JP2012084754A - Measurement method and measurement apparatus for piezoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement method and measurement apparatus for piezoelectric transducer, capable of achieving highly precise measurement of electrical properties and little effect of a lead wire on the electrical properties.SOLUTION: The measurement method for a piezoelectric transducer 1, which includes an electrode formed on each of surfaces to which a piezoelectric ceramics oppose and a lead wire for inputting and outputting electric signals electrically connected with the electrode, holds the lead wire with an elastic body 4 so as to cross at least a part of the lead wire 5.

Description

  The present invention relates to a measurement method and a measurement apparatus for a piezoelectric vibrator suitable for measuring a resonance frequency of a piezoelectric vibrator.

  In order to evaluate the electrical characteristics of a piezoelectric vibrator, a method is generally used in which a minute alternating voltage is applied via an electrode provided on the surface of the piezoelectric vibrator to evaluate the frequency characteristics of the impedance of the piezoelectric vibrator.

  FIG. 3 is a perspective view showing an outline of the piezoelectric vibrator. As shown in FIG. 3, the piezoelectric vibrator 1 is provided with electrodes 3 on the opposing upper and lower surfaces of the piezoelectric ceramic 2 and is polarized in the thickness direction as indicated by arrows in the figure. FIG. 4 is a schematic view showing a method for measuring a piezoelectric vibrator, FIG. 4 (a) is a diagram showing a case where electrical connection is made with a contact probe, and FIG. 4 (b) is an electrical connection made with lead wires. It is a figure which shows a case. In FIG. 4A, a terminal from the impedance analyzer 7 as a measurement analysis apparatus is connected to the contact probe 6, and the contact probe 6 is pressed and electrically connected to the upper and lower electrodes of the piezoelectric vibrator 1 from above and below, and AC A voltage is applied. In FIG. 4B, the upper and lower electrodes of the piezoelectric vibrator 1 are soldered and electrically connected to a lead wire 5 made of a copper wire or the like, and the other end of the lead wire 5 is connected to a terminal from the impedance analyzer 7. Connected and applied with AC voltage.

  As a method of using a contact probe, for example, in Patent Document 1, a measurement probe individually disposed on both front and back sides of a piezoelectric substrate, and a probe support mechanism that supports these measurement probes so that they can be approached and separated with a piezoelectric substrate interposed therebetween. An apparatus for measuring a material constant of a piezoelectric substrate provided has been proposed.

JP 2002-124844 A

  Conventionally, when the resonance frequency is measured as one of the electrical characteristics of the piezoelectric vibrator, the electrical connection between the piezoelectric vibrator and the measuring instrument or measurement analysis device is performed by one of the two methods described above, and the frequency characteristics of the impedance Is generally measured.

  However, in the method using the contact probe, since the contact direction of the contact probe is the same as the vibration direction for the piezoelectric vibrator that vibrates in the thickness direction, the resonance frequency, which is the frequency at which the impedance is minimized, is designed. There was a problem of being measured higher than the value. Further, in the case of the method of attaching the lead wire, there is a problem that a reliable contact with the piezoelectric vibrator can be obtained, but the minute vibration of the lead wire may affect the value of the resonance frequency of the piezoelectric vibrator.

  That is, when the shape of the lead wire, such as the length and diameter, is sufficiently small compared to the piezoelectric vibrator, the resonance frequency almost reflects the result of the piezoelectric vibrator only, but the external dimension that has been increasing in demand in recent years is several mm. In the case of a small-sized piezoelectric vibrator, there is a problem that the influence of the natural vibration of the lead wire is superimposed on the characteristics of the piezoelectric vibrator and may affect the value of the resonance frequency as described below. It was.

  FIG. 5 is a diagram showing frequency characteristics of impedance of a piezoelectric vibrator according to a conventional measurement method and calculated values. In the method using the contact probe, since the contact direction of the contact probe is the same as the thickness direction, which is the vibration direction of the piezoelectric vibrator, the contact probe acts to suppress the vibration of the piezoelectric vibrator. Therefore, when the resonance frequency of the piezoelectric vibrator is a design value of 650 kHz, a phenomenon may occur in which the measured value is measured as high as 680 kHz, for example.

  On the other hand, when measuring by a method using a lead wire, a large number of high-frequency vibrations are superimposed on the impedance waveform every several tens of kHz, and in particular, the resonance frequency may be divided into two and measured. This is considered that the natural vibration mode (resonance of 50 to 60 kHz and its higher mode) of the thin and long lead wire is superimposed on the original impedance waveform of the piezoelectric vibrator. In such an example, it is difficult to distinguish the resonance frequency and the anti-resonance frequency, and the measurement accuracy is greatly reduced.

  Therefore, an object of the present invention is to provide a measurement method and a measurement apparatus for a piezoelectric vibrator that can measure the resonance frequency with high accuracy and that is less affected by the vibration of the lead wire.

  In order to solve the above-described problems, in the present invention, in order to reduce the influence of the vibration of the lead wire on the value of the resonance frequency, the lead wire is held by an elastic body during measurement, and the vibration of the lead wire is A measuring method and a measuring device for damping are invented.

  That is, according to the present invention, there is provided a method for measuring a piezoelectric vibrator in which electrodes are formed on opposing surfaces of a piezoelectric ceramic, and lead wires for inputting and outputting electrical signals are electrically connected to the electrodes, A method for measuring a piezoelectric vibrator is provided, wherein the piezoelectric vibrator is held by an elastic body so as to cross at least a part of the lead wire.

  Also, according to the present invention, the elastic body has an international rubber hardness defined by JIS K 6253 of 40 or less (not including 0). It is done.

  Further, according to the present invention, a measuring apparatus using the above-described piezoelectric vibrator measuring method can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the measuring method and measuring apparatus of a piezoelectric vibrator which can measure the resonance frequency accurately with little influence of vibration of the lead wire.

FIG. 1A is a schematic diagram illustrating a measurement method and a measurement apparatus of a piezoelectric vibrator of the present invention, FIG. 1A is a schematic diagram illustrating a measurement method of a piezoelectric vibrator of the present invention, and FIG. Schematic which shows the measuring apparatus which measures a child. FIG. 2A is a diagram showing the frequency characteristics of impedance by the measuring method of the present invention, and FIG. 2A is a diagram showing the frequency characteristics of impedance of the piezoelectric vibrator when the lead terminal is held with elastic rubber having a hardness of 20, FIG. 2B is a diagram illustrating the frequency characteristics of the impedance of the piezoelectric vibrator when the lead terminal is sandwiched with a hard acrylic resin. The perspective view which shows the general form of a piezoelectric vibrator. FIG. 4A is a schematic diagram illustrating a measurement method of a piezoelectric vibrator, FIG. 4A is a diagram illustrating a case where electrical connection is performed using a contact probe, and FIG. 4B is a diagram illustrating a case where electrical connection is performed using a lead wire. Figure. The figure which shows the frequency characteristic of the impedance of the piezoelectric vibrator by the conventional measuring method and a calculated value.

  Embodiments of the present invention will be described below with reference to the drawings.

  The piezoelectric vibrator of the present invention is composed of a rectangular parallelepiped piezoelectric ceramic 2 as shown in FIG. 3, and electrodes 3 made of silver paste or the like are provided on the upper and lower surfaces. Further, polarization treatment is performed between the upper and lower electrodes, and the electrodes are polarized in the thickness direction as indicated by arrows in the figure. As the piezoelectric ceramic 2, various materials having piezoelectric characteristics such as lead zirconate titanate and barium titanate can be applied, and the shape is not limited to a rectangular parallelepiped.

  FIG. 1 is a schematic diagram illustrating a method and an apparatus for measuring a piezoelectric vibrator of the present invention, FIG. 1A is a schematic diagram illustrating a method of measuring a piezoelectric vibrator of the present invention, and FIG. FIG. 3 is a schematic view showing a measuring apparatus for measuring a plurality of piezoelectric vibrators. One end of a lead wire 5 is electrically connected to the electrodes formed on the upper and lower surfaces of the piezoelectric vibrator 1 by solder, conductive adhesive or the like. The other end of the lead wire 5 is connected to a measurement analysis device such as an impedance analyzer 7. It is configured to be held between two elastic bodies 4 so as to cross the lead wire 5 and to attenuate the vibration of the lead wire 5.

  As the elastic body 4 holding the lead wire 5, it is preferable to use an elastic rubber such as urethane rubber or silicon rubber. The elastic body 4 preferably has an international rubber hardness defined by JIS K 6253 of 40 or less (not including 0). When the hardness of the elastic body 4 is greater than 40, the effect of attenuating the vibration of the lead wire 5 is reduced, and the resonance frequency cannot be measured accurately. Also, if the hardness of the elastic body 4 is extremely small, such as 10 or less, the effect of attenuating the vibration of the lead wire can be obtained, but the price of the elastic body also increases, so the cost performance is selected. It is preferable to do this.

  The size of the elastic body 4 is not particularly limited, but it is preferable that the elastic body 4 should have a size that crosses at least a part of the lead wire 5 used to measure the piezoelectric vibrator 1. Since the effect of attenuating the vibration of the lead wire can be surely obtained by making it sufficiently large with respect to the diameter of the wire 5, the diameter is preferably 10 times or more the diameter of the lead wire 5.

  When the measurement method described above is applied to a measurement apparatus, as shown in FIG. 1 (b), it is preferable to use a measurement apparatus that can measure a plurality of piezoelectric vibrators 1 for efficient measurement. Also in the measuring apparatus according to the present embodiment, the lead wires 5 fixed to the plurality of piezoelectric vibrators 1 are collectively held by one elastic body 4. Although not shown in FIG. 1B, the elastic body 4 is provided with a support mechanism on the surface opposite to the surface in contact with the lead wire 5 so that the lead wire 5 can be sandwiched automatically or manually. It is preferable to design as follows. Furthermore, the lead wires 5 fixed and connected to the plurality of piezoelectric vibrators 1 are connected to a circuit board (not shown) designed to switch and measure the piezoelectric vibrators 1 automatically or manually. Is preferably connected to the impedance analyzer 7.

  The piezoelectric vibrator of this example has a rectangular parallelepiped shape as shown in FIG. 3 and is 1.5 mm × 1.5 mm × thickness 2 mm. The piezoelectric vibrator 1 is provided with electrodes 3 printed with silver paste on the upper and lower surfaces of the piezoelectric ceramic 2 facing each other, and is polarized in the thickness direction as indicated by arrows in the figure. Further, the piezoelectric vibrator 1 of this example vibrates in the thickness direction, and the resonance frequency is calculated to be 650 kHz.

  A lead wire made of copper wire having a diameter of 0.1 mm and a length of 50 mm was soldered and electrically connected to the electrode of the piezoelectric vibrator. The other end of the lead wire was connected to an impedance analyzer. The lead wire was sandwiched between 5 mm thick silicon rubber, and the hardness of the silicon rubber was changed to 10, 20, 40, 50, and the impedance frequency characteristics and the capacitance C at 1 kHz were measured with an impedance analyzer. . Also, as a comparative example, when the lead wire is not pinched with an elastic body, when the lead wire is not used and the contact probe is pressed, when the lead wire is pinched with a high-hardness plastic made of an acrylic resin block having a thickness of 10 mm Was also measured. The measurement voltage was 1 Vrms (effective value of AC voltage), and a sine wave of 100 kHz to 1000 kHz was input.

Table 1 shows the result of calculating typical parameters of the electrical characteristics of the piezoelectric vibrator under each condition from the impedance waveform. The evaluation item is a piezoelectric d constant (d ₃₃ : larger is better) calculated from the resonance frequency fr, antiresonance frequency fa, capacitance C, and fr, fa, C for evaluating piezoelectric characteristics.

As can be seen from Table 1, according to the measurement method of the present invention, although there is a measurement error of several Hz compared to the design value, it can be confirmed that the resonance frequency can be measured more accurately than the measurement method of the comparative example. It was. In the structure of the comparative example in which the lead wire is not held by an elastic body, the vicinity of the resonance frequency fr is divided into two peaks, so it cannot be determined which is the original fr, and accurate measurement is difficult. Further, when the influence of the contact probe of the comparative example is seen, the resonance frequency fr is measured 30 kHz higher than the design value, and d ₃₃ is calculated to be smaller than the design value due to the influence, and the piezoelectric frequency is shifted by the deviation of the resonance frequency. It was confirmed that the characteristics were affected. According to the present invention, unnecessary vibration due to the lead wire is attenuated by rubber and resin and hardly appears on the impedance waveform, so that it is possible to measure with high accuracy. However, when the hardness of silicon rubber, which is an elastic body, is larger than 40, and in the method of holding a lead wire with a high-hardness acrylic resin of a comparative example, unnecessary vibration is generated on the waveform indicating the frequency characteristics of impedance. It was confirmed that the measurement accuracy was lowered.

  FIG. 2 is a diagram showing the frequency characteristics of impedance by the measurement method of the present invention, and FIG. 2A shows the frequency characteristics of impedance of the piezoelectric vibrator when the lead terminal is held by elastic rubber having a hardness of 20. FIG. 2B is a diagram showing the frequency characteristics of the impedance of the piezoelectric vibrator when the lead terminal is sandwiched between high hardness acrylic resins. As can be seen from FIG. 2A, when the elastic rubber having a hardness of 20 is used, the higher order vibration of the lead wire, which is a relatively weak vibration, is attenuated and approaches the waveform of only the original piezoelectric vibrator. . Further, as can be seen from FIG. 2B, when the acrylic resin having high hardness is used, the resonance frequency fr is not divided, but an unnecessary vibration remains.

  Further, by applying the above-described measurement method, a measurement apparatus as shown in FIG. Six piezoelectric vibrators 1 were measured, and one end of a lead wire 5 having a diameter of 0.1 mm and a length of 50 mm was soldered to the upper and lower electrodes of the piezoelectric vibrator 1. The other end of the lead wire 5 was connected to a control mechanism incorporating a circuit designed to be sequentially switched and measured, and the control mechanism was connected to the impedance analyzer 7. Prepare two pieces of 10 mm x 50 mm x 5 mm thick elastic body 4 made of silicon rubber with one side of the elastic body 4 (the surface not in contact with the lead wire) and support them A measuring device was constructed by constructing a support mechanism having a function of holding and holding. When the elastic body 4 was nipped at a position crossing almost the center of the lead wire 5 and the resonance frequency was measured, it was confirmed that it was measured with high accuracy in the same manner as the result by the measurement method described above. The measuring apparatus of the present invention is not limited to the present embodiment, and any measuring apparatus using the measuring method of the present invention may be used.

  As described above, according to the present invention, a piezoelectric vibrator measurement method that can measure the resonance frequency with high accuracy can be obtained, and a plurality of measurements suitable for mass production can be performed. Application to a measuring device is also possible.

DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 2 Piezoelectric ceramics 3 Electrode 4 Elastic body 5 Lead wire 6 Contact probe 7 Impedance analyzer

Claims (3)

  A method of measuring a piezoelectric vibrator in which electrodes are formed on opposing surfaces of a piezoelectric ceramic, and lead wires for inputting and outputting electrical signals are electrically connected to the electrodes, wherein at least a part of the lead wires is traversed. A method for measuring a piezoelectric vibrator, wherein the piezoelectric vibrator is held by an elastic body.   The method for measuring a piezoelectric vibrator according to claim 1, wherein the elastic body has an international rubber hardness defined by JIS K 6253 of 40 or less (not including 0).   A measuring apparatus using the method for measuring a piezoelectric vibrator according to claim 1.

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