U.S. patent application number 10/325859 was filed with the patent office on 2003-09-11 for dielectric material and dielectric sintered body, and wiring board using the same.
This patent application is currently assigned to NGK SPARK PLUG CO., LTD.. Invention is credited to Mizutani, Hidetoshi, Sakai, Tsutomu, Sato, Manabu, Sumi, Hiroshi, Suzumura, Masashi.
Application Number | 20030170436 10/325859 |
Document ID | / |
Family ID | 26625228 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030170436 |
Kind Code |
A1 |
Sumi, Hiroshi ; et
al. |
September 11, 2003 |
Dielectric material and dielectric sintered body, and wiring board
using the same
Abstract
A dielectric material comprising: a glass powder constituted of
a glass comprising Si, B and an alkali metal element, the glass
being amorphous in sintering at a temperature of 1,050.degree. C.
or lower; and a ceramic filler comprising at least one member of
SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2Si.sub.2, and an
alkali metal element, wherein when a total sum of Si converted into
SiO.sub.2, B converted into B.sub.2O.sub.3 and the alkali metal
element converted into A.sub.2O, wherein A represents an alkali
metal element, all of which are contained in the glass, is 100 mole
%, the content of the alkali metal element converted into A.sub.2O,
which is contained in the glass, is 0.5 mole % or less; and when a
total sum of at least one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2, and the alkali metal element converted
into A.sub.2O, all of which are contained in the ceramic filler, is
100 mole %, a content of the alkali metal element converted into
A.sub.2O, which is contained in the ceramic filler, is 0.5 mole %
or less.
Inventors: |
Sumi, Hiroshi; (Niwa-gun,
JP) ; Suzumura, Masashi; (Kani-shi, JP) ;
Sakai, Tsutomu; (kasugai-shi, JP) ; Mizutani,
Hidetoshi; (Ama-gun, JP) ; Sato, Manabu;
(Nagoya-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
NGK SPARK PLUG CO., LTD.
|
Family ID: |
26625228 |
Appl. No.: |
10/325859 |
Filed: |
December 23, 2002 |
Current U.S.
Class: |
428/210 ;
257/E23.077; 501/49; 501/52 |
Current CPC
Class: |
H01L 23/49894 20130101;
C03C 14/004 20130101; C03C 8/14 20130101; H05K 1/162 20130101; C03C
2214/04 20130101; C03C 2214/30 20130101; H01L 2924/09701 20130101;
H05K 1/0306 20130101; Y10T 428/24926 20150115; H05K 3/4676
20130101; H01L 2924/0002 20130101; H05K 3/4629 20130101; H01L
2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
428/210 ; 501/49;
501/52 |
International
Class: |
B32B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2001 |
JP |
P. 2001-390735 |
Apr 11, 2002 |
JP |
P. 2002-109646 |
Claims
What is claimed is:
1. A dielectric material comprising: a glass powder constituted of
a glass comprising Si, B and an alkali metal element, the glass
being amorphous in sintering at a temperature of 1,050.degree. C.
or lower; and a ceramic filler comprising at least one member of
SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, and an
alkali metal element, wherein when a total sum of Si converted into
SiO.sub.2, B converted into B.sub.2O.sub.3 and the alkali metal
element converted into A.sub.2O, wherein A represents an alkali
metal element, all of which are contained in the glass, is 100 mole
%, the content of the alkali metal element converted into A.sub.2O,
which is contained in the glass, is 0.5 mole % or less; and when a
total sum of at least one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2, and the alkali metal element converted
into A.sub.2O, all of which are contained in the ceramic filler, is
100 mole %, a content of the alkali metal element converted into
A.sub.2O, which is contained in the ceramic filler, is 0.5 mole %
or less.
2. A dielectric material comprising: a glass powder constituted of
a glass comprising Si, B and an alkali metal element, the glass
being amorphous in sintering at a temperature of 1,050.degree. C.
or lower; and a ceramic filler comprising at least one member of
SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2 but not
comprising an alkali metal element, wherein when a total sum of Si
converted into SiO.sub.2, B converted into B.sub.2O. and the alkali
metal element converted into A.sub.2O, wherein A represents an
alkali metal element, all of which are contained in the glass, is
100 mole %, a content of the alkali metal element converted into
A.sub.2O, which is contained in the glass, is 0.5 mole % or
less.
3. The dielectric material according to claim 1, wherein the glass
further comprises at least one of Al and an alkaline earth metal
element, and when a total sum of Si converted into SiO.sub.2, B
converted into B.sub.2O.sub.3, the alkali metal element converted
into A.sub.2O, wherein A represents an alkali metal element, Al
converted into Al.sub.2O.sub.3 in a case where Al is contained, and
the alkaline earth metal element converted into EO, wherein E
represents an alkaline earth metal element, in a case where the
alkaline earth metal element is contained, is 100 mole %, a total
sum of Si converted into SiO.sub.2 and B converted into
B.sub.2O.sub.3 is from 80 to 95 mole %.
4. The dielectric material according to claim 2, wherein the glass
further comprises at least one of Al and an alkaline earth metal
element, and when a total sum of Si converted into SiO.sub.2, B
converted into B.sub.2O.sub.3, the alkali metal element converted
into A.sub.2O, wherein A represents an alkali metal element, Al
converted into Al.sub.2O.sub.3 in a case where Al is contained, and
the alkaline earth metal element converted into EO, wherein E
represents an alkaline earth metal element, in a case where the
alkaline earth metal element is contained, is 100 mole %, a total
sum of Si converted into SiO.sub.2 and B converted into
B.sub.2O.sub.3 is from 80 to 95 mole %.
5. The dielectric material according to claim 1, wherein the
ceramic filler does not comprise an alkaline earth metal
element.
6. The dielectric material according to claim 2, wherein the
ceramic filler does not comprise an alkaline earth metal
element.
7. The dielectric material according to claim 1, wherein the
ceramic filler further comprises an alkaline earth metal element,
and when a total sum of at least one member of SiO.sub.2,
Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, the alkali metal
element converted into A.sub.2O, in a case where the alkali metal
element is contained, and the alkaline earth metal element
converted into EO, wherein E represents an alkaline earth metal
element, all of which are contained in the ceramic filler, is 100
mole %, a content of the alkaline earth metal element converted
into EO is 1 mole % or less.
8. The dielectric material according to claim 2, wherein the
ceramic filler further comprises an alkaline earth metal element,
and when a total sum of at least one member of SiO.sub.2,
Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, the alkali metal
element converted into A.sub.2O, in a case where the alkali metal
element is contained, and the alkaline earth metal element
converted into EO, wherein E represents an alkaline earth metal
element, all of which are contained in the ceramic filler, is 100
mole %, a content of the alkaline earth metal element converted
into EO is 1 mole % or less.
9. The dielectric material according to claim 1, wherein when a
total sum of the glass powder and the ceramic filler is 100% by
volume, the glass powder accounts for from 55 to 70% by volume, and
the ceramic filler accounts for from 30 to 45% by volume.
10. The dielectric material according to claim 2, wherein when a
total sum of the glass powder and the ceramic filler is 100% by
volume, the glass powder accounts for from 55 to 70% by volume, and
the ceramic filler accounts for from 30 to 45% by volume.
11. A dielectric sintered body obtained by sintering the dielectric
material according to claim 1 at 800 to 1,050.degree. C., wherein
when a total sum of Si converted into SiO.sub.2, B converted into
B.sub.2O.sub.3, the alkali metal element converted into A.sub.2O,
wherein A represents an alkali metal element, Al converted into
Al.sub.2O.sub.3 in a case where Al is contained, and the alkaline
earth metal element converted into EO, wherein E represents an
alkaline earth metal element, in a case where the alkaline earth
metal element is contained, all of which are contained in the
glass, and at least one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2, the alkali metal element converted
into A.sub.2O, in a case where the alkali metal element is
contained, and the alkaline earth metal element converted into EO,
wherein E represents an alkaline earth metal element, in a case
where the alkaline earth metal element is contained, all of which
are contained in the ceramic filler, is 100 mole %, a content of
the alkali metal element converted into A.sub.2O is 0.5 mole % or
less.
12. A dielectric sintered body obtained by sintering the dielectric
material according to claim 2 at 800 to 1,050.degree. C., wherein
when a total sum of Si converted into SiO.sub.2, B converted into
B.sub.2O.sub.3, the alkali metal element converted into A.sub.2O,
wherein A represents an alkali metal element, Al converted into
Al.sub.2O.sub.3 in a case where Al is contained, and the alkaline
earth metal element converted into EO, wherein E represents an
alkaline earth metal element, in a case where the alkaline earth
metal element is contained, all of which are contained in the
glass, and at least one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2, the alkali metal element converted
into A.sub.2O, in a case where the alkali metal element is
contained, and the alkaline earth metal element converted into EO,
wherein E represents an alkaline earth metal element, in a case
where the alkaline earth metal element is contained, all of which
are contained in the ceramic filler, is 100 mole %, a content of
the alkali metal element converted into A.sub.2O is 0.5 mole % or
less.
13. A wiring board comprising: a dielectric layer comprising the
dielectric sintered body according to claim 11; and a conductor
layer provided at least one of on a surface of and inside of the
dielectric layer, the conductor layer comprising at least one
member selected from Ag, Au and Cu.
14. A wiring board comprising: a dielectric layer comprising the
dielectric sintered body according to claim 12; and a conductor
layer provided at least one of on a surface of and inside of the
dielectric layer, the conductor layer comprising at least one
member selected from Ag, Au and Cu.
15. A multilayered wiring board comprising: a dielectric layer
comprising a glass having a crystallization temperature exceeding
1,000.degree. C. and a ceramic filler; and a conductor layer
comprising a metal conductor, wherein a part of the conductor layer
is an entire electrode conductor layer having a forming area of 1
cm.sup.2 or more.
16. The multilayered wiring board according to claim 15, wherein
the entire electrode conductor layer is at least one of an ground
electrode and a capacitor electrode.
17. The multilayered wiring board according to claim 15, wherein
the dielectric layer has a specific dielectric constant of 7 or
less and a dielectric loss of 0.002 or less in a high-frequency
band of 10 GHz or more.
18. The multilayered wiring board according to claim 15, wherein
the glass comprises SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3 and
an alkaline earth metal oxide, in which a content of a sum of
SiO.sub.2 and B.sub.2O.sub.3 is from 80 to 95 mole %, and a crystal
phase caused by a crystallization of the glass does not exist in
the dielectric layer.
19. The multilayered wiring board according to claim 15, wherein
the glass consists essentially of SiO.sub.2, B.sub.2O.sub.3,
Al.sub.2O.sub.3 and an alkaline earth metal oxide, in which a
content of a sum of SiO.sub.2 and B.sub.2O.sub.3 is from 80 to 95
mole %, and a crystal phase caused by a crystallization of the
glass does not exist in the dielectric layer.
20. A process for producing a multilayered wiring board, which
comprises: sintering a multilayered wiring molding comprising a
green material comprising a glass having a crystallization
temperature exceeding 1,000.degree. C. and a ceramic filler and a
conductor layer comprising a metal conductor, a part of the
conductor layer being an entire electrode conductor layer having a
forming area of 1 cm.sup.2 or more, at a temperature lower than the
crystallization temperature of the glass to form a multilayered
wiring board.
21. The process according to claim 20, wherein the glass comprises
SiO.sub.2 and B.sub.2O.sub.3, Al.sub.2O.sub.3 and an alkaline earth
metal oxide, in which a content of a sum of SiO.sub.2 and
B.sub.2O.sub.3 is from 80 to 95 mole %.
22. The multilayered wiring board according to claim 15, further
comprising the dielectric sintered body according to claim 11,
wherein the conductor layer is provided at least one of: on a
surface of; and inside of the dielectric layer, the conductor layer
comprising at least one member selected from Ag, Au and Cu.
23. The multilayered wiring board according to claim 15, further
comprising the dielectric sintered body according to claim 12,
wherein the conductor layer is provided at least one of: on a
surface of; and inside of the dielectric layer, the conductor layer
comprising at least one member selected from Ag, Au and Cu.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a dielectric material and a
dielectric sintered body, and to a wiring board using the same.
More specifically, the invention relates to a dielectric material
that can be sintered simultaneously with a conductor comprising a
low-melting material such as Ag and Cu as a wiring board material
and to a dielectric sintered body obtained by sintering the same.
Particularly, the invention relates to a dielectric material having
a low dielectric constant and superior high-frequency
characteristics and having a wide width in optimum sintering
conditions and to a dielectric sintered body obtained by sintering
the same. In addition, the invention relates to a wiring board
using this dielectric sintering body as a dielectric layer, which
is suited for circuits having a high processing speed and
high-frequency circuits. The wiring board according to the
invention is widely used in high-frequency utilities such as
packages for high-frequency MPU and packages of optical
communication.
[0002] In addition, the present invention also relates to a
multilayered wiring board comprising a dielectric layer and a
conductor layer, a part of the conductor layer being an entire
electrode conductor layer having a forming area of 1 cm.sup.2 or
more, and a process of producing the same. In particular, the
invention relates to a multilayered wiring board in which an entire
electrode conductor layer is an ground electrode and/or a capacitor
electrode and which is suitable for high-frequency applications
having a strip line or micro-strip line.
BACKGROUND OF THE INVENTION
[0003] In recent years, in many cases, wiring boards are used in
high-frequency regions having a frequency band in the order of GHz
or more, with an increase in speed of information communication.
Thus, in order to reduce a transfer loss of electric signals, the
wiring boards are desired to use a metal having low conductor
resistance, such as Ag and Cu, as a conductor layer thereof,
thereby reducing a conductor loss. For this reason, low
temperature-sintering materials that can be sintered simultaneously
with a low-melting metal such as Ag and Cu and that have superior
high-frequency dielectric characteristics are being compared and
investigated.
[0004] Now, there are known crystallized glasses as a low
temperature-sintering material having superior high-frequency
characteristics, in which crystals having superior high-frequency
characteristics crystallize during the sintering step.
[0005] As these crystallized glasses, there are, for example, known
(1) crystallized glass of a spinel type crystal (for example,
JP-A-9-175853 (The term "JP-A" as used herein means an "unexamined
published Japanese patent application")), (2) crystallized glass of
diopside (for example, JP-A-10-120436), and (3) crystallized glass
of alumina and anorthite (for example, JP-A-2000-143332).
[0006] In addition, multilayered wiring boards that can realize
relatively high-density wiring are widely used as wiring boards
mounted with a semiconductor element such as LSI, IC, and discrete
parts, or having a varied thick-film printing element incorporated
therein. Most of these multilayered wiring boards are an alternate
laminate of a dielectric layer comprising a glass ceramic and a
conductor layer mainly composed of a metal conductor such as Cu,
Ag, Au, W, and Mo, and if desired, a semiconductor element is
mounted on the surface thereof.
[0007] Further, in recent years, in radiocommunication including
portable telephone, in order to enlarge the radio resource and
realize high density of the transmission volume, there have been
positively employed high-frequency bands from micro-wave bands to
millimeter wave bands. As parts for radiocommunication instruments
to be used, demands of multilayered wiring boards for dealing with
high-frequency signals are explosively increasing.
[0008] In the case of dealing with the high-frequency signals,
since a conductor layer connecting a working electric source of an
electronic part to the electronic part contributes as an
inductance, there may possibly occur inconveniences that are not
problematic in low-frequency signals, such as generation of
malfunction caused by superimposition of noises on wirings in the
conductor layer, delay of operation response of electronic parts,
and transmission loss of high-frequency signals. In order to
inhibit such inconveniences inherent to the high-frequency signals,
it is required to use multilayered wiring boards in which the
conductor layer is constituted of a low-resistivity material,
whereas the dielectric layer is constituted of a material having a
low specific dielectric constant and a low dielectric loss in a
high-frequency band.
[0009] However, in the case where Ag or Cu having a low resistivity
is employed as the material constituting the conductor layer, since
such a metal is low in melting point, in order to form a
multilayered wiring board by simultaneously sintering the conductor
layer and the dielectric layer, it is required to use a dielectric
material that can be sintered at a low sintering temperature of
from 800 to 1,050.degree. C. As such materials that can be sintered
at low temperatures and have a low specific dielectric constant and
a low dielectric loss in a high-frequency band are proposed various
crystallized glasses that are mainly composed of a borosilicate
glass and in which crystals are crystallized at the sintering
stage.
[0010] As examples of these crystallized glasses are enumerated
ones in which crystals of a spinel type structure are crystallized
(JP-A-9-175853), ones in which crystals of diopside are
crystallized (JP-A-10-120436), and ones in which crystals of
alumina, etc. are crystallized (Japanese Patent Application No.
10-320612).
[0011] Further, in order to enhance the transmission
characteristics of high-frequency signals, there is proposed a
multilayered wiring board in which a part of the conductor layer is
constituted as a strip line or micro-strip line (for example,
JP-A-11-214812). In the case where such a strip line or micro-strip
line is formed, it is necessary to coat one surface of the
dielectric layer substantially entirely and to form the entire
electrode conductor layer, which functions as the ground conductor,
as a part of the conductor layer. From the standpoint of
enhancement of the transmission characteristics of high-frequency
signals, it is desired that the entire electrode conductor layer is
formed in a multilayered state inside the multilayered wiring
board. Further, with-the modulation of wiring boards, there is a
demand such that the entire electrode conductor layer is formed as
a capacitor electrode, thereby forming a module wiring board with a
built-in capacitor.
SUMMARY OF THE INVENTION
[0012] However, in these crystallized glasses, a crystallinity is
liable to vary depending on the sintering conditions, and hence,
the high-frequency characteristics are influenced by the change of
the sintering conditions, resulting in a problem of readily causing
scattering. For this reason, the range of conditions such as
optimum sintering temperature is narrow.
[0013] Further, the crystallized glass is once softened during the
sintering step and thereafter loses fluidity with the progress of
the crystallization. Accordingly, warp is liable to generate during
the sintering step, and it is difficult to revise the warp by
changing the sintering conditions. In contrast, in the case where a
non-crystallized glass is used, such a problem hardly occurs.
However, in the non-crystallized glass, though there is no problem
in low-frequency regions of about 1 MHz, a dielectric loss often
abruptly increases in high-frequency regions. Thus, it is not
desired that the non-crystallized glass is used in the
high-frequency regions.
[0014] In order to solve the foregoing problems, a first embodiment
of the invention has been made and is aimed to provide a dielectric
material having a wide width of sintering conditions, in which a
dielectric sintered body after sintering has both characteristics
of a low dielectric constant and a low dielectric loss and to
provide a dielectric sintered body. Further, the first embodiment
of the invention is aimed to provide a dielectric material that can
undergo degreasing with a good efficiency, thereby stably obtaining
a dielectric sintered body and a dielectric sintered body, and to
provide a wiring board using the same.
[0015] The dielectric material according to the first embodiment of
the invention comprises a glass powder constituted of a glass
containing Si, B and an alkali metal element, the glass being
amorphous in sintering at a temperature of 1,050.degree. C. or
lower; and a ceramic filler containing at least one member of
SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, and an
alkali metal element, wherein when the total sum of Si converted
into SiO.sub.2, B converted into B.sub.2O.sub.3 and the alkali
metal element converted into A.sub.2O, wherein A represents an
alkali metal element, all of which are contained in the glass, is
100 mole %, a content of the alkali metal element converted into
A.sub.2O, which is contained in the glass, is 0.5 mole % or less;
and when the total sum of at least one member of SiO.sub.2,
Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, and the alkali
metal element converted into A.sub.2O, all of which are contained
in the ceramic filler, is 100 mole %, a content of the alkali metal
element converted into A.sub.2O, which is contained in the ceramic
filler, is 0.5 mole % or less.
[0016] Another dielectric material according to the first
embodiment of the invention comprises a glass powder constituted of
a glass containing Si, B and an alkali metal element, the glass
being amorphous in sintering at a temperature of 1,050.degree. C.
or lower; and a ceramic filler containing at least one member of
SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2 but not
containing an alkali metal element, wherein when the total sum of
Si converted into SiO.sub.2, B converted into B.sub.2O.sub.3 and
the alkali metal element converted into A.sub.2O, wherein A
represents an alkali metal element, all of which are contained in
the glass, is 100 mole %, a content of the alkali metal element
converted into A.sub.2O, which is contained in the glass, is 0.5
mole % or less.
[0017] Also, the glass can further contain Al and/or an alkaline
earth metal element, and when the total sum of Si converted into
SiO.sub.2, B converted into B.sub.2O.sub.3, the alkali metal
element converted into A.sub.2O, wherein A represents an alkali
metal element, Al converted into Al.sub.2O.sub.3 in the case where
Al is contained, and the alkaline earth metal element converted
into EO, wherein E represents an alkaline earth metal element, in
the case where the alkaline earth metal element is contained, is
100 mole %, the total sum of Si converted into SiO.sub.2 and B
converted into B.sub.2O.sub.3 is from 80 to 95 mole %.
[0018] Further, the ceramic filler may not contain an alkaline
earth metal element.
[0019] Also, the ceramic filler can further contain an alkaline
earth metal element, and when the total sum of at least one member
of SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, the
alkali metal element converted into A.sub.2O, in the case where the
alkali metal element is contained, and the alkaline earth metal
element converted into EO, wherein E represents an alkaline earth
metal element, all of which are contained in the ceramic filler, is
100 mole %, a content of the alkaline earth metal element converted
into EO is 1 mole % or less.
[0020] Further, when the total sum of the glass powder and the
ceramic filler is 100% by volume, the glass powder can account for
from 55 to 70% by volume, and the ceramic filler can account for
from 30 to 45% by volume.
[0021] The dielectric sintered body according to the first
embodiment of the invention is one obtained by sintering the
dielectric material, wherein when the total sum of Si converted
into SiO.sub.2, B converted into B.sub.2O.sub.3, the alkali metal
element converted into A.sub.2O, wherein A represents an alkali
metal element, Al converted into Al.sub.2O.sub.3 in the case where
Al is contained, and the alkaline earth metal element converted
into EO, wherein E represents an alkaline earth metal element, in
the case where the alkaline earth metal element is contained, all
of which are contained in the glass, is 100 mole %, and at least
one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2, the alkali metal element converted
into A.sub.2O, in the case where the alkali metal element is
contained, and the alkaline earth metal element converted into EO,
wherein E represents an alkaline earth metal element, all of which
are contained in the ceramic filler, is 100 mole %, a content of
the alkali metal element converted into A.sub.2O is 0.5 mole % or
less.
[0022] The wiring board according to the first embodiment of the
invention comprises a dielectric layer comprising the dielectric
sintered body and a conductor layer provided on the surface of or
inside the dielectric layer, the conductor layer comprising at
least one member selected from Ag, Au and Cu.
[0023] In the case where a conductor layer containing the entire
electrode conductor layer (hereinafter sometimes abbreviated as
"electrode layer") and a dielectric layer using the crystallized
glass are simultaneously sintered to prepare a multilayered wiring
board (second embodiment of the invention), as shown in a schematic
view of FIG. 4, there is a problem that a blister or gap is liable
to generate due to differences in the sintering temperature and
sintering shrinkage behavior between the dielectric layer and the
conductor layer. This is because since the crystallized glass has a
nature such that it is abruptly sintered and shrunk during the
sintering step, the sintering shrinkage behavior of the entire
electrode conductor layer cannot follow it. Especially, such a
blister or gap is liable to generate in the entire electrode
conductor layer (forming area: 1 cm.sup.2 or more) having a large
contact area with the dielectric layer. The generation of such a
blister or gap results in inconveniences such as reduction in
mechanical strength due to reduction of adhesiveness between the
conductor layer and the dielectric layer and increase of the
resistivity. Further, these inconveniences become remarkable when
the entire electrode conductor layer is formed in a multilayered
state in the multilayered wiring board.
[0024] The blister or gap generated in the electrode layer occurs
due to a difference of the shrinkage behavior caused by differences
in the sintering temperature and sintering shrinkage behavior
between the dielectric layer and the conductor layer during the
sintering. Thus, from the standpoint of reducing the difference of
the shrinkage behavior, it is attempted to regulate the amount of
the metal conductor component mainly constituting the conductor
layer or to add a metal conductor different from the metal
conductor mainly constituting the conductor layer to the conductor
layer. For example, JP-A-63-168904 and JP-A-62-48097 propose such
devices.
[0025] However, in the mere device to the constitutional components
of the conductor layer, in many cases, the inconveniences such as
blister generated in the electrode layer cannot be inhibited.
Further, in order to inhibit the inconveniences, a large amount of
additives (such as metal oxides) different from the metal conductor
mainly constituting the conductor layer must be added to the
conductor layer, leading to another problem to bring an increase of
the resistivity of the conductor layer.
[0026] Further, in the case where the conductor layer mainly formed
from low-resistivity Cu or Ag and the dielectric layer formed by
using a glass are simultaneously sintered, it is necessary that the
sintering be carried out at a sintering temperature lower than the
melting point of the metal, namely, at a low sintering temperature
of from 800 to 1,050.degree. C. Accordingly, the sintering
temperature region at which the simultaneous sintering with the
dielectric layer can be carried out is limited depending on the
species of the metal constituting the conductor layer. In addition,
in the case where the high-frequency signal is handled, the
dielectric layer is required to have a low specific dielectric
constant and a low dielectric loss, suited for the high-frequency
signal. Accordingly, a degree of crystallization in the
crystallized glass must be regulated, and hence, the sintering
temperature region will be made narrower. As a result, by the mere
device on the constitutional components of the conductor layer as
in the related art, it becomes more difficult to inhibit the
inconveniences generated in the electrode layer without worsening
the electric characteristics such as resistivity in the conductor
layer. In the light of the above, during the simultaneous sintering
of the dielectric layer and the conductor layer mainly composed of
Cu or Ag, it is preferred that the width of optimization of the
sintering conditions such as sintering temperature is as wide as
possible. Further, during the simultaneous sintering of the
dielectric layer and the conductor layer using Cu to form a wiring
board, in order to prevent the oxidation of Cu, the sintering is
carried out in a neutral atmosphere or reductive atmosphere. For
this reason, in particular, it is preferred that the width of
optimization of the sintering conditions is as wide as
possible.
[0027] In carrying out the simultaneous sintering, the dielectric
layer is sintered and formed in a state where besides the
constitutional components, a binder that is usually composed of an
organic material is contained, or a state where debinding is
effected in advance to some extent. The binder is degreased and
removed in the sintering stage or debinding stage in advance.
However, when the sintering is carried out in a state where the
debinding is incomplete, the constitutional components forming the
dielectric layer become minute before the binder has completely
come out, whereby a passage through which the binder comes out is
clogged, leading to a problem such that the debinding becomes
difficult. Taking into consideration these problems, it is
preferred that the width of optimization of the sintering
conditions in the simultaneous sintering is as wide as
possible.
[0028] Under these circumstances, a second embodiment of the
invention was made. That is, an object of the second embodiment of
the invention is to provide a wiring board in which even in the
case where the dielectric layer and the conductor layer are
simultaneously sintered, not only inconveniences such as blister
generated between the conductor layer (especially, the entire
electrode conductor layer having a forming area of 1 cm.sup.2 or
more) and the dielectric layer are inhibited, but also electric
characteristics represented by resistivity of the conductor layer
to be formed can be enhanced, especially the dielectric layer and
the conductor layer suited for high-frequency signals can be
formed, and the productivity can be enhanced, and to provide a
process of producing the same.
[0029] In order to overcome the foregoing problems, the
multilayered wiring board according to the second embodiment of the
invention comprises a dielectric layer constituted of a glass
having a crystallization temperature exceeding 1,000.degree. C. and
a ceramic filler and a conductor layer mainly constituted of a
metal conductor, wherein a part of the conductor layer is
constituted as an entire electrode conductor layer having a forming
area of 1 cm.sup.2 or more.
[0030] In the multilayered wiring board according to the second
embodiment of the invention, as the glass that is the raw material
of the glass matrix constituting the dielectric layer, one having a
crystallization temperature exceeding 1,000.degree. C. is used.
Accordingly, in the case where the dielectric layer is sintered
simultaneously with the conductor layer mainly constituted of a
low-melting metal conductor such as Ag and Cu by sintering at from
800 to 1,000.degree. C., the glass matrix constituting the
dielectric layer can be formed as one in which the crystallization
is inhibited during the sintering or one in which no
crystallization occurs. For this reason, it is possible to inhibit
the difference in shrinkage behavior caused by the particles of the
constitutional components of the dielectric layer and the conductor
layer during the sintering. As a result, when the dielectric layer
and the conductor layer are subjected to simultaneous sintering, it
is possible to inhibit the inconveniences such as blister and
peeling generated in the conductor layer, especially the entire
electrode conductor layer having a forming area of 1 cm.sup.2 or
more (hereinafter sometimes simply referred to "electrode layer"),
which constitutes a part of the conductor layer. Furthermore, it is
possible to enhance the electric characteristics of the conductor
layer, such as resistivity.
[0031] As described in the second embodiment of the invention, when
the dielectric layer is formed by using a glass in which the
crystallization is inhibited during the sintering step, or a glass
in which no crystallization occurs, it is possible to widen the
width of the sintering conditions such as the sintering temperature
for simultaneous sintering of the dielectric layer and the
conductor layer. Furthermore, it is possible to enhance the
productivity of the multilayered wiring board to be formed.
[0032] In the glass that will be a glass matrix constituting the
dielectric layer of the second embodiment of the invention, it is
necessary to inhibit at least the crystallization during the
sintering. More preferably, it is necessary that no crystallization
occurs. The crystallization is liable to occur as the sintering
temperature increases above the crystallization temperature. For
this reason, it is preferred that in order to form the dielectric
layer minutely, the crystallization temperature of the glass to be
used in the second embodiment of the invention is as high as
possible. Incidentally, what the crystallization of the glass is
inhibited during the sintering means that the crystallization of
the glass does not substantially occur during the time when the
dielectric layer becomes minute. Accordingly, ones in which the
glass is crystallized by a post-treatment (for example, prolonging
the holding time at the sintering temperature) after the dielectric
layer has become minute should be included in the concept of the
dielectric layer of the second embodiment of the invention.
Further, even in the case where after the dielectric layer has
become minute, the glass is crystallized, since the simultaneous
sintering of the dielectric layer and the conductor layer is
already completed, warp caused by mismatching of the sintering
shrinkage does not occur.
[0033] As a matter of course, it is desired that the metal
conductor mainly constituting the conductor layer in the
multilayered wiring board according to the second embodiment of the
invention is of a low resistivity. Especially, in the case of
dealing with high-frequency signals, from the standpoint of
transmission characteristics of the high-frequency signals, it is
desired that the resistivity of the conductor layer is low. As such
a metal conductor can be enumerated silver-based conductors (such
as silver alone, silver-metal oxide (oxides of, e.g., manganese,
vanadium, bismuth, aluminum, silicon, copper (hereinafter simply
referred to as "metal oxide")), silver-glass, silver-palladium,
silver-platinum, and silver-rhodium), gold-based conductors (gold
alone, gold-metal oxide, gold-palladium, gold-platinum, and
gold-rhodium), and copper-based conductors (such as copper alone,
copper-metal oxide, copper-palladium, copper-platinum, and
copper-rhodium).
[0034] From the standpoints of resistivity and melting point of the
metal conductor to be used, among the foregoing metal conductors,
those formed from at least one of Au, Ag and Cu are optimum.
[0035] In addition, among Cu, Ag and Au, Cu and Ag are of a low
resistivity. Accordingly, those mainly composed of Cu or Ag are
suitable as the metal conductor mainly constituting the conductor
layer. Especially, those mainly composed of Cu that is superior in
anti-migration to Ag are suitable as the metal conductor mainly
constituting the conductor layer. Further, in the second embodiment
of the invention, since the dielectric layer is sintered at from
800 to 1,000.degree. C. using the glass having a crystallization
temperature exceeding 1,000.degree. C., sintering proceeds slowly
as compared with the case of using a glass having a low
crystallization temperature. Accordingly, even in the case where
the simultaneous sintering is carried out in a neutral atmosphere
or a reductive atmosphere by using one mainly composed of Cu as the
conductor layer, the passage through which the binder comes out is
hardly clogged, so that the conductor layer can be made superior in
debinding properties.
[0036] Next, the multilayered wiring board according to the second
embodiment of the invention is characterized in that the entire
electrode conductor layer is an ground electrode and/or a capacitor
electrode.
[0037] It is desired that the ground electrode that is necessary in
the case where a part of the conductor layer functions a strip line
or a micro-strip line, or the capacitor electrode that is necessary
in the case where a capacitor (including known capacitors such as
laminate type capacitors in the concept) is built in the
multilayered wiring board corresponding to high-frequency signals,
is not only formed as a part of the conductor layer but also has a
forming area as large as possible, i.e., a forming area of at least
1 cm.sup.2. Such ground electrode and capacitor electrode
correspond to the entire electrode conductor layer.
[0038] As described above, in the second embodiment of the
invention, since nevertheless the crystallized glass is used, the
dielectric layer is sintered while inhibiting the crystallization
during the sintering, it is possible to inhibit the blister or gap
that is conventionally generated in the conductor layer, especially
the entire electrode conductor layer (forming area: 1 cm.sup.2 or
more) due to the difference in abrupt shrinkage behavior with the
progress of crystallization of the crystallized glass during the
sintering. For this reason, the entire electrode conductor layer
functioning as the ground electrode or capacitor electrode can have
a forming area of at least 1 cm.sup.2. As a result, not only the
functions as the ground electrode and the capacitor electrode can
be enhanced, but also the transmission characteristics of
high-frequency signals in the multilayered wiring board to be
formed can be enhanced.
[0039] Also, in addition to the forming area of the electrode
layer, even in the case where the electrode layer is formed in a
multilayered state inside the multilayered wiring board, it is
possible to inhibit effectively the blister or gap generated in the
electrode layer.
[0040] In addition, since it is not necessary to add a large
quantity of additives different from the metal conductor for
inhibiting the blister or gap to the conductor layer, it is
possible to reduce the resistivity of the conductor layer. By using
any one of the foregoing metal conductors, the conductor layer can
have a volume resistivity of 4.times.10.sup.-6 .OMEGA.cm or less
(particularly 3.times.10.sup.-6 .OMEGA.cm or less, and further
particularly 2.5.times.10.sup.-6 .OMEGA.cm or less). As a result,
not only the electric characteristics of the multilayered wiring
board can be enhanced, but also the transmission loss in
high-frequency signals can be inhibited.
[0041] Next, in the second embodiment of the invention, in order
that the multilayered wiring board is more suitable for the
high-frequency signals, it is desired that the specific dielectric
constant and the dielectric loss of the dielectric layer are as low
as possible. Specifically, the specific dielectric constant may be
7 or less, and the dielectric loss in a high high-frequency band of
10 GHz or more may be 0.002 or less.
[0042] In order that the dielectric layer has the above-specified
specific dielectric constant and dielectric loss, the glass as a
constitutional component of the dielectric layer can comprise
SiO.sub.2 and B.sub.2O.sub.3 as major components and
Al.sub.2O.sub.3 and an alkaline earth metal oxide as
sub-components, with a content of the major components being from
80 to 95 mole %. Preferably, the glass consists essentially of
SiO.sub.2 and B.sub.2O as major components and Al.sub.2O.sub.3 and
an alkaline earth metal oxide as sub-components. More preferably,
the glass consists of SiO.sub.2 and B.sub.2O.sub.3 as major
components and Al.sub.2O.sub.3 and an alkaline earth metal oxide as
sub-components. Further, by using the glass comprising such
components, even when the crystallization temperature exceeds
1,000.degree. C., and the sintering is carried out at from 800 to
1,000.degree. C., the glass is not crystallized. Accordingly, it is
possible to relieve effectively the mismatching of the sintering
shrinkage behavior during the simultaneous sintering with the metal
conductor such as Cu.
[0043] In the second embodiment of the invention, the content of
SiO.sub.2 and B.sub.2O.sub.3 (hereinafter sometimes abbreviated as
"major components") as the major components of the glass is from 80
to 95 mole %. When the content of the major components exceeds 95
mole %, crystals caused by SiO.sub.2, such as cristobalite, exist
in the sintering step (sintering temperature: 1,000.degree. C. or
lower). On the other hand, when the content of the major components
is less than 80 mole %, there occur inconveniences such that the
specific dielectric constant or dielectric loss in a high-frequency
band of the formed dielectric layer becomes high. Taking into
consideration these matters, it is desired that the content of the
major components is from 80 to 95 mole %.
[0044] In addition, in the second embodiment of the invention,
Al.sub.2O.sub.3 and an alkaline earth metal oxide as sub-components
of the glass have an effect for inhibiting the crystallization
caused by the major components in the sintering step, and
desirably, the content of each of Al.sub.2O.sub.3 and the alkaline
earth metal oxide is from 3 to 10 mole %.
[0045] When the content of Al.sub.2O.sub.3 is less than 3 mole %,
crystals caused by SiO.sub.2 exist in the sintering step. On the
other hand, when the content of Al.sub.2O.sub.3 exceeds 10 mole %,
there occur inconveniences such that Al.sub.2O.sub.3 crystals and
faldspar caused by Al.sub.2O.sub.3 exist in the sintering step.
Taking into consideration these matters, it is suitable that the
content of Al.sub.2O.sub.3 in the glass is from 3 to 10 mole %.
[0046] When the content of the alkaline earth metal oxide is less
than 3 mole %, the melting of the glass as the major components in
the sintering step becomes difficult. On the other hand, when it
exceeds 10 mole %, there occur inconveniences such that crystals
caused by the alkaline earth metal oxide exist in the sintering
step. Taking into consideration these matters, it is desired that
the content of the alkaline earth metal oxide is from 3 to 10 mole
%.
[0047] As the alkaline earth metal oxide can be enumerated MgO,
CaO, SriO, and BaO. Among them, MgO is liable to cause
crystallization in the sintering step, and SrO and Bao excessively
increase the specific dielectric constant of the formed dielectric
layer. Therefore, it is particularly optimum to choose CaO. When
CaO is chosen as the alkaline earth metal oxide, not only it is
possible to easily inhibit the generation of crystallization caused
by the constitutional components of the glass during the sintering,
but also it becomes possible to reduce the specific dielectric
constant of the dielectric layer.
[0048] In the conventional glasses, for the purpose of decreasing
the melting temperature of the glass, it was necessary to add
alkali metals and metal components such as Pb and Sb to the glass.
However, the formation of oxides caused by these metal components
in the sintering step increases the dielectric loss of the
dielectric layer in a high-frequency band. However, in the second
embodiment of the invention, it is possible to sinter and form the
dielectric layer by sintering at 1,000.degree. C. or lower without
containing alkali metals and metal components such as Pb and Sb in
the glass powder. As a result, it is possible to inhibit
inconveniences such as an increase of the dielectric loss in a
high-frequency band by the oxides caused by the metal components.
Furthermore, it is possible to further reduce the dielectric loss
of the formed dielectric layer in a high-frequency band.
[0049] Also, in the second embodiment of the invention, with
respect to the entire electrode conductor layer, in addition to the
function of an ground conductor of, e.g., a strip line
corresponding to high-frequency signals, there may be the case
where the entire electrode conductor layer is formed as an ground
conductor as a shield portion for noise protection irrespective of
the frequency of high-frequency signals. Even in such case, as
described in the second embodiment of the invention, it is possible
to inhibit inconveniences such as blister or gap as generated
during the sintering.
[0050] Next, the process of producing the multilayered wiring board
according to the second embodiment of the invention comprises
sintering a multilayered wiring board molding comprising a green
material mainly constituted of a glass having a crystallization
temperature exceeding 1,000.degree. C. and a ceramic filler and a
conductor layer mainly constituted of a metal conductor, a part of
the conductor layer being constituted as an entire electrode
conductor layer having a forming area of 1 cm.sup.2 or more, at a
temperature lower than the crystallization temperature of the
glass.
[0051] Since the crystallization temperature of the glass
constituting the green material that will be the dielectric layer
by sintering exceeds 1,000.degree. C., even in the case where
simultaneous sintering with the conductor layer mainly composed of
a metal conductor having a low melting point, such as Ag and Cu, is
carried out by sintering at from 800 to 1,000.degree. C., it is
possible to form the glass constituting the dielectric layer as a
glass in which the crystallization is inhibited during the
sintering, or a glass in which no crystallization occurs. For this
reason, it is possible to inhibit the difference in shrinkage
behavior caused in particles of the constitutional components
between the dielectric layer and the conductor layer during the
sintering. As a result, when the dielectric layer and the conductor
layer are subjected to simultaneous sintering, it is possible to
inhibit the inconveniences such as blister and peeling generated in
the conductor layer, especially the entire electrode conductor
layer having a forming area of 1 cm.sup.2 or more, which
constitutes a part of the conductor layer. Furthermore, it is
possible to produce a multilayered wiring board, namely a
multilayered wiring board, having enhanced electric characteristics
of the conductor layer, such as resistivity.
[0052] Further, in the production process according to the second
embodiment of the invention, since the glass constituting the green
material is a glass in which the crystallization is inhibited
during the sintering step, or a glass in which no crystallization
occurs, it is possible to widen the width of the sintering
conditions such as the sintering temperature for simultaneous
sintering of the dielectric layer and the conductor layer. As a
result, by widening the width of the sintering conditions, it is
possible to enhance the debinding properties of a binder comprising
an organic material, which is contained in the green material, in
the sintering step.
[0053] The multilayered wiring board produced by the production
process according to the second embodiment of the invention has the
same effects as in the above-described multilayered wiring board
according to the second embodiment of the invention. However, in
order that the dielectric layer has a specific dielectric constant
of 7 or less and a dielectric loss of 0.002 or less in a
high-frequency band of 10 GHz or more, it is possible to make the
glass powder in the production process according to the second
embodiment of the invention have SiO.sub.2 and B.sub.2O.sub.3 as
major components and Al.sub.2O.sub.3 and an alkaline earth metal
oxide as sub-components, with a content of the major components
being from 80 to 95 mole %.
BRIEF DESCRIPTION OF THE DRAWING
[0054] [FIG. 1]
[0055] A graph showing the results of X-ray diffraction of an
unsintered material and sintered material of glass B.
[0056] [FIG. 2]
[0057] An outline cross-sectional view showing one embodiment of
the multilayered wiring board according to the second embodiment of
the invention.
[0058] [FIG. 3]
[0059] A schematic view showing the multilayered wiring board in
the Examples.
[0060] [FIG. 4]
[0061] A schematic view explaining inconveniences as generated in
the conductor layer.
DESCRIPTION OF THE REFERENCE NUMERALS AND SIGNS
[0062] 1: Multilayered wiring board
[0063] 2: Dielectric layer
[0064] 3: Conductor layer
[0065] 11: Entire electrode conductor layer
DETAILED DESCRIPTION OF THE INVENTION
[0066] [1] Dielectric Material:
[0067] The dielectric material (one before sintering, which is
hereinafter sometimes simply referred to as "material") according
to the first embodiment of the invention contains a glass powder
and a ceramic filler. The glass powder preferably has a mean
particle size of from 0.5 to 5 .mu.m, and more preferably from 1 to
3 .mu.m.
[0068] The "glass powder" is constituted of a glass containing Si,
B and an alkali metal element, the glass being amorphous in
sintering at a temperature of 1,050.degree. C. or lower.
[0069] The term "amorphous" means that no peak is confirmed in the
X-ray diffraction. That is, it can be confirmed whether or not the
"glass" is amorphous by the matter that when the glass powder is
sintered at 1,050.degree. C. for 2 hours and then subjected to
X-ray diffraction measurement, no peak is present in the X-ray
diffraction.
[0070] Further, what Si and B are contained means that the glass is
constituted of a borosilicate glass. Accordingly, these are
contained mainly as oxides of Si and B.
[0071] Moreover, examples of the alkali metal element that is
contained in the glass include Li, Na, and K. Still further, the
alkali metal element is contained usually as its oxide. Also, the
alkali metal element may be contained singly or in admixture of two
or more thereof.
[0072] In addition, when the total sum of Si converted into
SiO.sub.2 (hereinafter referred to as "Si converted into oxide"), B
converted into B.sub.2O.sub.3 (hereinafter referred to as "B
converted into oxide") and the alkali metal element converted into
A.sub.2O (hereinafter referred to as "alkali metal element
converted into oxide"), wherein A represents an alkali metal
element, is 100 mole %, a content of the alkali metal element
converted into A.sub.2O, which is contained in the glass, is 0.5
mole % or less, preferably 0.3 mole % or less, and more preferably
0.2 mole % or less. When the content of the alkali metal element
converted into oxide exceeds 0.5 mole %, a dielectric loss of the
dielectric sintered body after sintering becomes large.
[0073] In the first embodiment of the invention, what the total sum
of Si, B and the alkali metal element (A) each converted into oxide
is 100 mole % means that the total sum of Si converted into
SiO.sub.2, B converted into B.sub.2O.sub.3 and A converted into
A.sub.2O is 100 mole % but does not mean mole % of Si, B and the
alkali metal element contained in the oxides. Concretely, assuming
that 10 mole % of B.sub.2O.sub.3 is contained in the glass, the
mole % of "B converted into B.sub.2O.sub.3" is 10 mole % but not
the mole % of "B contained in B.sub.2O.sub.3" (namely, 20 mole
%).
[0074] This glass preferably has a yielding point of from 700 to
850.degree. C., and more preferably from 720 to 800.degree. C. When
the yielding point is lower than 700.degree. C., it is difficult to
remove carbon generated from a binder during the sintering. On the
other hand, when it exceeds 850.degree. C., the sintering
temperature is too high, so that it becomes difficult to undergo
the sintering simultaneously with metals such as Au, Ag, and Cu,
and hence, such is not preferred.
[0075] The glass is not particularly limited so far as it is a
borosilicate glass that is amorphous in the sintering at
1,050.degree. C. or lower. But, it may further contain Al and/or an
alkaline earth metal element.
[0076] At this time, when the total sum of Si converted into oxide,
B converted into oxide, the alkali metal element converted into
oxide, Al converted into Al.sub.2O.sub.3 (hereinafter referred to
as "Al converted into oxide") in the case where Al is contained,
and the alkaline earth metal element converted into EO (hereinafter
referred to as "alkaline earth metal element converted into oxide),
wherein E represents an alkaline earth metal element (hereinafter
the same), in the case where the alkaline earth metal element is
contained, all of which are contained in the glass, is 100 mole %,
the total sum of Si and B each converted into oxide is preferably
from 80 to 95 mole %, more preferably from 82 to 93 mole %, and
most preferably from 85 to 90 mole %. When the total sum of Si and
B each converted into oxide is less than 80 mole %, the dielectric
loss becomes large, whereas when it exceeds 95 mole %,
SiO.sub.2-based crystals (such as cristobalite) crystallize, and
hence, the both are not preferred.
[0077] Further, when the total sum of Si converted into oxide, B
converted into oxide, the alkali metal element converted into
oxide, Al converted into oxide, and the alkaline earth metal
element converted into oxide in the case where the alkaline earth
metal element is contained, all of which are contained in the
glass, is 100 mole %, the content of Al converted into oxide is
preferably from 3 to 10 mole %. When the content of Al converted
into oxide is less than 3 mole %, SiO.sub.2-based crystals are
liable to crystallize during the sintering, whereas when it exceeds
10 mole %, Al.sub.2O.sub.3-based crystals or faldspar is liable to
crystallize during the sintering, and hence, the both are not
preferred.
[0078] Though examples of the alkaline earth metal element include
Ca, Mg, Sr, and Ba, Ca is particularly preferred. Mg is liable to
crystallize Mg-based crystals such as enstatite and cordierite
during the sintering, and Sr and Ba are liable to increase the
dielectric constant of the dielectric sintered body after the
sintering, and hence, the both are not preferred.
[0079] In addition, when the total sum of Si converted into oxide,
B converted into oxide, the alkali metal element converted into
oxide, Al converted into oxide in the case where Al is contained,
and the alkaline earth metal element converted into oxide, all of
which are contained in the glass, is 100 mole %, the content of the
alkaline earth metal element converted into oxide is preferably
from 3 to 10 mole %. When the content of the alkaline earth metal
element converted into oxide is less than 3 mole %, melting of the
glass is difficult, whereas when it exceeds 10 mole %, crystals are
liable to crystallize during the sintering, and hence, the both are
not preferred.
[0080] The "ceramic filler" means one containing at least one
member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2 (mullite).
[0081] While the ceramic filler may be one containing an alkali
metal element, those not containing an alkali metal element are
preferred. This is because in the case where the alkali metal
element is contained, an increase of dielectric loss of the
dielectric sintered body after the sintering is liable to occur.
Here, what the alkali metal element is not contained means that in
the chemical analysis (ICP emission), its detection amount is
smaller than the measurement limit. Further, in the case where the
alkali metal element is contained, when the total sum of at least
one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2 and the alkali metal element converted
into oxide, all of which are contained in the ceramic filler, is
100 mole %, the content of the alkali metal element converted into
oxide is 0.5 mole % or less, preferably 0.3 mole % or less, and
more preferably 0.2 mole % or less. When the content of the alkali
metal element converted into oxide exceeds 0.5 mole %, the
dielectric loss of the dielectric sintered body after the sintering
becomes large, and hence, such is not preferred.
[0082] In addition, while the ceramic filler may be one containing
an alkaline earth metal element, those not containing an alkaline
earth metal element are preferred. This is because in the case
where the alkaline earth metal element is contained, an increase of
dielectric loss of the dielectric sintered body after the sintering
is liable to occur. Here, what the alkaline earth metal element is
not contained means that in the chemical analysis (ICP emission),
its detection amount is smaller than the measurement limit.
[0083] Further, in the case where the alkaline earch metal element
is contained, when the total sum of at least one member of
SiO.sub.2, Al.sub.2O.sub.3 and 3Al.sub.2O.sub.3.2SiO.sub.2, the
alkali metal element converted into oxide in the case where the
alkali metal element is contained, and the alkaline earth metal
element converted into oxide, all of which are contained in the
ceramic filler, is 100 mole %, the content of the alkaline earth
metal element converted into oxide is 1 mole % or less, preferably
0.5 mole % or less, and more preferably 0.2 mole % or less. When
the content of the alkali metal element converted into oxide
exceeds 1 mole %, the dielectric loss of the dielectric sintered
body after the sintering becomes large, and hence, such is not
preferred.
[0084] The ceramic filler may be in a powdered state or fibrous
state, but preferably is in a powdered state. In the case where the
ceramic filler is in a powdered state, it preferably has a mean
particle size of from 0.5 to 5 .mu.m, and more preferably from 1 to
3 .mu.m.
[0085] Examples of the ceramic filler include an alumina powder, a
mullite powder, a quartz powder, and a silica glass powder. Of
these, the alumina powder is preferred because it can enhance the
strength of the dielectric sintered body. Incidentally, these
ceramic fillers may be used singly or in admixture of two or more
thereof depending upon the dielectric constant, strength and
coefficient of thermal expansion required for the dielectric
sintered body. Further, in the case where two or more of the
ceramic fillers are used in combination, ones having an alumina
powder mixed therewith are preferred because they can enhance the
strength of the dielectric sintered body after the sintering.
[0086] With respect to the proportions of the glass power and the
ceramic filler to be contained, when the total sum of the glass
powder and the ceramic filler is 100% by volume, it is preferred
that the glass powder accounts for from 55 to 70% by volume, and
the ceramic filler accounts for from 30 to 70% by volume, and it is
more preferred that the glass powder accounts for from 55% by
volume or more but less than 65% by volume, and the ceramic filler
accounts for more than 35% by volume but 45% by volume or less.
When the amount of the glass powder is less than 55% by volume, a
minute sintered body is hardly obtained during the sintering,
whereas when it exceeds 70% by volume, the debinding properties are
lowered, and hence, the both are not preferred. Incidentally, the
term "% by volume" means a volume ratio in a true volume, and the
true volume of each of the glass powder and the ceramic filler is
determined by dividing a weight of each powder by a particle
density of each powder. The particle density of the powder can be
measured by known methods (such as the pycnometer method of JIS R
1620 "Testing Method for Particle Density of Fine Ceramic
Powder").
[0087] The dielectric material according to the first embodiment of
the invention is usually obtained by compounding the glass powder
and the ceramic filler further with at least a solvent and a
binder.
[0088] The binder is not particularly limited so far as it is
generally used as a binder. But, acrylic resin-based binders such
as acrylic resins and butyral resins are preferred, and acrylic
resins are particularly preferably used. The binder may be used
singly or in admixture of two or more thereof.
[0089] When the total sum of the glass powder and the ceramic
filler is 100 parts by weight, a compounding amount of the binder
is from 1 to 30 parts by weight, and preferably from 3 to 25 parts
by weight.
[0090] In addition, the solvent is not particularly limited so far
as it is a solvent generally used for dielectric materials. But,
examples include toluene, methyl ethyl ketone, acetone, and
isopropyl alcohol. Of these are preferable toluene and methyl ethyl
ketone. The solvent may be used singly or in admixture of two or
more thereof.
[0091] When the total sum of the glass powder and the ceramic
filler is 100 parts by weight, a compounding amount of the solvent
is from 10 to 150 parts by weight, and preferably from 20 to 120
parts by weight.
[0092] If desired, the dielectric material according to the first
embodiment of the invention may be further compounded with a
plasticizer. Such compounding is carried out for the purpose of
enhancing the processing properties of a green sheet.
[0093] Examples of the plasticizer that can be used include dibutyl
phthalate, 2-ethylhexyl phthalate, and 2-ethylhexyl adipate, with
dibutyl phthalate being preferred. The plasticizer may be used
singly or in admixture of two or more thereof. When the total sum
of the glass powder and the ceramic filler is 100 parts by weight,
a compounding amount of the plasticizer is from 3 to 20 parts by
weight, and preferably from 5 to 15 parts by weight.
[0094] [2] Dielectric Sintered Body:
[0095] The dielectric sintered body according to the first
embodiment of the invention is obtained by sintering the dielectric
material.
[0096] When the dielectric sintered body is obtained from the
dielectric material according to the first embodiment of the
invention, it is usually carried out to mold the dielectric
material prior to the sintering.
[0097] The molding can be carried out by known molding methods
represented by sheet molding by the doctor blade process (including
a laminate of plural sheets), film formation by the screen printing
process, and press molding.
[0098] With respect to the conditions for carrying out the
"sintering", the sintering is carried out at from 800 to
1,050.degree. C., and preferably from 900 to 1,000.degree. C. for
from 0.5 to 10 hours, and preferably from 1 to 5 hours. When the
sintering temperature is lower than 800.degree. C., sufficient
sintering is hardly achieved, whereas when it exceeds 1,050.degree.
C., growth of metallized abnormal particles (Cu) to be
simultaneously sintered occurs, and hence, the both are not
preferred. Further, when the sintering time is shorter than 0.5
hour, sufficient sintering is hardly achieved, whereas when it
exceeds 10 hours, growth of metallized abnormal particles (Cu) to
be simultaneously sintered occurs, and hence, the both are not
preferred.
[0099] Further, the dielectric sintered body according to the first
embodiment of the invention may contain an alkali metal element
such as Li, Na, and K. But, it is preferred that the content of the
alkali metal element is low.
[0100] When the total sum of Si converted into oxide, B converted
into oxide, the alkali metal element converted into oxide, Al
converted into oxide in the case where Al is contained, and the
alkaline earth metal element converted into oxide in the case where
the alkaline earth metal element is contained, all of which are
contained in the glass of the dielectric sintered body, and at
least one member of SiO.sub.2, Al.sub.2O.sub.3 and
3Al.sub.2O.sub.3.2SiO.sub.2, the alkali metal element converted
into oxide in the case where the alkali metal element is contained,
and the alkaline earth metal element converted into oxide in the
case where the alkaline earth metal element is contained, all of
which are contained in the ceramic filler, is 100 mole %, a content
of the alkali metal element converted into oxide is 0.5 mole % or
less, preferably 0.3 mole % or less, and more preferably from 0.2
mole % or less. When the content of the alkali metal element
converted into oxide exceeds 0.5 mole %, the dielectric loss
becomes large, and hence, such is not preferred.
[0101] [3] Wiring Board:
[0102] The wiring board according to the first embodiment of the
invention comprises a dielectric layer comprising the dielectric
sintered body of the first embodiment of the invention and a
conductor layer provided on the surface of or inside the dielectric
layer.
[0103] Further, the conductor layer comprises at least one member
selected from Ag, Au and Cu.
[0104] The wiring board can be, for example, prepared by the
following method.
[0105] That is, in the case of the wiring board having the
conductor layer formed on the surface of the dielectric layer, the
glass powder, the ceramic filler, the binder, and the solvent are
mixed in predetermined ratios as described above. At this time, if
desired, the above-described plasticizer and the like may be
compounded. Thereafter, the mixture is molded into a green sheet of
the dielectric material by the above-described molding method.
Next, a conductor layer pattern comprising at least one member of
Au, Ag and Cu is formed on the surface of the green sheet by the
screen printing process or the like.
[0106] Then, the green sheet having the conductor layer formed on
the surface thereof is sintered under the sintering conditions as
described above. There is thus obtained the wiring board according
to the first embodiment of the invention.
[0107] Further, in the case of the wiring board having the
conductor layer formed inside the dielectric layer, the green sheet
having the conductor layer formed on the surface thereof is
laminated with other green sheet such that it covers the conductor
layer, and the laminate is sintered under the sintering conditions
as described above. There is thus obtained the wiring board having
the conductor layer formed inside the dielectric layer.
[0108] In the case where the dielectric sintered body according to
the first embodiment of the invention is measured at TE011 mode and
at a resonance frequency of from 8 to 12 GHz according to JIS R
1627, it has a specific dielectric constant of 5.8 or less, and
preferably 5.7 or less and a dielectric loss of 0.0015 or less,
preferably 0.0013 or less, and more preferably 0.0011 or less.
[0109] One embodiment of the multilayered wiring board according
the second embodiment of the invention will be described below.
[0110] FIG. 2 schematically shows an outline cross-sectional view
of a multilayered wiring board 1 (hereinafter sometimes abbreviated
as "board 1"), in which a dielectric layer 2 and a conductor layer
3 are alternately formed, and if desired, a semiconductor element
51 is mounted on the surface thereof. Respective wiring layers
playing a role of wiring in the conductor layer 3 are electrically
connected to each other by via holes 35 each penetrating through
the wiring layer in the thickness direction. Further, in FIG. 2,
there is constituted an entire electrode conductor layer 11 in
which a part of the conductor layer 3 functions as an ground
conductor for noise protection. In order that the board 1 functions
as a high-frequency board, a part of the wiring layer in the
conductor layer 3 can be constituted as a strip line. For example,
the wiring board 1 may be a high-frequency package or one provided
with an active element function having an ability for processing
high-frequency signals itself, or may be one mounting a
high-frequency element individually constituted, such as an antenna
switch module.
[0111] In addition, the board 1 of this embodiment is incorporated
with various thick-film circuit elements such as a capacitor 54, an
inductor 53, and a resistor 55, in addition to the conductor layer
3, but it may be constituted as a board having only the conductor
layer 3 without particularly having the thick-film circuit
elements. Further, the board 1 can be applied to known wiring
boards such as a mode comprising a high-frequency wiring layer 10
such as a high-frequency micro-strip line. Moreover, the capacitor
electrode in the capacitor 54 in FIG. 2 can be made the entire
electrode conductor layer 11.
[0112] In FIG. 2, the electrode layer 11 that functions as the
shield portion for noise protection, functions as the ground
conductor such as s trip line, or functions as the capacitor
electrode is required to be large so as to have a forming area of 1
cm.sup.2 or more. However, when the dielectric layer 2 using a
crystallized glass and the conductor layer 3 containing the
electrode layer 11 are simultaneously sintered, there was hitherto
a problem that blister or gap is liable to generate in the formed
conductor layer 3, especially in the electrode layer 11, leading to
reduction of the function of the electrode layer 11.
[0113] In the second embodiment of the invention, since the glass
as a constitutional component of the dielectric layer 2 has a
crystallization temperature exceeding 1,000.degree. C., the glass
is one in which the crystallization is inhibited during the
sintering or one in which no crystallization occurs at the
sintering temperature of from 800 to 1,000.degree. C. Accordingly,
it is possible to inhibit the generation of blister or gap as
conventionally observed in the formed conductor layer due to the
difference in the sintering shrinkage behavior between the
dielectric layer and the conductor layer. As a result, it is
possible to enhance the electric characteristics such as
resistivity in the conductor layer, especially to form a conductor
layer suitable for high-frequency signals. Further, since the
electrode layer can have a forming area of 1 cm.sup.2 or more, and
the number of formed layers can be increased, not only the function
of the electrode layer can be enhanced, but also a multilayered
wiring board suitable for high-frequency signals can be
provided.
[0114] As the glass constituting the dielectric layer of the second
embodiment of the invention can be employed ones comprising
SiO.sub.2 and B.sub.2O.sub.3 as major components and
Al.sub.2O.sub.3 and an alkaline earth metal oxide as
sub-components, in which a content of the major components is from
80 to 95 mole %.
[0115] In addition to the metal conductor mainly constituting the
conductor layer, in order to improve the matching with the
dielectric layer during the sintering, for example, silica,
alumina, magnesia, zirconia, titania, mullite, spinel, and glass
frit may be added.
[0116] While the production process of the glass in the second
embodiment of the invention is not particularly limited, one
example will be described below. Oxides of raw material elements in
the raw material constituting the glass are weighed and mixed such
that the material after sintering becomes one as specified
previously; and the mixture is, for example, calcined at
1,600.degree. C. in a crucible and then pulverized by a ball mill,
etc., to obtain a glass powder. In this case, the pulverization may
be achieved such that the glass powder has a mean particle size
ranging from 1 to 3 .mu.m. When the mean particle size of the glass
powder is larger than 3 .mu.m, the mechanical strength of the
formed dielectric layer is lowered, whereas when it is smaller than
1 .mu.m, the debinding properties are lowered. Incidentally, the
formed glass powder has a crystallization temperature exceeding
1,000.degree. C.
[0117] Next, one embodiment of the production process according to
the second embodiment of the invention for producing the
multilayered wiring board as shown in FIG. 2 will be described
below.
[0118] A green sheet that will become a dielectric layer is
prepared. The green sheet is prepared by compounding a glass powder
having a mean particle size ranging from 1 to 3 .mu.m, which can be
formed by the foregoing step, with ceramic fillers such as alumina,
mullite, aluminum nitride, and silicon nitride and additives such
as a binder, a solvent, a plasticizers a deflocculating agent, a
surfactant, and a wetting agent and molding the mixture in a
sheet-like state by the doctor blade process or the like.
[0119] Examples of the binder include acrylic resins (such as
polymethyl methacrylate and poly(t-butyl methacrylate)), cellulose
acetate butyrate, polyethylene, polyvinyl alcohol, and polyvinyl
butyral; and examples of the solvent include acetone, methyl ethyl
ketone, diacetone, methyl isobutyl ketone, benzene,
bromochloroethane, ethanol, butanol, propanol, toluene, and
xylene.
[0120] In addition, examples of the plasticizer include butylbenzyl
phthalate, dibutyl phthalate, dimethyl phthalate, di-2-ethylhexyl
phthalate, adipic esters, polyethylene glycol derivatives, and
tricresol phosphate; examples of the deflocculating agent include
fatty acids (such as glycerin triolate); examples of the surfactant
include benzenesulfonic acid; and examples of the wetting agent
include alkylaryl polyether alcohols, polyethylene glycol ethyl
ether, ethylphenyl glycol, and polyoxyethylene esters.
[0121] On the thus obtained green sheet are formed a plurality of
wiring patterns that will become a conductor layer containing an
entire electrode conductor layer having a forming area of 1
cm.sup.2 or more (in the case of incorporating a thick-film circuit
element, its element pattern is also included) by the known screen
printing process. Thereafter, another ceramic green sheet is
overlaid thereon, and steps of the green sheet formation and green
sheet lamination are repeated, followed by heat lamination under
pressure. There is thus obtained a multilayered wiring molding
having a green material mainly constituted of the glass powder and
the ceramic filler and the conductor layer. Incidentally, in the
case where the via hole 35 is formed, the green sheet is bored in
the position where the via is to be formed by a drill or the like,
into which a metal paste is then filled. The thus formed
multilayered wiring molding is sintered at the sintering
temperature of lower than the crystallization temperature of the
glass powder, to obtain a multilayered wiring board that will
become a multilayered wiring board.
[0122] The multilayered wiring board according the second
embodiment of the invention may have a dielectric layer containing
the dielectric sintered body according to the first embodiment of
the invention. In such a case, a conductor layer is preferably
provided on the surface of and/or inside the dielectric layer.
EXAMPLES
[0123] The invention will be described below in detail with
reference to the Examples.
[1] Example 1
[0124] (1) Evaluation of Glass Powder used in Example 1:
[0125] A glass powder (particle size: 2.5 .mu.m) constituted of
glass A as shown in Table 1, a binder (acrylic resin), and a
solvent (acetone) were mixed, and the mixture was then granulated
to obtain a granulated powder of glass A. At this time, the amount
of the binder was 4% by weight on a basis of 100% by weight of the
mixed powder. Further, the amount of the solvent was 100% by weight
on a basis of 100% by weight of the mixed powder. Thereafter, the
granulated powder was subjected to uniaxial molding and then to CIP
at 150 MPa. Next, the molding was sintered on a ceramic setter in
air at a temperature of 950.degree. C. for 2 hours to obtain a
sintered material of glass A. Similarly, sintered materials of
powders of glass B and glass C, each having a particle size of 2.5
.mu.m, were obtained. Incidentally, in Table 1, the glass marked
with "*" falls outside the predetermined amount in terms of the
content of the alkali metal element. Further, in Table 1, the
"composition (mole %)" column shows the content of each element of
Si, B, Al, Na, K, Ca and Mg converted into oxide on a basis of 100
mole % of the total sum of these elements each converted into
oxide; and the "In (SiO.sub.2+B.sub.2O.sub.3- +Na.sub.2O+K.sub.2O)
(mole %)" column shows the content of Na, K, or the sum of Na and K
converted into oxide on a basis of 100 mole % of the total sum of
Si, B, Na and K each converted into oxide. The differences in the
glass composition are caused by the differences in the raw
materials and conditions of melting crucibles. Further, the glass
compositions were identified by the chemical analysis (ICP
emission).
[0126] The sintered materials of glasses A, B and C were measured
for X-ray diffraction. Among the results, the results of X-ray
diffraction of an unsintered material and sintered material of
glass B are shown in FIG. 1. Incidentally, in FIG. 1, chart (1)
shows one before the sintering, and chart (2) shows one after the
sintering. It is understood from FIG. 1 that the sintered material
of glass B has the same crystals as in the unsintered material.
Further, in both of the sintered material and unsintered material
of glass B, there is not present a peak at which a crystal is
considered to be present. Thus, it can be understood that the
sintered material of glass B is amorphous. Incidentally, glasses A
and C showed similar results. Thus, it was confirmed that the
sintered materials of glasses A, B and C are amorphous.
1 TABLE 1 In (SiO.sub.2 + B.sub.2O.sub.3 + Na.sub.2O + K.sub.2O)
Composition (mole %) (mole %) SiO.sub.2 B.sub.2O.sub.3
Al.sub.2O.sub.3 MgO CaD Na.sub.2O K.sub.2O Na.sub.2O K.sub.2O
Na.sub.2O + K.sub.2O Glass 63.39 24.11 5.70 0.08 6.67 0.05 0.00
0.06 0.00 0.06 A Glass 65.77 23.59 5.39 0.07 5.05 0.06 0.06 0.07
0.07 0.13 B Glass 62.81 24.14 6.40 0.06 6.03 0.42 0.14 0.48 0.16
0.64* C*
[0127] (2) Preparation and Evaluation of Dielectric Material and
Dielectric Sintered Body:
[0128] The glass powder constituted of the glass having the
composition as shown in Table 1 and a ceramic filler (particle
size: 3 .mu.m) having a composition as shown in Table 2 were mixed
in a mixing ratio as shown in Table 3. Incidentally, in Tables 2
and 3, the glass or ceramic filler marked with "*" falls outside
the predetermined amount in terms of the content of the alkali
metal element. Further, the ceramic filler marked with "*" falls
outside the predetermined amount in terms of the content of the
alkaline earth metal element. Further, the "composition (mole %)"
column shows the content of each of the compounds as shown in Table
2 on a basis of 100 mole % of the total sum of these compounds; and
in Table 2, the "In (SiO.sub.2+Al.sub.2O.sub.3+Na.sub.2O+K.sub.2O)
(mole %)" column shows the content of Na.sub.2O, K.sub.2O, or the
sum of Na.sub.2O and K.sub.2O on a basis of 100 mole % of the total
sum of SiO.sub.2, Al.sub.2O.sub.3, Na.sub.2O and K.sub.2O. The
differences in the composition of the ceramic filler are caused by
the differences in the raw materials and conditions of melting
crucibles. Further, the compositions of the ceramic fillers were
identified by the chemical analysis (ICP emission).
[0129] Thereafter, the mixed powder was mixed with a binder
(acrylic resin binder) and a solvent (acetone), and the mixture was
then granulated to obtain a granulated powder of dielectric
material. At this time, the amount of the binder was 4% by weight
on a basis of 100% by weight of the mixed powder. Further, the
amount of the solvent was 100% by weight on a basis of 100% by
weight of the mixed powder. Thereafter, the granulated powder was
subjected to uniaxial molding and then to CIP at 150 MPa. Next, the
molding was sintered on a ceramic setter in air at a temperature of
950.degree. C. for 2 hours to obtain a dielectric sintered body.
Next, the dielectric sintered body was processed into a size having
a diameter of from 15 to 16 mm and a thickness of from 7.5 to 8 mm.
Thereafter, the dielectric sintered body was measured for specific
dielectric constant and dielectric loss at TE011 mode and at a
resonance frequency of from 8 to 12 GHz according to JIS R 1627.
The results are shown in Table 3.
2 TABLE 2 In (SiO.sub.2 + Al.sub.2O.sub.3 Na.sub.2O + K.sub.2O)
Composition (mole %) (mol %) SiO.sub.2 B.sub.2O.sub.3
Al.sub.2O.sub.3 MgO CaO Na.sub.2O K.sub.2O MgO + CaO Na.sub.2O
K.sub.2O Na.sub.2O + K.sub.2O Alumina A 0.00 0.00 100.0 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 Alumina B 0.03 0.00 99.89 0.00 0.00
0.08 0.00 0.00 0.08 0.00 0.08 Alumina C* 0.03 0.00 99.29 0.00 0.00
0.68 0.00 0.00 0.68 0.00 0.68* Alumina D 0.03 0.00 97.97 0.50 1.42
0.08 0.00 1.92** 0.08 0.00 0.08 Quartz 99.97 0.00 0.02 0.00 0.00
0.01 0.00 0.00 0.01 0.00 0.01 Wallastonite** 50.36 0.00 0.05 0.03
49.52 0.01 0.01 49.55** 0.02 0.02 0.04
[0130]
3TABLE 3 Evaluation results Glass: Specific Filler dielectric
Dielectric Glass Filler (Vol. %) constant loss Example 1-1 A
Alumina B 64:36 5.7 0.0010 Example 1-2 B Alumina B 64:36 5.7 0.0012
Example 1-3 C* Alumina B 64:36 5.7 0.0016 Example 1-4 B Alumina A
64:36 5.7 0.0010 Example 1-5 B Alumina C* 64:36 5.7 0.0017 Example
1-6 B Alumina D** 64:36 5.7 0.0016 Example 1-7 B Quartz 64:36 4.1
0.0014 Example 1-8 B Wallastonite** 60:40 6.1 0.0052
[0131] (3) Advantage of Example 1:
[0132] As shown in Table 3, when the total sum of Si, B, Na and K
each converted into oxide in the glass is 100 mole %, in the case
of using the glass having the content of the alkali metal element
converted into oxide exceeding 0.5 mole % (Example 1-3), the
specific dielectric constant showed an excellent value as 5.7, but
the dielectric loss showed a large value as 0.0016. Further, even
by using the glass having the content of the alkali metal element
converted into oxide of 0.5 mole % or less, when the total sum of
SiO.sub.2, Al.sub.2O.sub.3, Na.sub.2O, and K.sub.2O in the ceramic
filler is 100 mole %, in the case of using the ceramic filler
containing alumina as the major component and having the content of
the alkali metal element converted into oxide exceeding 0.5 mole %
(Example 1-5), the specific dielectric constant showed an excellent
value as 5.7, but the dielectric loss showed a large value as
0.0017. Accordingly, it can be understood that dielectric sintered
bodys using a glass having the content of the alkali metal element
exceeding 0.5 mole %, or a ceramic filler having the content of the
alkali metal element exceeding 0.5 mole % are inferior in the
dielectric characteristics in high-frequency regions.
[0133] Further, even if the content of the alkali metal element
converted into oxide is 0.5 mole % or less, when the total sum of
all of the components shown in Table 2 is 100 mole %, in the case
where the content of the alkaline earth metal element converted
into oxide largely exceeds 1 mole % (Example 1-8), the specific
dielectric constant was large as 6.1, and the dielectric loss was
considerably large as 0.0052. Moreover, in the case where the
content of the alkaline earth metal element converted into oxide
slightly exceeds 1 mole % (Example 1-6), the specific dielectric
constant showed an excellent value as 5.7, but the dielectric loss
showed a large value as 0.0016. Thus, it can be understood that
when the content of the alkaline earth metal element exceeds 1 mole
%, the dielectric characteristics in high-frequency regions are
inferior.
[0134] On the other hand, in the case where the content of the
alkali metal element converted into oxide, which is contained in
the glass, is 0.5 mole % or less, the content of the alkali metal
element converted into oxide, which is contained in the ceramic
filler, is 0.5 mole % or less, and the content of the alkaline
earth metal converted into oxide, which is contained in the ceramic
filler, is 1 mole % or less (Examples 1-4 to 6), the specific
dielectric constant is 5.7 or less, and the dielectric loss is
0.0014 or less. Accordingly, it can be understood that these
dielectric sintered bodys are superior in the dielectric
characteristics in high-frequency regions.
[0135] In the light of the above, it can be understood that
nevertheless an amorphous glass is used as the material, the
dielectric sintered bodys of this Example are superior in the
dielectric characteristics in high-frequency regions.
[2] Example 2
[0136] (1) Preparation and Evaluation of Wiring Board;
[0137] The glass powder (particle size: 2.5 .mu.m) of glass B as
shown in Table 1 and the ceramic filler of alumina B as shown in
Table 2 were mixed in a mixing ratio as shown in Table 4 to obtain
a mixed powder. Incidentally, the "% by volume" as referred to
herein means a rate in the true volume. Further, the true volume is
one calculated by dividing the weight of each powder by the
particle density. Moreover, the particle density of each of the
glass powder and the ceramic filler is measured by the pycnometer
method as described in JIS R 1620 "Testing Method for Particle
Density of Fine Ceramic Powder".
[0138] Thereafter, the mixed powder was mixed with a binder
(acrylic resin binder), a plasticizer (dibutyl phthalate), and a
solvent (toluene and methyl ethyl ketone) to obtain a dielectric
material in a slurry state. At this time, when the weight of the
mixed power is 100% by weight, the amount of the binder is 20% by
weight. Further, when the weight of the mixed powder is 100% by
weight, the amount of the plasticizer is 10% by weight. Moreover,
with respect to the amount of the solvent, when the weight of the
mixed powder is 100% by weight, the amount of toluene is 25% by
weight, and the amount of methyl ethyl ketone is 25% by weight.
Next, a green sheet having a thickness of 250 .mu.m was formed from
the material in the slurry state by the doctor blade process.
Thereafter, a Cu paste was screen printed on the surface of the
green sheet, to form an unsintered pattern as a conductor layer.
Next, the obtained unsintered laminate was degreased at 850.degree.
C. in a moistened nitrogen atmosphere and then sintered at
1,000.degree. C. for 2 hours in a nitrogen atmosphere, to obtain a
wiring board.
[0139] Warp of the obtained wiring board and the surface state of
the dielectric layer were visually observed. The results are shown
in Table 4. Further, the cross-section of the dielectric layer was
subjected to textural observation by SEM. The results are also
shown in Table 4.
4TABLE 4 Evaluation results Glass: Filler Surface Textural (Vol. %)
Warp state observation Example 75:25 Yes Gray and Bubbled 2-1
expanded Example 69:31 Ho Gray Minute 2-2 Example 64:36 No Good
Minute 2-3 Example 60:40 No Good Minute 2-4 Example 54:46 No Good
Porous 2-5
[0140] (2) Advantage of Example 2:
[0141] As shown in Table 4, in the case where the mixing amount of
the glass powder exceeds 70% by volume (Example 2-1), it was
confirmed that warp generated in the wiring board, and bubbles
generated on the surface and cross-section of the dielectric layer.
It is considered that such was caused by the matter that the binder
was not thoroughly removed because of a high content of the glass.
This material is not suitable for use as a wiring board
material.
[0142] Further, in the case where the mixing amount of the glass
powder is less than 55% by volume (namely, the mixing amount of the
ceramic filler exceeds 45% by volume), the wiring board was not
sintered because the mixing amount of the ceramic filler was too
high. This material is also not suitable for use as a wiring board
material.
[0143] On the other hand, in the case where the mixing amount of
the glass powder is from 55 to 70% by volume (Examples 2-2 to 4),
the occurrence of warp was not confirmed, and the states of the
surface and the cross-section were good.
[0144] Especially, in the case where the mixing amount of the glass
powder is from 60 to 64% by volume (Examples 2-3 to 4), carbon as a
residue of the binder during the sintering was not detected.
Therefore, these wiring boards were especially good.
[0145] In the light of the above, the material having a mixing
amount of the glass powder of from 55 to 70% by volume is extremely
suitable as a wiring board material.
[0146] Incidentally, it should be construed that the invention is
not limited to these concrete Examples. Depending on the object and
utility, there can be provided various specific embodiments by
changes within the scope of the invention. For example, other
components or inevitable impurities may be contained unless the
dielectric characteristics in high-frequency regions are
substantially influenced.
[0147] Since the dielectric materials according to the present
invention and other present invention are constituted of a glass in
which the glass powder is amorphous, they have a wide width of
sintering conditions such as sintering temperature and pressure, in
which a dielectric sintered body after sintering is small in
specific dielectric constant and small in dielectric loss in
high-frequency regions. Thus, it is possible to obtain a dielectric
sintered body having superior dielectric characteristics in
high-frequency regions. Further, by containing the glass powder and
the ceramic filler in a predetermined ratio, it is possible to
obtain a dielectric material that can undergo degreasing with a
good efficiency. Moreover, it is possible to use, as a conductor
layer, Cu that is complicated in terms of sintering schedule
because of its wide width of sintering conditions. In addition, the
wiring board according to the invention is substantially free from
warp and is superior in high-frequency characteristics in the
dielectric layer.
[3] Example 3
[0148] According to the production step as described above, 100
parts by weight of a mixed powder having a mean particle size of
2.5 .mu.m of 50 parts by weight of a glass powder comprising
SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3, and CaO as the alkaline
earth metal oxide and 50 parts by weight of a ceramic filler
comprising alumina was intimately mixed with 20 parts by weight of
a binder (acrylic resin), 10 parts by weight of a plasticizer
(dibutyl phthalate), and 75 parts by weight of a solvent (a mixed
liquid of toluene and isopropyl alcohol), to prepare a slurry.
Next, using the slurry, a green sheet having a thickness of 250
.mu.m was prepared by the doctor blade process. On the surface of
the obtained green sheet was pattern printed a Cu paste by the
screen printing process to form an electrode layer of 3.6.times.2.6
cm.sup.2 as a conductor layer. Further, steps of the green sheet
formation and green sheet lamination were repeated to form three
layers as the electrode layer. Thereafter, a green sheet was
laminated so as to cover the electrode layer, to form a
multilayered wiring molding. Subsequently, the multilayered wiring
molding was degreased at 850.degree. C. in a nitrogen atmosphere
(reductive atmosphere) and sintered at 1,000.degree. C. for 2
hours. There was thus obtained a multilayered board having the
electrode layer formed therein.
[0149] Incidentally, the Cu paste was prepared by intimately mixing
100 parts by weight of a copper powder (particle size: 5 .mu.m)
mainly constituting the electrode layer, 30 parts by weight of a
vehicle, and 0.5 parts by weight of silica using a three-roll
mill.
[4] Example 4
[0150] A multilayered wiring board was prepared under the same
conditions as in Example 3, except that CaO constituting the glass
powder in Example 3 was replaced by a mixed powder of 60 parts by
weight of a glass powder having MgO and ZnO added thereto and 40
parts by weight of a ceramic filler comprising alumina.
[5] Comparative Example 1
[0151] A multilayered wiring board was prepared under the same
conditions as in Example 3, except that a mixed powder of 60 parts
by weight of a glass powder in which MgO was added to CaO as the
component constituting the glass powder in Example 3 and 40 parts
by weight of a ceramic filler comprising alumina.
[6] Comparative Example 2
[0152] A multilayered wiring board was prepared under the same
conditions as in Example 3, except that CaO constituting the glass
powder in Example 3 was replaced by a mixed powder of 65 parts by
weight of a glass powder having MgO added thereto and 35 parts by
weight of a ceramic filler comprising alumina.
[0153] The contents of the constitutional components of the glass
powders in the Examples and Comparative Examples are shown in Table
5. The crystallization temperature in Table 5 is corresponding to
an exothermic peak temperature of a differential thermal curve
obtained by measuring a glass powder having the same components and
contents as in each of the glass powders of the Examples and
Comparative Examples by the known differential thermal analysis
(DTA), prior to carrying out each of the Examples and Comparative
Examples. The measurement of the differential thermal curve was
carried out at a temperature elevation rate of 10.degree. C./min
within the range of from 25.degree. C. to 1,100.degree. C. Further,
in the glass powder in Example 3, since the crystallization
temperature exceeded 1,100.degree. C., no exothermic peak was
observed within the temperature range of from 25.degree. C. to
1,100.degree. C.
[0154] Incidentally, the crystallization temperature of the glass
power as referred to in the specification and claims of this
application is corresponding to the exothermic peak temperature of
the differential thermal curve as described above.
5TABLE 5 Contents of constitutional components of glass powder
(mole %) Crystalliza- tion temperature SiO.sub.2 B.sub.2O.sub.3
Al.sub.2O.sub.3 MgO CaO ZnO (.degree. C.) Example 3 63.3 24.1 5.7
-- 6.9 -- >1,100 Example 4 44.8 9.7 19.2 20.2 -- 4.1 1,007
Comparative 46.3 7.4 17.8 19.3 9.2 -- 983 Example 1 Comparative
35.5 13.2 9.6 41.7 -- -- 906 Example 2
[0155] Each of the multilayered wiring boards as prepared in the
Examples and Comparative Examples was cut, and the electrode layer
was visually observed under a 20-power magnifying glass.
[0156] As a result, as is evident from Table 5, in the multilayered
wiring board as prepared in Example 3, in which the crystallization
temperature exceeded 1,000.degree. C., blister or peeling was not
confirmed in the electrode layer. Further, in the multilayered
wiring board as prepared in Example 4, the crystallization
temperature exceeded 1,000.degree. C., too. However, since the
crystallization temperature of the glass powder was lower than that
in Example 3, blister was slightly confirmed in the end portion of
the electrode layer. On the other hand, in the multilayered wiring
boards as prepared in Comparative Examples 1 and 2, since the
crystallization temperature was 1,000.degree. C. or lower, blister
or peeling was largely confirmed in the electrode layer.
[0157] It was understood from the foregoing results that the
multilayered wiring boards as prepared in Examples 3 and 4, each of
which was formed from the glass power having a crystallization
temperature exceeding 1,000.degree. C., could inhibit blister or
peeling in the electrode layer. Further, it was understood that the
multilayered wiring board as prepared in Example 3, which was
formed from the glass powder having a higher crystallization
temperature, could more inhibit blister or peeling in the electrode
layer.
[7] Example 5
[0158] Using the same green sheet and Cu paste as in Example 3, so
as to form a multilayered wiring molding as shown in a schematic
view of FIG. 31 the Cu paste was screen printed on the surface of
the green sheet to form an electrode layer pattern having a forming
area of 6 mm.sup.2, and then, steps of the green sheet formation
and green sheet lamination were repeated to form the multilayered
wiring molding having an electrode layer pattern and a wiring
pattern formed therein. Thereafter, the multilayered wiring molding
was degreased at 850.degree. C. in a nitrogen atmosphere (reductive
atmosphere) and sintered at 1,000.degree. C. for 2 hours. There was
thus obtained a multilayered wiring board having a strip line and a
micro-strip line corresponding to high-frequency signals.
[0159] The multilayered wiring board obtained in Example 6 was
subjected to dielectric measurement of specific dielectric constant
and dielectric loss of the dielectric layer and to resistivity
measurement of the conductor wiring as the conductor layer. The
dielectric measurement was carried out at TE011 mode (according to
JIS R 1627) and at a resonance frequency of from B to 12 GHz by the
terminal-based short-circuiting dielectric resonator method.
Further, a volume resistivity of the conductor layer was determined
from resistivity value of the conductor wiring obtained by the
resistivity measurement and the length, width and height of the
conductor wiring as measured. The both measurements were carried
out at a measurement temperature of 25.degree. C.
[0160] The dielectric measurement revealed that the specific
dielectric constant was 5.8 and that the dielectric loss at 10 GHz
was 0.0014. On the other hand, the resistivity measurement revealed
that the volume resistivity was 2.4.times.10.sup.-6 .OMEGA.cm.
[0161] It was confirmed from the measurement results of Example 6
that the multilayered wiring board having a strip line and a
micro-strip line as formed in Example 6 was low in the specific
dielectric constant and the dielectric loss in a high-frequency
band of the dielectric layer and was low in the resistivity of the
conductor layer and hence, was suitable for high-frequency
signals.
[0162] Incidentally, the high frequency as referred to in the
specification and claims of this application means that the
frequency is 1 GHz or more.
[0163] It was confirmed from the foregoing Examples that in the
multilayered wiring boards according to the invention, even in the
case where a conductor layer is constituted of a material having a
low resistivity and a low melting point, such as Cu, it is possible
to inhibit inconveniences such as blister or gap as generated in a
part of an electrode layer of the conductor layer, and furthermore,
it is possible to reduce the resistivity of the conductor layer,
thereby enhancing transmission characteristics of high-frequency
signals.
[0164] This application is based on Japanese Patent application JP
2002-109646, filed Apr. 11, 2002, and Japanese Patent application
JP 2001-390735, filed Dec. 25, 2001, the entire contents of those
are hereby incorporated by reference, the same as if set forth at
length.
* * * * *