JP3305605B2 - Multilayer ceramic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic ceramic capacitor, and more particularly to a multilayer ceramic capacitor in which an outer peripheral portion of an internal electrode is electrically connected to a metal oxide constituting the internal electrode except for a portion electrically connected to an external electrode. The present invention relates to an insulated multilayer ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, as a multilayer ceramic capacitor, a dielectric layer and one kind of internal electrode layer are alternately laminated, and a part of the internal electrode layer is alternately exposed at different places on the surface of the laminated body. In which a terminal electrode is formed.

A general manufacturing method of such a multilayer ceramic capacitor is, for example, a method of forming a ceramic green sheet by forming a ceramic slurry in which dielectric ceramic powder is dispersed in an organic binder into a sheet, and screen printing. Thus, an internal electrode pattern is printed with a conductive paste on the ceramic green sheet.
Then, the ceramic green sheets on which the internal electrode patterns are printed are stacked, and a plurality of ceramic green sheets on which the internal electrode patterns are not printed are stacked on both sides thereof.

[0004] The laminate thus obtained is cut into chips in such a manner that the internal electrodes are exposed at the end faces, and the chips are fired. And by polishing this sintered laminate,
A multilayer chip capacitor has been manufactured by exposing an internal electrode to the end face, applying a conductive paste to the end face, and baking the paste to form an external electrode.

[0005] As another method of manufacturing a multilayer ceramic capacitor, there is a manufacturing method in which a conductive paste is preliminarily baked on an end portion of the ceramic laminate before firing. Further, as a method for obtaining a laminate, a so-called printing method in which ceramic paste and a conductive paste are alternately printed, in addition to a so-called sheet method using ceramic green sheets, is also adopted.

[0006] In recent years, such multilayer capacitors have been required to have a large capacity as well as a small size. In order to meet this demand, the dielectric ceramic layers are made thinner to enable a higher lamination. However, when the number of laminations increases, the difference in lamination thickness between the portion where the internal electrodes overlap via the ceramic layer inside the laminate and the other margin portion increases due to the thickness of the internal electrodes. When the side margin is narrowed in order to obtain a large capacity, the adhesion between the ceramics located above and below the internal electrode is impaired, and delamination tends to occur.

As means for solving this problem, Japanese Patent Laid-Open Publication No. Hei 3-82005 proposes a multilayer ceramic capacitor in which the side edges of internal electrodes are oxidized. FIG. 5 shows a cross-sectional view of the multilayer ceramic capacitor. According to this, since the oxide 2 is formed by oxidizing the side end of the internal electrode 1, the coupling between the internal electrode 1 and the dielectric layer is strong, delamination is suppressed, and a high-capacitance capacitor is obtained. . Reference numeral 6 denotes an external electrode, and reference numeral 8 denotes an end margin area.

[0008]

In a multilayer ceramic capacitor, one end of an internal electrode is connected to an external electrode and the other end is insulated from the external electrode.
In the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. -82005, the so-called end margin area 8 is formed by controlling the internal electrode formation area by a printing pattern so that the other end of the internal electrode 1 is not connected to the external electrode 6. In order to prevent short circuit and delamination due to printing accuracy, it is necessary to form a large end margin region 8, and thus there is a limit in increasing the effective electrode area.

When the dielectric layer is made thinner and more highly laminated using this technique, the difference in the laminated thickness between the portion where the internal electrode 1 overlaps and the other end margin region 8 becomes large, There is still a problem that distortion due to the thickness difference is large.

According to the present invention, the effective electrode area can be increased to improve the capacitance, and even if the dielectric layer is made thinner and more laminated, there is no margin portion so that distortion due to thickness difference does not occur. It is an object to provide a ceramic capacitor.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above problems, and as a result, the internal electrodes of the multilayer ceramic capacitor were entirely formed using two types of internal electrode layer pastes containing different metals as main components. By forming and electrically insulating every other part of the internal electrode layer which is in contact with the external electrode with a metal oxide constituting the internal electrode, the effective electrode area can be increased and at the same time the internal electrode is formed on the entire surface. Therefore, the inventors have found that there is no thickness difference depending on the location of the capacitor, and have reached the present invention.

That is, in the multilayer ceramic capacitor of the present invention, external electrodes electrically connected to one end of the internal electrode layer are provided at both ends of a capacitor body in which dielectric layers and internal electrode layers are alternately stacked. The multilayer ceramic capacitor provided respectively, wherein the internal electrode layer is mainly composed of a noble metal portion mainly formed of a noble metal formed on a side electrically connected to the external electrode, and another base metal. And a base metal portion, and the entire outer peripheral portion of the internal electrode layer is exposed on the outer surface of the capacitor body, and the outer peripheral portion of the internal electrode layer except for a portion electrically connected to the external electrode. The part is oxidized. Further, it is desirable that the noble metal portion contains palladium as a main component and the base metal portion contains nickel as a main component.

[0013]

According to the multilayer ceramic capacitor of the present invention, the internal electrode layer is formed on the entire surface of the dielectric layer, and the outer peripheral portion of the internal electrode layer is removed except for one end of the internal electrode layer electrically connected to the external electrode. Is oxidized and an oxide is formed, so that it can be electrically insulated from the outside and the distance for insulation between the other end of the internal electrode and the external electrode can be minimized. The electrode area can be increased, and the capacitance can be increased.

That is, in the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. Hei 3-82005, the area for forming the internal electrodes is controlled by the printing pattern so that the other end of the internal electrodes is not connected to the external electrodes. Although a large end margin area had to be formed, in the present invention, it is possible to insulate the external electrode by oxidizing the end of the internal electrode layer without controlling the printing pattern for forming the internal electrode layer. Therefore, the effective electrode area can be increased.

Further, since the area of the internal electrode layer formed between the dielectric layers is the same as the area of the dielectric layer, there is no difference in thickness depending on the location of the capacitor. Thereby, it is possible to prevent the occurrence of delamination due to the internal stress caused by the thickness difference.

Further, the internal electrode layer is composed of a region mainly composed of palladium formed on the side electrically connected to the external electrode and another region mainly composed of nickel, so that the capacitor main body is formed. In manufacturing the semiconductor device, a region mainly composed of palladium is formed at one end of the internal electrode layer so as to be electrically connected to an external electrode, and a region mainly composed of nickel is formed in other portions.

Therefore, by oxidizing the capacitor body, the outer peripheral portion of the region containing nickel as a main component is oxidized to form nickel oxide. When the external electrode is formed on the capacitor body, one end of the internal electrode layer is formed. And the external electrode are electrically connected, the other end of the internal electrode layer is insulated from the external electrode, and the side surface of the internal electrode layer is oxidized to be insulated from the outside. .

[0018]

FIG. 1 shows an example of a multilayer ceramic capacitor according to the present invention. According to FIG. 1, a multilayer ceramic capacitor has a dielectric layer 11 and an internal electrode layer 13 alternately laminated. External electrodes 16 electrically connected to one end of the internal electrode layer 13 are provided at both ends of the capacitor body 15 thus formed.

As shown in FIG. 2, the entire outer peripheral portion of the internal electrode layer 13 of the capacitor body 15 is exposed to the outer surface, and except for a portion electrically connected to the external electrode 16, Is oxidized at its outer periphery.

That is, the outer periphery of the internal electrode layer 13 is oxidized to form the oxide 17 except for the end on the side of the external electrode 16.

The internal electrode layer 13 is composed of a noble metal portion 21 mainly composed of a noble metal formed on the side electrically connected to the external electrode 16 and a base metal portion 23 mainly composed of another base metal. It is configured. Au as a noble metal,
Ag, Pd, Pt, etc., and Ni, C
Although there are o, Fe, Cu and the like, palladium is preferred as the noble metal and nickel is preferred as the base metal because of its low cost.

The internal electrode layer may be a layer containing a metal as a main component, and may contain a metal oxide, glass or the like in addition to the metal.

The multilayer ceramic capacitor of the present invention is obtained, for example, 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.

Then, as shown in FIG. 3, a nickel conductive paste and a palladium conductive paste are applied on the upper surface of the green sheet 31 of the dielectric layer by, for example, a screen printing method to form a nickel internal electrode region 33 and a palladium conductive paste. The green sheets 31 coated with the conductive paste are laminated so that the internal electrode regions 35 are alternately arranged.

After cutting the obtained laminated molded body to a predetermined size, for example, the oxygen partial pressure is 3 × 10 ⁻⁸ to 3 × 10 ^−8.
-3 Pa, firing at a temperature of 1150-1300 ° C for 0.5-3 hours, and thereafter, a temperature of 800-1150 ° C in the air.
For 30 minutes to 5 hours to oxidize the nickel exposed on the surface of the sintered body to produce a capacitor body. This capacitor body is shown in FIG.

Next, a paste in which an organic plasticizer is added to copper powder is prepared, and the paste is baked on both ends of the capacitor body so as to be alternately electrically connected to the internal electrode layers, thereby preparing a multilayer ceramic capacitor. I do.

In the above example, the internal electrode made of a combination of nickel and palladium is formed, but the present invention is not limited to the above example. Furthermore, the effective electrode area can be further increased by forming the external electrodes on the sintered body so as to be electrically connected alternately with the internal electrode layers by using a thin film forming technique such as a sputtering method.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a dielectric material containing barium titanate as a main component, 1 mole portion of yttrium oxide, 2 mole portions of magnesium oxide and 0.1 mole portion of manganese oxide was added to 100 mole portions of the main component. Water and a dispersant were added to the powder, mixed and pulverized with a ball mill using ZrO ₂ balls, and then an organic binder was mixed. The resulting slurry was formed into a tape having a thickness of 8 μm.

On the other hand, a paste in which an organic plasticizer was added to nickel powder and a paste in which an organic plasticizer was added to palladium powder were prepared as internal electrodes, and nickel and palladium were respectively coated on the tape as shown in FIG. The tapes were formed by screen printing so that they were alternately arranged.

In order to manufacture a conventional general capacitor as shown in FIG. 6, a molded body in which nickel and nickel are used as internal electrodes and end and side margin regions are formed by screen printing is prepared. In order to manufacture such a capacitor, a molded body using nickel as an internal electrode and only forming an end margin portion by screen printing was prepared. In FIG. 6, reference numeral 1 denotes an internal electrode, reference numeral 6 denotes an external electrode, reference numeral 8 denotes an end margin area, and reference numeral 9 denotes a side margin area.

After cutting the obtained compact, it is fired at an oxygen partial pressure of 1 × 10 ⁻⁶ Pa and a temperature of 1260 ° C. for 2 hours, and then at an oxygen partial pressure of 1 × 10 ¹ Pa and a temperature of 1000 ° C. for 1 hour. Heat treatment was performed. Thereafter, an external electrode made of gold was formed on the sintered body by using a sputtering method, and the dielectric layer thickness was 9 μm.
Effective dielectric layer number 110 layers, external dimensions 1.6 mm x 0.8
mm × 0.8 mm, effective electrode area 1.19 (1.56 ×
0.76) mm ² was obtained.

Next, these samples were transferred to 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, the capacitance of the conventional general capacitor of FIG. 6 was 560 nF, and the capacitance of the capacitor as shown in FIG. 5 was 700 nF. In the case of the present invention in which palladium is formed alternately and the portions of the internal electrode layer that are in contact with the external electrodes are electrically insulated by a metal oxide constituting the internal electrodes every other layer, the capacitance is 800 nF. Was. This shows that a multilayer ceramic capacitor having a large capacitance can be manufactured.

[0036]

The multilayer ceramic capacitor of the present invention has the following features.
An internal electrode layer is formed on the entire surface of the dielectric layer, and except for one end of the internal electrode layer electrically connected to an external electrode,
Since the outer peripheral portion of the internal electrode layer is oxidized and an oxide is formed, it can be insulated from the outside and minimize the distance for insulation between the other end of the internal electrode layer and the external electrode. As a result, the effective electrode area can be increased, and the capacitance can be increased.

Further, since the area of the internal electrode layer formed between the dielectric layers is the same as that of the dielectric layer, there is no difference in thickness depending on the location of the capacitor. Thereby, it is possible to prevent the occurrence of delamination due to the internal stress caused by the thickness difference.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is an explanatory view showing a state in which a nickel internal electrode paste and a palladium internal electrode paste are applied to a green sheet and laminated.

FIG. 4 is a perspective view showing a capacitor body.

FIG. 5 is a cross-sectional view of a conventional multilayer ceramic capacitor formed by oxidizing a side end of an internal electrode.

FIG. 6 is a cross-sectional view of a conventional general multilayer ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Dielectric layer 13 ... Internal electrode layer 15 ... Capacitor main body 16 ... External electrode 17 ... Oxide 21 ... Noble metal part 23 ... Base metal part

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01G 4/00-4/42

Claims (2)

(57) [Claims] 1. A multilayer ceramic capacitor comprising a capacitor body in which dielectric layers and internal electrode layers are alternately stacked, and external electrodes electrically connected to one end of the internal electrode layer are provided at both ends of the capacitor body. The internal electrode layer includes a noble metal portion mainly composed of a noble metal formed on the side electrically connected to the external electrode, and a base metal portion mainly containing other base metal. The entire outer peripheral portion of the internal electrode layer is exposed on the outer surface of the capacitor body, and the outer peripheral portion of the internal electrode layer is oxidized except for a portion electrically connected to the external electrode. Characteristic multilayer ceramic capacitor. 2. The multilayer ceramic capacitor according to claim 1, wherein the noble metal portion contains palladium as a main component and the base metal portion contains nickel as a main component.