JP2003273695A - Crystal unit and crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal unit equipped with a microminiaturized tuning fork shaped bent crystal vibrator in which equivalent serial resistance R<SB>1</SB>is small and the Q value of a quality factor is high, and a crystal oscillator in which an output signal has high frequency stability in the frequency of basic wave mode vibration. <P>SOLUTION: In the tuning fork shaped bent crystal vibrator, a tuning fork arm and a tuning fork base are provided, grooves or through holes are provided on the upper and lower faces of the tuning fork arm or of the tuning fork arm and the tuning fork base, electrodes are located on the lateral sides of the grooves or through holes, and electrodes of different polarities are arranged on the lateral side of the tuning fork arm in opposition to the electrodes. In the crystal unit, the figure-of-merit of basic wave mode vibration becomes greater than the figure-of-merit of higher harmonic wave mode vibration. At the same time, the crystal vibrator in which the output signal is in the frequency of a basic wave mode on the basis of the relation of the amplification factor of an amplifier circuit and the feedback rate of a feedback circuit is realized with higher precision. <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 crystal oscillator having a tuning fork-shaped crystal unit consisting of a tuning fork arm and a tuning fork base which vibrate in a bending mode, a crystal unit consisting of a case and a lid, an amplifier circuit and a feedback circuit. In particular, with a crystal unit and crystal oscillator that are optimal as a reference signal source for information communication equipment that is strongly required to be compact, highly accurate, shock resistant, and inexpensive,
A crystal unit composed of an ultra-small tuning fork-shaped bent crystal unit having a new shape, new electrode configuration, and optimum dimensions,
The present invention relates to a crystal oscillator in which the frequency of fundamental mode vibration is an output signal.

[0002]

2. Description of the Related Art A conventional crystal unit is composed of a case, a lid, a tuning fork type bent crystal oscillator having electrodes arranged on the upper and lower surfaces and side surfaces of a tuning fork arm, and a crystal oscillator is an amplifier, a capacitor, a resistor and a tuning fork arm. A well-known crystal oscillator is composed of a tuning fork type bent crystal oscillator in which electrodes are arranged on the upper and lower surfaces and side surfaces. FIG. 9 shows a tuning fork-shaped bent crystal unit 200 used in the crystal unit and crystal oscillator of this conventional example.
Fig. In FIG. 9, the crystal oscillator 200 includes two tuning fork arms 201 and 202 and a tuning fork base portion 230. 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. Electrode 205 on the side
And 206 are provided. Electrode 207 is on the upper surface of the other tuning fork arm, electrode 208 is on the lower surface, and electrode 2 is on the side surface.
09 and 210 are arranged to form a two-electrode terminal H-H 'structure. 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. Further, JP-A-56-65517 and JP-A-2000-223992 (P2000-223992)
In A), a groove is provided on the tuning fork arm and an electrode structure is disclosed.

[0003]

In the tuning fork type bent crystal resonator, the loss equivalent series resistance R ₁ increases as the electric field component Ex increases.
Becomes smaller and the quality factor Q value becomes larger. However, as shown in FIG. 10, the conventional tuning fork-shaped bent crystal oscillator has electrodes arranged on the upper and lower surfaces and side surfaces of each tuning fork arm. For this reason, the electric field does not act linearly, and when the tuning fork type bent crystal oscillator is downsized, the electric field component Ex becomes small, the loss equivalent series resistance R ₁ becomes large, and the quality factor Q value becomes small. Was left unsolved. 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, Japanese Patent Application Laid-Open No. 56-65517 discloses a groove on a tuning fork arm and a groove structure and an electrode structure. However, regarding the configuration, size and vibration mode of the groove, the relationship between the equivalent series resistance R ₁ in the fundamental mode vibration and the equivalent series resistance R _n in the harmonic mode vibration, and the Figer of Merit M related to the frequency stability, Not disclosed at all. At the same time, if the oscillator provided with the groove is connected to a conventional circuit to configure a crystal oscillation circuit, the output signal of the fundamental mode vibration will be changed to the frequency of the harmonic mode vibration due to the impact such as shock or vibration. Problems such as change and detection occurred. Due to this, even if shock or vibration is received,
A crystal unit and a crystal oscillator having a tuning fork-shaped bent crystal oscillator that vibrates in a fundamental mode in which harmonic mode vibrations that are not affected by them are suppressed have been desired. further,
In order to reduce the current consumption of the crystal oscillator, the load capacitance _CL
If the value is reduced, vibrations in higher harmonic modes are likely to occur, and there remains a problem that the output frequency of fundamental mode vibrations cannot be obtained. 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. There has been a demand for a crystal oscillator having a bent crystal oscillator of (1) above and having an output signal at the frequency of fundamental mode vibration and high frequency stability (high time accuracy). At the same time, a crystal oscillator with low current consumption has been desired.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crystal unit and a crystal oscillator having a tuning-fork-shaped crystal resonator that vibrates in a bending mode, which has advantageously solved the conventional problems by the following method. It is what

That is, a first aspect of the crystal unit of the present invention is a crystal unit comprising a crystal resonator, a case and a lid, wherein the crystal resonator vibrates in a bending mode and a tuning fork arm and a tuning fork base. The tuning fork arm has a top surface, a bottom surface and a side surface, a groove is provided on the top surface and the bottom surface of the tuning fork shape tuning fork arm, and an electrode is provided on the side surface of the groove. The electrodes on the side surface of the groove and the electrodes on the side surface of the tuning fork arm opposite to the electrode are of different polarities, and the groove and the electrode are configured so that the tuning fork arm vibrates in the opposite phase, The bending crystal unit is housed in a surface-mounted or cylindrical unit, and the figurer-of-merit M ₁ of the fundamental mode vibration of the tuning-fork-shaped bending-quartz unit is the figurer-of-merit M of the harmonic mode vibration. greater than _n It is a crystal unit.

A first aspect of the crystal oscillator of the present invention 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 crystal resonator and a capacitor. With an oscillator,
The crystal unit is composed of a tuning-fork-shaped bending crystal unit 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 lower surface, and a side surface, and the upper surface of the tuning fork-shaped tuning fork arm. And a groove is provided on the lower surface, an electrode is arranged on the side surface of the groove, 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 of different polarities, and the tuning fork arm is in opposite phase. A groove and an electrode are configured to vibrate, and the tuning fork-shaped bent crystal oscillator is housed in a surface-mounting or cylindrical unit, and a finger for vibrating the fundamental wave mode of the tuning fork-shaped bent crystal oscillator. Amplification of the crystal oscillator, in which the crystal oscillator is configured to include a bending crystal oscillator in which Obmerit M ₁ is larger than the harmonicer mode vibration Figer of Merit M _n , and an amplifier circuit and a feedback circuit. Circuit Absolute value of the negative resistance of the wave mode vibration | -RL 1 _| and the fundamental mode absolute value of the negative resistance of the harmonic mode vibration of the ratio of the equivalent series resistance R ₁ of the vibration amplifier | -RL _n | And the equivalent series resistance R _n of the harmonic mode vibration is greater than the ratio, and the output signal of the crystal oscillator configured with the tuning fork-shaped bent crystal oscillator is basically It is a crystal oscillator having a frequency of wave mode vibration.

[0007]

As described above, the present invention provides a crystal unit and a crystal oscillator having a tuning-fork-shaped crystal unit that vibrates in a bending mode, and further improves the configuration of the tuning-fork-shaped groove and electrode, and an amplifier circuit and a feedback circuit. It is possible to obtain a crystal oscillator that suppresses the second harmonic vibration and outputs a frequency that vibrates in the fundamental wave vibration mode.

[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. At the same time, the load capacitance of the feedback circuit can be reduced. As a result, a crystal oscillator with low current consumption 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 is an embodiment of a crystal oscillation circuit diagram constituting a crystal oscillator of the present invention. In this embodiment, the crystal oscillation circuit 1 is an amplifier (CMOS inverter).
2, feedback resistor 4, drain resistor 7, capacitors 5, 6
And a bent crystal oscillator 3 having a tuning fork shape. That is, the crystal oscillating circuit 1 comprises an amplifier circuit 8 including an amplifier 2 and a feedback resistor 4, a drain resistor 7, capacitors 5, 6 and a feedback circuit 9 including a bent crystal oscillator 3. More specifically, the crystal oscillator of the present invention 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 the present invention will be described in detail with reference to FIGS.

FIG. 2 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. Further, the load capacitance C _L is C _L = C _g C _d /
Given by (C _g + C _d ), C _g = C _d = C _gs and Rd
>> When _{R ei,} feedback factor β _i is _{β i = 1 / (1 +} k
C _L ² ). However, k is ω _i , R _d , R _ei
It is represented by the function of. 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 , as 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 second 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.

It is an object of the crystal oscillator of the present invention to provide a crystal oscillator having a fundamental mode vibration, which has low power consumption and high frequency stability (high time accuracy). . Therefore, in order to reduce the current consumption, the load capacitance C _L is 18 pF or less. In order to further reduce the current consumption, C _L = 14 pF or less is preferable because the current consumption is proportional to the load capacitance. The capacitances C _g and C _{d mentioned} here are numerical values including the stray capacitance of the circuit. Further, in order to suppress the vibration of the harmonic mode and obtain the frequency of the fundamental mode vibration, the output signal of the oscillator satisfies α ₁ / αn> βn / β ₁ and α ₁ β ₁ > 1 in the present embodiment. The oscillator circuit is constructed. However, α ₁ ,
α _n is the amplification factor of the amplification circuit for the fundamental mode vibration and the harmonic mode vibration, and β ₁ and β _n are the feedback factors of the feedback circuit for the fundamental mode vibration and the harmonic mode vibration.

In other words, the ratio between the amplification factor α ₁ of the fundamental mode vibration of the amplifier circuit and the amplification factor α _n of the harmonic mode vibration is the feedback factor β _n of the harmonic mode vibration of the feedback circuit and the fundamental mode. greater than the ratio of the feedback factor beta ₁ of the vibration, and the product of the feedback factor beta ₁ amplification factor alpha ₁ and the fundamental mode vibration of the fundamental wave mode vibration is configured to be greater than 1. With such a configuration, it is possible to realize a crystal oscillator that consumes less current and has an output signal of a frequency of fundamental mode vibration.
The frequency is the reference frequency of the bent crystal oscillator or the frequency obtained by dividing the reference frequency. Further, high frequency stability will be described later. The output signal is output from the drain side via the buffer.

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 nth harmonic mode vibration.
n takes a numerical value of 2, 3 ... But here, simply,
Say negative resistance -RL _n of the harmonic mode vibration. In the crystal oscillator of this embodiment, the ratio between the absolute value of the negative resistance | -RL ₁ | of the fundamental mode vibration of the amplifier circuit and the equivalent series resistance R ₁ of the fundamental mode vibration is the harmonic mode vibration of the amplifier circuit. the absolute value of the negative resistance | -RL n _| and the oscillation circuit to be greater than the ratio of the equivalent series resistance R _n of the harmonic mode vibration is formed. That is, | -RL ₁ | / R ₁ > | -RL _n | / R _n
Is configured to satisfy. With such a configuration of the crystal oscillation circuit, the oscillation start of the harmonic mode vibration can be suppressed, so that the frequency of the fundamental wave mode vibration can be obtained as the output signal.

FIG. 3 is an external view of a tuning fork-shaped bent crystal oscillator 10 vibrating in a bending mode used in the crystal unit or crystal oscillator of 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 oscillator 10 according to the present embodiment includes a tuning fork arm 20, a tuning fork arm 26, and a tuning fork base 40, and the tuning fork arm 20 and the tuning fork arm 26 are connected to the tuning fork base 40. Also, tuning fork arm 20 and tuning fork arm 2
6 has 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, so as to include the neutral line, and a groove 27 is provided on the upper surface of the tuning fork arm 26 as with the tuning fork arm 20. Further, the tuning fork base portion 40 is provided with a groove 32 and a groove 36. The angle θ is a rotation angle around the x-axis, and is usually 0.
It is selected in the range of -10 °. Further, grooves are provided on the lower surfaces of the tuning fork arms 20 and 26 as well as the upper surfaces.

FIG. 4 is a cross-sectional view of the tuning fork base portion 40 of the bending quartz crystal resonator 10 of FIG. 4, the cross-sectional shape and electrode arrangement of the tuning fork base 40 of the crystal unit shown in FIG. 3 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. 5 is a tuning fork-shaped bent crystal unit 1 of FIG.
0 is a top view of FIG. In FIG. 5, 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 works in the tuning fork-shaped bent quartz 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.

Further, when the partial widths W ₁ and W ₃ and the groove width W ₂ are set, the arm width W of the tuning fork arms 20 and 26 is W = W ₁ + W ₂ + W ₃
Is given, and usually, some or all of W ₁ and W ₃ are W ₁ ≧
It is configured such that W ₃ or W ₁ <W ₃ . or,
The groove width W ₂ is formed under the condition that W ₂ ≧ W ₁ and W ₃ are satisfied. 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,
It is preferably 0.35 to 0.
At 95, 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 smaller than 0.79, preferably 0.01 to 0. A groove is formed in the tuning fork arm so as to be 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.

On the other hand, regarding the length l ₁ of the groove 21 and the groove 27, in this embodiment, the grooves 21 and 27 have the tuning fork arm 2
It is dimensioned to extend from 0, 26 to the length l ₂ of the tuning fork base 40 and to have the groove length l ₃ of the base. Therefore, the length of the groove provided in the tuning fork arms 20 and 26 is (l ₁ −
l ₃ ), to obtain an oscillator with a small R ₁ ,
_{(L 1 -l 3) / (} l-l 2) it has a value of 0.4 to 0.8. Further, the total length l of the tuning fork-shaped bent crystal unit 10
Is determined by the required frequency and the size of the storage container. At the same time, in order to obtain a bent quartz oscillator having a good tuning fork shape that vibrates in the fundamental mode, there is a close relationship between the groove length l ₁ and the groove length l ₁ .

That is, the tuning fork arm 20, 26 or the tuning fork arm 2
0, 26 and the length l _{1 of the} groove provided in the tuning fork base 40 and the total length 1 of the bending fork-shaped quartz crystal in the tuning fork shape (l ₁ / l) are set so that the ratio is 0.2 to 0.78. Is provided.
The reason for forming in this way is unnecessary vibration in particular.
Second-order and third-order harmonic vibrations can be suppressed and the frequency stability of fundamental-mode vibration can be improved. 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 crystal oscillator vibrating in the fundamental mode is smaller than the equivalent series resistance R _n in the harmonic mode vibration. That is, R ₁ <R _n (when n = 2, 3
In the crystal oscillator including the amplifier (CMOS inverter), the capacitor, the resistor, and the tuning fork-shaped bent crystal oscillator of the present embodiment, the oscillator is in the fundamental wave mode. A good crystal oscillator that vibrates easily can be realized. The length l _{1 of the} groove may be divided in the length direction of the tuning fork arm, and at least one of them may satisfy the side ratio (l ₁ / l) or is divided. It is sufficient that the length of the added groove in the length direction of the groove satisfies the side ratio (l ₁ / l).

In this embodiment, the tuning fork base 40 is the entire lower part of the length l ₂ of the vibrator 10 in FIG.
Further, the tuning fork arm 20 and the tuning fork arm 26 are the vibrator 10 in FIG.
From the length l ₂ portion to the entire upper portion. 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 l ₃ = 0. The groove length l ₁ in the present invention means the ratio of the groove width W ₂ to the tuning fork arm width W (W ₂ / when the groove is provided only on the tuning fork arm.
W) is the length of the groove formed so as to be larger than 0.35 and smaller than 1. Further, when the groove provided on the tuning fork arm extends to the tuning fork base, and further grooves are provided between the grooves extending to the tuning fork base, the length including the groove length l ₃ is It is l ₁ . However, if the groove of the tuning fork arm extends into the tuning fork base, but no further groove is provided between the grooves, the length l ₁ is the length of the groove of the tuning fork arm.

In other words, at least one groove is provided in the longitudinal 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 so as to have different polarities, and each of them is configured 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.

Further, the spacing between the tuning fork arms of this embodiment is given by W ₄ , and the spacing W ₄ and the groove width W ₂ are configured so as to satisfy W ₄ ≧ W ₂ , and the spacing W ₄ is 0.05 mm or more. 0.35 mm
The groove width W ₂ has a value of 0.03 mm to 0.12 mm. 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 the second harmonic mode vibration. in this case,
A crystal wafer having a thickness t of usually 0.05 mm to 0.12 mm is used. However, the present invention is not limited to this embodiment, and a quartz wafer having a thickness of more than 0.12 mm may be used.

[0026] If More specifically, the ratio of full Iga of merit M _i is the quality factor Q _i value and the capacitance ratio r _i representing the inductive electromechanical conversion efficiency and the quality factor of the flexural crystal resonator (Q _i
/ R _i ) (fundamental oscillation when i = 1,
(2nd harmonic vibration when i = 2, 3rd harmonic vibration when i = 3), mechanical series resonance frequency f _s that does not depend on the parallel capacitance of the bent crystal oscillator, and series resonance frequency f that depends on the parallel capacitance. The frequency difference Δf of _r is inversely proportional to the Figer-of-merit M _i , and the larger the value M _{i, the} smaller Δf. Therefore, as M _i is larger, the resonance frequency of the bent crystal unit is not affected by the parallel capacitance, and the frequency stability of the bent crystal unit is improved. 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, and the dimensions thereof, the figurer of merit M ₁ of fundamental mode vibration is the figurer of merit M ₂ and M _{3 of second} and _third harmonic mode vibration. Get bigger. That is, M ₁ > M _n . However, M _n is a figurer of merit of harmonic mode vibration. As an example, the frequency of the fundamental mode vibration is 32.768 kHz, W ₂ /W=0.5, t ₁ / t =
When 0.34, l ₁ /l=0.48, variations due to production occur, but M ₁ and M of the tuning fork-shaped bent crystal oscillator
₂ and M ₃ are M ₁ > 65, M ₂ <30, and M ₃ <1 respectively.
It becomes 8. That is, it is possible to obtain a bent quartz oscillator having high inductive property and good electromechanical conversion efficiency (small equivalent series resistance R ₁ ) and vibrating in a fundamental wave mode having a large quality factor. As a result, the frequency stability of the fundamental mode vibration becomes better than the frequency stability of the second and third harmonic mode vibrations, and the second and third harmonic mode vibrations can be suppressed. 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.

FIG. 6 is a top view of a tuning fork-shaped crystal oscillator 45 that vibrates in a bending mode used in the crystal unit or crystal oscillator of 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, one end of each tuning fork arm 46, 47 is connected to the tuning fork base 48. In this embodiment,
Notch portions 53 and 54 are provided in the tuning fork base portion 48. Further, the tuning fork arms 46 and 47 are provided with grooves 49 and 50 sandwiching (including) the neutral lines 51 and 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 and a length l _{1 respectively.}
Have. More specifically, the groove area S = W ₂ × l
₁ and S is configured to have a value of 0.025 to 0.12 mm ² . 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 unit including the crystal oscillator and a crystal oscillator in which an output signal has a frequency of fundamental mode vibration.

With the groove area S, 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. In addition, 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 an adhesive, W ₆ ≧ W ₅ is set in order to reduce the vibration energy loss of the vibrator. Need to meet. Further, the cutout portions 53 and 54 can also reduce the energy loss of the vibrating portion due to the fixing of the vibrator. The relationship between the arm width W of the tuning fork arm shown in FIG. 6, the partial widths W ₁ and W ₃ , the groove width W ₂ , the interval W _{4, the} groove length ₁₁ and the total length ₁ of the tuning fork vibrator is shown in FIG. Since it has been described above, it is omitted here.

FIG. 7 is a sectional view of a crystal unit according to the third embodiment of the present invention or a sectional view of a crystal unit used in a crystal oscillator according to the third embodiment. 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 the present embodiment, the oscillator 70 is the same oscillator as one of the tuning fork-shaped crystal oscillators 10 and 45 that oscillates in the bending mode described in detail in FIGS. 3 and 6. In the crystal oscillator of this embodiment, 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.

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 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. 8 is a sectional view of a crystal oscillator according to the fourth embodiment of the present invention. The crystal oscillator 190 includes a crystal oscillation circuit, 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 oscillator circuit comprises 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).
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 the 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 with reference to FIGS. 3 and 6 are used.

Next, a method of manufacturing the crystal unit and the crystal oscillator 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 on the upper and lower surfaces of a crystal wafer that has been polished or polished by a sputtering method or a vapor deposition method. 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.

According to 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.

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 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 step, a defective oscillator can be found early and the next step does not flow, so that 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 serving as a case and a lid in a vacuum to obtain a crystal unit. When the lid is made of glass, the third frequency adjustment is performed by the laser after the housing. In this step, the frequency adjustment is performed so that the frequency deviation is within the range of -50PPM to + 50PPM. 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, it is not necessary to adjust the frequency in the third 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 resistor. In other words, the amplifier circuit is composed of a CMOS inverter and a feedback resistor, and the feedback circuit is connected so as to be composed of a tuning fork-shaped bent crystal oscillator, a drain resistor, a gate side capacitor and a drain side capacitor. The third frequency adjustment may be performed after the crystal oscillation circuit is constructed.

Although the invention has been described above with reference to the illustrated example, the invention is not limited to the above-described example, and the bent fork-shaped crystal resonator used in the crystal oscillator of the first to fourth embodiments is used. In the above, a groove is provided in the tuning fork arm or the tuning fork arm and the tuning fork base. For example, a through hole (t ₁ = 0) is provided in the tuning fork arm.
May be provided. That is, the through hole is a special case of the groove, and the groove of the present invention includes the through hole.

Further, in the present 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 crystal oscillators of the first to fourth embodiments and the tuning fork-shaped bent crystal oscillators used therein have been described. The crystal oscillators used in the crystal oscillators of these examples are cases. It is housed in a so-called unit composed of a lid and constitutes a crystal unit. That is, the vibrator of the present embodiment is fixed to the fixing portion provided on the case or the lid by a conductive adhesive or solder or the like, and the case and the lid are joined via a joining member, The inside of the case is configured to be a vacuum.
With this configuration, it is possible to realize a microminiature crystal unit having a small equivalent series resistance R ₁ .

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

[0044]

As described above, by providing the crystal unit and the crystal oscillator according to the present invention, many effects can be obtained. Among them, the following remarkable effects can be obtained. (1) Since a plurality of grooves are provided in the tuning fork arm or the tuning fork arm and the tuning fork base, and electrodes having different polarities are arranged on their side surfaces, the electric field works vertically. As a result, since the electromechanical conversion efficiency is improved, a crystal unit and a crystal oscillator having a tuning fork-shaped bent crystal oscillator having a small equivalent series resistance R _{1 and} a high quality factor Q value can be obtained. (2) The moment of inertia is increased by optimizing the relationship between the groove width, the tuning fork arm width dimension, the groove thickness, and the tuning fork arm thickness dimension. That is, the equivalent series resistance R ₁ is small,
A crystal unit and a crystal oscillator having a tuning fork-shaped bent crystal oscillator having a high Q value and a small capacitance ratio can be realized. (3) fork fundamental off Iga of merit M ₁ mode vibration is secondary oscillator shape, the third harmonic mode vibration of full Iga of merit M _2, crystal oscillator comprises a M ₃ Ri large vibrator The absolute value | −RL ₁ | of the negative resistance of the fundamental mode vibration and the equivalent series resistance R ₁ of the fundamental mode vibration of the amplification circuit of the crystal oscillator configured to further include the amplification circuit and the feedback circuit. The load capacitance is larger than the ratio between the absolute value of negative resistance | -RL _n | of harmonic mode vibration of the amplifier circuit and the equivalent series resistance R _n of harmonic mode vibration of the amplifier circuit. Even if is small, the output signal of the crystal oscillator can obtain the frequency of the fundamental mode vibration as an output, and a crystal oscillator with low current consumption can be realized. (4) The tuning fork shape and groove can be formed by photolithography and chemical etching methods, which is excellent in mass productivity, and moreover, because a large number of vibrators can be formed on one quartz wafer at a time by batch processing, it is inexpensive. It is possible to obtain a bending quartz oscillator having a simple tuning fork shape. At the same time, an inexpensive crystal unit and crystal oscillator equipped with it can be realized. (5) Figuer-of-merit M ₁ of fundamental mode vibration is the figurer-of-merit M ₁ of second and third harmonic mode vibration
_Since the crystal oscillator is configured with a vibrator larger than M ₂ and M ₃ , it is possible to realize a crystal oscillator in which the output signal has the frequency of fundamental mode vibration and has high frequency stability. That is, a crystal oscillator having high time accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is an embodiment of a crystal oscillation circuit diagram constituting a crystal oscillator of the present invention.

FIG. 2 shows a feedback circuit diagram of FIG.

FIG. 3 is a crystal unit or a first embodiment of the present invention.
The external view of the tuning fork-shaped crystal oscillator vibrating in the bending mode used for the crystal oscillator of the embodiment and its coordinate system are shown.

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

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

FIG. 6 is a crystal unit or a second embodiment of the second embodiment of the present invention.
FIG. 3 is a top view of a tuning fork-shaped crystal resonator that vibrates in a bending mode used in the crystal oscillator of the example.

FIG. 7 is a sectional view of a crystal unit according to a third embodiment of the present invention or a sectional view of a crystal unit used in a crystal oscillator according to the third embodiment.

FIG. 8 shows a sectional view of a crystal oscillator according to a fourth 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]

1 amplifier circuit 9 feedback circuit V ₁ input voltage V ₂ output voltage 20, 26, 46, 47 tuning fork arm W ₂ groove width W tuning fork arm width W ₁ , W ₃ tuning fork arm partial width W ₄ tuning fork arm interval l Length of ₁ groove ₁ Length of ₂ tuning fork base 1 Total length of tuning fork-shaped bent crystal unit t Thickness of tuning fork arm or tuning fork arm and tuning fork base t ₁ Groove thickness

Claims (2)

[Claims] 1. A crystal unit comprising a crystal unit, a case, and a lid, wherein the crystal unit comprises a tuning fork-shaped bent crystal unit including 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 on the upper surface and the lower surface of the tuning fork-shaped tuning fork arm, an electrode is arranged on a side surface of the groove, and an electrode on the groove side surface and the electrode are provided. The electrodes and the electrodes on the side of the tuning fork arm that oppose each other have polarities different from each other, and the groove and the electrode are configured so that the tuning fork arms vibrate in the opposite phase. A crystal unit housed in a unit, wherein the tuning fork-shaped bent quartz 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 crystal oscillator comprising an amplifier circuit and a feedback circuit, the amplifier circuit comprising at least an amplifier, the feedback circuit comprising at least a crystal oscillator and a capacitor, wherein the crystal oscillator is in a bending mode. The tuning fork arm is composed of a tuning fork-shaped bent crystal unit including a tuning fork arm and a tuning fork base, and the tuning fork arm has an upper surface, a lower surface, and a side surface, and a groove is provided on the upper surface and the lower surface of the tuning fork shape tuning fork arm. An electrode is disposed on the side surface of the groove, the electrode on the side surface of the groove and the electrode on the side surface of the tuning fork arm opposite to the electrode are of different polarities, and the groove is formed so that the tuning fork arm vibrates in an opposite phase. constitutes an electrode, the bent crystal oscillator of the tuning fork is being housed in the unit of the surface-mounted type or a cylindrical type, the tuning fork fundamental mode oscillation of full Iga of merit M ₁ of flexural crystal oscillator shape high With wave modes oscillating in full Iga of merit M _n greater flexural quartz crystal vibrator comprising by the crystal oscillator is constructed, fundamental mode oscillation of amplifier circuit configured the crystal oscillator comprises an amplifier circuit and a feedback circuit Of the absolute value of negative resistance | -RL ₁ | of the fundamental mode vibration and the equivalent series resistance R ₁ of fundamental mode vibration of the absolute value of the negative resistance of harmonic mode vibration of the amplifier circuit | -RL _n | The crystal oscillator is configured so as to be larger than the ratio of vibration to the equivalent series resistance R _n, and the output signal of the crystal oscillator configured to include the tuning fork-shaped bent crystal oscillator is the fundamental mode vibration. A crystal oscillator characterized by a frequency.