i am designing the 4 layer pcb for the first time. I got typical 4 layer stackup - signal on the top, GND, PWR, signal on the bottom Most of the signals are routed on top, few are on bottom, and everything is connected to its respective GNDs (i got two gnds since there's USB isolator used in the design) and 4 different voltage levels (5V for Hall sensor, 3.3V digital for powering ADC of the STM32 and another 3.3VA for reference and etc) The question is more about manufacturing - since most of the signals are routed on top, the bottom has pretty few copper. I've red about the warping and mechanical PCBs (and especially multilayer PCBs) can be affected by in case of significant variation of copper density on opposite layers. It seems obvious to create huge poly on the bottom and connect it to GND, but i am a bit afraid of solderability - the board has 35um of copper thickness on all conductive layers.
Is it OK to create hatched poly on bottom and leave it floating?