FreeLists / pcdlist / [pcdlist] Re: CAF

["Doug Butler" <dbutler@xxxxxxxxxxx>]

It sounds like the question is if the standards are strict enough!  They may
be based on short term overload situation testing, and may not hold up for
long term use.  Testing for long term use unfortunately takes a long
time....  However TVs have used very high voltages for long product lives
for decades.  300V - 400V was "run of the mill" for vacuum tube gear, there
ought to be good data available somewhere.

Sherpa Doug

> -----Original Message-----
> From: pcdlist-bounce@xxxxxxxxxxxxx
> [mailto:pcdlist-bounce@xxxxxxxxxxxxx]On Behalf Of Clyde Sprowl
> Sent: Thursday, December 05, 2002 3:36 PM
> To: pcdlist@xxxxxxxxxxxxx
> Subject: [pcdlist] Re: CAF
>
>
>
> Your best bet is to follow the standard until you run a Design for
> Experiment for your particular situation to collect empirical
> data that
> justifies a deviation from the standard. That standard was
> written after
> doing testing. Your design standard needs the same type of
> data if you're
> wanting to reduce the spacings. My 2 cents worth..
> Clyde Sprowl
> C&B Contract PWB Design Services
> Phone 260.356.7421
> Fax 603.258.5520
> http://personal.myvine.com/~fpds
> ----- Original Message -----
> From: "Louis Guerin" <louis.guerin@xxxxxxxxxxx>
> To: <pcdlist@xxxxxxxxxxxxx>
> Sent: Thursday, December 05, 2002 15:23
> Subject: [pcdlist] CAF
>
>
> >
> > Hi,
> > I'm searching documentations about CAF (Conductive Anodic Filament)
> > formation. We are designing PCB's with circuitry generating
> pulses in the
> > 300V to 400V range and  having a supply around 450V. I know
> by IPC related
> > documentation which spaces I need to keep, but these values, in my
> opinion,
> > are like to be for a circuitry on the primary side (i.e. circuitry
> connected
> > to the wall plug) which need to withstand spike surge of a
> few hundreds
> > volts and remain operational. Our circuit is isolated from
> the primary
> side
> > and do not need this kind of extra security.
> > In the last PCD Design issue (December 2002), Bernard Voss
> wrote that the
> > dielectric strength of PCB's materials are based on a
> hi-pot test which is
> > measured on a short term period. Our circuits have to work
> 24 hours a day,
> > all year round.
> > Any info on the subject will be appreciated.
> > Thanks,
> >
> > Louis Guérin
> > PCB Designer
> > R/D Tech Inc.
> > 505 boul. du Parc-Technologique
> > Quebec, Qc
> > G1P 4S9
> >
> > Tel.: (418) 263-3647
> > Fax: (418) 263-3742
> > Email: louis.guerin@xxxxxxxxxxx
> >
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