U.S. patent application number 14/813234 was filed with the patent office on 2015-11-19 for laminated ceramic electronic component and method for producing laminated ceramic electronic component.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Koichi BANNO, Seiichi JONO, Taisuke KANZAKI, Masanori NAKAMURA, Masahiro OTSUKA, Akihiro SHIOTA, Shoichiro SUZUKI.
Application Number | 20150332854 14/813234 |
Document ID | / |
Family ID | 43242990 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150332854 |
Kind Code |
A1 |
SUZUKI; Shoichiro ; et
al. |
November 19, 2015 |
LAMINATED CERAMIC ELECTRONIC COMPONENT AND METHOD FOR PRODUCING
LAMINATED CERAMIC ELECTRONIC COMPONENT
Abstract
A laminated ceramic electronic component has a variety of
superior mechanical properties and electrical properties, including
a high degree of freedom in the design for ceramic materials, and
can be manufactured at low cost and with a low percentage of
defective products. The laminated ceramic electronic component
includes a laminate including a plurality of stacked ceramic layers
and a plurality of internal electrodes containing Al as a main
constituent, the internal electrodes being arranged along specific
interfaces between the ceramic layers, and external electrodes
located on an outer surface of the laminate, wherein surface layer
sections of the internal electrodes include an Al.sub.2O.sub.3
layer.
Inventors: |
SUZUKI; Shoichiro;
(Yasu-shi, JP) ; BANNO; Koichi; (Yasu-shi, JP)
; OTSUKA; Masahiro; (Yasu-shi, JP) ; NAKAMURA;
Masanori; (Izumo-shi, JP) ; JONO; Seiichi;
(Echizen-shi, JP) ; KANZAKI; Taisuke;
(Omihachiman-shi, JP) ; SHIOTA; Akihiro;
(Yasu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Nagaokakyo-shi |
|
JP |
|
|
Family ID: |
43242990 |
Appl. No.: |
14/813234 |
Filed: |
July 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12888442 |
Sep 23, 2010 |
9129745 |
|
|
14813234 |
|
|
|
|
Current U.S.
Class: |
156/89.11 |
Current CPC
Class: |
H01C 7/008 20130101;
H01G 4/30 20130101; H01G 4/12 20130101; H01G 4/0085 20130101; H01L
41/0471 20130101; H01L 41/0477 20130101; H01C 7/18 20130101; H01G
4/1209 20130101; H01G 4/224 20130101 |
International
Class: |
H01G 4/30 20060101
H01G004/30; H01G 4/224 20060101 H01G004/224; H01G 4/12 20060101
H01G004/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2009 |
JP |
2009-226823 |
Jun 29, 2010 |
JP |
2010-147792 |
Claims
1. A method for producing a laminated ceramic electronic component,
the method comprising the steps of: preparing a raw laminate
including a plurality of stacked ceramic green sheets and a
plurality of metal constituent containing layers containing Al as a
main constituent, the layers being formed along specific interfaces
between the ceramic green sheets; and firing the raw laminate at a
temperature of about 600.degree. C. to about 1000.degree. C. under
an atmosphere with an oxygen partial pressure of about
1.times.10.sup.-4 MPa or more.
2. The method for producing a laminated ceramic electronic
component according to claim 1, wherein an average rate of
temperature increase from room temperature up to a firing top
temperature is about 100.degree. C./min or more in the firing step.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a laminated ceramic
electronic component typified by a laminated ceramic capacitor, for
example, and more particularly, relates to a laminated ceramic
electronic component including an internal electrode containing Al
as its main constituent.
[0003] 2. Description of the Related Art
[0004] With reference to FIG. 1, a laminated ceramic capacitor will
be described first which is a typical example of a laminated
ceramic electronic component.
[0005] The laminated ceramic capacitor 1 includes a laminate 2
composed of a plurality of stacked dielectric ceramic layers 3 and
a plurality of internal electrodes 4 and 5 formed along specific
interfaces between the dielectric ceramic layers 3.
[0006] First and second external electrodes 8 and 9 are formed in
different positions from each other on the outer surface of the
laminate 2. The laminated ceramic capacitor 1 shown in FIG. 1 has
the first and second external electrodes 8 and 9 formed on
respective end surfaces 6 and 7 of the laminate 2 opposed to each
other, respectively. The internal electrodes 4 and 5 include a
plurality of first internal electrodes 4 electrically connected to
the first external electrode 8 and a plurality of second internal
electrodes 5 electrically connected to the second external
electrode 9, and these first and second internal electrodes 4 and 5
are alternately arranged with respect to the staking direction.
[0007] Since reduction in size is required, in particular, for
laminated ceramic capacitors, an approach in which green sheets of
a dielectric ceramic and internal electrode layers are stacked and
then fired simultaneously is employed in the production process. In
recent years, for the purpose of cost reduction, a base metal such
as Ni has been used for internal electrodes of laminated ceramic
capacitors.
[0008] However, since Ni is very likely to be oxidized in a
co-firing process with the ceramic, it has been necessary to bring
the atmosphere for firing into a reducing atmosphere and precisely
control the temperature condition and the oxygen partial pressure.
As a result, the material design is limited significantly. In
addition, problems such as delamination and cracks have occurred
and are caused by non-uniform stress associated with the
co-firing.
[0009] Therefore, in order to increase the degree of freedom in the
design of laminated ceramic electronic components, it is preferable
to study internal electrodes made from a variety of metal
materials.
[0010] For example, DE 19719174 A1 discloses a laminated ceramic
body employing Al as an internal electrode material instead of Ni.
However, since the melting point of Al is about 660.degree. C., the
ceramic has to be able to be sintered at about 660.degree. C. in
terms of the conventional rule of common sense. Thus, the laminated
ceramic body has a problem in that the degree of freedom in the
design of ceramic materials is limited significantly.
[0011] However, the laminated ceramic electronic component
disclosed in DE 19719174 A1 has a problem in that the Al internal
electrode is made into a spherical shape, resulting in an inability
to secure sufficient conductivity, because the firing temperature
is 1200.degree. C. which is much higher than the melting point of
Al at 660.degree. C.
[0012] Furthermore, the laminated ceramic electronic component
disclosed in DE 19719174 A1 has a problem in that the Al to define
the internal electrodes is changed to an aluminum nitride (AIN),
resulting in the inability to secure sufficient conductivity,
because the firing atmosphere is a nitrogen atmosphere with an
oxygen partial pressure of 10.sup.-5 atm.
SUMMARY OF THE INVENTION
[0013] Therefore, preferred embodiments of the present invention
provide a laminated ceramic electronic component which includes a
superior Al internal electrode in terms of smoothness and
conductivity and has superior mechanical properties and electrical
properties.
[0014] According to a preferred embodiment of the present
invention, a laminated ceramic electronic component includes a
laminate including a plurality of stacked ceramic layers and a
plurality of internal electrodes containing Al as their main
constituent, the internal electrodes being arranged along specific
interfaces between the ceramic layers, and external electrodes
disposed on an outer surface of the laminate, wherein surface layer
sections of the internal electrodes include an Al.sub.2O.sub.3
layer. The thickness of the Al.sub.2O.sub.3 layer is preferably
about 0.25% to about 10%, and more preferably about 0.5% to about
10% of the thickness of one of the internal electrodes, for
example.
[0015] According to another preferred embodiment of the present
invention, a method for producing a laminated ceramic electronic
component including an internal electrode containing Al as its main
constituent, includes the steps of preparing a raw laminate
including a plurality of stacked ceramic green sheets and a
plurality of metal constituent containing layers containing Al as
their main constituent, the layers being formed along specific
interfaces between the ceramic green sheets, and firing the raw
laminate at a temperature of about 600.degree. C. to about
1000.degree. C. under an atmosphere with an oxygen partial pressure
of about 1.times.10.sup.-4 MPa or more.
[0016] According to various preferred embodiments of the present
invention, laminated ceramic electronic components can be provided
which have superior mechanical properties and electrical properties
since the Al internal electrodes are superior in terms of
smoothness and conductivity.
[0017] In addition, according to various preferred embodiments of
the present invention, laminated ceramic electronic components can
be provided which have a high degree of dimensional accuracy, since
the Al.sub.2O.sub.3 layer constituting the surface layer of the Al
internal electrode adheres tightly to the ceramic layer which may
have a variety of compositions, thereby preventing shrinkage in the
planar direction during a firing process.
[0018] In addition, according to various preferred embodiments of
the present invention, laminated ceramic electronic components can
be provided which have a variety of properties at low cost and at a
low percentage defective, since the firing process is possible at a
higher temperature than the melting point of Al in an atmosphere
indicating an oxygen partial pressure close to that in the air,
thereby increasing the degree of freedom in the design of ceramic
materials.
[0019] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a view illustrating a laminated ceramic capacitor
as an example of a laminated ceramic electronic component according
to a preferred embodiment of the present invention.
[0021] FIG. 2 is an enlarged photograph in the vicinity of an Al
internal electrode of a laminate according to Example 3 of a
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A laminated ceramic electronic component according to a
preferred embodiment of the present invention includes internal
electrodes containing Al as their main constituent. Although the
internal electrodes may be an Al element or an Al alloy, the
content rate of Al is preferably about 70 mol %, and more
preferably about 90 mol % or more in the case of an Al alloy, for
example.
[0023] The surface layer sections of the internal electrodes, that
is, the sections in contact with the ceramic layers include a layer
containing Al.sub.2O.sub.3 as its main constituent. This mainly
arises from the oxidized surfaces of the Al internal electrodes.
This Al.sub.2O.sub.3 layer prevents the electrodes from being
broken due to the Al internal electrodes being made into a
spherical shape, and keeps the conductivity of the Al internal
electrodes favorable. In addition, this Al.sub.2O.sub.3 layer acts
to smooth the Al internal electrode layers, thereby preventing
delamination between the ceramic layer and the Al internal
electrode and also preventing the laminate from cracking. In order
to bring about this effect, the thickness of the Al.sub.2O.sub.3
layer is preferably about 0.25% or more of the thickness of the
internal electrode, for example. Furthermore, when the thickness of
the Al.sub.2O.sub.3 layer is about 0.5% or more, the effect
described is achieved more reliably.
[0024] In addition, when the thickness of the Al.sub.2O.sub.3 layer
is greater than about 10% of the thickness of the internal
electrode, more than about 20% of the total thickness of the
internal electrode layers will be composed of Al.sub.2O.sub.3,
resulting in concerns about decrease in conductivity. Therefore,
the thickness of the Al.sub.2O.sub.3 layer is preferably about 10%
or less of the thickness of the internal electrode, for
example.
[0025] Next, a method for producing a laminated ceramic electronic
component according to a preferred embodiment the present invention
will be described with a laminated ceramic capacitor as an
example.
[0026] First, a ceramic raw material is prepared. This ceramic raw
material is mixed with an organic binder component in a solvent, if
necessary, to obtain a ceramic slurry. This ceramic slurry is
subjected to sheet forming to obtain ceramic green sheets.
[0027] Next, an internal electrode containing Al as its main
component is formed onto the ceramic green sheets. While there are
several methods for the formation of the internal electrode, a
simple method in which an Al paste including an Al powder and an
organic vehicle is applied by screen printing into a desirable
pattern may preferably be used. In addition, also available are a
method of transferring Al metal foil and a method of forming an Al
film while carrying out masking in accordance with a vacuum
thin-film formation method.
[0028] In this way, a raw laminate which has not been fired yet is
obtained by stacking multiple layers of ceramic green sheets and Al
internal electrode layers, followed by pressure bonding.
[0029] This raw laminate is fired in a firing furnace at a
predetermined temperature in a predetermined atmosphere. For
example, in the case of an oxygen partial pressure of about
1.times.10.sup.-4 MPa or more and a firing temperature of about
600.degree. C. or more for firing, the surfaces of the Al internal
electrodes are progressively oxidized to form an Al.sub.2O.sub.3
layer with a moderate thickness. Preferably, the firing temperature
set to the melting point of Al or more, for example, about
670.degree. C. or more forms an Al.sub.2O.sub.3 layer with a
moderate thickness in a more reliable and stable manner.
[0030] In addition, for example, when the firing temperature is set
to about 1000.degree. C. or less, the Al internal electrodes are
prevented effectively from being made into a spherical shape. The
oxygen partial pressure is most preferably an atmospheric pressure
in view of simplicity of the process.
[0031] In addition, when the rate of temperature increase from room
temperature to the TOP temperature is set to about 100.degree.
C./min or more in the firing step, the Al.sub.2O.sub.3 layer is
more likely to be formed at the surface layers of the Al internal
electrodes with more certainty, even when various changes are made
to the composition of the ceramic material and the design of the
laminated structure. This is believed to be because the formation
of the Al.sub.2O.sub.3 layer at the surface layers and firing of
the ceramic are caused before the fluidity of Al arising from
melted Al is increased.
[0032] It is to be noted that while the melting point of Al is
about 660.degree. C., the production method according to a
preferred embodiment of the present invention allows co-firing
along with the ceramic even at temperatures much higher than about
660.degree. C. This is believed to be because of the
Al.sub.2O.sub.3 layers formed at the surface layer sections of the
Al internal electrodes. Therefore, a high degree of freedom is
offered in the design for the material composition of the ceramic
used, thereby allowing for application to a variety of
applications.
[0033] It is to be noted that the ceramic composition is not
particularly limited in the laminated ceramic electronic component
according to a preferred embodiment of the present invention. A
variety of materials can be applied within the scope of the present
invention so as not to interfere with the advantages achieved by
preferred embodiments of the present invention, such as barium
titanate series (including barium titanates substituted with Ca,
Sr, Zr, or the like), lead titanate series or lead zirconate
titanate series, alumina-based glass ceramic, ferrite, transition
element oxide-based semiconductor ceramics.
[0034] In addition, the laminated ceramic electronic component
according to a preferred embodiment of the present invention can be
applied to not only laminated ceramic capacitors, but also a
variety of electronic components such as laminated piezoelectric
elements, laminated thermistor elements, laminated chip coils, and
ceramic multi-layer substrates.
EXAMPLES
Example 1
[0035] The present example is intended to examine the dependence on
the presence or absence and thickness of an Al.sub.2O.sub.3 layer
in laminated ceramic electronic components which have six different
types of ceramic compositions and Al internal electrodes.
[0036] First, a BaTiO.sub.3 powder was prepared as a main
constituent of a ceramic, and Bi.sub.2O.sub.3, CuO, B.sub.2O.sub.3,
BaO, and SiO.sub.2 powders were prepared as accessory constituents.
These powders were mixed so as to satisfy the six types of content
rates shown in Table 1, thereby providing six types of ceramic raw
materials.
TABLE-US-00001 TABLE 1 BaTiO.sub.3 Bi.sub.2O.sub.3 CuO
B.sub.2O.sub.3 BaO SiO.sub.2 Composition (mol %) (mol %) (mol %)
(mol %) (mol %) (mol %) 1-1 90 9 1 0 0 0 1-2 90 7 3 0 0 0 1-3 90 8
0 0 2 0 1-4 90 8 0 2 0 0 1-5 50 25 0 0 0 25 1-6 50 35 0 0 0 15
[0037] An ethanol-based organic solvent and a polyvinyl butyral
based binder were added to each of these ceramic raw materials,
followed by wet mixing in a ball mill, to obtain ceramic slurries.
The ceramic slurries were subjected to sheet forming to obtain
ceramic green sheets.
[0038] Next, an Al paste including an Al powder and an organic
vehicle was applied by screen printing onto the ceramic green
sheets to form Al paste layers. The ceramic green sheets with the
Al paste applied were stacked so that the sides to which the Al
paste layers were drawn were alternated, followed by pressure
bonding, thereby providing raw laminates.
[0039] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired in the air at the firing temperatures
shown in Table 2 for approximately 1 minute. An Ag paste containing
low melting point glass frit was applied onto the both end surfaces
of the obtained laminates, and fired at about 600.degree. C. in the
air to obtain external electrodes connected to internal
electrodes.
[0040] The laminated ceramic capacitors thus obtained were
approximately 2.0 mm in length, 1.0 mm in width, and 0.5 mm in
thickness, and 50 .mu.m in thickness for each ceramic layer and 5
.mu.m in thickness for each internal electrode layer, and the
number of effective layers was 5, for example.
[0041] For the obtained samples, the capacitance and dielectric
loss (tan .delta.) were measured with an automatic bridge-type
measurement device. The results are shown in Table 2.
[0042] In addition, cross sections subjected to FIB processing were
analyzed with .mu.-SAM, to identify Al.sub.2O.sub.3 in the cross
sections of the internal electrodes. The thickness of the
Al.sub.2O.sub.3 layer was measured at 10 arbitrary points to
calculate the ratio of the average value for the 10 points to 5
.mu.m. The results are shown in Table 2.
TABLE-US-00002 TABLE 2 Oxygen Al.sub.2O.sub.3 Firing Partial Layer
Temperature Pressure Capacitance Tan .delta. Thickness Composition
(.degree. C.) (MPa) (pF) (%) (%) 1-1 700 2 .times. 10.sup.-2 1557
6.8 2.0 800 2 .times. 10.sup.-2 1053 5.2 4.0 900 1 .times.
10.sup.-5 -- -- -- 900 1 .times. 10.sup.-4 1608 5.2 2.0 900 1
.times. 10.sup.-3 908 4.8 5.0 900 2 .times. 10.sup.-2 711 3.2 7.0
900 1 .times. 10.sup.-1 538 3.2 10 1000 2 .times. 10.sup.-2 549 2.3
10 1100 2 .times. 10.sup.-2 -- -- 11 1-2 700 2 .times. 10.sup.-2
1489 6.5 2.0 800 2 .times. 10.sup.-2 1022 5.6 4.0 900 2 .times.
10.sup.-2 706 4.3 7.0 1-3 800 2 .times. 10.sup.-2 1089 5.6 4.0 900
2 .times. 10.sup.-2 739 4.1 7.0 1000 2 .times. 10.sup.-2 543 2.9 10
1100 2 .times. 10.sup.-2 -- -- 11 1-4 800 2 .times. 10.sup.-2 1091
4.9 4.0 900 2 .times. 10.sup.-2 703 3.8 7.0 1000 2 .times.
10.sup.-2 501 2.8 10 1100 2 .times. 10.sup.-2 -- -- 11 1-5 500 2
.times. 10.sup.-2 -- -- 0.2 600 2 .times. 10.sup.-2 703 0.8 0.25
670 2 .times. 10.sup.-2 682 0.6 0.5 700 2 .times. 10.sup.-2 606 0.2
2.0 800 2 .times. 10.sup.-2 523 0.2 4.0 1-6 500 2 .times. 10.sup.-2
-- -- 0.2 600 2 .times. 10.sup.-2 712 0.8 0.25 680 2 .times.
10.sup.-2 666 0.5 0.8 700 2 .times. 10.sup.-2 608 0.2 2.0 800 2
.times. 10.sup.-2 504 0.2 4.0
[0043] The results in Table 2 show that among the laminates using
the six types of ceramic compositions 1-1 to 1-6, the samples with
the Al.sub.2O.sub.3 layer accounting for about 0.25% to about 10%
in terms of thickness formed at the surface layer sections of the
Al internal electrodes had no electrodes made into a spherical
shape, thereby providing superior laminates in terms of
conductivity and smoothness, and thus providing desired
capacitances.
[0044] On the other hand, when the oxygen partial pressure was too
low, about 1.times.10.sup.-5 MPa, the Al of the internal electrodes
was nitrided, thereby increasing the resistance value, and then
resulting in the inability to obtain required conductivity.
[0045] In addition, the samples with the Al.sub.2O.sub.3 layer
accounting for a ratio less than about 0.25% in terms of thickness
because of the low firing temperature of about 500.degree. C. were
inferior in terms of the smoothness of the Al internal electrodes,
and insufficiently served as internal electrodes.
[0046] Furthermore, the samples with the Al.sub.2O.sub.3 layer
accounting for a ratio greater than about 10% in terms of thickness
because of the too high firing temperature of about 1100.degree. C.
provided insufficient conductivity due to increase in resistance
value.
Example 2
[0047] The present example is intended to examine the influence in
the case of changing internal electrodes from Ni to Al in a certain
dielectric ceramic material.
[0048] First, a ceramic raw material represented by the composition
formula
100(Ba.sub.0.95Ca.sub.0.05).sub.1.01TiO.sub.3+0.2Dy.sub.2O.sub.3+-
0.1MnO+0.6MgO+2.0SiO.sub.2+0.5Li.sub.2O was prepared.
[0049] This ceramic raw material was used to obtain ceramic green
sheets in the same way as in Example 1. In parallel, an Al paste
including an Al metal powder and an organic vehicle and a Ni paste
including a Ni metal powder and an organic vehicle were
prepared.
[0050] Next, the Al paste was applied by screen printing onto the
ceramic green sheets to form Al paste layers. The ceramic green
sheets with the Al paste applied were stacked so that the sides to
which the Al paste layers were drawn were alternated, followed by
pressure bonding, thereby providing a raw laminate. In the same
way, a raw laminate was obtained in the case of using the Ni
paste.
[0051] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired at about 1000.degree. C., for example. In
this way, samples of the laminates were obtained.
[0052] The thus obtained laminates were about 2.0 mm in length,
about 1.0 mm in width, and about 0.5 mm in thickness, and the
number of effective layers was 5, for example. An Al.sub.2O.sub.3
layer was formed at surface layer sections of the Al internal
electrodes.
[0053] Then, the area of the internal electrode per layer of the
laminate was measured to obtain the ratio to the area of the
internal electrode in the raw laminate before the firing, that is,
the area shrinkage ratio in the planar direction of the internal
electrode. Table 3 shows the results.
[0054] Furthermore, the thickness of the ceramic layer was measured
to obtain the ratio to the thickness of the ceramic layer in the
raw laminate before the firing, that is, the shrinkage ratio in the
thickness direction of the ceramic layer. Table 3 shows the
results.
TABLE-US-00003 TABLE 3 Area Shrinkage Ratio in Shrinkage Area of
Area of Planar Ratio in Main Internal Internal Direction of
Thickness of Thickness of Thickness Constituent Electrode Electrode
Internal Ceramic Ceramic Layer Direction Sample of Internal before
after Electrode Layer before after Firing of Ceramic Number
Electrode Firing (mm.sup.2) Firing (mm.sup.2) (%) Firing (.mu.m)
(.mu.m) Layer (%) 2-1 Al 2.47 2.02 82 18 10 56 2-2 Ni 2.89 1.74 60
18 13 74
[0055] When the laminate with the Al internal electrodes is
compared with the laminate with the Ni internal electrodes, it has
been determined that the Al internal electrodes are less likely to
be shrunk than the Ni internal electrodes. On the other hand, the
shrinkage ratio in the thickness direction of the ceramic layer is
higher in the case of the laminate with the Al internal electrodes.
This is believed to be because the Al internal electrodes
constrained shrinkage in the planar direction of the ceramic layer
during the firing process.
[0056] According to the results described above, the use of Al for
the internal electrodes allows laminates including thin ceramic
layers suitable for high capacitance products to be obtained even
when the ceramic green sheets are made relatively thick. Therefore,
defects such as pinholes can be expected to be reduced.
Accordingly, the laminate with the Al internal electrodes is useful
as laminated ceramic capacitors which have to made thinner and
thinner.
Example 3
[0057] The present example is intended to evaluate laminates
including Al internal electrodes with a variety of compositions as
ceramic compositions for firing at low temperatures.
[0058] First, respective starting raw materials were mixed so as to
satisfy the compositions shown in Table 4, thereby providing
ceramic raw materials of six types of compositions, raw materials
3-1 to 3-6.
TABLE-US-00004 TABLE 4 Raw Bi.sub.2O.sub.3 SiO.sub.2 CaZrO.sub.3
B.sub.2O.sub.3 PbO Al.sub.2O.sub.3 TeO.sub.2 Mater- (mol (mol (mol
(mol (mol (mol (mol ial %) %) %) %) %) %) %) 3-1 65 35 3-2 75 25
3-3 30 70 3-4 10 90 3-5 2 98 3-6 1.5 97 1.5
[0059] The ceramic raw materials were used to obtain ceramic green
sheets in the same way as in Example 1. In parallel, an Al paste
including an Al metal powder and an organic vehicle, a Ni paste
including a Ni metal powder and an organic vehicle, and a Cu paste
including a Cu metal powder and an organic vehicle were
prepared.
[0060] Next, the Al paste was applied by screen printing onto the
ceramic green sheets from the raw material 3-1 to 3-4 to form Al
paste layers. The ceramic green sheets with the Al paste applied
were stacked so that the sides to which the Al paste layers were
drawn were alternated, followed by pressure bonding, thereby
providing a raw laminate. In the same way, raw laminates were also
obtained in the case of using the Ni paste for the ceramic green
sheets from the raw material 3-5 and in the case of using the Cu
paste for the ceramic green sheets from the raw material 3-6. As
for the number of stacked layers, three types of 5 layers, 30
layers, and 100 layers were prepared respectively as shown in Table
5.
[0061] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired at the temperature shown in Table 5 for 1
minute. An Ag paste containing low melting point glass frit was
applied onto the both end surfaces of the obtained laminates, and
fired at about 600.degree. C. in the air to obtain external
electrodes connected to internal electrodes. In this way, samples
were obtained.
[0062] The thus obtained laminates were about 2.0 mm in length,
about 1.0 mm in width, and about 0.5 mm in thickness. The effective
area per layer was about 1.7.times.10.sup.-6 m.sup.2. The thickness
per ceramic layer was about 5 .mu.m. An Al.sub.2O.sub.3 layer was
formed at surface layer sections of the Al internal electrodes of
the laminates 3-1 to 3-4 using the Al paste. FIG. 2 shows a
magnified photograph in the vicinity of the Al internal electrode
of the sample 3-1.
[0063] For the six types of samples obtained, the dielectric
constant was measured with an automatic bridge-type measurement
device. In addition, the insulation resistivity log .rho.
(.OMEGA.m) in the case of applying a voltage of 5 kV/mm for 1
minute was measured. The results are shown in Table 5.
[0064] Furthermore, the six types of samples, 30 pieces for each
sample, were subjected to an ultrasonic inspection to confirm the
presence or absence of cracks. The results are shown in Table
5.
TABLE-US-00005 TABLE 5 The The Firing Number number Raw Internal
Temperature of Staked of crack Log .rho. Material Electrode
(.degree. C.) Layers defects .epsilon. (.OMEGA. m) 3-1 Al 600 5 0
33 11.8 30 0 33 11.8 100 0 33 11.8 3-2 Al 600 5 0 37 11.4 30 0 37
11.4 100 0 37 11.4 3-3 Al 600 5 0 30 11.9 30 0 30 11.9 100 0 30
11.9 3-4 Al 600 5 0 45 11.4 30 0 45 11.4 100 0 45 11.4 3-5 Ni 600 5
0 27 12.6 30 5 27 12.6 100 12 27 12.6 3-6 Cu 600 5 0 27 12.6 30 5
27 12.6 100 10 27 12.6
[0065] It has been determined from the results in Table 5 that when
the number of stacked layers is 30 or more, the use of the Al
internal electrodes significantly suppresses cracks. This is
believed to be because it is possible to form the smooth internal
electrodes of Al with its elastic modulus lower than Ni and Cu.
[0066] Therefore, the laminates including the Al internal
electrodes have a high degree of freedom in the design such as the
pattern design or laminated structure for the internal electrodes,
and are thus quite useful for laminated ceramic electronic
components.
Example 4
[0067] The present example provides an example of a multilayer
substrate including a glass ceramic and an Al internal electrode,
and is intended to be compared with Ag internal electrodes.
[0068] First, a glass powder with the composition of
43SiO.sub.2-44.9CaO-5.7B.sub.2O.sub.3-6.4Al.sub.2O.sub.3
(coefficient: wt %) and an Al.sub.2O.sub.3 powder were prepared.
The glass powder and the Al.sub.2O.sub.3 powder were weighed to
provide a weight ratio of 48:52, and mixed to obtain a ceramic raw
material powder.
[0069] This ceramic raw material was used to obtain ceramic green
sheets in the same way as in Example 1. In parallel, an Al paste
including an Al metal powder and an organic vehicle and an Ag paste
including an Ag metal powder and an organic vehicle were
prepared.
[0070] Next, the Al paste was applied by screen printing onto the
ceramic green sheets to form Al paste layers. The ceramic green
sheets with the Al paste applied were stacked so that the sides to
which the Al paste layers were drawn were alternated, followed by
pressure bonding, thereby providing a raw laminate. In the same
way, a raw laminate was obtained in the case of using the Ag paste.
In this case, the effective area per layer was about
1.7.times.10.sup.-6 m.sup.2, and the number of effective layers was
5, for example.
[0071] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired at the temperature shown in Table 6 for 1
minute. An Ag paste containing low melting point glass frit was
applied onto the both end surfaces of the obtained laminates, and
fired at about 600.degree. C. in the air to obtain external
electrodes connected to internal electrodes. In this way, samples
were obtained.
[0072] The thus obtained laminates were about 2.0 mm in length,
about 1.0 mm in width, and about 0.5 mm in thickness. The thickness
per ceramic layer was about 5 .mu.m. An Al.sub.2O.sub.3 layer was
formed at surface layer sections of the Al internal electrodes of
the laminates 4-1 to 4-3 using the Al paste.
[0073] For the four types of samples 4-1 to 4-4 obtained, the
dielectric constant was measured with an automatic bridge-type
measurement device. The results are shown in Table 6.
[0074] Likewise, the effective area per layer of the internal
electrodes in the laminate after the firing was measured to
evaluate the area shrinkage ratio (=(Effective Area after
Firing)/(Effective Area before Firing)) to the area of about
1.7.times.10.sup.-6 m.sup.2 before the firing. The results are
shown in Table 6.
TABLE-US-00006 TABLE 6 Firing Sample Internal Temperature
Dielectric Shrinkage Number Electrode (.degree. C.) Constant Ratio
(%) 4-1 Al 850 8 95.9 4-2 Al 900 8 94.2 4-3 Al 950 8 94.2 4-4 Ag
900 8 87.9
[0075] According to the results in Table 6, the shrinkage ratios
for the samples 4-1, 4-2, and 4-3 using the Al internal electrodes
were smaller than that for the sample 4-4 using the Ag internal
electrodes. This is believed to be because the Al.sub.2O.sub.3
layer formed at the surface layer sections of the Al internal
electrodes acted to cause the internal electrode to adhere tightly
to the glass ceramic layer.
[0076] Accordingly, the laminates including the Al internal
electrodes according to the present example of a preferred
embodiment are useful as laminates for ceramic multilayer
substrates which require a high degree of dimensional accuracy.
Example 5
[0077] The present example provides an example of a laminated NTC
thermistor including a semiconductor ceramic and an Al internal
electrode, and is intended to be compared with an Ag/Pd internal
electrode.
[0078] First, a powder with the composition of
0.60Mn-0.25Ni-0.1Fe-0.05Ti (coefficient:molar ratio) was prepared,
and used as a ceramic raw material powder.
[0079] This ceramic raw material was used to obtain ceramic green
sheets in the same way as in Example 1. In parallel, an Al paste
including an Al metal powder and an organic vehicle and an Ag/Pd
paste including an Ag/Pd=7/3 metal powder and an organic vehicle
were prepared.
[0080] Next, the Al paste was applied by screen printing onto the
ceramic green sheets to form Al paste layers. The ceramic green
sheets with the Al paste applied were stacked so that the sides to
which the Al paste layers were drawn were alternated, followed by
pressure bonding, thereby providing a raw laminate. In the same
way, a raw laminate was obtained in the case of using the Ag/Pd
paste. In this case, the effective area per layer was about
1.7.times.10.sup.-6 m.sup.2, and the number of effective layers was
1.
[0081] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired at the temperature shown in Table 7 for 1
minute. An Ag paste containing low melting point glass frit was
applied onto the both end surfaces of the obtained laminates, and
fired at about 600.degree. C. in the air to obtain external
electrodes connected to internal electrodes. In this way, samples
were obtained.
[0082] The thus obtained laminates were about 2.0 mm in length,
about 1.0 mm in width, and about 0.5 mm in thickness. The thickness
per ceramic layer was about 5 .mu.m. An Al.sub.2O.sub.3 layer was
formed at surface layer sections of the Al internal electrodes of
the laminates 5-1 to 5-3 using the Al paste.
[0083] For the four types of samples 5-1 to 5-4 obtained, the
resistance value was measured to evaluate the volume resistivity
from the effective area and the thickness of the ceramic layer. The
results are shown in Table 7.
[0084] Likewise, the effective area per layer of the internal
electrodes in the laminate after the firing was measured to
evaluate the area shrinkage ratio (=(Effective Area after
Firing)/(Effective Area before Firing)) to the area of about
1.7.times.10.sup.-6 m.sup.2 before the firing. The results are
shown in Table 7.
TABLE-US-00007 TABLE 7 Firing Volume Sample Internal Temperature
Resistivity Shrinkage Number Electrode (.degree. C.) (.OMEGA. m)
Ratio (%) 5-1 Al 850 520 92.5 5-2 Al 900 840 91.8 5-3 Al 950 390
90.5 5-4 Ag/Pd 900 450 85.2
[0085] According to the results in Table 7, the shrinkage ratios
for the samples 5-1, 5-2 and 5-3 using the Al internal electrodes
were smaller than that for the sample 5-4 using the Ag/Pd internal
electrodes. This is believed to be because the Al.sub.2O.sub.3
layer formed at the surface layer sections of the Al internal
electrodes acted to cause the internal electrode to adhere tightly
to the ceramic layer.
[0086] Therefore, the laminates including the Al internal
electrodes according to various preferred embodiments of the
present invention are useful as laminates for laminated thermistors
which require a high degree of dimensional accuracy and resistance
value accuracy.
Example 6
[0087] The present example provides an example of a laminated chip
coil including a magnetic ceramic and an Al internal electrode, and
is intended to be compared with an Ag internal electrode.
[0088] First, a ceramic powder for ferrite with the composition of
0.49Fe.sub.2O.sub.3-0.29ZnO-0.14NiO-0.08CuO (coefficient:molar
ratio) was prepared, and about 0.5 wt % of borosilicate glass was
added to and mixed with the ceramic powder for ferrite. This mixed
powder was used as a ceramic raw material powder.
[0089] This ceramic raw material was used to obtain ceramic green
sheets in the same way as in Example 1. In parallel, an Al paste
including an Al metal powder and an organic vehicle and an Ag paste
including an Ag metal powder and an organic vehicle were
prepared.
[0090] Next, after forming through holes in predetermined
positions, the Al paste was applied by screen printing onto the
ceramic green sheets to form a coil pattern composed of an Al paste
layer. The ceramic green sheets with the Al paste applied were
stacked, followed by pressure bonding, thereby providing a raw
laminate with coils formed. In the same way, a raw laminate was
obtained in the case of using the Ag paste.
[0091] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired at the temperature shown in Table 8 for 1
minute. The thus obtained laminates were about 1.0 mm in length,
about 0.5 mm width, and about 0.5 mm in thickness. The number of
coil turns was 7.5 turns for the obtained laminates, and the line
width of the coil was about 100 .mu.m.
[0092] An Ag paste containing low melting point glass frit was
applied onto the both end surfaces of the obtained laminates, and
fired at about 600.degree. C. in the air to obtain external
electrodes connected to internal electrodes. It is to be noted that
while the exposed surfaces of the internal electrodes are subjected
to polishing by sandblasting or the like in order to provide
sufficient contact between the internal electrodes and the external
electrode in the case of common laminated chip coils, this
polishing was not carried out in the present example.
[0093] In addition, an Al.sub.2O.sub.3 layer was formed at surface
layer sections of internal electrodes of the laminates 6-1, 6-2,
and 6-3 using the Al paste. In this way, samples for evaluation
were obtained.
[0094] The samples 6-1, 6-2, 6-3, and 6-4 obtained as shown in
Table 8, 20 pieces for each sample, were subjected to conduction
check between the both external electrodes. The results of the
number of conduction defects are shown in Table 8.
TABLE-US-00008 TABLE 8 The Number of Firing Defects in Sample
Internal Temperature Conduction Number Electrode (.degree. C.)
Check 6-1 Al 850 0/20 6-2 Al 900 0/20 6-3 Al 950 0/20 6-4 Ag 900
14/20
[0095] According to the result in Table 8, no conduction defects
were observed in the samples 6-1, 6-2, and 6-3 using the Al
internal electrodes, while a number of conduction defects were
caused in the sample 6-4 using the Ag internal electrodes. This is
believed to be because the Al.sub.2O.sub.3 layer formed at the
surface layer sections of the Al internal electrodes caused the
internal electrode to adhere tightly to the ceramic layer, thereby
preventing electrode retraction arising from shrinkage of the Al
internal electrode.
[0096] Therefore, the use of the Al internal electrode can
eliminate the step of polishing by sandblasting or the like before
the formation of the external electrodes, and reduce the potential
for conduction defects. Accordingly, the laminates using the Al
internal electrodes are quite useful for laminated chip coils.
Example 7
[0097] The present example is an example of a laminated
piezoelectric element including a piezoelectric ceramic and an Al
internal electrode, and is intended to be compared with an Ag/Pd
internal electrode.
[0098] First, a powder with the composition of
(Pb.sub.0.88Bi.sub.0.12){(Ni.sub.1/2Nb.sub.1/2).sub.0.15Ti.sub.0.45Zr.sub-
.0.40}O.sub.3 was prepared, and used as a ceramic raw material
powder.
[0099] This ceramic raw material was used to obtain ceramic green
sheets in the same way as in Example 1. In parallel, an Al paste
including an Al metal powder and an organic vehicle and an Ag/Pd
paste including an Ag/Pd=9/1 metal powder and an organic vehicle
were prepared.
[0100] Next, the Al paste was applied by screen printing onto the
ceramic green sheets to form Al paste layers. The ceramic green
sheets with the Al paste applied were stacked so that the sides to
which the Al paste layers were drawn were alternated, followed by
pressure bonding, thereby providing a raw laminate. In the same
way, a raw laminate was obtained in the case of using the Ag/Pd
paste.
[0101] The raw laminates were heated at about 270.degree. C. in the
air to remove the binder. After this, the temperature was increased
at a rate of temperature increase of about 100.degree. C./min, and
the laminates were fired at the temperature shown in Table 9 for 1
minute. An Al.sub.2O.sub.3 layer was formed at surface layer
sections of the Al internal electrodes of the laminates using the
Al paste.
[0102] An Ag paste containing low melting point glass frit was
applied onto the both end surfaces of the obtained laminates, and
fired at about 600.degree. C. in the air to obtain external
electrodes connected to internal electrodes.
[0103] The thus obtained laminates were about 5 mm in length, about
5 mm in width, and about 0.6 mm in thickness. In addition, the
thickness per ceramic layer was about 100 .mu.m, and the number of
effective layers was 3. In this case, the (Length of Laminate after
Firing)/(Length of Laminate before Firing).times.100 was obtained
as the shrinkage ratio (%), and the results for the shrinkage ratio
are shown in Table 9. Samples 7-1 and 7-2 include Al internal
electrodes, whereas samples 7-3 and 7-4 include Ag/Pd internal
electrodes.
TABLE-US-00009 TABLE 9 Firing Shrinkage Sample Internal Temperature
Ratio Number Electrode (.degree. C.) (%) 7-1 Al 900 95 7-2 Al 950
95 7-3 Ag/Pd 900 81 7-4 Ag/Pd 950 77
[0104] It has been determined that the shrinkage ratio is smaller
in spite of the same firing temperature in the case of using the Al
internal electrodes, as compared with the laminates using the Ag/Pd
internal electrodes. Therefore, piezoelectric elements can be
expected to be obtained which are superior in terms of dimensional
accuracy, and are useful for laminated piezoelectric actuators and
the like which require a particularly strict degree of dimensional
accuracy.
[0105] In addition, in parallel, a voltage of approximately 300 V
was applied at about 80.degree. C. for about 10 minutes between the
external electrodes of the laminates to carry out a polarization
treatment. Then, the simplified measurement of the piezoelectric d
constant provided values on the order of about 250 pC/N to about
500 pC/N in terms of piezoelectric d.sub.33 constant for all of the
samples. Therefore, it has been determined that the use of the Al
internal electrodes even provides a sufficient piezoelectric
property.
[0106] The laminated ceramic electronic components according to
various preferred embodiments of the present invention can be
applied to laminated ceramic capacitors, laminated piezoelectric
elements, laminated thermistors, laminated chip coils, ceramic
multilayer substrates, and the like, for example.
[0107] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *