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|Kinetic Modeling of LTCC-Shrinkage|
|Keywords: Glass Matrix Composites, Sintering Kinetics, Materials Development|
|Low Temperature Co-fired Ceramics (LTCC) are progressively used in ceramic packaging of sensors and microsystems for medical, telecommunication and automotive applications. Microstructure and properties of these ceramic composite materials can be widely tailored selecting appropriate glass and crystal powders, tuning volume fractions, powder processing and firing schedule. However, during firing complex phenomena as the influence of rigid inclusions on the effective viscosity and sintering as well as the effect of particle size distribution, partial dissolution and crystallization on sintering have to be controlled. Despite the great economic potential of LTCC up to now no systematic studies have been made for LTCC model composites of technological relevance, e.g. concerning the glass type, particle size distribution, heating rate etc.. Thus, materials design for LTCC is still restricted to empirical trial-and-error methods. The aim of the present paper is to study the sintering of glass matrix composites (GMC) for LTCC applications by means of dilatometry, hot stage microscopy and electron microscopy. The effective viscosity of the GMC was measured with a parallel plate viscometer. The model system studied here do not show detectable crystallization and solution during sintering, reflects the mere presence of varying volume factions Phi (<0.45) of Al2O3 filler particles dispersed in a alumoborosilicate glass matrix. Shrinkage is progressively retarded with increasing Phi. The retardation could be quantitative correlated with an effective viscosity due to the glass to dispersed phase ratio. This effective viscosity increasingly dominates the sintering behaviour and can be quantified in terms of the wetted surface fraction of the alumina particles. A mathematic model, which allows for prediction of the observed sintering behaviour based on technologic parameters, is introduced.|
|Markus Eberstein, Materials Developer
Federal Institute for Materials Research and Testing (BAM)