Copper thickness and power loss

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engr_joni_ee

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Hello,

I have the following settings in the Sierra circuit tool.

Ambient temperature = 40 degC
Temperature rise = 20 degC
Conductor width = 80 mil
Trace = External

I have changed the conductor thickness from 0.5 oz to 2 oz.
The maximum current capacity increases from 3.1 A to 6.2 A.
The resistance at ambient decreases from 25.7 mOhm to 6.4 mOhm.
The resistance at high temperature also decreases from 27.6 mOhm to 6.7 mOhm.
All make sense but no changes in power loss at max temperature ?



 

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Why do you expect the power loss to change?

Most heat gets spread and dissipated by the PCB ... and the area where the copper meets the PCB does not change at all.

And due to the increased copper thickness the area copper-to-air just increases by 15% and (again) does not contribute much to heat spreading.
Especially at a temperature rise of 20°C the convectional air flow is almost zero.
And heat radiation is even more negligible.

So where do you consider the heat to go?

Klaus
 
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All the metals have a positive temperature coefficient so the resistance increases with temperature. The cost of 2 ounce copper is four times the cost of the board over half ounce copper.(in volume) So it may be more economical to use bus bars for power and ground distribution, but it depends on how much money you have.
 
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