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.
Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 2. Heats of reaction
Abstract Differential thermal analysis of the thermal decomposition of aqueous manganese nitrate solutions in air and nitrogen shows three distinct endothermic heat effects. The first effect results from partial evaporation of water to a solution containing equimolar amounts of H2O and Mn(NO3)2. The two subsequent decomposition steps produce MnO2. The heat effect of each of the latter two steps depends on the sample weight but their sum remains constant at about 170 ± 14 kJ mole−1. Decomposition under vacuum of anhydrous Mn(NO3)2 shows only one heat effect of 155 ± 12 kJ mole−1. DTA and X-ray analysis indicate that decomposition of a Mn(NO3)2 solution results in γ-MnO2 and decomposition under vacuum of anhydrous Mn(NO3)2 results in γ-MnO2 with large amounts of Mn(NO3)2. A comparison between measured and calculated heats of reaction shows fair agreement.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.