On a PC board is the first dielectric layer looking into the board from the top or the bottom layer of copper always prepreg or can it be a core? Here "can" would mean conventional. If not then why?

I asked this leaving work for the weekend. This week I asked the board house this question and they said generally prepreg is always used under the outer layers. I didnt ask why though. If no one will do it then the why doesnt really matter.


1 Answer 1


It can be done either way, but conventionally the surface layers are copper foil over prepreg.

Here are two different ways to do a 6-layer board:


The one on the right is the standard stackup style of every board house I've used.

  • \$\begingroup\$ You can also do PPCPP as well - I've used that in one design. \$\endgroup\$ Commented Aug 20, 2016 at 0:49
  • \$\begingroup\$ You've done the left one before? Is the right one mainly better to control the board thickness? Since prepreg is pressed the thickness can be controlled right? \$\endgroup\$
    – Jason
    Commented Aug 20, 2016 at 13:29
  • \$\begingroup\$ @Jason No, I haven't made the left one. After I wrote this answer, I asked a related question about why these would be done. Please take a look! \$\endgroup\$
    – bitsmack
    Commented Aug 22, 2016 at 21:16

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