PCB Clearance and Creepage Distances (Part 2): Which Criteria Apply?

To determine the clearance and creepage distances between the primary and secondary side of a mains-connected circuit board, safety standards provide a number of criteria. Which are they and how do they apply? In this video we will find out.

When designing a PCB for a low-voltage circuit that connects to the mains, how much clearance must be used between the mains or primary side and the low-voltage or secondary side of the circuit? This may sound like a trivial question but, unfortunately, it isn't. A typical example would be a mains-switching relay controlled by a microcontroller. (Do you know you can back this project? It is an Elektor Jumpstarter!)

In the first part of this series, we concluded that IEC 62368-1 is the safety standard that applies to our situation. It provides a number of criteria to determine the clearance and creepage distances. In part two we will have a close look at every one of them.