Elastic wave device and module having the elastic wave device

Abstract

To provide an elastic wave device of which an attenuation characteristic is improved.SOLUTION: An elastic wave device comprises: a package substrate having a ground electrode; a piezoelectric substrate mounted onto the package substrate; a plurality of series resonators and a plurality of parallel resonators constructing a band pass filter to be formed onto the piezoelectric substrate; an antenna pad and a node pad that are formed onto the piezoelectric substrate; a first inductor that is formed onto the piezoelectric substrate, and is connected to a first parallel resonator that is one of the plurality of parallel resonators; a second inductor that is connected to between the node pad and the ground electrode; and a capacitor that is formed onto the piezoelectric substrate, and is parallely connected to the first inductor and the second inductor. The capacitor is directly connected to the antenna pad.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an elastic wave device and a module including the elastic wave device.

Background Art

[0002] Due to recent technological advancements, smartphones and the like, typified by mobile communication terminals, have been remarkably miniaturized and lightened. As an elastic wave device used in such mobile communication terminals, an elastic wave device that can be miniaturized is used. In addition, as a mobile communication system, the number of communication systems that perform simultaneous transmission and reception has increased rapidly, and the demand for duplexers has increased rapidly.

[0003] With the changes in mobile communication systems, the required specifications of elastic wave devices have become more stringent. That is, characteristics superior to those of the prior art are required.

[0004] On the low-frequency side of the passband, when the inductance value of the ground is increased, the attenuation characteristics in the frequency band away from the passband are improved. However, the attenuation characteristics in the frequency band close to the passband deteriorate.

[0005] On the high-frequency side of the passband, for example, in order to increase the attenuation amount of harmonics, Patent Document 1 discloses a technique using a capacitor for the purpose of improving attenuation characteristics and avoiding an increase in the size of an inductor.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the elastic wave device described in Patent Document 1, the attenuation characteristics on the low-frequency side and the high-frequency side of the passband are not sufficient.

[0008] The present disclosure has been made to solve the above-described problems. An object of the present disclosure is to provide an elastic wave device having improved attenuation characteristics on the low-frequency side and the high-frequency side of the passband and a module including the elastic wave device.

Means for Solving the Problems

[0009] The elastic wave device according to the present disclosure includes a package substrate including a ground electrode, a piezoelectric substrate mounted on the package substrate, a plurality of series resonators and a plurality of parallel resonators that form a band-pass filter formed on the piezoelectric substrate, an antenna pad and a node pad formed on the piezoelectric substrate, a first inductor formed on the piezoelectric substrate and connected to a first parallel resonator that is one of the plurality of parallel resonators, a second inductor connected between the node pad and the ground electrode, a capacitor formed on the piezoelectric substrate and connected in parallel between the first inductor and the second inductor, and the capacitor is connected to the antenna pad to form the elastic wave device.

[0010] In one embodiment of the present invention, the capacitor is formed by side wall portions of antenna wiring electrically connected to the antenna pad and side wall portions of capacitor wiring electrically connected to the node pad.

[0011] In one embodiment of the present disclosure, the area of the capacitor wiring is larger than the sum of the area of the antenna pad and the area of the node pad.

[0012] In one embodiment of the present invention, the width of the wiring for the capacitor is larger than the width of the antenna wiring.

[0013] In one embodiment of the present invention, the wiring for the capacitor is physically connected only to the node pad.

[0014] In one embodiment of the present disclosure, the inductance value of the second inductor is two times or more the inductance value of the first inductor.

[0015] In one embodiment of the present disclosure, a second parallel resonator, which is one of the plurality of parallel resonators, is connected to the first inductor.

[0016] In one embodiment of the present disclosure, the piezoelectric substrate further includes a reception pad formed thereon, the bandpass filter is a reception filter, and the antenna pad, the node pad, and the reception pad are arranged so as to form a right triangle when their respective positions are taken as vertices.

[0017] In one embodiment of the present disclosure, the piezoelectric substrate further includes a transmission filter formed thereon, and the bandpass filter is a reception filter.

[0018] In one embodiment of the present disclosure, there is a module including the elastic wave device.

Advantages of the Invention

[0019] According to the present disclosure, it is possible to improve the attenuation characteristics on the low-frequency side and the high-frequency side of the passband of the elastic wave device.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] Embodiments will be described with reference to the accompanying drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description of such parts will be simplified or omitted as appropriate.

[0022] Embodiment 1. FIG. 1 is a longitudinal sectional view of an elastic wave device according to Embodiment 1.

[0023] As shown in FIG. 1, the elastic wave device 20 includes a package substrate 23, external connection terminals 24, a device chip 25, electrode pads 26, bumps 27, and a sealing portion 28.

[0024] For example, the package substrate 23 is a multilayer substrate made of resin. For example, the package substrate 23 is a low-temperature co-fired ceramics (LTCC) multilayer substrate composed of a plurality of dielectric layers.

[0025] A plurality of external connection terminals 24 are formed on the lower surface of the package substrate 23.

[0026] The electrode pads 26 are formed in plurality on the main surface of the package substrate 23. For example, the electrode pads 26 are formed of copper or an alloy containing copper. For example, the thickness of the electrode pads 26 is from 10 μm to 20 μm.

[0027] The bumps 27 are formed on the upper surface of each of the electrode pads 26. For example, the bumps 27 are gold bumps. For example, the height of the bumps 27 is from 10 μm to 50 μm.

[0028] A gap 29 is formed between the package substrate 23 and the device chip 25.

[0029] The device chip 25 is mounted on the package substrate 23 by flip chip bonding via the bumps 27. The device chip 25 is electrically connected to a plurality of electrode pads 26 via a plurality of bumps 27.

[0030] The device chip 25 is, for example, a surface acoustic wave device chip. The device chip 25 includes a piezoelectric substrate formed of a piezoelectric material. The piezoelectric substrate is a substrate formed of a piezoelectric single crystal such as lithium tantalate, lithium niobate or quartz.

[0031] The thickness of the piezoelectric substrate can be, for example, from 100 μm to 300 μm. According to another example, the piezoelectric substrate is a substrate formed of piezoelectric ceramics.

[0032] According to still another example, the device chip 25 is a substrate in which a piezoelectric substrate and a support substrate are joined. The support substrate is, for example, a substrate formed of sapphire, silicon, alumina, spinel, quartz or glass. In this case, the thickness of the piezoelectric substrate can be, for example, from 0.3 μm to 5 μm.

[0033] An elastic wave element 52 is formed on the piezoelectric substrate. For example, on the main surface of the device chip 25, a transmission filter or a reception filter including a plurality of elastic wave elements 52 is formed.

[0034] According to another example, a duplexer including a transmission filter and a reception filter is formed on the main surface of the device chip 25.

[0035] 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 filter including a plurality of series resonators and a plurality of parallel resonators.

[0036] 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 filter.

[0037] The sealing portion 28 is formed so as to cover the device chip 25. For example, the sealing portion 28 is formed of an insulator such as a synthetic resin. For example, the sealing portion 28 is formed of metal.

[0038] When the sealing portion 28 is formed of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, or the like. Preferably, the sealing portion 28 is formed of an epoxy resin using a low-temperature curing process.

[0039] A gap 29 is formed in a region where the package substrate 23 and the device chip 25 face each other. Among the electrode pads 26 formed on the package substrate 23, the electrode pad bonded to the bump 27L2 joined to the node pad NODE to be described later constitutes, together with the bump 27L2, a second inductor L2.

[0040] That is, the second inductor L2 is the series sum of the inductances existing between the node pad NODE and the ground electrodes on the package substrate 23, and also includes the parasitic inductance of the bump.

[0041] Next, an example of the elastic wave element 52 formed on the device chip 25 will be described with reference to FIG. 2. FIG. 2 is a diagram showing an example of an elastic wave element (resonator) of the elastic wave device in the first embodiment.

[0042] As shown in FIG. 2, an IDT (Interdigital Transducer) electrode 52a and a pair of reflectors 52b are formed on the main surface of the device chip 25. The IDT electrode 52a and the pair of reflectors 52b are provided so as to be able to excite elastic waves (mainly SH waves).

[0043] For example, the IDT electrode 52a and the pair of reflectors 52b are formed of an alloy of aluminum and copper. For example, the IDT 52a and the pair of reflectors 52b are formed of an appropriate metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver or an alloy thereof.

[0044] For example, the IDT electrode 52a and the pair of reflectors 52b are formed of a laminated metal film in which a plurality of metal layers are laminated. For example, the thickness of the IDT electrode 52a and the pair of reflectors 52b is from 150 nm to 450 nm.

[0045] The IDT electrode 52a includes a pair of comb-shaped electrodes 52c. The pair of comb-shaped electrodes 52c face each other. The comb-shaped electrode 52c includes a plurality of electrode fingers 52d and a bus bar 52e.

[0046] The plurality of electrode fingers 52d are arranged with their longitudinal directions aligned. The bus bar 52e connects the plurality of electrode fingers 52d.

[0047] One of the pair of reflectors 52b is adjacent to one side of the IDT electrode 52a. The other of the pair of reflectors 52b is adjacent to the other side of the IDT electrode 52a.

[0048] Next, an example of a duplexer formed on the device chip 25 will be described with reference to FIG. 3. FIG. 3 is a diagram showing an example of an elastic wave device in Embodiment 1.

[0049] As shown in FIG. 3, a transmission filter 30, which is a band-pass filter, is formed on the device chip 25. The transmission filter 30 is a ladder-type filter including a transmission pad Tx, an antenna pad ANT, a ground pad GND, a plurality of series resonators S, and a plurality of parallel resonators P.

[0050] Also, the transmission filter 30 includes a capacitor CTx formed between the ground pad GND and the transmission pad Tx. Thereby, the bridging capacitance generated between the transmission pad Tx and the antenna pad ANT, and between the transmission pad Tx and the reception pad Rx is reduced, improving the attenuation characteristics and isolation of the transmission filter.

[0051] As shown in FIG. 3, a reception filter, which is a band-pass filter, is formed on the device chip 25. The reception filter is a ladder-type filter including a reception pad Rx, an antenna pad ANT, a ground pad GND, a plurality of series resonators S1 to S4, and a plurality of parallel resonators P1 to P4.

[0052] Also, the reception filter includes a first inductor L1, a node pad NODE, a capacitor wiring CP for a capacitor, and a capacitor C. Also, the reception filter includes a capacitor CRx formed between the ground pad GND and the reception pad Rx. Thereby, the bridging capacitance generated between the reception pad Rx and the antenna pad ANT, and between the reception pad Rx and the transmission pad Tx is reduced, improving the attenuation characteristics and isolation of the reception filter.

[0053] Also, a bump 27L2, which is a part of a second inductor, is formed on the node pad NODE. The second inductor L2 includes a part of the inductance parasitic on the bump 27L2 formed on the node pad NODE.

[0054] The capacitor C is constituted by the parasitic capacitance generated between the side wall of the wiring of the antenna pad ANT and the side wall of the wiring CP for capacitor as shown in the area surrounded by the dotted line. Thereby, while reducing the bridging capacitance generated between the antenna pad ANT and the reception pad Rx and between the antenna pad ANT and the transmission pad Tx and improving the attenuation characteristics of the reception filter and the transmission filter, a circuit is formed between the node pad NODE and the antenna pad ANT.

[0055] The average distance between the side wall of the wiring of the antenna pad ANT and the side wall of the wiring CP for capacitor in the capacitor C is, for example, 2 μm. The thickness of the wiring of the antenna pad ANT and the thickness of the wiring CP for capacitor in the capacitor C are, for example, 200 nm each.

[0056] As shown in FIG. 3, the wiring CP for capacitor is electrically and physically connected only to the node pad NODE. Also, the area of the wiring CP for capacitor can be made larger than the sum of the area of the antenna pad ANT and the area of the node pad NODE. By doing so, the wiring resistance of the wiring CP for capacitor becomes small.

[0057] Also, the antenna pad ANT, the reception pad Rx, and the node pad NODE are arranged so as to form a right triangle when taking their respective positions as vertices. The node pad NODE is arranged at the position of the right angle vertex. By doing so, while optimizing the transmission / reception isolation as a duplexer, the distance between the antenna pad ANT and the node pad NODE can be made the shortest, and the wiring resistance of the wiring CP for capacitor can be made even smaller.

[0058] FIG. 4 is an equivalent circuit diagram of the surface acoustic wave device in the first embodiment. The third parallel resonator P3 and the fourth parallel resonator P4 are bundled and connected to the first inductor L1 when viewed from the antenna pad ANT side.

[0059] The inductance of the first inductor L1 can be, for example, 0.05 nH. The first inductor L1 is connected to the node pad NODE. The first inductor L1 and the second inductor L2 are connected via the node pad NODE.

[0060] The inductance of the second inductor L2 can be, for example, 0.1 nH. The second inductor L2 is grounded. A capacitor C is connected between the node pad NODE and the antenna pad ANT via a capacitor wiring CP. The capacitor C can be, for example, 0.03 pF. Note that a part of the transmission filter 30 is omitted in the description.

[0061] FIG. 5 is a diagram showing the attenuation characteristics on the low-frequency side of the passband of the receiving filter of the surface acoustic wave device 20 in Embodiment 1. The attenuation characteristics on the low-frequency side of the passband of the receiving filter of the surface acoustic wave device 20 are shown by a solid line. Also, the attenuation characteristics of Comparative Example 1 are shown by a broken line. Further, the attenuation characteristics of Comparative Example 2 are shown by a one-dot chain line.

[0062] Comparative Example 1 has a configuration that does not include the capacitor C of Embodiment 1. Also, Comparative Example 2 does not include the capacitor C of Embodiment 1 and has an inductance of 0.2 nH for the inductor corresponding to the second inductor L2. Other configurations are the same as those of Embodiment 1.

[0063] As shown in FIG. 5, in the attenuation characteristics of Comparative Example 2, in the low-frequency side of the low-frequency side attenuation frequency region of the passband, the attenuation characteristics are improved compared to Comparative Example 1. However, in the high-frequency side of the low-frequency side attenuation frequency region of the passband, the attenuation characteristics are deteriorated.

[0064] Here, in Embodiment 1, in the low-frequency side of the low-frequency side attenuation frequency region of the passband, the attenuation characteristics are improved compared to Comparative Example 1 to the same extent as Comparative Example 2. Further, in the high-frequency side of the low-frequency side attenuation frequency region of the passband, the attenuation characteristics are improved compared to Comparative Example 1.

[0065] In the low-frequency side attenuation frequency region of the passband, although the attenuation characteristics deteriorate in the frequency region in the middle between the low-frequency side and the high-frequency side, the attenuation characteristics are realized in a well-balanced manner in the overall region of the low-frequency side attenuation frequency region of the passband.

[0066] FIG. 6 is a diagram showing the configuration of Comparative Example 3. FIG. 6 shows a region corresponding to the region R3 indicated by the dotted line in FIG. 3. That is, in Comparative Example 3, an inductor L1R3 corresponding to the first inductor L1 of Embodiment 1 is electrically connected to a capacitor wiring CPR3 corresponding to the capacitor wiring CP of Embodiment 1.

[0067] Further, a parallel resonator is electrically connected to the capacitor wiring CPR3. Note that the capacitor CR3 has a capacitance optimized in the configuration of Comparative Example 3. The capacitance of the capacitor CR3 is 0.015 pF. Other configurations of Comparative Example 3 are the same as those of Embodiment 1.

[0068] FIG. 7 is a characteristic diagram of the receiving filter of the surface acoustic wave device of Embodiment 1 and the receiving filter of Comparative Example 3. The solid line shows the characteristics of the receiving filter of the surface acoustic wave device of Embodiment 1. The broken line shows the characteristics of the receiving filter of Comparative Example 3.

[0069] As shown in FIG. 7, also on the high-frequency side of the passband of the receiving filter, in Embodiment 1, the poles can be dropped deeper. That is, by making the poles come at important frequencies of harmonics such as the second harmonic, it can be seen that Embodiment 1 can achieve better characteristics than Comparative Example 3.

[0070] According to Embodiment 1 described above, it is possible to provide a surface acoustic wave device with improved attenuation characteristics on the low-frequency side and the high-frequency side of the passband.

[0071] Embodiment 2. FIG. 8 is a longitudinal sectional view of a module to which the elastic wave device of Embodiment 1 is applied. The same or corresponding parts as those of Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0072] In FIG. 8, the module 100 includes a wiring board 130, a plurality of external connection terminals 131, an integrated circuit component IC, an elastic wave device 20, an inductor 111, and a sealing portion 117.

[0073] The plurality of external connection terminals 131 are formed on the lower surface of the wiring board 130. The plurality of external connection terminals 131 are mounted on a motherboard of a preset mobile communication terminal.

[0074] 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.

[0075] The elastic wave device 20 is mounted on the main surface of the wiring board 130.

[0076] 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).

[0077] The sealing portion 117 seals a plurality of electronic components including the elastic wave device 20.

[0078] According to Embodiment 2 described above, the module 100 includes the elastic wave device 20. Therefore, it is possible to provide a module including an elastic wave device with improved power resistance.

[0079] Although some aspects of at least one embodiment have been described, it should be understood that various modifications, corrections, and improvements can be easily conceived by those skilled in the art. Such modifications, corrections, and improvements are intended to be part of the present disclosure and are intended to be within the scope of the present disclosure.

[0080] 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.

[0081] Specific implementation examples are provided herein for illustrative purposes only and are not intended to be limiting.

[0082] 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.

[0083] References to "or" shall be construed as indicating any one, more than one, and all of the terms described using "or".

[0084] 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 the present disclosure to any one positional or spatial orientation. Therefore, the above description and drawings are merely illustrative.

Description of Reference Numerals

[0085] 20 Elastic wave device, 23 Package substrate, 24 External connection terminal 25 Device chip, 26 Electrode pad, 27 Bump 28 Sealing portion 30 Transmission filter 52 Elastic wave element, 52a IDT electrode, 52b Reflector 52c Comb electrode, 52d Electrode finger, 52e Bus bar C Capacitor, CP Wiring for capacitor L1 First inductor, L2 Second inductor ANT Antenna Pad, NODE Node Pad GND Ground Pad 100 Module, 130 Wiring Board, 131 External Connection Terminal IC Integrated Circuit Component, 111 Inductor, 117 Sealing Portion

Claims

1. A package substrate including a ground electrode; A piezoelectric substrate mounted on the package substrate; A plurality of series resonators and a plurality of parallel resonators that constitute a bandpass filter formed on the piezoelectric substrate; An antenna pad and a node pad formed on the piezoelectric substrate; A first inductor formed on the piezoelectric substrate and connected to a first parallel resonator that is one of the plurality of parallel resonators; A second inductor connected between the node pad and the ground electrode; A capacitor formed on the piezoelectric substrate and connected in parallel between the first inductor and the second inductor; Comprising; The capacitor is a surface acoustic wave device directly connected to the antenna pad.

2. The surface acoustic wave device according to claim 1, wherein the capacitor is formed by side wall portions of antenna wiring electrically connected to the antenna pad and side wall portions of capacitor wiring electrically connected to the node pad.

3. The surface acoustic wave device according to claim 2, wherein an area of the capacitor wiring is larger than a total of an area of the antenna pad and an area of the node pad.

4. The surface acoustic wave device according to claim 2, wherein a width of the capacitor wiring is larger than a width of the antenna wiring.

5. The surface acoustic wave device according to claim 2, wherein the capacitor wiring is physically connected only to the node pad.

6. The surface acoustic wave device according to claim 1, wherein an inductance value of the second inductor is two times or more an inductance value of the first inductor.

7. The surface acoustic wave device according to claim 1, wherein a second parallel resonator that is one of the plurality of parallel resonators is connected to the first inductor.

8. Further comprising a reception pad formed on the piezoelectric substrate, the bandpass filter is a reception filter, the antenna pad, the node pad, and the reception pad are arranged to form a right triangle when respective positions are vertices, and the node pad is arranged at a position of a right angle vertex. The surface acoustic wave device according to claim 1.

9. The surface acoustic wave device according to claim 1, further comprising a transmission filter formed on the piezoelectric substrate, and the bandpass filter is a reception filter.

10. A module including the surface acoustic wave device according to any one of claims 1 to 9.

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