High current trace

Hi @Naib, I recognized that Ninja-calc accepts the currents up to 25 amperes, what about the current of 80 amperes?

This book is a fabulous resource and the best I’ve found. It’s expensive but worth every penny:



@JuliaTruchsess thank you so much for your help, I really appreciate it!!!

It would be nice to know what you are moving - DC? Continuous AC? Surges? but i’ve been thee before - not continuous 70 amps, but surges, yes. Since traces are flat, you ought to be reasonably close if you either a) make them proportionaltely wider, or proportionally thicker. Most PCB houses can do 1,2,3,4,… oz copper. Doubling it doubles the thickness, which for constant resistivity, cuts the resistance and heat generation per unit by half.

I certainly hope these are kept short.

Are you an EE?

When in doubt, pull out CRC handbook and do some math.


1 Like

Thank you for your advice. I really appreciate it! I am moving DC current and AC current

that does not tell me much! You really need to explain what you are doing if you want more help. Again, are you an EE? Best of luck.

I am designing two buck converters that can deliver respectively 35A and 52A. Then I connect them to an output.
I am EE

OK, so you really could see a high duty cycle of 35/52A on those traces. Back to fundamentals. resistivity is (inversely) proportional to cross section. Cross section is proportional to width. The rest is noise. I would do my best to keep them short. resistance is proportional to length. But also keep in mind the trick of thicker copper. I did that on all my hgih current power supply boards. Note this was back int he day, and the day was the 1980s and 1990s!

Electrons’ behaviour has not changed a lot from those days. So everything you took in account about currents and cross sections is still valid today :wink:

I am learning a lot with this thread. I used to make the control circuitry (miliamperes and megahertzs) and now I am dealing with converters, high currents from 3A to 150A and kilohertzs.

1 Like

Yep, this is truly the fundamentals: one part ohms law and one part materials science.

Hi @pedro, Could you give me some advice about high current converters?

Hi @Kawtar,
Not really. So far my role in the projects is about pwm control and feedback, and another engineer is in charge of the power section. So for the high current circuits I also need advice.

I’m moving the old devices from THT to SMD. Instead of having the control circuit in the same pcb of the power converter we want to make it in a different pcb, to be plugged in the main board.

In the new pcbs I’m trying to layout all signals on the top layer and the power in, gnd in, power out and gnd out on the bottom layer with big clearances and using zones instead of wide tracks.

Hi @pedro, thank you so much for your advice, I really appreciate it!!

If you simply do not have enough cooling, your converter can get too hot. Efficiency and input voltage range or maximum output power may suffer. But where high frequency high AC current is involved, stray inductance is probably the bigger concern. The inductive spikes can avalanche switching FETs and cause electrical overstress, ringing, and other problems. Check out my earlier response regarding “hot loops.” The manufacturer of your controller IC probably has some applications information regarding layout with that IC.

1 Like

Often modern high frequency switch mode controllers and the low inductance leadless MOSFETs need 4 or 6 layer PCBs and fairly fine design rules, incompatible with anything heavier than 2oz copper.
The saviour is that synchronous buck boost converters can be incredibly efficient

1 Like

Just curious:
Different copper thicknesses could be used for different layer, which could also allow for different sets of design rules. In today’s world it seems a logical choice for motor controllers that need both high currents and delicate circuits to control the power devices. Are there many PCB manufacturers that do this?
Or would it be more logical to make a construction of 2 separate PCB’s?

For high current stuff such as audio amplifiers and power supplies it’s also fairly common to use thick copper bus bars to help distribute current over the board.

1 Like

My understanding (I am not an expert on pcb fab) is that you want the copper stackup to be symmetrical, so that (for example) top and bottom copper should be similar thickness. Similar for layers 2 and 5 of a 6-layer board. This is to reduce warping. (not the same as warp cursor. :slight_smile: )

But thicker copper increases minimum etched feature size so that there is some challenge to put a fine pitch controller IC on a board with thick copper on top and bottom.

1 Like