JP7368304B2 - piezoelectric device - Google Patents

Description

The present invention relates to a piezoelectric device that has a support structure that is easy to manufacture and vibrates in a thickness-shear vibration mode.

In various electronic devices such as mobile phones and personal computers, piezoelectric devices such as crystal resonators and crystal oscillators are often used for frequency selection and control.

As one type of such piezoelectric devices, there are known those using an AT-cut crystal piece and those using a so-called twice-rotated crystal piece, typified by an SC-cut crystal piece. A crystal resonator is known in which a crystal piece is fixed to a container by supporting one end of the crystal piece, that is, cantilevered, and the other end of the crystal piece is received by a pillow portion (for example, Patent Document 1).
FIG. 4 is an explanatory diagram of this type of crystal resonator 10. In particular, (A) is a top view, (B) is a side view of the crystal resonator 10, (A) is a side view looking through the container from direction P in the figure, and (C) is (A). FIG. 2 is a cross-sectional view of the crystal resonator 10 along the line QQ of FIG. However, FIG. 4A shows a state in which the lid member 17 is removed.

In this crystal resonator 10, a crystal piece 11 has an excitation electrode 11a and an extraction electrode 11b on its front and back sides. This crystal piece 11 has a rectangular planar shape, and is electrically and mechanically connected and fixed to a connection pad 13a of the container 13 by a conductive adhesive 15 at one end thereof, that is, on the extraction electrode 11b side. Furthermore, a pillow 13b is provided on the bottom surface of the container 13 at a position corresponding to the tip of the crystal piece 11, and the crystal piece 11 is mounted so as to span between the connection pad 13a and the pillow 13b. Then, the container 13 is hermetically sealed with a lid member 17. Furthermore, an external connection terminal 13c is provided on the outer bottom surface of the container 13. The external connection terminal 13c and the connection pad 13a are connected by via wiring (not shown).
The above support structure using a cantilever support and a pillow part can be mounted on the container 13 without bringing the crystal piece 11 into contact with the bottom surface of the container 13.

Japanese Patent Application Publication No. 2012-90083

By the way, when using an AT-cut crystal piece, one end of the crystal piece 11 along the X-axis direction of the crystal axis is held with a conductive adhesive 15, and the other end in the X-axis direction is left free (unfixed). However, it is easy to improve the characteristics of the piezoelectric device. However, in the case of the structure using the pillow 13b, in order to hold the crystal piece 11 in the container 13 in a well-balanced manner, the pillow 13b is provided near the center of the edge of the crystal piece 11 on the tip side. On the other hand, the thickness shear vibration that occurs in the crystal piece 11 propagates with stronger energy near the center of the side on the tip side of the crystal piece 11 than at the corner. If the pillow 13b is present, the piezoelectric device may be influenced by the pillow 13b, and the characteristics of the piezoelectric device may be impaired.

In order to avoid this, for example, as shown in FIG. It is also done to ensure good posture. However, this task is also difficult, and will become even more difficult as piezoelectric devices become smaller.
This application was made in view of these points, and it is an object of the present invention to provide a piezoelectric device having a cantilever support structure, which does not easily impair its characteristics and is easy to manufacture.

In order to achieve this objective, the inventor of this application has developed a piezoelectric vibrating piece that has a rectangular planar shape and vibrates through thickness sliding, and that one of the four corners of the piezoelectric vibrating piece is actively attached to a container. We focused on a structure that brings the objects into contact with or close to each other.
That is, according to the present invention, there is provided a piezoelectric vibrating piece having a rectangular planar shape, a container in which the piezoelectric vibrating piece is mounted, and a piezoelectric vibrating piece mounted in the container near both ends of a first side of the piezoelectric vibrating piece. A piezoelectric device comprising a first fixed part and a second fixed part,
The height of the first fixing part is higher than the height of the second fixing part,
The piezoelectric vibrating piece is mounted diagonally with respect to the container by utilizing a height difference between the first fixing part and the second fixing part, and
A corner portion of the piezoelectric vibrating piece located diagonally to the first fixing portion is mounted in contact with or in close proximity to the container.

In carrying out the present invention, the first fixing part and the second fixing part are composed of a first connection pad and a second connection pad having different heights as described above, and the fixation is performed using a conductive adhesive. It is preferable to do so.

In carrying out the present invention, the corner portion that contacts or is close to the container may be fixed to the container with an elastic adhesive, such as a silicone-based conductive adhesive. .

According to the piezoelectric device of the present invention, by simply placing the piezoelectric vibrating piece so that one side portion thereof is located in the first fixing part and the second fixing part, Due to the difference in height, the piezoelectric vibrating piece can be mounted in a diagonal positional relationship with respect to the container, and one of the predetermined corners is in contact with or in close proximity to the container. Further, although the corner portion of the tip of the piezoelectric vibrating piece touches or approaches the container, the center portion of the tip of the crystal piece does not come into contact with the container, so that the loss of energy due to thickness shear vibration can be reduced.
Therefore, it is possible to realize a piezoelectric device having a cantilever support structure, which does not easily deteriorate its characteristics and is easy to manufacture.

(A), (B), and (C) are diagrams for explaining the piezoelectric device 20 of the first embodiment. FIG. 3 is an explanatory diagram of a piezoelectric device 30 according to a second embodiment. FIG. 4 is an explanatory diagram of a piezoelectric device 40 according to a third embodiment. (A), (B), and (C) are diagrams illustrating the prior art and problems. FIG. 4 is an explanatory diagram following FIG. 3 illustrating the prior art and problems.

Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings used in the explanation are merely shown schematically to the extent that these inventions can be understood. Moreover, in each figure used for explanation, the same number is attached|subjected and shown about the same component, and the explanation may be abbreviate|omitted. Furthermore, the shapes, dimensions, materials, etc. described in the following embodiments are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited only to the following embodiments.

1. First Embodiment FIGS. 1A, 1B, and 1C are diagrams illustrating a piezoelectric device 20 of a first embodiment. In particular, (A) is a plan view showing the piezoelectric device 20, (B) is a side view of the piezoelectric device 20 seen through the container 13 from the P direction in (A), and (C) is ( A) A cross-sectional view of the piezoelectric device 20 taken along the line QQ in the figure. However, FIG. 1A shows a state in which the lid member 17 is removed.

The piezoelectric device 20 of the first embodiment includes a piezoelectric vibrating piece 11 , a container 13 that encloses the piezoelectric vibrating piece 11 , and a lid member 17 that seals the container 13 .
The piezoelectric vibrating piece 11 is, for example, an AT-cut crystal resonator having a rectangular planar shape. This piezoelectric vibrating piece 11 includes excitation electrodes 11a on each of its front and back surfaces, and an extraction electrode 11b drawn out from these excitation electrodes 11a to one end of the crystal piece.
The piezoelectric vibrating piece 11 may be manufactured by machining, or may be manufactured from a large wafer by photolithography and wet etching.

In this example, the container 13 has a recess that encloses the piezoelectric vibrating piece 11 . This container can be constructed, for example, from a ceramic container. This container 13 includes a first connection pad 21a on one side of the bottom plate near both ends of one side of the piezoelectric vibrating piece 11, and a second connection pad 21b on the other side. In this invention, the heights of the first connection pad 21a and the second connection pad 21b are different, for example, the height of the first connection pad 21a is made higher than the height of the second connection pad 21b. The difference in height between the two is determined by considering the degree to which the piezoelectric vibrating piece 11 is tilted, the storage space within the container 13, etc., and is, for example, 10 to 50 μm, preferably 20 to 40 μm, more preferably 25 to 40 μm. The thickness is preferably 40 μm.
Each of the first connection pad 21a and the second connection pad 21b can be realized with any suitable structure such as a metal pad, for example, a metal pad obtained by sintering a high melting point metal paste, such as a tungsten paste. realizable.

The piezoelectric vibrating piece 11 is mounted obliquely with respect to the bottom surface of the container 13 by utilizing the difference in height between the first connection pad 21a and the second connection pad 21b, and the piezoelectric vibrating piece 11 is The corner portion 11c located diagonally to the first connection pad is mounted in contact with or close to the bottom surface of the container 13. Note that the portions of the piezoelectric vibrating piece 11 that are connected to the container, that is, the both end portions on one side of the piezoelectric vibrating piece 11 are electrically connected to the first connection pad 21a and the second connection pad 21b by the conductive adhesive 15. and mechanically connected.

According to the piezoelectric device 20 of the first embodiment, the piezoelectric vibrating piece 11 is placed so that the portion on one side is also located at the first connection pad 21a and the second connection pad 21b. 11 is in a diagonal positional relationship with respect to the container 13 due to the difference in height between the first connection pad 21a and the second connection pad 21b, and the corner portion 11c is in contact with or close to the container 13. , can be implemented. Further, although the corner portion 11c of the tip of the piezoelectric vibrating piece 11 contacts or approaches the container, the center portion of the tip of the crystal piece does not come into contact with the container, so that the loss of energy due to thickness shear vibration can be reduced.
Therefore, it is possible to realize a piezoelectric device having a cantilever support structure, which does not easily deteriorate its characteristics and is easy to manufacture.

2. Second Embodiment FIG. 2 is a diagram illustrating a piezoelectric device 30 of a second embodiment, and is a perspective view from the side similar to FIG. 1(B).
The difference between the piezoelectric device 20 of the second embodiment and the first embodiment is that a predetermined corner 11c of the piezoelectric vibrating piece 11 is attached to the bottom surface of the container 13 with an elastic adhesive 31. This is something that has been fixed.
As the elastic adhesive 31, for example, a silicone-based conductive adhesive can be used. Of course, other adhesives, such as a non-conductive silicone adhesive that does not contain a conductive filler, may also be used, but the silicone-based conductive adhesive is suitable for connecting the piezoelectric vibrating piece 11, the first connection pad 21a, and the second connection pad 21a. Since it is used for adhesion to the connection pad 21b, it is possible to standardize members used in the manufacturing process, which is preferable.

In the case of the piezoelectric device of the second embodiment, since the corner portion 11c of the piezoelectric vibrating piece 11 is fixed to the container 13, in addition to the effect of the piezoelectric device 20 of the first embodiment, the piezoelectric vibrating piece 11 itself fluctuations can be reduced.

3. Third Embodiment FIG. 3 is a diagram illustrating a piezoelectric device 40 according to a third embodiment, and is a perspective view from the side similar to FIG. 1(B).
In the piezoelectric device 20 of the first embodiment, the container 13 had a deep part that contained the piezoelectric vibrating piece 11, and the lid member 17 had a flat plate shape. In the case of the piezoelectric device 40 of the third embodiment, the substrate 41 is a flat substrate having a first connection pad 21a and a second connection pad 21b, and a space containing the piezoelectric vibrator 11. This is an example in which a container is configured with a cap-shaped lid member 43.
In recent years, piezoelectric devices have been manufactured at the wafer level using large substrates. The present invention is also applicable to such cases.

4. Other Embodiments In the above example, a crystal resonator was illustrated as a piezoelectric device, but the present invention can also be applied to a crystal piece oscillator. Furthermore, although an AT-cut crystal piece has been described as an example of the piezoelectric vibrating piece, other cut crystal pieces, such as a twice-rotated crystal piece such as an SC-cut vibrator, may also be used. Furthermore, it can also be applied to piezoelectric vibrators and piezoelectric oscillators using piezoelectric materials other than crystal.

11: Piezoelectric vibrating piece 11a: Excitation electrode 11b: Extraction electrode 11c: Predetermined corner of piezoelectric vibrating piece 13: Container 13c: External connection terminal 15: Conductive adhesive 17: Lid member 20: First embodiment Piezoelectric device 21a: First fixing part (first connection pad) 21b: Second fixing part (second connection pad)
30: Piezoelectric device of the second embodiment, 31: Elastic adhesive 40: Piezoelectric device of the third embodiment 41: Flat substrate 43: Cap-shaped lid member

Claims (3)

A piezoelectric vibrating piece having a rectangular planar shape, a container in which the piezoelectric vibrating piece is mounted, and a first fixing part fixing the piezoelectric vibrating piece to the container near both ends of a first side of the piezoelectric vibrating piece. and a second fixing part, a piezoelectric device comprising:
The height of the first fixing part is higher than the height of the second fixing part,
The piezoelectric vibrating piece is mounted diagonally with respect to the container by utilizing a height difference between the first fixing part and the second fixing part, and
A piezoelectric device, characterized in that a corner portion of the piezoelectric vibrating piece located diagonally to the first fixing portion is mounted in contact with or in close proximity to the container. The first fixing part is a first connection pad made of metal, the second fixation part is a second connection pad made of metal,
The piezoelectric device according to claim 1, wherein the piezoelectric vibrating piece is fixed to the first connection pad and the second connection pad with a conductive adhesive .




3. The piezoelectric device according to claim 1, wherein the corner portion that contacts or is close to the container is fixed to the container with an elastic adhesive.

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