Chemical degradation of screen-printed thick films on LTCC

The degradation behavior of screen-printed thick films on LTCC was investigated in sulfuric and nitric acid. The samples were examined with regard to their mass loss as well as by means of scanning electron microscopy. Additionally, the eluates were analyzed with voltammetric and spectroscopic methods. In any case, the degradation is dominated by the dissolution of an alumosilicate phase. The degradation in sulfuric acid is generally lower than in nitric acid, caused by kinetic inhibition owing to the formation of sulfates. Delamination of the thick film, resulting from the low chemical resistance of the interphase, occurred in the case of the composite-containing additives. No thick film delamination was observed on the additive-free composite. However, selective dissolution of the substrate's alumosilicate phase takes place beneath the thick film.