Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-03-08
2003-12-09
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06661162
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric resonator such as a quartz crystal resonator or the like, and a method of producing the same. Particularly, the present invention relates to the technique of electrically connecting electrodes formed on a resonator piece and preventing a short circuit.
2. Description of Related Art
Of various flexural vibration mode, longitudinal vibration mode, or torsional vibration mode piezoelectric resonators, for example, as shown in
FIG. 11
, a tuning fork type quartz crystal resonator comprises a piezoelectric resonator piece
1002
comprising a sheet-shaped quartz crystal piece in which two arms
1022
and
1023
are extended from a base
1021
, internal terminals
1031
of a plug
1030
being connected to the base
1021
of the piezoelectric resonator piece. As shown in FIGS.
12
(A)and
12
(B) which are perspective views of the piezoelectric resonator piece
1002
used in a piezoelectric resonator (tuning fork type quartz crystal resonator) as viewed from the upper side and the lower side, respectively, two electrode patterns
1040
are formed with a predetermined gap therebetween on each of the upper side
1025
and the lower side
1026
of the arms
1022
and
1023
of the piezoelectric resonator piece
1002
to form exciting electrodes
1045
. In FIGS.
12
(A) and
12
(B), in order to discriminate the two electrode patterns
1040
, one of the electrode patterns
1040
is shown by lines inclined to the right, the other electrode pattern being shown by lines inclined to the left.
Since the exciting electrodes
1045
are formed on each of the upper side
1025
and the lower side
1026
of the piezoelectric resonator piece
1002
, the exciting electrodes
1045
formed on the upper side
1025
of the piezoelectric resonator
1002
are electrically connected to the exciting electrodes
1045
on the lower side
1026
through conduction electrodes
1046
respectively formed on the edges
1251
,
1252
,
1253
and
1254
of the upper side
1025
, the edges
126
l,
1262
,
1263
and
1264
of the lower side
1026
, and the sides
1271
and
1272
. Therefore, portions of the electrode patterns
1040
, which are formed on the base
1021
, are used as mounts, and the inner leads
1031
are electrically connected to the mounts with solder or a conductive adhesive so that an AC voltage is applied to the exciting electrodes
1045
through the inner leads
1031
to vibrate the arms
1022
and
1023
at a predetermined frequency.
In the piezoelectric resonator
1001
having the above construction, in some cases, the electrode patterns
1040
are formed in a chromium single layer However, in order to decrease the electric resistance of the electrode patterns
1040
, a noble metal layer such as a gold electrode layer, a silver electrode layer, or the like is used. However, the direct formation of a gold electrode layer on the surface of the piezoelectric resonator piece
1002
deteriorates adhesion between the piezoelectric resonator piece
1002
and the gold electrode layer. Therefore, as shown in FIG.
13
(A) which is a sectional view taken along line IV—IV of
FIG. 12
showing the piezoelectric resonator piece
1002
used in a conventional piezoelectric resonator, under metal layers
1041
each comprising a chromium layer are formed as under layers even when gold electrode layers
1042
are used for the electrode patterns
1040
.
On the other hand, in the arms
1022
and
1023
of the piezoelectric resonator (quartz crystal resonator)
1
, the gap between the electrode patterns
1040
is as small as the &mgr;m order, and thus a short circuit readily occurs between the electrode patterns
1040
. Therefore, as shown in FIGS.
13
(B) and
13
(C) which are sectional views taken along lines V-V′ and VI—VI, respectively, of FIGS.
12
(A) and
12
(B), surface protecting films
1047
each comprising a silicon oxide film are formed on the surfaces of the electrode patterns
1040
by sputtering. However, the silicon oxide films (the surface protecting films
1047
) have poor adhesion to the gold electrode layers
1042
, and thus the gold electrode layers
1042
are removed from the arms
1022
and
1023
to expose the under metal layers
1041
each comprising a chromium layer so that the surface protecting films
1047
are formed on the under metal layers
1041
.
As shown in FIG.
13
(A), the gap between the electrode patterns
1040
in the base
1021
side is large, and thus no short circuit occurs between the electrode patterns
1040
. Also, from the viewpoint of soldering between the inner leads
1031
of the plug
1030
and the mount, as shown in
FIG. 11
, the gold metal layers
1042
are preferably formed. Therefore, as shown in FIG.
13
(A), each of the electrode patterns
1040
has a two-layer structure comprising the under metal layer
1041
and the gold electrode layer
104
without the surface protecting film
1047
.
Furthermore, in the conventional piezoelectric resonator
1001
, the exciting electrodes
1045
are formed on each of the upper side
1025
and the lower side
1026
of the piezoelectric resonator piece
1002
, and the exciting electrodes
1045
formed on the upper side
1025
of the piezoelectric resonator
1002
are electrically connected to the exciting electrodes
1045
on the lower side
1026
through the conduction electrodes
1046
respectively formed on the edges
1251
,
1252
,
1253
and
1254
of the upper side
1025
, the edges
1261
,
1262
,
1263
and
1264
,of the lower side
1026
, and the sides
1271
and
1272
. However, each of the electrode patterns
1040
corresponding to the conduction electrodes
1046
comprises only the under metal layer
1041
comprising a chromium layer, thereby causing a problem in that the exciting electrodes
1045
formed on the upper side
1025
and the exciting electrodes
1045
formed on the lower side
1026
are readily brought into an open state. Namely, the under metal layer
1041
comprising a chromium layer which forms each of the conduction electrodes
1046
comprises a hard film, and thus cracks occurs in the curved or bent portions
1276
,
1277
,
1278
and
1279
of the sides
1271
and
1272
of the piezoelectric resonator piece
1002
to easily cause disconnection. In forming a mask for partially etching the gold electrode layers
1042
formed on the surfaces of the under metal layers
1041
comprising chromium layers, in some cases, misalignment occurs to cause the chromium layers (the under metal layers
1041
) to be etched off by etching the gold electrode layers
1042
, thereby producing defects in the conduction electrodes
1046
comprising chromium layers (the under metal layers
1041
). In this way, the exciting electrodes
1045
on the upper side
1025
of the piezoelectric resonator piece
1002
and the exciting electrodes
1045
on the lower side
1026
thereof are brought into an open state by disconnection of the conduction electrodes
1046
, causing the problem of increasing the CI value (crystal impedance/the resistance value when the mechanical vibration system of a resonator is represented by an equivalent circuit comprising a series resonant circuit containing resistance, capacitance and impedance, and parallel capacitance provided in parallel with the series resonant circuit) or disenabling oscillation.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems and provide a piezoelectric resonator in which exciting electrodes formed on the upper and lower sides of a piezoelectric resonator piece are not brought into an open state even when noble metal layers are partially removed for increasing adhesion of surface protecting films, and a method of producing the same.
The present invention provides a piezoelectric resonator comprising a flat plate piezoelectric resonator piece; exciting electrodes formed on each of the upper side and lower side of the piezoelectric resonator piece by electrode patterns formed on the piezoelectric resonator piece; conduction elect
Kasuga Yoshiharu
Nagai Mitsuru
Addison Karen Beth
Dougherty Thomas M.
Oliff & Berridg,e PLC
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