Metal working – Piezoelectric device making
Reexamination Certificate
2000-06-15
2003-06-03
Arbes, Carl J. (Department: 3729)
Metal working
Piezoelectric device making
C156S292000, C310S345000
Reexamination Certificate
active
06571442
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic component such as, for example, a piezoelectric component and, more particularly but not exclusively, to a surface-mount type electronic component. The present invention also relates to a method of producing such an electronic part.
2. Description of the Related Art
A surface-mount type electronic component, specifically a piezoelectric component, of the type shown in
FIGS. 1 and 2
is known. This electronic component incorporates an element
4
which makes use of piezoelectric vibration (referred to as “piezoelectric element”). The piezoelectric element
4
includes electrodes
4
a
and
4
b
disposed on upper and lower major surfaces thereof and is arranged to vibrate in a longitudinal vibration mode. Pattern electrodes
2
and
3
are provided on a substrate
1
which supports the piezoelectric element
4
. The lower electrode
4
b
disposed on the lower major surface of the piezoelectric element
4
is connected and fixed to a first one 2 of the pattern electrodes by a conductive adhesive
5
. The upper electrode
4
a
disposed on the upper major surface of the piezoelectric element
4
is connected to the other pattern electrode
3
by a wire
6
. A cap
7
is attached to the upper surface of the substrate
1
so as to cover and seal the piezoelectric element
4
.
In the piezoelectric component shown in
FIG. 1
, the upper electrode
4
a
of the piezoelectric element
4
and the pattern electrode
3
disposed on the substrate
1
are connected to each other by a wire bonding technique. It has been difficult, however, to optimize the wire-bonding process and resulting structural arrangement due to the difference in height or vertical location between the electrode
4
a
of the piezoelectric element
4
and the pattern electrode
3
disposed on the substrate
1
.
When a capillary is moved while the wire
6
is being connected to one of these electrodes
3
and
4
a
, it is necessary to optimize the length of feed of the wire
6
. If a feed length of the wire
6
is too small, the wire
6
may contact an edge of the piezoelectric element
4
as shown in
FIG. 3
, resulting in troubles such as cutting of the wire
6
or impairment of the electrical characteristics of the piezoelectric element
4
. Conversely, if the feed length of the wire
6
is too large, this causes problems such as the wire
6
sagging downwardly as shown in
FIG. 4
, with the result that the wire
6
contacts the piezoelectric element
4
to impair electrical characteristics of the element
4
.
For these reasons, mass-production of electronic components requiring wire bonding involves great manufacturing difficulty and experiences significant fluctuation of the quality.
Another problem is that the size of the electronic component must be large because of the need to provide a space between the substrate
1
and the cap
7
for accommodating the wire
6
which interconnects the upper electrode
4
a
of the piezoelectric element
4
and the pattern electrode
3
disposed on the substrate
1
.
In the meantime, electronic components having lead terminals suffer from the following problem. In general, an electronic component, specifically of the type in which a circuit element is sealed with a resin without being constrained by the resin, has such a structure as that disclosed in Japanese Patent Publication No. 1-48695, wherein lead terminals are electrically connected to the corresponding electrodes of the circuit element and, after the circuit element is enclosed in a case with the lead electrodes extending externally through openings formed in the case wall, these openings are sealed by a sealing resin.
This type of structure, however, requires that different design configurations of the openings be provided in conformity with the shapes of the lead terminals, at the time of design of the products. In addition, it is necessary to apply a sealing resin to each of the openings in a one-by-one fashion. This causes an impediment to mass-production of the electronic parts, thus raising the costs of production.
Prior to the application of the sealing resin, since the lead terminals are directly connected to the circuit element, any load or external force tends to be directly transmitted to the circuit element, often resulting in breakage or cracking of the circuit element especially when the circuit element is a fragile one such as a piezoelectric element. Consequently, throughput is lowered and the number of acceptable components manufactured is substantially reduced.
SUMMARY OF THE INVENTION
The preferred embodiments of the present invention provide an electronic component which allows for easy electrical connection between a circuit element and an electrode pattern on a substrate supporting the circuit element, thus providing stabilization of quality of the electronic components at reduced costs, as well as reduction in the size of the electronic component. The preferred embodiments of the present invention also provide a method for producing such an electronic component having these advantages.
The preferred embodiments of the present invention also provide an electronic component which is easily mass-producible at low costs and which has a structure which allows for completely sealing a circuit element of the electronic component while suppressing an application of load to the circuit element to prevent damage to the circuit element and deterioration of the electrical characteristics of the electronic component.
According to one preferred embodiment of the present invention, an electronic component comprises: an insulating substrate having an electrode pattern provided thereon; a circuit element mounted on the insulating substrate; and a cap bonded to the substrate so as to cover and seal the circuit element; wherein a conductive portion is provided on at least the inner surface of the cap, the conductive portion being connected to an electrode of the circuit element and also to the electrode pattern on the substrate, whereby the electrode of the circuit element is electrically connected to the electrode pattern on the substrate through the conductive portion of the cap.
In accordance with the preferred embodiments of the present invention, the cap preferably is used as a part of the electrical connection, for the purpose of achieving electrical connection between an electrode of the circuit element and the electrode pattern provided on the substrate. This connecting method considerably facilitates the establishment of an electrical connection between the circuit element and the electrode pattern on the substrate, as compared with the wire bonding method which has previously been used, thereby contributing to reduction in the costs and stabilization of the quality of the electronic component being manufactured. Furthermore, the size of the cap and, hence, the size of the whole electronic component, can be reduced because of elimination of the necessity for providing a wiring space which has previously been required in order to establish electrical connection between the electrode on the surface of the circuit element and the electrode on the substrate.
The conductive portion of the cap may be provided by forming the whole cap from a metallic material such as aluminum, copper or the like. Alternatively, the cap may be formed from an insulating material such as ceramics or resin, and a conductive film may be disposed at least on the inner surface of the cap by a suitable technique such as sputtering, evaporation deposition, printing or the like.
When the circuit element is a piezoelectric element which is provided at its upper and lower major surfaces with electrodes and which makes use of piezoelectric vibration, the arrangement is preferably such that the connection to the conductive portion of the cap is made at a region of the electrode on the upper surface of the circuit element near a nodal point of the vibration. Such an arrangement does not inhibit vibration of the piezoelectric element and, therefor
Fujii Choichiro
Hashimoto Takashi
Irie Makoto
Iwami Hidemasa
Iwamoto Takashi
Arbes Carl J.
Keating U & Bennett, LLP
Murata Manufacturing Co. Ltd.
Phan Thiem D
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