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.
Effect of Temperature Cycling and Exposure to Extreme Temperatures on Reliability of Solid Tantalum Capacitors
In this work, results of multiple temperature cycling (TC) (up to 1,000 cycles) of different types of solid tantalum capacitors are analyzed and reported. Deformation of chip tantalum during temperature variations simulating reflow soldering conditions was measured to evaluate the possibility of the pop-corning effect in the parts. To simulate the effect of short-time exposures to solder reflow temperatures on the reliability of tantalum capacitors, several part types were subjected to multiple cycles (up to 100) between room temperature and 240 C with periodical measurements of electrical characteristics of the parts. Mechanisms of degradation caused by temperature cycling and exposure to high temperatures, and the requirements of MIL-PRF-55365 for assessment of the resistance of the parts to soldering heat are discussed.
Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 1. Mechanism
Abstract The thermal decomposition of aqueous manganese nitrate solutions in air or nitrogen proceeds in three steps: 1. (i) partial evaporation of water to a concentrated solution containing equimolar amounts of water and Mn(NO3)2, 2. (ii) a first decomposition step in which the residual water evolves and part of the Mn(NO3)2 decomposes to MnO2, and 3. (iii) a second decomposition step in which the remaining Mn(NO3)2 decomposes to MnO2. Decomposition of part of the Mn(NO3)2 in the first step is caused by the presence of water (vapour) which accelerates the decomposition of anhydrous Mn(NO3)2 and lowers the temperature at which this reaction starts. Without water [anhydrous Mn(NO3)2] only one decomposition step occurs. Off-gas analysis with mass spectrometry, IR spectroscopy and chemiluminescence showed NO2 to be the main gaseous product, NO being formed in much smaller amounts. amounts.