Safety of traces on different sides of FR4

[samppa]

Hi everyone,

I am designing a two layer board for standard 0.063 inch FR4, which will have both 230VAC high voltage components and a low voltage SELV rated area after a safety transformer. I have investigated that for my purposes (according to IEC 60335-1) the creepage distance between 230VAC and low voltage must be 8 mm on the PCB. But what if the traces are on the opposite sides of the 0.063 inch FR4 board? Is the FR4 considered as "reinforced insulation", can I even route 230VAC and SELV signals across each other on opposite sides?

-Samppa

 

[chromatik]

Hello,

What is the type of FR-4 you're using ?
This might depends of the dielectric strength, I guess.
Check here (first data) https://en.wikipedia.org/wiki/FR-4
But I think this situation (flipped PCB) is detailled in the IEC norm

Regards