Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Flip chip
Reexamination Certificate
2000-08-09
2002-07-09
Talbott, David L. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Flip chip
C257S779000, C257S780000, C257S737000, C257S738000, C333S193000, C333S195000, C310S31300R
Reexamination Certificate
active
06417574
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to surface-acoustic-wave devices and more particularly to a surface-acoustic-wave device for flip-chip mounting.
Surface-acoustic-wave devices hereinafter designated as SAW devices are used extensively in various electronic apparatuses having a high-frequency circuit, including portable telephone sets, wireless telephone sets, and various radio sets. By using a surface-acoustic-wave device, it becomes possible to reduce the weight and size of these electronic apparatuses.
On the other hand, the demand for size and weight reduction is still continuing in electronic apparatuses and hence in the SAW devices used therein. In the case of SAW devices, the size reduction has to be achieved so as to avoid deterioration of attenuation characteristic outside the pass-band.
FIG.1
shows an equivalent circuit diagram of a SAW filter of a related art having a ladder-type construction, while
FIG.2
shows the actual construction of the SAW filter of
FIG.1
in a cross-sectional view.
Referring to
FIG.1
, the ladder-type SAW filter includes resonators
13
and
14
connected in series and interposed between an input terminal
11
and an output terminal
12
, and there are provided parallel resonators
15
,
16
and
17
respectively shunting a signal path between the input terminal
11
and the SAW filter
13
, a signal path between the SAW filters
13
and
14
, and a signal path between the SAW filter
14
and the output terminal
12
, to the ground. These resonators
13
-
17
are formed on a common piezoelectric substrate
10
of a LiTaO
3
or LiNbO
3
single crystal.
FIG.2
shows the piezoelectric substrate
10
in the state that the piezoelectric substrate
10
is mounted on a filter package
20
.
Referring to
FIG.2
, the filter package
20
includes a bottom part
21
A covered by a conductor film
21
a
and a side wall part
21
B, wherein the bottom part
21
A and the side wall part
21
B form together a depression
21
C. Thus, the piezoelectric substrate
10
is accommodated in the depression
21
C in such a manner that the piezoelectric substrate
10
is mounted on the conductor film
21
a
covering the bottom part
21
A in a face-up state by way of an adhesive layer
21
b
. Thus, an electrode pattern corresponding to the equivalent circuit diagram of
FIG.1
is formed on the top principal surface of the piezoelectric substrate
10
. Further, wiring patterns
21
c
and
21
d
are formed on the top surface of the side wall part
21
B, and the electrode pattern on the substrate
10
is connected to the wiring patterns
21
c
and
21
d
via respective bonding wires
22
A and
22
B.
It should be noted that the SAW device
20
of
FIG.2
further includes a frame part
21
D on the top surface of the side wall part
21
B so as to expose the wiring patterns
21
c
and
21
d
, and a metal cap
23
is provided on the frame part
21
D. The metal cap
23
is connected to the ground pads
21
e
and
21
f
provided on the bottom surface of the bottom part
21
A via respective ground patterns
22
e
and
22
f
formed on the frame part
21
D. Further, the wiring patterns
21
c
and
21
d
on the side wall part
21
B are connected also electrically to corresponding electrodes that are provided on the bottom surface of the bottom part
21
A.
In the filter package
20
of
FIG.2
, the bonding wires
22
A and
22
B are used for electrical connection between the SAW device on the piezoelectric substrate
10
and the wiring patterns
21
c
and
21
d
. In order to accommodate such bonding wires, the SAW device of
FIG.2
has used the frame part
21
D, while such a construction inevitably increases the height of the SAW package
20
and thus contradicts with the requirement of size reduction of SAW devices.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful SAW device wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a SAW filter device having a compact size and simultaneously an excellent spurious suppression performance outside a pass-band.
Another object of the present invention is to provide a surface-acoustic-wave device, comprising:
a piezoelectric substrate;
an electrode pattern provided on a principal surface of said piezoelectric substrate, said electrode pattern forming a ladder-type surface-acoustic-wave filter; and
a package body accommodating therein said piezoelectric substrate,
said package body comprising: a bottom part carrying said piezoelectric substrate in a face-down state; and a side wall part laterally surrounding said piezoelectric substrate on said bottom part,
said bottom part and said side wall part forming together a depression accommodating therein said piezoelectric substrate,
said bottom part carrying a wiring pattern for electrical connection with said electrode pattern,
said wiring pattern including a first ground pattern and a second ground pattern in a mutually separated relationship on said bottom part, said first ground pattern and said second ground pattern being connected electrically with each other.
Another object of the present invention is to provide a surface-acoustic-wave device, comprising:
a package body having a mounting surface;
a piezoelectric substrate mounted on said mounting surface in a face-down state;
a first electrode pattern provided on a principal surface of said piezoelectric substrate facing said mounting surface in said face-down state of said piezoelectric substrate, said first electrode pattern forming a ladder-type filter; and
a second electrode pattern provided on said principal surface of said piezoelectric substrate, said second electrode pattern forming a double-mode-type filter;
each of said first and second electrode patterns including a plurality of ground electrodes formed on said principal surface,
said mounting surface carrying a first ground pattern making a contact commonly with said plurality of ground electrodes of said first electrode pattern, said mounting surface further carrying a plurality of mutually separated second ground patterns each making an electrical contact with a corresponding one of said plurality of ground electrodes of said second electrode pattern.
According to the present invention, the space needed in the SAW device of the related art at the top part of the package body for accommodating the bonding wires is eliminated, and the size of the SAW device is reduced successfully. By forming the first ground pattern on the package body as a part of the electrode pattern of the ladder-type filter in such a manner that the first ground pattern makes a contact with the ground electrode of an input/output shunting resonator, and by forming the second ground pattern on the package body so as to make a contact with the ground electrode of the intermediate shunting resonator shunting an intermediate signal path of the ladder-type SAW filter, and further by connecting the first ground pattern and the second ground pattern electrically, suppression of spurious components outside a pass-band of the SAW filter is improved substantially. The degree of suppression of the spurious components is improved further by interposing an inductance between the first and second ground patterns and by optimizing the value of the inductance.
By forming the ground electrodes in the form of stacking of a plurality of bumps, or by forming the wiring patterns on the mounting surface in the form of stacking of a plurality of conductor patterns, the problem of short circuit caused between the electrode pattern on the piezoelectric substrate and the ground pattern on the mounting surface is successfully eliminated.
The present invention is applicable also to a SAW device in which a plurality of electrode patterns including the ladder-type electrode pattern is formed on the principal surface of the piezoelectric substrate. The SAW device includes the one in which an electrode pattern corresponding to a double-mode-type filter is provided on the p
Furusato Hiroyuki
Kawachi Osamu
Misawa Kiyohide
Ueda Masanori
Fujitsu Media Devices Limted
Talbott David L.
Thai Luan
LandOfFree
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