3D FEM simulation of stress evolution induced during sintering in silicon-ceramic composite substrates

Abstract:
The fabrication of silicon-ceramic composite (SiCer) substrates enables new architectures and possibilities for advanced microsystems, but some challenges, such as inhomogeneous adhesion and cracking, exist that need to be addressed. This research is especially focused on the issue of crack formation in patterned LTCC layers that is caused by inadequate designs, e.g. of cavities, and by the built-up of mechanical stress in the SiCer substrate. The mechanical stress evolution was studied mainly by numerical simulations using the finite element method assuming an experimental temperature profile with temperatures of up to 900 °C, but assuming constant material properties also for the ceramic material to significantly simplify the simulation in a first approach. Based on the simulations and in comparison, to experiments, we show that cavities influence the stress distribution and cracking in the examined parameter range mainly by their shape, number, and distribution rather than by their size. In this regard, top-view cavity shapes with rounded edges or with circular cross sections are, for instance, preferable.