Description
Overview: This check determines the approximate analytic temperature rise of trace segments on a specified high current nets.
Passing Criteria: This check passes if less than a specified percentage of the length of traces within the high current net has a temperature rise below a given threshold.
Reporting Units: Length Percentage (Tolerance: Celsius)
Examples
Passing Message:
Trace length with excess temp rise (20°C) of 2.06% within acceptable range (0% to 10%)
Failing Message:
Trace length with excess temp rise (20°C) of 46.57% outside acceptable range (0% to 10%)
Physics Justification
Minimizing the temperature rise of high-current nets is important because:
Resistive Heating (Joule Heating)
High current through a trace causes I²R losses, where electrical resistance (R) converts current (I) into heat. Excessive heat can damage the PCB or nearby components.
Board performance
Increased temperature (T) raises the resistance of the trace (R∝T), causing more heat in a feedback loop, which can degrade signal integrity and power delivery.
Thermal Expansion
Heat causes the PCB material to expand, potentially leading to mechanical stress, delamination, or cracks in the copper traces.
Electromigration
High temperatures accelerate electromigration, where metal atoms move due to current flow, degrading the trace over time and potentially causing failure.
Helpful Definitions
Electromigration
The gradual movement of metal atoms within a conductor caused by the flow of high electrical current. This occurs because the momentum transfer from moving electrons pushes atoms along the current's path. Over time, it can create voids or buildup in the conductor, leading to increased resistance, or signal degradation.