U.S. patent application number 11/240388 was filed with the patent office on 2006-03-02 for composite laminate and method for manufacturing the same.
This patent application is currently assigned to Murate Manufacturing Co., LTD.. Invention is credited to Hirokazu Kameda, Masaru Kojima, Shigeyuki Kuroda, Shuya Nakao, Kenji Tanaka.
Application Number | 20060046040 11/240388 |
Document ID | / |
Family ID | 17973422 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060046040 |
Kind Code |
A1 |
Kameda; Hirokazu ; et
al. |
March 2, 2006 |
Composite laminate and method for manufacturing the same
Abstract
A composite laminate includes first sheet layers and second
sheet layers. The first sheet layers include a first particulate
aggregate and the second sheet layers include a second particulate
aggregate. Each of internal second sheet layers is disposed between
two first sheet layers and two external second sheet layers
constitute two main faces of the composite laminate. The thickness
of the internal second sheet layers is greater than the thickness
of the external second sheet layers. The first sheet layers and the
second sheet layers are bonded to each other by penetration of a
part of the first particulate aggregate contained in the first
sheet layers into the second sheet layers. This configuration can
reduce the transverse shrinkage in the firing step of the composite
laminate.
Inventors: |
Kameda; Hirokazu;
(Kusatsu-shi, JP) ; Nakao; Shuya; (Yokaichi-shi,
JP) ; Kuroda; Shigeyuki; (Sabae-shi, JP) ;
Kojima; Masaru; (Hikone-shi, JP) ; Tanaka; Kenji;
(Shiga-ken, JP) |
Correspondence
Address: |
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
1177 AVENUE OF THE AMERICAS (6TH AVENUE)
41 ST FL.
NEW YORK
NY
10036-2714
US
|
Assignee: |
Murate Manufacturing Co.,
LTD.
|
Family ID: |
17973422 |
Appl. No.: |
11/240388 |
Filed: |
October 3, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10192594 |
Jul 11, 2002 |
|
|
|
11240388 |
Oct 3, 2005 |
|
|
|
09698394 |
Oct 27, 2000 |
6579392 |
|
|
10192594 |
Jul 11, 2002 |
|
|
|
Current U.S.
Class: |
428/212 ;
257/E23.009; 257/E23.062 |
Current CPC
Class: |
C04B 35/63 20130101;
C04B 2237/341 20130101; H01L 21/481 20130101; C04B 2237/68
20130101; H01L 2924/0002 20130101; C04B 37/042 20130101; C04B
2235/5445 20130101; C04B 2237/704 20130101; H01L 23/49822 20130101;
H05K 3/4629 20130101; Y10T 428/25 20150115; Y10T 428/249953
20150401; C04B 2235/9615 20130101; C04B 35/632 20130101; C04B
35/653 20130101; C04B 35/63456 20130101; C04B 35/111 20130101; C04B
2237/365 20130101; B32B 2315/08 20130101; H01L 21/4857 20130101;
C04B 35/6346 20130101; C04B 2237/525 20130101; Y10T 428/2495
20150115; C04B 35/6263 20130101; C04B 2237/30 20130101; C04B
35/63488 20130101; H01L 2924/09701 20130101; Y10T 428/2848
20150115; C04B 2237/36 20130101; H05K 1/0306 20130101; C04B
2235/6567 20130101; C04B 2237/343 20130101; H01L 2924/0002
20130101; C04B 2237/52 20130101; C04B 2235/656 20130101; Y10T
428/31504 20150401; C04B 2237/64 20130101; Y10T 428/252 20150115;
H01L 23/15 20130101; C04B 2237/345 20130101; B32B 18/00 20130101;
H05K 3/4688 20130101; Y10T 428/249994 20150401; Y10T 428/24942
20150115; H05K 2201/0195 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
428/212 |
International
Class: |
B32B 7/02 20060101
B32B007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 1999 |
JP |
11-307803 |
Claims
1. A composite laminate having two main external face layers and a
plurality of internal layers therebetween, comprising: at least two
first sheet layers each comprising a first particulate aggregate;
and at least three second sheet layers each comprising a second
particulate aggregate; wherein two of the second sheet layers
constitute the two main external faces of the composite laminate,
each internal second sheet layer is disposed between two first
sheet layers, the thickness of the internal second sheet layers is
greater than the thickness of the external second sheet layers, and
a part of the first particulate aggregate of the first sheet layers
penetrates into the second sheet layers and bonds the first sheet
layers to the second sheet layers.
2. A composite laminate according to claim 1, wherein the thickness
of the internal second sheet layers is about 1.75 to 2.67 times the
thickness of the external face second sheet layers.
3. A composite laminate according to claim 2, wherein each of the
first sheet layers have substantially the same thickness.
4. A composite laminate according to claim 3, wherein the first
particulate aggregate comprises powdered glass and the second
particulate aggregate comprises powdered ceramic.
5. A composite laminate according to claim 4, further comprising a
conductive film, whereby the first sheet layers, the second sheet
layers and the conductive film constitute a circuit board.
6. A composite laminate according to claim 5, further comprising a
cavity having an opening at least at one main face thereof.
Description
[0001] This is a division of application Ser. No. 10/192,594, filed
Jul. 11, 2002, which was a division of application Ser. No.
09/698,394, filed Oct. 27, 2000, now U.S. Pat. No. 6,579,392.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to composite laminates and to
methods for manufacturing the same. In particular, the present
invention relates to a composite laminate which shrinks less during
firing and to a method for manufacturing the same.
[0004] 2. Description of the Related Art
[0005] In recent years, there have been advances in the reduction
in size and weight of chip components. Reduction in size and weight
is also required for circuit boards for mounting the chip
components. Glass ceramic multilayered circuit boards are useful to
meet this need because the glass ceramic multilayered circuit
boards allow high-density wiring and reduction in thickness,
resulting in reduction in size and weight.
[0006] Glass ceramic multilayered circuit boards are generally
formed by a sintering process, and they shrink during sintering in
a direction perpendicular to the main faces of the boards
(longitudinal shrinkage) and in a direction parallel to the main
faces (transverse shrinkage). Thus, the current glass ceramic
multilayered circuit boards have dimensional variations of
approximately .A-inverted.0.5%. Glass ceramic multilayered circuit
boards having cavities for mounting necessary electronic components
exhibit noticeable variations.
[0007] Japanese Unexamined Patent Application Publication Nos.
5-102666 and 7-330445 disclose methods for making glass ceramic
multilayered circuit boards having high dimensional accuracy. Also,
Japanese Unexamined Patent Application Publication No. 6-329476
discloses a method for making a glass ceramic multilayered circuit
board having cavities. In each method, green sheets which cannot be
sintered at the sintering temperature of a glass ceramic compact
are laminated on one side or two sides of the glass ceramic
compact, and powdered layers of the green sheets are removed after
firing.
[0008] In such a process, an additional process is required to
remove the powdered layers. Moreover, it is difficult to
simultaneously fire conductive films, which are preliminarily
formed on an unsintered glass ceramic compact, in the firing
process. The resulting glass ceramic multilayered circuit board,
after removal of the powdered layers, may have a large degree of
surface roughness.
[0009] In a method disclosed in Japanese Unexamined Patent
Application Publication No. 9-266363, a laminate of glass ceramic
layers and alumina layers is fired to sinter only the glass ceramic
layers so that the glass component contained in the glass ceramic
layers penetrates unsintered alumina layers to bind the alumina
layers. The glass component in the glass ceramic layers, however,
does not penetrate the entity of the alumina layers in this method.
Therefore, unbounded portions of the alumina layers are removed and
the surfaces are polished before conductive films for circuit
patterns are formed.
[0010] Although the surface roughness is reduced by the removing
and polishing steps in this method, a removing step is required and
conductive films cannot be formed on surfaces of the circuit board
by simultaneous firing together with the glass ceramic layer.
[0011] In a method disclosed in Japanese Unexamined Patent
Application Publication No. 5-136572, green sheets which are not
sintered at a sintering temperature of a glass ceramic compact, are
stacked on one side or two sides of the glass ceramic compact so as
to sinter only the glass ceramic compact. Resin is loaded into
powdered layers of the unsintered green sheets. This method does
not require a step for removing the unsintered powdered layers, but
does require a step for loading the powder into the unsintered
powdered layers.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an object of the present invention to
provide a composite laminate exhibiting reduced transverse
shrinkage and high dimensional accuracy.
[0013] It is another object of the present invention to provide a
method for manufacturing the composite laminate which does not
require subsequent steps, such as a removing step and a
resin-loading step, after a firing step.
[0014] According to a first aspect of the present invention, a
composite laminate comprises first sheet layers including a first
particulate aggregate and second sheet layers including a second
particulate aggregate. Each internal second sheet layers is
disposed between two first sheet layers and two of the second sheet
layers are external constitute two main faces of the composite
laminate. The thickness of the internal second sheet layers is
greater than the thickness of the external second sheet layers. The
first sheet layers and the second sheet layers are bonded to each
other by penetration of a part of the first particulate aggregate
contained in the first sheet layers into the second sheet
layers.
[0015] Preferably, the thickness of the internal second sheet
layers is about 1.75 to 2.67 times the thickness of the external
second sheet layers.
[0016] Preferably, the first sheet layers have substantially the
same thickness.
[0017] Preferably, the first particulate aggregate contains glass
and the second particulate aggregate contains powdered ceramic.
[0018] The composite laminate may further comprises a conductive
film at one of the interior and the exterior thereof, wherein the
first sheet layers, the second sheet layers, and the conductive
film constitute a circuit board.
[0019] The composite laminate may further comprises a cavity having
an opening at least at one main face thereof.
[0020] According to a second aspect of the present invention, a
method for manufacturing a composite laminate comprises a first
step of preparing a green composite laminate including first green
sheet layers containing a first particulate aggregate and second
green sheet layers containing a second particulate aggregate
unsinterable at a temperature for melting at least a part of the
first particulate aggregate, wherein each second green sheet layer
is disposed between two first green sheet layers, two of the second
sheet layers constitute two main faces of the green composite
laminate, and the thickness of the second sheet layers laminated in
the interior of the green composite laminate is greater than the
thickness of the second sheet layers disposed on the main face of
the green composite laminate; and a second step of firing the green
composite laminate at a temperature capable of melting a part of
the first particulate aggregate and incapable of sintering the
second particulate aggregate so that the part of the first
particulate aggregate contained in the first green sheets is melted
and penetrates the second green sheet layers to bond the first
green sheet layers and the second sheet layers.
[0021] Preferably, the thickness of the second sheet layers
laminated in the interior of the green composite laminate is about
1.75 to 2.67 times the thickness of the second sheet layers on the
two main faces of the green composite laminate.
[0022] Preferably, the first step comprises a first sub-step of
forming each of the second green sheet layers on each of the first
green sheet layers to form a plurality of first green composite
stocks, a second sub-step of laminating the plurality of first
green composite stocks to form a plurality of second green
composite stocks so that the two first green sheets come into
contact with each other, and a third sub-step of laminating the
plurality of second green composite stocks so that the two second
green sheets come into contact with each other.
[0023] Alternatively, the first step comprises a first sub-step of
forming each of the first green sheet layers on each of the second
green sheet layers to form a plurality of first green composite
stocks, a second sub-step of laminating the plurality of first
green composite stocks to form a plurality of second green
composite stocks so that the two second green sheets come into
contact with each other, and a third sub-step of laminating the
plurality of second green composite stocks so that the two first
green sheets come into contact with each other.
[0024] Preferably, the thicknesses of the first green sheet layers
are substantially the same in the first step.
[0025] Preferably, the first particulate aggregate comprises glass
as a primary component and the second particulate aggregate
comprises powdered ceramic as a primary component.
[0026] According to a third aspect of the present invention, a
method for manufacturing a composite laminate comprises a first
step comprising the sub-steps of preparing a first particulate
aggregate, preparing a second particulate aggregate which is
unsinterable at a temperature for melting at least a part of the
first particulate aggregate, forming first green sheets containing
the first particulate aggregate, forming each of second green
sheets containing the second particulate aggregate on each of the
first green sheets to form a plurality of first green composite
stocks, and laminating the plurality of first green composite
stocks to form a green composite laminate so that the two adjacent
first green sheets form each of first green sheet layers and the
two adjacent second green sheets form each of second green sheet
layers; and a second step of firing the green composite laminate at
a temperature capable of melting a part of the first particulate
aggregate and incapable of sintering the second particulate
aggregate so that the part of the first particulate aggregate
contained in the first green sheet layers is melted and penetrates
the second green sheet layers to bond the first green sheet layers
and the second sheet layers.
[0027] Preferably, the first green sheet is resistant to a solvent
contained in a slurry which is used for forming the second green
sheet in the first step.
[0028] Preferably, the thicknesses of the first green sheet layers
are substantially the same in the first step.
[0029] Preferably, the first particulate aggregate comprises glass
as a primary component and the second particulate aggregate
comprises powdered ceramic as a primary component.
[0030] According to a fourth aspect of the present invention, a
method for manufacturing a composite laminate comprises a first
step comprising the sub-steps of preparing a first particulate
aggregate, preparing a second particulate aggregate which is
unsinterable at a temperature for melting at least a part of the
first particulate aggregate, forming second green sheets containing
the second particulate aggregate, forming each of first green
sheets containing the first particulate aggregate on each of the
second green sheets to form a plurality of first green composite
stocks, and laminating the plurality of first green composite
stocks to form a green composite laminate so that the two adjacent
first green sheets form each of first green sheet layers and the
two adjacent second green sheets form each of second green sheet
layers; and a second step of firing the green composite laminate at
a temperature capable of melting a part of the first particulate
aggregate and incapable of sintering the second particulate
aggregate so that the part of the first particulate aggregate
contained in the first green sheet layers is melted and penetrates
the second green sheet layers to bond the first green sheet layers
and the second sheet layers.
[0031] Preferably, the second green sheet is resistant to a solvent
contained in a slurry which is used for forming the first green
sheet in the first step.
[0032] Preferably, the thicknesses of the first green sheet layers
are substantially the same in the first step.
[0033] Preferably, the first particulate aggregate comprises glass
as a primary component and the second particulate aggregate
comprises powdered ceramic as a primary component.
[0034] The composite laminate of the present invention exhibits
reduced transverse shrinkage and high dimensional accuracy.
Moreover, the composite laminate after the firing step can be used
without additional steps, such as a removal step and a
resin-loading step.
[0035] When the first sheet layers have substantially the same
thickness, the first sheet layers have substantially the same
transverse shrinkage in the firing step, and the second sheet
layers suppress the transverse shrinkage. Thus, warping and
distortion due to transverse shrinkage are suppressed.
[0036] Since the method in accordance with the present invention
does not include the removal step of the second sheet layers and
the resin-loading step, conductive films formed on the composite
laminate and the composite laminate can be simultaneously
fired.
[0037] In particular, the transverse shrinkage and dimensional
variation readily occur in conventional composite laminates having
cavities. The composite laminate of the present invention, however,
exhibits reduced transverse shrinkage and dimensional variations
even when the composite laminate has a cavity due to the above
configuration.
[0038] The second particulate aggregate contained in the second
sheet layer may have any property, for example, insulating,
dielectric, piezoelectric or magnetic property. Thus, the resulting
composite laminate can exhibit a specific electromagnetic property.
An appropriate combination of these properties can produce, for
example, an L-C-R composite substrate. When a high-wear-resistance,
high-toughness second particulate aggregate is used, the composite
laminate can have high mechanical strength. When a light-reflective
or IR-reflective second particulate aggregate is used, the
composite laminate can have a specific optical function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a cross-sectional view of a composite laminate of
a first embodiment in accordance with the present invention;
[0040] FIG. 2 is a cross-sectional view of a composite laminate of
a second embodiment in accordance with the present invention;
[0041] FIG. 3 is a cross-sectional view of a composite laminate of
a third embodiment in accordance with the present invention;
[0042] FIG. 4 is a cross-sectional view of a composite laminate of
a fourth embodiment in accordance with the present invention;
[0043] FIGS. 5A to 5D are cross-sectional views for illustrating a
method for manufacturing the composite laminate of the first
embodiment of the present invention;
[0044] FIGS. 6A to 6C are cross-sectional views for illustrating a
method for manufacturing the composite laminate of the third
embodiment of the present invention; and
[0045] FIG. 7 is a cross-sectional view for illustrating a method
for manufacturing the composite laminate of the fourth embodiment
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] The composite laminate in accordance with the present
invention may have a variety of preferred embodiments. Four typical
embodiments will be described with reference to FIGS. 1 to 4. In
the embodiment shown in each of FIGS. 1 to 4, the composite
laminate includes first sheet layers 2, each composed of a first
particulate aggregate, and second sheet layers 3a and 3b, each
composed of a second particulate aggregate.
[0047] With reference to FIG. 1, a composite laminate 1 includes
the first sheet layers 2, each composed of the first particulate
aggregate, and the second sheet layers 3a and 3b, each composed of
the second particulate aggregate. The first sheet layers 2 and the
second sheet layers 3a are alternately stacked and the second sheet
layers 3b are stacked on the outer faces of the outermost first
sheet layers 2 to form two main faces of the composite laminate 1.
In this embodiment, the thickness A of the second sheet layers 3a
is greater than the thickness B of the second sheet layers 3b. The
thicknesses C1 to C4 of the second sheet layers 3b are preferably
greater than the thickness A of the second sheet layers 3a.
Moreover, the thicknesses C1 to C4 of the second sheet layers 3b
are preferably identical.
[0048] With reference to FIG. 2, a composite laminate 11 includes
the composite laminate 1 shown in FIG. 1 and conductive films 4
provided on both main faces thereof. The conductive films 4 are
formed by a screen printing process using an Ag paste and have
predetermined patterns. The Ag paste may be replaced with, for
example, an Ag-Pd paste, an Ag-Pt paste, a Cu paste or a Ni
paste.
[0049] With reference to FIG. 3, a composite laminate 21 includes
first sheet layers 2 and second sheet layers 3a and 3b. Each first
sheet layer 2 includes a conductive film 5 therein. Each conductive
film 5 has a predetermined pattern.
[0050] With reference to FIG. 4, a composite laminate 31 includes a
cavity 6 having an opening at one main face thereof. The cavity 6
has a predetermined depth and predetermined transverse dimensions.
Moreover, the composite laminate 31 includes conductive films 4, as
in the composite laminate 11.
[0051] In the composite laminates 1, 11, 21 and 31, it is
preferable that the first particulate aggregate in the first sheet
layers 2 partly penetrates the entity of the second sheet layers 3a
and 3b so that the second particles are completely bounded by the
first sheet layer material. The thicknesses of the second sheet
layers 3a and 3b are preferably lower than the thicknesses of the
first sheet layers 2 to ensure penetration of the first sheet layer
material.
[0052] The thicknesses of the second sheet layers 3a stacked in the
composite laminates 1, 11, 21 and 31 are greater than the
thicknesses of the second sheet layers 3b stacked on the main faces
of the composite laminates 1, 11, 21 and 31. If the thicknesses of
the second sheet layers 3a are less, the composite laminates 1, 11,
21 and 31 will shrink transversely in the vicinity of the center
thereof. When the thicknesses of the second sheet layers 3a stacked
in the interior are sufficiently great, warping and distortion due
to transverse shrinkage are suppressed. In such a case, however,
the first particulate aggregate does not penetrate the entity of
the second sheet layers 3a and 3b, reducing bonding force between
sheets. When the thicknesses of the second sheet layers 3a and 3b
are excessively great, the firing temperature must be increased in
order to yield a dense glass ceramic compact. The thicknesses of
the second sheet layers 3a stacked in the interior of the composite
laminates 1, 11, 21 and 31 are preferably about 1.75 times to 2.67
times or more, preferably about 2.0 times, greater than the
thicknesses of the second sheet layers 3b.
[0053] Preferably, in the composite laminates 1, 11, 21 and 31, the
first sheet layers 2 have substantially the same thickness. In such
a case, the first sheet layers 2 exhibits substantially the same
thermal shrinkage in the firing step while the second sheet layers
3a and 3b suppresses the transverse shrinkage of the first sheet
layers 2, resulting in suppressed warping and distortion due to
longitudinal and transverse shrinkage of the sintered composite
laminates 1, 11, 21 and 31.
[0054] It is preferable that the first particulate aggregate in the
first sheet layers 2 include glass and the second particulate
aggregate in the second sheet layers 3a and 3b include ceramic
powder. The glass in the first sheet layers 2 penetrates the second
sheet layers 3a and 3b to make the second sheet layers 3a and 3b
more dense.
[0055] In the composite laminates 11, 21 and 31 provided with the
conductive films 4 and/or 5, these conductive films 4 and/or 5 are
formed by applying a powdered metal paste on the main and/or
internal faces of the green composite, and then by sintering the
paste in the firing step of the green composite.
[0056] In FIG. 2, the conductive films 4 are provided on the two
main faces of the composite laminate 11. Alternatively, a
conductive film 4 may be formed on only one main face of the
composite laminate 11. The position of the conductive film 4 is
also not limited. In FIG. 3, the positions and number of the
conductive films 5 provided in the interior of the composite
laminate 21 are not limited. In FIG. 4, the positions and the
number of the conductive films 4 and 5 may be changed in the
composite laminate 31 having the cavity 6. Alternatively, the
conductive films 4 and 5 may be omitted in the composite laminate
31. These composites may have through holes and/or via holes for
electrically connecting conductive films formed on different
layers.
[0057] Methods for manufacturing the composite laminates in
accordance with the present invention will now be described with
reference to FIGS. 5A to 5D, 6A to 6C, and 7, for the composite
laminates 1, 21 and 31 shown in FIGS. 1, 3 and 4, respectively.
[0058] The method for manufacturing the composite laminate 1 shown
in FIG. 1 is described with reference to FIGS. 5A to 5D. A green
sheet is formed using a slurry containing a second particulate
aggregate, and another sheet is formed on the green sheet using a
slurry containing a first particulate aggregate. The laminated
sheet is cut into a predetermined size to form first green
composite stocks 1a, each including a second green sheet 13b
containing the second particulate aggregate and a first green sheet
12a containing the first particulate aggregate on the second green
sheet 13b, as shown in FIG. 5A.
[0059] With reference to FIG. 5B, two first green composite stocks
1a are laminated to form a second green composite stock 1b so that
the first green sheets 12a are bonded to each other by pressure.
The bonded first green sheets 12a are combined to form a first
green sheet layer 12.
[0060] With reference to FIG. 5C, two second green composite stocks
1b are laminated to form a green composite unit 1c so that the
second green sheets 13b are bonded to each other by pressure. The
bonded second green sheets 13b are combined to form a second green
sheet layer 13a.
[0061] With reference to FIG. 5D, two green composite units 1c are
laminated to form a green composite laminate so that the second
green sheets 13b are bonded to each other by pressure. The green
composite laminate is fired to form the composite laminate 1 shown
in FIG. 1.
[0062] The method for manufacturing the composite laminate 21 shown
in FIG. 3 is described with reference to FIGS. 6A to 6C. Components
having the same functions as in FIGS. 5A to 5D are referred to with
the same reference numerals, and a detailed description thereof
with reference to drawings is omitted.
[0063] With reference to FIG. 6A, a conductive film 15 is formed on
the first green sheet 12a of the first green composite stock 1a
shown in FIG. 5A to form a first green composite stock 21a. Since
the conductive film 15 has a predetermined pattern, the first green
sheet 12a may be partly exposed on one main face of the first green
composite stock 21a.
[0064] With reference to FIG. 6B, another first green composite
stock 1a and the first green composite stock 21a are laminated to
form a second green composite stock 21b so that the two first green
sheets 12a are bonded to each other via the conductive film 15 by
pressure. The two first green sheets 12a are combined to form a
first green sheet layer 12 including the conductive film 15.
[0065] With reference to FIG. 6C, the two second green composite
stocks 21b are laminated to form a green composite unit 21c so that
the second green sheets 13b are bonded to each other by pressure.
The two second green sheets 13b are combined to form a second green
sheet layer 13a.
[0066] Two green composite units 21c are laminated to form a green
composite laminate so that the two second green sheets 13b are
bonded to each other by pressure. The green composite laminate is
fired to form the composite laminate 21 shown in FIG. 3.
[0067] The method for manufacturing the composite laminate 31 is
described with reference to FIG. 7. Components having the same
functions as in FIGS. 5A to 5D and 6A to 6C are referred to with
the same reference numerals, and a detailed description thereof
with reference to drawings is omitted.
[0068] A green composite unit 21c shown in FIG. 6C is prepared. A
conductive film 14 is formed by printing on one main face of the
green composite unit 21c using a conductive paste. A cavity 16
having an opening at the main face provided with the conductive
film 14 is formed by punching to form a green composite unit
31a.
[0069] The green composite unit 31a and a green composite unit 21c
shown in FIG. 6C are laminated to form a green composite laminate
so that two second green sheets 13b are bonded to each other by
pressure. The green composite laminate is fired to form the
composite laminate 31 shown in FIG. 4.
[0070] In FIGS. 5A and 6A, the first green sheets 12a are formed on
the second green sheets 13b to form the first green composite
stocks 1a and 21a. Alternatively, the second green sheets 13b may
be formed on the first green sheets 12a.
[0071] The first green sheet 12a and the second green sheet 13b may
be formed by a doctor blade process, a gravure process, a dipping
process, a spray process, a rolling process, a thin-film forming
process or a powder compression process.
[0072] When a second sheet is formed on a first sheet, it is
preferable that the first sheet be resistant to the solvent which
is used in the slurry for forming the second sheet. For example,
when the first green sheet 12a is formed on the second green sheet
13b, the second green sheet 13b is resistant to the solvent which
is used in the slurry for forming the first green sheet 12a. If the
first sheet is not resistant to the solvent, the first sheet will
dissolve in the solvent contained in the second sheet, and the
second sheet will not be satisfactorily laminated.
[0073] In the methods shown in FIGS. 5A to 5D and 6A to 6C, the
conductive film 5 is formed on the first green sheet 12a. However,
the position and the shape of the conductive film 15 are not
limited to the above embodiments. For example, the conductive film
may be formed on the second green sheet 13b of the first green
composite stock 1a shown in FIG. 5A.
[0074] The composite laminates are schematically shown in FIGS. 1
to 4. Since the first particulate aggregate contained in the green
first sheet layer 2 partly penetrates the second sheet layers 3a
and 3b during firing, the boundaries between the first sheet layer
2 and the second sheet layers 3a and 3b may not be always as
distinct as illustrated in FIGS. 1 to 4.
EXAMPLES
[0075] Seven composite laminates 1 were prepared as follows to
measure transverse shrinkage factors, in which the second sheet
layers 3a laminated in the interior of the composite laminates 1
and the second sheet layers 3b formed on the main faces of the
composite laminates 1 had different thicknesses.
[0076] A second slurry including a second particulate aggregate was
prepared by mixing and dispersing 100 parts by weight of alumina
powder having a particle diameter of 0.5 .mu.m as second particles,
45 parts by weight of water as a dispersant, 50 parts by weight of
polyalkylene glycol as another dispersant, and 15 parts by weight
of urethane resin emulsion as a binder. The second slurry may
contain plasticizers, defoamers and tackifiers.
[0077] After defoaming, the second slurry was applied and dried
onto a polyethylene terephthalate (PET) film by a gravure process
to form green sheets as second green sheets, each having a
thickness of 1.0 .mu.m, 1.5 .mu.m, 2.0 .mu.m or 4.0 .mu.m. The
urethane resin emulsion was converted into water-insoluble gel
during the drying step. Thus, these green sheets were resistant to
an aqueous slurry.
[0078] A first slurry including a first particulate aggregate was
prepared by mixing and dispersing 60 parts by weight of
B--Si--Ca--Al--O-based glass having a diameter of 3.0 .mu.m as
first particles, 40 parts by weight of alumina powder having a
diameter of 0.5 .mu.m also as first particles, 36 parts by weight
of water as a dispersant, 1 part by weight of polyalkylene glycol
as another dispersant, and 12 parts by weight of urethane resin
emulsion as a binder. The first slurry may contain plasticizers,
defoamers and tackifiers.
[0079] The first slurry was applied onto one main face of each
green sheet as the second green sheet to form a green sheet having
a thickness of 75 .mu.m as a first green sheet. First green
composites were thereby prepared.
[0080] The two first green composites were laminated at 60.degree.
C. and 2,000 kgf/cm.sup.2 to form a second green composite so that
the first green sheets were bonded to each other. In this step,
these two first green sheets having a thickness of 75 .mu.m were
combined by pressure to form a first green sheet layer having a
thickness of 140 .mu.m.
[0081] Three second green composites were laminated at 60.degree.
C. and 100 kgf/cm.sup.2 so that the second green sheets were bonded
to each other by pressure. The composite was cut into a square of
100 mm.times.100 mm to form a green composite laminate. In this
step, the adjacent two second green sheets were combined to form a
second green sheet layer.
[0082] When the second green sheet layers, which were laminated in
the interior of the composite laminate, had a thickness of 2.0
.mu.m, two second green sheets having a thickness of 1.0 .mu.m were
combined. When the second green sheet layers had a thickness of 3.0
.mu.m, two second green sheets having a thickness of 1.5 .mu.m were
combined. When the second green sheet layers had a thickness of 3.5
.mu.m, a second green sheets having a thickness of 1.5 .mu.m and a
second green sheets having a thickness of 2.0 .mu.m were combined.
When the second green sheet layers had a thickness of 4.0 .mu.m,
two second green sheets having a thickness of 2.0 .mu.m were
combined.
[0083] For comparison, a laminate (sample No. 8) having a thickness
of 420 .mu.m was formed by preparing six green sheets, each having
a thickness of 75 .mu.m, using the first slurry, laminating the six
green sheets at 60.degree. C. under a pressure of 100 kgf/cm.sup.2,
and cutting the laminate into a square of 100 mm.times.100 mm.
[0084] The resulting green composite laminates (sample Nos. 1 to 7)
and the green laminate (sample No. 8) were fired at a temperature
in a range of 700.degree. C. to 1,000.degree. C., for example, at
850.degree. C. for 2 hours in air to form composite laminates
(sample Nos. 1 to 7) and a laminate (sample No. 8). In sample Nos.
1 to 7, the alumina particles contained in the first particulate
aggregate and the second particulate aggregate were not sintered
during the firing step, whereas the glass powder contained in the
first particulate aggregate was melted and penetrated the second
sheet layers from the first sheet layers. After cooling, the melt
glass was solidified to bind the first sheet layers and the second
sheet layers.
[0085] In sample Nos. 1 to 7, the thickness of the second sheet
layers formed in the interior of the composite laminate (referred
to as "internal layers" in Table 1), the thickness of the second
sheet layer formed on the main face (referred to as "external
layers" in Table 1), and the transverse shrinkage factor were
measured. In sample No. 8, the transverse shrinkage factor was
measured. The results are summarized in Table 1.
[0086] In the column "Evaluation", A indicates that the sample has
a small transverse shrinkage factor and high dimensional accuracy,
B indicates that the sample has a small transverse shrinkage factor
and average dimensional accuracy, and C indicates that the sample
has a large transverse shrinkage factor and poor dimensional
accuracy.
[0087] In sample Nos. 1 to 7, the second sheet layers are provided
in order to suppress the longitudinal shrinkage. The thickness of
the first green sheet layer decreases from 140 .mu.m to 100 .mu.m
by longitudinal shrinkage during firing. The total thicknesses of
the composite laminates in sample Nos. 1 to 7 and the laminate in
sample No. 8 are shown in Table 1. The green second sheet layer
does not substantially shrink longitudinally during firing.
TABLE-US-00001 TABLE 1 Thickness of Second Sheet Total Thickness of
Composite Layers (.mu.m) Ratio of Internal Transverse Laminate
(.mu.m) External Internal Layer to External Firing Shrinkage Sample
Before Firing After Firing Layers Layers Layer Temperature
(.degree. C.) Factor (%) Eval 1 420 300 2.0 4.0 2.00 850 0.3 2 420
310 2.0 2.0 1.00 850 2.3 3 420 300 4.0 4.0 1.00 900 0.3 4 420 305
2.0 3.0 1.50 850 1.4 5 420 300 2.0 3.5 1.75 850 0.5 6 420 305 1.0
4.0 4.00 850 1.1 7 420 300 1.5 4.0 2.67 850 0.4 8 420 375 -- -- --
850 11.0
[0088] Notes: Firing temperature in Table 1 indicates a minimum
temperature for facilitating penetration of glass into the second
sheet layer and for forming a dense laminate.
[0089] The second sheet layer does not transversely shrink during
firing and the thickness thereof does not vary by firing.
[0090] As shown in Table 1, each of sample Nos. 1, 4, 5, 6 and 7
has a ratio of the thickness of the internal second sheet layer to
the thickness of the external second sheet layer of 1.0 or more,
can be sintered at 850.degree. C., and exhibits a small transverse
shrinkage factor within a range of 0.3% to 1.4%. In contrast,
sample No. 8 exhibits a transverse shrinkage factor as high as
11.0%.
[0091] In particular, each of sample Nos. 1, 5 and 7 has a ratio in
a range of 1.75 to 2.67, can be sintered at 850.degree. C., and
exhibits a particularly small transverse shrinkage factor within a
range of 0.3% to 0.5%. These composites, therefore, show high
dimensional accuracy.
[0092] Sample No. 2, which can be sintered at 850.degree. C.,
exhibits a transverse shrinkage factor of 2.3%, which is two times
that of sample No. 4. This composite does not show satisfactory
dimensional accuracy.
[0093] Sample No. 3, which exhibits a small transverse shrinkage
factor of 0.3%, cannot be sintered at 850.degree. C. and must be
sintered at 900.degree. C.
[0094] The first particulate aggregate contained in the first sheet
layer and the second particulate aggregate contained in the second
sheet layer may be particulate aggregates of MgO, ZrO.sub.2,
SiO.sub.2, TiO.sub.2, BaTiO.sub.3, SrTiO.sub.3, MgO.sub.3,
Fe.sub.2O.sub.3, RuO, (Zr,Ti)O.sub.3, B.sub.4C, SiC and/or WC.
* * * * *