Patent Publication Number: US-2009240450-A1

Title: System and method for evaluating a temperature rise of a printed circuit board trace

Description:
FIELD OF THE INVENTION 
     Embodiments of the present disclosure relate to a system and method for analyzing printed circuit board (PCB) traces, and more particularly to a system and method for evaluating a temperature rise of a PCB trace. 
     DESCRIPTION OF RELATED ART 
     A printed circuit board (PCB) provides mechanical support and electrical connections between electronic components using traces. A temperature rise of a PCB trace may occur when a current passes through the PCB trace. The temperature rise of the PCB trace is critical because an excessive temperature rise may cause the PCB to become unstable and unreliable. Therefore, it is required for a designer to evaluate the temperature rise of a PCB trace before PCB layout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of one embodiment of a system for evaluating a temperature rise of a PCB trace. 
         FIG. 2  is a block diagram of one embodiment of a temperature rise calculator comprising function modules. 
         FIG. 3  is a flowchart of one embodiment of a method for evaluating a temperature rise of a PCB trace. 
         FIG. 4  illustrates one embodiment of relationship curves depicting a relationship between a trace current and a trace width. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS 
     All of the processes described below may be embodied in, and fully automated via, functional code modules executed by one or more general purpose computers or processors. The code modules may be stored in any type of computer-readable medium or other computer storage device. Some or all of the methods may alternatively be embodied in specialized computer hardware. 
       FIG. 1  is a block diagram of one embodiment of a system  1  for evaluating a temperature rise of a printed circuit board (PCB) trace. The system  1  may be used to calculate the temperature rise of the PCB trace quickly and accurately. In one embodiment, the system  1  includes a computing device  10 , and a memory  13  connected to the computing device  10 . Examples of the computing device  10  include personal computer systems, such as desktop or laptop computers, and personal digital assistants (PDAs). The computing device  10  includes a temperature rise calculator  11 . The memory  13  stores program instructions of the temperature rise calculator  11 , and stores data that are used, processed, and obtained while the temperature rise of the PCB trace is calculated. The computing device  10  may be further connected to at least one input device  14  and at least one output device  15 . The input device  14  may be a keyboard or a mouse. The output device  15  may be a monitor or a printer. 
     The temperature rise calculator  11  is configured for receiving a plurality of attribute parameters of the PCB trace from the input device  14 , and determining a temperature rise formula according to the attribute parameters. The temperature rise calculator  11  is further configured for calculating the temperature rise of the PCB trace by applying the temperature rise formula. In one embodiment, the computing device  10  may comprise one or more processors, such a processor  12 , to control the temperature rise calculator  11  to perform corresponding operations for calculating the temperature rise of the PCB trace. 
       FIG. 2  is a block diagram of one embodiment of the temperature rise calculator  11  comprising function modules. In one embodiment, the temperature rise calculator  11  may include a receiving module  210 , a determining module  220 , a calculating module  230 , an outputting module  240 , and a plotting module  250 . The processor  12  may be used to execute one or more operations for the receiving module  210 , the determining module  220 , the calculating module  230 , the outputting module  240 , and the plotting module  250 . 
     The receiving module  210  is configured for receiving the attribute parameters of the PCB trace. The attribute parameters may include a trace layer, a trace width (W), a trace thickness (Th), and a trace current (I). The trace layer denotes where the PCB trace is located. The trace layer may be an internal layer or an external layer of the PCB. It may be understood that a PCB trace in an internal layer of the PCB may cause a greater temperature rise than another PCB trace in an external layer of the PCB under a same condition. The trace current denotes a current value of the PCB trace. It may be understood that a cross-sectional area (A) of the PCB trace is the product of the trace width and the trace thickness, i.e. A=W×Th. A current density (J) of the PCB trace is the quotient of the trace current and the cross-sectional area, i.e. J=I/A. 
     The determining module  220  is configured for determining a temperature rise formula to calculate the temperature rise (ΔT) of the PCB trace according to the trace layer. In one embodiment, where the trace current I of the PCB trace is received, the determining module  220  may determine the temperature rise formula as 
     
       
         
           
             
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     if the trace layer is an external layer, and determine the temperature rise formula as 
     
       
         
           
             
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     if the trace layer is an internal layer. 
     In another embodiment, where the current density J of the PCB trace is received, the determining module  220  may determine the temperature rise formula as 
     
       
         
           
             
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     if the trace layer is an external layer, and determine the temperature rise formula as 
     
       
         
           
             
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     if the trace layer is an internal layer. 
     The calculating module  230  is configured for calculating the temperature rise of the PCB trace by applying the temperature rise formula. In one embodiment, the calculating module  230  is further configured for calculating a resistance (R) and a voltage drop (V) of the PCB trace according to the temperature rise, the trace width, the trace thickness, and the trace current of the PCB trace. In one embodiment, the calculating module  230  calculates the resistance and the voltage drop of the PCB trace by applying formulas 
     
       
         
           
             
               R 
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     and V=I×R, wherein T is an ambient temperature of an environment surrounding the PCB, and TL is a trace length of the trace. 
     The outputting module  240  is configured for outputting the temperature rise of the PCB trace to the output device  15 . 
     The plotting module  250  is configured for plotting a relationship curve for the temperature rise of the PCB trace. The plotting module  250  may plot the relationship curve to depict a relationship between the trace current and the trace width. In one embodiment, the calculating module  230  may calculate different temperature rises of the PCB trace based on different trace currents and trace widths. Accordingly, the plotting module  250  may plot more than one relationship curve for the different temperature rises of the PCB trace. 
       FIG. 3  is a flowchart of one embodiment of a method for evaluating a temperature rise of a PCB trace by implementing the system of  FIG. 1 . The method may be used to calculate a temperature rise of a PCB trace quickly and accurately. Depending on the embodiments, additional blocks may be added, others removed, and the ordering of the blocks may be changed. 
     In block  301 , the receiving module  210  receives a plurality of attribute parameters of the PCB trace from the input device  14 . In one embodiment, the attribute parameters include a trace layer, a trace width (W), a trace thickness (Th), and a trace current (I). In one embodiment, the temperature rise calculator  11  provides a user interface to receive the attribute parameters. For example, four input boxes are used in the user interface to respectively receive the trace layer, the trace width, the trace thickness, and the trace current. The trace layer may be an internal layer or an external layer. A cross-sectional area (A) of the PCB trace is the product of the trace width and the trace thickness, i.e. A=W×Th. A current density (J) of the PCB trace is the quotient of the trace current and the cross-sectional area, i.e. J=I/A. 
     In block  302 , the determining module  220  determines a temperature rise formula to calculate a temperature rise (ΔT) of the PCB trace according to the trace layer. In one example, the trace layer is an internal layer. Accordingly, the determining module  220  determines the temperature rise formula as 
     
       
         
           
             
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               T 
             
             = 
             
               
                 
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                         0.6732 
                       
                     
                   
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                   1 
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     In another example, the trace layer is an external layer. Accordingly, the determining module  220  determines the temperature rise formula as 
     
       
         
           
             
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               T 
             
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                         0.7349 
                       
                     
                   
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               . 
             
           
         
       
     
     In block  303 , the calculating module  230  calculates the temperature rise of the PCB trace by applying the temperature rise formula. For example, the calculating module  230  calculates the temperature rise by applying the temperature rise formula 
     
       
         
           
             
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                       0.6732 
                     
                   
                 
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                 1 
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     when the trace layer is an internal layer. 
     In block  304 , the calculating module  230  calculates a resistance (R) and a voltage drop (V) of the PCB trace according to the temperature rise of the PCB trace, the trace width, the trace thickness, and the trace current. In one embodiment, the calculating module  230  calculates the resistance and the voltage drop of the PCB trace by applying formulas 
     
       
         
           
             
               R 
               = 
               
                 
                   TL 
                   × 
                   
                     ( 
                     
                       0.6255 
                       + 
                       
                         0.00267 
                         × 
                         
                           ( 
                           
                             T 
                             + 
                             
                               Δ 
                                
                               
                                   
                               
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                               T 
                             
                           
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                   W 
                   × 
                   Th 
                 
               
             
             , 
           
         
       
     
     and V=I×R, wherein T is an ambient temperature, and TL is a trace length. 
     In block  305 , the outputting module  240  outputs the temperature rise, the resistance, and the voltage drop of the PCB trace to the output device  15 , such as a monitor. In one embodiment, the outputting module  240  outputs the temperature rise, the resistance, and the voltage drop of the PCB trace via the user interface. 
     In block  306 , the plotting module  250  plots a relationship curve for the temperature rise of the PCB trace. The plotting module  250  may plot a relationship curve to depict a relationship between the trace current and the trace width. 
     In one embodiment, the calculating module  230  may calculate different temperature rises of the PCB trace based on different trace currents and trace widths. Accordingly, the plotting module  250  may plot more than one relationship curve for the different temperature rises of the PCB trace. In another embodiment, the plotting module  250  may plot several relationship curves depicting a relationship between the trace current and the trace width for several given temperature rises of the PCB trace. In an example, with reference to  FIG. 4 , the plotting module  250  respectively plots three relationship curves for 20° C., 30° C., and 50° C. temperature rises of the PCB trace. 
     Although certain inventive embodiments of the present disclosure have been specifically described, the present disclosure is not to be construed as being limited thereto. Various changes or modifications may be made to the present disclosure without departing from the scope and spirit of the present disclosure.