Tuning-Fork Type Piezoelectric Vibrating Piece and Piezoelectric Device

Abstract

A tuning-fork type piezoelectric vibrating piece ( 20 ) is comprised of a base portion ( 23 ) comprising a piezoelectric material, a pair of vibrating arms ( 21 ) extends parallel from the base portion with a first thickness, a excitation electrode film ( 33, 34 ) formed on the vibrating arms, a pair of tuning portions ( 28 ) formed at the distal ends of the vibrating arms ( 21 ) with a second thickness which is less than the first thickness; and a metal film ( 18 ) formed on at least one surface o the tuning portion.

1 . A tuning-fork type piezoelectric vibrating piece comprising:
 a base portion comprising a piezoelectric material;   a pair of vibrating arms extends parallel from the base portion with a first thickness;   a excitation electrode film formed on the vibrating arms;   a tuning portion formed at the distal ends of the vibrating arms, said tuning portion having a second thickness which is less than the first thickness; and   a metal film formed on at least one surface of the tuning portion.   
   
   
       2 . The tuning-fork type piezoelectric vibrating piece of  claim 1 , wherein a thickness of the excitation electrode film and a thickness of the metal film are the same. 
   
   
       3 . The tuning-fork type piezoelectric vibrating piece of  claim 1 , wherein at a connection point of thickness from the vibrating arms to the tuning portion, a first width of the vibrating arms and a second width of the tuning portion are different and the second width is wider than the first width. 
   
   
       4 . The tuning-fork type piezoelectric vibrating piece of  claim 3 , wherein the second width of the tuning portion has a constant width from the distal end of the tuning portion to the connection point. 
   
   
       5 . The tuning-fork type piezoelectric vibrating piece of  claim 3 , wherein the second width of the tuning portion is changed from the distal end of the tuning portion to the connection point. 
   
   
       6 . The tuning-fork type piezoelectric vibrating piece of  claim 5 , wherein said second width is greatest at said connection point and is reduced per unit of distance from said connection point to the distal end of said tuning portion according to an exponential equation. 
   
   
       7 . The tuning-fork type piezoelectric vibrating piece of  claim 3 , wherein the tuning portions are configured to oscillate in separate planes whereby said tuning portions do not touch during oscillation. 
   
   
       8 . A piezoelectric device comprising:
 the tuning-fork type piezoelectric vibrating piece according to any of preceding claims;   a lid plate covering the piezoelectric vibrating piece; and   a base plate supporting the piezoelectric vibrating piece.   
   
   
       9 . A piezoelectric frame comprising:
 a pair of vibrating arms extends parallel from the base portion with a first thickness;   a excitation electrode film formed from the base portion to the vibrating arms and exciting the vibrating arms;   a pair of tuning portions at the distal ends of the vibrating arms, said tuning portion having a second thickness which is less than the first thickness;   a metal film formed on at least one surface o the tuning portion;   a pair of supporting arms extends parallel from the base portion with a first thickness at out side of the supporting arms;   a frame portion connecting the supporting arms and surrounding the base portion and the vibrating arms.   
   
   
       10 . The piezoelectric frame of  claim 9 , wherein a thickness of the excitation electrode film and a thickness of the metal film are the same. 
   
   
       11 . The piezoelectric frame of  claim 9 , wherein at a connection point of thickness from the vibrating arms to the tuning portion, a first width of the vibrating arms and a second width of the tuning portion are different and the second width is wider than the first width. 
   
   
       12 . The piezoelectric frame of  claim 11 , wherein the second width of the tuning portion has a constant width from the distal end of the tuning portion to the connection point. 
   
   
       13 . The piezoelectric frame of  claim 11 , wherein the second width of the tuning portion is changed from the distal end of the tuning portion to the connection point. 
   
   
       14 . The piezoelectric frame of  claim 13 , wherein said second width is greatest at said connection point and is reduced per unit of distance from said connection point to the distal end of said tuning portion according to an exponential equation. 
   
   
       15 . The piezoelectric frame of  claim 11 , wherein the tuning portions are configured to oscillate in separate planes whereby said tuning portions do not touch during oscillation. 
   
   
       16 . A piezoelectric device comprising:
 the piezoelectric frame according to the  claim 9 ;   a lid plate covering the piezoelectric frame; and   a base plate covering the piezoelectric frame, wherein the lid plate and the base plate sandwich the piezoelectric frame.   
   
   
       17 . A manufacturing method of a tuning-fork type piezoelectric vibrating piece or a piezoelectric frame having a pair of vibrating arms extends parallel from the base portion with a first thickness comprising:
 a first exposing step of exposing a profile of the tuning-fork type piezoelectric vibrating piece or the piezoelectric frame on a piezoelectric wafer having the first thickness by using a first mask corresponding to the profile of the tuning-fork type piezoelectric vibrating piece or the piezoelectric frame;   a second exposing step of exposing the tuning portion for frequency adjustment formed on the distal end of the vibrating arms and grooves formed at a root portion of the vibrating arms on the piezoelectric wafer by using a second mask corresponding to the tuning portion for frequency adjustment and the grooves;   a first etching step of etching the piezoelectric wafer after the first exposing step; and   a second etching step of etching the piezoelectric wafer after the second exposing step.   
   
   
       18 . A manufacturing method of  claim 17  further comprising:
 a metal film forming step of forming is a metal film on the entire surface of the piezoelectric wafer in order to form excitation electrodes; and   a third exposing step of exposing a profile of the excitation electrodes on the piezoelectric wafer by using a third mask corresponding to the profile of the excitation electrodes.   
   
   
       19 . A manufacturing method of  claim 18  further comprising:
 an irradiating step of irradiating the metal film with a laser beam for frequency adjustment.