Elastic wave device and method for manufacturing the same

Abstract

To provide a surface acoustic wave device which is compact, has reinforced shield effect and ground electrode of a signal line, and is excellent in adhesion between a sealing part and a wiring board.SOLUTION: A surface acoustic wave device includes: a wiring board having a mounting surface; a ground electrode formed on the mounting surface; a pad for antenna; a pad for transmission; a pad for reception; a metal ring for antenna surrounding the pad for antenna; a metal ring for transmission surrounding the pad for transmission and a metal ring for reception surrounding the pad for reception; and a device chip mounted on the wiring board. The metal ring for the antenna, the metal ring for transmission, and the metal ring for reception are connected to the ground electrode. A mean distance from extension of the wiring board to the ground electrode is longer than a mean distance from the extension of the wiring board to the metal ring for antenna, the metal ring for transmission, and the metal ring for reception.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an elastic wave device and a method for manufacturing the same. Specifically, it is an elastic surface wave device using SH waves or an FBAR using BAW, and relates to, for example, a duplexer or a multiplexer.

Background Art

[0002] In a high-frequency communication system for a mobile communication terminal represented by a smartphone, a high-frequency filter or the like is used to remove unnecessary signals outside the frequency band used for communication.

[0003] For a high-frequency filter or the like, an elastic wave device having an elastic surface wave (SAW: Surface acoustic wave) element or the like is used. The SAW element is an element in which an IDT (Interdigital Transducer) having a pair of comb-shaped electrodes is formed on a piezoelectric substrate.

[0004] For example, an elastic surface wave device is manufactured as follows. First, a multilayer substrate is created by bonding a piezoelectric substrate that propagates elastic waves and a support substrate having a thermal expansion coefficient smaller than that of the piezoelectric substrate. Next, a large number of IDT electrodes are formed on the multilayer substrate using photolithography technology, and then cut into a predetermined size by dicing to obtain an elastic surface wave device. In this manufacturing method, by using a multilayer substrate, the change in the size of the piezoelectric substrate when the temperature changes is suppressed by the support substrate, so that the frequency characteristics as an elastic wave device are stabilized.

[0005] Patent Document 1 discloses an example of a technique related to an elastic wave device.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The main problems to be solved by the present disclosure will be described.

[0008] In elastic wave devices such as band-pass filters and duplexers, a device chip such as a SAW filter is flip-chip bonded to a wiring substrate.

[0009] A resonator constituting a SAW filter forms a hollow region for mechanical vibration and is sealed with a synthetic resin, metal, or the like. In order to prevent the sealing portion and the wiring substrate from peeling off, it is desirable that the adhesion between the sealing portion and the wiring substrate is high. Also, in order to suppress the intrusion of moisture into the sealed hollow region, it is desirable that the adhesion between the sealing portion and the wiring substrate is high.

[0010] In addition, a metal pattern through which an electric signal in a desired frequency band passes may be interfered with by an external electromagnetic wave. Therefore, a structure with a high shielding effect is desired.

[0011] In addition, elastic wave devices are required to be more miniaturized. In order to enhance the shielding effect of the pads on the wiring substrate, if the periphery is surrounded by a metal pattern, the wiring substrate will become larger. Also, if there are too many metal patterns in the extension portion of the wiring substrate, the adhesion between the sealing portion and the wiring substrate will decrease, which may lead to peeling between the wiring substrate and the sealing portion.

[0012] The present disclosure has been made in view of the above problems, and an object thereof is to provide an elastic wave device having a small size, enhanced shielding effect of signal lines and ground electrodes, and excellent adhesion between a sealing portion and a wiring substrate.

Means for Solving the Problems

[0013] The elastic wave device according to the present disclosure is a wiring substrate having a mounting surface, The ground electrode, antenna pad, transmission pad, reception pad formed on the mounting surface, the antenna metal ring surrounding the antenna pad, the transmission metal ring surrounding the transmission pad, and the reception metal ring surrounding the reception pad, a device chip mounted on the wiring substrate, and are provided with the antenna metal ring, the transmission metal ring, and the reception metal ring are connected to the ground electrode, The average distance from the outer extension of the wiring substrate to the ground electrode is longer than the average distance from the outer extension of the wiring substrate to the antenna metal ring, the transmission metal ring, and the reception metal ring, and it is an elastic wave device.

[0014] In one embodiment of the present disclosure, the mounting surface includes an inductor pad and an inductor metal ring surrounding the inductor pad.

[0015] It includes a sealing portion for sealing the device chip together with the wiring substrate, In one embodiment of the present disclosure, the sealing portion is joined to an insulating region between the antenna pad and the antenna metal ring.

[0016] It includes a sealing portion for sealing the device chip together with the wiring substrate, In one embodiment of the present disclosure, the sealing portion is joined to an insulating region between the transmission pad and the transmission metal ring and an insulating region between the reception pad and the reception metal ring, respectively.

[0017] In one embodiment of the present invention, the shortest distance from the outer extension of the side of the wiring substrate to the transmission metal ring is shorter than the shortest distance from the outer extension of the corner of the wiring substrate to the transmission metal ring.

[0018] In one embodiment of the present invention, the shortest distance from the outer extension of the side of the wiring substrate to the receiving metal ring is shorter than the shortest distance from the outer extension of the corner of the wiring substrate to the receiving metal ring.

[0019] In one embodiment of the present invention, the thickness of the metal ring for the antenna is 10 μm to 35 μm.

[0020] In one embodiment of the present invention, the thicknesses of the transmitting metal ring and the receiving metal ring are 10 μm to 35 μm.

[0021] In one embodiment of the present invention, the device chip includes a piezoelectric substrate made of lithium tantalate, lithium niobate, or quartz.

[0022] In one embodiment of the present invention, the device chip is made of sapphire, silicon, alumina, spinel, silicon nitride, aluminum oxynitride, aluminum oxide, silicon carbide, silicon oxynitride, diamond, quartz, or glass.

[0023] In one embodiment of the present invention, there is a module including the elastic wave device.

Advantages of the Invention

[0024] According to the present disclosure, an elastic wave device with excellent characteristics can be provided, which has better heat dissipation, excellent adhesion between the sealing portion and the wiring substrate, and is less likely to generate coupling between a metal pattern through which an electrical signal in a desired frequency band passes and a metal pattern through which an electrical signal in a desired frequency band does not pass.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

[0026] Embodiments will be described with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions of such parts are appropriately simplified or omitted.

[0027] Embodiment 1. FIG. 1 is a sectional view showing the elastic wave device 1 according to Embodiment 1.

[0028] As shown in FIG. 1, the elastic wave device 1 includes a wiring substrate 3, external connection terminals 31, a device chip 5, bumps 15, and a sealing portion 17.

[0029] For example, the wiring substrate 3 is a multilayer substrate made of resin. For example, the wiring substrate 3 is a low-temperature co-fired ceramics (LTCC) multilayer substrate composed of a plurality of dielectric layers.

[0030] A plurality of external connection terminals 31 are formed on the main surface of the wiring substrate 3 opposite to the mounting surface.

[0031] On the mounting surface of the wiring substrate 3, a ground electrode 20, a transmission pad 22, a reception pad 23, a transmission metal ring 25 surrounding the transmission pad 22, and a reception metal ring 26 surrounding the reception pad 23 are formed.

[0032] The bumps 15 are formed on the upper surfaces of the respective electrode pads 9. For example, the bumps 15 are gold bumps. For example, the height of the bumps 15 is from 10 μm to 50 μm.

[0033] A gap 16 is formed between the wiring substrate 3 and the device chip 5.

[0034] The device chip 5 is mounted on the wiring substrate 3 by flip chip bonding via bumps 15. The device chip 5 is electrically connected to a plurality of pads via a plurality of bumps 15.

[0035] The device chip 5 is a substrate on which the elastic wave elements 50 are formed. For example, on the main surface of the device chip 5, a transmission filter and a reception filter including a plurality of elastic wave elements 50 are formed.

[0036] The transmission filter is formed so that an electrical signal in a desired frequency band can pass therethrough. For example, the transmission filter is a ladder type filter including a plurality of series resonators and a plurality of parallel resonators.

[0037] The reception filter is formed so that an electrical signal in a desired frequency band can pass therethrough. For example, the reception filter is a ladder type filter.

[0038] The device chip 5 includes a piezoelectric substrate 11 and a support substrate 13. The piezoelectric substrate 11 is a substrate formed of a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz, for example. In another example, the piezoelectric substrate 11 is a substrate formed of piezoelectric ceramics.

[0039] The thickness of the piezoelectric substrate 11 can be, for example, from 0.3 μm to 5 μm.

[0040] The support substrate 13 can be formed of, for example, sapphire, silicon, alumina, spinel, silicon nitride, aluminum oxynitride, aluminum oxide, silicon carbide, silicon oxynitride, diamond, quartz, glass, or the like. The smaller the thermal expansion coefficient of the support substrate 13, the better. This is because the temperature characteristics of the elastic wave device 1 are improved.

[0041] The thickness of the support substrate 13 can be, for example, from 50 μm to 200 μm.

[0042] The sealing portion 17 is formed so as to cover the device chip 5. The device chip 5 is hermetically sealed by the wiring board 3 and the sealing portion 17. For example, the sealing portion 17 is formed of an insulator such as a synthetic resin. For example, the sealing portion 17 is formed of metal.

[0043] When the sealing portion 17 is formed of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, or the like. Preferably, the sealing portion 17 is formed of an epoxy resin using a low-temperature curing process.

[0044] As shown in FIG. 1, the sealing portion 17 is joined to the insulating region 17Tx between the transmission pad 22 and the transmission metal ring 25. Further, the sealing portion 17 is joined to the insulating region 17Rx between the reception pad 23 and the reception metal ring 26. Thereby, the adhesion between the wiring board 3 and the sealing portion 17 is improved.

[0045] FIG. 2 is a schematic view of the mounting surface of the wiring board 3 of the surface acoustic wave device 1 according to Embodiment 1. As shown in FIG. 2, the mounting surface of the wiring board 3 includes a ground electrode 20, an antenna pad 21, a transmission pad 22, a reception pad 23, an antenna metal ring 24 surrounding the antenna pad 21, a transmission metal ring 25 surrounding the transmission pad 22, a reception metal ring 26 surrounding the reception pad 23, an inductor pad 27, and an inductor metal ring 28 surrounding the inductor pad 27.

[0046] As shown in FIG. 2, the antenna metal ring 24, the transmission metal ring 25, the reception metal ring 26, and the inductor metal ring 28 surround the antenna pad 21, the transmission pad 22, the reception pad 23, and the inductor pad 27, respectively. Thereby, the shielding effect on the electrical signals passing through the antenna pad 21, the transmission pad 22, and the reception pad 23 is enhanced.

[0047] The thicknesses of the ground electrode 20, the antenna pad 21, the transmission pad 22, the reception pad 23, the antenna metal ring 24 surrounding the antenna pad 21, the transmission metal ring 25 surrounding the transmission pad 22, the reception metal ring 26 surrounding the reception pad 23, the inductor pad 27, and the inductor metal ring 28 surrounding the inductor pad 27 are, for example, from 10 μm to 35 μm. A thickness from 15 μm to 30 μm is more desirable. In the elastic wave device 1 prototyped by the inventors, these thicknesses were 15 μm. Particularly in elastic wave devices for high-frequency applications such as 5 GHz and sub-6 GHz bands, each pad having such a thickness is subject to electrical interference from the lateral direction (the direction perpendicular to the thickness direction). Therefore, it is desirable to surround each pad with each metal ring.

[0048] Furthermore, as shown in FIG. 2, the antenna metal ring 24, the transmission metal ring 25, the reception metal ring 26, and the inductor metal ring 28 are connected to the ground electrode 20. Thereby, the shielding effect is further enhanced for the electrical signals passing through the antenna pad 21, the transmission pad 22, and the reception pad 23.

[0049] The ground electrode 20, the antenna pad 21, the transmission pad 22, the reception pad 23, the antenna metal ring 24 surrounding the antenna pad 21, the transmission metal ring 25 surrounding the transmission pad 22, the reception metal ring 26 surrounding the reception pad 23, the inductor pad 27, and the inductor metal ring 28 surrounding the inductor pad 27 are formed of, for example, copper or an alloy containing copper.

[0050] As shown in FIG. 2, the distance A and the average distance from the outer extension of the wiring board 3 to the ground electrode 20 are longer than the distance B and the average distance from the outer extension of the wiring board 3 to the antenna metal ring 24. The distance A and the average distance from the outer extension of the wiring board 3 to the ground electrode 20 are longer than the distance C and the average distance from the outer extension of the wiring board 3 to the transmission metal ring 25. The distance A and the average distance from the outer extension of the wiring board 3 to the ground electrode 20 are longer than the distance D and the average distance from the outer extension of the wiring board 3 to the reception metal ring 26.

[0051] In the prototype elastic wave device 1 fabricated by the inventors, the average distance from the outer extension of the wiring board 3 to the ground electrode 20 was about 75 μm. The average distance from the outer extension of the wiring board 3 to the antenna metal ring 24 was 15 μm. The average distance from the outer extension of the wiring board 3 to the transmission metal ring 25 was 15 μm. The average distance from the outer extension of the wiring board 3 to the reception metal ring 26 was 15 μm.

[0052] As shown in FIG. 2, the shortest distance from the outer extension of the wiring board 3 to the transmission metal ring 25 is shorter than the shortest distance E from the outer extension of the corner of the wiring board 3 to the transmission metal ring 25. In the prototype elastic wave device 1 fabricated by the inventors, the shortest distance from the outer extension of the wiring board 3 to the transmission metal ring 25 was 15 μm, and the shortest distance E was 75 μm.

[0053] The shortest distance from the outer extension of the wiring board 3 to the reception metal ring 26 is shorter than the shortest distance F from the outer extension of the corner of the wiring board 3 to the reception metal ring 26. In the prototype elastic wave device 1 fabricated by the inventors, the shortest distance from the outer extension of the wiring board 3 to the reception metal ring 26 was 15 μm, and the shortest distance F was 75 μm.

[0054] The corners of the transmission pad 22 and the corners of the reception pad 23 are less likely to be affected by electrical interference. On the other hand, the corners of the wiring board 3 are likely to be the starting points of the peeling between the wiring board 3 and the sealing portion 17. Therefore, at the corners of the wiring board 3, by increasing the area of the resin portion with good adhesion to the sealing portion, while accepting few demerits, great merits are enjoyed.

[0055] Next, an example of an elastic wave element formed on the piezoelectric substrate 11 will be described with reference to FIG. 3. FIG. 3 is a diagram showing an example of the elastic wave element 50 of the elastic wave device according to the first embodiment.

[0056] As shown in FIG. 3, the IDT (Interdigital Transducer) 51 and the pair of reflectors 52 are formed on the main surface of the piezoelectric substrate 11. The IDT electrode 51 and the pair of reflectors 52 are provided so as to be able to excite elastic waves (mainly SH waves).

[0057] For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an alloy of aluminum and copper. For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an appropriate metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver, or an alloy thereof.

[0058] For example, the IDT electrode 51 and the pair of reflectors 52 are formed of a laminated metal film in which a plurality of metal layers are laminated. For example, the thickness of the IDT electrode 51 and the pair of reflectors 52 is from 150 nm to 450 nm.

[0059] The IDT electrode 51 includes a pair of comb-shaped electrodes 51a. The pair of comb-shaped electrodes 51a face each other. The comb-shaped electrode 51a includes a plurality of electrode fingers 51b and bus bars 51c.

[0060] The plurality of electrode fingers 51b are arranged with their longitudinal directions aligned. The bus bar 51c connects the plurality of electrode fingers 51b.

[0061] One of the pair of reflectors 52 is adjacent to one side of the IDT electrode 51. The other of the pair of reflectors 52 is adjacent to the other side of the IDT electrode 51.

[0062] According to the first embodiment described above, it is possible to provide an elastic wave device that is small in size, enhances the shielding effect of signal lines and ground electrodes more, and has excellent adhesion between the sealing portion and the wiring board.

[0063] Second Embodiment. FIG. 4 is a longitudinal sectional view of a module to which the elastic wave device 1 according to the first embodiment is applied. Note that the same reference numerals are given to the same or corresponding parts as those in the first embodiment, and the description of such parts is omitted.

[0064] In FIG. 4, the module 100 includes a wiring board 130, a plurality of external connection terminals 131, an integrated circuit component IC, an elastic wave device 1, an inductor 111, and a sealing portion 117.

[0065] The plurality of external connection terminals 31 are formed on the lower surface of the wiring board 130. The plurality of external connection terminals 131 are mounted on the motherboard of a preset mobile communication terminal.

[0066] For example, the integrated circuit component IC is mounted inside the wiring board 130. The integrated circuit component IC includes a switching circuit and a low-noise amplifier.

[0067] The elastic wave device 1 is mounted on the main surface of the wiring board 130.

[0068] The inductor 111 is mounted on the main surface of the wiring board 130. The inductor 111 is mounted for impedance matching. For example, the inductor 111 is an Integrated Passive Device (IPD).

[0069] The sealing portion 117 seals a plurality of electronic components including the elastic wave device 1.

[0070] According to Embodiment 2 described above, the module 100 includes the surface acoustic wave device 1. Therefore, it is possible to provide a module that is small in size, enhances the shielding effect of the signal line and the ground electrode more, and includes a surface acoustic wave device having excellent adhesion between the sealing portion and the wiring board.

[0071] Although some aspects of at least one embodiment have been described, it should be understood that various modifications, corrections, and improvements will readily occur to those skilled in the art. Such modifications, corrections, and improvements are intended to be part of this disclosure and are intended to be within the scope of this disclosure.

[0072] It should be understood that the embodiments of the methods and apparatuses described herein are not limited to the details of the structures and arrangements of the components described in the above description or illustrated in the accompanying drawings. The methods and apparatuses can be implemented in other embodiments and can be carried out or executed in various manners.

[0073] Specific implementation examples are provided herein for illustrative purposes only and are not intended to be limiting.

[0074] The expressions and terms used in this disclosure are for explanatory purposes and should not be regarded as limiting. The use of "including", "comprising", "having", "containing" and variations thereof herein means the inclusion of the items listed hereinafter and their equivalents as well as additional items.

[0075] References to "or (alternatively)" can be construed such that any terms described using "or (alternatively)" indicate one, more than one, and all of the terms described.

[0076] References to front and back, left and right, top and bottom, horizontal and vertical, front and back are all for the convenience of description. Such references do not limit the components of this disclosure to any one positional or spatial orientation. Therefore, the above description and drawings are merely illustrative.

Description of Reference Numerals

[0077] 1 Elastic wave device, 3 Wiring board, 5 Device chip 11 Piezoelectric substrate, 13 Support substrate, 17 Sealing portion, 50 Elastic wave element 20 Ground electrode, 21 Antenna pad, 22 Transmission pad 23 Reception pad 24 Antenna metal ring, 25 Transmission metal ring 26 Reception metal ring 27 Inductor pad, 28 Inductor metal ring 100 Module, 111 Inductor, 117 Sealing portion 130 Wiring board

Claims

1. A wiring board having a mounting surface, a ground electrode, an antenna pad, a transmission pad, a reception pad formed on the mounting surface, an antenna metal ring surrounding the antenna pad, a transmission metal ring surrounding the transmission pad, and a reception metal ring surrounding the reception pad, and a device chip mounted on the wiring board, characterized in that: the antenna metal ring, the transmission metal ring, and the reception metal ring are connected to the ground electrode; the average distance from the outer extension of the wiring board to the ground electrode is longer than the average distance from the outer extension of the wiring board to the antenna metal ring, the transmission metal ring, and the reception metal ring, a surface acoustic wave device.

2. The surface acoustic wave device according to claim 1, wherein the mounting surface is provided with an inductor pad and an inductor metal ring surrounding the inductor pad.

3. The surface acoustic wave device according to claim 1, further comprising a sealing portion for sealing the device chip together with the wiring board, wherein the sealing portion is joined to an insulating region between the antenna pad and the antenna metal ring.

4. The surface acoustic wave device according to claim 1, further comprising a sealing portion for sealing the device chip together with the wiring board, wherein the sealing portion is joined to an insulating region between the transmission pad and the transmission metal ring and an insulating region between the reception pad and the reception metal ring, respectively.

5. The surface acoustic wave device according to claim 1, wherein the shortest distance from the outer extension of the side of the wiring board to the transmission metal ring is shorter than the shortest distance from the outer extension of the corner of the wiring board to the transmission metal ring.

6. The surface acoustic wave device according to claim 1, wherein the shortest distance from the outer extension of the side of the wiring board to the reception metal ring is shorter than the shortest distance from the outer extension of the corner of the wiring board to the reception metal ring.

7. The surface acoustic wave device according to claim 1, wherein the thickness of the antenna metal ring is 10 μm to 35 μm.

8. The surface acoustic wave device according to claim 1, wherein the thicknesses of the transmission metal ring and the reception metal ring are 10 μm to 35 μm.

9. The surface acoustic wave device according to claim 1, wherein the device chip includes a piezoelectric substrate made of lithium tantalate, lithium niobate, or quartz.

10. The elastic wave device according to claim 1, wherein the device chip includes a support substrate made of sapphire, silicon, alumina, spinel, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, silicon oxynitride, diamond, quartz, or glass.

11. A module comprising the elastic wave device according to any one of claims 1 to 10.

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