Electrolytic Internal Contamination

Gideon Analytical Laboratories performed failure analysis on good and bad Teapo electrolytic capacitors. A comparison leakage current test of the anode foil was set up. The leakage current over time is the best indicator as to whether the anode foil has an adequate crystal ratio of aluminum oxide forms to produce long-term reliability. The foil from the failed Teapo capacitors had multiple cracks like shown in the picture at the top left.

The bad foil (the failed Teapo Capacitors) had excessive outcroppings of aluminum protrusions which will work through the Kraft paper and cause hot spots and shorting. These aluminum clinkers (as they are called because they are very hard compared to the rest of the aluminum foil) will not etch or oxidize as fast as the normal foil. Usually the more clinkers one has more impurities and thus, the more inferior the foil quality. After the etching process, the foil is washed to remove enchants.The tape around the wound is supposed to be as the one shown on NCC capacitor. The tape on the failed Teapo failure has melted from excessive heat (around 190C) which is shown in the picture at the top right. The wound was completely dry with no solvent at all on the Kraft paper. A thorough examination of the Kraft paper revealed excessive aluminum clinkers which are indicative of poor purity foil.

The conclusion is that an acute aluminum particle problem exists on the winding machine, contaminating the Kraft paper. These foreign particles worked their way through the Kraft paper if they were deposited on the cathode side. If they were deposited on the anode side, the electrolyte would oxidize them and the aluminum oxide would hydrate making it soft and less likely to penetrate the Kraft paper barrier.

Failure analysis on components and other types of electronic devices can serve a vital need for a variety of electronics companies. Knowing how and why a failure occurs can save companies an enormous amount of time, money, and can help them better plan for the future. Bookmark Gideon Analytical Laboratories for your future needs.