JP2001185440A - Laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic capacitor wherein infiltration of a plating liquid to inner electrodes 3, 4 is prevented, crack generation can be also prevented in both a breakdown voltage test in wet condition and a thermal shock test, a connection status of internal and external electrodes is assured and a peeling of dielectric layers 1a to 1f is prevented. SOLUTION: In a laminated ceramic capacitor 10, the thickness of first and second internal electrodes 3, 4 in the regions that do not overlap with third internal electrodes 7 is made larger than the thickness in the regions of overlap, and further the internal electrodes near both main faces of a laminate 1 are arranged to make the third internal electrodes 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a multilayer ceramic capacitor in which a plurality of dielectric layers are laminated, and internal electrodes facing each other are formed between the dielectric layers, and in particular, a plurality of capacitors are connected in series. To a device having a structured structure.

[0002]

2. Description of the Related Art Multilayer ceramic capacitors are small and have a high capacity and are easy to mount on a substrate, which greatly contributes to miniaturization of electronic equipment. In recent years, with the miniaturization and improvement of functions of the device, the multilayer ceramic capacitor used in the device has been required to have a small size and a high capacity. It is intended to be realized by enabling use in a relatively high voltage range (medium pressure to high pressure range).

FIG. 4 is a view for explaining a conventional multilayer ceramic capacitor which can be used in a relatively high voltage range, that is, has improved withstand voltage. FIG. (B)
Shows a cross-sectional view in the horizontal direction.

According to FIG. 4, a laminate 41 in which a plurality of dielectric layers are laminated, and end faces 42 of the laminate 41 facing each other.
a and 42b respectively formed on the first and second external electrodes 45 and 46; a plurality of first internal electrodes 43 connected to the first external electrode 45 and formed in a stacked state; A second internal electrode 44 connected to the external electrode 46 and formed on the same dielectric layer as the first internal electrode 44 so as to face the first internal electrode 44; Hereinafter, extraction electrodes 43 and 44 and a third internal electrode (hereinafter referred to as a floating electrode) 47 that partially overlaps with a dielectric layer interposed therebetween. In particular, the capacitor units 48 are formed by the extraction electrodes 43 and 44 and the floating electrodes 47, and a plurality of capacitor units 48 are arranged in the laminating direction.

[0005]

In the above-described multilayer ceramic capacitor, when the laminated body 41 is integrally fired, the dielectric layer and the lead electrodes 43 and 44 and the floating electrode 47 have different shrinkage ratios and cause a difference between the dielectric layers. Cracks in the laminate 41 must be reduced by delamination or thermal shock tests. For this purpose, the extraction electrode 4
It is desirable that the thickness of the floating electrodes 47 is small. However, when the thicknesses of the lead electrodes 43 and 44 and the floating electrode 47 are simply reduced, the connectivity between the external electrodes 45 and 46 is hindered, and the ESR (equivalent series resistance) at a high frequency increases.

Particularly, in order to maintain the withstand voltage, it is necessary to increase the thickness of the dielectric sandwiched between the internal electrodes, and the number (number of layers) of the internal electrodes that can be arranged is reduced. , ESR (equivalent series resistance) tends to increase.

On the other hand, the lead electrodes 43 and 44 and the floating electrode 4 are interposed via a green sheet to be an unfired dielectric layer.
In the case where layers 7 and 7 are alternately stacked, there is a problem that the region where the extraction electrodes 43 and 44 and the floating electrode 47 overlap is raised, and the region that becomes the end after cutting is dented. Therefore, the plane parallelism on the main surface of the laminated body 41 cannot be maintained, and even when the laminated body 41 is pressed during lamination, the pressure is not uniformly applied due to a large step, and poor adhesion between the dielectric layers occurs. As a result, there is a problem that peeling and poor adhesion may occur when cut.

In order to form a multilayer ceramic capacitor having a low profile, a small size and a high capacitance, the number of capacitor units 48 is increased in the stacking direction. The distance (top margin) to the nearest electrode has to be reduced, and in such a case, the thickness of the corners of the stacked body 41 may be reduced. The reason for this is that the external electrodes 45 and 46 are formed by a dipping method, that is, the laminate 41 is placed in a tank containing a conductive paste.
In this method, the thickness of the outer electrodes 45 and 46 at the corners is larger than that at the center of the end surfaces of the conductive paste. This is because it is formed thin by tension.

Therefore, when the corners of the laminate 41 are thin, a plating solution is laminated from the external electrodes 45 and 46 in the next step of plating the external electrodes 45 and 46 for the following reasons. There was a problem of infiltration into the body 41. That is, (1) between the four surfaces where the laminated body 41 and the external electrodes 45 and 46 are in contact with each other, particularly when entering from the boundary between the main surface near the end face of the laminated body 41 and the external electrodes 45 and 46,
(2) External electrodes 4 directly formed on end faces 42a and 42b
The plating solution directly penetrates through the minute hollow holes existing in 5, 46. When the thickness of the external electrodes 45 and 46 is small, it becomes easy to enter.

Therefore, the extraction electrodes 43 and 44 closest to the main surface of the laminated body 41 are thinner in the external electrodes 45 and 46 which are covered at both ends, so that the plating solution can easily enter. When the plating solution enters the extraction electrodes 43 and 44, the internal electrode expands in a high-temperature environment and causes delamination and cracks.

The present invention has been devised in view of the above-mentioned problems, and has as its object to improve the connectivity with external electrodes, and to perform delamination at the time of firing a laminate and a thermal shock test. Cracks do not occur,
The plane parallelism of the laminate can be obtained, and the plating solution can be prevented from penetrating even in the step of plating the surface of the external electrode, and the internal electrode can be expanded in a high temperature environment to prevent delamination and cracking. It is an object of the present invention to provide a multilayer ceramic capacitor that can be used.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a laminated body formed by laminating a plurality of dielectric layers, extending inward from opposing both end faces, and having the tips of each other. A first and a second internal electrode arranged in abutting manner at a predetermined interval, a third internal electrode partially overlapping with both the first and the second internal electrodes via the dielectric layer, In a multilayer ceramic capacitor formed on both end surfaces of a multilayer body and including first and second external electrodes connected to the first and second internal electrodes, the first and second internal electrodes may include: A multilayer ceramic capacitor characterized in that the layer thickness of the region of the internal electrode that does not overlap with the third internal electrode is thicker than the layer thickness of the region that overlaps.

According to the structure of the present invention, of the first and second internal electrodes, the layer thickness of the region of the internal electrode which does not overlap with the third internal electrode is larger than the layer thickness of the overlapping region. Therefore, dents can be prevented at both ends of the laminate in the unfired state due to the thicknesses of the first and second internal electrodes, whereby the plane parallelism of the laminate can be maintained. As a result, peeling and poor adhesion between the dielectric layers can be significantly reduced, and the connectivity with the first and second external electrodes can be improved.

Further, an internal electrode near both main surfaces of the laminate may be used as the third internal electrode. That is, when the plating solution infiltrates from the external electrode in the plating step, the first and second internal electrodes formed to have a large thickness are easily in contact with the plating solution, but the third internal electrode is formed of the laminated body. Since the first and second internal electrodes are interposed between the two main surfaces and the first and second internal electrodes, the first and second internal electrodes are formed from a portion where the thickness of the external electrode, which is a corner of the laminated body, is thin. This can prevent the internal electrodes from expanding due to a high-temperature environment caused by the infiltration of the plating solution, thereby preventing the occurrence of delamination and cracks.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multilayer ceramic capacitor according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an external perspective view of a multilayer ceramic capacitor according to the present invention, and FIG.
FIG. 3 is a sectional view of the multilayer ceramic capacitor of FIG. 1, and FIG. 3 is a perspective plan view of the multilayer ceramic capacitor of FIG.

In this multilayer ceramic capacitor 10, a rectangular parallelepiped laminate 1 made of a dielectric material such as barium titanate or strontium titanate, and external electrodes 5 formed on a pair of opposed end surfaces of the laminate 1, respectively. It consists of six. The external electrodes 5 and 6 have thick film underlying conductor layers 5a and 6a formed directly on the end face of the multilayer body 1 and plating layers 5b and 6b formed on the surfaces thereof.

The laminate 1 is formed by laminating a plurality of dielectric layers 1a to 1f. Between each dielectric layer 1, Pd or Ag-
First and second internal electrodes 3 and 4 and third internal electrodes 7 made of a noble metal material such as a Pd alloy or a base metal material such as Ni are alternately arranged.

One end of the first internal electrode 3 is connected to the external electrode 5, one end of the internal electrode 4 is connected to the external electrode 6, and the other ends of the internal electrodes 3 and 4 are connected to each other. Are arranged facing each other at a predetermined interval. The internal electrode 3 is a floating electrode, and the first and second internal electrodes 3
4 are arranged so as to overlap each other at multiple ends.

Further, a third electrode 7 is disposed as an internal electrode close to the main surface of the multilayer body 1, and a dielectric layer 1a serving as a top margin layer on the upper side of the third internal electrode 7;
A dielectric layer 1f serving as a lower top margin layer is interposed. Here, the thickness of the region where the first and second internal electrodes 3 and 4 and the third internal electrode 7 overlap is formed to be thicker than the thickness of the non-overlapping region. Furthermore, both ends of the first and second internal electrodes 3 and 4 are exposed on the end surface of the multilayer body 1 and are connected to the external electrodes 5 and 6 in the thickness region.

The multilayer ceramic capacitor 10 having the above structure
Is prepared as follows. First and second internal electrodes 3 and 4
And the conductive layer pattern of the third internal electrode 7 are formed every other layer on the same screen. Then, the first and second internal electrodes 3 and 4 and the third internal electrode 7 are printed on the green sheet serving as the dielectric layer. At this time, when printing the first and second internal electrodes 3 and 4 to increase the thickness of the first and second internal electrodes in a portion that does not overlap with the third internal electrode 7, a mesh of a screen pattern is used. The area of the first and second internal electrodes 3 and 4 overlapping the third internal electrode is made thinner, and printing is performed using a screen in which the non-overlapping parts are made thicker.

After this printing, the green sheets on which the internal electrodes are formed are alternately laminated, and the laminated green sheets are temporarily pressed. Then, this is cut into dimensions according to the shape to form a chip material. Next, the chip material is fired in a predetermined atmosphere and temperature, and the internal electrodes are integrally sintered. Thus, the laminate 1 is manufactured.

Next, external electrodes 5 and 6 are formed on the end surfaces of the laminate 1. Specifically, the formation of the thick film underlying conductor layers 5a and 6a is performed by dipping, that is, by applying the end face of the laminate 1 in a bath containing a conductive paste. In this case, the conductor paste is made of Ag or an Ag-Pd alloy. Ni or Ni is coated on the surfaces of the thick base conductor layers 5a and 6a formed by coating.
By performing plating with -Sn or the like, a multilayer ceramic capacitor is manufactured.

Here, as shown in FIG. 5B, when the internal electrodes near the main surface of the laminate 1 are the first and second internal electrodes 3 and 4, the third internal electrode 3 is The thickness d2 of the film thickness of the base conductor film 5a from the end to the corner of the laminate 1 from the end is shorter than d1. As a result, the plating solution easily penetrates in the plating process because the length d2 of the film thickness is short, and as a result, the insulation resistance characteristics are deteriorated, and the reliability in the humidity and pressure resistance test is greatly reduced. I do.

However, as shown in FIG.
In the case where the internal electrode close to the main surface is the third internal electrode 7, the distance between the next first and second internal electrodes 3, 4 is the corner of the laminated body 1 where the external electrode 5 is thin. , And a distance d2 from the plating solution, thereby preventing problems caused by infiltration of the plating solution.

Thus, according to the multilayer ceramic capacitor of the present invention, the layer thickness of the first and second internal electrodes 3 and 4 which are not overlapped with the third internal electrode 7 are limited to the overlapped area. Since the thickness is larger than the thickness of each of the first and second internal electrodes 3 in the unfired state,
Depression can be prevented by the thickness of 4, whereby the plane parallelism of the laminate 1 can be maintained.
As a result, peeling and poor adhesion between the dielectric layers can be significantly reduced, and the connectivity with the first and second external electrodes 3 and 4 can be improved.

Further, by using the internal electrodes near both main surfaces of the laminated body 1 as the third internal electrodes 7, when the plating solution penetrates from the external electrodes 5 and 6 in the plating step, the internal electrodes are formed to be thick. Although the portions of the first and second internal electrodes 3 and 4 that have been formed easily come into contact with the plating solution, the third internal electrode 7 is
Between the two main surfaces and the first and second internal electrodes 3 and 4, the outer electrodes 5 and 6, which are the corners of the multilayer body 1, are formed from the thinner portions to the first and second inner electrodes 3 and 4. The first and second internal electrodes 3 and 4 can be kept away from each other, thereby preventing the occurrence of delamination and cracks due to the expansion of the internal electrodes due to the high temperature environment caused by the infiltration of the plating solution by the infiltration of the plating solution. be able to.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements may be made without departing from the scope of the present invention.

[0028]

As described above, according to the present invention, the first,
In the second internal electrode, since the layer thickness of the region of the internal electrode that does not overlap with the third internal electrode is larger than the layer thickness of the overlapping region, both ends of the stacked body are unfired in the first state. In addition, dents can be prevented by the thickness of the second internal electrode, whereby the plane parallelism of the stacked body can be maintained. As a result, peeling and poor adhesion between the dielectric layers can be significantly reduced, and the connectivity with the first and second external electrodes can be improved.

Further, by using the internal electrodes close to both main surfaces of the laminated body as the third internal electrodes, when the plating solution infiltrates from the external electrodes in the plating step, the first electrode is formed to have a large thickness. , The second internal electrode is likely to come into contact with the plating solution, but the third internal electrode is in contact with both main surfaces of the laminate and the first and second internal electrodes.
Since it is interposed between the second internal electrodes, the first and second internal electrodes can be kept away from the corners of the laminate where the thickness of the external electrodes is reduced. In addition, it is possible to prevent the occurrence of delamination and cracks due to expansion of the internal electrodes due to a high-temperature environment caused by intrusion of the plating solution due to intrusion of the plating solution.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a multilayer ceramic capacitor according to the present invention.

FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor of the present invention.

FIG. 3 is a perspective plan view of the multilayer ceramic capacitor of FIG. 2;

FIG. 4 is a cross-sectional view of a conventional multilayer ceramic capacitor.

FIG. 5 is a partial explanatory view of the multilayer ceramic capacitor.

[Explanation of symbols]

 10 Multilayer ceramic capacitor 1 Multilayer body 2, 42 Dielectric layer 3, 43 First internal electrode 4 , 44... Second internal electrode 5, 45... First external electrode 6, 46... Second external electrode 7, 47. electrode

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) JJ03 JJ05 JJ12 JJ21 JJ23 LL02 LL03 MM22 PP09

Claims (2)

[Claims] 1. A first and a second inner part which extend inward from opposing end faces of a laminated body formed by laminating a plurality of dielectric layers, and which are arranged so that their tips are spaced apart by a predetermined distance. An electrode, a third internal electrode that partially overlaps both the first and second internal electrodes via the dielectric layer, and a first internal electrode formed on both end surfaces of the multilayer body; In the multilayer ceramic capacitor including the first and second external electrodes connected to the internal electrode, a layer thickness of a region of the first and second internal electrodes that does not overlap with the third internal electrode However, the multilayer ceramic capacitor is characterized in that it is thicker than the layer thickness of the overlapping area. 2. The multilayer ceramic capacitor according to claim 1, wherein internal electrodes near both main surfaces of the multilayer body are used as the third internal electrodes.