Patent Publication Number: US-2005133901-A1

Title: System and method for delivering power to a semiconductor device

Description:
TECHNICAL FIELD OF THE INVENTION  
      The present invention relates generally to semiconductor devices and, more particularly, to a system and method for delivering power to a semiconductor device.  
     BACKGROUND OF THE INVENTION  
      The size of integrated circuit packages have grown in recent years. Increasing the size of package substrates results in levels of substrate warping which are unacceptable. Warping causes problems with the installation and retainment of the package on the motherboard. Such problems can lead to failure and disposal of the motherboards, which can be very expensive. In addition, delivery of power and ground to the substrate through the motherboard has become problematic due to the large number of power and ground connections required by the package substrate.  
     SUMMARY OF THE INVENTION  
      The present invention provides a system and method for delivering power to a semiconductor device that substantially eliminates or reduces at least some of the disadvantages and problems associated with previous systems and methods.  
      In accordance with a particular embodiment of the present invention, a system for delivering power to a semiconductor device includes a package substrate comprising a substrate top surface and a substrate bottom surface. The system includes a connector formed on the substrate top surface and a cable coupled to the connector. The cable is operable to deliver power and ground to a top of the package substrate.  
      The cable may be further operable to deliver input/output (I/O) to the top of the package substrate. The cable may comprise a single metal layer or multi-metal-layer polyimide cable or a ribbon cable. The cable may be formed on the substrate top surface using a solder reflow process. The system may also include at least one additional connector formed on the substrate top surface and at least one additional cable coupled to the at least one additional connector. The at least one additional cable may be operable to deliver power to the top of the package substrate.  
      In accordance with another embodiment, a method for delivering power to a semiconductor device includes forming a connector on a substrate top surface of a package substrate and coupling the package substrate to a printed circuit board. The method includes coupling a cable to the connector and delivering power and ground to a top of the package substrate through the cable. Forming a connector on the substrate top surface may comprise forming a connector on the substrate top surface using a solder reflow process in the semiconductor device manufacturing process.  
      In accordance with yet another embodiment, a printed circuit board comprises a plurality of package substrates formed upon the printed circuit board. Each package substrate comprises a substrate top surface. The printed circuit board includes a plurality of connectors formed directly upon each substrate top surface and a cable coupled to each connector. Each cable is operable to deliver power and ground to a top of at least one of the plurality of package substrates. The printed circuit board may further comprise a power regulation module coupled to at least one of the cables. The power regulation module may be operable to regulate the power delivered to the top of at least one of the plurality of package substrates.  
      Technical advantages of particular embodiments of the present invention include a connector merged with a package substrate so that a cable coupled with the connector may be used to deliver power, ground and I/O to the top of the package substrate. Thus, a manufacturer may be able to reduce the number of power and ground layers formed in the printed circuit board. Accordingly, the cost and labor of manufacturing the printed circuit board may be reduced. Moreover, the conducting metal in the cable may be thicker than the metal in the power and ground layers of the printed circuit board, thus increasing the efficiency of the conducting metal used to deliver power and ground to the package substrate. Moreover, use of power and ground connections on the top surface of the substrate results in a concomitant reduction in required number of terminals on the bottom of the substrate, allowing a reduction in the substrate size.  
      Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of particular embodiments of the invention and their advantages, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  illustrates a cross-sectional view of a partially completed semiconductor device with a connector, in accordance with an embodiment of the present invention;  
       FIG. 2  illustrates a cross-sectional view of a partially completed semiconductor device with two connectors, in accordance of a particular embodiment of the present invention;  
       FIG. 3  is a top view of a printed circuit board with package substrates and a power regulation module formed on the printed circuit board, in accordance of a particular embodiment of the present invention;  
       FIG. 4  is a top view illustrating a printed circuit board with package substrates formed on the printed circuit board, in accordance with another embodiment of the present invention; and  
       FIG. 5  is a flowchart illustrating a method for delivering power to a semiconductor device, in accordance with a particular embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  illustrates a cross-sectional view of a partially completed semiconductor device  10 , in accordance with an embodiment of the present invention. Semiconductor device  10  includes a printed circuit board  12 . A package substrate  14  is coupled to printed circuit board  12  by a plurality of solder balls  16  to provide electrical connectivity between circuitry associated with printed circuit board  12  and circuitry associated with package substrate  14 . For example, solder balls  16  may contact metal or other conductive material at both printed circuit board  12  and package substrate  14  such that solder balls  16  may provide electrical conductivity between circuitry associated with printed circuit board  12  and package substrate  14 . In particular embodiments, solder balls  16  may be used for power, ground and input/output (I/O) connections. Additionally, although a specific number of solder balls  16  are illustrated, semiconductor device  10  may include any suitable number of solder balls  16  according to particular needs. Semiconductor device  10  also includes semiconductor chip  22  and lid  24  formed upon package substrate  14 .  
      A surface mount connector  18 , such as a low inductance connector, is formed onto package substrate  14 . In particular embodiments connector  18  may be merged with package substrate  14  using a solder reflow process. Using a solder reflow process to merge connector  18  directly with package substrate  14  enables the connector to be formed on package substrate  14  during the normal manufacturing process of package substrate  14 . For example, package substrate  14  may be put through a furnace in order to include components such as chip capacitors with a substrate, and such furnace process may be utilized to merge connector  18  with package substrate  14 .  
      The formation of connector  18  upon package substrate  14  enables power, ground and I/O to be brought directly into package substrate  14  through a cable  20 . In particular embodiments, cable  20  may comprise a flex cable, such as a low inductance ribbon cable, or a single or multi-layer polyimide cable. Other embodiments may include other types of cables for bringing power, ground and/or I/O to package substrate  14  through connector  18 . In some embodiments, cable  20  may include bypass capacitors so that power regulation and filtering may be performed through the cable. Capacitors may be distributed along the top of the cable to enable decoupling of noise from power and ground planes of the cable.  
      In particular embodiments, the power and ground brought directly to package substrate  14  through cable  20  may comprise core power and ground. Such core power and ground supplies the circuitry for the die. In some embodiments, core power and ground may comprise approximately 15% to 40% of the total power and ground current of the package.  
      The ability to supply power, ground and I/O to the top of package substrate  14  through cable  20  may enable a manufacturer to reduce the number of power and ground layers formed in the printed circuit board. Thus, the cost and labor of manufacturing the printed circuit board may be reduced. Moreover, the conducting metal in the cable may be thicker than the metal in the power and ground layers of the printed circuit board, thus increasing the efficiency of the conducting metal. For example, metal in the printed circuit board may have a thickness of approximately 12 microns, while metal in a polyimide cable may have a thickness of approximately 25 microns. A ribbon cable may include metal having a thickness of approximately 500 microns.  
       FIG. 2  illustrates a cross-sectional view of a partially completed semiconductor device  11 , in accordance with another embodiment of the present invention. Like semiconductor device  10  of  FIG. 1 , semiconductor device  11  includes a package substrate  14  coupled to printed circuit board  12  by a plurality of solder balls  16 . Semiconductor device  11  includes semiconductor chip  22  and lid  24  formed upon package substrate  14 . Semiconductor device  11  also includes connector  18  formed onto package substrate  14 . Cable  20  delivers power, ground and I/O directly into package substrate  14 . Semiconductor device  11  additionally includes connector  19  formed onto package substrate  14 . Cable  21  couples to connector  19  to deliver power, ground and I/O directly into substrate  14 . Thus, as illustrated, some embodiments may include more than one cable for supplying power and ground to a package substrate through surface mount connectors merged directly with the substrate.  
       FIG. 3  is a top view of a printed circuit board  31  with package substrates  30  and a power regulation module  36  formed on the printed circuit board, in accordance of a particular embodiment of the present invention. Package substrates  30  include connectors  32  formed on the package substrates for bringing core power and ground to the top of package substrates  30 . The core power and ground is brought to the top of package substrates  30  through a cable  34  coupled to connectors  32 . A power regulation module  36  regulates the core power brought to the top of package substrates  30 .  FIG. 3  also includes balls  33  which serve only to illustrate the interconnection between package substrates  30  and printed circuit board  31  on the bottom surface of the package substrates.  
       FIG. 4  is a top view illustrating a printed circuit board  51  with package substrates  50  formed on the printed circuit board, in accordance with another embodiment of the present invention. Package substrates  50  include connectors  52 A and  52 B for bringing core power and ground to the top of package substrates  50 . Connectors  52 A are coupled directly to package substrates  50 , while connectors  52 B are coupled directly to printed circuit board  51 . Power is brought from connectors  52 B to connectors  52 A through cables  54  coupled between connectors  52 A and  52 B. It should be understood that particular embodiments may utilize any combination of shorter cables  54  of  FIG. 4  and longer cables  34  of  FIG. 3  according to particular needs. As discussed above with respect to  FIG. 3 ,  FIG. 4  also includes balls which serve only to illustrate the interconnection between package substrates  50  and printed circuit board  51  on the bottom surface of the package substrates.  
       FIG. 5  is a flowchart illustrating a method for delivering power to a semiconductor device, in accordance with a particular embodiment of the present invention. The method begins at step  100  where a connector is formed on a package substrate. The package substrate comprises a substrate top surface and a substrate bottom surface. The connector may be merged directly with the substrate top surface during the normal package manufacturing process. For example, the connector may be formed upon the substrate top surface using a solder reflow process. At step  102 , the package substrate is coupled to a printed circuit board. The package substrate may be formed upon solder balls coupled to the printed circuit board.  
      At step  104 , a cable is coupled to the connector. The cable may comprise a single or multi-layer polyimide cable. In some embodiments, the cable may comprise a flex cable or a ribbon cable. At step  106 , power and ground is delivered to the top of the package substrate through the cable. At step  108 , I/O is delivered to the top of the package substrate through the cable.  
      Some of the steps illustrated in  FIG. 5  may be combined, modified or deleted where appropriate, and additional steps may also be added to the flowchart. Additionally, steps may be performed in any suitable order without departing from the scope of the invention.  
      Although the present invention has been described in detail with reference to particular embodiments, it should be understood that various other changes, substitutions, and alterations may be made hereto without departing from the spirit and scope of the present invention. For example, although the present invention has been described with reference to a number of elements formed upon a printed circuit board and a package substrate, it should be understood that printed circuit boards and package substrates in accordance with particular embodiments may include other elements in order to accommodate particular needs. The present invention contemplates great flexibility in the arrangement of these elements as well as their internal components.  
      Numerous other changes, substitutions, variations, alterations and modifications may be ascertained by those skilled in the art and it is intended that the present invention encompass all such changes, substitutions, variations, alterations and modifications as falling within the spirit and scope of the appended claims. Moreover, the present invention is not intended to be limited in any way by any statement in the specification that is not otherwise reflected in the claims.