just curious, does anyone see high voltage CAF (I mean >700-1000V)?
thanks.
jk
abcd
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Hfjord
Sent: Tuesday, September 26, 2006 3:27 PM
To: [log in to unmask]
Subject: Re: [TN] High-Voltage Board Spacings
We are not allowed to have more than 500 Volts between surface traces and
layers below . Over 500 Volts, FR-4 is not used because of the humidity
risks, also high altitude phenomenons, like corona effects. For 1500 Volts
we would typically use PTFE 1500 Volts means a high activation and the
board is therefore much more susceptible to migration and other high voltage
driven disasters. The dielectric withstanding is expressed in kV/mm, e.g. 40
kV/mm, and it makes people think kV rather than Volts. I represent HiRel and
Mil manufacturing, I can imagine that the home electric equipment industry,
and other commercials, have a less stringent desing rule here.
Inge
----- Original Message -----
From: "Wayne Thayer" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, September 25, 2006 11:41 PM
Subject: Re: [TN] High-Voltage Board Spacings
> Your failure mode of deepest concern is most likely CAF (Conductive
> Anodic Filament). The most common spot for this problem is via to
> trace, and the seed is disturbances in the via side wall. CAF can also
> grow along glass filaments within pre-preg from layer to layer. Failure
> potentials are at less than 10% of the 750V/mil. Laminates are
> available with very high CAF resistance if you need to push things. I
> believe there are some BT based materials that are virtually immune, but
> 1500V is a lot of potential!
>
> Wayne Thayer
>
>>>> [log in to unmask] 9/25/2006 5:06 pm >>>
> Should I be using IPC Table 6.1 for conductor spacing for high voltage
> in the z-axis of the pcb?
> Or should I be using the approximately 750V/mil spec from the laminate
> supplier and derate that number?
> Board has +/- 1200V.
>
> Thank you.
>
> Kaye Clayo
> Sr. P. C. Layout Designer
> Keithley Instruments, Inc.
> 440-498-2862
>
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