U.S. patent application number 13/478599 was filed with the patent office on 2012-12-06 for multilayer ceramic electronic component.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Jae Hun Choe, Byung Soo Kim, Jun Hee Kim, Sang Huk KIM, Jae Sung Park, Seon Ki Song, Ju Myung Suh.
Application Number | 20120307417 13/478599 |
Document ID | / |
Family ID | 47234084 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120307417 |
Kind Code |
A1 |
KIM; Sang Huk ; et
al. |
December 6, 2012 |
MULTILAYER CERAMIC ELECTRONIC COMPONENT
Abstract
There is provided a multilayer ceramic electronic component
including: a lamination main body including a dielectric layer; and
a plurality of inner electrode layers formed within the lamination
main body and having ends exposed from one or more faces of the
laminated main body, wherein when a distance between central
portions of adjacent inner electrodes among the plurality of inner
electrodes is T1 and a distance between non-exposed edges of the
adjacent inner electrodes is T2, the ratio (T2/T1) of T2 to T1 is
0.80 to 0.95.
Inventors: |
KIM; Sang Huk; (Suwon,
KR) ; Choe; Jae Hun; (Suwon, KR) ; Park; Jae
Sung; (Suwon, KR) ; Kim; Byung Soo; (Suwon,
KR) ; Song; Seon Ki; (Anyang, KR) ; Kim; Jun
Hee; (Hwaseong, KR) ; Suh; Ju Myung; (Anyang,
KR) |
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
|
Family ID: |
47234084 |
Appl. No.: |
13/478599 |
Filed: |
May 23, 2012 |
Current U.S.
Class: |
361/321.2 |
Current CPC
Class: |
H01G 4/012 20130101;
H01G 4/12 20130101; H01G 4/30 20130101 |
Class at
Publication: |
361/321.2 |
International
Class: |
H01G 4/12 20060101
H01G004/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2011 |
KR |
10-2011-0052479 |
Claims
1. A multilayer ceramic electronic component comprising: a
lamination main body including a dielectric layer; and a plurality
of inner electrode layers formed within the lamination main body
and having ends exposed from one or more faces of the laminated
main body, wherein when a distance between central portions of
adjacent inner electrodes among the plurality of inner electrodes
is T1 and a distance between non-exposed edges of the adjacent
inner electrodes is T2, a ratio (T2/T1) of T2 to T1 is 0.80 to
0.95.
2. The multilayer ceramic electronic component of claim 1, wherein
the distance T1 between the central portions of the adjacent inner
electrodes in a lamination direction is less than 0.66 .mu.m.
3. The multilayer ceramic electronic component of claim 1, wherein
the distances T1 and T2 are measured in a section perpendicular to
a first face of the lamination main body, the edges of the inner
electrodes being not exposed from the first face of the lamination
main body.
4. The multilayer ceramic electronic component of claim 1, wherein
a thickness D1 of a central portion of the lamination main body is
greater than a thickness D2 of a first face of the lamination main
body, the edges of the inner electrodes being not exposed from the
first face of the lamination main body.
5. The multilayer ceramic electronic component of claim 4, wherein
a ratio of the thickness D2 of the first face of the lamination
main body to the thickness D1 of the central portion of the
lamination main body is 0.78 to 0.95.
6. The multilayer ceramic electronic component of claim 4, wherein
the thickness D1 of the central portion of the lamination main body
is measured at a capacity formation portion in which the plurality
of inner electrodes overlap each other.
7. The multilayer ceramic electronic component of claim 4, wherein
the thickness D1 of the central portion of the lamination main body
ranges from 200 .mu.m to 300 .mu.m.
8. The multilayer ceramic electronic component of claim 1, wherein
a thickness D1 of a central portion of the lamination main body is
greater than a thickness D3 of a second face of the lamination main
body, the ends of the inner electrodes being exposed from the
second face of the lamination main body.
9. The multilayer ceramic electronic component of claim 8, wherein
a ratio of the thickness D3 of the second face of the lamination
main body to the thickness D1 of the central portion of the
lamination main body is 0.75 to 0.97.
10. The multilayer ceramic electronic component of claim 9, wherein
the thickness D3 of the second face of the lamination main body is
measured at an area of the lamination main body in which the inner
electrodes are present.
11. The multilayer ceramic electronic component of claim 1, wherein
a thickness of one of the inner electrode layers is 0.7 .mu.m or
less.
12. A multilayer ceramic capacitor comprising: a lamination main
body having first and second faces; and a plurality of inner
electrode layers formed within the lamination main body and having
ends exposed from the first and second faces, respectively, wherein
when a distance between central portions of adjacent inner
electrodes among the plurality of inner electrodes is T1 and a
distance between non-exposed edges of the adjacent inner electrodes
in a lamination direction is T2, a ratio (T2/T1) of T2 to T1 is
0.80 to 0.95, and the distance between the central portions of the
adjacent inner electrodes is less than 0.66 .mu.m.
13. The multilayer ceramic capacitor of claim 12, wherein the first
and second faces oppose each other and are disposed in a lengthwise
direction of the lamination main body.
14. The multilayer ceramic capacitor of claim 12, wherein a
thickness D1 of a central portion of the lamination main body is
greater than a thickness D2 of a third face of the lamination main
body, the edges of the inner electrodes being not exposed from the
third face.
15. The multilayer ceramic capacitor of claim 14, wherein a ratio
of the thickness D2 of the third face of the lamination main body
to the thickness D1 of the central portion of the lamination main
body is 0.78 to 0.95.
16. The multilayer ceramic electronic component of claim 12,
wherein a ratio of the thickness D3 of one of the first and the
second faces of the lamination main body to the thickness D1 of a
central portion of the lamination main body is 0.75 to 0.97.
17. A multilayer ceramic capacitor comprising: a lamination main
body; a plurality of first and second inner electrode layers formed
within the lamination main body and having ends exposed from one of
end faces of the lamination main body in a lengthwise direction,
respectively; and a dielectric layer disposed between the first and
second inner electrode layers and having a thickness less than 0.66
.mu.m, wherein a thickness D1 of a central portion of the
lamination main body is greater than a thickness D2 of an edge
portion of the lamination main body in a widthwise direction, and
when a distance between adjacent inner electrodes in the central
portion of the lamination main body is T1 and a distance between
the adjacent inner electrodes at the edges of the inner electrodes
in the widthwise direction is T2, a ratio (T2/T1) of T2 to T1 is
0.80 to 0.95.
18. The multilayer ceramic capacitor of claim 17, wherein a ratio
of the thickness D2 of the edge portion of the lamination main body
in the widthwise direction to the thickness D1 of the central
portion of the lamination main body is 0.78 to 0.95.
19. The multilayer ceramic capacitor of claim 17, wherein the
thickness D1 of the central portion of the lamination main body is
greater than a thickness D3 of the end faces of the lamination main
body in the lengthwise direction.
20. The multilayer ceramic capacitor of claim 19, wherein a ratio
of the thickness D3 of the end faces of the lamination main body in
the lengthwise direction to the thickness D1 of the central portion
of the lamination main body is 0.75 to 0.97.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent
Application No. 10-2011-0052479 filed on May 31, 2011, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a multilayer ceramic
electronic component and, more particularly, to a multilayer
ceramic electronic component having excellent reliability.
[0004] 2. Description of the Related Art
[0005] In general, an electronic component using a ceramic material
such as a capacitor, an inductor, a piezoelectric element, a
varistor, a thermistor, or the like, includes a ceramic main body
made of a ceramic material, inner electrodes formed within the
interior of the ceramic main body, and outer electrodes installed
on a surface of the ceramic main body such that they are connected
with the inner electrode.
[0006] Among ceramic electronic components, a multilayer ceramic
capacitor includes a plurality of laminated dielectric layers,
inner electrodes disposed to face each other with a dielectric
layer interposed therebetween, and outer electrodes electrically
connected with the inner electrodes.
[0007] The multilayer ceramic capacitor is commonly used as a
component of mobile communication devices such as computers, PDAs
(Personal Digital Assistants), mobile phones, and the like, due to
its advantages of being small, guaranteeing high capacity, and
being easily mounted.
[0008] Recently, as electronic products have been reduced in size
and the multifunctionality thereof has been developed, chip
components have also become compact and highly functional, so a
multilayer ceramic capacitor product which is small but has high
capacity is therefore in demand.
[0009] In order to increase the capacity of the multilayer ceramic
capacitor, the thicknesses of a dielectric layer and the inner
electrode layer are required to be reduced and the number of
laminated layers thereof is required to be increased. However, as
the dielectric layer and the inner electrodes are thinned and the
number of laminated layers thereof increases, there is a high
possibility of a dielectric breakdown, a delamination and cracks to
thereby degrade the reliability of the multilayer ceramic
capacitor. Thus, there is a limitation in reducing the size of the
multilayer ceramic capacitor and increasing the capacity of the
multilayer ceramic capacitor.
SUMMARY OF THE INVENTION
[0010] An aspect of the present invention provides a multilayer
ceramic electronic component having excellent reliability.
[0011] According to an aspect of the present invention, there is
provided a multilayer ceramic electronic component including: a
lamination main body including a dielectric layer; and a plurality
of inner electrode layers formed within the lamination main body
and having ends exposed from one or more faces of the laminated
main body, wherein when a distance between central portions of
adjacent inner electrodes among the plurality of inner electrodes
is T1 and a distance between non-exposed edges of the adjacent
inner electrodes is T2, a ratio (T2/T1) of T2 to T1 is 0.80 to
0.95.
[0012] The distance T1 between the central portions of the adjacent
inner electrodes in a lamination direction may be less than 0.66
.mu.m.
[0013] The distances T1 and T2 may be measured in a section
perpendicular to a first face of the lamination main body, wherein
the edges of the inner electrodes are not exposed from the first
face of the lamination main body.
[0014] A thickness D1 of a central portion of the lamination main
body is greater than a thickness D2 of a first face of the
lamination main body, wherein the edges of the inner electrodes are
not exposed from the first face of the lamination main body.
[0015] A ratio of the thickness D2 of the first face of the
lamination main body to the thickness D1 of the central portion of
the lamination main body may be 0.78 to 0.95.
[0016] The thickness of the central portion of the lamination main
body may be measured at a capacity formation portion in which the
plurality of inner electrodes overlap each other.
[0017] The thickness D1 of the central portion of the lamination
main body may range from 200 .mu.m to 300 .mu.m.
[0018] A thickness D1 of a central portion of the lamination main
body may be greater than a thickness D3 of a second of the
lamination main body, wherein the ends of the inner electrodes are
exposed from the second face of the lamination main body.
[0019] A ratio of the thickness D3 of the second face of the
lamination main body to the thickness D1 of the central portion of
the lamination main body may be 0.75 to 0.97.
[0020] The thickness D3 of the second face of the lamination main
body may be measured at an area of the lamination main body in
which the inner electrodes are present.
[0021] A thickness of one of the inner electrode layers may be 0.7
.mu.m or less.
[0022] According to another aspect of the present invention, there
is provided a multilayer ceramic capacitor including: a lamination
main body having first and second faces; and a plurality of inner
electrode layers formed within the lamination main body and having
ends exposed from the first and second faces, respectively, wherein
when a distance between central portions of adjacent inner
electrodes among the plurality of inner electrodes is T1 and a
distance between non-exposed edges of the adjacent inner electrodes
in a lamination direction is T2, a ratio (T2/T1) of T2 to T1 is
0.80 to 0.95, and the distance between the central portions of the
adjacent inner electrodes is less than 0.66 .mu.m.
[0023] The first and second faces may oppose each other and be
disposed in a lengthwise direction of the lamination main body.
[0024] A thickness D1 of a central portion of the lamination main
body may be greater than a thickness D2 of a third face of the
lamination main body, wherein the edges of the inner electrodes are
not exposed from the third face.
[0025] A ratio of the thickness D2 of the third face of the
lamination main body to the thickness D1 of the central portion of
the lamination main body may be 0.78 to 0.95. A ratio of the
thickness D3 of one of the first and the second faces of the
lamination main body to the thickness D1 of a central portion of
the lamination main body may be 0.75 to 0.97.
[0026] According to another aspect of the present invention, there
is provided a multilayer ceramic capacitor including: a lamination
main body; a plurality of first and second inner electrode layers
formed within the lamination main body and having ends exposed from
one of end faces of the lamination main body in a lengthwise
direction, respectively; and a dielectric layer disposed between
the first and second inner electrode layers and having a thickness
less than 0.66 .mu.m, wherein a thickness D1 of a central portion
of the lamination main body is greater than a thickness D2 of an
edge portion of the lamination main body in a widthwise direction,
and when a distance between adjacent inner electrodes in the
central portion of the lamination main body is T1 and a distance
between the adjacent inner electrodes at the edges of the inner
electrodes in the widthwise direction is T2, a ratio (T2/T1) of T2
to T1 is 0.80 to 0.95.
[0027] A ratio of the thickness D2 of the edge portion of the
lamination main body in the widthwise direction to the thickness D1
of the central portion of the lamination main body may be 0.78 to
0.95.
[0028] The thickness D1 of the central portion of the lamination
main body may be greater than a thickness D3 of the end faces of
the lamination main body in the lengthwise direction.
[0029] A ratio of the thickness D3 of the end faces of the
lamination main body in the lengthwise direction to the thickness
D1 of the central portion of the lamination main body may be 0.75
to 0.97.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0031] FIG. 1 is a schematic perspective view of a multilayer
ceramic capacitor according to an embodiment of the present
invention;
[0032] FIG. 2 is a schematic exploded perspective view of a
lamination main body according to an embodiment of the present
invention;
[0033] FIG. 3 is a cross-sectional view taken along line A-A' in
FIG. 1;
[0034] FIG. 4 is a cross-sectional view taken along line B-B' in
FIG. 1;
[0035] FIG. 5 is an enlarged sectional view of a portion of a
section in a widthwise direction of the multilayer ceramic
capacitor; and
[0036] FIG. 6 is an enlarged sectional view of a portion of a
section of a multilayer ceramic capacitor according to another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0037] Embodiments of the present invention will now be described
in detail with reference to the accompanying drawings. The
invention may, however, be embodied in many different forms and
should not be construed as being limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. In the
drawings, the shapes and dimensions may be exaggerated for clarity,
and the same reference numerals will be used throughout to
designate the same or like components.
[0038] FIG. 1 is a schematic perspective view of a multilayer
ceramic capacitor according to an embodiment of the present
invention, and FIG. 2 is a schematic exploded perspective view of a
lamination main body. FIG. 3 is a cross-sectional view taken along
line A-A' in FIG. 1, namely, a cross-sectional view taken in a
widthwise direction (or in a W direction) of the multilayer ceramic
capacitor. FIG. 4 is a cross-sectional view taken along line B-B'
in FIG. 1, namely, a cross-sectional view taken in a lengthwise
direction (or in an L direction) of the multilayered ceramic
capacitor. FIG. 5 is an enlarged sectional view of a portion of a
section in a widthwise direction of the multilayer ceramic
capacitor.
[0039] In the present embodiment, it may be defined such that the
`lengthwise direction` of the multilayer ceramic capacitor is the
`L` direction, the `widthwise direction` is the `W` direction, a
`thicknesswise direction` is the `T` direction (or a vertical
direction) in FIG. 1. The `thicknesswise direction` may have the
same concept as a `lamination direction` in which dielectric layers
are laminated.
[0040] With reference to FIGS. 1 through 5, the multilayer ceramic
capacitor according to an embodiment of the present invention may
include a lamination main body 110, and outer electrodes 131 and
132 formed at both end portions of the lamination main body.
[0041] As shown in FIG. 2, the lamination main body 110 may be
formed by laminating a plurality of dielectric layers 111 in the
thicknesswise direction. The plurality of dielectric layers
constituting the lamination main body 110 are in a sintered state
to be integrated such that the boundary between adjacent dielectric
layers cannot easily be discerned.
[0042] The dielectric layers may be made of ceramic powder having
high permittivity. For example, a barium titanate
(BaTiO.sub.3)-based powder, a strontium titanate
(SrTiO.sub.3)-based powder, or the like, may be used, but the
present invention is not limited thereto. The thickness of one
dielectric layer 111 may be less than 0.66 .mu.m, but the present
invention is not limited thereto. Alternatively, the thickness of
one dielectric layer 111 may be 0.4 .mu.am or greater but less than
0.66 .mu.am. Alternatively, the thickness of one dielectric layer
111 may range from 0.45 .mu.m to 0.55 .mu.m.
[0043] In an embodiment of the present invention, the thickness of
one dielectric layer 111 may refer to an average thickness of one
dielectric layer 111 disposed between the inner electrode layers
121 and 122. The average thickness of the dielectric layer may be
measured by scanning an image of a section in the lengthwise
direction of the lamination main body 110 as shown in FIG. 4 by
using a scanning electron microscope (SEM) of 10,000
magnifications. In detail, the thickness of one dielectric layer
111 may be measured at 30 points at equal intervals in the
lengthwise direction in the scanned image, to thus measure the
average thickness value thereof. The 30 points at equal intervals
may be designated at a capacity formation portion E. As shown in
FIG. 4, the capacity formation portion E may refer to an area in
which the first and second inner electrodes 121 and 122 overlap
each other. Also, such an average value measurement may extend to
be performed at 10 dielectric layers to measure an average value,
whereby an average thickness of the dielectric layers can be
further generalized.
[0044] Also, the thickness of one dielectric layer may be defined
as an average distance between the central portions of the mutually
adjacent inner electrode layers 121 and 122. For example, the
distances between mutually adjacent inner electrode layers may be
measured at 30 points at equal intervals in the lengthwise
direction of the inner electrode layers may be measured on the
scanned image to calculate an average distance. Also, the average
distance between mutually adjacent inner electrode layers may
extend to ten pairs of inner electrode layers disposed at the
capacity formation portion E to measure an average distance,
whereby the average distance between mutually adjacent inner
electrode layers can be further generalized.
[0045] The distance between the central portions of the mutually
adjacent first inner electrode layer 121 and the second inner
electrode layer 122 may be less than 0.66 .mu.m, but the present
invention is not limited thereto. Alternatively, the distance
between the central portions of the mutually adjacent first and
second inner electrode layers 121 and 122 may be 0.4 .mu.m or
greater but less than 0.66 .mu.M. Alternatively, the distance
between the central portions of the mutually adjacent first and
second inner electrode layers 121 and 122 may range from 0.45 .mu.m
to 0.55 .mu.m.
[0046] A plurality of inner electrodes 121 and 122 may be formed in
the interior of the lamination main body 110. The inner electrodes
121 and 122 are formed on the dielectric layers 111 and may be
disposed such that the inner electrodes 121 and 122 face each other
with one dielectric layer interposed therebetween in the lamination
direction of the dielectric layers through sintering. The inner
electrode layers may be made of a conductive metal such as nickel
(Ni), copper (Cu), palladium (Pd), or the like, and the thickness
of one inner electrode layer may be 0.7 .mu.m or less, but the
present invention is not limited thereto
[0047] According to an embodiment of the present invention, more
than two hundred dielectric layers, on which the inner electrode
layers are respectively formed, may be laminated.
[0048] As for the plurality of inner electrodes 121 and 122, the
first and second inner electrodes 121 and 122, having different
polarities, may be paired.
[0049] A lengthwise directional marginal portion L1, in which the
first inner electrode 121 or the second inner electrode 122 are not
formed, may be formed in the lengthwise direction L of the
lamination main body 110, and widthwise directional marginal
portions W1 and W2, in which the first inner electrode 121 and the
second inner electrode 122 are not formed, may be formed in the
widthwise direction W of the lamination main body 110.
[0050] One end of each of the first and second inner electrodes 121
and 122 is spaced apart from one end face of the lamination main
body by the presence of the lengthwise directional marginal portion
L1, and the other end of each of the first and second inner
electrodes 121 and 122 may be exposed from one end face of the
lamination main body.
[0051] The ends of the first and second inner electrodes 121 and
122 exposed respectively from both end faces of the lamination main
body 110 may be respectively electrically connected with the first
and second outer electrodes 131 and 132 formed on both end faces of
the lamination main body.
[0052] Capacitance may be formed in an area of the lamination main
body 100, in which the first and second inner electrodes 121 and
122 overlap each other, when an electric field is applied thereto.
In an embodiment of the present invention, the area in which the
first and second inner electrodes 121 and 122 overlap each other
will be referred to as the capacity formation portion E. Also, an
area of the lamination main body, in which the first and second
inner electrodes do not overlap each other and only the first inner
electrode or the second inner electrode is formed, will be referred
to as an electrode draw-out portion. The electrode draw-out portion
may be formed by the lengthwise directional marginal portion L1.
According to an embodiment of the present invention, the first
inner electrode or the second inner electrode may be exposed to one
end of the lamination main body through the electrode draw-out
portion.
[0053] According to an embodiment of the present invention, the end
of each of the inner electrodes may be exposed from one or more
faces of the lamination main body, but the present invention is not
limited thereto.
[0054] Although not shown, the first or second inner electrodes may
be exposed from the same face of the lamination main body.
Alternatively, the ends of the first or second inner electrodes may
be exposed from two or more faces of the lamination main body by
two or more electrode draw-out portions.
[0055] According to an embodiment of the present invention, the
thickness of the central portion of the lamination main body may be
greater than that of one face, of the lamination main body, from
which the ends of the inner electrodes are not drawn out.
[0056] As shown in FIG. 3, according to an embodiment of the
present invention, the thickness D1 of the central portion of the
lamination main body may be greater than the thickness D2 of the
edge portion of the lamination main body in the widthwise
direction. The thickness D1 of the central portion of the
lamination main body may be measured at the capacity formation
portion E in which the first and second inner electrodes 121 and
122 overlap each other to form capacitance. Also, the thickness D1
of the central portion of the lamination main body may be a maximum
thickness of the lamination main body. The thickness D2 of the edge
portion of the lamination main body in the widthwise direction may
be measured at the widthwise directional marginal portions W1 and
W2 in which the inner electrodes are not formed.
[0057] There is a difference in density between the capacity
formation portion E of the lamination main body in which the first
and second inner electrodes overlap each other and the marginal
portions in which the first inner electrode or the second inner
electrode is not formed. When the difference in density between the
capacity formation portion E and the marginal portions is
increased, the marginal portion may be delaminated or cracked.
Then, a plating solution may infiltrate into the delaminated or
cracked portion, resulting in a degradation of the reliability of
the multilayer ceramic capacitor.
[0058] According to an embodiment of the present invention, the
capacity formation portion E and the widthwise directional marginal
portions W1 and W2 are differentially compressed to reduce the
difference in density. A delamination or cracking incidence of the
multilayer ceramic capacitor can be lowered and dielectric
breakdown voltage characteristics can be improved by adjusting the
ratio of the thicknesses of the capacity formation portion E and
the widthwise directional marginal portions W1 and W2.
[0059] According to an embodiment of the present invention, the
ratio (D2/D1) of the thickness of the edge portion of the
lamination main body to the thickness of the central portion of the
lamination main body may be 0.78 to 0.95. The thickness D1 of the
central portion of the lamination main body may range from 250
.mu.m to 350 .mu.m, but the present invention is not limited
thereto. Alternatively, the thickness D1 of the central portion of
the lamination main body may range from 310 .mu.m to 320 .mu.m.
[0060] If the ratio of D2 to D1 is less than 0.78, the edges of
each of the inner electrodes in the widthwise direction would be
overly bent to significantly reduce the interval between the
vertically adjacent inner electrodes compared with the central
portion. Then, an electric field would be concentrated in the edges
of each of the inner electrodes in the widthwise direction to
degrade the dielectric breakdown voltage characteristics, degrade
the characteristics under a high temperature condition and a
moisture resistance condition, and degrade an average life
span.
[0061] Also, if the ratio of D2 to D1 exceeds 0.95, there would be
high possibility of the generation of a delamination or cracks, and
the cracks would possibly degrade dielectric breakdown voltage
characteristics as well as high temperature and moisture resistance
characteristics.
[0062] FIG. 5 is an enlarged sectional view of a portion of a
section in a widthwise direction of the multilayer ceramic
capacitor. FIG. 5 may show a section perpendicular with respect to
one face, of the lamination main body, from which the edges of
inner electrodes are not exposed. FIG. 5 may be a sectional view
taken along a line across the central portion of the lamination
main body. The non-exposed edges of the inner electrodes formed in
the lamination main body can be understood with reference to FIG.
5.
[0063] With reference to FIG. 5, according to an embodiment of the
present invention, the distance between vertically adjacent inner
electrodes in the central portion of the lamination main body may
be greater than the distance between vertically adjacent inner
electrodes at the edges of the inner electrodes in the widthwise
direction.
[0064] The distance between the vertically adjacent inner
electrodes 121 and 122 in the central portion of the lamination
main body may be defined as T1. The central portion of the
lamination main body may refer to an area in which the edges of the
inner electrodes in the widthwise direction are not bent.
[0065] Also, the distance between the vertically adjacent inner
electrodes 121 and 122 at the edges of the inner electrodes in the
widthwise direction may be defined as T2. The edges of the inner
electrodes in the widthwise direction may include an oxidized area
of the inner electrodes.
[0066] The ratio (T2/T1) of T2 to T1 may be 0.80 to 0.95. The
distance T1 between the vertically adjacent inner electrodes 121
and 122 in the central portion of the lamination main body may be
less than 0.66 .mu.m, but the present invention is not limited
thereto.
[0067] If the ratio (T2/T1) of T2 to T1 is less than 0.80, the
widthwise directional marginal portions W1 and W2 would possibly be
overly compressed, and the edges of the inner electrodes in the
widthwise direction would possibly be overly bent. Then, the
distance between the edges of the vertically adjacent inner
electrodes in the widthwise direction would be shortened, making
the dielectric layer positioned therebetween thinner, to causing an
electric field to be concentrated therein. Then, the dielectric
breakdown voltage would possibly be lowered and high temperature
and moisture resistance characteristics would be degraded.
[0068] Also, if the ratio (T2/T1) of T2 to T1 exceeds 0.95, the
degree of compression of the widthwise directional marginal
portions W1 and W2 is so low as to cause a delamination and
cracking, the dielectric breakdown voltage would possibly be
lowered due to cracking, and the high temperature and moisture
resistance characteristics would be degraded.
[0069] FIG. 6 is an enlarged sectional view of a portion of a
section of a multilayer ceramic capacitor according to another
embodiment of the present invention. With reference to FIG. 6,
similar to that of FIG. 5, depicted is a section perpendicular to
one face from which the edges of the inner electrode of the
lamination main body are not exposed. Namely, FIG. 6 illustrates
the non-exposed edges of the inner electrodes formed in the
lamination main body.
[0070] With reference to FIG. 6, according to an embodiment of the
present invention, the distance T1 between the central portions of
the vertically adjacent inner electrodes 121 and 122 may be longer
than the distance T2 between the edges of the vertically adjacent
inner electrodes. The central portion of the lamination main body
may refer to an area in which the edges of the inner electrodes in
the widthwise direction are not bent. The edges of the inner
electrodes are portions not exposed from the lamination main body.
The edges of the inner electrodes in the widthwise direction may
include an oxidized area of the inner electrodes.
[0071] According to an embodiment of the present invention, in the
sectional view showing the edges of the inner electrodes not
exposed from one face of the lamination main body, the end portions
of the inner electrodes may not be arranged on a straight line. For
example, as shown in FIG. 6, based on a straight line virtually
drawn in the lamination direction, the edge of one inner electrode
122 may be shifted to the right, and the edge of one inner
electrode may be shifted to the left. Also, in the sectional view,
the lengths of the inner electrodes may not be uniform.
[0072] According to an embodiment of the present invention, as
shown in FIG. 6, the distance T2 between the edges of the
vertically adjacent inner electrodes may be defined as the shortest
distance from the edge of a non-protruded inner electrode to an
adjacent inner electrode, based on a vertical line virtually drawn
in the lamination direction from the edge of one inner electrode
among vertically adjacent inner electrodes. The virtual vertical
line may be drawn from an edge of one of two inner electrodes as a
measurement target. The shortest distance may be a length of the
vertical line drawn from the edge of the non-protruded inner
electrode to its adjacent inner electrode.
[0073] The ratio (T2/T1) of T2 to T1 may be 0.80 to 0.95. The
distance T1 between the vertically adjacent inner electrodes 121
and 122 in the central portion of the lamination main body may be
less than 0.66 .mu.m, but the present invention is not limited
thereto.
[0074] As described above, in order to reduce the size and increase
the capacity of the multilayer ceramic capacitor, the thicknesses
of the dielectric layers and the inner electrode layers are
required to be reduced and the number of laminated layers thereof
is required to be increased. However, if the dielectric layers and
the inner electrode layers are thinned and the number of laminated
layers is increased, the difference in density between the capacity
formation portion in which the inner electrodes overlap each other
and the marginal portions in which the inner electrodes are not
formed would be increased. Then, the electrode draw-out portion
might be delaminated or cracked.
[0075] Also, if the marginal portions are overly compressed to
increase the density of the marginal portions, the edges of the
inner electrodes would be overly bent to shorten the distance
between the adjacent inner electrodes. When the dielectric layers
have a predetermined thickness, even in the case that the distance
between the inner electrodes is shortened, the possibility of
dielectric breakdown is low, but as the dielectric layers are
thinned, the possibility of dielectric breakdown may be increased.
Namely, as the dielectric layers are thinned, the interval between
the inner electrodes becomes too narrow, increasing the possibility
of dielectric breakdown even at a low voltage.
[0076] However, according to the embodiment of the present
invention, the thickness of one dielectric layer may be less than
0.66 .mu.m and the thickness of one inner electrode layer may be
0.7 .mu.m or less. Also, two hundred or more of the dielectric
layers, on which the inner electrode layers are formed, may be
laminated.
[0077] As described above, according to the embodiment of the
present invention, although the dielectric layers and the inner
electrode layers are thinned, the concentration of an electric
field in a particular area can be prevented by adjusting the
compression ratio between the capacity formation portion and the
marginal portions, and the possibility of delamination and crack
generation can be reduced.
[0078] According to the embodiment of the present invention, the
thickness of the central portion of the lamination main body may be
greater than the thickness of one face of the lamination main body
to which the end of the inner electrode is drawn out.
[0079] As shown in FIG. 4, according to the embodiment of the
present invention, the thickness D1 of the central portion of the
lamination main body may be greater than the thickness D3 of the
end face of the lamination main body. The thickness D1 of the
central portion of the lamination main body may be measured at the
capacity formation portion E. Also, the end face of the lamination
main body may refer to a face from which the end of the first inner
electrode 121 or the second inner electrode 122 is exposed in the
lengthwise direction, which may be an end face formed in the
lengthwise direction of the lamination main body. The thickness D3
of the end face of the lamination main body may be measured at the
area in which the first inner electrodes 121 or the second inner
electrodes 122 are present.
[0080] As shown in FIG. 3, the widthwise directional marginal
portions W1 and W2 in which the first inner electrodes 121 and the
second inner electrodes 122 are not formed are disposed in the
widthwise direction of the lamination main body, and the thickness
D3 of the end face of the lamination main body may be the thickness
of the area in which the first inner electrodes 121 or the second
inner electrodes 122 are present, rather than the widthwise
directional marginal portions W1 and W2.
[0081] As described above, there may be a difference in density
between the capacity formation portion and the marginal portion,
and in this case, the difference in density may be adjusted by
differentially compressing the capacity formation portion and the
lengthwise directional marginal portion. The incidence of
delamination or cracks in the multilayer ceramic capacitor can be
lowered and dielectric breakdown voltage characteristics can be
improved by adjusting the ratio of the thickness between the
capacity formation portion and the marginal portion.
[0082] The ratio (D3/D1) of the thickness of the end face of the
lamination main body to that of the central portion of the
lamination main body may be 0.75 to 0.97.
[0083] If the ratio (D3/D1) of the thickness of the end face of the
lamination main body to that of the central portion of the
lamination main body is less than 0.75, an electric field would
possibly be concentrated in the ends of the inner electrodes in the
lengthwise direction to degrade the dielectric breakdown voltage
characteristics as well as high temperature and moisture resistance
characteristics, although the possibility of the generation of
delamination and cracking in the marginal portion is low.
[0084] Also, if the ratio (D3/D1) of the thickness of the end face
of the lamination main body to that of the central portion of the
lamination main body exceeds 0.97, there would be high possibility
that the marginal portion would be delaminated or cracked and
hightemperature and moisture resistance characteristics would
possibly be degraded.
[0085] A method of manufacturing a multilayer ceramic capacitor
(MLCC) according to an embodiment of the present invention will now
be described.
[0086] First, inner electrode patterns may be formed on a plurality
of ceramic green sheets. The ceramic green sheets may be formed of
ceramic paste including ceramic powder, an organic solvent, and an
organic binder.
[0087] The ceramic power having a high permeability, may include a
barium titanate (BaTiO.sub.3)-based material, strontium titanate
(SrTiO.sub.3)-based material, or the like, but the present
invention is not limited thereto. When the ceramic green sheets are
fired, dielectric layers constituting the lamination main body can
be obtained.
[0088] The inner electrode patterns may be formed of an inner
electrode paste including conductive metal. The conductive metal
may be nickel (Ni), copper (Cu), palladium (Pd), or an alloy
thereof, but the present invention is not limited thereto.
[0089] A method of forming the inner electrode patterns on the
ceramic green sheets is not particularly limited. For example, the
inner electrode patterns may be formed by a printing method such as
a screen printing method, a gravure printing method, or the
like.
[0090] A ceramic green sheet lamination may be formed by laminating
the ceramic green sheets such that the inner electrode patterns
formed on the individual ceramic green sheets are exposed from
different end faces by a follow-up cutting process. A thickness
ratio of the lamination main body can be adjusted by compressing
the ceramic green sheet lamination. As described above, according
to an embodiment of the present invention, the marginal portion may
be intensively compressed as compared with the capacity formation
portion. Also, the end faces and edge portions of the lamination
main body may be intensively compressed as compared with the
central portion of the lamination main body.
[0091] The compression may be performed with a certain pressure.
The compression may be performed by isostatic pressing, but the
present invention is not limited thereto. The compression may be
performed under pressure conditions of 500 kgf/cm.sup.2 to 1,500
kgf/cm.sup.2, but the present invention is not limited thereto. In
order to differentially compress the capacity formation portion and
the electrode draw-out portion of the lamination main body during
the isostatic pressing, a subsidiary material may be applied to
upper and lower surfaces of the ceramic green sheet lamination. A
polyethyleneterephtalate (PET) film, a vinyl film, rubber, or the
like, may be used as the subsidiary material, but the present
invention is not limited thereto.
[0092] Also, the compression may be performed at a certain
temperature. The compression may be performed at 50.quadrature. to
100.quadrature., but the present invention is not limited
thereto.
[0093] The ceramic green sheet lamination may be cut to expose the
ends of the inner electrodes in the lengthwise direction from the
end faces thereof, thereby forming a ceramic green chip. The
ceramic green chip may be plasticized and fired to form a
lamination main body.
[0094] The plasticization process may be performed for
de-binderizing, and it may be performed under an air atmosphere,
but the present invention is not limited thereto.
[0095] The firing process may be performed under a reduction
atmosphere such that the inner electrodes may not be oxidized.
[0096] The firing process may be performed at a temperature ranging
from 900.quadrature. to 1,300.quadrature..
[0097] Then, outer electrodes may be formed to be electrically
connected with the ends of the inner electrodes exposed from the
end faces of the lamination main body. Thereafter, the surface of
the external electrodes may be plated with nickel, tin, or the
like.
[0098] The present invention will be described in more detail with
reference to examples and comparative examples, but this is to help
understand the present invention properly and the scope of the
invention is not limited by these examples.
Example
[0099] Ceramic green sheets, having a thickness of 0.90 .mu.m, 1.00
.mu.m, and 1.25 .mu.m, respectively, were prepared. Inner electrode
paste was printed on each of the ceramic green sheets, and two
hundred ceramic green sheets were laminated to manufacture a
ceramic lamination. The ceramic lamination was subjected to
isostatic pressing under pressure conditions of 500 kgf/cm2, 800
kgf/cm2 and 1000 kgf/cm2, at 85.quadrature., respectively. In this
case, the ceramic lamination was compressed such that the central
portion of the lamination main body was larger than edge portions
of the lamination main body in the widthwise direction.
[0100] The compression-completed ceramic lamination was cut in the
form of individual chips. The separated individual chips were
maintained under an air atmosphere at 230 L for 60 hours to perform
de-binderizing. Thereafter, the individual chips were fired at
1,200 L under an oxygen partial pressure of 10.sup.-11 atm
.about.10.sup.-10 atm, lower than a Ni/NiO equilibrium oxygen
partial pressure, in a reduction atmosphere such that the inner
electrodes were not oxidized. After the firing operation, an
average thickness of the inner electrode layers was 0.65 .mu.m. The
size of the fired chips satisfied 0.6.+-.0.09
mm.times.0.3.+-.0.09=.times.0.3.+-.0.09=(L.times.W.times.T). Here,
T is the thickness of the central portion of the lamination main
body.
[0101] The characteristics of the fired chips were evaluated and
Table 1 below shows the corresponding results.
[0102] Sections of hundreds of fired chips were inspected, and the
incidence of delamination and cracking of the fired chips was
expressed by percentage.
[0103] Dielectric breakdown voltage (BDV) characteristics were
evaluated by applying a DC voltage at a rate of 10 V/sec, and an
average life span of the fired chips was determined as a duration
of time until insulation resistance was dropped to below
10.sup.4.OMEGA..
TABLE-US-00001 TABLE 1 Thickness of Lamination Delamination/
Average ceramic Pressure T1 T2 crack incidence life Span green
sheet (kgf/cm.sup.2) (.mu.m) (.mu.m) T2/T1 (%) BDV(V) (hr)
Comparative 1.25 500 0.69 0.65 0.94 0 83 115 example 1 Comparative
1.25 800 0.69 0.60 0.87 0 80 108 example 2 Comparative 1.25 1000
0.67 0.55 0.82 0 81 109 example 3 Comparative 1.25 1200 0.66 0.51
0.77 0 78 110 example 4 Comparative 1.00 500 0.55 0.53 0.96 17 73
35 example 5 Example 1 1.00 800 0.53 0.48 0.91 0 71 95 Example 2
1.00 1000 0.51 0.42 0.82 0 69 93 Comparative 1.00 1200 0.49 0.36
0.73 0 30 28 example 6 Comparative 0.90 500 0.50 0.49 0.98 22 68 27
example 7 Example 3 0.90 800 0.49 0.46 0.94 0 65 90 Example 4 0.90
1000 0.47 0.40 0.85 0 63 91 Comparative 0.90 1200 0.45 0.34 0.76 0
28 19 example 8
[0104] Here, T1 is the distance between the central portions of
vertically adjacent inner electrodes, and T2 is the distance
between the non-exposed edges of the vertically adjacent inner
electrodes. In this embodiment, a measurement was made in the
widthwise directional section obtained by cutting the central
portion of the lamination main body, as shown in FIG. 3.
[0105] In detail, an image of the widthwise directional section
obtained by cutting the central portion of the lamination main body
of each sample was scanned by a scanning electron microscope (SEM)
of 10,000 magnifications. Ten pairs of adjacent inner electrodes
were randomly extracted from the scanned images, the distance T1
between the central portions of the vertically adjacent inner
electrodes and the distance T2 between the edges of the vertically
adjacent inner electrodes in the widthwise direction were measured,
and average measurement values are shown in Table 1.
[0106] With reference to Table 1, in comparative examples 1 through
4 in which the thickness of the dielectric layers after firing was
0.60 .mu.m or greater, no delamination or cracking was generated,
irrespective of the ratio of T1 and T2 and a high DVB and an
excellent accelerated life span were achieved.
[0107] However, in comparative examples 5 and 7, the compression
rate of the marginal portion was low, and the ratio of T2 to T1 was
high. Thus, a delamination/cracking incidence was high and an
average life span was degraded. Also, in comparative examples 6 and
8, the comparison ratio of the marginal portion was high, and
delamination/cracking was not generated because the ratio of T2 to
T1 was low, but the BDV characteristics were degraded due to
excessive compression, and an average life span was degraded.
[0108] This is because the edges of the inner electrodes in the
widthwise direction were overly bent, shortening the distance
between the edges of the inner electrodes in the widthwise
direction, so an electric field was concentrated therein.
[0109] In examples 1 through 4, no delamination/cracking was
generated and the BDV characteristics and an average life span were
excellent.
[0110] As set forth above, according to the embodiments of the
present invention, the capacity formation portion and the widthwise
directional marginal portion are differentially compressed to
reduce a difference in density. The incidence of delamination or
cracking in the multilayer ceramic capacitor is lowered by
adjusting the thickness ratio between the capacity formation
portion and the marginal portion, and the dielectric breakdown
voltage characteristics can be improved.
[0111] According to the embodiments of the present invention, the
distance between vertically adjacent inner electrodes at the
central portion of the lamination main body is longer than the
distance between vertically adjacent inner electrodes at the edges
of the inner electrodes in the widthwise direction. The distance
between the vertically adjacent inner electrodes at the edges of
the inner electrodes in the widthwise direction can be adjusted to
prevent an electric field from being concentrated in the edges of
the inner electrodes. Accordingly, the possibility of the
generation of delamination or cracking in the marginal portion can
be reduced, and high temperature and moisture resistance
characteristics and an average life span can be improved.
[0112] According to the embodiments of the present invention, the
ratio between the thickness of the central portion of the
lamination main body and that of the end face of the lamination
main body can be adjusted to prevent an electric field from being
concentrated in the ends of the inner electrodes in the lengthwise
direction, whereby the possibility of the generation of
delamination or cracking can be lowered, and the dielectric
breakdown voltage characteristics can be enhanced.
[0113] According to the embodiments of the present invention,
although the dielectric layers and the inner electrode layers are
thinned, the concentration of an electric field in a particular
area can be prevented by adjusting the compression ratio between
the capacity formation portion and the marginal portion. Thus, the
possibility of the generation of delamination or cracking can be
lowered, and the dielectric breakdown voltage characteristics and
high temperature and moisture resistance characteristics can be
improved.
[0114] While the present invention has been shown and described in
connection with the embodiments, it will be apparent to those
skilled in the art that modifications and variations can be made
without departing from the spirit and scope of the invention as
defined by the appended claims.
* * * * *