JPS6321869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting and observing leak points in electrical materials or components in which a conductor and an insulator are laminated.

The following is an example of a ceramic capacitor that has leaked.

Figure 1 is a partially cutaway perspective view showing the structure of a ceramic capacitor; 1 is a ceramic capacitor;
a, 2b are external electrodes, 3a, 3b are internal electrodes, 4
is ceramic.

When a leak occurs in such a ceramic capacitor, the manufacturing process is improved by detecting the location of the leak and analyzing that part to determine the cause of the leak.

Detection of a leak point in a ceramic capacitor that has caused such a leak is performed in the following procedure.

First, as shown in Fig. 2, after scraping off the external electrode 2a on one side of the ceramic capacitor 1, the internal electrode 3 is exposed, and a ceramic leak detection circuit as shown in the figure is used to sequentially probe each internal electrode 3. A voltage is applied from the DC power supply 24 between the probe 23 and the opposite external electrode 2b, and the microammeter 22
The internal electrode 3a in contact with the leak ceramic layer is confirmed by the deflection of the needle. Next, use sandpaper or the like to carefully scrape away the leaking ceramic layer 4 from the surface side parallel to the internal electrode 3.
Immediately after cutting off one of the internal electrodes 3 that are in contact with and facing each other, stop cutting. In this way, the leaking ceramic layer 4 is exposed. Next, the leak location is detected using a scanning electron microscope. FIG. 3 is a diagram for explaining the principle. In the figure, 21 is an electron beam, 4 is a leaking ceramic layer, and one of the internal electrodes 3a and 3b which are in contact with this layer and facing each other. This is a sample in which the internal electrode 3b has been scraped off to expose the ceramic 4. 4a is the part where no leak occurs;
4b is a leaking part, and 22 is a minute current meter. When the surface of the ceramic layer 4 is scanned with the electron beam 21 under such a configuration, the electrons absorbed in the sample in the leaking portion 4b flow through the microcurrent meter 22 through the leak path, and the microcurrent meter 22 The needle swings. On the other hand, in the portion 4a where no leakage occurs, since the ceramic is an insulator, no path to ground is formed, so the needle of the microammeter 22 does not swing. In this way, a leak location can be detected from a change in the current flowing through the microammeter 22.

However, this conventional detection method has the following problems. That is, in general, in a scanning electron microscope, an electron beam source that irradiates a sample can be regarded as a constant current source in principle. Therefore, the circuit of FIG. 3 can be equivalently represented as shown in FIGS. 4A and 4B. Figure 4A shows the part 4a where no leak occurs.
This is the case where the electron beam is irradiated to the leaking portion 4b, and B in the same figure is the case where the electron beam is irradiated to the leaking portion 4b. In the figure, 25 is a constant current power supply, 26
is an equivalent capacitor, and 27 is an equivalent leak resistance.

When the sample is irradiated with the electron beam 21, the electrons absorbed by the sample are in the fourth position in the leaking part 4b.
As shown in Figure B, a current flows through the leak resistance 27, causing the needle of the microammeter 22 to swing. On the other hand, in the part 4a where no leakage occurs, as shown in FIG. 4A, the electrons absorbed by the sample accumulate there;
The part 4a where no leakage occurs is the capacitor 26
Therefore, the same amount of charge as the accumulated charge is expelled from the opposite electrode by the irradiated electron beam 21. In other words, the same number of electrons enter from one electrode of the capacitor 26 and exit from the opposite electrode, causing a current to flow.
The needle of the minute current meter 22 swings. In this way, the leaking part 4b and the non-leaking part 4
When a is irradiated with the electron beam 21, the needle of the micro-ammeter 22 swings in either case, so detecting a leak point must be done by distinguishing between subtle differences in the swing of the needle, which requires skill on the part of the operator. It took a long time.

This invention was made in order to eliminate the drawbacks of the conventional method as described above.Charging is caused by irradiating the sample surface with an electron beam, and secondary electrons generated from the sample surface are converted into secondary electrons. A secondary electron image captured by a detector is displayed on an observation display device, and the leak location can be detected and observed in detail from the image.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 5, 28 is a secondary electron detector for detecting secondary electrons generated from a sample, 29 is a secondary electron detector, and 30 is an observation display device.

First, the exposed entire surface of the ceramic layer 4 is scanned with an electron beam 21. Due to the irradiation of the electron beam 21, electrons accumulate on the sample surface in the portion 4a where no leakage occurs, causing charging. On the other hand, in the leaking part 4b, the leak path 27
The electrons absorbed by the sample are transferred to the internal electrode 3a through
Flows to ground through the , and does not cause charging. The presence or absence of this charging and its changes are expressed as changes in the amount of secondary electrons generated from the sample.

That is, the portion where charging occurs has negative polarity. Therefore, the area where charging occurs has an increased efficiency of generating secondary electrons compared to the area where charging does not occur.

These secondary electrons 29 are captured by a secondary electron detector 28, and a secondary electron image synchronized with the scanning of the electron beam 21 is displayed on a display device 30. In this secondary electron image, the leaking portion 4b is darker than the non-leaking portion 4a. In this way, the leak location and its detailed image can be observed.

The inventors were able to observe the leak location quickly and accurately under the following conditions.

In other words, the charging condition is the accelerating voltage
25KV beam current 1×10 ^-8 ~10 ^-6 A, magnification 100 ~
A magnification of 3000 times, a beam irradiation time of 2 to 10 minutes, and a beam scanning time of about 10 seconds per screen are appropriate, and charging is completed in 2 to 10 minutes. In addition, the conditions for observation were: acceleration voltage 25KV, beam current 1×
10 ^-11 A, magnification 10,000 times, beam irradiation time 1 to 2 minutes, beam scanning time 50 to 100 seconds/1 screen,
It goes without saying that the magnification and beam irradiation time may be arbitrary.

In addition, the amount of current applied for charging and the amount of current used for secondary electron image observation are changed, the former being increased as much as possible to shorten the time required for charging, and the latter being as low as possible. It would be even more convenient if it were possible to observe with high resolution.

In the above embodiment, the case of a ceramic capacitor has been described, but the present invention can also be applied to detection of insulation defects in electric material parts, electronic material parts, etc., which are composed of an insulator and a conductor.

As explained above, when observing a leakage point in a laminate of a conductor and an insulator using a scanning electron microscope, the present invention involves grounding the conductor and scanning the surface of the insulator with an electron beam. This system is characterized by performing charging and then observing the leak location from a secondary electron image.Since the amount of charge at the leak location and the non-leak area is different, the secondary electron image Since the difference in contrast increases, not only observation becomes easier, but also accuracy can be improved.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the cross-sectional structure of a ceramic capacitor, Figure 2 is a configuration diagram of a leak layer detection circuit,
FIG. 3 is an explanatory diagram of a conventional leak point detection method, FIGS. 4A and 4B are equivalent circuit diagrams of this conventional method, and FIG. 5 is an explanatory diagram of the principle of the present invention. In the figure, 1 is a ceramic capacitor, 2a
is an external electrode, 2b is an external electrode, 3a and 3b are internal electrodes, 4 is a ceramic, 4a is a non-leak part of the ceramic, 4b is a leaky part of the ceramic, 21 is an electron beam, and 22 is a microcurrent meter. , 23 is a probe, 24 is a DC power source, 25 is a constant current source, 26 is a capacitor, 27 is a leak resistor, 2
8 is a secondary electron detector, 29 is a secondary electron, and 30 is an image display device. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. When observing a leakage point in an electrical material or component in which a conductor and an insulator are laminated using a scanning electron microscope, the conductor of the sample is grounded and the insulation of the sample to be observed is A method for observing leak points in electrical materials and parts, characterized by scanning the surface of an object with an electron beam to cause charging, and observing the secondary electron image. 2. Charging is performed by first scanning the surface of the sample with a high-current electron beam, and then a secondary electron image is observed when scanning with a low-current electron beam. A method for observing leakage points in electrical materials and components according to claim 1.