Strategies for Manufacturing Ultra Low ESR Ta Capacitors
Leading edge designs for portable electronic devices require capacitors which deliver volumetric efficiency, high reliability, low cost, reduced propensity for ignition, and low Equivalent Series Resistance (ESR). Tantalum capacitors employing a conductive polymer cathode are uniquely capable of providing all of these critical characteristics. Tantalum capacitors have a long track record for unsurpassed volumetric efficiency and reliability. The introduction of conductive polymer cathodes enabled dramatic reductions in ESR and greatly increased resistance to ignition. The lower ESR and enhanced cap retention at high frequency of the conductive polymer construction enabled circuit designers to reduce the number of capacitors required to achieve design solutions, resulting in reduced cost. Although Multiple Anode Tantalum (MAT) designs are capable of achieving the lowest ESR possible with valve metal capacitors (< 6 milliohms), single anode Ta/polymer capacitors with ESR less than 9 milliohms are now. Single anode capacitors with ESR levels less than 7 milliohms are within reach. The ability to achieve ultra low ESR levels with single anode designs provides the lowest cost, high performance solution to many design requirements. This paper describes the strategy used by manufacturers to provide solid state capacitors with ever decreasing ESR levels.
Electrolytic capacitors from the postwar period to the present
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.
Kinetics of the thermal decomposition of aqueous manganese(II) nitrate solution
Abstract Isothermal weight studies were performed upon aqueous solutions of manganese(II) nitrate. The loss of water followed a first order rate law with activation energies varying from 6 to 10 kcal/mole depending upon the atmosphere. The resulting anhydrous nitrate decomposed to form manganese(II) oxynitrate in accordance with the Erofeev equation with n = 4. The activation energies are 20–25 kcal/mole and show little variation with atmosphere. The resulting oxynitrate decomposed to form manganese(IV) oxide. The rate fits several expressions satisfactorily but a contracting area form is chosen as generally best. The activation energy is about 12 kcal/mole lower in the presence of moisture but this effect upon the rate is partially offset by a substantial decrease in the preexponential term. The manganese(IV) oxide loses oxygen to form manganese(III) oxide. The best rate law is the Jander equation and activation energies are in the range of 47–57 kcal/mole.