Metal working – Piezoelectric device making
Reexamination Certificate
1999-09-03
2001-02-27
Hall, Carl E. (Department: 3729)
Metal working
Piezoelectric device making
C310S348000, C310S368000
Reexamination Certificate
active
06192562
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric component utilizing a longitudinal oscillation mode for use in an AM filter or other electronic components.
2. Description of the Related Art
Conventionally, as shown in Japanese Patent Unexamined Publication No. 2-224515, a piezoelectric component is known in which a piezoelectric element utilizing a longitudinal oscillation mode is disposed in a case. In this piezoelectric element, a first main surface of the piezoelectric element is provided with input and output electrodes that are formed by dividing electrode material by forming a longitudinally extending linear groove in the electrode material disposed on an entire are of the first main surface, and a second main surface of the piezoelectric element is provided with a common electrode, wherein a part of each of the input and output electrodes is provided with a separate, independent support section formed of an isotropic elastic conductive material and constitutes an electrical contact section to be electrically connected with an external conductor. The above-mentioned support sections are arranged on either side of the groove and disposed to extend along the longitudinal dimension of the input and output electrodes. By pressurizing the piezoelectric element via a spring member, the above-mentioned support sections are elastically biased into contact with input and output terminals fixed to the case to achieve conduction through contact.
In the above-described piezoelectric element, the distance between the support members which are spaced apart from each other is small. Thus, when the piezoelectric element as described above is connected to external conductors, such as terminals fixed to a case, it is necessary for the external conductors to be disposed in close proximity to each other. Thus, if there is a small positional deviation of the piezoelectric element, a short circuit may be developed between the input and output electrodes.
In the above-described piezoelectric component, the elastic support sections thereof are connected to terminals of a case by bringing support sections into elastically biased contact with the terminals. In effecting this connection, the piezoelectric element is liable to undergo positional deviation if vibrations or the like are applied to the piezoelectric element. In view of this, to enhance the force for holding the piezoelectric element in position and achieving the conductivity thereof, support sections may be connected and fixed to pattern electrodes of a mounting substrate or the like by using a conductive adhesive or the like. In this case, due to the small distance between the support sections of the input and output electrodes, a short circuit may be developed between the input and output electrodes if the conductive adhesive is spread only a small amount, resulting in a deterioration in reliability in the necessary electrical connection.
SUMMARY OF THE INVENTION
The preferred embodiments of the present invention provide a piezoelectric component in which a piezoelectric element utilizing a longitudinal oscillation mode is mounted on pattern electrode of a mounting substrate, wherein a short circuit is prevented from being developed between the separate electrodes of the piezoelectric element, thereby achieving an improvement in terms of reliability of electrical connection.
In accordance with the preferred embodiments of the present invention, a piezoelectric component in which a piezoelectric element utilizing longitudinal oscillation mode is mounted on pattern electrodes disposed on an upper surface of an insulating mounting substrate, wherein the piezoelectric element has on a first main surface thereof first and second electrodes divided by a longitudinally extending linear groove, wherein a third electrode is provided on the other main surface thereof, conductive support members being fixed to node portions of the first and second electrodes so as to be spaced apart from each other with respect to the longitudinal dimension, and wherein the first main surface of the piezoelectric element having the first and second electrodes faces the surface of the mounting substrate on which the pattern electrodes are provided, the support members being connected and secured to the pattern electrodes of the mounting substrate.
When the first and second electrodes of the piezoelectric element are connected to the pattern electrodes of the mounting substrate, it is possible for the pattern electrodes to be longitudinally spaced apart from each other since the support members fixed to the electrodes are provided so as to be spaced apart from each other with respect to the longitudinal dimension. Thus, a short circuit will not be developed between the first and second electrodes even when the piezoelectric element undergoes positional deviation.
The support members are preferably provided at the node portion of the piezoelectric element, that is, substantially in the middle portion with respect to the longitudinal dimension thereof. In the preferred embodiments of the present invention, the node portion includes not only a completely non-oscillating portion but also a range which will involve no problem in terms of oscillation characteristics even when this portion is constrained. Since it is desirable for the support members on the first and second electrodes to be spaced as far apart from each other as possible with respect to the longitudinal dimension, it is desirable for the support members to be fixed to positions near an interface between the node portion and the non-node portion. Generally speaking, in the case of a longitudinal oscillation mode element, the node range is approximately ¼ of the length of the element, so that it is possible for the support members to be spaced apart from each other by this desired distance.
There are various methods of connecting the support members to the pattern electrodes. For example, the support members may be formed of a conductive adhesive, metal bumps or the like, and glued to the pattern electrodes by a conductive adhesive or the like. When the support members are formed of an uncured conductive adhesive, they can be directly joined to the pattern electrodes. To enhance the adhesive strength between the piezoelectric element and the mounting substrate, it is possible to use an insulating adhesive in addition to the conductive adhesive. This insulating adhesive is preferably used in those portions of the piezoelectric element which belong to the node portion thereof and exclude the conductive support sections.
When two grooves are provided on one main surface of the piezoelectric element to form three electrodes by dividing the electrode material by forming grooves therein, it is desirable for the conductive support member fixed to the first, central electrode, obtained through division by the grooves, and the conductive support members fixed to the second electrodes on either side of the first electrode to be arranged in a zigzag pattern.
When the piezoelectric element is attached to the mounting substrate, the following problem may be involved. That is, if the piezoelectric element is attached in an inclined state, there is a concern that either of the first and second electrodes will be brought into contact with pattern electrodes of different electric potentials to thereby degenerate the oscillation characteristics. However, when the support members are arranged in a zigzag pattern as described above, a three-point support structure is obtained, so that horizontally is easily attained, thereby achieving an improvement in terms of stability.
Apart from the conductive support members, it is desirable to fix insulating support members to the node portions of the first and second electrodes. In this case, a plurality of support members are preferably provided for one electrode, or the support member has a large length, so that, when the piezoelectric element is attached to the mounting substrate by the support members, the support are
Hachinohe Satoru
Hashimoto Takashi
Irie Makoto
Nitta Koichi
Okeshi Motoyuki
Hall Carl E.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
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