ELECTRICAL CIRCUIT INTERCONNECTION

Abstract: An electrical connector arrangement of the solderless type has first and second planar arrays (14, 40) of pad-type contact terminals in face-to-face engagement to provide engaged pairs of contact terminals. Each pad-type contact terminal (112) has a planar contact surface (114) and one pad-type contact terminal of each engaged pair has a series of scraping edges (122) spaced along the length of its planar contact for surface. The connector arrangement further provides for lateral movement of one array of contact terminals relative to the other array in a direction transverse to the scraping edges to cause the plurality of spaced scraping edges of one contact terminal of each pair to engage the planar surface of the other contact terminal of the respective pair in a contact-wiping action for removing surface contamination.

Description: ELECTRICAL CIRCUIT INTERCONNECTION Background of the Invention This invention relates to electrical circuit interconnections, and more particularly to connector arrangements of the type, useful with electronic circuit components of the semiconductor type. Integrated circuitry developments require circuit interconnection configurations of greater density, as well as circuit path configurations that control impedance and resistive effects which may alter circuit performance. Conventionally employed methods of interconnecting electrical or electronic circuit components have included the "pin-and-socket" type and '• the so-called "zero force insertion" type in which a . circuit card may be inserted when cooperating contacts are in an open position, and the contacts are then cammed to a closed position. These and other techniques have required substantial space or generally have a tendency to utilize complex arrangements and complicated manufacturing procedures. Additionally, certain types of commercially employed connectors cannot be easily matched in impedance to the circuit cards being connected, thus causing reflections which degrade signal quality. Such problems are particularly acute when connectors are used with newer generation semiconductors which have high switching speeds (100 - 500 picosecond rise time) , low switching energy and signal swings in the microvolts range, the resulting disadvantages including poor signal quality caused by high crosstalk, rise time degradation^ and reflections due to impedance mismatch. Summary of the Inven ion According to the invention, an electrical connector arrangement of the solderless type comprises first and second planar arrays of pad-type contact terminals in face-to-face engagement, each pad-type contact terminal having a planar contact surface and one pad-type contact terminal of each engaged pair having a series of scraping edges spaced along the length of its planar contact surface, and means for providing lateral movement of one of the arrays of contact terminals relative to the other array of contact terminals in a direction tranverse to the scraping edges to cause the plurality of spaced scraping edges of one contact terminal of each pair to engage the plan surface of the other contact terminal of the respective pair in a contact-wiping action for removing surface contamination. In preferred embodiments, successive scraping edges are spaced at least about one hundred micrometers apart; the scraping edges are defined by recesses in the sidewalls of the pad-type contacts; the scraping edges are defined by recesses in the contact surfaces of the pad-type contact terminals; and the pad-type contact terminals are of elongated rectangular shape and the scraping edges are disposed diagonally to the length of the pad-type contact terminals, preferably the scraping edges are defined by recesses in the surfaces of a pad-type contact terminal, each recess being at least about ten micrometers in depth and extending across the width of the pad-type contact terminal, more preferably the array moving means includes camming structure for providing said contact wiping action. The connector assembly provides a controlled impedance connection with low crosstalk and high propagation velocity in an envi onmentally reliable, high density interconnection which is electrically invisible even at very high frequencies. Other features and advantages of the invention will be seen as the following description of a particular embodiment progresses, in conjunction with the drawings . Preferred Embodiments We first briefly describe the drawings. Fig. 1 is a plan view of a printed circuit board with a rectangular array of terminals; Fig. 2 is a perspective view of a module-to-board connector assembly in accordance with the invention for cooperation with the printed circuit board of Fig. 1, showing a chip carrier module and contact array; Fig. 3 is an exploded perspective view of components of the_ chip carrier module and contact array of Fig. 2, showing a terminal support assembly; Fig. 4 is a plan view of the carrier frame member of Fig. 3; Fig. 5 is a side view of the frame member of Fig. 4; Fig. 6 is a sectional view taken along the line 6-6 of Fig. 4; Fig. 7 is a plan view of a contact support bar of the terminal support assembly of Fig. 3; Fig. 8 is a front view of the support bar of Fig. 7; Fig. 9 is a sectional view taken along the line 9-9 of Fig. 7; Figs. 10A and 10B are plan views of flexible signal conductor arrays employed in a particular embodiment of the invention; Fig. IOC is an enlarged diagrammatic view of the superimposed contact arrays; Fig. 10D is a plan view of the contact arrays shown in Fig. IOC; Figs. 11A and 11B are enlarged views of contact pad configurations showing aspects of the scraping edge feature; and Figs. 12 and 13 are sectional diagrammatic views illustrating the wiping and electrical connection actions of the connector assembly of Fig. 2. Description of Particular Embodiment o Figure 1 is a diagrammatic view of a circuit board 10 having a substrate 11 on which is disposed one or more printed circuits, represented by area 12, with an associated rectangular "footprint" in the form of two rows of pad-type contact terminals in a terminal array 14 (signal terminals 14A and ground terminals 14B) . As is known, terminals 14 are connected to circuit(s) 12 (which may be located inside or outside "footprint" 14 (or both)) via pla ' ted-through holes to connector traces on the reverse side of the substrate. At each corner of the array of terminals is a f stener-receiving aperture 16 and two upstanding guide posts 18. Substrate 11 may be of suitable insulating material such as polyimide glass or epoxy glass, and an appropriate stiffening plate 20 may be secured on the rear side of the substrate 11 in alignment with terminal array 14 and alignment posts 18. Cooperating with printed circuit substrate 11 and terminal array 14 (as shown in Fig. 2) is connector assembly 30 that includes module 32 on which circuit elements (such as one or more chips or chip carriers, not shown) are mounted and that has a rectangular array of corresponding terminals (not shown) to which are soldered flexible plural conductor (preferably microstrip or strip line) fifty ohm characteristic impedance transmission line circuits 36 that fan out to the contact density of the circuit board 10. Each flexible circuit 36 has one or more rows of contact pad-type terminals in terminal array 40 at its other ends of the same size and spacing as terminal array 14. The four terminal arrays 40 are secured on corresponding carrier bars 42 that are in turn resiliently secured to carrier frame 44 by post structures 46 and spring members 48. Connector assembly 30 is shown in exploded view in Fig. 3, and further details of carrier frame 44 may be seen with reference to Figs. 4-6. Carrier frame 44 includes a transverse plate 52 with corner post structures 54 on one side on which module 32 is secured. Upstanding from the other side of plate 52 is a camming structure of rectangular configuration that includes a set of four planar ramp surfaces 56, each of which is disposed at an angle of 60° to the plane of plate 52. Centrally located in and extending perpendicularly through each ramp surface 56 is an elongated slot 58. At each corner of the ramp structure 56 is a fastener aperture 60. A clearance recess 62 is formed in base plate 52 in general alignment with slot 58, and a spring tip capturing recess 64 is formed in plate 52 on either side of each clearance recess 62. Each carrier bar 42, as may be seen with reference to Figs. 3 and 7-9, has a planar base surface 70 in which recess 72 is formed and receives resilent, open-cell polyurethane foam pad 74 (which may be of the type described in U.S. Patent 4,468,074) such that the outer surface of pad 74 projects about one millimeter beyond surface 70 of carrier bar 42. At each end of recess 72 is a threaded fastener recess 76 that cooperates with associated fastener portions 116 of flexible transmission line circuits 36. The end surfaces 80 of bars 42 are disposed at 45° angles to the length of the bar so that the surfaces are aligned with one another in the assembly as shown in Fig. 2, and a recess 82 (and corresponding recess 120 (Figs. 10A, 10B)) is formed in each surface for clamp fastener 88. Extending laterally from surface 70 at either end thereof are a pair of projections 84 that define a guide slot 86 that receives and cooperates with a Q corresponding guide post 18 on substrate 11. Each carrier bar 42 also include a ramp surface 90 that is disposed at an angle of 60° to surface 70, and in which is formed a threaded recess 92 for receiving post structure 46. 5 Carrier bars 42 are assembled to carrier frame 44 with coupling post structures 46 and spring members 48 such that their ramp surfaces 90 seat on frame ramp surfaces 56. Coupling post structures 46 extend through slots 58 and are threadedly secured in recesses 92, the o central portion of each stainless steel spring 48 is captured on the head of its post 46 and its end portions are seated in frame recesses 64, as indicated in Fig. 2, so that springs 48 bias the ramp surfaces 90 of carrier bars 42 against and along frame ramp surfaces 56 away 5 from plate 52. The pad-type contact terminal arrays 40 of flexible transmission line circuits 36 are secured to carrier bars 42 by threaded fasteners 98 in threaded fastener recesses 76. In this connector embodiment, two superimposed 0 flexible transmission line circuits 36 (Figs. 12, 13) are secured to each carrier bar 42, and provide a transition in terminal density between chip carrier module 32 and pad-type contact terminal arrays 40. Details of those flexible transmission line circuits 36 may be seen with reference to Figs. 10A - D. Each flexible circuit 36A, 36B is of "microstrip" configuration and includes one ounce copper ground plane 100 that terminates in exposed ground terminal strips 102, 104 at opposite ends of the circuit (the ground terminal strips 104 corresponding to contact pads 40A of Fig. 10D), three mil thick glass reinforced fluorocarbon (Rogers RO-2500) dielectric 106 that has a low dielectric constant (2.5) and a low loss factor, a set 0 of one ounce copper conductive circuit traces 108A, 108B that extend between terminals pads 110 and terminals pads 112 and cover film, the flexible circuits providing controlled impedence high density transmission line conductors (traces 108) between terminal strip 102 and 5 terminal pad 110 that are soldered to chip carrier module 32 and terminal strip 104 and terminal pads 112 (the signal pads 112 corresponding to contact pads 40B_ of Fig. 10D) . At either end of the contact pad terminal array 40 is a fastener portion 116 that includes an Q aperture 118 through which a threaded fastener 98 (Fig. 2) extends into its corresponding threaded fastener hole 76 (the fastener portions 116 being spaced about 2.5 centimeters apart). The conductive circuit traces 108 are one ounce (1.4 mil) copper and pads 112 are copper plated to about two ounces (about 3 mils). Referring to Fig. 11A, diagonal scraping edge portions 122 (defined by recesses of about one mil depth and two mils width that are disposed at an angle of about 30°) are formed in the 0 planar contact surface 114 in pads 112, e.g., by photoengraving, using appropriate artwork. A layer of nickel and a layer of gold, each about fifty microinches in thickness are then deposited on the surfaces of contact pads 112, providing planar contact surfaces in which are formed a series of scraping edge portions. In an alternate pad configuration, shown in Fig. 11B, scraping edge portions 122' are provided in the planar contact surface 114 by defining recesses 124' in sidewall portions of pad 112'. Referring, e.g., to Fig. 13 in conjunction with Fig. 1, the outlines of the arrays of contacts 14 on the circuit board 10 (and the corresponding arrays 40 on the flexible circuits 36) are of elongated form. The carrier bars 42 are of corresponding form. The camming structure that lies directly above each bar 42 is also of generally corresponding form (see, e.g., Fig. 3), lying predominantly within projection lines P, and P-, (Fig. 13), projected perpendicular to the face of the circuit board 10 from the outline of the carrier bar 42. Areas covered by the actuating mechanisms, i.e., camming ramp surfaces 56, 90, posts 46, etc., are substantially the same as those covered by the mating contact arrays, i.e., 14, 40, leaving adjoining areas of the circuit board available, e.g., for the mounting of components. For instance, in the square of terminal array 14 shown, e.g., in Fig. 1, a component, e.g., an active electrical component or a cooling device, can be mounted on the same side of the board as the contacts, and other electrical components mounted outside of the square of the terminal array on the same side of the board as the contacts. Interaction of the contact assembly 28 (Fig. 2) with the substrate 11 is indicated diagrammatically in Figs. 12 and 13. Contact assembly 28 is disposed on circuit board 10 as indicated in Fig. 12, with contact pad array 40 seated on but inwardly offset from cooperating substrate pad array 14. As fasteners 88 are tightened to urge contact assembly 28 toward substrate 11, (in the direction of arrow 130), the ramp surfaces 56 of frame 44 slide along ramp surfaces 90 of carrier bars 42 against the biasing forces of springs 48 and producing a transverse outward (sliding) movement (in the direction of arrow 132) and wiping action of scraping edge portions 122 of terminal pads 112 of contact pad array 40 across substrate contact pad array 14. That wiping action removes debris and surface contamination and, together with resilient actions of 10 springs 48 and pads 74, produces durable, electrically invisible (to pulses with 35 picosecond rise times at the pulse generator), low contact resistance (one to three milliohm) circuit interconnections with clamping forces of about thirty psi. j _5 The disclosed connector 'assembly provides multiple electrical connections in an arrangement resistant to mechanical and thermal shock which is relatively inexpensive to manufacture, simple to utilize, readily replaceable without the use of solder, 20 and provides reliable circuit interconnections with distributed mating forces and wiping actions of pad-type contacts. While particular embodiments have been shown and described, various modifications will be apparent to those skilled in the art, and therefore it is not 5 intended that the invention be limited to the disclosed embodiments or to details thereof, and departures may be made therefrom within the spirit and scope of the invention.

Claims: 1. An electrical connector arrangement of the solderless type comprising first and second planar arrays of pad-type contact terminals for face-to-face engagement to provide engaged pairs of contact terminals, each pad-type contact terminal having a planar contact surface and at least one pad-type contact terminal of each engaged pair having a series of scraping edges spaced along the length of its planar contact surface, and means for providing lateral movement of one of said arrays of contact terminals relative to the other array of contact terminals in a direction transverse to said scraping edges to cause said plurality of spaced scraping edges of one contact terminal of each pair to engage the planar surface of the other contact terminal of the respective pair in a 'contact-wiping action for removing surface contamination. 2. The connector arrangement of claim 1 wherein successive ones of said scraping edges are spaced at least about one hundred micrometers apart. 3. The arrangement of claim 1 or 2 wherein said scraping edges are defined by recesses in the sidewalls of said pad-type contact terminals. 4. The arrangement of claim 1 or 2 wherein said scraping edges are defined by recesses in the contact surfaces of said pad-type contact terminals. 5. The arrangment of claim 4 wherein each said recess is at least about ten micrometers in depth and extends across the width of the pad-type contact terminal. 6. The arrangement of any of the preceding claims wherein said pad-type contact terminals are of rectangular shape. 7. The arrangement of any of the preceding claims wherein said scraping edges are disposed diagonally to the length of said pad-type contact terminals. 8. The arrangement of any of the preceding claims wherein said array moving means includes camming structure for providing said contact wiping 'action.

Inventors: GORDON HERMAN B, KOSA BRUCE G, SIMPSON SCOTT S, GORDON, HERMAN, B., KOSA, BRUCE, G., SIMPSON, SCOTT, S.
Applicants: ROGERS CORP, ROGERS CORPORATION
Application year: 1987
Main classification: H05K1
IPC codes: H01L23, H01R12, H05K1, H05K3, H05K7