JP2000012375A - Laminated ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic electronic component for obtaining desired characteristics by preventing a part of an internal electrode from being absorbed by surrounding ceramic, or preventing any peeling from being generated on a boundary face between the internal electrode and the surrounding ceramic. SOLUTION: An isolation layer 6 for preventing the diffusion of base metallic materials constituting an internal electrode 1 is arranged on almost the whole face or one face of the part other than the part functioning as an element of a ceramic layer 2 (2a and 2b) being the outermost layer in the laminated direction of the internal electrode 1. In this case, the ceramic layer is provided as the isolation layer 6 by making the content of the base metallic materials constituting the internal electrode 1 higher than that of ceramic constituting the ceramic layer 2 other than the isolation layer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic electronic component, and more particularly, to a ceramic element in which a plurality of internal electrodes formed by using a base metal material are opposed to each other via a ceramic layer. The present invention relates to a multilayer ceramic electronic component having a structure as described above.

[0002]

2. Description of the Related Art For example, a multilayer ceramic capacitor, which is one of the typical multilayer ceramic electronic components, usually has a plurality of internal electrodes 1 as shown in FIG. End faces 3a, 3b which are arranged so as to face each other via
The external electrodes 4a and 4b are arranged so as to be electrically connected to the internal electrodes on the ceramic element 5 having the structure drawn out.

By the way, in recent years, downsizing of electronic devices and the like,
Due to surface mounting and the like, multilayer ceramic capacitors have been reduced in size and capacity, and demands for lower cost have been increasing. In order to respond to the demand for cost reduction, a multilayer ceramic capacitor in which an internal electrode is formed using an inexpensive base metal material such as nickel or copper as the internal electrode has been developed and used.

A multilayer ceramic capacitor using such a base metal internal electrode has an advantage that a significant cost reduction can be realized as compared with a multilayer ceramic capacitor using a noble metal internal electrode such as palladium or silver.

[0005] However, base metals such as nickel and copper are more easily oxidized than noble metals such as palladium and silver. Thus, not only is it impossible to obtain desired electrical characteristics, but also there is a problem that these substances move relatively quickly in the ceramic during the sintering process and are absorbed by the ceramic.

For example, when firing and integrally sintering a multilayer ceramic capacitor having a base metal internal electrode made of nickel, if the oxygen partial pressure in the firing atmosphere is too high, a part of the internal electrode is oxidized and oxidized. It becomes nickel (NiO). The nickel oxide has a high mass transfer rate in the ceramic, and is dispersed and absorbed in the surrounding ceramic during the sintering process, and as a result, the base metal internal electrode made of nickel becomes thin and the electrode breaks. Arises
There is a problem that the target characteristics cannot be obtained.

On the other hand, if the oxygen partial pressure in the firing atmosphere is too low, oxidation of the base metal such as nickel or copper constituting the internal electrode can be prevented, but the interface between the internal electrode and the surrounding ceramic is insufficiently bonded. As a result, there is a problem that the mechanical strength is reduced, the interface between the internal electrode and the ceramic is peeled off, and the desired characteristics cannot be obtained.

[0008] Such problems apply not only to multilayer ceramic capacitors, but also to various multilayer ceramic electronic components such as capacitor arrays having internal electrodes, varistors, and multilayer substrates.

The present invention has been made to solve the above problems, and it is possible that a part of the internal electrode is absorbed by the surrounding ceramic or that the interface between the internal electrode and the surrounding ceramic is peeled off. It is another object of the present invention to provide a multilayer ceramic electronic component capable of obtaining desired characteristics without causing any problem.

[0010]

Means for Solving the Problems To achieve the above object, the present inventors conducted various experiments on the influence of oxygen partial pressure when integrally sintering a multilayer ceramic electronic component using a base metal internal electrode. The study was conducted and the following findings were obtained.

For example, in the process of manufacturing a multilayer ceramic capacitor as shown in FIG. 5, when firing a ceramic element (laminate) 5 having a configuration as shown in FIG.
The firing atmosphere first diffuses into a portion (surface layer portion) close to the surface of the capacitor element 5, and then diffuses into the inside of the capacitor element 5.

When the ceramic element 5 is small,
Although the distance from the surface to the inside is small, when the ceramic element is large, the distance from the surface to the inside becomes large. In other words, when the capacitor element is large, the firing atmosphere should undergo mass transfer, and the distance from the surface of the ceramic element 5 to the inside becomes long. In the vicinity and inside of the ceramic element, the firing atmosphere (oxygen partial pressure condition) The apparent oxygen partial pressure becomes lower as one goes inside the capacitor element.

The gradient of the apparent partial pressure of oxygen allows a good internal electrode to be formed at a low oxygen partial pressure, for example, at the center of the capacitor element. Oxygen partial pressure increases, internal electrodes are oxidized, and in the worst case internal electrode breaks,
The target capacitance cannot be obtained, or the obtained capacitance varies. Further, a gap may be formed between the layers, and the reliability may be reduced.

On the basis of such knowledge, the inventors conducted further experiments and examinations, and cut off the ceramic layer, which is the outermost layer in the lamination direction of the internal electrodes, in order to prevent the base metal material constituting the internal electrodes from diffusing. By providing a layer,
The present inventor has found that it is possible to form a good internal electrode without causing electrode breakage and the like, and completed the present invention.

That is, in the multilayer ceramic electronic component of the present invention (claim 1), a plurality of internal electrodes formed using a base metal material are arranged in a ceramic element so as to face each other via a ceramic layer. In the laminated ceramic electronic component having the structure described above, the base metal constituting the internal electrode is substantially entirely or partially, other than the portion functioning as an element, of the ceramic layer which is the outermost layer in the laminating direction of the internal electrode. It is characterized in that a barrier layer for preventing material diffusion is provided.

A base metal material constituting an internal electrode is provided by disposing a cut-off layer substantially entirely or partially on a portion other than a portion functioning as an element of a ceramic layer which is an outermost layer in a laminating direction of the internal electrode. Can be prevented, and the internal electrodes can be prevented from being absorbed by the surrounding ceramics in the firing step to cause the internal electrodes to be cut off, so that good internal electrodes can be formed. . The blocking layer has a function of preventing the base metal material constituting the internal electrode contained therein from reacting with oxygen prior to the internal electrode in the firing step, thereby preventing the internal electrode from being oxidized. It is thought that it may fulfill.

Further, the multilayer ceramic electronic component according to claim 2 is characterized in that the blocking layer is a ceramic layer having a higher content of a base metal material forming an internal electrode than a ceramic forming the ceramic layer. I have.

By providing a ceramic layer having a higher content of the base metal material forming the internal electrode than the ceramic forming the ceramic layer as the blocking layer, the diffusion of the non-metal material forming the base metal internal electrode can be efficiently performed. It is possible to prevent the occurrence of internal electrode breakage and the like, and to reliably obtain a multilayer ceramic electronic component having desired characteristics, thereby making the present invention more effective. . In addition, when forming the ceramic layer for the barrier layer, when increasing the content of the base metal material, the increase rate of the content should be in the range of 0.2 to 5.0% by weight (for example, not the barrier layer). When the content of the base metal in the ceramic constituting the ceramic layer is 1.0% by weight, the content of the base metal in the blocking layer is changed from 1.2 (= 1.0 + 0.2) to 6.0 ( = 1.0 +
5.0) It is preferable to be in the range of% by weight.

Further, in the multilayer ceramic electronic component according to a third aspect, the internal electrode is a base metal internal electrode formed of nickel, and the blocking layer has a nickel content higher than that of the ceramic constituting the ceramic layer. It is characterized by an elevated ceramic layer.

By forming an internal electrode using nickel and disposing a ceramic layer having a higher nickel content than the ceramic forming the ceramic layer as a blocking layer, the diffusion of nickel forming the base metal internal electrode is prevented. As a result, it is possible to reliably obtain a multilayer ceramic electronic component having desired characteristics without breaking the internal electrodes.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described, and features thereof will be described in more detail. In the following embodiments, a multilayer ceramic capacitor having a base metal internal electrode will be described as an example.

In the multilayer ceramic capacitor according to this embodiment, as shown in FIG. 1, a plurality of internal electrodes (base metal internal electrodes) 1 made of nickel, which is a base metal, are disposed inside a ceramic element 5 via a ceramic layer 2. External electrodes 4a and 4b are provided on both end surfaces 3a and 3b of the ceramic element 5 so as to be electrically connected to the internal electrode 1.

In the multilayer ceramic capacitor of this embodiment, the upper and lower surfaces of the ceramic layers 2a, 2b, which are the outermost layers in the laminating direction of the base metal internal electrode 1, are provided.
The portion (which does not function as a capacitor element) serves as a blocking layer 6 for preventing the diffusion of the base metal material (nickel) constituting the base metal internal electrode 1.

The blocking layer 6 is a ceramic layer formed by adding nickel oxide to the ceramic material constituting the ceramic element 5 at a ratio of 0.5 to 5.0% by weight.

Next, a method of manufacturing the multilayer ceramic capacitor will be described.

First, a ceramic raw material slurry is prepared by adding a binder, a dispersant, a plasticizer, and the like to a ceramic material for forming a ceramic layer (dielectric ceramic layer) functioning as a dielectric other than the blocking layer. A green sheet (green sheet for forming a dielectric ceramic layer) is prepared from the ceramic raw material slurry. Then, a conductive paste mainly composed of nickel serving as an internal electrode is printed on the green sheet for forming the dielectric ceramic layer to form an electrode printing sheet. Further, a ceramic raw material slurry is prepared by adding a binder, a dispersant, a plasticizer, and the like to a material obtained by adding nickel oxide at a ratio of 0.5 to 5.0% by weight to the ceramic material for forming the dielectric ceramic layer. A green sheet for forming a barrier layer is prepared from this ceramic raw material slurry. Then, after stacking a predetermined number of green sheets for forming a blocking layer, and subsequently stacking a predetermined number of electrode printing sheets obtained by printing a conductive paste mainly containing nickel on the green sheets for forming the dielectric ceramic layer, A predetermined number of green sheets for forming a barrier layer are stacked on top. Then, the stacked body is pressed, and the respective layers are pressed together to form a laminated pressure-bonded body. Then, after heat-treating and degreasing this laminated pressure-bonded body,
Perform baking. Then, a conductive paste is applied to the fired ceramic element and baked to form external electrodes which are electrically connected to the internal electrodes, thereby obtaining a multilayer ceramic capacitor as shown in FIG.

For reference, a multilayer ceramic capacitor (comparative example) having no cut-off layer was prepared by the same method as shown in FIG.

With respect to the multilayer ceramic capacitor according to the embodiment of the present invention and the multilayer ceramic capacitor of the comparative example manufactured as described above, the formation state of the internal electrodes was examined, and the obtained capacitance value was measured.
Regarding the formation state of the internal electrodes, the multilayer ceramic capacitor was cut, and the state of the cut end face was visually observed to judge the quality.

[Evaluation of Internal Electrode Forming State] Regarding the internal electrode forming state, in the multilayer ceramic capacitor of the comparative example having no blocking layer, as shown schematically in FIG. The internal electrode of the outer layer was cut off. On the other hand, in the multilayer ceramic capacitor according to the embodiment of the present invention, as shown in FIG. 3B, no breakage of the electrodes was observed for all the internal electrodes including the outermost layer.

[Evaluation of acquired capacitance] The acquired capacitance value was as follows. (a) Multilayer ceramic capacitor of the comparative example: 88 nF, (b) Multilayer ceramic capacitor of the present invention provided with a blocking layer: 100 nF With respect to the multilayer ceramic capacitor of the comparative example, as described above, the upper and lower outermost inner electrodes were It is considered that the electrode has been cut and the acquired capacitance has decreased. On the other hand, in the multilayer ceramic capacitor of the present invention, as described above, since the internal electrodes did not break, a target capacitance could be obtained.

Although the above embodiment has been described with reference to a multilayer ceramic capacitor as an example, the present invention is not limited to a multilayer ceramic capacitor, but may be applied to various multilayer ceramic electronic devices such as a capacitor array having internal electrodes, a varistor, and a multilayer substrate. It can be applied to parts.

In the above embodiment, the case where the internal electrode is formed using nickel has been described. However, the present invention relates to a multilayer ceramic electronic component in which the internal electrode is formed from a base metal material other than nickel, such as copper. It is also possible to apply to.

In the above embodiment, the barrier layer is
A case has been described in which a ceramic layer having an increased content of nickel (nickel oxide), which is a base metal constituting the internal electrode, is provided. For example, as in the above embodiment, the internal electrode is formed of a nickel internal electrode. In this case, a ceramic layer to which an oxide such as Fe, Co, Mn, Cr, or Mo is added may be used as the blocking layer.

In the above embodiment, the case where the entire outermost ceramic layer is used as the blocking layer has been described. However, as shown in FIG. It is also possible to configure so that only the near portion is used as the blocking layer, or to configure only the middle portion of the outermost layer as the blocking layer (not shown). Also, instead of using the entire outermost layer as a blocking layer, as shown in FIG.
It is also possible for only the main part to be the barrier layer.

The present invention is not limited to the above embodiment in other respects, and various applications and modifications can be made within the scope of the present invention.

[0036]

As described above, in the multilayer ceramic electronic component of the present invention (claim 1), the ceramic layer which is the outermost layer in the lamination direction of the internal electrodes is substantially entirely covered by portions other than the portion functioning as an element. By partially or partially disposing the blocking layer, it becomes possible to prevent the diffusion of the base metal material constituting the internal electrode, and the internal electrode is absorbed by the surrounding ceramics in the firing step, and the internal electrode is cut. Or the like, and thereby, a good internal electrode can be formed.

In the case where a ceramic layer having a higher content of a base metal material forming an internal electrode than a ceramic forming a ceramic layer is provided as a barrier layer, as in the multilayer ceramic electronic component of the second aspect, It is possible to efficiently prevent the diffusion of the non-metallic material constituting the base metal internal electrode, to prevent the internal electrode from being cut or the like, and to reliably obtain a multilayer ceramic electronic component having desired characteristics. This makes it possible to make the present invention more effective.

Further, as in the multilayer ceramic electronic component of the third aspect, an internal electrode is formed using nickel, and a ceramic layer having a higher nickel content than the ceramic constituting the ceramic layer is disposed as a blocking layer. In this case, diffusion of nickel constituting the base metal internal electrode can be prevented, and a multilayer ceramic electronic component having desired characteristics can be reliably obtained without breaking the internal electrode.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a multilayer ceramic electronic component (multilayer ceramic capacitor) according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a multilayer ceramic capacitor manufactured for comparison.

3A and 3B are diagrams showing a state of forming an internal electrode, wherein FIG. 3A is a sectional view showing a state of forming an internal electrode of a multilayer ceramic capacitor of a comparative example, and FIG. 3B is a sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention; It is sectional drawing which shows the formation state of an internal electrode.

FIGS. 4A and 4B are cross-sectional views showing a modification of the multilayer ceramic capacitor according to the embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of a general multilayer ceramic capacitor.

FIG. 6 is a sectional view showing a ceramic element constituting a general multilayer ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal electrode 2 Ceramic layer 2a, 2b Upper and lower both sides ceramic layers 3a, 3b which are outermost layers 3a, 3b End faces 4a, 4b External electrodes 5 Ceramic element 6 Blocking layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E001 AB03 AC09 AF06 AG00 AH01 AJ04 5E082 AA01 AB03 BC40 EE04 EE23 EE35 FG06 FG26 FG54 GG10 HH43 LL02 MM22 MM24

Claims (3)

[Claims] 1. A multilayer ceramic electronic component having a structure in which a plurality of internal electrodes formed using a base metal material are arranged in a ceramic element so as to face each other with a ceramic layer interposed therebetween, A blocking layer for preventing diffusion of the base metal material constituting the internal electrode was provided on substantially the entire surface or part of the ceramic layer, which is the outermost layer in the stacking direction, other than the portion functioning as an element. A multilayer ceramic electronic component, characterized in that: 2. The multilayer ceramic electronic component according to claim 1, wherein said cut-off layer is a ceramic layer having a higher content of a base metal material constituting an internal electrode than a ceramic constituting said ceramic layer. . 3. The internal electrode is a base metal internal electrode formed using nickel, and the blocking layer is a ceramic layer having a higher nickel content than the ceramic constituting the ceramic layer. The multilayer ceramic electronic component according to claim 1.