Abstract:
A method of forming a solder joint between a coaxial cable and a coaxial connector includes the steps of: positioning a solder element between an end of an outer conductor of the coaxial cable and a connector body of the connector, wherein the connector includes an insulator with a suction passage; lowering the connector body and insulator onto a mounting structure; melting the solder element to form a solder joint between the outer conductor and the connector body, the solder joint including a lower surface formed by contact with the insulator and/or the connector body; and applying suction to the melting solder element from a suction source to reduce the formation of bubbles within the solder joint, wherein a suction path between the suction source and the solder element includes the suction passage in the insulator.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of and claims priority from U.S. patent application Ser. No. 15/143,039, filed Apr. 29, 2016, which claims priority from and the benefit of U.S. Provisional Patent Application No. 62/160,999, filed May 13, 2015, the disclosure of each of which is hereby incorporated herein 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 electromechanical 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. One issue that can arise with this technique is the formation of air bubbles within the solder; if such bubbles form in locations along the signal path, the electrical performance of the connector interface can be compromised. Thus, it may be desirable to provide a technique that addresses this shortcoming. 
       SUMMARY 
       [0007]    As a first aspect, embodiments of the invention are directed to a method of forming a solder joint between a coaxial cable and a coaxial connector. The method comprises the steps of: positioning a solder element between an end of an outer conductor of the coaxial cable and a connector body of the connector, wherein the connector includes an insulator with a suction passage; lowering the connector body and insulator onto a mounting structure; melting the solder element to form a solder joint between the outer conductor and the connector body, the solder joint including a lower surface formed by contact with the insulator and/or the insulator; and applying suction to the melting solder element from a suction source to reduce the formation of bubbles within the solder joint, wherein a suction path between the suction source and the solder element includes the suction passage in the insulator. 
         [0008]    As a second aspect, embodiments of the invention are directed to a method for attaching a connector to a coaxial cable, comprising the steps of: positioning a solder element between an end of an outer conductor of the coaxial cable and a connector body of the connector, wherein the connector includes an insulator with a suction passage; positioning the connector body and insulator on a mounting structure; melting the solder element to form a solder joint between the outer conductor and the connector body and/or the insulator, the solder joint including a surface formed by contact with the insulator; and applying suction to the melting solder element to prevent the formation of bubbles within the solder joint, wherein a suction path between the suction source and the solder element includes the suction passage in the insulator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic perspective view of a cable-connector assembly apparatus and a cable, wherein electrical interconnections, supporting and enclosure structures are removed for clarity. 
           [0010]      FIG. 2  is a schematic section view of a connector body seated upon the interface pedestal of the apparatus of  FIG. 1 . 
           [0011]      FIG. 3  is an enlarged section view of the pedestal and connector body of  FIG. 2  with a cable and solder preform inserted therein for solder interconnection. 
           [0012]      FIG. 4  is a section view as in  FIG. 3  with the solder preform melted to form a solder joint. 
           [0013]      FIG. 5  is a section view of a pedestal and connector body according to embodiments of the invention. 
           [0014]      FIG. 6  is an enlarged section view of the pedestal and connector body of  FIG. 5  along with a coaxial cable joined to the connector body via a solder joint. 
           [0015]      FIG. 7  is an end view of an insulator included on a connector according to embodiments of the invention. 
           [0016]      FIG. 8  is a cross-section of a connector including the insulator of  FIG. 7  in a connector body mounted on an interface pedestal as  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    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. 
         [0018]    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. 
         [0019]    Referring now to the figures, an apparatus  21  for soldering a connector body onto a coaxial cable such as is described in U.S. Patent Publication No. 2014/0201989, supra, is shown in  FIG. 1 . The apparatus includes a pedestal  19  mounted on a base  21 , a clamp  41  for holding a cable  1  in place, and an inductive heating element  37  for heating solder used to attach the connector body to the outer conductor of the cable  1 .  FIG. 2  shows a connector body  17  in place on the pedestal  19 , with a step in the connector body  17  resting on a shoulder  25  of the pedestal  19 . A cap  29 , formed of a dielectric, thermally insulative material, is mounted on the upper end of the pedestal  19  to provide thermal insulation to components of the cable  1  during soldering. As a result, the pedestal  19  and cap  29  act as a mounting structure for the connector body  17 . The pedestal  19  includes an inner conductor cavity  39  in its upper surface that is configured to receive the inner contact  11  of the cable  1  during soldering. 
         [0020]    As shown in  FIG. 3 , a solder preform  15  or other solder element circumscribes the end of the outer conductor  5  of the cable  1 . The connector body  17  is positioned on the pedestal  19 , with the solder cavity  27  of the connector body  17  (formed by the inner surface of the connector body  17 , the upper surface of the cap  29 , and the outer conductor  5 ) located above the pedestal  19 . The cable  1  with the solder preform  15  in place is lowered into the cavity  27  and onto the pedestal  19 , with the inner contact  11  of the cable  1  received in the inner conductor cavity  39 , and the end of the outer conductor  5  and the solder preform  15  abutting the cap  29 . Heat is applied to the end of the cable  1  via the heating element  37 , such that the solder preform  15  melts, flows downwardly within the solder cavity  27  between the inner surface of the connector body  17 , the upper surface of the cap  29 , and the outer conductor  5 , and freezes, thereby forming a solder joint  18  between the outer conductor  5  and the connector body  17  ( FIG. 4 ). 
         [0021]    As described above, and as shown in  FIG. 4 , in many instances the flowing solder from the solder preform will create bubbles  22  that remain in the frozen solder joint  18 . Such bubbles  22  can adversely impact the electrical performance of the interface between the outer conductor  5  and the connector body  17 , particularly if the bubbles  22  are located in the electrical signal path. 
         [0022]    An apparatus that can address the problem introduced by the bubbles  22  is shown in  FIGS. 5 and 6 . The apparatus  100  includes a pedestal  119  with a cap  129  as described above. However, the upper surface of the cap  129  is covered with a thin membrane  130  that is permeable to air, but is substantially impermeable to solder. Exemplary materials for the thin membrane  130  include woven polytetrafluoroethylene (PTFE). The material selected for the membrane  130  should have sufficient heat resistance that it does not melt at soldering temperatures. In addition, the cap  129  includes one or more vertical grooves  132  in its outer surface such that air channels are formed between the outer surface of the cap  129  and the inner surface of the connector body  17 ′ as the connector body  17 ′ is fitted over the cap  129 . 
         [0023]    Referring still to  FIGS. 5 and 6 , the pedestal  119  includes one or more vent holes  134  that originate from an empty space  136  below the lower edge of the cap  129 . The vent holes  134  are routed within the pedestal  119  to a vacuum port  138  in the side of the pedestal  119  that attaches to a vacuum source  140 . 
         [0024]    In operation, the connector body  17 ′ is positioned on the pedestal  119  as described above (see  FIG. 5 ). The cable  1 ′ with the solder preform in place is lowered onto the pedestal  119 . As heat is applied to the solder preform via the heating element discussed above, the vacuum source  140  is activated to apply suction to the solder cavity  127  through the vent holes  134 , the air channels created by the grooves  132  in the cap  129 , and the membrane  130 . As such, as the solder preform melts and freezes, air is drawn from the molten solder through the membrane  130 , which can prevent the formation bubbles in the solder joint  18 ′ (see  FIG. 6 ). The reduction or elimination of bubbles within the solder joint  18 ′ can improve the consistency of the electrical properties of the solder joint  18 ′, and in turn those of the cable  1 ′ and connector body  17 ′. 
         [0025]    Those skilled in this art will recognize that other variations of the components and techniques described above are possible. For example, the pedestal  119  and/or cap  129  may be replaced with other mounting structures, and in particular with other mounting structures that can help to form a solder cavity with the connector body  17 ′. The path between the vacuum source  140  and the solder cavity  127  provided by the vent holes  134  may be configured differently, or in some instances vacuum may be provided in another manner (see, e.g., U.S. patent application Ser. No. 15/065,468, filed Mar. 9, 2016, the disclosure of which is hereby incorporated herein in its entirety). Other variations may also be suitable for use herein. 
         [0026]    Referring now to  FIGS. 7 and 8 , another connector, designated broadly at  200 , is shown therein. The connector  200  includes a connector body  217  somewhat similar to that discussed above that engages an interface pedestal  219 . However, an insulator  220  is positioned in the connector body  217  and rests on the pedestal  219 . The insulator  220  includes two through holes  222 . 
         [0027]    In operation, the connector body  217  with the insulator  220  is positioned on the interface pedestal  219 , with a solder preform in placed on the outer conductor  16 ″ of the cable  1 ″. Suction is applied to the interface pedestal  219  as described above (i.e., via the suction source  240  through the vacuum port  238 ). However, in this instance suction reaches the solder cavity  227  via the through holes  222 , which connect the inner conductor cavity  239  with a cavity  241  within the insulator  220 ). The solder joint  218  forms within the solder cavity  227  with the upper surface of the connector body  217  serving to form one of the surfaces of the solder joint  218 . 
         [0028]    This modified technique may be particularly suitable for use with connectors the meet the proposed standard set forth in IEC 4.3/10. 
         [0029]    Those skilled in this art will appreciate that other configurations may be suitable. For example, the through holes  222  are illustrated as being bored within the body of the insulator  220  to provide a suction passage through the insulator  220  as part of the suction path between the suction source  240  and the solder joint  218 . However, in some embodiments a suction passage in the insulator  220  to the solder cavity  227  may be provided by holes, recesses, grooves or the like in the outer diameter of the insulator  220 . Alternatively, suction passage to the solder cavity  227  may be achieved by using an insulator with an outer diameter that is slightly less than the inner diameter of the connector body  217 . Combinations of these configurations may also be possible (e.g., a small outer diameter for the insulator may be used for half of the thickness of the insulator, and through holes or recesses used for the other half of the thickness). 
         [0030]    In addition, in some embodiments a portion of the upper surface of the insulator  220  may contribute to the formation of at least part of the lower surface of the solder joint  218 . 
         [0031]    Further, in some embodiments the upper surface of the pedestal  219  may be covered with a membrane as described above in connection with the pedestal  119 . 
         [0032]    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 be 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.