Packaging system

Abstract: A high density interconnection system for connecting large numbers of unique signal lines between orthogonally positioned circuit cards, utilizes pins (12) from the back of a zero insertion force connector (ZIF) (14) to extend through the interconnection card (10) and mate with a female socket connector (20) on a second circuit board (24). Pins from the ZIF connector which are not aligned with the sockets of the orthogonally positioned socket connector may be connected to pins on the interconnection card which are aligned with the socket connector but not the ZIF. Very high numbers of connections between circuit cards may be made in a small volume and maintain signal line length at a minimum to ensure maximum signal transfer speed.

Description: The invention relates to a packaging system. When large numbers of unique signal connections are required to interconnect the elements of an electrical network, such as the signal inputs and outputs of crosspoint switch elements or devices, the connection of the inputs and outputs to the switch device can require extensive circuit board complexity and interconnection distance design to provide the conductor paths on the circuit board necessary to make the interconnections. Further complications result from the requirement that in many cases, conductor paths between related inputs and connections to the crosspoint switching device be of equal length to make sure that all signals reaching the switching device are delayed by approximately the same amount of time. This requirement for large numbers of unique signals exists in several environments but is very prevalent in the area of parallel processing. When a computer is comprised of several processors operating simultaneously, the signals to and from each other or shared memory through a switch network necessitates many point-to-point connections and must all be timed to arrive at the receiving device at approximately the same time, and all the processors must be able to access the memory which is common to all processors. The cost of the interconnection of the crosspoint switching chips or devices to the input and output signal boards can become a significant cost element in an overall system. United States Patent 3,368,155, to N. E. Hoffman addresses the need to package several circuit boards in a module. United States Patent 4,401,351 to G. C. Record discloses a card cage approach to interconnecting several circuit boards to a mother board. Mother boards in adjacent cages are connected by a coupling means. United States Patent 4,490,000 to J. C. Asick et al discloses a device for interconnecting two adjacent parallel circuit boards. United States Patent 4,582,386 to J D Martins discloses a circuit board connector which provides electrical connections to a mating connector portion which has a pattern of four rows of pins uniformly spaced. Another example of a connector having receptors for pins and having multiple rows of receptors is United States Patent 4,932,885 to J P Scholz. WO 83/04466 discloses a tiered orthogonally related 3-D circuit board packaging system in which internal wire interconnections are not required. Plural parallel-disposed zero-insertion-force connectors are orthogonally related on opposite sides of mother-boards that divide tiers in the structure. Selected conductive points of the connectors are electrically connected to make necessary interconnections. Printed circuit cards are inserted in the zero-insertion-force connectors for carrying a large plurality of solid-state, or equivalent, crosspoints and are interconnected by the selected conductive pins. The present invention seeks to improve on the packaging arrangements of prior systems for use in environments requiring large numbers of unique signal connections and accordingly provides a packaging system for electrically interconnecting a plurality of circuit boards the packaging system comprising at least a first set and a second set of circuit boards said first set of circuit boards comprising electrical contacts disposed along a first edge of each of said circuit boards of said first set and said second set of circuit boards comprising electrical connectors disposed along at least one edge of each of said boards of said second set; the electrical contacts and the electrical connectors being electrically connected to electrical components on the plurality of circuit boards ; the packaging system further comprising: an interconnection circuit board for orthogonally electrically connecting first and second sets of circuit boards ; said interconnection circuit board comprising: a first plurality of zero insertion force (ZIF) connectors disposed along a first surface of said circuit board and adapted to receive said electrical contacts of the first set of circuit boards; said ZIF connectors include a first plurality of connector pins extending through the circuit board and disposed along a second surface of said interconnection circuit board opposite said first surface certain of said first plurality of connector pins being disposed to engage certain of said electrical connectors of said second set of circuit boards when said second set of boards are oriented orthogonally with respect to said first set of circuit boards; and said interconnection circuit board further comprising a second plurality of connector pins, extending from said second surface of said circuit board in an orthogonal direction with respect to said first plurality of connector pins, disposed to engage others of said electrical connectors of said second set of circuit boards, interconnection paths being provided in said interconnection circuit board to electrically connect selected ones of said second plurality of connector pins with selected ones of said first plurality of connector pins not disposed for connection to said connectors of said second set of circuit boards. The invention finds particular use in the area of crosspoint switching or to the area of parallel processing where several computer processors require access to the same switch network, memory or other system resource. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a view of an assembly of electronic circuit boards attached to the mounting boards, in a orthogonal arrangement. FIG. 2 illustrates the electrical connections of the Zero Insertion Force connectors through the connection board. FIG. 3 illustrates the local wiring arrangement for interconnecting pins that do not intersect with the connector on the outboard circuit boards to pins that will engage the connector. Referring to FIG. 1, a first interconnection board 10 is shown oriented in a vertical plane. The interconnection board is populated with a plurality of pins 12 to which a circuit board connector 14 is connected or which are part of connector 14 and pins 13 to which a second, female circuit board connector 20 may be connected. For example, on a first face 16 of the interconnection board 10 there is mounted a Zero Insertion Force (ZIF) card edge connector 14. The ZIF connector 14 is of the type which is provided with pins 12 that can extend through the interconnection board 10 to expose the pins 12 on the second face 18 of interconnection board 10. In addition to the pins 12 directly in electrical communication with contacts of the ZIF connector 14, the second face 18 of the interconnection board 10 has pins 13 protruding therefrom. The pins 13 are not a part of the ZIF connector 14 but rather are connected, by electrical conductors on or contained in interconnection board 10, to those pins 12 which are not plug connected to connector 20. The connection of pins 12 to pins 13 will be described later with respect to FIG. 3. Connector 20 is a conventional female connector with a plurality of rows of sockets oriented so the rows of sockets are vertical. As can be seen in FIG. 3 and with reference to FIG. 2, the pins 12 lying in the zone 42 which may be received by the sockets of connector 20, coincide with the pin locations for some of the pins 12 extending through interconnection board 10 from the back of ZIF connector 14. Pins 12 which extend through the interconnection board 10 from the back of ZIF connector 14 but which are not within zone 42 may be connected to pins 13 on an as needed basis to permit the conduction of signals between some of the pins 12 and pins 13. All of pins 13 lie within zone 42. Connected to connector 20 in a conventional manner is circuit board 24. If used to package fiber-optic crosspoint switches, for example, circuit board 24 may be a signal board which receives signals in, for example, a fiber optical input form from a source external to the package described. The signals could then be converted using an optical to electrical converter of the type which are readily available commercially. The signals, once converted to electrical signals are then conducted to the using device 26 on the circuit boards 28. Boards 28 are engaged by their edges 30 and the contacts thereon, by the ZIF connector 14. The utilizing device 26 could be a crosspoint switching chip or a computer chip, or it could just as appropriately be a memory chip which may be accessible by processors which may reside on board 24. In any event, the number of interconnections between the input/output board 24 and the circuit board 28 may be significantly increased over the number of connections possible with non-orthogonal layout, and with minimal local board wiring. The orthogonal arrangement of board 24, and board 10 and board 28 permits the connection of board 24 to multiple boards 28 without long runs of local board wiring. Referring to FIGS. 2 and 3, zone 42 includes direct pin connections to boards 24 and 28 simultaneously. As can be seen from the pin layout on interconnection board 10 and the use of a four row pin arrangement on the ZIF connector 14 and on the connector 20, at each intersection of the plane of board 24 with the plane of board 28, sixteen direct pin interconnections are available. By including three adjacent columns of pins 12 on either side of zone 42 and three rows of pins 13 above and below the pins 12 extending directly from ZIF connector 14 through the board, the number of connections from the board 24 to board 28 amounts to forty at each intersection of the circuit boards 24, 28. Assuming that a uniform pin spacing of 2.54 mm (.100 inches), a common standard in pin connection technology, is used, the pitch between adjacent boards could be as close as 25.4 mm (one inch). With pitches of 25.4 mm (one inch) 40 connections per square inch (645 mm 2 ) are achieved on the interconnection board 10. FIG. 1 illustrates only two vertical boards 24 and two horizontal boards 28. By lengthening the boards, the number of connections may be increased to handle additional boards; for example, on a board having an edge dimension of 101.6 mm (four inches) with boards connected on 25.4 mm (one inch) intersection spacings, the number of connections possible are 640 in a 101.6mmx101.6mm (4 inch by 4 inch area). This number of connections may be doubled if the opposite side of each circuit board 28 is similarly mounted in a second ZIF connector 14 on a second interconnection board 10. Accordingly, a module measuring approximately 101,6mm x 101,6 mm x 304,8 mm (4 inches by 4 inches by 12 inches) is capable of having 1280 unique signal connections within the module. Some of the pin interconnections may be used for voltage or ground connections between boards, simplifying the powering of the elements mounted to the various circuit boards. Referring to FIG. 1, the ZIF connector 14 mounted on boards 10 may advantageously be the type having a slot through which the board edge is inserted along a direction parallel to the axis of the ZIF connector 14. This permits insertion of and removal of boards 28 into and from the structure defined by the two parallel boards 10 when boards 10 are rigidly mounted. FIG. 2 shows the connections of the ZIF connector 14 within boundary 40. The connections 12 are arranged in four rows, equally spaced apart and protruding through the board 10. The pins 12 of the ZIF connector 14 are positioned in the holes of the board 10 and soldered to complete the mounting of the ZIF connector 14. The pins 13 protrude from the board in a pattern of typically four columns and occupying the area enclosed by boundary 42, between the connections of two adjacent ZIF connectors 14. Boundary 44 encloses the connections that will be contacted by the female connector 20 of FIG. 1. It is seen that some of the connections protruding from ZIF connector 14 and the connections within boundary 42 are contacted by female connector 20. The connection pins that are common to the ZIF connector 14 and the female connector 20 do not require further electrical connection to serve their intended purpose. However, the pin connections which are within boundary 40 and not within boundary 42 must be connected to the pin connections within boundary 42 in order for the electrical signals on one group of pins to be conveyed to the other group of pins. In order to connect the non-connected pins of ZIF connector 14 to the non-connected pins that engage female connector 20, local wiring must be accomplished. The local wiring is formed by conventional printed circuit board fabrication techniques. Conductors 50 are formed in the board 10 during the board manufacture and may be positioned to connect pins of one of the groups to a pin in another of the groups of non-common pin connections. For example, a pin 12 in one group may be connected to a pin 13 in another group by a conductor 50 as shown in FIG. 3. Conductors 50 are laid out with a desire to maintain all connections between non-common pins approximately equal. Conductors 52 are examples of a layout connecting pins 12 and 13 on board 10 when the length of the conductors relative to each other is not a critical consideration. Should it become necessary to lay out very intricate patterns of conductors to properly connect selected ones of pins 12 with selected ones of pins 13, multiple layers of conductors may be formed and separated by insulating layers as is well known in the circuit board art. It should be understood that the use of ZIF connectors 14 and female connectors 20 are described for illustrative purposes and that all connections of the board 10 could be made with ZIF connectors. Such connectors limit to some extent the flexibility of the design. The combination of ZIF connectors 14 and female connectors 20 is the preferred design. While the local wiring of board 10 is preferably accomplished as described above, it should be understood that this structure is also conducive to wire wrap interconnections and thus is useful in early level prototype designs. After the interconnections have proven to be as desired, the wiring approach may then give way to the local wiring of the circuit board during its manufacture and the total enclosure of the conductors within the board. The female connectors 20 have been shown as pin into socket type connectors but it should be recognized that a ZIF connector could be substituted. From the foregoing description and explanation, it is appreciated that a third edge of circuit board 28, preferably the leading edge as board 28 is inserted into the connectors 14, may be contacted by conventional connectors to provide power or signal connections to the circuit board 28. If air circulation is not required for cooling the components 26, an interconnection board 10 can be added to the back of the arrangement shown in FIG. 1 to further expand the interconnection capability between circuit board 28 and circuit boards 24 or their counterparts. Further, it should be understood that modifications and changes may be made by one of skill in the art to the preferred embodiment without departing from the scope of the invention.

Claims: A packaging system for electrically interconnecting a plurality of circuit boards, the packaging system comprising at least a first set (28) and a second set (24) of circuit boards; said first set of circuit boards (28) comprising electrical contacts (30) disposed along a first edge of each of said circuit boards of said first set (28), the electrical contacts (30) being electrically connected to electrical components (26) on the plurality of circuit boards (28); the packaging system further comprising: an interconnection circuit board (10) for orthogonally electrically connecting first (28) and second sets (24) of circuit boards; said interconnection circuit (10) board comprising: a first plurality of zero insertion force (ZIF) connectors (14) disposed along a first surface of said circuit board (10) and adapted to receive said electrical contacts (30) of the first set of circuit boards (28); said ZIF connectors (14) include a first plurality of connector pins (12) extending through said circuit board (10) and disposed along a second surface of said interconnection circuit board (10) opposite said first surface, the packaging system being characterised in that: said second set of circuit boards (24) comprises electrical connectors (20) disposed along at least one edge of each of said boards of said second set (24), the electrical connectors (20) being electrically connected to electrical components on the plurality of said circuit boards (24); certain of said first plurality of connector pins being disposed to engage certain of said electrical connectors (20) of said second set (24) of circuit boards when said second set (24) of boards are oriented orthogonally with respect to said first set (28) of circuit boards; and said interconnection circuit board (10) further comprising a second plurality of connector pins (13), extending from said second surface of said circuit board (10) in an orthogonal direction with respect to said first plurality of connector pins, disposed to engage others of said electrical connectors (20) of said second set (24) of circuit boards, interconnection paths (50,52) being provided in or on said interconnection circuit board (10) to electrically connect selected ones of said second plurality of connector pins (13) with selected ones of said first plurality of connector pins (12) not disposed for connection to said connectors (20) of said second set of circuit boards (24). A packaging system as claimed in claim 2 wherein said electrical interconnection paths comprise electrically conductive paths formed into or onto said interconnection circuit board (10). A packaging system as claimed in claim 1 or claim 2 wherein said zero insertion force connectors (14) have an insertion axis parallel to the axis of said connector.

Inventors: STUCKE ROBERT FREDERICK, STUCKE, ROBERT FREDERICK
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1993
Main classification: H05K7
IPC codes: H05K3, H05K1, H05K7, H01R12