JP2000021677A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation of capacitance effectively while preventing a Manhattan phenomenon by extending first and second inner electrode layers partially to different corners of a laminate and forming first and second outer terminal electrodes across two side faces defining the corner. SOLUTION: A first inner electrode layer 12 is extended to the upper right corner X of a rectangular dielectric ceramic layer 11 and a second inner electrode layer 13 is extended to the lower left corner Y thereof. The long side of the first inner electrode layer 12 is set longer than that of the second inner electrode layer 13 and the short side of the first inner electrode layer 12 is set longer than that of the second inner electrode layer 13. A first outer terminal electrode 2 to be connected with the first inner electrode layer 12 is formed at one corner X out of four corners of the laminate and a second outer terminal electrode 3 to be connected with the second inner electrode layer 13 is formed at a corner Y of the laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the shape of internal electrode layers and the shape of external terminal electrodes of a multilayer ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, a multilayer ceramic capacitor has a shape as shown in an external perspective view of FIG. In FIG. 5, a laminated body 51 is configured by laminating a plurality of dielectric ceramic layers. A first external terminal electrode 55 and a second external terminal electrode 56 are formed at a pair of opposite ends. A first internal electrode layer 53 having a rectangular shape is arranged between the dielectric ceramic layers constituting the laminated body 51 and the first dielectric layer.
A rectangular second internal electrode layer 54 was arranged between the layers where the internal electrode layers 53 were arranged and the dielectric ceramic layers adjacent in the thickness direction.

FIG. 6 is a schematic plan view showing the relationship between two internal electrode layers and the relationship with external terminal electrodes.

That is, the first internal electrode 53 located on one main surface side of the dielectric ceramic layer 52 has a substantially rectangular shape as shown by a solid line, and has one of a pair of short sides of the dielectric ceramic layer 52. It extends to the end (right side in the figure). The second internal electrode 54 located on the other main surface side of the dielectric ceramic layer 52 has a substantially rectangular shape as shown by a dotted line, and the other end of the pair of short sides of the dielectric ceramic layer 52 (in the figure, Left). That is, the first internal electrode layer 53 and the second internal electrode layer 54 have substantially the same shape, although they extend in different directions.

[0005] The end portion including one end surface of the laminated body 51, that is, the end surface, both main surfaces near the end portion, and both side surfaces are provided.
A first external terminal electrode 55 connected to the first internal electrode layer 53 is formed. Further, the second external terminal electrode 5 connected to the second internal electrode layer 54 is provided on an end portion including the other end surface of the multilayer body 51, that is, on the end surface, both main surfaces near the end portion, and both side surfaces.
6 are formed.

The conductive film serving as the first internal electrode layer shown in FIG. 6 is formed by printing and drying a conductive paste on a green serving as a dielectric porcelain, and serves as the second internal electrode layer. The conductor film is on the green which will be dielectric porcelain,
The conductive paste is formed by printing and drying. Then, each green sheet is alternately laminated and pressed in accordance with the lamination order of the laminated body, cut in accordance with the outer dimensions of the laminated body 51, and the green sheet and the conductive film are simultaneously fired integrally to form the laminated body 51. Had formed.

[0007] In this case, since the laminated ceramic capacitor is very small, a deviation occurs when a conductive film serving as an internal electrode layer is formed by printing a conductive paste and when a ceramic green sheet is laminated. As a result, there is a problem that the variation in the capacitance of the multilayer ceramic capacitor is increased.

When a green sheet on which a conductor film to be the internal electrode layers 53 and 54 is formed is laminated, a gap of about 0.1 to 2 μm is formed between the portion where the internal electrode layer exists and the periphery thereof.
Since the m is raised by about m, in the unfired laminated body when compressed, the unevenness of the density distribution due to the compression becomes conspicuous at the opposing portions of the internal electrode layers 53 and 54 and at the periphery thereof. This variation in the density distribution has a problem that it appears as non-uniformity of delamination, binder removal and sinterability due to poor press bonding.

To solve these problems, as shown in FIG. 7, the length (width) of the short side of the first internal electrode layer 73 shown by the solid line is changed to the short side of the second internal electrode layer 74 shown by the solid line. Is shorter than the length (width) of the device (Japanese Patent Laid-Open No.
35, see JP-A-8-250369).

With such a configuration, the first internal electrode layer 7
3. Even if the second internal electrode layer 74 slightly deviates from the second internal electrode layer 74 due to printing deviation or lamination deviation, the amount of deviation is reduced by the first internal electrode layer 73.
And the second internal electrode layer 74 can be absorbed by the difference in shape, so that the facing area between the internal electrode layers 73 and 74 does not easily change.

Considering the density distribution of the laminated body, the density distribution becomes gentler from the periphery to the center of the laminated body as compared with FIG. Delamination, non-uniformity of binder removal and sintering are alleviated.

[0012]

However, according to the multilayer ceramic capacitor shown in FIGS. 5 to 7, the first external terminal electrodes connected to the first internal electrode layers 53 and 73 and the second internal electrode layers 54 and 73 are provided. 55 and a second external terminal electrode 56 are formed on the entire surface of a pair of opposed end surfaces of the multilayer body 51.

Accordingly, when the first external terminal electrode 55 and the second external terminal electrode 56 of the multilayer ceramic capacitor are to be joined to the printed wiring board by the reflow process with the solders 57 and 58, as shown in FIG. Solder 57, 58
There was a problem that due to the difference in the dissolution rate of, the surface tension was generated only on one side and the Manhattan phenomenon occurred.

The present invention has been devised in view of the above-mentioned problems, and an object of the present invention is to provide a multilayer ceramic capacitor capable of effectively suppressing variation in capacitance and preventing the Manhattan phenomenon. is there.

[0015]

According to the present invention, there is provided a rectangular dielectric ceramic layer having a substantially rectangular first internal electrode layer, and a substantially rectangular shape having a longer side and a shorter side shorter than the first internal electrode layer. And a rectangular dielectric ceramic layer having the second internal electrode layer is laminated to form a laminate, and a part of the first and second internal electrode layers is extended to different corners of the laminate. And a first external terminal electrode on a corner of the laminated body from which the first internal electrode layer extends so as to straddle two side surfaces forming the corner.
A multilayer ceramic capacitor, characterized in that a second external terminal electrode is formed at a corner of the laminated body from which the second internal electrode layer extends so as to straddle two side surfaces constituting the corner. is there.

[0016]

According to the present invention, the first internal electrode layer having a rectangular shape and the second
In the shape of the internal electrode layer, the shape of the second internal electrode layer is
Both the long side and the short side are smaller than the first internal electrode layer. Therefore, even if the lamination misalignment occurs when printing the first and second internal electrode layers or when laminating the green sheets to be the dielectric ceramic layers on which the first and second internal electrode layers are formed, the first internal electrode can be used. Since the opposing area between the layer and the second internal electrode layer hardly fluctuates, the variation in capacitance can be effectively suppressed.

Further, the first internal electrode layer and the second internal electrode layer are respectively extended to different corners of the laminate, and are connected to the external terminal electrodes so as to straddle two side surfaces forming the corners. Is formed. That is, the positional relationship between the first external terminal electrode connected to the first internal electrode layer and the first external terminal electrode connected to the second internal electrode layer is respectively arranged at diagonal corners of the laminate, or Are present at the corners at both ends of one side of the laminate.

Therefore, when mounting the multilayer ceramic capacitor by reflow soldering on the printed wiring board, the attractive force due to the solder attached to the external terminal electrodes can be dispersed to the two sides constituting the laminate, It does not generate enough force to cause the Manhattan phenomenon.

As a result, at least the portion where the external terminal electrodes are formed does not rise, and stable bonding of the printed wiring board can be achieved.

[0020]

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 the multilayer ceramic capacitor of the present invention, and is a schematic plan view showing the shape of the internal electrode layer of FIG.

In the figure, 10 is a multilayer ceramic capacitor, 1 is a laminate, 2 is a first external terminal electrode, and 3 is a second external terminal electrode.

The laminate 1 is composed of dielectric ceramic layers 11...
And the internal electrode layers 12 and 13 are alternately laminated.

The dielectric ceramic layers 11 are made of, for example, a dielectric material having a perovskite crystal structure containing barium titanate, strontium titanate, and lead.

The first internal electrode 12 and the second internal electrode 1
3 has a substantially rectangular shape. The electrode material is made of, for example, a metal conductor film containing Pd, Cu, Ni, or the like as a main component, although it differs depending on the material of the dielectric ceramic layers 11. The first internal electrode layer 1 having a rectangular shape is provided between the dielectric ceramic layers 11 and 11.
2 are arranged. Also, the first internal electrode layer 1 having a rectangular shape
The second internal electrode layer 13 having a rectangular shape is provided between the layers between the dielectric ceramic layers 11 and 11 where
Is arranged.

FIG. 2 shows the relationship between the first internal electrode layer 12 and the second internal electrode layer 13, wherein a solid line indicates the first internal electrode layer 12 and a dotted line indicates the second internal electrode layer 13. I have.

Here, the long side of the first internal electrode layer 12 is l,
Assuming that the short side is w, the long side of the second internal electrode layer 13 is L, and the short side is W, L> l and W> w, respectively.

The first internal electrode layer 12 extends to the upper right corner X of the rectangular dielectric ceramic layer 11 in FIG. The second internal electrode layer 13 extends to the lower left corner Y of the rectangular dielectric ceramic layer 11 in FIG.

In the shape of the first internal electrode layer 12 and the second internal electrode layer 13, the long side L of the first internal electrode layer 12 is in relation to the long side 1 of the second internal electrode layer 13, First
The short side W of the internal electrode layer 12 is the short side w of the second internal electrode layer 13.
Are larger by 50 μm or more.

Further, the width of the extended conductor width 12a derived from the first internal electrode layer 12 to the corner portion X of the multilayer body 1 and the extension of the second internal electrode layer 13 extended to the corner portion Y of the multilayer body 1. The width of the output conductor width 13a is 70 μm or more.

The relationship between the difference in side length (50 μm or more) between the first internal electrode layer 12 and the second internal electrode layer 13 and the width of the extended conductor films 12 a and 13 a being 70 μm or more is as follows. The electrode layer 12 and the second internal electrode layer 12 may have a position shift amount of about 50 due to a printing shift or a stacking shift during the manufacturing process.
μm. That is, as described above, even if a positional shift due to a print shift or a stacking shift occurs, the first internal electrode layer 12
There is no change in the area of the portion facing the second internal electrode layer 13, and the extended lead film 12 a of the first internal electrode layer 12 is located at least at the corner X. Is located at least at the corner Y.

Of the four corners of such a laminate 1,
The first external terminal electrode 2 connected to the first internal electrode layer 12 is formed at the corner X. Further, a second external terminal electrode 3 connected to the second internal electrode layer 13 is formed at a corner Y located diagonally to the corner X of the multilayer body 1.

More specifically, the first external terminal electrodes 2 are formed on two intersecting side surfaces constituting the corner X of the laminate 1 and on both main surfaces near the corner. That is, the laminate 1
When viewed from above, the first external terminal electrode 2 and the second external terminal electrode 3 have a substantially right triangular shape, and have a substantially right triangular prism shape in consideration of the thickness direction.

First external terminal electrode 2, second external terminal electrode 3
Is composed of a thick film underlying conductor containing a metal mainly composed of Ag or Cu, and a surface plating layer such as a Ni plating layer or a solder plating layer.

Then, 2 constituting the external terminal electrodes 2 and 3
The width of the base conductor film formed on one end face portion is 50 μm or more on each side from the apex of the corners X and Y, and is actually about 100 μm.

In the above-described multilayer ceramic capacitor, the multilayer ceramic capacitor is manufactured by the following manufacturing method.

First, a ceramic green sheet to be each of the dielectric ceramic layers 11 is prepared. Each ceramic green sheet is a large sheet in which a plurality of element regions are arranged side by side.

Next, a conductive film to be the first internal electrode layer 12 and the extended conductive film 12a is printed on the element region of the ceramic green sheet by using a conductive paste, and is formed by drying. On each element region of another ceramic green sheet, a conductive film to be the second internal electrode layer 13 and the extended conductive film 13a is printed using a conductive paste, and is dried and formed.

Next, taking the layer structure of the laminate 1 into consideration, the first
A green sheet on which a conductor film serving as the internal electrode layer 12 is formed and a green sheet on which a conductor film serving as the second internal electrode layer 13 are alternately laminated, and a green sheet serving as a dielectric ceramic layer is formed on the uppermost layer. The sheets are laminated and crimped. At this time, the alignment is performed such that the first internal electrode layer 12 is included in the second internal electrode layer 13 having a large outer shape formed on the adjacent green sheet.

Next, the large laminated body is cut into a predetermined size in the laminating direction according to the shape of each laminated body 1 to obtain an unfired chip material. As a result, the conductive film serving as the extended conductor film 12a of the first internal electrode layer 12 is exposed at the corner X formed by the cutting, and the extension of the second internal electrode layer 13 is exposed at the corner Y. The conductor film serving as the conductor film 13a is exposed.

Next, the chip material is fired in a predetermined atmosphere and at a predetermined temperature, so that the first internal electrode layer 12, the second internal electrode layer 13, the conductor films to be the extended conductor films 12a, 13a, and the ceramic green sheets are obtained. The laminated body 1 is formed by integrally firing. After that, if necessary, barrel polishing is performed on the end surface of the cut portion to completely expose the extended conductor films 12a and 13a.

Next, the underlying conductor films serving as the first external terminal electrode 2 and the second external terminal electrode 3 are respectively formed on the corners X and Y located on the diagonal line of the laminate 1 by a conductive material made of Ag or Ag-Pd alloy. The paste is dipped or screen-printed and baked in a predetermined atmosphere and temperature so as to obtain a desired adhesive strength. Then, a Ni plating layer made of a material that is unlikely to cause solder erosion is formed on the surface of the underlying conductor film, and a plating layer made of a material such as Sn or Sn—Pb alloy is formed on this plating layer. Thus, the multilayer ceramic capacitor 10 shown in FIG. 1 is formed.

Thus, according to the multilayer ceramic capacitor 10 of the present invention, the outer shape of the first internal electrode layer 12 is longer than the outer shape of the first internal electrode layer 12 by 50 μm or more on each of the long side and the short side. It is getting bigger. An extended conductor film 12 a having a width of 75 μm or more extends from the first internal electrode layer 12 toward the corner X of the multilayer body 1. Further, an extended conductor film 13 a having a width of 75 μm or more extends from the second internal electrode layer 13 toward the corner Y of the multilayer body 1.

Therefore, even if printing misalignment occurs when printing the first internal electrode layer 12 and the second internal electrode layer 13 described above or laminating misalignment occurs when laminating green sheets, the first internal electrode layer 12 and the second internal electrode layer 13 do not. 13 overlaps and the area of the opposing portion can be kept constant. As a result, it is possible to prevent variations in capacitance due to printing shift and stacking shift.

Further, the extended conductor film 12a extending from the first internal electrode layer 12 to the corner X, and the second internal electrode layer 13 extending from the corner Y
Since the conductor width of the extended conductor film 13a extending to the
Even if a printing shift or a stacking shift occurs during stacking of the green sheets, it is derived including at least the vertices of the corners X and Y. Then, the extended conductor films 12 a and 13 a are covered with the first external terminal electrode 2 and the second external terminal electrode 3.

Conversely, after polishing, the extended conductor film 12
The ends of the a and 13a are separated from the corners X and Y of the laminated body 1 and are exposed on the side surfaces of the laminated body 1 constituting the corners X and Y so as to be largely separated from the corners X and Y. In such a case, it is possible to detect that a fatal displacement has occurred, and it is not necessary to perform a subsequent process.

For this reason, the first and second external terminal electrodes 2,
When the surface plating layer constituting the third internal electrode layer 3 is formed, the first internal electrode layer 12 and the second internal electrode layer 1 are not affected by the plating solution at all.
3 and the dielectric ceramic layers 1a, 1b, 1c...

The first external terminal electrode 2 and the second external terminal electrode 3 have a substantially right-angled triangular prism shape as described above, and the surfaces to which the solder adheres to the printed wiring board by reflow soldering. It is at right angles. Therefore, the solder attraction generated by the melting of the solder attached to the external terminal electrodes 2 and 3 is dispersed in the normal direction of the two side surfaces forming the corners X and Y. After all, since the solder attraction can be minimized, the Manhattan phenomenon can be effectively prevented.

Further, since the outer shapes of the first internal electrode layer 12 and the second internal electrode layer 13 are different, the opposing portion between the first internal electrode layer 12 and the second internal electrode layer Since there is a density distribution relaxation region in which only the first internal electrode layer 12 or the second internal electrode layer 13 exists, between the internal electrode layer 12 and the portion where the second internal electrode layer 13 does not exist at all, Non-uniformity of the density distribution in the stacking direction is reduced,
The frequency of occurrence of a defective rate due to dielectric breakdown of the peripheral portions of the internal electrode layer 12 and the second internal electrode layer 13 can be greatly reduced. Further, since the positions of the concentrated portions of the internal stress generated in the peripheral portions of the adjacent internal electrode layers 12 and 13 are not continuous in the laminating direction but shifted, the internal defects at the time of firing are suppressed, and the thermal resistance is reduced. Shock is greatly improved.

Further, the first external terminal electrode 2 and the second external terminal electrode 3 are centered on both corners X and Y of the diagonal line of the laminate 1.
Are formed, the first external terminal electrode 2 and the second
The distance between the external terminal electrode 3 and the external terminal electrode 3 becomes longer due to the oblique side. Therefore, when the external terminal electrodes 2 and 3 are arranged on the printed wiring board, a short circuit between the external terminal electrodes 2 and 3 due to the spread of the solder hardly occurs.

FIG. 3 is an external perspective view showing another embodiment of the present invention. FIG. 4 is a plan view showing the shapes of the first internal electrode layer 32 and the second internal electrode layer 33 of the multilayer ceramic capacitor 30.

In this embodiment, the first external terminal electrode 2 ′ and the second external terminal electrode 3 are formed at both ends of one side forming the same side surface of the laminate 31.

In such a structure, the first internal electrode layer 32
The external terminal electrodes 2 and 3 are led out from the same direction as the second internal electrode layer 33. That is, 2 of different potentials
The two external terminal electrodes 2 ′ and 3 are formed at the corners at both ends of one side, and the planar current direction flowing through the first internal electrode layer 32 is opposite to that of the second internal electrode layer 33, The inductance components generated by the current flow cancel each other out. Thus, the multilayer ceramic capacitor used in a circuit operating at a high frequency has an effect of reducing inductance.

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.

[0055]

According to the present invention, the first internal electrode layer is larger than the second internal electrode layer, and the extended conductive film extends from the first internal electrode layer and the second internal electrode layer. Is extended from two corners of the laminate, and an external terminal electrode is formed from the two corners.

For this reason, even when the internal electrode layer is deviated from a predetermined position due to printing deviation of the internal electrode layer or lamination deviation of the dielectric layer, the area where the two internal electrode layers face each other is not easily changed. In addition, variations in capacitance can be prevented.

In the laminate, a region where both internal electrode layers overlap, a region around which only the first internal electrode layer exists (a region where only the extended conductor film exists), and a region where no internal electrode layer exists Therefore, the variation in the density distribution at the time of lamination and compression is alleviated, and the thermal shock resistance is improved.

Further, external terminal electrodes are provided at the corners of the laminate,
Since it is formed so as to have a triangular prism shape over the two side surfaces forming the corner, even if reflow soldering is performed to perform surface mounting on a printed wiring board, the attractive force due to solder melting is reduced in two directions. Can be dispersed. This allows
The Manhattan phenomenon can be completely prevented.

[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 schematic plan view of a dielectric ceramic layer for explaining a shape of an internal electrode layer of the multilayer ceramic capacitor of the present invention.

FIG. 3 is an external perspective view showing another embodiment of the multilayer ceramic capacitor of the present invention.

FIG. 4 is a schematic plan view of a dielectric ceramic layer for explaining a shape of an internal electrode layer of the multilayer ceramic capacitor of the present invention.

FIG. 5 is an external perspective view of a conventional multilayer ceramic capacitor.

6 is a schematic plan view of a dielectric ceramic layer for explaining a shape of an internal electrode layer of the multilayer ceramic capacitor shown in FIG.

7 is a schematic plan view of a dielectric ceramic layer for explaining a shape of another internal electrode layer of the multilayer ceramic capacitor shown in FIG.

FIG. 8 is a schematic diagram illustrating a Manhattan phenomenon that occurs when a conventional multilayer ceramic capacitor is mounted on a surface.

[Explanation of symbols]

 10 Multilayer ceramic capacitor 1 Multilayer body 12, 32 First internal electrode layer 13, 33 Second internal electrode layer 2 First external terminal electrode 3... Second external terminal electrode

Claims (1)

[Claims] 1. A rectangular dielectric ceramic layer having a substantially rectangular first internal electrode layer, and a substantially rectangular second internal electrode layer having long sides and short sides shorter than the first internal electrode layer. Forming a laminate by laminating a rectangular dielectric ceramic layer and extending a part of the first and second internal electrode layers at different corners of the laminate; A first external terminal electrode is provided on a corner of the laminate where the second internal electrode layer extends, and a corner of the laminate where the second internal electrode layer extends. Wherein a second external terminal electrode is formed so as to straddle two side surfaces forming the corner portion.