[SI-LIST] Re: Inter-plane capacitance
- From: Istvan Novak - Board Design Technology <Istvan.Novak@xxxxxxx>
- To: kalevi@xxxxxxxxxx
- Date: Wed, 14 Jun 2006 18:50:41 -0400
Mak,
When you say you observe high leakage current while hi-pot testing: was
it with static DC voltage applied, or during ramp?
The capacitance can actually trip the hi-pot tester if the voltage ramps
too quickly or if the capacitance is too large. This would happen with
thin laminates and large planes. You can calculate the capacitance as
others suggested, and calculate the current as I=C*dV/dt, where dV/dt
is the voltage slew rate of the tester. If this is the current you
see during ramp, it is OK. If you see more during ramp, or see noticeable
current with static voltage applied, it is probably the true leakage.
Regards,
Istvan Novak
SUN Microsystems
Kai Keskinen wrote:
>If you are failing high pot, you do not have an issue with inter-plane
>capacitance. You have some medium resistive path between your hazardous
>voltage line and the board digital ground. It is either a fault in the
>board shop due to poor etching caused by a multitude of possible reasons, a
>conductive impurity on the board surface (something like washable solder
>flux that was not washed away properly) or some layout issue related to
>spacing, probably on the surface layers. When high potting, turn off the
>lights and you may actually see where the breakdown occurs.
>
>You can calculate your interplane capacitance if you open up your first year
>EM text book and look up parallel plate capacitance.
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Anupama
>Sent: Wednesday, June 14, 2006 7:30 AM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Inter-plane capacitance
>
>
>Hi
>
> Is there any tool available to measure the inter-plane capacitance
>specially for internal VCC and GND plane. in our case We are observing
>high leakage current while hi-pot testing ..... can we measure with
>Hyperlynx or any specific formula....
>
> Thanks in advance.
>
> Mak
>
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