PCB trace spacing for voltage levels

Safety regs aren't so much concerned with whether or not your circuit will function but more with spacing from HV or mains traces to traces on the LV side where GUI stuff, audio or whatever is connected. For example, in medical that would usually be 8mm.

An active device such as a TO220 FET between mains and LV is typically not considered kosher and will raise the neck hairs of the tester. That would be like blowing through a stop sign during a driving test ;-)

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Regards, Joerg

http://www.analogconsultants.com/

"Jamie Morken"

** A TO220 pack is not a PCB.

There are no traces & the insulation material is quite different.

You have made an entirely false comparison.

....... Phil

voltage levels from here:

"0.0002 in./volt" (0.00508 mm/volt)

devices, will they not pass UL (assuming UL

spacing between traces/pins?

function but more with spacing from HV or mains

connected. For example, in medical that would usually

considered kosher and will raise the neck hairs

test ;-)

UL is concerned with anything above 60vdc or 45Watts (might be 60W , I forget). Its a fire and saftey issue. Common practice is to skip pins in connectors to achieve the spacing or mill the board between component pins.

Cheers

I'd be interested in seeing a layout with a TO-220 that had trace spacing above 100mil :)

cheers, Jamie

The circuit I made has isolation between the HV and digital circuitry using two separate grounds, the 600V TO-220 fet is on the HV side only, and is a lowside switch, pulling a 450VDC peak signal to ground. Is a wider pin spacing package (ie. TO-247) required for this to avoid repaying for your driving test? ;)

cheers, Jamie

>

No problem, you just 'stagger' the leads. It's commonly done on triacs and such like. A minimum pad-to-pad spacing (not trace-to-trace) of

hole size.

Best regards, Spehro Pefhany

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450VDC is a bit much but there is precedence, for example in horizontal flyback drivers of TV sets and computer monitor (back when they still had them big pitchure glass thingies...). So I'd ask them whether they'd give you the same treatment.

--
Regards, Joerg

http://www.analogconsultants.com/

Some of those clearances are just stupid !

I always leave at least 12 thou (inch) for the PCB manufacturing to be sensible. If things are too close there could be man. errors.

Any there any particular spacings you're complaining about? There is no context here.

The PCB, manufacturers don't seem to have an issue with it. I've been quoted 7 thous trace/space with no premium.

Robert

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Hmmm... I leave only 8 mil when etching boards at home, and the fabs I use all do 6/6 rules with no premium.

Who's doing your 12 thou boards, so I know who to avoid?

I certainly would not avoid them as they do a great job at a great price !