I design 4 layer PCB
- Top - Signal layer
- Layer2 all voltage (2V8, 1V1...),
- Layer3 GND,
- Bottom - Signal Layer
I'm considering what should i do with free space on Top and Bottom. I always filled them with GND (It can remove crosstalk) but recently I heard that i should use gnd planes only in those places where i need to provide return path. So if i have gnd plane on layer 3 which covers whole circuit area there i should fill free spaces on top and bottom via gnd plane? I also know that the manufacturers recommended to ensure provide an equal field of copper on every layer to prevent from bending during soldering. What do you think?