WO2001071731A1

WO2001071731A1 - Massively wide parallel conductor cable and method for making same

Info

Publication number: WO2001071731A1
Application number: PCT/US2000/022153
Authority: WO
Inventors: Denis D. Springer; James H. Voth
Original assignee: 3M Innovative Properties Company
Priority date: 2000-03-20
Filing date: 2000-08-10
Publication date: 2001-09-27
Also published as: AU2000269036A1

Abstract

A massively wide ribbon cable is formed by laminating a plurality of conventionally formed ribbon cables onto a backing layer. The lamination process allows the production of ribbon cables much wider than currently available extrusion technology may produce. The cable maintains state of the art tolerances across the entire width of the cable.

Description

MASSIVELY WIDE PARALLEL CONDUCTOR CABLE AND METHOD FOR MAKING SAME

Background of the Invention The present invention relates to high performance parallel conductor cables, and more specifically to massively wide parallel conductor cables with virtually any number of conductors and widths .

The requirement for a large capacity of signal distribution in a compact cable has been met with the use of parallel conductor or "ribbon" cables m which a large number of conductors (often fifty or more) lie in a single plane and are encased in a common insulating material. The ribbon cable provides many signal conductors in a compact cable while affording ease of termmability with mass termination equipment. Examples of parallel conductor cables are disclosed in United States Patent Nos . 5,306,869, 5,360,944, and 5,900,588, for example. Ribbon cables are typically manufactured via extrusion n a cross-head die. In the cross-head extrusion process, conductive wires are pulled through a melt stream of insulating polymer and forced together through a profiled slot m the die exit such that the wires are approximately centered within profiled ridges of the extruded polymer, where the ridges in the extruded polymer indicate the location of the wires. This extrusion process is effective and m common use.

Unfortunately, as the dimensions of the finished cable increase in width difficulties are encountereα in extruding the cable. Specifically, without an attendant increase in cable thickness, the viscosity of the melted polymer and the quantity of polymer which must be distributed across the wires within the cross-head die begin to cause difficulty in maintaining the respective wire positions within the cable.

Currently available process controls allow cables having widths of slightly over three inches. For example, using the cross-head extrusion process satisfactory cables can be made with up to 96 conductors at 0.033 inches spacing (3.168 inches wide overall) and 64 conductors at 0.050 inches spacing (3.200 inches overall) . However, the limits of the currently available technology are quickly being reached as demands for wider cable grow.

As state of the art equipment needs continue to demand greater numbers of parallel conductors (and thus wider and wider cable widtns) maintaining state of the art tolerances between the parallel conductors m the cable is increasingly difficult. For example, in some special applications there are needs for cables having 200 or more conductors at 0.050 inch spacing (creating a cable 10 inches w de overall) . Providing a cable of such dimension (over three times the current state of the art technology) cannot simply be accomplished by extending currently known processes. For example, the required cross-head die dimensions would be severa± times larger than the current state of the art allows. Further, temperature and viscosity control of the polymer melt stream m such a wide cable are well beyond current state of the art capabilities. Therefore, a new approach for constructing such massively wide parallel conductor cables is needed. Any new process is further defined by the requirement that the massively wide cables must still be capable of being terminated by conventional mass termination connectors. Such connectors are limited in size (width) for reasons similar to those as discussed above with respect to cable widtn. Thus, the cable must be made not only very large (wide) , but also must be dimensionally controlled enough to allow the cable to be mass terminable and be capable of interfacing with currently available connectors.

What is clearly needed is a cable construction which provides much greater widths than allowed by current technology, while maintaining the dimensional tolerances currently demanded for the state of the art uses. In addition, a massively wide cable assembly which permits the use of conventional existing connectors is needed.

Summary of the Invention

The present invention provides a low cost method of forming parallel conductor (ribbon) cables having virtually any number of conductors and widths. Prior to forming the wide cable assembly, "standard" width cables are made m a conventional cable making process in widths equal to the widths of current mass termination insulation displacement (MTID) connectors commonly used for terminating this type of cable. Multiple "standard" cables are combined m a lamination process to form the wide cable assembly. For example, if a ten inch wide cable having 200 conductors at 0.050 inch spacing is required, and the finished cable will be terminated with four fifty position MTID connectors, then four fifty conductor cables with the required spacing will be used to make the finished ten inch wide cable.

The massively wide parallel conductor cable is not limited in width by currently available cable extrusion technology. The invention provides a lamination system wherein conventional and currently existing parallel cables are bonded together so as to meet the increasing dimensional requirements and tolerances of new applications, but at the same time may be easily terminated with conventional mass terminable connectors. The lamination system is designed to present the cables to a backing material in a manner in which all dimensional requirements are met. The width of the wide laminated cable assembly may be selected to match the various termination needs of the user, or may be selected independently or randomly, wherein the user would split the larger cable widths to widths that matched the desired connectors.

Brief Descriptions of the Drawings

Figure 1 is a schematic illustration of a typical extruded ribbon cable. Figure 2 is a schematic illustration of the inventive method of producing a wide cable assembly.

Figures 3-6 illustrate alternate embodiments of the inventive wide cable assembly described herein.

Detailed Description of the Invention

Figure 1 shows a common construction of an extruded ribbon cable 10 having multiple conductors 12 lying m a single plane and encased by insulating material 14. The insulating material 14 is preferably a material such as polyurethane, polyethylene, polypropylene, tetrafluoroethylene, fluorinated ethylene propylene, EPDM rubber or EP rubber. Depending upon the final application, conductors 12 and insulating material 14 may be surrounded by a conductive metal foil to provide electrical shielding, or encased m a protective jacket. It will be noted m Figure 1 that insulating material 14 is formed with ridges 20. While it is desirable electrically to have a cable insulating material 14 that is flat on both sides, such a cable is difficult to terminate, because it is difficult to accurately determine the position of conductors 12 within insulating material 14. Accordingly, ridges 20 are preferably formed in insulating material 14 to facilitate termination of cable 10. Ridges 20 correspond to the positions of conductors 12 and dramatically improve convenience when terminating a cable to connectors or circuit boards. When it is desired to terminate a cable, protective jackets or shielding (if present) are stripped away from the insulating material 14, and ridges 20 easily identify the location of conductors 12. Ridges 20 are formed during the extrusion process when conductors 12 are pulled through a melt stream of the insulating material 14 and extruded through a profiled slot in a cross-head extrusion process. This process is well Known by those skilled in the art.

As discussed above, the cross-head extrusion process technology is limited in the width of ribbon cables which may be produced by that process. In the present invention, multiple cables produced using the conventional cross-head die extruding technology are combined into a much wider cable, while maintaining state of the art tolerances between parallel conductors in the final cable assembly. A method of producing the wide cable assemblies is shown schematically in Figure 2. Multiple ribbon cables 10, produced m a conventional manner, are fed from rolls 24 into a laminating machine 26 with a polymeric backing material 28. As shown m Figure 2, the backing material 28 is provided from an extruder 30.

The bonding of the plurality of cables 10 together with a backing material 28 or tie layer is accomplisned by extruding backing material 28 in a film of appropriate thickness to cover the width of all of the cables 10. The extruded backing material may be applied m a single application or in multiple applications. Instead of being extruded immediately prior to the lamination step, the backing material 28 could also be a prefabricated film that would bond to the cables when the combination is subjected to heat and pressure, or alternatively, by a suitable adhesive such as a pressure sensitive adhesive, hot melt adhesive or other suitable bonding method.

The individual cables 10 are guided onto backing layer 28 by the top laminating roll 34. Preferably, grooves are cut into the surface of top laminating roll 34 to receive the ridges 20 of the insulating material 14. In this manner, the cables 10 are maintained in accurate alignment such that conductors 12 at the edge of each cable 10 are properly spaced from an adjacent edge conductor 12 of an adjacent cable 10, such that the final cable assembly 36 maintains a uniform conductor spacing across the entire width of the finished cable 36.

The lower laminating roll 38 may have either a smooth surface or a profiled surface (like that of top laminating roll 34) depending upon the desired profile of the backing material 28. Heat may be applied to the cables 10 before they enter the lammator nip 40 between the top and lower laminating rolls 34, 38 by infrared heating or by heating the upper laminating roll 34. If the materials of cables 10 and the extruded backing 28 are properly selected, heating may be unnecessary as adequate heat will be available from the extruded backing material 28. Following bonding of the cables 10 to the extruded backing material 28, the finished wide cable assembly 36 is wound on a suitable winder 41. Figures 3 and 4 illustrate two possible constructions of the laminated cable assembly 36. Figure 3 shows a plurality of ribbon cables 10 bonded to a backing material 28 which is smooth on its outer surface. It is contemplated that with this type of construction the bond between the backing material 28 and the plurality of cables 10 would be controlled so that the backing material may be removed for terminating the cables 10. If the total cable thickness is below 0.047 inches, the construction shown in Figure 3 could be terminated directly by mass termination insulation displacement (MTID) connectors without removing the backing material 28. If the cable thickness exceeds 0.047 inches as a result of cable properties such as impedance control, the backing 28 is preferably applied to the cables 10 in a controlled manner which limits the bond between the cables 10 and the backing material 28. The use of a controlled bond between the cables 10 and the backing material 28 allows the backing material 28 to be readily removed for termination, yet holds the cables 10 firmly in position during use.

In Figure 4, the backing material 28 is applied m such a manner that the ridged profile of the cables 10 is evident from both the top and bottom of the finished cable assembly 36. With this method of joining the cables 10, mass termination insulation displacement connectors can be applied directly to the cable if the overall thickness is less than 0.047 inches. If the thickness is greater than 0.047 inches, some amount of the backing material must be removed by grinding or some other suitable method.

In the cable constructions shown m Figures 3 and 4, the thickness of the backing layer 28 may be selected according to end user needs. For instance, if the application requires shielding for electromagnetic radiation interference (EMI) a layer of adhesive coated foil 29, such as that described in United States Patent No. 4,533,784 may be applied to the cable assembly, either on one side of the cable assembly, both sides of the cable assembly, or surrounding the cable in "cigarette" fashion. Any available width of foil may be used to form a metal backing or tie layer. The cable width is limited only by the width of the foil 29 available. If the end application of the cable assembly 36 requires increased impedance as well as EMI shielding, the polymeric backing layer 28 may increased in thickness to increase the cable impedance to the desired value before the foil is applied. The product width m this type of construction is limited only by the available width of an extruder for the backing layer and lamination process . Although a polymeric backing material 28 has been described, the backing may be made out of copper or aluminum foil 29 with bonding of the cables 10 to the foil 29 being accomplished by a pressure sensitive adhesive 31, hot melt adhesive or other suitable bonding method (see Figure 5) . If the backing layer is to be a metal foil, it is preferred that it be an extensible foil such as Minnesota Mining and Manufacturing Company' s pleated foil, as described in United States Patent No. 4,533,784, or an extensible Mylar foil such as that available from Nepco . By using these types of foils, the finished cable assembly 36 can be bent without the foil being forced to fracture or delammate from the cables. If electromagnetic interference and impedance are important factors in the final use of the assembled cable 36, a polymeric backing material is preferably used in addition to the metal foil backing described above as shown in Figure 6. The amount of polymeric backing material (i.e., the thickness) can be increased or decreased to adjust the capacitance and impedance between the cable conductors 12 and the foil layer, and thereby increase or decrease the impedance of the finished cable 36 as required by its intended application.

The inventive cable and method for making same as disclosed above has several advantages over prior art ribbon cables. In particular, the inventive cable may be made to any desired width while maintaining state of the art tolerances between the parallel conductors of the cable assembly. Thus, it can be seen that there has been shown and described a novel cable assembly and method for making the same. It is to be understood, however, that various changes, modifications, and substitutions m the form of the details of the present invention can be made by those skilled m the art without departing from the scope of the invention as defined by the following claims. For example, it will be recognized by those skilled m the art that combinations of backing layers other than those illustrated may be constructed. In addition, the laminated cable assembly 36 may further be protected by protective jackets or shielding as is known in the art.

Claims

What is claimed is:

1. An improved ribbon cable assembly comprising: a backing layer; a plurality of cables, each of the plurality of cables having parallel conductors spaced a uniform distance from each other, the plurality of cables laminated to the backing layer such that the uniform distance between parallel conductors is maintained across the width of the laminated cable assembly.

2. The ribbon cable assembly of claim 1, wherein each of the plurality of cables has the same distance between their respective parallel conductors.

3. The ribbon cable assembly of claim 1, wherein the backing layer is an extruded layer of polymeric material.

4. The ribbon cable assembly of claim 1, wherein the backing layer is a metal foil.

5. The ribbon cable assembly of claim 4, wherein the metal foil is a pleated metal foil.

6. The ribbon cable assembly of claim 1, wherein the backing layer comprises a polymeric material and a metal foil.

7. The ribbon cable assembly of claim 1, wherein the laminated cable assembly has a width of greater than four inches .

8. The ribbon cable assembly of claim 1, wherein the laminated cable is terminable using mass termination insulation displacement connectors.

9. The ribbon cable assembly of claim 1, wherein each of the plurality of cables has less than 100 conductors.

10. The ribbon cable assembly of claim 1, wherein the laminated cable assembly has more than 100 conductors.

11. A method for forming a wide ribbon cable assembly, the method including the steps of: feeding a plurality of ridged ribbon cables having parallel conductors spaced a uniform distance from each other over a grooved lamination roller, wherein the grooves of the lamination roller are spaced to accept the ridges of the ribbon cables and thereby position the plurality of cables such that the uniform distance between parallel conductors is maintained between adjacent cables; and laminating the ribbon cables to a backing layer.

12. The method of claim 11, further including the step of extruding the backing layer between the grooved lamination roller and a second lamination roller.

13. The method of claim 11, wherein the backing layer is a polymer material.

14. The method of claim 11, wherein the backing layer is a metal foil.

15. The method of claim 11, wherein the backing layer is a combination of a polymer and a metal foil.