Formulas Used

This design tool is based on the charts in IPC-2221.

First, the Area is calculated:

• Area[mils²] = ( Current[Amps] / (k*( Temp_Rise[°C] )^b) )^(1/c)

Then, the Width is calculated:

• Width[mils] = Area[mils²] / ( Thickness[oz] * 1.378[mils/oz] )

For IPC-2221 internal layers: k = 0.024, b = 0.44, c = 0.725

For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725

Note: k, b, and c are constants resulting from curve fitting to the IPC-2221 curves.

The IPC-2221(A) equations are different from those in IPC-D-275 in that they are more conservative and derated to compensate for manufacturing effects.

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