U.S. patent application number 10/732997 was filed with the patent office on 2004-07-15 for composite electronic component.
This patent application is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Kishimoto, Yasunori.
Application Number | 20040137972 10/732997 |
Document ID | / |
Family ID | 18795834 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040137972 |
Kind Code |
A1 |
Kishimoto, Yasunori |
July 15, 2004 |
Composite electronic component
Abstract
A composite electronic component that prevents the electrical
connection between a conductive case member of the composite
electronic component, which performs physical shielding against a
physical impact or dust adhesion and also performs an
electromagnetic shielding function, and a conductive member for
performing the electromagnetic shielding function for a surface
acoustic wave element built therein. A composite electronic
component includes surface acoustic wave devices therein, a first
case member, and a second metallic case member. In order to prevent
the electrical connection between the internal surface of the
metallic case connected to a ground potential and a conductor
disposed in a package of the surface acoustic wave devices and
connected to the ground potential to perform the electromagnetic
shielding function, an insulating material layer is provided on at
least one of the top surface of the conductor and the bottom
surface of a top plate of the metallic case.
Inventors: |
Kishimoto, Yasunori;
(Ishikawa-ken, JP) |
Correspondence
Address: |
Keating & Bennett LLP
Suite 312
10400 Eaton Place
Fairfax
VA
22030
US
|
Assignee: |
Murata Manufacturing Co.,
Ltd.
Nagaokakyo-shi
JP
|
Family ID: |
18795834 |
Appl. No.: |
10/732997 |
Filed: |
December 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10732997 |
Dec 11, 2003 |
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09962178 |
Sep 25, 2001 |
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6700061 |
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Current U.S.
Class: |
455/575.8 |
Current CPC
Class: |
H03H 9/6483 20130101;
H03H 7/19 20130101; H03H 9/02913 20130101; H03H 9/0576 20130101;
H03H 9/1071 20130101; H03H 9/725 20130101; H01L 2224/48091
20130101; H01L 2924/00014 20130101; H01L 2224/48227 20130101; H03H
9/72 20130101; H01L 2224/48091 20130101 |
Class at
Publication: |
455/575.8 |
International
Class: |
H04M 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2000 |
JP |
2000-316963 |
Claims
What is claimed is:
1. A composite electronic component comprising: a first case
member; a surface acoustic wave device mounted on the first case
member and which includes a package, a surface acoustic wave
element accommodated within the package, and a ground terminal, the
package having a conductor in at least one portion thereof; and a
conductive second case member to be connected to a ground potential
and fixed to the first case member; wherein at least one of the
external surface of the conductor of the package and the internal
surface of the second case member is provided with an insulating
material layer disposed in an opposing portion between the external
surface of the conductor of the package and the internal surface of
the second case member.
2. A component according to claim 1, wherein the insulating
material layer is provided on the external surface of the conductor
of the package.
3. A component according to claim 1, wherein the insulating
material layer is provided on the internal surface of the second
case member.
4. A component according to claim 1, wherein the first case member
is a planar case circuit board and the second case member includes
a top plate and an annular side-wall extending downwardly from the
periphery of the top plate so as to surround the surface acoustic
wave device mounted on the planar first case member.
5. A component according to claim 1, wherein the second case member
is made of a metal.
6. A component according to claim 1, wherein the second case member
is made of an insulator and a conductive film provided on the
external surface of the insulator.
7. A component according to claim 1, wherein the package includes
first and second package members, the surface acoustic wave element
being mounted on the first package member, the second package
member having the conductor.
8. A component according to claim 7, wherein the first package
member includes a bottom plate and an annular side-wall extending
upwardly from the periphery of the bottom plate so as to have an
opening opened upwardly and the second package member is a planar
lid which is fixed so as to close the opening of the first
package.
9. A component according to claim 7, wherein the first package
member is a planar package circuit board and the second package
member includes a top plate and an annular side-wall extending
downwardly from the periphery of the top plate so as to surround
the surface acoustic wave element mounted on the planar package
circuit board.
10. A component according to claim 9, wherein the second package
member includes a metallic cap.
11. A component according to claim 1, wherein a plurality of the
surface acoustic wave devices are mounted on the first case
member.
12. A component according to claim 1, wherein the surface acoustic
wave device includes a plurality of surface acoustic wave
elements.
13. A component according to claim 12, wherein each of the
plurality of surface acoustic wave elements has a ladder-type
circuit structure including a series arm resonator and a parallel
arm resonator.
14. A component according to claim 1, wherein the composite
electronic component is a duplexer.
15. A communication device comprising a composite electronic
component according claim 1.
16. A composite electronic component comprising: a first case
member; a surface acoustic wave device mounted on the first case
member and which includes a package, a surface acoustic wave
element accommodated within the package, and a ground terminal, the
package having a conductor in at least one portion thereof; and a
conductive second case member to be connected to a ground potential
and fixed to the first case member, the conductive second case
member having an opening in one portion opposing the conductor of
the package.
17. A component according to claim 16, wherein the first case
member is a planar case circuit board and the second case member
includes a top plate and an annular side-wall extending downwardly
from the periphery of the top plate so as to surround the surface
acoustic wave device mounted on the planar first case member.
18. A component according to claims 16, wherein the second case
member is made of a metal.
19. A component according to claim 16, wherein the second case
member is made of an insulator and a conductive film disposed on
the external surface of the insulator.
20. A component according to claim 16, wherein the package includes
first and second package members, the surface acoustic wave element
being mounted on the first package member, the second package
member having the conductor.
21. A component according to claim 20, wherein the first package
member includes a bottom plate and an annular side-wall extending
upwardly from the periphery of the bottom plate so as to have an
opening opened upwardly and the second package member is a planar
lid which is fixed so as to close the opening of the first
package.
22. A component according to claim 20, wherein the first package
member is a planar package circuit board and the second package
member includes a top plate and an annular side-wall extending
downwardly from the periphery of the top plate so as to surround
the surface acoustic wave element mounted on the planar package
circuit board.
23. A component according to claim 22, wherein the second package
member includes a metallic cap.
24. A component according to claim 16, wherein a plurality of the
surface acoustic wave devices are mounted on the first case
member.
25. A component according to claim 16, wherein the surface acoustic
wave device includes a plurality of surface acoustic wave
elements.
26. A component according to claim 25, wherein each of the
plurality of surface acoustic wave elements has a ladder-type
circuit structure including a series arm resonator and a parallel
arm resonator.
27. A component according to claim 16, wherein the composite
electronic component is a duplexer.
28. A communication device comprising a composite electronic
component according to claim 16.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to composite electronic
components defining duplexers for use in portable telephones, for
example, and in particular relates to a composite electronic
component including a surface acoustic wave device that has a
package structure having an electromagnetic shielding effect.
[0003] 2. Description of the Related Art
[0004] The size and weight of mobile and cellular telephones have
recently been reduced, and electronic components used therein also
have been miniaturized, reduced in height, and combined. When the
combination and high-packaging density of electronic components are
promoted, signal interference is likely to arise within the device.
Therefore, the prevention of signal interference is an important
aspect in an electronic component and a composite electronic
component formed by combining a plurality of electronic
components.
[0005] To prevent signal interference, various measures have been
taken. FIG. 16 is a schematic sectional view illustrating a surface
acoustic wave filter as an example of a conventional surface
acoustic wave device. In a surface acoustic wave filter 101, a
surface acoustic wave element 103 is accommodated within a package
102. The package 102 includes a package body 104 and a lid 105. The
package body 104 is formed of an insulating ceramic such as
alumina. The package body 104 is provided with a plurality of
electrodes that are connected to the surface acoustic wave element
103, and via bonding wires 106 and 107, the surface acoustic wave
element 103 and these electrodes are electrically connected
together.
[0006] In the plurality of electrodes provided in the package body
104, an electrode 108 is connected to the ground electric
potential, and a terminal to be connected to the ground electric
potential of the surface acoustic wave element 103 is connected to
the electrode 108 via a bonding wire.
[0007] The lid 105 made of a metal protects the surface acoustic
wave element 103 accommodated in the inside from external
electromagnetic waves. The lid 105 is electrically connected to an
electrode to be connected to the ground electric potential of the
surface acoustic wave element 103 and an electrode of the package
body 104, such that noises from the outside of the package are
prevented from entering therein. Such a structure is disclosed in
Japanese Unexamined Patent Application Publication No. 12-049565,
for example.
[0008] In a composite electronic component including the surface
acoustic wave device described above, similar measures have also
taken. For example, in Japanese Unexamined Patent Application
Publication No. 9-181567, a duplexer is schematically shown in FIG.
17. In the drawing, on a planar case circuit board 121, surface
acoustic wave devices 122 and 123, capacitors 124 and 125, and a
coil 126 are mounted. A metallic cover member 127 is provided on
the case circuit board 121 and is fixed thereto so as to surround
these elements.
[0009] In addition, although the surface acoustic wave devices 122
and 123 are schematically shown, the top surface thereof is made of
a conductive material to provide an electromagnetic shielding
effect similar to the surface acoustic wave device 101 described
above.
[0010] In the duplexer, due to the package structure of the surface
acoustic wave devices 122 and 123, a surface acoustic wave element
is shielded against electromagnetic noises, and moreover, noises
from the outside are prevented from entering therein by the
metallic cover member 127.
[0011] In a mobile or cellular telephone, the product is
constructed by combining a plurality of electronic circuit blocks
that perform different functions. FIG. 18 is a circuit block
diagram of a mobile or cellular telephone.
[0012] As is apparent from FIG. 18, high-frequency signals from a
base station are received by an antenna 131 and are converted into
IF signals by a duplexer 132 via receiving components 133 to 137.
In contrast, IF transmitting signals produced in the terminal are
output to the antenna 131 via the duplexer 132 after passing
through transmitting components 138 to 142.
[0013] In this case, in a receiving system which handles weak
signals, an RF receiving block 143 for filtering and amplifying
high-frequency signals and an IF receiving block 144 for filtering
and amplifying IF signals are shielded against external noises by
covering the respective entire blocks with conductive cover members
having the ground potential.
[0014] By connecting the conductive cover member mentioned above to
the ground potential, not only is the electromagnetically shielding
provided as described above, but also the ground potential in a
composite electronic component is reinforced.
[0015] As described above, by connecting the lid of the surface
acoustic wave device package to the ground potential, external
noises are prevented from entering the package. Likewise, in a
composite electronic component such as a duplexer, by connecting
the conductive cover member to the ground potential, external
noises are prevented from entering the composite electronic
component and the ground potential is reinforced.
[0016] On the other hand, in a surface acoustic wave device such as
a ladder type filter having a parallel arm resonator and a series
arm resonator, large changes in characteristics due to an
inductance component existing between the parallel-arm resonator
and the ground potential are present. In the surface acoustic wave
device, the inductance component is produced in a bonding wire for
achieving the connection between an electrode which is connected to
the ground potential and an electrode pad on a surface acoustic
wave element which is connected to the ground potential, a via hole
electrode in the package, or a wiring pattern.
[0017] Furthermore, in a composite electronic component having a
surface acoustic wave device mounted thereon, various inductance
components are provided to allow signals to pass through, such as a
via hole electrode provided on a case circuit board and a patterned
conductive pattern.
[0018] Therefore, the resultant total inductances existing between
the parallel arm resonator and the ground potential greatly effect
the characteristics of the surface acoustic wave device and the
composite electronic component using the surface acoustic wave
device.
[0019] Reduction in the height of an electronic component to be
mounted is necessary with the miniaturization and reduction in
thickness of a mobile or cellular telephone. Therefore, due to a
physical impact and stress applied to a mobile or cellular
telephone and conductive floating substances, such as solder scraps
and dust, the conductive member providing electromagnetic shielding
may come into contact with the conductive cover member of the
composite electronic component in the package of the surface
acoustic wave device. Accordingly, when these members come into
contact, the parasitic inductance component is changed, resulting
in deterioration in characteristics of the surface acoustic wave
device.
[0020] That is, in a composite electronic component having a
surface acoustic wave device built therein with a ladder-type
circuit structure shown in FIG. 19, for example, there are
inductances L1 to L3 generated by bonding wires in the surface
acoustic wave device, an inductance L4 generated by wiring or a
through-hole electrode in the package of the surface acoustic wave
device, and an inductance L5 generated by wiring disposed in a case
of the composite electronic component. In addition, in FIG. 19,
numeral P1 denotes a ground terminal of the surface acoustic wave
device package. When a conductive member providing electromagnetic
shielding comes in contact with a conductive cover member of the
composite electronic component so as to be connected, a connecting
route shown in a dotted line X is formed. Therefore, the inductance
between the parallel arm resonator in the surface acoustic wave
device and the ground potential is changed, resulting in
deteriorating in characteristics as mentioned above.
[0021] In addition, not only in a surface acoustic wave device with
a ladder-type circuit structure having a parallel arm resonator,
but also in a surface acoustic wave device with another structure,
deterioration in characteristics may be produced by changes in the
inductance component due to a signal route in the surface acoustic
wave device and a signal route in the composite electronic
component.
SUMMARY OF THE INVENTION
[0022] To overcome the above-described problems, preferred
embodiments of the present invention provide a composite electronic
component that securely prevents the occurrence of an electrical
connection, which is caused by physical impact and dust adhesion,
between a conductive case member of the composite electronic
component providing physical and electromagnetic shielding and a
conductive member of a surface acoustic wave device disposed
therein that provides electromagnetic shielding.
[0023] In addition, preferred embodiments of the present invention
provide a composite electronic component in which the
characteristics are not deteriorated due to changes in the
parasitic inductance component generated between a surface acoustic
wave device and the ground potential.
[0024] Also, preferred embodiments of the present invention provide
a composite electronic component having a conductive cover member
to be connected to the ground potential for providing the
electromagnetic shielding function and reinforcing the ground
potential function of the conductive cover member.
[0025] In accordance with a first preferred embodiment of the
present invention, a composite electronic component, having a
surface acoustic wave device disposed therein, includes a first
case member, a package, a surface acoustic wave element mounted on
the first case member and accommodated within the package, and a
ground terminal, the package being connected to the surface
acoustic wave device having a conductor in at least one portion
thereof and to the first case member, and a conductive second case
member connected to the ground potential, wherein at least one of
the external surface of the conductor and the internal surface of
the second case member is provided with an insulating material
layer disposed in an opposing portion between the external surface
of the conductor of the package and the internal surface of the
second case member.
[0026] In a specific example of the first preferred embodiment, the
insulating material layer is preferably provided on the external
surface of the conductor of the package.
[0027] In an alternative specific example of the first preferred
embodiment, the insulating material layer is preferably provided on
the internal surface of the second case member.
[0028] In accordance with a second preferred embodiment of the
present invention, a composite electronic component, having a
surface acoustic wave device disposed therein, includes a first
case member, a package, a surface acoustic wave element mounted on
the first case member and accommodated within the package, and a
ground terminal, the package being connected to the surface
acoustic wave device having a conductor in at least one portion
thereof and to the first case member, and a conductive second case
member connected to the ground potential, the conductive second
case member having an opening in a portion opposing the conductor
of the package.
[0029] In a specific example of the first and the second preferred
embodiments, the first case member is preferably a planar case
circuit board and the second case member preferably includes a top
plate and an annular side-wall extending downwardly from the
periphery of the top plate to surround the surface acoustic wave
device mounted on the planar first case member.
[0030] In another example of preferred embodiments of the present
invention, the second case member is made of a metal.
[0031] In another specific example of preferred embodiments of the
present invention, the second case member is defined by an
insulator and a conductive film provided on the external surface of
the insulator.
[0032] In another specific example of preferred embodiments of the
present invention, the package includes a first package member and
a second package member, the surface acoustic wave element being
mounted on the first package member and the second package member
including the conductor.
[0033] In another specific example of preferred embodiments of the
present invention, the first package member includes a bottom plate
and an annular side-wall extending upwardly from the periphery of
the bottom plate so as to form an upward opening and the second
package member defined by a planar lid fixed so as to close the
opening of the first package.
[0034] In another specific example of preferred embodiments of the
present invention, the first package member is a planar package
circuit board and the second package member includes a top plate
and an annular side-wall extending downwardly from the periphery of
the top plate to surround the surface acoustic wave element mounted
on the planar package circuit board.
[0035] In another specific example of preferred embodiments of the
present invention, the second package member includes a metallic
cap.
[0036] In another specific example of preferred embodiments of the
present invention, a plurality of the surface acoustic wave devices
is mounted on the first case member.
[0037] In another specific example of preferred embodiments of the
present invention, the surface acoustic wave device may include a
plurality of surface acoustic wave elements.
[0038] In another specific example of preferred embodiments of the
present invention, each of the plurality of surface acoustic wave
elements may have a ladder-type circuit configuration including a
series arm resonator and a parallel arm resonator.
[0039] In another specific example of preferred embodiments of the
present invention, a communication device including a composite
electronic component according to other preferred embodiments of
the present invention is provided.
[0040] In a composite electronic component according to the first
preferred embodiment of the present invention, because at least one
of an external surface of a conductor of a package and an internal
surface of a second case member is provided with an insulating
material layer provided in an opposing portion between the external
surface of the conductor and the internal surface of the second
case member, even when an external force is applied or solder
scraps or conductive dust are adhered thereto, an electrical
connection between the external surface of the conductor and the
internal surface of the second case member is prevented by the
insulating material layer. Accordingly, a reliable composite
electronic component having stable characteristics that do not
deteriorate is provided. Also, the second case member provides
greatly improved shielding effects.
[0041] In a composite electronic component according to the second
preferred embodiment of the present invention, a surface acoustic
wave device is mounted on a first case member while in a second
case member fixed to the first case member, an opening is provided
in a portion opposing a conductor of a package of the surface
acoustic wave device to surround the surface acoustic wave device.
Therefore, as in the first preferred embodiment, even when an
external force is applied or solder scraps or conductive dust are
adhered thereto, the electrical connection between the second case
member and the conductor of the package of the surface acoustic
wave device is prevented. Accordingly, a reliable composite
electronic component with stable characteristics is provided.
[0042] Other features, elements, characteristics and advantages of
the present invention will become more apparent from the following
detailed description of the preferred embodiments with reference to
the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is an assembly view of a duplexer as a composite
electronic component according to a first preferred embodiment of
the present invention.
[0044] FIG. 2 is a perspective view of the duplexer shown in FIG.
1.
[0045] FIG. 3 is a plan view for illustrating a case circuit board,
a surface acoustic wave device mounted on the case circuit board, a
coil, and a capacitor used in the duplexer according to the first
preferred embodiment of the present invention.
[0046] FIG. 4 is a sectional view of the surface acoustic wave
device used in the first preferred embodiment of the present
invention.
[0047] FIG. 5 is a plan view of a surface acoustic wave element
chip used in the surface acoustic wave device shown in FIG. 4.
[0048] FIG. 6 is a circuit diagram for illustrating a circuit
configuration defined by the surface acoustic wave element chip
shown in FIG. 5.
[0049] FIG. 7 is a diagram for illustrating a circuit configuration
of the duplexer according to the first preferred embodiment of the
present invention.
[0050] FIG. 8 is a graph for showing frequency characteristics of
the duplexer according to the first preferred embodiment and a
duplexer prepared for a comparative example.
[0051] FIG. 9 is a graph for showing isolation characteristics of
the duplexer according to the first preferred embodiment and the
duplexer prepared for the comparative example.
[0052] FIG. 10 is a sectional view of a surface acoustic wave
device according to a first modification of the first preferred
embodiment of the present invention.
[0053] FIG. 11 is a sectional view of a surface acoustic wave
device according to a second modification of the first preferred
embodiment of the present invention.
[0054] FIG. 12 is a sectional view of a surface acoustic wave
device according to a third modification of the first preferred
embodiment of the present invention.
[0055] FIG. 13 is a schematic assembly view of a duplexer according
to a second preferred embodiment of the present invention.
[0056] FIG. 14 is a schematic assembly view of a duplexer according
to a third preferred embodiment of the present invention.
[0057] FIG. 15 is a schematic assembly view of a duplexer according
to a fourth preferred embodiment of the present invention.
[0058] FIG. 16 is a sectional view of a conventional surface
acoustic wave device.
[0059] FIG. 17 is an assembly view of a duplexer as a conventional
composite electronic component.
[0060] FIG. 18 is a schematic block diagram of a circuit
configuration of the duplexer shown in FIG. 17.
[0061] FIG. 19 is a circuit diagram for illustrating problems of
the conventional duplexer.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0062] The present invention will be described in accordance with
specific preferred embodiments of the present invention, referring
to drawings.
[0063] FIG. 1 is an assembly view of a duplexer as a composite
electronic component according to a first preferred embodiment of
the present invention.
[0064] A duplexer 1 has a planar case circuit board 2 as a first
case member. The case circuit board 2 is made of a conventional
insulating circuit board such as a glass-fiber-reinforced epoxy
printed circuit board and an alumina circuit board. On the top
surface of the case circuit board 2, a plurality of electrodes
including electrodes 3 and 4 are provided.
[0065] On the top surface of the case circuit board 2, capacitors 7
and 8, a coil 9, and surface acoustic wave devices 5 and 6 are
provided. The capacitors 7 and 8 and the coil 9 are schematically
shown in FIGS. 1 and 2, and each preferably has a planar
configuration as shown in FIG. 3.
[0066] According to the present preferred embodiment, the
capacitors 7 and 8 are monolithic capacitors, however, another type
of capacitor may be used. Also, another inductance component such
as a monolithic inductor may be used instead of the coil 9.
[0067] The circuit of the duplexer according to the present
preferred embodiment is shown in FIG. 7.
[0068] Between an input terminal (Tx terminal) 11 of transmitting
signals and an input-output terminal (ANT terminal) 13 that is
connected to an antenna, a surface acoustic wave device 6 having
passing characteristics in a transmitting frequency band is
connected. Likewise, between a receiving terminal (Rx terminal) 12
for receiving signals and the ANT terminal 13, a surface acoustic
wave device 5 having passing characteristics at a receiving
frequency band is connected. Also, between the ANT terminal 13 and
the surface acoustic wave device 5, the coil 9 and the capacitors 7
and 8 are connected as shown in FIG. 7.
[0069] The circuit of the duplexer shown in FIG. 7 is preferably
the same as that of a conventional duplexer used for mobile or
cellular telephones. The surface acoustic wave devices 5 and 6, the
capacitors 7 and 8, and the coil 9 are electrically connected to
each other on the case circuit board 2 to produce the circuit shown
in FIG. 7.
[0070] As shown in FIGS. 1 and 2, a metallic second case member 16
is fixed on the top surface of the case circuit board 2 so as to
surround the surface acoustic wave devices 5 and 6, the capacitors
7 and 8, and the coil 9. The metallic case 16 preferably includes a
top plate 16a and an annular side-wall 16b extending downwardly
from the outer periphery of the top plate 16a. Tongue pieces 16c
and 16d protruding in the horizontal direction are provided on the
longer side of the annular side-wall 16b. The tongue pieces 16c and
16d are respectively joined and electrically connected to
electrodes 3 and 4 provided on the top surface of the case circuit
board 2. The electrodes 3 and 4 disposed on the case circuit board
2 are connected to the ground potential.
[0071] That is, the metallic case 16 is electrically connected to
the ground potential via the electrodes 3 and 4.
[0072] Next, the surface acoustic wave devices 5 and 6 will be
described in detail with reference to FIGS. 4 to 6. Since the
surface acoustic wave devices 5 and 6 have the same structure, only
the surface acoustic wave device 5 will be described.
[0073] As shown in FIG. 4, in the surface acoustic wave device 5, a
surface acoustic wave element chip 22 is provided in a package 21.
The package 21 preferably includes a first package member 21a and a
lid 21b defining a second package member. The first package member
21a includes a bottom plate 21a.sub.1 and an annular side-wall
21a.sub.2 extending upwardly on sides of the bottom plate
21a.sub.1. On the bottom plate 21a.sub.1 of the first package
member 21a, the surface acoustic wave element chip 22 is
mounted.
[0074] Although schematically shown in FIG. 4, on the first package
member 21a, a plurality of electrodes 23 and 24 are provided, which
are electrically connected to electrode pads provided on the
surface acoustic wave element chip 22 with bonding wires 25 and
26.
[0075] The metallic lid 21b defining the planar second package
member is joined to the first package member 21a with a conductive
adhesive 27 so as to close the upper opening of the first package
member 21a.
[0076] The first package member 21a is preferably made of an
insulating ceramic, such as alumina, and is produced by integrally
firing the first package member 21a with the electrodes 23 and 24
mentioned above.
[0077] The lid 21b is preferably made of an appropriate metal, such
as aluminum and stainless steel, and provides electromagnetic
shielding for the surface acoustic wave element chip 22
accommodated therein.
[0078] The surface acoustic wave element chip 22 having an
insulating material layer 28 provided thereon according to the
present preferred embodiment will be described in detail with
reference to FIGS. 5 and 6.
[0079] The surface acoustic wave element chip 22 includes a
piezoelectric circuit board 31. On the piezoelectric circuit board
31, plural IDTs 32 to 38 are provided. Surface acoustic wave
resonators are defined by the plural IDTs 32 to 38, respectively.
The surface acoustic wave resonators 32 to 38 are electrically
connected to each other to produce the circuit shown in FIG. 6.
That is, the resonators 32 to 38 are electrically connected to each
other to define a ladder-type circuit as a whole, in which the
surface acoustic wave resonators 32, 35, and 38 define parallel arm
resonators and the surface acoustic wave resonators 33, 34, 36, and
37 define series arm resonators.
[0080] In addition, although FIG. 4 illustrates only two bonding
wires 25 and 26, electrode pads on the surface acoustic wave
element chip 22 shown in FIG. 5 are connected to electrodes
provided on the first package member 21a with bonding wires,
respectively.
[0081] That is, the surface acoustic wave device 5 includes a
plurality of surface acoustic wave resonators disposed therein.
[0082] However, according to various preferred embodiments of the
present invention, each of surface acoustic wave devices 5 and 6
may have only one surface acoustic wave resonator built therein, or
may have one or more surface acoustic wave resonators built
therein.
[0083] Since the surface acoustic wave device 6 is the same as the
surface acoustic wave device 5 in structure, a detailed description
thereof is omitted.
[0084] Referring to FIG. 1 again, the duplexer 1 according to the
present preferred embodiment includes the insulating material
layers 28 provided on the top surfaces of the surface acoustic wave
devices 5 and 6, respectively. The insulating material layer 28
according to the present preferred embodiment is preferably formed
of an insulating tape. The insulating tape includes an adhesive
layer provided on one side of the insulating tape. However, the
insulating material layer 28 may be formed by coating a synthetic
resin or an insulating paint on the top surface of the lid 21b of
each of the surface acoustic wave devices 5 and 6.
[0085] In any case, in one portion of the external surface of the
package of the respective surface acoustic wave devices 5 and 6,
which is the portion opposing the metallic case 16 as the first
case member, which is the top surface of the lid 21b according to
the present preferred embodiment, the insulating material layer 28
is disposed.
[0086] Accordingly, even when the internal surface of the top plate
16a of the metallic case 16 is caused to contact with the top
surface of the respective surface acoustic wave devices 5 and 6 by
an external force, or solder scraps or conductive dust existing
between them, an electrical connection between the metallic case 16
and the lid 16b is reliably prevented by the insulating material
layer 28.
[0087] In the duplexer 1 according to the present preferred
embodiment, since the electrical connection due to an external
force, or solder scraps or conductive dust is securely prevented,
deterioration in characteristics due to the connection is reliably
prevented. These advantages will be described based on experimental
results.
[0088] FIG. 8 shows passing characteristics from the ANT terminal
to the Rx terminal of the duplexer 1 according to the present
preferred embodiment of the present invention. FIG. 9 shows
isolation characteristics of the duplexer 1. The solid lines in
FIGS. 8 and 9 indicate the characteristics according to the present
preferred embodiment, and the broken lines indicate the
characteristics of a comparative example in that the lid 21b is
brought into contact with the internal surface of the metallic case
16 without providing the insulating material layer 28 of the
surface acoustic wave device 5. In addition, in the present
preferred embodiment, the transmitting band is preferably about 824
MHz to about 849 MHz and the receiving band is preferably about 869
MHz to about 894 MHz.
[0089] As is apparent from FIGS. 8 and 9, when the internal surface
of the metallic case 16 is electrically connected to the lid 21b of
the surface acoustic wave device 5, the attenuation at the
transmitting band is reduced by approximately 4 dB while the
isolation at the same band is deteriorated by approximately 10 dB.
This is because the inductance component between the parallel arm
resonator of the surface acoustic wave device 5 and the ground
potential is changed due to the electrical connection.
[0090] In contrast, when the insulating material layer 28 is
provided as in the preferred embodiment, because the electrical
connection between the metallic case 16 and the lid 21b is
prevented, the characteristics indicated by solid lines in FIGS. 8
and 9 are maintained. That is, even when the internal surface of
the metallic case 16 is caused to contact with the top surface of
the insulating material layer 28 by an external force, or solder
scraps or conductive dust existing between them, because the
electrical connection is prevented, the desired characteristics are
stably maintained.
[0091] Furthermore, the metallic case 16 is maintained at the
ground potential, such that the electromagnetic shielding effect is
sufficiently exhibited. Therefore, the insulating material layer 28
reduces the distance between the top plate 16a of the metallic case
16 and the top surfaces of the surface acoustic wave devices 5 and
6, resulting in reduction in height of the duplexer.
[0092] FIG. 10 is a sectional view of a first modification of the
above-described preferred embodiments of the surface acoustic wave
device 5. In the surface acoustic wave device 5, the insulating
material layer 28 is provided on the top surface of the lid 21b
made of a metallic plate, as shown in FIG. 4.
[0093] On the other hand, in the modified surface acoustic wave
device 5A shown in FIG. 10, a metallized layer 28b is provided on
the bottom surface of an insulating plate 28a, such as a synthetic
resin plate. That is, the metallized layer 28b performs the
electromagnetic shielding function as a conductor and the
insulating plate 28a is an insulating material layer.
[0094] FIG. 11 is a longitudinal sectional view of a second
modification of the above-described preferred embodiments of the
surface acoustic wave device 5.
[0095] In the surface acoustic wave device 5, the surface acoustic
wave element chip 22 is electrically connected to the electrodes
disposed in the first package member 21a with the bonding wires 25
and 26. In a surface acoustic wave device 5B shown in FIG. 11, the
surface acoustic wave element chip 22 is mounted on the bottom
plate 21a.sub.1 of the first package member 21a by a face-down
method. Therefore, the electrode disposed in the first package
member 21a is electrically connected to electrodes of the surface
acoustic wave element chip 22 with bumps 41 and 42.
[0096] FIG. 12 is a sectional view of a third modification of the
above-described preferred embodiments of the surface acoustic wave
device 5. In a surface acoustic wave device 5C, the package is
defined by a first package member 43 and a metallic cap 44. That
is, the first package member 43 includes a planar package circuit
board and a second package member includes the metallic cap 44
having a top plate 44a and an annular side-wall 44b extending
downwardly from the periphery of the top plate 44a.
[0097] On the top surface of the metallic cap 44, an insulating
material layer 28A is provided by coating the metallic cap 44 with
a resin.
[0098] As described above, the configurations of the first and
second package members in the surface acoustic wave device
according to the present invention are not limited, and various
modifications can be made. Also, in the surface acoustic wave
devices 5A to 5C shown in FIGS. 10 to 12, because on the top
surface, i.e., on the portion opposing the internal surface of the
metallic case 16 functioning as the electromagnetic shielding of
the duplexer, the insulating plate 28a or the insulating material
layer 28 or 28A is disposed, such that the electrical connection of
the portion of the metallic case 16 of the duplexer opposing the
electromagnetic shielding conductor of the surface acoustic wave
device package is prevented as in the preferred embodiments
described above.
[0099] FIG. 13 is a schematic assembly view for illustrating a
duplexer according to a second preferred embodiment of the present
invention.
[0100] In a duplexer 51 according to the second preferred
embodiment, on the top surface of the second package member of each
of the surface acoustic wave devices 5 and 6, the insulating
material layer 28 is not provided. Instead, an insulating material
layer 52 is provided on the bottom surface of the top plate 16a of
the metallic first case member 16. Since the other structures are
the same as those in the first preferred embodiment, the
description in the first preferred embodiment is referred to by
designating like functional elements with like reference
characters.
[0101] The insulating material layer 52 is preferably formed of a
material similar to that of the insulating material layer 28.
[0102] The insulating material layer 52 may not be provided on the
surface of the acoustic wave devices 5 and 6, as in this preferred
embodiment, but on the internal surface of the top plate 16a that
defines the second case member. Also, in this case, because the
insulating material layer 52 is disposed in the portion functioning
as the electromagnetic shielding of the surface acoustic wave
devices 5 and 6, that is, the portion of the metallic case 16 that
is the second case member of the duplexer opposing the lid 21b, the
electrical connection between the metallic case 16 and the metallic
lid 21b is prevented, thereby preventing the deterioration in
frequency characteristics and isolation characteristics, similar to
the first preferred embodiment.
[0103] That is, according to various preferred embodiments of the
present invention, the insulating material layer may be disposed
either on the surface acoustic wave device or on the case member of
the composite electronic component. Furthermore, although not
shown, the insulating material layer 28 according to the first
preferred embodiment and the insulating material layer 52 according
to the second preferred embodiment may be used in combination. That
is, the insulating material layer may be provided either on the
surface acoustic wave device or on the case member of the composite
electronic component.
[0104] FIG. 14 is a schematic assembly view of a duplexer as a
composite electronic component according to a third preferred
embodiment of the present invention. The duplexer according to the
third preferred embodiment may be used instead of the duplexer 132
shown in FIG. 17, for example, thereby forming a communication
device according to the present invention.
[0105] In a duplexer 61 according to the third preferred
embodiment, an insulating material layer is not provided for
breaking the electrical connection between a metallic case 16A and
the surface acoustic wave devices 5 and 6. Instead, the top plate
16a of the metallic case 16A is provided with openings 16e and 16f
provided thereon. The openings 16e and 16f have planar square
shapes being positioned to oppose the lids 21b of the surface
acoustic wave devices 5 and 6, respectively.
[0106] That is, according to the present preferred embodiment, over
the lids 21b of the surface acoustic wave devices 5 and 6,
insulating material layers including air are providing by the
openings 16e and 16f, thereby preventing the electrical connection
between the metallic case 16A and the lids 21b of the surface
acoustic wave devices 5 and 6, similar to the first preferred
embodiment. Therefore, the planar shape of each of the openings 16e
and 16f has a greater area than that of the top surface of the lid
21b.
[0107] FIG. 15 is a schematic assembly view of a duplexer that is a
composite electronic component according to a fourth preferred
embodiment of the present invention. The duplexer according to the
third preferred embodiment may be used instead of the duplexer 132
shown in FIG. 17, for example, thereby defining a communication
device according to the present invention.
[0108] In a duplexer 71 according to the fourth preferred
embodiment, an insulating material layer is not provided for
preventing an electrical connection between a metallic case 16A and
the surface acoustic wave devices 5 and 6. Instead, a post 72 is
provided on the case circuit board 2 and between the surface
acoustic wave devices 5 and 6. The post 72 has a height h2 that is
larger than the height h1 of the surface acoustic wave devices 5
and 6 and supports the top plate 16a of the metallic first case
member 16 such that the top plate 16a is prevented from contacting
the lids 21b of the surface acoustic wave devices 5 and 6. The post
72 may have a substantially circular or a substantially rectangular
cross section, and even the cross section may be other shapes.
Further, a plurality of posts 72 may be provided on the case
circuit board 2. According to a fourth preferred embodiment, even
the metallic first case member 16 may be distorted due to an
external force, the post 72 prevents the metallic first case member
16 from contacting with the lids 21b of the surface acoustic wave
devices 5 and 6. Thus, a composite electronic component having very
stable device characteristics and high reliability is provided.
[0109] In the first and second preferred embodiments and the
modifications described above, the two surface acoustic wave
devices 5 and 6 are disposed in the duplexer 1. However, a
composite electronic component having only one surface acoustic
wave device disposed therein can be applied to the present
invention. Also, three or more surface acoustic wave devices may be
disposed in the composite electronic component.
[0110] Moreover, not only the duplexer but also various composite
electronic components such as a multimode RF filter and a
split-type RF filter in which a passing region is divided can be
applied to the present invention.
[0111] In the first to fourth preferred embodiments, the first case
member is preferably a planar case circuit board and the second
case member is preferably defined by the metallic case 16 or 16A
including the top plate and the side-wall extending downwardly from
the top plate. The first case member may have a bottom plate and a
side-wall extending upwardly from the bottom plate and the planar
second case member may be attached to the first case member so as
to close the upper opening of the first case member. In this case,
the planar second case member is preferably made of a metal or an
insulator having a conductive material layer provided on the
external surface thereof so as to perform the function of
electromagnetic shielding.
[0112] Also, in the first to fourth preferred embodiments, the
metallic case 16 or 16A is provided, the first case member may be
formed of an insulator such as alumina and a synthetic resin having
a conductive film provided on the external surface of the
insulator.
[0113] While preferred embodiments of the invention have been
described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the invention. The scope of the
invention, therefore, is to be determined solely by the following
claims.
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