Hi,
We all know on top layer, clearance for L and N should be 2.5mm. (no con. coat, IP67 sealed enclosure)
However, once you are downstream of the input fuse, the 2.5mm clearance is "relaxed"
(At least this is what you actually see in offline SMPS when you tear them down)
What is the actual standards clearance value when you are downstream of the input fuse?
Also, as you know, upstream of the mains FWB, capacitors must be X2 rated...downstream of it, and they dont need to be.
No regulation actually states that the FWB is the defining line , but it is the "accepted norm".
Has the new standards gotten round to this yet?
Also We all know the following in page 9 is good summary of current clearance standards.
https://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdfBut as we know, TO220 legs D and S in Flyback are often >800V and separated by <1mm
As you can see, for a TO220 FET, the through_hole of the pad needs to be 1.2mm in diameter, the “annulus ring” of copper of the pad needs to be at least 0.3mm thick. This means that there is a maximum of 0.74mm of clearance between Drain and Source PCB copper, and the flyback has a peak Vds of 600V.
TO220 FET datasheet....
https://www.st.com/web/en/resource/technical/document/datasheet/DM00049184.pdfZillions of offline SMPS have only 0.7mm clearance between D and S.