Hi all,

I'm trying to understand specs for PCB clearances for high-ish DC
voltages. I'm working on an industrial product which uses a 48V DC bus
(which can get as high as 80V under some conditions). There are traces
on a couple of the PCBs in this device (an industrial robot) which
carry this bus voltage. The PCBs will be in semi-sealed containers
(not water or gas tight but very well dust-tight) and will be
conformal coated. Normal operating environment will be below 50% RH,
but if it wouldn't take too much more effort from a PCB design
standpoint, I'd like it to be able to work in condensing humidity for
a planned future application.

What specs are out there for the minimum clearance between a trace
attached to the bus and any other trace (e.g. ground or a small-signal
trace)? Do I have to abide by such specs legally or are they simply
guidelines? If they are merely guidelines, what spacing do people
typically use?

Almost all of the specs I've seen so far are from the IEC and are for
AC line voltages. They also references things like "material class III
or IV" or "functional vs. basic insulation" for which I've not been
able to find definitions.

Thanks,

Sean
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