- Remember that ALL of the power pins, Vcc, GND, others can be tied to a single layer.
- If there isneed for video or other analog signals, then you need a layer for ANLG and AGND. That should reduce the pin counts.
- If there are address and data buses, those signals can be restrained to their own layers as first. Their physical lengths may need to be restrained to their own layers at first as well.
- Critical traces, such as clocks or other high-speed traces should never run parallel to non-high-speed traces or other clocks. Some of these can be run on extra ground plane layers.
- Also, ensure your PCB manufacturer can handle your project. I once had a 14-layer prototype PCB catch on fire due to reduced Pre-preg thickness to meet the mechanical fit.