Patent Publication Number: US-7723843-B2

Title: Multi-package module and electronic device using the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation of pending U.S. patent application Ser. No. 11/243,121, filed Oct. 4, 2005 and entitled “Multi-Package Module and Electronic Device Using the Same”, which is hereby incorporated by reference. 

   BACKGROUND 
   The invention relates to an electronic package and in particular to a package substrate for multi-package module for thermal dissipation and an electronic device using the same. 
   Demand for small, high performance portable electronic products such as cell phones, mobile computers, and the like have driven the industry to increase integration on individual semiconductor dice. Accordingly, the industry is achieving high integration by turning to 3D packaging by combining assembly technologies including wire bonding or flip chip to stack die packages to form a multi-package module (MPM). 
   MPM, a current assembly technology, integrates different functions of dice, such as microprocessors or memory, logic, optic ICs, instead of placing individual packages onto a large printed circuit board (PCB). MPM, however, has a much higher power density than an individual single die package. Thus, thermal management is a key factor in its successful development. 
     FIG. 1  illustrates a conventional electronic device  100  with an MPM. The electronic device  100  comprises a MPM  20  mounted on a PCB  101  and comprising a package substrate  12 . The upper and lower surfaces of the package substrate  12  have dice  16  and  14  with different functions thereon, respectively, to create the MPM  20 . For example, the die  16  is mounted on the upper surface of the package substrate  12  by bumps (or solder balls)  10 ′of a package substrate  12 ′. The die  14  is mounted on the lower surface of the package substrate  12  by flip chip. The lower surface of the package substrate  12  comprises a plurality of bumps  10  thereon to correspondingly connect to the bonding pads (not shown) on the PCB  101 . In the MPM  20 , heat generated from the die  16  can be dissipated by radiation and convection. The gap g between the die  14  and the PCB  101  is too narrow, however, to dissipate the heat generated from thereof by radiation and convection. Accordingly, the heat generated from the die  14  is dissipated by conduction only. Typically, a metal layer  102  is disposed on the PCB  101  corresponding to the die  14  and connected to the die  14  by a heat conductive paste  22 . That is, thermal dissipation is accomplished by a thermal conductive path created by the heat conductive paste  22 , the metal layer  102  and the PCB  101 . 
   Passive cooling, however, cannot provide adequate thermal dissipation at a higher rate for high power dice which may generate higher heat. That is, generated heat cannot be rapidly dissipated from dice by conducting the heat to the PCB through the heat conductive paste and the metal layer. 
   SUMMARY 
   A package substrate for multi-package module and an electronic device using the same are provided. An embodiment of a package substrate for a multi-package module comprises a substrate having a die region and at least one thermal channel region outwardly extending to an edge of the substrate from the die region. An array of bumps is arranged on the substrate except in the die and thermal channel regions, wherein the interval between the bumps is narrower than the width of the thermal channel region. 
   An exemplary embodiment of an electronic device comprises a package substrate, comprising a substrate having a die region and at least one thermal channel region outwardly extending to an edge of the substrate from the die region and an array of bumps arranged on the substrate except in the die and thermal channel regions. A circuit board comprises a plurality of bonding pads correspondingly connecting to the bumps. A heat sink is disposed between the circuit board and the package substrate, comprising a first portion corresponding to the die region and a second portion adjacent to the first portion, extending to the circuit board outside the package substrate along the thermal channel region. 
   An embodiment of an electronic device, additionally, comprises a package substrate, comprising a substrate having a die region and at least one thermal channel region outwardly extending to an edge of the substrate from the die region and an array of bumps arranged on the substrate except in the die and thermal channel regions. A circuit board comprises a plurality of bonding pads correspondingly connecting to the bumps and a metal layer underlying the package substrate. The metal layer comprises a first portion corresponding to the die region, a second portion adjacent to the first portion, extending to the circuit board outside the package substrate along the thermal channel region and a third portion adjacent to the end of the second portion. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, given by way of illustration only and thus not intended to be limitative of the invention. 
       FIG. 1  is a cross-section of a conventional electronic device with a multi-package module. 
       FIG. 2A  is a bottom plane view of an embodiment of a multi-package module. 
       FIG. 2B  is a cross-section along line  2 B- 2 B of  FIG. 2A . 
       FIG. 2C  is a bottom plane view of an embodiment of a multi-package module. 
       FIG. 3A  is a bottom plane view of an embodiment of electronic device with a multi-package module of the invention. 
       FIG. 3B  is a cross-section along line  3 B- 3 B of  FIG. 3A . 
       FIG. 4A  is a bottom plane view of an embodiment of electronic device with a multi-package module. 
       FIG. 4B  is a cross-section along line  4 B- 4 B of  FIG. 4A . 
   

   DETAILED DESCRIPTION 
   A package substrate for multi-package module (MPM) and an electronic device using the same will now be described in greater detail. 
     FIGS. 2A and 2B  illustrate an exemplary embodiment of an MPM, wherein  FIG. 2A  is a bottom plane view of the MPM and  FIG. 2B  is a cross-section along line  2 B- 2 B of  FIG. 2A . The MPM  40  comprises a package substrate  32 . The lower surface of the package substrate  32  has a die region  32   a  and at least one thermal channel region  32   b  and the upper surface of the package substrate  32  also has a die region (not shown). Here, the lower surface represents a surface facing the surface of a circuit board, such as a printed circuit board (PCB) and the upper surface represents the surface opposite to the lower surface. In this embodiment, the package substrate  32  may comprise plastic, ceramic, inorganic or organic material. Typically, the die region  32   a  is substantially at the center of the package substrate  32 . Unlike the conventional package substrate, the package substrate  32  comprises at least one thermal channel region  32   b  outwardly extending to an edge of the package substrate  32  from the die region  32   a.  In some embodiments, the thermal channel region  32   b  may extend to an opposite edge of the package substrate  32  across the die region  32   a,  as shown in  FIG. 2C . It will be apparent to those skilled in the art that the package substrate  32  may comprise one or more thermal channel regions extending to the edges of the package substrate  32  along different directions from the die region  32   a  and it is to be understood that the invention is not limited to  FIGS. 2A and 2C . 
   Dice  34  and  36  with different functions may be respectively mounted in the die region  32   a  of the lower surface and that of the upper surface of the package substrate  32  by the same or different electronic packages. For example, dice  34  and  36  may respectively be mounted on the package substrate  32  by flip chip or wire bonding. 
   An array of bumps  30 , such as metal bump, solder balls, signal balls or the like, is arranged on the lower surface of the package substrate  32  except in the die region  32   a  and the thermal channel region  32   b,  to transport signals to external circuits from the dice  34  and  36 . The interval between the bumps  30  is narrower than the width of the thermal channel region  32   b.    
     FIGS. 3A and 3B  illustrate an embodiment of an electronic device with an MPM of the invention, wherein  FIG. 3A  is a bottom plane view of the electronic device and  FIG. 3B  is a cross-section along line  3 B- 3 B of  FIG. 3A , and the same reference numbers as  FIGS. 2A and 2B  are used, wherefrom like descriptions are omitted. The electronic device  200  comprises MPM  40 , a circuit board  201  and a heat sink  203 . As mentioned, the MPM  40  comprises a package substrate  32  and dice  34  and  36 . The package substrate  32  comprises an array of bumps  30  arranged on the lower surface of the package substrate  32  except in the die region  32   an  and the thermal channel region  32   b.  Dice  34  and  36  are respectively disposed on the die region  32   a  of the lower surface and that of the upper surface of the package substrate  32 . 
   A circuit board  201 , such as a PCB, comprises a plurality of bonding pads  202  correspondingly connected to the bumps  30 , thereby electronically connecting the circuit board  201  and the dice  34  and  36 . Typically, the circuit board  201  comprises at least one or more metal layers and at least one or more insulating layers, in which the metal layer may serve as a signal layer, a power layer, and/or a grounding layer. In order to simplify the diagram, a flat substrate is depicted. 
   A heat sink  203  is disposed on the circuit board  201  and between the circuit board  201  and the package substrate  32 , comprising first and second portions  204  and  206 . The first portion  204  corresponds to the die region  32   a  and connected to the die  34  by a heat conductive paste  42 . The second portion  206  is adjacent to the first portion  204  and extends outside the package substrate  32  along the thermal channel region  32   b . In this embodiment, the heat sink  203  comprises gold, silver or copper. Moreover, the first portion  204  of the heat sink  203  may partially or fully overlap the die  34 . Here, only an example of the full overlap is depicted. Note that the shape of the heat sink  203  may be varied with the design of the thermal channel region  32   b.    
   A thermal dissipation module  208  is disposed on the second portion  206  of the heat sink  203  outside the package substrate  32 , providing an active thermal dissipation. In this embodiment, the thermal dissipation module  208  may comprise a fan  207  and an underlying heat dissipating component  205 , such as a heat plate or pipe. 
   According to the electronic device  200  of the invention, the thermal channel region  32   b  can be formed by rearranging the bumps  30 . Moreover, since the heat sink  203  may extend outside the package substrate  32  along the thermal channel region  32   b,  the heat generated from the die  34  on the lower surface of the package substrate  32  can be effectively and rapidly dissipated to the ambient environment by radiation, convection and conduction, as shown by the arrows in  FIG. 3B . Additionally, if the die  34  is a high power die, the heat can be dissipated quickly by the fan  207 . Compared to conventional thermal dissipation by conduction of the circuit board, the electronic device  200  with MPM  40  of this embodiment has better thermal dissipation and a higher thermal dissipation rate. 
     FIGS. 4A and 4B  illustrate an embodiment of an electronic device with an MPM, wherein  FIG. 4A  is a bottom plane view of the electronic device and  FIG. 4B  is a cross-section along line  4 B- 4 B of  FIG. 3A . The same reference numbers as  FIGS. 3A and 3B  are used, wherefrom like descriptions are omitted. Unlike the embodiment of  FIGS. 3A and 3B , the thermal conductive path is formed by defining a metal layer  209  of the circuit board  201 . In this embodiment, the metal layer  209  comprises a first portion  210 , a second portion  212  and a third portion  214 . The first portion  210  of the metal layer  209  corresponds to the die region  32   a  and is connected to the die  34  by a heat conductive paste  42 . The second portion  212  of the metal layer  209  is adjacent to the first portion  210  and extends outside the package substrate  32  along the thermal channel region  32   b.  The third portion  214  of the metal layer  209  is adjacent to the end of the second portion  212 . The first and second portions  210  and  212  of the metal layer  209  serve as a heat sink to conduct heat generated from the die  34  outside the package substrate  32 . The third portion  214  of the metal layer  209  serves as a heat dissipating component to dissipate heat to the ambient environment by a fan  207  disposed thereon, as shown by the arrows in  FIG. 4B . 
   In this embodiment, since the metal layer  209  may extend outside the package substrate  32  along the thermal channel region  32   b , the heat generated from the die  34  on the lower surface of the package substrate  32  can be effectively and rapidly dissipated to the ambient environment by radiation, convection and conduction. Compared to the conventional thermal dissipation by conduction of the circuit board, the electronic device  200  with MPM  40  has better thermal dissipation and a higher thermal dissipation rate. Moreover, since the metal layer  209  is included in the circuit board  201 , no additional heat sink and heat dissipating component are required. 
   While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.