JPH07326535A - Grain boundary insulated semiconductor ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a grain boundary insulated semiconductor ceramic capacitor in which a varistor characteristic is further improved. CONSTITUTION:A paste for an inner electrode 2 is made of Ni, or is made by dissolving at least one kind of Li, Na and K atoms and at least one kind of Cu, Mn, Pb, Bi, and Co atoms to a compound containing Ni atom to form a solid solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain boundary insulation type semiconductor ceramic capacitor.

[0002]

2. Description of the Related Art The inventors of the present invention have disclosed Japanese Unexamined Patent Publication No. 2-215112.
As described in Japanese Patent Publications, etc., Ti-rich SrTiO ₃
In addition to the semiconductor composition and the ceramic composition based on MnO ₂ —SiO ₂ system as a base material and the manufacturing method thereof,
It has become possible to develop a monolithic ceramic capacitor with varistor function that uses t, Rh, Pd or Ni as internal electrodes. Furthermore, as described in JP-A-4-251908, the internal electrode composition in which at least one kind of low-valence Li, Na, and K atoms is solid-dissolved in Ni or a compound containing Ni atoms, and In the manufacturing method, N
The development of a multilayer ceramic capacitor with a varistor function using i as an internal electrode has become possible.

[0003]

With the above structure, Ti
It is possible to co-fire the ceramic sheet and the internal electrode using the excess SrTiO ₃ , the semiconductor component, and the MnO ₂ —SiO ₂ system as the ceramic base material, which greatly contributes to the lamination of the ceramic capacitor with a varistor function.

It is an object of the present invention to provide a grain boundary insulation type semiconductor ceramic capacitor having improved electrical characteristics, particularly a voltage ratio linear index α.

[0005]

In order to achieve this object, the present invention uses Ni or a compound containing Ni atom and at least one or more of Li, Na and K atoms as a starting material for an electrode, and Cu, A paste in which at least one of Mn, Pb, Bi, and Co atoms is solid-dissolved is used.

[0006]

With this structure, the component dissolved in Ni or the compound containing Ni atom can improve the oxidation resistance of the electrode, and at the same time, the oxide insulator in the crystal grain boundary portion of the ceramic body such as the ceramic sheet. It is possible to further improve the conversion.

[0007]

EXAMPLES An example of the present invention will be described below.

FIG. 2 shows a manufacturing process diagram of this embodiment. First, SrTiO ₃ (Sr / Ti = 0.97): 97mo
1%, Nb ₂ O ₅ : 0.5 mol%, Ta ₂ O ₅ : 0.5 m
ol%, MnO ₂ : 1.0 mol%, SiO ₂ : 1.0 m
30μ by the doctor blade method with the composition of ol%
A raw sheet having a thickness of about m was prepared and cut into a predetermined size. Next, as shown in (Table 1), Ni, Li, N
At least one kind of a and K atoms and Cu, Mn,
An internal electrode paste containing at least one of Pb, Bi and Co atoms was prepared.

[0009]

[Table 1]

Then, on the cut raw sheet 1a, this internal electrode paste to be the internal electrodes 1a shown in FIGS. 1 and 3 was screen-printed to a predetermined size. At this time, the raw sheets 1b for the uppermost layer and the lowermost layer which are ineffective layers
The internal electrode paste is not printed, and the green sheet 1a laminated in the middle has the internal electrode paste
The printing was performed so that the opposite edges of the sheet were alternately reached. Then, green sheets 1b (usually a plurality of sheets are laminated respectively) are arranged on the uppermost layer and the lowermost layer, and a plurality of laminated green sheets 1a printed with the internal electrode paste are heated while pressing, It pressure-bonded and the laminated body was obtained. Next, after degreasing and calcining this laminated body in air at 1050 ° C. for 2 hours, a paste having the same composition as the internal electrode paste was applied to the exposed end surface of the internal electrode 1a of the laminated body as shown in FIG. The external electrode 3a was provided, and firing was performed at 1250 ° C. for 2 hours in a reducing atmosphere. Then, a paste to be the Ag external electrode 3b was applied on the external electrode 3a and baked at 850 ° C. in air to obtain a multilayer ceramic capacitor with a varistor function.

The monolithic ceramic capacitor with a varistor function shown in FIG. 1 of this embodiment is a 1.3 type having a width L * length W * height H of 1.60 * 3.20 * 1.20 mm. Then, the raw sheet 1 on which the internal electrodes 2 are formed
30 a is laminated.

Regarding the monolithic ceramic capacitor with varistor function thus obtained, the capacitance, tan δ,
Varistor voltage, voltage nonlinear index α, series equivalent resistance value ES
Various electrical characteristics such as R were measured and shown in (Table 1). In Table 1, the capacitance C is measured voltage 1.0V, frequency 1.
The value at 0 KHz and the varistor voltage V _{0.1 mA} are measured currents of 0.
It is a value at 1 mA. The voltage non-linear coefficient alpha, by using the value of the voltage V _0.1mA and V _{1.0 mA} measuring current 0.1mA and 1.0 mA, the equation of _{α = 1 / log (V 0.1mA} / V 1.0 mA) It was calculated. The series equivalent resistance value ESR is 1.
It is the resistance value at the resonance point at 0V. From Table 1, NiO
And at least one of Li, Na and K atoms,
It is understood that the voltage non-linearity index α is improved by using the internal electrode paste to which at least one kind of Cu, Mn, Pb, Bi and Co atoms is added. Furthermore, this grain boundary insulation type semiconductor ceramic capacitor is
It can be seen that it has a large capacity, a small varistor voltage and a series equivalent resistance value ESR, and is excellent in temperature characteristics, frequency characteristics, and noise characteristics. Therefore, normally, it works as a capacitor to absorb low-voltage noise and high-frequency noise.On the other hand, when a high voltage such as pulse or static electricity enters, it exerts a varistor function and protects against noise, pulse, static electricity, etc. It can exhibit excellent responsiveness.

Although NiO is used in this embodiment, Ni compounds other than Ni and NiO may be used. In addition, at least one kind of Li, Na, and K atoms is added to NiO in an amount of 0.1 to 0.2 mol%, Cu, Mn, and P.
At least one of b, Bi, and Co atoms is 0.1 or more.
Although it is shown in Table 1 only when ˜0.2 mol% is added, it is most effective when the added amount is 0.05 to 0.5 mol%, respectively. Further, the combination of atoms to be added is not limited to the case shown in (Table 1). Further, in the above-described embodiment, the green sheet 1b serving as a ceramic body is described as being laminated, but a single green sheet 1b may be provided and electrodes of the same material as the internal electrode 2 may be provided on the upper and lower surfaces thereof. The effect was obtained.

[0014]

As described above, the grain boundary insulation type semiconductor ceramic capacitor of the present invention has a larger voltage non-linearity index α and improved varistor characteristics as compared with the conventional one. Of course, this grain boundary insulation type semiconductor ceramic capacitor has a small size and a large capacity, a small varistor voltage and a series equivalent resistance value ESR, and is excellent in temperature characteristics, frequency characteristics and noise characteristics. As a result, it is expected to be applied as a surface-mounted component, and the effect is extremely large, such that it can be used as a high-density mounting element for video cameras, communication devices, and the like.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a grain boundary insulation type semiconductor ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a grain boundary insulation type semiconductor ceramic capacitor according to an embodiment of the present invention.

FIG. 3 is an exploded perspective view of a laminated body of a grain boundary insulation type semiconductor ceramic capacitor according to an embodiment of the present invention.

[Explanation of symbols]

 1a Raw sheet 2 Internal electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Wakabata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A ceramic body and an electrode provided on the ceramic body, wherein the electrode comprises Ni or a compound containing Ni and at least one or more of Li, Na and K atoms, and Cu and Mn. , A Pb, Bi, Co atom and at least one kind of solid solution, formed as a starting material, a grain boundary insulation type semiconductor ceramic capacitor.