Voltage Arcing

[fmartyn]

Hi Pro Tom,

I have some components with 6Kv on them and they need to be spaced far enough away from other pins so that arcing does not occur. Is there a rule of thumb for this calculation? I seem to remember hearing that about 25.4mm per 1Kv of voltage should be sufficient but I can not seem to locate the source of that figure.

Any help would be appreciated.

Thanks,

Frank

[Tom]

Frank,

This is an area I don't know much about (I'm into low voltage products).
http://www.ce-mag.com/ce-mag.com/archive/01/03/ProductSafety.html has some information, I would guess UL would have some requirements, if that is an appropriate agency for the product you are working on.

http://www.emclab.umr.edu/emc-pstc.html is a link to sign up for a group that discusses product safety, maybe someone would have an answer to your question.

Good Luck!

[RLS]

Hi,
Check on IPC Standard 2221, Table 6-1 pg 39, section 6.3 Electrical Clearance (Feb 1998 ver)

It give conductor spacing specs in mm/volt, depends upon altitude (air pressure) and type of board coating.
For DC or AC peak voltage. Info below applies to over 500 volts.

Type B2: Uncoated Under 3050m/10,000Ft (.005mm/V)
Type B3: Uncoated boards above 3050m/10,000Ft (.025mm/V)

Type B1: Changes to (.0025mm/V) for internal layers.
Type B4: Changes to (.00305mm/V) with permanent polymer coating.

Notes from a Copper Connection Class stated Solder Mask DOES NOT COUNT as conformal Coating!

Hope this helps.
RLS

[Tom]

Here is a response from Dave Carbonari - one of San Diego's top RF engineers:
I believe it is 9.4mm (0.37") per 1Kv this is in Consumer electronics UL specification#? for U.S. on FR4. For telephone EQ UL testing for spark arrest it is different. This question should be addressed to TUV in Mira Mesa for an accurate answer because there are different categories for proper 1Kv spacing in the type of product and country it is going to.

[robert Tarzwell]

Sorry but there is no right answer. I studied and wrote a book on high voltage printed circuits. Available at
megadawn.com THere are many factors such as construction type, material tempurature range and pressure. typicaly FR4 has a manufactures rating of about 1000-1200 volts per mil through the material, but this can de degrated to as low as 300 volts if the material sees to many high temperature cycles. THe problem lies in the rating between two parralle tracks, the solder mask /confornal construction and type then comes into play. In dry free air the arc over voltage is about .2 inch's per 10,000 volts, how ever at 6000 volts you have to be concerned with corona, all points and shapes must be round, even the solder joints. Todays solder mask is quite good at increasing the dialetric rating. a good coating or gliptal will help reduce arc and corona.