Question regarding Stack up.

List,

May I know what is the different between this 2 stack up (1-6-1) and (2-4-2), both have 8 layer?
Is it the stack up define by the via type, example through hole via, buried/blind via?
I bit confuse when someone ask about the stack up. I can find total layer but not the stack up.
Really appreciate if some on help me.

Best regards,
Farook

The stack is a manufacturing house problem. You should *never start routing * without talking before with your PCB house, asking them if your stack proposal is manufacturable. Any multilayer board could be manufactured with different sublaminate scheme. You must dimension carefully the vias tipe for different sublaminations.
Example:
* 1-6-1 means a central core of 6 layers (possible with FR4) having buried vias from layer 2 to layer7. The remaining is copper foil+prepreg for layer 1-2 and 7-8.
On those layers you can design 5 mil diameter microvias (if the aspect ratio is not bigger than 0.6:1)
* 2-4-2 has a sublamination core of 4 layers (possible scheme 2 layer FR4 core in the center and two prepreg + copper foil upper and above) and two sublaminations on top and bottom of the central core. The microvias on layers 1-3 and 6-8 are two layer deep and will usually do not allow connections on layers 2 and 7, for those you need separately microvias from layer 1-2 and 7-8 or 2-3 and 6-7.

Any microvia deeper than 2-3 layers need a stackable scheme which is very expensive. Any buried/through hole via has a minimal size of 8mil/18mil.

I hope is more clear now,

melc

Thanks Melc for your wonderful explanation about stack up.

Best regards,
farook