Abstract:
An anti-static module for a circuit board having a plurality of grounding traces comprises a copper region having a tip toward one of the grounding traces. Static electricity on the circuit board can be removed by discharging from the tip to the grounding trace, avoiding damage to the elements on the circuit board.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an anti-static module, and in particular relates to an anti-static module directing static electricity by point discharge. 
         [0003]    2. Description of the Related Art 
         [0004]    Static electricity may enter a circuit board from the exterior environment, for example by contacting with an interface of the circuit board. The static electricity accumulating on the circuit board can damage electronic elements thereon, for example, an IC chip can accept voltage of static electricity less than 2 kV. An anti-static element prevents the static electricity from accumulating on the circuit board. 
         [0005]    A typical anti-static element is a Zener diode. Referring to  FIG. 1 , a pad  40  for the Zener diode is formed on the circuit board. The region “A” in  FIG. 1  is an area for the Zener diode (not shown), through which four signal traces (the numeral  10 ) pass. Numeral  20  is a grounding trace, numeral  30  is a power trace and numeral  40  is pad for the Zener diode. The static electricity of the circuit board is directed to the grounding trace  30  to reduce the static electricity accumulating on the circuit board below the voltage limit of electronic elements. As the size of the circuit board is reduced, it is desired to use fewer electronic elements. 
       BRIEF SUMMARY OF INVENTION 
       [0006]    The invention provides an anti-static module in a circuit board without adding any external anti-static element. The anti-static module also cooperates with the Zener diode to enhance anti-static capability. 
         [0007]    An embodiment of an anti-static module of the invention comprises a copper region formed on a circuit board. The copper region comprises at least one tip toward one of the grounding traces on the circuit board, with an anti-static element is selectively disposed on the copper region. 
         [0008]    The tip is separated from the grounding trace by an appropriate distance, greater than or equal to the minimal distance between two traces formed during manufacture. 
         [0009]    When the anti-static element is disposed on the copper region, it connects the copper region and the grounding trace. The anti-static element can be a Zener diode. The copper region serves as a pad on which the anti-static element is disposed, whereby the anti-static element is connected to the circuit board. 
         [0010]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the office upon request and payment of the necessary fee. 
           [0012]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a layout diagram of a conventional circuit board; and 
           [0014]      FIG. 2  is a schematic view of a circuit board with anti-static module of the invention. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0015]    Referring to  FIG. 2 , a circuit board  1000  of the invention comprises a main body  500 , a plurality of signal traces  100 , a plurality of grounding traces  202 ,  204  and  206 , a power trace  300 , and a plurality of copper regions  602 ,  604 ,  606  and  608  formed on the main body  500 . The signal traces  100  are connected to the copper regions  602 ,  604 .  606  and  608  respectively. The power trace  300  is disposed between the upper copper regions  602  and  604 , and the grounding trace  206  is disposed between the lower copper regions  606  and  608 . Two grounding traces  202  and  204  are disposed between the upper copper regions and the lower copper regions. 
         [0016]    A triangular tip  6021  formed on the copper region  602  extends toward the grounding trace  202 . In this embodiment, a tip  2021  formed on the grounding trace  202  corresponds to the tip  6021 , which shortens the distance between the tip  6021  and the grounding trace  202 . Similarly, a tip  6041  formed on the copper region  604  extends toward the grounding trace  204 . A tip  2041  formed on the grounding trace  204  corresponds to the tip  6041 . 
         [0017]    Further, the grounding trace can have no tips, for example grounding trace  206 . The copper regions  606  and  608  have two tips  6061  and  6081 , respectively, toward the grounding trace  206 . As the tips  6061  and  6081  are close to the grounding trace  206 , no tips are needed on the grounding trace  206 . 
         [0018]    The tips on the copper region have potential difference from the grounding trace, whereby static electricity discharges from the tips to the grounding trace. The static electricity transmitted from exterior environment via the signal trace  100  to the circuit board  1000  discharges to the grounding traces  202 ,  204  and  206 . The amount, shape and positions of the tip are not limited, according to circuit design and layout. The distance between the tip to the grounding trace is as small as possible, but limited by the minimal distance between two traces formed during manufacture. Too small a distance may cause trace short. For the current technology, the minimal distance is 5 mil. 
         [0019]    The invention is applied to a main board (CAYMAN-RH) produced by GIGA-BYTE technology Co., LTD. Static electricity test is performed on the USB interface. For the circuit layout of  FIG. 1 , the voltage limit of the main board is 3.2 kV. For the circuit layout of  FIG. 2 , the voltage limit of the main board reaches 4 kV. 
         [0020]    In addition, for some circuit boards with high voltage limits, the Zener diode can be combined with the tips. In such a condition, the copper regions  602 ,  604 ,  606  and  608  and pads  400  can be served as pads for the Zener diode electrically connecting to the circuit board  1000 . Two pads  400  are connected to the power trace  300  and the grounding trace  206 . The combination of Zener diode and the tips raises the voltage limit to 9 kV. 
         [0021]    The tip can be formed on the pads for the Zener diode in certain circuit boards, thereby raising the voltage limit of the circuit board. The invention provides flexibility in anti-static design. Tips are added to the original circuit layout, which can reach the same voltage limit as the Zener diode used in conventional technology. The combination of the tips and the Zener diode can reach even higher voltage limit. 
         [0022]    In addition to the Zener diode, the invention can also be applied to the pads for anti-static element of Video chips or other I/O traces needed protection from static electricity. 
         [0023]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.