Laminated ceramic capacitor

The present invention relates to a laminated ceramic capacitor.

As a laminated ceramic capacitor, there is known a laminated ceramic capacitor having a plurality of terminal pairs, for example. A ceramic capacitor having a plurality of terminal pairs is used for decoupling a central processing unit (CPU) of a personal computer, and the like. For example, Patent Literature 1 (Japanese published patent application No. 2002-184647) has disclosed an internal electrode pattern of a laminated ceramic capacitor having eight terminals and a method for manufacturing the same.

And Patent Literature 2 (Japanese published patent application No. 2003-31435) has disclosed a laminated ceramic capacitor having eight terminals, being provided with a filling layer (dummy electrode) in a part having no lead electrode provided in it in order to prevent a ceramic dielectric layer from being depressed.

While a conventional laminated ceramic capacitor having no plural terminal pairs has an internal electrode exposed at a side face of a ceramic body on every second layer, a laminated ceramic capacitor having a plurality of terminal pairs, for example, a laminated ceramic capacitor having eight terminals has an internal electrode exposed at a side of a ceramic body on every eighth layer.

Therefore, a laminated ceramic capacitor having a plurality of terminal pairs has had a problem that defective connections occur frequently between internal and terminal electrodes and the yield rate of it is worsened due to a smaller number of internal electrodes exposed at a side of a ceramic body in comparison with a conventional laminated ceramic capacitor.

Further, with the miniaturization of a laminated ceramic capacitor, since a part to be exposed at a side of a ceramic body and connected to a terminal electrode is made smaller, a conventional laminated ceramic capacitor also has had a problem that defective connection to a terminal electrode occurs frequently.

An object of the present invention is to provide a laminated ceramic capacitor being capable of reducing defective connections between internal electrodes and terminal electrodes.

Another object of the present invention is to provide a laminated ceramic capacitor being capable of reducing occurrence of delamination.

Yet another object of the present invention is to provide a laminated ceramic capacitor being capable of reducing occurrence of cracks.

Still another object of the present invention is to provide a laminated ceramic capacitor being better in yield rate.

In order to achieve the above-mentioned objects, a laminated ceramic capacitor according to the present invention comprises a ceramic body, internal electrodes and dummy electrodes.

The internal electrodes are plural in number, each of them includes a facing electrode and a lead electrode, and these internal electrodes are laid in layers at spaces in the direction of thickness of the ceramic body.

A facing electrode is an electrode for acquiring a capacitance.

A lead electrode has one end connected with a facing electrode and the other end led out at a side of the ceramic body to form a lead portion.

A dummy electrode is provided separately from an internal electrode in a layer where the internal electrode and is led out to a side face of the ceramic body to form a lead portion.

The lead portion of a lead electrode of each layer is superposed over the lead portion of a dummy electrode belonging to another layer in the direction of thickness.

A laminated ceramic capacitor according to the present invention described above comprises internal electrodes. The internal electrodes are plural in number, each of them includes a facing electrode and a lead electrode, and these internal electrodes are laid in layers at spaces in the direction of thickness of a ceramic body. A facing electrode is an electrode for acquiring a capacitance. A lead electrode one end connected with a facing electrode and the other end led out to a side of the ceramic body to form a lead portion. The above-described structure connects a lead portion of a lead electrode led out to a side face of the ceramic body to a terminal electrode and thereby forms a laminated ceramic capacitor.

A laminated ceramic capacitor according to the present invention comprises dummy electrodes. Since a dummy electrode is provided in a layer where an internal electrode is provided, the difference in level caused by the raised internal electrode is reduced by the dummy electrode. Due to this, a strain in a ceramic body or an internal electrode is reduced and occurrence of delamination or cracks is reduced and thereby the yield rate is improved.

For example, a lead electrode of each layer is provided so as not to be superposed over at least one of lead electrodes belonging to other layers in the direction of thickness. Due to this, by providing a dummy electrode at a location being provided with no lead electrode and superposed over at least one of lead electrodes belonging to other layers, the difference in level caused by a raised lead electrode is reduced and the occurrence of delamination or cracks results in being reduced. Preferably every layer provided with a lead electrode has the above-described structure.

And since a dummy electrode is provided separately from an internal electrode, it has no influence on the electric characteristics.

Further, in a dummy electrode, one end of it is led out at a side face to form a lead portion. The lead portion of a lead electrode of each layer is superposed over the lead portion of at least one of dummy electrodes belonging to other layers. Due to this, lead portions of dummy electrodes and lead portions of lead electrodes come to be respectively aligned with one another at a side of a ceramic body along the direction of thickness.

Due to this, terminal electrodes formed along the direction of thickness can be connected to the lead electrodes and dummy electrodes aligned along the direction of thickness. Thanks to this, a laminated ceramic capacitor according to the present invention is improved in joining strength between internal electrodes and terminal electrodes by joining strength between dummy electrodes and terminal electrodes, and as a result the connection state is made better.

On the other hand, since a laminated ceramic capacitor disclosed in Patent Literature 2 for example has dummy electrodes not reaching an end of a ceramic body, in a capacitor having eight lead electrodes a lead electrode exposed at a side face of a ceramic body has a gap formed by seven layers in the direction of thickness and therefore is liable to make a defective connection with a terminal electrode.

Other features and their actions and effects of the present invention are described in more detail by means of embodiments with reference to the accompanying drawings.

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

FIG. 2 is an opened-up perspective view showing the laminated ceramic capacitor shown in FIG. 1 .

FIG. 3 is an exploded perspective view showing the structure of internal electrodes and dummy electrodes of the laminated ceramic capacitor shown in FIGS. 1 and 2 .

FIG. 4 is a magnified right side view of the laminated ceramic capacitor shown in FIG. 2 .

FIG. 5 is an opened-up plan view of the laminated ceramic capacitor shown in FIGS. 1 and 2 .

FIG. 6 is an opened-up perspective view showing another embodiment of a laminated ceramic capacitor according to the present invention.

FIG. 7 is an opened-up plan view of the laminated ceramic capacitor shown in FIG. 6 .

FIG. 8 is an opened-up perspective view showing further another embodiment of a laminated ceramic capacitor according to the present invention.

FIG. 9 is an opened-up plan view of the laminated ceramic capacitor shown in FIG. 8 .

FIG. 10 is an opened-up perspective view showing still another embodiment of a laminated ceramic capacitor according to the present invention.

FIG. 11 is an opened-up plan view of the laminated ceramic capacitor shown in FIG. 10 .

FIG. 12 is a figure for explaining a method for manufacturing a laminated ceramic capacitor according to the present invention.

FIG. 13 is another figure for explaining a method for manufacturing a laminated ceramic capacitor according to the present invention.

FIG. 14 is still another figure for explaining a method for manufacturing a laminated ceramic capacitor according to the present invention.

A laminated ceramic capacitor illustrated is a laminated ceramic capacitor having a plurality of terminal pairs and is used in CPU decoupling and the like, for example.

As shown in FIGS. 1 to 5 , a laminated ceramic capacitor comprises a ceramic body 1 , internal electrodes A 1 to D 1 and A 2 to D 2 , dummy electrodes 51 to 58 , and terminal electrodes 21 to 28 . The ceramic body 1 includes a ceramic dielectric.

In FIG. 3 , the internal electrodes A 1 to D 1 and A 2 to D 2 each comprise one of lead electrodes a 1 to d 1 and a 2 to d 2 and a facing electrode 4 , and are laid in layers at spaces in the direction of thickness of the ceramic body 1 . The internal electrodes A 1 and A 2 , B 1 and B 2 , C 1 and C 2 , and D 1 and D 2 respectively have the same shape as each other in pairs, and are turned from each other by 180 degrees in lamination.

In FIG. 3 , the internal electrodes A 1 to D 1 and A 2 to D 2 are laminated one over another with ceramic body 1 between them in order of A 1 , B 1 , C 1 , D 1 , A 2 , B 2 , C 2 and D 2 from below. The shapes and the number of layers of internal electrodes are optional. Two or more internal electrodes may be provided in one lamination layer.

The facing electrodes 4 are electrodes for acquiring a capacitance and face each other in lamination. The lead electrodes a 1 to d 1 and a 2 to d 2 each have one end connected to a facing electrode 4 and the other end led out to a side face of the ceramic body 1 to form a lead portion. The side face may be one of the right side, left side, front and back faces, and two or more side faces may be provided. The number of lead electrodes exposed at a side face of the ceramic body 1 may be one, two or more in one lamination layer. Two or more lead electrodes may be provided in one internal electrode.

In the figure, lead electrodes a 1 to d 1 are led out to the right side face, and lead electrodes a 2 to d 2 are led out to the left side face. In an embodiment, lead electrodes a 1 to d 1 and a 2 to d 2 are provided so as not to be superposed over lead electrodes a 1 to d 1 and a 2 to d 2 belonging to another layer in the direction of thickness.

The dummy electrodes 51 to 58 are respectively provided separately by spaces from the internal electrodes A 1 to D 1 and A 2 to D 2 in layers provided with the internal electrodes A 1 to D 1 and A 2 to D 2 . One end of each of the dummy electrodes 51 to 58 is led out to a side face to form a lead portion, and the dummy electrodes 51 to 58 of the respective layers are respectively superposed one over another in the direction of thickness. The widths of parts of the dummy electrodes 51 to 58 led out to a side face respectively correspond to the widths of parts of the internal electrodes a 1 to d 1 and a 2 to d 2 led out to a side face.

The dummy electrodes 51 to 58 are provided at locations of each layer in which the lead electrodes a 1 to d 1 and a 2 to d 2 are not provided and which are superposed over the lead electrodes a 1 to d 1 and a 2 to d 2 belonging to other layers in the direction of thickness. And the lead portion of the lead electrode a 1 to d 1 or a 2 to d 2 in each layer is superposed over the lead portion of the dummy electrode 51 to 58 belonging to another layer in the direction of thickness.

For example, in FIG. 3 , dummy electrodes 51 , 52 and 54 to 58 are provided in a layer provided with internal electrode C 1 , dummy electrodes 51 to 53 and 55 to 58 are provided in a layer provided with internal electrode D 1 , dummy electrodes 52 to 58 are provided in a layer provided with internal electrode A 1 , dummy electrodes 51 and 53 to 58 are provided in a layer provided with internal electrode B 1 , dummy electrodes 51 to 54 and 56 to 58 are provided in a layer provided with internal electrode A 2 , dummy electrodes 51 to 55 , 57 and 58 are provided in a layer provided with internal electrode B 2 , dummy electrodes 51 to 56 and 58 are provided in a layer provided with internal electrode C 2 , and dummy electrodes 51 to 57 are provided in a layer provided with internal electrode D 2 .

Referring to FIG. 1 again, terminal electrodes 21 to 24 are connected to lead electrodes a 1 to d 1 and dummy electrodes 51 to 54 on the right side, and terminal electrodes 25 to 28 are connected to lead electrodes a 2 to d 2 and dummy electrodes 55 to 58 on the left side.

A laminated ceramic capacitor according to this embodiment described above comprises internal electrodes A 1 to D 1 and A 2 to D 2 . The internal electrodes A 1 to D 1 and A 2 to D 2 are plural in number, and each of them includes a facing electrode 4 and a lead electrode a 1 to d 1 or a 2 to d 2 , and they are laid in layers at spaces in the direction of thickness of a ceramic body 1 . The facing electrode 4 is an electrode for acquiring a capacitance. Each of the lead electrodes a 1 to d 1 and a 2 to d 2 has one end connected to a facing electrode 4 and the other end led out to a side face of a ceramic body 1 to form a lead portion. Due to this, the lead portions of the lead electrodes a 1 to d 1 and a 2 to d 2 led out to a side face of the ceramic body 1 are connected to terminal electrodes for example to form a laminated ceramic capacitor.

A laminated ceramic capacitor according to the present invention comprises dummy electrodes 51 to 58 . Since dummy electrodes 51 to 58 are provided separately from internal electrode A 1 to D 1 or A 2 to D 2 in a layer where the internal electrode A 1 to D 1 or A 2 to D 2 is provided, the difference in level caused by a raised internal electrode is reduced by the dummy electrodes 51 to 58 . Due to this, a strain in ceramic body 1 or internal electrode A 1 to D 1 or A 2 to D 2 is reduced and the occurrence of delamination or cracks is reduced and thereby the yield rate is improved.

For example, a lead electrode a 1 to d 1 or a 2 to d 2 of each layer is provided so as not to be superposed over lead electrodes a 1 to d 1 and a 2 to d 2 belonging to other layers in the direction of thickness. Due to this, by providing dummy electrodes 51 to 58 at locations being not provided with lead electrodes a 1 to d 1 and a 2 to d 2 and being superposed over lead electrodes a 1 to d 1 and a 2 to d 2 belonging to other layers in the direction of thickness, the difference in level caused by a raised lead electrode is reduced and the occurrence of delamination or cracks results in being reduced. Preferably every layer provided with a lead electrode a 1 to d 1 or a 2 to d 2 has the above-described structure.

And since dummy electrodes 51 to 58 are provided separately from an internal electrode A 1 to D 1 or A 2 to D 2 , they have no influence on the electric characteristics.

Further, each of dummy electrodes 51 to 58 has one end led out to a side face to form a lead portion. The lead portion of a lead electrode a 1 to d 1 or a 2 to d 2 of each layer is superposed over the lead portion of at least one of dummy electrodes 51 to 58 belonging to another layer in the direction of thickness. Due to this, the lead portions of dummy electrodes 51 to 58 and the lead portions of lead electrodes a 1 to d 1 and a 2 to d 2 come to be respectively aligned with one another at a side of a ceramic body 1 along the direction of thickness.

Due to this, terminal electrodes formed along the direction of thickness can be connected to the lead electrodes a 1 to d 1 and a 2 to d 2 and dummy electrodes 51 to 58 aligned along the direction of thickness. The joining strength between internal electrodes A 1 to D 1 and A 2 to D 2 and terminal electrodes is increased by the joining strength between dummy electrodes 51 to 58 and terminal electrodes, and as a result the connection state is made better.

On the other hand, since a laminated ceramic capacitor disclosed in Patent Literature 2 for example has dummy electrodes not reaching an end of a ceramic body, in a capacitor having eight lead electrodes a lead electrode exposed at a side face of a ceramic body has a gap formed by seven layers in the direction of thickness and therefore is liable to make a defective connection with a terminal electrode.

And in a laminated ceramic capacitor illustrated, dummy electrodes 5 are formed on only the areas corresponding to areas where lead electrodes a 1 to d 1 and a 2 to d 2 or dummy electrodes 51 to 58 belonging to other layers are formed, being seen along the direction of thickness. Due to this, a ceramic body 1 can be firmly joined in areas where a lead electrode a 1 to d 1 or a 2 to d 2 and dummy electrodes 5 are not formed in each layer.

And since a laminated ceramic capacitor according to the present invention makes it possible to form dummy electrodes in the same process as a process of forming an internal electrode for example, it can be manufactured without making its manufacturing process complicated.

Further, a laminated ceramic capacitor according to the present invention allows auxiliary layers made of the same material as a ceramic body 1 and equal in thickness to internal electrodes A 1 to D 1 and A 2 to D 2 and dummy electrodes 51 to 58 to be provided in areas where the internal electrodes and the dummy electrodes are not provided. In this case, since the difference in level caused by raised electrodes can be more flattened in each of layers where internal electrodes A 1 to D 1 and A 2 to D 2 are formed, it is possible to more reduce the occurrence of delamination or cracks.

Table 1 shows the result of examining the occurrence ratios of delamination, crack and defective connection for 10,000 laminated ceramic capacitors according to the present invention and 10,000 comparative example laminated ceramic capacitors.

The laminated ceramic capacitor of embodiment 1 is a laminated ceramic capacitor according to the present invention shown in FIGS. 1 to 5 . Comparative example 1 is different from the laminated ceramic capacitor of embodiment 1 in having no dummy electrodes. Comparative example 2 is different from the laminated ceramic capacitor of embodiment 1 in that dummy electrodes are not exposed at a side face of a ceramic body.

Referring to Table 1, comparative example 1 is as very high as 1.0% in the occurrence ratios of delamination, crack and defective connection. Comparative example 2 is so high in occurrence ratio that the occurrence ratios of delamination and crack are 0.3% and the occurrence ratio of defective connection is 0.5%.

On the contrary, embodiment 1 is so sufficiently low in occurrence ratio that the occurrence ratios of delamination and crack are 0.2% and the occurrence ratio of defective connection is 0.1%. Particularly, a very low occurrence ratio of defective connection being one-fifth of comparative example 2 and one-tenth of comparative example 1 has been obtained.

FIG. 6 is an opened-up perspective view showing another embodiment of a laminated ceramic capacitor according to the present invention, and FIG. 7 is an opened-up plan view of the laminated ceramic capacitor shown in FIG. 6 . In these figures, the same components as the components shown in FIGS. 1 to 5 are given the same reference symbols and the repeated description is omitted.

In FIGS. 6 and 7 , a laminated ceramic capacitor illustrated comprises internal electrodes A 1 to D 1 and A 2 to D 2 and dummy electrodes 51 to 58 . The internal electrodes A 1 to D 1 and A 2 to D 2 include facing electrodes 4 and lead electrodes a 1 to d 1 and a 2 to d 2 .

Lead electrodes b 1 and c 1 and dummy electrodes 52 and 53 are led out to the right side face, lead electrodes b 2 and c 2 (not illustrated) and dummy electrodes 56 and 57 are led out to the left side face, lead electrodes a 1 (not illustrated) and d 2 and dummy electrodes 51 and 58 (not illustrated) are led out to the rear face, and lead electrodes a 2 and d 1 and dummy electrodes 54 and 55 are led out to the front face.

Since the laminated ceramic capacitor illustrated has a similar structure to the laminated ceramic capacitor shown in FIGS. 1 to 5 , it can provide a similar effect.

FIG. 8 is an opened-up perspective view showing further another embodiment of a laminated ceramic capacitor according to the present invention, and FIG. 9 is an opened-up plan view of the laminated ceramic capacitor shown in FIG. 8 . In these figures, the same components as shown in FIGS. 1 to 7 are given the same reference symbols and the repeated description is omitted.

In FIGS. 8 and 9 , the laminated ceramic capacitor illustrated comprises internal electrodes A 1 , D 1 , A 2 and D 2 and dummy electrodes 51 , 54 , 55 and 58 . The internal electrodes A 1 , D 1 , A 2 and D 2 include lead electrodes a 1 , d 1 , a 2 and d 2 .

The internal electrodes A 1 , D 1 , A 2 and D 2 are stacked one over another with ceramic body 1 between them in order of D 1 , A 1 , A 2 , D 2 , D 1 , A 1 , A 2 and D 2 from below. Lead electrodes a 1 and d 1 and dummy electrodes 51 and 54 are led out to the right side face, and lead electrodes a 2 (not illustrated) and d 2 and dummy electrodes 55 and 58 (not illustrated) are led out to the left side face.

Since the laminated ceramic capacitor illustrated has a similar structure to the laminated ceramic capacitor shown in FIGS. 1 to 7 , it can provide a similar effect.

FIG. 10 is an opened-up perspective view showing still another embodiment of a laminated ceramic capacitor according to the present invention, and FIG. 11 is an opened-up plan view of the laminated ceramic capacitor shown in FIG. 10 . In these figures, the same components as shown in FIGS. 1 to 9 are given the same reference symbols and the repeated description is omitted.

In FIGS. 10 and 11 , the laminated ceramic capacitor illustrated comprises internal electrodes A 1 , D 1 , A 2 and D 2 and dummy electrodes 51 , 54 , 55 and 58 . The internal electrodes A 1 , D 1 , A 2 and D 2 are stacked one over another with ceramic body 1 between them in order of D 1 , A 1 , A 2 , D 2 , D 1 , A 1 , A 2 and D 2 from below.

Lead electrode d 1 and dummy electrode 54 are led out to the right side face, lead electrodes a 2 and dummy electrode 55 are led out to the front face, lead electrode d 2 and dummy electrode 58 (not illustrated) are led out to the left side face, and lead electrodes a 1 (not illustrated) and dummy electrode 51 are led out to the rear face.

Since the laminated ceramic capacitor illustrated has a similar structure to the laminated ceramic capacitor shown in FIGS. 1 to 9 , it can provide a similar effect.

Next, a method for manufacturing a laminated ceramic capacitor shown in FIGS. 1 to 5 is described with reference to FIGS. 12 to 14 .

First, in FIG. 12 a feed roll 81 rotates in the direction of arrow R 1 and a take-up roll 82 rotates in the direction of arrow R 2 . A belt-shaped support 86 is stretched between the feed roll 81 and the take-up roll 82 . The support 86 is formed out of a flexible plastic film for example and carries a ceramic green sheet 91 in the direction of arrow F 1 .

A printing device 83 and a receiving stand 85 print internal electrodes A 1 to D 1 and A 2 to D 2 and dummy electrodes 51 to 58 onto the ceramic green sheet 91 . The printing can use screen printing, gravure printing, offset printing and the like.

FIG. 13 shows internal electrodes A 1 to D 1 and dummy electrodes 51 to 58 printed by the printing device 83 . In the figure, in the ceramic green sheet 91 , dummy electrodes 51 to 58 and internal electrodes A 1 (A 2 ) and B 1 (B 2 ) are repeatedly printed on odd lines, and dummy electrodes 51 to 58 and internal electrodes C 1 (C 2 ) and D 1 (D 2 ) are repeatedly printed on even lines. The internal electrodes A 2 to D 2 are obtained by turning the internal electrodes A 1 to D 1 by 180 degrees.

In FIG. 12 again, a ceramic green sheet 91 having electrodes printed on it goes through a drying process performed by a drying device 84 and is taken up by the take-up roll 82 .

Next, as shown in FIG. 14 , the ceramic green sheet 91 taken up by the take-up roll 82 is blanked out into a specified size and the pieces of ceramic green sheet obtained by the blanking process are stacked one over another on a stacking stand 92 . In the figure, reference symbol A shows an internal electrode A 1 or A 2 , reference symbol B shows an internal electrode B 1 or B 2 , reference symbol C shows an internal electrode C 1 or C 2 , and reference symbol D shows an internal electrode D 1 or D 2 .

The stacked ceramic green sheet 91 is cut between the internal electrodes A 1 to D 1 and A 2 to D 2 , is baked, and is given terminal electrodes 21 to 28 (see FIG. 1 ) to form a laminated ceramic capacitor shown in FIG. 1 .

As shown in FIGS. 13 and 14 , in the manufacturing method, the internal electrodes A 1 , B 1 , C 1 and D 1 are patterned on one prepress. Accordingly, by offsetting pattern of the prepress, the internal electrodes A 1 , B 1 , C 1 , D 1 , A 2 , B 2 , C 2 and D 2 are laminated in above order and a laminated object is provided. Therefore, it is possible to simplify the manufacturing process and easily manufacture a capacitor.

And the manufacturing method illustrated can form dummy electrodes 51 to 58 in the same process as a process of forming internal electrodes A 1 to D 1 and A 2 to D 2 . Due to this, it is possible to simplify the manufacturing process and easily manufacture a capacitor.

As described above, although the contents of the present invention have been concretely described with reference to the preferred embodiments, it is self-evident to the people in this technical field to be capable of taking various variations on the basis of the basic technical idea and teachings of the present invention.