We have developed a new method for measuring the value of breakdown voltage in air for electrode separations from 400nmto45μm. The electrodes used were thin film Au lines evaporated on sapphire. The resulting capacitors had an area of 80×80μm2. We demonstrate the ability to deduce the value of the separation of the plates by the value of the capacitance. The data acquired with this method do not agree with Paschen's law for electrode separations below 10μm, as expected from previous experiments. Amongst the improvements of our method are the measurement of plate separation and the very small surface roughness (average of 6nm).