PRINTED CIRCUIT BOARD (PCB) SPACING / CLEARANCE vs. VOLTAGE

IPC-2221 which supersedes IPC-D-275 is widely accepted throughout the world as a generic PCB design standard. The table below is adapted from IPC 2221A Table 6-1, which provides recommended minimum spacing between conductors and component leads as a function of working voltage level and application. This is not an official IPC table. The original IPC table 6-1 gives the spacings only up to 500V and provides formulas for the calculating the spacings above 500V. For your convenience, I added calculated distances for higher voltages based on these formulas, converted inches to mils, and annotated the columns. All my calculated numbers of course are rounded.


In my view, the IPC-2221 stepwise limits are baseless: the spacing vs. voltage curve should be linear. For power conversion circuits IPC-9592 provides the following circuit board spacing recommendations: SPACING (mm) = 0.6 + Vpeak x .005. In my view, IPC-9592 requirements are too conservative and sometimes are not even doable. Note that generally all IPC standards are voluntarily rather than mandatory. For products covered by UL safety standards the creepage and clearance requirements of the respective UL/IEC standard also apply. For example, for ITE equipment you need to use UL 60950-1 Tables 2L or 2N. For a comparative analysis of different IPC and UL requirements see the guide to PCB spacing vs. voltage. Also see pcb layout tutorial for routing tips and guidelines and custom circuit boards for the manufacturing process.


This page is for a general reference only and does not constitude a professional or a legal advice- see the Disclaimer linked at the bottom of this page. Consult with respective standards for final design decisions.