JP2000269073A - Multilayer ceramic capacitor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable attainment of sintering suppressing effects of conductive paste and at the same time the attainment of a high electrostatic capacitance without blocking continuity of internal electrodes similarly to when the same material is added much. SOLUTION: Upon manufacturing a multilayer ceramic capacitor, oxide powder of at least any of 0.5-3.0 weight % of La and Cr is contained, with respect to 100 weight % of Ni powder of conductive paste for the formation of internal electrodes 5 and 6. The oxide powder of La or Cr is set to have a main particle diameter of 0.5-1.0 μm. Since such an oxide as La2O3 or Cr2O3 contained in the conductive paste has sintering suppressing effects, the amount of material to be added can be reduced by the corresponding amount. In addition, after the paste is sintered, an element La or Cr is not precipitated within the conductor material of the internal electrodes 5 and 6 but is segregated at an interface between the internal electrodes 5, 6 and ceramic layers 7 which is stacked within a laminate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor having, for example, a laminate of an internal electrode pattern and a ceramic layer, and an external electrode provided at an end of the laminate so as to be electrically connected to the internal electrode. More particularly, the present invention relates to a multilayer ceramic capacitor having good electrical characteristics and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a multilayer ceramic capacitor, a plurality of ceramic layers made of a dielectric material having internal electrodes are laminated in layers, and the internal electrodes face each other inside the multilayer body. Are drawn out alternately. An external electrode is formed at an end including the end face of the laminate from which these internal electrodes are drawn, and the external electrodes are connected to the internal electrodes facing each other inside the laminate.

[0003] The laminate 3 of such a multilayer ceramic capacitor has, for example, a layer structure as shown in FIG. That is, the ceramic layers 7, 7,... Made of a dielectric having the internal electrodes 5, 6 are stacked in the order shown in FIG. 3, and the ceramic layers 7, 7,. Each is stacked in multiple layers. And
The internal electrodes 5 and 6 are alternately exposed at the ends of the laminate 3 having such a layer structure. As shown in FIG. Is formed.

[0004] Such a multilayer ceramic capacitor is
Normally, a single unit as shown in FIG. 3 is not manufactured individually, but the following manufacturing method is actually used. That is, first, a fine ceramic powder and an organic binder are kneaded to prepare a slurry, which is thinly spread on a carrier film made of a polyethylene terephthalate film or the like by a doctor blade method, and dried to produce a ceramic green sheet. Next, the ceramic green sheet is cut into a desired size with a cutting head while being placed on the support film, and a conductive paste is printed on one surface thereof by a screen printing method and dried. As a result, as shown in FIG. 4, ceramic green sheets 1a and 1b in which a plurality of sets of internal electrode patterns 2a and 2b are arranged vertically and horizontally are obtained.

Next, a plurality of ceramic green sheets 1a, 1b having the internal electrode patterns 2a, 2b are laminated, and some ceramic green sheets 1, 1,. Are stacked one on top of the other, and they are pressed together to form a laminate. Here, the ceramic green sheets 1a and 1b are alternately stacked such that the internal electrode patterns 2a and 2b are shifted by a half length in the longitudinal direction. Thereafter, the laminate is cut into a desired size to produce a laminated green chip, and the green chip is fired. Thus, a laminate as shown in FIGS. 1 and 3 is obtained. Next, a conductive paste is applied to both ends of the fired laminate 3 and baked, and the surface of the baked conductor film is plated to form external electrodes 2 and 2 at both ends as shown in FIG. Complete multilayer ceramic capacitor.

As the conductive paste for forming the internal electrodes 5 and 6 in the above-described multilayer ceramic capacitor, a conductive paste mainly composed of Ni powder to which a binder and a solvent are added is used. Further, such a conductive paste is used as a so-called common material in the conductive paste for the purpose of suppressing the sintering of the internal electrodes 5 and 6 at the time of firing and improving the adhesion between the internal electrodes 5 and 6 and the ceramic layer 7. The barium titanate powder contained in the ceramic layer 7 is added.

[0007]

When the amount of the above-mentioned co-material added to the conductive paste is increased, the effect of suppressing sintering and the adhesion between the internal electrodes 5 and 6 and the ceramic layer 7 are improved. The continuity of the internal electrodes 5 and 6 facing each other via the ceramic layer 7 is deteriorated. As a result, since the conductor structure of the internal electrodes 5 and 6 becomes sparse, it is difficult to obtain a large capacitance. On the other hand, when the amount of the above-mentioned common material added to the conductive paste is reduced, a large capacitance can be easily obtained, but a sufficient sintering suppressing effect and a close contact between the internal electrodes 5 and 6 and the ceramic layer 7 are obtained. The property cannot be obtained.

In order to obtain a small and larger capacitance, the thickness of the internal electrodes 5, 6 and the ceramic layer 7 is reduced.
It is necessary to stack more internal electrodes 5 and 6. Then, the ratio occupied by the internal electrodes 5 and 6 inside the laminate 3 increases, and it is necessary to add a larger amount of a co-material to the conductive paste to suppress sintering. However, for the above-described reason, when the amount of the common material added to the conductive paste is increased, a desired capacitance cannot be obtained.

In view of the above-mentioned problems of the prior art, the present invention obtains the effect of suppressing sintering of the conductive paste, and at the same time, does not hinder the continuity of the internal electrodes as in the case where a large amount of the common material is added. It is an object of the present invention to provide a multilayer ceramic capacitor capable of obtaining a high capacitance and a method for manufacturing the same.

[0010]

According to the present invention, in order to achieve the above object, a conductive paste for forming the internal electrodes 5 and 6 includes at least one of La and Cr oxides having a sintering control effect. La ₂ O ₃ and Cr ₂ O ₃ are added. As a result, the amount of the common material added can be reduced. In addition, the elements such as La and Cr segregate not at the inside of the internal electrodes 5 and 6 but at the interface between the internal electrodes 5 and 6 and the ceramic layer 7. Since it does not affect continuity,
The capacitance does not decrease.

That is, the multilayer ceramic capacitor according to the present invention comprises a laminated body 3 in which ceramic layers 7 and internal electrodes 5 and 6 are alternately laminated, and external electrodes 2 and 2 provided at the ends of the laminated body 3. And the internal electrodes 5 and 6 reach at least one of at least one pair of opposing edges of the ceramic layer 7, respectively, so that the internal electrodes 5 and 6 are Derived, the same laminate 3
The internal electrodes 5 and 6 led out to the end faces of the external electrodes 2 and
2 which are connected to the internal electrodes 5, 6 facing each other inside the laminate 3 via the ceramic layer 7.
Contains at least one element of La and Cr. In particular, at least one of La and Cr is segregated at the interface between the internal electrodes 5 and 6 and the ceramic layer 7.

Further, a method of manufacturing such a multilayer ceramic capacitor includes a step of obtaining ceramic green sheets 1, 1a, 1b for forming a ceramic layer 7, and a method of forming a part of these ceramic green sheets 1a, 1b. Using conductive paste, the internal electrode patterns 2a, 2a
b) and a step of printing the ceramic green sheets 1 and 1
a, a step of laminating the ceramic green sheets 1, 1a, 1b in a predetermined order; a step of cutting the laminated ceramic green sheets 1, 1a, 1b; Fired laminate 3 having
And a step of forming the external electrodes 2 and 2 at the ends where the internal electrodes 5 and 6 of the laminate 3 are led out. In this case, the conductive paste for forming the internal electrodes 5 and 6 is 0.5 to 100% by weight of the Ni powder.
3.0% by weight of an oxide powder of at least one of La and Cr is contained. The average particle size of the oxide powder of at least one of La and Cr added to the conductive paste is 0.1.
5 to 1.0 μm.

La ₂ O ₃ or Cr ₂ contained in the conductive paste
Oxides such as O ₃ have a higher sintering control effect than the co-material, so that the amount of the co-material added to the conductive paste can be reduced accordingly. Moreover, after firing, the elements such as La and Cr do not precipitate inside the conductors forming the internal electrodes 5 and 6, and the internal electrodes 5 and
Segregates at the interface between the ceramic layer 6 and the ceramic layer 7. Therefore, L
Since the elements a and Cr do not affect the continuity of the internal electrodes 5 and 6 opposed to each other via the ceramic layer 7, the obtained capacitance is not reduced.

The oxide powder of at least one of La and Cr added to the conductive paste is 100% by weight of the Ni powder.
If it is less than 0.5% by weight, the desired effect of suppressing sintering cannot be obtained. On the other hand, at least one of the oxide powders of La and Cr is added to 100% by weight of the Ni powder.
If it exceeds 0% by weight, the effect of suppressing sintering is too large, affecting the overall sinterability and making it impossible to obtain desired capacitance and electrical characteristics.

Also, La and C added to the conductive paste
r has an average particle size of 0.5
If it is not more than μm, the reactivity of these oxides at the time of firing is too strong, and the element of La or Cr stays inside the internal electrodes 5 and 6 after firing and is hardly segregated at the interface with the ceramic layer 7. On the other hand, La and C added to the conductive paste
r has an average particle size of at least one of the oxide powders of 1.0
When it is not less than μm, La and Cr elements tend to segregate at the interface between the internal electrodes 5 and 6 and the ceramic layer 7 after firing,
The surface of the internal electrodes 5 and 6 tends to have irregularities, and the film thickness of the internal electrodes 5 and 6 tends to be uneven.

[0016]

Embodiments of the present invention will now be described specifically and in detail with reference to the drawings. First, a dielectric ceramic raw material powder such as barium titanate is uniformly dispersed in an organic binder such as acryl dissolved in a solvent such as ethanol to prepare a ceramic slurry. This ceramic slurry is applied on a base film such as a polyethylene terephthalate film or the like in a thin and uniform thickness of 10 μm or less and dried to form a film-like ceramic green sheet. Thereafter, the ceramic green sheet is cut into an appropriate size.

Next, as shown in FIG.
Nickel on the lamic green sheets 1a and 1b
Conductive paste of copper, silver, palladium, silver palladium etc.
Used, two types of internal electrode patterns 2a, 2b are marked respectively
Print. For example, the conductive paste is 100% by weight of Ni powder.
%, Ethyl cellulose and acrylic
3 to 12% by weight of polyester, polyester, etc.
Lucarbitol, butyl carbitol acetate, ter
80-1 of pinoeol, ethyl cellosolve, hydrocarbon, etc.
20% by weight, barium titanate, acid
5-30% by weight of powder of barium oxide, titanium oxide, etc., L
a_TwoO_ThreeAnd Cr_TwoO_ThreeAt least one of the powders of 0.5
３3% by weight, uniformly mixed and dispersed
You. La _TwoO_ThreeAnd Cr_TwoO_ThreeAt least one of the powders
Used has an average particle size of 0.5 to 1.0 μm.

Using a conductive paste such as Ni paste, a thickness of 1. nm is applied on the ceramic green sheets 1a and 1b. The internal electrode patterns 2a and 2b each having a thickness of about 3.0 μm are printed. Such internal electrode patterns 2a, 2b
Are printed on the ceramic green sheets 1a and 1b,
As shown in FIG. 4, the ceramic green sheets 1 and 1, which are not printed with the internal electrode patterns 2a and 2b on both sides thereof, that is, so-called dummy sheets are stacked alternately, and these are pressed to obtain a laminate. Further, the laminate is cut vertically and horizontally and divided into individual chip-like laminates. Thereafter, these laminates are fired to obtain a fired laminate 3 having a layer structure as shown in FIG.

As shown in FIG. 3, the laminated body 3 is formed by laminating ceramic layers 7, 7... Made of a dielectric material having internal electrodes 5, 6, and further having ceramics on which no internal electrodes 5, 6 are formed on both sides. Each of the layers 7, 7,... Is stacked in a plurality of layers. Such a laminate 3 has a ceramic layer 7
The internal electrodes 5 and 6 facing each other are alternately led out to both end surfaces of the laminate 3.

As shown in FIG. 1, a conductive paste such as a Cu paste is applied to both ends of the laminated body 3 from which the internal electrodes 5 and 6 are led out, and is baked. Further, Ni plating and Sn or solder plating are performed on the conductive film, and external electrodes 2 and 2 are formed. Thus, the multilayer ceramic capacitor is completed.

In the baking step of the laminate 3 as described above, La ₂ O ₃ and Cr ₂ O ₃ added to the conductive paste are made of Ni or the like in the conductive paste similarly to the so-called common material added to the conductive paste. It suppresses sintering of metal components, but acts as a sintering inhibitor more effective than the co-material. as a result,
The metal components such as Ni do not oxidize and remain as metal particles separate from the ceramic layer 7, and the internal electrodes 5 and 6 are formed.

The particles of La ₂ O ₃ or Cr ₂ O ₃ do not react with metal elements such as Ni during the above-mentioned firing, and the elements of La and Cr are oxidized such as La ₂ O ₃ and Cr ₂ O _3. It deposits on the surfaces of the internal electrodes 5 and 6 in the state of an object. As a result, as shown in FIG. 2, elements such as La and Cr precipitate at the interface between the internal electrodes 5 and 6 and the surrounding ceramic layer 7. As described above, in the laminated body after firing, the elements such as La and Cr
6 and precipitate at the interface between the internal electrodes 5 and 6 and the ceramic layer 7 without affecting the continuity or the like of the internal electrodes 5 and 6 and reducing the capacitance and other electrical characteristics that can be obtained. Has no effect.

FIG. 2 shows that the obtained multilayer ceramic capacitor is embedded in an acrylic resin, polished in a direction perpendicular to the laminating direction of the ceramic layer 7 in a state of holding the multilayer ceramic capacitor, exposed, and observed by an optical microscope. 1 schematically shows the obtained micrograph. This corresponds to an enlarged view of the portion A in FIG. As shown in FIG. 2, approximately one flat conductor particle is placed between the ceramic layers 7.
Internal electrodes 5 and 6 are formed in a row in the interface direction with the electrodes. However, the internal electrodes 5 and 6 are not completely connected at all portions, and gap portions 9 where no conductive film exists are formed in some places in an island shape. The interface between the internal electrodes 5 and 6 and the surrounding ceramic layer 7 is La
Element 11 such as Cr and Cr is precipitated.

[0024]

Next, more specific examples of the present invention and comparative examples will be described. (Example) A ceramic slurry was prepared by uniformly dispersing a dielectric ceramic raw material powder such as barium titanate in an organic binder such as acryl dissolved in a solvent such as ethanol, and this was coated on a base film such as a polyethylene terephthalate film to a thickness of 10 μm. The thin film was applied in a uniform thickness and dried to form a film-shaped ceramic green sheet. Thereafter, the ceramic green sheets were peeled off from the base film, and a plurality of 150 mm square ceramic green sheets were produced.

On the other hand, for 100% by weight of the Ni powder,
8% by weight of ethyl cellulose as a binder, 100% by weight of terpineol as a solvent, 10% by weight of barium titanate powder as a so-called common material, and 0.5% of La ₂ O ₃
% By weight and uniformly mixed and dispersed to prepare a conductive paste. Using this Ni paste, internal electrode patterns 1a and 1b as shown in FIG. 4 were formed on each of the ceramic green sheets by a screen printer. A predetermined number of such ceramic green sheets on which the internal electrode patterns are printed are alternately stacked, and a ceramic green sheet on which no internal electrode patterns are printed, that is, a so-called dummy sheet, is stacked above and below the ceramic green sheets, and a total of 30 ceramic green sheets are stacked. did. This laminate was pressed at a temperature of 120 ° C. in the laminating direction at a pressure of 200 t and pressed to obtain a laminate.

This laminate was cut into a size of 5.3 mm × 5.0 mm, and the laminate was fired at a temperature of 1320 ° C. to obtain a fired laminate 3 as shown in FIG. Further, a Cu paste was applied to both ends of the fired laminate 3 and baked. Thereafter, the chip was placed in an electrolytic barrel plating bath, the Ag film was plated, and a Ni plating and a Sn plating film were sequentially applied on the Ag film. Thus, external electrodes 2 and 2 were formed, and a multilayer ceramic capacitor as shown in FIG. 1 was obtained.

Fifty of the laminated ceramic capacitors are embedded in an acrylic resin and polished in a direction perpendicular to the laminating direction of the internal electrodes 5 and 6 while being held, so that the laminated state of the internal electrodes 5 and 6 and the ceramic layer 7 is obtained. Was observed with an optical microscope. As a result, as shown in FIG. 2, La element segregation was observed at the interface between the internal electrodes 5 and 6 and the ceramic layer 7.

When the capacitance was measured between the external electrodes 2 and 2 at both ends of the multilayer ceramic capacitor, 140
It was 0 pF or more. 50 laminated ceramic capacitors were embedded in a resin, polished, and the polished surface was observed with an optical microscope to determine whether or not the ceramic layer 7 inside the laminated body 3 was peeled, that is, what was called delamination. No delamination occurred.

The results are shown in the column of sample 3 in Table 1. In Table 1, the oxides of La and Cr and the co-material are shown by weight ratio (wt%) added to 100 parts by weight of Ni powder of the conductive paste. When the capacitance value measured between the external electrodes 2 and 2 was 1400 pF or more, ○: when the capacitance value was less than 1400 pF, ×:
Indicated by. The number of occurrences of delamination indicates the number in 50 samples.

Similarly, as shown in Table 1, 2
Three types of multilayer ceramic capacitors were manufactured, and Samples 1 to 23 including Sample 3 were prepared. Except for La ₂ O ₃ , Cr ₂ O ₃ and the co-material added to the conductive paste, ethyl cellulose and terpineol were constant at 8 wt% and 100 wt% with respect to 100 wt% of the Ni powder. Also, in Sample 20, the co-material was added at 20% by weight with respect to 100% by weight of the Ni powder, but in all other samples, the co-material was added at 10% by weight with respect to 100% by weight of the Ni powder.

[0031]

[Table 1]

As is clear from Table 1, N of the conductive paste
i 2 powder and 100 parts by weight of La ₂ O ₃ and Cr ₂ O ₃
Of the multilayer ceramic capacitors made using the conductive paste containing 0.5 to 3% by weight of any one of Samples 3 to 7, Samples 12 to 17, and Samples 21 to 23, all have a static capacitance of 1400 pF or more. Capacitance could be obtained. In addition, there was no occurrence of delamination inside the laminate.
These multilayer ceramic capacitors were buried in resin and polished, and the internal electrodes were magnified and observed with an optical microscope.
Segregation of any of the elements was observed.

On the other hand, 1% of the Ni powder of the conductive paste
Samples 1, ₂ and ₁ in which at least one of La ₂ O ₃ and Cr ₂ O ₃ was added in an amount of less than 0.5% by weight with respect to 00 parts by weight.
In each of Examples 0 and 11, a capacitance of 1400 pF or more could be obtained, but the occurrence of delamination inside the laminate was frequently observed.

In Samples 8, 9, 18, and 19, any one of La ₂ O ₃ and Cr ₂ O ₃ exceeds 3% by weight with respect to 100 parts by weight of the Ni powder of the conductive paste. There was no occurrence of delamination inside the laminate,
A capacitance of 1400 pF or more could not be obtained. Sample 20 in which neither La ₂ O ₃ nor Cr ₂ O ₃ was added to the conductive paste, and the co-material was added to 100 parts by weight of the Ni powder of the conductive paste, that is, 20% by weight, which was double that of the other samples.
However, no delamination occurred inside the laminate, but a capacitance of 1400 pF or more could not be obtained. In this embodiment, the external electrodes are baked after the element body is fired. However, the present invention is not limited to this, and the same effect can be obtained by simultaneously firing the element body and the external electrode.

[0035]

As described above, in the multilayer ceramic capacitor according to the present invention, at least one of La ₂ O ₃ and Cr ₂ O ₃ is added to the conductive paste for forming the internal electrodes 5 and 6. In addition, the effect of suppressing the firing of the internal electrodes 5 and 6 when firing the laminate 3 can be obtained, and the occurrence of delamination during firing can be effectively prevented.
In addition, La ₂ O ₃ or Cr ₂ O added to the conductive paste
_{In 3} , after firing of the laminate 3, the segregation at the interface between the internal electrodes 5 and 6 and the ceramic layer 7 does not impair the continuity of the conductor structure of the internal electrodes 5 and 6. Therefore, required electric characteristics can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of a multilayer ceramic capacitor according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part showing a portion A of FIG. 1 of the multilayer ceramic capacitor.

FIG. 3 is an exploded perspective view showing layers of the multilayer body of the example of the multilayer ceramic capacitor separately.

FIG. 4 is an exploded perspective view of each layer showing a laminated state of ceramic green sheets for manufacturing a multilayer ceramic capacitor.

[Explanation of symbols]

 Reference Signs List 2 external electrode 3 laminate 5 internal electrode 6 internal electrode 7 ceramic layer 9 gap 11 element of La or Cr

Claims (4)

[Claims] A ceramic layer (7) and an internal electrode (5);
(6) and a laminate (3) alternately laminated, and external electrodes (2) and (2) provided at ends of the laminate (3). , (6) reach each of at least one pair of opposing edges of the ceramic layer (7), so that the internal electrodes (5), (6) are provided on the opposing end faces of the laminate (3). The internal electrodes (5) and (6) which are respectively led out and led to the end faces of the laminate (3)
Are connected to the external electrodes (2) and (2), respectively, and the internal electrodes (5) and (6) opposed to each other inside the multilayer body (3) via the ceramic layer (7). Characterized in that at least one element (11) of La or Cr is contained therein. 2. The method according to claim 1, wherein at least one element (11) of La or Cr is segregated at the interface between the internal electrodes (5) and (6) and the ceramic layer (7). The multilayer ceramic capacitor as described in the above. 3. A step of obtaining ceramic green sheets (1), (1a) and (1b) for forming a ceramic layer (7), and a step of obtaining these ceramic green sheets (1).
a) printing the internal electrode patterns (2a) and (2b) using a conductive paste on a part of (1b), and ordering the ceramic green sheets (1), (1a) and (1b) in a predetermined order And the step of cutting the laminated ceramic green sheets (1), (1a) and (1b), and the steps of cutting the ceramic green sheets (1), (1a) and (1).
b) firing the laminate to obtain a fired laminate (3) having internal electrodes (5) and (6);
Forming the external electrodes (2) and (2) at the end from which the internal electrodes (5) and (6) are led out.
The conductive paste for forming (6) is Ni powder 1
0.5 to 3.0% by weight of La and C relative to 00% by weight
A method for manufacturing a multilayer ceramic capacitor, characterized by containing at least one oxide powder of r. 4. An oxide powder of at least one of La and Cr added to the conductive paste has an average particle size of 0.5 to 0.5.
The method for manufacturing a multilayer ceramic capacitor according to claim 3, wherein the thickness is 1.0 μm.