PATENT DOCUMENT

Publication Number: US-8465327-B2
Application Number: US-90569210-A
Country: US
Kind Code: B2

Title: High-speed memory connector

Abstract:
Structures, methods, and apparatus that provide sockets or connectors that are capable of operating at high data rates. One example provides a connector that uses a flex board to form a connection between pins of a socket or connector and a printed circuit board. In another example, one or more flex boards are used to provide a signal path between a memory device, such as an SODIMM, and a printed circuit board. Another example provides a stack of wafers, each formed of an insulated material and supporting one or more conductive pins for making an electrical connection between a memory device and a flex board.

Claims:
What is claimed is: 
     
       1. A socket comprising:
 a flexible circuit board comprising:
 a ground plane having a top surface and a bottom surface; 
 a first insulating layer at least partially covering the top surface; 
 a second insulating layer at least partially covering the bottom surface; 
 a first plurality of conductive traces on the first insulating layer and a second plurality of conductive traces on the second insulating layer; and 
 a third insulating layer at least partially covering the first plurality of conductive traces and a fourth insulating layer at least partially covering the second plurality of conductive traces; 
 
 a plurality of pins coupled to the flexible circuit board, wherein a first number of the plurality of pins couple to the ground plane and a second number of the plurality of pins couple to the first plurality of conductive traces and the second plurality of conductive traces; and 
 a housing to mechanically support the plurality of pins. 
 
     
     
       2. The socket of  claim 1  wherein the first plurality of conductive traces and the second plurality of conductive traces are arranged as microstrips. 
     
     
       3. The socket of  claim 1  wherein the first number of pins and the second number of pins are arranged inside of the housing. 
     
     
       4. The socket of  claim 3  wherein the housing comprises a first opening for receiving a first memory device and a second opening for receiving a second memory device. 
     
     
       5. The socket of  claim 4  wherein the housing further comprises a frame to provide mechanical support for the socket. 
     
     
       6. A method of assembling a socket comprising:
 inserting a first plurality of pins in a first housing portion, the first housing portion having a plurality of slots on a top surface for holding the first plurality of pins, 
 placing a first flexible circuit board over a portion of the first housing; 
 inserting a second plurality of pins and a third plurality of pins in a second housing portion, the second housing portion having a plurality of slots on a bottom surface for holding the second plurality of pins and a plurality of slots on a top surface for holding the third plurality of pins; 
 placing the second housing portion over the first housing portion, such that the first flexible circuit board is at least partially between the first housing portion and the second housing portion; 
 placing a second flexible circuit board over a portion of the second housing; 
 inserting a fourth plurality of pins in a third housing portion, the third housing portion having a plurality of slots on a bottom surface for holding the third plurality of pins, and 
 placing the third housing portion over the second housing portion, such that the second flexible circuit board is at least partially between the second housing portion and the third housing portion, 
 wherein the first housing portion comprises a plurality of posts and the second housing portion comprises a plurality of holes, wherein the plurality of posts of the first housing portion fit in the plurality of holes in the second housing portion during assembly. 
 
     
     
       7. The method of  claim 6  wherein the first flexible circuit board comprises:
 a center conductor having a top surface and a bottom surface; 
 a first insulating layer at least partially covering the top surface; and 
 a second insulating layer at least partially covering the bottom surface. 
 
     
     
       8. The method of  claim 6  wherein the first housing portion, the second housing portion, and the third housing portion are plastic and the frame is metallic. 
     
     
       9. A method of assembling a socket comprising:
 inserting a first plurality of pins in a first housing portion, the first housing portion having a plurality of slots on a top surface for holding the first plurality of pins, 
 placing a first flexible circuit board over a portion of the first housing; 
 inserting a second plurality of pins and a third plurality of pins in a second housing portion, the second housing portion having a plurality of slots on a bottom surface for holding the second plurality of pins and a plurality of slots on a top surface for holding the third plurality of pins; 
 placing the second housing portion over the first housing portion, such that the first flexible circuit board is at least partially between the first housing portion and the second housing portion; 
 placing a second flexible circuit board over a portion of the second housing; 
 inserting a fourth plurality of pins in a third housing portion, the third housing portion having a plurality of slots on a bottom surface for holding the third plurality of pins, and 
 placing the third housing portion over the second housing portion, such that the second flexible circuit board is at least partially between the second housing portion and the third housing portion, 
 wherein the first housing portion comprises a plurality of posts and the first flexible circuit board comprises a plurality of holes, wherein the plurality of posts of the first housing portion fit in the plurality of holes in the first flexible circuit board during assembly. 
 
     
     
       10. The method of  claim 9  wherein the first flexible circuit board comprises:
 a center conductor having a top surface and a bottom surface; 
 a first insulating layer at least partially covering the top surface; and 
 a second insulating layer at least partially covering the bottom surface. 
 
     
     
       11. The method of  claim 9  wherein the first housing portion, the second housing portion, and the third housing portion are plastic and the frame is metallic. 
     
     
       12. A method of assembling a socket comprising:
 inserting a first plurality of pins in a first housing portion, the first housing portion having a plurality of slots on a top surface for holding the first plurality of pins, 
 placing a first flexible circuit board over a portion of the first housing; 
 inserting a second plurality of pins and a third plurality of pins in a second housing portion, the second housing portion having a plurality of slots on a bottom surface for holding the second plurality of pins and a plurality of slots on a top surface for holding the third plurality of pins; 
 placing the second housing portion over the first housing portion, such that the first flexible circuit board is at least partially between the first housing portion and the second housing portion; 
 placing a second flexible circuit board over a portion of the second housing; 
 inserting a fourth plurality of pins in a third housing portion, the third housing portion having a plurality of slots on a bottom surface for holding the third plurality of pins, 
 placing the third housing portion over the second housing portion, such that the second flexible circuit board is at least partially between the second housing portion and the third housing portion; and 
 inserting a frame to mechanically support the first housing portion, the second housing portion, and the third housing portion. 
 
     
     
       13. The method of  claim 12  wherein the first housing portion, the second housing portion, and the third housing portion are plastic and the frame is metallic. 
     
     
       14. The method of  claim 12  wherein the first flexible circuit board comprises:
 a center conductor having a top surface and a bottom surface; 
 a first insulating layer at least partially covering the top surface; and 
 a second insulating layer at least partially covering the bottom surface. 
 
     
     
       15. A socket comprising:
 a plurality of wafers, each wafer formed of a nonconductive material and arranged to hold one or more conductive pins, wherein each wafer includes an alignment mechanism such that each wafer aligns to a neighboring wafer; and 
 a housing to at least partially enclose the plurality of wafers and having a first opening and a second opening, wherein the first opening is arranged to accept a first memory device and the second opening is arranged to accept a second memory device, 
 wherein the conductive pins have a first end and a second end, where the first ends are arranged to mate with contacts on the first and second memory devices and the second ends are arranged in an array, and 
 wherein a first plurality of the second ends attach to a first flexible circuit board. 
 
     
     
       16. The socket of  claim 15  wherein second plurality of the second ends attach to a second flexible circuit board.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 61/257,431, filed Nov. 2, 2009, entitled “High-Speed Memory Connector,” which is incorporated by reference. 
    
    
     BACKGROUND 
     Memory devices for computer systems have been increasing in size and operating frequency for years, and these increases show no signs of abating. 
     Computers may use multiple levels of memory. For example, a central processing unit (CPU) may have a limited amount of on-chip cache memory. Additional memory may be included on a motherboard for easy access by the CPU. This additional memory may be random-access memory (RAM.) The RAM may be included on a small-outline dual inline memory module (SODIMM.) Still more memory may be made available in the form of a hard-disk drive. 
     It may be desirable to be able to replace this additional memory. For example, a user may want to upgrade the memory to a faster or larger memory. Also, a user may want to be able to replace a memory that has become defective. Accordingly, it has become common to use a socket or connector to form an interface between memory devices, such as an SODIMM, and a motherboard. Using a socket or connector allows a user to remove and insert memory devices in a computer system. 
     It is also desirable to use memory that can operate at a higher data rate. Such memories improve system performance by being more responsive, reducing wait times, providing improved graphical or audio performance, and speeding up background operations. Faster memories are consistently being developed and users want to be able to take advantage of their increased performance. 
     Unfortunately, the sockets or connectors that are typically used for these memories can degrade signals, create crosstalk between signals, and otherwise reduce performance. They may also generate noise that can degrade the performance of other circuits in a device, such as wireless transceivers, audio, or other types circuits. 
     Thus, what is needed are structures, methods, and apparatus that provide sockets or connectors that are capable of operating at high data rates with limited crosstalk and interfering emissions. 
     SUMMARY 
     Accordingly, embodiments of the present invention provide structures, methods, and apparatus that provide sockets or connectors that are capable of operating at high data rates. 
     An exemplary embodiment of the present invention may provide a connector that may use a flexible circuit board, or flex board, to form connections between pins of a socket or connector and a printed circuit board, such as a motherboard. The flex board may use microstrips to effectively shield data lines, thereby reducing the amount of electromagnetic interference (EMI) and crosstalk generated. Using a flex board may allow much of a signal path from a device, such as a memory device, to a printed circuit board to be shielded. This reduces the distance that signals travel while they are unshielded, which reduces crosstalk and EMI emissions. 
     Various embodiments of the present invention may use a flex board having a center ground plane that can be isolated using two isolation layers. Signal lines may be placed on the isolation layers to carry data signals. The signal lines may be protected using further isolation layers. The signal lines may be further electrically isolated by using shield layers, such that the signal lines are between a shield layer and the center ground plane. The shield layers may be tied to ground or other low-impedance point. 
     In other embodiments of the present invention, the center ground plane may be replaced by a more mechanically stable structure. For example, a center ground plane may be replaced by an insulating layer having a ground layer on each side. 
     In various embodiments of the present invention, ground and signal layers may be copper or other conductive material. The insulating layers may be polyamide or other insulating materials. In other embodiments of the present invention, other types of boards or signal conduits may be used in place of a flex board. For example, one or more printed circuit boards, ribbon cables, or other conduits may be used. In a specific embodiment of the present invention, an edge of a printed circuit board, such as a motherboard, may be used. In this embodiment, a socket housing is attached to an edge of a printed circuit board that has other associated circuitry attached. Conductive traces terminate in pads near the edge of the printed circuit board. Pins in the socket housing may connect contacts or pads on a memory or other type of device to the pads near the edge of the printed circuit board. 
     Another specific embodiment of the present invention may provide two sockets for memory devices. A first piece may form a holder for pins for ground and signals. A first flex board may be placed over a portion of the first piece. A second piece having contacts for ground and signals on each side may be located over the first piece and the first flex board. A second flex board may then be placed over the second piece. A third piece having contacts for signals and grounds on one side may be placed over the second piece and the second flex board. After assembly, a first memory device may be inserted between a portion of the first piece and a portion of the second piece, while a second memory device may be inserted between a portion of the second piece and a portion of the third piece. 
     In this embodiment, the first, second, and third pieces may be plastic or other material. The pins may be copper, aluminum, or other conductive material. A steel frame may be used to provide additional mechanical support for the connectors. In other embodiments of the present invention, sockets may be assembled using more or fewer than three pieces. For example, five pieces may be used to form a socket. In other embodiments of the present invention, a single piece is used to form a socket. In this embodiment of the present invention, flex boards are inserted into a socket housing. 
     In another embodiment of the present invention, one or more flex boards may be used to provide signal paths directly between a memory device, such as an SODIMM, and a printed circuit board. The flex boards may include contact areas that form a connection with contact areas on a memory device. Tension supplied by a pin or spring may be used to keep the flex board in contact with the memory device. The pin or spring may be plastic, metal, or made from another type of material. 
     Another exemplary embodiment of the present invention may provide a stack of wafers, each formed of an insulated material and supporting one or more conductive pins for making an electrical connection between a memory device and a flex board. The pins may be arranged such that one, two, or more than two memory devices may be connected to one or more flex boards. 
     In various embodiments of the present invention, the wafers may include one or more raised portions and holes or openings, such that the wafers may fit together in an aligned manner. The wafers may be housed in a housing to provide mechanical support for the wafer assembly. The pins may make contact with one or more flex boards to a printed circuit board, such as a motherboard. In various embodiments of the present invention, the wafers may be plastic or other nonconductive material. The pins may be formed using copper, aluminum, or other conductive material. 
     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 
         FIG. 1  illustrates a socket or connector according to an embodiment of the present invention; 
         FIG. 2  illustrates a socket or connector according to an embodiment of the present invention; 
         FIG. 3  illustrates a cross-section of a flex board, pins, and memory device according to an embodiment of the present invention; 
         FIG. 4  illustrates a top view of flex board, pins, and memory device according to an embodiment of the present invention; 
         FIG. 5  illustrates a socket or connector according to an embodiment of the present invention; 
         FIG. 6  illustrates a socket or connector according to an embodiment of the present invention; 
         FIG. 7  illustrates a cross-section of flex boards, pins, and memory devices according to an embodiment of the present invention; 
         FIG. 8  illustrates a flex board according to an embodiment of the present invention; 
         FIGS. 9-15  illustrate steps in the assembly of a socket or connector according to an embodiment of the present invention; 
         FIG. 16  illustrates a completed socket or connector according to an embodiment of the present invention; 
         FIG. 17  illustrates a socket or connector for high-speed memory devices where a flex board is directly connected to a memory device; 
         FIG. 18  illustrates a wafer stack that may be used to arrange a number of pins to electrically connect one or more memory devices to a flex board according to an embodiment of the present invention; 
         FIG. 19  illustrates a close-up of a wafer stack according to an embodiment of the present invention; 
         FIG. 20  illustrates a method of aligning wafer portions in a wafer stack according to an embodiment present invention; 
         FIG. 21  illustrates a housing that may be used to hold wafers in a wafer stack according to an embodiment of the present invention; and 
         FIG. 22  illustrates a method of attaching one or more flex boards to pins of a wafer stack according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  illustrates a connector  100  according to an embodiment of the present invention. This figure, as with the other included figures, is shown for illustrative purposes only and does not limit either the possible embodiments of the present invention or the claims. 
     In this example, connector  100  may connect a memory device  110  to a printed circuit board  120 . Memory device  110  may be an SODIMM or other type of memory board, module, or device. Memory device  110  may include a number of memory circuits  130 , which may be integrated circuits. Signals generated by circuitry on, or associated with, printed circuit board  120  may be provided to memory device  110  through a conductive path including flex board  160 , pins  140 , contacts  150 , and traces (not shown) on memory device  110 . Data from memory devices  130  may be provided to circuitry on, or associated with, printed circuit board  120  via a path including traces (not shown) on memory device  110 , contacts  150 , pins  140 , and flex board  160 . 
     Printed circuit board  120  may be a motherboard or a daughterboard. For example, printed circuit board  120  may be a graphics card, audio card, or other type of board. While a printed circuit board  120  is shown for exemplary purposes, flex board  160  may connect to another type of board, for example, a flex board or other type of board. 
     Flex board  160  may provide an electrical conduit from pins  140  to printed circuit board  120 . Flex board  160  may include microstrips to shield signals transferred between memory device  110  and printed circuit board  120 . Connector or socket  100  may be enclosed in a housing  170 . 
     In various embodiments of the present invention, pins  140  may be formed using aluminum, copper, or other metallic or conductive material. Flex board  160  may be formed of a plurality of layers including the metal and insulative layers. Housing  170  may be made of plastic or other nonconductive material. Housing  170  may be mechanically reinforced using a metallic frame or other type of structure. 
     Again, embodiments of the present invention provide high-speed connectors or sockets. While these connectors or sockets are particularly suited to memory devices, they may be used to hold or connect other types of devices, such as processors, co-processors, or bridges. Various embodiments of the present invention may be used to support operating frequencies of 1.33, 1.66, 1.8, 2.0, or 2.2 GHz, or other operating frequencies. Embodiments of the present invention may provide sockets or connectors for memory devices compatible with DDR3, DDR4, and other memory standards or proprietary methods that have been developed, are currently under development, or will be developed in the future. 
     In this example, memory device  110  may be roughly orthogonal to printed circuit board  120 . In such a configuration, it is relatively easy for a user to extract and insert memory devices  110  from connector  100 . In other embodiments of the present invention, it may be desirable that memory device  110  be parallel to printed circuit board  120 . This is particularly true in cases where space or clearance is of a concern. An example is shown in the following figure. 
       FIG. 2  illustrates a socket or connector  200  according to an embodiment of the present invention. In this configuration, memory device  210  may be parallel to printed circuit board  220  when it is inserted in connector  200 . Again, memory device  210  may include memory circuits  230  and contacts  250 . Memory device  210  may be an SODIMM or other type of memory circuit, module, or device. Connector  200  may include pins  240  that make electrical connections between contacts  250  and flex board  260 . In this example, additional pins  265  may be used to form connections between flex board  260  and printed circuit board  220 . Connector  200  may be enclosed in housing  270 . 
     In various embodiments of the present invention, pins  240  may be formed using aluminum, copper, or other metallic or conductive material. Flex board  260  may be formed of a plurality of layers including metal and insulative layers. Housing  270  may be made using plastic or other nonconductive material. Housing  270  may be mechanically reinforced using a metallic or other type of reinforcing structure. 
       FIG. 3  illustrates a cross-section of a flex board  310 , pins  320 , and memory device  330  according to an embodiment of the present invention. Flex board  310  may include a center ground plane  312 . Center ground plane  312  may have an insulative layer  314  on each side. Traces  316  may reside on insulative layers  314 . Optional outer insulative layer  318  may be included to protect traces  316 . 
     In other embodiments of the present invention, other layers may be in included as part of flex board  310 . For example, one or both of outer insulative layers  318  may be omitted. Alternately, shield layers (not shown) may be placed on the outside of layers  318  to provide electromagnetic shielding. These shield layers may be tied to ground or other low impedance point. The shield layers may be further protected by another insulative layer (not shown.) In still other embodiments of the present invention, center ground plane  312  may be replaced by an insulative layer having a conductive ground layer on each side. 
     In various embodiments of the present invention, ground  312  and trace signal lines  316  may be formed using copper, aluminum, or other conductive material. Insulative layers  314  and  318  may be formed using polyamide material or other insulative materials. 
     Pins  320  may form electrical connections between memory device  330  and board  310 . Pins  320  may include ground pins  324  and signal pins  322 . Signal pins  322  may form signal paths from memory device  330  to signal traces  316  on flex board  310 . Pins  324  may form ground connections between memory device  330  and ground plane  312  in flex board  310 . 
     Memory device  330  may include memory circuits  334  attached to printed circuit board  332 . Traces (not shown) may connect memory circuits  334  to contact areas  336  on memory device  330 . 
     Again, flex board  310  may use microstrips to reduce crosstalk and EMI from data signals on traces  316 . This reduces the unshielded distance to the length of pins  320  and any pins that may be needed to connect flex board  310  to a printed circuit board (not shown.) In a specific embodiment of the present invention, this distance may be on the order of 4-5 mm, as compared to a conventional 10-12 mm. By minimizing this unshielded distance, crosstalk, EMI and other emissions are reduced. This in turn reduces interference with other circuitry, such as wireless transceivers, graphics and audio, as well as other types of circuits. 
     Again, in other embodiments of the present invention, flex board  310  may be replaced with a printed circuit board, ribbon cable, or other conduit. In a specific embodiment of the present invention, an edge of a printed circuit board, such as a mother board, may replace the flex board  310 . In this embodiment, signal pins  322  may contact pads connected to conductive traces on the printed circuit board. Ground pins  324  may contact a center ground plane that extends beyond an edge of the printed circuit board, or ground pins  324  may contact ground pads may be made available on the surface of the printed circuit board. 
       FIG. 4  illustrates a top view of flex board  410 , pins  420 , and memory device  430  according to an embodiment of the present invention. Flex board  410  may include ground plane  412 , insulative layer  414 , and conductive traces  416 . Conductive traces  416  may be protected by optional insulating layers  418 . Pins  422  and  424  may form electrical connections between flex board  410  and memory device  430 . Signal pins  422  may connect signal traces  416  to pads  436  on memory device  430 . Ground pins  424  may connect ground plane  412  to pads  436  on memory device  430 . Memory circuits  434  may be soldered or otherwise attached to board  432 . Traces (not shown) may connect memory circuits  434  to pads  436 . 
     In this example, pairs of data or signal pins  422  may have a ground pin  424  on each side. This may create a microstrip structure. This microstrip structure may electrically isolate pairs of data pins  422 . As data signals on these data pins switch, this microstrip arrangement may limit the electromagnetic interference generated by memory device  430 . Crosstalk, that is electromagnetic interference between pairs of data pins, may be similarly reduced. This, in turn, may enhance signal integrity and allow memory device  430  to operate at higher data rates. 
     In various embodiments of the present invention, it may be desirable to provide a socket or connector for more than one memory device. Examples are shown in the following figures. 
       FIG. 5  illustrates a connector  500  according to an embodiment of the present invention. In this example, connector  500  may connect two memory devices  510  to printed circuit board  520 . Memory device  510  may be an SODIMM or other type of memory board, module, or device. Memory device  510  may include a number of memory circuits  530 , which may be integrated circuits. Signals generated by circuitry on, or associated with, printed circuit board  520  may be provided to memory devices  510  through a conductive path including flex boards  560 , pins  540 , contacts  550 , and traces (not shown) on in the memory devices  510 . Data from memory devices  530  may be provided to circuitry on, or associated with, printed circuit board  520  via a path including traces (not shown) on memory device  510 , contacts  550 , pins  540 , and flex board  560 . 
     Again, printed circuit board  520  may be a motherboard or a daughterboard. For example, printed circuit board  520  may be a graphics card, audio card, or other type of support. While a printed circuit board  520  is shown for exemplary purposes, flex boards  560  may connect to another type of board, for example a flex board or other type of board. 
     Flex boards  560  may provide an electrical conduit from pins  540  to printed circuit board  520 . Flex boards  560  may include microstrips to shield signals transferred between memory devices  510  and printed circuit board  520 . Connector or socket  500  may be enclosed in a housing  570 . 
     In various embodiment of the present invention, pins  540  may be formed using aluminum, copper, or other metallic or conductive material. Flex boards  560  may be formed of a plurality of layers including the metal and insulative layers. Housing  570  may be made of plastic or other nonconductive material. Housing  570  may be mechanically reinforced using a metallic frame or other type of structure. 
       FIG. 6  illustrates a socket or connector  600  according to an embodiment of the present invention. In this configuration, memory devices  610  may be parallel to printed circuit board  620  when they are inserted in connector  600 . Again, memory devices  610  may include memory circuits  630  and contacts  650 . Memory devices  610  may be SODIMMs or other type of memory circuits, modules, or devices. Connector  600  may include pins  640  that make electrical connections between contacts  650  and flex boards  660 . In this example, additional pins  665  may be used to form connections between flex boards  660  and printed circuit board  620 . Connector  600  may be enclosed in housing  670 . 
     In various embodiments of the present invention, pins  640  may be formed using aluminum, copper, or other metallic or conductive material. Flex boards  660  may be formed of a plurality of layers including metal and insulative layers. Housing  670  may be made using plastic or other nonconductive material. Housing  670  may be mechanically reinforced using a metallic or other type of reinforcing structure. 
       FIG. 7  illustrates a cross-section of flex boards  710 , pins  720 , and memory devices  730  according to an embodiment of the present invention. Flex boards  710  may include center ground planes  712 . Center ground planes  712  may have insulative layers  714  on each side. Traces  716  may reside on insulative layers  714 . Optional outer insulative layer  718  may be included to protect traces  716 . 
     In other embodiments of the present invention, other layers may be in included as part of flex boards  710 . For example, one or both of outer insulative layers  718  may be omitted. Alternately, shield layers (not shown) may be placed on the outside of layers  718  to provide electromagnetic shielding. These shield layers may be tied to ground or other low impedance point. The shield layers may be further protected by another insulative layer (not shown.) In still other embodiments of the present invention, center ground planes  712  may be replaced by insulative layers having conductive ground layers on each side. 
     In various embodiments of the present invention, center ground planes  712  and trace signal lines  716  may be formed using copper, aluminum, or other conductive material. Insulative layers  714  and  718  may be formed using polyamide or other insulative materials. 
     Pins  720  may form electrical connections between memory devices  730  and board  710 . Pins  720  may include ground pins  724  and signal pins  722 . Signal pins  722  may form signal paths from memory devices  730  to signal traces  716  on flex boards  710 . Pins  724  may form ground connections between memory device  730  and center ground planes  712  in flex boards  710 . 
     Memory devices  730  may include memory circuits  734  attached to printed circuit board  732 . Traces (not shown) may connect memory circuits  734  to contact areas  736  on memory devices  730 . 
     Embodiments of the present invention may incorporate one or more flex boards to carry signal and grounds. The signal lines may be arranged in a microstrip fashion to reduce the amount of electromagnetic interference that is generated and to improve signal integrity. An example of such a flex board is shown in the following figure. 
       FIG. 8  illustrates a flex board  800  according to an embodiment of the present invention. Flex board  800  may include ground plane  810 , insulative layers  820 , and conductive traces  830 . In a specific embodiment of the present invention, conductive traces  830  are sized and spaced to provide an impedance of approximately 40 or 50 ohms. In various embodiments of the present invention, various numbers of conductive traces may be included. For example, 68, or other number of traces, may be included on each side of one or more flex boards  800 . In a specific embodiment of the present invention, flex board  800  is 68 mm wide. 
     In a specific embodiment present invention, center ground plane  810  may be formed using copper, aluminum, or other conductive material. In a specific embodiment of the present invention, copper having a weight of 2 oz. and a thickness of 0.07 mm may be used. In this embodiment of the present invention, insulative layers  820  may be formed using polyamide. In a specific embodiment of the present invention, the polyamide may be 0.08 mm thick. In this embodiment of the present invention, signal traces  830  may be formed using copper, aluminum, or other conductive material. In a specific embodiment of the present invention, ½ oz. of copper having a thickness of 0.018 mm may be used. Signal traces  830  may terminate in pads, where the pads are wider than signal traces  830 . In a specific embodiment of the present invention, the pads may be 0.45 mm wide, with a gap of 0.15 mm between pads. A gap of 0.75 mm may separate signal traces  830 . In other embodiments of the present invention, other thicknesses, sizes, and spacings may be used. 
     Again, in a specific embodiment of the present invention, a socket or connector for two memory devices may be provided. One such socket or connector may be formed using three major pieces. An example is shown in the following figures. 
       FIG. 9  illustrates a first or bottom piece  900  of a high-speed memory socket or connector according to an embodiment of the present invention. Pins  910  and  920  may be inserted into piece  900  to form connections between a memory device and a flex board. In a specific embodiment of the present invention, 68 signal pins  910  and 34 ground pins  920  may be used, for a total of 102 pins. Post  930  may act as an alignment mechanism for later pieces. Notch  940  may be offset from a center of piece  900  in order to prevent memory devices from being inserted improperly by a user. After assembly, pins  910  and  920  may form connections with contacts on a bottom of a first memory device. 
       FIG. 10  illustrates a flex board  1000  placed on top of first piece  900 . Holes in flex board  1000  may align with posts  930 . Posts  930  may be asymmetrical to prevent flex  1000  from being installed improperly or backwards on first piece  900 . In this example, three posts  930  fit in three holes in flex board  1000 , though in other embodiments of the present invention, other numbers of posts and holes may be used. 
       FIG. 11  illustrates a middle or second piece  1100  of a high-speed memory socket or connector according to an embodiment of the present invention. Second piece  1100  may include top pins  1110  and bottom pins  1120 . As before, in a specific embodiment of the present invention, there maybe 68 signal pins and 34 ground pins for a total of 102 top pins  1110 , and 68 signal pins and 34 ground pins for a total of 102 bottom pins  1120 . After assembly, top pins  1110  may form electrical connections with contacts on a bottom of a second memory device, while bottom pins  1120  may make electrical contact with top contacts on a first memory device. 
       FIG. 12  illustrates middle or second piece  1100  that may be fitted to first or bottom piece  900 . 
     In  FIG. 13 , a second flex board  1300  may be fitted to middle or second piece  1100 . Posts  1330  may be used to align flex board  1300  to second piece  1100 . As before, posts  1330  may be asymmetrically arranged on second piece  1100  to prevent improper installation of flex board  1300 . 
       FIG. 14  illustrates a top or third piece  1400  that may be used in the assembly of a high-speed memory connector or socket according to an embodiment of the present invention. Pins  1400  may be located on top or third piece  1400 . As before, there may be 68 signal pins and 34 ground pins, for a total of 102 pins  1400 . After assembly, pins  1410  may form electrical connections with contacts on a top of a second memory device. 
     Again, users may wish to insert and extract memory devices from these high-speed memory sockets or connectors. Such insertion and removal may cause mechanical stress to the socket. Accordingly, various embodiments of the present invention may provide reinforcement for these high-speed sockets. An example is shown in the following figure. 
       FIG. 15  illustrates a frame  1510  that may be used to provide mechanical reinforcement for socket or connector  1500 . In a specific embodiment of the present invention, frame  1510  may be made of metal, for example steel, stainless steel, or other rigid material. Frame  1510  may fit around or inside socket  1500 . In a specific embodiment of the present invention, frame  1510  may fit inside pieces forming socket  1500  such that frame  1510  is not visible from the top, side, or front when viewed by a user. 
       FIG. 16  illustrates a completed socket or connector according to an embodiment of the present invention. This socket or connector may include a bottom or first piece  900 , middle or second piece  1100 , and top or third piece  1400 . These pieces may be fixed to each other by screws, fasteners, adhesive, or in other manners. A first memory device may be inserted between bottom or first piece  900  and middle or second piece  1100 . A second memory device may be inserted between middle or second piece  1100  and top or third piece  1400 . This socket or connector may sit flush on a printed circuit board, or it may be mounted to an enclosure, or other surface. The completed socket or connector may include a total of 408 pins to form connections with the first and second memory devices, though other embodiments of the present invention may include other numbers of pins. In a specific embodiment of the present invention, the complete socket of connector has a height of 8.66 mm, though other embodiments of the present invention may have other heights. 
     In the above example, three pieces are used to form a completed socket or connector. In other embodiments of the present invention, more or fewer than three pieces may be used to form a completed socket. For example, five pieces may be used to form a completed socket. In other embodiments of the present invention, the socket may be formed using a single piece. In this embodiment, the single piece may be plastic, where flex boards are inserted into an open end of the socket. 
     In the above embodiments of the present invention, pins are used to form electrical connections between memory devices and flex boards. Signals on the memory devices and on the flex boards are effectively shielded using microstrips to limit EMI and crosstalk. However, some EMI and crosstalk may occur due to the use of these pins. Accordingly, an embodiment of the present invention provides a direct connection between a flex board and a memory device. An example is shown in the following figure. 
       FIG. 17  illustrates a socket or connector for high-speed memory devices where a flex board is directly connected to a memory device. In this example, flex board  1700  may include a ground layer  1720 , insulating layer  1730 , and traces  1740 . A pin or mechanical finger  1710  may provide pressure on flex board  1700 , thereby holding flex board  1700  against contact  1750  on memory device  1760 . Vias  1770  may be used to route traces  1740  through insulating layer  1730  and ground plane  1720  such that they may make contact with contact pads  1750 . Memory device  1760  may include one or more memory circuits  1780 . Portions of flex board  1700  may be plated or otherwise protected to avoid damage during insertion and extraction of memory device  1760 . 
     In various embodiments of the present invention, pins in a connector or socket may connect to one or more flex boards in various ways. An example is shown in the following figure. 
       FIG. 18  illustrates a wafer stack  1800  that may be used to arrange a number of pins to electrically connect one or more memory devices to a flex board according to an embodiment of the present invention. Wafer stack  1800  may include pins  1810  held in place by insulative material  1820 . Wafers may be stacked as needed to provide electrical connections between memory devices (not shown) and a flex board (not shown.) The pins may have two ends, a first end to mate with contacts on one or more memory devices (not shown) and a second end forming an array. 
       FIG. 19  illustrates a close-up of a wafer stack  1800  according to an embodiment of the present invention. Memory devices (not shown) may be inserted such that they make contact with pin portions  1810 . One or more flex boards (not shown) may be attached to the wafer stack such that they make contacts with pin portions  1820 . 
     In this specific example, four different wafers may be used. Each wafer may include two contacts, and each wafer may be used 26 times. In another embodiment of the present invention, 204 wafers may be used. In other embodiments of the present invention, other numbers of wafers and contacts may be used, and each wafer may be used a different number of times. In this specific embodiment of the present invention, each wafer may be 0.3 mm wide, though other widths may be used in other embodiments of the present invention. In various embodiments of the present invention, one or more ground pins may contact each other in the wafer stack  1800  to improve socket performance. 
     As the wafers are stacked, it is desirable that they be properly aligned and secured to each other. A specific embodiment of the present invention achieves alignment by providing holes and corresponding raised surfaces. An example is shown in the following figure. 
       FIG. 20  illustrates a method of aligning wafer portions in a wafer stack according to an embodiment present invention. In this example, a raised portion  2030  on a second wafer layer  2035  may mate with a hole and a first layer  2010 . Similarly hole  2020  may mate with a raised portion on a next wafer (not shown), while raised portion  2040  may fit in an opening in the next wafer layer (not shown.) In this example, each wafer may include two holes for accepting raised areas from an adjoining wafer. 
       FIG. 21  illustrates a housing  2100  that may be used to hold wafers in wafer stack  1800  according to an embodiment of the present invention. 
       FIG. 22  illustrates a method of attaching one or more flex boards to pins of a wafer stack according to an embodiment of the present invention. Contacts  1810  from a wafer stack (not shown) may fit in through holes in flex boards  2210  and  2220 . Flex boards  2210  and  2220  may be attached to printed circuit board  2230 . For example, flex boards  2210  and  2220  may be press fit to printed circuit board  2230 . Flex boards  2210  and  2220  may be two separate flex boards, or they may be one flex board as indicated by dashed lines  2240 . 
     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.

Metadata:
Filing Date: 20101015
Publication Date: 20130618
Grant Date: 20130618
Priority Date: 20091102
Inventors: SPRINGER GREG
DUPERRON VINCE
SIMMEL MARC
MITCHELL PETER
FUNAMURA JOSHUA
Assignee: APPLE INC
CPC Classifications: [{"code": "Y10T29/49208", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/6471", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49208", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R13/6471", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 44761235