route signals in inner layer?

[pinki patel]

hello friends,
i am intrested to do 4 layer pcb.
in my circuit there are 3 diffrent supplies.
i.e one +vcc and othor two's are analog and digital ground.
in this designing i hav one problem
i.e. may i route the signal tracks at inner layer side
b'caz of more signal density (means no. of tracks more).
if not then suggest the better option

 

[dmd4raj]

You cannot Do this in four layer PCB
For 4layer the stackup should be
Layer 1-----Signal
Layer 2-----Ground or PWR(Gnd preferred)
Layer 3----PWR
Layer 4----Signal
All high speed traces shold be routed on top adjacent to Ground plane.

If u need any stripline environment u need to increase the layer numbers to 6 layer
The above stack up with 2 Inner signal layers in between the Gnd and pwr layers

This stack up is even not good for High speed Signal at >100MHZ,Below this frequency the above stackup can be used


\\Regards
Rajan.K

 

[cyberrat]

Of course you can put tracks on the planes.
You can have split planes and even have tracking on them.
Its not unheard of.

 

[FvM]

The original poster didn't tell about high speed. One ground plane and three signal layers can be an option.

 

[george1]

Is it a hi speed board? can you post more details of circuit
Thanks
George