JPH1096632A - Piezoelectric gyro sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high accuracy and small size by making the shapes of a pair of drive piece and detection piece and shapes of connection parts of support part and combining part similar, respectively. SOLUTION: A pair of a drive piece 3 and a detection piece 4 are combined on an X-Y plane of rectangular coordinates system at a combining part 5. In parallel to the drive piece 3 and the detection piece 4, support parts 6a and 6b are formed on both sides of the combining part 5 and the connection part 7a of the support part 6a and 6b and the combining part 5 is fabricated with thin drawdown by trimming. The drive piece 3 and the detection piece 4 as well as the combining part 5 and the support parts 6a and 6b are formed symmetrically with respect to a common Y-axis 8. This Y-axis 8 becomes the rotation axis for rotating a piezoelectric gyro sensor as an angular velocity sensor. By this, the vibration of the stable drive part with good balance and the stress due to the generation of Coriolis force can be transmitted efficiently to the detection part and thus, high accuracy and small size can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric gyro sensor using a piezoelectric member, particularly a tuning-fork type quartz vibrator formed of quartz.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable reduction in the size of electronic devices and the like. Accordingly, piezoelectric gyro sensors, which belong to angular velocity sensors for detecting the rotational movement of devices and the like, have also been made smaller, thinner and less expensive. Is strongly required.

That is, the piezoelectric gyro sensor is used not only for conventional navigation control and attitude control of ships, aircraft, automobiles and the like, but also for a hand-held camera shake detection sensor and a three-dimensional stereo mouse. It has begun to be widely applied to direction detection sensors and the like.

Accordingly, an example of a conventional piezoelectric gyro sensor will be described below with reference to Japanese Patent Application Laid-Open No. 7-55479.

FIG. 11 is a structural view of a piezoelectric gyro sensor described in Japanese Patent Application Laid-Open No. 7-55479.

In FIG. 11, a pair of driving pieces 101 and
The pair of detection pieces 102 are arranged with the rotation axis 103 symmetrical. The pair of driving pieces 101 and the pair of detecting pieces 102 are connected by a connecting section 104.

The connecting portion 104 has a space inside, and has a supporting portion 105 at the center thereof for supporting the pair of driving pieces 101, the pair of detecting pieces 102, and the connecting portion 104, respectively. ing.

Further, the support portion 105 is
06.

The pair of driving pieces 101 have driving electrodes 107, and the pair of detecting pieces 102 have detection electrodes 1.
08 is deposited with a metal such as Au. Then, wiring is performed from each of the electrodes 107 and 108 to the support portion 105, and a lead (not shown) of the housing 106 is formed from a pad provided on the support portion 105 by an Au wire bonding wire.
It is structured to be wired and input / output.

[0010]

In the conventional piezoelectric gyro sensor described above, the wiring from the driving electrode and the wiring from the detection electrode are formed concentrated on the same support portion 105, so that the wiring Problems such as crosstalk due to
It has a drawback that it has a bad influence such as noise on driving or detection signals.

When a conventional piezoelectric gyro sensor is formed of a quartz oscillator, a processing method by wet etching called photolithography is generally used in consideration of the mass production effect and the like.

However, in the conventional piezoelectric gyro sensor,
When the etching process is performed, projection-shaped fins are generated in the cross sections of the driving piece and the detecting piece, and in the connecting part between the driving piece, the detecting piece, and the support part, due to the anisotropy of the crystal. Further, since the size of the fins generated on both sides of the cross section is different, there is also a disadvantage that the cross-sectional shape becomes asymmetric. Also,
At the same time, the tip of the driving piece and the detecting piece and the corners of the coupling portion are not etched symmetrically, and the balance of the tuning fork shape is deteriorated.

As described above, if the shape of the piezoelectric gyro sensor is not symmetrical, the balance of the vibration is deteriorated, and the amplitude of the vibrating piece becomes unstable. In addition, there is a disadvantage that unnecessary leakage output and the like easily occur.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide high-precision and excellent electrical characteristics and excellent symmetry of the outer shape. Another object of the present invention is to provide a small-sized piezoelectric gyro sensor at low cost.

[0015]

According to the first aspect of the present invention,
In a piezoelectric gyro sensor using a piezoelectric vibrator as an angular velocity sensor, the piezoelectric gyro sensor has a pair of driving pieces, a pair of detecting pieces and a supporting portion, and the shape of each connecting portion with the coupling portion has a similar shape. It is characterized by having done.

According to a second aspect of the present invention, in the first aspect, the piezoelectric vibrator is a Z-cut crystal vibrator.

According to a third aspect of the present invention, in the piezoelectric gyro sensor according to the second aspect, wherein the piezoelectric vibrator is used as an angular velocity sensor, the -X direction of the driving piece, the detecting piece, or the supporting portion and the connecting portion is provided. Is about 60 °, and the angle c of the + X direction connecting part between the driving piece, the detecting piece or the supporting part and the connecting part is about 30 °.
And is formed to have a shape connected from the angle c to an angle b of about 60 °.

According to a fourth aspect of the present invention, in the piezoelectric gyro sensor according to the second aspect, wherein the piezoelectric vibrator is used as an angular velocity sensor, the connecting portion between the driving piece, the detecting piece, the supporting portion, and the connecting portion. Is formed by using an asymmetric mask having a surface having an angle of at least about 30 ° and about 60 ° with respect to the X axis.

According to a fifth aspect of the present invention, there is provided a piezoelectric gyro sensor according to the second aspect, wherein the piezoelectric vibrator is used as an angular velocity sensor. Wherein the piezoelectric vibrator is formed using a mask having an asymmetrical shape with respect to the Y axis.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a piezoelectric gyro sensor according to the present invention will be described with reference to the drawings, taking a piezoelectric gyro sensor using a quartz oscillator as a piezoelectric oscillator as an example.

FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 show a structural view of a piezoelectric gyro sensor and a quartz crystal according to the first, second, third, fourth and fifth aspects of the present invention. It is a structural drawing etc. of a board | substrate.

The piezoelectric gyro sensor 1 shown in FIGS. 1 and 2
In the structural diagram of FIG. 1, the piezoelectric crystal chip 2 has a pair of driving pieces 3 and a pair of detecting pieces 4. Coupled in the Y plane.

Further, supporting portions 6a and 6b are formed on both sides of the connecting portion 5 in parallel with the driving piece 3 and the detecting piece 4. Then, the connecting portion 7 between the supporting portions 6a and 6b and the connecting portion 5
“a” is narrowly processed by trimming.

The driving piece 3, the detecting piece 4, the connecting portion 5, and the supporting portions 6a and 6b are symmetrical with respect to the common Y axis 8. The Y axis 8 serves as a rotation axis for rotating the piezoelectric gyro sensor 1 as an angular velocity sensor.

The driving piece 3 has a driving electrode 9 formed thereon, and the detecting piece 4 has a detecting electrode 10 formed thereon. The support portions 6a and 6b have driving electrode pads 11a and 11b and detection electrode pads 12a, 12b and 12c for electrically connecting to the internal terminals 22 of the case 21 shown in FIG. 12d are formed respectively, and the electrode pads 11a, 11b, 12a, 12
b, 12c, and 12d, and the metal wiring 13 that connects the driving electrode 9 and the detection electrode 10 to each other.
And the support portions 6a and 6b. That is, the drive electrode 9 and the detection electrode 10 are separately arranged.

As shown in FIG. 2, the piezoelectric crystal chip 2 is mounted on a case 21 made of ceramics or the like, sealed with a cap 23 made of metal or the like, and packaged.

Here, the operation principle of the piezoelectric gyro sensor formed as described above will be described.

A voltage is applied to the driving piece of the piezoelectric gyro sensor formed of quartz, which is a piezoelectric material, and the driving piece is bending and vibrating in the X direction of FIG. 1 at its resonance frequency of about 9000 Hz. In this state, the piezoelectric gyro sensor is Y in FIG.
When rotated about the axis 8, a Coriolis force F acts on the rotation angular velocity ω in a direction perpendicular to the vibration direction of the driving piece, and the driving piece receives stress in the Z-axis direction due to the Coriolis force F and moves in the Z direction. Vibrates (this vibration is commonly called a walk vibration). This vibration propagates to the detecting piece via the coupling portion, and the detecting piece vibrates at its resonance frequency, about 11000 Hz. By detecting the Coriolis force F with a detection electrode formed on the detection piece with high sensitivity and performing electrical processing, the rotation angular velocity of the piezoelectric gyro sensor and the direction of the rotation can be obtained with high accuracy. .

Here, assuming that the mass of the driving piece is m, the speed of the driving piece is V, and the rotational angular velocity is ω, the Coriolis force F generated on the driving piece is

[0030]

(Equation 1)

Is given by the following equation.

Next, a method for manufacturing the piezoelectric gyro sensor formed of quartz according to the present invention will be described in detail.

FIG. 3 shows an external view of a general quartz crystal. As shown in FIG. 3, the crystal body 31 of the quartz crystal has an X axis called an electric axis, a Y axis called a mechanical axis, and a Z axis called an optical axis.

Then, a crystal substrate (crystal wafer) 32 for forming the piezoelectric crystal chip 2 is cut out from the crystal body 31.

The Z-cut quartz substrate 3 used in the present invention
2 is shown in FIG. 4 and FIG.

The quartz substrate 32 thus formed is
Next, a metal film is deposited by a sputtering device or the like. Then, a resist is applied to the crystal substrate 32 on which the metal film is deposited, and the outer shape of the piezoelectric crystal chip 2 is printed by an exposure machine. Then, by immersing the piezoelectric crystal chip 2 in an etching solution such as hydrofluoric acid, the external shape of the piezoelectric crystal chip 2 in FIG. 1 is formed.

Next, electrodes such as the drive electrode 9 and the detection electrode 10 are formed on the piezoelectric crystal chip 2 formed by the outer shape etching by depositing a metal film such as Au.

In the first electrode forming step, a metal mask made of metal is positioned and attached to the quartz substrate 32, and set in a vacuum evaporation machine. Then, metal particles of Cr + Au or the like (for example, an Au film is vapor-deposited on the Cr film) are vapor-deposited at an angle from the opening of the metal mask, and as shown in FIG. Then, a metal film is formed on the front surface 15 and the back surface 16. In this first electrode forming step, the driving piece 3, the detecting piece 4, the coupling section 5, and the supporting sections 6a, 6
A necessary pattern is formed on each side surface portion 14b, the slope 17 of the connection portion 7b, and the like. At the same time, a metal film such as Cr + Au is formed on almost the entire surface 15 and the back surface 16.

Here, since the metal mask is attached and vapor deposition is performed obliquely, the three-dimensional wiring portion 18 of the piezoelectric crystal chip 2 is particularly used.
Is wired using the side surface portion 14 and the inclined surface 17 and the like. By wiring in this way, it is possible to prevent disconnection of the pattern and improve the pattern strength and the like.

Next, in a second electrode forming step, a resist is coated on the quartz substrate 32 formed in the first electrode forming step, and necessary patterns are formed on the front surface 15 and the back surface 16 using a photomask. Is printed by an exposure machine so that

Then, the metal film such as Cr + Au is etched to trim the unnecessary metal film.

As described above, the drive electrode 9, the detection electrode 10, and the metal wiring 13 can be formed on the piezoelectric crystal chip 2.

FIG. 6 shows the configuration of the electrodes on the drive side and the detection side. Here, the detection side is divided into four electrodes.

As described above, by combining the mask deposition step and the photolithography step, a complicated electrode can be efficiently formed.

Further, a voltage is applied to the piezoelectric crystal chip 2 in a state where a plurality of the piezoelectric crystal chips 2 are formed on the crystal substrate 32, and the resonance frequencies of the driving piece 3 and the detection piece 4 are measured. Then, the deviation of the resonance frequency from the target value is weighted to the tip 19 of the driving piece 3 or the detection piece 4, and the frequency is adjusted.

The plurality of piezoelectric crystal chips 2 whose frequency has been adjusted in this manner are continuously cut off from the crystal substrate 32,
The case 21 shown in FIG. 2 is mounted with an adhesive or the like.

Further, the electrode pads 11a, 11b, 12a, 12b, 12c,
From 2d, the internal terminals 22 of the case 21 are electrically connected by wire bonding with an Au wire 24 or the like.

Here, the case 21 is made of ceramics or the like, and is provided with two convex seats for mounting the piezoelectric crystal chip 2 using the support portion 6. Furthermore,
An electrode pattern for grounding is formed around this seat.

Finally, the case 21 is sealed with a cap 23 made of metal or the like by seam welding or the like. Thus, a small and thin piezoelectric gyro sensor 1 is obtained.

FIG. 7 shows the X-axis of the Z-cut quartz substrate.
FIG. 4 is a polar coordinate diagram showing an etching rate in a Y plane. FIG. 7 shows that the etching rate is 0 at the center of the circle, and the etching rate becomes faster toward the outside.
Thus, it can be seen that the Z-cut quartz has anisotropic etching processability.

In particular, + 120 ° with respect to + X direction and X axis
In-plane etching speed in the -direction and -120 ° direction is high, and conversely, in the -X direction, + 30 ° direction and-
The in-plane etching speed in the 30 ° direction is reduced.

On the other hand, the etching speed in the Z direction is -X direction, + 30 ° direction with respect to the X axis, and -30 direction.
° direction becomes faster, + X direction, + 120 ° to X axis
Direction and -120 ° direction are slowed down.

As described above, since the etching processability is anisotropic, the shape of each connection portion 7a, 7b,
The shapes of the distal end portions or corners of the driving piece 3, the detection piece 4, the connecting portion 5, and the like are asymmetric as shown in FIG. In order to form this shape with good symmetry, the shape is printed by an optimal mask and photolithographically processed.

More specifically, as to the shapes of the connecting pieces 7a and 7b for connecting the driving piece 3, the detecting piece 4, and the supporting portions 6a and 6b to the connecting portion 5, as shown in FIG. Is X
A = about 60 °, b = about 60 °, c =
Using a mask formed at about 30 °, the connecting portions 7a and 7b are formed so as to have similar shapes.

Further, as shown in FIG. 9, the shape of the mask is formed asymmetrical with respect to the Y axis. That is, in order to improve the symmetry of the shapes of the connection portions 7a and 7b, the mask shape is designed so that the etching rate characteristics on the + X side and the -X side can be processed under optimized conditions.

The shape of the tip or corner of the driving piece 3, the detecting piece 4, the connecting portion 5, etc. is photolithographically processed using a mask having the shape shown in FIG. FIG. 10 shows, as an example, three types of mask shapes used for correcting the distal end portions of the driving piece 3 and the detecting piece 4. The corners of the joint 5 are also corrected in the same manner as this shape. In this manner, the shape of the piezoelectric crystal chip 2 is made to have a good symmetry by the asymmetric mask corrected at the corner on the −X side.

[0057]

According to the first aspect of the present invention, in the piezoelectric gyro sensor, the shape of each of the connecting portions of the pair of driving pieces, the pair of detecting pieces and the supporting portion, and the connecting portion is similar to each other. As a result, it is possible to efficiently propagate the vibration of the stable and well-balanced drive unit and the stress caused by the generation of the Coriolis force to the detection unit, and to provide a highly accurate and small piezoelectric gyro sensor. .

According to the second aspect of the present invention, since the piezoelectric vibrator is a Z-cut quartz crystal vibrator, the processability of the etching in the photolithography process is good, and the precise shape processing can be performed in a short time. It has the effect of.

According to the third and fourth aspects of the present invention, the shape of the connecting portion between the pair of driving pieces, the pair of detecting pieces and the supporting section, and the connecting section is at least about 30 ° and about 30 ° with respect to the X axis. 6
By using a mask having a plane having an angle of 0 °, the shape of the connection portion is symmetrical, and there is an effect that a well-balanced resonance vibration can be obtained. In addition, the stress generated in the connection portion is also made uniform, and there is also an effect that occurrence of cracks or the like near the connection portion due to stress concentration can be prevented.

According to the fifth aspect of the present invention, the ends of the pair of driving pieces and the pair of detecting pieces or the corners of the joint are formed by using an asymmetric mask whose shape is corrected at the -X side corner. By doing so, there is an effect that the shape of the tip or the corner can be formed with good symmetry.

[Brief description of the drawings]

FIG. 1 is a structural view showing one embodiment of a piezoelectric gyro sensor of the present invention.

FIG. 2 is a structural view showing one embodiment of a piezoelectric gyro sensor of the present invention.

FIG. 3 is a structural diagram showing a crystal structure of quartz.

FIG. 4 is a structural diagram showing a cut-out angle of a quartz substrate for a piezoelectric gyro sensor according to the present invention.

FIG. 5 is a structural diagram showing a cut-out angle of a quartz substrate for a piezoelectric gyro sensor according to the present invention.

FIG. 6 is an electrode wiring diagram of the piezoelectric gyro sensor of the present invention.

FIG. 7 is an etching characteristic diagram of a Z-cut quartz substrate.

FIG. 8 is a structural view of a connection portion of a conventional piezoelectric gyro sensor.

FIG. 9 is a mask drawing for forming the outer shape of the piezoelectric gyro sensor of the present invention.

FIG. 10 is a mask drawing for forming the outer shape of the piezoelectric gyro sensor of the present invention.

FIG. 11 is a structural diagram of a conventional piezoelectric gyro sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric gyro sensor 2 Piezoelectric crystal chip 3 Driving piece 4 Detecting piece 5 Coupling part 6a, 6b Supporting part 7a, 7b Connection part 8 Y axis 9, 10 Electrode 11a, 11b, 12a, 12b, 12c, 12d Electrode pad 13 Metal wiring DESCRIPTION OF SYMBOLS 14 Side surface part 15 Surface 16 Back surface 17 Slope 18 Three-dimensional wiring part 19 Tip part 21 Case 22 Internal terminal 23 Cap 24 Au wire 31 Crystal 32 Crystal substrate 101 Driving piece 102 Detecting piece 103 Rotating shaft 104 Coupling part 105 Support part 106 Housing 107 , 108 electrodes

Claims (5)

[Claims] 1. A piezoelectric gyro sensor using a piezoelectric vibrator as an angular velocity sensor, wherein the piezoelectric gyro sensor has a pair of driving pieces, a pair of detecting pieces, a supporting portion, and a connecting portion with a connecting portion. A piezoelectric gyro sensor having a similar shape. 2. The piezoelectric gyro sensor according to claim 1, wherein said piezoelectric vibrator is a Z-cut crystal vibrator. 3. A piezoelectric gyro sensor using a piezoelectric vibrator as an angular velocity sensor, wherein an angle a of a connecting portion in the −X direction between the driving piece, the detecting piece or the supporting portion and the coupling portion is about 60 °. An angle c of a connecting part in the + X direction between the driving piece, the detecting piece or the supporting part and the coupling part is about 30 °, and
3. The piezoelectric gyro sensor according to claim 2, wherein the piezoelectric gyro sensor is formed to have a shape connected from the angle c to an angle b of about 60 degrees. 4. A piezoelectric gyro sensor using a piezoelectric vibrator as an angular velocity sensor, wherein a shape of a connecting portion between the driving piece, the detecting piece, the supporting portion, and the coupling portion is at least about an X-axis. 30 °
3. The piezoelectric gyro sensor according to claim 2, wherein the piezoelectric gyro sensor is formed using an asymmetric mask having a surface having an angle of about 60 [deg.]. 5. A piezoelectric gyro sensor using a piezoelectric vibrator as an angular velocity sensor, wherein the shape of the tip of the driving piece and the detecting piece or the -X side corner of the coupling portion is corrected to be asymmetric with respect to the Y axis. The piezoelectric gyro sensor according to claim 2, wherein the piezoelectric vibrator is formed using a mask having a shape.