Abstract:
A printed circuit board includes first and second layers, a control chip, bonding pads, and several electronic elements. The bonding pads can be selectively applied to interconnect the first and second layers, and the control chip with any of the electronic elements in a simple layout.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a printed circuit board (PCB). 
         [0003]    2. Description of Related Art 
         [0004]    PCBs can be found in most electronic devices and must be able to support transmission of high-speed differential signals. If high-speed differential signals are transmitted to at least three electronic elements, laying out signal lines of the PCBs becomes overly complicated and may lead to design flaws affecting performance of the PCBs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0006]      FIG. 1  is a schematic diagram of an exemplary embodiment of a printed circuit board connected to a first electronic element. 
           [0007]      FIG. 2  is similar to  FIG. 1 , but showing a second electronic element connected. 
           [0008]      FIG. 3  is similar to  FIG. 1 , but showing a third electronic element connected. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The disclosure, including the accompanying drawings, is illustrated by way of example and not by way of limitation. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         [0010]    Referring to  FIG. 1 , an exemplary embodiment of a printed circuit board (PCB)  100  includes a first signal layer  10 , a second signal layer  20 , an insulation layer (omitted to provide clear view of connections between layers  10  and  20 ) located between the first and second signal layers  10  and  20 , a pair of first vias  40 A and  40 B, a pair of second vias  41 A and  41 B, and a control chip  4 . The first vias  40 A and  40 B, and the second vias  41 A and  41 B extend through the first signal layer  10 , the insulation layer, and the second signal layer  20 . 
         [0011]    A pair of first bonding pads  11 A and  11 B and a pair of second bonding pads  12 A and  12 B are mounted on the first signal layer  10 , and electrically connected to the pair of first vias  40 A and  40 B, and the pair of second vias  41 A and  41 B. The second bonding pads  12 A and  12 B are connected to a first electronic element  1 . The first bonding pads  11 A and  11 B are connected to a second electronic element  2 . 
         [0012]    A pair of third bonding pads  23 A and  23 B, a pair of fourth bonding pads  24 A and  24 B, a pair of fifth bonding pads  25 A and  25 B, a pair of sixth bonding pads  26 A and  26 B, a pair of seventh bonding pad  27 A and  27 B, and a pair of eighth bonding pads  28 A and  28 B are mounted on the second signal layer  20 . The fourth bonding pads  24 A and  24 B are mounted between the third bonding pads  23 A and  23 B and the fifth bonding pads  25 A and  25 B. The third bonding pads  23 A and  23 B are connected to the second bonding pads  12 A and  12 B by the second vias  41 A and  41 B. The seventh bonding pads  27 A and  27 B are mounted between the sixth bonding pads  26 A and  26 B and the eighth bonding pads  28 A and  28 B. The seventh bonding pads  27 A and  27 B are connected to the fifth bonding pads  25 A and  25 B. The sixth bonding pads  26 A and  26 B are connected to the first bonding pads  11 A and  11 B by the first vias  40 A and  40 B. The fourth bonding pads  24 A and  24 B are connected to the control chip  4  for transmission of a pair of high-speed signals therethrough such as a pair of differential signals from the control chip  4 . The eighth bonding pads  28 A and  28 B are connected to a third electronic element  3 . 
         [0013]    When the control chip  4  transmits the pair of high speed signals to the first electronic element  1 , a first passive element  21  is used to connect the third bonding pads  23 A to the fourth bonding pad  24 A. A second passive element  22  is used to connect the third bonding pads  23 B to the fourth bonding pad  24 B. The control chip  4  outputs the pair of high-speed signals to the first electronic element  1  through the fourth bonding pads  24 A and  24 B, the first and second passive elements  21  and  22 , the third bonding pads  23 A and  23 B, the second vias  41 A and  41 B, and the second bonding pads  12 A and  12 B. 
         [0014]    Referring to  FIG. 2 , when the control chip  4  transmits the pair of high-speed signals to the second electronic element  2 , the first passive element  21  is used to connect the fourth bonding pads  24 A to the fifth bonding pad  25 A. The second passive element  22  is used to connect the fourth bonding pad  24 B and to the fifth bonding pad  25 B. A third passive element  31  is used to connect the sixth bonding pads  26 A to the seventh bonding pad  27 A. A fourth passive element  32  is used to connect the sixth bonding pads  26 B to the seventh bonding pad  27 B. The control chip  4  outputs the pair of high-speed signals to the second electronic element  2  through the fourth bonding pads  24 A and  24 B, the first and second passive elements  21  and  22 , the fifth bonding pads  25 A and  25 B, the seventh bonding pads  27 A and  27 B, the third and fourth passive elements  31  and  32 , the sixth bonding pads  26 A and  26 B, the first vias  40 A and  40 B, and the first bonding pads  11 A and  11 B. 
         [0015]    Referring to  FIG. 3 , when the control chip  4  transmits the pair of high-speed signals to the third electronic element  3 , the first passive element  21  is used to connect the fourth bonding pads  24 A to the fifth bonding pad  25 A. The second passive element  22  is used to connect the fourth bonding pads  24 B to the fifth bonding pad  25 B. The third passive element  31  is used to connect the seventh bonding pads  27 A to the eighth bonding pad  28 A. The fourth passive element  32  is used to connect the seventh bonding pads  27 B to the eighth bonding pad  28 B. The control chip  4  outputs the pair of high-speed signals to the third electronic element  3  through the fourth bonding pads  24 A and  24 B, the first and second passive elements  21  and  22 , the fifth bonding pads  25 A and  25 B, the seventh bonding pads  27 A and  27 B, the third and fourth passive elements  31  and  32 , and the eighth bonding pads  28 A and  28 B. In the embodiment, the first passive element  21  aligns with the second passive element  22 . The third passive element  31  aligns with the fourth passive element  32 . The first to fourth passive elements  21 ,  22 ,  31 , and  32  may be resistors. 
         [0016]    It is to be understood, however, that even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of the disclosure, the disclosure is illustrative only, and changes may be made in details, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.