JP6035808B2 - Vibration element, vibrator, electronic device, and electronic apparatus - Google Patents

Description

  The present invention relates to a vibration element, a vibrator, an electronic device, and an electronic apparatus that excite thickness shear vibration.

  The AT-cut quartz resonator that excites the thickness-shear vibration, which is the main vibration, has a cubic curve that is suitable for miniaturization and higher frequency, and has excellent frequency temperature characteristics, so it is used in various fields such as oscillators and electronic devices. ing. In particular, in recent years, as the processing speed of transmission communication equipment and OA equipment has increased, or the capacity of communication data and processing volume has increased, the AT-cut crystal resonator used as the reference frequency signal source has a higher frequency. There is an increasing demand for conversion. In order to increase the frequency of an AT-cut crystal resonator excited by thickness shear vibration, it is common to increase the frequency by reducing the thickness of the vibrating portion.

However, when the thickness of the vibration portion is reduced as the frequency is increased, the frequency adjustment sensitivity is increased, so that the frequency tracking accuracy is deteriorated and the manufacturing yield of the vibrator is lowered. On the other hand, in Patent Document 1, in the vibration element of the temperature compensated oscillator, the four corners of the rectangular excitation electrode are cut out substantially evenly, and the area ratio is 95% to 98% before cutting out. It is disclosed that the frequency variable sensitivity can be increased and the margin for adjusting the oscillation frequency can be increased by reducing the capacitance ratio γ of the vibrator.
In paragraph [0024] of Patent Document 1, “if the area ratio is less than 95%, the excitation electrode part of the vibration part that actually contributes to vibration is missing, and the equivalent series capacitance C1 is small. Thus, the effect of reducing the capacity ratio γ cannot be obtained. ”

JP 2002-111435 A

However, as disclosed in Patent Document 1 described above, even if the four corners of the excitation electrode are cut out and the area ratio is 95% to 98% and the capacitance ratio γ can be reduced, the temperature compensated oscillator has the electrical characteristics. Although sufficient, the vibrator used in the voltage controlled oscillator has a problem that the frequency variable sensitivity that can compensate for the deteriorated frequency adjustment accuracy cannot be obtained.
Therefore, in order to increase the frequency variable range of the voltage controlled oscillator at a high frequency (200 MHz or more) and improve the manufacturing yield of the vibrator, a vibration element having a small capacitance ratio γ is provided.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A vibration element according to this application example includes a substrate that vibrates due to thickness shear vibration, a first excitation electrode that is provided on one main surface of the substrate and has a shape in which four corners of a rectangle are cut out, A second excitation electrode provided on the other main surface of the substrate, and a ratio (S2 / S1) of the rectangular area S1 to the area S2 of the first excitation electrode is 87.7%. ≦ (S2 / S1) <95.0%.

  According to this application example, in the high-frequency vibration element excited by the thickness shear vibration of the fundamental wave, the four corners of the excitation electrode that do not actually contribute to the vibration are removed, so that the equivalent series capacitance C1 has almost no effect and does not change. Since the parallel capacitance C0 is reduced in proportion to the reduced area, the capacitance ratio (γ = C0 / C1) of the vibration element is reduced, and a voltage-controlled oscillator having a large frequency variable sensitivity can be obtained.

  Application Example 2 In the resonator element according to the application example described above, when the first excitation electrode and the second excitation electrode are projected from a direction orthogonal to the main surface, the second excitation electrode The first and second excitation electrodes have different shapes so as to fit within the outer edge of the excitation electrode.

According to this application example, in the high-frequency vibration element excited by the thickness shear vibration of the fundamental wave, the electrode film thickness can be increased compared to the case where the areas of the first excitation electrode and the second excitation electrode are the same. There is an effect that the ohmic cross of the electrode film can be avoided and the deterioration of the CI value of the main vibration can be prevented.
Further, when the first excitation electrode and the second excitation electrode are formed by the metal mask method, the facing area between the first excitation electrode and the second excitation electrode is changed even if there is a slight misalignment. Therefore, since there is no variation between the equivalent series capacitance C1 and the equivalent parallel capacitance C0, there is an effect that a vibration element with a small variation in the capacitance ratio γ can be obtained.

  Application Example 3 The vibration element according to the application example described above includes a lead electrode that extends from the first excitation electrode and the second excitation electrode toward an end portion of the substrate. The lead electrode extending from the excitation electrode having the notched shape extends from an end of the excitation electrode except for the notched region.

  According to this application example, by extending from the end of the excitation electrode excluding the region where the lead electrode is notched, it is possible to avoid the four corner portions that are effective in reducing the capacitance ratio γ. The smaller vibration element can be obtained.

  Application Example 4 In the resonator element described in the application example, the energy confinement coefficient M is 17.1 ≦ M ≦ 35.7.

  According to this application example, in the high-frequency vibration element excited by the thickness shear vibration of the fundamental wave, the CI value can be reduced to 20Ω or less by setting the vibration energy confinement coefficient M to 17.1 or more. Has the effect of facilitating. In addition, by setting the energy confinement coefficient M to 35.7 or less, there is an effect that the influence of spurious in the inharmonic mode that inhibits the oscillation of the main vibration can be suppressed.

  Application Example 5 In the resonator element according to the application example, the resonance frequency of the thickness shear vibration is 200 MHz or more.

  According to this application example, the vibration element excited by the thickness-shear vibration can be increased in frequency by reducing the thickness of the vibration part. However, when the resonance frequency becomes a high frequency of 200 MHz or more, the plate thickness is 8.4 μm or less. Therefore, the frequency control in the process of adjusting the frequency by peeling off the film of the excitation electrode becomes very difficult, and the frequency deviation becomes very large. For this reason, reducing the capacitance ratio γ when the resonance frequency is 200 MHz or more can relax the frequency adjustment accuracy and improve the manufacturing yield of the vibrator.

  Application Example 6 In the resonator element according to the application example, the substrate is a quartz substrate.

  According to this application example, since the quartz substrate has a high Q value and a cutting angle with excellent temperature characteristics, there is an effect that a vibration element with small CI value and excellent temperature characteristics can be obtained.

  Application Example 7 A vibrator according to this application example includes the vibration element according to the application example described above and a package that houses the vibration element.

  According to this application example, since the vibration element is accommodated in the package, it is possible to prevent the influence of disturbance such as temperature change and humidity change and the influence of contamination. Therefore, frequency reproducibility, frequency temperature characteristic, CI temperature characteristic, In addition, there is an effect that a vibrator having excellent frequency aging characteristics can be obtained.

  Application Example 8 An electronic device according to this application example includes the vibration element according to the application example described above and an oscillation circuit that excites the vibration element.

  According to this application example, when an electronic device is configured using a high-frequency vibration element excited by a fundamental wave, the capacitance ratio γ of the vibration element is small, so the frequency variable width is wide, and further, excitation is performed by the fundamental wave. There is an effect that a high-frequency voltage-controlled oscillator having a good S / N ratio can be obtained.

  Application Example 9 An electronic apparatus according to this application example includes the vibration element described in the application example.

  According to this application example, an electronic device including a reference frequency source having a high frequency and excellent frequency stability and a good S / N ratio can be configured by using a high-frequency vibration element excited by a fundamental wave in an electronic device. There is an effect.

It is the schematic which showed the structure of the vibration element which concerns on one Embodiment of this invention, (a) is a top view, (b) is PP sectional drawing, (c) is QQ sectional drawing. The figure explaining the relationship between an AT cut quartz substrate and a crystal axis. It is explanatory drawing which shows the vibration displacement distribution in a rectangular-shaped excitation electrode, (a) is a top view, (b) is a longitudinal cross-sectional view. The figure which shows C1 value and C0 value of a vibration element with respect to electrode area ratio. The figure which shows capacitance ratio (gamma) of the vibration element with respect to electrode area ratio. The figure which shows the trial production conditions and measurement result of an AT cut crystal resonator element. The figure which shows CI value of the vibrator | oscillator with respect to the energy confinement factor M. The figure which shows CI value ratio of the main vibration CI value of a vibrator | oscillator with respect to the energy confinement factor M, and a spurious CI value. It is the schematic which showed the structure of the vibrator | oscillator which concerns on one Embodiment of this invention, (a) is a top view, (b) is a longitudinal cross-sectional view. It is the schematic which showed the structure of the electronic device which concerns on one Embodiment of this invention, (a) is a top view, (b) is a longitudinal cross-sectional view. The perspective view which shows the structure of the mobile type (or notebook type) personal computer to which the electronic device provided with the vibration element which concerns on one Embodiment of this invention is applied. The perspective view which shows the structure of the mobile telephone (PHS is also included) to which the electronic device provided with the vibration element which concerns on one Embodiment of this invention is applied. The perspective view which shows the structure of the digital still camera to which the electronic device provided with the vibration element which concerns on one Embodiment of this invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration of a vibration element according to an embodiment of the present invention. FIG. 1 (a) is a plan view of the vibration element, and FIG. 1 (b) is a PP line of FIG. 1 (a). Sectional drawing and FIG.1 (c) are QQ sectional drawings of Fig.1 (a).
The vibration element 1 is connected to the vibration part 12 and the vibration part 12, and includes a substrate 10 having a thick part 13 thicker than the vibration part 12 and both main surfaces of the vibration part 12 (front and back surfaces in the ± Y ′ direction). ), The first excitation electrode 25a and the second excitation electrode 25b formed so as to face each other, and the pad electrode 29a provided in the thick portion from the first excitation electrode 25a and the second excitation electrode 25b. , 29b, lead electrodes 27a, 27b formed to extend.

The substrate 10 has a rectangular shape, a thin plate-shaped vibrating portion 12 that is thin, perpendicular to the Y ′ axis, and has a constant thickness, and a first integrated along three sides excluding one side of the vibrating portion 12. A thick portion 13 comprising a thick portion 14, a second thick portion 15, and a third thick portion 16 (also referred to as first, second and third thick portions 14, 15, 16), , And a slit 17 for preventing transmission of mount stress generated when the support is fixed to the vibration part 12.
The first thick body 14a, the second thick body 15a, and the third thick body 16a (also referred to as first, second, and third thick bodies 14a, 15a, 16a) are: A region where the thickness parallel to the Y ′ axis is constant.
The first inclined portion 14b, the second inclined portion 15b, and the third inclined portion 16b (also referred to as first, second, and third inclined portions 14b, 15b, and 16b) are the first and first An inclined surface generated between the second and third thick-walled main bodies 14a, 15a, and 16a and the vibrating portion 12.
One principal surface of the vibration part 12 and one surface of each of the first, second and third thick parts 14, 15, 16 are on the same plane, that is, XZ of the coordinate axes shown in FIG. This surface (on the plane, the lower surface side in the −Y direction of FIG. 1B) is referred to as a flat surface (flat surface), and the opposite surface having the recess 11 (of FIG. 1B). The upper surface side in the + Y ′ direction is called a concave surface.

In the embodiment shown in FIG. 1, the first excitation electrode 25a and the second excitation electrode 25b are formed in a shape in which the four corners of the rectangle are cut out. The second excitation electrode 25b has a rectangular shape, and is formed so as to face the substantially central portion (both the upper surface and the lower surface) of the main surface of the vibration unit 12. The first excitation electrode 25a preferably has a uniform (substantially equal) area at the four corners that are notched. However, even if a difference of about 10% occurs in consideration of manufacturing variations, it affects the actual vibration. It has been confirmed that there is no problem that affects the effect obtained by this embodiment.
In addition, the first excitation electrode 25a and the second excitation electrode 25b are bounded by an extension line (virtual line) along the outer edge (outer side) of the excitation electrode shape at a portion connected to the lead electrodes 27a and 27b. It explains as a shape and an area.
The lead electrode 27a extends from the excitation electrode 25a formed on the concave surface, and passes through the third inclined portion 16b and the third thick main body 16a from above the vibration portion 12, and the second thick main body 15a. Is electrically connected to the pad electrode 29a formed on the concave surface of the. The lead electrode 27b extends from the excitation electrode 25b formed on the flat surface, and passes through the edge of the flat surface of the substrate 10 to be a pad electrode formed on the flat surface of the second thick body 15a. 29b is electrically connected.

The embodiment shown in FIG. 1A is an example of a lead-out structure of the lead electrodes 27a and 27b, and the lead electrode 27a may pass through another thick part. However, it is desirable that the lengths of the lead electrodes 27a and 27b are the shortest, and it is desirable to suppress an increase in capacitance by considering that the lead electrodes 27a and 27b do not intersect each other with the substrate 10 interposed therebetween.
Further, the first excitation electrode 25a, the second excitation electrode 25b, the lead electrodes 27a and 27b, and the pad electrodes 29a and 29b are made of, for example, nickel (Ni) as a base using a vapor deposition apparatus or a sputtering apparatus. A film is formed and gold (Au) is stacked thereon. As the electrode material, chromium (Cr) may be used instead of the underlying nickel (Ni), and silver (Ag) or platinum (Pt) may be used instead of gold (Au).

  A piezoelectric material such as quartz belongs to the trigonal system and has crystal axes X, Y, and Z orthogonal to each other as shown in FIG. The X axis, the Y axis, and the Z axis are referred to as an electric axis, a mechanical axis, and an optical axis, respectively. The quartz substrate used as the substrate 10 is a flat plate cut out from the quartz along a plane obtained by rotating the XZ plane around the X axis by a predetermined angle θ. For example, in the case of an AT-cut quartz substrate, the angle θ is approximately 35 ° 15 ′. Note that the Y-axis and the Z-axis are also rotated by θ around the X-axis to become the Y′-axis and the Z′-axis, respectively. Accordingly, the AT-cut quartz substrate has crystal axes X, Y ′, and Z ′ that are orthogonal to each other. The AT-cut quartz substrate has a thickness direction parallel to the Y ′ axis, an XZ ′ plane orthogonal to the Y ′ axis (a plane including the X axis and the Z ′ axis), and thickness shear vibration as the main vibration. Excited.

That is, as shown in FIG. 2, the substrate 10 is centered on the X axis of an orthogonal coordinate system composed of an X axis (electrical axis), a Y axis (mechanical axis), and a Z axis (optical axis). The axis tilted in the -Y direction is the Z 'axis, the Y axis is the axis tilted in the + Z direction of the Z axis, the Y' axis, and is composed of surfaces parallel to the X and Z 'axes, and is parallel to the Y' axis This is an AT-cut quartz substrate having a thickness in any direction.
The substrate 10 according to the present embodiment is not limited to the AT cut having an angle θ of about 35 ° 15 ′ shown in FIG. 2, and is widely applied to a substrate such as a BT cut that excites thickness shear vibration. it can.
Furthermore, although it demonstrated using the example which provided the thick part along the outer edge of the vibration part 12, it is not restricted to this, The board | substrate and thick part which provided the thick part along the outer edge perimeter of the vibration part 12 The present invention can be widely applied to a plate-like substrate in which no is provided.

  A voltage-controlled oscillator is composed of a control voltage terminal including a vibrator, an oscillation circuit unit, and a variable capacitance diode. As an important specification, there is a frequency variable range in which the oscillation frequency of the vibrator can be varied by a control voltage. This frequency variable range is the APR (absolute frequency variable range) and frequency tolerance (frequency room temperature deviation, frequency temperature characteristics, frequency fluctuation due to power supply voltage, frequency fluctuation due to load, frequency fluctuation due to reflow, frequency fluctuation due to reflow, etc. Therefore, in the voltage controlled oscillator, the oscillator itself compensates for the amount of frequency change caused by changes in the external environment of the oscillator and oscillation circuit conditions. For this reason, widening the frequency variable range is very important in improving the manufacturing yield of the vibrator because the allowable frequency deviation due to manufacturing and design can be relaxed.

Here, the frequency variable sensitivity S of the voltage controlled oscillator is expressed by the following formula (1).
S = −ΔCL / 2 · γ · C0 · (1 + CL / C0) ² (1)
Here, ΔCL is a change in load capacity, γ is a capacity ratio (C0 / C1), C0 is an equivalent parallel capacity, and CL is a load capacity.
From the equation (1), the frequency variable sensitivity S is determined by the equivalent parallel capacitance C0 of the vibration element and the capacitance ratio γ if the load capacitance CL constituted by the oscillation circuit is constant, and is particularly affected by the capacitance ratio γ. . Therefore, if the capacity ratio γ is small, the frequency variable sensitivity S of the voltage controlled oscillator can be increased, and the manufacturing yield of the vibrator can be improved.

  FIG. 3 shows the result of calculating the vibration displacement distribution in the thickness-shear vibration mode of the fundamental wave of the vibration element having the rectangular excitation electrode 23 by the finite element method. From this figure, it is understood that the vibration displacement is very small at the four corners of the excitation electrode 23, and this portion does not contribute to the actual vibration. Here, the equivalent parallel capacitance C0 of the vibration element is a capacitance between the front and back excitation electrodes and depends on the facing area. However, since the equivalent series capacitance C1 is a capacitance component in the actual vibration part, the area of the excitation electrode 23 is It doesn't depend if it's big enough. Therefore, removing a part of the excitation electrode 23 that does not contribute to actual vibration can reduce only the equivalent parallel capacitance C0 without affecting the equivalent series capacitance C1, so that a vibration element with a small capacitance ratio γ is obtained. It is done.

FIG. 4 shows the C1 value and the C0 value with respect to the electrode area ratio (S2 / S1) of the AT-cut quartz crystal resonator element having a resonance frequency in the 491 MHz band that was prototyped in the embodiment of FIG.
The main area with respect to the electrode area ratio (S2 / S1) when the area of the rectangular excitation electrode (0.30 mm × 0.24 mm) is defined as the reference area S1 and the area S2 of the electrode obtained by gradually removing the electrode portions at the four corners of the rectangle. It shows an equivalent series capacitance C1 value and an equivalent parallel capacitance C0 value of vibration.
As shown in FIG. 4, the equivalent series capacitance C1 shows a substantially constant value because the portion not contributing to vibration is removed up to about 90% as the electrode area ratio (S2 / S1) decreases. However, when it exceeded about 90%, it became clear that it began to influence a vibration and showed the tendency to become small. It was also confirmed that the equivalent parallel capacitance C0 is in proportion to the decrease in the electrode area ratio (S2 / S1) and tends to decrease.
Therefore, the inventors of the present application do not substantially adversely affect the main vibration characteristics of the AT-cut crystal resonator even when the electrode area ratio (S2 / S1) exceeds about 90%, and reduces the capacitance ratio γ. Experiments and simulations were repeated and analyzed in a region where the frequency variable sensitivity was further improved compared to the prior art.

FIG. 5 shows the capacitance ratio γ of the AT-cut quartz-crystal vibrating element with respect to the electrode area ratio (S2 / S1). As the electrode area ratio (S2 / S1) decreases, the capacitance ratio γ decreases, but 90%. It gradually increased when the ratio exceeded, and at 86% or more, it showed a tendency to become larger than the initial capacity ratio γ. From this result, the electrode area ratio (S2 / S1) to the area S1 of the rectangular excitation electrode based on the area S2 of the rectangular shape with the four corners cut out is 87.7% ≦ (S2 / S1) <95%. Thus, it was confirmed that a vibration element having a smaller capacity ratio γ can be obtained than in the prior art.
In Patent Document 1, which is a conventional technique, “If the area ratio is less than 95%, the excitation electrode part of the vibration part that actually contributes to vibration is missing, and the equivalent series capacitance C1 becomes small, and the capacitance ratio γ However, the inventors have stated that it is impossible to further reduce the capacitance ratio γ, but the inventors of the present application have an electrode area ratio (S2 / S1) of 87. It was possible to derive that there is a region where the capacity ratio γ can be further reduced in the region of 0.7% ≦ (S2 / S1) <95%, that is, in the region impossible in Patent Document 1.

Generally, in the thickness-shear vibration mode, when a partial electrode is formed on a substrate or a plate thickness difference is provided, vibration energy can be confined in the vicinity of the portion, and a stable resonance frequency can be obtained. The resonance frequency of the confinement mode in this case is expressed as a function of the energy confinement coefficient M determined by the thickness ts of the substrate, the film thickness te of the excitation electrode, and the dimension hx.
The energy confinement factor M is expressed by the following formula (2).
M = K · (hx / 2 · ts) · √Δ (2)
Here, K is the anisotropy coefficient of the substrate, hx is the size of the excitation electrode in the displacement direction of the vibration mode, ts is the thickness of the substrate, and Δ is the plate back amount.
The plate back amount Δ is expressed by the following formula (3).
Δ = (fs−fe) / fs (3)
Here, fs is a cutoff frequency of the substrate, and fe is a frequency when the excitation electrode is formed on the entire surface of the substrate.

When the shapes and areas of the front and back excitation electrodes are the same, the cut-off frequency fs of the substrate is expressed by the following formula (4), and the frequency fe when the excitation electrode is formed on the entire surface of the substrate is expressed by the following formula (5). Is done.
fs = R / ts (4)
fe = R / [ts + te · (ρe / ρx)] (5)
Here, R is the frequency constant of the substrate, ts is the thickness of the substrate, te is the sum of the film thicknesses of the front and back excitation electrodes, ρe is the density of the excitation electrodes, and ρx is the density of the substrate.

When the shape and area of the front and back excitation electrodes are different, the cut-off frequency fs of the substrate is expressed by the following formula (6), and the frequency fe when the excitation electrode is formed on the entire surface of the substrate is expressed by the following formula (7). The
fs = R / [ts + te2 · (ρe / ρx)] (6)
fe = R / [ts + te · (ρe / ρx)] (7)
Where R is the frequency constant of the substrate, ts is the thickness of the substrate, te2 is the thickness of the excitation electrode having a large area, te is the sum of the thicknesses of the excitation electrodes on the front and back sides, ρe is the density of the excitation electrode, and ρx is the substrate Density.

From the formulas (2) to (7), when the shape and area of the front and back excitation electrodes are different, the substrate thickness ts, the thickness te of the excitation electrode and the dimension hx are the same, and the front and back excitation Compared to the case where the shape and area of the electrode are the same, the thickness of the excitation electrode having a large area is added to the thickness of the substrate to increase the thickness of the substrate, thereby lowering the cutoff frequency fs of the substrate. Therefore, since the plate back amount Δ is small, the energy confinement coefficient M is small, and it is easy to avoid spurious in the inharmonic mode.
In addition, when the energy confinement factor M is the same, the thickness te of the excitation electrode can be increased as compared with the case where the shape and area of the excitation electrode on the front and back sides are the same, thereby suppressing the deterioration of the CI value. Can do.

Generally, in the thickness-shear vibration mode of an AT-cut quartz substrate, the condition for confining a single fundamental wave mode is said to be an energy confinement factor M = 2.8 or less.
For example, an AT-cut quartz crystal vibrating element that vibrates at a resonance frequency of 491 MHz band has a very large excitation electrode film thickness of about 1 nm with an energy confinement factor M = 2.8 when the excitation electrode dimension hx = 0.30 mm. Even if it is realized, the CI value becomes very large due to the effect of ohmic cross due to the electrode thinning, and the oscillation circuit cannot oscillate.
For this reason, the high-frequency vibration element needs to be thickened to avoid ohmic crossing of the electrode film thickness, so that the energy confinement factor M increases, and only the main vibration cannot be confined. Even trapped. However, if the CI value of the spurious is 1.8 times or more larger than the CI value of the main vibration, only the main vibration oscillates theoretically in the oscillation circuit, which is not a problem.

FIG. 6 shows prototype conditions and measurement results for an AT-cut quartz crystal resonator that vibrates at a resonance frequency in the 246 MHz to 491 MHz band, which was prototyped in the embodiment of FIG.
However, the first excitation electrode 25a has a rectangular shape and is not cut off at the four corners.
In the first excitation electrode 25a and the second excitation electrode 25b, the thickness of the underlying nickel (Ni) film is constant at 7 nm, and the film thickness of gold (Au) is 45 nm to 120 nm. In the first excitation electrode 25a, hx / hz is constant at about 1.28, and hx is 0.14 mm to 0.70 mm.
In addition, the lead electrodes 27a and 27b on the front and back sides and the pad electrodes 29a and 29b have a nickel (Ni) film thickness of 7 nm laminated on the upper layer portion formed with a film thickness equivalent to that of the excitation electrode in order to avoid the influence of ohmic cross. On top of that, gold (Au) is laminated to a thickness of 200 nm.

  FIG. 7 shows the CI value with respect to the energy confinement factor M of the AT-cut quartz resonator shown in FIG. The CI value tends to decrease as the energy confinement factor M increases, and the influence of ohmic cross decreases as the electrode film thickness increases, and the excitation charge increases and the resistance decreases as the electrode area increases. This is probably because of this. Therefore, as shown in FIG. 7, in order to satisfy the CI value standard (CI ≦ 20Ω) required by the oscillation circuit, the energy confinement factor M needs to be 17.1 or more.

  FIG. 8 shows a CI value ratio (CIs / CIm) between the CI value (CIm) of the main vibration and the CI value (CIs) of the spurious relative to the energy confinement factor M of the AT-cut quartz crystal resonator element shown in FIG. is there. This is because the CI value ratio (CIs / CIm) tends to decrease as the energy confinement factor M increases, and the in-harmonic mode spurious is confined strongly by increasing the film thickness and area of the excitation electrode. . From FIG. 8, it is necessary to set the energy confinement factor M to 35.7 or less in order to satisfy the spurious standard (CIs / CIm ≧ 2.0) required by the oscillation circuit.

Therefore, if the energy confinement coefficient M is set to 17.1 or more, an electrode film thickness of 50 nm or more, which is less affected by ohmic cross, can be secured. The vibration element which does not receive can be obtained. In addition, when the energy confinement coefficient M in the vibration element having a resonance frequency of 200 MHz or higher is larger than the energy confinement coefficient M as a design value in the 20 MHz or 30 MHz band, the vibration energy is more concentrated in the central portion of the excitation electrode. Make it possible. Therefore, since the amount of notching the four corners of the excitation electrode can be increased, the equivalent parallel capacitance C0 can be further reduced, and the capacitance ratio γ can be further reduced. For this reason, the inventors of the present application have conceived that notching the four corners of the excitation electrode while increasing the energy confinement factor M is very effective at high frequencies by repeating simulation and experiment.
However, when the energy confinement factor M exceeds 35.7, spurious having a smaller CI value than that of the main vibration frequently occurs. Therefore, it was found that the energy confinement factor M needs to be 35.7 or less.

In the embodiment shown in FIG. 1A, the size of the area of the first excitation electrode 25a on the concave surface side (surface side of FIG. 1B) is the flat surface side (FIG. 1B). The size is set to be within the outer edge of the outer shape of the excitation electrode 25b on the back surface side. That is, the first excitation electrode 25a is formed in a smaller shape than the second excitation electrode 25b. Therefore, when the first excitation electrode 25a and the second excitation electrode 25b are formed by the metal mask method, the first excitation electrode, the second excitation electrode, Therefore, the variation in the equivalent series capacitance C1 and the equivalent parallel capacitance C0 does not occur, and a vibration element with a small variation in the capacitance ratio γ can be obtained.
In the embodiment, a rectangular example is shown as the second excitation electrode 25b. However, the second excitation electrode 25b is not limited to this, and may be circular or elliptical.

The frequency adjustment accuracy of the vibrator can be adjusted within about 20 ppm in the frequency band where the resonance frequency is less than 200 MHz, and there was no problem in terms of yield. However, due to the reduction in the thickness of the vibration part due to the increase in frequency, the resonance frequency is about 30 ppm to 40 ppm in the frequency band of 200 MHz or more, which is about 1.5 to 2 times as degraded as the frequency band of less than 200 MHz. As a countermeasure, the adjustment time was slowed down and the rough adjustment and the main adjustment were divided into two times, but no significant improvement could be obtained. For this reason, changing the shape of the excitation electrode without changing the manufacturing process can reduce the capacitance ratio γ and expand the frequency variable range of the oscillator, which is very important in improving the frequency adjustment yield of the vibrator of 200 MHz or higher. It is effective for.
In addition, the upper limit of the frequency which can be manufactured with the current equipment is expected to be about 800 MHz.

FIG. 9 is a diagram illustrating a configuration of a vibrator according to an embodiment of the present invention. FIG. 9A is a plan view in which a lid member is omitted, and FIG. 9B is a longitudinal sectional view. The vibrator 2 includes a vibration element 1, a package body 40 formed in a rectangular box shape for housing the vibration element 1, and a lid member 49 made of metal, ceramic, glass, or the like. .
As shown in FIG. 9, the package body 40 is formed by laminating a first substrate 41, a second substrate 42, a third substrate 43, a seal ring 44, and mounting terminals 45. Yes. A plurality of mounting terminals 45 are formed on the outer bottom surface of the first substrate 41. The third substrate 43 is an annular body from which the central portion is removed, and a seal ring 44 such as Kovar is formed on the upper peripheral edge of the third substrate 43.
The third substrate 43 and the second substrate 42 form a recess (cavity) that houses the vibration element 1. A plurality of element mounting pads 47 that are electrically connected to the mounting terminals 45 by conductors 46 are provided at predetermined positions on the upper surface of the second substrate 42. The element mounting pad 47 is disposed so as to correspond to the pad electrode 29a formed on the second thick body 15a when the vibration element 1 is mounted.

  When fixing the vibration element 1, first, the vibration element 1 is inverted (turned over) and the pad electrode 29 a is placed on the element mounting pad 47 coated with the conductive adhesive 30 and a load is applied. The conductive adhesive 30 uses a polyimide adhesive with little degassing in consideration of aging.

Next, in order to cure the conductive adhesive 30 of the vibration element 1 mounted on the package body 40, it is placed in a high temperature furnace at a predetermined temperature for a predetermined time. After the conductive adhesive 30 is cured, the pad electrode 29b that is inverted and turned to the upper surface side and the electrode terminal 48 of the package body 40 are electrically connected by the bonding wire BW. As shown in FIG. 9B, since the vibration element 1 is supported / fixed to the package body 40 at one place (one point), it is possible to reduce the magnitude of the stress generated by the support fixation. .
After the annealing treatment, the frequency is adjusted by adding mass to the second excitation electrode 25b or reducing the mass. Thereafter, the lid member 49 is placed on the seal ring 44 formed on the upper surface of the package body 40, and the lid member 49 is sealed by seam welding in a vacuum or in an atmosphere of nitrogen gas, whereby the vibrator 2 is completed. To do. Alternatively, there is a method in which the lid member 49 is placed on the low-melting glass applied on the upper surface of the third substrate 43 of the package body 40 and melted and adhered. Also in this case, the cavity of the package is evacuated or filled with an inert gas such as nitrogen gas, and the vibrator 2 is completed.

The vibration element 1 formed by separating the pad electrodes 29a and 29b from each other in the Z′-axis direction may be configured. In this case as well, the vibrator can be configured similarly to the vibrator 2 described with reference to FIG. Moreover, you may comprise the vibration element 1 which formed the pad electrodes 29a and 29b on the same surface at intervals. In this case, the vibration element 1 has a structure in which the conductive adhesive 30 is applied at two locations (two points) so as to be conductive, supported, and fixed. Although the structure is suitable for reducing the height, the mounting stress due to the conductive adhesive 30 may be slightly increased.
In the above-described embodiment of the vibrator 2, an example in which a laminated plate is used for the package body 40 has been described. However, vibration is performed using a cap that uses a single-layer ceramic plate for the package body 40 and has a drawing process for the lid. You may comprise a child.

  As shown in FIG. 9, the portion that supports the vibration element 1 is a single point, and by providing the slit 17 between the thick portion 13 and the vibration portion 12, the stress caused by the conductive adhesive 30 is reduced. Since it can be made small, there is an effect that the vibrator 2 excellent in frequency reproducibility, frequency temperature characteristics, CI temperature characteristics, and frequency aging characteristics can be obtained.

  FIG. 10 is a diagram illustrating a configuration of an electronic device according to an embodiment of the present invention. FIG. 10A is a plan view in which a lid member is omitted, and FIG. 10B is a longitudinal sectional view. . The electronic device 3 includes a package body 50, a lid member 49, the vibration element 1, an IC component 51 on which an oscillation circuit for exciting the vibration element 1 is mounted, a variable capacitance element whose capacitance varies with voltage, and a resistance higher than temperature. And at least one electronic component 52 such as a changing thermistor or inductor.

As shown in FIG. 10, the package body 50 is formed by stacking a first substrate 61, a second substrate 62, and a third substrate 63. A plurality of mounting terminals 45 are formed on the outer bottom surface of the first substrate 61. The 2nd board | substrate 62 and the 3rd board | substrate 63 are formed with the annular body from which the center part was removed.
The first substrate 61, the second substrate 62, and the third substrate 63 form a recess (cavity) that accommodates the vibration element 1, the IC component 51, the electronic component 52, and the like. A plurality of element mounting pads 47 that are electrically connected to the mounting terminals 45 by conductors 46 are provided at predetermined positions on the upper surface of the second substrate 62. The element mounting pad 47 is disposed so as to correspond to the pad electrode 29a formed on the second thick body 15a when the vibration element 1 is mounted.

The pad electrode 29a of the inverted vibration element 1 is placed on the element mounting pad 47 of the package body 50 to which the conductive adhesive (polyimide) 30 is applied, and conduction between the pad electrode 29a and the element mounting pad 47 is achieved. One electrode of the IC component 51 is connected through a conductor formed between the substrates of the package body 50 by connecting the pad electrode 29b which is inverted to the upper surface side and the electrode terminal 48 of the package body 50 by a bonding wire BW. Conduction with the terminal 55 is intended. The IC component 51 is fixed at a predetermined position of the package body 50, and the terminal of the IC component 51 and the electrode terminal 55 of the package body 50 are connected by the bonding wire BW. Further, the electronic component 52 is placed at a predetermined position of the package body 50 and connected to the conductor 46 using a metal bump or the like. The package body 50 is filled with an inert gas such as vacuum or nitrogen, and the package body 50 is sealed with a lid member 49 to complete the electronic device 3.
In the method of connecting the pad electrode 29b and the electrode terminal 48 of the package body 50 with the bonding wire BW, the portion supporting the vibration element 1 is one place (one point), and the mount stress caused by the conductive adhesive 30 Make it smaller. Further, since the vibrating element 1 is inverted and the larger excitation electrode 25b is placed on the upper surface when housed in the package body 50, the frequency adjustment of the electronic device 3 is facilitated.

As shown in FIG. 10, by configuring the electronic device 3, the high-frequency vibrating element 1 excited by the fundamental wave is used, so that the capacitance ratio is small and the frequency variable width is widened. Furthermore, there is an effect that a voltage controlled oscillator having a good S / N ratio can be obtained.
In addition, an oscillator, a temperature compensated oscillator, and the like can be configured as the electronic device 3, and an oscillator excellent in frequency reproducibility, aging characteristics, and frequency temperature characteristics can be configured.

Next, an electronic device (electronic device of the present invention) to which the vibration element according to an embodiment of the present invention is applied will be described in detail with reference to FIGS.
FIG. 11 is a perspective view illustrating a configuration of a mobile (or notebook) personal computer as an electronic apparatus including the resonator element according to the embodiment of the invention. In this figure, a personal computer 1100 includes a main body portion 1104 provided with a keyboard 1102 and a display unit 1106 provided with a display portion 100. The display unit 1106 is rotated with respect to the main body portion 1104 via a hinge structure portion. It is supported movably. Such a personal computer 1100 incorporates a vibration element 1 that functions as a filter, a resonator, a reference clock, and the like.

  FIG. 12 is a perspective view illustrating a configuration of a mobile phone (including PHS) as an electronic apparatus including the resonator element according to the embodiment of the invention. In this figure, a cellular phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206, and the display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a cellular phone 1200 incorporates the vibration element 1 that functions as a filter, a resonator, or the like.

FIG. 13 is a perspective view showing a configuration of a digital still camera as an electronic apparatus including the resonator element according to the embodiment of the invention. In this figure, connection with an external device is also simply shown. Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an image sensor such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.
A display unit 100 is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to perform display based on an imaging signal from the CCD. The display unit 100 displays a subject as an electronic image. Functions as a viewfinder. A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side (the back side in the drawing) of the case 1302.
When the photographer confirms the subject image displayed on the display unit 100 and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory 1308. In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the input / output terminal 1314 for data communication as necessary. Further, the imaging signal stored in the memory 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation. Such a digital still camera 1300 incorporates a vibration element 1 that functions as a filter, a resonator, or the like.

  The electronic device including the vibration element according to the embodiment of the present invention includes, for example, an ink jet in addition to the personal computer (mobile personal computer) in FIG. 11, the mobile phone in FIG. 12, and the digital still camera in FIG. Dispenser (for example, ink jet printer), laptop personal computer, TV, video camera, video tape recorder, car navigation device, pager, electronic organizer (including communication function), electronic dictionary, calculator, electronic game machine, word processor , Workstations, videophones, crime prevention TV monitors, electronic binoculars, POS terminals, medical equipment (eg, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic devices, electronic endoscopes), fish detectors, Various measuring instruments and instruments (example If, gages for vehicles, aircraft, and ships), can be applied to a flight simulator or the like.

  DESCRIPTION OF SYMBOLS 1 ... Vibration element, 2 ... Vibrator, 3 ... Electronic device, 10 ... Board | substrate, 11 ... Recessed part, 12 ... Vibrating part, 13 ... Thick part, 14 ... 1st thick part, 14a ... 1st thickness Meat body, 14b ... 1st inclined part, 15 ... 2nd thick part, 15a ... 2nd thick body, 15b ... 2nd inclined part, 16 ... 3rd thick part, 16a ... 3rd Thick body, 16b ... third inclined portion, 17 ... slit, 23 ... excitation electrode, 25a ... first excitation electrode, 25b ... second excitation electrode, 27a, 27b ... lead electrode, 29a, 29b ... pad Electrode 30 ... conductive adhesive 40 ... package body 41 ... first substrate 42 ... second substrate 43 ... third substrate 44 ... seal ring 45 ... mounting terminal 46 ... conductor 47 ... element mounting pad, 48 ... electrode terminal, 49 ... lid member, 50 ... package body, 51 ... IC component, DESCRIPTION OF SYMBOLS 2 ... Electronic component, 55 ... Electrode terminal, 61 ... 1st board | substrate, 62 ... 2nd board | substrate, 63 ... 3rd board | substrate, 100 ... Display part, 1100 ... Personal computer, 1102 ... Keyboard, 1104 ... Main-body part, DESCRIPTION OF SYMBOLS 1106 ... Display unit, 1200 ... Mobile phone, 1202 ... Operation button, 1204 ... Earpiece, 1206 ... Mouthpiece, 1300 ... Digital still camera, 1302 ... Case, 1304 ... Light receiving unit, 1306 ... Shutter button, 1308 ... Memory, 1312: Video signal output terminal, 1314 ... Input / output terminal, 1430 ... TV monitor, 1440 ... Personal computer.

Claims (7)

And the AT-cut quartz substrate to a thickness smooth riffs dynamic,
A first excitation electrode provided on one main surface of the AT-cut quartz substrate and having a rectangular corner cut out;
A second excitation electrode provided on the other main surface of the AT-cut quartz substrate and having a different shape from the first excitation electrode;
Including
In plan view, the first excitation electrode is within the outer edge of the second excitation electrode;
The vibration element, wherein a ratio (S2 / S1) of the rectangular area S1 to the area S2 of the first excitation electrode is 87.7% ≦ (S2 / S1) <95.0%. In claim 1 ,
Includes a lead electrode that extends towards the end of the first excitation electrodes or al the AT-cut quartz substrate,
Before SL lead electrodes, the vibrating element, characterized in that is extended from an end portion of the first excitation electrode except the cutaway region. In claim 1 or 2 ,
Energy confinement factor M is,
M = K · (hx / 2 · ts) · (Δ) ^1/2
17.1 ≦ M ≦ 35.7
(K is the anisotropy coefficient of the AT-cut quartz substrate, hx is the first excitation electrode dimension along the displacement direction of the thickness-shear vibration, ts is the plate thickness of the AT-cut quartz substrate, and Δ is the first thickness) Plate back amount of the second excitation electrode and the second excitation electrode)
A vibrating element characterized by satisfying In any one of Claims 1 thru | or 3 ,
A resonance element having a resonance frequency of the thickness shear vibration of 200 MHz or more. The vibration element according to any one of claims 1 to 4 ,
A package containing the vibration element;
A vibrator characterized by comprising: The vibration element according to any one of claims 1 to 4 ,
An oscillation circuit for exciting the vibration element;
An electronic device comprising: An electronic apparatus characterized by comprising a vibration device according to any one of claims 1 to 4.

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