Abstract:
A connector comprises at least a first conductive layer in a first connector half and a plurality of second conductive layers in a second connector half. The second conductive layers are alternated with the first conductive layer when the second connector half is coupled with the first connector half. A plurality of signal lines are arranged between the first and second conductive layers. The first and second conductive layers in combination serve to establish a so-called strip line. Since the first and second conductive layers are adapted to function as ground or shield plates to absorb noise of the respective signal lines, the signal lines can reliably be shielded from noise caused by signals passing through the adjacent signal lines. Accordingly, it is possible to reduce the space between the adjacent signal lines so as to achieve a higher density of the signal lines. In addition, the alternated first and second conductive layers easily achieve a multilayered structure so as to contribute to an increased number of signal lines.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a connector for establishing a continuous signal channel between a pair of separate signal wires or lines when first and second connector halves are coupled with each other. 
     2. Description of the Prior Art 
     Computer systems such as super computer, global servers, UNIX office computers, and the like, in general, allows a CPU (central processing unit) board to exchange electric signals with other boards such as controller boards, memory boards, and the like. Signal channels should be established between the CPU board and the other boards when the signal exchange is realized. Separable connectors are usually employed to connect a signal line of a board to a signal line of another board. 
     Separable connectors in general employ a pin-socket structure. A pin-socket structure usually comprises a conductive pin protruding from a plug component or first connector half, and a conductive socket embedded within a receptacle component or second connector half. When the plug component is coupled with the receptacle component, the conductive pin is received within the conductive socket. The conductive socket holds the conductive pin by its own elasticity. Such elasticity is supposed to keep a reliable electric connection between the conductive pin and socket. 
     In recent years, the operating speed or frequency of a CPU has increased, so that a higher transmission rate or frequency is also required for signal or data channels. A higher transmission rate inevitably causes noise to cross over the adjacent signal channels. If the transmission rate is further accelerated in signal or data channels, reaching a level over 1 or more GHz, for example, a severe countermeasure is required to prevent noise form crossing over adjacent signal or data channels. 
     In addition, signal channels should face a demand of a higher density in the future. However, a further reduction in size or dimension is hardly achieved in the aforementioned pin-socket structure. A smaller conductive socket cannot establish an elasticity enough to hold a conductive pin within the conductive socket itself. Less elasticity may induce, for example, a failure in an electric connection between the conductive socket and the conductive pin. 
     SUMMARY OF INVENTION 
     It is accordingly an object of the present invention to provide a connector, for establishing a signal or data channel, capable of meeting the demand of a higher transmission rate and a higher density of signal channels without any difficulty. 
     According to a first aspect of the present invention, there is provided a connector for a signal channel, comprising: at least a first conductive layer in a first connector half, a plurality of second conductive layers in a second connector half, to be alternated with the first conductive layer when the second connector half is coupled with the first connector half, and a plurality of signal lines arranged between the first and second conductive layers. 
     With the above structure, the first and second conductive layers, in combination, serve to establish a so-called strip line. Since the first and second conductive layers are adapted to function as ground or shield plates to absorb noise of the respective signal lines, the signal lines can reliably be shielded from noise caused by signals passing through the adjacent signal lines. Accordingly, it is possible to reduce the space between the adjacent signal lines so as to achieve a higher density of the signal lines. In addition, the alternated first and second conductive layers easily achieve a multilayered structure so as to contribute to an increased number of signal lines. 
     The connector may further comprise a conductive wire disposed between the adjacent signal lines. The conductive wire serves to, in combination with the first and second conductive layers, surround the signal line so as to provide a structure similar to coaxial cable. Accordingly, the signal lines can be tightly shielded from noise caused by signals passing through the adjacent signal lines. 
     In place of the conductive wire, a conductive wall may be employed to connect the first and second conductive layers to each other between the adjacent signal lines. The conductive wall likewise serves to, in combination with the first and second conductive layers, completely surround the signal line so as to provide a true coaxial cable. Accordingly, the signal lines can be completely shielded from noise caused by signals passing through the adjacent signal lines. 
     According to a second aspect of the present invention, there is provided a connector for a signal channel, comprising: at least a first conductive layer in a first connector half; a first flexible insulation layer superposed on a surface of the first conductive layer; first signal lines extending on a surface of the first flexible insulation layer; at least a second conductive layer in a second connector half; a second flexible insulation layer superposed on a surface of the second conductive layer, the second flexible insulation layer being spaced from the first flexible insulation layer between the first and second conductive layers when the first and second connector halves are coupled with each other; and second signal lines extending on a surface of the second insulation layer, the second signal lines being connected to the corresponding first signal lines between the first and second connector halves are coupled with each other. 
     A flexible circuit board comprising the first flexible insulation layer and the first signal lines as well as a flexible circuit board comprising the second flexible insulation layer and the second signal lines may be employed to provide a so-called strip line. In the aforementioned manner, the first and second signal lines between the first and second conductive layers can reliably be shielded from noise caused by signals passing through the adjacent first and second signal lines. In addition, the alternated first and second conductive layers easily achieve a multilayered structure so as to contribute to an increased number of the first and second signal lines. Moreover, employment of the flexible circuit board also serves to prevent variation in electric characters such as a contact resistance and the like to the utmost. 
     In addition, the connector may further comprise: first conductive pads formed at tip ends of the first signal lines and located along a datum line intersecting, by a predetermined inclination angle, a lateral direction perpendicular to a longitudinal direction of the first signal lines; and second conductive pads formed at tip ends of the second signal lines, which extend on extensions of the first signal lines when the first and second connector halves are coupled with each other, and located along the datum line. With such a structure, the first and second connector halves can be coupled with or detached from each other, not only along the longitudinal directions of the first and second signal lines, but also along the lateral directions, perpendicular to the longitudinal directions, of the first and second signal lines. 
     Alternatively, the connector may further comprise: first conductive pads formed at tip ends of the first signal lines and located along a datum line intersecting, by a predetermined inclination angle, a lateral direction perpendicular to a longitudinal direction of the first signal lines; and second conductive pads formed at tip ends of the second signal lines, which extend across the first signal lines so as to reach the datum line when the first and second connector halves are coupled with each other, and located along the datum line. In the case where the first and second signal lines are designed to intersect each other by a predetermined inclination angle when the first and second connector halves are coupled with each other, the respective combinations of the first and second signal lines, connected to each other, may be designed to extend over a predetermined length. The length of the signal channels, each comprising the combination of the first and second signal lines, can be unified in the connector. Such a structure may contribute to avoidance of skews between the signal channels. 
     In order to keep a reliable contact between the first and second signal lines, the connector may further comprise a leaf spring interposed between the surface of the first conductive layer and the first flexible insulation layer so as to establish an elastic force for urging the first signal lines toward the second signal lines when the first and second connector halves are coupled with each other. Such a leaf spring may serve to keep enough contact pressure even when mechanical characters, such as the width and/or thickness, of the first and second signal lines are varied. The connector may accept variation in an electric character, such as a contact resistance, of the first and second signal lines without losing a reliable contact between the first and second signal lines. 
     In place of the aforementioned leaf spring, a common holding mechanism may be employed to keep together the first and second conductive layers, which are alternately superposed, when the first and second connector halves are coupled with each other. The common holding mechanism likewise allows the connector to accept variation in an electric character of the first and second signal lines without losing a reliable contact between the first and second signal lines. Moreover, the common holding mechanism may contribute to simplification of the structure of the connector even when an increased number of first and second conductive layers and/or the first and second signal lines are required in the connector. 
     The aforementioned connector may employ a connector half comprising: at least a conductive layer; a pair of flexible insulation layers superposed on opposite surfaces of the conductive layer; and a plurality of signal lines extending on surfaces of the respective flexible insulation layers. In addition, the connector may employ, in combination with the above connector half, a connector half comprising: a housing; at least a pair of conductive layers spaced each other within the housing; a pair of flexible insulation layers superposed on surfaces of the conductive layers facing each other; and a plurality of signal lines extending on surfaces of the flexible insulation layers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments in conjunction with the accompanying drawings, wherein: 
     FIG. 1A schematically illustrates a plan view of a CPU (central processing unit) board and a circuit board connected to each other through a cable assembly, while 
     FIG. 1B schematically illustrates a side view thereof; 
     FIG. 2 is a side view schematically illustrating a CPU board and a circuit board connected to each other through additional or supplemental cables; 
     FIG. 3 is an enlarged sectional view, taken along the line  3 — 3  in FIG. 1A, illustrating in part a separable connector; 
     FIG. 4 is a sectional view taken along the lines  4 — 4  in FIGS. 1A and 3; 
     FIG. 5 is an enlarged sectional view, corresponding to FIG. 4, illustrating in part a separable connector according to another specific embodiment; 
     FIG. 6 is an enlarged sectional view, corresponding to FIG. 4, illustrating in part a separable connector according to further specific embodiment; 
     FIG. 7 is a perspective view schematically illustrating the structure of a first conductive plate according to a specific example; 
     FIG. 8 is a partial sectional view schematically illustrating the connection between the plug and receptacle components in which the first conductive plate of FIG. 7 is assembled; 
     FIG. 9 is a perspective view schematically illustrating the structure of a first conductive plate according to another specific example; 
     FIG. 10 is a partial sectional view schematically illustrating the structure of a common holding mechanism according to a specific example; 
     FIG. 11 is a partial sectional view schematically illustrating the structure of a common holding mechanism according to another specific example; 
     FIG. 12 is a plan view illustrating the location of first and second conductive pads formed at the tip ends of first and second signal lines, respectively, according to a specific embodiment; 
     FIG. 13 is a plan view illustrating plug and receptacle components when coupled with each other in the lateral direction; 
     FIG. 14 is a plan view illustrating the location of first and second conductive pads formed at the tip ends of first and second signal lines, respectively, according to another embodiment; 
     FIG. 15 is a plan view illustrating plug and receptacle components when coupled with each other; 
     FIG. 16 is an enlarged sectional view schematically illustrating in part a separable connector according to another embodiment; and 
     FIG. 17 is an exploded perspective view schematically illustrating the structure of a plug component. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A computer system such as a super computer, a global server, or a UNIX office computer comprises, as shown in FIG.  1 A and FIG. 1B, a CPU (central processing unit) board  10  on which a CPU is mounted, and a circuit board  11  such as a controller board or memory board. Cable assembly  12  is interposed between the CPU board  10  and the circuit board  11  for establishing signal or data channels between the CPU board  10  and the circuit board  11 . The cable assembly  12  includes one or more first flexible printed circuit boards  13   a - 13   d  fixedly mounted on the CPU board  10 , and one or more second flexible printed circuit boards  14   a - 14   d  likewise mounted on the circuit board  11 . A separable connector  15  is employed to connect the first and second flexible printed circuit boards  13   a - 13   d ,  14   a - 14   d . Otherwise, additional or supplemental cables  16   a - 16   d  comprising flexible printed circuit boards may be employed to establish connection between the first and second flexible printed circuit boards  13   a - 13   d ,  14   a - 14   d , as shown in FIG. 2, for example. In this case, separable connectors  15  are likewise interposed between the first flexible printed circuit boards  13   a - 13   d  and the cables  16   a - 16   d  and between the second flexible printed circuit boards  14   a - 14   d  and the cables  16   a - 16   d.    
     The separable connector  15  comprises a first or plug component  21  and a second or receptacle component  22 . The plug and receptacle components  21 ,  22  can be detachably coupled with each other. The plug component  21  comprises, as shown in FIG. 3, one or more first conductive layers or plates  24   a ,  24   b  fixed within a housing  23  made from a synthetic resin material. On the other hand, the receptacle component  22  comprises two or more spaced second conductive layers or plates  26   a - 26   c  likewise fixed within a housing  25  made from a synthetic resin material. When the housing  23  of the plug component  21  is received within the housing  25  of the receptacle component  22 , the first conductive plates  24   a ,  24   b  are held between the adjacent second conductive plates  26   a - 26   c . Accordingly, the second conductive plates  26   a - 26   c  are alternated with the first conductive plates  24   a ,  24   b  when the housing  25  is coupled with the housing  23 . 
     Flexible insulation layers or films  27   a ,  27   b  of the first flexible printed circuit boards  13   a ,  13   b  are fixedly superposed on the opposite surfaces of the first conductive plate  24   a . Likewise, flexible insulation layers or films  27   c ,  27   d  of the first flexible printed circuit boards  13   c ,  13   d  are fixedly superposed on the opposite surfaces of the first conductive plate  24   b . Referring also to FIG. 4, stripes of first signal lines or printed wires  28   a - 28   d  extend in parallel on the exposed surfaces of the respective flexible insulation films  27   a - 27   d . The adjacent signal lines  28   a - 28   d  may be spaced by a constant interval. 
     A referring again to FIG. 3, flexible insulation layers or films  29   a ,  29   b  of the second flexible printed circuit boards  14   a ,  14   b  are fixedly superposed on the second conductive plates  26   a ,  26   b  at the surfaces facing each other. As is apparent from FIG. 4, stripes of second signal lines or printed wires  30   a ,  30   b  extend in parallel on the exposed surfaces of the respective flexible insulation films  29   a ,  29   b . When the plug and receptacle components  21 ,  22  are coupled with each other, the first conductive plates  24   a  is inserted between the second conductive plates  26   a ,  26   b . The flexible insulation film  27   a  of the first flexible printed circuit board  13   a  is allowed to face the flexible insulation film  29   a  of the second flexible printed circuit board  14   a , while the flexible insulation film  27   b  of the first flexible printed circuit board  13   b  is allowed to face the flexible insulation film  29   b  of the second flexible printed circuit board  14   b . The first signal lines  28   a ,  28   b  are electrically connected to the second signal lines  30   a ,  30   b , one by one, between the flexible insulation films  27   a ,  29   a  facing each other and between the flexible insulation films  27   b ,  29   b  facing each other. 
     In the same manner, flexible insulation layers or films  29   c ,  29   d  of the second flexible printed circuit boards  14   c ,  14   d  are fixedly superposed on the second conductive plates  26   b ,  26   c  at the surfaces facing each other. As is apparent from FIG. 4, stripes of second signal lines or printed wires  30   c ,  30   d  extend in parallel on the exposed surfaces of the respective flexible insulation films  29   c ,  29   d . When the plug and receptacle components  21 ,  22  are coupled with each other, the first conductive plates  24   b  is inserted between the second conductive plates  26   b ,  26   c . The flexible insulation film  27   c  of the first flexible printed circuit board  13   c  is allowed to face the flexible insulation film  29   c  of the second flexible printed circuit board  14   c , while the flexible insulation film  27   d  of the first flexible printed circuit board  13   d  is allowed to face the flexible insulation film  29   d  of the second flexible printed circuit board  14   d . The first signal lines  28   c ,  28   d  are electrically connected to the second signal lines  30   c ,  30   d , one by one, between the flexible insulation films  27   c ,  29   c  facing each other and between the flexible insulation films  27   d ,  29   d  facing each other. 
     As shown in FIG. 4, the separable connector  15  allows the first and second signal lines  28   a - 28   d ,  30   a - 30   d  to be connected to each other between the adjacent conductive plates  26   a ,  24   a ,  26   b ,  24   b ,  26   c . So-called strip lines can be established in the separable connector  15 . Accordingly, noise of the respective signal lines  28   a - 28   d ,  30   a - 30   d  can be absorbed by the first and second conductive plates  24   a ,  24   b ,  26   a - 26   c , namely, ground plates, so that the first and second signal lines  28   a - 28   d ,  30   a - 30   d  can reliably be shielded from noise caused by signals passing through the adjacent first and second signal lines  28   a - 28   d ,  30   a - 30   d.    
     As shown in FIG. 5, for example, conductive or ground wires  32  may be disposed between the adjacent first and second signal lines  28   a - 28   d ,  30   a - 30   d  on the surfaces of the respective flexible insulation films  27   a - 27   d ,  29   a - 29   d  in the separable connector  15 . The adjacent conductive wires  32  serve to, in combination with the first and second conductive plates  24   a ,  24   b ,  26   a - 26   c , surround the respective first and second signal lines  28   a - 28   d ,  30   a - 30   d  so as to provide a structure similar to a coaxial cable. Accordingly, the first and second signal lines  28   a - 28   d ,  30   a - 30   d  can much tightly be shielded from noise caused by signals passing through the adjacent first and second signal lines  28   a - 28   d ,  30   a - 30   d.    
     Otherwise, as shown in FIG. 6, conductive walls  33  may be disposed between the adjacent first and second signal lines  28   a - 28   d ,  30   a - 30   d  in the separable connector  15 . The conductive walls  33  stand upright on the surface of the first and second conductive plates  24   a ,  24   b ,  26   a - 26   c  so as to connect the first and second conductive plate  24   a ,  24   b ,  26   a - 26   c  to each other, for example. The adjacent conductive walls  33  serve to, in combination with the first and second conductive plates  24   a ,  24   b ,  26   a - 26   c , completely surround the respective first and second signal lines  28   a - 28   d ,  30   a - 30   d  so as to provide a structure identical to a coaxial cable. Accordingly, the first and second signal lines  28   a - 28   d ,  30   a - 30   d  can completely be shielded from noise caused by signals passing through the adjacent first and second signal lines  28   a - 28   d ,  30   a - 30   d . A via may be formed in the flexible insulation films  27   a - 27   d ,  29   a - 29   d  so as to provide the conductive wall  33 . 
     The aforementioned separable connector  15  may, as shown in FIG. 7, employ conductive elastic member or leaf springs  35  attached to the first signal lines  28   a - 28   d  at the tip ends for achieving a reliable contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d . For example, a solder, a conductive adhesive, and the like, may be employed to fix the leaf springs  35  to the first signal lines  28   a - 28   d . The leaf springs  35  serve to, as shown in FIG. 8, keep a reliable contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d . The first and second signal lines  28   a - 28   d ,  30   a - 30   d  can be prevented from suffering from a failure in electric connection. 
     The leaf springs  35  may be replaced, as shown in FIG. 9, with conductive bumps or protrusions  36  integrally formed at the tip ends of the first signal lines  28   a - 28   d , for example. The bumps  36  likewise serve to reliably hold the contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d . The first and second signal lines  28   a - 28   d ,  30   a - 30   d  can also be prevented from suffering from a failure in electric connection. It should be noted that the leaf springs  35  or the bumps  36  may be attached or formed on the second signal lines  30   a - 30   d  in place of the first signal lines  28   a - 28   d . At least either of the first and second signal lines  28   a - 28   d ,  30   a - 30   d  should be provided with the leaf springs  35  or the conductive bumps  36 . 
     Otherwise, as shown in FIG. 10, a common holding mechanism comprising leaf springs  37  may be employed to reliably hold the contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d . The leaf springs  37  serve to commonly hold the alternate first and second conductive plates  24   a ,  24   b ,  26   a - 26   c  therebetween. The leaf springs  37  may be attached to the housings  23 ,  25  of the plug and receptacle components  21 ,  22 , for example. 
     Also, as shown in FIG. 11, a common holding mechanism may employ a pressing or biasing mechanism  39  in place of the leaf springs  37 , to commonly bias or urge the alternate first and second conductive plates  24   a ,  24   b ,  26   a - 26   c  against a stationary plane  38 . The stationary plane  38  may be defined on the inner surface of the housing  23 ,  25  of the plug or receptacle component  21 ,  22 . The first and second conductive plates  24   a ,  24   b ,  26   a - 26   c  can reliably be held between the stationary plane  38  and the biasing mechanism  39 . The biasing mechanism  39  may comprise, for example, a receiving hole  41  formed in the housing  23 , and a piston member  42  received in the receiving hole  41 . In this case, a spring  43  is interposed between the piston member  42  and the receiving hole  41  for biasing the piston member  42  so as to protrude the piston member  42  out of the receiving hole  41 . 
     The common holding mechanism such as the leaf springs  37  and biasing mechanism  39  may be employed to simplify the structure of the separable connector  15  even when an increased number of first and second conductive plates  24   a ,  24   b ,  26   a - 26   c  and first and second signal lines  28   a - 28   d ,  30   a - 30   d  are to be provided in the separable connector  15 . In addition, such a common holding mechanism allows the separable connector  15  to accept variation in an electric character such as a contact resistance without losing a reliable contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d . In general, when a contact resistance is to be changed, the size such as thickness and/or width of the signal lines  28   a - 28   d ,  30   a - 30   d  should be changed. Such change in size may induce variation in mechanical character of the signal lines  28   a - 28   d ,  30   a - 30   d , for example, reduction in elasticity, given to the signal lines  28   a - 28   d ,  30   a - 30   d . The aforementioned common holding mechanism is supposed to keep the contact between the signal lines  28   a - 28   d ,  30   a - 30   d  even when the signal lines  28   a - 28   d ,  30   a - 30   d  fail to have an elasticity enough to hold the contact between the signal lines  28   a - 28   d ,  30   a - 30   d  by themselves. 
     Furthermore, as shown in FIG. 12, first conductive pads  45  may be formed at the tip ends of the first signal lines  28   a - 28   d  in the aforementioned separable connector  15 . The first conductive pads  45  are located along a datum line  46  intersecting by a predetermined inclination angle α the lateral direction DD 1  perpendicular to the longitudinal direction of the first signal lines  28   a - 28   d . Likewise, the second conductive pads  47  may be formed at the tip ends of the second signal lines  30   a - 30   d . The second conductive pads  47  are located along a datum line  48  intersecting by the inclination angle α the lateral direction DD 2  perpendicular to the longitudinal direction of the second signal lines  30   a - 30   d  in the same manner. 
     When the plug and receptacle components  21 ,  22  are coupled with each other, the second signal lines  30   a - 30   d  should be positioned to extend on extensions of the first signal lines  28   a - 28   d . If the datum lines  46 ,  48  are aligned with each other, the respective second conductive pads  47  are reliably allowed to individually contact with the corresponding first conductive pads  45 . In this case, the plug and receptacle components  21 ,  22  can be coupled with or detached from each other, not only along the longitudinal directions of the first and second signal lines  28   a - 28   d ,  30   a - 30   d  as shown in FIG. 12, but also along the lateral directions DD 1 , DD 2  of the first and second signal lines  28   a - 28   d ,  30   a - 30   d  as shown in FIG.  13 . 
     The first and second signal lines  28   a - 28   d ,  30   a - 30   d  may, not only extend along a single line or direction but also intersect each other by a predetermined angle. As shown in FIG. 14, the first conductive pads  51  formed at the tip ends of the first signal lines  28   a - 28   d  may be located along a datum line  52  intersecting by a predetermined inclination angle β the lateral direction DD 1  perpendicular to the longitudinal direction of the first signal lines  28   a - 28   d  in the aforementioned manner. On the other hand, second conductive pads  53  may be formed at the tip ends of the second signal lines  30   a - 30   d  so as to correspond to the respective first conductive pads  51 . In this case, the second signal lines  30   a - 30   d  is allowed to extend across the first signal lines  28   a - 28   d  so as to reach the datum line  52  when the plug and receptacle components  21 ,  22  are coupled with each other. 
     The length a, b, a of the first signal lines  28   a - 28   d  and the length d, e, f of the second signal lines  30   a - 30   d  can be adjusted in this separable connector  15 . The combinations of length a+d, b+e, c+f can be set constant so as to establish signal paths of the identical length as shown in FIG.  15 . It is possible to avoid skew between the signal paths each comprising the combination of the first and second signal lines  28   a - 28   d ,  30   a - 30   d . In this case, at least either one of the first and second signal lines  28   a - 28   d ,  30   a - 30   d  may be covered with an insulation layer or film on the surface of the flexible insulation films  27   a - 27   d ,  29   a - 29   d . Such an insulation layer serves to avoid an electric connection between the first and second signal lines  28   a - 28   d ,  30   a - 30   d  even when the second signal lines  30   a - 30   d  extend across the first signal lines  28   a - 28   d . The second signal lines  30   a - 30   d  need not intersect the first signal lines  28   a - 28   d  by right angles. 
     FIG. 16 illustrates a separable connector  15  according to another embodiment of the present invention. Leaf springs  55  are interposed between the surfaces of the first conductive plates  24   a ,  24   b  and the first flexible printed circuit boards  13   a - 13   d , namely, the first flexible insulation films  27   a - 27   d  in this separable connector  15 . The leaf springs  55  serve to establish an elastic force for urging the first signal lines  28   a - 28   d  against the corresponding second signal lines  30   a - 30   d  when the plug and receptacle components  21 ,  22  are coupled with each other. The elastic force serves to hold contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d . The lead springs  55  may establish a reliable contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d  irrespective of variation in size such as thickness and/or width of the first and/or second signal lines  28   a - 28   d ,  30   a - 30   d . The separable connector  15  in this manner can accept variation in an electric character such as a contact resistance of the first and second signal lines  28   a - 28   d ,  30   a - 30   d  without losing a reliable contact between the first and second signal lines  28   a - 28   d ,  30   a - 30   d.    
     Next, a description will be made on a method of making the plug component  21  according to this embodiment. As shown in FIG. 17, the first conductive plate  24   a  is punched out of a phosphor bronze plate, for example. The phosphor bronze plate may have a thickness of approximately 0.2 mm. The leaf springs  55  are adhered on the opposite surfaces of the first conductive plate  24   a . An adhesive may be employed in attachment. The leaf springs  55  may be shaped out of a beryllium copper plate having a thickness of approximately 0.2 mm, for example. The tip ends are folded to have an elasticity or biasing force. Slits  56  can be used to adjust or reduce the magnitude of the biasing force. Larger or wider slits  56  result in a smaller biasing force of the leaf spring  55 . 
     The first flexible printed circuit boards  13   a ,  13   b  are fixedly superposed on the surfaces of the leaf springs  55 . The first conductive plate  24   a  with the first flexible printed circuit boards  13   a ,  13   b  is embedded in the housing  23  of the plug component  21 . Another first conductive plate  24   b  is likewise embedded in the housing  23 , along with the first printed circuit boards  13   c ,  13   d  and the leaf springs  55 , in parallel with the first conductive plate  24   a . It should be noted that the housing  23  may receive more than three first conductive plates. 
     In this case, a pair of contact portions  57  may be formed by the leaf spring  55  at the opposite ends in the lateral direction, as clearly shown in FIG.  17 . The contact portions  57  are designed to contact the surface of the opposed second conductive plates  26   a ,  26   b  when the first conductive plate  24   a  is inserted between the adjacent second conductive plates  26   a ,  26   b . Since electric connection can be established between the contact portions  57  and the first conductive plate  24   a , the contact portions  57  allow the first and second conductive plates  24   a ,  26   a ,  26   b  to also establish electric connection therebetween. Noise generated from the signal lines  28   a - 28   d ,  30   a - 30   d  is allowed to spread all over the first and second conductive plates  24   a ,  26   a ,  26   b . Such release of noise may contribute to a further reliability to prevent the noise from crossing over the adjacent signal lines  28   a - 28   d ,  30   a - 30   d.    
     Furthermore, a connection terminal  58  may be formed at the rear end of the first conductive plate  24   a  for contacting a printed ground pattern, not shown, formed on the surface of the CPU board  10  and/or the other circuit board  11  when the plug component  21  is mounted on the CPU and/or circuit boards  10 ,  11 . Such release of noise to the printed ground pattern from the plug component  21  may contribute to a still further reliability to prevent the noise from crossing over the adjacent signal lines  28   a - 28   d ,  30   a - 30   d  in the plug component  21 . In the same manner, such connection terminal  58  may be formed at the rear end of the second conductive plates  26   a - 26   c.