Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-12-11
2002-10-29
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S345000, C310S348000, C310S324000, C310S332000, C310S359000
Reexamination Certificate
active
06472798
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric acoustic component, and more particularly, to a piezoelectric buzzer or a piezoelectric receiver and a method of manufacturing the same.
2. Description of the Related Art
Conventionally, a piezoelectric acoustic component is widely used as a piezoelectric buzzer or a piezoelectric receiver that generates an alarm sound or an operating sound in electronic equipment, household electrical appliances, or mobile telephones. This type of piezoelectric acoustic component is generally manufactured by the steps of adhering a circular piezoelectric element on one of the surfaces of a circular metal plate to provide a unimorph type diaphragm, retaining the peripheral edge of the metal plate in the circular case with silicone rubber, and closing the opening of the case with a cover.
However, the circular diaphragm has a reduced productive efficiency, and thus, the efficiency of acoustic conversion is low, and miniaturization is difficult.
Accordingly, the applicant of the present invention disclosed in Japanese Unexamined Patent Application No. 11-293204 a piezoelectric acoustic component in which a square diaphragm is used to improve the efficiency of productivity and acoustic conversion, and to enable miniaturization. This piezoelectric acoustic component includes a diaphragm having a square piezoelectric element attached on one of surfaces of the square metal plate and an insulating case having a top wall portion, four side wall portions, and a supporting portions within two opposing side walls, and a plate substrate provided with first and second external electrodes, wherein the diaphragm is mounted in the case, the opposing two sides of the diaphragm and the supporting portion are fixed by the supporting material, and the clearance between the remaining two sides of the diaphragm and the case is sealed by a resilient sealing material such that the acoustic space is defined between the diaphragm and the top wall portion of the case. Then, the end of an opening provided on the side wall of the case is adhered onto the substrate, the metal plate is electrically connected to the first external electrode, and the electrode of the piezoelectric element is electrically connected to the second external electrode.
In the currently manufactured electronic components, surface mounting using a reflow soldering method is generally used, and the components are assembled primarily by a machine. Thus, the piezoelectric acoustic component must also have a surface mounted structure. To this end, it is preferable to connect the diaphragm and the external electrode of the substrate electrically using a conductive adhesive. However, when a conventional epoxy conductive adhesive is used, sufficient performance cannot be obtained in terms of sound pressure characteristics and impact resistant properties. In other words, in mobile equipment such as a mobile telephone which is susceptible to large impact loads, for example, by dropping it on the floor accidentally, an epoxy conductive adhesive may be cracked due to the impact load, thereby disconnecting the diaphragm and the external electrode of the substrate.
SUMMARY OF THE INVENTION
To overcome the above-described problems, preferred embodiments of the present invention provide a piezoelectric acoustic component having excellent efficiencies of productivity and acoustic conversion, a greatly miniaturized size, and having excellent impact resistance properties.
According to a first preferred embodiment of the present invention, a piezoelectric acoustic component includes a square piezoelectric diaphragm having first and second diaphragm electrodes exposed on one end portion thereof and vibrating in the length bending mode, an insulating case having a top wall portion, four side wall portions, and supporting portions inside of two opposing side walls, and a substrate in the shape of a plate having first and second external electrodes thereon, wherein the diaphragm is stored within the case with the surface exposing the first and the second diaphragm electrodes facing toward the opposite side of the case from the top wall portion, the two opposite sides of the diaphragm are supported on the supporting portion with supporting material, and the clearance between the diaphragm and the remaining two sides are sealed with a resilient sealing material such that an acoustic space is defined between the diaphragm and the top wall portion of the case, the end of an opening provided on a side wall portion of the case is adhered onto the substrate, the first diaphragm electrode on the diaphragm is electrically connected to the first external electrode with a resilient conductive adhesive, and the second diaphragm electrode is electrically connected to the second external electrode with a resilient conductive adhesive.
According to a second preferred embodiment of the present invention, a piezoelectric acoustic component includes a square piezoelectric diaphragm having first and second diaphragm electrodes exposed on one of the end portions thereof and vibrating in the area bending mode, an insulating case having a top wall portion, four side wall portions, and a supporting portion inside of the four side wall portions, and a substrate in the shape of a plate having first and second external electrodes thereon, wherein the diaphragm is stored in the case with the surface exposing the first and the second diaphragm electrodes facing toward the opposite side of the case from the top wall portion, the four sides of the diaphragm are supported on the supporting portion with supporting material such that the acoustic space is defined between the diaphragm and the case, the end of an opening provided on a side wall portion of the case is adhered onto the substrate, the first diaphragm electrode of the diaphragm is electrically connected to the first external electrode with a resilient conductive adhesive, and the second diaphragm electrode is electrically connected to the second external electrode with a resilient conductive adhesive.
Another preferred embodiment of the present invention provides a method of manufacturing a piezoelectric acoustic component including the steps of providing a square piezoelectric diaphragm having first and second diaphragm electrodes exposed on one of the end portions thereof and vibrating in the length bending mode, providing an insulating case having a top wall portion, four side wall portions, and supporting portions inside of the opposing two side walls, and providing a substrate in the shape of a plate having first and a second external electrodes thereon, storing the diaphragm within the case with the surface exposing the first and the second diaphragm electrodes facing toward the opposite side of the case from the top wall portion and supporting the two opposite sides of the diaphragm on the supporting portion with supporting material, and sealing the clearance between the diaphragm and the remaining two sides with a resilient sealing material such that an acoustic space is defined between the diaphragm and the top wall portion of the case, applying a resilient conductive adhesive continuously from the first diaphragm electrode of the diaphragm to the end of an opening provided on a side wall portion of the case, applying a resilient conductive adhesive continuously from the second diaphragm electrode to the end of the opening provided on the side wall portion of the case, applying an insulating adhesive on the upper surface of the substrate or the end of the opening provided on the side wall portion of the case, adhering the end of the opening provided on the side wall portion of the case on the substrate with an insulating adhesive and connecting the first diaphragm electrode and the first external electrode, and the second diaphragm electrode and the second external electrode alternately with a conductive adhesive, and curing the insulating adhesive and a conductive adhesive simultaneously.
A further preferred embodiment of the pres
Budd Mark O.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
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