MICROSTRUCTURE DEVELOPMENT AND ELECTRICAL PROPERTIES OF RUTHENIUM DIOXIDE - GLASS THICK FILM RESISTORS - A NONISOTHERMAL STUDY (HYBRID CIRCUITS, ELECTROCERAMICS, MICROELECTRONICS)
Abstract
A nonisothermal constant heating rate study of the microstructure development in RuO(,2)-lead borosilicate glass-alumina substrate thick film resistor system was performed. Formalisms for describing the kinetics of the various microstructure development processes under constant heating rate processing conditions were developed. The effect of glass-substrate interaction was accounted for, throughout the entire resistor processing cycle. The glass sintering stages were evaluated by correlating the quantitative microscopy data with the theoretical predictions. At low volume fractions of the conductive, glass particles sinter together forming clusters or islands. The glass island size distribution observations were utilized to evaluate the glass sintering kinetics. The rearrangement of the conductive due to the phenomenon of Brownian motion during liquid phase sintering was addressed. The Brownian motion collision time and the liquid phase sintering kinetics of the conductive were evaluated as functions of materials properties and processing conditions such as the conductive particle size and volume fraction, the constant heating and cooling rate, the peak firing temperature, and hold time at the peak temperature. The formation of the chain-like, highly connected, skeletal microstructure of the thick film resistors was explained on the basis of the kinetics of conductive rearrangement process and the liquid phase sintering of the conductive. The RuO(,2) ring size distributions were studied and the effect of the RuO(,2) particle size and volume fraction and the glass island formation on these distributions is discussed. The effect of high volume fraction of the conductive on the thickness of the conductive rings and hence on the continuous change in the resistivity (blending curve) is discussed. Based on above observations and analyses, a new modified percolation model for the blending curve is proposed. This model is based on only two parameters and can explain the observed changes in room temperature resistivity with: (a) processing for constant resistor ink chemistry and (b) resistor ink chemistry for constant processing. The analyses presented in this work bring out the complexities involved in the thick film resistor system and shed light on the factors that need to be considered during resistor modeling. Such analyses show promise of converting the thick film technology from an 'art' to a 'science'.
Degree
Ph.D.
Subject Area
Materials science
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