Multilayer capacitor and method for producing the same

A multilayer capacitor includes a multilayer body with sides each about 0.3 mm or smaller when viewed from a stacking direction of the multilayer body, and first and second outer electrodes disposed on a surface of the multilayer body. An outermost one of the conductive layers is bent to be convex in the stacking direction and includes penetrating portions extending in the stacking direction. In a cross section perpendicular or substantially perpendicular to a lengthwise direction of the multilayer body, assuming the bent conductive layer is equally divided into four regions named region A, region B, region C, and region D arranged in the order named in a widthwise direction of the multilayer body, a sum of minimum diameters of the penetrating portions is larger in the region A than in the region B and larger in the region D than in the region C.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer capacitor and a method for producing the multilayer capacitor. In particular, the present invention relates to an ultra-small multilayer capacitor and a method for producing the ultra-small multilayer capacitor.

2. Description of the Related Art

In general, a multilayer capacitor is constituted by a multilayer body made up of conductive layers and dielectric layers arranged in an alternating manner; and outer electrodes disposed on the outside surface of the multilayer body. With electronic devices becoming smaller and thinner, there is a need for a small-sized multilayer capacitor with large electrostatic capacitance. General ways to increase the capacitance of the multilayer capacitor is to increase the area of overlap between adjacent conductive layers and increase the number of conductive layers.

In the case where the multilayer capacitor is reduced in size and the capacitance thereof is increased in the general ways described above, the distance from the conductive layers to the surface of the multilayer body becomes small. In general, the outer electrodes are likely to become thinner at the corners of the multilayer body. Because of these, conductive layers near the corners of the multilayer body become susceptible to moisture coming in through the outer electrodes, and the insulation resistance of the multilayer capacitor decreases. That is, the moisture resistance of the multilayer capacitor decreases.

Japanese Unexamined Patent Application Publication No. 2010-103566 discloses a highly moisture-resistant small multilayer capacitor. The multilayer capacitor disclosed in this document has a high moisture resistance because the concentration of magnesium is high in a dielectric disposed between conductive layers and the side surfaces of the multilayer body.

Increasing the number of conductive layers leads to an increase in internal stress, which results from the difference in thermal shrinkage between dielectric layers and conductive layers when the multilayer capacitor is fired. This makes the multilayer capacitor prone to layer separation.

SUMMARY OF THE INVENTION

Accordingly, preferred embodiments of the present invention provide a small-sized, large-capacitance multilayer capacitor that is highly moisture-resistant and less prone to layer separation.

According to a preferred embodiment of the present invention, a method for producing a multilayer capacitor including a multilayer body that includes conductive layers and dielectric layers arranged on top of each other in an alternating manner and that has external dimensions in which each side is about 0.3 mm or smaller when viewed from a stacking direction of the multilayer body, and first and second outer electrodes disposed on a surface of the multilayer body, includes the steps of: a) forming the multilayer body by stacking the conductive layers and the dielectric layers alternately, each of the conductive layers being located in a first arrangement or a second arrangement such that the conductive layers are located in the first arrangement and the second arrangement different from the first arrangement when viewed from the stacking direction; b) stretching the conductive layers in directions perpendicular or substantially perpendicular to the stacking direction by pressing the multilayer body; c) bending at least one of the conductive layers by pressing the multilayer body so that the at least one of the conductive layers is convex in the stacking direction; and d) forming the first and second outer electrodes on the surface of the multilayer body so that the first outer electrode is connected to those ones of the conductive layers which are in the first arrangement and the second outer electrode is connected to those ones of the conductive layers which are in the second arrangement.

The method may be performed such that each of the conductive layers is tapered in thickness from a center to an edge.

The method may be performed such that each of the conductive layers contains at least one of barium titanate and silicon.

The method may be performed such that step a) includes placing at least one pair of the conductive layers, which are adjacent to each other with one of the dielectric layers interposed therebetween, both in the first arrangement or both in the second arrangement.

The method may be performed such that the at least one pair of the conductive layers includes at least one of two of the conductive layers which are located outermost in the stacking direction.

According to another preferred embodiment of the present invention, a multilayer capacitor includes a multilayer body including conductive layers and dielectric layers arranged on each other in an alternating manner and that has external dimensions in which each side is about 0.3 mm or smaller when viewed from a stacking direction of the multilayer body; and first and second outer electrodes that are disposed on a surface of the multilayer body and that are spaced apart from each other in a lengthwise direction of the multilayer body. The multilayer body is structured such that the conductive layers and the dielectric layers are arranged on each other in the alternating manner, each of the conductive layers being disposed in a first arrangement or a second arrangement such that the conductive layers are located in the first arrangement and second arrangement different from the first arrangement when viewed from the stacking direction. The first outer electrode is connected to those ones of the conductive layers which are in the first arrangement. The second outer electrode is connected to those ones of the conductive layers which are in the second arrangement. At least one of the conductive layers which is located outermost in the stacking direction is bent so as to be convex in the stacking direction and includes penetrating portions which extend in the stacking direction. Assume that, in a cross section perpendicular or substantially perpendicular to the lengthwise direction, the bent conductive layer is equally divided into four regions named region A, region B, region C, and region D which are arranged in the order named in a widthwise direction of the multilayer body. The angle of inclination of the bent conductive layer is larger in the region A than in the region B and larger in the region D than in the region C, and the sum of the minimum diameters of the penetrating portions is larger in the region A than in the region B and larger in the region D than in the region C.

The multilayer capacitor may have a structure such that each of the conductive layers is not more than about 80% of the multilayer body in width and the maximum difference in width between the multilayer body and each of the conductive layers is less than about 0.07 mm, for example. It should be noted here that the width means the size in the widthwise direction of each body or layer.

The multilayer capacitor may have a structure such that at least one of the dielectric layers is an ineffective dielectric layer sandwiched between two of the conductive layers which are both in the first arrangement or both in the second arrangement and at least one of the dielectric layers is an effective dielectric layer sandwiched between two of the conductive layers which are in the first and second arrangements, respectively.

The multilayer capacitor may have a structure such that the ineffective dielectric layer adjoins at least one of two of the conductive layers which are outermost in the stacking direction.

The multilayer capacitor may have a structure such that the amount of convexity of the bent conductive layer in the cross section perpendicular or substantially perpendicular to the lengthwise direction is larger than the thickness of one of the dielectric layers which adjoins the bent conductive layer.

The multilayer capacitor may have a structure such that at least one of the penetrating portions contains filler in each of the regions A and D.

The multilayer capacitor may have a structure such that the filler contains a dielectric material which constitutes the dielectric layers.

The multilayer capacitor may have a structure such that the filler contains silicon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes multilayer capacitors and methods for producing the multilayer capacitors in accordance with preferred embodiments of the present invention with reference to the drawings. In the following description, the same or corresponding members in the drawings are assigned identical reference numbers and the descriptions for them are not repeated.

FIG. 1is a perspective view showing the appearance of a multilayer capacitor of Preferred Embodiment 1 of the present invention.FIG. 2is a cross-sectional view of the multilayer capacitor ofFIG. 1taken along line II-II.FIG. 3is a cross-sectional view of the multilayer capacitor ofFIG. 1taken along line III-III.FIG. 4is a cross-sectional view of the multilayer capacitor ofFIG. 2taken along line IV-IV.FIG. 5is a cross-sectional view of the multilayer capacitor ofFIG. 2taken along line V-V.FIG. 6is an enlarged cross-sectional view of the area VI enclosed by dot-dash lines inFIG. 3.FIG. 7is an enlarged cross-sectional view of a portion ofFIG. 6. InFIG. 1, a lengthwise direction L of the multilayer body, a widthwise direction W of the multilayer body, and a stacking direction T of the multilayer body are defined (these are described layer). It should be noted here that only some of the conductive layers and dielectric layers are illustrated for ease of understanding.

As illustrated inFIGS. 1 to 7, a multilayer capacitor100of Preferred Embodiment 1 of the present invention includes: a multilayer body110including conductive layers140and dielectric layers130arranged on top of each other in an alternating manner; and a pair of outer electrodes120(a first outer electrode121and a second outer electrode122) disposed on the surface of the multilayer body110.

The stacking direction T in which the dielectric layers130and the conductive layers140are stacked on top of each other is perpendicular or substantially perpendicular to the lengthwise direction L and the widthwise direction W of the multilayer body110.

The multilayer body110includes first and second main surfaces111and112opposite each other. The multilayer body110further includes: first and second end surfaces115and116opposite each other and adjacent to the first and second main surfaces111and112; and first and second side surfaces113and114opposite each other and adjacent to the first and second main surfaces111and112and the first and second end surfaces115and116. The shortest distance between the first and second side surfaces113and114is smaller than the shortest distance between the first and second end surfaces115and116. That is, the multilayer body110is shorter in the widthwise direction W than in the lengthwise direction L. Note, however, that the multilayer body110may be longer in the widthwise direction W than in the lengthwise direction L. The multilayer body110preferably is substantially in the shape of a cuboid. Here, at least one of the corners and edges of the cuboid may be rounded.

The multilayer capacitors in the preferred embodiments of the present invention include the multilayer body110which is substantially rectangle and whose sides are each about 0.3 mm or smaller in length when viewed from the stacking direction T (i.e., when viewed from above), for example. Preferably, the external dimensions of the multilayer body110are as follows: length is about 0.3 mm or smaller; and width is about 0.15 mm or smaller, for example. In the present preferred embodiment, the external dimensions (design dimensions) of the multilayer body110preferably are as follows: length is about 0.213 mm; width is about 0.103 mm; and thickness is about 0.103 mm, for example.

In the present preferred embodiment, the pair of outer electrodes120are disposed on the surface of the multilayer body110so as to be spaced apart from each other in the lengthwise direction L of the multilayer body110. Specifically, the pair of outer electrodes120include the first and second outer electrodes121and122disposed at the opposite ends in the lengthwise direction L (where there exist the first and second end surfaces115and116, respectively) of the multilayer body110.

In the multilayer body110, the conductive layers140and the dielectric layers130are arranged on top of each other in an alternating manner. Each of the conductive layers140is disposed in a first arrangement or a second arrangement different from the first arrangement so that the conductive layers140are present in the first and second arrangements when viewed from the stacking direction T.

The conductive layers140include: first conductive layers141disposed in the first arrangement and connected to the first outer electrode121; and second conductive layers142disposed in the second arrangement and connected to the second outer electrode122.

The first conductive layers141and the second conductive layers142each preferably have a rectangular or substantially rectangular shape when viewed from above. More specifically, when each of the first conductive layers141is viewed from above, three sides other than the first end surface115are each bowed outward in a convex curve and, when each of the second conductive layers142is viewed from above, three sides other than the second end surface116are each bowed outward in a convex curve.

It is preferable that, in each of the first and second conductive layers141and142, the total amount of curvature in the widthwise direction W of the two sides extending in the lengthwise direction L be larger than the amount of curvature in the lengthwise direction L of the side extending in the widthwise direction W. In this arrangement, the first and second conductive layers141and142are spaced away from the corners of the multilayer body110. This provides a better moisture resistance. In addition, the first and second conductive layers141and142are widened along their entire length. This increases the area of overlap between the first and second conductive layers141and142and provides a larger electrostatic capacitance. For the same reasons, it is preferable that the amount of curvature in the widthwise direction W of each of the two sides extending in the lengthwise direction L be larger than the amount of curvature in the lengthwise direction L of the side extending in the widthwise direction W.

The amount of curvature in the widthwise direction W of each of the two sides extending in the lengthwise direction L, the total amount of curvature in the widthwise direction W of the two sides extending in the lengthwise direction L, and the amount of curvature in the lengthwise direction L of the side extending in the widthwise direction W are each calculated in the following manner.

As shown inFIG. 4, two straight lines SL1, which are parallel or substantially parallel to the side surfaces of the multilayer body, are drawn from one end (one of the opposite ends in the lengthwise direction L which is exposed on the end surface115) of a first conductive layer141. A straight line SL3is drawn which passes through the intersections of the edge of the first conductive layer141and the two straight lines SL1. As shown inFIG. 5, two straight lines SL2, which are parallel or substantially parallel to the side surfaces of the multilayer body, are drawn from one end (one of the opposite ends in the lengthwise direction L which is exposed on the end surface116) of a second conductive layer142. A straight line SL3is drawn which passes through the intersections of the edge of the second conductive layer142and the two straight lines SL2.

InFIG. 4, the amount of curvature in the widthwise direction W of the two sides extending in the lengthwise direction L is (i) the longest distance V1from one of the straight lines SL1to the edge of the first conductive layer141running along the first side surface113and (ii) the longest distance V2from the other of the straight lines SL1to the edge of the first conductive layer141running along the second side surface114. The sum of these distances is (V1+V2). InFIG. 5, the amount of curvature in the widthwise direction W of the two sides extending in the lengthwise direction L is (i) the longest distance V1from one of the straight lines SL2to the edge of the second conductive layer142running along the first side surface113and (ii) the longest distance V2from the other of the straight lines SL2to the edge of the second conductive layer142running along the second side surface114. The sum of these distances is (V1+V2).

InFIG. 4, the amount of curvature in the lengthwise direction L of the side extending in the widthwise direction W is the longest distance V3from the straight line SL3to the edge of the first conductive layer141running along the second end surface116. InFIG. 5, the amount of curvature in the lengthwise direction L of the side extending in the widthwise direction W is the longest distance V3from the straight line SL3to the edge of the second conductive layer142running along the first end surface115.

In the present preferred embodiment, each of the first conductive layers141is exposed on the first end surface115of the multilayer body110and is connected to the first outer electrode121on the first end surface115, and each of the second conductive layers142is exposed on the second end surface116of the multilayer body110and is connected to the second outer electrode122on the second end surface116. In the present preferred embodiment, the number of the first conductive layers141is 21, and the number of the second conductive layers142preferably is 21, for example. That is, the number of the conductive layers140preferably is 42, for example.

As shown inFIG. 3, the width H140of each of the conductive layers140is not more than about 80% of the width H110of the multilayer body110. The maximum difference between the width H110of the multilayer body110and the width H140of each of the conductive layer140preferably is less than about 0.07 mm, for example. With this arrangement, the conductive layers140are easier to flatten out and bend (this is described later). In the present preferred embodiment, the width H140(design width) of each of the conductive layers140preferably is about 0.063 mm, for example. That is, the width H140(design width) of each of the conductive layers140preferably is about 61% of the width H110(design width) of the multilayer body110, for example. The maximum difference between the width H110(design width) of the multilayer body110and the width H140(design width) of each of the conductive layers140preferably is about 0.04 mm, for example.

The maximum distance G1(design distance) between the second side surface114of the multilayer body110and each of the conductive layers140in the widthwise direction W preferably is about 0.02 mm, and the maximum distance G2(design distance) between the first side surface113of the multilayer body110and each of the conductive layers140in the widthwise direction W preferably is about 0.02 mm, for example.

The length (design length) of each of the conductive layers140preferably is about 0.135 mm, for example. The maximum difference in length (design length) between the multilayer body110and each of the conductive layers140preferably is about 0.078 mm, for example. The thickness (design thickness) of each of the conductive layers140preferably is about 0.6 μm, for example.

The dielectric layers130include: a first outer layer portion131which constitutes the first main surface111; a second outer layer portion132which constitutes the second main surface112; and effective dielectric layers133sandwiched between the first and second conductive layers141and142. In the multilayer body110, the portion between the first and second outer layer portions131and132is referred to as an intermediate portion. In the present preferred embodiment, the thickness (design thickness) of each of the effective dielectric layers133preferably is about 0.75 μm, for example. The number of the effective dielectric layers133preferably is 41, for example. The thickness (design thickness) of each of the first and second outer layer portions131and132preferably is about 23 μm, for example.

The thickness of each of the conductive layers140and the dielectric layers130is measured by exposing a cross section of the multilayer body110perpendicular or substantially perpendicular to the lengthwise direction L (such a cross section is hereinafter referred to as a widthwise cross section) by grinding the multilayer body110and observing the exposed cross section under a scanning electron microscope. The thickness is measured along the following five lines: the center line running in the stacking direction T of the multilayer body110; and two equally-spaced lines on each side of the center line of the multilayer body110. The mean of these five thicknesses is calculated.

In the multilayer capacitor100of the present preferred embodiment, each of the conductive layers140is bent. Specifically, the conductive layers140are bent in the following manner. As shown inFIG. 2, in a cross section perpendicular or substantially perpendicular to the widthwise direction W (such a cross section is hereinafter referred to as a lengthwise cross section) of the multilayer body110, each of the conductive layers140is convex outward away from the center of the multilayer body110in the stacking direction T. As shown inFIG. 3, in a widthwise cross section of the multilayer body110, each of the conductive layers140is convex outward away from the center of the multilayer body110in the stacking direction T. It should be noted that not all the conductive layers140have to be convex in the stacking direction T, provided that at least one of the conductive layers140is convex in the stacking direction T.

It is preferable that the amount of convexity of the conductive layers140increases with approaching the outermost portions of the multilayer body110in the stacking direction T. This prevents the dielectric layers130from becoming too thick and thus prevents a decrease in electrostatic capacitance, and prevents the dielectric layers130from becoming too thin and thus prevents a decrease in insulation resistance.

As shown inFIG. 3, in the widthwise cross section of the multilayer body110, the amount of convexity of each of two conductive layers140which are outermost in the stacking direction T of the multilayer body110is larger than the thickness of the effective dielectric layer133adjoining this conductive layer140. The following provides specific examples. The amount of convexity B1of an outermost conductive layer148, which is closest to the first main surface111in the stacking direction T of the multilayer body110, is larger than the thickness of the effective dielectric layer133adjoining the outermost conductive layer148. The amount of convexity B2of an outermost conductive layer149, which is closest to the second main surface112in the stacking direction T of the multilayer body110, is larger than the thickness of the effective dielectric layer133adjoining the outermost conductive layer149. In the present preferred embodiment, the amount of convexity B1of the outermost conductive layer148and the amount of convexity B2of the outermost conductive layer149preferably are each about 7.1 μm, for example.

The amount of convexity of each of the outermost conductive layers148and149is preferably larger in a widthwise cross section of the multilayer body110than in a lengthwise cross section of the multilayer body110.

Assume that, in a widthwise cross section of the multilayer body110as shown inFIG. 6, a bent conductive layer140is equally divided into four regions named region A, region B, region C, and region D which are arranged in the order named in the widthwise direction W. The angle of inclination of the bent conductive layer140is larger in the region A than in the region B and is larger in the region D than in the region C.

This is specifically described below using the outermost conductive layer148as an example. Five straight lines X1to X5, each of which extends in the stacking direction T of the multilayer body110, are drawn so that the outermost conductive layer148is equally divided into four regions arranged in the widthwise direction W. The region between the straight lines X1and X2is the region A, the region between the straight lines X2and X3is the region B, the region between the straight lines X3and X4is the region C, and the region between the straight lines X4and X5is the region D.

Assume that, in the widthwise cross section of the multilayer body110, a curved center line passing through the center of the outermost conductive layer148is a center line Lwand each straight line parallel or substantially parallel to a straight line connecting the center of the first side surface113of the multilayer body110with the center of the second side surface114of the multilayer body110is a reference line L0. Assume that an acute angle θAbetween a line segment LA(i.e., a line secant to the curved center line Lwin the region A) and the reference line L0is the angle of inclination of the outermost conductive layer148in the region A. Similarly, assume that an acute angle θBbetween a line segment LB(i.e., a line secant to the curved center line Lwin the region B) and the reference line L0is the angle of inclination of the outermost conductive layer148in the region B, an acute angle θcbetween a line segment LC(i.e., a line secant to the curved center line Lwin the region C) and the reference line L0is the angle of inclination of the outermost conductive layer148in the region C, and an acute angle θDbetween a line segment LD(i.e., a line secant to the curved center line Lwin the region D) and the reference line L0is the angle of inclination of the outermost conductive layer148in the region D.

In the present preferred embodiment, the mean angle of inclination of the two outermost conductive layers148and149in the regions A, B, C, and D preferably is as follows: θAis about 22.4°; θBis about 6.0°; θCis about 7.3°; and θDis about 23.9°, for example. The angle of inclination of each conductive layer140can be measured by exposing a widthwise cross section of the multilayer body110by grinding the multilayer body110and observing the cross section under an optical microscope.

As shown inFIGS. 6 and 7, each conductive layer140has penetrating portions each extending in the stacking direction T of the multilayer body110. The penetrating portions are not illustrated inFIG. 3. It should be noted that not all the conductive layers140have to have the penetrating portions each extending in the stacking direction T of the multilayer body110, provided that at least one of the conductive layers140has the penetrating portions each extending in the stacking direction T of the multilayer body110.

This is specifically described using the outermost conductive layer148as an example. The outermost conductive layer148preferably includes three penetrating portions hA1, hA2, and hA3in the region A, one penetrating portion hB1in the region B, one penetrating portion hC1in the region C, and three penetrating portions hD1, hD2, and hD3in the region D.

The sum of the minimum diameter(s) of the penetrating portion(s) along a bent conductive layer140is larger in the region A than in the region B and is larger in the region D than in the region C. The minimum diameter of each penetrating portion along the bent conductive layer140is the shortest distance between the opposite ends of the penetrating portion on the center line Lw.

As has been described, in each conductive layer140, the total number of penetrating portions and the sum of the diameters of the penetrating portions both increase toward the opposite ends in the widthwise direction W. This is because each conductive layer140has been flattened out and bent and therefore has a low density (this is described later). In particular, the outermost conductive layers148and149, which are conductive layers140disposed outermost in the stacking direction T of the multilayer body110, have a small radius of curvature and have an even lower density after bending. Therefore, the outermost conductive layers148and149have a lot of relatively large penetrating portions.

In the present preferred embodiment, the mean number of penetrating portions in each of the regions A to D in all the conductive layers140preferably is as follows: about 1.5 in the region A; about 0.2 in the region B; about 0.2 in the region C; and about 1.2 in the region D, for example. Furthermore, the mean of the sum of the diameters of penetrating portions in each of the regions A to D in all the conductive layers140preferably is as follows: about 2.2 μm in the region A; about 0.2 μm in the region B; about 0.2 μm in the region C; and about 1.8 μm in the region D, for example.

The diameter of each penetrating portion can be measured by exposing a widthwise cross section of the multilayer body110by grinding the multilayer body110and observing the cross section under a scanning electron microscope.

InFIG. 6, all the penetrating portions contain filler which contains the dielectric material constituting the dielectric layers130. However, in reality, as shown inFIG. 7, some of the penetrating portions contain the filler but the other of the penetrating portions have voids150. Specifically, for example, in the case of the region A of the outermost conductive layer148, each of the penetrating portions hA1and hA3contains the filler containing the dielectric material whereas the penetrating portion hA2has a void150.

Since penetrating portions contain the filler containing the dielectric material, dielectric layers130, which are adjacent to each other with a conductive layer140therebetween, more strongly adhere to each other. For stronger adhesion between the dielectric layers130, it is preferable that, for example, barium titanate (the dielectric material) contain silicon. The composition of the filler can be identified by exposing a widthwise cross section of the multilayer body110by grinding the multilayer body110and observing the cross section with the use of a field emission wavelength dispersive X-ray spectrometer on a scanning electron microscope.

Furthermore, it is preferable that, for stronger adhesion between the adjacent dielectric layers130described above, the opposite ends of the conductive layers140in the widthwise direction W be displaced from each other (seeFIG. 6). One of the opposite ends in the width direction W of the outermost conductive layer148coincides with the straight line X1, that of the second conductive layer142adjacent to the outermost conductive layer148coincides with the straight line X11, and that of the first conductive layer141adjacent to the second conductive layer142coincides with the straight line X21. The straight lines X1, X11, and X21are displaced from each other in the widthwise direction W.

Similarly, the other of the opposite ends in the width direction W of the outermost conductive layer148coincides with the straight line X5, that of the second conductive layer142adjacent to the outermost conductive layer148coincides with the straight line X15, and that of the first conductive layer141adjacent to the second conductive layer142coincides with the straight line X25. The straight lines X5, X15, and X25are displaced from each other in the widthwise direction W.

The following specifically describes constituents of the multilayer capacitor100.

The dielectric layers130may be made from a dielectric ceramic material containing, as a main component, BaTiO3, CaTiO3, SrTiO3, CaZrO3, or the like. Alternatively, the dielectric layers130may be made from a dielectric ceramic material obtained by adding, to the main component, a secondary component such as a manganese compound, a magnesium compound, a silicon compound, a cobalt compound, a nickel compound, a rare earth compound, or the like. In the present preferred embodiment, the dielectric layers130preferably are made from a dielectric ceramic material containing BaTiO3(barium titanate) as a main component and having a relative permittivity of about 3400 so that the electrostatic capacitance (design capacitance) of the multilayer capacitor100is about 0.01 μF, for example.

The conductive layers140may be made from, for example, a metal such as nickel, copper, silver, palladium, gold, or the like or an alloy containing at least one of these metals such as a silver-palladium alloy. It is preferable that the conductive layers140further contain the same dielectric material as in the dielectric layers130(such a material is hereinafter referred to as a co-material). For example, in the case where the dielectric material constituting the dielectric layers130is BaTiO3, the conductive layers140preferably contain BaTiO3as a co-material. Furthermore, the conductive layers140preferably further contain silicon as a co-material. The thickness of each of the conductive layers140after firing is preferably about 0.2 μm or larger and about 2.0 μm or smaller, for example.

The pair of outer electrodes120includes: a base layer which covers the opposite ends of the multilayer body110; and a plating layer which covers the base layer. The base layer may be made from, for example, a metal such as nickel, copper, silver, palladium, gold, or the like or an alloy containing at least one of these metals such as a silver-palladium alloy. The thickness of the base layer is preferably about 5 μm or larger and about 20 μm or smaller, for example.

The base layer may be formed by applying a conductive paste to the opposite ends of the multilayer body110and baking the conductive paste or may be formed by firing the conductive paste together with the conductive layers140. Alternatively, the base layer may be formed by plating the opposite ends of the multilayer body110or may be formed by applying a resin paste containing metal particles to the opposite end of the multilayer body110and allowing the resin paste to cure.

The plating layer may be made from, for example, a metal such as nickel, copper, silver, palladium, gold, or the like or an alloy containing at least one of these metals such as a silver-palladium alloy.

The plating layer may include multiple layers. In this case, the plating layer is preferably a double layer composed of a nickel plating layer and a tin plating layer disposed on the nickel plating layer. The nickel plating layer defines and functions as a solder blocking layer. The tin plating layer is highly wettable with solder. The thickness of each layer in the plating layer is preferably about 0.5 μm or larger and about 5 μm or smaller, for example.

The following describes a method for producing the multilayer capacitor100of the present preferred embodiment.FIG. 8is a flowchart showing a method for producing a multilayer ceramic capacitor of Preferred Embodiment 1 of the present invention.

As shown inFIG. 8, the production of the multilayer capacitor100starts with preparation of a ceramic slurry (step S1). Specifically, ceramic powder, binder, solvent, and the like are mixed in a predetermined ratio, such that a ceramic slurry is made.

Next, ceramic green sheets are formed (step S2). Specifically, a ceramic green sheet is formed by shaping the ceramic slurry into a sheet on a carrier film with the use of a die coater, a gravure coater, a micro gravure coater, or the like.

Next, mother sheets are prepared (step S3). Specifically, a conductive paste for conductive layers is applied onto some of the above-obtained ceramic green sheets in a predetermined pattern by screen printing method or gravure printing method. The conductive paste preferably contains a co-material described earlier. As shown inFIG. 10(described later), each conductive pattern14has a curved shape which is tapered in thickness from the center thereof to the ends thereof.

The ceramic green sheets which have conductive patterns for conductive layers thereon and ceramic green sheets having no conductive patterns thereon thus prepared are used as mother sheets. It should be noted that the conductive paste for conductive layers may contain a known binder and solvent.

Next, the mother sheets are stacked together (step S4). Specifically, the mother sheets are stacked in the following manner. A predetermined number of ceramic green sheets having no conductive patterns thereon are stacked together to form a second outer layer portion132. On top of this, a plurality of ceramic green sheets having conductive patterns thereon are orderly stacked to define an intermediate portion. On top of this, a predetermined number of ceramic green sheets having no conductive patterns thereon are stacked together to define a first outer layer portion131. In this way, a stack of mother sheets is formed.

Next, the stack of mother sheets is pressed and thus the conductive patterns for conductive layers are stretched (step S5) and bent (step S6). It should be noted that, in the present preferred embodiment, step S5for stretching the conductive patterns for conductive layers and step S6for bending the conductive patterns for conductive layers are performed concurrently. Note, however, that this does not imply any limitation and that step S5and step S6may be performed separately. For example, the following process may be used. A stack of mother sheets only for the intermediate portion is pressed and thus the conductive patterns for conductive layers are stretched (this is step S5) and thereafter a predetermined number of ceramic green sheets, which constitute at least one of the first and second outer layer portions131and132, are stacked on the mother sheets and are pressed again, such that the conductive patterns for conductive layers are bent (this is step S6).

FIG. 9is a cross-sectional view of a stack of mother sheets, which is not pressed yet, of the multilayer capacitor of Preferred Embodiment 1 of the present invention in the lengthwise direction L of the multilayer capacitor.FIG. 10is a cross-sectional view of the stack of mother sheets, which is not pressed yet, of the multilayer capacitor of Preferred Embodiment 1 of the present invention in the widthwise direction W of the multilayer capacitor.FIG. 11is a cross-sectional view of the pressed stack of mother sheets (i.e., mother multilayer body) of the multilayer capacitor of Preferred Embodiment 1 of the present invention in the lengthwise direction L of the multilayer capacitor.FIG. 12is a cross-sectional view of the pressed stack of mother sheets (i.e., mother multilayer body) of the multilayer capacitor of Preferred Embodiment 1 of the present invention in the widthwise direction W of the multilayer capacitor.

As shown inFIG. 9, a stack of mother sheets11includes regions Y and regions Z arranged in an alternating manner in the lengthwise direction L. The regions Y include a lot of conductive patterns14and the regions Z include only a relatively small number of conductive patterns14. On the other hand, as shown inFIG. 10, the stack of mother sheets11includes the regions Y and regions N arranged in an alternating manner in the widthwise direction W. The regions Y include a lot of conductive patterns14and regions N only include a dielectric portion13and have no conductive patterns14.

As shown inFIGS. 9 to 12, the stack of mother sheets is pressed in the stacking direction T and pressure-bonded with the use of a pair of flat dies91. The stack of mother sheets11is arranged such that the number of layers is larger in the regions Y than in the regions Z and N. Therefore, the conductive patterns14in the regions Y are pressed out into the regions Z and N. The conductive patterns14have a curved shape which is tapered in thickness from the center thereof to the ends thereof when viewed in a cross section. Therefore, the edge portion of the conductive patterns14becomes very thin when pressed. In addition, the conductive patterns14, which are pressed out into the regions Z and N, are pushed by the flow of a ceramic material coming from the first or second outer layer portion and thus bent inward. This makes the edge portions of the conductive patterns14even thinner. It is preferable that, as shown inFIGS. 9 to 12, the pair of flat dies91for pressing the stack of mother sheets11have rubber portions92on their working surfaces. This makes it possible to bend the conductive patterns14more effectively. In this way, a mother multilayer body11ais formed.

Assume here that, in one of two multilayer bodies which are to be cut from the mother multilayer body (described later) and which are adjacent to each other in their lengthwise direction, a ceramic green sheet having a conductive pattern disposed in the first arrangement (this conductive pattern corresponds to a first conductive layer141) is referred to as a pattern-A sheet whereas a ceramic green sheet having a conductive pattern disposed in the second arrangement (this conductive pattern corresponds to a second conductive layer142) is referred to as a pattern-B sheet. When the pattern-A sheet and the pattern-B sheet are stacked together, the ceramic green sheet between the conductive patterns defines and functions as an effective dielectric layer133.

It should be noted that the pattern-A sheet and the pattern-B sheet may be the same ceramic green sheets having identical conductive patterns thereon, which are displaced from each other when stacked together. That is, the mother multilayer body may be produced from ceramic green sheets having identical conductive patterns thereon.

In the other of the multilayer bodies which are to be cut from the mother multilayer body (described later) and which are adjacent to each other in their lengthwise direction, a ceramic green sheet having a conductive pattern disposed in the first arrangement (this conductive pattern corresponds to a first conductive layer141) is the pattern-B sheet and a ceramic green sheet having a conductive pattern disposed in the second arrangement (this conductive pattern corresponds to a second conductive layer142) is the pattern-A sheet. As is clear from this, in each of the multilayer bodies which are to be cut from the mother multilayer body and which are adjacent to each other in their lengthwise direction, conductive layers disposed in the first arrangement and conductive layers disposed in the second arrangement are arranged one above the other with dielectric layers therebetween in the stacking step (step S4).

Next, the mother multilayer body is cut (step S7). Specifically, the mother multilayer body is cut with a hand cutter or a dicing machine along lines C1in the regions Z and N into a plurality of soft multilayer bodies substantially in the shape of a cuboid. Next, the soft multilayer bodies are barrel-finished if necessary (step S8) so that the outside surface (especially corners and edges) of the soft multilayer bodies is rounded.

Next, the soft multilayer bodies are fired (step S9). Specifically, the soft multilayer bodies are heated at a predetermined temperature, such that the ceramic material and conductive material are sintered. In this way, multilayer bodies110are formed. During heating, aggregation of the metal component in the conductive patterns14occurs. Since the edge portions of the conductive patterns14are very thin, the aggregation of metal component makes penetrating portions in the edge portions of the conductive patterns14. As described earlier, the conductive patterns14, which have a curved shape when viewed in a cross section, are flattened out and bent, and heated, such that a relatively large number of penetrating portions are made in the regions A and D.

Next, outer electrodes are formed (step S10). Specifically, a conductive paste for outer electrodes is applied to each end portion of the multilayer body110by a printing method or dipping method or the like and heated, such that a base layer is formed.

Next, a plating layer is formed on the base layer by attaching a metal component to the base layer by plating method. The step of forming the base layer and the step of forming the plating layer provide outer electrodes120at the opposite end portions of the multilayer body110in a way that the outer electrodes120are electrically connected to the conductive layers140. A series of processes described above produces the multilayer capacitor100of the present preferred embodiment.

In the multilayer capacitor100of the present preferred embodiment, conductive layers140, which have the effective dielectric layers133therebetween, have been stretched and bent. Therefore, the area of overlap between adjacent conductive layers140is large. This increases electrostatic capacitance without increasing the size of the multilayer capacitor100. That is, it is possible to provide a small-sized, large-capacitance multilayer capacitor100.

Furthermore, since the conductive layers140are bent, the end portions of the conductive layers140are positioned farther away from the corners of the multilayer body110. This imparts a high moisture resistance to the multilayer capacitor100. In particular, the bending of the outermost conductive layers148and149plays an important role in imparting a high moisture resistance to the multilayer capacitor100.

In the multilayer capacitor100, the width H140of each of the conductive layers140preferably is not more than about 80% of the width H110of the multilayer body110, and the maximum difference between the width H110of the multilayer body110and the width H140of each of the conductive layers140preferably is less than about 0.07 mm, for example. This makes it possible to effectively stretch and bend the conductive patterns.

Specifically, if the region N was too small inFIG. 10, it would be difficult to flatten out the conductive patterns. In this respect, in order to sufficiently flatten out the conductive patterns, it is preferable that the width of the conductive layers140be not more than about 80% of the width of the multilayer body110, for example. On the other hand, if the region N was too large, ceramic green sheets would be bonded together by pressure and voids in the region N would be filled before the conductive patterns are sufficiently flattened out. This would make it difficult to flatten out the conductive patterns. In this respect, in order to sufficiently flatten out the conductive patterns, it is preferable that the maximum difference between the width of the conductive layers140and the width of the multilayer body110be less than about 0.07 mm, for example. Sufficiently flattened-out conductive layers are easily bent sufficiently by the flow of ceramic green sheets into the region N.

The multilayer capacitor100of the present preferred embodiment is structured such that the amount of convexity B1or B2of at least one of the two outermost conductive layers148and149, which are disposed at the opposite ends in the stacking direction T of the multilayer body110, in a widthwise cross section of the multilayer body110is larger than the thickness of the effective dielectric layer133adjoining this conductive layer148or149. This is preferable to unfailingly obtain the area of substantial overlap between the conductive layers which contributes to electrostatic capacitance.

In the multilayer capacitor100of the present preferred embodiment, filler containing a dielectric material is contained in the penetrating portions in the conductive layers140. Therefore, dielectric layers133adjacent to each other with a conductive layer140therebetween strongly adhere to each other. This makes it possible to reduce the occurrence of separation of layers. In particular, the outermost conductive layers148and149, which are susceptible to separation because of internal stress resulting from the difference in thermal shrinkage between the dielectric layers130and conductive layers140when fired, have penetrating portions which contain filler containing a dielectric material. This reduces the occurrence of separation of layers of the multilayer capacitor100. Furthermore, when the conductive paste for conductive layers140contains a dielectric material as a co-material, it is possible to facilitate the formation of filler that contains the dielectric material.

It seems that the reason that the dielectric layers130strongly adhere to each other is as follows. In the multilayer capacitor100of the present preferred embodiment, the filler contains a dielectric material (barium titanate) which contains silicon. Therefore, the segregation of silicon occurs at grain boundaries of ceramics which grow and increase in grain size while firing. The segregated silicon moves along the grain boundaries of ceramics and collects at the interface between adjacent dielectric layers130. The adjacent dielectric layers130have a lot of minute gaps at the interface between them. These gaps are filled with silicon and thus the adjacent dielectric layers130are joined and strongly adhere to each other. Furthermore, when the conductive paste for conductive layers140contains silicon as a co-material, it is possible to facilitate the formation of filler that contains silicon. It should be noted that the filler may consist only of silicon.

In the multilayer capacitor100of the present preferred embodiment, the opposite ends of the conductive layers140in the widthwise direction W are displaced from each other as shown inFIG. 6. Therefore, adjacent dielectric layers130near these ends are joined in a zigzag manner and thus strongly adhere to each other. This further reduces the occurrence of separation of layers of the multilayer capacitor100.

The following is a description of an experiment to test the moisture resistance of the multilayer capacitor of the present preferred embodiment.

EXPERIMENT

The following describes the conditions in which a non-limiting experiment was conducted.72multilayer capacitors having an electrostatic capacitance of about 0.01 μF were left to stand for about 2000 hours in an atmosphere having a temperature of about 85° C. and a humidity of about 85% RH, and thereafter a voltage of about 6.3 V was applied and resistance was measured. If the resistance of a multilayer capacitor is about 1.0×108Ω or less, this multilayer capacitor is determined to have a poor moisture resistance. The results showed that none of the multilayer capacitors of the present preferred embodiment had a poor moisture resistance.

The above experiment showed that the multilayer capacitor100of the present preferred embodiment does not experience a decrease in moisture resistance. That is, a small-sized, large-capacitance multilayer capacitor was obtained without reducing moisture resistance.

The following describes a multilayer capacitor and a method for producing the multilayer capacitor of Preferred Embodiment 2 of the present invention. It should be noted that, since the multilayer capacitor and the method for producing the multilayer capacitor of the present preferred embodiment are different from the multilayer capacitor and the method for producing the multilayer capacitor of Preferred Embodiment 1 only in a way in which the layers of the multilayer body are stacked, the other constituents are not described here.

FIG. 13is a cross-sectional view showing a configuration of a multilayer capacitor of Preferred Embodiment of the present invention. The cross-sectional view of the multilayer capacitor inFIG. 13is taken along the same line asFIG. 2. A cross-sectional view of the multilayer capacitor ofFIG. 13taken along line III-III looks the same as that shown inFIG. 3.

As shown inFIG. 13, a multilayer capacitor200of Preferred Embodiment 2 of the present invention includes third conductive layers240that are connected to a second outer electrode122and that are positioned near but separate from end portions, which are closer to a second end surface116, of first conductive layers141. The multilayer capacitor200further includes fourth conductive layers241that are connected to a first outer electrode121and that are positioned near but separate from end portions, which are closer to a first end surface115, of second conductive layers142.

In the multilayer capacitor200of Preferred Embodiment 2 of the present invention, the third and fourth conductive layers240and241make it difficult for the first and second conductive layers141and142to spread out in the lengthwise direction L. As a result, the first and second conductive layers141and142become more likely to spread out in the widthwise direction W. With this arrangement, the first and second conductive layers141and142are kept away from the corners of the multilayer body110and thus a high moisture resistance is maintained and, at the same time, electrostatic capacitance is further increased because the first and second conductive layers141and142are widened throughout their length and thus the area of overlap between the first and second conductive layers141and142is large.

In the method for producing the multilayer capacitor of Preferred Embodiment 2 of the present invention, a stack of mother sheets is pressure-bonded in the following manner.

FIG. 14is a cross-sectional view of a stack of mother sheets, which is not pressed yet, of the multilayer capacitor of Preferred Embodiment 2 of the present invention in the lengthwise direction L of the multilayer capacitor.FIG. 15is a cross-sectional view of the pressed stack of mother sheets (i.e., a mother multilayer body) of the multilayer capacitor of Preferred Embodiment 2 of the present invention in the lengthwise direction L of the multilayer capacitor. It should be noted that cross-sections in the widthwise direction W of the multilayer capacitor are the same as those of the stack of mother sheets and the mother multilayer body of Preferred Embodiment 1, and therefore are not described here.

As shown inFIG. 14, a stack of mother sheets21includes regions Y1, Y2, Z1, and Z2repeatedly arranged in the order of Y1, Z1, Y2, and Z2in the lengthwise direction L. The regions Y1and Y2include a lot of conductive patterns24, and the regions Z1and Z2include only a relatively small number of conductive patterns24.

As shown inFIG. 14, the stack of mother sheets21is pressed in the stacking direction T and pressure-bonded with the use of a pair of flat dies91having rubber portions92on their work surfaces by, for example, isostatic pressing or the like. In the stack of mother sheets21, the number of layers is larger in the regions Y1and Y2than in the regions Z1and Z2. Therefore, the rubber portions92pressed against the stack of mother sheets21deform and flow from the regions Y1and Y2into the regions Z1and Z2and become convex inward as shown inFIG. 15, thus pressure-bonding, like drawing, the mother sheets in the regions Z1and Z2of the stack of mother sheets21. This causes the mother sheets to strongly adhere to each other. In this way, a mother multilayer body21ais formed.

Next, the mother multilayer body21ais cut (step S6). Specifically, the mother multilayer body21ais cut with a hand cutter or a dicing machine along lines C2in the regions Y2into a plurality of soft multilayer bodies substantially in the shape of a cuboid.

The method for producing the multilayer capacitor of the present preferred embodiment also provides a small-sized, large-capacitance multilayer capacitor that is highly moisture-resistant and less prone to layer separation.

The following describes a multilayer capacitor and a method for producing the multilayer capacitor of Preferred Embodiment 3 of the present invention. It should be noted that, since the multilayer capacitor and the method for producing the multilayer capacitor of the present preferred embodiment are different from the multilayer capacitor and the method for producing the multilayer capacitor of Preferred Embodiment 1 only in that the multilayer capacitor of the present preferred embodiment includes ineffective dielectric layers, the other constituents are not described here.

FIG. 16is a cross-sectional view showing a configuration of a multilayer capacitor of Preferred Embodiment 3 of the present invention.FIG. 17is a cross-sectional view of the multilayer capacitor ofFIG. 16taken along line XVII-XVII. The cross-sectional view of the multilayer capacitor inFIG. 16is taken along the same line asFIG. 2.

As shown inFIGS. 16 and 17, dielectric layers130of a multilayer capacitor300of Preferred Embodiment 3 of the present invention include: a first outer layer portion131which constitutes a first main surface111; a second outer layer portion132which constitutes a second main surface112; at least one effective dielectric layer133sandwiched between first and second conductive layers141and142; and at least one ineffective dielectric layer sandwiched between first conductive layers141or between second conductive layers142. Examples of the ineffective dielectric layer include: a first ineffective dielectric layer134between first conductive layers141; and a second ineffective dielectric layer135between second conductive layers142.

The thickness of the ineffective dielectric layer is substantially the same as the thickness of the effective dielectric layer133. Specifically, the thickness of the ineffective dielectric layer preferably is more than about 0.5 times and less than about 2 times the thickness of the effective dielectric layer133, for example. The ineffective dielectric layer and the effective dielectric layer133are made of ceramic green sheets of the same thickness.

The conductive layers140include a conductive layer140that is sandwiched between the effective dielectric layer133and the ineffective dielectric layer. Specifically, a first conductive layer141and a second conductive layer142, which include another first conductive layer141or another second conductive layer142located therebetween, are stacked together with dielectric layers130therebetween.

In the multilayer body110, a portion between the first and second outer layer portions131and132is referred to as an intermediate portion. In the present preferred embodiment, the intermediate portion includes one first ineffective dielectric layer134and two second ineffective dielectric layers135.

The first ineffective dielectric layer134is positioned outermost in the intermediate portion near the second main surface112. One of the two second ineffective dielectric layers135is positioned outermost in the intermediate portion near the first main surface111. That is, each of the two conductive layers140at the opposite ends in the stacking direction T of the multilayer body110adjoins an ineffective dielectric layer. Specifically, an outermost conductive layer348, which is closest to the first main surface111in the stacking direction T of the multilayer body110, adjoins the second ineffective dielectric layer135, whereas an outermost conductive layer349, which is closest to the second main surface112in the stacking direction T of the multilayer body110, adjoins the first ineffective dielectric layer134.

The other one of the two second ineffective dielectric layers135is, assuming that the region between the two conductive layers140at the opposite ends in the stacking direction T of the multilayer body110is divided equally into three regions, positioned in the middle one of the three regions in closest proximity to the center of the intermediate portion. That is, a conductive layer140in the middle one of the three regions, into which the region between the two conductive layers140at the opposite ends in the stacking direction T of the multilayer body110is equally divided, adjoins an ineffective dielectric layer.

Note, however, that the arrangement of ineffective dielectric layers is not limited to that described above, provided that an ineffective dielectric layer adjoins at least one of the outermost conductive layers349and348which are outermost in the stacking direction T of the multilayer body110.

As shown inFIG. 17, the amount of convexity of each of the two conductive layers140at the opposite ends in the stacking direction T of the multilayer body110is larger than the thickness of the ineffective dielectric layer adjoining this conductive layer140in a widthwise cross section of the multilayer body110. Specifically, the amount of convexity B1of the outermost conductive layer348, which is closest to the first main surface111in the stacking direction T of the multilayer body110, is larger than the thickness of the second ineffective dielectric layer135adjoining the outermost conductive layer348. The amount of convexity B2of the outermost conductive layer349, which is closest to the second main surface112in the stacking direction T of the multilayer body110, is larger than the thickness of the first ineffective dielectric layer134adjoining the outermost conductive layer349.

In the multilayer capacitor300of the present preferred embodiment, the outermost conductive layers348and349protect inner conductive layers140. In addition, since the number of conductive layers140is large, the difference between a pressure applied to the region in which the conductive patterns for conductive layers140are present and a pressure applied to the region in which no conductive patterns for conductive layers140are present becomes large. This makes it possible to flatten out the conductive patterns for conductive layers140to a larger extent in the pressing process.

In the method for producing the multilayer capacitor of Preferred Embodiment 3 of the present invention, a stack of mother sheets is pressure-bonded in the following manner.

FIG. 18is a cross-sectional view of a stack of mother sheets, which is not pressed yet, of the multilayer capacitor of Preferred Embodiment 3 of the present invention in the lengthwise direction L of the multilayer capacitor.FIG. 19is a cross-sectional view of the pressed stack of mother sheets (i.e., mother multilayer body) of the multilayer capacitor of Preferred Embodiment 3 of the present invention in the lengthwise direction L of the multilayer capacitor. It should be noted that the cross-sections in the widthwise direction W of the multilayer capacitor are the same as those of the stack of mother sheets and the mother multilayer body of Preferred Embodiment 1, and therefore are not described here.

As shown inFIGS. 18 and 19, a stack of mother sheets31includes regions Y and regions Z arranged in an alternating manner in the lengthwise direction L. The regions Y have a lot of conductive patterns14and the regions Z only have a relatively small number of conductive patterns14.

Assume that, in one of multilayer bodies which are to be cut from a mother multilayer body31aand which are adjacent to each other in their lengthwise direction, a ceramic green sheet having a conductive pattern disposed in the first arrangement (this conductive pattern corresponds to a first conductive layer141) is referred to as a pattern-A sheet and a ceramic green sheet having a conductive pattern disposed in the second arrangement (this conductive pattern corresponds to a second conductive layer142) is referred to as a pattern-B sheet. When the pattern-A sheets are stacked together, the ceramic green sheet between the conductive patterns defines and functions as a first ineffective dielectric layer134. When the pattern-B sheets are stacked together, the ceramic green sheet between the conductive patterns defines and functions as a second ineffective dielectric layer135.

That is, regarding the ceramic green sheets having conductive patterns thereon, preparing the pattern-A and pattern-B sheets makes it possible to provide the effective dielectric layer133and the first and second ineffective dielectric layers134and135. This makes it possible to readily and effectively produce a mother multilayer body. It should be noted that the pattern-A sheet and pattern-B sheet may be the same ceramic green sheets having identical conductive patterns, which are displaced from each other when stacked together. That is, the mother multilayer body may be produced from ceramic green sheets having identical conductive patterns.

In the present preferred embodiment, at least one pair of conductive layers adjacent to each other with any one of the dielectric layers130therebetween are both in the first arrangement or both in the second arrangement. The at least one pair of conductive layers includes at least one of the two conductive layers outermost in the stacking direction T of the multilayer body110.

Specifically, an ineffective dielectric layer is provided so that at least one of two conductive layers140at the opposite ends in the stacking direction T of the multilayer body110adjoins this ineffective dielectric layer. In this case, the ineffective dielectric layer at one of the opposite ends in the stacking direction T of the multilayer body110serves to protect effective dielectric layers inside the intermediate portion. This makes it possible to provide a highly moisture-resistant and more reliable multilayer capacitor100.

In the present preferred embodiment, another ineffective dielectric layer is provided so that a conductive layer140in the middle in the stacking direction T of the multilayer body110adjoins this ineffective dielectric layer. In this arrangement, the dielectric layer in the middle of the multilayer body110, which is most likely to become thin when mother sheets are pressure-bonded, is ineffective. Even if the ineffective dielectric layer becomes thin and insulation resistance decreases, this does not cause a short circuit. Therefore, it is possible to provide a more reliable multilayer capacitor300.

In the present preferred embodiment, it is also possible to produce a small-sized, large-capacitance multilayer capacitor that is highly moisture-resistant and less prone to layer separation.

The following describes a multilayer capacitor and a method for producing the multilayer capacitor of Preferred Embodiment 4 of the present invention. It should be noted that, since the multilayer capacitor and the method for producing the multilayer capacitor of the present preferred embodiment are different from the multilayer capacitor and the method for producing the multilayer capacitor of Preferred Embodiment 3 only in a way in which the layers of the multilayer body are stacked, the other constituents are not described here.

FIG. 20is a cross-sectional view showing a configuration of a multilayer capacitor of Preferred Embodiment of the present invention. The cross-sectional view of the multilayer capacitor inFIG. 20is taken along the same line asFIG. 2. A cross section taken along line XVII-XVII inFIG. 20of the multilayer capacitor looks the same as that shown inFIG. 17.

As shown inFIG. 20, a multilayer capacitor400of Preferred Embodiment 4 of the present invention includes third conductive layers240that are connected to a second outer electrode122and that are positioned near but separate from end portions, which are closer to a second end surface116, of first conductive layers141. The multilayer capacitor400further includes fourth conductive layers241that are connected to a first outer electrode121and that are positioned near but separate from end portions, which are closer to a first end surface115, of second conductive layers142. The multilayer capacitor400of the present preferred embodiment achieves the advantages of both the multilayer capacitor200of Preferred Embodiment 2 and the multilayer capacitor300of Preferred Embodiment 3.

In the method for producing the multilayer capacitor of Preferred Embodiment 4 of the present invention, a stack of mother sheets is pressure-bonded in the following manner.

FIG. 21is a cross-sectional view of a stack of mother sheets, which is not pressed yet, of the multilayer capacitor of Preferred Embodiment 4 of the present invention in the lengthwise direction L of the multilayer capacitor.FIG. 22is a cross-sectional view of the pressed stack of mother sheets (i.e., mother multilayer body) of the multilayer capacitor of Preferred Embodiment 4 of the present invention in the lengthwise direction L of the multilayer capacitor. It should be noted that the cross-sections in the widthwise direction W of the multilayer capacitor are the same as those of the stack of mother sheets and the mother multilayer body of Preferred Embodiment 1, and therefore are not described here.

As shown inFIG. 21, a stack of mother sheets41includes regions Y1, Y2, Z1, and Z2repeatedly arranged in the order of Y1, Z1, Y2, and Z2in the lengthwise direction L. The regions Y1and Y2have a lot of conductive patterns24, and the regions Z1and Z2have only a relatively small number of conductive patterns24.

As shown inFIG. 21, the stack of mother sheets41is pressed in the stacking direction T and pressure-bonded with the use of a pair of flat dies91including rubber portions92on their work surfaces by, for example, isostatic pressing. In the stack of mother sheets41, the number of layers is larger in the regions Y1and Y2than in the regions Z1and Z2. Therefore, the rubber portions92pressed against the stack of mother sheets41deform and flow from the regions Y1and Y2into the regions Z1and Z2and become convex inward as shown inFIG. 22, thus pressure-bonding, like drawing, the mother sheets in the regions Z1and Z2of the stack of mother sheets. This causes the mother sheets to strongly adhere to each other. In this way, a mother multilayer body41ais formed.

Next, the mother multilayer body is cut (step S6). Specifically, the mother multilayer body is cut with a hand cutter or a dicing machine along lines C2in the regions Y2into a plurality of soft multilayer bodies substantially in the shape of a cuboid.

The method for producing the multilayer capacitor of the present preferred embodiment also provides a small-sized, large-capacitance multilayer capacitor that is highly moisture-resistant and less prone to layer separation.