Micropower Sources Research Articles

Microinductor for flip-chip micropower source

The rapid reduction of line width of large-scale integration (LSI) processes to a width of under 100 nm and the lowering of voltage to below 1 V to drive LSI, in addition to the sharp market growth of personal IT devices using lithium batteries, have seriously raised energy consumption around the world, necessitating the adoption of energy-saving technology using distributed small dc-dc convertors. In light of these demands, using new power microelectromechanical system technology and continuous deposition technology, we have developed a new microinductor with a thickness of 300 /spl mu/m. The magnetic core, consisting of CoFeSiB-Ti-SiO/sub 2/ multilayer film on a polyimide sheet, is applicable to a microinductor using a helical coil. In comparison with a mono-layer core such as a ferrite core, due to the magnetic shielding effect of each magnetic layers, a composite multilayer magnetic core is very effective in maintaining inductance up to a high dc current over 1 A. This paper proposes the use of microinductors characterized by high quality, superior dc-biased properties and low height as flip-chip sized micropower sources.

Lithium micro-battery development at the Jet Propulsion Laboratory

Recent successes in the effort to miniaturize spacecraft components using MEMS technology, integrated passive components, and low power electronics have driven the need for very low power, low profile, low mass micro-power sources for micro/nanospacecraft applications. Recent work at JPL has focused upon developing thin film/micro-batteries compatible with temperature sensitive substrates. A process to prepare crystalline LiCoO/sub 2/ films with RF sputtering and moderate (<700/spl deg/C) annealing temperature has been developed. Thin film batteries with cathode films prepared with this process have specific capacities approaching the practical limit for LiCoO/sub 2/, with acceptable rate capabilities and discharge voltage profiles. Solid-state micro-scale batteries have also been fabricated with feature sizes on the order of 50 microns.

Solid state thin-film lithium battery systems

Thin-film rechargeable lithium batteries, less than 15 μm thick, are being developed as micro-power sources. Batteries with long cycle lives have been constructed with a variety of electrode materials and cell configurations onto thin ceramic, metal, and Si substrates. Improvements in the properties of several well-known cathode thin-film materials have been reported, while several novel thin-film anode materials have been introduced in recent papers. All recent thin-film batteries with moderate discharge powers and cycle lives rely on the amorphous lithium phosphorus oxynitride electrolyte, known as Lipon, deposited by rf magnetron sputtering.

Electrochemical studies on solid state cells with mol % 70AgI-20Ag2O-10(0.8V2O5-0.2P2O5) amorphous electrolyte and organic cathodes

The highest conducting amorphous solid electrolyte composition (mol %) 70AgI-20Ag2O-10(0.8V2O5-0.2P2O5) in the system AgI-Ag2O-V2O5-P2O5 was investigated as an electrolyte material for solid state cells with organic cathodes by studying the electrochemical properties. The variation of open circuit voltage (OCV) with temperature, current discharge and the load characteristics were determined for the cells with iodine, tetramethyl ammonium iodide and tetrabutyl ammonium iodide as cathode materials. The cell capacities were estimated from the load characteristic curves and, in general, the cells were found to have very good stability at low current discharges even at high temperatures. In addition, it was found that the silver on the working electrode is electrochemically active and can be oxidized to Ag+ ions, making the organic cathode cells rechargeable. Thus these cells find potential use in rechargeable micropower sources and uninterrupted power supplies for microelectronic circuit devices.