KR20190012988A - Multi layer ceramic capacitor making method and multi layer ceramic capacitor made with the same method - Google Patents

Abstract

A method of manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention includes forming a ceramic green sheet using a dielectric composition, forming an internal electrode on the ceramic green sheet, forming the ceramic green sheet A heating step of heating the ceramic laminate to a first temperature; a cooling step of cooling the ceramic laminate to a second temperature lower than the first temperature at the first temperature; And
And a first sintering step of sintering the ceramic laminate at the second temperature.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor and a multilayer ceramic capacitor using the multilayer ceramic capacitor. 2. Description of the Related Art Multilayer ceramic capacitors,

The present invention relates to a method of manufacturing a multilayer ceramic capacitor, and more particularly, to a method of manufacturing a multilayer ceramic capacitor in which a simple process is performed by a heat treatment process and sintering of a dielectric composition by changing only the oxygen partial pressure.

2. Description of the Related Art Recently, as electronic products using a multi-layer ceramic capacitor (MLCC) have become smaller and higher in performance, multi-layer ceramic capacitors (MLCCs) used therefor are becoming smaller and higher in capacity.

That is, as the miniaturization and the high capacity of the MLCC are demanded, the ceramic layer for the capacity implementation is becoming thinner and the stratified layer is formed, and accordingly, the implementation of the MLCC having the high density is becoming the main issue.

Conventionally, a separate additive such as xB2O3- (1-x) BaO or ZnO-B2O3-SiO2 (ZBS) glass was added to the conventional dielectric composition to increase the density or sinter at a low temperature. However, There is a problem that the kind of the additive, the amount of the additive, and the occurrence of the secondary phase must be considered for each of the adopted dielectric compositions.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a multilayer ceramic capacitor in which a heat treatment process and an oxygen partial pressure are changed only by a sintering process without a separate additive, So as to produce a multilayer ceramic capacitor including the dielectric composition.

A method of manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention includes:

Forming a ceramic green sheet by using a dielectric composition, forming an internal electrode on the ceramic green sheet, laminating and pressing the ceramic green sheet on which the internal electrode is formed to form a ceramic laminate, A heating step of heating the ceramic laminate to a first temperature, a cooling step of cooling the ceramic laminate to a second temperature lower than the first temperature at the first temperature, and a first sintering step of sintering the ceramic laminate at the second temperature .

A multilayer ceramic capacitor according to an embodiment of the present invention includes a ceramic green sheet including a dielectric composition, an internal electrode formed on the ceramic green sheet, And a ceramic laminate formed by laminating and pressing the ceramic green sheet having the internal electrode formed thereon, wherein the ceramic laminate is heated to a first temperature, and the ceramic laminate is heated from the first temperature to a second temperature lower than the first temperature And then performing a first sintering step of sintering the ceramic laminate at the second temperature.

According to one embodiment of the present invention, in the process of producing a multilayer ceramic capacitor, sintering is performed by changing only the heat treatment process and the oxygen partial pressure without any additive, so that it is not necessary to consider the kind and amount of additive to be considered when adding the additive, It is possible to produce a multilayer ceramic capacitor including a dielectric composition having a simple process and a high density in a short time at a low temperature.

In this case, the grain growth can be suppressed and the densification can be maximized, thereby making it possible to manufacture a high-capacity small-sized capacitor.

1 is a schematic perspective view of a multilayer ceramic capacitor according to an embodiment of the present invention.
2A to 2C are a sectional view taken along the line A-A 'in FIG. 1 and a detailed view of the ceramic green sheet 10 and the internal electrode 20.
3 shows a flow chart of a method of manufacturing the multilayer ceramic capacitor 1 according to the embodiment of the present invention.
4 to 6 are diagrams referred to describe a heat treatment process and an oxygen partial pressure change according to an embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, a method of manufacturing a multilayer ceramic capacitor 1 and a multilayer ceramic capacitor 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view of a multilayer ceramic capacitor 1 according to an embodiment of the present invention, and FIGS. 2A to 2C are sectional views taken along the line A-A 'in FIG. 1 and a sectional view of the ceramic green sheet 10 and the internal electrode 20b, Fig.

Referring to FIGS. 1 and 2, a multilayer ceramic capacitor 1 according to an embodiment of the present invention includes BaTiO ₃ A first external electrode 30a formed on one side of the ceramic multilayer body 100 and a first external electrode 30a formed on one side of the ceramic multilayer body 100. The first external electrode 30a and the second external electrode 30b are formed by laminating a plurality of ceramic green sheets 10, And a second external electrode 30b formed on the surface opposite to the surface on which the second electrode 30b is formed. The first internal electrode 20a and the second internal electrode 20a formed on the respective ceramic green sheets 10 so that the polarities of the ceramic green sheets 10 are different from those of the ceramic green sheets 10, (20b). The first external electrode 30a may be electrically connected to the first internal electrode 20a and the second external electrode 30b may be electrically connected to the second internal electrode 20b.

The ceramic green sheet 10 is made of BaTiO ₃ For example, a low-temperature firing dielectric composition. That is, by using the dielectric composition for low-temperature firing according to one embodiment of the present invention, firing can be performed at a temperature lower than a temperature at which nickel internal electrodes are oxidized or aggregated.

In the conventional case, the thickness of the ceramic green sheet 10 can not be made equal to or smaller than a certain thickness due to a short occurring due to the accumulation of nickel internal electrodes at high temperatures. However, since the multilayer ceramic capacitor 1 according to an embodiment of the present invention forms the ceramic green sheet 10 using the dielectric composition for low-temperature firing and fires at a low temperature, little. Therefore, even when the thickness of the dielectric layer 10 is reduced, the reliability is not lowered and a high capacity (high performance) can be secured.

Therefore, in one embodiment of the present invention, the thickness of the ceramic green sheet 10 may be between 1 [mu] m and 2 [mu] m. When the thickness of the ceramic green sheet 10 is less than 1 탆, adjacent internal electrodes 20a and 20b may contact each other and short-circuit may occur. When the thickness of the dielectric layer exceeds 2 탆, .

According to the embodiment of the present invention, the dielectric constant of the ceramic green sheet 10 is measured by using the dielectric composition for low-temperature firing and using a two-step sintering method and a hetero-atmosphere sintering method in combination. Can be improved to 97% or more.

Two-step sintering is a method of sintering at a lower temperature after cooling to a temperature higher than the temperature at which one-step sintering is performed, which is sintered at a certain temperature, without holding time, The cooled temperature may be the same as the temperature at which one-step sintering is performed. That is, after cooling to the same temperature as the one-step sintering, sintering is performed. The hetero-atmosphere sintering is to change the oxygen partial pressure during the sintering of the two-step sintering. The two-step sintering and the hetero-atmosphere sintering will be described later in detail with reference to FIG. 3 and below.

Meanwhile, the first internal electrode 20a according to the embodiment of the present invention is formed to be connected to the first external electrode 30a on the ceramic green sheet 10. The second internal electrode 20b is formed on the ceramic green sheet 10 to be connected to the second external electrode 30b.

The ceramic green sheet 10 in which the first internal electrode 20a is formed and the ceramic green sheet 10 in which the second internal electrode 20b is formed may be alternately laminated to provide the ceramic laminated body 100. [ For example, by connecting a positive voltage to the first external electrode 30a and a negative voltage to the second external electrode 30b, the first internal electrode 20a and the second internal electrode 20b have different polarities . Therefore, a dipole is formed on the ceramic electrode sheet 10 positioned between the first internal electrode 20a and the second internal electrode 20b, so that the multilayer ceramic capacitor according to the embodiment of the present invention operates. The first external electrode 30a and the second external electrode 30b may be formed on both surfaces of the ceramic laminated body 100 in the longitudinal direction.

2B to 2C are views showing the ceramic green sheet 10 and the internal electrode 20 of FIG. 1 in detail.

First, a plurality of first internal electrode patterns 20a 'may be formed on the ceramic green sheet 10 as shown in FIG. 2B. The plurality of first internal electrode patterns 20a 'may be formed parallel to each other with a predetermined distance d3.

The predetermined distance d3 is a distance for inserting the internal electrode 20 from the external electrode 30 having a polarity different from that of the internal electrode 20. The distance between the internal electrode 20 and the external electrode 30 2 < / RTI >

The ceramic green sheet 10 may be formed of a ceramic paste containing ceramic powder, organic solvent, and organic binder. The ceramic powder may be a BaTiO 3 -based material, a lead composite perovskite-based material, a SrTiO 3 -based material, or the like, and is preferably a barium titanate (BaTiO 3) BaTiO3) powder may be used.

The first internal electrode pattern 20a 'may be formed of an internal electrode paste containing a conductive metal. The conductive metal may be, but is not limited to, Ni, Cu, Pd, or an alloy thereof.

The method of forming the first internal electrode pattern 20a 'on the ceramic green sheet 10 is not particularly limited and may be formed by a printing method such as a screen printing method or a gravure printing method.

Further, although not shown, a plurality of second internal electrode patterns 20b 'may be formed on another ceramic green sheet 10.

The ceramic green sheet on which the first internal electrode pattern 20a 'is formed may be referred to as a first ceramic green sheet, and the ceramic green sheet on which the second internal electrode pattern 20b' is formed may be referred to as a second ceramic green sheet. .

Next, as shown in FIG. 2C, the first and second ceramic green sheets may be alternately stacked so that the first internal electrode pattern 20a 'and the second internal electrode pattern 20b' are alternately stacked.

Hereinafter, the first internal electrode pattern 20a 'may form a first internal electrode 20a, and the second internal electrode pattern 20b' may form a second internal electrode 20b.

When the MLCC is manufactured using the dielectric composition containing BaTiO 3, when the sintering temperature exceeds 1200 ° C., the internal electrode of the nickel shrinks and aggregates, and the internal stress is generated due to the difference in shrinkage behavior between the internal electrode and the dielectric composition . In addition, the probability of occurrence of a short circuit due to shrinkage of the inner electrode of the nickel sharply increases, and the oxidation of the inner electrode reduces the electrode connectivity or the coverage of the electrode. Further, there is a high possibility that the reliability is deteriorated due to a decrease in capacitance and a decrease in insulation resistance at a high temperature (> 1200 ° C). Therefore, there is a need for an MLCC including a dielectric composition having a high density at a low temperature of 1200 DEG C or lower. Conventionally, such an MLCC was prepared by adding a separate additive. However, according to an embodiment of the present invention, the MLCC can be manufactured by changing only the heat treatment process and the oxygen partial pressure without additional equipment. Hereinafter, such a process will be described in detail.

3 shows a flow chart of a method of manufacturing the multilayer ceramic capacitor 1 according to the embodiment of the present invention.

As shown in FIG. 3, a method of manufacturing a multilayer ceramic capacitor 1 according to an embodiment of the present invention may include forming (s310) a ceramic green sheet using a dielectric composition. The dielectric composition according to an embodiment of the present invention is BaTiO ₃ In _{addition, SrTiO 3, Ba 1/2} SR 1/2 TiO 3 .

In the step of forming a ceramic green sheet, a ceramic green sheet can be produced by mixing a low temperature firing dielectric composition, a binder and a solvent to prepare a slurry, and the slurry can be formed into a sheet having a thickness of several micrometers by a doctor blade method.

After forming the ceramic green sheet, an internal electrode may be formed on the ceramic green sheet (s320). The internal electrode 20 according to the embodiment of the present invention may be formed using a conductive paste composition containing a conductive metal powder. The conductive metal powder is not particularly limited and includes, for example, silver (Ag), lead (Pb), platinum (Pt), nickel (Ni), copper (Cu) and the like, Can be used.

After the internal electrode is formed on the ceramic green sheet, the ceramic green sheet on which the internal electrode is formed may be laminated and pressed to form a ceramic laminate (S330). At this time, a plurality of ceramic green sheets can be stacked and pressed to form a ceramic laminate, and after the lamination and compression, the ceramic laminate can be manufactured through firing, cutting, and polishing steps.

Next, the heating step (s340) of heating the ceramic laminate to the first temperature may be performed (s340). Here, the first temperature according to the embodiment of the present invention may be a predetermined temperature As shown in FIG. 4B, and may be about 1250 DEG C. + -. 0.08%, in one embodiment, about 1250 DEG C, and the heating time to the first temperature may be about 6 minutes. When the particle size is increased, the driving force required for the densification is decreased and the densification is less in the second temperature range. When the particle size is increased, The total sintering time may be increased. Therefore, in the present invention, it may be most preferable when the first temperature is in the range of about 1250 ° C ± 0.08%, especially 1250 ° C.

The predetermined sintering temperature according to the conventional heat treatment process as shown in FIG. 4A is about 1150 ° C.

After the heating step, cooling may be performed at a first temperature to a second temperature lower than the first temperature. (S350)

According to an embodiment of the present invention, the second temperature may be about 1150 ° C. + -. 0.13% to less than 1200 ° C as shown in FIGS. 4b, 5b, and 5c, for example, 1150 ° C. When the second temperature is lower than 1150 ° C-0.13%, the driving force required for densification is insufficient, and a high density of 90% or more may not be exhibited. For example, as shown in FIG. 5A, when the second temperature is 1050 DEG C, the density may be lowered. If the second temperature exceeds 1200 ° C., the internal electrode 20 may be clumped. More preferably, the second temperature may be 1200 < 0 > C. The preferable temperature of the second temperature will be described later in detail. The cooling time from the first temperature to the second temperature may be about 30 seconds. In this case, at the first temperature of about 1250 ° C ± 0.08%, the next cooling step can be performed without a predetermined holding time.

Then, a first sintering step of sintering the ceramic laminated body at the second temperature may be performed. (S360) At this time, the dielectric composition and the inner ceramic laminate alternately stacked in the ceramic laminate according to an embodiment of the present invention The electrodes can be simultaneously sintered. Here, as shown in FIG. 4B, the first sintering can be performed for about 10 minutes to 30 minutes.

Here, at the time of performing the first sintering step, as shown in FIG. 4C, the ceramic laminate can be sintered by adjusting the oxygen partial pressure at the second temperature for the first predetermined time. The oxygen partial pressure can be controlled by changing the atmosphere to a second temperature in a 99.99% atmosphere of hydrogen (H ₂ ) at a first temperature of 1250 ° C to a nitrogen (N ₂ ) 99.99% atmosphere. In this case, The oxygen partial pressure can be adjusted to 10 ^-3 atm or less. If the oxygen partial pressure is adjusted to less than 5 minutes, H ₂ may not be completely changed to N ₂ . If the oxygen partial pressure is changed in the course of performing the first sintering step after performing the cooling step described above, the grain growth can be suppressed and the densification can be further maximized. Then, a dielectric composition having a high density at a low temperature in a short time can be produced.

According to the compactness shown in Figs. 4A to 4C, when sintering is performed at a predetermined temperature of about 1150 DEG C without heating to the first temperature as in the comparative example of Fig. 4A, And a density of 93.78%. On the other hand, according to the embodiment of the present invention, as shown in FIG. 4B, after cooling to a first temperature of about 1250 ° C ± 0.08% and then cooling to a second temperature of about 1150 ± 0.13%, sintering at a cooling temperature yields about 94.73% It can be seen that the compact road is measured higher than the case of FIG. 4A. In addition to the heat treatment process as shown in FIG. 4B, when the oxygen partial pressure is further changed as shown in FIG. 4C, the density is improved to about 95.67% as compared with FIG. 4b.

The compactness shown in FIGS. 4A to 4C is shown in the table below.

Sintered at 1150 ° C Heating to 1250 ℃ Oxygen partial pressure control Compactness Comparative Example (Fig. 4A) O X X 93.78% Example 1 (Figure 4b) O O X 94.73% Example 2 (Figure 4c) O O O 95.67%

After the first sintering step, a second sintering step of sintering the ceramic laminate for a second predetermined time at a third temperature lower than the second temperature, as shown in Figs. 6A to 6B, may be further performed. ) According to an embodiment of the present invention, the third temperature may be about 900 ° C ± 0.33%, for example about 900 ° C, and the ceramic laminate may be sintered at the third temperature for about one hour . When the third temperature exceeds 900 ° C + 0.33%, there is a disadvantage that grain growth may occur. When the temperature is less than 900 ° C-0.33%, there may be a disadvantage that the time for densifying the particles increases.

FIG. 6A illustrates a case where the first temperature is about 1250 DEG C and the second temperature is about 1200 DEG C. FIG. 6B shows a case where the first temperature is about 1250 DEG C and the second temperature is about 1150 DEG C Fig. In both cases, when the second sintering was performed at about 900 ° C ± 0.33% for about 1 hour, the compactness was 97.93% (99.18%) when compared with that before the second sintering, 99.18% % (Denseness when the first sintering is performed for 30 minutes) to 97.87%.

With respect to the first sintering step (s360) and the second sintering step (s370) described above, when the second sintering step (s370) is not performed according to an embodiment of the present invention, the first sintering step (s360) An external electrode 30 electrically connected to the internal electrode 20 of the ceramic laminate may be formed. On the other hand, when the second sintering process (s370) is performed according to another embodiment of the present invention, after performing the first sintering process (s360) and the second sintering process (s370), the internal electrodes 20 And the external electrode 30 is electrically connected to the external electrode 30.

FIG. 5 is a graph showing that the density is varied according to the second temperature when the first temperature is cooled to the second temperature in FIG.

As shown in FIG. 5C, when the ceramic laminated body 100 is heated to a first temperature of about 1250 ° C ± 0.08% and then cooled to a second temperature of about 1200 ° C according to an embodiment of the present invention, As shown in FIG. 4B, it is understood that the density is improved as compared with the case of cooling to about 1150 ° C., which is the second temperature.

Specifically, in the case of FIG. 5A, when the temperature is cooled from about 1250 ° C. to about 1050 ° C., the density is about 67.30%, but when the temperature is cooled from about 1250 ° C. to about 1150 ° C., the density is about 95.67% And when it is cooled to about 1200 ° C at about 1250 ° C, it shows that it shows a density of about 97.93%.

That is, when cooling after heating to high temperature, cooling to a relatively low temperature, for example, in a range of less than 1150 占 폚 It can be seen that the density decreases rather than the density. Therefore, according to the embodiment of the present invention, the second temperature is preferably 1150 ° C ± 0.13% or more and less than 1250 ° C.

The features, structures, effects and the like described in the embodiments are included in one embodiment of the present invention and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects and the like illustrated in the embodiments can be combined and modified by other persons skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (15)

Forming a ceramic laminate by laminating and pressing a ceramic green sheet having an internal electrode formed on an upper surface thereof and composed of a dielectric composition;
A heating step of heating the ceramic laminate to a first temperature;
A cooling step of cooling from the first temperature to a second temperature lower than the first temperature; And
And a first sintering step of sintering the ceramic laminate at the second temperature,
(Method for manufacturing a multilayer ceramic capacitor).
The method according to claim 1,
Wherein the first sintering step comprises:
Wherein the dielectric composition contained in the ceramic laminate and the internal electrode are simultaneously sintered.
(Method for manufacturing a multilayer ceramic capacitor).
The method according to claim 1,
Wherein the first temperature is 1250 DEG C +/- 0.08%, the heating to the first temperature
Time is six minutes,
The second temperature is 1150 ° C ± 0.13% or more and 1200 ° C or less, the cooling time to the second temperature is 30 seconds,
And sintering the ceramic laminate at the second temperature for 10 to 30 minutes.
The method of claim 3,
Wherein the first sintering step comprises:
And the oxygen partial pressure is adjusted for the first predetermined time at the second temperature to sinter the ceramic laminated body.
5. The method of claim 4,
Wherein the first predetermined time is 5 minutes or more and 10 minutes or less, and the oxygen partial pressure is adjusted to 10 ^-3 atm or less.
6. The method according to any one of claims 1 to 5,
And a second sintering step of sintering the ceramic laminate for a second predetermined time at a third temperature lower than the second temperature after the first sintering step.
The method according to claim 6,
Wherein the third temperature is 900 DEG C +/- 0.33% and the ceramic laminate is sintered at the third temperature for one hour.
6. The method according to any one of claims 1 to 5,
The dielectric composition is BaTiO _3, the inner electrode is a Ni, a multilayer ceramic capacitor manufacturing method.
6. The method according to any one of claims 1 to 5,
Further comprising forming external electrodes electrically connected to the internal electrodes of the ceramic laminate after performing the first sintering step. ≪ Desc / Clms Page number 19 >
And a ceramic laminate formed by forming an internal electrode on an upper surface and laminating and pressing a ceramic green sheet composed of a dielectric composition,
Heating the ceramic laminate to a first temperature,
Cooling to a second temperature lower than the first temperature at the first temperature,
And a second sintering step of sintering the ceramic laminate at the second temperature,
Multilayer Ceramic Capacitors.
11. The method of claim 10,
Wherein the dielectric composition and the internal electrode contained in the ceramic laminate are simultaneously sintered,
Multilayer Ceramic Capacitors.
11. The method of claim 10,
And performing the first sintering step by sintering the ceramic laminate by controlling the partial pressure of oxygen for a predetermined time at the second temperature.
13. The method according to any one of claims 10 to 12,
And a second sintering step of sintering the ceramic laminate for a predetermined time at a third temperature lower than the second temperature after the first sintering step.
13. The method according to any one of claims 10 to 12,
The dielectric composition is BaTiO _3, the inner electrode is a Ni, a multilayer ceramic capacitor.
13. The method according to any one of claims 10 to 12,
And an external electrode electrically connected to the internal electrode of the ceramic laminated body.

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