HIGH-DENSITY CONTACT AREA ELECTRICAL CONNECTORS

Abstract: An improved electrical connector for making electrical connections between electronic components. The improved electrical connector includes an insu­ lating board interposed between metalized contact areas on the electronic components. The insulating board has openings at positions corresponding to the contact areas of the electronic components, with electrical connections between the contact areas established with conductive connector elements posi­ tioned in the openings of the insulating board. The connector elements are preferably each formed from a strand of metal wire, each strand being wadded together to form a nearly cylindrical "button" of material having a density of between twenty and thirty percent. The improved electrical connector provides high density contact areas, easy engagement and disengagement of the electronic components, and minimum electrical resistance between the contact areas.

Description: This invention relates generally to electrical connectors. Electrical connectors allow large electronic systems and subsystems to be assembled from many smaller electronic components, such as circuit boards, thus simplifying the manufacture, installation and maintenance of the electronic systems and subsystems. Typically, the circuit boards in these electronic systems and subsystems are interconnected with each other by means of a "mother" board, a large circuit board having edge card connectors into which the circuit boards are plugged. Alternatively, the circuit boards are interconnected by means of these same edge card connectors, but with cable harnesses and cable harness connectors in place of the mother board. Conventional edge card connectors generally utilize leaf-spring contacts for engaging contact areas at the edges of the circuit boards. Although these types of edge card connectors have many advantages, they do have some disadvantages. One disadvantage is that leaf-spring contacts can become bent and fail to make contact with the circuit board contact areas. Another disadvantage is that leaf-spring contacts have a relatively high electrical resistance. Still another disadvantage is that a comparatively high force is required to engage and disengage the circuit board from the edge card connector. However, the most significant disadvantage is that the contact areas at the circuit board edge require relatively large surface areas, thus severely limiting the number of contacts areas that can be placed along the edge of the circuit board. Circuit boards presently being manufactured are limited to about 250 edge contact areas, but in the very near future, as integrated-circuit chips become more complex, circuit boards having in excess of 400 contact areas will be required. Conventional cable harness connectors generally utilize male and female parts, such as pins and sockets, for connecting the leads of one cable harness to another. As with edge card connectors, cable harness connectors also have some disadvantages. One disadvantage is that the pins can become bent, thus preventing insertion of the pins into the sockets. Another disadvantage is that pins and sockets have relatively high electrical resistances. Still another disadvantage is that a comparatively high force is required to engage and disengage the cable harness connectors. However, the most significant disadvantage is that the pins and sockets require relatively large surface areas, thus severely limiting the number of contact areas that can be placed in one cable connector. In US-A-3324445 there is generally disclosed an electrical connector for making electrical connections between contact areas on two electronic components, comprising a connector housing attached to one of the electronic components, an insulating board disposed between the contact areas of the two electronic components, the insulating board having one or more openings at a position or positions corresponding to the contact areas, one or more conductive connector elements disposed respectively in the opening or in selected ones of the openings in the insulating board, and means for urging the connector housing and the two electronic components towards one another thereby compressing the or each conductive connector element and making electrical contact between the contact areas of the two electrical components. More particularly, in the electrical connector of US-A-3324445 each conductive connector element comprises a bundle of resilient conductors in the form of a length of braided wires. In accordance with the present invention as claimed, the aforesaid generally disclosed electrical connector is characterised in that the or each conductive connector element includes a wadded strand of conductive wire that is deformed when compressed and makes multiple electrical contacts with the contact areas of the two electronic components. An electrical connector constructed in accordance with the present invention provides high density contact areas, easy engagement and disengagement of the electronic components, and minimum electrical resistance between the contact areas. In a presently preferred embodiment of the invention, two cable harnesses are electrically connected by a cable harness connector using the technique of the present invention. The cable harness connector includes a first and second connector housing and an insulating board interposed between the two connector housings. The faces of the first and second connector housings have a plurality of metalized contact areas for connecting the leads of the two cable harnesses. The insulating board has a plurality of circular openings at positions corresponding to the connector housing contact areas. Compressing the connector housings together causes conductive connector elements positioned in the openings to be compressed against the metalized contact areas, thus making electrical connections between the contact areas. In another presently preferred embodiment of the invention, a circuit board and a mother board, and a circuit board and a cable harness, are electrically connected by an edge card connector using the technique of the present invention. The edge card connector includes a connector housing, an insulating board interposed between the connector housing and the circuit board, and another insulating board interposed between the connector housing and the mother board or between the connector housing and the cable harness. The first insulating board fits within a recessed area of the connector housing, with the recessed area having a plurality of metalized contact areas for connecting leads in the connector housing with a plurality of metalized contact areas along the edge of the circuit board. The bottom face of the connector housing has a plurality of metalized contact areas for connecting the leads in the connector housing with a plurality of metalized contact areas on the mother board or on the face of a cable harness connector housing attached to the cable harness. The insulating boards have a plurality of circular openings at positions corresponding to the contact areas of the connector housing, the circuit board and the mother board or cable harness connector housing. Compressing the connector housing, the circuit board and the mother board or cable harness together causes conductive connector elements positioned in the openings to be compressed against the metalized contact areas, thus making electrical connections between the contact areas. In still another presently preferred embodiment of the invention, two coaxial cables are electrically connected by a coaxial cable connector using the technique of the present invention. The coaxial cable connector is similar to the cable harness connector, with the exception that the coaxial cable connector has only a single conductive connector element in a circular opening at the center of the insulating board to electrically connect the center conductors of the two coaxial cables. An annular-shaped woven wire mesh, positioned about the circumference of the insulating board, electrically connects the outer conductors of the two coaxial cables. The wadded strand of conductive wire forming a conductive connector element preferably forms a nearly cylindrical "button" of material having a density of between twenty and thirty percent. Each such wadded-wire connector element fits snugly in an opening of the insulating board and protrudes slightly above and below the insulating board. The wadded-wire connector elements make electrical contact at multiple points when compressed against a contact area. Such connectors have significant advantages over other types of connectors, and provide connections of high integrity and reliability. In contrast to the other types of connectors, the present mechanical connector element has very few associated variables that can affect the quality of the connection. The only significant variables are the size of the connector element and the compressive force used to make the connection, both of which can be accurately controlled. In order that the present invention may be well understood there will now be described, in more detail, the aforesaid preferred embodiments thereof, which are given by way of example, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary perspective view of a cable harness connector embodying the present invention; Figure 2 is a fragmentary, exploded view of a wadded-wire connector element of the same cable harness connector; Figure 3 is a fragmentary, exploded sectional view of an insulating board with a plurality of wadded-wire connector elements of the same cable harness connector; Figure 4 is a fragmentary perspective view of an edge card connector embodying the present invention for electrically connecting a circuit board and a mother board; Figure 5 is a fragmentary sectional view of an edge card connector embodying the present invention for electrically connecting a circuit board and a cable harness; and Figure 6 is a fragmentary perspective view of a coaxial cable connector embodying the present invention. As shown in the drawings for purposes of illustration, the present invention is embodied in an improved electrical connector for making electrical connections between electronic components. In large electronic systems and subsystems, circuit boards are typically interconnected with each other by means of a "mother" board, a large circuit board having edge card connectors into which the circuit boards are plugged. Alternatively, the circuit boards can be interconnected by means of these same edge card connectors, but with cable harnesses and cable harness connectors in place of the mother board. However, conventional edge card and cable harness connectors have relatively high electrical resistances, are not easily engaged and disengaged and, most importantly, require relatively large surface areas for making the electrical connections. In accordance with the present invention, the improved electrical connector includes an insulating board interposed between metalized contact areas on the electronic components. The insulating board has one or more openings at positions corresponding to the contact areas of the electronic components, with electrical connections between the contact areas established with conductive connector elements positioned in the openings of the insulating board. In a presently preferred embodiment of the invention, two cable harnesses are electrically connected by a cable harness connector using the technique of the present invention. In another presently preferred embodiment of the invention, a circuit board and a mother board, and a circuit board and a cable harness, are electrically connected by an edge card connector using the technique of the present invention. In still another presently preferred embodiment of the invention, two coaxial cables are electrically connected by a coaxial cable connector using the technique of the present invention. These improved electrical connectors provide high density contact areas, easy engagement and disengagement of the electronic components, and minimum electrical resistance between the contact areas. Figure 1 shows a cable harness connector 10 for making electrical connections between a first cable harness 12 and a second cable harness (not shown). The cable harness connector 10 includes a first connector housing 14, a second connector housing 16 and a circular insulating board 18 interposed between the two connector housings 14, 16. The insulating board 18, commonly referred to as a button board, fits within a recessed area 20 of the first connector housing 14. The faces of the first and second connector housings 14, 16 have a plurality of metalized contact areas 22 for connecting leads 24 of cable harness 12 to leads 26 of the other cable harness. As shown more clearly in Figure 3, the insulating board 18 has a plurality of circular openings 28 at positions corresponding to the connector housing contact areas 22. Electrical connections between the contact areas 22 are established with connector elements 30 positioned in the openings 28 of the insulating board 18. Compressing the two connector housings 14, 16 together causes the connector elements 30 to be compressed against the metalized contact areas 22. Compression is provided by a flange 32 around the outer circumference of the first connector housing 14, a flange 34 around the outer circumference of the second connector housing 16 and two bolts 36, 38. The bolts 36, 38 engage a pair of threaded holes 40 in the flange 34. A slot 42 in the first connector housing 14 engages a key 44 protruding outwardly from the outer surface of the second connector housing 16, thus ensuring proper alignment of the contact areas 22 and the connector elements 30. The insulating or button board 18 is preferably formed from an insulating material, such as a glass ceramic or a plastic. The connector elements 30 employed in the illustrative embodiments are preferably each formed from a strand of metal wire, each strand being wadded together to form a nearly cylindrical "button" of material having a density of between twenty and thirty percent. As shown in Figure 2, each wadded-wire connector element 30 fits snugly in the opening 28 of the insulating board 18 and protrudes slightly above and below the insulating board 18. The wadded-wire connector elements 30 make electrical contact at multiple points when compressed against a contact area. Connectors of this type have significant advantages over other types of connectors and provide connections of high integrity and reliability. In contrast to the other types of connections, this mechanical connector element has very few associated variables that can affect the quality of the connection. The only significant variables are the size of the connector element and the compressive force used to make the connection, both of which can be accurately controlled. The wadded-wire connector elements 30 employed in the illustrative embodiments can be fabricated using nickel wire, or wire made from such alloys as beryllium and copper, silver and copper, or phosphorus and bronze. The compression of the wadded-wire connector elements 30 is substantially elastic so that, when the compressive force of the flanges 32, 34 and bolts 36, 38 is removed, the wadded-wire connector elements 30 return to their original shape. This allows the cable harness connector 10 to be taken apart and put back together as many times as is needed. In the embodiments described, the wadded-wire connector elements 30 are manufactured by Technical Wire Products, Inc. of Piscataway, New Jersey, under the trademark Fuzz Button. Figure 4 shows an edge card connector 50 for making electrical connections between a circuit board 52 and a mother board 54 and Figure 5 shows an edge card connector 50′ for making electrical connections between the circuit board 52 and a cable harness 56. The edge card connector 50 includes a connector housing 58, an insulating board 60 interposed between the connector housing 58 and the circuit board 52, and an insulating board 62 interposed between the connector housing 58 and the mother board 54. The edge card connector 50′ includes a connector housing 58′, an insulating board 60 interposed between the connector housing 58′ and the circuit board 52, and an insulating board 62 interposed between the connector housing 58′ and a cable harness connector housing 63. Each of the insulating boards 60 fits within a recessed area 64 of the connector housings 58, 58′. As shown in Figure 5, the recessed area 64 of each of the connector housings 58, 58′ has a plurality of metalized contact areas 66 for connecting leads 68 in the connector housings 58, 58′ with a plurality of metalized contact areas 70 along the edge of the circuit board 52. The bottom faces of the connector housings 58, 58′ have a plurality of metalized contact areas 72 for connecting the leads 68 in the connector housings 58, 58′ with a plurality of metalized contact areas 74 on the mother board 54 and a plurality of metalized contact areas 76 on the face of the cable harness connector housing 63, respectively. Each of the insulating boards 60 has a plurality of circular openings 78 at positions corresponding to the contact areas 66 of the connector housings 58, 58′ and the contact areas 70 of the circuit board 52, while each of the insulating boards 62 has a plurality of openings 78 at positions corresponding to the contact areas 72 of the connector housings 58, 58′ and the contact areas 74 of the mother board 54 and the contact areas 76 of the cable harness connector housing 63, respectively. Electrical connections between the contact areas 70 of the circuit board 52 and the contact areas 66 of the connector housings 58, 58′ and between the contact areas 72 of the connector housings 58, 58′ and the contact areas 74, 76 of the mother board 54 and cable harness connector housing 63, respectively, are established with wadded-wire connector elements 30 positioned in the openings 78 of the insulating boards 60, 62. Compressing the connector housings 58, 58′ and the circuit board 52 together causes the wadded-wire connector elements 30 to be compressed against the metalized contact areas 70, 66 and compressing the connector housings 58, 58′ and the mother board 54 and cable harness 56 together, respectively, causes the wadded-wire connector elements 30 to be compressed against the metalized contact areas 72, 74, 76. Compression of the connector housing 58 and the mother board 54 is provided by a bolt 82 that engages a threaded hole 84 in the mother board 54 and compression of the connector housing 58 and the circuit board 52 is provided by a bolt 86 that engages a threaded hole 88 in the circuit board 52. The circuit boards 52 employed in the illustrated embodiments preferably have four to six rows of contact areas 70 along each edge. The contact areas 70 are spaced on centers of between 0.030 to 0.040 inches, thereby providing approximately 800 contacts along each edge of a circuit board. Figure 6 shows a coaxial cable connector 100 for making electrical connections between a first coaxial cable 102 and a second coaxial cable 104. The coaxial cable connector 100 includes a connector housing 106 rotatably attached at the end of the first coaxial cable 102 and having a threaded inside surface, a collar 108 rigidly attached at the end of the second coaxial cable 104 and having a threaded outside surface for engagement with the threaded inside surface of the connector housing 106, and a circular insulating board 110 interposed between the ends of the two coaxial cables 102, 104. The insulating board 110 has a single circular opening 112 at its center, with a wadded-wire connector element 30 positioned in the opening 112 to electrically connect a center conductor 114 of the first coaxial cable 102 with a center conductor 116 of the second coaxial cable 104. An annular-shaped woven wire mesh 118, positioned about the circumference of the insulating board 110, electrically connects the outer conductors of the two coaxial cables 102, 104. The insulating board 110, which in the presently preferred embodiment of the invention is fabricated from Teflon, fits within an alignment ring 120 that slips over the outer surfaces of the two coaxial cables 102, 104 to properly align the opening 112 with the center conductors of the two coaxial cables 102, 104. Compressing the two coaxial cables 102, 104 together by screwing the threaded connector housing 106 onto the threaded collar 108 causes the wadded-wire connector element 30 and the woven wire mesh 118 to be compressed against the ends of the center and outer conductors, respectively, thus making electrical connections between the center and outer conductors.

Claims: An electrical connector for making electrical connections between contact areas (22; 66, 70; 72, 74; 72, 76; 114, 116) on two electronic components (12; 52, 54; 52, 56; 102, 104), comprising a connector housing (14; 58; 58'; 106) attached to one of the electronic components (12; 52; 102), an insulating board (18; 60; 62; 110) disposed between the contact areas (22; 66, 70; 72, 74; 72, 76; 114, 116) of the two electronic components (12; 52, 54; 52, 56; 102, 104), the insulating board (18; 60; 62; 110) having one or more openings (28; 78; 112) at a position or positions corresponding to the contact areas (22; 66, 70; 72, 74; 72, 76; 114, 116), one or more conductive connector elements (30) disposed respectively in the opening (112) or in selected ones of the openings (28; 78) in the insulating board (18; 60; 62; 110), and means (36, 38, 40; 82, 84, 86, 88; 106, 108)for urging the connector housing (14; 58; 58'; 106) and the two electronic components (12; 52, 54; 52, 56; 102, 104) towards one another thereby compressing the or each conductive connector element (30) and making electrical contact between the contact areas (22; 70, 74; 70, 76; 114, 116) of the two electrical components (12; 52, 54; 52, 56; 102, 104), characterised in that the or each conductive connector element (30) includes a wadded strand of conductive wire that is deformed when compressed and makes multiple electrical contacts with the contact areas (22; 70, 74; 70, 76; 114, 116) of the two electronic components (12; 52, 54; 52, 56; 102, 104). An electrical connector as claimed in claim 1, wherein the electronic components (12) are two cable harnesses (12), the connector housing (14) being attached to one cable harness (12) and a second connector housing (16) being provided which is attached to the other cable harness, each connector housing (14; 16) having a plurality of the contact areas (22) to which leads (24; 26) from an associated one of the cable harnesses (12) are connected, the insulating board (18) being disposed between the two connector housings (14, 16), the insulating board (18) having a plurality of the openings (28) at positions corresponding to the contact areas (22) of the two connector housings (14, 16), the compressing means (36, 38, 40) urging the connector housings (14, 16) towards one another thereby effecting said compressing of the conductive connector elements (30) and making electrical contact between the contact areas (22) of the two connector housings (14, 16). An electrical connector as claimed in claim 1, wherein one of the electronic components (52, 54; 52, 56) is a circuit board (52; 54) having an edge with said contact areas (70; 74), the connector housing (58; 58') being an edge card connector housing having a plurality of said contact areas (66; 72) to which leads (68) from the electronic component (52; 54; 56) are connected, the insulating board (60; 62) being disposed between the connector housing (58; 58') and the circuit board (52; 54), the insulating board (60; 62) having a plurality of said openings (78) at positions corresponding to the contact areas (66, 70, 72 74) of the connector housing (58; 58') and the circuit board (52; 54), a plurality of the conductive connector elements (30) being disposed in selected ones of the openings (78) in the insulating board (60; 62), the compressing means (82, 84, 86, 88) urging the connector housing (58; 58') and the circuit board (52; 54) towards one another thereby effecting said compression of the conductive connector elements (30) and making electrical contact between the connector housing (58; 58') and the circuit board (52; 54) contact areas (70; 74). An electrical connector as claimed in claim 3, wherein the connector housing (58; 58') has a first plurality of said contact areas (66) for connecting leads (68) in the connecting housing (58; 58') to the contact areas (70) of the circuit board (52) and a second plurality of said contact areas (72) for connecting the leads (68) in the connector housing (58; 58') to contact areas (74; 76) on the electronic component (54; 56), a second insulating board (62) being disposed between the connector housing (58; 58') and the electronic component (54; 56), the second insulating board (62) having openings (78) at positions corresponding to the contact areas (74; 76) of the connector housing (58; 58') and the electronic component (54; 56), further said conductive connector elements (30) being disposed in selected ones of the openings (78) in the second insulating board (62), the compressing means (82, 84) urging the connector housing (58; 58') and the electronic component (54; 56) towards one another thereby effecting compression of the further conductive elements (30) and making electrical contact between the contact areas (72, 74; 72, 76) of the connector housing (58; 58') and the electronic component (54; 56). An electrical connector as claimed in claim 4, wherein the electronic component (54; 56) is a second circuit board (54) or a cable harness (56). An electrical connector as claimed in claim 4 or claim 5, wherein the second insulating board (62) is fabricated from a glass ceramic or a plastic. An electrical connector as claimed in claim 1, wherein the electronic components (102, 104) are two coaxial cables (102, 104), each coaxial cable (102; 104) having a said contact area (114; 116) in the form of the end of a center conductor (114; 116), each coaxial cable (102; 104) also having an outer conductor, the connector housing (106) being attached to one (102) of the coaxial cables (102; 104), the insulating board (110) being disposed between the ends of the two coaxial cables (102, 104), the insulating board (110) having a single said opening (112) at a position corresponding to the center conductor (114; 116) of each of the coaxial cables (102, 104), the conductive connector element (30) being disposed in the opening (112) of the insulating board (110), a second conductive connector element (118) being disposed about the circumference of the insulating board (110), the compressing means (106, 108) urging the connector housing (106) and the two coaxial cables (102, 104) towards one another thereby effective said compression of the conductive connector element (30) and also compression of the second conductive connector element (118) and making electrical contact between the center conductors (114, 116) and the outer conductors. An electrical connector as claimed in claim 7, wherein the second conductive connector element (118) includes an annular-shaped woven wire mesh that is deformed when compressed and makes multiple electrical contacts with the ends of the two outer conductors. An electrical connector as claimed in any of the preceding claims, wherein the means for compressing (36, 38, 40; 82, 84, 86, 88; 106, 108) includes a screw mechanism (36, 38, 40; 82, 84, 86, 88; 106, 108). An electrical connector as claimed in any of claims 1 to 6, wherein the means for compressing (36, 38, 40; 82, 84, 86, 88) includes a clamp mechanism (36, 38, 40; 82, 84, 86, 88). An electrical connector as claimed in any of the preceding claims, wherein the or each wadded strand of wire has a density of approximately 20 to 30 percent. An electrical connector as claimed in any of the preceding claims, wherein the or each wadded strand of wire is a nickel wire. An electrical connector as claimed in any of claims 1 to 11, wherein the or each wadded strand of wire is an alloy wire, the alloy being selected from a group consisting of beyllium and copper, silver and copper, and phosphorus and bronze. An electrical connector as claimed in any of the preceding claims, wherein the insulating board (18; 60; 62; 110) is fabricated from a glass ceramic or a plastic.

Inventors: SMOLLEY, ROBERT
Applicants: TRW INC.
Application year: 1988
Main classification: H01R9
IPC codes: H05K3, H01R13