U.S. patent application number 11/955809 was filed with the patent office on 2008-10-23 for method for manufacturing ceramic plates.
This patent application is currently assigned to MURATA MANUFACTURING CO., LTD.. Invention is credited to Hiroshi Asano.
Application Number | 20080257472 11/955809 |
Document ID | / |
Family ID | 37532044 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257472 |
Kind Code |
A1 |
Asano; Hiroshi |
October 23, 2008 |
METHOD FOR MANUFACTURING CERAMIC PLATES
Abstract
In a method for manufacturing ceramic plates, a Pd paste which
does not diffuse into ceramic is formed in a metal paste forming
step; metal films each having a thickness such that ceramic layers
to be formed after firing are not connected to each other in the
lamination direction are formed on surfaces of ceramic green sheets
using the Pd paste in a metal film forming step; following a
laminate forming step, a firing treatment at a firing temperature,
which is a high temperature at which no glass component remains on
surfaces of the ceramic layers after the firing and which is equal
to or lower than a decomposition temperature of a ceramic material
forming the ceramic layers, is performed for a laminate in a firing
step; oxygen present at the interfaces between the ceramic layers
and the metal layers is removed by immersing a sintered body in
n-butyl alcohol in a separation step so as to separate the ceramic
layers and the metal layers. Accordingly, ceramic plates having a
very small thickness can be manufactured without causing any damage
thereto and with high efficiency and can be easily applied to
laminate type electronic components.
Inventors: |
Asano; Hiroshi;
(Moriyama-shi, JP) |
Correspondence
Address: |
MURATA MANUFACTURING COMPANY, LTD.;C/O KEATING & BENNETT, LLP
1800 Alexander Bell Drive, SUITE 200
Reston
VA
20191
US
|
Assignee: |
MURATA MANUFACTURING CO.,
LTD.
Nagaokakyo-shi
JP
|
Family ID: |
37532044 |
Appl. No.: |
11/955809 |
Filed: |
December 13, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2005/015141 |
Aug 19, 2005 |
|
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11955809 |
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Current U.S.
Class: |
156/47 |
Current CPC
Class: |
B32B 2311/08 20130101;
C04B 41/80 20130101; C04B 2235/3227 20130101; C04B 2237/40
20130101; H05K 1/0306 20130101; Y10T 156/1105 20150115; C04B 37/021
20130101; C04B 2237/346 20130101; C04B 2237/706 20130101; H05K
2203/1536 20130101; C04B 2235/3272 20130101; C04B 2235/656
20130101; H05K 3/0097 20130101; H05K 3/1291 20130101; C04B 37/006
20130101; C04B 2237/408 20130101; H05K 2201/0191 20130101; C04B
35/493 20130101; B32B 2311/09 20130101; C04B 2237/348 20130101;
B32B 18/00 20130101; C04B 2237/704 20130101; C04B 2235/3267
20130101; H05K 2203/1126 20130101; H05K 3/0011 20130101; C04B
35/491 20130101; Y10T 156/1111 20150115; C04B 2235/3251 20130101;
C04B 35/472 20130101 |
Class at
Publication: |
156/47 |
International
Class: |
H01B 13/32 20060101
H01B013/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2005 |
JP |
2005-173545 |
Claims
1. A method for manufacturing ceramic plates in which the ceramic
plates are obtained by separating ceramic layers from a sintered
body composed of the ceramic layers and metal layers alternately
laminated to each other, the method comprising: a ceramic
green-sheet forming step of forming ceramic green sheets from
ceramic raw materials; a metal paste forming step of forming a
metal paste using a metal component as a solid component which does
not diffuse into ceramic during firing; a metal film forming step
of applying the metal paste on surfaces of the ceramic green sheets
to form metal films each having a thickness such that ceramic
layers to be formed after firing are not connected to each other in
the lamination direction; a laminate forming step of laminating the
ceramic green sheets provided with the metal films to form a
laminate; a firing step of performing a firing treatment for the
laminate at a firing temperature which is set to a high temperature
at which no glass component remains on surfaces of the ceramic
layers after the firing and to a temperature equal to or lower than
a decomposition temperature of a ceramic material forming the
ceramic layers so as to form the sintered body composed of the
ceramic layers and the metal layers alternately laminated to each
other; and a separation step of immersing the sintered body in an
oxygen removal processing liquid which removes oxygen present
between the ceramic layers and the metal layers to separate the
ceramic layers and the metal layers.
2. The method for manufacturing ceramic plates, according to claim
1, the method further comprising an electrode paste forming step of
forming an electrode paste containing a conductive component which
diffuses into the ceramic during the firing, and an electrode film
forming step of applying the electrode paste on surfaces of the
ceramic green sheets to form electrode films, wherein the laminate
formed in the laminate forming step includes the ceramic green
sheets provided with the electrode films.
3. The method for manufacturing ceramic plates, according to claim
1, wherein the metal component comprises palladium.
4. The method for manufacturing ceramic plates, according to claim
1, wherein the oxygen removal processing liquid is a reducing
solution comprising an organic compound which includes at least one
of a hydroxyl group, an aldehyde group, and a carboxyl group.
5. The method for manufacturing ceramic plates, according to claim
4, wherein the oxygen removal processing liquid comprises a liquid
alcohol.
6. The method for manufacturing ceramic plates, according to claim
5, wherein the liquid alcohol is one of an aliphatic alcohol, a
cycloaliphatic alcohol, an aromatic alcohol, a heterocyclic
alcohol, and a mixture thereof.
7. The method for manufacturing ceramic plates, according to claim
6, wherein the aliphatic alcohol is n-butyl alcohol.
8. The method for manufacturing ceramic plates, according to claim
1, wherein the ceramic material forming the ceramic green sheets is
a lead-based piezoelectric ceramic material containing a lead
component.
9. The method for manufacturing ceramic plates, according to claims
1, wherein the metal films have a thickness of about pm to about 10
.mu.m.
10. The method for manufacturing ceramic plates, according to claim
1, wherein the ceramic green sheet forming step forms a plurality
types of ceramic green sheets which have different thicknesses.
Description
BACKGROUND OF THE INVENTION 1. Field of the Invention
[0001] The present invention relates to methods for manufacturing
ceramic plates, and more particularly, relates to a method for
manufacturing ceramic plates in which ceramic layers are separated
from a sintered body including ceramic layers and metal layers
alternately laminated to each other, to obtain the ceramic
plates.
[0002] 2. Description of the Related Art
[0003] In recent years, in various ceramic electronic components,
such as an IC substrate and a ceramic capacitor, a decrease in
thickness and a reduction in size have been advanced. It has also
been requested to further decrease the thickness of a ceramic plate
used for forming ceramic electronic components.
[0004] In addition, as a method for manufacturing the ceramic plate
as described above, a method for forming thin ceramic plates has
been proposed in which, after a laminate is formed by laminating
ceramic green sheets provided with un-sintered metal films, the
laminate is processed by a firing treatment to form a sintered body
103 composed of ceramic layers 101 and metal layers 102 alternately
laminated to each other, and as shown in FIG. 13, while the
sintered body 103 is immersed in an alcohol 104, an external force,
such as ultrasonic waves, is applied to the sintered body 103 as
shown by arrows to separate the metal layers 102 and the ceramic
layers 101.
[0005] However, according to Japanese Unexamined Patent Application
Publication No. 2005-15254, since the ceramic layers 101 and the
metal layers 102 are separated by application of an external force,
such as ultrasonic waves, to the sintered body 103, when the
ceramic layers 101 have an extremely small thickness (such as 10
.mu.m or less), a problem may arise in some cases in that the
ceramic layers 101 are damaged, for example, by cracks generated
therein caused by the external force applied thereto.
[0006] In addition, according to Japanese Unexamined Patent
Application Publication No. 2005-15254, since the external force is
applied to the sintered body as described above, the ceramic layers
101 and the metal layers 102 are separated into individual layers,
and as a result, a ceramic plate having a laminate structure cannot
be obtained. Hence, it has been difficult to apply a separated
ceramic plate to laminate type electronic components.
[0007] In addition, according to a technique of Japanese Unexamined
Patent Application Publication No. 2005-15255, although the
separation between the ceramic layer 101 and the metal layer 102
can be easily performed by the use of platinum or iridium as a
metal film component, since the ceramic layer 101 and the metal
layer 102 are separated from each other by applying an external
force, such as ultrasonic waves, to the sintered body 103 as in the
case of Japanese Unexamined Patent Application Publication No.
2005-15254, the ceramic layer 101 may also be damaged when the
thickness thereof is extremely small, and hence it is also
difficult to apply the above technique to laminate type electronic
components.
SUMMARY OF THE INVENTION
[0008] In order to overcome the problems described above, preferred
embodiments of the present invention provide a method for
manufacturing ceramic plates, which can efficiently manufacture
extremely thin ceramic plates without causing any damage thereto,
and which can be easily applied to laminate type electronic
components.
[0009] In a sintered body composed of ceramic layers and metal
layers alternately laminated to each other, it has been believed
that the ceramic layer and the metal layer are connected to each
other in combination among the following four factors:
[0010] (1) the presence of oxygen at the interface between the
ceramic layer and the metal layer,
[0011] (2) the presence of crosslinking connecting the ceramic
layers through the metal layer,
[0012] (3) the diffusion of a metal component to the ceramic layer
in firing, and
[0013] (4) the presence of a glass component on a surface of the
ceramic layer.
[0014] Hence, when the above connection factors (1) to (4) are all
removed, without applying any external force to the sintered body,
the ceramic layer and the metal layer can be easily separated from
each other.
[0015] Accordingly, through intensive research carried out by the
inventors of the present invention in order to remove all the
connection factors (1) to (4) described above, it was discovered
that as for the factor (1), oxygen present between the ceramic
layer and the metal layer can be removed when the sintered body is
immersed in an oxygen removal processing liquid so as to cause an
oxidation-reduction reaction at the interface; the factor (2) can
be resolved when an unsintered metal film is formed to have a large
thickness such that crosslinking does not occur between the ceramic
layers; the factor (3) can be resolved when a metal material which
does not diffuse into the ceramic layer side during a firing
treatment is used; and as for the factor (4), when the firing
temperature is set to a high temperature at which no glass
component remains on a surface of the ceramic layer after firing
and to a temperature equal to or lower than a decomposition
temperature of a ceramic material forming the ceramic layer, even
after the laminate is processed by the firing treatment, the glass
component can be prevented from remaining on the surface of the
ceramic layer without decomposition of the ceramic material.
[0016] Based on the discoveries and findings as described above,
preferred embodiments of the present invention were developed, and
a method for manufacturing ceramic plates according to a preferred
embodiment of the present invention is a method for manufacturing
ceramic plates by separating ceramic layers from a sintered body
composed of the ceramic layers and metal layers alternately
laminated to each other, and the method includes: a ceramic
green-sheet forming step of forming ceramic green sheets from
ceramic raw materials; a metal paste forming step of forming a
metal paste using a metal component as a solid component which does
not diffuse into the ceramic during firing; a metal film forming
step of applying the metal paste on surfaces of the ceramic green
sheets to form metal films each having a thickness such that
ceramic layers to be formed after firing are not connected to each
other in the lamination direction; a laminate forming step of
laminating the ceramic green sheets provided with the metal films
to form a laminate; a firing step of performing a firing treatment
for the laminate at a firing temperature which is set to a high
temperature at which no glass component remains on surfaces of the
ceramic layers after the firing and to a temperature equal to or
lower than a decomposition temperature of a ceramic material
forming the ceramic layers so as to form the sintered body composed
of the ceramic layers and the metal layers alternately laminated to
each other; and a separation step of immersing the sintered body in
an oxygen removal processing liquid which removes oxygen present
between the ceramic layers and the metal layers to separate the
ceramic layers and the metal layers.
[0017] In addition, when an electrode paste containing a conductive
component which diffuses into the ceramic during the firing is
applied to surfaces of the ceramic green sheets to form electrode
films, and the ceramic green sheets provided with the electrode
films and the ceramic green sheets provided with the metal films
are appropriately laminated to each other, ceramic plates having a
laminate structure can be obtained.
[0018] That is, the method for manufacturing ceramic plates,
according to a preferred embodiment of the present invention, may
further include: an electrode paste forming step of forming an
electrode paste containing a conductive component which diffuses
into the ceramic green sheets during the firing; and an electrode
film forming step of applying the electrode paste on surfaces of
the ceramic green sheets to form electrode films, and in addition,
the laminate formed in the laminate forming step includes the
ceramic green sheets provided with the electrode films.
[0019] In addition, as the metal component which does not diffuse
into the ceramic during the firing, palladium may be used.
[0020] That is, in the method for manufacturing ceramic plates,
according to a preferred embodiment of the present invention, the
metal component of the metal paste may include palladium.
[0021] Furthermore, as the oxygen removal processing liquid, a
reducing solution including an organic compound which includes at
least one of a hydroxyl group (--OH), an aldehyde group (--CHO),
and a carboxyl group (--COOH) may be used; in particular, a liquid
alcohol is preferably used which is one of an aliphatic alcohol, a
cycloaliphatic alcohol, an aromatic alcohol, a heterocyclic
alcohol, and a mixture thereof; and as the liquid alcohol, in
particular, as the aliphatic alcohol, n-butyl alcohol is more
preferably used.
[0022] That is, in the method for manufacturing ceramic plates,
according to a preferred embodiment of the present invention, the
oxygen removal processing liquid may be a reducing solution which
includes an organic compound containing at least one of a hydroxyl
group, an aldehyde group, and a carboxyl group.
[0023] In addition, the oxygen removal processing liquid may
comprise a liquid alcohol, and further, the liquid alcohol may be
one of an aliphatic alcohol, a cycloaliphatic alcohol, an aromatic
alcohol, a heterocyclic alcohol, and a mixture thereof.
[0024] Furthermore, the aliphatic alcohol is preferably n-butyl
alcohol.
[0025] In addition, preferred embodiments of the present invention
are suitable for use to obtain ceramic plates of a lead-based
piezoelectric ceramic material.
[0026] That is, in the method for manufacturing ceramic plates,
according to various preferred embodiments of the present
invention, the ceramic material forming the ceramic green sheets is
preferably a lead-based piezoelectric ceramic material containing a
lead component.
[0027] In addition, although it is believed that the thickness of
the metal film which prevents the ceramic layers to be formed by
the firing from being connected to each other in the lamination
direction varies depending on ceramic materials to be used, it was
discovered that from the results of the research carried out by the
inventors of the present invention, in the case in which a
piezoelectric ceramic material is used, when the thickness of the
metal film is set in the range of about 1.9 .mu.m to about 10
.mu.m, for example, the ceramic layers can be formed so as not to
be connected to each other.
[0028] That is, in the method for manufacturing ceramic plates,
according to a preferred embodiment of the present invention, the
thickness of the metal film is preferably in the range of about 1.9
.mu.m to about 10 .mu.m, for example.
[0029] In addition, in the method for manufacturing ceramic plates,
according to a preferred embodiment of the present invention, the
ceramic green-sheet forming step may form a plurality types of
ceramic green sheets which have different thicknesses.
[0030] The method for manufacturing ceramic plates, according to a
preferred embodiment of the present invention, includes: a ceramic
green-sheet forming step of forming ceramic green sheets from
ceramic raw materials; a metal paste forming step of forming a
metal paste using a metal component (such as palladium) as a solid
component which does not diffuse into ceramic during firing; a
metal film forming step of applying the metal paste on surfaces of
the ceramic green sheets to form metal films each having a
thickness (such as about 1.9 .mu.m to about 10 .mu.m) so that
ceramic layers to be formed after firing are not connected to each
other; a laminate forming step of laminating the ceramic green
sheets provided with the metal films to form a laminate; a firing
step of performing a firing treatment for the laminate at a firing
temperature which is set to a high temperature at which no glass
component remains on surfaces of the ceramic layers to be formed
after the firing and to a temperature equal to or lower than a
decomposition temperature of a ceramic material, such as a
lead-based piezoelectric ceramic material, forming the ceramic
layers so as to form the sintered body composed of the ceramic
layers and the metal layers alternately laminated to each other;
and a separation step of immersing the sintered body in an oxygen
removal processing liquid, such as a liquid alcohol (n-butyl
alcohol or the like), which removes oxygen present between the
ceramic layers and the metal layers to separate the ceramic layers
and the metal layers; hence, the ceramic layers and the metal
layers can be easily separated from each other without applying any
external force to the sintered body, and as a result, ceramic
plates even having a very small thickness can be efficiently
manufactured without causing any damage thereto.
[0031] In addition, since the method for manufacturing ceramic
plates, according to a preferred embodiment of the present
invention, may further include an electrode paste forming step of
forming an electrode paste containing a conductive component which
diffuses into the ceramic during the firing and an electrode film
forming step of applying the electrode paste on surfaces of the
ceramic green sheets to form electrode films, and the laminate
formed in the laminate forming step may include the ceramic green
sheets provided with the electrode films, when the ceramic green
sheets provided with the electrode films and the ceramic green
sheets provided with the metal films are appropriately laminated to
each other, ceramic layers each having a laminate structure
composed of the ceramic layers and the electrode layers, which are
alternately laminated to each other, can be separated from the
metal layers. Accordingly, the ceramic layers each having the
laminate structure described above can be used as ceramic plates
and can be easily applied to laminate type electronic
components.
[0032] In addition, since the ceramic green-sheet forming step may
form a plurality types of ceramic green sheets which have different
thicknesses, ceramic layers having different thicknesses can be
separated from the metal layers, and hence ceramic plates having
different thicknesses can be simultaneously and easily
manufactured.
[0033] Other features, elements, processes, steps, characteristics
and advantages of the present invention will become more apparent
from the following detailed description of preferred embodiments of
the present invention with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a flowchart of a method for manufacturing ceramic
plates of a preferred embodiment according to the present
invention.
[0035] FIG. 2 is a cross-sectional view showing the state in which
metal films are formed on ceramic green sheets in a metal film
forming step.
[0036] FIG. 3 is a view illustrating a problem in the case in which
a metal film has a small thickness.
[0037] FIG. 4 is a cross-sectional view of a sintered body obtained
in a sintering step.
[0038] FIG. 5 is a view showing the state in which a sintered body
is immersed in an oxygen removal processing liquid in a separation
step.
[0039] FIG. 6 is a cross-sectional view showing the state in which
ceramic layers and metal layers are separated from each other.
[0040] FIG. 7 is a flowchart of a method for manufacturing ceramic
plates of another preferred embodiment according to the present
invention.
[0041] FIG. 8 is a cross-sectional view of a sintered body obtained
in a sintering step of another preferred embodiment of the present
invention.
[0042] FIG. 9 is a cross-sectional view showing the state in which
ceramic layers each having a laminate structure and metal layers
are separated from each other.
[0043] FIG. 10 is a cross-sectional view of a first laminate formed
in Example 6.
[0044] FIG. 11 is a cross-sectional view of a second laminate
formed in Example 6.
[0045] FIG. 12 is a cross-sectional view of a third laminate formed
in Example 6.
[0046] FIG. 13 is a view showing a conventional method for
manufacturing ceramic plates.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0047] Next, preferred embodiments according to the present
invention will be described in detail with reference to the
drawings.
[0048] FIG. 1 is a flowchart showing a method for manufacturing
ceramic plates of a preferred embodiment according to the present
invention, and hereinafter, the case in which ceramic plates
containing a Pb component are manufactured will be described.
[0049] First, in a ceramic green-sheet forming step 1, ceramic
green sheets are formed from ceramic raw materials.
[0050] That is, after ceramic raw materials, such as
Pb.sub.3O.sub.4, TiO.sub.2, and ZrO.sub.2, in predetermined amounts
are weighed and charged in a ball mill containing pulverizing
media, followed by mixing and wet pulverization, drying is
performed, and a calcination treatment is then performed at a
predetermined temperature, so that a powdered piezoelectric ceramic
is formed.
[0051] Subsequently, an organic binder and a dispersing agent are
added to the powdered piezoelectric ceramic together with purified
water and are then again mixed and wet-pulverized in a ball mill to
form a ceramic slurry, and subsequently, the ceramic slurry is
processed by a forming method such as a doctor blade method,
thereby forming ceramic green sheets each having a predetermined
thickness.
[0052] In addition, in a metal paste forming step 2, a metal paste
to be applied to surfaces of the ceramic green sheets is
formed.
[0053] That is, a metal component, such as powdered Pd (palladium),
which does not diffuse into ceramic during firing is mixed with an
organic vehicle and is then compounded therewith using a
three-roller mill to form the metal paste.
[0054] In this preferred embodiment, as the organic vehicle, a
compound may be used which is formed of an organic solvent, such as
terpineol, and an organic binder, such as an ethyl cellulose resin,
dissolved therein. In addition, the ratio between the Pd powder and
the organic vehicle is not particularly limited; however, for
example, a compound containing powdered Pd and an organic vehicle
at a ratio of about 55% to about 45% on a weight percent basis may
be used.
[0055] Next, in a metal film forming step 3, as shown in FIG. 2,
the metal paste is applied to the entire surfaces of ceramic green
sheets 7a to 7d to form metal films 8a to 8d.
[0056] That is, although the ceramic green sheets 7a to 7d provided
with the metal films 8a to 8d, respectively, are laminated to each
other and are then fired as described below, when the thicknesses
of the metal films 8a to 8d are small, for example as shown in FIG.
3, holes are formed in a metal layer 10a' which is a sintered body
of the metal film 8a, and the holes are filled with a ceramic
material. As a result, through the metal layer 10a', ceramic layers
9a and 9b, which are sintered bodies of the ceramic green sheets 7a
and 7b, respectively, are connected to each other through the metal
layer 10a', and crosslinking 10a'' is formed. Accordingly, since
the ceramic layers are tightly connected to each other by the
crosslinking 10a'' interposed therebetween, it becomes difficult to
separate the ceramic layers 9a and 9b from the metal layer
10a'.
[0057] Accordingly, in this preferred embodiment, the thicknesses
of the metal films 8a to 8d are adjusted so that the ceramic layers
to be formed after the firing are not connected to each other. The
desired thickness of the metal film 8 as described above varies
depending on ceramic materials. However, in the case in which a
Pb-based piezoelectric ceramic is used as this preferred
embodiment, the thickness is preferably in the range of about 1.9
.mu.m to about 10 .mu.m and is more preferably in the range of
about 3 .mu.m to about 5 .mu.m, for example.
[0058] In the following laminate forming step 4, after the ceramic
green sheets 7a to 7d provided with the metal films 8a to 8d,
respectively, are laminated to each other, and a ceramic green
sheet 7e is laminated on the topmost layer, the ceramic green sheet
7 (7a to 7e) and the metal film 8 (8a to 8d) are pressure-bonded in
the lamination direction to form a laminate.
[0059] Subsequently, in a firing step 5, a firing treatment is
performed for the laminate described above, and as shown in FIG. 4,
a sintered body 11 composed of ceramic layers 9 (9a to 9e) and
metal layers 10 (10a to 10d) alternately laminated to each other is
formed.
[0060] In this preferred embodiment, the firing temperature is set
to a high temperature at which no glass component remains on
surfaces of the ceramic layers 9 and is also set to a temperature
equal to or lower than a decomposition temperature of a ceramic
material forming the ceramic layers 9.
[0061] That is, in the case of a Pb-based piezoelectric ceramic
material, since liquid phase PbO is generally generated when a
firing treatment is performed, a liquid phase sintering is also
performed. In addition, since the liquid phase PbO also permeates
the interfaces between the metal films 8 and the respective ceramic
green sheets 7 during the firing treatment, when the sintering is
completed in the state described above, low melting point glass
layers are formed at the interfaces between the metal layers 10
which are sintered bodies of the metal films 8 and the respective
ceramic layers 9 which are sintered bodies of the ceramic green
sheets 7. That is, the glass component remains on the surfaces of
the ceramic layers 9. In this case, since the glass component
described above functions as an adhesive to the metal layers 10, a
separation treatment, which will be described later, between the
ceramic layers 9 and the respective metal layers 10 will be
disturbed.
[0062] Accordingly, in this preferred embodiment, the firing
temperature is set to a high temperature so that no glass component
remains, and in this embodiment, the firing temperature is
preferably set to about 1,100.degree. C. or more.
[0063] However, when the firing temperature is increased at which
the ceramic material is decomposed, desired ceramic plates cannot
be obtained, and hence the upper limit of the firing temperature
must be set to the decomposition temperature of the ceramic
material or less.
[0064] Next, in a separation step 6, as shown in FIG. 5, the
sintered body 11 is immersed in a treatment bath 13 filled with an
oxygen removal processing liquid 12, and as shown in FIG. 6, the
ceramic layers 9 and the metal layers 10 are separated from each
other, so that the ceramic plates are obtained.
[0065] That is, since the ceramic layers 9 are prevented from being
connected to each other to form crosslinking by the control of the
thickness of the metal films 8; the metal component is prevented
from diffusing to the ceramic green sheet side by the use of Pd as
the metal component; and the glass component is prevented from
remaining on the surfaces of the ceramic layers by the adjustment
of the firing temperature, when the separation step 6 is actually
performed, the connection factor between the ceramic layers 9 and
the respective metal layers 10 is only oxygen present at the
interfaces therebetween.
[0066] Accordingly, in this preferred embodiment, the sintered body
11 is immersed in the oxygen removal processing liquid 12 for a
predetermined time, so that the oxygen present at the interfaces is
removed.
[0067] As the oxygen removal processing liquid 12, a reducing
solution of an organic compound including at least one of a
hydroxyl group, an aldehyde group, and a carboxyl group may be
used, and when the sintered body 11 is immersed in this type of
reducing solution, an oxidation-reduction reaction occurs at the
interface, so that the oxygen present at the interfaces can be
removed.
[0068] As the oxygen removal processing liquid 12 described above,
in particular, a liquid alcohol is preferably used. As the liquid
alcohol, one of an aliphatic alcohol, a cycloaliphatic alcohol, an
aromatic alcohol, a heterocyclic alcohol, and a mixture thereof may
be used. In particular, a lower aliphatic monovalent alcohol in
which the number of carbon atoms Cn is 1 to 6, such as ethyl
alcohol, n-propyl alcohol, isopropyl alcohol, or n-butyl alcohol,
which is an aliphatic alcohol, is preferably used, and more
particularly, n-butyl alcohol is preferably used.
[0069] Since the method for manufacturing ceramic plates described
above includes: the ceramic green-sheet forming step 1 of forming
the ceramic green sheets 7 from the ceramic raw materials; the
metal paste forming step 2 of forming the metal paste using Pd as a
solid component which does not diffuse into ceramic green sheet 7
sides during firing; the metal film forming step 3 of applying the
metal paste on the surfaces of the ceramic green sheets to form the
metal films 8 each having a thickness such that the ceramic layers
to be formed after firing are not connected to each other; the
laminate forming step 4 of laminating the ceramic green sheets 7
provided with the metal films 8 to form a laminate; the firing step
5 of performing a firing treatment for the laminate at a firing
temperature which is set to a high temperature at which no glass
component remains on the surfaces of the ceramic layers 9 to be
formed after the firing and to a temperature equal to or lower than
the decomposition temperature of the Pb-based piezoelectric ceramic
material so as to form the sintered body 11 composed of the ceramic
layers 9 and the metal layers 10 alternately laminated to each
other; and the separation step 6 of immersing the sintered body 11
in the oxygen removal processing liquid 12 which removes oxygen
present between the ceramic layers 9 and the respective metal
layers 10 to separate the ceramic layers 9 and the metal layers 10,
the following four connection factors between the ceramic layers 9
and the respective metal layers 10 can all be removed, which
are:
[0070] (1) the presence of oxygen between the ceramic layer and the
metal layer,
[0071] (2) the presence of the ceramic layers penetrating the metal
film,
[0072] (3) the diffusion of the metal component to the ceramic
layer in firing, and
[0073] (4) the presence of the glass component on the surface of
the ceramic layer.
[0074] Hence, without applying an external force, such as
ultrasonic waves, the ceramic layers 9 and the metal layers 10 can
be easily separated from each other, and as a result, good quality
ceramic plates having no damage, such as cracks, can be obtained
with high efficiency.
[0075] FIG. 7 is a flowchart showing a method for manufacturing
ceramic plates of another preferred embodiment according to the
present invention, and in this additional preferred embodiment,
electrode films which diffuse into ceramic during firing are
provided between ceramic green sheets, so that ceramic plates each
having a laminate structure are obtained.
[0076] That is, an electrode paste containing a conductive
component, such as Ag--Pd or Ag, as a primary component, which is
diffusible also to the ceramic when a laminate is co-sintered, is
formed in an electrode paste forming step 21, and in an electrode
film forming step 22, by using this electrode paste, screen
printing is performed on surfaces of the ceramic green sheets
formed in the ceramic green-sheet forming step 1, so that electrode
films each having a predetermined pattern are formed. In this case,
it is not necessary to increase the thickness of the electrode film
to that of the metal film.
[0077] In addition, in a laminate forming step 23, after the
ceramic green sheets provided with the electrode films and the
ceramic green sheets provided with the metal films are alternately
laminated to each other, a ceramic green sheet is laminated on the
topmost layer, followed by pressure bonding, so that the laminate
is formed. In a firing step 24, at a firing temperature which is
set under temperature conditions similar to those of the
above-described preferred embodiment, the laminate is processed by
a firing treatment, so that a sintered body 40 containing a ceramic
layer 26a, an electrode layer 27a, a ceramic layer 26b, a metal
layer 28a, . . . and a ceramic layer 26f laminated in that order as
shown in FIG. 8 is obtained.
[0078] Subsequently, in a separation step 25, the sintered body 40
is immersed in the oxygen removal processing liquid used in the
above-described preferred embodiment for a predetermined time.
Since a portion of the conductive component forming the electrode
layers 27 (27a to 27c) diffuses to the ceramic layers 26 (26a to
26e), the electrode layers 27 (27a to 27c) are tightly connected to
and are not separated from the ceramic layers 26 (26a to 26e) which
are in contact therewith so as to maintain laminate structures 29
(29a to 29c), and in addition, the other side surfaces of the
ceramic layers 26b, 26c, 26d, and 26e which are in contact with the
metal layers 28a and 28b are separated therefrom, so that ceramic
plates having laminate structures 29a to 29c can be obtained.
[0079] According to the additional preferred embodiment, the
ceramic plates each having a laminate structure can also be
obtained and can be applied to laminate type electronic components
having a laminate structure.
[0080] The present invention is not limited to the preferred
embodiments described above, and without departing from the spirit
and the scope of the present invention, various modifications may
be made. For example, in the ceramic green sheet forming step 1,
when various ceramic green sheets having different thicknesses are
formed, various ceramic plates having different thicknesses can be
easily obtained with high efficiency.
[0081] In addition, in the above-described preferred embodiments,
although the Pb-based piezoelectric ceramic material is preferably
used as a ceramic material, of course, another ceramic material,
such as a non-lead piezoelectric ceramic material or a dielectric
ceramic material, may also be used.
[0082] In addition, in the above-described preferred embodiments,
although the ceramic green sheets provided with the electrode films
and the ceramic green sheets provided with the metal films
preferably are alternately laminated to each other, of course, the
structure may be formed in which ceramic green sheets provided with
the electrode films are laminated to each other, and on one surface
in the above laminate at which the separation is desirably
performed, a ceramic green sheet provided with the metal film may
be provided.
[0083] Next, examples according to preferred embodiments of the
present invention will be described in detail.
EXAMPLES 1
[0084] After Pb.sub.3O.sub.4, TiO.sub.2, ZrO.sub.2, MnO.sub.2, and
Nb.sub.2O.sub.5 were prepared as ceramic raw materials, these
ceramic raw materials in predetermined amounts were weighed and
were then charged in a ball mill containing partially stabilized
zirconia (pulverizing media) for mixing and wet pulverization,
followed by drying, and subsequently, a calcination treatment was
performed at a predetermined temperature, so that a Pb{
(Mn,Nb)Ti,Zr}O.sub.3-based piezoelectric ceramic powder was
formed.
[0085] Next, after an organic binder and a dispersing agent were
added to this piezoelectric ceramic powder together with purified
water, mixing and wet pulverization were again performed in a ball
mill to form a ceramic slurry. Subsequently, this ceramic slurry
was processed by a doctor blade method to form a ceramic green
sheet having a thickness of about 20 .mu.m, and this ceramic green
sheet was then cut into sheets having a length of about 20 mm and a
width of about 30 mm.
[0086] Next, after a metal paste (hereinafter referred to as "Pd
paste") containing Pd as a solid component was formed, this Pd
paste was applied to the entire surfaces of the ceramic green
sheets obtained by the above cutting step while the thickness
thereof was being adjusted to about 3.0 .mu.m, so that metal films
were formed on the ceramic green sheets.
[0087] Subsequently, three ceramic green sheets provided with the
metal films thus obtained were laminated to each other, and a
ceramic green sheet provided with no metal film was laminated on
the topmost layer, followed by pressure bonding in the lamination
direction, so that a laminate was formed.
[0088] Then, a debinder treatment was performed for the laminate at
about 400.degree. C. in the air atmosphere, and the laminate was
then processed by a firing treatment.
[0089] That is, the firing treatment was performed for
approximately 2 hours at temperatures different by about 20.degree.
C. in the range of from about 1,060 to about 1,180, and as a
result, seven types of samples processed at the different firing
temperatures were obtained (Sample No. 1).
[0090] In addition, seven types of samples processed by different
sintering temperatures were obtained by a method and a procedure
similar to those described above except that instead of the above
Pd paste, an electrode paste (hereinafter referred to as "first
Ag--Pd paste") having a composition ratio of Ag to Pd of about 70
to about 30 on a weight percent basis and an electrode paste
(hereinafter referred to as "second Ag--Pd paste") having a
composition ratio of Ag to Pd of about 30 to about 70 on a weight
percent basis were used (Sample Nos. 2 and 3).
[0091] In addition, when the cross-sections of the individual
samples of Sample Nos. 1 to 3 were investigated by an electron
microscope, it was confirmed that the ceramic layers were not
connected to each other through the metal layers, and that the
crosslinking was not formed.
[0092] In addition, seven types of samples processed by different
sintering temperatures were obtained by a method and a procedure
similar to those of Sample No. 1 except that the metal films were
formed on the entire surfaces of the ceramic green sheets using the
above Pd paste and the first and the second Ag--Pd pastes while the
thickness was being adjusted to 1.5 .mu.m.
[0093] Subsequently, when the cross-sections of the individual
samples of Sample Nos. 4 to 6 were investigated by an electron
microscope, it was confirmed that the ceramic layers were connected
to each other in the lamination direction, and that the
crosslinking was formed.
[0094] Next, after the samples of Sample Nos. 1 to 6 were immersed
in a treatment bath filled with n-butyl alcohol for approximately
50 hours and were then recovered from the treatment bath, whether
the metal layers and the ceramic layers were separated or not was
investigated.
[0095] Table 1 shows the status of separation at the individual
temperatures. In Table 1, O indicates the case in which the ceramic
layer and the metal layer are completely separated from each other,
and .DELTA. indicates the case in which the metal layer is partly
adhered to one surface of the ceramic layer and cannot be
completely separated therefrom. In addition, X indicates the case
in which the ceramic layer cannot be separated from the metal layer
at all.
TABLE-US-00001 TABLE 1 Metal Film Sample Weight Firing Temperature
(.degree. C.) No. Component Ratio Thickness 1,060 1,080 1,100 1,120
1,140 1,160 1,180 1 Pd -- 3.0 x x .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. 2 Ag/Pd 70/30 3.0 x x x x
x x -- 3 Ag/Pd 30/70 3.0 x x .DELTA. .DELTA. .DELTA. .DELTA.
.DELTA. 4 Pd -- 1.5 x x .DELTA. .DELTA. .DELTA. .DELTA. .DELTA. 5
Ag/Pd 70/30 1.5 x x x x x x -- 6 Ag/Pd 30/70 1.5 x x x x x x x
[0096] As apparent from Table 1, it was confirmed that in Sample
No. 1, when the firing temperature was about 1,100.degree. C. or
more, the ceramic layer could be completely separated from the
metal layer. The reasons for this are believed to be that Pd does
not diffuse into the ceramic during the firing; no glass component
remains on the surface of the ceramic layer; the ceramic layers are
not connected to each other due to the metal film having a large
thickness of about 3.0 .mu.m; and furthermore, since an
oxidation-reduction reaction occurs at the interface by immersion
of the sample in n-butyl alcohol, the oxygen present at the
interface between the ceramic layer and the metal layer is
removed.
[0097] When the firing was performed at about 1,060.degree. C. and
about 1,080.degree. C. for the samples of Sample No. 1, the ceramic
layer and the metal layer could not be separated from each other,
and the reason for this is believed that the glass component
remains on the surface of the ceramic layer at the above firing
temperature and functions as an adhesive.
[0098] On the other hand, in Sample No. 2, even when the firing
treatment was performed at a firing temperature of about
1,100.degree. C. or more, the ceramic layer and the metal layer in
the sintered body could not be separated from each other. The
reason for this is believed that since the content of Ag in the
metal film is about 70 percent by weight, Ag diffuses to the
ceramic in the firing.
[0099] In addition, in Sample No. 3, even when the firing
temperature was set to about 1,100.degree. C. or more, the ceramic
layer and the metal layer could not be completely separated from
each other. The reason for this is believed that although the
content of Ag in the metal film is decreased to about 30 percent by
weight, there is still Ag diffusing to the ceramic in the
firing.
[0100] In addition, in Sample No. 4, even when the firing
temperature was set to about 1,100.degree. C. or more, the ceramic
layer and the metal layer could not be completely separated from
each other. The reason for this is believed that although the metal
film is formed only from Pd, since the thickness thereof is
decreased to about 1.5 .mu.m, the ceramic layers are connected to
each other.
[0101] In addition, in Sample Nos. 5 and 6, the ceramic layer and
the metal layer could not be completely separated from each other.
The reason for this is believed that since Ag is contained in the
metal film, and the thickness thereof is decreased to about 1.5
.mu.m, Ag diffuses into the ceramic and the ceramic layers are
connected to each other.
[0102] When ultrasonic waves were applied in n-butyl alcohol to the
samples (marked with x) in Table 1 in which the ceramic layer and
the metal layer could not be separated from each other at all, the
ceramic layer and the metal layer could be separated from each
other by increasing the intensity of the ultrasonic waves or by
increasing the time for applying the ultrasonic waves; however, it
was confirmed that cracks were generated in the separated ceramic
layer, that is, in the ceramic plate.
EXAMPLE 2
[0103] A Pb{(Ni,Nb)Zr,Ti}O.sub.3-based piezoelectric ceramic powder
was formed by a method and a procedure similar to those of Example
1 using Pb.sub.3O.sub.4, TiO.sub.2, ZrO.sub.2, NiO, and
Nb.sub.2O.sub.5 as ceramic raw materials.
[0104] Subsequently, after samples of Sample Nos. 11 to 16 were
formed in a manner similar to that in Example 1, were then immersed
in a treatment bath filled with n-butyl alcohol for approximately
50 hours, and were then recovered from the treatment bath, whether
the metal layer and the ceramic layer were separated or not was
investigated. In this example, the firing temperature was set to
approximately 1,050.degree. C., 1,110.degree. C., 1,150.degree. C.,
and 1,180.degree. C.
[0105] Table 2 shows the status of separation at the individual
firing temperatures. In Table 2, o indicates the case in which the
ceramic layer and the metal layer are completely separated from
each other, and x indicates the case in which the ceramic layer
cannot be separated from the metal layer at all.
TABLE-US-00002 TABLE 2 Metal Film Sample Weight Firing Temperature
(.degree. C.) No. component Ratio Thickness 1,050 1,110 1,150 1,180
11 Pd -- 3.0 x .smallcircle. .smallcircle. .smallcircle. 12 Ag/Pd
70/30 3.0 x x -- -- 13 Ag/Pd 30/70 3.0 x -- -- -- 14 Pd -- 1.5 x x
x x 15 Ag/Pd 70/30 1.5 x -- -- -- 16 Ag/Pd 30/70 1.5 x -- -- --
[0106] As apparent from Table 2, in Sample No. 11, for the reason
similar to that of Sample No. 1 of Example 1, when the firing was
performed at a low temperature of about 1,050.degree. C., the
ceramic layer and the metal layer could not be separated from each
other; however, it was found that when the firing temperature was
about 1,110.degree. C. or more, the ceramic layer could be
completely separated from the metal layer.
[0107] In addition, in Sample Nos. 12 to 16, by the reasons similar
to those of Sample Nos. 2 to 6 of Example 1, the ceramic layer and
the metal layer could not be separated from each other.
EXAMPLE 3
[0108] A (Pb,La)TiO.sub.3-based piezoelectric ceramic powder was
formed by a method and a procedure similar to those of Example 1
using Pb.sub.3O.sub.4, TiO.sub.2, and La.sub.2O.sub.3 as ceramic
raw materials.
[0109] Subsequently, after metal films having a thickness of about
3.0 .mu.m were formed on surfaces of ceramic green sheets using a
Pd-based paste by a method and a procedure similar to those of
Example 1 to form laminates, a firing treatment was performed at a
firing temperature of about 1,110.degree. C., so that sintered
bodies were formed.
[0110] After the sintered bodies were immersed in a treatment bath
filled with n-butyl alcohol for approximately 50 hours and were
then recovered from the treatment bath, whether the metal layer and
the ceramic layer were separated or not was investigated, and it
was confirmed that the ceramic layer and the metal layer were
separated from each other.
EXAMPLE 4
[0111] Metal films were formed by applying a Pd paste on surfaces
of the ceramic green sheets formed in Example 1 so as to have
thicknesses as shown in Table 3. Subsequently, samples of Sample
Nos. 21 to 24 were obtained by a method and a procedure similar to
those of Example 1 except that the firing was performed at a
constant firing temperature of about 1,110.degree. C.
[0112] Next, the samples were immersed in n-butyl alcohol for
approximately 50 hours, and the separation properties between the
ceramic layer and the metal layer was investigated.
[0113] In addition, the cross-sections of the individual samples
were observed by an electron microscope, and whether the ceramic
layers were connected to each other through crosslinking was
investigated.
[0114] Table 3 shows the results of the above investigation.
TABLE-US-00003 TABLE 3 Sample Thickness of Metal Separation
Presence of No. Film (.mu.m) Status Crosslinking 21 1.3 .DELTA. Yes
22 1.9 .smallcircle. No 23 2.5 .smallcircle. No 24 3.7
.smallcircle. No
[0115] As apparent from Table 3, in Sample No. 21, since the metal
film had a small thickness of about 1.3 .mu.m, it was confirmed
that the ceramic layers were connected to each other and that
crosslinking was formed. Hence, the metal layer and the ceramic
layer could not be successfully separated from each other.
[0116] On the other hand, in Sample Nos. 22 to 24, since the metal
film had a large thickness of about 1.9 .mu.m to about 3.7 .mu.m,
the ceramic layers did not form crosslinking therebetween, and
hence the metal layer and the ceramic layer could be completely
separated.
[0117] Accordingly, in the case of the Pb-based piezoelectric
ceramic material, it was confirmed that when the thickness of the
metal film was about 1.9 .mu.m or more, good separation properties
could be obtained between the metal layer and the ceramic
layer.
EXAMPLE 5
[0118] After the ceramic green sheets, the Pd paste, and the first
Ag--Pd paste, which were formed in Example 1, were prepared, the Pd
paste or the first Ag--Pd paste was applied on surfaces of the
ceramic green sheets, so that the metal films or the electrode
films were formed on the ceramic green sheets.
[0119] Next, after the ceramic green sheets provided with the
electrode films and the ceramic green sheets provided with the
metal films were alternately laminated to each other to form a
laminate, a sintered body was obtained by a method and a procedure
similar to those of Example 1 except that the firing was performed
at a constant firing temperature of about 1,120.degree. C.
[0120] Subsequently, after the sintered body was immersed in a
treatment bath filled with n-butyl alcohol for approximately 50
hours, the separation properties between the ceramic layer and the
metal layer were investigated, and as a result, it was found that
separation occurred only between the metal film and the ceramic
layer, and that ceramic plates having a laminate structure composed
of the electrode layer and the ceramic layer tightly connected to
each other were obtained.
EXAMPLE 6
[0121] By applying a doctor blade method to a ceramic slurry
composed of a piezoelectric ceramic material having a composition
similar to that of Example 1, first ceramic green sheets having a
thickness of about 10 .mu.m and second ceramic green sheets having
a thickness of about 100 .mu.m were formed, and metal films having
a thickness of about 3 .mu.m were then formed on surfaces of the
first and the second ceramic green sheets.
[0122] Next, as shown in FIG. 10, first ceramic green sheets 30a to
30c provided with metal films 31a to 31c, respectively, were
sequentially laminated to each other, and on the topmost layer
thereof, a first ceramic green sheet 30d was laminated, followed by
pressure bonding, so that a first laminate was formed.
Subsequently, a first sintered body was obtained by a method and a
procedure similar to those of Example 1 except that the firing was
performed at a constant firing temperature of about 1,120.degree.
C.
[0123] In addition, as shown in FIG. 11, a second laminate was
formed in which the first ceramic green sheets 30a and 30b provided
with the metal films 31a and 31b, respectively, were sandwiched by
a second ceramic green sheet 32a provided with a metal film 33a and
a second ceramic green sheet 32b provided with no metal film, those
having a thickness larger than that of the first ceramic green
sheets 30a and 30b, and a firing treatment similar to that
described above was performed, thereby forming a second sintered
body.
[0124] Furthermore, as shown in FIG. 12, the first ceramic green
sheet 30a provided with the metal film 31a was sandwiched by the
second ceramic green sheets 32a and 32b provided with the metal
film 33a and a metal film 33b, respectively, and having a thickness
larger than that of the first ceramic green sheet 30a, and on the
topmost surface, the first ceramic green sheet 30b was laminated to
form a third laminate, followed by a firing treatment similar to
that described above, so that a third sintered body was
obtained.
[0125] Subsequently, the first to the third sintered bodies were
immersed in n-butyl alcohol for approximately 50 hours, and it was
confirmed that the ceramic layers and the metal layers were
completely separated from each other.
[0126] 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.
* * * * *