KR20130087215A - Method of observing a core-shell structure of dielectrics - Google Patents

Abstract

PURPOSE: A core shell monitoring method of a dielectric is provided to equalize a fine structure by making the dielectric thin. CONSTITUTION: A dielectric is polished with sandpaper. The dielectric is milled with an ion beam. The dielectric is etched with etching solution. The dielectric is monitored. A scanning electron microscope is used for the monitoring. [Reference numerals] (AA) Ion beam milling; (BB) Etching; (CC) Use a scanning electron microscope for monitoring

Description

Method of observing a core-shell structure of dielectrics

The present invention relates to a method for observing a core shell structure of a dielectric.

Recently, due to the trend toward miniaturization and high capacity of electronic products, miniaturization and high capacity of electronic components used therein are required. Correspondingly, stacked electronic components are in demand.

In order to manufacture small, high capacity multilayer ceramic capacitors, it is necessary to make the dielectric thin. For this purpose, atomization of the barium titanate powder used as a raw material of the dielectric is essential, and the fired dielectric must exhibit a uniform core shell structure with a uniform microstructure.

It is known that the volume fraction of core and shell in the dielectric is closely related to the reliability of the multilayer ceramic capacitor. However, as the particles of the dielectric powder decrease, it becomes more difficult to form a uniform core shell structure.

Moreover, core shell structure analysis is more difficult in high capacity chips, where the matrix powder is atomized and composed of additives of complex composition.

When using transmission electron microscopy to observe the core shell structure, specimen making is complicated, difficult and time consuming. In addition, a large area cannot be observed with an electron transmission microscope, and sometimes the domain of the core may not be visible depending on the angle of the electron beam.

The present invention seeks to provide an easy and convenient method for observing the core shell structure of a dielectric.

Method for observing the core shell structure of the dielectric according to an embodiment of the present invention comprises the steps of etching using an etchant comprising 1000 parts by weight of distilled water, 4.0 to 6.0 parts by weight of nitric acid, 0.1 to 1.0 parts by weight of hydrofluoric acid; And observing using a scanning electron microscope.

Prior to milling with the ion beam, the method may further include polishing with sand paper.

The dielectric may be a dielectric of a multilayer ceramic electronic component.

The dielectric may comprise barium titanate.

In the etching step, the etching time may be less than 0.1 ~ 2.0 seconds.

In the etching step, the etching temperature may be 20 ~ 30 ℃.

According to the present invention, the core shell structure of the dielectric of the multilayer ceramic capacitor can be easily and simply observed.

1 is a flowchart of a method for observing a core shell structure of a dielectric according to one embodiment of the present invention.
2 is a perspective view of a multilayer ceramic capacitor.
3 is a cross-sectional view taken along line XX ′ of FIG. 2.
FIG. 4 is a partially enlarged view schematically showing the core shell structure of the dielectric of the Z portion in FIG. 3.
5 is a photograph observing a cross section after the ion beam milling according to an embodiment of the present invention.
6 to 8 are photographs of the core shell structures of the dielectrics of the multilayer ceramic capacitors having the A characteristics, the B characteristics, and the Y characteristics observed according to one embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

Furthermore, embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

Accordingly, the shapes and sizes of the elements in the drawings may be exaggerated for clarity of description, and the elements denoted by the same reference numerals in the drawings are the same elements.

1 is a flowchart of a method for observing a core shell structure of a dielectric according to one embodiment of the present invention. 2 is a perspective view of a multilayer ceramic capacitor. 3 is a cross-sectional view taken along line XX ′ of FIG. 2. FIG. 4 is a partially enlarged view schematically showing the core shell structure of the dielectric of the Z portion in FIG. 3. 5 is a photograph observing a cross section after the ion beam milling according to an embodiment of the present invention. 6 to 8 are photographs of the core shell structures of the dielectrics of the multilayer ceramic capacitors having the A characteristics, the B characteristics, and the C characteristics observed according to one embodiment of the present invention.

1, a method for observing a core shell structure of a dielectric according to an embodiment of the present invention includes milling the dielectric with an ion beam; Etching using an etchant including 1000 parts by weight of distilled water, 4.0 to 6.0 parts by weight of nitric acid, and 0.1 to 1.0 parts by weight of hydrofluoric acid; And observing using a scanning electron microscope.

Hereinafter, a method of observing a dielectric of a multilayer ceramic capacitor will be described by way of example, but the present invention is not limited to the method of observing a dielectric of the multilayer ceramic capacitor.

2 and 3, the multilayer ceramic capacitor may include a ceramic body 10, external electrodes 21 and 22 formed outside the ceramic body, and internal electrodes 31 and 32 disposed inside the ceramic body. have. The internal electrodes 31 and 32 may be disposed with the dielectric layer 11 interposed therebetween.

FIG. 4 is a partially enlarged view schematically showing the core shell structure of the dielectric of the Z portion in FIG. 3. Referring to FIG. 4, the grain of the dielectric layer 11 may include a core C and a shell S. FIG. The core (C) is a region existing on the center of grain, and is made of pure barium titanate, and the shell is a region existing on the outer side of grain, and refers to a region formed by diffusion of rare earth additives such as Dy and Y.

The core shell structure may be formed by mixing the rare earth additive in the barium titanate powder and then sintering the rare earth additive into the barium titanate particles. Since the core and the shell coexist, the characteristics of the core and the shell can be expressed together in the electrical and dielectric properties, so that the core shell structure can be employed in a small high capacity product.

A method of observing the core shell structure of the dielectric will be described.

First, the dielectric can be milled with an ion beam. After cutting the multilayer ceramic capacitor, the cross section may be preliminarily polished with sandpaper or the like and finally finished by ion beam milling to prepare the specimen.

Surface damage such as scratching may not occur by milling the surface using an ion beam. Since the core and shell are not very different in structure and composition, it may be very important to prepare the specimen without surface damage in order to observe the core shell structure.

5 is a photograph observing a cross section after the ion beam milling according to an embodiment of the present invention. Referring to FIG. 5, the dielectric layer A and the internal electrode layer B are alternately stacked, and there is no surface damage such as scratches on the cross-sectional surfaces of the dielectric layer A and the internal electrode layer B. FIG. It can be seen that.

If not finally finished by ion beam milling, i.e., polished with sandpaper and finally polished with 1 μm diamond slurry, surface scratches exist in the polishing direction, resulting in an uneven etching. And may not be able to observe the core shell microstructure of the dielectric.

Next, the dielectric milled by the ion beam may be etched using an etching solution including 100 parts by weight of distilled water, 4.0 to 6.0 parts by weight of nitric acid, and 0.1 to 1.0 parts by weight of hydrofluoric acid.

If the content of nitric acid is less than 4.0 parts by weight or more than 6.0 parts by weight, the core shell structure of the dielectric may not be clearly visible, and even if the content of hydrofluoric acid is less than 0.1 part or more than 1.0 part by weight, the core shell structure of the dielectric may be It may not be clear.

Next, it can be observed using a scanning electron microscope (SEM).

By using a scanning electron microscope instead of a transmission electron microscope, one can easily and quickly observe the core shell structure of the dielectric inside the laminated ceramic capacitor.

In the case of observing the core shell structure of a dielectric using a transmission electron microscope (TEM), it is difficult to analyze a large area and the process of preparing a specimen for analysis may be difficult and time consuming.

In the transmission electron microscope analysis, it is difficult to observe the core shell structure because the domain of the core may not be visible depending on the angle of the electron beam.

Prior to milling with an ion beam, the method may further include polishing with sand paper.

The cross section of the dielectric may be prepared at a higher speed using sand paper, and then finally the cross section without surface damage may be prepared by milling with an ion beam.

The dielectric may comprise barium titanate.

In the multilayer ceramic capacitor, a dielectric constant having a high dielectric constant may be used, and specific examples thereof include barium titanate or strontium titanate.

In multilayer ceramic capacitors, particularly X5R, X7R, and the like, it is required that the change in dielectric properties is not large even at high temperatures. In order to realize these characteristics, a core shell structure in which a rare earth element is partially diffused may be formed on the surface of the barium titanate particles.

The core (core) of the grain is still composed of barium titanate, which plays a role in realizing the high dielectric constant of the product.The outer layer (shell) of the grain is a layer in which rare earth elements are diffused. Can exert.

In the etching step, the etching time may be less than 0.1 ~ 2.0 seconds.

If the etching time is 2 seconds or more, the etching proceeds severely, so that the core shell structure of the dielectric cannot be clearly observed. If the etching time is less than 0.1 second, the core shell structure of the dielectric cannot be clearly observed.

In the etching step, the etching temperature may be 20 ~ 30 ℃.

When the etching temperature is higher than 30 ° C, the etching liquid is strongly active and etching may proceed rapidly, and the core shell structure of the dielectric cannot be clearly observed. When the etching temperature is less than 20 ℃, the activity of the etching solution is weak, it may take a long time to etch, the workability may be inferior.

By observing the etched sample using a scanning electron microscope, the core shell structure of the dielectric can be observed more simply and easily.

In the case of using a transmission electron microscope, there are problems such as the complexity of specimen manufacture and the long time required, and it is difficult to observe a large area, and the core may not be visible depending on the angle of the electron beam.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

The laminated ceramic capacitor was polished with sand paper to remove about half of the laminated ceramic capacitor, and then milled with an ion beam.

An etching solution was prepared while changing the content of nitric acid and hydrofluoric acid with respect to 1000 parts by weight of distilled water. The etching was performed at 25 ° C. for 1 second, and immediately after the etching, the specimen was washed with distilled water. The etched specimens were observed using a scanning electron microscope.

Table 1 shows the results of observing the core shell structure of the dielectric with a scanning electron microscope after etching using an etching solution in which the nitric acid and hydrofluoric acid content of the etching solution were changed. The comparative example is the same as the example except that the contents of nitric acid and hydrofluoric acid are different.

division Distilled Water (Gram) Nitric Acid (grams) Foshan (grams) Core shell structure Comparative Example 1 1000 3 0 X Comparative Example 2 0.1 X Comparative Example 3 1.0 X Comparative Example 4 1.5 X Comparative Example 5 4 0 X Example 1 0.1 O Example 2 1.0 O Comparative Example 6 1.5 X Comparative Example 7 5 0 X Example 3 0.1 O Example 4 1.0 O Comparative Example 8 1.5 X Comparative Example 9 6 0 X Example 5 0.1 O Example 6 1.0 O Comparative Example 10 1.5 X Comparative Example 11 7 0 X Comparative Example 12 0.1 X Comparative Example 13 1.0 X Comparative Example 14 1.5 X

O: core shell structure can be observed

X: Core shell structure cannot be observed

Referring to Table 1, Comparative Examples 1 to 4 were 3 grams of nitric acid and 0 to 1.5 grams of hydrofluoric acid, and no core shell structure could be observed regardless of the content of hydrofluoric acid. This is because the content of nitric acid is small and less etching.

In Comparative Examples 11 to 14, in the case of 7 grams of nitric acid and 0 to 1.5 grams of hydrofluoric acid, the core shell structure could not be observed regardless of the content of hydrofluoric acid. This is because the etching proceeded excessively because the content of nitric acid was too high.

In Comparative Example 5, the core shell structure could not be observed when 4 grams of nitric acid and hydrofluoric acid were not included. In Example 1, the core shell structure was observed when 4 grams of nitric acid and 0.1 gram of hydrofluoric acid. Therefore, it can be seen that the etching proceeds to include the hydrofluoric acid so that the core shell structure can be observed.

In Comparative Example 6, the core shell structure could not be observed in the case of 4 grams of nitric acid and 1.5 grams of hydrofluoric acid. In Example 2, the core shell structure was observed in the case of 4 grams of nitric acid and 1.0 gram of hydrofluoric acid. Therefore, when the content of hydrofluoric acid is greater than 1.0 grams, it can be confirmed that the etching proceeds excessively and the core shell structure cannot be observed.

In the case of Comparative Examples 7 and 8 and Examples 3 and 4, the content of nitric acid is different, but the same results as in Comparative Examples 5 and 6 and Examples 1 and 2 are shown.

In addition, in the case of Comparative Examples 9 and 10 and Examples 5 and 6, although the content of nitric acid differs, the result similar to Comparative Examples 5 and 6 and Examples 1 and 2 is shown.

In conclusion, referring to Table 1, it can be seen that the core shell structure of the dielectric can be clearly observed when using an etching solution added with 4 to 6 grams of nitric acid and 0.1 to 1.0 grams of hydrofluoric acid with respect to 1000 grams of distilled water.

Next, the core shell structure was observed using an etching solution to which 1000 grams of distilled water, 5 grams of nitric acid, and 0.5 grams of hydrofluoric acid were added to the multilayer ceramic capacitors having the characteristics A, B, and Y, as examples. 6 to 8 are shown.

6 to 8 are photographs of the structure of the core (C) shell (S) of the dielectric of each of the multilayer ceramic capacitors of the A characteristic, the B characteristic, and the Y characteristic. In the case of B and Y characteristics of FIGS. 7 and 8, the core (C) shell (S) structure is more pronounced than the A characteristic of FIG. 6.

This may be inferred that in the case of the A characteristic multilayer ceramic capacitor, the size of the barium titanate, which is a raw material powder, is about 200 nm and the firing temperature is high, thereby forming the shell S actively.

The terms used in the present invention are intended to illustrate specific embodiments and are not intended to limit the invention. The singular presentation should be understood to include plural meanings, unless the context clearly indicates otherwise.

The word " comprises " or " having " means that there is a feature, a number, a step, an operation, an element, or a combination thereof described in the specification.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims.

It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

10: Ceramic body
11: dielectric layer
21, 22: external electrode
31, 32: internal electrode
C: core
S: shell
A: dielectric layer
B: inner electrode layer

Claims (6)

Milling the dielectric with an ion beam;
Etching using an etchant including 1000 parts by weight of distilled water, 4.0 to 6.0 parts by weight of nitric acid, and 0.1 to 1.0 parts by weight of hydrofluoric acid; And
Observing using a scanning electron microscope;
Core shell structure observation method of the dielectric comprising a.
The method of claim 1,
A method of observing a core shell structure of a dielectric further comprising polishing with sand paper prior to milling with an ion beam.
The method of claim 1,
And said dielectric is a dielectric of a laminated ceramic electronic component.
The method of claim 1,
And a method for observing a core shell structure of a dielectric material comprising barium titanate.
The method of claim 1,
In the etching step, the etching time is 0.1 ~ 2.0 seconds core shell structure observation method of the dielectric.
The method of claim 1,
In the step of etching, the etching temperature is 20 ~ 30 ℃ the core shell structure observation method of the dielectric.

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