WO2023223955A1 - Piezoelectric element and ultrasonic transducer - Google Patents

Piezoelectric element and ultrasonic transducer Download PDF

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Publication number
WO2023223955A1
WO2023223955A1 PCT/JP2023/017878 JP2023017878W WO2023223955A1 WO 2023223955 A1 WO2023223955 A1 WO 2023223955A1 JP 2023017878 W JP2023017878 W JP 2023017878W WO 2023223955 A1 WO2023223955 A1 WO 2023223955A1
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WIPO (PCT)
Prior art keywords
piezoelectric element
outer edge
piezoelectric
lower electrode
electrode
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PCT/JP2023/017878
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French (fr)
Japanese (ja)
Inventor
優作 清水
悠佑 長田
清 山腰
隆文 福井
清彦 河野
Original Assignee
パナソニックＩｐマネジメント株式会社
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Publication of WO2023223955A1 publication Critical patent/WO2023223955A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
    • H10N30/853—Ceramic compositions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/88—Mounts; Supports; Enclosures; Casings

Definitions

  • the present disclosure relates to a piezoelectric element and an ultrasonic transducer, and more particularly to a piezoelectric element having a lower electrode and an upper electrode, and an ultrasonic transducer including the piezoelectric element.
  • Patent Document 1 describes an aerial ultrasonic transmitter/receiver using a piezoelectric element, which includes a piezoelectric ceramic, a silver electrode formed by sintering conductive paste provided on both sides of the piezoelectric ceramic, and a bottomed cylindrical case.
  • An ultrasonic transmitter/receiver (ultrasonic transducer) is disclosed.
  • An object of the present disclosure is to provide a piezoelectric element and an ultrasonic transducer that can increase the operating frequency of the piezoelectric element.
  • a piezoelectric element includes a metal substrate, a lower electrode, a piezoelectric layer, and an upper electrode.
  • the metal substrate contains at least iron and chromium.
  • the lower electrode is provided on the metal substrate.
  • the piezoelectric layer is provided on the lower electrode.
  • the upper electrode is provided on the piezoelectric layer.
  • the first outer edge of the lower electrode is located inside the second outer edge of the metal substrate.
  • the third outer edge of the piezoelectric layer is located inside the first outer edge of the lower electrode.
  • the fourth outer edge of the upper electrode is located inside the third outer edge of the piezoelectric layer.
  • An ultrasonic transducer includes the piezoelectric element, a diaphragm section, a first conductive member, a second conductive member, a first conductive joint, a second conductive joint, Equipped with.
  • the diaphragm portion is joined to the metal substrate of the piezoelectric element.
  • the first conductive member is connected to the lower electrode of the piezoelectric element.
  • the second conductive member is connected to the upper electrode of the piezoelectric element.
  • the first conductive joint portion joins the lower electrode and the first conductive member.
  • the second conductive joint portion joins the upper electrode and the second conductive member.
  • FIG. 1 is a plan view of a piezoelectric element according to a first embodiment.
  • FIG. 2 is a sectional view taken along line A1-A1 in FIG. 1 regarding the piezoelectric element same as above.
  • FIG. 3 is an explanatory diagram of a method of manufacturing the same piezoelectric element as above.
  • FIG. 4 is a plan view of an ultrasonic transducer including the same piezoelectric element as above.
  • FIG. 5 is a cross-sectional view taken along the line A2-A2 in FIG. 4 regarding an ultrasonic transducer including the piezoelectric element mentioned above.
  • FIG. 6 is a plan view of the piezoelectric element according to the second embodiment.
  • FIG. 7 is a sectional view taken along line A3-A3 in FIG.
  • FIG. 8 is a plan view of an ultrasonic transducer including the same piezoelectric element as above.
  • FIG. 9 is a sectional view taken along the line A4-A4 in FIG. 8 regarding an ultrasonic transducer including the piezoelectric element mentioned above.
  • FIG. 10 is a plan view of a piezoelectric element according to Embodiment 3.
  • FIG. 11 is a sectional view taken along line A5-A5 in FIG. 10 regarding the piezoelectric element same as above.
  • FIG. 12 is a sectional view of an ultrasonic transducer according to Embodiment 4.
  • the piezoelectric element 1 includes a metal substrate 2, an alumina layer 3, a lower electrode 4, a piezoelectric layer 5, and an upper electrode 6. , is provided.
  • Metal substrate 2 contains at least iron and chromium.
  • the lower electrode 4 is provided on the metal substrate 2.
  • the piezoelectric layer 5 is provided on the lower electrode 4 .
  • the upper electrode 6 is provided on the piezoelectric layer 5.
  • the outer edge of the piezoelectric element 1 has, for example, a square shape.
  • “In plan view” has the same meaning as "as seen from above the metal substrate 2 in the direction along the thickness direction of the metal substrate 2.” In other words, "in plan view” has the same meaning as "in plan view from the thickness direction of the metal substrate 2.”
  • the ultrasonic transducer 100 includes a piezoelectric element 1, a diaphragm section 120, a first lead wire 141, a second lead wire 142, a first conductive joint 131, and a first conductive joint 131. 2 conductive joint portion 132.
  • the first lead wire 141 constitutes a first conductive member
  • the second lead wire 142 constitutes a second conductive member.
  • the diaphragm section 120 is joined to the metal substrate 2 of the piezoelectric element 1. More specifically, the diaphragm section 120 is joined to the metal substrate 2 of the piezoelectric element 1 by the joining section 105.
  • the first lead wire 141 is connected to the lower electrode 4 of the piezoelectric element 1 .
  • the second lead wire 142 is connected to the upper electrode 6 of the piezoelectric element 1 .
  • the first conductive joint 131 joins the lower electrode 4 and the first lead wire 141.
  • the second conductive joint 132 joins the upper electrode 6 and the second lead wire 142.
  • the ultrasonic transducer 100 transmits ultrasonic waves by converting a first electric signal (AC voltage with a predetermined drive frequency) into a first mechanical vibration in the piezoelectric element 1.
  • a first electric signal AC voltage with a predetermined drive frequency
  • the diaphragm part 120 vibrates in the vertical direction due to the horizontal expansion and contraction movement of the piezoelectric element 1. It vibrates in the thickness direction, and ultrasonic waves are transmitted.
  • the ultrasonic transducer 100 includes, for example, a piezoelectric element 1 that accompanies vibration in the thickness direction of the diaphragm section 120 when a reflected wave of an ultrasonic wave transmitted from the ultrasonic transducer 100 is incident on the diaphragm section 120. is converted into a second electrical signal in the piezoelectric element 1.
  • the diaphragm portion 120 has a flat plate shape.
  • the ultrasonic transducer 100 further includes a case 101 housing the piezoelectric element 1.
  • Case 101 has a bottom plate portion 102 and a cylinder portion 103.
  • the bottom plate portion 102 has a flat plate shape.
  • the cylindrical portion 103 protrudes from the periphery of one surface of the bottom plate portion 102 in the thickness direction of the bottom plate portion 102 and surrounds the piezoelectric element 1 .
  • a portion of the bottom plate portion 102 surrounded by the cylindrical portion 103 also serves as a diaphragm portion 120.
  • the ultrasonic transducer 100 includes a sound absorbing member 150 disposed above the piezoelectric element 1 in the case 101, and a sealing portion disposed on the sound absorbing member 150 in the case 101. 160. Note that in FIG. 4, illustration of the sound absorbing member 150 and the sealing part 160 is omitted.
  • the metal substrate 2 has a flat plate shape.
  • the metal substrate 2 has an upper surface (first main surface) 21 and a lower surface (second main surface) 22, as shown in FIG.
  • the outer edge 20 of the metal substrate 2 has, for example, a square shape (for example, a rectangular shape) in plan view.
  • the thickness of the metal substrate 2 is, for example, 0.1 mm, but is not limited thereto.
  • the metal substrate 2 contains iron, chromium, and aluminum.
  • the metal substrate 2 is a stainless steel substrate containing iron as a main component, and contains chromium and aluminum in addition to iron.
  • the stainless steel substrate constituting the metal substrate 2 is, for example, an aluminum-containing ferritic stainless steel substrate.
  • the aluminum-containing ferritic stainless steel substrate has, for example, a chromium content of 18 wt% and an aluminum content of 3 wt%.
  • the content of chromium is not limited to 18 wt%.
  • the aluminum content is not limited to 3 wt%.
  • the metal substrate 2 may further contain elements other than iron, chromium, and aluminum.
  • the alumina layer 3 is provided on the upper surface 21 (see FIG. 2) of the metal substrate 2. As shown in FIG. 1, the outer edge 30 of the alumina layer 3 has a square shape (for example, a rectangular shape) in plan view. The thickness of the alumina layer 3 is, for example, 1 ⁇ m, but is not limited thereto.
  • the main phase of alumina forming the alumina layer 3 is a ⁇ -alumina phase. That is, the alumina layer 3 is mainly formed of particles of ⁇ -alumina phase. "Mainly formed of ⁇ -alumina phase particles” means that more than 50% by weight of the alumina layer 3 is formed of ⁇ -alumina phase particles.
  • the crystalline phase of the material (particles) constituting the alumina layer 3 can be identified by measuring the X-ray diffraction pattern of the exposed portion of the alumina layer 3 using an X-ray diffraction device.
  • the upper surface of the alumina layer 3 includes a part of the surface of a plurality of scale-like particles of the alumina layer 3. Considering the SEM (Scanning Electron Microscope) image of the upper surface of the alumina layer 3 and the measurement results of the X-ray diffraction pattern, it is estimated that the scale-like particles are ⁇ -alumina particles.
  • the lower electrode 4 is provided on the upper surface 31 (see FIG. 2) of the alumina layer 3. As shown in FIG. 1, the outer edge 40 of the lower electrode 4 has, for example, a rectangular shape in plan view, but the shape is not limited to this.
  • the thickness of the lower electrode 4 is, for example, 3 ⁇ m, but is not limited thereto.
  • the material of the lower electrode 4 includes, for example, silver (Ag) and palladium (Pd). More specifically, the material of the lower electrode 4 includes, for example, an Ag--Pd alloy.
  • the piezoelectric layer 5 is provided on the upper surface 41 (see FIG. 2) of the lower electrode 4. As shown in FIG. 1, the outer edge 50 of the piezoelectric layer 5 has, for example, a rectangular shape in plan view, but the shape is not limited to this.
  • the thickness of the piezoelectric layer 5 is, for example, 5 ⁇ m or more and 40 ⁇ m or less, preferably 10 ⁇ m or more and 30 ⁇ m or less.
  • the thickness of the piezoelectric layer 5 is, for example, 11 ⁇ m, but is not limited thereto.
  • the material of the piezoelectric layer 5 includes, for example, Pb, Zr, Zn, Nb, and O, but is not limited thereto. More specifically, the material of the piezoelectric layer 5 includes, for example, Pb 1.015 Zr 0.44 (Zn 1/3 Nb 2/3 ) 0.10 O 3.015; The composition ratio is not limited to this.
  • the upper electrode 6 is provided on the upper surface 51 (see FIG. 2) of the piezoelectric layer 5. As shown in FIG. 1, the outer edge 60 of the upper electrode 6 has, for example, a rectangular shape in plan view, but the shape is not limited to this.
  • the thickness of the upper electrode 6 is, for example, 3 ⁇ m, but is not limited thereto.
  • the material of the upper electrode 6 includes, for example, Ag and Pd. More specifically, the material of the upper electrode 6 includes, for example, an Ag--Pd alloy.
  • the outer edge 40 (first outer edge) of the lower electrode 4 is , located inside the outer edge 20 (second outer edge) of the metal substrate 2.
  • the outer edge 50 (third outer edge) of the piezoelectric layer 5 is located inside the outer edge 40 of the lower electrode 4.
  • the outer edge 60 (fourth outer edge) of the upper electrode 6 is located inside the outer edge 50 of the piezoelectric layer 5.
  • the area of the upper surface 41 (see FIG. 2) of the lower electrode 4 is smaller than the area of the upper surface 21 (see FIG.
  • orthogonal coordinates having three axes, the X-axis, Y-axis, and Z-axis that are orthogonal to each other, are defined, and in particular, the axis along the thickness direction of the metal substrate 2 is referred to as the "Z-axis".
  • the axis along the longitudinal direction of the metal substrate 2 is referred to as the "X axis”
  • the axis along the width direction of the metal substrate 2 is referred to as the "Y axis”.
  • the X-axis, Y-axis, and Z-axis are all virtual axes, and the arrows indicating "X,” “Y,” and “Z” in the drawings are only shown for explanation. , none of which involve substance.
  • a part of the portion 411 of the upper surface 41 of the lower electrode 4 that is not covered with the piezoelectric layer 5 also serves as a terminal portion for external connection.
  • the distance between the outer edge 40 of the lower electrode 4 and the outer edge 50 of the piezoelectric layer 5 is not uniform in plan view, and the first width W1 is wider than the second width W2. wide.
  • the first width W1 is the width between the outer edge 40 of the lower electrode 4 and the outer edge 50 of the piezoelectric layer 5 at the first end of the piezoelectric element 1 in the direction along the X axis.
  • the second width W2 is the width between the outer edge 40 of the lower electrode 4 and the outer edge 50 of the piezoelectric layer 5 at the second end of the piezoelectric element 1 in the direction along the X axis.
  • a metal substrate 2A (see FIG. 3) from which a large number of metal substrates 2 can be produced is prepared, and then a first step, a second step, and a third step are performed. , the fourth step, the fifth step, and the sixth step are performed sequentially.
  • the metal substrate 2A containing iron, chromium, and aluminum is heat-treated in the atmosphere to form an alumina layer 3A (see FIG. 3) that covers the entire upper surface 21A of the metal substrate 2A.
  • the heat treatment temperature is, for example, 850° C. or more and 900° C. or less
  • the heat treatment time is, for example, 2 hours.
  • a second alumina layer may be formed that covers the entire lower surface 22A of the metal substrate 2A.
  • a first pattern portion including a plurality of lower electrode material portions is formed on the alumina layer 3A by screen printing a paste containing the material of the lower electrode 4 (eg, Ag-Pd alloy paste).
  • a second pattern section including a plurality of piezoelectric material sections is formed on the first pattern section by printing a paste containing the material of the piezoelectric layer 5 with a metal mask.
  • the material of the piezoelectric layer 5 is, for example, Pb 1.015 Zr 0.44 (Zn 1/3 Nb 2/3 ) 0.10 O 3.015 .
  • a third pattern section including a plurality of upper electrode material sections is formed on the second pattern section by screen printing a paste containing the material of the upper electrode 6 (for example, Ag-Pd alloy paste).
  • a structure 1A including a plurality of piezoelectric elements 1 is formed (see FIG. 3).
  • the structure 1A is separated into individual piezoelectric elements 1 by dicing the structure 1A with a dicing blade 200 (see FIG. 3).
  • the metal substrate 2A and the alumina layer 3A are present in the dicing lane, but the lower electrode pattern section 4A, the piezoelectric layer pattern section 5A, and the upper electrode pattern section 6A are not present.
  • the thickness H2 of the dicing blade 200 is smaller than the first distance L1 between two adjacent lower electrodes 4 across the dicing lane in the structure 1A. Further, the thickness H2 of the dicing blade 200 is smaller than the second distance L2 between two adjacent piezoelectric layers 5 across the dicing lane in the structure 1A.
  • the thickness H2 of the dicing blade 200 is smaller than the third distance L3 between two adjacent upper electrodes 6 across the dicing lane in the structure 1A. As described above, in the sixth step, the relationship of thickness H2 of the dicing blade 200 ⁇ first distance L1 ⁇ second distance L2 ⁇ third distance L3 is satisfied.
  • the method for manufacturing the piezoelectric element 1 cracking and chipping of the lower electrode 4, piezoelectric layer 5, and upper electrode 6 are unlikely to occur in the sixth step. Therefore, according to the method for manufacturing the piezoelectric element 1, it is possible to improve the manufacturing yield. In addition, in the piezoelectric element 1, since it is possible to prevent a handling tool from coming into contact with the lower electrode 4, the piezoelectric layer 5, and the upper electrode 6 during handling, the lower electrode 4, the piezoelectric layer 5, and the upper Damage to the electrode 6 can be prevented. Therefore, in the piezoelectric element 1, the piezoelectric layer 5 can be made thinner than a bulk type piezoelectric element.
  • the structure 1A is diced using the dicing blade 200, but the method is not limited to the method using the dicing blade 200. Dicing may also be performed. In both the method using the dicing blade 200 and laser dicing, the first screen printing mask used in the second step, the first A metal mask used in the third step and a second screen printing mask used in the fourth step are designed.
  • the ultrasonic transducer 100 is configured to be capable of both transmitting (transmitting) ultrasonic waves and receiving (receiving) ultrasonic waves.
  • the ultrasonic transducer 100 is used, for example, as an ultrasonic sensor mounted on a vehicle such as an automobile to detect objects (obstacles, etc.) around the vehicle.
  • the ultrasonic sensor includes, for example, an ultrasonic transducer 100, a drive circuit, and a signal processing circuit.
  • the ultrasonic sensor is, for example, a TOF (Time of Flight) type ultrasonic sensor.
  • the drive circuit applies an electric signal to the piezoelectric element 1 of the ultrasonic transducer 100 to cause the ultrasonic transducer 100 to transmit ultrasonic waves.
  • the signal processing circuit processes an electrical signal output from the piezoelectric element 1 when the ultrasonic transducer 100 receives a reflected wave of an ultrasonic wave.
  • the signal processing circuit detects, for example, at least one of the presence or absence of an object within the detection area of the ultrasonic sensor and the distance from the ultrasonic transducer 100 to the object.
  • the ultrasonic transducer 100 of the ultrasonic sensor is attached to the bumper of an automobile, for example.
  • the ultrasonic transducer 100 has, for example, a vertical direction in the X-axis direction (the left-right direction in FIG. 4) and a vertical direction in the Y-axis direction (the vertical direction in FIG. 4).
  • the ultrasonic transducer 100 is installed so that the direction is horizontal, and the Z-axis direction (direction perpendicular to the plane of the paper in FIG. 4) is the detection direction (transmission/reception direction of ultrasonic waves).
  • the mounting direction of the ultrasonic transducer 100 can be changed as appropriate depending on the use of the ultrasonic transducer 100, for example.
  • the ultrasonic transducer 100 may include at least one of a drive circuit and a signal processing circuit.
  • the case 101 has a cylindrical shape with a bottom. In plan view, the outer edge of the case 101 has a circular shape.
  • the diaphragm section 120 has an upper surface 121 and a lower surface 122, as shown in FIG.
  • the thickness of the diaphragm portion 120 is, for example, 0.3 mm or more and 1.0 mm or less, and is, for example, 0.9 mm.
  • the outer diameter of the case 101 is, for example, 14 mm, but is not limited to this, and may be, for example, 15.5 mm.
  • the length of the case 101 in the Z-axis direction is, for example, 9 mm, but is not limited thereto.
  • the lower surface 122 of the diaphragm portion 120 constitutes an ultrasonic wave transmission/reception surface.
  • the material of the case 101 is, for example, an aluminum alloy, but is not limited thereto, and may be, for example, a magnesium alloy, stainless steel, a titanium alloy, or an engineered plastic.
  • the diaphragm portion 120 has a first maximum length R1 in the first direction (X-axis direction) that is larger than a second maximum length R2 in the second direction (Y-axis direction). It has a long shape. Thereby, in the ultrasonic transducer 100, the directivity angle in the X-axis direction can be narrower than the directivity angle in the Y-axis direction.
  • the first maximum length R1 is 12.6 mm
  • the second maximum length R2 is 8 mm, but is not limited to these values.
  • the joint 105 is interposed between the lower surface 22 of the metal substrate 2 of the piezoelectric element 1 and the upper surface 121 of the diaphragm section 120.
  • the material of the bonding portion 105 is, for example, a resin adhesive, a conductive bonding material, or DAF (Die Attach Film).
  • the resin adhesive includes, for example, an epoxy adhesive.
  • the conductive bonding material includes, for example, conductive paste (silver paste, etc.).
  • first lead wire 141 is connected to the lower electrode 4 of the piezoelectric element 1.
  • the second lead wire 142 constitutes a second conductive member connected to the upper electrode 6 of the piezoelectric element 1 .
  • a first end of the first lead wire 141 is joined to the lower electrode 4 by the first conductive joint 131 and is electrically connected to the lower electrode 4 .
  • a first end of the second lead wire 142 is joined to the upper electrode 6 by the second conductive joint 132 and is electrically connected to the upper electrode 6 .
  • the first lead wire 141 and the second lead wire 142 are flexible electric wires. A portion of the first lead wire 141 and a portion of the second lead wire 142 are led out of the case 101. The second end of the first lead wire 141 and the second end of the second lead wire 142 are connected to, for example, a drive circuit included in the ultrasonic sensor and a signal processing circuit included in the ultrasonic sensor.
  • the material of the first conductive joint 131 and the second conductive joint 132 includes, for example, solder.
  • the ultrasonic transducer 100 when the ultrasonic transducer 100 is used for transmitting ultrasonic waves, the ultrasonic transducer 100 is connected to a drive circuit. Furthermore, in the ultrasonic sensor, when the ultrasonic transducer 100 is used for receiving ultrasonic waves, the ultrasonic transducer 100 is connected to a signal processing circuit.
  • the sound absorbing member 150 is arranged above the piezoelectric element 1 in the case 101.
  • the material of the sound absorbing member 150 includes, for example, foam. Examples of the foam include urethane foam and silicone foam.
  • the sealing section 160 is arranged on the sound absorbing member 150 within the case 101.
  • the material of the sealing part 160 includes, for example, silicone resin.
  • the piezoelectric element 1 according to the first embodiment includes a metal substrate 2 containing iron, chromium, and aluminum.
  • the outer edge 40 (first outer edge) of the lower electrode 4 is located inside the outer edge 20 (second outer edge) of the metal substrate 2
  • the outer edge 50 (third outer edge) is located inside the outer edge 40 of the lower electrode 4
  • the outer edge 60 (fourth outer edge) of the upper electrode 6 is located inside the outer edge 50 (third outer edge) of the piezoelectric layer 5.
  • the piezoelectric element 1 according to the first embodiment it is possible to increase the operating frequency (resonant frequency) of the piezoelectric element 1. More specifically, in the piezoelectric element 1 according to the first embodiment, since the piezoelectric layer 5 can be made thinner, the resonance frequency of the piezoelectric element 1 can be made higher, and the driving frequency can be made higher. becomes possible.
  • the piezoelectric element 1 according to the first embodiment includes an alumina layer 3 interposed between the lower electrode 4 and the metal substrate 2, and the upper surface 31 of the alumina layer 3 has a plurality of scale-like shapes that the alumina layer 3 has. Since the lower electrode 4 includes a part of the surface of the particles, peeling of the lower electrode 4 can be suppressed.
  • the alumina layer 3 covers the entire upper surface 21 of the metal substrate 2, it is possible to improve piezoelectric characteristics. More specifically, in the piezoelectric element 1 according to the first embodiment, it is possible to suppress thermal diffusion between the metal substrate 2 and the piezoelectric layer 5 during manufacturing, and it is possible to improve the piezoelectric characteristics.
  • the ultrasonic transducer 100 includes the piezoelectric element 1 and the diaphragm portion 120 joined to the metal substrate 2 of the piezoelectric element 1. It becomes possible to increase the operating frequency (resonant frequency). Thereby, in the ultrasonic transducer 100, it becomes possible to make the drive frequency of the piezoelectric element 1 higher, and it becomes possible to narrow the directivity angle of the ultrasonic waves. Therefore, for example, when an ultrasonic sensor including the ultrasonic transducer 100 is installed and used in a car, it is possible to suppress the ultrasonic waves transmitted from the ultrasonic transducer 100 from entering the road surface, curb, etc.
  • FIGS. 6 and 7 A piezoelectric element 1a according to the second embodiment will be described with reference to FIGS. 6 and 7, and then an ultrasonic transducer 100a including the piezoelectric element 1a will be described with reference to FIGS. 8 and 9.
  • the same components as those of the piezoelectric element 1 according to the first embodiment are given the same reference numerals, and the description thereof will be omitted.
  • the ultrasonic transducer 100a according to the second embodiment the same components as those in the ultrasonic transducer 100 according to the first embodiment (see FIGS. 4 and 5) are given the same reference numerals, and the description thereof will be omitted as appropriate.
  • the piezoelectric element 1a according to the second embodiment is different from the first embodiment in that it further includes a terminal electrode 7 and a wiring part 8. This is different from the piezoelectric element 1 (see FIGS. 1 and 2).
  • the terminal electrode 7 is provided on the piezoelectric layer 5 and is separated from the upper electrode 6. More specifically, the terminal electrode 7 is provided on the upper surface 51 of the piezoelectric layer 5 and is separated from the upper electrode 6 in the X-axis direction. A gap 9 is formed between the terminal electrode 7 and the upper electrode 6. The portion of the terminal electrode 7 that is connected to the wiring portion 8 is not surrounded by the upper electrode 6 in the X-axis direction, for example.
  • the terminal electrode 7 is arranged on the upper surface 51 of the piezoelectric layer 5 at the first end in the direction along the X-axis.
  • the terminal electrode 7 is located inside the outer edge 50 of the piezoelectric layer 5 in plan view.
  • the terminal electrode 7 has, for example, a square shape, but is not limited to this, and may have a circular shape.
  • the thickness of the terminal electrode 7 is the same as the thickness of the upper electrode 6.
  • the thickness of the terminal electrode 7 is the same as the thickness of the upper electrode 6
  • the thickness of the terminal electrode 7 is 95% of the thickness of the upper electrode 6. This includes cases where the thickness is within a range of 105% or more.
  • the first height from the upper surface 21 of the metal substrate 2 to the upper surface 71 of the terminal electrode 7 is It is the same as the second height from the upper surface 21 to the upper surface 61 of the upper electrode 6.
  • the first height being the same as the second height is not limited to strictly the same case, but the first height is within the range of 95% or more and 105% or less of the second height. Including some cases.
  • the material of the terminal electrode 7 is the same as that of the upper electrode 6, and includes, for example, Ag and Pd.
  • the wiring section 8 is provided across the upper surface 41 of the lower electrode 4, the side surface 53 of the piezoelectric layer 5, and the upper surface 51 of the piezoelectric layer 5, and connects the lower electrode 4 and the terminal electrode 7. Therefore, the wiring section 8 includes a portion 81 formed on the upper surface 51 of the piezoelectric layer 5. The wiring portion 8 is not formed on the lower surface 52 of the piezoelectric layer 5.
  • the material of the wiring part 8 is the same as the material of the upper electrode 6 and the material of the terminal electrode 7, and includes, for example, Ag and Pd.
  • the wiring portion 8 is located inside the outer edge 20 of the metal substrate 2 in plan view.
  • the width of the wiring portion 8 in the Y-axis direction is narrower than the width of the terminal electrode 7 in the Y-axis direction.
  • the wiring portion 8 has an inverted L shape when viewed from the side in the Y-axis direction.
  • the terminal electrode 7 and the wiring portion 8 are formed in the same process as the upper electrode 6 by screen printing.
  • the manufacturing method of the piezoelectric element 1a is almost the same as the manufacturing method of the piezoelectric element 1, and instead of the screen mask used in the fourth step in the manufacturing method of the piezoelectric element 1, an opening for forming the upper electrode 6 and a terminal electrode 7 are used. A screen mask having an opening for forming the wiring portion 8 and an opening for forming the wiring portion 8 is used.
  • the third pattern portion includes a plurality of terminal electrode material portions and a plurality of wiring material portions in addition to the plurality of upper electrode material portions.
  • the lower electrode pattern portion including the plurality of lower electrodes 4 is formed by firing the first pattern portion, the second pattern portion, and the third pattern portion at a predetermined firing temperature (for example, 875° C.).
  • a piezoelectric layer pattern section 5A (see FIG. 3) including a plurality of piezoelectric layers 5, an upper electrode pattern section 6A (see FIG. 3) including a plurality of upper electrodes 6, and a plurality of terminal electrodes 7.
  • a terminal electrode pattern section including a terminal electrode pattern section and a wiring pattern section including a plurality of wiring sections 8 are formed.
  • a structure including a plurality of piezoelectric elements 1a is formed.
  • the ultrasonic transducer 100a according to the second embodiment is different from the embodiment in that the first conductive joint 131a is disposed on the terminal electrode 7. This is different from the ultrasonic transducer 100 according to No. 1 (see FIGS. 4 and 5).
  • the first lead wire 141 and the terminal electrode 7 are joined by the first conductive joint 131a.
  • the material of the first conductive joint 131a includes, for example, solder.
  • the piezoelectric element 1a according to the second embodiment includes a metal substrate 2 containing iron, chromium, and aluminum.
  • the outer edge 40 of the lower electrode 4 is located inside the outer edge 20 of the metal substrate 2
  • the outer edge 50 of the piezoelectric layer 5 is located inside the outer edge 40 of the lower electrode 4.
  • the outer edge 60 of the upper electrode 6 is located inside the outer edge 50 of the piezoelectric layer 5, and the terminal electrode 7 and the wiring portion 8 are located inside the outer edge 20 of the metal substrate 2.
  • the piezoelectric element 1a according to the second embodiment it is possible to increase the operating frequency (resonant frequency) of the piezoelectric element 1a. More specifically, in the piezoelectric element 1a according to the second embodiment, the piezoelectric layer 5 can be made thinner, similar to the piezoelectric element 1 according to the first embodiment, so that the resonant frequency of the piezoelectric element 1a can be made higher. This makes it possible to increase the driving frequency.
  • the piezoelectric element 1a includes the terminal electrode 7 and the wiring part 8, and since the terminal electrode 7 and the wiring part 8 are located inside the outer edge 20 of the metal substrate 2, there is no need to form a folded electrode. Manufacturing becomes easier, and it becomes possible to prevent damage to the terminal electrode 7 and wiring portion 8 during handling of the piezoelectric element 1a.
  • the first height from the upper surface 21 of the metal substrate 2 to the upper surface 71 of the terminal electrode 7 is the same as the second height from the upper surface 21 of the metal substrate 2 to the upper surface 61 of the upper electrode 6.
  • mounting on a flexible printed wiring board including a first lead electrode (first conductor part) and a second lead electrode (second conductor part) becomes easier, and connection reliability can be improved.
  • the first lead electrode (first conductor part) and the second lead electrode (second conductor part) included in the flexible printed wiring board are connected to the first lead wire 141.
  • the second lead wire 142 it is joined to the terminal electrode 7 and the upper electrode 6 of the piezoelectric element 1a by the first conductive joint 131a and the second conductive joint 132.
  • the terminal electrode 7 is located inside the outer edge 50 of the piezoelectric layer 5 in plan view.
  • the wiring portion 8 includes a portion 81 provided on the upper surface 51 of the piezoelectric layer 5 .
  • the terminal electrode 7 connected to the lower electrode 4 is arranged on the upper surface 51 of the piezoelectric layer 5 without adopting the folded electrode structure disclosed in Patent Document 1. It is possible to realize the following configuration.
  • the ultrasonic transducer 100a includes the piezoelectric element 1a and the diaphragm portion 120 joined to the metal substrate 2 of the piezoelectric element 1a. It becomes possible to increase the operating frequency (resonant frequency). Thereby, in the ultrasonic transducer 100a, it becomes possible to increase the driving frequency of the piezoelectric element 1a, and it becomes possible to narrow the directivity angle of the ultrasonic waves. Therefore, for example, when an ultrasonic sensor including the ultrasonic transducer 100a is installed and used in a car, it is possible to suppress the ultrasonic waves transmitted from the ultrasonic transducer 100a from entering the road surface and being reflected. Thereby, it becomes possible to improve the S/N ratio of the ultrasonic sensor, and it becomes possible to further increase the distance at which an object can be detected.
  • the first height from the upper surface 21 of the metal substrate 2 to the upper surface 71 of the terminal electrode 7 in the piezoelectric element 1a is from the upper surface 21 of the metal substrate 2 to the upper surface of the upper electrode 6. It is the same as the second height up to 61.
  • the first lead wire of the flexible printed wiring board is used instead of the first lead wire 141 and the second lead wire 142 as the first conductive member and the second conductive member. (first conductor part) and second lead electrode (second conductor part), mounting on a flexible printed wiring board becomes easy and connection reliability can be improved.
  • FIG. 10 A piezoelectric element 1b according to Embodiment 3 will be described with reference to FIG. 10.
  • the same components as those of the piezoelectric element 1 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted as appropriate.
  • the piezoelectric element 1b according to the third embodiment is different from the piezoelectric element 1 according to the first embodiment in that the piezoelectric layer 5 has an opening 54 that exposes a part of the upper surface 41 of the lower electrode 4. do.
  • the opening 54 of the piezoelectric layer 5 is formed along the thickness direction of the piezoelectric layer 5.
  • the opening shape of the opening portion 54 is square, but is not limited to this, and may be circular, for example.
  • a portion of the lower electrode 4 (portion 411b) exposed through the opening 54 of the piezoelectric layer 5 constitutes a terminal portion.
  • the method for manufacturing the piezoelectric element 1b is substantially the same as the method for manufacturing the piezoelectric element 1, and by changing the pattern of the screen mask used in the third step in the method for manufacturing the piezoelectric element 1, the openings 54 of the piezoelectric layer 5 are can be formed.
  • the piezoelectric element 1b according to the third embodiment includes a metal substrate 2 containing iron, chromium, and aluminum.
  • the outer edge 40 of the lower electrode 4 is located inside the outer edge 20 of the metal substrate 2
  • the outer edge 50 of the piezoelectric layer 5 is located inside the outer edge 40 of the lower electrode 4.
  • the outer edge 60 of the upper electrode 6 is located inner than the outer edge 50 of the piezoelectric layer 5 .
  • the piezoelectric layer 5 can be made thinner, similar to the piezoelectric element 1 according to the first embodiment, so that the resonant frequency of the piezoelectric element 1b can be made higher. This makes it possible to increase the driving frequency.
  • the piezoelectric element 1b according to the third embodiment since the piezoelectric layer 5 has an opening 54 that exposes a part of the upper surface 41 of the lower electrode 4, the part of the upper surface 41 of the lower electrode 4 can be used as a terminal part. Can be used for both purposes. As a result, the piezoelectric element 1b according to the third embodiment can have a narrower region functioning as a terminal part than the piezoelectric element 1 according to the first embodiment, and can suppress variations in characteristics during use. It becomes possible.
  • Embodiment 4 An ultrasonic transducer 100c according to Embodiment 4 will be described below with reference to FIG. 12. Regarding the ultrasonic transducer 100c according to the fourth embodiment, the same components as those of the ultrasonic transducer 100 according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.
  • the ultrasonic transducer 100c according to the fourth embodiment includes a conical diaphragm section 120c with an open bottom in place of the diaphragm section 120 in the ultrasonic transducer 100 according to the first embodiment.
  • the ultrasonic transducer 100c according to the fourth embodiment includes a case 101c instead of the case 101 in the ultrasonic transducer 100 according to the first embodiment.
  • the piezoelectric element 1 and the diaphragm portion 120c are housed in the case 101c.
  • the diaphragm portion 120c is joined to the lower surface 22 of the metal substrate 2 of the piezoelectric element 1.
  • the diaphragm portion 120c is a separate member from the case 101c and is separated from the case 101c.
  • the case 101c includes a pedestal 170, a cap 106, and a mesh member 165.
  • the ultrasonic transducer 100c also includes a support portion 180 that protrudes from the pedestal 170 and supports the piezoelectric element 1.
  • the ultrasonic transducer 100c also includes a first conductive joint 131 and a second conductive joint 132, a first lead wire 141 and a second lead wire 142, a first lead terminal 191 and a second lead terminal 192. , is provided.
  • the pedestal 170 is disc-shaped.
  • the material of the pedestal 170 is, for example, an aluminum alloy, but is not limited thereto, and may be, for example, a magnesium alloy, stainless steel, a titanium alloy, or an engineered plastic.
  • the cap 106 has a bottomed cylindrical shape having a bottom wall 161 and a cylindrical peripheral wall 162, and is fixed to the pedestal 170 so as to cover the piezoelectric element 1 and the diaphragm portion 120c.
  • the material of the cap 106 is, for example, an aluminum alloy, but is not limited thereto, and may be, for example, a magnesium alloy, stainless steel, a titanium alloy, or an engineered plastic.
  • the mesh member 165 is disposed within a window hole 163 formed in the bottom wall 161 of the cap 106, and is located in front of the diaphragm portion 120c.
  • the mesh member 165 has a plurality of openings 166 to allow ultrasound to pass therethrough.
  • the first lead wire 141 and the second lead wire 142 are flexible electric wires.
  • the first end of the first lead wire 141 is joined and electrically connected to the lower electrode 4 of the piezoelectric element 1 by the first conductive joint 131, and the second end of the first lead wire 141 The end is joined to the first lead terminal 191 and electrically connected.
  • the first end of the second lead wire 142 is joined and electrically connected to the upper electrode 6 of the piezoelectric element 1 by the second conductive joint portion 132. The second end is joined to and electrically connected to the second lead terminal 192.
  • Each of the first lead terminal 191 and the second lead terminal 192 is pin-shaped.
  • the first lead terminal 191 and the second lead terminal 192 penetrate the base 170 in the thickness direction of the base 170.
  • the first lead terminal 191 and the second lead terminal 192 are electrically insulated.
  • the first lead terminal 191 and the second lead terminal 192 are electrically connected to the pedestal 170 by the first insulating part and the second insulating part interposed between the first lead terminal 191 and the second lead terminal 192 and the pedestal 170.
  • it is insulated, it is not limited to this.
  • one of the first lead terminal 191 and the second lead terminal 192 may be electrically connected to the base 170.
  • the ultrasonic transducer 100c includes the piezoelectric element 1 and the diaphragm portion 120c joined to the metal substrate 2 of the piezoelectric element 1, so that the operating frequency (resonant frequency) of the piezoelectric element 1 can be adjusted to a high speed. This makes it possible to achieve Thereby, in the ultrasonic transducer 100c, it becomes possible to increase the driving frequency of the piezoelectric element 1, and it becomes possible to narrow the directivity angle of the ultrasonic waves.
  • Embodiments 1-4 are just one of various embodiments of the present disclosure. Embodiments 1 to 4 can be modified in various ways depending on the design, etc., as long as the objective of the present disclosure can be achieved.
  • the outer edge 20 of the metal substrate 2 in plan view is not limited to a rectangular shape, and may be, for example, square, circular, elliptical, or oval.
  • the metal substrate 2 does not necessarily need to contain aluminum, but only needs to contain at least iron and chromium.
  • the piezoelectric elements 1, 1a, and 1b include the alumina layer 3. That is, the piezoelectric elements 1, 1a, and 1b may not include the alumina layer 3, and the lower electrode 4 may be provided directly on the metal substrate 2.
  • the material of the piezoelectric layer 5 is a material containing Pb, Zr, Zn, Nb, and O, for example, Pb 1.015 Zr 0.44 (Zn 1/3 Nb 2/3 ) 0.10 O 3. 015 , but may be lead zirconate titanate (PZT), barium titanate, lead magnesium niobate (PMN), KNbO 3 , NaNbO 3 or K 0.5 Na 0.5 NbO 3 .
  • the piezoelectric layer 5 is provided directly on the lower electrode 4; however, the piezoelectric layer 5 is not limited to this, and the piezoelectric layer 5 may be provided on the lower electrode 4 via a buffer layer. You can leave it there.
  • the buffer layer includes, for example, at least a portion of the material of the lower electrode 4 and at least a portion of the material of the piezoelectric layer 5.
  • the wiring portion 8 is not limited to the configuration in which it is provided across the upper surface 41 of the lower electrode 4, the side surface 53 of the piezoelectric layer 5, and the upper surface 51 of the piezoelectric layer 5.
  • the wiring portion 8 connects the lower electrode 4 and the terminal electrode 7 and is not provided on the lower surface 52 of the piezoelectric layer 5. It suffices if it is provided astride the side surface 53.
  • the piezoelectric element 1b it is not essential for the piezoelectric element 1b to have a narrow portion between the outer edge 50 of the piezoelectric layer 5 near the opening 54 and the opening 54 of the piezoelectric layer 5; and may be opened laterally.
  • the first conductive member and the second conductive member are not limited to the first lead wire 141 and the second lead wire 142, but are, for example, the first lead included in the conductor pattern portion of the flexible printed wiring board. It may be an electrode (first conductor part) and a second lead electrode (second conductor part).
  • the first conductive member and the second conductive member are not limited to the first lead wire 141 and the second lead wire 142, but are, for example, a first conductive wire and a second conductive wire. Good too.
  • the ultrasonic transducer 100c may include a piezoelectric element 1a or a piezoelectric element 1b instead of the piezoelectric element 1.
  • the piezoelectric element (1; 1a; 1b) includes a metal substrate (2), a lower electrode (4), a piezoelectric layer (5), and an upper electrode (6).
  • the metal substrate (2) contains at least iron and chromium.
  • the lower electrode (4) is provided on the metal substrate (2).
  • the piezoelectric layer (5) is provided on the lower electrode (4).
  • the upper electrode (6) is provided on the piezoelectric layer (5).
  • the first outer edge (outer edge 40) of the lower electrode (4) is located inside the second outer edge (outer edge 20) of the metal substrate 2.
  • the third outer edge (outer edge 50) of the piezoelectric layer (5) is located inside the first outer edge (outer edge 40) of the lower electrode (4).
  • the fourth outer edge (outer edge 60) of the upper electrode (6) is located inside the third outer edge (outer edge 50) of the piezoelectric layer (5).
  • the piezoelectric element (1; 1a; 1b) according to the first aspect, it is possible to increase the operating frequency of the piezoelectric element (1; 1a; 1b).
  • the piezoelectric element (1; 1a; 1b) according to the second embodiment further includes an alumina layer (3) in the first embodiment.
  • the alumina layer (3) is interposed between the metal substrate (2) and the lower electrode (4).
  • the metal substrate (2) further contains aluminum.
  • the upper surface (31) of the alumina layer (3) includes a part of the surface of the plurality of scale-like particles of the alumina layer (3).
  • the piezoelectric element (1; 1a; 1b) according to the second aspect can suppress peeling of the lower electrode (4).
  • the alumina layer (3) covers the entire upper surface (21) of the metal substrate (2).
  • the piezoelectric element (1a) according to the fourth aspect in any one of the first to third aspects, further includes a terminal electrode (7) and a wiring part (8).
  • the terminal electrode (7) is provided on the piezoelectric layer (5) and is separated from the upper electrode (6).
  • the wiring section (8) is provided across the upper surface (41) of the lower electrode (4) and the side surface (53) of the piezoelectric layer (5), and is connected between the lower electrode (4) and the terminal electrode (7). are connected.
  • the wiring portion (8) is located inside the second outer edge (outer edge 20) of the metal substrate (2).
  • the piezoelectric element (1a) according to the fourth aspect can be easily mounted on a flexible printed wiring board and can improve connection reliability.
  • the terminal electrode (7) is located inside the third outer edge (outer edge 50) of the piezoelectric layer (5) in plan view.
  • the wiring portion (8) includes a portion (81) provided on the upper surface (51) of the piezoelectric layer (5).
  • the piezoelectric element (1a) according to the fifth aspect it is possible to improve the uniformity of the thickness of the terminal electrode (7).
  • the piezoelectric layer (5) exposes a part of the upper surface (41) of the lower electrode (4). It has an opening (54).
  • the piezoelectric element (1b) since a part of the upper surface (41) of the lower electrode (4) constitutes the terminal part, it is possible to narrow the area that functions as the terminal part, and when in use This makes it possible to suppress variations in the characteristics of.
  • An ultrasonic transducer (100; 100a; 100c) according to a seventh aspect includes a piezoelectric element (1; 1a; 1b) according to any one of the first to sixth aspects, a diaphragm section (120; 120c), Includes a first conductive member (first lead wire 141), a second conductive member (second lead wire 142), a first conductive joint (131), and a second conductive joint (132). .
  • the diaphragm portion (120; 120c) is joined to the metal substrate (2) of the piezoelectric element (1; 1a; 1b).
  • the first conductive member (first lead wire 141) is connected to the lower electrode (4) of the piezoelectric element (1; 1a; 1b).
  • the second conductive member (second lead wire 142) is connected to the upper electrode (6) of the piezoelectric element (1; 1a; 1b).
  • the first conductive joint (131) joins the lower electrode (4) and the first conductive member (first lead wire 141).
  • the second conductive joint (132) joins the upper electrode (6) and the second conductive member (second lead wire 142).
  • the ultrasonic transducer (100; 100a; 100c) according to the seventh aspect can increase the operating frequency of the piezoelectric element (1; 1a; 1b).
  • the ultrasonic transducer (100; 100a) further includes a case (101) housing the piezoelectric element (1; 1a; 1b) in the seventh aspect.
  • the case (101) has a bottom plate part (102) and a cylindrical part (103).
  • the bottom plate portion (102) has a flat plate shape.
  • the cylindrical portion (103) protrudes from the periphery of one surface of the bottom plate portion (102) in the thickness direction of the bottom plate portion (102), and surrounds the piezoelectric element (1; 1a; 1b).
  • a portion of the bottom plate portion (102) surrounded by the cylinder portion (103) also serves as a diaphragm portion (120).
  • the ultrasonic transducer (100; 100a) according to the eighth aspect can be used, for example, as an ultrasonic sensor that is attached to a vehicle and detects objects outside the vehicle.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
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  • Transducers For Ultrasonic Waves (AREA)

Abstract

Provided are a piezoelectric element and an ultrasonic transducer with which it is possible to increase the operation frequency of a piezoelectric element. A piezoelectric element (1) comprises a metal substrate (2), a lower electrode (4), a piezoelectric body layer (5), and an upper electrode (6). The metal substrate (2) contains at least iron and chromium. The lower electrode (4) is provided on the metal substrate (2). The piezoelectric body layer (5) is provided on the lower electrode (4). The upper electrode (6) is provided on the piezoelectric body layer (5). In a plan view, a first outer edge of the lower electrode (4) is positioned on the inside of a second outer edge of the metal substrate (2). In the plan view, a third outer edge of the piezoelectric body layer (5) is positioned on the inside of the first outer edge of the lower electrode (4). In the plan view, a fourth outer edge of the upper electrode (6) is positioned on the inside of the third outer edge of the piezoelectric body layer (5).

Description

圧電素子及び超音波トランスデューサPiezoelectric elements and ultrasonic transducers
　本開示は、圧電素子及び超音波トランスデューサに関し、より詳細には、下部電極及び上部電極を有する圧電素子、及び、圧電素子を備える超音波トランスデューサに関する。 The present disclosure relates to a piezoelectric element and an ultrasonic transducer, and more particularly to a piezoelectric element having a lower electrode and an upper electrode, and an ultrasonic transducer including the piezoelectric element.
　特許文献１には、圧電素子を用いた空中用の超音波送受信器として、圧電セラミックと、圧電セラミックの両面に設けられた導電ペーストを焼結してなる銀電極と、有底筒状ケースと、を備える超音波送受信器（超音波トランスデューサ）が開示されている。 Patent Document 1 describes an aerial ultrasonic transmitter/receiver using a piezoelectric element, which includes a piezoelectric ceramic, a silver electrode formed by sintering conductive paste provided on both sides of the piezoelectric ceramic, and a bottomed cylindrical case. An ultrasonic transmitter/receiver (ultrasonic transducer) is disclosed.
　圧電素子では、動作周波数（共振周波数）の高速化が望まれる場合がある。 In piezoelectric elements, there are cases where it is desired to increase the operating frequency (resonant frequency).
特開２０１４－８２６５５号公報JP2014-82655A
　本開示の目的は、圧電素子の動作周波数の高速化を図ることが可能な圧電素子及び超音波トランスデューサを提供することにある。 An object of the present disclosure is to provide a piezoelectric element and an ultrasonic transducer that can increase the operating frequency of the piezoelectric element.
　本開示の一態様に係る圧電素子は、金属基板と、下部電極と、圧電体層と、上部電極と、を備える。前記金属基板は、少なくとも鉄及びクロムを含む。前記下部電極は、前記金属基板上に設けられている。前記圧電体層は、前記下部電極上に設けられている。前記上部電極は、前記圧電体層上に設けられている。平面視で、前記下部電極の第１外縁は、前記金属基板の第２外縁よりも内側に位置している。前記平面視で、前記圧電体層の第３外縁は、前記下部電極の前記第１外縁よりも内側に位置している。前記平面視で、前記上部電極の第４外縁は、前記圧電体層の前記第３外縁よりも内側に位置している。 A piezoelectric element according to one aspect of the present disclosure includes a metal substrate, a lower electrode, a piezoelectric layer, and an upper electrode. The metal substrate contains at least iron and chromium. The lower electrode is provided on the metal substrate. The piezoelectric layer is provided on the lower electrode. The upper electrode is provided on the piezoelectric layer. In plan view, the first outer edge of the lower electrode is located inside the second outer edge of the metal substrate. In the plan view, the third outer edge of the piezoelectric layer is located inside the first outer edge of the lower electrode. In the plan view, the fourth outer edge of the upper electrode is located inside the third outer edge of the piezoelectric layer.
　本開示の一態様に係る超音波トランスデューサは、前記圧電素子と、振動板部と、第１導通部材と、第２導通部材と、第１導電性接合部と、第２導電性接合部と、を備える。前記振動板部は、前記圧電素子の前記金属基板と接合されている。前記第１導通部材は、前記圧電素子の前記下部電極に接続される。前記第２導通部材は、前記圧電素子の前記上部電極に接続される。前記第１導電性接合部は、前記下部電極と前記第１導通部材とを接合している。前記第２導電性接合部は、前記上部電極と前記第２導通部材とを接合している。 An ultrasonic transducer according to one aspect of the present disclosure includes the piezoelectric element, a diaphragm section, a first conductive member, a second conductive member, a first conductive joint, a second conductive joint, Equipped with. The diaphragm portion is joined to the metal substrate of the piezoelectric element. The first conductive member is connected to the lower electrode of the piezoelectric element. The second conductive member is connected to the upper electrode of the piezoelectric element. The first conductive joint portion joins the lower electrode and the first conductive member. The second conductive joint portion joins the upper electrode and the second conductive member.
図１は、実施形態１に係る圧電素子の平面図である。FIG. 1 is a plan view of a piezoelectric element according to a first embodiment. 図２は、同上の圧電素子に関し、図１のＡ１－Ａ１線断面図である。FIG. 2 is a sectional view taken along line A1-A1 in FIG. 1 regarding the piezoelectric element same as above. 図３は、同上の圧電素子の製造方法の説明図である。FIG. 3 is an explanatory diagram of a method of manufacturing the same piezoelectric element as above. 図４は、同上の圧電素子を備える超音波トランスデューサの平面図である。FIG. 4 is a plan view of an ultrasonic transducer including the same piezoelectric element as above. 図５は、同上の圧電素子を備える超音波トランスデューサに関し、図４のＡ２－Ａ２線断面図である。FIG. 5 is a cross-sectional view taken along the line A2-A2 in FIG. 4 regarding an ultrasonic transducer including the piezoelectric element mentioned above. 図６は、実施形態２に係る圧電素子の平面図である。FIG. 6 is a plan view of the piezoelectric element according to the second embodiment. 図７は、同上の圧電素子に関し、図６のＡ３－Ａ３線断面図である。FIG. 7 is a sectional view taken along line A3-A3 in FIG. 6 regarding the piezoelectric element same as above. 図８は、同上の圧電素子を備える超音波トランスデューサの平面図である。FIG. 8 is a plan view of an ultrasonic transducer including the same piezoelectric element as above. 図９は、同上の圧電素子を備える超音波トランスデューサに関し、図８のＡ４－Ａ４線断面図である。FIG. 9 is a sectional view taken along the line A4-A4 in FIG. 8 regarding an ultrasonic transducer including the piezoelectric element mentioned above. 図１０は、実施形態３に係る圧電素子の平面図である。FIG. 10 is a plan view of a piezoelectric element according to Embodiment 3. 図１１は、同上の圧電素子に関し、図１０のＡ５－Ａ５線断面図である。FIG. 11 is a sectional view taken along line A5-A5 in FIG. 10 regarding the piezoelectric element same as above. 図１２は、実施形態４に係る超音波トランスデューサの断面図である。FIG. 12 is a sectional view of an ultrasonic transducer according to Embodiment 4.
　以下の実施形態１～４等において参照する各図は、いずれも模式的な図であり、図中の各構成要素の大きさや厚さそれぞれの比が、必ずしも実際の寸法比を反映しているとは限らない。 The drawings referred to in Embodiments 1 to 4 below are all schematic drawings, and the size and thickness ratios of each component in the drawings do not necessarily reflect the actual dimensional ratios. Not necessarily.
　（実施形態１）
　以下、圧電素子１について図１～３に基づいて説明した後、圧電素子１を備える超音波トランスデューサ１００について図４及び５に基づいて説明する。 (Embodiment 1)
Hereinafter, the piezoelectric element 1 will be explained based on FIGS. 1 to 3, and then the ultrasonic transducer 100 including the piezoelectric element 1 will be explained based on FIGS. 4 and 5.
　（１）圧電素子及び超音波トランスデューサの概要
　圧電素子１は、図１及び２に示すように、金属基板２と、アルミナ層３と、下部電極４と、圧電体層５と、上部電極６と、を備える。金属基板２は、少なくとも鉄及びクロムを含む。下部電極４は、金属基板２上に設けられている。圧電体層５は、下部電極４上に設けられている。上部電極６は、圧電体層５上に設けられている。平面視で、圧電素子１の外縁は、例えば、四角形状である。「平面視で、」とは、「金属基板２の厚さ方向に沿った方向において金属基板２の上側から見て、」と同じ意味である。言い換えれば、「平面視で、」とは、「金属基板２の厚さ方向からの平面視で、」と同じ意味である。 (1) Outline of piezoelectric element and ultrasonic transducer As shown in FIGS. 1 and 2, the piezoelectric element 1 includes a metal substrate 2, an alumina layer 3, a lower electrode 4, a piezoelectric layer 5, and an upper electrode 6. , is provided. Metal substrate 2 contains at least iron and chromium. The lower electrode 4 is provided on the metal substrate 2. The piezoelectric layer 5 is provided on the lower electrode 4 . The upper electrode 6 is provided on the piezoelectric layer 5. In plan view, the outer edge of the piezoelectric element 1 has, for example, a square shape. "In plan view" has the same meaning as "as seen from above the metal substrate 2 in the direction along the thickness direction of the metal substrate 2." In other words, "in plan view" has the same meaning as "in plan view from the thickness direction of the metal substrate 2."
　超音波トランスデューサ１００は、図４及び５に示すように、圧電素子１と、振動板部１２０と、第１リード線１４１と、第２リード線１４２と、第１導電性接合部１３１と、第２導電性接合部１３２と、を備える。超音波トランスデューサ１００では、第１リード線１４１が、第１導通部材を構成し、第２リード線１４２が、第２導通部材を構成している。振動板部１２０は、圧電素子１の金属基板２と接合されている。より詳細には、振動板部１２０は、接合部１０５により、圧電素子１の金属基板２と接合されている。第１リード線１４１は、圧電素子１の下部電極４に接続される。第２リード線１４２は、圧電素子１の上部電極６に接続される。第１導電性接合部１３１は、下部電極４と、第１リード線１４１と、を接合している。第２導電性接合部１３２は、上部電極６と、第２リード線１４２と、を接合している。 As shown in FIGS. 4 and 5, the ultrasonic transducer 100 includes a piezoelectric element 1, a diaphragm section 120, a first lead wire 141, a second lead wire 142, a first conductive joint 131, and a first conductive joint 131. 2 conductive joint portion 132. In the ultrasonic transducer 100, the first lead wire 141 constitutes a first conductive member, and the second lead wire 142 constitutes a second conductive member. The diaphragm section 120 is joined to the metal substrate 2 of the piezoelectric element 1. More specifically, the diaphragm section 120 is joined to the metal substrate 2 of the piezoelectric element 1 by the joining section 105. The first lead wire 141 is connected to the lower electrode 4 of the piezoelectric element 1 . The second lead wire 142 is connected to the upper electrode 6 of the piezoelectric element 1 . The first conductive joint 131 joins the lower electrode 4 and the first lead wire 141. The second conductive joint 132 joins the upper electrode 6 and the second lead wire 142.
　超音波トランスデューサ１００は、圧電素子１において第１電気信号（所定の駆動周波数の交流電圧）を第１機械振動に変換することにより、超音波を送波する。超音波トランスデューサ１００では、第１電気信号が圧電素子１に印加されたときの圧電素子１の水平方向の伸縮運動による圧電素子１の垂直方向の振動に伴って振動板部１２０が振動板部１２０の厚さ方向に振動し、超音波が送波される。また、超音波トランスデューサ１００は、例えば、この超音波トランスデューサ１００から送波された超音波の反射波が振動板部１２０に入射したときの振動板部１２０の厚さ方向の振動に伴う圧電素子１の第２機械振動を、圧電素子１において第２電気信号に変換する。 The ultrasonic transducer 100 transmits ultrasonic waves by converting a first electric signal (AC voltage with a predetermined drive frequency) into a first mechanical vibration in the piezoelectric element 1. In the ultrasonic transducer 100, when the first electric signal is applied to the piezoelectric element 1, the diaphragm part 120 vibrates in the vertical direction due to the horizontal expansion and contraction movement of the piezoelectric element 1. It vibrates in the thickness direction, and ultrasonic waves are transmitted. Further, the ultrasonic transducer 100 includes, for example, a piezoelectric element 1 that accompanies vibration in the thickness direction of the diaphragm section 120 when a reflected wave of an ultrasonic wave transmitted from the ultrasonic transducer 100 is incident on the diaphragm section 120. is converted into a second electrical signal in the piezoelectric element 1.
　超音波トランスデューサ１００では、振動板部１２０は、平板状である。超音波トランスデューサ１００は、圧電素子１を収容しているケース１０１を更に備える。ケース１０１は、底板部１０２と、筒部１０３と、を有する。底板部１０２は、平板状である。筒部１０３は、底板部１０２の一面の周部から底板部１０２の厚さ方向に突出しており、圧電素子１を囲んでいる。底板部１０２のうち筒部１０３により囲まれた部分が、振動板部１２０を兼ねている。 In the ultrasonic transducer 100, the diaphragm portion 120 has a flat plate shape. The ultrasonic transducer 100 further includes a case 101 housing the piezoelectric element 1. Case 101 has a bottom plate portion 102 and a cylinder portion 103. The bottom plate portion 102 has a flat plate shape. The cylindrical portion 103 protrudes from the periphery of one surface of the bottom plate portion 102 in the thickness direction of the bottom plate portion 102 and surrounds the piezoelectric element 1 . A portion of the bottom plate portion 102 surrounded by the cylindrical portion 103 also serves as a diaphragm portion 120.
　また、超音波トランスデューサ１００は、図５に示すように、ケース１０１内において圧電素子１の上方に配置されている吸音部材１５０と、ケース１０１内において吸音部材１５０上に配置されている封止部１６０と、を更に備える。なお、図４では、吸音部材１５０及び封止部１６０の図示を省略してある。 Further, as shown in FIG. 5, the ultrasonic transducer 100 includes a sound absorbing member 150 disposed above the piezoelectric element 1 in the case 101, and a sealing portion disposed on the sound absorbing member 150 in the case 101. 160. Note that in FIG. 4, illustration of the sound absorbing member 150 and the sealing part 160 is omitted.
　（２）詳細
　（２．１）圧電素子
　以下、実施形態１に係る圧電素子１について、図１及び２を参照して、より詳細に説明する。 (2) Details (2.1) Piezoelectric Element Hereinafter, the piezoelectric element 1 according to the first embodiment will be described in more detail with reference to FIGS. 1 and 2.
　（２．１．１）金属基板
　金属基板２は、平板状である。金属基板２は、図２に示すように、上面（第１主面）２１及び下面（第２主面）２２を有する。図１に示すように、平面視で、金属基板２の外縁２０は、例えば、四角形状（例えば、長方形状）である。金属基板２の厚さは、例えば、０．１ｍｍであるが、これに限らない。 (2.1.1) Metal Substrate The metal substrate 2 has a flat plate shape. The metal substrate 2 has an upper surface (first main surface) 21 and a lower surface (second main surface) 22, as shown in FIG. As shown in FIG. 1, the outer edge 20 of the metal substrate 2 has, for example, a square shape (for example, a rectangular shape) in plan view. The thickness of the metal substrate 2 is, for example, 0.1 mm, but is not limited thereto.
　金属基板２は、鉄とクロムとアルミニウムとを含む。金属基板２は、鉄を主成分として含むステンレス鋼基板であり、鉄の他にクロム及びアルミニウムを含む。金属基板２を構成するステンレス鋼基板は、例えば、アルミニウム含有フェライト系ステンレス鋼基板である。アルミニウム含有フェライト系ステンレス鋼基板は、例えば、クロムの含有量が１８ｗｔ％であり、アルミニウムの含有量が３ｗｔ％である。クロムの含有量は、１８ｗｔ％に限定されない。また、アルミニウムの含有量は、３ｗｔ％に限定されない。金属基板２は、鉄、クロム及びアルミニウム以外の元素を更に含んでいてもよい。 The metal substrate 2 contains iron, chromium, and aluminum. The metal substrate 2 is a stainless steel substrate containing iron as a main component, and contains chromium and aluminum in addition to iron. The stainless steel substrate constituting the metal substrate 2 is, for example, an aluminum-containing ferritic stainless steel substrate. The aluminum-containing ferritic stainless steel substrate has, for example, a chromium content of 18 wt% and an aluminum content of 3 wt%. The content of chromium is not limited to 18 wt%. Further, the aluminum content is not limited to 3 wt%. The metal substrate 2 may further contain elements other than iron, chromium, and aluminum.
　（２．１．２）アルミナ層
　アルミナ層３は、金属基板２の上面２１（図２参照）上に設けられている。図１に示すように、平面視で、アルミナ層３の外縁３０は、四角形状（例えば、長方形状）である。アルミナ層３の厚さは、例えば、１μｍであるが、これに限らない。 (2.1.2) Alumina Layer The alumina layer 3 is provided on the upper surface 21 (see FIG. 2) of the metal substrate 2. As shown in FIG. 1, the outer edge 30 of the alumina layer 3 has a square shape (for example, a rectangular shape) in plan view. The thickness of the alumina layer 3 is, for example, 1 μm, but is not limited thereto.
　アルミナ層３を形成するアルミナの主相は、γ－アルミナ相である。すなわち、アルミナ層３は、主としてγ－アルミナ相の粒子で形成されている。「主としてγ－アルミナ相の粒子で形成されている」とは、アルミナ層３の５０重量％を超える部分がγ－アルミナ相の粒子で形成されていることを意味する。アルミナ層３を構成する材料（粒子）の結晶相は、アルミナ層３の露出した部位のＸ線回折パターンをＸ線回折装置によって測定することによって同定することができる。アルミナ層３の上面は、アルミナ層３の有する複数の鱗片状の粒子の表面の一部を含んでいる。アルミナ層３の上面のＳＥＭ（Scanning Electron Microscope）像及びＸ線回折パターンの測定結果をあわせて考えると、鱗片状の粒子は、γ－アルミナ粒子であると推定される。 The main phase of alumina forming the alumina layer 3 is a γ-alumina phase. That is, the alumina layer 3 is mainly formed of particles of γ-alumina phase. "Mainly formed of γ-alumina phase particles" means that more than 50% by weight of the alumina layer 3 is formed of γ-alumina phase particles. The crystalline phase of the material (particles) constituting the alumina layer 3 can be identified by measuring the X-ray diffraction pattern of the exposed portion of the alumina layer 3 using an X-ray diffraction device. The upper surface of the alumina layer 3 includes a part of the surface of a plurality of scale-like particles of the alumina layer 3. Considering the SEM (Scanning Electron Microscope) image of the upper surface of the alumina layer 3 and the measurement results of the X-ray diffraction pattern, it is estimated that the scale-like particles are γ-alumina particles.
　（２．１．３）下部電極
　下部電極４は、アルミナ層３の上面３１（図２参照）上に設けられている。図１に示すように、平面視で、下部電極４の外縁４０は、例えば、四角形状であるが、これに限らない。下部電極４の厚さは、例えば、３μｍであるが、これに限らない。 (2.1.3) Lower Electrode The lower electrode 4 is provided on the upper surface 31 (see FIG. 2) of the alumina layer 3. As shown in FIG. 1, the outer edge 40 of the lower electrode 4 has, for example, a rectangular shape in plan view, but the shape is not limited to this. The thickness of the lower electrode 4 is, for example, 3 μm, but is not limited thereto.
　下部電極４の材料は、例えば、銀（Ａｇ）及びパラジウム（Ｐｄ）を含む。より詳細には、下部電極４の材料は、例えば、Ａｇ－Ｐｄ合金を含む。 The material of the lower electrode 4 includes, for example, silver (Ag) and palladium (Pd). More specifically, the material of the lower electrode 4 includes, for example, an Ag--Pd alloy.
　（２．１．４）圧電体層
　圧電体層５は、下部電極４の上面４１（図２参照）上に設けられている。図１に示すように、平面視で、圧電体層５の外縁５０は、例えば、四角形状であるが、これに限らない。圧電体層５の厚さは、例えば、５μｍ以上４０μｍ以下であり、好ましくは、１０μｍ以上３０μｍ以下である。圧電体層５の厚さは、一例として１１μｍであるが、これに限らない。 (2.1.4) Piezoelectric layer The piezoelectric layer 5 is provided on the upper surface 41 (see FIG. 2) of the lower electrode 4. As shown in FIG. 1, the outer edge 50 of the piezoelectric layer 5 has, for example, a rectangular shape in plan view, but the shape is not limited to this. The thickness of the piezoelectric layer 5 is, for example, 5 μm or more and 40 μm or less, preferably 10 μm or more and 30 μm or less. The thickness of the piezoelectric layer 5 is, for example, 11 μm, but is not limited thereto.
　圧電体層５の材料は、例えば、ＰｂとＺｒとＺｎとＮｂとＯとを含むが、これに限らない。より詳細には、圧電体層５の材料は、例えば、Ｐｂ１．０１５Ｚｒ０．４４（Ｚｎ１／３Ｎｂ２／３）０．１０Ｏ３．０１５を含むが、圧電体層５の材料の組成比は、これに限らない。 The material of the piezoelectric layer 5 includes, for example, Pb, Zr, Zn, Nb, and O, but is not limited thereto. More specifically, the material of the piezoelectric layer 5 includes, for example, Pb 1.015 Zr 0.44 (Zn 1/3 Nb 2/3 ) 0.10 O 3.015; The composition ratio is not limited to this.
　（２．１．５）上部電極
　上部電極６は、圧電体層５の上面５１（図２参照）上に設けられている。図１に示すように、平面視で、上部電極６の外縁６０は、例えば、四角形状であるが、これに限らない。上部電極６の厚さは、例えば、３μｍであるが、これに限らない。 (2.1.5) Upper Electrode The upper electrode 6 is provided on the upper surface 51 (see FIG. 2) of the piezoelectric layer 5. As shown in FIG. 1, the outer edge 60 of the upper electrode 6 has, for example, a rectangular shape in plan view, but the shape is not limited to this. The thickness of the upper electrode 6 is, for example, 3 μm, but is not limited thereto.
　上部電極６の材料は、例えば、Ａｇ及びＰｄを含む。より詳細には、上部電極６の材料は、例えば、Ａｇ－Ｐｄ合金を含む。 The material of the upper electrode 6 includes, for example, Ag and Pd. More specifically, the material of the upper electrode 6 includes, for example, an Ag--Pd alloy.
　（２．１．６）圧電素子における、下部電極、圧電体層及び上部電極のレイアウト
　圧電素子１では、図１に示すように、平面視で、下部電極４の外縁４０（第１外縁）は、金属基板２の外縁２０（第２外縁）よりも内側に位置している。平面視で、圧電体層５の外縁５０（第３外縁）は、下部電極４の外縁４０よりも内側に位置している。平面視で、上部電極６の外縁６０（第４外縁）は、圧電体層５の外縁５０よりも内側に位置している。圧電素子１では、下部電極４の上面４１（図２参照）の面積が金属基板２の上面２１（図２参照）の面積よりも小さく、圧電体層５の上面５１（図２参照）の面積が下部電極４の上面４１の面積よりも小さく、上部電極６の上面６１（図２参照）の面積が圧電体層５の上面５１の面積よりも小さい。 (2.1.6) Layout of the lower electrode, piezoelectric layer, and upper electrode in the piezoelectric element In the piezoelectric element 1, as shown in FIG. 1, the outer edge 40 (first outer edge) of the lower electrode 4 is , located inside the outer edge 20 (second outer edge) of the metal substrate 2. In plan view, the outer edge 50 (third outer edge) of the piezoelectric layer 5 is located inside the outer edge 40 of the lower electrode 4. In plan view, the outer edge 60 (fourth outer edge) of the upper electrode 6 is located inside the outer edge 50 of the piezoelectric layer 5. In the piezoelectric element 1, the area of the upper surface 41 (see FIG. 2) of the lower electrode 4 is smaller than the area of the upper surface 21 (see FIG. 2) of the metal substrate 2, and the area of the upper surface 51 (see FIG. 2) of the piezoelectric layer 5 is smaller than the area of the upper surface 41 of the lower electrode 4, and the area of the upper surface 61 (see FIG. 2) of the upper electrode 6 is smaller than the area of the upper surface 51 of the piezoelectric layer 5.
　以下では、図１に示すように、互いに直交するＸ軸、Ｙ軸及びＺ軸の３軸を有する直交座標を規定し、特に、金属基板２の厚さ方向に沿った軸を「Ｚ軸」とし、金属基板２の長手方向に沿った軸を「Ｘ軸」とし、金属基板２の短手方向に沿った軸を「Ｙ軸」として説明する。Ｘ軸、Ｙ軸、及びＺ軸は、いずれも仮想的な軸であり、図面中の「Ｘ」、「Ｙ」、「Ｚ」を示す矢印は、説明のために表記しているに過ぎず、いずれも実体を伴わない。 In the following, as shown in FIG. 1, orthogonal coordinates having three axes, the X-axis, Y-axis, and Z-axis that are orthogonal to each other, are defined, and in particular, the axis along the thickness direction of the metal substrate 2 is referred to as the "Z-axis". In the following description, the axis along the longitudinal direction of the metal substrate 2 is referred to as the "X axis", and the axis along the width direction of the metal substrate 2 is referred to as the "Y axis". The X-axis, Y-axis, and Z-axis are all virtual axes, and the arrows indicating "X," "Y," and "Z" in the drawings are only shown for explanation. , none of which involve substance.
　圧電素子１では、下部電極４の上面４１のうち圧電体層５に覆われていない部位４１１の一部が、外部接続用の端子部を兼ねている。圧電素子１では、図１に示すように、平面視で、下部電極４の外縁４０と圧電体層５の外縁５０との距離が一様ではなく、第１幅Ｗ１が第２幅Ｗ２よりも広い。第１幅Ｗ１は、Ｘ軸に沿った方向の圧電素子１の第１端における、下部電極４の外縁４０と圧電体層５の外縁５０との間の幅である。第２幅Ｗ２は、Ｘ軸に沿った方向の圧電素子１の第２端における、下部電極４の外縁４０と圧電体層５の外縁５０との間の幅である。 In the piezoelectric element 1, a part of the portion 411 of the upper surface 41 of the lower electrode 4 that is not covered with the piezoelectric layer 5 also serves as a terminal portion for external connection. In the piezoelectric element 1, as shown in FIG. 1, the distance between the outer edge 40 of the lower electrode 4 and the outer edge 50 of the piezoelectric layer 5 is not uniform in plan view, and the first width W1 is wider than the second width W2. wide. The first width W1 is the width between the outer edge 40 of the lower electrode 4 and the outer edge 50 of the piezoelectric layer 5 at the first end of the piezoelectric element 1 in the direction along the X axis. The second width W2 is the width between the outer edge 40 of the lower electrode 4 and the outer edge 50 of the piezoelectric layer 5 at the second end of the piezoelectric element 1 in the direction along the X axis.
　（２．１．７）圧電素子の製造方法
　実施形態１に係る圧電素子１の製造方法について、図３を参照しながら簡単に説明する。 (2.1.7) Method for manufacturing piezoelectric element A method for manufacturing piezoelectric element 1 according to Embodiment 1 will be briefly described with reference to FIG. 3.
　実施形態１に係る圧電素子１の製造方法では、まず、金属基板２の多数個取りが可能な金属基板２Ａ（図３参照）を準備し、その後、第１工程、第２工程、第３工程、第４工程、第５工程及び第６工程を順次行う。 In the method for manufacturing the piezoelectric element 1 according to the first embodiment, first, a metal substrate 2A (see FIG. 3) from which a large number of metal substrates 2 can be produced is prepared, and then a first step, a second step, and a third step are performed. , the fourth step, the fifth step, and the sixth step are performed sequentially.
　第１工程では、鉄とクロムとアルミニウムとを含む金属基板２Ａを大気中で加熱処理することにより、金属基板２Ａの上面２１Ａの全域を覆うアルミナ層３Ａ（図３参照）を形成する。加熱処理の条件に関し、熱処理温度は、例えば、８５０℃以上９００℃以下であり、熱処理時間は、例えば、２時間である。なお、第１工程では、アルミナ層３Ａである第１アルミナ層３Ａの他に、金属基板２Ａの下面２２Ａの全域を覆う第２アルミナ層が形成されてもよい。 In the first step, the metal substrate 2A containing iron, chromium, and aluminum is heat-treated in the atmosphere to form an alumina layer 3A (see FIG. 3) that covers the entire upper surface 21A of the metal substrate 2A. Regarding the conditions of the heat treatment, the heat treatment temperature is, for example, 850° C. or more and 900° C. or less, and the heat treatment time is, for example, 2 hours. Note that in the first step, in addition to the first alumina layer 3A, which is the alumina layer 3A, a second alumina layer may be formed that covers the entire lower surface 22A of the metal substrate 2A.
　第２工程では、下部電極４の材料を含むペースト（例えば、Ａｇ－Ｐｄ合金ペースト）をスクリーン印刷することによって、複数の下部電極材料部を含む第１パターン部をアルミナ層３Ａ上に形成する。 In the second step, a first pattern portion including a plurality of lower electrode material portions is formed on the alumina layer 3A by screen printing a paste containing the material of the lower electrode 4 (eg, Ag-Pd alloy paste).
　第３工程では、圧電体層５の材料を含むペーストをメタルマスク印刷することによって、複数の圧電体材料部を含む第２パターン部を第１パターン部上に形成する。圧電体層５の材料は、例えば、Ｐｂ１．０１５Ｚｒ０．４４（Ｚｎ１／３Ｎｂ２／３）０．１０Ｏ３．０１５である。 In the third step, a second pattern section including a plurality of piezoelectric material sections is formed on the first pattern section by printing a paste containing the material of the piezoelectric layer 5 with a metal mask. The material of the piezoelectric layer 5 is, for example, Pb 1.015 Zr 0.44 (Zn 1/3 Nb 2/3 ) 0.10 O 3.015 .
　第４工程では、上部電極６の材料を含むペースト（例えば、Ａｇ－Ｐｄ合金ペースト）をスクリーン印刷することによって、第２パターン部上に複数の上部電極材料部を含む第３パターン部を形成する。 In the fourth step, a third pattern section including a plurality of upper electrode material sections is formed on the second pattern section by screen printing a paste containing the material of the upper electrode 6 (for example, Ag-Pd alloy paste). .
　第５工程では、第１パターン部、第２パターン部及び第３パターン部を所定の焼成温度（例えば、８７５℃）で焼成することによって、複数の下部電極４を含む下部電極パターン部４Ａ、複数の圧電体層５を含む圧電体層パターン部５Ａ及び複数の上部電極６を含む上部電極パターン部６Ａを形成する（図３参照）。これにより、複数の圧電素子１を含む構造体１Ａが形成される（図３参照）。 In the fifth step, by firing the first pattern part, the second pattern part, and the third pattern part at a predetermined firing temperature (e.g., 875° C.), the lower electrode pattern part 4A including the plurality of lower electrodes 4, the plurality of lower electrode pattern parts 4A, A piezoelectric layer pattern section 5A including a piezoelectric layer 5 and an upper electrode pattern section 6A including a plurality of upper electrodes 6 are formed (see FIG. 3). As a result, a structure 1A including a plurality of piezoelectric elements 1 is formed (see FIG. 3).
　第６工程では、ダイシングブレード２００（図３参照）により構造体１Ａをダイシングすることによって、構造体１Ａを個々の圧電素子１に分離する。構造体１Ａにおいてダイシングレーンには、金属基板２Ａ及びアルミナ層３Ａは存在するが、下部電極パターン部４Ａ、圧電体層パターン部５Ａ及び上部電極パターン部６Ａは存在しない。ここで、ダイシングブレード２００の厚みＨ２は、構造体１Ａにおいてダイシングレーンを挟んで隣り合う２つの下部電極４間の第１距離Ｌ１よりも小さい。また、ダイシングブレード２００の厚みＨ２は、構造体１Ａにおいてダイシングレーンを挟んで隣り合う２つの圧電体層５間の第２距離Ｌ２よりも小さい。また、ダイシングブレード２００の厚みＨ２は、構造体１Ａにおいてダイシングレーンを挟んで隣り合う２つの上部電極６間の第３距離Ｌ３よりも小さい。以上より、第６工程では、ダイシングブレード２００の厚みＨ２＜第１距離Ｌ１＜第２距離Ｌ２＜第３距離Ｌ３、の関係を満たす。 In the sixth step, the structure 1A is separated into individual piezoelectric elements 1 by dicing the structure 1A with a dicing blade 200 (see FIG. 3). In the structure 1A, the metal substrate 2A and the alumina layer 3A are present in the dicing lane, but the lower electrode pattern section 4A, the piezoelectric layer pattern section 5A, and the upper electrode pattern section 6A are not present. Here, the thickness H2 of the dicing blade 200 is smaller than the first distance L1 between two adjacent lower electrodes 4 across the dicing lane in the structure 1A. Further, the thickness H2 of the dicing blade 200 is smaller than the second distance L2 between two adjacent piezoelectric layers 5 across the dicing lane in the structure 1A. Further, the thickness H2 of the dicing blade 200 is smaller than the third distance L3 between two adjacent upper electrodes 6 across the dicing lane in the structure 1A. As described above, in the sixth step, the relationship of thickness H2 of the dicing blade 200<first distance L1<second distance L2<third distance L3 is satisfied.
　圧電素子１の製造方法によれば、第６工程において、下部電極４、圧電体層５及び上部電極６の割れ及び欠け（チッピング）が発生し難い。したがって、圧電素子１の製造方法によれば、製造歩留まりの向上を図れる。また、圧電素子１では、ハンドリングする際にハンドリング用のツールが下部電極４、圧電体層５及び上部電極６に接触するのを防止することができるので、下部電極４、圧電体層５及び上部電極６の破損を防止することができる。よって、圧電素子１は、バルク型の圧電素子と比べて、圧電体層５の薄型化が可能である。 According to the method for manufacturing the piezoelectric element 1, cracking and chipping of the lower electrode 4, piezoelectric layer 5, and upper electrode 6 are unlikely to occur in the sixth step. Therefore, according to the method for manufacturing the piezoelectric element 1, it is possible to improve the manufacturing yield. In addition, in the piezoelectric element 1, since it is possible to prevent a handling tool from coming into contact with the lower electrode 4, the piezoelectric layer 5, and the upper electrode 6 during handling, the lower electrode 4, the piezoelectric layer 5, and the upper Damage to the electrode 6 can be prevented. Therefore, in the piezoelectric element 1, the piezoelectric layer 5 can be made thinner than a bulk type piezoelectric element.
　なお、第６工程では、ダイシングブレード２００により構造体１Ａをダイシングしているが、ダイシングブレード２００を用いた方法に限らず、構造体１Ａのダイシングレーンに沿ってレーザ光を照射してダイシングするレーザダイシングを行ってもよい。ダイシングブレード２００を用いた方法、レーザダイシングのいずれの場合も、ダイシングレーンの幅寸法がダイシングによる切削幅（最大幅）よりも広くなるように、第２工程で用いる第１スクリーン印刷用マスク、第３工程で用いるメタルマスク及び第４工程で用いる第２スクリーン印刷用マスクを設計してある。 Note that in the sixth step, the structure 1A is diced using the dicing blade 200, but the method is not limited to the method using the dicing blade 200. Dicing may also be performed. In both the method using the dicing blade 200 and laser dicing, the first screen printing mask used in the second step, the first A metal mask used in the third step and a second screen printing mask used in the fourth step are designed.
　（２．２）超音波トランスデューサ
　以下、実施形態１に係る超音波トランスデューサ１００について、図４及び５を参照して、より詳細に説明する。 (2.2) Ultrasonic Transducer The ultrasonic transducer 100 according to the first embodiment will be described in more detail below with reference to FIGS. 4 and 5.
　超音波トランスデューサ１００は、超音波の送波（送信）と超音波の受波（受信）との両方が可能に構成されている。超音波トランスデューサ１００は、例えば、自動車等の車両に搭載されて車両の周囲の物体（障害物等）を検知する超音波センサに用いられる。超音波センサは、例えば、超音波トランスデューサ１００と、駆動回路と、信号処理回路と、を備える。超音波センサは、例えば、ＴＯＦ（Time of Flight）型の超音波センサである。駆動回路は、超音波トランスデューサ１００から超音波を送波させるために超音波トランスデューサ１００の圧電素子１を駆動する電気信号を圧電素子１へ印加する。信号処理回路は、超音波トランスデューサ１００が超音波の反射波を受波したときに圧電素子１から出力される電気信号を処理する。信号処理回路は、例えば、超音波センサの検知エリア内の物体の有無と、超音波トランスデューサ１００から物体までの距離と、の少なくとも一方を検知する。超音波センサの超音波トランスデューサ１００は、例えば、自動車のバンパーに取り付けられる。超音波トランスデューサ１００を自動車用の超音波センサとして用いる場合、超音波トランスデューサ１００は、例えば、Ｘ軸方向（図４での左右方向）が垂直方向となり、Ｙ軸方向（図４での上下方向）が水平方向となり、Ｚ軸方向（図４での紙面に直交する方向）が検知方向（超音波の送受波方向）となるように設置される。なお、超音波トランスデューサ１００の取り付けの向きは、例えば、超音波トランスデューサ１００の用途に応じて適宜変更可能である。なお、超音波トランスデューサ１００が駆動回路及び信号処理回路の少なくとも一方を含んでいてもよい。 The ultrasonic transducer 100 is configured to be capable of both transmitting (transmitting) ultrasonic waves and receiving (receiving) ultrasonic waves. The ultrasonic transducer 100 is used, for example, as an ultrasonic sensor mounted on a vehicle such as an automobile to detect objects (obstacles, etc.) around the vehicle. The ultrasonic sensor includes, for example, an ultrasonic transducer 100, a drive circuit, and a signal processing circuit. The ultrasonic sensor is, for example, a TOF (Time of Flight) type ultrasonic sensor. The drive circuit applies an electric signal to the piezoelectric element 1 of the ultrasonic transducer 100 to cause the ultrasonic transducer 100 to transmit ultrasonic waves. The signal processing circuit processes an electrical signal output from the piezoelectric element 1 when the ultrasonic transducer 100 receives a reflected wave of an ultrasonic wave. The signal processing circuit detects, for example, at least one of the presence or absence of an object within the detection area of the ultrasonic sensor and the distance from the ultrasonic transducer 100 to the object. The ultrasonic transducer 100 of the ultrasonic sensor is attached to the bumper of an automobile, for example. When the ultrasonic transducer 100 is used as an ultrasonic sensor for an automobile, the ultrasonic transducer 100 has, for example, a vertical direction in the X-axis direction (the left-right direction in FIG. 4) and a vertical direction in the Y-axis direction (the vertical direction in FIG. 4). is installed so that the direction is horizontal, and the Z-axis direction (direction perpendicular to the plane of the paper in FIG. 4) is the detection direction (transmission/reception direction of ultrasonic waves). Note that the mounting direction of the ultrasonic transducer 100 can be changed as appropriate depending on the use of the ultrasonic transducer 100, for example. Note that the ultrasonic transducer 100 may include at least one of a drive circuit and a signal processing circuit.
　（２．２．１）ケース
　ケース１０１では、底板部１０２と筒部１０３とが一体に形成されている。ケース１０１の形状は、有底筒状である。平面視で、ケース１０１の外縁は、円形状である。振動板部１２０は、図５に示すように、上面１２１及び下面１２２を有する。振動板部１２０の厚さは、例えば、０．３ｍｍ以上１．０ｍｍ以下であり、一例として、０．９ｍｍである。平面視で、ケース１０１の外径は、例えば、１４ｍｍであるが、これに限らず、例えば、１５．５ｍｍでもよい。また、Ｚ軸方向におけるケース１０１の長さは、例えば、９ｍｍであるが、これに限らない。ケース１０１では、振動板部１２０の下面１２２が超音波の送受波面を構成している。 (2.2.1) Case In the case 101, the bottom plate portion 102 and the cylindrical portion 103 are integrally formed. The case 101 has a cylindrical shape with a bottom. In plan view, the outer edge of the case 101 has a circular shape. The diaphragm section 120 has an upper surface 121 and a lower surface 122, as shown in FIG. The thickness of the diaphragm portion 120 is, for example, 0.3 mm or more and 1.0 mm or less, and is, for example, 0.9 mm. In plan view, the outer diameter of the case 101 is, for example, 14 mm, but is not limited to this, and may be, for example, 15.5 mm. Further, the length of the case 101 in the Z-axis direction is, for example, 9 mm, but is not limited thereto. In the case 101, the lower surface 122 of the diaphragm portion 120 constitutes an ultrasonic wave transmission/reception surface.
　ケース１０１の材料は、例えば、アルミニウム合金であるが、これに限らず、例えば、マグネシウム合金、ステンレス鋼、チタン合金又はエンジニアプラスチックでもよい。 The material of the case 101 is, for example, an aluminum alloy, but is not limited thereto, and may be, for example, a magnesium alloy, stainless steel, a titanium alloy, or an engineered plastic.
　図４に示すように、平面視で、振動板部１２０は、第１方向（Ｘ軸方向）における第１最大長さＲ１が第２方向（Ｙ軸方向）における第２最大長さＲ２に比べて長くなる形状である。これにより、超音波トランスデューサ１００では、Ｘ軸方向の指向角をＹ軸方向の指向角よりも狭くできる。なお、第１最大長さＲ１は、１２．６ｍｍ、第２最大長さＲ２は、８ｍｍであるが、これらの数値に限定されない。 As shown in FIG. 4, in plan view, the diaphragm portion 120 has a first maximum length R1 in the first direction (X-axis direction) that is larger than a second maximum length R2 in the second direction (Y-axis direction). It has a long shape. Thereby, in the ultrasonic transducer 100, the directivity angle in the X-axis direction can be narrower than the directivity angle in the Y-axis direction. Note that the first maximum length R1 is 12.6 mm, and the second maximum length R2 is 8 mm, but is not limited to these values.
　（２．２．２）接合部
　図５に示すように、接合部１０５は、圧電素子１の金属基板２の下面２２と振動板部１２０の上面１２１との間に介在している。接合部１０５の材料は、例えば、樹脂系接着剤、導電性接合材料又はＤＡＦ（Die Attach Film）である。樹脂系接着剤は、例えば、エポキシ接着剤を含む。導電性接合材料は、例えば、導電性ペースト（銀ペースト等）を含む。 (2.2.2) Joint As shown in FIG. 5, the joint 105 is interposed between the lower surface 22 of the metal substrate 2 of the piezoelectric element 1 and the upper surface 121 of the diaphragm section 120. The material of the bonding portion 105 is, for example, a resin adhesive, a conductive bonding material, or DAF (Die Attach Film). The resin adhesive includes, for example, an epoxy adhesive. The conductive bonding material includes, for example, conductive paste (silver paste, etc.).
　（２．２．３）第１リード線、第２リード線、第１導電性接合部、第２導電性接合部
　超音波トランスデューサ１００では、第１リード線１４１が、圧電素子１の下部電極４に接続される第１導通部材を構成し、第２リード線１４２が、圧電素子１の上部電極６に接続される第２導通部材を構成している。第１リード線１４１の第１端は、第１導電性接合部１３１によって下部電極４に接合されて下部電極４と電気的に接続されている。第２リード線１４２の第１端は、第２導電性接合部１３２によって上部電極６に接合されて上部電極６と電気的に接続されている。 (2.2.3) First lead wire, second lead wire, first conductive joint, second conductive joint In the ultrasonic transducer 100, the first lead wire 141 is connected to the lower electrode 4 of the piezoelectric element 1. The second lead wire 142 constitutes a second conductive member connected to the upper electrode 6 of the piezoelectric element 1 . A first end of the first lead wire 141 is joined to the lower electrode 4 by the first conductive joint 131 and is electrically connected to the lower electrode 4 . A first end of the second lead wire 142 is joined to the upper electrode 6 by the second conductive joint 132 and is electrically connected to the upper electrode 6 .
　第１リード線１４１及び第２リード線１４２は、可撓性を有する電線である。第１リード線１４１の一部及び第２リード線１４２の一部は、ケース１０１の外に導出されている。第１リード線１４１の第２端及び第２リード線１４２の第２端は、例えば、超音波センサの備える駆動回路と超音波センサの備える信号処理回路とに接続される。 The first lead wire 141 and the second lead wire 142 are flexible electric wires. A portion of the first lead wire 141 and a portion of the second lead wire 142 are led out of the case 101. The second end of the first lead wire 141 and the second end of the second lead wire 142 are connected to, for example, a drive circuit included in the ultrasonic sensor and a signal processing circuit included in the ultrasonic sensor.
　第１導電性接合部１３１及び第２導電性接合部１３２の材料は、例えば、はんだを含む。 The material of the first conductive joint 131 and the second conductive joint 132 includes, for example, solder.
　なお、超音波センサでは、超音波トランスデューサ１００を超音波の送波（送信）に用いる場合には、超音波トランスデューサ１００が駆動回路に接続される。また、超音波センサでは、超音波トランスデューサ１００を超音波の受波（受信）に用いる場合には、超音波トランスデューサ１００が信号処理回路に接続される。 Note that in the ultrasonic sensor, when the ultrasonic transducer 100 is used for transmitting ultrasonic waves, the ultrasonic transducer 100 is connected to a drive circuit. Furthermore, in the ultrasonic sensor, when the ultrasonic transducer 100 is used for receiving ultrasonic waves, the ultrasonic transducer 100 is connected to a signal processing circuit.
　（２．２．４）吸音部材
　吸音部材１５０は、ケース１０１内において圧電素子１の上方に配置されている。吸音部材１５０の材料は、例えば、発泡体を含む。発泡体は、例えば、ウレタン系の発泡体、発泡シリコーンを含む。 (2.2.4) Sound Absorbing Member The sound absorbing member 150 is arranged above the piezoelectric element 1 in the case 101. The material of the sound absorbing member 150 includes, for example, foam. Examples of the foam include urethane foam and silicone foam.
　（２．２．５）封止部
　封止部１６０は、ケース１０１内において吸音部材１５０上に配置されている。封止部１６０の材料は、例えば、シリコーン樹脂を含む。 (2.2.5) Sealing Section The sealing section 160 is arranged on the sound absorbing member 150 within the case 101. The material of the sealing part 160 includes, for example, silicone resin.
　（３）効果
　（３．１）圧電素子
　実施形態１に係る圧電素子１は、鉄とクロムとアルミニウムとを含む金属基板２を備える。実施形態１に係る圧電素子１では、平面視で、下部電極４の外縁４０（第１外縁）が、金属基板２の外縁２０（第２外縁）よりも内側に位置し、圧電体層５の外縁５０（第３外縁）が、下部電極４の外縁４０よりも内側に位置し、上部電極６の外縁６０（第４外縁）が、圧電体層５の外縁５０（第３外縁）よりも内側に位置している。これにより、実施形態１に係る圧電素子１によれば、圧電素子１の動作周波数（共振周波数）の高速化を図ることが可能となる。より詳細には、実施形態１に係る圧電素子１は、圧電体層５の薄型化を図ることができるので、圧電素子１の共振周波数をより高くすることが可能となり、駆動周波数をより高くすることが可能となる。 (3) Effects (3.1) Piezoelectric Element The piezoelectric element 1 according to the first embodiment includes a metal substrate 2 containing iron, chromium, and aluminum. In the piezoelectric element 1 according to the first embodiment, in plan view, the outer edge 40 (first outer edge) of the lower electrode 4 is located inside the outer edge 20 (second outer edge) of the metal substrate 2, and The outer edge 50 (third outer edge) is located inside the outer edge 40 of the lower electrode 4, and the outer edge 60 (fourth outer edge) of the upper electrode 6 is located inside the outer edge 50 (third outer edge) of the piezoelectric layer 5. It is located in Thereby, according to the piezoelectric element 1 according to the first embodiment, it is possible to increase the operating frequency (resonant frequency) of the piezoelectric element 1. More specifically, in the piezoelectric element 1 according to the first embodiment, since the piezoelectric layer 5 can be made thinner, the resonance frequency of the piezoelectric element 1 can be made higher, and the driving frequency can be made higher. becomes possible.
　また、実施形態１に係る圧電素子１は、下部電極４と金属基板２との間に介在しているアルミナ層３を備え、アルミナ層３の上面３１が、アルミナ層３の有する複数の鱗片状の粒子の表面の一部を含むので、下部電極４の剥離を抑制することが可能となる。 Furthermore, the piezoelectric element 1 according to the first embodiment includes an alumina layer 3 interposed between the lower electrode 4 and the metal substrate 2, and the upper surface 31 of the alumina layer 3 has a plurality of scale-like shapes that the alumina layer 3 has. Since the lower electrode 4 includes a part of the surface of the particles, peeling of the lower electrode 4 can be suppressed.
　実施形態１に係る圧電素子１では、アルミナ層３が金属基板２の上面２１の全域を覆っているので、圧電特性を向上させることが可能となる。より詳細には、実施形態１に係る圧電素子１では、製造時において金属基板２と圧電体層５との間で熱拡散が起こることを抑制でき、圧電特性を向上させることが可能となる。 In the piezoelectric element 1 according to the first embodiment, since the alumina layer 3 covers the entire upper surface 21 of the metal substrate 2, it is possible to improve piezoelectric characteristics. More specifically, in the piezoelectric element 1 according to the first embodiment, it is possible to suppress thermal diffusion between the metal substrate 2 and the piezoelectric layer 5 during manufacturing, and it is possible to improve the piezoelectric characteristics.
　（３．２）超音波トランスデューサ
　実施形態１に係る超音波トランスデューサ１００は、圧電素子１と、圧電素子１の金属基板２と接合されている振動板部１２０と、を備えるので、圧電素子１の動作周波数（共振周波数）の高速化を図ることが可能となる。これにより、超音波トランスデューサ１００では、圧電素子１の駆動周波数をより高くすることが可能となり、超音波の指向角の挟角化を図ることが可能となる。よって、例えば、超音波トランスデューサ１００を備える超音波センサを自動車に設置して用いる場合に、超音波トランスデューサ１００から送波された超音波が路面、縁石等に入射することを抑制でき、路面、縁石等からの反射波が超音波トランスデューサ１００で受波されることを抑制できる。これにより、超音波センサのＳ／Ｎ比を向上させることが可能となり、検知対象の物体を検知可能な距離をより長くすることが可能となる。 (3.2) Ultrasonic transducer The ultrasonic transducer 100 according to the first embodiment includes the piezoelectric element 1 and the diaphragm portion 120 joined to the metal substrate 2 of the piezoelectric element 1. It becomes possible to increase the operating frequency (resonant frequency). Thereby, in the ultrasonic transducer 100, it becomes possible to make the drive frequency of the piezoelectric element 1 higher, and it becomes possible to narrow the directivity angle of the ultrasonic waves. Therefore, for example, when an ultrasonic sensor including the ultrasonic transducer 100 is installed and used in a car, it is possible to suppress the ultrasonic waves transmitted from the ultrasonic transducer 100 from entering the road surface, curb, etc. It is possible to suppress reflected waves from the ultrasonic transducer 100 from being received by the ultrasonic transducer 100. Thereby, it becomes possible to improve the S/N ratio of the ultrasonic sensor, and it becomes possible to further increase the distance at which the object to be detected can be detected.
　（実施形態２）
　実施形態２に係る圧電素子１ａについて、図６及び７を参照して説明し、その後、圧電素子１ａを備える超音波トランスデューサ１００ａについて、図８及び９を参照して説明する。実施形態２に係る圧電素子１ａに関し、実施形態１に係る圧電素子１（図１及び２参照）と同様の構成要素については、同一の符号を付して説明を省略する。また、実施形態２に係る超音波トランスデューサ１００ａに関し、実施形態１に係る超音波トランスデューサ１００（図４及び５参照）と同様の構成要素については、同一の符号を付して説明を適宜省略する。 (Embodiment 2)
A piezoelectric element 1a according to the second embodiment will be described with reference to FIGS. 6 and 7, and then an ultrasonic transducer 100a including the piezoelectric element 1a will be described with reference to FIGS. 8 and 9. Regarding the piezoelectric element 1a according to the second embodiment, the same components as those of the piezoelectric element 1 according to the first embodiment (see FIGS. 1 and 2) are given the same reference numerals, and the description thereof will be omitted. Further, regarding the ultrasonic transducer 100a according to the second embodiment, the same components as those in the ultrasonic transducer 100 according to the first embodiment (see FIGS. 4 and 5) are given the same reference numerals, and the description thereof will be omitted as appropriate.
　（１）構成
　（１．１）圧電素子
　実施形態２に係る圧電素子１ａは、図６及び７に示すように、端子電極７と、配線部８と、を更に備える点で、実施形態１に係る圧電素子１（図１及び２参照）と相違する。 (1) Configuration (1.1) Piezoelectric element As shown in FIGS. 6 and 7, the piezoelectric element 1a according to the second embodiment is different from the first embodiment in that it further includes a terminal electrode 7 and a wiring part 8. This is different from the piezoelectric element 1 (see FIGS. 1 and 2).
　端子電極７は、圧電体層５上に設けられており、上部電極６から離れている。より詳細には、端子電極７は、圧電体層５の上面５１上に設けられており、Ｘ軸方向において上部電極６から離れている。端子電極７と上部電極６との間には空隙９が形成されている。端子電極７のうち配線部８につながっている部位は、例えば、Ｘ軸方向において上部電極６に囲まれていない。圧電素子１ａでは、端子電極７は、圧電体層５の上面５１において、Ｘ軸に沿った方向の第１端に、配置されている。ここで、平面視で、端子電極７は、圧電体層５の外縁５０よりも内側に位置している。平面視で、端子電極７は、例えば、四角形状であるが、これに限らず、円形状であってもよい。 The terminal electrode 7 is provided on the piezoelectric layer 5 and is separated from the upper electrode 6. More specifically, the terminal electrode 7 is provided on the upper surface 51 of the piezoelectric layer 5 and is separated from the upper electrode 6 in the X-axis direction. A gap 9 is formed between the terminal electrode 7 and the upper electrode 6. The portion of the terminal electrode 7 that is connected to the wiring portion 8 is not surrounded by the upper electrode 6 in the X-axis direction, for example. In the piezoelectric element 1a, the terminal electrode 7 is arranged on the upper surface 51 of the piezoelectric layer 5 at the first end in the direction along the X-axis. Here, the terminal electrode 7 is located inside the outer edge 50 of the piezoelectric layer 5 in plan view. In plan view, the terminal electrode 7 has, for example, a square shape, but is not limited to this, and may have a circular shape.
　端子電極７の厚さは、上部電極６の厚さと同じである。ここにおいて、「端子電極７の厚さは、上部電極６の厚さと同じ」とは、厳密に同じ場合のみに限定されず、端子電極７の厚さが、上部電極６の厚さの９５％以上１０５％以下の範囲内の厚さである場合を含む。 The thickness of the terminal electrode 7 is the same as the thickness of the upper electrode 6. Here, "the thickness of the terminal electrode 7 is the same as the thickness of the upper electrode 6" is not limited to strictly the same case, and the thickness of the terminal electrode 7 is 95% of the thickness of the upper electrode 6. This includes cases where the thickness is within a range of 105% or more.
　また、圧電素子１ａでは、端子電極７の厚さと上部電極６の厚さとが同じであることにより、金属基板２の上面２１から端子電極７の上面７１までの第１高さが、金属基板２の上面２１から上部電極６の上面６１までの第２高さと同じになっている。ここにおいて、第１高さが第２高さと同じとは、厳密に同じ場合のみに限定されず、第１高さが、第２高さの９５％以上１０５％以下の範囲内の高さである場合を含む。 In the piezoelectric element 1a, since the thickness of the terminal electrode 7 and the thickness of the upper electrode 6 are the same, the first height from the upper surface 21 of the metal substrate 2 to the upper surface 71 of the terminal electrode 7 is It is the same as the second height from the upper surface 21 to the upper surface 61 of the upper electrode 6. Here, the first height being the same as the second height is not limited to strictly the same case, but the first height is within the range of 95% or more and 105% or less of the second height. Including some cases.
　端子電極７の材料は、上部電極６の材料と同じであり、例えば、Ａｇ及びＰｄを含む。 The material of the terminal electrode 7 is the same as that of the upper electrode 6, and includes, for example, Ag and Pd.
　配線部８は、下部電極４の上面４１と圧電体層５の側面５３と圧電体層５の上面５１とに跨って設けられており、下部電極４と端子電極７とをつないでいる。したがって、配線部８は、圧電体層５の上面５１上に形成されている部分８１を含む。配線部８は、圧電体層５の下面５２には形成されていない。 The wiring section 8 is provided across the upper surface 41 of the lower electrode 4, the side surface 53 of the piezoelectric layer 5, and the upper surface 51 of the piezoelectric layer 5, and connects the lower electrode 4 and the terminal electrode 7. Therefore, the wiring section 8 includes a portion 81 formed on the upper surface 51 of the piezoelectric layer 5. The wiring portion 8 is not formed on the lower surface 52 of the piezoelectric layer 5.
　配線部８の材料は、上部電極６の材料及び端子電極７の材料と同じであり、例えば、Ａｇ及びＰｄを含む。 The material of the wiring part 8 is the same as the material of the upper electrode 6 and the material of the terminal electrode 7, and includes, for example, Ag and Pd.
　図６に示すように、平面視で、配線部８は、金属基板２の外縁２０よりも内側に位置している。平面視で、Ｙ軸方向における配線部８の幅は、Ｙ軸方向における端子電極７の幅よりも狭い。図７に示すように、Ｙ軸方向からの側面視で、配線部８は、逆Ｌ字状である。 As shown in FIG. 6, the wiring portion 8 is located inside the outer edge 20 of the metal substrate 2 in plan view. In plan view, the width of the wiring portion 8 in the Y-axis direction is narrower than the width of the terminal electrode 7 in the Y-axis direction. As shown in FIG. 7, the wiring portion 8 has an inverted L shape when viewed from the side in the Y-axis direction.
　圧電素子１ａでは、端子電極７及び配線部８は、スクリーン印刷によって上部電極６と同じ工程で形成されている。 In the piezoelectric element 1a, the terminal electrode 7 and the wiring portion 8 are formed in the same process as the upper electrode 6 by screen printing.
　圧電素子１ａの製造方法は、圧電素子１の製造方法と略同じであり、圧電素子１の製造方法における第４工程で用いるスクリーンマスクの代わりに、上部電極６形成用の開口部と端子電極７形成用の開口部と配線部８形成用の開口部とを有するスクリーンマスクを利用する。圧電素子１ａの製造方法における第４工程では、スキージを図６及び７の矢印Ｂ１の向きに移動させることによって、上部電極６、端子電極７及び配線部８それぞれの元になる上部電極材料部、端子電極材料部及び配線材料部を形成する。したがって、圧電素子１ａの製造方法では、第３パターン部が、複数の上部電極材料部の他に、複数の端子電極材料部及び複数の配線材料部を含んでいる。 The manufacturing method of the piezoelectric element 1a is almost the same as the manufacturing method of the piezoelectric element 1, and instead of the screen mask used in the fourth step in the manufacturing method of the piezoelectric element 1, an opening for forming the upper electrode 6 and a terminal electrode 7 are used. A screen mask having an opening for forming the wiring portion 8 and an opening for forming the wiring portion 8 is used. In the fourth step in the method for manufacturing the piezoelectric element 1a, by moving the squeegee in the direction of arrow B1 in FIGS. A terminal electrode material portion and a wiring material portion are formed. Therefore, in the method for manufacturing the piezoelectric element 1a, the third pattern portion includes a plurality of terminal electrode material portions and a plurality of wiring material portions in addition to the plurality of upper electrode material portions.
　圧電素子１ａの製造方法では、第１パターン部、第２パターン部及び第３パターン部を所定の焼成温度（例えば、８７５℃）で焼成することによって、複数の下部電極４を含む下部電極パターン部４Ａ（図３参照）、複数の圧電体層５を含む圧電体層パターン部５Ａ（図３参照）、複数の上部電極６を含む上部電極パターン部６Ａ（図３参照）、複数の端子電極７を含む端子電極パターン部及び複数の配線部８を含む配線パターン部を形成する。これにより、複数の圧電素子１ａを含む構造体が形成される。 In the method for manufacturing the piezoelectric element 1a, the lower electrode pattern portion including the plurality of lower electrodes 4 is formed by firing the first pattern portion, the second pattern portion, and the third pattern portion at a predetermined firing temperature (for example, 875° C.). 4A (see FIG. 3), a piezoelectric layer pattern section 5A (see FIG. 3) including a plurality of piezoelectric layers 5, an upper electrode pattern section 6A (see FIG. 3) including a plurality of upper electrodes 6, and a plurality of terminal electrodes 7. A terminal electrode pattern section including a terminal electrode pattern section and a wiring pattern section including a plurality of wiring sections 8 are formed. As a result, a structure including a plurality of piezoelectric elements 1a is formed.
　（１．２）超音波トランスデューサ
　実施形態２に係る超音波トランスデューサ１００ａは、図８及び９に示すように、第１導電性接合部１３１ａが端子電極７上に配置されている点で、実施形態１に係る超音波トランスデューサ１００（図４及び５参照）と相違する。 (1.2) Ultrasonic transducer As shown in FIGS. 8 and 9, the ultrasonic transducer 100a according to the second embodiment is different from the embodiment in that the first conductive joint 131a is disposed on the terminal electrode 7. This is different from the ultrasonic transducer 100 according to No. 1 (see FIGS. 4 and 5).
　実施形態２に係る超音波トランスデューサ１００ａでは、第１リード線１４１と端子電極７とが第１導電性接合部１３１ａによって接合されている。第１導電性接合部１３１ａの材料は、例えば、はんだを含む。 In the ultrasonic transducer 100a according to the second embodiment, the first lead wire 141 and the terminal electrode 7 are joined by the first conductive joint 131a. The material of the first conductive joint 131a includes, for example, solder.
　（２）効果
　（２．１）圧電素子
　実施形態２に係る圧電素子１ａは、鉄とクロムとアルミニウムとを含む金属基板２を備える。実施形態２に係る圧電素子１ａでは、平面視で、下部電極４の外縁４０が、金属基板２の外縁２０よりも内側に位置し、圧電体層５の外縁５０が、下部電極４の外縁４０よりも内側に位置し、上部電極６の外縁６０が、圧電体層５の外縁５０よりも内側に位置し、端子電極７及び配線部８が金属基板２の外縁２０よりも内側に位置している。これにより、実施形態２に係る圧電素子１ａによれば、圧電素子１ａの動作周波数（共振周波数）の高速化を図ることが可能となる。より詳細には、実施形態２に係る圧電素子１ａは、実施形態１に係る圧電素子１と同様、圧電体層５の薄型化を図ることができるので、圧電素子１ａの共振周波数をより高くすることが可能となり、駆動周波数をより高くすることが可能となる。 (2) Effects (2.1) Piezoelectric Element The piezoelectric element 1a according to the second embodiment includes a metal substrate 2 containing iron, chromium, and aluminum. In the piezoelectric element 1a according to the second embodiment, in plan view, the outer edge 40 of the lower electrode 4 is located inside the outer edge 20 of the metal substrate 2, and the outer edge 50 of the piezoelectric layer 5 is located inside the outer edge 40 of the lower electrode 4. The outer edge 60 of the upper electrode 6 is located inside the outer edge 50 of the piezoelectric layer 5, and the terminal electrode 7 and the wiring portion 8 are located inside the outer edge 20 of the metal substrate 2. There is. Thereby, according to the piezoelectric element 1a according to the second embodiment, it is possible to increase the operating frequency (resonant frequency) of the piezoelectric element 1a. More specifically, in the piezoelectric element 1a according to the second embodiment, the piezoelectric layer 5 can be made thinner, similar to the piezoelectric element 1 according to the first embodiment, so that the resonant frequency of the piezoelectric element 1a can be made higher. This makes it possible to increase the driving frequency.
　また、圧電素子１ａは、端子電極７及び配線部８を備え、端子電極７及び配線部８が金属基板２の外縁２０よりも内側に位置しているので、折り返し電極を形成する必要がなく、製造が容易になるとともに、圧電素子１ａのハンドリング時の端子電極７及び配線部８の破損を防止することが可能となる。 Moreover, the piezoelectric element 1a includes the terminal electrode 7 and the wiring part 8, and since the terminal electrode 7 and the wiring part 8 are located inside the outer edge 20 of the metal substrate 2, there is no need to form a folded electrode. Manufacturing becomes easier, and it becomes possible to prevent damage to the terminal electrode 7 and wiring portion 8 during handling of the piezoelectric element 1a.
　また、圧電素子１ａでは、金属基板２の上面２１から端子電極７の上面７１までの第１高さが、金属基板２の上面２１から上部電極６の上面６１までの第２高さと同じなので、例えば、第１リード電極（第１導体部）及び第２リード電極（第２導体部）を含むフレキシブルプリント配線板への実装が容易になるとともに、接続信頼性を向上させることが可能となる。圧電素子１ａをフレキシブルプリント配線板へ実装する場合には、フレキシブルプリント配線板に含まれる第１リード電極（第１導体部）及び第２リード電極（第２導体部）が、第１リード線１４１及び第２リード線１４２の代わりに、圧電素子１ａの端子電極７及び上部電極６に、第１導電性接合部１３１ａ及び第２導電性接合部１３２によって接合される。 Furthermore, in the piezoelectric element 1a, the first height from the upper surface 21 of the metal substrate 2 to the upper surface 71 of the terminal electrode 7 is the same as the second height from the upper surface 21 of the metal substrate 2 to the upper surface 61 of the upper electrode 6. For example, mounting on a flexible printed wiring board including a first lead electrode (first conductor part) and a second lead electrode (second conductor part) becomes easier, and connection reliability can be improved. When mounting the piezoelectric element 1a on a flexible printed wiring board, the first lead electrode (first conductor part) and the second lead electrode (second conductor part) included in the flexible printed wiring board are connected to the first lead wire 141. And instead of the second lead wire 142, it is joined to the terminal electrode 7 and the upper electrode 6 of the piezoelectric element 1a by the first conductive joint 131a and the second conductive joint 132.
　また、実施形態２に係る圧電素子１ａでは、平面視で、端子電極７は、圧電体層５の外縁５０よりも内側に位置している。配線部８は、圧電体層５の上面５１に設けられている部分８１を含む。これにより、実施形態２に係る圧電素子１ａは、端子電極７の厚さの均一性を向上させることが可能となる。 Furthermore, in the piezoelectric element 1a according to the second embodiment, the terminal electrode 7 is located inside the outer edge 50 of the piezoelectric layer 5 in plan view. The wiring portion 8 includes a portion 81 provided on the upper surface 51 of the piezoelectric layer 5 . Thereby, the piezoelectric element 1a according to the second embodiment can improve the uniformity of the thickness of the terminal electrode 7.
　また、実施形態２に係る圧電素子１ａは、特許文献１に開示された折り返し電極の構造を採用することなく、下部電極４に接続された端子電極７が圧電体層５の上面５１上に配置された構成を実現することができる。 Furthermore, in the piezoelectric element 1a according to the second embodiment, the terminal electrode 7 connected to the lower electrode 4 is arranged on the upper surface 51 of the piezoelectric layer 5 without adopting the folded electrode structure disclosed in Patent Document 1. It is possible to realize the following configuration.
　（２．２）超音波トランスデューサ
　実施形態２に係る超音波トランスデューサ１００ａは、圧電素子１ａと、圧電素子１ａの金属基板２と接合されている振動板部１２０と、を備えるので、圧電素子１ａの動作周波数（共振周波数）の高速化を図ることが可能となる。これにより、超音波トランスデューサ１００ａでは、圧電素子１ａの駆動周波数をより高くすることが可能となり、超音波の指向角の挟角化を図ることが可能となる。よって、例えば、超音波トランスデューサ１００ａを備える超音波センサを自動車に設置して用いる場合に、超音波トランスデューサ１００ａから送波された超音波が路面に入射して反射されることを抑制できる。これにより、超音波センサのＳ／Ｎ比を向上させることが可能となり、物体を検知可能な距離をより長くすることが可能となる。 (2.2) Ultrasonic transducer The ultrasonic transducer 100a according to the second embodiment includes the piezoelectric element 1a and the diaphragm portion 120 joined to the metal substrate 2 of the piezoelectric element 1a. It becomes possible to increase the operating frequency (resonant frequency). Thereby, in the ultrasonic transducer 100a, it becomes possible to increase the driving frequency of the piezoelectric element 1a, and it becomes possible to narrow the directivity angle of the ultrasonic waves. Therefore, for example, when an ultrasonic sensor including the ultrasonic transducer 100a is installed and used in a car, it is possible to suppress the ultrasonic waves transmitted from the ultrasonic transducer 100a from entering the road surface and being reflected. Thereby, it becomes possible to improve the S/N ratio of the ultrasonic sensor, and it becomes possible to further increase the distance at which an object can be detected.
　また、実施形態２に係る超音波トランスデューサ１００ａでは、圧電素子１ａにおける金属基板２の上面２１から端子電極７の上面７１までの第１高さが、金属基板２の上面２１から上部電極６の上面６１までの第２高さと同じである。これにより、実施形態２に係る超音波トランスデューサ１００ａでは、第１導通部材及び第２導通部材として、第１リード線１４１及び第２リード線１４２の代わりに、例えば、フレキシブルプリント配線板第１リード電極（第１導体部）及び第２リード電極（第２導体部）を採用する場合に、フレキシブルプリント配線板への実装が容易になるとともに、接続信頼性の向上を図れる。 Further, in the ultrasonic transducer 100a according to the second embodiment, the first height from the upper surface 21 of the metal substrate 2 to the upper surface 71 of the terminal electrode 7 in the piezoelectric element 1a is from the upper surface 21 of the metal substrate 2 to the upper surface of the upper electrode 6. It is the same as the second height up to 61. As a result, in the ultrasonic transducer 100a according to the second embodiment, for example, the first lead wire of the flexible printed wiring board is used instead of the first lead wire 141 and the second lead wire 142 as the first conductive member and the second conductive member. (first conductor part) and second lead electrode (second conductor part), mounting on a flexible printed wiring board becomes easy and connection reliability can be improved.
　（実施形態３）
　実施形態３に係る圧電素子１ｂについて、図１０を参照して説明する。実施形態３に係る圧電素子１ｂに関し、実施形態１に係る圧電素子１（図１及び２参照）と同様の構成要素については、同一の符号を付して説明を適宜省略する。 (Embodiment 3)
A piezoelectric element 1b according to Embodiment 3 will be described with reference to FIG. 10. Regarding the piezoelectric element 1b according to the third embodiment, the same components as those of the piezoelectric element 1 according to the first embodiment (see FIGS. 1 and 2) are designated by the same reference numerals, and the description thereof will be omitted as appropriate.
　（１）構成
　実施形態３に係る圧電素子１ｂでは、圧電体層５が、下部電極４の上面４１の一部を露出させる開口部５４を有する点で、実施形態１に係る圧電素子１と相違する。 (1) Configuration The piezoelectric element 1b according to the third embodiment is different from the piezoelectric element 1 according to the first embodiment in that the piezoelectric layer 5 has an opening 54 that exposes a part of the upper surface 41 of the lower electrode 4. do.
　圧電体層５の開口部５４は、圧電体層５の厚さ方向に沿って形成されている。平面視で、開口部５４の開口形状は、四角形状であるが、これに限らず、例えば、円形状であってもよい。圧電素子１ｂでは、下部電極４において圧電体層５の開口部５４により露出した下部電極４の一部（部位４１１ｂ）が、端子部を構成する。 The opening 54 of the piezoelectric layer 5 is formed along the thickness direction of the piezoelectric layer 5. In plan view, the opening shape of the opening portion 54 is square, but is not limited to this, and may be circular, for example. In the piezoelectric element 1b, a portion of the lower electrode 4 (portion 411b) exposed through the opening 54 of the piezoelectric layer 5 constitutes a terminal portion.
　圧電素子１ｂの製造方法は、圧電素子１の製造方法と略同じであり、圧電素子１の製造方法における第３工程で用いるスクリーンマスクのパターンを変更することにより、圧電体層５の開口部５４を形成することができる。 The method for manufacturing the piezoelectric element 1b is substantially the same as the method for manufacturing the piezoelectric element 1, and by changing the pattern of the screen mask used in the third step in the method for manufacturing the piezoelectric element 1, the openings 54 of the piezoelectric layer 5 are can be formed.
　（２）効果
　実施形態３に係る圧電素子１ｂは、鉄とクロムとアルミニウムとを含む金属基板２を備える。実施形態３に係る圧電素子１ｂでは、平面視で、下部電極４の外縁４０が、金属基板２の外縁２０よりも内側に位置し、圧電体層５の外縁５０が、下部電極４の外縁４０よりも内側に位置し、上部電極６の外縁６０が、圧電体層５の外縁５０よりも内側に位置している。これにより、実施形態３に係る圧電素子１ｂによれば、圧電素子１ｂの動作周波数（共振周波数）の高速化を図ることが可能となる。より詳細には、実施形態３に係る圧電素子１ｂは、実施形態１に係る圧電素子１と同様、圧電体層５の薄型化を図ることができるので、圧電素子１ｂの共振周波数をより高くすることが可能となり、駆動周波数をより高くすることが可能となる。 (2) Effects The piezoelectric element 1b according to the third embodiment includes a metal substrate 2 containing iron, chromium, and aluminum. In the piezoelectric element 1b according to the third embodiment, in plan view, the outer edge 40 of the lower electrode 4 is located inside the outer edge 20 of the metal substrate 2, and the outer edge 50 of the piezoelectric layer 5 is located inside the outer edge 40 of the lower electrode 4. The outer edge 60 of the upper electrode 6 is located inner than the outer edge 50 of the piezoelectric layer 5 . Thereby, according to the piezoelectric element 1b according to the third embodiment, it is possible to increase the operating frequency (resonant frequency) of the piezoelectric element 1b. More specifically, in the piezoelectric element 1b according to the third embodiment, the piezoelectric layer 5 can be made thinner, similar to the piezoelectric element 1 according to the first embodiment, so that the resonant frequency of the piezoelectric element 1b can be made higher. This makes it possible to increase the driving frequency.
　また、実施形態３に係る圧電素子１ｂは、圧電体層５が、下部電極４の上面４１の一部を露出させる開口部５４を有するので、下部電極４の上面４１の一部を端子部として兼用することができる。これにより、実施形態３に係る圧電素子１ｂは、実施形態１に係る圧電素子１と比べて、端子部として機能する領域を狭くすることが可能となり、使用時の特性のばらつきを抑制することが可能となる。 Furthermore, in the piezoelectric element 1b according to the third embodiment, since the piezoelectric layer 5 has an opening 54 that exposes a part of the upper surface 41 of the lower electrode 4, the part of the upper surface 41 of the lower electrode 4 can be used as a terminal part. Can be used for both purposes. As a result, the piezoelectric element 1b according to the third embodiment can have a narrower region functioning as a terminal part than the piezoelectric element 1 according to the first embodiment, and can suppress variations in characteristics during use. It becomes possible.
　（実施形態４）
　以下、実施形態４に係る超音波トランスデューサ１００ｃについて、図１２を参照しながら説明する。なお、実施形態４に係る超音波トランスデューサ１００ｃに関し、実施形態１に係る超音波トランスデューサ１００と同様の構成要素には、同一の符号を付して説明を適宜省略する。 (Embodiment 4)
An ultrasonic transducer 100c according to Embodiment 4 will be described below with reference to FIG. 12. Regarding the ultrasonic transducer 100c according to the fourth embodiment, the same components as those of the ultrasonic transducer 100 according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.
　実施形態４に係る超音波トランスデューサ１００ｃは、実施形態１に係る超音波トランスデューサ１００における振動板部１２０の代わりに、底面が開口した円錐状の振動板部１２０ｃを備える。 The ultrasonic transducer 100c according to the fourth embodiment includes a conical diaphragm section 120c with an open bottom in place of the diaphragm section 120 in the ultrasonic transducer 100 according to the first embodiment.
　また、実施形態４に係る超音波トランスデューサ１００ｃは、実施形態１に係る超音波トランスデューサ１００におけるケース１０１の代わりに、ケース１０１ｃを備える。 Furthermore, the ultrasonic transducer 100c according to the fourth embodiment includes a case 101c instead of the case 101 in the ultrasonic transducer 100 according to the first embodiment.
　超音波トランスデューサ１００ｃでは、ケース１０１ｃ内に、圧電素子１及び振動板部１２０ｃが収容されている。振動板部１２０ｃは、圧電素子１の金属基板２の下面２２に接合されている。振動板部１２０ｃは、ケース１０１ｃとは別部材であり、ケース１０１ｃから離れている。 In the ultrasonic transducer 100c, the piezoelectric element 1 and the diaphragm portion 120c are housed in the case 101c. The diaphragm portion 120c is joined to the lower surface 22 of the metal substrate 2 of the piezoelectric element 1. The diaphragm portion 120c is a separate member from the case 101c and is separated from the case 101c.
　ケース１０１ｃは、台座１７０と、キャップ１０６と、メッシュ部材１６５と、を含む。また、超音波トランスデューサ１００ｃは、台座１７０から突出しており、圧電素子１を支持している支持部１８０を備える。また、超音波トランスデューサ１００ｃは、第１導電性接合部１３１及び第２導電性接合部１３２と、第１リード線１４１及び第２リード線１４２と、第１リード端子１９１及び第２リード端子１９２と、を備える。 The case 101c includes a pedestal 170, a cap 106, and a mesh member 165. The ultrasonic transducer 100c also includes a support portion 180 that protrudes from the pedestal 170 and supports the piezoelectric element 1. The ultrasonic transducer 100c also includes a first conductive joint 131 and a second conductive joint 132, a first lead wire 141 and a second lead wire 142, a first lead terminal 191 and a second lead terminal 192. , is provided.
　台座１７０は、円盤状である。台座１７０の材料は、例えば、アルミニウム合金であるが、これに限らず、例えば、マグネシウム合金、ステンレス鋼、チタン合金又はエンジニアプラスチックでもよい。 The pedestal 170 is disc-shaped. The material of the pedestal 170 is, for example, an aluminum alloy, but is not limited thereto, and may be, for example, a magnesium alloy, stainless steel, a titanium alloy, or an engineered plastic.
　キャップ１０６は、底壁１６１と円筒状の周壁１６２とを有する有底円筒状であり、圧電素子１及び振動板部１２０ｃを覆うように台座１７０に固着されている。キャップ１０６の材料は、例えば、アルミニウム合金であるが、これに限らず、例えば、マグネシウム合金、ステンレス鋼、チタン合金又はエンジニアプラスチックでもよい。 The cap 106 has a bottomed cylindrical shape having a bottom wall 161 and a cylindrical peripheral wall 162, and is fixed to the pedestal 170 so as to cover the piezoelectric element 1 and the diaphragm portion 120c. The material of the cap 106 is, for example, an aluminum alloy, but is not limited thereto, and may be, for example, a magnesium alloy, stainless steel, a titanium alloy, or an engineered plastic.
　メッシュ部材１６５は、キャップ１０６の底壁１６１に形成された窓孔１６３内に配置されており、振動板部１２０ｃの前方に位置している。メッシュ部材１６５は、超音波を通すことができるように複数の開口部１６６を有する。 The mesh member 165 is disposed within a window hole 163 formed in the bottom wall 161 of the cap 106, and is located in front of the diaphragm portion 120c. The mesh member 165 has a plurality of openings 166 to allow ultrasound to pass therethrough.
　第１リード線１４１及び第２リード線１４２は、可撓性を有する電線である。超音波トランスデューサ１００ｃでは、第１リード線１４１の第１端は、第１導電性接合部１３１により圧電素子１の下部電極４に接合されて電気的に接続され、第１リード線１４１の第２端は、第１リード端子１９１に接合されて電気的に接続されている。また、超音波トランスデューサ１００ｃでは、第２リード線１４２の第１端は、第２導電性接合部１３２により圧電素子１の上部電極６に接合されて電気的に接続され、第２リード線１４２の第２端は、第２リード端子１９２に接合されて電気的に接続されている。 The first lead wire 141 and the second lead wire 142 are flexible electric wires. In the ultrasonic transducer 100c, the first end of the first lead wire 141 is joined and electrically connected to the lower electrode 4 of the piezoelectric element 1 by the first conductive joint 131, and the second end of the first lead wire 141 The end is joined to the first lead terminal 191 and electrically connected. Further, in the ultrasonic transducer 100c, the first end of the second lead wire 142 is joined and electrically connected to the upper electrode 6 of the piezoelectric element 1 by the second conductive joint portion 132. The second end is joined to and electrically connected to the second lead terminal 192.
　第１リード端子１９１及び第２リード端子１９２の各々は、ピン状である。第１リード端子１９１及び第２リード端子１９２は、台座１７０の厚さ方向において台座１７０を貫通している。第１リード端子１９１と第２リード端子１９２とは電気的に絶縁されている。第１リード端子１９１及び第２リード端子１９２は、台座１７０とは第１リード端子１９１及び第２リード端子１９２と台座１７０との間に介在する第１絶縁部及び第２絶縁部により電気的に絶縁されているが、これに限らない。例えば、第１リード端子１９１及び第２リード端子１９２のうちの一方が台座１７０と電気的に接続されていてもよい。 Each of the first lead terminal 191 and the second lead terminal 192 is pin-shaped. The first lead terminal 191 and the second lead terminal 192 penetrate the base 170 in the thickness direction of the base 170. The first lead terminal 191 and the second lead terminal 192 are electrically insulated. The first lead terminal 191 and the second lead terminal 192 are electrically connected to the pedestal 170 by the first insulating part and the second insulating part interposed between the first lead terminal 191 and the second lead terminal 192 and the pedestal 170. Although it is insulated, it is not limited to this. For example, one of the first lead terminal 191 and the second lead terminal 192 may be electrically connected to the base 170.
　実施形態４に係る超音波トランスデューサ１００ｃは、圧電素子１と、圧電素子１の金属基板２と接合されている振動板部１２０ｃと、を備えるので、圧電素子１の動作周波数（共振周波数）の高速化を図ることが可能となる。これにより、超音波トランスデューサ１００ｃでは、圧電素子１の駆動周波数をより高くすることが可能となり、超音波の指向角の挟角化を図ることが可能となる。 The ultrasonic transducer 100c according to the fourth embodiment includes the piezoelectric element 1 and the diaphragm portion 120c joined to the metal substrate 2 of the piezoelectric element 1, so that the operating frequency (resonant frequency) of the piezoelectric element 1 can be adjusted to a high speed. This makes it possible to achieve Thereby, in the ultrasonic transducer 100c, it becomes possible to increase the driving frequency of the piezoelectric element 1, and it becomes possible to narrow the directivity angle of the ultrasonic waves.
　（変形例）
　実施形態１～４は、本開示の様々な実施形態の一つに過ぎない。実施形態１～４は、本開示の目的を達成できれば、設計等に応じて種々の変更が可能である。 (Modified example)
Embodiments 1-4 are just one of various embodiments of the present disclosure. Embodiments 1 to 4 can be modified in various ways depending on the design, etc., as long as the objective of the present disclosure can be achieved.
　例えば、平面視での金属基板２の外縁２０は、長方形状である場合に限らず、例えば、正方形状であってもよいし、円形状、楕円状又は長円状であってもよい。 For example, the outer edge 20 of the metal substrate 2 in plan view is not limited to a rectangular shape, and may be, for example, square, circular, elliptical, or oval.
　金属基板２は、アルミニウムを含むことは必須ではなく、少なくとも鉄及びクロムを含んでいればよい。 The metal substrate 2 does not necessarily need to contain aluminum, but only needs to contain at least iron and chromium.
　また、圧電素子１、１ａ、１ｂにおいてアルミナ層３を含むことは必須ではない。つまり、圧電素子１、１ａ、１ｂは、アルミナ層３を含まず、下部電極４が金属基板２上に直接設けられていてもよい。 Furthermore, it is not essential that the piezoelectric elements 1, 1a, and 1b include the alumina layer 3. That is, the piezoelectric elements 1, 1a, and 1b may not include the alumina layer 3, and the lower electrode 4 may be provided directly on the metal substrate 2.
　また、圧電体層５の材料は、ＰｂとＺｒとＺｎとＮｂとＯとを含む材料、例えば、Ｐｂ１．０１５Ｚｒ０．４４（Ｚｎ１／３Ｎｂ２／３）０．１０Ｏ３．０１５に限らず、チタン酸ジルコン酸鉛（ＰＺＴ）、チタン酸バリウム、マグネシウムニオブ酸鉛（ＰＭＮ）、ＫＮｂＯ３、ＮａＮｂＯ３又はＫ０．５Ｎａ０．５ＮｂＯ３であってもよい。 The material of the piezoelectric layer 5 is a material containing Pb, Zr, Zn, Nb, and O, for example, Pb 1.015 Zr 0.44 (Zn 1/3 Nb 2/3 ) 0.10 O 3. 015 , but may be lead zirconate titanate (PZT), barium titanate, lead magnesium niobate (PMN), KNbO 3 , NaNbO 3 or K 0.5 Na 0.5 NbO 3 .
　また、圧電素子１、１ａ、１ｂでは、圧電体層５が下部電極４上に直接設けられているが、これに限らず、圧電体層５がバッファ層を介して下部電極４上に設けられていてもよい。バッファ層は、例えば、下部電極４の材料の少なくとも一部と圧電体層５の材料の少なくとも一部とを含む。 Furthermore, in the piezoelectric elements 1, 1a, and 1b, the piezoelectric layer 5 is provided directly on the lower electrode 4; however, the piezoelectric layer 5 is not limited to this, and the piezoelectric layer 5 may be provided on the lower electrode 4 via a buffer layer. You can leave it there. The buffer layer includes, for example, at least a portion of the material of the lower electrode 4 and at least a portion of the material of the piezoelectric layer 5.
　また、圧電素子１ａでは、配線部８は、下部電極４の上面４１と圧電体層５の側面５３と圧電体層５の上面５１とに跨って設けられている構成に限らない。例えば、配線部８は、下部電極４と端子電極７とをつないでおり、かつ、圧電体層５の下面５２に設けられていなければよく、少なくとも下部電極４の上面４１と圧電体層５の側面５３とに跨って設けられていればよい。 Furthermore, in the piezoelectric element 1a, the wiring portion 8 is not limited to the configuration in which it is provided across the upper surface 41 of the lower electrode 4, the side surface 53 of the piezoelectric layer 5, and the upper surface 51 of the piezoelectric layer 5. For example, it is sufficient that the wiring portion 8 connects the lower electrode 4 and the terminal electrode 7 and is not provided on the lower surface 52 of the piezoelectric layer 5. It suffices if it is provided astride the side surface 53.
　また、圧電素子１ｂは、圧電体層５の外縁５０のうち開口部５４の近い部分と圧電体層５の開口部５４との間の狭い部分を有することは必須ではなく、開口部５４が上方及び側方へ開放されていてもよい。 Furthermore, it is not essential for the piezoelectric element 1b to have a narrow portion between the outer edge 50 of the piezoelectric layer 5 near the opening 54 and the opening 54 of the piezoelectric layer 5; and may be opened laterally.
　超音波トランスデューサ１００、１００ａにおいて、第１導通部材及び第２導通部材は、第１リード線１４１及び第２リード線１４２に限らず、例えば、フレキシブルプリント配線板の導体パターン部に含まれる第１リード電極（第１導体部）及び第２リード電極（第２導体部）であってもよい。 In the ultrasonic transducer 100, 100a, the first conductive member and the second conductive member are not limited to the first lead wire 141 and the second lead wire 142, but are, for example, the first lead included in the conductor pattern portion of the flexible printed wiring board. It may be an electrode (first conductor part) and a second lead electrode (second conductor part).
　また、超音波トランスデューサ１００ｃにおいて、第１導通部材及び第２導通部材は、第１リード線１４１及び第２リード線１４２に限らず、例えば、第１導電性ワイヤ及び第２導電性ワイヤであってもよい。 Further, in the ultrasonic transducer 100c, the first conductive member and the second conductive member are not limited to the first lead wire 141 and the second lead wire 142, but are, for example, a first conductive wire and a second conductive wire. Good too.
　また、超音波トランスデューサ１００ｃは、圧電素子１の代わりに、圧電素子１ａ又は圧電素子１ｂを備えていてもよい。 Further, the ultrasonic transducer 100c may include a piezoelectric element 1a or a piezoelectric element 1b instead of the piezoelectric element 1.
　（態様）
　以上説明した実施形態１～４等から、本明細書には以下の態様が開示されている。 (mode)
From Embodiments 1 to 4 described above, the following aspects are disclosed in this specification.
　第１の態様に係る圧電素子（１；１ａ；１ｂ）は、金属基板（２）と、下部電極（４）と、圧電体層（５）と、上部電極（６）と、を備える。金属基板（２）は、少なくとも鉄及びクロムを含む。下部電極（４）は、金属基板（２）上に設けられている。圧電体層（５）は、下部電極（４）上に設けられている。上部電極（６）は、圧電体層（５）上に設けられている。平面視で、下部電極（４）の第１外縁（外縁４０）は、金属基板２の第２外縁（外縁２０）よりも内側に位置している。平面視で、圧電体層（５）の第３外縁（外縁５０）は、下部電極（４）の第１外縁（外縁４０）よりも内側に位置している。平面視で、上部電極（６）の第４外縁（外縁６０）は、圧電体層（５）の第３外縁（外縁５０）よりも内側に位置している。 The piezoelectric element (1; 1a; 1b) according to the first aspect includes a metal substrate (2), a lower electrode (4), a piezoelectric layer (5), and an upper electrode (6). The metal substrate (2) contains at least iron and chromium. The lower electrode (4) is provided on the metal substrate (2). The piezoelectric layer (5) is provided on the lower electrode (4). The upper electrode (6) is provided on the piezoelectric layer (5). In plan view, the first outer edge (outer edge 40) of the lower electrode (4) is located inside the second outer edge (outer edge 20) of the metal substrate 2. In plan view, the third outer edge (outer edge 50) of the piezoelectric layer (5) is located inside the first outer edge (outer edge 40) of the lower electrode (4). In plan view, the fourth outer edge (outer edge 60) of the upper electrode (6) is located inside the third outer edge (outer edge 50) of the piezoelectric layer (5).
　第１の態様に係る圧電素子（１；１ａ；１ｂ）によれば、圧電素子（１；１ａ；１ｂ）の動作周波数の高速化を図ることが可能となる。 According to the piezoelectric element (1; 1a; 1b) according to the first aspect, it is possible to increase the operating frequency of the piezoelectric element (1; 1a; 1b).
　第２の態様に係る圧電素子（１；１ａ；１ｂ）は、第１の態様において、アルミナ層（３）を更に含む。アルミナ層（３）は、金属基板（２）と下部電極（４）との間に介在している。金属基板（２）は、アルミニウムを更に含む。アルミナ層（３）の上面（３１）は、アルミナ層（３）の有する複数の鱗片状の粒子の表面の一部を含む。 The piezoelectric element (1; 1a; 1b) according to the second embodiment further includes an alumina layer (3) in the first embodiment. The alumina layer (3) is interposed between the metal substrate (2) and the lower electrode (4). The metal substrate (2) further contains aluminum. The upper surface (31) of the alumina layer (3) includes a part of the surface of the plurality of scale-like particles of the alumina layer (3).
　第２の態様に係る圧電素子（１；１ａ；１ｂ）は、下部電極（４）の剥離を抑制することが可能となる。 The piezoelectric element (1; 1a; 1b) according to the second aspect can suppress peeling of the lower electrode (4).
　第３の態様に係る圧電素子（１；１ａ；１ｂ）では、第２の態様において、アルミナ層（３）は、金属基板（２）の上面（２１）の全域を覆っている。 In the piezoelectric element (1; 1a; 1b) according to the third aspect, in the second aspect, the alumina layer (3) covers the entire upper surface (21) of the metal substrate (2).
　第３の態様に係る圧電素子（１；１ａ；１ｂ）では、圧電特性を向上させることが可能となる。 In the piezoelectric element (1; 1a; 1b) according to the third aspect, it is possible to improve piezoelectric characteristics.
　第４の態様に係る圧電素子（１ａ）は、第１～３の態様のいずれか一つにおいて、端子電極（７）と、配線部（８）と、を更に備える。端子電極（７）は、圧電体層（５）上に設けられており、上部電極（６）から離れている。配線部（８）は、下部電極（４）の上面（４１）と圧電体層（５）の側面（５３）とに跨って設けられており、下部電極（４）と端子電極（７）とをつないでいる。平面視で、配線部（８）は、金属基板（２）の第２外縁（外縁２０）よりも内側に位置している。 The piezoelectric element (1a) according to the fourth aspect, in any one of the first to third aspects, further includes a terminal electrode (7) and a wiring part (8). The terminal electrode (7) is provided on the piezoelectric layer (5) and is separated from the upper electrode (6). The wiring section (8) is provided across the upper surface (41) of the lower electrode (4) and the side surface (53) of the piezoelectric layer (5), and is connected between the lower electrode (4) and the terminal electrode (7). are connected. In plan view, the wiring portion (8) is located inside the second outer edge (outer edge 20) of the metal substrate (2).
　第４の態様に係る圧電素子（１ａ）では、フレキシブルプリント配線板への実装が容易になるとともに、接続信頼性を向上させることが可能となる。 The piezoelectric element (1a) according to the fourth aspect can be easily mounted on a flexible printed wiring board and can improve connection reliability.
　第５の態様に係る圧電素子（１ａ）では、第４の態様において、平面視で、端子電極（７）は、圧電体層（５）の第３外縁（外縁５０）よりも内側に位置している。配線部（８）は、圧電体層（５）の上面（５１）に設けられている部分（８１）を含む。 In the piezoelectric element (1a) according to the fifth aspect, in the fourth aspect, the terminal electrode (7) is located inside the third outer edge (outer edge 50) of the piezoelectric layer (5) in plan view. ing. The wiring portion (8) includes a portion (81) provided on the upper surface (51) of the piezoelectric layer (5).
　第５の態様に係る圧電素子（１ａ）では、端子電極（７）の厚さの均一性を向上させることが可能となる。 In the piezoelectric element (1a) according to the fifth aspect, it is possible to improve the uniformity of the thickness of the terminal electrode (7).
　第６の態様に係る圧電素子（１ｂ）では、第１～３の態様のいずれか一つにおいて、圧電体層（５）は、下部電極（４）の上面（４１）の一部を露出させる開口部（５４）を有する。 In the piezoelectric element (1b) according to the sixth aspect, in any one of the first to third aspects, the piezoelectric layer (5) exposes a part of the upper surface (41) of the lower electrode (4). It has an opening (54).
　第６の態様に係る圧電素子（１ｂ）では、下部電極（４）の上面（４１）の一部が端子部を構成するので、端子部として機能する領域を狭くすることが可能となり、使用時の特性のばらつきを抑制することが可能となる。 In the piezoelectric element (1b) according to the sixth aspect, since a part of the upper surface (41) of the lower electrode (4) constitutes the terminal part, it is possible to narrow the area that functions as the terminal part, and when in use This makes it possible to suppress variations in the characteristics of.
　第７の態様に係る超音波トランスデューサ（１００；１００ａ；１００ｃ）は、第１～６の態様のいずれか一つの圧電素子（１；１ａ；１ｂ）と、振動板部（１２０；１２０ｃ）と、第１導通部材（第１リード線１４１）と、第２導通部材（第２リード線１４２）と、第１導電性接合部（１３１）と、第２導電性接合部（１３２）と、を備える。振動板部（１２０；１２０ｃ）は、圧電素子（１；１ａ；１ｂ）の金属基板（２）と接合されている。第１導通部材（第１リード線１４１）は、圧電素子（１；１ａ；１ｂ）の下部電極（４）に接続される。第２導通部材（第２リード線１４２）は、圧電素子（１；１ａ；１ｂ）の上部電極（６）に接続される。第１導電性接合部（１３１）は、下部電極（４）と第１導通部材（第１リード線１４１）とを接合している。第２導電性接合部（１３２）は、上部電極（６）と第２導通部材（第２リード線１４２）とを接合している。 An ultrasonic transducer (100; 100a; 100c) according to a seventh aspect includes a piezoelectric element (1; 1a; 1b) according to any one of the first to sixth aspects, a diaphragm section (120; 120c), Includes a first conductive member (first lead wire 141), a second conductive member (second lead wire 142), a first conductive joint (131), and a second conductive joint (132). . The diaphragm portion (120; 120c) is joined to the metal substrate (2) of the piezoelectric element (1; 1a; 1b). The first conductive member (first lead wire 141) is connected to the lower electrode (4) of the piezoelectric element (1; 1a; 1b). The second conductive member (second lead wire 142) is connected to the upper electrode (6) of the piezoelectric element (1; 1a; 1b). The first conductive joint (131) joins the lower electrode (4) and the first conductive member (first lead wire 141). The second conductive joint (132) joins the upper electrode (6) and the second conductive member (second lead wire 142).
　第７の態様に係る超音波トランスデューサ（１００；１００ａ；１００ｃ）は、圧電素子（１；１ａ；１ｂ）の動作周波数の高速化を図ることが可能となる。 The ultrasonic transducer (100; 100a; 100c) according to the seventh aspect can increase the operating frequency of the piezoelectric element (1; 1a; 1b).
　第８の態様に係る超音波トランスデューサ（１００；１００ａ）では、第７の態様において、圧電素子（１；１ａ；１ｂ）を収容しているケース（１０１）を更に備える。ケース（１０１）は、底板部（１０２）と、筒部（１０３）と、を有する。底板部（１０２）は、平板状である。筒部（１０３）は、底板部（１０２）の一面の周部から底板部（１０２）の厚さ方向に突出しており、圧電素子（１；１ａ；１ｂ）を囲んでいる。底板部（１０２）のうち筒部（１０３）により囲まれた部分が、振動板部（１２０）を兼ねている。 The ultrasonic transducer (100; 100a) according to the eighth aspect further includes a case (101) housing the piezoelectric element (1; 1a; 1b) in the seventh aspect. The case (101) has a bottom plate part (102) and a cylindrical part (103). The bottom plate portion (102) has a flat plate shape. The cylindrical portion (103) protrudes from the periphery of one surface of the bottom plate portion (102) in the thickness direction of the bottom plate portion (102), and surrounds the piezoelectric element (1; 1a; 1b). A portion of the bottom plate portion (102) surrounded by the cylinder portion (103) also serves as a diaphragm portion (120).
　第８の態様に係る超音波トランスデューサ（１００；１００ａ）は、例えば、車両に取り付けられて車両の外部の物体を検知する超音波センサに用いることができる。 The ultrasonic transducer (100; 100a) according to the eighth aspect can be used, for example, as an ultrasonic sensor that is attached to a vehicle and detects objects outside the vehicle.
　１、１ａ、１ｂ　圧電素子
　２　金属基板
　２０　外縁（第２外縁）
　３　アルミナ層
　３０　外縁
　３１　上面
　４　下部電極
　４０　外縁（第１外縁）
　４１　上面
　４１１　部位
　５　圧電体層
　５０　外縁（第３外縁）
　５１　上面
　５３　側面
　５４　開口部
　６　上部電極
　６０　外縁（第４外縁）
　６１　上面
　７　端子電極
　７１　上面
　８　配線部
　８１　部分
　９　空隙
　１００、１００ａ、１００ｃ　超音波トランスデューサ
　１０１、１０１ｃ　ケース
　１０２　底板部
　１０３　筒部
　１２０、１２０ｃ　振動板部
　１３１　第１導電性接合部
　１３２　第２導電性接合部
　１４１　第１リード線（第１導通部材）
　１４２　第２リード線（第２導通部材） 1, 1a, 1b piezoelectric element 2 metal substrate 20 outer edge (second outer edge)
3 Alumina layer 30 Outer edge 31 Upper surface 4 Lower electrode 40 Outer edge (first outer edge)
41 Upper surface 411 Part 5 Piezoelectric layer 50 Outer edge (third outer edge)
51 Top surface 53 Side surface 54 Opening 6 Upper electrode 60 Outer edge (fourth outer edge)
61 Top surface 7 Terminal electrode 71 Top surface 8 Wiring section 81 Portion 9 Gap 100, 100a, 100c Ultrasonic transducer 101, 101c Case 102 Bottom plate section 103 Cylindrical section 120, 120c Vibration plate section 131 First conductive joint section 132 Second conductive section Joint part 141 First lead wire (first conductive member)
142 Second lead wire (second conductive member)

Claims (8)

  1. 　少なくとも鉄及びクロムを含む金属基板と、
    　前記金属基板上に設けられている下部電極と、
    　前記下部電極上に設けられている圧電体層と、
    　前記圧電体層上に設けられている上部電極と、を備え、
    　平面視で、前記下部電極の第１外縁は、前記金属基板の第２外縁よりも内側に位置しており、
    　前記平面視で、前記圧電体層の第３外縁は、前記下部電極の前記第１外縁よりも内側に位置しており、
    　前記平面視で、前記上部電極の第４外縁は、前記圧電体層の前記第３外縁よりも内側に位置している、
    　圧電素子。     a metal substrate containing at least iron and chromium;
    a lower electrode provided on the metal substrate;
    a piezoelectric layer provided on the lower electrode;
    an upper electrode provided on the piezoelectric layer,
    In plan view, the first outer edge of the lower electrode is located inside the second outer edge of the metal substrate,
    In the plan view, the third outer edge of the piezoelectric layer is located inside the first outer edge of the lower electrode,
    In the plan view, the fourth outer edge of the upper electrode is located inside the third outer edge of the piezoelectric layer.
    Piezoelectric element.
  2. 　前記金属基板と前記下部電極との間に介在しているアルミナ層を更に含み、
    　前記金属基板は、アルミニウムを更に含み、
    　前記アルミナ層の上面は、前記アルミナ層の有する複数の鱗片状の粒子の表面の一部を含む、
    　請求項１に記載の圧電素子。     further comprising an alumina layer interposed between the metal substrate and the lower electrode,
    The metal substrate further includes aluminum,
    The upper surface of the alumina layer includes a part of the surface of a plurality of scale-like particles of the alumina layer.
    The piezoelectric element according to claim 1.
  3. 　前記アルミナ層は、前記金属基板の上面の全域を覆っている、
    　請求項２に記載の圧電素子。     The alumina layer covers the entire upper surface of the metal substrate,
    The piezoelectric element according to claim 2.
  4. 　前記圧電体層上に設けられており、前記上部電極から離れている端子電極と、
    　前記下部電極の上面と前記圧電体層の側面とに跨って設けられており、前記下部電極と前記端子電極とをつないでいる配線部と、を更に備え、
    　前記平面視で、前記配線部は、前記金属基板の前記第２外縁よりも内側に位置している、
    　請求項１～３のいずれか一項に記載の圧電素子。     a terminal electrode provided on the piezoelectric layer and separated from the upper electrode;
    further comprising a wiring section provided across the upper surface of the lower electrode and the side surface of the piezoelectric layer and connecting the lower electrode and the terminal electrode,
    In the plan view, the wiring portion is located inside the second outer edge of the metal substrate.
    A piezoelectric element according to any one of claims 1 to 3.
  5. 　前記平面視で、前記端子電極は、前記圧電体層の前記第３外縁よりも内側に位置しており、
    　前記配線部は、前記圧電体層の上面に設けられている部分を含む、
    　請求項４に記載の圧電素子。     In the plan view, the terminal electrode is located inside the third outer edge of the piezoelectric layer,
    The wiring portion includes a portion provided on the top surface of the piezoelectric layer.
    The piezoelectric element according to claim 4.
  6. 　前記圧電体層は、前記下部電極の上面の一部を露出させる開口部を有する、
    　請求項１～３のいずれか一項に記載の圧電素子。     The piezoelectric layer has an opening that exposes a part of the upper surface of the lower electrode.
    A piezoelectric element according to any one of claims 1 to 3.
  7. 　請求項１～６のいずれか一項に記載の圧電素子と、
    　前記圧電素子の前記金属基板と接合されている振動板部と、
    　前記圧電素子の前記下部電極に接続される第１導通部材と、
    　前記圧電素子の前記上部電極に接続される第２導通部材と、
    　前記下部電極と前記第１導通部材とを接合している第１導電性接合部と、
    　前記上部電極と前記第２導通部材とを接合している第２導電性接合部と、を備える、
    　超音波トランスデューサ。     A piezoelectric element according to any one of claims 1 to 6,
    a diaphragm portion joined to the metal substrate of the piezoelectric element;
    a first conductive member connected to the lower electrode of the piezoelectric element;
    a second conductive member connected to the upper electrode of the piezoelectric element;
    a first conductive joint that joins the lower electrode and the first conductive member;
    a second conductive joint that joins the upper electrode and the second conductive member;
    Ultrasonic transducer.
  8. 　前記圧電素子を収容しているケースを更に備え、
    　前記ケースは、
    　　平板状の底板部と、
    　　前記底板部の一面の周部から前記底板部の厚さ方向に突出しており、前記圧電素子を囲んでいる筒部と、を有し、
    　前記底板部のうち前記筒部により囲まれた部分が、前記振動板部を兼ねている、
    　請求項７に記載の超音波トランスデューサ。     Further comprising a case housing the piezoelectric element,
    The said case is
    A flat bottom plate part,
    a cylindrical portion that protrudes from a peripheral portion of one surface of the bottom plate portion in the thickness direction of the bottom plate portion and surrounds the piezoelectric element;
    A portion of the bottom plate portion surrounded by the cylinder portion also serves as the diaphragm portion.
    The ultrasonic transducer according to claim 7.
PCT/JP2023/017878 2022-05-19 2023-05-12 Piezoelectric element and ultrasonic transducer WO2023223955A1 (en)

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JP2007165385A (en) * 2005-12-09 2007-06-28 Nec Tokin Corp Piezoelectric film lamination structure, and its manufacturing method
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