PCB design for 40 Amps

[ronsimpson]

You can also get ceramic pads which conduct heat better. The thin plastic pads are just to electrically isolate and don't do anything good for heat conduction.

I have used ceramic but have problem with price and they are very brittle. Had breakage in the factory.
"Plastic Pads" I don't know what they are made of, but it is the same thing you find in your PC, on the CPU. The data sheet says it passes heat.
We moved to "plastic" transistors that are isolated. (no metal showing) That saved much labor.

 

[sagor1]

I just built a 13.8V power distribution PCB kit that is rated for 30A. Looking at the PCB, the traces are wide, of course, but every 1/2" to 1" along the PCB strip there are several Vias (like 3 or 4 across) between the top and bottom trace. I assume this is to equalize the currents between the two traces. Both +13.8V and GND traces are the same, double sided with Vias every so often throughout the path.
I assume this helps with things like stray currents or hot spots as well. Pads for the connectors (25A) quite large as well as they are basically through the double sided "strips".