JP2015103888A - Elastic wave module and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elastic wave module which enables low height, and to provide a communication device.SOLUTION: An elastic wave module of the invention includes: an insulation substrate 4; an elastic wave device 2 including a first elastic wave element 5, which includes a first piezoelectric substrate 7a and a first excitation electrode 8a disposed on the first piezoelectric substrate 7a and is mounted on an upper surface 4A of the insulation substrate 4, and a second elastic wave element 6, which includes a second piezoelectric substrate 7b and a second excitation electrode 8b disposed on the second piezoelectric substrate 7b, is smaller than an outer periphery of the insulation substrate 4 in a plan view, and is mounted on a lower surface 4B of the insulation substrate 4; and a wiring board 3 having a recessed part 3' which is smaller than the outer periphery of the insulation substrate 4 and is larger than the second elastic wave element 6 on the upper surface 3A side. The elastic wave device 2 is mounted on the wiring board 3 so that the second elastic wave element 6 is positioned in the recessed part 3'.

Description

  The present invention relates to an elastic wave module and a communication device.

  Conventionally, an acoustic wave element in which an excitation electrode is formed on a piezoelectric substrate is known. This acoustic wave element is used as a filter that obtains a specific frequency by utilizing the characteristic that an electrical signal and a surface acoustic wave can be mutually converted by the relationship between an excitation electrode and a piezoelectric substrate.

  In recent years, an acoustic wave device in which a plurality of acoustic wave elements are mounted so that data can be transmitted and received is used for a mobile terminal such as a mobile phone. An acoustic wave module in which such an acoustic wave device is mounted on a wiring board is mounted on a circuit board on which a capacitor, an IC, and the like are arranged, and is used as a communication device. In a mobile terminal, an elastic wave module has a role of filtering an electric signal transmitted and received from an antenna unit into a reception signal and a transmission signal by a duplexer (see Patent Document 1 and the like).

JP 2005-123909 A

  By the way, an elastic wave module is required to have a low profile as the mobile terminal becomes thinner.

  Therefore, the present invention has been conceived under the above-described circumstances, and an object thereof is to provide an elastic wave module and a communication device that can be lowered.

  An elastic wave module according to the present invention includes an insulating substrate, a first piezoelectric substrate, and a first excitation electrode disposed on the first piezoelectric substrate, and the first elastic wave element mounted on the upper surface of the insulating substrate. And a second piezoelectric substrate, and a second excitation electrode disposed on the second piezoelectric substrate, and is mounted on the lower surface of the insulating substrate smaller than the outer periphery of the insulating substrate in plan view. An acoustic wave device having an acoustic wave element; and a wiring substrate having a recess on the upper surface side that is smaller than the outer periphery of the insulating substrate and larger than the second acoustic wave element in a plan view. Are mounted on the wiring board so that the second acoustic wave element is located in the recess.

  A communication device of the present invention includes the above-described elastic wave module and a circuit board on which the elastic wave module is mounted.

  ADVANTAGE OF THE INVENTION According to this invention, since the 2nd elastic wave element is located in the recessed part of a wiring board, the elastic wave module and communication apparatus which can be reduced in height can be provided.

It is sectional drawing of the elastic wave module which concerns on one Embodiment of this invention. 2 is an enlarged cross-sectional view in which the periphery of an elastic wave device is enlarged in the elastic wave module of FIG. It is sectional drawing which showed only the elastic wave apparatus of FIG. It is a top view of the elastic wave element used for the elastic wave module of FIG. 1, and FIG. 1 is equivalent when cut | disconnected by the II line. It is the expanded sectional view which expanded a part of elastic wave element of Drawing 4. FIG. 3 is a modified example of the elastic wave module of FIG. 1, (a) is an enlarged cross-sectional view corresponding to FIG. 2, and (b) is a plan view of the wiring board as viewed from above. FIG. 3 is a view showing a modification of the elastic wave module in FIG. 1 and is an enlarged sectional view corresponding to FIG. 2. FIG. 9 shows a modification of the elastic wave module of FIG. 8 and is an enlarged cross-sectional view in which a part of FIG. 8 is enlarged. FIG. 3 is a view showing a modification of the elastic wave module in FIG. 1 and is an enlarged sectional view corresponding to FIG. 2. FIG. 10 shows a modification of the elastic wave module of FIG. 9 and is an enlarged cross-sectional view corresponding to FIG. 2. FIG. 3 is a view showing a modification of the elastic wave module in FIG. 1 and is an enlarged sectional view corresponding to FIG. 2.

Hereinafter, an elastic wave (Surface Acoustic Wave: hereinafter sometimes referred to as SAW) module according to an embodiment of the present invention will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensional ratios and the like on the drawings do not necessarily match the actual ones.

<Configurations of SAW module>
(Configuration of SAW element)
A SAW module 1 according to an embodiment of the present invention will be described below. The SAW module 1 according to the present embodiment includes a SAW device 2 and a wiring board 3 as shown in FIGS. The SAW device 2 has an insulating substrate 4, a first SAW element 5, and a second SAW element 6. The first SAW element 5 and the second SAW element 6 generally include a piezoelectric substrate 7, an excitation (Inter Digital Transducer: hereinafter referred to as IDT) electrode 8, a wiring conductor 9, and an electrode pad 10.

  In the following description, the configuration of the first SAW element 5 is expressed as a piezoelectric substrate 7a, an IDT electrode 8a, a wiring conductor 9a, and an electrode pad 10a for convenience, and the configuration of the second SAW element 6 is a piezoelectric substrate 7b, an IDT electrode 8b, a wiring For convenience, the conductor 9b and the electrode pad 10b are indicated. In addition, when referring to the configuration of both the first SAW element 5 and the second SAW element 6, it is expressed as “piezoelectric substrate 7” without adding a or b.

  The first SAW element 5 and the second SAW element 6 are set to be a transmission filter or a reception filter. Both the first SAW element 5 and the second SAW element 6 may be transmission filters or reception filters, or transmission and reception may be configured by separate filters.

  The piezoelectric substrate 7 is composed of a single crystal substrate having piezoelectricity, such as a lithium tantalate single crystal, a lithium diobate single crystal, or a lithium tetraborate single crystal. The piezoelectric substrate 7 is formed in a rectangular parallelepiped shape, for example. The size of the piezoelectric substrate 7 is appropriately set. The thickness of the piezoelectric substrate 7 can be set to, for example, 0.2 mm or more and 0.5 mm or less. The length of one side of the piezoelectric substrate 7 can be set to 0.6 mm or more and 3 mm or less, for example.

An IDT electrode 8 is provided on the piezoelectric substrate 7. As shown in FIG. 5, the IDT electrode 8 is composed of a comb-like electrode. In the following description, the comb-like electrode 8 may be indicated. The comb-like electrode 8 is arranged so that at least two bus bar electrodes 8A face each other, and has electrode fingers 8B that extend in the directions of each other and intersect each other. The plurality of comb-like electrodes 8 may constitute a ladder-type SAW filter connected by direct connection or parallel connection. Further, the plurality of comb-like electrodes 8 may constitute a dual mode SAW resonator filter in which the plurality of IDT electrodes 8 are arranged in one direction. In addition, as shown in FIG. 5, you may have the reflector 8C.

  The electrode pad 10 is disposed on the piezoelectric substrate 7 as shown in FIGS. What is necessary is just to set the planar view shape of the electrode pad 10 suitably. In the present embodiment, the electrode pad 10 has a circular shape. What is necessary is just to set suitably the number and arrangement position of the electrode pad 10 according to the structure of the filter comprised by the some IDT electrode 8. FIG. The width of the electrode pad 10 can be set to be 60 μm or more and 100 μm or less, for example.

  The electrode pad 10 is electrically connected to the IDT electrode 8 (bus bar electrode 8A) by the wiring conductor 9, as shown in FIGS. The wiring conductor 9 is formed in layers on the upper surface 7A. Note that the wiring conductor 9 does not need to be formed on the upper surface 7A, and for example, there may be a portion that three-dimensionally intersects via an insulator.

  The IDT electrode 8, the electrode pad 10, and the wiring conductor 9 (part formed on the upper surface 7A) can be formed by the same manufacturing process. Therefore, the IDT electrode 8, the wiring conductor 9, and the electrode pad 10 are made of the same conductive material, for example. As the conductive material, for example, an Al alloy such as an Al—Cu alloy can be used. Moreover, the IDT electrode 8, the wiring conductor 9, and the electrode pad 10 are set to the same film thickness, for example. These thicknesses can be set to, for example, 100 nm or more and 500 nm or less.

The IDT electrode 8, the wiring conductor 9, and the electrode pad 10 are formed by forming a metal film formed by a thin film forming method such as a sputtering method, a vapor deposition method, or a CVD (Chemical Vapor Deposition) method, into a microprojection exposure machine (stepper) or RIE (Reactive Ion). It can be formed by photolithography using an etching apparatus.

A protective film may be formed on the IDT electrode 8, the wiring conductor 9 and the electrode pad 10. The protective film is made of an insulating material. For example, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), silicon (Si), or the like can be used. The thickness of the protective film can be set to 5 nm or more and 50 nm or less.

  The protective film can be obtained by patterning a film formed by a thin film forming method such as a CVD method or a sputtering method by a photolithography method. By forming such a protective film, it is possible to protect the IDT electrode 8 and the wiring conductor 9 and to prevent oxidation. The protective film is provided so that the upper surface of the electrode pad 10 is exposed.

  On the electrode pad 10, a connection electrode in which a metal material is laminated may be disposed in order to improve adhesion to the bump 11 described later or electrical characteristics. The thickness of the connection electrode can be set to be 1 μm or more and 2 μm or less, for example. Such a connection electrode can be formed by a lift-off method. What is necessary is just to select the material of a connection electrode suitably. When metal bumps made of copper are used as the bumps 11, for example, titanium and copper sequentially laminated can be used.

(Configuration of SAW device)
The first SAW element 5 and the second SAW element 6 are mounted on the insulating substrate 4 as shown in FIG. As the insulating substrate 4, for example, a ceramic substrate or an organic substrate can be used. In the present embodiment, a case where an organic substrate is used as the insulating substrate 4 will be described.

  As the insulating substrate 4 made of an organic substrate, for example, a substrate in which fibers made of glass or the like are arranged in a base material made of an organic material such as an epoxy resin can be used. The fiber extends in the planar direction (xy direction). The fibers extending in the x direction and the fibers extending in the y direction are knitted so as to have a mesh shape in plan view.

  The thickness of the insulating substrate 4 can be set to be, for example, 50 μm or more and 80 μm or less. The planar view shape of the insulating substrate 4 can be set so as to be, for example, a quadrangular shape. The width of the insulating substrate 4 can be set to be 0.5 μm or more and 1 mm or less, for example.

  The first SAW element 5 is mounted on the upper surface 4A of the insulating substrate 4 and the second SAW element 6 is mounted on the lower surface 4B. The second SAW element 6 is set so that the outer periphery is smaller than the outer periphery of the insulating substrate 4. With this setting, the lower surface 4B of the insulating substrate 4 can be exposed, and the SAW device 2 can be easily mounted on the wiring substrate 3.

  Specifically, the substrate electrode pad 12 is provided on the insulating substrate 4, and the first SAW element 5 and the second SAW element 6 are electrically connected to each other through the bumps 11 between the electrode pad 10 and the substrate electrode pad 12. ing. An inductor pattern or the like may be formed on the upper surface 4A or the lower surface 4B of the insulating substrate 4. In that case, since the inductor pattern does not need to be formed in the SAW element as compared with the configuration of the SAW element in which the inductor pattern is conventionally provided in the sealing member for sealing the IDT electrode, productivity is improved. And increase the degree of design freedom. Note that the present invention is not limited to the inductor pattern, and a band pass filter, a semiconductor switch, a capacitor, or the like may be provided.

  In the gap between the first SAW element 5 and the insulating substrate 4, a sealing member 13 is disposed across the peripheral edge of the first SAW element 5. By disposing the sealing member 13 over the periphery, the first SAW element 5 can be fixed to the insulating substrate 4 and the gap can be sealed. Moreover, it can suppress that sealing resin 16 mentioned later flows into a space | gap (structure of IDT electrode 8 grade | etc.,). For example, an epoxy resin or the like can be used for the sealing member 13.

(Configuration of SAW module)
The SAW device 2 described above is mounted on a wiring board 3 as shown in FIGS. Specifically, the SAW device 2 is mounted on the upper surface 3 </ b> A of the wiring board 3 so that the second SAW element 6 is positioned in the recess 3 ′ of the wiring board 3. Hereinafter, a specific configuration will be described.

  The wiring board 3 has a multilayer substrate structure in which 5 to 15 dielectric layers having the same size and shape are stacked. The dimensions are, for example, a vertical dimension of 3.0 mm or more and 6.0 mm or less, and a horizontal dimension of 3.0 mm or more. 6.0 mm or less, and the thickness of one layer is 0.3 mm or more and 0.6 mm or less. As the material of the multilayer wiring board, for example, a wiring conductor layer (metal pattern) is formed with a conductor such as copper foil on an organic dielectric substrate such as glass epoxy resin and fired at the same time, or a ceramic material For example, various wiring conductor layers (metal patterns) formed on an inorganic dielectric substrate such as those fired at the same time as the dielectric substrate can be used.

The ceramic material includes (1) a ceramic material whose main component is Al ₂ O ₃ , AlN, Si ₃ N ₄ , SiC, etc., with a firing temperature of 1100 ° C. or higher, and (2) 1100 ° C. or lower made of a mixture of metal oxides. A low-temperature fired ceramic material fired at 1050 ° C. or lower, (3) a group of low-temperature fired ceramic materials fired at 1100 ° C. or lower, particularly 1050 ° C. or lower, comprising glass powder or a mixture of glass powder and ceramic filler powder You can choose from.

  The wiring board 3 has an upper electrode pad 3a on the upper surface 3A, a lower electrode pad 3b on the lower surface 3B, and a wiring via 3c that electrically connects the upper electrode pad 3a and the lower electrode pad 3b.

  Since the wiring via 3c is formed by simultaneous firing with the dielectric substrate 3d, various combinations are made according to the firing temperature of the ceramic material forming the dielectric substrate 3d. For example, when the ceramic material is (1), a conductor material mainly containing at least one selected from the group consisting of tungsten, molybdenum, manganese, and copper is preferably used. Moreover, it is good also as a mixture with copper etc. for resistance reduction. When the ceramic material is the low-temperature fired ceramic material of (2) or (3), a low-resistance conductor material mainly containing at least one selected from the group consisting of copper, silver, gold, and aluminum is used.

  In the SAW device 2, a substrate electrode pad 12 provided on the lower surface 4 </ b> B of the insulating substrate 4 and an upper electrode pad 3 a of the wiring substrate 3 are mounted via bumps 11. In addition, an electronic component 50 such as a semiconductor switch, a capacitor, or a resistor is mounted on the upper surface 3A of the wiring board 3.

  Further, a sealing resin 16 is disposed on the wiring board 3. Specifically, the sealing resin 16 is disposed on the wiring board 3 so as to cover the SAW device 2. As the sealing resin 16, for example, an epoxy resin or the like can be used. The sealing resin 16 can be disposed, for example, by applying a resin and then curing it by heating at 150 ° C. for 30 minutes to 60 minutes, for example.

  In the SAW module of this embodiment, the SAW device 2 in which the first SAW element 5 and the second SAW element 6 are stacked in the vertical direction via the insulating substrate 4 is mounted on the wiring substrate 3 via the insulating substrate 4. Since such a SAW device 2 is used, the occupied area on the wiring board 3 can be reduced as compared with the case where two SAW elements are provided on the same plane. Further, by housing a part of the SAW device 2 (second SAW element 6) in the recess 3 ', the height of the SAW module 1 can be reduced.

(Modification 1 of SAW module)
The SAW module 1 may further include an annular sealing material 14 disposed along the outer periphery of the insulating substrate 4 in plan view. The annular sealing material 14 may be made of a resin material made of epoxy resin or the like as shown in FIG. 6, or a conductive material composed of the annular electrode pads 14a and 14c and the annular conductor 14b as shown in FIG. It may be used.

  A case where the annular sealing material 14 is formed of a conductive material will be described. The annular sealing material 14 includes a first annular electrode pad 14a, an annular conductor 14b, and a second annular electrode pad 14c. The annular electrode pad 14a is disposed on the lower surface 4B of the insulating substrate 4 so as to surround the outer periphery. On the other hand, the second annular electrode pad 14c is disposed on the upper surface 3A of the wiring board 3 so as to surround the recess 3 '. The annular electrode pad 14 a and the second annular electrode pad 14 c are firmly fixed by an annular conductor 14 b such as solder, whereby the recess 3 ′ is sealed and the SAW device 2 is mounted on the wiring board 3.

  The annular conductor 14b is formed by printing on the second annular electrode pad 14c formed in advance on the upper surface 3A of the wiring board 3 by screen printing or the like. Thereafter, the substrate electrode pad 12 formed on the lower surface 4B of the insulating substrate 4 is brought into contact with the coated annular conductor, and the annular sealing material 14 is formed by applying pressure and heating.

  Further, as shown in FIG. 8, the annular conductor 14 b of the annular sealing material 14 may be disposed so as to contact the side surface 4 </ b> C of the insulating substrate 4. Thus, the SAW device 2 can be firmly fixed by the annular conductor 14b being in contact with and fixed to the side surface 4C. Further, when the SAW device 2 has the sealing member 13, a part of the annular conductor 14 b (for example, solder) in contact with the side surface 4 </ b> C is prevented from flowing to the IDT electrode 8 a side of the first SAW element 5. be able to.

  When the annular sealing material 14 is made of a conductive material, the annular sealing material 14 may be electrically connected to the ground terminal. By comprising in this way, the cyclic | annular sealing material 14 can be set so that it may become a reference | standard (grounding) electric potential. As a result, the periphery of the second SAW element 6 is electromagnetically shielded, and electromagnetic interference between the first SAW element 5 and the second SAW element 6 can be reduced. Can be improved.

  Further, when the SAW module 1 has the annular sealing material 14, the upper electrode pad 3 a may be located on the inner side (second SAW element 6 side) than the annular sealing material 14. By being arranged in this manner, the bumps 11 are present in the sealed space, so that the bumps 11 can be hardly corroded.

(Modification 2 of the SAW module)
The second SAW element 6 may constitute a transmission filter. Since the transmission filter generally has heat more easily than the reception filter, even when the second SAW element 6 on the wiring board 3 side generates heat, the heat can be easily released to the wiring board 3. As a result, the power durability characteristics of the second SAW element 6 can be improved.

  Further, as shown in FIG. 9, the SAW module 1 may further include a heat conductive resin 15 that contacts the second SAW element 6 on the bottom surface of the recess 3 ′. By disposing the heat conductive resin 15 in contact with the second SAW element 6 in this manner, the heat of the second SAW element 6 can be more efficiently conducted to the wiring board 3 side. As the heat conductive resin 15, a material having higher heat conductivity than air can be used. Specifically, a resin obtained by adding a thermally conductive filler such as boron nitride, alumina, copper, aluminum, or zinc oxide to an epoxy resin or a silicone resin can be used.

  Further, as shown in FIG. 10, a heat radiation pad 17 may be formed on the bottom surface of the recess 3 '. When the heat dissipation pad 17 is provided, the heat conductive resin 15 is disposed so as to contact the heat dissipation pad 17 and the second SAW element 6. Thus, the heat radiation pad 17 and the heat conductive resin 15 are in contact with each other, so that the heat generated in the second SAW element 6 can be easily conducted to the heat radiation pad 17 and the temperature of the second SAW element 6 is reduced. Can do. The heat dissipating pad 17 may be connected to a heat dissipating via 17a or the like disposed in the wiring board 3 so as to facilitate heat conduction to the wiring board 3 side or the outside of the wiring board 3.

(Modification 3 of the SAW module)
As shown in FIG. 11, the SAW device 2 may have the first SAW element 5 smaller than the outer periphery of the insulating substrate 4 in plan view. With this configuration, since the upper surface 4A of the insulating substrate 4 is exposed, when the sealing resin 16 is used for sealing, the sealing resin 16 is also disposed on the upper surface 4A. The device 2 can be fixed more firmly. As a result, the long-term reliability of the SAW module 1 can be improved.

1. Elastic wave module (SAW module)
2 ... Elastic wave device (SAW device)
DESCRIPTION OF SYMBOLS 3 ... Wiring board 3A ... Upper surface 3B ... Lower surface 3 '... Recess 3a ... Upper electrode pad 3b ... Lower electrode pad 3c ... Wiring via 3d ... Dielectric substrate 4 ... Insulating substrate 4A ... Upper surface 4B ... Lower surface 4C ... Side surface 5 ... First Elastic wave element (first SAW element)
6 ... 2nd elastic wave element (2nd SAW element)
DESCRIPTION OF SYMBOLS 7 ... Piezoelectric substrate 8 ... Excitation electrode (IDT electrode), comb-like electrode 8A ... Bus-bar electrode 8B ... Electrode finger 8C ... Reflector 9 ... Wiring conductor 10 ... Electrode pad 11 ... Bump 12 ... Substrate electrode pad 13 ... Sealing member DESCRIPTION OF SYMBOLS 14 ... Ring sealing material 14a ... 1st ring electrode pad 14b ... Ring conductor 14c ... 2nd ring electrode pad 15 ... Thermal conductive resin 16 ... Sealing resin 17 ... Radiation pad 17a ... Radiation via 50 ... Electronic component

Claims (7)

An insulating substrate;
A first acoustic wave element having a first piezoelectric substrate and a first excitation electrode disposed on the first piezoelectric substrate, mounted on the upper surface of the insulating substrate, a second piezoelectric substrate, and the second piezoelectric substrate An acoustic wave device having a second excitation electrode disposed on the substrate and having a second acoustic wave element mounted on the lower surface of the insulating substrate, which is smaller than the outer periphery of the insulating substrate in plan view;
A wiring board having a recess on the upper surface side that is smaller than the outer periphery of the insulating substrate and larger than the second acoustic wave element in plan view,
The elastic wave device is an elastic wave module mounted on the wiring board so that the second elastic wave element is positioned in the recess. It further has an annular sealing material disposed along the outer periphery of the insulating substrate in plan view,
2. The elastic wave module according to claim 1, wherein in the elastic wave device, the insulating substrate is mounted on the wiring substrate via the annular sealing material.   The elastic wave module according to claim 2, wherein the annular sealing material is made of a conductive material, and the annular sealing material is set to have a reference potential. The wiring board has a wiring via that is conductive from the lower surface to the upper surface,
The elastic wave module according to claim 2, wherein a portion located on the upper surface of the wiring via is disposed inside the annular sealing material.   The elastic wave module according to claim 1, wherein the second elastic wave element constitutes a transmission filter.   The elastic wave module according to claim 1, further comprising a heat conductive resin that contacts the second elastic wave element on a bottom surface of the concave portion. The elastic wave module according to any one of claims 1 to 6,
A communication device having a circuit board on which the acoustic wave module is mounted.

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