Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a wire connection structure and an electrical connector with a cable. 
   2. Description of the Related Art 
   Recently, a bonding agent or anisotropic conductive material is widely used to connect cables for electronics equipment. An example of the anisotropic conductive material is an anisotropic conductive film. As JP 2003-176473 shows, the anisotropic conductive film is made by dispersing conductive particles and hardening and other additional agents in an epoxy resin. In use, the anisotropic conductive film is provided between two cables and heated and pressed in a high temperature atmosphere. The conductive particles are brought into close contact with each other in the film area under the pressure so that the portions of the cables are electrically connected through the conductive particles in the film area. Another example of the anisotropic conductive material is an anisotropic conductive paste. 
   The non-conductive bonding materials include a non-conductive film and paste. The non-conductive bonding material is locally eliminated by the pressure between two cables so that the two cables are connected directly. 
   For example, the anisotropic conductive film is provided on a terminal and the core wire of a cable is provided on the film, and the core wire is pressed against the terminal in a high temperature atmosphere for connection. In this method, however, the core wire is held only by the contact surface of the anisotropic conductive film so that the core wire tends to fall. In addition, part of the conductive particles escape to opposite sides of the core wire under the pressure so that the number of closely contact conductive particles becomes so low that the electrical property becomes unstable. Moreover, the core wire is exposed, coming in accidental contact with other objects. 
   An electrical connector with cables includes a housing for plugging with a mating connector and a plurality of terminals arranged in the housing. The connection section of a terminal is soldered to the core wire of a cable and, upon plugging, the contact section is brought into contact with the terminal of a mating connector. Alternatively, the connection section of a terminal is provided on the connection pad of a circuit board for connection to a mating connector. 
   JP 2004-63373 discloses a connector using a circuit board to which very thin coaxial cables are connected. In general, the core wire of a coaxial cable is soldered to the connection pad of a circuit board. Recently, there is a demand for thin coaxial cables and a small pitch with which the coaxial cables are arranged for small size, light weight electronic devices. When the thin coaxial cables are soldered with a pitch of no more than 0.4 mm, the adjacent terminals tend to be bridged with the solder, causing short circuit. 
   In order to solve such a problem, a jig is provided on the central conductors of thin coaxial cables on the connection pads and a laser is irradiated through the jig to connect the central conductors to the pads and, then, the laser is irradiated again to cut the pads between the central conductors. 
   The above method, however, requires not only the special jig through which a laser is irradiated but also the two doses of laser irradiation for melting solder and cutting the pad. If the diameter of central conductors or the number of cables is changed, another jig is required. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the invention to provide a cable connection structure capable of providing not only a higher retention force of the core wire but also a higher insulating property in the connection area. 
   It is another object of the invention to provide an electrical connector with cable capable of readily connecting thin cables with a small pitch. 
   According to an aspect of the invention there is provided a cable connection structure in which a core wire is connected to a connection section with a bonding agent. The cable connection structure includes an insulation holding body; a connection section supported by the insulation holding body; a core wire provided at a position corresponding to that of the connection section; a bonding agent provided on at least the insulation holding body; and an insulation member provided on the core wire and the bonding agent to press the bonding agent between the insulation member and the insulation holding body, thereby bonding the insulation member to the insulation holding body. 
   Since the insulation member bonded to the insulation holding body presses the core wire against the connection section for contact, the core wire is held on the connection section with a very strong force. The insulation member covers the core wire so that accidental short circuit can be prevented. 
   The connection section may be project from the insulation holding body or indented from the insulation holding body to increase the retention force of the insulation member or stabilize the position of the core wire. The connection section may have a concave surface for contact with the bonding agent to further stabilize the position of the core wire on the connection section. 
   The connection section may be a terminal and the insulation holding body may be a housing. The connection section may be a land provided on a circuit board and the insulation holding body may be a body of the circuit board. 
   The insulation member may be an insulation film or an insulation case. The core wire may be flattened before connection to increase the contact area between core wires or the core wire and the connection section and the positional stability of the core wire. The bonding agent may be made of an anisotropic conductive material. It may be in the form of a film or paste. The bonding agent may be non-conductive. 
   A method of making the cable connection structure includes the steps of holding the connection section on the insulation holding body; providing the bonding agent at least on the insulation holding body; providing the core wire at the position corresponding to the connection section; providing the insulation member over the core wire and the bonding agent; and applying a pressure on the insulation member while heating the bonding agent to bond the insulation member with the insulation holding body, thereby connecting the core wire to the connection section. 
   Where the insulation member is flexible, an elastic matt is used to press the insulation member which in turn presses the core wire. Even if the insulation member is deformed by the core wire, the matt undergoes elastic deformation so that the entire surface of the insulation member is pressed. 
   According to the one aspect of the invention, when the core wire of a cable is connected to the connection section with the bonding agent, the insulation member is provided so that the core wire and the bonding agent are pressed between the insulation member and the connection section, thereby increasing the retention force of the core wire by the bonding agent. Since the insulation member presses both sides of each core wire, the conductive particles will not escape to the sides to thereby stabilize the electrical connection. 
   According to another aspect of the invention there is provided a connector equipped with cables including a circuit board; a plurality of connection pads provided on the circuit board at predetermined intervals; a plurality of cables with core wires connected to the connection pads; a plurality of contact pads connected to the connection pads and brought into contact with terminals of a mating connector; and a conductive material for bonding the core wires with the connection pads. 
   The connection with the conductive material eliminates short circuit by the solder bridge and is suitable for the arrangement of cables with a small pitch. The connection is done by merely pinching in a high temperature atmosphere. 
   Every other the connection pads are connected to circuit trances provided on another face of the circuit board so that contact pads can be arranged with a pitch twice the pitch of the connection pads. Consequently, the terminals of a mating connector can be arranged twice the pitch of the connection pads, thus simplifying the manufacture. A pair of adjacent ones of the connection pads provided in an arranging direction may be connected to a pair of contact pads provided on another face of the circuit board on a line perpendicular to the arranging direction. 
   A ground member to which shields of the cables are connected may be provided. A window extending in the arranging direction beyond an arranging range of the cables may be provided so that a comb-shaped jig is insertable through the window. A reinforcing member may be attached to a surface of the circuit board on another surface of which the connection pads are provided. The reinforcing member may have another window corresponding to the window of the circuit board. 
   A connector equipped with cables, according to the invention, includes a housing; a plurality of terminals provided in the housing at predetermined intervals and having connection sections at one ends and contact sections at the other ends for contact with terminals of a mating connector; a plurality of cables with core wires connected to the connection sections of the terminals; and a conductive material for bonding the core wires to the connection sections of the terminals. 
   The terminals may be arranged alternately along opposite faces of the connector so that the connection sections are arranged alternately with a pitch that the cables are arranged. The conductive material may be an anisotropic conductive material. 
   As has been described above, the core wires are connected with the conductive material so that the connection operation is simplified. The core wires are connected to the connection pads via the conductive material so that the adjacent core wires are prevented from contacting. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1(A)  is a sectional view of a cable connection structure according to the first embodiment of the invention; 
       FIG. 1(B)  is a sectional view of the cable connection structure before connection; 
       FIG. 2  is a sectional view of a cable connection structure according to the second embodiment of the invention; 
       FIG. 3  is a sectional view of a cable connection structure according to the third embodiment of the invention; 
       FIG. 4  is a sectional view of a cable connection structure according to the fourth embodiment of the invention; 
       FIGS. 5(A)  and (B) are sectional views of core wires before and after flattening, respectively, according to the fifth embodiment of the invention; 
       FIG. 6  is a sectional view of a cable connection structure according to the sixth embodiment of the invention; 
       FIG. 7(A)  is a top plan view of a connector and a cable according to the seventh embodiment of the invention; 
       FIG. 7(B)  is a sectional view taken along line B—B of  FIG. 7(A) ; 
       FIG. 8  is a perspective view of a connector equipped with cables according to the eighth embodiment of the invention; 
       FIG. 9  is a perspective view, partially in section, of a circuit board of the connector of  FIG. 8 ; 
       FIG. 10  is a perspective view of the circuit board before connection; 
       FIG. 11  is a perspective view of a jig for use in connection of the connector of  FIG. 8 ; 
       FIG. 12  is a perspective view of the connector of  FIG. 8  under connection; 
       FIGS. 13(A)  and (B) are sectional views of the connection section of the connector of  FIG. 8  before and after connection, respectively; 
       FIG. 14  is a sectional view taken along line  14 — 14  of  FIG. 8 ; 
       FIGS. 15(A)  and (B) are sectional views taken along lines  15 (A)— 15 (A) and  15 (B)— 15 (B) of  FIG. 16 , respectively; and 
       FIG. 16  is a plan view of a connector equipped with cables according to the ninth embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the invention will now be described with reference to the accompanying drawings. 
   In  FIG. 1(A) , an electrical connector  1  includes the connection sections  2  of a plurality of terminals and an insulating housing  3  for supporting the connection section  2 . A plurality of retaining grooves  3 A are provided in the insulating housing  3  at predetermined intervals. The connection sections  2  are provided in the retaining grooves  3 A such that the top connection surfaces  2 A slightly project from the top surface of the insulating housing  3 . 
   The core wires  6  of a cable are pressed against the connection surface  2 A by an insulating material or flexible sheet  5  that is bonded to the top surface of the insulating housing  3  with a bonding agent  4 . The bonding agent may be any of those described above but the anisotropic conductive film or paste is preferred. The bonding agent  4  may be provided on the top surface of the insulating housing  3  except for the top connection surfaces  2 A of terminals. The core wires  6  are connected to the connection section  2  directly or indirectly via the conductive particles of the bonding agent  4 . The connection is held by the pressure of the insulating material  5  that is bonded to the insulating housing  3  by the bonding agent  4 . 
   In  FIG. 1(B) , the bonding agent or anisotropic conductive film  4 , the core wires  6  of a cable, and an insulating material sheet  5  are provided on the insulating housing  3  of the connector  1  and the connection sections  2  such that the core wires  6  are provided above the connection sections  2 . 
   Then, by means of an elastic pressure member or matt  7 , the insulating material  5  is pressed down in a high temperature atmosphere sufficiently hot to soften the bonding agent  4 . The insulating material  5  is deformed and holds the core wires on the top surfaces of the connection sections  2 . The core wires  6  is pressed to enter the soften film  4 , thus coming into contact with the connection sections  2  directly or indirectly via the conductive particles. The soften film  4  is bonded with the insulation member  5  and the insulating housing  5  and hardened in the heating atmosphere to hold the connection as shown in  FIG. 1(A) . Finally, the matt  7  is removed. 
   The conductive film  4  is held by the insulating member  5  on both sides of the core wires  6  during the connection process so that the conductive particles do not escape to the sides but make contribution to the connection. After further heating in the atmosphere, both of the conductive film  4  and the insulation member  5  are hardened so that the close contact among the conductive particles and the retention of the core wires  6  by the insulation member  5  are fixed. The insulation member  5  insulates the core wires  6  from the outside. The connection sections  2  slightly project from the insulating housing  3  so that the insulation member  5  can press down the core wires  6  and the bonding agent  4  with more forces. 
   In  FIG. 2 , the connection section  2  is slightly indented into the insulation housing  3  so that the retention groove  3 A prevents the core wires  6  from falling from the connection section  2  and the conductive particles from escaping. 
   In  FIG. 3 , the top surface  2 A of the connection section  2  is made concave so that not only the position of the core wires  6  is made stable but also the escape of conductive particles is prevented. 
   In  FIG. 4 , a circuit board  8  includes a board member  9  made of an insulation material and a plurality of connection lands  10  provided on the board member  9 . The conductive film  4 , the core wires  6 , and the insulation member  5  are provided on the connection lands  10  in the same manner as shown in  FIG. 1 . 
   In  FIGS. 5(A)  and (B), the core wires  6  are pressed from above and below prior to the connection process to be flattened as shown in  FIG. 5(B) . These flattened wires  6  assure not only large contact areas between the core wires  6 , and the core wires  6  and the conductive particles but also stable positions of the core wires  6 . 
   In  FIG. 6 , the insulation member is replaced by an insulation case  11  having rigidity. It is preferred that a recess  11 A is provided in the insulation case  11  to hold down the core wires  6  and assure a positional stability of the core wires and prevention of escape of conductive particles. The insulation case  11  can be used to press the core wires in the high temperature atmosphere so that the matt of  FIG. 1  can be eliminated. The insulation case  11  may be either part of the connector or another member. 
   The seventh embodiment of the invention will be described with reference to  FIGS. 7(A)  and (B). 
   In  FIG. 7(A) , a connector  21  includes an insulation housing  22  and a plurality of terminals  24 A planted in the housing  22 . It includes a plugging section  22 A for receiving a mating connector and a terminal arranging surface  23 . 
   In  FIG. 7(B) , on the terminal arranging surface  23  there are provided a plurality of ribs  26 A and  26 B to form grooves  25 A and  25 B in which the plate-shaped connection sections  24 A and  24 B of terminals are provided. The narrow grooves  25 A are provided on the upper side to receive the narrow connection sections  24 A of signal terminals while the narrow and broad grooves  25 A and  25 B are provided on the lower left and right sides to receive the narrow connection sections  24 A and the broad connection sections  24 B of power terminals. The core wires  6 A and  6 B of a flat cable C are pressed against the connection sections  24 A and  24 B of the terminals by the insulation film  5  for connection through the anisotropic conductive film. The insulation film  5  insulates the core wires  6 A and  6 B from a shield case  27 . 
   In  FIG. 8 , a plurality of coaxial cables  2  are connected to a circuit board  1 . Two types of connection pads  3 A and  3 B are arranged alternately with the same pitch as the arranging pitch of the cables  2 . A transmission path  4 A extends from the connection pad  3 A to an annular land  5 A which is connected via a through hole  5 C to an annular land  5 B which is connected to a contact pad  5 D on the back ( FIG. 9 ). The connection pad  3 B is connected to a transmission path  4 B on the back via a through hole  6  that passes through the circuit board  1 . The transmission path  4 B extends along the transmission path  4 A on the top face to a contact pad  4 C which is spaced from the contact pad  5 D by a distance δ ( FIG. 9 ). 
   Since the adjacent connection pads  3 A and  3 B on the top face of the circuit board  1  are connected to the contact pads  5 D and  4 C on the bottom face via the transmission paths  4 A and  4 B, the contact pads can be disposed with the pitch twice the pitch of the connection pads. The annular pads  5 A and  5 B are connected to narrow paths  7 A and  7 B that extend to the edge of the circuit board  1 . A window  8  is provided in the circuit board  1  adjacent to the connection pads  3 A and  3 B to extend in a direction perpendicular to the longitudinal direction of the cables  2  beyond the arrangement range of the cables  2 . A conductive ground pad  9  extends along the window  8 . 
   A reinforcing plate  10  of an insulative material is attached to the back of the circuit board  1  in the area covering the ground pad  9 , the window  8 , and the connection pads  3 A and  3 B. Another window is provided in the reinforcing plate  10  corresponding to the window  8  of the circuit board  1 . The core wires of the cables  2  are connected to the connection pads  3 A and  3 B of the circuit board  1 . The cables are a coaxial cable consisting of a jacket  2 A, a shield  2 B, a dielectric  2 C, and a core wire or central conductor  2 D. The central conductors  2 D are connected to the connection pads  2 A and  3 B via an anisotropic conductive film  11 . The conductive film  11  is covered by an insulation film  12 . The shields  2 B are connected to the ground pad  9  with solder or a conductive bond. 
   Such a connector as described above is used as follows. 
   (1) As shown in  FIG. 10 , the circuit board  1  with the reinforcing plate  10  is provided. The anisotropic conductive film  11  is disposed over the connection pads  3 A and  3 B. See  FIG. 13(A) . 
   (2) As shown in  FIG. 11 , a jig  20  is provided at the same time as above. The jig  20  consists of a comb-shaped arranging block  21  and a support plate  22  for supporting the arranging block  21 . The arranging block  21  projects upward through the window of the reinforcing plate  10  and the window  8  of the circuit board  1 . A plurality of grooves  21 A are provided in the top face of the arranging block  21  with the pitch of the cables  2  to receive the dielectric members  2 C of the cables  2 . 
   As shown in  FIG. 12 , the circuit board  1  with the reinforcing plate  10  is provided on the jig  20  and the dielectric members  2 C of cables  2  are placed in the grooves  21 A of the arranging block  21 . Also, see  FIG. 13(B) . 
   (3) Consequently, the central conductors  2 D are disposed on the connection pads  3 A and  3 B via the anisotropic conductive film  11 . 
   (4) The insulating film  12  is disposed to cover all of the central conductors  2 D on the connection pads  3 A and  3 B. In  FIG. 13(B) , the edge portions of the conductive film  12  and the insulating film  11  are removed to show the central conductor  2 D. Then, the insulating film  12  is pressed in a high temperature atmosphere. It is preferred that the pressure is done through an elastic member to ensure that the entire area is pressed even if the insulating film is deformed around the central conductors. 
   As shown in  FIG. 14 , as a result of the pressure, the central conductors  2 D are connected to the connection pads  3 A and  3 B via the conductive film  11 . The shield  2 B of each cable  2  is soldered to the ground pad  9 . 
   (5) The connector equipped with the cables is removed from the jig  20 . 
   (6) When the connector with the cables is plugged to a mating connector, the contact pads  5 D and  4 C are brought into spring contact with the contact sections of the mating connector for electrical connection. 
   The contact pads  5 D and  4 C on the bottom face may be provided separately on the top and bottom faces of a circuit board to slide on the terminals of a mating connector. In this case, the narrow paths  7 A and  7 B serve as guiding path. 
   Another embodiment will be described wherein cables are connected to terminals held by a housing instead of the circuit board described above. 
   In  FIG. 15 , a connector  30  includes a housing  31  with a recess  31 A and a plurality of terminals  32  held in the slits  31 B provided in the housing  1 . The terminal  32  has a contact section  32 A at the free end of an S-shaped spring section and a connection section  32 B extending along the top face of the housing  31 . As shown in  FIGS. 15(A)  and (B), the left and right side terminals  32  are arranged alternately at every other intervals in the terminal arranging direction perpendicular to the sheet so that the connection sections  32 B are arranged in alternate directions with the same pitch of the connection sections on the top face of the housing  31 . 
   A mating connector  40  includes a housing  41  with a recess  41 A for receiving the housing  31  of the connector  30  and a plurality of terminals  42  supported by the housing  41 . The terminal  42  housed in a slit  41 B of the housing  41  has a contact section  42 A at the free end of an S-shaped spring section and a connection section  42 B projecting from the housing  41  so as to be substantially flush with the bottom of the housing  41 . The connectors  30  and  40  are well known and their detailed description will be omitted. The form of the connector or terminals is not critical as far as the connection sections of terminals are arranged on a plane. 
   In  FIG. 16 , a plurality of cables  2  are connected to the connector  30 . The connection sections  32 B of left and right side terminals  32  are arranged alternately. For better understanding, reference is made to  FIGS. 15(A)  and (B) which are sectional views taken along line A—A and B—B of  FIG. 16 . The central conductors  2 D of the respective cables  2  are put on the connection sections  32 B in the respective grooves for connection by bonding with the conductive film in the same manner as in the above embodiment. 
   The shields  2 B of the cables  2  is held between a common ground bar  33  for connection. Alternatively, they may be connected to the ground bar  33  with solder or conductive bond. As shown in  FIGS. 15(A)  and (B), a shield plate  34  is attached to the connector  30  equipped with the cables  2 . In use, the connector  40  is provided on a circuit board (not shown) and the connection sections  42 B of the terminals  42  are soldered to the corresponding circuit traces of the circuit board. The connector  30  is plugged into the connector  40  so that the cables  2  are electrically connected to the corresponding circuit traces of the circuit board.

Technology Category: 5