JP5741869B2 - Piezoelectric device - Google Patents

Description

  The present invention relates to a piezoelectric device.

  A crystal oscillator is widely used as a frequency generation source for supplying a stable frequency, such as a clock signal source for broadcasting equipment, measurement equipment, and digital equipment. In particular, a crystal oscillator with a thermostatic chamber (Oven Controlled Crystal (X'tal) Oscillator: hereinafter sometimes referred to as OCXO) accommodates a crystal resonator in a small thermostat and keeps the ambient temperature of the crystal resonator constant. It has very good frequency stability. Therefore, OCXO is used for applications of stricter standards such as the reference frequency and frequency counter of communication base stations and the frequency reference of frequency synthesizers. In addition, various crystal oscillators including OCXO are required to be further downsized in response to downsizing of mounted devices.

  Japanese Patent Application Publication No. 2001-500715 discloses an oven-controlled crystal resonator in which a heater element and a resonator are provided on a thermally conductive base so as to be able to conduct heat with each other, and the whole is covered with a cover. The publication states that the resonator can be maintained at a high temperature without excessive consumption of battery energy.

Special table 2001-500715 gazette

  However, when the resonator is heated by heat conduction through the member, the member needs to have a size larger than the size that can hold the resonator. In this method, in order to cause a member having a specific size to conduct heat conduction, in order to heat the resonator or the like, it is necessary to first heat the member, and extra heat (energy) for that purpose is required. . Further, since the member has a large mass and volume, the member is fixed in a package to be accommodated by a bump, an adhesive, or the like. Therefore, the heat insulation between the member and the package is not always sufficient. Furthermore, this method makes it difficult to make the member smaller than the size of a resonator or the like, and is not necessarily a suitable method for obtaining a small oscillator.

  One of the objects according to some embodiments of the present invention is to provide a piezoelectric device capable of heating an element with less energy and sufficiently suppressing heat conduction outside the package.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
Package and
A piezoelectric element housed in the package;
A heater element housed in the package;
Have
The piezoelectric element has a base portion and a beam portion extending from the base portion, and is fixed in a cantilever shape or a cantilever shape by the base portion,
The heater element includes a support part and a heat generating part supported by the support part so as to be separated from the package,
The heat generating portion is fixed in a cantilever shape or a doubly supported beam shape by the support portion,
The piezoelectric device, wherein the heat generating portion and the beam portion are separated from each other.

  In such a piezoelectric device, since the heat generating portion of the heater element is supported (fixed) by the support portion, heat conduction to the outside of the package is suppressed, and the piezoelectric element can be heated with less energy.

[Application Example 2]
In application example 1,
The said support part is a piezoelectric device which has electroconductivity for supplying the electric current to the said heat-emitting part.

  Such a piezoelectric device is easy to manufacture while suppressing heat conduction from the heater element to the package.

[Application Example 3]
In application example 1,
The heat generating part and the support part include a conductive layer and are integrally formed.

  Such a piezoelectric device can suppress heat conduction from the heater element to the package, and can more reliably hold the heat generating portion.

[Application Example 4]
In any one of Application Examples 1 to 3,
And further comprising a support housed in the package,
The piezoelectric element and the support part are both piezoelectric devices fixed to the package via the support.

  Such a piezoelectric device is easier to manufacture in addition to the features of the above example.

[Application Example 5]
In any one of Application Examples 1 to 4,
A piezoelectric device having a plurality of the heat generating parts.

  Such a piezoelectric device has a higher efficiency of heating the piezoelectric element in addition to the features of the above-described example.

The schematic diagram of the cross section of the piezoelectric device 100 concerning embodiment. FIG. 2 is a plan view schematically showing the piezoelectric device 100 according to the embodiment. FIG. 2 is a plan view schematically showing the piezoelectric device 110 according to the embodiment. The schematic diagram of the cross section of the piezoelectric device 120 concerning embodiment. FIG. 3 is a plan view schematically showing the piezoelectric device 120 according to the embodiment. The schematic diagram of the cross section of the piezoelectric device 130 concerning embodiment. The top view which shows typically the piezoelectric device 130 concerning embodiment. The schematic diagram of the cross section of the piezoelectric device 140 concerning embodiment. The top view which shows typically the piezoelectric device 140 concerning embodiment. The schematic diagram of the cross section of the piezoelectric device 150 concerning embodiment. FIG. 3 is a plan view schematically showing the piezoelectric device 150 according to the embodiment. The schematic diagram of the cross section of the piezoelectric device 200 concerning a modification. The top view which shows typically the piezoelectric device 200 concerning a modification. The schematic diagram of the cross section of the piezoelectric device 210 concerning a modification. The schematic diagram of the cross section of the piezoelectric device 220 concerning a modification. The top view which shows typically the piezoelectric device 220 concerning a modification.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following embodiment, Various modifications implemented in the range which does not change the summary of this invention are also included.

  The piezoelectric device according to the present invention includes a package, a piezoelectric element, and a heater element.

  FIG. 1 is a schematic cross-sectional view of a piezoelectric device 100 that is an example of the present embodiment. FIG. 2 is a plan view schematically showing the piezoelectric device 100. A cross section taken along line AA in FIG. 2 corresponds to FIG. The piezoelectric device 100 includes a package 10, a piezoelectric element 20, and a heater element 30.

1. Package The package 10 is a housing that can accommodate at least the piezoelectric element 20 and the heater element 30. A cavity 12 is formed inside the package 10. A piezoelectric element 20 and a heater element 30 are installed in the cavity 12. The outer shape of the package 10 is not limited, and can be, for example, a rectangular parallelepiped shape or a cylindrical shape. The package 10 may be composed of a plurality of members. One function of the package 10 is to prevent external members from mechanically contacting the piezoelectric element 20 and the heater element 30. One function of the package 10 is to seal the piezoelectric element 20 and the heater element 30 in the cavity 12. Further, when the package 10 is sealed and the inside of the cavity 12 is decompressed, the package 10 can have at least one of a function of increasing the Q value of the piezoelectric element 20 and a function of suppressing heat flow to the outside. . In the piezoelectric device of the present embodiment, the package 10 includes a case body 14 and a lid body 16.

1.1. Case Body The case body 14 has a container shape that can accommodate the piezoelectric element 20 and the heater element 30. The planar shape of the case body 14 has a rectangular shape in the present embodiment, but is not limited thereto, and may be a circle or the like. The upper part of the case body 14 has an opening that allows the piezoelectric element 20 and the heater element 30 to be introduced into the case body 14. The opening of the case body 14 can be hermetically sealed by the lid body 16. The case body 14 can have a step on the inner bottom surface. This step can be installed as appropriate in order to install the piezoelectric element 20 in a cantilevered or doubly supported beam shape, for example. In the example of FIG. 1, the piezoelectric element 20 and the heater element 30 are each installed in a doubly-supported beam shape by a step. In FIG. 2, the lid 16 and the piezoelectric element 20 are seen through and outlined using a broken line.

Inside the case body 14, wiring inside the cavity 12, wiring that can be electrically connected to the outside, and the like can be formed. In the illustrated example, a wiring 18 for electrically connecting to the heater element 30 is illustrated as one type of such wiring. The case body 14
Can have through holes on the bottom surface. The through hole is filled with a conductive material, and can be a via hole that electrically connects the conductive member inside the case body 14 and the external conductive member. Examples of the conductive material used for the via hole include tungsten and molybdenum. The via hole can have airtightness. Furthermore, a pad for surface mounting or the like can be provided outside the case body 14. The material of the case body 14 can be an inorganic material such as ceramic or glass.

1.2. Lid Body The lid body 16 has a flat plate shape that seals the upper opening of the case body 14. The planar shape of the lid body 16 is not particularly limited, and is a shape that avoids contact with the piezoelectric element 20 from the outside, or a shape that can seal the opening of the case body 14 to form a sealed space. can do. Examples of the material of the lid body 16 include ceramic, glass, and metal. The adhesion between the case body 14 and the lid body 16 can be performed using, for example, plasma welding, seam welding, ultrasonic bonding, or an adhesive. The cavity 12 formed by the case body 14 and the lid body 16 becomes a space for operating the piezoelectric element 20 and the heater element 30. Further, since the cavity 12 can be sealed, the piezoelectric element 20 and the heater element 30 can be placed in a reduced pressure space or an inert gas atmosphere.

2. Piezoelectric Element The piezoelectric element 20 is provided in the package 10 (in the cavity 12 formed by the case body 14 and the lid body 16). Examples of the piezoelectric element 20 include an AT vibrating piece (including SC cut), a tuning fork type vibrating piece, a double tuning fork type vibrating piece, a walk type vibrating piece, a SAW resonator, and a vibrating gyroscope. The function of the piezoelectric device 100 as a device is determined by the type of the piezoelectric element 20. For example, when the piezoelectric element 20 is an AT vibrating piece, a tuning fork type vibrating piece, or a walk type vibrating piece, the piezoelectric device 100 can be a timing device such as an oscillator or a clock module. When the piezoelectric element 20 is a SAW resonator, the piezoelectric device 100 can be a frequency filter in addition to the timing device. Furthermore, when the piezoelectric element 20 is a double tuning fork type vibrating piece or a vibrating gyroscope, the piezoelectric device 100 can be a sensor such as an acceleration sensor, a pressure sensor, or an angular velocity sensor.

  The piezoelectric element 20 can be formed of quartz. The piezoelectric element 20 may be formed of a piezoelectric material such as lithium tantalate or lithium niobate. When the piezoelectric element 20 is formed of a material other than quartz, the crystal orientation (cut angle) or the like can be selected so that the same behavior as when formed by quartz can be produced.

  The piezoelectric element 20 can include an electrode corresponding to its form and function. The type, number and arrangement of the electrodes are not particularly limited. The electrodes may include an electrode for exciting the piezoelectric element 20, an electrode for detecting the operation of the piezoelectric element 20, an electrode wiring, a pad for external connection, and the like.

  The piezoelectric element 20 has a base portion 22 and a beam portion 24. The base portion 22 is a portion that is fixed to the inside of the package 10 when the piezoelectric element 20 is supported in a cantilever shape or a doubly supported beam shape. Therefore, the base 22 is located at one end or both ends when the piezoelectric element 20 is viewed in a plan view. The shape of the base 22 is not particularly limited according to the design of the piezoelectric element 20. A pad (not shown) for external connection can be formed on the base 22. The pad can be used for bump bonding or wire bonding, for example.

The beam portion 24 has a shape extending from the base portion 22. The beam portion 24 has a flat plate shape when the piezoelectric element 20 is an AT resonator element or a SAW resonator. When the piezoelectric element 20 is a tuning fork type, a walk type, a double tuning fork type vibrating piece, the beam portion 24 has a shape in which a plurality of beam-like vibrating arms are formed. The beam portion 24 is a portion that forms a beam when the piezoelectric element 20 is supported in a cantilever shape or a cantilever shape. Therefore, one end or both ends of the beam portion 24 are continuous with the base portion 22. The beam portion 24 is provided in the cavity 12 of the package 10 so as not to contact the package 10.

  Examples of the method for installing the piezoelectric element 20 in the package 10 include bump bonding and fixing with an adhesive. When fixing with a conductive adhesive is performed, both mechanical fixing and electrical connection can be achieved. A piezoelectric device 100 shown in FIGS. 1 and 2 is an example in the case where the piezoelectric element 20 is an AT vibrating piece, which has a beam portion 24 and two base portions 22 formed at both ends thereof, and has a double-supported beam shape. It is supported. In the example of the piezoelectric device 100, the piezoelectric element 20 is fixed by the conductive adhesive 26, and an electrode (not shown) of the piezoelectric element 20 and an electrode (not shown) formed inside the case body 14 are electrically connected. Connected.

3. Heater Element The heater element 30 is provided in the package 10 (in the cavity 12 formed by the case body 14 and the lid body 16). The heater element 30 has a support portion 32 and a heat generating portion 34.

  The support portion 32 of the heater element 30 is a portion that is fixed to the inside of the package 10 when the heater element 30 is supported in a cantilever shape or a cantilever shape. Accordingly, the support portion 32 is located at one end or both ends when the heater element 30 is viewed in plan. In the example of FIGS. 1 and 2, the support portion 32 is formed so as to protrude on both sides of the heat generating portion 34, and is installed in a doubly supported beam shape with respect to the step on the bottom surface of the case body 14. When installed in this manner, for example, even when an impact or the like is applied to the piezoelectric device 100, it is difficult for the support portion 32 to bend excessively. Therefore, the contact between the heater element 30 and the piezoelectric element 20 is further increased. Can be suppressed.

  FIG. 3 is a plan view schematically showing the piezoelectric device 110 in which the heater element 30 is provided in a cantilever shape. As shown in FIG. 3, the support portion 32 can be provided so as to protrude from the heat generating portion 34 to one side. In this way, for example, the wiring in the package 10 can be given flexibility.

  Examples of the method for installing the heater element 30 in the package 10 include bump bonding and fixing with an adhesive. When fixing with a conductive adhesive is performed, both mechanical fixing and electrical connection can be achieved. In the example of FIGS. 1 and 2, the heater element 30 is mechanically fixed by an adhesive 31 and is electrically connected to wiring in the package 10 by a bonding wire 33.

  Further, the heater element 30 is provided on the package 10 if there is an electrode (not shown) formed on the outer surface of the package 10 or an electronic component for controlling the heat generation of the heater element 30 in the package 10. It is conducted through a conductor path such as wiring.

The support portion 32 is provided with a conductor path 32 b so that a current can be supplied to the heat generating portion 34. The function of the support part 32 includes mechanically supporting at least the heat generating part 34 and supplying a current to the heat generating part 34. The support portion 32 may include a member that mechanically supports the heat generating portion 34 and a conductor path 32 b that supplies current to the heat generating portion 34. In addition, the support portion 32 can be configured to include a conductor that mechanically supports the heat generating portion 34 and supplies current. When the conductor path 32b formed in the support portion 32 or the support portion 32 itself is a conductor, it is more preferable that the electrical resistance for supplying current to the heat generating portion 34 is small.

  In the example of FIGS. 1 and 2, the support portion 32 includes, for example, a silicon substrate 32 a as an insulating substrate and a conductor path 32 b formed on the surface of the silicon substrate 32 a. The silicon substrate 32 a The conductor path 32b has a function as wiring for supplying a current to the heat generating portion 34.

  FIG. 4 is a schematic cross-sectional view of the piezoelectric device 120 in which the support portion 32 is configured by a conductive wire 36. FIG. 5 is a plan view schematically showing the piezoelectric device 120. A cross section taken along line AA in FIG. 5 corresponds to FIG. FIG. 6 is a schematic cross-sectional view of a piezoelectric device 130 in which the support portion 32 is configured by a conductive lead 38. FIG. 7 is a plan view schematically showing the piezoelectric device 130. A cross section taken along line AA in FIG. 7 corresponds to FIG. FIG. 8 is a schematic cross-sectional view of a piezoelectric device 140 in which the support portion 32 is configured by a conductive lead 38. FIG. 9 is a plan view schematically showing the piezoelectric device 140. A cross section taken along line AA in FIG. 9 corresponds to FIG. FIG. 10 is a schematic diagram of a cross section of the piezoelectric device 150 in which the support portion 32 is supported by the support body 40. FIG. 11 is a plan view schematically showing the piezoelectric device 150. A cross section taken along line AA in FIG. 11 corresponds to FIG. Each plan view is drawn through the lid 16 and the piezoelectric element 20.

  The support portion 32 can be a conductive wire 36 as in the piezoelectric device 120 shown in FIGS. 4 and 5. As the wire 36, for example, a bonding wire formed of gold or aluminum used for a semiconductor or the like can be used. The heater element 30 of the piezoelectric device 120 has two wires 36 (support portions 32), and is supported by the wires 36 in a doubly supported beam shape. In the illustrated example, the length of the wire 36 is given a margin, but the wire 36 may be formed so as to have tension.

  Further, the support portion 32 can be formed by a conductive lead 38 like the piezoelectric device 130 shown in FIGS. 6 and 7. As the lead 38, for example, a structure having a relatively large cross-sectional area to obtain a higher tension than that of the wire, or a structure in which the shape is formed in a band shape, an alloy of copper, iron and nickel, or the like is compared with gold or aluminum. And those formed of a hard material. The heater element 30 of the piezoelectric device 130 has two leads 38 (support portions 32), and is supported by the leads 38 in a doubly supported beam shape. If the support part 32 is comprised by the lead 38, the heat-emitting part 34 can be fixed more stably. Furthermore, like the piezoelectric device 140 shown in FIG. 8, the heater element 30 supported in the form of a double-supported beam may be provided along the direction intersecting the piezoelectric element 20 formed in the form of a double-supported beam. Such a deformation of the arrangement can be freely performed within a designable range. Further, in the piezoelectric device 140, an appropriate step is formed on the inner bottom surface of the package 10 so that the heater element 30 can be provided in a direction intersecting the piezoelectric element 20.

  In addition, the shape of the support portion 32 is not particularly limited. However, when there is no step on the inner bottom surface of the package 10, the heating portion 34 is supported in a suspended state when the heater element 30 is placed on the inner bottom surface. It is good also as a simple shape. For example, the support portion 32 may be connected to the support body 40 including the support plate 41 having the leg portions 42 having such a height that a space is obtained between the inner bottom surface of the package 10 and the heat generating portion 34. Good.

As such an example, the support part 32 is formed integrally with the support body 40 so as to be able to be fixed independently inside the package 10. In the piezoelectric device 150 shown in FIGS. 10 and 11, the heat generating portion 34 is supported in a doubly-supported beam shape inside the opening of the support plate 41 having an opening via a support portion 32 having a lead shape. . That is, the support part 32 connects the heat generating part 34 and the support plate 41. And the support plate 41 has the leg part 42,
The leg portion 42 is fixed to the inner bottom surface of the package 10.

  The shape of the support 40 is not particularly limited as long as the heating element 34 can be supported in a suspended state when the heater element 30 is fixed inside the package 10. In the illustrated example, the support body 40 includes a support plate 41 and leg portions 42. The support plate 41 in this case has a flat plate shape with an opening, and the heat generating portion 34 is supported in a doubly supported beam shape via the support portion 32 at the center portion of the opening as viewed in plan. Yes. The support body 40 has leg portions 42 that prevent the support plate 41 and the heat generating portion 34 from coming into contact with the package 10 when the heater element 30 is installed on the inner bottom surface of the package 10. In the example shown in the figure, the support 40 has a support plate 41 and a leg 42 formed integrally.

  The support body 40 can be fixed to the inner bottom surface of the package 10 with an adhesive or the like, for example. The support 40 can be formed of, for example, silicon, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, or the like.

  Moreover, wiring can be provided on the support 40 as appropriate. In the illustrated example, the conductor path 32 b which is a wiring on the support body 40 is electrically connected to the wiring 19 on the inner bottom surface of the package 10 by a bonding wire 37.

  In this way, when the support portion 32 is configured to be supported by the support body 40, the heater element 30 can be more stably installed in the package 10. In addition, when the support portion 32 is supported by the support body 40, the piezoelectric device can be easily manufactured by, for example, facilitating adjustment of the alignment and lead tension when the heater element 30 is installed in the package 10. Can be

  It is preferable that the support portion 32 has a shape in which the heat generating portion 34 is suspended in the package 10 and the heat generated by the heat generating portion 34 is not easily transmitted to the package 10. For example, the support portion 32 is preferably formed to be thin overall. For example, it is preferable that the cross-sectional area of the support part 32 is smaller than the cross-sectional area of the region where the heat generating part 34 is formed. Further, for example, the support portion 32 may have a constriction or the like as a configuration having a thin portion so as to hinder heat conduction.

  When the support portion 32 includes a mechanical support member, examples of the material of the support member include insulating materials such as silicon, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, and tantalum pentoxide. (In the example shown, it is the silicon substrate 32a). As a material of the member responsible for conductivity in the support portion 32 (in the illustrated example, the conductor path 32b), at least selected from gold, silver, copper, nickel, palladium, chromium, iron, platinum, and alloys thereof. One kind can be mentioned.

  The heat generating part 34 is provided and supported by the support part 32 in the package 10. That is, the heat generating portion 34 is provided apart from the package 10 and is not in contact with the inner wall of the package 10. The heat generating part 34 can generate heat when an electric current flows. The current of the heat generating part 34 is supplied via the support part 32 described above. The size and shape of the heat generating part 34 are not particularly limited. A function of the heat generating part 34 is to heat the beam part 24 of the piezoelectric element 20.

  The heat generating part 34 is not limited as long as it can generate heat by passing an electric current. For example, a fixed resistor such as a carbon film resistor or a metal film resistor, a variable resistor, a semi-fixed resistor, etc. Resistors, wiring having electric resistance made of platinum or other conductive materials, etc., such as element type or chip type, and micro heaters, can be mentioned.

  Here, the micro-heater is a resistance device manufactured by, for example, MEMS (Micro Electro Mechanical Systems) technology in semiconductor manufacturing, and is formed in a thin film shape on an insulating base material or insulating film such as silicon, glass, or polymer. This refers to a wiring with electrical resistance (conductive layer). Such electric resistance can be formed of, for example, carbon, tungsten, platinum, or the like.

  When such a micro-heater is used as the heat generating portion 34 of the heater element 30, the lead, the heat generating portion, and the step formed integrally can be disposed in the package 10, so that the assembly of the piezoelectric device is simplified. At the same time, it can contribute at least to miniaturization of the piezoelectric device. In addition, since the microheater can be formed to have a conductive layer as a heating element only on one side of an insulating substrate such as silicon, the degree of heat generation can be asymmetrical between the front and back surfaces. That is, when such a microheater is used, the heater element 30 can be disposed with the surface on which the conductive layer is formed facing the piezoelectric element 20, thereby further suppressing the outflow of heat to the outside. be able to. That is, the piezoelectric element 20 can be heated more efficiently by the heat of the heater element 30.

  Further, since it is difficult to transfer the heat of the heat generating part 34 to the package 10, it is possible to reduce the useless amount of heat released from the package 10. Therefore, even if the piezoelectric device 100 is configured as a surface mount type, the power consumption is relatively It can be kept small.

  In addition, when the metal dust has adhered to the surface of the piezoelectric element 20, if this falls and adheres to the heater element 30 surface, the heat generating function of the heater element 30 may be out of order. In some cases, current flows through the metal dust, and the metal dust reaches a high temperature and evaporates, and the evaporated substance adheres to the surface of the piezoelectric element 20, thereby deteriorating the electrical characteristics of the piezoelectric element 20. There is also sex. Therefore, when it is necessary to prevent the occurrence of such a problem, it is more desirable that the heater element 30 has a configuration in which at least the surface of the heat generating portion 34 is covered with an insulating thin film such as silicon oxide.

  In the piezoelectric device 100 illustrated in FIGS. 1 and 2, the heat generating portion 34 of the heater element 30 is a micro heater in which a conductive layer 34b (electric resistance) is formed on the surface of a silicon substrate 34a. The silicon substrate 34 a is formed integrally with the silicon substrate 32 a of the support portion 32. The conductive layer 34b is electrically connected to the conductor path 32b. The material of the conductive layer 34b and the conductor path 32b may be different.

  In plan view, at least a part of the contour of the heat generating portion 34 is inside the contour of the beam portion 24 of the piezoelectric element 20. In other words, the heat generating part 34 and the beam part 24 are arranged so as to overlap in a plan view. When the entire contour of the heat generating portion 34 is inside the contour of the beam portion 24, heat generated by the heat generating portion 34 is difficult to be transmitted to parts other than the beam portion 24, and more efficiently transmitted to the beam portion 24. Can do. In the example of the piezoelectric device shown in FIGS. 1 to 11, all of the outline of the heat generating portion 34 is provided inside the outline of the beam portion 24. Note that, even when the piezoelectric element 20 is a tuning-fork type vibrating piece and the contour of the beam portion 24 is notched, the heat generating portion 34 and the beam portion 24 overlap in plan view. Can be arranged. Further, the planar size of the heat generating portion 34 can be smaller than or equal to the planar size of the beam portion 24. If the planar size of the heat generating portion 34 is larger than the planar size of the beam portion 24, the efficiency of heating the beam portion 24 may be reduced.

The heat generating part 34 is provided spatially separated from the beam part 24. Heat and far infrared rays generated in the heat generating portion 34 are propagated to the beam portion 24 through the space. Even if the inside of the cavity 12 of the package 10 is in a reduced pressure state, the heat of the heat generating portion 34 and the far infrared rays can be transmitted to the beam portion 24 by radiation. In addition, when air or an inert gas exists in the cavity 12, heat may be propagated through these gases. When the inside of the cavity 12 is in a reduced pressure state, the energy efficiency in heating the beam portion 24 can be further increased.

  The distance between the heat generating part 34 and the beam part 24 is not particularly limited, but is preferably as small as possible considering at least one of the efficiency of heating the beam part 24 and the miniaturization of the piezoelectric device 100. For example, the distance between the heat generating part 34 and the beam part 24 can be 0.1 μm or more and 10 μm or less. If the distance between the heat generating portion 34 and the beam portion 24 is too small, it may become an obstacle to vibration of the beam portion 24 (thickness shear vibration, bending vibration, surface acoustic wave vibration, etc.). When the piezoelectric element 20 is a SAW resonator (surface acoustic wave element), the heat generating portion 34 can be brought into contact with the surface of the beam portion 24 where no surface acoustic wave is generated. In this way, direct heat transfer is possible, and the efficiency of heating the beam portion 24 can be further increased.

4). Other Configurations In addition to the above-described package, piezoelectric element, and heater element, the piezoelectric device of the present embodiment can include the following configurations.

  The piezoelectric device of the present embodiment can include a configuration for detecting the temperature of the piezoelectric element and maintaining it at a specific temperature in the package. Examples of such a configuration include a thermistor, a thermocouple, a diode, wiring for these, and a control IC. By including such a configuration, the piezoelectric device can be provided with a function of keeping the temperature constant. Furthermore, the piezoelectric device of this embodiment can include an IC or the like having an electronic circuit for driving the piezoelectric element in the package. By including such an IC or the like, functions such as an oscillator and a resonator can be imparted to the piezoelectric device.

  Furthermore, the piezoelectric device includes an electronic circuit having a function of compensating the frequency temperature characteristics of the piezoelectric element 20 by the temperature compensation circuit while heating the piezoelectric element 20 by the heater element 30 to an intermediate temperature or higher in the operating temperature range. It may be a configuration.

  Such a piezoelectric device is heated at a temperature lower than the maximum temperature in the usage temperature range of the piezoelectric element 20, so that the temperature of the environment of the piezoelectric element 20 is temperature-compensated to be a temperature range narrower than the usage temperature range. Compensated by the circuit.

  Therefore, the piezoelectric device having such a configuration can achieve high frequency stability even when a small heater element 30 having a heating capability lower than that of OCXO is used. The temperature compensation circuit is for variably controlling the load capacitance in the oscillation circuit as the temperature changes, thereby compensating the frequency temperature characteristic of the piezoelectric element 20 and stabilizing the frequency temperature characteristic of the piezoelectric device. is there.

  Furthermore, in the above embodiment, an example using one heater element 30 has been described. However, the present invention is not limited to this example, and the piezoelectric device of the present invention has a heater on a step in the package 10 or an inner bottom surface. A configuration in which a plurality of elements 30 are mounted may be used.

5. Operational Effect In the piezoelectric device of the present embodiment, since the heat generating part 34 is supported (fixed) by the support part 32, heat conduction to the outside of the package is suppressed, and the beam part of the piezoelectric element 20 with less energy. 24 can be heated. Thereby, the heat | fever (energy) leaking outside through a member can be made very small. Further, in the case where the heat generating portion 34 of the present embodiment is configured by a micro heater, the heat radiation to the side not facing the beam portion 24 can be reduced, so that the efficiency of heating the beam portion 24 can be further increased. it can.

6). Modification FIG. 12 is a schematic diagram of a cross section of a piezoelectric device 200 according to a modification. FIG. 13 is a plan view schematically showing the piezoelectric device 200. A cross section taken along line AA in FIG. 13 corresponds to FIG. FIG. 14 is a schematic diagram of a cross section of a piezoelectric device 210 according to a modification. FIG. 15 is a schematic diagram of a cross section of a piezoelectric device 220 according to a modification. FIG. 16 is a plan view schematically showing the piezoelectric device 220. A cross section taken along line AA in FIG. 16 corresponds to FIG. Each plan view is drawn through the lid 16 and the piezoelectric element 20.

  The piezoelectric device of the present invention can have a plurality of heater elements 30. As shown in FIGS. 12 and 13, the piezoelectric device 200 of the modified example is the same as the above-described piezoelectric device except that it includes two heater elements 30 (30a, 30b). Other configurations are denoted by the same reference numerals as described above, and detailed description thereof is omitted. The structure, shape, function, etc. of each heater element 30 are the same as described in “3. Heater element”.

  The piezoelectric device 200 includes two heater elements, a heater element 30a and a heater element 30b. As shown in FIG. 12, the heating element 34 c and the heating element 34 d of the heater element 30 a and the heater element 30 b are installed so as to be separated from the beam part 24 of the piezoelectric element 20 and sandwich the beam part 24 from each other. . Moreover, both the heat generating part 34c and the heat generating part 34d overlap with the beam part 24 in plan view. The piezoelectric device 200 of the modified example can heat the beam portion 24 more quickly by including two heater elements. In the piezoelectric device 200, a step is formed on the inner bottom surface of the package 10 to support two heater elements. In the example shown in the figure, the heat generating part 34 is constituted by a micro heater, and is installed so that heat radiation on the side facing the beam part 24 is increased. Therefore, the beam portion 24 can be heated extremely efficiently.

  The piezoelectric device 210 of the modification shown in FIG. 14 has two heater elements, a heater element 30c and a heater element 30d. The heating element 34e and the heating part 34f of the heater element 30c and the heater element 30d are installed so as to be separated from the beam part 24 of the piezoelectric element 20 and sandwich the beam part 24 therebetween. The size of the heat generating portion 34f of one heater element 30d (located above the piezoelectric element 20 in the figure) is the same as that of the other heater element 30c (located below the piezoelectric element 20 in the figure). It is formed larger than the size of 34e. In the case of this example, the heat generating part 34f has the same size as the beam part 24 in plan view. By heating the heat generating portion in a plan view and having the same size as the beam portion 24, heating suitable for the mode and shape of the piezoelectric element 20 can be performed. Further, as in the illustrated example, the size of the heat generating portion 34e and the heat generating portion 34f may be asymmetric on the front and back surfaces of the piezoelectric element 20. In this case, for example, a distribution can be generated in the degree of heating in the plane of the beam portion 24.

  In the piezoelectric device of the present invention, the piezoelectric element 20 can be mounted on the same member as the heater element 30. For example, both the piezoelectric element 20 and the heater element 30 may be fixed to the support body 40 and fixed to the package 10 via the support body 40. The piezoelectric device 220 of the modification shown in FIGS. 15 and 16 has the heater element 30 supported by the support body 40, and the piezoelectric element 20 is placed on the support body 40. As already described in the section “3. Heater element”, the support 40 is composed of the support plate 41 and the legs 42. In the piezoelectric device 220 of the modified example, the heater element 30 and the piezoelectric element 20 are both fixed to the support 40 in a doubly supported beam shape.

In the piezoelectric device 220, first, the support body 40 includes a support plate 41 and a leg portion 42, and supports the heater element 30 in a doubly supported beam shape in the opening of the support plate 41. And the piezoelectric element 30 is supported on the support plate 41 of the support body 40 in the form of a double-supported beam. The support 40 can be fixed to the inner bottom surface of the package 10 with an adhesive or the like. The heat generating portion 34 of the heater element 30 and the beam portion 24 of the piezoelectric element 20 are provided so as to overlap in a plan view. On the support 40, a wiring 35 for electrical connection of the piezoelectric element 20 and a conductor path 32b for electrical connection of the heater element 30 can be appropriately provided. In the illustrated example, the wiring 35 on the support 40 is electrically connected to the wiring 19 on the inner bottom surface of the package 10 by a bonding wire 37. Although not shown, a wiring electrically connected to the heater element 30 to generate heat is formed on the inner bottom surface of the package 20, and the conductor path 32 b connected to the wiring and the heater element 30 is a bonding wire or other These conductor paths are appropriately connected.

  In the piezoelectric device 220 of such a modification, both the heater element 30 and the piezoelectric element 20 are supported by the support body 40. That is, in the package 10, only the leg portion 42 of the support 40 is a part where the heater element 30 and the piezoelectric element 20 are fixed. In this way, the following effects can be obtained. First, it is not necessary to perform the process of fixing the piezoelectric element 20 in the package 10 in the manufacturing process. That is, the process of placing the piezoelectric element 20 on the package 10 is not necessary. For example, the piezoelectric element 20 can be mounted on the heater element 30 before being mounted on the package 10 in advance. Then, it becomes easier to precisely position (align) the piezoelectric element 20 with respect to the heat generating portion 34 of the heater element 30. Thereby, the precision of the piezoelectric device 220 can be further increased, and the yield in manufacturing can be improved. Next, when the piezoelectric device 220 of the modified example is used, the piezoelectric element 20 and the heater element 30 can be mounted on the package 10 after being assembled. Therefore, when manufacturing the piezoelectric device 220, the process of mounting elements on the package 10 can be reduced. Thereby, for example, the yield in manufacture can be improved.

  The modifications described in the embodiment and the modification examples can be applied to the piezoelectric device of the embodiment singly or in combination with each other. Thereby, the single effect for each deformation | transformation or the synergistic effect by the combination of each deformation | transformation can be acquired.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 10 ... Package, 12 ... Cavity, 14 ... Case body, 16 ... Cover body, 18, 19 ... Wiring, 20 ... Piezoelectric element, 22 ... Base part, 24 ... Beam part, 26 ... Conductive adhesive, 30, 30a, 30b, 30c, 30d ... heater element, 31 ... adhesive, 32 ... support part, 32b ... conductor path, 33 ... bonding wire, 34, 34c, 34d, 34e, 34f ... heating part, 32a, 34a ... silicon substrate, 34b ... conductive layer, 35 ... wiring, 36 ... wire, 37 ... bonding wire, 38 ... lead, 40 ... support, 41 ... support plate, 42 ... leg, 100, 110, 120, 130, 140, 150, 200, 210, 220 ... piezoelectric device

Claims (9)

Package and
A SAW resonator housed in the package and having a surface on which a surface acoustic wave is excited and a back surface with respect to the surface;
A heater element having a support part, a heat generating part supported by the support part, and an insulating film covering the heat generating part;
With
The SAW resonator has a base portion and a beam portion including a surface that is excited by a surface acoustic wave, and is fixed to a cantilever beam or a cantilever beam shape by the base portion.
The piezoelectric device, wherein the back surface of the SAW resonator and the heat generating portion are in contact with each other through the insulating film. In claim 1,
Furthermore, it has a support,
The piezoelectric device according to claim 1, wherein the heater element is formed integrally with the support. In claim 2,
The support has a conductive path formed on the surface of the support,
The piezoelectric device according to claim 1, wherein at least one of the SAW resonator and the heater element is connected to the conductive path. In claim 2 or claim 3,
The piezoelectric device is characterized in that the support is made of any material of silicon, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, or aluminum nitride. In any one of Claims 2 thru | or 4,
The piezoelectric device, wherein the SAW resonator and the heater element are fixed to the package via the support. In claim 5,
The SAW resonator has an external connection pad connected to an electrode for exciting the SAW resonator, and the pad is connected to a connection terminal in the package via a bonding wire. A piezoelectric device characterized by In any one of Claims 2 thru | or 6,
The support has a leg and a support plate,
The piezoelectric device, wherein the legs are fixed to the package. In any one of Claims 1 thru | or 7,
A piezoelectric device comprising a plurality of the heat generating parts. In any one of Claims 1 thru | or 8,
A piezoelectric device comprising at least one of a temperature sensitive element, a temperature control circuit, a temperature compensation circuit, and an oscillation circuit in the package.

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