JP2006005244A - Stacked piezo-electric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stacked piezo-electric device which restrains a displacement impediment and disconnection from occurring, is improved in reliability, and is reduced in size and price. <P>SOLUTION: The stacked piezo-electric device PE is equipped with a stack 1 composed of piezo-electric material layers 3 and 5 and internal electrodes 11 and 13 which are alternately stacked together; first external electrodes 23 which are provided on the side faces 1a and 1b of the stack 1 and alternately, electrically connected to the internal electrodes 11 and 13; and second external electrodes 25 which are arranged overlapping the first external electrodes 23 respectively and discontinuously, electrically, and mechanically connected to the first external electrodes 23 in the stacking direction of the stack 1. The second external electrode 25 is composed of first parts 25a which are discontinuously arranged in the stacking direction, and second parts 25b which are extended in a direction intersecting with the stacking direction and connect the first parts 25a together. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer piezoelectric element.

As this type of laminated piezoelectric element, a laminated body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and provided on the side surface of the laminated body, and the internal electrodes are alternately electrically connected. The thing provided with the some external electrode to perform is known (for example, refer patent documents 1-3). In the multilayer piezoelectric element described in Patent Document 1, the external electrode is formed so that the entirety extends in the stacking direction of the multilayer body. In the multilayer piezoelectric element described in Patent Document 2, the external electrode is a mesh member made of a conductive wire, and is fixed to the side surface of the multilayer body with a conductive adhesive. In the multilayer piezoelectric element described in Patent Document 3, the external electrode is a coiled elastic member.
JP 2000-340849 A Japanese Patent Laid-Open No. 2001-210884 JP 2002-171003 A

  However, the multilayer piezoelectric elements described in Patent Documents 1 to 3 have the following problems.

  In the multilayer piezoelectric element described in Patent Document 1, since the external electrode extends in the stacking direction of the multilayer body, the displacement (stretching operation) of the element in the stacking direction is hindered. Further, when the laminated piezoelectric element is continuously driven for a long period of time, the expansion / contraction operation of the element cannot be endured, and the external electrode may be disconnected.

  In the multilayer piezoelectric elements described in Patent Documents 2 and 3, since the external electrode is a mesh member or a coiled elastic member, the disconnection of the external electrode can be suppressed following the expansion and contraction operation of the element. However, the configuration of the external electrode itself is complicated, and it is difficult to make an electrical connection with the internal electrode, which may cause a connection failure. In addition, since the external electrode has a thickness in a direction perpendicular to the stacking direction, the element may be increased in size. Moreover, since it is necessary to prepare a specially shaped member such as a mesh member or a coiled elastic member, the cost may increase.

  An object of the present invention is to provide a multilayer piezoelectric element capable of suppressing the inhibition of displacement and occurrence of disconnection, and improving reliability, downsizing, and cost reduction.

  The multilayer piezoelectric element according to the present invention is provided on a side surface of a multilayer body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately stacked, and the internal electrodes are electrically connected alternately. A plurality of external electrodes, wherein the external electrodes extend discontinuously in the stacking direction of the stack, extend in a direction intersecting the stacking direction, and the first portions And a second portion connecting the two.

  In the multilayer piezoelectric element according to the present invention, since the external electrode has the first portion and the second portion, the entire external electrode extends in the stacking direction of the stacked body as compared to the stacking direction of the stack. Inhibition of displacement can be suppressed, and disconnection of the external electrode can be suppressed even when the laminated piezoelectric element is driven continuously for a long period of time.

  In the present invention, since the external electrode has a very simple configuration such as having the first portion and the second portion, it is not necessary to prepare a member having a special shape such as a mesh member or a coiled elastic member. As a result, cost reduction and size reduction can be achieved, and electrical connection with the internal electrode can be easily performed.

  The external electrode is preferably flat. In this case, further downsizing can be achieved.

  The multilayer piezoelectric element according to the present invention is provided on a side surface of a multilayer body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately stacked, and the internal electrodes are electrically connected alternately. A plurality of first external electrodes and a plurality of first external electrodes that are disposed so as to overlap the first external electrodes and are discontinuously and electrically connected to the first external electrodes in the stacking direction of the stacked body. A second external electrode, the second external electrode extending discontinuously in the stacking direction, extending in a direction crossing the stacking direction, and the first portions And a second portion connecting the two.

  In the multilayer piezoelectric element according to the present invention, the second external electrode has a first portion and a second portion, and is electrically and mechanically connected to the first external electrode discontinuously in the stacking direction. Therefore, it is possible to suppress the displacement of the element in the stacking direction compared to the case where the entire external electrode extends in the stacking direction of the stack, and when the stacked piezoelectric element is driven continuously for a long period of time. However, it is possible to suppress the disconnection of the second external electrode. Even when the first external electrode provided on the side surface of the laminate is disconnected, the second external electrode is connected as described above, so that a conduction path to the internal electrode is secured. The function as a piezoelectric element is not impaired.

  Further, in the present invention, since the second external electrode has a very simple configuration such as having the first portion and the second portion, it is necessary to prepare a specially shaped member such as a mesh member or a coiled elastic member. There is no. As a result, cost reduction and size reduction can be achieved, and electrical connection with the internal electrode can be easily performed through the first external electrode.

  The second external electrode is preferably flat. In this case, further downsizing can be achieved.

  The first portion preferably extends in the stacking direction.

  According to the present invention, it is possible to provide a multilayer piezoelectric element capable of suppressing the inhibition of displacement and occurrence of disconnection, and improving reliability, downsizing, and cost reduction.

  Hereinafter, preferred embodiments of a multilayer piezoelectric element according to the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  First, the configuration of the multilayer piezoelectric element according to the present embodiment will be described with reference to FIGS. FIG. 1 is a schematic perspective view showing a multilayer piezoelectric element according to this embodiment. FIG. 2 is a schematic diagram for explaining a cross-sectional configuration of the multilayer piezoelectric element according to the present embodiment. FIG. 3 is a schematic diagram showing a connection relationship between the first external electrode and the second external electrode.

  The multilayer piezoelectric element PE includes a multilayer body 1 having a polygonal column shape (in this embodiment, a quadrangular column shape). The laminated body 1 includes a first side face 1a and a second side face that are positioned so as to be parallel to and opposed to each other in the laminating direction in the laminated body 1 (hereinafter, “the laminating direction in the laminated body 1” is simply referred to as “lamination direction”). Side surface 1b.

  As shown in FIG. 1, the laminate 1 is configured by alternately laminating piezoelectric layers 3 and piezoelectric layers 5 and sandwiching the piezoelectric layers 7 and 9 from above and below. ing. Each of the piezoelectric layers 3, 5, 7, and 9 is made of, for example, a piezoelectric ceramic material mainly composed of lead zirconate titanate (PZT), and is formed in a rectangular thin plate shape. In the present embodiment, the thickness of the piezoelectric layers 3 and 5 is, for example, 80 to 100 μm.

  The multilayer body 1 includes a first internal electrode 11 and a second internal electrode 13 that are stacked. The first internal electrode 11 is formed on the piezoelectric layer 3. The second internal electrode 13 is formed on the piezoelectric layers 5 and 9. The first internal electrode 11 and the second internal electrode 13 are mainly composed of silver and palladium, for example, and can be patterned by screen printing.

  In the laminate 1, the first internal electrode 11 and the second internal electrode 13 are laminated with the piezoelectric layers 3 and 5 interposed therebetween. As a result, in the laminate 1, the plurality of piezoelectric layers 3 and 5 and the plurality of internal electrodes 11 and 13 are alternately laminated. In this embodiment, the thickness of the 1st and 2nd internal electrodes 11 and 13 is 0.5-5 micrometers, for example.

  As shown in FIG. 2, the first internal electrode 11 is formed so as to be exposed to the first side face 1a from the inner side than the second side face 1b. That is, the end of the first internal electrode 11 on the second side surface 1b side is located a predetermined length away from the second side surface 1b. The first internal electrode 11 is not exposed on the second side surface 1b.

  As shown in FIG. 2, the second internal electrode 13 is formed so as to be exposed to the second side surface 1b from the inner side than the first side surface 1a. That is, the end of the second internal electrode 13 on the first side surface 1b side is located a predetermined length away from the first side surface 1a. The second internal electrode 13 is not exposed on the first side face 1a. The second internal electrode 13 is positioned so that a portion thereof overlaps the first internal electrode 11 when viewed from the stacking direction.

  As shown in FIGS. 1 and 2, external electrodes 21 are respectively provided on the first and second side surfaces 1 a and 1 b of the multilayer body 1. The external electrode 21 includes a first external electrode 23 and a second external electrode 25. The first external electrode 23 is formed so as to cover a part of each of the first and second side surfaces 1a and 1b. For example, the first external electrode 23 is mainly composed of silver and can be patterned by screen printing. In the present embodiment, the thickness of the first external electrode 23 is, for example, 1 to 20 μm.

  The first external electrode 23 formed on the first side surface 1a is electrically connected to the first internal electrode 11 exposed on the first side surface 1a on the first side surface 1a. The first external electrode 23 formed on the second side surface 1b is electrically connected to the second internal electrode 13 exposed on the second side surface 1b on the second side surface 1b. As a result, the first external electrode 23 electrically connects the internal electrodes 11 and 13 alternately every other layer.

  The second external electrode 25 is disposed so as to overlap the first external electrode 23 when viewed from the direction orthogonal to the first and second side surfaces 1a and 1b. The second external electrode 25 has a flat plate shape, and is made of, for example, copper (Cu), nickel (Ni), beryllium copper, or the like. In the present embodiment, the thickness of the second external electrode 25 is, for example, about 150 μm.

  The second external electrode 25 has a first portion 25a and a second portion 25b. The first portion 25a extends in the stacking direction and is discontinuously arranged in the stacking direction. The second portion 25b extends in a direction intersecting the stacking direction (in the present embodiment, the orthogonal direction) and connects the first portions 25a. Thereby, the second external electrode 25 has a crank shape.

  As shown in FIG. 3, the second external electrode 25 is electrically and mechanically connected to the first external electrode 23 discontinuously in the stacking direction. In the present embodiment, the second external electrode 25 is connected to the first external electrode 23 at the location W by spot welding. The interval between the locations W where the first external electrode 23 and the second external electrode 25 are connected is set to several layers (for example, 5 and 6 layers) of the piezoelectric layers 3 and 5, that is, 400 to 600 μm. be able to.

  Between the first external electrode 23 formed on the first side surface 1a and the first external electrode 23 formed on the second side surface 1b (for example, the first formed on the first side surface 1a). Are applied to the first external electrode 23 and the second internal electrode 13, and the first external electrode 23 formed on the second side surface 1 b is set to a negative potential. A voltage is applied during the period. Thereby, in the piezoelectric layers 3 and 5, an electric field is generated in a region sandwiched between the first internal electrode 11 and the second internal electrode 13, and the region is displaced as an active portion.

  Next, a manufacturing procedure of the above-described multilayer piezoelectric element PE will be described.

  First, a base paste is prepared by mixing an organic binder, an organic solvent, or the like with a piezoelectric material mainly composed of ceramics such as lead zirconate titanate. Next, a raw material sheet (green sheet) that constitutes each of the piezoelectric layers 3, 5, 7, and 9 is formed using the manufactured base paste. In addition, a conductive paste for forming an electrode pattern by mixing an organic binder, an organic solvent, or the like with a metal material (for example, Ag: Pd = 7: 3) made of silver (Ag) and palladium (Pd) in a predetermined ratio. Is made.

  Next, an electrode pattern corresponding to the first internal electrode 11 is formed on the formed material sheet. In addition, an electrode pattern corresponding to the second internal electrode 13 is formed on a material sheet different from the material sheet on which the electrode pattern corresponding to the first internal electrode 11 is formed. Each electrode pattern is formed by screen printing using the conductive paste described above.

  Next, the material sheet on which the electrode pattern is formed and the material sheet on which the electrode pattern is not formed are laminated to produce a laminate green. At this time, the material sheet on which the electrode pattern is formed is laminated so that a part of the electrode pattern corresponding to the second internal electrode 13 overlaps the electrode pattern corresponding to the first internal electrode 11 when viewed from the lamination direction. The The number of material sheets stacked is, for example, about 350 layers.

  Next, the produced laminate green is pressed in the lamination direction at a predetermined pressure (for example, about 100 MPa) while being heated. The heating temperature is, for example, about 60 ° C. Then, the pressed laminate green is cut into a predetermined size. For cutting the laminate green, for example, a diamond blade can be used. At this time, the first internal electrode 11 and the second internal electrode 13 are exposed to the corresponding side surfaces.

  Next, the cut laminated green is degreased (debindered) at a predetermined temperature (for example, about 400 ° C.) and then fired. Thereby, the laminated body 1 will be obtained. The firing temperature is, for example, about 1100 ° C. The firing time is, for example, about 2 hours.

  Next, after printing a conductive paste mainly composed of silver on the first and second side surfaces 1a and 1b of the laminate 1 obtained by firing, baking is performed at a predetermined temperature (for example, about 700 ° C.), A first external electrode 23 is formed. As the conductive paste for forming the first external electrode 23, a paste containing gold (Ag) as a main component, a paste containing copper as a main component, or the like is used in addition to a paste containing silver as a main component. it can. As a method of forming the first external electrode 23, a sputtering method, an electroless plating method, or the like can be used instead of baking.

  Next, the prepared second external electrode 25 is connected to the first external electrode 23 by soldering. The second external electrode 25 can be obtained, for example, by processing a plate material made of beryllium copper into a crank shape and performing Ni plating and Sn plating. As a method of connecting the second external electrode 25 and the first external electrode 23, spot welding, brazing, adhesion with a conductive adhesive, or the like can be used instead of the spot welding described above.

  Next, polarization processing (for example, applying an electric field for 3 minutes so that intensity | strength will be 2 kV / mm in the environment of temperature 120 degreeC) is given, and the lamination type piezoelectric element PE is obtained.

  As described above, in the present embodiment, the second external electrode 25 includes the first portion 25a and the second portion 25b, and the first external electrode is discontinuously electrically and mechanically in the stacking direction. 23, the displacement of the multilayer piezoelectric element PE in the stacking direction can be suppressed from being inhibited as compared with the case where the entire external electrode extends in the stacking direction of the stacked body 1. Further, even when the multilayer piezoelectric element PE is continuously driven for a long period of time, it is possible to suppress the disconnection of the second external electrode 25, and the reliability is improved.

  Further, even when the first external electrode 23 provided on the side surface of the laminate 1 is disconnected, the second external electrode 25 is connected as described above, so that the conduction path to the internal electrodes 11 and 13 is achieved. Will be secured. For this reason, the multilayer piezoelectric element PE does not lose its function as a piezoelectric element.

  Further, since the second external electrode 25 has a very simple configuration such as having the first portion 25a and the second portion 25b, it is necessary to prepare a specially shaped member such as a mesh member or a coiled elastic member. Absent. As a result, cost reduction and size reduction can be achieved, and electrical connection with the internal electrodes 11 and 13 can be easily performed through the first external electrode 23.

  Further, since the second external electrode 25 has a flat plate shape, further miniaturization can be achieved.

  It is preferable that the interval between the locations W where the first external electrode 23 and the second external electrode 25 are connected is set to 5 or 6 layers (400 to 600 μm) of the piezoelectric layers 3 and 5. When the interval between the locations W is narrower than the set value, the effect of suppressing the inhibition of the displacement in the stacking direction is diminished. In the case where the interval between the locations W is wider than the set value, the internal electrodes 11 and 13 increase when the first external electrode 23 is disconnected, so that a conduction path to the internal electrodes 11 and 13 is secured. It becomes difficult to do. For these reasons, it is preferable to set the interval W between the piezoelectric layers 3 and 5 for 5 and 6 layers (400 to 600 μm).

  As mentioned above, although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the above embodiment. The shape of the laminated body 1 is not limited to a polygonal column shape, and may be a cylindrical shape. In the laminate 1, the side surface on which the external electrode 21 is provided is not limited to the two side surfaces positioned so as to face each other, and may be two adjacent side surfaces. Moreover, when the laminated body 1 is cylindrical, the external electrode 21 will be provided in the arbitrary area | region of a side surface, if it is a position which does not contact mutually.

  The shape of the second external electrode 25 is not limited to the crank shape described above, and may be a zigzag shape or a meandering shape as shown in FIGS. When the second external electrode 25 has a zigzag shape and a meandering shape, the first portion 25a extends in a direction crossing the stacking direction. The second external electrode 25 may be wavy as long as it can be connected to the first external electrode 23.

  The first internal electrode 11 may be exposed on the second side surface 1b as long as it is electrically insulated from the external electrode 21 provided on the second side surface 1b. Similarly, the second internal electrode 13 may be exposed to the first side face 1a as long as it is electrically insulated from the external electrode 21 provided on the first side face 1a.

  In the present embodiment, the external electrode 21 includes the first external electrode 23 and the second external electrode 25, but the first external electrode 23 is omitted and only the second external electrode 25 is used. It may be configured. In this case, the effect of suppressing the displacement in the stacking direction is less than that of the configuration including the first external electrode 23 and the second external electrode 25, but the entire external electrode is Compared to those extending in the stacking direction of the stacked body, the above-described suppressing effect is obtained.

It is a schematic perspective view which shows the lamination type piezoelectric element which concerns on this embodiment. It is a schematic diagram for demonstrating the cross-sectional structure of the laminated piezoelectric element which concerns on this embodiment. It is a schematic diagram which shows the connection relation of a 1st external electrode and a 2nd external electrode. It is a schematic perspective view which shows the modification of the lamination type piezoelectric element which concerns on this embodiment. It is a schematic perspective view which shows the modification of the lamination type piezoelectric element which concerns on this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated body, 1a ... 1st side surface, 1b ... 2nd side surface, 3,5 ... Piezoelectric layer, 11 ... 1st internal electrode, 13 ... 2nd internal electrode, 21 ... External electrode, 23 ... 1st external electrode, 25 ... 2nd external electrode, 25a ... 1st part, 25b ... 2nd part, PE ... Laminated piezoelectric element, W ... 1st external electrode and 2nd external electrode Location to be connected.

Claims (5)

A laminate formed by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes;
A plurality of external electrodes provided on a side surface of the laminate and alternately electrically connecting the internal electrodes;
The external electrode is
A first portion disposed discontinuously in the stacking direction of the stacked body;
A laminated piezoelectric element comprising: a second portion extending in a direction intersecting with the lamination direction and connecting the first portions.   The multilayer piezoelectric element according to claim 1, wherein the external electrode has a flat plate shape. A laminate formed by alternately laminating a plurality of piezoelectric bodies and a plurality of internal electrodes;
A plurality of first external electrodes provided on a side surface of the stacked body and alternately electrically connecting the internal electrodes;
A plurality of second external electrodes that are respectively disposed so as to overlap the first external electrodes and are electrically and mechanically connected to the first external electrodes discontinuously in the stacking direction of the stacked body; With
The second external electrode is
A first portion disposed discontinuously in the stacking direction;
A laminated piezoelectric element comprising: a second portion extending in a direction intersecting with the laminating direction and connecting the first portions.   The multilayer piezoelectric element according to claim 3, wherein the second external electrode has a flat plate shape.   The multilayer piezoelectric element according to claim 1, wherein the first portion extends in the stacking direction.

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