JP2003273703A - Quartz vibrator and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tuning fork type quartz vibrator allowed to be vibrated in a bent mode and setting up the frequency stability of basic wave mode vibration higher than that of secondary harmonic mode vibration. <P>SOLUTION: The tuning fork type bent quartz vibrator is provided with a tuning fork arm and a tuning fork base part and constituted of arranging grooves or through holes on the upper and lower surfaces of the tuning fork arm or the tuning fork arm and the tuning form base part, arranging electrodes on the side faces of the grooves or through holes and arranging electrodes of different polarity on the side face of the tuning fork arm oppositely to the former electrodes so that the figure of merit (FOM) of the basic wave mode vibration is larger than that of the harmonic mode vibration. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuning fork-shaped crystal unit including a tuning fork arm vibrating in a bending mode and a tuning fork base, and a method for manufacturing the same. In particular, it is a crystal oscillator best suited as a reference signal source for information and communication equipment that is strongly required to be compact, highly accurate, shock resistant, and inexpensive, and has a new shape, a new electrode configuration, and an ultra-compact tuning fork. TECHNICAL FIELD The present invention relates to a bent quartz crystal unit and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a conventional crystal oscillator, a tuning fork-shaped bent crystal oscillator in which electrodes are arranged on upper and lower surfaces and side surfaces of a tuning fork arm is well known. FIG. 9 is a schematic view of a tuning fork-shaped bent crystal unit 200 of this conventional example. In FIG. 9, a crystal unit 200 includes two tuning fork arms 201 and 202 and a tuning fork base portion 2.
30 and. FIG. 10 shows a sectional view of the tuning fork arm of FIG. As shown in FIG. 10, the excitation electrodes are arranged on the upper and lower surfaces and side surfaces of the tuning fork arm. The cross-sectional shape of the tuning fork arm is generally rectangular. An electrode 203 is arranged on the upper surface and an electrode 204 is arranged on the lower surface of the cross section of one tuning fork arm. Electrodes 205 and 206 are provided on the side surface. The electrode 207 is arranged on the upper surface of the other tuning fork arm, the electrode 208 is arranged on the lower surface, and the electrodes 209 and 210 are arranged on the side surfaces.
-H 'structure is formed. When a DC voltage is applied between H-H ', the electric field works in the direction of the arrow. As a result, when one tuning fork arm bends inward, the other tuning fork arm also bends inward. The reason is that the electric field components Ex in the x-axis direction are opposite in direction inside each tuning fork arm. Vibration can be sustained by applying an alternating voltage. Also, JP-A-56-
65517 and JP-A-2000-223992 (P2000
No. 223992A), a groove is provided on a tuning fork arm and an electrode structure is disclosed.

[0003]

In the tuning fork type bent crystal oscillator, the larger the electric field component Ex, the smaller the equivalent series resistance R _{1 and the} larger the quality factor Q value. However,
The tuning fork type bent crystal unit used conventionally is shown in Fig. 1.
As indicated by 0, electrodes are arranged on the upper and lower surfaces and side surfaces of each tuning fork arm. Therefore, the electric field does not work linearly,
When such a tuning fork type bent crystal oscillator is miniaturized, the electric field component Ex becomes small, the equivalent series resistance R ₁ becomes large, and the quality factor Q value becomes small. At the same time, it has been left as an issue to obtain a bent crystal oscillator having high accuracy as a time reference, that is, having high frequency stability and suppressing harmonic mode vibration. Further, as a method for solving the above-mentioned problems, for example, JP-A-56-6
5517 discloses a groove in the tuning fork arm, and discloses a groove structure and an electrode structure. However, the groove configuration,
There is no disclosure of dimensions and vibration modes, the relationship between the equivalent series resistance R ₁ in fundamental mode vibration and the equivalent series resistance R _{n in} harmonic mode vibration, and the Figer of Merit M related to frequency stability. Also, if a conventional crystal oscillator or oscillator with the above groove is connected to a conventional circuit to configure a crystal oscillation circuit, the output signal in the fundamental wave vibration mode causes harmonics in the output signal due to shock or vibration. There was a problem that the frequency of modal vibration was changed and detected.
Therefore, even if a shock or vibration is received, it is a tuning fork-shaped bent crystal unit that vibrates in the fundamental wave mode that suppresses the harmonic mode vibration that does not affect them. It had been. Therefore, a tuning fork shape having a groove configuration and an electrode configuration with a very small size that oscillates in the fundamental wave mode, a small equivalent series resistance R _{1, and} a high quality factor Q value and that has a high electromechanical conversion efficiency and an electrode configuration. Bending Quartz Resonator was desired. More specifically, a tuning fork-shaped bent crystal oscillator in which the frequency stability of fundamental mode vibration is higher than the frequency stability of second harmonic mode vibration has been desired.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tuning fork-shaped crystal unit that vibrates in a bending mode and a method for manufacturing the same in which the conventional problems are advantageously solved by the following method. is there.

That is, the first aspect of the crystal resonator of the present invention is a tuning fork-shaped bent crystal resonator including a tuning fork arm vibrating in a bending mode and a tuning fork base, and the tuning fork arm has an upper surface. A groove is provided on the tuning fork arm having a lower surface and a side surface, an electrode is arranged on the groove and the side surface of the tuning fork arm, and an electrode on the side surface of the groove and a side surface of the tuning fork arm that opposes the electrode. Of the tuning fork-shaped bent quartz crystal resonator having the fundamental wave mode vibration of the tuning fork-shaped bent crystal resonator, and the electrode and the electrode of the tuning fork arm vibrate in opposite phases. Reference numeral ₁ is a crystal oscillator having a harmonic mode vibration larger than the Figger of Merit M _n .

A first aspect of the method for manufacturing a crystal unit according to the present invention is a method for manufacturing a bending crystal unit having a tuning fork shape, which comprises a tuning fork arm vibrating in a bending mode and a tuning fork base.
The tuning fork arm has an upper surface, a lower surface, and a side surface, a groove is provided in the tuning fork-shaped tuning fork arm, electrodes are arranged on the groove and the side surface of the tuning fork arm, and an electrode on the side surface of the groove and its electrode are provided. Forming a groove and an electrode so that the electrodes on the side surfaces of the opposing tuning fork arms have different polarities, and the tuning fork arms vibrate in opposite phases; and And a step of accommodating in a cylindrical unit, wherein the figurer of merit M ₁ of the fundamental mode vibration of the bending fork crystal resonator of the tuning fork shape is larger than the figurer of merit M _n of the harmonic mode vibration. It is a method of manufacturing a child.

[0007]

As described above, the present invention is a tuning-fork-shaped crystal oscillator that vibrates in a bending mode, and further improves the configuration of the tuning-fork-shaped groove and electrode to suppress harmonic mode vibration and vibrate in the fundamental mode. You can get a crystal unit.

[0008] In addition, the neutral line of the tuning fork arm is sandwiched (included).
By providing a groove in the center and arranging the electrodes to optimize the dimensions of the groove, the equivalent series resistance R ₁ is small, the Q value is high, and the super-mode vibrates in a bending mode with high electromechanical conversion efficiency. A small tuning fork-shaped bent crystal oscillator can be obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows an external view of a tuning fork-shaped bent crystal oscillator 10 vibrating in a bending mode according to the first embodiment of the present invention and its coordinate system. The coordinate system O, the electric axis x, the mechanical axis y, and the optical axis z constitute O-xyz. The tuning fork-shaped bent crystal resonator 10 of the present embodiment includes a tuning fork arm 20, a tuning fork arm 26, and a tuning fork base 40.
0 and the tuning fork arm 26 are connected to the tuning fork base 40. The tuning fork arm 20 and the tuning fork arm 26 have an upper surface, a lower surface, and a side surface, respectively. Further, a groove 21 is provided on the upper surface of the tuning fork arm 20 so as to sandwich the neutral line, that is, to include the neutral line.
Further, a groove 27 is provided on the upper surface of the tuning fork arm 26 similarly to the tuning fork arm 20, and a groove 32 and a groove 36 are further provided on the tuning fork base portion 40. The angle θ is a rotation angle around the x-axis, and is usually selected in the range of 0 ° to 10 °. Further, grooves are provided on the lower surfaces of the tuning fork arms 20 and 26 as well as the upper surfaces.

FIG. 2 is a cross sectional view of the tuning fork base portion 40 of the bending fork crystal resonator 10 of FIG. 2, the cross-sectional shape and electrode arrangement of the tuning fork base 40 of the crystal unit shown in FIG. 1 will be described in detail. Grooves 21 and 22 are provided in the tuning fork base portion 40 that is connected to the tuning fork arm 20. Similarly, the tuning fork base portion 40 connected to the tuning fork arm 26 is provided with grooves 27 and 28. Further, a groove 3 is further provided between the groove 21 and the groove 27.
2 and a groove 36 are provided. Further, a groove 33 and a groove 37 are also provided between the groove 22 and the groove 28. And
Electrodes 23 and 24 are provided in the grooves 21 and 22, and grooves 32 and 33,
Electrodes 34, 35, 38, 39 are provided on the grooves 36, 37 in the groove 27.
The electrodes 29 and 30 are arranged in the groove 28 and the groove 28, and the tuning fork base 40
Electrodes 25 and 31 are arranged on both side surfaces of. In detail, electrodes are arranged on the side surfaces of the groove, and electrodes having different polarities are arranged opposite to the electrodes.

The tuning fork-shaped bent crystal oscillator 10 has a thickness t, and the groove has a thickness t ₁ . The thickness t _{1 mentioned} here means the thickness of the deepest part of the groove. The reason is that quartz is an anisotropic material, and therefore the etching speed differs depending on the direction of each crystal axis in the chemical etching method. Therefore, the chemical etching method causes variations in the depth of the groove, and it is extremely difficult to process into the uniform shape shown in FIG. In this embodiment, the ratio (t ₁ / t) between the thickness t _{1 of} the groove and the thickness t of the tuning fork arm or the tuning fork arm and the tuning fork base is 0.
It is preferably 0.01 to so as to be smaller than 79.
A groove is formed in the tuning fork arm or the tuning fork arm and the tuning fork base so as to be 0.79. In particular, in order to increase the distortion of the tuning fork base, it is preferable to set the ratio of the thickness of the groove of the tuning fork base to the thickness of the tuning fork base to 0.01 to 0.025. By forming in this way, the electric field Ex between the tuning fork arm or the tuning fork arm and the groove side surface electrode of the tuning fork base and the side surface electrode opposite thereto
Grows larger. That is, it is possible to obtain a bending oscillator having a high electromechanical conversion efficiency. That is, a tuning fork-shaped bent crystal oscillator having a small capacitance ratio can be obtained. Further, in this embodiment, since the grooves 32, 33, 36 and 37 are further provided between the grooves of the tuning fork base portion, the electric field strength thereof is further increased and the electromechanical conversion efficiency is improved. . Further, in this embodiment, the grooves 32 and 36 are provided on the upper surface of the tuning fork base 40 and the groove 3 is provided on the lower surface.
Although 3, 37 are provided, they may be provided only on one side.

Further, the electrodes 25, 29, 30, 34, 35
Has electrodes 23, 24, 31, 37, 38, and
39 is arranged so as to have the same polarity as the other, and constitutes a two-electrode terminal structure E-E '. That is, the groove electrodes facing the z-axis direction have the same polarity, and the electrodes facing the x-axis direction have the different poles. Now, 2 electrode terminal E-
When a DC voltage is applied to E '(E terminal is positive and E'terminal is negative), the electric field Ex acts as shown by the arrow in FIG.
The electric field Ex is extracted perpendicularly to the electrodes, that is, linearly by the electrodes arranged on the side surface of the crystal unit and the side surface inside the groove, so that the electric field Ex becomes large, and as a result, the amount of strain generated is also large. Become. Therefore, even when the tuning fork-shaped bent crystal unit is downsized, the equivalent series resistance R ₁ is small.
A tuning fork-shaped crystal unit having a high quality factor Q value and vibrating in a bending mode is obtained.

FIG. 3 is a tuning fork-shaped bent crystal unit 1 of FIG.
0 is a top view of FIG. In FIG. 3, the arrangement and dimensions of the grooves 21 and 27 will be described in detail. The groove 21 is provided so as to sandwich the neutral line 41 of the tuning fork arm 20. The other tuning fork arm 26 is also provided with a groove 27 so as to sandwich the neutral line 42. Further, in the tuning fork-shaped bent crystal oscillator 10 of the present embodiment, the groove 32 and the groove 36 are also provided in the portion of the tuning fork base portion 40 sandwiched between the groove 21 and the groove 27. By providing the grooves 21 and 27 and the grooves 32 and 36, as described above, the electric field Ex acts on the tuning fork-shaped bent crystal resonator 10 as shown by the arrow in FIG. Is drawn perpendicularly to the electrode, that is, linearly by the electrodes arranged on the side surface of the crystal unit and the side surface inside the groove, and especially the electric field Ex of the tuning fork base portion becomes large, and as a result, the amount of strain generated is also increased. growing. As described above, the shape and electrode configuration of the tuning fork-shaped bent crystal resonator 10 of this embodiment have excellent electrical characteristics even when the tuning fork-shaped bent crystal resonator is downsized, that is, the equivalent series resistance R. _A crystal unit having a small value of ₁ and a high quality factor Q value can be realized.

Furthermore, if the partial width _W 1, _{W 3} and groove width _{W 2,} the arm width W of the tuning fork arms 20 and 26 W = It is configured such that W ₁ <W ₃ . The groove width W ₂ is W
It is configured under the condition of satisfying ₂ ≧ W ₁ and W ₃ . More specifically, in this embodiment, the ratio (W ₂ / W) of the groove width W ₂ to the tuning fork arm width W is larger than 0.35 and smaller than 1, preferably 0.35. It is preferable that the ratio (t ₁ / t) of the thickness t ₁ of the groove and the thickness t of the tuning fork arm or the thickness t of the tuning fork arm and the tuning fork base is less than 0.79 at .about.0.95. A groove is formed on the tuning fork arm so that the groove number is from 01 to 0.79. By forming in this way, the moment of inertia from the neutral lines 41 and 42 of the tuning fork arm as a base point becomes large. That is, since the electromechanical conversion efficiency is improved, it is possible to obtain a bent quartz crystal resonator having a small equivalent series resistance R ₁ , a high Q value, and a small capacitance ratio.

[0015] In contrast, in the present embodiment the length _{1 1} of the groove 21 and the groove 27, the grooves 21 and 27 are tuning fork arms 2
Extends from 0,26 to the length 1 ₂ of the tuning fork base portion 40 is sized such that the length 1 ₃ of the grooves of the base. Therefore, the length of the groove provided in the tuning fork arms 20 and 26 is (1 ₁ −
1 ₃ ), to obtain an oscillator with a small R ₁ ,
(1 ₁ -1 ₃ ) / (1-1 ₂ ) has a value of 0.4 to 0.8. Further, the total length 1 of the tuning fork-shaped bent crystal unit 10
Is determined by the required frequency and the size of the storage container. Together, in order to obtain a flexural quartz crystal resonator good tuning fork vibrating at the fundamental mode, a close relationship exists between the length 1 ₁ and the total length 1 of the groove.

That is, the tuning fork arm 20, 26 or the tuning fork arm 2
Ratio of 0,26 and the total length 1 of the long _{1 1} and tuning fork flexural crystal oscillator of the groove provided in the fork base 40 ₍₁ 1/1) of the grooves so that from 0.2 to 0.78 Length is provided.
The reason for forming in this way is that it is possible to suppress harmonic mode vibration, which is unnecessary vibration, particularly second-order and third-order harmonic mode vibration, and to improve frequency stability of the fundamental wave mode vibration. Therefore, a good tuning fork-shaped bent crystal unit that easily vibrates in the fundamental mode can be realized. More specifically, the equivalent series resistance R _{1 of} the tuning fork-shaped bent quartz oscillator vibrating in the fundamental mode is smaller than the equivalent series resistance R _n of the harmonic mode vibration. That is, R ₁ <R
_n (equivalent series resistance of 2nd and 3rd harmonic mode vibrations when n = 2, 3), and is composed of an amplifier (CMOS inverter), a capacitor, a resistance element, a tuning fork-shaped bent crystal oscillator of this embodiment, and the like. In this crystal oscillator, a good crystal oscillator in which the oscillator easily vibrates in the fundamental wave mode can be realized. The length 1 ₁ of the groove may be divided in the longitudinal direction of the tuning fork arms, at least one of them may be satisfied the side ratio (1 _1/1), or are divided The length of the added groove in the length direction of the groove is the side ratio (1 ₁ /
It is sufficient to satisfy 1).

Further, in this embodiment, the tuning fork base portion 40 in FIG. 3, is the entire lower portion of the length 1 ₂ of the vibrator 10,
Further, the tuning fork arm 20 and the tuning fork arm 26 are the vibrator 10 in FIG.
There is a whole upper part of the length 1 ₂ of the portion of. In the present embodiment, the tuning fork has a rectangular shape, but the present invention is not limited to the above-mentioned shape, and the tuning fork may have a U shape. In this case as well, similar to the rectangular shape, the dimensional relationship between the tuning fork arm and the tuning fork base is the same as the above relationship. Further, in the present embodiment, the groove is provided in the tuning fork arm and the tuning fork base, but the present invention is not limited to this, and the groove may be provided only in the tuning fork arm, and the same effect can be obtained. . In this case, the groove length is 1 ₃ = 0. Further, the length 1 ₁ of the groove in the present invention, when the grooves only in the tuning fork arms are provided, the ratio of the groove width W ₂ and the tuning fork arm width W (W ₂ /
W) is the length of the groove formed so as to be larger than 0.35 and smaller than 1. Furthermore, a groove in which the provided tuning fork arm, extends to the fork base, when further groove between the groove extending in the fork base is provided, the length including the length 1 ₃ of the grooves It is 1 ₁ . However, although the grooves of the tuning fork arms extend in a tuning fork base, further when is not provided grooves between the groove, the length 1 ₁ is the length of the groove of the tuning fork arms.

In other words, at least one groove is provided in the length direction on the upper and lower surfaces of the tuning fork arm sandwiching the neutral line of the tuning fork arm, that is, including the neutral line, and both sides of the groove are provided. An electrode is arranged on the surface, and the electrode on the side surface of the groove and the electrode on the side surface of the tuning fork arm that opposes the electrode are configured to have different polarities, and each of the electrodes is arranged to increase the moment of inertia generated in the tuning fork arm. The ratio (W ₂ / W) of the groove width W ₂ of at least one of the at least one groove and the tuning fork arm width W is larger than 0.35 and smaller than 1, and the groove thickness t ₁ and the tuning fork are equal to or smaller than _1. The ratio (t ₁ / t) to the thickness t of the arm is 0.79
Grooves are formed to be smaller.

[0019] Is satisfied, and the distance W ₄ is 0.05 mm to
0.35 mm, groove width W ₂ is 0.03 mm to 0.12 m
has a value of m. The reason for configuring in this way is that it is a very small bending crystal oscillator, and the tuning fork shape and the groove of the tuning fork arm can be formed separately (separate steps) using photolithography technology. The stability can be made higher than the frequency stability of harmonic mode vibration. In this case, a crystal wafer having a thickness t of usually 0.05 mm to 0.15 mm is used. However, the present invention is not limited to this embodiment, and quartz wafers thicker than 0.15 mm may be used.

More specifically, the figurer of merit M _i , which represents the inductive property, electromechanical conversion efficiency, and quality of the tuning fork-shaped bent crystal unit, is a quality factor Q _{i of the} bent crystal unit.
It is defined by the ratio of the value to the capacity ratio r _i (Q _i / r _i ). That is, it is given by M _i = Q _i / r _i . Here, i represents the vibration order of the bending quartz crystal in the tuning fork shape. When i = 1, the fundamental mode vibration, when i = 2, the second harmonic mode vibration, and when i = 3, the third harmonic mode vibration. Is. Also, the frequency difference Δf is off Iga of merit M of the series resonance frequency f _r which depends on the parallel capacitance and mechanical series resonance frequency f ₈ that is independent of the parallel capacitance of the flexural quartz oscillator tuning fork
inversely proportional to the _{i, Δf} becomes smaller as the value _{M i} is large. Therefore, the larger M _{i, the} more the resonance frequency of the tuning fork-shaped bent crystal resonator is not affected by the parallel capacitance, and the better the frequency stability of the bent crystal resonator. That is, a tuning fork-shaped bent crystal oscillator with high time accuracy can be obtained.

More specifically, due to the configuration of the tuning fork shape, the groove, the electrode, and the dimensions thereof, the figurer of merit M ₁ of the fundamental mode vibration becomes larger than the figurer of merit M _n of the harmonic mode vibration. That is, M ₁ > M _n .
However, n represents the vibration order of harmonic mode vibration, and n =
In the case of 2 and 3, it is the Figurer of merit of the second and third harmonic mode vibration. As an example, the frequency of fundamental mode vibration is 32.768 kHz, and W ₂ /W=0.5, t
_{When 1 /} t = 0.34, ₁ 1/1 = 0.48, variations due to manufacturing occur, but M ₁ and M ₂ of the tuning fork-shaped bent crystal resonator are M ₁ > 65 and M ₂ <30, respectively. Becomes
That is, high inductivity and good electromechanical conversion efficiency (capacity ratio r
₁ and the equivalent series resistance R ₁ is small), and a bent quartz oscillator vibrating in the fundamental mode having a large quality coefficient can be obtained. As a result, the frequency stability of the fundamental mode vibration is better than that of the second harmonic mode vibration, and
Second harmonic mode vibration can be suppressed. Therefore, the crystal oscillator constituted by the bent crystal oscillator of the present embodiment can obtain the frequency of the fundamental mode vibration as an output signal and has high frequency stability (excellent time accuracy). In other words, the crystal oscillator of this embodiment has a remarkable effect that the frequency change due to aging becomes extremely small. Further, as described above, the reference frequency of the fundamental mode vibration of the present invention is 10 kHz to 200 kHz. In particular, 32.768 kHz is widely used, and for example, its frequency deviation is -100PPM to +10.
The frequency is adjusted so that it is within the range of 0 PPM.

FIG. 4 is a top view of a tuning fork-shaped crystal unit 45 vibrating in the bending mode according to the second embodiment of the present invention. The tuning fork-shaped bent crystal oscillator 45 is configured to include tuning fork arms 46 and 47 and a tuning fork base portion 48. That is, tuning fork arm 4
One end of 6, 47 is connected to the tuning fork base 48. In the present embodiment, the tuning fork base portion 48 is provided with cutout portions 53 and 54. Further, the tuning fork arms 46 and 47 have a neutral line 51,
Grooves 49 and 50 are provided so as to sandwich (include) 52.
Further, in this embodiment, the grooves 49 and 50 are provided in a part of the tuning fork arms 46 and 47, and the grooves 49 and 50 have a width W ₂ respectively.
And has a length 1 ₁ . More specifically, the groove area S
= Indicated _{W 2} × _{1 1,} S is 0.025～0.12Mm ²
Is configured to have a value of. The reason for forming the groove area in this way is that the groove can be easily formed by the chemical etching method, and further the groove can be formed so that the electromechanical conversion efficiency is improved. At the same time, a tuning-fork-shaped crystal oscillator that vibrates in a bending mode having a high quality factor Q value of fundamental mode vibration can be obtained. As a result, it is possible to realize a crystal oscillator in which the output signal is the frequency of fundamental mode vibration.

With the area S of the groove, the groove and the tuning fork arm can be processed in separate steps. However, in order to simultaneously process the tuning fork arm and the groove provided therein, it is necessary to optimize the thickness t of the tuning fork arm, the groove width W ₂ , the spacing W _{4 of the} tuning fork arm, and the area S. That is, the thickness t of the tuning fork arm is 0.06 mm to 0.15 m.
When m, the groove width W ₂ is within the range of 0.02 mm to 0.068 mm, and the area S is 0.023 mm ^{2 to} 0.08.
It is in the range of 8 mm ² , and the interval W ₄ is 0.05 mm to
It is configured to be 0.35 mm. The reason for configuring in this way is to utilize the crystallinity of quartz, and due to its crystallinity, a groove that is not a through hole (including a groove divided in the length direction of the tuning fork arm).
And the tuning fork shape can be formed at the same time. Also, FIG.
Although not shown in FIG. 3, grooves are also provided on the lower surfaces of the tuning fork arms 46 and 47 at positions facing the grooves 49 and 50.

Further, the width dimension of the notch portions 53, 54 provided on the tuning fork base portion 48 on the tuning fork portion side is given by W ₅ , and the dimension of the notch portions 53, 54 on the end portion side is given by W _6. . When the end portion of the tuning fork base portion 48 is fixed to a surface mounting type case or a cylindrical type case with solder or adhesive, in order to reduce the loss of vibration energy of the vibrator, The energy loss of the vibrating part due to the fixing can be reduced. The arm width W and the partial width W of the tuning fork arm shown in FIG.
_1, W _3, the relationship between the total length 1 of length 1 ₁ and the tuning fork vibrator of the groove width W ₂ and the spacing W ₄ and grooves have a similar relationship with FIG.

FIG. 5 is a sectional view of an embodiment of a crystal unit accommodating the crystal resonator according to the first or second embodiment of the present invention. The crystal unit 170 includes a tuning fork-shaped bent crystal oscillator 70, a case 71, and a lid 72. More specifically, the vibrator 70 is fixed to the fixing portion 74 provided on the case 71 with a conductive adhesive 76 or solder. Further, the case 71 and the lid 72 are joined via the joining member 73. In this embodiment, the oscillator 70 is a tuning fork-shaped bent crystal oscillator 1 described in detail with reference to FIGS. 1 and 4.
It is the same oscillator as one of 0 and 45. Further, when configuring a crystal oscillator, the circuit element is connected to the outside of the crystal unit. That is, only the tuning fork-shaped bent crystal oscillator is stored in the unit. At this time, the bent crystal unit is housed in a unit in vacuum. Although the surface mount type crystal unit is shown in the present embodiment, the bent crystal unit may be housed in the cylindrical unit. That is, a cylindrical crystal unit is obtained.

Further, the case member is made of ceramics or glass, the lid member is made of metal or glass, and the joining member is made of metal or low melting point glass. The relationship between the vibrator, the case, and the lid described in this embodiment is shown in FIG.
Also applied to the crystal oscillator.

FIG. 6 is an embodiment of a crystal oscillation circuit diagram which constitutes a crystal oscillator equipped with the crystal resonator of the present invention. In this embodiment, the crystal oscillation circuit 1 is composed of an amplifier (CMOS inverter) 2, a feedback resistor 4, a drain resistor 7, capacitors 5, 6 and a tuning fork-shaped bent crystal oscillator 3. That is, the crystal oscillation circuit 1 includes an amplifier circuit 8 including an amplifier 2 and a feedback resistor 4, a drain resistor 7, a capacitor 5,
6 and a feedback circuit 9 including a bent crystal unit 3. Further, the output signal of the crystal oscillating circuit 1 constituted by the tuning fork-shaped bent crystal oscillator 3 vibrating in the fundamental wave mode is output from the drain side through a buffer circuit (not shown). That is, the frequency of the fundamental wave mode vibration is output as an output signal through the buffer circuit.
In the present invention, the frequency of fundamental mode vibration is 10 kHz to
200 kHz is used. Further, in the present invention, the frequency of the fundamental wave mode vibration also includes the frequency obtained by dividing or multiplying the frequency of the output signal by the frequency dividing circuit or the frequency multiplying circuit. More specifically, the crystal oscillator of this embodiment is configured to include a crystal oscillation circuit and a buffer circuit. In other words, the crystal oscillation circuit is composed of an amplifier circuit and a feedback circuit, the amplifier circuit is composed of at least an amplifier, and the feedback circuit is composed of at least a tuning fork-shaped bent crystal oscillator and a capacitor. The tuning fork-shaped bent crystal oscillator used in the crystal oscillator of this embodiment has already been described in detail with reference to FIGS. 1 to 4.

FIG. 7 shows the feedback circuit diagram of FIG. The angular frequency of a tuning fork-shaped crystal unit that vibrates in the bending mode is now ω
_i , the resistance of the drain resistance 7 is R _d , and the capacitors 5 and 6 are
_Let C _{g be} the capacitance of C _d , C _{d be} the crystal impedance of the crystal be R _ei , be the input voltage be V ₁ and be the output voltage be V ₂ .
The feedback rate β _i is defined by β _i = | V ₂ | _i / | V ₁ | _i . However, i represents the vibration order of the bending vibration mode. For example, when i = 1, fundamental mode vibration, and when i = 2,
Second harmonic mode vibration, when i = 3, third harmonic mode vibration. That is, when i = n, the vibration is n-th harmonic mode vibration, but hereinafter simply referred to as harmonic mode vibration. Further, the load capacitance C _L is given by C _L = C _g C _d / (C _g + C _d ), and when C _g = C _d = C _gs and Rd >> R _ei , the feedback ratio β _i is β _i = It is given by 1 / (1 + kC _L ² ). However, k is represented by a function of ω _i , R _d , and R _ei . Also, R _ei is approximately equal to the equivalent series resistance R _i .

As described above, from the relationship between the feedback ratio β _i and the load capacitance C _L , if the load capacitance C _L becomes smaller, the feedback ratios at the resonance frequencies of the fundamental vibration mode and the harmonic vibration mode may increase. I understand. Therefore, the load capacity C
_{When L} becomes smaller, the harmonic mode vibration is more likely to oscillate than the fundamental wave mode vibration. The reason is that the maximum vibration amplitude of the harmonic mode vibration is smaller than the maximum vibration amplitude of the fundamental mode vibration, so that the amplitude condition and the phase condition that are the oscillation continuation conditions are satisfied at the same time. Further, the load capacitance C _L of the crystal oscillator equipped with the bent crystal oscillator of the present embodiment is
18 pF or less is used to reduce the current consumption.

Further, the amplifying portion of the amplifying circuit which constitutes the crystal oscillating circuit of this embodiment can exhibit its characteristic by the negative resistance -RL _i . When i = 1, it is a negative resistance of fundamental mode vibration, and when i = n, it is a negative resistance of harmonic mode vibration. That is, when n = 2 and 3, it is the negative resistance of the second and third harmonic mode vibrations. The crystal oscillator of this embodiment has an absolute value of the negative resistance of the fundamental mode vibration of the amplifier circuit | -RL ₁
The absolute value of the negative resistance of the harmonic mode vibration of the amplifier circuit | −RL _n is the ratio of | and the equivalent series resistance R ₁ of the fundamental mode vibration.
The oscillator circuit is configured so that it is larger than the ratio of | and the equivalent series resistance R _n of harmonic mode vibration. That is, |-
It is configured to satisfy RL ₁ | / R ₁ > | −RL _n | / R _n . By configuring the crystal oscillating circuit in this manner, the oscillation start of the harmonic mode vibration is suppressed, and as a result, the oscillation start of the fundamental mode vibration is obtained, so that the frequency of the fundamental mode vibration is obtained as the output signal.

FIG. 8 is a sectional view of an embodiment of a crystal oscillator equipped with the crystal resonator according to the first embodiment or the second embodiment of the present invention. The crystal oscillator 190 includes a crystal oscillator circuit and a case 91.
And a lid 92. In this embodiment, the crystal oscillator circuit is housed in a crystal unit including a case 91 and a lid 92. Further, the crystal oscillation circuit includes a tuning fork-shaped bent crystal oscillator 90, an amplifier 98 including a feedback resistor, a capacitor (not shown), and a drain resistor (not shown). C
A MOS inverter is used.

Further, in this embodiment, the vibrator 90 is fixed to the fixing portion 94 provided on the case 91 with an adhesive 96 or solder. On the other hand, the amplifier 98 has a case 91.
It is fixed to. Further, the case 91 and the lid 92 are joined via a joining member 93. Transducer 90 of this embodiment
The oscillators in the tuning fork-shaped bent crystal oscillators 10 and 45 described in detail in FIGS. 1 and 4 are used.

Next, a method of manufacturing the crystal unit of the present invention will be described. The tuning fork-shaped bent crystal oscillator is formed by a photolithography method and a chemical etching method using semiconductor technology. First, a metal film (for example,
Chromium and gold thereon is formed by sputtering or vapor deposition. Next, a resist is applied on the metal film. Then, after the resist and the metal film are removed by the photolithography process while leaving the tuning fork shape, a tuning fork shape including a tuning fork arm and a tuning fork base is formed by a chemical etching method. When forming this tuning fork shape, a notch may be formed in the tuning fork base. Further, the metal film and the resist shown in the above step are applied on the tuning fork-shaped surface, and grooves are formed in the tuning fork arm or the tuning fork arm and the tuning fork base by the photolithography step and the chemical etching method.

Next, a metal film and a resist are applied again in the shape of a tuning fork having a groove, and an electrode is formed by a photolithography process. That is, the electrode on the side surface of the tuning fork arm and the electrode on the side surface of the groove are arranged so as to have opposite polarities. More specifically, the side electrode of the first tuning fork arm and the groove electrode of the second tuning fork arm have the same polarity, and the groove electrode of the first tuning fork arm and the side electrode of the second tuning fork arm have the same polarity. The electrodes of the groove of the first tuning fork arm and the side electrodes are configured to have different polarities. That is, Two-electrode terminals are formed on the vibrator. As a result, when an alternating voltage is applied to the two-electrode terminals, the tuning fork arm flexurally vibrates in reverse phase. In this embodiment, the groove is formed in the tuning fork arm or the tuning fork arm and the tuning fork base after forming the tuning fork shape, but the present invention is not limited to the above embodiment, and first, the groove is formed. May be formed into a tuning fork shape. Alternatively, the tuning fork shape and the groove may be formed at the same time. Further, the dimensions and the like of the grooves in this step are the same as those described above and have already been described, so they are omitted here.

By the process of this embodiment, a large number of tuning fork-shaped bent crystal oscillators are formed on the crystal wafer.
Therefore, in the next step, in this wafer state, the first frequency adjustment is performed by laser or plasma etching or vapor deposition. At the same time, the defective oscillator is marked or removed from the wafer. In this process, 10 kHz-
The frequency deviation is -9 with respect to the reference frequency of 200 kHz.
The frequency is adjusted so that it is within the range of 000 PPM to +5000 PPM. Further, in the next step, the formed vibrator is fixed to the lead wire of the surface mount type case, the lid or the cylindrical type case with an adhesive or solder. After the fixing, the second frequency adjustment is performed by laser or plasma etching or vapor deposition. In this step, frequency adjustment is performed so that the frequency deviation is within the range of −100 PPM to +100 PPM. Further, in the present invention, the frequency adjustment performed after the fixing means that the frequency adjustment may be performed immediately after the fixing, or the frequency adjustment may be performed after the case and the lid are connected after the fixing. That is,
Even if any step is performed after fixing, the frequency adjustment may be performed after that, and the present invention includes all of these. Further, the frequency adjustment after connecting the case and the lid is performed by a laser through the glass.

When the third frequency adjustment is performed, the frequency deviation due to the second frequency adjustment is -9.
The frequency is adjusted so that it is within the range of 50 PPM to +950 PPM. Further, in the above embodiment, the first frequency adjustment is performed in the state of the wafer, and at the same time, the defective oscillator is marked or removed from the wafer, but the present invention is not limited to this. The present invention may include a step of inspecting a large number of tuning fork-shaped bent crystal oscillators formed on a crystal wafer in a wafer state and inspecting whether the oscillator is a good oscillator or a defective oscillator. That is, the defective oscillator is marked, removed from the wafer, or stored in the computer. By including such a process, it is possible to quickly find a defective vibrator and not to the next process.
The yield can be increased. As a result, an inexpensive bent crystal oscillator can be obtained.

Further, after the frequency adjustment, the vibrator is housed in a unit that serves as a case and a lid in a vacuum to obtain a crystal unit. When the lid is made of glass,
After the storage, the third frequency adjustment is performed by the laser.
In this step, the frequency deviation is −50 PPM to +50 PPM.
The frequency is adjusted to be within the range. In this embodiment, the frequency adjustment is performed in three separate steps, but it may be performed in at least two separate steps. For example, the third
It is not necessary to adjust the frequency in the second process. Further, in the next step, the above-mentioned two-electrode terminal of the vibrator is electrically connected to the amplifier, the capacitor and the resistance element. In other words, the amplifier circuit includes a CMOS inverter and a feedback resistance element, and the feedback circuit includes a tuning fork-shaped bent crystal oscillator, a drain resistance element, a gate side capacitor, and a drain side capacitor. Electrically connected as described above. The third frequency adjustment may be performed after the crystal oscillation circuit is constructed.

Although the invention has been described above based on the illustrated example, the invention is not limited to the above-mentioned example, and the tuning fork arm or the tuning fork arm is used in the bending fork-shaped crystal resonators of the first and second embodiments. Grooves are provided on the tuning fork arm and the tuning fork base.
A through hole (t ₁ = 0) may be provided in the tuning fork arm. That is, the through hole is a special case of the groove, and the groove of the present invention includes the through hole. In the above embodiment, the tuning fork arm has 2
Although composed of a book, the present invention includes three or more tuning fork arms. In this case, the electrodes may be configured so that at least two tuning fork arms vibrate in opposite phases.

Further, in this embodiment, the groove is provided on the tuning fork arm so as to sandwich (include) the neutral line, but the present invention is not limited to this, and the neutral line is left and both sides thereof are left. You may form a groove | channel in it. In this case, the partial width W ₇ including the neutral line of the tuning fork arm is configured to be smaller than 0.05 mm. The width of each groove is smaller than 0.04 mm, and the ratio of the groove thickness t ₁ to the tuning fork arm thickness t is 0.79 or less. With such a configuration, M ₁ can be made larger than M _n .

Further, the capacitance ratio r ₁ in the fundamental mode vibration of the tuning fork-shaped bent quartz crystal vibrators of the first and second embodiments is set to be smaller than the capacitance ratio r ₂ in the second harmonic mode vibration. Is configured. With such a configuration, with respect to the same change in the load capacitance C _L , the frequency change of the bent crystal resonator vibrating in the fundamental mode becomes larger than the frequency change of the bent crystal resonator vibrating in the second harmonic mode. That is, the variable range of the frequency of the fundamental mode vibration can be wider than that of the second harmonic mode vibration. More specifically,
For example, when the load capacitance C _L = 18 pF and the C _L value changes by 1 pF, the frequency change of the fundamental mode vibration becomes larger than the frequency change of the second harmonic mode vibration. Therefore, the fundamental mode vibration has a remarkable effect that the variable range of the frequency can be widened even if the variable amount of the load capacitance C _L is small. As a result, the range of variable capacitance of the capacitors can be reduced, so that the number of capacitors used can be reduced. As a result, an inexpensive crystal oscillator can be obtained by using the tuning fork-shaped bent crystal oscillator of this embodiment.

The capacitance ratios r ₁ and r ₂ of the tuning fork-shaped bent crystal oscillator are r ₁ = C ₀ / C ₁ and r ₂ = C ₀ /
Given by C ₂ . However, C ₀ is the parallel capacitance of the equivalent circuit, and C ₁ and C ₂ are the equivalent capacitances of the fundamental wave mode vibration and the second harmonic mode vibration of the equivalent circuit. Furthermore, the quality factors of the fundamental mode vibration and the second harmonic mode vibration of the tuning fork-shaped bent crystal oscillator are given by Q ₁ and Q ₂ values. And
The tuning fork-shaped bent quartz crystal resonator of the above embodiment is configured such that the dependence of the resonance frequency oscillating in the fundamental mode on the parallel capacitance is smaller than the dependence of the resonance frequency oscillating on the second harmonic mode on the parallel capacitance. To be done. In other _{words, r} 1/2
It is configured to satisfy Q ₁ ² <r ₂ / 2Q ₂ ² . With such a configuration, the influence of the parallel capacitance on the resonance frequency that vibrates in the fundamental mode is so small that it can be neglected, so that bending quartz vibration that vibrates in the fundamental mode having high frequency stability can be obtained. Further, in the present invention, r ₁ / 2Q ₁ ² and r ₂ / 2Q ₂ ² are set as S ₁ and S ₂ , respectively, and S ₁ and S ₂ are set to the frequency stabilization of the fundamental mode vibration and the second harmonic mode vibration, respectively. Called the coefficient. That is,
Given by S ₁ = r ₁ / 2Q ₁ ² and S ₂ = r ₂ / 2Q ₂ ² .

Further, the tuning fork shape and the groove of the bent crystal unit of this embodiment are processed by at least one of chemical, physical and mechanical methods. In the physical method, for example, ionized atoms and molecules are scattered and processed. In the mechanical method, for example, particles for blast processing are scattered and processed.

[0043]

As described above, it has already been described that many effects can be obtained by providing the crystal resonator of the present invention and the method for manufacturing the same, but in particular, the following remarkable effects can be obtained. To be (1) Since the figurer-of-merit M ₁ of the fundamental mode vibration of the bending quartz crystal in the tuning fork shape is larger than the figurer-of-merit M _n of the harmonic mode vibration, the fundamental quartz mode vibrates with high frequency stability. A crystal oscillator is obtained. (2) The tuning fork shape and the groove can be formed by photolithography and chemical etching methods, which is excellent in mass productivity, and moreover, a large number of vibrators can be formed on one quartz wafer at a time by batch processing, so it is inexpensive. It is possible to obtain various crystal units. At the same time, an inexpensive crystal unit and crystal oscillator equipped with it can be realized. (3) The crystal oscillator is configured with a bending crystal oscillator having a tuning fork shape in which the figurer of merit M ₁ of the fundamental wave mode vibration is larger than the figurer of merit of the harmonic mode vibration M _n. It is possible to obtain a crystal oscillator having a high frequency stability while obtaining the frequency of wave mode vibration. That is, a crystal oscillator with high time accuracy can be realized.

[Brief description of drawings]

FIG. 1 is an external view of a tuning fork-shaped crystal unit vibrating in a bending mode according to a first embodiment of the present invention and its coordinate system.

2 is a cross-sectional view of the tuning fork base portion of the tuning fork-shaped bent crystal resonator of FIG.

FIG. 3 shows a top view of the tuning fork-shaped bent crystal unit of FIG.

FIG. 4 is a top view of a tuning fork-shaped crystal resonator vibrating in a bending mode according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of an embodiment of a crystal unit accommodating a tuning fork-shaped bent crystal oscillator according to the first embodiment or the second embodiment of the present invention.

FIG. 6 is an example of a crystal oscillation circuit diagram that constitutes a crystal oscillator in which a tuning fork-shaped bent crystal oscillator of the present invention is mounted.

FIG. 7 shows a feedback circuit diagram of FIG.

FIG. 8 is a cross-sectional view of an embodiment of a crystal oscillator equipped with a tuning fork-shaped bent crystal oscillator according to the first embodiment or the second embodiment of the present invention.

FIG. 9 shows a perspective view of a conventional tuning fork-shaped bent crystal unit and its coordinate system.

FIG. 10 is a cross-sectional view of a tuning fork arm of the tuning fork crystal oscillator shown in FIG.

[Explanation of symbols]

W ₂ Groove width W Arm width of tuning fork arm W ₁ , W ₃ Partial width of tuning fork arm W ₄ Distance between tuning fork arms W ₇ Part width including neutral line of tuning fork arm ₁ Groove length 1 ₂ Length of tuning fork base 1 Length of tuning fork-shaped bent crystal unit t Thickness of tuning fork arm or tuning fork arm and tuning fork base t ₁ Thickness of groove

Claims (2)

[Claims] 1. A tuning fork-shaped bent quartz crystal resonator comprising a tuning fork arm vibrating in a bending mode and a tuning fork base, wherein the tuning fork arm has an upper surface, a lower surface and a side surface, and the tuning fork shaped tuning fork. A groove is provided in the arm, an electrode is arranged on the side surface of the groove and the side of the tuning fork arm, an electrode on the side surface of the groove and an electrode on the side surface of the tuning fork arm that opposes the electrode have different polarities, and the tuning fork Configure the groove and electrode so that the arm vibrates in the opposite phase, and further,
A crystal resonator, wherein the tuning fork-shaped bent crystal resonator has a figurer of merit M ₁ of fundamental mode vibration larger than a figurer of merit M _n of harmonic mode vibration. 2. A method of manufacturing a tuning fork-shaped bent quartz crystal resonator comprising a tuning fork arm vibrating in a bending mode and a tuning fork base, wherein the tuning fork arm has an upper surface, a lower surface and a side surface. A groove is provided in the shaped tuning fork arm, electrodes are arranged on the side surfaces of the groove and the tuning fork arm, and an electrode on the side surface of the groove and an electrode on the side surface of the tuning fork arm opposite to the electrode have different polarities, and And a step of forming a groove and an electrode so that the tuning fork arm vibrates in an opposite phase, and a step of housing the tuning fork-shaped bent quartz crystal unit in a surface mount type or cylindrical type unit. method for manufacturing a quartz oscillator off Iga of merit M ₁ of the fundamental wave mode vibration shapes of the bent crystal oscillator, characterized in that greater than full Iga of merit M _n harmonic mode vibration.