JPH07174802A - Method for detecting internal crack in electronic part - Google Patents

Abstract

PURPOSE:To easily and certainly detect any evidence of internal cracks by applying a voltage to an electronic part for measuring its resonance characteristics and comparing them with the resonance characteristics of an electronic part free of its internal cracks. CONSTITUTION:When a voltage is applied to an electronic part composed of electrodes arranged at required positions of a material having an electric strain effect, an electric or mechanical resonance is produced at a particular frequency due to the electric strain. The magnitude of the frequency or resonance at this time is roughly determined by the dimension of an electronic part and/or electric strain constants specific to the material. If the internal cracks exist in the electronic part, some change appears in the resonance frequency or magnitude. Therefore, the resonance characteristics of the electronic part are measured by using an impedance-frequency characteristics device and so on and compared them with the resonance characteristics of the electronic part free of its internal cracks measured in the similar method. Thereby, the evidence of the internal cracks can be detected easily, certainly, and quickly without damaging the electronic part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component such as a monolithic ceramic capacitor using a high dielectric constant ceramic material in which electrodes are arranged at predetermined positions of a material having an electrostrictive effect. The present invention relates to a method for detecting internal cracks.

[0002]

2. Description of the Related Art For example, as a method for detecting an internal crack in a multilayer ceramic capacitor using a high dielectric constant ceramic material, the following two methods have been generally used conventionally.

A method of detecting the presence or absence of internal cracks by cutting a monolithic ceramic capacitor, polishing the cross section, and observing with a microscope.

A method using an ultrasonic flaw detector, in which ultrasonic waves are applied to a sample, and when there is a defective portion such as an internal crack, the intensity of the sound wave reflected and returned by the defective portion and until it returns. The method of detecting the presence or absence and the position of defects such as internal cracks according to the time.

[0005]

However, in the above method, not only the cutting and polishing steps are required and the detection takes time, but also the monolithic ceramic capacitor is destroyed. Therefore, a method for selecting a good product from a defective product. However, there is a problem that it cannot be used.

The method (1) is characterized in that it is possible to detect the presence or absence of a defect such as an internal crack by a nondestructive method without cutting the monolithic ceramic capacitor. As in the case where the sound wave is not perpendicular to the surface of, the defect such as the internal crack may not be detected depending on the relationship between the direction of the sound wave and the surface direction of the internal crack. There is a problem that it is not enough. further,
Usually, it is necessary to apply a method of applying ultrasonic waves from a plurality of directions and measuring the reflection thereof, so that there is a problem that the measurement takes time and the efficiency is poor.

The present invention solves the above-mentioned problems and prevents internal cracks in electronic parts such as high dielectric constant type multilayer ceramic capacitors using a material having an electrostrictive effect without destroying the electronic parts. An object of the present invention is to provide an internal crack detection method for electronic components, which can be quickly detected and can be used as a method for selecting a good product and a defective product.

[0008]

In order to achieve the above object, the inventor has conducted various experiments and studies and applied a voltage to an electronic component in which an electrode is provided on a material having an electrostrictive effect. In this case, it was found that the resonance characteristics of the electronic component having an internal crack definitely changed, and further experiments and studies were conducted to complete the present invention.

That is, the internal crack detecting method for an electronic component according to the present invention is a method for detecting an internal crack in an electronic component in which an electrode is provided at a predetermined position of a material having an electrostrictive effect. Is applied to measure the resonance characteristic, and the presence or absence of the internal crack is detected by comparing with the resonance characteristic of the electronic component having no internal crack measured by the same method.

[0010]

When a voltage is applied to an electronic component in which an electrode is arranged at a predetermined position of a material having an electrostrictive effect, the electrostrictive effect causes electromechanical resonance at a specific frequency. The frequency and the magnitude of resonance at this time are generally determined by the dimensions of the electronic component and the electrostriction constant peculiar to the material. However, when an electronic component has an internal crack, the resonance frequency or magnitude changes due to the influence of the internal crack.

Therefore, the resonance characteristic of the electronic component is measured using an impedance-frequency characteristic measuring device,
By comparing with the resonance characteristics of electronic parts without internal cracks measured by the same method, the presence or absence of internal cracks can be detected easily, reliably, and quickly without cutting (destructing) the electronic parts. become able to. The term electrostrictive effect in the present invention is used in a broad sense, and is a broad concept that includes not only the electrostrictive effect but also the inverse piezoelectric effect.

[0012]

EXAMPLES The features of the present invention will be described in more detail below with reference to examples of the present invention.

In this embodiment, the internal crack detection target
As an electronic component that becomes 3 series high permittivity ceramics
While arranging the internal electrode at a predetermined position in the mick,
Providing external electrodes on both ends that are electrically connected to the internal electrodes
The monolithic ceramic capacitor formed by

In this embodiment, a plurality of monolithic ceramic capacitors without internal cracks and monolithic ceramic capacitors with internal cracks are prepared, and a DC voltage is applied to each monolithic ceramic capacitor to measure impedance-frequency characteristics. The resonance characteristic was investigated by.

1 (a), 1 (b), 1 (c), and 2 (a),
(b) and (c) show the relationship between the frequency and the equivalent series resistance component in the impedance. Note that FIG. 1 shows the resonance characteristics of a monolithic ceramic capacitor without internal cracks,
FIG. 2 shows the resonance characteristics of a monolithic ceramic capacitor having internal cracks.

From FIGS. 1 and 2, there is a clear difference in the peak frequency of resonance between the monolithic ceramic capacitor without internal cracks and the monolithic ceramic capacitor with internal cracks. It was possible to reliably detect the presence or absence of. Therefore, by examining the peak frequency of resonance, it is possible to easily, reliably, and promptly select a monolithic ceramic capacitor without internal cracks and a monolithic ceramic capacitor with internal cracks.

In the above-mentioned embodiment, the case where the presence / absence of an internal crack is detected by focusing on the peak frequency has been described. However, as shown in FIGS. 1 and 2, a laminated ceramic capacitor without an internal crack and an internal crack are detected. In some monolithic ceramic capacitors, there is a clear difference in the size of the resonance peak. Therefore, it is possible to easily select a monolithic ceramic capacitor having no internal crack and a monolithic ceramic capacitor having an internal crack by examining the magnitude of the resonance peak.

It is also possible to further improve the detection reliability by combining the measurement result of the peak frequency and the measurement result of the peak size of the resonance.

In the above embodiment, the case where the resonance characteristic is measured while applying the DC voltage has been described, but it is also possible to generate the same electromechanical resonance by the polarization process.

Further, in the above embodiment, the method of detecting the internal crack of the monolithic ceramic capacitor using the high dielectric constant ceramic material has been described, but the method of the present invention is not limited to this, and the electrostriction is not limited. The present invention can be applied to an inductor and an LC composite component using a ceramic material having an effect, and in that case, the same effect as that of the above embodiment can be obtained.

The present invention is not limited to the above embodiments in other points as well, and various applications and modifications can be made within the scope of the gist of the invention.

[0022]

As described above, according to the method of detecting an internal crack of an electronic component of the present invention, a resonance characteristic of an electronic component having no internal crack measured by a similar method is measured by applying a voltage to the electronic component. Since the presence / absence of an internal crack is detected by comparing with the characteristic, the presence / absence of an internal crack can be easily and reliably detected without cutting the electronic component.

Therefore, the method for detecting internal cracks of electronic parts according to the present invention is extremely significant as a screening method for selecting electronic parts without internal cracks and electronic parts with internal cracks.

Further, unlike the detection method using the ultrasonic flaw detector, erroneous detection does not occur due to the direction of the sound wave and the surface direction of the internal crack, and high detection reliability can be realized.

Further, unlike the detection method using the ultrasonic flaw detector, the detection time is not long, and the internal crack can be detected efficiently in a short time.

[Brief description of drawings]

FIG. 1 (a), (b), (c) is a diagram showing the relationship between the frequency and the equivalent series resistance component in impedance measured for a multilayer ceramic capacitor without internal cracks.

2 (a), (b), and (c) are diagrams showing the relationship between the frequency and the equivalent series resistance component in impedance measured with respect to a multilayer ceramic capacitor having internal cracks.

Claims (1)

[Claims] 1. A method for detecting an internal crack of an electronic component, which comprises electrodes arranged at predetermined positions of a material having an electrostrictive effect, wherein a voltage is applied to the electronic component to measure resonance characteristics, A method for detecting an internal crack in an electronic component, characterized by detecting the presence or absence of an internal crack by comparing the resonance characteristic of the electronic component without the internal crack measured by the method.