I am working on a 6 layer PCB for motor control applicatin using Altium and the stackup being used is as follows:

Sig GND1 PWR Sig GND2 Sig

I am little confused regarding the correct order of core and prepeg. Should it be CPCPC or PCPCP? And what difference does it make? (C is for core and P for prepeg)

  • \$\begingroup\$ May I ask what do C and P stand for? \$\endgroup\$
    – Ergophobia
    Sep 29 at 9:38
  • 3
    \$\begingroup\$ I used C for core and P for prepreg. \$\endgroup\$
    – Umair Ali
    Sep 29 at 9:40
  • \$\begingroup\$ Thank you, I'm new to PCB Design and still learning @Umair Ali \$\endgroup\$
    – Ergophobia
    Sep 29 at 9:42
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    \$\begingroup\$ It could also be PPCPP; any reasons not to include it? \$\endgroup\$ Sep 29 at 10:41
  • 1
    \$\begingroup\$ Also, please see my related question and the answer(s) :) \$\endgroup\$
    – bitsmack
    Sep 29 at 17:48

1 Answer 1


They are both 'correct', in that they will both work.

However, there are some considerations

  • The PCB fab will likely give you a different price on the two, depending on what they are set up to do. Ask them to quote both.
  • Generally core is much better defined thickness and dielectric constant than prepreg. You will want to run defined impedance tracks with respect to a ground the other side of core.
  • Generally core is thick, and prepreg is thin. This will affect which pairs of layers you want to run any low capacitance tracks on.
  • In dense boards, it's very handy to use a buried core pair of layers with buried vias between them as a Manhattan (top E-W, bottom N-S routing) to give you 'unblockable' arbitrary routing. This only works with a core.
  • Microvias, pretty much required if you use BGAs, require an outer prepreg/foil layer

Do you really need a power plane? Unless everything on the board works with just one rail, it's a waste of a layer that you could put signals on, and the waste of the ability to run power on other signal layers. I've always treated power as just another signal, albeit on wider tracks. If you are worried about signals crawling from one part of the board to another on power rails, then putting it all on one layer doesn't solve the problem, you still need to decouple in the right places to the right grounds, and you need to do the same to control signals.

  • \$\begingroup\$ Since my board has very tight size constraints and routing power tracks all around make it more messy. I want to be able to use that space for routing singals. \$\endgroup\$
    – Umair Ali
    Sep 29 at 9:35

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