JP2008233053A - Method of measuring frequency characteristic of piezo-electric vibrating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high reliability method of measuring frequency characteristics of piezoelectric vibrating elements; capable of eliminating unwanted waveforms generated in the measurement of the frequency characteristics of piezoelectric vibrating elements. <P>SOLUTION: This method comprises setting a test frequency range, setting a plurality of frequency test points in the test frequency range, adjusting the distance between the piezoelectric diaphragm and the electrode to a distance (gap distance) required for measurement, applying frequencies sequentially to test points preset by the setting process between the adjacent electrodes in this state, collecting characteristics data between electrodes, calculating correction data from the characteristics data between electrodes by this pre-measurement, placing a piezoelectric vibrating element between the electrodes, applying a test frequency to each test point between the electrodes, and obtaining measured frequency data of the piezoelectric vibration element at each test pint; wherein the frequency characteristic data of the piezoelectric vibrating element is obtained by applying the correction data to the measured data. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for measuring frequency characteristics of a piezoelectric vibration element.

  Currently, examples of the piezoelectric vibrating element include a piezoelectric vibrating device and a piezoelectric vibrating piece provided in the piezoelectric vibrating device. In this piezoelectric vibrating device, the piezoelectric vibrating piece is hermetically sealed by a base (package) and a cap.

  The piezoelectric vibration element described above performs frequency characteristic measurement a plurality of times in the manufacturing process, classifies each frequency range according to the measurement result, and adjusts the adjustment amount in the subsequent process.

The frequency characteristic of the piezoelectric vibration element is measured using an apparatus as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-25029 (cited document 1). In cited reference 1, in measuring the resonance frequency of a vibration substrate inserted between electrodes, the electrode gap is changed in the vicinity of the resonance frequency, and the resonance frequency is calculated by frequency measurement before and after the gap change. Is basically mounted on the electrode 3 with a vibration substrate (piezoelectric vibration element), and an alternating electric field is applied between the electrodes with the electrode 2 placed close to the top surface of the vibration substrate. Therefore, a configuration for measuring the frequency (air gap method) is adopted.
JP-A 61-25029

  Usually, when measuring by such an air gap method, an instrument calibration operation (calibration) is often performed in which power is supplied in a state where both electrodes are in contact with each other in advance. For example, when measurement is performed without performing instrument calibration, as shown in FIG. 6, when the measurement waveform is inclined as a whole and the resonance point is detected at the maximum peak, a frequency different from the original resonance point is set to the resonance point. Therefore, there is a possibility that proper frequency measurement is not performed. In order to avoid such problems, the above-mentioned instrument calibration work is performed, and the measurement accuracy is improved by starting the actual measurement after performing the process of removing all error components (zero reset) as shown in FIG. I was able to.

By the way, the number of ultra-thin piezoelectric diaphragms has been increasing recently, and in particular, the thickness of an AT-cut quartz crystal vibrating piece whose driving frequency is determined by its thickness has been several tens of microns. In such a case, in the configuration shown in Patent Document 1, when measurement is performed, the electrodes on the upper and lower sides of the piezoelectric vibrating piece are in extremely close proximity. When frequency characteristics are measured by applying a frequency (alternating electric field) to the piezoelectric vibrating piece in such a state, an unnecessary waveform that appears to be due to the proximity between the electrodes appears (see FIG. 3). In some cases, measurement was performed in a state of being superimposed on the waveform of the frequency characteristic of the piezoelectric vibrating piece. Such an unintended unnecessary waveform leads to erroneous detection of the resonance point in the frequency characteristic measurement of the piezoelectric vibrating piece, resulting in a decrease in reliability in the frequency characteristic measurement.

  In order to solve the above-described problems, an object of the present invention is to provide a highly reliable method for measuring the frequency characteristic of a piezoelectric vibration element by eliminating the influence of an unnecessary waveform generated in the measurement of the frequency characteristic of the piezoelectric vibration element.

  In order to achieve the above object, according to the present invention, as shown in claim 1, a sweeping frequency is provided in a state where a piezoelectric vibration element is disposed between a pair of electrode bodies and a gap is provided between at least one electrode body and the piezoelectric vibration element. Is a method for measuring the frequency characteristics of the piezoelectric vibration element, setting a measurement frequency range, setting a plurality of measurement points of the frequency to be measured within the measurement frequency range, and for frequency measurement A gap setting step for determining an interval between both electrode bodies, and an electrode body that gives the frequency of each measurement point with no piezoelectric vibrating piece between the gap-set electrode bodies and obtains electrode body characteristic data depending on the electrode body spacing. An inter-characteristic data acquisition step, a correction data acquisition step for obtaining correction data based on the inter-electrode body characteristic data, a piezoelectric vibration element is disposed between the electrode bodies, and each measurement is performed between the electrode bodies. The frequency characteristic data of the piezoelectric vibration element is obtained by applying the correction data to the actual measurement step of giving the frequency of the int and obtaining the measurement data of the frequency of the piezoelectric vibration piece for each measurement point, and the measurement data. It has the process of obtaining.

In the present invention, before measuring the frequency of the piezoelectric vibration element, first, a measurement frequency range is set, and a plurality of frequency measurement points are set within the measurement frequency range. In addition, a piezoelectric diaphragm is disposed between both electrode bodies, and the distance between the piezoelectric diaphragm and the electrode body is set to an interval (gap amount) necessary for measurement. The piezoelectric vibration element and the electrode body may be configured to have at least one electrode and an air gap. For example, the piezoelectric vibration element may be mounted flat on one electrode body, and the air gap may be formed in a state where the other electrode is close to the piezoelectric vibration element, or on both surfaces of the piezoelectric vibration element. The structure which arrange | positions an electrode body via an air gap may be sufficient. After the air gap amount is set, the arranged piezoelectric diaphragm is removed, and the frequency is sequentially applied to the measurement points set in the setting step between the two electrode bodies adjacent to each other in this state. By applying the frequency, an output depending on the electrode body is obtained, thereby obtaining the inter-electrode body characteristic data. Based on such preliminary work, correction data based on the inter-electrode body characteristic data is obtained. The generation of the correction data can be, for example, a data configuration in which a correction value that cancels the characteristics between the electrode bodies is given to each measurement point and substantially zero reset is performed by calculation.

And then, a step of disposing a piezoelectric vibration element between the electrode bodies, giving a frequency for each measurement point between the electrode bodies, obtaining measurement data of the frequency of the piezoelectric vibration piece for each measurement point, and the measurement data On the other hand, by applying the correction data, frequency characteristic data of the piezoelectric vibration element can be obtained.

As described above, there is a possibility that the measurement data of the piezoelectric vibration element is superimposed with the inter-electrode body characteristic data depending on the electrode body interval. Therefore, the original frequency characteristic data of the piezoelectric vibration element can be obtained by applying correction data for adjusting the inter-electrode body characteristic data to the measurement data.

According to the method for measuring the frequency characteristics of the piezoelectric vibration element described above, the frequency characteristics of the piezoelectric vibration element can be accurately measured even in the frequency characteristic measurement of an ultra-thin piezoelectric vibration element that generates noise between electrode bodies. Can do. In this case, it is not necessary to perform an apparatus calibration work for bringing both electrode bodies into contact with each other in advance.

In the apparatus calibration method in which both electrode bodies are brought into contact with each other in advance, this operation is performed in a state where both electrode bodies are short-circuited. However, in such a method, the electrode bodies may be deformed. When the electrode body is deformed, an appropriate gap is not formed, so that accurate measurement of the frequency characteristics of the piezoelectric vibration element may not be performed. However, in the present invention, since there is no such process, Long-term use is possible and accurate measurement can be performed.

  In the above method, each electrode body may be given a frequency from a network analyzer via a π circuit. The network analyzer applies each frequency signal to the device under test for a plurality of frequency measurement points set in advance, measures the gain obtained from it, and measures the frequency characteristics based on this gain. Since it can be determined arbitrarily, high-speed and accurate measurement can be performed.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of the unnecessary waveform which arises in the frequency characteristic measurement of a piezoelectric vibration element can be excluded, and the frequency characteristic measurement method of a piezoelectric vibration element with high reliability can be obtained.

  Embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a frequency characteristic measuring apparatus using an air gap method, and FIG. 2 is a block diagram showing each process step in the frequency characteristic measurement according to the present invention. 3 to 5 are waveform diagrams for explaining correction of a measurement waveform to which the present invention is applied.

  As shown in FIG. 1, a frequency characteristic measuring apparatus 1 using an air gap method has a configuration in which each component is acquired on a base 10. A lower electrode body 12 is disposed on the flat portion 10 a of the base 10 via a lower insulator 11. The upper electrode body 13 is disposed with a predetermined interval in a state of facing the upper surface of the lower electrode body 12. The upper electrode body 13 is attached to the upper insulator 14, and the upper insulator 14 is attached to the movable end 15 a of the micrometer 15. The micrometer 15 is held by a holding arm 16, and the holding arm 16 is joined to an actuator 17, whereby the micrometer 15 and the upper electrode body 13 can be operated. The actuator 17 is attached to the side wall 10b of the base so as to be movable up and down.

  The piezoelectric vibration element W as the object to be measured is, for example, an AT cut crystal diaphragm, and is mounted on the lower electrode body 11 and disposed between the upper and lower electrode bodies when measuring the frequency characteristics.

  The lower electrode body 12 is electrically connected to the π circuit 21 and the upper electrode body 13 is electrically connected to the π circuit 22 via cables, and each π circuit is electrically connected to the connector of the network analyzer 3. Further, a PC (personal computer) 4 is connected to the network analyzer 3 via an interface.

  The base 10 serves as a base on which the mechanical part of the frequency characteristic measuring apparatus is arranged, and has a flat portion 10a to which the lower insulator 11 is fixed and a side wall 10b to which the actuator 17 is attached.

  The lower insulator 11 is fixedly installed on the flat portion 10a of the base. The lower insulator 11 is made of a ceramic block having a predetermined thickness, and its upper surface is a flat surface.

  The lower electrode body 12 is attached to the upper portion of the lower insulator 11, and is made of a circular or square metal body or conductive ceramic having a flat upper surface. The surface of the lower electrode body 12 needs to be a smooth surface so as not to damage the piezoelectric vibration element such as scratches when the piezoelectric vibration element W is mounted.

  The upper electrode body 13 is disposed facing the lower electrode body 12 with a gap. The upper electrode body 13 has basically the same configuration as the lower electrode body 12 and is made of a circular or square metal body having a flat surface facing the lower electrode body 12.

However, since the lower electrode body 12 needs to be mounted with the piezoelectric vibration element W, the upper electrode body 13 has a larger upper surface area than the piezoelectric vibration element, but the upper electrode body 13 is smaller than the lower electrode body. This is to suppress the excitation of the unnecessary vibration mode of the piezoelectric vibration element. In the AT-cut crystal vibration plate (piezoelectric vibration element) exemplified in the present embodiment, when an excitation voltage is applied to the entire crystal vibration plate, for example, Unnecessary vibration modes such as the contour vibration mode are likely to be excited. Therefore, by reducing the size of the upper electrode body, an excitation voltage can be applied to the central portion of the quartz crystal diaphragm, and the originally used thickness shear vibration can be excited efficiently. Specifically, for example, a piezoelectric vibration element having a long side of 2.5 mm and a short side of 1.9 mm having an outer size of, for example, a 1.5 mmφ circular upper electrode body is used. A voltage is applied in the vicinity of the central part.

The upper insulator 14 supports and fixes the upper electrode body. Similarly to the lower insulator 11, the upper insulator 14 is made of a ceramic block having a predetermined thickness, and its front and back surfaces are flat.

The micrometer 15 supports and fixes the upper insulator 14 to the movable end 15a. The micrometer 15 is a fine adjustment mechanism for keeping the distance between the upper and lower electrodes within a predetermined range, and the movable end portion 15a is moved in the vertical direction in accordance with the thickness of the piezoelectric vibration element W as the object to be measured. adjust.

The holding arm 16 holds the micrometer 15 and supports and fixes the operation fixing side of the micrometer 15.

  The actuator 17 is joined to the support arm 16 and attached to the base side wall 10b so as to be vertically movable. The actuator 17 is configured to move up and down by an electric motor, an ultrasonic motor, or the like, and an operation direction and an operation amount are determined based on a control signal from the outside. By this vertical movement, the upper electrode body 13 can be brought close to and away from the lower electrode body 12.

For example, when the piezoelectric vibration element W is mounted on the lower electrode body, the upper electrode body is lifted to facilitate mounting the piezoelectric vibration element W from the supply device on the lower electrode body. After mounting on the lower electrode body 12, the upper electrode body 13 can be brought close to the piezoelectric vibration element W to the frequency characteristic measurement position by lowering the upper electrode body 13, that is, by lowering the actuator 17. The fine adjustment in the proximity is performed manually by the micrometer.

  Conductive cables are connected to the connector portions 12a and 13a of the lower electrode body 12 and the upper electrode body 13, and are electrically connected to the π circuits 21 and 22, respectively. The π circuit is used to perform the π circuit measurement method defined in JIS C6701.

  Further, the π circuits 21 and 22 are electrically connected to the network analyzer 3 through conductive cables. As is well known, the network analyzer 3 sets each measurement point in a predetermined frequency range with respect to, for example, a piezoelectric vibration element that is a measurement object, applies a predetermined frequency to each measurement point, and measures the gain characteristic obtained therefrom. Based on this, the frequency characteristics of the piezoelectric vibration element are measured. For example, the frequency range to be measured is set to 153 to 157 MHz, the measurement point is set to 1600 points in the meantime, the frequency in the frequency range is swept and given to each point, and the gain characteristic obtained therefrom is measured. I do.

  The PC 4 is connected via an interface (for example, GP-IB) of the network analyzer 3. The PC 4 sets the measurement frequency range, the number of measurement points, the measurement resolution, etc. of the network analyzer 3. In response to a measurement start command from the PC 4, the network analyzer measures all set measurement points.

The PC 4 receives the measurement value of the network analyzer 3 and stores the measurement value and performs an operation based on the measurement value. For example, the inter-electrode body characteristic data is received, and correction data is generated based on the data, or the measurement data of the piezoelectric vibration element is received and the correction processing based on the correction data is performed on the measurement data. The frequency characteristic data from which the component is removed can be obtained.

  Next, a method for obtaining frequency characteristic data that has been specifically corrected using the above apparatus will be described.

(A) Measurement setting process (frequency measurement point setting process)
A frequency measurement range is set according to the frequency of the piezoelectric vibration element W to be measured, and a large number of measurement points are set in the frequency measurement range at equal intervals or arbitrary spans. For example, the frequency range to be measured is set to 153 to 157 MHz, the measurement point is set to 1600 points in the meantime, the frequency in the frequency range is swept and given to each point, and the gain characteristics obtained from this are measured. I do. The frequency measurement range and the number of measurement points depend on the measurement capability of the network analyzer 3. However, since the measurement range and the number of measurement points (measurement span) are generally in a trade-off relationship, it is necessary to set them in consideration of measurement accuracy. .

(B) Gap setting process (adjustment of gap amount between upper and lower electrodes)
A piezoelectric vibration element W, which is an object to be measured, is mounted on the upper surface of the lower electrode body 12 of the frequency characteristic measuring apparatus shown in FIG. The piezoelectric vibration element W has a flat plate shape, and no excitation electrode is formed on the front and back surfaces. After mounting, the upper electrode body 13 attached to the movable end 15a of the micrometer is brought close to the piezoelectric vibration element W by the lowering operation of the actuator 17. Thereafter, the micrometer 15 is manually adjusted, and the gap between the upper electrode body 13 and the piezoelectric vibration element W is finely adjusted to set an appropriate gap.

(C) Inter-electrode body characteristic data acquisition process (dummy measurement with adjusted gap)
Next, the piezoelectric vibrating element W is removed from the lower electrode body 12, and the frequency is sequentially applied to the measurement points set in the measurement setting step while maintaining the set gap amount, and the gain characteristics based on this are given to the network analyzer. Measure with When the measurement of all the measurement points is completed, the measurement values of all the measurement points are stored in the PC memory.

  FIG. 3 is an example of a waveform diagram showing inter-electrode characteristic data obtained in this step. 3 to 5, the horizontal axis represents frequency (frequency MHz), and the vertical axis represents gain (dB). In FIG. 3, the gain characteristics tend to increase gradually on the high frequency side.

(D) Correction data acquisition step (calculation and acquisition of correction data)
Based on the inter-electrode body characteristic data, a correction value that cancels the inter-electrode body characteristic data for each measurement point is calculated by a PC so that the gain characteristic is substantially reset to zero. The correction data is stored in the PC memory.

(E) Actual measurement process (frequency measurement of the object to be measured)
After each of the above steps, the frequency characteristics of the piezoelectric vibration element that is the object to be measured are measured. The piezoelectric vibration element W is mounted on the upper surface of the lower electrode body, and a frequency (alternating current voltage) is applied between the upper and lower electrode bodies while maintaining the gap set in the gap setting step. Obtain actual measurement data from The actual measurement point is each measurement point set in the measurement setting step, and sequentially gives a frequency set for each measurement point. The measurement may be performed for each measurement point sequentially from the low frequency side to the high frequency side, or conversely for each measurement point sequentially from the high frequency side to the low frequency side.

FIG. 4 is an example of a waveform diagram showing actual measurement data obtained in this step. In FIG. 4, in addition to the steep peak gain that is considered to be the original resonance point f0, a characteristic having a high gain characteristic on the high frequency side as shown in FIG. 3 is superimposed.

(F) Frequency characteristic data acquisition step By applying the correction data for each measurement point to the actual measurement data for each measurement point, the characteristics of the piezoelectric vibration element from which the inter-electrode body characteristics have been removed are extracted. To do. For example, by giving correction data at the specific measurement point to the specific measurement point and calculating the correction data, the characteristics of the piezoelectric vibration element from which unnecessary waveform components are removed at the measurement point are obtained.

FIG. 5 is an example of a waveform diagram showing an example in which correction processing is performed on the actual measurement data obtained in this step using correction data. In FIG. 5, only the original resonance point f0 has a steep peak gain, and the frequency characteristics of the piezoelectric vibration element from which unnecessary waveform components are removed can be obtained.

  It should be noted that the present invention can be implemented in various other forms without departing from the spirit, gist, or main features. For this reason, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  The present invention is suitable for measuring the frequency characteristics of a piezoelectric resonator element, particularly a crystal resonator or a crystal resonator element.

It is a schematic block diagram of a frequency characteristic measuring apparatus. It is a figure which shows a frequency characteristic measurement process. It is a characteristic waveform diagram between electrode bodies. It is an actual measurement waveform figure by an air gap system. It is a wave form diagram of a piezoelectric vibration element after amendment. It is a wave form diagram which shows a prior art example. It is a wave form diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frequency characteristic measuring apparatus 10 Base 12 Lower electrode body 13 Upper electrode body 15 Micrometer 17 Actuator 21,22 pi circuit 3 Network analyzer 4 PC

Claims (2)

A method of measuring a frequency characteristic of the piezoelectric vibration element by disposing a piezoelectric vibration element between a pair of electrode bodies, giving a sweep frequency in a state having a gap between at least one electrode body and the piezoelectric vibration element,
A measurement setting step for setting a measurement frequency range and setting a plurality of measurement points of frequencies to be measured within the measurement frequency range;
A gap setting step for determining an interval between both electrode bodies for frequency measurement;
The inter-electrode body characteristic data acquisition step of giving the frequency of each measurement point in a state where there is no piezoelectric vibrating piece between the gap-set electrode bodies, and obtaining electrode body characteristic data depending on the electrode body interval,
A correction data obtaining step for obtaining correction data based on the inter-electrode body characteristic data;
An actual measurement step of arranging a piezoelectric vibration element between the electrode bodies, giving a frequency of each measurement point between the electrode bodies, and obtaining measurement data of a frequency of the piezoelectric vibration piece for each measurement point;
Obtaining the frequency characteristic data of the piezoelectric vibration element by applying the correction data to the measurement data.   The frequency characteristic measurement method for a piezoelectric vibration element according to claim 1, wherein each electrode body is given a frequency from a network analyzer via a π circuit.

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