JP2006246449A - Piezoelectric vibrator, piezoelectric vibrator package, and oscillation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tuning fork type piezoelectric vibrator provided with vibrating arms which can improve shock resistance while suppressing a CI value to a small value. <P>SOLUTION: A first groove (base end side) and a second groove (tip side) extending along the longitudinal direction from the base end of the vibrating arm and divided into two in the longitudinal direction are formed on at least one of a front surface or a back surface of the vibrating arms. Then, a ratio L2/L1 which is the ratio of the length L2 of the first groove to the length L1 from the base end of the vibrating arm to the tip of the second groove, is set between 0.35 and 0.65, and a ratio d/L1 which is the ratio of a space d between the first groove and the second groove to the length L1 from the base end of the vibrating arm to the tip of the second groove, is set between 0.010 and 0.018. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric vibrator in which two vibrating arms extend from a base and are formed in a tuning fork shape.

  This type of piezoelectric vibrator, for example, a tuning-fork type quartz vibrator, is generally known as a signal source for engraving the rate of a wristwatch, and has recently been adopted as a synchronization signal source in portable electronic devices. The quartz resonator is required to be further downsized in response to downsizing of electronic equipment.

  The configuration of the tuning fork type crystal resonator is described in Patent Document 1, for example. As shown in FIG. 11, the tuning fork type quartz crystal resonator is provided with tuning fork arms 2a and 2b as a pair of vibrating arms on the base 1, and groove portions 3 are formed on both main surfaces of the tuning fork arms 2a and 2b. Is provided. Excitation electrodes 5 for exciting tuning fork vibrations based on bending vibrations of the tuning fork arms 2a and 2b are provided on both side surfaces of the groove 3 and the tuning fork arms 2a and 2b. When a charge is applied to the tuning fork vibrator, the side surface of one tuning fork arm 2a and the groove 3 of the other tuning fork arm 2b have the same potential, and the side surface of the other tuning fork arm 2b and the groove 3 of one tuning fork arm 2a The excitation electrode 5 is connected so that becomes a reverse potential.

  According to such a tuning fork type crystal resonator, the electric field strength in the X-axis direction (tuning fork arm width direction) is increased as compared with the case where the groove 3 is not formed. Therefore, bending vibration in the Y-axis direction (tuning fork arm length direction) that expands and contracts in opposite directions between both side surfaces of the tuning fork arms 2a and 2b is strongly excited.

  With this configuration, the vibration loss of the tuning fork arms 2a and 2b is reduced, and a piezoelectric vibrator having a basically good CI (crystal impedance) value can be obtained.

  However, there is a demand for further reduction of the CI value in response to a request for power saving in electronic components using the crystal resonator. Since the tuning fork type crystal resonator described in Patent Document 1 is provided with a groove on the tuning fork arm as described above, the impact resistance is reduced when the crystal resonator is miniaturized, and the impact resistance such as dropping is reduced. Therefore, there is a possibility that problems such as breakage may occur when manufacturing electronic parts.

JP 2002-261575 A

  The present invention has been made to solve such a problem, and the object of the present invention is to provide a tuning fork type piezoelectric vibrator having two vibrating arms with a small CI value. An object is to provide a piezoelectric vibrator having high impact resistance. Another object is to provide a piezoelectric vibrator package and an oscillation circuit using this piezoelectric vibrator.

The piezoelectric vibrator of the present invention is a piezoelectric vibrator formed in a tuning fork shape with two vibrating arm portions extending from a base portion.
A groove formed on at least one of a front surface portion and a back surface portion of the vibrating arm portion, extending along a length direction from a base end portion of the vibrating arm portion and divided into two in the length direction, and the vibration And a pair of excitation electrodes provided in the side surface of the arm portion and in the groove portion, respectively.

  In this invention, if the groove portion on the base end side is the first groove portion and the groove portion on the tip end side is the second groove portion among the groove portions divided into two in the length direction, the base end portion of the vibrating arm portion The ratio L2 / L1 of the length L2 of the first groove portion to the distance L1 from the tip of the second groove portion to the second groove portion is preferably 0.35 to 0.65. The ratio d / L1 of the distance d between the first groove and the second groove with respect to the distance L1 from the base end of the vibrating arm to the tip of the second groove is preferably 0.010 to 0.016. .

  The piezoelectric vibrator package of the present invention is provided with a package, the piezoelectric vibrator of the present invention provided in the package, and provided outside the package and electrically connected to the lead electrode of the piezoelectric vibrator. And an electrode. Furthermore, an oscillator according to the present invention includes the piezoelectric vibrator according to the present invention and an oscillation circuit that outputs a pulse having a third harmonic frequency of the piezoelectric vibrator as an oscillation output.

  In the present invention, since the groove portion in the vibrating arm portion is divided into two in the length direction, a large impact resistance is obtained while reducing the crystal impedance (CI value) of the piezoelectric vibrator as will be apparent from the experimental results described later. Sex is obtained.

(First embodiment)
FIG. 1 is a diagram showing an embodiment of a tuning-fork type crystal resonator according to the present invention. A crystal resonator body (crystal piece) in this crystal resonator includes a substantially square base portion 1 having a notch portion 11 in which upper portions of both side portions are cut out in a rectangular shape, and an upper end side of the base portion 1. Two (a pair of) vibrating arm portions 2 (2a, 2b) extending in parallel with an interval are provided, and the entire shape is configured as a tuning fork type crystal piece. Further, the front surface portion and the back surface portion of the vibrating arm portion 2 (2a, 2b) are each divided into two in the length direction from the proximal end portion to the distal end side of the vibrating arm portion 2 (2a, 2b). A first groove 3 and a second groove 4 are formed.

    The position in the Y direction of the base end of the first groove 3 is the same as the lowermost part 20 of the tuning fork or the fork part (the tip side of the vibrating arm 2 is upward), but is lower than the lowermost part 20 ( It may be in a position close to the base 1 side. Note that the tuning fork or portion indicates the portion of the base 1 between the pair of vibrating arm portions 2a and 2b. In the drawing, the planar shape is curved and drawn, but it is actually a polygonal line shape.

  Here, the excitation electrode and the extraction electrode will be described with reference to FIG. 2. In this crystal resonator, there is a pair of one electrode and the other electrode. First, paying attention to the vibrating arm portion 2 a, one excitation electrode 51 is formed between the entire inner surfaces of the two groove portions 3 and 4 of the vibrating arm portion 2 a and the groove portions 3 and 4. That is, the excitation electrode 51 formed in the bridge portion between the two groove portions 3 and 4 is connected to the excitation electrode 51 in the groove portion 3 of the vibrating arm portion 2a and the excitation electrode 51 in the groove portion 4 of the vibrating arm portion 2a. Has been. And the other excitation electrode 61 is formed in the upper part rather than the 2nd groove part 4 of the front end side in both the side surfaces 21 and 21 and main surfaces 22 and 22 (surface part and back surface part) of this vibration arm part 2a. Yes. In FIG. 2, the excitation electrode 51 is represented by using a diagonal line and a black dotted area for easy understanding of the drawing, and the diagonal line in FIG. 2 does not indicate a cross section.

  When attention is paid to the vibrating arm portion 2 b, the other excitation electrode 61 is formed between the entire inner surfaces of the two groove portions 3 and 4 of the vibrating arm portion 2 b and the groove portions 3 and 4. Then, one excitation electrode 51 is formed at the upper side of the both side surfaces 21 and 21 and the main surfaces 22 and 22 (the front surface portion and the back surface portion) of the vibrating arm portion 2b above the second groove portion 4 on the front end side. Yes. The arrangement of the electrodes provided on the vibrating arm portions 2a and 2b is the same except that the excitation electrodes 51 and 61 are in an opposite relationship to each other. And the pattern which consists of the extraction electrode 52 is formed in the surface of the base 1 so that these one excitation electrodes 51 may be electrically connected, while the other excitation electrodes 61 are electrically connected A pattern made of extraction electrodes 62 is formed on the surface of the base 1.

When an example of the dimensions of each part of the crystal resonator is shown with reference to FIG. 3, the length L0 of the vibrating arm portion 2 (2a, 2b) is, for example, 1650 μm. The length L1 to the tip of the second groove 4 is 847 μm, the length L2 of the first groove 3 is, for example, 418 μm, and the distance d between the first groove 3 and the second groove 4 is 10 μm. is there. The length L3 from the bottom surface of the base 1 to the lowermost portion 20 of the tuning fork or portion is, for example, 600 μm. Further, the width W1 of the vibrating arm 2 (2a, 2b) is 100 μm, the width W2 of each of the grooves 3 and 4 is 65 μm, and the width W3 of the bottom surface of the base 1 is 500 μm.
Here, if the ratio L2 / L1 of L2 to L1 is 0.35 to 0.65 and the ratio d / L1 of d to L1 is 0.010, a large impact resistance can be obtained. If the ratio d / L1 is 0.016, the CI value can be made small.

For example, as shown in FIG. 4, the crystal resonator is used as a package device (crystal resonator package) having an SMD structure (substrate mounting structure). In FIG. 4, 7 is a package made of an insulator such as ceramics such as alumina or glass. The package 7 includes a case body 7a whose upper surface is open and a lid body 7b provided on the case body 7a via a sealing material 7c. In the tuning-fork type crystal resonator 70 described above, the lead electrodes 52 and 62 of the base 1 are fixed to the pedestal portion 71 in the package 7 by the conductive adhesive 7d and are arranged horizontally, and the vibrating arm portion 2 is a space. Is starting to grow. The lead electrodes 52 and 62 are connected to electrodes 74 and 75 provided outside the package 7 by conductive paths 72 and 73 (73 is a conductive path on the back side of the drawing) wired on the surface of the pedestal portion 71. Has been. This package type device is mounted on a wiring board (not shown) on which circuit components of an oscillation circuit are mounted, thereby forming a crystal oscillator. The crystal unit package is not limited to the SMD structure, and the crystal unit is provided in a metal cylinder sealed at one end with an insulating material, and drawn out to the inner ends of a pair of electrode pins that penetrate the insulating material. A structure in which the electrodes 52 and 62 are connected may be used.
FIG. 5 schematically shows an example of a circuit in which a crystal oscillator is incorporated in an oscillation circuit, where 101 is an amplifier composed of a CMOS inverter, 102 is a feedback resistor, 103 is a drain resistor, and 104 and 105 are capacitors. The oscillation output of the third harmonic is taken out from the output side of 101.

  Next, the operation and effect of the above embodiment will be described. Both side surfaces 21 and 21 and main surfaces 22 and 22 of the vibrating arm portion 2a and the groove portions 3 and 4 of the vibrating arm portion 2b have the same potential E1, and both the side surfaces 21 and 21 and the main surfaces 22 and 22 of the vibrating arm portion 2b The groove portions 3 and 4 of the vibrating arm portion 2a have the same potential E2, and E1 and E2 are in a relationship of opposite potentials. FIG. 4 is a diagram schematically showing electric lines of force generated in the vibrating arm portions 2a and 2b. By forming the first groove portion 3 and the second groove portion 4, the X-axis direction (vibrating arm portion) is shown. 2 in the width direction) and expands and contracts in the opposite direction between the vibrating arm portions 2a and 2b, thereby strengthening the bending vibration in the Y-axis direction. For this reason, the vibration efficiency is increased and the CI value is reduced. In FIG. 6, the cross-sectional shape of the groove portions 3 and 4 is described as a rectangle for convenience. However, in actuality, in a portion close to the bottom surface due to the influence of anisotropic etching performed at the time of processing, the groove width increases toward the bottom surface. The shape becomes narrower.

  As described above, since the groove portions are provided in the respective vibrating arm portions 2a and 2b, the CI value is reduced. Although the strength is reduced when the groove portion is provided, in this embodiment, the groove portion is divided into two in the length direction instead of providing one groove portion. In other words, the first groove portion 3 and the first groove portion Since the two groove portions 4 are provided, an insufficient strength can be avoided. If the groove is divided into three or more, the CI value becomes large as can be seen from an experimental example described later, so that it is difficult to apply it to a product. That is, the structure of the present invention is based on the conclusion that the splitting is optimal in consideration of the strength and the CI value when providing the groove portions in the respective vibrating arm portions 2a and 2b.

(Experiment 1)
In the tuning-fork type crystal resonator described in the above-described embodiment, the length L2 of the first groove 3 with respect to the length L1 from the base end of the first groove 3 to the tip of the second groove 4 is described. The ratio L2 / L1 was varied, and the strength of each crystal resonator was examined. Assuming that L2 / L1 is expressed in% ((L2 / L1) × 100), it was set in five ways: 0%, 12.5%, 35%, 50% and 65%. 0% means that one groove is formed without dividing the groove.
Regarding other conditions, the length L0 of the vibrating arm 2 (2a, 2b) is 1650 μm, the length L1 from the base end of the first groove 3 to the tip of the second groove 4 is 847 μm, The distance d between the first groove portion 3 and the second groove portion 4 is 10 μm, the length L3 from the bottom surface of the base portion 1 to the lowermost portion 20 of the tuning fork fork portion is 600 μm, and the width W1 of the vibrating arm portion 2 (2a, 2b) is 100 μm, the width W 2 of the groove 3 is 65 μm, and the width W 1 of the bottom surface of the base 1 is 500 μm.

  In the strength test, as shown in FIG. 7, the crystal unit 10 is vertically set on the base 7 and fixed with an adhesive 71, and stress is applied to the main surface 22 of the vibrating arm 2 (2a, 2b). The magnitude of the load when the vibrating arm 2 (2a, 2b) breaks was recorded. This test was performed on three crystal resonators, and the average of the magnitudes of loads at the time of destruction was determined, and the strength of the crystal resonator was evaluated based on this value. The results are as shown in Table 1 and FIG.

The strength when L2 / L1 is 12.5% is 8.0 g, and the strength is larger than 7.4 g when L2 / L1 is 0%. Although the strength values in the first to third tests vary, the above tendency can be clearly seen. And when L2 / L1 is 35% to 65%, the strength is as large as 9.5 g. On the other hand, for each crystal resonator, the CI value of each sample was measured using a CI meter and the average value was obtained. As a result, the CI value was 53 kΩ for all crystal resonators. That is, under this test condition, the CI value was not different from that in the case of one groove portion, and no increase in the CI value was observed due to the division of the groove portion into two. From the above results, it can be said that the strength is increased by dividing the groove into two parts, and it is particularly preferable to set L2 / L1 from 35% to 65% (0.35 to 0.65).
(Experiment 2)
Next, an experiment for finding an appropriate value of the distance d between the first groove portion 3 and the second groove portion 4 was performed. In this experiment, L2 / L1 is set to 35% (0.35), and the distance d between the first groove portion 3 and the second groove portion 4 is changed by changing the position of the second groove portion 4 on the base end side. Variously, d / L1 is 0%, 0.6%, 1.0%. Five types of 1.2% and 2.5% were set. Other conditions are the same as those in Experiment 1. The strength of each crystal resonator was examined in the same manner as in Experiment 1. The results are as shown in Table 2 and FIG. Note that d / L1 of 1.2% corresponds to d in the previous experiment 1 of 10 μm.

From this result, the strength of the crystal resonator increases as the distance d between the groove portions 3 and 4 increases, that is, as d / L1 increases. Accordingly, it can be said that the distance d should be as large as possible only from the strength of the crystal resonator. On the other hand, when the CI value of each sample was measured using a CI meter for the crystal resonator of each condition and the average value was obtained, the results shown in Table 3 and FIG. 10 were obtained.

From this result, it is not preferable to increase the interval d too much because the CI value increases. For this reason, the interval d needs to be set to such a size that the CI value is not too large. For example, d / L1 is set to 1% to 1.8% (0.010 to 0.018). preferable.
(Experiment 3)
Instead of dividing the groove into two, the groove was divided into three, and the distance d between the grooves was set to 10 μm. If the distance d is too small, the processing becomes difficult. Therefore, the size of 10 μm is selected in consideration of the actual production. Other conditions are the same as those in Experiment 1. The CI value of the quartz resonator having the groove divided into three was measured, and the CI value was 58 kΩ. Therefore, it can be seen that the three-divided crystal resonator has a larger CI value than the two-divided crystal resonator.

1 is a schematic plan view showing a tuning fork type crystal resonator according to an embodiment of the present invention. 1 is a perspective view showing a tuning fork type crystal resonator according to an embodiment of the present invention. It is explanatory drawing which shows the dimension of the said tuning fork type crystal resonator. It is sectional drawing which shows the crystal oscillator package which mounted | wore the crystal oscillator of this invention in the package. It is a figure which shows an example of the oscillator using the crystal oscillator of this invention. It is sectional drawing along the AA 'line of FIG. It is a side view which shows the destructive test of a tuning fork type crystal resonator. It is a characteristic view which shows the result of the destructive test of a tuning fork type crystal resonator. It is a characteristic view which shows the result of the destructive test of a tuning fork type crystal resonator. FIG. 6 is a characteristic diagram showing a relationship between a groove interval and a measured CI value in a tuning fork type crystal resonator. It is a schematic plan view showing a conventional tuning fork type crystal resonator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base part 11 Notch part 2 Vibrating arm part 20 Bottom part 3 1st groove part 4 2nd groove part 51 One excitation electrode 61 The other excitation electrode

Claims (5)

In the piezoelectric vibrator formed in a tuning fork shape with two vibrating arms extending from the base,
A groove portion formed on at least one of the front surface portion and the back surface portion of the vibrating arm portion and extending in the length direction from the base end portion of the vibrating arm portion and divided into two in the length direction;
A piezoelectric vibrator comprising a pair of excitation electrodes provided in a side surface and a groove portion of the vibrating arm portion, respectively.   Of the groove portions divided into two in the length direction, if the groove portion on the proximal end side is the first groove portion and the groove portion on the distal end side is the second groove portion, the second end portion from the proximal end portion of the vibrating arm portion 2. The piezoelectric vibrator according to claim 1, wherein a ratio L2 / L1 of the length L2 of the first groove to the length L1 to the tip of the groove is 0.35 to 0.65.   Of the groove portions divided into two in the length direction, if the groove portion on the proximal end side is the first groove portion and the groove portion on the distal end side is the second groove portion, the second end portion from the proximal end portion of the vibrating arm portion 3. The piezoelectric vibration according to claim 1, wherein a ratio d / L1 of a distance d between the first groove portion and the second groove portion with respect to a length L1 to the tip of the groove portion is 0.010 to 0.016. Child.   A crystal resonator according to claim 1, provided in the package, and an electrode provided outside the package and electrically connected to a lead electrode of the crystal resonator. The piezoelectric vibrator package according to any one of claims 1 to 3. 4. The crystal resonator according to claim 1, and an oscillation circuit that outputs a pulse having a third harmonic frequency of the crystal resonator as an oscillation output. The oscillator according to one.

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