WO2003092121A2

WO2003092121A2 - Three dimensional, high speed back-panel interconnection system

Info

Publication number: WO2003092121A2
Application number: PCT/US2003/013072
Authority: WO
Inventors: Timothy A. Lemke
Original assignee: Broadside Technology, Llc
Priority date: 2002-04-25
Filing date: 2003-04-25
Publication date: 2003-11-06
Also published as: AU2003234253A1; WO2003092121A3; AU2003234253A8

Abstract

A back-panel interconnection system useful in telecommunication, data communication and essentially any processing equipment capable of communicating data at a rate of 10GB/s and beyond. Included are systems and methods for constructing an interconnection system using an independent interconnection element or bridge (1) that is used to interconnect the various elements of a system. The plane of the bridge (1) may be perpendicular to the plane of the back-panel (2). The plane of the bridge may have projections (3) that are at right angles to the long axis of the bridge and which projects through an opening (4) in the back-panel (2) and extend through to the other side. An assembly comprising a header (7) and the bridge is capable of being mated to a printed circuit board (11) or cable connector, thus establishing a direct high speed interconnection between two components of the back-panel interconnection system and eliminating problematic connector mounting holes.

Description

TITLE

THREE DIMENSIONAL, HIGH SPEED BACK-PANEL INTERCONNECTION SYSTEM

Cross Reference to Related Application

This application claims priority, under 35 U.S.C. 119, from U.S. Provisional Patent Application Serial Number 60/376,152, filed April 25, 2002.

FIELD OF THE INVENTION

The present invention generally relates to interconnection arrangements among printed circuit boards or the like.

BACKGROUND OF THE INVENTION

In electrical equipment, such as high speed switchers, routers and servers used in the field of data communications and telecommunication, there is typically a need to interconnect multiple printed circuit boards in a system, and to be able to transmit high speed signals over the length of the system with sufficient fidelity to minimize errors. At present, the speed of such systems is limited by the design of the interconnection system and the properties of the material used in those designs, including the printed circuit boards and connectors. The problems that are of most concern are signal attenuation, signal reflections and noise, any of which could originate from sources both external and internal to the system. With conventional technology, any and all of the following can contribute to undesirably limited data rates: multilayer printed circuit boards, conductive losses of narrow printed circuit traces (e.g., traces with a width on the order of about .005"), dielectric losses of conventional printed circuit materials (which are typically made from epoxy or glass) and stubs and reflections caused by the via holes, or pin attachment holes for connectors. (Typically, via holes may be copper plated and are holes that are used to interconnect various circuit layers of a printed circuit board. Connectors with either solder tails or press-fit sections also use via holes as a manner of attachment to a printed circuit board.)

There are a number of solutions that have been proposed to solve the problems just described, including improved connector design, advanced printed circuit materials and improved processes; among these solutions, there are included, for example, smaller diameter vias and back-drilling of plated throughholes . However, problems definitely exist with these proposed solutions; with some of the best known technology, data rates are still limited to about 10 GB/sec and, at any rate the additional costs associated with the aforementioned solutions are usually prohibitive for most conventional applications.

SUMMARY OF THE INVENTION

The present invention relates to a unique back- panel interconnection system that is useful in telecommunication, data communication and essentially any processing equipment capable of communicating data at a rate of lOGB/s and beyond. There is provided a capability of high performance at a low cost, and the associated systems are suitable for a wide variety of system designs and applications. There are broadly contemplated herein systems and methods for constructing an interconnection system using an independent interconnection element, or interconnection bridge, to interconnect various elements of a system. The plane of the bridge is, preferably, essentially perpendicular to the plane of a back-panel . The bridge may have at least two tongue-like projections that are at right angles to a long axis of the bridge. These tongues can project through an opening in the back-panel and extend through to the other side. They are preferably latched into a plastic housing or header that precisely positions and mechanically secures the bridges. On the ends of the tongues, contact pads capable of receiving a mating connector may be provided, and the contact pads are preferably connected by circuitry on the bridge.

The need for connector mounting holes or vias is thereby eliminated, thus doing away with a primary cause of impedance discontinuities and signal reflections. The use of the bridge allows either increased circuit density or increased circuit width without increasing the size of the system. Alternative circuit designs and materials can be readily used, since the bridge can be designed and manufactured independently of the conventional back-plane system.

Presently contemplated circuits may be constructed in a variety of ways and can include matched impedance transmission lines including strip-line (i.e., a line sandwiched between two ground planes) and micro-strip (i.e., a line typically having only a single ground plane), low speed circuits and power. Printed circuit cards or cables with the appropriate connectors mounted to them can be then directly assembled to the back-panel by way of the header bridge combination. The back-panel can be either a simplified multilayer printed circuit board and can be used to transmit low speed signal and power, or it can be just a mechanical structure to fix the elements of the interconnection system.

One embodiment contemplated herein involves a point-to-point interconnection system in the cards in the system are interconnected to one another by one or multiple high speed serial links. All of the cards to be interconnected can be on one side of the back-panel, with the interconnection arrangement preferably exposed on the opposite side.

One embodiment contemplated herein involves a multi-drop interconnection system in which there are multiple tongues on the interconnection bridge, with the circuit cards being interconnected in a common bus configuration .

One embodiment contemplated herein involves a mid-plane, in which the printed circuit boards that are to be interconnected are on both sides of the back-panel . Here, the tongues of the bridge project in both directions and through back-planes on each side of the bridge. This "mid-plane" has the advantage of significantly reducing the maximum interconnection length between cards, allowing for higher system data rates.

One embodiment contemplated herein involves an orthogonal mid-plane in which the printed circuit card has multiple tongues which project through the back-panel into a header. The cards on the opposite side of the panel have connectors that are capable of mating with the header/ bridge combination. This minimizes the interconnection length, since the cards are directly interconnected to one another. One embodiment contemplated herein involves a connector attached to the end of the bridge. This allows the bridge to be manufactured in a more efficient manner, and provides for a high quality, low voltage stamped metal contact on the end of the bridge, without compromising the signal integrity of the system.

One embodiment contemplated herein involves a connector with stamped metal contacts that are capable of being attached to a printed circuit board that is assembled to the header. This provides a manner of direct interconnection to a printed circuit back-panel and allows the printed circuit board to be used for low speed signals and power interconnections.

Generally, there is broadly contemplated in accordance with at least one presently preferred embodiment of the present invention an electronic interconnection system comprising: a back-panel arrangement comprising a plurality of apertures; at least one insulative header arrangement associated with the apertures; and at least one interchangeable conductor element, the at least one conductor element comprising at least one extension arrangement adapted for insertion through at least one of the apertures; the at least one extension arrangement being further adapted to mate with at least one other connector when inserted through at least one of the apertures.

BRIEF SUMMARY OF THE DRAWINGS

The present invention and its presently preferred embodiments will be better understood by way of reference to the detailed disclosure herebelow and to the accompanying drawings, wherein: Figure 1 is a partial exploded view of a point- to-point embodiment;

Figure 2 is a perspective view of a point-to- point embodiment, showing all parts assembled;

Figure 3 is a close-up cross-sectional view of tongue connections in the embodiment of Figs. 1 and 2;

Figure 4 is a perspective view of an embodiment of the present invention involving a mid-plane interconnection system;

Figure 5 is a perspective view of an embodiment of the present invention involving an orthogonal mid-plane interconnection system;

Figure 6 is a perspective view of an embodiment involving a multi-drop interconnection system;

Figure 7 is a perspective view of connector assembled to the end of a bridge; and

Figure 8 is a perspective view of a connector with press fit terminations for a header;

DETAILED DESCRIPTION OF THE PREFERED EMBODIMENTS

Additional background information relating to the embodiments of the present invention may be found in U.S. Provisional Patent Application Serial No. 60/376,152, which is hereby incorporated by reference as if set forth in its entirety herein.

There are broadly contemplated herein unique back-panel interconnection systems useful in telecommunications, data communications and data processing systems, and which are capable of transmitting and receiving data at rates of lOGB/s and beyond without serious degradation of the system's signal integrity. The system provides high performance at exceptionally low cost and is capable of a wide variety of system configurations and applications.

Figure 1 and Figure 2 are perspective views of a "point-to-point" embodiment of the present invention, whereas Figure 3 is a close-up cross-sectional view of a single tongue connection. At present, reference will be made to all three drawings simultaneously.

Indicated at 1 are independent circuit elements, or bridges, 1 with matched impedance, high speed circuitry. Such elements 1 could typically be narrow printed circuit boards, but in actuality could be constructed of a wide variety of materials and configurations, including other rigid, semi-rigid or flexible materials with appropriate circuit configurations. In other words, a bridge 1 could be substantially rigid, could be configured for bendable plastic deformation (i.e., deformation that does not return to the original state on its own) , or could be configured for flexible elastic deformation (i.e., deformation that can return to the original state on its own) .

Bridge 1 is preferably positioned with its plane perpendicular to a back-panel 2, thus allowing the circuitry of bridge 1 to be routed along a "z-axis", as opposed to the "x-y" axes defined along the plane of back- panel 2. This will allow for wider circuit traces with less conductive losses, without causing the system size to increase in along the x-y-axes, an important consideration since the total length of the circuit informs considerably the bandwidth or data rate of the system. Bridge 1 preferably has projections or tongues 3 that are perpendicular to the longer axis of the bridge. Though a bridge 1 could preferably have two such tongues 3, an array of these tongues (i.e., three or more tongues) may be present, depending on the application at hand. These tongues 3 are preferably configured for insertion into suitably configured apertures 4 in the back-panel 2 and, preferably, will project through the back-panel 2 into an insulating support structure or header 7. Header 7 preferably includes guide posts 6 which serve to guide and mechanically secure a tongue 3 into a precise position and lock the same into place with a latch arrangement 8.

Headers 7 may preferably be embodied as individual insulated plastic housings that may be mechanically attached to back-plane 2 via rivets, screws or other mechanical fasteners. Guide posts 6, projecting perpendicularly from the base of a corresponding header 7, are preferably configured to guide and support a tongue 3 inserted through an aperture 4. As a tongue 3 proceeds through an aperture 4 and header 7, it preferably engages slots in a pair of opposing guide posts 6. Latch arrangement 8 may preferably be embodied by a cooperatively functioning combination of a notch on tongue 3 and a projection or bump in each of the guide posts 6 with which tongue 3 is engaging.

The end of a tongue 3 preferably has precious metal (e.g., gold) plated contact pads 5 that are configured for making contact with a mating connector 9.

It should be understood that multiple bridges 1 can be installed in a single back-panel system, and an array of tongues 3, belonging to different bridges 1, can even be installed into a single header 7. The bridges can be of differing lengths and can be designed to interconnect with headers in various positions on a back-panel 2.

Daughter cards 12, as well as right angle connectors 9 designed to mate with the header/bridge assembly 15, can be then mated with the headers. The various length bridges 1 directly interconnect the cards that are disposed in various positions along the back-panel 2. The connection is thus made directly to the connector, thereby eliminating the plated through via holes that normally, in conventional systems, are required to attach connector contacts to a back-panel .

The bridge 1 can be constructed of standard printed circuit board material and still have relatively high speed performance, since the height of the bridge (i.e., the dimension defined along the aforementioned "z- axis") is not a serious system design constraint. This means that the conductive circuits of the bridge can be significantly wider than those used in equivalent multilayer back-panels, and consequently the conductive losses are much lower. In addition, the circuits can use multi-strip transmission line designs, in which the circuits all are on the exterior of the bridge printed circuit board. This construction leads to lower dielectric losses, since a portion of the signal travels in air.

More costly, lower loss printed circuit board material can also be used for the bridges 1. Since only the high speed circuits require these costly materials, the amount of the material used can be optimized for cost.

An important factor in reducing the cost of back- panel 2 is the reduction of interconnection layers required for the system's interconnection. In complex systems, up to fifty or more layers can be required. The use of the high speed interconnecting bridges 1 can reduce the number of layers to four, or in some cases none. (Here, it should be understood that a multi-layer printed circuit board typically used in a back-panel application can have a number of circuit layers as defined by the layers of copper laminate in the system. These layers can have traces which carry signals or may be complete planes, which define ground and power planes. The various layers of the printed circuit board can be interconnected with via holes as discussed heretofore.) In an another embodiment of the invention, as shown in Figure 4 (a "mid-plane" design) , daughter-cards (not shown) can be interconnected on both sides of the back-panel 2. One of the reasons this is done is to minimize length of the maximum interconnection path. Since signal attenuation is directly related to interconnection length, higher bandwidth can be achieved. In this embodiment, the tongues 3 of the interconnection bridges 1 project in both directions, and two back-panels 2 are assembled to either side of the bridges 1, providing interconnection points on both sides of the panel .

Another embodiment of the present invention is shown in Figure 5 (an "orthogonal mid-plane" arrangement) . Here, there are preferably two sets of cards, namely, input cards 20 and output cards 21, wherein each card in the series needs to be interconnected to all of the other cards. The cards 20 on one side of the back-panel have a series of tongues 14 and circuits similar to the bridges 1 discussed heretofore. These are preferably inserted into a back-panel 2 having apertures 4 and headers 7. Cards 21 with connectors in corresponding positions are assembled at right angles (i.e., orthogonally) to cards 20. In this way, virtually direct interconnections can be made between the two sets of cards, minimizing the circuit path length. Preferably, the interconnections between tongues 3 and mating connectors 9 will be so configured as to optimally provide efficient functional connectivity between the cards 20/21 involved; specific manners of doing so would appear to be well within the purview of those of ordinary skill in the art .

Another embodiment of the present invention uses a multilayer bridge (Figure 6) to provide a common bus 22 for all of the connectors in the system. (It should be understood here that, with respect to Figure 6, the multiple layers are not visible but are "stacked" in the "thickness" of bridge 1, or in a dimension defined into and out of the drawing. Such multilayer arrangements are well- known to those of ordinary skill in the art.) This means that the same pins on each different card connector are connected together with the same circuit. This has been a common structure for parallel signal buses, and is often called a multi-drop bus; the advantage here resides in the provision of a well-known bus structure in the context of the unique interconnection systems contemplated herein.

Another embodiment (Figure 7) employs a connector module 16 configured to be attached to the end of an interconnection bridge. The connector has stamped metal contacts 17, preferably with precious metal plating, and is used where high quality, long life connections are required, such as in many telecommunications applications. If end connector 16 were to have a right angle (or L- shaped) configuration, the design of the bridge 1 could be simplified and could be made in essentially straight configurations and cut to length, as opposed to the essentially L-shaped design shown.

In another embodiment (Figure 8) , a connector module 18 with plated stamped metal contacts 19 and a printed circuit board attachment arrangement, such as a solder tail, solder ball or press fit tail 20, is assembled to the header 7 prior to its attachment to a back-panel .

This could be used as a stand-alone connector, or in a hybrid design, where some of the slots in the header use bridges and the others use the direct attach contacts. In this case, bridges would carry the high speed circuits while the printed circuit back-panel would carry the low speed signals and power.

If not otherwise stated herein, it may be assumed that all components and/or processes described heretofore may, if appropriate, be considered to be interchangeable with similar components and/or processes disclosed elsewhere in the specification, unless an express indication is made to the contrary.

If not otherwise stated herein, any and all patents, patent publications, articles and other* printed publications discussed or mentioned herein are hereby incorporated by reference as if set forth in their entirety herein.

It should be appreciated that the apparatus and method of the present invention may be configured and conducted as appropriate for any context at hand. The embodiments described above are to be considered in all respects only as illustrative and not restrictive. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope .

Claims

CLAIMSWhat is claimed is:

1. An electronic interconnection system comprising :

a back-panel arrangement comprising a plurality of apertures;

at least one insulative header arrangement associated with said apertures; and

at least one interchangeable conductor element, said at least one conductor element comprising at least one extension arrangement adapted for insertion through at least one of said apertures;

said at least one extension arrangement being further adapted to mate with at least one other connector when inserted through at least one of said apertures.

2. The system according to Claim 1, wherein said at least one header arrangement comprises at least one guiding arrangement for assisting in the guidance of at least one extension arrangement through at least one of said apertures .

3. The system according to Claim 1, wherein said at least one conductor element comprises a printed circuit board.

4. The system according to Claim 1, wherein said at least one conductor element is adapted for disposition with respect to said back-plane arrangement substantially perpendicularly with respect to a major plane of said backplane arrangement .

5. The system according to Claim 4, wherein said at least one extension arrangement comprises at least two projections extending from at least one conductor element substantially perpendicularly.

6. The system according to Claim 1, further comprising a latch arrangement for securing said at least one extension arrangement with respect to a header arrangement .

7. The system according to Claim 6, wherein said latch arrangement comprises at least one notch and at least one protrusion cooperable with said at least one notch, said at least one notch and said at least one protrusion being associated with said at least one header arrangement and said at least one extension arrangement .

8. The system according to Claim 1, wherein said at least one extension arrangement comprises contact pads for mating with said at least one other connector.

9. The system according to Claim 1, wherein said at least one said conductor element comprises a substantially rigid conductor element.

10. The system according to Claim 1, wherein said at least one said conductor element comprises a conductor element configured for bendable plastic deformation.

11. The system according to Claim 1, wherein said at least one said conductor element comprises a conductor element configured for flexible elastic deformation.

12. The system according to Claim 1, wherein:

said back-panel is a first back-panel;

said system further comprises a second back- panel ;

at least one conductor element is disposed between said first and second back-panel and comprises a plurality of extension arrangements, at least one extension arrangement being adapted for insertion into said first back-panel and at least one other extension arrangement being adapted for insertion into said second back-panel .

13. The system according to Claim 12, wherein said first and second back-panels are disposed in parallel with respect to one another.

14. The system according to Claim 1, wherein said at least one conductor element comprises an input card and said at least one other connector is associated with an output card, said input card and said output card being adapted for interconnection through said back-panel when disposed orthogonally with respect to one another.

15. The system according to Claim 1, wherein said at least one extension arrangement comprises a detachable connector module extending from one said conductor element.

16. The system according to Claim 15, wherein said connector module comprises stamped contacts for interconnecting with said at least one other connector.

17. The system according to Claim 1, wherein said back-panel integrally comprises at least one connection arrangement for interconnecting with said at least one other connector.

18. The system according to Claim 17, wherein said at least one connection arrangement for interconnecting with said at least one other connector is associated with at least one header.

19. The system according to Claim 18, wherein said at least one connection arrangement for interconnecting with said at least one other connector is assembled to said at least one header prior to said at least one header being attached to said back-panel .

20. The system according to Claim 1, wherein said at least one other connector is attached to one of: a printed circuit card and a cable.