JPH04276914A - Thickness-shear crystal vibrator - Google Patents

Abstract

PURPOSE:To prevent the effect of spurious vibration of contour vibration onto a temperature characteristic by adopting a specific relation between a thickness of an exciting electrode an oscillating frequency and a width. CONSTITUTION:An exciting electrode 2 to satisfy equation I is formed on a front and a rear side of a crystal chip of a rectangular thickness-shear crystal vibrator 1 cut off by the AT-cut. Thus, the effect of the spurious vibration of contour vibration onto the temperature characteristic (frequency - temperature characteristic) is prevented, in equation I, (t) is thickness of a crystal chip, (w) is a width of the crystal chip, (u) is a thickness in Angstrom of the electrode 2 and (f) is the oscillating frequency in MHz.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the shapes of electrodes and crystal pieces of a thickness-stretching crystal resonator.

0002

[Prior Art] Among the many crystal units currently available,
The most versatile vibrator is the AT vibrator.

[0003] This AT resonator has a relatively good frequency -
Because it has temperature characteristics (hereinafter abbreviated as temperature characteristics), it is used in consumer devices such as communication device clocks.

[0004] In recent years, the field of electronic equipment has become smaller, lighter, and higher frequency, and crystal resonators are also required to be smaller and higher frequency.

[0005] Therefore, the length l is the X axis, the width w is the Z' axis, and the Y
AT resonators that are machined into a rectangular shape that is long in the X-axis direction and have a thickness of t on the 'axis have come to be produced.

FIG. 3 shows a plan sectional view of a conventional rectangular thickness-stretching crystal resonator. Further, a side sectional view of a conventional rectangular thickness-stretching crystal resonator is shown in FIG. The conventional thickness sliding crystal resonator has an excitation electrode 8 formed of Cr and Ag on the main surface.
The crystal oscillation piece 7 having a connecting electrode 9 is connected to the end of the inner lead 10 passing through the stem 11 and the end of the connecting electrode using solder, and the stem 11 and the case 12 are connected by soldering. The crystal oscillation piece was kept in a vacuum by being sealed in a vacuum. Here, the crystal oscillation piece has a length l in the X-axis direction, a thickness t in the Y'-axis direction, and a width w in the Z'-axis direction.

At this time, the thickness of the excitation electrode is u(Å
), then u is 3200 Å and the side ratio w/t of width w and thickness t is,

[0008]

[Math. 5] w/t=20.9±0.2

[0009]

[Math. 6] w/t=19.8±0.2

0010

[Math. 7] w/t=17.6±0.2

[0011]

[Formula 8] w, t so that w/t=14.8±0.2
I had selected.

0012

[Problems to be Solved by the Invention] However, when a rectangular AT resonator is caused to oscillate at a high frequency, the excitation current flowing through the crystal resonator tends to increase, and as shown in FIG. When an excessive excitation current flows and the excitation power becomes excessive, for example, 2 mW, a nonlinear phenomenon occurs, and the frequency deviation increases to +5 ppm. At the same time, longitudinal vibrations other than thickness-stretching vibration and bending occur near the frequency of the main vibration of the crystal resonator. Spurious vibrations such as contour vibrations are likely to occur, and as shown in Figure 6, if a normal excitation current flows to the crystal oscillator and the excitation power is, for example, 100 μW, even if temperature characteristics without problems are obtained. As shown in FIG. 7, when an excessively large excitation current flows through the crystal resonator and the excitation power becomes excessively large, for example, 2 mW, there is a problem in that the temperature is particularly adversely affected.

The present invention has been made to solve the above-mentioned problems, and its purpose is to prevent longitudinal vibrations other than thickness sliding vibrations, bending vibrations, etc., even when an excessive excitation current is applied to a rectangular crystal resonator. The object of the present invention is to provide a method for preventing the influence of spurious vibrations of contour vibrations on temperature characteristics.

[0014]

[Means for Solving the Problems] (1) In the thickness-stretching crystal resonator of the present invention, the X-axis of a rectangular crystal piece cut by an AT cut has a length l, the Y'-axis has a thickness t, and Z' In a thickness sliding crystal resonator whose axis has a width w, excitation electrodes are formed on the front and back surfaces of the crystal piece, and the thickness of the excitation electrode is defined as u (Å).
) and the oscillation frequency is f (MHz), then the width w and the thickness t
The side ratio w/t of

[0015]

[Formula 9] w/t=20.735+2.1×10-6×u
It is characterized by ×f±0.15.

(2) In the thickness-stretching crystal resonator of the present invention, the X-axis of a rectangular crystal piece cut by AT cutting is defined as length l, the Y'-axis as thickness t, and the Z'-axis as width w. In a thickness-stretching crystal resonator, excitation electrodes are formed on the front and back surfaces of the crystal piece, and when the thickness of the excitation electrode is u (Å) and the oscillation frequency is f (MHz), the width w and the thickness t are The side ratio w/t is

[0017]

[Formula 10] w/t=19.60+2.1×10-6×u×
It is characterized by having f±0.15.

(3) In the thickness-stretching crystal resonator of the present invention, the X-axis of a rectangular crystal piece cut by AT cutting is defined as length l, the Y'-axis as thickness t, and the Z'-axis as width w. In a thickness-stretching crystal resonator, excitation electrodes are formed on the front and back surfaces of the crystal piece, and when the thickness of the excitation electrode is u (Å) and the oscillation frequency is f (MHz), the width w and the thickness t are The side ratio w/t is

[0019]

[Formula 11] w/t=17.33+2.1×10-6×u×
It is characterized by having f±0.1.

(4) In the thickness-stretching crystal resonator of the present invention, the X-axis of a rectangular crystal piece cut by AT cutting is defined as length l, the Y'-axis as thickness t, and the Z'-axis as width w. In a thickness-sliding crystal resonator, excitation electrodes are formed on the front and back surfaces of the crystal piece, and when the thickness of the excitation electrode is u (Å) and the oscillation frequency is f (MHz), the width w and the thickness t are The side ratio w/t is

[0021]

[Formula 12] w/t=14.57+2.1×10-6×u×
It is characterized by having f±0.1.

[0022]

[Function] Since the thickness-stretching crystal resonator of the present invention has the above-described configuration, nonlinear phenomena are unlikely to occur even when an excessive excitation current flows, and the contours of longitudinal vibrations and bending vibrations other than thickness-stretching vibrations are suppressed. It is possible to prevent the influence of spurious vibrations on temperature characteristics.

[0023] Possible reasons for this will be explained below.

Conventional thickness-stretching oscillators are rectangular crystal oscillators that are long in the X-axis direction and short in the Z-axis direction.Thickness-stretching vibrations are generated by electrodes, but because the crystal pieces are small, pure thickness Rather than a shuffling vibration, it is thought that the thickness shuffling vibration is a mixture of contour vibrations such as particularly short bending vibrations in the Z-axis direction and longitudinal vibrations.

Therefore, when a normal low excitation current is flowing through the crystal resonator, the thickness sliding vibration is mainly excited, and therefore phenomena such as frequency fluctuations do not occur particularly in temperature characteristics. However, when an excessive excitation current is flowing through the crystal resonator, energy is supplied to contour vibrations such as bending vibration and longitudinal vibration other than thickness sliding vibration, and the contour vibrations are strongly excited. A phenomenon occurs in which the frequency varies depending on the temperature.

In the thickness-stretching vibrator of the present invention, the energy confinement effect is weakened by reducing the thickness of the excitation electrode, and thickness-stretching vibration occurs even if an excessive excitation current is attempted to flow through the crystal resonator. Energy is consumed only for this purpose, and energy is supplied to contour system vibrations such as bending vibrations and longitudinal vibrations other than thickness sliding vibrations, and the contour system vibrations are not excited and the phenomenon that the frequency fluctuates due to temperature characteristics does not occur. becomes.

However, contour-related spurious components that are strongly coupled with thickness-shuffling vibrations can be avoided by reducing the film thickness of the excitation electrode to weaken the energy confinement effect, thereby suppressing contour-based spurious vibrations such as bending vibrations and longitudinal vibrations other than thickness-shuffling vibrations. Even if energy is not supplied to the vibrations, they may still be coupled to each other.Secondly, the vibrations of the contour system, such as bending vibrations in the Z-axis direction and longitudinal vibrations, must be set at a side ratio that does not combine with the thickness sliding system. By selecting this, it is possible to prevent the phenomenon of frequency fluctuation due to temperature characteristics from occurring.

[0028]

EXAMPLES The thickness-stretching crystal resonator of the present invention will be described in detail below based on examples. FIG. 1 shows a plan cross-sectional view of a rectangular thickness-stretching crystal resonator according to an embodiment of the present invention. Further, FIG. 2 shows a side cross-sectional view of a rectangular thickness-stretching crystal resonator according to an embodiment of the present invention. The thickness-stretching crystal resonator of this example has a crystal oscillation piece 1 having an excitation electrode 2 and a connection electrode 3 formed of Cr and Ag on the main surface, and the end of the inner lead 4 passing through the stem 5 and the connection. The ends of the electrodes are connected using solder, and the stem 5 and the case 6
The crystal oscillation piece is kept in a vacuum by being sealed using solder.

Here, the crystal oscillation piece has a length l in the X-axis direction, a thickness t in the Y'-axis direction, and a width w in the Z'-axis direction.

At this time, the thickness of the excitation electrode is u(Å
), then u is less than 2200 Å, and width w and thickness t
The side ratio w/t of

[0031]

[Formula 13] w/t=20.735+2.1×10-6×u
w, t, and u are selected so that xf±0.15.

Thickness u of the excitation electrode and width w of the crystal oscillation piece when an excessive excitation current is passed through the rectangular crystal resonator
FIG. 8 shows the state of coupling with spurious in the relationship between side ratio w/t and thickness t.

In the figure, by selecting the thickness and side ratio w/t of the excitation electrode in the shaded area, an excessive excitation current can be applied to the rectangular crystal resonator without coupling the main vibration and spurious. This shows that even if it is flushed, there will be no particular adverse effect on temperature.

As can be seen from the figure, in order to avoid coupling with spurious vibrations of contour vibrations such as longitudinal vibrations and bending vibrations other than thickness sliding vibrations, the thickness u of the excitation electrode should be set to 2200 Å.
The side ratio w of the width w and the thickness t of the crystal oscillator piece is as follows:
The relationship between /t and the thickness u of the excitation electrode is

[0035]

[Formula 14] w/t=20.735+2.1×10-6×u
It can be seen that it is sufficient to set xf±0.15.

[0036] In addition, similar effects can be obtained for other claims of the present application, in which case the side ratio w/ in Fig. 1 and Fig. 2
t and the thickness u of the excitation electrode are:

[0037]

[Formula 15] w/t=19.60+2.1×10−6×u×
f±0.15

[0038]

[Formula 16] w/t=17.33+2.1×10-6×u×
f±0.1

[0039]

[Formula 17] w/t=14.57+2.1×10-6×u×
f±0.1.

Further, in this example, the structure of the excitation electrode is Cr.
Although +Ag is considered, other configurations such as one layer of Ag, one layer of Au, multiple layers of Cr+Ag, multiple layers of Cr+Au, multiple layers of Ni+Ag, and multiple layers of Ni+Au have similar effects.

In particular, as shown in FIG. 9, the structure of the excitation electrode is
A Cr layer 14 with a thickness of 600 Å is formed on the main surface of the crystal oscillation piece 13, an Au layer 15 is formed with a thickness of 900 Å on the Cr layer 14, and the Au layer 15
If the four-layer structure has a Cr layer 16 of 600 Å on top and an Au layer 17 of 900 Å on top of the Cr layer 16, nonlinear phenomena will hardly occur even if an excessive excitation current flows especially in a rectangular crystal resonator, resulting in less thickness-stretching vibration. It is possible to prevent the influence of spurious vibrations of contour vibrations such as longitudinal vibrations and bending vibrations on temperature characteristics.

Furthermore, in this example, the connection electrode is made of Cr.
I am considering a two-layer structure of +Ag, but the thickness of the excitation electrode is 2
If it is 200 Å or less, for example 700 Å, for example 1000 Å
When the film thickness becomes extremely thin, such as Å, there is a problem that Cr diffuses into Ag, making it difficult for solder to flow.

In this case, as shown in FIG. 10, the structure of the excitation electrode is a two-layer structure of Cr18 and Ag19, and while the thickness of the excitation electrode is kept extremely thin, for example, 1000 Å, the structure of the connection electrode is changed to Cr18 and Ag19. Ag19 and Ag20
Setting the film thickness of the connection electrode to, for example, 3000 Å in the three-layer structure has a great effect on solder flow.

[0044]

As described above, according to the present invention, the thickness of the excitation electrode is set to 2200 Å or less, and an optimum side ratio is achieved that does not conflict with spurious vibrations of contour vibrations such as longitudinal vibrations and bending vibrations other than thickness sliding vibrations. By selecting this, nonlinear phenomena are less likely to occur even when an excessive excitation current flows in a rectangular crystal resonator, and the influence on temperature characteristics due to spurious vibrations of contour vibrations such as longitudinal vibrations other than thickness sliding vibrations and bending vibrations is prevented. It has the effect of being able to.

Furthermore, if the structure of the excitation electrode is a four-layer structure consisting of Cr layer + Au layer + Cr layer + Au layer on the main surface of the crystal oscillator piece, even if an excessive excitation current flows especially in a rectangular crystal resonator, nonlinearity will occur. This phenomenon is less likely to occur and has the effect of being able to prevent the effects on temperature characteristics due to spurious vibrations of contour vibrations such as longitudinal vibrations and bending vibrations other than thickness sliding vibrations.

[0046] Also, the film thickness of the excitation electrode is set to, for example, 700 Å,
For example, when the film thickness becomes extremely thin, such as 1000 Å, C
There is a problem that r diffuses into Ag, making it difficult for solder to flow, but in this case, the structure of the excitation electrode is Cr+Ag.
While keeping the layer structure of the excitation electrode extremely thin, for example, 1000 Å, the structure of the connection electrode is Cr+Ag+Ag.
By increasing the thickness of the connection electrode to, for example, 3000 Å, the three-layer structure has the effect of improving solder flow.

[Brief explanation of the drawing]

FIG. 1 is a plan cross-sectional view of a rectangular thickness-stripping crystal resonator according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a rectangular thickness-stripping crystal resonator according to an embodiment of the present invention.

FIG. 3 is a plan cross-sectional view of a conventional rectangular thickness-stretching crystal resonator.

FIG. 4 is a side sectional view of a conventional rectangular thickness-stretching crystal resonator.

FIG. 5 is a diagram showing the relationship between excitation current and frequency deviation.

FIG. 6 is a temperature characteristic diagram when a normal excitation current flows through a crystal resonator.

FIG. 7 is a temperature characteristic diagram when an excessive excitation current flows through a crystal resonator.

FIG. 8: Coupling with spurious in the relationship of the side ratio w/t between the thickness u of the excitation electrode and the width w and thickness t of the crystal oscillation piece when an excessive excitation current is passed through a rectangular crystal resonator. State diagram.

FIG. 9 is another configuration diagram of the excitation electrode of the present invention.

FIG. 10 is a configuration diagram of an excitation electrode and a connection electrode when the excitation electrode has a thin film thickness.

[Explanation of symbols]

1...Crystal oscillation piece 2...Excitation electrode 3...Connection electrode 4…Inner lead 5...Stem 6...Case 7...Crystal oscillation piece 8...Excitation electrode 9...Connection electrode 10...Inner lead 11...Stem 12...Case 13...Crystal oscillation piece 14...Cr layer 15...Au layer 16...Cr layer 17...Au layer 18...Cr 19...Ag 20...Ag

Claims (4)

[Claims] 1. In a thickness sliding crystal resonator in which the X-axis of a rectangular crystal piece cut by an AT cut is a length l, the Y'-axis is a thickness t, and the Z'-axis is a width w, the crystal Excitation electrodes are formed on the front and back surfaces of the pieces, and the thickness of the excitation electrodes is u (Å).
If the oscillation frequency is f (MHz), the side ratio w/t of the width w and the thickness t is [Equation 1] w/t=20.735+2.1×10−6×u
A thickness-stripping crystal resonator characterized by xf±0.15. 2. In a thickness sliding crystal resonator in which the X axis of a rectangular crystal piece cut by an AT cut is a length l, the Y' axis is a thickness t, and the Z' axis is a width w, the crystal Excitation electrodes are formed on the front and back surfaces of the pieces, and the thickness of the excitation electrodes is u (Å).
If the oscillation frequency is f (MHz), the side ratio w/t of the width w and the thickness t is [Equation 2] w/t=19.60+2.1×10−6×u×
A thick crystal resonator characterized by f±0.15. 3. In a thickness-stripping crystal resonator in which the X-axis of a rectangular crystal piece cut by an AT cut is a length l, the Y'-axis is a thickness t, and the Z'-axis is a width w, the crystal Excitation electrodes are formed on the front and back surfaces of the pieces, and the thickness of the excitation electrodes is u (Å).
If the oscillation frequency is f (MHz), then the side ratio w/t of width w and thickness t is [Equation 3] w/t=17.33+2.1×10−6×u×
A thick crystal resonator characterized by f±0.1. 4. In a thickness-stripping crystal resonator, the X-axis of a rectangular crystal piece cut by an AT cut has a length l, a Y'-axis a thickness t, and a Z'-axis a width w. Excitation electrodes are formed on the front and back surfaces of the pieces, and the thickness of the excitation electrodes is u (Å).
If the oscillation frequency is f (MHz), then the side ratio w/t of width w and thickness t is [Equation 4] w/t=14.57+2.1×10−6×u×
A thick crystal resonator characterized by f±0.1.