Elastic wave device and module provided with same

Abstract

The invention provides an elastic wave device capable of improving attenuation characteristics and a module thereof. This elastic wave device is provided with: a package substrate provided with a ground electrode; a piezoelectric substrate mounted on the package substrate; a plurality of series resonators and a plurality of parallel resonators which are formed on the piezoelectric substrate and constitute a band-pass filter; 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 of 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; wherein the capacitor is directly connected to the antenna pad.

Description

Technical Field

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

[0002] With technological advancements in recent years, mobile terminals represented by smartphones have become increasingly smaller and lighter. The elastic wave devices used in such mobile communication terminals are generally miniaturized elastic wave devices. In addition, communication systems that simultaneously transmit and receive have increased rapidly, leading to a surge in the demand for duplexers.

[0003] As mobile communication systems have evolved, the required specifications for elastic wave devices have become more stringent. That is, higher performance is required compared to the past.

[0004] On the low-frequency side of the passband, increasing the ground inductance value can improve the attenuation characteristics of a frequency band far from the passband. However, the attenuation characteristics of a 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 higher harmonics, Patent Document 1 discloses a method of using a capacitor to improve the attenuation characteristics and avoid the enlargement of an inductor. However, the elastic wave device described in Patent Document 1 is not sufficient in terms of the attenuation characteristics on the low-frequency side and the high-frequency side of the passband.

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-17537 Summary of the Invention

[0007] An object of the present invention is to provide an elastic wave device having improved attenuation characteristics on the low-frequency side and the high-frequency side of a passband, and a module including the elastic wave device.

[0008] The elastic wave device according to the present invention includes: a package substrate having a ground electrode; a piezoelectric substrate mounted on the package substrate; a plurality of series resonators and a plurality of parallel resonators formed on the piezoelectric substrate and constituting a band-pass filter; 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 among 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; wherein the capacitor is directly connected to the antenna pad.

[0009] In one embodiment of the present invention, the capacitor is formed by a side wall portion of an antenna wiring electrically connected to the antenna pad and a side wall portion of a capacitor wiring electrically connected to the node pad.

[0010] In one embodiment of the present invention, the area of the wiring for the capacitor is larger than the sum of the areas of the antenna pad and the node pad.

[0011] In one embodiment of the present invention, the width of the wiring for the capacitor is larger than the width of the antenna wiring.

[0012] In one embodiment of the present invention, the wiring for the capacitor is physically and electrically connected only to the node pad.

[0013] In one embodiment of the present invention, the inductance value of the second inductor is at least twice the inductance value of the first inductor.

[0014] In one embodiment of the present invention, one of the plurality of parallel resonators, i.e., the second parallel resonator, is connected to the first inductor.

[0015] In one embodiment of the present invention, the surface acoustic wave device further includes a receiving pad formed on the piezoelectric substrate, the band-pass filter is a receiving filter, and the positions of the antenna pad, the node pad, and the receiving pad form a right triangle, with the node pad located at the right-angle vertex.

[0016] In one embodiment of the present invention, the surface acoustic wave device further includes a transmitting filter formed on the piezoelectric substrate, and the band-pass filter is a receiving filter.

[0017] In one embodiment of the present invention, a module including the surface acoustic wave device is disclosed.

[0018] According to the present invention, the attenuation characteristics of the surface acoustic wave device on the low-frequency side and the high-frequency side of the passband can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present disclosure and form a part of the present disclosure. The illustrative embodiments and descriptions thereof of the present disclosure are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure.

[0020] Figure 1 is a longitudinal sectional view of the surface acoustic wave device in Embodiment 1.

[0021] Figure 2 is a schematic diagram of the surface acoustic wave element (resonator) of the surface acoustic wave device in Embodiment 1.

[0022] Figure 3 is a schematic diagram of the surface acoustic wave device in Embodiment 1.

[0023] Figure 4 is an equivalent circuit diagram of the surface acoustic wave device in Embodiment 1.

[0024] Figure 5 It is a graph of the attenuation characteristics of the receiving filter of the elastic wave device 20 in Example 1 on the low-frequency side of the passband.

[0025] Figure 6 It is a structural diagram of Comparative Example 3.

[0026] Figure 7 It is a graph of the characteristics of the receiving filter of the elastic wave device in Example 1 and the receiving filter of Comparative Example 3.

[0027] Figure 8 It is a longitudinal sectional view of the elastic wave device in Example 1 applied to a module.

[0028]

Symbol Explanation

[0029] The embodiments will be described below with reference to the accompanying drawings. In each figure, the same or corresponding parts are marked with the same symbols. The repeated description of the corresponding parts is appropriately simplified or omitted.

[0030] Unless otherwise defined, technical terms or scientific terms involved in this disclosure shall have the ordinary meanings understood by those with ordinary skills in the technical field to which this disclosure belongs. In this disclosure, words such as "a", "an", "one kind", "the", "these", etc. do not indicate a limitation in quantity, and they can be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this disclosure are intended to cover non-exclusive inclusion; for example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent in these processes, methods, products or devices. The words such as "connect", "be connected", "couple" and the like involved in this disclosure are not limited to physical or mechanical connections, but may include electrical connections, whether directly connected or indirectly connected. The "plurality" involved in this disclosure means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. Usually, the character " / " indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this disclosure only distinguish similar objects and do not represent a specific order for the objects.

[0031] Embodiment 1 Figure 1 is a longitudinal sectional view of the elastic wave device in Embodiment 1.

[0032] As Figure 1 shown, 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.

[0033] For example, the package substrate 23 is a multi-layer substrate made of resin. For example, the package substrate 23 is a low temperature co-fired ceramics (LTCC) multi-layer substrate composed of a plurality of dielectric layers.

[0034] A plurality of external connection terminals 24 are formed on the lower surface of the package substrate 23.

[0035] A plurality of electrode pads 26 are formed on the main surface of the package substrate 23. For example, the electrode pads 26 can be made of copper or a copper-containing alloy. For example, the thickness of the electrode pads 26 is 10 μm to 20 μm.

[0036] Bumps 27 are formed on the upper surface of each electrode pad 26. For example, the bumps 27 are gold bumps. For example, the height of the bumps 27 is from 10 μm to 50 μm.

[0037] A gap 29 is formed between the package substrate 23 and the device chip 25.

[0038] The device chip 25 is mounted on the package substrate 23 in a flip-chip bonding manner through the bumps 27. The device chip 25 is electrically connected to the plurality of electrode pads 26 through the plurality of bumps 27.

[0039] The device chip 25 is, for example, a surface acoustic wave device chip. The device chip 25 has a piezoelectric substrate made of a piezoelectric material. The piezoelectric substrate may be composed of a substrate made of a single crystal piezoelectric material such as lithium tantalate, lithium niobate, or quartz.

[0040] The thickness of the piezoelectric substrate may be from 100 μm to 300 μm.

[0041] In another example, the piezoelectric substrate may be a substrate made of a piezoelectric ceramic.

[0042] In another example, the device chip 25 may be a substrate formed by bonding a piezoelectric substrate and a support substrate. The support substrate may be a substrate made of sapphire, silicon, alumina, spinel, quartz, or glass. In this case, the thickness of the piezoelectric substrate may be from 0.3 μm to 5 μm.

[0043] An elastic wave element 52 is formed on the piezoelectric substrate. For example, a transmission filter or a reception filter including a plurality of elastic wave elements 52 is formed on the main surface of the device chip 25.

[0044] In another example, a duplexer including a transmission filter and a reception filter may be formed on the main surface of the device chip 25.

[0045] The transmission filter is designed to allow an electric signal in a desired frequency band to pass through. For example, the transmission filter is a ladder filter composed of a plurality of series resonators and a plurality of shunt resonators.

[0046] The reception filter is designed to allow an electric signal in a desired frequency band to pass through. For example, the reception filter is a ladder filter.

[0047] A sealing portion 28 is formed to cover the device chip 25. For example, the sealing portion 28 may be formed of an insulating material such as a synthetic resin. For example, the sealing portion 28 may also be formed of a metal.

[0048] When the sealing portion 28 is formed of a synthetic resin, the synthetic resin may be an epoxy resin, a polyimide, or the like. Preferably, the sealing portion 28 uses an epoxy resin and is formed through a low-temperature curing process.

[0049] A gap 29 is formed in the opposing portions of the package substrate 23 and the device chip 25. Among the electrode pads 26 formed on the package substrate 23, the bump 27L2 that is joined to the node pad NODE to be described later and the electrode pad bonded thereto together constitute the second inductor L2.

[0050] That is, the second inductor L2 is the total series inductance from the node pad NODE to the ground electrode on the package substrate 23, including the parasitic inductance of the bump.

[0051] Next, with reference to Figure 2 An example of the surface acoustic wave element 52 formed on the device chip 25 will be described. Figure 2 is a schematic diagram of the surface acoustic wave element (resonator) of the surface acoustic wave device in Embodiment 1.

[0052] As Figure 2 shown, 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 arranged so as to be able to excite surface acoustic waves (mainly SH waves).

[0053] For example, the IDT electrode 52a and the pair of reflectors 52b are made of an aluminum-copper alloy. For example, the IDT electrode 52a and the pair of reflectors 52b may also be made of a suitable metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver, or an alloy thereof.

[0054] For example, the IDT electrode 52a and the pair of reflectors 52b are formed of a multilayer metal film. For example, the thickness of the IDT electrode 52a and the pair of reflectors 52b is 150 nm to 450 nm.

[0055] The IDT electrode 52a has a pair of comb-shaped electrodes 52c. The pair of comb-shaped electrodes 52c face each other. The comb-shaped electrodes 52c include a plurality of electrode fingers 52d and bus bars 52e.

[0056] The plurality of electrode fingers 52d are arranged along the long axis direction. The bus bars 52e connect the plurality of electrode fingers 52d.

[0057] 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.

[0058] Next, with reference to Figure 3 An example of the duplexer formed on the device chip 25 will be described. Figure 3 is a schematic diagram of the surface acoustic wave device in Embodiment 1.

[0059] As Figure 3As shown, a band-pass filter, i.e., a transmit filter 30, is formed on the device chip 25. The transmit filter 30 is a ladder filter including a transmit pad Tx, an antenna pad ANT, a ground pad GND, a plurality of series resonators S, and a plurality of parallel resonators P.

[0060] In addition, the transmit filter 30 further includes a capacitor CTx formed between the ground pad GND and the transmit pad Tx. This reduces the parasitic capacitance between the transmit pad Tx and the antenna pad ANT, and between the transmit pad Tx and the receive pad Rx, improving the attenuation characteristics and isolation of the transmit filter.

[0061] As Figure 3 shown, a band-pass filter, i.e., a receive filter, is also formed on the device chip 25. The receive filter is a ladder filter including a receive 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.

[0062] In addition, the receive filter includes a first inductor L1, a node pad NODE, a capacitor wiring CP, and a capacitor C. The receive filter also includes a capacitor CRx formed between the ground pad GND and the receive pad Rx. This reduces the parasitic capacitance between the receive pad Rx and the antenna pad ANT, and between the receive pad Rx and the transmit pad Tx, improving the attenuation characteristics and isolation of the receive filter.

[0063] In addition, a bump 27L2 which is part of a second inductor L2 is formed on the node pad NODE. The second inductor L2 includes the parasitic inductance part of the bump 27L2 formed on the node pad NODE.

[0064] The capacitor C, as shown in the area indicated by the dashed line, is composed of the parasitic capacitance between the wiring sidewall part of the antenna pad ANT and the sidewall part of the capacitor wiring CP. This reduces the parasitic capacitance between the antenna pad ANT and the receive pad Rx, and between the antenna pad ANT and the transmit pad Tx, improving the attenuation characteristics of the receive filter and the transmit filter, while forming a circuit between the node pad NODE and the antenna pad ANT.

[0065] In the capacitor C, the average distance between the wiring sidewall part of the antenna pad ANT and the sidewall part of the capacitor wiring CP is 2 μm. The thickness of the wiring of the antenna pad ANT and the thickness of the capacitor wiring CP in the capacitor C are, for example, 200 nm respectively.

[0066] As Figure 3As shown, the wiring CP for the capacitor is only electrically and physically connected to the node pad NODE. In addition, the area of the wiring CP for the capacitor can be larger than the sum of the areas of the antenna pad ANT and the node pad NODE. This can reduce the wiring resistance of the wiring CP for the capacitor. In some embodiments, the width of the wiring CP for the capacitor is greater than the width of the wiring of the antenna pad ANT.

[0067] In addition, the position vertices of the antenna pad ANT, the receive pad Rx, and the node pad NODE form a right triangle, and the node pad NODE is located at the right-angle vertex. This can optimize the transmit and receive isolation of the duplexer and at the same time shorten the distance between the antenna pad ANT and the node pad NODE, further reducing the wiring resistance of the wiring CP for the capacitor.

[0068] Figure 4 is the equivalent circuit diagram of the surface acoustic wave device in Embodiment 1. Viewed from the antenna pad ANT side, the third parallel resonator P3 and the fourth parallel resonator P4 are connected in parallel to the first inductor L1.

[0069] In some embodiments, the inductance value of the second inductor L2 is at least twice the inductance value of the first inductor L1.

[0070] For example, the inductance value of the first inductor L1 can be 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 through the node pad NODE.

[0071] For example, the inductance value of the second inductor L2 can be 0.1 nH. The second inductor L2 is grounded. A capacitor C is connected between the node pad NODE and the antenna pad ANT through the wiring CP for the capacitor. The capacitance value of the capacitor C can be 0.03 pF. The part of the transmit filter 30 is not described in detail.

[0072] Figure 5 is the attenuation characteristic diagram of the receive filter of the surface acoustic wave device 20 in Embodiment 1 on the low-frequency side of the passband. The attenuation characteristic of the receive filter of the surface acoustic wave device 20 on the low-frequency side of the passband is represented by a solid line. In addition, the attenuation characteristic of Comparative Example 1 is represented by a dashed line. The attenuation characteristic of Comparative Example 2 is represented by a dotted line.

[0073] Comparative Example 1 is a structure without the capacitor C in Embodiment 1. Comparative Example 2 is a structure without the capacitor C in Embodiment 1 and with the inductance value of the second inductor L2 being 0.2 nH. Other structures are the same as those in Embodiment 1.

[0074] As Figure 5As shown, the attenuation characteristics of Comparative Example 2 are superior to those of Comparative Example 1 on the low-frequency side of the attenuation frequency region on the low-frequency side of the passband. However, on the high-frequency side of the attenuation frequency region on the low-frequency side of the passband, the attenuation characteristics deteriorate.

[0075] Here, Embodiment 1 is equivalent to Comparative Example 2 on the low-frequency side of the attenuation frequency region on the low-frequency side of the passband and is superior to Comparative Example 1. In addition, on the high-frequency side of the attenuation frequency region on the low-frequency side of the passband, the attenuation characteristics are also superior to those of Comparative Example 1.

[0076] Although the attenuation characteristics deteriorate in the intermediate frequency region between the low-frequency side and the high-frequency side of the attenuation frequency region on the low-frequency side of the passband, the attenuation characteristics can be better balanced within the overall range of the attenuation frequency region on the low-frequency side of the passband.

[0077] Figure 6 is the structural diagram of Comparative Example 3. Figure 6 shows Figure 3 the region corresponding to the region R3 shown by the dashed line in . That is, in Comparative Example 3, an inductor L1R3 corresponding to the first inductor L1 in Embodiment 1 is electrically connected to a capacitor wiring CPR3 corresponding to the capacitor wiring CP in Embodiment 1.

[0078] In addition, the capacitor wiring CPR3 is electrically connected to a parallel resonator. The capacitor CR3 is optimized in the structure of Comparative Example 3. The capacitance value of the capacitor CR3 is 0.015 pF. Other structures of Comparative Example 3 are the same as those of Embodiment 1.

[0079] Figure 7 is the characteristic diagram of the receiving filter of the surface acoustic wave device in Embodiment 1 and the receiving filter of Comparative Example 3. The solid line represents the characteristics of the receiving filter of the surface acoustic wave device in Embodiment 1. The dashed line represents the characteristics of the receiving filter of Comparative Example 3.

[0080] As Figure 7 shown, on the high-frequency side of the passband, the poles of the receiving filter of Embodiment 1 are deeper. That is, by making the poles fall on important frequencies such as the second harmonic, Embodiment 1 achieves more excellent characteristics than Comparative Example 3.

[0081] In summary, according to Embodiment 1, a surface acoustic wave device with improved attenuation characteristics on the low-frequency side and the high-frequency side of the passband can be provided.

[0082] Embodiment 2 Figure 8 is a longitudinal sectional view of the surface acoustic wave device in Embodiment 1 applied to a module. The same or corresponding parts of Embodiment 1 are marked with the same reference numerals. The description of the corresponding parts is omitted.

[0083] As Figure 8As shown, module 100 includes a wiring substrate 130, a plurality of external connection terminals 131, an integrated circuit component IC, a surface acoustic wave device 20, an inductor 111, and a sealing portion 117.

[0084] The plurality of external connection terminals 131 are formed on the lower surface of the wiring substrate 130. The plurality of external connection terminals 131 are pre-mounted on the main board of the mobile terminal.

[0085] For example, the integrated circuit component IC is mounted inside the wiring substrate 130. The integrated circuit component IC includes a switching circuit and a low noise amplifier.

[0086] The surface acoustic wave device 20 is mounted on the main surface of the wiring substrate 130.

[0087] The inductor 111 is mounted on the main surface of the wiring substrate 130. The inductor 111 is used for impedance matching. For example, the inductor 111 is an Integrated Passive Device (IPD).

[0088] The sealing portion 117 seals a plurality of electronic components including the surface acoustic wave device 20.

[0089] In summary, according to Embodiment 2, module 100 includes the surface acoustic wave device 20. Therefore, a surface acoustic wave device module with higher electrical resistance performance can be provided.

[0090] Although several aspects of at least one embodiment have been described, it should be understood that various modifications, corrections, and improvements are obvious to those skilled in the art. These 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.

[0091] It should be understood that the embodiments of the methods and devices described herein are not limited to the details of the structures and arrangements of the components described in the above description or shown in the drawings. The methods and devices can be implemented in other embodiments and can be implemented or executed in various ways.

[0092] The specific embodiments are given only as examples and are not intended to be limiting.

[0093] The terms and expressions used in the present disclosure are for the purpose of description and not for limitation. Here, the use of "including", "having", "comprising", "containing" and their variants means including the items listed hereinafter and their equivalents as well as additional items.

[0094] The reference to "or" can be interpreted as indicating any of the terms, which can refer to one, more than one, or all of the terms recited.

[0095] References to front and back, left and right, top and bottom, horizontal and vertical, and front and back are for convenience of description. These references do not imply that the components of the present disclosure are limited to a particular position or spatial orientation. Accordingly, the foregoing description and drawings are for illustrative purposes only.

Claims

1. An elastic wave device, comprising: A package substrate having a ground electrode; a piezoelectric substrate mounted on the packaging substrate; A plurality of series resonators and a plurality of parallel resonators formed on the piezoelectric substrate and constituting a bandpass filter; 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 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; Wherein, the capacitor is directly connected to the antenna pad.

2. The elastic wave device according to claim 1, characterized in that: The capacitor is formed by a side wall portion of an antenna wiring electrically connected to the antenna pad and a side wall portion of a capacitor wiring electrically connected to the node pad.

3. The elastic wave device according to claim 2, characterized in that: The capacitor wiring has an area larger than a sum of an area of ​​the antenna pad and an area of ​​the node pad.

4. The elastic wave device according to claim 2, characterized in that: The capacitor wiring has a width greater than a width of the antenna wiring.

5. The elastic wave device according to claim 2, characterized in that: The capacitor wiring is physically connected only to the node pad.

6. The elastic wave device according to claim 1, characterized in that: The inductance value of the second inductor is at least twice the inductance value of the first inductor.

7. The elastic wave device according to claim 1, characterized in that: A second parallel resonator of one of the plurality of parallel resonators is connected to the first inductor.

8. The elastic wave device according to claim 1, characterized in that: It also includes a receiving pad formed on the piezoelectric substrate, the bandpass filter is a receiving filter, the vertices of the antenna pad, the node pad and the receiving pad form a right triangle, and the node pad is located at the right-angle vertex.

9. The elastic wave device according to claim 1, characterized in that: Also included is a transmit filter formed on the piezoelectric substrate, the bandpass filter being a receive filter. 10 . An elastic wave device module comprising the elastic wave device according to claim 1 .

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