Oscillators – With outer casing or housing
Reexamination Certificate
2000-12-15
2004-11-16
Kinkead, Arnold (Department: 2817)
Oscillators
With outer casing or housing
C331S17700V, C331S158000, C331S10800D, C257S728000
Reexamination Certificate
active
06819191
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric oscillator unit, and more particularly, to a surface-mounted piezoelectric oscillator unit utilizing a quartz vibrator to provide a standard frequency used in a portable terminal.
2. Description of the Related Art
FIG. 6
shows a conventional quartz oscillator unit
31
using a surface-mounted quartz vibrator package. In this quartz oscillator unit
31
, a surface-mounted quartz vibrator package
33
is mounted on the top surface of a flat circuit substrate
32
, electrodes provided on the bottom surface of the quartz vibrator package
33
are electrically connected to electrode pads on the circuit substrate
32
by reflow soldering, and the quartz vibrator package
33
is mechanically fixed to the circuit substrate
32
with solder
34
. Circuit components
35
and
36
defining an oscillating circuit, and a temperature compensation circuit are mounted on the circuit substrate
32
, a shielding case
37
is provided on the circuit substrate
32
to cover the quartz vibrator package
33
and the circuit components
35
and
36
, and the shielding case
37
is soldered to the circuit substrate
32
with solder
38
.
In the quartz oscillator unit
31
having the structure described above, however, the quartz vibrator package
33
and the shielding case
37
are connected to the circuit substrate
32
mechanically and electrically only by solder, and hence, when attempting to solder the quartz oscillator unit
31
to a printed-circuit board by reflow soldering or flow soldering, the solder
34
which has bonded the quartz vibrator package
33
to the circuit substrate
32
melts in the process of reflow soldering or flow soldering, such that the quartz vibrator package
33
may be lifted from the circuit substrate
32
or may slide thereon. Also, when reflow soldering or flow soldering the printed-circuit substrate
32
while laying the circuit substrate face down with the quartz oscillator unit
31
at the lower side, the quartz vibrator package
33
may fall off from the circuit substrate
32
due to vibrations occurring during reflow soldering once the solder
34
melts.
Furthermore, when the quartz oscillator unit
31
is reflow soldered or flow soldered, not only the quartz vibrator package
33
, but also the shielding case
37
, may lift off of the circuit substrate
32
, move thereon, or fall off of the circuit substrate
32
.
Moreover, not only in the case where the quartz oscillator unit
31
is mounted, but also in the case where the equipment printed-circuit substrate on which the quartz oscillator unit
31
has been mounted is repaired, when the equipment printed-circuit substrate is placed on a heating plate to melt the solder, and the quartz oscillator unit
31
is removed from the equipment printed-circuit substrate, the heat of the melted solder and that of the heating plate causes the quartz vibrator package
33
and/or the shielding case
37
to lift or detach from the circuit substrate
32
.
In recent years, with the miniaturization of quartz oscillator units, circuit substrates have been miniaturized to a size comparable to that of the quartz vibrator package, and consequently the space for soldering the shielding case to the circuit substrate in the quartz oscillator unit is greatly reduced or eliminated. A quartz oscillator unit having no shielding case has been introduced, and which uses only the shielding effect of the quartz vibrator package itself. In such a quartz oscillator unit, since the quartz vibrator package thereof is not covered with a shielding case, the likelihood that the quartz vibrator package will lift from or fall off the circuit substrate due to the heat in the reflow soldering and the heat of the heating plate is greatly increased.
To prevent such problems, high-temperature solder may be used to fix the quartz vibrator package and the shielding case to the circuit substrate by reflow soldering. The high-temperature solder is, however, difficult to handle, because the use of the high-temperature solder requires a higher heating temperature reflow furnace which can produce adverse effects on semiconductor components.
SUMMARY OF THE INVENTION
To overcome the above-described problems, preferred embodiments of the present invention provide a piezoelectric oscillator unit which maintains the adhesive force of the vibrator package with respect to the circuit substrate even when the solder connecting the quartz vibrator package to the circuit substrate melts, that is, a piezoelectric oscillator unit which is capable of preventing the vibrator package from lifting from or falling off the circuit substrate even if the vibrator package is subjected to heating when the piezoelectric oscillator unit is mounted or repaired.
A first preferred embodiment of the present invention provides a piezoelectric oscillator unit including a vibrator package housing a piezoelectric component which is overlaid on a circuit substrate on which an oscillating circuit is mounted, and in which the electrodes provided on the top surface of the circuit substrate and the electrodes provided on the bottom surface of the vibrator package are bonded together using a brazing material such as solder, wherein the circuit substrate and the vibrator package are bonded together via an adhesive.
In the piezoelectric oscillator unit in accordance with the first preferred embodiment of the present invention, since the vibrator package housing the piezoelectric member (a quartz member for example) is overlaid on the circuit substrate, and the vibrator package and the circuit substrate are bonded together using an adhesive such as a thermosetting adhesive, the adhesive force between the vibrator package and the circuit substrate is maintained even when the solder bonding the quartz vibrator package to the circuit substrate is melted by the heat of a reflow furnace, a flow soldering device, a heating plate for repair, or other heat sources. This prevents the vibrator package from developing defects such as lifting from or falling off the circuit substrate in the mounting or repairing process.
Also, since the adhesion area between the vibrator package and the circuit substrate is greatly increased, the transverse rupture strength of the piezoelectric oscillator unit is greatly enhanced. Among the overlapping surfaces of the quartz vibrator package and the circuit substrate, the bonding surfaces to be bonded by an adhesive include the entire surfaces except for the electrode portions, or portions thereof.
A second preferred embodiment of the present invention provides a piezoelectric oscillator unit including a vibrator package housing a piezoelectric member which is overlaid on a circuit substrate on which an oscillating circuit is mounted, and in which the electrodes provided on the top surface of the circuit substrate and the electrodes provided on the bottom surface of the vibrator package are bonded together using a brazing material such as solder, wherein the vibrator package is covered with a shielding case, the vibrator package is held by the shielding case, and the shielding case is adhered to the circuit substrate by an adhesive.
In the piezoelectric oscillator unit in accordance with the second preferred embodiment of the present invention, since the shielding case covering the vibrator package is adhered to the circuit substrate by an adhesive such as a thermosetting adhesive, and the vibrator package is held by the shielding case, the vibrator package is retained by the shielding case, even when the solder bonding the quartz vibrator package to the circuit substrate is melted by the heat of are flow furnace, a flow soldering device, a heating plate for repair, or other heat source. This prevents the vibrator package from developing defects such as lifting from or falling off the circuit substrate.
Preferably, in the piezoelectric oscillator unit in accordance with the second preferred embodiment of the present invention, each of a plurality of protrusions provided on the sh
Fujita Makoto
Funahara Toshikazu
Keating & Bennett LLP
Kinkead Arnold
Murata Manufacturing Co. Ltd.
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