Patent Publication Number: US-7722394-B2

Title: Electrical termination device

Description:
TECHNICAL FIELD 
     The present invention relates to high speed electrical connectors. In particular, the present invention relates to electrical termination devices that can be used in these high speed electrical connectors to facilitate high signal line density and shielded controlled impedance (SCI) for the signal lines. 
     BACKGROUND 
     Interconnection of integrated circuits to other circuit boards, cables or electronic devices is known in the art. Such interconnections typically have not been difficult to form, especially when the signal line densities have been relatively low, and when the circuit switching speeds (also referred to as edge rates or signal rise times) have been slow when compared to the length of time required for a signal to propagate through a conductor in the interconnect or in the printed circuit board. As user requirements grow more demanding with respect to both interconnect sizes and circuit switching speeds, the design and manufacture of interconnects that can perform satisfactorily in terms of both physical size and electrical performance has grown more difficult. 
     Connectors have been developed to provide the necessary impedance control for high speed circuits, i.e., circuits with a transmission frequency of at least 5 GHz. Although many of these connectors are useful, there is still a need in the art for connector designs having increased signal line densities with closely controlled electrical characteristics to achieve satisfactory control of the signal integrity. 
     SUMMARY 
     In one aspect, the present invention provides an electrical termination device including an electrically conductive shield element, an insulator disposed within the shield element, and one or more electrical contacts. The one or more electrical contacts are supported within and electrically isolated from the shield element by the insulator, and are configured for making electrical connections through a front end and back end of the shield element. The insulator includes one or more first keying elements configured to orient and retain the one or more electrical contacts in the insulator. 
     In another aspect, the present invention provides an electrical connector including an electrical cable, one or more electrical contacts, an insulator disposed around the one or more electrical contacts, and an electrically conductive shield element. The electrical cable includes one or more conductors and a ground shield surrounding the one or more conductors. The one or more electrical contacts are connected to the one or more conductors. The electrically conductive shield element is disposed around the insulator and connected to the ground shield. The insulator includes one or more first keying elements configured to orient and retain the one or more electrical contacts in the insulator. 
     In another aspect, the present invention provides an insulator having one or more first keying elements configured to orient and retain one or more electrical contacts in the insulator and configured to prevent assembly of the insulator into an electrically conductive shield element when the one or more electrical contacts are incorrectly oriented in the insulator. The one or more first keying elements may be configured to prevent the one or more electrical contacts from rotating in the insulator when the one or more electrical contacts and the insulator are in a correctly assembled configuration. 
     The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and detailed description that follow below more particularly exemplify illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an exemplary embodiment of an electrical termination device according to an aspect of the present invention. 
         FIGS. 2A-2D  are plan views of the shield element of the electrical termination device of  FIG. 1 . 
         FIGS. 3A-3I  are plan and cross-sectional views of the insulator of the electrical termination device of  FIG. 1 . 
         FIGS. 4A-4C  are plan and cross-sectional views of the electrical contact of the electrical termination device of  FIG. 1 . 
         FIG. 5  is a plan view of the electrical contact and the insulator of the electrical termination device of  FIG. 1  used with an electrical cable in an assembled configuration. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof. The accompanying drawings show, by way of illustration, specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined by the appended claims. 
       FIGS. 1-5  illustrate an exemplary embodiment of an electrical termination device  12  according to an aspect of the present invention.  FIG. 1  shows an exploded view of the exemplary electrical termination device  12  used with an electrical cable  20 , while  FIGS. 2-5  provide detailed views of the individual components of an electrical termination device according to an aspect of the present invention. Electrical termination device  12  includes a longitudinal electrically conductive shield element  40 , an insulator  42 , and a single electrical contact  44 . Insulator  42  electrically isolates electrical contact  44  from conductive shield element  40 . 
     Referring to FIGS.  1  and  2 A- 2 D, electrically conductive shield element  40  has a front end  46 , a back end  48 , and side surfaces  50   a - 50   d  (collectively referred to herein as “sides  50 ”) defining a non-circular transverse cross-section. Although the illustrated embodiment includes four sides  50  defining a substantially square transverse cross-section, shield element  40  may have other numbers of sides defining other generally rectangular or non-circular transverse cross-sections. In other embodiments, shield element  40  may have a generally curvilinear (such as, e.g., a circular) transverse cross-section. As illustrated, shield element  40  includes laterally protruding resilient ground contact beams  52  disposed on opposed side surfaces  50   a  and  50   c.  In other embodiments, shield element  40  includes only a single ground contact beam  52 . A latch member  54  extends from at least one of sides  50 . Latch member  54  is configured to retain termination device  12  in a retainer or organizer plate (not shown) configured to receive, secure, and manage a plurality of electrical termination devices. In one embodiment, latch member  54  is designed to yield (i.e., deform) at a lower force than required to break the attached electrical cable  20 , so that an electrical termination device  12  can be pulled out of the retainer or organizer plate for the purpose of replacing or repairing an individual electrical termination device and cable assembly. In the illustrated embodiment of  FIG. 1 , latch member  54  is shown on a different side  50   d  as one of ground contact beams  52 . However, in other embodiments, latch member  54  may additionally, or alternatively, be positioned on a side  50  of the shield element  40  that includes a ground contact beam  52  ( FIGS. 2A-2D ). Shield element  40  may further include a keying member, in the form of tab  60 , laterally extending from back end  48  of shield element  40 . Tab  60  is configured to ensure that electrical termination device  12  is inserted into the retainer or organizer plate in the correct predetermined orientation. If electrical termination device  12  is not properly oriented within the retainer or organizer plate, electrical termination device  12  cannot be fully inserted. In one embodiment, tab  60  is deformable (such as by the use of a tool or the application of excess force in the insertion direction) and may be straightened to allow a damaged or defective electrical termination device  12  to be pushed completely through the retainer or organizer plate, such that the damaged or defective components can be replaced or repaired. Although the figures show that shield element  40  includes ground contact beams  52 , it is within the scope of the present invention to use other contact element configurations, such as Hertzian bumps, in place of the contact beams  52 . 
     Referring now to FIGS.  1  and  3 A- 3 I, insulator  42  according to an aspect of the present invention includes a first insulative member  70  disposed within shield element  40  adjacent front end  46 , and a second insulative member  72  disposed within shield element  40  adjacent back end  48 . First and second insulative members  70 ,  72  are configured to provide structural support to insulator  42 . In this embodiment, a spacer bar  74  is provided that properly positions and spaces first and second insulative members  70 ,  72  with respect to each other. The first and second insulative members  70 ,  72  and spacer bar  74  are shaped to receive an electrical contact  44  and are configured for slidable insertion into shield element  40 , such that electrical contact  44  lies substantially parallel to a longitudinal axis of shield element  40 . The first and second insulative members  70 ,  72  and spacer bar  74  are configured to guide electrical contact  44  during its insertion into insulator  42 . In this configuration, electrical termination device  12  can serve as a coaxial electrical termination device, whereby electrical contact  44  can be connected, e.g., to a single coaxial cable. 
     In another embodiment, one or more spacer bars  74  are shaped to receive two electrical contacts  44  and are configured for slidable insertion into shield element  40 , such that two electrical contacts  44  lie substantially parallel to a longitudinal axis of shield element  40 . One or more spacer bars  74  are configured to guide two electrical contacts  44  during their insertion into insulator  42 . In this configuration, electrical termination device  12  can serve as a twinaxial electrical termination device, whereby two electrical contacts  44  can be connected, e.g., to a single twinaxial cable. 
     Insulator  42  further includes a first keying element  76  configured to orient and retain electrical contact  44  in insulator  42 . In one aspect, retaining electrical contact  44  in insulator  42  prevents substantial movement of electrical contact  44  in a direction substantially parallel to a longitudinal axis of electrical contact  44 . In one embodiment, electrical contact  44  includes a second keying element  78  configured to engage with first keying element  76  when electrical contact  44  and insulator  42  are in a correctly assembled configuration. First keying element  76  may be configured to prevent electrical contact  44  from rotating in insulator  42  when electrical contact  44  and insulator  42  are in a correctly assembled configuration. 
     In a preferred embodiment, spacer bar  74  and first keying element  76  are shaped and positioned relative to one or more electrical contacts  44  and shield element  40  such that air is the major dielectric material surrounding one or more electrical contacts  44 , so as to lower the effective dielectric constant of electrical termination device  12  and thereby lower the characteristic impedance of the electrical termination device and cable assembly closer to the desired target value, such as, for example, 50 ohms. 
     In the embodiment illustrated in  FIG. 1 , first keying element  76  extends from insulative member  70  (as best seen in  FIG. 3D ) and includes a resilient beam  80 , and a male key portion  82  positioned at an end of resilient beam  80 . As can best be seen in  FIG. 5 , male key portion  82  engages with a female key portion  84  of second keying element  78  of electrical contact  44  to properly position, orient and retain electrical contact  44  in insulator  42 . As electrical contact  44  is inserted into insulator  42 , first keying element  76  with resilient beam  80  and male key portion  82  deflects outwardly (away from electrical contact  44 ) until engaging with female key portion  84 . Beneficially, if electrical contact  44  is incorrectly oriented or improperly assembled into insulator  42  (i.e., such that male key portion  82  is not aligned or engaged with female key portion  84 , the presence of male key portion  82  will cause first keying element  76  to remain deflected outwardly such that insulator  42  will not fit in shield element  40 , thereby preventing the installation and use of an improperly assembled electrical termination device  12 . Although in the embodiment of  FIG. 1  first keying element  76  includes male key portion  82  and second keying element  78  includes female key portion  84  configured to receive male key portion  82 , in other embodiments, the proper positioning, orienting, and retaining, as well as preventing rotation of contact  44 , may be accomplished by alternative embodiments of first keying element  76  and second keying element  78 . For example, second keying element  78  may include a male key portion and first keying element  76  may include a female key portion configured to receive the male key portion. In another example, first keying element  76  and second keying element  78  may include reciprocal key portions that, for example, include both male and female features. In alternative embodiments, insulator  42  may include two or more first keying elements  76  configured to orient and retain one or more electrical contacts  44  in insulator  42 . In other embodiments, first keying element  76  of insulator  42  may include a resilient beam  80  that spans between insulative member  70  and insulative member  72  of insulator  42 . 
     Still referring to FIGS.  1  and  3 A- 3 I, insulator  42  has a front end  94 , a back end  96 , and outer surfaces  98   a - 98   d  (collectively referred to herein as “outer surface  98 ”) defining a non-circular shape. Although the illustrated embodiment includes an outer surface  98  defining a substantially square shape, insulator  42  may have an outer surface  98  defining other suitable shapes, including generally rectangular, non-circular, or curvilinear (such as, e.g., circular) shapes. 
     Insulator  42  can be formed of any suitable material, such as, e.g., a polymeric material, by any suitable method, such as, e.g., injection molding, machining, or the like. 
     In one embodiment, insulator  42  and one or more first keying elements  76  may be monolithic. For example, insulator  42  and first keying elements  76  may be injection molded as a monolithic structure. In another embodiment, insulator  42  and one or more first keying elements  76  may comprise separate elements, assembled by any suitable method or structure, including but not limited to snap fit, friction fit, press fit, mechanical clamping, and adhesive. For example, insulator  42  may be injection molded and one or more first keying elements  76  may be machined and assembled to insulator  42  by press fit. 
     In one embodiment, electrical termination device  12  is configured for termination of an electrical cable  20 , such that a conductor  90  of electrical cable  20  is attached to electrical contact  44  and ground shield  92  of electrical cable  20  is attached to shield element  40  of electrical termination device  12  using conventional means, such as soldering. The type of electrical cable used in an aspect of the present invention can be a single wire cable (e.g., single coaxial or single twinaxial) or a multiple wire cable (e.g., multiple coaxial, multiple twinaxial, or twisted pair). In one embodiment, prior to attaching one or more electrical contacts  44  to one or more conductors  90  of electrical cable  20 , ground shield  92  is stiffened by a solder dip process. After one or more electrical contacts  44  are attached to one or more conductors  90 , the one or more electrical contacts  44  are slidably inserted into insulator  42 . The prepared end of electrical cable  20  and insulator  42  are configured such that the stiffened ground shield  92  bears against back end  96  of insulator  42  prior to one or more electrical contacts  44  being fully seated against front end  94  of insulator  42 . Thus, when insulator  42  (having one or more electrical contacts  44  therein) is next slidably inserted into shield element  40 , the stiffened ground shield  92  acts to push insulator  42  into shield element  40 , and one or more electrical contacts  44  are prevented from pushing against insulator  42  in the insertion direction. In this manner, one or more electrical contacts  44  are prevented from being pushed back into electrical cable  20  by reaction to force applied during insertion of insulator  42  into shield element  40 , which may prevent proper connection of one or more electrical contacts  44  with a header. In one embodiment, and as can be seen in  FIG. 5 , conductor  90  of electrical cable  20 , once attached to electrical contact  44 , provides additional structure to female key portion  84  of second keying element  78  of electrical contact  44  to help retain electrical contact  44  in insulator  42 . 
     In one embodiment, electrical termination device  12  includes two electrical contacts  44  and is configured for termination of an electrical cable  20  including two conductors  90 . Each conductor  90  of electrical cable  20  is connected to an electrical contact  44  of electrical termination device  12 , and ground shield  92  of electrical cable  20  is attached to shield element  40  of electrical termination device  12  using conventional means, such as soldering. The type of electrical cable used in this embodiment can be a single twinaxial cable. 
     In each of the embodiments and implementations described herein, the various components of the electrical termination device and elements thereof are formed of any suitable material. The materials are selected depending upon the intended application and may include both metals and non-metals (e.g., any one or combination of non-conductive materials including but not limited to polymers, glass, and ceramics). In one embodiment, insulator  42  is formed of a polymeric material by methods such as injection molding, extrusion, casting, machining, and the like, while the electrically conductive components are formed of metal by methods such as molding, casting, stamping, machining, and the like. Material selection will depend upon factors including, but not limited to, chemical exposure conditions, environmental exposure conditions including temperature and humidity conditions, flame-retardancy requirements, material strength, and rigidity, to name a few. 
     Although specific embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent implementations calculated to achieve the same purposes may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. Those with skill in the mechanical, electromechanical, and electrical arts will readily appreciate that the present invention may be implemented in a very wide variety of embodiments. This application is intended to cover any adaptations or variations of the preferred embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.