JPS6311700Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a ceramic capacitor, and particularly to a reduction and reoxidation type semiconductor ceramic capacitor that is small and has a large capacity.

Conventionally, cylindrical and plate-shaped capacitors have been used as ceramic capacitors, but when trying to obtain a capacitor with a large capacity of around 1 μF, the size of the capacitors becomes extremely large. There was a problem that it became too old to be put to practical use. For this reason, multilayer ceramic capacitors and semiconductor magnetic capacitors have been developed and put into practical use as small-sized magnetic capacitors with large capacity. Multilayer magnetic capacitors can be manufactured in a small size with a large capacity, but because of the manufacturing process of laminating multiple layers of ceramic sheets with internal electrodes formed on them and then firing them, they are not used as internal electrode materials.
Because expensive precious metals with high melting points such as Au, Pt, and Pd must be used, manufacturing capacitors with a large capacity of around 1 μF would be extremely expensive, and they could only be used for specific applications. There's a problem. On the other hand, among semiconductor magnetic capacitors, reduction and reoxidation type semiconductor ceramic capacitors form a reoxidation layer on the surface of a semiconductor and use this as a dielectric. Like capacitors, they are non-polar, have good heat resistance and frequency characteristics, have low leakage current, and are inexpensive. However, their areal capacitance is only about 300nF/ ^cm2 ,
There was a problem that when the capacitance was increased to around 1 μF, the size became larger. As a means to solve this problem with reduction and reoxidation type ceramic capacitors, a through hole is made in the center of the disk-shaped reduction and reoxidation type semiconductor ceramic capacitor.
A structure has been proposed in which an ohmic electrode is formed on the semiconductor portion exposed on the inner wall, and an electrode is formed on the dielectric portion, which is the outer surface. A capacitor with this structure has a structure in which a pair of electrodes are formed on both surfaces of a plate-shaped reduction-reoxidation type semiconductor porcelain.
The capacity can be increased by about three times, but even if the through-hole is formed in advance before the reduction-reoxidation treatment, the process of removing the re-oxidation layer formed on the wall of the through-hole is extremely complicated; Forming through-holes after reoxidation treatment is inefficient and therefore industrially inappropriate. For this reason, Jitsugan 56-46648
No. 57-159232 describes a structure in which an ohmic electrode is formed on the outer peripheral surface of a disk-shaped reduction-reoxidation type semiconductor ceramic instead of forming an ohmic electrode in the through hole. something was proposed. Capacitors with this structure have the advantage of being able to increase the capacitance even more than those with ohmic electrodes formed in the through holes, but when cutting the outer circumferential surface of the disk to expose the semiconductor to form the ohmic electrodes, However, it is complicated to process the disks individually, or to stack the disks and harden them with wax to form a column, which is complicated, and in the latter case, there is a problem in that the wax must be removed after processing. .

The present invention was developed in view of the above-mentioned problems, and the purpose is to provide a reduction and reoxidation type semiconductor ceramic capacitor that is small in size and excellent in mass production even though it has a large capacity of around 1 μF. , a rectangular plate-shaped reduction and reoxidation type semiconductor porcelain having a through hole formed in the thickness direction; and a rectangular plate-shaped reduced and reoxidized semiconductor porcelain having a through-hole formed on both surfaces of the rectangular plate-shaped porcelain and a wall surface of the through-hole opening to the surface, and being electrically conductive with each other. and an ohmic electrode formed on at least one end surface of the square plate-shaped ceramic and insulated from the non-ohmic electrode. It is in.

A non-ohmic electrode is a conductive part formed on both surfaces of the porcelain, that is, the front surface and the back surface, using a commonly used electrode material such as silver paste, and formed on the wall of the through hole between them. However, in order to insulate the ohmic electrode, it is not formed on the entire surface of both surfaces, and the porcelain reoxidation layer is exposed between the edge of the non-ohmic electrode and the edge of the porcelain. It is preferable to make the dimensions slightly smaller than the surface dimensions of. The conductive part that connects the non-ohmic electrodes on both surfaces can be formed by printing a non-ohmic electrode material on the surface of the porcelain without forming it in particular, so that the electrode material enters the through hole and is applied to the wall surface. Therefore, it can be formed by baking this. The ohmic electrode may be formed on at least one end face of the square plate-shaped porcelain, but better characteristics can be obtained if it is formed on two or more end faces. The material of this ohmic electrode is a commonly used material, for example,
Ag-Zn-Sb alloy or the like may be used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the figure, 1 is a square plate-shaped reduced and reoxidized semiconductor porcelain, 2 is a non-ohmic electrode, 3 is an ohmic electrode,
4 and 5 are lead wires, and the semiconductor ceramic 1 consists of a semiconductor portion 1a and a dielectric layer 1b, and the dielectric layer 1b is formed on both surfaces of the ceramic 1 and on the wall surface of the through hole 6. On both surfaces 7a and 7b of the porcelain 1, non-ohmic electrodes 2 having dimensions slightly smaller than the surface dimensions of the porcelain 1 are formed, surrounding the through holes 6 opening in the surfaces. It is short-circuited by a conductive portion 8 formed on the wall surface. The ohmic electrodes 3 are formed on opposing end faces of the porcelain 1 and are short-circuited by a lead wire 4.

The reduction and reoxidation type semiconductor ceramic capacitor having the above structure can be manufactured, for example, as follows.

That is, while a reduced and reoxidized semiconductor ceramic material, for example, a BaTiO ₃ -BaZrO ₃ -based semiconductor ceramic material, is formed into a sheet shape, through holes 6 are formed in the molded body 9 at predetermined intervals (see FIG. 3). ), and after firing it in air at 1200 to 1400℃,
Semiconductor by reduction treatment at ~1200℃, 800 ~ 1100
A dielectric layer is formed on the surface by reoxidation treatment at ℃.
Next, after applying silver paste to the surface of the reduced and reoxidized semiconductor ceramic 10, the non-ohmic electrode 2 and the conductive part 8 are formed on both surfaces and the wall surface of the through hole 6 by baking, and the individual capacitor chips are cut with a diamond cutter or the like. 11 (see Figure 3 C), and the semiconductor portion exposed on the cut surface (end surface) is coated with, for example,
A capacitor can be obtained by forming the electrode 3 with an Ag-Zn-Sb ohmic electrode material.

Example 1 BaTiO ₃ 86.0 mol%, BaZrO ₃ 9.6 mol%,
Using 1.4 mol% Bi ₂ O ₃ , 2.9 mol % TiO ₂ , and 0.1 mol % Y ₂ O ₃ as raw materials, 10 mm × 7 mm ×
A capacitor chip was obtained in which non-ohmic electrodes consisting of 8 mm x 5 mm baked silver electrodes were formed on both sides of a 0.5 mm square plate, and an ohmic electrode of Ag-Zn-Sb system was formed on one end surface to form a ceramic capacitor. Obtained. Its capacitance is 0.39μF, and the dielectric loss tangent (tanδ) at 10KHz is 13%
It was hot.

Example 2 Ohmic electrodes were formed on two opposing end faces of the capacitor chip obtained in Example 1 to obtain a ceramic capacitor having the structure shown in FIG. Its capacity is
The tan δ at 0.48 μF and 10 kHz was 9%.

Comparative Example 1 A ceramic capacitor was obtained by using a ceramic composition having the same composition as in Example 1 as a raw material, forming a chip of the same size without a through hole, and forming a counter electrode by a conventional method. Its capacitance was 0.11 μF, and tan δ at 10 KHz was 4%.

As is clear from the above description, the ceramic capacitor of the present invention exhibits a capacitance approximately four times larger than that of Comparative Example 1 with the conventional structure, even if the same ceramic composition is used. By forming ohmic electrodes on two or more end faces, it has the excellent advantage that almost all of the capacitance due to the dielectric portion can be extracted efficiently without impairing the frequency characteristics. In addition, since the part where the ohmic electrode is formed is the end face of the square plate-shaped porcelain, the semiconductor part is exposed just by cutting it, so it is necessary to remove the dielectric layer part formed by reduction and reoxidation treatment. It has the advantage of being easy to form ohmic electrodes, being easy to form, and being mass-producible, and can be manufactured at a significantly lower cost than multilayer ceramic capacitors.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a ceramic capacitor showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view taken along the line - in FIG. 1, and FIG. 3 is a perspective view showing the manufacturing process thereof. 1...Porcelain, 2...Non-ohmic electrode, 3...Ohmic electrode, 4, 5...Lead wire, 6...Through hole.

Claims (1)

[Claims for Utility Model Registration] A semiconductor porcelain having a through hole formed in the thickness direction, the semiconductor porcelain consisting of a semiconductor portion and a dielectric layer, the dielectric layer extending from both surface sides of the semiconductor porcelain and A rectangular plate-shaped reduction and reoxidation type semiconductor porcelain formed on the wall surface of the through-hole; A reduction and reoxidation semiconductor ceramic capacitor comprising: a non-ohmic electrode; and an ohmic electrode formed on at least one end surface of the square plate-shaped ceramic and insulated from the non-ohmic electrode.