JP2012103034A - Thin plate inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin plate inspection device enabling a stable measurement regarding a detection of the presence or absence of a crack on a thin plate as a measured object, regardless of variations of the shape etc. of the measured object and an installation position of support means.SOLUTION: A thin plate inspection device emits a sound wave from a vibration plate 12. A variation of sound pressure gives a buoyant force to a measured object 50, thereby vibrating the whole of the measured object 50 with a displacement magnitude Δr2.

Description

  The present invention relates to a thin plate inspection apparatus that stably detects cracks generated in a thin plate.

  2. Description of the Related Art Conventionally, there is a technique for detecting a crack (defect) by applying vibration to a thin plate-shaped measurement object such as a semiconductor substrate and analyzing the generated sound. As an example, by striking a substrate placed on the support means to generate a hitting sound, detecting the generated sound pressure and vibration, and analyzing the detected feature amount, A thin nondestructive inspection apparatus for determining the presence or absence has been proposed (see, for example, Patent Document 1).

JP 2002-333436 A (Example 1 etc.)

  In the nondestructive inspection apparatus described in Patent Document 1, the object to be measured is supported, and only a specific point is vibrated, and cracks are caused by the difference in vibration and sound pressure based on the presence or absence of cracks in the object to be measured. Is to be detected. However, in the excitation of only a specific point, the vibration is mainly a transverse wave and propagates from the excitation point, so that there is a great variation in the propagation method depending on the shape of the thin plate or the shape of the warp or the installation position of the support means, As a result, there is a problem that the propagation of vibration is weakened in the vicinity of the support means, and as a result, there is no difference in the analyzed feature amount, whether or not there is a crack, and the crack may not be detected.

  The present invention has been made to solve the above-described problems, and detects the presence or absence of cracks in the measurement object regardless of variations in the shape of the measurement object that is a thin plate or the installation position of the support means. An object of the present invention is to obtain a thin plate inspection apparatus capable of stable measurement.

  The thin plate inspection apparatus according to the present invention is mounted on the support unit via an air layer between the support unit on which the plate-shaped measurement object to be detected for the presence or absence of cracks is mounted, and the measurement object. A vibration unit that vibrates the measurement object without contacting the measurement object, and a sound generated when the measurement object vibrates, and detects the measurement object based on the sound information. A crack presence / absence determination unit that detects the presence or absence of a crack, and the vibration unit vibrates the entire measurement object in a direction substantially perpendicular to a surface of the measurement object that faces the vibration part. Is.

  According to the present invention, the vibration unit can apply uniform vibration mainly including longitudinal waves to the entire measurement object without contacting the measurement object, and the shape of the measurement object and the installation position of the support means. Regardless, it is possible to stably measure the detection of the presence or absence of cracks in the measurement object.

It is a schematic block diagram of the thin plate test | inspection apparatus 100 which concerns on Embodiment 1 of this invention. It is explanatory drawing of the principle of the vibration of the measuring object 50 used as the test object in the thin plate test | inspection apparatus 100 which concerns on Embodiment 1 of this invention. It is explanatory drawing of the principle in which the measurement target object 50 used as the test object in the thin plate inspection apparatus 100 according to Embodiment 1 of the present invention generates abnormal noise due to vibration. The example of the waveform after the FFT process of the sound which generate | occur | produces from the measuring object 50 used as the test object in the thin plate test | inspection apparatus 100 which concerns on Embodiment 1 of this invention is shown. It is a figure which shows the change accompanying the fluctuation | variation of displacement amount (DELTA) r2 of the measuring object 50 of the sound-pressure level waveform FFT-processed by the acoustic energy analysis part 15 in the thin plate inspection apparatus 100 which concerns on Embodiment 1 of this invention. It is a figure which shows the change accompanying the fluctuation | variation of displacement amount (DELTA) r2 of the measuring object 50 of the average value of the sound pressure level FFT-processed by the acoustic energy analysis part 15 in the thin plate inspection apparatus 100 which concerns on Embodiment 1 of this invention. .

Embodiment 1 FIG.
(Configuration of the thin plate inspection apparatus 100)
FIG. 1 is a schematic configuration diagram of a thin plate inspection apparatus 100 according to Embodiment 1 of the present invention. Hereinafter, the configuration of the thin plate inspection apparatus 100 will be described with reference to FIG. In the following drawings including FIG. 1, the size relationship between the constituent members is not limited, and may differ from the actual one.

The thin plate inspection apparatus 100 according to the present embodiment includes at least an ultrasonic generator 20 that emits ultrasonic waves to the measurement object 50 that is a thin plate, a support unit 21 that is installed without fixing the measurement object 50, A crack presence / absence determination unit 22 that detects and analyzes sound generated from the measurement object 50 vibrated by the ultrasonic wave generation unit 20 is configured.
The ultrasonic generator 20 corresponds to a “vibrator” of the present invention.

  The ultrasonic generator 20 includes at least a vibrating unit 10 provided with a piezoelectric element 10a such as PZT (lead zirconate titanate), a horn 11 attached to the lower surface of the vibrating unit 10 and configured in a truncated cone shape, The diaphragm 12 is fixed to the lower surface of the horn 11 and is composed of a diaphragm 12 made of a metal plate (rigid body) and an oscillating portion 13 that applies a pulse voltage to the piezoelectric element 10a.

The support means 21 is composed of at least a cone-shaped protrusion 17 that allows the measurement object 50 to be installed without being fixed to the cone-shaped tip, and an elastic body such as a spring, and is a vibration fixed to the lower portion of the cone-shaped protrusion 17. The shock absorber 18 and the installation base 19 to which the other end of the vibration shock absorber 18 is fixed.
In addition, in order to support the measuring object 50 from below by the support means 21, it is only necessary to provide three or more conical protrusions 17 and vibration buffer parts 18.

  The crack presence / absence determination unit 22 includes a sound detection device 14 that detects a sound generated when the measurement object 50 supported by the support unit 21 vibrates due to the ultrasonic wave emitted from the ultrasonic wave generation unit 20, and the sound. The acoustic energy analysis unit 15 analyzes the acoustic energy of the sound detected by the detection device 14.

  The vibration unit 10 includes a piezoelectric element 10a having a resonance frequency f0 in a 15 kHz to 45 kHz band, and is formed of a metal (rigid body) that propagates vibration generated by the piezoelectric element 10a.

  The piezoelectric element 10 a is connected to the oscillating unit 13 through a positive electrode terminal and a negative electrode terminal, and vibrates by a pulse voltage applied from the oscillating unit 13. At this time, the piezoelectric element 10a oscillates having a peak near the resonance frequency f0 when a pulse voltage near the resonance frequency f0 is applied from the oscillation unit 13.

  The horn 11 has a function of amplifying the amplitude of vibration generated from the vibration unit 10 including the piezoelectric element 10a. Both end surfaces are opened, and an acoustic path for amplifying and propagating vibration from the vibration unit 10 is provided inside. Formed and sandwiched between the vibration part 10 and the vibration plate 12. In addition, the horn 11 is preferably configured in a truncated cone shape, and is gradually reduced in diameter from the vibrating unit 10 side toward the diaphragm 12.

  The diaphragm 12 is composed of a metal plate (rigid body), and is fixed to the opening on the opposite side of one opening fixed to the vibrating section 10 by screwing or bonding, among the openings on both ends of the horn 11. Has been. Further, the vibration energy of the vibration generated from the vibration unit 10 is propagated through the horn 11 and the diaphragm 12 resonates with the vibration of the vibration unit 10 to generate a strong resonance wave. At this time, the diaphragm 12 is configured to similarly resonate at the resonance frequency f0 when the piezoelectric element 10a of the vibration unit 10 vibrates at the resonance frequency f0. As shown in FIG. 1, the width of vibration by the diaphragm 12 as described above is set as a displacement amount Δr1. Further, the diaphragm 12 radiates an ultrasonic acoustic stream from the entire surfaces (the surface on the horn 11 side and the surface on the opposite side) by vibration. Further, if the diaphragm 12 is fixed so as to hit the “belly” portion of the high-frequency vibration generated from the vibration section 10, the diaphragm 12 vibrates in a specific vibration mode. An acoustic flow is generated between the object 50 and a standing wave that repeats air density. In addition, the plate area, which is the plane area of the diaphragm 12, is greater than or equal to the plate area of the measurement object 50. Accordingly, the vibration of the diaphragm 12 can give a sound wave by uniform vibration mainly including longitudinal waves to the entire measurement object 50, regardless of the shape of the measurement object 50 and the installation position of the support means 21. Stable measurement is possible for detection of the presence or absence of cracks in the measurement object 50.

  As shown in FIG. 1, the horn 11 is installed between the vibration unit 10 and the diaphragm 12. However, the present invention is not limited to this. The horn 11 is not provided, and the diaphragm 12 is not provided. It is good also as what attaches directly to the vibration part 10. FIG. For example, the diaphragm 12 is made of a light material such as aluminum, which is a material having a small density and high elasticity, and the piezoelectric element 10a applies a higher pulse voltage from the oscillating unit 13 so that the horn 11 It is possible to radiate high-frequency sound waves even without it, and the horn 11 is not always necessary.

  The measurement object 50 is, for example, a semiconductor wafer substrate such as a silicon substrate or a solar battery cell, or a thin plate-like material such as a metal material. This measuring object 50 is in the support means 21 so as to face the surface of the diaphragm 12 opposite to the surface on which the horn 11 is installed in the air layer between the diaphragm 12 and the sound detection device 14. It is mounted on the conical protrusion 17 without being fixed. The measuring object 50 vibrates in response to the ultrasonic wave radiated from the diaphragm 12. As shown in FIG. 1, the width of vibration by the measurement object 50 as described above is defined as a displacement amount Δr2. The conical protrusion 17 is supported by a vibration buffer 18 that is an elastic body such as a spring and an installation base 19 on which the vibration buffer 18 is installed. It is formed in a shape. Thus, the measurement object 50 is supported by the support means 21, so that the contact area between the measurement object 50 and the conical protrusion 17 is reduced, and the measurement object 50 is vibrated by the ultrasonic waves from the diaphragm 12. The impact of the support means 21 on the operation to be performed is reduced, and the vibration between the measurement object 50 and the support means 21 is suppressed by receiving the vibration of the measurement object 50 by the vibration buffer 18, and the measurement object The generation of noise due to the contact between the measurement object 50 and the support means 21 can be suppressed without damaging the object 50.

  The sound detection device 14 is configured by, for example, a microphone, a sound sensor, an ultrasonic sensor, or a combination of any of these, and a sound generated from the measurement object 50 that vibrates due to the ultrasonic waves radiated from the diaphragm 12. Is detected. The sound information detected by the sound detection device 14 is transmitted to the acoustic energy analysis unit 15.

As shown in FIG. 1, only one sound detection device 14 is provided. However, the configuration is not limited to this, and a plurality of sound detection devices 14 may be provided. By providing a plurality of sound detection devices 14 in this manner, the detection range of cracks in the measurement object 50 becomes wider than in the case where one sound detection device 14 is provided, and further, cracks generated in the measurement object 50 are detected. The crack detection accuracy can be improved, for example, the position can be determined.
Also, a plurality of sound detection devices 14 having different sensitivities may be provided, and in this case, the size of a crack existing in the measurement object 50 can be grasped to some extent.

  The acoustic energy analysis unit 15 analyzes the acoustic energy of the sound based on the sound information from the measurement object 50 received from the sound detection device 14. At this time, the acoustic energy analysis unit 15 performs, for example, an FFT (Fast Fourier Transform) process on the sound information, and converts the sound pressure level of the sound into a function of the frequency, thereby obtaining the sound energy of the sound. And the presence or absence of cracks in the measurement object 50 is detected. Details of the operation of detecting cracks in the measurement object 50 by the acoustic energy analysis unit 15 will be described later.

  In addition, when detecting the presence or absence of a crack by this acoustic energy analysis part 15, you may provide the alerting | reporting means which alert | reports the detection result.

(Crack detection operation by the thin plate inspection apparatus 100)
FIG. 2 is an explanatory diagram of the principle of vibration of the measurement object 50 to be inspected in the thin plate inspection apparatus 100 according to Embodiment 1 of the present invention. FIG. FIG. 4 shows an example of the waveform after the FFT processing of the sound generated from the measurement object 50. Hereinafter, the crack detection operation by the thin plate inspection apparatus 100 will be described with reference to FIGS.

  First, a measurement object 50 that is an inspection object by the thin plate inspection apparatus 100 is placed on the support means 21. Next, the oscillator 13 applies a pulse voltage in the vicinity of the resonance frequency f0 of the piezoelectric element 10a and the diaphragm 12 to the piezoelectric element 10a. As a result, the piezoelectric element 10a vibrates at a frequency near the resonance frequency f0 by the applied pulse voltage, and the vibration propagates to the vibrating portion 10 sandwiching the piezoelectric element 10a. The vibration of the vibration unit 10 is amplified by the horn 11 and propagates to the diaphragm 12. The vibration plate 12 as a whole resonates with a displacement amount Δr1, and ultrasonic waves having a high sound pressure level associated with the resonance are radiated from the vibration plate 12 as a whole. The ultrasonic wave radiated from the diaphragm 12 becomes an acoustic flow, and as shown in FIG. 2, the sound pressure density is created in the air. In particular, when the sound wave radiated from the diaphragm 12 exceeds a certain sound pressure level, the measurement object 50 obtains buoyancy along with the density of the sound pressure, and the whole is vibrated, with a displacement amount Δr2. It will vibrate.

  Here, the resonance frequency f0 of the piezoelectric element 10a and the diaphragm 12 is preferably in the 15 kHz to 45 kHz band for the following reasons (1) and (2).

(1) If it is less than 15 kHz, it becomes a human audible region, so that it can be sensed by human hearing, and there is a possibility that the user may feel uncomfortable.
(2) If the frequency exceeds 45 kHz, the frequency is too high and sufficient amplitude cannot be obtained, so that the sound pressure level is lowered.

Next, the principle that the measurement object 50 vibrates due to the density of the sound pressure generated by the ultrasonic waves radiated by the diaphragm 12 will be described with reference to FIG.
The energy required for vibration differs depending on the measurement object 50, but when the measurement object 50 is, for example, a semiconductor wafer or a solar cell, the vibration requires a sound pressure level of 130 dB or more. I know that. Therefore, the ultrasonic wave generation unit 20 in the thin plate inspection apparatus 100 according to the present embodiment is configured to generate ultrasonic waves having a sound pressure level of 130 dB or more. As described above, the ultrasonic waves radiated from the diaphragm 12 cause fluctuations in the air, and the sound pressure (atmospheric pressure) portion of the sound pressure (atmospheric pressure) is reduced (decompressed) in accordance with the wavelength of the ultrasonic waves. Part) and "dense" part (pressurized part). That is, air movement occurs from the “sparse” part toward the “dense” part. As a result, the measurement object 50 placed on the support means 21 obtains buoyancy by the sound pressure of the ultrasonic wave radiated from the diaphragm 12, and the balance between the gravity applied to the measurement object 50 and the buoyancy is obtained. The whole will vibrate. In this case, the diaphragm 12 needs to be installed such that the upper surface of the measurement object 50, that is, the surface of the measurement object 50 that faces the vibration plate 12 is close to the “dense” portion. This is because, when the surface opposite to the surface facing the diaphragm 12 of the measurement object 50 is close to a “dense” portion, air movement occurs in the measurement object 50 in the direction of gravity. Is in a state of being pressed against the support means 21 and the vibration of the measuring object 50 is suppressed.

  As described above, when the measuring object 50 is vibrated by the ultrasonic wave radiated from the diaphragm 12, an elastic wave that is a sound wave is generated from the measuring object 50. Here, the propagation speed of the longitudinal wave of the elastic wave generated in the solid (free sound field) is expressed by the following equation (1), and the propagation speed of the transverse wave of the elastic wave generated in the solid (free sound field) is expressed by the following equation. It shows in Formula (2).

Cp = √ [{E · (1-σ)} / {ρ · (1 + σ) · (1-2σ)}] (1)
Cs = √ [E / {ρ · 2 (1 + σ)}] (2)
(Cp: longitudinal wave propagation velocity, Cs: transverse wave propagation velocity, E: Young's modulus, ρ: density, σ: Poisson's ratio)

  Longitudinal and transverse waves propagate inside the solid, but the Poisson's ratio σ is generally about 0.3 inside the solid, and the propagation speed of the longitudinal wave is faster than the transverse wave. Since the presence or absence of cracks in the measurement object 50 changes the value of the Young's modulus E, the change due to the presence or absence of cracks is more affected by the propagation speed of longitudinal waves than the propagation speed of transverse waves. It becomes clear from (1) and formula (2). In addition, since vibration using air as a medium propagates as a longitudinal wave that creates air pressure density in the air, the ultrasonic wave radiated from the diaphragm 12 also extends in the vertical direction to the measurement object 50 that is a solid. It will be easy to give vibration. That is, the presence or absence of cracks in the measurement object 50 greatly affects the way in which elastic waves, which are sound waves from the measurement object 50, propagate.

  Next, with reference to FIG. 3, the principle that abnormal noise (chattering noise) is generated when the measurement object 50 having cracks vibrates will be described. FIG. 3 shows a state in which a crack is generated in the measurement object 50. Moreover, Fig.3 (a) shows sectional drawing of the crack part of the measuring object 50, and FIG.3 (b) has shown the enlarged view of the crack part of the sectional drawing.

  As shown in FIG. 3A, in the measurement object 50, a right side portion is an area A and a left side portion is an area B with a crack as a boundary. Further, the width of area A, that is, the distance from the crack to the right end of measurement object 50 is a, and the width of area B, that is, the distance from the crack to the left end of measurement object 50 is b (> a). And At this time, the vibration frequency when the area A in the measurement object 50 vibrates by the ultrasonic wave radiated from the ultrasonic wave generation unit 20 is denoted by fa, and the vibration frequency when the area B vibrates is denoted by fb.

  As shown in FIG. 3B, when the measuring object 50 having a crack vibrates in the vertical direction due to the ultrasonic wave radiated from the ultrasonic wave generator 20, both the area A and the area B basically vibrate. Then, with the crack as a boundary, a difference occurs in the Young's modulus between the area A and the area B, and the vibration frequency is different. At this time, since the distance a in the area A is smaller than the distance b in the area B, the vibration frequency fa in the area A is higher than the vibration frequency fb in the area B. In addition, regardless of the distance from the crack to both ends of the measurement object 50, the phase difference φ also occurs in the vibrations in the areas A and B. As described above, the crack portion is rubbed due to the difference in vibration frequency between the area A and the area B with the crack as a boundary or the phase difference of vibration, and an abnormal sound (chattering noise) is generated.

Next, an operation in which the crack presence / absence determination unit 22 detects and analyzes the sound generated from the measurement target object 50 and determines the presence / absence of cracks in the measurement target object 50 will be described with reference to FIG.
As described above, the sound generated by the measurement object 50 is detected by the sound detection device 14 in the crack presence / absence determination unit 22. The sound information detected by the sound detection device 14 is transmitted to the acoustic energy analysis unit 15. The acoustic energy analysis unit 15 performs FFT processing on the sound information and converts the sound pressure level of the sound into a function of frequency. By this FFT process, the magnitude of the sound pressure level of each frequency component in various frequency components of the sound from the measurement object 50 can be known. FIG. 4 shows a waveform of a sound pressure level that is a function of the frequency subjected to the FFT processing by the acoustic energy analysis unit 15. 4A shows the waveform of the sound pressure level when there is no crack in the measurement object 50, and FIG. 4B shows the sound pressure when the measurement object 50 has a crack. It shows the waveform of the level. In FIG. 4, the horizontal axis indicates the vibration frequency [Hz], and the vertical axis indicates the response (sound pressure level) [dB].

  As shown in FIG. 4A, when no crack is generated in the measurement object 50, the measurement object shown in (a) when the diaphragm 12 vibrates at the resonance frequency f0. A sound wave having a peak frequency (oscillation frequency Fs), which is the main wavelength, is generated from 50, and no frequency change is observed in the other frequency regions indicated by (A). Here, when the waveform of the sound pressure level shown in FIG. 4A is compared with the line P showing the average of the sound pressure levels in the frequency domain shown in FIG. Only the portion near 50 oscillation frequency Fs exceeds line P, but does not exceed this line P in other frequency regions.

  On the other hand, as shown in FIG. 4B, when a crack occurs in the measurement object 50, the measurement shown in (a) when the diaphragm 12 vibrates at the resonance frequency f0. A sound wave having a peak frequency (oscillation frequency Fs), which is the main wavelength, is generated from the object 50, and a plurality of peak frequency components appear in the other frequency regions indicated by (c). In this way, when a sound wave having a plurality of peak frequency components is radiated from the measurement object 50, an abnormal sound called a chatter sound is generated. At this time, when the waveform of the sound pressure level shown in FIG. 4B is compared with the line Q showing the average of the sound pressure levels in the frequency region shown in FIG. Not only the vicinity portion exceeds the line Q, but also some of the peak frequency components in the frequency region indicated by (c) exceed the line Q. Further, as shown in FIG. 4B, the line Q has a higher value than the line P because the sound pressure level is averaged in the frequency region of (c) having a peak waveform.

  The acoustic energy analysis unit 15 calculates, for example, the above-described line Q obtained by averaging the sound pressure level waveform (line P when no crack is generated), and uses this line Q as a threshold value, and a peak waveform exceeding this threshold value. However, what is necessary is just to determine that the crack has generate | occur | produced in the measuring object 50, when it determines with existing other than the peak waveform in the oscillation frequency Fs shown by (a) in FIG.4 (b). Further, the frequency measurement band of the sound pressure level waveform subjected to the FFT processing by the acoustic energy analysis unit 15 is not particularly limited, but may be a band of 5 kHz to 80 kHz that can be detected by the sound detection device 14, for example.

  As described above, the sound detected by the sound detection device 14 is FFT processed by the acoustic energy analysis unit 15 and analyzed as a frequency response, whereby the presence or absence of a crack in the measurement object 50 can be easily determined.

  As described above, the threshold for determination by the acoustic energy analysis unit 15 is the line Q shown in FIG. 4B in which the sound pressure level shown as a function of frequency is averaged. However, the threshold value is limited to this. Instead, the acoustic energy analysis unit 15 determines a threshold value (for example, a line P) in advance from the measurement result when no crack is generated in the measurement object 50, and determines whether or not there is a crack based on the threshold value. The determination may be made, or the presence / absence of a crack may be determined based on a predetermined threshold.

  Moreover, it is good also as what is equipped with the display apparatus connected to the acoustic energy analysis part 15, and this display apparatus performs the FFT process by the acoustic energy analysis part 15, and the waveform of the sound pressure level shown as a function of frequency, And it is good also as what displays the determination result of the presence or absence of the crack in the measuring object 50 from the waveform. Thereby, the determination result of the presence or absence of a crack in the measurement object 50 can be easily recognized by human vision. In addition, the presence or absence of cracks can be determined to some extent by human hearing based on the abnormal sound (billing sound) generated from the measurement object 50. When in the sound wave region, by providing this display device, the sound pressure level waveform and the crack determination result can be easily confirmed visually.

(Changes in sound pressure level waveform due to fluctuations in displacement Δr2)
FIG. 5 is a diagram illustrating a change in the sound pressure level waveform subjected to the FFT processing by the acoustic energy analysis unit 15 in the thin plate inspection apparatus 100 according to the first embodiment of the present invention, as the displacement amount Δr2 of the measurement target 50 varies. It is.
The solid-line sound pressure level waveform shown in FIG. 5 is for the case where the displacement amount Δr2 of the measurement object 50 is the minimum value, and the broken-line sound pressure level waveform is that the displacement amount Δr2 is the maximum value. Is the case. As shown in FIG. 5, the waveform of the sound pressure level when the displacement amount Δr2 is the minimum value and the waveform of the sound pressure level when the displacement amount Δr2 is the maximum value have the same oscillation frequency Fs, and the displacement amount Δr2 Unaffected by fluctuations. Therefore, as shown in FIG. 5, the detection range of the presence or absence of cracks in the measurement object 50 is, for example, a detection range c in a frequency band different from the changing portion of the sound pressure level waveform due to the variation of the displacement amount Δr2. In this case, the operation for detecting the presence or absence of a crack in the measurement object 50 by the acoustic energy analysis unit 15 is not affected by the variation of the displacement amount Δr2. That is, the acoustic energy analysis unit 15 can detect the presence or absence of a crack regardless of the variation of the displacement amount Δr2 of the measurement object 50.

(Change in the average value of the sound pressure level waveform accompanying the variation of the displacement amount Δr2)
FIG. 6 shows the change of the average value of the sound pressure level subjected to the FFT processing by the acoustic energy analysis unit 15 in the thin plate inspection apparatus 100 according to Embodiment 1 of the present invention as the displacement amount Δr2 of the measurement object 50 varies. FIG.
The displacement amount Δr2 of the measurement object 50 varies depending on its shape and the like, and any value of the displacement amount Δr2 (that is, the range between the minimum value and the maximum value) of the measurement object 50 having cracks. The average value of the sound pressure level is higher than the average value of the sound pressure level of the good measurement object 50 without cracks. That is, even if the displacement amount Δr2 fluctuates due to variations in the shape or the like of the measurement object 50, for example, even if the threshold value is the line P shown in FIG. It can be seen that detection is possible.

(Effect of Embodiment 1)
As described above, the vibration of the diaphragm 12 can give the measurement object 50 the sound wave by the uniform vibration mainly including the longitudinal wave, and the shape of the measurement object 50 and the support means 21 can be obtained. Regardless of the installation position, stable measurement is possible for detection of the presence or absence of cracks in the measurement object 50.

  Further, the contact area between the measurement object 50 and the conical protrusion 17 is reduced, the influence of the support means 21 on the operation of the measurement object 50 vibrating by the ultrasonic waves from the diaphragm 12 is reduced, and the measurement object By receiving the vibration of 50 by the vibration buffer 18, the collision between the measurement object 50 and the support means 21 is suppressed, and the measurement object 50 and the support means 21 are not damaged without damaging the measurement object 50. It is possible to suppress noise generation due to contact with the.

  Moreover, the sound detected by the sound detection device 14 is subjected to FFT processing by the acoustic energy analysis unit 15 and analyzed as a frequency response, whereby the presence or absence of a crack in the measurement object 50 can be easily determined.

  The acoustic energy analysis unit 15 can detect the presence or absence of cracks in the measurement object 50 regardless of variations in the displacement amount Δr2 due to variations in the shape of the measurement object 50 and the like.

  Although the ultrasonic wave is emitted from the diaphragm 12 of the ultrasonic wave generator 20 toward the measurement object 50 as in the above configuration, it is not always necessary to use the ultrasonic wave, and the entire measurement object 50 is used. If it is possible to radiate sound waves capable of giving uniform vibrations mainly including longitudinal waves, it is possible to detect the presence or absence of cracks in the measurement object 50. However, by making the sound wave radiated from the diaphragm 12 into an ultrasonic wave, it cannot be sensed by human hearing and the user is not uncomfortable.

  DESCRIPTION OF SYMBOLS 10 Vibration part, 10a Piezoelectric element, 11 Horn, 12 Diaphragm, 13 Oscillation part, 14 Sound detection apparatus, 15 Acoustic energy analysis part, 17 Conical projection part, 18 Vibration buffer part, 19 Installation stand, 20 Ultrasonic wave generation part , 21 Support means, 22 Crack presence / absence determination unit, 50 measurement object, 100 Thin plate inspection device.

Claims (12)

A support part on which a plate-like measurement object is placed;
A vibration unit that emits a sound wave toward the measurement object via an air layer between the measurement object and vibrates the measurement object by the sound wave;
Detecting a sound generated when the measurement object vibrates, and based on the sound information, detects the presence or absence of a crack in the measurement object;
With
The said vibration part vibrates the said whole measurement object in a substantially perpendicular direction with the surface facing the said vibration part of the said measurement object. The thin plate inspection apparatus characterized by the above-mentioned. The excitation unit has a diaphragm that radiates sound waves toward the measurement object by facing the measurement object and vibrating, and a piezoelectric element, and the vibration of the piezoelectric element is propagated to the vibration plate. The thin plate inspection apparatus according to claim 1, further comprising: an oscillating unit that causes the piezoelectric element to vibrate by applying a pulse voltage to the piezoelectric element. It is installed between the diaphragm and the vibration part, and includes a horn formed in a truncated cone shape whose diameter gradually decreases from the vibration part toward the diaphragm,
The thin plate inspection apparatus according to claim 2, wherein the horn amplifies the vibration generated from the vibration section and propagates the vibration to the diaphragm. The plate inspection apparatus according to claim 2 or 3, wherein a plate area of the diaphragm is larger than a plate area of the measurement object. The diaphragm is a diaphragm having a high atmospheric pressure among a portion having a high atmospheric pressure and a portion having a low atmospheric pressure generated in an air layer between the diaphragm and the measurement object by radiated sound waves. The thin plate inspection apparatus according to any one of claims 2 to 4, wherein the sound wave is radiated so as to be positioned in a vicinity of a surface side facing the surface. The thin plate inspection apparatus according to any one of claims 2 to 5, wherein the sound wave radiated by the vibration plate is an ultrasonic wave of 15 kHz to 45 kHz. The support portion includes a plurality of protrusions having cone-shaped tips supported by an elastic body,
The thin plate inspection apparatus according to any one of claims 1 to 6, wherein the measurement object is placed on the protrusion. The crack presence / absence determining unit performs an FFT process on the sound information from the measurement object to convert a sound pressure level of the sound information into a sound pressure level waveform that is a function of frequency, and a predetermined threshold value The presence or absence of the crack of the said measuring object is detected by comparing the magnitude | size of the sound pressure level in the said sound pressure level waveform and the said sound pressure level waveform. Thin plate inspection device. The crack presence / absence determining unit calculates an average value of sound pressure levels in a waveform portion excluding a peak waveform portion corresponding to an oscillation frequency in the sound pressure level waveform of the measurement object, and calculates the average value as the threshold value. The thin plate inspection apparatus according to claim 8, wherein: The crack presence / absence determination unit is configured to measure the measurement target when a sound pressure level greater than the threshold exists in a waveform portion excluding a peak waveform portion corresponding to an oscillation frequency in the sound pressure level waveform of the measurement target. The thin plate inspection apparatus according to claim 8 or 9, wherein it is determined that there is a crack in an object. The crack presence / absence determination unit corresponds to a waveform portion in the vicinity of an oscillation frequency in which the sound pressure level waveform shape changes in accordance with a change in a displacement amount of the measurement object in the sound pressure level waveform of the measurement object. The thin plate inspection apparatus according to claim 8 or 9, wherein presence or absence of a crack of the measurement object is detected based on the threshold value in a frequency domain excluding the frequency domain. The display device for displaying the sound pressure level waveform of the measurement object determined by the crack presence / absence determination unit and the detection result of the presence / absence of cracks of the measurement object is provided. The thin plate inspection apparatus according to claim 11.

Images