From: "Patterson, Gordon" <[email protected]>
Subject: RE: Coated Printed Boards
Take a hint from note 6 for creepage table 6 where creepage distances
equal to clearances are permitted for glass, mica, ceramic, and similar
materials.
Then look at the requirements for suitable coating material in 2.9.5 and
all the testing required for that material as applied to the PCB.
Gordon Patterson
Racal-Datacom
-----Original Message-----
From: Douglas Mckean [SMTP:[email protected]]
Sent: Friday, May 08, 1998 11:34 AM
To: [email protected]
Subject: Re: Coated Printed Boards
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
> Solihull Parkway
> Birmingham Business Park
> Birmingham
> B37 7YU
> Telephone +44 121 717 6492
> FAX +44 121 717 6014/6018
> e.mail- [email protected]
