Hi Lidu,

the breakdown voltage (Vb) depends on the gas in the gap and its pressure.
Assuming you have air at atmospheric pressure, theoretically there will be
no breakdown below 327 V, no matter what the electrode distance is. (see
http://home.earthlink.net/~jimlux/hv/paschen.htm, for example). Below a
distance of about 5 um things become a bit more difficult, and it is hard to
find any conclusive data. At low distances breakdown depends on field
strength and therefore on the electrode geometry (including surface
roughness) and so on. At a fieldstrength above 100 V/um you might have some
field emission of electrons, which is likely to develop into a breakdown at
some point. To my opinion, there is a low risk of breakdown up to 50 V/um if
the electrodes are free standing. When they are connected by an insulator,
Vb is reduced.
The only way to be sure, is to try. I'd be interested in your results!

Here are some papers about the subject:
T. Ono, et al., Micro-discharge and electric breakdown in a micro-gap.
Journal of Micromechanics and Microengineering, 2000. 10(3): pp. 445-451.
J.-M. Torres, et al., Electric field breakdown at micrometre separations.
Nanotechnology, 1999. 10(1): pp. 102-107.
R.S. Dhariwal, et al., Breakdown electric field strength between small
electrode spacings in air. In: Micro Systems Technologies '94. 1994. Berlin:
VDE-Verlag GmbH.

Good luck!

Cheers,

Ralf G. Longwitz.

Research Assistant
Microsystems integration group
Swiss Fed. Inst. of Technology
_______________________________

EPFL-DMT-IMS  BM 3.125
CH-1015 Lausanne
http://dmtwww.epfl.ch/~rlongwit
tel: +41.21-693 6727
fax: +41.21-693 5950
_______________________________


> Message: 2
> Date: Tue, 02 Oct 2001 11:32:57 -0700
> From: Lidu Huang 
> Organization: Fujitsu Laboratories of America
> To: [email protected]
> Subject: [mems-talk] Electric breakdown in MEMS air gap
>
> Hi,
>
> Could someone provide some data on electric breakdown
> in MEMS air gap?
>
> For usual electro-mechanical device, the electric field
> strength to prevent arcing is typically set at 3 (V/um).
> Would the breakdown strength be higher for MEMS devices?
>
> Thanks!
> Lidu Huang