Thanks, we have live and neutral pads on our PCB which are 2mm apart. They are for hand soldering X2 capacitors in.
I had always taken it that between DC bus positive and negative , 2mm spacing is needed.....but indeed this is just hearsay from various companies.....ive never seen it written down.
Ive been to planty of places where a TO220 transistor has been mounted with non bent pins, and the distance from drain pad copper to source pad copper (which can be 800V+ in say a flyback) is no more than 0.5mm.
-Nobody ever says anything about this kind of thing.
Do you know what is the legal distance between conductors with 300v+ between them on the primary side of an SMPS?.....Its not written anywhere...at least not anywhere that you dont have to pay an arm and a leg to get the info.
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Page 9 of this...
https://www.alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf
...says 2.5mm is needed between pads which have 300-500v between them, but the standard (if any) from which this arises is not known.
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When reverse engineering OTS offline PSUs, ive seen loads of (non conformal coated) offline flybacks with less than 0.5mm between drain and source copper of a flyback SMPS....due to the TO220 main FET being mounted with the pins "in a line".
It makes you wonder if this is some very loose standard, that nobody really cares about? I mean, we always try and get 2.5mm minimum, but sometimes one is space constrained......there is after all some solder resist between the copper.
Are there suited standards officials opening up power supplies and measuring the distances?
And if there is a danger of a short, then there is always a fuse in the line....so does anyone care?
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In UK I’ve seen tons of domestic , non-isolated, offline led drivers where the leds are mounted on MCPCB, and the MCPCB is screwed to a metal heatsink which comes out to the external surface, where human hands touch. The dielectric distance on MCPCB is in the micrometers……that’s nowhere near 2.5mm.
How are they getting away with it if there is a standard?
Who is checking?
Look on the lightbulb teardowns on youtube and you see loads of these things
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Heres just one of them...mains led bulb with insufficient clearance...
https://www.youtube.com/watch?v=keaE7QTKTYE
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Also, if the “standard” says that there must be 2.5mm clearance between conductors with 300V plus between them, then this 400V rated 0805 size ERJP06 resistor is illegal……
https://www.farnell.com/datasheets/...0.1019522641.1501332265-1679746183.1489787856
…its an 0805 resistor , and is rated for 400V working voltage, and has a spacing between pads of just 1.2mm.
Is it illegal?
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I have always suspected that the standards are only really known to the huge corporations, (they influence the writing of the standards) ...and they are made deliberately opaque and expensive, so that smaller competitors, trying to muscle their way into the market, are sent packing....then we end up with led bulbs with mains live virtually direct to the outer casing...as above youtube shows....that would give a very nasty "bite" if you plugged it in with mains on.