Patent Publication Number: US-2023134299-A1

Title: Acoustic wave device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2021-179336 filed on Nov. 2, 2021. The entire contents of this application are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an acoustic wave device. 
     2. Description of the Related Art 
     Acoustic wave devices have been widely used in a filter of a mobile phone and the like. Japanese Unexamined Patent Application Publication No. 2018-093388 discloses an example of a filter having a piezoelectric thin-film resonator using acoustic waves. In the filter, a filter chip is flip-chip mounted on a substrate. A sealing portion is provided on the substrate. The filter chip is surrounded by the sealing portion. The sealing portion is covered with a protective film. The protective film is a metal film or an insulating film. Via wiring and a metal layer are provided in the substrate. The filter is electrically connected to the outside via the via wiring and the metal layer. 
     SUMMARY OF THE INVENTION 
     In the filter described in Japanese Unexamined Patent Application Publication No. 2018-093388, the via wiring and the metal layer in the substrate serve as a heat-dissipating path for heat generated in the filter. However, heat dissipation in the filter is insufficient. 
     Preferred embodiments of the present invention provide acoustic wave devices each capable of enhancing heat dissipation. 
     An acoustic wave device according to a broad aspect of a preferred embodiment of the present invention includes a package substrate including a first principal surface and a second principal surface which are opposed to each other, an acoustic wave element at the first principal surface of the package substrate, a sealing resin layer at the first principal surface of the package substrate and covering at least a portion of the acoustic wave element, and a metal shield film covering the sealing resin layer. The package substrate includes a ground connection electrode in the package substrate, electrically connected to the acoustic wave element, and connected to a ground potential. The package substrate includes a side surface connected to the first principal surface and a connection portion connected to at least a portion of an end edge on a side with the second principal surface in the side surface and at least a portion of an outer peripheral edge in the second principal surface. The connection portion is located inside a portion surrounded by an imaginary plane which is extended from the second principal surface and an imaginary plane which is extended from the side surface. The shield film reaches the side surface of the package substrate and does not reach the connection portion, and the shield film is connected to the ground connection electrode. 
     An acoustic wave device according to another broad aspect of another preferred embodiment of the present invention includes a package substrate including a first principal surface and a second principal surface which are opposed to each other, an acoustic wave element at the first principal surface of the package substrate, a sealing resin layer at the first principal surface of the package substrate and covering at least a portion of the acoustic wave element, and a non-metallic shield film covering the sealing resin layer. The package substrate includes a ground connection electrode in the package substrate, electrically connected to the acoustic wave element, and connected to a ground potential and a hot connection electrode in the package substrate, electrically connected to the acoustic wave element, and connected to a hot potential. The package substrate includes a side surface connected to the first principal surface and a connection portion connected to at least a portion of an end edge on a side with the second principal surface in the side surface and at least a portion of an outer peripheral edge in the second principal surface. The connection portion is located inside a portion surrounded by an imaginary plane extended from the second principal surface and an imaginary plane extended from the side surface. The shield film reaches the side surface of the package substrate and does not reach the connection portion, and the shield film is connected to at least one of the ground connection electrode and the hot connection electrode. 
     Acoustic wave devices according to preferred embodiments of the present invention achieve enhancement of heat dissipation. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic circuit diagram of an acoustic wave element according to a first preferred embodiment of the present invention. 
         FIG.  2    is a schematic front sectional view of an acoustic wave device according to the first preferred embodiment of the present invention. 
         FIG.  3    is a chart showing relationships between input power and output power in the first preferred embodiment of the present invention and a comparative example. 
         FIGS.  4 A to  4 D  are schematic front sectional views for explaining an acoustic wave element mounting process, a sealing resin layer formation process, a sealing resin layer division process, a package substrate half-cut process, and a shield film formation process in an example of a method for manufacturing the acoustic wave device according to the first preferred embodiment of the present invention. 
         FIG.  5    is a bottom view for explaining a package substrate division process in the example of the method for manufacturing the acoustic wave device according to the first preferred embodiment of the present invention. 
         FIG.  6    is a bottom view showing an electrode configuration of a series arm resonator in a transmitting filter according to the first preferred embodiment of the present invention. 
         FIG.  7    is a bottom view showing an electrode configuration of a longitudinally coupled resonator-type acoustic wave filter in a receiving filter according to the first preferred embodiment of the present invention. 
         FIG.  8    is a schematic front sectional view of an acoustic wave device according to a first modification of the first preferred embodiment of the present invention. 
         FIG.  9    is a schematic front sectional view of an acoustic wave device according to a second modification of the first preferred embodiment of the present invention. 
         FIG.  10    is a schematic front sectional view of an acoustic wave device according to a third modification of the first preferred embodiment of the present invention. 
         FIG.  11    is a schematic front sectional view of an acoustic wave device according to a second preferred embodiment of the present invention. 
         FIG.  12    is a schematic front sectional view of an acoustic wave device according to a third preferred embodiment of the present invention. 
         FIG.  13    is a schematic front sectional view of an acoustic wave device according to a fourth preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be clarified below by describing specific preferred embodiments of the present invention with reference to the drawings. 
     Note that the preferred embodiments described in the present specification are illustrative, and components in different preferred embodiments may be partially replaced or combined. 
       FIG.  1    is a schematic circuit diagram of an acoustic wave element according to a first preferred embodiment of the present invention. 
     An acoustic wave device according to the present preferred embodiment includes an acoustic wave element  1 . The acoustic wave element  1  is a duplexer. More specifically, the acoustic wave element  1  has a common connection terminal  2 , a transmitting filter  1 A, and a receiving filter  1 B. The transmitting filter  1 A and the receiving filter  1 B are commonly connected to the common connection terminal  2 . In the present preferred embodiment, the common connection terminal  2  is an antenna terminal. The antenna terminal is connected to an antenna. The common connection terminal  2  may be, for example, wiring or as an electrode pad. 
     The transmitting filter  1 A is a ladder filter. The transmitting filter  1 A has a plurality of series arm resonators and a plurality of parallel arm resonators. The plurality of series arm resonators and the plurality of parallel arm resonators in the transmitting filter  1 A are all acoustic wave resonators. Meanwhile, the receiving filter  1 B has a longitudinally coupled resonator-type acoustic wave filter  3 A, a longitudinally coupled resonator-type acoustic wave filter  3 B, a series arm resonator S 11 , and a parallel arm resonator P 11 . The series arm resonator S 11  and the parallel arm resonator P 11  are acoustic wave resonators for characteristics adjustment. Note that each acoustic wave resonator and each longitudinally coupled resonator-type acoustic wave filter are hereinafter sometimes simply referred to as resonators. 
     The acoustic wave element is a Band1 duplexer. More specifically, a pass band of the transmitting filter  1 A is approximately 1920 MHz to 1980 MHz, for example. A pass band of the receiving filter  1 B is approximately 2110 MHz to 2170 MHz, for example. A pass band of the acoustic wave element  1 , however, is not limited to the above-described ones. A specific configuration of the acoustic wave device according to the present preferred embodiment will be described below. 
       FIG.  2    is a schematic front sectional view of the acoustic wave device according to the first preferred embodiment. Referring to  FIG.  2   , a portion of an electrode structure in each of the transmitting filter  1 A and the receiving filter  1 B is indicated by a schematic representation having two diagonal lines added to a rectangle. 
     An acoustic wave device  10  has a package substrate  4 . The package substrate  4  has a first principal surface  4   a  and a second principal surface  4   b . The first principal surface  4   a  and the second principal surface  4   b  are opposed to each other. The above-described acoustic wave element  1  is provided at the first principal surface  4   a . More specifically, the plurality of resonators of the transmitting filter  1 A and the receiving filter  1 B share a same piezoelectric substrate  5 . For this reason, the transmitting filter  1 A and the receiving filter  1 B are regarded as one element chip. The acoustic wave element  1  as the element chip is flip-chip mounted on the first principal surface  4   a  of the package substrate  4 . Specifically, the acoustic wave element  1  is joined to the package substrate  4  by a plurality of bumps  9 . In the present preferred embodiment, the acoustic wave device  10  has a chip size package (CSP) structure. A structure of the acoustic wave device  10  may be, for example, such that the acoustic wave element  1  having a wafer level package (WLP) structure is mounted at the package substrate  4 . 
     A sealing resin layer  6  is provided at the first principal surface  4   a  of the package substrate  4  so as to cover the acoustic wave element  1 . A shield film  7  is further provided so as to cover the sealing resin layer  6 . In the present preferred embodiment, the shield film  7  is a metal film. The shield film  7  functions as an electromagnetic shield. This allows curbing of degradation in electrical characteristics of the acoustic wave element  1  due to, for example, an unnecessary electric signal from the outside. 
     The package substrate  4  further has a side surface  4   c  and a connection portion  4   d . The side surface  4   c  is connected to the first principal surface  4   a . The connection portion  4   d  is connected to the whole of an end edge on the second principal surface  4   b  side in the side surface  4   c  and the whole of an outer peripheral edge in the second principal surface  4   b . More specifically, in the package substrate  4  according to the present preferred embodiment, a recessed portion is provided over the whole of a portion facing the outer peripheral edge in the second principal surface  4   b . The recessed portion also faces the whole of the end edge on the second principal surface  4   b  side in the side surface  4   c . The portion constituting the recessed portion is the above-described connection portion  4   d . Thus, the connection portion  4   d  is located inside a portion surrounded by an imaginary plane A which is extended from the second principal surface  4   b  and an imaginary plane B which is extended from the side surface  4   c.    
     More specifically, the first principal surface  4   a  and the second principal surface  4   b  of the package substrate  4  have rectangular shapes. The package substrate  4  has four side surfaces  4   c . In the acoustic wave device  10 , four sides in the outer peripheral edge of the second principal surface  4   b  are all connected to the connection portion  4   d . The connection portion  4   d  only needs to be connected to at least a portion of the end edge on the second principal surface  4   b  side in each side surface  4   c  and at least a portion of the outer peripheral edge in the second principal surface  4   b . A portion of the side surfaces  4   c  and a portion of the second principal surface  4   b  may be connected. For example, at least one of the plurality of sides in the outer peripheral edge of the second principal surface  4   b  may be connected to the connection portion  4   d , and at least one of the plurality of sides may be connected to the side surface  4   c . Note that shapes of the first principal surface  4   a  and the second principal surface  4   b  are not limited to the rectangular shapes. 
     The package substrate  4  has at least one ground connection terminal  12 A, a plurality of hot connection terminals  13 A, a plurality of ground connection via electrodes  12 B, a plurality of hot connection via electrodes  13 B, at least one ground connection electrode  12 C, at least one ground connection outer electrode  12 D, and a plurality of hot connection outer electrodes  13 D. The ground connection terminal  12 A and the hot connection terminals  13 A are provided at the first principal surface  4   a  of the package substrate  4 . The ground connection via electrodes  12 B, the hot connection via electrodes  13 B, and the ground connection electrode  12 C are provided in the package substrate  4 . The ground connection outer electrode  12 D and the hot connection outer electrodes  13 D are provided at the second principal surface  4   b . One of the plurality of ground connection via electrodes  12 B connects the ground connection terminal  12 A and the ground connection electrode  12 C. Another one of the plurality of ground connection via electrodes  12 B connects the ground connection electrode  12 C and the ground connection outer electrode  12 D. Meanwhile, the hot connection via electrode  13 B connects the hot connection terminal  13 A and the hot connection outer electrode  13 D. 
     The acoustic wave element  1  is connected to an external ground potential via the bumps  9 , the ground connection terminal  12 A, the ground connection via electrodes  12 B, the ground connection electrode  12 C, and the ground connection outer electrode  12 D. Meanwhile, the acoustic wave element  1  is connected to an external hot potential via the bumps  9 , the hot connection terminals  13 A, the hot connection via electrodes  13 B, and the hot connection outer electrodes  13 D. Note that one of the plurality of ground connection via electrodes  12 B may connect the ground connection terminal  12 A and the ground connection outer electrode  12 D. 
     The feature of the present preferred embodiment lies in that the package substrate  4  has the above-described connection portion  4   d , the shield film  7  reaches the side surfaces  4   c  of the package substrate  4  and does not reach the connection portion  4   d , and the shield film  7  is connected to the ground connection electrode  12 C. More specifically, an end portion of the ground connection electrode  12 C is located at the side surface  4   c  of the package substrate  4 . The shield film  7  is connected to the end portion. A heat-dissipating path for heat generated in the acoustic wave element  1  is, for example, a path which extends through the ground connection via electrodes  12 B and the ground connection outer electrode  12 D. The heat-dissipating path is a path which extends from the first principal surface  4   a  of the package substrate  4  to the second principal surface  4   b . Additionally, in the present preferred embodiment, a heat-dissipating path which extends through the ground connection via electrode  12 B, the ground connection electrode  12 C, and the shield film  7  is provided. As described above, the acoustic wave device  10  also has a heat-dissipating path which extends from the first principal surface  4   a  of the package substrate  4  to the side surface  4   c . This allows an effective increase in heat-dissipating paths. It is thus possible to effectively enhance heat dissipation. 
     Since heat dissipation can be enhanced in the present preferred embodiment, electric power handling capability can be enhanced. Details of the effect will be illustrated below by comparing the present preferred embodiment and a comparative example. Note that the comparative example is different from the present preferred embodiment in that a ground connection electrode is not connected to a shield film. Power application tests were conducted on the acoustic wave device according to the present preferred embodiment and an acoustic wave device according to the comparative example. Results of the tests are shown in  FIG.  3   . 
       FIG.  3    is a chart showing relationships between input power and output power in the first preferred embodiment and the comparative example. 
     As shown in  FIG.  3   , it is apparent that output power is higher for any input power in the first preferred embodiment than in the comparative example. In the comparative example, if input power is not less than 30.5 dBm, an increase in the input power leads only to a small increase in output power. In contrast, in the first preferred embodiment, even if input power is not less than 30.5 dBm, a rate of increase in output power caused by an increase in the input power is high. 
     Generally, output power increases with an increase in input power in a region where the input power is low. However, in a region where the input power is high, heat generation of each resonator increases a temperature of the resonator. For this reason, bands with small insertion losses in a receiving filter and a transmitting filter are shifted. Even if input power of a signal of the same frequency is increased, a rise in temperature makes the signal less likely to pass through the receiving filter and the transmitting filter. As a result, even if input power is increased, a rate of increase in output power is low. 
     In contrast, in the first preferred embodiment, heat dissipation can be enhanced in the acoustic wave device  10 . This makes it possible to curb a rise in temperatures of the acoustic wave resonators and the longitudinally coupled resonator-type acoustic wave filters and curb changes in frequency characteristics. Thus, even if input power is increased, output power can be increased. As described above, electric power handling capability characteristics can be enhanced. 
     Referring back to  FIG.  2   , an area of the second principal surface  4   b  of the package substrate  4  is small in the small-sized acoustic wave device  10 . This limits a heat-dissipating path. In the first preferred embodiment, however, the side surface  4   c  side can also be used as a heat-dissipating path. The present invention is thus particularly preferable if the acoustic wave device  10  is small-sized. 
     Additionally, in the first preferred embodiment, the connection portion  4   d  is provided at the package substrate  4 . With this configuration, the acoustic wave device  10  can be more reliably miniaturized, and productivity can be enhanced. This will be described below together with an example of a method for manufacturing the acoustic wave device according to the first preferred embodiment. 
       FIGS.  4 A to  4 D  are schematic front sectional views for explaining an acoustic wave element mounting process, a sealing resin layer formation process, a sealing resin layer division process, a package substrate half-cut process, and a shield film formation process in the example of the method for manufacturing the acoustic wave device according to the first preferred embodiment.  FIG.  5    is a bottom view for explaining a package substrate division process in the example of the method for manufacturing the acoustic wave device according to the first preferred embodiment. Note that a direction from below in  FIG.  2    or the like is assumed as a bottom view in the present specification. A direction from above in  FIG.  2    or the like is assumed as a plan view. 
     As shown in  FIG.  4 A , a package substrate  14  having a first principal surface  14   a  and a second principal surface  14   b  is prepared. A plurality of acoustic wave elements  1  are then provided at the first principal surface  14   a  of the package substrate  14 . Specifically, each of the plurality of acoustic wave elements  1  is joined to the package substrate  14  by a plurality of bumps  9 . Note that an electrode structure corresponding to the plurality of acoustic wave elements  1  is provided at the package substrate  14 . 
     As shown in  FIG.  4 B , the sealing resin layer  6  is provided on the package substrate  14  so as to cover the plurality of acoustic wave elements  1 . The sealing resin layer  6  is then cut from the first principal surface  14   a  side by, for example, a dicing machine, and the package substrate  14  is half cut. With this operation, the sealing resin layer  6  is divided, as shown in  FIG.  4 C . Additionally, a groove portion  14   e  is formed in a package substrate  14 A. At this time, the groove portion  14   e  is formed such that an end portion of the ground connection electrode  12 C is exposed at the groove portion  14   e . Note that the groove portion  14   e  includes a bottom portion  14   f . Such half-cut portions are formed on lines overlapping with lines I-I and lines II-II in  FIG.  5   . 
     As shown in  FIG.  4 D , the shield film  7  is formed so as to cover the sealing resin layer  6  and the groove portion  14   e . As described above, an end portion of each ground connection electrode  12 C is exposed at the groove portion  14   e . In the shield film formation process, the shield film  7  is connected to the ground connection electrode  12 C. The shield film  7  can be formed by, for example, sputtering or vacuum vapor deposition. 
     As shown in  FIG.  5   , the package substrate  14 A is cut along lines I-I and lines II-II. More specifically, the package substrate  14 A is cut until the bottom portion  14   f  of each groove portion  14   e  shown in  FIG.  4 C  is reached. At this time, the cutting of the package substrate  14 A is performed from the second principal surface  14   b  side with a groove width wider than in the package substrate half-cut process shown in  FIG.  4 C . More specifically, the cutting of the package substrate  14 A is performed such that a portion where the shield film  7  and the ground connection electrode  12 C are connected is not reached. With this operation, the connection portion  4   d  of the package substrate  4  shown in  FIG.  2    is formed. In the above-described manner, the package substrate  14 A is divided into individual pieces. A plurality of acoustic wave devices  10  can be obtained. 
     In the package substrate division process shown in  FIG.  5   , the cutting is performed with the groove width wider than in the package substrate half-cut process shown in  FIG.  4 C , as described above. For this reason, even if a deviation of a cutting position in the package substrate  14 A occurs, the small-sized package substrate  4  can be more reliably obtained. It is thus possible to more reliably miniaturize the acoustic wave device  10  and enhance the productivity. 
     In the above-described package substrate division process, a portion of an electrode on a principal surface of the package substrate  14 A may be removed. A portion of the ground connection outer electrode  12 D and a portion of each hot connection outer electrode  13 D shown in  FIG.  2    are removed in the process. Thus, each of the ground connection outer electrode  12 D and the hot connection outer electrodes  13 D is in contact with a border between the connection portion  4   d  and the second principal surface  4   b  of the package substrate  4 . As described above, at least one of the ground connection outer electrode  12 D and each hot connection outer electrode  13 D is preferably in contact with the border between the connection portion  4   d  and the second principal surface  4   b . In this case, an area of an electrode to be connected to the outside can be more reliably increased. This allows more reliable enhancement of heat dissipation. Both the ground connection outer electrode  12 D and the hot connection outer electrode  13 D need not be in contact with the border between the connection portion  4   d  and the second principal surface  4   b.    
     Formation of the connection portion  4   d  of the package substrate  4  is performed after formation of the shield film  7 . Thus, the shield film  7  does not reach the connection portion  4   d  of the package substrate  4 . This makes it difficult for the shield film  7  and the hot connection outer electrode  13 D to be short-circuited. 
     A circuit configuration of the acoustic wave element  1  according to the first preferred embodiment will be described below. 
     As shown in  FIG.  1   , the transmitting filter  1 A has a first signal terminal  8 A, a plurality of series arm resonators, a plurality of parallel arm resonators, and a capacitive element C. More specifically, the plurality of series arm resonators include a series arm resonator S 1 , a series arm resonator S 2 , a series arm resonator S 3   a , a series arm resonator S 3   b , and a series arm resonator S 4 . The plurality of parallel arm resonators include a parallel arm resonator P 1 , a parallel arm resonator P 2 , and a parallel arm resonator P 3 . The first signal terminal  8 A is an input terminal. 
     The series arm resonator S 1 , the series arm resonator S 2 , the series arm resonator S 3   a , the series arm resonator S 3   b , and the series arm resonator S 4  are series-connected to one another between the first signal terminal  8 A and the common connection terminal  2 . The parallel arm resonator P 1  is connected between a ground potential and a junction between the series arm resonator S 1  and the series arm resonator S 2 . The parallel arm resonator P 2  is connected between the ground potential and a junction between the series arm resonator S 2  and the series arm resonator S 3   a . The parallel arm resonator P 3  is connected between the ground potential and a junction between the series arm resonator S 3   b  and the series arm resonator S 4 . Note that the capacitive element C is connected in parallel with the series arm resonator S 3   b.    
     As described above, the receiving filter  1 B has the longitudinally coupled resonator-type acoustic wave filter  3 A, the longitudinally coupled resonator-type acoustic wave filter  3 B, the series arm resonator S 11 , and the parallel arm resonator P 11 . The receiving filter  1 B further has a second signal terminal  8 B. The second signal terminal  8 B is an output terminal. The second signal terminal  8 B may be, for example, constructed as wiring or as an electrode pad. The same applies to the above-described first signal terminal  8 A. 
     The longitudinally coupled resonator-type acoustic wave filter  3 A and the longitudinally coupled resonator-type acoustic wave filter  3 B are connected in parallel with each other between the common connection terminal  2  and the second signal terminal  8 B. The series arm resonator S 11  is connected between the common connection terminal  2  and the longitudinally coupled resonator-type acoustic wave filters  3 A and  3 B. The parallel arm resonator P 11  is connected between the ground potential and a junction between the series arm resonator S 11  and the longitudinally coupled resonator-type acoustic wave filters  3 A and  3 B. The parallel arm resonator P 11  of the receiving filter  1 B, and the parallel arm resonator P 2  and the parallel arm resonator P 3  of the transmitting filter  1 A are commonly connected to the ground potential. 
     Note that the circuit configuration of the acoustic wave element  1  is not limited to the above-described one. Additionally, the acoustic wave element  1  is not limited to a duplexer. The acoustic wave element  1  may be, for example, a transmitting filter or a receiving filter or may be a multiplexer or the like. In addition, the acoustic wave element  1  may be, for example, a one-port acoustic wave resonator. 
     Specific configurations of an acoustic wave resonator and a longitudinally coupled resonator-type acoustic wave filter according to the first preferred embodiment will be illustrated below. 
       FIG.  6    is a bottom view showing an electrode configuration of a series arm resonator in a transmitting filter according to the first preferred embodiment. Referring to  FIG.  6   , wiring connected to the series arm resonator S 1  is not shown. 
     The series arm resonator S 1  includes the piezoelectric substrate  5 . As described above, the plurality of resonators of the transmitting filter  1 A and the receiving filter  1 B share the same piezoelectric substrate  5 . In the present preferred embodiment, the piezoelectric substrate  5  is a substrate which is composed only of a piezoelectric layer. The piezoelectric layer is made of lithium tantalate. In the present specification, the statement that a given member is made of a given material includes a case where impurities, an amount of which is small enough to avoid degradation in electrical characteristics of an acoustic wave device, are contained. A material for the piezoelectric layer is not limited to the above-described one, and, for example, lithium niobate, zinc oxide, aluminum nitride, crystal, lead zirconate titanate (PZT), or the like can be used. Note that the piezoelectric substrate  5  may be a multilayer substrate including a piezoelectric layer. 
     The piezoelectric substrate  5  has a third principal surface  5   a  and a fourth principal surface  5   b . The third principal surface  5   a  and the fourth principal surface  5   b  are opposed to each other. Of the third principal surface  5   a  and the fourth principal surface  5   b , the third principal surface  5   a  is located on the package substrate  4  side. An interdigital transducer (IDT) electrode  15  is provided at the third principal surface  5   a . Application of an AC voltage to the IDT electrode  15  excites acoustic waves. One pair of reflectors  16 A and  16 B is provided on both sides in an acoustic wave propagation direction of the IDT electrode  15  at the third principal surface  5   a.    
     The IDT electrode  15  has a first busbar  17   a , a second busbar  17   b , a plurality of first electrode fingers  18   a , and a plurality of second electrode fingers  18   b . The first busbar  17   a  and the second busbar  17   b  are opposed to each other. Respective one ends of the plurality of first electrode fingers  18   a  are connected to the first busbar  17   a . Respective one ends of the plurality of second electrode fingers  18   b  are connected to the second busbar  17   b . The plurality of first electrode fingers  18   a  and the plurality of second electrode fingers  18   b  interdigitate with each other. Note that the first electrode fingers  18   a  and the second electrode fingers  18   b  are hereinafter sometimes simply referred to as electrode fingers. If a direction in which the plurality of electrode fingers extend is assumed as an electrode finger extension direction, the electrode finger extension direction and the acoustic wave propagation direction are orthogonal to each other in the first preferred embodiment. 
     Each of the acoustic wave resonators other than the series arm resonator S 1  has an IDT electrode and reflectors, like the series arm resonator S 1 . In the first preferred embodiment, the plurality of series arm resonators and the plurality of parallel arm resonators are all surface acoustic wave resonators, for example. 
       FIG.  7    is a bottom view showing an electrode configuration of a longitudinally coupled resonator-type acoustic wave filter in a receiving filter according to the first preferred embodiment. Referring to  FIG.  7   , wiring connected to the longitudinally coupled resonator-type acoustic wave filter  3 A is not shown. 
     The longitudinally coupled resonator-type acoustic wave filter  3 A has the above-described piezoelectric substrate  5 . An IDT electrode  15 A, an IDT electrode  15 B, and an IDT electrode  15 C are provided at the third principal surface  5   a  of the piezoelectric substrate  5 . The IDT electrode  15 A, the IDT electrode  15 B, and the IDT electrode  15 C are lined up along an acoustic wave propagation direction. One pair of reflectors  16 C and  16 D is provided on both sides in the acoustic wave propagation direction of the IDT electrode  15 A, the IDT electrode  15 B, and the IDT electrode  15 C at the third principal surface  5   a . The longitudinally coupled resonator-type acoustic wave filter  3 A is of a 3IDT type. The number of IDT electrodes in the longitudinally coupled resonator-type acoustic wave filter  3 A, however, is not limited to the above-described one. The longitudinally coupled resonator-type acoustic wave filter  3 A may be, for example, of a 5IDT type, a 7IDT type, or the like. The longitudinally coupled resonator-type acoustic wave filter  3 B similarly has a plurality of IDT electrodes and a plurality of reflectors. 
     Referring back to  FIG.  2   , a plurality of terminals for external connection are provided at the third principal surface  5   a  of the piezoelectric substrate  5 . Each terminal for external connection is constructed as an electrode pad in the present preferred embodiment. Respective bumps  9  are joined to the plurality of terminals for external connection. The plurality of terminals for external connection include a ground connection electrode pad  19 . The ground connection electrode pad  19  is electrically connected to the ground connection terminal  12 A via the bump  9 . The plurality of terminals for external connection also include the first signal terminal  8 A, the second signal terminal  8 B, and the common connection terminal  2  shown in  FIG.  1   . The first signal terminal  8 A, the second signal terminal  8 B, and the common connection terminal  2  are electrically connected to separate hot connection terminals  13 A via the respective bumps  9 . 
     As described above, the piezoelectric substrate  5  according to the first preferred embodiment is composed only of the piezoelectric layer. The piezoelectric substrate  5 , however, may be a multilayer substrate including a piezoelectric layer. For example, in a first modification of the first preferred embodiment shown in  FIG.  8   , a piezoelectric substrate  25  has a support substrate  26 , a high-acoustic-velocity film  27  as a high-acoustic-velocity material layer, a low-acoustic-velocity film  28 , and a piezoelectric layer  29 . More specifically, the support substrate  26 , the high-acoustic-velocity film  27 , the low-acoustic-velocity film  28 , and the piezoelectric layer  29  are stacked in this order. In the present modification, the shield film  7  is connected to the ground connection electrode  12 C, as in the first preferred embodiment. This allows enhancement of heat dissipation. 
     Note that the low-acoustic-velocity film  28  is a film with a relatively low acoustic velocity. More specifically, an acoustic velocity of a bulk wave propagating through the low-acoustic-velocity film  28  is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer  29 . For example, a material having, as a main ingredient, glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum pentoxide, or a compound obtained by adding fluorine, carbon, or boron to silicon oxide can be used as a material for the low-acoustic-velocity film  28 . 
     A high-acoustic-velocity material layer is a layer with a relatively high acoustic velocity. In the present modification, the high-acoustic-velocity material layer is the high-acoustic-velocity film  27 . An acoustic velocity of a bulk wave propagating through the high-acoustic-velocity material layer is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer  29 . For example, silicon, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, sapphire, lithium tantalate, lithium niobate, crystal, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, a diamond-like carbon (DLC) film, diamond, or the like, or a medium having, as a main ingredient, any of the above-described materials can be used as a material for the high-acoustic-velocity material layer. 
     For example, a piezoelectric material, such as aluminum oxide, lithium tantalate, lithium niobate, or crystal; every type of ceramic, such as alumina, sapphire, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite; a dielectric, such as diamond or glass; a semiconductor, such as silicon or gallium nitride; a resin; or the like can be used as a material for the support substrate  26 . 
     In the present modification, the high-acoustic-velocity film  27  as the high-acoustic-velocity material layer, the low-acoustic-velocity film  28 , and the piezoelectric layer  29  are stacked in this order in the piezoelectric substrate  25 . With this configuration, energy of acoustic waves can be effectively confined to the piezoelectric layer  29  side. 
     Note that a multilayer structure of the piezoelectric substrate is not limited to the above-described one. For example, the piezoelectric substrate may be a multilayer substrate having a support substrate, a high-acoustic-velocity film, and a piezoelectric layer. Additionally, the high-acoustic-velocity material layer may be a high-acoustic-velocity support substrate. In this case, the piezoelectric substrate may be a multilayer substrate having a high-acoustic-velocity support substrate, a low-acoustic-velocity film, and a piezoelectric layer or a multilayer substrate having a high-acoustic-velocity support substrate and a piezoelectric layer. Even in these cases, energy of acoustic waves can be effectively confined to the piezoelectric layer side. Moreover, heat dissipation can be enhanced, as in the first modification. 
     In the first preferred embodiment, the sealing resin layer  6  covers the fourth principal surface  5   b  of the piezoelectric substrate  5 . The sealing resin layer  6  only needs to be provided at the first principal surface  4   a  of the package substrate  4  so as to cover at least a portion of the acoustic wave element  1 . For example, in a second modification of the first preferred embodiment shown in  FIG.  9   , the sealing resin layer  6  covers a side surface of the piezoelectric substrate  5  but does not cover the fourth principal surface  5   b . The sealing resin layer  6  is flush with the fourth principal surface  5   b . In the present modification, the shield film  7  covers the sealing resin layer  6  and the fourth principal surface  5   b . Even in this case, heat dissipation can be enhanced, as in the first preferred embodiment. 
     In the acoustic wave device  10 , all resonators share the same piezoelectric substrate  5 . The acoustic wave element  1  is flip-chip mounted as one element chip on the package substrate  4 . The acoustic wave device  10 , however, is not limited to this. For example, as in a third modification shown in  FIG.  10   , a transmitting filter  21 A and a receiving filter  21 B may have piezoelectric substrates different from each other. In the present modification, all resonators of the transmitting filter  21 A share a piezoelectric substrate  25 A. All resonators of the receiving filter  21 B share a piezoelectric substrate  25 B. The transmitting filter  21 A and the receiving filter  21 B are individual element chips. An acoustic wave element according to the present modification is flip-chip mounted as two element chips on a package substrate  24 . In the package substrate  24 , wiring is provided to correspond to the number of element chips. The sealing resin layer  6  is provided so as to cover the element chips. In the present modification, the shield film  7  is connected to the ground connection electrode  12 C, as in the first preferred embodiment. This allows enhancement of heat dissipation. 
     Note that the number of piezoelectric substrates is not particularly limited and that, for example, each resonator may have a separate piezoelectric substrate. Three or more element chips may be flip-chip mounted on the package substrate  24 . Even in this case, heat dissipation can be enhanced, as in the third modification. 
     Referring back to  FIG.  2   , the connection portion  4   d  of the package substrate  4  has a shape like a curved surface in the first preferred embodiment. The connection portion  4   d , however, may have, for example, a shape obtained by connecting a plurality of flat surfaces. The plurality of flat surfaces are, for example, different from each other in an angle of inclination to the second principal surface  4   b.    
       FIG.  11    is a schematic front sectional view of an acoustic wave device according to a second preferred embodiment. 
     The present preferred embodiment is different from the first preferred embodiment in that an acoustic wave element  31  has a WLP structure. The present preferred embodiment has the same configuration as the acoustic wave device  10  according to the first preferred embodiment except for the above-described point. 
     A first support member  32 A and a second support member  32 B are provided at a third principal surface  5   a  of a piezoelectric substrate  5 . Note that the first support member  32 A is a support member according to the present invention. The first support member  32 A is provided so as to surround a plurality of IDT electrodes in a plurality of resonators. The first support member  32 A has a frame-like shape. More specifically, the first support member  32 A has a cavity  32   a . The plurality of IDT electrodes are located in the cavity  32   a . A plurality of terminals for external connection are provided at the third principal surface  5   a , as in the first preferred embodiment. The first support member  32 A covers at least one or ones of the plurality of terminals for external connection. 
     The second support member  32 B is located in the cavity  32   a  of the first support member  32 A. The second support member  32 B has a columnar shape. The second support member  32 B, however, may have a wall-like shape. The second support member  32 B covers at least one or ones of the terminals for external connection. A cover member  33  is provided on the first support member  32 A and the second support member  32 B. The cover member  33  is provided so as to close the cavity  32   a  of the first support member  32 A. The plurality of IDT electrodes are surrounded by the piezoelectric substrate  5 , the first support member  32 A, and the cover member  33 . 
     A plurality of through-electrodes  34 A are provided so as to extend through the cover member  33  and the first support member  32 A. Similarly, a through-electrode  34 B is provided so as to extend through the cover member  33  and the second support member  32 B. Respective one ends of the through-electrodes  34 A and the through-electrode  34 B are connected to terminals for external connection. Respective bumps  9  are joined to the other ends of the through-electrodes  34 A and the through-electrode  34 B. The acoustic wave element  31  is joined to a package substrate  4  by the plurality of bumps  9 . 
     In the present preferred embodiment, a shield film  7  is connected to a ground connection electrode  12 C, as in the first preferred embodiment. This allows enhancement of heat dissipation. 
       FIG.  12    is a schematic front sectional view of an acoustic wave device according to a third preferred embodiment. 
     The present preferred embodiment is different from the first preferred embodiment in that the present preferred embodiment has a mounting board  46 . A package substrate  4  is provided above the mounting board  46 . The acoustic wave device according to the present preferred embodiment has the same configuration as the acoustic wave device  10  according to the first preferred embodiment except for the above-described point. 
     The mounting board  46  has a fifth principal surface  46   a  and a sixth principal surface  46   b . The fifth principal surface  46   a  and the sixth principal surface  46   b  are opposed to each other. Of the fifth principal surface  46   a  and the sixth principal surface  46   b , the fifth principal surface  46   a  is located on the package substrate  4  side. The mounting board  46  has at least one ground electrode  47  and a plurality of hot electrodes  48 . The ground electrode  47  and the hot electrodes  48  are provided at the fifth principal surface  46   a.    
     The package substrate  4  is joined to the mounting board  46  by a plurality of bumps  49 . More specifically, a ground connection outer electrode  12 D of the package substrate  4  is joined to the ground electrode  47  by the bump  49 . A hot connection outer electrode  13 D is joined to the hot electrode  48  by the bump  49 . An acoustic wave element  1  is electrically connected to the mounting board  46  via the package substrate  4 . 
     In the present preferred embodiment, a shield film  7  is connected to a ground connection electrode  12 C, as in the first preferred embodiment. This allows enhancement of heat dissipation. 
       FIG.  13    is a schematic front sectional view of an acoustic wave device according to a fourth preferred embodiment. 
     The present preferred embodiment is different from the first preferred embodiment in that a shield film  57  is a non-metallic film. The present preferred embodiment is also different from the first preferred embodiment in that a hot connection electrode  53 C is provided in a package substrate  54  and that the shield film  57  is connected to the hot connection electrode  53 C. An acoustic wave device  50  according to the present preferred embodiment has the same configuration as the acoustic wave device  10  according to the first preferred embodiment except for the above-described points. 
     The hot connection electrode  53 C is connected to a hot connection terminal  13 A by one of a plurality of hot connection via electrodes  13 B. The hot connection electrode  53 C is also connected to a hot connection outer electrode  13 D by another one of the plurality of hot connection via electrodes  13 B. An end portion of the hot connection electrode  53 C is located at a side surface  4   c  of the package substrate  54 . The shield film  57  is connected to the end portion. Since the shield film  57  is a non-metallic film, even if the shield film  57  is connected to the hot connection electrode  53 C, electrical characteristics of the acoustic wave device  50  are unlikely to degrade. 
     A heat-dissipating path for heat generated in an acoustic wave element  1  is, for example, a path which extends through the hot connection via electrodes  13 B and the hot connection outer electrode  13 D. The heat-dissipating path is a path which extends from a first principal surface  4   a  of the package substrate  54  to a second principal surface  4   b . Additionally, in the present preferred embodiment, a heat-dissipating path which extends through the hot connection via electrode  13 B, the hot connection electrode  53 C, and the shield film  57  is provided. As described above, the acoustic wave device  50  also has a heat-dissipating path which extends from the first principal surface  4   a  of the package substrate  54  to the side surface  4   c . This allows an effective increase in heat-dissipating paths. It is thus possible to effectively enhance heat dissipation. 
     As in the first preferred embodiment, the shield film  57  is also connected to a ground connection electrode  12 C. The shield film  57  is a non-metallic film and has a low electrical resistance. For this reason, the shield film  57  does not electrically connect the ground connection electrode  12 C and the hot connection electrode  53 C. The electrical characteristics of the acoustic wave device  50  are thus unlikely to degrade. 
     In the present preferred embodiment, the shield film  57  is connected to both the ground connection electrode  12 C and the hot connection electrode  53 C. Thus, the heat dissipation can be further enhanced. Note that the shield film  57  only needs to be connected to at least one of the ground connection electrode  12 C and the hot connection electrode  53 C. This allows effective enhancement of the heat dissipation. 
     A non-metal high in heat dissipation, such as silicon nitride, is preferably used as a material for the shield film  57 . In this case, the heat dissipation can be more reliably enhanced. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.