The co-sintering of LTCC materials

The sintering behavior of LTCC/silver-palladium conductor bi-layers was studied in situ using video observation. This allowed simultaneous measurement of length. of the. bi-layer, its curvature, as well as the thickness of each of the layers. The free sintering behavior of the, materials was also characterized using in situ video observation. The mismatch in the shrinkage kinetics between the LTCC and the conductors, which had the same composition but differed in that one was a mixture of Ag and Pd and the other was an alloy, caused the bi-layers to curve and the, layers to have anisotropic shrinkage. The curvature of the bi-layers during sintering was very different for the two conductors due to their greatly different free sintering behavior. The uniaxial viscosity Of the LTCC and the Ag-Pd alloy material were measured using cyclic loading dilatometry. The free sintering and uniaxial viscosity results were fit by empirical equations that were then used to model the shrinkage behavior of the bi-layers using a simple analytical model that neglects the bending stresses. The predictions of the model were consistent with the measured in-plane shrinkage. However, the thickness shrinkage predictions of the model did not fit the data as well. When bi-layers were sintered such that warping was constrained so that there were no bending stresses, the thickness shrinkage behavior was I nearly the same as when warping occurred. Finally, the viscous analog of the elastic bi-layer curvature equation fit the bi-layer curvature data reasonably well.