Multilayer capacitor

An element body includes a pair of principal surfaces, a pair of side surfaces, and another pair of side surfaces. Each of a pair of terminal electrodes includes a first electrode portion disposed on the principal surface and a second electrode portion disposed on the side surface. In the element body, a length in a direction in which the pair of principal surfaces oppose each other is smaller than a length in a direction in which the pair of side surfaces oppose each other and smaller than a length in a direction in which the other pair of side surfaces oppose each other. An arithmetic mean deviation of the surface of the first electrode portion is from 0.20 to 0.26 μm. An arithmetic mean deviation of the surface of the second electrode portion is from 0.27 to 0.38 μm.

TECHNICAL FIELD

The present invention relates to a multilayer capacitor.

BACKGROUND

Known multilayer capacitors include an element body of a rectangular parallelepiped shape, a plurality of internal electrodes, and a pair of terminal electrodes (e.g., cf. Japanese Unexamined Patent Publication No. 2005-243835). The element body includes a pair of principal surfaces opposing each other, a pair of side surfaces opposing each other, and another pair of side surfaces opposing each other. The plurality of internal electrodes are disposed in the element body to oppose each other in a direction in which the pair of principal surfaces opposing each other. The pair of terminal electrodes are disposed at the respective two ends of the element body in a direction in which the other pair of side surfaces oppose each other. The pair of terminal electrodes are connected each to corresponding internal electrodes out of the plurality of internal electrodes.

SUMMARY

Electronic equipment such as information terminal devices has been becoming smaller and thinner. In conjunction therewith, substrates mounted on the electronic equipment and electronic components mounted on the substrates have been downsized and mounted in higher density. Substrates with built-in electronic components have been developed for further reduction in size of electronic equipment in such substrates with built-in electronic components, the electronic components are mounted on the substrate to be embedded therein. The embedded electronic component needs to be securely electrically connected to wiring formed on the substrate. In the case of the multilayer capacitor described in Japanese Unexamined Patent Publication No. 2005-243835, however, no consideration is given to embedment in the substrate (built-in mounting in the substrate) and electrical connection to the wiring formed on the substrate.

One aspect of the present invention provides a multilayer capacitor that can be suitably built into a substrate, achieves reduction in height, and ensures connectivity to wiring formed on the substrate.

A multilayer capacitor according to one aspect of the present invention includes an element body of a rectangular parallelepiped shape, a plurality of internal electrodes, and a pair of terminal electrodes. The element body includes a pair of principal surfaces opposing each other, a pair of side surfaces opposing each other, and another pair of side surfaces opposing each other. The plurality of internal electrodes are disposed in the element body to oppose each other in a direction in which the pair of principal surfaces oppose each other. The pair of terminal electrodes are connected each to corresponding internal electrodes out of the plurality of internal electrodes. Each terminal electrode includes a first electrode portion disposed on the principal surface and a second electrode portion disposed on the side surface. A length of the element body in the direction in which the pair of principal surfaces oppose each other is smaller than a length of the element body in a direction in which the pair of side surfaces oppose each other and smaller than a length of the element body in a direction in which the other pair of side surfaces oppose each other. An arithmetic mean deviation of the surface of the first electrode portion is from 0.20 to 0.26 μm. An arithmetic mean deviation of the surface of the second electrode portion is from 0.27 to 0.38 μm.

In the multilayer capacitor according to the one aspect, the length of the element body in the direction in which the pair of principal surfaces oppose each other is smaller than the length of the element body in the direction in which the pair of side surfaces oppose each other and smaller than the length of the element body in the direction in which the other pair of side surfaces oppose each other. For this reason, the multilayer capacitor according to the foregoing aspect is obtained that has reduced height and is suitable for built-in mounting in a substrate. Each terminal electrode includes the first electrode portion disposed on the principal surface. For this reason, the multilayer capacitor according to the one aspect can be electrically connected to wiring formed on the substrate, on the foregoing principal surface side. Therefore, the multilayer capacitor according to the one aspect can be readily built into the substrate.

The multilayer capacitor is placed in a housing portion of the substrate and thereafter the housing portion is filled with a resin, whereby the multilayer capacitor is built into the substrate. After the multilayer capacitor is built into the substrate, via holes are formed in the substrate to reach the respective terminal electrodes (first electrode portions). Thereafter, conductors are formed in the respective via holes. The conductors formed in the via holes are connected to the first electrode portions.

In the multilayer capacitor according to the one aspect, the arithmetic mean deviation of the surface of the first electrode portion is from 0.20 to 0.26 μm and the arithmetic mean deviation of the surface of the second electrode portion is from 0.27 to 0.38 μm. For this reason, a void is prevented from occurring between the conductor formed in each via hole and the first electrode portion. A void is also prevented from occurring between the resin filled in the housing portion and the second electrode portion. Peeling is also prevented from occurring between the conductor and the first electrode portion. Peeling between the resin and the second electrode portion is also prevented. As a result of these, the multilayer capacitor according to the above aspect can be suitably built into the substrate, and ensures connectivity to the wiring formed on the substrate.

An arithmetic mean deviation of the surface of the element body exposed from the pair of terminal electrodes may be from 0.14 to 0.19 μm. In this case, a void is prevented from occurring between the resin filled in the housing portion and the element body. Peeling between the resin and the element body is also prevented. As a result of these, the multilayer capacitor of this embodiment can be more suitably built into the substrate.

DETAILED DESCRIPTION

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description, the same elements or elements with the same functionality will be denoted by the same reference signs, without redundant description.

A configuration of a multilayer capacitor C1according to the present embodiment will be described with reference toFIGS. 1 to 6.FIG. 1is a perspective view showing the multilayer capacitor according to the present embodiment.FIG. 2is a plan view showing the multilayer capacitor according to the present embodiment.FIG. 3in a drawing for explaining a cross-sectional configuration along the line III-III inFIG. 2.FIG. 4is a drawing for explaining a cross-sectional configuration along the line IV-IV inFIG. 2.FIG. 5is a drawing for explaining a cross-sectional configuration along the line V-V inFIG. 2.FIG. 6is a drawing for explaining a cross-sectional configuration along the line VI-VI inFIG. 2.

The multilayer capacitor C1, as shown inFIGS. 1 to 6, includes an element body2of a rectangular parallelepiped shape, and, a first terminal electrode5and a second terminal electrode7disposed on the exterior surface of the element body2. The first terminal electrode5and second terminal electrode7are separated from each other. The rectangular parallelepiped shape embraces a shape of a rectangular parallelepiped with chamfered corners and ridgelines, and a shape of a rectangular parallelepiped with rounded corners and ridgelines.

The element body2includes, as the outer surface, a pair of principal surfaces2a,2bof a substantially rectangular shape opposing each other, a pair of first side surfaces2c,2dopposing each other, and a pair of second side surfaces2e,2fopposing each other. A direction in which the pair of principal surfaces2a,2boppose is a first direction D1, a direction in which the pair of first side surfaces2c,2doppose is a second direction D2, and a direction in which the pair of second side surfaces2e,2foppose is a third direction D3. In the present embodiment, the first direction D1is a height direction of the element body2. The second direction D2is a width direction of the element body2and is perpendicular to the first direction D1. The third direction D3is the longitudinal direction of the element body2and is perpendicular to the first direction D1and to the second direction D2.

The length in the first direction D1of the element body2is smaller than the length in the third direction D3of the element body2and smaller than the length in the second direction D2of the element body2. The length in the third direction D3of the element body2is larger than the length in the second direction D2of the element body2. The length in the third direction D3of the element body2is, for example, from 0.4 to 1.6 mm. The length in the second direction D2of the element body2is, for example, from 0.2 to 0.8 mm. The length in the first direction D1of the element body2is, for example, from 0.1 to 0.35 mm. The multilayer capacitor C1is an ultra-low-profile multilayer capacitor. The length in the second direction D2of the element body2may be equivalent to the length in the third direction D3of the element body2. The length in the second direction D2of the element body2may be larger than the length in the third direction D3of the element body2.

It is noted herein that the term “equivalent” does not always mean that values are exactly equal. The values may also be said to be equivalent in cases where the values have a slight difference within a predetermined range or include a manufacturing error or the like. For example, when a plurality of values fall within the range of ±5% of an average of the plurality of values, the plurality of values may be defined as equivalent.

The pair of first side surfaces2c,2dextend in the first direction D1to connect the pair of principal surfaces2a,2b. The pair of first side surfaces2c,2dalso extend in the third direction D3(the long-side direction of the pair of principal surfaces2a,2b). The pair of second side surfaces2e,2fextend in the first direction D1to connect the pair of principal surfaces2a,2b. The pair of second side surfaces2e,2falso extend in the second direction D2(the short-side direction of the pair of principal surfaces2a,2b).

The element body2is constituted of a plurality of dielectric layers stacked in the direction in which the principal surface2aand the principal surface2boppose (the first direction D1). In the element body2, the direction in which the plurality of dielectric layers are stacked coincides with the first direction D1. For example, each dielectric layer includes a sintered body of a ceramic green sheet containing a dielectric material (BaTiO3-based, Ba(Ti, Zr)O3-based, (Ba, Ca)TiO3-based, or other dielectric ceramic). In the element body2in practice, the dielectric layers are so integrated that no boundary can be visually recognized between the dielectric layers.

The multilayer capacitor C1, as shown inFIGS. 3 to 6, includes a plurality of first internal electrodes11and a plurality of second Internal electrodes13. The first and second internal electrodes11,13contain an electroconductor material (e.g., Ni or Cu or the like) that is commonly used as internal electrodes of multilayer electric elements. Each of the first and second internal electrodes11,13includes a sintered body of an eleetroconductive paste containing the foregoing electroconductive material.

The first internal electrodes11and the second internal electrodes13are disposed at different positions (layers) in the first direction D1. The first internal electrodes11and the second internal electrodes13are alternately disposed to oppose with a space in between in the first direction D1, in the element body2. The first internal electrodes11and the second internal electrodes13have respective polarities different from each other.

Each first internal electrode11, as shown inFIG. 7A, includes a main electrode portion11aand a connection portion11b. The connection portion11bextends from one side (one short side) of the main electrode portion11aand is exposed on the second side surface2e. The first infernal electrode11is exposed on the second side surface2ebut not exposed in the pair of principal surfaces2a,2b, the pair of first side surfaces2c,2d, and the second side surface2f. The main electrode portion11aand the connection portion11bare integrally formed.

The main electrode portion11ais of a rectangular shape with the long sides along the third direction D3and the short sides along the second direction D2. In the main electrode portion11aof each first internal electrode11, the length thereof in the third direction D3is larger than the length thereof in the second direction D2. The connection portion11bextends from the end on the second side surface2eside of the main electrode portion11ato the second side surface2e. The length in the third direction D3of the connection portion11bis smaller than the length in the third direction D3of the main electrode portion11a. The length in the second direction D2of the connection portion11bis equivalent to the length in the second direction D2of the main electrode portion11a. The connection portion11bis connected at it end exposed on the second side surface2e, to the first terminal electrode5. The length in the second direction D2of the connection portion11bmay be smaller than the length in the second direction D2of the main electrode portion11a.

Each second internal electrode13, as shown inFIG. 7B, includes a main electrode portion13aand a connection portion13b. The main electrode portion13aopposes the main electrode portion11athrough a part (dielectric layer) of the element body2in the first direction D1. The connection portion13bextends from one side (one short side) of the main electrode portion13aand is exposed on the second side surface21. The second internal electrode13is exposed on the second side surface2fbut not exposed on the pair of principal surfaces2a,2b, the pair of first side surfaces2c,2d, and the second side surface2e. The main electrode portion13aand the connection portion13bare integrally formed.

The main electrode portion13ais of a rectangular shape with the long sides along the third direction D3and the short sides along the second direction D2. In the main electrode portion13aof each second internal electrode13, the length thereof in the third direction D3is larger than the length thereof in the second direction D2. The connection portion13bextends from the end on the second side surface2fside of the electrode portion13ato the second side surface2f. The length in the third direction D3of the connection portion13bis smaller than the length in the third direction D3of the main electrode portion13a. The length in the second direction D2of the connection portion13bis equivalent to the length in the second direction D2of the main electrode portion13a. The connection portion13bis connected at its end exposed on the second side surface2f, to the second terminal electrode7. The length in the second direction D2of the connection portion13bmay be smaller than the length in the second direction D2of the main electrode portion13a.

The first terminal electrode5is located at the end on the second side surface2eside of the element body2when viewed along the third direction D3. The first terminal electrode5includes an electrode portion5adisposed on the principal surface2a, an electrode portion5bdisposed on the principal surface2b, an electrode portion5cdisposed on the second side surface2e, and electrode portions5ddisposed on the pair of first side surfaces2c,2d. The first terminal electrode5is formed on the five surfaces2a,2b,2c,2d, and2e. The electrode portions5a,5b,5c,5dadjacent to each other are connected to each other at the ridgelines of the element body2to be electrically connected to each other.

The electrode portion5aand the electrode portion5care connected at the ridgeline between the principal surface2aand the second side surface2e. The electrode portion5aand the electrode portions5dare connected at the ridgelines between the principal surface2aand each of the first side surfaces2c,2d. The electrode portion5band the electrode portion5care connected at the ridgeline between the principal surface2band the second side surface2e. The electrode portion5band the electrode portions5dare connected at the ridgelines between the principal surface2band each of the first side surfaces2c,2d. The electrode portion5cand the electrode portions5dare connected at the ridgelines between the second side surface2eand each of the first side surfaces2c,2d.

The electrode portion5cis disposed to cover all exposed portions of the respective connection portions11bon the second side surface2e. Each connection portion11bis directly connected to the first terminal electrode5. The connection portion11bconnects the main electrode portion11aand the electrode portion5c. Each first internal electrode11is electrically connected to the first terminal electrode5.

The second terminal electrode7is located at the end on the second side surface2fside of the element body2when viewed along the third direction D3. The second terminal electrode7includes an electrode portion7adisposed on the principal surface2a, an electrode portion7bdisposed on the principal surface2b, in electrode portion7cdisposed on the second side surface2f, and electrode portions7ddisposed on the pair of first side surfaces2c,2d. The second terminal electrode7is formed on the five surfaces2a,2b,2c,2d, and2f. The electrode portions7a,7b,7c,7dadjacent to each other are connected to each other at the ridgelines of the element body2to be electrically connected to each other.

The electrode portion7aand the electrode portion7care connected at the ridgeline between the principal surface2aand the second side surface2f. The electrode portion7aand the electrode portions7dare connected at the ridgelines between the principal surface2aand each of the first side surfaces2c,2d. The electrode portion7band the electrode portion7care connected at the ridgeline between the principal surface2band the second side surface2f. The electrode portion7band the electrode portions7dare connected at the ridgelines between the principal surface2band each of the first side surfaces2c,2d. The electrode portion7cand the electrode portions7dare connected at the ridgelines between the second side surface2fand each of the first side surfaces2c,2d.

The electrode portion7cis disposed to cover all exposed portions of the respective connection portions13bon the second side surface2f. Each connection portion13bis directly connected to the second terminal electrode7. The connection portion13bconnects the main electrode portion13aand the electrode portion7c. Each second internal electrode13is electrically connected to the second terminal electrode7.

The first terminal electrode5and the second terminal electrode7are separated in the third direction D3. The element body2is exposed between the first terminal electrode5and the second terminal electrode7. The electrode portion5aand the electrode portion7adisposed on the principal surface2aare separated in the third direction D3on the principal surface2a. The electrode portion5band the electrode portion7bdisposed on the principal surface2bare separated in the third direction D3on the principal surface2b. The electrode portion5dand the electrode portion7ddisposed on the first side surface2care separated in the third direction D3on the first side surface2c. The electrode portion5dand the electrode portion7ddisposed on the first side surface2dare separated in the third direction D3on the first side surface2d.

Each of the first and second terminal electrodes5,7includes a first electrode layer21, a second electrode layer23, and a third electrode layer25. Each of the electrode portions5a,5b,5c,5dand the electrode portions7a,7b,7c,7dincludes the first electrode layer21, second electrode layer23, and third electrode layer25. The third electrode layer25constitutes the outermost layer of each of the first and second terminal electrodes5,7.

The first electrode layer21is formed by applying an electroconductive paste onto the surface of the element body2and sintering it. The first electrode layer21is a sintered conductor layer (sintered metal layer). In the present embodiment, the first electrode layer21is a sintered conductor layer made of Cu. The first electrode layer21may be a sintered conductor layer made of Ni. The first electrode layer21contains Cu or Ni. For example, the eleetroconductive paste is obtained by taking a powder made of Cu or Ni, a glass component, an organic binder, and an organic solvent. The thickness of the first electrode layer21is, for example, 20 μm at a maximum and 5 μm at a minimum.

The second electrode layer23is formed by plating on the first electrode layer21. In the present embodiment, the second electrode layer23is an Ni-plated layer formed by Ni plating on the first electrode layer21. The second electrode layer23may be an Sn-plated layer. The second electrode layer23contains Ni or Sn. The thickness of the second electrode layer23is, for example, from 1 to 5 μm.

The third electrode layer25is formed by plating on the second electrode layer23. In the present embodiment, the third electrode layer25is a Cu-plated layer formed by Cu plating on the second electrode layer23. The third electrode layer25may be an Au-plated layer. The third electrode layer25contains Cu or Au. The thickness of the third electrode layer25is, for example, from 1 to 15 μm.

In the present embodiment as described above, the length in the first direction D1of the element body2is smaller than the length in the third direction D3of the element body2and smaller than the length in the second direction D2of the element body2. For this reason, the multilayer capacitor C1is obtained that has reduced height, and is suitable for built-in mounting in a substrate. The first terminal electrode5includes the electrode portions5a,5bdisposed on the principal surfaces2a,2band the second terminal electrode7includes a the electrode portions7a,7bdisposed on the principal surfaces2a,2b. The multilayer capacitor C1can be electrically connected to wiring formed on the substrate, on the principal surface2aside of the element body2, on the principal surface2bside of the element body2, or, on both of the principal surface2a,2bsides of the element body2. Therefore, the multilayer capacitor C1can be readily built into the substrate.

The multilayer capacitor C1, as shown inFIG. 8, is mounted as embedded in a substrate31. The multilayer capacitor C1is built into the substrate31.FIG. 8is a drawing for explaining a mounted structure of the multilayer capacitor according to the present embodiment.

The substrate31is constructed by stacking a plurality of insulating layers33. The insulating layers33are made of an insulating material such as ceramic or resin, and are integrated with each other by adhesion or the like.

The multilayer capacitor C1is disposed in a housing portion31aformed in the substrate31. The multilayer capacitor C1is fixed to the substrate31by resin34filled in the housing portion31a. The multilayer capacitor C1is embedded in the substrate31. In the mounted structure shown inFIG. 8, the multilayer capacitor C1is disposed in the housing portion31ain such a manner that the principal surface2bof the element body2opposes a bottom portion of the housing portion31a.

The multilayer capacitor C1is electrically connected through via conductors45,47to electrodes35,37disposed on the surface of the substrate31. In the mounted structure shown inFIG. 8, the electrode portion5aof the first terminal electrode5is electrically connected through the via conductor45to the electrode35. The electrode portion7aof the second terminal electrode7is electrically connected through the via conductor47to the electrode37.

The via conductors45,47are formed by growing an electoconductive metal (e.g., Cu or Au or the like) in via holes formed in the substrate31. The growth of the electroconductive metal is realized, for example, by electroless plating. The via holes are formed to reach the electrode portions5a,7aof the first and second terminal electrodes5,7of the multilayer capacitor C1from the surface side of the substrate31. The visa holes are formed, for example, by laser processing.

In the multilayer capacitor C1, the electrode portions5a,7ainclude the third electrode layers25as plated layers. Therefore, the electrode portions5a,7acan be securely connected to the via conductors45,47formed in the via holes. When the via conductors45,47are formed by plating, the via conductors45,47are more securely connected to the electrode portions5a,7a.

The below will detail surface roughness of the electrode portions5a,5b,7a,7band surface roughness of the electrode portions5c,5d,7c,7d.

The inventors conducted the following tests in order to clarify a range of the surface roughness of the electrode portions5a,5b,7a,7band a range of the surface roughness of the electrode portions5c,5d,7c,7d. Samples 1 to 19 different in surface roughness of the electrode portions5a,5b,5c,5d,7a,7b,7c,7dare prepared, and the number of void occurrences and the number of peeling occurrences in each of Samples 1 to 19 are checked. The results are shown inFIG. 9.FIG. 9is a table showing the number of void occurrences and the number of peeling occurrences in each of the Samples.

The surface roughness of the electrode portions5a,5b,5c,5d,7a,7b,7c,7dcan be varied, for example, by using different electroconductive pastes to be used in forming the first electrode layers21. The surface roughness varies depending on particle sizes of metal powder (e.g., Ni powder or Cu powder or the like) contained in the electroconductive pastes. As the particle size of the metal powder increases, the surface roughness becomes larger. Therefore, the surface roughness can be differentiated, for example, by making a difference in particle size of the metal powder between the electroconductive paste used in forming the electrode portions5a,5b,7a,7band the electroconductive paste used in forming the electrode portions5c,5d,7c,7d. Besides the method of making the difference of the electroconductive pastes used in forming the first electrode layers21, the surface roughness can also be differentiated by a method of, after the first electrode layers21are formed, carrying out a roughening process or a polishing process for the surfaces of the first electrode layers21.

The arithmetic mean deviation (Ra) was employed to represent the surface roughness of the electrode portions5a,5b,5c,5d,7a,7b,7c,7d. The arithmetic mean deviation (Ra) is defined in JIS B 0601: 2013 (ISO 4287: 1997).

Each of Samples 1 to 19 is a lot including a plurality of specimens. The specimens in each Sample 1-19 have the same configuration except for the aforementioned difference in surface roughness. The specimens in each Sample 1-19 have the length of 0.17 mm in the first direction D1of the element body2, the length of 0.49 mm in the second direction D2of the element body2, and the length of 0.98 mm in the third direction D3of the element body2.

In each specimen of Sample 1, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.15 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.19 μm. In each specimen of Sample 2, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.15 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.25 μm. In each specimen of Sample 3, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.15 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.38 μm.

In each specimen of Sample 4, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.18 μm. In each specimen of Sample 5, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.27 μm. In each specimen of Sample 6, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.34 μm.

In each specimen of Sample 7, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.38 μm. In each specimen of Sample 8, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.40 μm. In each specimen of Sample 9, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.23 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.25 μm.

In each specimen of Sample 10, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.23 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.28 μm. In each specimen of Sample 11, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.23 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.32 μm. In each specimen of Sample 12, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.23 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.37 μm.

In each, specimen of Sample 13, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.23 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.40 μm. In each specimen of Sample 14, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.25 μm. In each specimen of Sample 15, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.27 μm.

In each specimen of Sample 16, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,7d,7c,7dis 0.32 μm. In each specimen of Sample 17, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.38 μm. In each specimen of Sample 18, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.40 μm. In each specimen of Sample 19, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.30 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.27 μm.

The number of void occurrences was determined as follows. First, ten specimens were chosen from each of Samples 1 to 19. Each chosen specimen was disposed in the housing portion31aof the substrate31and then the housing portion31awas filled with the resin34, thereby embedding the specimen in the substrate31. Thereafter, the via holes were formed in the substrate31(resin34) by laser processing to reach the first and second terminal electrodes5,7. The via conductors45,47were formed in the via holes by electroless plating, thereby connecting the first and second terminal electrodes5,7to the via conductors45,47. Through these processes, the substrates31with the respective specimens mounted thereon are prepared. The resin34used was an epoxy resin.

Each substrate31with the specimen thereon was cut at the position including the specimen (first and second terminal electrodes5,7) and the via conductors45,47. The presence or absence of a void in the cut plane was checked by visual inspection. The number of specimens with which occurrence of a void was confirmed was counted. In this case, it was determined whether a void occurred between the first and second terminal electrodes5,7(electrode portions5a,5b,7a,7b) and the via conductors45,47and whether a void occurred between the first and second terminal electrodes5,7(electrode portions5c,5d,7c,7d) and the resin34.

It was found that when the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bwas not less than 0.30 μm, there were specimens with the void occurring between the electrode portions5a,5b,7a,7band the via conductors45,47. It is presumed that when the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis not less than 0.30 μm, the metal is less likely to become suitably precipitated on the electrode portions5a,5b,7a,7bin a process of forming the via conductors45,47, because of unevenness of the surfaces of the electrode portions5a,5b,7a,7b, so as to result in occurrence of the void. It was confirmed that none of Samples 1 to 18 included any specimen with the void occurring between the electrode portions5a,5b,7a,7band the via conductors45,47.

It was found that when the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dwas not less than 0.4 μm, there were specimens with the void occurring between the electrode portions5c,5d,7c,7dand the resin34. It is presumed that when the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis not less than 0.40 μm, the void occurs because the resin34fails to fully intrude into depressions of the unevenness of the surfaces of the electrode portions5c,5d,7c,7d. It was confirmed that none of Samples 1 to 7, 9 to 12, 14 to 17, and 19 included any specimen with the void occurring between the electrode portions5c,5d,7c,7dand the resin34.

The number of peeling occurrences was determined as follows. First, ten specimens were chosen from each of Samples 1-7, 9-12, and 14-17 with which no void occurrence was confirmed, and the substrates31with the respective specimens mounted thereon were prepared by the same procedure as the above-described procedure. Each substrate31with the specimen thereon was subjected to five reflow tests under a nitrogen atmosphere. The conditions for the reflow tests were as follows. As a pretreatment, preheating was first conducted at 125° C. for twenty four hours and, thereafter, reflow at a peak temperature of 260° C. was carried out.

After the reflow tests, each substrate31with the specimen thereon was cut at the position including the specimen (first and second terminal electrodes5,7) and the via conductors45,47. The presence or absence of peeling is the cut plane was checked by visual inspection. The number of specimens with which occurrence of peeling was confirmed was counted. In this case, it was determined whether peeling occurred between the first and second terminal electrodes5,7(electrode portions5a,5b,7a,7b) and the via conductors45,47and whether peeling occurred between the first and second terminal electrodes5,7(electrode portions5c,5d,7c,7d) and the resin34.

It was found that when the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bwas not more than 0.15 μm, there were specimens with peeling occurring between the electrode portions5a,5b,7a,7band the via conductors45,47. It is presumed that when the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis not more than 0.15 μm sufficient adhesion is not achieved between the electrode portions5a,5b,7a,7band the via conductors45,47, so as to result in occurrence of peeling between the electrode portions5a,5b,7a,7band the via conductors45,47. It was confirmed that none of Samples 4-7, 9-12, and 14-17 included any specimen with peeling occurring between the electrode portions5a,5b,7a,7band the via conductors45,47.

It was found that when the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dwas not more than 0.25 μm, there were specimens with peeling occurring between the electrode portions5c,5d,7c,7dand the resin34. It is presumed that when the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis not more than 0.25 μm, peeling occurs between the electrode portions5c,5d,7c,7dand the resin34because, although the resin34can intrude into the depressions of the unevenness of the surfaces of the electrode portions5c,5d,7c,7d, the amount of intruding resin34is too small to achieve sufficient adhesion between the electrode portions5c,5d,7c,7dand the resin34. It was confirmed that none of Samples 3, 5-7, 10-12, and 15-17 included any specimen with peeling occurring between the electrode portions5c,5d,7c,7dand the resin34.

It was confirmed that none of Samples 5-7, 10-12, and 15-17 included any specimen with occurrence of the void and peeling.

It is seen from the above that when the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis from 0.20 to 0.26 μm and when the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis from 0.27 to 0.38 μm, the void is prevented from occurring between the electrode portions5a,5b,7a,7band the via conductors45,47. The void is also prevented from occurring between the electrode portions5c,5d,7c,7dand the resin34. Peeling is also prevented from occurring between the electrode portions5a,5b,7a,7band the via conductors45,47. Peeling is also prevented from occurring between the electrode portions5c,5d,7c,7dand the resin34. As a result of these, the multilayer capacitor C1is suitably built into the substrate31, and ensures the connectivity to the via conductors45,47formed in the substrate31.

The following will detail surface roughness of the element body2and, particularly, surface roughness of the portion of the element body2exposed from the first and second terminal electrodes5,7.

The inventors conducted the following tests to clarify a range of the surface roughness of the portion of the element body2exposed from the first and second terminal electrodes5,7. Samples 20 to 37 different in surface roughness of the element body2are prepared, and the number of void occurrences and the number of peeling occurrences in each of Samples 20 to 37 are checked. The results are shown inFIG. 10.FIG. 10is a table showing the number of void occurrences and the number of peeling occurrences in each of the Samples. The surface roughness employed herein was also the arithmetic mean deviation (Ra). The surface roughness of the element body2can be varied, for example, by using different dielectric materials for ceramic green sheets or by polishing a laminate body including a lamination of ceramic green sheets, in forming the element body.

Each of Samples 20 to 37 is a lot including a plurality of specimens. The specimens in each of Samples 20-24 have the same configuration except for the difference in surface roughness of the element body2. The specimens in respective Samples 25-28 have the same configuration except for the difference in surface roughness of the element body2. The specimens in respective Samples 29-33 have the same configuration except for the difference in surface roughness of the element body2. The specimens in respective Samples 34-37 have the same configuration except for the difference in surface roughness of the element body2. The specimens in respective Samples 20-37 have the length of 0.17 mm in the first direction D1of the element body2, the length of 0.49 mm in the second direction D2of the element body2, and the length of 0.98 mm in the third direction D3of the element body2.

In each specimen of Samples 20-24, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation, of the surfaces of the electrode portions5c,5d,7c,7dis 0.27 μm. In each specimen of Samples 25-28, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.27 μm. In each specimen of Samples 29-33, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.20 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.38 μm. In each specimen of Samples 34-37, the arithmetic mean deviation of the surfaces of the electrode portions5a,5b,7a,7bis 0.26 μm and the arithmetic mean deviation of the surfaces of the electrode portions5c,5d,7c,7dis 0.38 μm.

In each specimen of Sample 20, the arithmetic mean deviation of the surface of the element body2is 0.12 μm. In each specimen of Sample 21, the arithmetic mean deviation of the surface of the element body2is 0.14 μm. In each specimen of Sample 22, the arithmetic mean deviation of the surface of the element body2is 0.16 μm. In each specimen of Sample 23, the arithmetic mean deviation of the surface of the element body2is 0.19 μm. In each specimen of Sample 24, the arithmetic mean deviation of the surface of the element body2is 0.27 μm. In each specimen of Sample 25, the arithmetic mean deviation of the surface of the element body2is 0.14 μm. In each specimen of Sample 26, the arithmetic mean deviation of the surface of the element body2is 0.17 μm, in each specimen of Sample 27, the arithmetic mean deviation of the surface of the element body2is 0.19 μm. In each specimen of Sample 28, the arithmetic mean deviation of the surface of the element body2is 0.21 μm.

In each specimen of Sample 29, the arithmetic mean, deviation of the surface of the element body2is 0.11 μm. In each specimen of Sample 30, the arithmetic mean deviation of the surface of the element body2is 0.14 μm, in each specimen of Sample 31, the arithmetic mean deviation of the surface of the element body2is 0.15 μm. In each specimen of Sample 32, the arithmetic mean deviation of the surface of the element body2is 0.18 μm. In each specimen of Sample 33, the arithmetic mean deviation of the surface of the element body2is 0.25 μm. In each specimen of Sample 34, the arithmetic mean deviation of the surface of the element body2is 0.14 μm. In each specimen of Sample 35, the arithmetic mean deviation of the surface of the element body2is 0.17 μm. In each specimen of Sample 36, the arithmetic mean deviation of the surface of the element body2is 0.19 μm. In each specimen of Sample 37, the arithmetic mean deviation of the surface of the element body2is 0.22 μm.

The number of void occurrences was determined as follows. First ten specimens were chosen from each of Samples 20 to 37 and the substrates31with the respective specimens mounted thereon were prepared by the same procedure as the aforementioned procedure. Each substrate31with the specimen thereon was cut at the position including the portion of the element body2exposed from the first and second terminal electrodes5,7. The presence or absence of a void in the cut plane was checked by visual inspection. The number of specimens wife which occurrence of a void was confirmed was counted. In this case, it was determined whether a void occurred between the element body2(the portion exposed from the first and second terminal electrodes5,7) and the resin34.

It was found that when the arithmetic mean deviation of the surface of the element body2(the portion exposed from the first and second terminal electrodes5,7) was not less than 0.21 μm, there were specimens with the void occurring between the element body2and the resin34. It is presumed that when the arithmetic mean deviation of the surface of the element body2is not less than 0.21 μm, the void occurs because the resin34fails to fully intrude into depressions of the unevenness of the surface of the element body2. It was confirmed that none of Samples 20-23, 25-27, 29-32, and 34-36 included any specimen with the void occurring between the element body2and the resin34.

The number of peeling occurrences was determined as follows. First, ten specimens were chosen from each of Samples 20-23, 25-27, 29-32, and 34-36 with which no void occurrence was confirmed, and the substrates31with the respective specimens mounted thereon were prepared by the same procedure as the above-described procedure. Each substrate31with the specimen thereon was subjected to five reflow tests under a nitrogen atmosphere. The conditions for the reflow tests were as follows. As a pretreatment, preheating was first conducted at 125° C. for twenty four hours and, thereafter, reflow at a peak temperature of 260° C. was carried out.

After the reflow tests, each substrate31with the specimen thereon was cut at the position including the portion of the element body2exposed from the first and second terminal electrodes5,7. The presence or absence of peeling in the cut plane was checked by visual inspection. The number of specimens with which occurrence of peeling was confirmed was counted. In this case, it was determined whether peeling occurred between the element body2(the portion exposed from the first and second terminal electrodes5,7) and the resin34.

It was found that when the arithmetic mean deviation of the surface of the element body2was not more than 0.12 μm, there were specimens with peeling occurring between the element body2and the resin34. It is presumed that when the arithmetic mean deviation of the surface of the element body2is not more than 0.12 μm, the peeling occurs between the element body2and the resin34because, although the resin34can intrude into the depressions of the unevenness of the surface of the element body2, the amount of intruding resin34is too small to achieve sufficient adhesion between the element body2and the resin34. It was confirmed that none of Samples 21-23, 25-27, 30-32, and 34-36 included any specimen with peeling occurring between the element body2and the resin34.

It was confirmed that none of Samples 21-23, 25-27, 30-32, and 34-36 included any specimen with occurrence of the void and peeling.

It is seen from the above that when the arithmetic mean deviation of the surface of the element body2is from 0.14 to 0.19 μm, the void is prevented from occurring between the element body2and the resin34. Peeling is also prevented from occurring between the element body2and the resin34. As a result of these, the multilayer capacitor C1is more suitably built into the substrate.

The embodiment of the present invention has been described above, but it should be noted that the present invention is not always limited only to the above-described embodiment but can be modified in many ways without departing from the spirit and scope of the invention.

The first terminal electrode5does not have to include the electrode portions5d. The first terminal electrode5may be formed on the three surfaces2a,2b, and2c. The second terminal electrode7does not have to include the electrode portions7d. The first terminal electrode7may be formed on the three surfaces2a,2b, and2d.