Acoustic wave device
An acoustic wave device includes an acoustic wave element, bumps electrically connected to the acoustic wave element, an under-bump metal layer between the acoustic wave element and the bumps, a wiring substrate on which the acoustic wave element is mounted, and an encapsulating body covering the acoustic wave element on the wiring substrate. The acoustic wave element includes a support substrate, a piezoelectric layer on one main surface of the support substrate, and a functional electrode on at least one main surface of the piezoelectric layer. The wiring substrate is electrically connected to the acoustic wave element via the under-bump metal layer and the bumps. The piezoelectric layer includes a hole passing through the piezoelectric layer on at least a portion of a straight line connecting the functional electrode and the bumps to each other.
1 . An acoustic wave device comprising:
an acoustic wave element;
a plurality of bumps electrically connected to the acoustic wave element;
an under-bump metal layer between the acoustic wave element and the plurality of bumps;
a wiring substrate on which the acoustic wave element is mounted; and
an encapsulating body covering the acoustic wave element on the wiring substrate; wherein
the acoustic wave element includes a support substrate, a piezoelectric layer on one main surface of the support substrate, and a functional electrode on at least one main surface of the piezoelectric layer;
the wiring substrate is electrically connected to the acoustic wave element via the under-bump metal layer and the plurality of bumps;
the piezoelectric layer includes a hole passing through the piezoelectric layer on at least a portion of a straight line connecting the functional electrode and the bumps to each other;
the piezoelectric layer is made of a monocrystalline piezoelectric substance; and
a straight line connecting the functional electrode and one of the plurality of bumps to each other is parallel or substantially parallel to a crystal cleavage direction of the piezoelectric layer.
2 . The acoustic wave device according to claim 1 , wherein the hole is provided on a straight line connecting the functional electrode and one of the plurality of bumps that is closest to the functional electrode to each other.
3 . The acoustic wave device according to claim 1 , wherein the support substrate includes a dielectric layer on the one main surface thereof.
4 . An acoustic wave device comprising:
an acoustic wave element;
a plurality of bumps electrically connected to the acoustic wave element;
an under-bump metal layer between the acoustic wave element and the plurality of bumps;
a wiring substrate on which the acoustic wave element is mounted; and
an encapsulating body covering the acoustic wave element on the wiring substrate; wherein
the acoustic wave element includes a support substrate, a piezoelectric layer on one main surface of the support substrate, and a functional electrode on at least one main surface of the piezoelectric layer;
the wiring substrate is electrically connected to the acoustic wave element via the under-bump metal layer and the plurality of bumps;
the piezoelectric layer includes a hole passing through the piezoelectric layer on at least a portion of a straight line connecting the functional electrode and the bumps to each other;
the support substrate includes a dielectric layer on the one main surface thereof; and
the hole extends to the dielectric layer.
5 . The acoustic wave device according to claim 4 , wherein the piezoelectric layer is made of a monocrystalline piezoelectric substance.
6 . The acoustic wave device according to claim 4 , wherein the hole is provided on a straight line connecting the functional electrode and one of the plurality of bumps that is closest to the functional electrode to each other.
7 . An acoustic wave device comprising:
an acoustic wave element;
a plurality of bumps electrically connected to the acoustic wave element;
an under-bump metal layer between the acoustic wave element and the plurality of bumps;
a wiring substrate on which the acoustic wave element is mounted; and
an encapsulating body covering the acoustic wave element on the wiring substrate; wherein
the acoustic wave element includes a support substrate, a piezoelectric layer on one main surface of the support substrate, and a functional electrode on at least one main surface of the piezoelectric layer;
the wiring substrate is electrically connected to the acoustic wave element via the under-bump metal layer and the plurality of bumps;
the piezoelectric layer includes a hole passing through the piezoelectric layer on at least a portion of a straight line connecting the functional electrode and the bumps to each other;
the support substrate includes a hollow portion in the one main surface thereof;
the piezoelectric layer is provided on the one main surface of the support substrate to cover the hollow portion;
the functional electrode is provided such that a portion thereof overlaps the hollow portion in a direction in which the support substrate and the piezoelectric layer are laminated together; and
the hole communicates with the hollow portion.
8 . The acoustic wave device according to claim 7 , wherein the functional electrode includes one or more first electrodes, a first busbar electrode to which the one or more first electrodes are connected, one or more second electrodes, and a second busbar electrode to which the one or more second electrodes are connected.
9 . The acoustic wave device according to claim 8 , wherein, when a center-to-center distance between a first electrode and a second electrode that are adjacent to each other of the one or more first electrodes and the one or more second electrodes is p, a thickness of the piezoelectric layer is about 2p or smaller.
10 . The acoustic wave device according to claim 8 , wherein d/p≤about 0.5 is satisfied, where d is a thickness of the piezoelectric layer, and p is a center-to-center distance between a first electrode and a second electrode that are adjacent to each other of the one or more first electrodes and the one or more second electrodes.
11 . The acoustic wave device according to claim 10 , wherein d/p≤about 0.24 is satisfied.
12 . The acoustic wave device according to claim 8 , wherein MR≤about 1.75(d/p)+0.075 is satisfied, where MR is a metallization ratio, d is a thickness of the piezoelectric layer, and p is a center-to-center distance between a first electrode and a second electrode that are adjacent to each other of the one or more first electrodes and the one or more second electrodes, the metallization ratio being a ratio of an area of the first electrode and the second electrode that are adjacent to each other to an area of an excitation region in which the first electrode and the second electrode that are adjacent to each other overlap each other as viewed in a direction in which the first electrode and the second electrode that are adjacent to each other face each other.
13 . The acoustic wave device according to claim 12 , wherein MR≤about 1.75(d/p)+0.05 is satisfied.
14 . The acoustic wave device according to claim 7 , wherein the piezoelectric layer is made of lithium niobate or lithium tantalate.
15 . The acoustic wave device according to claim 14 , wherein the acoustic wave device is structured to generate a bulk wave of a thickness-shear mode.
16 . The acoustic wave device according to claim 14 , wherein
Euler angles (φ, θ, ψ) of the lithium niobate or the lithium tantalate are within a range of formula 1, formula 2, or formula 3:
(
0
°
±
10
°
,
0
°
to
20
°
,
arbitrary
ψ
)
;
Formula
1
(
0
°
±
10
°
,
20
°
to
80
°
,
0
°
to
60
°
(
1
-
(
θ
-
50
)
2
/
900
)
1
/
2
)
or
Formula
2
(
0
°
±
10
°
,
20
°
to
80
°
,
[
180
°
-
60
°
(
1
-
(
θ
-
50
)
2
/
900
)
1
/
2
]
to
180
°
)
;
and
(
0
°
±
10
°
,
[
180
°
-
30
°
(
1
-
(
ψ
-
90
)
2
/
8100
)
1
/
2
]
to
180
°
,
arbitrary
ψ
)
.
Formula
3
17 . The acoustic wave device according to claim 7 , wherein the functional electrode includes an upper electrode on one main surface of the piezoelectric layer and a lower electrode on another main surface of the piezoelectric layer.