[SI-LIST] Re: PCB High Voltage
- From: Bill Wurst <billw@xxxxxxxxxxx>
- To: ramesh.k@xxxxxxxxxxx
- Date: Mon, 11 Sep 2006 08:57:08 -0400
Ramesh,
As you know, the specified dielectric strength of FR-4 is 750V/mil.
Since there are 1000mils/inch and 25.4mm/inch, this equates to 30kV/mm.
Note that this is a specification of the material itself, and does not
account for any impurities that may be entrapped during the
manufacturing process.
It is unwise to try to achieve anything close to this in practice
because FR-4 can contain pockets of trapped air. If the dielectric
strength of the air pocket is exceeded, arcing can occur within the
pocket, eventually enlarging the pocket to the point where catastrophic
failure occurs. Thus, to be safe, one should constrain the design to
the breakdown voltage of air. For needle-point probes (the worst case)
at standard temperature and pressure, the dielectric strength of air is
usually considered to be approximately 40V/mil or 1.6kV/mm. If your
design can be operated in environments other than 25°C and atmospheric
pressure, then you must derate accordingly. You should also include a
safety factor.
I believe this is pretty much in line with what others on the list have
told you in prior responses.
Regards,
-Bill
==============================================================
RameshK Cozerv IN HO wrote:
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>
>
> Hi Folks,
>
>
> Its regarding the query posted by srikanth for high voltagesometime last
> week,what is the actual voltage for 1.6 mm of fr4 can withstand?And what one
> need to look for from the fabricator,
>
> As i had replied earlier as below
>
> According to MIL-P-13949/4C for FR4 material,the electric strength
> (perpendicular to lamination,average,minimun volts/mil=750v per
> mil which is 29.25 mm.,which i have red it in some article while
> browsing.Now because of mixed response in the forum,what will be the final
> conclusion for the same.
>
> Can someone refer some links related to this?.Advance thanx.
>
>
> -Ramesh
>
>
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