Abstract:
A power amplifier module includes a substrate, a power amplifier having a first surface on which an electrode is defined and a second surface opposite the first surface, the first surface faces a principal surface of the substrate, a surface acoustic wave duplexer having a first surface on which an electrode is defined and a second surface opposite the first surface, the first surface faces the principal surface of the substrate, a heat dissipation unit defined on another principal surface of the substrate, a heat dissipation path that connects a connecting portion between the power amplifier and the principal surface to the heat dissipation unit, an insulating resin that covers the power amplifier and the surface acoustic wave duplexer, a conductive shield that covers the insulating resin, and a first conductive unit defined on the second surface of the surface acoustic wave duplexer and electrically connected to the conductive shield.

Description:
[0001]    This is a continuation of International Application No. PCT/JP2015/079742 filed on Oct. 21, 2015 which claims priority from Japanese Patent Application No. 2015-009763 filed on Jan. 21, 2015. The contents of these applications are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
     Technical Field 
       [0002]    The present disclosure relates to a power amplifier module. 
         [0003]    In a radio communication device such as a cellular phone, a power amplifier (PA) is used to amplify power of a radio frequency (RF) signal to be transmitted to a base station. In the radio communication device, furthermore, a duplexer is used to separate a reception signal from a base station and a transmission signal to the base station to share an antenna between transmission and reception. Examples of the duplexer include a surface acoustic wave (SAW) duplexer (for example, Patent Document 1). 
         [0004]    In recent years, with increased compactness of radio communication devices, power amplifier modules in which a power amplifier and a duplexer are packaged as a single product have attracted attention (for example, Patent Document 2). Furthermore, face-down mounting is known as a mounting method for making a module compact (for example, Patent Document 3). 
         [0005]    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-120966 
         [0006]    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-311230 
         [0007]    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2007-266539 
       BRIEF SUMMARY 
       [0008]    In a power amplifier module, heat from a heat-producing component such as a power amplifier needs to be dissipated. For example, in a semiconductor device disclosed in Patent Document 3, an emitter electrode of a power amplifier mounted face-down on a front surface of a package substrate is connected to a thermal via formed in the package substrate, resulting in heat of the power amplifier being dissipated from a rear surface of the package substrate. In this manner, it is possible to dissipate the heat of the face-down mounted power amplifier from the rear surface of the package substrate through the thermal via. 
         [0009]    However, as disclosed in, for example, Patent Document 1, a SAW duplexer has a cavity that is an operating space of an interdigital electrode unit serving as a heating element. In a case where the SAW duplexer is mounted face-down, it is difficult to dissipate heat through a thermal via since the cavity exists between the interdigital electrode unit and the package substrate. 
         [0010]    The present disclosure has been made in view of the circumstances described above, and the present disclosure improves the heat dissipation capability of a power amplifier module including a power amplifier and a SAW duplexer. 
         [0011]    A power amplifier module according to an aspect of the present disclosure includes a substrate having first and second principal surfaces, a power amplifier having a first surface on which an electrode is defined and a second surface opposite the first surface, the power amplifier being mounted so that the first surface faces the first principal surface of the substrate, a surface acoustic wave duplexer having a first surface on which an electrode is defined and a second surface opposite the first surface, the surface acoustic wave duplexer being mounted so that the first surface faces the first principal surface of the substrate, a heat dissipation unit defined on the second principal surface of the substrate, a heat dissipation path that connects at least part of a connecting portion between the power amplifier and the first principal surface to the heat dissipation unit, an insulating resin that covers the power amplifier and the surface acoustic wave duplexer, a conductive shield that covers a surface of the insulating resin, and a first conductive unit defined on the second surface of the surface acoustic wave duplexer and electrically connected to the conductive shield. 
         [0012]    According to the present disclosure, the heat dissipation capability of a power amplifier module including a power amplifier and a SAW duplexer can be improved. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]      FIG. 1  is a diagram illustrating a configuration of a power amplifier module  10 A according to an embodiment of the present disclosure. 
           [0014]      FIG. 2A  is a diagram illustrating a face-down mounting step in a process of manufacturing the power amplifier module  10 A. 
           [0015]      FIG. 2B  is a diagram illustrating a wire forming step in the process of manufacturing the power amplifier module  10 A. 
           [0016]      FIG. 2C  is a diagram illustrating a resin sealing step in the process of manufacturing the power amplifier module  10 A. 
           [0017]      FIG. 2D  is a diagram illustrating a resin grinding step in the process of manufacturing the power amplifier module  10 A. 
           [0018]      FIG. 2E  is a diagram illustrating a conductive shield forming step in the process of manufacturing the power amplifier module  10 A. 
           [0019]      FIG. 3  is a diagram illustrating a configuration of a power amplifier module  10 B, which is an exemplary modification of the power amplifier module  10 A. 
           [0020]      FIG. 4  is a diagram illustrating a configuration of a power amplifier module  10 C, which is an exemplary modification of the power amplifier module  10 A. 
           [0021]      FIG. 5  is a diagram illustrating a configuration of a power amplifier module  10 D, which is an exemplary modification of the power amplifier module  10 A. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    An embodiment of the present disclosure will be described hereinafter with reference to the drawings.  FIG. 1  is a diagram illustrating a configuration of a power amplifier module  10 A according to an embodiment of the present disclosure. 
         [0023]    As illustrated in  FIG. 1 , the power amplifier module  10 A includes a power amplifier  30  and a SAW duplexer  40 , which are mounted face-down on a package substrate  20 . The power amplifier  30  and the SAW duplexer  40  are covered with an insulating resin  50 . The insulating resin  50  is formed of an epoxy resin, for example. A surface of the insulating resin  50  is covered with a conductive shield  60 . The conductive shield  60  is formed of a metal such as gold, silver, copper, or aluminum, for example. 
         [0024]    The package substrate  20  has a top surface  21  (a first principal surface) and a bottom surface  22  (a second principal surface). Wiring patterns  23   a  to  23   e  are defined on the top surface  21  of the package substrate  20 . Further, electrodes  24   a  to  24   c  are defined on the bottom surface  22  of the package substrate  20 . In addition, the package substrate  20  has thermal vias  25   a  and  25   b  extending therethrough from the top surface  21  to the bottom surface  22 . The thermal vias  25   a  and  25   b  (heat dissipation paths) electrically connect the wiring pattern  23   b  and the electrode  24   b  to each other. The electrode  24   b  is a ground electrode to which a ground potential is applied, and also serves as a heat dissipation unit. The package substrate  20  also has ground wiring  26  defined therein. The ground wiring  26  is connected to the electrode  24   b  through, for example, the thermal vias  25   a  and  25   b.    
         [0025]    The power amplifier  30  is a component that amplifies an RF signal to be transmitted to a base station, and includes a transistor for power amplification, for example. The power amplifier  30  has a surface  33  (a first surface) on which electrodes  31   a  to  31   c  are defined, and a surface  32  (a second surface) opposite the surface  33 . The power amplifier  30  is mounted face-down on the top surface  21  of the package substrate  20  via bumps  34   a  to  34   c  connected to the electrodes  31   a  to  31   c . For example, the electrode  31   b  is connected to an emitter of a transistor constituting the power amplifier  30 , and is electrically connected to the electrode  24   b  via the bump  34   b , the wiring pattern  23   b , and the thermal vias  25   a  and  25   b . Thus, heat produced at the emitter, which is a portion of the power amplifier  30  from which heat is generated, is transferred to the electrode  24   b  and is then dissipated thereby. 
         [0026]    A metal layer  35  is defined on the surface  32  of the power amplifier  30 , which is positioned closer to the conductive shield. The metal layer  35  is formed of a metal such as gold, silver, copper, aluminum, or titanium, for example. The metal layer  35  has a wire  36  (a conductive path) defined thereon. The wire  36  is cut on the conductive shield  60  side, and has cut portions  37   a  and  37   b  connected to the conductive shield  60 . That is, the metal layer  35  and the wire  36  form a conductive unit (a second conductive unit) electrically connected to the conductive shield  60 . The wire  36  is formed of a metal such as gold, silver, copper, or aluminum, for example. Since the metal layer  35  is defined on the surface  33  of the power amplifier  30 , heat produced by the power amplifier  30  is also dissipated via the metal layer  35 . Since the metal layer  35  is connected to the conductive shield  60  via the wire  36 , the heat dissipation effect can be further enhanced. 
         [0027]    Further, for example, on side surfaces of the package substrate  20 , the conductive shield  60  is connected to the ground wiring  26 . Accordingly, the potential of the metal layer  35  of the power amplifier  30  is fixed to a ground level. This makes it possible to stabilize the operation of the power amplifier  30 . 
         [0028]    The SAW duplexer  40  is a component that separates a reception signal from a base station and a transmission signal to the base station. The SAW duplexer  40  has a surface  43  (a first surface) on which electrodes  41   a  and  41   b  are defined, and a surface  42  (a second surface) opposite the surface  43 . The SAW duplexer  40  is mounted face-down on the top surface  21  of the package substrate  20  via bumps  44   a  and  44   b  connected to the electrodes  41   a  and  41   b . The SAW duplexer  40  has an interdigital electrode unit  45 . The SAW duplexer  40  further has a cavity  46  that is an operating space of the interdigital electrode unit  45 . 
         [0029]    A metal layer  47  (a first conductive unit) is defined on the surface  43  of the SAW duplexer  40 , which is positioned closer to the conductive shield. The metal layer  47  is formed of a metal such as gold, silver, copper, aluminum, or titanium, for example. The metal layer  47  has a wire  48  (a conductive path) defined thereon. The wire  48  is cut on the conductive shield  60  side, and has cut portions  49   a  and  49   b  connected to the conductive shield  60 . That is, the metal layer  47  and the wire  48  form a conductive unit (a first conductive unit) electrically connected to the conductive shield  60 . The wire  48  is formed of a metal such as gold, silver, copper, or aluminum, for example. Since the metal layer  47  is defined on the surface  43  of the SAW duplexer  40 , heat produced by the SAW duplexer  40  is dissipated via the metal layer  47 . Since the metal layer  47  is connected to the conductive shield  60  via the wire  48 , the heat dissipation effect can be further enhanced. 
         [0030]    Further, for example, on the side surfaces of the package substrate  20 , the conductive shield  60  is connected to the ground wiring  26 . Accordingly, the potential of the metal layer  47  of the SAW duplexer  40  is fixed to a ground level. This makes it possible to stabilize the operation of the SAW duplexer  40 . In the SAW duplexer  40 , in particular, a reception signal from a base station and a transmission signal to the base station may be crossed via the metal layer  47 . Hence, fixing the metal layer  47  to a ground level makes it possible to suppress such crossing (cross talk). 
         [0031]    Next, a process of manufacturing the power amplifier module  10 A will be described with reference to  FIGS. 2A to 2E . 
         [0032]    First, as illustrated in  FIG. 2A , the power amplifier  30  and the SAW duplexer  40  are mounted face-down on the top surface  21  of the package substrate  20 . 
         [0033]    Then, as illustrated in  FIG. 2B , the wire  36  is formed on the metal layer  35 , which is defined on the surface  32  of the power amplifier  30 , by wire bonding. Likewise, the wire  48  is formed on the metal layer  47 , which is defined on the surface  42  of the SAW duplexer  40 , by wire bonding. A plurality of wires  36  and a plurality of wires  48  may be formed. The wires  36  and  48  may be formed on the metal layers  35  and  47  prior to face-down mounting. 
         [0034]    The wire  36  may also be formed so as to be connected to a GND electrode (not illustrated) on the first principal surface of the package substrate  20  from the metal layer  35  defined on the surface  32  of the power amplifier  30 . The wire  48  of the SAW duplexer is also formed in a similar way. 
         [0035]    Thereafter, as illustrated in  FIG. 2C , the power amplifier  30  and the SAW duplexer  40  are covered (sealed) by the insulating resin  50 . The wires  36  and  48  are also covered by the insulating resin  50 . 
         [0036]    Subsequently, as illustrated in  FIG. 2D , a surface of the insulating resin  50  is ground with a grinder  100  to expose the wires  36  and  48 . Specifically, a portion of the wire  36  is cut and the cut portions  37   a  and  37   b  are exposed. Likewise, a portion of the wire  48  is cut and the cut portions  49   a  and  49   b  are exposed. The wires  36  and  48  may be exposed in such a way that the wires  36  and  48  are not cut. 
         [0037]    Finally, the conductive shield  60  is formed so as to cover the insulating resin  50 . Thus, the conductive shield  60  is connected to the metal layer  35  via the cut portions  37   a  and  37   b  of the wire  36 . Further, the conductive shield  60  is connected to the metal layer  47  via the cut portions  49   a  and  49   b  of the wire  48 . 
         [0038]    Through the steps described above, the power amplifier module  10 A illustrated in  FIG. 1  can be manufactured. 
         [0039]      FIG. 3  is a diagram illustrating a configuration of a power amplifier module  10 B, which is an exemplary modification of the power amplifier module  10 A. The same elements as those of the power amplifier module  10 A are assigned the same numerals and are not described herein. 
         [0040]    The power amplifier module  10 B includes a conductive unit  70  and a conductive paste  71 , instead of the wire  36 . The conductive unit  70  (a conductive path) is a columnar metal or a metal pin, for example, and has a bottom surface connected to the metal layer  35  by using the conductive paste  71 . Further, a top surface of the conductive unit  70  is connected to the conductive shield  60 . The conductive unit  70  is a metal such as gold, silver, copper, or aluminum, for example. The conductive paste  71  is, for example, a material or solder made by mixing conductive particles of silver, carbon, or the like into resin. 
         [0041]    The power amplifier module  10 B includes a conductive unit  80  and a conductive paste  81 , instead of the wire  48 . The conductive unit  80  is columnar, for example, and has a bottom surface connected to the metal layer  47  by using the conductive paste  81 . Further, a top surface of the conductive unit  80  is connected to the conductive shield  60 . The conductive unit  80  is a metal such as gold, silver, copper, or aluminum, for example. The conductive paste  81  is, for example, a material or solder made by mixing conductive particles of silver, carbon, or the like into resin. 
         [0042]    In the power amplifier module  10 B, the use of the conductive units  70  and  80  instead of the wires  36  and  48  improves the heat dissipation capability of the power amplifier  30  and the SAW duplexer  40 . In addition, similarly to the power amplifier module  10 A, the conductive shield  60  is connected to the ground wiring  26 , thus making it possible to stabilize the operation of the power amplifier  30  and the SAW duplexer  40 . 
         [0043]      FIG. 4  is a diagram illustrating a configuration of a power amplifier module  10 C, which is an exemplary modification of the power amplifier module  10 A. The same elements as those of the power amplifier module  10 A are assigned the same numerals and are not described herein. 
         [0044]    The power amplifier module  10 C does not include the wires  36  and  48  of the power amplifier module  10 A. Instead of them, the power amplifier  30  and the SAW duplexer  40  have holes  90  and  91  defined in upper portions thereof. The holes  90  and  91  are formed by, for example, applying a laser to the insulating resin  50  from above the power amplifier  30  and the SAW duplexer  40 . In a state where the holes  90  and  91  have been formed, surfaces of the metal layers  35  and  47  are exposed. Thereafter, the conductive shield  60  is formed by sputtering or the like, resulting in the conductive shield  60  and the metal layers  35  and  47  being connected to each other. 
         [0045]    In the power amplifier module  10 C, directly connecting the metal layers  35  and  47  to the conductive shield  60  improves the heat dissipation capability of the power amplifier  30  and the SAW duplexer  40 . In addition, similarly to the power amplifier module  10 A, the conductive shield  60  is connected to the ground wiring  26 , thus making it possible to stabilize the operation of the power amplifier  30  and the SAW duplexer  40 . 
         [0046]      FIG. 5  is a diagram illustrating a configuration of a power amplifier module  10 D, which is an exemplary modification of the power amplifier module  10 A. The same elements as those of the power amplifier module  10 A are assigned the same numerals and are not described herein. 
         [0047]    The power amplifier module  10 D does not include the wires  36  and  48  of the power amplifier module  10 A. Instead of them, the metal layers  35  and  47  have a larger thickness than those of the power amplifier module  10 A. Further, the top surfaces of the metal layers  35  and  47  are directly connected to the conductive shield  60 . 
         [0048]    In the power amplifier module  10 D, directly connecting the metal layers  35  and  47  to the conductive shield  60  improves the heat dissipation capability of the power amplifier  30  and the SAW duplexer  40 . In addition, similarly to the power amplifier module  10 A, the conductive shield  60  is connected to the ground wiring  26 , thus making it possible to stabilize the operation of the power amplifier  30  and the SAW duplexer  40 . 
         [0049]    The power amplifier modules  10 A to  10 D, which are examples of an embodiment of the present disclosure, have been described. 
         [0050]    In the power amplifier modules  10 A to  10 D, a conductive unit to be electrically connected to the conductive shield  60  is defined on a surface of the face-down mounted SAW duplexer  40 , which is positioned closer to the conductive shield  60 . Accordingly, heat of the SAW duplexer  40 , which is difficult to dissipate from the package substrate  20  side due to the influence of the cavity  46 , can be dissipated from the conductive shield  60  side. 
         [0051]    In the power amplifier module  10 A, the wire  48  is provided as a conductive path for connecting the metal layer  47  to the conductive shield  60 . The wire  48  can be easily formed on the metal layer  47  by wire bonding. Thus, the process of manufacturing the power amplifier module  10 A can be simplified. 
         [0052]    In the power amplifier module  10 A, furthermore, the insulating resin  50  is ground to cut a portion of the wire  48 , resulting in the cut portions  49   a  and  49   b  being formed. Then, the cut portions  49   a  and  49   b  are connected to the conductive shield  60 . As illustrated in  FIG. 2D , high-accuracy work is required to expose the wire  48  without cutting the wire  48  when the insulating resin  50  is ground. In the power amplifier module  10 A, in contrast, there is no need to stop the grinding of the insulating resin  50  at the portion where the wire  48  is not cut. Thus, the process of manufacturing the power amplifier module  10 A can be simplified. In addition, the cut portions  49   a  and  49   b  ensure that the wire  48  can be connected to the conductive shield  60 . 
         [0053]    In the power amplifier modules  10 A to  10 D, the conductive shield  60  is connected to the ground wiring  26  defined in the package substrate  20 . This allows the potential of the metal layer  47  of the SAW duplexer  40  to be fixed to a ground level and makes it possible to stabilize the operation of the SAW duplexer  40 . 
         [0054]    In the power amplifier modules  10 A to  10 D, furthermore, the power amplifier  30 , whose heat is dissipated from the bottom surface  22  of the package substrate  20  through the thermal vias  25   a  and  25   b , has also defined on a surface thereof, which is positioned closer to the conductive shield  60 , a conductive unit to be electrically connected to the conductive shield  60 . This makes it possible to improve the heat dissipation capability of the power amplifier  30 . 
         [0055]    In the power amplifier modules  10 A to  10 D, the power amplifier  30  also has defined on a surface thereof, which is positioned closer to the conductive shield  60 , a conductive unit to be electrically connected to the conductive shield  60 . However, the power amplifier  30  may not have such a conductive unit. 
         [0056]    The embodiments described above described above are intended for easy understanding of the present invention, and it is not intended to construe the present invention in a limiting fashion. Changes/improvements can be made to the present invention without departing from the gist of the present invention, and equivalents thereof are also included in the present invention. That is, the embodiments may be appropriately changed in design by those skilled in the art, and such changes also fall within the scope of the present invention so long as the changes include the features of the present invention. For example, the elements included in the embodiments and the arrangement, materials, conditions, shapes, sizes, and the like thereof are not limited to those described in the illustrated examples but can be changed as appropriate. In addition, the elements included in the embodiments can be combined as much as technically possible, and such combined elements also fall within the scope of the present invention so long as the combined elements include the features of the present invention. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               10 A,  10 B,  10 C,  10 D power amplifier module 
               20  package substrate 
               21  top surface 
               22  bottom surface 
               23   a ,  23   b ,  23   c ,  23   d ,  23   e  wiring pattern 
               24   a ,  24   b ,  24   c ,  31   a ,  31   b ,  31   c ,  41   a ,  41   b  electrode 
               25   a ,  25   b  thermal via 
               26  ground wiring 
               30  power amplifier 
               34   a ,  34   b ,  34   c ,  44   a ,  44   b  bump 
               35 ,  47  metal layer 
               36 ,  48  wire 
               37   a ,  37   b ,  49   a ,  49   b  cut portion 
               40  SAW duplexer 
               45  interdigital electrode unit 
               46  cavity 
               50  insulating resin 
               60  conductive shield 
               70 ,  80  conductive unit 
               71 ,  81  conductive paste 
               90 ,  91  hole