JP6076634B2 - Sensing element - Google Patents

Description

  The present invention relates to a sensing element suitable for use as, for example, an acceleration sensor or an angular velocity sensor.

  Recently, for example, an angular velocity sensor described in Patent Document 1 is known as an angular velocity sensor. The angular velocity sensor described in Patent Document 1 includes a base substrate, a pedestal installed on the base substrate, a flexible substrate installed on the pedestal and having an annular groove, and a piezoelectric element installed on the flexible substrate. And have. The flexible substrate integrally includes a fixed portion located outside, an action portion located inside, and a thin flexible portion located between the fix portion and the action portion. A weight body is installed at the lower end of the action portion. The piezoelectric element has a piezoelectric body, a lower electrode, and an upper electrode. Then, in a state where the weight body is supported so as to be movable with a predetermined degree of freedom, the weight body is circularly moved along the circular trajectory in the XY plane around the center axis of the weight body. At the moment of passing through the axis, the angular velocity around the X axis is detected by detecting the Coriolis force acting in the Z-axis direction on the weight body.

JP 2004-294450 A

  By the way, the conventional sensor like patent document 1 comprised from a some member needs to join or adhere | attach members when integrating each member, and there exists a joining layer between members. It becomes. The bonding layer has a vibration damping action and converts vibration energy of vibration on the solid surface into heat energy, and thus has a large loss coefficient. Therefore, vibration energy is attenuated, and detection accuracy is lowered. In addition, it becomes difficult to resonate the sensing element, and it takes time to resonate, causing a detection delay.

  The present invention has been made in consideration of such problems, and can reduce the loss coefficient of the entire sensing element, improve the detection accuracy of acceleration and angular velocity, and reduce the detection delay as much as possible. An object of the present invention is to provide a sensing element that can be used.

[1] A sensing element according to the present invention includes a piezoelectric body, a diaphragm provided to face one principal surface of the piezoelectric body, and a weight provided to face one principal surface of the diaphragm. Part, an upper electrode and a lower electrode provided in contact with the piezoelectric body, and a bonding layer provided at least between the vibration plate and the weight portion, and loss of the bonding layer and the vibration plate The coefficient is less than or equal to the loss coefficient of the piezoelectric body.

[2] In the present invention, loss factors of the bonding layer and the diaphragm may be 100 × 10 ⁻⁴ or less.

[3] In the present invention, the bonding layer may be made of an inorganic material.

[4] In this case, the bonding layer may be made of metal.

[5] In the present invention, the diaphragm may be made of an inorganic material.

[6] In this case, the diaphragm may be made of metal.

[7] In the present invention, the diaphragm is composed of a metal film that also serves as the lower electrode and the bonding layer, the weight portion is composed of an inorganic material other than metal, and the boundary between the diaphragm and the weight portion In the portion, a bonding region may be formed by room temperature bonding between the metal film and the inorganic material.

[8] In the present invention, the diaphragm is composed of a laminate of a metal film also serving as the lower electrode and a metal oxide film also serving as the bonding layer, and the weight portion is composed of an inorganic material other than metal, A joining region by room temperature joining between the metal oxide film and the inorganic material may be formed at a boundary portion between the vibration plate and the weight portion.

[9] In the present invention, the diaphragm is made of a metal film that also serves as the lower electrode and the bonding layer, the weight portion is made of an inorganic material other than metal, and the boundary between the diaphragm and the weight portion A bonding region by diffusion bonding between the metal film and the inorganic material may be formed in the portion.

[10] In the present invention, the piezoelectric body, the lower electrode, and the diaphragm are integrally fired to form one fired body, and the bonding layer is provided between the fired body and the weight portion. The bonding layer is formed of a metal film, the weight portion is formed of an inorganic material other than metal, and a bonding region formed by diffusion bonding of the metal film and the inorganic material is formed at a boundary portion between the bonding layer and the weight portion. It may be formed.

[11] In the present invention, the diaphragm is formed of a metal film that also serves as the lower electrode, and the bonding layer is formed by eutectic bonding of the metal film on the diaphragm side and the metal film on the weight side. A junction region may be formed.

[12] In the present invention, the piezoelectric body, the lower electrode, and the vibration plate are integrally formed by firing to form one fired body, and the bonding layer includes the metal film on the fired body side and the weight side. A junction region by eutectic bonding with the metal film may be formed.

[13] In the present invention, the vibration plate is made of a metal film, the weight portion is made of an inorganic material other than metal, and the bonding layer is formed between the vibration plate and the weight portion. It may be.

[14] In the present invention, at least the upper electrode is composed of a plurality of electrodes, and the plurality of electrodes are a driving electrode for driving the weight part and a detection for detecting a displacement of the weight part. For example.

[15] In the present invention, at least the upper electrode may be composed of a plurality of electrodes, and the plurality of electrodes may have only detection electrodes for detecting displacement of the weight portion.

[16] In [14] or [15], the lower electrode may be a counter electrode of the plurality of electrodes and a common electrode.

[17] In this case, the diaphragm may also serve as the lower electrode.

[18] In the present invention, the thickness of the piezoelectric body and the thickness of the diaphragm are such that a neutral axis in material mechanics when a beam composed of the piezoelectric body and the diaphragm is bent is on the diaphragm side. It may be defined to be located.

[19] In this case, the thickness of the diaphragm is equal to or greater than the reference thickness when the thickness of the diaphragm when the neutral axis is located at the boundary portion between the piezoelectric body and the diaphragm is a reference thickness. It is preferable.

  According to the sensing element of the present invention, the loss coefficient of the entire sensing element can be reduced, the detection accuracy of acceleration and angular velocity can be improved, and the detection delay can be shortened as much as possible.

FIG. 1A is a diagram (plan view) showing the sensing element according to the present embodiment from above, and is a cross-sectional view taken along the line IB-IB in FIG. 1A. FIG. 2A is a cross-sectional view showing an example in which a neutral axis in material mechanics when a beam composed of a piezoelectric body and a diaphragm is bent is located on the diaphragm side, and FIG. It is sectional drawing which abbreviate | omits and shows an example in case a neutral axis is located in the boundary of a piezoelectric material and a diaphragm. FIG. 3A is a schematic diagram showing a state where the beam is bent by applying a load to the central portion of the beam (deflected state), and FIG. 3B is a schematic diagram showing the deformation in the minute region of the beam and the position of the neutral axis. FIG. 3C is a view for explaining a neutral plane and a symmetry plane. It is a graph which shows the change of the film thickness ratio with respect to the thickness of a piezoelectric material (reference thickness tc of a diaphragm / thickness ta of a piezoelectric material) according to the material of a diaphragm. It is sectional drawing which shows the sensing element (1st sensing element) which concerns on a 1st specific example. It is process drawing which shows the manufacturing method of a 1st sensing element. It is sectional drawing which shows the sensing element (2nd sensing element) which concerns on a 2nd specific example. It is process drawing which shows the manufacturing method of a 2nd sensing element. It is sectional drawing which shows the sensing element (3rd sensing element) which concerns on a 3rd example. It is process drawing which shows the manufacturing method of a 3rd sensing element. It is sectional drawing which shows the sensing element (4th sensing element) which concerns on a 4th example. It is process drawing which shows the manufacturing method of a 4th sensing element. It is sectional drawing which shows the sensing element (5th sensing element) which concerns on a 5th example. It is process drawing which shows the manufacturing method of a 5th sensing element. It is sectional drawing which shows the sensing element (6th sensing element) which concerns on a 6th specific example. It is process drawing which shows the manufacturing method of a 6th sensing element. It is sectional drawing which shows the sensing element (7th sensing element) which concerns on a 7th specific example. It is process drawing which shows the manufacturing method of a 7th sensing element. FIG. 19A is a graph showing the detection sensitivity of Example 1, and FIG. 19B is a graph showing the detection sensitivity of Example 2. 20A is a graph showing the detection sensitivity of Example 3, and FIG. 20B is a graph showing the detection sensitivity of Example 4. 21A is a graph showing the detection sensitivity of Example 5, FIG. 21B is a graph showing the detection sensitivity of Example 6, and FIG. 21C is a graph showing the detection sensitivity of Example 7. 22A is a diagram (plan view) illustrating the sensing element according to Comparative Example 1 from above, and FIG. 22B is a cross-sectional view taken along the line XXIIB-XXIIB in FIG. 22A. 5 is a graph showing the detection sensitivity of Comparative Example 1.

  Hereinafter, embodiments of a sensing element according to the present invention will be described with reference to FIGS. 1A to 23.

  As shown in FIGS. 1A and 1B, the sensing element 10 according to the present embodiment includes a piezoelectric body 12, and a diaphragm 14 provided to face one main surface 12a (for example, the lower surface) of the piezoelectric body 12. A support portion 16 provided facing the outer peripheral portion of one main surface 14a (for example, the lower surface) of the diaphragm 14, and a weight portion 18 provided facing the central portion of the one main surface 14a of the diaphragm 14. A plurality of upper electrodes 20 (first upper electrode 20 a to fifth upper electrode 20 e) and lower electrode 22 provided in contact with the piezoelectric body 12 and a first electrode provided between the lower electrode 22 and the diaphragm 14. It has a bonding layer 24 a and a second bonding layer 24 b provided between the diaphragm 14, the support portion 16 and the weight portion 18.

And each loss coefficient of the 1st joining layer 24a, the 2nd joining layer 24b, and the diaphragm 14 is below the loss coefficient of a piezoelectric material, Preferably it is below ^100x10-4 .

  In the example of FIG. 1A, the planar shape of the sensing element 10 viewed from the top is circular, but it may be rectangular (square, rectangular) or polygonal (hexagon, octagon, etc.). Further, the hollow portion 26 (annular groove) formed between the support portion 16 and the weight portion 18 has an annular shape in accordance with the planar shape of the piezoelectric body 12 in the example of FIGS. 1A and 1B. An annular shape or a polygonal annular shape may be used.

  As the piezoelectric body 12, for example, piezoelectric ceramics having excellent piezoelectric characteristics such as lead zirconate titanate (PZT), lead magnesium niobate (PMN), and lead nickel niobate (PNN) are preferably used. In the present embodiment, either a piezoelectric material or an electrostrictive material may be used as the piezoelectric body 12. Further, the porosity of the piezoelectric body 12 is preferably 20% or less, and more preferably 10% or less. This is because it is difficult to obtain sufficient piezoelectric / electrostrictive characteristics when the porosity is too high. The porosity was defined as the ratio of the area of the pore portion to the visual field area when the cross section of the piezoelectric body 12 was mirror-polished so as not to drop and the cross section was observed using an SEM or the like.

  A plurality of upper electrodes 20 are formed, and in this example, a first upper electrode 20a to a fifth upper electrode 20e are formed. For the upper electrode 20, a screen printing method, a sputtering method, or the like is preferably used. The lower electrode 22 formed on one main surface 12a of the piezoelectric body 12 is a common counter electrode of the first upper electrode 20a to the fifth upper electrode 20e.

  As an electrode material of the upper electrode 20, it is preferable to use Ag (silver), Au (gold), Pd (palladium), Pt (platinum), or an alloy thereof. In particular, when a high melting point metal such as Pd or Pt is used, simultaneous firing with the piezoelectric body 12 can be easily performed, which is preferable. In addition, various metal materials such as Cu (copper), Ni (nickel), and Al (aluminum) can be used as electrodes and electrode leads.

  As shown in FIG. 1A, the upper electrode 20 is positioned on the outer peripheral side of the first upper electrode 20a having an annular shape centering on the central axis 28 (indicated by “+”) of the piezoelectric body 12 and the first upper electrode 20a. Similarly, the second upper electrode 20b to the fifth upper electrode 20e having an arc shape (in the example shown in the figure, an arc shape in which the annular shape is ¼) centered on the central axis 28 of the piezoelectric body 12 are provided. In this case, when the XY plane is defined on the other main surface 12b (for example, the upper surface) of the piezoelectric body 12, the second upper electrode 20b and the third upper electrode 20c are arranged such that the X axis crosses the center in the length direction of each arc. The fourth upper electrode 20d and the fifth upper electrode 20e are arranged such that the Y axis crosses the center in the length direction of each arc.

  The first upper electrode 20a is formed over the outer peripheral surface of the weight portion 18, and the second upper electrode 20b to the fifth upper electrode 20e are formed over the inner peripheral surface of the support portion 16. The

  Here, an outline of an acceleration detection principle and an angular velocity detection principle by the sensing element 10 will be described.

  First, acceleration detection will be described. In order to detect the acceleration, it is not necessary to vibrate the sensing element 10. The force fx in the X-axis direction acting on the center of gravity of the weight portion 18 is obtained by obtaining a difference between the amount of charge generated in the third upper electrode 20c and the amount of charge generated in the second upper electrode 20b. Similarly, the force fy in the Y-axis direction acting on the center of gravity of the weight portion 18 can be obtained by obtaining the difference between the charge generated at the fifth upper electrode 20e and the charge generated at the fourth upper electrode 20d. Similarly, the force fz in the Z-axis direction acting on the center of gravity of the weight portion 18 can be obtained from the amount of charge generated in the first upper electrode 20a. In addition, as the force in the X-axis direction, the force in the Y-axis direction, and the force in the Z-axis direction that acted on the center of gravity of the weight portion 18, the forces fx, fy, and fz caused by acceleration are also Coriolis forces Fx caused by angular velocity Fy and Fz are also equivalent, and cannot be distinguished as instantaneously detected forces.

  Further, since there is a relationship of f = m · α based on the mass m of the weight portion 18 between the force f caused by acceleration and the acceleration α, based on the obtained forces fx, fy, and fz, The accelerations αx, αy, αz in the respective axis directions can be detected.

  Next, the principle of angular velocity detection will be described. In detecting the angular velocity, it is necessary to vibrate the sensing element 10. Therefore, first, the application of vibration to the sensing element 10 will be briefly described.

  An AC voltage is applied between the lower electrode 22 and the third upper electrode 20c, and an AC voltage having a phase opposite to that of the AC voltage is applied between the lower electrode 22 and the second upper electrode 20b. The weight portion 18 vibrates along the X axis. That is, by applying the AC voltage described above, it is possible to apply the vibration Sx in the X-axis direction to the sensing element 10. The frequency of the vibration Sx can be controlled by the frequency of the applied AC voltage, and the amplitude of the vibration Sx can be controlled by the amplitude value of the applied AC voltage.

  Similarly, by supplying alternating voltages whose phases are reversed to each other between the lower electrode 22 and the fifth upper electrode 20e and between the lower electrode 22 and the fourth upper electrode 20d, the weight portion 18 is made to be Y It can be vibrated in the axial direction. That is, it is possible to apply the vibration Sy in the Y-axis direction to the sensing element 10 by applying the AC voltage described above.

  Similarly, when an AC voltage is applied between the lower electrode 22 and the first upper electrode 20a, the weight portion 18 vibrates along the Z axis. That is, the vibration Sz in the Z-axis direction can be applied to the sensing element 10.

  Then, by detecting the Coriolis force Fy acting in the Y-axis direction with the vibration Sz in the Z-axis direction applied to the sensing element 10, the X-axis is based on the relational expression Fy = 2m · vz · ωx. A surrounding angular velocity ωx can be obtained. Here, m is the mass of the weight 18 and vz is the instantaneous velocity of the weight 18 in the Z-axis direction. Therefore, an AC voltage is applied between the first upper electrode 20a and the lower electrode 22 to excite the weight portion 18 in the Z-axis direction. At this time, the fifth upper electrode 20e and the fourth upper electrode 20d By obtaining the Coriolis force Fy acting in the Y-axis direction from the amount of generated charges, the angular velocity ωx around the X-axis can be obtained by calculation.

  Similarly, by detecting the Coriolis force Fz acting in the Z-axis direction in a state in which the vibration Sx in the X-axis direction is applied to the sensing element 10, based on the relational expression Fz = 2m · vx · ωy, Y An angular velocity ωy about the axis can be obtained. vx is the instantaneous speed of the weight 18 in the X-axis direction. Therefore, an AC voltage having an opposite phase is applied between the third upper electrode 20c and the lower electrode 22 and between the second upper electrode 20b and the lower electrode 22 to excite the weight portion 18 in the X-axis direction. In this state, the Coriolis force Fz acting in the Z-axis direction is obtained from the amount of charge generated in the first upper electrode 20a at this time, whereby the angular velocity ωy about the Y-axis can be obtained by calculation.

  Similarly, by detecting the Coriolis force Fx acting in the X-axis direction in a state in which the vibration Sy in the Y-axis direction is applied to the sensing element 10, Z is determined based on the relational expression Fx = 2m · vy · ωz. An angular velocity ωz around the axis can be obtained. Here, vy is the instantaneous speed of the weight 18 in the Y-axis direction. Therefore, an AC voltage having an opposite phase is applied between the fifth upper electrode 20e and the lower electrode 22 and between the fourth upper electrode 20d and the lower electrode 22 to excite the weight portion 18 in the Y-axis direction. In this state, the angular velocity ωz around the Z-axis can be obtained by calculation by obtaining the Coriolis force Fx acting in the X-axis direction from the amount of charge generated in the third upper electrode 20c and the second upper electrode 20b. it can.

  In particular, in the sensing element 10 according to the present embodiment, each loss coefficient of the first bonding layer 24a, the second bonding layer 24b, and the diaphragm 14 is equal to or less than the loss coefficient of the piezoelectric body.

  In general, the bonding layer between the members has a damping effect, and has a function of converting vibration energy of vibration on the solid surface into heat energy and reducing vibration on the solid surface. There is a loss factor as one of the evaluation indexes of the damping action (characteristic). The loss coefficient is represented by the ratio (E ″ / E ′) of the elastic coefficient E ′ and the loss elastic coefficient E ″. Since the vibration energy is converted into thermal energy as the loss factor is larger, the vibration energy is attenuated, making it difficult to resonate the sensing element 10 or taking time to resonate, which causes detection delay.

On the other hand, in the present embodiment, as described above, the loss coefficients of the first bonding layer 24a, the second bonding layer 24b, and the diaphragm 14 are equal to or less than the loss coefficient of the piezoelectric body. Since the lower electrode 22 is formed of a metal film, the loss coefficient of the lower electrode 22 is also less than or equal to the loss coefficient of the piezoelectric body 12. That is, a member having a loss coefficient equal to or less than that of the piezoelectric body 12 is interposed between the piezoelectric body 12 and the weight portion 18. Therefore, vibration energy generated in the piezoelectric body 12 based on the alternating voltage applied between the upper electrode 20 and the lower electrode 22 is almost all due to the lower electrode 22, the first bonding layer 24a, the vibration plate 14, and the second bonding layer 24b. It is efficiently transmitted to the weight portion 18 without being attenuated, and the sensing element 10 can be easily resonated. This can improve the Coriolis force detection accuracy (angular velocity detection accuracy), and can detect the angular velocity early. In particular, by making each loss coefficient of the first bonding layer 24a, the second bonding layer 24b, and the diaphragm 14 equal to or less than 100 × 10 ⁻⁴ , vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently. The acceleration and angular velocity detection accuracy can be improved, and the detection delay can be shortened as much as possible.

  Further, in the present embodiment, as shown in FIGS. 2A and 2B, the thickness ta of the piezoelectric body 12 and the thickness tb of the diaphragm 14 are obtained by bending the beam 32 composed of the piezoelectric body 12 and the diaphragm 14. In this case, the neutral axis 34 in terms of material mechanics is defined so as to be located on the diaphragm 14 side. Positioning on the vibration plate 14 side means that, of the piezoelectric body 12, a portion from the central portion in the thickness direction of the piezoelectric body 12 to the vibration plate 14, a boundary portion between the piezoelectric body 12 and the vibration plate 14, or a neutral axis on the vibration plate 14. 34 is located. 2A and 2B, the diaphragm 14 is made of metal and also serves as the lower electrode 22.

Here, the neutral shaft 34 will be described below. First, as shown in FIG. 3A, a bending deformation in a minute region 32a of the beam 32 in a bending deformation of one beam 32 having a lateral cross section symmetrical is considered. As shown in FIG. 3B, it is assumed that the minute region 32a is bent almost uniformly in an arc shape by the bending moment M. Of the micro region 32a, the inner side of the bending deformation (concave portion side) contracts due to compressive stress, and the outer side of the bending deformation (convex portion side) extends due to tensile stress. Within the elastic range, this bending deformation linearly changes from compression to tension depending on the distance from the center O of the arc (see FIG. 3C). At this time, there is a place where the vertical stress and strain in the longitudinal direction of the beam 32 become zero. Since the virtual cross sections at both ends of the minute region 32a do not rotate due to the balance of static force, the compression force inside the bending deformation (recess side) and the tensile force outside the bending deformation (recess side) are balanced from such a place. However, this place is referred to as a neutral plane 36 (see FIG. 3C). As a premise, since the cross section is left-right symmetric, a line intersecting the neutral plane 36 and the plane of symmetry 38 is called a neutral axis 34. As shown in FIG. 3B, when the radius of curvature with the neutral axis 34 as an arc is R and the angle formed by the arc is dθ, the length L _AA of the neutral axis 34 is
L _AA = R · dθ
It is.

  In the present embodiment, the thickness tb of the diaphragm 14 when the neutral shaft 34 is located at the boundary between the piezoelectric body 12 and the diaphragm 14 in the beam 32 composed of the piezoelectric body 12 and the diaphragm 14. Is the reference thickness tc, the thickness tb of the diaphragm 14 is equal to or greater than the reference thickness tc.

  Specifically, the result of confirming the ratio (tc / ta) of the reference thickness tc of the diaphragm 14 and the thickness ta of the piezoelectric body 12 by simulation based on 1 to 100 μm which is a preferable range as the thickness ta of the piezoelectric body 12 is shown. It shows in the following Table 1 and FIG.

  When the constituent material of the diaphragm 14 is gold (Au), as shown by a solid line L1 in FIG. 4, when the thickness ta of the piezoelectric body 12 is x and the film thickness ratio (tc / ta) is y, the film The thickness ratio exists on a straight line indicated by y = −0.00039x + 0.79689. For example, when the thickness ta of the piezoelectric body 12 is 1 μm, the film thickness ratio (tc / ta) is 0.80, and when the thickness ta of the piezoelectric body 12 is 100 μm, the film thickness ratio (tc / ta) is 0.76. It is. Therefore, the ratio (tb / ta) between the thickness tb of the diaphragm 14 and the thickness ta of the piezoelectric body 12 may be 0.76 or more. Of course, if the film thickness ratio (tb / ta) is 0.80 or more, it can be applied over a preferable thickness range (1 to 100 μm) of the piezoelectric body 12. More precisely, the thickness tb of the diaphragm 14 may be set to x (−0.00039x + 0.796889) μm or more.

  When the constituent material of the diaphragm 14 is copper (Cu), when the thickness ta of the piezoelectric body 12 is x and the film thickness ratio (tc / ta) is y, as shown by a solid line L2 in FIG. The thickness ratio exists on a straight line indicated by y = −0.00040x + 0.65557. For example, when the thickness ta of the piezoelectric body 12 is 1 μm, the film thickness ratio (tc / ta) is 0.66, and when the thickness ta of the piezoelectric body 12 is 100 μm, the film thickness ratio (tc / ta) is 0.62. It is. Therefore, the ratio (tb / ta) between the thickness tb of the diaphragm 14 and the thickness ta of the piezoelectric body 12 may be 0.62 or more. Of course, if the film thickness ratio (tb / ta) is 0.66 or more, it can be applied over a preferable thickness range (1 to 100 μm) of the piezoelectric body 12. More precisely, the thickness tb of the diaphragm 14 may be set to x (−0.00040x + 0.65557) μm or more.

  The upper limit value of the thickness tb of the diaphragm 14 can be set according to the mass of the weight portion 18, the rigidity of the beam 32 by the piezoelectric body 12 and the diaphragm 14, and is, for example, 200 μm or less, 150 μm or less, 100 μm or less. Can be preferably employed.

  As described above, the neutral axis 34 in terms of material mechanics when the thickness ta of the piezoelectric body 12 and the thickness tb of the vibration plate 14 are bent and the beam 32 composed of the piezoelectric body 12 and the vibration plate 14 is bent is the vibration plate 14. By defining the piezoelectric body 12 to be located on the side, either the compressive stress or the tensile stress is applied to the piezoelectric body 12 according to the bending direction, and the compressive stress and the tensile stress are not mixed. There is no cancellation of tensile stress. Therefore, for example, in the detection of the angular velocity, vibration according to the frequency and amplitude of the alternating voltage applied to the upper electrode 20 can be faithfully applied to the weight portion 18, and thereby the Coriolis force acting on the sensing element 10 can be accurately measured. It can be obtained well, and the detection accuracy of angular velocity can be improved. Further, since the boundary between the piezoelectric body 12 and the vibration plate 14 is located at a portion where the compressive stress or tensile stress is linearly reduced, the vibration plate 14 is made of a metal film (a metal film formed by sputtering or plating). Even if it comprises, the diaphragm 14 becomes difficult to peel from the piezoelectric material 12, and it is not necessary to interpose the layer for joining separately. In particular, as shown in FIG. 2B, by setting the thickness tb of the diaphragm 14 to the reference thickness tc, the neutral shaft 34 is positioned at the boundary between the piezoelectric body 12 and the diaphragm 14. The stress and strain at the boundary with the diaphragm 14 become zero, and the diaphragm 14 can be reliably prevented from peeling from the piezoelectric body 12.

  Next, a specific example of the sensing element 10 according to the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 5, in the sensing element according to the first specific example (hereinafter referred to as the first sensing element 10A), the diaphragm 14 is formed of a metal film, and the support part 16 and the weight part 18 are respectively provided. It is composed of an inorganic material other than metal. Here, since the metal film constituting the diaphragm 14 also serves as the lower electrode 22 shown in FIG. 1B, it is not necessary to form the first bonding layer 24a, and the metal film constituting the diaphragm 14 is the first one. Since it also serves as the second bonding layer 24b, it is not necessary to separately form the second bonding layer 24b. A first joining region 40a is formed at a boundary portion between the diaphragm 14, the support portion 16, and the weight portion 18 by room temperature joining of a metal and an inorganic material (for example, glass).

  Specifically, the diaphragm 14 has, for example, a two-layer structure including a first metal film 42a and a second metal film 42b. As the first metal film 42a on the piezoelectric body 12 side, Cr (chromium), Cu ( A sputtered metal film such as copper), Au (gold), Al (aluminum), or Ni (nickel) is used, and the second metal film 42b on the support 16 and weight 18 side is the same as the first metal film 42a. A thick second sputtered metal film of metal can be used. Alternatively, the sputtered metal film described above can be used as the first metal film 42a, and an electrolytic plating layer of Au, Cu, Ni or the like can be used as the second metal film 42b. Alternatively, an electroless plating layer such as Au, Cu, or Ni can be used as the first metal film 42a, and an electroplating layer such as Au, Cu, or Ni can be used as the second metal film 42b. Alternatively, an electroless plating layer such as Au, Cu, or Ni can be used as the first metal film 42a, and the above-described sputtered metal film of metal can be used as the second metal film 42b.

  A manufacturing method of the first sensing element 10A will be described with reference to FIG. First, in step S <b> 1 of FIG. 6, after forming a green sheet, firing is performed to produce the piezoelectric body 12. Thereafter, in step S <b> 2, the first metal film 42 a is formed on one main surface of the piezoelectric body 12. For example, a sputtered metal film such as Cr, Cu, Au, Al or Ni is formed by sputtering, or an electrolytic plating layer such as Au, Cu or Ni is formed by electroless plating.

  Thereafter, in step S3, a second metal film 42b is formed on one main surface of the first metal film 42a. For example, a sputtered metal film such as Cr, Cu, Au, Al or Ni is formed by sputtering, or an electrolytic plating layer such as Au, Cu or Ni is formed by electrolytic plating. As a result, the diaphragm 14 having a two-layer structure of the metal film is formed on one main surface of the piezoelectric body 12.

  On the other hand, in step S4, for example, a cylindrical glass plate 44 that is a constituent material of the support portion 16 and the weight portion 18 is prepared. Thereafter, in step S5, a glass structure 48 having an annular groove 46 is produced by blasting. That is, after attaching a mask having an annular opening on one main surface of the glass plate 44, fine particles such as steel and sand are sprayed toward the one main surface, and a portion of the glass plate 44 exposed from the opening is exposed. By removing to a certain depth, a glass construction 48 having an annular groove 46 is produced. The glass structure 48 has a configuration in which the support portion 16 located on the outer periphery and the weight portion 18 located in the center are integrated by a connecting portion 50 therebetween.

  In step S <b> 6, the surface of the vibration plate 14 and the end surfaces of the glass constituent body 48 (end surfaces of the support portion 16 and the weight portion 18) are each polished, so The roughness is set to 1 nm or less in RMS (root mean square roughness).

In step S7, after activating the end face of the diaphragm 14 and the end face of the glass structure 48 (for example, forming a dangling bond by ion beam irradiation), the end face of the diaphragm 14 and the end face of the glass structure 48 Are directly bonded by applying a load (for example, 0.2 to 1.0 Nmm ⁻² ) in a high vacuum (0.1 to 10 ⁻⁵ Pa) and at normal temperature. At this time, a first bonding region 40 a is formed at the boundary portion between the vibration plate 14, the support portion 16, and the weight portion 18 by normal temperature bonding between the second metal film 42 b and the glass component 48.

  Thereafter, in step S8, the connecting portion 50 of the glass structure 48 is removed by etching, for example, by blast etching (or polishing), and the support portion 16 and the weight portion 18 are separated. Thereafter, as shown in FIG. 5, the upper electrode 20 (first upper electrode 20 a to fifth upper electrode 20 e) is formed on the other main surface 12 b of the piezoelectric body 12. For example, a sputtered metal film such as Ag, Cu, Au, Al, or Ni is formed by sputtering to form the upper electrode 20. Thereby, the first sensing element 10A is completed.

  In the first sensing element 10A, since the diaphragm 14 itself also serves as the lower electrode 22, the first bonding layer 24a, and the second bonding layer 24b, the first bonding layer 24a and the second bonding layer 24b are separately formed. There is no need to do. In addition, since the first bonding region 40a existing at the boundary between the diaphragm 14 and the weight portion 18 is due to room temperature bonding between the second metal film 42b and the glass component 48, the second metal film 42b is substantially formed. It functions as a bonding layer, and the loss coefficient of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently. As a result, the acceleration and angular velocity detection accuracy can be improved, and the detection delay can be shortened as much as possible.

  Next, as shown in FIG. 7, the sensing element according to the second specific example (hereinafter referred to as the second sensing element 10 </ b> B) includes a diaphragm 14 made of a metal and a metal oxide, and supports 16 and Each of the weight portions 18 is made of an inorganic material other than metal. Also in this case, similarly to the first sensing element 10 </ b> A, the metal film constituting the diaphragm 14 also serves as the lower electrode 22. A second bonding region 40b is formed at a boundary portion between the vibration plate 14, the support portion 16, and the weight portion 18 by room temperature bonding between a metal oxide and an inorganic material (for example, glass).

  Specifically, the diaphragm 14 has a two-layer structure (laminated body) composed of a metal film 52 and a metal oxide film 54, and a metal film such as Al is used as the metal film 52 on the piezoelectric body 12 side. For example, a metal oxide film such as TiO (titanium oxide) can be used as the metal oxide film 54 on the support portion 16 and the weight portion 18 side.

  A method for manufacturing the second sensing element 10B will be described with reference to FIG. First, in step S101 of FIG. 8, the piezoelectric body 12 is manufactured. Thereafter, in step S <b> 102, a metal film 52 is formed on one main surface of the piezoelectric body 12. For example, a sputtered metal film such as Al is formed by sputtering.

  Thereafter, in step S103, a metal oxide film 54 is formed on one main surface of the metal film 52. For example, a sputtered metal oxide film such as TiO is formed by sputtering. As a result, the diaphragm 14 having a two-layer structure including the metal film 52 and the metal oxide film 54 is formed on one main surface of the piezoelectric body 12.

Since the process after step S104 is substantially the same as step S4 to step S8 in the manufacturing method of the first sensing element 10A described above, a duplicate description thereof is omitted, but in step S104, for example, a cylindrical glass plate 44 is formed. In step S105, the glass structure 48 having the annular groove 46 is produced by blasting. In step S106, the end face of the diaphragm 14 and the end face of the glass structure 48 (the support portion 16 and the weight portion 18). In step S107, the end surface of the diaphragm 14 and the end surface of the glass component 48 are brought into close contact with each other, in a high vacuum (0.1 to 10 ⁻⁵ Pa), and at room temperature. Further, direct bonding is performed by applying a load (for example, 0.2 to 1.0 Nmm ⁻² ). At this time, a second bonding region 40 b is formed at the boundary portion between the vibration plate 14, the support portion 16, and the weight portion 18 by normal temperature bonding between the metal oxide film 54 and the glass component 48.

  Thereafter, in step S108, the connecting portion 50 of the glass structure 48 is removed by etching (blasting or polishing) to separate the support portion 16 and the weight portion 18 from each other. Thereafter, as shown in FIG. 7, the upper electrode 20 (first upper electrode 20a to fifth upper electrode 20e: see FIG. 1A) is formed on the other main surface 12b of the piezoelectric body 12, and the second sensing element 10B is completed. To do.

  Also in this second sensing element 10B, since the diaphragm 14 itself also serves as the lower electrode 22, the first bonding layer 24a, and the second bonding layer 24b, the first bonding layer 24a and the second bonding layer 24b are separately formed. There is no need to do. In addition, since the second bonding region 40b existing at the boundary between the diaphragm 14 and the weight portion 18 is due to room temperature bonding between the metal oxide film 54 and the glass component 48, the metal oxide film 54 is substantially formed of the bonding layer. The loss coefficient of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently.

  Next, as shown in FIG. 9, the sensing element according to the third specific example (hereinafter referred to as the third sensing element 10C) has substantially the same configuration as the first sensing element 10A described above. 14 is different in that a third bonding region 40c is formed by diffusion bonding between a metal and an inorganic material (for example, glass) at a boundary portion between the support portion 16 and the weight portion 18. Since the configuration of the diaphragm 14 is the same as that of the first sensing element 10 </ b> A, a duplicate description thereof is omitted.

  A method for manufacturing the third sensing element 10C will be described with reference to FIG. First, since the process shown in step S201 to step S206 in FIG. 10 is substantially the same as the process shown in step S1 to step S6 in the manufacturing method of the first sensing element 10A described above, the duplicate description is omitted. In step S201, the piezoelectric body 12 is manufactured. In step S202, the first metal film 42a is formed on one main surface of the piezoelectric body 12. In step S203, the second metal film 42b is formed on one main surface of the first metal film 42a. To form a two-layered diaphragm 14 made of a metal film. Thereafter, in step S204, for example, a cylindrical glass plate 44 is prepared. In step S205, a glass structure 48 having an annular groove 46 is produced by blasting. In step S206, the end face of the diaphragm 14 and the glass are formed. The end surfaces of the structural body 48 (end surfaces of the support portion 16 and the weight portion 18) are each polished.

In step S207, the end face of the diaphragm 14 and the end face of the glass component 48 are brought into close contact with each other, and a load (for example, 0.2 to 3.0 Nmm ⁻² ) is further applied at a high temperature of 400 ° C. In addition, diffusion bonding is performed. By adhering the diaphragm 14 and the glass component 48 (portions serving as the support portion 16 and the weight portion 18) and applying a load and heat, diffusion of atoms at the joint surface between the diaphragm 14 and the glass component 48 is performed. It happens and is joined. At this time, a third bonding region 40c is formed by diffusion bonding between the second metal film 42b of the vibration plate 14 and the inorganic material of the support portion 16 and the weight portion 18.

  Thereafter, as shown in step S208, the connecting portion 50 of the glass component 48 is removed by etching (blasting or polishing) to separate the support portion 16 and the weight portion 18, and further, as shown in FIG. By forming the upper electrode 20 (the first upper electrode 20a to the fifth upper electrode 20e: see FIG. 1A) on the other main surface 12b of the twelve, the third sensing element 10C is completed.

  Also in the third sensing element 10C, since the diaphragm 14 itself also serves as the lower electrode 22, the first bonding layer 24a, and the second bonding layer 24b, the first bonding layer 24a and the second bonding layer 24b are separately formed. There is no need to do. Moreover, since the third bonding region 40c existing at the boundary between the diaphragm 14 and the weight portion 18 is formed by diffusion bonding between the second metal film 42b and the glass component 48, the second metal film 42b is substantially formed. It functions as a bonding layer, and the loss coefficient of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently.

  Next, as shown in FIG. 11, the sensing element according to the fourth specific example (hereinafter referred to as a fourth sensing element 10D) includes the piezoelectric body 12, the third metal film 42c constituting the lower electrode 22, The metal oxide constituting the diaphragm 14 is integrally fired to form one fired body 56. On one main surface of the fired body 56, a fourth metal film 42d as a bonding layer is formed. Moreover, the support part 16 and the weight part 18 are each comprised with inorganic materials other than a metal. Further, a fourth bonding region 40d is formed at the boundary portion between the diaphragm 14, the support portion 16, and the weight portion 18 by diffusion bonding of the fourth metal film 42d and an inorganic material (for example, glass).

As the third metal film 42c constituting one fired body 56, a metal film such as Au can be used, for example, and as the metal oxide (diaphragm 14) constituting the fired body 56, for example, Al ₂ O ₃ A metal oxide film such as (alumina) can be used, and a metal film such as Au can be used as the fourth metal film 42d formed on one main surface of the fired body 56, for example.

  A method for manufacturing the fourth sensing element 10D will be described with reference to FIG. First, as shown in step S301 of FIG. 12, a green sheet is molded to produce a piezoelectric molded body 58 (a precursor of the piezoelectric body 12 before firing). As shown in step S <b> 302, a third metal film 42 c constituting the lower electrode 22 is formed on one main surface of the alumina green sheet 60 constituting the diaphragm 14. For example, a paste of an organometallic compound (resinate) of Pt is applied. Thereafter, in step S303, the piezoelectric molded body 58 is overlaid on the third metal film 42c and fired at a high temperature (900 to 1600 ° C.), and the piezoelectric body 12 and the third metal film 42c constituting the lower electrode 22 are formed. Then, one fired body 56 in which the metal oxide constituting the diaphragm 14 is fired and integrated is produced. Thereafter, in step S304, a fourth metal film 42d is formed on one main surface of the fired body 56. For example, a sputtered metal film such as Au is formed by sputtering.

  The processes shown in steps S305 to S307 are substantially the same as steps S204 to S206 in the method of manufacturing the third sensing element 10C described above, and thus redundant description thereof is omitted. However, in step S305, for example, cylindrical glass The plate 44 is prepared, and in step S306, the glass structure 48 having the annular groove 46 is produced by blasting. In step S307, the end face of the fourth metal film 42d and the end face of the glass structure 48 (supporting part 16). And the end face of the weight portion 18).

In step S308, the fourth metal film 42d formed on the end face of the vibration plate 14 and the end face of the glass constituting body 48 are brought into close contact with each other, and a load (for example, 0. ² to 3.0 Nmm ⁻² ) is added for diffusion bonding. At this time, a fourth bonding region 40d is formed by diffusion bonding of the fourth metal film 42d and the support member 16 and the inorganic material of the weight portion 18.

  Thereafter, in step S309, the connecting portion 50 of the glass structure 48 is removed by etching (blasting or polishing) to separate the support portion 16 and the weight portion 18, and further, as shown in FIG. By forming the upper electrode 20 (first upper electrode 20a to fifth upper electrode 20e: see FIG. 1A) on the main surface 12b, the fourth sensing element 10D is completed.

  In the fourth sensing element 10D, since the piezoelectric body 12, the lower electrode 22, and the diaphragm 14 are configured by one fired body 56, it is not necessary to form the first bonding layer 24a. Moreover, since the fourth bonding region 40d is formed by diffusion bonding between the fourth metal film 42d below the diaphragm 14 and the glass component 48, the fourth metal film 42d substantially functions as the second bonding layer 24b. The loss factor of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently.

  Next, in the sensing element according to the fifth specific example (hereinafter referred to as the fifth sensing element 10E), as shown in FIG. 13, the diaphragm 14 is made of metal, and the support portion 16 and the weight portion 18 are respectively It is composed of an inorganic material other than metal. Also in this case, similarly to the first sensing element 10 </ b> A, the metal film constituting the diaphragm 14 also serves as the lower electrode 22. Between the vibration plate 14 and the support portion 16 and the weight portion 18, eutectic bonding between the metal film formed on the end surface of the vibration plate 14 and the metal film formed on the end surface of the support portion 16 and the weight portion 18. Thus, a fifth bonding region 40e is formed.

  Specifically, the diaphragm 14 has a multilayer structure of, for example, a fifth metal film 42e and a sixth metal film 42f. As the fifth metal film 42e on the piezoelectric body 12 side, for example, Cr (piezoelectric side) / Au Alternatively, a sputtered metal film having a two-layer structure of Ti (piezoelectric side) / Au or a sputtered metal film having a three-layer structure of TiN (titanium nitride: piezoelectric material) / Cu (intermediate layer) / Au is used. As the sixth metal film 42f on the weight 18 side, for example, a Cu or Au plating layer can be used.

  Further, as the seventh metal film 42g for eutectic bonding formed on the end face of the diaphragm 14, for example, a sputtered metal film of Au is used, and the eutectic bonding formed on the end faces of the support portion 16 and the weight portion 18 is used. As an eighth metal film 42h for the purpose, for example, a sputtered metal film of Cr (support side and weight part side) / Au has a two-layer structure of Au (sputtered metal film side) / Sn (tin). A metal film having a multilayer structure in which plating layers are laminated can be used.

  A method for manufacturing the fifth sensing element 10E will be described with reference to FIG. First, in step S401 of FIG. 14, a green sheet is formed and then fired to produce the piezoelectric body 12. Thereafter, in step S402, a fifth metal film 42e is formed on one main surface of the piezoelectric body 12. For example, a sputtered metal film of Cr / Au, Ti / Au, or TiN / Cu / Au is formed. Thereafter, in step S403, a sixth metal film 42f is formed on one main surface of the fifth metal film 42e. For example, an electrolytic plating layer such as Cu or Au is formed by electrolytic plating. As a result, the diaphragm 14 having a multilayer structure including the fifth metal film 42e and the sixth metal film 42f is formed on one main surface of the piezoelectric body 12.

  On the other hand, after preparing a cylindrical glass plate 44 in step S404, for example, in step S405, a glass structure 48 having an annular groove 46 is produced by blasting.

  Thereafter, in step S406, the seventh metal film 42g is formed on the end face of the diaphragm 14, and the eighth metal film 42h is formed on the end face of the glass constituting body 48 (end face of the support portion 16 and the weight portion 18). Specifically, for example, a sputtered metal film of Au is formed on the end face of the diaphragm 14, and a sputtered metal film of, for example, Cr / Au is formed on the end face of the glass structure 48, and then on the sputtered metal film, An Au / Sn plating layer is laminated.

In step S407, the seventh metal film 42g formed on the end face of the vibration plate 14 and the eighth metal film 42h formed on the end face of the glass constituting body 48 are brought into close contact with each other, so that the maximum temperature is 350 ° C. Further, eutectic bonding is performed by applying a load (for example, 0.2 to 3.0 Nmm ⁻² ). The eutectic bonding is a liquid phase diffusion bonding using a eutectic reaction in liquefaction of metal. That is, the pressure is applied to the extent that plastic deformation does not occur as much as possible under a temperature condition equal to or lower than the melting point of the metal film, and bonding is performed using the diffusion of atoms generated on the bonding surface. At this time, a fifth bonding region 40e is formed by eutectic bonding between metals at the boundary between the seventh metal film 42g and the eighth metal film 42h.

  Thereafter, in step S408, the connecting portion 50 of the glass structure 48 is removed by etching (blasting or polishing) to separate the support portion 16 and the weight portion 18 from each other. Thereafter, as shown in FIG. 13, the upper electrode 20 (first upper electrode 20a to fifth upper electrode 20e: see FIG. 1A) is formed on the other main surface 12b of the piezoelectric body 12, and the fifth sensing element 10E is completed. To do.

  Also in the fifth sensing element 10E, since the metal film of the diaphragm 14 also serves as the lower electrode 22, it is not necessary to form the first bonding layer 24a. In addition, since the fifth bonding region 40e is formed by eutectic bonding between the seventh metal film 42g below the diaphragm 14 and the eighth metal film 42h on the glass structure 48, the seventh metal film 42g is substantially formed. The eighth metal film 42h functions as the second bonding layer 24b, and the loss coefficient of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently.

  Next, the sensing element according to the sixth specific example (hereinafter referred to as the sixth sensing element 10F) has substantially the same configuration as the fourth sensing element 10D as shown in FIG. The difference is that a sixth junction region 40f is formed by eutectic bonding between the ninth metal film 42i formed on the end surface and the tenth metal film 42j formed on the end surfaces of the support portion 16 and the weight portion 18.

  As in the case of the fifth sensing element 10E described above, for example, a sputtered metal film of Au is used as the ninth metal film 42i, and a sputtered metal film of, for example, a Cr / Au two-layer structure is used as the tenth metal film 42j. A metal film having a multilayer structure in which a plating layer having a two-layer structure of Au / Sn is laminated can be used.

  A method for manufacturing the sixth sensing element 10F will be described with reference to FIG. First, since the processes shown in steps S501 to S503 in FIG. 16 are substantially the same as steps S301 to S303 in the method for manufacturing the fourth sensing element 10D described above, the duplicate description thereof is omitted, but in step S501, A green sheet is molded to produce a piezoelectric molded body 58. In step S502, a third metal film 42c constituting the lower electrode 22 is formed on one main surface of an alumina green sheet constituting the diaphragm 14, In step S503, the piezoelectric molded body 58 is overlaid on the third metal film 42c and fired at a high temperature, and the piezoelectric body 12, the third metal film 42c constituting the lower electrode 22, and the metal constituting the diaphragm 14 are obtained. One fired body 56 in which the oxide and the fire are integrated is manufactured.

  The processes shown in steps S504 to S508 are substantially the same as steps S404 to S408 in the above-described method for manufacturing the fifth sensing element 10E, and thus redundant description thereof will be omitted. In step S504, for example, cylindrical glass A plate 44 is prepared, and in step S505, a glass structure 48 having an annular groove 46 is produced by blasting. In step S506, a ninth metal film 42i is formed on the end face of the diaphragm 14, and the glass structure is formed. A tenth metal film 42j is formed on the end surfaces 48 (end surfaces of the support portion 16 and the weight portion 18). Specifically, for example, a sputtered metal film of Au is formed on the end face of the diaphragm 14, and a sputtered metal film of, for example, Cr / Au is formed on the end face of the glass structure 48, and then on the sputtered metal film, An Au / Sn plating layer is laminated.

  Then, in step S507, the ninth metal film 42i formed on the end face of the diaphragm 14 and the tenth metal film 42j formed on the end face of the glass constituting body 48 are brought into close contact with each other, so that the maximum temperature is 350 ° C. Further, eutectic bonding is performed by applying a load. At this time, a sixth junction region 40f is formed by eutectic bonding between metals at the boundary between the ninth metal film 42i and the tenth metal film 42j.

  Thereafter, in step S508, the connecting portion 50 of the glass structure 48 is removed by etching (blasting or polishing), and the support portion 16 and the weight portion 18 are separated. After that, as shown in FIG. 15, the upper electrode 20 (first upper electrode 20a to fifth upper electrode 20e: see FIG. 1A) is formed on the other main surface 12b of the piezoelectric body 12, and the sixth sensing element 10F is completed. To do.

  In the sixth sensing element 10F, since the piezoelectric body 12, the lower electrode 22, and the diaphragm 14 are configured by one fired body 56, it is not necessary to form the first bonding layer 24a. In addition, since the sixth bonding region 40f is formed by eutectic bonding between the ninth metal film 42i below the diaphragm 14 and the tenth metal film 42j on the glass structure 48, the ninth metal film 42i is substantially formed. The tenth metal film 42j functions as the second bonding layer 24b, and the loss coefficient of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently.

  Next, the sensing element according to the seventh specific example (hereinafter referred to as the seventh sensing element 10G) has substantially the same configuration as the first sensing element 10A described above, as shown in FIG. 14 and the support part 16 and the weight part 18 are different in that they are joined via a brazing material 64.

  A sputtered metal film such as Au or Cu can be used as the first metal film 42a constituting the vibration plate 14, and an electrolytic plating layer such as Cu or Au can be used as the second metal film 42b. Further, as the brazing material, for example, a brazing material containing an active element may be used. The active elements are periodic table 2A group such as Mg, Sr, Ca, Ba and Be, 3A group such as Ce, 4A group such as Ti and Zr, or 5A group such as Nb, B and Si. Etc., at least one of the elements belonging to Group 4B can be used. In the seventh sensing element 10G, Ag—Cu—In—Ti was used as the brazing material.

  A method for manufacturing the seventh sensing element 10G will be described with reference to FIG. First, since the processes shown in steps S601 to S603 in FIG. 18 are substantially the same as steps S1 to S3 in the manufacturing method of the first sensing element 10A described above, redundant description thereof is omitted, but in step S601, In step S602, the first metal film 42a is formed on one main surface of the piezoelectric body 12, and in step S603, the second metal film 42b is formed on one main surface of the first metal film 42a. Thus, the diaphragm 14 having a two-layer structure made of a metal film is formed.

  In step S604, the brazing material 64 is formed on the end face of the diaphragm 14.

  Thereafter, in step S605, for example, a cylindrical glass plate 44 is prepared, and in step S606, a glass structure 48 having an annular groove 46 is produced by blasting.

  In step S607, the brazing material 64 formed on the end face of the diaphragm 14 and the end face of the glass component 48 (end faces of the support part 16 and the weight part 18) are brought into close contact with each other, and further at a maximum temperature of 800 ° C. When the load is applied, the diaphragm 14 is joined to the support portion 16 and the weight portion 18 via the brazing material 64.

  Thereafter, in step S608, the connecting portion 50 of the glass structure 48 is removed by etching, and the support portion 16 and the weight portion 18 are separated. Thereafter, as shown in FIG. 17, the upper electrode 20 (first upper electrode 20a to fifth upper electrode 20e: see FIG. 1A) is formed on the other main surface 12b of the piezoelectric body 12, and the seventh sensing element 10G is completed. To do.

  In the seventh sensing element 10G, since the diaphragm 14 itself serves as the lower electrode 22 and the first bonding layer 24a, the first bonding layer 24a need not be formed. Moreover, the brazing material 64 functions as the second bonding layer 24 b, and the loss coefficient of the bonding layer is lower than that of the piezoelectric body 12. Therefore, vibration generated in the piezoelectric body 12 can be transmitted to the weight portion 18 more efficiently.

[First embodiment]
About Examples 1-7 and a comparative example, in the state which gave vibration Sx of the X-axis direction, an experiment which detects Coriolis force Fz which acts on the Z-axis direction was performed, and a change in detection sensitivity due to a difference in frequency of vibration Sx confirmed.

(Examples 1-7)
The sensing element according to Example 1 has the same configuration as the first sensing element 10A shown in FIG. 5, and the sensing element according to Example 2 has the same configuration as the second sensing element 10B shown in FIG. The sensing element according to Example 3 has the same configuration as the third sensing element 10C illustrated in FIG. The sensing element according to the fourth embodiment has the same configuration as the fourth sensing element 10D shown in FIG. 11, and the sensing element according to the fifth embodiment has the same configuration as the fifth sensing element 10E shown in FIG. The sensing element according to Example 6 has the same configuration as the sixth sensing element 10F shown in FIG. 15, and the sensing element according to Example 7 is the same as the seventh sensing element 10G shown in FIG. It has the composition of.

  In each of the sensing elements according to Examples 1 to 7, the thickness ta of the piezoelectric body 12 was set to 20 μm, the thickness tb of the diaphragm 14 was set to 16 μm, and the neutral shaft 34 was set to be located on the diaphragm 14 side. The film thickness ratio (tb / ta) is 0.8.

  Then, for example, as shown in FIG. 1A, an AC power source is connected between the third upper electrode 20c and the lower electrode 22, and between the second upper electrode 20b and the lower electrode 22, and the first upper electrode 20a. A charge / voltage conversion circuit was connected between the first electrode 22 and the lower electrode 22. The charge / voltage conversion circuit converts the amount of charge generated in the first upper electrode 20a into a voltage value when the potential of the lower electrode 22 is a reference potential (for example, ground potential), that is, a detected value of the Coriolis force Fz. Circuit.

Then, the sensing elements according to Examples 1 to 6 are rotated at a constant angular velocity with the Y axis as the rotation axis. The angular velocity is a known value set in advance, and therefore the Coriolis force Fz acting in the Z-axis direction is also known. This Coriolis force Fz that has been found in advance is used as a reference value. In this state, an alternating voltage (frequency fa, amplitude A) having an opposite phase is applied between the third upper electrode 20c and the lower electrode 22 and between the second upper electrode 20b and the lower electrode 22, The weight 18 was excited in the X-axis direction, and the Coriolis force Fz (measured value) acting in the Z-axis direction was detected from the voltage value output from the charge / voltage conversion circuit at this time. The detection sensitivity at this time was expressed based on the following formula (1) by multiplying the logarithm of the ratio between the measurement value and the reference value by 10 (decibel notation).
Detection sensitivity [dB] = ₁₀ log ₁₀ (measured value / reference value) (1)

  In the same manner as described above, the Coriolis force Fz (measured value) when an AC voltage (frequency fb (> fa), amplitude A) is applied is detected, and the detection sensitivity at this time is obtained based on Equation (1). .

  Differences in detection sensitivity of Example 1 depending on the frequencies fa and fb of the vibration Sx are shown in plots A1 and A2 in FIG. 19A. Similarly, the difference in detection sensitivity in Example 2 is shown in plots B1 and B2 in FIG. 19B, the difference in detection sensitivity in Example 3 is shown in plots C1 and C2 in FIG. 20A, and the difference in detection sensitivity in Example 4 is shown. The difference in detection sensitivity of Example 5 is shown in plots E1 and E2 in FIG. 21A, and the difference in detection sensitivity of Example 6 is shown in plots F1 and F2 in FIG. 21B. 7 shows the difference in detection sensitivity in plots G1 and G2 in FIG. 21C.

  As can be seen from FIG. 19A to FIG. 21C, in Example 1, the detection sensitivity (hereinafter referred to as detection sensitivity (frequency fa)) when vibration of the frequency fa is applied is −2.5 [dB], and the frequency The detection sensitivity (hereinafter referred to as detection sensitivity (frequency fb)) when vibration of fb (> fa) was applied was −3.0 [dB]. In Example 2, the detection sensitivity (frequency fa) was −2.7 [dB], and the detection sensitivity (frequency fb) was −3.2 [dB]. In Example 3, the detection sensitivity (frequency fa) was −2.5 [dB], and the detection sensitivity (frequency fb) was −3.0 [dB]. In Example 4, the detection sensitivity (frequency fa) was −2.8 [dB], and the detection sensitivity (frequency fb) was −3.3 [dB]. In Example 5, the detection sensitivity (frequency fa) was −2.5 [dB], and the detection sensitivity (frequency fb) was −3.0 [dB]. In Example 6, the detection sensitivity (frequency fa) was −2.9 [dB], and the detection sensitivity (frequency fb) was −3.4 [dB]. In Example 7, the detection sensitivity (frequency fa) was −3.0 [dB], and the detection sensitivity (frequency fb) was −3.5 [dB].

(Comparative Example 1)
As shown in FIGS. 22A and 22B, the sensing element 100 according to Comparative Example 1 has the same configuration as that of the sensing element 10 according to the present embodiment shown in FIGS. 1A and 1B, but includes a lower electrode 22 and a diaphragm. 14 is performed by the first organic adhesive layer 102a, and the diaphragm 14, the support portion 16, and the weight portion 18 are bonded by the second organic adhesive layer 102b. The loss coefficients of the first organic adhesive layer 102 a and the second organic adhesive layer 102 b are both about 10 times the loss coefficient of the piezoelectric body 12.

  And also in the comparative example 1, similarly to Examples 1-7 mentioned above, the detection sensitivity of the Coriolis force Fz when the vibration of the frequency fa is applied, and the detection of the Coriolis force Fz when the vibration of the frequency fa is applied Sensitivity was determined. Differences in detection sensitivity of Comparative Example 1 depending on the frequencies fa and fb of the vibration Sx are shown in plots R1 and R2 in FIG. The detection sensitivity when the vibration with the frequency fa was applied was -10.0 [dB], and the detection sensitivity when the vibration with the frequency fb was applied was -32.0 [dB].

<Discussion>
From the results of FIGS. 19A to 21C and FIG. 23, it can be seen that both Examples 1 to 7 can obtain high detection sensitivity, and the detection sensitivity hardly depends on the frequency of the vibration Sx. This is because the first bonding layer 24a is omitted or the first bonding layer 24a and the second bonding layer 24b are omitted, and the loss coefficient of the second bonding layer 24b or the layer functioning as the bonding layer is piezoelectric. This is considered to be because the loss factor of the entire sensing element is small, and the sensing element can easily resonate regardless of the vibration frequency. Therefore, it is clear that Examples 1 to 7 have improved Coriolis force detection accuracy (angular velocity detection accuracy) compared to Comparative Example 1.

[Second Embodiment]
Regarding Examples 11 to 14, the difference in detection sensitivity was confirmed when the thickness ta of the piezoelectric body 12 was made constant (20 μm) and the thickness tb of the diaphragm 14 was changed. Examples 11-14 have the same configuration as that of Example 1 described above (first sensing element 10A shown in FIG. 5).

(Example 11)
Example 11 has the same configuration as that of Example 1 described above except that the thickness tb of the diaphragm 14 is 10 μm and the film thickness ratio (tb / ta) is 0.5.

(Example 12)
Example 12 has the same configuration as that of Example 1 described above except that the thickness tb of the diaphragm 14 is 20 μm and the film thickness ratio (tb / ta) is 1.0.

(Examples 13 and 14)
Examples 13 and 14 are the same as Example 1 described above, except that the thickness tb of the diaphragm 14 is 30 μm and 40 μm, and the film thickness ratio (tb / ta) is 1.5 and 2.0, respectively. It has the composition of.

<Evaluation>
As in the first embodiment, an AC power source is connected between the third upper electrode 20c and the lower electrode 22 and between the second upper electrode 20b and the lower electrode 22, respectively. A charge / voltage conversion circuit was connected between the lower electrodes 22.

  Then, similarly to the above-described first embodiment, the sensing elements according to the eleventh to fourteenth embodiments are rotated at a constant angular velocity (known) with the Y axis as a rotation axis. In this state, the third upper electrode 20c and the lower portion are moved. An AC voltage (frequency fa, amplitude A) having an opposite phase is applied between the electrode 22 and between the second upper electrode 20b and the lower electrode 22, and the weight portion 18 is excited in the X-axis direction. At this time, the Coriolis force Fz (measured value) acting in the Z-axis direction is detected from the voltage value output from the charge / voltage conversion circuit, and the detection sensitivity at this time is obtained based on the above-described equation (1). .

  The breakdown of Examples 11 to 14 and the results of detection sensitivity are shown in Table 2 below.

<Discussion>
In Examples 12, 13, and 14 in which the thickness tb of the diaphragm 14 is equal to or greater than the reference thickness tc, the detection sensitivities are -1.39 [dB], -0.56 [dB], and -1.19 [dB], respectively. It was good. In particular, in Example 13 where the film thickness ratio (tb / ta) was 1.5, the detection sensitivity was -0.56 [dB], which was the best. On the other hand, although Example 11 was -4.54 [dB] and was better than the comparative example of the first example described above, the detection sensitivity was lower than that of Examples 12-14. This is because the thickness tb of the diaphragm 14 is smaller than the reference thickness tc, and therefore there is a portion where the compressive stress and the tensile stress are mixed in the piezoelectric body 12, and there is a portion where the compressive stress and the tensile stress cancel each other. This is considered to be because vibration according to the frequency and amplitude of the AC voltage applied to 20 was not faithfully transmitted to the weight portion 18.

  The sensing element according to the present invention is not limited to the above-described embodiment, but can of course have various configurations without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Sensing element 10A-10G ... 1st sensing element-7th sensing element 12 ... Piezoelectric body 14 ... Diaphragm 16 ... Support part 18 ... Weight part 20 ... Upper electrode 20a-20e ... 1st upper electrode-5th upper electrode DESCRIPTION OF SYMBOLS 22 ... Lower electrode 24a ... 1st joining layer 24b ... 2nd joining layer 32 ... Beam 34 ... Neutral axis 36 ... Neutral surface 40a-40f ... 1st junction area-6th junction area 42a-42j ... 1st metal film- Tenth metal film 48 ... Glass structure 52 ... Metal film 54 ... Metal oxide film 56 ... Firing body

Claims (12)

A piezoelectric body;
A diaphragm provided to face one main surface of the piezoelectric body;
A weight portion provided to face one main surface of the diaphragm;
An upper electrode and a lower electrode provided in contact with the piezoelectric body;
At least a bonding layer provided between the diaphragm and the weight portion;
For it represented the loss factor by a ratio of elastic modulus E 'and loss modulus E''(E''/E'), loss factor of the bonding layer and the vibration plate Ri der loss factor less of the piezoelectric ,
The thickness of the piezoelectric body and the thickness of the diaphragm are defined so that a neutral axis in material mechanics when a beam composed of the piezoelectric body and the diaphragm is bent is positioned on the diaphragm side. A sensing element characterized by comprising: The sensing element according to claim 1 ,
When the thickness of the diaphragm when the neutral axis is located at a boundary portion between the piezoelectric body and the diaphragm is a reference thickness,
The sensing element according to claim 1, wherein a thickness of the diaphragm is equal to or greater than the reference thickness. The sensing element according to claim 1 or 2 ,
The sensing element, wherein the bonding layer and the diaphragm have a loss coefficient of 100 × 10 ⁻⁴ or less. In the sensing element according to any one of claims 1 to 3 ,
The sensing element, wherein the bonding layer is made of an inorganic material. The sensing element according to claim 4 ,
The sensing element, wherein the bonding layer is made of metal. In the sensing element according to any one of claims 1 to 5 ,
A sensing element, wherein the diaphragm is made of an inorganic material. The sensing element according to claim 6 ,
A sensing element, wherein the diaphragm is made of metal. In the sensing element according to any one of claims 1 to 3 ,
The diaphragm is made of a metal film,
The weight portion is made of an inorganic material other than metal,
The sensing element, wherein the bonding layer is a brazing material formed between the diaphragm and the weight portion. The sensing element according to any one of claims 1 to 8 ,
At least the upper electrode is composed of a plurality of electrodes,
The plurality of electrodes include a drive electrode for driving the weight portion and a detection electrode for detecting displacement of the weight portion. The sensing element according to any one of claims 1 to 8 ,
At least the upper electrode is composed of a plurality of electrodes,
The plurality of electrodes include only detection electrodes for detecting displacement of the weight portion. The sensing element according to claim 9 or 10 ,
The sensing element, wherein the lower electrode is a counter electrode of the plurality of electrodes and is a common electrode. The sensing element according to claim 11 ,
The sensing element, wherein the diaphragm also serves as the lower electrode.

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