Breakdown voltage vs IC gap : Paschen's Law ?

[Tucco]

paschen law

Hi,
I have two microstrips conductor with a gap 20 to 100 microns between.
Substrate is Alumina or FR4 and air above.

How can I calculate the DC Voltage breakdown of these "electrodes" ?

I read that , around these gap values (5 to a few hundred microns), the Paschen's Law can be valid in air, dependent of pressure by the product distance x pressure. Is it really valid for my case ? And for the E field in the substrate, this law is good ? Which method must I take ?

Help me please !
Thanks

 

[erikl]

voltage breakdown air

Hi,
I have two microstrips conductor with a gap 20 to 100 microns between.
Substrate is Alumina or FR4 and air above.

How can I calculate the DC Voltage breakdown of these "electrodes" ?

I read that , around these gap values (5 to a few hundred microns), the Paschen's Law can be valid in air, dependent of pressure by the product distance x pressure. Is it really valid for my case ? And for the E field in the substrate, this law is good ? Which method must I take ?

Help me please !
Thanks

With uncoated microstrip conductors you'll have to face air breakdown ("arc-over") if voltage is high enough. The two substrates m.a. have much higher dielectric strengths than the air above (15 .. 20 V/µm conf. to (a rather conservative value) of 3 V/µm for (dry) air @ STP conditions). Hence Paschen's Law should hold for a good approximation. S.a. the PDF below:

 

[Tucco]

breakdown voltage vs pressure

After investigations, I think that for my specific problem, it's better to use paschen's curves that give a minimum value of 327 Volts in dry air for electrodes close to 5 to 100 µm. It's a geater value than just applying the general electrical strength (50 µm x 3V/µm= 150V).

It seems that, under 5 µm, the breakdown law is more complex to calculate...

Electrical Breakdown in Atmospheric Air Between Closely Spaced (0.2pm-40pm) Electrical Contacts - Paul G. Slade & Erik D. Taylor - IEEE - 2001