Piezoelectric resonator and method of adjusting resonant frequency thereof

• US 6,111,480 A
• Filed: 07/06/1998
• Issued: 08/29/2000
• Est. Priority Date: 07/07/1997
• Status: Expired due to Fees

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Unami, Toshihiko, Iyama, Kiyoshi
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Summons, Barbara
• Application Number:
  US09/110,304
• Time in Patent Office: 785 Days
• Field of Search: 333/186-191, 310/311, 310/312, 310/320, 310/321, 310/322, 310/323, 310/334, 310/357, 310/358, 310/359, 310/366, 310/367
• US Class Current: 333/188
• CPC Class Codes: H03H 2003/0414 Resonance frequency
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/1014 the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the BAW device
• CPC Class Codes: H03H 9/178 of a laminated structure of multiple piezoelectric layers with inner electrodes

Abstract

A piezoelectric resonator having a small spurious resonance and a large difference .increment.F between the resonant frequency and the antiresonant frequency is constructed that a resonant frequency or antiresonant frequency can be easily and accurately adjusted to a low frequency. The piezoelectric resonator has a base member which includes a plurality of laminated piezoelectric layers and a plurality of inner electrodes disposed substantially perpendicularly to the longitudinal direction of the base member. The plurality of piezoelectric layers are polarized in the longitudinal direction of the base member. A first external electrode and a second external electrode are located on a surface of the base member and connected to the plurality of electrodes. The resonant frequency of the piezoelectric resonator is adjusted by cutting an intermediate portion in the longitudinal direction of the base member.

Claims

1. A piezoelectric resonator including:

a base member having a longitudinal direction;

a plurality of inner electrodes disposed substantially perpendicularly to the longitudinal direction of said base member at intervals in the longitudinal direction of said base member; and

a first external electrode and a second external electrode located on a surface of said base member and connected to said plurality of electrodes;

wherein

said base member includes a plurality of laminated piezoelectric layers polarized in the longitudinal direction of said base member;

said plurality of inner electrodes are located on surfaces of said plurality of piezoelectric layers so as to be substantially perpendicular to the longitudinal direction of said base member;

a cut is provided in an intermediate portion of said base member so that the cut extends along a longitudinal direction thereof and across a plurality of the inner electrodes and a plurality of the piezoelectric layers, the cut being arranged to adjust the resonant frequency of the piezoelectric resonator.

2. The piezoelectric resonator according to claim 1, wherein the cut has a substantially arc-shaped configuration.

3. The piezoelectric resonator according to claim 1, wherein the cut has a substantially rectangular shape.

4. The piezoelectric resonator according to claim 1, wherein the cut extends in a direction which is substantially perpendicular to the longitudinal direction of the base member.

5. The piezoelectric resonator according to claim 1, wherein the cut is provided on a surface of the base member which is disposed opposite to the surface of the base member upon which the first and second external electrodes are located.

6. The piezoelectric resonator according to claim 1, wherein the cut is provided on a surface of the base member which is disposed adjacent to the surface of the base member upon which the first and second external electrodes are located.

7. The piezoelectric resonator according to claim 1, wherein the cut in the intermediate portion in the longitudinal direction of said base member has a uniform depth along an entire dimension thereof.

8. The piezoelectric resonator according to claim 1, wherein the cut in the intermediate portion in the longitudinal direction of said base member has a varying depth.

9. The piezoelectric resonator according to claim 1, wherein a center of the intermediate portion in the longitudinal direction of said base member is thinner than other portions of the base member.

10. A method of adjusting a resonant frequency of piezoelectric resonator including a base member having a longitudinal direction, a plurality of inner electrodes disposed substantially perpendicularly to the longitudinal direction of the base member at intervals in the longitudinal direction of the base member, a first external electrode and a second external electrode located on a surface of said base member and connected to the plurality of electrodes, the base member including a plurality of laminated piezoelectric layers which are polarized in the longitudinal direction of said base member, and the plurality of inner electrodes being located on surfaces of the plurality of piezoelectric layers so as to be substantially perpendicular to the longitudinal direction of the base member;

the method comprising a step of cutting an intermediate portion of the base member along the longitudinal direction of the base member so that the cut extends across a plurality of the inner electrodes and a plurality of the piezoelectric layers in order to adjust a resonant frequency of the piezoelectric resonator.

11. The method according to claim 10, wherein the cut has a substantially arc-shaped configuration.

12. The method according to claim 10, wherein the cut has a substantially rectangular shape.

13. The method according to claim 10, wherein the cut extends in a direction which is substantially perpendicular to the longitudinal direction of the base member.

14. The method according to claim 10, wherein the cut is formed on a surface of the base member which is disposed opposite to the surface of the base member upon which the first and second external electrodes are located.

15. The method according to claim 10, wherein the cut is formed on a surface of the base member which is disposed adjacent to the surface of the base member upon which the first and second external electrodes are located.

16. The method according to claim 10, wherein the cut formed in the intermediate portion in the longitudinal direction of said base member has a uniform depth along an entire dimension thereof.

17. The method according to claim 10, wherein the cut in the intermediate portion in the longitudinal direction of said base member has a varying depth.