Composite piezoelectric component and chip-type composite...

Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices

Reexamination Certificate

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C310S348000, C310S366000

Reexamination Certificate

active

06351055

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite piezoelectric component such as a composite trap including a plurality of piezoelectric resonant elements, and more specifically, the present invention relates to a composite piezoelectric component having a structure in which a plurality of piezoelectric resonant elements are stacked and joined to each other via conductive joining members.
2. Description of the Related Art
Various composite piezoelectric components formed by electrically connecting a plurality of piezoelectric resonant elements are known.
For example, Japanese Unexamined Patent Publication No.4-192909 discloses a composite trap as an example of such composite piezoelectric components. As shown in
FIG. 6
, this composite trap
61
includes a first trap element
62
formed of double-mode ceramic resonators having the same resonant frequencies and a second trap element
63
formed of double-mode ceramic resonators having resonant frequencies which are different from each other. The first trap element
62
and the second trap element
63
are mounted on a rectangular-shaped base substrate
64
.
The first trap element
62
and the second trap element
63
are electrically connected to each other by electrodes provided on the base substrate
64
. Furthermore, lead terminals
65
to
67
are joined to the electrodes on the base substrate
64
. The entire composite trap except for a portion to which the lead terminals
65
to
67
are extended is covered by an exterior resin as shown by phantom lines “A”.
In the composite trap
61
, since the two elements, i.e., the first trap element
62
and the second trap element
63
, are mounted next to each other on the base substrate
64
, the overall size of the trap
61
is very large.
Japanese Unexamined Patent Publication No.4-192909 also discloses a composite trap having the first and second trap elements
62
and
63
stacked on each other and joined via a conductive joining member and a plurality of lead terminals connected thereto, and covered by an exterior resin. A special shaped lead terminal is used and arranged so as to be electrically connected to each terminal electrode to be connected to a ground of the first and second trap elements
62
and
63
, having branches in the sides to be connected to the first and second trap elements
62
and
63
. That is, each branch portion of the lead terminal is connected to each terminal electrode used to establish a ground for the first and second trap elements
62
and
63
.
The composite trap requires the special shaped lead terminal which increases the cost and requires very difficult assembly processes.
On the other hand, Japanese Unexamined Patent Publication No.6-326546 discloses a composite piezoelectric component
71
shown in FIG.
7
. In this component, a plurality of piezoelectric substrates
72
and
73
are bonded together via adhesives
74
.
FIGS. 8 and 9
are perspective views showing electrodes formed on the top surface and the bottom surface of the piezoelectric substrate
72
, respectively. On the top surface of the piezoelectric substrate
72
, vibrating electrodes
75
and
76
are provided. On the bottom surface of the piezoelectric substrate
72
, vibrating electrodes
77
and
78
are arranged so as to oppose the vibrating electrodes
75
and
76
at the front and the back with the piezoelectric substrate
72
disposed therebetween. A first piezoelectric vibrating unit is defined by the vibrating electrodes
75
and
77
while a second piezoelectric vibrating unit is defined by the vibrating electrodes
76
and
78
. Similarly, two piezoelectric vibrating units are also included in the piezoelectric substrate
73
.
On the one side edge of the piezoelectric substrate
72
, a plurality of notches
72
a
to
72
c
are provided. Extending electrodes
79
and
80
are connected to the vibrating electrodes
75
and
76
so as to extend therefrom toward the insides of the notches
72
a
and
72
c
, respectively. An extending electrode
81
to be electrically connected to the vibrating electrodes
77
and
78
is disposed on the bottom surface of the piezoelectric substrate
72
. The extending electrode
81
is arranged to extend to the inside of the notch
72
b
and in turn to extend toward the top surface of the substrate across the notch
72
b.
In the composite piezoelectric component
71
, the above-mentioned piezoelectric substrate
72
and the piezoelectric substrate
73
are joined together, although as for the piezoelectric substrate
73
, the top surface thereof is the surface on which the vibrating electrodes
77
and
78
are disposed.
In the composite piezoelectric component
71
, the piezoelectric substrates
72
and
73
, each having two piezoelectric vibrating units, define a composite unit by being joined together. Since the two piezoelectric substrates
72
and
73
are deposited on each other to define the composite unit, the composite piezoelectric component having plural piezoelectric elements is miniaturized.
However, for the purpose of achieving the electrical connections of the two piezoelectric elements, i.e., the piezoelectric vibrating units disposed on the piezoelectric substrate
72
and
73
and the electrodes to be electrically connected to a ground, the above-mentioned notches
72
a
to
72
c
are used. That is, electrical connections are achieved by stacking the piezoelectric substrates
72
and
73
on each other such that the notches formed on the side edge of the piezoelectric substrate
72
are positioned on the corresponding notches formed on the side edge of the piezoelectric substrate
73
and then by forming electrode thin-films inside the notches via vapor deposition, sputtering, or other methods.
Therefore, the extending electrodes
79
,
80
, and
81
must be extended from the piezoelectric vibrating units to the notches
72
a
to
72
c
formed on the side edge. As a result, the sizes of the piezoelectric substrates
72
and
73
must be large.
In addition, this structure causes the reliability of the electrical connections to be insufficient. Consequently, breaking of the electrode thin-film is liable to occur at the edge portion facing to the notch.
Furthermore, in the composite piezoelectric component
71
, the vibrating electrodes
75
and
76
are exposed on the top surface thereof. Therefore, in order to protect the piezoelectric vibrating units, a case member, or other protective member, must be disposed on the top surface of the composite piezoelectric component
71
so as to secure spaces for allowing for free vibration of the piezoelectric vibrating units, which prevents any reduction in the thickness and overall size of the component.
SUMMARY OF THE INVENTION
To overcome the above described problems, preferred embodiments of the present invention provide a composite piezoelectric component including a plurality of electrically connected piezoelectric elements, which achieves a significant reduction in size and a great increase in the reliability of electrical connections of the plurality of piezoelectric elements by solving the above-described problems of conventional techniques.
According to one preferred embodiment of the present invention, a composite piezoelectric component includes a plurality of piezoelectric resonant elements each including a substrate having a first major surface and a second major surface disposed opposite to each other, a pair of vibrating electrodes disposed on the first and second major surfaces, respectively, so as to oppose each other with the substrate disposed therebetween, a ground electrode connected to ground and disposed on at least one of the first and second major surfaces, and each of the plurality of piezoelectric resonant elements being stacked on each other so that the major surface of one substrate opposes the major surface of another substrate, a conductive joining member electrically connecting at least two of the vibrating electrodes and the ground electrode of the plurality of piezoelectric resonant elements

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