JP3135279B2 - Torsional crystal oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cut angle and a side ratio R _zx (thickness / width) of a torsional quartz crystal resonator. In particular, miniaturization,
The present invention relates to a new-cut torsional crystal resonator that is most suitable as a reference signal source for watches, pagers, IC cards, mobile radios, and the like that require high precision, shock resistance, and low cost.

[0002]

2. Description of the Related Art A tuning fork-shaped bent crystal resonator and a vertical crystal resonator have been used as a crystal resonator having a frequency of 200 kHz to 600 kHz.

[0003]

However, since the tuning fork-type bent quartz crystal resonator conventionally used uses the harmonic mode, the formation of the electrodes is complicated and the vibration energy loss due to the support of the lead wire is large. As a result, problems such equivalent series resistance R ₁ increases had been left. on the other hand,
Since the frequency of the vertical crystal resonator is inversely proportional to the length of the vibrating arm, there has been a problem that the size of the vertical crystal resonator is naturally increased to realize a resonator of 600 kHz or less, and the size cannot be reduced. Therefore, the frequency is 200
There has been a demand for a new-cut crystal unit which is ultra-small, has a zero temperature coefficient at a frequency in the range of kHz to 600 kHz, and is easy to chemically etch.

[0004]

The present invention solves the conventional problem by the following method. That is, a quartz crystal vibrating in a torsional vibration mode, a Z-plate crystal perpendicular to the z-axis (optical axis) is defined by an angle φ =
The vibrator is formed from a quartz plate rotated by −90 ° to + 90 ° and further rotated by an angle θ = 10 ° to 80 ° around a new axis z ′ of the z-axis, and further, the thickness z _{0 of} the vibrator is formed. the ratio of the width x ₀ R _zx (z
_The problem is solved by forming ( ₀ / x ₀ ) from 0.1 to 1.5.

[0005]

As described above, the present invention is directed to a torsional quartz oscillator, and the cut angle (φ, θ) is set such that the Z plate is rotated around the x-axis by φ = −90.
゜ ～ + 90 ° rotate, and θ = 10 ° ～ around z 'axis
It rotates by 80 °, and the side ratio R _zx (thickness / width) is 0.1 from this plate.
By forming a vibrator having .about.1.5 by an etching method, a torsional crystal vibrator having a zero temperature coefficient can be obtained.

[0006]

Next, the present invention will be specifically described based on examples.
Bell. FIG. 1 shows a torsional crystal resonator 1 of the present invention and its coordinate system.
Is shown. Coordinate system is origin 0, electric axis x, mechanical axis y, optical axis z
To form 0-xyz. First, the thickness
z ₀, Width x₀, Length y₀And twist mode around the y-axis.
Torsional quartz resonator 1 having a
Place it to match the sheet crystal. Next, rotate the x axis and z 'axis.
Assuming that the counterclockwise rotation is positive as the axis of rotation, the angle φ =
−90 ° to + 90 °, θ = 10 ° to 80 °. Since then,
Is called a TT cut. Next, the primary temperature coefficient α
Cut angle (φ, θ) and side ratio R to be zero_zx(Thickness z₀/width
x₀).

FIG. 2 shows a cut angle (φ, θ) and a side ratio R when the first-order temperature coefficient α of the torsional quartz resonator according to the present invention becomes zero.
Relationship with _zx (a) and value of secondary temperature coefficient β at that time (b)
It is. Calculated values of θ = 0 °, 10 °, 20 °, 30 ° and θ = 10
The experimental values at ゜ and 30 ゜ are shown. It is well understood that in the range of θ = 0 ° to 30 °, α = 0 infinitely _{depending on} the combination of the side ratio R _zx in φ = −50 ° to + 60 °. When the cut angle θ = 10 °, the absolute value of β shows the minimum value near φ = 30 °. For example, when φ = 28 ° and θ = 10 °, α = 0, and β at that time is a calculated value of −1.16 × 10 ⁻⁸ / ° C. ² , and an experimental value of a tuning fork shape of −1.29 × 10 ⁻ The absolute value of ⁸ / ° C. ² and its absolute value was about 1/3 times that of the tuning-fork type bent quartz resonator, which was considerably smaller.

Further, even when φ = −42 ° and θ = 30 °, α = 0
Where β is a calculated value, −1.06 × 10−8 / ° C.2
It can be seen that the experimental value is -1.22 × 10 -8 / ° C.2, and in this case also, the absolute value of β is considerably small. φ = −50 ゜ ～ + 60
°, depending on the theta, beta is an approximation β = - 1.2 × 10-8
/ ° C2 to -3.7 × 10-8 / ° C2, the cut angle (φ, θ) and the side ratio Rzx, α = 0, and β
Is small, so that a tuning-fork type torsional quartz resonator having excellent frequency-temperature characteristics was obtained.

FIG. 3 shows the same relationship as that of the vibrator of FIG. 2 when the cut angle θ is further increased to θ = 40 °, 60 °, and 80 °. That is, (a) shows the relationship between the cut angle (φ, θ) when α = 0 and the side ratio R _zx, and (b) shows the value of the secondary temperature coefficient β at that time. In the range of θ = 40 ° to 80 °, there is no side ratio R _zx where α = 0 near φ = 35 °, but α = 0 in the range of φ = −90 ° to + 90 ° except for the vicinity. Where β is about −1.0 × 10 ⁻⁸ / ° C. ²
~ - 3.8 × 10 ^-8 / ℃ similarly to the case ² and theta = 0 ° to 30 °, the resulting tuning fork type torsional quartz crystal resonator having excellent frequency temperature characteristic. Thus, the cut angle φ = −90 ° to +90
The relationship of α = 0 is obtained by the combination of ゜, θ = 0 ° to 80 ° and the side ratio R _zx = 0.1 to 1.5. This typical situation is shown in FIGS. 4 and 5 below.

FIG. 4 shows the cut angle φ = 28 ° and θ =
An example of the frequency temperature characteristic at 10 ° is shown. The solid line is the calculated value, and the circles are the measured values. On the other hand, the broken line shows the frequency temperature characteristics in the bending mode. As already described with reference to FIG. 2, it can be clearly understood that the tuning-fork type torsional quartz resonator according to the present invention is much more excellent in frequency-temperature characteristics. FIG. 5 shows another embodiment of the frequency temperature characteristic when the cut angle φ = −40 ° and θ = 30 ° according to the present invention. As in the case of FIG. 4, it can be seen that a tuning-fork type torsional crystal resonator superior to the bending mode crystal resonator can be obtained.

Next, an electrode configuration for exciting the tuning-fork type torsional quartz crystal resonator of the present invention will be described. FIG. 6 shows a cross-sectional view (b) of a tuning-fork type torsional quartz crystal resonator 1 '(a) formed from a quartz plate having a cut angle (φ, θ) of the present invention and its electrode configuration. Terminals A and B indicate electrode terminals, and terminal A is electrode 2,
5, 7, 8 while terminal B is connected to electrodes 3, 4, 6,.
9 is connected. Piezoelectric constant exciting the torsional quartz crystal resonator 1 'of the present invention when the electrode configuration is e _16, below, shows the relationship between e ₁₆ and the cut angle (phi, theta).

FIG. 7 shows the relationship between the piezoelectric constant e ₁₆ and the cut angle φ when the cut angle θ is used as a parameter. θ = 0
In the case of ゜, it can be seen that e ₁₆ becomes zero at any cut angle φ, and it is not possible to excite the present torsional crystal resonator.
However, when gradually increasing the cut angle theta, the absolute value of e ₁₆ also gradually increases, indicating the maximum theta = 30 °. Although not shown, when θ is further increased, the absolute value of e ₁₆ gradually decreases, becomes minimum at θ = 60 °, and when further increased, the absolute value of e ₁₆ increases again. From this,
With the electrode configuration shown in the present invention, the torsional quartz crystal resonator with θ = 0 ° cannot be excited. When θ is less than 10 °, e ₁₆
Since the absolute value is very small, the equivalent series resistance R ₁ is not greater practical. Therefore, in the present invention, θ is set to 10 ° or more in order to obtain a small R ₁ . Next, the reason why the vibrator can be reduced in size will be described.

FIG. 8 is a graph _{showing the relationship} between the cut angle φ and the frequency constant (f · y ₀ ) when the cut angle θ of the tuning-fork type torsional quartz crystal resonator of the present invention having a side ratio R _zx = 0.8 is used as a parameter. Show the relationship. Although the frequency constant varies depending on the cut angle (φ, θ), the frequency constant is larger than 7.9 kHz · cm of the tuning fork type bent crystal resonator having a side ratio (width to length) of 0.1 to 80 to 97 kHz · cm,
It is smaller than 270 kHz · cm of the vertical crystal oscillator, and lies between the bending vibration and the vertical vibration. The tuning fork type torsional crystal oscillator of the present invention is particularly effective when the frequency is in the range of about 200 kHz to 600 kHz.

Next, representative values of electrical equivalent circuit constants of the tuning fork type torsional quartz crystal resonator of the present invention will be shown.

[0015]

[Table 1]

Table 1 shows that the cut angles φ = 0 ° and θ =
The representative values of the electrical equivalent circuit constants of the tuning fork type torsional quartz resonator at 30 °, φ = 26 °, and θ = 10 ° are shown. φ = 0 ゜, θ =
At 30 °, frequency f = 444.1 kHz and R ₁ = 2.2 k
Ω, Q = 378,000, while φ = 26 °, θ = 10 °
In _{f = 385.8kHz, R 1 = 14.4kΩ} , small Q = 276,000 and R _1, high oscillator Q factor is obtained. In addition, at other cut angles (φ, θ) of the present invention, R
It is clear from the value of e ₁₆ that ₁ and Q value are obtained.

[0017]

As described above, the provision of the TT-cut torsional quartz resonator of the present invention has the following remarkable effects. (1) Excellent because the primary temperature coefficient α becomes zero by the combination of the cut angle φ = −90 ° to + 90 °, θ = 10 ° to 80 ° and the side ratio R _zx = 0.1 to 1.5. FIG. (2) In particular, since there is a cut angle (φ, θ) and a side ratio R _zx where the secondary temperature coefficient β is about １ ／ times that of the tuning-fork type bent quartz crystal resonator, the frequency change with respect to temperature causes It becomes smaller due to longitudinal vibration. (3) Among the cut angles (φ, θ) of the present invention, φ = −55 ° to
At a cut angle of + 30 ° and θ = 10 ° to 80 °, it can be easily formed by an etching method, so that the size and thickness can be reduced. At the same time, a large number of transducers can be batch-processed on one wafer at a time, so that the cost can be reduced. (4) Since the frequency constant is between the tuning-fork type bent crystal resonator of the fundamental wave and the vertical crystal resonator, the frequency is from 200 kHz to 600 kHz.
Particularly effective at kHz. (5) At the same time, ultra-miniaturization is possible. By placing the excitation electrode (6) top and bottom surfaces of the vibrator, a small equivalent series resistance R _1, high torsional quartz crystal resonator Q value is obtained. (7) Since the vibrator is processed into a tuning fork shape, vibration energy loss due to support of a lead wire or the like is reduced, and a torsional crystal vibrator excellent in impact resistance can be obtained.

[Brief description of the drawings]

FIG. 1 shows a torsional crystal resonator of the present invention and its coordinate system.

FIG. 2 shows the relationship (a) between the cut angle (φ, θ) and the side ratio R _zx when the primary temperature coefficient α of the torsional quartz crystal resonator of the present invention becomes zero, and the secondary temperature coefficient β at that time. Value (b).

[3] first order temperature coefficient of the torsional quartz crystal resonator of the present invention α cut angle Rutoki such to zero (φ, θ) and the relationship between the Henhi Rzx (a) and the secondary temperature coefficient β when the Value (b).

FIG. 4 is an embodiment of a frequency-temperature characteristic of the tuning-fork type torsional quartz crystal resonator of the present invention.

FIG. 5 is another embodiment of the frequency-temperature characteristics of the tuning-fork type torsional quartz crystal resonator of the present invention.

FIG. 6 shows a tuning-fork type torsional crystal resonator (a) formed from a crystal plate having a cut angle (φ, θ) according to the present invention, and a sectional view (b) of the electrode configuration thereof.

FIG. 7 shows the relationship between the piezoelectric constant e ₁₆ and the cut angle φ when the cut angle θ of the present invention is used as a parameter.

FIG. 8 is a graph showing the relationship between a cut angle φ and a frequency constant (f ·
y ₀ ).

[Explanation of symbols]

1 torsional quartz crystal resonator 1 'tuning fork type torsional quartz crystal resonator 2-9 excitation electrodes A, B electrode terminals x ₀ thickness length z ₀ resonator width y ₀ the vibration of the vibrating portion _phi, theta cut angle x electric axis y Mechanical axis z Optical axis

Continuation of the front page (56) References JP-A-1-236808 (JP, A) JP-A-54-138394 (JP, A) JP-A-54-100688 (JP, A) JP-A-53-91688 (JP) JP-A-2-131008 (JP, A) JP-A-2-112123 (JP, A) JP-A-64-58108 (JP, A) JP-B-62-46093 (JP, B2) JP-B-sho 62-46092 (JP, B2) JP-B 61-60611 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00-9/215

Claims (1)

(57) [Claims] 1. A quartz crystal vibrating in a torsional vibration mode, wherein a Z-plate crystal perpendicular to the z-axis (optical axis) is rotated about the x-axis (electric axis) at an angle φ = −90 ° to + 90 °. Rotate, and further around a new axis z ′ axis of the z axis, an angle θ = 10 ° to 8
A quartz plate rotated by 0 ° , and
The ratio R _zx (z ₀ / x ₀ ) of the thickness z ₀ to the width x ₀ is from 0.1 to 1.
5. A torsional crystal resonator characterized in that: