Abstract:
A connector device includes a plug including a plurality of plug terminals and a socket including a plurality of socket terminals. Ground plug terminals each have a recess on the contact surface, and ground socket terminals each have a dimple on the contact surface thereof. The dimple of the ground socket terminal is elastically urged to the recess of the ground plug terminal for obtaining a firm electric contact between the ground plug terminal and the ground socket terminal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a connector device including a plug and a socket, and particularly to a lock structure for locking together the plug and the socket.  
         [0003]     2. Description of the Related Art  
         [0004]     A card edge connector includes a combination of a plug including a plurality plug pins (plug terminals) and a socket including a plurality of socket pins (socket terminals). The plug is provided at an edge portion of a card member such as a printed circuit board. The socket pins are connected to an external circuit. The plug terminals of the card member are configured as pad electrodes. The socket terminals are configured as contact electrodes which contact surfaces of the pad electrodes when the plug of the card member is inserted into the socket. In a card edge connector, the pad electrodes are constructed as parts of printed wires of the card member. The card edge connector has a shorter wiring length, compared with a two-piece connector in which a plug is provided separately from the circuit body. Therefore, the card edge connector has an advantageous feature of capability of reducing electric loss under the condition of using high-speed signals.  
         [0005]     Sockets for the card edge connector are divided into several types, e.g., a type of socket which is provided at an edge portion of a printed circuit board like a plug, and another type of socket which is connected to an end portion of a cable. Particularly, the latter type has a problem in that the card member easily falls off when the cable connected to the socket is pulled by an external force. Patent Publication JP-2002-124327A (FIG. 1) and Utility Model Publication JM-61-76683A (FIG. 1) describe a card edge connector having a lock structure between a card member and a socket, as a kind of card edge connector which prevents the card member from falling off from the socket. In the lock structure described in JP-2002-124327A, the card member is provided with a hook-like protrusion and the socket is provided with a pivotable lever. When the card member is inserted into the socket, the lever is shut to engage with the protrusion. In the lock structure described in JM-61-76683A, through-holes are formed outside the area in which a plurality of pad electrodes are arranged in the card member, and protrusions which engage with the through-holes are provided in the socket for locking the body of the plug and the body of the socket.  
       DISCLOSURE OF THE INVENTION  
       [0000]     Problems to Be Solved by the Invention  
         [0006]     In recent years, electronic devices have been downsized. Connector devices to be mounted on electronic devices have hence been required to be downsized. To realize a connector device having a smaller size, for example, the connector device uses in many cases a serial transmission technique in place of using a conventional parallel transmission technique. This increases the signal transmission speed transmitted through the connector device.  
         [0007]     However, if a conventional lock structure described in any of the two publications described above is adopted, there arises a problem in that the size of the connector device becomes large due to the lock structure and hinders downsizing of the connector device. The larger size impedes the higher-speed signal transmission. Another problem is that the structure of the connector device is complicated and raises the cost thereof.  
         [0008]     In view of the above situation, it is an object of the present invention to provide a connector device having a small and simple lock structure for locking the plug and the socket.  
         [0000]     Means for Solving the Problems  
         [0009]     The present invention provides a connector device including a plug including a plug terminal and a socket including a socket terminal, the plug terminal having a contact surface adapted to a contact surface of the socket terminal wherein: the plug terminal has a dimple or recess on the contact surface; the socket terminal has a recess on the contact surface thereof corresponding to the dimple of the plug terminal or has a dimple on the contact surface thereof corresponding to the recess of the plug terminal; and the recess or the dimple of the socket terminal is elastically urged onto the dimple or the recess of the plug terminal.  
         [0010]     According to the connector device of the present invention, a lock structure can be realized which locks together the plug and the socket by using the protrusion or recess which is formed on the contact surface of the plug terminal and by using the recess or protrusion which is elastically urged against and engaged with the protrusion or recess of the plug terminal. Since the lock structure is formed at the contact surfaces contacting the plug terminal with the socket terminal, the connector device having the lock structure can be downsized without enlarging the connector device for the space of the lock structure. In addition, the connector device has a simple lock structure, and therefore, the costs necessary for manufacturing the connector having the lock structure can be reduced. Moreover, the lock structure improves the electric contact between the plug terminal and the socket terminal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view showing the structure of a connector device according to an embodiment of the present invention;  
         [0012]      FIGS. 2A and 2B  are sectional views taken along the lines a-a and b-b, respectively, shown in  FIG. 1 ;  
         [0013]      FIG. 3A  is an enlarged sectional view showing the vicinity of the curved portion of the contact electrode shown in  FIG. 2B , and  FIG. 3B  is a top plan view thereof where the vicinity of the curved portion in  FIG. 2B  is observed from the side of the contact surface; and  
         [0014]      FIG. 4A  is a sectional view corresponding to  FIG. 2B  in a state where the plug and the socket are locked together, and  FIG. 4B  is an enlarged sectional view showing the vicinity of the curved portion shown in  FIG. 4A . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]     Referring to the accompanying drawings, the present invention will now be described in detail below on the basis of an embodiment of the present invention.  FIG. 1  is a perspective view showing the structure of a connector device according to the embodiment. The connector device, generally designated by numeral  10 , is a card edge connector, and is configured by a combination of plug  12  and socket  22 . At an edge portion of a card member  11  configured by a multilayer printed circuit board, the plug  12  is provided as a part of the multilayer printed circuit board. The socket  22  is connected to an end portion of a cable  21 .  
         [0016]     On both board surfaces of the plug  12 , a plurality of pad electrodes (plug terminals)  13  are provided. The pad electrodes  13  each have a rectangular planar shape which is elongated in the direction of inserting the plug  12  into the socket  22 . The pad electrodes  13  each are 2.0 mm long in the direction of the longer edge of the rectangle and 1.5 mm long in the direction of the shorter edge. The pad electrodes  13  include signal pad electrodes  14  connected to signal lines of the printed circuit board, and ground pad electrodes  15  connected to the ground line of the printed circuit board. The signal pad electrodes  14  and the ground pad electrodes  15  are arrayed in a ground strip-line structure. In order that the cross-talk noise between adjacent signal pad electrodes  14  be reduced, one of the ground pad electrodes  15  is disposed for every one or two of the signal pad electrodes  14 .  
         [0017]     The pad electrodes  13  are formed on each of the front and rear surfaces of the printed circuit board. In the ground pad electrodes  15 , substantially circular through-holes  16  are formed in the vicinity of the distal end portion  12   a  of the plug  12 . The through-holes  16  are formed penetrating the printed circuit board underlying the ground pad electrodes  16  and also penetrating the other ground pad electrodes  15  disposed on the opposite side of the printed circuit board, which is sandwiched between these ground pad electrodes  15 . The through-holes  16  each have a diameter of 0.5 mm.  
         [0018]      FIG. 2A  shows a sectional view of the connector device  10  taken along the line a-a shown in  FIG. 1 . The socket  22  has a housing  23  for receiving therein plugs  12 . Signal contact electrodes  25  corresponding to the signal pad electrodes  14  are secured to the housing  23 . The signal contact electrodes  25  each have a curved portion  26  near the opening of the housing  23 , the curved portion  26  being curved to protrude toward one of board surfaces of the plug  12 .  
         [0019]      FIG. 2B  shows a sectional view taken along the line b-b shown in  FIG. 1 . Substantially U-shaped ground contact electrodes  27  coonding to the ground pad electrodes  15  provided on the plug  12  are secured to the housing  23 . The ground contact electrodes  27  each have a curved portion  28  near the distal end thereof, the curved portion  28  being curved to protrude toward the one of board surfaces of the plug  12 . The ground contact electrodes  27  are disposed such that the curved portions  28  are retracted in the housing  23  from the curved portions  26  of the signal contact electrodes  25 .  
         [0020]      FIG. 3A  is an enlarged sectional view showing the curved portion of the ground contact electrode  27 .  FIG. 3B  shows a top plan view of the ground contact electrode  27  where the curved portion of the contact electrode  27  is observed from the side of the contact surface.  FIG. 3A  shows a sectional-view taken along the line a-a in  FIG. 3B . The ground contact electrode  27  is configured as a stripe-like metal plate elongated in the direction of inserting the plug  12 . At the peak portion of the curved portion  28 , a dimple  29  protruding toward the board surface of the plug  12  is formed. The dimple  29  has a substantially semi-spherical shape having a diameter of around 0.6 mm, The dimple  29  is formed as by pressing the ground contact electrode  27 .  
         [0021]     Referring back to  FIG. 2B , a conductive film coat  17  is formed by a plating technique on the inner wall of the through-hole  16 , and is connected to a ground layer (not shown) configured by a conductive layer of the printed circuit board. The signal contact electrodes  25  and ground contact electrodes  27  are respectively connected, at the proximal ends thereof, to the signal lines  31  and ground lines  32  by using solder  30 . Alternatively, the signal contact electrodes  25  and ground contact electrodes  27  may be respectively connected to the signal lines  31  and ground lines  32  by using a pressure bonding technique. The signal lines  31  and ground lines  32  are led to the outside of the housing  23  to configure lead wires. Two signal lines  31  and two ground lines  32  configure a single cable  21 .  
         [0022]     When coupling together the plug  12  and the socket  22 , the distal end portion  12   a  of the plug  12  is aligned with the opening of the socket  22 , and the plug  12  is then moved into the socket  22 . As the plug  12  moves, the curved portions  26  of the signal contact electrodes  25  firstly contact the distal end portion  12   a  of the plug  12 , and get on the board surfaces. The curved portions  26  then smoothly slide on the signal pad electrodes  14  while being kept urged against the contact surfaces of the signal pad electrodes  14 . Secondly, the curved portions  28  of the ground contact electrodes  27  contact the distal end portion  12   a  of the plug  12 , and the dimples  29  get on the board surfaces. The curved portions  28  then smoothly slide on the ground pad electrodes  15  while being kept urged against the contact surfaces of the ground pad electrodes  15 .  
         [0023]     The dimples  29  slide through a predetermined distance on the contact surfaces of the ground pad electrodes  15 , to finally engage with the through-holes  16 . This state of the connector device  10  is shown in  FIG. 4A .  FIG. 4B  shows the vicinity of the dimple shown in  FIG. 4A . After the dimples  29  engage with the through-holes  16 , the plug  12  and the socket  22  are locked together. At the openings of the through-holes  16  configuring recesses, the dimples  29  contact the ground pad electrodes  15 , to thereby couple together the ground pad electrodes  15  and the ground contact electrodes  27  with a higher reliability.  
         [0024]     According to the connector device  10  of the present embodiment, the through-holes  16  which engage with the dimples  29  are formed penetrating the ground pad electrodes  15 . Therefore, the size of the connector device  10  need not be large. As a result, the connector device having a lock structure can be downsized, so that the packaging density of the connector device can be increased. Also, a simple lock structure to lock a plug and a socket is achieved by the normal connection operation of the connector device.  
         [0025]     The through-holes  16  and the conductive film coats  17  can be formed in the step of forming the multilayer printed circuit board configuring the card member  11 . Therefore, increase in the costs necessary for manufacture of connector devices can be reduced. The conductive film coats  17 , formed on the inner walls of the through-holes  16 , can efficiently contact the ground pad electrodes  15  with the ground contact electrodes  27 . Accordingly, reliability of the electric connection can be improved.  
         [0026]     In the above embodiment, the card edge connector has an arrangement of electrodes based on the ground strip-line structure, and the through-holes  16  are formed in the common ground pad electrodes  15 . Therefore, even when a poor contact occurs between one of the ground pad electrodes  15  and a corresponding one of the ground contact electrodes  27 , the desired electric contact can be achieved between the others of the ground pad electrodes  15  and the respective ground contact electrodes  27 . Thus, electric connection between the ground pad electrodes  15  and the ground contact electrodes  27  can be assured.  
         [0027]     In an alternative of the present embodiment, recesses may be formed in the contact surfaces of the ground pad electrodes  15 , in place of the through-holes  16 . In a further alternative, protrusions may be formed on the contact surfaces of the ground pad electrodes  15 , and recesses to engage with the protrusions may be formed in the contact surfaces of the ground contact electrodes  27 .  
         [0028]     The present invention has been described above based on a preferred embodiment thereof. However, the connector device according to the present invention is not limited to the structure described in the above embodiment. The scope of the present invention should be considered as including those connector devices that would be derived by making various changes and modifications to the structure of the above embodiment.