Distortion of an LTCC Bilayer during Constrained Sintering: Comparison between Ombroscopic Imaging and Modeling.

A complete methodology combining experiments and modeling has been developed to investigate the constrained sintering of low-temperature cofired ceramic (LTCC) systems. The thermomechanical and sintering behavior laws, previously identified for the selected commercial LTCC material, were implemented in a finite element model. The reliability and validity range of the built model has been investigated thanks to the development of a specific distortion experience. The distortion generated during the constrained sintering of a porous LTCC layer deposited on a dense one has been monitored in situ by ombroscopy. The measured camber evolution was compared with numerical results. The camber phenomena predicted numerically and observed experimentally are very similar, characterized by the onset of distortion around 918 K and a similar evolution during heating. However, at high temperatures (around 1100 K), the simulated camber slightly differs from the experimental one. It seems to be related to the damage to the dense LTCC layer by microcracking.