Abstract:
A printed circuit board capable of resisting electrostatic discharge and a routing method of the one or multi-layer printed circuit board are disclosed. The routing method includes planning a first routing area, planning a second routing area apart from the first routing area for a predetermined distance at least, and connecting an attenuating component between the first routing area and the second routing area for attenuating an impulse generated by electrostatic discharge in order to prevent the impulse spreading to the second routing area from the first routing area.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a printed circuit board and a related routing method, and more particularly, to a printed circuit board capable of resisting electrostatic discharge and a related routing method.  
         [0003]     2. Description of the Prior Art  
         [0004]     To improve the reliability of electronic products available on the market, before a product can be sold officially it must pass several kinds of safety tests to obtain a serial number that represents the product meets safety requirements. Every country, no matter whether in Europe, America, or Asia, has their own safety standards. For example, some common safety standards tests are Electro Magnetic Interference (EMI) test, Electro Magnetic Susceptibility (EMS) test, and Electrostatic Discharge (ESD) test.  
         [0005]     The electrostatic discharge test simulates the effects of static electricity moving from the human body or portable tools to the electronic product to be tested. According to the standard IEC61000-4-2, the test methods are divided into 1) air discharge method and 2) contact discharge method. The air discharge method comprises moving an ESD simulator toward the isolating surface of the tested product, utilizing the ESD simulator to discharge on the isolating surface with a test voltage between 2-15 kV, and letting the ESD simulator touch a test point on the electronic product after discharging, so as to spread a current to the tested product. The contact discharge method comprises letting the ESD simulator touch the test point, and utilizing the ESD simulator to discharge on the test point. The test point of the contact discharge method may be a screw, a visible connector, or any visible metal part of the tested product. The test voltage of the contact discharge method is 2-8 kV.  
         [0006]     To alleviate the damage caused by the air discharging, the shell of the tested product is made from an electric conductive compound material. The electric conductive compound material is an isolated plastic material mixed with conductive material to achieve the objectives of conductivity and prevention of electrostatic discharge. Common conductive materials are carbon powder, carbon fiber, metal fiber, and metal powder. Therefore, the electric conductive compound material will not generate a lot of static electricity, and will eliminate the stored static electricity before the stored static electricity can cause damage.  
         [0007]     The method for preventing contact discharge is more complex than the method for preventing air discharge, because the static electricity will spread to the printed circuit board from the visible I/O connector, such as a power jack. If there is no protective circuit to guide the static electricity to the ground terminal of the I/O connector, the static electricity may break the IC on the printed circuit board and cause irreparable damage to the electronic product.  
       SUMMARY OF THE INVENTION  
       [0008]     It is therefore an objective of the claimed invention to provide a printed circuit board capable of resisting electrostatic discharge, and a related routing method to reduce the damage caused by the electrostatic discharge to the electronic product.  
         [0009]     According to the claimed invention, a routing method capable of resisting an electrostatic discharge applied in a printed circuit board is disclosed. The routing method comprises: planning a first routing area; planning a second routing area, wherein the distance between the first routing area and the second routing area is not smaller than a predetermined distance; and connecting an attenuating component between the first routing area and the second routing area, wherein the attenuating component is utilized to attenuate a pulse generated by electrostatic discharge, in order to prevent the impulse spreading to the second routing area from the first routing area.  
         [0010]     According to the claimed invention, a printed circuit board capable of resisting an electrostatic discharge is disclosed. The printed circuit board comprises: a first routing area, for routing an I/O connector; a second routing area, for routing an electronic component on the printed circuit board, wherein the distance between the first routing area and the second routing area is not smaller than a predetermined distance; and an attenuating component, electrically connected between the first routing area and the second routing area, for attenuating a pulse generated by an electrostatic discharge, and for preventing the pulse being transmitted to the second routing area from the first routing area.  
         [0011]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic diagram of the printed circuit board according to a preferred embodiment of the present invention.  
         [0013]      FIG. 2  is a flow chart of the routing method capable of resisting the electrostatic discharge according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]     Please refer to  FIG. 1 .  FIG. 1  is a schematic diagram of the printed circuit board  10  according to a preferred embodiment of the present invention. The printed circuit board  10  is a single- or multi-layer printed circuit board, and includes a plurality of routing areas  20 ,  40 , a gap (i.e., the area where metal is absent)  60 , and a attenuating component  80 . The routing areas  20 ,  40  are located on the same layout layer according to the present embodiment. A conductive metal layer (i.e., the area with oblique lines)  22  and an I/O connector  24  are placed on the routing area  20 . The I/O connector  24  is utilized to connect an outside device of the one or multi-layer printed circuit board  10 . A conductive metal layer (area with oblique lines)  42 , a plurality of ICs  44 ,  46 , and a plurality of printed wires  48 ,  52  are placed at the routing area  40 . The printed wires  48  and  52  are utilized to connect the ICs  44  and  46 . In the present embodiment, the conductive metal layers  22 ,  42  correspond to a copper pour area of the printed circuit board  10  for proving a ground terminal to all devices on the printed circuit board  10 . The copper pour area is separate from the printed wires  48 ,  52  and the pads of the ICs  44 , 46  in order to avoid generating a short circuit. Since the method of copper pouring is well known to those skilled in the art, the description of copper pouring is omitted for the sake of brevity. Please note that every ground pin and shielding pin of the ICs  44 ,  46  or the I/O connector  24  is connected to the conductive metal layer  22  or  42 .  
         [0015]     Gap  60  separates the routing areas  20  and  40 . In the present embodiment, the minimum width of the gap  60  is 1.25 mm, and the I/O connector  24  is a power jack or an earpiece jack. When performing the electrostatic discharge test, the static electricity may spread to the conductive metal layer  22  from the ground pin or shielding pin of the I/O connector  24 . Since the gap  60  separates the conductive metal layers  22 ,  42 , the static electricity will not spread to the conductive metal layer  42  from the conductive metal layer  22 . As a result, the ICs  44 ,  46  located on the routing area  40  are protected by the gap  60 . Please note that the minimum width of the gap corresponds to the material, thickness, and other characteristics of the printed circuit board  10 , and is not limited to the present embodiment. When the width of the gap  60  is not wide enough, the static electricity may discharge to the conductive metal layer  42  from a peak of the conductive metal layer  22 .  
         [0016]     However, if the ground terminals of the routing areas  20 ,  40  are not connected to each other, the ground voltages of the routing areas  20 ,  40  may float. Therefore an attenuating component  80  is utilized to connect the conductive metal layers  22 ,  42  to equalize the DC voltages of the conductive metal layer  22 ,  42  and to attenuate a pulse pass through the attenuating component  80 . Please note that the immediately occurring static electricity is treated as a pulse, and includes a plurality of high-frequency signals in the view of the frequency spectrum. Hence, when the routing area  20  experiences a pulse, the largest part of the pulse cannot pass through the attenuating component  80  and therefore cannot arrive at the routing area  40 . Even when a smaller part of the pulse signal passes through the attenuating component  80  and arrives at the routing area  40 , the effect of the passed signal is very weak.  
         [0017]     In the present embodiment, the attenuating component  80  is a printed wire whose maximum wire width is 0.1 mm, because the thinner wire is an equivalent inductor to the high-frequency signals. As a result, the printed wire is capable of preventing the high-frequency signals from passing through. Pleas note that the maximum wire width of the printed wire corresponds to the material, thickness, and other characteristics of the printed circuit board  10 , and is not limited to the present embodiment. In addition, the attenuating component  80  may be a copper wire, a zero ohm resister, a real inductor, or other components capable of attenuating high-frequency signal according to the present invention.  
         [0018]     Please refer to  FIG. 2 .  FIG. 2  is a flow chart of the routing method capable of resisting the electrostatic discharge according to a preferred embodiment of the present invention. The routing method includes the following steps.  
         [0019]     Step  100 : start.  
         [0020]     Step  102 : divide a plurality of components into a group of I/O connectors and a group of the other components.  
         [0021]     Step  104 : plan a first routing area and a second routing area on a single- or multi-layer printed circuit board, wherein the distance between the first routing area and the second routing area is not smaller than a predetermined distance.  
         [0022]     Step  106 : place the I/O connectors in the first routing area, place the other components in the second routing area, and rout the I/O connectors and the other components.  
         [0023]     Step  108 : place a conductive metal layer on the first routing area and place a conductive metal layer on the second routing area, where the conductive metal layers are utilized as ground terminals.  
         [0024]     Step  110 : connect an attenuating component between the conductive metal layer on the first routing area and the conductive metal layer on the second routing area.  
         [0025]     Step  112 : end.  
         [0026]     Please note that the predetermined distance mentioned in step  104  is the minimum width of the gap  60  shown in  FIG. 1 .  
         [0027]     In summary, the present invention provides a gap to separate more than two routing areas of the single- or multi-layer printed circuit board. The I/O connectors shown in the outward appearance of a product are placed in a different routing area to the routing area for placing the other components, so as to prevent the other components from being influenced by the electrostatic discharge coming from the I/O connectors. In addition, an attenuating component is utilized to connect the ground terminals of different routing areas according to the present invention, in order to prevent the ground voltages from floating. Since the attenuating component utilized in the present invention is very cheap and easily obtained, the cost of manufacturing is significantly reduced.  
         [0028]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.