Abstract:
A method of forming a joint between a coaxial cable and, a coaxial connector includes the steps of: preparing a cable having an inner conductor, a dielectric, a corrugated outer conductor surrounding the dielectric layer, and a jacket such that an end of the inner conductor is exposed, an end of the outer conductor is exposed arid is flattened to form a ring devoid of corrugations, and a portion of the dielectric layer is cored out to form a solder chamber between the inner conductor and the ring of the outer conductor; preparing an assembly comprising a coaxial connector comprising an inner contact, a dielectric spacer, and an outer conductor body having a tail, with a solder preform encircling the tail; inserting the tail and solder preform into the solder chamber; and melting the solder preform to create a joint between the ring and the tail.

Description:
RELATED APPLICATION 
       [0001]    The present application claims priority from and the benefit of U.S. Provisional Patent Application No. 62/253,505, filed Nov. 10, 2015, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a connector and cable interconnection, and more specifically to a connector and cable interconnection method and apparatus with improved manufacturing efficiency and electrical performance characteristics. 
       BACKGROUND OF THE INVENTION 
       [0003]    Coaxial connectors are commonly utilized in RF communications systems. A typical coaxial cable includes an inner conductor, an outer conductor, a dielectric layer that separates the inner and outer conductors, and a jacket that covers the outer conductor. Coaxial cable connectors may be applied to terminate coaxial cables, for example, in communication systems requiring a high level of precision and reliability. 
         [0004]    Coaxial connector interfaces provide a connect/disconnect functionality between a cable terminated with a connector bearing the desired connector interface and a corresponding connector with a mating connector interface mounted on an apparatus or on another cable. Typically, one connector will include a structure such as a pin or post connected to an inner conductor and an outer conductor connector body connected to the outer conductor; these are mated with a mating sleeve (for the pin or post of the inner conductor) and another outer conductor connector body of a second connector. Coaxial connector interfaces often utilize a threaded coupling nut or other retainer that draws the connector interface pair into secure electro-mechanical engagement when the coupling nut (which is captured by one of the connectors) is threaded onto the other connector. 
         [0005]    Commonly-owned U.S. Pat. Nos. 5,802,710 and 7,900,344, hereby incorporated by reference in their entireties, disclose a technique for attaching a coaxial connector to a coaxial cable. The connector utilizes an insulating disc retained upon the inner contact and against the dielectric layer and outer conductor of the cable. Induction heating of a solder preform wrapped around the outer conductor creates a molten solder pool in a cylindrical solder cavity formed between the outer conductor, the insulating disc and the connector body. The insulating disc, prevents the molten solder from migrating out of the cavity, fouling the connector bore and/or shorting the outer and inner conductors. 
         [0006]    Commonly-owned U.S. Patent Publication No. 2014/0201989, also incorporated herein by reference in its entirety, illustrates a pedestal with an insulating seat on which the soldering of the outer conductor to the connector body can occur. Other techniques for attaching a connector to a cable may also be desirable. 
       SUMMARY 
       [0007]    As a first aspect, embodiments of the invention are directed to a method of forming a joint between a coaxial cable and a coaxial connector. The method comprises the steps of preparing a cable having an inner conductor, a dielectric layer surrounding the inner conductor, a corrugated outer conductor surrounding the dielectric layer, and a jacket surrounding the outer conductor such that an end of the inner conductor is exposed, an end of the outer conductor is exposed and is flattened to form a ring devoid of corrugations, and a portion of the end of the dielectric layer is cored out to form a solder chamber between the inner conductor and the ring of the outer conductor; preparing, an, assembly comprising a coaxial connector and a solder preform, the coaxial connector comprising an inner contact, a dielectric spacer, and an outer conductor body having a tail, the solder preform encircling the tail; inserting the tail and solder preform into the solder chamber; and melting the solder preform to create a joint between the ring of the outer conductor and the tail of the outer conductor body. 
         [0008]    As a second aspect, embodiments of the invention are directed to a coaxial cable-connector interface, comprising: a coaxial cable having an inner conductor, a dielectric layer surrounding the inner conductor, a corrugated outer conductor surrounding the dielectric layer, and a jacket surrounding the outer conductor, wherein an end of the outer conductor is, exposed and is flattened to form a ring devoid of corrugation, and a portion of the end of the dielectric layer is cored out to form a solder chamber between the inner conductor and the ring of the outer conductor; and a coaxial connector comprising an inner contact, a dielectric spacer, and an outer conductor body having a tail. The tail is inserted into the solder chamber, and a solder joint interconnects the tail and the ring of the outer conductor. 
         [0009]    As a third aspect, embodiments of the invention are directed to a coaxial connector assembly, comprising a coaxial connector and a solder preform. The coaxial connector comprises an inner contact, an outer conductor body, and a dielectric spacer interposed between the inner contact and the outer conductor body. The outer conductor body has a main sleeve, a forwardly-extending mating ring configured to mate with a mating connector and a rearwardly-extending tail, the tail having an outer diameter that is less than an outer diameter of the main sleeve. The solder preform circumferentially surrounds the tail of the outer conductor body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side view of a cable for attachment to a coaxial connector according to embodiments of the invention. 
           [0011]      FIG. 2  is a perspective view of the cable of  FIG. 1  illustrating a cored-out portion of the dielectric layer. 
           [0012]      FIG. 3  is a section view of a coaxial connector according to embodiments of the invention, with a solder preform in place over the tail of the outer conductor body. 
           [0013]      FIGS. 4-8  are sequential section views of a process for attaching the cable of  FIGS. 1 and 2  to the connector of  FIG. 3 . 
           [0014]      FIG. 9  is a perspective view of an exemplary soldering apparatus according to embodiments of the invention. 
           [0015]      FIG. 10  is a section view of a cable of  FIG. 1  and coaxial connector of  FIG. 3  in place in the apparatus of  FIG. 9  for soldering. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present invention is described with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments that are pictured and described herein; rather, these embodiments are provided, so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It will also be appreciated that the embodiments disclosed herein can be combined in any way and/or combination to provide many additional embodiments. 
         [0017]    Unless otherwise defined, all technical and scientific terms that are used in this disclosure have the same meaning as commonly understood by one of ordinary skill in, the art to which this invention belongs. The terminology used in the above description is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this disclosure, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when an element (e.g., a device, circuit, etc.) is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. in contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present 
         [0018]    Referring now to the figures, a coaxial cable, designated broadly at  10 , is shown in  FIGS. 1 and 2 . The cable  10  includes a inner conductor  12 , a dielectric layer  14  that circumferentially overlies the inner conductor  12 , an outer conductor  16  that circumferentially overlies the dielectric layer  14 , and a polymeric cable jacket  20  that circumferentially overlies the outer conductor  16 . These components will be well-known to those of skill in this art and need not be described in detail herein.  FIG. 1  illustrates that the outer conductor  16  has a corrugated profile, with alternating roots  16   a  and crests  16   b.    
         [0019]      FIG. 2  also illustrates that, at the end of the cable  10 , at least the last crest of the outer conductor  16  (and in some instances at least the last root) is flattened into a ring  18 . The ring  18  has, a diameter that is equal to or exceeds the diameter of the remainder of the crests  16   b.    FIG. 2  also illustrates that the end of the dielectric layer  14  radially inwardly from the ring  18  is cored out, thereby creating an annular solder chamber  22  within the ring  18  (see also  FIGS. 6 and 7 ). In some embodiments, the end of the dielectric layer  14  is cored out entirely, such that the solder chamber  22  extends radially between the ring  18  and the inner conductor  12 ; in other embodiments, an inner sleeve  19 ′ of the dielectric layer  14  may remain after coring, such a sleeve  19 ′ being interposed between the ring  18  and the inner conductor  12 , such that the solder chamber  12  extends radially between the inner sleeve  19 ′ of the dielectric layer  14  and the ring  18  (see  FIG. 6A ). The solder chamber  22  may have a thickness of between about 0.015 and 0.030 inches. 
         [0020]    Referring now to  FIG. 3 , a coaxial connector, designated broadly at  30 , is shown therein. The connector  30  includes an inner contact  32 , an outer conductor body  34 , and a dielectric spacer  36  positioned between the inner contact and the outer conductor body  34 . The inner contact  32  has a generally cylindrical post  32   a  and a split boss  33 , The inner contact  32  is configured to be mounted on and in electrical contact with the inner conductor  12  of the cable  10  via the boss  33 ; the split configuration of the boss  33  allows its tines to deflect slightly radially outwardly to receive the end of the inner conductor  12 . The post  32   a  is configured to mate with an inner contact (such as a sleeve) of a mating jack or other connector. 
         [0021]    Referring again to FIG,  3 , the outer conductor body  34  has a mating ring  34   a  that is configured to mate with the outer conductor body of a mating jack or other connector. A main sleeve  38  of the outer conductor body  34  has a radially inward flange  40  that provides a bearing surface for the dielectric spacer  36  and a radially outward flange  42  that provides a bearing surface for a coupling nut (not shown). A tail  44  extends rearwardly from the main sleeve  38 . The tail  44  has an inner diameter similar to that of the main sleeve  38 , but has an outer diameter that is less than that of the main sleeve  38 . 
         [0022]      FIG. 3  also shows an annular solder preform  50  that encircles the tail  44 . The solder preform  50  is formed of typical solder materials that melt upon the application of heat energy thereto. 
         [0023]      FIGS. 4.8  illustrate how the cable  10  can be connected to the connector  30  in a soldering operation.  FIG. 4  shows the end of a length of cable  10  prior to processing.  FIG. 5  illustrates the cable  10  with the end of the jacket  20  stripped back and the ends of the outer conductor  16  and the dielectric layer  14  removed, such that end portions of the inner conductor  12  and the outer conductor  16  are exposed, with the end of the outer conductor  16  extending axially beyond the jacket  20  and the end of the inner conductor  12  extending axially beyond the end of the outer conductor  16 .  FIG. 6  shows that the end of the dielectric layer  14  is cored out to create the solder chamber  22  discussed above. 
         [0024]      FIG. 7  illustrates that the end of the outer conductor  16  is formed into the ring  18  discussed above. The formation of the ring  18  may be performed with a dedicated tool or fixture that can produce a consistent shape (such as the ring  18 ) with closely controlled dimensions, Forming corrugations in the outer conductor  16  is typically carried out on a continuously running cable line. The corrugations that are formed under such conditions typically have much greater variations in dimension and shape than can be achieved through the use of dedicated tooling that forms the ring  18 . Those of skill in this art will recognize that, as used herein, the term “ring” is intended to include other radially symmetric shapes, such as truncated cones, and to include shapes with one or more radial indentations and/or projections. 
         [0025]      FIG. 8  shows that, once the dielectric layer  14  is cored out to form the solder chamber  22  and the preform  50  is inserted onto the tail  44  of the outer conductor body  34 , the connector-preform assembly can be inserted into the solder chamber  22  for soldering. The preform  50  is positioned between the tail  44  and the ring  18  of the outer conductor  16 , with the end of the tail  44  abutting the dielectric layer  14 . In this position, heat energy can be applied to the solder chamber  22  to melt the solder of the preform  50 , thereby forming a solder joint between the outer conductor  16  and the outer conductor body  34 . The boss  33  of the inner contact  32  receives the end of the inner conductor  12 . The soldered cable and connector form an interface  150 . 
         [0026]    Because the shape and dimensions of the ring  18  can be more closely controlled than those of a corrugation, the gap between the ring  18  and the tail  44  can be much smaller than typically seen. Thus, a thinner, solder preform  50  may be employed (for example, the solder preform  50  may have a thickness of between about 0.015 and 0.030 inches), thereby reducing the overall solder volume and, consequently, the variability associated with larger gaps and/or solder joints. 
         [0027]      FIG. 9  shows one potential apparatus  100  for conducting the soldering operation that involves a pedestal as disclosed in U.S. Patent Publication No. 2014/0201989, supra. The apparatus  100  includes a pedestal  119  mounted on a base  121 , a clamp  141  for holding a cable  10  in place, and an inductive heating element  137  for heating solder used to attach the connector body to the outer conductor of the cable  10 .  FIG. 10  shows the cable  10 , connector  30  and preform  50  of  FIG. 8  in place within the apparatus  100 , with the connector  30  mounted on the pedestal  119  and the cable  10  lowered onto the connector  30  so that the preform  50  resides within the solder chamber  22 . Once in this position, the heating element  137  (shown in  FIG. 9 ) can be used to heat the preform  50  to form a solder joint between the ring  18  of the outer conductor  16  and the tail  44  of the outer conductor body  34  within the solder chamber  22 . The solder joint typically has a thickness of between about 0.015 and 0.030 inches. 
         [0028]    The interface  150  may provide a soldered interconnection between the cable  10  and the connector  30  that has consistent electrical properties. The presence of the solder chamber  22  can enable the solder joint between the tail  44  of the outer conductor body  34  and the ring  18  of the outer conductor  16  to he consistently formed in size and shape, which can render the connection more predictable. This arrangement can also improve electrical properties such as return loss yield in the cable/connector interface. 
         [0029]    Those of skill in this art will appreciate that the soldering operation may occur in different soldering apparatus; for example, the soldering apparatus may include a vacuum source as described in U.S. Provisional Patent Application Nos. 62/160,999, filed May 13, 2015, and 62/131,105, filed Mar. 10, 2015, the disclosures of which are hereby incorporated by reference herein, It is also contemplated that other connector configurations, such as right angle connectors as are shown in U.S. Provisional Patent Application No. 62/111,300, filed Feb. 3, 2015 (also incorporated by reference herein) may also be suitable. 
         [0030]    While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may he made from such details without departure from the spirit or scope of applicant&#39;s general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.