Oscillators – With outer casing or housing
Reexamination Certificate
1999-08-31
2001-05-08
Mis, David (Department: 2817)
Oscillators
With outer casing or housing
C331S066000, C331S10800D, C331S158000, C257S698000, C257S700000, C257S704000, C257S724000, C310S315000, C310S318000, C361S730000, C361S753000, C361S820000
Reexamination Certificate
active
06229404
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a 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 oscillator 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 a reference clock signal having a stable frequency even if being used under an environment where ambient temperature drastically changes.
In response to the request for stabilized frequency, temperature compensation is performed to make the oscillating frequency constant and independent of ambient temperature against the intrinsic temperature-frequency variation characteristic of the crystal oscillator (e.g., an AT-cut crystal oscillating element has a temperature-frequency variation characteristic represented by a three-dimensional curve). In order to conduct this temperature compensation in a small crystal oscillator at a high accuracy, variations in oscillating frequency of a crystal oscillating element which varies with ambient temperature is flattened as a whole by use of an oscillating inverter and an IC (Integrated Circuit) chip capable of sensing a temperature, storing temperature compensation data for specified temperatures, converting the voltage, performing varicap diode function, and performing control. Specifically, oscillating frequency variations are flattened by setting the capacity value of varicap diode performance at a suitable predetermined value based on temperature compensation data.
In recent years, a crystal oscillator provided with a control circuit for compensating a temperature-frequency variation characteristic is welded to a printed circuit board by reflowed solder together with other electronic devices and devices. Accordingly, there have been proposed crystal oscillators formed with external terminal electrodes on a surface of a main body thereof. The conventional crystal oscillator provided with external terminal electrodes is formed with a cavity for accommodating a crystal oscillating element and a control circuit. Specifically, the control circuit including an IC chip is arranged in a lower portion of the cavity and the crystal oscillating element is arranged in an upper portion of the cavity or atop the control circuit. In other words, the both members are placed in the same space. Finally, the cavity is hermetically sealed by a metal cover. However, since the frequency variation characteristic of the crystal oscillating element varies due to deposition of impurities on the surface thereof or other causes, it is desirable to hermetically seal the crystal oscillating element in a space provided specially therefor. Further, it is desired to arrange the IC chip in a location which is not subject to the unnecessary heat.
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.
More specifically, as shown in
FIGS. 11
to
13
, the crystal oscillator is mainly comprised of a main body
51
, a rectangular crystal oscillating element
52
, an IC chip
53
constituting a control circuit and a metal cover
54
. In this crystal oscillator is used the main body
51
which is an integral assembly of a plate-like ceramic substrate
55
and a rectangular hollow member
56
attached on the bottom surface of the substrate
55
. The rectangular hollow member
56
has a rectangular space. Accordingly, a cavity
57
is defined in a lower portion of the main body
51
.
In the ceramic substrate
55
partitioning the top surface of the main body
51
and the ceiling surface of the cavity
57
is formed viahole conductors
58
for electrically connecting the top surface of the main body
51
and the ceiling surface of the cavity
57
. Also, a sealing conductive pattern
59
for sealing a gap between the metal cover
54
and the top surface is formed on the top surface of the ceramic substrate
55
. A wiring conductor
60
including an electrode pad for a controlling IC is formed on the ceiling surface of the cavity
57
. Further, external terminal electrodes
61
,
62
(
63
,
64
) are formed on each of, for example, longer sides of the bottom surface of the rectangular hollow member
56
. A plurality of recesses extending up to the bottom surface of the ceramic substrate
55
are formed in the opposite shorter sides of the main body
51
, and terminal electrodes
65
to
68
are formed on the inner wall surfaces of these recesses. The terminal electrodes
65
to
68
are adapted to write temperature compensation data or other data in the IC chip
53
.
The rectangular crystal oscillating element
52
is electrically coupled to the top surface of the main body
51
via electrode pads
69
and
70
using conductive adhesives
71
,
72
, and the metal cover
54
substantially in the form of a dish is integrally coupled using the sealing conductive pattern
59
in order to hermetically seal the crystal oscillating element
52
. A controlling IC chip
53
is mounted in the cavity
57
. This IC chip
53
is electrically connected to the electrode pad of the wiring conductor
60
via a bump or a bonding wire. In the cavity
57
, resin
73
is filled and cured, so that the IC chip
53
is completely covered to have an improved resistance to humidity. In the aforementioned construction, the crystal oscillating element
52
mounted on the top surface of the main body
51
is connected with the IC chip
53
via the viahole conductors
58
. The IC chip
53
and the IC control terminal electrodes
65
to
68
are connected via the wiring conductor
60
extending on the bottom surface of the ceramic substrate
55
. Also, the IC chip
53
and the external terminal electrodes
61
to
64
are connected by a viahole conductor extending through the rectangular hollow member
56
, or utilizing an inner wall surface of the rectangular hollow member
56
.
The crystal oscillator thus constructed is manufactured by the following process.
First, the main body
51
, the crystal oscillating element
52
, the IC chip
53
, etc. are prepared. Subsequently, the crystal oscillating element
52
is mounted on the electrode pads
69
,
70
on the top surface of the main body
51
, and is hermetically sealed by the metal cover
54
. For example, a seam member is placed on the top surface of the main body
51
in advance and the metal cover
54
is placed to be seam-welded. Then, the IC chip
53
is mounted in the cavity
57
in a lower portion of the main body
51
. Specifically, the IC chip
53
is bonded to the ceiling surface of the cavity
57
and is connected with the wiring conductor
60
including the IC electrode pad via an gold wire. Subsequently, the resin
73
is filled and cured in the cavity
57
. Thereafter, specified temperature compensation data are written in the IC chip
53
using the IC control terminal electrodes
65
to
68
exposed to the outside of the main body
51
.
However, in the aforementioned crystal oscillator, the IC chip
53
is required to be supplied with temperature compensation data to flatten a variation in the frequency of the mounted crystal oscillating element
52
in accordance with a temperature-frequency variation characteristic of the crystal oscillating element
52
. The temperature compensation data is writte
Hogan & Hartson LLP
Kyocera Corporation
Mis David
LandOfFree
Crystal oscillator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Crystal oscillator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Crystal oscillator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2498019