CN118174684A

CN118174684A - Elastic wave device

Info

Publication number: CN118174684A
Application number: CN202311668844.9A
Authority: CN
Inventors: 熊四辈
Original assignee: Sanyan Japan Technology Co ltd
Current assignee: Sanyan Japan Technology Co ltd
Priority date: 2022-12-09
Filing date: 2023-12-06
Publication date: 2024-06-11
Also published as: JP2024082872A

Abstract

The application provides an elastic wave device. The elastic wave device includes: a device chip; a functional element formed on a first face of the device chip and including an IDT electrode; wiring formed on the first surface of the device chip and electrically connected to the functional element; and a package substrate combined with the device chip in such a manner that a substrate surface faces the first surface of the device chip; at least a part of the wiring is a thick film wiring portion having a thickness in a direction orthogonal to the first surface that is larger than a thickness of the functional element in the direction; meanwhile, an insulating film is further arranged between the device chip and the packaging substrate, the insulating film is respectively connected with the thick film wiring part of the device chip and the substrate surface side of the packaging substrate, and an air gap is formed at the forming position of the functional element.

Description

Elastic wave device

Technical Field

The present invention relates to an improvement of an elastic wave device suitable for use as a frequency filter or the like in a mobile communication device or the like.

Background

As an elastic wave device used as a frequency filter or the like in a mobile communication device or the like, there is a device shown in patent document 1.

In the device shown in patent document 1, an insulating film is formed between a device chip and a package substrate, and a distance between the device chip and the insulating film or a distance between the insulating film and the substrate is made smaller at a formation position of the insulating film, so that heat generated in the device chip is released by the insulating film.

Patent document 1: japanese patent application laid-open No. 2018-201083.

Disclosure of Invention

In the device of patent document 1, the distance between the device chip and the substrate is made by connecting the bumps of both. Therefore, the distance between the device chip and the insulating film or the distance between the insulating film and the substrate at the position where the insulating film is formed is not properly controlled by the bump. The larger the distance, the lower the heat dissipation property of the heat dissipation path through the insulating film.

The main problem to be solved by the present invention is to properly and reasonably improve the heat dissipation of such elastic wave devices.

In order to achieve the above object, according to the present invention, there is provided an elastic wave device comprising: a device chip; a functional element formed on a first face of the device chip and including an IDT electrode; wiring formed on the first surface of the device chip and electrically connected to the functional element; and a package substrate combined with the device chip such that a substrate surface faces the first surface of the device chip, at least a part of the wiring being a thick film wiring portion having a thickness in a direction orthogonal to the first surface that is larger than a thickness of the functional element in the direction; meanwhile, an insulating film is further arranged between the device chip and the packaging substrate, the insulating film is respectively connected with the thick film wiring part of the device chip and the substrate surface side of the packaging substrate, and an air gap is formed at the forming position of the functional element.

As one aspect of the present invention, in the air gap, the insulating film is provided with a convex portion protruding toward the device chip, and the convex portion does not contact the functional element.

As one aspect of the present invention, the protruding portion is set to a size of one-fourth to three-quarters of a target distance, the target distance being a difference between the thickness of the functional element and the thickness of the thick film wiring portion.

In addition, according to one aspect of the present invention, the insulating film is made of a synthetic resin containing a filler having high thermal conductivity.

As one aspect of the present invention, the thickness of the air gap is a difference between the thickness of the functional element and the thickness of the thick film wiring portion.

As one aspect of the present invention, a distance between the functional element and the insulating film in the air gap is 2 μm or less.

As one aspect of the present invention, the package substrate has a wiring formed on a substrate surface thereof, and the thick film wiring portion is insulated from the wiring formed on the substrate surface side of the package substrate by an insulating film.

As one aspect of the present invention, the thick film wiring portion is formed in a region other than a region in which the functional element is formed on the first surface of the device chip.

As one aspect of the present invention, a part of the thick film wiring portion is located on both sides with the functional element interposed therebetween.

As one aspect of the present invention, the insulating film has a plate shape having a length and a width smaller than those of the device chip.

As one aspect of the present invention, a space is formed between an edge of the insulating film and an edge of the device chip and between an edge of the insulating film and an edge of the package substrate.

As one mode of the present invention, a portion of the wiring that is a bump pad is located within the space.

According to the present invention, the device chip can be incorporated into the package substrate so that the insulating film is closely adhered to the thick film wiring portion and the package substrate side, respectively, and covers the hidden functional element. Thereby, an air gap, which is a difference between the thickness of the functional element and the thickness of the thick film wiring portion, can be formed in a controllable state at the formation position of the functional element. The air gap is a fine gap formed by a difference between the thickness of the functional element and the thickness of the thick film wiring portion. According to the elastic wave device, when it is necessary to efficiently release heat generated in the device chip by resonance of the functional element or the like at the time of applying a signal, the heat of the device chip can be directly transferred from the insulating film to the package substrate through the air in the air gap by the minute air gap and efficiently released.

Drawings

Fig. 1 is a cross-sectional configuration diagram of an elastic wave device according to an embodiment of the present invention.

Fig. 2 is a sectional structural view at a B-B line position of the first example.

Fig. 3 is a sectional structural view at a C-C line position of the first example.

Fig. 4 is a block diagram showing one example of a resonator formed in a device chip constituting the first example.

Fig. 5 is a block diagram showing one example of a circuit formed in a device chip constituting the first example.

Fig. 6 is a sectional structural view showing one procedure of the manufacturing process of the first example.

Fig. 7 is a cross-sectional configuration diagram showing a modification of the structure of a part of the first example.

Reference numerals

1: An elastic wave device; 1a: a center; 2: packaging a substrate; 2a: a substrate surface; 2b: the other side; 2c: an external connection terminal; 2d: a collective substrate; 3: a device chip; 3a: a first face; 3b: the other side; 3c: a side surface; 4: a bump; 5: wiring; 5a: bump pads; 5b: a thick film wiring section; 6: wiring; 6a: bump pads; 7: a functional element; 7a, 7aa, 7ab: a resonator; 7b: an IDT electrode; 7c: electrode fingers; 7d: a bus bar; 7e: a reflector; 7f: electrode fingers; 7g: a bus bar; 8: a circuit; 9: a ground wire; 10: an insulating film; 10a: a first face; 10b: a second face; 10c: a convex portion; 11: spacing; 12: an air gap; 13: a sealing resin layer; x: propagation direction.

Detailed Description

An exemplary embodiment of the present invention will be described below with reference to fig. 1 to 7. The elastic wave device 1 according to the present embodiment is suitable for use as a frequency filter or the like in a mobile communication device or the like.

The acoustic wave device 1 according to the present application includes a device chip 3, and the device chip 3 is mounted on a package substrate 2 such that a first surface 3a on which a functional element 7 (typically, a resonator 7 a) including IDT electrodes is formed faces a substrate surface 2a of the package substrate 2.

Typically, the device chip 3 is formed in a quadrangular plate shape having a side of 0.5 to 1mm and a thickness of 0.15 to 0.2 mm. The package substrate 2 is formed in a quadrangular plate shape having a side of 0.7 to 3mm and a thickness of 0.15 to 0.2 mm. The thickness of the elastic wave device 1 is set to about 0.4 to 0.6 mm.

The cross-sectional structure of the elastic wave device 1 is shown in fig. 1. In the figure, reference numeral 3 denotes a device chip, reference numeral 3a denotes a first surface of the device chip 3, reference numeral 3b denotes another surface facing the first surface 3a, reference numeral 7 denotes a functional element, and reference numeral 4 denotes a bump made of a conductive metal such as gold. The device chip 3 and the package substrate 2 are electrically connected by the bump 4, the bump 4 being interposed between a bump pad 5a connected to the wiring 5 on the device chip 3 side and a bump pad 6a connected to the wiring 6 on the package substrate 2 side, and being fixed to the two bump pads 5a, 6a, respectively.

The bump pads 5a, 6a and the bump 4 are made of a common metal and bonded, typically a metal such as gold or aluminum.

An external connection terminal 2c for connecting the acoustic wave device 1 to a motherboard, not shown, is formed on the other surface 2b of the package substrate 2 opposite to the substrate surface 2a on the mounting side of the device chip 3.

The device chip 3 has a function of propagating an elastic wave. Typically, a piezoelectric material such as lithium tantalate or lithium niobate is used for the device chip 3. The device chip 3 may be formed by laminating these piezoelectric bodies on a support such as sapphire, silicon, alumina, spinel, crystal, or glass.

The functional element 7 made of a conductive metal film is formed on the first surface 3a of the device chip 3. Typically, a plurality of functional elements 7 are formed on the device chip 3.

The thickness L1 (see fig. 1) of the conductive metal film constituting the functional element 7, that is, the thickness L1 of the conductive metal film constituting the functional element 7 in the direction orthogonal to the first surface 3a of the device chip 3 is typically set to be in the range of 0.1 to 0.2 μm.

The conductive metal films involved are typically formed by photolithographic techniques.

An example of the resonator 7a as a SAW filter is shown in fig. 4. The resonator 7a includes an IDT electrode 7b and a reflector 7e formed so as to sandwich the IDT electrode 7 b. The IDT electrode 7a is constituted of electrode pairs, and a plurality of electrode fingers 7c are connected to each other at one end side thereof by bus bars 7d, and the plurality of electrode fingers 7c are arranged in parallel so that the longitudinal direction crosses the propagation direction x of the elastic wave. The reflector 7e is formed by connecting bus bars 7g between the ends of a plurality of electrode fingers 7f, and the plurality of electrode fingers 7f are arranged in parallel so that the longitudinal direction intersects the propagation direction x of the elastic wave.

In addition, a plurality of resonators 7a may be formed on one device chip 3.

Fig. 5 shows a concept of one example of the circuit 8 provided on one device chip 3. Reference numeral 7aa denotes a resonator 7a connected in series between the input and output ports, reference numeral 7ab denotes a resonator 7a connected in parallel between the input and output ports, reference numeral 9 denotes a ground line, and reference numeral 5 denotes a wiring. The number and configuration of the resonators 7a are changed as needed. That is, the ladder filter is constituted by the circuit of fig. 5.

Further, a wiring 5 connected to the functional element 7 and the bump pad 5a is formed on the first surface 3a of the device chip 3. The wiring 5 is also formed of a conductive metal film.

At least a part of the wiring 5 is a thick film wiring portion 5b, and the thickness of the thick film wiring portion 5b in a direction orthogonal to the first surface is larger than the thickness of the functional element 7 in the direction.

The wiring 5 is also made of a conductive metal film, and is typically formed by photolithography.

The thickness L2 (see fig. 1) of the conductive metal film constituting the wiring 5, that is, the thickness L2 of the conductive metal film constituting the wiring 5 in the direction orthogonal to the first surface 3a of the device chip 3 is typically set to be in the range of 2 to 4 μm.

In the illustrated example, a part of the wiring 5 becomes the bump pad 5a. The entire wiring 5 is a thick film wiring portion 5b.

The device chip 3 and the package substrate 2 are connected to each other through the bump 4 via an insulating film 10.

Specifically, the insulating film 10 is formed between the thick film wiring portion 5b of the device chip 3 and the package substrate 2 so as to be in contact with the substrate surface 2a side thereof, and an air gap 12 is formed at the formation position of the functional element 7, and the thickness of the air gap 12 is the difference between the thickness L1 of the functional element 7 and the thickness L2 of the thick film wiring portion 5b, and the air gap 12 is a hollow gap, and in this state, the device chip 3 and the package substrate 2 are connected/combined.

In the illustrated example, five functional elements 7 are formed in the device chip 3. The insulating film 10 has a quadrangular plate shape having a length and a width smaller than those of the device chip 3.

The first surface 10a of the insulating film 10 facing the first surface 3a of the device chip 3 is substantially parallel to the first surface 3a of the device chip 3, is closely adhered to the thick film wiring portion 5b, and allows the device chip 3 to cover and hide the five functional elements 7 in a state where the first surface 3a is viewed from a direction orthogonal to the first surface 3a of the device chip 3. A space 11 is also formed at any position around the center 1a (see fig. 2) of the elastic wave device between the edge of the insulating film 10 and the edge of the device chip 3 and between the edge of the insulating film 10 and the edge of the package substrate 2. The portion of the wiring 5 that is the bump pad 5a is located within the space 11.

A second surface 10b of the insulating film 10, which is back-to-back with the first surface 10a, is closely contacted with the substrate surface 2a side of the package substrate 2. In the illustrated example, the wiring 6 formed on the substrate surface 2a of the package substrate 2 is closely adhered to the wiring. In the illustrated example, the thickness of the wiring 6 is equal to the thickness of the bump pad 6a on the package substrate 2 side.

Typically, as shown in fig. 6, the insulating film 10 is formed as follows: before the device chip 3 having the functional element 7 and the wiring 5 formed thereon is mounted on the aggregate substrate 2d as the package substrate 2, the resin to be the insulating film 10 is applied by sputtering on the entire surface of the aggregate substrate 2d, and then unnecessary portions (the removed portions are shown by broken lines in fig. 6) are removed from the applied resin by etching, so that the spacers 11 are formed in the respective elastic wave devices 1.

The device chip 3 is mounted on the collective substrate 2d by covering the hidden functional element 7 as described above, with the first surface 10a of the insulating film 10 being in close contact with the thick film wiring portion 5b and the second surface 10b being in close contact with the package substrate 2 side, with respect to the collective substrate 2d on which the insulating film 10 is formed. Thereby, the air gap 12, which is the difference between the thickness L1 of the functional element 7 and the thickness L2 of the thick film wiring portion 5b, is formed in a controllable state at the formation position of the functional element 7. That is, the gap amount of the air gap 12 is fixed without being affected by the soldered state of the bump 4.

The insulating film 10 is supported by the thick film wiring portion 5b without contacting the functional element 7, and does not suppress the elastic wave of the functional element 7. The thick film wiring portion 5b is insulated from the wiring 6 and the like formed on the substrate surface 2a side of the package substrate 2 by an insulating film 10.

The thick film wiring portion 5b may be formed on the first surface 3a of the device chip 3 so that the first surface 3a is parallel to the first surface 10a of the insulating film 10 and can support the insulating film 10. The thick film wiring portion 5b is formed in a region other than the region where the functional element 7 is formed on the first surface 3a of the device chip 3, and its formation position and form can be changed as necessary.

In the illustrated example, for each functional element 7, a part of the thick film wiring portion 5b is located on both sides (both sides in the left-right direction in fig. 3) of the functional element 7, and a part of the thick film wiring portion 5b thus positioned supports the insulating film 10 on both sides of the air gap 12.

In a state where the plurality of device chips 3 are mounted on the collective substrate 2d in this way, the sealing resin layer 13 is formed on the collective substrate 2d, and then dicing is performed, thereby producing the plurality of elastic wave devices 1.

In each of the elastic wave devices 1 to be generated, a gap corresponding to the thickness of the insulating film 10 is formed between the device chip 3 and the package substrate 2. The sealing resin layer 13 covers the other surface 3b of the device chip 3 and the side surface 3c in the thickness direction of the device chip 3, and enters the gap between the device chip 3 and the package substrate 2 at the outer edge side of the device chip 3 and hermetically seals the gap over the entire circumference of the device chip 3 (see fig. 1).

The air gap 12 is a fine gap (typically 2 to 4 μm) formed by the difference between the thickness L1 of the functional element 7 and the thickness L2 of the thick film wiring portion. In the acoustic wave device 1, when it is necessary to efficiently release heat generated in the device chip 3 by resonance or the like of the functional element 7 at the time of applying a signal, the heat of the device chip 3 can be directly transferred from the insulating film 10 to the package substrate 2 through the air in the air gap 12 through the minute air gap 12 and efficiently released (the heat radiation path of the heat is denoted by reference symbol r1 in fig. 1).

In addition, the heat of the device chip 3 is also transferred to the package substrate 2 via the bump (reference symbol r2 in fig. 1 indicates a heat dissipation path of the heat).

From the viewpoint of achieving efficient heat dissipation, it is preferable that the distance between the functional element 7 and the insulating film 10 in the air gap 12 is 2 μm or less.

From the same point of view, it is preferable that the insulating film 10 be made of a synthetic resin containing a filler having high thermal conductivity.

Typically, the insulating film 10 concerned is preferably an insulating film containing the filler in a range of 70wt% to 90wt% in the thermosetting resin.

The filler is composed of a substance having high thermal conductivity such as alumina. The filler is typically formed into a granular body having a diameter in the range of 1 to 10 μm.

Fig. 7 shows an example in which a convex portion 10c protruding in a size not contacting the functional element 7 is formed in the air gap 12 on the insulating film 10. That is, the insulating film 10 is provided with a convex portion 10c, and the convex portion 10c is formed on the first surface 10a of the insulating film 10 and protrudes toward the first surface 3a side of the device chip 3.

In this way, the distance between the device chip 3 side and the insulating film 10 can be further reduced in the air gap 12.

If the dimension of the convex portion 10c, that is, the thickness L3 (see fig. 7) of the convex portion 10c in the direction orthogonal to the first surface 3a of the device chip 3 is set to be one-fourth to three-quarters of the target distance, which is the difference between the thickness L1 of the functional element 7 and the thickness L2 of the thick film wiring portion 5b, the gap amount of the air gap 12 in the formation position of the convex portion 10c can be set to be one-fourth to three-quarters of the gap amount of the air gap 12 in the position where the convex portion 10c is not formed.

The protruding portion 10c is typically formed on the first face 10a of the insulating film 10 in such a manner that the protruding portion 10c is located directly below the functional element 7.

It should be noted that, of course, the present invention is not limited to the above-described embodiments, and includes all embodiments capable of achieving the object of the present invention.

Claims

1. An elastic wave device, comprising:

A device chip;

A functional element formed on a first face of the device chip and including an IDT electrode;

wiring formed on the first surface of the device chip and electrically connected to the functional element; and

A package substrate combined with the device chip in such a manner that a substrate surface faces the first surface of the device chip;

At least a part of the wiring is a thick film wiring portion having a thickness in a direction orthogonal to the first surface that is larger than a thickness of the functional element in the direction; meanwhile, an insulating film is further arranged between the device chip and the packaging substrate, the insulating film is respectively connected with the thick film wiring part of the device chip and the substrate surface side of the packaging substrate, and an air gap is formed at the forming position of the functional element.

2. The elastic wave device according to claim 1, wherein in the air gap, the insulating film is provided with a convex portion protruding toward the device chip, and the convex portion does not contact the functional element.

3. The elastic wave device according to claim 2, wherein the size of the convex portion is set to be one-fourth to three-fourths of a target distance, the target distance being a difference between the thickness of the functional element and the thickness of the thick film wiring portion.

4. The elastic wave device according to any one of claims 1 to 3, wherein the insulating film is composed of a synthetic resin containing a filler having high thermal conductivity.

5. The elastic wave device according to claim 1, wherein a thickness of the air gap is a difference between the thickness of the functional element and the thickness of the thick film wiring portion.

6. The elastic wave device according to claim 1, wherein a distance between the functional element and the insulating film in the air gap is 2 μm or less.

7. The acoustic wave device according to claim 1, wherein a substrate surface of the package substrate is provided with a wiring, and the thick film wiring portion is insulated from the wiring formed on the substrate surface side of the package substrate by an insulating film.

8. The acoustic wave device according to claim 1, wherein the thick film wiring portion is formed in a region other than a region in which the functional element is formed on the first face of the device chip.

9. The acoustic wave device according to claim 1, wherein a portion of the thick film wiring portion is located on both sides of the functional element.

10. The elastic wave device according to claim 1, wherein the insulating film has a plate shape having a length and a width smaller than those of the device chip.

11. The elastic wave device according to claim 1, wherein a space is formed between an edge of the insulating film and an edge of the device chip and between an edge of the insulating film and an edge of the package substrate.

12. The elastic wave device according to claim 11, wherein a portion of the wiring that is a bump pad is located within the space.