Choosing power card's line width depends on voltaic magnitude.The electricity is bigger
power card needs wider vice versa.It deals with PCB board as the same.
Besides of electricity,you should thingk over minishing power supply coupling while
you are choosing power card.Therefore if condition permits ,choosing a wider one is better.
Currently power card's line width is 1mm at least,even though the electricity cross in it
is no more than 1 mA.
AC Power Cords