MICROSTRUCTURE DEVELOPMENT PROCESSES IN RUTHENIUM DIOXIDE - GLASS THICK-FILM RESISTORS
Abstract
The properties of commercial thick-film resistors depend on the interactions occurring among the substrate, the conductive, and the glass when the ingredients are processed. The resulting microstructure, which dictates the electrical characteristics of the resistor, is a nontrivial function of several materials properties and processing parameters. The sequence of microstructure development in FuO(,2)-lead borosilicate glass-alumina system is analyzed by developing formalisms to describe the kinetics of the individual stages, taking into account the effect of the dissolved substrate in the glass. The phenomena of glass sintering, glass infiltration, conductive rearrangement, and liquid phase sintering and ripening of the conductive are addressed. For each stage, kinetic equations are derived and utilized to identify the dominant materials and processing parameters, aiding in converting the art of resistor manufacturing into a science. A methodology is presented for the analysis of kinetics in nonisothermal processing and for considering the effect of the rate of dissolution of the substrate in isothermal processing. The importance of the solubility of the conductive in glass is discussed. Equations are developed for the intermediate stage sintering of glass. A description available in literature for spreading kinetics is shown to be inaccurate and an alternative description is provided. Parameters characterizing wettability are defined to aid in selection of materials. Time dependent contact angle and the temperature dependence of such time dependence are incorporated in the analysis of glass infiltration. The method of deriving sintering kinetics equations is critically reviewed, pointing out the inadequacies. Liquid phase sintering kinetics equations are derived for diffusion control and reaction control using chemical potential differences as driving forces. The utility of this analysis is illustrated using a typical time-temperature profile. All the processes except RuO(,2) sintering are completed before attaining the peak firing temperature. A finite extent of RuO(,2) sintering occurs at the peak temperature, and the role of RuO(,2) ripening in microstructure development is insignificant. The analysis presented in this work is a beginning in the direction of microstructural engineering of thick-film resistors.
Degree
Ph.D.
Subject Area
Materials science
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