ACOUSTIC WAVE ELEMENT AND ACOUSTIC WAVE DEVICE USING SAME

• US 20140145557A1
• Filed: 06/14/2012
• Published: 05/29/2014
• Est. Priority Date: 06/28/2011
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Tanaka, Hiroyuki
• Granted Patent: US 9,319,023 B2
• Time in Patent Office: Days
• US Class Current: 310/313.D
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H03H 9/059 consisting of mounting pads or bumps
• CPC Class Codes: H03H 9/1071 the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the SAW device
• CPC Class Codes: H03H 9/1452 by finger overlap length, apodisation
• CPC Class Codes: H03H 9/14594 Plan-rotated or plan-tilted transducers
• CPC Class Codes: H03H 9/25 Constructional features of resonators using surface acoustic waves devices for manipulating acoustic surface waves in general G10K11/36

Abstract

An IDT electrode of a SAW element has a plurality of first dummy electrodes which extend from the first bus bar to the second bus bar side and have tips which face the tips of the plurality of second electrode fingers through a plurality of first gaps, and a plurality of second dummy electrodes which extend from the second bus bar to the first bus bar side and have tips which face the tips of the plurality of first electrode fingers through a plurality of second gaps. The plurality of first gaps and the plurality of second gaps are arranged to be inclined to the same side relative to the propagation direction of SAW. When the inclination angles of the first gaps and the second gaps relative to the propagation direction are a first angle θA and a second angle θB, the following are true: 10°≦θA≦26°, and 10°≦θB≦26°.

Claims

1. An acoustic wave element, comprising:

a piezoelectric substrate and

an IDT electrode located on an upper surface of the piezoelectric substrate, wherein

the IDT electrode comprises

a first bus bar and a second bus bar which face each other in a direction which intersects with a propagation direction of the acoustic wave,

a plurality of first electrode fingers which extend from the first bus bar to the second bus bar side,

a plurality of second electrode fingers which

extend from the second bus bar to the first bus bar side and

have a portion adjacent to the plurality of first electrode fingers in the propagation direction,

a plurality of first dummy electrodes which

extend from the first bus bar to the second bus bar side and

have tips which face the tips of the plurality of second electrode fingers through a plurality of first gaps, and

a plurality of second dummy electrodes which

extend from the second bus bar to the first bus bar side and

have tips which face the tips of the plurality of first electrode fingers through a plurality of second gaps,

in a certain range of the propagation direction of the IDT electrode,

when the arrangement direction of the first gaps among the plurality of first gaps which are adjacent to each other is the first direction, the first direction is inclined relative to the propagation direction,

when the arrangement direction of the second gaps among the plurality of second gaps which are adjacent to each other is the second direction, the second direction is inclined to the side the same as the side to which the first direction is inclined relative to the propagation direction, and

when the inclination angle of the first direction relative to the propagation direction is a first angle θ

A and the inclination angle of the second direction relative to the propagation direction is a second angle θ

B, the first angle θ

A and the second angle θ

B are within a following ranges;

10°

≦

θ

A≦

26°

10°

≦

θ

B≦

26°

.

2. The acoustic wave element according to claim 1, wherein

the first angles θ

A are the same for all the adjacent first gaps, the second angles θ

B are the same for all the adjacent second gaps, and the first angles θ

A and the seconds angle θ

B are the same.

5. The acoustic wave element according to claim 1, wherein

when the wavelength of the acoustic wave is λ

(μ

m), within the certain range, the gap lengths G (μ

m) of the plurality of first gaps and the plurality of second gaps in the direction perpendicular to the propagation direction are within the following range;

0.1≦

G≦

0.28λ

.

6. The acoustic wave element according to claim 1, wherein

within the certain range,

the edge part of the first bus bar which is on the second bus bar side is inclined relative to the propagation direction so as to become parallel relative to the arrangement direction of the first gaps, and

the edge part of the second bus bar which is on the first bus bar side is inclined relative to the propagation direction so as to become parallel relative to the arrangement direction of the second gaps.

7. The acoustic wave element according to claim 1, wherein

the certain range is the whole of the propagation direction of the IDT electrode.

8. The acoustic wave element according to claim 1, further comprising a reflector which is adjacent to the IDT electrode in the propagation direction, wherein

the reflector comprises

a third bus bar on the first bus bar side and a fourth bus bar on the second bus bar side which face each other in the direction perpendicular to the propagation direction, and

a plurality of third electrode fingers extending so as to connect the third bus bar and the fourth bus bar,

the edge part of the third bus bar which is on the fourth bus bar side is inclined relative to the propagation direction so as to become parallel to the arrangement direction of the first gaps, and

the edge part of the fourth bus bar which is on the third bus bar side is inclined relative to the propagation direction so as to become parallel to the arrangement direction of the second gaps.

9. The acoustic wave element according to claim 7, wherein

the first outer side edge part of the first bus bar which is on the side opposite to the second bus bar is inclined relative to the propagation direction so as to become parallel to the arrangement direction of the first gaps,

the second outer edge part of the second bus bar which is on the side opposite to the first bus bar is inclined relative to the propagation direction so as to become parallel to the arrangement direction of the second gaps, and

the plurality of IDT electrodes are arranged in the direction perpendicular to the propagation direction.

10. The acoustic wave element according to claim 1, which is a double mode type SAW filter in which a plurality of the above IDT electrodes are arranged in a direction which is inclined relative to the propagation direction to the side the same as the side to which the arrays of the plurality of first gaps and the plurality of second gaps are inclined.

11. The acoustic wave element according to claim 1, further comprising:

a reflector which is adjacent to the IDT electrode in the propagation direction and

a protective layer which

is located on the upper surface of the piezoelectric substrate so as to cover the IDT electrode and the reflector and

has a larger thickness than those of the IDT electrode and the reflector, wherein

the reflector comprises

a third bus bar on the first bus bar side and a fourth bus bar on the second bus bar side which face each other in the direction perpendicular to the propagation direction, and

a plurality of third electrode fingers which extend so as to connect the third bus bar and the fourth bus bar, and

when the reflectivity of the acoustic wave generating a primary resonance in the IDT electrode is Γ

(%), the number of the third electrode fingers is within a following range;

{100(%)/Γ

(%)±

1}.

12. An acoustic wave device having

an acoustic wave element according to claim 1 and

a circuit board on which the acoustic wave element is mounted.

3. An acoustic wave element, comprising:

a piezoelectric substrate and

an IDT electrode located on an upper surface of the piezoelectric substrate, wherein

the IDT electrode comprises

a first bus bar and a second bus bar which face each other in a direction intersecting with a propagation direction of the acoustic wave,

a plurality of first electrode fingers which extend from the first bus bar to the second bus bar side,

a plurality of second electrode fingers which

extend from the second bus bar to the first bus bar side and

have a portion adjacent to the plurality of first electrode fingers in the propagation direction,

a plurality of first dummy electrodes which

extend from the first bus bar to the second bus bar side and

have tips which face the tips of the plurality of second electrode fingers through a plurality of first gaps,

a plurality of second dummy electrodes which

extend from the second bus bar to the first bus bar side and

have tips which face the tips of the plurality of first electrode fingers through a plurality of second gaps,

a first additional electrode which

is located between a first electrode finger and a first dummy electrode which are adjacent to each other and at a position which it closes at least a portion of a first gap when viewed in the propagation direction and

is connected to at least one of the first electrode finger or the first dummy electrode, and

a second additional electrode which

is located between a second electrode finger and a second dummy electrode which are adjacent to each other and at a position which it closes at least a portion of the second gaps when viewed in the propagation direction and

is connected to at least one of the second electrode finger or the second dummy electrode, and,

in a certain range of the propagation direction of the IDT electrode,

when the arrangement direction of the first gaps among the plurality of first gaps which are adjacent to each other is a third direction, the third direction is inclined relative to the propagation direction,

when the arrangement direction of the second gaps among the plurality of second gaps which are adjacent to each other is a fourth direction, the fourth direction is inclined to the side the same as the side to which the third direction is inclined relative to the propagation direction, and

when the inclination angle of the third direction relative to the propagation direction is a third angle θ

C and the inclination angle of the fourth direction relative to the propagation direction is a fourth angle θ

D, the third angle θ

C and the fourth angle θ

D are within a following ranges;

6°

≦

θ

C≦

26°

6°

≦

θ

D≦

26°

.

4. The acoustic wave element according to claim 3, wherein

the third angles θ

C are the same for all the adjacent first gaps, the fourth angles θ

D are the same for all the adjacent second gaps, and the third angles θ

C and the fourth angles θ

D are the same.