JPH11186087A - Stacked ceramic capacitor, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stacked ceramic capacitor capable of improving capacitance by enlarging the area of effective electrodes. SOLUTION: This is a stacked ceramic capacitor which is provided with outer electrodes 4 alternately connected to the ends of inner electrode layers 3, at both ends of the capacitor body 3 where dielectric layers 1 and inner electrode layers 2 are stacked alternately, and the inner electrode layer 2 is constituted of first conductor parts 2a and the second conductor layer parts (b) consisting of different kinds of material, and the first conductor part 2a is connected to an outer electrode 4, and furthermore one end of a second conductor part 2b is connected to the first conductor part 2a, and also the end face of the second conductor part 2a which is not connected to the first conductor part 2a is made on side which is inner than the peripheral face of the dielectric layer 1, and a gap 10 is made by the end face of the second conductor part 2b not connected to the first conductor part 1a and the dielectric layers 1 above and below the second conductor parts 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer ceramic capacitor and a method of manufacturing the same, and more particularly, to a multilayer ceramic capacitor using two types of internal electrode materials and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a laminated ceramic capacitor, a dielectric layer and one kind of internal electrode layer are alternately laminated, and end faces of the internal electrode layer are alternately exposed on both end faces of the laminated body. The structure was such that an external electrode was formed on the portion.

In such a conventional multilayer ceramic capacitor, first, a ceramic green sheet is formed by forming a ceramic slurry in which a dielectric ceramic powder and an organic binder are added to a solvent and dispersed into a sheet, and a ceramic green sheet is formed. Thus, a conductive paste is applied on this ceramic green sheet and an internal electrode pattern is printed.

Then, a plurality of ceramic green sheets on which the internal electrode patterns are printed are laminated, and a plurality of ceramic green sheets on which the internal electrode patterns are not printed are laminated above and below the ceramic green sheets.

[0005] The laminated molded body thus obtained is cut into chips so that the internal electrode pattern is exposed at both end faces,
This is fired to produce a capacitor body. Then, by polishing the exposed portion of the internal electrode layer of the capacitor body, the end surface of the internal electrode layer is exposed on the end surface of the capacitor body, and a conductive paste for an external electrode is applied to this end surface and baked. By forming external electrodes,
A desired multilayer chip capacitor has been manufactured.

As another method of manufacturing a multilayer ceramic capacitor, there is a method in which a conductive paste serving as an external electrode is applied in advance to both ends of a multilayer molded body before firing, and firing is performed simultaneously with firing.

Further, as a method of obtaining a laminated molded body, in addition to a so-called sheet laminating method using ceramic green sheets, a so-called printing method in which a ceramic paste and a conductive paste serving as an internal electrode layer are alternately printed. Has also been adopted.

Incidentally, the internal electrode layer in such a multilayer capacitor is made of a single kind of metal such as nickel, silver, copper, palladium or the like, and the internal electrode layer formed on the upper surface of the dielectric layer is formed. One end of the layer was formed to be spaced apart from the external electrode by a predetermined distance every other layer, and one end of the internal electrode layer was electrically insulated from the external electrode by the end margin region.

Conventionally, it is necessary to form a large margin area in order to prevent a short circuit due to printing accuracy, and there has been a problem that the effective electrode area is reduced and the capacitance is reduced.

As means for solving such problems,
For example, Japanese Patent Application Laid-Open No. 3-82004 proposes a method of manufacturing a multilayer capacitor in which a side margin region is formed on the side of an internal electrode layer by etching or physically removing a side end of the internal electrode layer. Have been.

[0011]

However, in the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. 3-82004, a so-called end margin region is formed in a printing process. However, it is necessary to form a large end margin region, and there is a problem that the effective electrode area is small and the capacitance is small.

That is, it is necessary to expose the internal electrode layers at both ends of the capacitor body in order to connect to the external electrodes. In the multilayer ceramic capacitor disclosed in the above publication, for example, one kind of internal electrode made of Ni is used. The side margins of the capacitor body can be formed by etching on the side surfaces of the capacitor body, but when etching is performed on both ends of the capacitor body, the end surfaces of the internal electrode layers are located inside the capacitor body and conduction with external electrodes is achieved. There is a problem that can not be taken. For this reason,
In the above publication, a so-called end margin region must be formed in the printing process, and the effective area of the internal electrode is reduced.

An object of the present invention is to provide a multilayer ceramic capacitor capable of increasing the effective electrode area and improving the capacitance.

[0014]

The multilayer ceramic capacitor according to the present invention is connected alternately to both ends of a capacitor body formed by alternately laminating dielectric layers and internal electrode layers with the ends of the internal electrode layers. A multilayer ceramic capacitor provided with external electrodes, wherein the internal electrode layer is composed of a first conductor portion and a second conductor portion made of dissimilar materials, and the first conductor portion is connected to the external electrode; Further, one end of the second conductor portion is connected to the first conductor portion, and an end surface of the second conductor portion not connected to the first conductor portion is formed inside an outer peripheral surface of the dielectric layer. An end surface of the second conductor portion not connected to the first conductor portion;
A gap is formed by the dielectric layers above and below the conductor.

Here, it is desirable that the void is filled with an insulator. Further, the first conductor portion is mainly composed of Pd,
It is desirable that the second conductor portion contains Ni as a main component.

In the multilayer ceramic capacitor of the present invention, a multilayer body formed by laminating a plurality of green sheets having an internal electrode layer pattern on the surface is fired to produce a capacitor body, and external electrodes are formed at both ends of the capacitor body. In the method for manufacturing a laminated ceramic capacitor, the internal electrode layer pattern is formed of a first conductor portion pattern formed on a surface of the green sheet on the side of the external electrode, and a green sheet having no first conductor portion pattern formed thereon. A second conductor portion pattern formed on the entire surface, and baking to produce a capacitor body in which the end surface of the second conductor portion is exposed to the outer peripheral surface except for one end connected to the first conductor portion, Thereafter, the end surface of the second conductor portion exposed on the outer peripheral surface of the capacitor body is removed, and external electrodes are formed on both ends of the capacitor body. That.

[0017]

According to the multilayer ceramic capacitor of the present invention,
For example, it is possible to employ a means in which the first conductor portion of the internal electrode layer is formed of Pd, the second conductor portion is formed of Ni, and only the second conductor portion made of Ni is etched. The connection with the external electrodes can be reliably performed, and a minimum side margin area can be formed on the side surface of the capacitor body by etching the second conductor portion. In the portion, the minimum end margin region can be formed by etching the second conductor portion, and the distance between the end surface of the second conductor portion and the external electrode that is electrically insulated can be minimized. . Therefore, the effective electrode area can be increased, and the capacitance can be increased.

That is, in the multilayer ceramic capacitor disclosed in the above-mentioned Japanese Patent Laid-Open Publication No. Hei 3-82004, the area for forming the internal electrode is controlled by the printing pattern so that the other end of the internal electrode is not connected to the external electrode. Although the end margin region had to be formed, in the present invention, without controlling the printing pattern for forming the internal electrode layer, one end of the internal electrode layer can be removed by etching and insulated from the external electrode. Therefore, the effective electrode area can be increased.

The internal electrode layer is composed of a first conductor portion mainly composed of palladium and a second conductor portion mainly composed of nickel formed on the side electrically connected to the external electrode. By etching the end surface of the second conductor portion mainly composed of nickel exposed on the outer peripheral surface of the capacitor body to produce a capacitor body, and forming an external electrode on the capacitor body, the first conductor portion of the internal electrode layer The external electrode is electrically connected, and the second conductor of the internal electrode is insulated from the external electrode. Further, since the formation region of the first conductor portion only needs to be in a range that cannot be etched, the area can be minimized, and the amount of palladium, which is an expensive noble metal, can be reduced.

Further, according to the present invention, since there is no change in the effective electrode area due to printing displacement of the internal electrode layer, the variation in capacitance can be made smaller than that of the conventional multilayer ceramic capacitor.

In addition, by filling the gap formed by the end face of the second conductor portion and the dielectric layer disposed above and below the second conductor portion with an insulator, the internal electrode layer is exposed to the outside. Therefore, the oxidation of the internal electrodes can be prevented, and the occurrence of cracks due to capacity reduction and expansion can be prevented.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a multilayer ceramic capacitor according to the present invention has an internal electrode layer at both ends of a capacitor body 3 in which dielectric layers 1 and internal electrode layers 2 are alternately laminated. External electrodes 4 alternately connected to the end portions 2 are provided.

Then, as shown in FIG.
Are connected to the external electrode 4 and the first conductor portion 2a,
One end is connected to the conductor portion 2a, and an end surface not connected to the first conductor portion 2a is formed of a second conductor portion 2b formed inside the outer peripheral surface of the dielectric layer 1. Thereby, the end surface of the second conductor portion 2b not connected to the first conductor portion 2a and the upper and lower dielectric layers 1 sandwiching the second conductor portion 2b allow the both end surfaces and side surfaces of the capacitor body 3 to be recessed. Gap 10 is formed. Therefore, when the external electrode 4 is formed, a gap 10 is formed between the external electrode 4 and the external electrode 4. In addition, on the side surfaces of the capacitor body 3 other than the both ends, the gap 10 is exposed on the outer surface.

The first conductor 2a is made of a conductor which is not easily etched, and is preferably made of, for example, a noble metal, particularly Pd. The noble metals include Au, Ag, and Pd. The second conductor 2b is made of a conductor that is easily etched, and is preferably made of, for example, a base metal, particularly Ni. As base metals, Ni,
There are Cu, Co, and Fe.

It is desirable to fill the gap 10 with an insulator such as glass, resin, or the like in order to prevent oxidation of the end surface of the second conductor 2b and to prevent a reduction in capacity and the occurrence of cracks. . In a multilayer ceramic capacitor used in high humidity, it is desirable to fill the gap 10 with an insulator. The filling of the insulator is performed by, for example, filling a glass paste or a resin paste, or filling by an electrophoresis method.

The multilayer ceramic capacitor of the present invention is obtained by first preparing a green sheet to be a dielectric layer. The green sheet contains, for example, barium titanate as a main component, yttrium oxide, a dielectric powder to which manganese carbonate and magnesium oxide are added, water and a dispersant, and after mixing and grinding in a ball mill, an organic binder is mixed. The obtained slurry is formed into a tape having a predetermined thickness.

As a material of the dielectric layer, barium titanate is a main component, and 0.5 to 8 mol parts of magnesium oxide and 0.05 to 0.5 mol part of manganese carbonate are per 100 mol parts of the main component. Molar parts, yttrium oxide 0.3 ~
It is desirable to use those containing 4 mol parts in terms of improving properties such as dielectric constant.

As the conductor paste, for example, a paste in which an organic plasticizer is added to nickel powder and a paste in which an organic plasticizer is added to palladium powder are prepared. It is desirable that nickel and palladium be contained in the paste in an amount of about 40 to 60% by weight.

Then, a laminated molded body in which a plurality of green sheets each having an internal electrode layer pattern on the surface are laminated is fired to produce a capacitor body as shown in FIG.

In the production of the laminated molded body, the internal electrode layer pattern includes a first conductor portion pattern mainly composed of Pd formed on the surface of the green sheet on the external electrode side, and a first conductor portion pattern.
And a second conductor pattern mainly composed of Ni formed on the entire surface of the green sheet on which the conductor pattern is not formed. By sintering, a capacitor body as shown in FIG. 3 in which the end surface of the second conductor portion is exposed to the outer peripheral surface except for the portion connected to the first conductor portion.

The production of the laminated molded body will be specifically described. As shown in FIG. 4, for example, a first conductor paste mainly containing palladium is screen-printed on the upper surface of the green sheet of the dielectric layer. And a second conductor paste containing nickel as a main component is applied to form a first conductor portion pattern region x and a second conductor portion pattern region y,
The green sheets (a) and (b) are prepared.

Then, the green sheets (a) and (b) to which the conductor paste is applied are alternately laminated to form an effective laminated body. On both upper and lower surfaces of the effective laminate, dielectric green sheets to which the conductor paste is not applied are laminated to form an ineffective laminate, thereby producing a laminated molded body.

Next, the production of the capacitor body will be specifically described. The laminated molded body obtained by the above method is cut into predetermined dimensions as shown in FIG. For example, oxygen partial pressure 3 × 10 ^{-8 to} 3 × 1
0 ^-3 Pa, and calcined at a temperature 1150 to 1300 ° C. 0.5 to 3 hours, after which the oxygen partial pressure ^{1 × 10 -2 ~2 × 10 4} P
a, heat treatment is performed at a temperature of 800 to 1100 ° C. for 1 to 5 hours. By polishing both end surfaces of the sintered body on which the external electrodes are formed and exposing the end surfaces of the first conductor portion and the second conductor portion to the surface of the sintered body, a capacitor body as shown in FIG. 3 is manufactured. You.

Thereafter, the second exposed on the outer surface of the capacitor body is etched by an etchant capable of etching only nickel.
The end face of the conductor is etched. As an etchant, for example, a strong acid such as nitric acid can be used.
It should be noted that an etchant that does not etch palladium is selected. For example, the capacitor body is immersed in an etchant, the end surface of the second conductor is etched, and the second conductor is removed except for the surface connected to the first conductor as shown in FIG. As a result, a concave gap is formed on the outer peripheral surface of the capacitor body. FIG. 5 shows a state in which the end surface of the second conductor is removed.

Thereafter, if necessary, the gap of the capacitor body is filled with an insulator such as glass or resin. The filling of the insulator can be achieved by applying an insulator paste or by electrophoresis.

Next, a paste in which an organic plasticizer is added to copper powder is prepared, and the paste is applied to both ends of the capacitor body and electrically baked so that the paste is alternately electrically connected to the internal electrode layers. Then, a desired multilayer ceramic capacitor is manufactured. Note that the external electrode may be made of a metal such as nickel, silver, or gold.

In the multilayer ceramic capacitor configured as described above, the non-connection portion with the external electrode can be completely insulated from the external electrode by removing the end surface of the second conductor portion of the internal electrode. Thus, the effective electrode area can be increased and the capacitance can be increased as compared with the conventional multilayer ceramic capacitor in which the margin region is formed by the above control.

That is, the conductive paste serving as the internal electrode layer is not formed at a predetermined distance from the external electrode, and the end face of the second conductor portion of the internal electrode layer is removed to insulate the external electrode from the external electrode. In addition, the area of the internal electrode that generates the capacitance can be greatly improved. In addition, it is possible to prevent a short circuit with an external electrode and a reduction in capacitance accuracy due to a reduction in printing accuracy as in the related art.

In the above example, the internal electrodes made of a combination of nickel and palladium are formed, but the present invention is not limited to the above example.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a dielectric material containing barium titanate as a main component, 100 mole parts of the main component, 1 mole portion of yttrium oxide, 2 mole portions of magnesium oxide, and 0.1 mole portion of manganese oxide was added. Water and a dispersant were added to the body powder, mixed and pulverized by a ball mill using ZrO ₂ balls, and then an organic binder was mixed. The resulting slurry was formed into a 13 μm-thick green sheet.

On the other hand, a paste in which an organic plasticizer is added to nickel powder and a paste in which an organic plasticizer is added to palladium powder are prepared as internal electrode layers, and the pastes are formed on the green sheet by a screen printing method. 4, and the green sheets (a) and (b) were alternately laminated to produce a laminated molded body of an effective laminated body.

Further, in order to manufacture a conventional general capacitor, nickel is used as an internal electrode layer, and the internal electrode pattern 31 is formed by screen printing as shown in FIG.
Was controlled by printing to prepare a laminate formed by laminating green sheets 33 each having an end margin area E and a side margin area S formed thereon.

Also, in order to reproduce the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. 3-82004, a laminated molded body in which nickel is used as an internal electrode layer and green sheets each having only an end margin region formed by screen printing are prepared. did.

Next, green sheets for a non-effective laminate were laminated on the upper and lower surfaces of the laminate formed from the effective laminate.

Next, after cutting the obtained laminate, it was baked at an oxygen partial pressure of 1 × 10 ⁻⁶ Pa and a temperature of 1,260 ° C. for 2 hours to produce a capacitor body. Thereafter, in the case of using the green sheet shown in FIG. 4, the exposed portion of the internal electrode mainly composed of nickel was removed using an acid mainly composed of nitric acid. Thereafter, a resin containing paraffin as a main component was adsorbed to the voids from which the internal electrodes had been removed, and then a copper paste was applied and baked at 900 ° C. to form external electrodes.

In the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. 3-82004, after the capacitor body was manufactured, the exposed portions of the internal electrodes were removed except for both ends where external electrodes were formed. Copper paste was applied and baked at 900 ° C. to form external electrodes.

Further, in the case of using the green sheet shown in FIG. 6, after preparing a capacitor body, a copper paste was applied and baked at 900 ° C. to form external electrodes.

Next, these samples were placed in an LCR meter 42
The capacitance at + 25 ° C. was measured using 84A at a frequency of 1.0 kHz and an input signal level of 1.0 Vrms.

As a result, in the case of the conventional general capacitor (using the green sheet shown in FIG. 6), the capacitance is 560 nF, and in the case of the capacitor in which only the end margin is formed by screen printing (particularly, Kaihei 3-
In contrast, the capacitance was 800 nF in the present invention using nickel and palladium as the internal electrode layers, whereas the capacitance was 800 nF. This shows that a multilayer ceramic capacitor having a large capacitance can be manufactured.

[0050]

The multilayer ceramic capacitor of the present invention has the following features.
An inner electrode layer composed of the first and second conductors is laminated with a dielectric layer interposed therebetween, and an outer peripheral portion of the inner electrode layer, leaving an end of the inner electrode layer electrically connected to the outer electrode. Can be completely insulated from the external electrode, and the distance between the other end of the internal electrode layer and the external electrode can be minimized, thereby increasing the effective electrode area. As a result, the capacitance can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a multilayer ceramic capacitor of the present invention.

FIG. 2 is an enlarged sectional view showing the capacitor body of FIG. 1;

FIG. 3 is a cross-sectional view of the capacitor body before etching.

FIG. 4 is a plan view showing a state where a first conductor portion pattern and a second conductor portion pattern are formed on a green sheet;
(A) is an odd layer, and (b) is an even layer.

FIG. 5 is a cross-sectional view of the capacitor main body in a state where an end face of a second conductor is removed.

6A and 6B are plan views showing a conventional internal electrode layer pattern, wherein FIG. 6A shows an odd-numbered layer and FIG. 6B shows an even-numbered layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric layer 2 ... Internal electrode layer 2a ... 1st conductor part 2b ... 2nd conductor part 3 ... Capacitor main body 4 ... External electrode 10 ... Void

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01G 4/30 311 H01G 1/147 A

Claims (4)

[Claims] 1. A multilayer ceramic capacitor comprising a capacitor body in which dielectric layers and internal electrode layers are alternately laminated, and external electrodes alternately connected to ends of the internal electrode layers are provided at both ends of the capacitor body. The internal electrode layer includes a first conductor portion and a second conductor portion made of different materials, the first conductor portion is connected to the external electrode, and one end of the second conductor portion is connected to the first conductor portion. An end surface of the second conductor portion connected to the conductor portion and not connected to the first conductor portion is formed inside an outer peripheral surface of the dielectric layer, and is connected to the first conductor portion. A gap is formed by an end face of the second conductor portion and upper and lower dielectric layers of the second conductor portion. 2. The multilayer ceramic capacitor according to claim 1, wherein the gap is filled with an insulator. 3. The multilayer ceramic capacitor according to claim 1, wherein the first conductor has Pd as a main component and the second conductor has Ni as a main component. 4. Manufacturing of a multilayer ceramic capacitor in which a multilayer molded body in which a plurality of green sheets having an internal electrode layer pattern are laminated on the surface is fired to produce a capacitor body, and external electrodes are formed on both ends of the capacitor body. In the method, the internal electrode layer pattern is formed on a first conductor portion pattern formed on a surface of the green sheet on an external electrode side, and on the entire surface of the green sheet on which the first conductor portion pattern is not formed. The capacitor body is formed from the second conductor portion pattern, and is fired to produce a capacitor body in which the end surface of the second conductor portion is exposed to the outer peripheral surface except for one end connected to the first conductor portion. An end surface of a second conductor portion exposed on an outer peripheral surface is removed, and external electrodes are formed on both ends of a capacitor body. Production method.