JP2000182888A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise due to by piezoelectricity. SOLUTION: Metal terminals 16, conductively connected to internal electrodes, are provided at both ends of an element assembly 13 to form external terminal electrodes. The metal terminals 16 are projected from the bottom surface of the element assembly 13. A silicon resin or the like, having a hardness and density different from those of the element assembly 13 is provided as a vibration buffer member 15 to cover the element assembly 13 and external electrodes 14. Consequently, when the element body is mounted on a circuit board, the vibration buffer member 15 is provided between the circuit board and the element body surface facing opposite thereto (the bottom surface of the element assembly 13). Therefore, if vibration due to piezoelectric effect occurs in the element body 13, the vibration at the central part of the element assembly 13, which has the largest amplitude, is absorbed by the vibration buffer member 15. Since the vibration of the element body is not transmitted directly to the circuit board, the occurrence of audible sound can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor capable of reducing a sound generated by a piezoelectric phenomenon.

[0002]

2. Description of the Related Art Conventionally, in a smoothing circuit in a power supply circuit such as a DC-DC converter, an aluminum electrolytic capacitor has been often used as a power supply smoothing capacitor.

However, with the recent miniaturization of electronic circuits and electronic devices, tantalum electrolytic capacitors having the same capacitance and small size have been used for electronic circuits requiring high capacitance, such as power supply smoothing circuits. Was.

On the other hand, with the recent miniaturization and energy saving of electronic circuits and electronic devices, most of capacitors used in electronic circuits have been shifted to multilayer ceramic capacitors.

[0005] Multilayer ceramic capacitors are rapidly becoming popular because of their small size and excellent reliability and durability.

[0006]

However, since a multilayer ceramic capacitor uses a ferroelectric material as a dielectric material, when an AC voltage is applied while a DC voltage is applied, a piezoelectric phenomenon occurs and vibration occurs. . This vibration tends to appear more remarkably for a material having a large dielectric constant and a shape having a large shape.

For this reason, in a smoothing circuit of a power supply circuit, a multilayer ceramic capacitor having a relatively large shape and a large capacitance is often used, so that this kind of vibration often occurs.

Further, when the above-described vibration occurs in the multilayer ceramic capacitor, the vibration of the capacitor may be transmitted to the mounting substrate, and the substrate may resonate and the sound may be amplified. That is,
Due to the vibration of the capacitor, the surrounding air vibrates to generate sound and the substrate also vibrates in resonance. For this reason, there has been a problem that the sound pressure becomes large and the sound becomes harsh as an audible sound.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a monolithic ceramic capacitor capable of reducing noise caused by a piezoelectric phenomenon.

[0010]

In order to achieve the above object, the present invention provides a rectangular parallelepiped element formed by alternately laminating dielectric layers made of dielectric ceramic and internal electrode layers. A vibration damping member that covers the element body with a predetermined thickness, and internal electrodes formed on the internal electrode layers at both ends of the element body are alternately connected in parallel and at least a part of the vibration damping member is connected. A multilayer ceramic capacitor comprising a pair of external terminal electrodes exposed to the outside is proposed.

According to the multilayer ceramic capacitor, when mounted on a circuit board, a vibration damping member having a predetermined thickness is interposed between the circuit board and a surface facing the circuit board. When vibration due to the piezoelectric effect occurs,
The vibration is absorbed by the vibration damping member, and the transmission rate of the element body vibration to the circuit board is reduced.

According to a second aspect of the present invention, in the multilayer ceramic capacitor according to the first aspect, the external terminal electrode comprises:
A multilayer ceramic capacitor comprising an external electrode formed at an end of the element so as to connect the internal electrodes alternately in parallel and a metal terminal conductively connected to the external electrode is proposed.

According to the multilayer ceramic capacitor, an external terminal is formed from an external electrode formed at an end of the element body and a metal terminal conductively connected to the external electrode so as to alternately connect the internal electrodes in parallel. Since the electrodes are formed, the external terminal electrodes exposed to the outside of the vibration damping member can be easily formed by appropriately changing the shape or size of the metal terminal.

According to a third aspect of the present invention, there is provided the multilayer ceramic capacitor according to the first or second aspect, wherein the vibration damping member is a resin having a density and hardness different from those of the dielectric ceramic.

According to the multilayer ceramic capacitor, since the vibration damping member is made of a resin having a density and hardness different from that of the dielectric ceramic, the vibration generated in the element can be efficiently absorbed and the manufacturing is easy. Can be done.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view showing a multilayer ceramic capacitor according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a main part, and FIG. 3 is a side sectional view. In the drawing, reference numeral 1 denotes a multilayer ceramic capacitor (hereinafter, simply referred to as a capacitor), in which a body 13 in which dielectric layers 11 and internal electrodes 12 are alternately laminated, and internal electrodes alternately provided at both ends of the body 13. A pair of external electrodes 14 connected in parallel to each other, a vibration damping member 15 covering the element body 13 and the external electrodes 14 with a predetermined thickness, and a metal terminal 16 conductively connected to the external electrodes 14.
It is composed of In the present embodiment, the external electrodes 14
An external terminal electrode is formed by the metal terminal 16 and the metal terminal 16 conductively connected thereto.

The dielectric layer 11 is formed of a rectangular sheet-shaped ceramic sintered body, and the ceramic sintered body is formed of a dielectric ceramic material whose main component is, for example, magnesium titanate or the like.

The internal electrode 12 is made of a metal thin film obtained by sintering a metal paste.
A material mainly composed of a noble metal material such as Ag or Pd is used. The external electrode 14 is also formed of the same material as the internal electrode 12, and the surface is plated with solder to improve solder wettability.

The vibration damping member 15 is made of, for example, silicon resin and has a density and hardness different from those of the ceramic sintered body and the metal terminals 16 forming the element body 13.

Here, the thickness of the vibration damping member 15 is preferably set to a value of at least 0.1 mm or more in order to obtain the desired effect of the present invention.

The metal terminal 16 is made of, for example, a copper piece having the same width as that of the capacitor 1, and has one end 16a.
Is electrically conductively connected to the external electrode 14, and the other end 16b is bent in a substantially U-shape. This metal terminal 16 is
3 are electrically connected to external electrodes 14 formed on the both end surfaces and the periphery thereof by using high-temperature solder 17. Here, the melting point of the high-temperature solder is higher than the melting point of the solder used when mounting the capacitor 1 on a circuit board.

The one end 16a of the metal terminal 16 comes into close contact with the end and the end face of the element body 13, but the other end 16b has a U-shaped bent portion protruding from the lower surface of the element body 13. It will be in the state of having done. Thereby, the other end 16 b of the metal terminal 16 is exposed outside the vibration damping member 15.

The capacitor 1 is manufactured by the following procedure.

First, after the element body 13 is formed by a conventional manufacturing method, external electrodes 14 are formed on both ends of the element body 13. Thereafter, the metal terminals 16 are soldered to the external electrodes 14. Further, the capacitor 1 is completed by applying and curing a silicone resin to be the vibration damping member 16 so as to include the element body 13 and the external electrode 14.

According to the capacitor 1 having the above-described structure, as shown in FIGS. 4 and 5, when the capacitor 1 is mounted on the circuit board 2, the other end 16b of the metal terminal 16 is brought into contact with the land 21 of the circuit board 2. The metal terminals 16 are conductively connected to the lands 21 by soldering or solder bonding.

In this state, the surface of the circuit board 2 and the element 13
And a vibration damping member 15 is interposed between them.

Accordingly, when an AC voltage is applied while applying a DC voltage between a pair of metal terminals 16 using a power supply smoothing circuit such as a DC-DC converter or the like, a piezoelectric phenomenon occurs and the element 13 vibrates. Although it occurs, both ends of the element 13 are fixed to the circuit board 2 by the metal terminals 16, so that they appear remarkably in the center of the element 13.

However, the vibration generated in the element 13 is
The transmission rate of the vibration of the element body 13 to the circuit board 2 is reduced by being absorbed by the vibration damping member 15. Thus, resonance of the circuit board 2 due to vibration of the element body 13 can be prevented, and generation of audible sound due to vibration caused by the piezoelectric effect as in the related art can be prevented.

The present embodiment is an example, and the present invention is not limited to this. For example, in the present embodiment, silicon resin is used as the vibration damping member 16, but other materials may be used. Further, in this embodiment, the U-shaped metal terminal 16 is soldered to the external electrode 14 to form an external terminal electrode. However, the shape of the metal terminal 16 is not limited to this. As shown in (1), a rectangular metal piece larger than the end face of the element body 13 may be used as a metal terminal (external terminal electrode) 16 ', and the central portion thereof may be soldered to the external electrode 14. In this case, the vibration damping member 15 may be filled between the metal terminals 16 ′ attached to both ends of the element body 13.

[0031]

As described above, according to the first to third aspects of the present invention, when vibration due to the piezoelectric effect occurs in the element, the vibration is absorbed by the vibration damping member covering the element, and Since the transmission rate of the element body vibration to the circuit board is reduced, resonance of the board due to the vibration can be prevented. Thus, it is possible to prevent the generation of an audible sound due to the piezoelectric effect caused by the body vibration as in the related art.

According to the second aspect, in addition to the above effects, the external electrodes formed on the end face of the element body and the conductive electrodes are electrically connected to the external electrodes so that the internal electrodes are alternately connected in parallel. Since the external terminal electrode is formed from the metal terminal, the external terminal electrode exposed outside the vibration damping member can be easily formed.

According to the third aspect, in addition to the above effects, the vibration damping member is made of a resin having a density and hardness different from those of the dielectric ceramic forming the element. The generated vibration can be efficiently absorbed, and the manufacturing can be easily performed.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing a multilayer ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a main part of the multilayer ceramic capacitor according to the embodiment of the present invention.

FIG. 3 is a side sectional view showing the multilayer ceramic capacitor according to one embodiment of the present invention.

FIG. 4 is a perspective view showing a state in which the multilayer ceramic capacitor according to one embodiment of the present invention is mounted on a circuit board.

FIG. 5 is a side sectional view showing a state in which the multilayer ceramic capacitor according to the embodiment of the present invention is mounted on a circuit board.

FIG. 6 is an external perspective view showing a multilayer ceramic capacitor according to another embodiment of the present invention.

FIG. 7 is an exploded perspective view showing a main part of a multilayer ceramic capacitor according to another embodiment of the present invention.

FIG. 8 is a side sectional view showing a multilayer ceramic capacitor according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor, 11 ... Dielectric layer, 12
... internal electrode, 13 ... body, 14 ... external electrode, 15 ... vibration damping member, 16 ... metal terminal, 17 ... high-temperature solder, 2 ... circuit board, 21 ... land.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E351 AA07 AA18 BB03 BB24 BB32 BB35 BB38 BB47 DD04 DD05 DD12 DD24 DD43 GG01 GG09 5E001 AB03 AF06 AG01 5E082 AA02 AB03 EE05 EE23 FG26 GG08 GG10 GG26 HH25H47H47H47H

Claims (3)

[Claims] 1. A rectangular parallelepiped element formed by alternately laminating dielectric layers made of dielectric ceramic and internal electrode layers; a vibration damping member for covering the element with a predetermined thickness; The internal electrodes formed on the internal electrode layer are alternately connected in parallel at both end portions, and at least a part of the internal electrode layer comprises a pair of external terminal electrodes exposed to the outside of the vibration damping member. Multilayer ceramic capacitor. 2. The external terminal electrode includes an external electrode formed at an end of the element body so as to alternately connect the internal electrodes in parallel, and a metal terminal conductively connected to the external electrode. The multilayer ceramic capacitor according to claim 1, wherein: 3. The multilayer ceramic capacitor according to claim 1, wherein the vibration damping member is made of a resin having a different density and hardness from the dielectric ceramic.