Abstract:
The present invention provides an apparatus and method for connecting an array of cables (e.g., coaxial cables) to a circuit board (e.g., the surface of the circuit board).

Description:
The present application claims the benefit of U.S. Provisional Patent Application No. 60/849,019, filed on Oct. 4, 2006, which is incorporated herein by this reference. 
    
    
     BACKGROUND 
     1. Field of the invention 
     The invention relates to apparatuses and methods for connecting an array of cables to a circuit board. 
     2. Discussion of the Background 
     The need to connect an array of coaxial cables to a circuit board often arises. The present invention aims to provide an apparatus and method for meeting this need. 
     SUMMARY 
     The present invention provides an apparatus and method for connecting an array of cables (e.g., coaxial cables) to a circuit board (e.g., the surface of the circuit board). 
     In some embodiments the apparatus includes: a frame; a plurality of holes in the frame, each hole extending from a first surface of the frame to a second surface of the frame, which second surface faces in a direction opposite of the direction in which the first surface faces, and each hole being configured to house an end portion of one of the plurality of cables, wherein the plurality of holes forms a plurality of rows of holes, wherein, for each of the rows, all holes in the row are arranged in a straight line; a plurality of rows of raised ground pads on the second surface of the frame, each raised ground pad having a mating face and projecting outwardly from the second surface, wherein (a) the mating faces of the ground pads are coplanar, (b) for each row of ground pads, the plurality of ground pads in the row are arranged in a straight line, and (c) at least a portion of each row of holes is positioned between one of the ground pad rows and another of the ground pad rows; and a plurality of contacts, each being configured to fit into one of the holes and to receive an end of an inner conductor of one of the cables. 
     In other embodiments the apparatus includes: a frame having a hole extending from a first surface of the frame to a second surface of the frame; a cable comprising a signal conductor and an outer conductor surrounding the signal conductor, a tip of the signal conductor being located within the hole of the frame and the outer conductor being electrically connected to the frame; a printed circuit board comprising an array of signal pads and a ground plane; a plurality of rows of raised ground pads on the second surface of the frame and electrically connecting the frame to the ground plane of the printed circuit board; and a contact at least partially within the hole and electrically connecting the signal conductor of the cable to one of the signal pads. 
     In other embodiments the apparatus includes: (1) a contact, the contact comprising: (i) a cylindrical body portion, and (ii) a cylindrical distal end portion connected to a distal end of the body portion, wherein the outer diameter of the distal end portion is less than the outer diameter of the cylindrical body portion, the distal end portion includes a mating face, and a proximal end of the body portion forms a cup; (2) a cable comprising (i) a signal conductor having an end that is in the cup and (ii) an outer conductor surrounding the signal conductor; and (3) adhesive in the cup, the adhesive bonding the end of the signal conductor to the contact. The adhesive may include or consists of solder. 
     In some embodiment the method includes: obtaining a plurality of cables, each cable comprising a signal conductor and an outer conductor; obtaining a frame comprising (i) a plurality of holes extending from a first surface of the frame to a second surface of the frame and (ii) a plurality of raised ground pads projecting outwardly from the second surface of the frame; obtaining a circuit board comprising an array of signal pads and a ground plane; obtaining a plurality of contacts; arranging the frame relative to the circuit board such that the raised ground pads contact the ground plane of the circuit board; for each cable, connecting an end of the signal conductor of the cable to one of the contacts and connecting the outer conductor of the cable to the frame; placing each contact in one of the holes; and connecting each contact to one of the signal pads. 
     In other embodiments the method includes: (A) obtaining a plurality of cables; (B) obtaining a frame comprising: (1) a plurality of holes, each hole extending from a first surface of the frame to a second surface of the frame, which second surface faces in a direction opposite of the direction in which the first surface faces, and each hole being configured to house an end portion of one of the plurality of cables, wherein the plurality of holes forms a plurality of rows of holes, wherein, for each of the rows, all of the holes in the row are arranged in a straight line; and (2) a plurality of rows of raised ground pads on the second surface of the frame, each raised ground pad having a mating face and projecting outwardly from the second surface, wherein (a) the mating faces of the ground pads are coplanar, (b) for each row of ground pads, the plurality of ground pads in the row are arranged in a straight line, and (c) at least a portion of each row of holes is positioned between one of the ground pad rows and another of the ground pad rows; (C) for each of the cables, physically and electrically connecting an end portion of an inner conductor of the cable to a contact having a mating face; and (D) for each contact, fixing the contact in one of the holes so that the mating face of the contact is substantially coplanar with the mating faces of the raised ground pads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and form part of the specification, help illustrate various embodiments of the present invention. In the drawings, like reference numbers indicate identical or functionally similar elements. 
         FIG. 1  illustrates an apparatus according to an embodiment. 
         FIG. 2  illustrates a circuit board according to an embodiment. 
         FIG. 3  illustrates a frame according to an embodiment. 
         FIG. 4  illustrates the apparatus of  FIG. 1  being mated with the circuit board of  FIG. 2 . 
         FIG. 5  is a cross-sectional view of an apparatus according to an embodiment. 
         FIG. 6  illustrates a contact according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an apparatus  100  according to an embodiment of the invention. Apparatus  100  includes an array of cables  102  connected to a frame  104 . In this embodiment, each cable  102  is a coaxial cable. Also, in this embodiment, a mating face  106  of apparatus  100  is configured to mate with a corresponding mating face of a printed circuit board (e.g., to mating face  202  of printed circuit board  200 , which is shown in  FIG. 2 ). 
     Referring now to  FIG. 2 ,  FIG. 2  illustrates a portion of a printed circuit board  200  with which apparatus  100  is designed to mate. As shown in  FIG. 2 , circuit board  200  includes an array of signal pads  210 , each of which may be completely surrounded by a dielectric  215  (“anti-pad”  215 ). Dielectric  215  may be air or other dielectric. As also shown, each signal pad  210  may be generally elongate (i.e., having a length greater than its width), be oval or rectangular in shape, and have a hole  217  (“via”  217 ) located at one end of the pad. 
     Referring now to  FIG. 3 ,  FIG. 3  shows frame  104  without the array of cables  102  attached thereto. As illustrated in  FIG. 3 , frame  104  may include a plurality of alignment holes  302  for facilitating proper alignment when mating with circuit board  200 . As shown, in  FIG. 2 , circuit board  200  may have corresponding alignment holes  230 . 
     Frame  104  also includes an array of cable receiving holes  304  and an array of ground pads  306 . Preferably, the grounds pads  306  are raised to create points in a spatial array across the face  106  to facilitate adequate ground return path for the cable  102  to the circuit board  200 . That is, each ground pad  306  projects outwardly from mating face  106 . In one embodiment, the distance between mating face  308  of ground pad  306  and mating face  106  of frame  104  may be between about 0.01 inches and 0.1 inches. Preferably, the distance between mating face  308  of ground pad  306  and mating face  106  of frame  104  may be about 0.015 inches. Also, it is preferred that each ground pad is raised the same amount so that the face of each is coplanar with the face of the others. 
     As shown in  FIG. 3 , the array of cable apertures  304  may be disposed within the array of ground pads  306 . That is, in the embodiment shown, the array of holes  304  forms a plurality of rows, the array of pads  306  forms a plurality of rows, and each row of holes  304  is disposed between two rows of pads  306 . 
     Each cable aperture  304  is sized to receive an end portion of a cable  102  and each ground pad  306  is configured to contact a ground plane of a corresponding printed circuit board. 
     Referring back to  FIG. 1 ,  FIG. 1  shows an end portion of each cable  102  being inserted into a corresponding cable aperture  304 . As also shown in  FIG. 1 , a contact  108  is connected to each end of each cable  102 , and the tip of the contact  108  extends beyond the mating face  106  so that is it not coplanar with mating face  106 . However, in one embodiment, the mating face of each contact  108  is coplanar with the mating faces of the raised ground pads  306 . Preferably, the diameter of contact  108  and holes  304  are sized to produce a system impedance of 50 ohms. In one embodiment, air is used to electrically insulate contact  108  from frame  104 , which may be constructed from an electrically conducting material or coated with an electrically conducting material. In another embodiment, a bead of dielectric material (e.g., rexalite or other dielectric) may be placed in hole  304  to stabilize and facilitate concentricity of contact  108  with respect to hole  304 . 
     Referring now to  FIGS. 4 and 5 ,  FIG. 4  is a perspective, cross-sectional view of apparatus  100  and  FIG. 5  is a cross-sectional view of apparatus  100  and both show apparatus  100  being connected to circuit board  200 . In the embodiment shown in  FIGS. 4 and 5 , cables  102  are coaxial cables. As shown in  FIGS. 4 and 5 , an end portion of each cable  102  is inserted into a cable aperture  304  (e.g., cable  102   a  is inserted into aperture  304   a  and cable  102   b  is inserted into aperture  304   b ). In one embodiment, an end portion of the inner conductor  402  of each cable  102  extends beyond the insulator  404  and shielding  406  of cable  102 . In one embodiment, this end portion (e.g., tip) of inner conductor  402  is physically and electrically attached to contact  108  (e.g., in one embodiment the end portion is inserted into a cavity of contact  108  and an adhesive, such as solder, is used to maintain the end portion within the cavity and to facilitate electrical contact). 
     As discussed above, and as shown in  FIGS. 4 and 5 , air may be used to electrically insulate contact  108  from frame  104 , however, it is contemplated that a bead of dielectric material may be placed in hole  304 . As also discussed above and as shown in  FIGS. 4 and 5 , the mating face  602  (see  FIG. 6 ) of contact  108  is positioned beyond mating face  106  of frame  104 . Thus, when apparatus  100  is mated with circuit board  200 , mating face  602  of each contact  108  may press against a corresponding signal pad  210 . Similarly, each ground pad  306  of frame  104  presses against a ground plane  212  of circuit board  200 . 
     In some embodiments, a first type of solder (e.g., solder  523 ) is used to bond contacts  108  with signal pads  210 , a second type of solder (e.g., solder  515 ) is used to bond contacts  108  with the signal conductors of cables  102 , and, in the case cable  102  is a coaxial cable, a third type of solder (e.g., solder  513 ) (or other conductive adhesive—e.g., a conductive glue, tape, etc.) is used to fasten the outer conductor  406  of cable  102  to frame  104 . In such an embodiment, the first type of solder may have the lowest melting point, the second type of solder may have the highest melting point, and the third type of solder may have a melting point between the melting point of the first and second types of solder. As shown, solder  513  is used to connect outer conductor  406  to frame  104 , and solder  523  is used to connect contact  108  to signal pad  210 . 
     In some embodiments, elements other than solder may be used for bonding contacts  108  to signal pads  210 , contacts  108  to the signal conductors and/or the outer conductor  406  to frame  104 , including: an epoxy adhesive (e.g., a two part, temperature curing, silver filled epoxy adhesive or other epoxy), a stensil to screen and attach, and other bonding mechanism. 
     Referring now to  FIG. 6 ,  FIG. 6  illustrates contact  108  according to one embodiment. As illustrated, contact  108  may include a cylindrical body portion  690  and a cylindrical distal end portion  680 , and the outer diameter of body portion  690  may be greater than the outer diameter of end portion  680 . As further illustrated, the proximal end  675  of body portion  690  forms a solder cup  670  for receiving the end portion of inner conductor  402  and for receiving solder, which is used to physically fasten contact  108  to conductor  402  and to electrically connect contact  108  with conductor  402 . Solder cup  670  may have an aperture  660  in a wall thereof for allowing some solder to flow out of and/or into solder cup  670 . The diameter of body portion  690  is sized to achieve a desired system impedance. 
     While various embodiments/variations of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments. Further, unless stated, none of the above embodiments are mutually exclusive. Thus, the present invention may include any combinations and/or integrations of the features of the various embodiments.