JPH04273416A - Capacitor - Google Patents

Abstract

PURPOSE:To provide a capacitor which can eliminate both a pulsive noise and a change in a low-frequency voltage. CONSTITUTION:The following are installed: first counter electrodes (internal electrode layers 11a, 11b) composed of a conductive material whose resistivity is low; and second counter electrodes (internal electrode layers 12a, 12b) composed of a conductive material whose resistivity is high. Thereby, a pulse-shaped noise is removed by a capacitor constituted of the first counter electrodes and a change in a low-frequency voltage is removed by a capacitor constituted of the second counter electrodes. A mounting area used to arrange the capacitor can be made narrow as compared with that in conventional cases, and an apparatus can be made small-sized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor having opposing electrodes of different resistivities.

0002

2. Description of the Related Art Conventionally, in electronic circuits using ICs, operational amplifiers, etc., malfunctions of the electronic circuits are often caused by fluctuations in power supply voltage and noise superimposed on power supply lines. Therefore, as shown in Figure 2, for example, an aluminum or tantalum electrolytic capacitor 3 and a ceramic capacitor 4 are connected in parallel between the power line 2 of the electronic circuit 1 and the ground conductor to eliminate voltage fluctuations and noise. ing.

FIG. 3 is a diagram showing an equivalent circuit when a capacitor 5 is connected between the power supply line 2 and the ground conductor. In the figure, R is the equivalent series resistance (ESR
), L is the equivalent series inductance of the capacitor (ESL
), C is the capacitance of the capacitor 5, and L' is the equivalent inductance of the power supply line 2. That is, an equivalent series resistance R is generated by the resistance of the lead wire and electrode of the capacitor 5, and an equivalent series inductance L is generated by the inductance of the lead wire. Therefore, a known RLC series circuit is formed between the power supply line 2 and the ground conductor.

[0004] In order to remove pulse-like voltage fluctuations (hereinafter referred to as pulse-like noise) superimposed on the power supply line 2 due to the high-frequency square wave output from the OP amplifier, IC, etc. in the electronic circuit 1, an equivalent It is necessary to connect a capacitor 5 with a small series resistance R and equivalent series inductance L. For this reason, ceramic capacitors 4 are used whose electrodes have a lower resistivity than other types of capacitors.

[0005] Furthermore, in order to remove voltage fluctuations (hereinafter referred to as low-frequency voltage fluctuations) superimposed on the power supply line 2 due to low-frequency square waves caused by OP amplifiers, ICs, etc. in the power supply circuit, equivalent series It is necessary to connect a capacitor 5 with a large resistance R. That is, when the voltage of the power supply line 2 fluctuates at low frequency, in a transient state until the circuit obtained by adding the equivalent inductance L' of the power supply line 2 to the RLC series circuit formed by the capacitor 5 reaches a steady state, (1) As shown in the equation, when the equivalent series resistance R is small, the voltage of the power supply line 2 oscillates. For example, when the power is turned on, the voltage of the power line 2 oscillates as shown in FIG. 4(a) and reaches a steady state. Therefore, malfunction of the electronic circuit 1 is likely to occur. In addition, the OP amplifier and IC in the electronic circuit 1
etc. outputs a low frequency square wave, power line 2
The voltage changes oscillally as shown in Figure 4(b),
Since it takes time to stabilize, the electronic circuit 1 is likely to malfunction. R<2・{(L+L')/C}1/2...(1
) Furthermore, as shown in equation (2), when the equivalent series resistance is large, the voltage of the power supply line 2 changes exponentially. For example, when the power is turned on, the voltage of the power supply line 2 exponentially reaches a steady state as shown in FIG. 5(a), and the electronic circuit 1 does not malfunction. In addition, when an OP amplifier, IC, etc. in the power supply circuit outputs a low-frequency square wave, the voltage of power supply line 2 changes instantaneously and exponentially and becomes stable, as shown in Figure 5(b). Therefore, malfunction of the electronic circuit 1 is not caused. R>2・{(L+L')/C}1/2...(2
) ◎For this reason, in order to eliminate voltage fluctuations due to low frequencies superimposed on the power line 2, a capacitor with electrode resistivity larger than other types, such as an aluminum or tantalum electrolytic capacitor 3, is used. There is.

Therefore, in order to eliminate both pulse-like noise and low frequency fluctuations, for example, a ceramic capacitor 4 and an aluminum or tantalum electrolytic capacitor 3 are connected in parallel between the power supply line 2 and the ground conductor.

[0007]

However, as mentioned above, in order to eliminate both pulse noise and low frequency fluctuations, it is necessary to connect a ceramic capacitor 4 and an aluminum or tantalum electrolytic capacitor between the power supply line 2 and the ground conductor. capacitor 3
Since the two capacitors must be connected in parallel, a large mounting area is required for arranging them, which is an obstacle to miniaturizing the device.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a capacitor that can eliminate both pulse-like noise and low-frequency voltage fluctuations.

[0009]

Means for Solving the Problems In order to achieve the above object, the present invention provides a capacitor comprising a counter electrode and a dielectric interposed between the counter electrodes. at least one pair of first conductive materials having a specific resistance;
The present invention proposes a capacitor provided with a counter electrode of 1 and at least a pair of second counter electrodes made of a conductive material with high specific resistance.

A second aspect of the present invention proposes a capacitor according to the first aspect, in which the first and second opposing electrodes are arranged in a stacked manner.

[0011]

According to claim 1 of the present invention, the first counter electrode is made of a conductive material with low specific resistance, and the second counter electrode is made of a conductive material with high specific resistance. As a result, the equivalent series resistance of the capacitor formed by the first opposing electrode becomes small, and the equivalent series resistance of the capacitor formed by the second opposing electrode increases. When this capacitor is used to remove noise and voltage fluctuations in a power supply line, pulse-like noise is removed by the capacitor formed by the first opposing electrode, and low-frequency voltage fluctuations are removed by the second opposing electrode. removed by a capacitor.

According to a second aspect of the present invention, the first and second opposing electrodes are arranged in a stacked manner.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing an embodiment of the present invention. In the figure, 10 is a capacitor main body (hereinafter referred to as main body), which has a rectangular parallelepiped shape and has a size of, for example, 3.
It is 2mm x 2.5mm x 2.5mm. Further, the main body 10 has a plurality of internal electrode layers 11a, 11b, 12a.
, 12b and a dielectric layer 13 are stacked, and the internal electrode layers 11a and 12a are led out to one end side in the longitudinal direction of the main body 10, and the internal electrode layers 11b and 12b are led out to the other end side. A pair of opposing electrodes is formed by the internal electrode layer 11a and the internal electrode layer 11b, and a pair of opposing electrode layer is formed by the internal electrode layer 12a and the internal electrode layer 12b. Furthermore, internal electrode layers 11a, 11b,
An external electrode 14 is formed which is conductive to 12a and 12b, and can be connected to an external circuit via this external electrode 14.

The internal electrode layers 11a and 11b are made of a conductive material with low resistivity, such as nickel, and are formed in 26 layers on the upper part of the main body 10 in the thickness direction.
b is made of a conductive material with high specific resistance, such as a mixture of nickel (90%), chromium (8%), and others (2%), and is formed in 70 layers at the bottom of the main body 10 in the thickness direction.

Next, a procedure for manufacturing a capacitor having the above-described structure will be explained. Internal electrode layers 11a and 11b were formed by screen printing nickel mixed with a binder material and made into a paste on a green sheet made of a BaTi2O3-based F-characteristic material with a thickness of 18 μm. Stack 26 pieces. Further, a mixture of nickel and chromium made into a paste by mixing with a binder material is screen printed on the green sheets to form internal electrode layers 12a and 12b, and 70 sheets are laminated. At this time, as described above, internal electrode layers 11a, 11b, 12a, 1
2b are derived alternately. Furthermore, after these are laminated into one piece and crimped together, they are cut to match the shape described above and subjected to a binder removal process. The binder removal process is performed, for example, in an air atmosphere at 250°C. Thereafter, reduction firing is performed at a temperature of 1300°C. Further, external electrodes 14 were formed from nickel at both ends of the main body 10, and solder plating was applied thereon to form a capacitor.

As a result of manufacturing under the above conditions, the capacitance was 4.
．． 7μF, equivalent series resistance at 1MHz frequency is 24
A capacitor of 0 mΩ was obtained, and was able to sufficiently absorb pulse-like noise with a rise of 0.1 nS. moreover,
Good characteristics were also obtained against low frequency voltage fluctuations. As shown in the equivalent circuit of FIG. 6, the capacitor 11, which is composed of internal electrode layers 11a and 11b made of nickel with low resistivity, is effective against pulse-like noise.
This is because the capacitor 12 constituted by the internal electrode layers 12a and 12b formed of a nickel-chromium alloy with high resistivity acts effectively against low-frequency voltage fluctuations. In addition, in FIG. 6, R1
, L1, and C1 represent the equivalent series resistance, equivalent series inductance, and capacitance of the capacitor 11, respectively,
R2, L2, and C2 represent the equivalent series resistance, equivalent series inductance, and capacitance of the capacitor 12, respectively.

The specific resistance value of the conductive material of the high specific resistance internal electrode layers 12a, 12b is the same as that of the low specific resistance internal electrode layers 11a, 11.
It is preferable that the resistivity value is 10 times or more the specific resistance value of the conductive material b. The volume resistivity of nickel in the example is 7 x 10-6 Ωcm at room temperature, whereas nickel (
The volume resistivity of the chromium (80%), chromium (8%), and other (2%) alloys is 69 x 10-6 Ωcm at room temperature, which is approximately 10 times as large. Furthermore, the equivalent series resistance of the capacitor 12 constituted by the high resistivity internal electrode layers 12a and 12b may be increased by increasing the chromium content. For example, nickel (80%), chromium (16%), others (4
%) The volume resistivity of the alloy is 108 x 10-6 at room temperature.
It becomes Ωcm.

Furthermore, since the capacitor of this embodiment is a ceramic capacitor and can be formed smaller than an electrolytic capacitor, a large mounting area for arranging the capacitor is not required, and the device can be made smaller. can. Furthermore, internal electrode layers 11a, 11b, 12a, 12
Since the capacitors b are formed in a laminated manner, it is possible to obtain a large capacitance with a small size.

In this embodiment, the internal electrode layers 11a, 1
As described above, nickel and a nickel-chromium alloy were used as the conductive material forming the conductive materials 1b, 12a, and 12b, but the present invention is not limited thereto. For example, general resistance materials such as copper-nickel alloys can also be used.

Further, in this embodiment, the capacitor 11 consisting of the internal electrode layers 11a and 11b is formed in the upper part of the main body 10, and the capacitor 12 consisting of the internal conductive layers 12a and 12b is formed in the lower part, but the present invention is not limited to this. There isn't. For example, as shown in FIG. 7, internal electrode layers 11a and 11b made of a conductive material with low resistivity and internal electrode layers 12a and 12b made of a conductive material with high resistivity may be stacked alternately in pairs. effect can be obtained.

[0021]

[Effect of the invention] As explained above, claim 1 of the present invention
According to the authors, when the capacitor of the present invention is used to remove noise and voltage fluctuations in a power supply line, it is possible to remove both pulse-like noise and low-frequency voltage fluctuations with one capacitor. It is not necessary to use two capacitors for each, and a large mounting area for arranging the capacitors is not required, and the device can be made smaller.

According to claim 2, in addition to the above-mentioned effects, since the first and second opposing electrodes are laminated, it is possible to obtain a large capacitance with a small size. It has excellent effects.

[Brief explanation of the drawing]

[Fig. 1] Cross-sectional view showing one embodiment of the present invention

[Figure 2]
Diagram explaining noise countermeasures for electronic circuits

[Figure 3] Diagram showing the equivalent circuit of a capacitor

[Figure 4] Diagram showing the vibration characteristics of an RLC series circuit

[Figure 5] Diagram showing the exponential characteristic of the RLC series circuit

[Fig. 6] A diagram showing an equivalent circuit of an embodiment of the present invention.

[Fig. 7] Cross-sectional view showing another embodiment of the present invention

[Explanation of symbols]

1...electronic circuit, 2...power line, 3...electrolytic capacitor,
4... Ceramic capacitor, 5, 11, 12... Capacitor, 10... Capacitor body, 11a, 11b, 12a,
12b...Internal electrode layer, 13...Dielectric layer, 14...External electrode.

Claims (2)

[Claims] 1. A capacitor comprising a counter electrode and a dielectric interposed between the counter electrodes, wherein at least one pair of first counter electrodes made of a conductive material with a low specific resistance and a dielectric material with a high specific resistance. A capacitor comprising at least one pair of second opposing electrodes made of a conductive material. 2. The capacitor according to claim 1, wherein the first and second opposing electrodes are arranged in a stacked manner.