Brief Description of Prior Developments: The use of shielding which incorporates judiciously stamped and formed structures is now a quite common means for improving connector electrical signal integrity for high clock-speed applications. A pre-requisite of a truly coaxial environment is the encirclement of the signal lead over its total length, from its start to exit locations, surrounded by a ground or floating metal shield with an interposing annulus of insulator space; such space being either air or a plastic dielectric medium. For board-to-board inter-mating connectors, ideally such a shielding means includes the use of a lead adjointment on the two boards, the implication being that in the mated condition, besides the interconnection of the signal leads, there is an adequate electrical and functional (spring) connection between the metal shield on receptacle and the plug sides.

Several means are available for the shielding of the METRAL receptacle available from Berg Electronics Group, Inc., Etters Pennsylvania, although only one for the plug, namely a die-cast header.

Such a header is costly to manufacture and has the additional constraint that the impedance change, over the inter-connection length, at the board interface is relatively large, resulting in problems associated with signal reflection. There is, therefore, a need for an alternative to the die-cast header. That is, there is a need for a means of controlling this impedance drop near the header bottom, while permitting adequate pin attachment both to plastic and later to board holes. There is also an additional requirement for use with an interstitial product as described in U. S.

Patent Application Serial No. (EL-6170), filed December 17, 1997, entitled HIGH DENSITY INTERSTITAL CONNECTOR SYSTEM for signal routing and space limitations to accommodate tracks and limit force for press-fit board application. Such applications require a preferably common shield to board connections located longitudinally along the outer (width) edge of the connector.

Summary of the Invention The present invention is an electrical connector in which there is a shield accessory plate having a dielectric air space. Preferably the accessory plate has a plurality of ground pin receiving apertures having pin retaining lips and a plurality of signal pin receiving apertures having peripheral walls extending perpendicularly from the planar base structures and there being a plurality of link walls extending perpendicularly from, the planar base structure to connect adjacent signal pin receiving structure peripheral walls.

This accessory plate can improve the high-speed signal integrity performance of the plug connector. The plug can simply be the conventional plastic walled header, or another variant (for previously mentioned difficulties not a die-cast header) satisfying previously mentioned goals. The basic idea is to have a thin metal plate located either above or below (or both simultaneously) the plastic header bottom with appropriately positioned holes to clear the contour of the signal pins.

Such plates may or may not have pins projecting from the planar face of the plate, as continuation of the shield fixture. Such plates can simultaneously have perpendicularly projecting press-fit tails and oppositely located spring lobes for contacting the outer shields of the receptacle connector. Basically, this integral shield unit is an accessory and may be fixed to a normal plastic header, as and when required.

Common to any future concept is the reduction in diameter (size) of the signal pin cross-section (at least in the plug bottom area) to offset and control the impedance drop due to adjacently positioned metal plate. This also facilitates adequate space/means of fixation of signal pins in plug bottom, while contributing towards increasing the space between tracks on board to ease routing.

Brief Description of the Drawings The application is further described with reference to the accompanying drawings in which: FIG. la is a top plan view of a plate representing a preferred embodiment of the present invention; FIG. I b is a cross sectional view through 1 b-1 b in FIG. la; FIG. 2a is a top plan view similar to FIG. la in which the plate is engaged with a plurality of ground and signal pins; FIG. 2b is a view through 2b-2b in FIG. 2a; FIG. 3a is a perspective view of the accessory plate shown in FIG la used in conjunction with a header in which the accessory plate is interposed between the header and the PCB; FIG. 3b is an exploded view of the assembly in FIG. 3a; FIG. 4a is a perspective view of the header shown in FIG. 3a in which the accessory plate is superimposed over the header; FIG. 4b is an exploded view of the assembly shown in FIG. 4a; FIG. 5a is a perspective view of an assembly comprising a different header than that is shown in FIG 3a and an accessory plate similar to the one shown in FIG. la with identical pins and grounding springs in which the accessory plate is interposed between the header and the printed circuit board (PCB); FIG. 5b is an exploded view of the assembly shown in FIG. 5a; FIG. 6a is a perspective view of an assembly comprising the header shown in FIG. 5a in which the accessory plate shown in FIG. 5a is superimposed over the header; FIG. 6b is an exploded view of the assembly shown in Fig, 6a; FIG. 7a is a perspective view of an assembly comprising a header similar to the one shown in FIG 5a in which an accessory plate is interposed between the header and the PCB and a second accessory plate is superimposed over the header; FIG. 7b is an exploded view of the assembly shown in FIG. 7a; FIG. 8 is a cut-away end view of the header and accessory plates shown in FIG. 4a; FIG. 9 is a cross sectional schematic view of a right angle receptacle connector system making use of the accessory plate shown in FIG. 1; and FIGS. lOa-lOd are schematic views in which FIG. lOa is a partial plan view of the accessory plate shown in FIG. lwith ground and signal pins, FIG. 10b is a cross section through 1-1 in FIG. 10a, FIG. lOc is a cross section through 2-2 or 4-4 in FIG. 10a, and FIG. 10d is a cross section through 3-3 and 5-5 in FIG. 10a.

FIG. 1 la is a bottom plan view of the plate shown in FIG. la in use with a METRAL connector mounted on a PCB; FIGS. 1 b-11 d are schematic views in which 1 b is a partial top plan view of the accessory plate shown in FIG. 9, FIG. 1 lc is a cross section through 1-1 in FIG. 1 lb, FIG. 1 ld is a cross section through 2-2 or 4-4 in FIG. 1 lb. and FIG. 1 le is a cross section through 3-3 or 5-5 in FIG 11b; FIGS. 12a and 12b are respectively further exploded perspective views of the accessory plate shown in FIG. la with a plug and a receptacle and FIG. 12c is a detailed view of circle 12c in FIG. 12a; FIGS. 13a and 13b are further exploded detailed views of the assemblies shown in FIGS. 12a and 12b and FIG. 13c is a detailed view if circle 13c in FIG 13a; and FIGS. 14a and 14b are further perspective views of the plug and receptacle shown respectively in FIGS. 12a and 12b, FIG. 14c is a detailed view from 14c-14c in FIG. 14a, and FIG 14d is a detailed view of signal and ground pins from FIG. 14a.

Detailed Description of the Preferred Embodiment The basic plate 10 made of metal is shown in FIG. 1, which represents the front planar view as observed from the pin tip to header bottom. This plate has a pattern of preferably rectangular punched holes 12 corresponding and meant to freely clear the array of signal pins. As described in U. S. Patent Application Serial No. 08/992,042 (EL-6170), filed December 17,1997, entitled HIGH DENSITY INTERSTITAL CONNECTOR SYSTEM, the contents of which are herein incorporated by reference, the ground pins are located at the centroid of a circle circumscribed by the four adjacently located signal pins, i. e. this grid is displaced diagonally at lmm with respect to signal grid at 2mm spacing.

Such an array of ground locations 14 on the basic plate 10 are defined by oppositely positioned lips 16 and 18.

A longitudinal cross-section of this plate is shown in FIG. lb. To ensure adequate insulation between the basic plate 10 and (any of) the signal pins of the header, plastic insert-molding can be used to develop lead-in areas 20 and 22 at punched holes 12 on either side in a cross- wise fashion over both planar faces. Such cross-wise plastic links 24 and 24'extend from adjacently located punched holes 12 of the basic plate, and possibly on both faces. Such a basic plate is an accessory which by virtue of its lead-in (s) 20 and 22, permit its assembly on a normal full plastic wall header. In doing so, this plate rests at the bottom of the header as shown in FIGS. 2a and 2b, forming one integral unit. In this condition, the signal pins 26 protrude through the (insulated) punched hole 12 while the oppositely positioned metal lips 16 and 18 allow the ground pins 28 to be contacted at locations 14 in the basic plate 10. Due to track routing and space availability reasons, it may be desirable to locate the ground pins 28 to be located not in the mid-field but towards the outer-bounds 30 and 32 of the basic plate 10. Alternatively, instead of having ground pins fixed and located in the plastic bottom of the header, such pins may be integrally fixed part of the basic plate 10, protruding perpendicularly in the connector mid-field on one (or either) side of its surface similar to a"bed of nails". Such protruding ground pin portions may, or may not have locating portions in appropriately positioned recessed in the header bottom, while its opposite pin side is available for (spring) mating with opposing mating receptacle contacts. In an alternative embodiment shown in FIGS. 3a and 3b, such a basic plate 10 integral with upstanding ground pins with corner press-fit pegs, can be located from the bottom side of plastic header in a longitudinal recessed area. These ground pins protrude only towards the contacting side and flush with the rear surface of the basic plate 10. Furthermore, the basic plate has punched holes 12 in a lmm diagonally offset grid, which allows free passage of the press-fit area of the signal pins.

Depending on the envisaged interconnection signal traffic on the PCB, the ground pins can be evenly distributed, at only outer-bounds, also in connector mid-field. It should be noted in FIG. 3, that the height of the plastic standoff ridge along two sides of the plug bottom exceeds the thickness of the metal basic plate to insulate PCB tracks.

Ground pins in the outer-bound are directly available to contact the outer shields of receptacle. Alternatively, ground pins in the mid-field can contact opposing receptacle contacts.

Referring to FIGS. 3a and 3b, the header is shown generally at numeral 34. This header has a plurality of pins as in pin 36. The accessory pin shown generally at numeral 38 and has pins as at pin 40.

The accessory plate 38 is positioning a bottom recess 42 of the header 34 and is interposed between the PCB 44. The PCB has a plurality of apertures as at aperture 46 to receive pins from the assembly.

FIG. 4a and 4b shows the option of locating the basic plate from the contact side. The ground pins are fixed on the basic plate and protrude on either side of it; the protrusion towards the header bottom is slightly smaller than the plastic bottom thickness. Al other features are the same as in foregoing.

Referring to FIGS. 4a and 4b, the header is shown generally at 48 and has a plurality of pins as at pin 50. The accessory plate is shown generally at 52 and has pins as at pin 54, which is a ground pin that engages a lateral grove as at 56 in the header. The header has an upper recess 58 and walls 60 and 62. It will be seen that the grate 52 fits between the walls 60 and 62 in the upper recess 58. The header 48 is superimposed directly on PCB 64, which has apertures as at aperture 66 for receiving pins from the header.

Similar to FIGS. 3a and 3b, conventional METRAL connector accessory plate may be positioned from the rear as is evident from FIGS.

5a and 5b. Again, the basic plate has press-fit terminals extending rearwardly along outer-bounds and forwardly projecting spring members along outer-bounds at slight spaced offset with respect to the location of the press-fit pegs. These springs fit into side-walls of plastic shroud of the plug, still allowing the contacting portions adjoined to the basic plate to project through window openings in the two side-walls for the desired electro-mechanical connections with receptacle shield.

Referring to FIGS. 5a and 5b, the header shown generally at numeral 68 and has walls 70 and 72. There is also a base 74 having apertures as at aperture 76 through which pins as at pin 78 extend. The header has a lower recess 80 and an upper recess 82 as well as a plurality of side oppugns as at openings 84 and 86. There is also a side press pin receiving recess at 88. The plate is shown generally at numeral 90 has apertures as at 92 and pins as at 94 and it also has lateral springs as at springs 96 and 98. The accessory plate also has ground pins as at pin 100, which engage apertures as at apertures 101 on the PCB 102.

During application of shield plate accessory as in FIGS. 5a and 5b within the METRAL connector, a conventional plastic can be readily altered to the shielded version. The only additional requirement is that customer adapts board to accept the press-fit ground terminals located along the outer-bounds of connector. Because of the additional spring contacting functions attributed to the integral parts of the basic plate, it is clear that the material is of a type Ph-Br or Be-Cu with appropriate plating.

As a test, samples were made of the METRAL connector product according to FIGS. 5a and 5b. The purpose was to compare high-speed performance of three plug versions; die-cast, accessory type, normal plastic. As expected, the results for the die-cast were best and of the normal plastic were poorest, with the accessory type in between. These results confirm usefulness of the present invention as a means for an easy method for adapting a conventional product towards high-speed applications. This advantage is in many instances also important for customer cost savings, based on the die-cast header.

FIGS. 6a and 6b show another option similar to FIGS. 4a and 4b with the basic plate with integral contact clips and press-fit on outer- bound with ground pins on mid-field, is mounted from the open shroud signal pin contacting side. The integral ground pin has a length slightly smaller than the bottom wall thickness of shroud; this allows signal contact screening up to the PCB surface. Again, testing has shown that the subsequent performance of product according to FIGS. 6a and 6b is similar to that found earlier for FIGS. 5a and 5b.

Referring to FIGS. 6a and 6b, the header shown generally at numeral 104 which has opposed walls 106 and 108 and a base 110 in which there are inserted pins as pin 112. The header has a lower recess 114 and an upper recess 116 as well as a plurality of side openings as at 118 and 120 and a press pin receiving recess 122. There is also an accessory plate 124 positioned in the upper recess 116 and which has a plurality of apertures as at aperture 126 and springs as at springs 128 and 130.

Finally according to FIGS. 7a and 7b, as a result of combinations of ideas made using FIGS. 5a and 5b and FIGS. 6a and 6b, the plastic bottom of the shroud can be sandwiched between two basic plates. The rear basic plate has punched holes to allow the free passage of the signal terminals and having holes for fixation of ground pins; simultaneously press-fit grounding terminals are located on the outer-bounds. The front basic plates have the contacting springs on outer-bounds and integrated ground pins with punched holes to permit free passage, towards the connector mid-field. The length of these ground pins is similar but slightly larger than the shroud bottom wall thickness. During the assembly of accessories assembly on shroud, the ground pins enter appropriately positioned holes in the shroud bottom to be mechanically fixed in holes of the rear basic plate. In this assembled condition, the tips of the ground pins are flush with the rear surface of the rear basic plate.

Also, the desired electro-mechanical connection between the two basic plates is complete via the ground pins.

Referring to FIGS. 7a and 7b, the header shown generally at numeral 132 which has opposed walls 134 and 136 and a base 138 in which there are inserted pins as pin 140. The header has a lower recess 142 and an upper recess 144 as well as a plurality of side openings as at 146 and 148 and a press pin receiving recess 150. There is also an accessory plate 152 positioned in the upper recess 144 and which has a plurality of apertures as in aperture 154 and springs as at spring 155.

Another accessory plate 156 is also positioned between the header and the PCB 158 in the lower recess 142 of the header. This accessory plate has apertures as at 160 and ground pins as at 162 that are received in apertures as at 164 in the PCB.

Air is a superior dielectric compared with either plastic or PCB. In a structure as proposed in FIGS. 7a and 7b, the plastic material in between the front and rear basic plates should preferably be substituted by air to optimize the performance. Conceptually, this is shown in FIG. 8 in which there are air spaces such as spaces 166 and 168. Further due to signal tracking difficulties the actual grounding press-fit locations and connection to outer shield is preferably located in the outer-bound.

Again, this concept can be used both for the plug, but also for the receptacle as applicable to an interstitial connector structure discussed in U. S. Patent Application Serial No. 08/992,042 (EL-6170), filed December 17,1997, entitled HIGH DENSITY INTERSTITAL CONNECTOR SYSTEM.

Referring to FIG. 9 this embodiment includes a module 170. This module includes a contact element 172, which has a forward portion 174, a middle portion 176, a fixing portion 178 and a tail portion 180. The tail portion of the contacts engage an accessory plate 182 as shown in FIG. la. Beneath the accessory plate there is a PCB 184.

Additionally, the metal accessory plate can be placed above or above the plug bottom, or both. Also this type of single plate may be used for the receptacle side. Such plates may be placed in the interstitial or conventional product.

FIGS. 10a-1 le show the accessory plate with a conventional plastic METRAL plug, by example. Here the ground locations for outer boundary is lmm staggered from the signal conductor. Also, by way of demonstration we show that the ground locations for mid-field may occur either by spring or SMT (or both) to a small ground pad preferably 0.75 x 0.75mm square located at staggered locations on the PCB; this can be joined by a small via in board to the ground location. This approach is quite important to be claimed since press fitting is difficult with density packed circuitry. Further, the force of press fitting is deleterious towards, and often results in a rupture of circuitry. In addition, the impedance change with adjacent plated through holes with press-fit, can be avoided by SMT/spring grounding in mid-field. The ground pins in outer boundary are means for fixation of accessory plate to connector. The shield includes a plurality of insulation members as at member 186 adjacent pins as at pin 188. The apertures as at aperture 190 in the shield may or may not receive a pin. Tangs as at tang 192 on the shield can touch the ground track on the PCB. The shield can also be turned upwardly to engage a mating shield on a mating connector.

FIGS. 12a-14d show the ground locations on outer boundary in-line with the signal locations, while the ground locations on towards mid-field are staggered lmm from the signal locations. Grounding positions may be at all (or some positions) in the outer boundary locations.

It will be appreciated that an accessory plate has been described, which allows an electrical connector to be quickly and inexpensively adapted for high signal integrity for high speed applications.

Although the METRAL connector was used as an example to illustrate the present invention, this invention may easily and cost effectively be extrapolated to adapt other existing vertical and horizontal mating connector designs. There is a freedom of choice in the use of the front or rear plate (or both) with location of ground pins, press-fit ground tails and contact spring location/and number. The figures are only to illustrate features, but specific modifications can be made based on the application and connector dimensions.

While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom.

Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.