Ceramic electronic component

A ceramic electronic component includes a ceramic body having a substantially rectangular parallelpiped shape. The ceramic body includes a central portion in which first and second internal electrodes are arranged, and first and second end portions in which the first and second internal electrodes are not arranged. The ceramic electronic component satisfies Expressions (1) and (2) below:W1>T  (1)W2>T  (2)where T denotes the dimension of the ceramic body in a thickness direction, W1 denotes the dimension of the first end portion in a width direction, and W2 denotes the dimension of the second end portion in the width direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ceramic electronic component.

2. Description of the Related Art

As electronic apparatuses, such as mobile phones and portable music players, have become smaller in recent years, ceramic electronic components included in such electronic apparatuses have rapidly become thinner and smaller. Accordingly, various types of thin and small ceramic electronic components are being developed.

With the reductions in the thicknesses and sizes of ceramic electronic components, the strengths of ceramic electronic components have decreased correspondingly. Therefore, thin and small ceramic electronic components may crack when mounted on circuit boards or during use.

For example, Japanese Unexamined Patent Application Publication No. 6-163311 discloses a monolithic ceramic capacitor including a substantially rectangular parallelpiped ceramic body and first and second external electrodes provided at two respective ends of the ceramic body. In this monolithic ceramic capacitor, cracks tend to occur at the two ends of the ceramic body at which the external electrodes are provided. Such a crack tends to extend from a principal surface and in the thickness direction. Japanese Unexamined Patent Application Publication No. 6-163311 also discloses a technique of preventing the occurrence of a short circuit between first and second internal electrodes provided in the ceramic body that may occur if water or other fluids enter such a crack.

As described above, ceramic electronic components are becoming thinner and smaller. In particular, thin ceramic electronic components that are configured to be embedded into circuit boards are highly desirable. Thus, the inventors of the present invention performed experiments for further reducing the thickness of ceramic electronic components. Consequently, the inventors of the present invention have found that, even if the technique disclosed in Japanese Unexamined Patent Application Publication No. 6-163311 is applied to thin ceramic electronic components, there are some cases in which a short circuit between the internal electrodes cannot be sufficiently prevented.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the present invention provide a ceramic electronic component preferably including a ceramic body and first and second internal electrodes provided in the ceramic body, wherein the first and second internal electrodes are arranged so as not to cause a short circuit therebetween even if the ceramic body has a small thickness.

When a ceramic electronic component including a thin ceramic body having a small thickness is mounted on a circuit board, the impact of mounting may cause cracks. According to a diligent study performed by the inventors of the present invention, it was found that about 80% of such cracks occur from locations near edges of the ceramic body at the tips of external electrodes, which extend in the length direction, toward the inside of the ceramic body. The inventors of the present invention have also found that, when any cracks occur and each of such cracks is projected to a width-thickness (W-T) section of the ceramic body, the angle (entrance angle) between a virtual line projected in the W-T section and a side surface of the ceramic body is less than about 30°. This result led the inventors of the present invention to develop the present invention.

According to a preferred embodiment of the present invention, a ceramic electronic component preferably includes a ceramic body having a substantially rectangular parallelpiped shape, for example, and a first internal electrode and a second internal electrode. The first and second internal electrodes are provided in the ceramic body and each extends in a length direction and a width direction of the ceramic body. The first and second internal electrodes each extend to one of lengthwise end surfaces of the ceramic body. The ceramic body preferably includes a central portion in the approximate center on the ceramic body in the width direction, a first end portion disposed on one side of the central portion in the width direction, and a second end portion disposed on the other side of the central portion in the width direction. The first and second internal electrodes are preferably arranged in the central portion and are not arranged in the first and second end portions. The ceramic electronic component according to a preferred embodiment of the present invention preferably satisfies Expressions (1) and (2) below:
W1>T  (1)
W2>T  (2)
where T denotes the dimension of the ceramic body in a thickness direction, W1denotes the dimension of the first end portion in the width direction, and W2denotes the dimension of the second end portion in the width direction.

According to another preferred embodiment of the present invention, the first internal electrode and the second internal electrode preferably face each other in the thickness direction.

According to another preferred embodiment of the present invention, the ceramic electronic component preferably further includes a first external electrode and a second external electrode. The first external electrode is provided on the ceramic body. The first external electrode is electrically connected to the first internal electrode. The second external electrode is provided on the ceramic body. The second external electrode is electrically connected to the second internal electrode. The ceramic body includes a first principal surface, a second principal surface, a first side surface, a second side surface, a first end surface, and a second end surface. Each of the first and second principal surfaces extends in the length direction and the width direction. Each of the first and second side surfaces extends in the length direction and the thickness direction. Each of the first and second end surfaces extends in the width direction and the thickness direction. Each of the first external electrode and the second external electrode is preferably substantially provided on the first and second principal surfaces and a corresponding one of the first and second end surfaces among the first and second principal surfaces, the first and second side surfaces, and the first and second end surfaces. With such a configuration, each of the first and second external electrodes is not substantially provided on the first and second side surfaces. Therefore, even if, for example, the temperature of the ceramic electronic component changes and the ceramic electronic component expands or contracts, the stresses to be applied from the first and second external electrodes to the ceramic body are limited to low levels. Thus, the occurrence of any cracks in the ceramic body is effectively prevented.

According to a preferred embodiment of the present invention, the conditions W1>T and W2>T are preferably satisfied. Therefore, even if any cracks occur from locations near edges of the ceramic body at the tips of the external electrodes, which extend in the length direction, toward the inside of the ceramic electronic component because of the impact that occurs during mounting of the ceramic electronic component onto a circuit board, the cracks do not extend to the central portion including the first and second internal electrodes. Thus, the first and second internal electrodes are prevented from short-circuiting therebetween.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

A first preferred embodiment of the present invention will be described with reference to a ceramic electronic component1illustrated inFIG. 1as an example. The ceramic electronic component1is only exemplary. Preferred embodiments of the present invention are not limited in any way to the ceramic electronic component1and a method of manufacturing the ceramic electronic component1described below.

FIG. 1is a schematic perspective view of the ceramic electronic component1according to a first preferred embodiment of the present invention.FIG. 2is a schematic side view of the ceramic electronic component1according to the first preferred embodiment.FIG. 3is a schematic sectional view of the ceramic electronic component1taken along line III-III ofFIG. 1. FIG.4is a schematic sectional view of the ceramic electronic component1taken along line IV-IV ofFIG. 1.FIG. 5is a schematic sectional view of the ceramic electronic component1taken along line V-V ofFIG. 3.

Referring toFIGS. 1 to 5, the configuration of the ceramic electronic component1will be described first.

As illustrated inFIGS. 1 to 5, the ceramic electronic component1preferably includes a ceramic body10. The ceramic body10is preferably made of a ceramic material suitable for the function of the ceramic electronic component1. Specifically, if the ceramic electronic component1is a capacitor, the ceramic body10may preferably be made of a dielectric ceramic material. Exemplary dielectric ceramic materials include BaTiO3, CaTiO3, SrTiO3, CaZrO3, and other suitable dielectric ceramic materials. Considering the desired characteristics of the ceramic electronic component1, the ceramic body10may be made of any of the above ceramic materials as a primary ingredient with a secondary ingredient such as a Mn compound, Mg compound, Si compound, Fe compound, Cr compound, Co compound, Ni compound, or rare-earth compound, for example, added thereto according to need.

If the ceramic electronic component1is a ceramic piezoelectric device, the ceramic body10may preferably be made of a piezoelectric ceramic material. Exemplary piezoelectric ceramic materials include a lead-zirconate-titanate (PZT)-based ceramic material and other suitable piezoelectric ceramic materials.

If the ceramic electronic component1is a thermistor device, the ceramic body10may preferably be made of a semiconductor ceramic material. Exemplary semiconductor ceramic materials include a spinel-based ceramic material and other suitable semiconductor ceramic materials.

If the ceramic electronic component1is an inductor device, the ceramic body10may preferably be made of a magnetic ceramic material. Exemplary magnetic ceramic materials include a ferrite ceramic material and other suitable magnetic ceramic materials.

The ceramic body10preferably has a substantially rectangular parallelpiped shape. As illustrated inFIGS. 1 to 4, the ceramic body10includes a first principal surface10aand a second principal surface10beach extending in a length direction x and a width direction y. As illustrated inFIGS. 1,2,4, and5, the ceramic body10also includes a first side surface10cand a second side surface10deach extending in a thickness direction z and the length direction x. As illustrated inFIGS. 2,3, and5, the ceramic body10also includes a first end surface10eand a second end surface10feach extending in the thickness direction z and the width direction y.

In this specification, the term “substantially rectangular parallelpiped” includes a rectangular parallelpiped in which the corners defined by a first principal surface, a second principal surface, a first side surface, a second side surface, a first end surface, and a second end surface, and the edges defined by the first principal surface, the second principal surface, the first side surface, and the second side surface are chamfered or round chamfered. That is, a “substantially rectangular parallelpiped” member refers to any member having a first principal surface, a second principal surface, a first side surface, a second side surface, a first end surface, and a second end surface. Moreover, a portion or the entirety of the principal, side, and end surfaces may include projections and/or recesses.

In the first preferred embodiment, denoting the thickness, length, and width of the ceramic body10as T, L, and W, respectively, the ceramic body10is preferably, but is not limited to, a thin body that satisfies T≦W<L, 1/5W≦T≦1/2W, and T≦about 0.3 mm, for example. Specifically, the thickness, length, and width of the ceramic body10are preferably as follows: about 0.1 mm≦T≦about 0.4 mm, about 0.4 mm≦L≦about 1 mm, and about 0.2 mm≦W≦about 0.5 mm, for example, where L denotes the length of the ceramic body10, W denotes the width of the ceramic body10, and T denotes the thickness of the ceramic body10.

As illustrated inFIGS. 3 to 5, the ceramic body10preferably includes a plurality of first internal electrodes11and a plurality of second internal electrodes12each having a substantially rectangular shape. The first internal electrodes11and the second internal electrodes12are alternately provided at regular intervals in the thickness direction z. The first and second internal electrodes11and12preferably extend parallel or substantially parallel to the first and second principal surfaces10aand10b. The first internal electrodes11and the second internal electrodes12are preferably arranged to face one another with ceramic layers10ginterposed therebetween in the thickness direction z.

The thicknesses of the ceramic layers10gmay preferably be, but are not limited to, about 0.5 μm to about 10 μm, for example. The thicknesses of the first and second internal electrodes11and12may preferably be, but are not limited to, about 0.3 μm to about 2 μm, for example.

Each of the first and second internal electrodes11and12may be made of any suitable conductive material, for example, a metal such as Ni, Cu, Ag, Pd, or Au; or an alloy of one or more of the foregoing metals, such as an Ag—Pd alloy.

As illustrated inFIGS. 4 and 5, the first and second internal electrodes11and12do not extend over the entire the ceramic body10in the width direction y. In the width direction y, the first and second internal electrodes11and12are arranged in a central portion of the ceramic body10and are not arranged in portions at the ends of the ceramic body10. That is, the ceramic body10includes a central portion10A defined in the approximate center thereof in the width direction y and including the first and second internal electrodes11and12, a first end portion10B defined on one side y1thereof in the width direction y with respect to the central portion10A and not including the first and second internal electrodes11and12, and a second end portion10C defined on the other side y2thereof in the width direction y with respect to the central portion10A and not including the first and second internal electrodes11and12.

Here, denoting the width of the first end portion10B be W1and the width of the second end portion10C be W2, the ceramic electronic component1according to the first preferred embodiment preferably satisfies Expressions (1) and (2) below:
W1>T  (1)
W2>T  (2)

As illustrated inFIGS. 1 to 5, a first external electrode13and a second external electrode14are provided on the ceramic body10. The first external electrode13is electrically connected to the first internal electrodes11. The second external electrode14is electrically connected to the second internal electrodes12. The tips of the first internal electrodes11that are not connected to the first external electrode13are preferably located between a first portion14aand a second portion14bof the second external electrode14in the T-direction inFIG. 3. The tips of the second internal electrodes12that are not connected to the second external electrode14are preferably located between a first portion13aand a second portion13bof the first external electrode13in the T-direction inFIG. 3.

The first external electrode13is preferably substantially provided on the first and second principal surfaces10aand10band the first end surface10eamong the first and second principal surfaces10aand10b, the first and second side surfaces10cand10d, and the first and second end surfaces10eand10f. Specifically, the first external electrode13preferably includes the first portion13aprovided on the first principal surface10a, the second portion13bprovided on the second principal surface10b, and a third portion13cprovided on the first end surface10e. In the first preferred embodiment, the first external electrode13is preferably not substantially provided on the first and second side surfaces10cand10d.

The second external electrode14is preferably substantially provided on the first and second principal surfaces10aand10band the second end surface10famong the first and second principal surfaces10aand10b, the first and second side surfaces10cand10d, and the first and second end surfaces10eand10f. Specifically, the second external electrode14preferably includes the first portion14aprovided on the first principal surface10a, the second portion14bprovided on the second principal surface10b, and a third portion14cprovided on the second end surface10f. In the first preferred embodiment, the second external electrode14is preferably not substantially provided on the first and second side surfaces10cand10d.

Thus, in the first preferred embodiment, each of the first external electrode13and the second external electrode14is preferably not substantially provided on the first and second side surfaces10cand10d. Therefore, the size of the ceramic electronic component1is effectively reduced.

Each of the first and second external electrodes13and14may preferably be made of, but are not limited to, a metal such as Cu, Ni, Ag, Pd, or Au; or an alloy of one or more of the foregoing metals, such as a Ag—Pd alloy, for example. Moreover, each of the first and second external electrodes13and14may preferably include a plurality of conductive layers made of any of the above metals and alloys. For example, the first and second external electrodes13and14may preferably include an underlayer formed on the ceramic body10by co-firing or post-firing and one or a plurality of plated layers formed on the underlayer. Furthermore, a resin layer arranged to reduce stress may preferably be interposed between the underlayer and the plated layers. The thicknesses of the plated layers may preferably be about 1 μm to about 10 μm, for example.

The thicknesses of the first and second external electrodes13and14may preferably be, but are not limited to, about 10 μm to about 50 μm, for example.

An exemplary method of manufacturing ceramic electronic components1according to the first preferred embodiment will now be described.

First, a plurality of ceramic green sheets20(seeFIG. 6) that include a ceramic material and are to form ceramic bodies are prepared. Subsequently, as illustrated inFIG. 6, conductive paste is applied to some of the ceramic green sheets such that conductive patterns21that are to form the respective first and second internal electrodes11and12are formed. The application of the conductive paste may preferably be performed by any of various printing methods, such as screen printing, for example. The conductive paste may preferably include a publicly known binder or solution in addition to conductive particles.

Subsequently, some of the ceramic green sheets20that do not include any conductive patterns21, the ceramic green sheets20including the conductive patterns21that are to form the respective first and second internal electrodes11and12, and the other ceramic green sheets20that do not include any conductive patterns21are preferably stacked in that order. The resulting body is hydrostatically pressed in the direction of the stacking, whereby a mother stack22illustrated inFIG. 7is obtained.

Subsequently, a conductive pattern23that is to form the underlayers of the respective first and second external electrodes13and14is preferably formed on the mother stack22by any printing method, such as screen printing, for example.

Subsequently, the mother stack22is cut along cutting lines L, whereby a plurality of raw ceramic stacks are obtained from the mother stack22. The cutting of the mother stack22may be performed by dicing or shearing, for example.

After obtaining the raw ceramic stacks, barrel polishing or other suitable processing may preferably be performed on the raw ceramic stacks such that the corners and edges thereof are chamfered or round chamfered and such that the surfaces thereof are polished.

Subsequently, conductive paste that is to form the underlayers of the respective first and second external electrodes13and14is applied to two end surfaces of each of the raw ceramic stacks. The application of the conductive paste may preferably be performed by dipping, screen printing, or other suitable method, for example.

Subsequently, the raw ceramic stacks are fired. In the firing process, the first and second internal electrodes11and the underlayers of the first and second external electrodes13and14are simultaneously fired (co-fired). The firing temperature may be set suitably in accordance with the types of the ceramic material and the conductive paste used. The firing temperature may preferably be, for example, about 900° C. to about 1300° C., for example.

Subsequently, plating is preferably performed on the underlayers, whereby the first and second external electrodes13and14each including an underlayer and a plated layer are obtained. Thus, finished ceramic electronic components1are obtained.

In a thin ceramic electronic component, such as the ceramic electronic component1according to the first preferred embodiment that preferably satisfies the conditions of W1>T and W2>T, the ceramic body tends to crack because of the impact applied when the ceramic electronic component is mounted on a circuit board. Such cracks tend to occur from locations near edges of the ceramic body at the tips of the external electrodes extending in the length direction x. According to a diligent study performed by the inventors of the present invention, it has been discovered that, when such a crack is projected to a width-thickness (W-T) section of the ceramic body, an angle θ between a virtual line projected in the W-T section and either of the side surfaces is about 30° or less.

In the first preferred embodiment, the conditions W1>T and W2>T are preferably satisfied. Therefore, even if cracks occur with entrance angles less than about 30° from locations near edges of the ceramic body10at the tips of the first and second external electrodes13and14, the cracks are prevented from extending to the first and second internal electrodes11and12. Thus, despite the reduced thickness of the ceramic electronic component1, the first and second internal electrodes11and12of the ceramic electronic component1are effectively prevented from short-circuiting therebetween.

In the first preferred embodiment, each of the first and second external electrodes13and14are preferably not substantially provided on the first and second side surfaces10cand10d. Therefore, even if, for example, the temperature of the ceramic electronic component1changes and the ceramic electronic component1expands or contracts, the stresses to be applied from the first and second external electrodes13and14to the ceramic body10are minimized. Thus, the occurrence of cracks in the ceramic body10is effectively prevented.

Other preferred embodiments of the present invention will now be described. In the following description, elements and components having substantially the same functions as those in the first preferred embodiment are denoted by the same reference numerals as those in the first preferred embodiment, and descriptions thereof are omitted.

Second Preferred Embodiment

FIG. 8is a schematic sectional view of a ceramic electronic component1according to a second preferred embodiment of the present invention.

In the first preferred embodiment, portions of the first and second principal surfaces10aand10bthat are each covered with either of the first and second external electrodes13and14and portions of the first and second principal surfaces10aand10bthat are each covered with neither of the first and second external electrodes13and14are preferably flush with each other. Preferred embodiments of the present invention are not limited to such a configuration. The portions of the first and second principal surfaces10aand10bthat are each covered with either of the first and second external electrodes13and14and the portions of the first and second principal surfaces10aand10bthat are each covered with neither of the first and second external electrodes13and14may not necessarily be flush with each other.

For example, as illustrated inFIG. 8, the portions of the first and second principal surfaces10aand10bthat are each covered with either of the first and second external electrodes13and14may preferably be disposed inwardly in the thickness direction z with respect to the portions of the first and second principal surfaces10aand10bthat are each covered with neither of the first and second external electrodes13and14. In such a case, the thickness of the ceramic electronic component1is further reduced.

Third Preferred Embodiment

FIG. 9is a schematic side view of a ceramic electronic component1according to a third preferred embodiment of the present invention.

In the first preferred embodiment, the first and second external electrodes13and14are not substantially provided on the first and second side surfaces10cand10d. Alternatively, as illustrated inFIG. 9, the first and second external electrodes13and14may preferably also be provided on the first and second side surfaces10cand10d.

In such a configuration, the reliability of the connection between the ceramic electronic component1and a circuit board to be established when the ceramic electronic component1is mounted on the circuit board is improved.