Piezoelectric element

Abstract

To provide a piezoelectric element with improved connection reliability.SOLUTION: In a piezoelectric element 10, third regions 62C, 63C, 64C are adjacent to first regions 62A, 63A, 64A and second regions 62B, 63B, 64B, and do not overlap with any of the first regions 62A, 63A, 64A and the second regions 62B, 63B, 64B viewed from the third direction D3. That is, in the piezoelectric element 10, protrusions are smoothed out to be nearly flat by the third regions 62C, 63C, and 64C, thereby achieving high connection reliability.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a piezoelectric element.

Background Art

[0002] Conventionally, a piezoelectric element having a driving portion in which a piezoelectric body is interposed between a pair of conductor layers is known. In such a piezoelectric element, the driving portion is displaced (for example, extended in a predetermined direction) by applying a voltage between the pair of conductor layers. The piezoelectric element disclosed in Patent Document 1 below has a piezoelectric body having a laminated structure in which a plurality of piezoelectric body layers provided with internal electrodes are laminated, and adjacent internal electrodes in the lamination direction are connected via a plurality of via conductors (via conductor group) located in the same layer, and the via conductors of adjacent via conductor groups in the lamination direction do not overlap when viewed from the lamination direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors have conducted repeated research on the connection reliability of via conductors and newly found a technique capable of improving the connection reliability.

[0005] One aspect of the present invention aims to provide a piezoelectric element with improved connection reliability.

Means for Solving the Problems

[0006] A piezoelectric element according to one aspect of the present invention comprises a body made of a piezoelectric material and a plurality of internal conductor layers provided within the body and stacked in a first direction, and includes a driving region where portions of internal conductor layers with different polarities overlap when viewed from the first direction, and a plurality of connection regions where portions of internal conductor layers with the same polarity overlap and are connected via a plurality of via conductors extending along the first direction, wherein adjacent via conductors in the first direction do not overlap when viewed from the first direction, and the plurality of via conductors are contained within the connection region. The system includes a first group of via conductors located within a region, a second group of via conductors located within a second region which is in a different layer from the first group of via conductors and is contained within the connection region, and a third group of via conductors located within a third region which is in a different layer from the first and second groups of via conductors and is contained within the connection region. Viewed from a first direction, the first and second regions overlap in at least part, and the third region is adjacent to the first and second regions. In the first direction, different groups of via conductors from the first, second, and third groups of via conductors are adjacent to each other.

[0007] The inventors have found that bulges may occur around each via conductor in the first region where the first via conductor group is located, the second region where the second via conductor group is located, and the third region where the third via conductor group is located. Even when such bulges occur, it is necessary to maintain sufficient connection reliability between the internal conductor layers. In particular, larger bulges may occur when the first region and the second region overlap when viewed from the first direction. In the piezoelectric element described above, when viewed from the first direction, the third region where the third via conductor group is located is adjacent to the first region where the first via conductor group is located and the second region where the second via conductor group is located, and does not overlap with either the first or second region. That is, in the piezoelectric element described above, the bulges are smoothed out by the third region, thereby improving connection reliability.

[0008] In the piezoelectric element relating to the other side, in the first direction, the first via conductor group and the second via conductor group are arranged alternately via the third via conductor group.

[0009] In piezoelectric elements relating to other aspects, the third region where the third group of via conductors is located is divided into multiple regions when viewed from the first direction.

[0010] In piezoelectric elements relating to other aspects, when viewed from the first direction, multiple third regions sandwich the first and second regions.

[0011] In piezoelectric elements relating to other aspects, when viewed from the first direction, all of the multiple via conductors within each connection region are located at the intersections of the grid. [Effects of the Invention]

[0012] According to various aspects of the present invention, a piezoelectric element with improved connection reliability is provided. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic perspective view showing a piezoelectric element according to one embodiment. [Figure 2] Figure 2 is a plan view of the piezoelectric element shown in Figure 1. [Figure 3] Figure 3 is an exploded perspective view of the piezoelectric element shown in Figure 1. [Figure 4] Figure 4 is a cross-sectional view of the piezoelectric element shown in Figure 1, taken along line IV-IV. [Figure 5] Figure 5 shows (a) the arrangement of the first via conductor, (b) the arrangement of the second via conductor, and (c) the arrangement of the third via conductor. [Figure 6] Figure 6 shows the positional relationship between the first to third regions in the connection region. [Figure 7] Figure 7 shows (a) the arrangement of the first via conductor, (b) the arrangement of the second via conductor, and (c) the arrangement of the third via conductor. [Figure 8] Figure 8 shows the positional relationship between the first to third regions in the connection region. [Figure 9] FIG. 9 is an enlarged view of the main part of FIG. 4.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0015] FIG. 1 is a perspective view showing a piezoelectric element 10 according to an embodiment, and FIG. 3 is a plan view of the piezoelectric element 10. As shown in FIGS. 1 and 2, the piezoelectric element 10 is of a bimorph type and includes a body 11 made of a piezoelectric material and a plurality of external electrodes 13, .......

[0016] The body 11 has a rectangular parallelepiped shape. The body 11 has a pair of main surfaces 11a and 11b facing each other, a pair of side surfaces 11c facing each other, and a pair of side surfaces 11e facing each other. The rectangular parallelepiped shape includes, for example, a rectangular parallelepiped shape with chamfered corners and ridge lines, and a rectangular parallelepiped shape with rounded corners and ridge lines. The direction in which the pair of side surfaces 11c face each other is the first direction D1. The first direction D1 is also a direction orthogonal to each side surface 11c. The direction in which the pair of side surfaces 11e face each other is the second direction D2. The second direction D2 is also a direction orthogonal to each side surface 11e. The direction in which the pair of main surfaces 11a and 11b face each other is the third direction D3 (the first direction). The third direction D3 is also a direction orthogonal to each main surface 11a and 11b.

[0017] Each of the main surfaces 11a and 11b has a pair of long sides and a pair of short sides. Each of the main surfaces 11a and 11b has a rectangular shape having a pair of long sides and a pair of short sides. That is, the piezoelectric element 10 (the element body 11) has a rectangular shape having a pair of long sides and a pair of short sides in a plan view. The rectangular shape includes, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. In the present embodiment, the long side direction of the main surfaces 11a and 11b coincides with the second direction D2. The short side direction of the main surfaces 11a and 11b coincides with the first direction D1.

[0018] The pair of side surfaces 11c extend in the third direction D3 so as to connect the pair of main surfaces 11a and 11b. The pair of side surfaces 11c also extend in the second direction D2. The pair of side surfaces 11e extend in the third direction D3 so as to connect the pair of main surfaces 11a and 11b. The pair of side surfaces 11e also extend in the first direction D1. The length of the element body 11 in the first direction D1 is, for example, 10 mm. The length of the element body 11 in the second direction D2 is, for example, 20 mm. The length of the element body 11 in the third direction D3 is, for example, 0.25 mm. Each of the main surfaces 11a and 11b and each of the side surfaces 11c and 11e may be indirectly adjacent to each other. In this case, a ridge line portion is located between each of the main surfaces 11a and 11b and each of the side surfaces 11c and 11e.

[0019] In the element body 11, as shown in FIGS. 3 and 4, a plurality of piezoelectric layers 16a, 17a to 17h, and 16b are laminated in this order in the third direction D3. The piezoelectric layer 16a constitutes the main surface 11a of the element body 11. The piezoelectric layer 16b constitutes the main surface 11b of the element body 11. The piezoelectric layers 17a to 17h are located between the piezoelectric layer 16a and the piezoelectric layer 16b. In the present embodiment, the thicknesses of the piezoelectric layers 16a, 16b, and 17a to 17h are the same. The "same" includes the range of manufacturing errors.

[0020] The piezoelectric layers 17a to 17h are composed of four pairs: a first piezoelectric layer pair 18A consisting of piezoelectric layer 17a and piezoelectric layer 17b, a second piezoelectric layer pair 18B consisting of piezoelectric layer 17c and piezoelectric layer 17d, a third piezoelectric layer pair 18C consisting of piezoelectric layer 17e and piezoelectric layer 17f, and a fourth piezoelectric layer pair 18D consisting of piezoelectric layer 17g and piezoelectric layer 17h. The polarization direction of the two piezoelectric layers constituting each piezoelectric layer pair 18A to 18D is the same. The polarization direction of the first piezoelectric layer pair 18A and the third piezoelectric layer pair 18C is opposite to the polarization direction of the second piezoelectric layer pair 18B and the fourth piezoelectric layer pair 18D. In other words, in the element 11, pairs of piezoelectric layers 18A, 18B, 18C, and 18D with opposite polarization directions are arranged alternately in the third direction D3.

[0021] Each piezoelectric layer 16a, 16b, and 17a-17h is made of a piezoelectric material. In this embodiment, each piezoelectric layer 16a, 16b, and 17a-17h is made of a piezoelectric ceramic material. Examples of piezoelectric ceramic materials include PZT[Pb(Zr,Ti)O3], PT(PbTiO3), PLZT[(Pb,La)(Zr,Ti)O3], or barium titanate (BaTiO3). Each piezoelectric layer 16a, 16b, and 17a-17h is made of, for example, a sintered body of a ceramic green sheet containing the piezoelectric ceramic material described above. In the actual body 11, each piezoelectric layer 16a, 16b, and 17a-17h are integrated to such an extent that the boundaries between the layers are not recognizable.

[0022] Each external electrode 13, 14 has a rectangular shape when viewed from a third direction D3. The rectangular shape includes, for example, shapes with chamfered corners and shapes with rounded corners. In this embodiment, the corners of the rectangular shape are rounded. The external electrode 15 has a square shape when viewed from a third direction D3. The square shape includes, for example, shapes with chamfered corners and shapes with rounded corners. In this embodiment, the corners of the square shape are rounded. Each external electrode 13, 14, 15 is made of a conductive material. For example, Ag, Pd, Pt, or Ag-Pd alloy can be used as the conductive material. Each external electrode 13, 14, 15 is constructed, for example, as a sintered body of a conductive paste containing the above conductive material.

[0023] As shown in Figures 3 and 4, the piezoelectric element 10 comprises a plurality of internal conductive layers 21 to 29 arranged within the base body 11. Each internal conductive layer 21 to 29 is made of a conductive material. Examples of conductive materials include Ag, Pd, Pt, or Ag-Pd alloy. Each internal conductive layer 21 to 29 is configured, for example, as a sintered body of a conductive paste containing the above conductive material.

[0024] Each internal conductor layer 21-29 is positioned (layer) at a different location in the third direction D3. The internal conductor layers 21-29 are spaced apart from each other in the third direction D3, and at least a portion of them face each other. Each internal conductor layer 21-29 is not exposed on the surface of the base body 11. That is, each internal conductor layer 21-29 is not exposed on the sides 11c and 11e. Each internal conductor layer 21-29 is spaced apart from all edges (four sides) of the main surfaces 11a and 11b when viewed from the third direction D3.

[0025] The internal conductor layer 21 is located between the piezoelectric layer 16a and the piezoelectric layer 17a. The internal conductor layer 21 has a configuration in which a drive unit 32 having a rectangular outer shape and connection units 33 and 34 having the same shape as the external electrodes 13 and 14 when viewed from the third direction D3 and positioned to completely overlap with the external electrodes 13 and 14 are arranged within the same layer. Both connection units 33 and 34 have a rectangular shape when viewed from the third direction D3. The rectangular shape includes, for example, shapes where each corner is chamfered and shapes where each corner is rounded. In this embodiment, each corner of the rectangular shape is rounded. The connection units 33 and 34 are located within an opening formed in the drive unit 32. The opening is formed at a position corresponding to the external electrodes 13 and 14 when viewed from the third direction D3, and the connection units 33 and 34 are located adjacent to each other within the same opening. That is, the connection units 33 and 34 are surrounded by the drive unit 32 when viewed from the third direction D3. The connecting parts 33 and 34 are spaced apart from the drive unit 32.

[0026] The internal conductor layer 22 is located between the piezoelectric layer 17a and the piezoelectric layer 17b. The internal conductor layer 22 has a configuration in which connection portions 33, 34, and 35 are arranged within the same layer, having the same shape as the external electrodes 13, 14, and 15 when viewed from the third direction D3, and positioned to completely overlap with the external electrodes 13, 14, and 15.

[0027] The internal conductor layer 23 is located between the piezoelectric layer 17b and the piezoelectric layer 17c. The internal conductor layer 23 has a configuration in which a drive unit 32 having a rectangular outer shape and connection units 33 and 35 having the same shape as the external electrodes 13 and 15 when viewed from the third direction D3 and positioned to completely overlap with the external electrodes 13 and 15 are arranged within the same layer. The connection unit 35 has a square shape when viewed from the third direction D3. The square shape includes, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. In this embodiment, each corner of the square shape is rounded. The connection units 33 and 35 are located within openings formed in the drive unit 32. Each opening is formed in a position corresponding to the external electrodes 13 and 15 when viewed from the third direction D3. That is, the connection units 33 and 35 are surrounded by the drive unit 32 when viewed from the third direction D3. The connection units 33 and 35 are spaced apart from the drive unit 32.

[0028] The internal conductor layer 24 is located between the piezoelectric layer 17c and the piezoelectric layer 17d. Similar to the internal conductor layer 22, the internal conductor layer 24 has a configuration in which connection portions 33, 34, and 35 are arranged within the same layer, having the same shape as the external electrodes 13, 14, and 15 when viewed from the third direction D3, and are positioned to completely overlap with the external electrodes 13, 14, and 15.

[0029] The internal conductor layer 25 is located between the piezoelectric layer 17d and the piezoelectric layer 17e. The internal conductor layer 25 has the same configuration as the internal conductor layer 21, and has a configuration in which a drive unit 32 having a rectangular outer shape and connection units 33 and 34 having the same shape as the external electrodes 13 and 14 when viewed from the third direction D3 and positioned to completely overlap with the external electrodes 13 and 14 are arranged within the same layer.

[0030] The internal conductor layer 26 is located between the piezoelectric layer 17e and the piezoelectric layer 17f. Similar to the internal conductor layers 22 and 24, the internal conductor layer 26 has a configuration in which connection portions 33, 34, and 35 are arranged within the same layer, having the same shape as the external electrodes 13, 14, and 15 when viewed from the third direction D3, and positioned to completely overlap with the external electrodes 13, 14, and 15.

[0031] The internal conductor layer 27 is located between the piezoelectric layer 17f and the piezoelectric layer 17g. The internal conductor layer 27 has a configuration in which a drive unit 32 having a rectangular outer shape and connection units 34 and 35 having the same shape as the external electrodes 14 and 15 when viewed from the third direction D3 and positioned to completely overlap with the external electrodes 14 and 15 are arranged within the same layer. Specifically, the connection units 34 and 35 are located within openings formed in the drive unit 32. Each opening is formed at a position corresponding to the external electrodes 14 and 15 when viewed from the third direction D3. That is, the connection units 34 and 35 are surrounded by the drive unit 32 when viewed from the third direction D3. The connection units 34 and 35 are spaced apart from the drive unit 32.

[0032] The internal conductor layer 28 is located between the piezoelectric layer 17g and the piezoelectric layer 17h. Similar to the internal conductor layers 22, 24, and 26, the internal conductor layer 28 has a configuration in which connection portions 33, 34, and 35 are arranged within the same layer, having the same shape as the external electrodes 13, 14, and 15 when viewed from the third direction D3, and positioned to completely overlap with the external electrodes 13, 14, and 15.

[0033] The internal conductor layer 29 is located between the piezoelectric layer 17h and the piezoelectric layer 16b. The internal conductor layer 29 has the same configuration as the internal conductor layers 21 and 25, and has a configuration in which a drive unit 32 having a rectangular outer shape and connection units 33 and 34 having the same shape as the external electrodes 13 and 14 when viewed from the third direction D3 and positioned to completely overlap with the external electrodes 13 and 14 are arranged within the same layer.

[0034] The external electrode 13 is electrically connected to the drive portion 32 of the internal conductor layer 27 and the connection portions 33 of the other internal conductor layers 21-26, 28, and 29 via a plurality of via conductors 43. Each connection portion 33 faces the drive portion 32 of the internal conductor layer 27 in the third direction D3 and is positioned to overlap with the drive portion 32 of the internal conductor layer 27 when viewed from the third direction D3. As shown in Figure 4, the plurality of via conductors 43 are each located between the external electrode 13 and the connection portions 33 of the internal conductor layers 21-26, 28, and 29 and the drive portion 32 of the internal conductor layer 27, and are positioned to overlap with the external electrode 13 when viewed from the third direction D3. Each of the plurality of via conductors 43 penetrates the corresponding piezoelectric layers 16a, 17a-17h in the third direction D3. Adjacent via conductors 43 in the third direction D3 are designed not to overlap when viewed from the third direction D3.

[0035] The external electrode 14 is electrically connected to the drive portion 32 of the internal conductor layer 23 and the connection portions 34 of the other internal conductor layers 21-26, 28, and 29 via a plurality of via conductors 44. Each connection portion 34 faces the drive portion 32 of the internal conductor layer 23 in the third direction D3 and is positioned to overlap with the drive portion 32 of the internal conductor layer 23 when viewed from the third direction D3. As shown in Figure 4, each of the plurality of via conductors 44 is located between the external electrode 14 and the connection portions 34 of the internal conductor layers 21, 22, 24-29 and the drive portion 32 of the internal conductor layer 23, and is positioned to overlap with the external electrode 14 when viewed from the third direction D3. Each of the plurality of via conductors 44 penetrates the corresponding piezoelectric layers 16a, 17a-17h in the third direction D3. Adjacent via conductors 44 in the third direction D3 are designed not to overlap when viewed from the third direction D3.

[0036] The external electrode 15 is electrically connected to the connection points 35 of the internal conductor layers 23 and 27 and the drive points 32 of the internal conductor layers 21, 25, and 29 via a plurality of via conductors 45. Each connection point 35 faces the drive points 32 of the internal conductor layers 21, 25, and 29 in the third direction D3 and is positioned to overlap with the drive points 32 of the internal conductor layers 21, 25, and 29 when viewed from the third direction D3. Each of the plurality of via conductors 45 is located between the external electrode 15 and the connection points 35 of the internal conductor layers 23 and 27 and the drive points 32 of the internal conductor layers 21, 25, and 29, and is positioned to overlap with the external electrode 15 when viewed from the third direction D3. Each of the plurality of via conductors 45 penetrates the corresponding piezoelectric layers 16a, 17a to 17h in the third direction D3. Adjacent via conductors 45 in the third direction D3 are designed not to overlap when viewed from the third direction D3.

[0037] The internal conductor layers 21-29 and via conductors 43, 44, and 45 are made of a conductive material. Examples of conductive materials include Ag, Pd, Pt, or Ag-Pd alloys. The internal conductor layers 21-29 and via conductors 43, 44, and 45 are constructed, for example, as sintered bodies of conductive paste containing the above-mentioned conductive material. The via conductors 43, 44, and 45 are formed by sintering conductive paste filled into through-holes formed in a ceramic green sheet for forming the corresponding piezoelectric layers 16a, 17a-17h.

[0038] The piezoelectric element 10 described above includes a drive region 50 and a plurality of connection regions 62, 63, and 64.

[0039] As shown in Figure 3, the drive region 50 is the region where the drive units 32 of the internal conductor layers 21, 23, 25, 27, and 29 (drive conductor layers), including the drive unit 32, overlap when viewed from the third direction D3. Specifically, the drive region 50 is the region where the drive units 32 of the internal conductor layers 21, 25, and 29 connected to the external electrode 15 overlap with the drive units 32 of the internal conductor layer 27 connected to the external electrode 13 and the internal conductor layer 23 connected to the external electrode 14. As shown in Figure 4, the drive region 50 includes a first drive region 51 sandwiched between the internal conductor layers 21 and 25 connected to the external electrode 15 and the internal conductor layer 23 connected to the external electrode 14, and a second drive region 52 sandwiched between the internal conductor layers 25 and 29 connected to the external electrode 15 and the internal conductor layer 27 connected to the external electrode 13.

[0040] As shown in Figure 3, the multiple connection regions 62, 63, and 64 are regions where, viewed from a third direction D3, parts of the internal conductor layers 21 to 29 with the same polarity overlap. In this embodiment, the multiple connection regions consist of three: a first connection region 62, a second connection region 63, and a third connection region 64. The first connection region 62 is the region where, viewed from a third direction D3, the connection portion 33 of the internal conductor layers 21 to 26, 28, and 29 overlaps with the part of the internal conductor layer 27 corresponding to the connection portion 33. The second connection region 63 is the region where, viewed from a third direction D3, the connection portion 34 of the internal conductor layers 21, 22, and 24 to 29 overlaps with the part of the internal conductor layer 23 corresponding to the connection portion 34. The third connection region 64 is the region where, viewed from a third direction D3, the connection portion 35 of the internal conductor layers 22 to 24 and 26 to 28 overlaps with the part of the internal conductor layers 21, 25, and 29 corresponding to the connection portion 35. In this embodiment, when viewed from the third direction D3, the drive region 50 is positioned to surround multiple connection regions 62, 63, and 64.

[0041] Next, we will explain how to drive the piezoelectric element 10 described above.

[0042] Voltages with different polarities are applied to external electrodes 13 and 14. No voltage is applied to external electrode 15, unlike the voltages applied to external electrodes 13 and 14. External electrode 15 functions as a ground electrode. When the above-mentioned voltage is applied to external electrode 13, an electric field is generated between internal conductor layer 25 and internal conductor layer 27, and between internal conductor layer 27 and internal conductor layer 29. When an electric field is generated between internal conductor layer 27 and internal conductor layers 25 and 29, an electric field is applied to the third piezoelectric layer pair 18C and the fourth piezoelectric layer pair 18D of the second drive region 52, and a force is generated in the second drive region 52 in accordance with this electric field. As a result, the second drive region 52 is displaced by an amount corresponding to this force.

[0043] When the above-mentioned voltage is applied to the external electrode 14, an electric field is generated between the internal conductor layer 21 and the internal conductor layer 23, and between the internal conductor layer 23 and the internal conductor layer 25. When an electric field is generated between the internal conductor layer 23 and the internal conductor layers 21 and 25, an electric field is applied to the first piezoelectric layer pair 18A and the second piezoelectric layer pair 18B of the first drive region 51, and a force is generated in the first drive region 51 in accordance with this electric field. As a result, the first drive region 51 is displaced by an amount corresponding to this force. At this time, the first drive region 51 and the second drive region 52 are displaced in opposite directions. Therefore, when a voltage is applied to the external electrodes 13 and 14, the piezoelectric element 10 is deflected.

[0044] In the piezoelectric element 10, when an AC voltage is applied to the external electrodes 13 and 14, the first drive region 51 and the second drive region 52 repeatedly expand and contract in accordance with the frequency of the applied AC voltage. As a result, the first drive region 51 and the second drive region 52 expand and contract in opposite directions, causing the piezoelectric element 10 to flex and vibrate.

[0045] The following describes the multiple via conductors 43, 44, and 45 in more detail, referring to Figures 5-8.

[0046] In Figure 4, for illustrative purposes, a single via conductor 43 is shown penetrating the piezoelectric layers 16a and 17a-17h, respectively. However, in reality, multiple via conductors 43 penetrate the piezoelectric layers 16a and 17a-17h.

[0047] As shown in Figure 5, the multiple via conductors 43 include three types of via conductor groups: a first via conductor group 43A consisting of multiple via conductors 43 located in the same layer, a second via conductor group 43B consisting of multiple via conductors 43 located in the same layer, and a third via conductor group 43C consisting of multiple via conductors 43 located in the same layer.

[0048] The first via conductor group 43A is provided so as to fit within a rectangular first region 62A located near the center of the connection region 62, as shown in Figure 5(a). The first via conductor group 43A is composed of a plurality of via conductors 43 aligned in the first region 62A. In this embodiment, the first via conductor group 43A is composed of 20 via conductors 43 arranged (lattice arrangement) so as to be located at the intersections of a grid, with rows of 5 via conductors 43 arranged at equal intervals in the first direction D1 and 4 rows arranged at equal intervals in the second direction D2.

[0049] The second via conductor group 43B is provided so as to fit within a rectangular second region 62B located near the center of the connection region 62, as shown in Figure 5(b). The second via conductor group 43B consists of a plurality of via conductors 43 aligned in the second region 62B. In this embodiment, the second via conductor group 43B, like the first via conductor group 43A, consists of 20 via conductors 43 arranged in a grid, with rows of 5 via conductors 43 arranged at equal intervals in the first direction D1 and 4 rows arranged at equal intervals in the second direction D2.

[0050] The third via conductor group 43C is provided so as to fit within a pair of rectangular third regions 62C located at both ends of the connection region 62 (both ends with respect to the first direction D1), as shown in Figure 5(c). The third via conductor group 43C is composed of a plurality of via conductors 43 aligned in each third region 62C. In this embodiment, the third via conductor group 43C is composed of a total of 20 via conductors 43, 11 of which are arranged in a grid in one of the pair of third regions 62C and 9 of which are arranged in a grid in the other third region 62C.

[0051] Figure 6 shows the positional relationship of the three via conductor groups 43A, 43B, and 43C as viewed from the third direction D3. As shown in Figure 6, as viewed from the third direction D3, all of the multiple via conductors 43 within the connection region 62 are arranged in a grid by the three via conductor groups 43A, 43B, and 43C. As viewed from the third direction D3, the first region 62A where the first via conductor group 43A is located and the second region 62B where the second via conductor group 43B is located partially overlap. More specifically, the first region 62A and the second region 62B overlap with a shift in the first direction D1 and the second direction D2, respectively, by half the spacing (half pitch) of the equally spaced via conductors 43. Viewed from the third direction D3, the third region 62C where the third via conductor group 43C is located is adjacent to the first region 62A and the second region 62B, sandwiching them between them, and does not overlap with either the first region 62A or the second region 62B.

[0052] Of the multiple via conductors 43, the first via conductor group 43A is provided so as to penetrate the piezoelectric layers 16a, 17c, and 17g, respectively; the second via conductor group 43B is provided so as to penetrate the piezoelectric layers 17a and 17e, respectively; and the third via conductor group 43C is provided so as to penetrate the piezoelectric layers 17b, 17d, 17f, and 17h, respectively. In particular, in the piezoelectric layers 17a to 17h, the via conductors are arranged in the following order from the main surface 11a side of the element 11: second via conductor group 43B, third via conductor group 43C, first via conductor group 43A, third via conductor group 43C, second via conductor group 43B, third via conductor group 43C, first via conductor group 43A, and third via conductor group 43C. In other words, in the third direction D3, the multiple via conductors 43 are arranged alternately, with the second via conductor group 43B and the first via conductor group 43A separated by the third via conductor group 43C.

[0053] The multiple via conductors 44 include three types of via conductor groups: a first via conductor group 44A consisting of multiple via conductors 44 located in the same layer, a second via conductor group 44B consisting of multiple via conductors 44 located in the same layer, and a third via conductor group 44C consisting of multiple via conductors 44 located in the same layer.

[0054] The configurations of the three types of via conductor groups 44A to 44C of the multiple via conductors 44, and the first region 63A, second region 63B, and third region 63C in which each of the via conductor groups 44A to 44C is located, are the same as or similar to the configurations of the three types of via conductor groups 43A to 43C of the multiple via conductors 43, and the first region 62A, second region 62B, and third region 62C, so no explanation is provided.

[0055] Of the multiple via conductors 44, the first via conductor group 44A is provided so as to penetrate the piezoelectric layers 16a, 17c, and 17g, respectively; the second via conductor group 44B is provided so as to penetrate the piezoelectric layers 17a and 17e, respectively; and the third via conductor group 44C is provided so as to penetrate the piezoelectric layers 17b, 17d, 17f, and 17h, respectively. In particular, in the piezoelectric layers 17a to 17h, the via conductors are arranged in the following order from the main surface 11a side of the element 11: second via conductor group 44B, third via conductor group 44C, first via conductor group 44A, third via conductor group 44C, second via conductor group 44B, third via conductor group 44C, first via conductor group 44A, and third via conductor group 44C. In other words, in the third direction D3, the multiple via conductors 44 are arranged alternately, with the second via conductor group 44B and the first via conductor group 44A separated by the third via conductor group 44C.

[0056] The multiple via conductors 45 include three types of via conductor groups: a first via conductor group 45A consisting of multiple via conductors 45 located in the same layer, a second via conductor group 45B consisting of multiple via conductors 45 located in the same layer, and a third via conductor group 45C consisting of multiple via conductors 45 located in the same layer.

[0057] The first via conductor group 45A is provided so as to fit within a rectangular first region 64A located near the center of the connection region 64, as shown in Figure 7(a). The first via conductor group 45A is composed of a plurality of via conductors 45 aligned in the first region 64A. In this embodiment, the first via conductor group 45A is composed of 40 via conductors 45 arranged in a grid, with rows of 5 via conductors 45 arranged at equal intervals in the first direction D1 and 8 rows arranged at equal intervals in the second direction D2.

[0058] The second via conductor group 45B is provided so as to fit within a rectangular second region 64B located near the center of the connection region 64, as shown in Figure 7(b). The second via conductor group 45B consists of a plurality of via conductors 45 aligned in the second region 64B. In this embodiment, the second via conductor group 45B, like the first via conductor group 45A, consists of 40 via conductors 45 arranged in a grid, with rows of 5 via conductors 43 arranged at equal intervals in the first direction D1 and 8 rows arranged at equal intervals in the second direction D2.

[0059] The third via conductor group 45C is provided so as to fit within a pair of rectangular third regions 64C located at both ends of the connection region 64 (both ends with respect to the first direction D1), as shown in Figure 7(c). The third via conductor group 45C is composed of a plurality of via conductors 45 aligned in each third region 64C. In this embodiment, the third via conductor group 45C is composed of a total of 33 via conductors 45: 18 arranged in a grid in one of the pair of third regions 64C and 15 arranged in a grid in the other.

[0060] Figure 8 shows the positional relationship of the three via conductor groups 45A, 45B, and 45C as viewed from the third direction D3. As shown in Figure 8, as viewed from the third direction D3, all of the multiple via conductors 44 within the connection region 64 are arranged in a grid by the three via conductor groups 45A, 45B, and 45C. As viewed from the third direction D3, the first region 64A where the first via conductor group 45A is located and the second region 64B where the second via conductor group 45B is located partially overlap. More specifically, the first region 64A and the second region 64B overlap with a shift in the first direction D1 and the second direction D2, respectively, by half the spacing (half-pitch) of the equally spaced via conductors 45. Viewed from the third direction D3, the third region 64C, where the third via conductor group 45C is located, is adjacent to the first region 64A and the second region 64B, sandwiching them between them, and does not overlap with either the first region 64A or the second region 64B.

[0061] Of the multiple via conductors 45, the first via conductor group 45A is provided so as to penetrate the piezoelectric layers 16a, 17c, and 17g, respectively; the second via conductor group 45B is provided so as to penetrate the piezoelectric layers 17a and 17e, respectively; and the third via conductor group 45C is provided so as to penetrate the piezoelectric layers 17b, 17d, 17f, and 17h, respectively. In particular, in the piezoelectric layers 17a to 17h, the via conductors are arranged in the following order from the main surface 11a side of the element 11: second via conductor group 45B, third via conductor group 45C, first via conductor group 45A, third via conductor group 45C, second via conductor group 45B, third via conductor group 45C, first via conductor group 45A, and third via conductor group 45C. In other words, in the third direction D3, the multiple via conductors 45 are arranged alternately, with the second via conductor group 45B and the first via conductor group 45A separated by the third via conductor group 45C.

[0062] Here, when via conductors 42, 43, and 44 are formed by filling through holes formed in a ceramic green sheet that forms a piezoelectric layer with conductive paste and sintering, forming the via conductors 42, 43, and 44 can be difficult, and if the via conductors are arranged in an overlapping manner, they may not connect properly. Therefore, connection reliability is improved by intentionally not overlapping adjacent via conductors 42, 43, and 44 in the third direction D3. In addition, bulges may occur around each via conductor 42, 43, and 44, and the regions 62A~62C, 63A~63C, and 64A~64C where the via conductors 42, 43, and 44 are formed may bulge as a whole. When such bulges occur, it is required to maintain sufficient connection reliability between the internal conductor layers 21~29. In particular, as in this embodiment, when the first regions 62A, 63A, 64A and the second regions 62B, 63B, 64B overlap when viewed from the third direction D3, the thickness of the overlapping region becomes locally thicker, thus requiring high connection reliability.

[0063] In the piezoelectric element 10 described above, when viewed from the third direction D3, the third regions 62C, 63C, and 64C are adjacent to the first regions 62A, 63A, and 64A and the second regions 62B, 63B, and 64B, and do not overlap with any of the first regions 62A, 63A, and 64A or the second regions 62B, 63B, and 64B. In addition, in the third direction D3, the same via conductor groups from the first via conductor group 43A, 44A, and 45A, the second via conductor group 43B, 44B, and 45B, and the third via conductor group 43C, 44C, and 45C are not adjacent to each other, while different via conductor groups are adjacent to each other. Therefore, in the piezoelectric element 10, the third regions 62C, 63C, and 64C smooth out the above-mentioned bulges so that they become nearly flat, that is, it is difficult for locally thickened regions to occur, thereby achieving high connection reliability.

[0064] In the piezoelectric element 10, the multiple via conductors 43, 44, and 45 are arranged alternately in the third direction D3, with the second via conductor group 43B, 44B, 45B and the first via conductor group 43A, 44A, 45A separated by the third via conductor group 43C, 44C, 45C. This ensures that the third region 62C, 63C, 64C provides sufficient uniformity, further improving connection reliability. The order of the first via conductor group 43A, 44A, 45A, the second via conductor group 43B, 44B, 45B, and the third via conductor group 43C, 44C, 45C in the third direction D3 can be changed as appropriate.

[0065] In each connection region 62, 63, and 64 of the piezoelectric element 10, internal conductor layers 21 to 29 are present in all interlayers of the piezoelectric layers 16a, 16b, 17a, and 17h. In other words, in each connection region 62, 63, and 64, the internal conductor layers 21 to 29 are spaced apart by the thickness of one piezoelectric layer 16a, 16b, 17a, and 17h. On the other hand, in the driving region 50 of the piezoelectric element 10, internal conductor layers 21 to 29 are not present in all interlayers of the piezoelectric layers 16a, 16b, 17a, and 17h, and some of the internal conductor layers 21, 23, 25, 27, and 29 are spaced apart by the thickness of two piezoelectric layers 16a, 16b, 17a, and 17h. In other words, in the drive region 50, a first piezoelectric layer pair 18A is interposed between the internal conductor layers 21 and 23, a second piezoelectric layer pair 18B is interposed between the internal conductor layers 23 and 25, a third piezoelectric layer pair 18C is interposed between the internal conductor layers 25 and 27, and a fourth piezoelectric layer pair 18D is interposed between the internal conductor layers 27 and 29.

[0066] Therefore, as shown in Figure 9, the spacing between the internal conductor layers 21-29 in the third direction D3 is such that the spacing D in the drive region 50 is wider than the spacing d in each connection region 62, 63, and 64. In this embodiment, the spacing D in the drive region 50 is approximately twice the spacing d in each connection region 62, 63, and 64. When the spacing D of the internal conductor layers 21, 23, 25, 27, and 29 in the drive region 50 is relatively wide, the capacitance of the piezoelectric element 10 is reduced, making it less likely for problems such as short circuits and overheating to occur even when a high voltage is applied to the piezoelectric element 10.

[0067] However, simply widening the spacing between internal conductor layers would also widen the spacing between internal conductor layers in the connection region, which could reduce the reliability of the interlayer connection via via conductors. Therefore, in the piezoelectric element 10 according to this embodiment, the spacing d of the connection regions 62, 63, and 64 is narrower than the spacing D of the drive region 50 by interposing internal conductor layers 22, 24, 26, and 28 between internal conductor layers 21, 23, 25, 27, and 29, respectively, thereby improving the reliability of the connection between internal conductor layers via via conductors.

[0068] Furthermore, in the piezoelectric element 10, with respect to the third direction D3, the main surfaces 11a and 11b of the element 11 are composed of piezoelectric layers 16a and 16b, and the internal conductor layers 21, 23, 25, 27, and 29, including the drive unit 32, are not exposed on the main surfaces 11a and 11b of the element 11. In addition, each connection region 62, 63, and 64 is surrounded by the drive region 50 and is not exposed from any of the side surfaces 11c, 11c of the element 11. Therefore, even when a high voltage is applied to the piezoelectric element 10, short circuits and leaks of the internal conductor layers 21-29 on the surface of the element 11 are less likely to occur, and the drive voltage is improved.

[0069] While embodiments of the present invention have been described above, the present invention is not necessarily limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0070] In the above embodiment, a configuration in which the piezoelectric element 10 is of the bimorph type was described as an example. However, the piezoelectric element 10 may be of the unimorph type, for example, or may be a piezoelectric element of other configurations.

[0071] As can be understood from the above description, this specification discloses the following: [Note 1] The device comprises a body made of piezoelectric material and a plurality of internal conductor layers provided within the body and stacked in a first direction. Viewed from the first direction, the device includes a driving region where portions of the plurality of internal conductor layers with different polarities overlap, and a plurality of connection regions where portions of the plurality of internal conductor layers with the same polarity overlap and are connected via a plurality of via conductors extending along the first direction. The plurality of via conductors are not adjacent to each other in the first direction when viewed from the first direction, and the plurality of via conductors include a first group of via conductors located in a first region that fits within the connection region, a second group of via conductors located in a second region that is in a different layer from the first group of via conductors and fits within the connection region, and a third group of via conductors located in a third region that is in a different layer from the first group of via conductors and the second group of via conductors and fits within the connection region. Viewed from the first direction, the first region and the second region overlap in at least part, and the third region is adjacent to the first region and the second region. A piezoelectric element in which, in the first direction, different via conductor groups from the first via conductor group, the second via conductor group, and the third via conductor group are adjacent to each other. [Note 2] The piezoelectric element according to Appendix 1, wherein, in the first direction, the first group of via conductors and the second group of via conductors are arranged alternately via the third group of via conductors. [Note 3] The piezoelectric element according to Appendix 1 or 2, wherein, when viewed from the first direction, the third region in which the third group of via conductors is located is divided into multiple parts. [Note 4] The piezoelectric element according to Appendix 3, wherein, when viewed from the first direction, the plurality of third regions sandwich the first region and the second region. [Note 5] A piezoelectric element according to any one of the appendices 1 to 4, wherein, when viewed from the first direction, all of the plurality of via conductors within each connection region are located at the intersection of the grid. [Explanation of symbols]

[0072] 10...Piezoelectric element, 11...Element, 13, 14, 15...External electrodes, 16a, 16b, 17a~17h...Piezoelectric layer, 21~29...Internal conductor layer, 32...Drive unit, 33, 34...Connection unit, 43~45...Via conductors, 43A, 44A, 45A...First via conductor group, 43B, 44B, 45B...Second via conductor group, 43C, 44C, 45C...Third via conductor group, 62, 63, 64...Connection region, 62A, 63A, 64A...First region, 62B, 63B, 64B...Second region, 62C, 63C, 64C...Third region.

Claims

1. The device comprises a body made of piezoelectric material and a plurality of internal conductor layers provided within the body and stacked in a first direction. Viewed from the first direction, the device includes a driving region where portions of the plurality of internal conductor layers with different polarities overlap, and a plurality of connection regions where portions of the plurality of internal conductor layers with the same polarity overlap and are connected via a plurality of via conductors extending along the first direction. The plurality of via conductors are not adjacent to each other in the first direction when viewed from the first direction, and the plurality of via conductors include a first group of via conductors located in a first region that fits within the connection region, a second group of via conductors located in a second region that is in a different layer from the first group of via conductors and fits within the connection region, and a third group of via conductors located in a third region that is in a different layer from the first group of via conductors and the second group of via conductors and fits within the connection region. Viewed from the first direction, the first region and the second region overlap in at least part, and the third region is adjacent to the first region and the second region, and the third region does not overlap with either the first region or the second region. A piezoelectric element in which, in the first direction, different via conductor groups from the first via conductor group, the second via conductor group, and the third via conductor group are adjacent to each other.

2. The piezoelectric element according to claim 1, wherein in the first direction, the first via group and the second via group are arranged alternately via the third via group.

3. The piezoelectric element according to claim 1 or 2, wherein, when viewed from the first direction, the third region in which the third via conductor group is located is divided into a plurality of parts.

4. The piezoelectric element according to claim 3, wherein, when viewed from the first direction, the plurality of third regions sandwich the first region and the second region.

5. The piezoelectric element according to claim 1, wherein, when viewed from the first direction, all of the plurality of via conductors within each connection region are located at the intersections of the grid.

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