US007808770B2
`
`(12) United States Patent
`Itamura et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,808,770 B2
`Oct. 5, 2010
`
`(54) MONOLITHIC CERAMIC CAPACITOR
`
`(75)
`
`1“"em°rS‘ Hi“’t° I““““”‘= Echizen (H93 Masaaki
`Taniguchi, Nyuu-gun (JP); Yoshio
`Kawaguchi, Fukui (JP)
`
`(73) Assignee: Murata Manufacturing Co., Ltd.,
`Kyoto (JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. l54(b) by 338 days.
`
`(21) Appl.No.: 12/140,341
`
`(22)
`
`Filed:
`
`Jun. 17, 2008
`
`6,388,864 B1*
`6,771,485 B2*
`6,773,827 B2 *
`
`........ .. 361/309
`5/2002 Nakagawa et a1.
`........ .. 361/309
`8/2004 Yokoyama et al.
`8/2004 Higuchi
`.................... .. 428/646
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`JP
`
`2-116720 U
`
`9/1990
`
`(Continued)
`OTHER PUBLICATIONS
`
`(65)
`
`(30)
`
`Prior Publication Data
`
`US 2009/0002920 A1
`
`Jan. 1, 2009
`
`Partial English translation of JP 2-116720, published on Sep. 19,
`1990; Kind Code: U.
`
`Foreign Application Priority Data
`
`(Continued)
`
`Jun. 27, 2007
`Mar. 28, 2008
`
`(JP)
`(JP)
`
`........................... .. 2007-169175
`........................... .. 2008-085617
`
`Primary Examiner—Eric Thomas
`(74) Attorney, Agent, or Firm—Keating & Bennett, LLP
`
`(51)
`
`Int. Cl.
`(2006.01)
`H01G 4/228
`(2006.01)
`H01G 4/005
`(52) U.S. Cl.
`................... .. 361/309; 361/306.3; 361/303
`(58) Field of Classification Search
`361/306.1—306.3,
`361/31 1, 303
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`8/1986 Senda et al.
`4,604,676 A
`............... .. 361/309
`4/1992 Naito et al.
`5,107,394 A *
`...... .. 361/309
`6/1995 Amaya et al.
`5,426,560 A *
`
`.......... .. 361/321.2
`1/1998 Amano et al.
`5,712,758 A *
`9/1998 Takahara et al.
`.......... .. 361/303
`5,805,409 A *
`7/2001 Moriwaki et al.
`......... .. 361/303
`6,259,593 B1*
`6,310,757 B1* 10/2001 Tuzuki et al.
`.......... .. 361/308.1
`6,344,963 B1 *
`2/2002 Mori
`..................... .. 361/306.3
`6,381,118 B1*
`4/2002 Yokoyama et al.
`..... .. 361/308.1
`
`(57)
`
`ABSTRACT
`
`In an LW-reverse-type monolithic ceramic capacitor includ-
`ing external terminal electrodes each including a resistance
`component, internal electrodes include nickel or a nickel
`alloy, and the external terminal electrodes each include a first
`layer, a second layer provided on the first layer, and a third
`layer provided on the second layer. The first layer has a
`wrap-around portion extending from an end surface to prin-
`cipal surfaces and side surfaces of a capacitor main body, and
`contains a glass component and a compound oxide that reacts
`with Ni or the Ni alloy. The second layer covers the first layer
`such that the edge ofthe wrap-around portion ofthe first layer
`remains exposed, and contains a metal. The third layer covers
`the edge of the wrap-around portion of the first layer and the
`second layer, and is formed by plating.
`
`8 Claims, 4 Drawing Sheets
`
`\\\V.\\\\‘‘’(I5\\\\\\\“
`
`
`"02:: 1'
`
`
`
`000001
`
`Exhibit 1004
`
`PGR2017-00010
`
`Exhibit 1004
`PGR2017-00010
`AVX CORPORATION
`
`AVX CORPORATION
`
`000001
`
`

`

`US 7,808,770 B2
`Page2
`
`U.S. PATENT DOCUMENTS
`
`5/2006 Ritter et al.
`7,054,136 B2
`7,304,831 B2 * 12/2007 Yoshii et al.
`........... .. 361/321.2
`
`7,436,649 B2 * 10/2008 Omura
`. 361/306.3
`.................. .. 428/210
`2006/0234022 A1 * 10/2006 Liu et al.
`2007/0128794 A1
`6/2007 Kusano et al.
`2007/0242416 A1 * 10/2007 Saito et al.
`............. .. 361/321.1
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`Jp
`Jp
`W0
`
`08-097072 A
`09-148174 A.
`2000357627 A
`2002_217054 A
`2006/022253 A1
`
`4/1996
`6/1997
`12/2000
`3/2002
`3/2006
`
`OTHER PUBLICATIONS
`_
`_
`_
`_
`_
`_
`Oflicial Communication issued in corresponding Japanese Patent
`Application No. 2008-085617, mailed on Oct. 6, 2009.
`
`JP
`
`06096986 A *
`
`4/1994
`
`* cited by examiner
`
`000002
`
`000002
`
`

`

`U.S. Patent
`
`Oct. 5, 2010
`
`Sheet 1 of4
`
`US 7,808,770 B2
`
`000003
`
`000003
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`

`

`U.S. Patent
`
`Oct. 5, 2010
`
`Sheet 2 of4
`
`US 7,808,770 B2
`
`FIG. 2
`
`1
`
`17
`
`8
`
`3
`
`17
`
`
`
`
`14
`
`.
`
`000004
`
`1 4
`15
`
`7
`
`’ V
`fl
`
`
`
`»\,,\,,A\\\\\\\\\\“‘
`
`000004
`
`

`

`U.S. Patent
`
`Oct. 5, 2010
`
`Sheet 3 of4
`
`US 7,808,770 B2
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`2
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`4 1
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`1
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`2
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`5 1
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`1
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`FIG. 3A
`
`3
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`13
`
`10
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`10
`
`FIG. 3B
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`13
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`12
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`12
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`000005
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`000005
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`

`

`U.S. Patent
`
`Oct. 5, 2010
`
`Sheet 4 of4
`
`US 7,808,770 B2
`
`FIG. 4
`
`IIIIIIIIUIIUIIIICI
`flldrfllf
`...vJVJvIf/I/5..
`
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`000006
`
`
`
`
`

`

`US 7,808,770 B2
`
`2
`
`direction of the ceramic layers. In such LW-reverse-type
`monolithic ceramic capacitors, a current path of a capacitor
`main body is wide and short, thereby decreasing the ESL.
`Another known example of a low-ESL monolithic ceramic
`capacitor is a multiterminal monolithic ceramic capacitor. In
`multiterminal monolithic ceramic capacitors, the current path
`inside a capacitor main body is separated into a plurality of
`paths, thereby decreasing the ESL.
`In low-ESL monolithic ceramic capacitors, the current
`path is wide and short or is separated as described above. As
`a result,
`the equivalent series resistance (ESR)
`is also
`decreased.
`
`On the other hand, an increase in the capacitance ofmono-
`lithic ceramic capacitors has been required. In order to
`increase the capacitance of a monolithic ceramic capacitor,
`the number of ceramic layers and the number of laminated
`internal electrodes may be increased. In this case, the number
`of current paths is increased, thereby decreasing the ESR.
`Accordingly, in response to the requirements to decrease
`the ESL and increase the capacitance, the ESR of monolithic
`ceramic capacitors tends to be further decreased.
`However, it is known that when the ESR of a capacitor is
`excessively decreased, a mismatch of impedance occurs in a
`circuit and a damped oscillation called “ringing” in which the
`rising of a signal waveform deforms easily occurs. The ring-
`ing may cause a malfunction of an IC because of disordered
`signals.
`In addition, when the ESR of a capacitor is excessively
`decreased,
`the impedance-frequency characteristic of the
`capacitor becomes excessively steep near the resonance fre-
`quency. More specifically, the valley of the impedance curve
`becomes excessively deep. Consequently, it may be difficult
`to absorb noise over a wide frequency range.
`In order to prevent ringing or to broaden the impedance-
`frequency characteristic, a resistance element may be con-
`nected in series to a line. In addition, recently, it has been
`required that a capacitor itself includes a resistance compo-
`nent, and thus, a method of controlling the ESR of such a
`capacitor using this technique has attracted attention.
`For example, Japanese Unexamined Patent Application
`Publication No. 2004-47983 (document ’983) and PCT Pub-
`lication No. WO 2006/022258 pamphlet (document ’258)
`have disclosed that a resistance component is included in
`external terminal electrodes that are electrically connected to
`internal electrodes, thereby controlling the ESR. More spe-
`cifically, document ’983 discloses a thick-film resistance
`including RuO2. Document ’258 discloses that paste includ-
`ing a material having a relatively high specific resistance,
`such as ITO, is baked on a capacitor main body. However, the
`techniques described in documents ’983 and ’258 have prob-
`lems to be solved as described below.
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`1
`MONOLITHIC CERAMIC CAPACITOR
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to a monolithic ceramic
`capacitor, and in particular, to an LW-reverse-type monolithic
`ceramic capacitor including external terminal electrodes each
`including a resistance component.
`2. Description of the Related Art
`In a power supply circuit, when a voltage variation in a
`power supply line is increased by an impedance that is present
`in the power supply line or a ground, the operation of circuits
`to be driven becomes unstable, interference between the cir-
`cuits occurs due to the power supply circuit, or oscillation
`occurs. Consequently, a decoupling capacitor is usually con-
`nected between the power supply line and the ground. The
`decoupling capacitor decreases the impedance between the
`power supply line and the ground, thereby suppressing the
`variation in the power supply voltage and interference
`between the circuits.
`
`in communication equipment such as a cell
`Recently,
`phone and information processing equipment such as a per-
`sonal computer, as the speed of signals has been increased in
`order to allow a large amount of information to be processed,
`the clock frequency of an IC used has also increased. Accord-
`ingly, noise that primarily includes harmonic wave compo-
`nents is often generated. Therefore, it has become necessary
`to provide stronger decoupling in an IC power supply circuit.
`In order to increase the decoupling effect, it is effective to
`use a decoupling capacitor having an excellent impedance-
`frequency characteristic. An example of such a decoupling
`capacitor is a monolithic ceramic capacitor. Because of its
`low equivalent series inductance (ESL),
`the monolithic
`ceramic capacitor has an excellent noise-absorbing effect
`over a wide frequency range as compared to an electrolytic
`capacitor.
`Another function of a decoupling capacitor is to supply
`electric charges to an IC. A decoupling capacitor is usually
`disposed in the vicinity of an IC. When a voltage variation
`occurs in a power supply line, electric charges are rapidly
`supplied from the decoupling capacitor to the IC, thus pre-
`venting a delay of the IC.
`When a charge and a discharge occur in a capacitor, a
`counter-electromotive force represented by a
`formula
`dV:L~di/dt is generated in the capacitor. With a large dV, the
`supply speed of electric charges to the IC is decreased. With
`an increase in the clock frequency of an IC, the amount of
`current variation per unit time di/dt tends to increase. Accord-
`ingly, in order to decrease the value of dV, it is necessary to
`decrease the inductance L. For this purpose, it is desirable to
`further decrease the ESL of a capacitor.
`A known example of a low-ESL monolithic ceramic
`capacitor in which the ESL is further decreased is an LW-
`reverse-type monolithic ceramic capacitor. In typical mono-
`lithic ceramic capacitors, the dimension (dimension W) of
`each end surface of a capacitor main body in the extending
`direction of the ceramic layers, the end surface having an
`external terminal electrode thereon, is less than the dimension
`(dimension L) of each side surface ofthe capacitor main body
`in the extending direction of the ceramic layers, the side
`surface being adjacent to the end surfaces. In contrast, in
`LW-reverse-type monolithic ceramic capacitors, the dimen-
`sion (dimension W) of each end surface in the extending
`direction of the ceramic layers, the end surface having an
`external terminal electrode thereon, is greater than the dimen-
`sion (dimension L) of each side surface in the extending
`
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`
`According to the technique disclosed in document ’983, a
`plating film is formed directly on an underlayer including the
`resistance component. However, unlike metal particles, neck-
`ing does not occur in metal oxide particles, such as RuO2
`particles, included in the underlayer by baking. Therefore, the
`density of the resulting film is not significantly high. Conse-
`quently, a plating solution or moisture easily intrudes into the
`film, thus causing a problem of reduced reliability.
`In the technique disclosed in document ’258, a first layer
`including a resistance component is completely covered with
`a second layer composed of a thick film including a metal
`such as Cu, and a plating film is formed on the second layer.
`In this configuration, since the first layer is covered with the
`dense second layer, the reliability ofthe capacitor is improved
`as compared to the capacitor disclosed in document ’983.
`However, since the entire thickness of each of the external
`000007
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`

`US 7,808,770 B2
`
`3
`terminal electrodes is increased by forming the first layer and
`the second layer, the dimensions of the monolithic ceramic
`capacitor in the in-plane directions and the height direction
`increase. Accordingly, it is difiicult to reduce the size of the
`monolithic ceramic capacitor. This problem tends to be par-
`ticularly troublesome in LW-reverse-type monolithic ceramic
`capacitors, which have a large area of external terminal elec-
`trodes.
`An external terminal electrode is formed on each end sur-
`
`face of a capacitor main body. In order to achieve satisfactory
`mountability, the external terminal electrode typically has a
`wrap-around portion which is formed so as to extend from an
`end surface to principal surfaces and side surfaces. As
`described in document ’258, when the first layer is com-
`pletely covered with the second layer, the second layer is
`affected by a variation in the thickness of the first layer.
`Therefore, it is difiicult to stabilize the dimensions of the
`wrap-around portion. If the dimensions of the wrap-around
`portion vary, the mountability may be adversely affected.
`
`SUMMARY OF THE INVENTION
`
`To overcome the problems described above, preferred
`embodiments of the present invention provide an LW-re-
`verse-type monolithic ceramic capacitor including external
`terminal electrodes each including a resistance component,
`the structure being suitable for improving the mountability of
`the LW-reverse-type monolithic ceramic capacitor without
`decreasing the reliability thereof.
`A monolithic ceramic capacitor according to a preferred
`embodiment of the present invention includes a substantially
`rectangular parallelepiped capacitor main body including a
`plurality of laminated ceramic layers and having a pair of
`principal surfaces facing each other, a pair of side surfaces
`facing each other, and a pair of end surfaces facing each other;
`at least one pair of internal electrodes provided inside the
`capacitor main body and each extending to one of the end
`surfaces; and a pair of external terminal electrodes provided
`on the end surfaces of the capacitor main body and each
`electrically connected to any of the internal electrodes,
`wherein the dimension of each end surface in the extending
`direction of the ceramic layers is greater than the dimension
`of each side surface in the extending direction of the ceramic
`layers.
`In order to solve the problems described above, the mono-
`lithic ceramic capacitor has the following unique structure.
`Specifically, the internal electrodes include nickel (Ni) or a
`nickel (Ni) alloy. Each of the external terminal electrodes
`includes a first layer, a second layer provided on the first layer,
`and a third layer provided on the second layer. The first layer
`has a wrap -around portion extending from one of the end
`surfaces to the principal surfaces and the side surfaces, and
`includes a glass component and a compound oxide that reacts
`with the Ni or the Ni alloy. The second layer covers the first
`layer such that the edge ofthe wrap -around portion ofthe first
`layer remains exposed, and includes a metal. The third layer
`covers the edge of the wrap-around portion of the first layer
`and the second layer, and is formed by plating.
`According to a preferred embodiment ofthe present inven-
`tion, since the second layer is arranged such that the edge of
`the wrap-around portion of the first layer remains exposed,
`the dimensions of the wrap-around portion of the external
`terminal electrode are defined by the first layer. As a result, the
`dimensions of the wrap -around portion of the external termi-
`nal electrode are consistent. Thus, satisfactory mountability
`of the monolithic ceramic capacitor can be reliably achieved.
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`Furthermore, since the second layer is arranged such that
`the edge of the wrap -around portion of the first layer remains
`exposed, a plating solution or moisture may easily intrude
`from the edge of the wrap-around portion of the first layer.
`However, the distance between the edge of the wrap-around
`portion and a capacitance-forming portion of the internal
`electrodes is sufiiciently large, and thus, the plating solution
`or moisture does not easily reach the capacitance-forming
`portion. Therefore, the reliability of the monolithic ceramic
`capacitor is not significantly decreased.
`In addition, since the second layer does not completely
`cover the first layer and is formed such that the edge of the
`wrap-around portion remains exposed, this structure enables
`a decrease in the thickness of the external terminal electrode
`
`at the wrap-around portion. Consequently, the size of the
`monolithic ceramic capacitor can be reduced accordingly.
`In order to reduce the size of the monolithic ceramic
`
`capacitor, a first layer having a small thickness may be
`formed. However, it is difficult to use this structure from the
`standpoint ofthe ESR. When the capacitor main body is cut in
`a direction substantially parallel to a side surface thereof and
`the cross section is viewed, the thickness at both ends of the
`first layer is less than the thickness at the center of the first
`layer. Therefore, the current path at both ends ofthe first layer
`is reduced. In addition to this structure, when the thickness of
`the first layer is reduced, the current path at both ends of the
`first layer is further reduced. Consequently, even though a
`material having a high specific resistance is used as the first
`layer, current concentrates at an area in which the current path
`is short. In such a case, a desired ESR may not be achieved.
`Furthermore, according to a preferred embodiment of the
`present invention, the internal electrodes include nickel (Ni)
`or a nickel (Ni) alloy, and the first layer of each ofthe external
`terminal electrodes includes a compound oxide that reacts
`with Ni or the Ni alloy. Accordingly, a satisfactory connection
`state can be provided between the internal electrodes and the
`external terminal electrodes.
`
`Other features, elements, characteristics and advantages of
`the present invention will become more apparent from the
`following detailed description of preferred embodiments of
`the present invention with reference to the attached drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective view showing a monolithic ceramic
`capacitor according to a preferred embodiment of the present
`invention.
`FIG. 2 is a cross-sectional view of the monolithic ceramic
`
`capacitor taken along line A-A in FIG. 1.
`FIG. 3A is a view showing a cross section through which a
`first internal electrode in a capacitor main body shown in FIG.
`1 passes.
`FIG. 3B is a view showing a cross section through which a
`second internal electrode in the capacitor main body shown in
`FIG. 1 passes.
`FIG. 4 is a partially enlarged cross-sectional view of a
`second external terminal electrode included in the monolithic
`
`ceramic capacitor shown in FIG. 1.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`FIG. 1 is a perspective view showing a monolithic ceramic
`capacitor 1 according to a preferred embodiment of the
`present invention. FIG. 2 is a cross-sectional view of the
`monolithic ceramic capacitor 1 taken along line A-A in FIG.
`1.
`
`000008
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`

`

`US 7,808,770 B2
`
`5
`The monolithic ceramic capacitor 1 includes a capacitor
`main body 3 including a plurality of laminated ceramic layers
`2, at least one pair of internal electrodes 4 and 5 provided
`inside the capacitor main body 3, a first external terminal
`electrode 6, and a second external terminal electrode 7. The
`first external terminal electrode 6 and the second external
`
`terminal electrode 7 are provided on outer surfaces of the
`capacitor main body 3 so as to face each other.
`Each of the ceramic layers 2 in the capacitor main body 3
`is preferably made of, for example, a dielectric ceramic
`including, as a main component, BaTiO3, CaTiO3, SrTiO3,
`CaZrO3, or other suitable material. An auxiliary component
`such as a manganese (Mn) compound, an iron (Fe) com-
`pound, a chromium (Cr) compound, a cobalt (Co) compound,
`or a nickel (Ni) compound may be added to the main compo-
`nent. The thickness of each of the ceramic layers 2 is prefer-
`ably, for example, in the range of about 1 pm to about 10 pm,
`for example.
`The capacitor main body 3 preferably has a substantially
`rectangular parallelepiped shape having a first principal sur-
`face 8 and a second principal surface 9 facing each other, a
`first side surface 10 and a second side surface 11 facing each
`other, and a first end surface 12 and a second end surface 13
`facing each other.
`In the capacitor main body 3, the dimension (dimension W)
`of each ofthe first end surface 12 and the second surface 13 in
`
`the extending direction of the ceramic layers 2 is greater than
`the dimension (dimension L) of each of the first side surface
`10 and the second side surface 11 in the extending direction of
`the ceramic layers 2. The dimension W is preferably in the
`range of about 1.5 to about 2.5 times the dimension L, for
`example. The first external terminal electrode 6 is provided on
`the first end surface 12, and the second external terminal
`electrode 7 is provided on the second end surface 13.
`FIG. 3A is a view showing a cross section through which
`the first internal electrode 4 in the capacitor main body 3
`passes, and FIG. 3B is a view showing a cross section through
`which the second internal electrode 5 in the capacitor main
`body 3 passes.
`As shown in FIG. 3A, the first internal electrode 4 extends
`to the first end surface 12 of the capacitor main body 3.
`Accordingly, the first internal electrode 4 is electrically con-
`nected to the first external terminal electrode 6. On the other
`hand, as shown in FIG. 3B, the second internal electrode 5
`extends to the second end surface 13 of the capacitor main
`body 3. Accordingly, the second internal electrode 5 is elec-
`trically connected to the second external terminal electrode 7.
`As is apparent from FIG. 2, the first internal electrodes 4 and
`the second internal electrodes 5 are alternately disposed in the
`laminating direction, with the ceramic layers 2 therebetween.
`Nickel (Ni) or a nickel (Ni) alloy is preferably used as a
`conductive component included in the internal electrodes 4
`and 5. The thickness of each of the internal electrodes 4 and 5
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`capacitance provided by the monolithic ceramic capacitor 1.
`Thus, the ESR of the monolithic ceramic capacitor 1 can be
`increased.
`
`Note that the term “resistance component” means a com-
`ponent having a relatively high specific resistance excluding
`metals and glass included in typical external terminal elec-
`trodes. More specifically, the resistance component is prefer-
`ably a metal oxide excluding glass, for example. Examples of
`the metal oxide used in this preferred embodiment include
`compound oxides such as an In—Sn compound oxide (ITO),
`a La—Cu compound oxide, a Sr—Fe compound oxide, and a
`Ca—Sr—Ru compound oxide. These compound oxides such
`as an In—Sn compound oxide (ITO), a La—Cu compound
`oxide, a Sr—Fe compound oxide, and a Ca—Sr—Ru com-
`pound oxide have satisfactory reactivity with Ni. Therefore,
`as described above, a satisfactory connection between the
`internal electrodes 4 and 5 including Ni and a Ni alloy and the
`external terminal electrodes 6 and 7 can be achieved.
`
`Glass is preferably added to the first layer 14. For example,
`B—Si glass, B—Si—Zn glass, B—Si—Zn—Ba glass, or
`B—Si—Zn—Ba—Ca—Al glass can be used as the glass.
`When glass is added to the first layer 14, the volume ratio of
`the resistance component to the glass is preferably in the
`range of about 30:70 to about 70:30, for example.
`The first layer 14 may include a metal such as Ni, Cu, Mo,
`Cr, or Nb and a metal oxide such as A1203, TiO2, ZrO2, or
`ZnO2. These substances adjust the specific resistance pro-
`vided by the first layer 14 and the density of the first layer 14.
`More specifically, the addition of the above metal decreases
`the specific resistance, whereas the addition of the above
`metal oxide increases the specific resistance. The addition of
`Ni, Cu, A1203, or TiO2 accelerates densification of the first
`layer 14. On the other hand, the addition of Mo, Cr, Nb, ZrO2,
`or ZnO2 suppresses densification of the first layer 14. Note
`that suppression of densification means to prevent the gen-
`eration of a blister due to excessive firing of the first layer 14.
`The first layer 14 includes a wrap-around portion 17
`extending from the end surface 12 or 13 to the principal
`surfaces 8 and 9 and the side surfaces 10 and 11. The edge of
`the wrap-around portion 17 is covered with the third layer 16
`as described below. When the third layer 16 is formed by
`electrolytic plating, the first layer 14 preferably has a conduc-
`tivity to the extent that a plated film can be precipitated.
`Accordingly, when electrolytic plating is performed, a metal
`such as Ni is preferably added to the first layer 14 as described
`above. More specifically, the specific resistance of the first
`layer 14 is preferably in the range of about 0.1 §2~cm to about
`1.0 §2~cm, for example.
`In this preferred embodiment, the dimensions of the wrap-
`around portion of the external terminal electrodes 6 and 7 are
`defined by the wrap-around portion 17 of the first layer 14.
`Accordingly, the dimensions of the wrap-around portion of
`the external terminal electrodes 6 and 7 are substantially
`consistent.
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`is preferably in the range of about 1 pm to about 10 pm, for
`example.
`The first external terminal electrode 6 includes a first layer
`14 provided on the first end surface 12 of the capacitor main
`body 3, a second layer 15 provided on the first layer 14, and a
`third layer 16 provided on the second layer 15. Similarly, the
`second external terminal electrode 7 includes a first layer 14
`provided on the second end surface 13 of the capacitor main
`body 3, a second layer 15 provided on the first layer 14, and a
`third layer 16 provided on the second layer 15.
`The first layer 14 includes a resistance component and is
`formed by applying resistance paste including the resistance
`component followed by baking. By forming the first layer 14,
`the resistance component
`is provided in series with the
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`The second layer 15 covers the first layer 14 such that the
`edge of the wrap-around portion 17 of the first layer 14
`remains exposed. The second layer 15 improves moisture
`resistance and a plating film-forming property.
`The second layer 15 primarily includes a metal and is
`formed by applying conductive paste including a metal pow-
`der and baking the conductive paste. Examples of the metal
`included in the second layer 15 include Cu, Ni, Ag, Pd, a
`Ag—Pd alloy, and Au, for example. In addition, glass is
`preferably added to the second layer 15. As this glass, the
`same glass as that included in the first layer 14 or glass
`including the same main component as that included in the
`glass in the first layer 14 is preferably used.
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`Furthermore, the thickness T1 of the first layer 14 is pref-
`erably in the range of about 20 pm to about 30 pm, for
`example, the thickness T2 ofthe second layer 15 is preferably
`in the range of about 20 pm to about 30 pm, for example, and
`the thickness T3 ofthe third layer 16 is preferably in the range
`ofabout 5 um to about 15 um, for example. Ifthe thickness T1
`of the first layer 14 is outside of the above range of about 20
`pm to about 30 um and less than about 20 pm, the variation in
`the film thickness of the first layer 14 is increased, and thus,
`the variation in the ESR is increased. On the other hand, ifthe
`thickness T1 of the first layer 14 is greater than about 30 pm,
`in a production process described below, it is necessary to dip
`the capacitor main body 3 into resistance paste more deeply.
`In such a case, the resistance paste is applied on the capacitor
`main body 3 in a state in which the capacitor main body 3 is
`slanted. As a result, the length L1 of the wrap-around portion
`17 of the first layer 14 may vary.
`An example of a method of producing the above mono-
`lithic ceramic capacitor 1 will now be described.
`First, ceramic green sheets used for the ceramic layers 2,
`conductive paste for the internal electrodes 4 and 5, and
`resistance paste and conductive paste for the external terminal
`electrodes 6 and 7 are prepared. The ceramic green sheets, the
`conductive paste for the internal electrodes 4 and 5, and the
`conductive paste for the external terminal electrodes 6 and 7
`include binders and solvents. Known organic binders and
`organic solvents can be used as the binders and the solvents,
`for example.
`Next, the conductive paste for the internal electrodes 4 and
`5 is printed on each of the ceramic green sheets so as to have
`a predetermined pattern by, for example, a screen printing
`method. Accordingly, ceramic green sheets having a conduc-
`tive paste film for each of the inner electrodes 4 and 5 thereon
`are obtained.
`
`Next, a predetermined number of ceramic green sheets on
`which the conductive paste film is formed as described above
`are laminated in a predetermined order. A predetermined
`number of ceramic green sheets for outer layers, the green
`sheets not having conductive paste film thereon, are further
`laminated on the top and the bottom ofthe laminated ceramic
`green sheets. Thus, an unfired mother laminate is prepared.
`The unfired mother laminate is optionally pressure-bonded in
`the laminating direction by, for example, isostatic pressing.
`Next, the unfired mother laminate is cut so as to have a
`predetermined size, thus allowing an unfired capacitor main
`body 3 to be prepared.
`The unfired capacitor main body 3 is then fired. The firing
`temperature depends on the ceramic material contained in the
`ceramic green sheets and the metal material contained in the
`conductive paste films, but is preferably selected from the
`range of about 900° C. to about l,300° C., for example.
`Next, the resistance paste is applied on the first end surface
`12 and the second end surface 13 of the fired capacitor main
`body 3 and then baked to form the first layer 14 for the first
`external terminal electrode 6 and the second external terminal
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`Since the second layer 15 is arranged such that the edge of
`the wrap-around portion 17 of the first layer 14 remains
`exposed, the size ofthe monolithic ceramic capacitor 1 can be
`reduced. In this structure, although a portion of the first layer
`14 is exposed, the position of the edge of the wrap-around
`portion 17 is spaced from the positions of the internal elec-
`trodes 4 and 5, which define a capacitance-forming portion.
`Accordingly, even if a plating solution or moisture intrudes
`from the edge of the wrap-around portion 17, the plating
`solution or moisture does not reach the capacitance-forming
`portion. Therefore, this structure prevents a decrease in the
`reliability.
`The third layer 16 is arranged so as to cover the edge of the
`wrap-around portion 17 of the first layer 14 and the second
`layer 15. The third layer 16 is preferably formed by plating.
`When the monolithic ceramic capacitor 1 is mounted using
`solder, the third layer 16 preferably has a two-layer structure
`including a Ni plating film and a Sn plating film disposed on
`the Ni plating film, for example. When the monolithic
`ceramic capacitor 1 is mounted with a conductive adhesive or
`by wire bonding, the third layer 16 preferably has a two -layer
`structure including a Ni plating film and an Au plating film
`disposed on the Ni plating film, for example. When the mono-
`lithic ceramic capacitor 1 is embedded in a resin substrate, at
`least the outermost layer of the third layer 16 is preferably
`formed by copper (Cu) plating, for example.
`The structure of the third layer 16 is not limited to the
`two-layer structure described above. The third layer 16 may
`include a single layer or three or more layers. Preferably, the
`thickness of each layer of the plating films defining the third
`layer 16 is in the range of about 1 um to about 10 pm, for
`example. Furthermore, a resin layer for relieving stress may
`be provided between the second layer 15 and the third layer
`16.
`
`FIG. 4 is a partially enlarged cross-sectional view of the
`second external terminal electrode 7. Although the first exter-
`nal terminal electrode 6 is not shown in FIG. 4, the first
`external terminal electrode 6 has substantially the same struc-
`ture as the second external terminal electrode 7.
`
`In FIG. 4, examples of dimensions of the second external
`terminal electrode 7 are shown. Specifically, the length of the
`wrap-around portion 17 of the first layer 14 is denoted by L1,
`and the length of the exposed edge of the first layer 14 is
`denoted by L2. The thickness of the thickest portion of the
`first layer 14 on the second end surface 13 is denoted by T1,
`the thickness of the thickest portion of the second layer 15 is
`denoted by T2, and the thickness ofthe thickest portion of the
`third layer 1 6 is denoted by T3. Note that, for convenience, the