PCB Stack-Up and Impedance Calculation

[mostafa222]

hi dear robert.
i send my request eXceptionPcbSolution and they sent me this stack-up(Attachment). i have two question.
Question 1: if i want use this stack-up, i want set my layer as:
1: signal
2: GND
3: signal 4: GND
5: Power
6: Power
7: GND
8:Signal
9: GND
10: Signal
is it good?



Question 2: in Stack-up file,In impedance calculation, they use the term "reference plane in layer". what this mean? is it GND layer? in micro-strip and strip-line impedance calculation, what is reference plane? if we have stack as follow:
layer 1: signal
layer 2: gnd
layer 3: signal
layer 4: power
layer 5: gnd
....

when we try to calculate impedance in strip-line in layer 3, in impedance calculation formula, the reference layer must be layer 2 and 5. am i right? what we do with layer 4. is it reference layer too?

Mostefa_Barhrami_10L_VT47.pdf

[robertferanec]

1) correct
2) GND plane is usually good reference layer (sometimes, power can be reference plane for example if there are a lot of decoupling capacitors). Important is, ideally you would like to have this reference plane solid covering the whole layer and it is then the closest solid layer to your signal layer. So, for layer 3, in your stackup layer 2 and 4 would be reference layers. Have a look at the table, they tell you what are the reference planes (Ref Plane 2 / Ref plane 1).