LOW OR ZERO INSERTION FORCE CONNECTOR FOR MULTI-PIN ARRAYS

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. The connector preferably includes cooperating camming surfaces having inclined ramps and slots. Selective longitudinal movement of a cam actuator causes vertical movement of a cam plate whereby self-biasing of connector contacts is opposed for ready pin insertion. Engagement between the cam plate and contacts ceases upon reverse movement of the cam actuator to permit the contacts to tightly engage the pins.

Description: LOW OR ZERO INSERTION FORCE CONNECTOR FOR MULTI-PIN ARRAYS 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 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 necessary within a square of about two inches per side, i.e., about one-tenth inch pin spacings in both column and row directions. Further connections may envision forty-by-forty pin arrays or more. There are generally two types of zero insertion force connectors, one in which the contacts are normally closed and the other in which the contacts are normally open. The present invention relates to a zero or low insertion force connector having normally closed contacts. There are a number of known zero insertion force connectors of the closed-contact type which are used to make connection to conductors on printed circuit boards as well as to the leads of electronic packages or components and which employ camming devices for opening such contacts. Such connectors for printed circuit board connections are shown, for example, in U.S. Patents 4,196,955; 4,159,861; 4,159,154; 3,553,630; 3,426,313 and 3,395,377 and in German Patent 1118852. References showing connections to a multi-pin device in a closed contact connector include U.S. Patents 4,080,032 and 4,050,758, the latter reference also being useful in connections to printed circuit boards. SUMMARY OF THE INVENTION: The primary object of the present invention is an improved connector for the interconnection of multipin arrays to corresponding contacts. A more particular object of the present invention is to provide such interconnection of the multipin/contact arrays with zero or low insertion force. In accordance with the invention, an electrical connector has a plurality of contacts having socket terminals disposed in an array corresponding to the multipin 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. Each facing element is defined to-provide a partial boundary surface for the pin upon receipt thereof. A cam is supported for movement in the connector, such cam being adapted for receiving the terminal pins therein, the cam defining a further partial boundary surface for each terminal pin upon receipt thereof. The cam is movable from one position opposing such closing bias of the contact elements and displacing 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 a particular form of the invention, a cam actuator is provided for moving the cam between its first and second positions, the cam actuator being movable in a direction transverse to the movement of the cam. The cam defines a plurality of openings, one connector contact being situate in each, the openings adapted to receive the terminal pins therein. Each cam opening has a cam surface therein that is movable with the cam to engage the facing contact elements upon movement of the cam to the first position. In its particularly preferred embodiment, the cam and cam actuator are plates, the cam plate being movable in an upward direction in response to lateral movement of the cam actuator plate. Both the cam and cam actuator plates comprise cooperating camming surfaces, each including a plurality of successively spaced, inclined cam ramps and slots for effecting movement of the cam between the first and second positions. BRIEF DESCRIPTION OF THE DRAWING: 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 invthe socket. Fig. 12 is an exploded perspective view of an alternative construction of the connector of the present invention utilizing a different camming mechanism for opening the electrical contacts. 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 side walls 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 side walls 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. For example, alternative camming mechanisms may be used to reduce the connector profile or to enhance its strength by resisting bowing, especially in connectors with greater numbers of connections, such as in forty-by-forty pin arrays. Referring to the drawing, Fig. 12 depicts an electronic component such as a VLSI device 110 similar to the device 10 of Fig. 1 and having a plurality of terminal pins 112 projecting from the undersurface 114 of the device 110 and companion apparatus 116 for connection thereto, for example, a printed circuit board (PCB). An alternative approach for effecting such interconnection in accordance with the present invention includes a connector 118 comprising a housing including a base 120 having a compartment 122 defined by upstanding side walls 124 and 126, end wall 128 and floor 130. The undersurface 131 of the base 120 may include a plurality of longitudinally extending ribs 133 that provide stiffness to the base while permitting a minimal thickness. A cam actuator 132 is configured in the form of an elongate plate within the base compartment 122 for sliding longitudinal movement relative thereto, as illustrated by the arrow 134. The undersurface 136 of the cam actuator 132 includes a plurality of longitudinally extending, laterally spaced teeth 138 that are adapted to slide within a like plurality of tracks 140 formed in the base floor 130. Movement of the cam actuator 132 is effected by an actuator pin 142 having a shaft 144 and an eccentric portion 146. The shaft 144 is adapted to be received in an aperture 148 in the base 120 and the eccentric portion 146 is captively retained in an elongate opening 150 provided through a solid portion 132a of the cam actuator 132. The opening 150 is formed to closely receive the eccentric portion 146 such that upon rotation of the pin 142, the eccentric portion 146 will engage the walls of the cam actuator adjacent the opening 150 and move the cam EMI9.1 actuator plate longitudinally relative to the base 120. A slot 143 is provided in the upper surface of the pin shaft 144 to receive a screwdriver or like instrument for facilitating rotation of the pin 142. The cam actuator 132, in its preferred form, includes a plurality of fingers 152 extending longitudinally from the cam actuator solid portion 132a and terminating in free ends 152a. Each of the fingers is laterally spaced by an opening (not shown). The upper surface of each finger 152 is a camming surface and includes thereon a plurality of inclined cam ramps 154 and slots 156, successively spaced in the longitudinal direction and described in more detail hereinbelow. The free ends 152a of the fingers 152 are adapted to be slidably received in corresponding openings 128a provided in the end wall 128 of the base 120 upon movement of the actuator 132. A cam plate 158 overlies cam actuator 132, the cam plate 158 adapted to fit within the compartment 122 of base 120 and to move vertically relative thereto as shown by arrow 160. The bottom surface 158a of the cam plate 158 is a camming surface and comprises a plurality of laterally spaced, longitudinally extending rows of inclined cam ramps 162 and slots 164 that are adapted to cooperate with the cam ramps 154 and slots 156 on the cam actuator plate 132. Movement of the cam plate 158 is restricted to the vertical direction by the base end wall 128 and a front wall 166 of a cap 168 that is secured to the base 120 as by screws 170 (only one of which is shown). Tabs 172 and 174 project from the cam plate 158 and slide vertically within slots 128b in the rear wall 128 while tabs 176 and 178 slide vertically within slots 166a in the front wall 166 in cap 168. The cap 168 further includes an aperture 169 for receiving the shaft 144 of the pin 142 for external access thereto. For assembly of the cap 168 to the base 120, the cap 168 has apertures 180 and 182 and base 120 has suitably threaded registering bores 184 and 186. In the preferred form, the base 120, cam actuator 132, cam plate 158 and the cap 168 are made of a suitably rigid plastic material. VLSI device 110 has X-Y dimensions compatible with the base 120, base 120 having internal ledges as at 124a and 126a to support the VLSI device 110 in the connector 118. The pins 112 depend from the undersurface 114 of VLSI device 110 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. A like number of contacts 188 are supported in the base in a like array of apertures 190 provided in the base floor 130. The cam plate 158 has apertures 192 extending therethrough and arranged in the same array as the contacts 188. The contacts 188 project upwardly from the base 120 through the lateral openings (not shown) between the fingers 152 and into the apertures 192 in the cam plate 158. The contacts 188 may receive the terminal pins 112 between their biased facing elements without the lances as described with reference to Figs. 2-5. In operation, rotation of the pin 142 provides longitudinal movement of the cam actuator 132 which, in turn, with the cam ramps 162 of the cam plate riding on the cam ramps 154 of the cam actuator provides vertical upward or downward movement of the cam plate 158 within the connector 118. Cam surfaces disposed within the apertures 192, similar to those described with reference to the arrangement in Figs. 6-8 hereinabove, move the contacts to an open position to freely receive the terminal pins 112 therein. Camming plates having such apertures constructed to receive both the contact facing elements and the VLSI terminals while defining partial boundaries about the VLSI pins contribute to the low profile of the connector. It should be noted that the connector arrangement as described herein and shown in Fig. 12 places both the cam plate 158 and cam actuator 132 in compression against the bottom floor 130 of the base 120 under the influence of the spring force of the contacts 188. Such construction substantially minimizes the problems of bowing or bending of the cam plate 158 upon movement upward to spread apart the contact elements. As a result, a larger array of pins than in the known art having very close centers in both row and column directions (e.g., 0.1 inch by 0.1 inch) can be accommodated without problems of the strength of the material or the stiffness of the cam plate itself. Having described the construction and operation of the connectors herein, it should now be appreciated that multi-pin connections between the pins of a VLSI device and a companion PCB may be readily effected with zero or low insertion force. The particularly described arrangements are intended to be illustrative and not limited thereto. The true scope of the invention is set forth in the following claims. EMI12.1

Claims: CLAIMS: 1. An electrical connector for interconnecting a plurality of terminal pins in predetermined array to companion apparatus, comprising: (a) a housing; (b) a plurality of contacts supported by said housing in said array and extending in a common direction, each such contact having a first terminal for connection to said companion apparatus and a second terminal adapted for receiving one such terminal pin and having facing elements self-biased into preselected attitude, each facing element defining a partial boundary surface for said terminal pin upon receipt thereof; and (c) cam means supported for movement in said housing in said common direction, said cam means adapted for receiving said terminal pins and defining a further partial boundary surface for each said terminal pin upon receipt thereof, said cam means being movable between a first position wherein said cam means engages said facing elements of all such second terminals to oppose such selfbias thereof and displace said facing elements from said preselected attitude whereby said pins may be readily received in said second terminals, and a second position wherein said cam means does not oppose said second terminal self-bias whereby said facing elements may exert full force of said self-bias upon pins therebetween. 2. An electrical connector according to claim 1, wherein said cam means defines a plurality of openings, each receiving one of said contacts therein and for receiving one of said terminal pins therein, said cam means including a cam surface within each of said openings, wherein said cam surfaces in the first position of said cam means engage said facing elements of all such second terminals to oppose such self-bias thereof and displace said facing elements from said preselected attitude whereby said pins may be readily received in said second terminals, and wherein said cam surfaces in the second position of said cam means do not oppose said second terminal self-bias whereby said facing elements may exert full force of said self-bias upon pins therebetween. 3. An electrical connector according to claim 2, wherein said cam means defines an additional partial boundary surface spaced from and opposing said further partial surface, whereby the partial boundary surfaces defined by said facing elements and said cam means fully peri metrically bound said terminal pin upon receipt thereof. 4. An electrical connector according to claim 2, wherein each of said openings fully bound individual contacts and wherein the cam surfaces in such openings are collectively movable. 5. An electrical connector according to claim 2, wherein said cam means comprises a plate member defining said plurality of openings therethrough, each opening being in registry with said second terminals in receiving such second terminals therein, said housing supporting said plate member for movement in said common direction. 6. An electrical connector according to claim 5, wherein said plate member defines said cam surfaces, said cam surfaces partially bounding each such opening and being in interference path with the facing elements in each said opening to engage same in the course of movement of said plate member into said first position. 7. An electrical connector according to claim 5, wherein said cam surfaces for each such opening are resident respectively in said second terminals throughout the course of movement of said plate member between such first and second positions. 8. An electrical connector according to claim 1, further including cam actuator means movable in a direction transverse to said common direction for moving said cam means between said first position and said second positlon. 9. An electrical connector according to claim 8, wherein said cam means and said cam actuator means comprise cooperating adjacent camming surfaces for effecting movement of said cam means, and wherein said camming surfaces of said cam means and said cam actuator means each comprise a plurality of opposed cooperating inclined cam ramps and slots successively spaced on each camming surface. 10. An electrical connector according to claim 9, wherein said cam means comprises a plate member overlying said cam actuator means, and having a lower surface comprising said inclined cam ramps and slots, said housing supporting said plate member for movement in said common direction wherein said cam actuator means comprises a plate element underlying said plate member, and having an upper surface comprising said inclined cam ramps and slots, said housing supporting said plate element for transverse sliding movement, and wherein said inclined cam ramps of said plate member and plate element respectively terminate in flat surfaces, said flat surfaces of cooperating cam ramps being in contact when said plate member is in said first position and said flat surfaces being disposed in opposing slots when said plate member is in said second position.

Inventors: CHRISTENSEN, GORDON D., DONAHER, CHARLES J.
Applicants: THOMAS & BETTS CORPORATION
Application year: 1982
Main classification: H01R23
IPC codes: H01R12