Distance from pad with 6KV on it to other pads at 12V?

[grizedale]

Hello,

I am routing a dense double sided PCB for a xenon flash lamp.

The pad which is attached to the output of the trigger coil has 6KV pulses on it.

Due to space constraints, this pad is just 1.2mm away from another pad which has 12V on it.

Will i suffer arcing between the pads?

 

[barry]

You might be in trouble. Even with conformal coating on the PCB, the IPC spec is 14.53mm at 5000 volts. (You require even more spacing at higher altitudes). You may not get arcing, but you might get leakage currents that can cause problems.

 

[grizedale]

Thanks,

I must confess i am not interested in any safety standards etc.......i am just interested in whether i will see faulty circuit operation......i am wondering if i can just smother the pad in silicone or RTV?

 

[albbg]

Yes, I think you could experience arcing. You can have a look to:

https://en.wikipedia.org/wiki/Paschen's_law
**broken link removed**

 

[grizedale]

thanks albbg,

Paschens law states that in air at standard atmospheric pressure, the electric field strength for arcing is 34 Kilovolts/mm

Due to my 1.2mm of spacing i have 5KV/mm so i should be on the margin of disaster?


But no....surely i always thought it was 3KV/mm for high voltage breakdown of air?...............so i am in big trouble?