Wet chemical porosification of LTCC in phosphoric acid: Anorthite forming tapes

With the porosification of sintered Low Temperature Co-fired Ceramic (LTCC) surfaces areas with alternating dielectric properties can be created by embedding air. The method, including a wet-chemical treatment with phosphoric acid, is also investigated in detail for several commercial celsian forming tapes. Since the results of these materials cannot provide the required selectivity, in this work the analysis is extended to anorthite forming tapes. Furthermore, the investigations include a LTCC based on lanthanum borate. The results show that the porosification with phosphoric acid is not applicable to the latter material. In contrast, the silicate based, corundum containing tapes feature the most satisfying porosification results. Thereby, the stability of the glass, the size of the grains, the exclusivity of the crystallized phase and its degree of crystallization are identified as the tape features which directly influence the porosification results.