Effect of Friction on Inhomogeneous Shrinkage Behavior of Structured LTCC Tapes
Abstract:Vias, cavities, and other cutouts are significant inhomogeneities in low temperature co-fired ceramics (LTCC) tapes and lead to inhomogeneous shrinkage during sintering, which has a negative effect on the quality of the final multilayer device. The influence of such cutouts on the shrinkage behavior of LTCC tapes was investigated by an exact measurement of the geometry before and after sintering and by in situ observations with an optical dilatometer. The investigations show a strong influence of cutouts on the magnitude of shrinkage inhomogeneities. This effect is more pronounced, if the tapes become thinner, the dimensions of the cutouts become larger, or their position becomes less centric. It is shown that the most important factor on the occurrence of shrinkage inhomogeneities in tapes with cutouts is the static friction of the LTCC material on the setter. Severe warpage is caused by interlocking effects, which occur at bumps of the rough setter surface when the inner edges of the cutouts are pulled over the setter. By using a separating agent between the LTCC tape and the setter, the static friction could be minimized, which eliminates the sintering inhomogeneities.
Document Type: Research Article
Affiliations: Department of Materials Science, Glass and Ceramics, University of Erlangen-Nuremberg, 91058 Erlangen, Germany
Publication date: 2006-09-01