Oscillators – With outer casing or housing
Reexamination Certificate
2001-09-20
2003-07-01
Kinkead, Arnold (Department: 2817)
Oscillators
With outer casing or housing
C331S1160FE, C331S158000, C331S10800D, C257S784000, C257S786000, C257S758000, C333S191000, C333S192000
Reexamination Certificate
active
06587008
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a piezoelectric oscillator accommodating a piezoelectric oscillating element in a cavity of a container unit and particularly to a piezoelectric oscillator suited to high-frequency oscillation utilizing overtone oscillation. Here, piezoelectric oscillating elements include those using a crystal substrate, a piezoelectric ceramic substrate and a monocrystalline piezoelectric substrate.
A crystal oscillator as an example of the piezoelectric oscillator is mounted in a mobile communication controller or a controller for controlling a LAN and is a very important component for generating an oscillation frequency for controlling such a controller. For example, the crystal oscillator used in the mobile communication controller or the like is required to extremely reduce its volume as the mobile communication controller is becoming smaller.
As a surface mount crystal oscillator for accomplishing such a miniaturization, for example, Japanese Unexamined Patent Publication No. 10-28024 discloses a construction in which a crystal oscillating element is mounted on the surface of a container unit comprised of a rectangular single-plate substrate and a frame-shaped leg portion and having a cavity whose opening is rectangular formed in its bottom surface, and a crystal oscillating element is mounted on the outer surface of the container unit while an IC chip is mounted in the cavity of the container unit.
FIGS. 23
to
26
show such a conventional surface mount crystal oscillator
150
.
This crystal oscillator
150
is mainly comprised of a container unit
151
, a rectangular crystal oscillating element
152
, an IC chip
153
forming an oscillation control circuit, and a metallic lid
154
.
This crystal oscillator
150
uses the container unit
151
in which a rectangular single-plate ceramic substrate
155
and a frame-shaped leg portion
156
are assembled into a unit, and a cavity
157
is formed in the bottom surface of this container unit
151
.
The ceramic substrate
155
partitioning the outer surface of the container unit
151
and the bottom surface of the cavity
157
is formed with via hole conductors
158
for electrically connecting the outer surface of the ceramic substrate
155
and the bottom surface of the cavity
157
. A sealing conductive pattern
159
for sealing the metallic lid
154
is formed on the outer surface of the ceramic substrate
155
. Further, a wiring pattern
160
including IC electrode pads is formed on the bottom surface of the cavity
157
, and external terminal electrodes
161
to
164
are formed on the four corners of the bottom surface of the frame-shaped leg portion
156
.
The rectangular crystal oscillating element
152
is bonded on the outer surface of the container unit
151
via crystal oscillating element mounts
169
,
170
using conductive adhesive materials
171
,
172
so as to be electrically conductive. Further, the saucer-shaped metallic lid
154
is integrally joined using the sealing conductive pattern
159
in order to hermetically seal the crystal oscillating element
152
. The IC chip
153
is accommodated in the cavity
157
. This IC chip
153
is connected with the IC electrode pads as part of the wiring pattern
160
via bumps or bonding wires. The crystal oscillating element
152
mounted on the outer surface of the container unit
151
is connected with the IC chip
153
via the via hole conductors
158
, and the IC chip
153
is connected with the external terminal electrodes
161
to
164
via the wiring pattern
160
. A filling resin
173
is filled into the cavity
157
and cured therein. Thus, the IC chip
153
is completely covered by the filling resin
173
to have an improved humidity resistance.
However, the aforementioned conventional crystal oscillator is a relatively low-frequency oscillator used in an oscillation frequency band of a fundamental wave, e.g., a frequency band of about 13 MHz to 28 MHz. Thus, in the case of assuming a LAN
90
constructing a giga-bit ether net as shown in
FIG. 27
for performing a high-speed communication processing of a large quantity of communication information including data such as sounds, still images and animated images, the communication controller using such a crystal oscillator has a problem in communication ability.
Specifically, in a network group A, a plurality of information terminals
91
provided with a communication ability of 10 Mbps are connected with a giga-bit ether net switch
95
via hubs
93
. A plurality of information terminals
92
provided with a communication ability of 100 Mbps are connected with a giga-bit ether net switch
95
A via 100M repeaters
94
. The gaga-bit ether net switch
95
A is connected with a server
96
provided with a communication ability of 1000 Mbps. Network groups B, C are similarly constructed. A gaga-bit ether net switch
95
B of the network group B is connected with the gaga-bit ether net switch
95
A via a router
97
, whereas a gaga-bit ether net switch
95
C of the network group C is connected with the gaga-bit ether net switch
95
A via a router
98
.
In the above LAN
90
, a clock frequency of about 25 MHz is used in communications at locations indicated at ∘, and a clock frequency of about 125 MHz is used in communications at locations indicated at &Circlesolid;. The respective communication controllers necessitating a crystal oscillator for performing a high-frequency oscillation of 125 MHz is required to precisely process a huge amount of communication information of the entire network at high speeds. Further, in order to meet a demand for speeding up an information communication, crystal oscillators capable of performing high-frequency oscillation of 125 MHz or higher are becoming necessary.
On the other hand, among the characteristics of the crystal oscillator for the high-frequency oscillation used in the high-speed communication controller, a characteristic of a jitter J which is a phase variation of an oscillation waveform in every cycle t
1
shown in
FIG. 28
is essential in precisely processing an information.
The jitter J is described in detail. The jitter J is expressed as a total jitter TJ comprised of a jitter DJ which is a nonvariable component and a jitter RJ which is a variable component. In other words, a relationship defined by following equation (1) is satisfied:
TJ=DJ+
14
RJ
(1)
Accordingly, the total jitter TJ can be suppressed by suppressing the jitter RJ to low level, and high-frequency oscillation utilizing overtone oscillation can be stably and satisfactorily performed. Specifically, a standard deviation &sgr; centered at 8 ns needs to be 10 ps or lower at a clock frequency of 125 MHz.
Since the aforementioned conventional crystal oscillator
150
is not provided with such a characteristic, it has been impossible to use it, for example, in a communication controller for precisely processing a huge amount of communication information of an entire network at high speeds as mentioned above.
Further, a ground potential for grounding an oscillating circuit needs to be stable for the precise and stable oscillation. If a ground pattern takes up a larger area for this purpose, it partly overlaps a wiring pattern for connecting a piezoelectric oscillating element with the oscillating circuit. A parasitic capacity occurring at the overlapping portion makes the oscillation unstable, thereby causing a problem of reduced oscillation characteristics.
Further, in the aforementioned conventional crystal oscillator
150
, when plasma cleaning is applied to the wiring pattern
160
provided in the cavity
157
as shown in
FIG. 25
before the connection by wire bonding, a conductive external matter removed from the outer surface of the wiring pattern
160
is adhered to the wiring pattern
160
again, thereby disadvantageously reducing connection by wire bonding between the IC chip
153
and the wiring pattern
160
.
Further, in this crystal oscillator
150
, the oscillating circuit of the crystal oscillating element
152
is for
Hatanaka Hidefumi
Morimoto Masaru
Hogan & Hartson LLP
Kinkead Arnold
Kyocera Corporation
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