JP2013225937A - Quartz vibrator, quartz unit, quartz oscillator and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quartz vibrator, a quartz unit, a quartz oscillator and a manufacturing method thereof.SOLUTION: A manufacturing method of a tuning fork quartz vibrator is provided. In the tuning fork quartz vibrator, a first groove and a second groove are formed at both sides of a neutral line on at least one of a top face and a bottom face of each of a first tuning fork arm and a second tuning fork arm. The manufacturing method of the quartz vibrator includes a step for determining dimensions of the first groove and the second groove to have a relation that, when a distance between the first groove and the second groove in a width direction is defined as a partial width W, the partial width Wis smaller than 0.05 mm, a groove width of each of the first groove and the second groove is smaller than 0.04 mm and a ratio (t/t) of thickness tof each of the first groove and the second groove and thickness (t) of the tuning fork arm is smaller than 0.79 such that a figure-of-merit Mof basic wave mode vibration of the tuning fork quartz vibrator becomes larger than figure-of-merit Mof secondary higher harmonic wave mode vibration.

Description

  The present invention relates to a crystal unit composed of a tuning fork-shaped quartz crystal resonator composed of a tuning fork arm and a tuning fork base, a case and a lid, a manufacturing method thereof, a crystal oscillator composed of an amplifier circuit and a feedback circuit. In particular, it is a crystal unit and crystal oscillator that are optimal as a reference signal source for information communication equipment that is strongly demanded for miniaturization, high accuracy, impact resistance, and low cost. Ultra-compact with new shape, new electrode configuration and optimum dimensions. The present invention relates to a crystal unit comprising a tuning fork-shaped bent crystal resonator and a crystal oscillator whose fundamental mode vibration frequency is an output signal.

The conventional crystal unit is composed of a tuning fork-type bending crystal unit with electrodes placed on the upper, lower, and side surfaces of the case, lid, and tuning fork arm. The crystal oscillator is composed of an amplifier, capacitor, resistor, upper and lower surfaces and side surface of the tuning fork arm. A crystal oscillator composed of a tuning-fork type bending crystal resonator in which an electrode is disposed on the crystal is well known. FIG. 9 shows an overview of a tuning-fork-shaped bent quartz crystal resonator 200 used in this conventional crystal unit and crystal oscillator. In FIG. 9, the crystal unit 200 includes two tuning fork arms 201 and 202 and a tuning fork base 230. FIG. 10 shows a cross-sectional view of the tuning fork arm of FIG. As shown in FIG. 10, the excitation electrodes are disposed 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 disposed on the upper surface of the cross-section of one tuning fork arm, and an electrode 204 is disposed on the lower surface. Electrodes 205 and 206 are provided on the side surfaces. An electrode 207 is arranged on the upper surface of the other tuning fork arm, an electrode 208 is arranged on the lower surface, and electrodes 209 and 210 are arranged on the side surfaces to form a two-electrode terminal HH ′ structure. Now, 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 is bent inward, the other tuning fork arm is also bent inward. This is because the direction of the electric field component Ex in the x-axis direction is opposite in each tuning fork arm. By applying an alternating voltage, vibration can be sustained. JP-A-56-65517 and JP-A-2000-223992 (P2000-223992A) disclose a tuning fork arm with a groove and an electrode configuration.
JP-A-56-65517 2000-223992 International Publication No. 00/44092

The tuning-fork type flexural quartz crystal resonator, the more the electric field component Ex is greater losses equivalent series resistance R ₁ becomes smaller, the quality factor Q value increases. However, in the tuning fork-type bent quartz crystal resonator that has been conventionally used, as shown in FIG. 10, 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, and if the tuning fork type bent quartz resonator is reduced in size, the electric field component Ex becomes smaller, the loss equivalent series resistance R ₁ becomes larger, the quality factor Q value becomes smaller, etc. The problem was left. At the same time, there remains a problem to obtain a bent crystal resonator that has high accuracy as a time reference, that is, has high frequency stability and suppresses harmonic mode vibration. As a method for solving the above-mentioned problem, for example, Japanese Patent Laid-Open No. 56-65517 discloses a groove on a tuning fork arm, and discloses a groove structure and an electrode structure.

However, with regard to the structure of the groove, dimensions and vibration modes, the relation 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 FIG. It is not disclosed at all. At the same time, when the vibrator with the groove is connected to a conventional circuit to form a crystal oscillation circuit, the output signal of the fundamental vibration mode becomes the frequency of the harmonic mode vibration due to the impact or vibration. Problems such as changes and detection occurred. For this reason, a crystal unit and a crystal oscillator having a tuning-fork-shaped bent quartz crystal that vibrates in the fundamental wave mode that suppresses harmonic mode vibration that is not affected by shock or vibration are desirable. It had been. Furthermore, in order to reduce the current consumption of the crystal oscillator, and to reduce the load capacitance C _L liable to vibration harmonic mode, problems such as not to obtain the output frequency of the fundamental mode oscillation has been left. Therefore, a tuning fork shape that has an ultra-small size that vibrates in the fundamental mode, a small equivalent series resistance R _1, a high quality factor Q value, a groove configuration and an electrode configuration with good electromechanical conversion efficiency. Therefore, there has been a demand for a crystal oscillator that has a bent crystal resonator, an output signal having a fundamental mode vibration frequency, high frequency stability (high time accuracy), and low current consumption.

  An object of the present invention is to provide a tuning fork-shaped quartz crystal vibrator that vibrates in a bending mode, which advantageously solves the conventional problems by the following methods, a quartz unit including the quartz vibrator, and a method for manufacturing each quartz oscillator. It is.

That is, the first aspect of the method for manufacturing a crystal resonator according to the present invention includes a tuning fork base, and at least a first tuning fork arm and a second tuning fork arm connected to the tuning fork base, and the first tuning fork arm. And a tuning fork type crystal resonator in which a first groove and a second groove are formed on both sides of a neutral line on at least one of the upper and lower surfaces of each of the second tuning fork arms. If the distance in the width direction is a partial width W ₇ , the FIG. Of merit M ₁ of the fundamental mode vibration of the tuning fork crystal resonator is the FIG. M ₂ of the second harmonic mode vibration of the tuning fork crystal resonator. as larger, the partial width _{W 7} is less than 0.05 mm, and each of the groove width of the first groove and the second groove is smaller than 0.04 mm, and each of the first and second grooves The ratio (t ₁ / t) between the thickness t ₁ and the tuning fork arm thickness t is 0.79 It is a method for manufacturing a crystal resonator including a step of determining each dimension of a first groove and a second groove having a decreasing relationship.
A first aspect of a method for manufacturing a crystal unit according to the present invention is a method for manufacturing a crystal unit comprising the method for manufacturing a crystal resonator according to the first aspect and a step of connecting a lid to a case. The overall length of the tuning fork crystal unit, the first tuning fork arm, and the first tuning fork crystal resonator are set so that the equivalent series resistance R ₁ of the fundamental mode vibration is smaller than the equivalent series resistance R _{2 of the second} harmonic mode vibration. Determining a length dimension of each of the first groove and the second groove formed on both sides of the neutral line of at least one of the upper surface and the lower surface of each of the two tuning fork arms. is there.

A first aspect of a method for manufacturing a crystal oscillator according to the present invention is a method for manufacturing a crystal oscillator comprising the method for manufacturing a crystal resonator according to the first aspect and a step of connecting a lid to a case, or A method for manufacturing a crystal oscillator comprising the method for manufacturing a crystal unit according to the first aspect, comprising the step of electrically connecting the tuning fork type crystal resonator, an amplifier, a resistor, and a capacitor. It is.
According to a first aspect of the crystal resonator of the present invention, the tuning fork base includes at least a first tuning fork arm and a second tuning fork arm connected to the tuning fork base, the first tuning fork arm and the second tuning fork arm. A tuning fork type crystal resonator in which a first groove and a second groove are formed on both sides of at least one neutral line on each of the upper surface and the lower surface of each arm. The distance in the width direction of the first groove and the second groove is a partial width W. When _7, as Figa of merit M ₁ of the fundamental wave mode vibration of the tuning fork crystal is greater than Figa of merit M ₂ of the second harmonic mode vibration of the tuning fork crystal, said portion The width W ₇ is smaller than 0.05 mm, the width of each of the first groove and the second groove is smaller than 0.04 mm, the thickness t ₁ of each of the first groove and the second groove, and the tuning fork arm The first having a relationship in which the ratio (t ₁ / t) to the thickness t is smaller than 0.79 This is a crystal resonator in which the dimensions of the groove and the second groove are determined.
According to a first aspect of the crystal unit of the present invention, in the first aspect, the tuning fork type crystal resonator is fixed to a fixing portion of a case, and a lid is connected to the case.

  As described above, the present invention provides a crystal unit including a tuning fork-shaped crystal resonator that vibrates in a bending mode, a method for manufacturing the crystal unit, and a crystal oscillator. By showing the relationship with the circuit, it is possible to obtain a crystal oscillator that suppresses harmonic vibration and outputs a frequency that vibrates in the fundamental wave vibration mode.

In addition, by providing a groove at the center of (including) the tuning fork arm neutral line, and by arranging electrodes and optimizing the dimensions of the groove, the equivalent series resistance R ₁ is reduced and the Q value is reduced. An ultra-small tuning-fork-shaped bent quartz resonator that vibrates in a bending mode that is high and has good electromechanical conversion efficiency can be obtained. At the same time, the load capacity of the feedback circuit can be reduced. As a result, a crystal oscillator with low current consumption can be obtained.

  Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an example of a crystal oscillation circuit diagram constituting a crystal oscillator of the present invention. In this embodiment, the crystal oscillation circuit 1 includes an amplifier (CMOS inverter) 2, a feedback resistor 4, a drain resistor 7, capacitors 5 and 6, and a tuning fork-shaped bent crystal resonator 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, capacitors 5 and 6, and a feedback circuit 9 including a bent crystal resonator 3. 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 resonator and a capacitor. Further, the tuning fork-shaped bent crystal resonator used in the crystal oscillator and the crystal unit of the present invention will be described in detail with reference to FIGS.

FIG. 2 shows the feedback circuit diagram of FIG. Now, the angular frequency of the tuning-fork-shaped quartz crystal vibrating in the bending mode is ω _i , the resistance of the drain resistor 7 is R _d , the capacitances of the capacitors 5 and 6 are C _g and C _d , and the crystal impedance of the crystal is R _ei , When the input voltage is V ₁ and the output voltage is 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, when i = 2, second harmonic mode vibration, when i = 3, third harmonic mode It is vibration. That is, when i = n, it is n-order harmonic mode vibration, but hereinafter simply referred to as harmonic mode vibration. Further, the load capacity 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 rate β _i is β _i = 1 / (1 + kC _L ² ) However, k is expressed by a function of ω _i , R _d , and R _ei . R _ei is approximately equal to the equivalent series resistance R _i .

Thus, from the relationship between the feedback rate β _i and the load capacitance C _L , it is well understood that the feedback rates of the resonance frequencies of the fundamental vibration mode and the harmonic vibration mode increase as the load capacitance C _L decreases. Therefore, when the load capacity _CL is reduced, the harmonic mode vibration is more likely to oscillate than the fundamental mode vibration. The reason is that since the maximum vibration amplitude of the harmonic mode vibration is smaller than the maximum vibration amplitude of the fundamental mode vibration, the amplitude condition and the phase condition which are oscillation continuation conditions are satisfied simultaneously.

An object of the crystal oscillator of the present invention is to provide a crystal oscillator having a frequency of fundamental mode vibration that has low current consumption and high frequency stability (high time accuracy). Therefore, in order to reduce current consumption, in the present embodiment, the load capacitance C _L is used under 10pF. In order to further reduce the current consumption, since the current consumption is proportional to the load capacity, C _L = 8 pF or less is preferable. The capacitances C _g and C _{d referred to} here are numerical values that do not include the stray capacitance of the circuit, but actually there are stray capacitances depending on the circuit configuration. Therefore, in this embodiment, the load capacitance C _L containing the stray capacitance of this circuit configuration uses the following 18 pF. Further, in order to suppress the harmonic mode vibration and the output signal of the oscillator obtains the frequency of the fundamental mode vibration, the main signal is satisfied so that α ₁ / α _n > β _n / β ₁ and α ₁ β ₁ > 1 are satisfied. The crystal oscillation circuit of the embodiment is configured. However, α ₁ and α _n are amplification factors of the fundamental wave mode vibration and the harmonic mode vibration amplification circuit, and β ₁ and β _n are feedback rates of the feedback circuit of the fundamental wave mode vibration and the harmonic mode vibration. That is, when n = 2 and 3, they are the second and third harmonic mode vibrations, respectively.

In other words, the ratio of 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 of the feedback factor β _n of the harmonic mode vibration of the feedback circuit and the fundamental mode vibration. greater than the ratio of the rate beta _1, 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 whose output signal has a frequency of fundamental mode vibration. Note that the frequency is a reference frequency of the bent quartz crystal resonator or a frequency obtained by dividing the reference frequency. Further, high frequency stability will be described later. The output signal is output from the drain side of the circuit via the buffer.

Further, the amplifying part of the amplifying circuit constituting the crystal oscillation circuit of the present embodiment can exhibit the characteristic by a 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, 3, it is the negative resistance of the second and third harmonic mode vibration. In the crystal oscillator of this embodiment, the ratio of the absolute value | −RL ₁ | of the negative resistance of the fundamental mode vibration of the amplifier circuit to the equivalent series resistance R ₁ of the fundamental mode vibration is the harmonic mode vibration of the amplifier circuit. The oscillation circuit is configured to be larger than the ratio of the absolute value | -RL _n | of the negative resistance to the equivalent series resistance R _n of the harmonic mode vibration. That is, it is configured to satisfy | −RL ₁ / R ₁ > | −RL _n | / R _n . By configuring the crystal oscillation circuit in this way, the oscillation activation of the harmonic mode vibration is suppressed, and as a result, the oscillation activation of the fundamental wave mode vibration is obtained, so that the frequency of the fundamental wave mode vibration is obtained as the output signal.

  FIG. 3 shows an external view of a tuning-fork-shaped bent quartz resonator 10 that vibrates in a bending mode used in the crystal unit or crystal oscillator of the first embodiment of the present invention and its coordinate system. An O-xyz including a coordinate system O, an electric axis x, a mechanical axis y, and an optical axis z is configured. The tuning fork-shaped bent quartz crystal resonator 10 according to this 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. 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 with a neutral line interposed therebetween, 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 in the same manner as the tuning fork arm 20. Further, the tuning fork base 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 selected in the range of 0 to 10 °. Further, grooves on the lower surfaces of the tuning fork arms 20 and 26 are provided in the same manner as the upper surface.

  4 shows a DD ′ cross-sectional view of the tuning fork base 40 of the tuning fork-shaped bent quartz resonator 10 of FIG. FIG. 4 details the cross-sectional shape and electrode arrangement of the tuning fork base 40 of the crystal resonator of FIG. The tuning fork base 40 connected to the tuning fork arm 20 is provided with grooves 21 and 22. Similarly, the tuning fork base 40 connected to the tuning fork arm 26 is provided with grooves 27 and 28. Further, a groove 32 and a groove 36 are further provided between the groove 21 and the groove 27. A groove 33 and a groove 37 are also provided between the groove 22 and the groove 28. The electrodes 21 and 24 are disposed in the grooves 21 and 22, the electrodes 34, 35, 38, and 39 are disposed in the grooves 32, 33, 36, and 37, and the electrodes 29 and 30 are disposed in the grooves 27 and 28, respectively. Electrodes 25 and 31 are disposed on both side surfaces of the tuning fork base 40. Specifically, electrodes are disposed on the side surfaces of the grooves, and electrodes having different polarities are disposed to oppose the electrodes.

Further, the bent quartz resonator 10 of the tuning fork has a thickness t, groove has a thickness t _1. The thickness t ₁ here refers to the thickness of the deepest part of the groove. The reason for this is that quartz is an anisotropic material, and the etching speed varies 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 the uniform shape shown in FIG. In the present embodiment, the ratio (t ₁ / t) between the groove thickness t ₁ and the tuning fork arm or the tuning fork arm and the tuning fork base thickness t is preferably less than 0.79. A groove is formed in the tuning fork arm or the tuning fork arm and the tuning fork base so as to be 79. In particular, in order to increase the distortion of the tuning fork base, it is preferable to set the ratio of the groove thickness of the tuning fork base and 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 electrode facing it increases. That is, a flexural vibrator with good electromechanical conversion efficiency can be obtained. That is, a tuning fork-shaped bent quartz crystal resonator with a small capacity ratio can be obtained. Furthermore, in this embodiment, since the grooves 32, 33, 36, and 37 are further provided between the grooves of the tuning fork base, the electric field strength is further increased and the electromechanical conversion efficiency is further improved. . Further, in this embodiment, the grooves 32 and 36 are provided on the upper surface of the tuning fork base 40 and the grooves 33 and 37 are provided on the lower surface, but they may be provided only on one side.

Further, the electrodes 25, 29, 30, 34, and 35 are arranged to have one same polarity, and the electrodes 23, 24, 31, 37, 38, and 39 are arranged to have the other same polarity. -E '. That is, the groove electrode that opposes the z-axis direction has the same polarity, and the electrode that opposes the x-axis direction has a different polarity. Now, when a DC voltage is applied to the two-electrode terminal EE ′ (the positive electrode is applied to the E terminal and the negative electrode is applied to the E ′ terminal), the electric field Ex works as indicated by the arrows shown in FIG. Since the electric field Ex is drawn perpendicularly to the electrodes by the electrodes arranged on the side surface of the crystal unit and the side surface in the groove, that is, linearly, the electric field Ex is increased, and as a result, the amount of distortion generated is large. Become. Therefore, even when the tuning fork-shaped bent quartz crystal is reduced in size, a tuning-fork-shaped quartz crystal that vibrates in a bending mode having a small equivalent series resistance R ₁ and a high quality factor Q value can be obtained.

FIG. 5 shows a top view of the tuning-fork-shaped bent quartz crystal resonator 10 of FIG. In FIG. 5, the arrangement and dimensions of the grooves 21 and 27 will be particularly described in detail. A 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 quartz crystal resonator 10 of this embodiment, the groove 32 and the groove 36 are also provided in the portion of the tuning fork base 40 sandwiched between the groove 21 and the groove 27. By providing the grooves 21 and 27 and the grooves 32 and 36, the electric field Ex acts on the tuning fork-shaped bent quartz resonator 10 as indicated by the arrow shown in FIG. Is drawn perpendicularly to the electrodes by the electrodes arranged on the side surface of the crystal unit and the side surface in the groove, that is, linearly, and in particular, the electric field Ex of the tuning fork base is increased, and as a result, the amount of distortion generated is also increased. growing. As described above, the shape and electrode configuration of the tuning-fork-shaped bent quartz crystal resonator 10 of this embodiment are excellent in electrical characteristics even when the tuning-fork-shaped bent quartz resonator is downsized, that is, equivalent series resistance R _A crystal resonator with a small quality factor Q of ₁ can be realized.

Further, assuming that the partial widths W ₁ and W ₃ and the groove width W ₂ , the arm width W of the tuning fork arms 20 and 26 is given by W = W ₁ + W ₂ + W ₃ , and usually a part of W ₁ and W ₃ or All are configured such that W ₁ ≧ W ₃ or W ₁ <W ₃ . Further, the groove width W ₂ is configured under the condition that satisfies W 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. The ratio (t ₁ / t) between the groove thickness t ₁ and the tuning fork arm thickness t or the tuning fork arm and tuning fork base thickness t (t ₁ / t) is preferably less than 0.79. Grooves are formed in the tuning fork arm so as to be 01 to 0.79. By forming in this way, the moment of inertia with the tuning fork arm neutral lines 41 and 42 as base points is increased. That is, since the electro-mechanical conversion efficiency is improved, a small equivalent series resistance R _1, a high Q value, moreover, it is possible to obtain a bending crystal oscillator of a small tuning fork capacity ratio.

On the other hand, with respect to the length l ₁ of the groove 21 and the groove 27, in this embodiment, the grooves 21 and 27 extend from the tuning fork arms 20 and 26 to the length l ₂ of the tuning fork base 40, The dimensions are such that the length l ₃ is obtained. Therefore, the length of the groove provided in the tuning fork arms 20 and 26 is given by (l ₁ −l ₃ ), and in order to obtain a vibrator having a small R ₁ , (l ₁ −l ₃ ) / (l− l ₂ ) has a value of 0.4 to 0.8. Further, the overall length l of the tuning fork-shaped bent quartz crystal resonator 10 is determined from the required frequency, the size of the storage container, and the like. At the same time, in order to obtain a good tuning-fork-shaped bent quartz crystal resonator that vibrates in the fundamental wave mode, there is a close relationship between the groove length l ₁ and the total length l.

That is, the ratio (l ₁ / l) between the tuning fork arms 20 and 26 or the tuning fork arms 20 and 26 and the length l _{1 of the} groove provided in the tuning fork base 40 and the total length l of the tuning fork-shaped bent crystal resonator is 0. The length of the groove is provided to be 2 to 0.78. The reason for forming in this way is that it is possible to suppress harmonic mode vibrations, particularly secondary and third harmonic mode vibrations, which are unwanted vibrations, and to improve the frequency stability of fundamental wave mode vibrations. Therefore, a good tuning fork-shaped bent quartz crystal that easily vibrates in the fundamental wave mode can be realized. If More specifically, the equivalent series resistance R ₁ of the bending quartz oscillator tuning fork vibrating at 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 second-order and third-order harmonic mode vibration when n = 2, 3), and an amplifier (CMOS inverter), a capacitor, a resistor, and a bending fork shape of this embodiment In a crystal oscillator composed of a crystal oscillator or the like, a good crystal oscillator in which the oscillator easily vibrates in the fundamental wave mode can be realized. Further, the groove length l ₁ 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 may be 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).

Further, in this embodiment, in the tuning fork base portion 40 is 5, is the entire lower portion of the length l ₂ of the transducer 10, also tuning fork arms 20 and tuning fork arms 26, in FIG. 5, the vibrator 10 there is a whole upper portion from the portion of the length l _2. In this embodiment, the tuning fork fork has a rectangular shape. However, the present invention is not limited to the shape described above, and the tuning fork fork may have a U-shape. In this case, as in the rectangular shape, the dimensional relationship between the tuning fork arm and the tuning fork base is the same as that described above. Further, in this 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. Further, the length l 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 than 0.35 The length of the groove formed to be larger and smaller than 1. Further, when the groove provided in the tuning fork arm extends to the tuning fork base, and a groove is further provided between the grooves extending to the tuning fork base, the length including the groove length l ₃ is set. l ₁ . However, when the tuning fork arm groove extends to the tuning fork base, but no further groove is provided between the grooves, the length l ₁ is the length of the tuning fork arm groove.

In other words, at least one groove is provided in the length direction on the upper and lower surfaces of the tuning fork arm that includes the neutral line, ie, the tuning fork arm including the neutral line, and electrodes are formed on both sides of the groove. Are arranged such that 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 different from each other, and each of the at least one of the at least one so as 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 grooves to the tuning fork arm width W is larger than 0.35 and smaller than 1, and the thickness t _{1 of the} groove and the thickness of the tuning fork arm The groove is formed so that the ratio (t ₁ / t) to t is smaller than 0.79.

Further, the interval between the tuning fork arms of the present embodiment is given by W ₄ , and the interval W ₄ and the groove width W ₂ are configured to satisfy W ₄ ≧ W ₂ , and the interval W ₄ is 0.05 mm to 0.35 mm. in, the groove width _{W 2} has a value of 0.03Mm～0.12Mm. The reason for this configuration is an ultra-compact bent quartz crystal unit, and the tuning fork shape and tuning fork arm groove can be formed separately (separate steps) using photolithography technology. The stability can be higher than the frequency stability of the harmonic mode vibration. In this case, a quartz 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 thicker than 0.12 mm may be used.

More specifically, the Figer of Merit M _i representing the inductivity, electromechanical conversion efficiency, and quality factor of the bent quartz resonator is the ratio of the quality factor Q _i value to the capacity ratio r _i (Q _i / r _i ). Defined by (fundamental vibration when i = 1, second harmonic vibration when i = 2, third harmonic vibration when i = 3), and mechanical series resonance independent of the parallel capacitance of the bent quartz crystal frequency difference Delta] f of the series resonance frequency f _r which depends on the parallel capacitance and the frequency f _s is inversely proportional to the off Iga of merit M _i, Delta] f becomes smaller as the value M _i is large. Therefore, as M _i is large, the resonance frequency of the bending crystal oscillator does not influenced by the parallel capacitance, the frequency stability of a flexural quartz crystal resonator is improved. That is, a tuning fork-shaped bent quartz crystal with high time accuracy can be obtained.

In detail, depending on the configuration of the tuning fork shape, groove, electrode, and dimensions thereof, the fibre-of-merit M ₁ of the fundamental mode vibration is derived from the fibre-of-merits M ₂ and M _{3 of the second} and _third harmonic mode vibrations. growing. That is, M ₁ > M _n . However, _Mn is the fibre of merit of harmonic mode vibration. As an example, at the frequency of the fundamental mode oscillation _32.768kHz, when W ₂ /W=0.5,t ₁ /t=0.34,l ₁ /1=0.48, although variations due to manufacturing may occur M ₁ , M ₂ , and M ₃ of the tuning-fork-shaped bent quartz crystal resonator are M ₁ > 65, M ₂ <30, and M ₃ <18, respectively. That is, (a small equivalent series resistance R ₁₎ Good high inductive electromechanical conversion efficiency, can be obtained flexural quartz oscillator that vibrates at a large fundamental mode of the 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. Further, the reference frequency of the fundamental wave 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 resonator 45 that vibrates in a bending mode used in the crystal unit or crystal oscillator according to the second embodiment of the present invention. The tuning fork-shaped bent quartz crystal unit 45 includes tuning fork arms 46 and 47 and a tuning fork base 48. That is, one end of the tuning fork arms 46 and 47 is connected to the tuning fork base 48. In this embodiment, the tuning fork base 48 is provided with notches 53 and 54. Further, the tuning fork arms 46 and 47 are provided with grooves 49 and 50 with (including) the neutral lines 51 and 52, respectively. Further, the grooves 49 and 50 in this embodiment is provided in a part of the tuning fork arms 46 and 47, the grooves 49 and 50 each have a width _{W 2} and length _{l 1.} More specifically, the groove area S = W ₂ × ₁₁ is shown, and S is configured to have a value of 0.025 to 0.12 mm ² . The reason for configuring the groove area in this way is that it is easy to form a groove by a chemical etching method, and it is possible to form a groove with improved electromechanical conversion efficiency. At the same time, a tuning fork-shaped crystal resonator that vibrates in a bending mode having a high quality factor Q value of fundamental mode vibration can be obtained. As a result, a crystal unit including the crystal unit and a crystal oscillator whose output signal has the frequency of the fundamental mode vibration can be realized.

In the groove area S, the groove and the tuning fork arm can be processed in separate steps. However, in processing the tuning fork arms and grooves provided in it at the same time, should there be an interval W ₄ and the area S of the thickness t and groove width W ₂ and the tuning fork arm of the tuning fork arms to the optimum dimensions. In other words, the tuning fork arms of thickness t when 0.06Mm～0.15Mm, within the groove width _{W 2} is 0.02Mm～0.068Mm, further area S of 0.023mm ² ~0.088mm ² in the range, the interval _{W 4} is configured to be 0.05 mm to 0.35 mm. The reason for such a configuration is that the crystallinity of quartz is used, and from the crystallinity, a groove (including a groove divided in the length direction of the tuning fork arm) and a tuning fork shape can be formed simultaneously. Although not shown in FIG. 6, grooves are also provided on the lower surfaces of the tuning fork arms 46 and 47 at positions facing the grooves 49 and 50.

Furthermore, the width of the tuning fork portion of the cutout portions 53 and 54 provided in the fork base 48 is given by W _5, the dimensions of the end of the cutout portions 53 and 54 is given by W _6. In order to reduce the vibration energy loss of the vibrator when it is fixed to the surface mount type case or the cylindrical type case on the end side of the tuning fork base 48 with solder or adhesive, W ₆ ≧ W ₅ is set. It is necessary to satisfy. The notches 53 and 54 can also reduce the energy loss of the vibration part due to the fixation of the vibrator. The relationship between the arm width W, the partial widths W ₁ and W ₃ , the groove width W ₂ , the interval W _{4, the} groove length ₁₁ and the overall length ₁ of the tuning fork vibrator shown in FIG. Is omitted here.

  FIG. 7 is a cross-sectional view of a crystal unit according to a third embodiment of the present invention or a cross-sectional view of a crystal unit used in the crystal oscillator of the third embodiment. The crystal unit 170 includes a tuning fork-shaped bent crystal resonator 70, a case 71, and a lid 72. More specifically, the vibrator 70 is fixed to a fixing portion 74 provided on the case 71 with a conductive adhesive 76 or solder. The case 71 and the lid 72 are joined via a joining member 73. In the present embodiment, the vibrator 70 is the same vibrator as one of the tuning-fork-shaped crystal vibrators 10 and 45 that vibrate in the bending mode described in detail in FIGS. In the crystal oscillator of this embodiment, the circuit element is connected to the outside of the crystal unit. That is, only a tuning fork-shaped bent quartz crystal is housed in the unit. At this time, the bent crystal resonator is housed in a vacuum unit.

  Further, the case member is made of ceramic or glass, the lid member is made of metal or glass, and the joining member is made of metal or low-melting glass. Further, the relationship between the vibrator, the case, and the lid described in this embodiment is also applied to the crystal oscillator of FIG. 8 described below.

  FIG. 8 is a sectional view of a crystal oscillator according to a 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 oscillation circuit is housed in a crystal unit composed of a case 91 and a lid 92. The crystal oscillation circuit includes a tuning fork-shaped bent crystal resonator 90, an amplifier 98 including a feedback resistor, a capacitor (not shown), and a drain resistor (not shown). An inverter is used.

  Further, in this embodiment, the vibrator 90 is fixed to a fixing portion 94 provided in the case 91 by an adhesive 96 or solder. On the other hand, the amplifier 98 is fixed to the case 91. Further, the case 91 and the lid 92 are joined via a joining member 93. As the vibrator 90 of this embodiment, the vibrator in the tuning fork-shaped bent quartz crystal vibrators 10 and 45 described in detail in FIGS. 3 and 6 is used.

  Next, the manufacturing method of the crystal unit and crystal oscillator of the present invention will be described. The tuning fork-shaped bent quartz crystal resonator is formed by a photolithography method using a semiconductor technique and a chemical etching method. First, metal films (for example, chromium and gold thereon) are formed on the upper and lower surfaces of a polished or polished quartz crystal wafer by sputtering or vapor deposition. Next, a resist is applied on the metal film. Then, after the resist and the metal film are removed while leaving the tuning fork shape by a photolitho process, 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 resist shown in the above process 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 a photolitho process and a chemical etching method.

  Next, a metal film and a resist are again applied to the tuning fork shape having a groove, and an electrode is formed by a photolitho 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 to oppose each other so as to have different polarities. More specifically, the side electrode of the first tuning fork arm and the electrode of the groove of the second tuning fork arm have the same polarity, and the electrode of the groove of the first tuning fork arm and the side electrode of the second tuning fork arm have the same polarity. The electrode of the groove | channel of a 1st tuning fork arm and a side electrode are comprised so that polarity may differ. That is. Two electrode terminals are formed on the vibrator. As a result, by applying an alternating voltage to the two electrode terminals, the tuning fork arm bends and 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 the tuning fork shape is formed. However, the present invention is not limited to the above embodiment, and the groove is first formed. A tuning fork shape may be formed. Or you may form a tuning fork shape and a groove | channel simultaneously. Further, the dimensions and the like of the grooves in this step are the same as those described above and have already been described, and therefore are omitted here.

  By the process of this embodiment, a large number of tuning fork-shaped bent quartz resonators are formed on the quartz wafer. Therefore, in the next step, the first frequency adjustment is performed by laser or plasma etching or vapor deposition in this wafer state. At the same time, the defective vibrator is marked or removed from the wafer. In this step, the frequency is adjusted so that the frequency deviation is within the range of −9000 PPM to +5000 PPM with respect to the reference frequency of 10 kHz to 200 kHz. Further, in the next step, the formed vibrator is fixed to a lead wire of a surface mount type case, a lid or a cylindrical case with an adhesive or solder. After the fixing, the second frequency adjustment is performed by laser, plasma etching or vapor deposition. In this step, the frequency is adjusted so that the frequency deviation is within the range of −100 PPM to +100 PPM. The fact that the frequency adjustment is performed after fixing in the present invention may be performed immediately after fixing, or may be performed after connecting the case and the lid after fixing. That is, whatever process is performed after fixing, the frequency may be adjusted after that, and the present invention encompasses all of these.

  When the third frequency adjustment is performed, the frequency adjustment is performed so that the frequency deviation due to the second frequency adjustment is in the range of −950 PPM to +950 PPM. In the above embodiment, the first frequency adjustment is performed in the state of the wafer, and at the same time, the defective vibrator is marked or removed from the wafer. However, 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 resonators formed on a crystal wafer in the state of the wafer and inspecting a good resonator or a defective resonator. That is, the defective vibrator is marked, removed from the wafer, or stored in a computer. By including such a process, a defective vibrator can be found quickly, and since it does not flow to the next process, the yield can be increased. As a result, an inexpensive bent quartz resonator can be obtained.

  Furthermore, after adjusting the frequency, 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 with a laser after storage. In this step, the frequency is adjusted so that the frequency deviation is within the range of −50 PPM to +50 PPM. In this embodiment, the frequency adjustment is performed in three separate steps, but may be performed in at least two separate steps. For example, the frequency adjustment in the third process may not be performed. In the next step, the two electrode terminals of the vibrator are electrically connected to an amplifier, a capacitor, and a 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 resonator, 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 configured.

Although the present invention has been described based on the illustrated example, the present invention is not limited to the above-described example. In the tuning-fork-shaped bent crystal resonator used in the crystal oscillators of the first to fourth embodiments, the tuning fork Although the groove is provided in the arm or the tuning fork arm and the tuning fork base, for example, a through hole (t ₁ = 0) may be provided in the tuning fork arm. That is, the through hole is a special case of a groove, and the groove of the present invention includes the through hole. In the above embodiment, the tuning fork arm is composed of two, but 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 groove is formed on both sides of the neutral line. It may be formed. In this case, partial width W ₇ including the neutral line of the tuning fork arms are configured to be less than 0.05 mm. Further, the width of each groove is configured to be smaller than 0.04 mm, and the ratio of the thickness t _{1 of} the groove to the thickness t of the tuning fork arm is configured to be 0.79 or less. With such a configuration, M ₁ can be made larger than M _n .

Furthermore, the crystal oscillators of the first to fourth embodiments and the tuning-fork-shaped bent crystal resonators used in the crystal oscillators have been described. The crystal resonators used in the crystal oscillators of these embodiments include a case and a lid. The crystal unit is configured by being housed in a so-called unit. That is, the vibrator of the present embodiment is fixed to the fixing portion by a conductive adhesive or solder or the like on the fixing portion provided on the case or the lid, and the case and the lid are bonded via the bonding member, The case is configured to be a vacuum. With this configuration, a small equivalent series resistance R _1, it is possible to realize a subminiature quartz crystal unit.

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

As described above, it has already been described that many effects can be obtained by providing the crystal unit, the manufacturing method thereof, and the crystal oscillator of the present invention. 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 the side surfaces thereof, the electric field works vertically. As a result, the electromechanical conversion efficiency is improved, the equivalent series resistance R ₁ small crystal units and crystal oscillator comprises a flexural quartz crystal resonator with high tuning fork quality factor Q value is obtained.
(2) crystal oscillator off Iga of merit M ₁ of the fundamental wave mode vibrations comprises a full Iga of merit M _n greater than oscillator harmonic mode oscillation in the flexural quartz crystal tuning fork is configured, furthermore, amplification The ratio of the amplification factor α ₁ of the fundamental mode vibration of the circuit and the amplification factor α _n of the harmonic mode vibration is the ratio of the feedback factor β _n of the harmonic mode vibration of the feedback circuit and the feedback factor β ₁ of the fundamental mode vibration. Since the crystal oscillator is configured so that the product of the amplification factor α ₁ of the fundamental wave mode vibration and the feedback factor β ₁ of the fundamental wave mode vibration is larger than ₁ , even if the load capacitance is small, the crystal oscillator As an output signal of the oscillator, a fundamental mode vibration frequency can be obtained as an output, and a crystal oscillator with low current consumption can be realized.
(3) Tuning fork shape and groove can be formed by photolithography method and chemical etching method, which is excellent in mass productivity, and furthermore, since many vibrators can be formed on one crystal wafer at a time by batch processing, it is inexpensive. Crystal unit can be obtained. At the same time, an inexpensive crystal unit and crystal oscillator with it can be realized.
(4) Since the full Iga of merit M ₁ of the fundamental wave mode vibration crystal oscillator comprises a full Iga of merit M _n greater than oscillator harmonic mode vibration is configured, the output signal of the fundamental mode vibration frequencies And a crystal oscillator having high frequency stability can be realized. That is, a crystal oscillator having high time accuracy can be obtained.

  Since the crystal unit, crystal unit and crystal oscillator of the present invention are ultra-compact and have high frequency stability, they are especially applicable to electronic devices such as portable devices and consumer devices that are ultra-compact and require high frequency stability. it can.

It is one Example of the crystal oscillation circuit diagram which comprises the crystal oscillator of this invention. The feedback circuit diagram of FIG. 1 is shown. FIG. 2 shows an external view and a coordinate system of a tuning fork-shaped crystal resonator that vibrates in a bending mode used in the crystal unit of the first embodiment of the present invention or the crystal oscillator of the first embodiment. FIG. 4 shows a DD ′ cross-sectional view of the tuning fork base of the tuning fork-shaped bent crystal resonator of FIG. 3. FIG. 4 is a top view of the tuning fork-shaped bent quartz crystal resonator of FIG. 3. It is a top view of the crystal unit of the tuning fork shape which vibrates in the bending mode used for the crystal unit of 2nd Example of this invention, or the crystal oscillator of 2nd Example. It is sectional drawing of the crystal unit of 3rd Example of this invention, or sectional drawing of the crystal unit used for the crystal oscillator of 3rd Example. Sectional drawing of the crystal oscillator of 4th Example of this invention is shown. A perspective view and a coordinate system of a conventional tuning fork-shaped bent quartz crystal resonator are shown. FIG. 10 is a cross-sectional view of a tuning fork arm of the tuning fork-shaped crystal resonator of FIG. 9.

DESCRIPTION OF SYMBOLS 1 Amplifying 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 arm width W ₁ , W ₃ Tuning fork arm partial width W ₄ Tuning fork arm interval W partial width l ₁ groove length l ₂ tuning fork base portion of the full-length t tuning fork arms or thicknesses of t ₁ groove of the tuning fork arms and fork base of length l tuning fork of the bent crystal oscillator containing ₇ tuning fork arms of the neutral line

Claims (5)

A tuning fork base and at least a first tuning fork arm and a second tuning fork arm connected to the tuning fork base, and a neutral line on at least one of the upper and lower surfaces of each of the first tuning fork arm and the second tuning fork arm. A tuning fork type crystal resonator having a first groove and a second groove formed on both sides thereof,
If the distance in the width direction between the first groove and the second groove is a partial width W ₇ , the FIG. Of merit M ₁ of the fundamental wave mode vibration of the tuning fork crystal resonator is the second harmonic of the tuning fork crystal resonator. to be larger than Figa of merit _{M 2} mode vibration, the partial width _{W 7} is less than 0.05 mm, and each of the groove width of the first groove and the second groove is smaller than 0.04 mm, and the The respective dimensions of the first groove and the second groove are determined so that the ratio (t ₁ / t) between the thickness t ₁ of each of the first groove and the second groove and the thickness t of the tuning fork arm is smaller than 0.79. The manufacturing method of the crystal oscillator characterized by including the process to do. A method for manufacturing a crystal unit according to claim 1, and a method for manufacturing a crystal unit comprising a step of connecting a lid to a case, wherein the equivalent series resistance R ₁ of the fundamental mode vibration is the second harmonic. The total length of the tuning fork crystal resonator and the neutral line of at least one of the upper and lower surfaces of each of the first tuning fork arm and the second tuning fork arm so as to be smaller than the equivalent series resistance R ₂ of the wave mode vibration. Determining a length dimension of each of the first groove and the second groove formed on both sides of the crystal unit. A method for manufacturing a crystal oscillator according to claim 1 and a method for manufacturing a crystal oscillator comprising the step of connecting a lid to a case, or a crystal oscillator including the method for manufacturing a crystal unit according to claim 2. A method of manufacturing a crystal oscillator comprising the step of electrically connecting the tuning fork type crystal resonator, an amplifier, a resistor, and a capacitor. A tuning fork base and at least a first tuning fork arm and a second tuning fork arm connected to the tuning fork base, and a neutral line on at least one of the upper and lower surfaces of each of the first tuning fork arm and the second tuning fork arm A tuning fork type crystal resonator having a first groove and a second groove formed on both sides thereof,
If the distance in the width direction between the first groove and the second groove is a partial width W ₇ , the FIG. Of merit M ₁ of the fundamental wave mode vibration of the tuning fork crystal resonator is the second harmonic of the tuning fork crystal resonator. The partial width W ₇ is smaller than 0.05 mm, the groove widths of the first groove and the second groove are smaller than 0.04 mm, and the first width and the second groove are smaller than 0.05 mm so as to be larger than the mode vibration figure of merit M ₂ . The dimensions of the first groove and the second groove having a relationship in which the ratio (t ₁ / t) between the thickness t ₁ of each of the first groove and the second groove and the thickness t of the tuning fork arm is smaller than 0.79 are determined. A crystal resonator characterized by being made. 5. The crystal unit according to claim 4, wherein the tuning fork type crystal resonator is fixed to a fixing portion of a case, and a lid is connected to the case.

Images