JP5167576B2 - Multilayer piezoelectric element - Google Patents

Description

  The present invention relates to a multilayer piezoelectric element.

As a conventional multilayer piezoelectric element, a multilayer body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately stacked, and an external part provided on the side surface of the multilayer body and electrically connected to a predetermined internal electrode The thing provided with the electrode 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 as to extend 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 entire external electrode extends in the stacking direction of the multilayer body, displacement (stretching operation) of the multilayer body in the stacking direction is hindered. Further, when the multilayer piezoelectric element is used for a long period of time, the external electrode may be disconnected without being able to withstand the expansion and contraction operation of the multilayer body.

  In the multilayer piezoelectric elements described in Patent Documents 2 and 3, the external electrode is a mesh member or a coiled elastic member, and can follow the expansion and contraction operation of the multilayer body. The occurrence of disconnection is suppressed. However, since a specially shaped member such as a mesh member or a coiled elastic member is employed for the external electrode, the configuration of the piezoelectric element becomes complicated.

  Therefore, the present invention has been made in view of such circumstances, and provides a multilayer piezoelectric element that can suppress the displacement of the multilayer body and the occurrence of disconnection of the external electrode with a simple configuration. With the goal.

In order to achieve the above object, a multilayer piezoelectric element according to the present invention includes a multilayer body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately stacked, a side surface of the multilayer body, and a predetermined internal structure. A first external electrode electrically connected to the electrode, and a second external electrode provided outside the first external electrode and extending in the stacking direction of the stacked body, The external electrode is wavy when viewed from the direction orthogonal to the side surface, is flat when viewed from the direction orthogonal to the direction orthogonal to the side surface, and the second external electrode is on the first external electrode side A plurality of projections projecting to the first external electrode by soldering at the projections and facing the projections on the outer surface of the first external electrode. the portion excluding the portions, the first resist layer so as to separate the respective said portion Vignetting is, the portion except for the portion having a convex portion formed in the inner surface of the second external electrode, wherein the second resist layer so as to separate the respective said portions is provided with .

In the multilayer piezoelectric element, the second external electrode extends in a wave shape along the stacking direction of the multilayer body, and is electrically and physically connected to the first external electrode at a plurality of convex portions. Yes. Accordingly, since the second external electrode has elasticity in the stacking direction, it is possible to suppress the displacement of the stacked body in the stacking direction and to suppress the piezoelectric element for a long period of time. Even if it is used, it can suppress that the 2nd external electrode breaks. Even if the first external electrode provided on the side surface of the laminate is disconnected, the second external electrode is electrically and physically connected to the first external electrode via the plurality of convex portions. Therefore, a conduction path to a predetermined internal electrode can be secured, and the function as a piezoelectric element can be maintained. In this multilayer piezoelectric element, a very simple member such as a flat plate extending in a wave shape along the stacking direction of the multilayer body is adopted as the second external electrode. Can be simplified. Furthermore, since the second external electrode is electrically and physically connected to the first external electrode at the plurality of convex portions protruding toward the first external electrode, the first external electrode and the second external electrode The connection with the external electrode can be ensured. The second external electrode is electrically and physically connected to the first external electrode by solder at the convex portion. Thereby, the connection between the first external electrode and the second external electrode can be facilitated at the time of manufacturing the piezoelectric element.

  The convex portion is formed when a part of the second external electrode is pushed out to the first external electrode side, or a part of the second external electrode is on the first external electrode side. It may be formed by being bent.

  Moreover, it is preferable that each front-end | tip of a convex part is located on substantially the same plane. Thereby, the gap between the first external electrode and the second external electrode can be kept constant, and the connection between the first external electrode and the second external electrode is further ensured at each convex portion. It becomes possible to do.

  According to the present invention, it is possible to suppress the inhibition of the displacement of the laminated body and the occurrence of the disconnection of the external electrode with a simple configuration.

  Hereinafter, preferred embodiments of a multilayer piezoelectric element according to the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or equivalent part, and the overlapping description is abbreviate | omitted.

[First Embodiment]
As shown in FIGS. 1 and 2, the multilayer piezoelectric element 1 according to the first embodiment includes a multilayer body 2 having a polygonal column shape (in this case, a quadrangular column shape). The stacked body 2 has a first side surface 2a and a second side surface 2b which are positioned so as to be parallel to and opposed to each other in the stacking direction of the stacked body 2 (hereinafter simply referred to as “stacking direction”). .

  The laminated body 2 is configured such that the piezoelectric bodies 3 and the piezoelectric bodies 5 are alternately laminated, and further sandwiched between the piezoelectric bodies 7 and 9 from above and below. Each of the piezoelectric bodies 3, 5, 7, and 9 is made of, for example, a piezoelectric ceramic material mainly composed of lead zirconate titanate, and is formed in a rectangular thin plate shape. Here, the thickness of each piezoelectric body 3 and 5 is 50 to 100 μm.

  The stacked body 2 has a first internal electrode 11 and a second internal electrode 13. The first internal electrode 11 is formed on the upper surface of the piezoelectric body 3, and the second internal electrode 13 is formed on the upper surfaces of the piezoelectric bodies 5 and 9. Each of the internal electrodes 11 and 13 is made of, for example, a conductive material mainly composed of silver and palladium, and is patterned by screen printing. Here, the thickness of each internal electrode 11 and 13 is 0.5-5 micrometers.

  In the laminated body 2, the first internal electrode 11 and the second internal electrode 13 are laminated with the piezoelectric bodies 3 and 5 interposed therebetween. Thereby, in the multilayer body 2, the plurality of piezoelectric bodies 3 and 5 and the plurality of internal electrodes 11 and 13 are alternately stacked.

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

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

  External electrodes 21 are provided on the side surfaces 2 a and 2 b of the multilayer body 2. 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 side surfaces 2a and 2b. The first external electrode 23 is made of, for example, a conductive material containing silver as a main component, and is patterned by screen printing. Here, the thickness of the first external electrode 23 is 1 to 40 μm.

  The first external electrode 23 formed on the first side surface 2a is electrically connected to the first internal electrode 11 exposed on the first side surface 2a on the first side surface 2a. The first external electrode 23 formed on the second side surface 2b is electrically connected to the second internal electrode 13 exposed on the second side surface 2b on the second side surface 2b.

  The second external electrode 25 is disposed outside each first external electrode 23, extends in a wave shape along the stacking direction, and includes a first portion 25a and a second portion 25b. Yes. The first portions 25a extend along the stacking direction and are discontinuously arranged in the stacking direction. The second portion 25b extends along a direction crossing the stacking direction (here, a direction orthogonal to the stacking direction), and connects the first portions 25a. Accordingly, the second external electrode 25 as a whole extends in a rectangular wave shape (that is, a pulse wave shape) along the stacking direction.

  As shown in FIG. 3, the second external electrode 25 has a convex portion 31 protruding to the first external electrode 23 side in each first portion 25 a, and is discontinuous at each convex portion 31. The first external electrode 23 is electrically and physically (that is, mechanically) connected. That is, the second external electrode 25 is electrically and physically connected to the first external electrode 23 discontinuously at the plurality of convex portions 31 arranged in a staggered manner. Here, the distance along the stacking direction between the adjacent protrusions 31 on the second external electrode 25 is 400 to 1000 μm.

  As shown in FIG. 4, the second external electrode 25 includes a metal plate 32 and a tin plating layer 33 provided on the inner surface of the metal plate 32, and is configured in a flat plate shape. The metal plate 32 is made of, for example, a conductive material such as copper or an alloy thereof, nickel or an alloy thereof, stainless steel, or beryllium copper. Here, the thickness of the metal plate 32 is about 50 to 150 μm. The convex portion 31 is formed by pushing out a part of the first portion 25a of the second external electrode 25 to the first external electrode 23 side, and the tip 31a of each convex portion 31 is substantially in the same plane. Located on the top.

  On the outer surface of the first external electrode 23, a solder layer 33 is provided in a portion facing the convex portion 31 of the second external electrode 25, and a resist layer 34 is provided in a portion excluding the solder layer 33. ing. On the other hand, a solder plating layer 36 is provided on the inner surface of the tin plating layer 33 of the second external electrode 25, and a resist is formed on the inner surface of the solder plating layer 36 except for a portion where the convex portion 31 is formed. A layer 37 is provided. The resist layers 34 and 37 are made of, for example, an epoxy or acrylic resin.

  Then, the first external electrode 23 and the second external electrode 25 are soldered by reflow in a state where the solder layer 33 and the solder plating layer 36 are abutted with each other on the convex portions 31 of the second external electrode 25. It is attached. As a result, the second external electrode 25 is electrically and physically connected to the first external electrode 23 by soldering at each convex portion 31.

  The resist layers 34 and 37 are provided to prevent the molten solder from flowing out during reflow, and the first external electrode 23 and the second external electrode 25 are connected to each convex portion 31 by solder. Although it is possible to securely connect, the first external electrode 23 and the second external electrode 25 can be connected to each convex portion 31 with solder without providing either or both of the resist layers 34 and 37. It is possible to connect sufficiently. In addition, as shown in FIG. 5, the first external electrode 23, the second external electrode 25, and the like can be provided without providing the solder plating layer 36 on the inner surface of the tin plating layer 33 of the second external electrode 25. Can be sufficiently connected to each convex portion 31 by soldering. Furthermore, without providing the solder layer 33 and the solder plating layer 36, the first external electrode 23 and the second external electrode 25 may be connected to each convex portion 31 with a conductive adhesive or the like.

  In the multilayer piezoelectric element 1 configured as described above, between the first external electrode 23 formed on the first side surface 2a and the first external electrode 23 formed on the second side surface 2b. When a voltage is applied, a voltage is applied between the first internal electrode 11 and the second internal electrode 13. Thereby, in the piezoelectric bodies 3 and 5, an electric field is generated in a portion sandwiched between the first internal electrode 11 and the second internal electrode 13, and the portion is displaced as an active portion.

  Next, a method for manufacturing the multilayer piezoelectric element 1 according to the first embodiment will be described.

  First, a base paste is prepared by mixing a piezoelectric ceramic material mainly composed of lead zirconate titanate with an organic binder, an organic solvent, or the like, and each of the piezoelectric layers 3, 5, 7, 9 is prepared using the base paste. A green sheet is formed. In addition, an organic binder, an organic solvent, or the like is mixed with a metal material (for example, silver: palladium = 7: 3) made of silver and palladium in a predetermined ratio to produce a conductive paste for electrode pattern formation.

  Subsequently, an electrode pattern corresponding to the first internal electrode 11 is formed on the green sheet. Further, an electrode pattern corresponding to the second internal electrode 13 is formed on another green sheet. Each electrode pattern is formed by screen printing the above-described conductive paste.

  Subsequently, a green sheet on which an electrode pattern corresponding to the first internal electrode 11 is formed and a green sheet on which an electrode pattern corresponding to the second internal electrode 13 is formed are alternately stacked. A green sheet in which no is formed is laminated on the outermost layer to produce a laminate green. Here, the number of stacked green sheets is about 350 layers.

  Subsequently, while the laminate green is heated at a predetermined temperature (eg, about 60 ° C.) and pressed in the stacking direction at a predetermined pressure (eg, about 100 MPa), the laminate green is cut into a predetermined size. To do. The laminate green is cut by, for example, a diamond blade. As a result, the first internal electrode 11 is exposed to the first side surface 2a, and the second internal electrode 13 is exposed to the second side surface 2b.

  Subsequently, the laminate green is degreased (that is, debindered) at a predetermined temperature (for example, about 400 ° C.), and then fired at a predetermined temperature (for example, about 1100 ° C.) for a predetermined time (for example, about 2 hours). Thus, the laminate 2 is obtained.

  Subsequently, a conductive paste mainly composed of silver is screen-printed on each of the side surfaces 2a and 2b of the laminate 2, and then baked at a predetermined temperature (for example, about 700 ° C.) to form the first external electrode 23. To do. Then, a solder layer 33 and a resist layer 34 are provided on the first external electrode 23. Note that a sputtering method, an electroless plating method, or the like may be applied to the formation of the first external electrode 23.

  Subsequently, a solder plating layer 36 and a resist layer 37 are provided on the prepared second external electrode 25. Then, the second external electrode 25 is soldered to the first external electrode 23 by reflowing in a state where the solder layer 33 and the solder plating layer 36 are abutted with each other in each convex portion 31 of the second external electrode 25.

  In this way, since the first external electrode 23 and the second external electrode 25 are connected to each convex portion 31, the connection area between the first external electrode 23 and the second external electrode 25 can be reduced. it can. In addition, since the first external electrode 23 and the second external electrode 25 can be soldered by reflow, the second external electrode 25 is pressed against the first external electrode 23 with a large pressure during soldering. There is no need, and productivity can be improved.

  Finally, 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 performed, and the laminated piezoelectric element 1 is obtained.

  As described above, in the multilayer piezoelectric element 1 according to the first embodiment, the second external electrode 25 extends in a wave shape along the stacking direction, and the first convex portion 31 has the first convex portion 31. The external electrode 23 is electrically and physically connected. As a result, the second external electrode 25 has elasticity in the stacking direction, so that the entire external electrode extends in the stacking direction of the stack in the stacking direction of the stack 2. Inhibition of the displacement can be suppressed, and even when the piezoelectric element 1 is used for a long period of time, the disconnection of the second external electrode 25 can be suppressed.

  And even if the 1st external electrode 23 formed in each side surface 2a, 2b of the laminated body 2 is disconnected, the 2nd external electrode 25 goes through several convex part 31 to the 1st external electrode 23. Are electrically and physically connected. Therefore, a conduction path to the first internal electrode 11 and a conduction path to the second internal electrode 13 can be secured, and the function as the piezoelectric element 1 can be maintained.

  In the multilayer piezoelectric element 1 according to the first embodiment, a very simple member such as a flat plate extending in a wave shape along the stacking direction is employed for the second external electrode 25. Therefore, the configuration of the piezoelectric element 1 can be simplified as compared with the case where a specially shaped member such as a mesh member or a coiled elastic member is used for the external electrode.

  In addition, the second external electrode 25 is electrically and physically connected to the first external electrode 23 at a plurality of convex portions 31 protruding toward the first external electrode 23 such that the tip 31a is positioned on substantially the same plane. It is connected to the. Therefore, the gap between the first external electrode 23 and the second external electrode 25 can be easily kept constant, and the connection between the first external electrode 23 and the second external electrode 25 is ensured. It becomes possible.

  Further, the second external electrode 25 is electrically and physically connected to the first external electrode 23 by solder at each convex portion 31. Therefore, the connection between the first external electrode 23 and the second external electrode 25 can be facilitated during the manufacture of the piezoelectric element 1.

  In the multilayer piezoelectric element 1 according to the first embodiment described above, the protrusions 31 are arranged in a staggered manner on each first portion 25a of the second external electrode 25, but are shown in FIG. As described above, the convex portion 31 may be linearly arranged in the central portion between the first portions 25a adjacent to each other in the second external electrode 25 (that is, the central portion of each second portion 25b).

[Second Embodiment]
In the multilayer piezoelectric element 1 according to the second embodiment, a part of the second external electrode 25 is extruded in that the convex part 31 is formed by bending a part of the second external electrode 25. This is different from the multilayer piezoelectric element 1 according to the first embodiment in which the convex portion 31 is formed. Hereinafter, the multilayer piezoelectric element 1 according to the second embodiment will be described focusing on the differences.

  As shown in FIGS. 7 and 8, the second external electrode 25 includes a metal plate 32 and a tin plating layer 33 provided on the inner surface and the outer surface of the metal plate 32 and is configured in a flat plate shape. Has been. The convex portion 31 is formed by bending a part of the first portion 25a of the second external electrode 25 to the first external electrode 23 side, and the tip 31a of each convex portion 31 is substantially the same. Located on a plane.

  On the outer surface of the first external electrode 23, a solder layer 33 is provided in a portion facing the convex portion 31 of the second external electrode 25, and a resist layer 34 is provided in a portion excluding the solder layer 33. ing. On the other hand, in the second external electrode 25, a resist layer 37 is provided on the inner surface of the inner tin plating layer 33 and the outer surface of the outer tin plating layer 33 except for the convex portions 31.

  The first external electrode 23 and the second external electrode 25 are reflowed in a state where the solder layer 33 and the tip 31a of the convex portion 31 are abutted with each other on each convex portion 31 of the second external electrode 25. It is soldered by. As a result, the second external electrode 25 is electrically and physically connected to the first external electrode 23 by soldering at each convex portion 31.

  The resist layers 34 and 37 are provided to prevent the molten solder from flowing out during reflow, and the first external electrode 23 and the second external electrode 25 are connected to each convex portion 31 by solder. Although it is possible to securely connect, the first external electrode 23 and the second external electrode 25 can be connected to each convex portion 31 with solder without providing either or both of the resist layers 34 and 37. It is possible to connect sufficiently. Further, without providing the solder layer 33, the first external electrode 23 and the second external electrode 25 may be connected to each convex portion 31 by a conductive adhesive or the like.

  According to the multilayer piezoelectric element 1 according to the second embodiment configured as described above, similarly to the multilayer piezoelectric element 1 according to the first embodiment described above, inhibition of displacement of the multilayer body 2 and external The occurrence of disconnection of the electrode 21 can be suppressed with a simple configuration, and the connection between the first external electrode 23 and the second external electrode 25 can be ensured.

  The present invention is not limited to the first and second embodiments described above.

  For example, the shape of the laminated body 2 is not limited to a polygonal column shape, and may be a cylindrical shape. And the side surface in which the external electrode 21 is provided in the laminated body 2 is not limited to two side surfaces positioned so as to face each other, but may be two adjacent side surfaces. In addition, when the laminated body 2 is cylindrical, the external electrode 21 is provided in the arbitrary area | region of a side surface, if it is a position which does not contact mutually.

  Further, the second external electrode 25 is not limited to a rectangular wave extending along the laminating direction, and may be a triangular wave extending along the laminating direction as shown in FIG. Alternatively, as shown in FIG. 10, it may extend sinusoidally along the stacking direction.

  Further, the first internal electrode 11 may be exposed on the second side surface 2b as long as it is electrically insulated from the external electrode 21 provided on the second side surface 2b. Similarly, the second internal electrode 13 may be exposed to the first side surface 2a as long as it is electrically insulated from the external electrode 21 provided on the first side surface 2a.

1 is a perspective view of a multilayer piezoelectric element according to a first embodiment. It is a schematic diagram for demonstrating the cross-sectional structure of the lamination type piezoelectric element shown by FIG. It is a front view of the external electrode of the multilayer piezoelectric element shown in FIG. FIG. 4 is a partial cross-sectional view taken along the line IV-IV shown in FIG. 3. It is a fragmentary sectional view showing one modification of an external electrode. It is a front view which shows one modification of an external electrode. It is a front view of the external electrode of the multilayer piezoelectric element according to the second embodiment. FIG. 8 is a partial cross-sectional view taken along the line VIII-VIII shown in FIG. 7. It is a front view which shows one modification of an external electrode. It is a front view which shows one modification of an external electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer piezoelectric element, 2 ... Laminated body, 2a ... 1st side surface, 2b ... 2nd side surface, 3,5 ... Piezoelectric body, 11 ... 1st internal electrode, 13 ... 2nd internal electrode, 23 DESCRIPTION OF SYMBOLS 1st external electrode 25 ... 2nd external electrode 31 ... Convex part 31a ... Tip, 33 ... Solder layer, 36 ... Solder plating layer

Claims (4)

A laminate in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated;
A first external electrode provided on a side surface of the laminate and electrically connected to the predetermined internal electrode;
A second external electrode provided outside the first external electrode and extending along the stacking direction of the stacked body,
The second external electrode is wavy when viewed from a direction orthogonal to the side surface, and is flat when viewed from a direction orthogonal to the direction orthogonal to the side surface,
The second external electrode has a plurality of protrusions protruding toward the first external electrode, and the protrusions are electrically and physically connected to the first external electrode by solder. And
A portion of the outer surface of the first external electrode excluding the portion facing the convex portion is provided with a first resist layer so as to separate each of the portions, and the inner side of the second external electrode. A laminated piezoelectric element characterized in that a second resist layer is provided on a portion of the surface excluding a portion where the convex portion is formed so as to separate each of the portions .   The multilayer piezoelectric element according to claim 1, wherein the convex portion is formed by pushing out a part of the second external electrode toward the first external electrode.   2. The multilayer piezoelectric element according to claim 1, wherein the convex portion is formed by bending a part of the second external electrode toward the first external electrode.   4. The multilayer piezoelectric element according to claim 1, wherein the tips of the convex portions are positioned on substantially the same plane.

Images