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PCB has lipo battery input Vcc and GND. The motor connected to PCB will draw max 30A. While trying to allocate plane for Vcc and GND a question came to my mind as which one is more important for current draw.

I have inner 0.5oz layer and outer 1oz layer.

My questions are:

1)Should i allocate 1oz outer layer for Vcc and inner layer for GND or viceversa.

2)Or since there will be a return current are they both equally important for current handling (for example even if i allocate enough copper area for Vcc and poor area for GND will this be a problem due to return current).

3) If we draw 30A from Vcc, is the return current also 30A.

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    \$\begingroup\$ What else is on your PCB? Can you show the schematic? I assume there is other stuff and you're not just using each whole plane as a trace \$\endgroup\$ – BeB00 Oct 20 '17 at 19:22
  • \$\begingroup\$ There is microcontroller and transistors to drive the motors. And to be able to meat the current rating i am thinking about 4 layer design where i can easily allocate 2 plane to Vcc and GND. But i think the question is straightforward regardless of the schematic detail. \$\endgroup\$ – ssdflash01 Oct 20 '17 at 19:25
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    \$\begingroup\$ The currents will be the same. 30A is a LOT for a PCB, especially at 1oz. or less! Can these lines be wired separately from your PCB? \$\endgroup\$ – evildemonic Oct 20 '17 at 19:25
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    \$\begingroup\$ 40mm trace.. an inch and a half.. that is a trace? \$\endgroup\$ – Trevor_G Oct 20 '17 at 19:29
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    \$\begingroup\$ If possible, use 4oz copper. If not, consider using wires to route high current. You can also buy copper busbars, which you could consider. \$\endgroup\$ – mkeith Oct 21 '17 at 0:05
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Currents will be the same on both layers, assuming you only have a single supply.

The bigger issue is making sure the motor connections / driver is connected really close to the power connection on the board. Do not have them on opposite corners..... I might even suggest going as far as routing the motor power and return using traces on their own and tieing them back at the power connector so they do not run through the power and ground plane. And yes.. heavier copper is better.

Further, if there are control signals coming to this board from elsewhere you may have issues with the cabling and ground level shifting between them that can mess up the logic levels.

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    \$\begingroup\$ I would agree with the separate non-plane routing, especially if he's using pwm. The traces should be as tightly coupled as possible \$\endgroup\$ – BeB00 Oct 20 '17 at 19:29
  • \$\begingroup\$ Ok noted that. Can i ask one more. PDB board for 4 esc powering where each esc draws 10-15A average the board has each esc power connections at corners is this a problem. Example pdb matek hubosd 8 \$\endgroup\$ – ssdflash01 Oct 20 '17 at 19:33
  • \$\begingroup\$ @ssdflash01 it's certainly not optimal. But sometimes you do not have much choice. \$\endgroup\$ – Trevor_G Oct 20 '17 at 19:36

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