When analyzing printed circuit boards, BOTH clearance AND creepage
are issues. The flat pcb fab (no parts installed or soldered) would
most likely have nothing but creepage issues - distances along
the surface of the board ("as the crow walks").
An assembled pcb with parts that could compromise creepage
(parts laid down on the board for example or wires added
as a mod after assembly or maybe even a piggyback board)
would have clearance issues as well ("as the crow flies").
Thus, the reason why both clearance and creepage are included
in all the IEC-950 based standards that I've seen: UL-1950,
EN-60950, ...
Regards, Doug
Alan Booth wrote:
>
> Dear Treggers,
>
> I am having a problem with clause 2.9.5 of EN60950 regarding Coated
> Printed Boards.
>
> The second paragraph, second sentence reads :
>
> 'Between any two uncoated conductive parts and over the outside of the
> coating, the minimum distances in tables 3, 4 or 5 apply.'
>
> Tables 3, 4 and 5 only deal with clearance distances. I would have
> thought that table 6 for creepage was a more appropriate application in
> this instance.
>
> Can anyone explain the reasoning behind this?
>
> Many thanks,
>
>
> Alan Booth.
>
> Equipment Engineering Group
> Fujitsu Telecommunications Europe Limited
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