UltraCAD Design, Inc
 

PCB Trace Calculator

 

UltraCAD's newest PCB Trace Calculator makes a variety of calculations related to PCB traces, including trace current/temperature, fusing current, skin effect impacts, and simple Ohm's Law calculations. This new version incorporates data from the latest IPC standard, IPC-2152 "Standard for Determining Current Carrying Capacity in Printed Board Designs." The four major calculational functions of the calculator are illustrated in the screen shots that follow.

Users now have the option of 5 different data sources for trace current/temperature calculations. The first three are the new IPC standards for internal and external traces in still air, and traces in a vacuum. A fourth is the old (now obsolete) IPC-D-275 standard. Although obsolete, this standard has been used for over 50 years and many engineers feel that is has withstood the test of time. The final source is data Doug found in a Design News article from 1968. The new IPC data is the most conservative; the old IPC data is the most aggressive.

The new IPC standard states that there is little difference between the trace heating/cooling relationships for internal and external traces, a significant departure from past thinking.

Look at our article section on Trace Current/Temperature/Power/Resistance   to locate articles on these topics.

This calculator requires a license to purchase and run. It is NOT backward compatible with the previous version of the calculator; a new license is required. However, holders of a previous license can purchase a new license at a significant discount. Click here to learn more about how to acquire a license. The license fee is $200 USD for a new license, $50 USD for holders of existing licenses.

Click Here to acquire a license.

Click here to download the calculator itself.

Click here for a copy of the Operator's Manual.

 

    

 

This is the main calculator screen. It illustrates trace current/temperature calculations for a 250 mil wide, 1 Oz trace. The crossover frequency for this trace dimension is 14.81 MHz. At a frequency of 18 MHz the skin depth is .6128 mils, reducing the effective cross-sectional area of the trace to 90.785% of its nominal value. If this trace carries 15 Amps at this frequency, the trace's temperature would increase 62.08 degrees C. based on the IPC-2152 standard for an internal trace in still air.

  
     
   
  Version 3.2 of the calculator now has provision for making some modifications to the results based on suggestions in the Appendix of IPC-2152. These suggestions are primarily contained in Sections A.4.2 and A.4.6. For example, assuming the trace above is 10 mils above a plane, the board is more than 25 in^2 in area, and the board is 65 mils thick, the adjustments show that the actual temperature will be only 20 oC. On the other hand, if we entered 182 oC in the Temp CHANGE box above, the resulting trace width would only be 94 mils for a 60 oC modified temperature rise. See the Operator's Manual for more details about these adjustments. (Credit Jack Olson for pushing me to incorporate these adjustments into the calcuilator.)  
     

 

If we wanted to know how long this trace would last before it melted (fused) carrying 60 Amps, the calculator tells us .92 seconds (just under one second). The Skin Effect is limiting this result. At a lower frequency, the trace would last a little longer.

  
     

 

The calculator, then can tell us what the resistance of this trace is at ambient and at operating temperatures, based on the trace geometries above. These values can be adjusted for Skin Effect.

  
     

 

Finally, the calculator can perform basic algebraic and Ohm's Law calculations related to the trace. These calculations are not impacted by the skin Effect entries, above. Those effects are inherent in the data entered in this section.

  
     
     


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