Pre-Irradiation Biasing Effects in Tantalum Capacitors

The radiation-induced voltage buildup in several types of moderate to high working voltage sintered slug Ta capacitors has been found to be significantly modified by the application of reverse bias (Ta electrode -) prior to irradiation. Alteration of the internal field in the Ta2O5 dielectric caused reduced negative voltage buildups in Sprague capacitors and enhanced buildup in Kemet units. To a first approximation the effect varied with the duration of application of bias and reverse leakage through the capacitor at that bias. The effect is eliminated by irradiation of the shorted capacitor to approximately 60 krad(Ta) or by heating to 100°C for approximately 12 h. Some back-to-back series pairs of Ta capacitors also showed radiation response changes after biasing.