Piezoelectric resonator and manufacturing method therefor

Abstract

A piezoelectric resonator includes a piezoelectric resonator element having a base portion and a resonating arm extending from the base portion, a package including a bottom to which the piezoelectric resonator element is fixed and a frame wall that surrounds the bottom and having an opening above the bottom, and a lid for closing the opening of the package. In this piezoelectric resonator, the lid includes a main body having a through-hole formed therein, a flange formed to surround a periphery of the main body and to be thinner than the main body, and an optically transparent member located in the through-hole. The flange has a joining portion with an upper end surface of the frame wall, and the main body projects in a direction from the flange to the bottom in a thickness direction. Also, the through-hole is at a position displaced in a first direction approaching a first end of the main body from a center of the main body. Also, the flange is joined with the frame wall such that a clearance between the first end and the joining portion of the flange nearest to the first end is larger than a clearance between a second end in a second direction opposite to the first direction of the main body and the joining portion of the flange nearest to the second end.

1 . A method for manufacturing a piezoelectric resonator, comprising:
 (a) preparing a package that includes a bottom and a frame wall surrounding the bottom and has an opening above the bottom;   (b) fixing to the bottom a piezoelectric resonator element having a base portion and a resonating arm extending from the base portion;   (c) preparing a lid that includes a main body having a through-hole formed therein, an optically transparent member located in the through-hole, and a flange formed to surround a periphery of the main body and to be thinner than a thickness of the main body, the main body projecting in a direction from the flange in a thickness direction;   (d) arranging the lid such that a portion projecting from the flange of the main body is inside the frame wall with a clearance from the frame wall and the flange overlaps the frame wall so as to close the opening of the package; and   (e) joining the flange to the upper end surface of the frame wall by locally heating, wherein:   the through-hole is at a position displaced in a first direction approaching a first end of the main body from a center of the main body; and   in step (d), the lid is arranged such that a clearance between the first end and a portion overlapping the frame wall closest to the first end of the flange is larger than a clearance between a second end in a second direction opposite to the first direction of the main body and a portion overlapping the frame wall nearest to the second end of the flange.   
   
   
       2 . The method for manufacturing a piezoelectric resonator according to  claim 1 , wherein:
 the lid has a flange surface facing the package of the flange, a main body surface facing the package of the main body, and a connection surface connecting the flange surface with the main body surface; and   in the step (d), at least part of the connection surface is brought into contact with the frame wall.   
   
   
       3 . The method for manufacturing a piezoelectric resonator according to  claim 2 , wherein:
 the connection surface includes a first connection portion connecting to a margin of the main body surface, a second connection portion connecting to the flange surface, and an intermediate portion between the first and second connection portions;   the intermediate portion is depressed from the margin of the main body surface; and   in the step (d), the first connection portion is brought into contact with the frame wall to form a space between the intermediate portion and the frame wall.   
   
   
       4 . The method for manufacturing a piezoelectric resonator according to  claim 1 , wherein, in the step (d), after the second end in the second direction of the main body is arranged inside the frame wall with the lid inclined, the first end is arranged inside the frame wall.