JP5198135B2 - Piezoelectric vibrator and electronic component - Google Patents

Description

  The present invention relates to a piezoelectric vibrator having high frequency stability and an electronic component using the same.

A crystal resonator, which is a piezoelectric vibrator, forms electrodes by depositing metal such as gold, silver, or aluminum on both the front and back sides of a plate-shaped crystal piece, and adjusts the weight of the electrode to adjust the natural frequency. However, in this crystal resonator, an electrode is directly formed on a crystal piece which is a vibration part. For this reason, since the stress generated by the electrode is directly transmitted to the crystal piece, the stress of the electrode changes with time due to the elastic fatigue of the electrode, and as a result, the frequency stability is deteriorated. In addition, secondary vibration is likely to occur, which is one of the factors that cause a bad S / N ratio of the oscillation frequency.

  On the other hand, users demand crystal oscillators with even higher frequency stability, and manufacturers are struggling to deal with them. As a crystal resonator capable of obtaining high frequency stability, a crystal resonator called a BVA resonator is known (Non-Patent Document 1). In this crystal resonator, as shown in FIG. 11A, a crystal piece 10 for main vibration part is sandwiched between crystal pieces 11 and 12 for electrode parts, and electrodes are placed on the crystal pieces 11 and 12 for electrode parts via gaps 13 and 14, respectively. 15 and 16 are provided. Further, as shown in FIG. 11 (b), the main vibrating part crystal piece 10 has a main vibrating part 17 formed in a convex lens shape to increase the frequency stability, and an outer peripheral edge of the main vibrating part 17 at a predetermined position. The support portions 18a, 18b, 18c, and 18d are supported at intervals, and the frame portion 19 is connected to the support portions 18a, 18b, 18c, and 18d. By adopting such a configuration, since the stress generated by the vibration of the electrodes 15 and 16 is not directly transmitted to the main vibration portion 17, the deterioration of the frequency stability due to the stress change of the electrode is prevented, and the performance is extremely excellent. Yes. As its application, it is used in combination with an atomic oscillator having extremely high frequency stability utilizing electron resonance, or used alone for an application close to an atomic oscillator.

  The above-described main vibration crystal piece 10 is mechanically cut out from one crystal piece, and the main vibration part 17 and the support part 18 having a convex lens shape are processed and formed. Similarly, the electrode crystal pieces 11 and 12 are mechanically cut out from one crystal piece, and the main vibration portion 17 and the electrode crystal pieces 11 and 12 are formed on one surface of the electrode crystal pieces 11 and 12. A recess for forming the gaps 13 and 14 is formed between them. However, such processing has a long processing time and special skills and is very expensive. In recent years, the BVA vibrator has been required to be miniaturized, and it is extremely difficult to process and form the convex lens-shaped main vibration portion 17 and the support portion 18 in order to reduce the size of the BVA vibrator.

A COST-EFFECTIVE TIME AND FREQUENCY REFERENCE (Vincent Candelier, Gerard Marotel, Didier Thorax, and Claude Trialoup)

  The present invention has been made in view of such circumstances, and an object thereof is to provide a novel crystal resonator that can obtain high frequency stability and is suitable for downsizing. . Another object is to provide an electronic component using the crystal resonator.

A piezoelectric vibrator according to the present invention includes a diaphragm made of a strip-like piezoelectric piece,
A first electrode plate and a second electrode which are provided on both sides of the diaphragm so as to face and separate from the diaphragm, and electrodes for applying a voltage to the diaphragm are formed on the diaphragm side. Electrode plate,
A support portion for supporting the diaphragm, the first electrode plate and the second electrode plate in a cantilever manner,
A separation portion for elastically separating the vibration region and the support region is formed between the vibration region of the diaphragm and the support region supported by the support portion .

More specific embodiments of the present invention will be listed.
The support portion includes a separation intermediate member that is interposed between the vibration plate and the first electrode plate and the second electrode plate, respectively, and regulates a separation distance between the vibration plate and the electrode plate. The separation intermediate member is a rod-like body extending in the width direction of the diaphragm.

  The support portion is disposed from a surface of the first electrode plate opposite to the diaphragm to a surface of the second electrode plate opposite to the diaphragm, the diaphragm, the first electrode plate, A U-shaped member fixed to the second electrode plate assembly by an adhesive means is included. A lead electrode connected to the electrode on the diaphragm side is provided on the surface of the first electrode plate opposite to the diaphragm, and the U-shaped member uses the lead electrode to vibrate on the second electrode plate. It also serves as a conductive path for electrically drawing out to a terminal provided on the surface opposite to the plate. In this case, the U-shaped member also serves as a lead-out conductive path for electrically connecting the electrode provided on the first electrode plate and the terminal provided on the second electrode plate side. The first electrode plate and the second electrode plate are configured by forming an electrode film that forms an electrode on a plate-like body made of a dielectric.

  According to the present invention, the pair of electrode plates on which the electrodes for applying a voltage to the diaphragm are formed on both sides of the diaphragm composed of strip-shaped piezoelectric pieces are provided separately from the diaphragm. Since the diaphragm and the pair of electrode plates are supported in a cantilever manner, the stress of the electrode does not affect the diaphragm, so that high frequency stability can be obtained over a long period of time, and secondary vibration is hardly generated. . Then, if a separation part for elastically separating the vibration area and the support area, for example, a through hole, is formed between the vibration area of the diaphragm and the support area supported by the support part, the stress generated in the support part Can be prevented from being transmitted to the vibration region, so that the flatness of the vibration region can be maintained, and therefore, adverse effects on the long-term stability of the frequency can be suppressed. Further, since the diaphragm has a strip shape and employs a cantilever support structure, it is easy to process, and therefore can be easily downsized.

  As shown in FIGS. 1 to 3, the embodiments relating to the crystal resonator which is a piezoelectric resonator of the present invention are respectively provided on both sides of the vibration plate 1 made of a thickness-shearing crystal piece which is a strip-like piezoelectric piece. The first electrode plate 2 and the second electrode plate 3 having the same size as the size of the diaphragm 1 are arranged so as to be spaced apart from the diaphragm 1 and the diaphragm 1 and the electrode plates 2 and 3 are, for example, It is configured to be cantilevered on the short side of the strip shape. For example, the diaphragm 1 has an equivalent thickness of 1 μm to 300 μm, for example, 185 μm. In the drawings, the thicknesses of the diaphragm 1 and the electrode plates 2 and 3 are exaggerated. On one edge side (the edge portion on the short side) of the diaphragm 1, between one surface of the diaphragm 1 and the first electrode plate 2, and between the other surface of the diaphragm 1 and the second electrode plate 3. There are intervening intermediate members 4 and 4 which are square rods extending along the width direction (short side direction) of the diaphragm 1. These separation intermediate members 4 and 4 have a role of regulating the separation distance between the diaphragm 1 and the first electrode plates 2 and 3, and the separation distance is determined by the electric field formed by the electrode plates 2 and 3. The distance is sufficiently small to be applied to the diaphragm 1, and is set to, for example, 50 μm or less, for example, 20 μm.

  The first electrode plate 2 on the upper side in FIGS. 1 and 2 includes a dielectric piece, for example, a crystal piece 20 and one side edge of the surface of the crystal piece 20 on the side opposite to the vibration plate 1 from the entire surface on the vibration plate 1 side. And an electrode film formed over the portion. The electrode film is shown with multiple points for convenience of illustration. Of this electrode film, the entire surface portion on the diaphragm 1 side acts as the excitation electrode 21, and the opposite surface portion functions as the extraction electrode 22. Here, for the sake of convenience, the description will proceed with the one side edge side as the right side and the other side edge side as the left side. The second electrode plate 3 on the lower side in FIGS. 1 and 2 also has a dielectric, for example, a crystal piece 30 and a left side of the crystal piece 30 on the surface opposite to the vibration plate 1 from the entire surface on the vibration plate 1 side. And an electrode film (shaded portion) formed over the side edge (the other side edge). Of this electrode film, the entire surface portion on the diaphragm 1 side functions as the excitation electrode 31, and the opposite surface portion functions as the extraction electrode 32.

  In the figure, reference numeral 5 denotes a U-shaped member having at least a surface made of, for example, a metal, and a bent surface on the upper end side of the U-shaped member 5 is in contact with the lead electrode 22 of the first electrode plate 2. In addition, the assembly of the diaphragm 1 and the electrode plates 2 and 3 and the U-shaped member 5 so that the bent surface on the lower end side is in contact with the surface of the second electrode plate 3 opposite to the diaphragm 1. Are engaged. A conductive adhesive is interposed between the U-shaped member 5 and the assembly, so that a conductive path is formed from the extraction electrode 22 to the lower bent surface of the U-shaped member 5, and The side rectangular bent surface constitutes one terminal 23 of the crystal resonator of the present invention.

  In the figure, reference numeral 6 denotes an L-shaped member having at least a surface made of a conductor, for example, a metal. The L-shaped member 6 extends from the end face of the assembly to the extraction electrode 32 on the second electrode plate 3. The assembly is bonded to the assembly via a conductive adhesive. The lower surface of the L-shaped member 6 overlaps with the extraction electrode 32 to form a square shape, and this square portion constitutes the other terminal 33 of the crystal resonator of the present invention.

Thus, the diaphragm 1 and the two electrode plates 2 and 3 are separated from each other via the separation intermediate members 4 and 4, and the U-shaped member 5 is fitted into the assembly via the conductive adhesive. The diaphragm 1 and the two electrode plates 2 and 3 are cantilevered. In this example, the separation intermediate members 4, 4, the U-shaped member 5, and the L-shaped member 6 form a support portion that supports the diaphragm 1 and the electrode plates 2, 3 in a cantilever manner.
Further, the bonding of the U-shaped member 5 and the electrode 22 or the bonding of the L-shaped member 6 and the electrode 32 is not limited to the conductive adhesive, but other methods such as a method of forming a eutectic alloy. There may be. The L-shaped member 6 has a role of increasing the bonding strength of the assembly and a role of constituting the other terminal 33. In the present invention, a flat plate is used instead of the L-shaped member 6, and this flat plate is used. The terminal 33 may be configured by overlapping the lead electrode 32 on the lead electrode 32.
In the vicinity of the support portion of the diaphragm 1, there is an elastic separation portion 3 in order to prevent the stress caused by the support region (region in contact with the separating intermediate member 4) from affecting the vibration region. Two rectangular through holes 7 are formed. That is, the through hole 7 divides the vibration region and the support region so that unnecessary stress in the support region is not transmitted to the vibration region. Further, in this example, the vibration plate 1 is formed on the vibration region side (tip side when viewed from the support portion) than the region supported by the support portion in the diaphragm 1, in this example, the region in contact with the separation intermediate member 4. However, when entering the region in contact with the separation intermediate member 4, the separation intermediate member 4 serves as a reinforcing member for compensating for the insufficient strength of the diaphragm 1 due to the provision of the through hole 7. Will also have a role.

  The crystal unit as described above can be manufactured as follows. FIG. 4 shows a part of the crystal wafer 100. A strip-shaped diaphragm 1 is formed on the crystal wafer 100 by wet etching, and the first electrode plate 2 and the second electrode plate 3 are similarly formed. The crystal pieces 20 and 30 corresponding to the electrode holder are similarly formed from a crystal wafer. For the crystal pieces 20 and 30, an electrode film is formed as described above by sputtering or the like. For example, after the separation intermediate member 4 is bonded to the vibration plate 1, the vibration plate 1 and the electrode plates 2, 3 are cut out from the crystal wafer and overlapped, and then the U-shaped member 5 is attached to the assembly. The L-shaped member 6 is bonded.

  FIG. 5 shows an electronic component in which the above-described crystal resonator (assigned with reference numeral 200) is packaged. The package 8 is composed of a package body 81 made of, for example, a ceramic having a flat rectangular shape whose upper surface is open and a lid 82. A crystal resonator 200 is accommodated in the inside. Two electrodes 91 (only one is visible in FIG. 5A) formed on the bottom of the package 8 in the width direction and the terminals 23 and 33 on the crystal resonator 200 side are, for example, conductive adhesives. It is adhered by. The electrode 91 is electrically connected to two electrode pads (see FIG. 5B) provided on the lower surface (outer surface) of the bottom portion through a conductive path 93 penetrating the bottom portion of the package 8. Reference numerals 95 and 95 denote dummy electrodes for supporting the vicinity of the edge on the opposite side of the crystal resonator 200 from the electrode pad 94. FIG. 6 is an exploded perspective view showing the electronic component. The lid body 82 is provided with a ring body 83 constituting an exhaust hole. The inside of the package 8 is evacuated through the ring body 83, and the inside of the package 8 is maintained in a vacuum atmosphere by closing the ring body 83. The exhaust hole may be a hole formed in the lid 82 instead of the ring body 83. With this configuration, the residual gas component in the atmosphere in the package 8, especially the amount of water, is reduced, so that the adsorption of the residual gas component to the diaphragm 1 and the electrodes 21 and 31 can be suppressed, and the long-term stable performance of the frequency Will be better.

Such a crystal resonator has the following operations and effects. When a DC voltage is applied between the excitation electrodes 21 and 31 that are separated from the diaphragm 1 via the electrode pads 94 and 94, the separation distance is sufficiently small to apply an electric field to the diaphragm 1. The plate (crystal piece) 1 oscillates. Since the excitation electrodes 21 and 31 are separated from the diaphragm 1, stress due to vibrations of the excitation electrodes 21 and 31 is not directly transmitted to the diaphragm 1, so that high frequency long-term stability can be obtained.
And since the support area | region and the vibration area | region were isolate | separated by providing the through-hole 7 in the diaphragm 1, it can reduce that the stress by a support part influences a vibration area, ie, the flatness of a vibration area can be maintained, Therefore The adverse effect on long-term stability can be suppressed. In addition, since the diaphragm 1 has a strip shape and employs a cantilever support structure, it is easy to process, and therefore can be easily downsized.

  In addition, the separating portion for elastically separating the support region and the vibration region in the diaphragm 1 is not limited to the through hole 7 and is parallel to the short side of the diaphragm 1 as shown in FIG. The step part 71 comprised so that thickness may become thicker than the support part side may be sufficient, or the groove part and protruding item | line part extended in parallel with the short side of the diaphragm 1 may be sufficient. Further, the electrode plates 2 and 3 may be similarly provided with a separating portion. In the example of FIG. 8, an example is shown in which each of the electrode plates 2 and 3 is similarly provided with a through hole 72 at a position corresponding to the through hole of the diaphragm 1 shown in the above-described embodiment. The separating intermediate members 4 and 4 and the U-shaped member 5 may be integrated. In addition, you may make it support in a cantilever at the long side of a diaphragm.

It is sectional drawing and the bottom view which show the crystal resonator which concerns on embodiment of this invention. 1 is an exploded perspective view and a perspective view showing a crystal resonator according to an embodiment of the present invention. 1 is an exploded perspective view and a perspective view showing a crystal resonator according to an embodiment of the present invention. It is a figure which shows a part of manufacturing process of the said crystal oscillator. It is sectional drawing and the top view which show the electronic component using the said crystal oscillator. It is a disassembled perspective view which shows the said electronic component. FIG. 6 is an exploded perspective view and a perspective view showing a crystal resonator according to another embodiment of the present invention. FIG. 6 is an exploded perspective view and a perspective view showing a crystal resonator according to still another embodiment of the present invention. It is the schematic sectional drawing and schematic principal part top view which show the conventional crystal oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diaphragm 2 1st electrode plate 3 2nd electrode plate 21, 31 Excitation electrode 22, 32 Extraction electrode plate 4 Separation intermediate member 5 U-shaped member 6 L-shaped member 7 Through-hole 71 Step part 8 Package 200 Crystal oscillator

Claims (9)

A diaphragm made of a strip-shaped piezoelectric piece;
A first electrode plate and a second electrode which are provided on both sides of the diaphragm so as to face and separate from the diaphragm, and electrodes for applying a voltage to the diaphragm are formed on the diaphragm side. Electrode plate,
A support portion for supporting the diaphragm, the first electrode plate and the second electrode plate in a cantilever manner,
A piezoelectric vibrator, wherein a separation portion for elastically separating the vibration region and the support region is formed between a vibration region of the diaphragm and a support region supported by the support portion . The separation portion, the diaphragm through-hole formed, the stepped portion, the piezoelectric vibrator according to claim 1, characterized in that selected from among concave and convex portions. The support portion includes a separation intermediate member that is interposed between the vibration plate and the first electrode plate and the second electrode plate and regulates a separation distance between the vibration plate and the electrode plate. The piezoelectric vibrator according to claim 1 or 2 . 4. The piezoelectric vibrator according to claim 3, wherein the separating intermediate member is a rod-like body extending in the width direction of the diaphragm. The support portion is disposed from a surface of the first electrode plate opposite to the diaphragm to a surface of the second electrode plate opposite to the diaphragm, the diaphragm, the first electrode plate, the piezoelectric vibrator according to any one of claims 1 to 4, characterized in that it comprises a U-shaped member which is secured by adhesive means against the assembly of the second electrode plate. A lead electrode connected to the electrode on the diaphragm side is provided on the surface of the first electrode plate opposite to the diaphragm, and the U-shaped member uses the lead electrode to vibrate on the second electrode plate. 6. The piezoelectric vibrator according to claim 5 , wherein the piezoelectric vibrator is also used as a conductive path for electrically drawing out to a terminal provided on a surface opposite to the plate. The U-shaped member also serves as a lead-out conductive path for electrically connecting an electrode provided on the first electrode plate and a terminal provided on the second electrode plate side. The piezoelectric vibrator according to claim 6 . The first electrode plate and second electrode plate, any one of claims 1 to 7, characterized in that the electrode film constituting the electrode to the plate-like member made of a dielectric is formed is formed The piezoelectric vibrator as described in one. A package containing the piezoelectric vibrator according to any one of claims 1 to 8 , and an external terminal provided in the package and electrically connected to the first electrode and the second electrode, An electronic component characterized by comprising.

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