In a 4 layer PCB, the outer layers 1 and 4 have 1 oz copper thickness and inner layers 2 and 3 have 0.5 oz copper thickness.

For example, if I allocate a VCC voltage to 3rd and 4th layer, can I say the copper thickness makes 1.5 oz. for pcb current vs heat calculation. (The question is theoretical not PCB design specific)

  • \$\begingroup\$ If this is for resistance/voltage-drop calculations then yes. \$\endgroup\$
    – user253751
    Nov 23, 2017 at 23:21
  • \$\begingroup\$ Keep in mind your Gnd needs to be just low resistance as Vcc. \$\endgroup\$ Nov 23, 2017 at 23:22
  • \$\begingroup\$ I am wondering this for pcb current calculation. 2 oz 4 layer pcb are expensive so if i allocate more layer to high current will they add up in thickness. Also yes same consideration is given to both VCC and Gnd but just wrote the VCC as example. \$\endgroup\$
    – ssdflash01
    Nov 23, 2017 at 23:23
  • \$\begingroup\$ Don't forget about heat dissipation for internal layers which is much worse. Don't know how much current you are talking about but.. you should probably keep that in mind. \$\endgroup\$
    – Wesley Lee
    Nov 23, 2017 at 23:24
  • \$\begingroup\$ Yes i learned that the outer layer is important for heat dissipation. Thank you. But also i do not have much to do rather that allocating as much as copper area possible. Current is 10-15A average and some peaks to 30-40A for a few seconds. \$\endgroup\$
    – ssdflash01
    Nov 23, 2017 at 23:28

1 Answer 1


Yes, but - the layer 3 trace temperatures will be higher than the lay 4 trace temperatures, because the layer 3 traces are insulated from ambient air by the prepreg or fiberglass between layers 3 and 4.


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