) are perspective views, cross-sectional views, and side views of the cylindrical semiconductor ceramic capacitor of this embodiment;
(B) and (C) are perspective views, cross-sectional views, and side views of conventional single-layer ceramic capacitors, and Figures 6 (A) and (B) are the structures of conventional reduction-reoxidation type ceramic capacitors in each manufacturing process. FIG. In the figure, 11 is an irreversible oxidation thick film green sheet, 12 is a reversible oxidation thick film green sheet, 13 is a thick film double layer green sheet, 11° is a semiconductor ceramic layer, 12゛ is a dielectric material 6
'FF layer, 13° is the ceramic capacitor body, 14.15
16 is an electrode, 16 is a semiconductor ceramic capacitor, 17 is an irreversible oxidizing green cylinder part, 18 is a reversible oxidizing green cylinder part, 19 is a two-layer green body, 17゛ is a semiconductor layer, 18'
2 is a dielectric layer, 20 and 21 are electrodes, and 22 is a semiconductor ceramic capacitor. June 3, 1988 Figure 1 Figure 2 Figure 3 Figure 5

Claims (4)

[Claims] (1) By forming a two-layer body of an irreversibly oxidizable thick-film green body and a reversibly oxidizable thick-film green body, and using a combination of reduction firing treatment and oxidation firing treatment on the two-layer body, the reversible oxidation thickness is It is characterized by comprising the steps of forming a dielectric layer from the film green body, forming a semiconductor layer from the irreversibly oxidizable thick film green body, and forming a ceramic capacitor body composed of the dielectric layer and the semiconductor layer. A method of manufacturing a porcelain capacitor. (2) Combining reduction firing treatment and oxidation firing treatment for a two-layer body involves firing the two-layer body in a reducing atmosphere to form a semiconductor layer for each layer, and then firing it in an oxidizing atmosphere to obtain a reversible oxidation thickness. 2. The method of manufacturing a ceramic capacitor according to claim 1, wherein the dielectric layer is formed by oxidizing a film semiconductor. (3) Combining reduction firing treatment and oxidation firing treatment for a two-layer body involves firing the two-layer body in an oxidizing atmosphere, then firing it in a reducing atmosphere to convert each layer into a semiconductor, and then firing it in an oxidizing atmosphere. 2. A method of manufacturing a ceramic capacitor according to claim 1, wherein the dielectric layer is formed by reoxidizing a reversibly oxidizable thick film semiconductor. (4) The method for manufacturing a ceramic capacitor according to claim 1, 2 or 3, wherein the reversibly oxidizable thick film green body is a reversibly oxidizable thick film green body. .