Microstructural evolution of co-fired ceramic tapes for MEMS applications

A study of the structure and thermodynamics of the densification process in a model alumina-based ceramic tape system during thermal processing is presented. DuPont's Green Tape(TM) 951, which is primarily composed of frit (>50% silica), alumina and an organic binder, is used as the model system. The microstructures of annealed specimens are characterized by scanning electron microscopy as a function of annealing time and temperature. The distribution and shape of pre-existent pores and frit particles are found to be strongly dependent on the processing conditions. With the processing temperatures significantly below conventional sintering temperature of alumina, the behavior of the frit is the critical determinant of the final microstructure and mechanical behavior.