JP2013012656A - Piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element that prevents damage to displacement portions while suppressing an increase in power consumption.SOLUTION: A laminated piezoelectric element includes a laminate that has: a basal portion formed of a piezoelectric layer 30; and displacement portions 50, each having first internal electrodes 31 and second internal electrodes 32 alternately laminated with piezoelectric layers 30 interposed therebetween and each extending from the basal portion in a lamination direction of the first internal electrodes 31 and the second internal electrodes 32. As seen from the lamination direction, each of the displacement portions 50 has an approximately rectangular shape, and has a length, along a first direction perpendicular to the lamination direction, that is longer than a length along a second direction perpendicular to the first direction. As seen from the first direction, each displacement portion 50 has a width, on the side of the basal portion, that is greater than a width on the side of a leading end.

Description

  The present invention relates to a piezoelectric element.

  As a conventional multilayer piezoelectric element, for example, one described in Patent Document 1 is known. The multilayer piezoelectric element described in Patent Document 1 has a driving unit in which piezoelectric layers and first and second driving internal electrodes are alternately stacked, and a piezoelectric layer and connecting internal electrodes are stacked. A laminated body having a connection portion; a driving external electrode formed on one side of the laminated body and electrically connected to the first driving internal electrode; and a connecting internal electrode formed on one side of the laminated body; An external electrode for connection that conducts, and a common external electrode that is formed on the other side surface of the laminate and is electrically connected to each of the second drive internal electrode and the connection internal electrode. In the drive part, a displacement part (actuator part) is constituted by a slit formed along the lamination direction of the piezoelectric layers from the upper surface side to the lower surface side of the laminated body.

JP 2003-37307 A

  By the way, the displacement part has a width of about several tens of μm. For this reason, when the displacement portion is formed or when the piezoelectric element is handled, the displacement portion may be bent from the proximal end side. In particular, the displacement portion is easily broken at the joint portion between the piezoelectric layer and the internal electrode on the base end side. Regarding this problem, if the displacement portion is formed wide to prevent the displacement portion from being broken, the capacitance increases in accordance with the increase in the facing area of the internal electrodes. As a result, there is a problem that current increases and power consumption increases.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a piezoelectric element that can prevent the displacement portion from being damaged while suppressing an increase in power consumption.

  In order to solve the above problems, a piezoelectric element according to the present invention is configured by alternately laminating a base portion constituted by a piezoelectric layer and first and second internal electrodes with the piezoelectric layer interposed therebetween. And a piezoelectric element comprising a laminate having a displacement portion extending from the base in the lamination direction of the first internal electrode and the second internal electrode, wherein the displacement portion has a substantially rectangular shape when viewed from the lamination direction, The length in the first direction orthogonal to the first direction is longer than the length in the second direction orthogonal to the first direction, and the width on the base side is wider than the width on the tip side when viewed from the first direction. It is characterized by that.

  In this piezoelectric element, the width on the base side of the displacement portion is wider than the width on the tip side. That is, the width of the base end portion of the displacement portion is formed wider than the width of the distal end portion. Therefore, since the strength of the proximal end portion side of the mutated portion that is easily broken is ensured, the displacement portion can be prevented from being damaged. In addition, since the width of the tip of the displacement portion is narrow, the increase in the facing area of the internal electrodes can be suppressed compared to the case where the width of the displacement portion is broadened and the strength is ensured. Increase in capacity can be suppressed. As a result, an increase in current can be suppressed, and an increase in power consumption can be suppressed.

  It is preferable that the first internal electrode and the second internal electrode have substantially the same width when viewed from the first direction. Since the first and second internal electrodes and the piezoelectric layer are made of different materials, the bonding strength between the first and second internal electrodes and the piezoelectric layer is lower than the bonding strength between the piezoelectric layers. Therefore, the joint between the first and second internal electrodes and the piezoelectric layer is easily broken. Therefore, by making the widths of the first internal electrode and the second internal electrode substantially the same, the bonding area between the piezoelectric layers increases toward the base side in the displacement portion. Therefore, since the joining strength on the base end side of the easily displaced breakable portion can be ensured, breakage of the displaced portion can be further suppressed.

  Preferably, the first internal electrode and the second internal electrode have a first portion that overlaps in the stacking direction and a second portion that does not overlap in the stacking direction, and an opening is formed in the second portion. . According to such a configuration, in the second portion of the first and second internal electrodes, the bonding area (contact area) between the piezoelectric layers facing each other with the first internal electrode or the second internal electrode interposed therebetween is increased. Can do. Therefore, the bonding strength at the displacement portion can be further ensured, and damage to the displacement portion can be further suppressed. In addition, since the opening is formed in the inactive portion where the first internal electrode and the second internal electrode do not overlap, the strength of the displacement portion can be ensured without affecting the displacement characteristics of the displacement portion.

  According to the present invention, it is possible to prevent the displacement portion from being damaged while suppressing an increase in power consumption.

1 is a perspective view showing a multilayer piezoelectric element according to a first embodiment. It is the perspective view which looked at the lamination type piezoelectric element shown in Drawing 1 from the lower part. (A) is the sectional view on the aa line in FIG. 1, (b) is the sectional view on the bb line in FIG. It is a perspective view which expands and shows a displacement part. It is the front view which looked at FIG. 4 from the front. It is a perspective view which shows the lamination type piezoelectric element which concerns on 2nd Embodiment. It is a perspective view which shows the lamination type piezoelectric element which concerns on 3rd Embodiment. It is a figure which shows the structure of the internal electrode arrange | positioned at the displacement part shown in FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

[First Embodiment]
FIG. 1 is a perspective view showing the multilayer piezoelectric element according to the first embodiment. FIG. 2 is a perspective view of the multilayer piezoelectric element shown in FIG. 1 as viewed from below. 3A is a cross-sectional view taken along the line aa in FIG. 1, and FIG. 3B is a cross-sectional view taken along the line bb in FIG.

  As shown in each drawing, the multilayer piezoelectric element 1 includes a multilayer body 2, a first external electrode 3, a second external electrode 4, third external electrodes 5 a and 5 b, and a fourth external electrode 6. ing. The multilayer piezoelectric element 1 has a length set to about 36.95 mm to 37.05 mm, a width set to about 1.85 mm to 1.95 mm, and a thickness set to about 0.95 mm to 1.05 mm, for example. Has been.

  The laminated body 2 extends so as to connect the pair of first and second end faces 2a, 2b facing the longitudinal direction of the laminated body 2 and the pair of first and second end faces 2a, 2b. A pair of first and second main surfaces 2c, 2d facing each other in the stacking direction of the piezoelectric layer 30 (described later) and the pair of first and second main surfaces 2c, 2d extend so as to connect to each other and face each other. It has a pair of first and second side surfaces 2e, 2f. In FIG. 1, the opposing direction of the pair of first and second end faces 2a, 2b is the X direction, the opposing direction of the pair of first and second side faces 2e, 2f is the Y direction, and the pair of first and second main faces 2c. , 2d is the Z direction.

  The stacked body 2 includes a first portion 20, a second portion 21a, and a third portion 21b. The first portion 20 is a portion including a piezoelectrically active active portion (active region), and is positioned between the first and second end faces 2 a and 2 b in the stacked body 2. Specifically, the first portion 20 is located at the central portion of the stacked body 2.

As shown in FIGS. 4 and 5, a displacement portion 50 is formed in the first portion 20. The displacement part 50 extends from the base part 51 configured by the piezoelectric layer 30 (is erected on the base part 51). The displacement part 50 and the base part 51 are integrally formed. In the displacement portion 50, the first internal electrodes 31 and the second internal electrodes 32 are alternately stacked with the piezoelectric layers 30 interposed therebetween. That is, the displacement part 50 extends from the base part 51 in the stacking direction of the first internal electrode 31 and the second internal electrode 32 (hereinafter simply referred to as the stacking direction). Each piezoelectric layer 30 is made of, for example, a piezoelectric ceramic material mainly composed of lead zirconate titanate (PZT: Pb (Zr _x , Ti _1-x ) O ₃ ). In the actual multilayer piezoelectric element 1, the piezoelectric layers 30 are integrated so as not to be visually recognized. In the present embodiment, the thickness of each piezoelectric layer 30 is about 10 μm to 50 μm.

  A plurality of (in this case, eight) displacement parts 50 are arranged in the X direction, and are spaced apart at a predetermined interval. The displacement part 50 has a rectangular shape when viewed from the stacking direction (Z direction), and the length of the first direction (Y direction) orthogonal to the stacking direction is the second direction orthogonal to the first direction. It is longer than the length in the (X direction).

  The displacement part 50 is exhibiting substantially trapezoid shape seeing from the 1st direction (1st side surface 2e side). Specifically, the displacement part 50 has a width D1 on the base end side (base 51 side) wider than a width D2 on the tip end side when viewed from the first direction. In other words, the width D2 on the distal end side of the displacement portion 50 is narrower than the width D1 on the proximal end side. That is, the width of the displacement portion 50 becomes narrower toward the tip. The side surface of the displacement part 50 is a flat inclined surface. As shown in FIG. 4, in the displacement part 50, the 1st internal electrode 31 and the 2nd internal electrode 32 are exposed to the side surface.

  A plurality of (here, nine) slits S formed at equal intervals are formed between adjacent displacement portions 50. The slit S is formed to open to the first main surface 2c side and extend in the Y direction. The slit S is formed in a substantially trapezoidal shape, and its width is narrowed from the first main surface 2c side toward the second main surface 2d side.

  A plurality (six layers in this case) of the first internal electrodes 31 are arranged at a predetermined interval in the stacking direction. One end of the first internal electrode 31 is drawn out to the first side surface 2e, and is exposed to the first side surface 2e. A plurality of (in this case, seven layers) second internal electrodes 32 are arranged at predetermined intervals in the stacking direction. One end of the second internal electrode 32 is drawn out to the second side face 2f and is exposed to the second side face 2f. The first internal electrode 31 and the second internal electrode 32 are made of a conductive material mainly composed of silver (Ag) and palladium (Pd). In the present embodiment, the thickness of the first internal electrode 31 and the second internal electrode 32 is about 0.5 μm to 3 μm. Note that Cu (copper) can also be used as the conductive material.

  The first internal electrodes 31 and the second internal electrodes 32 are alternately arranged along the facing direction of the piezoelectric layers 30 so as to face each other with the piezoelectric layers 30 interposed therebetween. The second internal electrode 32 is located on the first main surface 2c side and the second main surface 2d side when viewed in the stacking direction.

  The second portion 21a and the third portion 21b are portions including a piezoelectrically inactive portion (inactive region), and are located on the first end surface 2a side and the second end surface 2b side of the laminate 2, respectively. ing. That is, the second portion 21a and the third portion 21b are provided so as to sandwich the first portion 20 in the longitudinal direction of the stacked body 2 (the opposing direction of the first and second end faces 2a and 2b). In the second portion 21a and the third portion 21b, a plurality of piezoelectric layers 30 and third internal electrodes 33 are alternately stacked. The second portion 21a and the third portion 21b have the same configuration.

  A plurality of (in this case, nine) third internal electrodes 33 are arranged at predetermined intervals in the stacking direction of the piezoelectric layers 30. One end of the third internal electrode 33 is drawn out to the first side face 2e, and the other end is drawn out to the second side face 2f, and is exposed to the first side face 2e and the second side face 2f. The third internal electrode 33 is physically and electrically insulated from the first internal electrode 31 and the second internal electrode 32. The third internal electrode 33 is a connection electrode that connects the second external electrode 4 and the third external electrodes 5a and 5b. The third internal electrode 33 is made of a conductive material containing silver (Ag) and palladium (Pd) as main components. In the present embodiment, the thickness of the third internal electrode 33 is about 0.5 μm to 3 μm.

  The first external electrode 3 is provided on the first side surface 2e. The first external electrode 3 is formed at a position corresponding to the first portion 20 on the first side surface 2 e and is physically and electrically connected to one end of the first internal electrode 31. Each of the first external electrodes 3 is physically and electrically independent from each other. The first external electrode 3 is made of a three-layer metal film of Cr, Cu / Ni, and Au. The thickness of the first external electrode 3 is about 0.3 μm to 5.0 μm. The configuration of this external electrode is the same for the second to fourth external electrodes 4 to 6. Instead of the Au metal film, Ag, Ag-Pd, or Ag-Sn can be used.

  The second external electrode 4 is provided on the second side surface 2f. The second external electrode 4 is formed over the entire second side surface 2 f and is physically and electrically connected to one end of the second internal electrode 32 and the third internal electrode 33. The second external electrode 4 is a common external electrode connected to both the second internal electrode 32 and the third internal electrode 33. The second external electrode 4 has a shape corresponding to the shape of the displacement portion 50, and has irregularities at a position corresponding to the displacement portion 50.

  The third external electrodes 5a and 5b are provided on the first side surface 2e. The third external electrodes 5a and 5b are formed at positions corresponding to the second portion 21a and the third portion 21b on the first side surface 2e, that is, at both ends in the longitudinal direction of the first side surface 2e. Is physically and electrically connected to one end of the. The third external electrodes 5a and 5b and the first external electrode 3 are electrically insulated from each other on the first side surface 2e.

  The fourth external electrode 6 is provided on the second main surface 2d. The fourth external electrode 6 is formed over the entire surface of the second main surface 2d, and is physically and electrically connected to the second external electrode 4 and the third external electrodes 5a and 5b. That is, the fourth external electrode 6 electrically connects the second external electrode 4 and the third external electrodes 5a and 5b. The fourth external electrode 6 is electrically insulated from the first external electrode 3. The fourth external electrode 6 is a connection electrode that connects the second external electrode 4 and the third external electrodes 5a and 5b. The fourth external electrode 6 serves as a connection surface when connected to a substrate (support) or the like with a conductive adhesive.

  Grooves 34 and 35 are formed between the first external electrode 3 and the third external electrodes 5a and 5b, respectively. That is, the grooves 34 and 35 are formed at the boundary between the first portion 20, the second portion 21a, and the third portion 21b. The grooves 34 and 35 are formed along the stacking direction on the first side surface 2 e of the stacked body 2. By the grooves 34 and 35, the first external electrode 3 and the third external electrodes 5a and 5b are physically and electrically insulated.

  In the first portion 20 of the stacked body 2, a notch 36 is provided at a corner portion between the side surface 2 e and the main surface 2 d. The notch 36 is formed along the longitudinal direction of the laminate 2 at the corner between the side surface 2e and the main surface 2d, and is provided between the groove 34 and the groove 35. The notch 36 is an inclined surface that is inclined with respect to the side surface 2e and the main surface 2d. The first external electrode 3 and the fourth external electrode 6 are physically and electrically insulated by the notch 36.

  In the multilayer piezoelectric element 1, when a voltage is applied between the first external electrode 3 and the second external electrode 4, a voltage is also applied between the first internal electrode 31 and the second internal electrode 32. In the displacement portion 50 (first portion 20), an electric field is generated in a region between the first internal electrode 31 and the second internal electrode 32 in the piezoelectric layer 30, and the region is displaced. At this time, in the second portion 21 a and the third portion 21 b, no electric field is generated between the third internal electrodes 33 in the piezoelectric layer 30, so that no displacement occurs.

  Then, the manufacturing method of the multilayer piezoelectric element 1 which has the above-mentioned structure is demonstrated.

  First, a base paste is prepared by mixing an organic binder, an organic solvent, or the like with a piezoelectric ceramic material mainly composed of lead zirconate titanate, and a green sheet to be the piezoelectric layer 30 is formed using the base paste using a doctor blade method. Molded by Moreover, an organic binder, an organic solvent, etc. are mixed with the metal material which consists of silver and palladium of a predetermined ratio, and the electrically conductive paste for electrode pattern formation is produced.

  Next, each of the electrode patterns corresponding to the first to third internal electrodes 31 to 33 is formed on the green sheet by screen printing using a conductive paste. A green sheet on which electrode patterns corresponding to the first internal electrode 31 and the third internal electrode 33 are formed, a green sheet on which electrode patterns corresponding to the second internal electrode 32 and the third internal electrode 33 are formed, and piezoelectric A green sheet to be the body layer 30 is laminated to produce a laminate green.

  Subsequently, the laminate green is pressed at a predetermined pressure in the stacking direction while being heated at a predetermined temperature (for example, about 60 ° C.), and then the stacked green is cut into a predetermined size. The laminate green is degreased 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 to obtain the stack 2.

  Subsequently, three layers of metal films of Cr, Cu / Ni, and Au are formed in this order on the surfaces corresponding to the side surfaces 2e and 2f and the main surface 2d of the multilayer body 2 to form external electrodes. Then, by forming grooves 34 and 35 along the stacking direction on the surface corresponding to the side surface 2e in the multilayer body 2, the external electrodes are divided to form the first external electrode 3 and the third external electrodes 5a and 5b. . In addition, by forming a notch 36 at the corner between the side surface 2e and the main surface 2d of the laminate 2, the external electrode is divided to form the first external electrode 3 and the fourth external electrode 6.

  Subsequently, the slit S is formed in the first portion 20 by, for example, a dicing blade. At this time, the slit S is formed so that the width D1 on the proximal end side of the displacement portion 50 is wider than the width D2 on the distal end side. That is, the slit S whose width becomes narrower (tapered) is formed from the first main surface 2c side toward the second main surface 2d. Thereby, the displacement part 50 is comprised in the 1st part 20. As shown in FIG. Thus, the multilayer piezoelectric element 1 is obtained.

  As described above, in the multilayer piezoelectric element 1, the width D1 on the proximal end side of the displacement portion 50 is wider than the width D2 on the distal end side. Therefore, since the strength at the base end side that is easy to break is secured, the displacement portion 50 can be prevented from being damaged. In addition, since the width D2 on the distal end side of the displacement portion 50 is formed narrow, an increase in capacitance can be suppressed as compared with a case where the width of the displacement portion 50 is increased as a whole. As a result, an increase in current can be suppressed, and an increase in power consumption can be suppressed.

[Second Embodiment]
Next, the second embodiment will be described. FIG. 6 is a perspective view showing a displacement portion of the multilayer piezoelectric element according to the second embodiment. As shown in FIG. 6, the displacement portion 50A formed in the first portion 20 is different from the first embodiment in the configuration of the first internal electrode 31A and the second internal electrode 32A.

  The first internal electrode 31A has substantially the same width when viewed from the first direction of the displacement portion 50A. That is, both end portions of the first internal electrode 31A are aligned on a substantially straight line in the stacking direction. The second internal electrode 32A has substantially the same width when viewed from the first direction of the displacement portion 50A. That is, both end portions of the second internal electrode 32A are aligned on a substantially straight line in the stacking direction. In addition, the substantially same thing said here may have the width | variety of 1st internal electrode 31A and 2nd internal electrode 32A, for example, and there may be a dimensional difference of about 0.01-0.1 micrometer, for example.

  Here, since the first internal electrode 31A and the second internal electrode 32A and the piezoelectric layer 30 are made of different materials, the bonding strength between the first internal electrode 31A and the second internal electrode 32A and the piezoelectric layer 30 is piezoelectric. The bonding strength between the body layers 30 is low. Therefore, by making the widths of the first internal electrode 31A and the second internal electrode 32A substantially the same, in the displacement portion 50A, the bonding area between the piezoelectric layers 30 increases toward the base end side. Therefore, in the displacement part 50A, the joining strength on the base end part side can be ensured, and damage can be prevented.

[Third Embodiment]
Subsequently, the third embodiment will be described. FIG. 7 is a perspective view showing a displacement portion of the multilayer piezoelectric element according to the third embodiment. FIG. 8 is a diagram showing the configuration of the internal electrodes arranged in the displacement portion shown in FIG. As shown in FIGS. 7 and 8, the displacement portion 50B formed in the first portion 20 is different from the first embodiment in the configuration of the first internal electrode 31B and the second internal electrode 32B.

  The first internal electrode 31B and the second internal electrode 32B have a first portion P that overlaps in the stacking direction and a second portion Q that does not overlap in the stacking direction. In FIG. 7, the part corresponding to the 1st part P and the 2nd part Q in the displacement part 50B is shown. An opening K is formed in the second portion Q of the first internal electrode 31B, that is, the end 31Ba on the first side face 2e side. A plurality of (here, five) openings K are formed along the width direction of the first internal electrode 31B.

  An opening K is formed in the second portion Q of the second internal electrode 32B, that is, the end portion 32Ba on the second side surface 2f side. A plurality of (here, five) openings K are formed along the width direction of the second internal electrode 32B.

  In the displacement part 50B, since the opening K is formed in the second part of the first internal electrode 31B and the second internal electrode 32B, the piezoelectric layers facing each other with the first internal electrode 31B and the second internal electrode 32B interposed therebetween. 30 are joined at the opening K. Since the first internal electrode 31B, the second internal electrode 32B, and the piezoelectric layer 30 are made of different materials, the bonding strength of the first internal electrode 31B, the second internal electrode 32B, and the piezoelectric layer 30 is the piezoelectric layer 30. It is weak compared to the bonding strength between them.

  Therefore, by forming the opening K at the ends of the first internal electrode 31B and the second internal electrode 32B, the piezoelectric layers 30 can be bonded to each other through the opening K. Thereby, the joint strength can be further ensured at both ends of the displacement portion 50B in the first direction, and the strength of the displacement portion 50B (first portion 20) can be improved. Therefore, for example, when the slit S is formed by a dicing blade, it is possible to prevent the displacement portion 50B from being damaged due to the entrance of the dicing blade.

  The opening K is formed in the second portion Q of the first internal electrode 31B and the second internal electrode 32B where the first internal electrode 31B and the second internal electrode 32B do not overlap. That is, the opening K is formed in an inactive portion that is piezoelectrically inactive. Therefore, the strength of the displacement portion 50B can be ensured without affecting the displacement characteristics of the displacement portion 50B.

  The present invention is not limited to the above embodiment. For example, in the said embodiment, although the laminated body 2 is set as the structure containing the 1st part 20, the 2nd part 21a, and the 3rd part 21b, the structure of the laminated body 2 is not limited to this.

  Moreover, in the said embodiment, although the 4th external electrode 6 which connects the 2nd external electrode 4 and the 3rd external electrodes 5a and 5b is formed in the 2nd main surface 2d of the laminated body 2, The electrode 6 may not be provided. That is, the connection between the second external electrode 4 and the third external electrodes 5a and 5b may be only the third internal electrode 33.

  DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element, 2 ... Laminated body, 30 ... Piezoelectric layer, 31, 31A, 31B ... 1st internal electrode, 32, 32A, 32B ... 2nd internal electrode, 50, 50A, 50B ... Displacement part, 51 ... base, D1 ... base end side width, D2 ... tip end side width, K ... opening, P ... first part, Q ... second part.

Claims (3)

A base portion configured by a piezoelectric layer, and first internal electrodes and second internal electrodes are alternately stacked with the piezoelectric layer interposed therebetween, and the first internal electrode and the second internal electrode are formed from the base portion. A piezoelectric element comprising a laminate having a displacement portion extending in the lamination direction of
The displacement part is
Presenting a substantially rectangular shape when viewed from the stacking direction, the length of the first direction orthogonal to the stacking direction is longer than the length of the second direction orthogonal to the first direction,
The piezoelectric element, wherein the width on the base side is wider than the width on the tip side when viewed from the first direction.   2. The piezoelectric element according to claim 1, wherein the first internal electrode and the second internal electrode have substantially the same width as viewed from the first direction. The first internal electrode and the second internal electrode have a first portion that overlaps in the stacking direction and a second portion that does not overlap in the stacking direction,
The piezoelectric element according to claim 1, wherein an opening is formed in the second portion.

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