JP6742797B2 - Vibration waveform sensor - Google Patents

Description

The present invention relates to a vibration waveform sensor that measures various waveforms such as a pulse, and more specifically, to maintaining sensitivity and reducing noise in a sensor that uses a piezoelectric element.

Among sensor devices complaining about health management by continuous measurement of pulse waves, a vibration waveform sensor using a piezoelectric element has been devised. For example, Patent Document 1 below discloses an arteriosclerosis evaluation device that evaluates the degree of arteriosclerosis by detecting a pulse wave with a piezoelectric element. The most important component of the vibration waveform sensor is a piezoelectric element that picks up vibration. In order to efficiently capture the pulse wave signal and increase the sensitivity of the sensor, the piezoelectric element needs to be polarized in the d31 direction. In the vibration waveform sensor, this is done by capturing the pulse wave by transmitting the vibration from the artery under the finger to the ring and then transmitting it to the element through the substrate, but efficiently capturing the vibration from the substrate. This is because it is necessary to capture the vibration in the direction perpendicular to the substrate with respect to the mounting direction of the element, that is, the d31 direction.

On the other hand, in consideration of the signal quality of the sensor, the generation of noise is a problem. Although the noise depends on the capacitance of the element, the design in which polarization is performed so that the sensitivity in the d31 direction is high is, at the same time, a design in which noise is likely to occur. Therefore, the piezoelectric element having higher sensitivity is more affected by noise, which is a drawback. If the noise is large, the baseline of the obtained pulse wave waveform will shift and adversely affect the accuracy of waveform analysis.Therefore, baseline correction was performed with software or applications, but the baseline of the original data became stable. Needless to say, the waveform analysis accuracy is improved.

International Publication No. 2010/024417 pamphlet

Conventionally, in order to avoid the above-mentioned problems, it has been proposed to polarize the piezoelectric element and then scrape off the outer conductor, insulate the end face, and re-bak the outer conductor. By including the above steps, the piezoelectric element itself is surely polarized in the d31 direction, but since the internal conductor does not contribute to the capacitance, a piezoelectric element with high sensitivity and low noise generation can be obtained. However, this method has a problem that productivity is too low and it is not practical.

The present invention focuses on the above points, and an object thereof is to provide a vibration waveform sensor using a piezoelectric element capable of achieving both high sensor sensitivity and noise resistance.

The present invention provides a substrate, a pair of conductive pads formed on the substrate, a pair of external conductors drawn from each of the pair of conductive pads, a piezoelectric body, and a pair of terminals formed on the piezoelectric body. An electrode, and the polarization direction of the piezoelectric body is perpendicular to the direction in which the pair of terminal electrodes face each other, and each of the pair of terminal electrodes is connected to the pair of conductive pads to provide the polarization. A piezoelectric element mounted so that the direction is perpendicular to the substrate; and a spacer formed around the piezoelectric element and the pair of conductive pads to have a height higher than the mounting height of the piezoelectric element. It is characterized in that the spacer is connected to the ground potential.
According to one of the main aspects , a conductive film is formed on the substrate around the conductive pad, and the spacer is provided on the conductive film. Further, the spacer is electrically conductive.

One of the main forms is characterized in that the spacer is formed so as to surround the piezoelectric element and the pair of conductive pads. One of the other modes is characterized in that the piezoelectric element has a pair of first internal conductors facing each other in the polarization direction inside the piezoelectric body. Still another embodiment is characterized in that an intersecting area of the pair of first internal conductors is 70 to 99% of an area when the piezoelectric body is viewed from the polarization direction. In still another embodiment, the piezoelectric element has a pair of second internal conductors connected to each of the pair of terminal electrodes, and an intersection area of the pair of second internal conductors is It is characterized in that it is 50% or less of the area when the piezoelectric body is viewed from the polarization direction. The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

According to the present invention, a substrate, a pair of conductive pads formed on the substrate, a pair of external conductors drawn from each of the pair of conductive pads, a piezoelectric body, and a pair formed on the piezoelectric body. A terminal electrode of, the polarization direction of the piezoelectric body is a direction perpendicular to the opposing direction of the pair of terminal electrodes, each of the pair of terminal electrodes is connected to the pair of conductive pads, A piezoelectric element mounted so that the polarization direction is perpendicular to the substrate, and a spacer formed around the piezoelectric element and the pair of conductive pads to have a height higher than the mounting height of the piezoelectric element. In addition, the spacer is connected to the ground potential . Therefore, since the polarization direction of the piezoelectric element is d31, high sensitivity is exhibited, and even if there is no internal conductor that contributes to capacitance, the crossing area can be narrowed to suppress the noise component even if there is any. ..

It is a figure which shows the vibration waveform sensor of Example 1 of this invention, (A) is sectional drawing, (B) is an assembly drawing, (C) is the top view seen from the mounting surface side of a board|substrate. It is a diagram showing a piezoelectric element of the first embodiment, (A) is an external perspective view, (B) is a cross-sectional view taken along line #A-#A of (A) and seen in the arrow direction, (C) is a cross-sectional view showing a state during polarization. 7A and 7B are graphs showing pulse wave waveforms, where FIG. 9A shows the pulse wave waveform of the piezoelectric element of Example 1, and FIG. 9B shows the pulse wave waveform of the conventional piezoelectric element. It is a figure which shows Example 2 of this invention, (A) is an external appearance perspective view of a piezoelectric element, (B) is the sectional view which cut|disconnected said (A) along the line #B-#B, and was seen in the arrow direction. , (C) are plan views showing internal conductors of the piezoelectric element. It is a figure which shows Example 3 of this invention, (A) is an external appearance perspective view of a piezoelectric element, (B) is sectional drawing which saw said (A) along line #C-#C, and was seen in the arrow direction. , (C) are plan views showing internal conductors of the piezoelectric element. It is a figure which shows the conventional piezoelectric element, (A) is an external perspective view of a piezoelectric element, (B) is sectional drawing which shows a mode at the time of polarization, (C) is a top view which shows the internal conductor of the said piezoelectric element. ..

Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

First, the first embodiment of the present invention will be described with reference to FIGS. 1 to 3 and 6. FIG. 1 shows a case where the present invention is used as a pulse wave sensor. (A) is a cross-sectional view of the vibration waveform sensor, (B) is an assembly view, and (C) is a view from the mounting surface side of the board. FIG. 2A is an external perspective view of the piezoelectric element of the present embodiment, and FIG. 2B is a cross-sectional view of the piezoelectric element cut along the line #A-#A as seen in the direction of the arrow in FIG. C) is a cross-sectional view showing a state during polarization. 3A and 3B are diagrams showing pulse wave waveforms. FIG. 3A shows a pulse wave waveform of the piezoelectric element of the present embodiment, and FIG. 3B shows a pulse wave waveform of the conventional piezoelectric element. 6A and 6B are views showing a conventional piezoelectric element, where FIG. 6A is an external perspective view of the piezoelectric element, FIG. 6B is a cross-sectional view showing a state during polarization, and FIG. 6C is an internal conductor of the piezoelectric element. It is a top view. 1A to 1C, the vibration waveform sensor 10 has a structure in which a piezoelectric element 30 is arranged on the main surface of a substrate 20, and the piezoelectric element 30 is covered with a ring-shaped spacer 40. There is. In this embodiment, the piezoelectric element 30 is rectangular and has a longitudinal direction as shown in FIG. 1(C).

Of the above parts, the substrate 20 is for fixing and supporting the piezoelectric element 30, and for extracting the electrode of the piezoelectric element 30 and amplifying the signal, and is made of glass epoxy or ceramic. On the main surface of the substrate 20, a pair of conductive pads 22 and 23 are provided near the center, and a conductive film 24 is formed around the conductive pads 22 and 23. The conductive pads 22 and 23 are drawn out to the back surface side of the substrate 20 by through holes 22A and 23A and connected to the external conductors 22B and 23B. The terminal electrodes 34 and 36 of the piezoelectric element 30 are bonded to the conductive pads 22 and 23 with a conductive adhesive or the like. In this manner, the piezoelectric element 30 is connected to an amplifier (not shown) provided on the back surface side of the substrate 20 by the conductive pads 22 and 23 and the through holes 22A and 23A.

In this embodiment, the piezoelectric element 30 has a single-plate structure including a piezoelectric body 32 and a pair of opposing terminal electrodes 34 and 36 formed on the piezoelectric body 32. The piezoelectric body 32 has a polarization direction perpendicular to the direction in which the pair of terminal electrodes 34 and 36 face each other. Then, the pair of terminal electrodes 34 and 36 are connected to the conductive pads 22 and 23, and the piezoelectric element 30 is mounted so that the polarization direction of the piezoelectric body 32 is perpendicular to the substrate 20. As the piezoelectric body 32, for example, PZT (lead zirconate titanate) is used. Further, an insulating resin may be provided so as to cover the conductive pads 22 and 23. At this time, the piezoelectric element 30 may also be covered with resin.

Next, a ring-shaped spacer 40 is provided around the conductive pads 22 and 23 and the piezoelectric element 30 so as to surround them. The height of the spacer 40 is higher than the mounting height when the piezoelectric element 30 is mounted on the substrate 20. The spacer 40 is electrically connected to the conductive film 24. In addition, the conductive film 24 is drawn out to the back surface side of the substrate 20 by through holes 24A and 24B (illustrated only in FIG. 1A). The spacer 40 is made of, for example, stainless steel and has conductivity, and has a common ground potential with the skin of a human body in contact therewith, and also introduces vibration of the skin and further transmits it to the substrate 20. Functions as a vibration introducing body.

The vibration of the skin is transmitted to the spacer 40 and also transmitted from the spacer 40 to the substrate 20. The substrate 20 also functions as a vibrating body, and the vibration transmitted from the spacer 40 is transmitted to the piezoelectric element 30. The spacer 40 is not limited to metal as long as it is hard and has electrical conductivity, and may be, for example, hard plastic whose surface is plated with metal. By sandwiching the hard and conductive spacer 40 in this manner, the pulse wave vibration can be reliably transmitted and electrical noise can be released to the ground, so that a pulse wave signal of higher quality can be obtained. This is the basic structure of the vibration waveform sensor.

The vibration waveform sensor 10 as described above is attached to an appropriate position such as a finger of a human body with a medical fixing tape or the like so that the spacer 40 contacts the skin of the human body. The part to which the vibration waveform sensor 10 is attached may be the arm, and the attaching method may be winding using a surface fastener. The pulsating arterial waves are transmitted to the piezoelectric element 30 via the substrate 20 through the spacer 40 having conductivity. The piezoelectric element 30 detects this vibration, converts it into a voltage, and outputs it as a pulse wave signal to an analyzer (not shown) or the like.

In this embodiment, the single plate element is polarized in the d31 direction only during polarization, that is, in the direction perpendicular to the facing direction of the terminal electrodes 34 and 36 (in other words, the direction perpendicular to the substrate 20 when mounted). To produce the element. That is, since the polarization direction is the d31 direction, the same high sensitivity as the conventional product is shown, but since the capacity is a single plate, the capacity is about 1/10 of the conventional product, and while maintaining high sensitivity, the influence of noise is suppressed. It can be avoided.

Next, an example of the manufacturing procedure of this embodiment will be described. First, a piezoelectric powder containing PZT as a main component was kneaded with a PVB binder for 20 hours, and then formed into a sheet having a thickness of 27 μm with a doctor blade. In this example, 38 layers of this sheet molded body were laminated by thermocompression, cut into a 3.2×1.6 mm shape, and fired at 950° C. to obtain a 3216 shape (thickness t=1.0 mm). A single plate fired body was obtained. Further, Ag was formed on the fired body as an external conductor (terminal electrodes 34, 36) and baked at 850° C. to form a single plate element. Then, as shown in FIG. 2(C), the polarization terminals 42 and 44 have rectangular cross sections that are slightly smaller than the upper and lower surfaces of the element, and have a predetermined voltage from the d31 direction orthogonal to the external conductors (terminal electrodes 34 and 36). Was applied to polarize.

Then, the piezoelectric element 30 was mounted on the vibration waveform sensor 10 to perform pulse wave sensing. As a result, the capacitance of the device was 20 pF, which was a low capacitance effective for noise reduction. The waveform data of the velocity pulse wave in the vibration waveform sensor 10 is shown in FIG. In the figure, the horizontal axis represents time t[s], and the vertical axis represents sensitivity (electromotive force) [mV].

For comparison, a conventional piezoelectric element 100 shown in FIG. 6 was formed. Specifically, in the above-mentioned laminating step, two sheets S (see FIG. 6C) coated with Ag/Pd having a thickness of 2 μm are arranged for the internal conductors 110 and 112 to laminate one piezoelectric layer. A d31 type device was obtained. Then, Ag was baked to form external conductors (terminal electrodes 104 and 106). One terminal electrode 104 is connected to one internal conductor 110, and the other terminal electrode 106 is connected to the other internal conductor 112. Then, it was polarized through the terminal electrodes 104 and 106 as shown in FIG. 6(B). The polarization direction of such a conventional piezoelectric element 100 is as shown by the arrow in FIG. 6B and is the d31 direction, which is the same as the polarization direction of the embodiment of the present invention. Also in this comparative example, when the same was mounted on the vibration waveform sensor and the pulse wave was sensed, the capacitance of the element was as high as 147 pF. Further, the pulse wave waveform of this vibration waveform sensor is shown in FIG. 3(B).

As shown in FIG. 3(A), in this example, a clean waveform with a uniform baseline was obtained. On the other hand, as shown in FIG. 3(B), in the conventional product, the baseline fluctuates due to the influence of noise, and as shown by the broken line in the figure, the baseline BL has waviness and the waveform is disturbed. .. A conventional piezoelectric element used for a displacement element or the like is designed to have a large crossing area of internal conductors (internal electrodes) in order to increase the displacement amount. When polarization is performed using this internal conductor, the polarization direction is the d31 direction, but when used in a sensor, the internal conductor contributes to the capacitance and increases the electrostatic capacitance, so that noise easily enters. ..

Thus, according to the first embodiment, the substrate 20, the pair of conductive pads 22 and 23 formed on the substrate 20, and the pair of external conductors drawn from the pair of conductive pads 22 and 23, respectively. 22B and 23B, a piezoelectric body 32, and a pair of terminal electrodes 34 and 36 formed on the piezoelectric body 32, and the polarization direction is perpendicular to the facing direction of the pair of terminal electrodes 34 and 36. And a piezoelectric element 30 mounted so that each of the pair of terminal electrodes 34 and 36 is connected to the pair of conductive pads 22 and 23 so that the polarization direction is perpendicular to the substrate 20. A spacer 40 is formed around the piezoelectric element 30 and the pair of conductive pads 22 and 23 so as to have a height higher than the mounting height of the piezoelectric element 30. As described above, by polarizing the piezoelectric element 30 having a single plate structure in the d31 direction, it is possible to exhibit the same high sensitivity as in the conventional case. In addition, since the structure uses the polarization terminals 42 and 44 only during polarization and does not use an internal conductor for polarization, the capacity is a single piezoelectric plate, which is about 1/10 of the capacity of the conventional structure, and the influence of noise. Can be avoided. Further, since an internal conductor using an expensive precious metal is unnecessary, it is also effective in cost reduction.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. Although the above-described embodiment has a structure in which no conductor is provided inside the piezoelectric body, this embodiment has a structure in which an internal conductor is used only during polarization and not used after mounting on the substrate. 4A is an external perspective view of the piezoelectric element of the present embodiment, and FIG. 4B is a cross-sectional view taken along line #B-#B of FIG. C) is a plan view showing an internal conductor of the piezoelectric element.

As shown in FIG. 4, in the piezoelectric element 50 of the present embodiment, a pair of terminal electrodes 56 and 58 are formed on a pair of side surfaces of a piezoelectric body 52 facing each other, and on the other pair of side surfaces of the piezoelectric body 52. The other pair of terminal electrodes 60, 62 is formed. Further, inside the piezoelectric body 52, a pair of internal conductors 64 and 66 facing each other in the polarization direction are provided. One inner conductor 64 has a lead-out portion 64A as shown in FIG. 4C, and is connected to the terminal electrode 60. Further, the other inner conductor 66 is connected to the other terminal electrode 62 by the lead-out portion 66A. These terminal electrodes 60 and 62 are for polarization and do not function after mounting the piezoelectric element 50 on the substrate (but do not prevent its use). Further, the internal conductors 64 and 66 are not connected to the terminal electrodes 56 and 58 that function in the circuit.

The polarization direction of the piezoelectric body 52 is perpendicular to the facing direction of the pair of terminal electrodes 56 and 58, as in the first embodiment. The crossing area of the internal conductors 64 and 66 is 70 to 99% when viewed in the polarization direction of the piezoelectric body 52. This is because the area is 70% or more and 99% or less of the area obtained by L×W (length×width) of the chip to enhance the sensitivity so that the entire chip can be polarized. The structure of the vibration waveform sensor in which the piezoelectric element 50 of this embodiment is mounted on the substrate 20 is the same as that of the first embodiment.

Next, an example of the manufacturing procedure of this embodiment will be described. First, a piezoelectric powder containing PZT as a main component was kneaded with a PVB binder for 20 hours, and then formed into a sheet having a thickness of 27 μm with a doctor blade. In this example, the internal conductors 64 and 66 having the structure shown in FIG. 4C were printed by the screen printing method and laminated in the layer structure shown in FIG. 4B. The internal conductors 64 and 66 were printed with Ag/Pd to a thickness of 2 μm. These sheets S were laminated, thermocompression-bonded, cut into a 3.2×1.6 mm shape, and fired at 950° C. to obtain a fired body having a 3216 shape (thickness t=1.0 mm). Further, Ag was formed as an external conductor (terminal electrodes 56, 58, 60, 62) on the fired body and baked at 850° C. to form a laminated piezoelectric element.

One inner conductor 64 is connected to one terminal electrode 60, and the other inner conductor 66 is connected to the other terminal electrode 62. Then, the terminal electrodes 60 and 62 for polarization were polarized at a predetermined voltage. Since the polarization is performed in the d31 direction through the entire chip, a high-sensitivity sensor element with a large amount of charges obtained can be obtained. In this embodiment, the internal conductors 64 and 66 and the terminal electrodes 60 and 62 are for polarization, and after the piezoelectric element 50 is mounted on the substrate 20, it is not connected to a circuit and does not function. Therefore, while maintaining high sensitivity by polarizing the piezoelectric element in the d31 direction, noise is suppressed because the internal conductors 64 and 66 do not contribute to the capacitance, which is the same effect as in the first embodiment described above.

Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment has a structure in which a pair of a polarization inner conductor and a circuit inner conductor are provided inside the piezoelectric body. 5A is an external perspective view of the piezoelectric element, FIG. 5B is a cross-sectional view taken along line #C-#C of FIG. 5A and seen in the direction of the arrow, and FIG. It is a top view which shows the internal conductor of a piezoelectric element. The external appearance of the piezoelectric element 70 of the present embodiment is the same as that of the piezoelectric element 50 of the second embodiment and has a four-terminal structure.

As shown in FIG. 5, in the piezoelectric element 70 of this embodiment, a pair of terminal electrodes 76 and 78 are formed on a pair of side surfaces of a piezoelectric body 72 that face each other, and a pair of other pairs of the piezoelectric body 72 that face each other. It has a structure in which a pair of terminal electrodes 80 and 82 are formed on the side surface. Further, inside the piezoelectric body 72, a pair of first inner conductors 84, 86 and a pair of second inner conductors 90, 92 facing each other in the polarization direction are provided. One first inner conductor 84 is connected to the terminal electrode 80 by a lead-out portion 84A, and the other first inner conductor 86 is connected to the terminal electrode 82 by a lead-out portion 86A. The first inner conductors 84 and 86 and the terminal electrodes 80 and 82 are for polarization and do not function after the piezoelectric element 70 is mounted on the substrate. One end portion 90A of the second inner conductor 90 is connected to the terminal electrode 76, and the other end portion 92A of the second inner conductor 92 is connected to the terminal electrode 78.

The polarization direction of the piezoelectric body 72 is perpendicular to the facing direction of the pair of terminal electrodes 76 and 78, as in the first embodiment. The cross-sectional area of the internal conductors 84, 86 is 70% to 99% of the chip area when viewed from the polarization direction of the piezoelectric body 72, as in the second embodiment. On the other hand, the second inner conductors 90 and 92 are connected to a circuit and function after the piezoelectric element 70 is mounted on the substrate 20. The crossing area of the second inner conductors 90 and 92 is set to 10% or more and 50% or less of the chip area when viewed from the polarization direction of the piezoelectric body 72, and the capacitance is suppressed to be low. The structure itself of the vibration waveform sensor in which the piezoelectric element 70 of this embodiment is mounted on the substrate 20 is the same as that of the first embodiment.

Next, an example of the manufacturing procedure of this embodiment will be described. First, a piezoelectric powder containing PZT as a main component was kneaded with a PVB binder for 20 hours, and then formed into a sheet having a thickness of 27 μm with a doctor blade. In this example, the internal conductors 84, 86, 90, 92 having the structure shown in FIG. 5C were printed by the screen printing method and laminated in the layer structure shown in FIG. 5B. The inner conductor was printed with Ag/Pd to a thickness of 2 μm. These sheets S were laminated, thermocompression-bonded, cut into a 3.2×1.6 mm shape, and fired at 950° C. to obtain a fired body having a 3216 shape (thickness t=1.0 mm). Further, Ag was formed as an external conductor (terminal electrodes 76, 78, 80, 82) on the fired body and baked at 850° C. to form a laminated piezoelectric element.

The first inner conductor 84 is connected to the terminal electrode 80, and the other first inner conductor 86 is connected to the terminal electrode 82. The second inner conductor 90 is connected to the terminal electrode 76, and the other second inner conductor 92 is connected to the terminal electrode 78. Then, polarization was performed at a predetermined voltage from the terminal electrodes 80 and 82 for polarization. In this embodiment, the first inner conductors 84 and 86 and the terminal electrodes 80 and 82 are dedicated to polarization, and after the piezoelectric element 70 is mounted on the substrate 20, it is not connected to a circuit and does not function. Therefore, the first internal conductors 84 and 86 do not contribute to the capacitance while maintaining high sensitivity by polarizing the piezoelectric element in the d31 direction. In this embodiment, since the capacitance component is obtained by the second inner conductors 90 and 92 having a narrow crossing area, the noise component can be suppressed low.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the following is also included.
(1) In the first embodiment, the pulse wave was measured, but the measurement object of the vibration waveform sensor of the present invention is not limited to the pulse wave, and the respiratory wave and various other known waveforms are targets. Good. For example, the vibration waveform of an engine or a motor is analyzed.
(2) In the first embodiment, the ring-shaped spacer 40 is used, but this is also an example, and a square frame-shaped spacer may be used. It may be a prism having only two sides bonded. Alternatively, a plate-shaped or rod-shaped spacer may be provided upright on the substrate 20, and the piezoelectric element 30 may be arranged in the vicinity thereof. As described above, the spacer may have any shape as long as the spacer comes into contact with the object and the vibration thereof is transmitted to the substrate 20.

(3) In the first embodiment, the metal spacer 40 is used, but this is also an example, and the spacer may not be made of metal as long as it is hard and conductive. For example, a conductive film may be provided on the surface of an insulator such as resin or ceramic.
(4) In the above-mentioned embodiment, the piezoelectric body used is a general PZT, but the piezoelectric body is not limited to this, and may be any one having appropriate sensitivity (piezoelectric constant, capacitance) that produces the same effect. .. Also, the shape and size of the piezoelectric element may be changed as appropriate according to the application.
(5) In the above embodiment, the glass epoxy resin was used as the substrate 20, but this is also an example, and a harder one such as ceramic may be used.
(6) An insulating resin or the like may be filled inside the spacer 40.

According to the present invention, a substrate, a pair of conductive pads formed on the substrate, a pair of external conductors drawn from each of the pair of conductive pads, a piezoelectric body, and a pair formed on the piezoelectric body. A terminal electrode of, the polarization direction of the piezoelectric body is a direction perpendicular to the opposing direction of the pair of terminal electrodes, each of the pair of terminal electrodes is connected to the pair of conductive pads, A piezoelectric element mounted so that the polarization direction is perpendicular to the substrate, and a spacer formed around the piezoelectric element and the pair of conductive pads to have a height higher than the mounting height of the piezoelectric element. In addition, the spacer is connected to the ground potential . Therefore, the piezoelectric element exhibits high sensitivity because the polarization direction is d31, and even if there is no internal conductor that contributes to the capacitance, the crossing area can be narrowed and the noise component can be suppressed to a low level. It can be applied to sensor applications.

10: Vibration waveform sensor 20: Substrate 22, 23: Conductive pad 22A, 23A: Through hole 22B, 23B: External conductor 24: Conductive film 24A, 24B: Through hole 30: Piezoelectric element 32: Piezoelectric body 34, 36: Terminal electrode 40: Spacer 42, 44: Polarization terminal 50: Piezoelectric element 52: Piezoelectric body 56, 58: Terminal electrode (for circuit)
60, 62; terminal electrode (for polarization)
64, 66: internal conductor (dummy electrode)
64A, 66A: Lead-out part 70: Piezoelectric element 72: Piezoelectric body 76, 78: Terminal electrode (for circuit)
80, 82: Terminal electrode (for polarization)
84, 86: first internal conductor (dummy electrode)
84A, 86A: Lead portion 90, 92: Second internal conductor (capacitance electrode)
90A, 90B: End portion 100: Piezoelectric element 102: Piezoelectric bodies 104, 106: Terminal electrodes 110, 112: Internal electrodes (also used as polarization electrodes)
110A, 112A: Ends 114, 116: Polarized terminal BL: Base line S: Piezoelectric sheet

Claims (7)

Board,
A pair of conductive pads formed on the substrate,
A pair of outer conductors drawn from each of the pair of conductive pads,
Each of the pair of terminal electrodes has a piezoelectric body and a pair of terminal electrodes formed on the piezoelectric body, and the polarization direction of the piezoelectric body is a direction perpendicular to the facing direction of the pair of terminal electrodes. Is connected to the pair of conductive pads, the piezoelectric element mounted so that the polarization direction is perpendicular to the substrate,
Around the piezoelectric element and the pair of conductive pads, a spacer formed higher than the mounting height of the piezoelectric element,
Equipped with a,
A vibration waveform sensor, wherein the spacer is connected to a ground potential . A conductive film is formed on the substrate around the conductive pad,
The vibration waveform sensor according to claim 1, wherein the spacer is provided on the conductive film. The vibration waveform sensor according to claim 1, wherein the spacer has conductivity. The spacer is
The vibration waveform sensor according to claim 1 , wherein the vibration waveform sensor is formed so as to surround the piezoelectric element and the pair of conductive pads. The said piezoelectric element has a pair of 1st internal conductor which opposes the said polarization direction inside the said piezoelectric body, The vibration waveform sensor as described in any one of Claims 1-5 characterized by the above-mentioned. The vibration waveform sensor according to claim 5 , wherein an intersecting area of the pair of first inner conductors is 70 to 99% of an area of the piezoelectric body when viewed from the polarization direction. The piezoelectric element has a pair of second internal conductors connected to each of the pair of terminal electrodes, and a crossing area of the pair of second internal conductors is the piezoelectric body viewed from the polarization direction. The vibration waveform sensor according to claim 5 or 6 , wherein the area is 50% or less of the area.

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