Abstract:
A high density connector element and its associated method of manufacture. The high density connector element contains a plurality of conductive wires that are arranged in parallel on the top surface of a flexible substrate. To manufacture the high density connector element, the flexible substrate is coated with an adhesive and wrapped around a cylindrical drum with the adhesive facing outwardly. Conductive wire is then wound around the cylindrical drum in a helical pattern. The conductive wire is densely wrapped around the flexible substrate on the cylindrical drum and is bound by the adhesive, thereby creating the high density connector element. After the winding is complete and the adhesive cured, at least one strip is cut from the high density connector element. The high density connector element has a flexible substrate and multiple conductive wires laid in parallel across the top surface of the substrate. Each of the conductive wires is electrically isolated from each of the other conductive wires, even when the wires are present in a highly dense pattern.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to the structure and manufacturing techniques of high density connector elements. More particularly the present invention relates to high density connector elements that are flexible and contain parallel conductors densely arranged on at least one surface.  
           [0003]    2. Description of the Prior Art  
           [0004]    As electronic circuitry becomes smaller and more densely populated with components, it is often difficult to interconnect separate electronic circuits using traditional soldering techniques. In many electronic assemblies, separate electronic components are placed in different areas of the assembly. Although the various electronic components will be near each other when the assembly is fully assembled, these same parts are kept apart while the assembly is dissembled. In order to electrically interconnect the various electronic components prior to the final assembly, a manufacturer often uses long connection cables to interconnect the various separated electronic components. The long connection cables are then folded up into the device as the separated electronic components are assembled. The use of such long cables is expensive, labor intensive and requires space in the final assembly to hold the folded long cables. Furthermore, the long cables often become pinched as they are folded up into the final assembly, thus causing defective assemblies.  
           [0005]    Another solution to this problem, has been the use of elastomeric connectors. Elastomeric connectors are a class of contact connectors that contain conductive elements supported by an elastomeric body. By placing an elastomeric connector between two electronic components, the two components can be electrically interconnected as the final product is assembled and two electronic components are biased against the same elastomeric connector.  
           [0006]    There are many different styles and designs of elastomeric connectors. The present invention addresses the family of elastomeric connectors that contain high density parallel conductors as part of their structure. In the prior art, many different manufacturing techniques have been developed to produce densely packed parallel conductors on a substrate. Such prior art techniques include the use of photo lithography, such as is exemplified by U.S. Pat. No. 3,421,961 to Joyce, entitled Method Of Making High Density Electrical Connections. Other techniques include chemical addition processes, where the conductors are plated onto a substrate, and plasma removal processes, where lines are removed from a conductive film on a substrate.  
           [0007]    Although such prior art techniques work, they require very expensive manufacturing tools. Furthermore, due to the high dimensional tolerances needed, such prior art manufacturing techniques have a high rate of defective products that are scrapped.  
           [0008]    Once high density conductors are produced on a substrate, that substrate can be cut into strips to produce high density flexible cables. Alternatively, the substrate can be wrapped around an elastomeric body to produce an elastomeric connector. Such elastomeric connectors are exemplified by U.S. Pat. No. 5,632,626 to Collins, entitled Retention Of Elastomeric Connector In A Housing and U.S. Pat. No. 5,588,845, entitled Connectors For Base Boards And Methods Of Connector For Base Boards. However, since these prior art elastomeric connectors are made with expensive high density parallel conductors, the prices of these elastomeric connectors are also high.  
           [0009]    A need therefore exists for a new way to manufacture high density parallel connectors on a substrate that is low cost and does not require expensive manufacturing equipment. A need also exists for a method of producing high density parallel connectors in a more reliable manner. These needs are met by the present invention as described and claimed below.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is a high density connector element and its associated method of manufacture. The high density connector element contains a plurality of conductive wires that are arranged in parallel on the top surface of a flexible substrate. To manufacture the high density connector element, the flexible substrate is coated with an adhesive and wrapped around a cylindrical drum with the adhesive facing outwardly. Conductive wire is then wound around the cylindrical drum in a helical pattern. The conductive wire is densely wrapped around the flexible substrate on the cylindrical drum and is bound by the adhesive, thereby creating the high density connector element. After the winding is complete and the adhesive cured, at least one strip is cut from the high density connector element. The high density connector element has a flexible substrate and multiple conductive wires laid in parallel across the top surface of the substrate. Each of the conductive wires is electrically isolated from each of the other conductive wires, even when the wires are present in a highly dense pattern.  
           [0011]    The high density connector element can be used to produce flexible cable connectors or can be used in the manufacture of elastomeric connectors. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a perspective view of a segment of a high density connector element in accordance with the present invention, in the view are three enlarged areas, wherein each of the enlarged areas shows a slightly different exemplary configuration;  
         [0014]    [0014]FIG. 2 is schematic showing the method of manufacture for a high density connector element; and  
         [0015]    [0015]FIG. 3 is a perspective view of an elastomeric connector that utilizes a high density connector element as part of its structure. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring to FIG. 1, an exemplary embodiment of high density connector element  10  is shown in accordance with the present invention. The high density connector element  10  is comprised of a flexible dielectric substrate  12 . Attached to the flexible dielectric substrate  12  are a plurality of parallel conductive wires  14 . The conductive wires  14  are permanently bonded to the flexible dielectric substrate  12  in a parallel orientation so that each of the conductive wires  14  are electrically isolated from each of the other conductive wires  14 .  
         [0017]    The conductive wires  14  are bonded to just the top surface of the flexible dielectric substrate  12 . As such, any object that touches the top of the high density connector element  10  would contact at least some of the conductive wires  14 .  
         [0018]    The flexible dielectric substrate  12  can be any flexible dielectric material. However, experience has shown that b-stage cured silicone rubber or polyimide films work well as the substrate  12 . Such substrate materials are currently commercially available at thicknesses of 0.005 inches. The high density connector element  10  preferably uses the thinnest flexible dielectric substrate  12  possible. As such, should the desired substrate materials be made thinner in the future, these thinner substrates can be adapted for use with the present invention.  
         [0019]    The flexible dielectric substrate  12  is coated with an adhesive that remains flexible when cured. In the prior art, there are several thermoset adhesives that are used to manufacture flexible circuits. A thin film of any such thermoset adhesive can be adapted for use with the present invention. Prior to the curing of the flexible adhesive, the conductive wires  14  are applied to the top surface of the flexible dielectric substrate  12 . The conductive wires  14  are uninsulated and are manufactured using known metal extrusion techniques. Using modern extrusion techniques, conductive wire can be made with very exacting tolerances. For the present invention high density conductive element, the conductive wires can have any diameter, however, wire diameter of between 0.0005 inches and 0.002 inches is preferred, depending upon the composition of the conductive wire. Alloys, such as Cu/Be/Ni/Au alloys are commercially produced into wires as thin as 0.0005 inches. Less exotic alloys, such as Cu/Be alloys are commercially produced into wires as thin as 0.001 inches. Pure gold is commonly made into wires that have a diameter of 0.002 inches.  
         [0020]    The conductive wire can be made of various metals and alloys commonly used in the production of ultra-thin circuitry wire. However, unless the conductive wires  14  are made of a gold alloy, the conductive wires  14  preferably have a gold over nickel finish to ensure good contact conductivity.  
         [0021]    In circle A of FIG. 1, an embodiment of the high density connector element  10 A is shown where the conductive wire  14 A is at its maximum density. In this embodiment, wire from the thinnest possible range is used. The conductive wire  14 A is spaced so that the space S 1  between the various stands of conductive wire  14 A is no greater than the diameter of the conductive wire  14 A being used. However, the space S 1  in between strands of conductive wire  14 A is larger than the dimensional tolerances used in the manufacture of the conductive wire  14 A. In this manner, each strand of conductive wire  14 A is positioned as close as possible to the adjacent wires without risk of any one conductive wire touching an adjacent conductive wire.  
         [0022]    In circle B of FIG. 1, an embodiment of the connector element  10 B is shown where larger diameter conductive wire  14 B is used. Furthermore, the pitch of the spaces between the strands of conductive wire  14 B is greatly increased. As such, a uniform spacing S 2  exists between the conductive wires. The uniform spacing S 2  can be any desired distance. However, spacing less than ten times the diameter of the conductive wire  14 B is typically preferred.  
         [0023]    In circle C of FIG. 1, an embodiment of the high density connector element  10 C is shown where the pitch pattern of the spaces between the stands of conductive wire  14 C is not uniform. Rather, the conductive wire  14 C can be laid onto the dielectric substrate  12 C with any desired pitch pattern. In the shown pitch pattern, the conductive wire  14 C is laid down in groups of three. In each group, the conductive wires  14 C are separated by a space no larger than the diameter of the conductive wire  14 C being used. In between each group, the space may be any distance and it is preferably less than ten times the diameter of the conductive wire  14 C being used. The use of three strands of conductive wire  14 C in each group is merely exemplary and it should be understood that any plurality of conductive wires  14 C can constitute a group.  
         [0024]    Referring now to FIG. 2, an exemplary method of manufacturing the high density connector element can be described. From Step  1  in FIG. 2, it can be seen that a roll  20  of flexible dielectric substrate  12  is provided. The flexible dielectric substrate  12  in the roll  20  has a coating of thermoset adhesive  22  applied to its top surface. The thermoset adhesive  22  is covered with a removable protective cover sheet  24  to prevent the inadvertent contamination of the thermoset adhesive  22 . The flexible dielectric substrate  12  can be purchased precoated with the thermoset adhesive  22  already applied, or else the thermoset adhesive  22  can be added to the flexible dielectric substrate  12  in an undescribed preparation procedure.  
         [0025]    In Step  2  of the manufacturing method, a predetermined segment of flexible dielectric substrate  12  is cut from the role  20 . The cut segment of the flexible dielectric substrate  12  has a length L and a width W. In Step  3 , the segment of flexible dielectric substrate  12  is then mounted to the exterior of a cylindrical drum  26 . The segment of flexible dielectric substrate  12  is mounted so that the thermoset adhesive faces away from the cylindrical drum  26 . The cylindrical drum  26  has a length that is at least as long as the length L of the cut segment of flexible dielectric substrate  12 . The external circumference of the cylindrical drum  26  is equal to the width W of the cut segment of flexible dielectric substrate  12 . As a result, when the cut segment of flexible dielectric substrate  12  is placed on the cylindrical drum  26 , the segment of flexible dielectric substrate  26  completely surrounds the cylindrical drum  26  without any significant seam, gap or overlap.  
         [0026]    A strip of double sided tape  28  is applied to the cylindrical drum  26 . The double sided tape  28  is applied in a straight line along the length of the cylindrical drum  26 . To hold the segment of flexible dielectric substrate  12  in place, one edge of the segment is placed on the tape  28 . The segment of flexible dielectric substrate  12  is then wound around the cylindrical drum  26 , wherein the opposite edge also comes to rest over the double sided tape  28 .  
         [0027]    In Step  4 , the cylindrical drum  26  is attached to a larger winding assembly  30 . The winding assembly  30  contains a rotational drive mechanism  32  that rotates the cylindrical drum  26  around its central axis. The winding assembly  30  also contains a lateral drive mechanism  34  that moves the cylindrical drum  26  laterally back and forth along the line of the cylindrical drum&#39;s central axis. The rotational drive mechanism  32  and the lateral drive mechanism  34  are both controlled by a programmable systems controller  37 .  
         [0028]    Above the cylindrical drum  26  is located a stationary capillary head  36  and a tensioning mechanism  38 . Conductive wire  14  from a spool  40  is fed through the tensioning mechanism  38  and the stationary capillary head  36 . After the conductive wire  14  is installed in the capillary head, the protective cover sheet  24  is removed from the surface of the flexible dielectric substrate  12 , thereby exposing the thermoset adhesive that coats the flexible dielectric substrate  12 .  
         [0029]    After the thermoset adhesive is exposed, the systems controller  37  then moves the cylindrical drum  26  so that the capillary head  36  is aligned with one end of the flexible dielectric substrate  12 . A lead of wire  14  is then pulled through the capillary head  36  and is attached to the side of the cylindrical drum  26  with a piece of tape or another equivalent mechanical fastener. The cylindrical drum  26  is then turned manually at least one turn to start the rotation of the conductive wire  14  around the cylindrical drum  26 .  
         [0030]    Once the conductive wire  14  is properly primed around the cylindrical drum  26 , the systems controller  37  enables the rotational drive mechanism  32  and the lateral drive mechanism  34 . As has been previously explained, the rotational drive mechanism controls the rotation of the cylindrical drum  26 . The lateral drive mechanism  34  controls the lateral movement of the cylindrical drum  26  under the stationary capillary head  36 . The systems controller  37  is preprogrammed with a desired pitch pattern. The systems controller  37  selectively controls the rotational drive mechanism  32  and the lateral drive mechanism  34  to create the preprogrammed pitch pattern on the exterior of the cylindrical drum  26 . As has been previously explained in reference to FIG. 1, the pitch pattern can cause uniform spaces between each rotation of wire  14  or can create patterns of wire groupings.  
         [0031]    The winding assembly  30  creates the preprogrammed pitch pattern across the entire length of the segment of flexible dielectric substrate  12 . After, the desired pitch pattern of conductive wire  14  is created along the flexible dielectric substrate  12 , the conductive wire  14  is cut and secured to the cylindrical drum  26 . The cylindrical drum  26  is then removed from the winding assembly  30 .  
         [0032]    The pitch pattern of conductive wire  14  contacts the thermoset adhesive coating the flexible dielectric substrate  12 . As is indicated by Step  5 , the entire cylindrical drum/substrate assembly  50  is then placed into a curing chamber  52 . In the curing chamber  52 , the temperature is sufficient to cure the thermoset adhesive. Once the thermoset adhesive achieves its activation temperature, cylindrical drum/substrate assembly  50  is allowed to set. Once set, the cylindrical drum/substrate  50  is removed from the curing chamber. When the thermoset adhesive is heated, the thermoset material flows around and between the bottom of the conductive wires  14 . The coating of thermoset adhesive, however, is kept too thin to completely surround any part of the conductive wires  14 . When the thermoset adhesive cures, the conductive wires  14  become bonded to the flexible dielectric substrate  12  via the thermoset adhesive.  
         [0033]    In Step  6 , after the cylindrical drum/substrate assembly  50  is cooled, the conductive wires  14  are cut along the seam between the two opposing edges of the flexible dielectric substrate  12 . Optionally, both the flexible dielectric substrate  12  and the surrounding conductive wires  14  can also be cut along other lines that are parallel to the line of the seam.  
         [0034]    Once the conductive wires  14  and underlying dielectric substrate  12  is cut, the cut section or sections can be removed from the cylindrical drum  26 . Each removed section creates a section of high density connector element  10 , such as that described with reference to FIG. 1.  
         [0035]    Each section of high density connector element  10  can be cut into strips to create high-density flexible cables and ribbons. Alternatively, the sections of high density connector element can be used to create an elastomeric connector. Referring to FIG. 3, it can be seen that a section of a high density connector element  10  can be wrapped around a core  60  of elastomeric material. The high density connector element  10  can be attached to the elastomeric core  60  either mechanically or with the use of an adhesive. The resulting final product is an elastomeric connector  62  having rows of conductive wires  14  on its exterior, yet being low cost to manufacture.  
         [0036]    It will be understood that the embodiments of the present invention described and illustrated herein are merely exemplary and a person skilled in the art can make many variations to the embodiment shown without departing from the scope of the present invention. For example, in the described method of manufacture, a laterally moving cylindrical drum was moved relative a stationary wire capillary. The same product could be made by providing both a cylindrical drum that is laterally stationary and the wire capillary that moves along the length of the cylindrical drum. All such variations, modifications and alternate embodiments are intended to be included within the scope of the present invention as defined by the appended claims.