Maximum Voltage for 4-layer PCBs

Hi everyone,

I am working on wide bandgap-based power electronics at voltages up to 1200 V. I’ve already used boards based on the 4-layer stackup for voltages up to 400 V and it works out nicely, but I wanted to ask if the distance between Layers 1 and 2 is also enough to withstand 1200 V as well. The resulting system doesn’t need to be 100% reliable (I’m working in academia, so reliability isn’t the biggest concern), but it should be reliable enough for doing measurements during a few months of operation.

Would you suggest going for a 2-layer stackup or is the 4-layer stackup still fine for that? Additionally, which size of ground plane cutouts for VIAs (etc.) would you suggest?

Thanks and best regards