Ceramic electronic component

A ceramic electronic component includes a plurality of first reinforcement layers. The plurality of first reinforcement layers are arranged in a first outer layer portion so as to extend in the length direction and in the width direction, and are stacked in the thickness direction. The volume proportion of the plurality of first reinforcement layers in a region of the ceramic body in which the plurality of first reinforcement layers are provided is greater than the volume proportion of the first and second internal electrodes in an effective portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ceramic electronic component.

2. Description of the Related Art

With the recent reduction in the size and thickness of electronic devices, such as mobile phones and portable music players, wiring boards mounted in the electronic devices have become increasingly compact. Accordingly, ceramic electronic components mounted on the wiring boards have also become smaller and thinner.

In the related art, ceramic electronic components having rectangular-parallelepiped ceramic bodies have a relatively high mechanical strength, whereas ceramic electronic components having thin flat ceramic bodies have a relatively low mechanical strength. Furthermore, the mechanical strength of the ceramic electronic components tends to decrease as the thickness of the ceramic bodies decrease. Therefore, it is a problem to increase the mechanical strength of a ceramic electronic component that includes a flat ceramic body.

Examples of a method for increasing the mechanical strength of a ceramic electronic component include a method for forming reinforcement conductor layers (buffer layers) in a ceramic body, as described in Japanese Unexamined Patent Application Publication No. 11-26295.

However, even reinforcement conductor layers provided in a ceramic body may not sufficiently prevent the occurrence of cracks in a ceramic electronic component. Therefore, it is difficult to sufficiently improve the mechanical durability of the ceramic electronic component.

SUMMARY OF THE INVENTION

Accordingly, preferred embodiments of the present invention provide a ceramic electronic component with high mechanical durability.

According to a preferred embodiment of the present invention, a ceramic electronic component preferably includes a ceramic body having a substantially rectangular parallelepiped shape, a first internal electrode, and a second internal electrode. The ceramic body includes a first main surface, a second main surface, a first side surface, a second side surface, a first end surface, and a second end surface. The first main surface and the second main surface extend in a length direction of the ceramic body and in a width direction of the ceramic body. The first side surface and the second side surface extend in the length direction and in a thickness direction of the ceramic body. The first end surface and the second end surface extend in the width direction and in the thickness direction. The first internal electrode and the second internal electrode are provided inside the ceramic body. The first internal electrode and the second internal electrode extend in the length direction and in the width direction. The first internal electrode and the second internal electrode face each other in the thickness direction. The ceramic body includes an effective portion in which the first internal electrode and the second internal electrode face each other in the thickness direction, a first outer layer portion that is located closer to the first main surface than the effective portion, and a second outer layer portion that is located closer to the second main surface than the effective portion. The ceramic electronic component preferably further includes a plurality of first reinforcement layers. The plurality of first reinforcement layers are provided in the first outer layer portion so as to extend in the length direction and in the width direction, and are stacked in the thickness direction. A volume proportion of the plurality of first reinforcement layers in a region of the ceramic body in which the plurality of first reinforcement layers are provided is preferably greater than a volume proportion of the first internal electrode and the second internal electrode in the effective portion.

In the ceramic electronic component, the number of first reinforcement layers may preferably be greater than the total number of first and second internal electrodes.

In the ceramic electronic component, a distance between first reinforcement layers that are adjacent in the thickness direction among the plurality of first reinforcement layers may preferably be less than a distance between the first internal electrode and the second internal electrode that are adjacent in the thickness direction.

In the ceramic electronic component, each of the plurality of first reinforcement layers may preferably have a thickness greater than the first internal electrode or the second internal electrode.

In the ceramic electronic component, each of the plurality of first reinforcement layers may preferably be made of a metal or an alloy, for example. That is, in a preferred embodiment of the present invention, the reinforcement layer may be made of a conductor layer.

The ceramic electronic component may preferably further include a plurality of second reinforcement layers that are provided in the second outer layer portion so as to extend in the length direction and in the width direction and that are stacked in the thickness direction. A volume proportion of the plurality of second reinforcement layers in a region of the ceramic body where the plurality of second reinforcement layers are provided may preferably be greater than a volume proportion of the first internal electrode and the second internal electrode in the effective portion.

According to another preferred embodiment of the present invention, a ceramic electronic component preferably includes a ceramic body having a rectangular parallelepiped, a first internal electrode, and a second internal electrode. The ceramic body includes a first main surface, a second main surface, a first side surface, a second side surface, a first end surface, and a second end surface. The first main surface and the second main surface extend in a length direction of the ceramic body and in a width direction of the ceramic body. The first side surface and the second side surface extend in the length direction and in a thickness direction of the ceramic body. The first end surface and the second end surface extend in the width direction and in the thickness direction. The first internal electrode and the second internal electrode are provided inside the ceramic body. The first internal electrode and the second internal electrode extend in the length direction and in the width direction. The first internal electrode and the second internal electrode face each other in the thickness direction. The ceramic body includes an effective portion where the first internal electrode and the second internal electrode face each other in the thickness direction, a first outer layer portion that is located closer to the first main surface than the effective portion, and a second outer layer portion that is located closer to the second main surface than the effective portion. The ceramic electronic component preferably further includes a plurality of first reinforcement layers. The plurality of first reinforcement layers are provided in the first outer layer portion so as to extend in the length direction and in the width direction, and are stacked in the thickness direction. The number of first reinforcement layers is preferably greater than the total number of first and second internal electrodes.

In the ceramic electronic component, a distance between first reinforcement layers that are adjacent in the thickness direction among the plurality of first reinforcement layers may be smaller than a distance between the first internal electrode and the second internal electrode that are adjacent in the thickness direction.

In the ceramic electronic component, each of the plurality of first reinforcement layers may preferably have a thickness greater than the first internal electrode or the second internal electrode.

In the ceramic electronic component, each of the plurality of first reinforcement layers may preferably be made of a metal or an alloy, for example.

The ceramic electronic component may preferably further include a plurality of second reinforcement layers that are provided in the second outer layer portion so as to extend in the length direction and in the width direction and that are stacked in the thickness direction. The number of second reinforcement layers may preferably be greater than the total number of first and second internal electrodes.

According to a preferred embodiment of the present invention, the volume proportion of a plurality of first reinforcement layers in a region of a ceramic body in which the plurality of first reinforcement layers are provided is greater than the volume proportion of first and second internal electrodes in an effective portion. Alternatively, the number of first reinforcement layers may be greater than the total number of first and second internal electrodes. Therefore, the rigidity of the region of the ceramic body in which the plurality of first reinforcement layers are provided is high, which results in high mechanical durability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

A first preferred embodiment of the present invention will be described hereinafter in the context of a ceramic electronic component1illustrated inFIG. 1, by way of example. However, the ceramic electronic component1is merely illustrative. Preferred embodiments of the present invention are not limited to the ceramic electronic component1described below and a method for manufacturing the ceramic electronic component1.

FIG. 1is a schematic perspective view of a ceramic electronic component according to a first preferred embodiment of the present invention.FIG. 2is a schematic side view of the ceramic electronic component according to the first preferred embodiment.FIG. 3is a schematic cross-sectional view taken along line III-III inFIG. 1.FIG. 4is a schematic cross-sectional view of an enlarged portion of the ceramic electronic component according to this preferred embodiment.FIG. 5is a schematic cross-sectional view taken along line V-V inFIG. 3.FIG. 6is a schematic cross-sectional view taken along line VI-VI inFIG. 3.FIG. 7is a schematic cross-sectional view taken along line VII-VII inFIG. 3.

First, the configuration of the ceramic electronic component1will be described with reference toFIGS. 1 to 7.

As illustrated inFIGS. 1 to 7, the ceramic electronic component1includes a ceramic body10. The ceramic body10is made of an appropriate ceramic material in accordance with the functionality of the ceramic electronic component1. Specifically, when the ceramic electronic component1is a capacitor, the ceramic body10may preferably be made of a dielectric ceramic material. Specific examples of the dielectric ceramic material include BaTiO3, CaTiO3, SrTiO3, and CaZrO3. The ceramic body10may preferably include any of the ceramic materials described above as a main component, and, as sub-components, for example, a Mn compound, a Mg compound, a Si compound, a Fe compound, a Cr compound, a Co compound, a Ni compound, a rare-earth compound, and other suitable sub-components may be optionally added in accordance with the desired characteristics of the ceramic electronic component1.

When the ceramic electronic component1is a ceramic piezoelectric element, the ceramic body10may preferably be made of a piezoelectric ceramic material. Specific examples of the piezoelectric ceramic material include lead zirconate titanate (PZT) ceramic materials.

When the ceramic electronic component1is a thermistor element, the ceramic body10may preferably be made of a semiconductor ceramic material. Specific examples of the semiconductor ceramic material include spinel ceramic materials.

When the ceramic electronic component1is an inductor element, the ceramic body10may preferably be made of a magnetic ceramic material. Specific examples of the magnetic ceramic material may include ferrite ceramic materials.

In the following description of this preferred embodiment, the ceramic electronic component1is a ceramic capacitor, by way of example. More specifically, in this preferred embodiment, by way of example, the ceramic electronic component1is a ceramic capacitor having a relatively low capacitance of about 0.1 nF to about 100 nF.

The ceramic body10preferably has a substantially rectangular parallelepiped shape. As illustrated inFIGS. 1 to 7, the ceramic body10includes a first main surface10a, a second main surface10b, a first side surface10c, a second side surface10d, a first end surface10e, and a second end surface10f. As illustrated inFIGS. 1 to 3, the first and second main surfaces10aand10bextend in the length direction L and in the width direction W. As illustrated inFIGS. 1 and 5to7, the first and second side surfaces10cand10dextend in the thickness direction T and in the length direction L. As illustrated inFIGS. 2 to 7, the first and second end surfaces10eand10fextend in the thickness direction T and in the width direction W.

The term “rectangular parallelepiped” or “substantially rectangular parallelepiped”, as used herein, includes a rectangular parallelepiped shape with chamfered or R-chamfered corners or edges. That is, the term “rectangular parallelepiped member” or “substantially rectangular parallelepiped member” means a member including first and second main surfaces, first and second side surfaces, and first and second end surfaces. Further, a portion or the entirety of the main surfaces, the side surfaces, and the end surfaces may include irregularities. That is, the main surfaces, the side surfaces, and the end surfaces may not necessarily be flat.

The dimensions of the ceramic body10are not particularly limited. However, the ceramic body10is preferably thin, satisfying T≦W<L, about ⅕ W≦T≦about ½ W, and T≦about 0.3 mm, where T, L, and W denote the thickness, length, and width of the ceramic body10, respectively. Specifically, the dimensions of the ceramic body10are preferably, about 0.1 mm T≦about 0.3 mm, about 0.4 mm≦L≦about 1 mm, and about 0.2 mm≦W≦about 0.5 mm, for example.

The thickness of a ceramic layer10gis not particularly limited. The thickness of the ceramic layer10gmay preferably be in the range of, for example, about 0.5 μm to about 10 μm.

As illustrated inFIG. 3, in the ceramic body10, a plurality of first substantially rectangular internal electrodes11and a plurality of second substantially rectangular internal electrodes12are alternately arranged at equal or substantially equal intervals in the thickness direction T. Each of the first internal electrodes11and the second internal electrodes12is substantially parallel to the first main surface10aand the second main surface10b.

As illustrated inFIGS. 3 and 5, the first internal electrodes11are arranged so as to extend in the length direction L and in the width direction W. The first internal electrodes11are exposed from the first end surface10eof the ceramic body10, and extend from the first end surface10etoward the second end surface10f. The first internal electrodes11do not extend to the second end surface10f, the first side surface10c, or the second side surface10d. The second internal electrodes12are also arranged so as to extend in the length direction L and in the width direction W. As illustrated inFIGS. 3 and 6, the second internal electrodes12are exposed from the second end surface10fof the ceramic body10, and extend from the second end surface10ftoward the first end surface10e. The second internal electrodes12do not extend to the first end surface10e, the first side surface10c, or the second side surface10d. The first and second internal electrodes11and12are arranged at the same or substantially the same position in the width direction W. Thus, the first internal electrodes11and the second internal electrodes12face each other with the ceramic layer10gdisposed therebetween in a central portion of the ceramic body10in the length direction L. In both end portions of the ceramic body10in the length direction L, the first internal electrodes11and the second internal electrodes12do not face each other in the thickness direction T.

A portion of the ceramic body10in which the first internal electrodes11and the second internal electrodes12face each other defines an effective portion10A that functions as a capacitor. A portion of the ceramic body10that is located closer to the first main surface10athan the effective portion10A defines a first outer layer portion10B, and a portion of the ceramic body10that is located closer to the second main surface10bthan the effective portion10A defines a second outer layer portion10C.

As described above, since the ceramic electronic component1is a ceramic capacitor having a relatively low capacitance, the proportion of the effective portion10A in the ceramic body10is relatively small. The length of the effective portion10A in the thickness direction T is, for example, preferably about 0.1 times to about 0.5 times the maximum length of the ceramic body10in the thickness direction T. The length of the effective portion10A in the length direction L is, for example, preferably about 0.2 times to about 0.7 times the maximum length of the ceramic body10in the length direction L.

Further, preferably, for example, one to ten pairs of first and second internal electrodes11and12(one first internal electrode11and one second internal electrode12, i.e., two internal electrodes in total, to ten first internal electrodes11and ten second internal electrodes12, i.e., twenty internal electrodes in total) are provided.

Furthermore, as in this preferred embodiment, in a ceramic capacitor having a relatively low capacitance, the distance between first and second internal electrodes may preferably be equal to two to eight ceramic layers10g, for example.

The ceramic body10also preferably includes first and second dummy electrodes18and19. The first dummy electrodes18are provided at the same position as the first internal electrodes11in the thickness direction T so as to face the first internal electrodes11at intervals in the length direction L. Thus, the same number of first dummy electrodes18as the number of first internal electrodes11is preferably provided. The second dummy electrodes19are provided at the same position as the second internal electrodes12in the thickness direction T so as to face the second internal electrodes12at intervals in the length direction L. Thus, the same number of second dummy electrodes19as the number of second internal electrodes12is provided. The first and second dummy electrodes18and19do not substantially contribute to the production of electrical characteristics of the ceramic electronic component1.

The material of the first and second internal electrodes11and12and the material of the first and second dummy electrodes18and19are not particularly limited. Each of the first and second internal electrodes11and12and the first and second dummy electrodes18and19may preferably be made of, for example, a metal such as Ni, Cu, Ag, Pd, or Au or an alloy containing at least one of the above metals, such as an Ag—Pd alloy. The first and second internal electrodes11and12may be made of the same material as or a different material from the first and second dummy electrodes18and19.

Further, the thickness of the first and second internal electrodes11and12and the thickness of the first and second dummy electrodes18and19are not particularly limited. The thickness of each of the first and second internal electrodes11and12and the first and second dummy electrodes18and19may preferably be, for example, about 0.3 μm to about 2 μm. The thickness of the first and second internal electrodes11and12is preferably the same as the thickness of the first and second dummy electrodes18and19.

As illustrated inFIGS. 1 to 3, a first external electrode13and a second external electrode14are provided on surfaces of the ceramic body10. The first external electrode13is electrically connected to the first internal electrodes11. The first external electrode13preferably includes a first portion13aprovided on the first main surface10a, a third portion13cprovided on the second main surface10b, and a second portion13bprovided on the first end surface10e. In this preferred embodiment, the first external electrode13is arranged so as to be shallowly wrapped around end portions of the first and second side surfaces10cand10din the length direction L. Specifically, the length of the portions of the first external electrode13on the first and second side surfaces10cand10din the length direction L is preferably less than substantially half the length of the first and third portions13aand13cin the length direction L. The length of the first and third portions13aand13cin the length direction L is preferably, for example, about 200 μm to about 350 μm. The first external electrode13does not substantially project from the first side surface10cor the second side surface10din the width direction W. With this configuration, the dimension of the ceramic electronic component in the width direction W is reduced. The first external electrode13may not necessarily be provided substantially on the first side surface10cor the second side surface10d.

The second external electrode14is electrically connected to the second internal electrodes12. The second external electrode14includes a first portion14aprovided on the first main surface10a, a third portion14cprovided on the second main surface10b, and a second portion14bprovided on the second end surface10f. In this preferred embodiment, the second external electrode14is arranged so as to be shallowly wrapped around end portions of the first and second side surfaces10cand10din the length direction L. Specifically, the length of the portions of the second external electrode14on the first and second side surfaces10cand10din the length direction L is preferably less than substantially half the length of the first and third portions14aand14cin the length direction L. The length of the first and third portions14aand14cin the length direction L is preferably, for example, about 200 μm to about 350 μm. The second external electrode14does not substantially project from the first side surface10cor the second side surface10din the width direction W. With this configuration, the dimension of the ceramic electronic component1in the width direction W is reduced. The second external electrode14may not necessarily be arranged substantially on the first side surface10cor the second side surface10d.

The maximum thickness of each of the first and second external electrodes13and14may preferably range from, for example, about 10 μm to about 50 μm.

Next, the configuration of the first and second external electrodes13and14will be described with reference toFIG. 3. In this preferred embodiment, each of the first and second external electrodes13and14includes a laminate of a first conductor layer15and a second conductor layer16.

The first conductor layer15is provided on the first end surface10eor the second end surface10fand on an end of the first main surface10aor the second main surface10bin the length direction L.

Outer end portions of portions of the first conductor layers15of the first and second external electrodes13and14, which respectively define the first portions13aand14a, in the length direction L are preferably relatively thick. Similarly, outer end portions of portions of the first conductor layers15of the first and second external electrodes13and14, which respectively define the third portions13cand14c, in the length direction L are preferably relatively thick. Specifically, in portions of the first conductor layers15of the first and second external electrodes13and14, which respectively define the first portions13aand14a, portions that do not face first reinforcement layers17aare thicker than portions that face the first reinforcement layers17a. Similarly, in portions of the first conductor layers15of the first and second external electrodes13and14, which respectively define the third portion13cand14c, portions that do not face second reinforcement layers17bare thicker than portions that face the second reinforcement layers17b. Therefore, in each of the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14, a portion that does not face the first reinforcement layers17aor the second reinforcement layers17bis thicker than a portion that faces the first reinforcement layers17aor the second reinforcement layers17b. For example, the thickness of the outer end portion of the first conductor layer15may preferably be maximally in the range from about 5 μm to about 20 μm, whereas the thickness of an inner end portion of the first conductor layer15may preferably be maximally in the range from about 1 μm to about 10 μm.

A portion of the first conductor layer15that is provided on the first end surface10eor the second end surface10fis preferably thinner than a portion of the first conductor layer15that is provided on the first main surface10aor the second main surface10b. A portion of the second conductor layer16that is provided on the first end surface10eor the second end surface10fis preferably thinner than a portion of the second conductor layer16that is provided on the first end surface10eor the second end surface10f. For example, the thickness of a portion of each of the conductor layers15and16that is provided on the first end surface10eor the second end surface10fmay preferably be maximally in the range from about 3 μm to about 10 μm.

The material of the first conductor layer15is not particularly limited. The first conductor layer15may preferably be made of a metal such as Ni, Cu, Ag, Pd, or Au or an alloy containing at least one of the above metals, such as an Ag—Pd alloy, for example. The first conductor layer15may also include an inorganic binder. Examples of the inorganic binder include the same type of ceramic material as the ceramic material included in the ceramic body10and a glass component. The content of the inorganic binder in the first conductor layer15is preferably in the range of, for example, about 40% by volume to about 60% by volume.

The second conductor layer16is arranged so as to cover end portions of the first and second main surfaces10aand10bin the length direction L and the first end surface10eor the second end surface10f. The second conductor layer16covers the first conductor layer15.

In this preferred embodiment, the second conductor layer16preferably includes one plating film or a laminate of a plurality of plating films. The thickness of the second conductor layer16is not particularly limited. The maximum thickness of the second conductor layer16may preferably range from, for example, about 5 μm to about 15 μm.

The material of the second conductor layer16is not particularly limited. The second conductor layer16may preferably be made of one metal selected from a group consisting of, for example, Cu, Ni, Sn, Pb, Au, Ag, Pd, Al, Bi, and Zn or may be formed of an alloy including this metal, for example. In particular, when the ceramic electronic component1is embedded in a wiring board, the outermost layer of the second conductor layer16is preferably made of, for example, one metal selected from a group consisting of Cu, Au, Ag, and Al or made of an alloy including this metal for the following reason. In some cases, the ceramic electronic component1may be embedded in a wiring board by irradiating the first and second external electrodes13and14with laser beams propagating through the wiring board, and the above metals efficiently reflect the laser beams.

An additional layer, such as a conductive resin layer arranged to relax stress, may preferably be provided between the first conductor layer15and the second conductor layer16.

As illustrated inFIGS. 3 and 7, the first outer layer portion10B includes the plurality of first reinforcement layers17a. The plurality of first reinforcement layers17aare arranged in the length direction L and in the width direction W. The plurality of first reinforcement layers17aare stacked in the thickness direction T. The plurality of first reinforcement layers17aare not provided in either end portion of the ceramic body10in the length direction L. The plurality of first reinforcement layers17aare successively arranged over a central portion of the ceramic body10, except at both end portions in the length direction L. The plurality of first reinforcement layers17aare disposed inside the ceramic body10, and are not exposed from the surface of the ceramic body10.

As illustrated inFIG. 3, portions of the plurality of first reinforcement layers17a, namely, outer end portions in the length direction L, face the first portions13aand14aof the first and second external electrodes13and14in the thickness direction T. That is, the outer end portions of the plurality of first reinforcement layers17ain the length direction L face the first portions13aand14aof the first and second external electrodes13and14in the thickness direction T.

In this preferred embodiment, the plurality of first reinforcement layers17aare provided in a first reinforcement region10F of the ceramic body10, and the volume proportion of the first reinforcement layers17ain the first reinforcement region10F is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A.

As illustrated inFIG. 3, the second outer layer portion10C includes the plurality of second reinforcement layers17b. The plurality of second reinforcement layers17bare arranged in the length direction L and in the width direction W. The plurality of second reinforcement layers17bare stacked in the thickness direction T. The plurality of second reinforcement layers17bare not provided in either end portion of the ceramic body10in the length direction L. The plurality of second reinforcement layers17bare successively arranged over a central portion of the ceramic body10, except at both end portions in the length direction L. The plurality of second reinforcement layers17bare disposed inside the ceramic body10, and are not exposed from the surface of the ceramic body10. In this preferred embodiment, the first reinforcement layers17aand the second reinforcement layers17bhave substantially the same shape when viewed in plan.

As illustrated inFIG. 3, portions of the plurality of second reinforcement layers17b, namely, outer end portions in the length direction L, face the third portions13cand14cof the first and second external electrodes13and14in the thickness direction T. That is, the outer end portions of the plurality of second reinforcement layers17bin the length direction L face the third portions13cand14cof the first and second external electrodes13and14in the thickness direction T.

In this preferred embodiment, the plurality of second reinforcement layers17bare provided in a second reinforcement region10G of the ceramic body10, and the volume proportion of the second reinforcement layers17bin the second reinforcement region10G is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A.

The first and second reinforcement layers17aand17bmay be made of any material that is more ductile and malleable than the material of the ceramic body10. Each of the first and second reinforcement layers17aand17bmay preferably be made of, for example, a metal such as Ni, Cu, Ag, Pd, or Au or an alloy containing at least one of the above metals, such as an Ag—Pd alloy.

Each of the first and second reinforcement layers17aand17bmay preferably have a thickness of, for example, about 0.3 μm to about 2.0 μm.

Preferably, the length of the first and second reinforcement layers17aand17bin the length direction L, the sum of the length of the first internal electrodes11and the length of the first dummy electrodes18in the length direction L, and the sum of the length of the second internal electrodes12and the length of the second dummy electrodes19in the length direction L are equal or substantially equal to one another. In this case, the number of kinds of ceramic green sheets having a conductive paste printed on a surface thereof, which are needed to manufacture the ceramic electronic component1, is significantly reduced. Accordingly, the ceramic electronic component1can be manufactured easily and inexpensively.

In this preferred embodiment, as illustrated inFIG. 3, a thickness T2of both end portions of the ceramic body10in which the first reinforcement layers17aor the second reinforcement layers17bare not provided in the length direction is preferably less than a thickness T1of a portion of the ceramic body10in which the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14face the first and second reinforcement layers17aand17bin the thickness direction T. Thus, as illustrated in detail inFIG. 4, in a portion of the first main surface10aof the ceramic body10in which the first portion13aor14aof the first external electrode13or the second external electrode14is provided, an end portion10a1or10a2that does not overlap the first reinforcement layers17ain the length direction L is preferably closer to the center in the thickness direction T than a portion that overlaps the first reinforcement layers17a. Further, in a portion of the second main surface10bof the ceramic body10in which the third portion13cor14cof the first external electrode13or the second external electrode14is provided, an end portion10b1or10b2that does not overlap the second reinforcement layers17bin the length direction L is preferably closer to the center in the thickness direction T than a portion that overlaps the second reinforcement layers17b.

Additionally, the outer end portions of the first portions13aand14aof the first and second external electrodes and14in the length direction L in which the first reinforcement layers17aare not provided (the end portion near the first end surface10eor the second end surface10f) are preferably thicker than other portions. The outer end portions of the third portions13cand14cof the first and second external electrodes13and14in the length direction L in which the second reinforcement layers17bare not provided (the end portion near the first end surface10eor the second end surface10f) are preferably thicker than other portions.

Next, an example of a method for manufacturing the ceramic electronic component1according to a preferred embodiment will be described.

First, a ceramic green sheet20(seeFIG. 8) including a ceramic material for forming the ceramic body10is prepared. Then, as illustrated inFIG. 8, a conductive paste is applied onto the ceramic green sheet20to form conductor patterns21. Conductor patterns may be formed using, for example, any printing method, such as a screen printing method. The conductive paste may preferably include conductive particles and any known binder and solvent.

In this preferred embodiment, the length of the first and second reinforcement layers17aand17bin the length direction L, the sum of the length of the first internal electrodes11and the length of the first dummy electrodes18in the length direction L, and the sum of the length of the second internal electrodes12and the length of the second dummy electrodes19in the length direction L are preferably substantially equal to one another. Thus, a ceramic green sheet for forming the first internal electrodes11and the first dummy electrodes18, a ceramic green sheet20for forming the second internal electrodes12and the second dummy electrodes19, a ceramic green sheet20for forming the first reinforcement layers17a, and a ceramic green sheet20for forming the second reinforcement layers17bmay have common specifications. That is, only one kind of ceramic green sheet20with a conductive paste printed thereon needs to be prepared.

Then, as illustrated inFIGS. 10 to 12, a ceramic green sheet20on which no conductor patterns21are formed, and a ceramic green sheet20on which conductor patterns21are formed are stacked such that the ceramic green sheets20are shifted in the length direction L as desired, and are pressed in the stacking direction by hydrostatic pressure or other suitable pressing device to fabricate a mother laminate22illustrated inFIG. 9.

In this preferred embodiment, one ceramic green sheet20is located between the adjacent reinforcement layers17aand17b. In contrast, a plurality of ceramic green sheets20are located between the first and second internal electrodes11and12adjacent in the thickness direction T.

Then, as illustrated inFIG. 9, conductor patterns23having shapes corresponding to the portions forming the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14on the first conductor layers15are formed on the mother laminate22using an appropriate printing method, such as a screen printing method, for example.

Then, the mother laminate22is pressed in the stacking direction again. In this case, the mother laminate22is pressed so that the thickness of the portions at which the reinforcement layers17aand17band the first and second internal electrodes11and12do not overlap is reduced, that is, so that, as illustrated inFIG. 3, the thickness T2is less than the thickness T1. For example, pressing with an elastic body disposed between a press mold and the main surface of the mother laminate22allows a portion at which the reinforcement layers17aand17band the first and second internal electrodes11and12do not overlap to be effectively pressed. Thus, the thickness relationship described above is achieved.

Then, the mother laminate22is cut along imaginary cut lines CL to fabricate a plurality of raw ceramic laminates from the mother laminate22. The mother laminate22may be cut by dicing or press-cutting, for example.

After the formation of raw ceramic laminates, the corners and edges of the raw ceramic laminates may be chamfered or R-chamfered and surface layers of the raw ceramic laminates may be polished using barrel polishing, for example.

After that, conductive pastes are applied to both end surfaces of each of the raw ceramic laminates using a suitable method, for example, a dipping method. The applied conductive pastes and the conductor patterns23form the conductor layers15illustrated inFIG. 3.

If conductive pastes are applied to both end surfaces of a raw ceramic laminate using, for example, a dipping method or other suitable method, the conductive pastes may also be slightly wrapped around the first and second side surfaces and the first and second main surfaces. Thus, a conductive paste layer that forms a first conductor layer15in the following firing process is relatively thick in the end portions of the first and second main surfaces10aand10bnear the first end surface10eor the second end surface10f. Accordingly, the outer end portions of the first conductor layer15in the length direction L are relatively thick, resulting in the outer end portions of the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14in the length direction L being relatively thick. Further, the thickness of the first conductor layer15formed on the first end surface10eor the second end surface10fcan be reduced by, after applying a conductive paste to the first end surface10eor the second end surface10f, pressing the first end surface10eor the second end surface10fagainst a surface plate, and removing the excess conductive paste.

Then, the raw ceramic laminates are fired. In this firing process, the conductive paste layer formed in the manner described above is also fired (co-fired), and the conductor layers15are formed. The firing temperature can be set as desired in accordance with the type of the ceramic material and conductive paste to be used. The firing temperature may preferably be set to, for example, about 900° C. to about 1300° C.

After that, polishing, such as barrel polishing, for example, is performed as necessary.

Finally, the conductor layers16are formed by plating to complete the first and second external electrodes13and14. In preferred embodiments of the present invention, the conductor layers16formed of plating films are not essential. For example, the first and second external electrodes13and14may include only the conductor layers15.

As described above, in this preferred embodiment, the volume proportion of the first reinforcement layers17ain the first reinforcement region10F is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A. In addition, the volume proportion of the second reinforcement layers17bin the second reinforcement region10G is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A. Therefore, the rigidity of the first and second reinforcement regions10F and10G can be effectively increased. Furthermore, the high-rigidity first and second reinforcement regions10F and10G effectively reinforce the outer layer portions10B and10C, which are susceptible to cracking, breakage, or other damage. Furthermore, even if cracks occur in the first main surface10aor the second main surface10b, the cracks do not easily extend to the effective portion10A located closer to the central portion than the first and second reinforcement regions10F and10G. Consequently, high mechanical durability is effectively achieved.

In view of higher mechanical durability, the volume proportion of the first and second reinforcement layers17aand17bin the first and second reinforcement regions10F and10G is, for example, preferably about 1.5 times or more, and more preferably, about three times or more, the volume proportion of the first and second internal electrodes11and12in the effective portion10A. The volume proportion of the first and second reinforcement layers17aand17bin the first and second reinforcement regions10F and10G is, for example, preferably about five times or less the volume proportion of the first and second internal electrodes11and12in the effective portion10A.

The method for making the volume proportion of the first and second reinforcement layers17aand17bin the first and second reinforcement regions10F and10G greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A is not particularly limited. For example, as in this preferred embodiment, the volume proportion of the first and second reinforcement layers17aand17bin the first and second reinforcement regions10F and10G may be greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A by making the distance between the first and second reinforcement layers17aand17badjacent in the thickness direction T less than the distance between the first and second internal electrodes11and12adjacent in the thickness direction T. In this case, preferably, the distance between the first and second reinforcement layers17aand17badjacent in the thickness direction T is, for example, in the range of about 0.125 times to about 0.5 times the distance between the first and second internal electrodes11and12adjacent in the thickness direction T.

Alternatively, the volume proportion of the first and second reinforcement layers17aand17bin the first and second reinforcement regions10F and10G may be greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A by making the first reinforcement layer17aor the second reinforcement layer17bthicker than the first internal electrode11or the second internal electrode12. In this case, the thickness of the first and second reinforcement layers17aand17bis, for example, preferably about 1.3 times or more, and more preferably about twice or more, the thickness of the first internal electrode11or the second internal electrode12. However, if the first and second reinforcement layers17aand17bare too thick, the ceramic layers10gmay be easily separated from the first and second reinforcement layers17aand17b. Therefore, preferably, the thickness of the first reinforcement layers17aor the second reinforcement layers17bis, for example, about four times or less the thickness of the first internal electrode11or the second internal electrode12.

The volume proportion of the first and second reinforcement layers17aand17bin the first and second reinforcement regions10F and10G may also be made greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A by making the distance between the first and second reinforcement layers17aand17badjacent in the thickness direction T less than the distance between the first and second internal electrodes11and12adjacent in the thickness direction T and by making the first reinforcement layers17aor the second reinforcement layers17bthicker than the first internal electrode11or the second internal electrode12.

Furthermore, in this preferred embodiment, each of the number of first reinforcement layers17aand the number of second reinforcement layers17bis preferably greater than the total number of first and second internal electrodes11and12. Therefore, the mechanical durability of the ceramic electronic component1is further increased. Each of the number of first reinforcement layers17aand the number of second reinforcement layers17bis preferably about 1.5 times or more, and more preferably about twice or more, the total number of first and second internal electrodes11and12, for example. However, too many first reinforcement layers17aand too many second reinforcement layers17bcan excessively increase the thickness of the ceramic electronic component1. Therefore, preferably, each of the number of first reinforcement layers17aand the number of second reinforcement layers17bis, for example, about five times or less the total number of first and second internal electrodes11and12.

It is assumed that the comparison between volume proportions does not take into account margin portions in the first and second reinforcement regions10F and10G that are adjacent in the length direction L and in the width direction W (portions that do not overlap the first and second reinforcement layers17aand17bin the thickness direction). It is also assumed that the comparison between volume proportions does not take into account margin portions in the effective portion10A that are adjacent in the length direction L and in the width direction W (portions that do not overlap the first and second internal electrodes11and12in the thickness direction).

Furthermore, as in this preferred embodiment, when the width dimension of the first and second reinforcement layers17aand17bis substantially the same as the width dimension of the first and second internal electrodes11and12, only the length dimension and the thickness dimension of the first and second reinforcement regions10F and10G and the effective portion10A may be taken into account. In addition, as in this preferred embodiment, when the length dimension of the first and second reinforcement regions10F and10G is greater than that of the effective portion10A, the volume proportion of the first and second reinforcement regions10F and10G is greater than the volume proportion of the effective portion10A if the thickness dimension of the first and second reinforcement regions10F and10G is greater than the thickness dimension of the effective portion10A.

Therefore, in some cases, all the three-dimensional dimensions may not necessarily be taken into account but only the thickness dimension may be taken into account. The thickness dimension of the first and second reinforcement regions10F and10G can be determined by (the thickness of the first and second reinforcement layers17aand17b)×(the number of first reinforcement layers17aand the number of second reinforcement layers17b)+(the thickness of the ceramic layer10g)×(the number of ceramic layers10g). The thickness dimension of the effective portion A can be determined by (the thickness of the first and second internal electrodes11and12)×(the number of first internal electrodes11and the number of second internal electrodes12)+(the thickness of the ceramic layer10g)×(the number of ceramic layers10g). In the above calculation formulae, the thickness dimension of each element is preferably the value obtained by measuring six desired portions, i.e., the upper end and the lower end of each of the left end, the center, and the right end of each region in the length direction, and by determining the average value of the measured values.

The length dimension and the width dimension are also preferably the values obtained by measuring six desired portions and by determining the average value of the measured values.

In this preferred embodiment, in the portion of the first main surface10aof the ceramic body10in which the first portion13aor14aof the first external electrode13or the second external electrode14is provided, the end portion10a1or10a2that does not overlap the first reinforcement layers17ain the length direction L is preferably closer to the center in the thickness direction T than the portion that overlaps the first reinforcement layers17a. Therefore, for example, if stress is applied from outside in cases such as when the ceramic electronic component1is mounted on a wiring board with the first main surface10adirected toward the wiring board, the ceramic electronic component1can be effectively prevented from being damaged. Thus, the mechanical durability of the ceramic electronic component1is improved. This advantage will be described in detail hereinafter.

In the ceramic electronic component1, the first and second external electrodes13and14are provided on the first and second main surfaces10aand10b. Thus, both end portions of the ceramic electronic component1in the length direction L project in the thickness direction T. Therefore, both end portions of the ceramic electronic component1in the length direction L are susceptible to stress. The stress applied to both end portions of the ceramic electronic component1in the length direction L produces stress concentration in portions10D and10E (seeFIG. 3) in which the leading ends of the first and third portions13aand14aand13cand14care located and in which the thickness of the ceramic electronic component1greatly changes, and the portions10D and10E are susceptible to cracks.

Here, for example, if both end portions of the ceramic electronic component1are the thickest, the distance between end portions of the ceramic electronic component1that define fulcra and the portions10D and10E that define points of action is large, which results in large stress being applied to the portions10D and10E.

In contrast, in this preferred embodiment, in the portion of the first main surface10aof the ceramic body10in which the first portion13aor14aof the first external electrode13or the second external electrode14is provided, the end portion10a1or10a2that does not overlap the first reinforcement layers17ain the length direction L is preferably closer to the center in the thickness direction T than the portion that overlaps the first reinforcement layers17a. Therefore, the most projecting portions of the ceramic electronic component1in the thickness direction T are closer to the center than end portions. Consequently, the distance between the portions10D and10E defining points of action and the fulcra is reduced. The reduction in distance prevents large stress from being exerted on the portions10D and10E, and prevents the portions10D and10E in the ceramic body10from being damaged. Therefore, increased mechanical durability is achieved.

Furthermore, in this preferred embodiment, the portions10D and10E, which may be easily damaged, include the first and second reinforcement layers17aand17b. Thus, the mechanical strength of the portions10D and10E is effectively improved.

In this preferred embodiment, the first and second reinforcement layers17aand17bare successively arranged over the central portion of the ceramic body10, except at both end portions in the length direction L. Thus, the mechanical strength of the central portion of the portions ceramic body10in the length direction L, which may also be easily damaged in addition to the portions10D and10E, is also effectively increased.

In this preferred embodiment, the thickness T2of both end portions of the ceramic body10in the length direction at which the first reinforcement layers17aor the second reinforcement layers17bare not provided is preferably less than the thickness T1of the portion of the ceramic body10in which the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14face the first and second reinforcement layers17aand17bin the thickness direction T. Further, the portions of the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14, which are provided on the portion at which the thickness T2is less than the thickness T1, are relatively thick. Thus, the surfaces of the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14are substantially flat. The substantially flat surfaces allow stress to be applied to the entire first and third portions13aand14aand13cand14cwithout causing stress concentration to a portion thereof. Thus, large stress is effectively prevented from being applied to a portion of the first and third portions13aand14aand13cand14c. Therefore, increased mechanical durability is achieved.

When the number of internal electrodes11and12is relatively large, the effect of the internal electrodes11and12on improving mechanical strength is large, and the thickness of the ceramic body10is also large, which results in an increase in the mechanical strength of the ceramic electronic component1. In contrast, when the number of internal electrodes11and12is relatively small, for example, about 2 to about 20, the effect of the internal electrodes11and12on improving mechanical strength is relatively small, and the ceramic body10is thin, which results in the mechanical strength problem with the ceramic electronic component1being noticeable. Therefore, as in this preferred embodiment, the technology to improve the mechanical durability of the ceramic electronic component1by providing the reinforcement layers17aand17band by lowering the end portions of the first main surface10ain the length direction L so that the end portions are close to the center in the thickness direction T is effective particularly when the number of layers of the internal electrodes11and12is small, for example, about 2 to about 20.

Other examples of preferred embodiments of the present invention will be described hereinafter. In the following description, members having functions substantially the same as those in the first preferred embodiment are represented by common numerals and descriptions thereof are omitted.

Second Preferred Embodiment

FIG. 13is a schematic cross-sectional view of a ceramic electronic component according to a second preferred embodiment of the present invention.

In this preferred embodiment, as illustrated inFIG. 13, at least a portion of the first and third portions13aand14aand13cand14cof the first and second external electrodes13and14is preferably embedded in the first main surface10aor the second main surface10b. Even in this case, similarly to the first preferred embodiment, the mechanical durability of the ceramic electronic component1is effectively improved.

The ceramic electronic component according to this preferred embodiment may preferably be formed by, for example, printing, on the main surfaces of a mother laminate, conductor patterns23having shapes corresponding to the portions forming the first and third portion13aand14aand13cand14cand then by pressing the mother laminate in the stacking direction such that the mother laminate is pressed with stronger force. Therefore, the embedded portions as described above can be formed.

Third Preferred Embodiment

FIG. 14is a schematic cross-sectional view of a ceramic electronic component according to a third preferred embodiment of the present invention.

In the first preferred embodiment, the first and second external electrodes13and14are provided on each of the first and second main surfaces10aand10b, by way of example. However, preferred embodiments of the present invention are not limited to this configuration. At least one external electrode may be provided on the first main surface10a.

For example, as illustrated inFIG. 14, the first and second external electrodes13and14may be arranged so as to cover the first end surface10eor the second end surface10fand the first main surface10a. That is, as long as the first and second external electrodes13and14include the first portions13aand14a, respectively, and are electrically connected to the first internal electrode11or the second internal electrode12, the shapes of the first and second external electrodes13and14are not particularly limited.

Also in this preferred embodiment, the second reinforcement layers17bmay preferably be provided in addition to the first reinforcement layers17a. However, since the ceramic electronic component1often suffers damage from the impact caused when mounted, the mechanical durability of the ceramic electronic component1may be effectively improved by providing only the first reinforcement layers17aon the side at which the first portions13aand14aare provided. Furthermore, the thickness of the ceramic electronic component1may be further reduced by not providing the third portion13cor14cor the second reinforcement layers17b.

Fourth Preferred Embodiment

FIG. 15is a schematic cross-sectional view of a ceramic electronic component according to a fourth preferred embodiment of the present invention.

In the first preferred embodiment, the first and second internal electrodes11and12are electrically connected to the first external electrode13or the second external electrode14by extending the first and second internal electrodes11and12to the first end surface10eor the second end surface10fand by providing the first external electrode13or the second external electrode14on the first and second end surfaces10eand10f, by way of example. However, preferred embodiments of the present invention are not limited to this configuration.

For example, as illustrated inFIG. 15, via-hole electrodes24and25may preferably be provided, and the first and second internal electrodes11and12may extend to the first and second main surfaces10aand10bso as to be electrically connected to the first and second external electrodes13and14on the first and second main surfaces10aand10b. In this case, the first and second external electrodes13and14may preferably be provided on at least one of the first and second main surfaces10aand10b, and the first and second external electrodes13and14may not necessarily be provided on the first and second side surfaces10cand10dand on the first and second end surfaces10eand10f.

Fifth Preferred Embodiment

FIG. 16is a schematic cross-sectional view of a ceramic electronic component according to a fifth preferred embodiment of the present invention. As illustrated inFIG. 16, in the ceramic electronic component according to the fifth preferred embodiment, a plurality of first reinforcement layers17athat are arranged so as to extend in the length direction L and in the width direction W and that are stacked in the thickness direction T are preferably provided in the first outer layer portion10B. Further, a plurality of second reinforcement layers17bthat are arranged so as to extend in the length direction L and in the width direction W and that are stacked in the thickness direction T are preferably provided in the second outer layer portion10C. The volume proportion of the plurality of first reinforcement layers17ain a region of the ceramic body10in which the plurality of first reinforcement layers17aare provided is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A. The volume proportion of the plurality of second reinforcement layers17bin a region of the ceramic body10in which the plurality of second reinforcement layers17bare provided is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A. Each of the number of first reinforcement layers17aand the number of second reinforcement layers17bis preferably greater than the total number of first and second internal electrodes11and12. Therefore, in this preferred embodiment, similarly to the first preferred embodiment, high mechanical durability is achieved.

In addition, similarly to the first preferred embodiment, the first and second reinforcement layers17aand17bare arranged so as to extend in an area from a region in which the first and third portions13aand13cof the first external electrode13are provided to a region in which the first and third portions14aand14cof the second external electrode14, including the central portion in the length direction L. Therefore, increased mechanical durability is achieved.

In this preferred embodiment, each of the plurality of reinforcement layers17aand each of the plurality of reinforcement layers17bare separated into a plurality of reinforcement layer pieces in the length direction L in regions that are regions outside of the effective portion10A and that are regions in which the first and third portions13aand14aand13cand14care provided in the length direction L. Thus, one reinforcement layer portion of each of the reinforcement layers17a, which is separated into a plurality of reinforcement layer pieces, and one reinforcement layer piece of each of the reinforcement layers17b, which is separated into a plurality of reinforcement layer pieces, preferably include the central portion of the ceramic body10in the length direction L, and are arranged so as to extend over the portions10D and10E. The above configuration prevents, similarly to the first preferred embodiment, large stress from being exerted on the portions10D and10E, and prevents the portions10D and10E in the ceramic body10from being damaged. Consequently, increased mechanical durability is achieved.

It is noted that a reinforcement layer separated into a plurality of reinforcement layer pieces in the length direction L is also referred to as one reinforcement layer.

Sixth Preferred Embodiment

FIG. 17is a schematic cross-sectional view of a ceramic electronic component according to a sixth preferred embodiment of the present invention. As illustrated inFIG. 17, in the ceramic electronic component according to the sixth preferred embodiment, a plurality of first reinforcement layers17athat are arranged so as to extend in the length direction L and in the width direction W and that are stacked in the thickness direction T are preferably provided in the first outer layer portion10B. Further, a plurality of second reinforcement layers17bthat are arranged so as to extend in the length direction L and in the width direction W and that are stacked in the thickness direction T are preferably provided in the second outer layer portion10C. The volume proportion of the plurality of first reinforcement layers17ain the region of the ceramic body10in which the plurality of first reinforcement layers17aare provided is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A. The volume proportion of the plurality of second reinforcement layers17bin the region of the ceramic body10in which the plurality of second reinforcement layers17bare provided is preferably greater than the volume proportion of the first and second internal electrodes11and12in the effective portion10A. Each of the number of first reinforcement layers17aand the number of second reinforcement layer17bis preferably greater than the total number of first and second internal electrodes11and12. Therefore, in this preferred embodiment, similarly to the first preferred embodiment, high mechanical durability is achieved.

In addition, similarly to the first preferred embodiment, the first and second reinforcement layers17aand17bare arranged so as to extend in an area from a region in which the first and third portions13aand13cof the first external electrode13are provided to a region in which the first and third portions14aand14cof the second external electrode are provided, including the central portion in the length direction L. Therefore, increased mechanical durability is achieved.

In this preferred embodiment, some of the plurality of reinforcement layers17aand some of the plurality of reinforcement layers17bare preferably separated into a plurality of reinforcement layer pieces in the length direction L in regions that are regions outside of the effective portion10A and that are regions in which the first and third portions13aand14aand13cand14care provided in the length direction L. Thus, the reinforcement layers17aand17bthat are not separated into a plurality of reinforcement layer pieces include the central portion of the ceramic body10in the length direction L, and are provided so as to extend over the portions10D and10E. Also, one reinforcement layer piece of each of the reinforcement layers17athat is separated into a plurality of reinforcement layer pieces and one reinforcement layer piece of each of the reinforcement layers17bthat is separated into a plurality of reinforcement layer pieces include the central portion of the ceramic body10in the length direction L, and are arranged so as to extend over the portions10D and10E. The above configuration prevents, similarly to the first preferred embodiment, large stress from being exerted on the portions10D and10E, and prevents the portions10D and10E in the ceramic body10from being damaged. Consequently, increased mechanical durability is achieved.