Abstract:
High-speed memory systems that consume a reduced amount of board space, have a low height or profile, or both. This reduction in board space and height may result in shorter signal paths from a board to a memory device, thereby improving the high-speed performance of the high-speed memory system. One example may provide a space-efficient memory system that consumes a reduced amount of board space. Space efficiency may gained by arraying memory devices on an interposer that mates with a socket attached to a board. Another example may provide a memory system that has a reduced height or profile. This reduced height may be achieved by employing a socket that accepts an interposer in a lateral or rotational direction.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application No. 61/408,147, filed Oct. 29, 2010, which is incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The number and types of electronic devices that are available to consumers has skyrocketed in recent years, and this increase shows no signs of abating. Laptop, netbook, desktop, tablet, and other computers, media players, portable media players, cell, media, and smart phones, and other devices have become ubiquitous. 
         [0003]    These devices require memory for storing data. Often this memory is realized in the form of a memory system that includes a card or board that may be inserted into a socket on a main or motherboard. Specifically, the card or board may include a number of memory devices. The card or board may be inserted into a socket that is fixed on a printed circuit board. This arrangement allows the memory to be replaced if it is, or becomes, defective. It also allows a user to upgrade the memory as the user&#39;s needs change. 
         [0004]    But these boards and sockets consume space in these electronic devices. This space may be in the form of area on a main or motherboard. The consumption of this main or motherboard area means that the electronic device either needs to be made larger to accommodate the boards and sockets, or the device may have a reduced functionality (or a combination of both) 
         [0005]    This space may also or alternatively be in the form of an increased height or profile. This increased height or profile means that the electronic device may need to have an increased thickness. 
         [0006]    Moreover, these boards and sockets may have long signal traces between the memory devices and components on a main or motherboard. These relatively long traces may increase coupling between signals, increase insertion losses, and degrade signal quality. 
         [0007]    Accordingly, what is needed are high-speed memory systems that have a reduced size. This reduction in size may be in terms of board area consumed by the memory system, the height of the memory system, or both. 
       SUMMARY 
       [0008]    Accordingly, embodiments of the present invention may provide high-speed memory systems that have a reduced size. This reduction in size may be in terms of board space consumed, or reduced height or profile, or both. This reduction in board space and height may result in shorter signal paths from a board to a memory device, thereby improving the high-speed performance of the high-speed memory system. 
         [0009]    An exemplary embodiment of the present invention may provide a space-efficient memory system that consumes a reduced amount of board space. Space efficiency may be gained by arraying memory devices on an interposer that mates with a socket attached to a board. 
         [0010]    In various embodiments of the present invention, the memory devices may be single memory chips, single packaged memories, stacked memory chips, stacked packaged memories, or other type of memory device. The memories may be arrayed in a square, rectangular, circular, or other manner. The array of memory devices may have openings for control, passive, or other components that may be required for operation of the memory devices. 
         [0011]    In various embodiments of the present invention, the interposer may be a printed circuit board or other appropriate substrate. The interposer may include traces on one or more layers to provide electrical connections between the memory devices and pins of the socket. Various embodiments of the present invention may provide interposer and socket combinations that have a reduced signal path length. This may lead to increased signal quality, reduced cross talk, and reduced insertion losses. In various embodiments of the present invention, these interposers may be at least approximately square, rectangular, circular, or they may have other shapes. 
         [0012]    In various embodiments of the present invention, the socket may be an FPGA ball grid array socket or other type of socket. The socket may be fixed to a motherboard of a desktop, laptop, netbook, tablet, or other type of computer, media device, portable media device or player, daughter board, or other type of board or card. 
         [0013]    Another exemplary embodiment of the present invention may provide a memory system that has a reduced height or profile. This reduced height may be achieved by employing a socket that accepts an interposer in a lateral or rotational direction. 
         [0014]    In one specific embodiment of the present invention, the socket and interposer may be at least approximately square or rectangular in shape. The interposer may have a number of memory devices and control, passive, or other components on a top side and a number of contacts on a bottom side. The interposer may be inserted in the socket by moving in a primarily lateral direction. Once inserted, the interposer may be held in place by tabs or flanges. 
         [0015]    In another specific embodiment of the present invention, the socket and interposer may be at least approximately circular in shape. The interposer may have a number of memory devices and control, passive, or other components on a top side and a number of contacts on a bottom side. The interposer may be placed in the socket and rotated until properly inserted. Once inserted, the interposer may be held in place by tabs or flanges. 
         [0016]    In various embodiments of the present invention, high-speed performance may be improved by reducing the length of signal paths from a board to a memory device. This reduction may occur as a result of the reduction of the size and height of memory systems consistent with embodiments of the present invention. Again, this may lead to increased signal quality, reduced cross talk, and reduced insertion losses. 
         [0017]    Various embodiments of the present invention may incorporate one or more of these and the other features described herein. A better understanding of the nature and advantages of the present invention may be gained by reference to the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  illustrates a high-speed memory system according to an embodiment of the present invention; 
           [0019]      FIG. 2  illustrates another memory system according to an embodiment of the present invention; 
           [0020]      FIG. 3  illustrates a memory system according to an embodiment of the present invention; 
           [0021]      FIG. 4  illustrates the insertion of an interposer into a socket of a memory system according to an embodiment of the present invention; 
           [0022]      FIG. 5  illustrates a memory system according to an embodiment of the present invention; 
           [0023]      FIG. 6  illustrates a memory system according to an embodiment of the present invention; 
           [0024]      FIG. 7  illustrates a circular socket consistent with an embodiment of the present invention; 
           [0025]      FIG. 8  illustrates a bottom of a circular interposer according to an embodiment of the present invention; and 
           [0026]      FIG. 9  illustrates electrical connections formed between and interposer and a socket according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0027]      FIG. 1  illustrates a high-speed memory system according to an embodiment of the present invention. This figure, as with the other included figures, is shown for illustrative purposes and does not limit either the possible embodiments of the present invention or the claims. High-speed memory system  100  may include interposer  110  and socket  120 . Interposer  110  may be arranged to mate with socket  120 . 
         [0028]    Interposer  110  may include a number of memory devices  112  on a top surface. In various embodiments of the present invention, memory devices, such as memory devices  112 , may be integrated circuit chips that are not packaged and are directly placed on interposer  120  or another substrate attached to interposer  120 . In such a situation, interposer  110  may include a cover (not shown), to protect memory devices  112 . In other embodiments of the present invention, memory devices  112  may be packaged integrated circuits. In still other embodiments of the present invention, memory devices  112  may be either stacked die or packaged integrated circuits. The top surface of interposer  110  may also include control circuits, passive component, or other circuitry for the operation of memory devices  112 . These passive components may include resistors and power supply decoupling capacitors. Other circuitry for other functions either related to, or separate from, memory devices  112  may also be included on one or both sides of interposer  110 . 
         [0029]    A bottom of interposer  110  may include a number of contacts. These contacts may be pins or balls arrayed as a pin grid array or ball grid array, though in various embodiments of the present invention, they may have different arrangements and they may be different types of contacts. In various embodiment of the present invention, interposer  110  may include an excess number of contacts over what is needed to support memory devices  112  and other circuitry that may be included on interposer  110 . These extra contacts may be used as a thermal vias to dissipate heat from memory devices  112 . These extra contacts may also be used as ground connections to provide isolation between signal pins. 
         [0030]    Interposer  110  may include a number of traces connecting memory devices  112  to contacts on a bottom of interposer  110 . These traces may be routed through interposer  110  on its various layers. Since the size of interposer  110  and socket  120  are reduced, trace lengths from memory devices  112  to pins of socket  120  may be shortened. This shortening may reduce cross-talk between signal lines, reduces insertion losses, and improve signal quality. Interposer  110  may be formed as a multilayer printed circuit board, hybrid device package, or other appropriate structure. 
         [0031]    The contacts of interposer  110  may be arranged to mate with contacts  122  on socket  120 . Socket  120  may be fixed to a board, such as a main or motherboard. This main or motherboard may be located in a laptop, netbook, desktop, tablet, or other type of computer, media player, portable media player, cell, media, or smart phone, or other type of electronic device. In various embodiments of the present invention, a processor may be placed on the other side of the main or motherboard away from socket  122 . This provides a short path from the processor to memory devices  112 . 
         [0032]    In this example, interposer  110  has a similar size as socket  120 . In other embodiments of the present invention, interposer  110  may be larger than socket  120 . For example, interposer  110  may extend beyond one or more edges of socket  120 . This allows a larger topside surface area for interposer  110 , which increases the number of memory devices  112  or other circuits that may be supported. Additional memory devices  112  or other circuitry may also be included on an underside of the overhanging portion of interposer  110 . In embodiments of the present invention where one or more edges of interposer  110  extends beyond edges of socket  120 , area on the main or motherboard below the overhanging portion of interposer  110  may be populated with components, traces, or other circuitry. 
         [0033]    Memory system  100  may provide an efficient memory arrangement that reduces the amount of board area consumed. This may be achieved by arraying memory devices  112  in an efficient manner. In some embodiments the present invention, portions of the array may be omitted to provide space for other active circuitry or passive components. This circuitry may support the functionality of memory devices  112 , or they may provide other functions. An example of an embodiment of the present invention where portions of an array of memory devices are omitted is shown in the following figure. 
         [0034]      FIG. 2  illustrates another memory system according to an embodiment of the present invention. Memory system  200  may include interposer  210  and socket  220 . Interposer  210  may include a number of memory devices  212 . As before, memory devices  212  may be arrayed in a space efficient manner. This arrangement may be interrupted by one or more open spaces  214 . These open spaces may be used as locations for control circuits, passive component, or other circuitry. This circuitry may be used for the operation of memory devices  212 , or for other purposes. 
         [0035]    Socket  220  may include a number of contacts  222 . Socket  220  may also include one or more open areas  224 . These open areas may provide room for circuitry which may be located on a bottom of interposer  210 . 
         [0036]    In various embodiment of the present invention, sockets  120  and  220  may be ball grid array sockets, pin grid array sockets, or other type of sockets. In various embodiment of the present invention, these may be sockets conventionally used for central processing units, graphics processing units, or other types of circuits or processors. Often these sockets provide a vertical clamping force to maintain connections between contacts on a device in the socket and contacts of the socket. The addition of mechanical components to provide this vertical clamping force may increase the height of sockets  120  and  220 . Again, this increase in height may require an electronic device including these memory systems to have an increased thickness. Accordingly, other embodiments of the present invention may replace this vertical clamping force by a lateral force. This may provide a memory system having a consistent height. Examples are shown in the following figures. 
         [0037]      FIG. 3  illustrates a memory system according to an embodiment of the present invention. Memory system  300  may include interposer  310  and socket  320 . Interposer  310  may include a number of memory devices  312 . Again, memory devices  312  may be arrayed in an efficient manner to save board space. As before, memory devices  312  may be integrated circuit chips that are not packaged and are directly placed on interposer  320  or another substrate attached to interposer  320 . In such a situation, interposer  310  may include a cover (not shown), to protect memory devices  312 . In other embodiments of the present invention, memory devices  312  may be packaged integrated circuits. In still other embodiments of the present invention, memory devices  312  may be either stacked die or packaged integrated circuits. The top surface of interposer  310  may also include control circuits, passive component, or other circuitry for the operation of memory devices  312 . These passive components may include resistors and power supply decoupling capacitors. Other circuitry for other functions either related to, or separate from, memory devices  312  may also be included on one or both sides of interposer  310 . 
         [0038]    Socket  320  may include a number of contacts  322 . As before, contacts on a bottom of interposer  310  may mate with contacts  322  in socket  320  to form electrical pathways between memory devices  312  and circuitry on a main or mother board. Signal traces from memory devices  312  to pins of socket  320  may be shortened. The shortening in this and various other embodiments of the present invention may provide increase signal quality, reduced insertion losses, and reduced signal cross-talk. 
         [0039]    Interposer  310  may include a number of tabs  314 . These tabs  314  may define openings  316  between tabs  314 . Openings  316  may be arranged to match flanges  326  on socket  320 . That is, interposer  320  may be mated with socket  320  by aligning tabs  314  on interposer  310  with openings  324  between flanges  326  on socket  320 . Similarly, flanges  326  on socket  320  may fit in openings  316  between tabs  314  on interposer  310 . An example is shown in the following figure. 
         [0040]      FIG. 4  illustrates the insertion of an interposer into a socket of a memory system according to an embodiment of the present invention. In this figure, tabs  314  on interposer  310  may fit between flanges  326  on socket  320 . Once in place, interposer  310  may be moved laterally relative to socket  320 . In this way, interposer  310  may be seated in socket  320 . Specifically, tabs  314  on interposer  310  may slide under flanges  326  on socket  320 . Flanges  326  may include stops (not shown) to limit the lateral movement of interposer  310  relative to socket  320  to ensure that interposer  310  is properly aligned with socket  320 . Flanges  326  hold tabs  314  on interposer  310 , which secures interposer  310  in place relative to socket  320 . 
         [0041]    As interposer  310  is moved laterally relative to socket  320 , contacts on a bottom side of interposer  310  may make temporary electrical connections with one or more contacts on socket  320 . Accordingly, various embodiments of the present invention take measures to ensure that these temporary electrical connections do not damage circuitry in, or associated with, memory system  300 . In various embodiments of the present invention, power may be disconnected to the memory system while interposer  310  is inserted into socket  320 . In still other embodiments of the present invention, the functionality associated with contacts on interposer  310  may be arranged such that these temporary electrical connections do not cause damage. In still other embodiments of the present invention, contacts  322  are arranged having and enough space between rows such that these temporary electrical connections are not created. 
         [0042]    In this specific embodiment of the present invention, interposer  310  may be sized to approximately match socket  320 . As before, in other embodiments of the present invention, one or more edges of interposer  310  may be extended to overhang edges of socket  320 . An example is shown in the following figure. 
         [0043]      FIG. 5  illustrates a memory system according to an embodiment of the present invention. Memory system  500  may include interposer  510  and socket  520 . As before, interposer  510  may include a number of memory devices  512 . Interposer  510  may include an overhang portion  518  that extends beyond an edge of socket  520 . Overhang portion  518  may be used to support additional memory devices  512 . These additional memory devices  512  may be located either on a top or a bottom of overhang portion  518 . Space on a board below overhang portion  518  may be populated with active circuitry, passive component, traces, or other electrical components. 
         [0044]    While in this example, portion  518  overhangs an edge of socket  520 , in other embodiments of the present invention, other edges of interpose  510  may be extended to create portions of interposer  510  that overhang socket  520 . For example, edges  517 ,  519 , or other edges of interposer  510  may overhang, or extend beyond, edges of socket  520 . 
         [0045]    In the above embodiments of the present invention, interposer  310  and socket  320  are shown as being at least approximately square or rectangular in shape. The forces provided by flanges  326  onto tabs  314  on interposer  310  may cause interposer  310  two bend or otherwise distort. Interposer  310  may need to have an increased thickness to support these forces. These forces may be more evenly distributed in a circular memory system, which may allow interposers  310  to have a reduced thickness, which in turn may result in a reduced profile or height for the memory system. An example is shown in the following figure. 
         [0046]      FIG. 6  illustrates a memory system according to an embodiment of the present invention. Memory system  600  may include interposer  610  and socket  620 . Interposer  610  may include a number of memory devices  612  as well as control, passive, or other components  613 . As before, memory devices  612  may be integrated circuit chips that are not packaged and are directly placed on interposer  620  or another substrate attached to interposer  620 . In such a situation, interposer  610  may include a cover (not shown), to protect memory devices  612 . In other embodiments of the present invention, memory devices  612  may be packaged integrated circuits. In still other embodiments of the present invention, memory devices  612  may be either stacked die or packaged integrated circuits. The top surface of interposer  610  may also include control circuits, passive component, or other circuitry for the operation of memory devices  612 . These passive components may include resistors and power supply decoupling capacitors. Other circuitry for other functions either related to, or separate from, memory devices  612  may also be included on one or both sides of interposer  610 . 
         [0047]    Tabs  614  on interposer  610  may be arranged to fit between flanges  626  on socket  620 . Once interposer  610  is placed in socket  620 , interposer  610  may be rotated, in this example counter clockwise, and seated or inserted in socket  620 . Specifically, tabs  614  on interposer  610  may slide under flanges  626  on socket  620 . Flanges  626  may include stops (not shown) to ensure that interposer  610  is correctly aligned with socket  620  when inserted. This may allow contacts on a bottom of interposer  610  to mate with contacts in socket  620 . In this way, holding forces provided by flanges  626  on tabs  614  of interposer  610  may be distributed around an edge of interposer  610 . This may reduce the tendency of interposer  610  to warp, bend, or distort. This in turn may allow interposer  610  to have a reduced thickness. 
         [0048]      FIG. 7  illustrates a circular socket consistent with an embodiment of the present invention. Socket  620  may include a number of flanges  626  placed around an edge. Once an interposer is inserted into socket  620 , tabs of the interposer may slide under flanges  626 . This may hold the interposer in place in socket  620 . Flanges  626  may include stops (not shown) to ensure that interpose  610  is properly aligned when inserted into socket  620 . Socket  620  may include a number of contacts  622 , only a few of which are shown for clarity. Contacts  622  may be arranged in a circular manner, or they may be arranged in other patterns. 
         [0049]      FIG. 8  illustrates a bottom of a circular interposer according to an embodiment of the present invention. Interposer  610  may include a number of tabs  614 . Tabs  614  may define open spaces  616 . Open spaces  616  may be aligned with flanges  626  on socket  620 . Interposer  610  may then be seated or inserted into socket  620  by rotating interposer  610  such that tabs  614  slide under flanges  626  on socket  620 . 
         [0050]    Interposer  610  may include a number of contacts  619 . Contacts  619  may be arranged in a circular or other manner. These contacts may have a ramp shape to mate with spring contacts on socket  620 . An example is shown in the following figure. 
         [0051]      FIG. 9  illustrates electrical connections formed between and interposer and a socket according to an embodiment of the present invention. Specifically, this figure illustrates a connection between contacts  619  on interposer  610  and contacts  622  on socket  620 . In this figure, portions of interposer  610  and socket  620  have been removed to illustrate contacts  619  on interposer  610  and contacts  622  on socket  620  more clearly. As interposer  610  is rotated relative to socket  620 , spring contacts  622  may be compressed and may form electrical connects with contacts  619  on interposer  610 . 
         [0052]    As before, interposer  610  may rotate through an angle such that a particular contact  622  on socket  620  may form temporary electrical connections with one or more contacts  619  on interposer  610 . Accordingly, various embodiments of the present invention take measures to ensure that these temporary electrical connections do not damage circuitry in, or associated with, memory system  600 . In various embodiments of the present invention, power may be disconnected to the memory system while interposer  610  is inserted into socket  620 . In still other embodiments of the present invention, the functionality associated with contacts  619  on interposer  610  is arranged such that these temporary electrical connections do not cause damage. In still other embodiments of the present invention, contacts  619  and  622  are arranged having and enough space between themselves such that these temporary electrical connections are not created. 
         [0053]    The above description of embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Thus, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.