Abstract:
A connector for zero or low insertion force receipt of multi-pin arrays, such as those in very large scale integration (VLSI) components, includes cam surfaces for selective movement to oppose the self-biasing forces of connector contacts for pin insertion and reverse movement to permit the contacts to effect tight engagement with the pins under the influence of such self-biasing forces.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to electrical connectors and pertains more particularly to connectors of so-called zero or low insertion force type for use with multi-pin arrays. 
     BACKGROUND OF THE INVENTION 
     The primary advantage in the use of zero insertion force connectors, namely, minimizing loading of interfitting contacts during connection, takes on particularly great significance as the number of contacts simultaneously made increases to levels today seen with circuit components produced by very large scale integration (VLSI) techniques. In this sector, a VLSI device may present a twenty-by-twenty pin array, i.e., a total of four hundred pins, for simultaneous individual mating with collectively supported sockets. The loading forces attending such connection are, of course, cumulative of the force per mating contact pair and can readily amount to a level which may be unattainable for an assembler or not sustainable by support housings of the respective pins and sockets. 
     A further problem presented to the connector designer by VLSI is that of readily facilitating connection and disconnection and while minimizing the space in which such insertion connection and disconnection are to be effected. Customary practices in the art in larger environs are not applicable. In the above example of VLSI connection, the twenty-by-twenty pin array may be presented in a square of less than two inches per side. In such limited space, the use of such measure as translation of separate socket contact parts into engagement with a pin following positioning of the pin in residence between the parts is unlikely, as is use of such measure as translating a contact-making slide through the plane of a contact array. One known VLSI zero-insertion force practice looks, rather than to such customary measures, to the deformation of a socket upon a pin resident therein. Use is made, for example, of a ring loosely encircling the socket when exposed to refrigerant-produced temperatures. Following assembly, the ring is responsive to return to ambient temperatures and shrinks tightly upon the socket to effect electrical connection thereof to the pin. Resort to such exotic measure both evidences the difficulty of the problem presented by VLSI to the connector art and present costliness of approaches to solve the problem. 
     SUMMARY OF THE INVENTION 
     The present invention has as its primary object the provision of a simplified connector for interconnecting multi-pin arrays to corresponding sockets. 
     A more particular object of the invention is to provide separable interconnection of multi-pin/socket arrays with zero or low insertion force. 
     A still further object of the invention is to provide a connector for interconnection of VLSI devices and companion components without need for resort to thermally-adaptive connector components. 
     In attaining these and other objects, the invention provides a connector having a plurality of contacts having socket terminals disposed in an array corresponding to the multi-pin array and opposite terminals for connection to companion apparatus. The socket terminals are each formed with facing elements thereof closingly biased toward one another to electrically engage a pin to be received therein. A cam is supported for movement in the connector and defines cam surfaces collectively movable from one position opposing such closing bias of the contact elements and displacing the same to facilitate low-insertion force entry of pins therein to a second position wherein the cam surfaces are inactive in such function and permit self-biased tight engagement of the contact elements with the pins. 
     In its preferred configuration for VLSI device usage, the cam is a plate member of x-y dimensions approximating those of the VLSI device defining the pin array, and having channels therethrough for the passage of the contacts. Such cam surfaces are arranged contiguously with the passages. 
     In its particularly preferred embodiment, the connector of the invention has its constituent parts selected and arranged to provide low rather than zero insertion force. Thus, the invention looks toward socket terminals which slightly frictionally engage pins while the cam is operative, i.e., opposes the natural closing self-bias of contact elements to facilitate pin entry therein. Upon movement of the cam to its inoperative position, the contact elements, under self-bias, effect a wiping action upon the pins to effect gas-tight connection therewith. 
     The foregoing and other features of the invention will be further evident from the following detailed discussion of the particularly preferred embodiment thereof and from the drawings wherein like reference numerals identify like parts throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a connector in accordance with the invention and showing both a VLSI device and a companion component to be connected thereby with the VLSI device. 
     FIG. 2 is a perspective view of a contact for use in the connector of FIG. 1. 
     FIGS. 3-5 are respective front, side and top plan elevations of the FIG. 2 contact. 
     FIG. 6 is a plan elevation of a segment of the cam plate of the connector of FIG. 1 with one contact seated therein for purposes of explanation. 
     FIG. 7 is a partial sectional view of the cam plate of the connector of FIG. 1 as seen from plane VII--VII of FIG. 6. 
     FIG. 8 is a partial sectional view of the cam plate of the connector of FIG. 1 as seen from plane VIII--VIII of FIG. 6. 
     FIG. 9 is a sectional view as seen from broken plane IX--IX of FIG. 6 with the cam actuating pin, contact, VLSI device, device pin and companion apparatus being shown without sectioning for convenience and simplification of discussion. 
     FIG. 10 is a partial sectional view as seen from broken plane X--X of FIG. 6, with the contact, VLSI device, device pin and companion apparatus being shown without sectioning for like convenience and simplification of discussion. 
     FIG. 11 is a sectional view, as in FIG. 9, but with the cam plate in operative position, i.e., opposing socket element self-bias and displacing the socket elements to facilitate pin entry in the socket. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 depicts VLSI device 10 and companion apparatus 12 for connection thereto, for example, a printed circuit board (PCB). A connector for effecting such interconnection in accordance with the present invention comprises a housing having a base 14, defining compartment 16 upstanding from base floor 18 and bounded by sidewalls 20 and 22 and end walls 24 and 26. A cam plate 28 is shown above base 14. Cover or cap 30 of the housing has compartment 32 upstanding from cover floor 34 and bounded by sidewalls 36 and 38, end walls 40 and 42, and keying wall 44 which extends between side wall 36 and end wall 42. For assembly of connector parts, cover 30 has through-bores 46,48,50 and 52 and base 14 has suitably threaded registering bores 54,56,58 and 60. Fastener bolts (not shown) are passed through bores 46-52 and threaded into bores 54-60 for securing cover 30 to base 14, entrapping cam plate 28 within the housing. 
     VLSI device 10 has x-y dimensions compatible with like dimensions of compartment 32 of cover 30, with keying wall 10a orientated compatibly with keying wall 44 of cover 30. Pins 62 depend from undersurface 61 of VLSI device 10 in an x-y square array, of rows and columns for example, a twenty pin by twenty pin predetermined array having a total of four hundred pins. Contacts 64 are supported in base 14 in the same array as pins 62 on floor 18. As will be seen in detail in enlarged views below, cam plate 28 has apertures 66 extending therethrough and arranged in the same array as the contacts 64. Cover 30 similarly includes passages 68 in such array, whereby contacts 64 may extend through cam plate 28 and cover 30 to be accessible from the upper exterior of the housing to receive pins 62. 
     Cam plate 28 has end wings 70 and 72 providing detents 74 and 76 for the retentive seating of inserts 78 and 80. Such inserts each have an interiorly threaded bore for receipt of exteriorly threaded cam actuating pin members 82 and 84. Cover 30 is provided with openings 86 and 88 for passage of members 82 and 84 therethrough. Members 82 and 84 are accessible exteriorly of the housing and are secured to cover 30, as by use of snap rings (ring 85 also being shown in FIG. 9) applied thereto at the undersurface of cover 30. Upon such assembly of members 82 and 84 with cover 30 and subsequent fastening of cover 30 to base 14, as above discussed, the lower ends of members 82 and 84 seat freely in base recesses, one such recess being shown at 90. 
     As is described in detail below, members 82 and 84 function as position control means for cam plate 28, i.e., by turning the members, the plate may be disposed to confront base floor 18 or to confront the undersurface of cover 30. 
     Turning now to FIGS. 2-5, contact 64 has a first terminal 64a which extends through base 12 to be accessible below the base for engaging a terminal of companion apparatus, e.g., terminal 64a may be wave soldered to a conductive strip on PCB 12 (FIG. 1). Terminal 64a may also be formed in straight downward configuration for insertion into suitable metallized openings provided in PCB 12 and soldered therein by conventional wave-flow soldering techniques. A second terminal, serving as a pin-receiving socket, is provided opposite such first terminal and is defined by facing elements 64b and 64c which are formed in self-biased preselected attitude to assume generally parallel stance (FIG. 3). Contact 64 is formed of beryllium copper, phosphorous bronze or like material having sufficient resilience to exhibit self-bias, whereby facing elements 64b and 64c will seek to return to such parallel relation, or other preselected self-biased attitude, after release from mutually outward forces thereon opposing such inward self-bias. 
     Lances 64d and 64e are struck from elements 64b and 64c to extend inwardly thereof and preferably have arcuate facing surfaces at ends 64d-1 and 64e-1. A central support section 64g and an outwardly flared upper pin entry section 64f complete the contact, parts 64f-1 and 64f-2 flowing arcuately as shown to define inturned undersurfaces 64f-3 and 64f-4 inboard of facing elements 64b and 64c. 
     One such contact 64 is shown in conjunction with cam plate 28 in FIG. 6, which is a view enlarged approximately twenty times actual size for the two-inch square, twenty-by-twenty array alluded to above. A contact 64 would, of course, be resident in each of plate apertures 66, but such other contacts are here omitted for convenience and to simplify exposition. The segment of plate 28 shown in FIG. 6 includes apertures 66a through 66p, each of which has identical outline, as now discussed for aperture 66b. 
     Considering FIGS. 6-8 jointly with FIGS. 2-5, wall 92 and the left side walls of cam elements 94 and 96 provide a residence channel for contact facing element 64b. Similarly, right wall 98 and the right side walls of cam elements 94 and 96 provide a residence channel for contact facing element 64c. Contact lances 64d and 64e are situated in a non-interference path with plate 28, being of expanse less than the spacing across the aperture between opposed cam elements 94 and 96. Conversely, the cam elements extend marginally into the space 64h between contact facing elements 64b and 64c. Accordingly, if plate 28 were to be moved forwardly outwardly of the plane of FIG. 6, contact 64 remaining fixed, cam surfaces 94a and 96a would engage contact undersurfaces 64f-3 and 64f-4 and oppose the self-bias of facing elements 64b and 64c to displace same outwardly of each other. 
     As cam plate 28 is actually disposed in the plane of FIG. 6, the cam surfaces are inactive, being remote from the cammed contact surfaces 64f-3 and 64f-4, this condition of the connector being further seen in FIGS. 9 and 10. Here, member 82 is rotated fully counterclockwise in insert 78, placing cam plate 28 in its lowermost position, adjacent base floor 18. In such cam inoperative position, contact facing elements exert the full force of contact self-bias upon pin 62 therebetween. 
     The converse condition of the connector, i.e., cam operative position, is seen in FIG. 11. Here, member 82 is rotated fully clockwise in insert 78, placing cam plate 28 in its uppermost position, adjacent cover 30. In such cam operative position, contact self-bias is opposed and contact facing elements are displaced outwardly of one another, bending elastically about the locations of their exit from base apertures 100. Pin 62 is readily inserted into contact 64 under this condition and is shown in such seated condition. 
     The extent of deflection of facing elements 64b and 64c in the cam operative position may be readily established by selection of the width (W in FIG. 7) of cam elements 94 and 96, once the configuration of contacts 62 is established. Thus, while FIG. 11 shows a zero insertion force condition, the contact lances being non-contiguous with pin 62, advantage attends a low, rather than zero, insertion force. Thus, the invention prefers selection of cam element and contact dimensions to provide, in the cam operative position, for the spacing between opposing lance end surfaces from one another to be less than the diameter of pin 62. The lance end surfaces thus frictionally slidably engage pin 62 upon insertion giving rise to measurable insertion force. The lance end surfaces are preferably arcuate, as noted above. Upon release of the opposing force exerted on the facing contact elements 64b and 64c by the cam plate 28, the lances 64d and 64e, under the influence of the self-bias force of the contact, provide a further wiping action as between such arcuate surfaces and the pins. By virtue of the pin wiping action, surface oxides may be removed and gas-tight electrical connection readily realized. 
     Various modifications to the foregoing disclosed connector will be evident to those skilled in the art and may be introduced without departing from the invention. Thus, the particularly described preferred embodiment is intended in an illustrative and not in a limiting sense. The true spirit and scope of the invention is set forth in the following claims.