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.
Improved SMT Performance of Tantalum Conductive Polymer Capacitors with Very Low ESR
KEMET Electronics Corp has implemented several process and material improvements in order to improve the surface mount (SMT) performance of low ESR conductive polymer tantalum capacitors. This includes large case size (up to 7343-43) capacitors with ESR as low as 5 mΩ. Six Sigma methodologies (DMAIC: define-measure-analyze-improve-control) were used to structure the improvement process. This paper describes the project goals (define phase), new measurement techniques that had to be developed (measure phase), the conceptual model to explain SMT failures (analyze phase), process and material improvements (improve phase), and new control measures put in place (control phase).
The thermal decomposition of aqueous manganese (II) nitrate solution
Abstract The thermal decomposition of commercially available aqueous solutions of manganese(II) nitrate was investigated using the conventional thermal analytical techniques of thermogravimetry (TG), differential thermal analysis (DTA), and evolved gas analysis (EGA). Infrared spectra and X-ray diffraction patterns were used to help characterize intermediate species. TG and DTA experiments were performed in both wet and dry oxygen and nitrogen. The solution rapidly looses water around 100°C until it approaches a glassy type material near Mn(NO3)2·2H2O. Between 200–300°C the material loses, in close succession, its remaining water, a molecule of NO2 to form MNONO3, and finally another NO2 to form MnO2. The intermediate manganese(III) oxynitrate cannot be isolated. Wet atmospheres reduce the temperature separations between these reactions. Between 500–550°C the MnO2 loses oxygen to form Mn2O3 and finally at 800–1000°C Mn3O4 is formed.