SCREENING METHOD FOR ELECTROLYTIC CAPACITORS

• Main Authors: WILLIAM A. MILLMAN, MICHAEL I. MILLER, MARK LEINONEN, MARC V. BEAULIEU
• Format: Patent
• Language: English; Korean
• Published: 10.03.2014
• Subjects: BASIC ELECTRIC ELEMENTS; CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES ORLIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE; ELECTRICITY

A method of iteratively screening a sample of electrolytic capacitors having a predetermined rated voltage is provided. The method includes the steps of: measuring a first leakage current of a first set of capacitors; calculating a first mean leakage current therefrom; and removing capacitors from the first set having a first leakage current equal to or above a first predetermined value, thereby forming a second set of capacitors. The second set can be subjected to a burn in heat treatment where a test voltage can be applied, and then a second leakage current of the second set of capacitors can be measured and a second mean leakage current can be calculated. Capacitors having a second leakage current equal to or above a second predetermined value can be removed from the second set, forming a third set of capacitors. Because of such iterative screening, the capacitors in the third set have low failure rates. [Reference numerals] (100) Screening method for electrolytic capacitors; (102) Process steps; (104) Screening steps; (106) Output; (108) First DCL measurement; (110) First DCL limit determined from normalized population; (112) First iteration part screening and removal of potential unstable units; (114) Heating/burn-in treatment; (116) Heating/burn-in treatment performed at a predetermined test voltage; (118) Reduction in the DCL of the base population and exposure of unstable units; (120) Reflow; (122) Convection linear oven with a peak temperature profile; (124) Application of thermomechanical stress to expose unstable units; (126) Second DCL measurement; (128) Second DCL limit determined from normalized population; (130) Second iteration part screening and removal of potential unstable units; (132) Third DCL measurement; (134) Third DCL limit determined from normalized population; (136) Third iteration part screening and removal of potential unstable units