An exploration of leakage current

Abstract

A simple programmable sequence of measurements which allows classification of leakage currents of capacitors based on their time, temperature, and voltage characteristics has been devised. The method adopts the concept that the measured current is the sum of independent flow mechanisms, one of which is present to a consistent extent in all the capacitors. By removal of this part from the total, the true behavior pattern of the excess current can be determined. This method was applied to solid tantalum capacitors. Examination of capacitors in this manner produces a wide range of behavior patterns. In some instances, the voltage dependence is essentially ohmic, while in others there is a very steep slope to the current/voltage plots. These plots can also display sudden breaks due to self-healing or catastrophic localized breakdown. From the temperature characteristics, activation energies for the current flow can be estimated, and these are generally in the region of 0.1 to 0.4 eV. However, detailed comparison of these activation energies often suggests that the simple Arrhenius equation may not adequately represent the behavior. In addition to the measurement of leakage current, further evidence of flaws can be gleaned from the discharge currents. Direct contact between the manganese dioxide and the tantalum due, for instance, to rupture of the dielectric under high mechanical stress can produce a battery effect leading to low currents which are detectable in the discharge mode. >