Partial discharge (PD) is a critical reliability concern in medium-voltage (MV) and high-voltage (HV) printed circuit boards (PCBs), as it can initiate insulation degradation long before complete breakdown occurs. Current PCB design standards, including IPC-2221, primarily address arcing prevention and do not explicitly consider PD inception. This work experimentally evaluates the applicability of IPC-2221 clearance guidelines for uncoated PCBs in standard atmospheric conditions and proposes a novel finite-element-based 'critical-area' metric for PD prediction. Five PCB designs, fabricated to IPC-2221 spacings for voltage ratings from 1 kV to 11 kV, were evaluated per IEC 60270 using a 60 Hz AC source. Simulation studies in COMSOL Multiphysics compared the traditional peak-field method with the proposed critical-area integration method. Results show IPC-2221 is conservative for PD prevention, and the new metric offers improved correlation with experimental PD inception voltage (PDIV) trends. These findings motivate refined PCB design guidelines for high-voltage applications.
