Screening method for electrolytic capacitors that maintains individual capacitor unit identity

A method of iteratively screening a lot of electrolytic capacitors having a predetermined rated voltage, the method comprising:

• measuring a first leakage current of each individual capacitor in a first set of capacitors in the lot and calculating a first mean leakage current therefrom;
• removing each of the individual capacitors from the first set that have a measured first leakage current equal to or above a first predetermined value, thereby forming a second set of capacitors, the first predetermined value being equal to one or more standard deviations above the first mean leakage current;
• subjecting the second set of capacitors to a burn in treatment, wherein the burn in treatment comprises applying a predetermined test voltage to the capacitors;
• after the burn in treatment, measuring a second leakage current for each of the individual capacitors in the second set of capacitors and calculating a second mean leakage current therefrom;
• comparing the second leakage current measured for each of the individual capacitors in the second set to the first leakage current measured for each of the individual capacitors in the second set;
• and
• removing from the lot each of the individual capacitors from the second set that have a second leakage current equal to or above a second predetermined value and/or that have a second leakage current that does not change by a specified amount compared to the first leakage current measured for each of the individual capacitors, thereby forming a third set of capacitors, the second predetermined value being equal to one or more standard deviations above the second mean leakage current, wherein each of the capacitors in the first set is located in a unique position on a carrier plate on a leakage current measurement apparatus, further wherein each of the individual capacitors in the second set of capacitors is maintained in its respective unique position on the carrier plate on the leakage current measurement apparatus, further wherein the carrier plate is positioned on the leakage current measurement apparatus in the same manner as when the first leakage current was measured.