EFFECT OF MISMATCHED SINTERING KINETICS ON CAMBER IN A LOW-TEMPERATURE COFIRED CERAMIC PACKAGE

Linear shrinkage profiles of an unconstrained gold thick film material and a low-temperature cofireable glass-ceramic (LTCC) green tape were measured using a noncontact optical technique. A laser beam scans across a sample, determining the width of the sample at various times during the sintering process. The unconstrained sintering kinetics of the gold film were found to differ significantly from those of the LTCC tape. The densification of the gold film was nearly completed before the LTCC began to densify. The development of camber (warpage) during cosintering of a gold/LTCC composite structure was monitored and recorded with a video camera. This camber development is analyzed based on the viscous constitutive relations for porous sintering bodies. The mismatched sintering kinetics of the two materials lead to the development of in-plane stresses in the two constituents of the composite structure as one material being constrained from sintering by the other. The resulting camber during the cosintering process is explained by the development of these stresses.