JP2007158486A - Crystal resonator element, crystal resonator, and crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for improving a series resonance resistance of a small-sized AT-cut crystal resonator element and suppressing spurious vibration in the vicinity of a resonance frequency. <P>SOLUTION: The crystal resonator element is configured to include: a crystal substrate wherein the X axis direction is a long side direction, the Z' axis direction is a short side direction, and which is formed semi-elliptically at both ends in the long side direction with a major axis versus minor axis ratio is about 1.26; and electrodes formed on both principal sides of the crystal substrate in a similar shape to the shape of the crystal substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a crystal resonator element, a crystal resonator, and a crystal oscillator in which a series resonance resistance of a small crystal resonator element is improved and unnecessary modes are suppressed.

A crystal resonator is widely used as a reference frequency source for industrial equipment and consumer equipment because it has advantages such as small size, small secular change, high accuracy, and high frequency stability. In recent years, the size and weight of devices have been reduced, and the demand for miniaturization of crystal resonators has increased, and there is a great demand for surface mount crystal resonators suitable for automating the assembly of electronic components.
Quartz is a physically and chemically stable substance, but natural quartz is problematic in terms of quality and quantity, so today we use artificial quartz that is superior in terms of quality stability and supply stability. To manufacture crystal units. Among them, AT-cut crystal resonators having a frequency-temperature characteristic exhibiting a cubic curve are used in large quantities in communication devices such as mobile phones. As is well known, an AT-cut crystal unit is a crystal plate (AT-cut crystal plate) obtained by rotating a crystal plate (Y plate) perpendicular to the crystal axis Y of the crystal around the crystal axis X for about 35 degrees 15 minutes. ) And a metal film attached to both main surfaces using vacuum deposition or a sputtering apparatus, and hermetically sealed in the package. The vibration mode of the AT-cut quartz resonator is thickness shear vibration, the resonance frequency f is proportional to the reciprocal of the thickness t, and the proportional constant k is determined from the crystal density ρ and the elastic constant c ′ that depends on the cutting angle. Approx. 1.65 MHz
-Mm.

Due to the strong demand for miniaturization and cost reduction in recent AT-cut quartz crystal units, the quartz plate has a rectangular shape suitable for mass production, and rectangular electrodes are formed on both main surfaces of the quartz plate. After being accommodated in the ceramic package, a metal lid is hermetically sealed using a resistance welding apparatus on the metallized portion formed on the upper peripheral edge of the ceramic package.
FIG. 6 is a diagram showing a configuration of a conventional AT-cut crystal resonator element, in which FIG.
FIG. 4B is a cross-sectional view taken along the line PP, and FIG. 5C is a cross-sectional view taken along the line Q-Q. Also,
6D and 6E are diagrams showing the displacement distribution of the thickness shear vibration viewed from the longitudinal direction and the short direction. As shown in the coordinate axis on the left side of FIG. 6, the rectangular AT-cut quartz plate 31 generally has the longitudinal direction (length L) as the X-axis direction and the short direction (width W) as the Z′-axis direction. is there. On the front and back surfaces of the AT-cut quartz plate 31, the electrode 3 is applied via a mask in a vacuum deposition or sputtering apparatus.
2a and 32b are formed, the crystal resonator element is accommodated in an inner bottom portion of a surface mount package (not shown), and terminal electrodes (not shown) on the package side and leads extending from the electrodes 32a and 32b to the edge of the crystal plate 31 are formed. A crystal resonator is formed by electrically connecting and fixing the electrodes with conductive adhesives 33a and 33b.

An electrical equivalent circuit of a crystal resonator element configured as described above generally has an inductance L
1, a circuit in which a capacitance C0 is connected in parallel to a series circuit of a capacitor C1 and a resistor R1. Here, the inductance L1, the capacitance C1, and the capacitance C0 depend on the thickness of the crystal plate and the area of the electrode, and the resistance R1 represents the loss of vibration energy. Further, the resistance at the frequency at which the crystal resonator element is in a resonance state, that is, the phase is zero when viewed from the two terminals, is the effective resistance Re (≈ series resonance resistance R1)
That's it.
In order to use a crystal resonator as a reference frequency source, it is necessary to configure a crystal oscillator by connecting the crystal resonator and an amplifier circuit. Colpitts-type crystal oscillators with a simple circuit are common as crystal oscillation circuits, and the amplification factor on the circuit side (called negative resistance) when the circuit side is viewed from the crystal unit
Requires several times the effective resistance Re of the crystal resonator.
As shown in FIGS. 6D and 6E, the vibration displacement distribution is small, that is, the side ratio (
When the length L or the ratio of the width W to the thickness t (L / t or W / t) of the quartz plate is reduced,
Even if the distance between the electrodes 32a and 32b and the end of the quartz plate 31 is narrowed and the design is made using the energy confinement theory, the vibration energy is not confined under the electrodes but leaks to the support portion, and the series resonance resistance R1 is reduced. growing. Even if the side ratio is selected to be an optimum value, a part of the vibration energy of the main vibration is converted into the contour mode at the end of the crystal plate 31, and the series resonance resistance R1 of the crystal vibration element is deteriorated.

As shown in FIG. 7, as a crystal resonator element that solves this problem, as shown in FIG.
By using a quartz plate with beveled at both ends (in the X-axis direction) and confining the vibration energy of thickness-shear vibration in the center of the quartz plate, the effect of the support part, conversion to other modes at the edge part Is used as much as possible to improve the resistance R1. In addition, the same code | symbol is attached | subjected to the same site | part as FIG. 6, and description is abbreviate | omitted.
Further, Patent Document 1 discloses a crystal resonator element as shown in FIG. Note that FIG.
The same parts as those in FIG. FIG. 8A is a plan view, FIG.
c) are cross-sectional views along PP and QQ, respectively. As shown in FIGS. 8A, 8 </ b> B, and 8 </ b> C, the front and back of the edges corresponding to each of the four sides of the crystal plate 51 are changed by the curvature R, and the crystal plate 51
At the edge corresponding to the four sides, a gradually decreasing portion 52 is formed that gradually decreases so that the thickness gradually decreases toward the end face of the quartz plate. The electrodes 32a, 3 are formed on both main surfaces of the quartz plate 51 thus processed.
It is disclosed that when a crystal resonator element is configured by attaching 2b, the vibration energy of the thickness shear vibration is confined in the center of the crystal plate 51, and the series resonance resistance R1 can be improved.
JP 2003-174353 A

However, in the crystal resonator element having the configuration shown in FIG. 7, the effect of energy confinement varies, and not only the series resonance resistance R1 is sufficiently improved, but the main vibration is combined with the contour mode, and the frequency temperature There is a problem that the characteristics are deformed from an ideal cubic curve.
Further, the crystal plate in which gradually decreasing portions are formed at the edge portions corresponding to the four sides of the crystal plate shown in FIG. 8 has a problem that the time required for processing increases and the cost of the crystal resonator element increases.
An object of the present invention is to provide a small crystal resonator element, a crystal resonator, and a crystal oscillator that are improved in series resonance resistance R1, suppress unnecessary modes, and are low in cost.

In order to improve the small-sized crystal resonator element, the crystal resonator element according to the present invention has the X-axis direction as the longitudinal direction, the Z′-axis direction as the short direction, and both ends of the longitudinal direction have a major axis to minor axis ratio of approximately A quartz plate formed in a semi-elliptical shape of 1.26 and electrodes formed on both main surfaces of the quartz plate in a shape similar to the shape of the quartz plate are provided. In such an invention, both ends of the quartz plate and the electrode are made semi-elliptical, and the ratio of the major axis to the minor axis of the ellipse is matched to the vibration displacement distribution, thereby improving the series resonance resistance of the quartz resonator element. Since the coupling between the main vibration and the contour vibration can be suppressed, there is an advantage that the yield of the small crystal resonator element with less unnecessary vibration is improved.
The crystal resonator element according to the present invention has a semi-elliptical shape in which the X-axis direction is the longitudinal direction, the Z′-axis direction is the short-side direction, and both ends of the longitudinal direction have a major-to-minor axis ratio of approximately 1.26. And forming
A crystal plate in which the central part of both main surfaces is thicker than the peripheral part and the shape of the central part is similar to the outer shape, and the crystal plate is similar to the shape of the crystal plate on both sides of the central part of the crystal plate The formed electrode;
I was prepared to. In such an invention, the quartz plate is a mesa type, the center portion of the quartz plate and both ends of the electrode are semi-elliptical, and the ratio of the major axis to the minor axis of the ellipse is matched to the vibration displacement distribution,
There are advantages that the series resonance resistance of the small crystal resonator element is further improved, and that the coupling between the main vibration and the contour vibration is suppressed, and a small crystal resonator element with less unnecessary vibration can be obtained.
The crystal resonator element according to the present invention has a semi-elliptical shape in which the X-axis direction is the longitudinal direction, the Z′-axis direction is the short direction, and one end of the long direction is a major axis to minor axis ratio of approximately 1.26. And forming
A quartz plate in which the central part of both main surfaces is a mesa type thicker than the peripheral part, and both ends of the central part are formed in a semi-elliptical shape having a major axis to minor axis ratio of approximately 1.26, and the center of the quartz plate And electrodes formed on both surfaces of the part in a shape similar to the shape of the central part. In such an invention, one end of the quartz plate is semi-elliptical, the quartz plate is mesa-shaped, the center of the quartz plate and both ends of the electrode are semi-elliptical, and the major axis and minor axis of the ellipse By adjusting the ratio to the vibration displacement distribution, there are advantages that the series resonance resistance of the small crystal resonator element can be further improved and a small crystal resonator element in which unnecessary vibration is suppressed can be configured.
In addition, a crystal resonator can be constructed by hermetically sealing the crystal resonator element in a surface mounting package.
Further, a crystal oscillator can be constructed by adding an oscillation circuit component to the above-described crystal resonator.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of a small-sized AT-cut quartz crystal resonator element according to the present invention. FIG. 1 (a) is a plan view, FIG. 1 (b) is a cross-sectional view at PP, and FIG. ) Is a cross-sectional view taken along Q-Q, and FIGS. 4D and 4E are vibration displacement distribution diagrams viewed from the longitudinal direction and the lateral direction, respectively. The longitudinal direction of a rectangular crystal plate (AT-cut crystal plate) cut out by rotating a crystal plate (Y plate) orthogonal to the crystal axis Y of the crystal about 35 degrees 15 minutes around the crystal axis X is the X-axis direction and short Let the direction be the Z′-axis direction. Then, both ends in the longitudinal direction are processed into a semi-elliptical shape, and the ellipse has a ratio of major axis to minor axis (
The major axis / minor axis is about 1.26. Accordingly, as shown in FIG. 1A, when the length of the quartz plate 1 in the short direction is h, the left end portion of the quartz plate 1 in the drawing and the reference line S1, or the right end portion of the drawing and the reference line S2 in the drawing. Is 0.63h which is 1/2 of the long axis.
As shown in FIG. 1A, the quartz plate 1 has a semi-elliptical shape at both ends in the longitudinal direction and a rectangular oval shape at the intermediate portion. A crystal resonator element A is obtained by forming electrodes 2a and 2b similar to the crystal plate 1 on both main surfaces of the crystal plate 1 through a mask using a vacuum evaporation apparatus or a sputtering apparatus. The crystal resonator element A is placed on the inner bottom of a package (not shown), and the terminal electrode of the package and the lead electrodes 3a and 3b of the crystal resonator element A are conductively fixed with a conductive adhesive, and then formed on the upper peripheral edge of the package. The metallized portion and a metal lid (not shown) are hermetically sealed using a resistance welding apparatus to constitute a small crystal resonator element A.

A characteristic configuration of the crystal resonator element A according to the embodiment of the present invention is the longitudinal direction of the crystal plate 1 (X
The shape of both ends in the axial direction) and both ends in the X-axis direction of the electrodes 2a, 2b are semi-elliptical, and the ratio of the major axis to the minor axis (major axis / minor axis) of the ellipse is approximately 1.26. Is a point. Here, the constant 1.2
The reason for using 6 will be described.
In the well-known energy confinement theory, if the propagation constant used in the equation of vibration displacement u is k for the electrodeless portion and ke for the electrode portion, it can be expressed by the following equations.
k = μ (mπ / h) (1− (f / (mfs)) ² ) ^1/2 (1)
ke = μ (mπ / h) ((f / (mfe)) ² −1) ^1/2 (2)
Here, the constant μ is a constant determined by an elastic constant, m is the harmonic order, h is the thickness of the quartz plate, fs is the cutoff frequency of the electrodeless portion, and fe is the frequency of the electrode portion.
Since quartz is a crystal belonging to the trigonal system, it has anisotropy, and its elastic constant varies depending on the crystal axis direction. In the case of an AT-cut quartz plate, the elastic constant of the wave propagating in the X-axis direction is different from the elastic constant of the wave propagating in the Z′-axis direction. As a result, the constant μ used for the propagation constants k and ke is also μx in the X-axis direction propagation and μz in the Z′-axis direction propagation,
The ratio of μx / μz is 1.26. For this reason, the vibration displacement distribution of the AT-cut crystal resonator element is different in the X-axis direction and the Z′-axis direction in the spread of the displacement distribution, and is elliptical with the X-axis direction as the major axis and the Z′-axis direction as the minor axis. Distribution. The ratio of major axis / minor axis is μx / μz, which is 1.26.
In the crystal resonator element A according to the present invention, the fact that the vibration displacement distribution is distributed in an elliptical shape is taken into the design of the small AT cut crystal resonator element, and both ends of the crystal plate 1 and the electrodes 2a and 2b are made into a semi-elliptical shape, The ratio of the major axis to the minor axis of the ellipse was approximately 1.26 in accordance with the vibration displacement distribution. The vibration displacement distribution of the crystal resonator element configured as shown in FIG. 1 is as shown in FIG. 1D in the longitudinal direction and in FIG. 1E in the short direction, and the series resonance resistance R1 is improved. Unnecessary modes near the vibration are also sufficiently suppressed.

FIG. 2 shows a second embodiment according to the present invention. FIG. 2A is a plan view, and FIG.
The cross-sectional view at P, (c) is a cross-sectional view at Q-Q, and (d), (e) are diagrams showing the vibration displacement distribution as viewed from the longitudinal direction and the short-side direction, respectively. The same parts as those in FIG. The outer peripheral portion of the quartz plate 11 is processed into a semi-elliptical shape at both ends in the longitudinal direction (X-axis direction) as in FIG. 1, and the ratio of the major axis / minor axis of the ellipse is 1.26. And crystal plate 11
As shown in FIGS. 1 (a), (b), and (c), both main surfaces are processed into a so-called mesa type (plateau type) in which the central portion is thicker than the peripheral portion, and the central portion (plateau portion) that is thicker than the peripheral portion. ) The shape of both ends in the longitudinal direction of 12 is processed into a semi-elliptical shape like the outer peripheral contour shape of the quartz plate 11. The major axis / minor axis ratio of this ellipse is also 1.26. Further, the shape of the electrodes 2a and 2b attached to both surfaces of the central portion 12 of the quartz plate 11 is formed to be similar to that of the central portion 12 to constitute the quartz crystal vibrating element A.
The vibration displacement distribution of the crystal resonator element A configured as shown in FIG.
The solid line 14 in the short direction is distributed as shown by the solid line 15 shown in FIG. 1E, and the crystal plate 11 is not processed into a mesa shape, that is, the central part 12 thicker than the peripheral part is not formed. It can be seen that the vibration displacement distribution is concentrated in the central portion as compared with the vibration displacement distributions 4 and 5 of the quartz crystal vibration element of FIG. That is, the energy confinement becomes deeper, and a part of the vibration energy leaks to the support part or is converted into another contour vibration, so that the amount lost is reduced, and the series resonance resistance R1 is improved accordingly. Unnecessary modes are also suppressed.

FIG. 3 shows a third embodiment according to the present invention. FIG. 3A is a plan view, and FIG.
A cross-sectional view at P and FIG. 10C are cross-sectional views at QQ. The difference in configuration between the crystal resonator element A according to the present embodiment and the crystal resonator element of FIG. 2 is the outer peripheral contour shape of the crystal plate 21, and in this embodiment, one end of the crystal plate 21 in the longitudinal direction. Is processed into a semi-elliptical shape, and the other end is rectangular. Then, the crystal plate 21 is processed into a mesa shape, and the central portion 2 that is thicker than the peripheral portion.
The shape of both ends in the longitudinal direction of 2 is processed into a semi-elliptical shape. Also in this case, the ratio of the major axis / minor axis of the ellipse is 1.26. A crystal resonator element A is configured by forming electrodes 2 a and 2 b similar to the center portion 22 on the center portion 22 of the thus configured quartz plate 21. It has been found that the series resonance resistance R1 of the crystal resonator element configured as described above is also improved from the conventional one, and unnecessary modes near the main vibration are suppressed.
In the conventional example shown in FIG. 8 (a), the gradually decreasing portion has an elliptical shape, but the ratio of the major axis / minor axis is not clearly shown, and the major axis / minor axis ratio is specified as in the present invention. Obviously, it cannot be controlled within the range.

Next, FIG. 4 is a cross-sectional view illustrating a configuration example of a crystal resonator configured using the crystal resonator element according to the embodiment of FIG. 1, and the crystal resonator element A is accommodated in the inner bottom portion of the surface mounting package 61. The two terminal electrodes 62 provided on the inner bottom of the package and the lead electrodes 3a and 3b extending from the electrodes 2a and 2b to the edges of the crystal plate 1 are electrically fixed using a conductive adhesive 63 and then the lid The quartz crystal resonator B is configured by hermetically sealing with 64. Mounting electrodes 65 for surface mounting are disposed on the outer bottom surface of the package 61.
Note that the quartz crystal resonator according to the other embodiments shown in FIGS. 2 and 3 can also be built in the package 61 and hermetically sealed to construct a quartz crystal resonator. .
This crystal resonator B can exhibit a unique effect of the crystal resonator element A according to each embodiment of the present invention.
Next, FIG. 5 is a cross-sectional view illustrating a configuration example of a crystal oscillator configured using the crystal resonator B according to the embodiment of FIG. 4, and the crystal oscillator C includes the crystal resonator B illustrated in FIG. 4. It has a substantially H-shaped structure in which a lower package 71 is continuously provided at the bottom of the package, and has a configuration in which an IC chip 73 constituting an oscillation circuit or the like is flip-chip mounted on a pad 72 provided on the ceiling surface of the lower package 71. Yes. A mounting terminal 74 for surface mounting is formed on the bottom surface of the lower package 71.
This crystal oscillator C can exhibit a unique effect of the crystal resonator element A according to each embodiment of the present invention.

Schematic which showed the structure of the crystal oscillation element which concerns on this invention. Schematic which showed the structure of 2nd Embodiment which concerns on this invention. Schematic which showed the structure of 3rd Embodiment which concerns on this invention. The block diagram of the crystal oscillator comprised using the crystal | crystallization vibration element which concerns on this invention. The block diagram of the crystal oscillator comprised using the crystal oscillator based on this invention. Schematic which showed the structure of the conventional crystal oscillation element. Schematic which showed the other structure of the conventional crystal oscillation element. Schematic which showed the other structure of the conventional crystal oscillation element.

Explanation of symbols

A Quartz vibrating element 1, 11, 21 Quartz plate, 2a, 2b electrode, 3a, 3b Lead electrode, 4, 5, 14, 15 Vibration displacement distribution, 12, 22 Central part, h Ellipse short axis, S1
, S2 reference line, B crystal resonator, 61 surface mount package, 62 terminal electrode, 63
Conductive adhesive, 64 lid, 65 mounting electrode, 71 lower package, 72 pad, 7
3 IC chip, 74 mounting terminal, C crystal oscillator.

Claims (5)

An AT-cut quartz plate in which the X-axis direction is the longitudinal direction, the Z′-axis direction is the short-side direction, and the shape of both ends in the longitudinal direction is a semi-elliptical shape having a long-to-short-axis ratio of approximately 1.26 And an electrode formed on both main surfaces of the crystal plate in a shape similar to the outer peripheral contour shape of the crystal plate. The X-axis direction is the longitudinal direction, the Z′-axis direction is the short-side direction, and both end portions of the long-side direction are formed in a semi-elliptical shape having a long-to-short-axis ratio of approximately 1.26, and both main surfaces An AT-cut quartz plate in which the central portion of the quartz plate is thicker than the peripheral portion, and the shape of the central portion is similar to the outer peripheral contour shape, and the outer peripheral contour shape of the crystal plate on both sides of the central portion of the crystal plate A crystal resonator element comprising: an electrode formed in a similar shape. The X-axis direction is the longitudinal direction, the Z′-axis direction is the short-side direction, and the shape of one end of the long-side direction is formed into a semi-elliptical shape with a long-axis to short-axis ratio of approximately 1.26, and both main surfaces An AT-cut quartz plate in which the central portion is a mesa type thicker than the peripheral portion, and the shape of both ends of the central portion is a semi-elliptical shape having a major axis to minor axis ratio of approximately 1.26, and the quartz plate An electrode formed on both surfaces of the central portion of the central portion so as to have a shape similar to the shape of the central portion. A crystal resonator element according to any one of claims 1, 2, and 3, a package for surface mounting, and a lid for sealing an opening of the package, wherein the crystal resonator element is disposed in the package. And the package is hermetically sealed by the lid.   A crystal oscillator comprising the crystal resonator according to claim 4 and an oscillation circuit.

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