Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-08-31
2001-05-08
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06229249
ABSTRACT:
This application is based on Japanese patent application Nos. 10-217291, 10-244278, 10-244279, 10-309661, 10-309662, 10-309663 and 10-309664 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
This invention relates to a surface-mount type crystal oscillator, for example, a crystal oscillator for use in a mobile communications apparatus.
A crystal oscillator of this type is an essential part for generating an oscillation signal for control of signal reception and transmission between mobile communications apparatus or the like. Such a crystal oscillator is required to have a very small volume as the mobile communications apparatus is constructed smaller and to have an oscillation signal having a stable frequency even if being used under environment where ambient temperature drastically changes.
In response to such request, temperature compensation is performed to make an oscillating frequency independent of ambient temperature against an intrinsic temperature-frequency variation characteristic of the crystal oscillator (for example, an AT-cut sliding crystal oscillator has a temperature-frequency variation characteristic represented by a three-dimensional curve). In order to conduct this temperature compensation in a small crystal oscillator with high accuracy, the variation in oscillating frequency of the crystal oscillator which varies with ambient temperature is flattened as a whole by setting a capacity value of a varicap diode at a suitable predetermined value based on temperature compensation data, using an oscillating inverter and an IC chip having integration of memory function for storing temperature compensation data corresponding to specified temperatures, voltage converting function, varicap diode function and control function.
Another crystal oscillator is known in which a crystal oscillating element is mounted in a main body as it is and an accommodation space therefor is hermetically sealed. A typical construction is as follows. A main body is formed with a cavity having a stepped portion. A control device is placed on a bottom surface of the cavity. A crystal oscillating element is placed on the stepped portion and the entire cavity is hermetically sealed by a metal cover. Such a construction does not use a can case and, therefore, can be made smaller because the crystal oscillating element and the control device are placed one on top of the other in the cavity along thickness direction. However, since the control device and the crystal oscillating element are arranged in the same cavity, the crystal oscillating element operates in an unstable manner if members for coupling or protecting the control device produce unnecessary gases.
Japanese Unexamined Patent Publication No. 10-28024 discloses a small crystal oscillator provided with external terminal electrodes on a surface thereof which satisfies the aforementioned demands and is able to highly accurately conduct a temperature compensation. This crystal oscillator includes a plate-like substrate and a rectangular hollow member attached on a bottom surface of the plate-like substrate. The rectangular hollow member has a rectangular space. The plate-like substrate and the rectangular hollow member defines a cavity. A crystal oscillating element is mounted on a top surface of the plate-like substrate while a control circuit is provided on a bottom surface of the plate-like substrate and in the cavity.
FIGS. 27
to
29
show a conventional temperature compensating crystal oscillator. This crystal oscillator is mainly comprised of a main body
1051
, a rectangular crystal oscillating element
1052
, an IC chip
1053
or controlling element constituting an oscillation control circuit and a metal cover
1054
. This crystal oscillator includes a main body
1051
which is an integral assembly of a single-plate ceramic substrate
1055
and a rectangular hollow member
1056
provided on the bottom surface of the substrate
1055
. The rectangular hollow member
1056
has a rectangular space. Thus, a cavity
1057
is defined in a lower portion of the main body
1051
.
The ceramic substrate
1055
partitioning the top surface of the main body
1051
and the ceiling surface of the cavity
1057
is formed with viahole conductors
1058
in the thickness direction of the main body
1051
for electrically connecting the top surface side of the main body
1051
and the cavity
1057
. A sealing conductive layer
1059
for sealing the metal cover
1054
is formed on the top surface of the ceramic substrate
1055
. A wiring conductor
1060
including an IC electrode pad is formed on the ceiling surface of the cavity
1057
. Further, external terminal electrodes
1061
,
1062
,
1063
,
1064
are formed on the opposite longer sides of the bottom surface of the rectangular hollow member
1056
. Four recesses extending up to the bottom surface of the rectangular hollow member
1056
are formed in the opposite shorter sides of the rectangular hollow member
1056
, and terminal electrodes
1065
to
1068
are formed on the inner wall surfaces of these recesses. The terminal electrodes
1065
to
1068
are adapted to write temperature compensation data or other data in an IC (integrated circuit) chip
1053
mounted on the cavity
1057
.
The rectangular crystal oscillating element
1052
is electrically coupled to the top surface of the main body
105
via mounts
1069
and
1070
using conductive resin adhesives
1071
,
1072
, and the metal cover
1054
substantially in the form of a dish is integrally coupled using the sealing conductive layer
1059
in order to hermetically seal the crystal oscillating element
1052
. The IC chip
1053
is bonded to an IC electrode pad via a bump or a bonding wire. In the cavity
1057
, resin
1073
is filled and cured, so that the IC chip
1053
is completely covered to have an improved resistance to humidity. In the aforementioned construction, the crystal oscillating element
1052
mounted on the top surface of the main body
1051
is connected with the IC chip
1053
via the viahole conductors
1058
, and the IC chip
1053
is connected with the external terminal electrodes
1061
to
1064
and the temperature compensation data writing terminal electrodes
1065
to
1068
via the wiring conductors
1060
. The IC chip
1053
and the terminal electrodes
1065
to
1068
are connected via the wiring conductor
1060
formed on a plane of the bottom surface side of the ceramic substrate
1055
, and the IC chip
1053
and the external terminal electrodes
1061
to
1064
are connected by the viahole conductors
1058
extending through the thickness of the rectangular hollow member
1056
, utilizing the inner wall surface of the hollow member
1056
.
In the above crystal oscillator, the rectangular IC chip
1053
is used as a control circuit for controlling the oscillation of the crystal oscillating element. Thus, the cavity
1057
of the main body
1051
for accommodating the IC chip
1053
has a rectangular shape. The external terminal electrodes
1061
to
1064
connected to the IC chip
1053
are formed on the opposite longer sides of the bottom of the rectangular hollow member
1056
.
However, it is very difficult to realize a stable operation of the crystal oscillator only by the aforementioned IC chip
1053
. Specifically, high-frequency noise is likely to be added onto a power supply voltage supplied from an external terminal electrode, e.g., the VCC external terminal electrode
1061
. Also, alternating-current components is likely to be added onto an output signal of an external terminal electrode, e.g., the external terminal electrode
1062
. These noises can be removed by a large capacity capacitor, which is, however, difficult to integrate into the IC chip
1053
.
In the conventional crystal oscillator, in order to avoid the oscillator becoming larger, a capacitor for performing the above operation needs to be mounted side by side with the crystal oscillator on a printed circuit board. However, this complicates the circuit construction of t
Hatanaka Hidefumi
Hayashi Naoki
Sasagawa Ryouma
Yonemura Hideomi
Dougherty Thomas M.
Hogan & Hartson LLP
Kyocera Corporation
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