SURFACE ACOUSTIC WAVE DEVICE, ELECTRONIC APPARATUS, AND SENSOR APPARATUS

• US 20120062069A1
• Filed: 09/01/2011
• Published: 03/15/2012
• Est. Priority Date: 09/09/2010
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: YAMANAKA, Kunihito
• Granted Patent: US 8,723,395 B2
• Time in Patent Office: Days
• US Class Current: 310/313.A
• CPC Class Codes: H03H 9/02551 of quartz substrates
• CPC Class Codes: H03H 9/0542 consisting of a lateral arrangement H03H9/0566 takes precedence
• CPC Class Codes: H03H 9/14594 Plan-rotated or plan-tilted transducers

Abstract

A SAW device has an IDT which is provided on the principal surface of a quartz crystal substrate having Euler angles (−1.5°≦φ≦1.5°, 117°≦θ≦142°, 42.79≦|ψ|≦49.57°) and excites a SAW in a stopband upper end mode, and a pair of reflectors which are arranged on both sides of the IDT. Inter-electrode-finger grooves are recessed between the electrode fingers of the IDT, and inter-conductor-strip grooves are recessed between the conductor strips of the reflectors. A first direction (X′ axis) perpendicular to the electrode fingers and the conductor strips intersects the electrical axis (X axis) of the quartz crystal substrate at an angle ψ. At least a part of the IDT and the reflectors are arranged in a second direction intersecting the first direction at an angle α of 1.0°≦α≦2.75°. An excellent frequency-temperature characteristic and a high Q value in an operation temperature range are realized simultaneously.

Claims

1. A surface acoustic wave device comprising:

a quartz crystal substrate having Euler angles (−

1.5°

≦

φ

≦

1.5°

, 117°

≦

θ

≦

142°

, 42.79°

≦

|ψ

|≦

49.57°

);

an IDT which has a plurality of electrode fingers on the principal surface of the quartz crystal substrate and excites a surface acoustic wave in a stopband upper end mode; and

a pair of reflectors which respectively have a plurality of conductor strips and are arranged on both sides of the IDT with the IDT sandwiched therebetween along the propagation direction of the surface acoustic wave,

wherein inter-electrode-finger grooves are recessed in the surface of the quartz crystal substrate between adjacent electrode fingers of the IDT,

inter-conductor-strip grooves are recessed in the surface of the quartz crystal substrate between adjacent conductor strips of the reflectors,

the wavelength λ

of the surface acoustic wave and the depth G of the inter-electrode-finger grooves satisfy the relationship 0.01λ

≦

G,

an IDT line occupancy η and

the depth G of the inter-electrode-finger grooves satisfy the following relationships,

−

2.0000×

G/λ

+0.7200≦

η

≦

−

2.5000×

G/λ

+0.7775 where 0.0100λ

≦

G≦

0.0500λ

;

−

3.5898×

G/λ

+0.7995≦

η

≦

−

2.5000×

G/λ

+0.7775 where 0.0500λ

≦

G≦

0.0695λ

;

an angle between a first direction perpendicular to the electrode fingers and the conductor strips and the electrical axis of the quartz crystal substrate is the Euler angle ψ

, and

at least a part of the IDT and the reflectors are arranged in a second direction intersecting the first direction at an angle α

, and the angle α

is within a range of 1.0°

≦

α

≦

2.75°

.

2. The surface acoustic wave device according to claim 1,

wherein the angle α

and the Euler angle ψ

satisfy the relationship ψ

=1.06α

+43.69°

+0.05°

.

3. The surface acoustic wave device according to claim 1,

wherein the IDT line occupancy η

satisfies the following relationship;

4. The surface acoustic wave device according to claim 1,

wherein the sum of the depth G of the inter-electrode-finger grooves and the thickness H of the electrode fingers satisfies 0.0407λ

≦

G+H.

5. The surface acoustic wave device according to claim 3,

wherein the sum of the depth G of the inter-electrode-finger grooves and the thickness H of the electrode fingers satisfies 0.0407λ

≦

G+H.

6. The surface acoustic wave device according to claim 1, further comprising:

an IC which drives the IDT.

7. The surface acoustic wave device according to claim 3, further comprising:

an IC which drives the IDT.

8. The surface acoustic wave device according to claim 4, further comprising:

an IC which drives the IDT.

9. An electronic apparatus comprising:

the surface acoustic wave device according to claim 1.

10. A sensor apparatus comprising:

the surface acoustic wave device according to claim 1.

11. The surface acoustic wave device according to claim 2,

wherein the IDT line occupancy η

satisfies the following relationship;

12. The surface acoustic wave device according to claim 2,

wherein the sum of the depth G of the inter-electrode-finger grooves and the thickness H of the electrode fingers satisfies 0.0407λ

≦

G+H.

13. The surface acoustic wave device according to claim 2, further comprising:

an IC which drives the IDT.

14. An electronic apparatus comprising:

the surface acoustic wave device according to claim 2.

15. A sensor apparatus comprising:

the surface acoustic wave device according to claim 2.