JP2014230056A - Crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal oscillator which prevents vibration energy from leaking.SOLUTION: A crystal oscillator includes: a rectangular crystal piece having a predetermined thickness; a convex part provided on a principal surface of the crystal piece; an excitation electrode provided on the crystal piece to cover the convex part; and a pair of connection terminals connected to the excitation electrode and provided at end parts of the crystal piece. On a side surface in a side where m-plane of the crystal piece appears, m-plane being a crystal plane of the crystal and a plane perpendicular to R-plane are formed. In a first range from corners of the crystal piece where the connection terminals are provided to a portion where the convex part is not provided, a rate of a region being m-plane occupying in a thickness direction of the crystal piece is 0.7-0.8, and in a second range from a portion where the convex part is provided to the other corner of the crystal piece, the rate of the region being m-plane occupying in the thickness direction thereof is 0.5.

Description

  The present invention relates to a crystal resonator element used in a crystal device.

2. Description of the Related Art Conventionally, a quartz crystal element in which a quartz crystal is provided with a metal film serving as an excitation electrode is used for a quartz crystal device.
This crystal piece can be formed by etching an AT-cut crystal wafer.
An AT-cut quartz wafer is a plate material obtained by cutting an artificial quartz crystal. Of the X-axis, Y-axis, and Z-axis that are crystal axes of the quartz, the surface facing the Y-axis side is θ ° around the X-axis. Of the X-axis, Y′-axis, and Z′-axis that are newly set by rotation, the surface that faces the Y-axis is cut in a state that faces the Y′-axis.
The cut quartz wafer has a surface polished and finished to a predetermined thickness T.
Such a crystal wafer is provided with masks on both main surfaces, and is open except for the position of the crystal piece, the outer peripheral frame portion, and the crystal pieces or the connection portion connecting the outer peripheral frames.
When the crystal wafer is wet-etched in this state, a penetrating portion penetrating in the thickness direction of the crystal wafer is formed.
This penetrating portion serves as a side surface of the crystal resonator element, and a surface orthogonal to the m-plane and the R-plane is formed by wet etching for a predetermined time (see, for example, Patent Document 1).

JP 2011-193175 A

  Conventionally, it is ideal for a crystal resonator element to confine vibration energy generated by an excitation electrode provided on a crystal piece, for example, at the outer edge of the crystal piece. However, when the crystal piece is designed to be a small crystal device, vibration energy generated in the excitation electrode may leak without being confined by the crystal piece.

  Accordingly, an object of the present invention is to provide a crystal resonator element that solves the above-described problems and prevents leakage of vibration energy.

  In order to solve the above problems, the present invention provides a crystal resonator element, a rectangular crystal piece having a predetermined thickness, a protrusion provided on a main surface of the crystal piece, and covering the protrusion An excitation electrode provided on the crystal piece, and two pairs of connection terminals connected to the excitation electrode and provided at an end portion of the crystal piece, on a side surface on the side where the m-plane of the crystal piece is formed, In the first range from the corner of the crystal piece where the connection terminal is provided to the m-plane which is the crystal plane of the crystal and the plane orthogonal to the R-plane, the m-plane is not provided. The ratio in the thickness direction of the region to be 0.7 to 0.8, and the thickness direction of the region that becomes the m-plane in the second range from the portion where the convex portion is provided to the other end of the crystal piece It is characterized in that it is configured with a ratio of 0.5 to 0.5.

  Moreover, the present invention is characterized in that the convex portion has an elliptical shape. In the present invention, the convex portion is provided on both main surfaces of the crystal piece, and the convex portion provided on one main surface is provided so that the size is different from the convex portion provided on the other main surface. It is characterized by being.

  According to such a crystal resonator element, the m-plane which is the crystal plane of the crystal and the plane orthogonal to the R-plane are formed on the side surface of the crystal piece on which the m-plane is formed, and the connection terminal is provided. The ratio of the area that becomes the m-plane in the thickness direction in the first range from the corner of the crystal piece to which the convex portion is not provided is 0.7 to 0.8, and from the portion where the convex portion is provided In the second range up to the other end of the crystal piece, the ratio of the area that becomes the m-plane in the thickness direction is 0.5, so that the energy confinement of vibration energy on the connection terminal side is increased, Vibration leakage can be prevented.

  Further, according to such a crystal resonator element, since the convex portion has an elliptical shape, the shape approximates the speed of propagation of vibration generated by the excitation electrode, and therefore, unnecessary vibration is generated at the convex portion. Can be prevented. Further, the convex portions are provided on both main surfaces of the crystal piece, and the convex portions provided on one main surface are provided so as to be different in size from the convex portions provided on the other main surface. The vibrational energy confinement can be increased.

It is a top view which shows an example of the crystal vibration element which concerns on embodiment of this invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is the figure which compared the CI value of the crystal oscillation element which concerns on embodiment of this invention, and the conventional crystal oscillation element.

  Next, the best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described in detail with reference to the drawings as appropriate. Note that each component is exaggerated for easy understanding of the state. Further, the widest plane with respect to the crystal piece and a plane parallel to the plane are defined as main surfaces, and a surface surrounding the main surface is defined as a side surface.

  As shown in FIG. 1, the crystal resonator element 10 according to the embodiment of the present invention mainly includes a crystal piece 11, a convex portion 12, an excitation electrode 13, and a connection terminal 14.

The convex part 12 is provided in the surface center of the main surface of the crystal piece 11 mentioned later, as shown in FIG.1 and FIG.2. Further, the convex portion 12 has an elliptical shape, and is provided such that the center of the ellipse coincides with the surface center of the main surface of the crystal piece 11 and the major axis of the ellipse is parallel to the long side of the crystal piece 11. .
Here, the convex part 12 provided in one main surface of the crystal piece 11 is provided so that a magnitude | size may differ from the convex part 12 provided in the other main surface. For example, as shown in FIG. 2 and FIG. 3, the shape is the same elliptical shape, but the elliptical shape of the convex portion 12 provided on one main surface is the elliptical shape of the convex portion provided on the other main surface. The plane area is smaller than that.

  As shown in FIGS. 1 and 2, the excitation electrode 13 has an elliptical shape and is provided on the crystal piece 11 so as to cover the convex portion 12. The excitation electrode 13 is provided to face both main surfaces of the crystal piece 11. The elliptical excitation electrode 13 is provided on the crystal piece 11 so that the long side of the crystal piece 11 and the major axis of the ellipse are parallel to each other.

  As shown in FIG. 1, the connection terminals 14 are used in pairs, and are connected to the excitation electrode 13 and provided at one end of the crystal piece 11. One connection terminal 14 is connected to the excitation electrode 13 provided on one main surface of the crystal piece 11, and the other connection terminal 14 is connected to the excitation electrode 13 provided on the other main surface of the crystal piece 11. doing.

As shown in FIG. 1, the crystal piece 11 is formed in a rectangular shape having a predetermined thickness. In this crystal piece 11, for example, the direction from the end where the connection terminal 14 is provided to the opposite end is the X-axis direction, and the direction orthogonal to the X-axis direction is the Z-axis direction. The width W of the crystal piece 11 is set.
An m-plane is formed on the side surface of the crystal piece 11 that is parallel to the X-axis direction and orthogonal to the Z-axis direction. On the side surface on which the m-plane is formed, an m-plane that is a crystal plane of quartz and a plane orthogonal to the R-plane are formed.
The plane orthogonal to the m-plane and the R-plane is formed by wet-etching a crystal wafer formed in a plate shape.

Here, on the side surface of the crystal piece 11 on which the m-plane is formed, the range from the corner of the crystal piece 11 where the connection terminal 14 is provided to the convex portion 12 is not provided as the first range D1, and the convex portion 12 A range from the portion where the is provided to the other end of the crystal piece 11 is defined as a second range D2.
1st area | region D1 is a range from the front-end | tip of the convex part 12 located in the outermost side to one corner part of a crystal piece, Comprising: The plane part in which the convex part 12 is not formed is pointed out.
The second region D2 is a range from the tip of the outermost convex portion 12 serving as a reference for the boundary of the first region D1 to the other corner of the crystal piece 11, and is the outermost convex portion. 12 and the plane portion of the other crystal piece 11.

At this time, as shown in FIGS. 1-3, the ratio which occupies for the m surface differs in the 1st range D1 and the 2nd range D2.
First, in the first range D1 from the corner of the crystal piece 11 where the connection terminal 14 is provided to when the convex portion 12 is not provided, the m-plane F1a is m when the thickness of the crystal piece 11 is “1”. The ratio of the region to be the surface F1a in the thickness direction is 0.7 to 0.8.

  That is, when the side surface of the crystal piece 11 is viewed from the front, the m-plane F1a and the surface F2a orthogonal to the R-plane can be visually recognized in a state of being divided in the thickness direction. In the state divided in the thickness direction, when the thickness of the crystal piece 11 is “1”, the ratio of the m-plane F1a in the thickness direction is 0.7 to 0.8.

  In the second range D2 from the portion where the convex portion 12 is provided to the other end of the crystal piece 11, the m-plane F1b becomes the m-plane F1b when the thickness of the crystal piece 11 is “1”. The ratio of the area in the thickness direction is 0.5.

  That is, when the side surface of the crystal piece 11 is viewed from the front, the m-plane F1b and the surface F2b orthogonal to the R-plane can be viewed in a state of being divided in the thickness direction. In the state divided in the thickness direction, when the thickness of the crystal piece 11 is “1”, the ratio of the m-plane F1b in the thickness direction is 0.5.

Therefore, since the m-plane F1a in the first range D1 has a larger area than the m-plane F1b in the second range D2, the effect of energy confinement can be increased.
In addition, since the first range D1 is on the side where the connection terminal 14 of the crystal piece 11 is provided and the m-plane F1a is wider than the other m-plane F1b, m in the first range D1 is prevented while preventing vibration leakage from the connection terminal 14. By enlarging the energy confinement at the surface F1a, vibration leakage can be further prevented.

  Next, the crystal resonator element 10 according to the embodiment of the present invention can be manufactured as follows.

First, a quartz wafer will be described.
An AT-cut quartz wafer is a plate material obtained by cutting an artificial quartz crystal. Of the X-axis, Y-axis, and Z-axis that are crystal axes of the quartz, the surface facing the Y-axis side is θ ° around the X-axis. Of the X-axis, Y′-axis, and Z′-axis that are newly set by rotation, the surface that faces the Y-axis is cut in a state that faces the Y′-axis. The cut quartz wafer has a surface polished and finished with a predetermined thickness T (μm).
A plane parallel to the X axis and the Z ′ axis is a main surface.

  Various methods for providing a crystal piece having a convex portion on a crystal wafer have been proposed. For example, a crystal piece having a convex portion is provided on a crystal wafer as follows.

First, a corrosion resistant film is provided on a quartz wafer, and a photoresist film is provided on the corrosion resistant film.
Exposure / development is carried out by superposing a mask having a portion between the adjacent crystal pieces, with the crystal wafer remaining, leaving a portion to be the crystal piece on the crystal wafer. The exposed photoresist is peeled off and the exposed corrosion-resistant film is removed. With the surface of the quartz wafer exposed, the exposed portion is removed to a predetermined thickness by wet etching.

After removing the remaining photoresist, the photoresist is again applied to the crystal wafer, and a mask having a penetrating part corresponding to the shape of the crystal piece is left on the crystal wafer, leaving a portion to be a projection, and exposure and development are performed. I do. The exposed photoresist is peeled off and the exposed corrosion-resistant film is removed. Since the surface of the quartz wafer is exposed, the exposed portion is removed to a predetermined thickness by wet etching. As a result, the quartz wafer is provided with a plurality of portions to be quartz pieces having convex portions. At this time, the side surface parallel to the X axis of the crystal piece is provided with a surface that is orthogonal to the m-plane and the R-plane, and the proportion of the m-plane in the thickness direction is 0.5. ing.
That is, wet etching is performed until the ratio of the m-plane in the thickness direction of the crystal piece becomes 0.5.

In this state, a photoresist is provided in the second range, and wet etching is performed again.
As a result, the surface of the quartz wafer in the first range, which is the exposed portion of the quartz wafer, is removed, and the area of the m-plane increases. Wet etching is terminated when the ratio of the m-plane in the thickness direction becomes 0.7 to 0.8.

Thereafter, a mask having a pattern corresponding to the shape of the excitation electrode and the connection terminal is superimposed on the crystal wafer provided with the crystal piece, and the excitation electrode and the connection terminal are provided on the crystal piece by sputtering or vapor deposition, To do.
Each crystal resonator element is folded from the crystal wafer to obtain individual crystal resonator elements.
Thus, the crystal resonator element according to the embodiment of the present invention can be easily manufactured.

In addition, this invention can be changed suitably.
For example, the convex portion 12 provided on the crystal piece 11 may be formed only on one main surface of the crystal piece 11, and the size of the convex portion 12 provided on both main surfaces of the crystal piece 11 is the same shape. Even if they are provided with the same plane area, the same effects as in the embodiment of the present invention can be obtained.

Next, examples will be described.
In this embodiment, the result of promoting the CI value (crystal impedance value) when the W dimension of the crystal piece is changed within a predetermined range is confirmed. In each W dimension, the lower the CI value, the better.

  Example 1 is a crystal resonator element according to an embodiment of the present invention, in which convex portions having different sizes are provided on both main surfaces of a crystal piece, and the m plane occupies the thickness direction of the crystal piece in the first range. This is a crystal resonator element in which the ratio is 0.75, and the ratio of the m-plane in the thickness direction of the quartz piece in the second range is 0.5 (see FIG. 1).

  As shown in FIG. 4, in the quartz resonator element of Example 1, the CI value was less than 300Ω in the range of W dimension from 628 μm to 632 μm and from 646 μm to 650 μm. Further, in the range of W dimension from 634 μm to 638 μm, the distribution was mountain-shaped with a CI value of about 600Ω at 636 μm. Further, the CI value was less than 400Ω in the range of W dimension from 638 μm to 642 μm. In addition, in the range of W dimension from 642 μm to 646 μm, the distribution was mountain-shaped with a CI value of about 700Ω at 644 μm.

  Comparative Example 1 is a crystal in which convex portions having different sizes are provided on both main surfaces of the crystal piece, and the ratio of the m-plane in the thickness direction of the crystal piece in the first range and the second range is 0.5. It is a vibration element.

  As shown in FIG. 4, the quartz resonator element of Comparative Example 1 had a distribution in which the CI value was unstable and varied in the range of W dimension from 628 μm to 650 μm. In each W dimension, the CI value did not fall below the CI value of Example 1.

  Thus, the quartz resonator element of Example 1 was able to have a lower CI value than the conventional quartz resonator element.

DESCRIPTION OF SYMBOLS 10 Crystal resonator element 11 Crystal piece 12 Convex part 13 Excitation electrode 14 Connection terminal D1 1st range D2 2nd range F1a, F1b m surface F2a, F2b Surface orthogonal to R surface

Claims (3)

A rectangular crystal piece having a predetermined thickness;
A convex portion provided on the main surface of the crystal piece;
An excitation electrode provided on the crystal piece covering the convex portion;
A pair of connection terminals connected to the excitation electrode and provided at an end of the crystal piece;
With
In the side surface on which the m-plane of the crystal piece is formed,
The m plane which is the crystal plane of quartz and the plane orthogonal to the R plane are formed,
The ratio in the thickness direction of the region that becomes the m-plane in the first range from the corner of the crystal piece where the connection terminal is provided to the projection is not provided is 0.7 to 0.8,
The quartz crystal is characterized in that the ratio of the area that becomes the m-plane in the thickness direction in the second range from the portion where the convex portion is provided to the other end of the crystal piece is 0.5. Vibration element.   The quartz crystal resonator element according to claim 1, wherein the convex portion has an elliptical shape.   The convex portions are provided on both main surfaces of the crystal piece, and the convex portions provided on one main surface are provided so as to be different in size from the convex portions provided on the other main surface. The crystal resonator element according to claim 1 or 2.

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