High Voltage Tantalum Polymer Capacitors
Solid tantalum (Ta) capacitors with intrinsically conductive polymers as the cathode material have been widely used in the electronics industry due to their low equivalent series resistance (ESR) and “non-burning/non-ignition” failure mode. Intrinsically conductive polymers, commonly known as conductive polymers, are electrically conductive at the molecular level. Unlike polymeric materials whose electrical conductivity is imported from the presence of foreign conductive particles (for example silver paints or adhesives), a single molecule (a polymer chain) of an intrinsically conductive polymer is conductive. Various types of conductive polymers including polypyrrole, polyaniline, and polyethyldioxythiophene (PEDT) can be applied to dielectric oxides to serve as the primary cathode material for solid electrolytic capacitors. Two methods of coating the dielectric oxide with conductive polymers are widely used in the industry, in-situ polymerization and electrochemical polymerization. In in-situ polymerization the monomer of an intrinsically conductive polymer is brought into contact with an oxidizer to drive the polymerization reaction. In electrochemical polymerization the reaction is driven by an externally supplied current. The major drawback of conductive polymer capacitors, regardless of the type or method of application, is their relatively low working voltages compared to their MnO2 counterparts. For example, the maximum voltage rating of existing surface mount polymer tantalum capacitors is 25 volts, while that of their MnO2 counterparts is 50 volts. When subjected to voltages exceeding 25 volts, the existing polymer capacitors have, to varying degrees, reliability issues. This limitation has restricted the use of these devices to relatively low voltage applications (<20 volts). New developments in material and process technologies have overcome these limitations leading to the introduction of a new line of high voltage tantalum polymer capacitors with excellent long term reliability.
New Tantalum Capacitors in Power Supply Applications 1998 IEEE Industry Applications Society Annual Meeting
Capacitors used in various applications are usually selected for the usage by the type of capacitor. This selection process is most visible in the selection of the aluminum electrolytic for power supply applications. Developments related to improve per$ormance of an alternative type of capacitor is sometimes lost to the user because of the narrow focus given to the one type. It is of the designer's best interest to be aware of the developments of all types for all applications, It is the intent of this paper to present the latest developments for power applications with the tantalum capacitor.
Prediction of Muscular Endurance (Work Performance) From Individual Differences in Initial and Post Training Increments in Static Strength
Forty college men were given tests for static strength and strength endurance prior to an isotonic strength training program. Experimental results indicate that individual differences in static strength are a poor criterion in the prediction of muscular endurance. Following an increase in static strength resulting from isotonic strength training pre-training static strength and post-training strength increments are not indicative of an individual's performance in a hand grip endurance activity.