[SI-LIST] Re: BT Laminate substrates for high voltage application
- From: "Pommerenke, David" <davidjp@xxxxxxx>
- To: "Gumaste, Vijaylaxmi" <Vijaylaxmi.Gumaste@xxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 29 Jan 2010 12:01:06 -0600
This is not an easy question. The high voltage stability will depend on many
factors:
- Is it short term stability (like 1 min) or long term stability (like 5 years)?
- Is the high voltage a DC voltage, a pulse voltage? Does it change polarity?
This will change the breakdown mechanism. Short term even very thin dielectric
can handle a lot of field strength, like 100kV/mm should not be a problem. But
if the high voltage is changing polarity, is pulsed or AC, then you will have
partial discharge breakdown. Small sparks eat paths through the dielectric. If
this happens depends not really on the overall field strength, but on the field
strengths at corners or edges. That is where the partial discharge process will
start.
If you look at the stability of insulators one can hardly speak of a bulk
breakdown limit. The breakdown limit field strength depends strongly on the
sample thickness. A thin sample will hold much higher field strengths than a
thick sample. So breakdown field strengths like 30kV/mm are really only
meaningful if the test conditions are known.
Other questions that influence the high voltage stability are:
- Is the field vertical through the material, or along the surface?
Sparks love to be guided by surfaces, especially, if they have ground backing.
Dr. David Pommerenke
Missouri University of Science and Technology
emclab.mst.edu
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx on behalf of Gumaste, Vijaylaxmi
Sent: Fri 1/29/2010 11:12 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] BT Laminate substrates for high voltage application
Hi,
I want to check feasibility of using laminate substrates for an application
that needs high voltage isolation (several kV) between certain traces.
I am looking at breakdown voltage strength for different materials.
Is the formula sufficient to determine usability?
Breakdown voltage = Dielectric strength x laminate thickness
Or are there any potential concerns with using laminate materials at HV.
I came across some references that mentioned micro-voids in laminate material
can result in lower effective breakdown strength. How can I quantify the
reduced effective strength?
Regards,
Vijaya
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