A printed circuit board assembly (PCBA) for downhole applications has a printed circuit board (PCB) and a plurality of electronic components installed on the PCB. The PCB comprises a polyimide substrate, a lead-free surface finish, a plurality of traces, a plurality of surface mount pads, and a plurality of VIAs. The ratio between the width of one of the plurality of surface mount pads to the width of the trace connected thereto is 2 or less.