JP2000269562A - Multilayer piezoelectric ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid decrease in characteristics due to damages of external electrodes and also suppress occurrence of damages with respect to the external electrodes. SOLUTION: Multilayer single elements (multilayer piezoelectric ceramic single elements) 10, 11 and 12 are of the identical construction, excepting external input/output terminals 6A and 6B of the multilayer single element 10. The multilayer single elements 10, 11 and 12 are provided with leads 7A and 7B (internal connection conductors) which connect two or more points of the external electrodes 4A and 4B. When the multilayer single elements 10, 11 and 12 are stacked in the direction of the ceramic lamination and are connected, leads 91A and 91B (connecting conductor between single elements) connect conductive connecting parts 8A and 8B of the respective leads 91A and 91B. The leads 7A and 7B of inner connection conductor may be a whole surface conductor which cover the whole surface of the external electrodes 4A and 4B. Also, it is preferable that leads 7A, 7B, 91A and 91B exist in multitude or are metal rigid bodies, such as metal plates for prevention of cut of the external electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated body which is laminated on three or more piezoelectric ceramic layers with an internal electrode layer interposed therebetween, and a counter electrode which is provided on both sides of the laminated body with an internal electrode layer provided every other layer. A multilayer piezoelectric ceramic unit formed by an insulator layer formed so as to form a pair of external electrodes for electrically connecting an internal electrode layer by covering an upper portion of each of the insulator layers, and the multilayer piezoelectric ceramic unit More particularly, the present invention relates to a laminated piezoelectric ceramic which can avoid deterioration of characteristics with respect to damage to external electrodes and can suppress occurrence of damage to external electrodes.

[0002]

2. Description of the Related Art Conventionally, in this type of laminated piezoelectric ceramic, as shown in FIG. 5, a laminated piezoelectric ceramic unit (hereinafter simply referred to as a laminated unit) 100 is composed of, for example, seven piezoelectric ceramic layers 1 respectively. Are three internal electrode layers 2 each
A, 2A, and 2B, and the insulator layers 3A, 3B and the insulator layers 3A, in which the internal electrode layers 2A, 2B are alternately formed as opposing electrodes on both side surfaces of the laminate. , 3B to cover the upper portions of the internal electrode layers 2
A and 2B are formed by external electrodes 4A and 4B which electrically connect three layers respectively. External electrode 4A,
The input / output terminal connection portions 5A and 5B formed in a bump shape by a conductor such as solder are connected to the external input / output terminals 6A and 6B, respectively.

[0003] Further, as shown in FIG.
In the case where a plurality of layers 00, 101, and 102 are stacked in the stacking direction and connected in multiple stages, the external electrodes 4A and 4B of the stacks 100, 101, and 102 each have an end formed in a strip shape with a conductor such as solder. Electrode connecting portion 109A, 1
09B are electrically connected in series. Laminated single unit 10
1 and 102 are laminated single units 100 shown in FIG.
In this embodiment, the input / output terminal connection portions 5A and 5B and the external input / output terminals 6A and 6B are deleted.

[0004]

In the above-mentioned conventional laminated piezoelectric ceramic, the external electrodes of the laminated single body are each connected to the external input / output terminal at the input / output terminal connection portion made of one bump solder. In addition, when the external electrode is cut by a crack or the like, there is a problem that only the characteristics in the vicinity of the input / output terminal connection portion that is electrically connected to the external input / output terminals can be confirmed, and the characteristics of other portions cannot be confirmed.

In addition, when a plurality of laminated units are connected in multiple stages, external electrodes are arranged in series and adjacent electrodes are connected by soldering. Therefore, when the external electrodes are cut, only the characteristics up to the cut point are confirmed. Will be.

FIG. 7 shows a multi-layered piezoelectric ceramic having a five-stage structure in which a multi-layer structure having external input / output terminals is the first stage, and two stages are further superposed on the three stages of FIG. The displacement amount characteristic when the external electrode of one laminated single unit is cut off by applying the voltage from the external input / output terminal of the laminated single unit of FIG. According to this example, the displacement amount shows a value “60” in a normal state. However, when the external electrodes are cut off in each of the stacked single layers from the fifth stage to the second stage, the displacement amount becomes the value sequentially. "54, 42, 30, 18"
When the external electrode is cut by a laminate having an external input / output terminal, the value is reduced to "6", that is, to 10%.

The object of the present invention is to solve the above problems and to prevent the deterioration of the characteristics with respect to the damage of the external electrode.
It is still another object of the present invention to provide a laminated piezoelectric ceramic capable of suppressing the occurrence of damage to external electrodes.

[0008]

According to the present invention, there is provided a laminated piezoelectric ceramic comprising a laminate laminated on three or more piezoelectric ceramic layers with an internal electrode layer interposed therebetween, and the internal electrodes on both side surfaces of the laminate. A laminate formed by an insulator layer formed so that every other layer becomes a counter electrode, and a pair of external electrodes covering the upper portion of each of the insulator layers and electrically connecting the internal electrode layers every other layer Type piezoelectric ceramic is a single-layer piezoelectric ceramic having an internal connection conductor for connecting at least two places on the external electrode, or covers the entire surface of the external electrode with a conductor instead of the internal connection conductor. This is a laminated piezoelectric ceramic simple substance including an entire surface conductor.

As a result, when the internal connection conductor is connected to the external electrode, for example, when two places are at the ends of the external electrode, the cutting of the intermediate part of the external electrode does not affect the characteristics. . Further, in the case where a large number of connection portions are provided by a large number of internal connection conductors, or in the case where the entire surface of the external electrode is covered with the conductor, the external electrode is strengthened and the occurrence of damage to the external electrode can be suppressed.

Further, in the laminated piezoelectric ceramic in which a plurality of the laminated piezoelectric ceramics are stacked and connected in a ceramic laminating direction, a single internal conductor is connected on an external electrode of the laminated piezoelectric ceramic to an internal connecting conductor or the whole surface. A single internal conductor formed as a conductor and an inter-unit connecting conductor for sequentially connecting the single internal conductors of each of the plurality of multilayer piezoelectric ceramics are provided. With this configuration, while having the characteristics of the above-described laminated piezoelectric ceramic simple substance, the external electrodes of the laminated simple substance in which the inter-unit connecting conductor and the single internal conductor are further stacked in multiple stages are connected to the external input / output terminals. Even if the external electrode of the laminate alone is cut, no change in characteristics occurs.

Further, a laminated body laminated on each of three or more piezoelectric ceramic layers with an internal electrode layer interposed therebetween, and the internal electrode layers are formed on both side surfaces of the laminated body so as to serve as opposing electrodes every other layer. A laminate in which a plurality of conventional laminated piezoelectric ceramics each formed by an insulator layer and an external electrode covering an upper portion of each of the insulator layers and electrically connecting the internal electrode layer are stacked in a ceramic laminating direction and connected. The type piezoelectric ceramic may include only a single-unit connection conductor that sequentially connects one place on the external electrode of each of the plurality of single-layer piezoelectric ceramics. In this configuration, although the function is inferior to the case of stacking the above-described laminated single units in multiple stages, the deterioration of the characteristics can be limited to only the laminated single unit in which the cutting has occurred.

Preferably, the above-mentioned internal connection conductor or inter-unit connection conductor is at least one of a metal conductor and a metal rigid body. In the case of a rigid metal body such as a metal plate, the function can be further enhanced as compared with a metal conductor.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a side view of a laminated piezoelectric ceramic single body (laminated single body) 10 according to an embodiment of the present invention. As shown in FIG. 1, the laminated unit 10 is, for example,
A laminate in which seven piezoelectric ceramic layers 1 are alternately laminated with three internal electrode layers 2A and 2B interposed therebetween, and the internal electrode layers 2A and 2B are alternately provided on both side surfaces of the laminate with a counter electrode. Each of three insulator layers 3A to be formed,
3B and a pair of external electrodes 4A and 4B which cover the upper portions of the insulator layers 3A and 3B and electrically connect the three internal electrode layers 2A and 2B respectively. Each of the external electrodes 4A and 4B has an input / output terminal connection portion 5A, 5
B connects the external input / output terminals 6A and 6B. The above configuration is the same as the conventional one.

The difference from the prior art is that the pair of external electrodes 4
In addition to the knob-shaped input / output terminal connecting portions 5A and 5B for connecting the external input / output terminals 6A and 6B on the surfaces of the external electrodes 4A and 4B, lead wires 7A and 7B, which are metal conductors of internal connection conductors, are connected to the external electrodes 4A. , 4B, each of which has one bump-shaped conductor connecting portion 8A, 8B made of solder.

As a result of this configuration, for example, when the external electrode 4A is damaged and cut between the input / output terminal connection portion 5A and the conductor connection portion 8A, information over the entire surface of the external electrode 4A can be input to and output from the external input / output terminal 6A. Therefore, a change in characteristics due to cutting of the external electrode 4A can be significantly reduced. Further, by adding the lead wire 7A and the conductor connecting portion 8A, the surface of the external electrode 4A is strengthened against external stress.

Next, referring to FIG. 2 and FIG. 1, a multilayer piezoelectric ceramic in which a plurality of single layers are laminated will be described.

In FIG. 2, the laminated single bodies 10, 11, 1
2 are stacked and connected in three layers in the laminating direction. The laminated unit 10 is the one shown in FIG. Laminated single unit 11, 1
Reference numeral 2 denotes the external input / output terminal 6 from the laminated unit 10 shown in FIG.
A and 6B are removed, and the input / output terminal connection portions 5A and 5B are replaced with conductor connection portions 8A and 8B. In the case of a multi-layer piezoelectric ceramic in which the multi-layer units 10, 11, and 12 are connected in a multi-stage relationship in the upper-lower relationship and the input / output terminal connection units 5 </ b> A and 5 </ b> B are at the lowest position, the conductor connection at the upper position of each multi-layer unit The portions 8A and 8B and the conductor connecting portions 8A and 8B at the lower positions of the laminated units 11 and 12 are connected by lead wires 91A and 91B, which are metal conductors of the inter-unit connecting conductor. Therefore, for example, the external input / output terminal 6A
Are connected from the laminated unit 10 to the laminated unit 12 via the lead wires 7A and the lead wires 91A alternately.

According to this configuration, even if the external electrode is cut off in each laminated unit, the entire surface of the external electrode can be connected to the external input / output terminal. As shown in the example of the displacement amount characteristic, when the displacement amount shows the value “60” in the normal state, the second to fifth stages
Even if the external electrode is cut in any one of the stacks up to the stage, the displacement amount does not change and the value is “60”.

In the above description, the lead wire of each external electrode is
Although described as a book, further improvement in function and effect can be expected by providing a plurality of conductor connection portions and increasing the number of lead wires.

Next, an embodiment of a laminated piezoelectric ceramic different from that of FIG. 2 will be described with reference to FIG. 3 and FIG.

The laminated single bodies 20, 21, 22 shown in FIG.
Are stacked and connected in three layers in the stacking direction. The laminated unit 20 is the same as that shown in FIG. Laminated single unit 2
Reference numerals 1 and 22 denote external input / output terminals 6A and 6B from the laminated unit 100 shown in FIG.
B is replaced with conductor connection parts 8A and 8B.
In the case of a multi-layer piezoelectric ceramic in which the multi-layered units 20, 21, and 22 are connected in a multi-stage relationship in a vertical relationship, and have input / output terminal connecting portions 5A, 5B at the lowest level, the multi-layered units 20, 21, 2
2, the input / output terminal connection part 5 which is in a vertical positional relationship.
A, 5B and the conductor connection portions 8A, 8B are connected by lead wires 92A, 92B, which are metal conductors of the inter-unit connection conductor.

In this configuration, the characteristics are degraded only by the laminated single unit where the external electrode is cut. Therefore, as shown in FIG. 7, as shown in the example of the displacement amount characteristic when the external electrode of one single laminated unit is cut, When the displacement amount shows a value “60” in a normal state, even if the external electrode is cut in any one of the stacked layers from the fifth stage to the second stage, the displacement amount shows a deterioration amount for one. It can be confirmed that the value becomes “54”.

Next, referring to FIG. 4 and FIGS. 1 and 5, a laminated unit 30 different from the above-described laminated units 10 and 100 will be described.

The entire surface of each of the external electrodes 4A and 4B of the laminated unit 100 in FIG. 5 can be covered with, for example, solder as the entire conductors 73A and 73B of the unit internal conductor. This condition is due to the large number of interconnecting conductors (8A, 7B) and the large number of conductor connections (8
A, 8B) are equivalent to being provided continuously. As a result, many obstacles such as cracking or cutting of the multilayer piezoelectric ceramic alone can be avoided.

In the above description, a lead wire made of a metal conductor is used as the internal connection conductor and the inter-unit connection conductor. However, a rigid conductor such as a metal plate may be used. Since the used portion is protected by the rigidity of such a metal, the laminated piezoelectric ceramic is further strengthened against external stress or impact.

[0027]

As described above, according to the present invention, there is provided a single-layer piezoelectric ceramic having an internal connection conductor for connecting two or more locations on an external electrode, or an external piezoelectric ceramic instead of an internal connection conductor. This is a single-layer piezoelectric ceramic having an entire conductor covering the entire surface of the electrode with a conductor.

Based on this configuration, when the internal connection conductor is connected to the external electrode, for example, when two places are at the ends of the external electrode, cutting of the intermediate part of the external electrode affects the characteristics. In addition, when providing a large number of connection portions by a large number of internal connection conductors, or when covering the entire surface of the external electrode with a conductor, the external electrode is strengthened and the damage to the external electrode can be suppressed. Is obtained.

A multilayer piezoelectric ceramic in which a plurality of laminated piezoelectric ceramics are stacked in a plurality of layers in the ceramic laminating direction and connected to each other is a single piezoelectric ceramic in which each of the plurality of laminated piezoelectric ceramics is sequentially connected at one or more locations on an external electrode. An interconnecting conductor is provided.

According to this structure, even if there is a cut in the connection portion of the multilayer piezoelectric ceramic unit, there is obtained an effect that the characteristics do not deteriorate.

[Brief description of the drawings]

FIG. 1 is a front explanatory view showing one embodiment of a laminated single body of the present invention.

FIG. 2 is an explanatory front view showing an embodiment in a case where the single layers of FIG. 1 are stacked in three layers.

FIG. 3 is an explanatory front view showing an embodiment in the case of stacking a single layer different from that of FIG. 2;

FIG. 4 is an explanatory front view showing an embodiment of a laminated unit different from that of FIG. 1;

FIG. 5 is an explanatory front view showing an example of a conventional laminated unit.

FIG. 6 is an explanatory front view showing an embodiment in a case where the single layers of FIG. 5 are stacked in three layers.

FIG. 7 is a characteristic diagram at the time of cutting an external electrode in a case where a single layer is stacked in five stages.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic layer 2A, 2B Internal electrode layer 3A, 3B Insulator layer 4A, 4B External electrode 5A, 5B Input / output terminal connection part 6A, 6B External input / output terminal 7A, 7B Lead wire (internal connection conductor, single internal conductive Body) 8A, 8B Conductor connection parts 10, 11, 12, 20, 21, 22, 30 Single layer (single-layer piezoelectric ceramic single) 73A, 73B Full-surface conductor (single internal conductor) 91A, 91B, 92A, 92B Lead wire (conductor connected between individual units)

Claims (5)

[Claims] 1. A laminate which is laminated on three or more piezoelectric ceramic layers with an internal electrode layer interposed therebetween, and the internal electrode layers are formed on both sides of the laminate so as to serve as counter electrodes every other layer. At least two laminated piezoelectric ceramics formed by an insulator layer and a pair of external electrodes covering an upper portion of each of the insulator layers and electrically connecting the internal electrode layers to each other are provided. A multilayer piezoelectric ceramic which is a single layer piezoelectric ceramic having one of an internal connection conductor for connecting a place and an entire surface conductor. 2. A laminate which is laminated on three or more piezoelectric ceramic layers with an internal electrode layer interposed therebetween, and the internal electrode layers are formed on both sides of the laminate so as to serve as opposite electrodes every other layer. A plurality of single-layer piezoelectric ceramics each formed of an insulator layer and a pair of external electrodes that cover the upper portion of each of the insulator layers and electrically connect the internal electrode layers to each other are stacked in a plurality of layers in the ceramic stacking direction. In the multilayer piezoelectric ceramics to be connected, a single internal conductor forming at least one of an internal connection conductor connecting at least two places on the external electrode of the multilayer piezoelectric ceramic alone and a whole surface conductor; A single-layer connecting conductor for sequentially connecting the single-layer internal conductors of each of the single-layer piezoelectric ceramics. 3. A laminated body laminated on each of three or more piezoelectric ceramic layers with an internal electrode layer interposed therebetween, and the internal electrode layers are formed on both side surfaces of the laminated body so as to serve as opposing electrodes every other layer. A plurality of single-layer piezoelectric ceramics each formed of an insulator layer and a pair of external electrodes that cover the upper portion of each of the insulator layers and electrically connect the internal electrode layers to each other are stacked in a plurality of layers in the ceramic stacking direction. A multilayer piezoelectric ceramic to be connected, comprising: an inter-unit connecting conductor for sequentially connecting one portion on each of the external electrodes of each of the plurality of single multilayer piezoelectric ceramics. 4. The multilayer piezoelectric ceramic according to claim 1, wherein the internal connection conductor is at least one of a metal conductor and a metal rigid body. 5. The multilayer piezoelectric ceramic according to claim 2, wherein the inter-unit connecting conductor is at least one of a metal conductor and a metal rigid body.