Shielded back plane connector

Abstract: A shielded back plane connector comprises a header assembly (2) and a daughter board connector (4). The daughter board connector includes an upper and lower shield (22, 24) where the upper and lower shields (22, 24) include stamped windows (84) thereby forming passages for allowing structural ribs (32) of the housing to pass therethrough while providing a contact (82 for contact with grounding pins (48) disposed in the header assembly. A cross talk shield (100) can be positioned intermediate each of the terminal sub-assemblies (20) thereby reducing the cross talk between adjacent terminals. The shield (100) includes a contact portion for contacting the centre terminal in the shielded sub-assembly, for using the centre terminal as a ground terminal.

Description: The present invention relates to a shielded back plane connector which can be mounted to a back plane, which receives a shielded daughter card connector. It is common in electronic architecture to provide for a header connector having a plurality of male pins to be mounted to a mother board connector. A daughter board connector is mounted to a daughter card and is profiled for receipt within the header connector, the daughter board connector having a plurality of receptacle sockets for electrical connection with the male pins in the header. It is known to provide a shield between the vertical rows of terminals to prevent cross-talk between the vertical columns. For example, as shown in German patent application, DE-A-40 40 551, a cross-talk shield is placed intermediate the terminal subassemblies which form the connector. One of the drawbacks to the above-mentioned design is that a different terminal subassembly is necessary due to the thickness of the shield itself. It is an object of the invention then to provide a backplane connector having a cross-talk shield. A further object of the invention is to provide for a shielded back plane assembly having overall reduced dimensions, without compromising on other characteristics such as EMI/RFI, signal speed, and the like. A further object of the invention is to substantially eliminate the cross-talk between adjacent terminals. The objects were accomplished by providing an electrical connector as defined in claim 1. There is disclosed herein a high density shielded back plane connector comprising a front housing portion and a plurality of terminal sub assemblies fixed to the front housing, the terminal sub assemblies comprising front mating contact portions positioned in the front housing portion, an intermediate portion moulded in an insulative web of material and a rear contact portion extending from the web of material and adapted for mating with further conductors. A shield portion is positioned intermediate each of the plastic webs where the web includes a reduced thickness of a reduced thickness section in the web on both sides thereof the reduced thickness portion forms a thin membrane over a substantial portion of the intermediate portions thereby increasing the impedance along the intermediate portions interiorly of the shields. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is an isometric view of the shielded daughter board connector exploded from the complementary header; Figure 2 is an isometric view of an enlarged section of the connectors shown in Figure 1; Figure 3 is a cross-sectional view through the connector of Figure 1 or 2 showing the internal structure thereof; Figure 4 is a cross-sectional view similar to that of Figure 3 showing an alternative embodiment having a cross talk shield; Figure 5 is a side plan view of the terminal sub-assembly for use in the embodiment of Figure 4; Figure 6 is a cross-sectional view through lines 6-6 of Figure 5; Figure 7 is a lower plan view of the terminal sub-assembly shown in Figure 5; Figure 8 is a plan view of the cross talk shield in a stamped blank form; Figure 9 is a side plan view showing the cross talk shield in place on the terminal sub-assembly; Figure 10 shows a cross-sectional view of the terminal sub-assembly through lines 10-10; and Figure 11 shows a lower plan view of two of the sub-assemblies stacked together with the cross talk shield in place. Figure 1 is an isometric view of a header connector shown generally at 2 and a shielded daughter card connector shown generally at 4. The header assembly 2 is generally comprised of an insulating housing 6 having a lower surface 8 for mounting to a mother board and side walls 10 upstanding from the floor portion 8. With reference still to Figure 1, the daughter board connector 4 is generally comprised of a forward housing portion 12 having a front mating face 14 side surfaces 16 and a rear surface 18. A plurality of terminal sub-assemblies 20 are shown assembled to the housing 12 and encapsulated in upper and lower shield members 22, 24 respectively. With reference now to Figure 2, the header assembly 2 and daughter board assembly will be described in greater detail, where Figure 2 is an enlarged section of the assemblies shown in Figure 1. As shown in Figure 2, the header housing 6 has side walls 10 comprised of thin side wall sections 26 having end strengthening ribs 28 and 30. Along the interior length of the thin side wall section 26, a plurality of strengthening ribs 32 are positioned integral with the sidewall 10 to rigidify these thin side wall sections. The header assembly 2 further comprises a plurality of signal contacts 36 having compliant pin portions 38 extending outwardly from the floor 8 and further include male pin portions 40 positioned within the header intermediate the side walls 10. The header assembly 2 further comprises a plurality of grounding contacts 44 having compliant pin portions 46 and a grounding pin portion 48 positioned between strengthening ribs 32. With reference now to Figures 2 and 3, the daughter board connector 4 will be described in greater detail. Housing 12 includes a plurality of signal pin contact receiving openings shown at 50 leading into a terminal receiving passageway 52, the passageway 52 extending rearwardly to a face 54. A plurality of terminal subassemblies 20 are positioned against the housing 12 where each subassembly includes a plurality of electrical terminals 56 encapsulated in an overmoulded web of plastic material 58. Each contact 56 includes a receptacle portion 60 for mating contact with one of the male signal pins 40 and further comprises an intermediate portion 62, which interconnects the receptacle portions to and compliant pin portions 64. With reference again to Figure 2, the upper shield member 22 includes an upper plate portion 70 for positioning above the housing portion 12 and above the terminal subassemblies 20. The upper shield member 22 further includes a rear plate portion 72 for positioning behind the terminal subassemblies 20, the rear plate portion 72 including a plurality of integral compliant pin sections 74 for mechanical and electrical connection to a printed circuit board 75, as shown in Figure 3. The upper shield member 22 further includes a thin plate portion 78 (Figure 3) formed by a premilling operation to reduce the thickness of the shield portion over the housing 20 to reduce the overall width dimension of the shielded data board connection. As shown in Figure 2, the upper shield 22 is kinked adjacent to the front mating face 14 to form projections 82 extending above the plane formed by the upper plate portion 70. A plurality of windows 84 are stamped from the upper plate portion 70 whereby the windows are laterally positioned to receive the strengthening ribs 32 therein, while the projections 82 form shield contacts, which span the strengthening ribs 32, for mating with the ground pins 48. To rigidify the plurality of shield contacts 82 a strengthening strap 85 extends transversely of the shields contacts 82 and is held to the housing by a folded front edge 86 positioned in a laterally extending groove 88 (Figure 3). To improve the resiliency of the shield contacts 82 a laterally extending channel 90 is positioned below the shield contacts 82. The lower shield member 24 is similar to the upper shield portion including a plate portion 95 having a thin wall section 96, shield contacts at 98, and compliant portions 99 for interconnection to the printed circuit board. With reference now to Figure 4, the above mentioned daughter board connector 4 can alternatively be used with an additional shield placed intermediate the plurality of terminal sub-assemblies 20 to reduce the cross talk between the adjacent terminal strips. For this purpose, a cross talk shield 100 can be positioned between each adjacent stacked terminal sub-assembly 20. In the preferred embodiment of the invention the cross talk shield 100 contacts the center terminal 56C leaving terminals 56A, 56B and 56D, 56E for signal contacts thereby forming a modified strip line connector. With reference now to Figure 5, the shielded sub-assembly 20 will be described in greater detail for use with the cross talk shield. As mentioned above, the terminal sub-assembly 20 has an overmoulded web of material 58 having a recessed pocket at 102 and a recessed surface 104. As shown in Figures 5 and 6, a window is formed at 106 exposing a portion of the central terminal 56C for contacting with the cross talk shield 100. With reference again to Figure 5, two apertures are formed through the insulating web 58 at 110 and a lower slot 112 is formed by two upstanding ribs 114 having a thickness equal to the raised portion 104 with the intermediate portion between the slot being recessed to the surface 102. With reference now to Figure 8, the cross talk shield 100 has a flat plate portion 120 including two lower contact arms 122 for contact with a trace on a printed circuit board, and further comprises an upper contact arm shown at 124. The cross talk shield 100 further comprises locking tabs 126 at an upper edge thereof, and locking tab 128 at a lower edge thereof. As shown in Figure 10, the cross talk shield is formed with the contact arm 124 bent around an upper edge of the flat plate portion 122, and the end of the contact arm 124 is formed with a radius section thereby forming a contact surface 127 for contacting the central contact 56C. Figure 10 also shows cross-talk shield positioned on the surface 104, with the cooperation between the tabs 126 within the openings 110, and shows the tab 128 frictionally held between the two upstanding ribs 114 in the slot thereof. As shown in Figures 10 and 11, a plurality of cross talk shields 100 can be placed against the terminal sub-assemblies 20 to reduce the cross talk between adjacent terminal sub-assemblies. The cross-talk shields can be added without increasing the stack thickness of the terminal sub-assemblies and the shields 100, as the shields are positioned against the recessed surface 104. Advantageously then, as the center line distance between adjacent terminals in adjacent terminal sub-assemblies 20 has been reduced by half, by the addition of the cross talk shield 100, the impedance has been increased by the formation of the recessed surface 102, thereby providing a pocket of air adjacent to the terminals. Furthermore the ground signal path has been reduced by providing two contact arms 122 adjacent to the daughter board and by providing the contact to the centre terminal 56C. Moreover, as shown in Figure 11, the modules 20 can be stacked one against the other with the shield member therebetween. Due to the recessed area 104, which is profiled to receive the shield 100, the stacking thickness of the modules 20, remains the same, with or without the shields 100 therebetween. Thus, the connector system described above can be used without the cross talk shields 100, without having to change the contact modules 20.

Claims: An electrical connector (4) having a front housing portion (12) and a plurality of side by side terminal subassemblies (20) fixed to said front housing portion (12), the terminal subassemblies (20) comprising a front mating contact portion (60) positioned in said front housing portion (12), an intermediate portion (62) moulded in an insulative web (58) of material, and a rear contact portion (64) extending from said web of material (58) and adapted for mating with further conductors, and a shield portion (100) positioned intermediate each pair of adjacent webs (38), said connector (4) being characterized in that each web (58) includes a pocket (102) on both sides of said intermediate portions (62), said pocket (102) forming a thin membrane of said insulative material over a substantial portion of said intermediate portions (62) with the shield portion (100) positioned, thereby forming a pocket of air between said intermediate portions (62) and said shield portion (100), thereby increasing the impedance along the intermediate portions (62), interiorly of said shield portions (100). An electrical connector (4) according to claim 1, characterized in that, said web (58) includes a window (106) therethrough exposing one of said intermediate portions (62) of one select terminal (56c), and said shield portion (100) includes a resilient contact portion (126) for contacting said selected intermediate portion (62). An electrical connector (4) according to claim 1, characterized in that said resilient contact portion (126) is formed from a reversely bent contact leg (124) which extends integrally from said shield portion (100). An electrical connector (4) according to claims 2 or 3, characterized in that the resilient contact portion (126) is formed by a portion extending from one edge thereof. An electrical connector (4) according to any one of claims 1 to 4, characterized in that said connector includes five electrical terminals (56) positioned in said subassemblies (20). An electrical connector (4) according to any one of claims 1 to 5, characterized in that said terminals (56) are arranged in two pairs of signal contacts with the intermediate contact (56c) being said selected one, to ground said shield portion (100). An electrical connector (4) according to any one of claims 1 to 6, characterized in that said connector (4) is profiled as a right angled connector where said rear mating contact portions (64) extend from said web (58) at a substantial right angle relative to said front mating contact portions (60), said webs (58) including a lower edge profiled for receiving a printed circuit board thereagainst. An electrical connector (4) according to claim 7, characterized in that said shield portion (100) includes a second resilient contact portion (122) extending below said web lower edge, for contacting a ground plate on said printed circuit board. An electrical connector (4) according to any one of claims 1 to 8, characterized in that said shield portion (100) includes two resilient contact arms (122) extending from a lower edge thereof, profiled to contact a grounding pad on a printed circuit board. An electrical connector (4) according to any one of claims 1 to 9, characterized in that said web (58) includes a recess (104)about each pocket (102), profiled for receiving the shield portion (100) thereagainst, such that the stacking thickness of the subassemblies (20) remains constant whether the shield portion (100) is present or not.

Inventors: BROEKSTEEG JOHANNES MARCELUS, BROEKSTEEG, JOHANNES MARCELUS
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1993
Main classification: H01R13
IPC codes: H01R12, H01R13, H01R31, H01R24