currently i'm placing parts on pcb software, and i'm running out of space from specification. so i think i have to split the parts, some on the bottom and some on above. parts on the above is directly interfacing to the user, pots and switches, and all of them are through hole. for the smd parts, i think i cannot split sides since to make reflow or such (diy and soldering) process later to become easier. so they all have to go to the bottom since i cannot put UI parts on the bottom. so most functionality (mcu, radio, amplifier) will be at the bottom, facing the plastic housing below, when assembled, we will see the large ground plane, with other UI parts on the top, hence "upside down pcb". my concern is, the circuit is detecting EMF pulse (with varying magnitude, max recorded around 30Vpp) from below, may it interfere with circuit functionality? will it corrupt/degrade mcu signal, radio signal and amplifier? if so, how do i overcome this? will just placing an aluminium foil in the housing (below) can avoid this emf interference? is this a common or bad practice? the space (housing) constraint is around 6 x 5 x 1.5 cm as pictured (with its pcb inside) below. hope to get some advice.