Abstract:
In one aspect, an electrical connector to connect circuit cards includes a compliant member that includes a first end portion and a second end portion, a first rigid member attached to the first end portion of the compliant member and including a first bore extending along an axis, a second rigid member attached to the second end portion of the compliant member and including a second bore extending along the axis and a pin secured in the first bore and configured to move within the second bore. The compliant member is configured to translate along the axis from a first position corresponding to the first and second rigid members being separated to a second position corresponding to the first and second rigid members being in direct contact.

Description:
RELATED PATENT APPLICATION 
     This application claims priority to provisional application Ser. No. 61/162,769, entitled “ELECTRICAL CONNECTOR TO CONNECT STACKED CIRCUIT CARDS,” filed Mar. 24, 2009, which is incorporated herein in its entirety. 
    
    
     BACKGROUND 
     Sometimes it is desirable to transfer signals (e.g., power signals) from one circuit board to another circuit board. In one example, an interconnection between circuit cards includes a busbar blade and a corresponding busbar blade connector to receive the busbar blade. Generally, the busbar blade interconnection is used for low inductance requirements. In another example, a pin-and-socket connection is used. For example, one part of the interconnection includes a series of pins and another part of the interconnection includes a series of sockets, each socket configured to receive a corresponding pin. Generally, the pin-and-socket connection is used for high current requirements. 
     SUMMARY 
     In one aspect, an electrical connector to connect circuit cards includes a compliant member that includes a first end portion and a second end portion, a first rigid member attached to the first end portion of the compliant member and including a first bore extending along an axis, a second rigid member attached to the second end portion of the compliant member and including a second bore extending along the axis and a pin secured in the first bore and configured to move within the second bore. The compliant member is configured to translate along the axis from a first position corresponding to the first and second rigid members being separated to a second position corresponding to the first and second rigid members being in direct contact. 
     In another aspect, an electrical connector to connect circuit cards includes a compliant member that includes a first end portion and a second end portion, a spring assembly extending along an axis and configured to translate along the axis; the spring assembly forming a cavity extending along the axis and a pin configured to pass through the cavity and to engage the first end portion and the second end portion. The compliant member is configured to translate along the axis from a first position to a second position. 
     In a further aspect, a system includes a line replaceable unit that includes panels configured to provide radio frequency signals and disposed an exterior surface of the line replaceable unit and electrical circuitry disposed in an interior of the line replaceable unit. The circuitry includes a first circuit card, a second circuit card and an electrical connector electrically connecting the first circuit card to the second circuit card. The electrical connector includes a compliant member that includes a first end portion and a second end portion, a first rigid member attached to the first end portion of the compliant member and including a first bore extending along an axis, a second rigid member attached to the second end portion of the compliant member and including a second bore extending along the axis and a pin secured in the first bore and configured to move within the second bore. The compliant member is configured to translate along the axis from a first position corresponding to the first and second rigid members being separated to a second position corresponding to the first and second rigid members being in direct contact. 
     In a still further aspect, an electrical connector to connect circuit cards includes a compliant member including a first end portion and a second end portion and further including an electrically conductive layer, a first insulator layer disposed on a first surface of the electrically conductive layer and a second insulator layer disposed on a second surface of the electrically conductive layer opposite the first surface of the electrically conductive layer. The connector further includes a first rigid member attached to the first end portion of the compliant member and comprising a first bore extending along an axis, a second rigid member attached to the second end portion of the compliant member and comprising a second bore extending along the axis; and a pin secured in the first bore and configured to move within the second bore. The compliant member is configured to translate along the axis from a first position corresponding to the first and second rigid members being separated to a second position corresponding to the first and second rigid members being in direct contact. The compliant member further includes a first aperture aligned with the first bore and a second aperture aligned with the second bore. The first bore is configured to receive a first fastener through the first aperture to secure the connector to a first circuit card. The second bore is configured to receive a second fastener through the second aperture to secure the connector to a second circuit card. 
     In another aspect, a method to connect circuit cards includes providing an electrical connector. The electrical connector includes a compliant member that includes a first end portion and a second end portion, an electrically conductive layer, a first insulator layer disposed on a first surface of the electrically conductive layer and a second insulator layer disposed on a second surface of the electrically conductive layer opposite the first surface of the electrically conductive layer. The electrical connector also includes a first rigid member attached to the first end portion of the compliant member and comprising a first bore extending along an axis, a second rigid member attached to the second end portion of the compliant member and comprising a second bore extending along the axis and a pin secured in the first bore and configured to move within the second bore. The method also includes using a first fastener to connect the compliant member of the electrical connector to a first circuit card and using a second fastener to connect the electrical connector to a second circuit card spaced apart from the first circuit card. The compliant member is configured to translate along the axis from a first position corresponding to the first and second rigid members being separated to a second position corresponding to the first and second rigid members being in direct contact. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 3  are a series of isometric views showing front, back and side views of a radio frequency (RF) transmit/receive system. 
         FIG. 3A  is a cross-sectional view of an LRU shown in  FIG. 3  and taken across lines  3 A- 3 A in  FIG. 3 . 
         FIG. 3B  an enlarged top view of a hinge on the radio frequency (RF) transmit/receive system taken across lines  3 B- 3 B in  FIG. 2 . 
         FIGS. 4A to 4C  are views of an example of an electrical connector. 
         FIG. 4D  is a view of the electrical connector in  FIGS. 4A to 4C  with the alignment screws exploded. 
         FIG. 5A  is an exploded view of a compliant element. 
         FIG. 5B  is a view of the compliant element before being shaped. 
         FIG. 5C  is a cross-section of the compliant member of  FIG. 5B  taken along the lines  5 C- 5 C. 
         FIG. 5D  is a view of the compliant element after being shaped. 
         FIGS. 6A and 6B  are views of a rigid member. 
         FIG. 6C  is a cross-sectional view of the rigid member in  FIG. 6B  taken along the lines  6 C- 6 C. 
         FIG. 6D  is a cross-sectional view of the electrical connector in  FIG. 4A  taken long along the line  6 D- 6 D. 
         FIG. 6E  is another cross-sectional view of the electrical connector of  FIG. 6D  with the connector flexed. 
         FIG. 7  is a cross-sectional view of the electrical connector of  FIGS. 4A to 4D  connecting two circuit cards. 
         FIGS. 8A to 8C  are views of connecting a first circuit card to a second circuit card in a panel array subsystem. 
         FIG. 9A  is a view of another example of an electrical connector. 
         FIG. 9B  is an exploded view of the electrical connector of  FIG. 9A . 
         FIG. 10A  is an exploded view of a compliant element for the connector in  FIG. 9A . 
         FIGS. 10B and 10C  are views of the compliant member of the connector in  FIG. 9A . 
         FIG. 11A  is a cross-sectional view of the electrical connector in  FIG. 9A  taken along the line  11 A- 11 A. 
         FIG. 11B  is another cross-sectional view of the electrical connector of  FIG. 9A  with the connector flexed. 
         FIG. 12A  is a view of a further example of an electrical connector. 
         FIG. 12B  is an exploded view of the electrical connector of  FIG. 12A . 
     
    
    
     DETAILED DESCRIPTION 
     Sometimes it is desirable to transfer signals (e.g., power signals, digital signals and so forth) from one circuit board to another circuit board, where the circuit cards are stacked, for example. The circuit cards may be stacked in a parallel or substantially parallel configuration to one another. In situations, where cabling cannot be used due to mechanical packaging, electrical, cable length or other restrictions, other methods are required. In other situations, the connections between two circuit cards may be required to meet certain tolerance requirements. 
     As described herein, various examples of electrical connectors may be used to mate two circuit cards, for example, two circuit cards that are stacked together. As described herein, the term “stacked” means that the two circuit cards are spaced apart. As will be shown, when the two circuit cards are electrically connected, an electrical connector is disposed between the two circuit cards (e.g., an electrical connector  50  in  FIG. 8C  is disposed between circuit cards  102 ,  104 ). In one particular example, the two circuit cards are parallel or substantially parallel. While the embodiments of the electrical connector described herein are used in an antenna panel array radio frequency (RF) system environment, the electrical connector may be used in any environment that electrically connects circuit cards together. 
     Referring now to  FIGS. 1 to 3 , in which like elements are provided having like reference designations throughout the several views, an antenna panel array subsystem  10  is a portion of a radar, communications or other RF transmit/receive system. The antenna panel array subsystem  10  includes an array antenna  11  provided from a plurality (or an array) of so-called RF “antenna panels”  12  (sometimes more simply referred to herein as “panel  12 ”). The array antenna  11  has a so-called “panel architecture.” The panels  12  are removably attached to LRUs  20 . For example, a panel  12 ′ is shown detached (e.g., in an exploded view) from the LRUs  20 . 
     In one example, the panels  12  are stand-alone units. That is, the panels  12  are each independently functional units (i.e., the functionality of one panel does not depend on any other panel). For example, the feed circuit for each panel  12  is wholly contained within the panel itself and is not coupled directly to any other panel. In the event that one panel  12  fails, the panel  12  may simply be removed from the array  11  and another panel can be inserted in its place. This characteristic is particularly advantageous in RF transmit/receive systems deployed in sites or locations where it is difficult to service the RF system in the event of some failure. 
     In one example, the antenna panel array subsystem  10  is a phased array RF system. The relatively high cost of phased arrays has precluded the use of phased arrays in all but the most specialized applications. Assembly and component costs, particularly for active transmit/receive channels, are major cost drivers. Phased array costs can be reduced by utilizing batch processing and minimizing touch labor of components and assemblies. Therefore, it is advantageous to provide a tile sub-array (e.g., the panel  12 ), for an Active, Electronically Scanned Array (AESA) that is compact, which can be manufactured in a cost-effective manner, that can be assembled using an automated process, and that can be individually tested prior to assembly into the AESA. By using a tile sub-array (e.g., a panel) configuration, acquisition and life cycle costs of phased arrays are lowered, while at the same time improving bandwidth, polarization diversity and robust RF performance characteristics to meet increasingly more challenging antenna performance requirements. 
     In one example, the panel array subsystem  10  enables a cost-effective phased array solution for a wide variety of phased array radar missions or communication missions for ground, sea and airborne platforms. In at least one example, the panel array system  10  provides a thin, lightweight construction that can also be applied to conformal arrays attached to an aircraft wing or a fuselage or a sea vessel or a Unmanned Aerial Vehicle (UAV) or a land vehicle. 
     Other panels, phased arrays and phased array configurations may be found in U.S. Pat. No. 7,348,932 and U.S. Pat. No. 6,624,787, which are incorporated herein in their entirety and are assigned to the same assignee (Raytheon Company of Waltham, Mass.) as the present patent application. 
     The panel  12  maintains a low profile, for example, by stacking a plurality of multilayer circuit boards that provide one or more circuit assemblies in which RF and other electronic components are disposed in close proximity with each other. The operation of such electronic components uses electrical power and dissipates energy in the form of heat so that the panels  12  are cooled to reduce the heat. For example, as shown in  FIGS. 1 to 3 , array antenna  11  (and more specifically the panels  12 ) is coupled to a panel heat sink  14 . In this example, the panel heat sink  14  includes, for example, four separate sections  14   a - 14   d . A first surface of each heat sink section  14   a - 14   d  is designated  15   a  and a second opposing surface of each heat sink section  14   a - 14   d  is designated  15   b  so that RF panels  12  are coupled to the first surface  15   a  of heat sink  14 . 
     A rear heat sink  16  is coupled to surface  15   b  of heat sink  14 . In this example, the rear heat sink  16  includes, for example, four separate sections  16   a - 16   d  ( FIG. 2 ). A first surface of each heat sink section  16   a - 16   d  is designated  17   a  and a second opposing surface of each heat sink section  16   a - 16   d  is designated  17   b  so that portions of the heat sink surface  15   b  contact portions of heat sink surface  17   a.    
     A set or combination of heat sink sections and associated panels can be removed from the array  11  and replaced with another set of heat sink sections and associated panels. Such a combination is referred to as a line replaceable unit (LRU). For example, heat sink sections  14   a ,  16   a  and the panels dispose on heat sink section  14   a  form a LRU  20   a . In one particular example, the panel array system  10  includes four LRUs  20   a - 20   d  with each of the LRUs including eight panels  12 , a corresponding one of the panel heat sink sections  14   a - 14   d  and a corresponding one of the rear heat sink sections  16   a - 16   d.    
     Referring briefly to  FIG. 3A , taking the LRU  20   d  as representative of the LRUs  20   a - 20   c , each of the heat sinks  14   d ,  16   d  are provided having respective recess regions  22 ,  24  in which electronics  26 ,  28  are disposed. When the heats sinks  14 ,  16  are coupled together, the electronics  26 ,  28  are effectively disposed in a cavity region formed by the recesses  22 ,  24  and associated internal surfaces of the respective heat sinks  14 ,  16 . In one example, the panel heat sink  14  primarily cools the panels  12  and the electronics  26  while the rear heat sink  16  primarily cools the electronics  28 . In one example, the electronics  26  and the electronics  24  each include circuit cards  102 ,  104  ( FIG. 7 ) connected by an electrical connector  50 . The connector  50  supplies signals (e.g., power signals) between the circuit cards  102 ,  104 . 
     Other heat sink configurations are known to one of ordinary skill in the art. For example, only one of the heat sinks  14 ,  16  may be provided having a recess region with electronics disposed therein. Alternatively, in some examples, neither of the heat sinks  14 ,  16  may be provided having a recess region. The particular manner in which to provide the heat sinks and in which to couple the electronics depends upon the particular application and the factors associated with the application. 
     In one example, the heat sinks  14 ,  16  are provided as so-called cold plates which use a liquid, for example, to cool any heat generating structures (such as the panels  12  and the electronics  26 ,  28 ) coupled thereto. For example, the liquid is fed through channels (not shown) provided in the heat sinks  14 ,  16  via fluid fittings  29  and fluid paths  18 . In one example, each of the heat sinks  14 ,  16  may include different components or subassemblies coupled together (as shown in  FIGS. 1 to 3 ) or alternatively heat sinks  14 ,  16  may be provided as monolithic structures. 
     Since the electronics are disposed between a surface of the panel heat sink and an internal surface of the rear heat sink, the electronics  26 ,  28  are not accessible when the panel heat sink  14  and rear heat sink  16  are coupled as shown in  FIGS. 1 to 3 . In order to provide access to the recess region of the rear heat sink  16  (and thereby provide access to the electronics disposed in the recess region of rear heat sink  16 ), one or more translating hinges  30  couples panel heat sinks  14   a - 14   d  to respective ones of rear heat sinks  16   a - 16   d.    
     As may be more clearly seen with reference to  FIGS. 2 to 4  heat sinks  14   a - 14   d  are coupled to heat sinks  16   a - 16   d  respectfully via fasteners  36  and translating hinges  30 . In one example, the fasteners  36  are provided as screws which are captive in heat sink  16  and which mate with threaded holes provided in the heat sink  14 . It should be appreciated that one of ordinary skill in the art would understand how to select an appropriate type and number of fasteners  36  to use in any particular application. 
     As seen in  FIGS. 3 and 3B , translating hinge  30  couples panel heat sink  14   d  to rear heat sink  16   d . Hinging panel heat sink  14   d  and rear heat sink  16   d  is beneficial since when servicing either of the assemblies, hinges  30  captivate the heat sinks  14   d ,  16   d  and thus neither heat sink  14   d ,  16   d  is loose. This reduces the chance of damage to either of heat sinks  14   d ,  16   d . Also, since neither heat sink is ever loose, the translating hinges  30  improve serviceability of the heat sinks  14 ,  16  as well as the serviceability of the electronics  26 ,  28  disposed in the recess regions of heat sinks  14   d ,  16   d.    
     It should be appreciated that in  FIGS. 2 and 3  each of panel heat sinks  14   a - 14   d  are coupled to respective rear heat sinks  16   a - 16   d  by a pair of translating hinges  30 , in other embodiments fewer or more than two translating hinges may be used. 
     The translating hinge approach eliminates the need for a coolant quick disconnect that would be required to separate the two cold plates. Fewer quick disconnects mean fewer leaks and a more robust, reliable system. Furthermore, electrical interconnections to (e.g., from external locations as through RF and DC/logic connectors  32 ,  34  in  FIG. 3B ) and/or between electronics  26 ,  28  can remain intact during servicing. This reduces the possibility of damage to connectors (e.g., due to disconnecting and reconnecting electrical connectors) and also allows access to and testing of the electronics in an easily accessible configuration. 
     Referring to  FIGS. 4A to 4D , an electrical connector  50  is used to transfer signals (e.g., power signals, digital signals and so forth) between the first and second circuit cards  102 ,  104  ( FIG. 7 ). In one example, the electrical connector  50  is used as a low-inductance connector. The electrical connector  50  includes rigid members  52   a ,  52   b , alignment pins  56   a ,  56   b  and a compliant member  58 . The rigid member  52   a  is attached to one end portion  51  of the compliant member  58  and the rigid member  52   b  is attached to the other end portion  53  of the compliant member  58 . In one example, the rigid members  52   a ,  52   b  are attached to the compliant member  58  using an epoxy or an adhesive. 
     The connector  50  includes four apertures on the compliant member  58 . A first set of apertures  72   a ,  74   a  on the one end  51  of the compliant member  58  and a second set of apertures  72   b ,  74   a  on the other end  53  of the compliant member  58   
     The alignment pins  56   a ,  56   b  each include a body portion and a threaded head portion (e.g., the alignment pin  56   a  includes a body portion  57   a  and a head portion  59   a  and the alignment pin  56   b  includes a body portion  57   b  and a head portion  59   b ). The alignment pins  56   a ,  56   b  are secured within a corresponding one of the rigid member  52   a ,  52   b  and the body portions  57   a ,  57   b  extend along a Z-axis into the other of the rigid member  52   b ,  52   a . As will be shown further, the compliant member  58  flexes along the Z-axis and conducts electricity between its end portions  51 ,  53  which allows electrical signals to pass between, for example, the first and second circuit cards  102 ,  104  ( FIG. 7 ). 
     Referring to  FIGS. 5A to 5D , the compliant member  58  includes a first insulator layer  62   a , a first electrically conductive layer  64   a , a second insulator layer  62   b , a second electrically conductive layer  64   b  and a third insulator layer  62   c . The first electrically conductive layer  64   a  includes apertures  74   a ″,  72   b ″, the second electrically conductive layer  64   b  includes apertures  72   a ″,  74   b ″, and the third insulator layer  62   c  includes apertures  72   a ′,  74   a ′,  72   b ′,  74   b ′. When the layers  62   a - 62   c ,  64   a ,  64   b  are combined the apertures  72   a ′,  72   a ″ form the aperture  72   a , the apertures  72   b ′,  72   b ″ form the aperture  72   b , the apertures  74   a ′,  74   a ″ form the aperture  74   a  and the apertures  74   b ′,  74   b ″ form the aperture  74   b.    
     In one example, the insulator layers  62   a ,  62   c  protect the electrically conductive layers  64   a ,  64   b  respectively from external damage such as nicks and scratches. The insulation layers  62   a - 62   c  also prevent an electrical short-circuit between the electrically conductive layers  64   a ,  64   b  by separating the electrically conductive layers to prevent the electrically conductive layers from touching ( FIG. 5C ). Generally, in fabricating the compliant member  58 , the insulator layers  62   a - 62   c  and the electrically conductive layers  64   a ,  64   b  are flat initially and subsequently bent and shaped. For example, the compliant member  58  is shaped to include a flex point  76  so that the compliant member may flex in the Z-axis. In one example, the electrically conductive layers  64   a ,  64   b  are metal layers such as copper, aluminum and so forth. In one example, the insulator layers  62   a - 62   c  are polyimide laminate layers. In one example, the compliant member  58  allows for an inductance of the connector  50  to be about 0.5 nH. 
     The electrically conductive layers  64   a ,  64   b  may be resized to meet various system requirements (e.g., current requirements, inductance requirements). In some examples, shape, height, and amount of tolerance compensation of the compliant member  58  may be tailored to fit different applications. 
     Referring to  FIGS. 6A to 6C , the rigid members  52   a ,  52   b  are substantially the same so that the rigid member  52   b  may be represented by the rigid member  52   a  in  FIGS. 6A to 6C . In one example, the rigid members  52   a ,  52   b  are an epoxy glass laminate such as FR-4 and G-10, for example. 
     The rigid member  52   a  includes bores  82   a ,  84   a  to receive the alignment pins  56   a ,  56   b . For example, the bore  82   a  includes an aperture  73   a  for receiving the alignment pin  56   a  and the bore  84   a  includes an aperture  69   a  for receiving the alignment pin  56   b . The aperture  73   a  is aligned with the aperture  74   a  of the compliant member  58 . 
     The bore  82   a  included two portions  83   a ,  85   a . The first portion  83   a  is threaded and has a first diameter, D 1 , to engage the head portion  59   a  of the alignment pin  56   a . The second portion  85   a  has a second diameter, D 2 , that is smaller than the first diameter, D 1 , but large enough for the body portion  57   a  of the alignment pin  56   a  to pass through. The bore  82   a  is sufficiently long enough to accommodate a fastener  112  ( FIG. 7 ). 
     The bore  84   a  included two portions  87   a ,  89   a . The first portion  87   a  is threaded and has a first diameter, D 3 , to engage a fastener  112  ( FIG. 7 ). The aperture  75   a  is aligned with the aperture  72   a  of the compliant member  58 . The second portion  89   a  has a second diameter, D 4 , that is smaller than the first diameter, D 3 , but large enough for the body portion  57   b  of the alignment pin  56   b  to pass through the aperture  69   a . The bore  87   a  is sufficiently long enough to accommodate a fastener  112  ( FIG. 7 ). 
     In one example, the diameters D 1  and D 3  are equal. In another example, the diameters D 2  and D 3  are equal. 
     Referring to  FIGS. 6D and 6E , in one example, the alignment pin  56   a  is installed into the connector  50  by passing the alignment pin  56   a  through the aperture  74   a  into the bore  82   a  and is screwed into the first portion  83   a  of the bore  82   a  so that the head portion  59   a  of the alignment pin  56   a  is secured in the first portion  83   a  of the bore  82   a . The body portion  57   a  of the alignment pin  56   a  extends through the second portion  85   a  of the bore  82   a  into a second portion  89   b  of the bore  84   b  of the rigid member  52   b.    
     The alignment pin  56   b  is installed into the connector  50  by passing the alignment pin  56   b  through the aperture  74   b  into the bore  82   b  and screwed into the first portion  83   b  of the bore  82   b  so that the head portion  59   b  of the alignment pin  56   b  is secured in the first portion  83   b  of the bore  82   b . The body portion  57   b  of the alignment pin  56   b  extends through the second portion  85   b  of the bore  82   b  into a second portion  89   a  of the bore  84   a  of the rigid member  52   a.    
     Without any force being applied to the electrical connector  50 , a distance from a top surface  91  of the electrical connector to a bottom surface  93  of the electrical connector is an extension distance, D E . When a force F 1  is applied to one end of the connector  50  and an equal force F 2  is applied to the opposite end of the connector, the compliant member  58  bends at the flex point  76  until the rigid members  52   a ,  52   b  are in contact so that the rigid members  52   a ,  52   b  function as mechanical stops ( FIG. 6E ). A distance from a top surface  91  of the electrical connector to a bottom surface  93  of the electrical connector shrinks to a compression distance, D C . The ability of the electrical connector  50  to flex in the Z direction accounts for tolerances which arise due to fabrication and assembly variations. For example, the Z-axis compensation by the electrical connector  50  absorbs inherent tolerances that exist between two circuit cards  102 ,  104  that are mounted to unique surfaces. In particular, a thickness tolerance, D TOL1 , ( FIG. 8B ) of the first circuit card  102  and a thickness tolerance, D TOL2 , ( FIG. 8B ) of the second card  104  are added together to determine the amount of the extension distance, D E  and the compression distance, D C  that are required by the electrical connector  50 . In one example, the electrical connector  50  accounts for differences in circuit card thickness of +/−10%. Other tolerances may rise from machining of the heat sink sections  14 ,  16 , for example, a tolerance distance D TOL3 , ( FIG. 8B ) for the heat sink section  14  and a tolerance distance for the heat sink section  16  D TOL4  ( FIG. 8B ). 
     Referring to  FIG. 7 , in one example, the electrical connector  50  is used to connect a first circuit card  102  and a second circuit card  104 . The electrical connector  50  is secured to the first circuit card  102  by fasteners  112 . The fasteners  112  extend through the first circuit card  102  through a contact pad  116   a  (e.g., a metal contact pad), through apertures  74   a ,  72   a  into a corresponding bore  82   a ,  84   a . The electrical connector  50  is also secured to the second circuit card  104  by the fasteners  112 . The fasteners  112  extend through the second circuit card  104  through a contact pad  116   b  (e.g., a metal contact pad), through apertures  74   b ,  72   b  into a corresponding bore  82   b ,  84   b . The fasteners complete an electrical connection between the first circuit card  102  and the second circuit card  104  so that the signals between the circuit cards passes through the compliant member  58 . In one example, the fasteners  112  are screws (e.g., threaded screws) that engage the threads in the bores  82   a ,  82   b ,  84   a ,  84   b.    
     Referring to  FIGS. 8A to 8C  and using the LRU  20   d , one example of a process to connect the connector  50  in the panel array subsystem  10  is to secure the connector  50  to the first circuit card  102  using fasteners  112  ( FIG. 8A ). The cold plate  16   d  is rotated using the hinge  36  so that the cold plate  16   d  is directly above the cold plate  14   d  leaving a gap, G ( FIG. 8B ). To close the gap, G, a force F 3  is applied on the cold plate  16   d  ( FIG. 8B ). Perimeter screws (not shown) are used to provide the Force, F 3 , to close the gap, G. After the gap G is closed fasteners  112  are used to secure the connector  50  to the second circuit card  104  in the cold plate  16   d.    
     Referring to  FIGS. 9A and 9B , another example of an electrical connector is an electrical connector  50 ′. In one example, the electrical connector  50 ′ is used as a high-current connector. The electrical connector  50 ′ includes rigid members  152 ,  154 , alignment pins  156   a ,  156   b  and a compliant member  158 . The rigid member  152  is attached to one end portion  151  of the compliant member  158  and the rigid member  154  is attached to the other end portion  153  of the compliant member  158 . In one example, the rigid members  152 ,  154  are attached to the compliant member  158  using an epoxy or an adhesive, for example. In one example, the rigid members  152 ,  154  are an epoxy glass laminate such as FR-4 and G-10, for example. 
     The electrical connector  50 ′ includes two apertures on the compliant member  158 . An aperture  172  on the one end  151  of the compliant member  158  and a second aperture  174  on the other end  153  of the compliant member  158 . 
     The alignment pins  156   a ,  156   b  each include a body portion and a threaded head portion (e.g., the alignment pin  156   a  includes a body portion  157   a  and a head portion  159   a  and the alignment pin  156   b  includes a body portion  157   b  and a head portion  159   b ). The alignment pins  156   a ,  156   b  are secured within a corresponding one of the rigid member  152 ,  154  and the body portions  157   a ,  157   b  extend along a Z-axis into the other of the rigid member  154 ,  152 . The compliant member  158  flexes along the Z-axis and conducts electricity between its end portions  151 ,  153  which allows electrical signals to pass between, for example, the first and second circuit cards  102 ,  104  ( FIG. 7 ). 
     The rigid member  152  includes bores  182 ,  184  to receive the alignment pins  156   a ,  156   b . For example, the bore  182  is configured to receive the alignment pin  156   a  and the bore  184  is configured to receive the alignment pin  156   b.    
     The bore  182  included two portions  183 ,  185 . The first portion  183  is threaded and has a diameter, D 5 , to engage the head portion  159   a  of the alignment pin  156   a . The second portion  185  has a diameter, D 6 , that is smaller than the diameter, D 5 , but large enough for the body portion  157   a  of the alignment pin  156   a  to pass through. The bore  182  is sufficiently long enough to accommodate the fastener  112  ( FIG. 7 ). The bore  184  has a first diameter, D 7 , large enough for the body portion  157   b  of the alignment pin  156   b  to pass through. The bore  184  is sufficiently long enough to accommodate the body portion  157   b  of the alignment pin  156   b.    
     The rigid member  154  includes bores  192 ,  194  to receive the alignment pins  156   a ,  156   b . For example, the bore  192  is configured to receive the alignment pin  156   b  and the bore  194  is configured to receive the alignment pin  156   a.    
     The bore  192  included two portions  193 ,  195 . The first portion  193  is threaded and has a diameter, D 8 , to engage the head portion  179   b  of the alignment pin  156   b . The second portion  195  has a diameter, D 9 , that is smaller than the diameter, D 8 , but large enough for the body portion  157   b  of the alignment pin  156   b  to pass through. The bore  192  is sufficiently long enough to accommodate the fastener  112  ( FIG. 7 ). The bore  194  has a diameter, D 10 , large enough for the body portion  157   a  of the alignment pin  156   a  to pass through. The bore  194  is sufficiently long enough to accommodate the body portion  157   a  of the alignment pin  156   a.    
     In one example, the diameter D 6  is equal to the diameter D 10 . In another example, the diameter D 7  is equal to the diameter D 9 . 
     Referring to  FIGS. 10A to 10C , the compliant member  50  includes a first insulator layer  162   a , an electrically conductive layer  164   a  and a second insulator layer  62   b . The electrically conductive layer  164  includes apertures  172 ″,  174 ″ and the first insulator layer  162   a  includes apertures  172 ′,  174 ′. When the layers  162   a ,  164 ,  162   b  are combined the apertures  172 ′,  172 ″ form the aperture  172  and the apertures  174 ′,  174 ″ form the aperture  174 . 
     In one example, the insulator layers  162   a ,  162   b  protect the electrically conductive layer  164  respectively from external damage such as nicks and scratches. Generally, in fabricating the compliant member  158 , the insulator layers  162   a ,  162   b  and the electrically conductive layer  164  are flat initially and subsequently bent and shaped. For example, the compliant member  158  is shaped to include a flex point  176  so that the compliant member may flex in the Z-axis. In one example, the electrically conductive layer  164  is a metal layer such as copper, aluminum and so forth. In one example, the insulator layers  162   a ,  162   b  are polyimide laminate layers. 
     Referring to  FIGS. 11A and 11B , in one example, the alignment pin  156   a  is installed into the connector  50 ′ by passing the alignment pin  156   a  through the aperture  172  and through the bore  182  and is screwed into the first portion  183  of the bore  182  so that the head portion  159   a  of the alignment pin  156   a  is secured tight. The body portion  157   a  of the alignment pin  156   a  extends through the second portion  185  of the bore  182  into the bore  194  of the rigid member  154 . 
     The alignment pin  156   b  is installed into the connector  50 ′ by passing the alignment pin  156   b  through the aperture  174  and is screwed into the first portion  193  of the bore  192  so that the head portion  159   b  of the alignment pin  156   b  is secured tight. The body portion  157   b  of the alignment pin  156   b  extends through the second portion  195   b  of the bore  192  into the bore  184  of the rigid member  152 . 
     When a force F 4  is applied to one end of the connector  50 ′ and an equal force F 5  is applied to the opposite end of the connector, the compliant member  158  bends at the flex point  176  until the rigid members  52   a ,  52   b  are in contact ( FIG. 11B ). Therefore, the rigid members  52   a ,  52   b  act as mechanical stops. 
     Referring to  FIGS. 12A and 12B , another example of an electrical connector is an electrical connector  50 ″. The connector  50 ″ includes nested spring assembly  252 , a compliant member  258 , and rigid members  262   a ,  262   b . The nested spring assembly  252  includes a first spring  274  and a second spring  278  nested within the first spring. A pin  282  runs through the centers of the first and second springs  274 ,  278  in a Z direction and includes a pin  284 . The pin  282  is connected in a cavity  290  of the rigid member  262   b  and is securely attached in a cavity (not shown) in the rigid member  262   a  using the pin  284 . The springs  274 ,  278  are selected to provide adequate force on electrical surfaces (e.g., electrical pads  116   a ,  116   b  ( FIG. 7 ) and the compliant member  258 ). One of ordinary skill in the art would understand how to select the appropriate springs  274 ,  278  and understand that the nested spring assembly  252  may be replaced by a single spring. 
     The nested spring assembly  252  provides the compression force required for a low electrical contact resistance interface, replacing a need for any additional hardware such as alignment pins (e.g., alignment pins,  56   a ,  56   b ,  156   a ,  156   b ) or fasteners  112  in the electrical connectors  50 ,  50 ′. The connector  50 ″ reduces the average maintenance cycle time and eliminates foreign object debris (i.e., loose hardware) that could possibly be misplaced and damage sensitive electronics. 
     In other examples, one or more of the electrical connectors  50 ,  50 ′,  50 ″ described herein may be fabricated using different amounts of alignment pins, fastening methods and so forth to achieve the results set forth above. 
     Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Other embodiments not specifically described herein are also within the scope of the following claims.