The most time consuming step in the manufacture of aluminum electrolytic capacitors occurs during aging. Aging is performed after assembly and impregnation with electrolyte when the capacitor is placed on voltage for a given amount of time. During the aging process, oxide is re-grown on areas of the anode foil that were damaged during the manufacturing process. Simply decreasing this time at voltage leads to higher leakage, due to insufficient oxide thickness. Increasing the applied current during the aging process is one way of increasing the number of coulombs of charge passed in a given amount of time, but thermal heating of the capacitor can be problematic. Another way of reducing the time at age is to increase the average current during age by incorporating "multiphase" aging in which the capacitor is charged and discharged repeatedly during its time at age. During the aging process once the capacitor reaches voltage the applied current begins decreasing or "bleeding down". The longer the capacitor is at voltage, the lower the current. Because the current during each step of "multi-phase" aging does not decrease as much as in single phase aging, the average current is greater allowing more coulombs of charge to pass during an equivalent amount of time. If aging is only concerned with the amount of Coulombs passed, then this can result in a reduction of the leakage currents. This paper explores and contrasts the results of aging capacitors using a single-phase aging procedure versus various "multi-phase" aging procedures, as well as the role of heat during age, in which the length and number of phases are changed.
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