Piezoelectric acoustic components and methods of manufacturing the same

Abstract

A piezoelectric acoustic component having excellent efficiencies of productivity and of acoustic conversion, a greatly miniaturized size, and excellent impact resistance properties, includes a unimorph type diaphragm. The unimorph type diaphragm is defined by adhering a substantially square piezoelectric element onto a substantially square metal plate, the shorter sides of the diaphragm are supported on the supporting portion provided within the two opposing side wall portions of the case, the clearance between the remaining two sides of the diaphragm, and the case is sealed with a resilient sealing agent. The case is adhered on the substrate having external electrodes, the metal plate is connected to the external electrode with a resilient conductive paste, and the surface electrode of the piezoelectric element is connected to the external electrode with a resilient conductive paste. In this arrangement, the reliability of connection between the diaphragm and the external terminals on the substrate against the impact is greatly improved.

What is claimed is:  
     
         1 . A piezoelectric acoustic component comprising: 
 a substantially square piezoelectric diaphragm having first and second diaphragm electrodes exposed on one of the end portions 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 a first and a second external electrodes thereon; wherein 
 said 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 being supported on said supporting portion with supporting material, and the clearance between the diaphragm and the remaining two side walls 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 at least one of said four side wall portions of said case is adhered onto said substrate, the first diaphragm electrode on said diaphragm is electrically connected to the first external electrode with a resilient conductive adhesive, and said second diaphragm electrode is electrically connected to the second external electrode with a resilient conductive adhesive.  
   
     
     
         2 . A piezoelectric acoustic component as set forth in  claim 1 , wherein said diaphragm is a unimorph type piezoelectric diaphragm having a piezoelectric element adhered on one of the surfaces of the metal plate at the position displaced toward one of the side which is supported by the supporting portion of the case, the electrode on one of the surfaces of the piezoelectric element exposed outside constitutes the first diaphragm electrode, an exposed portion of the metal plate is provided on the other side of the surface having a piezoelectric element of the diaphragm is adhered, said exposed portion constitutes the second diaphragm electrode, and the diaphragm is mounted to the case with the metal plate facing toward the top wall of the case.  
     
     
         3 . A piezoelectric acoustic component as set forth in  claim 1 , wherein said resilient conductive adhesive is a conductive adhesive having Young's modulus of about 1×10 5 -2×10 9  N/m 2 .  
     
     
         4 . A piezoelectric acoustic component as set forth in  claim 1 , wherein the supporting material that supports the two opposing sides of the diaphragm on the supporting portion is the same material as the resilient sealing material.  
     
     
         5 . A piezoelectric acoustic component as set forth in  claim 1 , wherein the piezoelectric diaphragm is made of PZT.  
     
     
         6 . A piezoelectric acoustic component as set forth in  claim 1 , wherein the case is made of resin.  
     
     
         7 . A piezoelectric acoustic component as set forth in  claim 1 , wherein said first and second external electrodes extend from a front surface to a back surface of said case via through holes provided in said case.  
     
     
         8 . A piezoelectric acoustic component as set forth in  claim 1 , wherein a sound releasing hole is provided at the approximate center of the top wall portion of said case.  
     
     
         9 . A piezoelectric acoustic component as set forth in  claim 1 , wherein grooves are provided on the opening edges of the two opposing side wall portions of said case.  
     
     
         10 . A piezoelectric acoustic component as set forth in  claim 1 , wherein the opening edge of one of the side wall portions is provided with a braking notch.  
     
     
         11 . A piezoelectric acoustic component comprising: 
 a substantially square piezoelectric diaphragm having a 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 said four side wall portions; and    a substrate in the shape of a plate having first and second external electrodes thereon; wherein 
 said 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 said supporting portion with the supporting material such that an acoustic space is defined between the diaphragm and the case, an end of an opening provided on at least one of said side wall portions of said case is adhered onto said substrate, the first diaphragm electrode of said diaphragm is electrically connected to the first external electrode with a resilient conductive adhesive, and said second diaphragm electrode is electrically connected to the second external electrode with a resilient conductive adhesive.  
   
     
     
         12 . A piezoelectric acoustic component as set forth in  claim 11 , wherein said diaphragm is a unimorph type piezoelectric diaphragm having a piezoelectric element adhered on one of the surfaces of the metal plate at the position displaced toward one of the side which is supported by the supporting portion of the case, the electrode on one of the surfaces of the piezoelectric element exposed outside constitutes the first diaphragm electrode, an exposed portion of the metal plate is provided on the other side of the surface having a piezoelectric element of the diaphragm is adhered, said exposed portion constitutes the second diaphragm electrode, and the diaphragm is mounted to the case with the metal plate facing toward the top wall of the case.  
     
     
         13 . A piezoelectric acoustic component as set forth in  claim 11 , wherein said resilient conductive adhesive is a conductive adhesive having a Young's modulus of about 1×10 5 -2×10 9  N/m 2 .  
     
     
         14 . A piezoelectric acoustic component as set forth in  claim 11 , wherein the supporting material that supports the two opposing sides of the diaphragm on the supporting portion is formed of the same material as the resilient sealing material.  
     
     
         15 . A piezoelectric acoustic component as set forth in  claim 11 , wherein the piezoelectric diaphragm is made of PZT.  
     
     
         16 . A piezoelectric acoustic component as set forth in  claim 11 , wherein the case is made of resin.  
     
     
         17 . A piezoelectric acoustic component as set forth in  claim 11 , wherein said first and second external electrodes extends from a front surface to a back surface of said case via through holes provided in said case.  
     
     
         18 . A piezoelectric acoustic component as set forth in  claim 11 , wherein a sound releasing hole is provided at the approximate center of the top wall portion of said case.  
     
     
         19 . A method of manufacturing a piezoelectric acoustic component comprising the steps of: 
 providing a substantially square piezoelectric diaphragm having first and second diaphragm electrodes exposed on one end portion 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 wall portions;    providing a substrate in the shape of a plate having first and second external electrodes thereon;    storing said diaphragm within the case with the surface exposing the first and the second diaphragm electrodes facing toward the opposite side from the top wall portion of the case and supporting the two opposite sides of the diaphragm on said supporting portion with the supporting material; and    sealing the clearance between the diaphragm and the remaining two sides with a resilient sealing material so 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 said diaphragm to the end of the opening formed on the side wall portion of the case;    applying a resilient conductive adhesive continuously from the second diaphragm electrode to the end of the opening formed on the side wall portion of the case;    applying an insulating adhesive on the upper surface of said substrate or the end of the opening formed on the side wall portion of said case;    adhering the end of the opening formed on the side wall portion of the case on said 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 said insulating adhesive and a conductive adhesive simultaneously.    
     
     
         20 . A method of piezoelectric acoustic component comprising the steps of: 
 providing a substantially square piezoelectric diaphragm having first and second diaphragm electrodes exposed on one of the end portions thereof and vibrating in the area bending mode;    providing an insulating case having a top wall portion, four side wall portions, and a supporting portion inside of said four side wall portions;    providing a substrate in the shape of a plate having a first and second external electrodes thereon;    storing said diaphragm in the case with the surface exposing the first and second diaphragm electrodes facing toward the opposite side from the top wall portion of the case and supporting the four sides of the diaphragm on said supporting portion with the supporting material so that the acoustic space is defined between the diaphragm and the case;    applying a resilient conductive adhesive continuously from the first diaphragm electrode of said diaphragm to the end of the opening formed on the side wall portion of the case;    applying a resilient conductive adhesive continuously from the second diaphragm electrode to the end of the opening formed on the side wall portion of the case;    applying an insulating adhesive on the upper surface of said substrate or the end of the opening formed on the side wall portion of said case;    adhering the end of the opening formed on the side wall portion of the case on said 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 said insulating adhesive and a conductive adhesive simultaneously.