Defect free carbon tapes as thermal fugitives for multilayer ceramic application

Rheological studies of carbon powder were carried out with different dispersants and solvent systems. Irrespective of the dispersant used, in Xyl-EtOH (50∶50), when the dispersant concentration is 0–2 wt-%, shear thinning behaviour only is observed. Optimum dispersant concentration for MFO and KD-1 is found to be 3 wt-%. Even for other solvent systems such as Tol-EtOH and MEK-EtOH, MFO and KD-1 were found to be good dispersants. For a given dispersant, Xyl-EtOH with 50∶50 ratio was found to be the optimum with minimum viscosity and yield stress. Based on this, tape casting of carbon powder was carried out using Xyl-EtOH (50∶50) as the solvent system with KD-1 (3 wt-%) as the dispersant for a solid loading of 30 wt-%. The tapes were agglomerate free yet severe drying related problems were observed. Defect free carbon tapes of desired thickness were achieved by controlling the evaporation and diffusion rates of solvents.