[MOVED]pcb stack up problem

[patelvimal20]

Dear all,

In 4 layer PCB usually we are using stack up as Signal-VCC-GND-Signal.

My question is that if we swap VCC & GND then what will happen.
If we can do that one then which kind type of problem arise. (new stack up Signal-Gnd-VCC-Signal)

is it advisable???

Pls rely me on asap.

Thanks

Vimal Patel

 

[ea.arun]

basically nothing will happen if we change the order.......if you consider high speed signals both VCC and GND will act same as reference.....only thing it suppose to be a low impedance path......
by changing the stack-up either you will increase the power supply path inductance and reduce the GND path(both through VIA's) or vice versa.....

Regards,
ea

 

[cks3976]

Well, depends on where most of your critical fast switching signals are routed. If it's TOP, then a TOP-VCC-GND-BOT will have a longer return path for these signals. Otherwise if this is not a very high-speed (fast switching) PCB, then ideally nothing should change..

 

[marce]

The signals will couple to the next adjacent plane as pointed out earlier, the only possible problem is if your power plane has splits, then running high speed signals across these splits can cause return discontinuityies. Whether the plane is a GND plane or a VCC the signal layer will use the next layer as the return layer, this is the layer where the h and e-field terminate.