The first article in this series [1] covered the early history of electrolytic capacitors, from their invention around 1880 to the invention of the modern Al electrolytic capacitor structure in 1925. The second article [2] takes us from Samuel Ruben’s 1925 invention to the wide range of Al electrolytic capacitors presently on the market. The present article discusses electrolytic capacitors based on metals other than Al.

Electrolytic capacitors from the postwar period to the present

Life model for tantalum electrolytic capacitors with conductive polymers

Deep space and Icy Moon missions (Titan, Enceladus, Ceres, Europa, & Ganymede) will need qualified extreme environment capable components for electronic systems located in extremities of their rovers and spacecraft. Commercial off the shelf (COTS) components would be advantageous to use for some aspects of such projects, given that they are easier to procure and offer a broad range of functionalities. Furthermore, theoretical and experimental data suggest that many COTS parts are capable of operation, and not just storage, at temperatures well beyond the manufacturer specified temperature limits. To help address the challenges presented at near cryogenic temperatures, a COTS selection knowledge base is being developed to estimate the performance of COTS components within cold environments. The knowledge base captures queries from a range of information sources such as cold functionality test results for part types and families, theoretical and experimental literature reviews and key findings are summarized here. In addition, a selection of components are planned to be examined for their performance to near cryogenic temperatures to generate a methodology for identification and verification of the COTS candidates. As the qualification of COTS parts for extreme environments can be very costly, this knowledge base can serve to reduce qualification time and cost by pre-selecting and limiting candidates.

Evaluation of commercial-off-the-shelf (COTS) electronics for extreme cold environments

Due to their high specific volumetric capacitance, electrolytic capacitors are used in many fields of power electronics, mainly for filtering and energy storage functions. Their characteristics change strongly with frequency, temperature and aging time. Electrolytic capacitors are among the components whose lifetime has the greatest influence on the reliability of electrical systems. Over the past three decades, many efforts in academic research have been devoted to improving reliability capacitor. Industrial applications require more reliable power electronic products. It is in this context that the different electrolytic capacitors and their characteristics are discussed. The aging process of aluminum electrolytic capacitors is explained. Finally, this paper reviews existing methods of failure prognosis of electrolytic capacitors. 

Electrolytic capacitor: Properties and operation

Despite being highly reliable under steady state operating conditions, manganese dioxide (MnO2) tantalum capacitors are prone to catastrophic exothermic failures under surge current conditions. Such failures can be mitigated by the use of conductive polymers in place of MnO2. However, these polymers are more susceptible to failure at elevated humidity levels. In this paper, the electrical performances of both MnO2 and polymer tantalum capacitors are compared by subjecting them to temperature humidity bias testing at 85°C and 85% RH. The test population consists of tantalum capacitors with two voltage ratings (50V and 16V). At each of these voltage ratings, two sets of tantalum capacitors, one each with MnO2 and conductive polymer electrodes, were tested. The voltage levels used to bias the capacitors were periodically increased in multiples of the rated voltage to accelerate degradation. The performance of the capacitors was tracked by monitoring their capacitance, dissipation factors and leakage currents...

Reliability of Manganese Dioxide and Conductive Polymer Tantalum Capacitors under Temperature Humidity Bias Testing

Overview Reviewed data Caution must be taken when accelerating test conditions Data not useful to establish an acceleration model Introduction of new failure mechanism skewing results Evidence of Anti-Wear-Out De-doping of polymer Decreased capacitance Increased ESR Not dielectric breakdown Needs further investigation Further investigation into tantalum polymer capacitor technology Promising acceleration model for Manufacturer A Possibility for use in high-reliability space applications with suitable voltage derating.

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Penelope Spence

Papers

Characterization of Tantalum Polymer Capacitors