JP2005026843A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device capable of reducing the deviation of an oscillation frequency caused by a change in an external environment such as temperature, or the like, and of enabling miniaturization. <P>SOLUTION: The piezoelectric device 21 is provided with a piezoelectric vibrator 22, a semiconductor circuit element 23 for driving the piezoelectric vibrator, and a package 24 for loading them. The piezoelectric vibrator 22 has a natural oscillation frequency generated by a Lame's vibration of 1-4.2MHz and is provided with a piezoelectric vibration section 25 supported by the package through a support arm section lengthwise extended from the nodal point of vibration. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric device that is packaged with a piezoelectric vibrator and a semiconductor circuit element that drives and controls the piezoelectric vibrator and is incorporated as a clock source for various electronic devices.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is a real-time clock module (piezoelectric device) as disclosed in Patent Document 1 as a device that realizes a clock function and a calendar function of various electronic devices such as computers, OA devices, and communication devices. As shown in FIG. 9, the piezoelectric device 1 includes a piezoelectric vibrator 2 and a semiconductor circuit element 3 that drives and controls the piezoelectric vibrator 2 in the same package 4. For the piezoelectric vibrator 2, a tuning fork type crystal vibrating piece that emits a reference vibration frequency is used. A terminal electrode part 6 is joined to a mount electrode part 7 provided in the package 4 and is cantilevered. The semiconductor circuit element 3 incorporates an oscillation circuit, a frequency dividing circuit, and a control circuit for managing and controlling the date and time, and converts the vibration generated by the piezoelectric vibrator 2 into an electric signal to realize a clock and calendar function. I am letting.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2003-51719
[Problems to be solved by the invention]
By the way, with the progress of computerization in recent years, it is necessary to perform time management of each electronic device and synchronization between devices with high accuracy. However, the piezoelectric vibrator 2 which is a clock source for operating such an electronic device has a deviation in vibration frequency due to a change in the external environment such as temperature. Therefore, a clock or calendar built in the semiconductor circuit element 3 is used. An error may occur in the function. Such an error is related to a normal temperature deviation that causes a deviation in the vibration frequency at a certain reference temperature and a frequency temperature characteristic in which the vibration frequency changes in accordance with a temperature change. The room temperature deviation can be suppressed to substantially zero by adjusting the weight of the electrode in the manufacturing process of the piezoelectric vibrator 2, but the frequency temperature characteristic depends on the characteristic characteristic of the piezoelectric vibrator 2. It is difficult to adjust later.
[0005]
In order to improve the above problems, there is a piezoelectric device including the piezoelectric vibrator 2 having a thickness-shear vibration mode with good frequency temperature characteristics. However, in order to obtain a vibration frequency of about 2 MHz, the size of the vibration piece becomes large. The package cannot be downsized.
[0006]
Accordingly, an object of the present invention is to provide a piezoelectric device that can reduce the deviation of the vibration frequency with respect to changes in the external environment such as temperature and can be miniaturized.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, a piezoelectric device according to claim 1 of the present invention is a piezoelectric device including a piezoelectric vibrator, a semiconductor circuit element for driving the piezoelectric vibrator, and a package on which the piezoelectric vibrator is mounted. Is provided with a piezoelectric vibration part having a natural vibration frequency due to a lame vibration of 1 MHz to 4.2 MHz.
[0008]
According to the present invention, since the piezoelectric vibrator is formed by the piezoelectric vibration portion of the lame vibration mode having an excellent frequency temperature characteristic, it is not easily affected by the surrounding temperature change, and the vibration frequency deviation width is suppressed to be small. Can do. Thereby, the signal processing in the driving semiconductor circuit element becomes highly accurate, and the clock and calendar function can be executed more accurately. In addition, according to the piezoelectric vibration portion in the lame vibration mode, a vibration frequency of 1 MHz or more can be obtained according to the design size, and further miniaturization is facilitated.
[0009]
In addition, since the piezoelectric vibration part can be supported on the package via a support arm part that extends long outward from the node, the resistance force against the contour vibration generated in the piezoelectric vibration part can be kept small. For this reason, the equivalent series resistance value can be reduced, and the distortion of the piezoelectric vibrating portion caused by the difference in thermal expansion from the package can be reduced, and a stable vibration frequency can be obtained over a wide temperature range.
[0010]
In addition, since the piezoelectric vibration unit has a natural vibration frequency of 1 MHz to 4.2 MHz, a reference clock frequency of 32.768 kHz can be easily generated by frequency division.
[0011]
The piezoelectric vibrator rotates a Y plate made of an XZ plane of a crystal crystal having a three-dimensional crystal orientation composed of an X axis, a Y axis, and a Z axis around the X axis in a range of −40 ° to −60 °. The lame vibration mode obtained by rotating the Y ′ plate composed of the XZ ′ plane by this rotation in the range of 40 ° to 50 °, or the Y plate in the range of 40 ° to 60 ° opposite to the rotation direction. Any suitable vibration mode can be selected and used from the width / length longitudinally coupled vibration modes obtained by rotating around the X axis.
[0012]
By forming the piezoelectric vibrator in the lame vibration mode or the width / length longitudinally coupled vibration mode, a piezoelectric device with less vibration frequency deviation with respect to temperature change is obtained. In addition, since the piezoelectric vibrator in the vibration mode can obtain a relatively high natural vibration frequency of 1 MHz to 4.2 MHz, various vibration frequencies including a clock frequency of 32.768 kHz are generated. Can do.
[0013]
Further, since the natural vibration frequency can be output directly or after being divided, it is possible to supply a clock source of an external circuit that operates at various frequencies in addition to the application of the clock frequency.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a piezoelectric device according to the present invention will be described in detail with reference to the accompanying drawings.
[0015]
1 and 2 show a basic configuration of a piezoelectric device 21 according to the present invention. The piezoelectric device 21 includes a piezoelectric vibrator 22 having a contour-type vibration mode and a semiconductor circuit element 23 for driving and controlling the piezoelectric vibrator 22 separately in the upper and lower portions of the same package 24. The package 24 is made of ceramic, and includes a rectangular recess 24a for mounting the semiconductor circuit element 23 at the center, and a step portion 24b for mounting the piezoelectric vibrator 22 on the outer periphery of the recess 24a. . The semiconductor circuit element 23 converts a mechanical vibration of the piezoelectric vibrator 22 into an electrical signal and divides the frequency into a predetermined period, and a memory unit storing a program for realizing a clock and calendar function And a CPU unit that performs overall control.
[0016]
The piezoelectric vibrator 22 includes a pair of base portions 26a that connect a rectangular piezoelectric vibration portion 25 with a lame vibration mode and support arm portions 28 that extend from the four corner nodes (25a to 25d). 26b and is formed in a flat plate shape. As shown in FIG. 3, the piezoelectric vibrator 22 is a quartz crystal having a three-dimensional crystal orientation composed of an X axis (electric axis), a Y axis (mechanical axis), and a Z axis (optical axis). A plane Y plate is rotated around the X axis in the range of −40 ° to −60 °, and the XZ ′ plane (Y ′ plate) obtained by this rotation is flat in the range of 40 ° to 50 °. A cut substrate formed by rotation is used. A typical example of such a cut substrate is an LQ2T cut substrate.
[0017]
The piezoelectric vibrator 22 can also be formed as a width-length longitudinally coupled vibration mode. In the case of such a width / length longitudinally coupled vibration mode, as shown in FIG. 4, the Y plate made of the XZ plane is rotated around the X axis in the range of 40 ° to 60 °. A cut substrate formed by rotating the XZ ′ plane (Y ′ plate) obtained by the rotation in the range of 40 ° to 50 ° is used. A typical example of this cut substrate is an NS-GT cut substrate.
[0018]
In addition, independent excitation electrode patterns are formed on substantially the entire front and back surfaces of the piezoelectric vibration portion 25, and the electrode patterns extend to the base portions 26 a and 26 b through the support arm portions 28. The base portions 26 a and 26 b support the piezoelectric vibrating portion 25 on the package 24 and also serve as terminal electrodes that are electrically connected to the semiconductor circuit element 23. The piezoelectric vibrator 22 has the base portions 26a and 26b mounted on a mount electrode portion 27 provided on a step portion 24b of a package 24 on which a semiconductor circuit element 23 is mounted, and is connected via a conductive adhesive. In this manner, after the mounting of the semiconductor circuit element 23 and the piezoelectric vibrator 22 is finished, the lid 30 is attached to the upper portion of the package 24 and hermetically sealed.
[0019]
In the piezoelectric device 21 of the present embodiment, in order to easily obtain a reference clock frequency of 32.768 kHz or a clock frequency that is an integer multiple thereof, 1.048576 MHz, 2.097152 MHz, or 4.194304 MHz of 1 MHz to 4.2 MHz. A piezoelectric vibrator 22 having a natural vibration frequency is used. Note that the size of this piezoelectric vibrator is about 2300 μm at 1 MHz and about 550 μm at 4.2 MHz, taking Lamé vibration as an example. For this reason, in order to reduce the size of the entire piezoelectric device, it is preferable to select a piezoelectric vibrator having a high natural vibration frequency and to design a circuit so that the frequency division ratio can be set finely.
[0020]
FIG. 5 is a graph comparing frequency temperature characteristics of a conventional tuning fork type piezoelectric vibrator and a piezoelectric vibrator having a contour vibration mode of the present invention. As can be seen from this graph, the piezoelectric vibrator of the present invention has a maximum frequency deviation of −20 ppm as compared to the conventional piezoelectric vibrator that has a maximum frequency deviation of −70 ppm as it deviates from the room temperature of 20 ° C. to 30 ° C. It was possible to reduce it to the extent.
[0021]
Next, the functional configuration of the piezoelectric device 21 of the present invention is shown in FIG. The semiconductor circuit element 23 provided in the piezoelectric device 21 mainly includes an oscillation circuit 31, a frequency dividing circuit 32, and a control circuit 33 that controls a clock and a calendar function. The oscillation circuit 31 drives the piezoelectric vibrator 22 and converts the vibration into an electric signal. The frequency dividing circuit 32 divides the vibration frequency sent from the oscillation circuit 31 to generate a frequency of 32.768 kHz that becomes a reference clock signal. The control circuit 33 activates a clock function and a calendar function by the reference clock signal, and outputs the information from the data input / output unit 34 to an external display circuit unit (not shown) or the like for time setting or calendar display setting. Data can be input and stored.
[0022]
In addition to the above function, the piezoelectric device 21 of the present invention includes a first output terminal 35 that directly outputs the vibration frequency of the piezoelectric vibrator 22 to the outside, and a first frequency that outputs a divided frequency of 32.768 kHz. Two output terminals composed of two output terminals 36 are provided, and can be used as a clock supply source for a plurality of electronic devices. In particular, the first output terminal 35 in the MHz band can be applied as a clock source at startup, and the second output terminal 36 in the kHz band can be applied as a clock source in sleep.
[0023]
Further, the contour vibration mode piezoelectric vibrator can obtain vibration characteristics having no practical problem even if it is not placed in a vacuum state as compared with a tuning fork type piezoelectric vibrator. For this reason, there is no need to strictly define the management of the operation in the sealing process, and there is an advantage that it is difficult to be directly affected by the gas generated from the semiconductor circuit element 23.
[0024]
Next, various forms of piezoelectric vibrators that can be mounted on the piezoelectric device will be described. FIG. 7 shows the shape of an LQ2T-cut crystal resonator 42 having a lame vibration mode. The crystal resonator 42 includes a piezoelectric vibration part 45 having vibration nodes (45a to 45d) at four corners, and a base part 46 that supports the piezoelectric vibration part 45 and serves as a contact point for conduction. It is connected to the nodes 45 a to 45 d via a support arm portion 48 that is bent and extended, and has a structure that supports the piezoelectric vibrating portion 45. Like the crystal resonator 42 of this embodiment, the longer the support arm portion 48 extending from the vibration nodes (45a to 45d) is, the more the resistance is reduced and the effect of suppressing the equivalent series resistance value is obtained. Further, the crystal resonator 42 is formed in the (1, 1) -order lame vibration mode including a pair of excitation electrodes on the front and back surfaces of the piezoelectric vibration portion 45 in consideration of the miniaturization of the entire piezoelectric device. For this reason, when the excitation electrode has a square shape and is designed so as to obtain a vibration frequency of 2.0 MHz, the length of one side of the piezoelectric vibration portion 45 is set to about 1150 μm.
[0025]
Further, the piezoelectric vibrator 52 shown in FIG. 8 shows a typical planar shape of the crystal vibrator 52 in the NS-GT cut having the width-length longitudinally coupled vibration mode. The crystal unit 52 includes a piezoelectric vibrating portion 55 on which an excitation electrode is formed, a support arm portion 58 that is bent and extends greatly from one end of both sides sandwiching the piezoelectric vibrating portion 55, and outward from the support arm portion 58. It is integrally formed with a pair of protruding bases 56. Also in the piezoelectric vibrator 52 of this embodiment, since the piezoelectric vibrating portion 55 is supported by the support arm portion 58 extended from the base portion 56 in the same manner as the quartz crystal vibrator 42, the resistance force is reduced and the equivalent is reduced. Series resistance value can be suppressed.
[0026]
Since the piezoelectric vibrator of the lame vibration mode as shown above has a structure in which the piezoelectric vibration part is supported at the nodes of the four corners, an increase in equivalent series resistance value and a decrease in Q value can be suppressed. . For this reason, a stable vibration frequency can be obtained, and a reference vibration frequency in which fluctuation of the vibration frequency due to a temperature change or the like is minimized can be obtained.
[0027]
Since each piezoelectric vibrator shown in the above embodiment has a complicated shape, it is formed by punching a piezoelectric vibrating portion and a supporting arm portion from a quartz substrate by a powder beam method capable of fine processing.
[0028]
【The invention's effect】
As described above, according to the piezoelectric device of the present invention, since the piezoelectric vibrator of the piezoelectric device having the real-time clock module function is composed of the resonator element having the contour vibration mode, the vibration frequency with respect to the temperature change Variation can be reduced. As described above, since the frequency variation of the piezoelectric vibrator that generates the reference vibration frequency is small, the timepiece and calendar function built in the semiconductor circuit element can be accurately started without error.
[0029]
In addition, since the piezoelectric vibrator having the contour vibration mode can be downsized and a relatively high vibration frequency can be obtained, the entire piezoelectric device can be downsized, and an electronic device that operates at various frequencies can be used. It can be used as a clock source.
[Brief description of the drawings]
FIG. 1 is an assembled perspective view showing a configuration of a piezoelectric device according to the present invention.
FIG. 2 is a cross-sectional view of the piezoelectric device.
FIG. 3 is a diagram illustrating a cut angle when a piezoelectric vibrator is formed in a contour sliding vibration mode.
FIG. 4 is a diagram showing a cut angle when a piezoelectric vibrator is formed in a width / length longitudinally coupled vibration mode.
FIG. 5 is a graph comparing frequency temperature characteristics of the piezoelectric device and a conventional piezoelectric device.
FIG. 6 is a functional block diagram of the piezoelectric device.
FIG. 7 is a plan view of a crystal resonator by LQ2T cut.
FIG. 8 is a plan view of a crystal resonator by NS-GT cut.
FIG. 9 is an assembled perspective view showing a configuration of a conventional piezoelectric device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 21 Piezoelectric device 22 Piezoelectric vibrator 23 Semiconductor circuit element 24 Package 24a Recessed part 24b Step part 25 Piezoelectric vibration part 26a, 26b Base part 27 Mount electrode 28 Support arm part

Claims (7)

In a piezoelectric device including a piezoelectric vibrator, a semiconductor circuit element for driving the piezoelectric vibrator, and a package on which these are mounted,
A piezoelectric device, wherein the piezoelectric vibrator includes a piezoelectric vibration unit having a natural vibration frequency by a lame vibration of 1 MHz to 4.2 MHz. 2. The piezoelectric device according to claim 1, wherein the piezoelectric vibration portion has a vibration node at an end portion, and is supported by the package via a support arm portion extending long outward from the node. 3. The piezoelectric device according to claim 1, wherein the vibration frequency obtained from the piezoelectric vibrator is divided to output a reference clock frequency of 32.768 kHz. A crystal resonator cut out from a crystal crystal having a three-dimensional crystal orientation composed of an X-axis, a Y-axis, and a Z-axis at a predetermined cut angle, a semiconductor circuit element for driving the crystal oscillator, and a package on which these are mounted In piezoelectric devices,
The quartz crystal is rotated by rotating the Y plate made of the XZ plane around the X axis in the range of −40 ° to −60 °, and the Y ′ plate made of the XZ ′ surface obtained by this rotation is made 40 ° to 50 °. A piezoelectric device having a piezoelectric vibration part of a lame vibration mode obtained by rotating a plane within a range of °. The quartz crystal unit rotates the Y plate made of the XZ plane around the X axis in the range of 40 ° to 60 °, and further, the Y ′ plate made of the XZ ′ surface obtained by this rotation has the angle of 40 ° to 50 °. The piezoelectric device according to claim 4, further comprising a piezoelectric vibration portion in a width / length longitudinally coupled vibration mode obtained by rotating the plane in a range. The piezoelectric device according to claim 4 or 5, wherein the piezoelectric vibration section has a natural vibration frequency of 1.048576 MHz, 2.097152 MHz, or 4.194304 MHz. The piezoelectric device according to claim 6, wherein the piezoelectric device outputs the natural vibration frequency and a clock frequency of 32.768 kHz obtained by dividing the natural vibration frequency.

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