Effects of combined stressing on the electrical properties of film and ceramic capacitors
Advanced power systems which generate, control and distribute electrical power to many large loads are a requirement for future space exploration missions. The development of high temperature insulating materials and power components constitute a key element in systems which are lightweight, efficient, and are capable of surviving the hostile space environment. In previous work, experiments were carried out to evaluate film and ceramic capacitors for potential use in high temperature applications. The effects of thermal stressing, in air and without electrical bias, on the electrical properties of the capacitors as a function of thermal aging up to 12 weeks were determined. In this work, the combined effects of thermal aging and electrical stresses on the properties of teflon film and ceramic power capacitors were examined. The ceramic capacitors were thermally aged for 35 weeks and the teflon capacitors for 15 weeks at 200/spl deg/C under full electrical bias and were characterized, on a weekly basis, in terms of their capacitance stability and electrical loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also obtained. The results obtained represent the influence that short-term thermal aging and electrical bias, have on the electrical properties of the power capacitors characterized.<<ETX>>
On-wafer capacitors under mechanical stress
New packaging materials make it possible to produce flexible system in package (SIP) and system on package (SOP) modules. However, in these the integrated circuits are exposed to increased mechanical stresses. The stresses may become even more severe when thinned chips are used. The effect of mechanical stress on the characteristics of on-wafer capacitors was studied. The mechanical stress increased clearly the resonance frequency of poly-insulator-poly capacitors, but caused only minor impedance changes for metal-insulator-metal capacitors. No fatal stress-induced phenomenon was found and the on-wafer capacitors should also operate correctly in SIP and SOP modules. The test chips were processed with two different complementary metal oxide semiconductor processes and the tested on-wafer capacitors had values of 4.8-47 pF.
Toward an electrical power utility for space exploration
Plans for space exploration depend on today's technology programs addressing the novel requirements of space-based enterprise. The requirements for electrical power will be formidable: megawatts in magnitude, reliability for multi-year missions and the flexibility to adapt to needs unanticipated at design time. The reasons for considering the power management and distribution in the various systems from a total mission perspective, rather than simply extrapolating current spacecraft design practice, are discussed. A utility approach to electric power being developed at the Lewis Research Center is described. It integrates requirements from a broad selection of current development programs with studies in which both space and terrestrial technologies are conceptually applied to exploration mission scenarios.