Experimental determination of the uniaxial viscosity of low-temperature co-fired ceramic tapes by vertical sintering

This paper reports the experimental determination of the uniaxial viscosity for ceramic tapes made of three commercially available low-temperature cofired ceramic (LTCC), DuPont 951 (glass–ceramic), Ferro A6M (glass) and Yinfeng 8.5 (glass) by utilizing a novel vertical sintering in an optical dilatometer. The green tapes were vertically sintered at different isothermal temperatures ranging from 760 °C to 820 °C under their own weights. The densification behavior was systematically investigated through the measured sintering strains and the uniaxial viscosity was determined as a function of relative density based on a theoretical equation developed for ceramic tapes. The calculated uniaxial viscosities were compared with a previously reported model and good agreements were achieved. The activation energy for the uniaxial viscosity was found to be independent of the relative density and showed an average value of 290±47 kJ/mol for the DuPont tapes but was not accessible currently for the other glass-based LTCC tapes.