Effect of Stress on the Densification of a Low-Temperature Cofired Ceramic (LTCC) System Under Constrained Sintering

The effect of stress on the densification behavior of a low-temperature cofired borosilicate glass (BSG)+alumina system during constrained sintering of a multilayer BSG+alumina/alumina laminate has been investigated. Poorer densification and larger porous bulk viscosity are observed for the BSG+alumina densified under pressure-less constrained sintering in comparison to free sintering. This is caused by the in-plane tensile stress and anisotropic development generated in the transverse directions of the laminate during constrained sintering. The applied uniaxial stress required in the thickness direction to densify BSG+alumina under constrained sintering at 700-800oC varies in the range of 50-400 kPa, in agreement with those calculated theoretically.