Patent Publication Number: US-2023132991-A1

Title: Signal transmission device

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates to a technical filed of signal transmission, in particular to, a signal transmission device which improves a grounding structure design to effectively enhance signal transmission efficiency. 
     Related Art 
     A general signal transmission device includes a bus cable (for example, a PCIE bus, a SATA bus and other signal transmission cable used in computers) and connectors respectively arranged at both ends of the bus cable. The connector is electrically connected to the bus cable, and is connected to a corresponding connector of an external device (for example, the corresponding male or female connector), and the signal can be transmitted to the external device through the signal wires in the bus cable and through the connector. 
     Refer to  FIG.  1    and  FIG.  2    at the same time.  FIG.  1    is a plan view of a conventional bus cable, and  FIG.  2    is a cross-sectional view of A-A section of the conventional bus cable shown in  FIG.  1   . As shown in  FIG.  1    and  FIG.  2   , the conventional bus cable  9  is formed by sequentially stacking a conductor layer  91 , foam layer  92 , a metal layer  93  and an insulation layer  94 , and the conductor layer  91  comprises signal wires  911  and ground wires  912 . In the conventional manner, one of the ground wires  912  is arranged between the two adjacent signal wires  911 , and by repeating the above arrangement, the bus cable  9  is configured to have a specification width. For example, the bus cable  9  may have the specification width of 48 wires or 72 wires. 
     As mentioned above, since the conductor layer  91  of the bus cable  9  has the ground wires  912  and the bus cable  9  is under the limitation of the specification width, the width of the signal wire  911  is limited, which may decrease transmission speed. The structure of the bus cable  9  must be designed well, and that is the design should consider the skin effect and the characteristic impedance. 
     The skin effect is a phenomenon in which the current distribution inside the conductor (such as signal wire  911 ) is uneven when there is an alternating current or alternating electromagnetic field in the conductor. As the distance from the surface of the conductor gradually increases, the current density in the conductor becomes exponential decay, that is, the current in the conductor will be concentrated on the surface of the conductor. When viewed from a cross section perpendicular to the direction of the current, almost no current flows in the center of the conductor, and current flows only at the surface of the conductor. Simply speaking, the current is concentrated in the skin part of the conductor. Because the skin effect makes the alternating current only pass through the surface of the conductor, the current only produces a thermal effect on the surface of the conductor. For example, in the iron and steel industry, the skin effect can be used to quench the surface of steel to increase the hardness of the surface of the steel. The method of mitigating the skin effect can be, for example, the so-called litz wire, that is, multiple metal wires are twisted with each other so that the electromagnetic field can be more evenly distributed; or the solid wire can be replaced with a hollow wire tube, with insulating materials in the middle. 
     In addition, the aforementioned characteristic impedance refers to the resistance encountered when a high-frequency signal or electromagnetic wave propagates in a conductor, in ohms. The fluctuation difference of the impedance value in the conductor must be controlled so that the signal can be transmitted at the correct speed. For transmission lines formed by different types of conductors (such as coaxial transmission lines, linear transmission lines, micro-strip transmission lines, coplanar transmission lines, etc.), there will be different impedance calculation formulas. Different design conditions can be changed to achieve impedance control, such as changing the material, thickness, and dielectric coefficient of the foam layer in the transmission line. 
     In summary, under the above-mentioned principle, by setting different design conditions, the width of the signal wire  91  can be widened as a factor for the signal wire  911  to increase the transmission distance and transmission speed. In other words, the improvement of transmission efficiency is extremely important in today&#39;s technological development, so how to make the width of the conventional signal wire  911  under the condition of the specification width of bus cable  9  be widened to improve the transmission efficiency while still maintaining the grounding effect of the bus cable  9  is an urgent issue to be solved. 
     SUMMARY 
     In order to solve the above-mentioned problem of reduced transmission efficiency of the conventional signal transmission device due to the limitation of the specification width of the bus cable, the signal transmission device proposed in the present disclosure uses an improved grounding structure design to widen the width of the signal wire of the bus cable for signal transmission, and thus the signal transmission efficiency can be effectively improved. 
     The present disclosure provides a signal transmission device at least comprising a bus cable, at least a conductive part and a connection device. The bus cable is formed by sequentially stacking a conductor layer, a metal layer and an insulation layer. The conductor layer comprises a plurality of signal wires, each of the signal wires has a predetermined width, and each adjacent twos of the signal wires have a predetermined gap therebetween. The conductive part has a first contact terminal and a second contact terminal thereon, and the first contact terminal of the conductive part electrically contacts the metal layer. The connection device is electrically connected to the bus cable, and comprises a plurality of signal conduction wires and a plurality of ground wires. A number of the signal conduction wires is equal to a number of the signal wires, the signal conduction wires electrically contact the signal wires one by one. The ground wires electrically contact the conductive part, and the second contact terminal of the conductive part electrically contacts each of the ground wires. 
     As mentioned above, the signal transmission device proposed in the present disclosure is designed to electrically contact at least a conductive part directly with the metal layer of the bus cable, thereby as a grounding structure design. In other words, the conductor layer of the bus cable can only have the signal wire but have no ground wire. Therefore, even under the limitation of the specification width of the bus cable, the width of the signal wire can be widened, which can effectively improve the signal transmission efficiency. 
     Optionally, in a non-limited exemplary embodiment, the predetermined width is 0.4 mm through 1.0 mm. 
     Optionally, in a non-limited exemplary embodiment, the conductive part is a sheet shaped conductive adhesive, and the first contact terminal and the second contact terminal are opposite sides of the sheet shaped conductive adhesive. 
     Optionally, in a non-limited exemplary embodiment, the bus cable further comprises a dielectric layer with a low dielectric coefficient, and the dielectric layer with the low dielectric coefficient is stacked between the conductor layer and the metal layer, and material of the dielectric layer with the low dielectric coefficient is one of polypropylene (PP), polyethylene (PE), non-woven fabric and polytetrafluoroethylene (PTFE). 
     Optionally, in a non-limited exemplary embodiment, each of the signal conduction wires electrically contacts one of the signal wires via a connection part, such as a conductive adhesive. 
     Optionally, in a non-limited exemplary embodiment, a length of each of the signal conduction wires is larger than a length of each of the ground wires. 
     Optionally, in a non-limited exemplary embodiment, each of the signal conduction wires comprises a long rectangular body part and a rectangular head part connected to the long rectangular body part, wherein a width of the rectangular head part is large than a width of the long rectangular body part, and that is, the rectangular head part is expanded relative to the long rectangular body part in a horizontal axis direction. 
     Optionally, in a non-limited exemplary embodiment, the bus cable is a flexible flat cable (FFC). 
     The present disclosure provides a signal transmission device at least comprising a bus cable, conductive parts, a connector and a connection device. The bus cable is formed by sequentially stacking a conductor layer, a metal layer and an insulation layer, wherein the conductor layer comprises a plurality of signal wires, each of the signal wires has a predetermined width, and each adjacent twos of the signal wires have a predetermined gap therebetween. The connector comprises a top part and a bottom part connected to the top part. Each two of the conductive parts have a specific gap therebetween, the conductive parts are disposed between the top part and the bottom part, each of the conductive parts has a first contact terminal and a second contact terminal thereon, and the contact terminals of the conductive parts electrically contact the metal layer. The connection device is electrically connected to the bus cable, and comprises a plurality of signal conduction wires and a plurality of ground wires, wherein a number of the signal conduction wires is equal to a number of the signal wires, the signal conduction wires electrically contact the signal wires one by one, a number of the ground wires is equal to a number of the conductive parts, and the second contact terminals of the conductive parts electrically contact the ground wires one by one. 
     As mentioned above, optionally, in a non-limited exemplary embodiment, the predetermined width is 0.4 mm through 1.0 mm, the predetermined gap is 0.4 mm through 1.2 mm, and the specific gap is 0.2 mm through 2.7 mm. 
     Optionally, in a non-limited exemplary embodiment, at least one of the top part and the bottom part has a plurality grooves, each adjacent twos of them are disposed by an interval, a number of the grooves is equal to the number of the conductive parts, and each of the conductive parts is a rod-shaped conductive strip and disposed in corresponding one of the grooves. 
     Optionally, in a non-limited exemplary embodiment, the top part and the bottom part are rectangles, and one of the top part and the bottom part includes snaps at both ends thereof, other one of the top part and the bottom part includes slots at both ends thereof, and the snap and the corresponding slot are correspondingly engaged with each other. 
     Optionally, in anon-limited exemplary embodiment, the first contact terminal of each of the conductive parts is in a ridge shape the second contact terminal of each of the conductive parts is in an arc shape. 
     As mentioned above, optionally, in a non-limited exemplary embodiment, the bus cable further comprises a dielectric layer with a low dielectric coefficient, and the dielectric layer with the low dielectric coefficient is stacked between the conductor layer and the metal layer, and material of the dielectric laver with the low dielectric coefficient is one of polypropylene (PP), polyethylene (PE), non-woven fabric and polytetrafluoroethylene (PTFE) 
     As mentioned above, optionally, in a non-limited exemplary embodiment, each of the signal conduction wires electrically contacts one of the signal wires via a connection part, such as a conductive adhesive. 
     As mentioned above, optionally, in a non-limited exemplary embodiment a length of each of the signal conduction wires is larger than a length of each of the ground wires. 
     As mentioned above, optionally, in a non-limited exemplary embodiment, each of the signal conduction wires comprises a long rectangular body part and a rectangular head part connected to the long rectangular body part, wherein a width of the rectangular head part is large than a width of the long rectangular body part, and that is, the rectangular head part is expanded relative to the long rectangular body part in a horizontal axis direction. 
     As mentioned above, optionally, in a non-limited exemplary embodiment, the bus cable is a flexible flat cable (FFC). 
     As mentioned above, optionally, in a non-limited exemplary embodiment, the conductive parts are formed by an integrally formed conductive body, and the integrally formed conductive body is stamped to form the first contact terminals and the second contact terminals. 
    
    
     
       BRIEF DESCRIPTIONS OF DRAWINGS 
       Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. All of the drawings of the present disclosure are listed and briefly described as follows. 
         FIG.  1    is a plan view of a conventional bus cable. 
         FIG.  2    is across-sectional view of A-A section of the conventional bus cable shown in  FIG.  1   . 
         FIG.  3    is an explosive diagram of a signal transmission device according to a first embodiment of the present disclosure. 
         FIG.  4    is a cross-sectional view of the signal transmission device according to the first embodiment of the present disclosure. 
         FIG.  5    is a three-dimensional view of a signal transmission device according to a second embodiment of the present disclosure. 
         FIG.  6    is a three-dimensional view of the signal transmission device observed with another view angle according to the second embodiment of the present disclosure. 
         FIG.  7 A  is an explosive diagram of a signal transmission device according to the second embodiment of the present disclosure. 
         FIG.  7 B  is an explosive diagram of a signal transmission device with another kind of a conductive part according to another one embodiment of the present disclosure. 
         FIG.  8    is a cross-sectional view of the signal transmission device according to the second embodiment of the present disclosure. 
         FIG.  9    is a cross-sectional view of the signal transmission device according to a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTIONS OF EXEMPLARY EMBODIMENT 
     While embodiments are described herein by way of example for several embodiments and illustrative drawings, those skilled in the art will recognize that embodiments are not limited to the embodiments or drawings described. It should be understood that the drawings and detailed description thereto are not intended to limit embodiments to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope as defined by the appended claims. 
     Refer to  FIG.  3    and  FIG.  4    at the same time.  FIG.  3    is an explosive diagram of a signal transmission device according to a first embodiment of the present disclosure, and  FIG.  4    is a cross-sectional view of the signal transmission device according to the first embodiment of the present disclosure. The signal transmission device  1  is shown in  FIG.  3    and  FIG.  4   , and comprises a bus cable  2  and at least a conductive part  4 . 
     As shown in  FIG.  3    and  FIG.  4   , the bus cable  2  is formed by sequentially stacking a conductor layer  21 , a metal layer  22  and an insulation layer  23 , wherein the conductor layer  21  comprises a plurality of signal wires  211 , each of the signal wires  211  has a predetermined width W. and each adjacent twos of the signal wires  211  have a predetermined gap P therebetween. The conductive part  4  has a first contact terminal  41  and a second contact terminal  42  thereon, wherein the first contact terminal  41  of the conductive part  4  electrically contacts the metal layer  22  of the bus cable  2 . 
     Equation (I) is used to calculate a characteristic impedance value of the bus cable, and is cited as follows: 
     
       
         
           
             
               
                 
                   
                     
                       Z 
                       0 
                     
                     = 
                     
                       
                         60 
                         
                           
                             ε 
                             r 
                           
                         
                       
                       × 
                       
                         ln 
                         ( 
                         
                           
                             4 
                             ⁢ 
                             
                               ( 
                               
                                 
                                   2 
                                   ⁢ 
                                   H 
                                 
                                 + 
                                 T 
                               
                               ) 
                             
                           
                           
                             2.1 
                             
                               ( 
                               
                                 
                                   8 
                                   ⁢ 
                                   W 
                                 
                                 + 
                                 T 
                               
                               ) 
                             
                           
                         
                         ) 
                       
                     
                   
                   , 
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     I 
                     ) 
                   
                 
               
             
           
         
       
     
     wherein Z 0  is the value of the characteristic impedance, ε r  is a dielectric coefficient, W is the line width, and H is the height of the insulation layer, and T is the thickness of the conductive layer. In the above-mentioned bus cable  2 , if the bus cable  2  has the same thickness and the same dielectric coefficient, the wider the line width W of the signal wire is, the better the transmission efficiency is. In other words, in this case, because the bus cable  2  does not have the grounding structure, the line width W of the signal wire can be widened, and the transmission length of the bus cable  2  can be made longer, so that it can improve the transmission efficiency. 
     Regarding the description of the difference between the embodiment and the comparative example, according to Table 1, the comparative example 1 is a conventional bus cable with ground wire and signal wire, and the signal wire has a line width of 0.3 mm; in one embodiment of the present disclosure, there is no ground wire in the bus cable  2 , in addition, depending on the actual structure design needs, the predetermined width W of each of the plurality of signal wires  211  can be between 0.4 mm and 1.0 mm, the predetermined gap P between each twos of the plurality of signal wires  211  may be between 0.4 mm and 1.2 mm. Therefore, in the embodiments 1-4 of the present disclosure, under the premise of the same thickness and the same dielectric coefficient, when the line width W of the signal wire is widened, the transmission length can be made longer, thereby improving the transmission efficiency. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 bus cable/ 
                 line width 
                 transmission 
                 Possible maximum 
               
               
                 signal wire 
                 W(mm) 
                 speed(G/s) 
                 transmission length (M) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Embodiment 1 
                 0.4 
                 6 
                 1.0 
               
               
                 Embodiment 2 
                 0.5 
                 6 
                 2.0 
               
               
                 Embodiment 3 
                 0.6 
                 6 
                 2.5 
               
               
                 Embodiment 4 
                 0.7 
                 6 
                 3.0 
               
               
                 Comparative 
                 0.3 
                 6 
                 0.5 
               
               
                 Example 1 
               
               
                   
               
            
           
         
       
     
     Further, it can be known from  FIG.  3    and  FIG.  4    that the signal transmission device  1  in the embodiment further comprises a connection device  5 . In the embodiment of the present disclosure, the connection device  5  is a circuit board, and the connection device  5  is electrically connected to the bus cable  2 . The connection device  5  includes a plurality of signal conduction wires  51  and a plurality of ground wires  52 . Among them, the number of the plurality of signal conduction wires  51  is equal to the number of the plurality of signal wires  211  of the conductor layer  21  of the bus cable  2 , and the signal conduction wires  51  electrically contact signal wires  211  one by one. That is, one signal conduction wire  51  and corresponding one signal wire  211  are in electrical contact, for example, through a connection part  61 . In a preferred embodiment of the present disclosure, the connection part  61  is preferably solder or conductive adhesive, and the connection part  61  is used for conducting the signal conduction wire  51  and the signal wire  211 . In addition, the number of the ground wires  52  is equal to the conductive part  4 , and the ground wires  52  electrically contact the corresponding conductive parts  4 . The second contact terminals  42  of the conductive parts  4  electrically contact the ground wires  52  one by one. The connection device  5  can be one of a circuit board, a connector, and so on. 
     In this embodiment, the length of each of the plurality of signal conduction wires  51  of the connection device  5  is greater than the length of each of the plurality of ground wires  52 , and the difference in length can form an easily recognizable effect. In addition, in this embodiment, each of the plurality of signal conduction wires  51  of the connection device  5  includes a long rectangular body part  511  and a rectangular head part  512 , and both of them connected to each other. A width of the rectangular head part  512  is large than a width of the long rectangular body part  511 , and that is, the rectangular head part is expanded relative to the long rectangular body part in a horizontal axis direction. The larger area of the rectangular head part  512  of the signal conduction wire  51  can easily make electrical contact with the connection part  61  to electrically contact the signal wire  211 . In another embodiment of the present disclosure, each of the plurality of ground wires  52  of the connection device  5  includes a ground terminal  521  connected to each other, and each of the ground terminals is connected to each other with a ground plane  522 . The ground plane  522  and the second contact terminal  42  of the conductive part  4  are in electrical contact, and the first contact terminal  41  of the conductive part  4  is in electrical contact with the metal layer  22  of the bus cable  2  to achieve a ground connection state. 
     As shown in  FIG.  3    and  FIG.  4   , the conductive part  4  is a sheet shaped conductive adhesive (a rectangular sheet as shown in the drawings) in this embodiment, and the first contact terminal  41  and the second contact terminal  42  are the opposite sides of sheet shaped conductive adhesive. The aforementioned conductive part  4  is in the form of a sheet shaped conductive adhesive in this embodiment, but other methods may also be used, such as soldering with metal shrapnel or solder (i.e. the solder forms the conductive part). 
     It can be seen from the above that the grounding structure design of the bus cable  2  is directly formed based on the metal layer  22 , that is, the grounding structure design is formed by electrically contacting the metal layer  22  of the bus cable  2  and the ground wires  52  of the connection device  5  through the conductive parts  4 , respectively. The conductor layer  21  of bus cable  2  can only have the signal wires  211  without the need to set ground wires as in the prior art. On the other hand, without affecting the specification width of the bus cable  2 , the signal wires  211  can have more space to widen the width of the signal wires  211 , and therefore effectively achieve the purpose of improving signal transmission efficiency. 
     In this embodiment, the above-mentioned bus cable  2  is a flexible flat cable (FFC), of course, but it is not limited to this. For example, the bus cable  2  may also be a flexible printed circuitry (FPC). In addition, the bus cable  2  may further include a dielectric layer  24  with a low dielectric coefficient, the dielectric layer  24  with a low dielectric coefficient is laminated between the conductor layer  21  and the metal layer  22 , and the material of the dielectric layer  24  with the low dielectric coefficient may be poly One of propylene (PP), polyethylene (PE), non-woven fabric or polytetrafluoroethylene (PTFE). In the manufacture of the bus cable  2 , the bus cable  2  can also include a film layer or a glue layer, for example, the film layer can be made of PET. 
     Refer to  FIG.  5    through  FIG.  9    at the same time,  FIG.  5    is a three-dimensional view of a signal transmission device according to a second embodiment of the present disclosure,  FIG.  6    is a three-dimensional view of the signal transmission device observed with another view angle according to the second embodiment of the present disclosure,  FIG.  7 A  is an explosive diagram of a signal transmission device according to the second embodiment of the present disclosure,  FIG.  7 B  is an explosive diagram of a signal transmission device with another kind of a conductive part according to another one embodiment of the present disclosure.  FIG.  8    is a cross-sectional view of the signal transmission device according to the second embodiment of the present disclosure, and  FIG.  9    is a cross-sectional view of the signal transmission device according to a third embodiment of the present disclosure. 
     In this embodiment, the main structure is the same as the first embodiment, except that the signal transmission device  1  further includes a connector  3 , and the connector  3  includes a top part  31  and a bottom part  32  that are joined to each other. Each of the plurality of conductive parts  4  is a rod-shaped conductive strip and is disposed between the top part  31  and the bottom part  32 . 
     Similarly, the connection device  5  is electrically connected to the bus cable  2 , and the connection device  5  includes a plurality of signal conduction wires  51  and a plurality of ground wires  52 , wherein the number of the plurality of signal conduction wires  51  is equal to the number of the plurality of signal wires  211 , and the signal conduction wires  51  are in electrical contact with the signal wires  211  one by one. The number of the ground wires  52  is equal to the number of the conductive parts  4 , and the second contact terminals  42  of the conductive parts  4  are in electrical contact with the ground wires  52  one by one. 
     Like the first embodiment described above, this embodiment uses a conductive part  4  in the form of a rod-shaped conductive strip to electrically contact the metal layer  22  of the bus cable  2  and the ground wires  52  of the connection device  5  to achieve the grounding effect. Similarly, the bus cable  2  does not need to have a ground wire set thereof, so that the width of the signal wire  211  of the bus cable  2  can be widened, thereby achieving the purpose of effectively improving the transmission efficiency. 
     In the embodiment, the top part  31  includes a plurality of grooves  310  arranged at intervals (of course, a plurality of grooves  310  may also be arranged at intervals of each other in the bottom part  32 , or at the same time as the top part  31  and the bottom part  32 ). The number of the plurality of grooves  310  is equal to the number of the plurality of conductive parts  4 , and each of the plurality of conductive parts  4  corresponds to one of the plurality of grooves  310 , that is, one conductive part  4  is corresponding to one groove  310 . For example, the conductive part  4  can be inserted in a tight-fitting manner to set on the groove  310  to prevent it from falling. 
     In this embodiment, the top part  31  and the bottom part  32  are respectively elongated rectangles, and the top part  31  (or bottom part  32 ) includes snaps  311  at both ends, and the bottom part  32  (or top part  31 ) includes slots  321  at both ends. The snap  311  and the corresponding slot  321  are engaged with each other. Of course, the joining method of the top part  31  and the bottom part  32  is not used to limit the present disclosure, for example, screw locking, bolting, or bonding may also be used. 
     In order to make it easier for the plurality of conductive parts  4  to electrically contact the metal layer  22  of the bus cable  2  and the ground wires  52  of the connection device  5 , in this embodiment, the first contact terminal  41  of each of the plurality of conductive parts  4  is in a ridge shape, the second contact terminal  42  of each of the plurality of conductive parts  4  is in an arc shape. In other words, the ridge-shaped and arc-shaped structure design can make the first contact terminal  41  and the second contact terminal  42  form protruding points, which can make electrical contact with the metal layer  22  of the bus cable  2  and the ground wire  52  of the connection device  5  more conveniently. Of course, the shapes of the first contact terminals  41  and the second contact terminals  42  of the plurality of conductive parts  4  are not limited to the aforementioned ones, and other shapes are also possible, such as a pointed shape, a polygonal shape, and the like. As shown in  FIG.  7 B , in another embodiment of the present disclosure, the plurality of conductive parts  4  are formed by an integrally formed conductive body (not shown in the drawings), and the integrally formed conductive body is stamped to form the first contact terminals  41  and the second contact terminals  42 ; accordingly. Thus, the conductive body after stamping can be directly formed on the top part  31  or the bottom part  32  of the connector  3 . 
     Please refer to  FIG.  9    again. In another embodiment of the present disclosure, the signal transmission device is composed of two bus cables  2 , a connection device  5 , and a connector  3 . The connection device  5  is a double-sided connection device, and the two surfaces of the double-sided connection device are electrically connected to a structure of the bus cable  2 , wherein in both of the up and down directions the bus cable  2  is formed by sequentially stacked a conductor layer  21 , a metal layer  22 , and an insulation laver  23 . The conductor layer  21  includes a plurality of signal wires  211 . Each of the plurality of signal wires  211  has a predetermined width W, and each adjacent twos of the plurality of signal wires  211  is separated from each other by a predetermined gap P. 
     Various modifications and changes may be made as would be obvious to a person skilled in the art having the benefit of this disclosure. It is intended to embrace all such modifications and changes and, accordingly, the above descriptions to be regarded in an illustrative rather than a restrictive sense.