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.
2007 CARTS-Low Impedance Ta Capacitors
Trends in circuit design for miniature consumer electronics are driving the need for very low impedance capacitors. Increasingly complex IC’s requiring higher current and operating at higher frequencies have led to a need to reduce operating voltages to minimize heat buildup. All of these factors contribute to the need for low impedance decoupling capacitors. In order to meet the challenges posed by the changes in circuit design passive component manufacturers have increased capacitance density and reduced ESR and ESL. This paper reviews enabling technologies currently being used, as well as those being developed, by tantalum component manufacturers to continue to provide low cost solutions to fulfill the needs of the electronics industry. Low Impedance Applications Capacitors are used in electronic circuits to store and manage energy. Their functions include filtering, tuning, energy storage, decoupling, etc. Tantalum capacitors have been the components of choice for years in applications requiring high volumetric efficiency and reliability. In applications such as output voltage filtering or decoupling, low impedance, excellent surge performance, and high ripple current capability are critical. Impedance is a measure of the sum of elements in a capacitor that resist the flow of AC current. Within a capacitor, three quantities comprise the impedance: Equation for Impedance ( ) 2 L C X X R Z − + = (1) R = Equivalent Series Resistance (ESR) XC = Capacitive reactance= 1/(2πfC) XL = Inductive reactance= 2πfL f = frequency C = capacitance L = Equivalent Series Inductance (ESL) ESR for tantalum capacitors is measured at a test frequency of 100k Hz. Due to the porous internal structure of tantalum capacitors, their performance at higher operating frequencies is inferior to ceramic capacitors, but generally
Numerical and experimental investigation on air distributor design of fluidized bed reactor of sawdust pyrolysis
Abstract An improved biomass conversion in a lab-scale fluidized bed reactor (FBR) is achieved by optimizing the air distributor orifice size and number. Two approaches for introducing air were numerically and experimentally examined. These included perforated plate and downward orifice sparger. 3 mm and 5 mm orifice diameters, and 7, 9 and 13 holes were simulated at flow velocities of 2, 4, 6, and 8 times the minimum fluidization velocity, Umf. The simulation results revealed that increasing the orifice number has a positive effect on gas holdup, particularly for the perforated plate, which showed a uniform distribution of bubbles. The sparger configuration produced larger bubbles sizes, which could lead to better recirculation of solid flux, while stagnant particle zones were observed at the lower section of both distributors. A pyrolysis unit is also inserted at the top of freeboard of the FBR. For perforated plate with 6Umf, the pyrolysis process achieved thermal and cold gas efficiencies of 82.91% and 52.03%, respectively, while combustible gases with 41.6%mol CO, 8.7%mol CH 4 and 2.17%mol HC, were obtained. For sparger pipe and 6U mf _sp, 35.33 ppm NOx and 111 ppm SO 2 were measured in flue gas from combustion process at bed region.