PCB Design on width

Question

I would like to construct a 25A on board. How much mil or mm should I use for wire width? I have search for it size shown that 300mil/7.62mm for 10A.

Answer 1

There are several factors that need to be considered as it can depend on the number of layers you have on the PCBA that you can allot to the traces as well as the copper weight,ambient temperature and the temperature rise that you can tolerate and/or dissipate. I would suggest taking a look at a PCB calculator. It is derived from IPC2221 which discusses this. I use one of the following:

https://www.desmith.net/NMdS/Electronics/TraceWidth.html

https://www.4pcb.com/trace-width-calculator.html

If you are using KiCAD there is a tool-set built-in that uses the same calculator or something similar. Now a simplified answer to your question-> Based on 25amb and 10 deg temp rise.

1. At 25Amps on 1oz copper single layer - 1000mils or 1in wide trace
2. At 25Amps on 2oz single layer - ~500mil wide
3. At 25Amps on 4oz single layer - ~250mil wide

Internal layers require more spacing as you will see from the tool.

Hope that helps :)

Answer 2

I use a rule of thumb of 4A per square mm of copper cross-section. For high current you may want to specify a relatively high copper thickness. You can also use multiple layers, but it’s wise to fill any vias with conductive material (solder or copper).