Piezoelectric unit
The piezoelectric unit design addresses reliability issues by positioning external electrodes and conductors to face each other with internal via conductors, minimizing exposure to harsh environments and maintaining connectivity, thus enhancing stability.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TDK CORP
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-18
Smart Images
Figure 2026099057000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a piezoelectric unit.
Background Art
[0002] A known piezoelectric unit includes a piezoelectric element including a piezoelectric body and an external electrode disposed on the piezoelectric body, and a diaphragm on which the piezoelectric element is disposed (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] One aspect of the present invention aims to provide a piezoelectric unit that surely suppresses a decrease in reliability.
Means for Solving the Problems
[0005] A piezoelectric unit according to one aspect of the present invention includes a piezoelectric element including a piezoelectric body and an external electrode disposed on the piezoelectric body, a base material, and a conductor disposed on the base material, and further includes a diaphragm on which the piezoelectric element is disposed. The piezoelectric body includes a first main surface facing the diaphragm, the first main surface including a first region where the external electrode is disposed and a second region different from the first region. The base material includes a second main surface facing the piezoelectric element, the second main surface including a third region where the conductor is disposed and a fourth region different from the third region. The first region and the third region face each other, and the second region and the fourth region face each other. The external electrode and the conductor are connected to each other, and the second region and the fourth region are connected to each other.
[0006] In the above embodiment, the external electrode is positioned in a first region included in the first main surface facing the diaphragm. The conductor is positioned in a third region included in the second main surface facing the piezoelectric element. The first region and the third region face each other. The external electrode and the conductor are connected to each other between the opposing piezoelectric element and the diaphragm. The connection point between the external electrode and the conductor is located between the piezoelectric element and the diaphragm. Therefore, the connection point between the external electrode and the conductor is less likely to be exposed to the external environment. For example, even when exposed to a high-temperature, high-humidity environment, the above embodiment makes it less likely for a short circuit to occur in the piezoelectric element and the diaphragm. The opposing second and fourth regions are connected to each other. The piezoelectric element and the diaphragm are connected even at points other than the connection point between the external electrode and the conductor. This one embodiment ensures physical and electrical connection between the piezoelectric element and the diaphragm. In this embodiment, the connection point between the second and fourth regions is located between the piezoelectric element and the diaphragm. Therefore, the connection point between the second and fourth regions is less likely to be exposed to the external environment. For example, even when exposed to a high-temperature, high-humidity environment, this embodiment is less likely to degrade the connectivity between the piezoelectric element and the diaphragm. As a result, the above-described embodiment reliably suppresses a decline in reliability. [Effects of the Invention]
[0007] One aspect of the present invention provides a piezoelectric unit that reliably suppresses a decrease in reliability. [Brief explanation of the drawing]
[0008] [Figure 1] Figure 1 is a perspective view of a piezoelectric unit according to one embodiment. [Figure 2] Figure 2 shows the cross-sectional configuration of the piezoelectric unit according to this embodiment. [Figure 3] Figure 3 shows the cross-sectional configuration of the piezoelectric unit according to this embodiment. [Figure 4] Figure 4 shows the cross-sectional configuration of the piezoelectric unit according to this embodiment. [Figure 5] Figure 5 is a plan view showing a piezoelectric element. [Figure 6] Figure 6 is an exploded perspective view schematically showing the configuration of a piezoelectric element. [Figure 7] Figure 7 is a plan view showing the diaphragm. [Figure 8] Figure 8 is a plan view showing one modified example of a diaphragm. [Figure 9] Figure 9 is a plan view showing one modified example of a diaphragm. [Figure 10] Figure 10 shows a cross-sectional configuration of one modified example of a diaphragm. [Figure 11] Figure 11 shows a cross-sectional configuration of one modified example of a diaphragm. [Figure 12] Figure 12 is a plan view showing one modified example of the piezoelectric unit according to this embodiment. [Modes for carrying out the invention]
[0009] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In this description, the same reference numerals will be used for the same element or element having the same function, and redundant explanations will be omitted.
[0010] The configuration of the piezoelectric unit PU according to this embodiment will be described with reference to Figures 1 to 7. Figure 1 is a perspective view of the piezoelectric unit according to this embodiment. Figures 2, 3, and 4 are diagrams showing the cross-sectional configuration of the piezoelectric unit according to this embodiment. Figure 5 is a plan view showing the piezoelectric element. Figure 6 is an exploded perspective view schematically showing the configuration of the piezoelectric element. Figure 7 is a plan view showing the diaphragm. In Figures 2, 3, and 4, the hatching indicating the cross-section is omitted. As shown in Figures 1 to 4, the piezoelectric unit PU includes a piezoelectric element PE and a diaphragm VP. The piezoelectric element PE is positioned on the diaphragm VP. The piezoelectric element PE and the diaphragm VP face each other. The piezoelectric element PE is connected to the diaphragm VP. The piezoelectric element PE includes a piezoelectric element 1 and a plurality of external electrodes 3, 5. The plurality of external electrodes 3, 5 are positioned on the piezoelectric element 1. The piezoelectric element PE includes, for example, a pair of external electrodes 3, 5. The diaphragm VP includes a base material 21 and a plurality of conductors 23, 25. The plurality of conductors 23, 25 are positioned on the base material 21. The diaphragm VP includes, for example, a pair of conductors 23, 25.
[0011] The piezoelectric element 1 includes a pair of opposing main surfaces 1a and 1b. The piezoelectric element 1 includes a side surface 1c connecting the pair of main surfaces 1a and 1b. The side surface 1c includes, for example, a plurality of adjacent side surfaces. The side surface 1c is arranged, for example, so that it extends in a direction in which the pair of main surfaces 1a and 1b face each other. The surface of the piezoelectric element 1 includes the pair of main surfaces 1a and 1b and the side surface 1c. The surface of the piezoelectric element 1 includes surfaces that define the outer shape of the piezoelectric element 1.
[0012] As shown in Figure 5, the piezoelectric element 1 has a shape having a major axis and a minor axis when viewed from a direction perpendicular to the main surface 1a. The direction perpendicular to the main surface 1a includes, for example, the direction in which the pair of main surfaces 1a and 1b face each other. The piezoelectric element 1 may also have a polygonal shape having a major axis and a minor axis when viewed from a direction perpendicular to the main surface 1a. The piezoelectric element 1 may also have a rectangular shape when viewed from a direction perpendicular to the main surface 1a. In a configuration in which the piezoelectric element 1 has a rectangular shape when viewed from a direction perpendicular to the main surface 1a, each of the pair of main surfaces 1a and 1b has a rectangular shape. The rectangular shape includes, for example, a shape in which each corner is chamfered or a shape in which each corner is rounded. The rectangular shape includes, for example, a rounded rectangle. The piezoelectric element 1 may also have an oval shape when viewed from a direction perpendicular to the main surface 1a. The oval shape includes, for example, an ellipse.
[0013] The main surface 1a faces the diaphragm VP. The main surface 1a includes a plurality of regions R1, R2. The plurality of regions R1, R2 are distinct from each other. The main surface 1a includes, for example, a pair of regions R1, R2. The plurality of regions R1, R2 may be in contact with each other or may be separated from each other. A plurality of external electrodes 3, 5 are disposed in the region R1. The region R1 is located at one end of the main surface 1a in the direction of the major axis. In the configuration where the main surface 1a has a rectangular shape, the main surface 1a includes a pair of long sides and a pair of short sides. In this configuration, the region R1 is located closer to one of the pair of short sides. For example, when the region R1 includes a first region, the region R2 includes a second region. The plurality of external electrodes 3, 5 include a conductive material. The plurality of external electrodes 3, 5 are, for example, made of a conductive material. This conductive material includes, for example, Pt, Ag, Pd, Au, Cu, or an alloy containing two or more of these metals. The plurality of external electrodes 3, 5 are configured, for example, as a sintered body of a conductive paste containing the above conductive material. The plurality of external electrodes 3, 5 may include a sputtered film on the outermost layer. The sputtered film includes, for example, Au, Sn, Ag, Cr, Cu, or an alloy containing two or more of these metals.
[0014] The piezoelectric body 1 is configured, for example, by laminating a plurality of piezoelectric layers. The piezoelectric body 1 includes, for example, a plurality of laminated piezoelectric layers. In the piezoelectric body 1, the plurality of piezoelectric layers are laminated in the direction in which the pair of main surfaces 1a, 1b face each other. Each piezoelectric layer is made of a piezoelectric ceramic material. The piezoelectric body 1 is made of a piezoelectric ceramic material. The piezoelectric ceramic material includes, for example, PZT [Pb(Zr,Ti)O3], PT (PbTiO3), PLZT [(Pb,La)(Zr,Ti)O3], PZN [Pb(Zn,Nb)O3], or barium titanate (BaTiO3). Each piezoelectric layer is configured, for example, from a sintered body of a ceramic green sheet containing the above-described piezoelectric ceramic material. In the actual piezoelectric body 1, each piezoelectric layer is integrated to such an extent that the boundary between each piezoelectric layer cannot be recognized.
[0015] As shown in Figure 6, the piezoelectric element PE includes a plurality of internal electrodes 11, 13, and 15. For example, the piezoelectric element PE includes three internal electrodes 11, 13, and 15. The plurality of internal electrodes 11, 13, and 15 are arranged in different positions (layers) in the direction in which a pair of main surfaces 1a and 1b face each other. The main surface 1a and the internal electrode 11 face each other with a gap in the direction in which the pair of main surfaces 1a and 1b face each other. The internal electrode 11 and the internal electrode 13 face each other with a gap in the direction in which the pair of main surfaces 1a and 1b face each other with a gap in the direction in which the pair of main surfaces 1a and 1b face each other. The internal electrode 15 and the main surface 1b face each other with a gap in the direction in which the pair of main surfaces 1a and 1b face each other. In Figure 6, each piezoelectric layer is shown by a dashed line.
[0016] Each of the multiple internal electrodes 11, 13, 15 is located between two corresponding piezoelectric layers that are adjacent to each other in the direction in which a pair of main surfaces 1a, 1b face each other. The multiple internal electrodes 11, 13, 15 are not exposed on the surface of the piezoelectric element 1. The multiple internal electrodes 11, 13, 15 are away from the side surface 1c and are not exposed to the side surface 1c. Each of the multiple internal electrodes 11, 13, 15 is away from all edges of the main surfaces 1a, 1b when viewed from the direction in which the pair of main surfaces 1a, 1b face each other. Each of the multiple internal electrodes 11, 13, 15 is away from, for example, each of the four sides of the pair of main surfaces 1a, 1b when viewed from the direction in which the pair of main surfaces 1a, 1b face each other. Among the multiple internal electrodes 11, 13, 15, the region sandwiched between adjacent internal electrodes in the piezoelectric layer located between adjacent internal electrodes includes a piezoelectrically activated region.
[0017] Each of the multiple internal electrodes 11, 13, 15 has a shape having, for example, a major axis and a minor axis when viewed from a direction perpendicular to the main surface 1a. For example, the direction of the major axis in each of the multiple internal electrodes 11, 13, 15 is substantially parallel to the direction of the major axis in the piezoelectric element 1. Each of the multiple internal electrodes 11, 13, 15 has a roughly rectangular shape when viewed from a direction in which the pair of main surfaces 1a, 1b face each other, for example, with one corner cut off. The outer edges of each of the multiple internal electrodes 11, 13, 15 include portions that coincide with each other when viewed from a direction in which the pair of main surfaces 1a, 1b face each other. The multiple corners of each of the multiple internal electrodes 11, 13, 15 may be rounded, exhibiting a so-called R shape. A rounded corner means a curved corner formed by the ends of two straight lines being connected by a curve, rather than a corner formed by the intersection of two straight lines.
[0018] The external electrode 3 is electrically connected to the connecting conductor 12a through a via conductor V1. The connecting conductor 12a is located on the same layer as the internal electrode 11. The connecting conductor 12a is positioned at a location corresponding to a notched corner in the internal electrode 11. The internal electrode 11 has a generally rectangular shape, such that when viewed from a direction in which the pair of main surfaces 1a and 1b face each other, the position corresponding to the external electrode 3 is notched. The connecting conductor 12a has, for example, a rectangular shape when viewed from a direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 12a may also have, for example, a circular shape when viewed from a direction in which the pair of main surfaces 1a and 1b face each other.
[0019] The connecting conductor 12a is located between two corresponding piezoelectric layers, with the internal electrode 11 situated between them. The connecting conductor 12a and the internal electrode 11 are separated from each other. The connecting conductor 12a faces the external electrode 3 in the direction in which the pair of main surfaces 1a and 1b face each other. The via conductor V1 is connected to the external electrode 3 and also to the connecting conductor 12a. The number of via conductors V1 located in a single layer may be two or more. The connecting conductor 12a is electrically connected to the internal electrode 13 through via conductors V2 and connecting conductor 12b. The connecting conductor 12a faces the connecting conductor 12b in the direction in which the pair of main surfaces 1a and 1b face each other.
[0020] The connecting conductor 12b faces the internal electrode 13 in the direction in which the pair of main surfaces 1a, 1b face each other. The via conductor V2 is connected to the connecting conductor 12b and also to the internal electrode 13. The piezoelectric element PE includes, for example, a plurality of via conductors V2 and a plurality of connecting conductors 12b. The plurality of via conductors V2 include, for example, a via conductor V2 connecting connecting conductor 12a and connecting conductor 12b, a via conductor V2 connecting connecting conductors 12b to each other, and a via conductor V2 connecting connecting conductor 12b to the internal electrode 13. The number of via conductors V2 located in a single layer may be two or more. Each of the plurality of connecting conductors 12b is arranged in a different position (layer) between the connecting conductor 12a and the internal electrode 13. The connecting conductor 12b has, for example, a rectangular shape when viewed from the direction in which the pair of main surfaces 1a, 1b face each other. The connecting conductor 12b may have, for example, a circular shape when viewed from the direction in which the pair of main surfaces 1a, 1b face each other.
[0021] The internal electrode 13 is electrically connected to the connecting conductor 16 through a via conductor V3 and a connecting conductor 12c. The via conductor V3 is connected to the connecting conductor 12c and also to the connecting conductor 16. The connecting conductor 12c faces the internal electrode 13 in the direction in which the pair of main surfaces 1a and 1b face each other. The piezoelectric element PE includes, for example, a plurality of via conductors V3 and a plurality of connecting conductors 12c. The plurality of via conductors V3 include, for example, a via conductor V3 connecting the internal electrode 13 and the connecting conductor 12c, a via conductor V3 connecting the connecting conductors 12c to each other, and a via conductor V3 connecting the connecting conductor 12c to the connecting conductor 16. The number of via conductors V3 located in a single layer may be two or more. Each of the plurality of connecting conductors 12c is located in a different position (layer) between the internal electrode 13 and the connecting conductor 16. The connecting conductor 12c has, for example, a rectangular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 12c may, for example, have a circular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other.
[0022] The connecting conductor 16 is located in the same layer as the internal electrode 15. The connecting conductor 16 is positioned at a location corresponding to a notched corner in the internal electrode 15. The internal electrode 15 has a roughly rectangular shape, such that when viewed from the direction in which the pair of main surfaces 1a and 1b face each other, a notch is cut out at the location corresponding to the external electrode 3 (connecting conductors 12a to 12c). The connecting conductor 16 has, for example, a rectangular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 16 may also have, for example, a circular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 16 is located between two corresponding piezoelectric layers, with the internal electrode 15 located between them. The internal electrode 15 and the connecting conductor 16 are separated from each other. The connecting conductor 16 faces the connecting conductor 12c in the direction in which the pair of main surfaces 1a and 1b face each other.
[0023] The external electrode 5 is electrically connected to the internal electrode 11 through a via conductor V4. The internal electrode 11 faces the external electrode 5 in a direction in which a pair of main surfaces 1a and 1b are opposite each other. The via conductor V4 is connected to both the external electrode 5 and the internal electrode 11. The number of via conductors V4 located in a single layer may be two or more.
[0024] The internal electrode 11 is electrically connected to the connecting conductor 14b through a via conductor V5 and a connecting conductor 14a. The via conductor V5 is connected to the connecting conductor 14a and also to the connecting conductor 14b. The connecting conductor 14a faces the internal electrode 11 in the direction in which the pair of main surfaces 1a and 1b face each other. The piezoelectric element PE includes, for example, a plurality of via conductors V5 and a plurality of connecting conductors 14a. The plurality of via conductors V5 include, for example, a via conductor V5 connecting the internal electrode 11 and the connecting conductor 14a, a via conductor V5 connecting the connecting conductors 14a to each other, and a via conductor V5 connecting the connecting conductor 14a and the connecting conductor 14b. The number of via conductors V5 located in a single layer may be two or more. Each of the plurality of connecting conductors 14a is located in a different position (layer) between the internal electrode 11 and the connecting conductor 14b. The connecting conductor 14a has, for example, a rectangular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 14a may, for example, have a circular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other.
[0025] The connecting conductor 14b is located in the same layer as the internal electrode 13. The connecting conductor 14b is positioned at a location corresponding to a notched corner in the internal electrode 13. The internal electrode 13 has a roughly rectangular shape, such that when viewed from the direction in which the pair of main surfaces 1a and 1b face each other, a notch is cut out at the location corresponding to the external electrode 5 (connecting conductors 14a and 14b). The connecting conductor 14b has, for example, a rectangular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 14b may also have, for example, a circular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 14b is located between two corresponding piezoelectric layers, with the internal electrode 13 located between them. The internal electrode 13 and the connecting conductor 14b are separated from each other. The connecting conductor 14b faces the connecting conductor 14a in the direction in which the pair of main surfaces 1a and 1b face each other.
[0026] The connecting conductor 14b is electrically connected to the internal electrode 15 through the via conductor V6 and the connecting conductor 14c. The connecting conductor 14c faces the connecting conductor 14b in the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 14c faces the internal electrode 15 in the direction in which the pair of main surfaces 1a and 1b face each other. The via conductor V6 is connected to the connecting conductor 14c and also to the internal electrode 15. The piezoelectric element PE includes, for example, a plurality of via conductors V6 and a plurality of connecting conductors 14c. The plurality of via conductors V6 include, for example, a via conductor V6 connecting the connecting conductor 14b and the connecting conductor 14c, a via conductor V6 connecting the connecting conductors 14c to each other, and a via conductor V6 connecting the connecting conductor 14c to the internal electrode 15. The number of via conductors V6 located in a single layer may be two or more. Each of the plurality of connecting conductors 14c is located in a different position (layer) between the connecting conductor 14b and the internal electrode 15. The connecting conductor 14c may, for example, have a rectangular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other. The connecting conductor 14c may also have a circular shape when viewed from the direction in which the pair of main surfaces 1a and 1b face each other.
[0027] External electrode 3 is electrically connected to via conductor V1, connecting conductor 12a, via conductor V2, connecting conductor 12b, internal electrode 13, via conductor V3, connecting conductor 12c, and connecting conductor 16. External electrode 5 is electrically connected to via conductor V4, internal electrode 11, via conductor V5, connecting conductor 14a, connecting conductor 14b, via conductor V6, connecting conductor 14c, and internal electrode 15. Piezoelectric element PE includes multiple via conductors V1 to V6 and multiple connecting conductors 12a to 12c, 14a to 14c, and 16. Piezoelectric element PE does not necessarily include via conductor V3, connecting conductor 12c, and connecting conductor 16. When a driving voltage is applied to piezoelectric element PE, the polarity of internal electrode 11 and internal electrode 15 is the same, while the polarity of internal electrodes 11, 15 and internal electrode 13 are different. Multiple via conductors V1 to V6 and multiple connecting conductors 12, 14, and 16 are located, for example, near one end of the piezoelectric element 1 in the direction of its long axis.
[0028] Multiple internal electrodes 11, 13, 15, multiple via conductors V1 to V6, and multiple connecting conductors 12, 14, 16 contain a conductive material. The multiple internal electrodes 11, 13, 15, multiple via conductors V1 to V6, and multiple connecting conductors 12, 14, 16 are made of, for example, a conductive material. This conductive material includes, for example, Pt, Ag, Pd, Au, Cu, or an alloy containing two or more of these metals. The multiple internal electrodes 11, 13, 15, multiple via conductors V1 to V6, and multiple connecting conductors 12, 14, 16 are formed, for example, by co-firing with a piezoelectric element 1, and are configured as a sintered body of a conductive paste containing the conductive material. Multiple via conductors V1 to V6 are formed by sintering conductive paste filled into through holes formed in a ceramic green sheet for forming the corresponding piezoelectric layer among multiple piezoelectric layers.
[0029] The base material 21 includes a pair of opposing main surfaces 21a and 21b. The base material 21 includes a side surface 21c connecting the pair of main surfaces 21a and 21b. The side surface 21c includes, for example, a plurality of adjacent sides. The side surface 21c is arranged, for example, so that the pair of main surfaces 21a and 21b extend in a direction opposite to each other. The main surface 21a is opposite to the main surface 1a of the piezoelectric element 1. For example, if the main surface 1a includes a first main surface, then the main surface 21a includes a second main surface.
[0030] As shown in Figure 7, the base material 21 has a shape having a major axis and a minor axis when viewed from a direction perpendicular to the main surface 21a. The direction perpendicular to the main surface 21a includes, for example, the direction in which the pair of main surfaces 21a and 21b face each other. The base material 21 may have a polygonal shape having, for example, a major axis and a minor axis when viewed from a direction perpendicular to the main surface 21a. The base material 21 may have a rectangular shape when viewed from a direction perpendicular to the main surface 21a. In a configuration in which the base material 21 has a rectangular shape when viewed from a direction perpendicular to the main surface 21a, each of the pair of main surfaces 21a and 21b has a rectangular shape. The rectangular shape includes, for example, a shape in which each corner is chamfered or a shape in which each corner is rounded. The rectangular shape includes, for example, a rounded rectangle. The base material 21 may have an oval shape when viewed from a direction perpendicular to the main surface 21a. The oval shape includes, for example, the elliptical shape.
[0031] The main surface 21a faces the piezoelectric element PE. The main surface 21a includes multiple regions R3 and R4. The multiple regions R3 and R4 are separate from each other. For example, the main surface 21a includes a pair of regions R3 and R4. The multiple regions R3 and R4 may be in contact with each other or may be separated from each other. Multiple conductors 23 and 25 are arranged in region R3. Region R3 is located at one end of the main surface 21a in the direction of the major axis. In a configuration where the main surface 21a is rectangular, the main surface 21a includes a pair of long sides and a pair of short sides. In this configuration, region R3 is located closer to one of the short sides. For example, the direction of the major axis in the base material 21 is approximately parallel to the direction of the major axis in the piezoelectric element 1. For example, if region R3 includes a third region, then region R4 includes a fourth region.
[0032] The main surface 1a includes a region that overlaps with the main surface 21a in a direction perpendicular to the main surface 1a. For example, the main surface 1a does not include a region exposed from the main surface 21a in a direction perpendicular to the main surface 1a. The region of the main surface 1a that overlaps with the main surface 21a includes multiple regions R1, R2. The main surface 21a includes a region that overlaps with the main surface 1a in a direction perpendicular to the main surface 21a, and a region that is exposed from the main surface 1a in a direction perpendicular to the main surface 21a. When viewed from a direction perpendicular to the main surface 21a, the region that overlaps with the main surface 1a is located, for example, inside the region exposed from the main surface 1a. When viewed from a direction perpendicular to the main surface 21a, the outer edge of the main surface 21a includes the outer edge of the region exposed from the main surface 1a. When viewed from a direction perpendicular to the main surface 21a, the outer edge of the main surface 21a includes, for example, only the outer edge of the region exposed from the main surface 1a. The region of the main surface 21a that overlaps with the main surface 1a includes multiple regions R3, R4.
[0033] Each of the multiple conductors 23, 25 is located in region R3. Each of the multiple conductors 23, 25 is located, for example, in region R3 and in the region exposed from the main surface 1a. Each of the multiple conductors 23, 25 is located, for example, in region R3 and in the region exposed from the main surface 1a, so as to extend in a predetermined direction. Each of the multiple conductors 23, 25 is located, for example, in the direction of the major axis. One end of each of the multiple conductors 23, 25 is located, for example, on the aforementioned short side included in the main surface 21a. One end of each of the multiple conductors 23, 25 may be located, for example, in the vicinity of the aforementioned short side included in the main surface 21a. Conductors 23 and 25 are separated from each other on the main surface 21a. The multiple conductors 23, 25 are included, for example, in a circuit patterned on the base material 21. That is, the multiple conductors 23, 25 may be part of a circuit patterned on the base material 21.
[0034] Each of the plurality of conductors 23, 25 includes a region covered by the piezoelectric element PE and a region exposed from the piezoelectric element PE, when viewed from a direction perpendicular to the main surface 21a. Each of the plurality of conductors 23, 25 is connected, for example, to a wiring member (not shown) in the region exposed from the piezoelectric element PE. The wiring member includes, for example, lead wires, cables, or connectors. The piezoelectric unit PU is connected, for example, to a drive unit (not shown) through the wiring member. The drive unit includes, for example, a power supply that applies a drive voltage to the piezoelectric unit PU.
[0035] The base material 21 includes a resin. The base material 21 consists of, for example, a resin. The base material 21 includes, for example, a laser-direct structuring additive. The laser-direct structuring additive includes, for example, a palladium complex, a copper complex, or a metal oxide. The metal oxide includes, for example, chromium copper oxide. In addition to the laser-direct structuring additive, the resin forming the base material 21 includes, for example, a phenolic resin, a liquid crystal polymer, a polyimide resin, a crystalline polystyrene, an epoxy resin, a bismaleimide resin, or a fluororesin. The resin contained in the base material 21 may contain a filler. The base material 21, for example, contains a resin containing a filler. The base material 21 consists of, for example, a resin containing a filler. The filler includes, for example, glass fiber, carbon fiber, or ceramic powder. The ceramic powder is, for example, SiO2 powder, Al2O3 powder, or talc (Mg3Si4O 10 Contains (OH)2).
[0036] The multiple conductors 23, 25 are formed, for example, through a plating process. For example, the substrate 21 includes an activated pattern. Each of the multiple conductors 23, 25 includes a plating layer formed on the activated pattern of the substrate 21. That is, each of the multiple conductors 23, 25 includes, for example, a plating layer. The activated pattern of the substrate 21 includes portions of the substrate 21 that are in contact with a plurality of conductors 23, 25. Each of the plurality of conductors 23, 25 may be formed by a laser direct structuring (LDS) process. The activated pattern of the substrate 21 is, for example, a portion in which a laser direct structuring additive has been activated by laser irradiation. The plurality of conductors 23, 25 include, for example, at least one selected from gold, nickel, tin, silver, copper, or aluminum. The multiple conductors 23, 25 may be integrally molded with the base material 21, for example, through an insert molding process.
[0037] Regions R1 and R3 face each other. Each of the multiple external electrodes 3 and 5 faces a corresponding conductor among the multiple conductors 23 and 25. Each of the multiple external electrodes 3 and 5 is connected to a corresponding conductor among the multiple conductors 23 and 25. For example, external electrode 3 is connected to conductor 23, and external electrode 5 is connected to conductor 25. External electrode 3 is electrically connected to conductor 23. External electrode 3 may be electrically and physically connected to conductor 23. External electrode 5 may be electrically and physically connected to conductor 25.
[0038] Each of the multiple external electrodes 3, 5 is connected to a corresponding conductor among the multiple conductors 23, 25 by a conductive member 31. That is, the piezoelectric unit PU includes a conductive member 31 that connects the multiple external electrodes 3, 5 and the multiple conductors 23, 25. The conductive member 31 includes solder or an anisotropic conductive member. The anisotropic conductive member includes, for example, a cured product of an anisotropic conductive paste or an anisotropic conductive film. The anisotropic conductive member includes a resin and a plurality of conductive particles dispersed in the resin. The resin included in the anisotropic conductive member includes, for example, a thermosetting resin. The thermosetting resin includes, for example, a phenolic resin, an acrylic resin, a silicone resin, an epoxy resin, or a polyimide resin. The resin included in the anisotropic conductive member may also include, for example, a photocurable resin or an anaerobic curable resin.
[0039] Regions R2 and R4 are opposite each other. Regions R2 and R4 are connected to each other. Regions R2 and R4 are physically connected to each other. Regions R2 and R4 are connected to each other by a joining member 41. That is, the piezoelectric unit PU includes a joining member 41 that connects region R2 and region R4. The joining member 41 includes, for example, an adhesive or a double-sided pressure-sensitive adhesive tape. The adhesive includes, for example, a resin. This resin includes, for example, a thermosetting resin. The thermosetting resin includes, for example, a phenolic resin, an acrylic resin, a silicone resin, an epoxy resin, or a polyimide resin. The resin contained in the adhesive may also include, for example, a photocurable resin or an anaerobic curable resin. The joining member 41 includes, for example, a resin layer between region R2 and region R4.
[0040] The surfaces defining the external shape of the piezoelectric unit PU include the main surface 1b and the side surface 1c of the piezoelectric element 1. In other words, the surface of the piezoelectric element 1, excluding the main surface 1a, is included in the surfaces defining the external shape of the piezoelectric unit PU. The surfaces defining the outer shape of the piezoelectric unit PU include the main surface 21b and side surface 21c of the base material 21, and a portion of the main surface 21a. The portion of the main surface 21a includes the area exposed from the main surface 1a. Multiple internal electrodes 11, 13, and 15 are not exposed on the surface that defines the outer shape of the piezoelectric unit PU. Multiple external electrodes 3 and 5 are located between the piezoelectric element 1 and the substrate 21. Multiple external electrodes 3 and 5 are not exposed on the surface that defines the outer shape of the piezoelectric unit PU.
[0041] The base material 21 includes a pair of ends in the direction of the long axis of the base material 21. The piezoelectric unit PU is mounted to the device, for example, such that one of the pair of ends included in the base material 21 is a fixed end and the other end is a free end. In the device to which the piezoelectric unit PU is mounted, for example, when a driving voltage is applied to the piezoelectric element PE through a plurality of conductors 23, 25, the piezoelectric unit PU bends so that the other end of the base material 21 is displaced. In the piezoelectric unit PU, the diaphragm VP bends so that the piezoelectric element PE is on the inside of the curve. The one end of the base material 21 includes, for example, one of the short sides included in the main surface 21a. Therefore, region R3 is located closer to the fixed end than region R4. Region R1 is located closer to the fixed end than region R2. In the piezoelectric unit PU, for example, in the state after the polarization process of the piezoelectric element PE, that is, when no driving voltage is applied to the piezoelectric element PE, the piezoelectric element PE and the diaphragm VP may be bent such that the piezoelectric element PE is on the inside of the curve.
[0042] Referring to Figures 8 to 11, the configuration of one modified example of the diaphragm VP will be explained. Figures 8 and 9 are plan views showing one modified example of the diaphragm. Figures 10 and 11 are diagrams showing the cross-sectional configuration of one modified example of the diaphragm. In Figures 10 and 11, the hatching indicating the cross-section is omitted. The diaphragm VP includes a base material 21, a plurality of conductors 23, 25, a plurality of conductors 33, 35, and a plurality of via conductors 37. The plurality of conductors 33, 35 and the plurality of via conductors 37 are arranged on the base material 21. The diaphragm VP includes, for example, a pair of conductors 33, 35.
[0043] Each of the multiple conductors 33, 35 is positioned on the main surface 21b. The multiple via conductors 37 are located within the base material 21. The multiple via conductors 37 are arranged, for example, so that a pair of main surfaces 21a, 21b extend in directions opposite to each other. Conductor 23 is connected to a corresponding via conductor 37 among a plurality of via conductors 37. Conductor 33 is connected to the corresponding via conductor 37 as described above. The corresponding conductors 23 and 33 are connected to the corresponding via conductor 37 as described above, for example, both physically and electrically. The corresponding via conductor 37 as described above electrically connects conductor 23 and conductor 33. Conductor 25 is connected to another corresponding via conductor 37 among a plurality of via conductors 37. Conductor 35 is connected to another corresponding via conductor 37 as described above. The corresponding conductors 25 and 35 are connected, for example, physically and electrically, to the other corresponding via conductor 37 as described above. The other corresponding via conductor 37 as described above electrically connects conductor 25 and conductor 35.
[0044] Each of the plurality of conductors 33, 35 is electrically connected to a corresponding conductor among the plurality of conductors 23, 25. Each of the plurality of conductors 33, 35 is arranged to extend in a predetermined direction on the main surface 1b, for example. Each of the plurality of conductors 33, 35 is arranged to extend in the direction of the major axis, for example. The main surface 21b, like the main surface 21a, includes a pair of long sides and a pair of short sides. One end of each of the plurality of conductors 33, 35 is located, for example, on one of the short sides included in the main surface 21b. One end of each of the plurality of conductors 33, 35 may be located, for example, in the vicinity of the aforementioned short side included in the main surface 21b. Conductors 33 and 35 are separated from each other on the main surface 21b. Each of the multiple conductors 33, 35 is exposed when viewed from a direction perpendicular to the main surface 21b. Each of the multiple conductors 33, 35 is connected to, for example, a wiring member (not shown). The wiring member includes, for example, lead wires, cables, or connectors.
[0045] The multiple conductors 33, 35 and the multiple via conductors 37 are formed, for example, through a plating process, similar to the multiple conductors 23, 25. Each of the multiple conductors 33, 35 and the multiple via conductors 37 includes, for example, a plating layer formed on an activated pattern of the substrate 21. That is, each of the multiple conductors 33, 35 and the multiple via conductors 37 includes, for example, a plating layer. The activated pattern of the substrate 21 includes portions of the substrate 21 in contact with a plurality of conductors 33, 35 and portions in contact with a plurality of via conductors 37. Each of the plurality of conductors 33, 35 and the plurality of via conductors 37 may be formed by a laser direct structuring process. The plurality of conductors 33, 35 and the plurality of via conductors 37 include, for example, at least one selected from gold, nickel, tin, silver, copper, or aluminum.
[0046] As shown in Figure 12, the piezoelectric unit PU may include at least one electronic component EC. Figure 12 is a plan view showing one modified example of the piezoelectric unit according to this embodiment. At least one electronic component EC is mounted on the diaphragm VP. At least one electronic component EC is solder-mounted to the diaphragm VP, for example. In Figure 12, the solder fillet is not shown. At least one electronic component EC is connected to at least one of a plurality of conductors 23, 25, corresponding to the purpose of inserting the electronic component EC. At least one electronic component EC is, for example, inserted between a plurality of conductors 23, 25. At least one electronic component EC is, for example, connected to a plurality of conductors 23, 25. At least one electronic component EC is, for example, electrically connected to a plurality of conductors 23, 25. At least one electronic component EC includes, for example, a chip resistor, a chip capacitor, or a chip inductor. At least one electronic component EC is located, for example, on the region exposed from the main surface 1a. At least one electronic component EC may be located, for example, within the substrate 21 or on the main surface 1b.
[0047] As described above, in the piezoelectric unit PU, multiple external electrodes 3 and 5 are arranged in region R1 included in the main surface 1a facing the diaphragm VP. Multiple conductors 23 and 25 are arranged in region R3 included in the main surface 21a facing the piezoelectric element PE. Regions R1 and R3 face each other. External electrodes 3 and conductor 23 are connected to each other between the opposing piezoelectric element PE and the diaphragm VP. External electrodes 5 and conductor 25 are connected to each other between the opposing piezoelectric element PE and the diaphragm VP. The connection points between external electrodes 3 and conductor 23, and between external electrodes 5 and conductor 25, are located between the piezoelectric element PE and the diaphragm VP. Therefore, the connection points between external electrodes 3 and conductor 23, and between external electrodes 5 and conductor 25 are less likely to be exposed to the external environment. For example, even when exposed to a high temperature and high humidity environment, the piezoelectric unit PU is less likely to cause a short circuit in the piezoelectric element PE and the diaphragm VP. Regions R2 and R4, which are opposite each other, are connected to each other. The piezoelectric element PE and the diaphragm VP are connected at locations other than the connection points between the external electrode 3 and the conductor 23, and between the external electrode 5 and the conductor 25. The piezoelectric unit PU ensures the physical and electrical connection between the piezoelectric element PE and the diaphragm VP. In the piezoelectric unit PU, the connection point between region R2 and region R4 is located between the piezoelectric element PE and the diaphragm VP. Therefore, the connection point between region R2 and region R4 is less likely to be exposed to the external environment. For example, even when exposed to a high temperature and high humidity environment, the piezoelectric unit PU is less likely to experience a decrease in the connectivity between the piezoelectric element PE and the diaphragm VP. As a result, the piezoelectric unit (PU) reliably suppresses a decrease in reliability.
[0048] The piezoelectric unit PU may include a conductive member 31 that connects the corresponding external electrodes 3, 5 and conductors 23, 25, and a connecting member 41 that connects region R2 and region R4. The piezoelectric unit PU, which includes the conductive member 31 and the bonding member 41, further ensures the physical and electrical connection between the piezoelectric element PE and the diaphragm VP. Therefore, the piezoelectric unit PU, which includes the conductive member 31 and the bonding member 41, more reliably suppresses a decrease in reliability.
[0049] The piezoelectric element 1 may have a shape having a major axis and a minor axis when viewed from a direction perpendicular to the main surface 1a. Region R1 may be located at one end of the main surface 1a in the direction of the major axis. In a piezoelectric unit PU where region R1 is located at one end of the main surface 1a in the direction of the long axis, displacement of the piezoelectric unit PU is easily ensured.
[0050] The base material 21 may have a shape having a major axis and a minor axis when viewed from a direction perpendicular to the main surface 21a. Region R3 may be located at one end of the main surface 21a in the direction of the major axis. In a piezoelectric unit PU where region R3 is located at one end of the main surface 21a in the direction of the long axis, displacement of the piezoelectric unit PU is easily ensured.
[0051] Each of the multiple conductors 23, 25 may include a region exposed from the piezoelectric element PE when viewed from a direction perpendicular to the main surface 21a. In a piezoelectric unit PU in which each of the multiple conductors 23, 25 includes a region exposed from the piezoelectric element PE when viewed from a direction perpendicular to the main surface 21a, the multiple conductors 23, 25 and the wiring member can be easily connected.
[0052] The surface of the piezoelectric element 1, excluding the main surface 1a, may be included in the surfaces that define the outer shape of the piezoelectric unit PU. In a piezoelectric unit PU where the surface of the piezoelectric element 1, excluding the main surface 1a, is included in the surface defining the outer shape of the piezoelectric unit PU, the main surface 1a is less likely to be exposed to the external environment. Therefore, the connection points between the external electrode 3 and the conductor 23, the connection points between the external electrode 5 and the conductor 25, and the connection points between region R2 and region R4 are reliably less likely to be exposed to the external environment. As a result, the deterioration of the reliability of the piezoelectric unit PU is reliably suppressed.
[0053] Multiple external electrodes 3,5 do not necessarily have to be exposed on the surface that defines the outer shape of the piezoelectric unit PU. In a piezoelectric unit PU where multiple external electrodes 3 and 5 are not exposed on the surface defining the outer shape of the piezoelectric unit PU, the multiple external electrodes 3 and 5 are less likely to be exposed to the external environment. Therefore, the connection points between external electrode 3 and conductor 23, and the connection points between external electrode 5 and conductor 25 are reliably less likely to be exposed to the external environment. As a result, the deterioration of the reliability of the piezoelectric unit PU is reliably suppressed.
[0054] The piezoelectric unit PU may include an electronic component EC. In configurations where the piezoelectric unit PU includes an electronic component EC, for example, it is not necessary to mount the electronic component EC on the device to which the piezoelectric unit PU is attached. Therefore, a piezoelectric unit PU including an electronic component EC can simplify the configuration of the device to which the piezoelectric unit PU is attached.
[0055] The base material 21 may have a shape having a major axis and a minor axis when viewed from a direction perpendicular to the main surface 21a. The multiple via conductors V1 to V6 and the multiple connecting conductors 12, 14, 16 may be located closer to one end of the piezoelectric element 1 in the direction of the major axis. In a piezoelectric unit PU where multiple via conductors V1 to V6 and multiple connecting conductors 12, 14, and 16 are located near one end of the piezoelectric element 1 in the direction of the long axis, displacement of the piezoelectric unit PU is easily ensured.
[0056] The multiple internal electrodes 11, 13, and 15 do not necessarily have to be exposed on the surface of the piezoelectric element 1. In a piezoelectric unit PU in which multiple internal electrodes 11, 13, and 15 are not exposed on the surface of the piezoelectric element 1, for example, the multiple internal electrodes 11, 13, and 15 are less likely to come into contact with conductive members other than the multiple internal electrodes 11, 13, and 15. Therefore, electrical short circuits are less likely to occur in the piezoelectric unit PU. As a result, a decrease in the reliability of the piezoelectric unit PU is reliably suppressed.
[0057] The base material 21 may be made of resin. In a configuration where the base material 21 is made of resin, the base material 21 is more flexible than in a configuration where the base material 21 is made of metal. Therefore, in a piezoelectric unit PU where the base material 21 is made of resin, it is easier to ensure the displacement of the piezoelectric unit PU.
[0058] While embodiments and modifications of the present invention have been described above, the present invention is not necessarily limited to the embodiments and modifications described above, and various modifications are possible without departing from the spirit of the invention.
[0059] The piezoelectric unit PU is applied, for example, to a piezoelectric valve. A piezoelectric valve is, for example, installed in compressed air piping and has the function of maintaining a constant pressure in the piping. In addition to piezoelectric valves, the piezoelectric unit PU is applied to hubtics devices, acoustic devices, sensing devices, or liquid dispensing heads. Acoustic devices include, for example, speakers or buzzers. Liquid dispensing heads are included in, for example, printing equipment. The piezoelectric unit PU may also be placed in an IC card.
[0060] As can be seen from the embodiments and modifications described above, this specification includes disclosures of the following aspects. (Note 1) A piezoelectric element comprising a piezoelectric element and external electrodes disposed on the piezoelectric element, The device comprises a base material and a conductor disposed on the base material, and a diaphragm on which the piezoelectric element is disposed, The piezoelectric element has a first main surface facing the diaphragm, which includes a first main surface that includes a first region on which the external electrodes are arranged and a second region separate from the first region. The substrate includes a second main surface facing the piezoelectric element, which includes a third region on which the conductor is arranged and a fourth region separate from the third region. The first region and the third region face each other, and the second region and the fourth region face each other. A piezoelectric unit in which the external electrode and the conductor are connected to each other, and the second region and the fourth region are connected to each other. (Note 2) A conductive member connecting the external electrode and the conductor, The piezoelectric unit according to Appendix 1, further comprising a joining member connecting the second region and the fourth region. (Note 3) The piezoelectric element has a shape having a major axis and a minor axis when viewed from a direction perpendicular to the first main surface. The first region is a piezoelectric unit according to Appendix 1 or 2, located at one end of the first main surface in the direction of the long axis. (Note 4) The substrate has a shape having a long axis and a short axis when viewed from a direction perpendicular to the second main surface. The third region is a piezoelectric unit according to any one of the appendices 1 to 3, located at one end of the second main surface in the direction of the long axis. (Note 5) The piezoelectric unit according to any one of the appendices 1 to 4, wherein the conductor includes a region exposed from the piezoelectric element when viewed from a direction perpendicular to the second main surface. (Note 6) The piezoelectric unit according to any one of the appendices 1 to 5, wherein the surface of the piezoelectric element, excluding the first main surface, is included in the surface that defines the outer shape of the piezoelectric unit. (Note 7) The piezoelectric unit according to any one of the appendices 1 to 6, wherein the external electrode is not exposed on the surface that defines the outer shape of the piezoelectric unit. (Note 8) A piezoelectric unit according to any one of the appendices 1 to 7, further comprising an electronic component connected to the conductor. (Note 9) The piezoelectric unit according to any one of the appendices 1 to 8, further comprising an internal electrode and a via conductor connecting the external electrode and the internal electrode within the piezoelectric element. (Note 10) The piezoelectric unit as described in Appendix 9, wherein the internal electrodes are not exposed on the surface of the piezoelectric element. (Note 11) The substrate is a piezoelectric unit made of resin, as described in any one of appendices 1 to 10. [Explanation of symbols]
[0061] 1...Piezoelectric element, 1a...Main surface, 3,5...External electrodes, 11,13,15...Internal electrodes, V1,V2,V4,V5,V6...Via conductors, 21...Base material, 21a...Main surface, 23,25...Conductors, 31...Conductive member, 41...Bonding member, EC...Electronic component, PE...Piezoelectric element, PU...Piezoelectric unit, R1,R2...Regions included in the main surface of the piezoelectric element, R3,R4...Regions included in the main surface of the base material, VP...Diaphragm.
Claims
1. A piezoelectric element comprising a piezoelectric element and external electrodes disposed on the piezoelectric element, The device comprises a base material and a conductor disposed on the base material, and a diaphragm on which the piezoelectric element is disposed, The piezoelectric element has a first main surface facing the diaphragm, which includes a first main surface that includes a first region on which the external electrodes are arranged and a second region separate from the first region. The substrate includes a second main surface facing the piezoelectric element, which includes a third region on which the conductor is arranged and a fourth region separate from the third region. The first region and the third region face each other, and the second region and the fourth region face each other. A piezoelectric unit in which the external electrode and the conductor are connected to each other, and the second region and the fourth region are connected to each other.
2. A conductive member connecting the external electrode and the conductor, The piezoelectric unit according to claim 1, further comprising a joining member connecting the second region and the fourth region.
3. The piezoelectric element has a shape having a major axis and a minor axis when viewed from a direction perpendicular to the first main surface. The piezoelectric unit according to claim 1, wherein the first region is located at one end of the first main surface in the direction of the long axis.
4. The substrate has a shape having a long axis and a short axis when viewed from a direction perpendicular to the second main surface. The piezoelectric unit according to claim 1, wherein the third region is located at one end of the second main surface in the direction of the long axis.
5. The piezoelectric unit according to claim 1, wherein the conductor includes a region exposed from the piezoelectric element when viewed from a direction perpendicular to the second main surface.
6. The piezoelectric unit according to claim 1, wherein the surface of the piezoelectric element, excluding the first main surface, is included in the surface that defines the outer shape of the piezoelectric unit.
7. The piezoelectric unit according to claim 1, wherein the external electrode is not exposed on the surface that defines the outer shape of the piezoelectric unit.
8. The piezoelectric unit according to claim 1, further comprising an electronic component connected to the conductor.
9. The piezoelectric unit according to claim 1, wherein the piezoelectric element further includes an internal electrode and a via conductor connecting the external electrode and the internal electrode within the piezoelectric element.
10. The piezoelectric unit according to claim 9, wherein the internal electrode is not exposed on the surface of the piezoelectric element.
11. The piezoelectric unit according to claim 1, wherein the substrate is made of resin.