JP2009027306A - Surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave device capable of maintaining a prescribed resonance frequency with high accuracy regardless of a temperature change. <P>SOLUTION: The surface acoustic wave device is provided with a surface acoustic wave element piece 10 with an interdigital electrode 11 formed on one principal plane 14 of a piezoelectric substrate 16, a spacer 20 fixed to a part of the other principal plane 15 of the piezoelectric substrate 16 in the surface acoustic wave element piece 10, and a package 30 for housing the surface acoustic wave element piece 10 and the spacer 20, wherein the coefficient of linear expansion of the spacer 20 is approximate to or the same as the coefficient of linear expansion of the piezoelectric substrate 16, and the spacer 20 fixed to the surface acoustic wave element piece 10 is fixed to the bottom 33 in the package 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave device including a surface acoustic wave element that excites surface acoustic waves.

As surface acoustic wave devices using surface acoustic waves, for example, surface acoustic wave resonators, surface acoustic wave oscillators and surface acoustic wave filters are used as reference frequency sources for electronic devices, frequency selectors in transmission circuits, etc. Yes.
The surface acoustic wave element constituting the surface acoustic wave device has a configuration in which interdigital electrodes are formed on the surface of the piezoelectric substrate and reflectors are formed at both ends of the interdigital electrodes.
When an electric signal is applied to the interdigital electrode, the surface acoustic wave element piece excites surface waves between the interdigital fingers of the interdigital electrode by the piezoelectric effect, and the surface acoustic wave element piece is formed on the piezoelectric substrate on which the interdigital electrode and the reflector are formed. Surface acoustic waves propagate on the surface.

  In the surface acoustic wave element piece, the back surface of the piezoelectric substrate is fixed to the package with an adhesive. This adhesive may shrink with a change in ambient temperature and generate stress on the piezoelectric substrate. Therefore, in order to eliminate the influence on the resonance frequency due to the stress generated in the piezoelectric substrate, a configuration of a surface acoustic wave device in which the back surface of the piezoelectric substrate that does not overlap with the interdigital transducer is fixed to the package with an adhesive is disclosed. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 2005-136938

However, in the surface acoustic wave device configured as described above, in addition to the shrinkage of the adhesive, the stress generated as the package expands and contracts affects the resonance frequency.
A ceramic is used as the package material of the surface acoustic wave device, and a piezoelectric material such as quartz is used as the piezoelectric substrate constituting the surface acoustic wave element piece. Since the linear expansion coefficient differs greatly between the package material and the piezoelectric material, the expansion / contraction state of the package and the expansion / contraction state of the piezoelectric substrate due to changes in ambient temperature are different. Stress is generated.

The piezoelectric substrate is deformed by this stress, and the pitch between the interdigital fingers of the interdigital electrode changes, whereby the resonance frequency of the surface acoustic wave element piece changes.
For this reason, it becomes difficult for the surface acoustic wave device to maintain a predetermined resonance frequency with high accuracy due to a change in ambient temperature.

  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 forms or application examples.

  [Application Example 1] A surface acoustic wave device according to this application example includes a surface acoustic wave element piece in which interdigital electrodes are formed on one main surface of a piezoelectric substrate, and the other of the piezoelectric substrate in the surface acoustic wave element piece. And a package in which the surface acoustic wave element piece and the support member are accommodated, and the linear expansion coefficient of the support member is the linear expansion coefficient of the piezoelectric substrate. And the support member is fixed to a fixing portion in the package.

According to such a configuration, in the surface acoustic wave device, the linear expansion coefficient of the support member is approximately or the same as the linear expansion coefficient of the piezoelectric substrate. Therefore, the surface acoustic wave device has a stress between the fixed part and the support member in the package due to the difference in linear expansion coefficient between the fixed part and the support member in the package due to the change in ambient temperature. However, this stress is absorbed by the support member. On the other hand, since the linear expansion coefficient of the support member and the piezoelectric substrate of the surface acoustic wave element piece is approximately or the same, there is almost no stress generation between the two due to expansion and contraction.
As a result, since the surface acoustic wave element piece is fixed to a support member having an approximate or same linear expansion coefficient, a frequency change caused by expansion and contraction of the fixing portion and the support member in the package due to a change in ambient temperature occurs. Hateful.
Thereby, the surface acoustic wave device can maintain a predetermined resonance frequency with high accuracy regardless of the ambient temperature change.

  Application Example 2 In the surface acoustic wave device according to the application example, it is preferable that the piezoelectric substrate is made of a piezoelectric single crystal material, and the support member is made of the same material as the piezoelectric substrate.

According to such a configuration, in the surface acoustic wave device, the piezoelectric substrate is formed from a piezoelectric single crystal material, and the support member is formed from the same material as the piezoelectric substrate. For this reason, in the surface acoustic wave device, since the support member and the piezoelectric substrate have substantially the same linear expansion coefficient, no stress is generated between them due to expansion and contraction due to a change in ambient temperature.
Thereby, the surface acoustic wave device can maintain the predetermined resonance frequency with higher accuracy regardless of the ambient temperature change.

  Application Example 3 In the surface acoustic wave device according to the application example described above, it is preferable that the cut angle of the support member is the same as the cut angle of the piezoelectric substrate.

According to such a configuration, in the surface acoustic wave device, the cut angle of the support member is the same as the cut angle of the piezoelectric substrate. Therefore, in the surface acoustic wave device, since the support member and the piezoelectric substrate have the same linear expansion coefficient, no stress is generated between the two due to expansion and contraction due to a change in ambient temperature.
Thereby, the surface acoustic wave device can maintain the predetermined resonance frequency with higher accuracy regardless of the ambient temperature change.

  Application Example 4 In the surface acoustic wave device according to the application example, it is preferable that the piezoelectric single crystal material is quartz.

  According to such a configuration, since the surface acoustic wave device uses a crystal having excellent temperature characteristics as the piezoelectric single crystal material, a stable resonance frequency can be obtained regardless of a change in ambient temperature.

  Application Example 5 In the surface acoustic wave device according to the application example, it is preferable that the fixing portion in the package to which the support member is fixed is a base portion of the package.

  According to such a configuration, in the surface acoustic wave device, the fixed portion in the package to which the support member is fixed is the base portion of the package. For this reason, in the surface acoustic wave device, when the base portion of the package and the support member expand and contract due to changes in ambient temperature, stress is generated between the two due to the difference in the linear expansion coefficient between the base portion of the package and the support member. However, this stress is absorbed by the support member and hardly transmitted to the surface acoustic wave element. Thereby, the surface acoustic wave device can maintain a predetermined resonance frequency with high accuracy regardless of the ambient temperature change.

  Application Example 6 In the surface acoustic wave device according to the application example, the surface acoustic wave device further includes a circuit element electrically connected to the surface acoustic wave element piece in the package, and the support member It is preferable that the fixing portion in the package to which the is fixed is the surface of the circuit element.

  According to such a configuration, in the surface acoustic wave device, the fixing portion in the package to which the support member is fixed is the surface of the circuit element. From this, the surface acoustic wave device generates stress between the circuit element and the support member due to the difference in linear expansion coefficient between the circuit element and the support member when the circuit element and the support member expand and contract due to the ambient temperature change. Is absorbed in the support member and hardly propagates to the surface acoustic wave element. Thereby, the surface acoustic wave device can maintain a predetermined resonance frequency with high accuracy regardless of the ambient temperature change.

Hereinafter, an embodiment of a surface acoustic wave device will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a configuration diagram showing a schematic configuration of a surface acoustic wave resonator as an example of a surface acoustic wave device. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along the line AA in FIG. In the plan view, the lid portion of the component is omitted for easy understanding.

  As shown in FIG. 1, the surface acoustic wave resonator 1 according to the first embodiment includes a surface acoustic wave element piece 10, a spacer 20 as a support member, a package 30, a seam ring 31, a lid 32, and the like. Yes.

The surface acoustic wave element piece 10 is composed of a piezoelectric substrate 16, a comb electrode 11, reflectors 12a and 12b, and the like.
The piezoelectric substrate 16 is formed in a substantially rectangular plate shape by cutting or the like from quartz, which is a piezoelectric single crystal material polished to a predetermined thickness. A pair of interdigital electrodes 11 are formed on one main surface 14 of the piezoelectric substrate 16, and the pair of interdigital electrodes 11 are arranged by alternately engaging electrode fingers. At both ends of the interdigital electrode 11, reflectors 12a and 12b that reflect surface acoustic waves are formed.
Bonding pads 13a and 13b for connecting the interdigital electrode 11 and the reflector 12a to external terminals are formed on one main surface 14 of the piezoelectric substrate 16. The interdigital electrode 11, the reflectors 12a and 12b, and the bonding pads 13a and 13b are formed of a material having excellent conductivity such as aluminum or an aluminum alloy. In the present embodiment, the linear expansion coefficient of the piezoelectric substrate 16 using quartz is about 13.8 × 10 ⁻⁶ / ° C.

  The spacer 20 is formed using a crystal of a piezoelectric single crystal material whose linear expansion coefficient is similar to or the same as the linear expansion coefficient of the piezoelectric substrate 16. The spacer 20 is formed in a substantially rectangular plate shape. In FIG. 1A, the planar size of the spacer 20 is shown smaller than the surface acoustic wave element piece 10, but may be the same as or larger than the surface acoustic wave element piece 10 and is set as appropriate.

  The spacer 20 is fixed to a part of the other main surface 15 of the piezoelectric substrate 16 in the surface acoustic wave element piece 10 and is fixed to a bottom surface 33 as a base portion of the package 30 which is a fixing portion in the package 30 described later. Yes. The other main surface 15 of the piezoelectric substrate 16 and the spacer 20 are fixed with an adhesive 50, and the spacer 20 and the bottom surface 33 of the package 30 are fixed with an adhesive 40. As the adhesives 40 and 50, elastic adhesives such as silicone adhesives and butadiene rubber adhesives are used. These adhesives have an effect of absorbing a part of stress generated in the bonded portion due to a change in ambient temperature due to elasticity. The range of application of the adhesive 50 is preferably a range that does not overlap with the interdigital electrode 11 of the surface acoustic wave element piece 10 in a plan view, but is not limited to this and covers the range that overlaps the interdigital electrode 11. Also good.

  The cut angle of the spacer 20 is preferably the same as the cut angle of the piezoelectric substrate 16 of the surface acoustic wave element piece 10. According to this, the linear expansion coefficients of the spacer 20 and the piezoelectric substrate 16 are the same.

The package 30 is formed by laminating and firing ceramic green sheets. Internal terminals 34 a and 34 b are formed in the package 30. The internal terminals 34 a and 34 b are connected to the bonding pads 13 a and 13 b of the surface acoustic wave element piece 10 by bonding a metal wire 60. The internal terminals 34 a and 34 b are connected to external terminals (not shown) formed outside the package 30. The linear expansion coefficient of the package 30 using the ceramic green sheet is about 7 × 10 ⁻⁶ / ° C.

  The lid 32 is formed of a metal such as Kovar, and is seam welded to a seam ring 31 formed of a metal such as Kovar. The package 30 is joined to the lid 32 via a seam ring 31 and hermetically sealed. Note that the inside of the package 30 is sealed with a vacuum or an inert gas such as nitrogen, helium, or argon.

  The surface acoustic wave resonator 1 has an interdigital shape of the surface acoustic wave element piece 10 from the outside via the internal terminals 34 a and 34 b of the package 30, the metal wires 60 and 60, and the bonding pads 13 a and 13 b of the surface acoustic wave element piece 10. When an electric signal is applied to the electrode 11, a surface acoustic wave is excited between the electrode fingers of the interdigital electrode 11 by the piezoelectric effect of the surface acoustic wave element 10. Specifically, this surface acoustic wave is excited in a region where the interdigital electrode 11 is disposed on the surface acoustic wave element piece 10. A high-frequency signal corresponding to the resonance frequency of the excited surface acoustic wave is output to the outside through the bonding pads 13a and 13b, the metal wires 60 and 60, and the internal terminals 34a and 34b. A surface acoustic wave excitation region is formed between the reflector 12a and the reflector 12b.

Here, when the temperature around the surface acoustic wave resonator 1 changes, each component expands and contracts in accordance with the linear expansion coefficient of the material forming each component as the temperature changes. At this time, the linear expansion coefficient (about 7 × 10 ⁻⁶ / ° C.) of the package 30 and the linear expansion coefficient (about 13.8 × 10 ⁻⁶ / ° C.) of the spacer 20 fixed to the bottom surface 33 of the package 30 are obtained. Because of the difference, stress is generated between the two due to the difference in expansion and contraction. This stress is absorbed by the spacer 20.

  On the other hand, the piezoelectric substrate 16 of the surface acoustic wave element piece 10 fixed to the spacer 20 has the same material and the same cut angle as the spacer 20. For this reason, even when the ambient temperature changes, there is almost no difference in expansion and contraction between the two, and stress is hardly generated between the two. Therefore, there is almost no deformation of the piezoelectric substrate 16 of the surface acoustic wave element piece 10 due to this stress.

For these reasons, the surface acoustic wave element piece 10 is unlikely to change in frequency due to expansion and contraction of the package 30 and the spacer 20 due to changes in ambient temperature.
As a result, the surface acoustic wave resonator 1 according to the first embodiment can accurately maintain a predetermined resonance frequency regardless of a change in ambient temperature.
In addition, since the surface acoustic wave resonator 1 uses quartz having excellent temperature characteristics as the piezoelectric single crystal material for the piezoelectric substrate 16, a stable resonance frequency can be obtained regardless of ambient temperature changes.

  In the first embodiment, the base portion in the package 30 is the bottom surface 33. However, the present invention is not limited to this. For example, a portion where the spacer 20 can be fixed, such as a stepped portion protruding from the bottom surface 33 or a side surface portion. Any part in the package 30 is acceptable.

(Second Embodiment)
FIG. 2 is a configuration diagram showing a schematic configuration of a surface acoustic wave oscillator as an example of a surface acoustic wave device. 2A is a plan view, and FIG. 2B is a cross-sectional view taken along the line BB in FIG. 2A. In the plan view, the lid portion of the component is omitted for easy understanding. Also, the same reference numerals are given to common parts with the first embodiment.

  As shown in FIG. 2, the surface acoustic wave oscillator 101 according to the second embodiment includes a surface acoustic wave element piece 10, a spacer 20 as a support member, a package 130, a seam ring 131, a lid 132, and an IC ( Integrated Circuit) 70 and the like.

The surface acoustic wave element piece 10 is composed of a piezoelectric substrate 16, a comb electrode 11, reflectors 12a and 12b, and the like.
The piezoelectric substrate 16 is formed in a substantially rectangular plate shape by cutting or the like from quartz, which is a piezoelectric single crystal material polished to a predetermined thickness. A pair of interdigital electrodes 11 are formed on one main surface 14 of the piezoelectric substrate 16, and the pair of interdigital electrodes 11 are arranged by alternately engaging electrode fingers. At both ends of the interdigital electrode 11, reflectors 12a and 12b that reflect surface acoustic waves are formed.
Bonding pads 13a and 13b for connecting the interdigital electrode 11 and the reflector 12a to external terminals are formed on one main surface 14 of the piezoelectric substrate 16. The interdigital electrode 11, the reflectors 12a and 12b, and the bonding pads 13a and 13b are formed of a material having excellent conductivity such as aluminum or an aluminum alloy. In the present embodiment, the linear expansion coefficient of the piezoelectric substrate 16 using quartz is about 13.8 × 10 ⁻⁶ / ° C.

  The spacer 20 is formed using a crystal of a piezoelectric single crystal material whose linear expansion coefficient is similar to or the same as the linear expansion coefficient of the piezoelectric substrate 16. The spacer 20 is formed in a substantially rectangular plate shape. In FIG. 2A, the planar size of the spacer 20 is shown smaller than the surface acoustic wave element piece 10, but may be the same as or larger than the surface acoustic wave element piece 10, and is set as appropriate.

  The spacer 20 is fixed to a part of the other main surface 15 of the piezoelectric substrate 16 in the surface acoustic wave element piece 10 and is fixed to a bottom surface 133 as a base portion of the package 130 which is a fixing portion in the package 130 described later. Yes. The other main surface 15 of the piezoelectric substrate 16 and the spacer 20 are fixed with an adhesive 50, and the spacer 20 and the bottom surface 133 of the package 130 are fixed with an adhesive 40. As the adhesives 40 and 50, elastic adhesives such as silicone adhesives and butadiene rubber adhesives are used. These adhesives have an effect of absorbing a part of stress generated in the bonded portion due to a change in ambient temperature due to elasticity. The range of application of the adhesive 50 is preferably a range that does not overlap with the interdigital electrode 11 of the surface acoustic wave element piece 10 in a plan view, but is not limited to this and covers the range that overlaps the interdigital electrode 11. Also good.

  The cut angle of the spacer 20 is preferably the same as the cut angle of the piezoelectric substrate 16 of the surface acoustic wave element piece 10. According to this, the linear expansion coefficients of the spacer 20 and the piezoelectric substrate 16 are the same.

The package 130 is formed by laminating and firing ceramic green sheets. Internal terminals 134a to 134d are formed on the package 130, and the internal terminals 134a and 134b are connected to bonding pads 13a and 13b of the surface acoustic wave element piece 10 and an IC 70 to be described later by bonding the metal wire 60, and the internal terminals 134c. , 134d are connected to the IC 70. The internal terminals 134c and 134d are connected to external terminals (not shown) formed outside the package 130. Note that the linear expansion coefficient of the package 130 using the ceramic green sheet is about 7 × 10 ⁻⁶ / ° C.

  The lid 132 is formed of a metal such as Kovar, and is seam welded to a seam ring 131 that is also formed of a metal such as Kovar. The package 130 is joined to the lid 132 via a seam ring 131 and hermetically sealed. Note that the inside of the package 130 is sealed with a vacuum or an inert gas such as nitrogen, helium, or argon.

  The IC 70 is made of a silicon substrate or the like, and is formed with an oscillation circuit that excites the surface acoustic wave element 10. The IC 70 is connected to the internal terminals 134a to 134d of the package 130 as described above. With this connection, the IC 70 is electrically connected to the surface acoustic wave element piece 10. The IC 70 is fixed to the bottom surface 133 of the package 130 with an epoxy-based adhesive 80.

  When the ground potential and the power supply voltage are applied from the outside via the internal terminals 134 c and 134 d of the package 130, the IC 70 receives the internal terminals 134 a and 134 b of the package 130 and the bonding pads 13 a of the surface acoustic wave element piece 10 from the oscillation circuit. An electric signal is applied to the interdigital electrode 11 of the surface acoustic wave element piece 10 through 13b. Thereby, the surface acoustic wave is excited in the region where the interdigital electrode 11 is disposed by the piezoelectric effect of the surface acoustic wave element piece 10. An oscillation signal corresponding to the resonance frequency of the excited surface acoustic wave is output from the IC 70 to the outside. A surface acoustic wave excitation region is formed between the reflector 12a and the reflector 12b.

Here, when the temperature around the surface acoustic wave oscillator 101 changes, each component expands and contracts according to the linear expansion coefficient of the material forming each component as the temperature changes. At this time, the linear expansion coefficient (about 7 × 10 ⁻⁶ / ° C.) of the package 130 and the linear expansion coefficient (about 13.8 × 10 ⁻⁶ / ° C.) of the spacer 20 fixed to the bottom surface 133 of the package 130 are obtained. Because of the difference, stress is generated between the two due to the difference in expansion and contraction. This stress is absorbed by the spacer 20.

  On the other hand, the piezoelectric substrate 16 of the surface acoustic wave element piece 10 to which the spacer 20 is fixed has the same material and the same cut angle as the spacer 20. For this reason, even when the ambient temperature changes, there is almost no difference in expansion and contraction between the two, and stress is hardly generated between the two. Therefore, there is almost no deformation of the piezoelectric substrate 16 of the surface acoustic wave element piece 10 due to this stress.

For these reasons, the surface acoustic wave element piece 10 is unlikely to change in frequency due to expansion and contraction of the package 130 and the spacer 20 due to changes in ambient temperature.
As a result, the surface acoustic wave oscillator 101 of the second embodiment can maintain a predetermined resonance frequency with high accuracy regardless of ambient temperature changes.
In addition, since the surface acoustic wave oscillator 101 uses quartz having excellent temperature characteristics as the piezoelectric single crystal material for the piezoelectric substrate 16, it is possible to obtain a stable resonance frequency regardless of ambient temperature changes.

  In the second embodiment, the base portion in the package 130 is the bottom surface 133. However, the present invention is not limited to this. For example, a portion where the spacer 20 can be fixed such as a stepped portion and a side surface portion protruding from the bottom surface 133. Any portion in the package 130 may be used.

Here, modifications of the surface acoustic wave oscillator 101 according to the second embodiment will be described below. Note that the modification is not limited to this, and various modes are possible.
(Modification 1)
FIG. 3 is a configuration diagram showing a schematic configuration of a surface acoustic wave oscillator as an example of a surface acoustic wave device. 3A is a plan view, and FIG. 3B is a cross-sectional view taken along the line CC in FIG. 3A. In the plan view, the lid portion of the component is omitted for easy understanding. Also, the same reference numerals are given to the common parts with the second embodiment.

  As shown in FIG. 3, the surface acoustic wave oscillator 201 which is Modification 1 of the second embodiment includes a surface acoustic wave element piece 10, a spacer 120 as a support member, a package 230, a seam ring 231, a lid 232, a circuit. It is composed of an IC 170 as an element.

  The difference between the surface acoustic wave oscillator 201 and the surface acoustic wave oscillator 101 of the second embodiment is the position of the IC. In the surface acoustic wave oscillator 201, the spacer 120 is made thicker than the IC 170 so that the gap between the surface acoustic wave element 10 and the bottom surface 233 as the base portion of the package 230 is larger than the thickness of the IC 170. Is formed.

As a result, the IC 170 can be disposed below the surface acoustic wave element piece 10 at a position partially overlapping with the surface acoustic wave element piece 10 in plan view of the bottom surface 233 of the package 230. The IC 170 is fixed to the bottom surface 233 of the package 230 by the adhesive 80 and is connected to the internal terminals 234 a to 234 d of the package 230 by bonding of the metal wire 60 in a region that does not overlap the surface acoustic wave element piece 10.
Since the other configuration of the surface acoustic wave oscillator 201 is the same as that of the surface acoustic wave oscillator 101 of the second embodiment, the description thereof is omitted.

With such a configuration, the surface acoustic wave oscillator 201 has the following effects in addition to the same effects as those of the second embodiment.
As described above, in the surface acoustic wave oscillator 201, the IC 170 is disposed below the surface acoustic wave element piece 10 and at a position partially overlapping the surface acoustic wave element piece 10 in a plan view of the bottom surface 233 of the package 230. ing. As a result, the surface acoustic wave oscillator 201 has a space in the package 230 as compared with an arrangement in which the IC 70 and the surface acoustic wave element piece 10 do not overlap in a plan view, like the surface acoustic wave oscillator 101 of the second embodiment. Is efficiently used, the planar size of the package 230 can be reduced. Therefore, the surface acoustic wave oscillator 201 can be reduced in planar size.

(Modification 2)
FIG. 4 is a configuration diagram showing a schematic configuration of a surface acoustic wave oscillator as an example of a surface acoustic wave device. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line DD in FIG. 4A. In the plan view, the lid portion of the component is omitted for easy understanding. Also, the same reference numerals are given to the common parts with the second embodiment.

  As shown in FIG. 4, the surface acoustic wave oscillator 301 which is the second modification of the second embodiment includes a surface acoustic wave element piece 10, a spacer 220 as a support member, a package 330, a seam ring 331, a lid 332, a circuit. It is composed of an IC 270 as an element.

  The difference between the surface acoustic wave oscillator 301 and the surface acoustic wave oscillator 101 of the second embodiment is the place where the IC is mounted. In the surface acoustic wave oscillator 301, the planar size of the spacer 220 is formed such that the surface acoustic wave element piece 10 and the IC 270 can be mounted, as shown in FIG. Thus, in the surface acoustic wave oscillator 301, the IC 270 is mounted on the spacer 220 along with the surface acoustic wave element piece 10. The spacer 220 is fixed to a bottom surface 333 as a base portion of the package 330 with an adhesive 40, and the IC 270 is fixed to the spacer 220 with an adhesive 80. The IC 270 is connected to the internal terminals 334 a and 334 b of the package 330 and the bonding pads 13 a and 13 b of the surface acoustic wave element piece 10 by bonding of the metal wire 60.

With this configuration, the surface acoustic wave oscillator 301 has the following effects in addition to the same effects as those of the second embodiment.
In the surface acoustic wave oscillator 301, the IC 270 is mounted on the spacer 220 along with the surface acoustic wave element piece 10 as described above. As a result, the surface acoustic wave oscillator 301 can reduce the level difference between the IC 270 and the surface acoustic wave element piece 10 as shown in FIG. Therefore, the surface acoustic wave oscillator 301 can easily perform the bonding operation when the IC 270 and the bonding pads 13a and 13b of the surface acoustic wave element piece 10 are connected by bonding the metal wire 60.

(Third embodiment)
FIG. 5 is a configuration diagram showing a schematic configuration of a surface acoustic wave oscillator as an example of a surface acoustic wave device. 5A is a plan view, and FIG. 5B is a cross-sectional view taken along line EE in FIG. 5A. In the plan view, the lid portion of the component is omitted for easy understanding. Also, the same reference numerals are given to the common parts with the second embodiment.

  As shown in FIG. 5, the surface acoustic wave oscillator 401 according to the third embodiment is composed of a surface acoustic wave element piece 10, a spacer 20, a package 430, a seam ring 431, a lid 432, an IC 370 as a circuit element, and the like. Yes.

  The difference between the surface acoustic wave oscillator 401 of the third embodiment and the surface acoustic wave oscillator 101 of the second embodiment is that the spacer 20 fixed to a part of the other main surface 15 of the piezoelectric substrate 16 is a package 430. It is fixed to the surface 371 of the IC 370 as an internal fixed portion. Hereinafter, a description will be given centering on differences from the second embodiment.

The IC 370 is made of a silicon substrate or the like, is formed with an oscillation circuit for exciting the surface acoustic wave element piece 10, and is fixed to the bottom surface 433 of the package 430 with an adhesive 80. The IC 370 is connected to the bonding pads 13 a and 13 b of the surface acoustic wave element piece 10 and the internal terminals 434 a and 434 b of the package 430 by bonding metal wires 60. With this connection, the IC 370 is electrically connected to the surface acoustic wave element piece 10. The internal terminals 434a and 434b are connected to external terminals (not shown) formed outside the package 430. The linear expansion coefficient of IC 370 is about 2.5 × 10 ⁻⁶ / ° C.
As described above, the spacer 20 is fixed to the surface 371 of the IC 370 by the adhesive 40.

  Thus, by arranging the spacer 20 fixed to a part of the other main surface 15 of the piezoelectric substrate 16 and the IC 370 in an overlapping manner, the surface acoustic wave oscillator 401 uses the space in the package 430 efficiently. As a result, the planar size can be reduced.

Here, when the temperature around the surface acoustic wave oscillator 401 changes, each component expands and contracts in accordance with the linear expansion coefficient of the material forming each component as the temperature changes. At this time, the linear expansion coefficient (about 2.5 × 10 ⁻⁶ / ° C.) of the IC 370 and the linear expansion coefficient (about 13.8 × 10 ⁻⁶ / ° C.) of the spacer 20 fixed to the surface 371 of the IC 370 are obtained. Because of the difference, stress is generated between the two due to the difference in expansion and contraction. This stress is absorbed by the spacer 20.

  On the other hand, the piezoelectric substrate 16 of the surface acoustic wave element piece 10 to which the spacer 20 is fixed has the same material and the same cut angle as the spacer 20. For this reason, even when the ambient temperature changes, there is almost no difference in expansion and contraction between the two, and stress is hardly generated between the two. Therefore, there is almost no deformation of the piezoelectric substrate 16 of the surface acoustic wave element piece 10 due to this stress.

For these reasons, the surface acoustic wave element piece 10 is less likely to change in frequency due to expansion and contraction of the IC 370 and the spacer 20 due to changes in ambient temperature.
As a result, the surface acoustic wave oscillator 401 according to the third embodiment can accurately maintain a predetermined resonance frequency regardless of a change in ambient temperature.
Further, since the surface acoustic wave oscillator 401 uses quartz having excellent temperature characteristics as the piezoelectric single crystal material for the piezoelectric substrate 16, it can obtain a stable resonance frequency regardless of ambient temperature changes.

In each of the embodiments described above, the material of the piezoelectric substrate 16 of the surface acoustic wave element piece 10 is quartz. However, the material is not limited to quartz. For example, a piezoelectric material such as lithium tantalate or lithium niobate may be used. At this time, the spacers 20, 120, and 220 may be made of a material whose linear expansion coefficient is similar to or the same as that of the piezoelectric substrate 16.
In each of the above embodiments, the piezoelectric substrate 16 and the spacers 20, 120, and 220 are fixed. In the first and second embodiments, the spacers 20, 120, and 220 and the packages 30, 130, 230, and 330 are fixed. The fixing is performed with the adhesives 40 and 50, but may be performed by soldering.

1 is a configuration diagram showing a schematic configuration of a surface acoustic wave resonator according to a first embodiment. The block diagram which shows schematic structure of the surface acoustic wave oscillator of 2nd Embodiment. The block diagram which shows schematic structure of the surface acoustic wave oscillator of the modification 1 of 2nd Embodiment. The block diagram which shows schematic structure of the surface acoustic wave oscillator of the modification 2 of 2nd Embodiment. The block diagram which shows schematic structure of the surface acoustic wave oscillator of 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave resonator as surface acoustic wave device, 10 ... Surface acoustic wave element piece, 11 ... Interdigital electrode, 12a, 12b ... Reflector, 14 ... One main surface of piezoelectric substrate, 15 ... Piezoelectric substrate The other main surface, 16 ... piezoelectric substrate, 20, 120, 220 ... spacer as a support member, 30, 130, 230, 330, 430 ... package, 33, 133, 233, 333 ... bottom surface as a base part of the package, 70, 170, 270, 370... IC as a circuit element, 371... Surface of IC 370 as a fixed portion of the package, 101, 201, 301, 401... Surface acoustic wave oscillator as surface acoustic wave device.

Claims (6)

A surface acoustic wave element in which interdigital electrodes are formed on one main surface of the piezoelectric substrate;
A support member fixed to a part of the other main surface of the piezoelectric substrate in the surface acoustic wave element piece;
A package in which the surface acoustic wave element piece and the support member are housed,
The surface acoustic wave device according to claim 1, wherein a linear expansion coefficient of the support member is approximately or the same as a linear expansion coefficient of the piezoelectric substrate, and the support member is fixed to a fixing portion in the package.   The surface acoustic wave device according to claim 1, wherein the piezoelectric substrate is made of a piezoelectric single crystal material, and the support member is made of the same material as the piezoelectric substrate.   The surface acoustic wave device according to claim 2, wherein a cut angle of the support member is the same as a cut angle of the piezoelectric substrate.   The surface acoustic wave device according to claim 2, wherein the piezoelectric single crystal material is quartz.   The surface acoustic wave device according to claim 1, wherein the fixing portion in the package to which the support member is fixed is a base portion of the package. The surface acoustic wave device further includes a circuit element electrically connected to the surface acoustic wave element piece in the package,
The surface acoustic wave device according to any one of claims 1 to 4, wherein a fixing portion in the package to which the support member is fixed is a surface of the circuit element.

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